WO2025024575A1

WO2025024575A1 - Capturing carbon dioxide

Info

Publication number: WO2025024575A1
Application number: PCT/US2024/039378
Authority: WO
Inventors: Chris Bowman; Markus Bernward FELDKAMP; Christoph SCHEMMANN; Todd Ernest Wilke; Andrew Logan OSTERICHER; Maxwell Douglas Horner; John Mitchell PACE; III Frank M. Kulick
Original assignee: Carbon Engineering Ulc
Priority date: 2023-07-25
Filing date: 2024-07-24
Publication date: 2025-01-30
Also published as: CN119367965A

Abstract

A packing sheet includes a leading edge and a trailing edge spaced apart by an air travel depth. The leading edge is substantially parallel to the vertical in an installed configuration. Upper and lower edges of the packing sheet are spaced apart by a liquid travel dimension substantially parallel to a direction along which a CO₂ capture solution travels from the upper edge to the lower edge. A mass-transfer zone of the packing sheet includes mass-transfer microstructures having a microstructure height and configured to receive the CO₂ capture solution and to contact the atmospheric air with the CO₂ capture solution. Stiffening elements of the packing sheet extend and have an orientation substantially parallel to the liquid travel dimension. Spacers of the packing sheet are disposed on the mass-transfer zone and are spaced apart along the liquid travel dimension. Related apparatuses, systems, and methods are also disclosed.

Description

CAPTURING CARBON DIOXIDE

TECHNICAL FIELD

[0001] This disclosure describes systems, apparatus, and methods for capturing carbon dioxide.

BACKGROUND

[0002] Capturing carbon dioxide (CO2) from the atmosphere is one approach to mitigating greenhouse gas emissions and slowing climate change. However, many technologies designed for CO2 capture from point sources of emissions, such as from flue gas of industrial facilities, are generally ineffective in capturing CO2 from the atmosphere due to the significantly lower CO2 concentrations and large volumes of atmospheric air required to process. In recent years, progress has been made in finding technologies better suited to capture CO2 directly from the atmosphere. Some of these direct air capture (DAC) systems use a solid sorbent where an active agent is attached to a substrate. These DAC systems typically employ a cyclic adsorption-desorption process where, after the solid sorbent is saturated with CO2, it releases the CO2 using a humidity or thermal swing and is regenerated.

[0003] Other DAC systems use a liquid sorbent (sometimes referred to as a solvent) to capture CO2 from the atmosphere. An example of such a DAC system would be one where a fan is used to draw air across a high surface area packing that is wetted with a solution comprising the liquid sorbent. CO2 in the air reacts with the liquid sorbent to generate a CO2 rich solution. The rich solution is processed to regenerate a lean solution and to release a concentrated carbon stream, for example, CO, CO2 or other carbon products.

SUMMARY

[0004] In an example implementation, a packing sheet for transferring carbon dioxide (CO2) from atmospheric air to a CO2 capture solution includes a first side; a second side opposite the first side; a leading edge substantially parallel to the vertical in an installed configuration of the packing sheet; a trailing edge spaced apart from the leading edge by an air travel depth substantially parallel to a direction along which the atmospheric air travels from the leading edge to the trailing edge; a plurality of interconnecting edges, a mass-transfer zone, a plurality of stiffening elements that extends from the first side and from the second side, and a plurality of spacers disposed on the mass-transfer zone and that extends from the first side and from the second side. The plurality of interconnecting edges includes an upper edge that extends between the leading and trailing edges; and a lower edge that extends between the leading and trailing edges, the upper and lower edges spaced apart by a liquid travel dimension substantially parallel to a direction along which the CO2 capture solution travels from the upper edge to the lower edge. The mass-transfer zone is on the first side and on the second side between the leading edge, the trailing edge, the upper edge, and the lower edge, and the masstransfer zone includes a plurality of mass-transfer microstructures configured to receive the CO2 capture solution and to contact the atmospheric air with the CO2 capture solution, the plurality of mass-transfer microstructures having a microstructure height. Each stiffening element of the plurality of stiffening elements has an orientation substantially parallel to the liquid travel dimension. The plurality of spacers are spaced apart along the liquid travel dimension and have a spacer height greater than the microstructure height.

[0005] In an aspect combinable with the example implementation, the packing sheet includes a spacer alignment axis that extends between the upper edge and the lower edge on the first side and on the second side, the spacer alignment axis extending between at least two spacers of the plurality of spacers aligned along the liquid travel dimension, the spacer alignment axis substantially parallel to the vertical in the installed configuration of the packing sheet.

[0006] In another aspect combinable with one, some, or all of the previous aspects, the packing sheet includes a stiffening element alignment axis that extends between the upper edge and the lower edge on the first side and on the second side, the stiffening element alignment axis extending between at least two stiffening elements of the plurality of stiffening elements aligned along the liquid travel dimension, the stiffening element alignment axis substantially parallel to the vertical in the installed configuration of the packing sheet.

[0007] In another aspect combinable with one, some, or all of the previous aspects, the plurality of stiffening elements include a plurality of intermediate stiffening elements between the leading edge and the trailing edge, the plurality of intermediate stiffening elements including a plurality of intermediate stiffening bodies positioned adjacent each other along the liquid travel dimension, each intermediate stiffening body of the plurality of intermediate stiffening bodies extends from one of the first side and the second side to an attachment wall, the attachment wall defining a stiffening body height greater than the microstructure height.

[0008] In another aspect combinable with one, some, or all of the previous aspects, the plurality of intermediate stiffening bodies includes a first set of intermediate stiffening bodies that extends from the first side and a second set of intermediate stiffening bodies that extends from the second side, the first set of intermediate stiffening bodies forming a first set of depressions on the second side and the second set of intermediate stiffening bodies forming a second set of depressions on the first side, the first set of intermediate stiffening bodies alternating along an axis with the second set of depressions on the first side, and the second set of intermediate stiffening bodies alternating with the first set of depressions along the axis on the second side.

[0009] In another aspect combinable with one, some, or all of the previous aspects, each intermediate stiffening body of the plurality of intermediate stiffening bodies includes a plurality of planar walls that extends from one of the first side and the second side to the attachment wall; and a plurality of flow channels, each flow channel of the plurality of flow channels disposed in a planar wall of the plurality of planar walls.

[0010] In another aspect combinable with one, some, or all of the previous aspects, the plurality of flow channels include at least one longitudinal flow channel substantially parallel to the liquid travel dimension; and at least one lateral flow channel including an inlet end and an outlet end, the inlet end being closer to the attachment wall than the outlet end.

[0011] In another aspect combinable with one, some, or all of the previous aspects, the plurality of stiffening elements includes a plurality of peripheral ribs adjacent to at least one of the trailing edge and the leading edge, each peripheral rib of the plurality of peripheral ribs extends from one of the first side and the second side, and forming a corresponding depression in the other one of the first side and the second side.

[0012] In another aspect combinable with one, some, or all of the previous aspects, the plurality of peripheral ribs includes a plurality of leading edge ribs adjacent to the leading edge, the plurality of leading edge ribs including an innermost set of ribs that extends from the first side and forming corresponding depressions in the second side; and an outermost set of ribs that extends from the second side and forming corresponding depressions in the first side, the outermost set of ribs spaced further from the leading edge along the air travel depth than the innermost set of ribs.

[0013] In another aspect combinable with one, some, or all of the previous aspects, the plurality of peripheral ribs includes a plurality of trailing edge ribs adjacent to the trailing edge, the plurality of trailing edge ribs including a third set of ribs that extends from the first side and forming corresponding depressions in the second side; and a fourth set of ribs that extends from the second side and forming corresponding depressions in the first side, the fourth set of ribs spaced further from the trailing edge along the air travel depth than the third set of ribs, the third set of ribs. [0014] In another aspect combinable with one, some, or all of the previous aspects, the plurality of peripheral ribs includes at least one longitudinal rib pairing of two peripheral ribs spaced apart from each other in a direction substantially parallel to the liquid travel dimension to define a longitudinal pairing gap, wherein some mass-transfer microstructures of the plurality of mass-transfer microstructures are present in the longitudinal pairing gap.

[0015] In another aspect combinable with one, some, or all of the previous aspects, the plurality of peripheral ribs includes at least one lateral rib pairing of two peripheral ribs spaced apart from each other in a direction substantially parallel to the air travel depth to define a lateral pairing gap, and some mass-transfer microstructures of the plurality of mass-transfer microstructures are present in the lateral pairing gap.

[0016] In another aspect combinable with one, some, or all of the previous aspects, the plurality of stiffening elements includes a plurality of peripheral stiffening bodies positioned adjacent each other along the liquid travel dimension, the plurality of peripheral stiffening bodies defining at least one of the trailing edge and the leading edge.

[0017] In another aspect combinable with one, some, or all of the previous aspects, the plurality of spacers includes a plurality of spacer pairings spaced apart along the liquid travel dimension and along the air travel depth, the spacers in each spacer pairing of the plurality of spacer pairings spaced apart in a direction subtantially parallel to the air travel depth.

[0018] In another aspect combinable with one, some, or all of the previous aspects, the spacers in each spacer pairing include a first spacer that extends from the first side and forms a corresponding depression in the second side, and a second spacerthat extends from the second side and forms a corresponding depression in the first side.

[0019] In another aspect combinable with one, some, or all of the previous aspects, the plurality of stiffening elements include a plurality of intermediate stiffening elements positioned between the leading edge and the trailing edge, at least the plurality of intermediate stiffening elements including a plurality of intermediate ribs having an orientation substantially parallel to the liquid travel dimension, the plurality of intermediate ribs including a first set of ribs spaced apart in the liquid travel dimension and that extends from the first side and forms corresponding depressions in the second side; and a second set of ribs spaced apart in the liquid travel dimension and that extends from the second side and forms corresponding depressions in the first side, the second set of ribs spaced apart from the first set of ribs in a direction substantially parallel to the air travel depth.

[0020] In another aspect combinable with one, some, or all of the previous aspects, each rib of the first set of ribs includes a first rib end and a second rib end; and each rib of the second set of ribs includes a third rib end and a fourth rib end, the third rib end of at least one rib of the second set of ribs positioned between the first rib end and the second rib end of at least one rib of the first set of ribs.

[0021] In another aspect combinable with one, some, or all of the previous aspects, the packing sheet has a rectangular shape, the leading edge and the trailing edge substantially parallel to the vertical in the installed configuration of the packing sheet, the upper edge substantially perpendicular to the leading edge and the trailing edge, and the lower edge substantially perpendicular to the leading edge and the trailing edge.

[0022] In another aspect combinable with one, some, or all of the previous aspects, the liquid travel dimension is greater than the air travel depth.

[0023] In another aspect combinable with one, some, or all of the previous aspects, the air travel depth is between 3 ft. and 5 ft.

[0024] In another aspect combinable with one, some, or all of the previous aspects, at least some mass-transfer microstructures of the plurality of mass-transfer microstructures include a first wall portion that extends toward a first apex on a first side; and a second wall portion that extends from the first apex to a second apex on the second side, at least one of the first wall portion and the second wall portion including at least one wall feature extending from the at least one of the first wall portion and the second wall portion.

[0025] In another aspect combinable with one, some, or all of the previous aspects, the at least one wall feature includes a first wall feature that extends outwardly from the first wall portion on the first side; and a second wall feature that extends from the second wall portion on the second side.

[0026] In another aspect combinable with one, some, or all of the previous aspects, the packing sheet includes a centroid, the packing sheet having point symmetry about the centroid. [0027] In another aspect combinable with one, some, or all of the previous aspects, the plurality of stiffening elements includes a plurality of reinforcement bodies positioned adjacent each other along the air travel depth and between the leading edge and the trailing edge.

[0028] In another aspect combinable with one, some, or all of the previous aspects, the plurality of reinforcement bodies is disposed between the upper edge and the lower edge.

[0029] In another aspect combinable with one, some, or all of the previous aspects, the plurality of reinforcement bodies defines at least one of the upper edge and the lower edge.

[0030] In another aspect combinable with one, some, or all of the previous aspects, each reinforcement body of the plurality of reinforcement bodies extends outwardly from at least one of the first side or the second side to an attachment wall, the attachment wall defining a body height greater than the microstructure height.

[0031] In another aspect combinable with one, some, or all of the previous aspects, the plurality of reinforcement bodies includes a first set of reinforcement bodies that extends from the first side and a second set of reinforcement bodies that extends from the second side. The first set of reinforcement bodies forms a first set of depressions on the second side and the second set of reinforcement bodies forms a second set of depressions on the first side. The first set of reinforcement bodies alternates along a horizontal axis with the second set of depressions on the first side, and the second set of reinforcement bodies alternates with the first set of depressions along the horizontal axis on the second side.

[0032] In another aspect combinable with one, some, or all of the previous aspects, each reinforcement body of the plurality of reinforcement bodies includes: a plurality of planar walls that extends from at least one of the first side or the second side to the attachment wall; and at least one flow channel that extends into a planar wall of the plurality of planar walls on at least one of the first side or the second side, the at least one flow channel substantially parallel to the air travel depth.

[0033] In another aspect combinable with one, some, or all of the previous aspects, each reinforcement body of the plurality of reinforcement bodies includes a plurality of planar walls that extends from at least one of the first side or the second side to the attachment wall, the attachment wall having an attachment wall slope, at least one planar wall of the plurality of planar walls including a stepped member. The stepped member includes a first wall segment that extends from the attachment wall and having a first slope different from the attachment wall slope; a second wall segment that extends from the first wall segment and having a second slope different from the first slope; and a third wall segment that extends from the second wall segment and having a third slope different from the second slope.

[0034] In another aspect combinable with one, some, or all of the previous aspects, at least some mass-transfer microstructures of the plurality of mass-transfer microstructures include a plurality of base microstructures that include a first wall portion and a second wall portion that extends toward a first apex on one of the first and second sides; and a plurality of supplemental microstructures protruding outwardly from the first and second wall portions of the plurality of base microstructures.

[0035] In another example implementation, a structured packing for transferring carbon dioxide (CO2) from atmospheric air to a CO2 capture solution includes a plurality of packing sheets attached together. At least one packing sheet of the plurality of packing sheets includes a first side; a second side opposite the first side; a leading edge; a trailing edge spaced apart from the leading edge by an air travel depth substantially parallel to a direction along which the atmospheric air travels from the leading edge to the trailing edge, a plurality of interconnecting edges, a mass-transfer zone, a plurality of stiffening elements that extends from the first side and from the second side, and a plurality of spacers disposed on the mass-transfer zone and that extends from the first side and from the second side. The leading edge of the at least one packing sheet is substantially parallel to the vertical in an installed configuration of the at least one packing sheet. The plurality of interconnecting edges includes an upper edge that extends between the leading edge and the trailing edge; and a lower edge that extends between the leading edge and the trailing edge, the upper and lower edges being spaced apart by a liquid travel dimension substantially parallel to a direction along which the CO2 capture solution travels from the upper edge to the lower edge. The mass-transfer zone is on the first side and on the second side between the leading edge, the trailing edge, the upper edge, and the lower edge, the mass-transfer zone including a plurality of mass-transfer microstructures having a microstructure height and configured to contact the CO2 capture solution with the atmospheric air. Each stiffening element of the plurality of stiffening elements has an orientation substantially parallel to the liquid travel dimension. The plurality of spacers are spaced apart along the liquid travel dimension and have a spacer height greater than the microstructure height. Adjacent packing sheets of the plurality of packing sheets are attached along a respective plurality of spacers and define an airflow channel through which the atmospheric air travels from the leading edge to the trailing edge.

[0036] In an aspect combinable with the example implementation, the airflow channel has a rectangular channel shape defined in a plane normal to the liquid travel dimension.

[0037] In another aspect combinable with one, some, or all of the previous aspects, the plurality of stiffening elements includes a plurality of intermediate stiffening elements between the leading edge and the trailing edge, the plurality of intermediate stiffening elements including a plurality of intermediate stiffening bodies positioned adjacent each other along the liquid travel dimension, each intermediate stiffening body of the plurality of intermediate stiffening bodies extends from one of the first side and the second side to an attachment wall, the attachment wall defining a stiffening body height greater than the microstructure height, the adjacent packing sheets attached along their attachment walls.

[0038] In another aspect combinable with one, some, or all of the previous aspects, each intermediate stiffening body of the plurality of intermediate stiffening bodies includes a plurality of planar walls that extends from one of the first side and the second side to the attachment wall, and a plurality of flow channels, each flow channel of the plurality of flow channels disposed in a planar wall of the plurality of planar walls, the plurality of flow channels including at least one longitudinal flow channel substantially parallel to the liquid travel dimension and that extends from the attached attachment walls of the adjacent packing sheets. [0039] In another aspect combinable with one, some, or all of the previous aspects, the plurality of intermediate stiffening bodies includes a first set of stiffening bodies that extends from the first side and a second set of stiffening bodies that extends from the second side, the first set of stiffening bodies forming a first set of depressions on the second side and the second set of stiffening bodies forming a second set of depressions on the first side, the first set of stiffening bodies alternating along an axis with the second set of depressions on the first side, and the second set of stiffening bodies alternating along the axis with the first set of depressions on the second side, the airflow channel between the adjacent packing sheets extends through the first sets of depressions and the second sets of depressions.

[0040] In another aspect combinable with one, some, or all of the previous aspects, the plurality of stiffening elements includes a plurality of intermediate stiffening elements between the leading edge and the trailing edge, at least the plurality of intermediate stiffening elements including a plurality of intermediate ribs having an orientation substantially parallel to the liquid travel dimension; the plurality of stiffening elements includes a plurality of peripheral stiffening elements disposed adjacent to at least one of the trailing edge and the leading edge, the plurality of peripheral stiffening elements including a plurality of peripheral stiffening bodies positioned adjacent each other along the liquid travel dimension, the plurality of peripheral stiffening bodies defining at least one of the trailing edge and the leading edge; and the plurality of intermediate ribs having an intermediate rib height less than a peripheral stiffening body height of the plurality of peripheral stiffening bodies.

[0041] In another aspect combinable with one, some, or all of the previous aspects, the plurality of stiffening elements includes a plurality of peripheral stiffening bodies positioned adjacent each other along the liquid travel dimension, the plurality of peripheral stiffening bodies defining at least one of the trailing edge and the leading edge, the plurality of peripheral stiffening bodies including a first set of stiffening bodies that extends from the first side and a second set of stiffening bodies that extends from the second side, the first set of stiffening bodies forming a first set of depressions on the second side and the second set of stiffening bodies forming a second set of depressions on the first side, the first set of stiffening bodies alternating along an axis with the second set of depressions on the first side, and the second set of stiffening bodies alternating along the axis with the first set of depressions on the second side, the first set of stiffening bodies of a first packing sheet of the adjacent packing sheets attached to the second set of stiffening bodies of a second packing sheet of the adjacent packing sheets, stiffening body flow passages formed between the first set of depressions and the second set of depressions of the adjacent packing sheets, the stiffening body flow passages in fluid communication with the airflow channel.

[0042] In another aspect combinable with one, some, or all of the previous aspects, the structured packing includes a spacer alignment axis that extends between the upper edge and the lower edge on the first side and on the second side, the spacer alignment axis extending between at least two spacers of the plurality of spacers aligned along the liquid travel dimension, the spacer alignment axis being substantially parallel to the vertical in the installed configuration of the at least one packing sheet.

[0043] In another aspect combinable with one, some, or all of the previous aspects, the structured packing includes a stiffening element alignment axis that extends between the upper and lower edges on the first side and on the second side, the stiffening element alignment axis extending between at least two stiffening elements of the plurality of stiffening elements aligned along the liquid travel dimension, the stiffening element alignment axis being substantially parallel to the vertical in the installed configuration of the at least one packing sheet.

[0044] In another aspect combinable with one, some, or all of the previous aspects the plurality of stiffening elements include a plurality of intermediate stiffening elements between the leading edge and the trailing edge, at least the plurality of intermediate stiffening elements including a plurality of intermediate stiffening bodies positioned adjacent each other along the liquid travel dimension, each intermediate stiffening body of the plurality of intermediate stiffening bodies extends from one of the first side and the second side to an attachment wall, the attachment wall defining a stiffening body height greater than the microstructure height.

[0045] In another aspect combinable with one, some, or all of the previous aspects, the plurality of intermediate stiffening bodies includes a first set of intermediate stiffening bodies that extends from the first side and a second set of intermediate stiffening bodies that extends from the second side, the first set of intermediate stiffening bodies forming a first set of depressions on the second side and the second set of intermediate stiffening bodies forming a second set of depressions on the first side, the first set of intermediate stiffening bodies alternating along an axis with the second set of depressions on the first side, and the second set of intermediate stiffening bodies alternating along the axis with the first set of depressions on the second side. [0046] In another aspect combinable with one, some, or all of the previous aspects, each intermediate stiffening body of the plurality of intermediate stiffening bodies includes a plurality of planar walls that extends outwardly from one of the first side and the second side to the attachment wall, and a plurality of flow channels, each flow channel of the plurality of flow channels disposed in a planar wall of the plurality of planar walls.

[0047] In another aspect combinable with one, some, or all of the previous aspects, the plurality of flow channels includes at least one longitudinal flow channel substantially parallel to the liquid travel dimension, and at least one lateral flow channel including an inlet end and an outlet end, the inlet end being closer to the attachment wall than the outlet end.

[0048] In another aspect combinable with one, some, or all of the previous aspects, the plurality of stiffening elements includes a plurality of peripheral ribs adjacent to at least one of the trailing edge and the leading edge, each peripheral rib of the plurality of peripheral ribs that extends from one of the first side and the second side and forming a corresponding depression in the other one of the first side and the second side.

[0049] In another aspect combinable with one, some, or all of the previous aspects, the plurality of peripheral ribs includes a plurality of leading edge ribs adjacent to the leading edge, the plurality of leading edge ribs including an innermost set of ribs; and an outermost set of ribs spaced further from the leading edge along the air travel depth than the innermost set of ribs, the innermost set of ribs extends from the first side and forming corresponding depressions in the second side, the outermost set of ribs extendds from the second side and forming corresponding depressions in the first side.

[0050] In another aspect combinable with one, some, or all of the previous aspects, the plurality of peripheral ribs includes a plurality of trailing edge ribs adjacent to the trailing edge, the plurality of trailing edge ribs including a third set of ribs and a fourth set of ribs spaced further from the trailing edge along the air travel depth than the third set of ribs, the third set of ribs extends from the first side and forming corresponding depressions in the second side, the fourth set of ribs extends from the second side and forming corresponding depressions in the first side.

[0051] In another aspect combinable with one, some, or all of the previous aspects, the plurality of peripheral ribs includes at least one longitudinal rib pairing of two peripheral ribs spaced apart from each other in a direction substantially parallel to the liquid travel dimension to define a longitudinal pairing gap, wherein some mass-transfer microstructures of the plurality of mass-transfer microstructures are present in the longitudinal pairing gap. [0052] In another aspect combinable with one, some, or all of the previous aspects, the plurality of peripheral ribs includes at least one lateral rib pairing of two peripheral ribs spaced apart from each other in a direction substantially parallel to the air travel depth to define a lateral pairing gap, and some mass-transfer microstructures of the plurality of mass-transfer microstructures are present in the lateral pairing gap.

[0053] In another aspect combinable with one, some, or all of the previous aspects, the plurality of stiffening elements includes a plurality of peripheral stiffening bodies positioned adjacent each other along the liquid travel dimension, the plurality of peripheral stiffening bodies defining at least one of the trailing edge and the leading edge.

[0054] In another aspect combinable with one, some, or all of the previous aspects, the plurality of spacers includes a plurality of spacer pairings spaced apart along the liquid travel dimension and along the air travel depth, the spacers in each spacer pairing spaced apart in a direction substantially parallel to the air travel depth.

[0055] In another aspect combinable with one, some, or all of the previous aspects, the spacers in each spacer pairing include a first spacer that extends from the first side and forming a corresponding depression in the second side, and a second spacerthat extends from the second side and forming a corresponding depression in the first side.

[0056] In another aspect combinable with one, some, or all of the previous aspects, the plurality of stiffening elements includes a plurality of intermediate stiffening elements between the leading edge and the trailing edge, at least the plurality of intermediate stiffening elements including a plurality of intermediate ribs having an orientation substantially parallel to the liquid travel dimension, the plurality of intermediate ribs including a first set of ribs spaced apart in the liquid travel dimension; and a second set of ribs spaced apart in the liquid travel dimension, the second set of ribs spaced apart from the first set of ribs in a direction substantially parallel to the air travel depth, the first set of ribs extends from the first side and forming corresponding depressions in the second side, the second set of ribs extends from the second side and forming corresponding depressions in the first side.

[0057] In another aspect combinable with one, some, or all of the previous aspects, each rib of the first set of ribs includes a first rib end and a second rib end; and each rib of the second set of ribs includes a third rib end and a fourth rib end, the third rib end of at least one rib of the second set of ribs positioned between the first rib end and the second rib end of at least one rib of the first set of ribs.

[0058] In another aspect combinable with one, some, or all of the previous aspects, the packing sheet has a rectangular shape, the leading edge and the trailing edge being substantially parallel to the vertical in the installed configuration of the at least one packing sheet; the upper edge is substantially perpendicular to the leading edge and the trailing edge; and the lower edge is substantially perpendicular to the leading edge and the trailing edge.

[0059] In another aspect combinable with one, some, or all of the previous aspects, the liquid travel dimension is greater than the air travel depth.

[0060] In another aspect combinable with one, some, or all of the previous aspects the air travel depth is between 3 ft. and 5 ft.

[0061] In another aspect combinable with one, some, or all of the previous aspects, at least one mass-transfer microstructure of the plurality of mass-transfer microstructures includes a first wall portion that extends toward a first apex on a first side, and a second wall portion that extends from the first apex to a second apex on the second side, at least one of the first wall portion and the second wall portion including at least one wall feature extending from the at least one of the first wall portion and the second wall portion.

[0062] In another aspect combinable with one, some, or all of the previous aspects, the at least one wall feature includes a first wall feature that extends from the first wall portion on the first side, and a second wall feature that extends from the second wall portion on the second side.

[0063] In another aspect combinable with one, some, or all of the previous aspects, the structured packing includes a centroid, the at least one packing sheet having point symmetry about the centroid.

[0064] In another example implementation, a gas-liquid contactor for capturing carbon dioxide (CO2) from atmospheric air includes: at least one inlet; at least one outlet spaced apart from the at least one inlet; at least one packing section disposed between the at least one inlet and the at least one outlet, the at least one packing section including at least one structured packing, one or more liquid collection devices including a bottom liquid collection device positioned at least partially below the at least one packing section, the one or more liquid collection devices configured to hold a CO2 capture solution; a fan operable to flow the atmospheric air (1) from the at least one inlet to the at least one outlet and (2) along the airflow channels of the at least one structured packing substantially parallel to the air travel depth; and a liquid distribution system fluidly coupled to the at least one packing section. The at least one structured packing including a plurality of packing sheets attached together. At least one packing sheet of the plurality of packing sheets includes: a first side; a second side opposite the first side; a leading edge substantially parallel to the vertical; a trailing edge spaced apart from the leading edge by an air travel depth; a plurality of interconnecting edges including an upper edge that extends between the leading edge and the trailing edge and a lower edge that extends between the leading edge and the trailing edge, the upper edge and the lower edge spaced apart by a liquid travel dimension; a mass-transfer zone on the first side and on the second side between the leading edge, the trailing edge, the upper edge, and the lower edge, the masstransfer zone including a plurality of mass-transfer microstructures having a microstructure height; a plurality of stiffening elements that extends from the first side and from the second side, each stiffening element of the plurality of stiffening elements having an orientation substantially parallel to the liquid travel dimension; and a plurality of spacers disposed on the mass-transfer zone and tjat extends from the first side and from the second side, the plurality of spacers spaced apart and having a spacer height greater than the microstructure height. Adjacent packing sheets of the plurality of packing sheets are attached along a respective plurality of spacers and define an airflow channel. The liquid distribution system is operable to flow the CO2 capture solution along the plurality of mass-transfer microstructures in the liquid travel dimension to contact the atmospheric air with the CO2 capture solution and absorb CO2 from the atmospheric air into the CO2 capture solution.

[0065] In an aspect combinable with the example implementation, the gas-liquid contactor includes a housing defining an interior at least partially exposed to the atmospheric air, the interior disposed between the at least one inlet and the at least one outlet, and the at least one structured packing includes a plurality of structured packings disposed within the interior and forming at least one arrangement of structured packings, the structured packings of the at least one arrangement of structured packings positioned vertically and laterally adjacent each other.

[0066] In another aspect combinable with one, some, or all of the previous aspects, the at least one arrangement of structured packings includes an upper arrangement of structured packings, a lower arrangement of structured packings vertically spaced beneath the upper arrangement of structured packings, and a redistribution spacing defined between the upper and lower arrangements of structured packings; and the one or more liquid collection devices include a redistribution basin positioned in the redistribution spacing between the upper and lower arrangements of structured packings, the redistribution basin configured to collect the CO2 capture solution from the upper arrangement of structured packings and to redistribute the CO2 capture solution over the lower arrangement of structured packings.

[0067] In another aspect combinable with one, some, or all of the previous aspects, the housing includes a plurality of interconnected structural members, the plurality of structured packings mounted to at least one of: an interconnected structural member of the plurality of interconnected structured members, or another structured packing of the plurality of structured packings.

[0068] In another aspect combinable with one, some, or all of the previous aspects, the liquid distribution system is operable to flow the CO2 capture solution at a liquid loading rate ranging from 0.5 L/m²s to 10 L/m²s.

[0069] In another aspect combinable with one, some, or all of the previous aspects, the at least one packing section includes a first packing section, and a second packing section spaced apart from the first packing section by a plenum; the fan is operable to flow the atmospheric air to enter the first packing section and the second packing section at airspeeds between 0.1 m/s and 5 m/s, and flow through the first packing section and the second packing section along a horizontal flow direction into the plenum; and the liquid distribution system is operable to flow the CO2 capture solution in the liquid travel dimension being predominantly vertically downward.

[0070] In another example implementation, a packing sheet for transferring carbon dioxide (CO2) from atmospheric air to a CO2 capture solution includes: a first side; a second side opposite the first side; a leading edge; a trailing edge spaced apart from the leading edge by an air travel depth substantially parallel to a direction along which the atmospheric air travels from the leading edge to the trailing edge, the leading edge substantially parallel to the vertical in an installed configuration of the packing sheet; a plurality of interconnecting edges including an upper edge that extends between the leading edge and the trailing edge, and a lower edge that extends between the leading edge and the trailing edge, the upper edge and the lower edge spaced apart by a liquid travel dimension substantially parallel to a direction along which the CO2 capture solution travels from the upper edge to the lower edge; a mass-transfer zone on the first side and on the second side between the leading edge, the trailing edge, the upper edge, and the lower edge, the mass-transfer zone including a plurality of mass-transfer microstructures having a microstructure height, the plurality of mass-transfer microstructures configured to receive the CO2 capture solution and to contact the atmospheric air with the CO2 capture solution; at least one stiffening element that extends from one of the first side and the second side, the at least one stiffening element having an orientation substantially parallel to the liquid travel dimension, one or more mass-transfer microstructures of the plurality of masstransfer microstructures disposed on the at least one stiffening element; and a plurality of spacers disposed on the mass-transfer zone and that extends from the first side and from the second side, the plurality of spacers spaced apart along the liquid travel dimension and having a spacer height greater than the microstructure height. [0071] In another example implementation, a method for capturing carbon dioxide (CO2) from atmospheric air includes: flowing the atmospheric air in a first flow direction from leading edges of a plurality of packing sheets to trailing edges of the plurality of packing sheets, the first flow direction being substantially perpendicular to the leading edges of the plurality of packing sheets; and flowing a CO2 capture solution in a second flow direction over the plurality of packing sheets to absorb CO2 from the atmospheric air into the CO2 capture solution, the second flow direction being substantially perpendicular to the first flow direction. [0072] In another example implementation, a direct air capture (DAC) system for capturing carbon dioxide (CO2) from atmospheric air includes: at least one gas-liquid contactor, a liquid distribution system, a regeneration system in fluid communication with the liquid distribution system. The at least one gas-liquid contactor includes: at least one inlet; at least one outlet spaced apart from the at least one inlet; at least one packing section disposed between the at least one inlet and the at least one outlet, and a fan. The at least one packing section includes at least one structured packing. The at least one structured packing includes a plurality of packing sheets attached together. At least one packing sheet of the plurality of packing sheets includes: a first side, a second side opposite the first side; a leading edge substantially parallel to the vertical; a trailing edge spaced apart from the leading edge by an air travel depth; a plurality of interconnecting edges including an upper edge that extends between the leading edge and the trailing edge and a lower edge that extends between the leading edge and the trailing edge, the upper edge and the lower edge spaced apart by a liquid travel dimension; a mass-transfer zone on the first side and on the second side between the leading edge, the trailing edge, the upper edge, and the lower edge, the mass-transfer zone including a plurality of mass-transfer microstructures having a microstructure height; a plurality of stiffening elements that extends from the first side and from the second side, each stiffening element of the plurality of stiffening elements having an orientation substantially parallel to the liquid travel dimension; and a plurality of spacers disposed on the mass-transfer zone and that extends from the first side and from the second side, the plurality of spacers spaced apart and having a spacer height greater than the microstructure height, adjacent packing sheets of the plurality of packing sheets attached along a respective plurality of spacers and defining airflow channels. The fan is operable to flow the atmospheric air (1) from the at least one inlet to the at least one outlet and (2) along the airflow channels of the at least one structured packing substantially parallel to the air travel depth. The liquid distribution system is fluidly coupled to the at least one packing section and operable to flow a CO2 capture solution over the mass-transfer microstructures of the at least one packing section, the CO2 capture solution configured to absorb CO2 from the atmospheric air. The liquid distribution system includes one or more liquid collection devices including a bottom liquid collection device positioned at least partially below the at least one packing section, the one or more liquid collection devices configured to hold the CO2 capture solution. The regeneration system receives the CO2 capture solution, and is configured to regenerate the CO2 capture solution and form a CO2-lean liquid to return to the at least one gas-liquid contactor

[0073] In an aspect combinable with the example implementation, the regeneration system is configured to provide a CO2 product stream.

[0074] Implementations of systems and methods for capturing carbon dioxide according to the present disclosure can include one, some, or all of the following features. For example, packing with the features described in this invention are designed specifically for commercial DAC applications and as such have the ability to reduce at least one of air volume, packing depth, liquid flow, and air contactor footprint without significant sacrifice to CO2 uptake performance. Design criteria of DAC packing that reflect good performance include: low static pressure design, ability to distribute liquid evenly throughout fill height, low fouling capabilities, increase in air contacting efficiency, lower material requirements, efficiency effects of larger pack sizes, and manufacturability.

[0075] The details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0076] FIG. 1 shows an example gas-liquid contactor.

[0077] FIG. 2A shows another example gas-liquid contactor.

[0078] FIG. 2B shows another example gas-liquid contactor.

[0079] FIG. 3 shows an example packing sheet for a gas-liquid contactor of the present disclosure.

[0080] FIG. 4 is an enlarged view of portion IV-IV of the packing sheet of FIG. 3.

[0081] FIG. 4A is a cross-sectional view taken along line 4A-4A in FIG. 4.

[0082] FIG. 4B is a cross-sectional view taken along line 4B-4B in FIG. 4.

[0083] FIG. 4C is a cross-sectional view taken along line 4C-4C in FIG. 4.

[0084] FIG. 4D is a cross-sectional view taken along line 4D-4D in FIG. 4.

[0085] FIG. 4E is a cross-sectional view taken along line 4E-4E in FIG. 4. [0086] FIG. 5 is an enlarged view of portion V-V of FIG. 4.

[0087] FIG. 5A is an enlarged view of a portion of an example packing sheet for a gasliquid contactor of the present disclosure.

[0088] FIG. 6 shows an example packing sheet for a gas-liquid contactor of the present disclosure.

[0089] FIG. 7 shows an example packing sheet for a gas-liquid contactor of the present disclosure.

[0090] FIG. 7A is a cross-sectional view taken along line 7A-7A in FIG. 7.

[0091] FIG. 8 shows an example packing sheet for a gas-liquid contactor of the present disclosure.

[0092] FIG. 8A is an enlarged view of portion VIIIA of FIG. 8.

[0093] FIG. 8 Al is a cross-sectional view taken along line 8 Al -8 Al in FIG. 8 A.

[0094] FIG. 8A2 is a cross-sectional view taken along line 8A2-8A2 in FIG. 8A.

[0095] FIG. 8B is an enlarged view of portion VIIIB of FIG. 8.

[0096] FIG. 8B1 is a cross-sectional view taken along line 8B1 -8B1 in FIG. 8B.

[0097] FIG. 8B2 is a cross-sectional view taken along line 8B2 -8B2 in FIG. 8B.

[0098] FIG. 8C is an enlarged perspective view of a portion of the example packing sheet of FIG. 8.

[0099] FIG. 9 is a perspective view of a portion of an example packing sheet for a gasliquid contactor of the present disclosure.

[00100] FIG. 10 shows an example structured packing formed of packing sheets of the present disclosure.

[00101] FIG. 11 is a front end view of the structured packing of FIG. 10.

[00102] FIG. 12 is a top view of the structured packing of FIG. 10.

[00103] FIG. 13 shows example mass-transfer microstructures of packing sheets of the present disclosure.

[00104] FIG. 14 shows example mass-transfer microstructures of packing sheets of the present disclosure.

[00105] FIG. 15 is a schematic illustration of a direct air capture system having a gasliquid contactor of the present disclosure.

[00106] FIG. 16 is a schematic flow diagram of a method for capturing carbon dioxide (CO2) from atmospheric air.

[00107] FIG. 17 is a schematic diagram of a control system (or controller) for a gasliquid contactor of the present disclosure. [00108] FIG. 18A shows example mass-transfer microstructures of packing sheets of the present disclosure.

[00109] FIG. 18B is an enlarged view of portion 18B-18B of FIG. 18 A.

[00110] FIG. 19 is a schematic illustration of another direct air capture system having a gas-liquid contactor of the present disclosure.

[00111] FIG. 20 is a schematic illustration of another direct air capture system having a gas-liquid contactor of the present disclosure.

DETAILED DESCRIPTION

[00112] Referring to FIG. 1, the present disclosure describes systems and methods for capturing carbon dioxide (CO2) with a gas-liquid contactor 100, from the atmosphere (e.g., ambient or atmospheric air) or from another fluid source that contains dilute concentrations of CO2. Concentrations of CO2 in the atmosphere are dilute, in that they are presently in the range of 400-420 parts per million (“ppm”) or approximately 0.04-0.042% v/v, and less than 1% v/v. These atmospheric concentrations of CO2 are at least one order of magnitude lower than the concentration of CO2 in point-source emissions, such as flue gases, where point-source emissions can have concentrations of CO2 ranging from 5-15% v/v depending on the source of emissions. In example implementations, the gas-liquid contactor 100 is operated to capture the dilute CO2 present in ambient air by ingesting the ambient air as a flow of CCE-laden air 101, and by treating the CCE-laden air 101 so as to transfer CO2 present therein to a CO2 capture solution 114 (e.g., a CO2 sorbent) via absorption. Some or all of the CO2 in the CCE-laden air 101 is removed, and the treated CCh-laden air 101 is then discharged by the gas-liquid contactor 100 as a flow of CCh-lean gas 105 (or, CO2-IOW air). In operating to treat atmospheric air in this manner, the gas-liquid contactor 100 can sometimes be referred to herein as an “air contactor” because it facilitates absorption of CO2 from the atmospheric air into the CO2 capture solution 114. In contrast to water cooling towers which function primarily to transfer heat between water and atmospheric air, the gas-liquid contactor 100 functions primarily to achieve mass transfer of CO2 from the atmospheric air to the CO2 capture solution 114. In operating in this manner, the gas-liquid contactor 100 can be used as part of a direct air capture (DAC) system 1200, described in greater detail below in reference to FIG. 15.

[00113] In example implementations, and referring to FIG. 1, the CO2 capture solution 114 is a caustic solution. In example implementations, the CO2 capture solution 114 has a pH of 10 or higher. In example implementations, the CO2 capture solution 114 has a pH of approximately 14. Non-limiting examples of the CO2 capture solution 114 include aqueous alkaline solutions (e.g., KOH, NaOH, or a combination thereof), aqueous amines, aqueous amino acid salt solutions, non-aqueous solutions of amines, non-aqueous organic liquids/solutions (e.g., dimethyl sulfoxide or DMSO), aqueous carbonate and/or bicarbonate solutions, phenoxides/phenoxide salts, ionic liquids, non-aqueous solvents, diamines with an aminocyclohexyl group (e.g., IPDA), or a combination thereof. In some cases, the CO2 capture solution 114 can include promoters and/or additives that increase the rate of CO2 uptake. Nonlimiting examples of promoters include carbonic anhydrase, amines (primary, secondary, tertiary), and boric acid. Non-limiting examples of additives include chlorides, sulfates, acetates, phosphates, surfactants, oxides and metal oxides. For example, a surfactant can be added to the CO2 capture solution 114 to lower the surface tension of the CO2 capture solution 114 to improve the ability of the CO2 capture solution 114 to wet the material of the packing. Non-limiting examples of rate-enhancing additives include carbonic anhydrase, piperazine, monoethanolamine (MEA), diethanolamine (DEA), zinc triazacycles, zinc tetraazacycles, copper glycinates, hydroxopentaaminecobalt perchlorate, formaldehyde hydrate, saccharose, fructose, glucose, phenols, phenolates, glycerin, arsenite, hypochlorite, hypobromite, or other oxyanionic species.

[00114] In example implementations, at a given reference temperature, the density of the CO2 capture solution 114 is greater than the density of water at the same reference temperature. At comparable reference temperatures, in example implementations, the density of the CO2 capture solution 114 is at least 10% greater than the density of water. In example implementations, at comparable reference temperatures, the density of the CO2 capture solution 114 is approximately 10% greater than the density of water. The density and the viscosity of the CO2 capture solution 114 can vary depending on the composition of the CO2 capture solution 114 and the temperature. For example, at temperatures of 0°C to 20°C, the CO2 capture solution 114 or a CCh-laden capture solution 111 can comprise 1 M KOH and 0.5 M K2CO3 and can have a density ranging from 1115 kg/m³ - 1119 kg/m³ and a viscosity ranging from 1.3 mPa-s - 2.3 mPa-s. In another example, at temperatures of 20°C to 0°C, the CO2 capture solution 114 or the CO2-laden capture solution 111 can comprise 2 M KOH and 1 M K2CO3, and can have a density ranging from 1260 kg/m³ - 1266 kg/m³ and a viscosity ranging from 1.8 mPa-s - 3.1 mPa-s. In comparison, water has a density of 998 kg/m³ and viscosity of 1 mPa-s at 20°C.

[00115] In example implementations, and referring to FIG. 1, CO2 from the CO2-laden air 101 is captured by contacting the CO2-laden air 101 with the CO2 capture solution 114 in the gas-liquid contactor 100. Reacting the CO2 from the CO2-laden air 101 with an alkaline CO₂ capture solution 114 (for example) can form a CCh-laden capture solution 111. In some embodiments, the CO₂ capture solution 114 comprises an alkali hydroxide, and CO2 is absorbed by reacting with the alkali hydroxide to form a carbonate-rich capture solution (e.g., K2CO3, Na₂CO3, or a combination thereof). The CCh-laden capture solution 111 can include the carbonate-rich capture solution and is thus sometimes referred to herein as the “carbonate- rich capture solution 111.” The CCh-laden capture solution 111 can be processed to recover the captured CO2 for downstream use and to regenerate the alkali hydroxide for use in the CO2 capture solution 114. In example implementations, recovered CO2 can be delivered downhole and sequestered in a geological formation, subsurface reservoir, carbon sink, or the like. In example implementations, the recovered CO2 can be used for enhanced oil recovery by injecting the recovered CO2 into one or more wellbores to enhance production of hydrocarbons from a reservoir. In example implementations, recovered CO2 can be fed to a downstream fuel synthesis system, which can include a syngas generation reactor.

[00116] The CCh-laden capture solution 111 can also include other components in smaller amounts, such as hydroxide ions, alkali metal hydroxide (e.g., KOH, NaOH), water, and impurities. For example, the carbonate-rich capture solution 111 can comprise between 0.4 M to 6 M K2CO3 and between 1 M to 10 M KOH. In another implementation, the carbonate-rich capture solution 111 can comprise an aqueous Na2CO3-NaOH mixture. In example implementations, the carbonate-rich capture solution 111 can comprise a mixture of K2CO3 and Na₂CO₃.

[00117] The capture kinetics of capturing CO2 from the CO2-laden air 101 to form carbonate can be improved by the introduction of an additive such as a promoter species in the CO2 capture solution 114. Non-limiting examples of promoters for boosting CO2 capture with carbonate include carbonic anhydrase, amines (primary, secondary, tertiary), zwitterionic amino acids, and boric acid. The resulting carbonate-rich capture solution 111 produced by the gas-liquid contactor 100 includes carbonates and bicarbonates and includes the promoter as well. An example composition of such a carbonate-rich capture solution 111 can include K2CO3/KHCO3 and a promoter. The carbonate-rich capture solution 111 resulting from such a CO2 capture solution 114 can have a pH in the range of 11-13 and can have little residual hydroxide from the CO2 capture solution 114. In some cases, additives that are not considered promoters can be used to improve the uptake of CO2 in the CO2 capture solution 114.

[00118] Referring to FIG. 1, the gas-liquid contactor 100 includes a housing 102. The housing 102 defines part of the corpus of the gas-liquid contactor 100 and provides structure thereto. The housing 102 includes exterior structure or walls that partially enclose any combination of interconnected structural members 115. The structural members 115 provide structural support and stability to the gas-liquid contactor 100 and provide a body for supporting components of the gas-liquid contactor 100 within the housing 102. The structural members 115 can include, but are not limited to, walls, panels, beams, frames, etc. The housing 102 can include other components as well, such as cladding, panels, etc. which help to close off parts of the housing 102 and define the enclosure of the housing 102. The housing 102 at least partially encloses and defines an interior 113 of the housing 102. The interior 113 of the housing 102 is an inner volume or inner space in which components of the gas-liquid contactor 100 are positioned. The housing 102 also includes openings 103 that allow for movement of gases into and out of the gas-liquid contactor 100. For example, and referring to FIG. 1, the housing 102 has one or more inlet(s) 1031. In the implementation of FIG. 1, the one or more inlet(s) 1031 are formed by the openings 103, such that the inlet(s) 1031 can be referred to herein as one or more inlet opening(s) 1031 through which the CCh-laden air 101 enters the interior 113 of the housing 102. The housing 102 has one or more outlet(s) 1030. In the implementation of FIG. 1, the one or more outlet(s) 1030 are formed by the openings 103, such that the outlet(s) 1030 can be referred to herein as one or more outlet opening(s) 1030 through which the CO2-lean gas 105 exits the interior 113 of the housing 102. In the example implementation of the gas-liquid contactor 100 of FIG. 1, the housing 102 defines two inlets 1031 and one outlet 1030. The outlet 1030 can be defined by a component of the gas-liquid contactor 100. For example, in the implementation of the gas-liquid contactor 100 of FIG. 1, the gas-liquid contactor 100 has a fan stack 107 with an upright orientation. The fan stack 107 extends upwardly from the housing 102 and helps to discharge the CCh-lean gas 105. The outlet 1030 is positioned along the fan stack 107. In such an implementation, the CO2-laden air 101 enters the interior 113 of the housing 102 along a substantially horizontal direction through one or both of the inlets 1031, and the CO2-lean gas 105 exits the interior 113 along a substantially vertical direction through the outlet 1030. The outlet 1030 is located at the upper extremity of the fan stack 107. In implementations of the gas-liquid contactor 100 without a fan stack 107, the outlet 1030 can be located elsewhere. Other configurations for the inlets 1031 and outlets 1030 of the housing 102 are possible.

[00119] The housing 102 at least partially encloses and protects components of the gasliquid contactor 100 positioned in the interior 113 of the housing 102. One example of such a component is a packing section 106, which is protected from the surrounding atmosphere by the housing 102. As can be seen in FIG. 1, one or more packing sections 106, which are sometimes referred to herein collectively as “fill 106” or “packing 106,” are located within the interior 113 in a position adjacent to the one or more inlets 1031. In this position, the one or more packing sections 106 receive the CCh-laden air 101 which enters the interior 113 via the one or more inlets 1031. The one or more packing sections 106 function to increase transfer of CO2 present in the CCh-laden air 101 to a flow of the capture solution 114, in that the one or more packing sections 106 provide a large surface area for the capture solution 114 to disperse on, thereby increasing the reactive area between the CCh-laden air 101 and the capture solution 114. The capture solution 114 transforms the CCh-laden air 101 into the CCh-lean gas 105 which is discharged from the one or more outlet(s) 1030 of the gas-liquid contactor 100. The packing sections 106 receives the CO2 capture solution 114 and facilitates absorption of the CO2 present in the CO2-laden air 101 into the CO2 capture solution 114 on the packing sections 106, as described in greater detail below.

[00120] Referring to FIG. 1, one possible arrangement of the packing sections 106 includes two or more packing sections 106A, 106B. Each packing section 106A, 106B is positioned adjacent to and downstream of one of the inlets 1031. The packing sections 106A, 106B are spaced apart from each other within the housing 102. The direction along which the packing sections 106A, 106B are spaced apart is parallel to the direction along which the CCh- laden air 101 flows through the packing sections 106 A, 106B. The space or volume defined between the packing sections 106A, 106B and/or one or more structural members of the housing 102 is a plenum 108. The plenum 108 is flanked by the packing sections 106A, 106B. The plenum 108 is a void or space within the housing 102 into which gases flow downstream of the packing sections 106 A, 106B (e.g., the CCh-lean gas 105), and from which the CCh-lean gas 105 flows out of the housing 102 through the outlet 1030. The plenum 108 is part of the interior 113 of the housing 102. The volume of the plenum 108 is less than a volume of the interior 113. In example implementations, the volume of the interior 113 of the housing 102 is approximately equal to the combined volume of the packing sections 106A, 106B and the plenum 108. Referring to FIG. 1, the packing sections 106A, 106B are positioned along the same level, or are positioned along the same horizontal lower plane, as the plenum 108. Referring to FIG. 1, the plenum 108 can include an upper plenum portion 108U that is an uppermost portion of the plenum 108, and a lower plenum portion 108L that is a lowermost portion of the plenum 108. A total height of the plenum 108 is defined as the height of the upper plenum portion 108U plus the height of the lower plenum portion 108L. Part of the upper plenum portion 108U is defined by housing plenum walls 102W of the housing 102, and a remainder of the upper plenum portion 108U is defined by the portion of the fan stack 107 positioned beneath the fan 212. The housing plenum walls 102W extend upwardly from a 1 remainder of the housing 102. In some embodiments, and referring to FIG. 1, the housing plenum walls 102W are the uppermost portion of the housing 102. The height of the upper plenum portion 108U includes a lower height portion defined by the housing plenum walls 102W, and an upper height portion defined by the portion of the fan stack 107 positioned beneath the fan 212. In example implementations, the lower height portion defined by the housing plenum walls 102W is two thirds of the height of the upper plenum portion 108U, and the upper height portion defined by the portion of the fan stack 107 positioned beneath the fan 212 is one third of the height of the upper plenum portion 108U. This configuration of the upper plenum portion 108U can reduce reingestion of part of the CCh-lean gas 105 at the inlet 1031. Referring to FIG. 1, part of the upper plenum portion 108U, and thus part of the plenum 108, extends into the fan stack 107 or cowling. After the C Ch-laden air 101 flows through the packing sections 106A, 106B, the CCh-lean gas 105 flows through the plenum 108 before being discharged to the ambient environment. In other implementations of the gas-liquid contactor 100, the plenum is absent. The gas-liquid contactor 100 can include one or more portions of drift eliminators to remove or reduce CO2 capture solution 114 that can be entrained in the CCh-lean gas 105 flowing through the plenum 108.

[00121] In the example implementation of the gas-liquid contactor 100 of FIG. 1, the CC>2-laden air 101 enters the interior 113 of the housing 102 along a substantially horizontal direction through both of the inlets 1031. The CCh-laden air 101 then flows through the packing sections 106A, 106B along a substantially horizontal direction, where the CO2 present in the CCh-laden air 101 contacts the CO2 capture solution 114 present on the packing sections 106 A, 106B and/or flowing in a substantially downward direction over the packing sections 106A, 106B. The exposed surface of the liquid film on the packing sections 106A, 106B is a gasliquid interface between the CCh-laden air 101 and the CO2 capture solution 114. CO2 from the CCh-laden air 101 is absorbed into the liquid film to form the CCh-laden capture solution 111 and the CCh-lean gas 105. The CCh-laden capture solution 111 flows downwardly off the packing sections 106 A, 106B in a mixed solution with unreacted CO2 capture solution 114 and is collected. The CCh-laden air 101 treated by the packing sections 106A, 106B exits the packing sections 106 A, 106B as the CCh-lean gas 105. The CCh-lean gas 105 from both packing sections 106 A, 106B converges in the plenum 108, and then flows in a vertically upward direction out of the plenum 108 through the outlet 1030. The gas-liquid contactor 100 of FIG. 1 can be considered a dual-cell (because of the two packing sections 106 A, 106B), cross-flow air contactor. Other configurations of a gas-liquid contactor are possible, as described in greater detail below. [00122] Each packing section 106 defines a packing depth 106D, which represents the distance traversed by the CCL-laden air 101 as it flows through the packing section 106. The packing depth 106D can be in the range of 2-10 meters. Each packing section 106 also defines a packing liquid travel dimension 106L (sometimes referred to herein as the “packing LTD 106L”), which represents the distance traversed by the capture solution 114 as it flows through the packing section 106. In the gas-liquid contactor 100 of FIG. 1, the packing depth 106D is transverse to the packing LTD 106L. In the gas-liquid contactor 100 of FIG. 1, the packing depth 106D is defined along a substantially horizontal direction, and the packing LTD 106L is a vertical dimension. In example implementations, the packing LTD 106L (, e.g., the height of each packing section 106) is greater than 2 m. In example implementations, the packing LTD 106L is greater than 5 m. In example implementations, the packing LTD 106L is between 2 m and 20 m. In example implementations, the packing depth 106D is greater than 3 m. In example implementations, the packing depth 106D is greater than 5 m. In example implementations, the packing depth 106D is between 3 m and 10 m. In other configurations of the gas-liquid contactor 100, the packing depth 106D and the packing LTD 106L can be defined differently, as described in greater detail below.

[00123] Referring to FIG. 1, each packing section 106 includes one or more structured packings 116. In the implementation of the packing sections 106 of FIG. 1, each packing section 106 includes multiple structured packings 116. Within one of the packing sections 106, each structured packing 116 is arranged adjacent to another structured packing 116. The structured packings 116 of each packing section 106 can be arranged adjacent to each other in the direction of one or more of the packing depth 106D, the packing LTD 106L, and a direction perpendicular to both of the packing depth 106D and the packing LTD 106L. Within one of the packing sections 106, in example implementations one structured packing 116 is attached to another structured packing 116. Within one of the packing sections 106, in example implementations the structured packings 116 of each packing section 106 are arranged next to one another with minimal separation or gaps along one or more of the packing depth 106D, the packing LTD 106L, and a direction perpendicular to both of the packing depth 10D and the packing LTD 106L.

[00124] Referring to FIG. 1 , some of the structured packings 116 of each packing section 106 are mounted to one or both of 1) a structural member 115 of the housing 102, and 2) at least one other structured packing 116. This support of the structured packings 116 reinforces their arrangement within each packing section 106, helps to rigidify each packing section 106, and can also help each structured packing 116 resist or support loads acting upon it during operation of the gas-liquid contactor 100. For example, in mounting the structured packings 116 as described above, the structured packings 116 become constrained which can result in an increase in the overall strength (e.g., crush strength) of each structured packing 116 and of each packing section 106, compared to a packing structure that is unconstrained.

[00125] The structured packings 116 can be arranged to form packing sections 106 of any desired shape or configuration. For example, and referring to FIG. 1, the structured packings 116 are arranged such that each packing section 106 A, 106B includes at least one arrangement 118 of the structured packings 116. In FIG. 1, each packing section 106A, 106B includes two arrangements 118 of the structured packing 116 - an upper arrangement 118U and a lower arrangement 118L. The structured packings 116 of each arrangement 118 can be arranged adjacent to each other in the direction of one or more of the packing depth 106D, the packing LTD 106L, and the direction perpendicular to both of the packing depth 106D and the packing LTD 106L. All the structured packings 116 of each upper arrangement 118U are positioned above all the structured packings 116 of each lower arrangement 118L. Each arrangement 118 can be considered a “slab” of packing. Other configurations of each arrangement 118, and of the positioning of the arrangements 118 of each packing section 106, are possible. The packing sections 106 A, 106B of FIG. 1 are thus vertically sectioned, and include one or more arrangements 118 of structured packings 116 positioned one above another.

[00126] In the example implementation of the packing sections 106 of FIG. 1, each packing section 106A, 106B has a respective packing section height that is substantially equal to a height of the inlets 1031. Providing the packing sections 106 with substantially the same height as the height of the inlet 1031 can help to prevent or reduce the ability of the CCh-laden air 101 to bypass the packing sections 106 (e.g., flow around the packing sections 106), thereby helping to ensure that the greatest possible volume of CCh-laden air 101 is treated by the packing sections 106. By “substantially equal” or “substantially the same,” it is understood that the heights are approximately equal in value, with any differences being minimal compared to the overall height dimension, where said differences can result from manufacturing tolerances, packing installation requirements, and/or adjustments in dimensions to allow for seals, baffles or other features. Other configurations for the packing sections 106 are possible. For example, in another implementation, the heights of the packing sections 106 A, 106B are less than the height of the inlet 1031, and any gaps between the packing sections 106A, 106B and the housing 102 are sealed using suitable techniques. [00127] Referring to FIG. 1, the gas-liquid contactor 100 has, includes components of, or is functionally linked to, a liquid distribution system 120. The liquid distribution system 120 operates to move, collect and distribute the CO2 capture solution 114 and/or the CCh-laden capture solution 111. At least some of the features of the liquid distribution system 120 are supported by the housing 102. In the example implementation of FIG. 1, the support provided by the housing 102 includes structural support, in that components of the liquid distribution system 120 are structurally supported by the housing 102, such as by the structural members 115, so that loads generated by these components are supported by the housing 102. Some or all of the features of the liquid distribution system 120 can be part of the gas-liquid contactor 100, or part of a DAC system (such as DAC system 1200 of FIG. 15).

[00128] Referring to FIG. 1, the liquid distribution system 120 includes one or more liquid collection devices 109. Each liquid collection device 109 is configured to receive one or both of the CO2 capture solution 114 and the CCh-laden capture solution 111 and to hold a volume thereof temporarily or for a longer duration, thereby serving as a source of the CO2 capture solution 114 and/or of the CCh-laden capture solution 111. Each liquid collection device 109 can have any configuration or be made of any material suitable to achieve the function ascribed to it in the present description. For example, one or more of the liquid collection devices 109 can be open-topped, or partially or fully covered. In FIG. 1, one or more of the liquid collection devices 109 include, or are in the form of, basins. Other configurations of the liquid collection device 109 are possible, such as a reservoir, a bed, a sheet, a culvert, a container, a receptacle, a network of pressurized pipes with openings or spray nozzles, or any other device capable of retaining liquid.

[00129] The liquid collection devices 109 of the liquid distribution system 120 include one or more top basins 104 and one or more bottom basins 110. The top basins 104 are supported by the housing 102. In example implementations, the top basins 104 are formed from portions of the housing 102. The top basins 104 are configured to at least partially enclose or store the CO2 capture solution 114. Referring to FIG. 1, the top basins 104 are each positioned at least partially above the packing sections 106. Referring to FIG. 1, the top basins 104 are positioned above the inlets 1031. Referring to FIG. 1, the top basins 104 are positioned beneath the upper plenum portion 108U. Part of the plenum 108 (e.g., the upper plenum portion 108U) thus extends beyond or above the top basins 104. When stored (at least transiently) within the top basins 104, the CO2 capture solution 114 is positioned to be circulated (e.g., through pumping, gravity flow or both) downwards, through the packing sections 106 and ultimately into the bottom basin 110. As the CO2 capture solution 114 is circulated through the packing sections 106, the CCh-laden air 101 is circulated through the packing sections 106 to contact the CO2 capture solution 114, through the plenum 108, and to an ambient environment as the CCh-lean gas 105. A process stream is formed by contacting the CCh-laden air 101 and the liquid CO2 capture solution 114, where the process stream is or includes the CCh-laden capture solution 111 having CO2 absorbed from the CCh-laden air 101 by the CO2 capture solution 114. The top basins 104 can each have any suitable form or feature for distributing the CO2 capture solution 114 over the packing sections 106. In the example implementation of the gas-liquid contactor 100 of FIG. 1, the liquid collection devices 109 include two top basins 104. Each top basin 104 is positioned above one of the packing sections 106A, 106B to distribute the CO2 capture solution 114 to the respective packing section 106A, 106B. The top basins 104 of FIG. 1 are fluidly isolated from one another (e.g., no fluid communication between the two top basins 104). Other configurations and numbers of the top basins 104 are possible. Other configurations for the distribution of the CO2 capture solution 114 over the packing sections 106 is possible. In one such possible configuration, the one or more of the liquid collection devices 109 include, or are in the form of, a network of pressurized pipes with openings or spray nozzles which distribute the CO2 capture solution 114 over the uppermost portions of the packing sections 106.

[00130] Referring to FIG. 1, the one or more bottom basins 110 are positioned at the bottom of the gas-liquid contactor 100 opposite the top basins 104. As can be seen in FIG. 1, the bottom basin 110 is positioned below the packing sections 106. The bottom basin 110 acts as a collection tank for the process stream (e.g., the CCh-laden capture solution 111). The CO2- laden capture solution 111 including absorbed CO2, as well as unreacted CO2 capture solution 114, collects in the bottom basin 110, and can then be pumped or otherwise moved out of the bottom basin 110 for further processing. For example, at least a portion of the liquids collected in the bottom basin 110 can be processed and then pumped for redistribution over the packing sections 106 for use in CO2 capture. In another possible implementation, some or all of the liquids collected in the bottom basin 110 is pumped to the top basins 104 without being processed, for redistribution over the packing sections 106 for CO2 capture. In another possible implementation, some or all of the liquids collected in the bottom basin 110 are pumped to components of a DAC system (such as DAC system 1200 of FIG. 15) for further processing, as described in greater detail below. The bottom basin 110 can be compatible with a containment structure and prevent loss of various CO2 capture solutions 114, many of which have corrosive, caustic or high pH properties. In some aspects, the bottom basin 110 can be lined or coated with one or more materials that are resistant to caustic induced corrosion or degradation. In example implementations of the gas-liquid contactor 100, components can be kept out of the bottom basin 110 holding the CO2 capture solution 114. Additionally, the gasliquid contactor 100 can be designed to keep most or all the structural components out of the wettable area of the gas-liquid contactor 100, e.g., any portion of the gas-liquid contactor 100 that is in contact with the CO2 capture solution 114. Examples of wettable areas of the gasliquid contactor 100 includes components supporting the packing sections 106. FIG. 1 depicts a single bottom basin 110. However, other configurations and numbers of bottom basins 110 are possible.

[00131] In example implementations, the gas-liquid contactor 100 includes vertically sectioned packing sections 106 with redistribution of the CO2 capture solution 114 between the vertically-spaced apart packing. For example, and referring to FIG. 1, the liquid collection devices 109 of the liquid distribution system 120 include one or more redistribution basins 119. The one or more redistribution basins 119 are each positioned in a redistribution spacing that is defined between the upper and lower arrangements 118U, 118L of each packing section 106A, 106B. The redistribution spacing is a vertically-extending gap defined between the upper and lower arrangements 118U, 118L of each packing section 106 A, 106B. Each packing section 106A, 106B includes a redistribution basin 119, which is positioned in the redistribution spacing of that packing section 106 A, 106B. Thus, in the configuration of packing sections 106A, 106B of FIG. 1, each redistribution basin 119 divides each packing section 106A, 106B into at least a top section (e.g., the upper arrangement 118U of structured packings 116) and a bottom section (e.g., the lower arrangement 118L of structured packings 116). Each redistribution basin 119 is located vertically between the one or more top basins 104 and the bottom basin 110. During operation of the gas-liquid contactor 100, a process stream including the CCE-laden capture solution 111 including absorbed CO2 as well as unreacted CO2 capture solution 114 flows from each upper arrangement 118U of structured packings 116 and collects in each redistribution basin 119. When stored (at least transiently) within the redistribution basins 119, the process stream is positioned to be redistributed (e.g., through pumping, gravity flow or both) downwards, through the remaining structured packings 116 of the lower arrangement 118L and eventually into the bottom basin 110. In example implementations, the process stream is pumped into the redistribution basins 119 from the bottom basin 110. The redistribution basins 119 can each have any suitable form or feature for redistributing the process stream over the structured packings 116 of the of the lower arrangement 118L. Nonlimiting examples of features of the redistribution basins 119 include basin walls, redistribution apertures, and redistribution nozzles. Thus, in the gas-liquid contactor 100, there can be a collector/distributor system between vertical sections of packing that collects fluid flowing from above and redistributes it evenly to the packing below. The description and one, some, or all of the advantages, and functions of features of the top basins 104 and of the bottom basin 110 apply mutatis mutandis to the redistribution basins 119.

[00132] In alternate implementations of redistribution of the CO2 capture solution 114 between the vertically-spaced apart packing, the packing sections 106 themselves include redistribution features. The redistribution features can be part of redistribution packing that is different from the structured packings 116. The redistribution packing can have a vertical extent and be positioned between arrangements 118U, 118L of structured packings 116, for example mid-way up the packing LTD 106L. Alternatively, the redistribution packing can include multiple redistribution packing portions alternating with arrangements 118U, 118L of structured packings 116. The redistribution features promote redistribution of the CO2 capture solution 114 to lower portions of the packing sections 106. In alternate implementations of the gas-liquid contactor 100, the gas-liquid contactor 100 does not include vertically-sectioned packing or redistribution.

[00133] Referring to FIG. 1, the CO2 capture solution 114 flows over the packing sections 106 in a direction that is substantially perpendicular or transverse to the average direction along which the CCh-laden air 101 circulates through the packing sections 106, also known as a “cross flow” configuration. In another possible implementation, the CO2 capture solution 114 flows over the packing sections 106 in a direction that is opposite to the average direction along which the CCh-laden air 101 circulates through the packing sections 106, also known as a “counter flow” configuration. In another possible implementation, the CO2 capture solution 114 flows over the packing sections 106 in a direction that is parallel with the direction along which the CCh-laden air 101 circulates through the packing sections 106, also known as a “co-current flow” configuration. In another possible configuration, the CO2 capture solution 114 flows over the packing sections 106 according to a configuration that is a combination of one or more of cross flow, counter flow and co-current flow configurations.

[00134] The gas-liquid contactor 100 can include supports positioned within the packing sections 106 between the top basins 104 and bottom basin 110. For example, the packing sections 106 can include additional support, such as one or more structural members 115, for a specific portion of the packing sections 106, such as for an upper portion of the packing sections 106, so that the loads (e.g., the weight of the portion of structured packings 116 when dry plus the weight of the liquid hold up of the CO2 capture solution 114 on the portion of the structured packings 116) do not bear upon another portion of the packing sections 106 (e.g., a bottom portion of the packing sections 106). In some aspects, the packing sections 106 can not include the support. In some aspects, at least one structural support can be positioned between the structured packings 116 of the packing sections 106.

[00135] The liquid distribution system 120 can include any suitable componentry, such as piping, weir(s), pump(s), valve(s), manifold(s), etc., fluidly coupled in any suitable arrangement, to achieve the functionality ascribed to the liquid distribution system 120 herein. One non-limiting example of such componentry is one or more pump(s) 122, an example of which is shown in FIG. 1. The pumps 122 function to move liquids under pressure, such as the CO2 capture solution 114 and/or the CO2-laden capture solution 111, from their source to where they are used. Some non-limiting examples of possible functions of the pumps 122 include moving the CO2 capture solution 114 to the top basins 104, moving the process streams from the bottom basin 110 to the redistribution basins 119, moving the CO2 capture solution 114 and/or the CCh-laden capture solution 111 from the bottom basin 110 to the top basins 104 for redistribution over the packing sections 106, moving the CO2 capture solution 114 and/or the CCh-laden capture solution 111 from the bottom basin 110 to components of the DAC system 1200 for further processing, and any combination of the preceding flows. The pumps 122 can thus be used to move liquid to, from and within the gas-liquid contactor 100.

[00136] A control system (e.g., control system 999 shown in FIG. 1) can be used to control the flow of fluid by the pumps 122 of the liquid distribution system 120. For example, a control system can be used to control the pumps 122 in order to pump the CO2 capture solution 114 from the bottom basin 110 to the top basins 104. The pumps 122 can also be controlled such that a constant velocity of flow is provided to the liquid distribution system 120 regardless of changes of liquid flow throughout the gas-liquid contactor 100.

[00137] The pumps 122 can help to distribute the CO2 capture solution 114 over the packing sections 106 at relatively low liquid flow rates, which can help to reduce costs associated with pumping or moving the CO2 capture solution 114. Further, low liquid flow rates of the CO2 capture solution 114 over the packing sections 106 can result in a lower pressure drop of the CCh-laden air 101 as it flows through the packing sections 106, which reduces the energy requirements of the device used for moving the CCh-laden air 101 across the packing sections 106 (e.g., a fan 212 described below). The pumps 122 can be configured to generate intermittent or pulsed flow of the CO2 capture solution 114 over the packing sections 106, which can allow for intermittent wetting of the packing sections 106 using relatively low liquid flows. The CO2 capture solution 114 sprayed, flowed, or otherwise distributed over the packing sections 106 is collected in the bottom basin 110 and can then be moved by the pumps 122 back to the top basin 104, or sent downstream for processing.

[00138] In example implementations, and referring to FIG. 1, the one or more pump(s) 122 of the liquid distribution system are operable to flow the CO2 capture solution 114 over each packing section 106 at a liquid loading rate ranging from 0.5 L/m²s to 10 L/m²s. In example implementations, the liquid loading rate is between 2 L/m²s and 6 L/m²s. The units L/m²s of the liquid loading rate refer to a given volume of the CO2 capture solution 114 covering a given area of the packing section 106, each second. The given area of the packing section 106 can refer to a plane area of a top of the packing section 106, such as the area of the packing section 106 underneath the top basin 104 (e.g., looking down on the top part of the packing section 106 from the top basin 104). When determined using the plane area, a liquid loading rate of 2 L/m²s means that the pump(s) 122 is configured to flow the CO2 capture solution 114 over each packing section 106 such that every second each square meter of the plane area of the packing section 106 receives 2 L of the CO2 capture solution 114. The given area of the liquid loading rate can not refer to the area of a surface of the structured packing 116. The liquid loading rate can refer to, or be reflective of, an initial flow condition where the CO2 capture solution 114 is applied to the top of the packing section 106. The liquid loading rate can not reflect subsequent flow conditions present lower down the packing section 106.

[00139] The liquid process streams in the gas-liquid contactor 100, as well as process streams within any downstream processes with which the gas-liquid contactor 100 is fluidly coupled, can be flowed using one or more flow control systems (e.g., control system 999). A flow control system can include one or more flow pumps (including or in addition to the pumps 122), fans, blowers, or solids conveyors to move the process streams, one or more flow pipes through which the process streams are flowed and one or more valves to regulate the flow of streams through the pipes. Each of the configurations described herein can include at least one variable frequency drive (VFD) coupled to a respective pump that is capable of controlling at least one liquid flow rate. In example implementations, liquid flow rates are controlled by at least one flow control valve.

[00140] In some embodiments, a flow control system can be operated manually. For example, an operator can set a flow rate for each pump or transfer device and set valve open or closed positions to regulate the flow of the process streams through the pipes in the flow control system. Once the operator has set the flow rates and the valve open or closed positions for all flow control systems distributed across the system, the flow control system can flow the streams under constant flow conditions, for example, constant volumetric rate or other flow conditions. To change the flow conditions, the operator can manually operate the flow control system, for example, by changing the pump flow rate or the valve open or closed position.

[00141] In some embodiments, a flow control system can be operated automatically. For example, the flow control system can be connected to a computer or control system (e.g., control system 999) to operate the flow control system. The control system can include a computer-readable medium storing instructions (such as flow control instructions and other instructions) executable by one or more processors to perform operations (such as flow control operations). An operator can set the flow rates and the valve open or closed positions for all flow control systems distributed across the facility using the control system. In such embodiments, the operator can manually change the flow conditions by providing inputs through the control system. Also, in such embodiments, the control system can automatically (that is, without manual intervention) control one or more of the flow control systems, for example, using feedback systems connected to the control system. For example, a sensor (such as a pressure sensor, temperature sensor or other sensor) can be connected to a pipe through which a process stream flows. The sensor can monitor and provide a flow condition (such as a pressure, temperature, or other flow condition) of the process stream to the control system. In response to the flow condition exceeding a threshold (such as a threshold pressure value, a threshold temperature value, or other threshold value), the control system can automatically perform operations. For example, if the pressure or temperature in the pipe exceeds the threshold pressure value or the threshold temperature value, respectively, the control system can provide a signal to the pump to decrease a flow rate, a signal to open a valve to relieve the pressure, a signal to shut down process stream flow, or other signals.

[00142] The gas-liquid contactor 100 has a gas-circulating device which functions to move or circulate gas flows into and out of the gas-liquid contactor 100. In the implementation of the gas-liquid contactor of FIG. 1, the gas-circulating device of the gas-liquid contactor 100 is a fan 212. The fan 212 functions to circulate gases like ambient air, such that the CCh-laden air 101 is caused by the fan 212 to flow into the gas-liquid contactor 100, and such that the CCh-lean gas 105 is caused by the fan 212 to be discharged from the gas-liquid contactor 100. The fan 212 thus functions to circulate the CCh-laden air 101 and the CCh-lean gas 105 in the manner described herein. Referring to FIG. 1, the fan 212 is rotatable about a fan axis defined by a fan shaft. In the implementation of the fan 212 depicted in FIG. 1, the fan axis has an upright or vertical orientation. Other orientations for the shaft and for the fan axis are possible, as described in greater detail below. Referring to FIG. 1, the fan 212 is positioned upstream of the end of the fan stack 107 that defines the outlet 1030 and functions to induce a flow of the CCh-lean gas 105 through the outlet 1030. In another possible configuration, the fan 212 is positioned elsewhere between the vertically-opposite ends of the fan stack 107 and upstream of the outlet 1030, such that the fan 212 flows the CO2-lean gas 105 through the outlet 1030. Referring to FIG. 1, the fan 212 is positioned downstream of, and above, the upper plenum portion 108U. Rotation of the fan 212 about the fan axis causes gases to circulate into the inlets 1031 and through the gas-liquid contactor 100. For example, in the implementation of the gasliquid contactor of FIG. 1, rotation of the fan 212 causes the CCh-laden air 101 to be drawn into the gas-liquid contactor 100 and causes the CCh-lean gas 105 to be discharged from the gas-liquid contactor 100. The fan 212 can cause the CCh-laden air 101 to enter the packing sections 106 at airspeeds below 5 m/s. The fan 212 can cause the CCh-laden air 101 to enter the packing sections 106 at airspeeds between 0.1 m/s and 5 m/s.

[00143] Other configurations of the gas-liquid contactor 100 are possible, some of which are now described in greater detail.

[00144] In one such possible configuration, and referring to FIG. 2A, the gas-liquid contactor 100a can have an upright body and an air inlet 2103 along a bottom portion through which the CCh-laden air 101 is admitted into the gas-liquid contactor 100a. The fan 2112 rotates to draw the CCh-laden air 101 through the inlet 2103 in an upward direction to contact the packing section 2106. In the configuration of FIG. 2A, the gas-liquid contactor 100a has only one packing section 2106 and can therefore be referred to as a “single cell” gas-liquid contactor 100a. The CO2 capture solution 114 circulates downwards by, for example, gravity flow, uniform or laminar flow, etc., within the packing 2106 and eventually flows into one or more bottom basins 2110. As the CO2 capture solution 114 circulates through and over the packing 2106, the CCh-laden air 101 is flowing (e.g., by action of the fan 2112) upwardly through the packing 2106 to contact the CO2 capture solution 114. Thus, the flow of the CO2 capture solution 114 through the packing 2106 in FIG. 2A is counter-current (or counterflow) to the flow of the CCh-laden air 101 through the packing 2106. The packing liquid travel dimension along which the CO2 capture solution 114 flows through the packing 2106 is defined along the vertical direction and is the same as the packing depth along which the CCh-laden air 101 flows upwardly through the packing 2106. A portion of the CO2 within the CCh-laden air 101 is transferred to (e.g., absorbed by) the CO2 capture solution 114, and the fan 2112 moves the CO2 lean gas 105 out of the gas-liquid contactor 100a to an ambient environment. The CO2 rich solution flows into the at least one bottom basin 2110.

[00145] Referring to FIG. 2B, another possible configuration of a gas-liquid contactor 100b has an upright body and an inlet 3103 along an upright side portion through which the CCh-laden air 101 is admitted into the gas-liquid contactor 100b. The fan 3112 rotates about a horizontal fan axis to draw the CCh-laden air 101 through the inlet 3103 in a substantially horizontal direction to contact the packing section 3106. In another possible implementation of the gas-liquid contactor 100b, the fan 3112 is upstream of the packing section 3106 relative to the flow direction of the CCh-laden air 101. In such an implementation, the gas-liquid contactor 100b employs forced draft in which the fan 3112 rotates about a horizontal fan axis to “push” the CCh-laden air 101 through the inlet 3103 in a substantially horizontal direction to contact the packing section 3106. In the configuration of FIG. 2B, the gas-liquid contactor 100b has only one section of packing 3106 and can therefore be referred to as a “single cell” gas-liquid contactor 100b. The CO2 capture solution 114 circulates downwards by, for example, gravity flow, uniform or laminar flow, etc., within the packing 3106 and eventually flows into one or more bottom basins 3110. As the CO2 capture solution 114 circulates through the packing 3106, the CCh-laden air 101 is flowing (e.g., by action of the fan 3112) substantially horizontally through the packing 3106 to thereby contact the CO2 capture solution 114. Thus, the flow of CO2 capture solution 114 through the packing 3106 in FIG. 2B is substantially perpendicular to the flow of the CCh-laden air 101 through the packing 3106. Such a configuration of the flows can be referred to as a “cross flow” configuration. The packing liquid travel dimension along which the CO2 capture solution 114 flows through the packing 2106 is defined along the vertical direction and is perpendicular to the packing depth along which the CCh-laden air 101 flows horizontally through the packing 2106. A portion of the CO2 within the CCh-laden air 101 is transferred to the CO2 capture solution 114, and the fan 3112 moves the CCh-lean gas 105 out of the gas-liquid contactor 100b to an ambient environment. The CO2 rich solution flows into the at least one bottom basin 3110.

[00146] The description and one, some, or all of the advantages, and functions of features of the gas-liquid contactor 100 of FIG. 1 that are shown in FIGS. 2A and 2B apply mutatis mutandis to the features of FIGS. 2 A and 2B.

[00147] Referring to FIG. 1, each structured packing 116 includes, or is composed of, multiple packing sheets 130 attached together to form a three-dimensional structured packing 116. The packing sheets 130 of each structured packing 116 can be made of any suitable material, or have any suitable configuration, to achieve the function ascribed to the packing sections 106 herein. Some or all of the packing sheets 130 can be made from PVC, which is relatively light, moldable, affordable, and resists degradation caused by many chemicals. The packing sheets 130 are arranged, constructed, treated or otherwise configured to promote spreading of the liquid CO2 capture solution 114 into a thin film on the surfaces of the packing sheets 130, which can enable maximum exposure of the liquid CO2 capture solution 114 to the CO2 present in the CCh-laden air 101. For example, the liquid-gas interface surface of one or more of the packing sheets 130 can be treated with a coating, have shapes or formations, and/or be made of a material that vary the surface energy (e.g., increase the surface energy) of portions of the packing sheet 130 and/or lower the contact angle of the liquid CO2 capture solution 114. For example, the hydrophilicity of the liquid-gas interface surface of one or more of the packing sheets 130 can be increased by applying a coating to increase the surface free energy. Coatings can be applied to some or all of the structured packing 116 to make the structured packing 116 even more suitable for low liquid loading rates ranging from 0.5 L/m²s to 2.5 L/m²s. In this regard, reference is made to such surface treatments and modifications described in U.S. Patent Application Publication No. 2022/0176312, the entire contents of which are incorporated herein by reference. Such “film-type” packing sheets 130 are suitable for DAC systems since they have the capacity for more effective mass transfer per unit volume of fill space. For example, film-type fill offers a relatively high ratio of specific surface area to volume, the ratio defined in units of m²/m³. A high specific surface area helps to expose more CO2 to the surface of the CO2 capture solution 114, and also has cost and structural implications.

[00148] An example implementation of a packing sheet 130 of the structured packing 116 is shown in FIG. 3. The packing sheet 130 supports and directs the CO2 capture solution 114 as it flows along the packing sheet 130. The packing sheet 130 is shaped, sized, formed, and configured to assist with the transfer of CO2 from the CCh-laden air 101 to the CO2 capture solution 114. The packing sheet 130 is thus a medium intended to optimise CO2 from the flowing atmospheric air being absorbed into the flowing CO2 capture solution 114. Other fill sheets, for example, those used in water cooling tower applications, function primarily to transfer heat between water and atmospheric air, with little or no mass transfer occurring between the constituent gases of the air flow and the water being cooled. By optimizing for the mass transfer of CO2 as disclosed herein, the packing sheet 130 can be able to achieve lower pressure losses of air flowing across the packing sheet 130 and more optimal distribution of the CO2 capture solution 114, compared to if the mass transfer of CO2 was attempted with a fill sheet optimised for heat transfer. The packing sheet 130 can be referred to using other terms similar to “sheet,” such as panel, pane, plate, and layer. The packing sheet 130 in some cross-flow implementations is also shaped, sized, formed, and configured to assist with the transfer of CO2 from the CCh-laden air 101 to the CO2 capture solution 114 at low liquid loading rates (e.g., 0.5 L/m²s to 2.5 L/m²s) compared to the higher liquid loading rates (often greater than 15 L/m²s) of cross-flow water cooling tower applications. [00149] Referring to FIG. 3, the packing sheet 130 has a body 132 defining part of the corpus of the packing sheet 130 and providing structure thereto. As depicted in FIG. 4 A, the body 132 has a first side 134A and a second side 134Blocated on an opposite side of the body 132 as the first side 134A. The body 132 has a leading edge 136A and a trailing edge 136B. When the packing sheet 130 is installed in the gas-liquid contactor 100, 100A, 100B, sometimes referred to herein as the “installed configuration” of the packing sheet 130, the leading edge 136A is the edge of the body 132 which first receives the CCh-laden air 101. The trailing edge 136B is the edge of the body 132 over which the CCh-laden air 101, depleted of some of its CO2, flows after having traversed the body 132. The leading and trailing edges 136A, 136B are thus spaced apart such that they define between them an air travel depth 138D of the packing sheet 130. The air travel depth 138D (sometimes referred to herein as “the ATD 138D”) is parallel to the predominant direction along which the CCh-laden air 101 flows across the packing sheet 130 during operation of the gas-liquid contactor 100, 100 A, 100B. The ATD 138D represents the distance travelled by the CCh-laden air 101 as it flows across the body 132 from the leading edge 136A to the trailing edge 136B. The ATD 138D is a dimension that is greater than zero. In the configuration of the packing sheet 130 of FIG. 3 which is intended to be used in the cross-flow gas-liquid contactor 100 of FIG. 1, the ATD 138D is a horizontal or lateral dimension, such that the ATD 138D relates to a horizontal flow direction of the CO2- laden air 101. The body 132 has a thickness defined along a direction perpendicular to the plane defined by the body 132. The thickness of the body 132 can sometimes be referred to as its width.

[00150] Referring to FIG. 3, the body 132 has multiple interconnecting edges that connect to each other and/or to the leading and trailing edges 136A, 136B. In the packing sheet 130 of FIG. 3, the interconnecting edges include an upper edge 136U that extends between the leading and trailing edges 136A, 136B, and a lower edge 136L that also extends between the leading and trailing edges 136A, 136B. The edges 136A, 136B, 136U, 136L define or delimit the body 132, and the boundaries between the first and second sides 134A, 134B. The upper and lower edges 136A, 136B are spaced apart such that they define between them a liquid travel dimension 138L of the packing sheet 130. The liquid travel dimension 138L (sometimes referred to herein as “the LTD 138L”) is parallel to the predominant direction along which the CO2 capture solution 114 flows along the packing sheet 130 during operation of the gas-liquid contactor 100, 100A, 100B. The LTD 138L represents the distance travelled by the CO2 capture solution 114 as it flows across the body 132 from the upper edge 136U to the lower edge 136L. The LTD 138L is a dimension that is greater than zero. In the configuration of the packing sheet 130 of FIG. 3 which is intended to be used in the cross-flow gas-liquid contactor 100 of FIG. 1, the LTD 138L is a vertical dimension, such that the lower edge 136L is positioned below the upper edge 136U. In the configuration of the packing sheet 130 of FIG. 3 which is intended to be used in the cross-flow gas-liquid contactor 100 of FIG. 1, the LTD 138L represents the height of the packing sheet 130.

[00151] Referring to FIG. 3, the LTD 138L is greater than the ATD 138D. The packing sheet 130 of FIG. 3 can thus be “taller” than it is “deep” in implementations where it is installed in the cross-flow gas-liquid contactor 100 of FIG. 1. In example implementations, the ATD 138D is between 2 ft. and 24 ft. In example implementations, the ATD 138D is between 2 ft. and 5 ft. In example implementations, the ATD 138D is between 3 ft. and 5 ft. In example implementations, the LTD 138L (e.g., the height of the packing sheet 130 in example implementations) is between 2 ft. and 24 ft. In example implementations, the LTD 138L is between 4 ft. and 7 ft. In an example implementation of the packing sheet 130, the ATD 138D is between 3 ft. and 5 ft. and the LTD 138L is between 4 ft. and 7 ft. Such a relatively large packing sheet 130, along with adjacent and attached other such large packing sheets 130, provide a structured packing 116 that enables liquid film distribution on its surfaces and that offers a relatively high ratio of specific surface area to volume (defined in units of m²/m³), where a high specific surface area helps to expose more CO2 to the surface of the CO2 capture solution 114. In example implementations, the thickness of the body 132 is between one and two orders of magnitude less than one or both of the ATD 138D and the LTD 138L of the body 132.

[00152] Other configurations of the packing sheet 130 are possible. For example, in the counter-flow gas-liquid contactor 100 A of FIG. 2 A, the leading and trailing edges have a horizontal orientation, and the upper and lower edges are the same as the leading and trailing edges respectively. In the counter-flow gas-liquid contactor 100A of FIG. 2A, the ATD and the LTD can be equal and defined along the same axis. In another possible implementation, the LTD 138L is less than the ATD 138D when the packing sheet 130 is installed in the gasliquid contactor 100, 100 A, 100B.

[00153] Referring to FIG. 3, the body 132 includes a mass-transfer zone 131. In the packing sheet 130 of FIG. 3, the mass-transfer zone 131 is present or disposed on both the first side 134A and on the second side 134B. The mass-transfer zone 131 defines some of the surface area of the body 132 between the leading, trailing, upper and lower edges 136A, 136B, 136U, 136L. In the implementation of FIG. 3, the mass-transfer zone 131 defines almost all the surface area of the packing sheet 130. The mass-transfer zone 131 includes, or is defined by, multiple mass-transfer microstructures 133. The mass-transfer microstructures 133 are surface formations or features present on the body 132 which are shaped, sized, and configured to assist with the transfer of CO2 from the CCh-laden air 101 to the CO2 capture solution 114. In the implementation of FIG. 3, the mass-transfer microstructures 133 include herringbones or chevrons which allow the CO2 capture solution 114 to follow a serpentine or tortuous path, as the CO2 capture solution 114 flows along the LTD 138L. The mass-transfer microstructures 133 help to increase the “liquid hold-up” of the packing sheet 130 (e.g., the ability of the packing sheet 130 to retain the CO2 capture solution 114 for longer periods of time) and thus help to increase the duration for transfer of CO2 from the CCh-laden air 101 to the CO2 capture solution 114. The mass-transfer microstructures 133 are arranged, constructed, treated or otherwise configured to promote spreading of the liquid CO2 capture solution 114 into a thin film on the surfaces of the packing sheets 130, which can enable maximum exposure of the liquid CO2 capture solution 114 to the CO2 present in the CCh-laden air 101. The mass-transfer microstructures 133 can be arranged, constructed, treated or otherwise configured to increase the mass-transfer area (e.g., the surface area of the mass-transfer zone 131) of the body 132. For example, in implementations where the mass-transfer microstructures 133 include herringbones or chevrons, one or more of the acute angles formed by the arms of the chevrons, the chevrons’ amplitude measured parallel to the LTD 138L, and their height measured in a direction perpendicular to the plane of the body 132, can be optimised increase the masstransfer area (e.g., the surface area of the mass-transfer zone 131) of the body 132.

[00154] The term “microstructure” in mass-transfer microstructures 133 is understood in the art to designate multiple and distinct surface features that are integral to the packing sheet 130 and is contrasted in the art with the term “macrostructure” that are larger in scale than microstructures and typically affect the overall shape of the sheet. For example, a fill sheet can have larger macrostructures to affect the air flow across the fill sheet, and/or have microstructures on its surface to affect properties of liquid flow, such as the liquid contact angle. Macrostructures can include patterns such as corrugations and flutes that affect the tendency of the air to move along the sheet depending on the air velocity and the sheet’s rigidity. Microstructures are smaller-scale patterns or structures that can reduce the apparent liquid contact angle and enable film flow of capture solution. Microstructures can be present on macrostructures, but macrostructures are typically not present on microstructures. The prefix “micro” is not understood in the art to designate features on a micron scale.

[00155] Different mass-transfer microstructures 133 are possible. For example, and referring to FIGS. 13 and 14, one or more mass-transfer microstructures 833 can include a first wall portion 833A that extends toward a first apex 833B. The mass-transfer microstructures 833 of FIGS. 13 and 14 are shown in a cross-sectional plane that is normal to the leading edge 136A of the body 132. The first apex 833B is the furthest point of the mass-transfer microstructure 833 on one side 134A, 134B of the body 132. Each mass-transfer microstructure 833 has a second wall portion 833 C that extends from the first apex 833B to a second apex 833D on the other side 134B, 134A of the body 132. The second apex 833D is the furthest point of the mass-transfer microstructure 833 on the other side 134B, 134A of the body 132. In the cross-sectional plane of FIG. 13, an acute angle is formed between the first and second wall portions 833 A, 833C joined at the first apex 833B and the second apex 833D. [00156] Referring to FIG. 13, one or both of the first wall portion 833A and the second wall portion 833 C includes at least one wall feature 833E that extends outwardly from the respective wall portion 833A, 833C. The wall feature 833E can include a first wall feature 835A extending outwardly from the first wall portion 833A on the first side 134A of the body 132 and forming corresponding depression on the second side 134B. A second wall feature 835B extends outwardly from the second wall portion 833C on the second side 134B and forms a corresponding depression on the first side 134A. In example implementations, the wall feature 833E can be a compound wall feature.

[00157] In such implementations, and referring to FIG. 14, each wall feature 933E includes multiple bumps or protrusions 935 to increase the surface area of the wall feature 933E and of the mass-transfer microstructure 933. Irrespective of their shape or configuration, the wall features 833E, 933E can increase the surface tension acting on the CO2 capture solution 114 as it flows along the corresponding mass-transfer microstructure 833, 933, which can increase the liquid hold-up on the packing sheet 130 and the ability of the CO2 capture solution 114 to capture CO2 from the CCh-laden air 101. The wall features 833E, 933E can increase the specific surface area of the structured packing 116 while having a minimal impact, if any, on the pressure drop of the CCh-laden air 101 flowing through the structured packing 116. The wall features 833E, 933E can form repeating patterns of surface protrusions along the ATD 138D.

[00158] In alternate implementations, the wall features 833E, 933E can be present on only some of the mass-transfer microstructures 833. A wall feature 833E, 933E can be present along all or only some of the extent of a wall portion 833 A, 833C defined along the LTD 138L. Axes defined by each of the first wall feature 835 A and the second wall feature, 835B can be transverse to each other. In example implementations, and referring to FIGS. 13 and 14, each wall feature 833E, 933E is positioned on its wall portion 833A, 833C between the extremities (e.g., between the first apex 833B and the second apex 833D) of the mass-transfer microstructure 833, 933. The wall feature 833E, 933E can be understood as forming or being a microstructure on, or of, the mass-transfer microstructure 833, 933. The mass-transfer microstructures 833, 933 of FIGS. 13 and 14 can thus be considered examples of microstructures present on other microstructures of the mass-transfer zone 131.

[00159] Different mass-transfer microstructures 133 are possible. FIGS. 18A and 18B provide another example configuration of the mass-transfer zone 131 formed of, or including, microstructures present on other microstructures. Referring to FIG. 18 A, the mass-transfer microstructures 1833 include base microstructures 1833B and supplemental microstructures 1833S. The base microstructures 1833B, one of which is shown in dashed outline 1805 in FIG. 18 A, are arranged, in this example, in a chevron or herringbone pattern. Each base microstructure 1833B extends along a principal axis that is parallel to the LTD 138L. The cross-sectional profile of the base microstructures 1833B, when viewed in a cross-sectional plane that is normal to a plane of the body 132, is similar to the profile of the mass-transfer microstructures 133 of FIG. 4E described in greater detail below.

[00160] Referring to FIG. 18A, the supplemental microstructures 1833S, one of which is shown in dashed outline 1807 in FIG. 18A having different stippled lines than the dashed outline 1805, are present on the base microstructures 1833B. Each supplemental microstructure 1833S extends along a principal axis that is parallel to the LTD 138L. Each supplemental microstructure 1833S is arranged in a chevron or herringbone pattern, as shown by the dashed outline 1807. Referring to FIG. 18 A, multiple supplemental microstructures 1833S are present on each base microstructure 1833B.

[00161] Referring to FIG. 18B, the supplemental microstructures 1833S protrude from the base microstructures 1833B, on one of the first and second sides 134A, 134B of the body 132. In example implementations, and referring to FIG. 18B, each supplemental microstructure 1833S undulates as it extends over adjacent base microstructures 1833B. Each base microstructure 1833B includes a first wall portion 1833 A that extends toward a first apex 1833C. The first apex 1833C is the furthest point of the base microstructure 1833B on one side 134A, 134B of the body 132. Each base microstructure 1833B, in this example, includes a second wall portion 1833D that extends from the first apex 1833C to a second apex 1833E on the other side 134B, 134A of the body 132. The second apex 1833E is the furthest point of the base microstructure 1833B on the other side 134B, 134A of the body 132. In the cross- sectional plane described above, an acute angle is formed between the first and second wall portions 1833A, 1833D joined at the first apex 1833C and the second apex 1833E. [00162] Similarly to each base microstructure 1833B, each supplemental microstructure 1833S, in this example, includes first and second wall portions 1833SA, 1833SD joined at a first apex 1833SC and at a second apex 1833SE on the same side 134B, 134A of the body 132. The first wall portion 1833 SA of each supplemental microstructure 1833S protrudes from the first wall portion 1833 A of the corresponding base microstructure 1833B along a direction that is perpendicular to a plane defined by the first wall portion 1833 A. The second wall portion 1833SD of each exemplary supplemental microstructure 1833S protrudes from the second wall portion 1833D of the corresponding base microstructure 1833B along a direction that is perpendicular to a plane defined by the second wall portion 1833D.

[00163] In the illustrated example, the height of the first apex 1833 SC of each supplemental microstructure 1833S is greater than the height of the first apex 1833C of the underlying base microstructure 1833B. The height of the first and second wall portions 1833 SA, 1833SD of each supplemental microstructure 1833S is greater than the height of the first and second wall portions 1833 A, 1833D of the underlying base microstructure 1833B. In example implementations, a height of each supplemental microstructure 1833S measured between its first and second apexes 1833 SC, 1833SE, is less than the height of the corresponding base microstructure 1833B measured between its first and second apexes 1833C, 1833E. All heights being compared are measured from a datum common to the compared heights, and along a direction perpendicular to the plane of the body 132, as described herein.

[00164] In example implementations, a thickness of each supplemental microstructure 1833S, measured along a direction perpendicular to either one of the corresponding first or second wall portions 1833 SA, 1833SD, is less than the height of the corresponding base microstructure 1833B measured between its first and second apexes 1833C, 1833E. In example implementations, and referring to FIG. 18B, each supplemental microstructure 1833S protrudes from a surrounding surface of the underlying base microstructure 1833B on one side 134A, 134B of the body 132, and forms a corresponding depression or groove relative to the surrounding surface of the same base microstructure 1833B on the other side 134A, 134B of the body 132.

[00165] In example implementations, and referring to FIG. 18B, each supplemental microstructure 1833S undulates by transitioning between the first and second apexes 1833 SC, 1833SE as it extends over adjacent base microstructures 1833B, while the base microstructures do not undulate by transitioning between their first and second apexes 1833C, 1833E. In example implementations, and referring to FIG. 18B, the mass-transfer microstructure 1833 can be considered as a transitioning surface having raised portions (e.g., the supplemental microstructures 1833 S) and lower portions (e.g., the portions of the base microstructures 1833B between two adjacent supplemental microstructures 1833S), rather than being considered as being composed of supplemental microstructures 1833S overlayed onto base microstructures 1833B.

[00166] The orientation of a base microstructure 1833B can be transverse, or nonparallel, to the orientation of the supplemental microstructures 1833S along portions of the base microstructure 1833B from which the supplemental microstructures 1833S protrude. For example, and referring to FIG. 18A, a segment of one of the base microstructures 1833B has a base orientation axis 1850. The segments of the supplemental microstructures 1833S that protrude from the same segment of the base microstructure 1833B each have a supplemental orientation axis 1852. The segments of the supplemental microstructures 1833S are spaced apart from each other on the segment of the base microstructure 1833B along a direction parallel to the base orientation axis 1850.

[00167] Each supplemental orientation axis 1852 can be transverse to the base orientation axis 1850, when viewed in a plane parallel to the body 132. Each supplemental orientation axis 1852 forms an angle 9 with the base orientation axis 1850, when viewed in a plane parallel to the body 132. In example implementations, the angle 9 is greater than 0 degrees and less than 180 degrees. In example implementations, the angle 9 is approximately 90 degrees.

[00168] The mass-transfer microstructures 1833 of FIGS. 18A and 18B can therefore be considered, or include, “opposed” microstructures 1833B, 1833S. Adjusting the angle 9 at which the base and supplemental microstructures 1833B, 1833S intersect can allow for adjusting the liquid flow properties along the packing sheet 130. For example, if the angle 9 is decreased in value (e.g., closer to 0 degrees), it can allow for “flattening” the intersection of the base and supplemental microstructures 1833B, 1833S, which can assist in slowing the flow of the CO2 capture solution 114 along the LTD 138L. In example implementations, and referring to FIG. 18A, segments of each base microstructure 1833B have an orientation that is parallel to the orientation of segments of the supplemental microstructures 1833S that do not protrude from the same segments of the base microstructure 1833B.

[00169] The mass-transfer microstructures 833 can promote spreading of the liquid CO2 capture solution 114 into a thin film on the surfaces of the packing sheets 130 (sometimes referred to as the phenomenon of “wetting”), which can enable maximum exposure of the liquid CO2 capture solution 114 to the CO2 present in the CCE-laden air 101. The opposed base and supplemental microstructures 1833B, 1833S can increase the liquid hold-up on the packing sheet 130 and the ability of the CO2 capture solution 114 to capture CO2 from the CCL-laden air 101. In example implementations, the mass-transfer microstructures 833 is present along all of the mass-transfer zone 131. In alternate implementations, the mass-transfer microstructures 833 can be present on only some of the mass-transfer zone 131.

[00170] In alternate implementations of the packing sheet 130, the mass-transfer zone 131 is present or disposed on only one of the first and second sides 134A, 134B. In alternate implementations of the packing sheet 130, the mass-transfer zone 131 is present or disposed on only some of one or both of the first and second sides 134A, 134B.

[00171] Referring to FIG. 3, the body 132 has multiple stiffening elements 140. Each stiffening element 140 extends outwardly from one or both of the first and second sides 134A, 134B of the body 132. In the packing sheet 130 of FIG. 3, the stiffening elements 140 extend outwardly from both of the first and second sides 134A, 134B (see, for example, FIGS. 4A to 4E). In the colour scheme of FIG. 3, the darker grey shading on the stiffening elements 140 indicates that the shaded portion extends outwardly from the body 132 on the first side 134A, and the lighter grey shading on the stiffening elements 140 indicates that the shaded portion extends outwardly from the body 132 on the second side 134B. This colour scheme is used throughout the figures for the sole purpose of explaining features of the figures and does not limit the direction of extension of any feature. In example implementations, the expression “extending outwardly” is used herein to mean that a feature is a protrusion or an extension from a plane defined by the body 132, typically in a direction that is perpendicular to the plane.

[00172] Each stiffening element 140 is an elongated body that has an orientation parallel to the LTD 138L. The stiffening elements 140 strengthen the packing sheet 130, by supporting it against lateral or bending loads caused by the weight of the packing sheet 130 itself, the liquid hold up of the CO2 capture solution 114 on the packing sheet 130, any scaling present on the packing sheet 130, and/or other loads. The stiffening elements 140 can thus be any structures that are elongated or that extend parallel to the LTD 138L, and that can support the loads described herein. The stiffening elements 140 can have any arrangement, number, location, form, shape or size to achieve the functionality ascribed to them herein, and examples of possible configurations for the stiffening elements 140 are described in greater detail below. [00173] In example implementations, and referring to FIG. 3, the stiffening elements 140 are disposed on, or adjacent to, the mass-transfer zone 131 and its mass-transfer microstructures 133. In example implementations, the stiffening elements 140 contribute little or nothing to the transfer of CO2 from the CCL-laden air 101 to the CO2 capture solution 114. In alternate implementations, the packing sheet 130 is free of stiffening elements 140 and derives its strength against loads from the material and size of the packing sheet 130 itself.

[00174] Referring to FIG. 3, the body 132 has multiple spacers 150 disposed on the mass-transfer zone 131. Each spacer 150 extends outwardly from one or both of the first and second sides 134A, 134B of the body 132. In the packing sheet 130 of FIG. 3, the spacers 150 extend outwardly from both of the first and second sides 134A, 134B. In the colour scheme of FIG. 3, the darker grey shading on the spacers 150 indicates that the shaded portion extends outwardly from the body 132 on the first side 134 A, and the lighter grey shading on the spacers 150 indicates that the shaded portion extends outwardly from the body 132 on the second side 134B. The spacers 150 are spaced apart from one another on each side 134A, 134B of the body 132. Referring to FIG. 3, the spacers 150 are spaced apart from one another in a direction parallel to the LTD 138L. The packing sheet 130 can include multiple sets of spacers 150, where the spacers 150 of each set of spacers 150 are aligned parallel to the LTD 138L.

[00175] Referring to FIG. 3, the spacers 150 are vertically spaced apart along the height of the packing sheet 130. Referring to FIG. 3, the spacers 150 are also spaced apart from one another in a direction parallel to the ATD 138D. The spacers 150 help to maintain a separation between the mass-transfer zones 131 of adjacent packing sheets 130 of a structured packing 116. The spacers 150 of one packing sheet 130 align with, and abut against, the spacers 150 of another packing sheet 130, thereby defining airflow channels or flutes between adjacent packing sheets 130 through which the CCh-laden air 101 can flow, as explained in greater detail below. In example implementations, the abutting spacers 150 of adjacent packing sheets 130 are glued or bonded together, thereby creating a structural link between the adjacent packing sheets 130.

[00176] Referring to FIG. 3, abutment surfaces 152 of the spacers 150 have an oval or circular shape, and fully align with the abutment surfaces 152 of the spacers 150 of the adjacent packing sheet 130 to which they are bonded (see, e.g., FIG. 5). The spacers 150 can have any arrangement, number, location, form, shape or size to achieve the functionality ascribed to them herein, and examples of possible configurations for the spacers 150 are described in greater detail below. In example implementations, the spacers 150 contribute little or nothing to the transfer of CO2 from the CCL-laden air 101 to the CO2 capture solution 114.

[00177] Referring to FIG. 3, the spacers 150 are arranged in spacer pairings 150P. Each spacer pairing 150P is spaced apart from another spacer pairing 150P along both the LTD 138L and the ATD 138D. Referring to FIG. 3, the spacer pairings 150P are aligned along the LTD 138L. Referring to FIG. 3, the spacer pairings 150P are aligned along the ATD 138D. In alternate implementations, the spacer pairings 150P are misaligned, staggered or offset across the body 132 of the packing sheet 130. The spacers 150 in each spacer pairing 150P are spaced apart from each other in a direction parallel to the ATD 138D. A distance between the spacers 150 of each spacer pairing 150P is parallel to the ATD 138D. In example implementations, the distance is less than a third of the ATD 138D. In example implementations, the distance is less than a diameter or size of one of the spacers 150. Referring to FIG. 3, the mass-transfer microstructures 133 are present on the body 132 between the spacers 150 of each spacer pairing 150P, and between the spacer pairings 150P. Referring to FIG. 3, each spacer pairing 150P includes a first spacer 150 that extends outwardly from the first side 134A of the body 132 (shown in FIG. 3 as the spacers 150 with darker grey shading) and a second spacer 150 that extends outwardly from the second side 134B (as shown in FIG. 3 as the spacers 150 with lighter grey shading, see also FIG. 4B). Each spacer 150 is a hollow body (see, e.g., FIG. 4B), such that they form corresponding depressions on the other side of the body 132 from which they extend. Thus, each spacer 150 forms a protrusion on one side 134A, 134B of the body 132 and an indentation on the other side 134B, 134A.

[00178] The packing sheet 130 is optimised to maximise its surface area available for CO2 transfer from the CCh-laden air 101 to the CO2 capture solution 114. When the packing sheets 130 are assembled into a structured packing 116 and the structured packing 116 forms part of a packing section 106 installed in the gas-liquid contactor 100, the leading edge 136A of each packing sheet 130 of the structured packing 116 is substantially parallel to a vertical axis 135 or plumb line. The leading edges 136A thus have a substantially vertical orientation in the installed configurations of the packing sheets 130. In example implementations, and referring to FIG. 3, the leading edges 136A are substantially perpendicular to the ATD 138D of the packing sheet 130 and to the packing depth 106D of each packing section 106. The air intake side edges (e.g., the leading edges 136A) of each packing sheet 130 are substantially perpendicular with the predominant direction along which the CCh-laden air 101 flows across the packing sheet 130.

[00179] In example implementations, the term “substantially” refers to the packing sheets 130 being positionable so that, when installed as part of each packing section 106, their leading edges 136A are parallel to the vertical axis 135, it being understood that there might be slight deviations from the vertical due to the following non-exhaustive list of factors: manufacturing tolerances during production of the packing sheet 130, minor misalignment during assembly of the packing sheets 130 into a structured packing 116, minor misalignment during assembly of the structured packing 116 into an arrangement 118 of structured packing 116, and damage caused to a packing sheet 130 during transportation, assembly, and installation. In example implementations, the term “substantially” refers to the packing sheets 130 being designed so that, when installed, their leading edges 136A are parallel to the vertical axis 135, within a tolerance of less than 2 degrees variation from parallel.

[00180] The alignment of the leading edges 136A of the packing sheets 130 with the vertical axis 135 in their installed configuration contrasts with some fill sheets used in water cooling towers, which function primarily to transfer heat between water and atmospheric air. These cooling tower fill sheets are oriented in the cooling tower such that their leading edges from an offset angle A relative to the vertical axis 135. The offset angle A is sometimes referred to as a “pack angle,” or the pack of fill sheets is sometimes said to have “a forward lean.” The offset leading edge of such cooling tower fill sheets is shown schematically in FIG. 3 for the purposes of comparison, as phantom leading edge 137. The offset angle A of such cooling tower fill sheets can be approximately five to ten (5-10) degrees. Such cooling tower fill sheets form such offset angles A with the vertical axis 135 in order to offset the effects of the higher velocity crossing airflow on the vertically flowing water on the fill sheet surfaces during operation.

[00181] As the water flows down the sheets, generally parallel to the vertical axis 135, the higher velocity air tends to push the water toward the outlet side or trailing edge of the fill sheets due to friction at the air-water interface, particularly along lower leading sections of the fill sheet. This can result in such lower leading sections being dry, and thus less available for heat transfer. To eliminate such dry zones, such cooling tower fill sheets eliminate these lower leading sections by “leaning” into the direction of air flow, such that a top comer of the fill sheets near the intersection of the leading edge 137 and a top edge is positioned closest to the air inlet of the cooling tower. The lower front corner of these cooling tower fill sheets near the intersection of the leading edge 137 and a bottom edge is the portion of the air intake side that is positioned furthest from the air inlet of the cooling tower.

[00182] In DAC applications where the packing sheets 130 are installed in cross-flow gas-liquid contactors 100 which operate at lower air velocities (e.g., between 0.1 m/s and 5 m/s) compared to typical water cooling tower applications, there is no comparable problem of dry zones formed by air pushing liquid horizontally along the lower sections of the packing sheet 130 adjacent to the leading edge 136A. Thus, in such DAC applications, the offset angle A of cooling tower fill sheets is detrimental to performance because it results in missing surface area adjacent to the leading edge which would otherwise be available to facilitate the transfer of CO2 from the CCh-laden air 101 to the CO2 capture solution 114. This missing surface area at the leading edge can result in reduced overall efficiency for each packing section 106.

[00183] The packing sheet 130 of FIG. 3 does not have the “forward lean” associated with the cooling tower fill sheets described above. Stated differently, the offset angle A of the packing sheet 130 of FIG. 3 is approximately zero degrees. Thus, referring to FIG. 3, the packing sheet 130 has an additional leading edge surface area 139 adjacent to its leading edge 136A that is defined between the leading edge 136A, the phantom leading edge 137, and the segment of the lower edge 136L between the phantom leading edge 137 and the leading edge 136A. The additional leading edge surface area 139 is shown schematically in FIG. 3 with transparent shading. The additional leading edge surface area 139 represents the surface area present in the packing sheet 130 that is missing near the leading edge of some cooling tower fill sheets with similar dimensions but whose leading edge 137 forms the offset angle A relative to the vertical axis 135. Such cooling tower fill sheets can make up for the missing surface area along their leading edges by having a forward-leading trailing edge that adds the missing surface area along the trailing edge.

[00184] Considering the relatively large number of packing sheets 130 in the gas-liquid contactor 100, the additional leading edge surface area 139 available to each packing sheet 130 at its leading edge 136A amounts to a larger additional mass transfer surface along the leading edge 136A at the level of the gas-liquid contactor 100. This is made clearer with reference to Table 1 below, which calculates the additional leading edge surface area 139 adjacent to the leading edge 136A for offset angles A of 5 degrees and 10 degrees. The additional leading edge surface area 139 is calculated at the level of each packing sheet 130, each structured packing 116, each packing section 106 and the gas-liquid contactor 100. The following example dimensions and configurations of packing sheets 130, structured packings 116, and packing sections 106 are provided for the sole purpose of explaining Table 1, it being understood that other dimensions and configurations are possible:

[00185] 1) the ATD 138D and the LTD 138L of each packing sheet 130 are 1 m (e.g., each packing sheet 130 is 1 m deep by 1 m tall);

[00186] 2) Each packing sheet 130 has a mass-transfer zone 131 present on all of its first and second sides 134A, 134B;

[00187] 3) There are ten packing sheets 130 in each structured packing 116;

[00188] 4) There are ten structured packings 116 in each packing section 106; and

[00189] 5) there are two packing sections 106 in the gas-liquid contactor 100.

Table 1: Comparison of additional surface area for two offset angles

[00190] Table 1 thus shows that the additional leading edge surface area 139 available to each packing sheet 130 along its leading edge 136A in cross-flow applications at relatively low air velocities, due to the leading edge 136A being substantially parallel to the vertical axis 135, propagates through each structured packing 116, each packing section 106 and ultimately to the cross-flow gas-liquid contactor 100. The additional leading edge surface area 139 includes additional, wettable, mass transfer surface area, which can result in more CO2 being absorbed in the CO2 capture solution 114 at the level of each packing sheet 130, each structured packing 116 and each packing section 106. This additional mass transfer surface can increase the ratio of specific surface area to volume (defined in units of m²/m³) for each packing section 106 due to the increased surface area, where higher specific surface areas are understood to result in more CO2 being exposed to the surface of the CO2 capture solution 114.

[00191] The packing sheet 130 with no offset angle A along its leading edge 136A can be designed and implemented in view of the performance characteristics (liquid loading, masstransfer capture efficiency, mechanical strength at maximum size, etc.) related to transferring CO2 from the atmospheric air to a liquid capture solution in cross-flow configurations with lower air velocities. These performance characteristics can differ from those of some cooling tower fill sheets which are optimised to transfer heat from water to the air.

[00192] The leading edge 136A being substantially parallel to the vertical axis 135 can result in the packing sheet 130 being more rigid in a vertical direction compared to fill sheets with non-zero offset angles A. When such packing sheets 130 are assembled into a structured packing 116, the structured packing 116 can thus be able to withstand greater loading compared to if it included fill sheets with non-zero offset angles A.

[00193] In example implementations, other features of the packing sheet 130, in addition to the leading edge 136A, are also substantially parallel with the vertical axis 135 when the packing sheet 130 is installed in the gas-liquid contactor 100. For example, and referring to FIG. 3, the packing sheet 130 has one or more spacer alignment axes 150 A. Each spacer alignment axis 150A extends between the upper and lower edges 136U, 136L on one or both of the first and second sides 134A, 134B of the packing sheet 130. Each spacer alignment axis 150A also extends between the spacers 150 which are aligned with one another along the LTD 138L.

[00194] When the packing sheet 130 of FIG. 3 is installed in the gas-liquid contactor 100, each spacer alignment axis 150A has a substantially vertical orientation. When the packing sheet 130 of FIG. 3 is installed in the gas-liquid contactor 100, each spacer alignment axis 150A is substantially parallel to the vertical axis 135. When the packing sheet 130 of FIG. 3 is installed in the gas-liquid contactor 100, each spacer alignment axis 150A is substantially parallel to the leading edge 136A. Thus, and referring to FIG. 3, each set of spacers 150 which are aligned along the LTD 138L are also aligned with the vertical axis 135. FIG. 3 shows only one spacer alignment axis 150A for simplicity, but the packing sheet 130 can include multiple spacer alignment axes 150A each being substantially parallel with the vertical axis 135, where each spacer alignment axis 150A is spaced apart from an adjacent spacer alignment axis 150A along the direction of the ATD 138D.

[00195] The stiffening elements 140 are additional features of the packing sheet 130 which can be substantially parallel with the vertical axis 135 when the packing sheet 130 is installed in the gas-liquid contactor 100. Referring to FIG. 3, the packing sheet 130 has one or more stiffening element alignment axes 140A. Each stiffening element alignment axis 140A extends between the upper and lower edges 136U, 136L on one or both of the first and second sides 134A, 134B of the packing sheet 130. Each stiffening element alignment axis 140A also extends between the stiffening elements 140 which are aligned with one another along the LTD 138L.

[00196] When the packing sheet 130 of FIG. 3 is installed in the gas-liquid contactor 100, each stiffening element alignment axis 140A has a substantially vertical orientation. When the packing sheet 130 of FIG. 3 is installed in the gas-liquid contactor 100, each stiffening element alignment axis 140A is substantially parallel to the vertical axis 135. When the packing sheet 130 of FIG. 3 is installed in the gas-liquid contactor 100, each stiffening element alignment axis 140A is substantially parallel to the leading edge 136A. Thus, and referring to FIG. 3, each set of stiffening elements 140 which are aligned along the LTD 138L are also aligned with the vertical axis 135. FIG. 3 shows only one stiffening element alignment axis 140A for simplicity, but the packing sheet 130 can include multiple stiffening element alignment axes 140A each being substantially parallel with the vertical axis 135, where each stiffening element alignment axis 140A is spaced apart from an adjacent stiffening element alignment axis 140A along the direction of the ATD 138D. [00197] The mass-transfer microstructures 133 are additional features of the packing sheet 130 which can be substantially parallel with the vertical axis 135 when the packing sheet 130 is installed in the gas-liquid contactor 100. Referring to FIG. 3, the packing sheet 130 has one or more microstructure alignment axes 133A. In the configuration of FIG. 3 where the mass-transfer microstructures 133 are chevrons extending along the LTD 138L, each microstructure alignment axis 133A extends between the maxima or minima of one chevron, on one or both of the first and second sides 134A, 134B of the packing sheet 130.

[00198] When the packing sheet 130 of FIG. 3 is installed in the gas-liquid contactor 100, each microstructure alignment axis 133A has a substantially vertical orientation. When the packing sheet 130 of FIG. 3 is installed in the gas-liquid contactor 100, each microstructure alignment axis 133A is substantially parallel to the vertical axis 135. When the packing sheet 130 of FIG. 3 is installed in the gas-liquid contactor 100, each microstructure alignment axis 133A is substantially parallel to the leading edge 136A. FIG. 3 shows only one microstructure alignment axis 133A for simplicity, but the packing sheet 130 can include multiple microstructure alignment axes 133 A each being substantially parallel with the vertical axis 135, where each microstructure alignment axis 133A is spaced apart from an adjacent microstructure alignment axis 133A along the direction of the ATD 138D.

[00199] The packing sheet 130 of FIG. 3 has a rectangular shape. Like the leading edge 136A, the trailing edge 136B is substantially parallel to the vertical axis 135. The upper edge 136U and the lower edge 136L are both substantially perpendicular to the leading and trailing edges 136A, 136B. Thus, when the packing sheet 130 of FIG. 3 is installed in the cross-flow gas-liquid contactor 100, the leading and trailing edges 136B have a substantially vertical orientation, and the upper and lower edges 136U, 136L have a substantially horizontal orientation. In other configurations of the body 132, the packing sheet 130 can have more or fewer edges 136A, 136B, 136U, 136L than shown in FIG. 3. In such configurations, the edges 136 of the body 132 can intersect at non-zero, non-right angles.

[00200] In view of the preceding, in at least one implementation of the packing sheet 130 of FIG. 3, one or more of the stiffening element alignment axes 140A, the spacer alignment axes 150A, the microstructure alignment axes 133A, and the trailing edge 136B, in any combination, are aligned with the leading edge 136A and substantially parallel with the vertical axis 135. The expression “substantially parallel” refers to the packing sheets 130 being positionable so that, when installed as part of each packing section 106, these features are parallel to the vertical axis 135, it being understood that there might be slight deviations from parallel as explained above. [00201] Referring to FIG. 3, the body 132 has or defines a centroid 132C. The centroid 132C is also known as the geometric center in the two-dimensional plane of the body 132 shown in FIG. 3. The packing sheet 130 of FIG. 3 has a rectangular shape, and the centroid 132C is the point at which the diagonals of the body 132 intersect. The packing sheet 130 and/or its features have point symmetry about the centroid 132C. When rotated 180 degrees about the centroid 132C, the packing sheet 130 and its features look the same.

[00202] The point symmetry of the packing sheet 130 about its centroid 132C can result from the zero-degree offset angle A of the packing sheet 130. The point symmetry of the packing sheet 130 about its centroid 132C can allow for the attachment features of adjacent packing sheets 130 (e.g., the abutting surfaces of the spacers 150 and of the stiffening elements 140) to be abutted against one another, which can facilitate the formation of a structured packing 116 by assembling multiple packing sheets 130. The point symmetry of the packing sheet 130 about its centroid 132C can allow for a single tool (e.g., a mold) to be used to manufacture a common packing sheet 130 of the packing section 106, where adjacent attached packing sheets 130 of a structured packing 116 are point symmetric translations of one another. This contrasts with forward-leaning packing in some cross-flow water cooling tower applications which consist of two or more types of fill sheets (e.g., an “A” fill sheet and a “B” fill sheet). In alternate implementations, the packing sheet 130 is asymmetric about its centroid 132C. In alternate implementations, each structured packing 116 includes one or more types of packing sheets 130.

[00203] The packing sheet 130 can have any number, shape, and/or arrangement of features to achieve the functions ascribed to the packing sheet 130 herein. For example, and referring to FIG. 4, the stiffening elements 140 include an intermediate stiffening element 142. The intermediate stiffening element 142 reinforces or strengthens the body 132 along a middle portion of the packing sheet 130. The intermediate stiffening element 142 reinforces or strengthens the body 132 along a middle portion, by supporting it against lateral or bending loads, and/or other loads, described above. The intermediate stiffening element 142 includes intermediate stiffening bodies 142 A. The intermediate stiffening bodies 142 A are located on the body 132 between the leading and trailing edges 136A, 136B.

[00204] For the packing sheet 130 of FIG. 4, the intermediate stiffening bodies 142A are located along the middle of the body 132 between the leading and trailing edges 136A, 136B, at a position from the leading edge 136A that is half of the ATD 138D. For the packing sheet 130 of FIG. 4, the intermediate stiffening bodies 142A are located along the middle of the body 132 between spacers 150 on either side of the intermediate stiffening bodies 142A in the ATD 138D. The intermediate stiffening bodies 142A are positioned adjacent each other along the LTD 138L to form the intermediate stiffening element 142. The intermediate stiffening bodies 142 A are positioned vertically adjacent to each other along the middle of the packing sheet 130. The packing sheet 130 of FIG. 4 has one intermediate stiffening element 142. In alternate implementations, the packing sheet 130 has two or more intermediate stiffening elements 142.

[00205] The packing sheet 130 can be cut or sectioned through a lateral midpoint (measured along the ATD 138D) of the intermediate stiffening element 142 to form packing sheets 130 of desirable sizes that can be laterally aligned with the leading or trailing edges 136A, 136B of an adjacent packing sheet 130 (e.g., abutting one packing sheet 130 against another along their abutting edges 136A, 136B). In an example implementation where the packing sheet 130 of FIG. 3 has a width of 4 feet measured from a vertical datum along a direction parallel to the ATD 138D, and the intermediate stiffening element 142 is 2 feet measured from the vertical datum, the packing sheet 130 can be vertically sectioned through the lateral midpoint of the intermediate stiffening element 142 to produce two packing sheets 130 each with a width of 2 feet. Sectioning the intermediate stiffening element 142 forms leading or trailing edges 136A, 136B, such that the resulting two packing sheets 130 have no intermediate stiffening element 142. Each of the two 2-ft packing sheets 130 can be bonded to similarly-sized packing sheets 130 to form a structured packing 116 with a width of 2 feet.

[00206] Referring to FIGS. 4, 4C and 4D, each intermediate stiffening body 142 A extends outwardly from one of the first and second sides 134A, 134B. Each intermediate stiffening body 142 A extends outwardly to a local maximum, shown as an attachment wall 142B. Each attachment wall 142B defines a surface of the intermediate stiffening body 142 A that is located further from the plane of the body 132 than other portions of the intermediate stiffening body 142 A. Each attachment wall 142B defines a surface of the intermediate stiffening body 142A that is located further from the mass-transfer microstructures 133 than other portions of the intermediate stiffening body 142A. In the colour scheme of FIGS. 4 and 5, the darker grey shading on the stiffening elements 140 indicates that the shaded portion extends outwardly from the body 132 on the first side 134A and the lighter grey shading on the stiffening elements 140 indicates that the shaded portion extends outwardly from the body 132 on the second side 134B.

[00207] In example implementations, one or more attachment walls 142B of adjacent packing sheets 130 are glued or bonded together, thereby creating a structural link between the adjacent packing sheets 130. Such attached attachment walls 142B of the intermediate stiffening bodies 142 A also help to space the adjacent packing sheets 130 apart from each other, thereby helping to define the airflow channels between adjacent packing sheets 130 through which the CCh-laden air 101 can flow, as described in greater detail below. When the adjacent packing sheets 130 are attached together in this manner, the attached intermediate stiffening elements 140 help to reinforce or strengthen the structured packing 116 along its middle portions, which can be helpful if each packing sheet 130 has a relatively large ATD 138D (e.g., between 4 ft. and 7 ft.) and is configured for installation in a cross-flow gas-liquid contactor 100.

[00208] Referring to FIG. 4, the intermediate stiffening element 142 has an orientation that is substantially parallel to the leading edge 136A. The intermediate stiffening bodies 142A of the intermediate stiffening element 142 are aligned with each other in a direction parallel to the LTD 138L. In example implementations, an axis extending through the attachment walls 142B of the intermediate stiffening bodies 142A is substantially parallel to the leading edge 136A of the packing sheet 130. In example implementations, an axis extending through the attachment walls 142B of the intermediate stiffening bodies 142A is substantially parallel to the vertical axis 135.

[00209] Features of the packing sheet 130 have heights defined in a direction that is perpendicular to a plane defined by the body 132, such as a datum plane 132D. The datum plane 132D is parallel to both the ATD 138D and LTD 138L. Referring to FIGS. 4B and 4D, each attachment wall 142B defines a stiffening body height 142H, each mass-transfer microstructure 133 defines a microstructure height 133H, and each spacer 150 defines a spacer height 150H. The datum plane 132D can be defined relative to any suitable common reference from which to make measurements. In example implementations, the datum plane 132D corresponds to the sheet plane of the body 132 and is positioned at a midpoint of a distance measured between opposed peaks of the mass-transfer microstructure 133 on opposite sides of the body 132.

[00210] The smallest of the stiffening body height 142H, the microstructure height 133H, and the spacer heights 150H is the microstructure height 133H. Referring to FIG. 4B, the microstructure height 133H is measured relative to the datum plane 132D, which can be located on either the first or second side 134A, 134B of the body 132. In the configuration of FIG. 4B where the mass-transfer microstructures 133 are chevrons, the microstructure height 133H is defined between the peaks and the valleys of each chevron. Referring to FIG. 4D, the stiffening body height 142H is measured relative to the datum plane 132D on the side 134A, 134B of the body 132 that is opposite to the side 134A, 134B of the body 132 on which the attachment wall 142B of the intermediate stiffening body 142A is located. For example, in FIG. 4D, the stiffening body height 142H is measured relative to the datum plane 132D on the first side 134A of the body 132 because the attachment wall 142B of the shown intermediate stiffening body 142A is on the second side 134B of the body 132.

[00211] Referring to FIG. 4B, the spacer height 150H is measured relative to the datum plane 132D on the side 134A, 134B of the body 132 that is opposite to the side 134A, 134B on which the abutment surface 152 of the spacer 150 is located. For example, in FIG. 4B, one of the spacers 150 has a spacer height 150H measured relative to the datum plane 132D on the first side 134A of the body 132 because its abutment surface 152 is on the second side 134B of the body 132, and the other illustrated spacer 150 has a spacer height 150H measured relative to the datum plane 132D on the second side 134B of the body 132 because its abutment surface 152 is on the first side 134A of the body 132.

[00212] The stiffening body height 142H, the microstructure height 133H, and the spacer height, 150H are different so that each packing sheet 130 can be attached to, and spaced apart from, an adjacent packing sheet 130 of a structured packing 116. Referring to FIG. 4B, the spacer height 150H is greater than the microstructure height 133H, when both heights are measured from the same datum plane 132D. Referring to FIGS. 4B and 4D, the stiffening body height 142H is greater than the microstructure height 133H, when both heights are measured from the same datum plane 132D. In example implementations, and referring to FIGS. 4B and 4D, the stiffening body height 142H is greater than the microstructure height 133H and is equal to the spacer height 150H, when all heights are measured from the same datum plane 132D. The height difference between the microstructure height 133H, the stiffening body height 142H, and spacer height 150H allows adjacent packing sheets 130 to be spaced apart sufficiently from each other so that both the CO2 capture solution 114 and the CCh-laden air 101 can flow between the adjacent packing sheets 130, when the adjacent packing sheets 130 are bonded together along their spacers 150 and their stiffening bodies 142.

[00213] In example implementations, and referring to FIGS. 4 to 4E, each of the stiffening bodies 142 A has the same stiffening body height 142H, each of the mass-transfer microstructures 133 has the same microstructure height 133H, and each of the spacers 150 has the same spacer height 150H. In alternate implementations, the stiffening bodies 142A can have varying stiffening body heights 142H, the mass-transfer microstructures 133 can have varying microstructure heights 133H, and/or the spacers 150 can have varying spacer heights 150H, in any combination. [00214] In an example implementation of the intermediate stiffening element 142, and referring to FIGS. 4, 4C and 4D, the intermediate stiffening bodies 142 A which make up the intermediate stiffening element 142 are arranged into a first set 142C and a second set 142D of intermediate stiffening bodies 142A. The intermediate stiffening bodies 142A of the first set 142C are shown in dark grey shading in FIG. 4 and extend outwardly from the first side 134A of the body 132 as shown in FIG. 4C. The intermediate stiffening bodies 142A of the second set 142D are shown in light grey shading in FIG. 4 and extend outwardly from the second side 134B of the body 132 as shown in FIG. 4D. The intermediate stiffening bodies 142A of the first and second sets 142C, 142D are hollow bodies, such that they form corresponding depressions on the other side of the body 132 from which they extend. For example, and referring to FIG. 4C, the intermediate stiffening bodies 142 A of the first set 142C extending outwardly from the first side 134A form a first set of depressions 144A on the second side 134B. Similarly, and referring to FIGS. 4 and 4D, the intermediate stiffening bodies 142A of the second set 142D extending outwardly from the second side 134B form a second set of depressions 144B on the first side 134A. The first and second sets of depressions 144A, 144B are grooves or recesses which extend into the body 132 in an extension direction that is transverse to the datum plane 132D. The first and second sets of depressions 144A, 144B have a height or dimension defined between the attachment wall 142B of the corresponding intermediate stiffening body 142A and the datum plane 132D on the side 134A, 134B of the body 132 opposite to the side 134B, 134A on which the attachment wall 142B is located. In the configuration of the intermediate stiffening element 142 of FIG. 4, the first and second sets of depressions 144A, 144B alternate with each other along a direction that is parallel to the LTD 138L. On the first side 134A of the body 132 of FIG. 4, the intermediate stiffening bodies 142 of the first set 142C protrude outwardly on the first side 134A and the adjacent depressions of the second set of depressions 144B are present on the second side 134B. Similarly, on the second side 134B of the body 132 of FIG. 4, the intermediate stiffening bodies 142 of the second set 142D protrude outwardly on the second side 134B and the adjacent depressions of the first set of depressions 144A are present on the first side 134A.

[00215] In the configuration of the intermediate stiffening elements 142 of FIG. 4, each stiffening body 142A is adjacent to one or two of its negative imprints in the LTD 138L. In particular, on the first side 134A, the first set 142C of intermediate stiffening bodies 142 alternate along an axis 403 with the second set of depressions 144B. Similarly, on the second side 134B, the second set 142D of intermediate stiffening bodies 142 alternate along the axis 403 with the first set of depressions 144 A. [00216] The intermediate stiffening bodies 142A can have any suitable shape. For example, and referring to FIGS. 4C and 5, each intermediate stiffening body 142A is a polygonal object defined by multiple planar walls 142P which extend outwardly from one of the first and second sides 134A, 134B to the attachment wall 142B. Referring to FIG. 5, each intermediate stiffening body 142A can be shaped as a planar body, where four planar walls 142P extend outwardly from one of the first and second sides 134A, 134B to the attachment wall 142B on the same side 134A, 134B. Each planar wall 142P in FIG. 5 has a trapezoidal shape and is delimited by four edges. Other shapes of the planar walls 142P, and thus other shapes for each intermediate stiffening body 142 A, are possible. In FIG. 4, the intermediate stiffening bodies 142 A of the intermediate stiffening element 142 have the same shapes and sizes.

[00217] In other possible implementations, the shapes and/or sizes of the intermediate stiffening bodies 142 A of an intermediate stiffening element 142 can vary. For example, in one such other possible implementation, the intermediate stiffening body 142 A includes one or more curved walls which form a sinusoidal shape in a sectional view (such as in the cross- sectional plane of FIG. 4C).

[00218] Referring to FIG. 5, each intermediate stiffening body 142A has one or more longitudinal flow channels 142F. Each longitudinal flow channel 142F is a groove or elongated depression that extends into each planar wall 142P. Each of the longitudinal flow channels 142F has an orientation being parallel to the LTD 138L. Each longitudinal flow channel 142F helps to guide the flow of the CO2 capture solution 114 along the LTD 138L, as the CO2 capture solution 114 flows along and/or between the intermediate stiffening bodies 142A. In the implementation of intermediate stiffening bodies 142A of FIG. 5, each intermediate stiffening body 142A has two longitudinal flow channels 142F on opposite sides of the attachment wall 142B. In the implementation of intermediate stiffening bodies 142A of FIG. 5, each intermediate stiffening body 142 A has two longitudinal flow channels 142F, and each longitudinal flow channel 142F is positioned in a lateral middle of its planar wall 142P. When the CO2 capture solution 114 is flowing along the packing sheet 130, it can enter each longitudinal flow channel 142F at its inlet and flow in a direction parallel to the LTD 138L to an outlet of the longitudinal flow channel 142F. In some embodiments, the CO2 capture solution 114 can flow through each longitudinal flow channel 142F in a direction that is substantially parallel to the vertical axis 135.

[00219] Each intermediate stiffening body 142 A can have fewer, more, or different configurations of flow guides for guiding the flow of the CO2 capture solution 114 along the intermediate stiffening body 142A. For example, and referring to FIG. 5, one or more of the intermediate stiffening bodies 142A has one or more lateral flow channels 142L. Each lateral flow channel 142L functions to divert or guide the CO2 capture solution 114 in a direction transverse to the LTD 138L, from the intermediate stiffening body 142 A toward the masstransfer microstructures 133 that are adjacent to the intermediate stiffening body 142 A. Each lateral flow channel 142L thus has an inlet end and an outlet end, where the inlet end is closer (e.g., relative to a direction parallel to the ATD 138D) to the attachment wall 142B than the outlet end. Each lateral flow channel 142L can have any shape, orientation, or arrangement on the intermediate stiffening body 142A to achieve this function. For example, and referring to FIG. 5, the lateral flow channel 142L extends along a common edge between two planar walls 142P from the inlet end adjacent to the attachment wall 142B to the outlet end adjacent to the mass-transfer microstructures 133.

[00220] The lateral flow channel 142L of FIG. 5 forms a non-zero angle with both the LTD 138L and the ATD 138D. In another possible implementation of the one or more lateral flow channels 142L, the lateral flow channel 142L extends along one planar wall 142P in a direction parallel to the ATD 138D, from the inlet end adjacent to the attachment wall 142B to the outlet end adjacent the mass-transfer microstructures 133. In another possible implementation of the one or more lateral flow channels 142L, and referring to FIG. 5A, the sloped planar walls 142P on opposite sides of the attachment wall 142B in the LTD 138L have multiple lateral flow channels 142LA. Each lateral flow channel 142LA of FIG. 5 A forms a non-zero angle with both the LTD 138L and the ATD 138D. The lateral flow channels 142LA intersect each other on the same planar wall 142P of one of the intermediate stiffening bodies 142A of FIG. 5A and form an “X”-shaped microstructure. The X shape formed by the lateral flow channels 142LA allows for the packing sheet 130 to be oriented or inserted with either one of the upper and lower edges 136U, 136L, while still preserving the functionality of the lateral flow channels 142LA.

[00221] Each lateral flow channel 142L, 142LA can help to reduce or prevent channeling of the CO2 capture solution 114 as it flows along the intermediate stiffening bodies 142A, thereby helping to better distribute the CO2 capture solution 114 to the mass-transfer microstructures 133 and improve the ability of the CO2 capture solution 114 to capture CO2 from the CCh-laden air 101. The CO2 capture solution 114 flowing in the LTD 138L can encounter a flow obstruction at the bonded attachment walls 142B of adjacent packing sheets 130, and the lateral flow channels 142L, 142LA can help to minimize channeling or streaming of the CO2 capture solution 114 in this location throughout the LTD 138L of the packing sheet 130 by helping to divert at least some of the CO2 capture solution 114 away from the bonded attachment walls 142B and back to the mass-transfer microstructures 133.

[00222] Other features of the packing sheet 130 can have the flow channels 142F, 142L. For example, in example implementations, one or more flow channels 142F, 142L can be present in a stiffening rib. The flow channels 142F, 142L, 142LA of the present disclosure form grooves or elongated depressions on one of the first and second sides 134A, 134B of the packing sheet 130, and form corresponding mounds or protrusions on the other one of the first and second sidesl34A, 134B. In example implementations, other features of the packing sheet 130 have the flow channels 142F, 142L, 142LA of the present disclosure. For example, in one such implementation, one or more the spacers 150 has one or more flow channels 142F, 142L, 142LA to help divert at least some of the CO2 capture solution 114 away from the bonded spacers 150 and back to the mass-transfer microstructures 133.

[00223] The stiffening elements 140 can include other stiffening bodies. For example, and referring to FIG. 4, the stiffening elements 140 include one or more peripheral stiffening bodies 148. The peripheral stiffening bodies 148 can be present adjacent to each other along the LTD 138L to form a peripheral stiffening element. In example implementations, and referring to FIG. 4, the peripheral stiffening bodies 148 are similar to the intermediate stiffening bodies 142A, such that the description, features, and advantages of the present disclosure that are associated with the intermediate stiffening bodies 142 A apply mutatis mutandis to the peripheral stiffening bodies 148.

[00224] The peripheral stiffening bodies 148 reinforce or strengthen the body 132 along peripheral portions and can be used to attach adjacent packing sheets 130 together along attachment walls of the peripheral stiffening bodies 148. The peripheral stiffening bodies 148 of FIG. 4 define some or all of both the leading and trailing edges 136A, 136B of the body 132. In alternate implementations, the peripheral stiffening bodies 148 define some or all of one of the leading and trailing edges 136A, 136B. In alternate implementations, the packing sheet 130 is free of peripheral stiffening bodies 148 along its leading and trailing edges 136A, 136B. [00225] In example implementations, the peripheral stiffening bodies 148 include longitudinal and/or lateral flow channels 142F, 142L (such as those shown in FIG. 5). In example implementations, packing sheets 130 are positioned adjacent to each other along the packing depth 106D to form a packing section 106, and these packing sheets 130 interface along their respective peripheral stiffening bodies 148. In such implementations, the presence of longitudinal and/or lateral flow channels 142F, 142L in the peripheral stiffening bodies 148 can help to reduce or eliminate the CO2 capture solution 114 that reaches these interface points of the packing section 106 where the CO2 capture solution 114 can bypass the reactive surface area of the packing section 106 and thus be less effective at capturing CO2 from the CCh-laden air 101. The presence of longitudinal and/or lateral flow channels 142F, 142L in the peripheral stiffening bodies 148 of these implementations can also help to reduce liquid pooling along the peripheral stiffening bodies 148 and/or along the interfaces, which can help to reduce the pressure drop of the CCL-laden air 101 flowing along the packing depth 106D.

[00226] Referring to FIG. 4, the stiffening elements 140 include one or more peripheral ribs 146. The peripheral ribs 146 are located on the body 132 adjacent to one or both of the leading and trailing edges 136A, 136B. The peripheral ribs 146 are stiffening bodies that reinforce or strengthen the body 132 along side portions of the packing sheet 130. For the packing sheet 130 of FIG. 4, the peripheral ribs 146 are located adjacent to one or both of the leading and trailing edges 136A, 136B at a distance measured from the corresponding leading or trailing edge 136A, 136B. The distance can be less than a third of the ATD 138D. In alternate implementations, one or more of the peripheral ribs 146 is located more than this distance inwardly on the body 132 from the leading or trailing edge 136A, 136B.

[00227] The packing sheet 130 of FIG. 4 includes peripheral stiffening bodies 148 and peripheral ribs 146, and the peripheral ribs 146 are positioned further inwardly on the body 132 from the leading and trailing edges 136A, 136B than the peripheral stiffening bodies 148. Referring to FIG. 4, the peripheral ribs 146 can be positioned adjacent each other along the LTD 138L and can be positioned adjacent each other along the ATD 138D, as described in greater detail below. Each peripheral rib 146 is an elongated body that extends in a direction parallel to the LTD 138L. Referring to FIGS. 4A, 4B and 4E, each peripheral rib 146 has an arcuate or semi-circular cross-sectional shape, where the cross-sectional shape is defined in a plane that is transverse to the LTD 138L.

[00228] Referring to FIG. 4, each peripheral rib 146 has an orientation that is substantially parallel to the leading edge 136A. In example implementations, an axis extends through multiple peripheral ribs 146 that are aligned along the LTD 138L, and the axis is substantially parallel to the vertical axis 135. In example implementations, the axis is substantially parallel to the leading edge 136A of the packing sheet 130.

[00229] Referring to FIGS. 4, 4 A, 4B and 4E, each peripheral rib 146 extends outwardly from one of the first and second sides 134A, 134B. Each peripheral rib 146 extends outwardly to a local maximum which defines a surface of the peripheral rib 146 that is located further from the plane of the body 132 than other portions of the peripheral rib 146. Each local maximum defines a surface of the peripheral rib 146 that is located further from the mass- transfer microstructures 133 than other portions of the peripheral rib 146. In the colour scheme of FIG. 4, the darker grey shading on the peripheral ribs 146 indicates that the shaded portion extends outwardly from the body 132 on the first side 134A, and the lighter grey shading on the peripheral ribs 146 indicates that the shaded portion extends outwardly from the body 132 on the second side 134B.

[00230] The peripheral ribs 146 are hollow bodies, such that they form corresponding depressions on the other side of the body 132 from which they extend. For example, and referring to FIGS. 4A and 4E, the peripheral ribs 146 extending outwardly from the first side 134A form a first set of depressions 146A on the second side 134B. Similarly, and referring to FIG. 4A, the peripheral ribs 146 extending outwardly from the second side 134B form a second set of depressions 146B on the first side 134A. The first and second sets of depressions 146A, 146B are grooves or recesses which extend into the body 132 in an extension direction that is transverse to the datum plane 132D. The first and second sets of depressions 146A, 146B have a thickness or height defined between the local maximum of the corresponding peripheral rib 146 and the datum plane 132D on the side 134A, 134B of the body 132 opposite to the side 134B, 134A on which the local maximum is located. Thus, each peripheral rib 146 forms a protrusion on one side 134A, 134B of the body 132 and an indentation on the other side 134B, 134A.

[00231] Referring to FIG. 4B, each peripheral rib 146 has a rib height 146H defined in a direction that is perpendicular to the datum plane 132D. The rib height 146H is measured relative to the datum plane 132D on the side 134A, 134B of the body 132 that is opposite to the side 134A, 134B on which the local maximum of the peripheral rib 146 is located. For example, in FIG. 4B, the rib height 146H is measured relative to the datum plane 132D on the first side 134A of the body 132 because the local maximum of the peripheral rib 146 is on the second side 134B of the body 132. Referring to FIG. 4B, the rib height 146H is greater than the microstructure height 133H, when both heights are measured from the same datum plane 132D. Referring to FIG. 4B, the rib height 146H is less than the spacer height 150H, when both heights are measured from the same datum plane 132D.

[00232] Referring to FIGS. 4B and 4D, the rib height 146H is less than the stiffening body height 142H, when both heights are measured from the same datum plane 132D. The height difference between the rib height 146H, the microstructure height 133H, the stiffening body height 142H, and the and spacer height 150H allows adjacent packing sheets 130 to be spaced apart sufficiently from each other so that both the CO2 capture solution 114 and the CCh-laden air 101 can flow between the adjacent packing sheets 130, when the adjacent packing sheets 130 are bonded together along their spacers 150 and/or their stiffening bodies 142. The peripheral ribs 146 protrude past the mass-transfer microstructures 133 into the flow of the CCL-laden air 101.

[00233] The peripheral ribs 146 can be arranged in any desired configuration on the packing sheet 130 to achieve the function(s) ascribed to the peripheral ribs 146 in the present disclosure. For example, and referring to FIG. 4, the peripheral ribs 146 include multiple leading edge ribs 146L which are located adjacent to the leading edge 136A of the body 132. The leading edge ribs 146L are arranged in two different sets of leading edge ribs 146L. The leading edge ribs 146L of the first set include innermost ribs 146L1, and the leading edge ribs 146L of the second set include outermost ribs 146L2. The outermost ribs 146L2 are spaced further from the leading edge 136A along the ATD 138D than the innermost ribs 146L1. The innermost ribs 146L1 are aligned with each other along the LTD 138L. The innermost ribs 146L1 have an orientation that is substantially parallel with the leading edge 136A. The outermost ribs 146L2 are aligned with each other along the LTD 138L. The outermost ribs 146L2 have an orientation that is substantially parallel with the leading edge 136A.

[00234] Referring to FIGS. 4 and 4 A, the innermost ribs 146L1 extend outwardly from the first side 134A of the body 132 and form corresponding depressions 146A in the second side 134B. Referring to FIGS. 4 and 4A, the outermost ribs 146L2 extend outwardly from the second side 134B of the body 132 and form corresponding depressions 146B in the first side 134A. In example implementations, and referring to FIG. 4, the innermost and outermost ribs 146L1, 146L2 are offset from each other in the LTD 138L. When the packing sheet 130 of FIG. 4 is part of a structured packing 116 intended for use in a cross-flow configuration, the upper and lower ends of each of the innermost and outermost ribs 146L1, 146L2 are vertically misaligned. When the packing sheet 130 of FIG. 4 is part of a structured packing 116 intended for use in a cross-flow configuration, portions of the innermost/outermost ribs 146L1, 146L2 vertically overlap with the upper and lower ends of the outermost/innermost ribs 146L2, 146L1. [00235] Another possible configuration of the peripheral ribs 146 is shown in FIG. 4. The peripheral ribs 146 includes multiple trailing edge ribs 146T which are located adjacent to the trailing edge 136B of the body 132. The trailing edge ribs 146T are arranged in two different sets of trailing edge ribs 146T. The trailing edge ribs 146T include a third set of ribs 146T3 and a fourth set of ribs 146T4. The fourth set of ribs 146T4 are spaced further from the trailing edge 136B along the ATD 138D than the third set of ribs 146T3. The third set of ribs 146T3 are aligned with each other along the LTD 138L. The third set of ribs 146T3 have an orientation that is substantially parallel with the trailing edge 136B. The fourth set of ribs 146T4 are aligned with each other along the LTD 138L. The fourth set of ribs 146T4 have an orientation that is substantially parallel with the trailing edge 136B. Referring to FIG. 4, the third set of ribs 146T3 (the trailing edge ribs 146T closest to the trailing edge 136B) extend outwardly from the first side 134A of the body 132 and form corresponding depressions 146A in the second side 134B, as shown in FIG. 4 with the darker grey shading. The fourth set of ribs 146T4 (the trailing edge ribs 146T furthest from the trailing edge 136B) extend outwardly from the second side 134B of the body 132 and form corresponding depressions 146B in the first side 134A, as shown in FIG. 4 with the lighter grey shading. In example implementations, and referring to FIG. 4, the third and fourth sets of ribs 146T3, 146T4 are offset from each other in the LTD 138L.

[00236] When the packing sheet 130 of FIG. 4 is part of a structured packing 116 intended for use in a cross-flow configuration, the upper and lower ends of each of the third and fourth sets of ribs 146T3, 146T4 are vertically misaligned. When the packing sheet 130 of FIG. 4 is part of a structured packing 116 intended for use in a cross-flow configuration, portions of the third/fourth sets of ribs 146T3, 146T4 vertically overlap with the upper and lower ends of the fourth/third sets of ribs 146T4, 146T3.

[00237] The peripheral ribs 146 can be spaced apart from each other to optimise the surface area of the mass-transfer zone 131 that is available for CO2 to be absorbed into the CO2 capture solution 114. For example, and referring to FIG. 4, the peripheral ribs 146 include one or more longitudinal rib pairings 146C. The two peripheral ribs 146 of each longitudinal rib pairing 146C are spaced apart from each other in a direction that is parallel to the LTD 138L. A longitudinal pairing gap 146G1 is defined between the two peripheral ribs 146 of each longitudinal rib pairing 146C.

[00238] Referring to FIG. 4, the mass-transfer microstructures 133 are present in the longitudinal pairing gap 146G1. The mass-transfer microstructures 133 in the longitudinal pairing gap 146G1 are shown with respect to only the third set of ribs 146T3 in FIG. 4 for the purposes of simplicity, it being understood that the packing sheet 130 can have multiple longitudinal pairing gaps 146G1. The peripheral ribs 146 of the packing sheet 130 of FIG. 4 are discontinuous in the liquid travel dimension LTD 138L. The peripheral ribs 146 of the packing sheet 130 of FIG. 4 are spaced apart in the liquid travel dimension LTD 138L by masstransfer microstructures 133. The longitudinal pairing gaps 146G1 are the same size in the packing sheet 130 of FIG. 4. In alternate implementations, the longitudinal pairing gaps 146G1 are different sizes in the same packing sheet 130 of FIG. 4. [00239] The peripheral ribs 146 can also be spaced apart in a direction parallel to the ATD 138D, to optimise the surface area of the mass-transfer zone 131 that is available for CO2 to be absorbed into the CO2 capture solution 114. For example, and referring to FIG. 4, the peripheral ribs 146 include one or more lateral rib pairings 146D. The two peripheral ribs 146 of each lateral rib pairing 146D are spaced apart from each other in a direction that is parallel to the ATD 138D. A lateral pairing gap 146G2 is defined between the two peripheral ribs 146 of each lateral rib pairing 146D. Referring to FIG. 4, the mass-transfer microstructures 133 are present in the lateral pairing gap 146G2. The mass-transfer microstructures 133 in the lateral pairing gap 146G2 are shown with respect to only two trailing edge ribs 146T in FIG. 4 for the purposes of simplicity, it being understood that the packing sheet 130 can have multiple lateral pairing gaps 146G2. The lateral pairing gap 146G2 has a longitudinal extent defined along the LTD 138L.

[00240] In FIG. 4, the same mass-transfer microstructures 133 are present in both of the longitudinal pairing gaps 146G1 and lateral pairing gaps 146G2. In alternate implementations, the mass-transfer microstructures 133 can be different in the longitudinal pairing gaps 146G1 and lateral pairing gaps 146G2. In example implementations, the mass-transfer microstructures 133 can be different among the longitudinal pairing gaps 146G1 of the same packing sheet 130, or among the lateral pairing gaps 146G2 of the same packing sheet 130.

[00241] Another possible implementation of the packing sheet 630 is shown in FIG. 6. The stiffening elements 640 of the packing sheet 630 include intermediate ribs 646. The intermediate ribs 646 are located on the body 632 between the leading edge 636A and the trailing edge 636B. The intermediate ribs 646 are located along the middle of the body 632 between the leading and trailing edges 636A, 636B, at a position from the leading edge 636A that is half of the ATD 138D. The intermediate ribs 646 are located along the middle of the body 632 between spacers 150 on either side of the intermediate ribs 646 in the ATD 138D. A first set of intermediate ribs 646A are spaced apart from each other, and aligned, in a direction parallel to the LTD 138L. A second set of intermediate ribs 646B are also spaced apart from each other, and aligned, in a direction parallel to the LTD 138L. The second set of intermediate ribs 646B is spaced apart from the first set of intermediate ribs 646A in a direction parallel to the ATD 138D. The mass-transfer microstructures 133 are present in the spaces between the intermediate ribs 646. The first set of intermediate ribs 646A extend outwardly from the first side 634A of the body 632 and form corresponding depressions in the second side 634B. The second set of intermediate ribs 646B extend outwardly from the second side 634B and form corresponding depressions in the first side 634A. These protrusions and depressions of the intermediate ribs 646 are shown with the grey shading colour scheme of FIG. 6.

[00242] When the packing sheet 630 of FIG. 6 is part of a structured packing 116 intended for use in a cross-flow configuration, portions of the first and second sets of intermediate ribs 646A, 646B vertically overlap. Each intermediate rib 646 of the first set of intermediate ribs 646A has a first rib end 647A and a second rib end 647B that is spaced apart from the first rib end 647A in a direction parallel to the LTD 138L. The first rib end 647A is located closer to the upper edge 636U of the body 632 than the second rib end 647B. Each intermediate rib 646 of the second set of intermediate ribs 646B has a third rib end 647C and a fourth rib end 647D that is spaced apart from the third rib end 647C in a direction parallel to the LTD 138L. The third rib end 647C is located closer to the upper edge 636U of the body 632 than the fourth rib end 647D. The third rib end 647C of one or more of the second set of ribs 646B is positioned vertically between the first rib end 647A and the second rib end 647B of one of the first set of ribs 646 A. The fourth rib end 647D of one or more of the second set of ribs 646B is positioned vertically between the first rib end 647A and the second rib end647B of one of the first set of ribs 646A.

[00243] In at least example implementations, the intermediate ribs 646 are stiffening elements 640 that overlap in the middle of the depth of the packing sheet 630, which can help to reinforce or strengthen the packing sheet 630 against loads. The description, features, and advantages of the present disclosure that are associated with the packing sheet 130 of the preceding figures apply mutatis mutandis to the packing sheet 630 of FIG. 6. For example, the height of the intermediate ribs 646, which is measured similarly to the heights 133H, 142H, 150H described above, can be less than a height of the peripheral stiffening bodies 148. The description, features, and advantages of the present disclosure that are associated with the peripheral ribs 146 apply mutatis mutandis to the intermediate ribs 646 of FIG. 6.

[00244] The spacers 150 and stiffening elements 140, 640 of the packing sheet 130, 630 described above and illustrated in the figures can be present, or absent, in any combination to provide any desired configuration of the packing sheet 130, 630, the structured packing 116 and/or the packing section 106.

[00245] Another possible configuration of a packing sheet with an approximately zero degree offset angle A is shown in FIGS. 7 and 7A. The packing sheet 730 of FIGS. 7 and 7A includes one or more stiffening elements 740. In contrast to the stiffening elements 140, 640 described previously which are protrusions from the surface of the body 132, 632 of the packing sheet 130, 630, the stiffening elements 740 of the packing sheet 730 form the body 732 itself. [00246] Referring to FIGS. 7 and 7A, each stiffening element 740 is a localised deviation from a plane defined by a remaining portion of the body 732 that does not include the stiffening elements 740. The out-of-plane stiffening elements 740 provide the packing sheet 730 with a wavy or sinusoidal shape in the cross-sectional view of FIG. 7 A. The mass-transfer zone 131 and the mass-transfer microstructures 133 are present along all or some of the extent of the stiffening elements 740, such that the stiffening elements 740 define part of the reactive surface area of the packing sheet 730 that contributes to capturing CO2 from the CCh-laden air 101. The stiffening elements 740 help to reinforce or strengthen the body 732 against anticipated loads on the packing sheet 730. By forming the body 732 of the packing sheet 730, the stiffening elements 740 help to strengthen the packing sheet 730 while having a minimal impact, if any, on the pressure drop of the CCh-laden air 101 flowing through a structured packing 116 formed from the packing sheets 730. In example implementations, the packing sheet 730 can be further stiffened by the material of construction (MOC) of the packing sheet 730. The description, features, and advantages of the present disclosure that are associated with the packing sheet 130, 630 of the preceding figures apply mutatis mutandis to the packing sheet 730 of FIG. 7.

[00247] Another possible configuration of a packing sheet with an approximately zero degree offset angle A is shown in FIGS. 8 to 8C. The packing sheet 830 of FIGS. 8 to 8C includes reinforcement bodies 842. The reinforcement bodies 842 are another implementation of the stiffening elements 140,640 of the present disclosure, and can be present on a packing sheet 130, 630, 730, 830 in any combination with the stiffening elements 140, 640 of the present disclosure. The reinforcement bodies 842 extend outwardly from both of the first and second sides 834A, 834B of the packing sheet 830. In the colour scheme of FIGS. 8 to 8B, the darker grey shading on the reinforcement bodies 842 indicates that the shaded portion of the reinforcement bodies 842 extends outwardly from the body 832 of the packing sheet 830 on the first side 834A, and the lighter grey shading on the reinforcement bodies 842 indicates that the shaded portion of the reinforcement bodies 842 extends outwardly from the body 832 on the second side 834B. The reinforcement bodies 842 of FIGS. 8 to 8C form structures similar to those of the intermediate stiffening bodies 142A of FIG. 5, where each structure has four planar walls 842P extending outwardly from one of the first and second sides 834A, 834B to the attachment wall 842B on the same side 834A, 834B (see, for example, FIGS. 8A to 8B2). [00248] The description, features, reference numbers, and advantages of the present disclosure that are associated with the intermediate stiffening bodies 142A apply mutatis mutandis to the reinforcement bodies 842 of FIGS. 8 to 8C. For example, like the intermediate stiffening bodies 142 A, the reinforcement bodies 842 are hollow and form corresponding depressions on the other (e.g., opposite) side of the body 832 from which they extend. In the configuration of the reinforcement bodies 842 of FIG. 8, the depressions and extensions on one side of the body 832 alternate with each other along a direction that is parallel to the ATD 138D. In alternate implementations, the reinforcement bodies 842 have a different shape, geometry and/or configuration than the intermediate stiffening bodies 142A.

[00249] Each reinforcement body 842 is an elongated body that has a predominant dimension defined parallel to the ATD 138D. Each reinforcement body 842 has a width defined parallel to the ATD 138D that is longer than its length defined parallel to the LTD 138L. The reinforcement bodies 842 are positioned adjacent each other along the ATD 138D. The reinforcement bodies 842 are positioned between the leading and trailing edges 836A, 836B of the packing sheet 830, to form a row of reinforcement bodies 842 that is parallel to the ATD 138D. The reinforcement bodies 842 help to strengthen the packing sheet 830, by supporting it against lateral or bending loads caused by the weight of the packing sheet 830 itself or of other packing sheets 830 bonded thereto, the liquid hold up of the CO2 capture solution 114 on the packing sheet 830, any scaling present on the packing sheet 830, and/or other loads. As described in greater detail below, portions of the reinforcement bodies 842 are bonded to corresponding portions of the reinforcement bodies 842 of an adjacent packing sheet

830 when two packing sheets 830 are attached together, which can help reinforce the bonded packing sheets 830 and help prevent their collapse toward each other in regions of the packing sheets 830 where there is a relatively large distance between bonded supports. The reinforcement bodies 842 can thus be any structures that can support the loads described herein. The reinforcement bodies 842 can have any arrangement, number, location, form, shape or size to achieve the functionality ascribed to them herein. In example implementations, and referring to FIG. 8, the reinforcement bodies 842 are disposed on, or adjacent to, the mass-transfer zone

831 and its mass-transfer microstructures 133.

[00250] Referring to FIG. 8, the reinforcement bodies 842 form a continuous or uninterrupted row of reinforcement bodies 842 extending fully between the leading and trailing edges 836 A, 836B. In alternate implementations, the reinforcement bodies 842 form a discontinuous or interrupted row of reinforcement bodies 842 between the leading and trailing edges 836 A, 836B. In example implementations, and referring to FIG. 8, the reinforcement bodies 842 are free of mass-transfer microstructures 133.

[00251] The reinforcement bodies 842 can be present in any arrangement along the packing sheet 830. For example, and referring to FIG. 8, the reinforcement bodies 842 include middle reinforcement bodies 842M which form a middle row 844M, and edge reinforcement bodies 842E which form an upper row 844U and a lower row 844L. The middle, upper and lower rows 844M, 844U, 844L are distinct arrangements of reinforcement bodies 842, and are separated from each other along the LTD 138L. The edge reinforcement bodies 842E of the upper row 844U define some or all of the upper edge 836U. The edge reinforcement bodies 842E of the lower row 844L define some or all of the lower edge 836L. When adjacent packing sheets 830 are bonded together along the edge reinforcement bodies 842E of the upper and lower rows 844U, 844L, the horizontally-extending upper and lower rows 844U, 844L help to maintain sheet stability along the upper and lower edges 836U, 836L of the packing sheet 830. A horizontal honeycomb feature at the top and bottom of the packing sheet 830, in its installed configuration, can help to provide more stable upper and lower edges 836U, 836L of a structured packing 116 formed from bonded packing sheets 830, and can help to better translate bottom-supported loads into the packing sheets 830 of the structured packing 116.

[00252] The middle reinforcement bodies 842M of the middle row 844M are disposed between the upper and lower edges 836U, 836L of the packing sheet 830. In example implementations, and referring to FIG. 8, the middle row 844M of middle reinforcement bodies 842M extends across a vertical middle of the packing sheet 830, where the vertical middle is defined as half the distance between the upper and lower edges 836U, 836L. In example implementations, and referring to FIG. 8, the middle row 844M of middle reinforcement bodies 842M extends through the centroid 132C of the packing sheet 830. In example implementations, the middle row 844M of middle reinforcement bodies 842M is offset from the vertical middle and positioned between the upper and lower edges 836U, 836L. In example implementations, the packing sheet 830 includes multiple middle rows 844M of middle reinforcement bodies 842M extending parallel to the ATD 138D and positioned between the upper and lower edges 836U, 836L. The middle reinforcement bodies 842M of the middle row 844M each have a greater length than the length of each of the edge reinforcement bodies 842E of both the upper and lower rows 844U, 844L, where the lengths of the middle reinforcement bodies 842M and the edge reinforcement bodies 842E are measured parallel to the LTD 138L. [00253] In example implementations, the middle reinforcement bodies 842M have a length that is twice the length of the edge reinforcement bodies 842E. In example implementations, removing a vertical half of one of the middle reinforcement bodies 842M provides a shape which corresponds to the shape of one of the edge reinforcement bodies 842E. The similarities in shapes between the middle and edge reinforcement bodies 842M, 842E can result from the indexing interval of the tool used to form the packing sheet 830. In some embodiments, and referring to FIG. 8, the packing sheet 830 has a middle row 844M of middle reinforcement bodies 842M and edge reinforcement bodies 842E on both the upper and lower rows 844U, 844L. In alternate implementations, the packing sheet 830 is free of a middle row 844M of middle reinforcement bodies 842M yet still includes the edge reinforcement bodies 842E of both the upper and lower rows 844U, 844L. In alternate implementations, the packing sheet 830 is free of a middle row 844M of middle reinforcement bodies 842M yet still includes the edge reinforcement bodies 842E of one of the upper and lower rows 844U, 844L.

[00254] The packing sheet 830 can be cut or sectioned through a vertical midpoint of the middle reinforcement bodies 842M of the middle row 844M to form packing sheets 830 of desirable sizes that can be vertically aligned with the upper or lower edges 836U, 836L of an adjacent packing sheet 830 (e.g., stacking one packing sheet 830 on top of another along their abutting edges 836U, 836L). In an example implementation where the packing sheet 830 of FIG. 8 has a length of 4 feet measured from a horizontal datum along a direction parallel to the LTD 138L, and the middle row 844M has a length of 2 feet measured from the horizontal datum, the packing sheet 830 can be sectioned along the middle row 844M to produce two packing sheets 830 each with a length of 2 feet. Sectioning the middle reinforcement bodies 842M of the middle row 844M forms upper or lower rows 844U, 844L of edge reinforcement bodies 842E, such that the resulting two packing sheets 830 have no middle row 844M of middle reinforcement bodies 842M. Each of the two 2-ft packing sheets 830 can be bonded to similarly-sized packing sheets 830 along the attachment walls 842B of the edge reinforcement bodies 842E to form a structured packing 116 with a length of 2 feet. Thus, in example implementations, the packing sheet is a sectioned version of the packing sheet 830 of FIG. 8 and is free of a middle row 844M of middle reinforcement bodies 842M.

[00255] In addition to their structural function, the reinforcement bodies 842 arranged across the ATD 138D can also help, or can have features which help, to redistribute some the CO2 capture solution 114 that flows in the LTD 138L along the packing sheet 830, or between packing sheets 830 abutted along the LTD 138L. The reinforcement bodies 842 can help to intercept and disrupt streams or rivulets of the CO2 capture solution 114 that can form in the LTD 138L, thereby helping to prevent such rivulets from forming, from being transmitted along the packing sheet 830, or from flowing between vertically-adjacent packing sheets 830. The reinforcement bodies 842 can help to disperse the CO2 capture solution 114 into the masstransfer zone 831 and its mass-transfer microstructures 133.

[00256] Some of the features of the reinforcement bodies 842 which can disrupt or divert rivulets of the CO2 capture solution 114 are now described in greater detail with reference to FIGS. 8A to 8C. For example, FIG. 8A shows an enlarged view of one of the middle reinforcement bodies 842M in the region VIIIA in FIG. 8. Referring to FIGS. 8A and 8A1, the middle reinforcement body 842M has one or more lateral flow channels 842L. Each lateral flow channel 842L functions to divert or guide the CO2 capture solution 114 in a direction transverse to the LTD 138L and away from the attachment wall 842B. Each lateral flow channel 842L thus has an inlet end and an outlet end, where the inlet end is closer (e.g., relative to a direction parallel to the ATD 138D) to the attachment wall 842B than the outlet end. Each lateral flow channel 842L can have any shape, orientation, or arrangement on the middle reinforcement body 842M to achieve this function.

[00257] For example, and referring to FIG. 8 A, the lateral flow channel 842L extends along a direction parallel to the ATD 138D on some of the planar walls 842P of the middle reinforcement body 842M. Referring to FIG. 8A, the two planar walls 842P of the middle reinforcement body 842M which are separated from each other in the ATD 138D by the attachment wall 842B have lateral flow channels 842L. Each of these planar walls 842P has two lateral flow channels 842L which are spaced apart from each other in the LTD 138L. The other two planar walls 842P of the middle reinforcement body 842M are free of lateral flow channels 842L.

[00258] FIG. 8B shows an enlarged view of one of the edge reinforcement bodies 842E in the region VIIIB in FIG. 8. Referring to FIGS. 8B, 8B1 and 8C, the two planar walls 842P of the edge reinforcement body 842E which are separated from each other in the ATD 138D by the attachment wall 842B have lateral flow channels 842L. Each of these planar walls 842P has one lateral flow channel 842L. The other two planar walls 842P of the edge reinforcement body 842E are free of lateral flow channels 842L. In example implementations, there are more than two flow channels 842L on the planar walls 842P having flow channels 842L.

[00259] Referring to FIGS. 8A, 8A1, 8B, 8B1 and 8C, each lateral flow channel 842L extends into its planar wall 842P, forming a groove on one side of the body 832 of the packing sheet 830 (e.g., on the first side 834A) and a protrusion on the other side of the body 832 (e.g., on the second side 834B). Referring to FIG. 8C, each lateral flow channel 842L extends between the attachment walls 842B (see FIG. 8C) of laterally-adjacent reinforcement bodies 842. In example implementations, the height or thickness of the lateral flow channels 842L is measured in a direction perpendicular to the plane of the corresponding planar wall 842P. The CO2 capture solution 114 flowing in the LTD 138L can encounter a flow obstruction at the bonded attachment walls 842B of adjacent packing sheets 830, and the lateral flow channels 842L can help to minimize channeling, rivulet-formation, and/or streaming of the CO2 capture solution 114 in this location by diverting at least some of the CO2 capture solution 114 away from the bonded attachment walls 842B and along the sloped planar walls 842P. The description, features, and advantages of the present disclosure that are associated with the lateral flow channels 142L, 142LA of the preceding figures apply mutatis mutandis to the lateral flow channels 842L of FIGS. 8 to 8C.

[00260] One or both of the middle reinforcement bodies 842M and the edge reinforcement bodies 842E can include other features to assist with diverting the flow of CO2 capture solution 114 around the bonded attachment walls 842B of adjacent packing sheets 830. For example, and referring to FIGS. 8A, 8A2, 8B, 8B2 and 8C, one or more of the planar walls 842P can include a stepped member 850. The stepped member 850 can form a disconnected and segmented rib along the edge of the mass-transfer zone 831 to help direct CO2 capture solution 114 around the bonded attachment walls 842B and minimize streaming of the CO2 capture solution 114. Referring to FIGS. 8A and 8A2, the two planar walls 842P of the middle reinforcement body 842M which are separated from each other in the LTD 138L by the attachment wall 842B have stepped members 850. Each of these planar walls 842P has one step feature (or member) 850. The other two planar walls 842P of the middle reinforcement body 842M are free of stepped members 850. The stepped member 850 includes a plurality of sloped segments. The stepped member 850 includes a first wall segment 852 that extends from the attachment wall 842B and has a first slope that is different from the slope of the attachment wall. The stepped member 850 includes a second wall segment 854 that extends from the first wall segment 852 and has a second slope different from the first slope of the fist wall segment 852. The stepped member 850 includes a third wall segment 856 that extends from the second wall segment 854 and has a third slope different from the second slope of the second wall segment 854. The attachment slope and first, second and third slopes are defined in the same cross-sectional plane and shown in FIG. 8A2.

[00261] In the implementation of the stepped member 850 of FIG. 8A2, the second slope of the second wall segment 854 is less than the both the first and third slopes and is greater than the slope of the attachment wall 842B. In another implementation, one or more of the first, second and third wall segments 852, 854, 856 have a curved sloped. The stepped member 850 of the edge reinforcement body 842E of FIGS. 8B, 8B2 and 8C is described similarly, mutatis mutandis. In example implementations, and referring to FIGS. 8 A to 8C, a middle reinforcement body 842M and/or an edge reinforcement body 842E includes both the stepped member 850 and at least one lateral flow channel 842L to assist with diverting the flow of CO2 capture solution 114 around the bonded attachment walls 842B of adjacent packing sheets 830. In another implementation, a middle reinforcement body 842M and/or an edge reinforcement body 842E includes one of the stepped member 850 and at least one lateral flow channel 842L to assist with diverting the flow of CO2 capture solution 114 around the bonded attachment walls 842B.

[00262] The description, features, and advantages of the present disclosure that are associated with the packing sheet 130, 630, 730 of the preceding figures apply mutatis mutandis to the packing sheet 830 of FIGS. 8 to 8C.

[00263] FIG. 9 is a perspective view of a recessed body 960 of the packing sheet 130, 630, 730, 830 of the present disclosure. The recessed body 960 is an elongated body that has a predominant dimension defined parallel to the LTD 138L. The recessed body 960 has a length defined substantially parallel to the LTD 138L that is longer than its width defined parallel to the ATD 138D. The recessed body 960 is positioned below one of the edge reinforcement bodies 842E in the lateral middle of the packing sheet 130, 630, 730, 830, near the upper edge 136U, 636U, 836U of the packing sheet 130, 630, 730, 830. The recessed body 960 can assist in forming the packing sheet 130, 630, 730, 830, for example by helping with indexing when using a forming tool like a stamping mold. The recessed body 960 has a height that is greater than the microstructure height 133H and that is less than the spacer height 150H. The recessed body 960 has a height that is less than the stiffening body height 142H. The heights of the recessed body 960, microstructure height 133H, spacer height 150H, and stiffening body height 142H described herein are measured from the same datum. When two packing sheets 130, 630, 730, 830 are bonded to each other and define airflow channels or flutes between the pair of bonded packing sheets 130, 630, 730, 830, the recessed bodies 960 of both packing sheets 130, 630, 730, 830 are spaced from each other and delimit part of the airflow channels or flutes. In example implementations, and referring to FIG. 9, the recessed body 960 is free of mass-transfer microstructures 133. In example implementations, the recessed body 960 has a smooth, planar surface.

[00264] The packing sheets 130, 630, 730, 830 can be arranged to form a structured packing 116 having any shape, such as a block, a column, a cube, or other suitable shape. Each structured packing 116 can sometimes be referred to as a “fill pack.” In example implementations, and referring to FIG. 10, the packing sheets 130, 630, 730, 830 (referred to below as “packing sheet 130” or “packing sheets 130” for simplicity) are attached together to form a structured packing 116 that is self-supporting such that the structured packing 116 has the ability to remain upright and assembled without being supported by something else. One or more packing sheets 130 of each structured packing 116 can be mounted to, or supported by, one or both of: 1) a structural member 115 of the housing 102, and 2) at least one other packing sheet 130 of another structured packing 116.

[00265] In the structured packing 116 of FIG. 10, all the packing sheets 130 are identical. In alternate implementations, one or more of the packing sheets 130 of the structured packing 116 is different from another packing sheet 130 of the structured packing 116. In one example of such an alternate implementation of the structured packing 116, one or more of the packing sheets 130 has no stiffening elements 140, 640, 740 and is optimised for minimal pressure drop, while another one of the packing sheets 130 has one or more stiffening elements 140, 640, 740 to strengthen the structured packing 116. The assembly of the packing sheets 130 into the structured packing 116 helps the structured packing 116 to meet loading requirements, such as crush strength requirements, in which the structured packing 116 is exposed to a crush test whose purpose is to simulate the different loads (e.g., liquid loading, liquid hold-up, fouling/scaling, weight of structured packing 116 itself) to which the structured packing 116 can be exposed during operation of the gas-liquid contactor 100, 100 A, 100B.

[00266] Referring to FIG. 11, the leading edges 136A of the packing sheets 130 are substantially parallel to the vertical axis 135, thereby providing the structured packing 116 with the additional leading edge surface area 139 described above and the associated advantages. FIG. 12 shows attached packing sheets 130 which are adjacent to each other and spaced apart from each other in a direction perpendicular to both the ATD 138D and the LTD 138L. The adjacent packing sheets 130 are attached along the abutment surfaces 152 of their spacers 150. The adjacent packing sheets 130 can also be attached together using other features, such as one or more of the stiffening elements 140, 640.

[00267] For example, and referring to FIG. 12, the intermediate stiffening bodies 142A of one or more packing sheets 130 are attached to the intermediate stiffening bodies 142 A of other packing sheets 130 via their abutted attachment walls 142B. In FIG. 12, the attachment wall 142B on the first side 134A of a packing sheet 130 abuts against the attachment wall 142B on the second side 134B of the adjacent packing sheet 130. These features space the adjacent packing sheets 130 apart such that an airflow channel 160 or flute is defined between a pair of adjacent packing sheets 130. The airflow channels 160 can thus be defined by touch points between adjacent packing sheets 130. Each airflow channel 160 is delimited by the surfaces and features of the adjacent packing sheets 130 and defines a volume extending in both the ATD 138D and the LTD 138L. The CCL-laden air 101 flows through each airflow channel 160 from the leading edge 136A to the trailing edge 136B of the adjacent packing sheets 130. [00268] Referring to FIG. 12, each airflow channel 160 is continuous or uninterrupted along the ATD 138D and along the LTD 138L, from the leading edge 136A to the trailing edge 136B of the adjacent packing sheets 130. In example implementations, one or more of the airflow channels 160 has a channel shape 160S. The channel shape 160S is defined in a plane that is normal to the LTD 138L. In example implementations, the channel shape 160S is rectangular along the entire extent of the airflow channel 160, as shown with grey shading in FIG. 12. In example implementations, and referring to FIG. 12, the structured packing 116 is composed of planar or straight packing sheets 130. In example implementations, and referring to FIG. 12, the structured packing 116 is free of corrugations in its packing sheets 130 and is free of wave-like or corrugated channel shapes 160S between its packing sheets 130.

[00269] Referring to FIG. 12, a sheet spacing 160H of the packing sheets 130 of the structured packing 116 can be defined. The sheet spacing 160H also defines a “width” or extent of each airflow channel 160. The sheet spacing 160H is defined as the extent between a pair of adjacent packing sheets 130 and is measured in a plane that is normal to the LTD 138L. The sheet spacing 160H can vary along the ATD 138B and along the LTD 138L because of the presence of features of the adjacent packing sheets 130 (e.g., the stiffening elements 140 and the spacers 150). In example implementations, the sheet spacing 160H is defined along a portion of the ATD 138B and/or the LTD 138L between the mass-transfer microstructures 133 of the adjacent packing sheets 130. In example implementations, the sheet spacing 160H is greater than each of the microstructure height 133H, the spacer height 150H and the stiffening body height 142H of one of the packing sheets 130 of the pair of packing sheets 130 which delimit the airflow channel 160. In example implementations, and referring to FIG. 12, the sheet spacing 160H is substantially uniform between all pairs of adjacent packing sheets 130 that make up the structured packing 116.

[00270] In alternate implementations, the sheet spacing 160H between a first pair of packing sheets 130 of the structured packing 116 can be different than the sheet spacing 160H between at least another pair of the packing sheets 130 of the same structured packing 116. Some possible and non-limiting examples of dimensions for the sheet spacing 160H include 5/8 in. (1.587 cm) to 1.5 in. (3.81 cm). The number of packing sheets 130 within each structured packing 116, as well as their sheet spacing 160H within the structured packing 116, can be varied to provide the structured packing 116 with the desired sheet density and performance characteristics.

[00271] When a pair of adjacent packing sheets 130 are attached along the attachment walls 142B of their intermediate stiffening bodies 142A to form joints, the joints can obstruct the flow of the CO2 capture solution 114 in the LTD 138L. The planar walls 142P of the intermediate stiffening bodies 142A can therefore have one or more flow channels, such as the longitudinal or lateral flow channels 142F, 142L described above. The flow channels can extend from the joined attachment walls 142B and help to reduce liquid pooling along the joints between the adjacent packing sheets 130. The description, features, and advantages of the present disclosure that are associated with the longitudinal or lateral flow channels 142F, 142L of the peripheral stiffening bodies 148 apply mutatis mutandis to flow channels of the intermediate stiffening bodies 142 A.

[00272] The airflow channels 160 can extend around the planar and attachment walls 142P, 142B of some of the intermediate stiffening bodies 142 A. The intermediate stiffening bodies 142A of the first set 142C extend outwardly from the first side 134A of the body 132, and thus form corresponding depressions 144A on the second side 134B. The intermediate stiffening bodies 142A of the second set 142D extend outwardly from the second side 134B of the body 132, and thus form corresponding depressions 144B on the first side 134A. The depressions 144 A, 144B of attached packing sheets 130 face each other across the sheet spacing 160H and are aligned along the LTD 138L. The airflow channels 160 extend through, and are partially defined by, the spaces between the facing depressions 144 A, 144B of the pair of attached packing sheets 130. The airflow channels 160 detour around the attached attachment walls 142B of the intermediate stiffening bodies 142A.

[00273] The peripheral stiffening bodies 148 can similarly contribute to the size, shape and configuration of the airflow channels 160. For example, and referring to FIG. 11, the peripheral stiffening bodies 148 of each packing sheet 130 extend outwardly from one of the first and second sides 134A, 134B, and form corresponding depressions 148D in the other of the first and second sides 134A, 134B. In example implementations, a first set of peripheral stiffening bodies 148 alternates along an axis on the first side 134A with a second set of depressions, and a second set of peripheral stiffening bodies 148 alternates along the axis on the second side 134B with a first set of depressions. Adjacent packing sheets 130 are joined along the attachment walls of their peripheral stiffening bodies 148, with the attachment walls on the first side 134A of one packing sheet 130 joined to the attachment walls on the second side 134B of the adjacent packing sheet 130. Peripheral stiffening body flow passages 148F are formed between the aligned depressions 148D of the adjacent packing sheets 130. The peripheral stiffening body flow passages 148F are in fluid communication with the airflow channels 160, such that the CCh-laden air 101 first enters the structured packing 116 via the peripheral stiffening body flow passages 148F, and then flows through the airflow channels 160. The peripheral stiffening body flow passages 148F can be defined or delimited by the abutting peripheral stiffening bodies 148. In example implementations, adjacent packing sheets 130 are only joined along their peripheral stiffening bodies 148.

[00274] When adjacent packing sheets 130 are bonded along the attachment walls 142B of their intermediate stiffening bodies 142A and/or of their peripheral stiffening bodies 148, the bonded stiffening bodies 142A, 148 form a honeycomb or hexagonal shape when the adjacent packing sheets 130 are viewed from one of the edges 136A, 136B, 136L, 136U, as shown in FIGS. 10 to 12. In other implementations of the bonded stiffening bodies 142A, 148 in which the bonded stiffening bodies 142A, 148 have one or more curved walls which form a sinusoidal shape in a sectional view, as described above, the stiffening bodies 142 A, 148 can be bonded along an attachment point of a curved slope, such that the bonded stiffening bodies 142A, 148 form a non-planar shape when the adjacent packing sheets 130 are viewed from one of the edges 136A, 136B, 136L, 136U.

[00275] In an example implementation of the stiffening bodies 142 A, 148 having one or more curved walls which form a sinusoidal shape, the stiffening bodies 142A, 148 can be bonded along some or all of the extent of a curved wall. The stiffening bodies 142A, 148 of FIGS. 10 to 12 are bonded such that their “peaks” (e.g., their attachment walls 142B) are aligned with those of the adjacent packing sheet 130. In other possible implementations, the stiffening bodies 142A, 148 are bonded such that their maxima and minima are misaligned with those of the adjacent packing sheet 130. This paragraph applies mutatis mutandis to the reinforcement bodies 842 of FIGS. 8 to 8C.

[00276] Features of the packing sheet 130, 630, 730, 830 can allow for increased masstransfer capture efficiency. Features of the packing sheet 130, 630, 730, 830 can reduce the pressure drop experienced by the CCh-laden air 101 flowing across the packing sheet 130, 630, 730, 830. For a given pressure drop tolerance across the packing section 106, features of the packing sheet 130, 630, 730, 830 can allow for improved overall performance such that the ATD 138D can be reduced, which could allow for one or more of the following advantages: a shorter gas-liquid contactor 100, 100 A, 100B with reduced pumping requirements for CO2 capture solution 114, a smaller footprint for the gas-liquid contactor 100, 100A, 100B, lower energy requirements for operating the fan 212, and/or additional drift elimination to be added (if necessary) without significant pressure drop penalty.

[00277] Any packing sheet 130, 630, 730, 830 features described herein or illustrated in the figures can be present, or absent, in any combination to provide any desired configuration of the packing sheet 130, 630, 730, 830, the structured packing 116 and/or the packing section 106. For example, the packing sheet 130, 630, 730, 830 can be free of a stiffening element 140, 640, 740, 842 (which can also be referred to as a reinforcement body) in the middle of the packing sheet 130, 630, 730, 830 along the ATD 138D. According to another example, features that help with diverting or dispersing CO2 capture solution 114 to the mass-transfer microstructures 133 can be present or absent, in any combination, on one or more of the stiffening elements (or reinforcement bodies) 140, 640, 740, 842.

[00278] Referring to FIG. 15, the gas-liquid contactor 100, 100A, 100B, with the structured packing 116 and its packing sheets 130, 630, 730, 830 disclosed herein is part of a direct-air-capture (DAC) system 1200 for capturing CO2 directly from atmospheric air, according to one possible and non-limiting example of a use for the gas-liquid contactor 100, 100A, 100B. One or multiple gas-liquid contactor(s) 100, 100A, 100B absorb some of the CO2 from the CO2-laden air 101 using the CO2 capture solution 114 to form the CO2-laden capture solution 111. The CO2 capture solution 114 can need to be regenerated from the 002- laden capture solution 111, which can be carried out in a regeneration system 1230 of the DAC system 1200. The regeneration system 1230 functions to process the CO2-laden capture solution 111 (e.g., spent capture solution) to recover and/or concentrate the CO2 content laden in the CO2-laden capture solution 111.

[00279] The CCh-laden capture solution 111 flows from the gas-liquid contactor 100, 100A, 100B to a pellet reactor 1210 of the DAC system 1200. A slurry of calcium hydroxide 1224 is injected into the pellet reactor 1210. A reaction between the CCh-laden capture solution 111 and the calcium hydroxide 1224 occurs in the pellet reactor. Ca²⁺ reacts with COs²' in the pellet reactor 1210 to form calcium carbonate solids and an aqueous alkaline solution as the CO2 capture solution 114 (such as hydroxide), thereby regenerating the CO2 capture solution 114. For example, potassium carbonate in the CCh-laden capture solution 111 can react with calcium hydroxide to form calcium carbonate and potassium hydroxide, thereby regenerating the CO2 capture solution 114 that includes potassium hydroxide.

[00280] The reaction of the CCh-laden capture solution 111 with Ca(OH)2 causes precipitation of calcium carbonate (CaCCh) onto calcium carbonate particles in the pellet reactor 1210. Further processing of the calcium carbonate solids, including but not limited to filtering, dewatering or drying, can occur prior to sending the calcium carbonate solids to downstream process units. A stream 1214 of calcium carbonate solids is transported from the pellet reactor 1210 to a calciner 1216 of the DAC system 1200. The calciner 1216 calcines the calcium carbonate of the stream 1214 from the pellet reactor 1210 to produce a stream of gaseous CO2 1218 and a stream of calcium oxide (CaO) 1220, possibly by oxy-combustion of a fuel source in the calciner 1216. The stream of gaseous CO2 1218 is processed for sequestration or other uses, thereby removing some of the CCh from the CCh-laden air 101 processed in the gas-liquid contactor 100, 100A, 100B. The stream of gaseous CO2 1218, either directly or after processing, can be provided as a product stream for use as desired, or for export. The stream of calcium oxide (CaO) 1220 is slaked with water in a slaker 1222 of the DAC system 1200 to produce the slurry of calcium hydroxide 1224 that is provided to the pellet reactor 1210. The DAC system 1200 can include multiple gas-liquid contactors 100, 100A, 100B, where each gas-liquid contactor 100, 100A, 100B forms a cell of a train/assembly of gas-liquid contactors 100, 100 A, 100B.

[00281] The stream 1214 of calcium carbonate solids of the DAC system 1200 that is calcined in the calciner 1216 can be produced according to other techniques for capturing CO2 from the CCh-laden air 101. For example, on an example implementation, the gas-liquid contactor 100, 100A, 100B of the DAC system 1200 uses a liquid sorbent, and a carbonate- forming reactor which receives the CCh-laden capture solution 111 includes one or more reactors similar to those used in the Kraft pulping process to form calcium carbonate solids. In some examples, the DAC system 1200 is free of a causticization process, and the gas-liquid contactor 100, 100A, 100B of the DAC system 1200 uses a liquid sorbent such as a calcium hydroxide slurry and contacts the liquid sorbent with air to form the stream 1214 of calcium carbonate solids which are then calcined.

[00282] In example implementations, the CO2 capture solution 114 can be regenerated using a different regeneration system. The regeneration system 1230 can be part of the gasliquid contactor 100, 100 A, 100B or separate therefrom. In an example alternate regeneration system 1235, the CCh-laden capture solution 111 can flow to an electrochemical system that includes a cell stack, which can include a set of one or more membranes, and a set of electrodes (such as shown in FIG. 20). The electrochemical system can regenerate the CO2 capture solution 114 from the CCh-laden capture solution 111 by applying an electric potential to an electrolyte including the CCh-laden capture solution 111. The difference in electric potential causes ion exchange, thereby forming the recovered CO2 1218 and regenerating the CO2 capture solution 114.

[00283] In another possible implementation of the alternate regeneration system 1235, the CCh-laden capture solution 111 can flow to a thermal stripping column that employs steam to desorb CO2 from the CCh-laden capture solution 111, thereby forming the recovered CO2 stream 1218 and regenerating the CO2 capture solution 114 (e.g., CCh-lean liquid). For example, the DAC system 1900 of FIG. 19 includes one or multiple gas-liquid contactor(s) 100, 100A, 100B and a regeneration subsystem 1980. The regeneration subsystem 1980 is configured to regenerate a CO2 capture solution (e.g., the CO2 capture solution 114).

[00284] In implementations where the CO2 capture solution 114 includes an amine capture species, the CO2 in the CCh-laden air 101 reacts with the amine capture species to form the CCh-laden capture solution 111 including carbamates. Non-limiting examples of the amine capture species of the CCh-capture solution 114 include, furan-bis(iminoguanidine) (FuBIG), isophorone diamine (IPDA), a hindered amine group having alkanolamine and alcoholic hydroxyl can be used. Examples of the alkanolamine include monoethanolamine (MEA), diethanolamine, triethanolamine, methyldiethanolamine, diisopropanolamine, and diglycolamine. Examples of the hindered amine having alcoholic hydroxyl include 2-amino- 2 -m ethyl- 1 -propanol (AMP), 2-(ethylamino)-ethanol (EAE), and 2-(methylamino)-ethanol (MAE).

[00285] The regeneration subsystem 1980 includes at least a concentrator 505, a heat exchanger 509, and a regeneration reactor 507. The CCh-laden capture solution 111 can include solids (e.g., carbamate solids) and be in the form of a slurry. The slurry is flowed to the concentrator 505, which functions to increase the concentration of the solids by separating solids from liquids. A solids slurry stream 521 is generated by the concentrator 505. The solids slurry stream 521 includes a higher concentration of solids than the concentration of solids in the CCh-laden capture solution 111. At least some of the liquid separated from the CCh-laden capture solution 111 by the concentrator 505 form a separated liquid stream 523, which can include unreacted CO2 capture solution 114. The separated liquid stream 523 is flowed back to any suitable component or unit of the gas-liquid contactor(s) 100, 100 A, 100B.

[00286] Referring to FIG. 19, the solids slurry stream 521 flows to the heat exchanger 509, where thermal energy from a regenerated, CCh-lean capture solution 511 is transferred to the solids slurry stream 521, as described below. The heated solids slurry stream 521 flows from the heat exchanger 509 to the regeneration reactor 507. The heat exchanger 509 can be considered a preheat heat exchanger that heat integrates a concentrated slurry (e.g., the solids slurry stream 521) with a higher temperature regenerated capture solution (e.g., the CCh-lean capture solution 511). In example implementations, the solids in the heated solids slurry stream 521 are at least partially regenerated in the heat exchanger 509 or downstream thereof, releasing CO2, prior to entering the regeneration reactor 507.

[00287] In example implementations, the heat exchanger 509 is upstream of the concentrator 505, relative to a flow direction of the CCh-laden capture solution 111 from the gas-liquid contactor(s) 100, 100A, 100B to the concentrator 505. In such implementations, the heat exchanger 509 functions to transfer thermal energy from the CCh-lean capture solution 511 to the CCh-laden capture solution 111 before it undergoes solid-liquid separation in the concentrator 505. In transferring thermal energy to streams entering the regeneration reactor 507, the heat exchanger 509 helps to reduce the duty of the regeneration reactor 507 in implementations where the regeneration reactor 507 uses heat to regenerate the CCh-laden capture solution 111. In other implementations, the regeneration subsystem 1980 does not have a heat exchanger.

[00288] In implementations where the regeneration reactor 507 is, or includes, a packed column, the heated solids slurry stream 521 flows through packing 503 within the regeneration reactor 507. A regeneration heater 506 supplies a source of heat, such as a stream of heated gas 517 (e.g., steam), which contacts the heated solids slurry stream 521 flowing along the packing 503. In example implementations, the regeneration reactor 507 includes one or more nozzles for flowing the heated solids slurry stream 521 onto the packing 503. In alternate example implementations, the regeneration reactor 507 includes a column with trays instead of, or in addition to, the packing column. In example implementations, the packing 503 is nonstructured (e.g., random packing).

[00289] By contacting the heated solids slurry stream 521 and its carbamate solids with the stream of heated gas 517, the CCh-lean capture solution 511 (e.g., regenerated CO2 capture solution 114) is generated and a CO2 gas 519 is desorbed. The CCh-lean capture solution 511 collects at the bottom of the regeneration reactor 507. Referring to FIG. 19, the CCh-lean capture solution 511 is at a relatively high temperature and is flowed to the heat exchanger 509 to transfer at least some of its thermal energy to the solids slurry stream 521 flowing from the concentrator 505, as described above. In implementations where the regeneration subsystem 1980 does not have a heat exchanger, the CCh-lean capture solution 511 is flowed directly to one or more components of the gas-liquid contactor(s) 100, 100 A, 100B and reused in the gasliquid contactor(s) 100, 100 A, 100B for CO2 capture.

[00290] The CO2 gas 519 is released from the regeneration reactor 507 along with water vapor 518 via a gas discharging line. The mixed gas stream (CO2 gas 519 and water vapor 518) flow from the regeneration reactor 507 to a condenser 508. Depending on the capture species of the CO2 capture solution 114, the mixed gas stream can also include volatile amines/organics. The condenser 508 condenses the water vapor 518 (and the volatile amines/organics), forms a water stream 1920 (which can have condensable amines/organics), and separates the CO2 gas 519 from the water stream 1920. The CO2 gas 519 is released from the condenser 508 as a CO2 product stream 525. The CO2 product stream 525 can be treated or processed as desired, such as by being compressed. The compressed CO2 product stream 525, either directly or after processing, can be provided for use as desired, or for export. In example implementations, the condensed water stream 1920 flows from the condenser 508 to the regeneration heater 506 to be used to generate the stream of heated gas 517 in the regeneration reactor 507. In example implementations, the condensed water stream 1920 flows directly to the heat exchanger 509.

[00291] Other configurations for the regeneration reactor 507 are contemplated by the present disclosure. For example, in some configurations, the regeneration reactor 507 does not include a packed column and is thus free of packing. In such a configuration, the regeneration reactor 507 can be, or can include, any one of the following non-limiting examples of reaction vessels: a tubular reactor, a continuous stirred tank reactor (CSTR) in which reagents, reactants, and solvents flow into the reactor while the products of the reaction concurrently exit the vessel, or a fluidized-bed reactor.

[00292] In implementations where the regeneration reactor 507 is, or includes, a tubular reactor, the tubular reactor can have an internal heating device (e.g., an electric heating element) and/or an external heating device (e.g., a heating jacket), inlet and outlet ports, and a phase separator or other suitable outlet to permit CO2 to degas from the tubular reactor. In implementations where the regeneration reactor 507 is, or includes, a CSTR, the CSTR can have an internal heating device (e.g., an electric heating element) and/or an external heating device (e.g., a heating jacket), a mixing element (such as a rotor and/or baffles), inlet and outlet ports, and a phase separator or other suitable outlet to permit CO2 to degas from the CSTR.

[00293] In implementations where the regeneration reactor 507 is, or includes, a fluidized-bed reactor, the solids slurry stream 521 can enter the fluidized-bed reactor from a top of the reactor, and a heating medium (e.g., steam) can be heated externally and flowed to the fluidized-bed reactor to fluidize the bed of solids and transfer heat thereto. The fluidized- bed reactor can have a distribution plate or mesh at a bottom thereof to support the solids being fluidized. The fluidized-bed reactor can also have inlet and outlet ports, and a phase separator or other suitable outlet to permit CO2 to degas from the fluidized-bed reactor.

[00294] In another example implementation of the alternate regeneration system 1235, the DAC system 2000 of FIG. 20 includes regeneration subsystem 2080. The regeneration subsystem 2080 is configured to regenerate a CCh-rich sorbent (e.g., the CCh-laden capture solution 111) received from one or multiple gas-liquid contactor(s) 100, 100 A, 100B. The gasliquid contactor(s) 100, 100A, 100B are fluidly coupled to a products generation subsystem 606 via a carbonate separation subsystem 604. The gas-liquid contactor(s) 100, 100A, 100B provides the CCh-laden capture solution 111 to the carbonate separation subsystem 604.

[00295] The CCh-laden capture solution 111 can be an aqueous mixture comprising primarily carbonate ions, alkaline metal carbonate (e.g., K2CO3, Na2COs), or a combination thereof. The CCh-laden capture solution 111 can also include other components in smaller amounts, such as hydroxide ions, alkali metal hydroxide (e.g., KOH, NaOH), water, and impurities. For example, the CO2-laden capture solution 111 can comprise between 0.4 M to 6 M K2CO3 and between 1 M to 10 M KOH. In example implementations, the CO2-laden capture solution 111 can comprise an aqueous Na2COs — NaOH mixture. In example implementations, the CO2-laden capture solution 111 can comprise a mixture of K2CO3 and Na₂CO₃.

[00296] In example implementations, the carbonate separation subsystem 604 can include a caustic evaporator or a crystallizer (or both). In example implementations, the carbonate separation subsystem 604 can include a nanofiltration unit or a crystallizer (or both). The carbonate separation subsystem 604 yields a crystalline carbonate hydrate 614. Crystalline carbonate hydrate 614 can include carbonate sesquihydrate (M2CO3 1.5 H2O) or an anhydrous carbonate. For example, crystalline carbonate hydrate 614 can include potassium carbonate sesquihydrate (K2CO3 1.5 H2O). In some examples, the crystalline carbonate hydrate 614 can include sodium carbonate decahydrate QSfeCCh lO H2O). In some examples, the crystalline carbonate hydrate 614 can include potassium sodium carbonate hexahydrate (KNaCCh 6 H2O). In example implementations, the crystalline carbonate hydrate 614 can include a different stoichiometry of water molecules per unit carbonate in the crystalline carbonate (e.g., M2CO3 n H2O where M is an alkali metal and n is an integer or fractional value).

[00297] The products generation subsystem 606 receives the crystalline carbonate hydrate 614. In example implementations, the products generation subsystem 606 includes a dissolving tank 608 fluidly coupled to an electrochemical cell 610. In example implementations, the products generation subsystem 606 can include a caustic evaporator.

[00298] The dissolving tank 608 can receive crystalline carbonate hydrate 614 from the carbonate separation subsystem 604, a water stream 620, and a brine stream 622. In example implementations, a polished aqueous solution can be used instead of or in addition to the water stream 620. A polished aqueous solution can be substantially free of particulates and dissolved contaminants (e.g., only contain an insignificant amount of particulates and dissolved contaminants, if any). The crystalline carbonate hydrate 614 dissolves in water and combines with bicarbonate HCO3 in brine stream 622 to form a feed solution 616. The feed solution 616 can include a bicarbonate HCO3 -rich solution with a mixture of other components such as carbonate and water.

[00299] The electrochemical cell 610 receives the feed solution 616 and a water stream 620. The electrochemical cell 610 yields at least two product streams including a first product stream 626 that comprises a hydroxide (regenerated CO2 capture solution 114) and is returned to the gas-liquid contactor(s) 100, 100A, 100B for reuse. The second product stream 628 is sent to a flash tank 612 where a gaseous CO2 product stream 624 is partially or fully released from the flash tank 612 and sent to one or more downstream processing units (e.g., compression unit, electroreduction subsystem, carbon products manufacturing system, syngas generation reactor). For further details and alternate implementations, reference is made to the patent application entitled “Systems and methods for capturing carbon dioxide and regenerating a capture solution” and published as US 2022/0362707 Al, the entire contents of which are incorporated by reference herein.

[00300] The regeneration system 1230, 1980, 2080 can include liquid distribution pipes, solids conveying equipment, filtration systems, intermediate components like storage vessels, and/or an assembly of components which function cooperatively to regenerate the CO2 capture solution 114. The regeneration system 1230, 1980, 2080 also includes pumps which flow liquids to and from the regeneration system 1230, 1980, 2080.

[00301] Referring to FIG. 16, a method 1400 for capturing CO2 from atmospheric air is disclosed. At 1402, the method 1400 includes flowing the atmospheric air (e.g., the CCh-laden air 101) in a first flow direction (e.g., the ATD 138D) from leading edges 136A of the packing sheets 130, 630, 730, 830 to trailing edges 136B. The first flow direction is substantially perpendicular to the leading edges 136A. At 1404, the method 1400 includes flowing the CO2 capture solution 114 in a second flow direction (e.g., the LTD 138L) over the packing sheets 130, 630, 730, 830 to absorb CO2 from the atmospheric air into the CO2 capture solution 114. The second flow direction is substantially perpendicular to the first flow direction.

[00302] FIG. 17 is a schematic diagram of a control system (or controller) 1600 for a gas-liquid contactor, such as gas-liquid contactor 100, 100A, 100B disclosed herein. The control system 1600 can be used for the operations described in association with any of the computer-implemented methods described previously, for example as or as part of the control system 999 or other controllers described herein.

[00303] The control system 1600 is intended to include various forms of digital computers, such as laptops, desktops, workstations, personal digital assistants, servers, blade servers, mainframes, and other appropriate computers. The control system 1600 can also include mobile devices, such as personal digital assistants, cellular telephones, smartphones, and other similar computing devices. Additionally, the system can include portable storage media, such as, Universal Serial Bus (USB) flash drives. For example, the USB flash drives can store operating systems and other applications. The USB flash drives can include input/output components, such as a wireless transmitter or USB connector that can be inserted into a USB port of another computing device.

[00304] The control system 1600 includes a processor 510, a memory 520, a storage device 530, and an input/output device 540. Each of the components 510, 520, 530, and 540 are interconnected using a system bus 550. The processor 510 is capable of processing instructions for execution within the control system 1600. The processor 510 can be designed using any of a number of architectures. For example, the processor 510 can be a CISC (Complex Instruction Set Computers) processor, a RISC (Reduced Instruction Set Computer) processor, or a MISC (Minimal Instruction Set Computer) processor.

[00305] In one implementation, the processor 510 is a single-threaded processor. In example implementations, the processor 510 is a multi -threaded processor. The processor 510 is capable of processing instructions stored in the memory 520 or on the storage device 530 to display graphical information for a user interface on the input/output device 540.

[00306] The memory 520 stores information within the control system 1600. In one implementation, the memory 520 is a computer-readable medium. In one implementation, the memory 520 is a volatile memory unit. In example implementations, the memory 520 is a nonvolatile memory unit.

[00307] The storage device 530 is capable of providing mass storage for the control system 1600. In one implementation, the storage device 530 is a computer-readable medium. In various different implementations, the storage device 530 can be a floppy disk device, a hard disk device, an optical disk device, or a tape device.

[00308] The input/output device 540 provides input/output operations for the control system 1600. In one implementation, the input/output device 540 includes a keyboard and/or pointing device. In example implementations, the input/output device 540 includes a display unit for displaying graphical user interfaces.

[00309] Certain features described can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. The apparatus can be implemented in a computer program product tangibly embodied in an information carrier, e.g., in a machine-readable storage device for execution by a programmable processor; and method steps can be performed by a programmable processor executing a program of instructions to perform functions of the described implementations by operating on input data and generating output. The described features can be implemented advantageously in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. A computer program is a set of instructions that can be used, directly or indirectly, in a computer to perform a certain activity or bring about a certain result. A computer program can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment.

[00310] Suitable processors for the execution of a program of instructions include, by way of example, both general and special purpose microprocessors, and the sole processor or one of multiple processors of any kind of computer. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. The essential elements of a computer are a processor for executing instructions and one or more memories for storing instructions and data. Generally, a computer will also include, or be operatively coupled to communicate with, one or more mass storage devices for storing data files; such devices include magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and optical disks. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magnetooptical disks; and CD-ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, ASICs (application-specific integrated circuits).

[00311] To provide for interaction with a user, the features can be implemented on a computer having a display device such as a CRT (cathode ray tube) or LCD (liquid crystal display) monitor for displaying information to the user and a keyboard and a pointing device such as a mouse or a trackball by which the user can provide input to the computer. Additionally, such activities can be implemented via touchscreen flat-panel displays and other appropriate mechanisms.

[00312] The features can be implemented in a control system that includes a back-end component, such as a data server, or that includes a middleware component, such as an application server or an Internet server, or that includes a front-end component, such as a client computer having a graphical user interface or an Internet browser, or any combination of them. The components of the system can be connected by any form or medium of digital data communication such as a communication network. Examples of communication networks include a local area network (“LAN”), a wide area network (“WAN”), peer-to-peer networks (having ad-hoc or static members), grid computing infrastructures, and the Internet.

[00313] A number of embodiments of the disclosure have been described. Nevertheless, it will be understood that various modifications can be made without departing from the spirit and scope of the disclosure. Accordingly, other embodiments are within the scope of the following claims. Further modifications and alternative embodiments of various aspects will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only. It is to be understood that the forms shown and described herein are to be taken as examples of embodiments. Elements and materials can be substituted for those illustrated and described herein, parts and processes can be reversed, and certain features can be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description. Changes can be made in the elements described herein without departing from the spirit and scope as described in the following claims.

Claims

WHAT IS CLAIMED IS:

1. A packing sheet for transferring carbon dioxide (CO2) from atmospheric air to a CO2 capture solution, the packing sheet comprising: a first side; a second side opposite the first side; a leading edge substantially parallel to the vertical in an installed configuration of the packing sheet; a trailing edge spaced apart from the leading edge by an air travel depth substantially parallel to a direction along which the atmospheric air travels from the leading edge to the trailing edge; a plurality of interconnecting edges, comprising: an upper edge that extends between the leading and trailing edges; and a lower edge that extends between the leading and trailing edges, the upper and lower edges spaced apart by a liquid travel dimension substantially parallel to a direction along which the CO2 capture solution travels from the upper edge to the lower edge; a mass-transfer zone on the first side and on the second side between the leading edge, the trailing edge, the upper edge, and the lower edge, the mass-transfer zone comprising a plurality of mass-transfer microstructures configured to receive the CO2 capture solution and to contact the atmospheric air with the CO2 capture solution, the plurality of mass-transfer microstructures having a microstructure height; a plurality of stiffening elements that extends from the first side and from the second side, each stiffening element of the plurality of stiffening elements having an orientation substantially parallel to the liquid travel dimension; and a plurality of spacers disposed on the mass-transfer zone and that extends from the first side and from the second side, the plurality of spacers spaced apart along the liquid travel dimension and having a spacer height greater than the microstructure height.

2. The packing sheet of claim 1, comprising a spacer alignment axis that extends between the upper edge and the lower edge on the first side and on the second side, the spacer alignment axis extending between at least two spacers of the plurality of spacers aligned along the liquid travel dimension, the spacer alignment axis substantially parallel to the vertical in the installed configuration of the packing sheet.

3. The packing sheet of claim 1 or 2, comprising a stiffening element alignment axis that extends between the upper edge and the lower edge on the first side and on the second side, the stiffening element alignment axis extending between at least two stiffening elements of the plurality of stiffening elements aligned along the liquid travel dimension, the stiffening element alignment axis substantially parallel to the vertical in the installed configuration of the packing sheet.

4. The packing sheet of any one of claims 1 to 3, wherein the plurality of stiffening elements comprise a plurality of intermediate stiffening elements between the leading edge and the trailing edge, the plurality of intermediate stiffening elements comprising a plurality of intermediate stiffening bodies positioned adjacent each other along the liquid travel dimension, each intermediate stiffening body of the plurality of intermediate stiffening bodies extends from one of the first side and the second side to an attachment wall, the attachment wall defining a stiffening body height greater than the microstructure height.

5. The packing sheet of claim 4, wherein the plurality of intermediate stiffening bodies comprises a first set of intermediate stiffening bodies that extends outwardly from the first side and a second set of intermediate stiffening bodies that extends outwardly from the second side, the first set of intermediate stiffening bodies forming a first set of depressions on the second side and the second set of intermediate stiffening bodies forming a second set of depressions on the first side, the first set of intermediate stiffening bodies alternating along an axis with the second set of depressions on the first side, and the second set of intermediate stiffening bodies alternating with the first set of depressions along the axis on the second side.

6. The packing sheet of claim 4 or 5, wherein each intermediate stiffening body of the plurality of intermediate stiffening bodies comprises a plurality of planar walls that extends outwardly from one of the first side and the second side to the attachment wall; and a plurality of flow channels, each flow channel of the plurality of flow channels disposed in a planar wall of the plurality of planar walls.

7. The packing sheet of claim 6, wherein the plurality of flow channels comprise at least one longitudinal flow channel substantially parallel to the liquid travel dimension; and at least one lateral flow channel comprising an inlet end and an outlet end, the inlet end being closer to the attachment wall than the outlet end.

8. The packing sheet of any one of claims 1 to 7, wherein the plurality of stiffening elements comprises a plurality of peripheral ribs adjacent to at least one of the trailing edge and the leading edge, each peripheral rib of the plurality of peripheral ribs extends outwardly from one of the first side and the second side, and forming a corresponding depression in the other one of the first side and the second side.

9. The packing sheet of claim 8, wherein the plurality of peripheral ribs comprises a plurality of leading edge ribs adjacent to the leading edge, the plurality of leading edge ribs comprising an innermost set of ribs that extends from the first side and forming corresponding depressions in the second side; and an outermost set of ribs that extends from the second side and forming corresponding depressions in the first side, the outermost set of ribs spaced further from the leading edge along the air travel depth than the innermost set of ribs.

10. The packing sheet of claim 8 or 9, wherein the plurality of peripheral ribs comprises a plurality of trailing edge ribs adjacent to the trailing edge, the plurality of trailing edge ribs comprising a third set of ribs that extends from the first side and forming corresponding depressions in the second side; and a fourth set of ribs that extends from the second side and forming corresponding depressions in the first side, the fourth set of ribs spaced further from the trailing edge along the air travel depth than the third set of ribs.

11. The packing sheet of any one of claims 8 to 10, wherein the plurality of peripheral ribs comprises at least one longitudinal rib pairing of two peripheral ribs spaced apart from each other in a direction substantially parallel to the liquid travel dimension to define a longitudinal pairing gap, and some mass-transfer microstructures of the plurality of masstransfer microstructures are present in the longitudinal pairing gap.

12. The packing sheet of any one of claims 8 to 11, wherein the plurality of peripheral ribs comprises at least one lateral rib pairing of two peripheral ribs spaced apart from each other in a direction substantially parallel to the air travel depth to define a lateral pairing gap, and some mass-transfer microstructures of the plurality of mass-transfer microstructures are present in the lateral pairing gap.

13. The packing sheet of any one of claims 1 to 12, wherein the plurality of stiffening elements comprises a plurality of peripheral stiffening bodies positioned adjacent each other along the liquid travel dimension, the plurality of peripheral stiffening bodies defining at least one of the trailing edge and the leading edge.

14. The packing sheet of any one of claims 1 to 13, wherein the plurality of spacers comprises a plurality of spacer pairings spaced apart along the liquid travel dimension and along the air travel depth, the spacers in each spacer pairing of the plurality of spacer pairings spaced apart in a direction substantially parallel to the air travel depth.

15. The packing sheet of claim 14, wherein the spacers in each spacer pairing comprise a first spacer that extends from the first side and forms a corresponding depression in the second side, and a second spacer that extends from the second side and forms a corresponding depression in the first side.

16. The packing sheet of any one of claims 1 to 15, wherein the plurality of stiffening elements comprises a plurality of intermediate stiffening elements positioned between the leading edge and the trailing edge, at least the plurality of intermediate stiffening elements comprising a plurality of intermediate ribs having an orientation substantially parallel to the liquid travel dimension, the plurality of intermediate ribs comprising a first set of ribs spaced apart in the liquid travel dimension and that extends from the first side and forms corresponding depressions in the second side; and a second set of ribs spaced apart in the liquid travel dimension and that extends from the second side and forms corresponding depressions in the first side, the second set of ribs spaced apart from the first set of ribs in a direction substantially parallel to the air travel depth.

17. The packing sheet of claim 16, wherein: each rib of the first set of ribs comprises a first rib end and a second rib end; and each rib of the second set of ribs comprises a third rib end and a fourth rib end, the third rib end of at least one rib of the second set of ribs positioned between the first rib end and the second rib end of at least one rib of the first set of ribs.

18. The packing sheet of any one of claims 1 to 17, wherein the packing sheet has a rectangular shape, the leading edge and the trailing edge substantially parallel to the vertical in the installed configuration of the packing sheet, the upper edge substantially perpendicular to the leading edge and the trailing edge, and the lower edge substantially perpendicular to the leading edge and the trailing edge.

19. The packing sheet of any one of claims 1 to 18, wherein the liquid travel dimension is greater than the air travel depth.

20. The packing sheet of any one of claims 1 to 19, wherein the air travel depth is between 3 ft. and 5 ft.

21. The packing sheet of any one of claims 1 to 20, wherein at least some masstransfer microstructures of the plurality of mass-transfer microstructures comprises a first wall portion that extends toward a first apex on a first side; and a second wall portion that extends from the first apex to a second apex on the second side, at least one of the first wall portion and the second wall portion comprising at least one wall feature extending from the at least one of the first wall portion and the second wall portion.

22. The packing sheet of claim 21, wherein the at least one wall feature comprises a first wall feature that extends from the first wall portion on the first side; and a second wall feature that extends from the second wall portion on the second side.

23. The packing sheet of any one of claims 1 to 22, comprising a centroid, the packing sheet having point symmetry about the centroid.

24. The packing sheet of any one of claims 1 to 3, wherein the plurality of stiffening elements comprises a plurality of reinforcement bodies positioned adjacent each other along the air travel depth and between the leading edge and the trailing edge.

25. The packing sheet of claim 24, wherein the plurality of reinforcement bodies is disposed between the upper edge and the lower edge.

26. The packing sheet of claim 24, wherein the plurality of reinforcement bodies defines at least one of the upper edge and the lower edge.

27. The packing sheet of any one of claims 24 to 26, wherein each reinforcement body of the plurality of reinforcement bodies extends outwardly from at least one of the first side or the second side to an attachment wall, the attachment wall defining a body height greater than the microstructure height.

28. The packing sheet of claim 27, wherein the plurality of reinforcement bodies comprises a first set of reinforcement bodies that extends from the first side and a second set of reinforcement bodies that extends from the second side, the first set of reinforcement bodies forming a first set of depressions on the second side and the second set of reinforcement bodies forming a second set of depressions on the first side, the first set of reinforcement bodies alternating along a horizontal axis with the second set of depressions on the first side, and the second set of reinforcement bodies alternating with the first set of depressions along the horizontal axis on the second side.

29. The packing sheet of claim 27 or 28, wherein each reinforcement body of the plurality of reinforcement bodies comprises: a plurality of planar walls that extends outwardly from at least one of the first side or the second side to the attachment wall; and at least one flow channel that extends into a planar wall of the plurality of planar walls on at least one of the first side or the second side, the at least one flow channel substantially parallel to the air travel depth.

30. The packing sheet of claim 27 or 28, wherein each reinforcement body of the plurality of reinforcement bodies comprises a plurality of planar walls that extends from at least one of the first side or the second side to the attachment wall, the attachment wall having an attachment wall slope, at least one planar wall of the plurality of planar walls comprising a stepped member, the stepped member comprising: a first wall segment that extends from the attachment wall and having a first slope different from the attachment wall slope; a second wall segment that extends from the first wall segment and having a second slope different from the first slope; and a third wall segment that extends from the second wall segment and having a third slope different from the second slope.

31. The packing sheet of claim 1, wherein at least some mass-transfer microstructures of the plurality of mass-transfer microstructures comprise: a plurality of base microstructures comprising a first wall portion and a second wall portion that extends toward a first apex on one of the first and second sides; and a plurality of supplemental microstructures protruding outwardly from the first and second wall portions of the plurality of base microstructures.

32. A structured packing for transferring carbon dioxide (CO2) from atmospheric air to a CO2 capture solution, the structured packing comprising: a plurality of packing sheets attached together, at least one packing sheet of the plurality of packing sheets comprising: a first side; a second side opposite the first side; a leading edge; a trailing edge spaced apart from the leading edge by an air travel depth substantially parallel to a direction along which the atmospheric air travels from the leading edge to the trailing edge, the leading edge of the at least one packing sheet beingsubstantially parallel to the vertical in an installed configuration of the at least one packing sheet; a plurality of interconnecting edges comprising: an upper edge that extends between the leading edge and the trailing edge; and a lower edge that extends between the leading edge and the trailing edge, the upper and lower edges spaced apart by a liquid travel dimension substantially parallel to a direction along which the CO2 capture solution travels from the upper edge to the lower edge; a mass-transfer zone on the first side and on the second side between the leading edge, the trailing edge, the upper edge, and the lower edge, the mass-transfer zone comprising a plurality of mass-transfer microstructures having a microstructure height and configured to contact the CO2 capture solution with the atmospheric air; a plurality of stiffening elements that extends from the first side and from the second side, each stiffening element of the plurality of stiffening elements having an orientation substantially parallel to the liquid travel dimension; and a plurality of spacers disposed on the mass-transfer zone and that extends from the first side and from the second side, the plurality of spacers spaced apart along the liquid travel dimension and having a spacer height greater than the microstructure height, adjacent packing sheets of the plurality of packing sheets attached along a respective plurality of spacers and defining an airflow channel through which the atmospheric air travels from the leading edge to the trailing edge.

33. The structured packing of claim 32, wherein the airflow channel has a rectangular channel shape defined in a plane normal to the liquid travel dimension.

34. The structured packing of claim 32 or 33, wherein the plurality of stiffening elements comprises a plurality of intermediate stiffening elements between the leading edge and the trailing edge, the plurality of intermediate stiffening elements comprising a plurality of intermediate stiffening bodies positioned adjacent each other along the liquid travel dimension, each intermediate stiffening body of the plurality of intermediate stiffening bodies extends from one of the first side and the second side to an attachment wall, the attachment wall defining a stiffening body height greater than the microstructure height, the adjacent packing sheets attached along their attachment walls.

35. The structured packing claim 34, wherein each intermediate stiffening body of the plurality of intermediate stiffening bodies comprises a plurality of planar walls that extends from one of the first side and the second side to the attachment wall, and a plurality of flow channels, each flow channel of the plurality of flow channels disposed in a planar wall of the plurality of planar walls, the plurality of flow channels comprising at least one longitudinal flow channel substantially parallel to the liquid travel dimension and that extends from the attached attachment walls of the adjacent packing sheets.

36. The structured packing of claim 34 or 35, wherein the plurality of intermediate stiffening bodies comprises a first set of stiffening bodies that extends from the first side and a second set of stiffening bodies that extends from the second side, the first set of stiffening bodies forming a first set of depressions on the second side and the second set of stiffening bodies forming a second set of depressions on the first side, the first set of stiffening bodies alternating along an axis with the second set of depressions on the first side, and the second set of stiffening bodies alternating along the axis with the first set of depressions on the second side, the airflow channel between the adjacent packing sheets extends through the first sets of depressions and the second sets of depressions.

37. The structured packing of claim 32 or 33, wherein: the plurality of stiffening elements comprises a plurality of intermediate stiffening elements between the leading edge and the trailing edge, at least the plurality of intermediate stiffening elements comprising a plurality of intermediate ribs having an orientation substantially parallel to the liquid travel dimension; the plurality of stiffening elements comprises a plurality of peripheral stiffening elements disposed adjacent to at least one of the trailing edge and the leading edge, the plurality of peripheral stiffening elements comprising a plurality of peripheral stiffening bodies positioned adjacent each other along the liquid travel dimension, the plurality of peripheral stiffening bodies defining at least one of the trailing edge and the leading edge; and the plurality of intermediate ribs having an intermediate rib height less than a peripheral stiffening body height of the plurality of peripheral stiffening bodies.

38. The structured packing of claim 32 or 33, wherein the plurality of stiffening elements comprises a plurality of peripheral stiffening bodies positioned adjacent each other along the liquid travel dimension, the plurality of peripheral stiffening bodies defining at least one of the trailing edge and the leading edge, the plurality of peripheral stiffening bodies comprising a first set of stiffening bodies that extends from the first side and a second set of stiffening bodies that extends from the second side, the first set of stiffening bodies forming a first set of depressions on the second side and the second set of stiffening bodies forming a second set of depressions on the first side, the first set of stiffening bodies alternating along an axis with the second set of depressions on the first side, and the second set of stiffening bodies alternating along the axis with the first set of depressions on the second side, the first set of stiffening bodies of a first packing sheet of the adjacent packing sheets attached to the second set of stiffening bodies of a second packing sheet of the adjacent packing sheets, stiffening body flow passages formed between the first set of depressions and the second set of depressions of the adjacent packing sheets, the stiffening body flow passages in fluid communication with the airflow channel.

39. The structured packing of any one of claims 32 to 38, comprising a spacer alignment axis that extends between the upper edge and the lower edge on the first side and on the second side, the spacer alignment axis extending between at least two spacers of the plurality of spacers aligned along the liquid travel dimension, the spacer alignment axis being substantially parallel to the vertical in the installed configuration of the at least one packing sheet.

40. The structured packing of claim 39, comprising a stiffening element alignment axis that extends between the upper and lower edges on the first side and on the second side, the stiffening element alignment axis extending between at least two stiffening elements of the plurality of stiffening elements aligned along the liquid travel dimension, the stiffening element alignment axis being substantially parallel to the vertical in the installed configuration of the at least one packing sheet.

41. The structured packing of any one of claims 32 to 40, wherein the plurality of stiffening elements comprises a plurality of intermediate stiffening elements between the leading edge and the trailing edge, at least the plurality of intermediate stiffening elements comprising a plurality of intermediate stiffening bodies positioned adjacent each other along the liquid travel dimension, each intermediate stiffening body of the plurality of intermediate stiffening bodies extends from one of the first side and the second side to an attachment wall, the attachment wall defining a stiffening body height greater than the microstructure height.

42. The structured packing of claim 41, wherein the plurality of intermediate stiffening bodies comprises a first set of intermediate stiffening bodies that extends from the first side and a second set of intermediate stiffening bodies that extends from the second side, the first set of intermediate stiffening bodies forming a first set of depressions on the second side and the second set of intermediate stiffening bodies forming a second set of depressions on the first side, the first set of intermediate stiffening bodies alternating along an axis with the second set of depressions on the first side, and the second set of intermediate stiffening bodies alternating along the axis with the first set of depressions on the second side.

43. The structured packing of claim 41 or 42, wherein each intermediate stiffening body of the plurality of intermediate stiffening bodies comprises a plurality of planar walls that extends from one of the first side and the second side to the attachment wall, and a plurality of flow channels, each flow channel of the plurality of flow channels disposed in a planar wall of the plurality of planar walls.

44. The structured packing of claim 43, wherein the plurality of flow channels comprises at least one longitudinal flow channel substantially parallel to the liquid travel dimension, and at least one lateral flow channel comprising an inlet end and an outlet end, the inlet end being closer to the attachment wall than the outlet end.

45. The structured packing of any one of claims 39 to 44, wherein the plurality of stiffening elements comprises a plurality of peripheral ribs adj acent to at least one of the trailing edge and the leading edge, each peripheral rib of the plurality of peripheral ribs that extend from one of the first side and the second side and forming a corresponding depression in the other one of the first side and the second side.

46. The structured packing of claim 45, wherein the plurality of peripheral ribs comprises a plurality of leading edge ribs adjacent to the leading edge, the plurality of leading edge ribs comprising an innermost set of ribs; and an outermost set of ribs spaced further from the leading edge along the air travel depth than the innermost set of ribs, the innermost set of ribs extends from the first side and forming corresponding depressions in the second side, the outermost set of ribs extends from the second side and forming corresponding depressions in the first side.

47. The structured packing of claim 45 or 46, wherein the plurality of peripheral ribs comprises a plurality of trailing edge ribs adjacent to the trailing edge, the plurality of trailing edge ribs comprising a third set of ribs; and a fourth set of ribs spaced further from the trailing edge along the air travel depth than the third set of ribs, the third set of ribs extends from the first side and forming corresponding depressions in the second side, the fourth set of ribs extends from the second side and forming corresponding depressions in the first side.

48. The structured packing of any one of claims 45 to 47, wherein the plurality of peripheral ribs comprises at least one longitudinal rib pairing of two peripheral ribs spaced apart from each other in a direction substantially parallel to the liquid travel dimension to define a longitudinal pairing gap, wherein some mass-transfer microstructures of the plurality of masstransfer microstructures are present in the longitudinal pairing gap.

49. The structured packing of any one of claims 45 to 48, wherein the plurality of peripheral ribs comprises at least one lateral rib pairing of two peripheral ribs spaced apart from each other in a direction substantially parallel to the air travel depth to define a lateral pairing gap, and some mass-transfer microstructures of the plurality of mass-transfer microstructures are present in the lateral pairing gap.

50. The structured packing of any one of claims 39 to 49, wherein the plurality of stiffening elements comprises a plurality of peripheral stiffening bodies positioned adjacent each other along the liquid travel dimension, the plurality of peripheral stiffening bodies defining at least one of the trailing edge and the leading edge.

51. The structured packing of any one of claims 39 to 50, wherein the plurality of spacers comprises a plurality of spacer pairings spaced apart along the liquid travel dimension and along the air travel depth, the spacers in each spacer pairing spaced apart in a direction substantially parallel to the air travel depth.

52. The structured packing of claim 51, wherein the spacers in each spacer pairing comprise a first spacer that extends from the first side and forming a corresponding depression in the second side; and a second spacer that extends from the second side and forming a corresponding depression in the first side.

53. The structured packing of any one of claims 39 to 52, wherein the plurality of stiffening elements comprises a plurality of intermediate stiffening elements between the leading edge and the trailing edge, at least the plurality of intermediate stiffening elements comprising a plurality of intermediate ribs having an orientation substantially parallel to the liquid travel dimension, the plurality of intermediate ribs comprising a first set of ribs spaced apart in the liquid travel dimension; and a second set of ribs spaced apart in the liquid travel dimension, the second set of ribs spaced apart from the first set of ribs in a direction substantially parallel to the air travel depth, the first set of ribs extends from the first side and forming corresponding depressions in the second side, the second set of ribs extends from the second side and forming corresponding depressions in the first side.

54. The structured packing of claim 53, wherein: each rib of the first set of ribs comprises a first rib end and a second rib end; and each rib of the second set of ribs comprises a third rib end and a fourth rib end, the third rib end of at least one rib of the second set of ribs positioned between the first rib end and the second rib end of at least one rib of the first set of ribs.

55. The structured packing of any one of claims 39 to 54, wherein: the packing sheet has a rectangular shape, the leading edge and the trailing edge being substantially parallel to the vertical in the installed configuration of the at least one packing sheet; the upper edge is substantially perpendicular to the leading edge and the trailing edge; and the lower edge is substantially perpendicular to the leading edge and the trailing edge.

56. The structured packing of any one of claims 39 to 55, wherein the liquid travel dimension is greater than the air travel depth.

57. The structured packing of any one of claims 39 to 56, wherein the air travel depth is between 3 ft. and 5 ft.

58. The structured packing of any one of claims 39 to 57, wherein at least one masstransfer microstructure of the plurality of mass-transfer microstructures comprises a first wall portion that extends toward a first apex on a first side; and a second wall portion that extends from the first apex to a second apex on the second side, at least one of the first wall portion and the second wall portion comprising at least one wall feature that extends from the at least one of the first wall portion and the second wall portion.

59. The structured packing of claim 58, wherein the at least one wall feature comprises a first wall feature that extends from the first wall portion on the first side; and a second wall feature that extends from the second wall portion on the second side.

60. The structured packing of any one of claims 39 to 59, comprising a centroid, the at least one packing sheet having point symmetry about the centroid.

61. A gas-liquid contactor for capturing carbon dioxide (CO2) from atmospheric air, the gas-liquid contactor comprising: at least one inlet; at least one outlet spaced apart from the at least one inlet; at least one packing section disposed between the at least one inlet and the at least one outlet, the at least one packing section comprising at least one structured packing, the at least one structured packing comprising a plurality of packing sheets attached together, at least one packing sheet of the plurality of packing sheets comprising: a first side; a second side opposite the first side; a leading edge substantially parallel to the vertical; a trailing edge spaced apart from the leading edge by an air travel depth; and a plurality of interconnecting edges comprising an upper edge that extends between the leading edge and the trailing edge and a lower edge that extends between the leading edge and the trailing edge, the upper edge and the lower edge spaced apart by a liquid travel dimension; a mass-transfer zone on the first side and on the second side between the leading edge, the trailing edge, the upper edge, and the lower edge, the mass-transfer zone comprising a plurality of mass-transfer microstructures having a microstructure height; a plurality of stiffening elements that extends from the first side and from the second side, each stiffening element of the plurality of stiffening elements having an orientation substantially parallel to the liquid travel dimension; a plurality of spacers disposed on the mass-transfer zone and that extends from the first side and from the second side, the plurality of spacers spaced apart and having a spacer height greater than the microstructure height, adj acent packing sheets of the plurality of packing sheets attached along a respective plurality of spacers and defining an airflow channel; one or more liquid collection devices comprising a bottom liquid collection device positioned at least partially below the at least one packing section, the one or more liquid collection devices configured to hold a CO2 capture solution; at least one fan operable to flow the atmospheric air: (1) from the at least one inlet to the at least one outlet, and (2) along the airflow channels of the at least one structured packing substantially parallel to the air travel depth; and a liquid distribution system fluidly coupled to the at least one packing section and operable to flow the CO2 capture solution along the plurality of mass-transfer microstructures in the liquid travel dimension to contact the atmospheric air with the CO2 capture solution and absorb CO2 from the atmospheric air into the CO2 capture solution.

62. The gas-liquid contactor of claim 61, comprising a housing defining an interior at least partially exposed to the atmospheric air, the interior disposed between the at least one inlet and the at least one outlet, the at least one structured packing comprises a plurality of structured packings disposed within the interior and forming at least one arrangement of structured packings, the structured packings of the at least one arrangement of structured packings positioned vertically and laterally adjacent each other.

63. The gas-liquid contactor of claim 62, wherein the at least one arrangement of structured packings comprises: an upper arrangement of structured packings; a lower arrangement of structured packings vertically spaced beneath the upper arrangement of structured packings, a redistribution spacing defined between the upper and lower arrangements of structured packings; and the one or more liquid collection devices comprise a redistribution basin positioned in the redistribution spacing between the upper and lower arrangements of structured packings, the redistribution basin configured to collect the CO2 capture solution from the upper arrangement of structured packings and to redistribute the CO2 capture solution over the lower arrangement of structured packings.

64. The gas-liquid contactor of claim 62 or 63, wherein the housing comprises a plurality of interconnected structural members, the plurality of structured packings mounted to at least one of: an interconnected structural member of the plurality of interconnected structured members, or another structured packing of the plurality of structured packings.

65. The gas-liquid contactor of any one of claims 61 to 64, wherein the liquid distribution system is operable to flow the CO2 capture solution at a liquid loading rate ranging from 0.5 L/m²s to 10 L/m²s.

66. The gas-liquid contactor of any one of claims 61 to 65, wherein: the at least one packing section comprises a first packing section and a second packing section spaced apart from the first packing section by a plenum; the fan is operable to flow the atmospheric air to enter the first packing section and the second packing section at airspeeds between 0.1 m/s and 5 m/s, and flow through the first packing section and the second packing section along a horizontal flow direction into the plenum; and the liquid distribution system is operable to flow the CO2 capture solution in the liquid travel dimension being predominantly vertically downward.

67. A packing sheet for transferring carbon dioxide (CO2) from atmospheric air to a CO2 capture solution, the packing sheet comprising: a first side; a second side opposite the first side; a leading edge; a trailing edge spaced apart from the leading edge by an air travel depth substantially parallel to a direction along which the atmospheric air travels from the leading edge to the trailing edge, the leading edge substantially parallel to the vertical in an installed configuration of the packing sheet; a plurality of interconnecting edges comprising an upper edge that extends between the leading edge and the trailing edge; a lower edge that extends between the leading edge and the trailing edge, the upper edge and the lower edge spaced apart by a liquid travel dimension substantially parallel to a direction along which the CO2 capture solution travels from the upper edge to the lower edge; a mass-transfer zone on the first side and on the second side between the leading edge, the trailing edge, the upper edge, and the lower edge, the mass-transfer zone comprising a plurality of mass-transfer microstructures having a microstructure height, the plurality of masstransfer microstructures configured to receive the CO2 capture solution and to contact the atmospheric air with the CO2 capture solution; at least one stiffening element that extends from one of the first side and the second side, the at least one stiffening element having an orientation substantially parallel to the liquid travel dimension, one or more mass-transfer microstructures of the plurality of mass-transfer microstructures disposed on the at least one stiffening element; and a plurality of spacers disposed on the mass-transfer zone and that extends from the first side and from the second side, the plurality of spacers spaced apart along the liquid travel dimension and having a spacer height greater than the microstructure height.

68. A method for capturing carbon dioxide (CO2) from atmospheric air, the method comprising: flowing the atmospheric air in a first flow direction from leading edges of a plurality of packing sheets to trailing edges of the plurality of packing sheets, the first flow direction being substantially perpendicular to the leading edges of the plurality of packing sheets; and flowing a CO2 capture solution in a second flow direction over the plurality of packing sheets to absorb CO2 from the atmospheric air into the CO2 capture solution, the second flow direction being substantially perpendicular to the first flow direction.

69. A direct air capture (DAC) system for capturing carbon dioxide (CO2) from atmospheric air, the DAC system comprising: at least one gas-liquid contactor comprising: at least one inlet; at least one outlet spaced apart from the at least one inlet; and at least one packing section disposed between the at least one inlet and the at least one outlet, the at least one packing section comprising at least one structured packing, the at least one structured packing comprising a plurality of packing sheets attached together, at least one packing sheet of the plurality of packing sheets comprising: a first side; a second side opposite the first side; a leading edge substantially parallel to the vertical; a trailing edge spaced apart from the leading edge by an air travel depth; a plurality of interconnecting edges comprising an upper edge that extends between the leading edge and the trailing edge; a lower edge that extends between the leading edge and the trailing edge, the upper edge and the lower edge spaced apart by a liquid travel dimension; a mass-transfer zone on the first side and on the second side between the leading edge, the trailing edge, the upper edge, and the lower edge, the masstransfer zone comprising a plurality of mass-transfer microstructures having a microstructure height; a plurality of stiffening elements that extends from the first side and from the second side, each stiffening element of the plurality of stiffening elements having an orientation substantially parallel to the liquid travel dimension; and a plurality of spacers disposed on the mass-transfer zone and that extends from the first side and from the second side, the plurality of spacers spaced apart and having a spacer height greater than the microstructure height, adjacent packing sheets of the plurality of packing sheets attached along a respective plurality of spacers and defining airflow channels; a fan operable to flow the atmospheric air: (1) from the at least one inlet to the at least one outlet, and (2) along the airflow channels of the at least one structured packing substantially parallel to the air travel depth; a liquid distribution system fluidly coupled to the at least one packing section and operable to flow a CO2 capture solution over the mass-transfer microstructures of the at least one packing section, the CO2 capture solution configured to absorb CO2 from the atmospheric air, the liquid distribution system comprising one or more liquid collection devices comprising a bottom liquid collection device positioned at least partially below the at least one packing section, the one or more liquid collection devices configured to hold the CO2 capture solution; and a regeneration system in fluid communication with the liquid distribution system to receive the CO2 capture solution, the regeneration system configured to regenerate the CO2 capture solution and form a CCh-lean liquid to return to the at least one gas-liquid contactor.

70. The DAC system of claim 69, wherein the regeneration system is configured to provide a CO2 product stream.