US20240141512A1

US20240141512A1 - Co2 electrolysis plant

Info

Publication number: US20240141512A1
Application number: US18/499,074
Authority: US
Inventors: Lisa C. Wynia; Gregory J. Dicosola; Kendra P. Kuhl; Sichao Ma; Carter S. Haines; Timothy A. Bekkedahl; Heegun PARK; Nicholas A. Taylor
Original assignee: Twelve Benefit Corp
Current assignee: Twelve Benefit Corp
Priority date: 2022-10-31
Filing date: 2023-10-31
Publication date: 2024-05-02
Also published as: WO2024097216A3; WO2024097216A2

Abstract

Aspects of the present disclosure provide a system for a carbon oxide electrolysis plant incorporating advanced electrochemical reactors incorporating membrane electrode assemblies as well as control mechanisms. The system provides efficient transport and production rates while minimizing the competing hydrogen formation reaction. The system may use multiple electrochemical reactors, scaling up production with high energy efficiency, while providing flexibility in the types of chemical product outputs.

Description

RELATED APPLICATION(S)

An Application Data Sheet is filed concurrently with this specification as part of the present application. Each application that the present application claims benefit of or priority to as identified in the concurrently filed Application Data Sheet is incorporated by reference herein in its entirety and for all purposes.

BACKGROUND

Carbon-based products are the foundation of our modern world. Carbon is part of many products we use daily, from household goods and articles of clothing to fuels, paints and detergents. At the same time, anthropogenic CO₂emissions are a significant focus of efforts to address climate change and the increase in greenhouse gas emissions. Most of the carbon used today comes from fossil fuels in the form of petrochemicals. The carbon footprint of fossil fuels and petrochemicals has received increased scientific attention with alternative sources coming into greater use.
A byproduct of fossil fuel use is increased carbon dioxide being emitted into Earth's atmosphere. Removing this excess carbon dioxide has become a key component of proposals to reduce carbon emissions. Future industrial processes can utilize the carbon dioxide to produce new materials that do not rely on petrochemicals as inputs. Electrochemical reduction of CO_x(CO₂, CO, or combinations thereof) utilizes three inputs: CO_x, a source of protons, and electricity, which can then create feedstock such as CO or hydrocarbons for downstream process integration for conversion into fuels, chemicals, or other products such as methanol, ethanol, and acetic acid. Electrochemical reactors have been developed that provide improved transport of CO_xto the surface of the catalyst in the reactor, advances in catalyst and polymer membrane design and improved control over the hydrogen evolution reaction, which combine to increase Faradaic yield (i.e., Faradaic efficiency) and lifetime of the reactor, making it more viable for commercial use.
Examples of carbon oxide (CO_x) reactants include carbon dioxide and carbon monoxide, including carbonate ions and compounds, as well as bicarbonate ions and compounds. Such reactants may be provided primarily in gaseous form.
Background and contextual descriptions contained herein are provided solely for the purpose of generally presenting the context of the disclosure. Much of this disclosure presents work of the inventors, and simply because such work is described in the background section or presented as context elsewhere herein does not mean that such work is admitted prior art.

SUMMARY

Aspects of the present disclosure provide a system for an electrolysis plant incorporating advanced electrochemical reactors incorporating membrane electrode assemblies as well as control mechanisms to achieve industrial-scale production. The system provides efficient transport and production rates while minimizing competing hydrogen formation reactions. The system may use multiple electrochemical reactors, scaling up production with high energy efficiency, while providing flexibility in the types of chemical products output. The carbon oxide electrolyzer system includes a carbon oxide reduction reactor that is in communication with a power system, a water system, and a gas system. The water system includes an anolyte (also referred to as anode water or anolyte water) circulation system and a catholyte circulation system where the anolyte and catholyte (also referred to as cathode water or catholyte water) are primarily composed of water with additional constituents including, but not limited to, a salt or salts. The water system also includes an optional anolyte recirculation system and an optional catholyte recirculation system. The anolyte circulation system operates within a predetermined temperature range, in some examples, and may also provide recirculation of the anolyte to the carbon oxide electrolyzer.
A further aspect of the present disclosure provides a method for large-scale carbon oxide electrolysis. The method includes receiving, at a carbon oxide reduction reactor, a gaseous carbon oxide from a gas system, and water from a water system. The water system has an anolyte circulation system and a catholyte circulation system, and both the anolyte and catholyte systems may provide for recirculation of anolyte and catholyte fluids. Electrical power is provided by an electrical power system. The carbon oxide reduction reactor electrolyzes a molecular carbon-containing species (CCS) in a selected hydrogen to CCS ratio using the input gaseous carbon oxide, water, and electrical power.
A still further aspect of the carbon oxide electrolyzer system includes an electrolyzer system having a programmable control system. The control system includes a computer storage media and a processing device that is operatively coupled to the computer storage media. The processing device, among other things, may control input of gaseous carbon oxide to a gas inlet of the carbon oxide electrolyzer system. The control system may also control input of water to a water inlet of the carbon oxide electrolyzer system. The water system may incorporate an anolyte circulation system and an optional anolyte recirculation system, as well as a catholyte circulation system and an optional catholyte recirculation system. The control system may also control the operating temperature range of the anolyte circulation system to maintain the anolyte within a predetermined temperature range, and may also control flow rate of the anolyte in order to control the temperature differential that develops within the anolyte as it flows through the carbon oxide electrolyzer system. Water is also input and controlled at an inlet to a carbon oxide reduction reactor. The processing device also monitors and controls electrical power supplied to the carbon oxide electrolyzer system as well as monitors and controls the electrolyzing process in order to output a molecular hydrogen and carbon-containing species (CCS) in a selected hydrogen to CCS ratio range.
In addition to the above implementations, the present disclosure is also directed at at least the following numbered implementations.
Implementation 1: A carbon oxide electrolyzer system including a carbon oxide reduction reactor configured to electrochemically reduce a gaseous carbon oxide to produce a molecular carbon-containing species, a gas source configured to provide the gaseous carbon oxide to a cathode of the carbon oxide reduction reactor, a power source configured to supply electrical power to the carbon oxide reduction reactor, and an anolyte circulation system configured to provide anolyte solution to an anode of the carbon oxide reduction reactor, the anolyte circulation system including a temperature control system operable to control a temperature differential of the anolyte solution across the anode.
Implementation 2: The carbon oxide electrolyzer system of implementation 1, in which the temperature control system maintains a temperature differential of not more than 5° C.
Implementation 3: The carbon oxide electrolyzer system of either implementation 1 or implementation 2, in which the temperature control system includes one or more pumps and/or one or more valves configured to control an anode inlet flow rate of the anolyte solution.
Implementation 4: The carbon oxide electrolyzer system of any one of implementations 1 to 3, further including a catholyte circulation system configured to recover at least a portion of cathode water produced during reduction of the gaseous carbon oxide.
Implementation 5: The carbon oxide electrolyzer system of implementation 4, in which the catholyte circulation system includes a catholyte separator unit fluidically connected with a reduction product outlet of the carbon oxide reduction reactor and configured to produce a liquid stream enriched in water and a gaseous stream enriched in carbon-containing species (CCS).
Implementation 6: The carbon oxide electrolyzer system of implementation 5, further including a catholyte recirculation system configured to direct at least a portion of the liquid stream into the anolyte circulation system.
Implementation 7: The carbon oxide electrolyzer system of any one of implementations 1 through 6, in which the carbon oxide reduction reactor includes a membrane electrode assembly including one or more ion-conductive polymer layers and a cathode catalyst layer for facilitating chemical reduction of the carbon oxide to the carbon-containing species (CCS).
Implementation 8: The carbon oxide electrolyzer system of any one of implementations 1 through 7, further including an anolyte separator unit configured to receive an oxidation product stream produced from the carbon oxide reduction reactor and to produce a liquid stream enriched in water and a gaseous stream enriched in molecular oxygen.
Implementation 9: The carbon oxide electrolyzer system of any one of implementations 1 through 8, in which the carbon oxide reduction reactor includes an electrolyzer stack having more than one electrolyzer cell.
Implementation 10: The carbon oxide electrolyzer system of implementation 9, in which the system includes a plurality of carbon oxide electrolyzer stacks connected in parallel or series.
Implementation 11: The carbon oxide electrolyzer system of any one of implementations 1 through 10, in which the anolyte circulation system includes a salt-dosing system configured to control a salt concentration and/or ion conductivity of the anolyte solution introduced into the carbon oxide reduction reactor.
Implementation 12: The carbon oxide electrolyzer system of any one of implementations 1 through 11, in which the anolyte circulation system further includes a pump configured to purge anolyte solution to an external wastewater tank.
Implementation 13: A method for carbon oxide electrolysis, the method including inputting a source of gaseous carbon oxide to a cathode of a carbon oxide reduction reactor, inputting anolyte solution from an anolyte circulation system to an anode of the carbon oxide reduction reactor, controlling a temperature differential of the anolyte solution across the anode, inputting electrical power to the carbon oxide reduction reactor, and electrochemically reducing the gaseous carbon oxide to produce a molecular carbon containing species.
Implementation 14: The method of implementation 13, in which the controlling includes one or more of controlling an anode inlet flow rate of the anolyte solution.
Implementation 15: The method of either implementation 13 or 14, in which controlling the temperature differential includes maintaining a temperature differential of not more than 5° C.
Implementation 16: The method of any one of implementations 13 through 15, further including recovering at least a portion of cathode water produced during reduction of the gaseous carbon oxide in a catholyte circulation system.
Implementation 17: The method of implementation 16, in which the recovering includes introducing a reduction product stream from the carbon oxide reactor to a catholyte separator and separating the reduction product stream to produce a liquid stream enriched in water and a gaseous stream enriched in carbon-containing species.
Implementation 18: The method of implementation 17, further including recycling at least a portion of liquid stream to the anolyte circulation system.
Implementation 19: The method of any one of implementations 13 through 18, in which the carbon oxide reduction reactor includes a membrane electrode assembly including one or more ion conductive polymer layers and a cathode catalyst layer for facilitating chemical reduction of the carbon oxide to the carbon-containing species.
Implementation 20: The method of any one of implementations 13 through 19, further including introducing an oxidation product stream produced from the carbon oxide reduction reactor to an anolyte separator unit and separating the oxidation product stream to produce a liquid stream enriched in water and a gaseous stream enriched in molecular oxygen.
Implementation 21: The method of any one of implementations 13 through 20, in which the carbon oxide reduction reactor includes an electrolyzer stack having more than one cell.
Implementation 22: The method of any one of implementations 13 through 21, further including introducing a salt into the anolyte solution to control a salt concentration and/or ion conductivity of the anolyte solution introduced into the carbon oxide reduction reactor.
Implementation 23: The method of any one of implementations 13 through 22, further including purging at least a portion of the anolyte solution to an external wastewater tank.
Implementation 24: A carbon oxide electrolyzer system including a carbon oxide reduction reactor configured to electrochemically reduce a gaseous carbon oxide to produce a molecular carbon containing species, a gas source configured to provide the gaseous carbon oxide to a cathode of the carbon oxide reduction reactor, a power source configured to supply electrical power to the carbon oxide reduction reactor, and an anolyte circulation system configured to provide anolyte solution to an anode of the carbon oxide reduction reactor, the anolyte circulation system including a temperature control system operable to maintain the anolyte solution provided to the anode within a predetermined temperature range.
Implementation 25: The carbon oxide electrolyzer system of implementation 24, in which the predetermined temperature range is 10° C. to 80° C.
Implementation 26: The carbon oxide electrolyzer system of either of implementations 24 or 25, in which the temperature control system includes one or more of i) one or more heat exchangers configured to control an anode inlet temperature of the anolyte solution, and ii) one or more pumps configured to control an anode inlet flow rate of the anolyte solution.
Implementation 27: The carbon oxide electrolyzer system of any one of implementations 24 through 26, further including a catholyte circulation system configured to recover at least a portion of cathode water produced during reduction of the gaseous carbon oxide.
Implementation 28: The carbon oxide electrolyzer system of implementation 27, in which the catholyte circulation system includes a catholyte separator unit fluidically connected to a reduction product outlet of the carbon oxide reduction reactor and configured to produce a liquid stream enriched in water and a gaseous stream enriched in carbon-containing species.
Implementation 29: The carbon oxide electrolyzer system of implementation 28, further including a catholyte recirculation system configured to recycle at least a portion of the liquid stream to the anolyte circulation system.
Implementation 30: The carbon oxide electrolyzer system of any one of implementations 24 through 29, in which the carbon oxide reduction reactor includes a membrane electrode assembly including one or more ion conductive polymer layers and a cathode catalyst layer for facilitating chemical reduction of the carbon oxide to the carbon-containing species.
Implementation 31: The carbon oxide electrolyzer system of any one of implementations 24 through 30, further including an anolyte separator unit configured to receive an oxidation product stream produced from the carbon oxide reduction reactor, and to produce a liquid stream enriched in water and a gaseous stream enriched in molecular oxygen.
Implementation 32: The carbon oxide electrolyzer system of any one of implementations 24 through 31, in which the carbon oxide reduction reactor includes an electrolyzer stack having more than one cell.
Implementation 33: The carbon oxide electrolyzer system of implementation 32, in which the system includes a plurality of carbon oxide electrolyzer stacks connected in parallel or series.
Implementation 34: The carbon oxide electrolyzer system of any one of implementations 24 through 33, in which the anolyte circulation system includes a salt dosing system configured to control a salt concentration and/or ion conductivity of the anolyte solution introduced into the carbon oxide reduction reactor.
Implementation 35: The carbon oxide electrolyzer system of any one of implementations 24 through 34, in which the anolyte circulation system further includes a pump configured to purge anolyte solution to an external wastewater tank.
Implementation 36: A method for carbon oxide electrolysis, the method including inputting a source of gaseous carbon oxide to a cathode of a carbon oxide reduction reactor, inputting anolyte solution from an anolyte circulation system to an anode of the carbon oxide reduction reactor, maintaining the anolyte solution provided to the anode within a predetermined temperature range, inputting electrical power to the carbon oxide reduction reactor, and electrochemically reducing the gaseous carbon oxide to produce a molecular carbon-containing species (CCS).
Implementation 37: The method of implementation 36, in which the predetermined temperature range is 10° C. to 80° C.
Implementation 38: The method of either of implementations 36 or 37, further including recovering at least a portion of cathode water produced during reduction of the gaseous carbon oxide in a catholyte circulation system.
Implementation 39: The method of implementation 38, in which the recovering includes introducing a reduction product stream from the carbon oxide reactor to a catholyte separator and separating the reduction product stream to produce a liquid stream enriched in water and a gaseous stream enriched in carbon-containing species.
Implementation 40: The method of implementation 39, further including recycling at least a portion of liquid stream to the anolyte circulation system.
Implementation 41: The method of any one of implementations 36 through 40, in which the carbon oxide reduction reactor includes a membrane electrode assembly including one or more ion conductive polymer layers and a cathode catalyst layer for facilitating chemical reduction of the carbon oxide to the carbon-containing species.
Implementation 42: The method of any one of implementations 36 through 41, further including introducing an oxidation product stream produced from the carbon oxide reduction reactor to an anolyte separator unit and separating the oxidation product stream to produce a liquid stream enriched in water and a gaseous stream enriched in molecular oxygen.
Implementation 43: The method of any one of implementations 36 through 42, in which the carbon oxide reduction reactor includes an electrolyzer stack having more than one cell.
Implementation 44: The method of any one of implementations 36 through 43, further including introducing a salt into the anolyte solution to control a salt concentration and/or ion conductivity of the anolyte solution introduced into the carbon oxide reduction reactor.
Implementation 45: The method of any one of implementations 36 through 44, further including purging at least a portion of the anolyte solution to an external wastewater tank.
Implementation 46: A method of operating a carbon oxide electrolyzer system, the method including introducing a first input including gaseous carbon oxide and a second input including an anolyte solution into a carbon oxide reduction reactor system including a plurality of fluidically connected carbon oxide reduction electrolyzers, thereby producing a reduction product stream including a carbon-containing species and an oxidation product stream, and selectively terminating at least one of the carbon oxide reduction electrolyzers upon detecting one or more sensed parameters outside of a threshold value range.
Implementation 47: The method of implementation 46, in which the one or more sensed parameters includes a reduction product stream and/or an oxidation product stream composition value.
Implementation 48: The method of implementation 46, further including decoupling the terminated carbon oxide reduction electrolyzer from the carbon oxide reduction reactor and removing it from the system.
Implementation 49: A system including a carbon oxide electrolyzer system having a programmable control system, a computer storage media, and a processing device, operatively coupled to the computer storage media and configured to control input, at a gas inlet of the carbon oxide electrolyzer system, of gaseous carbon dioxide, control input, at a water inlet of the carbon oxide electrolyzer system, of water, the water provided by a water system incorporating an anolyte circulation system and an anolyte recirculation system and a catholyte circulation system, monitor and control, at a power input of the carbon oxide electrolyzer system, electrical power, and monitor and control electrolysis, by the carbon oxide electrolyzer, to output a molecular hydrogen and carbon-containing species in a selected hydrogen to carbon-containing species ratio range.
Implementation 50: The system of implementation 49, in which the processing device is further configured to terminate the carbon oxide electrolyzer output if an input parameter exceeds or falls below one or more predetermined input range levels, the input parameter selected from a cathode output composition, an anode input composition, and/or an anode output composition.
Implementation 51: The system of either of implementations 49 or 50, in which the selected hydrogen to carbon-containing species ratio range is no more than 1:1.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and others will be apparent to one of ordinary skill in the relevant art from the following description of illustrative embodiments when read in conjunction with the accompanying drawings.

The present invention is described in detail below with reference to the attached drawing figures.

FIG. 1A is a schematic diagram that depicts the major components of a CO_xreduction reactor (CRR) including a single CO_xreduction electrolyzer cell, in accordance with some implementations of the present disclosure.

FIG. 1B is a schematic diagram of a CO_xreduction reactor (CRR) including a CO_xelectrolyzer reduction cell stack, in accordance with certain embodiments.

FIGS. 1C and 1D are schematic diagrams of a CO_xreduction reactor (CRR) including a plurality of CO_xreduction electrolyzer cell stacks, in accordance with certain embodiments.

FIG. 2 is a logical flow diagram illustrating input and output flows of the CRR, in accordance with some implementations of the present disclosure.

FIG. 3 is a controller flow chart of a method of carbon oxide reactor control, in accordance with some implementations of the present disclosure.

FIG. 4 is a schematic diagram of a CO_xrecycling unit operating in conjunction with a carbon oxide electrolyzer system, in accordance with some implementations of the present disclosure.

FIG. 5 illustrates an electrolytic carbon oxide reduction system that can be used to control water composition and flow in a membrane electrode assembly (MEA) of a carbon oxide electrolyzer system, in accordance with some implementations of the present disclosure.

FIG. 6 illustrates an example electrolytic carbon oxide reduction system that can be used to control water composition and flow in a membrane electrode assembly cell, in accordance with some implementations of the present disclosure.

FIG. 7 is a schematic diagram of a carbon oxide electrolyzer plant including a carbon oxide electrolyzer system, in accordance with some implementations of the present disclosure.

FIGS. 8A and 8B are flow diagrams of methods of operating a carbon oxide electrolyzer plant including a carbon oxide electrolyzer system, in accordance with some implementations of the present disclosure.

FIG. 9 is a block diagram of an example computing environment suitable for use in implementations of the present disclosure.

FIGS. 10 and 11 are schematic diagrams of a system including a plurality of carbon oxide reduction reactors, in accordance with some implementations of the present disclosure.

FIG. 12 is a schematic diagram of a carbon oxide reduction reactor assembly.

FIGS. 13A-13C are perspective views of a carbon oxide reduction reactor according to some embodiments.

DETAILED DESCRIPTION

Aspects of the present disclosure provide a system for an electrolysis plant incorporating advanced electrochemical reactors incorporating membrane electrode assemblies (MEAs) as well as control mechanisms. The system provides efficient transport and production rates while minimizing competing hydrogen formation reactions. The system uses multiple electrochemical reactors, scaling up production with high energy efficiency while providing flexibility in the types of chemical product outputs.
Carbon oxide electrolyzers containing polymer-based membrane electrode assemblies are designed or configured to produce oxygen from water at an anode and produce one or more carbon-based compounds through the electrochemical reduction of carbon dioxide or other carbon oxide at a cathode. Various examples of MEAs and MEA-based carbon oxide electrolyzers are described in the following references: Published PCT Application No. 2017/192788, published Nov. 9, 2017, and titled “REACTOR WITH ADVANCED ARCHITECTURE FOR THE ELECTROCHEMICAL REACTION OF CO₂, CO, AND OTHER CHEMICAL COMPOUNDS,” Published PCT Application No. 2019/144135, published Jul. 25, 2019, and titled “SYSTEM AND METHOD FOR CARBON DIOXIDE REACTOR CONTROL,” and Published PCT Application No. 2021/108446, published Jun. 3, 2021, and titled “MEMBRANE ELECTRODE ASSEMBLY FOR CO_xREDUCTION,” each of which is incorporated herein by reference in its entirety and for all purposes. Carbon oxide electrolyzers may be integrated into any of various industrial systems. The integration may involve producing any of various chemical products that can be used for downstream processing. Examples of such products include carbon monoxide, methane, ethene, hydrogen, oxygen, and any combination thereof. Downstream processing may produce intermediate products for production of valuable industrial products such as polymers, liquid hydrocarbons, fuels, and the like. Various examples of carbon oxide electrolyzers integrated in industrial operations are described in the following references: PCT Application Publication No. 2019/144135, published Jul. 25, 2019, and titled “SYSTEM AND METHOD FOR CARBON DIOXIDE REACTOR CONTROL” and PCT Application No. PCT/US2021/044378, filed Aug. 3, 2021, and titled “SYSTEM AND METHOD FOR CARBON DIOXIDE REACTOR CONTROL,” each of which is incorporated herein by reference in its entirety and for all purposes.
In some embodiments, a system (e.g., a CO_xelectrolyzer system) may include one or more carbon oxide (CO_x) reduction reactors is described herein. The CO_xreduction reactors, according to some embodiments, may be configured to electrochemically reduce a cathode gas, e.g., gaseous CO_x, into one or more reduction products. The CO_xreduction reactor, according to some embodiments, may include one or more CO_xreduction electrolyzers arranged in any appropriate fashion. At least one (or each) of the CO_xreduction electrolyzers, according to some embodiments, may include one or more CO_xreduction electrolyzer cells arranged in any appropriate fashion. For example, in some cases, the carbon oxide reduction electrolyzer may be in the form of a single-cell CO_xreduction electrolyzer or a multi-cell CO_xreduction electrolyzer stack (i.e., a stack). FIGS. 1A-1D illustrate various embodiments of a CO_xreduction reactor.
A non-limiting example of a CO_xreduction reactor in the form a single-cell CO_xreduction electrolyzer is illustrated in FIG. 1A. As shown, FIG. 1A is a schematic diagram that depicts the major components of a CO_xreduction reactor (CRR) (e.g., a single-cell CO_xreduction electrolyzer), in accordance with some implementations of the present disclosure. At the heart of the CRR is a membrane electrode assembly (MEA). According to some embodiments, the CO_xreduction electrolyzer includes an MEA including one or more ion-conductive polymer layers positioned between a cathode layer (e.g., a cathode catalyst layer) and an anode layer (e.g., an anode catalyst layer). For example, in one set of embodiments, the MEA may include a cathode layer including a reduction catalyst and a first ion-conducting polymer as well as an anode layer including an oxidation catalyst and a second ion-conducting polymer. In some cases, the reduction catalyst in the cathode layer may be capable of facilitating chemical reduction of CO_xto a carbon-containing species (CCS). In some cases, a polymer electrolyte membrane including a third ion-conducting polymer may be positioned between the anode layer and the cathode layer. The polymer electrolyte membrane may provide ionic transfer between the anode and cathode layers. A fourth ion-conducting polymer may be provided, in some embodiments, between the cathode layer and the polymer electrolyte membrane to act as a cathode buffer.
The CO_xreduction reactor may include one or more electrodes (e.g., anode, cathode), catalysts (e.g., within and/or adjacent the cathode and/or anode), gas diffusion layers (e.g., adjacent the cathode and/or anode), and/or flow fields (e.g., defined within and/or adjacent the electrodes and/or gas diffusion layers, such as one or more channels defined opposing the cathode across the gas diffusion layer). In some embodiments, the CO_xreduction reactor includes a membrane stack or membrane electrode assembly (MEA) having one or more polymer electrolyte membranes (PEMs), providing ionic communication between the anode and cathode of the reactor. In certain embodiments, the reactor includes a membrane stack including a cathode layer including a reduction catalyst and an ion-conducting polymer; one or more PEM membranes (e.g., a bipolar membrane, a monopolar membrane, etc.); one or more membranes including one or more anion conductors such as anion exchange membranes (AEMs), proton and/or cation conductors such as proton exchange membranes, and/or any other suitable ion-conducting polymers; one or more membranes including one or more buffer layers; etc.); and one or more anode layer including an oxidation catalyst and an ion-conducting polymer. The ion-conducting polymers of each layer can be the same or different ion-conducting polymers.
In some embodiments, one or more of the catalysts (e.g., reduction catalyst, oxidation catalyst) can include catalyst particles (e.g., defining a porous network of particles), such as nanoparticles. One or more of the catalysts can additionally or alternatively include one or more polymer electrolytes, optionally wherein the polymer electrolyte is mixed with the catalyst nanoparticles (e.g., arranged within the porous network, such as loaded into the open regions defined by the porous network). The catalyst nanoparticles can define one or more characteristic sizes (e.g., mean size, median size, minimum size, maximum size, size at a particular percentile of the particle size distribution, etc.), and/or the porous network can define a porosity (e.g., fraction of empty space within the network), density, circuitousness (e.g., characteristic path length per layer thickness, area, and/or volume, such as path through the empty spaces or path along interconnected particles, etc.), and/or any other suitable porous network metrics.
In some configurations, a bipolar MEA has the following stacked arrangement: cathode layer/cathode buffer layer (an anion-conducting layer)/cation-conductive layer (which may be a PEM)/anode layer. In some implementations, the bipolar MEA may have a cathode layer containing an anion-conductive polymer and/or an anode layer containing a cation-conductive layer. In some implementations, the bipolar MEA may have an anode buffer layer, which may contain a cation-conductive material, between the cation-conductive layer and the anode layer.
In some configurations, a bipolar MEA may have the following stacked arrangement: cathode layer/cation-conducting layer (which may be a PEM)/anion-conductive layer/anode layer. In some applications, a bipolar MEA having this arrangement may be configured in a system for reducing a carbonate and/or bicarbonate feedstock such as an aqueous solution of carbonate and/or bicarbonate.
In some configurations, an MEA may have the following stacked arrangement: cathode layer/anion-conducting layer/anode layer. In some implementations, this MEA has no cation-conductive layers between the cathode layer and the anode layer. In some applications, an MEA containing only anion-conductive material between the cathode and anode may be used in a system for reducing carbon monoxide feedstock. In one example, a carbon oxide reduction reactor may use a carbon fiber paper gas diffusion layer (e.g., Sigracet 39BC); a catalyst layer including approximately 20% by weight of approximately 4 nm gold particles on Vulcan carbon and an anion-conducting polymer (e.g., Fumasep FAA-3); a bipolar PEM; and a flow field such as a single, double, triple, or quadruple serpentine flow field or an interdigitated flow field. In a specific example, the electrodes may define an area of approximately 25 cm², but can additionally or alternatively define any other suitable area.
FIG. 1A illustrates the flow of reactants, products, ions, and electrons through a CRR 100 (e.g., a single-cell CO_xreduction electrolyzer). An MEA 102 incorporates a cathode 112 and an anode 120 that are separated by an ion-exchange layer 104. The ion-exchange layer 104 can include three sublayers: a cathode buffer layer 114, a polymer electrolyte membrane 116, and an optional anode buffer layer 118. The CRR 100 also has a cathode support structure 110 located adjacent to the cathode 112. In addition, an anode support structure 122 is adjacent to the anode 120.
The cathode support structure 110 may be formed of graphite, and/or other suitable electrically conductive material to which a voltage can be applied. Flow field channels can be cut or formed into an inside surface of a cathode polar plate 108 that is part of the cathode support structure 110. These flow field channels may be cut or formed as serpentine, parallel, interdigitated, or other channel designs, such as pin fields. A cathode gas diffusion layer 106 may be positioned adjacent to the inside surface of the cathode polar plate 108. In an alternative embodiment, there may be additional cathode gas diffusion layers 106 that abut the cathode gas diffusion layer 106 shown in FIG. 1A. These additional cathode gas diffusion layers 106 are not shown in FIG. 1A. The cathode gas diffusion layer(s) 106 facilitate the flow of gas into and out of the MEA 102.
Similarly, the anode support structure 122 may have an anode polar plate 124 to which a voltage can be applied. The anode polar plate 124 may be formed of metal and/or other suitable electrically conductive material(s). The anode support structure 122 can also incorporate flow field channels, such as the serpentine and other channel designs described above, including pin fields, that are formed in the inside surface of the anode polar plate 124. Some embodiments may incorporate more than one anode gas diffusion layer (e.g., adjacent to, abutting, or offset from other anode gas diffusion layer(s)), not shown in FIG. 1A. The anode gas diffusion layer 126 facilitates the flow of gas into and out of the MEA 102. In some implementations, the anode gas diffusion layer 126 may be made from titanium mesh or titanium felt, but other suitable materials can be used as well. An additional embodiment provides microporous cathode gas diffusion and/or anode gas diffusion layers 106, 126 to adjust the flow of gas into and out of the MEA 102.
Additional inlets and outlets can be provided in the cathode support structures 110 and anode support structures 122 to allow products and reactants to flow to and from the MEA 102. For example, according to some embodiments, the CO_xreduction electrolyzer may include a cathode inlet, a cathode outlet, an anode inlet, and an anode outlet, e.g., as represented by the arrows indicating anode feed material and oxidation product (anode inlet & anode outlet) and CO_xand reduction product (cathode inlet & cathode outlet) shown in FIG. 1A. In some cases, the cathode inlet may be configured to accept a cathode reactant such as carbon oxide (CO_x) (e.g., gaseous carbon oxide), and the cathode outlet may be configured to output a reduction product stream including one or more reduction products formed from electrochemical reduction of CO_x. According to some embodiments, the anode inlet may be configured to accept an anode reactant or feed material, and the anode outlet may be configured to output an oxidation product stream including one or more oxidation products formed from electrochemical oxidation of the anode reactant or feed material. In some cases, gaskets can also be incorporated into the support structures to prevent leakage of products and reactants from the cell.
According to some embodiments, CO_xis supplied to the cathode 112 (e.g., via the cathode inlet) and reduced over CO_xreduction catalysts in the presence of protons and electrons. CO_xcan be supplied to the cathode 112 (e.g., via the cathode inlet) in concentrations below 100%, or other suitable percentages, along with a mixture of other gases. The CO_xconcentration can be as low as 0.5%, 5% or 20%, or any suitable percentage. One embodiment provides for a CO_xconcentration between 10% and 100% of unreacted CO_xto be collected at an outlet (e.g., the cathode outlet) adjacent to the cathode 112. Unreacted CO_xcan be provided by another industrial process and input directly into the electrolyzer, in an example. In some cases, unreacted CO_xcan be separated from the reduction reaction products and recycled back to an inlet adjacent to cathode 112. The oxidation products at the anode 120 can be compressed to between 0 psig and 1500 psig.
While FIG. 1A illustrates an embodiment in which the CRR is in the form of a single-cell CO_xreduction electrolyzer, it should be understood that the disclosure is not so limited, and that in certain embodiments, the CRR may be in the form of one or more multi-cell CO_xreduction electrolyzer stacks. For example, the system described herein may incorporate multiple reactor assemblies where each reactor assembly can incorporate one MEA cell or many MEA cells called a stack. Multiple stacks can be arranged and operated in combination. The CRRs forming the individual electrochemical cells can be electrically and mechanically connected in series and/or in parallel. Multiple stacks can also be electrically and mechanically connected in series and/or in parallel to provide increased output and/or throughput. FIGS. 1B-1D illustrate one or more of the above-referenced CRR configurations.
A non-limiting example of a CO_xreduction reactor in the form of a multi-cell CO_xelectrolyzer stack is illustrated in FIG. 1B. As noted elsewhere herein, the cell stack may include a plurality of MEAs arranged as a stack. The individual cells and/or MEAs in the stack may include any appropriate component/layer described elsewhere herein, such as with respect to the electrolyzer cell described in FIG. 1A.
For example, FIG. 1B shows a multi-cell electrolyzer 170 with a stack of ten cells 100. The cells 100 may generally each include the elements shown in FIG. 1A, and be placed in series such that current from a single voltage source can be passed through all ten of the cells 100 simultaneously. The multi-cell electrolyzer 170 may have an anode-side compression plate 177 and a cathode-side compression plate 179 that may, for example, be designed so as to evenly compress the cells 100 so as to compress the various layers within each cell 100 into contact with one another such that the layers of the cells 100 form a liquid- and gas-tight assembly. Bolts or threaded rods (visible, but not called out) may be inserted through holes in the anode-side compression plate 177 and the cathode-side compression plate 179 and tightened in order to compression the cells 100 in between the anode-side compression plate 177 and the cathode-side compression plate 179.
The electrolyzer 170 may also include one or more manifold blocks 181 that may include fittings that provide fluidic interfaces for delivering fluids to, or receiving fluids from, the cells 100. For example, the manifold block 181 in this example includes a cathode inlet 172, a cathode outlet 174, two anode inlets 176, and two anode outlets 178. In this particular design, each cell has two symmetrical sets of channels within the anode flow field. Each set of channels is designed to flow the anolyte through approximately half of the corresponding cell 100. Each set of channels may thus flow fluid received from a respective one of the anode inlets 176 and deliver fluid to a respective one of the anode outlets 178. In contrast, the fluid (CO_xgas) that is provided to the electrolyzer 100 via the cathode inlet 172 is provided to channels within each cell that flow the CO_xgas received thereby through all of the cell 100. However, other implementations may see a single anode inlet 176 and/or a single anode outlet 178, and/or multiple cathode inlets 172 and/or multiple cathode outlets 174. In FIG. 1B, the cathode and anode inlets/ outlets 172, 174, 176, and 178 are shown both in the manifold block 181 and in the cells 100 fed by the manifold block 181.
A voltage may be applied to the stack of cells 100 via a cathode electrode 128 and an anode electrode 130, which may be located in between the stack of cells 100 and the cathode-side compression plate 179 or in between the stack of cells 100 and the anode-side compression plate 177, respectively.
A multi-cell CO_xreduction electrolyzer stack may include any of a variety of appropriate number of cells, such as at least 2, at least 4, at least 10, at least 20, at least 40, at least 50, at least 80, at least 100, or more, and/or up to up to 100, up to 150, up to 200, up to 400, up to 600, up to 800, or more. Any combinations of the above-referenced ranges are possible (e.g., at least 2 and up to 50, at least 50 and up to 100, etc.). Other ranges are also possible.
In some embodiments, the CRR may include a plurality of CO_x, reduction electrolyzers (e.g., multi-cell CO_xreduction electrolyzer stacks). A non-limiting example of one such embodiment of CRR is shown in FIGS. 1C and 1D. For example, as shown, CO_xreduction reactor (CRR) 100C may include a plurality of CO_xreduction electrolyzers, such as electrolyzers 170A-170D. At least one (or each) of the plurality of CO_xreduction electrolyzers (e.g., electrolyzers 170A-170D) may be in the form of a multi-cell CO_xreduction electrolyzer cell stack, e.g., such as the cell stack shown in FIG. 1B. Alternatively or additionally, at least one of the electrolyzers (e.g., electrolyzers 170A-170D) may be in the form of a single-cell CO_xreduction electrolyzer, e.g., such as the cell shown in FIG. 1A.
While FIG. 1C illustrates an embodiment in which the CRR includes four CO_xreduction electrolyzers (e.g., multi-cell CO_xreduction electrolyzer stacks), it should be understood that the disclosure is not so limited and that the CRR may include any of a variety of appropriate numbers of CO_xreduction electrolyzers. For example, the CRR may include at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 8, at least 10, at least 12, at least 15, at least 20, or more, and/or up to 40, up to 50, up to 80, up to 100, up to 500, or more electrolyzers. Any combinations of the above-referenced ranges are possible (e.g., at least 2 and up to 10, or at least 4 and up to 8, etc.). Other ranges are also possible.
In some embodiments, at least one (or each) of the plurality of CO_xreduction electrolyzers within the CRR may include a cathode inlet, a cathode outlet, an anode inlet, and an anode outlet. For example, as shown in FIGS. 1C and 1D, the plurality of carbon oxide reduction electrolyzers 170A-170D include, respectively, cathode inlets 172A-172D, cathode outlets 174A-174D, anode inlets 176A-176D, and anode outlets 178A-178D. In some cases, the cathode inlets (e.g., cathode inlets 172A-172D) may be configured to accept a cathode reactant (e.g., cathode gas such as carbon oxide (CO₂)), and the cathode outlets (e.g., cathode outlets 174A-174D) may be configured to output a reduction product stream including one or more reduction products formed from electrochemical reduction of CO_x, as well as any unreacted CO_xand/or byproducts. The anode inlets (e.g., anode inlets 176A-176D) may be configured to accept an anode reactant or feed material, and the anode outlets (e.g., anode outlets 178A-178D) may be configured to output an oxidation product stream including one or more oxidation products formed from electrochemical oxidation of the anode reactant or feed material, as well as any unreacted anode reactant and/or byproducts.
As noted elsewhere herein, the plurality of CO_xreduction electrolyzers within a CRR may be arranged in any appropriate fashion, e.g., in parallel and/or in series. A non-limiting example of electrolyzers connected in parallel is shown in FIGS. 1C and 1D. For example, as shown in FIGS. 1C and 1D, electrolyzers 170A-170D are fluidically connected in parallel, where the corresponding inlets (or outlets) of the electrolyzers are fluidically connected with one another and with a common inlet (or outlet) of the CRR, respectively. FIGS. 1C and 1D show the same elements, but in FIG. 1C, the anode-side fluid flow paths/components are shown greyed-out and the cathode-side fluid flow paths/components shown in black, while in FIG. 1D, the cathode-side fluid flow paths/components are shown greyed-out and the anode-side fluid flow paths/components shown in black.
In some embodiments, the CRR may include a first inlet, a first outlet, a second inlet, and a second outlet. As shown in FIGS. 1C and 1D, CRR 100C may include first inlet 180, first outlet 182, second inlet 184, and second outlet 186. In some cases, the first inlet 180 may be fluidically connected with corresponding cathode inlets 172A-172D of CO_xreduction electrolyzers 170A-170D, first outlet 182 may be fluidically connected with corresponding cathode outlets 174A-174D of the electrolyzers, second inlet 184 may be fluidically connected with corresponding anode inlets 176A-176D of the electrolyzers, and second outlet 186 may be fluidically connected with corresponding anode outlets 178A-178D of the electrolyzers.
In some embodiments, the first inlet (e.g., first inlet 180 as shown in FIG. 1C) of the CRR may be configured to accept a cathode reactant (e.g., a cathode gas such as gaseous carbon oxide (CO_x)) and transport it to the corresponding cathode inlets (e.g., cathode inlets 172A-172D) and into the electrolyzers (e.g., electrolyzers 170A-170D), such that an electrochemical reduction reaction may take place to electrochemically produce one or more reduction products of the cathode reactant (e.g., gaseous CO_x). In some cases, the first inlet of the CRR may be a cathode gas inlet, e.g., a gaseous CO_xinlet. In some embodiments, the first outlet (e.g., first outlet 182 of FIG. 1C) of the CRR may be configured to output a reduction product stream (via the corresponding cathode outlets (e.g., cathode outlets 174A-174D) of the electrolyzers) including the one or more reduction products (e.g., a carbon-containing species (CCS) produced from electrochemical reduction of gaseous CO_x), any unreacted cathode reactant (e.g., gaseous CO_x), and/or byproducts.
In some embodiments, the second inlet (e.g., second inlet 184 as shown in FIG. 1D) of the CRR may be configured to accept an anode reactant or feed material and transport it to the corresponding anode inlets (e.g., anode inlets 176A-176D) into the electrolyzers (e.g., electrolyzers 170A-170D), such that an electrochemical oxidation reaction may take place to electrochemically produce one or more oxidation products of the anode feed material. In some cases, the anode reactant or feed material includes anode water or solution (i.e., an anolyte) and the second inlet is an anolyte inlet. The second outlet (e.g., second outlet 186 as shown in FIG. 1D) of the CRR may be configured to output an oxidation product stream (via the corresponding anode outlets (e.g., anode outlets 178A-178D) of the electrolyzers) including the one or more oxidation products, any unreacted anode reactant (e.g., anode water or anolyte), and/or byproducts.
While FIGS. 1C and 1D illustrate an embodiment in which the CRR includes a plurality of CO_xreduction electrolyzers arranged in parallel, it should be understood that the disclosure is not so limited and that in certain embodiments, some (or all) of the electrolyzers in the CRR may be connected in series. For example, in some such embodiments, the cathode inlet of an electrolyzer (e.g., electrolyzer 170D) may be fluidically connected with the cathode outlet of a preceding electrolyzer (e.g., electrolyzer 170C), while the anode inlet of an electrolyzer (e.g., electrolyzer 170D) may be fluidically connected with the anode outlet of a preceding electrolyzer (e.g., electrolyzer 170C). One or more additional components, e.g., separators, purification units, etc., may be positioned between consecutive electrolyzers to remove undesirable species in the outlet streams prior to transporting the outlet streams into the inlets of the next electrolyzer(s).
In some embodiments, the CRR may include one or more additional components, including, but not limited to, resin bed(s), filter(s), analyzer(s) (e.g., gas analyzer(s)), sample separator(s), feedback control(s), valving(s), etc. For example, the CRR may include an optional resin bed (e.g., bed 188 as shown in FIG. 1D) fluidically connecting an inlet (e.g., second inlet 184) of the CRR with the anode inlets (e.g., anode inlets 176A-176D) of the electrolyzers, such that an anode reactant stream (e.g., anolyte input) may first pass through the resin bed before reaching the electrolyzer. The resin bed may advantageously remove contaminants (e.g., dissolved metal ions) capable of causing catalyst poisoning from the anode reactant stream, thus preventing deactivation of catalyst within the electrolyzers. Additionally or alternatively, the CRR may further include a filter (e.g., a particulate filter) (e.g., filter 190 as shown in FIG. 1D) configured to remove particulates from the anode reactant stream (e.g., anolyte input) to prevent clogging of the electrolyzers. The filter may be positioned between the inlet of the CRR (e.g., second inlet 184) and the electrolyzers, in any appropriate location, such as between the resin bed and the electrolyzers.
In some embodiments, the CRR may optionally include one or more gas analyzers configured to detect composition of the outlet streams (e.g., anode outlet stream or cathode outlet stream) of one or more electrolyzers. For example, the CRR may include an anode-side analyzer (e.g., gas analyzer 192 as shown in FIGS. 1C and 1D) configured to detect the composition of the anode outlet streams from the anode outlets (e.g., anode outlets 178A-178C), and a cathode-side analyzer (e.g., gas analyzer 194) configured to detect the composition of the cathode outlet streams from the cathode outlet (e.g., cathode outlets 174A-174D). As described in more detail below, the various analyzers may be configured to detect and/or monitor one or more parameters associated with the composition of the outlet streams, such as the presence or concentration of certain (undesirable) gases. In embodiments in which the outlet streams include a gas-liquid mixture, one or more separators (e.g., liquid/gas separators) may be coupled to the inlet of the gas analyzers to separate liquid from gas, so that the separated gas can be sent to the gas analyzer for analysis.
While FIGS. 1C and 1D illustrate an embodiment in which the anode (or cathode) outlet streams are collectively coupled to a single analyzer, it should be understood that the disclosure is not so limited and that in some embodiments, each of the anode (or cathode) outlet streams may be coupled to an analyzer.
In some embodiments, the CRR may be electrically coupled to a power module configured to provide electricity to the CRR and/or the electrolyzers. In some cases, the power module is a DC power module. For example, as shown in FIGS. 1C and 1D, CRR 100C and associated electrolyzers 170A-170D may be electrically coupled to power module 196.
While FIGS. 1C and 1D illustrate an embodiment in which the system includes a single CRR, it should be understood that the disclosure is not so limited, and that in certain embodiments, the CRR may include a CRR assembly including a plurality of CRRs, where at least one (or each) of the CRRs includes a plurality of CO_xreduction electrolyzers (e.g., electrolyzer cell stacks), a power module, and one or more optional additional components described above. A non-limiting example of multiple CRR(s) is shown in FIG. 12 , where multiple CRR(s) on electrolyzer skids 803A-803H are connected in parallel to a source of electricity input, a source of anolyte (e.g., water, and a source of cathode gas, as described in more detail below. At least one (or each) of the CRRs may have a configuration described elsewhere herein, such as with respect to CRR 100C in FIGS. 1C and 1D.
The system may include any of a variety of an appropriate number of CRRs, such as at least 1, at least 2, at least 3, at least 4, at 5, at least 6, at least 8, at least 10, at least 20, at least 30, at least 40, at least 50, at least 75, at least 100, at least 200, at least 500, or more, and/or up to 10, up to 50, up to 100, up to 200, up to 500, up to 1000, or more. Any combinations of the above-referenced ranges are possible (e.g., at least 1 and up to 10, or at least 5 and up to 50). Other ranges are also possible.
In some embodiments, the various outflows of the CRR, or portions thereof, may be recycled into the inflows of the CRR via one more recirculation or recycling loops. In some cases, the recycling loops may include one or more cathode gas (e.g., CO_x) recycle loops configured to recycle at least a portion of unreacted cathode gas from an outlet of the CRR into the inlet of the CRR. The recycle loops may further include one or more anode reactant (e.g., anode water or anolyte) recycle loops configured to recycle unreacted anode reactant into the inlet of the CRR. A non-limiting example of a CRR coupled to various recycle loops is illustrated in FIG. 2 .
FIG. 2 is a logical flow diagram 200 illustrating input and output flows of the CRR 208, in accordance with implementations of the present disclosure. CO_xfeed material 204 (e.g., gaseous CO_xsuch as gaseous CO₂), anode feed material 206 (e.g., anode water or anolyte) or reactants and electrical power from electrical power source 202 are fed into the CRR 208 via a first inlet. CO_xreduction products and any unreacted CO _x 210 may leave the reactor via a first outlet. Any unreacted CO_x(e.g., CO₂) 218 can be separated from the reduction products and recycled or returned to the CO_x(e.g., CO₂) feed material 204 of the reactor via a CO_xrecycle loop into the first inlet. Anode oxidation products 212 and any unreacted anode feed material 219 may leave the reactor separately (via a second outlet). In some cases, unreacted anode feed material 219 can also be recycled back via an anolyte recycle loop to the input side of the reactor via the second inlet. The reduction product 220 and the oxidation product 222 are the outputs of the CRR 208. The CRR 208 described herein may have any of a variety of configurations described elsewhere herein, such as CRR 100, 100B and/or 100C as shown in FIGS. 1A-1D.
In one particular set of embodiments, the cathode gas (e.g., the stream of feed material 204) includes gaseous CO₂and the anode reactant feed material includes water (i.e., anode water or anolyte), e.g., salt water or ionized water. In some such embodiments, the cathode output (e.g., reduction product stream 210) includes unreacted gaseous CO₂, reduction products such as CO, byproducts such as H₂, formic acid, and others such as ion, water (e.g., formed as a byproduct and/or migrated from the anolyte), etc. The anode output stream (e.g., oxidation product stream 212) includes unreacted water, oxidation products such as O₂, and byproduct (if any), in some embodiments.
A variety of catalysts can be used in the cathode of a CRR and can generate different products or mixtures of products during CO_xreduction reactions. The control and management system of the production system described in FIG. 2 controls the input flow and output product flow to optimize product generation.
FIG. 3 depicts a method 300 of carbon oxide reduction reactor control, in accordance with some implementations of the present disclosure. Controlling the carbon oxide reactor includes controlling aspects pertaining to quantity, concentration, and/or ratios of reactor products. Previously, carbon dioxide reactor control systems have addressed maximizing carbon monoxide production and other carbon-containing products (e.g., carbon-containing species (CCS)), including CO concentration, total CO output, or CO output rate. For some applications, maximizing product outputs is not suitable and selective aspect control, such as meeting a value within a range of target values, provides greater benefits. The present control method in FIG. 3 provides more efficient use of the reactor output for a variety of processes.
The method described in FIG. 3 can be implemented in the larger-scale system described in greater detail below. The method includes running the reactor under controlled process conditions to produce the desired outputs in the selected ratios, including molecular hydrogen-to-carbon-containing species (CCS) ratio (HCR), and/or CCS-to-molecular hydrogen ratio, as well as varying the process conditions to adjust outputs and/or output ratios.
Operating the reactor can include: providing inputs, such as gases, liquids, solids, and others. In one set of embodiments, these inputs can be carbon dioxide, a carbon dioxide source such as carbon dioxide-containing waste gas, and/or water. Some or all of the inputs undergo reactions when a voltage is applied across electrodes of the reactor. Utilizing various transition metal catalysts, these reactions generate products that can then be removed from the reactor. Examples of reactions include: reducing CO₂and/or water products to generate CO and/or other CCPs, such as formic acid, methanol, glyoxal, methane, acetic acid, glycoaldehyde, ethylene glycol, acetaldehyde, ethanol, ethylene, hydroxyacetone, acetone, allyl alcohol, propionaldehyde, n-propanol, and others, as well as H₂, and/or O₂. The CRR control operations method 300 can also be run to cause other desired reactions to occur and can include additional or alternate elements performed in any suitable manner.
The CRR control operations method 300 may include controlling the CRR to achieve a selected set of process conditions, which may be known as aspects. Aspects may include process conditions known to produce a desired metric output value, such as a desired CCS:H₂ratio, or CO:H₂ratio. CRR control operations method 300 may also include altering process conditions, such as process conditions based on differences between actual and desired outputs. Some examples of process control can include: imposing an initial set of process conditions; monitoring one or more output metrics, such as CCS:H₂ratio (e.g., CO:H₂ratio); determining that an output metric differs from a target output metric; altering one or more process conditions to reduce the output metric difference, such as reducing or increasing a process condition value for a condition where the output metric tends to increase or decrease along with increasing said process condition value; and optionally continuing to monitor the output metrics and/or alter the process conditions. One example of the latter can be implementing closed-loop process control of the process conditions based on the output metrics.
In addition, CRR control operations method 300 can include determining the target output metrics and determining which parameters or aspects to target, such as key parameters for a downstream system. One example is determining target reactor output metrics 302, which also provides an input to controlling reactor process conditions 304. The output metric can be determined through iterative testing and/or monitoring downstream application performance.
Determining target reactor output metrics 302 functions to identify a value to target. The value may, in some instances, be a desired range of values, a maximum value, or a minimum value. The value(s) may also be a predetermined value or values associated with downstream performance. The target reactor output metrics provide input for controlling reactor process conditions 304. Determining target reactor output metrics 302 also provides input to selecting system configuration 308. Selecting system configuration 308 also affects controlling reactor process conditions 304. Once the reactor process conditions 304 have been controlled, determining the actual reactor output metrics 306 can occur.
CRR control operations method 300 also includes delivering reactor products 310 to a downstream consumer 312, e.g., a downstream device or system that may use the reactor product(s) to perform some task, e.g., synthesizing another product or performing some other industrially useful operation using the product(s). In some implementations, the reactor products may be altered before providing the products to the downstream consumer(s). Altering the reactor products 310 may include purifying the products or mixing additional gases and/or substances into the reactor output stream to achieve a desired output metric. To give one example, if the CCS:H₂(e.g., CO:H₂) ratio of the reactor output differs from a desired value, the ratio may be adjusted by mixing the reactor output with other gases, for instance potentially pure CCS (e.g., CO) and/or H₂. The ratio can be monitored and deviations can be corrected by mixing to adjust the ratio. This example may also include altering the process conditions to correct the reactor outputs. A further variation provides for feeding an external gas supply to a downstream consumer. An example would be feeding the outputs and/or waste gases of a steel mill to a gas fermenter with the reactor products used to alter the CCS: H₂ratio (or HCR) of the external gas supply, and then mixing in the reactor products to obtain the desired value (or HCR).
Further embodiments provide for determining operation metrics associated with upstream or downstream elements of the system. These operation metrics can include: reactor conditions such as temperature and/or pressure, output quantity and/or rate, output composition, output purity, reactor efficiency, and others.
In some embodiments, the system described herein may include a CO_xrecycling unit or loop. The CO_xrecycling unit, according to some embodiments, may be fluidically connected with a CO_xelectrolyzer, e.g., either directly or indirectly via one or more intervening downstream units. FIG. 4 is a schematic diagram of a system 400 including a CO_xrecycling unit 402 operating in conjunction with an electrolyzer 410, in accordance with some implementations of the present disclosure. The system 400 can include an upstream source of CO_xconnected to an input of electrolyzer 410. For example, the upstream source may be, but is not limited to, a biogas production system, a direct air capture system, an ethanol fermentation system, a natural gas production system, a cement production system, or a steel blast furnace. Other systems can also serve as an upstream source. Water and electricity are also input to the electrolyzer 410.
The electrolyzer 410 outputs high pressure CO_x, H₂, and/or CO. The outputs of the electrolyzer 410 are input to bioreactor 412. The bioreactor 412 outputs low pressure CO_x, water vapor, as well as volatile compounds and bioproduct. Low-pressure CO_xis input to the CO_xrecycling unit 402. The first step in the CO_xrecycling unit 402 is water removal by the water removal apparatus 408. The water removal apparatus outputs low pressure CO_xand volatile compounds, which are then input to a volatile compounds removal apparatus 406. The low-pressure CO_xoutput by the volatile compounds removal apparatus 406 is then input to a CO_xcompressor 404 to produce high pressure CO_x. The high-pressure CO_xcan be input to the electrolyzer 410, thus starting the cycle again using recycled products.
The CRRs described herein can make a range of products including methane, ethylene, formate, CO, molecular hydrogen, acetic acid, propanol, butane, and others. Different carbon oxide reactors with different layer stacks, catalysts, catalyst layers, flow fields, and/or gas diffusion layers can be used to produce different reaction products, based on adjusting the operation parameters as described above.
FIG. 5 illustrates an electrolytic carbon oxide reduction system 500 that can be used to control water composition and flow in a membrane electrode assembly (MEA), in accordance with some implementations of the present disclosure. As shown in FIG. 5 , the system 500 includes an MEA cell 524 including an anode 534, a cathode 516, and an MEA 526. The system 500 also includes an anode water recirculation loop 532 and a gaseous carbon oxide recirculation loop 510.
In the system 500, the anode water recirculation loop 532 delivers water to and removes water from anode 534. Anode water recirculation loop 532 includes an anode water reservoir 540 and water flow paths 530, 536, and 538. Anode water recirculation loop 532 can interface with a water source 528 and/or a source of concentrated salt solution 542. These sources can be used to adjust the anode water with purified water and/or a concentrated salt solution to adjust the composition of the anode water. The anolyte solution may primarily include water with additional constituents including, but not limited to, a salt or salts. Purified water, such as purified deionized water, can also be provided by water source 528. As shown in FIG. 5 , the source of the concentrated salt solution can be directly connected to anode water reservoir 540, but it can also be present at other positions along anode water recirculation loop 532.
The water used in the system 500 can be purified by a water purification component, not shown in FIG. 5 . The water purification component can be a filter, resin column, or other suitable water purifier capable of removing ions, such as iron ions or other transition metal ions, from the anode water. The water purification component can be provided in any one or more of the water flow paths 530, 536, and 538.
Gaseous carbon oxide recirculation loop 510 provides a gaseous carbon oxide feed stream to the cathode 516 and removes a gaseous product stream from the cathode 516. The cathode outlet stream can contain reaction products as well as substantial quantities of unreacted gaseous carbon dioxide. A gaseous carbon oxide recirculation loop 510 includes a water separator 512, such as a water condenser, a reduction product recovery component 508, a humidifier 504, and flow paths 518, 520, 506, and 514. Fresh carbon oxide reactant gas can be provided from a carbon oxide source 502 that connects into the humidifier 504 and from the humidifier 504 into gaseous carbon oxide recirculation loop 510.
The humidifier 504 can humidify an input stream of the carbon oxide gaseous reactant that is upstream from the cathode 516. The humidifier 504 provides carbon oxide with a relatively high partial pressure of water vapor, which may act to prevent drying of the cathode 516 or other components of the MEA 526. Some embodiments may omit the humidifier 504.
When the gaseous carbon oxide reactant flows through the cathode 516, it can remove anode water that flowed through the anode 534 through the MEA 526 and into the cathode 516. In the gaseous carbon oxide recirculation loop 510, anode water that is present in the gaseous carbon oxide stream leaving the cathode 516 may be flowed through the water separator 512, in which at least a fraction of the water present in the carbon oxide outlet stream may be removed. The relatively drier carbon oxide stream leaving the water separator 512 enters the reduction product recovery component 522. The reduction product recovery component 522 may remove one or more reduction products from the carbon oxide outlet stream. The reduction products removed can include carbon monoxide, hydrocarbons, and other organic compounds.
Some of the reaction product produced at the cathode of the MEA 526 may be dissolved or contained in the water removed by the water separator 512. The water processed at the water separator 512 can incorporate a reduction product recovery component 508 that is configured to remove the reaction products from the water provided by the water separator 512.
In alternative embodiments, substantial quantities of anode water can cross from the anode to the cathode of the MEA 526, where the anode water, with the salts dissolved, may be transferred from the anode loop to the cathode loop. A connection between the two loops that returns water from gaseous carbon oxide recirculation loop 510 to anode water recirculation loop 532 can be used to improve the system 500. The anode water can have very low concentrations of some inorganic and/or organic materials, such as iron and other transition metal ions. The cathode solution may primarily include water with additional constituents including, but not limited to, a salt or salts. The anode water can also contain intentionally added salts. Processed water recovered from the cathode side can be returned to the anode side. Water that has been removed from the gaseous carbon oxide recirculation loop 510 is delivered via a water line 543 to the anode water reservoir 540, where it reenters the anode water recirculation loop 532.
Other embodiments do not provide a direct connection between the gaseous carbon oxide recirculation loop 510 and the anode water recirculation loop 532. An alternate embodiment provides for filtration or purification of the cathode water before reintroducing the cathode water to the anode loop. The filtration or purification can be provided after water source 528 and before entry to anode water recirculation loop 532. In this embodiment, filtration or purification can be provided in water line 543 or in water flow path or line 538. A further alternate embodiment provides for filtration and purification of the recovered water from the reduction product recovery component 522.
While FIG. 5 illustrates an embodiment in which the system includes a CRR in the form of a single-cell CO_xelectrolyzer (e.g., cell 524), it should be understood that the disclosure is not so limited and that in some embodiments, the CRR may be in the form of one or more multi-cell CO_xelectrolyzer stacks and/or a CRR assembly, as described elsewhere herein.
In some embodiments, the system may include one or more salt controls and/or recirculation loops, as described in more detail below.
FIG. 6 illustrates an example electrolytic carbon oxide reduction system 600 that can be used to control water composition and flow in a membrane electrode assembly (MEA) cell 604, in accordance with some implementations of the present disclosure. In FIG. 6 , the system 600 includes the MEA cell 604 and two recirculation loops: a salt recirculation loop 612 and a purified water recirculation loop 614. Outputs of these two loops can be combined in the cell input reservoir 608, where anode water is produced. The anode water has a salt composition and concentration suitable for use with the MEA cell 604. Anode water is supplied from the cell input reservoir 608 through a conduit.
Anode water leaving the MEA cell 604 is provided to salt ion harvester 610, which is configured to remove all or some of the salt from the anode water. The water leaving the salt ion harvester 610 is relatively pure. Conduit 622 feeds the water from the salt ion harvester 610 to a water purifier 623. The water purifier 623 may remove any remaining impurities that can remain after the desirable salt ions have been removed. Water purifier 623 may include a small pore filter and/or an ion exchange resin. The output purified water can have very low concentrations of potentially detrimental ions such as transition ions and/or halides. The low concentrations may be on the order of ppm or ppb levels. The purified water leaving the water purifier 623 leaves through conduit 624 to water reservoir 606. Water reservoir 606 provides water as needed to the cell input reservoir 608, where the water is combined with salt or a concentrated salt solution to prepare the anode water for use in MEA cell 604. As shown in FIG. 6 , purified water is provided to the cell input reservoir 608 through conduit 618.
The purified water recirculation loop 614 includes the water purifier 623, water reservoir 606, cell input reservoir 608, and salt ion harvester 610. Other embodiments may provide a purified water loop that does not include one or more of the above elements.
In FIG. 6 , salt or a concentrated salt solution produced by salt ion harvester 610 is delivered through conduit 620 to the salt reservoir 602. The salt reservoir 602 maintains salt in either solid or solution form. Salt is provided on an as-needed basis from the salt reservoir 602 to the cell input reservoir 608, where the salt is combined with purified water to prepare the anode water for use by the MEA cell 604. Purified water is provided to cell input reservoir 608 through conduit 616. The salt reservoir 602 can serve as a holding point for desired salt ions to be pumped into the cell input reservoir 608.
The embodiments illustrated in FIG. 6 in the salt recirculation loop 612 include the salt reservoir 602 as well as salt ion harvester 610. Other embodiments may provide a salt recirculation loop that does not contain one or more of the elements described above.
Salt ion harvesters include devices containing an ion-selective membrane as well as devices incorporating salt chelating and releasing agents. These devices can select for the salt ions desired in an anode water stream. In some embodiments, a salt ion harvester produces a solid salt precipitate that can then be selectively fed back into the salt recirculation loop or another portion of the anode water management system.
The electrolytic carbon oxide reduction system depicted can incorporate a control system that includes a controller and one or more controllable components, such as pumps, sensors, valves, and power supplies. The sensors can be pressure sensors, temperature sensors, flow sensors, conductivity sensors, pH sensors, optical sensors, chromatography systems, as well as absorbance measuring tools.
The control system may be configured to provide anode water while the MEA cell 604 is operating. The control system can act to maintain salt concentrations at predetermined or desirable levels, recirculate anode water flowing out of the anode, adjust the composition and flow rate of anode water into the anode, move water from the cathode outflow back to the anode water, and adjust the composition and flow rate of the water recovered from the cathode stream.
The control system can be configured to incorporate feedback from the sensors including those listed above to adjust the mix of pure water and introduced salt ions in order to produce a bulk conductivity or other desired water parameter. The control system can operate to ensure that the anode water remains within desired levels, which may be predetermined or adjusted on the basis of sensor readings. For example, if a sensor determines that the salt concentration in the anode water is too low, or below a nominal salt concentrate flow rate (e.g. 0.1 gph to 0.30 gph (0.3793 lph to 1.136 lph)) for mixing, the controller can direct that higher concentration water be added from a reservoir. Conversely, pure water can be added to dilute the salt concentration. The control system can also provide level control in the cathode water reservoir, cathode water inlet and discharge flow rate, and can also track pressure in the carbon oxide electrolyzer stack.
In addition, the control system of the controller can incorporate any number of processors and memory devices. The controller can incorporate control logic to execute instructions input from another source, such as an operator, or another sensor. The controller electronics can provide control of flow through the electrolytic cells at multiple points in the process, such as control of the input flows, intermediate operational parameters, and output rate. The controller can be programmed to manage the input of gases, liquids, temperature settings, pressure settings, electrical current, and flow rates throughout the system.
The controller need not be a single device but can be a distributed computing system incorporating multiple discrete controllers that are networked together. The distributed computing resources could be located at multiple points in the system. With reference to FIG. 6 , examples include the MEA cell 604, but could also be incorporated at water reservoir 606, salt ion harvester 610 and cell input reservoir 608, to name just a few options. The controller, in an example, operates to control the MEA cell 604 such that salt is not precipitated in the MEA cell 604.
Carbon oxide electrolyzer plant 702 of FIG. 7 also incorporates control and automation tools, in an example. A programmable logic system is incorporated and provides expandable input/outputs, relay outputs, and voltage and current input/output. The programmable logic system also incorporates at least one high speed interface, such as Ethernet IP, or other interface, as well as remote communications and networking, using local area networks (LANs) or wireless communication systems such as 5G, or other similar systems. The control system incorporates digital gas controllers, backpressure regulators, and power regulation. In addition, the control system provides startup sequencing, allowing the carbon oxide electrolyzer plant 702 to start the carbon dioxide and water flows before electrical current flow begins. The startup sequence can also include a heating step for input water prior to application of electrical current. The control system manages the series of process variable changes that can be made before applying electrical current. Set points for each subsystem can be changed as needed from the control panel. The control system may also provide recovery sequencing for the carbon oxide electrolyzer plant 702. On shut down, the applied current is reduced to zero and the control system may place the power supply at open circuit voltage using a contactor. Carbon dioxide and water flow capabilities are adjustable as needed. The control system incorporates an automatic shutdown sequence that can be triggered by defined process variables trending outside of normal operating ranges.
In some embodiments, the system (e.g., the CO_xreduction electrolyzer system) includes one or more CRRs coupled to various upstream and/or downstream units, such as an anolyte circulation system, a catholyte circulation system, a temperature control system, a salt dosing system, one or more separators, one or more detectors and/or analyzers, gaseous CO_xrecycle loop(s), water recycle loop(s), etc. By coupling the CRRs with these upstream and/or downstream units, the system may allow for controlled production of reduction products and/or oxidation products in an automated and continuous manner, while allowing for efficient utilization of energy and/or waste heat. Non-limiting examples of various embodiments of the system are illustrated in FIG. 7 and FIGS. 10 and 11 , as described in more detail below.
According to some embodiments, the system includes a single CRR (e.g., CRR 704 as shown in FIG. 7 ) or a plurality of CRRs (e.g., CRR assembly 803 as shown in FIGS. 10 and 11 ). As described elsewhere herein, the CRR may include a plurality of CO_xreduction electrolyzers, e.g., as shown in FIGS. 1C and 1D. The CRR assembly, in some embodiments, may include a plurality of CRRs, at least one (or each) of which includes a plurality of CO_xreduction electrolyzers. At least one (or each) of the plurality of CO_xreduction electrolyzers may be in the form of a CO_xreduction electrolyzer stack, e.g., as shown in FIG. 1B, in some embodiments.
In some embodiments, the CRR or CRR assembly (e.g., CRR 704 or CRR assembly 803 as shown in FIGS. 7 and 10 and 11 ) includes a first inlet (e.g., first inlet 780 or 880), such as a cathode gas inlet, fluidically connected with a source of gaseous CO_x(e.g., first input 710 or 810) and configured to receive a gaseous CO_xinput (e.g., cathode gas input flow 781 or 881). The source of gaseous CO_xand/or the CO_xinput may include substantially pure CO_x, with negligible amounts of impurities and/or other gases, in some embodiments. For example, CO_xmay be present in a mole fraction of at least 80 mol %, at least 90 mol %, at least 95 mol %, at least 97 mol %, or more, and/up to 99 mol %, up to 99.9 mol %, or up to 100 mol %) in the gaseous CO_xand/or the CO_xinput. In some embodiments, the gaseous CO_xand/or the CO_xinput is essentially free of water vapor. Alternatively, the gaseous CO_xand/or the CO_xinput may include a small amount of saturated water vapor, such as in mole fractions of up to 1 mol %, up to 2 mol %, up to 5 mol %, or up to 10 mol %, according to some embodiments. In some cases, the first inlet (e.g., first inlet 780 or 880) of the CRR or CRR assembly may be fluidically connected with the one or more CO_xreduction electrolyzers within the CRR or CRR assembly via the respective CO_xelectrolyzer cathode inlets, e.g., similar to the fluidic connectivity discussed elsewhere herein, such as with respect to FIGS. 1C and 1D.
In some embodiments, the CRR or CRR assembly (e.g., CRR 704 or CRR assembly 803 as shown in FIGS. 7, 10 and 11 ) includes a first outlet (e.g., first outlet 782 or 882), such as a reduction product stream outlet, configured to output a reduction product stream (e.g., stream 783 or 883). As described elsewhere herein, the reduction product stream may include one or more electrochemical reduction products of the gaseous CO_x(e.g., a carbon-containing species (CCS)), any unreacted CO_x, any byproducts, and/or residue species (if any). For example, in embodiments in which the inputs include gaseous CO₂, the reduction product stream may include CCS (e.g., CO), H₂, unreacted CO₂, water, along with a small amount (if any) of byproducts (e.g., formic acid, ions, etc.). In some cases, the first outlet (e.g., first outlet 782 or 882) of the CRR or CRR assembly may be fluidically connected with the one or more CO_xreduction electrolyzers within the CRR or CRR assembly via the respective CO_xelectrolyzer cathode outlets, e.g., similar to the fluidic connectivity discussed elsewhere herein, such as with respect to FIGS. 1C and 1D.
In some embodiments, the reduction product stream may include either a single-phase mixture or a two-phase mixture, depending on the particular operating conditions and boiling point of individual species within the reduction product stream. For example, in some cases, the reduction product stream may be a gaseous mixture of reduction product(s), unreacted species, and/or byproducts. Alternatively, the reduction product stream may be a gas-liquid two-phase mixture. For example, the reduction product stream of gaseous CO_x(e.g., CO₂) may include a gaseous carbon-containing species (CCS) (e.g., CO) and H₂, unreacted gaseous CO_x, water (either in vapor or liquid form), byproducts (e.g., formic acid either in vapor or liquid form), etc.
The reduction product stream may have any of a variety of appropriate molecular hydrogen-to-carbon-containing species (CCS) ratio (i.e., HCR). In some embodiments, the HCR is at least 1:100, at least 1:50, at least 1:20, at least 1:15, at least 1:12, at least 1:11, at least 1:10, at least 1:9, at least 1:8, at least 1:5, at least 3:7, at least 1:2, at least 1:1, at least 1.2:1, at least 1.4:1, at least 1.5:1, at least 1.6:1, at least 1.7:1, at least 1.8:1, at least 1.9:1, at least 2:1, at least 2.1:1, at least 2.2:1, at least 2.3:1, at least 2.4:1, at least 2.5:1, or more. In some embodiments, the HCR is no more than 3:1, no more than 2.5:1, no more than 2.4:1, no more than 2.3:1, no more than 2.2:1, no more than 2.1:1, no more than 2:1, no more than 1.9:1, no more than 1.8:1, no more than 1.7:1, no more than 1.6:1, no more than 1.5:1, no more than 1.4:1, no more than 1.2:1, no more than 1:1, no more than 1:2, no more than 3:7, no more than 1:5, no more than 1:8, no more than 1:9, no more than 1:10, no more than 1:12, no more than 1:15, no more than 1:20, or less. Any of the above-referenced ranges are possible (e.g., at least 1.5:1 and no more than 2.4:1, at least 1.6:1 and no more than 2.2:1, at least 1.9:1 and no more than 2.1:1, at least 1:20 and no more than 1:5, at least 1:15 and no more than 1:8, or at least 1:50 and no more than 1:1, etc.). Other ranges are also possible. In one set of embodiments, the CCS includes carbon monoxide and the HCR is the molecular hydrogen to carbon monoxide ratio.
In some embodiments, the system may be controlled to produce a reduction product stream including predominately a reduction product of CO_x(e.g., a CCS) compared to other species (e.g., molecular hydrogen). This may advantageously give rise to a relatively low, e.g., lower than 1:1, molecular hydrogen-to-carbon-containing species (CCS) ratio (i.e., HCR), such as an HCR of at least 1:50 and no more than 1:1, at least 1:20 and no more than 1:2, at least 1:15 and no more than 1:5, at least 1:20 and no more than 1:6, at least 1:12 and no more than 1:8, etc. Other ranges are also possible.
In some embodiments, the CRR or CRR assembly (e.g., CRR 704 or CRR assembly 803 as shown in FIG. 7, 10 , or 11) includes a second inlet (e.g., second inlet 784 or 884), such as an anolyte or anode water inlet, fluidically connected with a source of anolyte (e.g., anode water) and configured to receive an anolyte input (e.g. input 785 or 885). The anolyte, according to some embodiments, is a salt- or ion-containing anolyte, such as salt water or ionized water. As described elsewhere herein, the anolyte may include any of a variety of appropriate salts (e.g., in the form of dissociated cations and/or anions) and may be present in any of a variety of appropriate concentrations.
In some cases, the source of salt- or ion-containing anolyte (e.g., tank 722 or 822) may be fluidically connected with a source of fresh anolyte (e.g., anolyte source 716 or 816) and a source of salt or ions (e.g., salt-containing source 720 or 820). The anolyte sources 716 and 816 may, for example, be deionized (DI) or ionized water source(s). In some cases, the second inlet (e.g., second inlet 784 or 884) of the CRR or CRR assembly may be fluidically connected with the one or more CO_xreduction electrolyzers therein via the respective CO_xelectrolyzer anode inlets, similar to the fluidic connectivity discussed elsewhere herein, such as with respect to FIGS. 1C and 1D.
In some embodiments, the CRR or CRR assembly (e.g., CRR 704 or CRR assembly 803 as shown in FIG. 7, 10 , or 11) includes a second outlet (e.g., outlet 786 or 886), such as an oxidation product stream outlet (i.e., anolyte outlet), configured to output an oxidation product stream (e.g., stream 787 or 887). The oxidation product stream may include one or more electrochemical oxidation products of the anolyte, any unreacted anolyte, any byproducts and/or residue species (if any). For example, the oxidation product stream may include 02 and/or unreacted anolyte (e.g., salt-containing water), along with a small amount (if any) of byproducts. In some cases, the second outlet (e.g., second outlet 786 or 886) of the CRR or CRR assembly may be fluidically connected with the one or more CO_xreduction electrolyzers within the CRR or CRR assembly via the respective CO_xelectrolyzer anode outlets, e.g., similar to the fluidic connectivity discussed elsewhere herein, such as with respect to FIGS. 1C and 1D.
In some embodiments, the system includes an anolyte circulation system in fluidic communication with the CRR(s). In some cases, the anolyte circulation system may be configured to continuously introduce an anolyte input into the CRR(s) from a source of anolyte, and to recover or recycle at least a portion of unreacted anolyte from the outlet CRR(s) during operation for additional input into the CRR(s). As described elsewhere herein, the anolyte circulation system may include any of a variety of components associated with the processing of the various anolyte streams (e.g., anode water) within the CRR(s) (e.g., CRR(s) 704 or 803 as shown in FIGS. 7, 10, and 11 ), such as an anolyte separator unit (e.g., items 724 or 824), salt-containing anolyte reservoir (e.g., items 722 or 822), fresh anolyte source (e.g., items 716 or 816), anolyte tank (e.g., item 726), pressurizing unit (e.g., item 738), anolyte filter (e.g., items 718 or 836), salt-containing source (e.g., items 720 or 820), various temperature control(s) (e.g., items 734, 736, or 836), a salt dosing system, anolyte recirculation loops, etc., as well as the various fluidic connectivity therein between.
In some embodiments, the anolyte circulation system includes an anolyte recirculation system. The anolyte recirculation system may be configured to transport (e.g., recycle) at least a portion (e.g., at least 50%, at least 60%, at least 70%, and/or up to 80%, up to 90%, or up to 100%) of the unreacted anolyte contained within the oxidation product stream (e.g., stream 787 or 887 as shown in FIGS. 7, 10, and 11 ) into the anolyte input (e.g., input 785 or 885) fed into the anolyte inlet (e.g., second inlet 784 or 884) of the CRR(s) (e.g., CRR(s) 704 or 803). The unreacted anolyte includes water, such as ionized water or salt-containing water, in some embodiments. The anolyte recirculation system may include a variety of components associated with the processing of the recycled anolyte output from the CRR(s), such as an anolyte separator unit (e.g., unit 724 or 824 as shown in FIGS. 7, 10, and 11 ), anolyte tank (e.g., unit 726), pressurizing unit (e.g., unit 738), etc., as well as the various components providing fluidic connectivity therebetween.
As mentioned above, the anolyte recirculation system may include an anolyte separator unit, e.g., such as anolyte separator tank or unit 724 or 824 as shown in FIGS. 7, 10, and 11 . In some embodiments, the anolyte separator unit (e.g., unit 724 or 824) may be fluidically connected with the second outlet (e.g., second outlet 786 or 886) of the CRR(s) and to the source of salt-containing anolyte (e.g., tank 722 or 822). In some cases, the anolyte separator unit may be configured accept at least a portion (e.g., at least 50%, at least 70%, at least 80%, at least 90%, and/or up to 95%, up to 100%) of the oxidation product stream (e.g., stream 787 or 887) from the second outlet (e.g., second outlet 786 or 886) of the CRR(s) (e.g., CRR(s) 704 or 803). The anolyte separator unit may be configured to separate one or more oxidation products (e.g., molecular oxygen) from unreacted anolyte (e.g., water such as salt- or ion-containing water) to produce an outlet stream (e.g., stream 725 or 827) enriched in the anolyte (e.g., water) relative to the oxidation product stream (e.g., stream 787 or 887) and an outlet stream (e.g., stream 715 or 815) enriched in one or more oxidation products (e.g., molecular oxygen) relative to the oxidation product stream in some embodiments. In some cases, the outlet stream enriched in the one or more oxidation products may be a substantially pure stream of oxidation product(s), such as having a purity of at least 70%, at least 80%, at least 90%, at least 99%, and/or up to 99.9%, or up to 100%.
The anolyte separator unit may include any of a variety of separation units, including, but not limited to, a gas-liquid separator, a chiller, a condenser, centrifugal separators, membrane based separators, etc.
In some embodiments, the anolyte circulation system includes a temperature control system configured (e.g., operable) to control the temperature of one or more anolyte streams (e.g., anolyte input and/or output streams) and/or a temperature differential of an anolyte stream across an anode side of the CRR(s) and/or associated CO_xreduction electrolyzer(s). In some cases, the temperature control system may include one or more temperature sensors, one or more heating devices, one or more cooling devices, one or more pressurizing systems or pressure-control systems (such as pumps and/or valves), one or more feedback controllers, and/or one or more flow controls, according to some embodiments. In some cases, the heating and/or cooling devices may include one or more heat exchanger(s). The heat exchangers may be configured to control an anode inlet temperature of the anolyte solution provided to the CRR(s) and/or associated electrolyzers. In some embodiments, the one or more pressurizing systems include one or more pumps. The one or more pumps may be configured to control an anode inlet flow rate of the anolyte solution provided to the CRR(s) and/or associated electrolyzers.
In some embodiments, by controlling one or more components within the temperature control system, the temperature control system may be configured to maintain, during operation, a desired temperature differential (e.g., dT) across an anode side of the CRR(s) and/or across an anode side of at least one (or each) of the CO_xreduction electrolyzer(s) (e.g., CO_xreduction electrolyzer stacks) within the CRR(s). In some cases, it may be beneficial to maintain a relatively small anode-side dT across individual CO_xreduction electrolyzers (e.g., CO_xreduction electrolyzer stacks). This may advantageously allow for controlled anolyte flow across the anode, controlled electrochemical reactions to take place in a substantially uniform manner throughout the electrolyzer stack, prevention or reduction of non-uniform heating (thereby resulting in a relatively uniform temperature profile across the electrolyzer stack), prevent or reduction of undesirable overheating of the electrolyzer stack, and/or the prevention of structural and/or chemical degradation of components within the electrolyzer stack, and may thus lead to an overall increase in the performance and lifetime of the electrolyzer(s). Without wishing to be bound by any particular theory, it is believed that temperature differential may be affected by various parameters, such as the flow rate (e.g., mass flow rate, volumetric flow rate, etc.) of the anolyte entering into the CRR(s) and/or electrolyzer(s), the specific heat capacity of the anolyte, electrolyzer stack performance parameters such as the applied cell voltage, stack current, number of cells within the stack, amount of waste heat produced by the CRR(s) and/or electrolyzer(s), etc.
In some cases, one or more components within the temperature control system (e.g., pressurizing units (e.g., pumps), flow control(s) (e.g., valves), heat exchanger(s), etc.) may be configured (e.g., sized) such that a desired temperature differential is maintained across the anode inlet(s) and anode outlet(s) of the CO_xreduction electrolyzer(s). In some embodiments, a desired dT may be maintained, at least in part, by controlling the anolyte flow rate entering into the CRR(s) and/or electrolyzer(s) via the one or more components. For example, a pressurizing unit (e.g., pump) and/or flow controls (e.g., valves) may be configured (e.g., sized, regulated, etc.) such that a desired anolyte flow rate is established, which would at least in part contribute to a desired dT. In some cases, when the measured dT exceeds a threshold value, the pressurizing unit and/or flow controls may be configured to increase the anolyte flow rate to a predetermined value such that dT of the anolyte across the anode side can be lowered and maintained below the threshold value. One or more sensors (e.g., temperature sensors, flow rate sensors) and/or feedback controllers may be employed during operation to allow for in-situ monitoring and controlling of dT and/or anolyte flow rate, according to some embodiments.
According to some embodiments, the temperature control system may be configured to maintain, during operation, a predetermined temperature differential (dT) between the anolyte inlet (e.g., second inlet 784 or 884 as shown in FIGS. 7, 10, and 11 ) and the anolyte outlet (e.g., second outlet 786 or 886) of the CRR(s) and/or between the corresponding anode inlet(s) (e.g., inlet 884A) and anode outlet(s) (e.g., outlet 886A) of the associated electrolyzer(s) (e.g., electrolyzer skid 803A). As an example, for individual electrolyzer stacks, the temperature differential across an anode side of the electrolyzer stack (e.g., dT_{anode, electrolyzer}) may be calculated by subtracting the temperature at an anode side inlet (e.g., T_{anode, inlet}) from the temperature at the anode side outlet (e.g., T_{anode, outlet}). Alternatively or additionally, for individual CRRs, the temperature differential across a CRR (e.g., dT_{anolyte, CRR}) may be calculated by subtracting the temperature at an anolyte inlet (e.g., T_{anolyte, inlet}) from the temperature at the anolyte outlet (e.g., T_{anolyte,outlet}).
In some embodiments, the temperature control system may be configured to maintain one or more predetermined temperature differentials (e.g., dT_{anode, electrolyzer}, dT_{anolyte, CRR}). In some cases, the one or more temperature differentials may be maintained at a relatively small value, such as at least 0.001° C., at least 0.01° C., at least 0.1° C., at least 0.5° C., at least 0.8° C., at least 1° C., at least 1.5° C., at least 2° C., at least 2.5° C., at least 3° C., at least 3.5° C., at least 4° C., or more, and no more than 8° C., no more than 5° C., no more than 4° C., no more than 3.5° C., no more than 3° C., no more than 2.5° C., no more than 2° C., no more than 1.5° C., no more than 1° C., no more than 0.8° C., no more than 0.5° C., no more than 0.1° C., or less. Combinations of the above-referenced ranges are possible (e.g., at least 0.001° C. and no more than 5° C., at least 0.1° C. and no more than 5° C., at least 0.5° C. and no more than 3° C., at least 1° C. and no more than 2° C., at least 0.5° C. and no more than 1.5° C., etc.). Other ranges are also possible. In some cases, for reasons explained elsewhere herein, it may be desirable to maintain the temperature differential below a predetermined value (e.g., threshold value), such as no more than 10° C., no more than 5° C., no more than 3° C., no more than 1.5° C., no more than 1° C., no more than 0.5° C., no more than 0.1° C., etc. In some cases, the dT may maintained so as to be negligible (e.g., at about or equal to 0° C.).
For example, in some implementations, a controller that controls the temperature control system may monitor the anode-side dT, e.g., by checking temperature sensors located at the anode inlet(s) and the anode outlet(s) and then tracking whether or not the anode-side dT exceeds a specified threshold or range of permissible dT values. If the controller determines that the anode-side dT has exceeded the specified threshold or is higher than the maximum dT value in the range of permissible dT values, the controller may control one or more elements of the temperature control system to cause an increase in the flow rate of the anolyte into the electrolyzer, e.g., via the anode inlet(s). For example, the controller may cause a pump that pressurizes the anolyte and drives it through the electrolyzer to increase the flow rate of the anolyte through the electrolyzer, thereby increasing the rate of cooling that the anolyte may provide to the electrolyzer as it flows therethrough and decreasing the amount of heat per unit volume of anolyte that is conducted into the anolyte (and thus reducing the dT of the anolyte) as it flows through the electrolyzer. The controller may, for example, be a proportional-integral-derivative (PID) controller or similar controller that controls the speed at which the pump may cause anolyte to be pumped through the electrolyzer based on the difference between, for example, a target dT and the currently measured dT. The target dT, for example, may be a value that is less than or equal to a maximum dT threshold or may be a value that lies within a specified range of dTs, e.g., such as 3° C. or between 0° C. and 3.5° C. If the currently measured dT is above the target dT, then the controller may control the pump to increase the flow of anolyte through the electrolyzer, whereas if the currently measured dT is below the target dT, then the controller may cause the pump to decrease the flow of anolyte through the electrolyzer. In some implementations, each electrolyzer may have a separate flow control system, e.g., pump and/or valve, that may be controlled independently of the flow control systems of the other electrolyzers, thereby allowing the flow rate through each electrolyzer of a plurality of electrolyzers to be independently controlled. Such implementations may allow for the dT of the anolyte that passes through each such electrolyzer to be separately controlled by tailoring the flow rate of the anolyte per the needs of each individual electrolyzer. In some such implementations, the temperature control systems, e.g., heater and/or heat exchanger, that may be used to control the temperature of the anolyte delivered to each electrolyzer may be common to multiple electrolyzers. For example, the temperature of the anolyte delivered to each electrolyzer in a plurality of electrolyzers may be the same (or close to the same) for each electrolyzer, and may thus be controlled using a common heating/cooling system for those multiple electrolyzers. However, the conditions within each electrolyzer may vary, resulting in different dTs for different electrolyzers. Having a dedicated flow control system for each electrolyzer downstream of the temperature control system may allow the temperature control system to individually control each electrolyzer so as to address the differing performance of each electrolyzer (and thus the different heat-generation characteristics of each electrolyzer). In other implementations, however, there may be a single flow control system that may be used to adjust the flow rate of anolyte to a plurality of electrolyzers simultaneously. Such an approach may be more cost-effective in terms of equipment, but may result in a wider variation in anolyte dT between different electrolyzers.
In other or additional implementations, the controller may additionally or alternatively control one or more flow-control devices, e.g., a valve or valves, that are configured to regulate the flow rate of the anolyte through the electrolyzer in order to control the flow rate of the anolyte through the electrolyzer. For example, the controller may cause a valve or other flow-control device to move into a configuration that permits increased flow from a configuration that permits reduced flow in response to the currently measured dT exceeding the target dT value.
In some embodiments, the temperature control system may be configured to maintain the anolyte solution provided to the anode(s) of the CRR(s) and/or associated electrolyzer(s) within a predetermined temperature range. In some such embodiments, by controlling one or more components within the temperature control system (e.g., pressurizing units, cooling and/or heating devices, etc.), the temperature of the anolyte input (e.g., input 785 or 885 as shown in FIGS. 7, 10, and 11 ) introduced into the anolyte inlet (e.g., second inlet 784 or 884) of the CRR(s) and/or the anode inlet(s) of the associated CO_xreduction electrolyzer stacks may be maintained within a predetermined temperature range, e.g., such that the anolyte outlet temperature (e.g., the anolyte inlet temperature plus the temperature differential in the anolyte across the electrolyzer) is at a desired level. In some cases, the anolyte input and/or output may be maintained within a desirable temperature range, such that the anolyte flowing into the CRR(s) and/or electrolyzer(s) can absorb a desired amount of excess heat (e.g., waste heat) generated within the CRR(s) and/or electrolyzers to prevent overheating of the electrolyzers during operation. This may prevent undesirable degradation of one of more components within the electrolyzers (e.g., MEAs and associated ionomers) at elevated temperatures to maintain both the chemical and structural stability of the electrolyzers. Furthermore, the anolyte flowing into the CRR(s) may be maintained within a temperature range that allows for more efficient electrochemical reactions to take place. The above may advantageously lead to prolonged lifetime of the CRR(s) and the associated CO_xreduction electrolyzers and increase their overall performance.
In one set of embodiments, the anolyte input temperature may be maintained to be within a predetermined range, at least in part, by controlling one or more heating and/or cooling devices. In one set of embodiments, when a measured anolyte input temperature exceeds a first threshold value (e.g., an upper bound of the predetermined temperature range), one or more cooling devices (e.g., heat exchangers) may be employed to cool the anolyte input stream to a temperature less than the first threshold value. Conversely, when a measured anolyte input temperature is less than a second threshold value (e.g., a lower bound of the predetermined temperature range), one or more heating devices (e.g., heat exchangers) may be employed to heat the anolyte input stream to a temperature greater the second threshold value.
For example, the temperature of the anolyte input (or the temperature at the anolyte inlet of CRR(s) and/or at the anode inlet(s) of associated CO_xreduction electrolyzer stack(s)) may be maintained within any of a variety of temperature ranges. For example, the temperature of the anolyte input may be at least 5° C., at least 10° C., at least 20° C., at least 30° C., at least 35° C., at least 40° C., at least 45° C., at least 50° C., at least 60° C., at least 66° C., at least 70° C., or more, and/or no more than 80° C., no more than 70° C., no more than 60° C., no more than 50° C., no more than 45° C., no more than 40° C., no more than 35° C., no more than 30° C., no more than 20° C., or less. Combinations of the above-referenced ranges are possible (e.g., at least 10° C. and no more than 80° C., at least 10° C. and no more than 66° C., at least 20° C. and no more than 60° C., at least 30° C. and no more than 65° C., at least 35° C. and no more than 45° C., at least 35° C. and no more than 40° C., etc.). Such temperatures may prevent water from vaporizing, the MEA/polymer from degrading, and may also more efficiently cool the cell stack. Other ranges are also possible.
In some embodiments, by controlling one or more components within the temperature control system (e.g., pressurizing units, cooling and/or heating devices, etc.), the temperature of the anolyte output (e.g., output 786 or 886 as shown in FIGS. 7 and 10-11 ) from the anolyte outlet (e.g., second outlet 786 or 886) of the CRR(s) and/or the anode outlet(s) of the associated CO_xreduction electrolyzer stacks may be maintained within a predetermined temperature range. For example, the temperature may be maintained at a relatively low temperature, such as at least 5° C., at least 10° C., at least 20° C., at least 30° C., at least 35° C., at least 40° C., at least 45° C., at least 50° C., at least 60° C., at least 66° C., at least 70° C., or more, and no more than 80° C., no more than 70° C., no more than 60° C., no more than 50° C., no more than 45° C., no more than 40° C., no more than 35° C., no more than 30° C., no more than 20° C., or less. Combinations of the above-referenced ranges are possible (e.g., at least 10° C. and no more than 80° C., at least 10° C. and no more than 66° C., at least 20° C. and no more than 60° C., at least 35° C. and no more than 45° C., at least 40° C. and no more than 45° C., etc.). Other ranges are also possible.
In some embodiments, the temperature of the anolyte output (or at the anolyte outlet) may be maintained at a temperature that is at least 0.1° C. (e.g., at least 0.5° C., at least 0.8° C., at least 1° C., at least 1.5° C., at least 2° C., at least 2.5° C., at least 3° C., at least 3.5° C., at least 4° C., or more) and no more than 5° C. (e.g., no more than 4° C., no more than 3.5° C., no more than 3° C., no more than 2.5° C., no more than 2° C., no more than 1.5° C., no more than 1° C., no more than 0.8° C., no more than 0.5° C., or less) higher than the temperature of the anolyte input (or at the anolyte inlet). Combinations of the above-referenced ranges are possible (e.g., at least 0.1° C. and no more than 5° C., at least 0.5° C. and no more than 3° C., at least 1° C. and no more than 2° C., at least 0.5° C. and no more than 1.5° C., etc.). Other ranges are also possible.
In some embodiments, maintaining one or more of the temperature differentials noted above and/or the temperatures of various anolyte streams may correlate with an increase in performance and lifetime of the CO_xreduction electrolyzer(s) and the CRR(s). For example, by doing so, the CO_xreduction electrolyzers may be operated until reaching at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, up to 95%, up to 97%, up to 99%, or up to 100% of its theoretical lifetime (e.g., how long the electrolyzer can be operated for before the voltage required to operate the electrolyzer for a given set of otherwise constant operating conditions increases by a specified threshold value from an initial voltage, for example, 20% from an initial voltage). Combinations of the above-referenced ranges are possible (e.g., at least 70% and up to 99%, at least 75% and up to 90%, at least 90% and up to 100%, etc.). Other ranges are also possible.
In some embodiments, the system includes a flow control system (e.g., pressurizing units, flow controls, flow rate sensors, etc.) configured to maintain the flow rate of various anolyte streams in the anolyte. In some cases, the pressurizing units (e.g., pumps) and/or flow controls (e.g., valves) may be configured such that the flow rate of the anolyte input stream into the anolyte inlet of the CRR(s) and/or anode inlet of the electrolyzer(s) (e.g., individual electrolyzer stacks) is maintained within a predetermined range. For example, the flow rate of the anolyte input stream may be at least 20 gallons per minute, at least 40 gallons per minute, at least at least 60 gallons per minute, at least 80 gallons per minute, at least 100 gallons per minute, at least 120 gallons per minute, at least 140 gallons per minute, at least 160 gallons per minute, or more, and/or no more than 200 gallons per minute, no more than 160 gallons per minute, no more than 140 gallons per minute, no more than 120 gallons per minute, no more than 100 gallons per minute, no more than 80 gallons per minute, no more than 60 gallons per minute, no more than 40 gallons per minute, or less. Combinations of the above-referenced ranges are possible (e.g., at least 20 gallons per minute and no more than 200 gallons per minute, at least 40 gallons per minute and no more than 180 gallons per minute, at least 100 gallons per minute and no more than 180 gallons per minute, etc.). Other ranges are also possible.
In some embodiments, the anolyte circulation system may include a salt dosing system configured to control the concentration of salt (in dissociated ion form) and ion conductivity of the anolyte input stream (e.g., input 785 or 885 as shown in FIGS. 7, 10, and 11 ) introduced into the anolyte inlet of the CRR(s). In some cases, the salt dosing system may include a salt-containing source (e.g., salt-containing source 720 or 820), a salt-water reservoir or mixing tank (e.g., unit 722 or 822) for mixing the salt with fresh anolyte (e.g., fresh water) to achieve a desired ion conductivity, conductivity sensors, and/or one or more feedback controllers. The anolyte input may include any of a variety of salts (or dissociated cations and/or anions) and have any of a variety of salt concentrations and/or conductivities described elsewhere herein.
For example, in some embodiments, the salt dosing system may be configured such that the conductivity of the anolyte input into the CRR(s) and/or associated electrolyzer(s) is maintained within a predetermined range, such as at least 100 μS/cm, at least 150 μS/cm, at least 200 μS/cm, at least 300 μS/cm, at least 400 μS/cm, at least 500 μS/cm, at least 1000 μS/cm, at least 2000 μS/cm, at least 3000 μS/cm, or more, and/or no more than 10,000 μS/cm, no more than 5000 μS/cm, no more than 3000 μS/cm, no more than 2000 μS/cm, no more than 1000 μS/cm, no more than 500 μS/cm, no more than 400 μS/cm, no more than 300 μS/cm, no more than 200 μS/cm, no more than 100 μS/cm, or less. Combinations of the above-referenced ranges are possible (e.g., at least 100 μS/cm and no more than 1000 μS/cm, at least 200 μS/cm and no more than 3000 μS/cm, at least 300 μS/cm and no more than 1000 μS/cm, or at least 600 μS/cm and no more than 1000 μS/cm). Other ranges are also possible.
The anolyte input into the CRR(s) and/or associated electrolyzer(s) may have any appropriate salt concentration, such as molarities of at least 0.1 mM, at least 0.5 mM, at least 1 mM, at least 1.5 mM, at least 2 mM, at least 2.5 mM, at least 3 mM, at least 3.5 mM, at least 5 mM, at least 10 mM, and/or no more than 20 mM, no more than 10 mM, no more than 5 mM, no more than 3.5 mM, no more than 3 mM, no more than 2.5 mM, no more than 2 mM, no more than 1.5 mM, no more than 1 mM, or less. Combinations of the above-referenced ranges are possible (e.g., at least 0.5 mM and no more than 10 mM, at least 0.5 mM and no more than 5 mM, at least 0.5 mM and no more than 4 mM). Other ranges are also possible.
The presence of salt ions (e.g., cations and/or anions) in the anolyte input can have a positive impact on carbon oxide electrolyzer performance, according to some embodiments. In some cases, cations and/or anions may be introduced to the carbon oxide electrolyzer through water circulating through the anode of the electrolyzer or by incorporation into the polymer-electrolyte membrane, catalyst, or catalyst support used to make the membrane-electrode assembly. The presence of salts has been observed to decrease the MEA cell voltage, improve Faradaic yield, change the product selectivity, and/or decrease the decay rate of operating parameters (e.g., voltage efficiency) during operation of a carbon oxide reduction electrolyzer.
Various types of salt may be dosed into the anolyte circulation system. Such salts may have inorganic or organic cations and anions. The salt composition may affect cell operating conditions such as overpotential, Faradaic efficiency, and/or selectivity among multiple carbon oxide reduction reactions. Various factors influencing the choice of salt composition are described herein.
In certain embodiments, a salt employed in the reactor has cations that are not ions of transition metals. In certain embodiments, the salt contains a cation that is an alkali metal ion or an alkaline earth metal ion. In certain embodiments, the salt contains a lithium ion, a sodium ion, a potassium ion, a cesium ion, and/or a rubidium ion. In certain embodiments, the salt contains no cations other than sodium and/or potassium ions. In some implementations, the salt contains only cations that are monovalent such as alkali metal ions.
In certain embodiments, the salt contains an anion that is a hydroxide, a bicarbonate, a carbonate, a perchlorate, a phosphate, or a sulfate. In some cases, the salt contains an anion that is a hydroxide, a bicarbonate, a carbonate, or a sulfate. In certain embodiments, the salt contains no halide ions. In certain embodiments, the salt contains an anion that is produced from the carbon oxide reduction reaction. Examples include carboxylates such as formate, oxalate, and acetate.
In certain embodiments, the salt is selected from the group including sodium bicarbonate, potassium bicarbonate, potassium sulfate, sodium sulfate, cesium bicarbonate, cesium sulfate, and any combination thereof.
In some cases, multiple salts or a mixed salt may be employed. For example, the system may employ multiple cations (e.g., sodium and potassium ions) but only a single anion (e.g., sulfate). In another example, the system employs only a single cation (e.g., sodium ions) but multiple anions (e.g., bicarbonate and sulfate). In yet another example, the system employs at least two cations and at least two anions. In certain embodiments, the salts include a combination of sodium bicarbonate and potassium bicarbonate. In certain embodiments, the salts include a combination of potassium bicarbonate and potassium phosphate.
In some cases, other types of salts and/or composition may be employed, depending on the type of application and/or type of MEA. Various examples are described in the following references: published PCT Application No. PCT/US2019/063471, published Jun. 4, 2020, and titled “ELECTROLYZER AND METHOD OF USE,” and Published U.S. application Ser. No. 16/697,066, published Jul. 30, 2020, each of which is incorporated herein by reference in its entirety and for all purposes.
In some embodiments, the system further includes a catholyte circulation system (e.g., a cathode water circulation system) in fluidic communication with the CRR(s). In some cases, the catholyte circulation system may be configured to recover at least a portion of cathode water present within the reduction product stream of the CRR(s) and optionally recycle at least a portion of the recovered cathode water into the anolyte input fed into the CRR(s). As described elsewhere herein, the anolyte circulation system may include any of a variety of components associated with the processing of cathode water within the reduction product stream output from the CRR(s). Non-limiting examples of such components include a catholyte separator unit (e.g., unit 730 or 830), a cathode water reservoir or tank (e.g., cathode water tank 732 or 832), a catholyte or cathode water recirculation loop (e.g., loop 733 or 833), one or more cooling units (e.g., unit 728), etc., as well as components providing the various fluidic connections therebetween.
As mentioned above, the catholyte recirculation system may include a catholyte separator unit, e.g., such as cathode separator 730 or 830 as shown in FIGS. 7, 10, and 11 . In some embodiments, the catholyte separator unit (e.g., unit 730 or 830) may be fluidically connected with the first outlet (e.g., first outlet 782 or 882) of the CRR(s). In some cases, the catholyte separator unit may be configured to accept at least a portion (e.g., at least 50%, at least 60%, at least 70%, and/or up to 80%, up to 90%, or up to 100%) of the reduction product stream (e.g., stream 783 or 883 as shown in FIGS. 7, 10, and 11 ) from the cathode outlet (e.g., first outlet 782 or 882) to separate water from unreacted CO_x(e.g., CO₂) and one or more gaseous reduction products, such as a carbon-containing species (e.g., CO) and/or H₂. In some cases, the catholyte separator unit may be configured produce a liquid stream (e.g., stream 731 or 831) enriched in water relative to the reduction product stream and a gaseous stream (e.g., stream 729 or 829) enriched in one or more reduction products (e.g., carbon-containing species (CCS)) and/or unreacted CO_xrelative to the reduction product stream. In some cases, the gaseous outlet stream may be a substantially pure stream of reduction product(s) and/or unreacted CO_x, such as having a purity of at least 70%, at least 80%, at least 90%, at least 99%, and/or up to 99.9%, or up to 100%.
In some embodiments, the catholyte circulation system includes a catholyte recirculation system fluidically connected with an outlet of the catholyte separator unit. In some cases, the catholyte recirculation system may be configured to transport at least a portion of water contained within the reduction product stream (e.g., stream 783 or 883 as shown in FIGS. 7, 10, and 11 ) into the anolyte circulation system and subsequently into the anolyte inlet (e.g., second inlet 784 or 884) of the carbon oxide reduction reactor. Specifically, the catholyte recirculation system may be configured to transport (e.g., recycle) at least a portion (e.g., at least 10%, at least 25%, at least 50%, at least 60%, at least 70%, and/or up to 80%, up to 90%, or up to 100%) of the separated cathode water (e.g., stream 731 or 831), via a cathode water recycle loop (e.g., loop 733 or 833), into the anolyte input (e.g., input 785 or 885) fed into the anolyte inlet (e.g., second inlet 784 or 884) of the CRR(s) (e.g., CRR(s) 704 or 803). In some such embodiments, the catholyte recycling loop within the catholyte recirculation system merges or cojoins with at least a portion of the anolyte circulation system (e.g., anolyte recycling loop) via an optional anolyte tank (e.g., anolyte tank 726 or 826).
The catholyte separator unit may include any of a variety of separation units, including, but not limited to, a gas-liquid separator, a water knockout system, a chiller, a condenser, centrifugal separator, membrane based separators, coalescing filters, and/or mist eliminators.
In some embodiments, the system may further include one or more units downstream the anolyte and/or catholyte circulation systems, including one or more gas separation modules, one or more CO_xrecycle loops, one or more downstream processing units, etc. For example, the system may include a gas separation module (e.g., unit 740 or 840), e.g., such as a carbon oxide separation module, configured to separate unreacted CO_x(e.g., CO₂) from one or more reduction products (e.g., a CCS such as CO) and/or syngas in a catholyte separator outlet stream (e.g., stream 729 or 829) to produce an outlet stream (e.g., stream 741 or 841) enriched in CO_xand an outlet stream (e.g., stream 743 or 843) enriched in the one or more reduction products (e.g., a carbon-containing species (CCS)) and/or syngas relative to the catholyte separator outlet stream.
Any of a variety of appropriate gas separation technologies may be employed, including, but not limited to, a temperature-swing, electro-swing, pressure-swing, and/or a moisture swing CO_x(e.g., CO₂) capture system that employs a solid or liquid absorbent or adsorbent. In some cases, a temperature, electrical, pressure or moisture swing can be applied to the CO_xcapture system, thereby causing the absorbed or adsorbed CO_x(e.g., CO₂) to be released.
In some cases, the system further includes a CO_xrecycle loop configured to transport (e.g., recycle) at least a portion (e.g., at least 50%, at least 60%, at least 70%, at least 90%, and/or up to 99%, or up to 100%) of the unreacted CO_xcontained within the reduction product stream (e.g., stream 783 or 883) into the cathode gas inlet (e.g., first inlet 780 or 880) of the CRR(s). In some cases, the system may further include a gas separation module (e.g., unit 850) configured to separate the CCS (e.g., CO) from other gases (e.g., H₂) to produce an outlet stream enriched in the CCS (e.g., CO) and an outlet stream (e.g., stream 853) enriched in the other gaseous species. In some cases, the system may further include a product processing unit (e.g., unit 742 or 842) configured to accept at least a portion of the resulting stream enriched in CCS and/or syngas (e.g., stream 743 or 853) for conversion into one or more end products of interest.
FIG. 7 is a schematic diagram of a carbon oxide electrolyzer plant 702, which is part of a carbon oxide electrolyzer system 700, in accordance with some implementations of the present disclosure. Operating the carbon oxide electrolyzer plant requires three main inputs: water, carbon oxide, such as carbon dioxide, and controlled current. Each input is provided through a specialized system allowing for control of variables affecting output of the carbon oxide electrolyzer plant 702. A water system includes flow control, salt addition and mixing, a circulation pump, temperature control for startup as well as normal operating conditions, automated freshwater makeup, conductivity and/or pH control, and drain capability from the anolyte circulation system. A gas system, using, for example, carbon dioxide, may include controls for inlet pressure control, outlet water and formic acid knockout, gas separator 714, and gas speciation measurement. The gas system may also includes a combustible gas detector on the 02 product stream 712. In some embodiments, the combustible gas detector may be configured to detect the presence of certain flammable gases contained within the product stream and/or determine the concentration of the gases. The power source includes a programmable power supply that provides constant current, a contactor, and a bleed-down resistor. The carbon oxide electrolyzer plant may also include monitoring, data recording, and automation systems.
In operation, the carbon oxide electrolyzer plant 702 may be designed to produce at least 0.10 tons per day of carbon monoxide when the electrochemical reactor is operated using up to 1 MW of input power. The amount of input power may vary according to the output production selected. The carbon oxide electrolyzer plant 702 can include at least one 100-cell electrolyzer stack of multiple membranes, with a turndown capability to run one 50-cell stack of membranes. Other combinations of electrolyzer cells and membranes are also possible and may be used, depending on input variables. Operating the carbon oxide electrolyzer plant includes providing inputs such as gases, liquids, solids, and other inputs. The inputs can be carbon dioxide, including a carbon dioxide source, such as waste gas, and/or water. Other carbon oxides may also be used as inputs. A power input provides power to apply a voltage across the device electrodes of the carbon oxide electrolyzer plant to cause reactions to occur. The reactions generate products which are then removed from the reactor.
Operating the carbon oxide electrolyzer plant begins with providing the three main inputs needed: power, water, and carbon oxides. Input power is provided by power source 706. Power source 706 includes a programmable power supply capable of controlling current delivery. The power source incorporates a contactor to provide a true open circuit voltage. The power system can also include an uninterruptible power supply (not shown in FIG. 7 ). The power system also includes current control module 708, which can include a bleed-down resistor. The bleed-down resistor is capable of discharging power from the carbon oxide reduction reactor 704 on power loss. The current control module provides direct input to the carbon oxide reduction reactor 704. The control system can also provide voltage monitoring of individual cells in the carbon oxide reduction reactor 704. The voltage monitoring system may include a plurality of data collection channels, each of which can measure the voltage differential with a selected resolution. Each channel may provide rejection of 500 VDC common mode voltage and may be isolated from ground by a selected voltage value. A contactor may be incorporated to ensure true open circuit voltage from the power source 706, through the current control module 708, to the carbon oxide reduction reactor 704. A switch multimeter with field effect transistor (FET) multiplexer (not shown in FIG. 7 ) can be incorporated in the voltage monitoring system.
The second main input to the carbon oxide electrolyzer plant 702 is water, which is provided through anolyte source 716. The inlet water can be input to water filtration module 718. Anolyte source 716 is the inlet to the anode water recirculation loop that delivers water to and removes water from the anode portion of the carbon oxide reduction reactor 704. The water recirculation loop includes the water filtration module 718 and the brine mix tank 722. The water filtration module 718 provides input to the brine mix tank 722 and also to the anolyte tank 726. The water filtration module 718 can be a filter, resin column, or other purifier capable of removing ions, such as iron ions, or other transition metal ions from the anode water.
The brine mix tank 722 receives water from the water filtration module 718 and also receives an input of solid salt at salt-containing source 720. The solid salt from salt-containing source 720 is input to the brine mix tank 722 to ensure a source of concentrated salt solution is available. In an alternate embodiment, the brine mix tank 722 is eliminated and the anolyte circulation loop has the capability to remove a gaseous oxygen product, which may incorporate a separator (not shown in FIG. 7 ). A still further alternate embodiment eliminates the anolyte tank 726 and removes gaseous oxygen product using a separator. The inputs of water and solid salt are used to dose the anode water with purified water and/or concentrated salt to adjust the composition of the anode water fed into the carbon oxide reduction reactor 704.
The third input to the carbon oxide electrolyzer plant 702 is gaseous carbon oxide, shown as gas inlet 710. The gas inlet 710 is a part of the gaseous carbon oxide recirculation loop that provides gaseous carbon oxides as a feed stream to the anode side of the carbon oxide reduction reactor 704. After passing through the carbon oxide reduction reactor 704 and the electrolyzer process, a gaseous product stream is output through the gas outlet of the carbon oxide reduction reactor 704.
After the three inputs of power, water, and gaseous carbon oxides have been input to the carbon oxide reduction reactor 704, the electrolysis process can begin. The electrochemical process is illustrated in FIG. 1A. The carbon oxide reduction reactor 704 includes multiple membrane electrode assemblies, as described above in reference to FIG. 1A. The membrane electrode assembly (MEA) 102 has a cathode 112 and an anode 120, which are separated by an ion-exchange layer 104. The ion-exchange layer 104 may include three sublayers: a cathode buffer layer 114, a polymer electrolyte membrane 116, and may include an optional anode buffer layer 118. The carbon oxide reduction reactor can also include a cathode support structure 110 that is adjacent to the cathode 112 and a corresponding anode support structure 122 this is adjacent to the anode 120.
The cathode support structure 110 has a cathode polar plate 108 to which a voltage is applied during the electrolyzing process. The cathode polar plate 108 can also include flow field channels, such as serpentine channels, cut into the inside surfaces of the cathode polar plate 108. The cathode gas diffusion layer 106 facilitates the flow of gas provided from gas inlet 710 into and out of the MEA 102. Similarly, the anode support structure 122 has an anode polar plate 124 to which a voltage supplied by power source 706 and passing through current control module 708 is applied. The anode support structure 122 may also contain flow field channels, as described above, cut into the inside surfaces of the anode polar plate 124. An anode gas diffusion layer 126 is adjacent to the inside surface of the anode polar plate 124. The anode gas diffusion layer 126 facilitates the flow of gas into and out of the MEA 102.
In operation, the carbon oxide reduction reactor 704 is supplied with carbon oxide gas to the cathode 112. This carbon oxide gas is reduced over the carbon oxide reduction catalysts in the presence of protons and electrons. The carbon oxide electrolyzer plant 702 can incorporate multiple carbon oxide reduction reactors 704, each of which may include multiple membrane electrode assemblies. The individual carbon oxide reduction reactors can be connected in series or in parallel. Reactants can be supplied to each individual carbon oxide reduction reactor.
Once the electrolyzing process has been completed there may be remaining unreacted carbon oxide. Reduction products leaving the carbon oxide reduction reactor 704 are fed via a gas outlet to a water knockout system 730, where the gas product is removed and the water removed is sent to a cathode water tank 732. After water knockout, the gas product is sent to chiller 728. The output of the chiller 728 leave the carbon oxide electrolyzer plant 702 and is sent to external gas separation module 740. The output of the external gas separation module 740 is sent for further processing to the external product processing module 742.
The cathode water collected in the cathode water tank 732 can be recirculated by sending it to the anolyte tank 726. If the cathode water is not used for recirculation to the anolyte tank 726, it leaves the carbon oxide electrolyzer plant 702 and is sent to external wastewater tank 744. Wastewater tank 744 can alternatively be considered as two or more tanks (not shown), where the anolyte purge waste, which may be less acidic than the catholyte purge waste, is sent to its own waste-water tank. Catholyte purge waste, which may be more acidic than the anolyte purge waste, is sent to its own separate waste-water tank. In an embodiment, if the cathode water is used for recirculation to the anolyte tank 726, the cathode water will need to be treated, such as with, e.g., a resin column or reverse osmosis system (not shown) to purify the cathode water, before it is introduced into anolyte tank 726.
The anolyte water collected in anolyte tank 726 can also be recirculated. Anolyte tank 726 can also be referred to as an anolyte recirculation tank. Anolyte circulation includes the anolyte tank 726, used to store the anolyte mixture for circulation. The anolyte separator 724 allows for separation of the oxygen product from the carbon oxide reduction reactor 704 outlet water. The anolyte circulation system also incorporates an anolyte circulation pump 738 which provides a predetermined amount of anolyte circulation through the carbon oxide reduction reactor 704. Anolyte leaving the carbon oxide reduction reactor 704 for recirculation enters the anolyte separator 724. The anolyte separator 724 directs anolyte to anolyte tank 726 after removing the oxygen product. The input line to the anolyte tank 726 connected to anolyte separator 724 can also be connected to a line connected to the brine mix tank 722. This input from the brine mix tank 722 allows adjustment of the composition of the anolyte in anolyte tank 726. Anolyte circulation is provided via anolyte circulation pump 738. Anolyte circulation temperature is controlled through heat exchanger 736 and heat exchanger 734. The anolyte circulation can be controlled through control programming and measurements of the anolyte concentration. As part of the anolyte circulation, some of the anolyte can be purged to external wastewater tank 744, assisted by anolyte circulation pump 738. Anolyte can also bypass the carbon oxide reactor such as via bypass line 746 for maintenance and troubleshooting purposes for the anolyte loop. This would typically not be done during normal operation, but to diagnose an operational issue within the loop.
The carbon oxide electrolyzer plant 702 also includes controls and automation tools. These controls can include a programmable logic control (PLC) system that can be expanded and provide digital input/output, relay outputs, voltage input/output, and a 4-20 mA input/output, as well as at least one high speed digital interface, such as Ethernet, internet protocol, or other similar interface. The PLC system can also incorporate remote communications and networking, such as LAN and LTE.
The control and automation system can also include digital communication for gas controllers, a backpressure regulator, and a power supply. The power supply can be an analog power supply that provides at least 4-20 mA, 16 bit+ resolution.
In addition, the control and automation system can assist with startup of the carbon oxide electrolyzer plant 702 through startup sequencing. The control and automation system can start up the carbon dioxide and water flows before starting current flow. The control and automation system also allows changing the operating set points for the carbon oxide electrolyzer plant 702 as needed. For example, as discussed elsewhere herein, during startup, the temperature control system may be caused to preheat the anolyte that is provided to the electrolyzer stack to a preset initial operating temperature; once the electrolysis reaction is established, the controller may cause the temperature control system to instead switch to a cooling mode (for example, if anolyte is being recirculated, latent heat in the anolyte from a prior passage of the anolyte through the electrolyzer may need to be removed prior to reintroducing the anolyte into the electrolyzer, e.g., via the anolyte recirculation system.
Recovery sequencing is also provided by the control and automation system. On shutdown, the current can be paused with the cell of the carbon oxide reduction reactor 704 in an open circuit mode. The flow of carbon dioxide and water are maintained during shutdown, with the set point being adjustable as needed. A built-in automated shutdown sequence can also be incorporated into the control and automation system with an automated shutdown sequence triggered by predetermined and preselected variables.
The gas side of the carbon oxide electrolyzer plant 702 includes an inlet carbon dioxide manifold (not shown) and a gas separator 714. The inlet carbon dioxide manifold controls carbon dioxide flow to the carbon oxide reduction reactor 704 and also measures inlet gas composition. The gas outlet of the carbon oxide reduction reactor 704 provides input to the water knockout system 730. The water knockout system 730 removes both the water and the formic acid from the carbon oxide reduction reactor 704 outlet gas. The water knockout system 730 can incorporate a chiller 728 and output gas to the external gas separation module 740. The gas side of the carbon oxide electrolyzer plant 702 further includes backpressure controllers (not shown in FIG. 7 ). One backpressure controller maintains a constant backpressure on the carbon oxide reduction reactor 704 and another backpressure controller is used in conjunction with a gas chromatograph or gas analyzer (not shown in FIG. 7 ). Each backpressure controller is separately programmable for different pressure set points. A gas analyzer is also incorporated into the gas side, e.g., cathode side, of the carbon oxide electrolyzer plant 702 to measure the gas composition on the inlet to and the outlet from the carbon oxide reduction reactor 704. Alternatively, the gas analyzer can measure the gas composition on the outlet of gas separator 714.
Operating parameters for the gas side or cathode side of the carbon oxide electrolyzer plant include the parameters below. Gas pressure in the carbon oxide reduction reactor 704 can range from zero minimum pressure to a maximum of 430 psig and can include a number of sub-ranges used depending on the operating conditions. The sub-range can be a smaller range such as 0 psig to 100 psig, 100 psig to 200 psig, 200 psig to 300 psig, and 300 psig to 430 psig. Normal pressure at the gas inlet 710 can range between 70 psig and 110 psig. The gas inlet 710 may need to be fully depressurized during recovery modes to ensure complete recovery. The carbon dioxide source pressure can range from a minimum of 50 psig to a maximum of 500 psig with smaller sub-ranges selectable for various operating conditions. The sub-ranges can be 50 psig to 100 psig, 100 psig to 200 psig, 200 psig to 300 psig, 300 psig to 400 psig, 400 psig to 500 psig. The actual range used in the carbon oxide electrolyzer plant 702 depends on the available source pressure. The inlet pressure will be higher than the maximum required carbon dioxide control pressure. The flow controller on the gas inlet 710 needs to be able to manage a high differential pressure (dP) during the initial carbon dioxide feed introduction to the carbon oxide electrolyzer plant 702. The carbon dioxide feed rate can range from a minimum of 6 standard cubic feet per minute (SCFM) to a maximum of 27 SCFM, with operational sub-ranges such as 6 SCRM-12 SCFM, 12 SCFM-18 SCFM and 18 SCFM-27 SCFM. Other pressures and ranges are also contemplated and may vary depending on the size and complexity of the carbon oxide reduction reactor 704. The carbon dioxide feed rate per unit area basis can range from a minimum of 2 SCCM/cm²to a maximum of 10 SCCM/cm², with operational sub-ranges such as 2 SCCM/cm²-5 SCCM/cm², 5 SCCM/cm²-8 SCCM/cm²and 8 SCCM/cm²-10 SCCM/cm². In some embodiments, the carbon oxide electrolyzer plant 702 may include multiple stacks, which may be connected in series or in parallel, depending on the desired outputs.
The outlet gas from the carbon oxide reduction reactor 704 can have a composition ranging from 2 to 3, e.g., 2.6, percent hydrogen, 22 to 33, e.g., 27.7, percent carbon monoxide, 56 to 83, e.g., 69.5 percent carbon dioxide, and 0.15 to 0.25, e.g., 0.16, percent water (these ranges are molar percentages). The carbon oxide reduction reactor 704 operates using a stack inlet between zero psi and 500 psi and may include a number of operational sub-ranges such as 0 psi to 100 psi, 100 psi to 200 psi, 200 psi to 300 psi to 400 psi, and 400 psi to 500 psi. The stack outlet pressure operates within the same ranges. For both inlet and outlet pressures, the dP ranges between zero and 30 and may include a number of operational sub-ranges, such as 0 psi to 10 psi, 10 psi to 20 psi, and 20 psi to 30 psi. The gas flow system described above can also include a combustible gas detector that can measure from the anolyte separator 724. The combustible gas detector can detect the flammability of multiple compounds including H₂and carbon monoxide within the anolyte separator outlet stream. This can be accomplished by diverting a slipstream of the O₂product, dehumidifying it and then passing it through the combustible gas detector.
The water side of the carbon oxide electrolyzer plant 702 may include m apparatus for salt dosing. Salt dosing is a method for injecting salt or ionized water into the deionized water to produce a specific conductivity in the anolyte. The brine mix tank 722 can be used in the salt dosing method. An example of a target salt concentration is 0.5-10 mM solution of KHCO₃or NaHCO₃solution in water, which can be defined by concentration or, indirectly, by conductivity. The range may also include a number of operational sub-ranges such as 0.5 mM-5 mM, 5 mM-8 mM, and 8 mM-12 mM. The brine solution can be a 1M solution of the target salt. The brine solution can be dosed with fresh water as needed to achieve the desired target concentration for the anolyte. Sample ports can be located throughout the anolyte circulation system to monitor the composition and concentration of the anolyte solution.
On startup the anolyte can be heated with a heater, such as the heat exchanger 734 to bring the anolyte up to the operating temperature, which may be a temperature elevated above ambient temperature and up to 40° C. (104° F.). Once the carbon oxide electrolyzer plant 702 has been started and operating, the heat exchanger 736 may be used to cool the anolyte. After operating for a period of time the anolyte temperature may increase to greater than 70° C. (158° F.) and the heat exchanger 736 ensures that the anolyte temperature remains within the desired operating temperature parameters, as specified above, for successful operation of the carbon oxide reduction reactor 704.
An additional component of the anolyte circulation system is the anolyte particulate filter (not shown), which may be a 40-micron filter located downstream of the carbon oxide reduction reactor 704, before the anolyte is returned to anolyte tank 726. The filter may incorporate a differential pressure measurement sensor to monitor potential plugging of the filter. Monitoring of the differential pressure measurement sensor may be performed to allow scheduling preventative maintenance on the filter in the event that dP increases significantly.
The anolyte recirculation system may also incorporates a combustible gas detector. The combustible gas detector may be a part of the safety systems for operating the carbon oxide electrolyzer plant 702. A portion of the oxygen product stream may be separated and passed through the combustible gas detector. The combustible gas detector can incorporate a variety of alert mechanisms, such as lights, sounds, horns, or other means, to indicate the presence of potentially combustible gases.
The anolyte recirculation system may also incorporate temperature controls and monitoring for the anolyte mixture input to the carbon oxide reduction reactor 704. Upon startup of the carbon oxide electrolyzer plant 702, the anolyte mixture may be heated. Once normal operation of the carbon oxide reduction reactor 704 is established, temperature control may be provided using a heat exchanger 736 to cool the anolyte as needed and to control the outlet temperature of the carbon oxide reduction reactor 704. Additional control can be provided by monitoring dT on the carbon oxide reduction reactor 704 in combination with adjusting the water flow rate, as discussed earlier. Precise temperature control of the carbon oxide reduction reactor 704 may help ensure continued operation within desired parameters and ensures equipment longevity.
In some implementations, the level of anolyte solution in the anolyte tank may be measured and a mechanism is provided to automatically refill the anolyte tank 726 as needed and to also to shut off the carbon oxide electrolyzer plant 702 if the anolyte level in the anolyte tank 726 falls to empty, or conversely, overflows. The target concentration can range from 0.5 to 10 mM solution of KHCO₃or NaHCO₃in water. To meet the anolyte concentration, deionized water can be dosed with salt to form the anolyte solution and to control the concentration and/or conductivity. Salt concentrate can be added at a rate ranging from 0.18 gph-0.26 gph for mixing based on a 3 mM solution target. Anolyte pH can range widely depending on recycle streams and may range from 2 pH to 8 pH. Some embodiments provide for a range of anolyte pH from a minimum of 1.5 pH to a maximum of 8 pH, with a normal value of approximately 6 pH. This target concentration can also be defined as the conductivity in the solution. Anolyte conductivity can range from 10 uS/cm to 10,000 uS/cm, with operational sub-ranges of 10 uS/cm-1000 uS/cm, 1000 uS/cm-5000 uS/cm, 5000 uS/cm-8000 uS/cm, and 8000 uS/cm. For example, in some implementations, the anolyte conductivities can range from a minimum of 200 uS/cm to a maximum of 3000 uS/cm, with operational sub-ranges of 200 uS/cm-1000 uS/cm, 1000 uS/cm-2000 uS/cm, and 2000 uS/cm-3000 uS/cm. The brine solution can be dosed with water in the brine mix tank 722 to reach the desired target concentration for the anolyte.
The water side of the carbon oxide electrolyzer plant 702 may include a cathode water circulation system. The cathode water circulation system includes the water knockout system 730. The water knockout system 730 collects the cathode water recovered from the gas side water knockout operation. The amount of cathode water accumulating in the water knockout system 730 is the rate of water exiting the carbon oxide reduction reactor with the gas stream through the gas outlet of the carbon oxide reduction reactor 704. The water in the water knockout system 730 is very low pH and can be treated and purged to the external wastewater tank 744. A further embodiment provides for recycling the collected cathode water and returning the recycled cathode water to the anolyte circulation system.
The carbon oxide reduction reactor 704 can also incorporate a reactor water drain line (not shown in FIG. 7 ). The reactor water drain line can be used when carbon oxide reduction reactors are being changed out. The reactor drain line drains the water remaining in the carbon oxide reduction reactor 704 after water flow is shut off and the carbon oxide reduction reactor 704 is isolated from the remainder of the carbon oxide electrolyzer plant 702.
The operating parameters of the water side of the carbon oxide electrolyzer plant 702 include the parameters below. Water from anolyte source 716 can be provided from a municipal supply or other source at a rate of 5 gph lph) to 85 gph, smaller sub-ranges, such as 5 gph-20 gph, 20 gph-40 gph, and 60 gph-80 gph may also be used. The inlet water should have a resistivity ranging from 1 MΩ-cm-20 MΩ-cm with operation possible in a narrower range such as 1MΩ-cm to 5 MΩ-cm, 5 MΩ-cm-10 MΩ-cm, 10 MΩ-cm-15 MΩ-cm, and 15 MΩ-cm-20 MΩ-cm, with a nominal resistivity of 10 MΩ-cm.
Water management also includes anolyte circulation, which uses one or more anolyte tanks 726. Anolyte circulation also incorporates a circulation pump, such as the anolyte circulation pump 738 of FIG. 7 that can deliver a set or predetermined amount of anolyte circulation through the carbon oxide reduction reactor 704. Anolyte circulation can range from a minimum of 20 gpm to a maximum of 115 gpm, with a normal rate of 90 gpm. Sub-ranges can also be used, such as 20 gpm to 40 gpm, 40 gpm to 60 gpm, 60 gpm to 80 gpm 227.125 lpm to 302.833 lpm), 80 gpm to 100 gpm, and 100 gpm to 115 gpm.
The anolyte circulation system may also include an anolyte particulate filter (not shown in FIG. 7 ) that is downstream of the carbon oxide reduction reactor 704. The anolyte particulate filter can be placed before the anolyte is returned to the anolyte tank 726. Alternatively, the anolyte particulate filter can be placed upstream of the carbon oxide reduction reactor 704, such as after the heat exchanger 734. The anolyte particulate filter may have a differential pressure measurement sensor configured to monitor a pressure differential across the filter in order to provide monitoring for potential filter plugging. The absolute value of the dP may be monitored and preventative maintenance to change out the particulate filter scheduled if the dP starts to increase significantly. To assist with monitoring various anolyte parameters, sample ports can be located throughout the anolyte circulation system. The dP across the carbon oxide reduction reactor 704 may, in some implementations, be from a minimum of zero psi to a maximum of 60 psi, with operational sub-ranges of 0 psi to 10 psi, 10 psi to 20 psi, 20 psi to 30 psi, 30 psi to 40 psi, 40 psi to 50 psi, 50 psi to 60 psi. Anolyte waste, such as the material collected by the anolyte particulate filter can also be tracked and measured.
The carbon oxide electrolyzer plant 702 may also incorporate a combustible gas detector. The combustible gas detector may operate on a portion of the oxygen product stream 712 that is separated from the water phase. This may be provided to ensure safe operation of the plant and the surrounding area.
The electrical side of the carbon oxide electrolyzer plant 702 may include a programmable power supply, which can be the power source 706, shown in FIG. 7 . The programmable power supply can be an independent power supply for the carbon oxide reduction reactor 704. The independent power supply includes the capability to control current delivery, with programmatic control to achieve true open circuit voltage. A contactor can also be included to ensure true open circuit voltage from the power source 706 to the carbon oxide reduction reactor 704. The power delivered by the independent power supply can be up to 340 kW of power, 680 A at 500 vdc and able to pulse across the full current range of 0 A to 680 A in less than one second. In addition, the independent power supply should have a preferred slewing rate at least 1 kV/s and 1 kA/s.
The independent power supply, which can also be power source 706, may also include a bleed-down resistor (not shown in FIG. 7 ) that allows discharge of any charge in the carbon oxide reduction reactor 704 when a power loss occurs. In addition, the independent power supply can also include a backup uninterruptible power supply (UPS).
To ensure that all cells in the carbon oxide reduction reactor 704 have adequate voltage, the individual cells in the carbon oxide reduction reactor 704 can be individually monitored. The monitoring device can measure from −2 V to +10 V differential on each channel for all cells in the carbon oxide reduction reactor 704. It is contemplated that up to 100 cells or more can be incorporated in the carbon oxide reduction reactor 704. For voltage monitoring, each channel can use a resolution of >1 mV, with 0.2 mV or less being preferable. Each voltage monitoring channel can reject 500 VDC common-mode voltage and can be isolated from ground by at least 1,000 V. The voltage monitoring device or system can also incorporate a switch multimeter instrument with a FET multiplexer.
The carbon oxide electrolyzer plant 702 may operate with a stack backpressure from a minimum of 10 psig to a maximum of 450 psig and may include operational subranges such as 10 psig to 100 psig to 200 psig, 100 psig to 200 psig, 200 psig to 300 psig, 300 psig to 400 psig and 400 psig to 450 psig, with a backpressure controller capable of holding over the full range of pressures. The power supply for the carbon oxide electrolyzer plant 702 may operate over a voltage range of 60 VDC to 500 VDC with a current capability between 6 amps to 680 amps with the capability to pulse the current between 0 and 600 mA/cm². The current may be programmable and can be varied throughout operation of the carbon oxide electrolyzer plant 702. In some implementations, the power input for the carbon oxide electrolyzer plant may be able to operate with a minimum of −10 volts to a maximum of 50 volts, with 100 channels. The 100 channels allow the voltage to be measured across each cell in the carbon oxide reduction reactor 704 individually in range from zero to five volts.
The invention may be described in the general context of computer code or machine-useable instructions, including computer-executable instructions such as program modules, being executed by a computer or other machine, such as a personal data assistant or other handheld device. Generally, program modules including routines, programs, objects, components, data structures, etc., or refer to code that performs particular tasks or implements particular abstract data types. The invention may be practiced in a variety of system configurations, including hand-held devices, consumer electronics, general-purpose computers, more specialty computing devices, etc. The invention may also be practiced in distributed computing environments where tasks are performed by remote-processing devices that are linked through a communications network.
FIG. 8A is a flow diagram of a method of operating a carbon oxide electrolyzer plant or system, in accordance with some implementations of the present disclosure. The plant or system may include one or more CRR(s), each including one or more CO_xreduction electrolyzers, as described elsewhere herein, such as with respect to FIGS. 7 and 10-13 .
The method 800 begins with receiving, from a gas system, gaseous carbon oxide (e.g., gaseous carbon dioxide) in step 802, in some embodiments. For example, the method includes introducing a first input (e.g., first input 710 or 810 as shown in FIGS. 7, 10, and 11 ) including the gaseous carbon oxide into a first inlet (e.g., first inlet 780 or 880) of the CRR(s). The gaseous carbon oxide may be input into the cathode side of the CRR(s). The first input may be a substantially pure gaseous CO_xstream or a gaseous mixture composed, at least in part, of CO_x. The gaseous carbon oxide (e.g., gaseous carbon dioxide) can vary in concentration and may contain various impurities.
The method continues with step 804, receiving, from a water system, a second input such as water, according to some embodiments. In some cases, the method may include introducing a second input (e.g., input 785 or 885) including a salt-containing anolyte (e.g., salt-containing water) into a second inlet (e.g., second inlet 784 or 884) of the CRR(s). The water may be from a municipal source or other water source. The water may be filtered by a water filtration unit prior to being input to the carbon oxide electrolyzer or CRR. According to some embodiments, the water system includes an anolyte circulation system and an anolyte recirculation system, as well as a catholyte circulation system and an optional catholyte recirculation system, as described elsewhere herein. For example, the second input may include a fresh anolyte (e.g., fresh water) from an anolyte source (e.g., fresh anolyte source 716 or 816 as shown in FIGS. 7, 10, and 11 ), recycled anolyte (e.g., stream 725 or 827) from the CRR(s), and optionally recycled catholyte (e.g., stream 733 or 833). The anolyte may be input into the anode side of the CRR(s) via the anolyte circulation system.
Step 806 provides for receiving, from a power system, electrical power. The electrical power can be provided by a municipal power source or can be provided by renewable sources, such as wind, solar, or other systems, including hydrothermal power systems. The electrical power, in some cases, may be input into the CRR(s). Then, in step 808, the method continues with electrolyzing, by the carbon oxide electrolyzer stack, the various inputs (e.g., water and carbon oxide) to produce a molecular hydrogen and carbon-containing species (CCS), in a selected hydrogen to CCS ratio. The molecular hydrogen and CCS may have any of a variety of molecular hydrogen to CCS ratio described elsewhere herein. The output product can be controlled by varying the composition of the input gas as well as the composition of the brine mix used by the anolyte system. The electrolyzer system can also incorporate anolyte recirculation as part of controlling output product characteristics and energy consumption.
In some embodiments, the electrolyzing includes electrochemically producing a reduction product stream including a carbon-containing species (CCS), unreacted CO_x, and various byproducts and/or impurities (e.g., molecular hydrogen, water, formic acid, ions). The CCS may be produced from electrochemical reduction of gaseous CO_x. The method may further include producing an oxidation product stream including one or more oxidation products of the second input (e.g., anolyte or anode water), such as molecular oxygen, and any unreacted anolyte (e.g., unreacted anode water).
The electrolyzing, according to some embodiments, may include selectively electrolyzing the inputs to produce a reduction product stream including predominately CCS compared to at least one or more other species (e.g., byproducts and/or impurities). For example, in one set of embodiments, the method includes selectively electrolyzing to minimize a ratio of molecular hydrogen to CCS, such as giving rise to an HCR of at least 1:20 and no more than 1:1, at least 1:15 and no more than 1:5, at least 1:12 and no more than 1:8, or at least 1:50 and no more than 1:10, etc. Other ranges described elsewhere herein are also possible.
In some embodiments, the method includes transporting (e.g., recycling), via the anolyte circulation system described herein, at least a portion (e.g., at least 10%, at least 25%, at least 50%, at least 70%, or more, and/or up to 80%, up to 90%, or up to 100%) of unreacted anolyte (e.g., anode water) contained within the oxidation product stream (e.g., stream 787 or 887 as shown in FIGS. 7, 10, and 11 ) into the second input (e.g., input 785 or 885). Prior to the transporting (e.g., recycling), the method may include separating, via an anolyte separator unit (e.g., unit 724 or 824), the oxidation product stream to produce a liquid outlet stream (e.g., stream 725 or 827) enriched in water relative to the oxidation product and a gas outlet stream (e.g., stream 715 or 815) enriched an oxidation product (e.g., molecular oxygen) relative to the oxidation product stream. Upon separation, at least a portion (e.g., at least 10%, at least 25%, at least 50%, at least 70%, or more, and/or up to 80%, up to 90%, or up to 100%) of the outlet stream enriched in water relative to the oxidation product stream may be transported into the second input for recycling into the CRR(s).
In some embodiments, the method further includes recovering, via a catholyte circulation system, at least a portion (e.g., at least 10%, at least 25%, at least 50%, at least 70%, or more, and/or up to 80%, up to 90%, or up to 100%) of water contained within the reduction product stream (e.g., stream 783 or 883 as shown in FIGS. 7, 10, and 11 ). In some cases, at least a portion of the recovered water may be transported (e.g., recycled) into the first input. Prior to the transporting (e.g., recycling), via a catholyte separator unit (e.g., unit 730 or 830), the reduction product stream may be separated to produce an outlet stream (e.g., stream 731 or 831) enriched in water relative to the reduction product stream and an outlet stream (e.g., stream 729 or 829) enriched in one or more gases (e.g., a carbon-containing species (CCS), unreacted CO_x, and/or molecular hydrogen) relative to the reduction product stream. At least a portion of the outlet stream enriched in water may be transported into the first input (e.g., first input 781 or 881) into the first inlet (e.g., first inlet 780 or 880).
In some embodiments, the method further includes introducing the outlet stream (e.g., stream 729 or 829) enriched in the one or more gases into a gas separator to produce a first gas stream enriched in carbon oxide (e.g., stream 741 or 841) and a second gas stream (e.g., stream 743 or 841) enriched in the CCS (and/or syngas) relative to the outlet stream. The method may further include transporting (e.g., recycling) at least a portion of the first gas stream enriched in carbon oxide into the first inlet (e.g., first inlet 780 or 880).
In some embodiments, the method includes controlling a temperature differential (dT) of the CRR(s) and/or associated electrolyzer(s). In some such embodiments, the method includes maintaining, during operation, a predetermined temperature differential (dT) of an anolyte solution across an anode side of the CRR(s) and/or at least one carbon oxide reduction electrolyzer(s) via a temperature control system. The temperature differential may have any of a variety of values described elsewhere herein, such as no more than 10° C., no more than 5° C., no more than 3° C., no more than 2° C., no more than 1.5° C., no more than 1° C., no more than 0.5° C., no more than 0.1° C., etc.
In some cases, one or more components (e.g., pumps, flow controls, heat exchangers, etc.) in the anolyte circulation loop may be controlled to maintain the predetermined temperature differential, as described elsewhere herein. In some cases, via the one or more components, an inlet flow rate of the anolyte stream may be controlled to maintain the predetermined temperature differential. For example, in some cases, when a measured dT is higher than desired, e.g., such as exceeding a predetermined threshold value, a pressurizing unit (e.g., pumps such as 738 in FIG. 7 ) and/or flow controls (e.g., valves) may be controlled to increase a flow rate of the input anolyte stream introduced into the CRR and/or electrolyzer so that dT can be decreased.
Alternatively or additionally, the method may include maintaining the anolyte solution provided to the anode(s) of the CRR(s) and/or the associated electrolyzer(s) within a predetermined range. For example, the method may include maintaining, via the temperature control system, a temperature of the anolyte input (e.g., input 785 or 885 as shown in FIGS. 7, 10, and 11 ) and/or output (e.g., via stream 787 or 887) to be within a predetermined temperature range, as described elsewhere herein, e.g., at least 10° C. and no more than 66° C., at least 20° C. and no more than 60° C., at least 35° C. and no more than 45° C., at least 40° C. and no more than 45° C., etc. In some cases, one or more components (e.g., pumps, flow controls, heat exchangers) in the anolyte circulation loop may be controlled to maintain the anolyte input stream (or anode inlet temperature) to be within a predetermined temperature range, as described elsewhere herein. For example, when a measured anolyte input temperature is higher than desired, such as exceeding an upper threshold (e.g., an upper bound of the predetermined range), the one or more cooling devices (e.g., heat exchanger 736 as shown in FIG. 7 ) may be employed to cool the anolyte input stream to be within the predetermined range. Conversely, when a measured anolyte input temperature is lower than desired, such as less than a lower threshold (e.g., lower bound of the predetermined range), the one or more heating devices (e.g., heat exchanger 734 as shown in FIG. 7 ) may be employed to heat the anolyte input stream to be within the predetermined range.
In some embodiments, the method includes introducing a salt into the anolyte solution introduced into the CRR(s). In some such embodiments, the method further includes adjusting, via a salt dosing system, the concentration of ions (e.g., cations and/or anions) within the second input (e.g., anolyte or anode water) such that one or more parameters associated the second input (e.g., input 785 or 885 as shown in FIGS. 7, 10, and 11 ) are maintained within a predetermined range, as described elsewhere herein. The one or more parameters may include a salt concentration, a concentration of dissociated ions (e.g., cation and/or anions), an ion conductivity, etc.
In some cases, prior to the adjusting, the method includes monitoring the one or more parameters within the water system (e.g., the anolyte circulation system, the catholyte circulation system) and determining the necessary amount of salt dosed into the system based on the one or more parameters. The one or more parameters may be determined at any of a variety of appropriate locations, e.g., at various inlet/outlet streams and/or within particular units of the water system. Non-limiting examples of locations may include the first input (e.g., first input 781 or 881), the recycled anolyte stream (e.g., stream 725 or 827), the recycled catholyte stream (e.g., via loops 733 or 833), the salt mixing tank or reservoir (e.g., tank 722 or 822) and associated inlet/outlet streams, the anolyte circulation tank (e.g., anolyte tank 726) and associated inlet and/or outlets streams, the anolyte separator unit (e.g., unit 724 or 824) and/or associated inlet and/or outlets streams, etc. In some embodiments, based on the one or more parameters, the salt-dosing system may be operated to control the amount of fresh anolyte (e.g., fresh water) and/or salt dosed into the system.
In some embodiments, the method further includes adjusting, via at least a portion of the water system, the amount of anolyte circulating throughout the system and/or the anolyte (e.g., second input) entering the CRR(s), such that a desired amount of anolyte is maintained during operation. In some cases, via a level control, a level measurement may be performed to measure amount of water accumulated within one or more components within the system, such as within the catholyte separator unit, the anolyte separator unit, the anolyte circulation tank (when present), etc.
In some embodiments, the method further includes controlling a pH of the second input (e.g., anolyte input) introduced into the CRR(s). In some embodiments, the pH of the second input may be maintained between 1 and 8, between 1.5 and 7.5, between 2 and 7, between 6 and 8, or between 5 and 7, etc. In some embodiments, it may be beneficial to maintain the pH of the anolyte within a neutral or slightly acidic environment.
In some embodiments, the method further includes establishing a predetermined pressure difference across an anode side of the CO_xreduction electrolyzers. In some cases, the CO_xreduction electrolyzers may have an anode inlet pressure of between 0 psig and 150 psig, between 0 psig and 120 psig, between 50 psig and 150 psig, between 70 psig and 120 psig, between 80 psig and 110 psig, etc. In some cases, at least one of the CO_xreduction electrolyzers may have an anode outlet pressure of between 5 psig and 80 psig, between 15 psig and 60 psig, between 15 psig and 50 psig, between 20 psig and 60 psig, etc. The predetermined pressure difference may be between 10 psig and 60 psig, between 15 psig and 50 psig, between 60 psig and 80 psig, etc.
In some embodiments, the method further includes establishing a predetermined pressure difference across a cathode side of the CO_xreduction electrolyzers. In some cases, at least one of the CO_xreduction electrolyzers may have a cathode inlet and/or cathode outlet pressure of between 0 psig and 500 psig, between 0 psig and 300 psig, between 50 psig and 200 psig, between 100 psig and 300 psig, between 80 psig and 300 psig, etc. The predetermined pressure difference may be between 0 psig and 50 psig, between 0 psig and 30 psig, between 0 psig and 20 psig, etc.
The process conditions associated with the CO_xelectrolyzer may include a pressure (e.g., input gas pressure, reactor pressure, etc.) greater than atmospheric pressure (e.g., within and/or greater than a threshold pressure range, such as about 1-5, about 5-10, about 10-20, about 20-50, about 30-70, about 50-100, about 100-300, about 300-1000, about 1-10, about 5-50, about 10-100, about 20-500, and/or greater than about 1000 atm, about 14-50, about 50-150, about 100-300, about 200-500, about 500-1000, about 750-1500, about 1000-3000, about 3000-10,000, about 10,000-20,000, and/or greater than about 20,000 psi, etc.) and/or greater than pressures typically feasible in electrolyzers other than gas-phase electrolyzers, but can additionally or alternatively include pressures substantially equal to 1 atmosphere, less than about 1 atmosphere, and/or any other suitable pressures (e.g., between 1 atm and 80 atm, between 10 atm and 70 atm, between 20 atm and 60 atm, etc.)
The process conditions associated with the CO_xelectrolyzer may include a temperature (e.g., reactor temperature) greater than typical room temperature (e.g., within and/or greater than a threshold temperature range, such as about 25-50, about 40-60, about 50-100, about 50-75, about 70-100, and/or greater than about 100° C., etc.) and/or greater than temperatures typically feasible in electrolyzers other than gas-phase electrolyzers, but can additionally or alternatively include temperatures substantially equal to room temperature (e.g., about 20-30° C.), less than room temperature, and/or any other suitable temperatures (e.g., between 20° C. and 100° C., between 20° C. and 90° C., between 25° C. and 50° C., or between 50° C. and 80° C., etc.). However, the process conditions can additionally or alternatively include any other suitable process conditions.
A higher carbon dioxide flow rate can lead to increased production of CCPs such as CO (e.g., due to greater availability of carbon dioxide for reduction), and thus an increased CCS:H₂ratio (and correspondingly, lower carbon dioxide flow rate can lead to decreased CCS production and CCS:H₂ratio). In some embodiments, higher carbon dioxide flow rate can also result in reduced carbon dioxide conversion efficiency, thereby diluting the output stream (e.g., syngas output) with unreacted carbon dioxide. For example, carbon dioxide flow rate (e.g., measured at the reactor inlet) can be maintained at one or more values in the range of about 0.1-1000 sccm/cm²(e.g., about 0.1-1, about 1-10, about 10-100, and/or about 100-1000 sccm/cm²).
While FIG. 7 illustrates an embodiment in which the carbon oxide electrolyzer plant includes a single CRR 704, it should be understood that the disclosure is not so limited and that in certain embodiments, the carbon oxide electrolyzer plant may include a plurality of CRRs, each of which includes a stack of membrane electrode assemblies or cells. A non-limiting example of such an embodiment is illustrated in FIGS. 10-13C, as described in more detail below.
FIGS. 10 and 11 are schematic diagrams illustrating a non-limiting example of a CO_xreduction system including a plurality of CRRs. The system may be employed to electrochemically produce carbon monoxide from carbon dioxide, in one embodiment. For example, as shown, the system can include CRR assembly 803 containing multiple CRR(s) (i.e., electrolyzer skid(s) 803A-803C). Each of the skids can include multiple electrolyzer stacks, and each stack can contain multiple individual electrolyzer reduction cells (e.g., at least 50, at least 100, etc.). Any appropriate number of electrolyzer skid(s) and/or electrolyzer stacks may be present. A non-limiting example of CRR assembly 803 including multiple electrolyzer skids 803A-803H and associated components is shown in FIGS. 12-13C.
As shown in FIG. 12 , CRR assembly 803 can include multiple CRRs or skids, e.g., electrolyzer skid 803A-803H, each coupled to a corresponding power module, e.g., module 896A-896H. As shown in FIGS. 13A-13C, electrolyzer skid 803A can be electrically coupled to power module 896A and can include multiple electrolyzers 870 a-870 h, ion exchange resin bed 888, filter 890, catholyte sample separator, catholyte product gas separator, anolyte sample separator, and various instrumentation and controls surrounding the components.
For example, each electrolyzer skid can include sample separators and gas analyzers for both the anolyte and catholyte to allow measurement of individual stack performance. Specifically, on the anolyte side, anolyte gas analyzer 892 can serve as an important piece of safety instrumentation to monitor the presence and/or concentration of a flammable gas. For example, the oxygen gas produced from the anolyte, in addition to CO and H₂(if any) that diffused through the stack membranes from the cathode side, may potentially lead to the formation of an explosive gas mixture. The anode gas analyzer may be configured to constantly cycle through the stacks to ensure that a flammable environment is not produced inside the system. Similarly, cathode gas analyzer 894 can be used to measure individual stack cathode gas concentrations to monitor stack performance.
Referring back to FIGS. 10-12 , the electrolyzer stacks can have three main inputs: anolyte, cathode gas, and electricity. The electrolyzer stacks can be individually controlled and operate in controlled current mode, with a target current density. Voltage across the stack may vary with cell lifetime. That is, as cell voltage increases over its lifetime, a larger amount of heat can be generated in the stack and needed to be removed by the anolyte system to maintain performance. The anolyte can advantageously serve a dual purpose in the system, such as serving as an anode side reaction medium for the electrolyzer stacks and serving as a heat sink to absorb and remove excess heat generated in the stacks.
As shown in FIGS. 10 and 11 , during operation, anolyte can be pumped over to electrolyzer skids 803A-803C from anolyte separator 824 via input 885. FIG. 13B can be used to show anolyte flow through input 885 and through electrolyzer skid 803A. As shown, the cation exchange resin bed 888 on each of the electrolyzer skids 803A-803C can remove contaminant metal ions from the anolyte input. Anolyte 885 can then flow through a particulate filter before entering the electrolyzer stacks. Anolyte outlet stream from the stacks can then return via stream 887 to anolyte separator 824 where oxygen gas produced in the stack can be separated from the bulk liquid.
Referring back to FIGS. 10 and 11 , the cathode gas may include primarily CO₂, which can include both pure makeup CO₂and recycled CO₂from downstream processes. During operation, cathode gas can be fed to the electrolyzer skids via stream 881, where the CO₂can be converted to CO and some H₂can be produced along with a small amount of formic acid and water (e.g., water that migrate from the anode side of the membranes). FIG. 13C can be used to illustrate cathode gas input flow 881 into electrolyzer skid 803A and product in output stream 883 out of the electrolyzer. Referring back to FIGS. 10 and 11 , this CO₂/CO/H₂/liquid mixture 883 can then be transported to cathode gas/liquid separator 830 to remove the bulk liquid. The bulk liquid can be sent to a downstream wastewater treatment system 832, which may, for example, include the cathode water tank. In addition to facilitating separation, the cathode separator 830 can provide enough holdup to reliably level control the liquid to wastewater treatment. In some cases, a liquid level can be maintained in the separator to ensure that no vapor blows through to wastewater treatment. The gas from the cathode separator 830 can be sent through a gas chiller and coalescing filter to remove any remaining humidity from the gas stream.
Furthermore, as shown in FIGS. 10 and 11 , during operation, electricity can be converted by one or more rectifiers in power module 809 from site AC supply to DC current to power the stacks. In some cases, each individual stack can be coupled to a single rectifier for precise control. Alternatively, multiple stacks may be coupled to a single rectifier. The system can further include a process skid, which can include the anolyte pumps, resin beds, anolyte filter, anolyte startup heater, anolyte cooler, cathode gas cooler, and cathode gas coalescing filter.
Referring again to FIGS. 10 and 11 , the anolyte solution may include a mixture of DI water and a salt (e.g., potassium bicarbonate salt), which can be dosed into the DI water to achieve a desired conductivity described elsewhere herein (e.g., at least 200 μS/cm and no more than 3000 μS/cm, at least 100 μS/cm and no more than 1000 μS/cm, or at least 300 μS/cm and no more than 800 μS/cm, at least 600 μS/cm and no more than 1000 μS/cm, at least 100 μS/cm and no more than 600 μS/cm). Fresh DI water and brine solution can be added continuously (as needed) to separator tank 824 to maintain anolyte level and conductivity.
The anolyte can be next pumped from anolyte separator 824 through a filter to and a cooler (within temperature control unit 836) before being sent to the electrolyzer skid. The filter can remove any particles which could cause plugging or other mechanical damage to downstream equipment. The cooler can be used to maintain the anolyte loop temperature during normal operation, by removing the heat imparted from the stacks to the anolyte. At each individual stack, anolyte flow can be controlled by cascade from the temperature differential on the anode side between the anode inlet and the anode outlet. In some cases, the anolyte pumps and coolers can be sized to maintain a relatively small temperature differential (e.g., no more than 3° C., no more than 1.5° C., no more than 1° C., etc.) with all stacks on average operating at about 75% of lifetime (e.g., about 85%, about 95%, etc), which is expected to be advantageous for stack performance. In some cases, a heater can be used to increase the temperature of anolyte during startup, and a cooler can be used to cool the anolyte during normal operation.
Anolyte stream from outlet 887 returning from the electrolyzers can contain an oxygen gas mixture with some small amount of CO₂, CO, and hydrogen. This stream can be returned to anolyte separator 824 for further separation.
FIG. 8B shows a non-limiting example of a flow diagram for operating a system including one or more CRRs.
As shown by step 903, method 901 may include introducing a first input (e.g., first inlet 880 as shown in FIGS. 10-12 ) including gaseous carbon oxide into the one or more CRRs (e.g., CRRs 803) to electrochemically produce a reduction product stream (e.g., output stream 883) including a carbon-containing species (CCS), which is a product of the electrochemical reduction of carbon oxide. A second input (e.g., input 885) including a salt-containing anolyte may be simultaneously introduced into the one or more CRR(s) to produce an oxidation product stream (e.g., output stream 887) including an oxidation product of the anolyte. The one or more CRR(s) may have any appropriate configurations, such as being arranged in parallel into a CRR assembly (e.g., CRRs on electrolyzer skids 803A-803H as shown in FIGS. 10-12 ). Other configurations are also possible (e.g., such as being in series). Referring back to FIG. 12 , the one or more CRR(s) may be fluidically connected via various feed streams, including, but not limited to, an electrical input, the first input including gas, and the second input including anolyte. In some cases, at least one (or each) of the CRR(s) may include a plurality of carbon oxide reduction electrolyzers in the form of electrolyzer stacks fluidically connected with one another, e.g., as shown by the fluidic connectivity amongst electrolyzers 870 a-870 h as shown in FIG. 12 or electrolyzer stacks 170A-170D as shown in FIG. 1D.
As shown by step 905 in FIG. 8B, method 901 further includes selectively controlling at least one of the carbon oxide reduction electrolyzers based on, at least in part, one or more sensed parameters associated with an input and/or output of the carbon oxide reduction electrolyzers, e.g., such the first input, the second input, the reduction product stream, and/or the oxidation product stream. In some cases, the one or more sensed parameters may include a presence, a concentration, and/or a composition of certain (undesirable) species in the input and/or output of the electrolyzer(s). For example, in some embodiments, the one or more sensed parameters may include the presence, concentration, and/or composition of particular toxic species (e.g., toxic to a catalyst within the MEA), particular species that pose a safety hazard (e.g., a flammable gas or gas mixture), and/or particular species indicative of runaway reactions, electrolyzer malfunctioning and/or aging (e.g., reaching end of life).
In some cases, the method includes monitoring (e.g., continuously monitoring) the one or more sensed parameters associated with the input and/or output of some (or all) of the carbon oxide reduction electrolyzers (e.g., electrolyzer stacks 870 a-870 h as shown in FIG. 13A). In some cases, by monitoring the one or more sensed parameters associated with the input and/or output streams, the system may be capable of identifying the particular electrolyzer stack(s) that exhibit undesirable performance and/or that can potentially pose a safety risk.
In some embodiments, as shown by step 907, the selectively controlling includes selectively terminating at least one carbon oxide reduction electrolyzer upon detecting one or more sensed parameters and/or when the sensed parameters exceed a threshold value. (e.g., outside of a threshold value range). In some cases, the one or more sensed parameters includes an input stream and/or output stream (e.g., reduction product stream and/or an oxidation product stream) composition value. For example, upon detecting the presence of a particular species (e.g., toxic or flammable species) in the input and/or output of the one or more electrolyzers (e.g., electrolyzers 870 a-870 h as shown in FIGS. 13A-13C), and/or when the concentration of the particular species in the input and/or output exceed a threshold level, the corresponding one or more electrolyzer(s) may be identified and selectively terminated (while the other electrolyzer(s) in the CRR may be allowed to continue operating). Alternatively or additionally, in embodiments in which the system includes a plurality of CRR(s) (e.g., as shown in FIG. 12 ), the entire CRR (e.g., the CRR on electrolyzer skid 803A) including the identified electrolyzer(s) may be selectively terminated as a whole. The system described herein may allow for both selective control (e.g., selectively terminating) of individual electrolyzer stack(s) and/or of individual CRR(s).
In some embodiments, the method further includes selectively controlling the power introduced to at least one of the carbon oxide reduction electrolyzers and/or CRRs based on one or more sensed parameters described above. In some cases, upon detecting the sensed parameters and identifying the corresponding electrolyzer(s) and/or CRR(s) associated with sensed parameter, the power introduced to the identified electrolyzer(s) and/or CRR(s) may be selectively terminated, according to some embodiments. In some embodiments, individual electrolyzers and/or CRRs may be separately controlled such a predetermined amount of power may be introduced into the individual electrolyzers and/or CRRs.
In some embodiments, the method further includes decoupling the terminated carbon oxide reduction electrolyzer(s) from the carbon oxide reduction reactor and removing it. In some such cases, a new electrolyzer may be removably coupled to the other remaining electrolyzers and CRR to replace the removed electrolyzer. According to some embodiments, the electrolyzers can be removably coupled to or decoupled from one another or from the CRR with ease as desired.
Having described implementations of the present disclosure, an example operating environment in which embodiments of the present invention may be implemented is described below in order to provide a general context for various aspects of the present disclosure. Referring initially to FIG. 9 in particular, an example operating environment for implementing embodiments of the present invention is shown and designated generally as computing device 900. Computing device 900 is but one example of a suitable computing environment and is not intended to suggest any limitation as to the scope of use or functionality of the invention. Neither should the computing device 900 be interpreted as having any dependency or requirement relating to any one or combination of components illustrated.
With reference to FIG. 9 , a carbon oxide electrolyzer computing environment can utilize an example computing device such as computing device 900. Computing device 900 includes bus 910 that directly or indirectly couples the following devices: memory 912, one or more processors 914, one or more presentation components 916, input/output (I/O) ports 918, input/output components 920, and illustrative power supply 922. Bus 910 represents what may be one or more busses (such as an address bus, data bus, or combination thereof). Although the various blocks of FIG. 9 are shown with lines for the sake of clarity, in reality, delineating various components is not so clear, and metaphorically, the lines would more accurately be grey and fuzzy. For example, one may consider a presentation component such as a display device to be an I/O component. Also, processors have memory. The inventors recognize that such is the nature of the art, and reiterate that the diagram of FIG. 9 is merely illustrative of an example computing device that can be used in connection with one or more embodiments of the present invention. Distinction is not made between such categories as “workstation,” “server,” “laptop,” “hand-held device,” etc., as all are contemplated within the scope of FIG. 9 and reference to “computing device.”
Computing device 900 may typically include a variety of computer-readable media. Computer-readable media can be any available media that can be accessed by computing device 900 and includes both volatile and nonvolatile media, removable and non-removable media. By way of example, and not limitation, computer-readable media may include computer storage media and communication media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by computing device 900. Computer storage media does not include signals per se. Communication media typically embodies computer-readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media. Combinations of any of the above should also be included within the scope of computer-readable media.
Memory 912 includes computer storage media in the form of volatile and/or nonvolatile memory. The memory may be removable, non-removable, or a combination thereof. Example hardware devices include solid-state memory, hard drives, optical-disc drives, etc. Computing device 900 includes one or more processors that read data from various entities such as memory 912 or I/O components 920. Presentation component(s) 916 present data indications to a user or other device. Example presentation components include a display device, speaker, printing component, vibrating component, etc.
I/O ports 918 allow computing device 900 to be logically coupled to other devices including I/O components 920, some of which may be built in. Illustrative components include a microphone, joystick, game pad, satellite dish, scanner, printer, wireless device, etc. The 1/O components 920 may provide a natural user interface (NUI) that processes air gestures, voice, or other physiological inputs generated by a user. In some instance, inputs may be transmitted to an appropriate network element for further processing. A NUI may implement any combination of speech recognition, touch and stylus recognition, facial recognition, biometric recognition, gesture recognition both on screen and adjacent to the screen, air gestures, head and eye-tracking, and touch recognition associated with displays on the computing device 900. The computing device 900 may be equipped with depth cameras, such as, stereoscopic camera systems, infrared camera systems, RGB camera systems, and combinations of these for gesture detection and recognition. Additionally, the computing device 900 may be equipped with accelerometers or gyroscopes that enable detection of motion.
Aspects of the present invention have been described in relation to particular embodiments, which are intended in all respects to be illustrative rather than restrictive. Alternative embodiments will become apparent to those of ordinary skill in the art to which the present invention pertains without departing from its scope.
Having identified various components utilized herein, it should be understood that any number of components and arrangements may be employed to achieve the desired functionality within the scope of the present disclosure. For example, the components in the embodiments depicted in the figures are shown with lines for the sake of conceptual clarity. Other arrangements of these and other components may also be implemented. For example, although some components are depicted as single components, many of the elements described herein may be implemented as discrete or distributed components or in conjunction with other components, and in any suitable combination and location. Some elements may be omitted altogether. Moreover, various functions described herein as being performed by one or more entities may be carried out by hardware, firmware, and/or software, as described below. For instance, various functions may be carried out by a processor executing instructions stored in memory. As such, other arrangements and elements (e.g., machines, interfaces, functions, orders, and groupings of functions) can be used in addition to or instead of those shown.
Embodiments described herein may be combined with one or more of the specifically described alternatives. In particular, an embodiment that is claimed may contain a reference, in the alternative, to more than one other embodiment. The embodiment that is claimed may specify a further limitation of the subject matter claimed.
The subject matter of embodiments of the invention is described with specificity herein to meet statutory requirements. However, the description itself is not intended to limit the scope of this patent. Rather, the inventors have contemplated that the claimed subject matter might also be embodied in other ways, to include different steps or combinations of steps similar to the ones described in this document, in conjunction with other present or future technologies. Moreover, although the terms “step” and/or “block” may be used herein to connote different elements of methods employed, the terms should not be interpreted as implying any particular order among or between various steps herein disclosed unless and except when the order of individual steps is explicitly described.
For purposes of this disclosure, the word “including” has the same broad meaning as the word “comprising,” and the word “accessing” includes “receiving,” “referencing,” or “retrieving.” Further, the word “communicating” has the same broad meaning as the word “receiving,” or “transmitting” facilitated by software or hardware-based buses, receivers, or transmitters using communication media described herein. In addition, words such as “a” and “an,” unless otherwise indicated to the contrary, include the plural as well as the singular. Thus, for example, the constraint of “a feature” is satisfied where one or more features are present. Also, the term “or” includes the conjunctive, the disjunctive, and both (a or b thus includes either a or b, as well as a and b).
For the purposes of this disclosure, the term “fluidically connected” is used with respect to volumes, plenums, holes, etc., that may be connected with one another, either directly or via one or more intervening components or volumes, in order to form a fluidic connection, similar to how the term “electrically connected” is used with respect to components that are connected together to form an electric connection. The term “fluidically interposed,” if used, may be used to refer to a component, volume, plenum, or hole that is fluidically connected with at least two other components, volumes, plenums, or holes such that fluid flowing from one of those other components, volumes, plenums, or holes to the other or another of those components, volumes, plenums, or holes would first flow through the “fluidically interposed” component before reaching that other or another of those components, volumes, plenums, or holes. For example, if a pump is fluidically interposed between a reservoir and an outlet, fluid that flowed from the reservoir to the outlet would first flow through the pump before reaching the outlet. The term “fluidically adjacent,” if used, refers to placement of a fluidic element relative to another fluidic element such that there are no potential structures fluidically interposed between the two elements that might potentially interrupt fluid flow between the two fluidic elements. For example, in a flow path having a first valve, a second valve, and a third valve placed sequentially therealong, the first valve would be fluidically adjacent to the second valve, the second valve fluidically adjacent to both the first and third valves, and the third valve fluidically adjacent to the second valve.
For purposes of a detailed discussion above, embodiments of the present invention are described with reference to a distributed computing environment; however, the distributed computing environment depicted herein is merely an example. Components can be configured for performing novel embodiments of embodiments, where the term “configured for” can refer to “programmed to” perform particular tasks or implement particular abstract data types using code. Further, while embodiments of the present invention may generally refer to the technical solution environment and the schematics described herein, it is understood that the techniques described may be extended to other implementation contexts.
From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects set forth above, together with other advantages which are obvious and inherent to the system and method. It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of the claims.

Claims

What is claimed is:

1. A method for carbon oxide electrolysis, comprising:

inputting a source of gaseous carbon oxide to a cathode of a carbon oxide reduction reactor;

inputting anolyte solution from an anolyte circulation system to an anode of the carbon oxide reduction reactor;

controlling a temperature differential of the anolyte solution across the anode;

inputting electrical power to the carbon oxide reduction reactor; and

electrochemically reducing the gaseous carbon oxide to produce a molecular carbon containing species.

2. The method of claim 1, wherein the controlling comprises one or more of controlling an anode inlet flow rate of the anolyte solution.

3. The method of claim 1, wherein controlling the temperature differential comprises maintaining a temperature differential of not more than 5° C.

4. The method of claim 1, further comprising introducing a reduction product stream from the carbon oxide reactor to a catholyte separator and separating the reduction product stream to produce a liquid stream enriched in water and a gaseous stream enriched in carbon-containing species.

5. The method of claim 4, further comprising recycling at least a portion of liquid stream to the anolyte circulation system.

6. The method of claim 1, wherein the carbon oxide reduction reactor comprises a membrane electrode assembly comprising one or more ion conductive polymer layers and a cathode catalyst layer for facilitating chemical reduction of the carbon oxide to the carbon-containing species.

7. The method of claim 1, further comprising introducing an oxidation product stream produced from the carbon oxide reduction reactor to an anolyte separator unit and separating the oxidation product stream to produce a liquid stream enriched in water and a gaseous stream enriched in molecular oxygen.

8. The method of claim 1, wherein the carbon oxide reduction reactor comprises an electrolyzer stack having more than one cell.

9. The method of claim 1, further comprising introducing a salt into the anolyte solution to control a salt concentration and/or ion conductivity of the anolyte solution introduced into the carbon oxide reduction reactor.

10. A method for carbon oxide electrolysis, comprising:

maintaining the anolyte solution provided to the anode within a predetermined temperature range;

inputting electrical power to the carbon oxide reduction reactor; and

11. The method of claim 10, wherein the predetermined temperature range is 10° C. to 80° C.

12. The method of claim 10, further comprising introducing a reduction product stream from the carbon oxide reactor to a catholyte separator and separating the reduction product stream to produce a liquid stream enriched in water and a gaseous stream enriched in carbon-containing species.

13. The method of claim 12, further comprising recycling at least a portion of liquid stream to the anolyte circulation system.

14. The method of claim 10, wherein the carbon oxide reduction reactor comprises a membrane electrode assembly comprising one or more ion conductive polymer layers and a cathode catalyst layer for facilitating chemical reduction of the carbon oxide to the carbon-containing species.

15. The method of claim 10, further comprising introducing an oxidation product stream produced from the carbon oxide reduction reactor to an anolyte separator unit and separating the oxidation product stream to produce a liquid stream enriched in water and a gaseous stream enriched in molecular oxygen.

16. The method of claim 10, wherein the carbon oxide reduction reactor comprises an electrolyzer stack having more than one cell.

17. The method of claim 10, further comprising introducing a salt into the anolyte solution to control a salt concentration and/or ion conductivity of the anolyte solution introduced into the carbon oxide reduction reactor.

18. A method of operating a carbon oxide electrolyzer system, the method comprising:

introducing a first input comprising gaseous carbon oxide and a second input comprising an anolyte solution into a carbon oxide reduction reactor system comprising a plurality of fluidically connected carbon oxide reduction electrolyzers, thereby producing a reduction product stream comprising a carbon-containing species and an oxidation product stream; and

selectively terminating at least one of the carbon oxide reduction electrolyzers upon detecting one or more sensed parameters outside of a threshold value range.

19. The method of claim 18, wherein the one or more sensed parameters comprises a reduction product stream and/or an oxidation product stream composition value.

20. The method of claim 18, further comprising decoupling the terminated carbon oxide reduction electrolyzer from the carbon oxide reduction reactor and removing it from the system.