WO2024130301A1

WO2024130301A1 - Carbonation device

Info

Publication number: WO2024130301A1
Application number: PCT/AU2023/051316
Authority: WO
Inventors: Luong Ngoc NGUYEN; Peter Ralph; DucLong NGHIEM
Original assignee: University Of Technology Sydney
Priority date: 2022-12-19
Filing date: 2023-12-18
Publication date: 2024-06-27

Abstract

The invention relates to a carbonation device, including: a fluid vessel; a fluid supply system disposed on an upper portion of the fluid vessel to supply fluid to the fluid vessel; a gas injection inlet disposed on a lower portion of the fluid vessel to supply gas to the fluid vessel; at least one mixing element arranged within the fluid vessel and below the fluid supply system; a diffuser arranged within the fluid vessel such that gas supplied through the gas injection inlet passes at least partially through the diffuser to produce a diffused gas, wherein the diffused gas and the fluid mix within the fluid vessel to produce a mixed fluid; and an outlet disposed on the fluid vessel to release the mixed fluid.

Description

Carbonation Device

REFERENCE TO RELATED APPLICATIONS

[0001] This application claims Convention priority to Australian Provisional Patent Application No. 2022903902, filed 19 December 2022, the contents of which are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

[0002] The present invention relates to devices for carbonation of fluids. More particularly, the invention relates to a carbonation device for use in a photobioreactor.

[0003] The invention has been developed primarily for use as a carbonation device for use in cultivating algae in a photobioreactor. However, while some embodiments will be described herein with particular reference to that application, it will be appreciated that the invention is not limited to such a field of use, and is applicable in broader contexts.

BACKGROUND

[0004] The following discussion of the prior art is intended to facilitate an understanding of the invention and to enable the advantages of it to be more fully understood. It should be appreciated, however, that any reference to prior art throughout the specification in no way be considered as an admission that such art is widely known or forms part of the common general knowledge in the field.

[0005] Microalgae are capable of fixing carbon dioxide (CO2) through photosynthesis 40 times more efficiently than terrestrial plants. For every 1kg of microalgal biomass, 2kg of CO2 is captured. This biomass is also a versatile feedstock that can replace fossil materials for raw chemicals, fuels, and industrial products. Microalgae cultivation is a process of creating suitable conditions for algae to bloom. Replicating the conditions for algae to bloom is expected to produce more algae biomass while capturing CO2for greenhouse gas mitigations.

[0006] In the current large-scale microalgae cultivation (such as raceway or photobioreactors), CO2 supply is not optimal. CO2 sparging (like aeration in an aquarium tank) results in a limited contact time between gas bubbles and microalgal culture for mass transfer. Raceway systems involve direct bubbling into the algae pond and may utilize a mixing tank. In pond systems, a supplementary CO2 solvent is provided, utilising a holding tank through which the algae solution is pumped through. This provides indirect bubbling via a solvent and membrane, but does not provide enough contact time between the CO2 gas and the algae solution.

[0007] Up to 80% of CO2 is lost to the atmosphere in both of these systems. Other methods such as a membrane contactor, bicarbonate solution addition and micro air diffuser systems suffer scalability and efficiency limitations.

[0008] It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

SUMMARY OF THE INVENTION

[0009] According to a first aspect of the invention, there is provided a carbonation device, including: a fluid vessel; a fluid supply system disposed on an upper portion of the fluid vessel to supply fluid to the fluid vessel; a gas injection inlet disposed on a lower portion of the fluid vessel to supply gas to the fluid vessel; at least one mixing element arranged within the fluid vessel and below the fluid supply system; a diffuser arranged within the fluid vessel such that gas supplied through the gas injection inlet passes at least partially through the diffuser to produce a diffused gas, wherein the diffused gas and the fluid mix within the fluid vessel to produce a mixed fluid; and an outlet disposed on the fluid vessel to release the mixed fluid.

[0010] Preferably, the outlet is disposed on the fluid vessel and below the diffuser. More preferably, the fluid vessel is enclosed.

[0011] In one embodiment, the gas is carbon dioxide (CO2), and supply of the CO2 results in at least partial carbonation of the fluid. Preferably, the supply of gas provides at least partial gas dissociation in the fluid. More preferably, the supply of gas provides substantially 100% gas dissociation in the fluid. In another embodiment, the direction of gas flow is opposite to the direction of fluid flow. [0012] In a further embodiment, the fluid vessel is column-shaped. Preferably, the fluid vessel is substantially cylindrical.

[0013] In another embodiment, the at least one mixing element defines a gas trap. Preferably, the at least one mixing element provides static mixing of the fluid and the gas. More preferably, the at least one mixing element is a static mixer. In a further embodiment, the carbonation device includes a plurality of mixing elements.

[0014] Preferably, the at least one mixing element is substantially round. More preferably, the at least one mixing element is substantially spherical. In one embodiment, the at least one mixing element is at least partially buoyant. The at least one mixing element is preferably a floatable ball.

[0015] In a further embodiment, the at least one mixing element is fixedly attached to the fluid vessel. In yet another embodiment, the diffuser is an air stone.

[0016] Preferably, the fluid supply system includes a fluid supply inlet through which fluid is supplied to the fluid vessel. More preferably, the fluid supply inlet includes a valve configured to regulate inflow of the fluid. The fluid supply system preferably further includes a manifold disposed adjacent the fluid inlet such that the fluid passes through the manifold and into the fluid vessel. In one embodiment, the manifold includes a plurality of outlets through which the fluid leaves the manifold and enters the fluid vessel. Preferably, the plurality of outlets are a plurality of spray nozzles.

[0017] In another embodiment, the carbonation device further includes a controller to control the gas being supplied through the gas injection inlet. Preferably, the gas supplied through the gas injection inlet is controlled on the basis of at least one characteristic of the fluid. In one embodiment, the at least one characteristic of the fluid is pH.

[0018] In a further embodiment, the fluid comprises algae. Preferably, the fluid is alkaline.

[0019] The outlet is preferably configured to allow the mixed fluid to exit the fluid vessel. Preferably, the outlet includes a pipe to transport the mixed fluid from the fluid vessel to a terraced illumination apparatus. In one embodiment, the mixed fluid is transported to a secondary vessel in a terraced illumination apparatus. In a further embodiment, the secondary vessel is a holding tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Preferred embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

[0021] Fig. 1 A is a diagram of the carbonation device according to one embodiment of the present invention;

[0022] Fig. 1 B is an annotated version of Figure 1A showing the direction of fluid and gas flow;

[0023] Fig. 2 is an image of the enclosed column fluid vessel of the carbonation device according to one embodiment of the present invention;

[0024] Fig. 3 is an image of the lower portion of the fluid vessel of Figure 2, showing the gas injection inlet and a mixing element; and

[0025] Fig. 4 is a graph showing CO2 level in the atmosphere with and without use of the carbonation device according to one embodiment of the present invention.

DETAILED DESCRIPTION

[0026] The device described herein relates to a carbonation device for use with a photobioreactor to introduce carbon dioxide into an algae solution. As shown in Figure 1A, in one embodiment, there is provided carbonation device 100 including a fluid vessel, a fluid supply system disposed on an upper portion of the fluid vessel to supply fluid to the fluid vessel and a gas injection inlet disposed on a lower portion of the fluid vessel to supply gas to the fluid vessel. The device includes at least one mixing element arranged within the fluid vessel and below the fluid supply system. A diffuser is arranged within the fluid vessel such that gas supplied through the gas injection inlet passes at least partially through the diffuser to produce a diffused gas, and the diffused gas and fluid mix within the fluid vessel to produce a mixed fluid. An outlet is disposed on the fluid vessel to release the mixed fluid. Fig. 1 B shows the carbonation device 100 with direction of fluid and gas flow annotated.

[0027] The carbonation device 100 is able to carbonate a microalgae culture effectively and efficiently, and different scales. The carbonation device 100 may also be referred to as a carbonation jet. The carbonation device 100 facilitates the interface of CO2 gas bubbles with a microalgae solution in an enclosed column 105 from which highly carbonated algae solution will flow out for algae photosynthesis. In the carbonation device 100, the CO2 gas and algae solution flow in opposite directions. CO2gas is introduced via air stone 160 at the lower portion of the column. Algae solution 115 is pumped in on the top of the column 105. CO2gas bubbles upwards and hits the water flow. The column 105 includes a plurality of floatable balls 120 as a mixing element disposed at the CO2 gas and algae solution injection points. The floatable balls 120 create static mixing and shear of CO2 gas and algae solution on their surface. The saturated CO2 algae solution flows out at the bottom of the column to distribute onto terraced illumination layers for algae cultivation.

[0028] The dissolved CO2 in the algae solution is in three different species (CO2, HCO³' and CO₃ ²') with concentrations depending on the pH level of the algae solution. Amongst these species, algae can use most of CC^ and HCO³'. The relevant dose of CO2to the carbonation jet is controlled on the basis of the detected pH level of the algae solution. The carbonation device 100 provides substantially no CO2 gas loss, high CO2 transfer, and easy control to match CO2 demand by the algae. CO2 dissociation into a fluid depends on pH and retention time. The device of the present invention provides both conditions for efficient mass transfer.

[0029] While the embodiments herein reference algae, it will be appreciated that the carbonation device can be used to saturate fluids with CO2 in applications relating to various plants, plant materials, bacteria and archaea, and that the devices can be used in various applications including, but not limited to, horticultural, agricultural, and aquacultural environments, as well as commercial glasshouses, hydroponics, tank-based seaweed, algae farms, and vertical farming production.

[0030] In one embodiment, fluid vessel 101 is enclosed. By enclosing the column 105, this prevents the gas from escaping at a surface of the fluid. In other embodiments, the fluid vessel 101 may be open. For example, the top of the fluid vessel 101 may be open at the top, or may include an aperture which extends at least partially across the top of the fluid vessel. The fluid vessel 101 may be column-shaped and elongate, such that it has an upper portion and a lower portion. In some embodiments, the lower portion is defined by the lower two-thirds of the fluid vessel 101 , and the upper portion is defined by the upper one-third of the fluid vessel 101. The fluid vessel 101 may be substantially cylindrical in shape. However, it will be appreciated that the fluid vessel 101 may be in other forms such as rectilinear or prismatic configurations. The fluid vessel 101 should provide enough area for the fluid and gas to adequately mix. The more contact that the gas has with the fluid within the fluid vessel, the greater the amount of gas dissociation within the fluid. The fluid vessel 101 may have a volume of between 5 L and 20 L. However, it will be appreciated that the size and volume of the vessel 101 can be changed depending on the scale of the algae solution. In one embodiment, the fluid vessel is designed for a 2.5 m³ algae culture. In a further embodiment, the vessel 101 is 12 L, with a height of about 1500 mm and diameter: of about 100 mm.

[0031] A fluid supply system 150 is disposed on an upper portion of the fluid vessel 101 to supply fluid to the fluid vessel. In some embodiments, the fluid supply system 150 is located on the upper one-third of the fluid vessel 101. The fluid supply system may be disposed on the top of the fluid vessel. Alternatively, the fluid supply system 150 may be located on a side of the fluid vessel 101. In one embodiment, the fluid supply system 150 includes a fluid supply inlet 155 through which fluid is supplied to the vessel. The fluid supply inlet 155 may be located on the top of the fluid vessel 101 , or it may be located on a side of the vessel. In some embodiments, the fluid supply system 150 may include a plurality of fluid supply inlets. The fluid supply system 150 may also include a supply pipe through which fluid is transported to the fluid supply inlet. The supply pipe enables the fluid supply system to be in fluid communication with at least one storage tank (e.g., 152), such that fluid flows from the at least one storage tank to the fluid supply system 150. The at least one storage tank 152 may include a pump 157 to enable the fluid 115 to be pumped to the fluid supply system 150 at the top of the fluid vessel 101. At least one sensor may be positioned within the supply pipe. The at least one sensor may be a pH sensor (e.g., 156). In one embodiment, there may be a plurality of sensors. The carbonation device 100 may further include a dissolved CO2 sensor. In some embodiments, a pH sensor and a dissolved CO2 sensor can be used to measure the fluid flow out of the fluid vessel. In further embodiments, the carbonation device may include an atmospheric CO2 sensor for measuring concentration of CO2 in the atmosphere. The pH sensor 156 is configured to measure the pH of the fluid before it enters the fluid vessel. The fluid supply inlet 155 includes a valve configured to regulate inflow of the fluid. The valve may include a check valve to prevent backflow of the fluid from the fluid vessel back through the supply inlet. The fluid supply system 150 may also include at least one supply sensor. The supply sensor may include a volume meter for measuring the amount of fluid flowing into the fluid vessel.

[0032] The fluid supply system 150 may include at least one spray nozzle for introducing the fluid to the fluid vessel. In an alternative embodiment, the fluid supply system 150 may further include a manifold adjacent to the fluid inlet such that the fluid passes through the manifold and into the fluid vessel. The manifold may be attached to the fluid inlet. The manifold may include at least one outlet through which the fluid leaves. The manifold may include a plurality of outlets through which the fluid leaves the manifold and enters the fluid vessel. The plurality of outlets may include a plurality of spray nozzles. The spray nozzles may provide an increased fluid velocity with which the fluid enters the vessel. The fluid 115 is supplied to the fluid vessel 101 such that the flow direction of the fluid is downwards with respect of the fluid vessel as indicated by arrow 170. That is, the direction of fluid flow is towards the lower portion of the vessel. In one embodiment, the fluid provided by the fluid supply system is a liquid. The liquid may be an algae solution. The algae solution may be an alkaline algae solution. An alkaline algae solution may provide better dissociation than water. By using an alkaline solution, dissolved CO2 turns into HCO³' which is the ideal form of carbon for algae to use. Furthermore, in the form of HCO³', it is possible to prevent the release of CO2 back to the atmosphere. Additionally, utilising an alkaline algae solution enables the injection of CO2 in a precise manner so as not to kill algae.

[0033] A gas injection inlet 180 is disposed on a lower portion of the fluid vessel 101 to supply gas to the fluid vessel. In some embodiments, the gas injection inlet 180 is provided on the lower third of the fluid vessel 101. The gas injection inlet 180 may be disposed on a side of the fluid vessel 101. The gas injection inlet 180 may include a valve to regulate injection of the gas into the fluid vessel 101. The gas injection inlet 180 may be connected to a gas pipe

181 which supplies gas to the gas injection inlet. The gas pipe 181 may include a controller

182 to control the amount of gas being injected into the fluid vessel 101 at any time. The controller 182 may be in the form of a switch or valve. The controller 182 may control the gas being supplied through the gas injection inlet 180 on the basis of at least one characteristic of the fluid. The at least one characteristic of the fluid may be a pH level. In some embodiments, the controller 182 may be in communication with the at least one sensor 156, configured to obtain measurements of characteristics of the fluid 115 to then adjust the dosing of the gas accordingly.

[0034] The gas can be injected directly into the enclosed vessel 101 , meaning that there is substantially no gas loss. The gas may be dosed upon algae consumption, which increases the efficiency and ease with which the carbonation device can be scaled up. That is, where the fluid vessel is larger in volume, more gas can be injection as required.

[0035] In another embodiment, the gas supply inlet 180 may extend through the side of the fluid vessel 101 and into the fluid vessel 101 such that the gas is injected centrally with respect to the fluid vessel. In other embodiments, the gas supply inlet 180 is configured to inject gas through a diffuser.

[0036] A diffuser may be arranged within the fluid vessel 101 such that gas supplied through the gas injection inlet 180 passes at least partially through the diffuser to produce a diffused gas. The gas may be diffused into a plurality of microbubbles to define the diffused gas. In some embodiments, the gas injection inlet 180 is attached to the diffuser. In other embodiments, the gas injection inlet 180 injects gas into an intermediate pipe or an intermediate area before reaching the diffuser. The gas injection inlet 180 may inject gas in an area below the air stone 160. The diffuser may be in the form of a diffusion plate. Alternatively, the diffuser may be in the form of an air stone. The air stone may be substantially round. The air stone may be substantially spherical or disc-shaped. Alternatively, the air stone may be cylindrical in shape. In some embodiments, the air stone is the same diameter as the fluid vessel 101. The air stone may be constructed from at least one of wood, stone, fibreglass, limewood, or glass. In one embodiment, the air stone is constructed from limewood. The air stone may have a pore size of between about 3 microns and 4 microns. The air stone may be cylindrically shaped.

[0037] When the gas is injected into the vessel 101 , the gas passes through the diffuser and bubbles upwards with respect to the fluid vessel 101. The gas is supplied to the fluid vessel 101 such that the flow direction of the gas is upwards with respect of the fluid vessel as indicated by arrow 190. That is, the direction of gas flow is towards the upper portion of the vessel 101. Once injected into the fluid vessel 101 , the gas contacts the fluid in an opposite flow direction, as indicated in Figure 1 B. Shear and brush between the fluid and the gas enhances the gas dissociation. This provides significant contact time between the fluid and the gas to improve the amount of gas supplied to the fluid. The diffused gas and the fluid mix within the fluid vessel 101 produce a mixed fluid.

[0038] In one embodiment, the gas supplied through the gas injection inlet 180 is carbon dioxide (CO2). In embodiments where the fluid 115 is an algae solution, the CO2 is dissolved in the algae solution to provide a mixed fluid in the form of a carbon saturated algae solution, the diffused CO2 in the algae solution may be in three different species: CO2, HCO³' and CCh²' . The concentrations of each depending on the pH level of the algae solution. Algae can use most of CO2 and HCO^3-. The amount of CO2 provided by the gas injection inlet is controlled by the pH of the algae solution. In this way, the carbonation device 100 is able to easily control and match the specific CO2 demand required by the algae. In other embodiments, carbonation device 100 may be in communication with a carbon capture device such that the CO2 gas is supplied from atmosphere or flue gas, or from a concentrated source.

[0039] The device further includes at least one mixing element (120). The mixing element 120 is arranged within the fluid vessel and below the fluid supply system. In some embodiments, the mixing element 120 is arranged within the upper portion of the fluid vessel. Alternatively, or additionally, the mixing element 120 is arranged in a lower portion. The at least one mixing element 120 defines a gas trap 195 within the fluid vessel. As the gas is injected into the vessel and bubbles up through the diffuser, the mixing element 120 acts as an obstacle on which a concentration of the gas bubbles becomes trapped. The gas may be trapped on the surface areas of the mixing element 120. Alternatively or additionally, the gas bubbles may become trapped within crevices or gaps in the mixing element 120. In some embodiments, the mixing element 120 may be a static mixer. The static mixer may include a helical static mixer or a plate type static mixer. In other embodiments, the static mixer may include a spherical static mixer. The at least one mixing element may be attached to the inner sides of the fluid vessel. The mixing element may be rotatably mounted to the inside of the fluid vessel.

[0040] In some embodiments, there may be a plurality of mixing elements 120. The mixing elements 120 may be substantially round, or substantially spherical. The mixing elements 120 may be at least partially buoyant. When the mixing element 120 is partially buoyant, it does not need to be attached to the inside of the fluid vessel, but may sit in the upper portion of the fluid vessel by nature of its buoyancy. In other embodiments, the buoyant mixing element may be attached or partially attached to fix it in a specific area (such as in the lower portion of the fluid vessel) or within a predefined area (such as keeping it within in a range of the upper portion of the vessel). In some embodiments, a barrier is used to hold the buoyant mixing element in place, such as a grate placed within the fluid vessel that allows the fluid and gas to pass through but prevents the buoyant mixing element from rising above a predetermined height. In one embodiment, the at least one mixing element is a floatable ball. The mixing element provides static mixing of the fluid and the gas. In one embodiment, the device includes between 1 and 20 floatable balls as the mixing element 120. The floatable balls create static mixing and shear of the gas and fluid on their surfaces.

[0041] The floatable balls 120 create a large amount of surface area to trap the gas and increase the contact time between the gas and fluid to enable more shear and brush and increase gas dissociation within the fluid. The floatable balls can easily be scaled to different sized systems and controlled by increasing the number of mixing elements in the vessel.

[0042] An outlet 196 is disposed on the fluid vessel 101 to release the mixed fluid from the fluid vessel 101. In some embodiments, the outlet 196 is disposed on the base of the fluid vessel 101. In other embodiments, the outlet 196 is disposed on a side of the fluid vessel 101. The outlet 196 may be positioned below the diffuser. This enables the mixed fluid to be released from the fluid vessel 101 without substantive gas loss. The outlet 196 may include at least one valve. The at least one valve may be at least one of a backflow preventer valve, a check valve, non-turn valve, reflux valve, retention valve, foot valve or one-way valve. The outlet 196 may be connected to an outflow pipe 197 to transport the mixed fluid away from the fluid vessel. In some embodiments, the outflow pipe 197 is also connected to a secondary vessel. The secondary vessel may be an algae solution holding tank. Alternatively, the outflow pipe 197 may transport the mixed fluid to a cultivation unit 199. The cultivation unit 199 may be a photobioreactor. Alternatively, the cultivation unit may be a terraced illumination apparatus. The outflow pipe 197 may transport the mixed fluid to at least one of a plurality of cultivation trays. The cultivation trays may be illuminated surfaces.

[0043] In one embodiment, an algae solution is supplied by the fluid supply system 150 to the fluid vessel 101. Fig. 2 shows an example image 200 of an enclosed column fluid vessel of the carbonation device 100. Fig. 3 shows an example image 300 of a lower portion of the fluid vessel of Fig. 2 showing a gas injection inlet 380 and a mixing element 320 (corresponding to 180 and 120 respectively). The fluid vessel 101 is a cylindrical column 205, as shown in the example of Fig. 2. The algae solution 115 is pumped from a separate tank through the fluid supply inlet 155 provided on the top of the fluid vessel 101 . The algae solution flow downwards towards a lower portion of the fluid vessel. At the same time, CO2 is injected into the fluid vessel through the gas injection inlet at the lower portion of the column, for example the gas injection inlet 380 as shown in Fig. 3. The CO2 gas is provided to the column on the basis of measurements obtained by a pH sensor (e.g., 156) positioned on a supply pipe (e.g., 157) that feeds into the fluid supply inlet. The pH sensor determines the pH level of the algae solution, and a controller (182) then controls the amount of CO2 dosing required for the algae solution having a particular pH level. In some embodiments, the pH of the algae solution is maintained above 8.5 to minimize dissolved CO2 level.

[0044] The CO2 gas passes through the diffuser as it enters the fluid vessel 101. The diffuser may be in the form of an air stone which is the same diameter as the cylindrical column, ensuring that the gas must pass through the diffuser. The air stone is positioned proximate the gas injection inlet such that the CO2 gas is diffused into microbubbles as it hits the fluid flow. The CO2 gas bubbles move upwards with a flow direction towards the upper portion of the column 105. The algae solution 115 flow direction is opposite to the gas flow direction. As the gas bubbles move upwards, the gas bubbles hit the mixing element 120. In this embodiment, the mixing elements are in the form of 20 floatable balls, disposed within the fluid vessel. Given their buoyancy, they sit at the top of the fluid vessel just in front of the fluid supply inlet. However, there is also one floatable ball provided just above the diffuser such that the CO2 hits this almost immediately when entering the column. The floatable balls provide a large surface area for bubbles to be trapped, and the plurality of floatable balls therefor defines a gas trap. Fig. 4 shows a graph 400 of CO2 level in the atmosphere (405) over time (407). The graph 400 shows CO2 level in the atmosphere with (410) and without (415) use of an embodiment of the carbonation device 100. As shown in Fig. 4, substantially no CO2 is lost to the atmosphere when using the device 100. In contrast, the graph 400 also reveals the comparative CO2 gas loss when injected CO2 gas directly into an algae solution. Fig. 4 shows that the carbonation device 100 is very effective at reducing and/or eliminating gas loss to the environment.

[0045] As the fluid moves past the gas trapped on the surface of the floatable balls, enhanced shear and brush occurs to mix the CC^ and the algae solution, and disperse the CO2 into the algae solution. This then provides a saturated CO2 algae solution. The saturated CO2 algae solution flows out the outlet positioned at the bottom of the column. The saturated CO2 algae solution can then be provided, e.g., to a photobioreactor. Specifically, the carbonated algae solution can be provided to a plurality of terraced trays or illuminated surfaces to cultivate algae.

[0046] The carbonation advice provides a number of distinct advantages over existing systems. Inline CO2 dosing directly into the algae solution is used over a separated CO2 aqueous solution to minimize gas lost to the environment. An alkaline algae solution is used for better dissociation over using water. Additionally, the use of spherical mixing elements to provide a static mixing provides an improved surface area for increasing contact time and providing a gas trap to enable mixing of the gas and fluid, which is advantageous over static mixing with circulation and an inclined plate.

[0047] The carbonation device may be integrated with existing algae cultivation systems to replace existing methods of CO2 saturation, such that the algae solution of the existing systems is passed through the enclosed column of the carbonation device and dispersed with the CO2 gas in order to enhance the CO2 saturation. Alternatively or additionally, the carbonation device may also be used with a modular photobioreactor or algae cultivation system, including a terraced illumination apparatus.

[0048] Although the invention has been described with reference to specific examples it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Claims

CLAIMS:

1. A carbonation device, including: a fluid vessel; a fluid supply system disposed on an upper portion of the fluid vessel to supply fluid to the fluid vessel; a gas injection inlet disposed on a lower portion of the fluid vessel to supply gas to the fluid vessel; at least one mixing element arranged within the fluid vessel and below the fluid supply system; a diffuser arranged within the fluid vessel such that gas supplied through the gas injection inlet passes at least partially through the diffuser to produce a diffused gas, wherein the diffused gas and the fluid mix within the fluid vessel to produce a mixed fluid; and an outlet disposed on the fluid vessel to release the mixed fluid.

2. The carbonation device of claim 1 wherein the outlet is disposed on the fluid vessel and below the diffuser.

3. The carbonation device of claim 1 or claim 2 wherein the fluid vessel is enclosed.

4. The carbonation device of any one of the preceding claims wherein the gas is carbon dioxide (CO2), and supply of the CO2 results in at least partial carbonation of the fluid.

5. The carbonation device of any one of the preceding claims wherein the supply of gas provides at least partial gas dissociation in the fluid.

6. The carbonation device of any one of the preceding claims wherein the supply of gas provides substantially 100% gas dissociation in the fluid.

7. The carbonation device of any one of the preceding claims wherein the direction of gas flow is opposite to the direction of fluid flow.

8. The carbonation device of any one of the preceding claims wherein the fluid vessel is column-shaped.

9. The carbonation device of any one of the preceding claims wherein the fluid vessel is substantially cylindrical.

10. The carbonation device of any one of the preceding claims wherein the at least one mixing element defines a gas trap.

11 . The carbonation device of any one of the preceding claims wherein the at least one mixing element provides static mixing of the fluid and the gas.

12. The carbonation device of any one of the preceding claims wherein the at least one mixing element is a static mixer.

13. The carbonation device of any one of the preceding claims comprising a plurality of mixing elements.

14. The carbonation device of any one of the preceding claims wherein the at least one mixing element is substantially round.

15. The carbonation device of any one of the preceding claims wherein the at least one mixing element is substantially spherical.

16. The carbonation device of any one of the preceding claims wherein the at least one mixing element is at least partially buoyant.

17. The carbonation device of any one of the preceding claims wherein the at least one mixing element is a floatable ball.

18. The carbonation device of any one of the preceding claims wherein at least one mixing element is fixedly attached to the fluid vessel.

19. The carbonation device of any one of the preceding claims wherein the diffuser is an air stone.

20. The carbonation device of any one of the preceding claims wherein the fluid supply system includes a fluid supply inlet through which fluid is supplied to the fluid vessel.

21. The carbonation device of claim 20 wherein the fluid supply inlet includes a valve configured to regulate inflow of the fluid.

22. The carbonation device of claim 21 wherein the fluid supply system further includes a manifold disposed adjacent the fluid inlet such that the fluid passes through the manifold and into the fluid vessel.

23. The carbonation device of claim 22 wherein the manifold includes a plurality of outlets through which the fluid leaves the manifold and enters the fluid vessel.

24. The carbonation device of claim 23 wherein the plurality of outlets are a plurality of spray nozzles.

25. The carbonation device of any one of the preceding claims, further including a controller to control the gas being supplied through the gas injection inlet.

26. The carbonation device of any one of the preceding claims wherein the gas supplied through the gas injection inlet is controlled on the basis of at least one characteristic of the fluid.

27. The carbonation device of claim 26, wherein the at least one characteristic of the fluid is pH.

28. The carbonation device of any one of the preceding claims wherein the fluid comprises algae.

29. The carbonation device of claim 28 wherein the fluid is alkaline.

30. The carbonation device of any one of the preceding claims wherein the outlet is configured to allow the mixed fluid to exit the fluid vessel.

31 . The carbonation device of any one of the preceding claims wherein the outlet includes a pipe to transport the mixed fluid from the fluid vessel to a terraced illumination apparatus.

32. The carbonation device of claim 31 wherein the mixed fluid is transported to a secondary vessel in a terraced illumination apparatus.

33. The carbonation device of claim 32, wherein the secondary vessel is a holding tank.