Carbon dioxide conversion device

Abstract

To provide a carbon dioxide conversion device that can improve the utilization rate of carbon dioxide. [Solution] The carbon dioxide conversion device according to the embodiment is an electrolytic unit that produces carbon monoxide by electrolyzing carbon dioxide, and includes an electrolytic unit that discharges an electrolytic unit discharge fluid containing oxygen and carbon dioxide, and a recovery unit that recovers carbon dioxide from the electrolytic unit discharge fluid. The recovery unit includes an oxygen separator, a first recovery separator, and an electrolytic unit return channel. The oxygen separator removes oxygen from the electrolytic unit discharge fluid and discharges a first recovery fluid containing carbon dioxide and water. The first recovery separator separates and removes water from the first recovery fluid and discharges a second recovery fluid containing carbon dioxide. The electrolytic unit return channel supplies the second recovery fluid to the electrolytic unit.

Description

[Technical Field]

[0001] This embodiment relates to a carbon dioxide conversion device. [Background technology]

[0002] As global warming progresses, there is a growing need to reduce the use of natural gas, coal, and oil, which produce carbon dioxide (CO2). Furthermore, the development of chemical synthesis using carbon dioxide as a raw material is progressing. As part of this effort, carbon dioxide conversion devices are known that electrolyze carbon dioxide to produce gas containing carbon monoxide (CO). In these devices, the same amount of carbon dioxide as the carbon compounds produced, such as carbon monoxide, moves to the anode and is released along with oxygen. As a result, the effective utilization rate of the carbon dioxide supplied to the device is low, at less than 50%. In conventionally considered carbon dioxide conversion devices, the same amount of carbon dioxide as the amount of carbon monoxide produced is released along with oxygen. As a result, the conversion rate from supplied carbon dioxide to carbon monoxide is low, leading to a low utilization rate of carbon dioxide. Therefore, there is a need for carbon dioxide conversion devices with a high utilization rate of carbon dioxide. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] JA Rabinowiz, MW Kanan, The future of low-temperature carbon dioxide electrolysis depends on solving one basic problem, Nature Communications, 11, Article number:5231(2020)<https: / / doi.org / 10.1038 / s41467-020-19135-8> [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] An embodiment aims to provide a carbon dioxide conversion device capable of improving the utilization rate of carbon dioxide.

Means for Solving the Problems

[0005] The carbon dioxide conversion device according to the embodiment includes an electrolysis unit that electrolyzes carbon dioxide to generate carbon monoxide, and an electrolysis unit that discharges an electrolysis unit discharge fluid containing oxygen and carbon dioxide, and a recovery unit that recovers carbon dioxide from the electrolysis unit discharge fluid. The recovery unit includes an oxygen separator that electrolyzes the electrolysis unit discharge fluid using water to remove oxygen from the electrolysis unit discharge fluid and discharges a first recovery fluid containing carbon dioxide and water, a first recovery separator that separates and removes water from the first recovery fluid and discharges a second recovery fluid containing carbon dioxide, and an electrolysis unit return flow path that supplies the second recovery fluid to the electrolysis unit.

Effects of the Invention

[0006] According to the embodiment, the utilization rate of carbon dioxide can be improved.

Brief Description of the Drawings

[0007] [Figure 1] FIG. 1 is a diagram showing a carbon dioxide conversion device according to the present embodiment. [[ID=!24]] [[ID=!25]] [Figure 2] [[ID=!26]]FIG. 2 is a cross-sectional view showing an electrolytic cell stack of the carbon dioxide conversion device shown in FIG. 1. [[ID=!27]] [[ID=!28]] [Figure 3] [[ID=!29]]FIG. 3 is a diagram showing the configuration of the recovery unit shown in FIG. 1. [[ID=!30]] [[ID=!31]] [Figure 4] [[ID=!32]]FIG. 4 is a cross-sectional view showing an electrolytic cell stack of the oxygen separator shown in FIG. 3. [[ID=!33]] [[ID=!34]] [[ID=!35]]

Modes for Carrying Out the Invention

[0008] [[ID=!39]] [[ID=!40]]Hereinafter, the embodiment will be described with reference to the drawings. [[ID=!41]] [[ID=!42]]

[0009] [[ID=!43]] The carbon dioxide conversion device according to the present embodiment will be described with reference to FIGS. 1 to 4. As shown in FIG. 1, the carbon dioxide conversion device 1 includes an electrolysis unit 10 and a recovery unit 40.

[0010] The electrolysis unit 10 is configured to electrolyze carbon dioxide to generate carbon monoxide. The electrolysis unit 10 is configured to discharge a first anode discharge fluid AF11 containing oxygen and carbon dioxide and a first cathode discharge fluid CF11 containing carbon dioxide and carbon monoxide.

[0011] More specifically, the electrolysis unit 10 includes an electrolysis cell stack 11, a first gas-liquid separator 12, a first cooler 13, a second gas-liquid separator 14, a second cooler 15, a storage tank 16, a pump 17, a third cooler 18, a third gas-liquid separator 19, and a pressure reducing valve 20.

[0012] The electrolysis cell stack 11 is configured to perform an electrolysis reaction. As shown in FIG. 2, the electrolysis cell stack 11 includes a plurality of anodes 11a, a plurality of cathodes 11b, a plurality of diaphragms 11c, and a plurality of flow path plates 11d. The anodes 11a, cathodes 11b, and diaphragms 11c are stacked in the stacking direction to form a carbon dioxide electrolysis cell 11e. The electrolysis cell stack 11 is composed of a plurality of carbon dioxide electrolysis cells 11e. The number of carbon dioxide electrolysis cells 11e constituting the electrolysis cell stack 11 is arbitrary. A flow path plate 11d is interposed between two adjacent carbon dioxide electrolysis cells 11e.

[0013] The electrolysis cell stack 11 includes current collectors (not shown) located at both ends in the stacking direction of the carbon dioxide electrolysis cells 11e. The current collectors are connected to a power source (not shown). By applying a voltage to the current collectors, an electrolysis reaction is performed. The plurality of carbon dioxide electrolysis cells 11e may be arranged between supports (not shown). The electrolysis unit 10 may include a plurality of electrolysis cell stacks 11.

[0014] The anode 11a is connected to the current collector described above and functions as an electrode. The anode 11a includes a conductive substrate made of metal or the like, and a catalyst that promotes the electrolytic reaction. The catalyst is supported on the surface of the conductive substrate and may constitute a catalyst layer formed on the surface of the conductive substrate.

[0015] The cathode 11b is connected to the current collector described above and functions as an electrode. The cathode 11b includes a conductive substrate made of metal or the like, and a catalyst that promotes the electrolytic reaction. The catalyst is supported on the surface of the conductive substrate and may constitute a catalyst layer formed on the surface of the conductive substrate.

[0016] The diaphragm 11c is interposed between the anode 11a and the cathode 11b. The diaphragm 11c may be in contact with both the anode 11a and the cathode 11b. The diaphragm 11c may contain, for example, hydrogen ions (H + ), hydroxide ion (OH - ), carbonate ions (CO3 2- ), bicarbonate ions (HCO3) - The diaphragm 11c is configured to allow the flow of ions such as ions.

[0017] The channel plate 11d is positioned to separate two adjacent carbon dioxide electrolytic cells 11e. The channel plate 11d includes an anode channel 11f and a cathode channel 11g. The anode channel 11f is formed on the surface of the channel plate 11d facing the anode 11a. The cathode channel 11g is formed on the surface of the channel plate 11d facing the cathode 11b. The anode channel 11f and the cathode channel 11g are isolated in the stacking direction.

[0018] The channel plate 11d may be formed using a conductive material such as metal, carbon material, or ceramic. The anode channel 11f and cathode channel 11g may be formed in a serpentine shape or a strip shape when viewed in the stacking direction, and this is arbitrary.

[0019] As shown in FIG. 1, an anode supply channel 21 is connected to the inlet of the anode 11a, and the anode supply fluid AF10 is supplied to the anode channel 11f. A storage tank 16 (described later) for storing the anode supply fluid AF10 may be connected to the anode supply channel 21.

[0020] The anode supply fluid AF10 contains, for example, an electrolytic solution. For the electrolytic solution, a solution using water (H2O) or an aqueous solution containing any electrolyte is used. Examples of the aqueous solution containing an electrolyte include an aqueous solution containing phosphate ions (PO4 2- ), borate ions (BO3 3- ), sodium ions (Na + ), potassium ions (K + ), calcium ions (Ca 2+ ), lithium ions (Li + ), cesium ions (Cs + ), magnesium ions (Mg 2+ ), chloride ions (Cl - ), hydrogen carbonate ions (HCO3 - ), carbonate ions (CO3 2- ), hydroxide ions (OH - ), etc. Examples of the electrolytic solution include an alkaline aqueous solution in which a compound such as potassium hydroxide (KOH), potassium hydrogen carbonate (KHCO3), or potassium carbonate (K2CO3) is dissolved.

[0021] As shown in Figure 1, a cathode supply channel 22 is connected to the inlet of cathode 11b, and cathode supply fluid CF10 is supplied to it. A carbon dioxide supply source S that supplies the cathode supply fluid CF10 may be connected to the cathode supply channel 22. The carbon dioxide supply source S may be configured to supply cathode supply fluid CF10 containing gaseous carbon dioxide to cathode channel 11g, for example. The carbon dioxide supply source S may be, for example, a carbon dioxide separation and recovery device (not shown). The carbon dioxide separation and recovery device may be configured to separate and recover carbon dioxide gas from exhaust gas (carbon dioxide-containing gas) that contains carbon dioxide gas emitted from facilities such as thermal power plants, waste incinerators, and steel mills. Alternatively, the carbon dioxide supply source S may have a configuration that employs methods such as a chemical absorption method using a chemical absorbent such as an amine aqueous solution, a physical absorption method using a physical absorbent such as methanol or polyethylene glycol solution, a solid absorption method using a solid absorbent such as an amine compound, a membrane separation method using a carbon dioxide separation membrane, a physical adsorption method using inorganic materials such as zeolites as adsorbents, pressure swing adsorption (PSA) method, or thermal swing adsorption (TSA) method. For example, a chemical absorption method and apparatus using an amine aqueous solution can absorb carbon dioxide by supplying exhaust gas to an absorption tower through which the amine aqueous solution is sprayed or flowed, and then recover the carbon dioxide released from the amine aqueous solution by heating the amine aqueous solution that has absorbed carbon dioxide in a regeneration tower. Various methods and apparatus capable of recovering carbon dioxide from exhaust gas (carbon dioxide-containing gas) can be applied to the carbon dioxide supply source S. The carbon dioxide conversion device 1 may have a humidifier for humidifying the carbon dioxide gas from the carbon dioxide supply source S. In this case, the carbon dioxide gas humidified by the humidifier may be supplied to the electrolytic cell stack 11 as a cathode supply fluid CF10.

[0022] At anode 11a, for example, as shown in equations (1) to (3) below, the carbonate ions and bicarbonate ions generated at cathode 11b, which will be described later, can be oxidized to produce oxygen and carbon dioxide. CO32- +H2O→CO2+2OH - (1) HCO3 - →CO2+OH - (2) 2OH - → 0.5O2 + H2O + 2e - (3)

[0023] The oxygen and carbon dioxide generated at anode 11a are discharged together with the electrolyte from the outlet of anode 11a. A first anode discharge channel 23 is connected to the outlet of anode 11a, and the first anode discharge fluid AF11 is discharged into the first anode discharge channel 23. The first anode discharge fluid AF11 contains oxygen, carbon dioxide, and electrolyte, and is a gas-liquid two-phase fluid.

[0024] At cathode 11b, for example, carbon dioxide can be reduced to produce carbon compounds such as carbon monoxide, as shown in equations (4) to (7) below. CO2 + H2O + 2e - →CO+2OH - (4) 2H2O + 2e - →H2+2OH - (5) CO2 + 2OH - →CO3 2- +H2O (6) CO2 + OH - →HCO3 - (7)

[0025] Carbon monoxide and unreacted carbon dioxide produced at cathode 11b are discharged from the outlet of cathode 11b. A first cathode discharge channel 28 is connected to the outlet of cathode 11b, and the first cathode discharge fluid CF11 is discharged from cathode channel 11g. The first cathode discharge fluid CF11 contains carbon monoxide and carbon dioxide. The first cathode discharge fluid CF11 also contains hydrogen and water vapor produced at cathode 11b.

[0026] As shown in Figure 1, the first gas-liquid separator 12 is connected to the outlet of the anode 11a of the electrolytic cell stack 11 via the first anode discharge channel 23. The first gas-liquid separator 12 is configured to separate the gas-liquid two-phase fluid constituting the first anode discharge fluid AF11 into a gas phase and a liquid phase. In this embodiment, the first gas-liquid separator 12 separates the first anode discharge fluid AF11 into a second anode discharge fluid AF12 and a third anode discharge fluid AF13. The second anode discharge fluid AF12 contains a gas containing oxygen and carbon dioxide. The second anode discharge fluid AF12 also contains water vapor generated at the anode 11a. The third anode discharge fluid AF13 contains the electrolyte.

[0027] A second anode discharge channel 24 is connected to the first gas-liquid separator 12, and the second anode discharge fluid AF12 is discharged from the first gas-liquid separator 12 into the second anode discharge channel 24. In addition, a third anode discharge channel 25 is connected to the first gas-liquid separator 12, and the third anode discharge fluid AF13 is discharged from the first gas-liquid separator 12 into the third anode discharge channel 25.

[0028] The first cooler 13 is located in the second anode discharge channel 24. The first cooler 13 cools the second anode discharge fluid AF12, and the water vapor contained in the second anode discharge fluid AF12 condenses into water. The second anode discharge fluid AF12 cooled by the first cooler 13 is discharged from the first cooler 13.

[0029] The second gas-liquid separator 14 is connected to the first gas-liquid separator 12 via the second anode discharge channel 24. The second gas-liquid separator 14 is supplied with the second anode discharge fluid AF12, which has been cooled by the first cooler 13. The second gas-liquid separator 14 is configured to separate the second anode discharge fluid AF12 into a gas phase and a liquid phase. In this embodiment, the second gas-liquid separator 14 separates the second anode discharge fluid AF12 into a fourth anode discharge fluid AF14 (electrolytic unit discharge fluid) and a fifth anode discharge fluid AF15. The fourth anode discharge fluid AF14 contains a gas containing oxygen and carbon dioxide. The fifth anode discharge fluid AF15 contains water condensed by the first cooler 13.

[0030] A fourth anode discharge channel 26 is connected to the second gas-liquid separator 14, and the fourth anode discharge fluid AF14 is discharged from the second gas-liquid separator 14 into the fourth anode discharge channel 26. In addition, a fifth anode discharge channel 27 is connected to the second gas-liquid separator 14, and the fifth anode discharge fluid AF15 is discharged from the second gas-liquid separator 14 into the fifth anode discharge channel 27.

[0031] The second cooler 15 is located in the third anode discharge channel 25. The second cooler 15 cools the third anode discharge fluid AF13. This lowers the temperature of the third anode discharge fluid AF13, which had risen due to heating at the anode 11a. The third anode discharge fluid AF13, cooled by the second cooler 15, is discharged from the second cooler 15.

[0032] The storage tank 16 is connected to the first gas-liquid separator 12 via the third anode discharge channel 25. The third anode discharge fluid AF13, cooled by the second cooler 15, is supplied to the storage tank 16. The storage tank 16 is configured to store the third anode discharge fluid AF13. The fifth anode discharge channel 27 described above is connected to the storage tank 16, and the fifth anode discharge fluid AF15 is supplied to it. The fifth anode discharge fluid AF15 is mixed with the third anode discharge fluid AF13 and stored in the storage tank 16 as anode supply fluid AF10. The third cathode discharge channel 30, described later, is connected to the storage tank 16, and the third cathode discharge fluid CF13 is supplied to it. The third cathode discharge fluid CF13 is mixed with the third anode discharge fluid AF13 and stored in the storage tank 16 as anode supply fluid AF10. The third anode discharge fluid AF13 contains electrolyte, while the fifth anode discharge fluid AF15 and the third cathode discharge fluid CF13 each contain water. As a result, the storage tank 16 stores electrolyte as the anode supply fluid AF10.

[0033] An anode supply channel 21 is connected to the storage tank 16. The storage tank 16 is connected to the inlet of the anode 11a of the electrolytic cell stack 11 via the anode supply channel 21.

[0034] Pump 17 is located in the anode supply channel 21. Pump 17 supplies the anode supply fluid AF10 stored in the storage tank 16 to the inlet of the anode 11a of the electrolytic cell stack 11. In this way, the electrolyte of the anode supply fluid AF10 is configured to circulate.

[0035] As shown in Figure 1, the third cooler 18 is located in the first cathode discharge channel 28. The third cooler 18 cools the first cathode discharge fluid CF11, and the water vapor contained in the first cathode discharge fluid CF11 condenses into water. The first cathode discharge fluid CF11, cooled by the third cooler 18, is discharged from the third cooler 18.

[0036] The third gas-liquid separator 19 is connected to the outlet of the cathode 11b via the first cathode discharge channel 28. The third gas-liquid separator 19 is supplied with the first cathode discharge fluid CF11, which has been cooled by the third cooler 18. The third gas-liquid separator 19 is configured to separate the first cathode discharge fluid CF11 into a gas phase and a liquid phase. In this embodiment, the third gas-liquid separator 19 separates the first cathode discharge fluid CF11 into a second cathode discharge fluid CF12 and a third cathode discharge fluid CF13. The second cathode discharge fluid CF12 contains a gas containing carbon monoxide and carbon dioxide. The third cathode discharge fluid CF13 contains water condensed by the third cooler 18.

[0037] A second cathode discharge channel 29 is connected to the third gas-liquid separator 19, and the second cathode discharge fluid CF12 is discharged from the third gas-liquid separator 19 into the second cathode discharge channel 29. A synthesis apparatus (not shown) for synthesizing compounds using carbon monoxide as a raw material may be connected to the second cathode discharge channel 29. In addition, a third cathode discharge channel 30 is connected to the third gas-liquid separator 19, and the third cathode discharge fluid CF13 is discharged from the third gas-liquid separator 19 into the third cathode discharge channel 30. The storage tank 16 described above is connected to the third cathode discharge channel 30, and the third cathode discharge fluid CF13 is supplied to the storage tank 16.

[0038] The pressure reducing valve 20 is located in the third cathode discharge passage 30. The pressure reducing valve 20 is configured to adjust the pressure of the third cathode discharge fluid CF13 supplied from the third gas-liquid separator 19 to the storage tank 16. The pressure reducing valve 20 can suppress the backflow of the third cathode discharge fluid CF13 from the storage tank 16 to the third gas-liquid separator 19.

[0039] As shown in Figure 1, the recovery unit 40 is configured to recover carbon dioxide from the fourth anode discharge fluid AF14 (electrolysis unit discharge fluid). The recovery unit 40 is connected to the fourth anode discharge channel 26 described above, and the fourth anode discharge fluid AF14 discharged from the second gas-liquid separator 14 of the electrolysis unit 10 is supplied to it.

[0040] As shown in Figure 3, the recovery unit 40 includes an oxygen separator 41, a first recovery cooler 42, a first recovery separator 43, a second recovery cooler 44, and a second recovery separator 45.

[0041] The oxygen separator 41 is configured to remove oxygen from the fourth anode discharge fluid AF14 by electrolyzing the fourth anode discharge fluid AF14 with water, and to discharge a first cathode discharge fluid CF21 (first recovered fluid) containing carbon dioxide and water. The oxygen separator 41 may also include an electrolytic cell stack 46. The electrolytic cell stack 46 is configured to carry out an electrolytic reaction. As shown in Figure 4, the electrolytic cell stack 46 includes a plurality of anodes 46a, a plurality of cathodes 46b, a plurality of diaphragms 46c, and a plurality of flow channel plates 46d. The anodes 46a, cathodes 46b, and diaphragms 46c are stacked in the stacking direction to form a cell 46e. The electrolytic cell stack 46 is composed of a plurality of cells 46e. The number of cells 46e constituting the electrolytic cell stack 46 is arbitrary. A flow channel plate 46d is interposed between two adjacent cells 46e.

[0042] The electrolytic cell stack 46 includes current collectors (not shown) located at both ends in the stacking direction of the cells 46e. The current collectors are connected to a power supply (not shown). By applying a voltage to the current collectors, an electrolytic reaction is carried out. Multiple cells 46e may be arranged between supports (not shown). The recovery unit 40 may include multiple electrolytic cell stacks 46.

[0043] The anode 46a is connected to the current collector described above and functions as an electrode. The anode 46a includes a conductive substrate made of metal or the like, and a catalyst that promotes the electrolytic reaction. The catalyst is supported on the surface of the conductive substrate and may constitute a catalyst layer formed on the surface of the conductive substrate.

[0044] A general-purpose water electrolysis anode may be used for anode 46a. Examples of water electrolysis anodes include iridium oxide-coated titanium, iridium ruthenium cobalt oxide, iridium ruthenium tin oxide, iridium ruthenium iron oxide, iridium ruthenium nickel oxide, iridium tin oxide, iridium zirconium oxide, ruthenium titanium oxide, ruthenium zirconium oxide, ruthenium tantalum oxide, ruthenium titanium cerium oxide, and nickel nanowire carbon nitride containing nickel sulfide.

[0045] The cathode 46b is connected to the current collector described above and functions as an electrode. The cathode 46b includes a conductive substrate made of metal or the like, and a catalyst that promotes the electrolytic reaction. The catalyst is supported on the surface of the conductive substrate and may constitute a catalyst layer formed on the surface of the conductive substrate.

[0046] For cathode 46b, iridium oxide-coated titanium, iridium ruthenium cobalt oxide, iridium ruthenium tin oxide, iridium ruthenium iron oxide, iridium ruthenium nickel oxide, iridium tin oxide, iridium zirconium oxide, ruthenium titanium oxide, ruthenium zirconium oxide, ruthenium tantalum oxide, ruthenium titanium cerium oxide, carbon nitride-containing nickel sulfide nanowire, nickel platinum-coated titanium, platinum-supported carbon, palladium-supported carbon, cobalt glyoxime, and nickel glyoxime may be used.

[0047] The diaphragm 46c is interposed between the anode 46a and the cathode 46b. The diaphragm 46c may be in contact with both the anode 46a and the cathode 46b. For example, when water is supplied to the anode 46a, the diaphragm 46c may be formed of a proton conductive film. As the proton conductive film, for example, a perfluorosulfone polymer film such as Nafion or a sulfonated polystyrene film such as Celemion may be used. When an aqueous sulfuric acid solution is supplied to the anode 46a, the diaphragm 46c may be formed of a nonconductive porous film.

[0048] The channel plate 46d is positioned to separate two adjacent cells 46e. The channel plate 46d includes an anode channel 46f and a cathode channel 46g. The anode channel 46f is formed on the surface of the channel plate 46d facing the anode 46a. The cathode channel 46g is formed on the surface of the channel plate 46d facing the cathode 46b. The anode channel 46f and the cathode channel 46g are isolated in the stacking direction.

[0049] The channel plate 46d may be formed using a conductive material such as metal, carbon material, or ceramic. The anode channel 46f and cathode channel 46g may be formed in a serpentine shape or a strip shape when viewed in the stacking direction, and this is arbitrary.

[0050] As shown in Figure 3, an anode supply channel 47 is connected to the inlet of the anode 46a, and anode supply fluid AF20 is supplied to it. The anode supply channel 47 may also be connected to a first return channel 50 and a second return channel 53, which will be described later. The anode supply channel 47 may also be connected to a supply source (not shown) that supplies the anode supply fluid AF20. However, if the supply amount from the first return channel 50 and the second return channel 53 can be secured, the supply source does not need to be connected. The anode supply fluid AF20 contains water.

[0051] The inlet of cathode 46b is connected to the fourth anode discharge channel 26 described above, and the fourth anode discharge fluid AF14 is supplied to it. As described above, the fourth anode discharge fluid AF14 contains a gas containing oxygen and carbon dioxide.

[0052] At anode 46a, for example, as shown in equation (8) below, water supplied as the anode supply fluid AF20 can be electrolyzed to produce hydrogen ions and oxygen ions. The hydrogen ions produced at anode 46a move through the diaphragm 46c to cathode 46b.

[0053] At cathode 46b, for example, as shown in equation (9) below, the oxygen supplied as the fourth anode discharge fluid AF14 is reduced to water by hydrogen ions that have moved from anode 46a. 2H2O → 4H + +O2+2e - (8) 4H + +O2+2e - →2H2O (9)

[0054] When viewed as cell 46e, the oxygen contained in the fourth anode discharge fluid AF14 supplied to cathode 46b moves to anode 46a.

[0055] The water produced in cathode 46b is discharged from the outlet of cathode 46b along with carbon dioxide. A cathode discharge channel 48 is connected to the outlet of cathode 46b, and the first cathode discharge fluid CF21 (first recovered fluid) is discharged from the outlet of cathode 46b. The first cathode discharge fluid CF21 contains water and carbon dioxide and is a gas-liquid two-phase fluid. The first cathode discharge fluid CF21 also contains water vapor.

[0056] As shown in Figure 3, the first recovery cooler 42 is located in the cathode discharge channel 48. The first recovery cooler 42 cools the first cathode discharge fluid CF21, and the water vapor contained in the first cathode discharge fluid CF21 condenses into water. The first cathode discharge fluid CF21 cooled by the first recovery cooler 42 is discharged from the first recovery cooler 42. The first recovery cooler 42 may be formed separately from the first recovery separator 43, or it may be formed integrally with the first recovery separator 43.

[0057] The first recovery separator 43 is connected to the outlet of the cathode 46b of the electrolytic cell stack 46 via a cathode discharge channel 48. The first recovery separator 43 is supplied with the first cathode discharge fluid CF21 cooled by the first recovery cooler 42. The first recovery separator 43 is configured to separate and remove water from the first cathode discharge fluid CF21. In this embodiment, the first recovery separator 43 separates the first cathode discharge fluid CF21 into a second cathode discharge fluid CF22 (second recovery fluid) and a third cathode discharge fluid CF23 (third recovery fluid). The second cathode discharge fluid CF22 contains a gas containing carbon dioxide. The third cathode discharge fluid CF23 contains water.

[0058] An electrolytic return channel 49 is connected to the first recovery separator 43, and the second cathode discharge fluid CF22 is discharged from the first recovery separator 43 into the electrolytic return channel 49. The cathode supply channel 22 described above is connected to the electrolytic return channel 49, and the second cathode discharge fluid CF22 discharged into the electrolytic return channel 49 is supplied as cathode supply fluid CF10 to the inlet of the cathode 11b of the electrolytic cell stack 11.

[0059] Furthermore, a first return channel 50 is connected to the first recovery separator 43, and the third cathode discharge fluid CF23 is discharged from the first recovery separator 43 into the first return channel 50. The anode supply channel 47 described above is connected to the first return channel 50, and the third cathode discharge fluid CF23 discharged into the first return channel 50 is supplied as anode supply fluid AF20 to the inlet of the anode 46a of the electrolytic cell stack 46.

[0060] As shown in Figure 3, the oxygen produced at anode 46a is discharged along with water from the outlet of anode 46a. A first anode discharge channel 51 is connected to the outlet of anode 46a, and the first anode discharge fluid AF21 (fourth recovered fluid) is discharged from anode 46a. The first anode discharge fluid AF21 contains oxygen and water and is a gas-liquid two-phase fluid. The first anode discharge fluid AF21 also contains water vapor.

[0061] The second recovery cooler 44 is located in the first anode discharge channel 51. The second recovery cooler 44 cools the first anode discharge fluid AF21, and the water vapor contained in the first anode discharge fluid AF21 condenses into water. The first anode discharge fluid AF21 cooled by the second recovery cooler 44 is discharged from the second recovery cooler 44. The second recovery cooler 44 may be formed separately from the second recovery separator 45, or it may be formed integrally with the second recovery separator 45.

[0062] The second recovery separator 45 is connected to the outlet of the anode 46a of the electrolytic cell stack 46 via the first anode discharge channel 51. The second recovery separator 45 is supplied with the first anode discharge fluid AF21 cooled by the second recovery cooler 44. The second recovery separator 45 is configured to separate and remove water from the first anode discharge fluid AF21. In this embodiment, the second recovery separator 45 separates the first anode discharge fluid AF21 into a second anode discharge fluid AF22 (fifth recovery fluid) and a third anode discharge fluid AF23 (sixth recovery fluid). The second anode discharge fluid AF22 contains an oxygen-containing gas. The third anode discharge fluid AF23 contains water.

[0063] A second anode discharge channel 52 is connected to the second recovery separator 45, and the second anode discharge fluid AF22 is discharged from the second recovery separator 45 into the second anode discharge channel 52. A storage unit (not shown) for storing the second anode discharge fluid AF22 may be connected to the second anode discharge channel 52.

[0064] Furthermore, a second return channel 53 is connected to the second recovery separator 45, and the third anode discharge fluid AF23 is discharged from the second recovery separator 45 into the second return channel 53. The anode supply channel 47 described above is connected to the second return channel 53, and the third anode discharge fluid AF23 discharged into the second return channel 53 is supplied as anode supply fluid AF20 to the inlet of the anode 46a of the electrolytic cell stack 46.

[0065] As described above, according to this embodiment, the oxygen separator 41 of the recovery unit 40 uses water to electrolyze the fourth anode discharge fluid AF14 discharged from the electrolytic unit 10 to remove oxygen from the fourth anode discharge fluid AF14 and discharge the first cathode discharge fluid CF21 containing carbon dioxide and water. The first recovery separator 43 separates and removes water from the first cathode discharge fluid CF21 and discharges the second cathode discharge fluid CF22 containing carbon dioxide. The first return channel 50 supplies the second cathode discharge fluid CF22 to the electrolytic unit 10. This makes it possible to supply carbon dioxide contained in the fourth anode discharge fluid AF14 discharged from the electrolytic unit 10 to the electrolytic unit 10. Therefore, the utilization rate of carbon dioxide can be increased. In addition, oxygen contained in the fourth anode discharge fluid AF14 can be removed, and the concentration of carbon dioxide contained in the second cathode discharge fluid CF22 supplied to the electrolytic unit 10 can be increased. This makes it possible to supply carbon dioxide to the electrolytic unit 10 at a high concentration.

[0066] Furthermore, according to this embodiment, the recovery unit 40 includes a first recovery cooler 42 for cooling the first cathode discharge fluid CF21. The first cathode discharge fluid CF21, cooled by the first recovery cooler 42, is supplied to the first recovery separator 43. This allows the water vapor contained in the first cathode discharge fluid CF21 to be condensed, and the first recovery separator 43 can effectively remove water from the first cathode discharge fluid CF21.

[0067] Furthermore, according to this embodiment, the oxygen separator 41 includes an electrolytic cell stack 46, the electrolytic cell stack 46 includes an anode 46a to which an anode supply fluid AF20 containing water is supplied, a cathode 46b to which a fourth anode discharge fluid AF14 is supplied and a first cathode discharge fluid CF21 is discharged, and a diaphragm 46c interposed between the anode 46a and the cathode 46b. As a result, water can be electrolyzed in the anode 46a to generate hydrogen ions. The hydrogen ions can pass through the diaphragm 46c and move to the cathode 46b, where they can reduce the oxygen contained in the fourth anode discharge fluid AF14 and convert it into water. Therefore, oxygen can be separated and removed from the fourth anode discharge fluid AF14, and the concentration of carbon dioxide supplied to the electrolytic unit 10 can be increased.

[0068] Furthermore, according to this embodiment, the third cathode discharge fluid CF23, which contains water separated from the first cathode discharge fluid CF21 in the first recovery separator 43, is supplied to the anode 46a of the oxygen separator 41 via the first return channel 50. This makes it possible to effectively utilize the water contained in the first cathode discharge fluid CF21 discharged from the cathode 46b of the oxygen separator 41. In this case, the water can be circulated, and a water supply source for supplying water to the anode 46a can be eliminated.

[0069] Furthermore, according to this embodiment, the recovery unit 40 includes a second recovery separator 45 that separates and removes water from the first anode discharge fluid AF21, which contains oxygen and water discharged from the anode 46a of the oxygen separator 41, and discharges a second anode discharge fluid AF22 containing oxygen. This makes it possible to remove water from the second anode discharge fluid AF22 and discharge an oxygen-containing gas.

[0070] Furthermore, according to this embodiment, the recovery unit 40 includes a second recovery cooler 44 for cooling the first anode discharge fluid AF21. The first anode discharge fluid AF21, cooled by the second recovery cooler 44, is supplied to the second recovery separator 45. This allows the water vapor contained in the first anode discharge fluid AF21 to be condensed, and the second recovery separator 45 can effectively remove water from the first anode discharge fluid AF21.

[0071] Furthermore, according to this embodiment, the third anode discharge fluid AF23, which contains water separated from the first anode discharge fluid AF21 in the second recovery separator 45, is supplied to the anode 46a of the oxygen separator 41 via the second return channel 53. This makes it possible to effectively utilize the water contained in the first anode discharge fluid AF21 discharged from the anode 46a of the oxygen separator 41. In this case, the water can be circulated, and a water supply source for supplying water to the anode 46a can be eliminated.

[0072] Furthermore, the carbon dioxide conversion device according to the above-described embodiment may include devices such as blowers, pumps, and compressors as appropriate, and these devices may be used to control the flow of fluids including gases and liquids.

[0073] According to the embodiments described above, the utilization rate of carbon dioxide can be improved.

[0074] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. Naturally, these embodiments can also be combined in part as appropriate within the scope of the spirit of the invention. [Explanation of Symbols]

[0075] 1: Carbon dioxide conversion unit, 10: Electrolysis unit, 40: Recovery unit, 41: Oxygen separator, 42: First recovery cooler, 43: First recovery separator, 44: Second recovery cooler, 45: Second recovery separator, 46: Electrolytic cell stack, 46a: Anode, 46b: Cathode, 46c: Diaphragm, 49: Electrolysis unit return channel, 50: First return channel, 53: Second return channel, AF14: Fourth anode discharge fluid, CF21: First cathode discharge fluid, CF22: Second cathode discharge fluid, CF23: Third cathode discharge fluid, AF21: First anode discharge fluid, AF22: Second anode discharge fluid, AF23: Third anode discharge fluid

Claims

1. An electrolytic unit that produces carbon monoxide by electrolyzing carbon dioxide, comprising an electrolytic unit that discharges an electrolytic unit discharge fluid containing oxygen and the carbon dioxide, A recovery unit for recovering carbon dioxide from the discharge fluid of the electrolysis unit, Equipped with, The recovery unit includes an oxygen separator that uses water to electrolyze the discharge fluid from the electrolytic unit to remove the oxygen from the discharge fluid and discharge a first recovered fluid containing carbon dioxide and water; a first recovery separator that separates and removes the water from the first recovered fluid and discharges a second recovered fluid containing carbon dioxide; and an electrolytic unit return channel that supplies the second recovered fluid to the electrolytic unit. Carbon dioxide conversion device.

2. The recovery unit includes a first recovery cooler for cooling the first recovered fluid. The first recovery fluid, cooled by the first recovery cooler, is supplied to the first recovery separator. The carbon dioxide conversion apparatus according to claim 1.

3. The oxygen separator includes an electrolytic cell stack comprising an anode to which an anode supply fluid containing water is supplied, a cathode to which the electrolytic unit discharge fluid is supplied and the first recovered fluid is discharged, and a diaphragm interposed between the anode and the cathode. The carbon dioxide conversion apparatus according to claim 1.

4. The first recovery separator further comprises a first return channel for supplying the third recovery fluid, which contains water and has been separated from the first recovery fluid, to the anode of the oxygen separator. The carbon dioxide conversion apparatus according to claim 3.

5. The recovery unit includes a second recovery separator that separates and removes the water from a fourth recovery fluid containing the oxygen and water discharged from the anode of the oxygen separator, and discharges a fifth recovery fluid containing the oxygen. The carbon dioxide conversion apparatus according to claim 3 or 4.

6. The recovery unit includes a second recovery cooler for cooling the fourth recovery fluid. The fourth recovered fluid, cooled by the second recovered cooler, is supplied to the second recovered separator. The carbon dioxide conversion apparatus according to claim 5.

7. The second recovery separator further comprises a second return channel for supplying the sixth recovery fluid, which contains the water separated from the fourth recovery fluid, to the anode of the oxygen separator. The carbon dioxide conversion apparatus according to claim 5.

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