Carbon dioxide concentration device

Abstract

This technology provides a flow path that allows the electrolyte to be circulated according to its state. [Solution] The carbon dioxide concentrator comprises an absorption unit that absorbs carbon dioxide into an electrolyte, an electrochemical cell that generates carbon dioxide from the electrolyte, and a passage for flowing the electrolyte. The electrochemical cell comprises an anode, a cathode, an electrolyte membrane provided between the anode and the cathode, a first liquid chamber provided between the anode and the electrolyte membrane and supplied with the electrolyte, and a second liquid chamber provided between the electrolyte membrane and the cathode and supplied with the electrolyte. The passage includes a first passage that sends the electrolyte discharged from the second liquid chamber to the absorption unit and a second passage that returns it to the second liquid chamber, and the flow path of the electrolyte can be switched between the first passage and the second passage.

Description

[Technical Field]

[0001] This invention relates to a carbon dioxide concentration device. [Background technology]

[0002] One of the causes of global warming is the increase in emissions of greenhouse gases such as carbon dioxide. To reduce carbon dioxide emissions, technologies are being developed to separate and concentrate carbon dioxide from exhaust gases and the atmosphere.

[0003] Patent Document 1 discloses a carbon dioxide recovery system that includes a carbon dioxide release device and a carbon dioxide dissolving unit configured to dissolve carbon dioxide in exhaust gas in a first alkaline solution. The carbon dioxide release device is configured to fill the space between the anode electrode and the cation exchange membrane with the first alkaline solution in which carbon dioxide is dissolved, and to fill the space between the cation exchange membrane and the cathode electrode with a second alkaline solution, thereby supplying hydrogen to the anode electrode. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2024-31641 [Overview of the project] [Problems that the invention aims to solve]

[0005] In a device comprising an absorption unit that absorbs carbon dioxide into an electrolyte and an electrochemical cell that generates carbon dioxide, a configuration in which the electrolyte is circulated between the absorption unit and the electrochemical cell is conceivable for improving operational efficiency. However, if the electrolyte is continuously flowed through each circulation unit, there is a possibility that an incompletely reacted electrolyte will flow into the next circulation unit. A technology that can circulate the electrolyte through a flow path appropriate to its state is desired.

[0006] The purpose of this disclosure is to provide a technology that allows the electrolyte to be circulated through a flow path that corresponds to the state of the electrolyte. [Means for solving the problem]

[0007] A carbon dioxide concentration apparatus according to one aspect of the present disclosure comprises an absorption unit for absorbing carbon dioxide into an electrolyte, an electrochemical cell for generating carbon dioxide from the electrolyte, and a passage for flowing the electrolyte, wherein the electrochemical cell comprises an anode, a cathode, an electrolyte membrane provided between the anode and the cathode, a first liquid chamber provided between the anode and the electrolyte membrane and supplied with the electrolyte, and a second liquid chamber provided between the electrolyte membrane and the cathode and supplied with the electrolyte, wherein the passage includes a first passage for sending the electrolyte discharged from the second liquid chamber to the absorption unit and a second passage for returning it to the second liquid chamber, and the flow path of the electrolyte can be switched between the first passage and the second passage.

[0008] A carbon dioxide concentrator according to one aspect of the present disclosure comprises an absorption unit for absorbing carbon dioxide into an electrolyte, an electrochemical cell for generating carbon dioxide from the electrolyte, and a passage for flowing the electrolyte, wherein the electrochemical cell comprises an anode, a cathode, an electrolyte membrane provided between the anode and the cathode, a first liquid chamber provided between the anode and the electrolyte membrane and supplied with the electrolyte, and a second liquid chamber provided between the electrolyte membrane and the cathode and supplied with the electrolyte, and the passage includes a first passage for sending the electrolyte discharged from the second liquid chamber to the absorption unit and a second passage for returning it to the second liquid chamber, a third passage for sending the electrolyte discharged from the first liquid chamber to the second liquid chamber and a fourth passage for returning it to the first liquid chamber. [Effects of the Invention]

[0009] According to this disclosure, the electrolyte can be circulated through a flow path that corresponds to the state of the electrolyte. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of a carbon dioxide concentration device. [Figure 2] This is a cross-sectional view showing an example of the configuration of the concentration unit 20. [Figure 3] This is an explanatory diagram illustrating the operation of a carbon dioxide concentration device. [Modes for carrying out the invention]

[0011] (1) A carbon dioxide concentrator according to one aspect of the present disclosure comprises an absorption unit for absorbing carbon dioxide into an electrolyte, an electrochemical cell for generating carbon dioxide from the electrolyte, and a passage for flowing the electrolyte, wherein the electrochemical cell comprises an anode, a cathode, an electrolyte membrane provided between the anode and the cathode, a first liquid chamber provided between the anode and the electrolyte membrane and supplied with the electrolyte, and a second liquid chamber provided between the electrolyte membrane and the cathode and supplied with the electrolyte, wherein the passage includes a first passage for sending the electrolyte discharged from the second liquid chamber to the absorption unit and a second passage for returning it to the second liquid chamber, and the flow path of the electrolyte can be switched between the first passage and the second passage.

[0012] In the carbon dioxide concentration apparatus described in (1) above, the first liquid chamber may be supplied with an electrolyte that has absorbed carbon dioxide. The second liquid chamber may be supplied with an electrolyte that has generated carbon dioxide. The anode may be one that generates protons from hydrogen.

[0013] In a carbon dioxide concentration device utilizing hydrogen pumping or similar methods, the operating efficiency of the device can be improved by circulating the electrolyte between the absorption unit, which absorbs carbon dioxide into the electrolyte, and the first and second liquid chambers of an electrochemical cell that generates carbon dioxide from the electrolyte. The first liquid chamber is located between the anode and the electrolyte membrane, and the second liquid chamber is located between the electrolyte membrane and the cathode. When the electrolytes in the absorption unit, the first liquid chamber, and the second liquid chamber are continuously circulated, if the reaction of the electrolyte in any of these chambers is insufficient, the unreacted electrolyte flows to the next circulation point. The influx of unreacted electrolyte leads to a reduction in the carbon dioxide concentration efficiency.

[0014] As a method for reducing the unreacted electrolytic solution, it is conceivable to increase the utilization rate of the electrolytic solution, for example, to reduce the flow rate of the electrolytic solution. However, in response to the reduction of the flow rate of the electrolytic solution, the amount of carbon dioxide gas generated with respect to the flow rate of the electrolytic solution increases, and the amount of carbon dioxide gas staying in the flow path through which the electrolytic solution and the carbon dioxide gas flow increases. The increase in the amount of carbon dioxide gas staying in the flow path leads to an increase in the voltage required for the electrolysis of the electrochemical cell and an increase in the consumed energy, which is not desirable.

[0015] According to the carbon dioxide concentrating device of (1) above, since a plurality of switchable passages are provided in the carbon dioxide concentrating device, the electrolytic solution can be circulated through a flow path according to the state of the electrolytic solution by appropriately switching the plurality of passages. According to the state of the electrolytic solution, the flow path of the electrolytic solution discharged from the second liquid chamber can be switched between the absorption part and the second liquid chamber. For example, when the reaction of the electrolytic solution has sufficiently progressed, the electrolytic solution is circulated to the absorption part, and when the reaction of the electrolytic solution has not sufficiently progressed, the flow path is switched so that the electrolytic solution is circulated to the second liquid chamber, whereby the electrolytic solution can be supplied to a circulation destination suitable for the state of the electrolytic solution. By returning the electrolytic solution discharged from the second liquid chamber to the second liquid chamber, the electrolytic solution can be reacted again in the second liquid chamber, so that the inflow of the unreacted electrolytic solution into the next circulation destination can be suppressed. Since the electrolytic solution with insufficient reaction is repeatedly processed, the amount of recovered carbon dioxide can be increased.

[0016] (2) In the carbon dioxide concentrating device of (1) above, based on the pH of the electrolytic solution, the flow path of the electrolytic solution may be switched to the first passage or the second passage.

[0017] According to the carbon dioxide concentrating device of (2) above, considering the pH that changes corresponding to the degree of reaction of the electrolytic solution, the flow path of the electrolytic solution can be switched. Corresponding to the degree of reaction of the electrolytic solution, the flow path of the electrolytic solution can be switched to an appropriate passage at an appropriate timing.

[0018] (3) In the carbon dioxide concentration apparatus described in (2) above, if the pH of the electrolyte is above a predetermined value, the flow path of the electrolyte may be switched to the first passage, and if the pH of the electrolyte is below a predetermined value, the flow path of the electrolyte may be switched to the second passage.

[0019] According to the carbon dioxide concentration apparatus described in (3) above, if the pH of the electrolyte is above a predetermined value, the electrolyte discharged from the second liquid chamber is sent to the absorption section, allowing a new carbon dioxide absorption reaction to proceed. If the pH is below the predetermined value, the electrolyte is sent to the second liquid chamber and reacted again in the second liquid chamber, thereby reducing the amount of unreacted electrolyte in the second liquid chamber.

[0020] (4) Any one of the carbon dioxide concentrators described in (1) to (3) above may be equipped with a sensor for measuring the pH of the electrolyte.

[0021] According to the carbon dioxide concentration device described in (4) above, the pH of the electrolyte can be accurately determined in real time, allowing for precise and rapid switching based on pH.

[0022] (5) In the carbon dioxide concentration apparatus described in (4) above, the sensor may be provided inside the second liquid chamber or near the end of the passage that connects to the second liquid chamber.

[0023] According to the carbon dioxide concentration apparatus described in (5) above, the pH of the electrolyte can be measured inside the second liquid chamber or near the end of the passage connected to the second liquid chamber. In the first liquid chamber, where the electrolyte that has absorbed carbon dioxide is supplied, bicarbonate ions are present in the electrolyte due to the dissolution of carbon dioxide, and a buffering effect occurs, so the change in pH associated with the reaction of the electrolyte is small. In the second liquid chamber, where the electrolyte after carbon dioxide has been generated is supplied, no buffering effect occurs, so the change in pH associated with the reaction of the electrolyte is larger than in the first liquid chamber. By measuring the pH inside the second liquid chamber or near the end of the passage connected to the second liquid chamber, the progress of the reaction can be estimated more accurately.

[0024] (6) In any one of the carbon dioxide concentrators described in (1) to (5) above, the passage may include a third passage for sending the electrolyte discharged from the first liquid chamber to the second liquid chamber and a fourth passage for returning it to the first liquid chamber, and the flow path of the electrolyte may be switchable between the third passage and the fourth passage.

[0025] According to the carbon dioxide concentration apparatus described in (6) above, in addition to the flow path for the electrolyte discharged from the second liquid chamber, the flow path for the electrolyte discharged from the first liquid chamber can be switched between the second and first liquid chambers. For example, by switching the flow path so that the electrolyte discharged from the first liquid chamber is circulated to the second liquid chamber when the electrolyte reaction is progressing sufficiently, and the electrolyte is circulated to the first liquid chamber when the electrolyte reaction is not progressing sufficiently, the electrolyte can be circulated more effectively throughout the entire apparatus.

[0026] (7) In the carbon dioxide concentration apparatus described in (6) above, if the pH of the electrolyte is above a predetermined value, the flow path of the electrolyte may be switched to the third passage, and if the pH of the electrolyte is below a predetermined value, the flow path of the electrolyte may be switched to the fourth passage.

[0027] According to the carbon dioxide concentration apparatus described in (7) above, if the pH of the electrolyte is above a predetermined value, the electrolyte discharged from the first liquid chamber is sent to the second liquid chamber, thereby allowing the predetermined reaction of the electrolyte after carbon dioxide generation to proceed. If the pH is below the predetermined value, the electrolyte is sent to the first liquid chamber and reacted again in the first liquid chamber, thereby reducing the amount of unreacted electrolyte in the first liquid chamber.

[0028] (8) Any one of the carbon dioxide concentrators described in (1) to (7) above may be equipped with a control device that switches the flow path of the electrolyte between the first passage and the second passage.

[0029] According to the carbon dioxide concentration apparatus described in (8) above, the control device can appropriately control the switching of the flow path.

[0030] (9) A carbon dioxide concentration apparatus according to one aspect of the present disclosure comprises an absorption unit for absorbing carbon dioxide into an electrolyte, an electrochemical cell for generating carbon dioxide from the electrolyte, and a passage for flowing the electrolyte, wherein the electrochemical cell comprises an anode, a cathode, an electrolyte membrane provided between the anode and the cathode, a first liquid chamber provided between the anode and the electrolyte membrane and supplied with the electrolyte, and a second liquid chamber provided between the electrolyte membrane and the cathode and supplied with the electrolyte, and the passage includes a first passage for sending the electrolyte discharged from the second liquid chamber to the absorption unit and a second passage for returning it to the second liquid chamber, a third passage for sending the electrolyte discharged from the first liquid chamber to the second liquid chamber and a fourth passage for returning it to the first liquid chamber.

[0031] According to the carbon dioxide concentration apparatus described in (9) above, by appropriately switching between multiple passages, the electrolyte discharged from the second liquid chamber and the electrolyte discharged from the first liquid chamber can be circulated in a flow path corresponding to the state of the electrolyte.

[0032] This disclosure will be described in detail with reference to drawings illustrating embodiments thereof.

[0033] Figure 1 is a schematic diagram of the carbon dioxide concentration apparatus 100. The carbon dioxide concentration apparatus 100 is a device for concentrating and recovering carbon dioxide from a source gas G1 containing low concentrations of carbon dioxide. The carbon dioxide concentration apparatus 100 comprises an absorption tower 10, a concentration unit 20, a gas-liquid separation unit 30, and a control device 40.

[0034] The absorption tower 10 brings gas G1 and electrolyte S into gas-liquid contact to absorb carbon dioxide in gas G1 into electrolyte S. In this specification, "absorption" means dissolving into predetermined ions through a chemical reaction.

[0035] Gas G1 is a gas containing a low concentration of carbon dioxide, such as air or exhaust gas. The concentration of carbon dioxide in gas G1 is, for example, 0.01 vol% to 30 vol%. Gas G1 may also contain components other than carbon dioxide, such as nitrogen, water vapor, carbon monoxide, hydrogen sulfide, carbonyl sulfide, sulfur dioxide, nitrogen dioxide, methane, hydrogen, etc.

[0036] The concentration unit 20 desorbs and releases carbon dioxide from the electrolyte S that has absorbed carbon dioxide, thereby producing gas G2 containing carbon dioxide. Gas G2 is a concentrated carbon dioxide gas containing a higher concentration of carbon dioxide than gas G1. The concentration of carbon dioxide in gas G2 is typically 90 vol% to 100 vol%.

[0037] The concentration unit 20 includes an electrochemical hydrogen pump (electrochemical cell) comprising an anode 22, an electrolyte unit 23, and a cathode 24. The electrolyte unit 23 includes an anode liquid chamber 231 (first liquid chamber), an electrolyte membrane 232, and a cathode liquid chamber 233 (second liquid chamber). Electrolyte S is supplied to the anode liquid chamber 231 and the cathode liquid chamber 233.

[0038] Although Figure 1 shows two electrolyte units 23 for simplicity of explanation, the concentration unit 20 may be equipped with a large number of electrolyte units 23, such as 50 or 100. The number of electrolyte units 23 provided in the concentration unit 20 is not limited to multiple units; it may be just one.

[0039] The concentration unit 20 uses an electrodialysis method by hydrogen pumping to remove carbon dioxide from the electrolyte S that has absorbed carbon dioxide, and regenerates the electrolyte of the electrolyte S by moving predetermined ions through the electrolyte membrane 232. Gas G3 containing hydrogen is supplied to the anode 22 of the concentration unit 20. The cathode 24 generates gas G4, which is at a higher pressure than gas G3, by the hydrogen pressurization operation of the electrochemical hydrogen pump.

[0040] The hydrogen concentration in gas G3 may be 100 vol% or less. The lower limit of the hydrogen concentration in gas G3 is not particularly limited, but may be, for example, 0.01 vol% or higher.

[0041] The carbon dioxide concentrator 100 is equipped with passages 6 that connect the various components of the carbon dioxide concentrator 100. The passages 6 include the first passage 61 to the sixth passage 66. The carbon dioxide concentrator 100 circulates the electrolyte S within the carbon dioxide concentrator 100 using the circulation system formed by the passages 6. The composition of the electrolyte S may change depending on the circulation state. Hereinafter, in order to distinguish the electrolyte S according to its state, it will also be referred to as electrolyte S1, electrolyte S2, and electrolyte S3 for convenience.

[0042] The absorption tower 10 comprises a main body 11 extending vertically, a gas inlet 12 provided at the lower part of the side wall of the main body 11, a liquid inlet 13 and a gas outlet 14 provided at the upper part of the main body 11, and a liquid outlet 15 provided at the bottom of the main body 11. The gas inlet 12 is connected to a carbon dioxide-containing gas supply source (not shown).

[0043] Gas G1 is supplied to the gas inlet 12. Gas G1 is supplied into the tower, flows through the tower, and is then discharged from the gas outlet 14. Electrolyte S1 for absorbing carbon dioxide is supplied to the liquid inlet 13. Electrolyte S1 absorbs carbon dioxide by coming into contact with the carbon dioxide-containing gas in the tower. Electrolyte S2, which has absorbed carbon dioxide, is discharged from the liquid outlet 15. The electrolyte S2 discharged from the absorption tower 10 is supplied to the concentration unit 20. Details of the electrolyte S will be described later.

[0044] The method of bringing the gas G1 and the electrolyte S1 into contact is not particularly limited. For example, methods include bubbling the gas G1 into the electrolyte S1, atomizing the electrolyte S1 into the gas G1 using a spray or atomizing method, or bringing high-pressure gas G1 and electrolyte S1 into countercurrent contact in an absorption tower 10 filled with a magnetic or metal mesh packing material.

[0045] Figure 2 is a cross-sectional view showing an example of the configuration of the concentration unit 20. As shown in Figures 1 and 2, the concentration unit 20 has a substantially rectangular cross-section and an overall substantially rectangular parallelepiped shape. The concentration unit 20 comprises an anode plate 21 having an anode gas chamber 211, an anode 22, a plurality of electrolyte units 23, a cathode 24, a cathode plate 25 having a cathode gas chamber 251, and a power supply 26.

[0046] The anode plate 21, anode 22, multiple electrolyte units 23, cathode 24, and cathode plate 25 are arranged in this order and are fastened together, for example, by fastening members (not shown). Gaskets (not shown) may be placed between the anode plate 21 and the anode 22, and between the cathode 24 and the cathode plate 25.

[0047] Each electrolyte unit 23 comprises an electrolyte membrane 232, an anode liquid chamber 231 located on the anode 22 side via the electrolyte membrane 232, and a cathode liquid chamber 233 located on the cathode 24 side. Multiple electrolyte units 23 are stacked with an intermediate layer 28 in between, forming a laminate.

[0048] The anode plate 21 comprises an anode gas chamber 211 and a first supply port 212 into which hydrogen-containing gas G3 is supplied. The anode gas chamber 211 functions as a gas flow path for the gas G3. The gas G3 is supplied to the anode 22 as it passes through the anode gas chamber 211. The anode gas chamber 211 restricts the flow of gas G3 supplied to the anode 22. The anode plate 21 may also include a first discharge port 213 for discharging the gas G3 that has flowed through the anode gas chamber 211.

[0049] The anode gas chamber 211 is, for example, a groove-shaped channel formed on the surface of the anode plate 21, and is arranged to fold back within the region of the surface of the anode plate 21 facing the anode 22. Within the region of the surface of the anode plate 21 facing the anode 22, the portion other than where the anode gas chamber 211 is formed is in contact with the surface of the anode 22, thereby enabling the movement of electrons between the anode plate 21 and the anode 22.

[0050] The configuration of the anode plate 21 is not limited, and may be constructed by stacking, for example, an end plate, a current collector plate, and a plate member having an anode gas chamber 211 on one side in that order.

[0051] The cathode plate 25 includes a cathode gas chamber 251 and a second outlet 252 for discharging hydrogen-containing gas G4. The cathode gas chamber 251 functions as a gas flow path for the gas G4. The gas G4 generated in the cathode 24 passes through the cathode gas chamber 251 and is discharged from the second outlet 252. The gas G4 discharged from the second outlet 252 is recovered, for example, in a hydrogen recovery unit (not shown). Alternatively, the second outlet 252 may be connected to a first supply port 212, and the gas G4 discharged from the second outlet 252 may be supplied to the anode 22.

[0052] The cathode gas chamber 251 is, for example, a groove-shaped channel formed on the surface of the cathode plate 25, and is arranged so as to fold back within the region of the cathode plate 25 facing the cathode 24. Within the region of the cathode plate 25 facing the cathode 24, the portion of the surface other than where the cathode gas chamber 251 is formed is in contact with the surface of the cathode 24, thereby enabling the movement of electrons between the cathode plate 25 and the cathode 24. The configuration of the cathode plate 25 is not limited, and for example, it may be constructed by stacking a plate member with a cathode gas chamber 251 on one side, a current collector plate, and an end plate in that order.

[0053] The anode plate 21 is electrically connected to the anode 22. The cathode plate 25 is electrically connected to the cathode 24. The anode plate 21 and cathode plate 25 are connected to the power supply 26 via wiring.

[0054] The power supply 26 applies voltage to the anode 22 and cathode 24 via the anode plate 21 and cathode plate 25. The high-potential terminal of the power supply 26 is connected to the anode plate 21, and the low-potential terminal is connected to the cathode plate 25.

[0055] The concentration unit 20 may be equipped with measuring instruments such as a current sensor for detecting the current flowing between the anode 22 and the cathode 24, and a voltage sensor for detecting the voltage.

[0056] Anode 22 is an electrode that generates protons from hydrogen in gas G3. Anode 22 is, for example, a gas diffusion electrode and comprises an anode catalyst layer 221 containing an anode catalyst and an anode gas diffusion layer 222. The anode catalyst layer 221 is provided on one surface of the anode gas diffusion layer 222. The anode liquid chamber 231 is in contact with the surface of anode 22 on the anode catalyst layer 221 side, and the anode plate 21 (anode gas chamber 211) is in contact with the surface on the anode gas diffusion layer 222 side. The anode catalyst layer 221 may be formed by supporting fine particles of the anode catalyst in a highly dispersed manner on the anode gas diffusion layer 222.

[0057] Examples of anode catalysts include platinum, ruthenium, rhodium, palladium, and iridium. Anode catalysts may be used individually or in combination of two or more. When using a combination of two or more, for example, a combination containing at least platinum and ruthenium can be used.

[0058] The anode gas diffusion layer 222 is composed of a porous material and has conductivity and gas diffusivity. The anode gas diffusion layer 222 uniformly diffuses the gas G3 supplied through the anode gas chamber 211 into the anode catalyst layer 221. Examples of the anode gas diffusion layer 222 include porous carbon fiber sheets such as carbon paper, carbon cloth, and carbon felt, and sintered bodies made of carbon particles, with carbon paper being preferred. The anode gas diffusion layer 222 may also be a sintered body of metal fibers made of titanium alloy, stainless steel, etc., a sintered body of powdered metal, a metal mesh, a foamed metal body, etc.

[0059] The method for producing the anode 22 is not particularly limited. For example, it can be produced by applying a slurry of a liquid composition containing the anode catalyst to one surface of the anode gas diffusion layer 222 and drying it.

[0060] The cathode 24 is an electrode that generates hydrogen from protons supplied from the anode 22. The cathode 24 is, for example, a gas diffusion electrode and includes a cathode catalyst layer 241 containing a cathode catalyst and a cathode gas diffusion layer 242. The cathode catalyst layer 241 is provided on one surface of the cathode gas diffusion layer 242. The cathode liquid chamber 233 is in contact with the surface of the cathode 24 on the cathode catalyst layer 241 side, and the cathode plate 25 (cathode gas chamber 251) is in contact with the surface on the cathode gas diffusion layer 242 side. The cathode catalyst layer 241 may be formed by highly dispersed supporting of fine particles of the cathode catalyst on the cathode gas diffusion layer 242.

[0061] Examples of cathode catalysts include those similar to the anode catalyst described above, and platinum is preferred. The cathode catalyst may be used alone or in combination of two or more types.

[0062] The cathode gas diffusion layer 242 is composed of a porous material and has conductivity and gas diffusivity. The material for the cathode gas diffusion layer 242 is the same as that used for the anode gas diffusion layer 222.

[0063] The method for producing the cathode 24 is not particularly limited. For example, it can be produced by applying a slurry of a liquid composition containing a cathode catalyst to one surface of the cathode gas diffusion layer 242 and drying it.

[0064] A polymer membrane having ion exchange groups may be provided between the anode 22 and the anode liquid chamber 231, and between the cathode 24 and the cathode liquid chamber 233. Examples of materials for the polymer membrane having ion exchange groups include Nafion®. By providing such a membrane, it is possible to suppress the movement of the liquid in the liquid chamber towards the electrode while maintaining charge transfer.

[0065] The electrolyte unit 23 comprises an anode liquid chamber 231, an electrolyte membrane 232, and a cathode liquid chamber 233. Each electrolyte unit 23 has the same configuration.

[0066] The electrolyte membrane 232 is a cation exchange membrane (CEM) and is composed of an electrolyte material that has cationic conductivity. Examples of electrolyte membranes 232 include fluorine-based cation exchange membranes such as perfluorosulfonic acid-based membranes.

[0067] The anode liquid chamber 231 is composed of, for example, a roughly rectangular parallelepiped frame made of resin. The anode liquid chamber 231 includes a third supply port 234 provided at the bottom, a third outlet port 235 provided at the top, and an anode liquid flow path 236 formed between the third supply port 234 and the third outlet port 235. Electrolyte S2, which has absorbed carbon dioxide, is supplied to the third supply port 234. The electrolyte S2 desorbs (generates) carbon dioxide as it flows through the anode liquid flow path 236. The third outlet port 235 discharges a gas-liquid mixture of gas G2 containing the desorbed carbon dioxide and electrolyte S3 after the carbon dioxide has been removed. Electrolyte S3 may be circulated and supplied to the third supply port 234. In the anode liquid flow path 236, gas G2 and electrolyte S flow from the third supply port 234 (inlet) to the third outlet port 235 (outlet).

[0068] The anode liquid channel 236 is a space formed between the anode catalyst layer 221 and the electrolyte membrane 232. The anode liquid channel 236 is separated from the outside by a frame that constitutes the anode liquid chamber 231. The anode catalyst layer 221 is arranged so that when the electrolyte S is filled into this space, the entire surface of one side of the anode catalyst layer 221 is in contact with the electrolyte S. The anode liquid channel 236 may also be formed by a network of channel-forming members used as spacers, with the space created by the three-dimensional intersection of these channel-forming members.

[0069] The shape of the anode liquid chamber 231 and the positions of the third supply port 234 and the third discharge port 235 can be set as appropriate.

[0070] The cathode liquid chamber 233 is composed of, for example, a roughly rectangular parallelepiped frame made of resin. The cathode liquid chamber 233 includes a fourth supply port 237 provided at the top, a fourth outlet port 238 provided at the bottom, and a cathode liquid flow path 239 formed between the fourth supply port 237 and the fourth outlet port 238. The electrolyte S3 after carbon dioxide has been generated is supplied to the fourth supply port 237. The fourth outlet port 238 discharges the electrolyte S4 from which the absorbent liquid described later has been regenerated. The electrolyte S4 may be circulated and supplied to the fourth supply port 237. In the cathode liquid flow path 239, the electrolyte S flows from the fourth supply port 237 (inlet) to the fourth outlet port 238 (outlet).

[0071] The cathode liquid channel 239 is a space formed between the electrolyte membrane 232 and the cathode catalyst layer 241. The cathode liquid chamber 233 is separated from the outside by the frame that constitutes the cathode liquid channel 239. When the space is filled with electrolyte S, the cathode catalyst layer 241 is positioned so that the entire surface of one side of the cathode catalyst layer 241 is in contact with the electrolyte S. The cathode liquid channel 239 may also be equipped with a spacer, similar to the anode liquid channel 236.

[0072] Each cathode liquid chamber 233 is equipped with a pH sensor 8 for measuring the pH of the electrolyte S inside the cathode liquid chamber 233. Preferably, the pH sensor 8 is located near the fourth outlet 238 inside the cathode liquid chamber 233 so as to measure the pH of the electrolyte S as it is discharged from the cathode liquid chamber 233. The pH sensor 8 measures the pH at predetermined time intervals.

[0073] Alternatively, the pH sensor 8 may be located in the first passage 61 connected to the fourth outlet 238 of the cathode liquid chamber 233. The pH sensor 8 may be located near one end of the first passage 61, inside the end connected to the fourth outlet 238. The area near the end is, for example, the region between the end of the first passage 61 connected to the fourth outlet 238 and the second switching valve 72, which will be described later.

[0074] Figure 2 shows an example in which a pH sensor 8 is provided in each cathode liquid chamber 233. Alternatively, the pH sensor 8 may be provided in the first passage 61 connected to the fourth outlet 238 of at least one of the multiple cathode liquid chambers 233 or to the fourth outlet 238 of at least one cathode liquid chamber 233.

[0075] In the concentration section 20, adjacent electrolyte units 23 and the other electrolyte unit 23 are stacked in the same orientation with an intermediate layer 28 in between. One surface of the intermediate layer 28 contacts the cathode liquid chamber 233 of one electrolyte unit 23, and the other surface of the intermediate layer 28 contacts the anode liquid chamber 231 of the other electrolyte unit 23. The intermediate layer 28 supplies protons supplied from the cathode liquid chamber 233 of one electrolyte unit 23 to the anode liquid chamber 231 of the adjacent other electrolyte unit 23.

[0076] The intermediate layer 28 includes a catalyst layer 281 containing a catalyst and a gas diffusion layer 282. The catalyst layer 281 is formed on both surfaces of the gas diffusion layer 282. The catalyst layer 281 may also be constructed by supporting fine particles of the catalyst in a highly dispersed manner on the surface of the gas diffusion layer 282.

[0077] Examples of catalysts include those similar to the anode catalyst described above, and platinum is preferred. The catalyst may be used alone or in combination of two or more types.

[0078] The gas diffusion layer 282 is composed of a porous material and has conductivity and gas diffusivity. The gas diffusion layer 282 uniformly diffuses hydrogen molecules supplied from the catalyst layer 281 in contact with the cathode liquid chamber 233 to the catalyst layer 281 in contact with the anode liquid chamber 231. The material constituting the gas diffusion layer 282 is the same as that of the anode gas diffusion layer 222, and is preferably carbon paper.

[0079] The method for producing the intermediate layer 28 is not particularly limited; for example, it can be produced by applying a slurry of a liquid composition containing a catalyst to the surface of the gas diffusion layer 282 and drying it.

[0080] The intermediate layer 28 may include a leakage suppression section (not shown) to suppress the leakage of liquid from the anode liquid chamber 231 and the cathode liquid chamber 233 to the intermediate layer 28. The leakage suppression section is formed, for example, by adding or laminating a water-repellent material such as polytetrafluoroethylene to at least one of the pair of catalyst layers 281 and gas diffusion layers 282.

[0081] Figures 1 and 2 show a configuration in which electrolyte units 23 are stacked using an intermediate layer 28 having a gas diffusion layer 282 with catalyst layers 281 supported on both sides. The intermediate layer 28 only needs to be capable of supplying protons from the cathode liquid chamber 233 to the anode liquid chamber 231. The intermediate layer 28 may be, for example, a bipolar membrane formed by laminating a cation exchange membrane and an anion exchange membrane. An intermediate layer 28 using a gas diffusion layer and an intermediate layer 28 using a bipolar membrane may be used in combination.

[0082] The gas-liquid separation unit 30 performs gas-liquid separation by, for example, a water displacement method or a gravity separation method. The gas-liquid separation unit 30 is supplied with a gas-liquid mixture of gas G2 discharged from the anode liquid chamber 231 and electrolyte S3. The gas-liquid separation unit 30 separates the gas G2 and electrolyte S3 in the mixture and discharges the gas G2 containing carbon dioxide and the electrolyte S3, respectively.

[0083] The gas G2 separated in the gas-liquid separation unit 30 is recovered in a carbon dioxide recovery unit (not shown). Alternatively, the gas-liquid separation unit 30 may be connected to another device (not shown) to supply the gas G2 discharged from the gas-liquid separation unit 30 to the other device. An example of a device to which gas G2 is supplied is an electrolytic reduction device that produces hydrocarbons (e.g., methane, ethylene, etc.) and carbon compounds such as carbon monoxide by electrolytically reducing carbon dioxide.

[0084] The passage configuration in the carbon dioxide concentrator 100 will now be described. The carbon dioxide concentrator 100 includes passages 6, including the first passage 61 to the sixth passage 66.

[0085] The fifth passage 65 connects the liquid outlet 15 of the absorption tower 10 to the third supply port 234 of the anode liquid chamber 231. The fifth passage 65 flows the electrolyte S2 from the absorption tower 10 to the anode liquid chamber 231. The fifth passage 65 branches into multiple branches at the first branching point 65a, each connected to the third supply port 234 of each anode liquid chamber 231.

[0086] The sixth passage 66 connects the third outlet 235 of the anode liquid chamber 231 to the gas-liquid separation unit 30. The sixth passage 66 allows the electrolyte S3 and gas G4 to flow from the anode liquid chamber 231 to the gas-liquid separation unit 30. The upstream side of the sixth passage 66 branches out to correspond to each of the third supply ports 234 and merges at the first confluence point 66a.

[0087] The third passage 63 connects the gas-liquid separation unit 30 to the fourth supply port 237 of the cathode liquid chamber 233. The third passage 63 flows the electrolytes S3 and S4 from the gas-liquid separation unit 30 to the cathode liquid chamber 233. The third passage 63 branches into multiple branches at the second branching point 63a, each connected to the fourth supply port 237 of each cathode liquid chamber 233.

[0088] A fourth passage 64 is connected upstream of the second branching point 63a of the third passage 63. A first switching valve 71 is provided at the connection point between the third passage 63 and the fourth passage 64. One end of the fourth passage 64 is connected to the first switching valve 71, and the other end is connected upstream of the first branching point 65a of the fifth passage 65.

[0089] The first switching valve 71 is composed of a known solenoid valve or the like. The first switching valve 71 switches the flow path of the electrolyte S3 discharged from the gas-liquid separation unit 30 between the third passage 63 and the fourth passage 64. That is, the first switching valve 71 switches between a state in which the upstream side of the third passage 63 is connected to the downstream side of the third passage 63 and a state in which the upstream side of the third passage 63 is connected to the fourth passage 64. The first switching valve 71 is an example of a switching unit that switches the flow path of the electrolyte between the third passage 63 and the fourth passage 64.

[0090] The first passage 61 connects the fourth outlet 238 of the cathode liquid chamber 233 to the absorption tower 10. The first passage 61 flows the electrolyte S4 from the cathode liquid chamber 233 to the absorption tower 10. The upstream side of the first passage 61 branches into multiple paths corresponding to each of the fourth outlets 238, and these branches merge at the second confluence point 61a.

[0091] The second passage 62 is connected downstream of the second confluence point 61a of the first passage 61. A second switching valve 72 is provided at the connection point between the first passage 61 and the second passage 62. One end of the second passage 62 is connected to the second switching valve 72, and the other end is connected downstream of the first switching valve 71 and upstream of the second branching point 63a of the third passage 63.

[0092] The second switching valve 72 is composed of a known solenoid valve or the like. The second switching valve 72 can switch the flow path of the electrolyte S4 discharged from the cathode liquid chamber 233 between the first passage 61 and the second passage 62. That is, the second switching valve 72 switches between a state in which the upstream side of the first passage 61 is connected to the downstream side of the first passage 61 and a state in which the upstream side of the first passage 61 is connected to the second passage 62. The second switching valve 72 is an example of a switching unit that switches the flow path of the electrolyte between the first passage 61 and the second passage 62.

[0093] The absorption tower 10, the fifth passage 65, the anode liquid chamber 231, the sixth passage 66, the gas-liquid separation unit 30, the third passage 63, the cathode liquid chamber 233, and the first passage 61 constitute the first circulation system for the electrolyte S. Through this first circulation system, the electrolyte S is circulated so that it absorbs carbon dioxide in the absorption tower 10, decarbonizes carbon dioxide in the concentration unit 20, and then absorbs carbon dioxide again in the absorption tower 10. By regenerating the absorbent solution, the electrolyte S can be continuously circulated without adding solutes or performing other actions during the circulation process.

[0094] Furthermore, the cathode liquid chamber 233, a portion of the first passage 61, the second passage 62, and a portion of the third passage 63 constitute a second circulation system for the electrolyte S4. Through the second circulation system, the electrolyte S4 is discharged from the cathode liquid chamber 233 and then resupplied to the cathode liquid chamber 233. The anode liquid chamber 231, the sixth passage 66, the gas-liquid separation unit 30, a portion of the third passage 63, the fourth passage 64, and a portion of the fifth passage 65 constitute a third circulation system for the electrolyte S3. Through the third circulation system, the electrolyte S3 is discharged from the anode liquid chamber 231 and then resupplied to the anode liquid chamber 231.

[0095] The first passage 61 to the sixth passage 66 are not particularly limited, and known piping etc. can be used as appropriate. Each of the first passage 61 to the sixth passage 66 may be provided, as necessary, with control equipment such as a pump for delivering fluid, a control valve for controlling the volumetric flow rate or mass flow rate of the fluid flowing through the passage, a flow meter for measuring the volumetric flow rate or mass flow rate of the fluid flowing through the passage, and a gas sensor for detecting the concentration of the gas flowing through the passage.

[0096] The control device 40 is a computer that controls the operation of the carbon dioxide concentration unit 100. The control device 40 includes a processor such as a CPU (Central Processing Unit) (not shown), memory, a communication unit, and an input / output interface. The memory stores various computer programs and data referenced by the processor. The input / output interface is connected to the power supply 26, the first switching valve 71, the second switching valve 72, the pH sensor 8, various control devices, and various measuring instruments. The control device 40 acquires measured values ​​from the pH sensor 8 and various measuring instruments. Based on the acquired measured values, the control device 40 outputs control signals to the power supply 26, the first switching valve 71, the second switching valve 72, and various control devices to control their operation.

[0097] Figure 3 is an explanatory diagram illustrating the operation of the carbon dioxide concentrator 100. The operation of the carbon dioxide concentrator 100 will be explained using Figure 3. For the sake of simplicity, Figure 3 shows an example in which two electrolyte units 23 are stacked.

[0098] Gas G1 containing a low concentration of carbon dioxide is supplied to the absorption tower 10, along with electrolyte S1.

[0099] Electrolyte S1 is an alkaline electrolyte and is a mixture containing an absorbent solution that mainly contributes to the absorption of carbon dioxide and an electrolyte solution containing a predetermined electrolyte. The absorbent solution and the electrolyte solution are aqueous solutions containing the same cations. In this specification, "mixture" means a liquid containing the components corresponding to the absorbent solution and the components corresponding to the electrolyte solution, and does not require the actual mixing of separate absorbent solutions and electrolyte solutions.

[0100] The absorbent solution contained in electrolyte S1 is an alkaline aqueous solution. Examples of alkaline aqueous solutions include aqueous solutions of alkali metal compounds, alkaline earth metal compounds, and amine compounds, with alkali metal compounds being preferred.

[0101] Examples of alkali metal compounds and alkaline earth metal compounds include alkali metals such as sodium, lithium, and potassium, or alkaline earth metals such as calcium, magnesium, and barium. Preferably, alkali metal compounds and alkaline earth metal compounds are hydroxides, oxides, or nitrates of alkali metals or alkaline earth metals, and more preferably hydroxides. Specific examples of alkaline aqueous solutions include aqueous solutions of potassium hydroxide, sodium hydroxide, and calcium hydroxide, and preferably aqueous solutions of potassium hydroxide.

[0102] Examples of amine compounds include basic amines such as monoethanolamine, diethanolamine, diisopropanolamine, methyldiethanolamine, and triethanolamine. The alkaline aqueous solution may be used alone or in combination of two or more types.

[0103] Examples of electrolyte solutions included in electrolyte solution S1 include aqueous potassium chloride solution and aqueous sodium chloride solution, with aqueous potassium chloride solution being preferred. The electrolyte solution may be used individually or in combination of two or more types.

[0104] In this embodiment, the electrolyte S1 is assumed to be a mixture of an aqueous potassium hydroxide solution as an absorbent and an aqueous potassium chloride solution as an electrolyte solution (KOH-KCl solution).

[0105] In the absorption tower 10, the carbon dioxide absorption reaction represented by the following reaction equations (1) and (2) proceeds, yielding the electrolyte S2 (KHCO3-KCl solution) from which carbon dioxide has been absorbed. In the electrolyte S2, carbon dioxide is absorbed by bicarbonate ions (HCO3 - ) can be formed. The obtained electrolyte S2 is supplied to the concentration unit 20. 2KOH + CO2 → K2CO3 + H2O···(1) K2CO3+H2O+CO2→2KHCO3···(2)

[0106] The electrolyte S2 (KHCO3-KCL solution) that has absorbed carbon dioxide may be an electrolyte in which KOH has completely reacted with KHCO3, or may be an electrolyte that partially contains K2CO3, which is the product of the above reaction formula (1).

[0107] In the concentration unit 20, a gas G3 containing hydrogen is supplied to the anode gas chamber 211, an electrolyte S2 that has absorbed carbon dioxide is supplied to the anode liquid chamber 231, and an electrolyte S3 after carbon dioxide has been generated is supplied to the cathode liquid chamber 233. When a voltage is applied from the power supply 26 to the anode 22 and the cathode 24, the following reaction occurs.

[0108] At the anode 22, the gas G3 is supplied from the anode gas chamber 211. The gas G3 is supplied from the anode gas diffusion layer 222 to the anode catalyst layer 221. At the anode 22, hydrogen molecules in the gas G3 are separated into protons (H + ) and electrons by the reaction shown in the following reaction formula (3). Protons (H + ) generated in the anode catalyst layer 221 move to the anode liquid chamber 231 adjacent to the anode 22. H2→2H + +2e - ···(3)

[0109] In the anode liquid chamber 231, the pH of the KHCO3 solution in the anode liquid chamber 231 decreases due to the protons (H + ) supplied from the anode catalyst layer 221 compared to before the oxidation reaction. In the anode liquid chamber 231, the chemical equilibrium of the following reaction formula (4) shifts to the right, and carbon dioxide is generated as a gaseous product. Potassium ions (K + ) in the electrolyte move through the inside of the electrolyte membrane 232 to the cathode liquid chamber 233. HCO3 - +H + ⇔CO2+H2O···(4)

[0110] In the anode liquid chamber 231, the electrolyte S3 after carbon dioxide generation becomes a KCl solution mainly composed of potassium chloride. The electrolyte S3 after carbon dioxide generation may also contain KHCO3. The gas G4 containing carbon dioxide generated in the anode liquid chamber 231 and the electrolyte S3 after carbon dioxide generation are separated into gas and liquid in the gas-liquid separation unit 30 and then supplied to the gas recovery unit and cathode liquid chamber 233, respectively. This yields concentrated carbon dioxide. The electrolyte S3 separated in the gas-liquid separation unit 30 may be supplied again to the anode liquid chamber 231 as electrolyte S2. The electrolyte S3 (electrolyte S2) supplied again to the anode liquid chamber 231 generates carbon dioxide through the desorption reaction of reaction equation (4) above.

[0111] In the cathode liquid chamber 233, potassium ions (K) in the KCl solution within the cathode liquid chamber 233 + As ) increases, protons (H + ) is supplied to the mesolayer 28. Protons (H + In response to the consumption of ), the pH of the KCl solution rises, and the absorbent solution (KOH) is regenerated. After the regeneration of the absorbent solution, the electrolyte S4 becomes a KOH-KCl solution containing the absorbent solution and the electrolyte solution. The electrolyte S4 is circulated and supplied to the absorption tower 10 as electrolyte S1. The electrolyte S4 may be supplied again to the cathode liquid chamber 233. The electrolyte S4 supplied again to the cathode liquid chamber 233 regenerates the absorbent solution.

[0112] Protons (H) supplied to the intermediate layer 28 + The hydrogen molecules are adsorbed onto the catalyst layer 281 on the anode 22 side and then supplied to the gas diffusion layer 282 as hydrogen molecules. The hydrogen molecules pass through the inside of the gas diffusion layer 282 and are converted into protons (H) in the catalyst layer 281 on the cathode 24 side. + It is converted to a proton (H + ) is supplied to the anode liquid chamber 231 of the adjacent electrolyte unit 23.

[0113] A similar reaction occurs in each electrolyte unit 23, resulting in protons (H) +The liquid moves from the anode 22 side to the cathode 24 side and is supplied to the cathode 24 from the cathode liquid chamber 233 adjacent to the cathode 24.

[0114] Protons (H) supplied to cathode 24 + The hydrogen molecules are adsorbed onto the cathode catalyst layer 241. At cathode 24, hydrogen molecules are again generated by the reaction shown in the following reaction equation (5). 2H + +2e - →H2···(5)

[0115] The hydrogen generated in cathode 24 permeates through cathode gas diffusion layer 242 and is discharged from second outlet 252 as gas G4 containing high-pressure hydrogen gas. Gas G4 has, for example, a hydrogen concentration of 99 vol% or higher.

[0116] In the carbon dioxide concentrator 100, the flow path of the electrolyte S is switched by switching the state of the first switching valve 71 and the second switching valve 72 based on the pH value of the electrolyte S measured by the pH sensor 8. The pH value of the electrolyte S changes in accordance with the progress of the reaction in reaction equation (4) above. If the reaction in which the chemical equilibrium in reaction equation (4) above shifts to the right has not progressed sufficiently, the pH value of the electrolyte S in the anode liquid chamber 231 will be relatively high, and the pH value of the electrolyte S in the cathode liquid chamber 233 will be relatively low. If the reaction in which the chemical equilibrium in reaction equation (4) above shifts to the right has progressed sufficiently, the pH value of the electrolyte S in the anode liquid chamber 231 will be relatively low, and the pH value of the electrolyte S in the cathode liquid chamber 233 will be relatively high. In particular, in the cathode liquid chamber 233, HCO3 - In contrast to the anode chamber 231, where a buffering action occurs due to the absorption solution containing a large amount of , the pH value of the cathode chamber 233 tends to fluctuate more easily in response to the degree of reaction. By measuring the pH value of the electrolyte S flowing into the cathode chamber 233, the progress of the reaction can be accurately determined.

[0117] If the pH value of the electrolyte S in the cathode liquid chamber 233, measured by the pH sensor 8, is above a preset threshold, the electrolyte S3 discharged from the anode liquid chamber 231 is supplied to the cathode liquid chamber 233 via the sixth passage 66, the gas-liquid separation unit 30, and the third passage 63. The electrolyte S4 discharged from the cathode liquid chamber 233 is supplied to the absorption tower 10 as electrolyte S1 via the first passage 61, and carbon dioxide is absorbed again into the electrolyte S1.

[0118] If the pH value of the electrolyte S in the cathode liquid chamber 233 is below the threshold, the electrolyte S discharged from the concentration unit 20 is not supplied to the absorption tower 10, but is recirculated back to the concentration unit 20 in order to raise the pH value to above the threshold. If the pH value is below the threshold, the electrolyte S3 discharged from the anode liquid chamber 231 is resupplied to the anode liquid chamber 231 as electrolyte S2 via the sixth passage 66, the gas-liquid separation unit 30, part of the third passage 63, part of the fourth passage 64 and part of the fifth passage 65. By returning the electrolyte S3 to the anode liquid chamber 231, it is prevented that unreacted electrolyte S3 flows into the cathode liquid chamber 233.

[0119] Furthermore, if the pH value is below the above threshold, the electrolyte S4 discharged from the cathode liquid chamber 233 is resupplied to the cathode liquid chamber 233 via a portion of the first passage 61, the second passage 62, and a portion of the third passage 63. By returning the electrolyte S4 to the cathode liquid chamber 233, it is prevented that unreacted electrolyte S4 flows into the absorption tower 10.

[0120] Since the electrolyte S4 contains regenerated KOH, when the electrolyte S4 discharged from the cathode liquid chamber 233 is circulated to the anode liquid chamber 231, a neutralization reaction between KOH and protons occurs in the anode liquid chamber 231, preventing the desorption reaction of carbon dioxide. In this embodiment, if the reaction is insufficient, the electrolyte S is circulated in both the anode liquid chamber 231 and the cathode liquid chamber 233, thereby suppressing the aforementioned neutralization reaction and increasing the efficiency of carbon dioxide production.

[0121] The switching of the first switching valve 71 and the second switching valve 72 is performed automatically, for example, by the control device 40. The control device 40 acquires pH values ​​through the pH sensor 8 at predetermined or appropriate time intervals while the carbon dioxide concentrator 100 is in operation. The control device 40 determines whether the acquired pH value is above a preset threshold. If it determines that the acquired pH value is above the threshold, the control device 40 controls the first switching valve 71 so that the upstream side of the third passage 63 is connected to the downstream side of the third passage 63, and controls the second switching valve 72 so that the upstream side of the first passage 61 is connected to the downstream side of the first passage 61.

[0122] If the acquired pH value is determined to be not above the threshold, i.e., below the threshold, the control device 40 controls the first switching valve 71 to connect the upstream side of the third passage 63 to the fourth passage 64, and controls the second switching valve 72 to connect the upstream side of the first passage 61 to the second passage 62. It is preferable that the switching timing of the first switching valve 71 and the second switching valve 72 are synchronized.

[0123] If the carbon dioxide concentrator 100 is equipped with multiple pH sensors 8, the control device 40 may determine whether the measured values ​​of all pH sensors 8 are above a threshold, or whether the measured values ​​of a predetermined number or more of pH sensors 8 are above a threshold. If all or a predetermined number or more of the measured values ​​are above a threshold, the control device 40 controls the first switching valve 71 to connect the upstream side of the third passage 63 to the downstream side of the third passage 63, and controls the second switching valve 72 to connect the upstream side of the first passage 61 to the downstream side of the first passage 61. Alternatively, the flow path of the electrolyte S may be switched based on the measured value of any one representative pH sensor 8.

[0124] When the pH of the electrolyte S flowing through the anode chamber 231 is measured by the pH sensor 8, the threshold determination described above is reversed. If the pH value of the electrolyte S in the anode chamber 231 is less than a preset threshold, the flow path of the electrolyte S is switched to supply the electrolyte S3 discharged from the anode chamber 231 to the cathode chamber 233. If the pH value of the electrolyte S in the anode chamber 231 is equal to or greater than the threshold, the flow path of the electrolyte S is switched to supply the electrolyte S3 discharged from the anode chamber 231 back to the anode chamber 231 as electrolyte S2, and to supply the electrolyte S4 discharged from the cathode chamber 233 back to the cathode chamber 233.

[0125] The switching of the electrolyte S flow path may be performed manually. The control device 40 may, for example, receive a switching instruction from an operator and control the switching of the first switching valve 71 and the second switching valve 72 in accordance with the received switching instruction.

[0126] The passage configuration of the carbon dioxide concentrator 100 can be any appropriate passage configuration as long as the flow path of the electrolyte S can be switched as described above. For example, the second passage 62 may connect the fourth outlet 238 of the cathode liquid chamber 233 to the third passage or the fourth supply port 237 of the cathode liquid chamber 233. When the second passage 62 is provided, an on-off valve as an example of a switching unit may be provided in both the second passage 62 and the first passage 61, and the flow path of the electrolyte S4 may be switched by controlling the combination of opening and closing of each on-off valve. The fourth passage 64 may connect the third outlet 235 of the gas-liquid separation unit 30 or the anode liquid chamber 231 to the fifth passage 65 or the third supply port 234 of the anode liquid chamber 231. When the third passage 63 is provided, an on-off valve as an example of a switching unit may be provided in both the third passage 63 and the fourth passage 64, and the flow path of the electrolyte S3 may be switched by controlling the combination of opening and closing of each on-off valve.

[0127] The electrolyte S resupplied to the anode liquid chamber 231 may not pass through the gas-liquid separation section 30. The first passage 61, third passage 63, fifth passage 65, and sixth passage 66, etc., may be provided in multiples corresponding to each liquid chamber, instead of being connected to each liquid chamber by branching paths.

[0128] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The technical features described in each embodiment can be combined with each other, and the scope of the present invention is intended to include all modifications within the claims and equivalents thereof. The sequences shown in each embodiment are not limiting, and within the bounds of consistency, the order of each processing step may be changed, and multiple processes may be executed in parallel. The processing entity for each process is not limiting, and within the bounds of consistency, the processing of each device may be executed by other devices.

[0129] The matters described in each embodiment can be combined with each other. Furthermore, the independent and dependent claims described in the claims can be combined with each other in any combination, regardless of the form of reference. In addition, the claims use a form in which claims referencing two or more other claims (multi-claim form), but are not limited to this. A form in which multi-claims referencing at least one multi-claim (multi-multi-claim) may also be used. [Explanation of symbols]

[0130] 100 Carbon Dioxide Concentrator 10 Absorption Towers 20 Concentration section 22 Anodes 231 Anode liquid chamber 232 Electrolyte membrane 233 Cathode Liquid Chamber 24 Cathode 30 Gas-liquid separation section 40 Control device 6 aisles 61 1st aisle 62 2nd aisle 63 3rd aisle 64 4th aisle 65 5th aisle 66 6th aisle 8 pH sensors

Claims

1. An absorption section that absorbs carbon dioxide into the electrolyte, An electrochemical cell that generates carbon dioxide from the aforementioned electrolyte, The system includes a passage through which the aforementioned electrolyte flows, The aforementioned electrochemical cell is A-scatter, Cathode and, An electrolyte membrane is provided between the anode and the cathode, A first liquid chamber is provided between the anode and the electrolyte membrane, and the electrolyte is supplied to it. The system comprises a second liquid chamber provided between the electrolyte membrane and the cathode, through which the electrolyte is supplied, The passage includes a first passage for sending the electrolyte discharged from the second liquid chamber to the absorption section, and a second passage for returning it to the second liquid chamber, and the flow path of the electrolyte can be switched between the first passage and the second passage. Carbon dioxide concentration device.

2. Based on the pH of the electrolyte, the flow path of the electrolyte is switched to either the first or second passage. The carbon dioxide concentration apparatus according to claim 1.

3. If the pH of the electrolyte is above a predetermined value, the electrolyte flow path is switched to the first passage; if the pH of the electrolyte is below a predetermined value, the electrolyte flow path is switched to the second passage. The carbon dioxide concentration apparatus according to claim 2.

4. The system includes a sensor for measuring the pH of the electrolyte. A carbon dioxide concentration apparatus according to claim 1 or claim 2.

5. The sensor is provided inside the second liquid chamber or near the end of the passage that connects to the second liquid chamber. The carbon dioxide concentration apparatus according to claim 4.

6. The passage includes a third passage that sends the electrolyte discharged from the first liquid chamber to the second liquid chamber, and a fourth passage that returns it to the first liquid chamber, and the flow path of the electrolyte can be switched between the third passage and the fourth passage. A carbon dioxide concentration apparatus according to claim 1 or claim 2.

7. If the pH of the electrolyte is above a predetermined value, the electrolyte flow path is switched to the third passage; if the pH of the electrolyte is below a predetermined value, the electrolyte flow path is switched to the fourth passage. The carbon dioxide concentration apparatus according to claim 6.

8. The system includes a control device that switches the flow path of the electrolyte between a first passage and a second passage. A carbon dioxide concentration apparatus according to claim 1 or claim 2.

9. An absorption section that absorbs carbon dioxide into the electrolyte, An electrochemical cell that generates carbon dioxide from the aforementioned electrolyte, The system includes a passage through which the aforementioned electrolyte flows, The aforementioned electrochemical cell is A-scatter, Cathode and, An electrolyte membrane is provided between the anode and the cathode, A first liquid chamber is provided between the anode and the electrolyte membrane, and the electrolyte is supplied to it. The system comprises a second liquid chamber provided between the electrolyte membrane and the cathode, through which the electrolyte is supplied, The passage includes a first passage for sending the electrolyte discharged from the second liquid chamber to the absorption section and a second passage for returning it to the second liquid chamber, and a third passage for sending the electrolyte discharged from the first liquid chamber to the second liquid chamber and a fourth passage for returning it to the first liquid chamber. Carbon dioxide concentration device.

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