Carbon dioxide concentration device and information processing method

Abstract

Provided is a technology that enables circulation of an electrolyte solution in a flow path according to the state of the electrolyte solution.　This carbon dioxide concentration device comprises: an absorption unit by which carbon dioxide is absorbed into an electrolyte solution; an electrochemical cell by which carbon dioxide is generated from the electrolyte solution; and a passage through which the electrolyte solution passes. The electrochemical cell comprises: an anode; a cathode; an electrolyte membrane provided between the anode and the cathode; a first liquid chamber which is provided between the anode and the electrolyte membrane and to which the electrolyte solution is supplied; and a second liquid chamber which is provided between the electrolyte membrane and the cathode and to which the electrolyte solution is supplied. The passage includes: a first passage through which the electrolyte solution discharged from the second liquid chamber is sent to the absorption unit; and a second passage through which the electrolyte solution is returned to the second liquid chamber. The flow path of the electrolyte solution is switchable between the first passage and the second passage.

Description

Carbon dioxide concentration apparatus and information processing method

[0001] The present invention relates to a carbon dioxide concentration apparatus and an information processing method.

[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 a 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.

[0004] Japanese Patent Publication No. 2024-31641

[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] In the carbon dioxide recovery system described in Patent Document 1, it is not possible to determine the electrical conductivity of the solution in the carbon dioxide concentration device.

[0007] One objective is to provide a technology that allows the electrolyte to be circulated through a flow path that corresponds to the state of the electrolyte. Another objective is to provide a technology that allows the electrical conductivity of the solution in a carbon dioxide concentrator to be determined.

[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, 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.

[0009] 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, 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.

[0010] A carbon dioxide concentration apparatus according to one aspect of the present disclosure comprises an absorption unit that absorbs carbon dioxide in a process gas into a predetermined solution, and an electrochemical cell that generates a gas containing carbon dioxide at a higher concentration than the process gas from the predetermined solution that has absorbed carbon dioxide, wherein the electrochemical cell comprises an anode, a cathode, an anode liquid chamber through which predetermined ions are supplied from the anode and through which the predetermined solution that has absorbed carbon dioxide flows, a cathode liquid chamber that supplies the predetermined solution to the cathode, and an electrolyte membrane provided between the anode liquid chamber and the cathode liquid chamber, wherein a conductivity meter for measuring the electrical conductivity of the predetermined solution is provided inside the anode liquid chamber or the cathode liquid chamber or in a passage connected to the anode liquid chamber or the cathode liquid chamber.

[0011] An information processing method relating to one aspect of the present disclosure is an information processing method relating to a carbon dioxide concentrator, wherein the carbon dioxide concentrator comprises an absorption unit that absorbs carbon dioxide in a process gas into a predetermined solution, an electrochemical cell that generates a gas containing carbon dioxide at a higher concentration than the process gas from the predetermined solution, and a passage configured to switch the flow path of the predetermined solution, wherein the electrochemical cell comprises an anode, a cathode, an anode liquid chamber through which predetermined ions are supplied from the anode and a predetermined solution that has absorbed carbon dioxide flows, a cathode liquid chamber that supplies the predetermined solution to the cathode, and an electrolyte membrane provided between the anode liquid chamber and the cathode liquid chamber, wherein an electrical conductivity meter for measuring the electrical conductivity of the predetermined solution is provided inside the anode liquid chamber or the cathode liquid chamber or in a passage connected to the anode liquid chamber or the cathode liquid chamber, and a computer acquires the electrical conductivity measured by the electrical conductivity meter and executes a process to switch the flow path of the predetermined solution discharged from the anode liquid chamber or the cathode liquid chamber based on the acquired electrical conductivity.

[0012] One aspect allows for the circulation of the electrolyte through a flow path adapted to its state. Another aspect allows for the determination of the electrical conductivity of the solution in a carbon dioxide concentrator.

[0013] This is a schematic diagram of a carbon dioxide concentration device. This is a cross-sectional view showing an example of the configuration of the concentration section. This is an explanatory diagram illustrating the operation of the carbon dioxide concentration device. This is a schematic diagram of the carbon dioxide concentration system of the second embodiment. This is a cross-sectional view showing an example of the configuration of the concentration section of the second embodiment. This is an explanatory diagram illustrating the operation of the carbon dioxide concentration device of the second embodiment.

[0014] (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.

[0015] 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.

[0016] In a carbon dioxide concentration device using hydrogen pumping or the like, 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 a liquid chamber provided between the anode and the electrolyte membrane, and the second liquid chamber is a liquid chamber provided 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 in a circulation system, if the reaction of the electrolyte in any of the absorption unit, the first liquid chamber, or the second liquid chamber is insufficient, the unreacted electrolyte flows to the next circulation destination. The inflow of unreacted electrolyte leads to a reduction in the carbon dioxide concentration efficiency.

[0017] One way to reduce unreacted electrolyte is to increase the utilization rate of the electrolyte, for example, by reducing the electrolyte flow rate. However, in response to a decrease in the electrolyte flow rate, the amount of carbon dioxide gas generated relative to the electrolyte flow rate increases, and the amount of carbon dioxide gas accumulating in the flow path of the electrolyte and carbon dioxide gas increases. An increase in the amount of carbon dioxide gas accumulating in the flow path is undesirable because it leads to an increase in the voltage required for electrolysis in the electrochemical cell and an increase in energy consumption.

[0018] According to the carbon dioxide concentrator described in (1) above, since the carbon dioxide concentrator is provided with multiple switchable passages, the electrolyte can be circulated in a flow path that corresponds to the state of the electrolyte by appropriately switching between the multiple passages. Depending on the state of the electrolyte, the flow path of the electrolyte discharged from the second liquid chamber can be switched between the absorption section and the second liquid chamber. For example, by switching the flow path so that the electrolyte is circulated to the absorption section when the reaction of the electrolyte has progressed sufficiently, and circulated to the second liquid chamber when the reaction of the electrolyte has not progressed sufficiently, the electrolyte can be supplied to a circulation destination that is appropriate for the state of the electrolyte. By returning the electrolyte discharged from the second liquid chamber to the second liquid chamber, the electrolyte can be reacted again in the second liquid chamber, so the inflow of unreacted electrolyte to the next circulation destination can be suppressed. Since the electrolyte with insufficient reaction is repeatedly processed, the amount of carbon dioxide recovered can be increased.

[0019] (2) In the carbon dioxide concentration apparatus described in (1) above, the flow path of the electrolyte may be switched to the first passage or the second passage based on the pH of the electrolyte.

[0020] According to the carbon dioxide concentrator described in (2) above, the electrolyte passage can be switched while taking into account the pH which changes in accordance with the reaction rate of the electrolyte. The electrolyte flow path can be switched to the appropriate passage at the appropriate timing in accordance with the reaction rate of the electrolyte.

[0021] (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.

[0022] According to the carbon dioxide concentrator of (3) above, when the pH of the electrolytic solution is greater than or equal to a predetermined value, the electrolytic solution discharged from the second liquid chamber can be sent to the absorption section to promote a new carbon dioxide absorption reaction. When the pH is less than the predetermined value, the electrolytic solution is sent to the second liquid chamber and reacted again in the second liquid chamber, whereby the unreacted electrolytic solution in the second liquid chamber can be reduced.

[0023] (4) In any one of the carbon dioxide concentrators of (1) to (3) above, a sensor for measuring the pH of the electrolytic solution may be provided.

[0024] According to the carbon dioxide concentrator of (4) above, since the pH of the electrolytic solution can be accurately grasped in real time, switching based on the pH can be executed accurately and promptly.

[0025] (5) In the carbon dioxide concentrator of (4) above, the sensor may be provided inside the second liquid chamber or near the inner side of the end portion of the passage connecting to the second liquid chamber.

[0026] According to the carbon dioxide concentrator of (5) above, the pH of the electrolytic solution inside the second liquid chamber or near the inner side of the end portion of the passage connecting to the second liquid chamber can be measured. In the first liquid chamber to which the electrolytic solution that has absorbed carbon dioxide is supplied, hydrogen carbonate ions due to the dissolution of carbon dioxide exist in the electrolytic solution and a buffering action occurs, so the change in pH accompanying the reaction of the electrolytic solution is reduced. In the second liquid chamber to which the electrolytic solution after generating carbon dioxide is supplied, no buffering action occurs, so the change in pH accompanying the reaction of the electrolytic solution is larger than that in the first liquid chamber. By measuring the pH inside the second liquid chamber or near the inner side of the end portion of the passage connecting to the second liquid chamber, the progress of the reaction can be estimated more accurately.

[0027] (6) In any one of the carbon dioxide concentrators of (1) to (5) above, the passage includes a third passage for sending the electrolytic solution 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 electrolytic solution may be switchable between the third passage and the fourth passage.

[0028] According to the carbon dioxide concentrator of (6) above, in addition to the flow path of the electrolytic solution discharged from the second liquid chamber, the flow path of the electrolytic solution discharged from the first liquid chamber can be switched between the second liquid chamber and the first liquid chamber. For example, when the reaction of the electrolytic solution has proceeded sufficiently, the electrolytic solution discharged from the first liquid chamber is circulated to the second liquid chamber, and when the reaction of the electrolytic solution has not proceeded sufficiently, the flow path is switched so that the electrolytic solution is circulated to the first liquid chamber, whereby the electrolytic solution can be circulated more suitably throughout the apparatus.

[0029] (7) In the carbon dioxide concentrator of (6) above, when the pH of the electrolytic solution is greater than or equal to a predetermined value, the flow path of the electrolytic solution may be switched to the third passage, and when the pH of the electrolytic solution is less than the predetermined value, the flow path of the electrolytic solution may be switched to the fourth passage.

[0030] According to the carbon dioxide concentrator of (7) above, when the pH of the electrolytic solution is greater than or equal to a predetermined value, by sending the electrolytic solution discharged from the first liquid chamber to the second liquid chamber, a predetermined reaction of the electrolytic solution after carbon dioxide is generated can be advanced. When the pH is less than the predetermined value, the electrolytic solution is sent to the first liquid chamber and reacted again in the first liquid chamber, whereby the unreacted electrolytic solution in the first liquid chamber can be reduced.

[0031] (8) The carbon dioxide concentrator according to any one of (1) to (7) above may include a control device that switches the flow path of the electrolytic solution between the first passage and the second passage.

[0032] According to the carbon dioxide concentrator of (8) above, the control device can appropriately control the switching of the flow path.

[0033] (9) 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, 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.

[0034] 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.

[0035] (10) A carbon dioxide concentration apparatus according to one aspect of the present disclosure comprises an absorption unit that absorbs carbon dioxide in a process gas into a predetermined solution, and an electrochemical cell that generates a gas containing carbon dioxide at a higher concentration than the process gas from the predetermined solution that has absorbed carbon dioxide, wherein the electrochemical cell comprises an anode, a cathode, an anode liquid chamber through which predetermined ions are supplied from the anode and through which the predetermined solution that has absorbed carbon dioxide flows, a cathode liquid chamber that supplies the predetermined solution to the cathode, and an electrolyte membrane provided between the anode liquid chamber and the cathode liquid chamber, wherein an electrical conductivity meter for measuring the electrical conductivity of the predetermined solution is provided inside the anode liquid chamber or the cathode liquid chamber or in a passage connected to the anode liquid chamber or the cathode liquid chamber.

[0036] In the carbon dioxide concentrator described in (10) above, the anode may generate protons from hydrogen, and the cathode may generate hydrogen or hydroxide ions. The anode liquid chamber may be supplied with a predetermined solution that has absorbed carbon dioxide, and the cathode liquid chamber may be supplied with a predetermined solution from which carbon dioxide has been removed. In this specification, "absorption" means dissolving into predetermined ions through a chemical reaction.

[0037] According to the carbon dioxide concentrator described in (10) above, the electrical conductivity of a predetermined solution flowing through the anode liquid chamber or cathode liquid chamber can be measured by an electrical conductivity meter installed in the carbon dioxide concentrator, so the electrical conductivity of a predetermined solution flowing through the anode liquid chamber or cathode liquid chamber can be accurately determined.

[0038] The electrical conductivity of a predetermined solution flowing through the anode and cathode liquid chambers changes in accordance with the degree of reaction of the predetermined solution in the liquid chambers. By measuring the electrical conductivity, the degree of reaction of the predetermined solution in the liquid chambers can be estimated. By using electrical conductivity, which shows a linear change in accordance with the degree of reaction of the predetermined solution, the degree of reaction can be estimated easily and accurately. Depending on the degree of reaction, the operating state of the carbon dioxide concentrator, such as the contents of the predetermined solution supplied to each liquid chamber and the flow path of the predetermined solution discharged from each liquid chamber, can be suitably controlled, thereby optimizing the operation of the carbon dioxide concentrator.

[0039] (11) In the carbon dioxide concentrator described in (10) above, the passage includes a passage configured to switch the flow path of a predetermined solution discharged from the anode liquid chamber or the cathode liquid chamber, and the flow path of the predetermined solution may be switched based on the electrical conductivity measured by the electrical conductivity meter.

[0040] In a carbon dioxide concentrator, the operating efficiency of the device can be improved by circulating a predetermined solution between the absorption section, the anode liquid chamber, and the cathode liquid chamber. When the predetermined solution is continuously flowed between the absorption section, the anode liquid chamber, and the cathode liquid chamber, the overall operating efficiency of the carbon dioxide concentrator can be improved by supplying the predetermined solution to the next circulation destination after the reaction has sufficiently progressed in each of the three chambers.

[0041] According to the above configuration, it is possible to circulate the predetermined solution discharged from each liquid chamber in a flow path corresponding to the degree of reaction of the predetermined solution. For example, by switching the flow path of the predetermined solution discharged from each liquid chamber between the next circulation destination and the original liquid chamber from which the predetermined solution was discharged, the degree of reaction of the predetermined solution can be adjusted, and the carbon dioxide generation rate can be improved.

[0042] (12) In the carbon dioxide concentrator described in (10) or (11) above, the passage may be switchable between a first state in which a predetermined solution discharged from the anode liquid chamber is supplied to the cathode liquid chamber and the predetermined solution discharged from the cathode liquid chamber is supplied to the absorption section, and a second state in which a predetermined solution discharged from the anode liquid chamber is supplied to the anode liquid chamber and the predetermined solution discharged from the cathode liquid chamber is supplied to the cathode liquid chamber.

[0043] According to the above configuration, if the reaction in each liquid chamber is proceeding sufficiently, the predetermined solution after the reaction in each liquid chamber is supplied to the next circulation destination via the first-state passage, allowing the next reaction to proceed continuously. If the reaction in each liquid chamber is insufficient, the predetermined solution after the reaction in each liquid chamber is returned to the original liquid chamber via the second-state passage, allowing the insufficiently reacted predetermined solution to be repeatedly processed and preventing unreacted predetermined solution from flowing into the next circulation destination. The predetermined solution can be reacted sufficiently in each liquid chamber, improving the carbon dioxide production rate.

[0044] (13) In any one of the carbon dioxide concentrators described in (10) to (12) above, the conductivity meter may measure the electrical conductivity of a predetermined solution discharged from the anode liquid chamber or the cathode liquid chamber.

[0045] With the above configuration, the electrical conductivity of the predetermined solution after the reaction in each liquid chamber can be measured, allowing for an accurate estimation of the degree of reaction of the predetermined solution in each liquid chamber.

[0046] (14) In any one of the carbon dioxide concentrators described in (10) to (13) above, a gas-liquid separator is provided on the passage through which a predetermined solution discharged from the anode liquid chamber flows, for separating the predetermined solution and the gas from each other, and the electrical conductivity meter may be located downstream of the gas-liquid separator in the passage.

[0047] In a carbon dioxide concentrator, a gas containing carbon dioxide is generated from a predetermined solution in the anode liquid chamber, and a mixture of this gas and the predetermined solution is discharged from the anode liquid chamber. With the above configuration, the electrical conductivity can be measured after separating the gas and the predetermined solution using a gas-liquid separator, allowing for more accurate measurement of the electrical conductivity of the predetermined solution discharged from the anode liquid chamber, and enabling a more precise estimation of the reaction degree of the predetermined solution.

[0048] (15) An information processing method according to one aspect of the present disclosure is an information processing method for a carbon dioxide concentrator, the carbon dioxide concentrator comprising: an absorption unit for absorbing carbon dioxide in a process gas into a predetermined solution; an electrochemical cell for generating a gas containing carbon dioxide at a higher concentration than the process gas from the predetermined solution; and a passage configured to switch the flow path of the predetermined solution, the electrochemical cell comprising: an anode; a cathode; an anode liquid chamber through which predetermined ions are supplied from the anode and a predetermined solution that has absorbed carbon dioxide flows; a cathode liquid chamber for supplying the predetermined solution to the cathode; and an electrolyte membrane provided between the anode liquid chamber and the cathode liquid chamber, the electrical conductivity meter for measuring the electrical conductivity of the predetermined solution is provided inside the anode liquid chamber or the cathode liquid chamber or in a passage connected to the anode liquid chamber or the cathode liquid chamber, the computer acquires the electrical conductivity measured by the electrical conductivity meter and executes a process to switch the flow path of the predetermined solution discharged from the anode liquid chamber or the cathode liquid chamber based on the acquired electrical conductivity.

[0049] According to the information processing method described in (15) above, the flow path of a predetermined solution can be automatically switched to the appropriate state at the appropriate timing based on the electrical conductivity of the predetermined solution, thereby optimizing the operation of the carbon dioxide concentrator. This reduces the human cost required to identify the timing and state of the switch and enables stable switching operations that do not depend on the operator's skills.

[0050] (16) In any one of the carbon dioxide concentrators described in (1) to (9) above, the flow path of the electrolyte may be switched to the first passage or the second passage based on the electrical conductivity of the electrolyte.

[0051] According to the carbon dioxide concentrator described in (16) above, the electrolyte passage can be switched by taking into account the electrical conductivity, which changes in accordance with the degree of reaction of the electrolyte. By using the electrical conductivity, which exhibits a linear change, the degree of reaction can be easily and accurately estimated, and the electrolyte flow path can be switched to the appropriate passage at the appropriate timing.

[0052] (17) In the carbon dioxide concentrator described in (16) above, if the electrical conductivity of the electrolyte is greater than or equal to a predetermined value, the flow path of the electrolyte may be switched to the first passage, and if the electrical conductivity of the electrolyte is less than a predetermined value, the flow path of the electrolyte may be switched to the second passage.

[0053] According to the carbon dioxide concentration apparatus described in (17) above, if the electrical conductivity 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 electrical conductivity 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.

[0054] (18) In the carbon dioxide concentrator according to (16) or (17) above, the passage includes 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.

[0055] According to the carbon dioxide concentration apparatus described in (18) 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 liquid chamber and the first liquid chamber. 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.

[0056] (19) In the carbon dioxide concentration apparatus described in (18) above, if the electrical conductivity of the electrolyte is less than a predetermined value, the flow path of the electrolyte may be switched to the third passage, and if the electrical conductivity of the electrolyte is equal to or greater than a predetermined value, the flow path of the electrolyte may be switched to the fourth passage.

[0057] According to the carbon dioxide concentration apparatus described in (19) above, if the electrical conductivity of the electrolyte is below 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 electrical conductivity is above 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.

[0058] (20) Any one of the carbon dioxide concentrators described in (16) to (19) above may be equipped with an electrical conductivity meter for measuring the electrical conductivity of the electrolyte. The electrical conductivity meter may be located inside the anode liquid chamber or the cathode liquid chamber or in a passage connected to the anode liquid chamber or the cathode liquid chamber.

[0059] According to the carbon dioxide concentration apparatus described in (20) above, the electrical conductivity of the electrolyte can be accurately determined in real time, so switching based on electrical conductivity can be performed accurately and quickly.

[0060] (21) In the carbon dioxide concentrator described in (20) above, a gas-liquid separator for separating the electrolyte and carbon dioxide from each other is provided on the passage through which the electrolyte discharged from the first liquid chamber flows, and the electrical conductivity meter may be located downstream of the gas-liquid separator in the passage.

[0061] In a carbon dioxide concentrator, a gas containing carbon dioxide is generated from the electrolyte in the first liquid chamber, and a mixture of this gas and the electrolyte is discharged from the first liquid chamber. With the above configuration, the electrical conductivity can be measured after separating the gas and the electrolyte using a gas-liquid separator, so the electrical conductivity of the electrolyte discharged from the first liquid chamber can be measured more accurately, and the degree of reaction of the electrolyte can be estimated with greater precision.

[0062] This disclosure will be described in detail with reference to drawings illustrating embodiments thereof.

[0063] (First Embodiment) Figure 1 is a schematic diagram of a carbon dioxide concentration apparatus 1. The carbon dioxide concentration apparatus 1 is a device for concentrating and recovering carbon dioxide from a raw material gas G1 containing low concentrations of carbon dioxide. The carbon dioxide concentration apparatus 1 comprises an absorption tower 10, a concentration unit 20, a gas-liquid separation unit 30, and a control device 40.

[0064] 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.

[0065] 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.

[0066] 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%.

[0067] 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 27 (first liquid chamber), an electrolyte membrane 231, and a cathode liquid chamber 28 (second liquid chamber). Electrolyte S is supplied to the anode liquid chamber 27 and the cathode liquid chamber 28.

[0068] 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.

[0069] 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 231. 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.

[0070] 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.

[0071] The carbon dioxide concentrator 1 is equipped with passages 60 that connect the various components of the carbon dioxide concentrator 1. The passages 60 include the first passage 601 to the sixth passage 606. The carbon dioxide concentrator 1 circulates and utilizes the electrolyte S within the carbon dioxide concentrator 1 using a circulation system formed by the passages 60. The composition of the electrolyte S may change depending on the circulation state. Hereinafter, for convenience, the electrolyte S will be referred to as electrolyte S1, electrolyte S2, and electrolyte S3, depending on its state as needed.

[0072] 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).

[0073] 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.

[0074] 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 packing material made of porcelain or metal mesh.

[0075] 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.

[0076] 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.

[0077] Each electrolyte unit 23 comprises an electrolyte membrane 231, an anode liquid chamber 27 located on the anode 22 side via the electrolyte membrane 231, and a cathode liquid chamber 28 located on the cathode 24 side. Multiple electrolyte units 23 are stacked with an intermediate layer 29 in between, forming a laminate.

[0078] The anode plate 21 includes 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.

[0079] 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.

[0080] The configuration of the anode plate 21 is not limited, and for example, it may be constructed by stacking an end plate, a current collector plate, and a plate member having an anode gas chamber 211 on one side in that order.

[0081] The cathode plate 25 includes a cathode gas chamber 251 and a second outlet 252 for discharging gas G4 containing hydrogen. The cathode gas chamber 251 functions as a gas flow path for the gas G4. The gas G4 generated in the cathode 24 is discharged from the second outlet 252 through the cathode gas chamber 251. 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.

[0082] 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.

[0083] 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 the cathode plate 25 are connected to the power supply 26 via wiring.

[0084] 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.

[0085] 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.

[0086] The anode 22 is an electrode that generates protons from hydrogen in gas G3. The 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 27 is in contact with the surface of the 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.

[0087] 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.

[0088] The anode gas diffusion layer 222 is made 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 materials for 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, for example, a sintered body of metal fibers, a sintered body of powdered metal, a metal mesh, or a foamed metal body. The metal may be a titanium alloy or stainless steel.

[0089] 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.

[0090] 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 28 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 supporting fine particles of the cathode catalyst in a highly dispersed manner on the cathode gas diffusion layer 242.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] A polymer membrane having ion exchange groups may be provided between the anode 22 and the anode liquid chamber 27, and between the cathode 24 and the cathode liquid chamber 28, at least one of these. 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 toward the electrode while maintaining the transfer of charge.

[0095] The electrolyte unit 23 comprises an anode liquid chamber 27, an electrolyte membrane 231, and a cathode liquid chamber 28. Each electrolyte unit 23 has the same configuration.

[0096] The electrolyte membrane 231 is a cation exchange membrane (CEM) and is composed of an electrolyte material having cationic conductivity. Examples of electrolyte membranes 231 include fluorine-based cation exchange membranes such as perfluorosulfonic acid-based membranes.

[0097] The anode liquid chamber 27 is composed of, for example, a roughly rectangular parallelepiped frame made of resin. The anode liquid chamber 27 includes a third supply port 275 provided at the bottom, a third outlet port 276 provided at the top, and an anode liquid flow path 271 formed between the third supply port 275 and the third outlet port 276. Electrolyte S2, which has absorbed carbon dioxide, is supplied to the third supply port 275. The electrolyte S2 desorbs (generates) carbon dioxide as it flows through the anode liquid flow path 271. The third outlet port 276 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 275. In the anode liquid flow path 271, gas G2 and electrolyte S flow from the third supply port 275 (inlet) to the third outlet port 276 (outlet).

[0098] The anode liquid channel 271 is a space formed between the anode catalyst layer 221 and the electrolyte membrane 231. The anode liquid channel 271 is separated from the outside by a frame that constitutes the anode liquid chamber 27. The anode catalyst layer 221 is arranged so that when the electrolyte S fills the space, the entire surface of one side of the anode catalyst layer 221 is in contact with the electrolyte S. The anode liquid channel 271 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.

[0099] The shape of the anode liquid chamber 27 and the positions of the third supply port 275 and the third discharge port 276 can be set as appropriate.

[0100] The cathode liquid chamber 28 is composed of, for example, a roughly rectangular parallelepiped frame made of resin. The cathode liquid chamber 28 includes a fourth supply port 285 provided at the top, a fourth outlet port 286 provided at the bottom, and a cathode liquid flow path 281 formed between the fourth supply port 285 and the fourth outlet port 286. The electrolyte S3 after carbon dioxide has been generated is supplied to the fourth supply port 285. The fourth outlet port 286 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 285. In the cathode liquid flow path 281, the electrolyte S flows from the fourth supply port 285 (inlet) to the fourth outlet port 286 (outlet).

[0101] The cathode liquid channel 281 is a space formed between the electrolyte membrane 231 and the cathode catalyst layer 241. The cathode liquid chamber 28 is separated from the outside by the frame that constitutes the cathode liquid channel 281. 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 281 may also be equipped with a spacer, similar to the anode liquid channel 271.

[0102] Each cathode liquid chamber 28 is equipped with a pH sensor 8 for measuring the pH of the electrolyte S within the cathode liquid chamber 28. The pH sensor 8 is preferably located near the fourth outlet 286 within the cathode liquid chamber 28 so as to measure the pH of the electrolyte S as it is discharged from the cathode liquid chamber 28. The pH sensor 8 measures the pH at predetermined time intervals.

[0103] Alternatively, the pH sensor 8 may be provided in the first passage 601 connected to the fourth outlet 286 of the cathode liquid chamber 28. The pH sensor 8 may be provided near one end of the first passage 601, inside the end connected to the fourth outlet 286. The area near the end is, for example, the region between the end of the first passage 601 connected to the fourth outlet 286 and the second switching valve V2, which will be described later.

[0104] Figure 2 shows an example in which a pH sensor 8 is provided in each cathode liquid chamber 28. Alternatively, the pH sensor 8 may be provided in the first passage 601 connected to the fourth outlet 286 of at least one of the multiple cathode liquid chambers 28 or to the fourth outlet 286 of at least one cathode liquid chamber 28.

[0105] In the concentration section 20, one adjacent electrolyte unit 23 and the other electrolyte unit 23 are stacked in the same orientation with an intermediate layer 29 in between. One surface of the intermediate layer 29 contacts the cathode liquid chamber 28 of one electrolyte unit 23, and the other surface of the intermediate layer 29 contacts the anode liquid chamber 27 of the other electrolyte unit 23. The intermediate layer 29 supplies protons supplied from the cathode liquid chamber 28 of one electrolyte unit 23 to the anode liquid chamber 27 of the adjacent other electrolyte unit 23.

[0106] The intermediate layer 29 includes a catalyst layer 291 containing a catalyst and a gas diffusion layer 292. The catalyst layer 291 is formed on both surfaces of the gas diffusion layer 292. The catalyst layer 291 may also be constructed by supporting fine particles of the catalyst in a highly dispersed manner on the surface of the gas diffusion layer 292.

[0107] 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.

[0108] The gas diffusion layer 292 is made of a porous material and has electrical conductivity and gas diffusivity. The gas diffusion layer 292 uniformly diffuses hydrogen molecules supplied from the catalyst layer 291 in contact with the cathode liquid chamber 28 to the catalyst layer 291 in contact with the anode liquid chamber 27. The material constituting the gas diffusion layer 292 is the same as that of the anode gas diffusion layer 222, and is preferably carbon paper.

[0109] The method for producing the intermediate layer 29 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 292 and drying it.

[0110] The intermediate layer 29 may include a leakage suppression section (not shown) to suppress the leakage of liquid from the anode liquid chamber 27 and the cathode liquid chamber 28 to the intermediate layer 29. 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 291 and gas diffusion layers 292.

[0111] Figures 1 and 2 show a configuration in which electrolyte units 23 are stacked using an intermediate layer 29 having a gas diffusion layer 292 with catalyst layers 291 supported on both sides. The intermediate layer 29 only needs to be capable of supplying protons from the cathode liquid chamber 28 to the anode liquid chamber 27. The intermediate layer 29 may be, for example, a bipolar membrane formed by laminating a cation exchange membrane and an anion exchange membrane. An intermediate layer 29 using a gas diffusion layer and an intermediate layer 29 using a bipolar membrane may be used in combination.

[0112] The gas-liquid separation unit 30 performs gas-liquid separation by, for example, a water displacement method or a gravity separation method. A gas-liquid mixture of gas G2 discharged from the anode liquid chamber 27 and electrolyte S3 is supplied to the gas-liquid separation unit 30. 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.

[0113] 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.

[0114] The passage configuration in the carbon dioxide concentration device 1 will now be described. The carbon dioxide concentration device 1 includes passages 60, including the first passage 601 to the sixth passage 606.

[0115] The fifth passage 605 connects the liquid outlet 15 of the absorption tower 10 to the third supply port 275 of the anode liquid chamber 27. The fifth passage 605 flows the electrolyte S2 from the absorption tower 10 to the anode liquid chamber 27. The fifth passage 605 branches into multiple branches at the first branching point 605a, each connected to the third supply port 275 of each anode liquid chamber 27.

[0116] The sixth passage 606 connects the third outlet 276 of the anode liquid chamber 27 to the gas-liquid separation unit 30. The sixth passage 606 allows the electrolyte S3 and gas G4 to flow from the anode liquid chamber 27 to the gas-liquid separation unit 30. The upstream side of the sixth passage 606 branches out to correspond to each of the third supply ports 275 and merges at the first confluence point 606a.

[0117] The third passage 603 connects the gas-liquid separation unit 30 to the fourth supply port 285 of the cathode liquid chamber 28. The third passage 603 allows the electrolytes S3 and S4 to flow from the gas-liquid separation unit 30 to the cathode liquid chamber 28. The third passage 603 branches into multiple branches at the second branching point 603a, each connected to the fourth supply port 285 of each cathode liquid chamber 28.

[0118] A fourth passage 604 is connected upstream of the second branching point 603a of the third passage 603. A first switching valve V1 is provided at the connection point between the third passage 603 and the fourth passage 604. One end of the fourth passage 604 is connected to the first switching valve V1, and the other end is connected upstream of the first branching point 605a of the fifth passage 605.

[0119] The first switching valve V1 is composed of a known solenoid valve or the like. The first switching valve V1 switches the flow path of the electrolyte S3 discharged from the gas-liquid separation unit 30 between the third passage 603 and the fourth passage 604. That is, the first switching valve V1 switches between a state in which the upstream side of the third passage 603 is connected to the downstream side of the third passage 603 and a state in which the upstream side of the third passage 603 is connected to the fourth passage 604. The first switching valve V1 is an example of a switching unit that switches the flow path of the electrolyte between the third passage 603 and the fourth passage 604.

[0120] The first passage 601 connects the fourth outlet 286 of the cathode liquid chamber 28 to the absorption tower 10. The first passage 601 flows the electrolyte S4 from the cathode liquid chamber 28 to the absorption tower 10. The upstream side of the first passage 601 branches into multiple paths corresponding to each of the fourth outlets 286, and these branches merge at the second confluence point 601a.

[0121] The second passage 602 is connected downstream of the second confluence point 601a of the first passage 601. A second switching valve V2 is provided at the connection point between the first passage 601 and the second passage 602. One end of the second passage 602 is connected to the second switching valve V2, and the other end is connected downstream of the first switching valve V1 of the third passage 603 and upstream of the second branching point 603a.

[0122] The second switching valve V2 is composed of a known solenoid valve or the like. The second switching valve V2 can switch the flow path of the electrolyte S4 discharged from the cathode liquid chamber 28 between the first passage 601 and the second passage 602. That is, the second switching valve V2 switches between a state in which the upstream side of the first passage 601 is connected to the downstream side of the first passage 601 and a state in which the upstream side of the first passage 601 is connected to the second passage 602. The second switching valve V2 is an example of a switching unit that switches the flow path of the electrolyte between the first passage 601 and the second passage 602.

[0123] The absorption tower 10, the fifth passage 605, the anode liquid chamber 27, the sixth passage 606, the gas-liquid separation unit 30, the third passage 603, the cathode liquid chamber 28, and the first passage 601 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.

[0124] Furthermore, the cathode liquid chamber 28, a portion of the first passage 601, the second passage 602, and a portion of the third passage 603 constitute a second circulation system for the electrolyte S4. Through the second circulation system, the electrolyte S4 is discharged from the cathode liquid chamber 28 and then supplied back to the cathode liquid chamber 28. The anode liquid chamber 27, the sixth passage 606, the gas-liquid separation unit 30, a portion of the third passage 603, the fourth passage 604, and a portion of the fifth passage 605 constitute a third circulation system for the electrolyte S3. Through the third circulation system, the electrolyte S3 is discharged from the anode liquid chamber 27 and then supplied back to the anode liquid chamber 27.

[0125] The first passage 601 to the sixth passage 606 are not particularly limited, and known piping and the like can be used as appropriate. Each of the first passage 601 to the sixth passage 606 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 measuring equipment such as a gas sensor for detecting the concentration of the gas flowing through the passage.

[0126] The control device 40 is a computer that controls the operation of the carbon dioxide concentration device 1. 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 V1, the second switching valve V2, 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 V1, the second switching valve V2, and various control devices to control their operation.

[0127] Figure 3 is an explanatory diagram illustrating the operation of the carbon dioxide concentrator 1. The operation of the carbon dioxide concentrator 1 will be explained using Figure 3. For the sake of simplicity, Figure 3 shows an example in which two electrolyte units 23 are stacked.

[0128] A gas G1 containing a low concentration of carbon dioxide is supplied to the absorption tower 10, along with an electrolyte S1.

[0129] 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.

[0130] The absorbent solution contained in the 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, and an aqueous solution of an alkali metal compound is preferred.

[0131] 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.

[0132] Examples of amine compounds include basic amines such as monoethanolamine, diethanolamine, diisopropanolamine, methyldiethanolamine, and triethanolamine. The alkaline aqueous solution may be used individually or in combination of two or more types.

[0133] Examples of electrolytes included in the electrolyte solution S1 include potassium chloride and sodium chloride, with potassium chloride being preferred. The electrolyte may be used individually or in combination of two or more types. By incorporating an electrolyte into the electrolyte solution S1, the voltage required for electrodialysis can be reduced. Alternatively, the electrolyte solution S1 may not contain an electrolyte, or it may contain at least an absorbent solution.

[0134] In this embodiment, the electrolyte S1 is assumed to be a mixed solution (KOH-KCl solution) of potassium hydroxide aqueous solution as an absorbent and potassium chloride aqueous solution as an electrolyte solution.

[0135] In the absorption tower 10, the carbon dioxide absorption reaction represented by the following reaction equations (1) and (2) proceeds, and the electrolyte S2 (KHCO) absorbs carbon dioxide. 3 A KCl solution is obtained. In the electrolyte S2, carbon dioxide is converted into bicarbonate ions (HCO3). - ) can be formed. The obtained electrolyte S2 is supplied to the concentration unit 20. 2KOH + CO 2 →K2CO 3 +H2O...(1) K2CO 3 +H2O+CO 2 → 2KHCO 3 ... (2)

[0136] The electrolyte solution S2 (KHCO 3 -KCL solution) that has absorbed carbon dioxide may be an electrolyte solution in which KOH has completely reacted to form KHCO 3 or may be an electrolyte solution that partially contains K2CO3, which is the product of the above reaction formula (1).

[0137] In the concentration unit 20, a gas G3 containing hydrogen is supplied to the anode gas chamber 211, an electrolyte solution S2 (KHCO 3 -KCL solution) that has absorbed carbon dioxide is supplied to the anode liquid chamber 27, and an electrolyte solution S3 (KCL solution) after carbon dioxide has been generated is supplied to the cathode liquid chamber 28. When a voltage is applied from the power source 26 to the anode 22 and the cathode 24, the following reaction occurs.

[0138] At the anode 22, gas G3 is supplied from the anode gas chamber 211. Gas G3 is supplied from the anode gas diffusion layer 222 to the anode catalyst layer 221. At the anode 22, hydrogen molecules in gas G3 are separated into protons (H + ) and electrons by the reaction represented by the following reaction formula (3). Protons (H + ) generated in the anode catalyst layer 221 move to the anode liquid chamber 27 adjacent to the anode 22. H 2 → 2H + + 2e - ... (3)

[0139] In the anode liquid chamber 27, the pH of the KHCO + solution in the anode liquid chamber 27 decreases due to the protons (H 3 ) supplied from the anode catalyst layer 221. In the anode liquid chamber 27, due to the decrease in pH, 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 solution move through the inside of the electrolyte membrane 231 to the cathode liquid chamber 28. HCO3 - + H + ⇔ CO 2 + H2O... (4)

[0140] In the anode liquid chamber 27, the electrolyte S2 flowing through the anode liquid chamber 27 becomes electrolyte S3, from which carbon dioxide has been removed by the carbon dioxide desorption reaction of reaction equation (4) above, and is discharged from the anode liquid chamber 27. After carbon dioxide is generated, the electrolyte S3 becomes a KCl solution mainly composed of potassium chloride. After carbon dioxide is generated, the electrolyte S3 contains KHCO 3 It may also contain. The gas G4 containing carbon dioxide generated in the anode liquid chamber 27 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 the cathode liquid chamber 28, respectively. This yields concentrated carbon dioxide. If the electrolyte S3 discharged from the anode liquid chamber 27 contains a large amount of unreacted electrolyte S2, the electrolyte S3 separated in the gas-liquid separation unit 30 may be supplied back to the anode liquid chamber 27 as electrolyte S2. The electrolyte S3 (electrolyte S2) supplied back to the anode liquid chamber 27 generates carbon dioxide through the desorption reaction of reaction equation (4) described above.

[0141] In the cathode liquid chamber 28, potassium ions (K) in the KCl solution within the cathode liquid chamber 28 + As the number of protons increases, + ) is supplied to the intermediate layer 29. Protons (H + In response to the consumption of ), the pH of the KCl solution rises, and the absorbent solution (KOH) is regenerated. After the absorbent solution is regenerated, the electrolyte S4 becomes a KOH-KCl solution containing the absorbent solution and the electrolyte solution. The electrolyte S4 is discharged from the cathode liquid chamber 28 and circulated back to the absorption tower 10 as electrolyte S1. If the electrolyte S1 discharged from the cathode liquid chamber 28 contains a large amount of unreacted electrolyte S3, the electrolyte S4 may be supplied back to the cathode liquid chamber 28. The electrolyte S4 supplied back to the cathode liquid chamber 28 regenerates the absorbent solution.

[0142] Protons (H) supplied to the intermediate layer 29 + The hydrogen molecules are adsorbed onto the catalyst layer 291 on the anode 22 side and then supplied to the gas diffusion layer 292 as hydrogen molecules. The hydrogen molecules pass through the gas diffusion layer 292 and are converted into protons (H) in the catalyst layer 291 on the cathode 24 side. + It is converted into a proton (H) that passes through the intermediate layer 29. + ) is supplied to the anode liquid chamber 27 of the adjacent electrolyte unit 23.

[0143] 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 28 adjacent to the cathode 24.

[0144] Protons (H) supplied to cathode 24 + ) is adsorbed onto the cathode catalyst layer 241. At the cathode 24, hydrogen molecules are again generated by the reaction shown in the following reaction equation (5). 2H + +2e - →H 2 ... (5)

[0145] The hydrogen produced at cathode 24 may be hydrogen produced by the reduction reaction of water, as shown in the following reaction equation (6). Electrolyte S2 (KHCO 3 Hydrogen can be generated when water contained in the KCl solution or electrolyte S3 (KCl solution) is reduced in the cathode catalyst layer 241. 2H2O + 2e - →H2 + 2OH - ... (6)

[0146] 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 more.

[0147] In the carbon dioxide concentrator 1, the flow path of the electrolyte S is switched by switching the state of the first switching valve V1 and the second switching valve V2 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 27 will be relatively high, and the pH value of the electrolyte S in the cathode liquid chamber 28 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 27 will be relatively low, and the pH value of the electrolyte S in the cathode liquid chamber 28 will be relatively high. In particular, in the cathode liquid chamber 28, HCO3 - In contrast to the anode liquid chamber 27, where a buffering action occurs due to the absorption solution containing a large amount of , the pH value of the cathode liquid chamber 28 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 liquid chamber 28, the progress of the reaction can be accurately determined.

[0148] If the pH value of the electrolyte S in the cathode liquid chamber 28, measured by the pH sensor 8, is above a preset threshold, the electrolyte S3 discharged from the anode liquid chamber 27 is supplied to the cathode liquid chamber 28 via the sixth passage 606, the gas-liquid separation unit 30, and the third passage 603. The electrolyte S4 discharged from the cathode liquid chamber 28 is supplied to the absorption tower 10 as electrolyte S1 via the first passage 601, and carbon dioxide is absorbed into the electrolyte S1 again.

[0149] If the pH value of the electrolyte S in the cathode liquid chamber 28 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 27 is resupplied to the anode liquid chamber 27 as electrolyte S2 via the sixth passage 606, the gas-liquid separation unit 30, part of the third passage 603, part of the fourth passage 604 and part of the fifth passage 605. By returning the electrolyte S3 to the anode liquid chamber 27, it is prevented that unreacted electrolyte S3 flows into the cathode liquid chamber 28.

[0150] Furthermore, if the pH value is below the above threshold, the electrolyte S4 discharged from the cathode liquid chamber 28 is supplied back to the cathode liquid chamber 28 via a portion of the first passage 601, the second passage 602, and a portion of the third passage 603. By returning the electrolyte S4 to the cathode liquid chamber 28, it is prevented that unreacted electrolyte S4 flows into the absorption tower 10.

[0151] Since the electrolyte S4 contains regenerated KOH, when the electrolyte S4 discharged from the cathode liquid chamber 28 is circulated to the anode liquid chamber 27, a neutralization reaction between KOH and protons occurs in the anode liquid chamber 27, 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 27 and the cathode liquid chamber 28, thereby suppressing the aforementioned neutralization reaction and increasing the efficiency of carbon dioxide production.

[0152] The switching of the first switching valve V1 and the second switching valve V2 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 1 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 V1 so that the upstream side of the third passage 603 is connected to the downstream side of the third passage 603, and controls the second switching valve V2 so that the upstream side of the first passage 601 is connected to the downstream side of the first passage 601.

[0153] 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 V1 to connect the upstream side of the third passage 603 to the fourth passage 604, and controls the second switching valve V2 to connect the upstream side of the first passage 601 to the second passage 602. It is preferable that the switching timing of the first switching valve V1 and the second switching valve V2 are synchronized.

[0154] If the carbon dioxide concentrator 1 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 V1 to connect the upstream side of the third passage 603 to the downstream side of the third passage 603, and controls the second switching valve V2 to connect the upstream side of the first passage 601 to the downstream side of the first passage 601. Alternatively, the flow path of the electrolyte S may be switched based on the measured value of any one representative pH sensor 8.

[0155] When the pH of the electrolyte S flowing through the anode chamber 27 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 27 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 27 to the cathode chamber 28. If the pH value of the electrolyte S in the anode chamber 27 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 27 back to the anode chamber 27 as electrolyte S2, and to supply the electrolyte S4 discharged from the cathode chamber 28 back to the cathode chamber 28.

[0156] 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 V1 and the second switching valve V2 in accordance with the received switching instruction.

[0157] As described above, the passage configuration of the carbon dioxide concentrator 1 can be any appropriate passage configuration as long as the flow path of the electrolyte S can be switched. For example, the second passage 602 may connect the fourth outlet 286 of the cathode liquid chamber 28 to the third passage or the fourth supply port 285 of the cathode liquid chamber 28. When the second passage 602 is provided, an on-off valve as an example of a switching unit may be provided in both the second passage 602 and the first passage 601, 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 604 may connect the third outlet 276 of the gas-liquid separation unit 30 or the anode liquid chamber 27 to the fifth passage 605 or the third supply port 275 of the anode liquid chamber 27. When the third passage 603 is provided, an on-off valve as an example of a switching unit may be provided in both the third passage 603 and the fourth passage 604, and the flow path of the electrolyte S3 may be switched by controlling the combination of opening and closing of each on-off valve.

[0158] The electrolyte S resupplied to the anode liquid chamber 27 may not pass through the gas-liquid separation section 30. The first passage 601, third passage 603, fifth passage 605, and sixth passage 606, etc., may be provided in multiples corresponding to each liquid chamber, instead of being connected to each liquid chamber by branching paths.

[0159] In the first embodiment, the flow path of the electrolyte S may be switched using an electrical conductivity meter instead of or in addition to the pH sensor 8. The flow path can be switched considering the electrical conductivity which changes in accordance with the degree of reaction of the electrolyte S. The electrical conductivity of the electrolyte S flowing through the anode liquid chamber 27 and the cathode liquid chamber 28 changes in accordance with the degree of reaction of the electrolyte S in the liquid chambers. By measuring the electrical conductivity, the degree of reaction of the electrolyte S in the liquid chambers can be estimated. By using electrical conductivity which shows a linear change in accordance with the degree of reaction of the electrolyte S, the degree of reaction can be estimated easily and accurately.

[0160] (Second Embodiment) Figure 4 is a schematic diagram of the carbon dioxide concentration system 100 of the second embodiment. The carbon dioxide concentration system 100 comprises a carbon dioxide concentration device 1 and a control device 40. The carbon dioxide concentration system 100 is a system for concentrating and recovering carbon dioxide from a gas G1 containing low concentrations of carbon dioxide, which is used as a process gas (raw material gas).

[0161] The carbon dioxide concentrator 1 comprises an absorption tower 10, a concentration unit 20, a gas-liquid separation unit 30, and an electrical conductivity meter 50. The absorption tower 10, the concentration unit 20, and the gas-liquid separation unit 30 are connected by a passage 60, forming a circulation system for the electrolyte S.

[0162] The absorption tower 10 brings gas G1 and electrolyte S into gas-liquid contact, causing carbon dioxide in gas G1 to be absorbed by the electrolyte S.

[0163] 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.

[0164] The absorption tower 10 comprises a main body 11 extending vertically, and a gas supply port 16, a liquid supply port 17, a first gas discharge port 18, and a first liquid discharge port 19 provided on the main body 11. The gas supply port 16 is connected to a gas supply source (not shown).

[0165] Gas G1 is supplied to the gas supply port 16. Gas G1 is supplied into the tower, flows through the tower, and is then discharged from the first gas discharge port 18. Electrolyte S for absorbing carbon dioxide is supplied to the liquid supply port 17. Electrolyte S absorbs carbon dioxide by coming into contact with gas G1 inside the tower. The electrolyte S, which has absorbed carbon dioxide, is discharged from the first liquid discharge port 19.

[0166] The method of bringing the gas G1 and the electrolyte S into contact is not particularly limited. For example, methods include bubbling the gas G1 into the electrolyte S, atomizing the electrolyte S into the gas G1 using a spray or atomizing method, or bringing high-pressure gas G1 and electrolyte S into countercurrent contact in an absorption tower 10 filled with a packing material made of porcelain or metal mesh.

[0167] The concentration unit 20 removes carbon dioxide from the electrolyte S that has absorbed carbon dioxide, generating gas G2 containing carbon dioxide. Gas G2 is concentrated carbon dioxide gas with a higher concentration of carbon dioxide, and contains carbon dioxide at a higher concentration than gas G1. The concentration of carbon dioxide in gas G2 is usually 90 vol% to 100 vol%.

[0168] The concentration unit 20 comprises an electrochemical cell including an anode 22, an electrolyte unit 23, and a cathode 24. The electrolyte unit 23 includes an electrolyte membrane 231, an anode liquid chamber 27, and a cathode liquid chamber 28. Electrolyte S is supplied to the anode liquid chamber 27 and the cathode liquid chamber 28.

[0169] Although Figure 4 shows two electrolyte units 23, the concentration unit 20 may be equipped with a large number of electrolyte units 23, such as 50 or 100 units, or it may be equipped with just one electrolyte unit 23.

[0170] The concentration unit 20 removes carbon dioxide from the electrolyte S that has absorbed carbon dioxide, and regenerates the electrolyte in the electrolyte S by allowing specific ions to pass through the electrolyte membrane 231 using electrodialysis. In this embodiment, the concentration unit 20 is an electrochemical hydrogen pump, and a configuration in which protons are generated by the oxidation-reduction reaction of hydrogen will be described.

[0171] The anode 22 of the enrichment unit 20 is supplied with gas G3 containing hydrogen. The cathode 24 generates gas G4, which is at a higher pressure than gas G3, through the hydrogen pressurization operation of the hydrogen pump. Details of the enrichment unit 20 will be described later.

[0172] 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.

[0173] The gas-liquid separation unit 30 is equipped with a device that performs gas-liquid separation by means of, for example, water displacement, gravity separation, or hollow fiber membrane. A gas-liquid mixture of gas G2 discharged from the anode liquid chamber 27 and electrolyte S is supplied to the gas-liquid separation unit 30. The gas-liquid separation unit 30 separates the gas G2 and electrolyte S in the mixture, and after separation, discharges the gas G2 from the second gas outlet 301 and the electrolyte S from the second liquid outlet 302. The gas G2 discharged from the second gas outlet 301 is recovered in a carbon dioxide recovery unit (not shown).

[0174] Alternatively, the gas-liquid separation unit 30 may be connected to another device (not shown) and configured 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.

[0175] The conductivity meter 50 is a measuring instrument for measuring the electrical conductivity of the electrolyte S flowing through the carbon dioxide concentrator 1. The conductivity meter 50 outputs the measured value obtained from the measurement to the control device 40.

[0176] The control device 40 is a computer that controls the operation of the carbon dioxide concentration unit 1. 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 control device 40 is connected to the carbon dioxide concentration unit 1 by wire or wireless connection. The control device 40 outputs control signals to the carbon dioxide concentration unit 1 according to the measured values ​​obtained from the electrical conductivity meter 50, thereby controlling the operation of the carbon dioxide concentration unit 1.

[0177] The control device 40 may be located away from the carbon dioxide concentration device 1. The control device 40 may be connected to the carbon dioxide concentration device 1 via a communication network such as the Internet or a LAN (Local Area Network), and may send and receive measured values ​​and control information to and from the carbon dioxide concentration device 1 via the communication network. The control device 40 may also send and receive various information to and from the carbon dioxide concentration device 1 via a computer located near the carbon dioxide concentration device 1.

[0178] Figure 5 is a cross-sectional view showing an example of the configuration of the concentration unit 20 of the second embodiment. As shown in Figures 4 and 5, 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, and a cathode plate 25 having a cathode gas chamber 251.

[0179] A power supply 26 is connected to the anode 22 and cathode 24. The power supply 26 applies a voltage between 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. The power supply 26 may be a battery or a commercial power supply, or it may be power supplied by renewable energy such as solar cells or wind power generation. The concentration unit 20 may be equipped with a current sensor for measuring the current flowing through the concentration unit 20 (electrochemical cell), a voltage sensor for measuring the voltage applied to the electrochemical cell, and the like.

[0180] 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.

[0181] Each electrolyte unit 23 comprises an electrolyte membrane 231, an anode liquid chamber 27 located on the anode 22 side via the electrolyte membrane 231, and a cathode liquid chamber 28 located on the cathode 24 side. Multiple electrolyte units 23 are stacked with an intermediate layer 29 in between, forming a laminate.

[0182] The anode plate 21 includes an anode gas chamber 211 which serves as a flow path for gas G3, and a first supply port 214 into which hydrogen-containing gas G3 is supplied. The anode gas chamber 211 is, for example, a groove-shaped flow path formed on the surface of the anode plate 21, and is arranged to fold back in the region of the surface of the anode plate 21 facing the anode 22. Alternatively, the anode gas chamber 211 may have multiple flow paths or branched paths. Gas G3 is supplied to the anode 22 as it passes through the anode gas chamber 211. The anode plate 21 may also include a first discharge port 215 for discharging the gas G3 that has flowed through the anode gas chamber 211. The anode plate 21 is electrically connected to the anode 22.

[0183] The cathode plate 25 includes a cathode gas chamber 251 which serves as a flow path for gas G4, and a second discharge port 253 for discharging gas G4 containing hydrogen. The cathode gas chamber 251 is, for example, a groove-shaped flow path formed on the surface of the cathode plate 25, and is arranged to fold back within the region of the surface of the cathode plate 25 facing the cathode 24. Alternatively, the cathode gas chamber 251 may have multiple flow paths or branched paths. The gas G4 generated in the cathode 24 is discharged from the second discharge port 253 through the cathode gas chamber 251. The gas G4 discharged from the second discharge port 253 is recovered, for example, by a hydrogen recovery unit (not shown). Alternatively, the second discharge port 253 may be connected to a first supply port 214, and the gas G4 discharged from the second discharge port 253 may be supplied to the anode 22 and used as gas G3. The cathode plate 25 is electrically connected to the cathode 24.

[0184] The configuration of the anode plate 21 and cathode plate 25 is not limited, and for example, they may be constructed by stacking a plate member having a cathode gas chamber 251 or an anode gas chamber 211 on one side, a current collector plate, and an end plate in that order.

[0185] The anode 22 is an electrode that generates protons from hydrogen in gas G3. The 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 27 is in contact with the surface of the 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.

[0186] 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.

[0187] The anode gas diffusion layer 222 is composed of a porous material and has conductivity and gas diffusion properties. 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, for example, a sintered body of metal fibers, a sintered body of powdered metal, a metal mesh, or a foamed metal body. The metal may be a titanium alloy or stainless steel.

[0188] 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 28 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 supporting fine particles of the cathode catalyst in a highly dispersed manner on the cathode gas diffusion layer 242.

[0189] 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.

[0190] 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.

[0191] The method for forming the anode 22 and cathode 24 is not particularly limited. For example, they can be formed by applying a slurry of a liquid composition containing the anode catalyst or cathode catalyst to one surface of the anode gas diffusion layer 222 or the cathode gas diffusion layer 242 and drying it.

[0192] Preferably, the anode 22 and cathode 24 are treated to be water-repellent. The water-repellent treatment is performed, for example, by adding or laminating a water-repellent material such as polytetrafluoroethylene to the anode gas diffusion layer 222 and cathode gas diffusion layer 242, or to the anode catalyst layer 221 and cathode catalyst layer 241. By imparting water repellency to the anode 22 and cathode 24, leakage of liquid from the anode liquid chamber 27 to the anode 22 and leakage of liquid from the cathode liquid chamber 28 to the cathode 24 can be suppressed. Alternatively, leakage of liquid between them may be suppressed by providing a polymer membrane having ion exchange groups between the anode 22 and the anode liquid chamber 27, and between the cathode 24 and the cathode liquid chamber 28. An example of a polymer membrane having ion exchange groups is Nafion®. By providing such a membrane, it is possible to suppress the movement of the liquid in the liquid chamber toward the electrode side while maintaining the transfer of charge.

[0193] Each electrolyte unit 23 has a similar configuration and includes an anode liquid chamber 27, an electrolyte membrane 231, and a cathode liquid chamber 28, respectively.

[0194] The electrolyte membrane 231 is a cation exchange membrane (CEM) and is composed of an electrolyte material having cation conductivity. Examples of electrolyte membranes 231 include fluorine-based cation exchange membranes such as perfluorosulfonic acid-based membranes and hydrocarbon-based cation exchange membranes.

[0195] The anode liquid chamber 27 is composed of a frame with a rectangular, flat frame having an opening in the center. In the anode liquid chamber 27, the opening is located between the anode catalyst layer 221 and the electrolyte membrane 231, and forms a space separated from the outside by the frame surrounding the opening. The space formed by the opening becomes the anode liquid channel 271 through which the electrolyte S flows. The anode liquid chamber 27 is arranged such that when the space is filled with the electrolyte S, the entire surface of one side of the anode catalyst layer 221 is in contact with the electrolyte S. The anode liquid chamber 27 may also be provided with a mesh member at the opening, and the space created by the three-dimensional intersection of the channel forming members becomes the anode liquid channel 271.

[0196] The frame material is preferably an elastic and transparent material, such as resin or rubber. By constructing the frame from an elastic material, the liquid-tightness and airtightness of the anode liquid chamber 27 when stacked are improved.

[0197] A third supply port 272 for supplying electrolyte S is provided at the bottom of the anode liquid chamber 27. A third discharge port 273 for discharging electrolyte S and carbon dioxide gas is provided at the top of the anode liquid chamber 27. The third supply port 272 and the third discharge port 273 are each connected to the anode liquid flow path 271.

[0198] In the anode liquid chamber 27, gas G4 and electrolyte S flow from the third supply port 272 to the third discharge port 273. Electrolyte S, which has absorbed carbon dioxide, is supplied to the third supply port 272. As the electrolyte S flows through the anode liquid flow path 271, it decarbonizes carbon dioxide. The gas-liquid mixture of gas G4 containing the decarbonized carbon dioxide and electrolyte S from which carbon dioxide has been removed flows through the anode liquid chamber 27 and is then discharged from the third discharge port 273.

[0199] The shape of the anode liquid chamber 27 and the positions of the third supply port 272 and the third discharge port 273 can be set as appropriate.

[0200] The cathode liquid chamber 28 is equipped with a frame having the same configuration as the anode liquid chamber 27. The cathode liquid chamber 28 is composed of a frame having a rectangular flat plate-shaped frame with an opening in the center, similar to the anode liquid chamber 27. The space formed by the opening becomes the cathode liquid channel 281 through which the electrolyte S flows. The frame of the cathode liquid chamber 28 may be positioned with its left and right sides reversed compared to the frame of the anode liquid chamber 27.

[0201] A fourth supply port 282 for supplying electrolyte S is provided at the top of the cathode liquid chamber 28, and a fourth discharge port 283 for discharging electrolyte S is provided at the bottom of the cathode liquid chamber 28. The fourth supply port 282 and the fourth discharge port 283 are each connected to the cathode liquid flow path 281.

[0202] In the cathode liquid chamber 28, the electrolyte S flows from the fourth supply port 282 to the fourth discharge port 283. The fourth supply port 282 is supplied with the electrolyte S from which carbon dioxide has been removed. The fourth discharge port 283 discharges the electrolyte S from which the absorbent liquid described later has been regenerated.

[0203] In this embodiment, the anode liquid chamber 27 and the cathode liquid chamber 28 use frames with the same configuration, thereby commonizing components, simplifying assembly, and reducing costs. Alternatively, the anode liquid chamber 27 and the cathode liquid chamber 28 may use separate components.

[0204] As shown in Figure 5, in the concentration unit 20, one adjacent electrolyte unit 23 and the other electrolyte unit 23 are stacked in the same orientation with an intermediate layer 29 in between. One surface of the intermediate layer 29 contacts the cathode liquid chamber 28 of one electrolyte unit 23, and the other surface of the intermediate layer 29 contacts the anode liquid chamber 27 of the other electrolyte unit 23. The intermediate layer 29 supplies protons supplied from the cathode liquid chamber 28 of one electrolyte unit 23 to the anode liquid chamber 27 of the adjacent other electrolyte unit 23.

[0205] The intermediate layer 29 includes a catalyst layer 291 containing a catalyst and a gas diffusion layer 292. The catalyst layer 291 is formed on both surfaces of the gas diffusion layer 292. The catalyst layer 291 may also be formed by supporting fine particles of the catalyst in a highly dispersed manner on the surface of the gas diffusion layer 292.

[0206] The catalyst included in the catalyst layer 291 is the same as the anode catalyst described above, and is preferably platinum. The catalyst may be used alone or in combination of two or more types.

[0207] The gas diffusion layer 292 is composed of a porous material and has electrical conductivity and gas diffusivity. The material constituting the gas diffusion layer 292 is the same as that used for the anode gas diffusion layer 222, and is preferably carbon paper.

[0208] The method for forming the intermediate layer 29 is not particularly limited; for example, it can be formed by applying a slurry of a liquid composition containing a catalyst to the surface of the gas diffusion layer 292 and drying it.

[0209] Figure 5 shows a configuration in which electrolyte units 23 are stacked using an intermediate layer 29 having a gas diffusion layer 292 with catalyst layers 291 supported on both sides. The intermediate layer 29 only needs to be capable of supplying protons from the cathode liquid chamber 28 to the anode liquid chamber 27. The intermediate layer 29 may be, for example, a bipolar membrane formed by laminating a cation exchange membrane and an anion exchange membrane. An intermediate layer 29 using a gas diffusion layer and an intermediate layer 29 using a bipolar membrane may be used in combination.

[0210] The passage configuration in the carbon dioxide concentration device 1 will now be explained. As shown in Figure 4, the carbon dioxide concentration device 1 includes passages 60, including the seventh passage 611 to the eleventh passage 615.

[0211] The seventh passage 611 connects the absorption tower 10 and the anode liquid chamber 27. The seventh passage 611 flows the electrolyte S discharged from the first liquid outlet 19 of the absorption tower 10 to the third supply port 272 of the anode liquid chamber 27. The seventh passage 611 branches into multiple branches at the third branching point 611a, each connected to a different anode liquid chamber 27.

[0212] The eighth passage 612 connects the anode liquid chamber 27 and the cathode liquid chamber 28. The eighth passage 612 flows the electrolyte S and gas G4 discharged from the third discharge port 273 of the anode liquid chamber 27 to the fourth supply port 282 of the cathode liquid chamber 28. The upstream side of the eighth passage 612 branches out to correspond to each anode liquid chamber 27 and merges at the third confluence point 612a. The downstream side of the eighth passage 612 branches into multiple branches at the fourth branching point 612b and connects to each cathode liquid chamber 28.

[0213] A gas-liquid separation unit 30 is provided on the eighth passage 612, downstream of the third confluence point 612a and upstream of the fourth branching point 612b. The gas-liquid separation unit 30 receives the electrolyte S and gas G4 discharged from the anode liquid chamber 27 via the eighth passage 612. The gas-liquid separation unit 30 discharges the separated electrolyte S into the eighth passage 612 via the second liquid discharge port 302.

[0214] The ninth passage 613 is connected to a portion of the eighth passage 612 that is downstream of the gas-liquid separation section 30 and upstream of the fourth branching point 612b. A third switching valve V3 is provided at the connection point between the eighth passage 612 and the ninth passage 613. One end of the ninth passage 613 is connected to the third switching valve V3, and the other end is connected to a portion of the seventh passage 611 that is upstream of the third branching point 611a.

[0215] The tenth passage 614 connects the cathode liquid chamber 28 and the absorption tower 10. The tenth passage 614 flows the electrolyte S4 discharged from the fourth discharge port 283 of the cathode liquid chamber 28 to the liquid supply port 17 of the absorption tower 10. The upstream side of the tenth passage 614 branches into multiple sections corresponding to each cathode liquid chamber 28, and these branches merge at the fourth confluence point 614a.

[0216] The 11th passage 615 is connected to the portion of the 10th passage 614 downstream of the 4th confluence point 614a. A 4th switching valve V4 is provided at the connection point between the 10th passage 614 and the 11th passage 615. One end of the 11th passage 615 is connected to the 4th switching valve V4, and the other end is connected to the portion of the 8th passage 612 downstream of the 3rd switching valve V3 and upstream of the 4th branch point 612b.

[0217] The third switching valve V3 and the fourth switching valve V4 are composed of known solenoid valves or the like. The third switching valve V3 and the fourth switching valve V4 can switch the flow path in response to a signal provided by the control device 40, and selectively allow fluid to flow through a specific flow path. The third switching valve V3 and the fourth switching valve V4 may also have the function of flow control valves that adjust the flow rate of the fluid passing through when they are in communication. The third switching valve V3 and the fourth switching valve V4 are examples of switching units that switch the flow path of the electrolyte S.

[0218] The third switching valve V3 can switch the flow path of the electrolyte S discharged from the anode liquid chamber 27 and the gas-liquid separation unit 30 between the eighth passage 612 and the ninth passage 613. In other words, the third switching valve V3 switches between a first state in which the upstream side of the eighth passage 612 is connected to the downstream side of the eighth passage 612 and the electrolyte S discharged from the anode liquid chamber 27 is supplied to the cathode liquid chamber 28, and a second state in which the upstream side of the eighth passage 612 is connected to the ninth passage 613 and the electrolyte S discharged from the anode liquid chamber 27 is supplied to the anode liquid chamber 27.

[0219] The fourth switching valve V4 can switch the flow path of the electrolyte S discharged from the cathode liquid chamber 28 between the tenth passage 614 and the eleventh passage 615. In other words, the fourth switching valve V4 switches between a first state in which the upstream side of the tenth passage 614 is connected to the downstream side of the tenth passage 614 and the electrolyte S discharged from the cathode liquid chamber 28 is supplied to the absorption tower 10, and a second state in which the upstream side of the tenth passage 614 is connected to the eleventh passage 615 and the electrolyte S discharged from the cathode liquid chamber 28 is supplied to the cathode liquid chamber 28.

[0220] By switching the third switching valve V3 and the fourth switching valve V4 to the first state, the first circulation system for the electrolyte S is established. 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.

[0221] Switching the third switching valve V3 and the fourth switching valve V4 to the second state constitutes a second circulation system for the electrolyte S. Through the second circulation system, the electrolyte S is discharged from the anode liquid chamber 27 and then supplied back to the anode liquid chamber 27, and is discharged from the cathode liquid chamber 28 and then supplied back to the cathode liquid chamber 28.

[0222] An electrical conductivity meter 50 for measuring the electrical conductivity of the electrolyte S is provided in at least one of the eighth passage 612 and the tenth passage 614. Preferably, the electrical conductivity meter 50 is located downstream of the gas-liquid separation section 30 and upstream of the third switching valve V3 in the eighth passage 612, or downstream of the fourth confluence point 614a and upstream of the fourth switching valve V4 in the tenth passage 614. By placing the electrical conductivity meter 50 in the above position, the electrical conductivity of the electrolyte S from the time it is discharged from the anode liquid chamber 27 or the cathode liquid chamber 28 until it is supplied to the next circulation destination can be measured, and the electrical conductivity of the electrolyte S without gas G2 can also be measured. The carbon dioxide concentrator 1 may also be equipped with one electrical conductivity meter 50 corresponding to either the electrolyte S discharged from the anode liquid chamber 27 or the electrolyte S discharged from the cathode liquid chamber 28.

[0223] The location of the conductivity meter 50 is not limited to the eighth passage 612 and the tenth passage 614. The conductivity meter 50 may be provided, for example, inside the anode liquid chamber 27 or the cathode liquid chamber 28, or at the third outlet 273 or the fourth outlet 283. The location of the conductivity meter 50 inside the anode liquid chamber 27 or the cathode liquid chamber 28 is preferably downstream of the anode liquid flow path 271 or the cathode liquid flow path 281, and more preferably near the third outlet 273 or the fourth outlet 283. Multiple conductivity meters 50 may be provided.

[0224] Pumps P1 and P2 are provided in the seventh passage 611 and the tenth passage 614, respectively. By driving pumps P1 and P2, the electrolyte S is delivered. Pumps for delivering the fluid may also be provided in passages other than the seventh passage 611 and the tenth passage 614.

[0225] The seventh passage 611 to the eleventh passage 615 may be equipped with control devices such as control valves to control the flow rate of fluid flowing through the passage, and measuring devices such as flow meters to measure the flow rate of fluid flowing through the passage, and gas sensors to detect the concentration of gas flowing through the passage, as needed.

[0226] As described above, the passage configuration of the carbon dioxide concentrator 1 can be any appropriate passage configuration as long as it is possible to circulate the electrolyte S and switch the flow path. For example, the 11th passage 615 may connect the 4th discharge port 283 of the cathode liquid chamber 28 to the 8th passage 612 or the 4th supply port 282 of the cathode liquid chamber 28. The 9th passage 613 may connect the 3rd discharge port 273 of the gas-liquid separation unit 30 or the anode liquid chamber 27 to the 11th passage 615 or the 3rd supply port 272 of the anode liquid chamber 27. The 7th passage 611, the 8th passage 612, and the 10th passage 614 may be provided in multiples corresponding to each liquid chamber instead of being connected to each liquid chamber by branching paths. Switching the flow path of the electrolyte S may be performed by controlling the combination of opening and closing of each on / off valve provided in each passage.

[0227] The carbon dioxide concentrator 1 may be configured to circulate the electrolyte S in either the anode liquid chamber 27 (which has a ninth passage 613) or the cathode liquid chamber 28 (which has an eleventh passage 615), thereby circulating the electrolyte S in either one of the liquid chambers.

[0228] Figure 6 is an explanatory diagram illustrating the operation of the carbon dioxide concentrator 1 of the second embodiment. The main operation of the carbon dioxide concentrator 1 of the second embodiment is the same as that of the carbon dioxide concentrator 1 of the first embodiment, so a detailed explanation is omitted.

[0229] As described above, the carbon dioxide concentrator 1 continuously absorbs and desorbs carbon dioxide by circulating an electrolyte solution, which is a mixed solution of potassium hydroxide, potassium chloride, and potassium bicarbonate. By allowing cations to permeate through the electrolyte membrane 231 and the intermediate layer 29 and regenerating the absorbent solution, the electrolyte solution S can be circulated without adding solutes during the circulation process.

[0230] In this embodiment, the carbon dioxide concentrator 1 is configured to generate protons by supplying a hydrogen-containing gas to the anode, but the carbon dioxide concentrator 1 may use other reactions, such as a water electrolysis reaction. The carbon dioxide concentrator 1 is only required to include an anode that generates protons and a cathode that generates hydrogen or hydroxide ions, and to be capable of generating carbon dioxide gas from the electrolyte supplied to the anode liquid chamber. The gas G4 generated in the cathode 24 is not limited to being at a higher pressure than gas G3. The cathode liquid chamber 28 adjacent to the cathode 24 is not limited to being located between the electrolyte membrane 231 and the cathode 24, but may be in the order of electrolyte membrane 231, cathode 24, and cathode liquid chamber 28.

[0231] In the carbon dioxide concentration system 100, the operation of the carbon dioxide concentration device 1 is optimized by switching the third switching valve V3 and the fourth switching valve V4 based on the electrical conductivity of the electrolyte S measured by the electrical conductivity meter 50 to control the flow path of the electrolyte S.

[0232] The electrical conductivity of the electrolyte S changes almost linearly in accordance with the progress of the reaction in reaction equation (4) above. As the reaction progresses and the chemical equilibrium in reaction equation (4) shifts to the right, the electrical conductivity of the electrolyte S in the anode chamber 27 decreases linearly, and the electrical conductivity of the electrolyte S in the cathode chamber 28 increases linearly. Therefore, the current reaction rate of the electrolyte S can be estimated by measuring its electrical conductivity.

[0233] The following explanation will use the case where the switching of the flow path is controlled using the electrical conductivity of the electrolyte S discharged from the anode liquid chamber 27 as an example.

[0234] If the electrical conductivity of the electrolyte S discharged from the anode liquid chamber 27 is below a preset threshold, it is presumed that the reaction is proceeding sufficiently, and the third switching valve V3 and the fourth switching valve V4 switch the flow path of the electrolyte S to the first state or maintain the first state. In the first state, the electrolyte S discharged from the anode liquid chamber 27 is supplied to the cathode liquid chamber 28, and the electrolyte S discharged from the cathode liquid chamber 28 is supplied to the absorption tower 10.

[0235] If the electrical conductivity of the electrolyte S discharged from the anode liquid chamber 27 is above a preset threshold, it is presumed that the reaction is not progressing sufficiently, so the third switching valve V3 and the fourth switching valve V4 switch the flow path of the electrolyte S to the second state or maintain the second state. In the second state, the electrolyte S discharged from the anode liquid chamber 27 is supplied to the anode liquid chamber 27, and the electrolyte S discharged from the cathode liquid chamber 28 is supplied to the cathode liquid chamber 28.

[0236] The threshold electrical conductivity used for the determination can be determined by considering factors such as the composition of the electrolyte S and the required operating efficiency of the carbon dioxide concentrator 1.

[0237] The switching of the third switching valve V3 and the fourth switching valve V4 is performed automatically by, for example, the control device 40. During the operation of the carbon dioxide concentrator 1, the control device 40 acquires the electrical conductivity of the electrolyte S in the anode liquid chamber 27, measured by the electrical conductivity meter 50, at predetermined or appropriate time intervals.

[0238] If the control device 40 determines that the acquired electrical conductivity is below the threshold, it generates a signal to instruct the third switching valve V3 to open or close in order to connect the upstream side of the eighth passage 612 to the downstream side of the eighth passage 612. The control device 40 also generates a signal to instruct the fourth switching valve V4 to open or close in order to connect the upstream side of the tenth passage 614 to the downstream side of the tenth passage 614.

[0239] If the control device 40 determines that the acquired electrical conductivity is equal to or greater than the threshold value, it generates a signal to instruct the third switching valve V3 to open or close so that the upstream side of the eighth passage 612 is connected to the ninth passage 613. The control device 40 also generates a signal to instruct the fourth switching valve V4 to open or close so that the upstream side of the tenth passage 614 is connected to the eleventh passage 615.

[0240] The control device 40 outputs the generated signals to the third switching valve V3 and the fourth switching valve V4. Preferably, the switching timing of the third switching valve V3 and the fourth switching valve V4 are synchronized, but switching of at least one of the third switching valve V3 and the fourth switching valve V4 may be performed. The generation and output of the control signal may be performed only when switching of the flow path is necessary because the state of the newly identified flow path differs from the state of the current flow path.

[0241] If the carbon dioxide concentrator 1 is equipped with multiple electrical conductivity meters 50, the control device 40 may determine whether the measured values ​​of all electrical conductivity meters 50 are above a threshold, or it may determine whether the measured values ​​of a predetermined number or more electrical conductivity meters 50 are above a threshold.

[0242] It is predicted that the degree of decrease in electrical conductivity in the anode liquid chamber 27 and the degree of increase in electrical conductivity in the cathode liquid chamber 28 will be correlated. Therefore, it is considered that the overall state of the device can be understood by monitoring the electrolyte S in either the anode liquid chamber 27 or the cathode liquid chamber 28.

[0243] When the electrical conductivity of the electrolyte S flowing through the cathode liquid chamber 28 is measured by the electrical conductivity meter 50, the threshold determination described above is reversed. If the electrical conductivity of the electrolyte S in the cathode liquid chamber 28 is greater than or equal to a preset threshold, the flow path of the electrolyte S is switched so that the electrolyte S discharged from the anode liquid chamber 27 is supplied to the cathode liquid chamber 28, and the electrolyte S discharged from the cathode liquid chamber 28 is supplied to the absorption tower 10. If the electrical conductivity of the electrolyte S in the cathode liquid chamber 28 is less than the threshold, the flow path of the electrolyte S is switched so that the electrolyte S discharged from the anode liquid chamber 27 is supplied to the anode liquid chamber 27, and the electrolyte S discharged from the cathode liquid chamber 28 is supplied to the cathode liquid chamber 28.

[0244] The switching of the electrolyte S flow path may be performed manually. The control device 40 may, for example, receive a request from a user such as an operator to indicate whether or not to switch the flow path to a specific state, and only output control signals to the third switching valve V3 and the fourth switching valve V4 if the switching is permitted.

[0245] 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 a consistent scope, each processing step may be performed in a different order, and multiple processes may be performed in parallel. The processing entities for each process are not limiting, and within a consistent scope, the processing of each device may be performed by other devices.

[0246] The matters described in each embodiment can be combined with each other. For example, a single carbon dioxide concentrator 1 may be equipped with both an electrical conductivity meter 50 and a pH sensor 8. 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. Moreover, although the claims use a form in which claims referencing two or more other claims (multi-claim form), the claims are not limited to this. A form in which multi-claims referencing at least one multi-claim (multi-multi-claim) may also be used.

[0247] 100 Carbon Dioxide Concentration System 1 Carbon Dioxide Concentrator 10 Absorption Tower (Absorption Section) 20 Concentration Section 22 Anode 231 Electrolyte Membrane 24 Cathode 27 Anode Liquid Chamber 28 Cathode Liquid Chamber 30 Gas-Liquid Separation Section 50 Electrical Conductivity Meter 60 Passageway 40 Control Device 8 pH Sensor

Claims

1. A carbon dioxide concentration device comprising: 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 is switchable between the first passage and the second passage.

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

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

4. The carbon dioxide concentration apparatus according to claim 1 or claim 2, further comprising a sensor for measuring the pH of the electrolyte.

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

6. The carbon dioxide concentration apparatus according to claim 1 or 2, wherein the passage includes 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 is switchable between the third passage and the fourth passage.

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

8. The carbon dioxide concentration apparatus according to claim 1 or claim 2, comprising a control device for switching the flow path of the electrolyte between a first passage and a second passage.

9. A carbon dioxide concentration apparatus comprising: 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 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.

10. A carbon dioxide concentrator comprising: an absorption unit for absorbing carbon dioxide in a process gas into a predetermined solution; and an electrochemical cell for generating a gas containing carbon dioxide at a higher concentration than the process gas from the predetermined solution that has absorbed carbon dioxide, wherein the electrochemical cell comprises: an anode; a cathode; an anode liquid chamber through which predetermined ions are supplied from the anode and through which the predetermined solution that has absorbed carbon dioxide flows; a cathode liquid chamber for supplying the predetermined solution to the cathode; and an electrolyte membrane provided between the anode liquid chamber and the cathode liquid chamber, wherein an electrical conductivity meter for measuring the electrical conductivity of the predetermined solution is provided inside the anode liquid chamber or the cathode liquid chamber or in a passage connected to the anode liquid chamber or the cathode liquid chamber.

11. The carbon dioxide concentrator according to claim 10, wherein the passage includes a passage configured to switch the flow path of a predetermined solution discharged from the anode liquid chamber or the cathode liquid chamber, and the flow path of the predetermined solution is switched based on the electrical conductivity measured by the electrical conductivity meter.

12. The carbon dioxide concentration apparatus according to claim 11, wherein the passage is switchable between a first state in which a predetermined solution discharged from the anode liquid chamber is supplied to the cathode liquid chamber and the predetermined solution discharged from the cathode liquid chamber is supplied to the absorption section, and a second state in which a predetermined solution discharged from the anode liquid chamber is supplied to the anode liquid chamber and the predetermined solution discharged from the cathode liquid chamber is supplied to the cathode liquid chamber.

13. The carbon dioxide concentration apparatus according to claim 10 or claim 11, wherein the electrical conductivity meter measures the electrical conductivity of a predetermined solution discharged from the anode liquid chamber or the cathode liquid chamber.

14. The carbon dioxide concentrator according to claim 10 or 11, wherein a gas-liquid separator for separating the predetermined solution and the gas is provided on the passage through which the predetermined solution discharged from the anode liquid chamber flows, and the electrical conductivity meter is located downstream of the gas-liquid separator in the passage.

15. Information processing method for a carbon dioxide concentrator, wherein the carbon dioxide concentrator comprises: an absorption unit for absorbing carbon dioxide in a process gas into a predetermined solution; an electrochemical cell for generating a gas containing carbon dioxide at a higher concentration than the process gas from the predetermined solution; and a passage configured to allow switching of the flow path of the predetermined solution, wherein the electrochemical cell comprises: an anode; a cathode; an anode liquid chamber through which predetermined ions are supplied from the anode and a predetermined solution that has absorbed carbon dioxide flows; a cathode liquid chamber for supplying the predetermined solution to the cathode; and an electrolyte membrane provided between the anode liquid chamber and the cathode liquid chamber, wherein an electrical conductivity meter for measuring the electrical conductivity of the predetermined solution is provided inside the anode liquid chamber or the cathode liquid chamber or in a passage connected to the anode liquid chamber or the cathode liquid chamber, and a computer acquires the electrical conductivity measured by the electrical conductivity meter, and executes a process to switch the flow path of the predetermined solution discharged from the anode liquid chamber or the cathode liquid chamber based on the acquired electrical conductivity.

16. The carbon dioxide concentration apparatus according to claim 1 or claim 2, wherein the flow path of the electrolyte is switched to the first passage or the second passage based on the electrical conductivity of the electrolyte.

17. The carbon dioxide concentration apparatus according to claim 16, wherein if the electrical conductivity of the electrolyte is greater than or equal to a predetermined value, the flow path of the electrolyte is switched to the first passage, and if the electrical conductivity of the electrolyte is less than a predetermined value, the flow path of the electrolyte is switched to the second passage.

18. The carbon dioxide concentration apparatus according to claim 16, wherein the passage includes 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 is switchable between the third passage and the fourth passage.

19. The carbon dioxide concentration apparatus according to claim 18, wherein if the electrical conductivity of the electrolyte is less than a predetermined value, the flow path of the electrolyte is switched to the third passage, and if the electrical conductivity of the electrolyte is equal to or greater than a predetermined value, the flow path of the electrolyte is switched to the fourth passage.

20. The carbon dioxide concentration apparatus according to claim 16, further comprising an electrical conductivity meter for measuring the electrical conductivity of the electrolyte.

21. The carbon dioxide concentration apparatus according to claim 20, wherein a gas-liquid separation device for separating the electrolyte and carbon dioxide from each other is provided on the passage through which the electrolyte discharged from the first liquid chamber flows, and the electrical conductivity meter is positioned downstream of the gas-liquid separation device in the passage.

Images