Apparatus for producing carbon dioxide

Abstract

This apparatus for producing carbon dioxide is provided with: an anode which is provided on one side of an electrolyte membrane and generates protons from hydrogen; a cathode which is provided on the other side of the electrolyte membrane and generates hydrogen; a first liquid chamber which is provided between the anode and the electrolyte membrane and to which a first electrolyte solution that has absorbed carbon dioxide is supplied; and a second liquid chamber which is provided between the electrolyte membrane and the cathode and to which a second electrolyte solution is supplied. The anode is supplied with a gas that has a hydrogen concentration of less than 99 vol%.

Description

Carbon dioxide production equipment

[0001] The present invention relates to a carbon dioxide production apparatus, a carbon compound production system, a carbon dioxide production method, and a carbon dioxide concentration method.

[0002] One of the causes of global warming is the increase in greenhouse gas emissions such as carbon dioxide. In order to reduce carbon dioxide emissions, development is underway to separate and concentrate carbon dioxide from exhaust gases and the atmosphere.

[0003] The carbon dioxide recovery, desorption, and concentration device disclosed in Patent Document 1 concentrates carbon dioxide by continuously recovering carbon dioxide from a carbon dioxide-containing gas into an electrolyte solution using a water decomposition reaction and desorbing the recovered carbon dioxide from the electrolyte solution.

[0004] Japanese Patent Application Laid-Open No. 2023-125258

[0005] The technology described in Patent Document 1 requires a large amount of electrical energy to electrolyze water.

[0006] An object of the present disclosure is to provide a technology that can reduce energy consumption in the production of carbon dioxide.

[0007] A carbon dioxide production device according to one aspect of the present disclosure includes an electrolyte membrane, an anode provided on one side of the electrolyte membrane and generating protons from hydrogen, a cathode provided on the other side of the electrolyte membrane and generating hydrogen, a first liquid chamber provided between the anode and the electrolyte membrane and supplied with a first electrolytic solution that has absorbed carbon dioxide, and a second liquid chamber provided between the electrolyte membrane and the cathode and supplied with a second electrolytic solution, and a gas having a hydrogen concentration of less than 99 vol% is supplied to the anode.

[0008] A carbon dioxide production device according to another aspect of the present disclosure includes an anode that generates protons from hydrogen, a cathode that generates hydrogen, a first liquid chamber to which a first electrolytic solution that has absorbed carbon dioxide is supplied, a second liquid chamber to which a second electrolytic solution is supplied, and an electrolyte membrane provided between the first liquid chamber and the second liquid chamber, and a gas having a hydrogen concentration of less than 99 vol% is supplied to the anode.

[0009] A carbon dioxide production device according to one aspect of the present disclosure includes an electrolyte membrane, an anode provided on one side of the electrolyte membrane and generating protons from hydrogen, a cathode provided on the other side of the electrolyte membrane and generating hydrogen, a first liquid chamber provided between the anode and the electrolyte membrane and supplied with a first electrolytic solution that has absorbed carbon dioxide, and a second liquid chamber provided between the electrolyte membrane and the cathode and supplied with a second electrolytic solution, and a mixed gas of hydrogen and a carbon compound is supplied to the anode.

[0010] According to the present disclosure, it is possible to reduce energy consumption in the production of carbon dioxide.

[0011] It is a schematic diagram of a carbon compound production system. It is a cross-sectional view showing a configuration example of a concentration separation part. It is an explanatory diagram explaining the operation of a concentration separation device.

[0012] (1) A carbon dioxide production device according to one aspect of the present disclosure includes an electrolyte membrane, an anode provided on one side of the electrolyte membrane and generating protons from hydrogen, a cathode provided on the other side of the electrolyte membrane and generating hydrogen from protons, a first liquid chamber provided between the anode and the electrolyte membrane and supplied with a first electrolytic solution that has absorbed carbon dioxide, and a second liquid chamber provided between the electrolyte membrane and the cathode and supplied with a second electrolytic solution, and the anode is supplied with a gas having a hydrogen concentration of less than 99 vol%.

[0013] A carbon dioxide generating device according to another aspect of the present disclosure includes an electrolyte membrane, an anode provided on one side of the electrolyte membrane for generating protons from hydrogen, a cathode provided on the other side of the electrolyte membrane for generating hydrogen, a first liquid chamber provided between the anode and the electrolyte membrane and supplied with a first electrolytic solution that has absorbed carbon dioxide, and a second liquid chamber provided between the electrolyte membrane and the cathode and supplied with a second electrolytic solution, wherein a gas having a hydrogen concentration of less than 99 vol% is supplied to the anode. Examples of the cathode that generates hydrogen include a cathode that generates hydrogen from protons and a cathode that generates hydrogen from water.

[0014] (2) A carbon dioxide generating device according to one aspect of the present disclosure includes an anode that generates protons from hydrogen, a cathode that generates hydrogen, a first liquid chamber to which a first electrolytic solution having carbon dioxide absorbed therein is supplied, a second liquid chamber to which a second electrolytic solution is supplied, and an electrolyte membrane provided between the first liquid chamber and the second liquid chamber, wherein a gas having a hydrogen concentration of less than 99 vol% is supplied to the anode. The cathode may be a cathode that generates hydrogen from protons.

[0015] The present inventors have investigated the practical application of a carbon dioxide production apparatus using hydrogen pumping. Conventional technologies utilizing the principle of hydrogen pumping use high-purity hydrogen gas as the hydrogen source for pumping hydrogen (hereinafter also referred to as the hydrogen feedstock). Since lowering the hydrogen concentration in the hydrogen gas is expected to have disadvantages such as reduced reaction efficiency, no efforts have been made to lower the purity of the hydrogen. "Pumping hydrogen" refers to the hydrogen used in the hydrogen pumping principle. During their own investigations, the present inventors came up with the new idea of ​​using low-purity hydrogen gas as the hydrogen feedstock. After extensive investigations, they discovered that gas with a hydrogen concentration of less than 99 vol% can be used as the hydrogen feedstock. This situation is described in detail below.

[0016] A conventional technology utilizing the principle of hydrogen pumping is a device (hereinafter also referred to as a hydrogen gas booster) that converts low-pressure hydrogen gas into high-pressure hydrogen gas using the principle of hydrogen pumping. This device uses low-pressure hydrogen gas as the hydrogen source. This device is often used in combination with a hydrogen gas production device, rather than alone. The low-pressure hydrogen gas produced by the hydrogen gas production device is supplied to the hydrogen gas booster device and converted into high-pressure hydrogen gas. The hydrogen gas production device may produce hydrogen gas by steam reforming a raw material such as methane or LPG. The high-purity gas produced by this device achieves a hydrogen concentration of 99 vol% or higher, even if it contains components other than hydrogen, with only trace amounts of unavoidable impurities such as nitrogen, carbon monoxide, and carbon dioxide. When used in combination with a device that produces high-purity hydrogen gas, no one other than the inventors would have any motivation to reduce the purity of the hydrogen gas supplied to the hydrogen gas booster device. As described above, conventional technology utilizing the principle of hydrogen pumping includes a device that converts low-pressure hydrogen gas into high-pressure hydrogen gas using the principle of hydrogen pumping. However, this device is generally used in combination with a hydrogen gas production device that produces high-purity hydrogen gas, and at present, the idea of ​​reducing the purity of the gas that serves as the hydrogen raw material is unknown to anyone other than the present inventors.

[0017] Furthermore, in carbon dioxide production devices that utilize the principle of hydrogen pumping, high-purity hydrogen gas is produced at the cathode simultaneously with the production of carbon dioxide, so it can be said that it is difficult for anyone other than the present inventors to come up with the idea of ​​reducing the purity of the hydrogen gas supplied to the anode side as a hydrogen feedstock. This is because the high-purity hydrogen gas produced at the cathode can be reused as a hydrogen source to be supplied to the anode, and there is an option to circulate and reuse this high-purity hydrogen gas. Because this option is reasonable from the perspective of reducing raw material costs, the option of purchasing new hydrogen as a hydrogen feedstock and supplying it is unlikely to be considered, and the option of supplying low-purity hydrogen gas is even more difficult to consider.

[0018] In considering the practical application of a carbon dioxide production apparatus using hydrogen pumping, the inventors focused on an embodiment in which this apparatus is used in combination with an electrolysis device that reduces carbon dioxide. Despite the above background, during the process of developing a carbon compound production system combining these devices, they came up with the novel idea of ​​using low-purity hydrogen gas as a hydrogen source for hydrogen pumping. This idea arose from the fact that the gas produced in the electrolysis device contains low concentrations of hydrogen due to unavoidable side reactions that occur in parallel with the reduction of carbon dioxide. While investigating how to handle this gas containing low concentrations of hydrogen, the inventors attempted to use this gas as a hydrogen feedstock for a carbon dioxide production apparatus, and discovered that certain problems could be solved by using gas with a hydrogen concentration of less than 99 vol% as the hydrogen feedstock.

[0019] According to the carbon dioxide production apparatus described in (1) or (2) above, carbon dioxide gas can be produced by electrodialysis using hydrogen pumping with gas having a hydrogen concentration of less than 99 vol%. For example, the voltage applied to the carbon dioxide production apparatus can be lowered compared to methods using water electrolysis, thereby reducing energy consumption. Furthermore, since gas having a hydrogen concentration of less than 99 vol% is used as the hydrogen source, the degree of freedom in selecting the hydrogen source is increased, and the degree of freedom in system design is also increased.

[0020] (3) In the carbon dioxide production apparatus according to (1) or (2) above, the gas supplied to the anode may have a hydrogen concentration of 50 vol % or less.

[0021] According to the carbon dioxide production apparatus described in (3) above, the degree of freedom in selecting the hydrogen raw material is further increased.

[0022] (4) In the carbon dioxide production apparatus described in (1) to (3) above, the gas supplied to the anode may contain a mixed gas of hydrogen and a carbon compound obtained when carbon dioxide produced in the carbon dioxide production apparatus is reduced.

[0023] According to the carbon dioxide production apparatus described in (4) above, hydrogen in the mixed gas derived from the carbon dioxide gas produced in the carbon dioxide production apparatus can be used as pumping hydrogen, so that gas can be efficiently cycled within the system.

[0024] (5) In the carbon dioxide production apparatus according to any one of (1) to (4) above, the gas supplied to the anode may be mixed with a gas having a hydrogen concentration of 99 vol % or more.

[0025] According to the carbon dioxide production apparatus described in (5) above, by further including a gas with a hydrogen concentration of 99 vol % or more in the hydrogen source material, the hydrogen concentration of the hydrogen source material can be increased, thereby increasing the rate at which carbon dioxide is produced in the carbon dioxide production apparatus, and increasing the rate at which a mixed gas derived from the carbon dioxide gas produced in the carbon dioxide production apparatus is produced, thereby improving the operating efficiency of the entire system.

[0026] (6) In the carbon dioxide production apparatus described in (5) above, the gas having a hydrogen concentration of 99 vol % or more may contain hydrogen produced at the cathode.

[0027] According to the carbon dioxide production apparatus described in (6) above, the hydrogen gas obtained by the carbon dioxide production apparatus can be used as a hydrogen source, and therefore the gas can be efficiently cycled within the system.

[0028] (7) The carbon dioxide production apparatus according to any one of (1) to (6) above may further include a confluence section that combines a gas having a hydrogen concentration of less than 99 vol % with a gas having a hydrogen concentration of 99 vol % or more and supplies the combined gas to the anode.

[0029] According to the carbon dioxide production apparatus described in (7) above, gases having different hydrogen concentrations can be joined together, so that the hydrogen concentration of the hydrogen raw material can be appropriately adjusted.

[0030] (8) The carbon dioxide generating apparatus according to any one of (1) to (7) above may further include a gas-liquid separator that separates the carbon dioxide released from the first electrolytic solution from the first electrolytic solution.

[0031] According to the carbon dioxide generating device described in (8) above, carbon dioxide and the first electrolytic solution can be separated appropriately.

[0032] (9) In the carbon dioxide generating apparatus described in (8) above, the first electrolytic solution separated by the gas-liquid separator may be supplied to the second liquid chamber as the second electrolytic solution.

[0033] According to the carbon dioxide generating device described in (9) above, the first electrolytic solution can be regenerated and recycled, thereby reducing the amount of energy required for absorbing and releasing carbon dioxide and improving the operating efficiency.

[0034] (10) The carbon dioxide production apparatus described in any one of (1) to (9) above may further include a first gas chamber through which the gas supplied to the anode flows, and the first gas chamber may include an outlet for discharging a portion of the gas supplied to the anode.

[0035] According to the carbon dioxide production apparatus described in (10) above, it is possible to discharge unreacted components that are not used in the reaction at the anode among the components contained in the raw material gas, and to prevent the unreacted components from accumulating in the carbon dioxide production apparatus even when the raw material gas contains components other than hydrogen.

[0036] (11) The carbon dioxide production device according to any one of (1) to (10) above may further include a recovery unit that recovers the gas discharged from the discharge port.

[0037] According to the carbon dioxide production apparatus described in (11) above, unreacted components contained in the raw material gas can be recovered. By supplying a gas containing hydrogen and specific components other than hydrogen to the anode and recovering the components other than hydrogen as exhaust gas, hydrogen can be separated from the gas.

[0038] (12) The carbon dioxide production device described in any one of (1) to (11) above may include a gas-liquid contact section that brings a gas containing carbon dioxide into contact with a liquid, and the first liquid chamber may be supplied with the first electrolytic solution that has absorbed carbon dioxide by contacting the gas containing carbon dioxide in the gas-liquid contact section.

[0039] The carbon dioxide producing apparatus described in (12) above can function as a concentrated carbon dioxide producing apparatus that produces high-concentration carbon dioxide from low-concentration carbon dioxide.

[0040] (13) In the carbon dioxide generating apparatus described in any one of (1) to (4) above, a plurality of units each having the electrolyte membrane, and the first liquid chamber and the second liquid chamber arranged with the electrolyte membrane interposed therebetween may be provided between the anode and the cathode, and each of the plurality of first liquid chambers may be connected to a gas-liquid separator that separates carbon dioxide released from the first electrolytic solution from the first electrolytic solution, and to a supply path that supplies the first electrolytic solution.

[0041] According to the carbon dioxide generating device described in (13) above, by including a plurality of stacked electrolyte units, it is possible to achieve equivalent carbon dioxide gas production performance in a compact device compared to a case where a plurality of carbon dioxide generating devices each having a single electrolyte unit are prepared and operated. The gas-liquid mixture from each first liquid chamber can be reliably separated by the gas-liquid separator, and the first electrolytic solution can be reliably supplied to each first liquid chamber.

[0042] (14) The carbon dioxide production apparatus described in any one of (1) to (4) above may include a first gas chamber through which gas supplied to the anode flows and a second gas chamber through which hydrogen generated at the cathode flows, and the flow rate of the gas per unit time in the first gas chamber may be greater than the flow rate of the gas per unit time in the second gas chamber.

[0043] According to the carbon dioxide production apparatus described in (14) above, even when gas having a hydrogen concentration of less than 99 vol % is used, a sufficient amount of gas can be supplied to the anode, thereby preventing insufficient hydrogen oxidation reaction.

[0044] (15) A carbon dioxide production device according to one aspect of the present disclosure includes an electrolyte membrane, an anode provided on one side of the electrolyte membrane and generating protons from hydrogen, a cathode provided on the other side of the electrolyte membrane and generating hydrogen from protons, a first liquid chamber provided between the anode and the electrolyte membrane and supplied with a first electrolytic solution that has absorbed carbon dioxide, and a second liquid chamber provided between the electrolyte membrane and the cathode and supplied with a second electrolytic solution, and the anode is supplied with a mixed gas of hydrogen and a carbon compound obtained when carbon dioxide produced by the device itself is reduced.

[0045] Instead of a cathode that generates hydrogen from protons, the cathode may be a cathode that generates hydrogen. Instead of a mixed gas of hydrogen and a carbon compound obtained when carbon dioxide produced in the apparatus itself is reduced, the mixed gas may be a mixed gas of hydrogen and a carbon compound, or a mixed gas of hydrogen and a carbon compound obtained when carbon dioxide is reduced.

[0046] A carbon dioxide production device according to another aspect of the present disclosure includes an anode that generates protons from hydrogen, a cathode that generates hydrogen, a first liquid chamber to which a first electrolytic solution having carbon dioxide absorbed therein is supplied, a second liquid chamber to which a second electrolytic solution is supplied, and an electrolyte membrane provided between the first liquid chamber and the second liquid chamber, and a mixed gas of hydrogen and a carbon compound is supplied to the anode. The cathode may be a cathode that generates hydrogen from protons. The mixed gas may be a mixed gas of hydrogen and a carbon compound obtained when carbon dioxide is reduced, or a mixed gas of hydrogen and a carbon compound obtained when carbon dioxide produced by the device itself is reduced.

[0047] According to the carbon dioxide production apparatus described in (15) above, the hydrogen in the mixed gas derived from the carbon dioxide gas produced in the carbon dioxide production apparatus can be used as pumping hydrogen to drive the carbon dioxide production apparatus, thereby enabling efficient gas cycling within the system. The concentration of hydrogen in the mixed gas of hydrogen and carbon compounds is not particularly limited, and may be, for example, less than 99 vol % or 99 vol % or more.

[0048] (16) A carbon compound production system according to one aspect of the present disclosure includes a carbon dioxide production device and a reduction device that produces a carbon compound by reducing carbon dioxide produced in the carbon dioxide production device, the carbon dioxide production device including an electrolyte membrane, an anode provided on one side of the electrolyte membrane and that produces protons from hydrogen, a cathode provided on the other side of the electrolyte membrane and that produces hydrogen from protons, a first liquid chamber provided between the anode and the electrolyte membrane and that is supplied with a first electrolytic solution that has absorbed carbon dioxide, and a second liquid chamber provided between the electrolyte membrane and the cathode and that is supplied with a second electrolytic solution, and the anode is supplied with a gas having a hydrogen concentration of less than 99 vol%.

[0049] Instead of a cathode that produces hydrogen from protons, the cathode may be a cathode that produces hydrogen.

[0050] A carbon compound production system according to another aspect of the present disclosure includes a carbon dioxide production apparatus and a reduction apparatus that produces carbon compounds by reducing carbon dioxide produced in the carbon dioxide production apparatus, the carbon dioxide production apparatus including an anode that produces protons from hydrogen, a cathode that produces hydrogen, a first liquid chamber to which a first electrolytic solution having carbon dioxide absorbed therein is supplied, a second liquid chamber to which a second electrolytic solution is supplied, and an electrolyte membrane provided between the first liquid chamber and the second liquid chamber, and the anode is supplied with gas having a hydrogen concentration of less than 99 vol%. The cathode may be a cathode that produces hydrogen from protons.

[0051] The carbon compound production system may include the carbon dioxide production apparatus described in any one of (1) to (15) above, and a reduction apparatus that reduces the carbon dioxide produced in the carbon dioxide production apparatus to produce a carbon compound.

[0052] According to the carbon compound production system described in (16) above, the energy consumption of the entire system can be reduced.

[0053] (17) In the carbon compound production system described in (16) above, the reduction device may be an electrolytic reduction device.

[0054] (18) In the carbon compound production system described in (16) or (17) above, the reduction device may produce a mixed gas containing the carbon compound and hydrogen, and the mixed gas produced by the reduction device may be supplied to the anode.

[0055] According to the carbon compound production system described in (17) and (18) above, a mixed gas of carbon compounds and hydrogen produced by an electrolytic reduction device can be used as the hydrogen source, allowing efficient gas cycling within the system. Since carbon dioxide is produced by a carbon dioxide production device and hydrogen is separated from the reduction product derived from the produced carbon dioxide, there is no need to provide a separate hydrogen separation process, improving operational efficiency and further reducing energy consumption. The system configuration is simplified because there is no need to provide a separate carbon dioxide production device and separation device.

[0056] (19) A carbon dioxide production method according to one aspect of the present disclosure is a carbon dioxide production method using a carbon dioxide production apparatus, the carbon dioxide production apparatus including: an electrolyte membrane; an anode provided on one side of the electrolyte membrane and producing protons from hydrogen; a cathode provided on the other side of the electrolyte membrane and producing hydrogen from protons; a first liquid chamber provided between the anode and the electrolyte membrane and supplied with a first electrolytic solution that has absorbed carbon dioxide; and a second liquid chamber provided between the electrolyte membrane and the cathode and supplied with a second electrolytic solution, and a gas having a hydrogen concentration of less than 99 vol% is supplied to the anode.

[0057] Instead of a cathode that produces hydrogen from protons, the cathode may be a cathode that produces hydrogen.

[0058] A carbon dioxide production method according to another aspect of the present disclosure is a carbon dioxide production method using a carbon dioxide production apparatus, the carbon dioxide production apparatus including an anode that produces protons from hydrogen, a cathode that produces hydrogen, a first liquid chamber to which a first electrolytic solution having carbon dioxide absorbed therein is supplied, a second liquid chamber to which a second electrolytic solution is supplied, and an electrolyte membrane provided between the first liquid chamber and the second liquid chamber, and a gas having a hydrogen concentration of less than 99 vol% is supplied to the anode. The cathode may be a cathode that produces hydrogen from protons.

[0059] (19) A carbon dioxide concentration method according to one aspect of the present disclosure is a carbon dioxide concentration method using a carbon dioxide production apparatus, the carbon dioxide production apparatus including: an electrolyte membrane; an anode provided on one side of the electrolyte membrane and producing protons from hydrogen; a cathode provided on the other side of the electrolyte membrane and producing hydrogen from protons; a first liquid chamber provided between the anode and the electrolyte membrane and supplied with a first electrolytic solution that has absorbed carbon dioxide; and a second liquid chamber provided between the electrolyte membrane and the cathode and supplied with a second electrolytic solution, and a gas having a hydrogen concentration of less than 99 vol% is supplied to the anode.

[0060] Instead of a cathode that produces hydrogen from protons, the cathode may be a cathode that produces hydrogen.

[0061] A carbon dioxide concentrating method according to another aspect of the present disclosure is a carbon dioxide concentrating method using a carbon dioxide producing apparatus, the carbon dioxide producing apparatus including an anode that produces protons from hydrogen, a cathode that produces hydrogen, a first liquid chamber to which a first electrolytic solution having carbon dioxide absorbed therein is supplied, a second liquid chamber to which a second electrolytic solution is supplied, and an electrolyte membrane provided between the first liquid chamber and the second liquid chamber, and a gas having a hydrogen concentration of less than 99 vol% is supplied to the anode. The cathode may be a cathode that produces hydrogen from protons.

[0062] The present disclosure will be specifically described with reference to the drawings showing embodiments thereof.

[0063] FIG. 1 is a schematic diagram of a carbon compound production system S. The carbon compound production system S of this embodiment is a system that uses a carbon dioxide-containing gas containing a low concentration of carbon dioxide as a raw material gas, concentrates and recovers carbon dioxide from the raw material gas, and produces carbon compounds that become valuable resources from the recovered carbon dioxide. The carbon compound production system S of this embodiment includes a concentration and separation device 1, an electrolytic reduction device 2, and a control device 3. The concentration and separation device 1 includes an absorption tower 10, a concentration and separation section 20, a recovery section 30, a gas-liquid separation section 40, and a hydrogen storage section 50. The concentration and separation device 1 is an example of a carbon dioxide production device.

[0064] The absorption tower 10 absorbs carbon dioxide into the first electrolytic solution by bringing the carbon dioxide-containing gas into gas-liquid contact with the first electrolytic solution. In this specification, "absorption" means that carbon dioxide chemically reacts with the first electrolytic solution to form predetermined ions and dissolve. The absorption tower 10 is an example of a gas-liquid contact section.

[0065] The carbon dioxide-containing gas is a gas containing a low concentration of carbon dioxide, such as the atmosphere or exhaust gas. The concentration of carbon dioxide in the carbon dioxide-containing gas is, for example, 0.01 vol % to 30 vol %. The carbon dioxide-containing gas may contain gases other than carbon dioxide, such as nitrogen, water vapor, carbon monoxide, hydrogen sulfide, carbonyl sulfide, sulfur dioxide, nitrogen dioxide, methane, and hydrogen.

[0066] The concentration / separation unit 20 desorbs and releases carbon dioxide from the liquid that has absorbed it, thereby producing concentrated carbon dioxide gas. The concentrated carbon dioxide gas contains a higher concentration of carbon dioxide than the carbon dioxide-containing gas. The carbon dioxide concentration in the concentrated carbon dioxide gas is typically 90 vol % to 100 vol %. The concentrated carbon dioxide gas produced in the concentration / separation unit 20 is supplied to the electrolytic reduction device 2.

[0067] The concentration / separation unit 20 constitutes an electrochemical hydrogen pump (electrochemical cell) including an anode 22 and a cathode 24. The concentration / separation unit 20 desorbs carbon dioxide from a liquid that has absorbed carbon dioxide using electrodialysis by hydrogen pumping. A hydrogen-containing gas containing hydrogen is supplied to the concentration / separation unit 20. Hydrogen gas at a higher pressure than the hydrogen-containing gas is generated by the hydrogen pressure boosting operation of the electrochemical hydrogen pump.

[0068] The hydrogen concentration of the hydrogen-containing gas is less than 99 vol% in the hydrogen-containing gas. The hydrogen concentration in the hydrogen-containing gas is preferably 50 vol% or less, more preferably 30 vol% or less, and even more preferably 10 vol% or less. The lower limit of the hydrogen concentration in the hydrogen-containing gas is not particularly limited, but may be, for example, 0.01 vol% or more. The hydrogen-containing gas may be a gas containing hydrogen as an impurity. When the hydrogen concentration in the gas is 100 vol%, it means a gas consisting only of hydrogen, i.e., pure hydrogen.

[0069] The hydrogen-containing gas may be a gas adjusted to have an overall hydrogen concentration of less than 99 vol% by mixing a gas having a hydrogen concentration of less than 99 vol% with a gas having a hydrogen concentration of 99 vol% or more.

[0070] In the concentration / separation unit 20, hydrogen contained in the hydrogen-containing gas is supplied to the anode 22 of the electrochemical hydrogen pump, where protons are generated by an oxidation reaction. Components contained in the hydrogen-containing gas other than hydrogen remain unreacted. By supplying a mixed gas containing hydrogen and components other than hydrogen to the concentration / separation unit 20, it is possible to separate (remove) hydrogen from the mixed gas and discharge a gas containing components other than hydrogen. The gas containing components other than hydrogen is recovered in the recovery unit 30.

[0071] The concentration / separation apparatus 1 of this embodiment functions as a carbon dioxide production apparatus that produces high-concentration carbon dioxide, and also functions as a hydrogen separation apparatus that separates hydrogen from a hydrogen-containing gas.

[0072] The electrolytic reduction device 2 generates a gas containing carbon compounds by electrolytically reducing carbon dioxide in the concentrated carbon dioxide gas obtained in the concentration / separation section 20. The electrolytic reduction device 2 is an example of a reduction device. The electrolytic reduction device 2 generates a mixed gas containing carbon compounds such as hydrocarbons (e.g., methane, ethylene, etc.) and carbon monoxide, and hydrogen. The concentration of hydrogen in the mixed gas is, for example, less than 99 vol% in the mixed gas, preferably 50 vol% or less, more preferably 30 vol% or less, and even more preferably 10 vol% or less.

[0073] The mixed gas of carbon compounds and hydrogen produced in the electrolytic reduction device 2 is supplied to the concentration / separation unit 20. The concentration / separation unit 20 separates hydrogen from the mixed gas and discharges a gas containing carbon compounds. The gas containing carbon compounds can be used as a valuable resource.

[0074] The carbon compound production system S can realize carbon recycling, which converts carbon dioxide contained in the atmosphere or exhaust gases into various carbon compounds as a carbon resource and reuses them. The carbon compound production system S will be described in detail below.

[0075] The absorption tower 10 includes a main body 11 extending vertically, a gas inlet 12 provided at the bottom of the side wall of the main body 11, a liquid inlet 13 and a gas outlet 14 provided at the top 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) via a first passage 601.

[0076] The carbon dioxide-containing gas is supplied into the tower from the gas inlet 12 via the first passage 601, flows through the tower, and is then discharged from the gas outlet 14.

[0077] The first electrolytic solution for absorbing carbon dioxide is supplied from a liquid inlet 13 and absorbs carbon dioxide by coming into contact with a carbon dioxide-containing gas in the tower. The first electrolytic solution that has absorbed carbon dioxide is supplied from a liquid outlet 15 to the concentration / separation section 20 via a second passage 602.

[0078] The method for contacting the carbon dioxide-containing gas with the first electrolytic solution is not particularly limited. Examples include a method of bubbling the carbon dioxide-containing gas into the first electrolytic solution, a method of dropping the first electrolytic solution in the form of mist into the carbon dioxide-containing gas by a spraying method, and a method of bringing high-pressure carbon dioxide-containing gas into countercurrent contact with the absorbing solution in an absorption tower 10 filled with a porcelain or metal mesh filler. This produces a first electrolytic solution that has absorbed carbon dioxide.

[0079] The first electrolytic solution of this embodiment is a mixed solution containing an absorbing solution that contributes to the absorption of carbon dioxide and an electrolyte solution that contributes to the oxidation-reduction reaction of hydrogen, which will be described later. The absorbing solution and the electrolyte solution contain the same cations (e.g., K +In this specification, the term "mixed liquid" means a liquid containing a component corresponding to the absorption liquid and a component corresponding to the electrolyte solution, and does not necessarily mean that the absorption liquid and the electrolyte solution are actually mixed separately.

[0080] The absorbing liquid contained in the first electrolytic solution is an alkaline aqueous solution. Examples of the alkaline aqueous solution 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.

[0081] Examples of alkali metal compounds and alkaline earth metal compounds include compounds of alkali metals such as sodium, lithium, and potassium, and alkaline earth metals such as calcium, magnesium, and barium. The alkali metal compounds and alkaline earth metal compounds are preferably hydroxides, oxides, and nitrates of alkali metals or alkaline earth metals, more preferably hydroxides. Specific examples of alkaline aqueous solutions include aqueous solutions of potassium hydroxide, sodium hydroxide, calcium hydroxide, and the like, with potassium hydroxide being preferred.

[0082] Examples of the amine compound include basic amines such as monoethanolamine, diethanolamine, diisopropanolamine, methyldiethanolamine, triethanolamine, etc. The aqueous alkaline solution may be used alone or in combination of two or more.

[0083] Examples of the electrolyte solution contained in the first electrolytic solution include an aqueous potassium chloride solution and an aqueous sodium chloride solution, and preferably an aqueous potassium chloride solution. The electrolyte solutions may be used alone or in combination of two or more.

[0084] FIG. 2 is a cross-sectional view showing an example of the configuration of the enrichment / separation unit 20. As shown in FIGS. 1 and 2 , the enrichment / separation unit 20 has a substantially rectangular cross section and a substantially rectangular parallelepiped shape overall. The enrichment / separation unit 20 further includes an anode plate 21 having an anode gas chamber (first gas chamber) 211, an anode 22, a plurality of electrolyte units 23, a cathode 24, a cathode plate 25 having a cathode gas chamber (second gas chamber) 251, and a power source 26. The anode plate 21, the anode 22, the plurality of electrolyte units 23, the cathode 24, and the cathode plate 25 are arranged in this order and are fastened together by, for example, fastening members (not shown). Gaskets (not shown) may be disposed between the anode plate 21 and the anode 22 and between the cathode 24 and the cathode plate 25, respectively. For ease of explanation, two electrolyte units 23 are shown in FIG. 1, but the concentration / separation section 20 may include a large number of electrolyte units 23, for example, 50 or 100 units.

[0085] Each electrolyte unit 23 includes an anode fluid chamber (first fluid chamber) 231, an electrolyte membrane 232, and a cathode fluid chamber (second fluid chamber) 233. In each electrolyte unit 23, the anode fluid chamber 231 is disposed on the anode 22 side, with the electrolyte membrane 232 interposed therebetween, and the cathode fluid chamber 233 is disposed on the cathode 24 side. A plurality of electrolyte units 23 are stacked with intermediate layers 28 interposed therebetween to form a stack.

[0086] The anode plate 21 has an anode gas chamber 211 formed in a portion facing the anode 22, through which a hydrogen-containing gas flows. The anode gas chamber 211 regulates the flow of the hydrogen-containing gas supplied to the anode 22.

[0087] The anode gas chamber 211 includes an anode gas flow channel 212, a first supply port 213 connected to one end (inlet) of the anode gas flow channel 212, and a first exhaust port 214 connected to the other end (outlet) of the anode gas flow channel 212. As an example, the anode gas flow channel 212 is a groove-shaped flow channel formed in the surface of the anode plate 21. The anode gas flow channel 212 is a single flow channel that is arranged so as to turn back in a region of the surface of the anode plate 21 facing the anode 22. Alternatively, the anode gas flow channel 212 may include multiple flow channels or may include a branched channel. The hydrogen-containing gas supplied from the first supply port 213 flows through the anode gas flow channel 212 and is then exhausted from the first exhaust port 214. In the region of the surface of the anode plate 21 facing the anode 22, a portion other than the anode gas flow channel 212 is in contact with the surface of the anode 22, thereby allowing electrons to move between the anode plate 21 and the anode 22.

[0088] The anode plate 21 can also be composed of multiple components, each with a different function. The anode plate 21 can also be composed by stacking, for example, an end plate, a current collector plate, and a plate member having an anode gas flow channel 212 on one surface thereof, in this order. The end plate fastens and integrates the components that make up the concentration / separation unit 20 in cooperation with the fastening members (not shown) and the cathode-side end plate. Electrons are transferred between the current collector plate and the anode 22 via the plate member having the anode gas flow channel 212, and the plate member is connected to the power source 26 via wiring. The plate member having the anode gas flow channel 212 forms an anode gas chamber 211 through the flow channel, and regulates the flow of hydrogen-containing gas supplied to the anode 22.

[0089] 2, a first supply port 213 is provided at the bottom of the anode plate 21, and a first exhaust port 214 is provided at the top of the anode plate 21. When the anode plate 21 has a substantially rectangular parallelepiped shape extending vertically, the first supply port 213 and the first exhaust port 214 may be provided near the vertices of the diagonal corners or near the center of the short sides.

[0090] The first discharge port 214 is connected to the recovery unit 30 via a third passage 603. The first supply port 213 is connected to the electrolytic reduction device 2 via a fourth passage 604, the junction 70, and a fifth passage 605. The first supply port 213 is also connected to the hydrogen storage unit 50 via the fourth passage 604, the junction 70, and a sixth passage 606.

[0091] The cathode plate 25 has a cathode gas chamber 251 formed in a portion facing the cathode 24, through which the hydrogen gas generated in the cathode 24 flows. Hereinafter, the hydrogen gas generated in the cathode 24 will also be referred to as high-pressure hydrogen gas.

[0092] The cathode gas chamber 251 includes a cathode gas flow channel 252 and a second outlet 253 connected to one end (outlet) of the cathode gas flow channel 252. As an example, the cathode gas flow channel 252 is a groove-shaped flow channel formed in the surface of the cathode plate 25. The cathode gas flow channel 252 is a single flow channel that is arranged so as to turn back in a region of the surface of the cathode plate 25 that faces the cathode 24. Alternatively, the cathode gas flow channel 252 may include multiple flow channels or may include a branched channel. High-pressure hydrogen gas supplied to the cathode gas flow channel 252 flows toward the second outlet 253. In the region of the surface of the cathode plate 25 that faces the cathode 24, the portion other than the portion where the cathode gas flow channel 252 is formed is in contact with the surface of the cathode 24, thereby enabling electrons to move between the cathode plate 25 and the cathode 24. Like the anode plate 21, the cathode plate 25 can also be made up of a plurality of components each having a different function.

[0093] 2, a second exhaust port 253 is provided on the upper part of the cathode plate 25. The second exhaust port 253 is connected to the hydrogen storage unit 50 via an eleventh passage 611. The hydrogen storage unit 50 stores the high-pressure hydrogen gas discharged from the cathode gas chamber 251.

[0094] In the concentration / separation unit 20, the gas flow rate per unit time in the anode gas flow channel 212 is preferably greater than the gas flow rate per unit time in the cathode gas flow channel 252. For example, the flow channel cross-sectional area of ​​the anode gas flow channel 212 may be greater than the flow channel cross-sectional area of ​​the cathode gas flow channel 252, thereby making the gas flow rate per unit time in the anode gas flow channel 212 greater than the gas flow rate per unit time in the cathode gas flow channel 252. The flow rate of the hydrogen-containing gas supplied to the anode gas chamber 211 may be adjusted by the compressor 93b. With the above configuration, even when a hydrogen-containing gas containing a low concentration of hydrogen is used, a sufficient amount of gas can be supplied to the anode 22, thereby preventing insufficient hydrogen oxidation reaction.

[0095] The gas flow rate per unit time in the anode gas flow channel 212 refers to the flow rate near the inlet of the anode gas flow channel 212. The gas flow rate per unit time in the anode gas flow channel 212 is the same as the flow rate per unit time of the hydrogen-containing gas supplied to the first supply port 213. The gas flow rate per unit time in the cathode gas flow channel 252 refers to the flow rate near the outlet of the cathode gas flow channel 252. The gas flow rate per unit time in the cathode gas flow channel 252 is the same as the flow rate per unit time of the high-pressure hydrogen gas discharged from the second discharge port 253.

[0096] The cross-sectional areas of the anode gas flow channel 212 and the cathode gas flow channel 252 refer to the cross-sectional areas of the respective channels cut along a plane perpendicular to the direction of fluid flow. When the cross-sectional areas are substantially uniform from the inlet to the outlet of the channel, the cross-sectional areas at any distance from the inlet are used as the cross-sectional areas. When the cross-sectional areas change with increasing distance from the inlet, the cross-sectional areas may be the average values ​​of the cross-sectional areas near the inlet and the outlet, or the average values ​​of the cross-sectional areas near the inlet, the outlet, and one or more positions within the channel. The one or more positions within the channel may be half the distance from the inlet to the outlet. In the case of the anode gas flow channel 212, the inlet and outlet refer to the inlet and outlet of the anode gas flow channel 212, and in the case of the cathode gas flow channel 252, the inlet and outlet refer to the inlet and outlet of the cathode gas flow channel 252.

[0097] 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 a power source 26 via wiring. The concentration / separation unit 20 includes a current sensor 91 that detects the current flowing between the anode 22 and the cathode 24.

[0098] The power supply 26 applies a voltage to the anode 22 and the cathode 24 via the anode plate 21 and the 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.

[0099] The anode 22 is supplied with a hydrogen-containing gas and generates protons from hydrogen in the hydrogen-containing gas. The anode 22 is a gas diffusion electrode and includes an anode catalyst layer 221 containing an anode catalyst and an anode gas diffusion layer 222. The anode catalyst layer 221 is provided on one surface of the anode gas diffusion layer 222. The anode liquid chamber 231 is in contact with the surface of the anode 22 facing the anode catalyst layer 221, and the anode plate 21 (anode gas chamber 211) is in contact with the surface of the anode 22 facing the anode gas diffusion layer 222. The anode catalyst layer 221 may be formed by supporting highly dispersed anode catalyst particles on the anode gas diffusion layer 222. Such an anode catalyst layer 221 can be manufactured, for example, by applying a mixture containing anode catalyst particles, a cation exchange resin, and a solvent to a predetermined substrate, drying the solvent, and transferring the dried mixture from the substrate to the surface of the anode gas diffusion layer 222. Alternatively, by using the anode gas diffusion layer 222 as the predetermined substrate, the anode catalyst layer 221 can be formed directly on the surface of the anode gas diffusion layer 222 and within a predetermined thickness from the surface.

[0100] Examples of anode catalysts include platinum, ruthenium, rhodium, palladium, and iridium. Anode catalysts may be used singly or in combination of two or more. When two or more types are combined, a combination containing at least platinum and ruthenium may be used. Anode catalysts using such a combination have improved durability against catalyst poisoning by carbon monoxide compared to, for example, a catalyst using platinum alone. The thickness of the anode catalyst layer 221 is, for example, 5 μm to 50 μm. When the thickness of the anode catalyst layer 221 is within the above range, protons can be generated effectively.

[0101] The anode gas diffusion layer 222 is made of a porous material and has electrical conductivity and gas diffusibility. The anode gas diffusion layer 222 uniformly diffuses the hydrogen-containing gas supplied from the fourth passage 604 through the anode gas flow channel 212 to the anode catalyst layer 221. Examples of the anode gas diffusion layer 222 include porous carbon fiber sheets such as carbon paper, carbon cloth, and carbon felt, and sintered bodies made from carbon particles, with carbon paper being preferred. The anode gas diffusion layer 222 may also be a sintered body of metal fibers made from titanium alloy, stainless steel, or the like, a sintered body of powdered metal, a metal mesh, or a foamed metal body. The thickness of the anode gas diffusion layer 222 is, for example, 100 μm to 1000 μm. A thickness of the anode gas diffusion layer 222 within the above range can improve gas diffusibility in the direction from the anode 22 to the cathode 24.

[0102] The cathode 24 generates hydrogen from protons supplied from the anode 22. The cathode 24 is a gas diffusion electrode and includes a cathode catalyst layer 241 containing a cathode catalyst and a cathode gas diffusion layer 242. The cathode catalyst layer 241 is provided on one surface of the cathode gas diffusion layer 242. The cathode liquid chamber 233 contacts the surface of the cathode 24 facing the cathode catalyst layer 241, and the cathode plate 25 (cathode gas chamber 251) contacts the surface of the cathode 24 facing the cathode gas diffusion layer 242. The cathode catalyst layer 241 may be formed by supporting highly dispersed fine particles of the cathode catalyst on the cathode gas diffusion layer 242. The cathode catalyst layer 241 can be manufactured by methods similar to those used for the anode catalyst layer 221. For example, the cathode catalyst layer 241 can be manufactured by a method including the steps of applying a mixture containing fine particles of the cathode catalyst, a cation exchange resin, and a solvent to a predetermined substrate and then drying the solvent.

[0103] The cathode catalyst may be the same as the anode catalyst described above, preferably platinum. The cathode catalyst may be used alone or in combination of two or more. The thickness of the cathode catalyst layer 241 is, for example, 5 μm to 50 μm. When the thickness of the cathode catalyst layer 241 is within the above range, hydrogen can be generated effectively.

[0104] The cathode gas diffusion layer 242 is made of a porous material and has electrical conductivity and gas diffusibility. Examples of materials for the cathode gas diffusion layer 242 include those similar to those for the anode gas diffusion layer 222. The thickness of the cathode gas diffusion layer 242 is, for example, 100 μm to 1000 μm. When the thickness of the cathode gas diffusion layer 242 is within this range, the diffusibility of hydrogen in the direction from the anode 22 side to the cathode 24 side can be improved.

[0105] The anode 22 and the cathode 24 are preferably 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 the cathode gas diffusion layer 242. The anode 22 and the cathode 24 can also be made water-repellent by performing a similar water-repellent treatment on the anode catalyst layer 221 and the cathode catalyst layer 241. By making the anode 22 and the cathode 24 water-repellent, leakage of liquid from the anode fluid chamber 231 to the anode 22 and leakage of liquid from the cathode fluid chamber 233 to the cathode 24 can be suppressed. Besides the water-repellent treatment of the anode 22 and the cathode 24, a polymer membrane having ion exchange groups may be provided between the anode 22 and the anode fluid chamber 231 and between the cathode 24 and the cathode fluid chamber 233 to suppress such liquid leakage. Examples of materials for the polymer membrane having ion exchange groups include Nafion (registered trademark). By providing such a film, it is possible to prevent the liquid in the liquid chamber from moving toward the electrode while maintaining the movement of charges.

[0106] The electrolyte unit 23 includes an electrolyte membrane 232, an anode fluid chamber 231 disposed on the anode 22 side via the electrolyte membrane 232, and a cathode fluid chamber 233 disposed on the cathode 24 side. Each electrolyte unit 23 has the same configuration. The electrolyte membrane 232 is a cation exchange membrane (CEM) and is made of an electrolyte material having cation conductivity. Examples of the electrolyte membrane 232 include fluorine-based cation exchange membranes such as perfluorosulfonic acid-based membranes. The thickness of the electrolyte membrane 232 is, for example, 2 μm to 500 μm.

[0107] The anode fluid chamber 231 is made of, for example, resin and has the shape of a vertically extending flat plate. The anode fluid chamber 231 includes a third supply port 234 provided in a lower portion, a third outlet 235 provided in an upper portion, and an anode fluid flow path 236 formed between the third supply port 234 and the third outlet 235. One end (inlet) of the anode fluid flow path 236 is connected to the third supply port 234, and the other end (outlet) of the anode fluid flow path 236 is connected to the third outlet 235. In the anode fluid flow path 236, the liquid flows from the inlet to the outlet.

[0108] The shape of the anode fluid chamber 231 and the positions of the third supply port 234 and the third discharge port 235 in the anode fluid chamber 231 are not limited to the above example. For example, the third supply port 234 may be provided on the upper part or side of the anode fluid chamber 231, and the third discharge port 235 may be provided on the lower part or side of the anode fluid chamber 231.

[0109] Concentrated carbon dioxide gas is released from the first electrolytic solution in the anolyte flow path 236. A gas-liquid mixture of the released concentrated carbon dioxide gas and the second electrolytic solution, which is the electrolytic solution after releasing the carbon dioxide, flows through the anolyte flow path 236 and is then discharged from the third outlet 235.

[0110] The anode fluid flow path 236 is a space defined between the anode catalyst layer 221 and the electrolyte membrane 232, and is separated from the outside by a frame made of resin or the like that defines the anode fluid chamber 231. The anode catalyst layer 221 is disposed so that the entire surface of one side of the anode catalyst layer 221 comes into contact with the electrolyte when the space is filled with the electrolyte. The anode fluid flow path 236 may be formed by using a mesh-shaped flow path forming member as a spacer, and by a space created by the flow path forming member crossing three-dimensionally. The spacer prevents the anode fluid flow path 236 from being blocked due to deformation of the anode catalyst layer 221 and the electrolyte membrane 232, for example.

[0111] The third supply port 234 of each anode fluid chamber 231 is connected to the absorber 10 via a second passage 602. The second passage 602 branches at a branch point 602a to connect to each anode fluid chamber 231. The third discharge port 235 of each anode fluid chamber 231 is connected to the gas-liquid separation unit 40 via a seventh passage 607. A plurality of seventh passages 607 are provided corresponding to each anode fluid chamber 231. The seventh passages 607 may be joined downstream.

[0112] The cathode fluid chamber 233 is made of, for example, resin and has a flat plate shape that extends vertically. The cathode fluid chamber 233 includes a fourth supply port 237 provided at an upper portion, a fourth discharge port 238 provided at a lower portion, and a cathode fluid flow path 239 formed between the fourth supply port 237 and the fourth discharge port 238. One end (inlet) of the cathode fluid flow path 239 is connected to the fourth supply port 237, and the other end (outlet) of the cathode fluid flow path 239 is connected to the fourth discharge port 238. In the cathode fluid flow path 239, liquid flows from the inlet to the outlet.

[0113] The cathode fluid flow path 239 is a space defined between the electrolyte membrane 232 and the cathode catalyst layer 241, and is separated from the outside by a frame made of resin or the like that defines the cathode fluid chamber 233. The cathode fluid flow path 239 is disposed so that one entire surface of the cathode catalyst layer 241 comes into contact with the electrolyte when the space is filled with the electrolyte. The cathode fluid flow path 239 may be provided with a spacer, similar to the anode fluid flow path 236.

[0114] In the cathode fluid chamber 233 , the second electrolytic solution is supplied through a fourth supply port 237 , and the first electrolytic solution from which the absorbed solution component has been regenerated is discharged from a fourth discharge port 238 .

[0115] The fourth supply port 237 of each cathode fluid chamber 233 is connected to the gas-liquid separation unit 40 via an eighth passage 608. A plurality of eighth passages 608 are provided corresponding to each cathode fluid chamber 233. The eighth passages 608 may be joined upstream. The fourth discharge port 238 of each cathode fluid chamber 233 is connected to the absorption tower 10 via a ninth passage 609. The ninth passage 609 branches out corresponding to each cathode fluid chamber 233 and joins at a joining point 609 a.

[0116] Each cathode fluid chamber 233 is provided with a liquid sensor 92. The liquid sensor 92 is, for example, a pH meter, and measures the pH of the liquid in the cathode fluid chamber 233. The liquid sensor 92 may be provided in the eighth passage 608 or the ninth passage 609.

[0117] In the concentration / separation section 20, adjacent electrolyte units 23 and the other electrolyte unit 23 are stacked in the same direction with an intermediate layer 28 interposed therebetween. One surface of the intermediate layer 28 contacts the cathode fluid chamber 233 of one electrolyte unit 23, and the other surface of the intermediate layer 28 contacts the anode fluid chamber 231 of the other electrolyte unit 23. The intermediate layer 28 supplies protons supplied from the cathode fluid chamber 233 of one electrolyte unit 23 to the anode fluid chamber 231 of the other adjacent electrolyte unit 23.

[0118] The intermediate layer 28 includes a catalyst layer 281 containing a catalyst and a gas diffusion layer 282. The catalyst layer 281 is formed on both surfaces of the gas diffusion layer 282. The catalyst layer 281 may be configured by supporting fine catalyst particles in a highly dispersed state on the surface of the gas diffusion layer 282.

[0119] Examples of catalysts include those similar to the anode catalyst described above, preferably platinum. The catalysts may be used alone or in combination of two or more. The catalyst is preferably used in the form of fine particles. Fine particles of a metal that functions as a catalyst, such as platinum, may be used. Alternatively, fine particles of the metal may be supported on the surface of an electronically conductive carrier, such as carbon black. Such catalyst layer 281 can be manufactured, for example, by applying a mixture containing fine catalyst particles, a cation exchange resin, and a solvent to a predetermined substrate, drying the solvent, and transferring the dried mixture from the substrate to the surface of the gas diffusion layer 282. Alternatively, by using the gas diffusion layer 282 as the predetermined substrate, the catalyst layer 281 can be formed directly on the surface of the gas diffusion layer 282 and within a predetermined thickness from the surface.

[0120] The thickness of the catalyst layer 281 is, for example, 5 μm to 50 μm. When the thickness of the catalyst layer 281 is 5 μm or more, the catalytic reactivity can be increased. When the thickness is 50 μm or less, the migration distance of protons can be shortened, and the operating voltage of the electrochemical cell can be further reduced.

[0121] The gas diffusion layer 282 is made of a porous material and has electrical conductivity and gas diffusibility. The gas diffusion layer 282 uniformly diffuses hydrogen molecules supplied from the catalyst layer 281 in contact with the cathode fluid chamber 233 to the catalyst layer 281 in contact with the anode fluid chamber 231. Materials constituting the gas diffusion layer 282 include the same materials as those used for the anode gas diffusion layer 222, and carbon paper is preferred. The thickness of the gas diffusion layer 282 is, for example, 100 μm to 1000 μm. When the thickness of the gas diffusion layer 282 is within the above range, the diffusibility of hydrogen in the direction from the anode 22 to the cathode 24 can be improved.

[0122] The intermediate layer 28 is preferably 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 at least one of the pair of catalyst layer 281 and gas diffusion layer 282. By imparting water-repellent properties, leakage of liquid from the anode fluid chamber 231 and the cathode fluid chamber 233 into the intermediate layer 28 can be suppressed.

[0123] In addition to imparting water repellency to the intermediate layer 28, a method for suppressing such liquid leakage may be achieved by providing a polymer membrane having ion exchange groups between the cathode fluid chamber 233 and the catalyst layer 281 in contact with the cathode fluid chamber 233, or between the anode fluid chamber 231 and the catalyst layer 281 in contact with the anode fluid chamber 231. An example of a material for the polymer membrane having ion exchange groups is Nafion (registered trademark). By providing such a membrane, it is possible to suppress the liquid in the fluid chamber from migrating into the intermediate layer while maintaining charge transfer. In particular, when a polymer membrane having ion exchange groups is provided between the cathode fluid chamber 233 and the catalyst layer 281 in contact with the cathode fluid chamber 233, it is preferable to adhere the catalyst layer 281 and the polymer membrane having ion exchange groups to each other, or to bring them into contact with each other and then apply pressure to them so that they are in close contact with each other. By adopting such a configuration, it is possible to prevent the hydrogen gas generated in the catalyst layer 281 from migrating to the cathode liquid chamber 233 side, and to increase the proportion of hydrogen gas that migrates to the gas diffusion layer 282 side.

[0124] Methods for bonding the catalyst layer 281 and the polymer membrane having ion exchange groups include a method in which a mixture containing a polymer having ion exchange groups and a solvent is applied to the surface of the catalyst layer 281 to a predetermined thickness and then dried to form a polymer membrane in an adhered state, and a method in which a polymer membrane having ion exchange groups is pressed against the surface of the catalyst layer 281 and heat-treated at a predetermined temperature, so-called hot pressing, for pressure bonding. Note that in the latter method, the heat treatment temperature is preferably equal to or higher than the glass transition temperature of the polymer membrane having ion exchange groups.

[0125] The intermediate layer 28 preferably further includes a sixth outlet 283 for discharging the liquid and a valve 284 for opening and closing the sixth outlet 283. The sixth outlet 283 may be provided in the lower part of the gas diffusion layer 282. The sixth outlet 283 discharges water generated inside the gas diffusion layer 282 of the intermediate layer 28 as protons pass through to the outside. When protons pass through the catalyst layer 281 of the intermediate layer 28, they move while carrying water (so-called hydration water), and the water remains inside the gas diffusion layer 282 as liquid water. Discharging the remaining water through the sixth outlet 283 improves the diffusibility of hydrogen inside the gas diffusion layer 282. Switching the valve 284 between open and closed allows for appropriate water discharge and suppresses hydrogen leakage.

[0126] The gas-liquid separation unit 40 separates the concentrated carbon dioxide gas from the second electrolytic solution. The gas-liquid separation unit 40 performs gas-liquid separation by, for example, water displacement, gravity separation, or the like. The gas-liquid separation unit 40 receives the gas-liquid mixture discharged from each anode fluid chamber 231 via a seventh passage 607. The gas-liquid separation unit 40 supplies the second electrolytic solution, from which the concentrated carbon dioxide gas has been separated, to each cathode fluid chamber 233 via an eighth passage 608.

[0127] The gas-liquid separation unit 40 is connected to the electrolytic reduction device 2 via a tenth passage 610. The gas-liquid separation unit 40 supplies the separated concentrated carbon dioxide gas to the electrolytic reduction device 2 via the tenth passage 610.

[0128] The electrolytic reduction device 2 generates carbon compounds by electrolyzing carbon dioxide together with water. The configuration of the electrolytic reduction device 2 is not particularly limited, but may include, for example, an anode, a cathode, and an ion exchange membrane disposed between the anode and the cathode. The gas obtained by the electrolytic reduction device 2 is a mixed gas containing carbon compounds as reduced products and hydrogen as a by-product. The electrolytic reduction device 2 is connected to the confluence 70 via a fifth passage 605.

[0129] The confluence unit 70 combines the mixed gas sent from the electrolytic reduction device 2 as the first hydrogen source and the hydrogen gas sent from the hydrogen storage unit 50 as the second hydrogen source, as necessary, and supplies the combined gas to the concentration / separation unit 20. The confluence unit 70 may further be connected to a third hydrogen source. The third hydrogen source is, for example, a hydrogen tank pre-filled with pure hydrogen having a hydrogen concentration of 100 vol %. Hydrogen from the third hydrogen source may be supplied to the hydrogen storage unit 50.

[0130] 1 shows an example in which the confluence part 70 is provided outside the concentration and separation part 20. Alternatively, the confluence part 70 may be provided inside the concentration and separation part 20. When the confluence part 70 is provided inside the concentration and separation part 20, it may be configured as follows. The concentration and separation part 20 includes a first first supply port 213 connected to the fifth passage 605 and a second first supply port 213 connected to the sixth passage 606. The first first supply port 213 and the second first supply port 213 are both connected to the inlet of the anode gas flow path 212 via the confluence part 70 inside the concentration and separation part 20.

[0131] As described above, the carbon compound production system S includes the first passage 601 to the eleventh passage 611. The first passage 601 flows the carbon dioxide-containing gas from the carbon dioxide-containing gas supply source to the absorption tower 10. The first passage 601 includes a compressor 93a. The second passage 602 flows the first electrolytic solution from the absorption tower 10 to the anode fluid chamber 231. The second passage 602 includes a pump 94a, a control valve 95a, and a flow meter 96a. The third passage 603 flows the exhaust gas from which hydrogen has been separated from the anode gas chamber 211 to the recovery unit 30. The fourth passage 604 flows the hydrogen-containing gas containing the mixed gas and / or high-pressure hydrogen gas from the junction 70 to the anode gas chamber 211. The fourth passage 604 includes a compressor 93b. The fifth passage 605 flows the mixed gas from the electrolytic reduction device 2 to the junction 70. The fifth passage 605 includes a control valve 95b and a flow meter 96b. The sixth passage 606 allows high-pressure hydrogen gas to flow from the hydrogen storage section 50 to the junction section 70. The sixth passage 606 includes a control valve 95c and a flow meter 96c.

[0132] The seventh passage 607 allows the gas-liquid mixture to flow from the anode fluid chamber 231 to the gas-liquid separation unit 40. The seventh passage 607 is equipped with a flow meter 96d. The eighth passage 608 allows the second electrolytic solution to flow from the gas-liquid separation unit 40 to the cathode fluid chamber 233. The eighth passage 608 is equipped with a control valve 95e and a flow meter 96e. The ninth passage 609 allows the first electrolytic solution to flow from the cathode fluid chamber 233 to the absorption tower 10. The ninth passage 609 is equipped with a pump 94f, a control valve 95f, and a flow meter 96f. The tenth passage 610 allows the concentrated carbon dioxide gas to flow from the gas-liquid separation unit 40 to the electrolytic reduction device 2. The eleventh passage 611 allows the high-pressure hydrogen gas to flow from the cathode gas chamber 251 to the hydrogen storage unit 50.

[0133] The compressors 93a and 93b compress and deliver gas. The pumps 94a and 94f deliver fluid. The control valves 95a, 95b, 95c, 95e, and 95f control the volumetric flow rate or mass flow rate of the fluid flowing through the passages. The flow meters 96a, 96b, 96c, 96d, 96e, and 96f measure the volumetric flow rate or mass flow rate of the fluid flowing through the passages. The fourth passage 604 and the fifth passage 605 may be equipped with gas sensors that detect the concentration of gas. Hereinafter, the compressors 93a and 93b will also be collectively referred to as compressors 93. The pumps 94a and 94f will also be collectively referred to as pumps 94. The control valves 95a, 95b, 95c, 95e, and 95f will also be collectively referred to as control valves 95. The flow meters 96 a , 96 b , 96 c , 96 d , 96 e , and 96 f are also collectively referred to as flow meters 96 .

[0134] An electrolytic solution circulation system is configured by the absorption tower 10, the second passage 602, the concentration / separation section 20, the seventh passage 607, the gas-liquid separation section 40, the eighth passage 608, and the ninth passage 609. The electrolytic solution containing the absorbing liquid and the electrolyte solution is recycled by absorbing carbon dioxide in the absorption tower 10, releasing the carbon dioxide in the concentration / separation section 20, and then absorbing carbon dioxide again in the absorption tower 10.

[0135] The carbon compound production system S includes a first bypass passage 612 that allows the second electrolytic solution discharged from the anode fluid chamber 231 to bypass the cathode fluid chamber 233. The first bypass passage 612 allows the first electrolytic solution to flow from the gas-liquid separation unit 40 to the second passage 602, bypassing the cathode fluid chamber 233. One end of the first bypass passage 612 is connected to the second passage 602 upstream of the branch point 602a. Alternatively, the first bypass passage 612 may connect the second passage 602 and the eighth passage 608. The carbon compound production system S may further include a second bypass passage (not shown) that allows the first electrolytic solution discharged from the cathode fluid chamber 233 to bypass the absorption tower 10 and the anode fluid chamber 231. One end of the second bypass passage is connected to the ninth passage 609, and the other end is connected to the eighth passage 608.

[0136] The control device 3 is a computer and includes a processor such as a central processing unit (CPU) (not shown), a memory, an input / output interface, etc. The memory stores various computer programs and data referenced by the processor. The input / output interface is connected to the current sensor 91, the liquid sensor 92, the compressor 93, the pump 94, the control valve 95, and the flow meter 96. The control device 3 acquires measurement values ​​from the current sensor 91, the liquid sensor 92, and the flow meter 96. The control device 3 outputs control signals to the compressor 93, the pump 94, and the control valve 95 to control their operation. Details of the control performed by the control device 3 will be described later.

[0137] Fig. 3 is an explanatory diagram illustrating the operation of the concentration and separation device 1. The operation of the concentration and separation device 1 and the carbon compound production system S will be described using Fig. 3. For the sake of simplicity, Fig. 3 shows an example in which two electrolyte units 23 are stacked.

[0138] A carbon dioxide-containing gas containing a low concentration of carbon dioxide is supplied to the absorption tower 10, and a first electrolytic solution is also supplied. The carbon dioxide-containing gas is pressurized by a compressor 93a as needed and then supplied. The first electrolytic solution is supplied at a predetermined flow rate by driving a pump 94f. In this embodiment, the first electrolytic solution is a mixed solution (KOH-KCL solution) of an aqueous potassium hydroxide solution as an absorption solution and an aqueous potassium chloride solution as an electrolyte solution.

[0139] The absorption reaction of the carbon dioxide-containing gas in the absorption tower 10 is expressed by the following reaction formula (1): KOH + CO → KHCO (1)

[0140] The absorption reaction produces a first electrolytic solution (KHCO3-KCL solution) that has absorbed carbon dioxide. In the first electrolytic solution, the carbon dioxide becomes bicarbonate ions. The first electrolytic solution (KHCO3-KCL solution) that has absorbed carbon dioxide is supplied to the concentration / separation unit 20 at a predetermined flow rate via the second passage 602 by driving the pump 94a.

[0141] More specifically, the carbon dioxide absorption reactions represented by the following reaction formulas (1-1) and (1-2) proceed, thereby obtaining a first electrolytic solution (KHCO3-KCL solution) that has absorbed carbon dioxide: 2KOH + CO2 → K2CO3 + H2O (1-1) K2CO3 + H2O + CO2 → 2KHCO3 (1-2)

[0142] The first electrolytic solution may be an electrolytic solution in which potassium hydroxide (KOH) has completely reacted to potassium bicarbonate (KHCO3), or an electrolytic solution containing a portion of potassium carbonate (K2CO3), which is the product of the above reaction formula (1-1). The first electrolytic solution may be an electrolytic solution in which most of the carbon dioxide has reacted to potassium carbonate (K2CO3), which is obtained by stopping the carbon dioxide absorption reaction at the above reaction formula (1-1). In the first electrolytic solution, carbon dioxide is converted to bicarbonate ions (HCO3 - ) can be formed.

[0143] In the concentration / separation unit 20, a first electrolytic solution (KHCO3-KCL solution) that has absorbed carbon dioxide is supplied from the third supply port 234 of the anode fluid chamber 231, and a hydrogen-containing gas is supplied from the first supply port 213 of the anode gas chamber 211. A voltage is applied to the anode 22 and the cathode 24 from the power source 26. The hydrogen-containing gas may contain only the mixed gas from the electrolytic reduction device 2, or may contain a combined gas obtained by combining the mixed gas and high-pressure hydrogen gas from the hydrogen storage unit 50. The hydrogen-containing gas contains hydrogen and a carbon compound. The hydrogen-containing gas is pressurized by the compressor 93b as necessary before being supplied.

[0144] While the hydrogen-containing gas passes through the anode gas flow channel 212, the hydrogen-containing gas is supplied from the anode gas diffusion layer 222 to the anode catalyst layer 221. As represented by the following reaction formula (2), hydrogen molecules are converted into protons (H + ) and electrons. H2 → 2H + +2e - ... (2)

[0145] Of the components contained in the hydrogen-containing gas, hydrogen is consumed in the anode catalyst layer 221, while carbon compounds (components other than hydrogen) remain unreacted. The gas containing carbon compounds, i.e., the exhaust gas after hydrogen separation, is discharged from the first outlet 214. The recovery unit 30 recovers the discharged exhaust gas.

[0146] Protons (H + ) moves to the anolyte chamber 231 adjacent to the anode 22. The protons (H + ), the pH of the KHCO3 solution in the anolyte chamber 231 decreases compared to before the oxidation reaction. The chemical equilibrium of the following reaction formula (3) shifts to the right, and carbon dioxide is produced. - +H + ⇔CO2+H2O...(3)

[0147] As carbon dioxide is released from the first electrolytic solution, the liquid in the anolyte flow path 236 becomes a second electrolytic solution (KCL solution) composed mainly of potassium chloride. The second electrolytic solution may contain a small amount of KHCO. The gas-liquid mixture of the generated concentrated carbon dioxide gas containing carbon dioxide and the second electrolytic solution (KCL solution) is supplied to the gas-liquid separation unit 40 via the third outlet 235 and the seventh passage 607.

[0148] The concentrated carbon dioxide gas and the second electrolytic solution (KCL solution) are separated from each other in the gas-liquid separation unit 40. The concentrated carbon dioxide gas is supplied to the electrolytic reduction device 2 via a tenth passage 610. The second electrolytic solution (KCL solution) is supplied to the cathode fluid chamber 233 via an eighth passage 608 and a fourth supply port 237.

[0149] In the electrolyte membrane 232, potassium ions (K + ) passes through the inside of the electrolyte membrane 232 and moves into the cathode fluid chamber 233.

[0150] Potassium ions (K + ) in the second electrolyte (KCL solution) in the cathode fluid chamber 233. + ) increases. Potassium ions (K + ) increases, the proton (H + ) is supplied to the intermediate layer 28. + ) is consumed, the pH of the second electrolytic solution (KCL solution) increases. This causes the absorption solution (KOH) to be regenerated. By regenerating the absorption solution, the liquid in the cathode solution flow path 239 becomes a first electrolytic solution (KOH-KCL solution) containing the absorption solution and the electrolyte solution. The first electrolytic solution (KOH-KCL solution) is circulated and supplied to the absorption tower 10 via the fourth outlet 238 and the ninth passage 609.

[0151] Protons (H + ) are adsorbed by the catalyst layer 281 on the anode 22 side and then supplied as hydrogen molecules to the gas diffusion layer 282. The hydrogen molecules pass through the inside of the gas diffusion layer 282 and are converted into protons (H + ) is converted to a proton (H +) is supplied to the anolyte chamber 231 of the adjacent electrolyte unit 23.

[0152] Similar reactions occur in each electrolyte unit 23, resulting in the formation of protons (H + ) moves from the anode 22 side to the cathode 24 side and is supplied to the cathode 24.

[0153] Protons (H + ) is adsorbed onto the cathode catalyst layer 241. As shown in the following reaction formula (4), hydrogen molecules are regenerated in the cathode catalyst layer 241 by a reduction reaction. + +2e - →H2...(4)

[0154] The hydrogen gas generated at the cathode 24 may be hydrogen gas generated by a reduction reaction of water, as represented by the following reaction formula (5): 2H2O+2e - →H2 + 2OH - ...(5)

[0155] The hydrogen gas generated at the cathode 24 can be at a higher pressure than the hydrogen-containing gas supplied to the anode 22. The hydrogen gas generated at the cathode 24 is a gas containing hydrogen and water, and hydrogen gas with a hydrogen concentration of 99 vol% or more can be obtained by removing the water. The hydrogen gas generated at the cathode 24 is discharged from the second outlet 253 and stored in the hydrogen storage unit 50 in a water-removed state. Alternatively, the hydrogen gas generated at the cathode 24 may be stored in the hydrogen storage unit 50 while still containing water.

[0156] In the electrolytic reduction device 2, the concentrated carbon dioxide gas is electrolyzed together with water to generate a mixed gas containing carbon compounds derived from the concentrated carbon dioxide gas and hydrogen.

[0157] The mixed gas is supplied to the concentration separation section 20 via the fifth passage 605, the junction section 70, and the fourth passage 604. In the concentration separation section 20, carbon compounds and hydrogen are separated, and an exhaust gas containing carbon compounds is discharged.

[0158] In the carbon compound production system S, the entire amount of the mixed gas produced in the electrolytic reduction device 2 is usually supplied to the concentration and separation device 1 as a hydrogen-containing gas. The flow rate of the mixed gas may be adjusted as appropriate by a control valve 95b. When the flow rate of the mixed gas discharged from the electrolytic reduction device 2 or the amount of mixed gas produced in the electrolytic reduction device 2 is less than a predetermined value, the amount of hydrogen in the hydrogen-containing gas is increased by adding high-pressure hydrogen gas to the hydrogen-containing gas. The ratio of the mixed gas and high-pressure hydrogen gas contained in the hydrogen-containing gas can be set based on the hydrogen concentrations of the mixed gas and high-pressure hydrogen gas and the flow rate of the mixed gas. At the start of operation, a hydrogen-containing gas containing only high-pressure hydrogen gas may be supplied to the concentration and separation device 1.

[0159] In the carbon compound production system S, the flow paths of the first electrolytic solution and the second electrolytic solution can be switched based on the pH value of the liquid flowing through the cathode fluid chamber 233. The pH value of the liquid may be, for example, the pH of the second electrolytic solution supplied to the cathode fluid chamber 233, or the pH of the first electrolytic solution discharged from the cathode fluid chamber 233. If the pH value is less than a predetermined value, it is considered that the reaction in the anode fluid chamber 231, which shifts the chemical equilibrium of the reaction formula (3) to the right, has not progressed sufficiently.

[0160] If the pH value is equal to or higher than a predetermined value, the second electrolytic solution discharged from the third outlet 235 of the anode fluid chamber 231 is supplied to the cathode fluid chamber 233 via the seventh passage 607, the gas-liquid separation unit 40, and the eighth passage 608. If the pH value is equal to or higher than a predetermined value, the first electrolytic solution discharged from the fourth outlet 238 of the cathode fluid chamber 233 is supplied to the absorption tower 10 via the ninth passage 609, so that the first electrolytic solution absorbs carbon dioxide again.

[0161] If the pH value is less than the predetermined value, the second electrolytic solution discharged from the third outlet 235 of the anode fluid chamber 231 is supplied again to the anode fluid chamber 231 as the first electrolytic solution via the first bypass passage 612 and the second passage 602. If the pH value is less than the predetermined value, the first electrolytic solution discharged from the fourth outlet 238 of the cathode fluid chamber 233 may be supplied again to the cathode fluid chamber 233 as the second electrolytic solution via the second bypass passage and the eighth passage 608 (not shown) in order to raise the pH value to at least the predetermined value.

[0162] The following describes the control processing executed by the control device 3. The control device 3 manages the operating status of the carbon compound production system S based on the measured values ​​of the current sensor 91, the liquid sensor 92, and the flow meter 96. The control device 3 estimates the amount of hydrogen consumed in the concentration / separation unit 20, the amount of carbon dioxide produced in the concentration / separation unit 20, the amount of mixed gas produced in the electrolytic reduction device 2, and the like, based on, for example, the current value of the DC power supply energizing the concentration / separation unit 20 detected by the current sensor 91 and the amount of electricity obtained by integrating the current value.

[0163] Based on the estimation result, the control device 3 may automatically control the operation of the compressor 93, the pump 94, and the control valve 95. Examples of the automatic control will be described below.

[0164] The control device 3 adjusts the content and supply amount of the hydrogen-containing gas supplied to the concentration / separation unit 20 based on the flow rate of the mixed gas discharged from the electrolytic reduction device 2 or the amount of mixed gas produced in the electrolytic reduction device 2. The content and supply amount of the hydrogen-containing gas may be adjusted by controlling the aperture of the control valves 95b and 95c. The content of the hydrogen-containing gas may be the mixing ratio of the mixed gas and hydrogen gas. When the flow rate of the mixed gas discharged from the electrolytic reduction device 2 is less than a predetermined flow rate value, the control device 3 adds high-pressure hydrogen gas from the hydrogen storage unit 50 to make up for the shortfall in the flow rate of the mixed gas.

[0165] The control device 3 switches the flow path for the first electrolytic solution discharged from the cathode fluid chamber 233 and the flow path for the second electrolytic solution discharged from the anode fluid chamber 231 based on the pH value of the liquid flowing through the cathode fluid chamber 233. If the pH value is equal to or greater than a predetermined value, the control device 3 controls the second electrolytic solution discharged from the anode fluid chamber 231 to be supplied to the cathode fluid chamber 233 without flowing through the first bypass passage 612. The control device 3 also controls the first electrolytic solution discharged from the cathode fluid chamber 233 to be supplied to the absorption tower 10. If the pH value is less than the predetermined value, the control device 3 controls the second electrolytic solution discharged from the anode fluid chamber 231 to be flowed through the first bypass passage 612 and supplied to the anode fluid chamber 231. The control device 3 also controls the first electrolytic solution discharged from the cathode fluid chamber 233 to be flowed through a second bypass passage (not shown) and supplied to the cathode fluid chamber 233.

[0166] In the above embodiment, the mixed gas is used as the hydrogen source. Alternatively, hydrogen gas may be supplied to the enrichment / separation unit 20 from a hydrogen source other than the mixed gas.

[0167] In the above-described configuration, the electrolyte units 23 are stacked using intermediate layers 28 each including a gas diffusion layer 282 supporting a catalyst layer 281 on both sides. The intermediate layer 28 may be any layer as long as it is capable of supplying protons from the cathode fluid chamber 233 to the anode fluid chamber 231. The intermediate layer 28 may be, for example, a bipolar membrane formed by laminating a cation exchange membrane and an anion exchange membrane. An intermediate layer 28 using a gas diffusion layer and an intermediate layer 28 using a bipolar membrane may be used in combination. The number of electrolyte units 23 provided in the concentration / separation section 20 is not limited to multiple, and may be one.

[0168] According to the above configuration, concentrated carbon dioxide gas can be produced by electrodialysis using hydrogen pumping with hydrogen-containing gas containing low concentrations of hydrogen in the concentration / separation unit 20. For example, the voltage applied to the concentration / separation unit 20 can be lower than in methods using water electrolysis, thereby reducing energy consumption. Because gas containing low concentrations of hydrogen is used as the hydrogen source, there is greater freedom in selecting the hydrogen source and greater freedom in system design.

[0169] Furthermore, with the above configuration, since the intermediate layer 83 is provided, the voltage required for the permeation of protons between the plurality of electrolyte units can be reduced compared to when a bipolar membrane is used. This is because, while a bipolar membrane requires the application of a voltage at least sufficient to dissociate water, the use of the intermediate layer 83 eliminates the need to apply such a voltage. Specifically, the voltage required in the intermediate layer 83 is the sum of the voltages required for the reaction in which protons become hydrogen molecules and the reaction in which hydrogen molecules become protons, and this total voltage is significantly smaller than the voltage required to dissociate water.

[0170] The hydrogen gas obtained by the concentration / separation unit 20 or a mixed gas derived from concentrated carbon dioxide gas can be used as the hydrogen source, allowing for efficient gas cycling within the system. Since the concentration / separation unit 20 produces carbon dioxide and separates hydrogen from the reduced product, there is no need to provide a separate hydrogen separation process, improving operating efficiency and further reducing energy consumption. There is no need to provide a separate carbon dioxide production device and separation device, simplifying the system configuration.

[0171] By circulating the mixed solution of the absorption liquid and the electrolyte liquid, the amount of energy required for absorbing and releasing carbon dioxide can be reduced, and the operating efficiency can be improved. By stacking the electrolyte units 23 using the intermediate layer 28 having the gas diffusion layer 282 with the catalyst layer 281 supported on both sides, the voltage required for the permeation of hydrogen ions between the electrolyte units 23 can be reduced compared to when a bipolar membrane is used, for example. This is because when a bipolar membrane is used, at least water molecules are converted into protons (H + ) and hydroxyl groups (OH - ), but by using the intermediate layer 28, the application of such a voltage becomes unnecessary. Specifically, the voltage required in the intermediate layer 28 is the sum of the voltages required for the reaction in which protons become hydrogen molecules and the reaction in which hydrogen molecules become protons, and this total voltage is significantly smaller than the voltage required to dissociate water. Note that, in the bipolar membrane, when water molecules are converted into protons (H + ) and hydroxyl groups (OH - The theoretical voltage for dissociating protons into hydrogen molecules and hydrogen molecules into protons in the intermediate layer 28 is approximately 0.83 V, and the theoretical voltage for the reaction in which protons become hydrogen molecules and the reaction in which hydrogen molecules become protons is 0 V. In other words, by stacking multiple liquid chambers using the intermediate layer 28, the voltage applied to the concentration / separation unit 20 can be further reduced compared to when a similar stacking is performed using a bipolar membrane, and energy consumption can be reduced.

[0172] The embodiments disclosed herein are illustrative in all respects and should not be considered limiting. 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 scope of the claims and equivalents thereto. The sequences shown in each embodiment are not limited, and within the scope of no contradiction, each processing step may be executed in a different order, or multiple processes may be executed in parallel. The entity that performs each process is not limited, and within the scope of no contradiction, the process of each device may be executed by another device.

[0173] The matters described in each embodiment can be combined with each other. Furthermore, the independent claims and dependent claims described in the claims can be combined with each other in any and all combinations, regardless of the reference format. Furthermore, the claims use a format in which a claim references two or more other claims (multiple claim format), but this is not limited to this. A multiple claim (multi-multi claim) that references at least one other multiple claim may also be used.

[0174] REFERENCE SIGNS LIST Carbon compound production system 1 Concentration / separation device 2 Electrolytic reduction device 3 Control device 10 Absorption tower 20 Concentration section 21 Anode plate 211 Anode gas chamber 212 Anode gas flow path 213 First supply port 214 First outlet 22 Anode 221 Anode catalyst layer 222 Anode gas diffusion layer 23 Electrolyte unit 231 Anode liquid chamber 232 Electrolyte membrane 233 Cathode liquid chamber 24 Cathode 241 Cathode catalyst layer 242 Cathode gas diffusion layer 25 Cathode plate 251 Cathode gas chamber 252 Cathode gas flow path 253 Second outlet 26 Power source 28 Intermediate layer 281 Catalyst layer 282 Gas diffusion layer 283 Sixth outlet 284 Valve 30 Recovery section 40 Gas-liquid separation device 50 Hydrogen storage section 70 Confluence

Claims

1. A carbon dioxide generating device comprising: an electrolyte membrane; an anode provided on one side of the electrolyte membrane for generating protons from hydrogen; a cathode provided on the other side of the electrolyte membrane for generating hydrogen; a first liquid chamber provided between the anode and the electrolyte membrane and supplied with a first electrolytic solution that has absorbed carbon dioxide; and a second liquid chamber provided between the electrolyte membrane and the cathode and supplied with a second electrolytic solution, wherein a gas having a hydrogen concentration of less than 99 vol% is supplied to the anode.

2. A carbon dioxide production device comprising: an anode that generates protons from hydrogen; a cathode that generates hydrogen; a first liquid chamber to which a first electrolytic solution having carbon dioxide absorbed therein is supplied; a second liquid chamber to which a second electrolytic solution is supplied; and an electrolyte membrane provided between the first liquid chamber and the second liquid chamber, wherein gas having a hydrogen concentration of less than 99 vol% is supplied to the anode.

3. The carbon dioxide production device according to claim 1 or 2, wherein the gas supplied to the anode has a hydrogen concentration of 50 vol % or less.

4. A carbon dioxide production device according to claim 1 or 2, wherein the gas supplied to the anode contains a mixed gas of hydrogen and carbon compounds obtained when carbon dioxide produced in the carbon dioxide production device is reduced.

5. A carbon dioxide production device according to claim 1 or 2, wherein the gas supplied to the anode is mixed with a gas having a hydrogen concentration of 99 vol % or more.

6. The carbon dioxide production device according to claim 5, wherein the gas having a hydrogen concentration of 99 vol % or more contains hydrogen produced at the cathode.

7. A carbon dioxide production device according to claim 1 or claim 2, comprising a confluence section that combines gas having a hydrogen concentration of less than 99 vol % with gas having a hydrogen concentration of 99 vol % or more and supplies the combined gas to the anode.

8. A carbon dioxide generating device according to claim 1 or claim 2, further comprising a gas-liquid separator that separates the carbon dioxide released from the first electrolytic solution from the first electrolytic solution.

9. The carbon dioxide generating device according to claim 8, wherein the first electrolytic solution separated by the gas-liquid separator is supplied to the second liquid chamber as the second electrolytic solution.

10. The carbon dioxide generating device according to claim 1 or 2, further comprising a first gas chamber through which the gas supplied to the anode flows, the first gas chamber having an outlet for discharging a portion of the gas supplied to the anode.

11. The carbon dioxide production device according to claim 10, further comprising a recovery section for recovering the gas discharged from the exhaust port.

12. A carbon dioxide production device as described in claim 1 or claim 2, comprising a gas-liquid contact section that brings a gas containing carbon dioxide into contact with a liquid, and the first liquid chamber is supplied with the first electrolytic solution that has absorbed carbon dioxide by contacting the gas containing carbon dioxide in the gas-liquid contact section.

13. A carbon dioxide generating device as described in claim 1 or claim 2, comprising a plurality of units each having the electrolyte membrane, and the first liquid chamber and the second liquid chamber arranged with the electrolyte membrane interposed between the anode and the cathode, and each of the plurality of first liquid chambers is connected to a gas-liquid separator that separates the carbon dioxide released from the first electrolytic solution from the first electrolytic solution, and to a supply path that supplies the first electrolytic solution.

14. A carbon dioxide production device according to claim 1 or claim 2, comprising a first gas chamber through which gas supplied to the anode flows and a second gas chamber through which hydrogen produced at the cathode flows, wherein the flow rate of the gas per unit time in the first gas chamber is greater than the flow rate of the gas per unit time in the second gas chamber.

15. A carbon dioxide generating device comprising: an electrolyte membrane; an anode provided on one side of the electrolyte membrane for generating protons from hydrogen; a cathode provided on the other side of the electrolyte membrane for generating hydrogen; a first liquid chamber provided between the anode and the electrolyte membrane and supplied with a first electrolytic solution having absorbed carbon dioxide; and a second liquid chamber provided between the electrolyte membrane and the cathode and supplied with a second electrolytic solution, wherein a mixed gas of hydrogen and a carbon compound is supplied to the anode.

16. A carbon compound production system comprising the carbon dioxide production apparatus according to claim 1 or 2, and a reduction apparatus that reduces the carbon dioxide produced by the carbon dioxide production apparatus to produce a carbon compound.

17. The carbon compound production system according to claim 16, wherein the reduction device is an electrolytic reduction device.

18. The carbon compound production system according to claim 16, wherein the reduction device produces a mixed gas containing the carbon compound and hydrogen, and the mixed gas produced by the reduction device is supplied to the anode.

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