Carbon dioxide electrolysis device and control method of carbon dioxide electrolysis device

Abstract

The present invention relates to a carbon dioxide electrolysis device and a control method thereof. The present invention aims to improve carbon dioxide utilization rate of a carbon dioxide electrolysis device. The carbon dioxide electrolysis device includes: a carbon dioxide electrolysis cell having a cathode flow path, an anode flow path, a cathode, an anode, and a first diaphragm; a first current regulator that supplies a first current; a first gas-liquid separator that separates a first fluid discharged from the anode flow path into a first liquid and a first gas; an electro-dialysis cell having a first housing portion, a first electrode, a second housing portion, a second electrode, a third housing portion, a fourth housing portion, a second diaphragm, a third diaphragm, and a fourth diaphragm; a second current regulator that supplies a second current; at least one of a first detector that detects a flow rate of the first gas or a concentration of carbon dioxide contained in the first gas and a second detector that detects a pH or a concentration of at least one ion of the first fluid; and a first controller that adjusts a value of the second current based on at least one detection signal.

Description

[0001] This application is based on and enjoys priority from Japanese Patent Application 2022-040387 (filed on 3 / 15 / 2022). The entire contents of the aforementioned application are incorporated herein by reference. Technical Field

[0002] The embodiments of the present invention relate to a carbon dioxide electrolysis device and a control method for the carbon dioxide electrolysis device. Background Technology

[0003] In recent years, as an attempt at decarbonization, carbon dioxide electrolysis technology, which electrochemically reduces carbon dioxide (CO2) into chemical substances (chemical energy) such as carbon monoxide (CO), formic acid (HCOOH), methanol (CH3OH), methane (CH4), ethanol (C2H5OH), ethane (C2H6), and ethylene (C2H4), has attracted much attention. For carbon dioxide electrolyzers with two chambers separated by a membrane, a portion of the carbon dioxide introduced into the electrolyzer moves from the cathode flow path to the anode flow path and is discharged from the anode flow path along with the electrolyte, resulting in a decrease in carbon dioxide utilization. Summary of the Invention

[0004] The problem to be solved by this invention is to improve the carbon dioxide utilization rate of carbon dioxide electrolysis devices.

[0005] The carbon dioxide electrolysis apparatus of the embodiment includes: a carbon dioxide electrolyzer having a cathode flow path through which carbon dioxide flows, an anode flow path through which an aqueous electrolyte flows, a cathode facing the cathode flow path and generating carbon compounds by reducing carbon dioxide, an anode facing the anode flow path and generating oxygen by oxidizing water, and a first diaphragm disposed between the anode flow path and the cathode flow path; a first current regulator that supplies a first current between the anode and the cathode; a first gas-liquid separator that separates a first fluid discharged from the anode flow path into a first liquid and a first gas; and an electrodialysis cell having a first housing, a first electrode disposed in the first housing, a second housing, a second electrode disposed in the second housing, and a diaphragm disposed between the first housing and the second housing that houses a first electrode from the first liquid. The gas-liquid separator includes a third housing for a first liquid, a fourth housing between the third and second housings, a second diaphragm between the first and third housings, a third diaphragm between the second and fourth housings, and a fourth diaphragm between the third and fourth housings; a second current regulator that supplies a second current between a first electrode and a second electrode; a detector selected from at least one of a first detector that detects the flow rate of a first gas or the concentration of carbon dioxide contained in the first gas, and a second detector that detects the pH of a first fluid or the concentration of at least one ion contained in the first fluid; and a first controller that controls the second current regulator based on at least one detection signal from at least one detector to adjust the value of the second current.

[0006] A control method for a carbon dioxide electrolysis apparatus according to an embodiment, wherein the carbon dioxide electrolysis apparatus comprises:

[0007] A carbon dioxide electrolyzer, the carbon dioxide electrolyzer having a cathode flow path through which carbon dioxide flows, an anode flow path through which an aqueous electrolyte flows, a cathode facing the cathode flow path and generating carbon compounds by reducing the carbon dioxide, an anode facing the anode flow path and generating oxygen by oxidizing the water, and a first diaphragm disposed between the anode flow path and the cathode flow path.

[0008] A first gas-liquid separator separates the first fluid discharged from the anode flow path into a first liquid and a second gas; and

[0009] An electrodialysis cell, the electrodialysis cell having a first receiving portion, a first electrode disposed in the first receiving portion, a second receiving portion, a second electrode disposed in the second receiving portion, a third receiving portion disposed between the first receiving portion and the second receiving portion and receiving a first liquid supplied from the first gas-liquid separator, a fourth receiving portion disposed between the third receiving portion and the second receiving portion, a second diaphragm disposed between the first receiving portion and the third receiving portion, a third diaphragm disposed between the second receiving portion and the fourth receiving portion, and a fourth diaphragm disposed between the third receiving portion and the fourth receiving portion;

[0010] The method comprises the following steps:

[0011] The steps include separating the first fluid discharged from the anode flow path into the first liquid and the first gas, and detecting at least one of the following: the flow rate of the first gas or the concentration of carbon dioxide contained in the first gas; and the pH of the first fluid or the concentration of at least one ion contained in the first fluid; and

[0012] The step of adjusting the value of the current supplied to the electrodialysis cell based on the detection results of at least one of the above. Attached Figure Description

[0013] Figure 1 This is a schematic diagram showing an example of the configuration of the carbon dioxide electrolysis apparatus according to the first embodiment.

[0014] Figure 2 This is a schematic diagram showing a structural example of the carbon dioxide electrolyzer 100 according to the first embodiment.

[0015] Figure 3 This is a schematic diagram illustrating an example of the structure of an electrodialysis cell.

[0016] Figure 4 This is a schematic diagram showing another structural example of an electrodialysis cell.

[0017] Figure 5 This is a schematic diagram showing a structural example of the carbon dioxide electrolyzer 100 according to the second embodiment.

[0018] Figure 6 This is a schematic diagram illustrating the configuration of the carbon dioxide electrolysis apparatus in the embodiment.

[0019] Figure 7 This is a graph showing the concentration of carbon dioxide in the generated gas at various current densities.

[0020] Figure 8 This is a graph showing the pH of the electrolyte after passing through the anolyte flow path 102 at various current densities.

[0021] Figure 9 This is a graph showing the relationship between the carbon dioxide concentration in the anode exhaust and the pH of the electrolyte.

[0022] (Symbol Explanation)

[0023] 1: Carbon dioxide electrolysis unit; 1A: Carbon dioxide electrolysis unit; 31: Gas-liquid separator; 32: Gas-liquid separator; 34: Flow meter; 41: Carbon dioxide detector; 42: Carbon dioxide detector; 43: pH-ion concentration detector; 44: Water quality detector; 51: Current regulator; 52: Current regulator; 61: Pump; 62: Discharge valve; 63: Pump; 64: Pump; 71: Carbon dioxide supply source; 72: Carbon dioxide flow regulator; 73: Argon supply source; 81: Controller; 82: Controller; 91: Gas exhaust path; 92: Electrolyte path; 93: Electrolyte tank; 94: Electrolyte supply source; 100: Carbon dioxide electrolysis cell; 101: Cathode flow path; 102: Anode flow path; 103: Diaphragm; 104: Cathode. 105: Anode, 106: Supply path, 107: Supply path, 108: Discharge path, 109: Supply path, 110: Discharge path, 121: Flow path plate, 122: Flow path plate, 123: Cathode path, 124: Anode path, 124: Flow path plate, 125: Current collector, 126: Current collector, 200: Electrodialysis cell, 201: Reception section, 202: Reception section, 203: Reception section, 204: Reception section, 205: Electrode, 206: Electrode, 207: Diaphragm, 208: Diaphragm, 209: Diaphragm, 211: Supply path, 212: Discharge path, 213: Supply path, 214: Discharge path, 215: Supply path, 216: Discharge path, 217: Supply path, 218: Discharge path. Detailed Implementation

[0024] The carbon dioxide electrolysis apparatus of the embodiments will now be described with reference to the accompanying drawings. Furthermore, in each embodiment, the same symbols are used to mark the same components, and sometimes descriptions are omitted. The accompanying drawings are schematic diagrams, and the relationship between the thickness of each part and its planar dimensions, the ratio of the thickness of each part, etc., may sometimes differ from reality.

[0025] Furthermore, in this specification, the term "connection" includes not only direct connections but also indirect connections, unless otherwise specified.

[0026] (First Embodiment)

[0027] Figure 1 This is a diagram showing the carbon dioxide electrolysis apparatus of the first embodiment. Figure 1The carbon dioxide electrolysis device 1 shown includes: a carbon dioxide electrolysis cell 100, an electrodialysis cell 200, a carbon dioxide detector 41, a carbon dioxide detector 42, a pH-ion concentration detector 43, a gas-liquid separator 31, a gas-liquid separator 32, a water quality detector 44, a current regulator 51, a current regulator 52 supplying current to the carbon dioxide electrolysis cell 100, a pump 61, a discharge valve 62, a pump 63, a pump 64, a carbon dioxide supply source 71, a carbon dioxide flow regulator 72, a controller 81, a controller 82, and an electrolyte tank 93.

[0028] Figure 2 This is a schematic diagram showing a structural example of the carbon dioxide electrolyzer 100 in the first embodiment. Figure 2 The carbon dioxide electrolyzer 100 shown includes: a cathode flow path 101, an anode flow path 102, a diaphragm 103, a cathode 104, an anode 105, a supply flow path 106, a supply flow path 107, a discharge flow path 108, a supply flow path 109, and a discharge flow path 110. Each flow path can also be connected to a pump as needed.

[0029] The cathode flow path 101 is provided, for example, in a first containment section capable of containing carbon dioxide. Carbon dioxide can be contained within the cathode flow path 101, for example, as a first electrolyte containing it. The first electrolyte functions as a cathode solution, containing carbon dioxide as the substance to be reduced. The form of carbon dioxide present in the first electrolyte does not need to be gaseous; it can be dissolved carbon dioxide or carbonate ions (CO3). 2- ) and bicarbonate ions (HCO3) - The electrolyte may contain hydrogen ions and hydroxide ions, and is preferably an aqueous solution.

[0030] The anode flow path 102 is provided, for example, in a second containment section capable of containing a second electrolyte containing water or water vapor. The second electrolyte functions as the anode solution and contains, for example, water (H2O) and chloride ions (Cl-). - ), carbonate ions (CO3) 2- ), bicarbonate ions (HCO3) - The second electrolyte can be an aqueous solution of alcohol, amine, or other organic compounds, or an aqueous solution of organic compounds such as amine.

[0031] By changing the amount of water and the composition of the electrolytes in the first and second electrolytes, the reactivity can be altered, changing the selectivity of the substance to be reduced and the proportion of the chemical substances generated. The first and second electrolytes may also contain redox pairs as needed. Examples of redox pairs include Fe. 3+ / Fe 2+ and IO3 - / I - .

[0032] The first and second containment sections can be formed, for example, from quartz glass, acrylic resin (PMMA), polystyrene (PS), etc. A light-transmitting material is used in a portion of the cathode flow path 101 and the anode flow path 102, while a resin material can be used in the remaining portions. Examples of resin materials include polyetheretherketone (PEEK), polyamide (PA), polyvinylidene fluoride (PVDF), polyoxymethylene (POM) (polymer), polyphenylene ether (PPE), acrylonitrile-butadiene-styrene copolymer (ABS), polypropylene (PP), polyethylene (PE), etc. The first and second containment sections may also have spaces for containing gases contained in the reactants or products.

[0033] The pressure within the first and second containment sections is preferably set to a pressure at which carbon dioxide does not liquefy, for example, preferably adjusted to a range of 0.1 MPa or higher and 6.4 MPa or lower. If the pressure within the containment section is lower than 0.1 MPa, there is a concern that the efficiency of the carbon dioxide reduction reaction may decrease. If the pressure within the containment section exceeds 6.4 MPa, there is a concern that carbon dioxide may liquefy and the efficiency of the carbon dioxide reduction reaction may decrease. Furthermore, sometimes the pressure difference between the first and second containment sections can cause damage to the diaphragm 103. Therefore, it is preferable to set the pressure difference between the first and second containment sections to 1 MPa or lower.

[0034] The lower the temperature of the electrolyte, the higher the solubility of carbon dioxide. However, from the perspective of carbon dioxide electrolysis, the theoretical voltage of the reaction increases with the increase of solution resistance at low temperatures, which is disadvantageous. On the other hand, if the electrolyte temperature is high, the solubility of carbon dioxide decreases, but this is advantageous for carbon dioxide electrolysis. Therefore, the operating temperature conditions of the carbon dioxide electrolyzer 100 are preferably in the intermediate temperature range, for example, above atmospheric temperature and below the boiling point of the electrolyte. When the electrolyte is an aqueous solution, it is preferably above 10°C and below 100°C, more preferably above 25°C and below 80°C. Furthermore, when the cathode flow path 101 is filled with a raw material gas containing carbon dioxide and the anode flow path 102 is filled with water vapor, it can operate at higher temperatures. In this case, the operating temperature is determined considering the heat resistance of components such as the diaphragm 103. When the diaphragm 103 is an ion exchange membrane or the like, the maximum operating temperature is 180°C, and when it is a porous polymer membrane such as Teflon (registered trademark), the maximum temperature reaches 300°C. The first electrolyte and the second electrolyte can be electrolytes containing different substances, or they can be the same electrolyte containing the same substances. When the first electrolyte and the second electrolyte contain the same substances and the same solvent, they can also be considered as one electrolyte. Furthermore, the pH of the first electrolyte can be higher than that of the second electrolyte. This allows hydrogen ions and hydroxide ions to easily move through the membrane 103. Moreover, the potential difference created by the pH difference enables efficient redox reactions.

[0035] The first electrolyte is preferably a solution with a high carbon dioxide absorption rate. The form in which carbon dioxide exists in the first electrolyte is not necessarily limited to a dissolved state; it can also be present in bubbly form. Examples of electrolytes containing carbon dioxide include aqueous solutions containing bicarbonates or carbonates such as lithium bicarbonate (LiHCO3), sodium bicarbonate (NaHCO3), potassium bicarbonate (KHCO3), cesium bicarbonate (CsHCO3), sodium carbonate (Na2CO3), and potassium carbonate (K2CO3), as well as phosphoric acid and boric acid. Electrolytes containing carbon dioxide can also contain alcohols such as methanol and ethanol, acetone, or be alcohol solutions. The first electrolyte can also be an electrolyte with high ionic conductivity that lowers the reduction potential of carbon dioxide and contains a carbon dioxide absorbent.

[0036] As the second electrolyte, a solution containing water (H2O) can be used, such as an aqueous solution containing any electrolyte. This solution is preferably an aqueous solution that promotes the oxidation reaction of water. Examples of aqueous solutions containing electrolytes include those containing phosphate ions (PO42O). 2- ), borate ions (BO3) 3- ), hydrogen ions (H) +Sodium ions (Na) + ), potassium ions (K) + ), calcium ions (Ca 2+ Lithium ion (Li) + ), cesium ions (Cs) + ), magnesium ions (Mg 2+ ), chloride ions (Cl) - ), bicarbonate ions (HCO3) - ), carbonate ions (CO3) - ), hydroxide ions (OH-) - Aqueous solutions of , etc.

[0037] As the electrolyte mentioned above, for example, a mixture of cations such as imidazolium ions and pyridinium ions and BF4 can be used. - and PF6 - Ionic liquids or their aqueous solutions, which are composed of anionic salts and are liquid over a wide temperature range, are examples of electrolytes. Other examples include solutions of amines such as ethanolamine, imidazole, and pyridine, or their aqueous solutions. Examples of amines include primary amines, secondary amines, and tertiary amines. These electrolytes exhibit high ionic conductivity, absorb carbon dioxide, and may also possess the property of reducing reducing power.

[0038] Examples of primary amines include methylamine, ethylamine, propylamine, butylamine, pentamine, and hexylamine. The hydrocarbon in an amine can also be substituted with alcohols or halogens. Substances obtained by substituting the hydrocarbon in an amine include methanolamine, ethanolamine, and chloromethylamine. Furthermore, unsaturated bonds can also exist. This is also true for secondary and tertiary amines.

[0039] Examples of secondary amines include dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, diethanolamine, and dipropanolamine. The substituted hydrocarbons can also be different. This is also true for tertiary amines. For example, substances that are different from the hydrocarbon can include methylethylamine and methylpropylamine.

[0040] Examples of tertiary amines include trimethylamine, triethylamine, tripropylamine, tributylamine, trihexylamine, triethanolamine, triethanolamine, tripropanolamine, tributanolamine, trihexanolamine, methyldiethylamine, and methyldipropylamine.

[0041] Examples of cations that can be used as ionic liquids include 1-ethyl-3-methylimidazolium ion, 1-methyl-3-propylimidazolium ion, 1-butyl-3-methylimidazolium ion, 1-methyl-3-pentylimidazolium ion, and 1-hexyl-3-methylimidazolium ion.

[0042] The 2-position of the imidazolium ion can also be substituted. Examples of cations that can substitute the 2-position of the imidazolium ion include 1-ethyl-2,3-dimethylimidazolium ion, 1,2-dimethyl-3-propylimidazolium ion, 1-butyl-2,3-dimethylimidazolium ion, 1,2-dimethyl-3-pentylimidazolium ion, and 1-hexyl-2,3-dimethylimidazolium ion.

[0043] Examples of pyridinium ions include methylpyridinium, ethylpyridinium, propylpyridinium, butylpyridinium, pentylpyridinium, and hexylpyridinium. Both imidazolium and pyridinium ions can have alkyl groups substituted and can contain unsaturated bonds.

[0044] As an anion, fluoride ions (F) can be listed as examples. - ), chloride ions (Cl) - ), bromide ions (Br) - ), iodide ions (I - ), BF4 - PF6 - CF3COO - CF3SO3 - NO3 - SCN - (CF3SO2)3C - Examples of suitable ionic liquids include bis(trifluoromethoxysulfonyl)imide and bis(perfluoroethylsulfonyl)imide. They can also be bipolar ions that connect the cation and anion of an ionic liquid via a hydrocarbon. Furthermore, buffer solutions such as potassium phosphate solution can be supplied to the cathode flow path 101 and the anolyte flow path 102.

[0045] A diaphragm 103 can be disposed between the cathode flow path 101 and the anode flow path 102, separating the cathode flow path 101 and the anode flow path 102. The diaphragm 103 can allow hydrogen ions (H+) to pass through. + ), hydroxide ions (OH-) - ), carbonate ions (CO2) 3- ), bicarbonate ions (HCO3) - Plasma movement.

[0046] As the diaphragm 103, a membrane capable of selectively allowing the passage of anions or cations can be used. This allows the electrolytes in contact with the cathode 104 and anode 105 to be configured to contain different substances, and reduction and oxidation reactions can be promoted through differences in ionic strength, pH, etc. By employing the diaphragm 103, the first electrolyte and the second electrolyte can be separated. The diaphragm 103 can also have the function of allowing some ions contained in the electrolyte impregnated with the two electrodes to permeate, i.e., blocking more than one type of ion contained in the electrolyte. Thus, for example, the two electrolytes can be configured as solutions with different pH values.

[0047] As the separator 103, ion exchange membranes such as Neosepta (registered trademark) from ASTOM, Selemion (registered trademark) and Aciplex (registered trademark) from Asahi Glass, Fumasep (registered trademark) and fumapem (registered trademark) from Fumatech, Nafion (registered trademark) from DuPont (a fluoropolymer of polytetrafluoroethylene sulfonated), lewabrane (registered trademark) from LANXESS, IONSEP (registered trademark) from IONTECH, Mustang (registered trademark) from PALL, ralex (registered trademark) from mega, and GORE-TEX (registered trademark) from GORE-TEX can be used. Furthermore, membranes with hydrocarbons as the basic framework or membranes containing amine groups in anion exchange can also be used to construct the ion exchange membrane. When there is a pH difference between the first electrolyte and the second electrolyte, a bipolar membrane composed of stacked cation exchange membranes and anion exchange membranes can be used to stably maintain the pH of each electrolyte.

[0048] Besides ion exchange membranes, the diaphragm 103 can also be made of silicone resin, fluorinated resins (perfluoroalkoxyalkane (PFA), perfluoroethylene propylene copolymer (FEP), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyethersulfone (PES), etc.), porous ceramic membranes, fillers such as glass filters and agar, insulating porous materials such as zeolites and oxides, etc. In particular, hydrophilic porous membranes are preferred as diaphragm 103 because they do not cause pore blockage due to air bubbles.

[0049] Cathode 104 faces cathode flow path 101. Cathode 104 is an electrode (reduction electrode) for generating carbon compounds by reducing carbon dioxide. Cathode 104 is disposed inside the first housing and immersed in the first electrolyte. Cathode 104 contains, for example, a reduction catalyst for generating carbon compounds through the reduction reaction of carbon dioxide. Examples of reduction catalysts include materials that reduce the activation energy of carbon dioxide reduction. In other words, examples include materials that reduce the overvoltage during the generation of carbon compounds through the reduction reaction of carbon dioxide.

[0050] The cathode 104 can be made of metallic or carbon materials, for example. Metallic materials include, for example, metals such as gold, aluminum, copper, silver, platinum, palladium, zinc, mercury, indium, nickel, and titanium, as well as alloys containing these metals. Carbon materials include, for example, graphene, carbon nanotubes (CNTs), fullerenes, and Ketjen Black. Furthermore, it is not limited to these; as a reduction catalyst, metal complexes such as Ru or Re complexes, or organic molecules with imidazole or pyridine skeletons, can also be used. The reduction catalyst can also be a mixture of various materials. The cathode 104 can also have a structure in which a reduction catalyst, such as a thin film, lattice, particle, or filament, is disposed on a conductive substrate.

[0051] The carbon compounds generated by the reduction reaction in cathode 104 vary depending on the type of reduction catalyst, and examples include carbon monoxide (CO), formic acid (HCOOH), methane (CH4), methanol (CH3OH), ethane (C2H6), ethylene (C2H4), ethanol (C2H5OH), formaldehyde (HCHO), and ethylene glycol (C2H6O2). Furthermore, sometimes, a side reaction to produce hydrogen (H2) occurs simultaneously with the reduction reaction of carbon dioxide (CO2) in the cathode.

[0052] Anode 105 faces anode flow path 102. Anode 105 is an electrode (oxidation electrode) that oxidizes substances and ions in the second electrolyte. For example, it oxidizes water to produce oxygen and hydrogen peroxide, or it oxidizes chloride ions (Cl... - The oxidation process generates chlorine. The anode 105 is disposed inside the second containment section and immersed in the second electrolyte. The anode 105 contains an oxidation catalyst for the substance to be oxidized. As the oxidation catalyst, a material that reduces the activation energy during the oxidation of the substance to be oxidized can be used; in other words, a material that reduces the reaction overvoltage can be used.

[0053] Examples of metals that can be used as oxidation catalysts include ruthenium, iridium, platinum, cobalt, nickel, iron, and manganese. Furthermore, binary, ternary, and quaternary metal oxides can be used. Examples of binary metal oxides include manganese oxide (Mn-O), iridium oxide (Ir-O), nickel oxide (Ni-O), cobalt oxide (Co-O), iron oxide (Fe-O), tin oxide (Sn-O), indium oxide (In-O), and ruthenium oxide (Ru-O). Examples of ternary metal oxides include Ni-Fe-O, Ni-Co-O, La-Co-O, Ni-La-O, and Sr-Fe-O. Examples of quaternary metal oxides include Pb-Ru-Ir-O and La-Sr-Co-O. Moreover, these are not limited to these; metal hydroxides containing cobalt, nickel, iron, manganese, etc., Ru complexes, and Fe complexes can also be used as oxidation catalysts. In addition, multiple materials can be used in combination.

[0054] The anode 105 can also be a composite material containing both an oxidation catalyst and a conductive material. Examples of conductive materials include carbon materials such as carbon black, activated carbon, fullerenes, carbon nanotubes, graphene, Ketjen black, and diamond; transparent conductive oxides such as indium tin oxide (ITO), zinc oxide (ZnO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), and antimony-doped tin oxide (ATO); metals such as Cu, Al, Ti, Ni, Ag, W, Co, and Au; and alloys containing at least one of these metals. The anode 105 can also have a structure in which an oxidation catalyst, such as a thin film, lattice structure, particle structure, or filament structure, is disposed on a conductive substrate. Examples of conductive substrates include metallic materials such as titanium, titanium alloys, or stainless steel.

[0055] The supply flow path 106 is connected to the cathode flow path 101. The carbon dioxide electrolyzer 100 can supply carbon dioxide-containing raw material gas to the cathode flow path 101 from the supply flow path 106. Figure 2 The supply flow path 106 shown extends inside the cathode flow path 101, but the location of the supply flow path 106 is not limited to... Figure 2 The location shown.

[0056] The supply flow path 107 is connected to the cathode flow path 101. The carbon dioxide electrolyzer 100 can supply the first electrolyte to the containment section 101 via the supply flow path 107.

[0057] The discharge flow path 108 is connected to the cathode flow path 101. The carbon dioxide electrolyzer 100 can discharge the fluid containing the reaction gas and the first electrolyte from the cathode flow path 101 via the discharge flow path 108.

[0058] The supply flow path 109 is connected to the anode flow path 102. The carbon dioxide electrolyzer 100 can supply the second electrolyte to the anode flow path 102 via the supply flow path 109.

[0059] The discharge flow path 110 is connected to the anode flow path 102. The carbon dioxide electrolyzer 100 can discharge the fluid containing the reaction gas and the second electrolyte from the anode flow path 102 via the discharge flow path 110.

[0060] Figure 3 and Figure 4 This is a schematic diagram showing a structural example of an electrodialysis cell 200. Figure 3 The electrodialysis cell 200 shown includes: a housing 201, a housing 202, a housing 203, a housing 204, an electrode 205, an electrode 206, a diaphragm 207, a diaphragm 208, a diaphragm 209, a supply flow path 211, a discharge flow path 212, a supply flow path 213, a discharge flow path 214, a supply flow path 215, a discharge flow path 216, a supply flow path 217, and a discharge flow path 218.

[0061] The containment section 201 is located on the outside of the containment section 203.

[0062] The containment section 202 is located on the outside of the containment section 204.

[0063] The containment section 203 is located between the containment sections 201 and 202. The containment section 203 can contain, for example, a liquid containing ionized carbon dioxide.

[0064] The containment section 204 is located between the containment sections 202 and 203. The containment section 204 may contain electrolyte, for example.

[0065] Electrode 205 is disposed within housing 201. Electrode 206 is disposed within housing 202. The polarity of electrodes 205 and 206 changes depending on the device configuration. That is, when one of electrodes 205 and 206 is an anode, the other is a cathode.

[0066] Materials used for electrodes 205 and 206 include, for example, elemental metals such as gold, aluminum, copper, silver, platinum, palladium, zinc, mercury, indium, nickel, and titanium, as well as alloys containing such metals and carbon materials such as graphene and carbon nanotubes.

[0067] A diaphragm 207 is disposed between the containment section 201 and the containment section 203, separating the containment section 201 and the containment section 203.

[0068] A diaphragm 208 is disposed between the containment section 202 and the containment section 204, separating the containment section 202 and the containment section 204.

[0069] A diaphragm 209 is provided between the containment section 203 and the containment section 204, separating the containment section 203 and the containment section 204.

[0070] Diaphragms 207, 208, and 209 are, for example, cation exchange membranes, anion exchange membranes, or bipolar membranes formed by bonding cation exchange membranes and anion exchange membranes together. The orientation of the polarity when current is supplied from the current regulator 52 between electrodes 205 and 206, and which of the discharged carbon dioxide regenerated liquid and alkaline regenerated liquid corresponds to in discharge flow path 212 and discharge flow path 214, can be determined by the position and type of diaphragms used.

[0071] The supply path 211 is connected to the containment section 201. The electrodialysis cell 200 may use a pump 63 to supply electrolyte from the electrolyte tank 93 to the containment section 201 via the supply path 211.

[0072] The discharge path 212 is connected to the containment section 201. The electrodialysis cell 200 can discharge the gas generated in the containment section 201 and the fluid containing the first electrolyte or the second electrolyte from the containment section 201.

[0073] The supply path 213 is connected to the containment section 202. The electrodialysis cell 200 can be supplied with electrolyte from the electrolyte tank 93 to the containment section 202 via the supply path 213 using a pump 64.

[0074] The discharge path 214 is connected to the containment section 202. The electrodialysis cell 200 can discharge the gas generated in the containment section 202 and the fluid containing the first electrolyte or the second electrolyte from the containment section 202.

[0075] The supply flow path 215 is connected to the receiving section 203. The supply flow path 215 can also be connected to the gas-liquid separator 31. The electrodialysis cell 200 can supply the reaction gas discharged from the discharge flow path 108 via the supply flow path 215 and the anolyte separated from the fluid containing the second electrolyte to the receiving section 203.

[0076] The discharge path 216 is connected to the receiving section 203. The supply path 215 can also be connected to the gas-liquid separator 32. The electrodialysis cell 200 can discharge the fluid containing gas and liquid from the receiving section 203 via the discharge path 216.

[0077] The supply flow path 217 is connected to the receiving section 204. The supply flow path 217 can also be connected to the gas-liquid separator 32. The electrodialysis cell 200 can supply the liquid separated by the gas-liquid separator 32 as a circulating liquid to the receiving section 204 via the supply flow path 217.

[0078] The discharge path 218 is connected to the housing 204. The discharge path 218 can also be connected to the pump 61. The electrodialysis cell 200 can discharge fluid containing gas and liquid through the discharge path 218.

[0079] 200 electrodialysis cells Figure 4 In this way, the constituent unit consisting of receiving section 203, receiving section 204, diaphragm 207, diaphragm 209, supply flow path 215, discharge flow path 216, supply flow path 217, and discharge flow path 218 can be used as a slot constituent unit U. Alternatively, multiple slot constituent units U can be arranged between receiving section 201 and receiving section 202. Figure 4 In the structure shown, to achieve left-right symmetry, the diaphragm 207 contained in the groove constituting unit U can be replaced by the diaphragm 208. Furthermore, the positional relationship between the receiving portion 203 and the receiving portion 204 can be reversed depending on the combination of the diaphragms and the sign of the voltage applied to the electrodes.

[0080] A gas-liquid separator 31 is disposed at the downstream end of the carbon dioxide electrolyzer 100. The gas-liquid separator 31 separates the fluid discharged from the anode flow path 102 of the carbon dioxide electrolyzer 100 into a first liquid (anode discharge) and a first gas (anode exhaust). The gas-liquid separator 31 has, for example, a gas-liquid separation membrane.

[0081] A gas-liquid separator 32 is disposed at the downstream end of the electrodialysis cell 200. The gas-liquid separator 32 separates the fluid discharged from the discharge path 216 of the electrodialysis cell 200 into a second liquid and a second gas. The gas-liquid separator 32 has, for example, a gas-liquid separation membrane.

[0082] The carbon dioxide detector 41 can detect the concentration of carbon dioxide in the fluid discharged from the cathode flow path 101 of the carbon dioxide electrolysis cell 100. Based on the carbon dioxide concentration measured by the carbon dioxide detector 41, the flow rate of carbon dioxide supplied to the cathode flow path 101 of the carbon dioxide electrolysis cell 100 is changed, thereby adjusting the carbon dioxide concentration in the fluid discharged from the cathode flow path 101 to an optimal value. This simplifies or eliminates the need for mechanisms or processes to adjust the carbon dioxide concentration in the fluid discharged from the cathode flow path 101, enabling cost reduction for the carbon dioxide electrolysis apparatus 1 and the valuable product manufacturing system.

[0083] The carbon dioxide detector 42 can detect the concentration of carbon dioxide contained in the fluid discharged from the containment section 203 of the electrodialysis tank 200.

[0084] Regarding carbon dioxide detectors 41 and 42, examples of carbon dioxide detector 41 include gas chromatography (GC) and carbon dioxide concentration meters using specific heat, IR absorption, etc.

[0085] The pH-ion concentration detector 43 can detect the pH of the fluid discharged from the anolyte flow path 102 of the carbon dioxide electrolyzer 100 or at least one ion contained in the fluid. The pH-ion concentration detector 43 can also be connected to the downstream section of the discharge flow path 110 or the gas-liquid separator 31.

[0086] The water quality detector 44 monitors the water quality of the anode discharge by detecting the concentration of at least one component contained in the anode discharge separated by the gas-liquid separator 31. The water quality detector 44 can perform detection by extracting a portion of the liquid for analysis using liquid chromatography, or by detecting specific compounds. The water quality detector 44 can also be connected downstream of the gas-liquid separator 31, or before or after the pump 61.

[0087] The current regulator 51 is connected to the carbon dioxide electrolyzer 100. The current regulator 51 can supply a first current between the cathode 104 and the anode 105 of the carbon dioxide electrolyzer 100.

[0088] The current regulator 52 is connected to the electrodialysis cell 200. The current regulator 52 can supply a second current between the electrodes 205 and 206 of the electrodialysis cell 200.

[0089] The current regulators 51 and 52 may include, for example, AC power supplied from a power plant, DC power supplied via a conversion circuit, or a variable power source, i.e., a power source that converts renewable energy into electrical energy. Examples of such power sources include those that convert kinetic and potential energy from wind, water, geothermal, and tidal forces into electrical energy; power sources such as solar cells with photoelectric conversion elements that convert light energy into electrical energy; power sources such as fuel cells or batteries that convert chemical energy into electrical energy; and devices that convert vibrational energy from sound, etc., into electrical energy. Furthermore, the current regulators 51 and 52 may also include a power controller for controlling the aforementioned power sources.

[0090] Pump 61 is located at the rear end of electrodialysis cell 200. Pump 61 can supply fluid discharged from housing 204 to the anode flow path 102 of carbon dioxide electrolysis cell 100.

[0091] The drain valve 62 is located at the rear end of the electrodialysis cell 200. The drain valve 62 can supply the first electrolyte or discharge a portion of the anolyte from the electrolyte path 92.

[0092] The discharge valve 62 can be connected to the downstream section of the gas-liquid separator 31, or it can be connected to the front or rear of the pump 61.

[0093] Pump 63 is, for example, disposed in the middle of the supply flow path 211. Pump 63 can supply the degassed electrolyte from electrolyte tank 93 to the containment section 201.

[0094] Pump 64 is, for example, positioned midway through the supply flow path 213. Pump 64 can supply degassed electrolyte from electrolyte tank 93 to containment section 201.

[0095] The carbon dioxide supply source 71 can contain carbon dioxide for supplying to the cathode flow path 101 of the carbon dioxide electrolyzer 100.

[0096] A carbon dioxide flow regulator 72 is located between the carbon dioxide supply source 71 and the carbon dioxide flow regulator 72. The carbon dioxide flow regulator 72 uses a mass flow controller or similar device to regulate the flow rate of the carbon dioxide-containing fluid supplied to the cathode flow path 101. By increasing or decreasing the amount of carbon dioxide supplied to the cathode flow path 101 using the carbon dioxide flow regulator 72, the concentration of unreacted carbon dioxide in the fluid discharged from the cathode flow path 101 can be regulated, thereby improving carbon dioxide utilization and stabilizing the carbon dioxide concentration in the generated gas.

[0097] The controller 81 is connected to the carbon dioxide detector 41, the water quality detector 44, the discharge valve 62, and the carbon dioxide flow regulator 72, respectively. Figure 1 The flow of signals in controller 81 is indicated by dashed lines. Controller 81 can control carbon dioxide flow regulator 72 to adjust the flow rate of fluid supplied from carbon dioxide supply source 71 to cathode flow path 101 to an appropriate value based on a control signal generated from a detection signal from carbon dioxide detector 41. Controller 81 can also control discharge valve 62 based on a detection signal from water quality detector 44 to perform operations such as replenishing electrolyte or other liquids from electrolyte path 92 or discharging a first liquid into electrolyte path 92.

[0098] The controller 82 is connected to the carbon dioxide detector 42, the pH-ion concentration detector 43, the water quality detector 44, the current regulator 52, and the pump 61, respectively. Figure 1 The flow of signals in controller 82 is indicated by dashed lines. Controller 82 is capable of controlling current regulator 52 to adjust the value of the second current supplied to electrodialysis cell 200 based on a control signal generated from at least one of the detection signals from carbon dioxide detector 42, pH-ion concentration detector 43, and water quality detector 44, and controlling pump 61 to adjust the flow rate of fluid supplied to anode flow path 102 based on the generated control signal.

[0099] The electrolyte tank 93 can contain the electrolyte discharged from the discharge passages 212 and 214. The electrolyte tank 93 may also have a gas discharge section or a gas-liquid separation membrane for removing gas from the fluid discharged from the discharge passages 212 and 214.

[0100] Next, an example of the operation of the carbon dioxide electrolyzer 100 will be described. Here, the case in which an aqueous solution containing carbon dioxide is used as the first electrolyte, an aqueous solution of potassium hydroxide is used as the second electrolyte, carbon dioxide is reduced through the cathode 104 to mainly produce ethylene, and water or hydroxide ions are oxidized through the anode 105 to produce oxygen will be described.

[0101] If a voltage higher than the electrolysis voltage is applied between the cathode 104 and the anode 105, a carbon dioxide reduction reaction occurs near the cathode 104, which is in contact with the first electrolyte. As shown in equation (1) below, this reduction reaction occurs through electrons (e) supplied from the power source. - The carbon dioxide contained in the first electrolyte is reduced to produce ethylene (C2H4) and hydroxide ions (OH-). - The generated hydroxide ions (OH-) - A portion of the ions reacts with carbon dioxide to produce bicarbonate ions (HCO3-). - ), carbonate ions (CO3) 2- (Equations (2) and (3)). Through the voltage between the cathode 104 and the anode 105, a portion of hydroxide ions, bicarbonate ions, and carbonate ions move into the second electrolyte via the diaphragm 103. Furthermore, the reduction reaction of carbon dioxide is not limited to the formation of ethylene, but can also be the formation reaction of carbon monoxide, ethanol, ethane, methane, methanol, formic acid, acetic acid, propanol, etc.

[0102] 2CO2 + 8H2O + 12e - →C2H4+12OH - (1)

[0103] 12CO2 + 12OH - →12HCO3 - (2)

[0104] HCO3 - +OH - ←→CO3 2- +H2O (3)

[0105] Near the anode 105, which is in contact with the second electrolyte, an oxidation reaction of water occurs. As shown in equation (4) below, an oxidation reaction of H2O contained in the second electrolyte is produced, losing electrons to generate oxygen (O2) and hydrogen ions (H2O). + ).

[0106] 6H2O→12H + +3O2+12e - (4)

[0107] The generated hydrogen ions (H) +The bicarbonate ions (HCO3-) move through the diaphragm 103 and neutralize with the second electrolyte, determining the pH near the anode 105. - ) or carbonate ions (CO3) 2- Depending on the pH near the anode 105, the solution is either directly dissolved in the liquid as is or discharged from the outlet flow path 110 along with oxygen produced as carbon dioxide through the equilibrium reaction of equation (5). In the equilibrium reaction of equation (5), the higher the pH (closer to alkalinity), the more the equilibrium shifts to the right.

[0108] CO2 + H2O → HCO3 - +H + ←→CO3 2- +2H + (5)

[0109] As described above, when hydroxide ions are generated at the cathode 104, a larger current supply results in the generation of more hydroxide ions, causing a large amount of carbon dioxide to dissolve into the first electrolyte and move towards the anode 105. In other words, a larger current supply results in less carbon dioxide being used in the carbon dioxide reduction reaction, thus reducing carbon dioxide utilization. Furthermore, it is believed that a portion of the carbon dioxide supplied to the cathode 104 dissolves into the electrolyte and moves towards the anode 105 through the diaphragm 103 (exchange).

[0110] In the carbon dioxide electrolysis device 1, carbon dioxide that has moved to the anode 105 side in the electrodialysis cell 200 as carbon dioxide gas or as bicarbonate ions or carbonate ions is regenerated into carbon dioxide gas and then supplied to the carbon dioxide electrolysis cell 100 again, thereby improving the overall carbon dioxide utilization rate of the device.

[0111] As a method for recovering unused carbon dioxide in the carbon dioxide reduction reaction, it is known to use a scrubbing tower to absorb carbon dioxide gas and then regenerate it using an electrodialysis cell. In contrast, in the carbon dioxide electrolysis unit 1, carbon dioxide gas can be regenerated without using a scrubbing tower.

[0112] Since carbonate or bicarbonate ions dissolved in the second electrolyte are regenerated into carbon dioxide in the electrodialysis cell 200, the carbon dioxide gas moving to the anode 105 side needs to be dissolved in the solution as carbonate or bicarbonate ions through the equilibrium reaction of equation (5). Therefore, the equilibrium reaction of equation (5) needs to be shifted to the right by adjusting the pH of the fluid near the anode 105. The pH of the fluid near the anode 105 can be determined based on the flow rate of the fluid supplied from the pump 61 connected to the supply flow path 109 to the anode flow path 102, the pH of the second electrolyte before the anode flow path 102, and the amount of current supplied to the carbon dioxide electrolyzer 100.

[0113] The pH of the fluid near the anode 105 of the equilibrium reaction of formula (5) can be determined by pH-ion concentration detector 43.

[0114] When the pH in the equilibrium reaction of equation (5) is lower than the pH where carbon dioxide exists as bicarbonate or carbonate ions, i.e., the carbon dioxide moving to the anode 105 side is not completely dissolved in the solution, the pH can be adjusted so that most of the carbon dioxide moving to the anode 105 side exists as bicarbonate or carbonate ions by adjusting the flow rate of the fluid supplied from pump 61 to the anode flow path 102, or by adjusting the current supplied to the electrodialysis cell 200, i.e., by adjusting the pH of the second electrolyte before the anode flow path 102. It is assumed that when the pH is approximately 8.35 or higher, most of the carbon dioxide in the aqueous solution exists as bicarbonate or carbonate ions, and therefore control is performed to ensure that the pH measured by the pH-ion concentration detector 43 reaches 8.35 or higher.

[0115] The gas-liquid two-phase flow discharged from the discharge path 110 is separated into anode exhaust and anode liquid by the gas-liquid separator 31. The anode exhaust is recovered or discarded through the gas exhaust path 91 connected to the gas-liquid separator 31, and the anode liquid continues to be supplied to the receiving part 203 of the electrodialysis cell 200 through the supply path 215.

[0116] Examples of anode exhaust gas include oxygen and carbon dioxide, as well as mixed gases formed by the reduction of carbon dioxide into gaseous products such as carbon monoxide and ethylene, which move through diaphragm 103 to the anode 105 side and mix. Regarding anode exhaust gas, its gas composition is measured using a carbon dioxide detector 42. When the carbon dioxide concentration reaches a certain value or higher, the pH of the electrolyte can be controlled by adjusting the flow rate of pump 61 or the current supplied to the electrodialysis cell 200, causing the carbon dioxide contained in the anode exhaust gas to dissolve in the anode discharge solution. From the perspective of secondary utilization of the oxygen generated in anode 105, the anode exhaust gas discharged from gas exhaust path 91 is preferably high-purity oxygen, which can be considered for use as a getter gas or reaction gas.

[0117] The composition of the anolyte separated in the gas-liquid separator 31 can be determined by the water quality detector 44. Liquid products such as methanol, ethanol, and formic acid, which may be generated through the carbon dioxide reduction reaction, could potentially affect various electrodes and membranes, causing performance degradation. Therefore, when the concentration of these compounds in the liquid exceeds a certain level (specified value), the liquid can be discharged and supplied via the discharge valve 62 at a concentration below the specified value. The supplied liquid is an aqueous solution or ionic liquid used in the second electrolyte.

[0118] Anode drain solution is supplied to the receiving section 203 of the electrodialysis cell 200 via supply flow path 215, and gas and liquid are discharged via discharge flow path 216. Circulating fluid is supplied to the receiving section 204 via supply flow path 217, and gas and liquid are discharged via discharge flow path 218. The first electrolyte and the second electrolyte are contained in the receiving sections 203 and 204.

[0119] When a cation exchange membrane is used as diaphragm 209, and bipolar membranes are used as diaphragms 207 and 208 respectively, electrode 205 is the anode and electrode 206 is the cathode. Carbon dioxide regenerated liquid is discharged through discharge flow path 212, and alkaline regenerated liquid is discharged through discharge flow path 214.

[0120] When a bipolar membrane is used as diaphragm 209, and cation exchange membranes are used as diaphragms 207 and 208 respectively, electrode 205 is the cathode and electrode 206 is the anode. Carbon dioxide regenerated liquid is discharged through discharge flow path 212, and alkaline regenerated liquid is discharged through discharge flow path 214.

[0121] When an anion exchange membrane is used as diaphragm 209, and bipolar membranes are used as diaphragms 207 and 208 respectively, electrode 205 is the cathode and electrode 206 is the anode. Alkaline regenerated liquid is discharged through discharge flow path 212, and carbon dioxide regenerated liquid is discharged through discharge flow path 214.

[0122] When a bipolar membrane is used as diaphragm 209, and anion exchange membranes are used as diaphragms 207 and 208 respectively, electrode 205 is the anode and electrode 206 is the cathode. Alkaline regenerated liquid is discharged through discharge flow path 212, and carbon dioxide regenerated liquid is discharged through discharge flow path 214.

[0123] By applying a positive potential to the anode via the current regulator 52, the bipolar membrane is arranged with the anion exchange membrane facing the anode and the cation exchange membrane facing the cathode. This causes cations to move through the cation exchange membrane toward the cathode side and anions to move through the anion exchange membrane toward the anode side.

[0124] The carbon dioxide regenerated liquid is separated into a water-containing liquid (second liquid) and a carbon dioxide-containing gas (second gas) by the gas-liquid separator 32. The second liquid is supplied as a circulating liquid to the receiving section 204 via the supply flow path 213, and the second gas is supplied to the cathode flow path 101 of the carbon dioxide electrolyzer 100. In other words, the carbon dioxide dissolved in the second electrolyte in the carbon dioxide electrolyzer 100 and not used in the carbon dioxide reduction reaction is regenerated as carbon dioxide gas in the electrodialysis tank 200 and used again in the carbon dioxide electrolyzer 100 for the carbon dioxide reduction reaction, thus improving the carbon dioxide utilization rate of the carbon dioxide reduction reaction in the entire device. The alkaline regenerated liquid is pumped into the anode flow path 102 of the carbon dioxide electrolyzer 100 as the second electrolyte via the corresponding discharge flow path and pump 61.

[0125] The bipolar membrane dissociates water into hydrogen ions (H+) through the following reaction (6). + ) and hydroxide ions (OH) - The product is formed by the reaction of hydrogen ions with anions remaining in the containment, and by the reaction of hydroxide ions with cations remaining in the containment.

[0126] H2O→H + +OH - (6)

[0127] At this point, redox reactions occur at electrodes 205 and 206; oxidation occurs at the anode, and reduction occurs at the cathode. When an aqueous solution is used, oxygen is primarily generated as an oxidation reaction, and hydrogen is generated as a reduction reaction. There is also the possibility of redox reactions based on other residual ion species.

[0128] The current regulator 52 allows for variation of the current value supplied to the electrodialysis cell 200. This enables control over the rates of water dissociation in the bipolar membrane and redox reactions in the electrodes, thereby adjusting the carbon dioxide concentration in the carbon dioxide regenerated solution and the pH of the alkaline regenerated solution. As described above, a higher current value in the carbon dioxide electrolyzer 100 results in a lower pH of the second electrolyte. However, for carbon dioxide to be regenerated using the electrodialysis cell 200, a sufficiently high pH must be maintained in the electrolyte supplied to the carbon dioxide electrolyzer 100, i.e., the alkaline regenerated solution, to ensure complete dissolution of carbon dioxide as bicarbonate or carbonate ions in the electrolyte.

[0129] The circulating solution and electrode solution are pure water or aqueous solution, preferably an aqueous solution containing the same components as the second electrolyte. However, when using a cation exchange membrane, it can also be an aqueous solution containing ions of the same cation species but different anion species, and vice versa. Preferably, it is an aqueous solution with low resistance that minimizes the impact on the diaphragm and reduces the resistance between the electrodes.

[0130] Next, based on the operating results of the carbon dioxide electrolyzer 100, an example of the operation of the electrodialysis cell 200 will be described, in which an aqueous solution containing potassium ions, bicarbonate ions, and carbonate ions is used as the anode drain solution, a 0.02M KHCO3 aqueous solution is used as the circulating solution, a 1M K2CO3 aqueous solution is used as the electrode solution, a cation exchange membrane is used as the diaphragm 209, and bipolar membranes are used as the diaphragms 207 and 208 respectively.

[0131] Potassium ions in the anolyte contained in containment section 203 move into containment section 204 due to the voltage applied between electrodes 205 and 206. Containment section 203 becomes a state with abundant bicarbonate and carbonate ions, while containment section 204 becomes a state with abundant potassium ions. A water dissociation reaction occurs in diaphragms 207 and 208 through potential, causing hydrogen ions to move into containment section 203 and hydroxide ions to move into containment section 204. As a result, the pH of the anolyte decreases in containment section 203 due to hydrogen ions, shifting the equilibrium reaction of equation (5) to the left, resulting in water and carbon dioxide. Alternatively, as in equations (7) and (8), hydrogen ions react with bicarbonate or carbonate ions to produce water and carbon dioxide. In containment section 204, as in equation (9), potassium ions react with hydroxide ions to produce potassium hydroxide.

[0132] H + +HCO3 - →H2O+CO2 (7)

[0133] 2H + +CO3 2- →H2O+CO2 (8)

[0134] K + +OH - →KOH (9)

[0135] The water dissociation reactions occurring in diaphragms 207 and 208 result in the movement of hydroxide ions in containment 201, making the first electrolyte in containment 201 more hydroxide-rich, and the movement of hydrogen ions in containment 202, making the second electrolyte in containment 202 more hydrogen-rich. An oxidation reaction of hydroxide ions occurs in electrode 205, which is positively charged in containment 201, producing oxygen; and a reduction reaction of hydrogen ions occurs in electrode 206, which is negatively charged in containment 202, producing hydrogen gas. These generated gases are discharged, discarded, or recycled via discharge paths 212 and 214.

[0136] Thus, in the carbon dioxide supplied to the carbon dioxide electrolyzer 100, apart from the carbon dioxide that remains in the generated gas due to not being used in the reaction, the carbon dioxide dissolved in the liquid in the cathode 104 moves to the anode 105 to form carbon dioxide, and the carbon dioxide that dissolves in the alkaline solution when the electrolyte is used and becomes carbon dioxide gas in the anode 105 and is discharged as gas, is not used in the electrolysis reaction, thus reducing the overall carbon dioxide utilization rate of the device.

[0137] In this embodiment, in the electric field device that combines the electrodialysis cell 200 and the carbon dioxide electrolysis cell 100, the carbon dioxide concentration in the generated gas, the pH of the electrolyte, and the carbon dioxide concentration in the anode exhaust are monitored. Based on these values, the flow rate of carbon dioxide supplied to the carbon dioxide electrolysis cell 100, the current value supplied to the electrodialysis cell 200, and the flow rate of the fluid supplied from the pump 61 to the anode flow path 102 are adjusted, thereby improving the carbon dioxide utilization rate. Furthermore, the power supplied to the electrodialysis cell can be reduced.

[0138] (Second Implementation)

[0139] The carbon dioxide electrolysis apparatus of the second embodiment has a different structure from the carbon dioxide electrolysis cell 100 of the carbon dioxide electrolysis apparatus of the first embodiment.

[0140] Figure 5 This is a schematic diagram showing a structural example of the carbon dioxide electrolyzer 100 in the second embodiment. Figure 5 The carbon dioxide electrolyzer 100 shown has a solid polymer structure and includes a flow path plate 121, a flow path plate 122, a diaphragm 103, a cathode 104, an anode 105, a supply flow path 106, a supply flow path 107, a discharge flow path 108, a supply flow path 109, a discharge flow path 110, a current collector 125, and a current collector 126.

[0141] The flow path plate 121 forms a cathode flow path 123 that includes a groove facing the cathode 104. The cathode flow path 123 is connected to the supply flow path 106 and the discharge flow path 108.

[0142] The flow path plate 122 forms an anode flow path 124 that includes a groove facing the anode 105. The anode flow path 124 is connected to the supply flow path 109 and the discharge flow path 110.

[0143] Current collector 125 is electrically connected to flow path plate 121 and cathode 104. Current collector 126 is electrically connected to flow path plate 122 and anode 105. Current collectors 125 and 126 are electrically connected to current regulator 52 via wiring.

[0144] The flow path plate 121, flow path plate 122, diaphragm 103, cathode 104 and anode 105 are integrated under a certain pressure.

[0145] Regarding other descriptions, since they are the same as those for the carbon dioxide electrolyzer 100 of the first embodiment, the descriptions of the first embodiment can be appropriately referenced.

[0146] During the operation of the carbon dioxide electrolyzer 100, the reduction products of carbon dioxide and components of the second electrolyte that move to the cathode 104 side solidify and precipitate in the cathode flow path 123, thus clogging the cathode flow path 123 and sometimes stopping the supply of carbon dioxide-containing gas. Therefore, in order to suppress the formation of precipitates, it is preferable to have moisture in the carbon dioxide-containing gas.

[0147] On the other hand, when the water content in the carbon dioxide-containing gas is too high, hydrogen is easily generated due to the excessive supply of water to the catalyst surface within the cathode 104, which is undesirable. Therefore, the relative humidity of the water content in the carbon dioxide-containing gas is preferably 20% or more and 90% or less, more preferably 30% or more and 70% or less.

[0148] A gas containing carbon dioxide is supplied to the cathode flow path 123 via the supply flow path 106, and the product generated at the cathode 104 is discharged via the discharge flow path 108. As described above, since it is preferable that the gas containing carbon dioxide contains a certain amount of moisture, it is preferable to connect a humidifier to the supply flow path 106 to control the humidity of the supplied gas. A second electrolyte is supplied to the anode flow path 124 via the supply flow path 109, and the product generated at the anode 105 and the carbon dioxide moving from the cathode 104 are discharged together with the second electrolyte via the discharge flow path 110.

[0149] Similar to the first embodiment, in Figure 2In the carbon dioxide electrolysis apparatus shown, the overall carbon dioxide utilization rate of the apparatus can be improved by dissolving unused carbon dioxide from the carbon dioxide reduction reaction into the electrolyte in the carbon dioxide electrolysis cell 100. In particular, the carbon dioxide utilization rate can be improved by measuring the carbon dioxide concentration in the generated gas, the carbon dioxide concentration in the anode exhaust gas, and the pH of the anode drain liquid, thereby controlling the amount of carbon dioxide supplied to the carbon dioxide electrolysis cell 100 and the flow rate of the pump 61.

[0150] In addition, Figure 2 In the carbon dioxide electrolysis apparatus shown, carbon dioxide in the electrodialysis cell 200 can be regenerated by dissolving unused carbon dioxide from the carbon dioxide reduction reaction into the electrolyte in the carbon dioxide electrolysis cell 100. In particular, by measuring the carbon dioxide concentration in the generated gas, the carbon dioxide concentration in the anode exhaust gas, and the pH of the anode drain, the flow rate of carbon dioxide supplied to the carbon dioxide electrolysis cell 100, the current value supplied to the electrodialysis cell 200, and the flow rate of the fluid supplied from the pump 61 to the anode flow path 102 can be controlled, thereby improving carbon dioxide utilization efficiency.

[0151] Furthermore, this embodiment can be appropriately combined with other embodiments.

[0152] Example

[0153] Next, the embodiments and their evaluation results will be described.

[0154] (Examples 1-9)

[0155] Figure 6 This is a schematic diagram illustrating the structure of the carbon dioxide electrolysis apparatus of Example 1. Figure 6 The carbon dioxide electrolysis apparatus 1A shown includes: a carbon dioxide electrolysis cell 100, a carbon dioxide detector 41, a carbon dioxide detector 42, a gas-liquid separator 31, a flow meter 34, a pH-ion concentration detector 43, a current regulator 51, a pump 61, a carbon dioxide supply source 71, a carbon dioxide flow regulator 72, an argon supply source 73, and an electrolyte supply source 94.

[0156] The carbon dioxide electrolyzer 100 has Figure 5 The structure shown is as follows. The cathode 104 is formed by coating copper nanoparticles onto a substrate cut into 4cm sections. 2 Electrodes formed on square pieces of carbon paper. Anode 105 is made by coating IrO2 nanoparticles onto a 4cm sheet of carbon paper. 2 The electrode is formed on a square piece of Ti nonwoven fabric. The diaphragm 103 is an anion exchange membrane. Further details regarding the carbon dioxide electrolyzer 100 may be provided. Figure 1 Explanation.

[0157] The carbon dioxide detector 41 is connected to the discharge path 108 of the carbon dioxide electrolyzer 100 via a flow meter 34. The carbon dioxide detector 41 is a gas chromatograph. Further descriptions of the carbon dioxide detector 41 may be provided as appropriate. Figure 1 Explanation.

[0158] The carbon dioxide detector 42 is connected to the gas-liquid separator 31. The carbon dioxide detector 42 is a gas chromatograph. Further descriptions of the carbon dioxide detector 42 may be appropriately referenced. Figure 1 Explanation.

[0159] The pH-ion concentration detector 43 is connected to the gas-liquid separator 31. The pH-ion concentration detector 43 is a pH sensor.

[0160] The current regulator 51 has a constant current device. A constant current is applied to the carbon dioxide electrolyzer 100 via the constant current device. Further descriptions of the current regulator 51 may be appropriately referenced. Figure 1 Explanation.

[0161] Pump 61 is provided for supplying electrolyte from electrolyte supply source 94 to the supply path 109 of carbon dioxide electrolyzer 100. Further description of pump 61 may be adapted accordingly. Figure 1 Explanation.

[0162] The carbon dioxide supply source 71 has a carbon dioxide tank for containing carbon dioxide gas. The carbon dioxide supply source 71 may also have a pump for supplying carbon dioxide.

[0163] The carbon dioxide flow regulator 72 is a mass flow controller.

[0164] Argon supply source 73 has an argon tank for containing argon gas. Argon supply source 73 may also have a pump for supplying argon.

[0165] The electrolyte supply source 94 has an electrolyte tank for containing electrolyte.

[0166] Using a carbon dioxide electrolysis apparatus 1A, the pH and flow rate of the electrolyte required for carbon dioxide to be dissolved in the electrolyte in the form of bicarbonate ions or carbonate ions were investigated. A constant current was applied to the carbon dioxide electrolysis cell 100 using a constant current regulator in the current control section.

[0167] The carbon dioxide electrolysis unit 1A is operated under the conditions described below. Carbon dioxide gas with a purity exceeding 99.9% is introduced into the cathode flow path 123 at a prescribed flow rate. After the generated gas discharged from the cathode flow path 123 is diluted to 10 times its original concentration by argon gas, it is introduced into the carbon dioxide detector 41. Electrolyte is introduced from the electrolyte supply source 94 into the anode flow path 124 at a prescribed flow rate. A constant current is applied between the cathode 104 and anode 105 of the carbon dioxide electrolysis cell 100 to achieve a current density of 0 mA / cm². 2 50mA / cm 2 100mA / cm 2 200mA / cm 2 300mA / cm 2 By varying the applied voltage under different conditions, the composition of the generated gas, the composition of the anolyte discharged from the gas-liquid separator 31, and the pH of the anolyte discharged from the gas-liquid separator 31 were measured using a water quality detector 41 after a certain period of time for each current value. 0.1M potassium hydroxide aqueous solution, 0.1M potassium carbonate aqueous solution, and 0.1M potassium bicarbonate aqueous solution were used as the electrolyte. Measurements were performed by varying the carbon dioxide flow rate to 20 mL / min and 40 mL / min, and the electrolyte flow rate to 5 mL / min and 10 mL / min. The conditions for each embodiment are shown in Table 1.

[0168] Table 1

[0169] Example 1 <![CDATA[KHCO3]]> 10 mL / min 40 mL / min Example 2 <![CDATA[K2CO3]]> 10 mL / min 40 mL / min Example 3 KOH 10 mL / min 40 mL / min Example 4 <![CDATA[KHCO3]]> 5mL / min 40 mL / min Example 5 <![CDATA[K2CO3]]> 5mL / min 40 mL / min Example 6 KOH 5mL / min 40 mL / min Example 7 <![CDATA[KHCO3]]> 10 mL / min 20 mL / min Example 8 <![CDATA[K2CO3]]> 10 mL / min 20 mL / min Example 9 KOH 10 mL / min 20 mL / min

[0170] Figure 7 This is a graph showing the carbon dioxide concentration in the generated gas at various current densities. Current density: 0 mA / cm² 2 The values ​​are concentrations measured without current flow. The mass concentration of the generated gas is approximately 10% because it was determined by GC after passing through a carbon dioxide electrolyzer 100 and diluting it 10-fold with argon. The graphs marked with circles represent the results at a carbon dioxide flow rate of 40 mL / min and an electrolyte flow rate of 10 mL / min; those marked with triangles represent the results at a carbon dioxide flow rate of 40 mL / min and an electrolyte flow rate of 5 mL / min; and those marked with squares represent the results at a carbon dioxide flow rate of 20 mL / min and an electrolyte flow rate of 10 mL / min. All results show that as the current density increases, the amount of carbon dioxide used in the carbon dioxide electrolysis reaction increases, leading to a decrease in the carbon dioxide concentration in the generated gas. It is known that decreasing the carbon dioxide flow rate relatively decreases the carbon dioxide concentration in the generated gas. By controlling the carbon dioxide supply at the optimal current density, the amount of carbon dioxide in the generated gas can be controlled.

[0171] Figure 8This is a graph showing the pH of the electrolyte after passing through the anolyte flow path 102 at various current densities. Current density: 0 mA / cm² 2 The value represents the pH of the electrolyte in the electrolyte tank before measurement. The measurement conditions for each graph are as described above. Regardless of the electrolyte, the pH of the electrolyte decreases with increasing current density. This is believed to be because it becomes significant when the electrolyte flow rate is low, resulting in a longer time that hydrogen ions remain near the anode 105 where they are generated. Therefore, it is known that by increasing the flow rate of pump 61, the pH of the electrolyte after passing through anode 105 is maintained at a high level, while conversely, by decreasing the flow rate, the pH of the electrolyte after passing through anode 105 decreases.

[0172] Figure 9 This indicates that a current density of 300 mA / cm² is applied to the carbon dioxide electrolyzer 100. 2 The graph shows the relationship between the concentration of carbon dioxide in the anode exhaust separated by the gas-liquid separator 31 and the pH of the electrolyte. Since all measurements were taken at the same current density, the total amount of carbon dioxide moving from the cathode flow path 101 to the anode flow path 102 is the same at all points. However, the lower the pH of the electrolyte after passing through the carbon dioxide electrolysis cell 100, the greater the amount of carbon dioxide present as gas. If the pH exceeds 9, the concentration of carbon dioxide in the gas on the anode 105 side can be suppressed to below 1%. This embodiment demonstrates that by controlling the pH of the electrolyte supplied to the carbon dioxide electrolysis cell 100, the current value supplied to the electrodialysis cell 200, and the flow rate of the pump 61, the pH of the anode exhaust can be controlled. By controlling the pH of the anode exhaust and the amount of carbon dioxide introduced into the cathode 104, the amount of carbon dioxide discharged as unused gas in the reaction can be reduced. This indicates that the method of this embodiment can improve the carbon dioxide utilization rate of the carbon dioxide electrolysis device.

[0173] The above embodiments are provided as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the invention described in the claims and its equivalents.

[0174] The above-described implementation methods can be summarized into the following technical solutions.

[0175] (Technical Solution 1)

[0176] A carbon dioxide electrolysis device, comprising:

[0177] A carbon dioxide electrolyzer, the carbon dioxide electrolyzer having a cathode flow path through which carbon dioxide flows, an anode flow path through which an aqueous electrolyte flows, a cathode facing the cathode flow path and generating carbon compounds by reducing the carbon dioxide, an anode facing the anode flow path and generating oxygen by oxidizing the water, and a first diaphragm disposed between the anode flow path and the cathode flow path.

[0178] A first current regulator supplies a first current to the carbon dioxide electrolyzer;

[0179] The first gas-liquid separator separates the first fluid discharged from the anode flow path into a first liquid and a first gas;

[0180] An electrodialysis cell, the electrodialysis cell having a first receiving portion, a first electrode disposed in the first receiving portion, a second receiving portion, a second electrode disposed in the second receiving portion, a third receiving portion disposed between the first receiving portion and the second receiving portion and receiving a first liquid supplied from the first gas-liquid separator, a fourth receiving portion disposed between the third receiving portion and the second receiving portion, a second diaphragm disposed between the first receiving portion and the third receiving portion, a third diaphragm disposed between the second receiving portion and the fourth receiving portion, and a fourth diaphragm disposed between the third receiving portion and the fourth receiving portion;

[0181] A second current regulator supplies a second current to the electrodialysis cell;

[0182] The detector is selected from at least one of a first detector that detects the flow rate of the first gas or the concentration of carbon dioxide contained in the first gas, and a second detector that detects the pH of the first fluid or the concentration of at least one ion contained in the first fluid; and

[0183] The first controller controls the second current regulator based on at least one detection signal from the at least one detector, thereby adjusting the value of the second current.

[0184] (Technical Solution 2)

[0185] The carbon dioxide electrolysis apparatus according to technical solution 1 further comprises:

[0186] A third detector detects the concentration of carbon dioxide contained in the first fluid; and

[0187] The second controller controls the first current regulator based on the detection signal from the third detector, thereby adjusting the value of the first current.

[0188] (Technical Solution 3)

[0189] According to the carbon dioxide electrolysis device described in technical solution 2, wherein...

[0190] It further includes a flow regulator for regulating the flow rate of a second fluid containing carbon dioxide supplied to the cathode flow path;

[0191] The second controller controls the flow regulator based on the detection signal from the third detector, thereby regulating the flow rate of the second fluid.

[0192] (Technical Solution 4)

[0193] According to any one of technical solutions 1 to 3, in the carbon dioxide electrolysis device, wherein...

[0194] It further includes a pump for supplying the third fluid discharged from the fourth containment section to the anode flow path;

[0195] The first controller controls the pump based on at least one detection signal from the at least one detector, adjusting the flow rate of the third fluid supplied to the anode flow path.

[0196] (Technical Solution 5)

[0197] According to any one of technical solutions 1 to 4, in the carbon dioxide electrolysis device, wherein...

[0198] It further includes a second gas-liquid separator that separates the fourth fluid discharged from the third containment section into a second liquid containing the electrolyte and a second gas containing the carbon dioxide;

[0199] The second liquid is supplied to the fourth containment section.

[0200] The second gas is supplied to the cathode flow path.

[0201] (Technical Solution 6)

[0202] According to any one of technical solutions 1 to 5, the carbon dioxide electrolysis device contains at least one ion selected from hydroxide ions, carbonate ions and bicarbonate ions.

[0203] (Technical Solution 7)

[0204] The carbon dioxide electrolysis apparatus according to any one of technical solutions 1 to 6 further comprises:

[0205] A fourth detector, which detects the concentration of at least one component contained in the first liquid; and

[0206] A drain valve, used to replenish the electrolyte to the first liquid or to drain a portion of the first liquid;

[0207] The first controller controls the discharge valve based on the detection signal from the fourth detector to replenish the electrolyte or discharge a portion of the first liquid in such a way that the concentration of at least one component contained in the first liquid reaches below a predetermined value.

[0208] (Technical Solution 8)

[0209] A control method for a carbon dioxide electrolysis device, wherein,

[0210] The carbon dioxide electrolysis apparatus includes:

[0211] A carbon dioxide electrolyzer, the carbon dioxide electrolyzer having a cathode flow path through which carbon dioxide flows, an anode flow path through which an aqueous electrolyte flows, a cathode facing the cathode flow path and generating carbon compounds by reducing the carbon dioxide, an anode facing the anode flow path and generating oxygen by oxidizing the water, and a first diaphragm disposed between the anode flow path and the cathode flow path.

[0212] A first gas-liquid separator separates the first fluid discharged from the anode flow path into a first liquid and a second gas; and

[0213] An electrodialysis cell, the electrodialysis cell having a first receiving portion, a first electrode disposed in the first receiving portion, a second receiving portion, a second electrode disposed in the second receiving portion, a third receiving portion disposed between the first receiving portion and the second receiving portion and receiving a first liquid supplied from the first gas-liquid separator, a fourth receiving portion disposed between the third receiving portion and the second receiving portion, a second diaphragm disposed between the first receiving portion and the third receiving portion, a third diaphragm disposed between the second receiving portion and the fourth receiving portion, and a fourth diaphragm disposed between the third receiving portion and the fourth receiving portion;

[0214] The method comprises the following steps:

[0215] The steps include separating the first fluid discharged from the anode flow path into the first liquid and the first gas, and detecting at least one of the following: the flow rate of the first gas or the concentration of carbon dioxide contained in the first gas; and the pH of the first fluid or the concentration of at least one ion contained in the first fluid; and

[0216] The step of adjusting the value of the current supplied to the electrodialysis cell based on the detection results of at least one of the above.

Claims

1. A carbon dioxide electrolysis device, comprising: A carbon dioxide electrolyzer, the carbon dioxide electrolyzer having a cathode flow path through which carbon dioxide flows, an anode flow path through which an aqueous electrolyte flows, a cathode facing the cathode flow path and generating carbon compounds by reducing the carbon dioxide, an anode facing the anode flow path and generating oxygen by oxidizing the water, and a first diaphragm disposed between the anode flow path and the cathode flow path. A first current regulator supplies a first current to the carbon dioxide electrolyzer; The first gas-liquid separator separates the first fluid discharged from the anode flow path into a first liquid and a first gas; An electrodialysis cell, the electrodialysis cell having a first receiving portion, a first electrode disposed in the first receiving portion, a second receiving portion, a second electrode disposed in the second receiving portion, a third receiving portion disposed between the first receiving portion and the second receiving portion and receiving a first liquid supplied from the first gas-liquid separator, a fourth receiving portion disposed between the third receiving portion and the second receiving portion, a second diaphragm disposed between the first receiving portion and the third receiving portion, a third diaphragm disposed between the second receiving portion and the fourth receiving portion, and a fourth diaphragm disposed between the third receiving portion and the fourth receiving portion; A second current regulator supplies a second current to the electrodialysis cell; The detector is selected from at least one of a first detector that detects the flow rate of the first gas or the concentration of carbon dioxide contained in the first gas, and a second detector that detects the pH of the first fluid or the concentration of at least one ion contained in the first fluid. and The first controller controls the second current regulator based on at least one detection signal from the at least one detector, thereby adjusting the value of the second current.

2. The carbon dioxide electrolysis apparatus according to claim 1, wherein, Further features include: A third detector detects the concentration of carbon dioxide contained in the first fluid; and The second controller controls the first current regulator based on the detection signal from the third detector, thereby adjusting the value of the first current.

3. The carbon dioxide electrolysis apparatus according to claim 2, wherein, It further includes a flow regulator for regulating the flow rate of a second fluid containing carbon dioxide supplied to the cathode flow path; The second controller controls the flow regulator based on the detection signal from the third detector, thereby regulating the flow rate of the second fluid.

4. The carbon dioxide electrolysis apparatus according to any one of claims 1 to 3, wherein, It further includes a pump for supplying the third fluid discharged from the fourth containment section to the anode flow path; The first controller controls the pump based on at least one detection signal from the at least one detector, adjusting the flow rate of the third fluid supplied to the anode flow path.

5. The carbon dioxide electrolysis apparatus according to any one of claims 1 to 3, wherein, It further includes a second gas-liquid separator that separates the fourth fluid discharged from the third containment section into a second liquid containing the electrolyte and a second gas containing the carbon dioxide; The second liquid is supplied to the fourth containment section. The second gas is supplied to the cathode flow path.

6. The carbon dioxide electrolysis apparatus according to any one of claims 1 to 3, wherein, The electrolyte contains at least one ion selected from hydroxide ions, carbonate ions, and bicarbonate ions.

7. The carbon dioxide electrolysis apparatus according to any one of claims 1 to 3, wherein, Further features include: A fourth detector, which detects the concentration of at least one component contained in the first liquid; and A drain valve, used to replenish the electrolyte to the first liquid or to drain a portion of the first liquid; The first controller controls the discharge valve based on the detection signal from the fourth detector to replenish the electrolyte or discharge a portion of the first liquid in such a way that the concentration of at least one component contained in the first liquid reaches below a predetermined value.

8. A control method for a carbon dioxide electrolysis device, wherein, The carbon dioxide electrolysis apparatus includes: A carbon dioxide electrolyzer, the carbon dioxide electrolyzer having a cathode flow path through which carbon dioxide flows, an anode flow path through which an aqueous electrolyte flows, a cathode facing the cathode flow path and generating carbon compounds by reducing the carbon dioxide, an anode facing the anode flow path and generating oxygen by oxidizing the water, and a first diaphragm disposed between the anode flow path and the cathode flow path. The first gas-liquid separator separates the first fluid discharged from the anode flow path into a first liquid and a first gas; and An electrodialysis cell, the electrodialysis cell having a first receiving portion, a first electrode disposed in the first receiving portion, a second receiving portion, a second electrode disposed in the second receiving portion, a third receiving portion disposed between the first receiving portion and the second receiving portion and receiving a first liquid supplied from the first gas-liquid separator, a fourth receiving portion disposed between the third receiving portion and the second receiving portion, a second diaphragm disposed between the first receiving portion and the third receiving portion, a third diaphragm disposed between the second receiving portion and the fourth receiving portion, and a fourth diaphragm disposed between the third receiving portion and the fourth receiving portion; The method comprises the following steps: The step of separating the first fluid discharged from the anode flow path into the first liquid and the first gas, and detecting at least one of the following: the flow rate of the first gas or the concentration of carbon dioxide contained in the first gas, and the pH of the first fluid or the concentration of at least one ion contained in the first fluid; and The step of adjusting the value of the current supplied to the electrodialysis cell based on the detection results of at least one of the above.

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