Carbon dioxide recovery desorption concentration device and carbon dioxide recovery desorption concentration method

Abstract

To provide a carbon dioxide recovery desorption concentration device and a carbon dioxide recovery desorption concentration method capable of efficiently recovering and concentrating carbon dioxide with low energy consumption by separating carbon dioxide from water decomposition products in recovery of carbon dioxide from carbon dioxide-containing gas utilizing electrochemical reactions.SOLUTION: A carbon dioxide recovery desorption concentration device 1 performs recovery of carbon dioxide from carbon dioxide-containing gas and desorption of the recovered carbon dioxide using intermittently progressed water electrolysis reactions to concentrate carbon dioxide.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an apparatus for recovering, desorbing, and concentrating carbon dioxide and a method for recovering, desorbing, and concentrating carbon dioxide. [Background technology]

[0002] As one of the measures to address issues such as global warming, technologies to separate, capture, and store carbon dioxide (CO2) from the atmosphere are being considered.

[0003] For example, Patent Document 1 describes a carbon dioxide recovery system that generates a sodium hydroxide solution and hydrochloric acid by electrolyzing a sodium chloride solution, supplies air to the generated sodium hydroxide solution, dissolves carbon dioxide in the air, and supplies the generated hydrochloric acid to the generated aqueous solution containing sodium carbonate and sodium hydrogen carbonate, and extracts the dissolved carbon dioxide as a gas.

[0004] Patent Document 2 describes a carbon dioxide recovery apparatus and a carbon dioxide recovery method in which an exhaust gas containing carbon dioxide is brought into gas-liquid contact with an absorption liquid containing an amino group-containing compound to absorb carbon dioxide, and the carbon dioxide absorption liquid is electrolyzed and subjected to gas-liquid separation to desorb carbon dioxide and regenerate the absorption liquid.

[0005] Patent Document 3 describes a carbon dioxide fixation method and device in which a direct current is applied to a solid electrolyte having a positive electrode and a negative electrode to fix carbon dioxide on the negative electrode, and a reverse potential is applied between the electrodes to extract the fixed carbon dioxide as a gas.

[0006] Non-Patent Document 1 describes a technology that utilizes hydroxide ions and protons generated in a water splitting reaction using an electrochemical flow cell for carbon dioxide capture and desorption.

[0007] Non-Patent Document 2 describes a technology for recovering and desorbing carbon dioxide using hydroxide ions and protons produced in a water splitting reaction, and for producing methanol from the resulting carbon dioxide / hydrogen mixed gas.

[0008] Non-Patent Document 3 describes a carbon dioxide recovery technology that utilizes a water splitting reaction in an electrochemical cell that uses a bipolar membrane as the diaphragm in the electrolytic cell.

[0009] Non-Patent Document 4 describes a carbon dioxide recovery technology that utilizes an electrolytic reaction in a multi-chamber electrochemical cell consisting of metal electrodes and ion exchange membranes.

[0010] The method of Patent Document 1 recovers and desorbs carbon dioxide using sodium hydroxide and hydrochloric acid produced by the electrolysis reaction of a sodium chloride aqueous solution, but because each step is independent, continuous carbon dioxide recovery, desorption, and concentration cannot be performed.

[0011] The method of Patent Document 2 uses an electrochemical reaction to desorb the captured carbon dioxide, but uses an amine group-containing compound as a carbon dioxide capture agent, which poses issues of odor and toxicity caused by the amino group-containing compound due to evaporation and diffusion of the absorption solution.

[0012] The method of Patent Document 3 is a carbon dioxide recovery technology that utilizes an electrochemical reaction, but it utilizes a solid electrolyte and has a different electrochemical cell configuration from that of the present invention.

[0013] The methods of Non-Patent Documents 1 to 3 are carbon dioxide capture and desorption technologies that utilize a water decomposition reaction, but they do not realize control of the amount of carbon dioxide captured or released using an intermittent electrochemical reaction such as pulse electrolysis, and the configuration of the electrochemical cell differs from that of the present invention.

[0014] The method in Non-Patent Document 4 is a carbon dioxide capture and desorption technology that utilizes an electrochemical reaction, but the chemical reaction that proceeds on the electrodes is different from that of the present invention, and there is no mention of pulse electrolysis. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Japanese Patent Application Publication No. 2019-181451 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-199042 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-073978 [Non-patent literature]

[0016] [Non-Patent Document 1] J. Electrochem. Soc., 169 (2022) 044527 [Non-patent document 2] Int. J. Hydrogen Energy, Vol. 20, No. 8, pp.653-663, 1995 [Non-patent document 3] AICHE JOURNAL, Vol. 55, No.12, (2009), pp.3286-3293 [Non-patent document 4] Electrochimica Acta, 219, (2016), pp.655-663 Summary of the Invention [Problem to be solved by the invention]

[0017] An object of the present invention is to provide a carbon dioxide recovery, desorption and concentration apparatus and a carbon dioxide recovery, desorption and concentration method that can separate, recover, and concentrate carbon dioxide from a carbon dioxide-containing gas using an electrochemical reaction efficiently and with low energy consumption. [Means for solving the problem]

[0018] The present invention is a carbon dioxide recovery / desorption / concentration device that utilizes an intermittently proceeding electrolysis reaction of water to recover carbon dioxide from a carbon dioxide-containing gas and desorb the recovered carbon dioxide, thereby concentrating the carbon dioxide.

[0019] In the carbon dioxide recovery, desorption, and concentration apparatus, it is preferable that the water electrolysis reaction that is allowed to proceed intermittently be carried out by repeatedly varying, at predetermined intervals, the current passed through or the voltage applied to the water electrolysis device that performs the electrolysis reaction, thereby controlling the amounts of hydroxide ions and protons that are generated by the electrolysis reaction and supplied to the electrolyte solution.

[0020] In the carbon dioxide recovery, desorption, and concentration device, it is preferable that the carbon dioxide is recovered by reacting hydroxide ions generated in the electrolysis reaction with carbon dioxide to capture the carbon dioxide in the electrolyte, and that the recovered carbon dioxide is desorbed by reacting protons generated in the electrolysis reaction with the carbon dioxide captured in the electrolyte.

[0021] In the carbon dioxide recovery, desorption, and concentration apparatus, it is preferable that the intermittently proceeding water electrolysis reaction involves repeatedly varying the current passed through or the voltage applied to the water electrolysis device that performs the electrolysis reaction at predetermined intervals to control the amount of hydroxide ions and protons produced in the electrolysis reaction that are supplied to the electrolyte; the carbon dioxide recovery involves reacting the hydroxide ions produced in the electrolysis reaction with carbon dioxide to incorporate the carbon dioxide into the electrolyte; and the desorption of the recovered carbon dioxide involves reacting the protons produced in the electrolysis reaction with the carbon dioxide incorporated into the electrolyte; and the carbon dioxide recovery and desorption of the recovered carbon dioxide are carried out continuously while the intermittently proceeding water electrolysis reaction is carried out.

[0022] The carbon dioxide recovery, desorption, and concentration apparatus preferably comprises an electrochemical flow cell that performs the electrolysis reaction of water, a power supply system that repeatedly varies the current passed through or the voltage applied to the electrochemical flow cell at predetermined intervals, a gas-liquid contact reaction device that recovers the carbon dioxide, a gas-liquid separation device that separates the desorbed carbon dioxide from an electrolyte, and a circulation pipe that circulates the electrolyte through the electrochemical flow cell, the gas-liquid contact reaction device, and the gas-liquid separation device.

[0023] The present invention is a method for recovering, desorbing, and concentrating carbon dioxide, which utilizes an intermittently proceeding electrolysis reaction of water to recover carbon dioxide from a carbon dioxide-containing gas and desorb the recovered carbon dioxide, thereby concentrating the carbon dioxide.

[0024] In the method for recovering, desorbing, and concentrating carbon dioxide, it is preferable that the water electrolysis reaction be allowed to proceed intermittently by repeatedly varying, at predetermined intervals, the current passed through or the voltage applied to a water electrolysis device that performs the electrolysis reaction, to control the amounts of hydroxide ions and protons generated by the electrolysis reaction that are supplied to the electrolytic solution.

[0025] In the method for recovering, desorbing, and concentrating carbon dioxide, it is preferable that the recovery of the carbon dioxide involves reacting hydroxide ions generated in the electrolysis reaction with carbon dioxide to incorporate the carbon dioxide into the electrolyte, and that the desorption of the recovered carbon dioxide involves reacting protons generated in the electrolysis reaction with the carbon dioxide incorporated into the electrolyte.

[0026] In the method for recovering, desorbing, and concentrating carbon dioxide, it is preferable that the intermittently proceeding water electrolysis reaction involves repeatedly varying, at predetermined intervals, the current passed through or the voltage applied to a water electrolysis device that performs the electrolysis reaction to control the amount of hydroxide ions and protons produced in the electrolysis reaction that are supplied to the electrolyte; the recovery of carbon dioxide involves reacting the hydroxide ions produced in the electrolysis reaction with carbon dioxide to incorporate the carbon dioxide into the electrolyte; and the desorption of the recovered carbon dioxide involves reacting the protons produced in the electrolysis reaction with the carbon dioxide incorporated into the electrolyte; and the recovery of carbon dioxide and the desorption of the recovered carbon dioxide are carried out continuously while the intermittently proceeding water electrolysis reaction is being carried out.

[0027] In the method for recovering, desorbing, and concentrating carbon dioxide, it is preferable to use a carbon dioxide recovery, desorption, and concentration apparatus that includes: an electrochemical flow cell that performs the electrolysis reaction of water; a power supply system that repeatedly varies the current passed through or the voltage applied to the electrochemical flow cell at predetermined intervals; a gas-liquid contact reactor that recovers the carbon dioxide; a gas-liquid separator that separates the desorbed carbon dioxide from an electrolyte; and a circulation pipe that circulates the electrolyte through the electrochemical flow cell, the gas-liquid contact reactor, and the gas-liquid separator. [Effects of the Invention]

[0028] The present invention provides a carbon dioxide recovery, desorption and concentration apparatus and a carbon dioxide recovery, desorption and concentration method that can separate, recover, and concentrate carbon dioxide from a carbon dioxide-containing gas using an electrochemical reaction efficiently and with low energy consumption. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a diagram showing a schematic configuration of an example of a carbon dioxide capture / desorption / concentration apparatus according to an embodiment of the present invention and a flow of an electrolyte. FIG. [Figure 2] FIG. 4 is a diagram showing a schematic configuration of another example of a carbon dioxide capture / desorption / concentration apparatus according to an embodiment of the present invention and a flow of an electrolyte. [Figure 3] 3A and 3B are graphs showing the change over time in carbon dioxide concentration in the carbon dioxide storage container to be captured (solid line) and in the separated carbon dioxide storage container (dashed line) in a carbon dioxide capture and concentration evaluation (FIG. 3A: Comparative Example, FIG. 3B: Example 1, FIG. 3C: Example 2, FIG. 3D: Example 3, FIG. 3E: Example 4, FIG. 3F: Example 5). [Figure 4] Figure 4A shows the change over time in the voltage applied to the hydrogen generating electrode during water electrolysis, Figure 4B shows the change over time in the voltage applied to the oxygen generating electrode, and Figure 4C is a graph showing the change over time in the voltage between the two electrodes (a: Example 3, b: Comparative Example). [Figure 5]Figure 5A is a graph showing the change in pH of the electrolyte over time in a comparative example during evaluation of carbon dioxide recovery and concentration, and Figure 5B is a graph showing the change in pH of the electrolyte over time in Example 3 (a: pH of the electrolyte flowing out from the first electrolyte tank in contact with the hydrogen generation electrode, b: pH of the electrolyte flowing out from the second electrolyte tank in contact with the oxygen generation electrode). DETAILED DESCRIPTION OF THE INVENTION

[0030] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes an embodiment of the present invention. The embodiment is an example of implementing the present invention, and the present invention is not limited to the embodiment.

[0031] The carbon dioxide capture / desorption / concentration apparatus according to this embodiment is an apparatus that utilizes an intermittently proceeding water electrolysis reaction (pulse electrolysis) to capture carbon dioxide from a carbon dioxide-containing gas and desorb the captured carbon dioxide, thereby concentrating the carbon dioxide.

[0032] An example of a carbon dioxide capture, desorption, and concentration apparatus according to this embodiment is outlined in FIG. 1, and its configuration will be described.

[0033] 1 includes, for example, an electrochemical flow cell 5 for performing an electrolysis reaction of water, a power supply system 28 for performing pulse electrolysis by repeatedly varying the current passed through or the voltage applied to the electrochemical flow cell 5 at predetermined intervals, a gas-liquid contact reactor 36 for recovering carbon dioxide, a gas-liquid separator 42 for separating the desorbed carbon dioxide from the electrolyte, and a circulation pipe 34 for circulating the electrolyte through the electrochemical flow cell 5, the gas-liquid contact reactor 36, and the gas-liquid separator 42. The carbon dioxide capture / desorption / concentration system 1 may also include at least one pump 46a, 46b as circulation means for circulating the electrolyte through the electrochemical flow cell 5, the gas-liquid contact reactor 36, and the gas-liquid separator 42, and at least one pH sensor 32a, 32b as pH measurement means for measuring the pH of the electrolyte, all installed at any position on the circulation pipe 34. The power supply system 28 and the hydrogen generating electrode 10 are connected by a wiring 30a that supplies power, and the power supply system 28 and the oxygen generating electrode 22 are connected by a wiring 30b that supplies power.

[0034] The electrochemical flow cell 5 has a hydrogen generating electrode 10, an oxygen generating electrode 22, a first electrolyte tank 14 having an electrolyte inlet 24a for the inflow of the electrolyte and an electrolyte outlet 26a for the outflow of the electrolyte, a second electrolyte tank 18 having an electrolyte inlet 24b for the inflow of the electrolyte and an electrolyte outlet 26b for the outflow of the electrolyte, a diaphragm 16 separating the hydrogen generating electrode 10 and the oxygen generating electrode 22, a first separation tank 12 as a first separation means for spatially separating the products (hydrogen and hydroxide ions) at the hydrogen generating electrode 10, and a second separation tank 20 as a second separation means for spatially separating the products (oxygen and protons) at the oxygen generating electrode 22. The circulation piping 34 is connected between the electrolyte outlet 26a of the first electrolytic solution tank 14 and the electrolyte inlet of the gas-liquid contact reactor 36, the electrolyte outlet of the gas-liquid contact reactor 36 and the electrolyte inlets 24a, 24b, the electrolyte outlet 26b of the second electrolytic solution tank 18 and the electrolyte inlet of the gas-liquid separator 42, and the electrolyte outlet of the gas-liquid separator 42 and the electrolyte inlets 24a, 24b so that the electrolyte circulates.

[0035] The gas-liquid contact reaction device 36 is a reaction vessel that brings the electrolytic solution supplied from the first electrolytic solution tank 14 on the hydrogen generation electrode 10 side of the electrochemical flow cell 5 into contact with the carbon dioxide to be recovered, and has a carbon dioxide to be recovered inlet 38 for introducing a carbon dioxide-containing gas containing the carbon dioxide to be recovered, and a post-recovery gas outlet 40 for releasing the gas after the recovery process.

[0036] The gas-liquid separator 42 is a device that separates the desorbed carbon dioxide generated in the second electrolyte tank 18 on the oxygen generating electrode 22 side of the electrochemical flow cell 5 from the electrolyte, and has a separated carbon dioxide storage container for storing the separated desorbed carbon dioxide or a desorbed carbon dioxide outlet 44 for introducing the separated desorbed carbon dioxide into the next process such as a reuse process.

[0037] The method for capturing and concentrating carbon dioxide and the operation of the carbon dioxide capture, desorption, and concentration apparatus 1 according to this embodiment will be described.

[0038] The electrolyte is supplied to the first electrolytic solution tank 14 from the electrolyte inlet 24a, and to the second electrolytic solution tank 18 from the electrolyte inlet 24b, through the circulation pipe 34. The electrolyte supplied to the first electrolytic solution tank 14 is sent from the electrolyte outlet 26a through the circulation pipe 34 to the gas-liquid contacting reactor 36, and the electrolyte supplied to the second electrolytic solution tank 18 is sent from the electrolyte outlet 26b through the circulation pipe 34 to the gas-liquid separator 42. The electrolyte discharged from the gas-liquid contacting reactor 36 is circulated to the first electrolytic solution tank 14 and the second electrolytic solution tank 18 through the circulation pipe 34, and the electrolyte discharged from the gas-liquid separator 42 is circulated to the first electrolytic solution tank 14 and the second electrolytic solution tank 18 through the circulation pipe 34.

[0039] In the carbon dioxide capture, desorption, and concentration apparatus 1, a current or voltage is applied between the hydrogen-producing electrode 10 and the oxygen-producing electrode 22 by the power supply system 28 in the electrolyte, and a water decomposition reaction occurs. The water decomposition reaction occurs in the hydrogen-producing electrode 10, where water (HO) is converted into hydrogen (H) and hydroxide ions (OH - ), and oxygen (O) and protons (H + ) is an electrochemical reaction that produces Hydrogen generating electrode 10 (cathode): 4H2O+4e - → 2H2+4OH - Oxygen generating electrode 22 (anode): 2H2O → O2 + 4H + +4e -

[0040] In the first separation tank 12, hydrogen (H) and hydroxide ions (OH - ) are spatially separated, and hydroxide ions (OH - ) moves to the first electrolyte tank 14. In the second separation tank 20, oxygen (O2) and protons (H + ) are spatially separated, and protons (H + ) moves to the second electrolyte tank 18.

[0041] The hydroxide ions (OH - ) is sent to a gas-liquid contact reactor 36. In the gas-liquid contact reactor 36, a carbon dioxide-containing gas containing carbon dioxide (CO2) to be recovered is introduced into the electrolyte from a carbon dioxide to be recovered inlet 38, and the carbon dioxide to be recovered (CO2) and hydroxide ions (OH - ) reaction converts the target carbon dioxide (CO2) into hydrogen carbonate ions (HCO3 - The post-recovery gas, which may contain excess carbon dioxide (CO2), is discharged from post-recovery gas outlet 40 and recovered as needed.

[0042] From the gas-liquid contact reactor 36, hydrogen carbonate ions (HCO3 - ) is sent to the second electrolytic solution tank 18. In the second electrolytic solution tank 18, protons (H + ) and bicarbonate ions (HCO3 - ) reacts with the desorbed carbon dioxide (CO2) and is chemically converted into carbon dioxide (CO2) and water (H2O). The electrolytic solution supplied to the second electrolytic solution tank 18 is sent to the gas-liquid separator 42 through the circulation pipe 34 together with the desorbed carbon dioxide (CO2).

[0043] Gas-liquid separation is carried out in the gas-liquid separator 42, and the separated desorbed carbon dioxide (CO2) is discharged from a desorbed carbon dioxide outlet 44 and recovered.

[0044] As described above, in the carbon dioxide capture and concentration method and the carbon dioxide capture and desorption and concentration apparatus according to this embodiment, carbon dioxide is captured by the hydroxide ions (OH - The carbon dioxide-containing gas is brought into contact with an electrolyte solution containing protons (H + ) and hydrogen carbonate ions (HCO3 - ) is brought into contact with an electrolyte solution containing

[0045] Carbon dioxide is concentrated by circulating the electrolyte between the hydrogen generation electrode 10 and oxygen generation electrode 22 of the electrochemical flow cell 5, a gas-liquid contact reaction device 36 that recovers carbon dioxide, and a gas-liquid separation device 42 that separates the desorbed carbon dioxide from the electrolyte, thereby allowing the recovery and desorption of carbon dioxide to proceed continuously.

[0046] With this configuration of the carbon dioxide capture, desorption, and concentration device 1, hydrogen (H2) and oxygen (O2), which are the electrolysis products of water, are converted into a gas phase, and hydroxide ions (OH - ) and protons (H + ) is separated into the electrolyte phase. Hydroxide ions (OH - ) converts carbon dioxide (CO2) from carbon dioxide-containing gases into bicarbonate ions (HCO3 - ) and bicarbonate ions (HCO3 - ) is generated at the oxygen generating electrode 22. + ), carbon dioxide (CO2) is released by reacting with water. In addition, by separating the electrolysis product of water, it is possible to prevent hydrogen (H2) and oxygen (O2) from being mixed into the carbon dioxide-containing gas after recovery processing or the released carbon dioxide (CO2).

[0047] Furthermore, by continuously capturing and desorbing carbon dioxide using the electrolysis reaction of water through the circulation of an electrolyte, it is possible to concentrate low-concentration carbon dioxide and produce high-concentration carbon dioxide. Furthermore, the capture and desorption of carbon dioxide can be electrically controlled, and the input electrical energy can be recovered and stored as useful substances (hydrogen (H2) and oxygen (O2)). This allows for a significant reduction in the energy costs required for carbon dioxide capture and desorption.

[0048] In the carbon dioxide capture and concentration method and the carbon dioxide capture and desorption and concentration device 1 according to this embodiment, hydroxide ions (OH - ) and protons (H + ) are spatially separated, enabling the capture and desorption of carbon dioxide. The separation of cathode and anode products is achieved by placing a diaphragm 16 between the electrodes of the electrochemical flow cell 5. Furthermore, by circulating the electrolyte through each electrolytic cell and continuously and uninterruptedly proceeding with the capture and desorption of carbon dioxide, high-concentration carbon dioxide can be produced from low-concentration carbon dioxide. Because the electrical energy input to this device is used for the water electrolysis reaction, there is almost no direct consumption of electrical energy in the carbon dioxide capture and desorption process. Furthermore, the energy input to the electrochemical reaction can be recovered and stored as hydrogen and oxygen. Therefore, unlike conventional carbon dioxide capture and fixation technologies, energy production (hydrogen generation) and carbon dioxide capture, desorption, and concentration can proceed in parallel, significantly reducing the carbon dioxide capture and desorption energy required.

[0049] Furthermore, in the carbon dioxide capture and concentration method and carbon dioxide capture and desorption concentration apparatus 1 according to this embodiment, the electrolysis reaction of water is carried out intermittently. Then, while the electrolysis reaction of water is carried out intermittently, the capture of carbon dioxide and the desorption of the captured carbon dioxide are carried out continuously. The current passed through or the voltage applied to the water electrolysis device where the electrolysis reaction is carried out is repeatedly varied at predetermined intervals to control the supply amounts of hydroxide ions and protons generated in the electrolysis reaction to the electrolyte. The hydroxide ions (OH - ) and protons (H + The carbon dioxide capture process utilizes electrolysis to capture carbon dioxide from the water decomposition product. The carbon dioxide capture, desorption, and concentration process links the carbon dioxide desorption process, and by controlling the amounts of carbon dioxide captured and desorbed through intermittent electrolysis at predetermined intervals, the amounts of carbon dioxide captured and desorbed are increased, and carbon dioxide can be separated from the water decomposition product, captured, and concentrated more efficiently and with less energy consumption than with steady electrolysis.

[0050] In steady-state water electrolysis, hydroxide ions (OH - ), proton (H + ), bicarbonate ion (HCO3 - ) equilibrium state is quickly formed, and a chemical equilibrium state is formed where the concentrations of each chemical species are constant. On the other hand, in intermittent water electrolysis, hydroxide ions (OH - ), proton (H + ), bicarbonate ion (HCO3 - ) equilibrium state fluctuates at regular intervals, so compared to the steady-state electrolysis of water, the hydroxide ions (OH - ) temporarily becomes highly concentrated. This is thought to allow the carbon dioxide capture reaction and carbon dioxide desorption reaction to proceed efficiently, increasing the amount of captured and desorbed carbon dioxide. In addition, because water electrolysis proceeds intermittently, the amount of electrical energy input is reduced. These two effects are thought to reduce the amount of energy required for carbon dioxide capture, desorption, and concentration.

[0051] The power supply system 28 for performing pulse electrolysis is a DC or AC power supply connected to the hydrogen generation electrode 10 and the oxygen generation electrode 22 of the electrochemical flow cell 5, and is a power supply that supplies current or voltage to the electrochemical flow cell 5 while varying the current or voltage at predetermined intervals.

[0052] The fluctuation interval of the current or voltage may be set so that the pH of the electrolyte supplied from the electrochemical flow cell 5 to the gas-liquid contact reactor 36 during water electrolysis is higher than pH 7, preferably higher than pH 9. The fluctuation interval of the current or voltage may be automatically controlled by a control device such as a programmable logic controller (PLC) or a personal computer (PC) by feeding back the pH value of the electrolyte obtained from the pH sensors 32a and 32b.

[0053] The carbon dioxide-containing gas to be recovered is, for example, air containing carbon dioxide.

[0054] Examples of the hydrogen generation electrode 10 include platinum-supported titanium plates and platinum foils (platinum (Pt) electrodes), as well as hydrogen generation catalysts such as carbon (C), iron (Fe), nickel (Ni), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), iridium (Ir), platinum (Pt), gold (Au), and compounds thereof, but are not limited to these.

[0055] Examples of oxygen generating electrodes 22 include porous titanium sheets carrying iridium oxide (IrO2) (iridium oxide (IrO2) electrodes), as well as oxygen generating catalysts such as manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), iridium (Ir), and compounds thereof, but are not limited to these.

[0056] The diaphragm 16 between the hydrogen-producing electrode 10 and the oxygen-producing electrode 22 is made of a material that contains cathode products (hydrogen: H2, hydroxide ions: OH - ) and anode products (oxygen: O2, protons: H +There are no particular limitations on the diaphragm 16 as long as it can spatially separate the generation sites of the ions. Examples of the diaphragm 16 include, but are not limited to, a cation exchange membrane such as Nafion (registered trademark), a commercially available general cation exchange membrane, and a membrane made of a polymer chain having a cation exchange group such as a sulfonic acid group, a carboxylic acid group, or a phosphate group.

[0057] The first separation tank 12 contains hydrogen (H) and hydroxide ions (OH - ) can be spatially separated from the hydrogen-evolution electrode 10. For example, a gas-liquid separator or an anion exchange membrane may be used. The first separation tank 12 may be installed near the hydrogen-evolution electrode 10 as shown in Fig. 1, or may be installed in a liquid supply path for the electrolyte, such as a circulation pipe 34, as shown in Fig. 2 (described later).

[0058] The second separation tank 20 is a tank for separating oxygen (O) and protons (H + ) can be spatially separated from the oxygen-evolving electrode 22. The second separation tank 20 may be disposed near the oxygen-evolving electrode 22 as shown in FIG. 1, or may be disposed in a liquid-transport path for the electrolyte, such as the circulation pipe 34. Examples of the second separation tank 20 include a cation-exchange membrane such as Nafion (registered trademark), a commercially available cation-exchange membrane, and a membrane made of a polymer chain having a cation-exchange group such as a sulfonic acid group, a carboxylic acid group, or a phosphate group.

[0059] The electrolyte is a potassium sulfate solution, an alkali metal element, and hydroxide ions (OH - ), bicarbonate ion (HCO3 - ), hydrogen sulfate ion (HSO4 - ), thiosulfate ion (S2O3 2- ), carbonate ions (CO3 2- ) and aqueous solutions containing anions such as, but not limited to, these.

[0060] The electrochemical flow cell may be, for example, an electrochemical flow cell having a structure in which a hydrogen generating electrode and an oxygen generating electrode are provided, a diaphragm is placed between the two electrodes, a first separation tank is placed in a circulation pipe that is a liquid flow path for the electrolyte as a first separation means for spatially separating the products (hydrogen and hydroxide ions) at the hydrogen generating electrode, and a cation exchange membrane, for example, is placed in close contact with the oxygen generating electrode as a second separation tank for spatially separating the products (oxygen and protons) at the oxygen generating electrode.

[0061] An example of a carbon dioxide capture, desorption, and concentration device equipped with an electrochemical flow cell having such a configuration is shown in FIG.

[0062] In the carbon dioxide capture / desorption / concentration apparatus 2 shown in Figure 2, the electrochemical flow cell 6 is an electrochemical flow cell having, for example, a hydrogen generation electrode 50 and an oxygen generation electrode 60, a diaphragm 54 installed between the hydrogen generation electrode 50 and the oxygen generation electrode 60, and a second separation tank 56 that spatially separates the products (oxygen and protons) at the oxygen generation electrode 60, for example, a cation exchange membrane installed in close contact with the oxygen generation electrode 60.

[0063] 2 includes, for example, an electrochemical flow cell 6 for performing a water electrolysis reaction, a power supply system 84 for performing pulse electrolysis by repeatedly varying the current passed through or the voltage applied to the electrochemical flow cell 6 at predetermined intervals, a gas-liquid contact reactor 76 for recovering carbon dioxide, a gas-liquid separator 78 for separating the desorbed carbon dioxide from the electrolyte, and a circulation pipe 86 for circulating the electrolyte through the electrochemical flow cell 6, the gas-liquid contact reactor 76, and the gas-liquid separator 78. The carbon dioxide capture / desorption / concentration system 2 may also include at least one pump 72a and at least one pH sensor 66a, 66b installed at any position on the circulation pipe 86. The power supply system 84 and the hydrogen generation electrode 50 are connected by a wiring 88a for supplying power, and the power supply system 84 and the oxygen generation electrode 60 are connected by a wiring 88b for supplying power.

[0064] The electrochemical flow cell 5 includes a hydrogen generating electrode 50, an oxygen generating electrode 60, a first electrolyte tank 52 having an electrolyte inlet for the inflow of the electrolyte and an electrolyte outlet for the outflow of the electrolyte, a second electrolyte tank 58 having an electrolyte inlet for the inflow of the electrolyte and an electrolyte outlet for the outflow of the electrolyte, a diaphragm 54 separating the hydrogen generating electrode 50 from the oxygen generating electrode 60, a first separation tank 74 for spatially separating the products (hydrogen and hydroxide ions) at the hydrogen generating electrode 50, and a second separation tank 56 for spatially separating the products (oxygen and protons) at the oxygen generating electrode 60. The first separation tank 74 is installed in the circulation pipe 86 between the first electrolyte tank 52 and the gas-liquid contact reactor 76. The second separation tank 56 is installed in close contact with the oxygen generating electrode 60, for example, as a cation exchange membrane. The circulation piping 86 is connected so that the electrolyte circulates between the electrolyte outlet of the first electrolytic solution tank 52 and the electrolyte inlet of the first separation tank 74, between the electrolyte outlet of the first separation tank 74 and the electrolyte inlet of the gas-liquid contact reactor 76, between the electrolyte outlet of the gas-liquid contact reactor 76 and the electrolyte inlet of the first electrolytic solution tank 52, between the electrolyte inlet of the second electrolytic solution tank 58, between the electrolyte outlet of the second electrolytic solution tank 58 and the electrolyte inlet of the gas-liquid separator 78, between the electrolyte outlet of the gas-liquid separator 78 and the electrolyte inlet of the first electrolytic solution tank 52, and between the electrolyte inlet of the second electrolytic solution tank 58.

[0065] The gas-liquid contact reaction device 76 is a reaction vessel that brings the electrolytic solution supplied from the first electrolytic solution tank 52 on the hydrogen generation electrode 50 side of the electrochemical flow cell 6 into contact with the carbon dioxide to be recovered, and has a carbon dioxide to be recovered inlet for introducing a carbon dioxide-containing gas containing the carbon dioxide to be recovered from the carbon dioxide to be recovered storage container 80, and a post-recovery gas outlet for releasing the gas after the recovery process.

[0066] The gas-liquid separator 78 is a device that separates the desorbed carbon dioxide generated in the second electrolyte tank 58 on the oxygen generating electrode 60 side of the electrochemical flow cell 6 from the electrolyte, and has a separated carbon dioxide storage container 82 that stores the separated desorbed carbon dioxide or a desorbed carbon dioxide outlet for introducing it into the next process, such as a reuse process.

[0067] The method for capturing and concentrating carbon dioxide according to this embodiment and the operation of the carbon dioxide capture, desorption, and concentration apparatus 2 will be described.

[0068] The electrolyte is supplied to the first electrolytic solution tank 52 from its electrolyte inlet and to the second electrolytic solution tank 58 from its electrolyte inlet through the circulation pipe 86. The electrolyte supplied to the first electrolytic solution tank 52 is sent from its electrolyte outlet through the circulation pipe 86 to the first separation tank 74 and then sent to the gas-liquid contact reactor 76 through the circulation pipe 86. The electrolyte supplied to the second electrolytic solution tank 58 is sent from its electrolyte outlet through the circulation pipe 86 to the gas-liquid separator 78. The electrolyte discharged from the gas-liquid contact reactor 76 is circulated to the first electrolytic solution tank 52 and the second electrolytic solution tank 58 through the circulation pipe 86, and the electrolyte discharged from the gas-liquid separator 78 is circulated to the first electrolytic solution tank 52 and the second electrolytic solution tank 58 through the circulation pipe 86.

[0069] In the carbon dioxide capture, desorption, and concentration apparatus 2, a current or voltage is applied between the hydrogen-producing electrode 50 and the oxygen-producing electrode 60 by the power supply system 84 in the electrolyte, causing a water decomposition reaction. The water decomposition reaction occurs in the hydrogen-producing electrode 50, where water (HO) is converted into hydrogen (H) and hydroxide ions (OH - ), and oxygen (O) and protons (H + ) is an electrochemical reaction that produces

[0070] Hydrogen (H2) and hydroxide ions (OH - The electrolyte solution containing hydrogen (H) and hydroxide ions (OH) is sent to the first separation tank 74 through the circulation pipe 86. In the first separation tank 74, the electrolyte solution containing hydrogen (H) and hydroxide ions (OH) is separated from the hydrogen-evolving electrode 50. - ) are spatially separated, and hydroxide ions (OH - The electrolyte solution containing oxygen (O2) and protons (H + ) are spatially separated, and protons (H + ) moves to the second electrolyte tank 58.

[0071] The hydroxide ions (OH - ) is sent to the gas-liquid contact reaction device 76. In the gas-liquid contact reaction device 76, a carbon dioxide-containing gas containing the carbon dioxide (CO2) to be captured introduced from the carbon dioxide storage container 80 to be captured is introduced by the pump 72b from the carbon dioxide to be captured inlet, and the carbon dioxide (CO2) to be captured and hydroxide ions (OH - ) reaction converts the target carbon dioxide (CO2) into hydrogen carbonate ions (HCO3 - The post-capture treatment gas, which may contain excess carbon dioxide (CO2), is discharged from the post-capture treatment gas outlet and collected in the carbon dioxide storage container 80 to be collected.

[0072] From the gas-liquid contact reactor 76, hydrogen carbonate ions (HCO3 - ) is sent to the second electrolyte tank 58. In the second electrolyte tank 58, bicarbonate ions (HCO3 - ) and protons (H + ) reacts with the desorbed carbon dioxide (CO2) and is chemically converted into carbon dioxide (CO2) and water (H2O). The electrolytic solution supplied to the second electrolytic solution tank 58 is sent to the gas-liquid separator 78 through the circulation pipe 86 together with the desorbed carbon dioxide (CO2).

[0073] In the gas-liquid separator 78, gas-liquid separation is carried out, and the separated desorbed carbon dioxide (CO 2 ) is discharged from a desorbed carbon dioxide outlet and collected in a separated carbon dioxide storage container 82.

[0074] In this way, the recovery of carbon dioxide is achieved by converting hydroxide ions (OH - The carbon dioxide-containing gas is brought into contact with an electrolytic solution containing protons (H + ) and hydrogen carbonate ions (HCO3 - ) is brought into contact with an electrolyte solution containing

[0075] Carbon dioxide is concentrated by circulating the electrolyte between the hydrogen generation electrode 50 and oxygen generation electrode 60 of the electrochemical flow cell 6, a gas-liquid contact reaction device 76 that recovers carbon dioxide, and a gas-liquid separation device 78 that separates the desorbed carbon dioxide from the electrolyte, thereby allowing the recovery and desorption of carbon dioxide to proceed continuously.

[0076] Furthermore, in the carbon dioxide capture and concentration method and carbon dioxide capture and desorption concentration device 2 according to this embodiment, the electrolysis reaction of water is carried out intermittently. Then, while the electrolysis reaction of water is carried out intermittently, the capture of carbon dioxide and the desorption of the captured carbon dioxide are carried out continuously. The current passed through or the voltage applied to the water electrolysis device where the electrolysis reaction is carried out is repeatedly varied at predetermined intervals to control the supply amounts of hydroxide ions and protons generated in the electrolysis reaction to the electrolyte. The hydroxide ions (OH - ) and protons (H + The carbon dioxide capture process uses hydrogen to generate hydroxide ions (OH) by electrolysis at predetermined intervals. - ) and protons (H + By controlling the amount of carbon dioxide supplied to the electrolyte, the amount of carbon dioxide recovered and the amount of carbon dioxide desorbed can be increased, and carbon dioxide can be separated from the water decomposition products, recovered, and concentrated more efficiently and with less energy consumption than steady-state electrolysis.

[0077] The present specification includes the following embodiments. (1) A carbon dioxide recovery / desorption / concentration device that utilizes an intermittent electrolysis reaction of water to recover carbon dioxide from a carbon dioxide-containing gas and desorb the recovered carbon dioxide, thereby concentrating the carbon dioxide.

[0078] (2) The carbon dioxide recovery, desorption and concentration apparatus according to (1), The apparatus for recovering, desorbing, and concentrating carbon dioxide includes a water electrolysis device that performs the electrolysis reaction by repeatedly varying, at predetermined intervals, the current passed through or the voltage applied to the water electrolysis device, thereby controlling the amounts of hydroxide ions and protons generated by the electrolysis reaction that are supplied to the electrolyte.

[0079] (3) The carbon dioxide capture, desorption and concentration apparatus according to (1) or (2), The carbon dioxide is recovered by reacting hydroxide ions generated in the electrolysis reaction with carbon dioxide to capture the carbon dioxide in the electrolyte solution, The recovered carbon dioxide is desorbed by reacting protons generated in the electrolysis reaction with the carbon dioxide captured in the electrolytic solution.

[0080] (4) The carbon dioxide recovery, desorption and concentration apparatus according to (1), the intermittently proceeding water electrolysis reaction involves repeatedly varying, at predetermined intervals, a current passed through or a voltage applied to a water electrolysis device in which the electrolysis reaction occurs, to control the amounts of hydroxide ions and protons generated by the electrolysis reaction that are supplied to the electrolyte; The carbon dioxide is recovered by reacting hydroxide ions generated in the electrolysis reaction with carbon dioxide to capture the carbon dioxide in the electrolyte solution, The desorption of the recovered carbon dioxide is performed by reacting protons generated by the electrolysis reaction with the carbon dioxide captured in the electrolytic solution, A carbon dioxide recovery, desorption, and concentration apparatus that continuously recovers the carbon dioxide and desorbs the recovered carbon dioxide while performing the intermittently progressing water electrolysis reaction.

[0081] (5) A carbon dioxide recovery, desorption and concentration apparatus according to any one of (1) to (4), an electrochemical flow cell in which the water electrolysis reaction is performed; a power supply system that repeatedly varies the current flowing through or the voltage applied to the electrochemical flow cell at predetermined intervals; a gas-liquid contact reactor for recovering the carbon dioxide; a gas-liquid separator that separates the desorbed carbon dioxide from the electrolyte; a circulation pipe for circulating an electrolytic solution through the electrochemical flow cell, the gas-liquid contact reaction device, and the gas-liquid separation device; A carbon dioxide capture, desorption and concentration device comprising:

[0082] (6) A method for recovering, desorbing, and concentrating carbon dioxide, which utilizes an intermittently proceeding electrolysis reaction of water to recover carbon dioxide from a carbon dioxide-containing gas and desorb the recovered carbon dioxide, thereby concentrating the carbon dioxide.

[0083] (7) The method for recovering, desorbing, and concentrating carbon dioxide according to (6), The method for recovering, desorbing, and concentrating carbon dioxide includes repeatedly varying, at predetermined intervals, a current passed through or a voltage applied to a water electrolysis device that performs the electrolysis reaction, thereby controlling the amounts of hydroxide ions and protons generated by the electrolysis reaction that are supplied to the electrolyte solution.

[0084] (8) A method for recovering, desorbing, and concentrating carbon dioxide according to (6) or (7), The carbon dioxide is recovered by reacting hydroxide ions generated in the electrolysis reaction with carbon dioxide to capture the carbon dioxide in the electrolyte solution, The method for recovering, desorbing, and concentrating carbon dioxide comprises reacting protons generated by the electrolysis reaction with the carbon dioxide captured in the electrolytic solution.

[0085] (9) The method for recovering, desorbing, and concentrating carbon dioxide according to (6), the intermittently proceeding water electrolysis reaction involves repeatedly varying, at predetermined intervals, a current passed through or a voltage applied to a water electrolysis device in which the electrolysis reaction occurs, to control the amounts of hydroxide ions and protons generated by the electrolysis reaction that are supplied to the electrolyte; The carbon dioxide is recovered by reacting hydroxide ions generated in the electrolysis reaction with carbon dioxide to capture the carbon dioxide in the electrolyte solution, The desorption of the recovered carbon dioxide is performed by reacting protons generated by the electrolysis reaction with the carbon dioxide captured in the electrolytic solution, A method for recovering, desorbing, and concentrating carbon dioxide, wherein the recovery of carbon dioxide and the desorption of the recovered carbon dioxide are continuously carried out while the intermittently proceeding water electrolysis reaction is carried out.

[0086] (10) A method for recovering, desorbing, and concentrating carbon dioxide according to any one of (6) to (9), an electrochemical flow cell in which the water electrolysis reaction is performed; a power supply system that repeatedly varies the current flowing through or the voltage applied to the electrochemical flow cell at predetermined intervals; a gas-liquid contact reactor for recovering the carbon dioxide; a gas-liquid separator that separates the desorbed carbon dioxide from the electrolyte; a circulation pipe for circulating an electrolytic solution through the electrochemical flow cell, the gas-liquid contact reaction device, and the gas-liquid separation device; A method for recovering, desorbing, and concentrating carbon dioxide using a carbon dioxide recovery, desorption, and concentration apparatus comprising: [Example]

[0087] EXAMPLES The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0088] <Example 1, Comparative Example 1> [Carbon dioxide capture, desorption and concentration system used in the evaluation] The carbon dioxide capture / desorption / concentration system used for the carbon dioxide capture / desorption / concentration evaluation was the carbon dioxide capture / desorption / concentration apparatus 2 shown in Figure 2. This system consisted of an electrochemical flow cell 6, a hydrogen separation device as the first separation tank 74, a gas-liquid contact reactor 76, a gas-liquid separator 78, a sealed container for storing the carbon dioxide to be captured (storage container 80 for carbon dioxide to be captured), a sealed container for storing the desorbed carbon dioxide (storage container 82 for separated carbon dioxide), and a power supply system 84. The power supply system 84 was connected by wiring 88a, 88b, and 88c to the hydrogen generation electrode 50, oxygen generation electrode 60, and reference electrode 62 (Ag / AgCl electrode, RE-14, EC Frontier) installed in the first electrolyte tank 52 on the hydrogen generation electrode 50 side of the electrochemical flow cell 6, respectively.

[0089] [Circulation of electrolyte in the carbon dioxide capture / desorption / concentration system used in the evaluation] The electrolyte was an aqueous potassium sulfate solution (concentration: 0.5 mol / L). A constant-flow pump (MP-2000, EYELA, flow rate: 10–15 mL / min) was used as pump 72a. The electrolyte was circulated through (1) a path connecting the electrolyte outlet of the first electrolyte tank 52 on the hydrogen-producing electrode 50 side of the electrochemical flow cell 6 to a gas-liquid contact reactor 76 via a first separation tank 74 (hydrogen separator), (2) a path connecting the electrolyte outlet of the second electrolyte tank 58 on the oxygen-producing electrode 60 side of the electrochemical flow cell 6 to a gas-liquid separator 78, and (3) a flow path combining these paths and connecting them to the electrolyte inlets of the first electrolyte tank 52 on the hydrogen-producing electrode 50 side and the second electrolyte tank 58 on the oxygen-producing electrode 60 side of the electrochemical flow cell 6. pH sensors 66a and 66b were installed in the paths (1) and (2), respectively, to measure the pH of the electrolyte.

[0090] [Electrochemical flow cell used for evaluation] The electrochemical flow cell 6 used for the evaluation of carbon dioxide capture, desorption, and concentration was equipped with a platinum particle-supported titanium plate (3.14 cm) on the hydrogen generation electrode 50. 2 ), and the oxygen generating electrode 60 is an iridium oxide-supported titanium mesh (3.14 cm 2 ), and the diaphragm 54 between the electrodes was made of Nafion (registered trademark) 212 (3.14 cm 2The hydrogen gas and hydroxide ions produced at the hydrogen-producing electrode 50 were separated in a hydrogen separator, which was a first separation tank 74, installed between the first electrolytic solution tank 52 in contact with the hydrogen-producing electrode 50 and the gas-liquid contact reactor 76. The oxygen and protons produced at the oxygen-producing electrode 60 were separated in a second separation tank 56, which was installed at the interface between the oxygen-producing electrode 60 and the second electrolytic solution tank 58 on the oxygen-producing electrode 60 side, and which contained Nafion (registered trademark) 212 (3.14 cm 2 ) was separated.

[0091] [Water electrolysis by pulsed constant current electrolysis] An electrochemical measurement device (SP-150, Bio-Logic Science Instruments) was used as the power supply system 84 for driving the water electrolysis reaction in the electrochemical flow cell 6. A reference electrode 62 (Ag / AgCl electrode, RE-14, EC Frontier) was installed in the first electrolyte tank 52 on the hydrogen generation electrode 50 side of the electrochemical flow cell 6, and pulse constant-current electrolysis was performed by repeatedly passing and stopping a current between the hydrogen generation electrode 50 and the oxygen generation electrode 60. The current value during current passing was −35 mA, and the intervals between current passing and stopping (pulse interval, current passing time (seconds) / stopping time (seconds)) were 360 / 360 for Example 1, 180 / 180 for Example 2, 90 / 90 for Example 3, 30 / 30 for Example 4, and 10 / 10 for Example 5. At each pulse interval, current passing and stopping were repeated until the total current passing time reached 2 hours. The current efficiency of the water electrolysis reaction was estimated by quantitatively analyzing the oxygen (O2) or hydrogen (H2) produced from the electrode using a gas chromatograph (Multigas Analyzer #5, SRI Instruments).

[0092] [Water electrolysis by steady-state constant current electrolysis] As a comparative example of pulse constant-current electrolysis, constant-current electrolysis was performed by continuously passing a current of -35 mA between the hydrogen generating electrode 50 and the oxygen generating electrode 60 of the electrochemical flow cell 6. For comparison with the above-described pulse constant-current electrolysis, the constant-current electrolysis time was set to 2 hours, so that the amount of charge input into the water electrolysis reaction was the same as in the pulse constant-current electrolysis of Examples 1 to 5. Other evaluation conditions and equipment used were the same as in Examples 1 to 5.

[0093] [Quantitative method for carbon dioxide recovery and desorbed carbon dioxide amount] The carbon dioxide to be captured was carbon dioxide-containing air (carbon dioxide concentration: approximately 2000 ppm) prepared in a 12 L volume of a carbon dioxide storage container 80 to be captured. The carbon dioxide storage container 80 to be captured was connected to the carbon dioxide inlet to be captured and the post-capture treatment gas outlet of the gas-liquid contact reaction device 76, and the carbon dioxide-containing air was circulated between the carbon dioxide storage container 80 to be captured and the gas-liquid contact reaction device 76 using a pump 72b (flow rate: 1 to 1.5 L / min). The desorbed carbon dioxide generated in the second electrolyte tank 58 in contact with the oxygen-generating electrode 60 was separated from the electrolyte in a gas-liquid separator 78 and stored in a separated carbon dioxide storage container 82 with a volume of 1.3 L, which was connected to the desorbed carbon dioxide outlet of the gas-liquid separator 78. The carbon dioxide concentrations in the carbon dioxide storage container 80 to be recovered and the separated carbon dioxide storage container 82 were measured using non-dispersive infrared absorption carbon dioxide sensors (TR-76Ui, T&D Corporation) as carbon dioxide concentration measuring devices 70a and 70b, and the amount of recovered carbon dioxide and the amount of desorbed carbon dioxide were calculated.

[0094] 3 shows the change over time in carbon dioxide concentration in carbon dioxide storage container 80 to be captured (solid line) and in separated carbon dioxide storage container 82 (dashed line) in an evaluation of carbon dioxide capture and concentration (A: Comparative Example, B: Example 1, C: Example 2, D: Example 3, E: Example 4, F: Example 5). The area between the dashed lines indicates the time period during which water decomposition was carried out by constant-current electrolysis.

[0095] [Evaluation of carbon dioxide capture and desorption] As shown in FIG. 3, in all of Examples 1 to 5 and the Comparative Example, the carbon dioxide concentration in the carbon dioxide storage container 80 to be recovered decreased as the water electrolysis reaction progressed, and the carbon dioxide concentration in the separated carbon dioxide storage container 82 increased. Table 1 shows the amount of carbon dioxide recovered (mL) and the amount of carbon dioxide released (mL) in each system. In Examples 1 and 2, the amount of carbon dioxide recovered was 7.5 mL and 8.1 mL, respectively, and the amount of carbon dioxide released was 2.2 mL and 2.4 mL, respectively. This was a slight increase in carbon dioxide recovery and a slight decrease in the amount of carbon dioxide released compared to the Comparative Example (amount of carbon dioxide recovered: 7.4 mL, amount of carbon dioxide released: 2.8 mL). In Examples 3, 4, and 5, the amount of carbon dioxide recovered and the amount of carbon dioxide released were 10.4 mL, 9.8 mL, and 9.8 mL, respectively, and the amount of carbon dioxide released was 3.7 mL, 3.8 mL, and 4.0 mL, respectively. In all of Examples 3, 4, and 5, the amount of carbon dioxide recovered and the amount of carbon dioxide released increased compared to the Comparative Example, and in particular, Example 3 had the greatest amount of carbon dioxide recovered.

[0096] [Evaluation of carbon dioxide recovery energy] Table 1 shows the energy consumption (J) and carbon dioxide recovery energy (GJ / ton-CO2) for each system.

[0097] [Table 1]

[0098] The energy consumption, calculated by subtracting the energy of produced H2 from the water electrolysis energy calculated from the product of the average current value between the two electrodes, the average voltage, and the electrolysis time during water electrolysis, was 564 J (Comparative Example), 555 J (Example 1), 613 J (Example 2), 579 J (Example 3), 553 J (Example 4), and 578 J (Example 5). The carbon dioxide recovery energy calculated from the energy consumption and the amount of carbon dioxide recovered was 42.5 GJ / ton-CO2 (Comparative Example), 41.4 GJ / ton-CO2 (Example 1), 42.3 GJ / ton-CO2 (Example 2), 31.0 GJ / ton-CO2 (Example 3), 31.7 GJ / ton-CO2 (Example 4), and 33.0 GJ / ton-CO2 (Example 5), confirming that the amount of carbon dioxide recovery energy could be reduced by adjusting the pulse interval.

[0099] [Effect of pulsed galvanostatic electrolysis on water electrolysis behavior] To verify the effect of pulsed constant-current electrolysis, the behavior of water electrolysis was compared between Example 3, which had the highest carbon dioxide recovery amount, and the comparative example. Figure 4 shows the time-dependent changes in the applied voltage to the hydrogen generating electrode 50 and the oxygen generating electrode 60 and the voltage between the two electrodes during water electrolysis. Figure 4A shows the time-dependent changes in the applied voltage to the hydrogen generating electrode 50, Figure 4B shows the time-dependent changes in the applied voltage to the oxygen generating electrode 60, and Figure 4C shows the time-dependent changes in the voltage between the two electrodes (a: Example 3, b: Comparative example).

[0100] As shown in FIG. 4A, the average applied voltage to the hydrogen generating electrode 50 was almost the same: −1.04 V in Example 3 and −1.09 V in the Comparative Example. As shown in FIG. 4B, the average applied voltage to the oxygen generating electrode 60 was 2.41 V in Example 3 and 2.36 V in the Comparative Example, with Example 3 being slightly higher. As shown in FIG. 4C, the average value of the voltage between the two electrodes was −3.54 V in Example 3 and −3.44 V in the Comparative Example, reflecting the voltages applied to both electrodes. This indicates that the water electrolysis behavior is almost the same in Example 3 and the Comparative Example.

[0101] [Effect of pulsed constant current electrolysis on electrolyte pH] To verify the effect of pulse constant-current electrolysis, the change in the pH of the electrolyte over time was compared between Example 3, which had the largest amount of carbon dioxide recovery, and the Comparative Example. The change in the pH of the electrolyte over time during the evaluation of carbon dioxide recovery, desorption, and concentration is shown in FIG. 5. FIG. 5A shows the change in the pH of the electrolyte over time in the Comparative Example, and FIG. 5B shows the change in the pH of the electrolyte over time in Example 3 (a: pH of the electrolyte flowing out from the first electrolyte tank 52 in contact with the hydrogen generation electrode 50; b: pH of the electrolyte flowing out from the second electrolyte tank 58 in contact with the oxygen generation electrode 60).

[0102] As shown in FIG. 5Aa, the pH of the electrolyte solution flowing out from the first electrolyte solution tank 52 on the hydrogen-generating electrode 50 side was almost constant at around pH 9 in the comparative example. However, as shown in FIG. 5Ba, in Example 3, the pH rose with current application and fell with current cessation, fluctuating between pH 10 and pH 7.5. This is because the electrolyte solution in Example 3 during current application contained more hydroxide ions (OH) than the electrolyte solution in the comparative example. - ) is contained in a large amount. The pH of the electrolyte solution flowing out from the second electrolyte tank 58 on the oxygen-evolving electrode 60 side was around pH 4 in the comparative example as shown in FIG. 5Ab, and in Example 3, as shown in FIG. 5Bb, it fluctuated between pH 4 and pH 5 depending on whether the current was turned on or off. This is because the electrolyte solution in Example 3 contained more protons (H + ) indicates that there is little

[0103] [Changes in electrolyte pH due to water electrolysis method] The measurement results of the change in the pH of the electrolyte over time in Example 3 and the Comparative Example shown in Figure 5 indicate that the pH of the electrolyte can be controlled by the method of supplying power from the power supply system to the electrochemical flow cell. In other words, in the steady-state constant current electrolysis as in the Comparative Example, the pH of the electrolyte is controlled by the chemical species (hydroxide ions (OH - ), proton (H + ), carbonate ion species (hydrogen carbonate ion (HCO3 - It is considered that the pH of the electrolyte solution fluctuates little and converges to a nearly constant value because a chemical equilibrium of the chemical species in the electrolyte solution is quickly established and a steady state is formed. On the other hand, in pulsed constant-current electrolysis such as in Example 3, the pH of the electrolyte solution fluctuates greatly because the equilibrium state of the chemical species in the electrolyte solution constantly fluctuates.

[0104] [Mechanism of carbon dioxide capture and desorption by pulsed constant current electrolysis] From the above-mentioned behavior of the amount of recovered carbon dioxide and the pH of the electrolyte, the mechanism of carbon dioxide recovery and desorption by pulse constant-current electrolysis is considered as follows. In pulse constant-current electrolysis, hydroxide ions (OH - ) increases, and the amount of carbon dioxide recovered in the gas-liquid contact reactor 76 increases. As the amount of carbon dioxide recovered increases, the amount of bicarbonate ions (HCO3 - ) also increases, so the protons (H + ) and bicarbonate ions (HCO3 - ) efficiently proceeds, increasing the amount of carbon dioxide released. + ) is consumed, the pH of the electrolyte flowing out from the second electrolyte tank 58 on the oxygen generating electrode 60 side increases.

[0105] [Pulse constant current electrolysis conditions suitable for carbon dioxide capture and desorption] The above results show that controlling the pH of the electrolyte by pulse constant-current electrolysis increases the amount of carbon dioxide recovered and the amount of carbon dioxide released, and reduces the energy required to recover carbon dioxide. In the carbon dioxide recovery / desorption / concentration system used in the examples, the amount of carbon dioxide recovered increased by shortening the pulse interval from the 180 seconds / 180 seconds pulse interval of Example 2, and the amount of carbon dioxide recovered was particularly maximized at the 90 seconds / 90 seconds pulse interval of Example 3. The optimal pulse interval for carbon dioxide recovery varies depending on the water electrolysis rate, electrolyte flow rate, electrolyte volume, etc., so it was found that it is preferable to set the pulse interval so that the pH of the electrolyte flowing out of the first electrolyte tank 52 on the hydrogen generation electrode 50 side is pH 9 or higher.

[0106] In this way, the carbon dioxide capture, desorption, and concentration system of the embodiment was able to capture carbon dioxide from a carbon dioxide-containing gas using an electrochemical reaction, and the carbon dioxide was separated from the water decomposition products, and was captured and concentrated efficiently and with low energy consumption. [Explanation of symbols]

[0107] 1, 2 Carbon dioxide capture and desorption concentration device, 5, 6 Electrochemical flow cell, 10, 50 Hydrogen generation electrode, 12 First separation tank, 14, 52 First electrolyte tank, 16, 54 Diaphragm, 18, 58 Second electrolyte tank, 20, 56 Second separation tank, 22, 60 Oxygen generation electrode, 24a, 24b Electrolyte inlet, 26a, 26b Electrolyte outlet, 28, 84 Power supply system, 30a, 30b, 88a, 88b, 88c Wiring, 32a, 32b, 66a, 66b pH sensor, 34, 86 Circulation piping, 36, 76 Gas-liquid contact reactor, 38 Carbon dioxide to be captured inlet, 40 Gas outlet after capture treatment, 42, 78 Gas-liquid separator, 44 Desorbed carbon dioxide outlet, 46a, 46b, 72a, 72b Pump, 62 Reference electrode, 64 oxygen release port, 68 hydrogen release port, 70a, 70b carbon dioxide concentration measuring device, 74 hydrogen separation device, 80 carbon dioxide storage container to be recovered, 82 separated carbon dioxide storage container.

Claims

1. A carbon dioxide recovery / desorption / concentration device that utilizes an intermittently progressing electrolysis reaction of water to recover carbon dioxide from a carbon dioxide-containing gas and desorb the recovered carbon dioxide, thereby concentrating the carbon dioxide.

2. The carbon dioxide recovery, desorption and concentration apparatus according to claim 1, The apparatus for recovering, desorbing, and concentrating carbon dioxide is characterized in that the water electrolysis reaction that is allowed to proceed intermittently is performed by repeatedly varying, at predetermined intervals, the current passed through or the voltage applied to a water electrolysis device that performs the electrolysis reaction, thereby controlling the amounts of hydroxide ions and protons that are generated by the electrolysis reaction and supplied to the electrolyte.

3. The carbon dioxide recovery, desorption and concentration apparatus according to claim 1, The carbon dioxide is recovered by reacting hydroxide ions generated in the electrolysis reaction with carbon dioxide to capture the carbon dioxide in the electrolyte solution, The carbon dioxide recovery, desorption and concentration device is characterized in that the recovered carbon dioxide is desorbed by reacting protons generated in the electrolysis reaction with the carbon dioxide captured in the electrolyte.

4. The carbon dioxide recovery, desorption and concentration apparatus according to claim 1, the intermittently proceeding water electrolysis reaction involves repeatedly varying, at predetermined intervals, a current passed through or a voltage applied to a water electrolysis device in which the electrolysis reaction occurs, to control the amounts of hydroxide ions and protons generated by the electrolysis reaction that are supplied to the electrolyte; The carbon dioxide is recovered by reacting hydroxide ions generated in the electrolysis reaction with carbon dioxide to capture the carbon dioxide in the electrolyte solution, The desorption of the recovered carbon dioxide is performed by reacting protons generated by the electrolysis reaction with the carbon dioxide captured in the electrolytic solution, A carbon dioxide recovery, desorption, and concentration apparatus, characterized in that the recovery of carbon dioxide and the desorption of the recovered carbon dioxide are continuously carried out while the water electrolysis reaction is carried out intermittently.

5. The carbon dioxide recovery, desorption and concentration apparatus according to claim 1, an electrochemical flow cell in which the water electrolysis reaction is performed; a power supply system that repeatedly varies the current flowing through or the voltage applied to the electrochemical flow cell at predetermined intervals; a gas-liquid contact reactor for recovering the carbon dioxide; a gas-liquid separator that separates the desorbed carbon dioxide from the electrolyte; a circulation pipe for circulating an electrolytic solution through the electrochemical flow cell, the gas-liquid contact reaction device, and the gas-liquid separation device; A carbon dioxide recovery, desorption and concentration device comprising:

6. A method for recovering, desorbing, and concentrating carbon dioxide, characterized by using an intermittently progressing electrolysis reaction of water to recover carbon dioxide from a carbon dioxide-containing gas and desorb the recovered carbon dioxide, thereby concentrating the carbon dioxide.

7. The method for recovering, desorbing, and concentrating carbon dioxide according to claim 6, the method for recovering, desorbing, and concentrating carbon dioxide, characterized in that the intermittently progressing water electrolysis reaction is performed by repeatedly varying, at predetermined intervals, a current passed through or a voltage applied to a water electrolysis device in which the electrolysis reaction is performed, thereby controlling the amounts of hydroxide ions and protons generated by the electrolysis reaction that are supplied to the electrolyte.

8. The method for recovering, desorbing, and concentrating carbon dioxide according to claim 6, The carbon dioxide is recovered by reacting hydroxide ions generated in the electrolysis reaction with carbon dioxide to capture the carbon dioxide in the electrolyte solution, A method for recovering, desorbing, and concentrating carbon dioxide, characterized in that the recovered carbon dioxide is desorbed by reacting protons generated in the electrolysis reaction with the carbon dioxide captured in the electrolyte.

9. The method for recovering, desorbing, and concentrating carbon dioxide according to claim 6, the intermittently proceeding water electrolysis reaction involves repeatedly varying, at predetermined intervals, a current passed through or a voltage applied to a water electrolysis device in which the electrolysis reaction occurs, to control the amounts of hydroxide ions and protons generated by the electrolysis reaction that are supplied to the electrolyte; The carbon dioxide is recovered by reacting hydroxide ions generated in the electrolysis reaction with carbon dioxide to capture the carbon dioxide in the electrolyte solution, The desorption of the recovered carbon dioxide is performed by reacting protons generated by the electrolysis reaction with the carbon dioxide captured in the electrolytic solution, A method for recovering, desorbing, and concentrating carbon dioxide, characterized in that the recovery of carbon dioxide and the desorption of the recovered carbon dioxide are continuously carried out while the intermittently proceeding water electrolysis reaction is carried out.

10. The method for recovering, desorbing, and concentrating carbon dioxide according to claim 6, an electrochemical flow cell in which the water electrolysis reaction is performed; a power supply system that repeatedly varies the current flowing through or the voltage applied to the electrochemical flow cell at predetermined intervals; a gas-liquid contact reactor for recovering the carbon dioxide; a gas-liquid separator that separates the desorbed carbon dioxide from the electrolyte; a circulation pipe for circulating an electrolytic solution through the electrochemical flow cell, the gas-liquid contact reaction device, and the gas-liquid separation device; A method for recovering, desorbing, and concentrating carbon dioxide, comprising:

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