Carbon dioxide recovery system

Abstract

To provide a carbon dioxide recovery system that is able to improve the ability to recover carbon dioxide.SOLUTION: A carbon dioxide recovery system 1 has an electrochemical cell 101 including a working electrode 102 and a counter electrode 103. The system repeats an adsorption mode in which carbon dioxide is adsorbed by the working electrode 102 by applying a first voltage V1 between the working electrode 102 and the counter electrode 103, and a desorption mode in which carbon dioxide is desorbed and discharged from the working electrode 102 by applying a second voltage V2 between the working electrode 102 and the counter electrode 103. In the adsorption mode, the electrochemical cell 101 generates active oxygen by applying a voltage between the working electrode 102 and the counter electrode 103 and supplying electrons to the working electrode 102, in a state where oxygen is supplied together with carbon dioxide to the vicinity of the working electrode 102 in an electrolyte layer 106, and adsorbs carbon dioxide by generating carbon dioxide adsorbing molecules.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a carbon dioxide recovery system.

Background Art

[0002] As a system for recovering carbon dioxide, for example, as disclosed in Patent Document 1, a system having an electrochemical cell including a working electrode and a counter electrode has been proposed. In this carbon dioxide recovery system, a CO2 adsorbent that adsorbs carbon dioxide is fixed to the working electrode.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the above-described conventional carbon dioxide recovery system has room for improvement from the viewpoint of processing capacity. That is, there is a limit to the amount of the CO 2 adsorbent that can be fixed to the working electrode. Therefore, the carbon dioxide recovery ability is limited by the fixed amount of the CO 2 adsorbent. As a result, there is room for improvement in the above-described conventional carbon dioxide recovery system from the viewpoint of the carbon dioxide recovery ability.

[0005] The present invention has been made in view of such problems, and an object thereof is to provide a carbon dioxide recovery system capable of improving the carbon dioxide recovery ability.

Means for Solving the Problems

[0006] One aspect of the present invention is a carbon dioxide recovery system (1) for separating carbon dioxide from a gas to be treated containing carbon dioxide by an electrochemical reaction, It has an electrochemical cell (101) including a working electrode (102) that contacts the gas to be treated, a counter electrode (103), and an insulating layer (104) and an electrolyte layer (106) disposed between the working electrode and the counter electrode. By applying a first voltage (V1) between the working electrode and the counter electrode, electrons are supplied to the working electrode, and the carbon dioxide in the gas to be treated is adsorbed on the working electrode, in an adsorption mode. By applying a second voltage (V2) different from the first voltage between the working electrode and the counter electrode, electrons are released from the working electrode, and the carbon dioxide is desorbed and discharged from the working electrode, in a desorption mode, and it is configured to repeat these modes. In the adsorption mode, with oxygen supplied to the vicinity of the working electrode in the electrolyte layer together with the carbon dioxide, a voltage is applied between the working electrode and the counter electrode to supply electrons to the working electrode, so that the oxygen receives electrons to generate active oxygen, and the active oxygen combines with the carbon dioxide to generate a carbon dioxide adsorption molecule, thereby adsorbing carbon dioxide, in a carbon dioxide recovery system.

Advantages of the Invention

[0007] In the above carbon dioxide recovery system, the electrochemical cell is configured to adsorb carbon dioxide by the active species of oxygen supplied to the working electrode combining with the carbon dioxide as described above. That is, the active oxygen generated in the vicinity of the working electrode in the electrolyte layer adsorbs carbon dioxide. Therefore, the amount of carbon dioxide that can be recovered can be increased. As a result, the carbon dioxide recovery ability can be improved.

[0008] As described above, according to the above aspect, a carbon dioxide recovery system capable of improving the carbon dioxide recovery ability can be provided. Note that the reference numerals in parentheses described in the claims and the means for solving the problems indicate the correspondence with the specific means described in the embodiments described later, and do not limit the technical scope of the present invention.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0010] (Embodiment 1) Embodiments of the carbon dioxide recovery system will be described with reference to FIGS. 1 to 7. The carbon dioxide recovery system 1 of this embodiment is a system that separates carbon dioxide from a gas to be treated containing carbon dioxide (CO 2 ).

[0011] As shown in FIGS. 1 to 3, the carbon dioxide recovery system 1 has an electrochemical cell 101. The electrochemical cell 101 includes a working electrode 102 that contacts the gas to be treated, a counter electrode 103, an insulating layer 104, and an electrolyte layer 106. The insulating layer 104 and the electrolyte layer 106 are disposed between the working electrode 102 and the counter electrode 103. The working electrode 102 and the counter electrode 103 are disposed opposite to each other with the insulating layer 104 and the electrolyte layer 106 interposed therebetween.

[0012] As shown in FIG. 4, the carbon dioxide recovery system 1 is configured to repeat an adsorption mode and a desorption mode. The adsorption mode is a mode in which a first voltage V1 is applied between the working electrode 102 and the counter electrode 103 to supply electrons to the working electrode 102 and adsorb carbon dioxide in the gas to be treated on the working electrode 102. The desorption mode is a mode in which a second voltage V2 different from the first voltage V1 is applied between the working electrode 102 and the counter electrode 103 to release electrons from the working electrode 102 and desorb and discharge carbon dioxide from the working electrode 102.

[0013] In the adsorption mode, the electrochemical cell 101 is configured such that a voltage is applied between the working electrode 102 and the counter electrode 103 while oxygen is supplied to the vicinity of the working electrode 102 in the electrolyte layer 106 together with carbon dioxide, and electrons are supplied to the working electrode 102. Thereby, oxygen receives electrons to generate active oxygen, and the active oxygen combines with carbon dioxide to generate a carbon dioxide adsorption molecule, thereby adsorbing carbon dioxide.

[0014] Note that, as the carbon dioxide adsorption molecule, for example, carbonate ion (CO 3 2- ) is conceivable. In this embodiment, the carbon dioxide adsorption molecule is mainly carbonate ion (CO 3 2- ).

[0015] As shown in FIG. 1, the carbon dioxide recovery system 1 includes a compressor 11, a CO 2 recovery device 100, a flow path switching valve 12, a CO 2 utilization device 13, and a control device 14.

[0016] The compressor 11 pumps the gas to be treated to the CO 2 recovery device 100. The gas to be treated is a mixed gas containing gases other than CO 2 and CO 2 . In this embodiment, the gas to be treated also contains oxygen (O 2 ). The gas to be treated can be, for example, air or the exhaust gas of an internal combustion engine.

[0017] CO2 The recovery device 100 is a device that separates and recovers CO from the gas to be treated. 2 from the gas to be treated. 2 The recovery device 100 is a device that separates and recovers CO 2 from the gas to be treated, and after the CO is recovered and removed, 2 the CO removal gas, or the CO recovered from the gas to be treated, 2 is discharged. 2 The configuration of the recovery device 100 will be described in detail later.

[0018] The flow path switching valve 12 is a three-way valve that switches the flow path of the exhaust gas of the recovery device 100. When the CO removal gas is discharged from the recovery device 100, the flow path switching valve 12 connects the flow path of the exhaust gas to the atmosphere side. When the CO is discharged from the recovery device 100, the flow path switching valve 12 connects the flow path of the exhaust gas to the CO utilization device 13 side. 2 The flow path switching valve 12 is a three-way valve that switches the flow path of the exhaust gas of the recovery device 100. When the CO removal gas is discharged from the recovery device 100, the flow path switching valve 12 connects the flow path of the exhaust gas to the atmosphere side. When the CO is discharged from the recovery device 100, the flow path switching valve 12 connects the flow path of the exhaust gas to the CO 2 from the recovery device 100 2 utilization device 13 side. 2 from the recovery device 100 2 is discharged, the flow path switching valve 12 connects the flow path of the exhaust gas to the CO 2 utilization device 13 side.

[0019] The CO 2 utilization device 13 is a device that uses CO. 2 As the CO 2 utilization device 13, for example, a storage tank that stores CO 2 or a conversion device that converts CO 2 into fuel can be used. The conversion device can use a device that converts CO 2 into hydrocarbon fuel such as methane. The hydrocarbon fuel may be a gaseous fuel or a liquid fuel at normal temperature and pressure.

[0020] The control device 14 is composed of a well-known microcomputer including a CPU, ROM, and RAM, etc., and its peripheral circuits. The control device 14 performs various calculations and processes based on the control program stored in the ROM, and controls the operations of various controlled devices. The control device 14 of this embodiment performs the operation control of the compressor 11, the operation control of the CO 2 recovery device 100, the flow path switching control of the flow path switching valve 12, etc.

[0021] Next, the CO 2 recovery device 100 will be described with reference to FIG. 2. As shown in the figure, the CO 2 recovery device 100 has an electroadsorption-type electrochemical cell 101 that adsorbs and desorbs CO 2 by electrochemical reaction. The electrochemical cell 101 includes a working electrode 102, a counter electrode 103, and an insulating layer 104. The insulating layer 104 is interposed between the working electrode 102 and the counter electrode 103. In the example shown in FIG. 2, the working electrode 102, the counter electrode 103, and the insulating layer 104 are each configured in a plate shape. Although not shown in FIG. 2, as shown in FIG. 3, an electrolyte layer 106 is provided between the working electrode 102 and the counter electrode 103, and the insulating layer 104 is provided in the electrolyte layer 106.

[0022] The electrochemical cell 101 may be housed in a container (not shown). The container may be provided with a gas inlet for allowing the gas to be treated to flow into the container, and a gas outlet for allowing the removed gas or CO 2 to flow out of the container. 2 can be provided.

[0023] CO 2 The recovery device 100 performs adsorption and desorption of CO 2 by the electrochemical reaction of the electrochemical cell 101, and separates and recovers CO 2 from the gas to be treated. The CO 2 recovery device 100 is provided with a power supply 105 for applying a predetermined voltage to the working electrode 102 and the counter electrode 103, and the potential difference between the working electrode 102 and the counter electrode 103 can be changed. The working electrode 102 is the negative electrode, and the counter electrode 103 is the positive electrode.

[0024] As shown in FIG. 5, the electrochemical cell 101 can operate by switching between an adsorption mode and a desorption mode by changing the potential difference between the working electrode 102 and the counter electrode 103. The adsorption mode is a mode in which CO 2 is recovered at the working electrode 102. The desorption mode is a mode in which CO 2It is a mode of discharging. The adsorption mode is a charging mode for charging the electrochemical cell 101, and the desorption mode is a discharging mode for discharging the electrochemical cell 101.

[0025] In the adsorption mode, a first voltage V1 is applied between the working electrode 102 and the counter electrode 103, and electrons are supplied to the working electrode 102. At the first voltage V1, (working electrode potential) < (counter electrode potential). The first voltage V1 can be, for example, in the range of -0.1 to -5.0 V. Note that the first voltage V1 is expressed as the working electrode potential with reference to the counter electrode potential. The same applies to the second voltage V2. However, when referring to the first voltage V1, the second voltage V2, etc., as being large or small, it means the magnitude of the absolute value.

[0026] In the desorption mode, a second voltage V2 is applied between the working electrode 102 and the counter electrode 103, and electrons are supplied to the counter electrode 103. The second voltage V2 is a voltage different from the first voltage V1. When (working electrode potential) ≥ (counter electrode potential), the magnitude relationship with the first voltage V1 is not particularly limited, but when (working electrode potential) < (counter electrode potential), the voltage is smaller than the first voltage V1.

[0027] As shown in FIG. 3, the working electrode 102 has a working electrode side base material 102a, a working electrode side conductive auxiliary material 102c, and a working electrode side binder 102d provided on the working electrode side base material 102a. In FIG. 3, for the sake of convenience, the working electrode side conductive auxiliary material 102c and the working electrode side binder 102d are illustrated as being arranged on one surface side of the working electrode side base material 102a, but actually, the working electrode side conductive auxiliary material 102c and the working electrode side binder 102d are provided inside the porous working electrode side base material 102a.

[0028] The working electrode side base material 102a is CO 2It is made of a porous conductive material having pores through which a gas containing [it] can pass. As the working electrode side base material 102a, for example, a carbonaceous material or a metal material can be used. As the carbonaceous material constituting the working electrode side base material 102a, for example, carbon paper, carbon cloth, non-woven carbon mat, porous gas diffusion layer (GDL), etc. can be used. As the metal material constituting the working electrode side base material 102a, for example, a metal mesh formed by making a metal (such as Al, Ni, etc.) into a mesh shape can be used.

[0029] The working electrode side conductive auxiliary material 102c forms a conductive path that protrudes from the working electrode side base material 102a into the electrolyte layer 106. As the working electrode side conductive auxiliary material 102c, it is preferable to use one that has sufficient oxygen activity and is difficult to react with active oxygen. The working electrode side conductive auxiliary material 102c can be made of a transition metal, an oxide of a transition metal, a noble metal, or a carbon material. For example, as the working electrode side conductive auxiliary material 102c, carbon materials such as carbon nanotubes, carbon black, and graphene can be used. Alternatively, transition metals such as Ni, Al, SUS, etc. or their oxides can be used as the working electrode side conductive auxiliary material 102c. Alternatively, noble metals such as Pt, Au, Ag, etc. can also be used as the working electrode side conductive auxiliary material 102c.

[0030] The working electrode side binder 102d is provided to hold the working electrode side conductive auxiliary material 102c to the working electrode side base material 102a. The working electrode side binder 102d has an adhesive force and is provided between the working electrode side conductive auxiliary material 102c and the working electrode side base material 102a.

[0031] In this embodiment, the working electrode side conductive auxiliary material 102c and the working electrode side binder 102d are used in a mixed state. A mixture of the working electrode side conductive auxiliary material 102c and the working electrode side binder 102d is formed, and this mixture is adhered to the working electrode side base material 102a.

[0032] As the working electrode side binder 102d, a conductive resin can be used. As the conductive resin, an epoxy resin, a fluororesin such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF) containing Ag or the like as a conductive filler can be used.

[0033] The counter electrode 103 has a counter electrode side base material 103a, and an electrochemically active auxiliary material 103b, a counter electrode side conductive auxiliary material 103c, and a counter electrode side binder 103d provided on the counter electrode side base material 103a. In FIG. 3, for the sake of convenience, the electrochemically active auxiliary material 103b, the counter electrode side conductive auxiliary material 103c, and the counter electrode side binder 103d are illustrated as being disposed on one surface side of the counter electrode side base material 103a. However, actually, the electrochemically active auxiliary material 103b, the counter electrode side conductive auxiliary material 103c, and the counter electrode side binder 103d are provided inside the porous counter electrode side base material 103a. The counter electrode side base material 103a, the counter electrode side conductive auxiliary material 103c, and the counter electrode side binder 103d can have the same structure and material as the working electrode side base material 102a, the working electrode side conductive auxiliary material 102c, and the working electrode side binder 102d in the working electrode 102, respectively.

[0034] As the electrochemically active auxiliary material 103b, for example, a metal complex that enables the transfer of electrons by changing the valence of metal ions can be used. Examples of such metal complexes include cyclopentadienyl metal complexes such as ferrocene, nickelocene, and cobaltocene, or porphyrin metal complexes. These metal complexes may be polymers or monomers.

[0035] Also, as the electrochemically active auxiliary material 103b, an organic compound such as phenothiazine, an inorganic compound such as RuO 2 , MnO 2 , MoS 2 or the like, or a carbon material such as carbon black or activated carbon can be used.

[0036] As the electroactive auxiliary material 103b, for example, a metal complex that enables the transfer of electrons by changing the valence of metal ions can be used. Examples of such metal complexes include cyclopentadienyl metal complexes such as ferrocene, nickelocene, and cobaltocene, or porphyrin metal complexes. These metal complexes may be polymers or monomers. In this embodiment, polyvinylferrocene is used as the electroactive auxiliary material 103b. Ferrocene transfers electrons by changing the valence of Fe between divalent and trivalent.

[0037] Alternatively, the electroactive auxiliary material 103b is an auxiliary electroactive species that transfers electrons with the working electrode 102, and can be a substance whose valence of elements in the molecule or crystal changes to donate electrons when a potential is applied. As the electroactive auxiliary material 103b, for example, transition metal oxides from Group 5 to Group 11 of the periodic table can be used. Preferably, oxides of Cr, Mn, Fe, Co, Ni, Cu, Ru, Mo, Pd, Ag are used as the transition metal, and more preferably, oxides of Cr, Mn, Fe, Ru can be used. Further, the electroactive auxiliary material 103b may have the property of taking in ions (e.g., electrolyte ions) in the electrolytic solution during an electrochemical reaction and not releasing protons into the electrolytic solution 108 during electron transfer.

[0038] In this embodiment, polyvinylferrocene is used as the electroactive auxiliary material 103b. Ferrocene transfers electrons by changing the valence of Fe between divalent and trivalent.

[0039] The insulating layer 104 is disposed between the working electrode 102 and the counter electrode 103, separating the working electrode 102 and the counter electrode 103. The insulating layer 104 is an insulating ion-permeable membrane that prevents physical contact between the working electrode 102 and the counter electrode 103 and suppresses electrical short circuits, while allowing ions to permeate.

[0040] As the insulating layer 104, a separator or a gas layer such as air can be used. In this embodiment, a porous separator is used as the insulating layer 104. As the material of the separator, a separator made of a cellulose membrane, a polymer, a composite material of a polymer and a ceramic, or the like can be used.

[0041] An electrolyte layer 106 having ion conductivity is provided between the working electrode 102 and the counter electrode 103. The electrolyte layer 106 is provided between the working electrode 102 and the counter electrode 103. The electrolyte layer 106 is provided so as to be in contact with the working electrode 102, the counter electrode 103, and the insulating layer 104.

[0042] As the electrolyte layer 106, an ionic liquid, a solid electrolyte, or the like can be used. An ionic liquid is a liquid salt having non-volatility under normal temperature and pressure. When an ionic liquid is used as the electrolyte layer 106, the ionic liquid may be gelled in order to prevent elution from the electrochemical cell 101. When a solid electrolyte is used as the electrolyte layer 106, it is desirable to use an ionomer made of a polymer electrolyte or the like.

[0043] Examples of the ionic liquid include 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIM][Tf 2 N]), 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([BMIM][Tf 2 N]), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF 4 4]), 1-ethyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide, N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, and the like can be used.

[0044] Alternatively, as the electrolyte layer 106, H 2 2 4 SO2 SO 4 、 KOH, etc. can be used.

[0045] The electrolyte layer 106 preferably has a lower solubility of carbon dioxide than that of oxygen. Here, the solubility is calculated as the molar amount of carbon dioxide or oxygen as the solute with respect to the molar amount of the electrolyte material as the solvent.

[0046] From this perspective, as the electrolyte layer 106, in particular, for example, TMPATFSI (abbreviation of trimethylpropylammonium bis(trifluoromethanesulfonyl)imide), BIMITFST (abbreviation of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide), etc. are preferably used. Note that the solubility of carbon dioxide and the solubility of oxygen in the electrolyte layer 106 are also affected by the partial pressure of carbon dioxide and the partial pressure of oxygen in the gas to be treated. Therefore, in order to achieve (solubility of carbon dioxide) < (solubility of oxygen), it is desirable that the partial pressure of carbon dioxide is not too large and the partial pressure of oxygen is not too small.

[0047] Next, the operation of the carbon dioxide recovery system 1 of this embodiment will be described with reference to FIGS. 4 to 7.

[0048] As shown in FIG. 4, the carbon dioxide recovery system 1 operates by alternately switching between the adsorption mode and the desorption mode. The operation of the carbon dioxide recovery system 1 is controlled by the control device 14.

[0049] First, the adsorption mode will be described. In the adsorption mode, the compressor 11 operates and the gas to be treated is supplied to the CO 2 recovery device 100. In the CO 2 recovery device 100, the voltage applied between the working electrode 102 and the counter electrode 103 is defined as the first voltage V1. Thereby, the electroactive auxiliary material 103b of the counter electrode 103 emits electrons and becomes an oxidized state, and electrons are supplied from the power source 105 to the working electrode 102.

[0050] As shown in FIGS. 5 and 6, the electrons supplied to the working electrode 102 move along the working electrode side conductive auxiliary material 102c to the three-phase interface TB between the working electrode side conductive auxiliary material 102c, the electrolyte layer 106, and the gas to be treated G. At the three-phase interface TB, oxygen (O 2 ) in the gas to be treated G receives electrons (e - ) from the working electrode side conductive auxiliary material 102c and becomes active oxygen (O 2 - ). That is, active oxygen is generated at the three-phase interface TB. This active oxygen combines with carbon dioxide (CO 2 ) in the gas to be treated G, so that carbon dioxide is adsorbed near the working electrode 102. In this state, carbon dioxide (CO 2 ) is adsorbed near the working electrode 102 in a state where it has combined with active oxygen (O 2 - ) to form carbonate ions (CO 3 2- ).

[0051] Note that CO 2 is actually adsorbed by active oxygen in the electrolyte layer 106 near the working electrode 102 (more specifically, the working electrode side conductive auxiliary material 102c), but it can also be considered to be adsorbed by the working electrode 102 substantially. Therefore, in this specification, this state, that is, the state where carbon dioxide is adsorbed by active oxygen near the working electrode 102, will also be expressed as "adsorbed on the working electrode".

[0052] Also, as shown in FIG. 6, the three-phase interface TB is formed, for example, between a part of the electrolyte layer 106 attached to the working electrode side conductive auxiliary material 102c, the working electrode side conductive auxiliary material 102c, and the gas to be treated G.

[0053] Also, in the adsorption mode, it is preferable to have a time period during which the supply rate of carbon dioxide to the working electrode 102 is greater than the generation rate of active oxygen at the working electrode 102. To achieve this, for example, the first voltage V1 is adjusted so that the current value supplied to the electrochemical cell 101 is set to a sufficiently small value. Note that the comparison between the supply rate of carbon dioxide and the generation rate of active oxygen at the working electrode 102 is made in terms of the number of moles per unit time. Also, the time period during which the supply rate of carbon dioxide to the working electrode 102 is greater than the generation rate of active oxygen at the working electrode 102 may be the entire adsorption mode or a part thereof.

[0054] The gas to be treated is CO by the adsorption mode. 2 After carbon dioxide is removed in the recovery device 100, CO 2 As the removed gas, CO 2 is discharged from the recovery device 100. In the adsorption mode, the flow path switching valve 12 connects the gas flow path to the atmosphere side, and CO 2 The CO discharged from the recovery device 100 2 removed gas is discharged to the atmosphere (see Fig. 1).

[0055] The time of each adsorption mode is shorter than the diffusion time of the carbonate ions (i.e., carbon dioxide adsorption molecules) generated at the working electrode 102 to the counter electrode 103. Note that the "diffusion time of the carbonate ions generated at the working electrode 102 to the counter electrode 103" can be calculated from Fick's equation using, for example, the carbonate ion concentration generated at the working electrode 102, the distance between the working electrode 102 and the counter electrode 103, and the carbonate ion diffusion coefficient in the electrolyte.

[0056] Next, the desorption mode will be described. In the desorption mode, the compressor 11 stops operating, and the supply of the gas to be treated to the recovery device 100 2 stops.

[0057] As shown in Figs. 4 and 7, CO 2In the recovery device 100, the voltage applied between the working electrode 102 and the counter electrode 103 is defined as the second voltage V2. As a result, the electrochemically active auxiliary material 103b of the counter electrode 103 receives electrons from the power supply 105 and enters a reduced state.

[0058] As shown in FIG. 7, the working electrode 102 emits electrons. As a result, the CO adsorbed on the working electrode 102 by electrostatic interaction 2 is desorbed from the working electrode 102.

[0059] The CO released from the working electrode 102 2 is 2 discharged from the recovery device 100. In the desorption mode, the flow path switching valve 12 connects the gas flow path to the utilization device 13 side, and the CO 2 discharged from the recovery device 100 2 is supplied to the utilization device 13 (see FIG. 1). 2 is 2

[0060] Next, the operation and effect of this embodiment will be described. As described above, the electrochemical cell 101 is configured such that the active species of oxygen supplied to the working electrode 102 combines with carbon dioxide to adsorb carbon dioxide. That is, the active oxygen generated in the vicinity of the working electrode 102 in the electrolyte layer 106 adsorbs carbon dioxide.

[0061] That is, carbon dioxide is not directly adsorbed on the surface of the working electrode 102, but is adsorbed by the active oxygen generated in the electrolyte layer 106 in the vicinity of the working electrode 102, so that the adsorption area can be increased dramatically. Therefore, the amount of carbon dioxide that can be recovered can be increased. As a result, the carbon dioxide recovery ability can be improved.

[0062] In addition, in the carbon dioxide recovery system 1, both the adsorption and desorption of carbon dioxide are performed at the working electrode 102. That is, the gas to be treated is supplied to the working electrode 102 to adsorb carbon dioxide on the working electrode 102, and the carbon dioxide is converted from the working electrode 102 to CO 2 ​It is discharged to the utilization device 13. That is, carbon dioxide is captured by the working electrode 102 and discharged from the working electrode 102. As a result, it is not necessary to move the recovered carbon dioxide from the working electrode 102 to the counter electrode 103. Therefore, the recovery efficiency of carbon dioxide is not limited by the diffusion rate of carbonate ions in the electrolyte layer 106. As a result, the carbon dioxide recovery ability can be improved.

[0063] Also, as described above, the carbon dioxide recovery system 1 of this embodiment adsorbs carbon dioxide to the working electrode 102 and discharges the carbon dioxide from the working electrode 102 to the 2 utilization device 13. Therefore, a supply flow path for supplying the gas to be treated and a 2 CO 2 discharge flow path for discharging the removed gas are provided on the working electrode 102 side and do not need to be provided on the counter electrode 103 side. Therefore, it is easy to reduce the size and simplify the carbon dioxide recovery system 1.

[0064] The time of each adsorption mode is shorter than the diffusion time of carbonate ions (that is, carbon dioxide adsorption molecules) generated at the working electrode 102 to the counter electrode 103. Therefore, the carbon dioxide adsorbed on the working electrode 102 can be efficiently discharged from the working electrode 102 to the 2 utilization device 13 in the desorption mode. That is, in the adsorption mode, as described above, carbon dioxide is adsorbed by the formation of carbonate ions in the electrolyte layer 106 near the working electrode 102. However, it is conceivable that this carbonate ion diffuses in the electrolyte layer 106 and a part of it goes to the counter electrode 103. When the carbonate ion diffuses to the counter electrode 103, the recovered amount of carbon dioxide decreases. Therefore, the time of each adsorption mode is made shorter than the diffusion time of the carbonate ions generated at the working electrode 102 to the counter electrode 103.

[0065] From such a viewpoint, it is more preferable that the time of each adsorption mode is 1 / 10 or less of the diffusion time of the carbonate ions generated at the working electrode 102 to the counter electrode 103.

[0066] On the other hand, in the adsorption mode, it is also necessary to ensure a time sufficient to adsorb carbon dioxide. For example, it is desirable to set the time longer than the time until the charge of the capacitor component composed of the working electrode 102 and the counter electrode 103 is charged.

[0067] Also, in the adsorption mode, there is a time period in which the supply rate of carbon dioxide to the working electrode 102 is greater than the generation rate of active oxygen at the working electrode 102. Thereby, excessive generation of active oxygen can be prevented, and deterioration of the working electrode 102 and reduction of energy efficiency can be prevented.

[0068] The working electrode side conductive auxiliary material 102c is made of a transition metal, an oxide of a transition metal, a noble metal, or a carbon material. Thereby, active oxygen can be efficiently generated and deterioration of the working electrode 102 can be suppressed.

[0069] The electrolyte layer 106 has a lower solubility of carbon dioxide than that of oxygen. Thereby, active oxygen can be sufficiently generated in the vicinity of the working electrode 102. As a result, the recovery amount of carbon dioxide can be effectively improved.

[0070] As described above, according to the present embodiment, it is possible to provide a carbon dioxide recovery system capable of improving the carbon dioxide recovery ability.

[0071] The present invention is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the gist thereof.

[0072] The features of the present invention are shown as follows. [1] A carbon dioxide recovery system (1) for separating carbon dioxide from a gas to be treated containing carbon dioxide by an electrochemical reaction, having an electrochemical cell (101) including a working electrode (102) in contact with the gas to be treated, a counter electrode (103), an insulating layer (104) and an electrolyte layer (106) disposed between the working electrode and the counter electrode, By applying a first voltage (V1) between the working electrode and the counter electrode, electrons are supplied to the working electrode, and the carbon dioxide in the gas to be treated is adsorbed on the working electrode, in an adsorption mode, By applying a second voltage (V2) different from the first voltage between the working electrode and the counter electrode, electrons are emitted from the working electrode, and the carbon dioxide is desorbed and discharged from the working electrode, in a desorption mode, and is configured to repeat, In the adsorption mode, the electrochemical cell is configured such that oxygen is supplied near the working electrode in the electrolyte layer together with the carbon dioxide, a voltage is applied between the working electrode and the counter electrode, electrons are supplied to the working electrode, the oxygen receives the electrons to generate active oxygen, and the active oxygen combines with the carbon dioxide to generate a carbon dioxide adsorption molecule, thereby adsorbing carbon dioxide. A carbon dioxide recovery system. [2] The time of each adsorption mode is shorter than the diffusion time of the carbon dioxide adsorption molecule generated at the working electrode to the counter electrode, the carbon dioxide recovery system according to [1]. [3] The electrolyte layer has a lower solubility of carbon dioxide than that of oxygen, the carbon dioxide recovery system according to [1] or [2]. [4] The working electrode has a working electrode-side base material (102a) and a working electrode-side conductive auxiliary material (102c) provided on the working electrode-side base material, and has a three-phase interface (TB) between the working electrode-side conductive auxiliary material, the electrolyte layer, and the gas to be treated. The carbon dioxide recovery system according to any one of [1] to [3]. [5] The working electrode-side conductive auxiliary material is made of a transition metal, an oxide of a transition metal, a noble metal, or a carbon material, the carbon dioxide recovery system according to [4]. [6] In the adsorption mode, the carbon dioxide recovery system according to any one of [1] to [5], having a time period in which the supply rate of carbon dioxide to the working electrode is greater than the generation rate of active oxygen at the working electrode.

Explanation of symbols

[0073] 1 Carbon dioxide recovery system 101 Electrochemical cell 102 Working electrode 103 Counter electrode 104 Insulating layer 106 Electrolyte layer V1 First voltage V2 Second voltage

Claims

1. A carbon dioxide recovery system (1) for separating carbon dioxide from a gas to be treated containing carbon dioxide by an electrochemical reaction, comprising: an electrochemical cell (101) including a working electrode (102) in contact with the gas to be treated, a counter electrode (103), and an insulating layer (104) and an electrolyte layer (106) disposed between the working electrode and the counter electrode; an adsorption mode in which a first voltage (V1) is applied between the working electrode and the counter electrode to supply electrons to the working electrode and adsorb the carbon dioxide in the gas to be treated onto the working electrode; a desorption mode in which a second voltage (V2) different from the first voltage is applied between the working electrode and the counter electrode to release electrons from the working electrode and desorb and discharge the carbon dioxide from the working electrode, and the adsorption mode and the desorption mode are repeated; In the adsorption mode, the electrochemical cell is configured to adsorb carbon dioxide by supplying oxygen to the vicinity of the working electrode in the electrolyte layer together with the carbon dioxide, applying a voltage between the working electrode and the counter electrode to supply electrons to the working electrode, causing the oxygen to receive electrons to generate active oxygen, and causing the active oxygen to combine with the carbon dioxide to generate a carbon dioxide adsorption molecule. Carbon dioxide recovery system.

2. The carbon dioxide recovery system according to claim 1, wherein the time of each adsorption mode is shorter than the diffusion time of the carbon dioxide adsorption molecules generated at the working electrode to the counter electrode.

3. The carbon dioxide recovery system according to claim 1 or 2, wherein the solubility of carbon dioxide in the electrolyte layer is smaller than the solubility of oxygen.

4. The working electrode has a working electrode side base material (102a) and a working electrode side conductive auxiliary material (102c) provided on the working electrode side base material, and has a three-phase interface (TB) between the working electrode side conductive auxiliary material, the electrolyte layer, and the gas to be treated. The carbon dioxide recovery system according to claim 1 or 2.

5. The carbon dioxide recovery system according to claim 4, wherein the working electrode side conductive auxiliary material is made of a transition metal, an oxide of a transition metal, a noble metal, or a carbon material.

6. The carbon dioxide recovery system according to claim 1 or 2, wherein in the adsorption mode, there is a time period in which the supply rate of carbon dioxide to the working electrode is higher than the generation rate of active oxygen at the working electrode.

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