Carbon Dioxide Electrolysis Device

Abstract

To provide a carbon dioxide electrolytic apparatus configured such that a carbon compound obtained by an electrolytic reaction is reacted with hydrogen in an appropriate ratio.SOLUTION: An apparatus 100 comprises: an electrolytic stack 10 for performing electrolysis by electric power generated by renewable energy; a carbon dioxide supply part 30 for supplying carbon dioxide to the electrolytic stack 10; a first storage part 60a for storing a first gas generated by electrolysis in the electrolytic stack 10 when carbon dioxide is supplied; a second storage part 60b for storing a second gas generated by electrolysis in the electrolytic stack 10 when the supply of carbon dioxide is stopped; a reactor 70 for guiding the first gas and the second gas; a voltage sensor 16 for detecting a voltage of the electrolytic stack 10; and a control part for controlling the carbon dioxide supply part 30 so as to supply carbon dioxide to the electrolytic stack 10 when the voltage exceeds a predetermined value, and for controlling the carbon dioxide supply part 30 so as to stop the supply of carbon dioxide to the electrolytic stack 10 when the voltage is equal to or less than a predetermined value.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a carbon dioxide electrolysis device for electrolytically reducing carbon dioxide. [Background technology]

[0002] Conventionally, devices for electrolytically reducing carbon dioxide have been known (see, for example, Patent Document 1). In the device described in Patent Document 1, an electrolyte solution consisting of a strong alkaline aqueous solution in which carbon dioxide is dissolved is passed through a liquid flow path provided between a cathode and an anode, and the carbon dioxide dissolved in the electrolyte solution is electrolytically reduced at the cathode.

[0003] By capturing carbon dioxide from exhaust gases and the atmosphere and using it as a carbon source, carbon emissions can be reduced, contributing to mitigating or reducing the effects of climate change. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-131811 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the device described in Patent Document 1, when carbon dioxide is electrolyzed, hydrogen gas is generated as a by-product in addition to the desired carbon compounds. By reacting the carbon compounds obtained by such an electrolytic reaction with hydrogen in an appropriate ratio, more useful compounds such as fuel can be obtained, but Patent Document 1 does not make any proposal on this point. [Means for solving the problem]

[0006] A carbon dioxide electrolysis device according to one aspect of the present invention includes an electrolysis stack that performs electrolysis using electricity generated by renewable energy, a carbon dioxide supply unit that supplies carbon dioxide to the electrolysis stack, and a carbon dioxide supply unit that supplies carbon dioxide generated by electrolysis in the electrolysis stack when carbon dioxide is supplied by the carbon dioxide supply unit. Contains carbon compounds A first storage section for storing a first gas, and a carbon dioxide supply section for supplying carbon dioxide when the supply of carbon dioxide is stopped, Water Produced by electrolysis Contains hydrogen The electrolysis stack includes a second storage section for storing a second gas, a reactor to which the first gas stored in the first storage section and the second gas stored in the second storage section are introduced, a voltage sensor for detecting a voltage of the electrolysis stack, and a control section for controlling the carbon dioxide supply section to supply carbon dioxide to the electrolysis stack when the voltage detected by the voltage sensor exceeds a predetermined value, and for controlling the carbon dioxide supply section to stop the supply of carbon dioxide to the electrolysis stack when the voltage detected by the voltage sensor is equal to or lower than the predetermined value. Effect of the Invention

[0007] According to the present invention, the carbon compound obtained by the electrolytic reaction can be reacted with hydrogen in an appropriate ratio. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view illustrating an example of an electrolysis stack of a carbon dioxide electrolysis device according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a block diagram illustrating an example of the overall configuration of a carbon dioxide electrolysis device according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram for explaining the voltage fluctuations of the electrolysis stack of FIG. 2. [Figure 4] FIG. 2 is a block diagram illustrating an example of a control configuration of the carbon dioxide electrolysis device according to an embodiment of the present invention. [Diagram 5] 4 is a flowchart showing an example of an electrolysis reaction switching process performed by the carbon dioxide electrolysis device according to the embodiment of the present invention. [Figure 6]4 is a flowchart showing an example of a reactor on / off process in the carbon dioxide electrolysis device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to Fig. 1 to Fig. 6. The average temperature of the earth is kept warm enough for living things by greenhouse gases in the atmosphere. Specifically, greenhouse gases absorb a part of the heat radiated from the earth's surface, which is warmed by sunlight, into space, and re-radiate it back to the earth's surface, thereby keeping the atmosphere warm. When the concentration of such greenhouse gases in the atmosphere increases, the average temperature of the earth rises (global warming).

[0010] Carbon dioxide, which is one of the greenhouse gases that contributes most to global warming, has a concentration in the atmosphere that is determined by the balance between carbon fixed on the ground or in the earth as plants and fossil fuels, and carbon present in the atmosphere as carbon dioxide. For example, when carbon dioxide in the atmosphere is absorbed by plants through photosynthesis during growth, the concentration of carbon dioxide in the atmosphere decreases, and when carbon dioxide is released into the atmosphere through the combustion of fossil fuels, the concentration of carbon dioxide in the atmosphere increases. To prevent global warming, it is necessary to replace fossil fuels with renewable energy sources such as solar, wind, hydroelectric, geothermal, or biomass, and reduce carbon emissions.

[0011] Carbon dioxide in exhaust gas or the atmosphere is collected and used as a carbon source, thereby reducing carbon dioxide emissions. In this embodiment, a carbon dioxide electrolysis device is configured as follows so that carbon dioxide is reduced to generate carbon compounds through an electrolytic reaction using renewable electricity, and further reduced using hydrogen obtained as a by-product to produce renewable fuels, etc.

[0012] FIG. 1 is a cross-sectional view showing a schematic example of an electrolysis stack 10 of a carbon dioxide electrolysis (hereinafter, referred to as an apparatus) 100 according to an embodiment of the present invention. As shown in FIG. 1, the electrolysis stack 10 is configured as an electrolysis cell in which an anion exchange type solid polymer electrolyte membrane (AEM (Anion Exchange Membrane)) 12 is sandwiched between an anode section 11a and a cathode section 11b, or an electrolysis stack in which electrolysis cells are stacked (connected in series). The anode section 11a and the cathode section 11b each include liquid flow paths 13a, 13b, electrode catalysts 14a, 14b, and gas flow paths 15a, 15b. The liquid flow paths 13a, 13b and the gas flow paths 15a, 15b are provided adjacent to the electrode catalysts 14a, 14b, respectively.

[0013] An electrolyte solution consisting of a strong alkaline aqueous solution such as an aqueous potassium hydroxide solution can be introduced and circulated into the liquid flow paths 13a and 13b from outside the electrolysis stack 10. The electrolyte solution flowing out of the liquid flow paths 13a and 13b may be introduced back into the liquid flow paths 13a and 13b and circulated.

[0014] Carbon dioxide can be supplied to the gas flow passage 15b of the cathode section 11b from outside the electrolysis stack 10. In addition, gas generated by the electrolysis reaction can be discharged to the outside of the electrolysis stack 10 via the gas flow passages 15a and 15b.

[0015] The electrode catalyst 14a (anode) of the anode section 11a is made of a non-precious metal such as nickel or a precious metal such as platinum, and is connected to the positive electrode of a DC power supply (hereinafter, electrolysis power supply) 20 provided outside the electrolysis stack 10. The electrode catalyst 14b (cathode) of the cathode section 11b is made of copper or the like, and is connected to the negative electrode of the electrolysis power supply 20.

[0016] When power is supplied from the electrolysis power source 20 to the electrolysis stack 10, a potential difference occurs between the anode and the cathode depending on the magnitude of the power, and when the potential difference reaches the electrolysis voltage, the electrolysis reaction proceeds. More specifically, when carbon dioxide is supplied to the gas flow path 15b, carbon dioxide is reduced by an electrolysis reaction at the three-phase interface between the liquid flow path 13b, the electrode catalyst 14b, and the gas flow path 15b of the cathode section 11b, to generate carbon compounds such as carbon monoxide, methane, and ethylene. For example, carbon monoxide is generated by the electrolysis reaction of the following formula (i). Furthermore, regardless of whether carbon dioxide is supplied to the gas flow path 15b, water in the electrolytic solution is reduced by the electrolysis reaction of the following formula (ii) to generate hydroxide ions. The carbon compounds (gas) and hydrogen (gas) generated in the cathode section 11b are discharged to the outside of the electrolysis stack 10 through the gas flow path 15b. CO 2 +H 2 O→CO+2OH - (i) 2H 2 O→H 2 +2OH - (ii)

[0017] On the other hand, hydroxide ions generated in the cathode section 11b move through the electrolyte in the liquid flow path 13b of the cathode section 11b, then permeate the AEM 12, and move through the electrolyte in the liquid flow path 13a of the anode section 11a to the interface with the electrode catalyst 14a of the anode section 11a. On the surface of the electrode catalyst 14a of the anode section 11a, the hydroxide ions are oxidized by the electrolytic reaction of the following formula (iii) to generate oxygen. The oxygen (gas) generated in the anode section 11a is discharged to the outside of the electrolysis stack 10 via the gas flow path 15a, and water (liquid) flows and circulates through the liquid flow path 13a as it is. 4OH - →O 2 +2H 2 O (iii)

[0018] The electrolysis voltage required for the electrolysis reaction of carbon dioxide, i.e., the electrolysis voltage required for the electrolysis reactions of the above formulas (i) and (iii) (approximately 1.35 V), is higher than the electrolysis voltage required for the electrolysis reaction of water, i.e., the electrolysis voltage required for the electrolysis reactions of the above formulas (ii) and (iii) (approximately 1.23 V).

[0019] Fig. 2 is a block diagram illustrating an example of the overall configuration of the apparatus 100. As illustrated in Fig. 2, the apparatus 100 includes an electrolytic stack 10, an electrolysis power supply 20 that supplies power to the electrolytic stack 10, a carbon dioxide supply unit 30 that supplies carbon dioxide to the electrolytic stack 10, and electrolyte supply units 40a and 40b that supply an electrolyte to the electrolytic stack 10.

[0020] The electrolytic stack 10 is provided with a voltage sensor 16 that detects the voltage (hereinafter, stack voltage) of the electrolytic stack 10. The voltage sensor 16 is connected to a controller 90 (FIG. 4), and the sensor value of the voltage sensor 16 is output to the controller 90.

[0021] The electrolysis power supply 20 is configured as a power generation device that generates DC power (renewable power) by utilizing renewable energy such as sunlight, and supplies the generated DC power to the electrolysis stack 10. The positive electrode of the electrolysis power supply 20 is connected to the anode (electrode catalyst 14a of the anode section 11a) of the electrolysis stack 10, and the negative electrode of the electrolysis power supply 20 is connected to the cathode (electrode catalyst 14b of the cathode section 11b) of the electrolysis stack 10. The amount of power generated by the electrolysis power supply 20 that utilizes natural energy such as sunlight varies depending on weather conditions such as sunlight, which causes the stack voltage of the electrolysis stack 10 to vary.

[0022] Fig. 3 is a diagram for explaining fluctuations in stack voltage. As shown in Fig. 3, when natural energy such as sunlight is used, the amount of power generation varies depending on weather conditions such as sunlight, and the stack voltage also varies with the fluctuations in the amount of power generation. When the stack voltage is equal to or lower than the electrolysis voltage (predetermined value) required for the electrolysis reaction of carbon dioxide, even if carbon dioxide is supplied to the electrolysis stack 10, the electrolysis reaction of carbon dioxide (formulas (i) and (iii)) does not proceed, and only the electrolysis reaction of water (formulas (ii) and (iii)) proceeds.

[0023] The carbon dioxide supply unit 30 includes a pump and the like. The carbon dioxide supply unit 30 is connected to the inlet of the gas flow path 15b of the cathode 11b of the electrolysis stack 10 via a pipe 31, and supplies carbon dioxide (gas) to the electrolysis stack 10 by pumping air containing carbon dioxide at a predetermined concentration or more. The air containing carbon dioxide at a predetermined concentration or more may be exhaust gas from an apparatus or facility that involves the combustion of fossil fuels, or may be air in which carbon dioxide has been concentrated by a concentration device. An electric valve 32 that can be opened and closed is provided in the pipe 31 between the carbon dioxide supply unit 30 and the electrolysis stack 10. The carbon dioxide supply unit 30 and the electric valve 32 are controlled by a controller 90 (FIG. 4).

[0024] Each of the electrolytic solution supply units 40a, 40b includes a pump, etc. The electrolytic solution supply units 40a, 40b are connected to the inlets of the liquid flow paths 13a, 13b of the electrolytic stack 10 via pipes 41a, 41b, respectively, and supply the electrolytic solution to the electrolytic stack 10 by pumping the electrolytic solution. The electrolytic solution supply units 40a, 40b receive the electrolytic solution from the outlets of the liquid flow paths 13a, 13b of the electrolytic stack 10 via pipes (not shown), respectively, as a reflux.

[0025] The apparatus 100 further includes a first purification unit 50a and a second purification unit 50b that purify the gas generated by electrolysis in the electrolysis stack 10, and a first storage unit 60a and a second storage unit 60b that store the gas supplied from the first purification unit 50a and the second purification unit 50b, respectively. The apparatus 100 also includes a reactor 70 to which the gas stored in the first storage unit 60a and the second storage unit 60b is introduced, and a heating unit 80 that heats the reactor 70.

[0026] When carbon dioxide is supplied from the carbon dioxide supply unit 30, the first purification unit 50a purifies a first gas mainly composed of carbon compounds produced by electrolysis in the electrolysis stack 10. The first purification unit 50a is configured as an adsorption / separation device of a PSA (Pressure Swing Adsorption) type or a TSA (Thermal Swing Adsorption) type using an adsorbent.

[0027] The first purification section 50a is connected to the outlet of the gas flow passage 15b of the cathode section 11b of the electrolysis stack 10 via a pipe 51a, and an openable and closable motorized valve 52a is provided on the pipe 51a. When carbon dioxide is supplied from the carbon dioxide supply section 30, the motorized valve 52a is opened, and the first gas generated by electrolysis is supplied from the electrolysis stack 10 to the first purification section 50a, and the mixture other than the carbon compounds contained in the first gas is adsorbed by the adsorbent (pressurized adsorption in the case of the PSA method, and room temperature adsorption in the case of the TSA method). The motorized valve 52a is controlled by a controller 90 (FIG. 4).

[0028] The first purification section 50a is further connected to a first storage section 60a via a pipe 53a, and is connected to a temperature raising section 80 via a pipe 54a. An openable and closable motor-operated valve 55a is provided in the pipe 53a between the first purification section 50a and the first storage section 60a, and an openable and closable motor-operated valve 56a is provided in the pipe 54a between the first purification section 50a and the temperature raising section 80.

[0029] When the mixture other than the carbon compounds contained in the first gas is adsorbed by the adsorbent in the first purification section 50a, the motorized valve 55a is opened and the motorized valve 56a is closed, and the purified high-purity carbon compounds are supplied from the first purification section 50a to the first storage section 60a and stored therein. On the other hand, when the mixture other than the carbon compounds is desorbed from the adsorbent in the first purification section 50a (reduced pressure desorption in the case of the PSA method, and high temperature desorption in the case of the TSA method), the motorized valve 55a is closed and the motorized valve 56a is opened, and the off-gas containing the mixture desorbed from the adsorbent is supplied from the first purification section 50a to the temperature raising section 80. The first purification section 50a and the motorized valves 55a and 56a are controlled by a controller 90 (FIG. 4).

[0030] The second purification unit 50b purifies the second gas mainly composed of hydrogen produced by electrolysis in the electrolysis stack 10 when the supply of carbon dioxide from the carbon dioxide supply unit 30 is stopped. The second purification unit 50b is also configured as a PSA or TSA adsorption separation device using an adsorbent.

[0031] The second purification unit 50b is connected to an outlet of the gas flow path 15b of the cathode unit 11b of the electrolysis stack 10 via a pipe 51b, and an openable and closable motorized valve 52b is provided on the pipe 51b. When the supply of carbon dioxide from the carbon dioxide supply unit 30 is stopped, the motorized valve 52b is opened, and the second gas generated by electrolysis is supplied from the electrolysis stack 10 to the second purification unit 50b, and the mixture other than hydrogen contained in the second gas is adsorbed by the adsorbent. The motorized valve 52b is controlled by a controller 90 (FIG. 4).

[0032] The second purification section 50b is further connected to a second storage section 60b via a pipe 53b, and is connected to a temperature raising section 80 via a pipe 54b. An openable and closable motor-operated valve 55b is provided in the pipe 53b between the second purification section 50b and the second storage section 60b, and an openable and closable motor-operated valve 56b is provided in the pipe 54b between the second purification section 50b and the temperature raising section 80.

[0033] When the mixture other than hydrogen contained in the second gas is adsorbed by the adsorbent in the second purification section 50b, the motorized valve 55b is opened and the motorized valve 56b is closed, and the purified high-purity hydrogen is supplied from the second purification section 50b to the second storage section 60b and stored therein. On the other hand, when the mixture other than hydrogen is desorbed from the adsorbent in the second purification section 50b, the motorized valve 55b is closed and the motorized valve 56b is opened, and the off-gas containing the mixture desorbed from the adsorbent is supplied from the second purification section 50b to the temperature raising section 80. The second purification section 50b and the motorized valves 55b, 56b are controlled by a controller 90 (FIG. 4).

[0034] The reactor 70 is connected to the first storage section 60a via a pipe 71a, and is connected to the second storage section 60b via a pipe 71b. The pipes 71a and 71b are provided with motorized valves 72a and 72b configured to be capable of adjusting the flow rate, respectively. The high-purity carbon compound stored in the first storage section 60a is introduced to the reactor 70 according to the opening degree of the motorized valve 72a, and the high-purity hydrogen stored in the second storage section 60b is introduced to the reactor 70 according to the opening degree of the motorized valve 72b. The motorized valves 72a and 72b are controlled by a controller 90 (FIG. 4).

[0035] The temperature increasing section 80 is configured as a heat exchanger provided so as to cover the entire reactor 70, and increases the temperature of the reactor 70 by off-gas (heat medium) supplied from the first purification section 50a and the second purification section 50b. The reactor 70 is provided with a temperature sensor 73 that detects the temperature of the reactor 70. The temperature sensor 73 is connected to a controller 90 (FIG. 4), and the sensor value of the temperature sensor 73 is output to the controller 90.

[0036] In the reactor 70, the carbon compounds supplied from the first storage section 60a are reduced by hydrogen supplied from the second storage section 60b to produce renewable fuels, etc. For example, renewable methanol fuel is produced by FT (Fischer-Tropsch) synthesis. The reactor 70 is configured as a catalytic reaction device provided with a catalyst capable of promoting a reaction for obtaining a desired renewable fuel, etc. The temperature of the reactor 70 can be adjusted by the motorized valves 56a, 56b via the flow rate of the heat medium according to the type of reaction for obtaining the desired renewable fuel, etc. The ratio and flow rate of the reactants (carbon dioxide, hydrogen) introduced into the reactor 70 can be adjusted by the motorized valves 72a, 72b, taking into consideration the temperature, pressure, etc. in the reactor 70 according to the type of reaction for obtaining the desired renewable fuel, etc.

[0037] FIG. 4 is a block diagram showing an example of a control configuration of the device 100. As shown in FIG. 4, the device 100 further includes a controller 90 that controls the carbon dioxide supply unit 30, the electrolyte supply units 40a and 40b, the first purification unit 50a, the second purification unit 50b, and the motorized valves 32 to 72b. The voltage sensor 16 and the temperature sensor 73 are each connected to the controller 90. The controller 90 includes a computer having a calculation unit 91 such as a CPU, a storage unit 92 such as a ROM and a RAM, and peripheral circuits thereof. The storage unit 92 of the controller 90 stores information such as programs executed by the calculation unit 91 and set values.

[0038] When the stack voltage detected by the voltage sensor 16 exceeds a predetermined value (FIG. 3), the controller 90 (calculation unit 91) controls the carbon dioxide supply unit 30 and the motorized valve 32 to supply carbon dioxide to the electrolysis stack 10. The controller 90 also controls the motorized valves 52a, 52b to supply the first gas from the electrolysis stack 10 to the first purification unit 50a, and controls the first purification unit 50a to purify the supplied first gas. The controller 90 also controls the motorized valves 55a, 56a to supply the high-purity carbon compounds purified in the first purification unit 50a to the first storage unit 60a, and to supply the off-gas containing the mixture desorbed from the adsorbent to the temperature raising unit 80.

[0039] The controller 90 controls the carbon dioxide supply unit 30 and the motorized valve 32 to stop the supply of carbon dioxide to the electrolysis stack 10 when the stack voltage detected by the voltage sensor 16 is equal to or lower than a predetermined value. The controller 90 also controls the motorized valves 52a, 52b to supply the second gas from the electrolysis stack 10 to the second purification unit 50b, and controls the second purification unit 50b to purify the supplied second gas. The controller 90 also controls the motorized valves 55b, 56b to supply high-purity hydrogen purified by the second purification unit 50b to the second storage unit 60b, and to supply the off-gas containing the mixture desorbed from the adsorbent to the temperature raising unit 80.

[0040] The controller 90 further controls the motorized valves 56a and 56b in accordance with the temperature of the reactor 70 detected by the temperature sensor 73 so that the temperature of the reactor 70 becomes a predetermined temperature capable of promoting a reaction for obtaining a desired renewable fuel, etc. When the temperature of the reactor 70 is equal to or higher than the predetermined temperature, the controller 90 controls the motorized valves 72a and 72b so that reactants (carbon dioxide, hydrogen) are supplied to the reactor 70 from the first storage section 60a and the second storage section 60b. When the temperature of the reactor 70 is lower than the predetermined temperature, the desired reaction does not proceed even if the reactants (carbon dioxide, hydrogen) are supplied to the reactor 70, so the controller 90 controls the motorized valves 72a and 72b so as to stop the supply of the reactants from the first storage section 60a and the second storage section 60b to the reactor 70.

[0041] 5 is a flowchart showing an example of an electrolytic reaction switching process by the device 100, and shows an example of a process executed by the calculation unit 91 of the controller 90. The process shown in this flowchart is repeatedly executed at predetermined time intervals. As shown in FIG. 5, first, in step S1, the stack voltage of the electrolytic stack 10 detected by the voltage sensor 16 is read. Next, in step S2, it is determined whether or not the stack voltage read in step S1 exceeds a predetermined value (FIG. 3).

[0042] If the result of step S2 is YES, the process proceeds to step S3, where the carbon dioxide supply unit 30 and the motorized valve 32 are controlled to supply carbon dioxide to the electrolysis stack 10. In addition, the motorized valves 52a and 52b are controlled to supply the first gas from the electrolysis stack 10 to the first purification unit 50a, and the first purification unit 50a is controlled to purify the first gas. In addition, the motorized valves 55a and 56a are controlled to supply the first gas (high-purity carbon compounds) purified in the first purification unit 50a to the first storage unit 60a, and to supply the off-gas containing the mixture desorbed from the adsorbent to the temperature raising unit 80.

[0043] On the other hand, if the result in step S2 is negative, the process proceeds to step S4, where the carbon dioxide supply unit 30 and the motorized valve 32 are controlled to stop the supply of carbon dioxide to the electrolysis stack 10. In addition, the motorized valves 52a and 52b are controlled to supply the second gas from the electrolysis stack 10 to the second purification unit 50b, and the second purification unit 50b is controlled to purify the second gas. In addition, the motorized valves 55b and 56b are controlled to supply the second gas (high-purity hydrogen) purified in the second purification unit 50b to the second storage unit 60b, and to supply the off-gas containing the mixture desorbed from the adsorbent to the temperature raising unit 80.

[0044] When natural energy such as sunlight is used, the amount of power generation fluctuates depending on weather conditions such as sunlight, and the stack voltage fluctuates with the fluctuation in the amount of power generation. When the stack voltage is equal to or lower than the carbon dioxide electrolysis voltage (a predetermined value), the supply of carbon dioxide to the electrolysis stack 10 is stopped and only water electrolysis is performed, and only when the stack voltage exceeds the predetermined value is carbon dioxide supplied to the electrolysis stack 10 to perform carbon dioxide electrolysis. In this way, by switching between multiple electrolysis reactions with different electrolysis voltages in response to fluctuations in renewable power, multiple substances (carbon compounds and hydrogen) can be efficiently produced.

[0045] Fig. 6 is a flow chart showing an example of reactor on / off processing by the apparatus 100, and shows an example of processing executed by the calculation unit 91 of the controller 90. The processing shown in this flow chart is repeatedly executed at predetermined time intervals. As shown in Fig. 6, first, in step S10, the temperature of the reactor 70 detected by the temperature sensor 73 is read. Next, in step S11, it is determined whether the temperature read in step S10 is equal to or higher than a predetermined temperature.

[0046] If the result in step S11 is YES, the process proceeds to step S12, where the motorized valves 72a, 72b are controlled so that reactants (carbon dioxide, hydrogen) are supplied from the first storage unit 60a and the second storage unit 60b to the reactor 70. On the other hand, if the result in step S11 is NO, the process proceeds to step S13, where the motorized valves 72a, 72b are controlled so as to stop the supply of reactants from the first storage unit 60a and the second storage unit 60b to the reactor 70.

[0047] In this way, the generated carbon compounds and hydrogen are stored and then introduced into the reactor 70, so that the carbon compounds and hydrogen obtained by the electrolytic reaction in the single electrolysis stack 10 can be reacted in an appropriate ratio. In addition, the reactor 70 can be heated by utilizing waste heat of the off-gas generated by the refining process, and the reaction gas is supplied to the reactor 70 when the reaction temperature is ensured, so that the efficiency of the entire device 100 can be further improved.

[0048] According to this embodiment, the following advantageous effects can be obtained. (1) The device 100 includes an electrolysis stack 10 that performs electrolysis using electricity generated by renewable energy, a carbon dioxide supply unit 30 that supplies carbon dioxide to the electrolysis stack 10, a first storage unit 60a that stores a first gas generated by electrolysis in the electrolysis stack 10 when carbon dioxide is supplied by the carbon dioxide supply unit 30, a second storage unit 60b that stores a second gas generated by electrolysis in the electrolysis stack 10 when the supply of carbon dioxide by the carbon dioxide supply unit 30 is stopped, a reactor 70 to which the first gas stored in the first storage unit 60a and the second gas stored in the second storage unit 60b are guided, a voltage sensor 16 that detects a stack voltage of the electrolysis stack 10, and a controller 90 that controls the carbon dioxide supply unit 30 to supply carbon dioxide to the electrolysis stack 10 when the stack voltage detected by the voltage sensor 16 exceeds a predetermined value, and controls the carbon dioxide supply unit 30 to stop the supply of carbon dioxide to the electrolysis stack 10 when the stack voltage detected by the voltage sensor 16 is equal to or lower than the predetermined value (FIGS. 2 and 4).

[0049] In this way, carbon compounds and hydrogen can be efficiently produced by switching between supplying and not supplying carbon dioxide in response to fluctuations in stack voltage caused by fluctuations in renewable power. In addition, the carbon compounds and hydrogen obtained by electrolysis in the single electrolysis stack 10 can be reacted in an appropriate ratio by storing the carbon compounds and hydrogen obtained by electrolysis in the single electrolysis stack 10 and then introducing them into the reactor 70.

[0050] (2) The apparatus 100 further includes a first purification section 50a that purifies the first gas and supplies it to the first storage section 60a, a second purification section 50b that purifies the second gas and supplies it to the second storage section 60b, and a temperature raising section 80 that raises the temperature of the reactor 70 by using off-gas generated in the first purification section 50a and the second purification section 50b (FIG. 2). By utilizing the waste heat of the off-gas generated by the purification, the efficiency of the entire apparatus 100 can be further improved.

[0051] (3) The apparatus 100 further includes a temperature sensor 73 that detects the temperature of the reactor 70, and motorized valves 72a, 72b (FIGS. 2 and 4). The controller 90 controls the flow of the first gas and the second gas to the reactor 70 in accordance with the temperature of the reactor 70 detected by the temperature sensor 73. By supplying the reaction gases in accordance with the temperature of the reactor 70, the efficiency of the entire apparatus 100 can be further improved.

[0052] In the above embodiment, the electrolytic reaction that proceeds on the cathode side of the electrolytic stack 10 when carbon dioxide is supplied has been described as an electrolytic reduction reaction from carbon dioxide to carbon monoxide in Fig. 1 and other figures, but carbon monoxide is just one example, and the first gas generated by electrolysis when carbon dioxide is supplied is not limited to carbon monoxide. The electrolytic reaction for refining the first gas from carbon dioxide may be any reaction that is different from the electrolytic reaction of water in which the electrolytic voltage is a by-reaction.

[0053] The above description is merely an example, and the present invention is not limited to the above-mentioned embodiment and modifications, as long as the features of the present invention are not impaired. The above-mentioned embodiment and one or more modifications can be arbitrarily combined, and modifications can be combined with each other. [Explanation of symbols]

[0054] 10 electrolysis stack, 16 voltage sensor, 20 electrolysis power supply, 30 carbon dioxide supply section, 32, 52a, 52b, 55a, 55b, 56a, 56b, 72a, 72b motor valve, 40a, 40b electrolyte supply section, 50a first purification section, 50b second purification section, 60a first storage section, 60b second storage section, 70 reactor, 73 temperature sensor, 80 heating section, 90 controller, 91 calculation section, 92 memory section, 100 carbon dioxide electrolysis device (device)

Claims

1. an electrolysis stack that performs electrolysis using electricity generated from renewable energy; a carbon dioxide supply unit that supplies carbon dioxide to the electrolysis stack; a first storage unit that stores a first gas containing a carbon compound produced by electrolysis in the electrolysis stack when carbon dioxide is supplied by the carbon dioxide supply unit; a second storage unit configured to store a second gas including hydrogen generated by electrolysis of water in the electrolysis stack when the supply of carbon dioxide by the carbon dioxide supply unit is stopped; a reactor to which the first gas stored in the first storage section and the second gas stored in the second storage section are introduced; a voltage sensor for detecting a voltage of the electrolytic stack; a control unit that controls the carbon dioxide supply unit to supply carbon dioxide to the electrolysis stack when the voltage detected by the voltage sensor exceeds a predetermined value, and controls the carbon dioxide supply unit to stop supplying carbon dioxide to the electrolysis stack when the voltage detected by the voltage sensor is equal to or lower than the predetermined value.

2. The carbon dioxide electrolysis device according to claim 1, a first purification section that purifies the first gas and supplies a carbon compound to the first storage section; a second purification section that purifies the second gas and supplies hydrogen to the second storage section; a temperature raising section that raises the temperature of the reactor by off-gas generated in the first purification section and the second purification section.

3. The carbon dioxide electrolysis device according to claim 1 or 2, A temperature sensor for detecting the temperature of the reactor; a flow control unit that controls a flow of the first gas and the second gas to the reactor in accordance with a temperature of the reactor detected by the temperature sensor.

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