JP7651540B2 - Carbon Dioxide Electrolysis Device - Google Patents

Description

The present invention relates to a carbon dioxide electrolysis device that electrolytically reduces carbon dioxide.

Conventionally, devices that perform the electrolytic reduction of carbon dioxide have been known (see, for example, Patent Document 1). In the device described in Patent Document 1, an electrolyte 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 is electrolytically reduced at the cathode.

Capturing carbon dioxide from exhaust gases and the atmosphere and using it as a carbon source can reduce carbon emissions and contribute to mitigating or reducing the impact of climate change.

JP 2022-131811 A

An anion exchange solid polymer electrolyte membrane (AEM (Anion Exchange Membrane)) can be used as the diaphragm between the cathode and anode of the electrolysis stack, but because AEMs have poor durability, it is difficult to shorten the start-up time of the electrolysis stack without degrading the AEM.

A carbon dioxide electrolysis device according to one embodiment of the present invention includes an electrolysis stack having a diaphragm including an anion-exchange solid polymer electrolyte membrane, an anode and a cathode separated by the diaphragm, a carbon dioxide supply unit that supplies carbon dioxide to a gas flow path provided adjacent to the cathode, a power supply unit that supplies power to the electrolysis stack, a voltage sensor that detects the voltage of the electrolysis stack, a current sensor that detects the current of the electrolysis stack, a temperature sensor that detects the temperature of the electrolysis stack, and a control unit that controls the power supply unit. After the power supply unit starts supplying power to the electrolysis stack, during a startup period until the temperature of the electrolysis stack reaches a predetermined temperature, the control unit controls the power supply unit so that the current of the electrolysis stack decreases when the voltage of the electrolysis stack falls below a target value that is lower than a predetermined upper limit value of the voltage of the electrolysis stack corresponding to the temperature of the electrolysis stack, and controls the power supply unit so that the current of the electrolysis stack increases when the voltage of the electrolysis stack reaches the target value, based on the voltage of the electrolysis stack detected by the voltage sensor, the current of the electrolysis stack detected by the current sensor, and the temperature of the electrolysis stack detected by the temperature sensor.

According to the present invention, the start-up time of the electrolytic stack can be shortened without degrading the AEM.

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. 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. 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. FIG. 4 is a diagram for explaining an appropriate range of a stack voltage. FIG. 13 is a diagram for explaining a case where the stack voltage at startup becomes excessive. FIG. 13 is a diagram for explaining a case where it takes time for the stack temperature to reach a rated temperature. 6 is a diagram for explaining a case where the stack voltage is adjusted to a target value. 6 is a diagram for explaining a target value of a stack current when a stack voltage reaches a target value. FIG. FIG. 13 is a diagram for explaining a case where the stack voltage reaches a maximum value. 4 is a flowchart showing an example of a stack startup process performed by the carbon dioxide electrolysis device according to an embodiment of the present invention. 4 is a flowchart showing an example of a stack current target value calculation process performed by the carbon dioxide electrolysis device according to the embodiment of the present invention.

Below, an embodiment of the present invention will be described with reference to Figs. 1 to 11. The average temperature of the Earth is kept warm enough for living things by greenhouse gases in the atmosphere. Specifically, greenhouse gases absorb some 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).

Of all greenhouse gases, carbon dioxide contributes greatly to global warming. Its concentration in the atmosphere is determined by the balance between carbon fixed on the ground or underground as plants and fossil fuels, and carbon present in the atmosphere as carbon dioxide. For example, when carbon dioxide in the atmosphere is absorbed through photosynthesis during plant 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 curb 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.

By using carbon dioxide captured from exhaust gas or the atmosphere as a carbon source, it is possible to reduce carbon emissions. In the carbon dioxide electrolysis device according to an embodiment of the present invention, carbon dioxide is electrolytically reduced to produce carbon compounds, which are then used as a carbon source.

Figure 1 is a cross-sectional view showing a schematic example of an electrolysis stack 10 of a carbon dioxide electrolysis device (hereinafter, device) 100 according to an embodiment of the present invention. As shown in Figure 1, the electrolysis stack 10 is configured as an electrolysis cell in which an anion exchange solid polymer electrolyte membrane (AEM (Anion Exchange Membrane)) 12 is sandwiched between an anode part 11a and a cathode part 11b as a diaphragm, or an electrolysis stack in which electrolysis cells are stacked (connected in series).

The anode section 11a and the cathode section 11b are separated from each other by the AEM 12, and each includes a liquid flow path 13a, 13b, an electrode catalyst 14a, 14b, and a gas flow path 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.

An electrolyte 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 that flows out of the liquid flow paths 13a and 13b can be introduced back into the liquid flow paths 13a and 13b and circulated.

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

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 direct current power supply (hereinafter, electrolytic power supply) 20 provided outside the electrolytic 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 electrolytic power supply 20.

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, at the three-phase interface between the liquid flow path 13b, the electrode catalyst 14b, and the gas flow path 15b in the cathode section 11b, carbon dioxide is reduced by an electrolysis reaction to generate carbon compounds such as ethylene. For example, ethylene is generated by the electrolysis reactions of the following formulas (i) and (ii). In addition, water in the electrolytic solution is reduced by the electrolysis reaction of the following formula (iii) 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 via the gas flow path 15b.
CO ₂ +H ₂ O→CO+2OH ^-... (i)
2CO+8H ₂ O→C ₂ H ₄ +8OH ^- +2H ₂ O...(ii)
2H ₂ O→H ₂ +2OH ^-... (iii)

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 (iv) 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...(iv)

Figure 2 is a block diagram showing an example of the overall configuration of the device 100. As shown in Figure 2, the device 100 includes an electrolytic stack 10, an electrolytic 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 electrolyte to the electrolytic stack 10.

The electrolytic stack 10 is provided with a voltage sensor 16 that detects the voltage of the electrolytic stack 10 (hereinafter, stack voltage), more specifically, the potential difference generated between the anode and cathode of the electrolytic stack 10 due to the power supplied by the electrolytic power source 20. The voltage sensor 16 is connected to a controller 90 (FIG. 3), and the sensor value of the voltage sensor 16 is output to the controller 90.

The electrolytic stack 10 is also provided with a current sensor 17 that detects the current of the electrolytic stack 10 (hereinafter, stack current), more specifically, the current flowing from the positive electrode of the electrolytic power supply 20 through the anode and cathode of the electrolytic stack 10 to the negative electrode of the electrolytic power supply 20. The current sensor 17 is connected to a controller 90 (FIG. 3), and the sensor value of the current sensor 17 is output to the controller 90.

The electrolytic stack 10 is also provided with a temperature sensor 18 that detects a representative temperature of the electrolytic stack 10 (hereinafter, stack temperature). The temperature sensor 18 detects, for example, the surface temperature of the AEM 12 as the representative temperature of the electrolytic stack 10. The temperature sensor 18 is connected to a controller 90 (FIG. 3), and the sensor value of the temperature sensor 18 is output to the controller 90.

The electrolytic power supply 20 is configured as a power generation device that supplies DC power to the electrolytic stack 10. The positive electrode of the electrolytic power supply 20 is connected to the anode of the electrolytic stack 10 (electrode catalyst 14a of the anode portion 11a), and the negative electrode of the electrolytic power supply 20 is connected to the cathode of the electrolytic stack 10 (electrode catalyst 14b of the cathode portion 11b).

The carbon dioxide supply unit 30 includes a pump and other components. 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 a predetermined concentration or more of carbon dioxide. The air containing a predetermined concentration or more of carbon dioxide may be exhaust gas from a device or facility that burns fossil fuels, or may be air in which carbon dioxide has been concentrated by a concentration device. The carbon dioxide supply unit 30 is controlled by a controller 90 (Figure 3).

The electrolyte supply units 40a and 40b each include a pump and the like. The electrolyte supply units 40a and 40b are connected to the inlets of the liquid flow paths 13a and 13b of the electrolytic stack 10 via pipes 41a and 41b, respectively, and supply the electrolyte to the electrolytic stack 10 by pumping the electrolyte. The electrolyte supply units 40a and 40b receive the electrolyte from the outlets of the liquid flow paths 13a and 13b of the electrolytic stack 10 via pipes (not shown).

Figure 3 is a block diagram showing an example of the control configuration of the device 100. As shown in Figure 3, the device 100 further includes a controller 90 that controls the electrolytic power source 20, the carbon dioxide supply unit 30, and the electrolyte supply units 40a and 40b. A voltage sensor 16, a current sensor 17, and a temperature sensor 18 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 the program executed by the calculation unit 91 and setting values.

The calculation unit 91 of the controller 90 controls the electrolytic power supply 20, the carbon dioxide supply unit 30, and the electrolyte supply units 40a, 40b based on the stack voltage, stack current, and stack temperature detected by the voltage sensor 16, current sensor 17, and temperature sensor 18. In particular, after the supply of power from the electrolytic power supply 20 to the electrolytic stack 10 is started, the calculation unit 91 controls the electrolytic power supply 20 so that the stack voltage is within an appropriate range during the startup period until the stack temperature reaches a rated temperature (e.g., about 60 to 70°C) from room temperature.

Figure 4 is a diagram for explaining the appropriate range of the stack voltage. During the start-up period of the electrolysis stack 10, the temperature of the AEM 12 and other components constituting the electrolysis stack 10 is low, and the internal resistance of the electrolysis stack 10, including the resistance when hydroxide ions pass through the AEM 12, is large. For this reason, the stack voltage becomes excessive, which may deteriorate the electrode catalysts 14a, 14b and the AEM 12 constituting the electrolysis stack 10. On the other hand, if the stack voltage falls below the electrolysis voltage required for the electrolysis reaction (formulas (i) to (iv)), the electrolysis reaction does not proceed, and the desired product (carbon compound such as ethylene) is not obtained despite the supply of power, and the efficiency of the entire device 100 decreases. Therefore, in order to prevent the components of the electrolysis stack 10 from deteriorating and to prevent the efficiency of the entire device 100 from decreasing, it is necessary to operate the electrolysis stack 10 within the appropriate range as shown in Figure 4.

The upper and lower limits of the stack voltage change depending on the stack temperature. The characteristics (solid lines in FIG. 4) showing the relationship between the stack temperature and the upper and lower limits of the stack voltage are determined in advance by testing and are stored in the memory unit 92 of the controller 90 as, for example, a characteristics map. The upper and lower limits of the stack voltage are determined in advance based on the theoretical electrolysis voltage value for each carbon compound generated. Furthermore, they may be determined in advance based on the degree of aging deterioration from the beginning to the end of the life of the electrolysis stack 10.

The memory unit 92 of the controller 90 also stores current-voltage (IV) characteristics that represent the relationship between a predetermined stack voltage and stack current. As the stack current increases, the internal resistance of the electrolytic stack 10 increases, and the stack voltage decreases. Also, as the stack temperature increases, the internal resistance of the electrolytic stack 10 decreases, the stack current increases, and the stack voltage decreases. The IV characteristics for each stack temperature are predetermined by performing tests while changing the stack temperature, and are stored in the memory unit 92 of the controller 90, for example, as a characteristics map for each stack temperature.

As shown in FIG. 4, for the upper and lower limit values of the stack voltage, a maximum value lower than the upper limit value and a minimum value higher than the lower limit value are preset based on the sensor error of the voltage sensor 16, etc. Also, a target value even lower than the maximum value is preset based on the electrolysis efficiency of the electrolysis stack 10, etc. The characteristics (dashed lines in FIG. 4) showing the relationship between the stack temperature and the minimum, maximum, and target values of the stack voltage are also determined in advance by testing, similar to the upper and lower limit values, and are stored in the memory unit 92 of the controller 90, for example, as a characteristics map.

Figure 5 is a diagram for explaining a case where the stack voltage becomes excessive at startup. As shown in Figure 5, during the startup period of the electrolytic stack 10, especially immediately after the start of power supply from the electrolytic power source 20 to the electrolytic stack 10, the temperature of the AEM 12 and other components that make up the electrolytic stack 10 is low, and the internal resistance of the electrolytic stack 10 is high. If power is supplied during such a period without monitoring and limiting the stack voltage, the stack voltage may exceed the target value and become excessive, causing deterioration of the AEM 12 and other components that make up the electrolytic stack 10.

Figure 6 is a diagram for explaining the case where it takes time for the stack temperature to reach the rated temperature. When power is supplied to the electrolytic stack 10 and the potential difference between the anode and the cathode reaches the electrolytic voltage, the electrolytic reaction (formulas (i) to (iv)) proceeds, and the temperature of the AEM 12 and other components constituting the electrolytic stack 10 increases with the movement of hydroxide ions, etc., and the stack temperature increases. When the stack temperature increases, the internal resistance of the electrolytic stack 10 decreases, the stack current increases, and the stack voltage decreases. As shown in Figure 6, when power is supplied to the electrolytic stack 10 without increasing the stack voltage, it is possible to avoid the stack voltage becoming excessive as shown in Figure 5, but it takes a long time for the stack temperature to reach the rated temperature.

Figure 7 is a diagram for explaining the case where the stack voltage is adjusted to a target value. As shown in Figure 7, the calculation unit 91 of the controller 90 controls the electrolytic power supply 20 so that the stack voltage detected by the voltage sensor 16 approaches a target value (Figure 4) that is predetermined in accordance with the stack temperature detected by the temperature sensor 18. More specifically, when the stack voltage reaches the target value, the electrolytic power supply 20 is controlled so that the stack current detected by the current sensor 17 increases, and when the stack voltage falls below the target value, the electrolytic power supply 20 is controlled so that the stack current decreases. As a result, the stack voltage is maintained near the upper limit value within the appropriate range of Figure 4, so that the AEM 12 and other components of the electrolytic stack 10 can be heated early within a range that does not deteriorate, and the start-up time of the electrolytic stack 10 until the stack temperature reaches the rated temperature can be shortened.

Figure 8 is a diagram for explaining the target value of the stack current when the stack voltage reaches the target value. As shown in Figure 8, when the stack voltage reaches the target value, the calculation unit 91 of the controller 90 increases the target value of the stack current and controls the electrolytic power source 20 so that the stack current increases. Also, when the stack voltage falls below the target value, the calculation unit 91 controls the electrolytic power source 20 so that the target value of the stack current decreases and the stack current decreases. At this time, the target value of the stack current is set within an appropriate range that does not deteriorate the AEM 12 and the like that constitute the electrolytic stack 10. Such an appropriate range (upper and lower limit values) of the stack current changes depending on the stack temperature. The characteristics showing the relationship between the stack temperature and the upper and lower limit values of the stack current are determined in advance by testing and are stored in the memory unit 92 of the controller 90 as, for example, a characteristic map.

Figure 9 is a diagram for explaining the case where the stack voltage reaches the maximum value (Figure 4). As shown in Figure 9, the calculation unit 91 of the controller 90 controls the electrolysis power source 20 to stop the supply of power to the electrolysis stack 10 when the stack voltage reaches the maximum value. This makes it possible to reliably prevent deterioration of the AEM 12 and other components that make up the electrolysis stack 10.

Figure 10 is a flowchart showing an example of stack startup processing by the device 100, and shows an example of processing executed by the calculation unit 91 of the controller 90. The processing shown in this flowchart is started when a command to start the electrolytic stack 10 is issued.

As shown in FIG. 10, first, in step S1, the electrolyte supply units 40a and 40b are controlled to supply electrolyte to the electrolytic stack 10. Next, in step S2, the carbon dioxide supply unit 30 is controlled to supply carbon dioxide (gas) to the electrolytic stack 10. Next, in step S3, the stack temperature detected by the temperature sensor 18 is read.

Next, in step S4, it is determined whether the stack temperature read in step S3 is within the normal temperature range (e.g., room temperature) immediately after starting the supply of power from the electrolytic power source 20 to the electrolytic stack 10. If the result in step S4 is negative, the process returns to step S3, and if the result is positive, the process proceeds to step S5. In step S5, the electrolytic power source 20 is controlled to start supplying power to the electrolytic stack 10. Next, the process proceeds to step S6, where the stack current target value calculation process is executed.

Figure 11 is a flowchart showing an example of a process for calculating a stack current target value 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. 11, first, in step S10, the stack voltage, stack current, and stack temperature detected by the voltage sensor 16, current sensor 17, and temperature sensor 18, respectively, are read. Next, in step S11, it is determined whether the stack temperature read in step S10 is below the rated temperature. If the result in step S11 is negative, the process ends, and if the result is positive, the process proceeds to step S12. In step S12, it is determined whether the stack voltage read in step S10 is below the target value (FIG. 4).

If the result in step S12 is positive, the process proceeds to step S13, where the target value of the stack current (FIG. 8) is lowered by subtracting a predetermined value from the previous value, and the electrolytic power supply 20 is controlled so that the stack current decreases. Next, in step S14, it is determined whether the target value of the stack current calculated in step S13 is less than the lower limit value. If the result in step S14 is positive, the process proceeds to step S15, where the target value of the stack current is set to the lower limit value. If the result in step S14 is negative, the target value of the stack current is set to the value calculated in step S13.

If the result in step S12 is negative, the process proceeds to step S16, where it is determined whether the stack voltage read in step S10 is less than the maximum value (FIG. 4). If the result in step S16 is positive, the process proceeds to step S17, where the target value of the stack current (FIG. 8) is increased by adding a predetermined value to the previous value, and the electrolytic power supply 20 is controlled so that the stack current increases. Next, in step S18, it is determined whether the target value of the stack current calculated in step S17 exceeds the upper limit value. If the result in step S18 is positive, the process proceeds to step S19, where the target value of the stack current is set to the upper limit value. If the result in step S18 is negative, the target value of the stack current is set to the value calculated in step S17. If the result in step S16 is negative, the process proceeds to step S20, where the electrolytic power supply 20 is controlled to stop the power supply to the electrolytic stack 10.

In this way, by adjusting the stack voltage to the target value (Figure 4) and maintaining it near the upper limit within the appropriate range (steps S10 to S15, S17 to S19), the electrolytic stack 10 can be heated early without degrading the AEM 12, etc., and the start-up time can be shortened. In addition, by controlling the electrolytic power source 20 to stop supplying power to the electrolytic stack 10 when the stack voltage reaches its maximum value (steps S16, S20), degradation of the AEM 12, etc. that constitute the electrolytic stack 10 can be reliably prevented.

According to this embodiment, the following advantageous effects can be obtained.
(1) The device 100 includes an AEM 12, an electrolysis stack 10 having an electrode catalyst 14a in an anode portion 11a and an electrode catalyst 14b in a cathode portion 11b separated by the AEM 12, a carbon dioxide supply unit 30 that supplies carbon dioxide to a gas flow path 15b provided adjacent to the electrode catalyst 14b in the cathode portion 11b, an electrolysis power supply 20 that supplies power to the electrolysis stack 10, a voltage sensor 16 that detects a stack voltage, a temperature sensor 18 that detects a stack temperature, and a controller 90 that controls the electrolysis power supply 20 (FIGS. 1 to 3).

After starting the supply of power from the electrolytic power source 20 to the electrolytic stack 10, the controller 90 controls the electrolytic power source 20 based on the stack voltage detected by the voltage sensor 16 and the stack temperature detected by the temperature sensor 18 during the startup period until the stack temperature reaches a predetermined temperature, so that the stack voltage is equal to or lower than the upper limit of the stack voltage that is predetermined corresponding to the stack temperature. In this way, by maintaining the stack voltage within an appropriate range (FIG. 4), particularly below the upper limit, the temperature of the AEM 12 and other components that make up the electrolytic stack 10 can be raised early without deteriorating, and the startup time of the electrolytic stack 10 can be shortened.

(2) The controller 90 further controls the electrolysis power supply 20 during the startup period based on the stack voltage detected by the voltage sensor 16 and the stack temperature detected by the temperature sensor 18 so that the stack voltage is equal to or higher than a lower limit of the stack voltage that is predetermined in accordance with the stack temperature. In this way, by maintaining the stack voltage within the appropriate range (FIG. 4), particularly at or above the lower limit, the electrolysis reaction (formulas (i) to (iv)) can proceed even during the startup period, improving the efficiency of the entire device 100.

(3) The upper limit value is determined in advance based on the degree of deterioration of the electrolytic stack 10. This makes it possible to reliably prevent deterioration of the AEM 12 and other components of the electrolytic stack 10, regardless of the degree of deterioration of the electrolytic stack 10.

(4) The lower limit is determined in advance based on the degree of deterioration of the electrolytic stack 10. This allows the electrolytic reaction (equations (i) to (iv)) to proceed reliably even during the startup period, regardless of the degree of deterioration of the electrolytic stack 10.

(5) The controller 90 controls the electrolysis power supply 20 so that the voltage is equal to or lower than a target value that is lower than the upper limit and is set in advance based on the sensor error of the voltage sensor 16 and the electrolysis efficiency of the electrolysis stack 10. This makes it possible to more reliably prevent deterioration of the AEM 12 and other components that make up the electrolysis stack 10.

(6) The device 100 further includes a current sensor 17 that detects the stack current (FIGS. 2 and 3). The controller 90 controls the electrolytic power supply 20 so that, during the startup period, when the stack voltage detected by the voltage sensor 16 reaches a target value, the stack current detected by the current sensor 17 increases, and when the stack voltage detected by the voltage sensor 16 falls below the target value, the stack current detected by the current sensor 17 decreases. That is, since there is a certain correlation (IV characteristics) between the stack voltage and the stack current, the stack voltage can be adjusted by adjusting the stack current. By adjusting the stack voltage via the stack current in this way, the stack current can also be managed to be within an appropriate range, so that deterioration of the AEM 12 and other components that make up the electrolytic stack 10 can be more reliably prevented.

(7) When the stack voltage detected by the voltage sensor 16 reaches a maximum value set according to the upper limit, the controller 90 controls the electrolysis power source 20 to stop the supply of power to the electrolysis stack 10. This makes it possible to more reliably prevent deterioration of the AEM 12 and other components that make up the electrolysis stack 10.

In the above embodiment, the electrolytic reaction that proceeds on the cathode side of the electrolytic stack 10 when carbon dioxide is supplied in FIG. 1 etc. has been described as an electrolytic reduction reaction from carbon dioxide to ethylene, but ethylene is just one example, and the carbon compound generated by the electrolytic reduction of carbon dioxide is not limited to ethylene. In addition, the carbon compound generated by the electrolytic reduction of carbon dioxide is not limited to gas components, and may be liquid components such as formic acid, acetic acid, methanol, and ethanol.

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 characteristics of the present invention are not impaired. It is also possible to arbitrarily combine one or more of the above-mentioned embodiment and modifications, and it is also possible to combine modifications together.

10 electrolysis stack, 11a anode section, 11b cathode section, 12 AEM, 13a, 13b liquid flow path, 14a, 14b electrode catalyst, 15a, 15b gas flow path, 16 voltage sensor, 17 current sensor, 18 temperature sensor, 20 electrolysis power source, 30 carbon dioxide supply section, 40a, 40b electrolyte supply section, 90 controller, 91 calculation section, 92 memory section, 100 carbon dioxide electrolysis device (device)

Claims (6)

an electrolysis stack having a diaphragm including an anion exchange type solid polymer electrolyte membrane, and an anode and a cathode separated by the diaphragm;
a carbon dioxide supply unit that supplies carbon dioxide to a gas flow path provided adjacent to the cathode;
a power supply for supplying power to the electrolysis stack;
a voltage sensor for detecting a voltage of the electrolytic stack;
a current sensor for detecting a current in the electrolytic stack;
a temperature sensor for detecting a temperature of the electrolysis stack;
A control unit that controls the power supply unit,
The control unit controls the power supply unit to reduce the current of the electrolytic stack when the voltage of the electrolytic stack falls below a target value that is lower than an upper limit value of the voltage of the electrolytic stack that is predetermined corresponding to the temperature of the electrolytic stack, based on the voltage of the electrolytic stack detected by the voltage sensor, the current of the electrolytic stack detected by the current sensor, and the temperature of the electrolytic stack detected by the temperature sensor, during a startup period until the temperature of the electrolytic stack reaches a predetermined temperature after starting the supply of power from the power supply unit to the electrolytic stack . The carbon dioxide electrolysis device characterized in that: The carbon dioxide electrolysis device according to claim 1,
The control unit further controls the power supply unit during the start-up period based on the voltage of the electrolysis stack detected by the voltage sensor and the temperature of the electrolysis stack detected by the temperature sensor so that the voltage of the electrolysis stack is equal to or higher than a lower limit voltage of the electrolysis stack predetermined corresponding to the temperature of the electrolysis stack. The carbon dioxide electrolysis device according to claim 1 or 2,
The carbon dioxide electrolysis device according to claim 1, wherein the upper limit is determined in advance based on a degree of deterioration of the electrolysis stack over time. The carbon dioxide electrolysis device according to claim 2,
The carbon dioxide electrolysis device, wherein the lower limit is determined in advance based on a degree of deterioration over time of the electrolysis stack. The carbon dioxide electrolysis device according to claim 1,
4. The carbon dioxide electrolysis device according to claim 3, wherein the target value is set in advance based on a sensor error of the voltage sensor and an electrolysis efficiency of the electrolysis stack. The carbon dioxide electrolysis device according to claim 1,
the control unit controls the power supply unit to stop supplying power to the electrolysis stack when the voltage of the electrolysis stack detected by the voltage sensor reaches a maximum value set according to the upper limit value.

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