Reaction processing system

Abstract

To obtain a reaction processing system that can stabilize the temperature of the water circulating in the water circulation path of a water electrolysis cell stack. [Solution] The reaction processing system 2 comprises a water electrolysis cell stack 12, a water circulation path 14, a power supply unit 16, and a control device 50. The water circulation path 14 is equipped with a heat exchanger 18 that absorbs the reaction heat in the methane synthesis apparatus 40, and a temperature sensor 30 that detects the temperature of the water flowing through the water circulation path 14 downstream of the heat exchanger 18 and upstream of the water electrolysis cell stack 12. The control device 50 controls the temperature of the water circulating through the water circulation path 14 by controlling the current of the power supply unit 16 based on the temperature detected by the temperature sensor 30, thereby increasing or decreasing the waste heat from water electrolysis in the water electrolysis cell stack 12, and increasing or decreasing the reaction heat in the methane synthesis apparatus 40 in accordance with the increase or decrease in the amount of hydrogen produced by the water electrolysis cell stack.

Description

Technical Field

[0001] The present invention relates to a reaction processing system.

Background Art

[0002] For example, Patent Document 1 discloses a water electrolysis system including a differential pressure type high-pressure water electrolysis device, a water supply pipe for supplying water to a water supply port of the differential pressure type high-pressure water electrolysis device, and a water discharge pipe for discharging water from a water discharge port of the differential pressure type high-pressure water electrolysis device. A radiator for cooling water is provided in the water supply pipe, and a first temperature sensor is provided between the radiator and the water supply port to monitor the temperature of the supply water supplied to the water supply port. A second temperature sensor for monitoring the temperature of the discharged water discharged from the water discharge port is provided in the water discharge pipe.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the configuration described in Patent Document 1, after the temperature of the discharged water monitored by the second temperature sensor exceeds a predetermined temperature, the temperature of the supply water supplied to the water supply port is monitored by the first temperature sensor, and control by the radiator is started to control the temperature of the supply water. Therefore, power for controlling the radiator is required, and the temperature of the supply water tends to be unstable. <00​​​​​​​​The reaction processing system described in the first embodiment includes: a water electrolysis cell stack that generates hydrogen and oxygen by water electrolysis; a water circulation path provided with a pump that circulates water discharged from the water electrolysis cell stack and supplies it to the water electrolysis cell stack; a power supply device that supplies current to the water electrolysis cell stack; a heat exchanger provided in the water circulation path that absorbs reaction heat in a synthetic compound manufacturing apparatus that reacts carbon oxides with hydrogen generated in the water electrolysis cell stack to produce a synthetic compound; a temperature sensor provided downstream of the heat exchanger in the water flow direction of the water circulation path and upstream of the water electrolysis cell stack, which detects the temperature of the water flowing through the water circulation path; and a control device that controls the temperature of the water circulating through the water circulation path by controlling the current of the power supply device based on the temperature detected by the temperature sensor, thereby increasing or decreasing the waste heat from water electrolysis in the water electrolysis cell stack and increasing or decreasing the reaction heat in the synthetic compound manufacturing apparatus in accordance with the increase or decrease in the amount of hydrogen produced in the water electrolysis cell stack.

[0007] In the reaction processing system described in the first embodiment, a pump installed in the water circulation path is driven to circulate water discharged from the water electrolysis cell stack and supply it to the water electrolysis cell stack. A power supply unit supplies current to the water electrolysis cell stack, causing hydrogen and oxygen to be produced by water electrolysis in the water electrolysis cell stack. A heat exchanger is provided in the water circulation path, and the reaction heat from the synthetic compound production apparatus, which reacts hydrogen with carbon oxides to produce synthetic compounds, is absorbed into the water in the water circulation path by the heat exchanger. In this way, the water circulating in the water circulation path is heated by utilizing the reaction heat from the synthetic compound production apparatus. A temperature sensor is provided downstream of the heat exchanger in the direction of water flow in the water circulation path and upstream of the water electrolysis cell stack, and the temperature of the water flowing in the water circulation path is detected by the temperature sensor. Based on the temperature detected by the temperature sensor, the control device controls the current of the power supply unit to increase or decrease the waste heat from water electrolysis in the water electrolysis cell stack, and also to increase or decrease the reaction heat in the synthetic compound production apparatus in accordance with the increase or decrease in the amount of hydrogen produced in the water electrolysis cell stack. In this way, the temperature of the water circulating in the water circulation path is controlled. Therefore, the temperature of the water circulating in the water circulation path can be stabilized.

[0008] The reaction processing system described in the second embodiment, in the reaction processing system described in the first embodiment, increases the current of the power supply when the temperature detected by the temperature sensor falls below a first threshold, thereby increasing the waste heat from water electrolysis in the water electrolysis cell stack and increasing the reaction heat in the synthetic compound production apparatus due to the increase in the amount of hydrogen produced by the water electrolysis cell stack, thereby raising the temperature of the water circulating in the water circulation path.

[0009] In the reaction processing system described in the second embodiment, when the temperature detected by the temperature sensor falls below a first threshold, the control device increases the current of the power supply to increase the waste heat from water electrolysis in the water electrolysis cell stack and also increases the reaction heat in the synthetic compound production apparatus due to the increase in the amount of hydrogen produced by the water electrolysis cell stack. This raises the temperature of the water circulating in the water circulation path, thereby stabilizing the temperature of the water circulating in the water circulation path.

[0010] The reaction processing system according to the third embodiment, in the reaction processing system according to the first embodiment, the control device, when the temperature detected by the temperature sensor rises to a second threshold or higher, reduces the current of the power supply, thereby reducing the waste heat from water electrolysis in the water electrolysis cell stack and reducing the reaction heat in the synthetic compound production apparatus due to the decrease in the amount of hydrogen produced by the water electrolysis cell stack, and thereby lowering the temperature of the water circulating in the water circulation path.

[0011] In the reaction processing system described in the third embodiment, when the temperature detected by the temperature sensor rises above a second threshold, the control device reduces the current of the power supply to reduce the waste heat from water electrolysis in the water electrolysis cell stack and the reaction heat in the synthesis compound production apparatus due to the decrease in the amount of hydrogen produced in the water electrolysis cell stack. This lowers the temperature of the water circulating in the water circulation path, thereby stabilizing the temperature of the water circulating in the water circulation path.

[0012] The reaction processing system described in the fourth embodiment is the reaction processing system described in the first embodiment, wherein the water circulation path is provided with a water separator for separating the water discharged from the water electrolysis cell stack from the gas, and a water introduction section for introducing new water.

[0013] In the reaction processing system described in the fourth embodiment, water discharged from the water electrolysis cell stack is separated from the gas by a water separator provided in the water circulation path. Furthermore, new water is introduced into the water circulation path by a water inlet. As a result, water discharged from the water electrolysis cell stack can be circulated in the water circulation path, and water can be supplied to the water electrolysis cell stack while new water is being introduced.

[0014] The reaction processing system described in the fifth embodiment is the reaction processing system described in the fourth embodiment, wherein the water separator and the water introduction section are provided downstream of the water electrolysis cell stack in the water flow direction of the water circulation path and upstream of the heat exchanger.

[0015] In the reaction processing system described in the fifth embodiment, the water separator and the water introduction section are located downstream of the water electrolysis cell stack in the water flow direction of the water circulation path and upstream of the heat exchanger, so that the temperature of the water supplied to the water electrolysis cell stack through the heat exchanger can be controlled more reliably.

[0016] The reaction processing system described in the sixth embodiment is the reaction processing system described in the first embodiment, wherein the power supply device is provided with a predetermined voltage upper limit.

[0017] In the reaction processing system described in the sixth embodiment, when water electrolysis is performed in the water electrolysis cell stack by controlling the current, a predetermined voltage upper limit is provided in the power supply unit, so that the deterioration of the catalyst in the water electrolysis cell stack can be suppressed. [Effects of the Invention]

[0018] According to this disclosure, the temperature of the water circulating in the water circulation path of a water electrolysis cell stack can be stabilized. [Brief explanation of the drawing]

[0019] [Figure 1] This is a schematic diagram showing a reaction processing system according to the first embodiment. [Figure 2]It is a block diagram showing the hardware configuration of the reaction processing system according to the first embodiment. [Figure 3] It is a block diagram showing an example of the functional configuration of the reaction processing system according to the first embodiment. [Figure 4] It is a graph showing the relationship between the elapsed time, the circulating water temperature, the Sabatier heat medium temperature, the electrolysis current density, and the hydrogen flow rate in the reaction processing system according to the first embodiment. [Figure 5] It is a schematic configuration diagram showing the reaction processing system of the comparative example. [Figure 6] It is a graph showing the relationship between the elapsed time, the circulating water temperature, the Sabatier heat medium temperature, the electrolysis current density, the state of the heater, the state of the chiller, and the hydrogen flow rate in the reaction processing system of the comparative example.

Embodiments for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present disclosure will be described based on the drawings. In each drawing, those having low relevance to the technology of the present disclosure are omitted from illustration.

[0021] 〔First Embodiment〕 The reaction processing system according to the first embodiment will be described. FIG. 1 shows the overall configuration of the reaction processing system 2 according to the first embodiment.

[0022] <Configuration of Reaction Processing System> As shown in FIG. 1, the reaction processing system 2 includes a water electrolysis system 10 and a methane synthesis device 40. The water electrolysis system 10 includes a water electrolysis cell stack 12, a water circulation path 14, a power supply device 16, a heat exchanger 18, and a temperature sensor 30. Further, the reaction processing system 2 includes a control device 50 that controls each part of the reaction processing system 2. Note that the dotted lines in FIG. 1 include cases where they indicate functional relationships different from the actual connection relationships.

[0023] (Water Electrolysis Cell Stack) The water electrolysis cell stack 12 generates hydrogen and oxygen through water electrolysis (i.e., electrolysis of water). More specifically, the water electrolysis cell stack 12 is formed by stacking water electrolysis cells (not shown) that form an anode and a cathode with an electrolyte membrane in between. In the water electrolysis cell stack 12, when power is supplied by the power supply unit 16, the water supplied to the anode is electrolyzed, generating oxygen at the anode and hydrogen at the cathode.

[0024] The supply end 14A of the water circulation path 14 is connected to the anode inlet of the water electrolysis cell stack 12, and water is supplied from the supply end 14A of the water circulation path 14. The hydrogen transfer path 38 is connected to the cathode outlet of the water electrolysis cell stack 12, and hydrogen is discharged from the hydrogen transfer path 38. The discharge end 14B of the water circulation path 14 is connected to the anode outlet of the water electrolysis cell stack 12, and oxygen and water are discharged from the discharge end 14B of the water circulation path 14.

[0025] (Water circulation path and temperature sensor) The water circulation path 14 circulates the water discharged from the water electrolysis cell stack 12 to the discharge end 14B, and supplies water to the water electrolysis cell stack 12 from the supply end 14A. In other words, the water circulation path 14 circulates water via the water electrolysis cell stack 12.

[0026] A pump 22 is installed in the middle of the water circulation path 14. By driving the pump 22, the water in the water circulation path 14 is circulated.

[0027] In the water electrolysis cell stack 12, heat may be generated due to an exothermic reaction when hydrogen and oxygen are produced by water electrolysis. The water electrolysis system 10 is configured to utilize the waste heat from water electrolysis in the water electrolysis cell stack 12 to raise the temperature of the water circulating in the water circulation path 14.

[0028] The temperature sensor 30 is located near the supply end 14A of the water circulation path 14 that supplies water to the water electrolysis cell stack 12. More specifically, the temperature sensor 30 is located downstream of the heat exchanger 18 in the direction of water flow in the water circulation path 14, and upstream of the water electrolysis cell stack 12. The temperature sensor 30 detects the temperature of the water flowing through the water circulation path 14.

[0029] A gas-liquid separator 20 is provided in the middle of the water circulation path 14. The gas-liquid separator 20 is an example of a water separator and separates the water discharged from the water electrolysis cell stack 12 from the gas. Specifically, the gas-liquid separator 20 separates oxygen and water from the water circulation path 14 and stores the separated water W. An oxygen supply passage 21 is connected to the gas-liquid separator 20, and oxygen is supplied from the oxygen supply passage 21. As an example, the gas-liquid separator 20 is provided downstream of the water electrolysis cell stack 12 in the water circulation path 14's water transfer direction (i.e., the water flow direction) and upstream of the pump 22.

[0030] The water circulation path 14 is equipped with a water inlet 24 for introducing new pure water. Pure water is an example of new water. New water is pure water supplied from outside the water electrolysis system 10. For example, the water inlet 24 supplies new pure water into the gas-liquid separator 20 located in the water circulation path 14. The water inlet 24 includes an inlet passage 26 connected between the pure water storage section 25 and the gas-liquid separator 20, and a control valve 27 for adjusting the flow rate of water through the inlet passage 26. The gas-liquid separator 20 is equipped with a water level gauge 28 for detecting the water level of the water W inside, and the control valve 27 is controlled based on the water level detected by the water level gauge 28. For example, when the water level detected by the water level gauge 28 falls below a predetermined value, the control valve 27 is opened, and pure water is supplied from the pure water storage section 25 to the gas-liquid separator 20 via the inlet passage 26.

[0031] An ion exchange resin 36 is provided in the middle of the water circulation path 14. The ion exchange resin 36 removes impurities from the circulating water by ion exchange treatment and maintains the electrical resistivity at a value close to the electrical exchange rate of theoretically pure water. As an example, the ion exchange resin 36 is provided downstream of the pump 22 in the water transfer direction of the water circulation path 14 and upstream of the water electrolysis cell stack 12 and the heat exchanger 18.

[0032] (Methane synthesis apparatus and heat exchanger) The downstream end of the hydrogen transfer path 38 of the water electrolysis cell stack 12 is connected to the methane synthesis apparatus 40. In the reaction treatment system 2, hydrogen produced by the water electrolysis cell stack 12 is supplied to the methane synthesis apparatus 40 via the hydrogen transfer path 38. The methane synthesis apparatus 40 is an example of a synthesizer for producing synthetic compounds.

[0033] The methane synthesis apparatus 40 is a device that synthesizes methane by reacting hydrogen and carbon dioxide using the Sabatier reaction. Methane is an example of a synthesized compound. Carbon dioxide is an example of a carbon oxide. A supply channel 44 for supplying carbon dioxide is connected to the hydrogen transfer channel 38. As a result, carbon dioxide is supplied from the supply channel 44 to the hydrogen being transported in the hydrogen transfer channel 38, and both hydrogen and carbon dioxide are supplied to the methane synthesis apparatus 40.

[0034] The methane synthesis apparatus 40 is equipped with a reactor (not shown) that reacts hydrogen and carbon dioxide by the Sabatier reaction. The methane synthesis apparatus 40 is also equipped with a heat transfer medium circulation path 42 that circulates a heat transfer medium such as oil between the reactor and the heat exchanger 18. In the heat transfer medium circulation path 42, the heat transfer medium is transferred from the reactor to the heat exchanger 18, so that the reaction heat generated in the methane synthesis apparatus 40 is absorbed by the water in the water circulation path 14 by the heat exchanger 18. The methane synthesis apparatus 40 is connected to a methane discharge path 46, and the methane produced in the reactor is discharged to the methane discharge path 46.

[0035] Although not shown in the diagram, the hydrogen transfer path 38 may be equipped with a hydrogen drain through which hydrogen and water discharged from the water electrolysis cell stack 12 can pass. This allows the hydrogen transfer path 38 to supply hydrogen to the methane synthesis unit 40 by draining water through the hydrogen drain. The hydrogen transfer path 38 may also be equipped with a deoxygenator to remove oxygen from the hydrogen-containing gas.

[0036] Although not shown in the diagram, the methane synthesis apparatus 40 may be equipped with a preheater for preheating the raw material gases (hydrogen and carbon dioxide). Furthermore, the methane synthesis apparatus 40 may be equipped with a drain downstream of the reactor to drain water from the reaction products and deliver methane.

[0037] The heat exchanger 18 is located downstream of the ion exchange resin 36 in the water flow direction of the water circulation path 14, and upstream of the water electrolysis cell stack 12 and the temperature sensor 30. Because the heat exchanger 18 is provided in the water circulation path 14, the reaction heat in the methane synthesis apparatus 40 is absorbed by the heat exchanger 18, and the water transported through the water circulation path 14 is heated.

[0038] (power supply) The power supply unit 16 is electrically connected to the water electrolysis cell stack 12 by wiring 17. The power supply unit 16 has the function of operating the water electrolysis cell stack 12 by supplying current (e.g., DC current) to the water electrolysis cell stack 12 via the wiring 17.

[0039] For example, the power supply unit 16 is electrically connected to the control device 50, and the control device 50 controls the operation of the power supply unit 16. For example, the control device 50 controls the current (e.g., DC current) supplied from the power supply unit 16 to the water electrolysis cell stack 12. For example, since the DC current supplied to the water electrolysis cell stack 12 is proportional to the amount of hydrogen produced by water electrolysis in the water electrolysis cell stack 12, the amount of hydrogen produced can be adjusted by controlling the DC current of the power supply unit 16 with the control device 50.

[0040] Furthermore, the power supply unit 16 is provided with a predetermined voltage limit. By providing a predetermined voltage limit, it is possible to prevent the deterioration of the catalyst in the water electrolysis cell stack 12 from accelerating. The voltage limit may be a limit controlled by the power supply unit 16, or an upper limit may be set by the power supply unit 16 itself. For example, a protection circuit, a voltage regulator, or a Zener diode can be used to set the upper limit of the power supply unit 16.

[0041] (Control device) Figure 2 is a block diagram showing the hardware configuration of reaction processing system 2.

[0042] As shown in Figure 2, the reaction processing system 2 includes a control device 50. The control device 50 consists of a CPU (Central Processing Unit) 51, ROM (Read Only Memory) 52, RAM (Random Access Memory) 53, storage 54, and an input / output interface 55. Each component is connected to the others via a bus 59 so that they can communicate with each other.

[0043] The CPU 51 is a central processing unit that executes various programs and controls various parts. Specifically, the CPU 51 reads a program from the ROM 52 or storage 54 and executes the program using the RAM 53 as a working area. The CPU 51 controls each of the above components and performs various calculations according to the program stored in the ROM 52 or storage 54. In the first embodiment, the ROM 52 or storage 54 stores a program that operates the reaction processing system 2.

[0044] ROM 52 stores various programs and data. RAM 53 temporarily stores programs or data as a working area. Storage 54 consists of an HDD (Hard Disk Drive) or SSD (Solid State Drive) and stores various programs, including the operating system, and various data.

[0045] The input / output interface 55 is an interface for sending and receiving information between the CPU and each component mounted on the reaction processing system 2. For example, the input / output interface 55 is electrically connected to the power supply unit 16, the pump 22, the temperature sensor 30, the current detection unit 62, the heat medium temperature detection unit 64, the hydrogen flow meter 66, the voltage detection unit 68, and the methane synthesis apparatus 40. As a result, the CPU 51 controls the operation of the power supply unit 16 and the pump 22 via the input / output interface 55. Furthermore, the CPU 51 controls the operation of the methane synthesis apparatus 40 via the input / output interface 55. In addition, the CPU 51 receives detection values ​​detected by the temperature sensor 30, the current detection unit 62, the heat medium temperature detection unit 64, the hydrogen flow meter 66, and the voltage detection unit 68, respectively, via the input / output interface 55.

[0046] The current detection unit 62 is provided, for example, in the water electrolysis cell stack 12 and detects the current of the water electrolysis cell stack 12. The CPU 51 acquires the current detected by the current detection unit 62 and converts it into an electrolysis current density.

[0047] The heat medium temperature detection unit 64 detects the temperature of the heat medium flowing through the heat medium circulation path 42. For example, the heat medium temperature detection unit 64 is located upstream of the heat exchanger 18 in the direction of heat medium flow in the heat medium circulation path 42, and downstream of the methane synthesis apparatus 40.

[0048] The hydrogen flow meter 66 is installed, for example, in the hydrogen transfer path 38 and detects the hydrogen flow rate in the hydrogen transfer path 38.

[0049] The voltage detection unit 68 is provided, for example, in the water electrolysis cell stack 12 and detects the cell voltage of the water electrolysis cell stack 12.

[0050] Figure 3 is a block diagram showing an example of the functional configuration of the control device 50 in the reaction processing system 2.

[0051] As shown in Figure 3, the control device 50 in the reaction processing system 2 has the following functional configuration: a circulating water temperature acquisition unit 71, a pump control unit 72, a current density acquisition unit 73, a power supply unit control unit 74, and a hydrogen flow rate acquisition unit 75. Each functional configuration is realized by the CPU 51 reading a program stored in the ROM 52, loading it into the RAM 53, and executing it.

[0052] The circulating water temperature acquisition unit 71 acquires the temperature of the circulating water in the water circulation path 14, which is detected by the temperature sensor 30.

[0053] The pump control unit 72 controls the operation of the pump 22. By driving the pump 22, water is circulated through the water circulation path 14.

[0054] The current density acquisition unit 73 acquires the electrolytic current density converted based on the current detection value of the water electrolytic cell stack 12 detected by the current detection unit 62.

[0055] The power supply control unit 74 controls the operation of the power supply unit 16. Based on the temperature detected by the temperature sensor 30, the power supply control unit 74 controls the current (e.g., DC current) of the power supply unit 16. More specifically, the CPU 51 controls the current of the power supply unit 16 to increase or decrease the waste heat from water electrolysis in the water electrolysis cell stack 12, and also to increase or decrease the reaction heat in the methane synthesis apparatus 40 in accordance with the increase or decrease in the amount of hydrogen produced in the water electrolysis cell stack 12. This controls the temperature of the water circulating in the water circulation path 14.

[0056] As an example, the power supply control unit 74 increases the current of the power supply unit 16 when the temperature detected by the temperature sensor 30 falls below a first threshold. More specifically, by increasing the current of the power supply unit 16, the power supply control unit 74 increases the waste heat from water electrolysis in the water electrolysis cell stack 12 and increases the reaction heat in the methane synthesis apparatus 40 due to the increase in the amount of hydrogen produced by the water electrolysis cell stack 12. This raises the temperature of the water circulating in the water circulation path 14. As an example, the first threshold is a temperature set according to the temperature difference from a reference temperature (e.g., 80°C). If the absolute value of the temperature difference from the reference temperature (e.g., 80°C) is to be kept within a predetermined range (e.g., within 10°C), the first threshold is, for example, 70°C. When the temperature detected by the temperature sensor 30 falls below a first threshold (e.g., 70°C), the current of the power supply unit 16 is increased.

[0057] As an example, the power supply control unit 74 reduces the current of the power supply 16 if the temperature detected by the temperature sensor 30 rises above the second threshold. More specifically, by reducing the current of the power supply 16, the power supply control unit 74 reduces the waste heat from water electrolysis in the water electrolysis cell stack 12 and reduces the reaction heat in the methane synthesis apparatus 40 that occurs when the amount of hydrogen produced in the water electrolysis cell stack 12 decreases. This lowers the temperature of the water circulating in the water circulation path 14. As an example, the second threshold is a temperature set according to the temperature difference from a reference temperature (e.g., 80°C). If the absolute value of the temperature difference from the reference temperature (e.g., 80°C) is to be kept within a predetermined range (e.g., within 10°C), the second threshold will be, for example, 90°C. If the temperature detected by the temperature sensor 30 rises above the second threshold (e.g., 90°C), the current of the power supply 16 is reduced.

[0058] Furthermore, the power supply control unit 74 controls the current supplied to the water electrolysis cell stack 12 by the power supply unit 16, for example, based on the cell voltage detected by the voltage detection unit 68, so as not to exceed a predetermined voltage upper limit.

[0059] The hydrogen flow rate acquisition unit 75 acquires the hydrogen flow rate of the hydrogen transfer path 38 measured by the hydrogen flow meter 66.

[0060] (Example of operation of reaction processing system 2) Next, we will describe an example of the operation of reaction processing system 2.

[0061] Figure 4 is a graph showing the relationship between the elapsed time in the reaction system 2 and the circulating water temperature, electrolytic current density, Sabatier heat medium temperature, and hydrogen flow rate. The Sabatier heat medium temperature is the temperature of the heat medium circulating in the heat medium circulation path 42, and is a value detected by the heat medium temperature detection unit 64.

[0062] In the reaction processing system 2, the pump 22 is driven to circulate the water in the water circulation path 14. Furthermore, by supplying current from the power supply unit 16 to the water electrolysis cell stack 12, the water electrolysis cell stack 12 is operated to produce hydrogen and oxygen through water electrolysis (i.e., electrolysis of water). The operation of the power supply unit 16 is controlled by the CPU 51 of the control device 50. The CPU 51 obtains the temperature of the water in the water circulation path 14 detected by the temperature sensor 30. As shown in Figure 4, when the operation of the water electrolysis cell stack 12 is stable, the temperature of the water in the water circulation path 14 detected by the temperature sensor 30 is approximately 80°C, which is near the reference temperature.

[0063] As shown in Figure 4, the CPU 51 increases the current of the power supply 16 when the temperature detected by the temperature sensor 30 drops to or above a first threshold (e.g., 70°C). For example, it increases the DC current of the power supply 16 to an acceptable value. That is, by increasing the current of the power supply 16, the waste heat from water electrolysis in the water electrolysis cell stack 12 is increased, and the reaction heat in the methane synthesis apparatus 40 increases with the increase in the amount of hydrogen produced in the water electrolysis cell stack 12. This raises the temperature of the water circulating in the water circulation path 14.

[0064] As shown in Figure 4, as the current value of the power supply 16 increases, the electrolysis current density of the water electrolysis cell stack 12 increases, and the hydrogen flow rate sent from the water electrolysis cell stack 12 to the hydrogen transfer path 38 increases. As a result, the reaction heat in the methane synthesis apparatus 40 increases due to the increase in the amount of hydrogen produced by the water electrolysis cell stack 12, causing the Sabatier heat transfer medium temperature (i.e., the temperature of the heat transfer medium circulating in the heat transfer medium circulation path 42) to rise. In addition, as the current of the power supply 16 increases, the voltage also increases, and the temperature of the water electrolysis cell stack 12 rises as the overvoltage from the electrolysis thermal neutral point voltage increases. Therefore, the waste heat from the water electrolysis cell stack 12 increases, and the heat absorbed by the heat exchanger 18 also increases, causing the temperature of the water in the water circulation path 14 (i.e., circulating water) to gradually rise. Then, when the temperature detected by the temperature sensor 30 reaches the reference temperature (for example, 80°C), the CPU 51 returns the current value of the power supply 16 to its original value. As a result, the temperature of the water circulating in the water circulation path 14 stabilizes at approximately 80°C, which is near the reference temperature.

[0065] As shown in Figure 4, the CPU 51 reduces the current of the power supply 16 when the temperature detected by the temperature sensor 30 rises above a second threshold (for example, 90°C). That is, by reducing the current of the power supply 16, the waste heat from water electrolysis in the water electrolysis cell stack 12 is reduced, and the reaction heat in the methane synthesis apparatus 40 associated with the decrease in hydrogen production in the water electrolysis cell stack 12 is also reduced. This lowers the temperature of the water circulating in the water circulation path 14.

[0066] As shown in Figure 4, as the current value of the power supply 16 decreases, the electrolysis current density of the water electrolysis cell stack 12 decreases, and the hydrogen flow rate sent from the water electrolysis cell stack 12 to the hydrogen transfer path 38 decreases. As a result, the reaction heat in the methane synthesis apparatus 40 decreases due to the decrease in the amount of hydrogen produced by the water electrolysis cell stack 12, and the Sabatier heat transfer medium temperature (i.e., the temperature of the heat transfer medium circulating in the heat transfer medium circulation path 42) decreases. Also, when the current of the power supply 16 is reduced, the voltage also decreases, approaching or falling below the voltage of the electrolysis thermal neutral point, so the temperature of the water electrolysis cell stack 12 decreases. Therefore, the waste heat from the water electrolysis cell stack 12 decreases, and the heat absorbed by the heat exchanger 18 also decreases, and the temperature of the water in the water circulation path 14 (i.e., circulating water) gradually decreases. Then, when the temperature detected by the temperature sensor 30 reaches the reference temperature (for example, 80°C), the CPU 51 returns the current value of the power supply 16 to its original value. As a result, the temperature of the water circulating in the water circulation path 14 stabilizes at approximately 80°C, which is near the reference temperature.

[0067] <Mechanism and Effects> Next, the operation and effects of the first embodiment will be described.

[0068] In reaction processing system 2, a pump 22 installed in the water circulation path 14 is driven to circulate water discharged from the water electrolysis cell stack 12 and supply it to the water electrolysis cell stack 12. The power supply unit 16 supplies current to the water electrolysis cell stack 12, causing hydrogen and oxygen to be produced in the water electrolysis cell stack 12 by water electrolysis (i.e., electrolysis of water). A heat exchanger 18 is installed in the water circulation path 14, and the reaction heat from the methane synthesis device 40, which synthesizes methane by reacting hydrogen and carbon dioxide using the Sabatier reaction, is absorbed by the water in the water circulation path 14 by the heat exchanger 18. In this way, the water circulating in the water circulation path 14 is heated by utilizing the reaction heat from the methane synthesis device 40.

[0069] A temperature sensor 30 is provided downstream of the heat exchanger 18 and upstream of the water electrolysis cell stack 12 in the water flow direction of the water circulation path 14, and the temperature of the water flowing through the water circulation path 14 is detected by the temperature sensor 30. Based on the temperature detected by the temperature sensor 30, the control device 50 controls the current of the power supply 16 to increase or decrease the waste heat from water electrolysis in the water electrolysis cell stack 12, and also to increase or decrease the reaction heat in the methane synthesis apparatus 40 in accordance with the increase or decrease in the amount of hydrogen produced in the water electrolysis cell stack 12. In this way, the temperature of the water circulating in the water circulation path 14 is controlled. For this reason, the reaction treatment system 2 can stabilize the temperature of the water circulating in the water circulation path 14 of the water electrolysis cell stack 12.

[0070] Furthermore, in the reaction processing system 2, if the temperature detected by the temperature sensor 30 falls below a first threshold, the control device 50 increases the current of the power supply unit 16, increasing the waste heat from water electrolysis in the water electrolysis cell stack 12 and increasing the reaction heat in the methane synthesis unit 40 due to the increase in hydrogen production in the water electrolysis cell stack 12. This raises the temperature of the water circulating in the water circulation path 14. As a result, the reaction processing system 2 can more reliably stabilize the temperature of the water circulating in the water circulation path 14 of the water electrolysis cell stack 12.

[0071] Furthermore, in the reaction processing system 2, if the temperature detected by the temperature sensor 30 rises above the second threshold, the control device 50 reduces the current of the power supply unit 16, thereby reducing the waste heat from water electrolysis in the water electrolysis cell stack 12 and reducing the reaction heat in the methane synthesis unit 40 due to the decrease in the amount of hydrogen produced in the water electrolysis cell stack 12. This lowers the temperature of the water circulating in the water circulation path 14. As a result, the reaction processing system 2 can more reliably stabilize the temperature of the water circulating in the water circulation path 14 of the water electrolysis cell stack 12.

[0072] Furthermore, in the reaction processing system 2, the water discharged from the water electrolysis cell stack 12 is separated from the gas by a gas-liquid separator 20 installed in the water circulation path 14. In addition, new water is introduced into the water circulation path 14 by a water introduction section 24. Therefore, in the reaction processing system 2, the water discharged from the water electrolysis cell stack 12 is circulated in the water circulation path 14, and water can be supplied to the water electrolysis cell stack 12 while new water is being introduced.

[0073] Furthermore, in the reaction processing system 2, the gas-liquid separator 20 and the water inlet 24 are located downstream of the water electrolysis cell stack 12 in the water flow direction of the water circulation path 14 and upstream of the heat exchanger 18. Therefore, in the reaction processing system 2, the temperature of the water supplied to the water electrolysis cell stack 12 through the heat exchanger 18 can be controlled more reliably.

[0074] Furthermore, in reaction processing system 2, a predetermined voltage upper limit is provided for the power supply unit 16. Therefore, in reaction processing system 2, when water electrolysis is performed in the water electrolysis cell stack 12 by controlling the current, the deterioration of the catalyst in the water electrolysis cell stack 12 can be suppressed.

[0075] Here, we will describe the comparative reaction system 200. Figure 5 is a schematic diagram showing the comparative reaction system 200.

[0076] As shown in Figure 5, the comparative example reaction system 200 is equipped with a heat exchanger 210 and a heater 220 in the middle of the water circulation path 14. A hydrogen transfer pipe 202 is connected to the water electrolysis cell stack 12. Although not shown in the figure, the downstream end of the hydrogen transfer pipe 202 is connected to the methane synthesis apparatus 40.

[0077] The heat exchanger 210 is equipped with a heat transfer medium circulation path 214 that circulates a heat transfer medium such as oil between it and the chiller 212. The chiller 212 cools the water in the water circulation path 14 by circulating the heat transfer medium through the heat transfer medium circulation path 214 while controlling the liquid temperature of the heat transfer medium. The heat exchanger 210 is located downstream of the pump 22 in the water transfer direction of the water circulation path 14 and upstream of the ion exchange resin 36.

[0078] The heater 220 raises the temperature of the water in the water circulation path 14. The heater 220 is located downstream of the heat exchanger 18 in the water transfer direction of the water circulation path 14, and upstream of the water electrolysis cell stack 12 and the temperature sensor 30.

[0079] Figure 6 is a graph showing the relationship between the elapsed time in the comparative reaction treatment system 200, the circulating water temperature, the Sabatier heat transfer medium temperature, the electrolytic current density, the ON or OFF state of the heater 220, the ON or OFF state of the chiller 212, and the hydrogen flow rate.

[0080] As shown in Figure 6, in the comparative example reaction system 200, the electrolytic current density of the water electrolysis cell stack 12 is controlled to be constant at a predetermined value. As a result, the hydrogen flow rate delivered from the water electrolysis cell stack 12 to the hydrogen transfer pipe 202 remains at a nearly constant value. Furthermore, since the amount of methane synthesized by the methane synthesis apparatus 40 hardly changes, the Sabatier heat transfer medium temperature also remains at a nearly constant value.

[0081] As shown in Figure 6, in the comparative example reaction system 200, when the temperature of the water in the water circulation path 14 (i.e., circulating water) falls below a first threshold (e.g., 70°C) during water electrolysis by the water electrolysis cell stack 12, the heater 220 is turned ON to raise the temperature of the water in the water circulation path 14. As a result, the temperature of the water in the water circulation path 14 gradually rises, and when the temperature of the water in the water circulation path 14 (i.e., circulating water) reaches a reference temperature (e.g., 80°C), the heater 220 is turned OFF. Furthermore, when the temperature of the water in the water circulation path 14 (i.e., circulating water) rises above a second threshold (e.g., 90°C) during water electrolysis by the water electrolysis cell stack 12, the chiller 212 is turned ON to lower the temperature of the water in the water circulation path 14. As a result, the temperature of the water in the water circulation path 14 gradually decreases, and when the temperature of the water in the water circulation path 14 (i.e., circulating water) reaches a reference temperature (e.g., 80°C), the chiller 212 is turned OFF.

[0082] In the comparative example reaction system 200, a heater 220 and a chiller 212 are required. Furthermore, the heater 220 and chiller 212 control the water temperature in the water circulation path 14, which increases power consumption.

[0083] In contrast, the reaction processing system 2 of the first embodiment does not require the installation of a heater and chiller, thus enabling cost reduction. Furthermore, in the reaction processing system 2, the control device 50 controls the current of the power supply unit 16 based on the temperature detected by the temperature sensor 30, thereby increasing or decreasing the waste heat from water electrolysis in the water electrolysis cell stack 12, and increasing or decreasing the reaction heat in the methane synthesis unit 40 in accordance with the increase or decrease in the amount of hydrogen produced in the water electrolysis cell stack 12. This controls the temperature of the water circulating in the water circulation path 14. For this reason, the reaction processing system 2 can reduce power consumption compared to the case where the temperature of the water in the water circulation path 14 is controlled by a heater and chiller.

[0084] 〔supplementary explanation〕 In the reaction processing system 2 of the first embodiment, the configuration of each part of the water electrolysis system 10 and the methane synthesis apparatus 40 may be changed, or other equipment may be added, without departing from the spirit of the present disclosure.

[0085] Furthermore, in the above description, a methane synthesis apparatus for synthesizing methane was used as an example of a synthetic compound manufacturing apparatus, and the Sabatier reaction was used as an example of the reaction. The technology relating to this disclosure is not limited to methane synthesis or the Sabatier reaction, but can also be applied to other technologies for reacting carbon dioxide and hydrogen. For example, it can be applied to reactions that produce carbon monoxide and water from carbon dioxide and hydrogen (reverse shift reaction), reactions that produce methanol, reactions that produce ethylene, and synthetic compound manufacturing apparatuses equipped with these reactors.

[0086] Furthermore, for example, the technology relating to this disclosure may also be applied to reactions that produce other carbon compounds, and to synthetic compound manufacturing apparatuses equipped with these reaction facilities. For example, it may also be applied to reactions that produce e-fuel represented by (CH2)n and water, and to synthetic compound manufacturing apparatuses equipped with these reaction facilities.

[0087] Although embodiments of this disclosure have been described with reference to specific examples, these embodiments are merely examples and can be modified in various ways without departing from the spirit of the disclosure. Furthermore, it goes without saying that the scope of rights of this disclosure is not limited to these embodiments and can be implemented in various ways without departing from the spirit of the disclosure. [Explanation of symbols]

[0088] 2…Reaction processing system, 12…Water electrolysis cell stack, 14…Water circulation path, 16…Power supply unit, 18…Heat exchanger, 20…Gas-liquid separator (water separator), 22…Pump, 24…Water inlet, 30…Temperature sensor, 40…Methane synthesis apparatus (synthetic compound production apparatus), 50…Control device

Claims

1. A water electrolysis cell stack that generates hydrogen and oxygen through water electrolysis, A pump is provided, and a water circulation path is provided to circulate the water discharged from the water electrolysis cell stack and supply it to the water electrolysis cell stack. A power supply device that supplies current to the aforementioned water electrolysis cell stack, A heat exchanger provided in the water circulation path absorbs the reaction heat in a synthetic compound manufacturing apparatus that reacts carbon oxide with hydrogen produced in the water electrolysis cell stack to produce a synthetic compound, A temperature sensor is provided on the downstream side of the heat exchanger and upstream side of the water electrolysis cell stack in the water flow direction of the water circulation path to detect the temperature of the water flowing through the water circulation path. A control device that controls the temperature of the water circulating through the water circulation path by controlling the current of the power supply device based on the temperature detected by the temperature sensor, thereby increasing or decreasing the waste heat from water electrolysis in the water electrolysis cell stack, and increasing or decreasing the reaction heat in the synthetic compound production apparatus in response to an increase or decrease in the amount of hydrogen produced in the water electrolysis cell stack, thereby raising or lowering the temperature of the water. A reaction processing system having the following characteristics.

2. The reaction processing system according to claim 1, wherein the control device, when the temperature detected by the temperature sensor falls below a first threshold, increases the current of the power supply, increases the waste heat from water electrolysis in the water electrolysis cell stack, and increases the reaction heat in the synthetic compound production apparatus due to the increase in the amount of hydrogen produced by the water electrolysis cell stack, thereby raising the temperature of the water circulating in the water circulation path.

3. The reaction processing system according to claim 1, wherein the control device, when the temperature detected by the temperature sensor rises to a second threshold, reduces the current of the power supply, thereby reducing the waste heat from water electrolysis in the water electrolysis cell stack and reducing the reaction heat in the synthetic compound production apparatus due to the decrease in the amount of hydrogen produced in the water electrolysis cell stack, thereby lowering the temperature of the water circulating in the water circulation path.

4. The reaction processing system according to claim 1, wherein the water circulation path is provided with a water separator for separating the water discharged from the water electrolysis cell stack from the gas, and a water introduction section for introducing new water.

5. The reaction processing system according to claim 4, wherein the water separator and the water introduction section are provided downstream of the water electrolysis cell stack in the water flow direction of the water circulation path and upstream of the heat exchanger.

6. The reaction processing system according to claim 1, wherein the power supply device is provided with a predetermined voltage upper limit.

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