Electrolytic system

Abstract

This invention provides an electrolysis system. The electrolysis system (10) includes an oxygen-consuming device (44), a valve device (46), and a control device (58), wherein the oxygen-consuming device uses hydrogen to consume oxygen in the exhaust gas; the valve device is capable of switching the supply destination of hydrogen-containing gas output from a solid oxide electrolytic reactor (18) to either the oxygen-consuming device (44) or the generating device (20); the control device controls the valve device according to the oxygen concentration in the exhaust gas output from the oxygen-consuming device (44), thereby switching the supply destination of the hydrogen-containing gas. Accordingly, it is possible to suppress oxygen from reaching the generating device.

Description

Technical Field

[0001] This invention relates to an electrolysis system having a solid oxide type electrolytic reactor. Background Technology

[0002] Japanese Patent Publication No. 2012-236123 discloses a system having a stack and a methanation reactor, wherein the stack has a solid oxide fuel cell cell. The methanation reactor reacts carbon dioxide and hydrogen in exhaust gas discharged from the fuel electrode of the solid oxide fuel cell cell to convert it into methane. The exhaust gas from the methanation reactor is then supplied to the fuel electrode of the solid oxide fuel cell cell. Summary of the Invention

[0003] Additionally, waste gas from biomass-containing devices (biogas), or waste gas from power plants or iron smelters, is sometimes used as a source of carbon dioxide emissions for solid oxide fuel cell units. However, these waste gases sometimes contain oxygen. In this case, the oxygen in the waste gas may reach the catalyst used in the methanation reactor via the solid oxide fuel cell unit. When oxygen reaches the catalyst in the methanation reactor, there is a problem of catalyst degradation due to oxidation.

[0004] The purpose of this invention is to solve the above-mentioned technical problems.

[0005] One aspect of the present invention is an electrolysis system comprising a solid oxide electrolytic reactor and a generating device, wherein the solid oxide electrolytic reactor electrolyzes carbon dioxide gas and water vapor; the generating device generates hydrocarbons from hydrogen-containing gas, wherein the hydrogen-containing gas contains hydrogen gas generated by the electrolysis of the solid oxide electrolytic reactor; the electrolysis system includes an oxygen-consuming device, an exhaust gas path, a hydrogen-containing gas path, a hydrogen-containing gas branch path, an oxygen concentration sensor, a valve device, and a control device; wherein the oxygen-consuming device uses hydrogen to consume oxygen in the exhaust gas containing the carbon dioxide gas; the exhaust gas path is used to improve the purity of the carbon dioxide gas by consuming oxygen. Exhaust gas is supplied from the oxygen-consuming device to the solid oxide electrolytic reactor; the hydrogen-containing gas path is used to supply the hydrogen-containing gas from the solid oxide electrolytic reactor to the generating device; the hydrogen-containing gas branch path branches off from the hydrogen-containing gas path and connects to the oxygen-consuming device; the oxygen concentration sensor detects the oxygen concentration in the exhaust gas output from the oxygen-consuming device; the valve device can switch the supply destination of the hydrogen-containing gas output from the solid oxide electrolytic reactor to either the oxygen-consuming device or the generating device; the control device controls the valve device according to the oxygen concentration, thereby switching the supply destination of the hydrogen-containing gas.

[0006] Another aspect of the present invention is an electrolysis system comprising a solid oxide electrolytic reactor and a generating device, wherein the solid oxide electrolytic reactor electrolyzes carbon dioxide gas and water vapor; the generating device generates hydrocarbons from hydrogen-containing gas, wherein the hydrogen-containing gas contains hydrogen gas generated by the electrolysis of the solid oxide electrolytic reactor; the electrolysis system comprises an oxygen-consuming device, an exhaust gas path, an exhaust gas branch path, an oxygen concentration sensor, a valve device, a storage tank, and a control device; wherein the oxygen-consuming device uses hydrogen to consume oxygen in the exhaust gas containing the carbon dioxide gas; the exhaust gas path is used to supply the exhaust gas from the oxygen-consuming device to... The solid oxide electrolytic reactor; the exhaust gas branch path branches off from the exhaust gas path and connects to the oxygen-consuming device; the oxygen concentration sensor detects the oxygen concentration in the exhaust gas output from the oxygen-consuming device; the valve device is capable of switching the supply destination of the exhaust gas output from the oxygen-consuming device to the oxygen-consuming device or the solid oxide electrolytic reactor; the storage tank is capable of storing the hydrogen supplied to the oxygen-consuming device; the control device controls the valve device according to the oxygen concentration to switch the supply destination of the exhaust gas to the oxygen-consuming device, and opens the switch valve that opens and closes the outlet of the storage tank.

[0007] According to the method described above, oxygen can be suppressed from reaching the generating device. As a result, the degradation of the catalyst used in the generating device can be reduced.

[0008] The above-described objectives, features, and advantages should be readily understood from the following description of the embodiments with reference to the accompanying drawings. Attached Figure Description

[0009] Figure 1 This is a schematic diagram showing the structure of the electrolysis system according to the first embodiment.

[0010] Figure 2 This is a flowchart representing the steps of the first control process.

[0011] Figure 3 This is a flowchart representing the steps of the second control process.

[0012] Figure 4 This is a flowchart representing the first control process step of the modified example.

[0013] Figure 5 This is a flowchart illustrating the steps of the second control process in the modified example.

[0014] Figure 6 This is a schematic diagram showing the structure of the electrolysis system according to the second embodiment.

[0015] Figure 7This is a schematic diagram showing the structure of the electrolysis system according to the third embodiment.

[0016] Figure 8 This is a flowchart representing the steps of the third control process. Detailed Implementation

[0017] [First Embodiment]

[0018] Figure 1 This is a schematic diagram showing the structure of the electrolysis system 10 according to the first embodiment. The electrolysis system 10 includes a steam generator 16, a solid oxide type electrolytic reactor 18, a generation device 20, a first heat exchanger 22, a first dehumidifier 24, a second heat exchanger 26, and a second dehumidifier 28.

[0019] Steam generator 16 heats water supplied from a water source to generate steam. The water source can be a water supply device or a storage tank. Alternatively, the water source can be a factory facility that discharges waste gas containing moisture. When the water source is a factory facility, steam generator 16 can extract steam from waste gas discharged from factory facilities such as power plants or ironworks. In this case, energy savings can be achieved compared to generating steam from a water supply device. Steam generator 16 outputs the steam generated by heating water to steam path 30.

[0020] Steam path 30 is a flow path for supplying steam from steam generator 16 to exhaust gas path 34. Steam path 30 passes sequentially through first heat exchanger 22 and heater 32. The steam output to steam path 30 is heated by first heat exchanger 22 and heater 32 and flows into exhaust gas path 34.

[0021] Heater 32 is used to heat the solid oxide reactor 18 and is positioned near the solid oxide reactor 18. Exhaust gas path 34 is a flow path for supplying exhaust gas containing carbon dioxide from a carbon dioxide discharge source to the solid oxide reactor 18. The carbon dioxide gas output to exhaust gas path 34 flows into the solid oxide reactor 18 together with water vapor supplied from steam path 30.

[0022] Carbon dioxide emission sources can be extraction devices that extract carbon dioxide gas from the atmosphere, storage tanks that store carbon dioxide gas, or factory equipment that can recover and release carbon dioxide gas. When the carbon dioxide emission source is factory equipment, it is the same as the equipment used in factories that produce water.

[0023] The solid oxide electrolyzer 18 electrolyzes carbon dioxide gas. In this embodiment, the solid oxide electrolyzer 18 co-electrolyzes carbon dioxide gas and water vapor. The solid oxide electrolyzer 18 has multiple individual cells. Each individual cell has a membrane electrode assembly (MEA) in which an electrolytic membrane is sandwiched between an anode electrode and a cathode electrode.

[0024] The solid oxide reactor 18 is heated to a predetermined temperature above which is the temperature at which electrolysis is possible. In this embodiment, the solid oxide reactor 18 is heated by a heater 32. The temperature of the solid oxide reactor 18 is detected by a temperature sensor 35. The temperature sensor 35 is provided at a location on the solid oxide reactor 18 that reflects the representative temperature of the solid oxide reactor 18. For example, the temperature sensor 35 is provided at the outlet portion of the solid oxide reactor 18.

[0025] The solid oxide electrolyzer 18 supplies externally supplied electricity between the anode and cathode electrodes of each individual cell, and supplies carbon dioxide gas and water vapor to the cathode electrode of each individual cell. As the temperature of the solid oxide electrolyzer 18 rises, the electrolysis of carbon dioxide gas and water vapor begins in each individual cell. When the electrolysis of carbon dioxide gas and water vapor begins, carbon monoxide and hydrogen are generated at the cathode electrode, and oxygen is generated at the anode electrode.

[0026] The solid oxide electrolyzer 18 collects oxygen generated by each individual cell and outputs this oxygen to oxygen path 36. Oxygen path 36 is a flow path for supplying oxygen from the solid oxide electrolyzer 18 to an oxygen-demanding device. The oxygen-demanding device can be a storage tank. As described above, if the carbon dioxide emission source is a plant facility, that plant facility can be the oxygen-demanding device. The oxygen output to oxygen path 36 flows into the oxygen-demanding device.

[0027] The solid oxide electrolyzer 18 collects hydrogen-containing gas containing hydrogen generated by each individual cell and outputs this hydrogen-containing gas to the hydrogen-containing gas path 38. The hydrogen-containing gas contains carbon monoxide gas generated by each individual cell and unelectrolyzed water vapor.

[0028] Hydrogen-containing gas path 38 is a flow path for supplying hydrogen-containing gas from the solid oxide electrolytic reactor 18 to the generating unit 20. Hydrogen-containing gas path 38 sequentially passes through a first heat exchanger 22, a first dehumidifier 24, and a second heat exchanger 26. The hydrogen-containing gas output to hydrogen-containing gas path 38 is cooled by the first heat exchanger 22. The water vapor contained in the cooled hydrogen-containing gas is dehumidified by the first dehumidifier 24. The hydrogen-containing gas after the water vapor is removed is heated by the second heat exchanger 26 and flows into the generating unit 20.

[0029] The generating unit 20 produces hydrocarbons from carbon monoxide and hydrogen contained in hydrogen-containing gas via a catalytic reaction. The generating unit 20 can utilize the Fischer-Tropsch process to produce hydrocarbons. The generating unit 20 outputs the hydrocarbons produced by the catalytic reaction to hydrocarbon pathway 40.

[0030] Hydrocarbon path 40 is a flow path for supplying hydrocarbons from generating unit 20 to hydrocarbon-consuming unit. The hydrocarbon-consuming unit can be a storage tank. Hydrocarbon path 40 passes sequentially through a second heat exchanger 26 and a second dehumidifier 28. The hydrocarbons output to hydrocarbon path 40 are cooled by the second heat exchanger 26. The moisture generated by this cooling is dehumidified by the second dehumidifier 28. The dehumidified hydrocarbons then flow into the hydrocarbon-consuming unit.

[0031] The electrolysis system 10 of this embodiment also includes an oxygen consumption mechanism 42. The oxygen consumption mechanism 42 is a mechanism for consuming oxygen in the waste gas discharged from the carbon dioxide emission source. The oxygen consumption mechanism 42 includes an oxygen consumption device 44, a valve device 46, a carbon monoxide removal device 48, a storage tank 50, a second valve device 52, a booster pump 54, an oxygen concentration sensor 56, and a control device 58.

[0032] An oxygen-consuming device 44 is installed on the exhaust gas path 34. The oxygen-consuming device 44 uses hydrogen to consume the oxygen in the exhaust gas. The exhaust gas, with its carbon dioxide purity increased by oxygen consumption, is supplied from the oxygen-consuming device 44 to the solid oxide reactor 18 via the exhaust gas path 34. As the exhaust gas with increased carbon dioxide purity, it contains water vapor and carbon dioxide generated by the combustion of oxygen and hydrogen.

[0033] The oxygen-consuming device 44 may also include a catalyst for reacting oxygen with hydrogen to produce water. In this case, the oxygen-consuming device 44 heats the catalyst and oxidizes and decomposes impurities in the exhaust gas using the heated catalyst. In this oxidation and decomposition process, oxygen is consumed by reacting with hydrogen to convert it into water. Furthermore, examples of oxygen-consuming devices 44 with a catalyst include catalyst combustion heaters. Additionally, examples of catalysts include palladium catalysts. The water generated in the oxygen-consuming device 44 can be supplied to the steam generator 16. In this case, water used by the steam generator 16 can be saved.

[0034] The hydrogen-containing gas branch path 60 is connected to the oxygen-consuming device 44. The hydrogen-containing gas branch path 60 branches off from the hydrogen-containing gas path 38 between the solid oxide electrolytic reactor 18 and the first heat exchanger 22, and is connected to the oxygen-consuming device 44.

[0035] The valve device 46 is configured to switch the supply destination of hydrogen-containing gas output from the solid oxide electrolyzer 18 to either the oxygen-consuming device 44 or the generating device 20. The valve device 46 may consist of a three-way valve or two on / off valves.

[0036] When the valve device 46 is composed of a three-way valve, the three-way valve is located at the junction of the hydrogen-containing gas path 38 and the hydrogen-containing gas branch path 60 (first contact point). When the valve device 46 is composed of two switching valves, one of the two switching valves is located in the hydrogen-containing gas path 38 between the first contact point and the first heat exchanger 22. The other of the two switching valves is located in the hydrogen-containing gas branch path 60 near the first contact point. In this embodiment, the valve device 46 is composed of a three-way valve (see reference...). Figure 1 ).

[0037] A carbon monoxide removal device 48 is disposed on a hydrogen-containing gas branch path 60. The carbon monoxide removal device 48 removes carbon monoxide by oxidizing it to carbon dioxide. The carbon monoxide removal device 48 may use a catalyst to oxidize the carbon monoxide.

[0038] Furthermore, the carbon monoxide removal device 48 is not an essential component. If the oxygen-consuming device 44 does not have a catalyst, or if the catalyst in the oxygen-consuming device 44 has properties that are not easily degraded by carbon monoxide (resistance), the carbon monoxide removal device 48 can be omitted. Examples of catalysts with properties that are not easily degraded by carbon monoxide include palladium catalysts.

[0039] Storage tank 50 is a container capable of storing hydrogen supplied to oxygen-consuming device 44. The hydrogen stored in storage tank 50 is either hydrogen gas filled by a filling device or hydrogen-containing gas supplied from hydrogen-containing gas branch path 60. Storage tank 50 is located on bypass path 62.

[0040] The bypass path 62 branches off from the hydrogen-containing gas branch path 60 between the carbon monoxide removal device 48 and the oxygen-consuming device 44, passes through the storage tank 50, and merges with the hydrogen-containing gas branch path 60. The portion where the bypass path 62 merges with the hydrogen-containing gas branch path 60 is downstream of the portion where the bypass path 62 branches off from the hydrogen-containing gas branch path 60. Furthermore, if the carbon monoxide removal device 48 is removed, the bypass path 62 can branch off from any position within the hydrogen-containing gas branch path 60.

[0041] A switch valve 66 is installed at the outlet 64 of the storage tank 50, and a pressure sensor 68 is installed inside the storage tank 50. The pressure sensor 68 detects the pressure inside the storage tank 50.

[0042] The second valve device 52 is configured to switch the supply destination of hydrogen-containing gas supplied from the hydrogen-containing gas path 38 to either the oxygen-consuming device 44 or the storage tank 50. The second valve device 52 may consist of a three-way valve or two on / off valves.

[0043] When the second valve device 52 is composed of a three-way valve, the three-way valve is located at the junction of the hydrogen-containing gas branch path 60 and the bypass path 62 (the second contact point). When the second valve device 52 is composed of two switching valves, one of the two switching valves is located at the position of the hydrogen-containing gas branch path 60 between the second contact point and the oxygen-consuming device 44. The other of the two switching valves is located at the position of the bypass path 62 near the second contact point. In this embodiment, the second valve device 52 is composed of a three-way valve (see reference...). Figure 1 ).

[0044] The booster pump 54 pressurizes the hydrogen-containing gas supplied from the hydrogen-containing gas branch path 60 and supplies the pressurized hydrogen-containing gas to the storage tank 50. However, the booster pump 54 is not an essential component. That is, the booster pump 54 can be omitted. In this case, the hydrogen-containing gas supplied from the hydrogen-containing gas branch path 60 flows into the storage tank 50 without being pressurized.

[0045] The oxygen concentration sensor 56 is a sensor that detects the oxygen concentration in the exhaust gas output from the oxygen-consuming device 44. The oxygen concentration sensor 56 is installed in the exhaust gas path 34 near the outlet of the oxygen-consuming device 44.

[0046] The control device 58 controls the valve device 46, the second valve device 52, and the switching valve 66 based on the temperature detected by the temperature sensor 35, the oxygen concentration detected by the oxygen concentration sensor 56, and the pressure detected by the pressure sensor 68.

[0047] When the solid oxide electrolytic reactor 18 is started, the control device 58 performs the first control process. Figure 2 This is a flowchart illustrating the steps of the first control process. The first control process begins when an instruction to start the solid oxide electrolytic reactor 18 is received.

[0048] In step S1, the control device 58 causes the oxygen concentration sensor 56 to start measuring. When the oxygen concentration sensor 56 starts measuring, the first control process transfers to step S2.

[0049] In step S2, the control device 58 compares the oxygen concentration detected by the oxygen concentration sensor 56 with a predetermined concentration threshold. If the oxygen concentration is greater than the concentration threshold (step S2: No), the first control process proceeds to step S3.

[0050] In step S3, the control device 58 opens the switch valve 66 of the storage tank 50, supplying the hydrogen (hydrogen gas or hydrogen-containing gas) stored in the storage tank 50 to the oxygen-consuming device 44 via the hydrogen-containing gas branch path 60. When the switch valve 66 of the storage tank 50 is opened, the first control process proceeds to step S4.

[0051] In step S4, control device 58 controls valve device 46 to switch the supply destination of hydrogen-containing gas from solid oxide reactor 18 to oxygen-consuming device 44. Additionally, control device 58 controls second valve device 52 to switch the supply destination of hydrogen-containing gas supplied to hydrogen-containing gas branch path 60 to oxygen-consuming device 44. Thus, hydrogen-containing gas from solid oxide reactor 18 is supplied to oxygen-consuming device 44 via hydrogen-containing gas branch path 60. Therefore, oxygen reaching generation device 20 can be suppressed. When the supply destination of hydrogen-containing gas is switched to oxygen-consuming device 44, the first control process returns to step S2.

[0052] In step S2, if the oxygen concentration is below the concentration threshold (step S2: yes), the first control process is transferred to step S5.

[0053] In step S5, the control device 58 closes the switch valve 66 of the storage tank 50, stopping the supply of hydrogen (hydrogen or hydrogen-containing gas) to the oxygen-consuming device 44. When the switch valve 66 of the storage tank 50 is closed, the first control process proceeds to step S6.

[0054] In step S6, control device 58 controls valve device 46 to switch the supply destination of hydrogen-containing gas from solid oxide reactor 18 to generation device 20. As a result, hydrogen-containing gas from solid oxide reactor 18 is supplied to generation device 20 via hydrogen-containing gas path 38. Consequently, hydrocarbon generation begins in generation device 20. When the supply destination of hydrogen-containing gas is switched to generation device 20, control device 58 terminates the measurement performed by oxygen concentration sensor 56. Afterwards, the first control process ends.

[0055] After completing the first control process, the control device 58 executes the second control process. Figure 3 This is a flowchart illustrating the steps of the second control process. The second control process is repeatedly executed at predetermined intervals until an instruction to stop the solid oxide electrolyzer 18 is received.

[0056] In step S11, the control device 58 causes the oxygen concentration sensor 56 to start measuring. When the oxygen concentration sensor 56 starts measuring, the second control process transfers to step S12.

[0057] In step S12, the control device 58 compares the oxygen concentration detected by the oxygen concentration sensor 56 with a predetermined concentration threshold. If the oxygen concentration is greater than the concentration threshold (step S12: No), the second control process proceeds to step S13.

[0058] In step S13, control device 58 controls valve device 46 to switch the supply destination of hydrogen-containing gas from solid oxide reactor 18 to oxygen-consuming device 44. Additionally, control device 58 controls second valve device 52 to switch the supply destination of hydrogen-containing gas supplied to hydrogen-containing gas branch path 60 to oxygen-consuming device 44. Thus, hydrogen-containing gas from solid oxide reactor 18 is supplied to oxygen-consuming device 44 via hydrogen-containing gas branch path 60. In this case, hydrocarbon generation by generation device 20 is interrupted. Furthermore, oxygen reaching generation device 20 is suppressed. When the supply destination of hydrogen-containing gas is switched to oxygen-consuming device 44, the second control process returns to step S12.

[0059] In step S12, if the oxygen concentration is below the concentration threshold (step S12: yes), the second control process is transferred to step S14.

[0060] In step S14, the control device 58 compares the pressure of the storage tank 50 detected by the pressure sensor 68 with a predetermined pressure threshold. If the pressure of the storage tank 50 is below the pressure threshold (step S14: No), the control device 58 determines that hydrogen needs to be added to the storage tank 50. In this case, the second control process proceeds to step S15.

[0061] In step S15, control device 58 controls valve device 46 to switch the supply destination of hydrogen-containing gas output from solid oxide reactor 18 to oxygen-consuming device 44. Additionally, control device 58 controls second valve device 52 to switch the supply destination of hydrogen-containing gas supplied to hydrogen-containing gas branch path 60 to storage tank 50. When the supply destination of hydrogen-containing gas is switched to storage tank 50, the second control process returns to step S14.

[0062] Furthermore, when the hydrogen-containing gas supply destination is switched to storage tank 50, the hydrogen-containing gas output from the solid oxide reactor 18 is replenished to storage tank 50 via hydrogen-containing gas branch path 60 and bypass path 62. The hydrogen-containing gas replenished to storage tank 50 is then utilized in oxygen-consuming device 44. Thus, in this embodiment, the hydrogen-containing gas generated by the solid oxide reactor 18 can be utilized in oxygen-consuming device 44. As a result, efficient hydrogen utilization can be achieved.

[0063] Hydrogen stored in tank 50 has a tendency to leak to the outside. Therefore, even if the hydrogen stored in tank 50 is not supplied to oxygen-consuming device 44, the amount of hydrogen stored in tank 50 may sometimes decrease. In this embodiment, the hydrogen-containing gas generated by solid oxide reactor 18 is automatically replenished to tank 50, thus achieving efficient hydrogen replenishment.

[0064] In step S14, if the pressure in storage tank 50 is greater than the pressure threshold (step S14: Yes), the control device 58 determines that it is not necessary to replenish hydrogen to storage tank 50. In this case, the second control process proceeds to step S16.

[0065] In step S16, control device 58 controls valve device 46 to switch the supply destination of hydrogen-containing gas from solid oxide reactor 18 to generation device 20. As a result, hydrogen-containing gas from solid oxide reactor 18 is supplied to generation device 20 via hydrogen-containing gas path 38. Consequently, hydrocarbon generation by generation device 20 restarts. When the supply destination of hydrogen-containing gas is switched to generation device 20, control device 58 terminates the measurement performed by oxygen concentration sensor 56. Afterwards, the second control process ends.

[0066] As described above, in the first embodiment, when the oxygen concentration exceeds a concentration threshold, the control device 58 switches the supply destination of the hydrogen-containing gas output from the solid oxide reactor 18 to the oxygen-consuming device 44. This suppresses the arrival of oxygen in the generating device 20, thereby reducing the degradation of the catalyst used in the generating device 20.

[0067] The first embodiment described above can be modified as follows.

[0068] Control device 58 can control the exhaust gas switching valve 70 based on the pressure detected by pressure sensor 68. Figure 1 The exhaust gas switching valve 70 is located in the exhaust gas path 34 between the carbon dioxide emission source and the oxygen consumption device 44. The exhaust gas switching valve 70 can be switched on and off by the reactor control device. The reactor control device is a device for controlling the solid oxide electrolytic reactor 18.

[0069] Figure 4 This is a flowchart illustrating the steps of the first control process in the modified example. Figure 4 In this variation, the same reference numerals are used for steps that are identical to those described in the first embodiment. Furthermore, in this variation, descriptions that are repeated in the first embodiment are omitted. In the first control process of this variation, steps S21, S22, and S23 are newly added.

[0070] When an instruction to start the solid oxide electrolytic reactor 18 is received, the first control process of this variant is transferred to step S21.

[0071] In step S21, the control device 58 compares the pressure of the storage tank 50 detected by the pressure sensor 68 with a predetermined pressure threshold. If the pressure of the storage tank 50 is below the pressure threshold (step S21: No), the control device 58 determines that hydrogen needs to be added to the storage tank 50. In this case, the first control process proceeds to step S22.

[0072] In step S22, the control device 58 closes the exhaust gas switching valve 70. This prevents oxygen from reaching the generation unit 20 via the solid oxide reactor 18. Furthermore, the control device 58 can also output a stop command to the reactor control device to stop the solid oxide reactor 18. Additionally, the control device 58 can control at least one of the display device, speaker, and light-emitting device to issue a warning indicating that the hydrogen remaining in the storage tank 50 is low. This eliminates the possibility of insufficient hydrogen in the storage tank 50 when the solid oxide reactor 18 is started.

[0073] On the other hand, if the pressure is greater than the pressure threshold (step S21: Yes), the control device 58 determines that it is not necessary to replenish hydrogen to the storage tank 50. In this case, the first control process proceeds to step S23.

[0074] In step S23, the control device 58 opens the exhaust gas switching valve 70 to supply exhaust gas to the oxygen-consuming device 44. When the exhaust gas switching valve 70 is opened, the first control process transfers to step S1.

[0075] Figure 5 This is a flowchart illustrating the steps of the second control process in the modified example. Figure 5 In this variation, the same reference numerals are used for steps that are identical to those described in the first embodiment. Furthermore, in this variation, descriptions that are repeated in the first embodiment are omitted. In the second control process of this variation, steps S31, S32, and S33 are newly added. The second control process of this variation shifts from step S13 to step S31 as described above.

[0076] In step S31, the control device 58 compares the pressure detected by the pressure sensor 68 with a predetermined pressure threshold. If the pressure in the storage tank 50 is greater than the pressure threshold (step S31: Yes), the second control process returns to step S12. Conversely, if the pressure in the storage tank 50 is less than the pressure threshold (step S31: No), the second control process proceeds to step S32.

[0077] In step S32, the control device 58 closes the exhaust gas switching valve 70. This prevents oxygen from reaching the generation device 20 via the solid oxide reactor 18. When the exhaust gas switching valve 70 is closed, the second control process proceeds to step S33.

[0078] In step S33, the control device 58 outputs a stop command to the reactor control device, causing the solid oxide electrolytic reactor 18 to stop. This prevents oxygen from reaching the generation device 20 via the solid oxide electrolytic reactor 18. Furthermore, unnecessary operation of the solid oxide electrolytic reactor 18 can be avoided.

[0079] [Second Implementation]

[0080] Figure 6 This is a schematic diagram showing the structure of the electrolysis system 10 according to the second embodiment. Figure 6 In this embodiment, the same reference numerals are used to denote the same constituent elements as those described in the first embodiment. Furthermore, descriptions that are repeated in the first embodiment are omitted in this embodiment.

[0081] In the electrolysis system 10 of this embodiment, the components of the oxygen consumption mechanism 42 are different from those of the first embodiment. The oxygen consumption mechanism 42 of this embodiment includes an oxygen-consuming device 44, a storage tank 50, an oxygen concentration sensor 56, a control device 58, a circulation pump 72, and a valve device 74.

[0082] A recirculation pump 72 is installed in the exhaust gas branch path 76. The exhaust gas branch path 76 branches off from the exhaust gas path 34 and connects to the oxygen-consuming device 44. The recirculation pump 72 pressurizes the exhaust gas supplied from the exhaust gas path 34 to the exhaust gas branch path 76 and returns it to the oxygen-consuming device 44. However, the recirculation pump 72 is not a necessary component. That is, the recirculation pump 72 can be removed. In this case, the exhaust gas supplied from the exhaust gas path 34 to the exhaust gas branch path 76 returns to the oxygen-consuming device 44 without being pressurized.

[0083] The valve device 74 is configured to switch the destination of the exhaust gas output from the oxygen-consuming device 44 to either the oxygen-consuming device 44 or the solid oxide electrolytic reactor 18. The valve device 74 may consist of a three-way valve or two on / off valves.

[0084] When the valve device 74 is a three-way valve, it is located at the junction of the exhaust gas path 34 and the exhaust gas branch path 76 (the third contact). When the valve device 74 is composed of two switching valves, one of the two switching valves is located in the exhaust gas path 34 between the third contact and the solid oxide reactor 18. The other of the two switching valves is located in the exhaust gas branch path 76 near the third contact. In this embodiment, the valve device 74 is composed of a three-way valve (see reference). Figure 6 ).

[0085] Valve device 74 is controlled by control device 58. When the oxygen concentration detected by oxygen concentration sensor 56 exceeds a predetermined concentration threshold, control device 58 controls valve device 74 to switch the exhaust gas supply destination to oxygen-consuming device 44. In this case, control device 58 opens the switch valve 66 of storage tank 50 to supply hydrogen to oxygen-consuming device 44. As a result, oxygen in the exhaust gas can be consumed in oxygen-consuming device 44, thereby obtaining exhaust gas with improved carbon dioxide purity.

[0086] Furthermore, when the oxygen concentration is greater than the concentration threshold, the control device 58 maintains the state of switching the exhaust gas supply destination to the oxygen-consuming device 44 until the oxygen concentration falls below the concentration threshold. Therefore, the exhaust gas circulates in the oxygen-consuming device 44. Thus, the purity of carbon dioxide can be reliably improved.

[0087] If the oxygen concentration detected by oxygen concentration sensor 56 is below a predetermined concentration threshold, control device 58 controls valve device 74 to switch the exhaust gas supply destination to solid oxide reactor 18. In this case, control device 58 closes the on / off valve 66 of storage tank 50. Therefore, exhaust gas with high carbon dioxide purity is supplied to solid oxide reactor 18.

[0088] Thus, in this embodiment, similar to the first embodiment, oxygen can be suppressed from reaching the generating device 20, thereby reducing the degradation of the catalyst used in the generating device 20.

[0089] Furthermore, this embodiment can be combined with the first embodiment. In this case, the oxygen consumption mechanism 42 of the first embodiment ( Figure 1 It has a valve device 74 as a third valve device. In addition, the oxygen consumption mechanism 42 of the first embodiment has an exhaust gas branch path 76.

[0090] [Third Implementation]

[0091] When the power supply to the electrolysis system 10 is cut off due to a power outage or other reasons, the operation of the solid oxide reactor 18 stops, and the temperature of the solid oxide reactor 18 begins to drop. In this situation, there is a tendency for the solid oxide reactor 18 to become under negative pressure due to the condensation of water vapor remaining inside the solid oxide reactor 18. When the solid oxide reactor 18 becomes under negative pressure, air flows into the solid oxide reactor 18, increasing the oxygen partial pressure inside. Therefore, the fuel electrodes (anode electrodes) of the high-temperature solid oxide reactor 18 are prone to oxidation. When the fuel electrodes (anode electrodes) are oxidized, MEA (Mechanical Engineering Area) deterioration occurs, such as reduced catalyst performance and internal cracks.

[0092] As a third embodiment, an embodiment for suppressing the increase of oxygen partial pressure inside the solid oxide type electrolytic reactor 18 will be described when the power supplied to the electrolysis system 10 is cut off. Figure 7 This is a schematic diagram showing the structure of the electrolysis system 10 according to the third embodiment. Figure 7 The diagram shows components common to both the first and second embodiments. This embodiment can be applied to both the first and second embodiments. In the electrolysis system 10 of this embodiment, a temperature sensor 82 and multiple sealing valves 84 are newly provided.

[0093] Temperature sensor 82 is a sensor used to detect the temperature of the solid oxide electrolytic reactor 18. Temperature sensor 82 is, for example, installed at the outlet of the solid oxide electrolytic reactor 18 for connection to the hydrogen-containing gas path 38.

[0094] Multiple sealing valves 84 are used to seal the solid oxide reactor 18. One of the sealing valves 84 is located at the inlet of the solid oxide reactor 18, where it is connected to the exhaust gas path 34. Another sealing valve 84 is located at the outlet of the solid oxide reactor 18, where it is connected to the hydrogen-containing gas path 38. The remaining sealing valve 84 is located at the outlet of the solid oxide reactor 18, where it is connected to the oxygen path 36.

[0095] In the event that the power supply to the electrolysis system 10 is cut off due to a power outage or other reasons, the switch valve 66 of the storage tank 50 automatically opens without relying on the control device 58. Furthermore, in the event that the power supply to the electrolysis system 10 is cut off, the exhaust gas switch valve 70 automatically closes without relying on the control device 58. That is, the switch valve 66 is a normally open valve, and the exhaust gas switch valve 70 is a normally closed valve. When the power supply to the electrolysis system 10 is cut off and the switch valve 66 opens, the hydrogen stored in the storage tank 50 is supplied to the solid oxide reactor 18 via the oxygen-consuming device 44.

[0096] Furthermore, in the event that the power supply to the electrolysis system 10 is cut off, backup power is supplied to the control device 58 from a backup power source or the like. The control device 58 then performs the third control process based on the backup power. Figure 8 This is a flowchart illustrating the steps of the third control process. The third control process begins after the power supply to the electrolysis system 10 is cut off. When the third control process begins, the switching valve 66 opens, supplying hydrogen to the solid oxide reactor 18.

[0097] In step S41, the control device 58 compares the temperature of the solid oxide reactor 18 (reactor temperature) detected by the temperature sensor 82 with a predetermined temperature threshold. The temperature threshold is, for example, the atmospheric temperature. The atmospheric temperature can be preset in the control device 58, or it can be the temperature detected by an atmospheric temperature sensor. The atmospheric temperature sensor is positioned where the change in atmospheric temperature caused by the heat generated by the solid oxide reactor 18 is below a certain value.

[0098] If the stack temperature is below the temperature threshold (step S41: No), the third control process proceeds to step S44. On the other hand, if the stack temperature is above the temperature threshold (step S41: Yes), the third control process proceeds to step S42.

[0099] In step S42, the control device 58 measures the predetermined standby time. During the standby time, the switching valve 66 remains open, and hydrogen is continuously supplied to the solid oxide electrolytic reactor 18. When the predetermined standby time is reached, the third control process proceeds to step S43.

[0100] In step S43, the control device 58 compares the stack temperature with a predetermined temperature threshold. If the stack temperature is below the temperature threshold (step S43: Yes), the third control process proceeds to step S44. On the other hand, if the stack temperature is above the temperature threshold (step S43: No), the third control process proceeds to step S45.

[0101] In step S44, the control device 58 closes the switching valve 66. In this case, the control device 58 supplies reserve power to the switching valve 66. When the switching valve 66 is closed, the third control process ends.

[0102] In step S45, the control device 58 compares the pressure (tank pressure) detected by the pressure sensor 68 with a predetermined pressure threshold. If the tank pressure is greater than the pressure threshold (step S45: No), the third control process returns to step S42. On the other hand, if the tank pressure is below the pressure threshold (step S45: Yes), the third control process proceeds to step S46.

[0103] In step S46, the control device 58 closes all sealing valves 84 to seal the solid oxide electrolytic reactor 18. The third control process ends when all sealing valves 84 are closed.

[0104] In this embodiment, when the reactor temperature exceeds a temperature threshold during a power supply interruption, the control device 58 will not close the switching valve 66 until the reactor temperature falls below the temperature threshold. In this case, hydrogen is continuously supplied from the storage tank 50 to the solid oxide reactor 18. This suppresses the increase in oxygen partial pressure inside the solid oxide reactor 18, thereby suppressing the degradation of the MEA of the solid oxide reactor 18 due to oxidation at high temperatures.

[0105] Furthermore, in this embodiment, when the tank pressure is below a predetermined pressure threshold before the reactor temperature falls below the temperature threshold, the control device 58 closes each sealing valve 84 to seal the solid oxide reactor 18. Therefore, even if hydrogen cannot be supplied to the solid oxide reactor 18, the increase in the internal oxygen partial pressure of the solid oxide reactor 18 can be suppressed.

[0106] 〔invention〕

[0107] The inventions and effects that can be understood based on the above description are recorded below.

[0108] (1) The present invention is an electrolysis system (10) comprising a solid oxide type electrolytic reactor (18) and a generating device (20), wherein the solid oxide type electrolytic reactor electrolyzes carbon dioxide gas and water vapor; the generating device generates hydrocarbons from hydrogen-containing gas, wherein the hydrogen-containing gas contains hydrogen gas generated by electrolysis of the solid oxide type electrolytic reactor; the electrolysis system comprises an oxygen-consuming device (44), an exhaust gas path (34), a hydrogen-containing gas path (38), a hydrogen-containing gas branch path (60), an oxygen concentration sensor (56), a valve device (46), and a control device (58), wherein the oxygen-consuming device uses hydrogen to consume oxygen in the exhaust gas containing the carbon dioxide gas; the exhaust gas path is used to decompose the oxygen gas containing the carbon dioxide gas. The exhaust gas, after its purity is increased by consuming carbon dioxide, is supplied from the oxygen-consuming device to the solid oxide reactor; the hydrogen-containing gas path is used to supply the hydrogen-containing gas from the solid oxide reactor to the generating device; the hydrogen-containing gas branch path branches off from the hydrogen-containing gas path and connects to the oxygen-consuming device; the oxygen concentration sensor detects the oxygen concentration in the exhaust gas output from the oxygen-consuming device; the valve device can switch the supply destination of the hydrogen-containing gas output from the solid oxide reactor to either the oxygen-consuming device or the generating device; the control device controls the valve device according to the oxygen concentration, thereby switching the supply destination of the hydrogen-containing gas.

[0109] This allows oxygen to be suppressed from reaching the generating unit, thereby reducing the degradation of the catalyst used in the generating unit.

[0110] (2) In the electrolysis system of the present invention, when the oxygen concentration is greater than a predetermined concentration threshold, the control device controls the valve device to switch the supply destination of the hydrogen-containing gas to the oxygen-consuming device. Thus, only when the oxygen concentration in the waste gas is high is the oxygen in the waste gas consumed by the oxygen-consuming device.

[0111] (3) In the electrolysis system of the present invention, it may include: a storage tank (50) and a switching valve (66), wherein the storage tank is capable of storing the hydrogen supplied to the oxygen-consuming device; the switching valve is capable of opening and closing the outlet (64) of the storage tank, and when the solid oxide type electrolytic reactor is started, the control device opens the switching valve to supply the hydrogen stored in the storage tank to the oxygen-consuming device via the hydrogen-containing gas branch path. Thus, even if hydrogen is not sufficiently generated by the solid oxide type electrolytic reactor, the oxygen in the waste gas can be consumed by the oxygen-consuming device. As a result, the oxygen concentration in the waste gas can be reduced more quickly.

[0112] (4) In the electrolysis system of the present invention, the switching valve can be opened when the power supply to the electrolysis system is cut off, and the hydrogen stored in the storage tank can be supplied to the solid oxide reactor via the oxygen-consuming device. Therefore, when the power supply is cut off, the increase in the internal oxygen partial pressure of the solid oxide reactor can be suppressed. As a result, the degradation of the MEA of the solid oxide reactor due to oxidation at high temperatures can be suppressed.

[0113] (5) In the electrolysis system of the present invention, when the power supply to the electrolysis system is cut off, and the temperature of the solid oxide reactor is greater than a predetermined temperature threshold, the control device keeps the switching valve open and continues to supply hydrogen from the storage tank to the solid oxide reactor until the temperature is below the temperature threshold. This maintains and suppresses the degradation of the MEA of the solid oxide reactor caused by oxidation at high temperatures.

[0114] (6) In the electrolysis system of the present invention, it may have a plurality of sealing valves (84) for sealing the solid oxide electrolytic reactor. Before the temperature is below the temperature threshold, when the pressure of the storage tank is below a predetermined pressure threshold, the control device closes each of the sealing valves to seal the solid oxide electrolytic reactor. Thus, even if hydrogen cannot be supplied to the solid oxide electrolytic reactor, the increase in the internal oxygen partial pressure of the solid oxide electrolytic reactor can be suppressed.

[0115] (7) In the electrolysis system of the present invention, it may include: a bypass path (62), a pressure sensor (68), and a second valve device (52), wherein the bypass path branches off from the hydrogen-containing gas branch path and passes through the storage tank, merging with the hydrogen-containing gas branch path; the pressure sensor detects the pressure of the storage tank; the second valve device can switch the supply destination of the hydrogen-containing gas supplied from the hydrogen-containing gas path to either the oxygen-consuming device or the storage tank, and when the pressure is below a predetermined pressure threshold and the oxygen concentration is below a predetermined concentration threshold, the control device controls the second valve device to switch the supply destination of the hydrogen-containing gas to the storage tank. Thus, the hydrogen in the storage tank can be replenished by hydrogen-containing gas. Furthermore, the hydrogen-containing gas generated by the solid oxide reactor can be utilized in the oxygen-consuming device. As a result, efficient hydrogen utilization can be achieved.

[0116] (8) In the electrolysis system of the present invention, the oxygen-consuming device may have a catalyst, which is used to react the oxygen with hydrogen to produce water. Thus, oxygen can be consumed efficiently.

[0117] (9) In the electrolysis system of the present invention, it may have: an exhaust gas branch path (76) and a third valve device (74), wherein the exhaust gas branch path branches off from the exhaust gas path and is connected to the oxygen-consuming device; the third valve device is capable of switching the supply destination of the exhaust gas output from the oxygen-consuming device to either the oxygen-consuming device or the solid oxide electrolytic reactor; when the oxygen concentration is greater than a predetermined concentration threshold, the control device controls the third valve device to switch the supply destination of the exhaust gas to the oxygen-consuming device. Thus, the exhaust gas circulates in the oxygen-consuming device. Therefore, the purity of carbon dioxide can be reliably improved.

[0118] (10) The present invention is an electrolysis system (10) having a solid oxide type electrolytic reactor (18) and a generating device (20), wherein the solid oxide type electrolytic reactor electrolyzes carbon dioxide gas and water vapor; the generating device generates hydrocarbons from hydrogen-containing gas, wherein the hydrogen-containing gas contains hydrogen gas generated by electrolysis of the solid oxide type electrolytic reactor; the electrolysis system has an oxygen-consuming device (44), an exhaust gas path (34), an exhaust gas branch path (76), an oxygen concentration sensor (56), a valve device (74), a storage tank (50), and a control device (58), wherein the oxygen-consuming device uses hydrogen to consume oxygen in the exhaust gas containing the carbon dioxide gas; the exhaust gas path is used to... The exhaust gas is supplied from the oxygen-consuming device to the solid oxide electrolytic reactor; the exhaust gas branch path branches off from the exhaust gas path and connects to the oxygen-consuming device; the oxygen concentration sensor detects the oxygen concentration in the exhaust gas output from the oxygen-consuming device; the valve device can switch the supply destination of the exhaust gas output from the oxygen-consuming device to the oxygen-consuming device or the solid oxide electrolytic reactor; the storage tank can store the hydrogen supplied to the oxygen-consuming device; the control device controls the valve device according to the oxygen concentration to switch the supply destination of the exhaust gas to the oxygen-consuming device, and opens the switch valve (66) that opens and closes the outlet (64) of the storage tank.

[0119] This allows oxygen to be suppressed from reaching the generating unit, thereby reducing the degradation of the catalyst used in the generating unit.

[0120] Furthermore, the present invention is not limited to the above-described contents, and various structures can be adopted without departing from the spirit of the present invention.

Claims

1. An electrolysis system (10) having a solid oxide type electrolysis stack (18) and a generating device (20), wherein, The solid oxide electrolytic reactor electrolyzes carbon dioxide gas and water vapor; the generating device has a catalyst, through which hydrogen-containing gas is generated from hydrocarbons via a catalytic reaction, wherein the hydrogen-containing gas contains carbon monoxide and hydrogen generated by the electrolysis of the solid oxide electrolytic reactor, characterized in that... It includes an oxygen-consuming device (44), an exhaust gas path (34), a hydrogen-containing gas path (38), a hydrogen-containing gas branch path (60), an oxygen concentration sensor (56), a valve device (46), and a control device (58), wherein, The oxygen-consuming device uses hydrogen to consume the oxygen in the exhaust gas containing the carbon dioxide gas; The exhaust gas path is used to supply the exhaust gas, after the purity of the carbon dioxide gas has been increased by the consumption of oxygen, from the oxygen-consuming device to the solid oxide electrolytic reactor; The hydrogen-containing gas path is used to supply the hydrogen-containing gas from the solid oxide electrolytic reactor to the generating device; The hydrogen-containing gas branch path branches off from the hydrogen-containing gas path and is connected to the oxygen-consuming device; The oxygen concentration sensor detects the oxygen concentration in the exhaust gas output from the oxygen-consuming device. The valve device can switch the supply destination of the hydrogen-containing gas output from the solid oxide electrolyzer to either the oxygen-consuming device or the generating device. The control device controls the valve device according to the oxygen concentration, thereby switching the supply destination of the hydrogen-containing gas.

2. The electrolysis system according to claim 1, characterized in that, When the oxygen concentration is greater than a predetermined concentration threshold, the control device controls the valve device to switch the supply destination of the hydrogen-containing gas to the oxygen-consuming device.

3. The electrolysis system according to claim 2, characterized in that, It has a storage tank (50) and an on / off valve (66), wherein, The storage tank is capable of storing the hydrogen supplied to the oxygen-consuming device; The switching valve can open and close the outlet (64) of the storage tank. When the solid oxide electrolytic reactor is started, the control device opens the switching valve to supply the hydrogen stored in the tank to the oxygen-consuming device via the hydrogen-containing gas branch path.

4. The electrolysis system according to claim 3, characterized in that, When the power supply to the electrolysis system is cut off, the switching valve opens, supplying the hydrogen stored in the tank to the solid oxide reactor via the oxygen-consuming device.

5. The electrolysis system according to claim 3, characterized in that, When the power supply to the electrolysis system is cut off, and the temperature of the solid oxide electrolytic reactor is higher than a predetermined temperature threshold, the control device keeps the switching valve open and continues to supply hydrogen from the storage tank to the solid oxide electrolytic reactor until the temperature is below the temperature threshold.

6. The electrolysis system according to claim 5, characterized in that, It has multiple sealing valves (84) for sealing the solid oxide electrolytic reactor. Before the temperature is below the temperature threshold, when the pressure of the storage tank is below the specified pressure threshold, the control device closes each of the sealing valves to seal the solid oxide electrolytic reactor.

7. The electrolysis system according to claim 3, characterized in that, It has a bypass path (62), a pressure sensor (68), and a second valve device (52), wherein, The bypass path branches off from the hydrogen-containing gas branch path and passes through the storage tank, merging with the hydrogen-containing gas branch path; The pressure sensor detects the pressure in the storage tank; The second valve device can switch the supply destination of the hydrogen-containing gas from the hydrogen-containing gas path to either the oxygen-consuming device or the storage tank. When the pressure is below a specified pressure threshold and the oxygen concentration is below a specified concentration threshold, the control device controls the second valve device to switch the supply destination of the hydrogen-containing gas to the storage tank.

8. The electrolysis system according to claim 1, characterized in that, The oxygen-consuming device has a catalyst that reacts the oxygen with hydrogen to produce water.

9. The electrolysis system according to claim 1, characterized in that, It has an exhaust gas branch path (76) and a third valve device (74), wherein, The exhaust gas branch path branches off from the exhaust gas path and connects to the oxygen-consuming device; The third valve device can switch the supply destination of the exhaust gas output from the oxygen-consuming device to either the oxygen-consuming device or the solid oxide electrolytic reactor. When the oxygen concentration is greater than a predetermined concentration threshold, the control device controls the third valve device to switch the destination of the exhaust gas supply to the oxygen-consuming device.

10. An electrolysis system having a solid oxide type electrolysis stack and a generating device, wherein, The solid oxide electrolytic reactor electrolyzes carbon dioxide gas and water vapor; the generating device has a catalyst, through which hydrogen-containing gas is generated from hydrocarbons via a catalytic reaction, wherein the hydrogen-containing gas contains carbon monoxide and hydrogen generated by the electrolysis of the solid oxide electrolytic reactor, characterized in that... It includes an oxygen-consuming device, an exhaust gas path, an exhaust gas branch path, an oxygen concentration sensor, valve devices, a storage tank, and a control device, among which, The oxygen-consuming device uses hydrogen to consume the oxygen in the exhaust gas containing the carbon dioxide gas; The exhaust gas path is used to supply the exhaust gas from the oxygen-consuming device to the solid oxide electrolytic reactor; The exhaust gas branch path branches off from the exhaust gas path and connects to the oxygen-consuming device; The oxygen concentration sensor detects the oxygen concentration in the exhaust gas output from the oxygen-consuming device. The valve device can switch the supply destination of the exhaust gas output from the oxygen-consuming device to the oxygen-consuming device or the solid oxide electrolytic reactor. The storage tank is capable of storing the hydrogen supplied to the oxygen-consuming device; The control device controls the valve device according to the oxygen concentration to switch the supply destination of the waste gas to the oxygen-consuming device, and opens the switch valve that controls the outlet of the storage tank.

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