Hydrogen production system and method for controlling hydrogen production system

Abstract

Provided is a hydrogen production system (100) which comprises: an electrolysis module (19) that supplies steam to a hydrogen electrode and produces hydrogen through steam electrolysis; a steam supply unit (20) that supplies steam to a hydrogen electrode (11); an air supply unit (70) that supplies air to an oxygen electrode (12); a hydrogen supply pipe (43) that supplies hydrogen to the oxygen electrode (12); a power supply unit (18) that supplies power to the electrolysis module (19); and a control device (80) that controls the hydrogen production system (100). The control device (80) controls the power supply unit (18) so as to start supplying power to the electrolysis module (19) in response to the temperature of the electrolysis module (19) exceeding Temp4 that is lower than the ignition temperature of hydrogen.

Description

Hydrogen generation system and method for controlling the hydrogen generation system

[0001] The present disclosure relates to a hydrogen generation system and a method for controlling the hydrogen generation system.

[0002] Conventionally, a hydrogen generation system that generates hydrogen by steam electrolysis is known (see, for example, Patent Document 1). The hydrogen generation system disclosed in Patent Document 1 includes an electrolysis module having a solid oxide electrolysis cell (SOEC). Patent Document 1 discloses that hydrogen is supplied not only to the hydrogen electrode of the electrolysis module but also to the oxygen electrode, whereby hydrogen is combusted by catalytic action at the oxygen electrode, thereby increasing the temperature of the electrolysis module.

[0003] Patent No. 7282968

[0004] However, if the temperature of the hydrogen supplied to the oxygen electrode exceeds its ignition temperature and spontaneous combustion occurs, the electrolysis module may be damaged. Although spontaneous combustion can be prevented by reducing the concentration of hydrogen supplied to the oxygen electrode, the heat generated by hydrogen combustion due to the catalytic action of the oxygen electrode is reduced. As a result, the rate at which the temperature of the electrolysis module rises slows, and the start-up time of the hydrogen generation system becomes longer.

[0005] The present disclosure has been made in consideration of the above circumstances, and aims to provide a hydrogen generation system and a control method for a hydrogen generation system that can appropriately increase the temperature of the electrolysis module and shorten the start-up time even when the heat generated by the combustion of fuel gas due to the catalytic action of the oxygen electrode is insufficient.

[0006] In order to solve the above problems, the present disclosure employs the following measures: A hydrogen generation system according to the present disclosure comprises an electrolysis module including an electrolysis cell having a hydrogen electrode, an oxygen electrode, and an electrolyte layer disposed between the hydrogen electrode and the oxygen electrode, and which supplies water vapor to the hydrogen electrode to generate hydrogen by water vapor electrolysis, a water vapor supply unit that supplies the water vapor to the hydrogen electrode, an air supply unit that supplies air to the oxygen electrode, a fuel gas system that supplies fuel gas to the oxygen electrode, a power supply unit that supplies power to the electrolysis module, and a controller that controls the hydrogen generation system, wherein the controller controls the power supply unit to start supplying power to the electrolysis module when the temperature of the electrolysis module exceeds a first predetermined temperature that is lower than the ignition temperature of the fuel gas.

[0007] In the control method for a hydrogen generation system according to the present disclosure, the hydrogen generation system includes an electrolysis module including an electrolysis cell having a hydrogen electrode, an oxygen electrode, and an electrolyte layer disposed between the hydrogen electrode and the oxygen electrode, the electrolysis module supplying water vapor to the hydrogen electrode to generate hydrogen by water vapor electrolysis, a water vapor supply unit supplying the water vapor to the hydrogen electrode, an air supply unit supplying air to the oxygen electrode, a fuel gas system supplying fuel gas to the oxygen electrode, and a power supply unit supplying power to the electrolysis module, and the method includes a control step of controlling the power supply unit to start supplying power to the electrolysis module when the temperature of the electrolysis module exceeds a first predetermined temperature that is lower than the ignition temperature of the fuel gas.

[0008] According to the present disclosure, it is possible to provide a hydrogen generation system and a control method for a hydrogen generation system that can appropriately increase the temperature of the electrolysis module and shorten the start-up time even when the heat generated by the combustion of fuel gas due to the catalytic action of the oxygen electrode is insufficient.

[0009] Fig. 1 is a diagram showing a schematic configuration of a hydrogen generation system according to an embodiment of the present disclosure. Fig. 2 is a partial cross-sectional view showing an example of a cylindrical electrolysis module according to an embodiment of the present disclosure. Fig. 3 is a longitudinal cross-sectional view of the electrolysis module shown in Fig. 1. Fig. 4 is a flowchart showing the operation at start-up of the hydrogen generation system. Fig. 5 is a flowchart showing the operation at start-up of the hydrogen generation system.

[0010] A hydrogen generation system 100 according to an embodiment of the present disclosure will be described below with reference to Fig. 1. Fig. 1 is a diagram showing a schematic configuration of the hydrogen generation system 100 according to an embodiment of the present disclosure. As shown in Fig. 1, the hydrogen generation system 100 of this embodiment includes an electrolysis module 19, a power supply unit 18, a water vapor supply unit 20, a hydrogen separation facility 30, a hydrogen storage facility (hydrogen supply unit) 40, an adjustment unit 50, an air supply unit (heating medium supply unit) 70, and a control device (control unit) 80.

[0011] Although the present disclosure shows a system equipped with a hydrogen storage facility (hydrogen supply unit), the hydrogen storage facility (hydrogen supply unit) 40 may be a hydrogen pipeline, and hydrogen may be extracted from the pipeline and supplied to the present system, or the generated hydrogen may be supplied directly to the hydrogen pipeline.

[0012] A solid oxide electrolysis cell (hereinafter referred to as an electrolysis cell) 10 is a component of an electrolysis module 19 that supplies water vapor from a water vapor supply unit 20 to a hydrogen electrode 11 to produce hydrogen and oxygen by steam electrolysis, and includes a hydrogen electrode 11, an oxygen electrode 12, and an electrolyte layer 13 disposed between the hydrogen electrode 11 and the oxygen electrode 12. The electrolysis module 19 is an assembly of electrolysis cells 10. Steam electrolysis is the reverse reaction of a fuel cell that generates electricity, and the electrolysis cell 10 can use substantially the same configuration and materials as a solid oxide fuel cell (SOFC).

[0013] 1 schematically shows the relationship between the electrolysis module 19, the hydrogen electrode 11, the oxygen electrode 12, and the electrolyte layer 13. The electrolysis module 19 can be, for example, a cylindrical cell stack in which the hydrogen electrode 11 is arranged in a cylindrical tube made of a porous material, the electrolyte layer 13 is arranged on the hydrogen electrode 11, and the oxygen electrode 12 is arranged on the electrolyte layer 13. The electrolysis module 19 also has a temperature sensor 17 that measures the operating temperature.

[0014] 2 is a partial cross-sectional view showing an example of a cylindrical cell stack CS according to this embodiment. The cell stack CS includes, for example, a cylindrical base tube 14, electrolysis cells 10 formed at multiple locations on the outer peripheral surface of the base tube 14, and interconnectors 15 formed between adjacent electrolysis cells 10. The electrolysis cells 10 are formed by stacking a hydrogen electrode 11, an electrolyte layer 13, and an oxygen electrode 12 on the surface of the base tube 14.

[0015] Of the multiple electrolytic cells 10 formed on the outer peripheral surface of the base tube 14, one electrolytic cell 10 formed at the furthest end in the axial direction of the base tube 14 has a lead film 16 electrically connected via an interconnector 15 to the oxygen electrode 12, and another electrolytic cell 10 formed at the furthest end has a lead film 16 electrically connected to the hydrogen electrode 11 of the electrolytic cell 10 formed at the other furthest end. In the following description, "supplying a medium (air, water vapor, hydrogen, etc.) to the hydrogen electrode 11" means circulating the medium in the space inside the base tube 14 of the cell stack CS, thereby diffusing the medium in the pores of the base tube 14 and supplying the medium to the hydrogen electrode 11 formed on the outer peripheral surface of the base tube 14.

[0016] The substrate tube 14 is made of a porous material, for example, CaO-stabilized ZrO ２ (CSZ), a mixture of CSZ and nickel oxide (NiO) (CSZ+NiO), or Y ２ O ３ Stabilized ZrO ２ (YSZ), or MgAl ２ O ４ The base tube 14 supports the electrolytic cell 10, the interconnector 15, and the lead film 16, and also diffuses water vapor supplied to the inner peripheral surface of the base tube 14 through the pores of the base tube 14 to the hydrogen electrode 11 formed on the outer peripheral surface of the base tube 14.

[0017] The hydrogen electrode 11 is made of a composite oxide of a metal material (such as Ni) and a zirconia-based electrolyte material, for example, Ni / YSZ. The oxygen electrode 12 is made of, for example, LaSrMnO ３ based oxides, or LaCoO ３The electrolyte layer 13 is mainly made of YSZ, which has gas-tightness that makes it difficult for gas to pass through and high oxygen ion conductivity at high temperatures.

[0018] The interconnector 15 is, for example, SrTiO ３ M such as １－ｘ L ｘ TiO ３ (M is an alkaline earth metal element, and L is a lanthanoid element). The interconnector 15 is a dense film that prevents mixing of water vapor and air (oxidizing gas).

[0019] Furthermore, the interconnector 15 has stable durability and electrical conductivity in both an oxidizing atmosphere and a reducing atmosphere. The interconnector 15 electrically connects the oxygen electrode 12 of one electrolytic cell 10 to the hydrogen electrode 11 of the other electrolytic cell 10, thereby connecting the adjacent electrolytic cells 10 in series.

[0020] The lead film 16 has electronic conductivity and is made of a composite material of Ni and a zirconia-based electrolyte material, such as Ni / YSZ, or SrTiO ３ M1-xLxTiO ３ (M is an alkaline earth metal element, and L is a lanthanoid element.) The lead film 16 supplies DC power to the plurality of electrolytic cells 10 connected in series by the interconnectors 15.

[0021] When external power is supplied between the hydrogen electrode 11 and the oxygen electrode 12 via the lead film 16, some of the high-temperature water vapor supplied to the hydrogen electrode 11 receives electrons and is separated into hydrogen and oxygen ions, generating hydrogen. The separated oxygen ions move inside the electrolyte layer 13 to the oxygen electrode 12, release electrons, and generate oxygen.

[0022] The temperature sensor 17 is a sensor that detects the temperature of the electrolysis module 19 (the temperature of the electrolysis cell 10 itself or the ambient temperature of the space in which the electrolysis cell 10 is placed). The temperature of the electrolysis module 19 detected by the temperature sensor 17 is transmitted to the control device 80.

[0023] The power supply unit 18 is a device that supplies power for performing steam electrolysis to the electrolysis module 19. The state of power supply from the power supply unit 18 to the electrolysis module 19 is controlled by a control device 80.

[0024] The water vapor supply unit 20 is a device that generates water vapor and supplies it to the electrolysis module 19. The water vapor is supplied to the hydrogen electrode 11 of the electrolysis module 19 through a water vapor supply pipe 21. The temperature of the hydrogen electrode inlet gas supplied to the hydrogen electrode space 11a is, for example, 200°C or higher.

[0025] The hydrogen separation equipment 30 separates hydrogen from a mixed gas of hydrogen and water vapor generated at the hydrogen electrode 11 of the electrolysis module 19. When the hydrogen discharge valve 31 is opened, the hydrogen generated at the hydrogen electrode 11 is supplied to the hydrogen separation equipment 30 via a hydrogen discharge pipe 33. The hydrogen separated by the hydrogen separation equipment 30 is supplied to the hydrogen storage equipment 40 by a hydrogen booster 32. The hydrogen separation equipment 30 cools the mixed gas of hydrogen and water vapor supplied from the hydrogen discharge pipe 33, for example, and condenses the water vapor contained in the mixed gas to recover it as recovered water.

[0026] The hydrogen storage equipment 40 stores hydrogen produced by the electrolysis module 19 and supplies the hydrogen to a hydrogen supply destination via a hydrogen supply pipe 41. The hydrogen storage equipment 40 can also supply hydrogen to the hydrogen electrode 11 via a hydrogen supply pipe 42 and a water vapor supply pipe 21. In order to maintain the hydrogen electrode 11 at a desired temperature, the hydrogen supplied from the hydrogen storage equipment 40 to the hydrogen electrode 11 is preferably heated while flowing through the hydrogen supply pipe 42 and then supplied to the water vapor supply pipe 21. The hydrogen storage equipment 40 can also supply hydrogen via a hydrogen supply pipe (fuel gas system) 43 to the oxygen electrode space 12a in which the oxygen electrode 12 of the electrolysis module 19 is disposed.

[0027] The adjustment unit 50 is a device that adjusts the amount of water vapor supplied from the water vapor supply unit 20, the amount of hydrogen supplied from the hydrogen storage equipment 40 to the hydrogen electrode 11, the amount of hydrogen supplied from the hydrogen storage equipment 40 to the oxygen electrode 12, the amount of air supplied from the air supply unit 70 to the oxygen electrode 12, and the amount of air supplied from the air supply unit 70 to the hydrogen electrode 11.

[0028] The adjustment unit 50 includes a water vapor adjustment valve 51 arranged in the water vapor supply pipe 21, a hydrogen adjustment valve 52 arranged in the hydrogen supply pipe 42, a hydrogen adjustment valve (or gate valve) 53 arranged in a position close to the water vapor supply pipe 21 downstream of the hydrogen supply pipe 42, an air adjustment valve 54 arranged in the air supply pipe 72, an air side discharge adjustment valve 55 for hydrogen electrode vent gas arranged in the air discharge pipe 73, a hydrogen supply valve 56, and an air adjustment valve 57.

[0029] The hydrogen adjustment valve 53 is a valve that is closed when water vapor is supplied to the hydrogen electrode but hydrogen is not supplied. By closing the hydrogen adjustment valve 53, when water vapor is supplied to the hydrogen electrode but hydrogen is not supplied, it is possible to prevent water vapor from entering the hydrogen supply pipe 42.

[0030] The hydrogen supply valve 56 is a valve that adjusts the amount of hydrogen supplied from the hydrogen storage facility 40 to the oxygen electrode 12 via the hydrogen supply pipe 43 and the air supply pipe 74. The hydrogen supplied to the air supply pipe 74 is supplied to the oxygen electrode 12 side of the electrolysis module 19. The hydrogen supplied to the oxygen electrode space 12a of the electrolysis module 19 is combusted by catalytic action, increasing the temperature of the electrolysis module 19.

[0031] 1 supplies hydrogen stored in the hydrogen storage facility 40 to the oxygen electrode space 12a by opening the hydrogen supply valve 56, but other configurations are also possible. For example, a fuel supply unit (not shown) that supplies hydrogen or other fuel gas (methane gas, etc.) may be provided, and the fuel gas may be supplied from the fuel supply unit to the oxygen electrode space 12a of the electrolysis module 19 and combusted by catalytic action.

[0032] The air supply unit 70 is a device that supplies air (heating medium) heated to a high temperature (e.g., less than 400°C) to the oxygen electrode 12. That is, the air supplied from the air supply unit 70 is supplied to the oxygen electrode space 12a of the electrolysis module 19 via an air supply pipe 74. The air supplied from the air supply unit 70 can also be supplied to the hydrogen electrode space 11a via a hydrogen electrode air supply pipe (heating medium supply system) 72. The amount of air supplied from the air supply unit 70 to the oxygen electrode 12 and the hydrogen electrode 11 is adjusted by an air adjustment valve 57. The amount of air supplied from the air supply unit 70 to the hydrogen electrode 11 is adjusted by an air adjustment valve 54. Note that "supplying a medium (e.g., air) to the oxygen electrode 12" refers to supplying the medium to the oxygen electrode 12 by circulating the medium in the space outside the oxygen electrode 12 of the cell stack CS.

[0033] The control device 80 is a device that controls the hydrogen generation system 100. The control device 80 has a storage unit (not shown) that stores a control program and a calculation unit (not shown) that executes the program, and performs various operations that control the hydrogen generation system 100 by executing the program read from the storage unit in the calculation unit.

[0034] Next, the electrolysis module 19 will be described in detail with reference to Fig. 3 . Fig. 3 is a vertical cross-sectional view of the electrolysis module 19 shown in Fig. 1 . As shown in Fig. 3 , the electrolysis module 19 includes a plurality of electrolysis cells 10, a water vapor supply header 217, a hydrogen discharge header 219, an air supply header 221, and an oxygen discharge header 223.

[0035] The electrolysis module 19 also includes an upper tube sheet 225 a, a lower tube sheet 225 b, an upper insulator 227 a, a lower insulator 227 b, and a side insulator 227 c. In this embodiment, the electrolysis module 19 has a structure in which the water vapor supply header 217, the hydrogen discharge header 219, the air supply header 221, and the oxygen discharge header 223 are arranged as shown in Fig. 3 so that water vapor and air flow in opposite directions between the inside and outside of the electrolysis cell 10. However, this is not necessarily required. For example, the water vapor and air may flow in parallel between the inside and outside of the electrolysis cell 10, or the air may flow in a direction perpendicular to the longitudinal direction of the electrolysis cell 10.

[0036] The reaction chamber 215 is a space formed between the upper insulator 227a, the lower insulator 227b, and the side insulator 227c. The reaction chamber 215 is a region in which the electrolysis cell 10 is disposed, and hydrogen and oxygen are generated by the steam electrolysis reaction of water vapor. The temperature near the longitudinal center of the cell stack CS in the reaction chamber 215 may be monitored by a temperature measurement unit (such as a temperature sensor or a thermocouple). During steady-state operation of the electrolysis module 19, the temperature near the longitudinal center of the cell stack CS in the reaction chamber 215 becomes a high-temperature atmosphere of approximately 700°C to 1000°C.

[0037] The steam supply header 217 is an area surrounded by the upper casing 229a and upper tube plate 225a of the electrolysis module 19, and is in communication with the steam supply pipe 21 via steam supply holes 231a provided in the upper part of the upper casing 229a. The multiple cell stacks CS are joined to the upper tube plate 225a with seal members 237a, and the steam supply header 217 guides the steam supplied from the steam supply pipe 21 via the steam supply holes 231a into the interiors of the base tubes 14 of the multiple cell stacks CS at a substantially uniform flow rate.

[0038] The hydrogen discharge header 219 is an area surrounded by the lower casing 229b and lower tube plate 225b of the electrolysis module 19, and is in communication with the hydrogen discharge pipe 33 via hydrogen discharge holes 231b provided in the lower casing 229b. The multiple electrolytic cells 10 are joined to the lower tube plate 225b with seal members 237b, and the hydrogen discharge header 219 collects hydrogen and water vapor that pass through the interiors of the base tubes 14 of the multiple cell stacks CS and is discharged to the hydrogen discharge header 219, and guides the collected hydrogen and water vapor to the hydrogen discharge pipe 33 via the hydrogen discharge holes 231b.

[0039] The air supply header 221 is an area surrounded by the lower casing 229b, lower tube sheet 225b, and lower heat insulator 227b of the electrolysis module 19, and is in communication with the air supply pipe 74 via air supply holes 233a provided on the side surface of the lower casing 229b. The air supply header 221 guides air at a predetermined flow rate, which is supplied from the air supply pipe 74 via the air supply holes 233a, to the reaction chamber 215 via an air supply gap 235a.

[0040] The oxygen discharge header 223 is an area surrounded by the upper casing 229a, upper tube plate 225a, and upper heat insulator 227a of the electrolysis module 19, and is connected to the oxygen discharge pipe 76 via oxygen discharge holes 233b provided in the side surface of the upper casing 229a. The oxygen discharge header 223 guides oxygen-enriched air, which is discharged from the reaction chamber 215 to the oxygen discharge header 223 through the oxygen discharge gap 235b, to the oxygen discharge pipe 76 via the oxygen discharge holes 233b.

[0041] The upper tube plate 225a is fixed to the side plate of the upper casing 229a, between the top plate of the upper casing 229a and the upper heat insulator 227a, such that the upper tube plate 225a, the top plate of the upper casing 229a, and the upper heat insulator 227a are approximately parallel to each other. The upper tube plate 225a has a plurality of holes corresponding to the number of cell stacks CS included in the electrolysis module 19, and the cell stacks CS are inserted into the holes. The upper tube plate 225a airtightly supports one end of the plurality of cell stacks CS via either or both of a sealing member 237a and an adhesive member, and isolates the steam supply header 217 from the oxygen discharge header 223.

[0042] The upper heat insulator 227a is disposed at the lower end of the upper casing 229a so that the upper heat insulator 227a, the top plate of the upper casing 229a, and the upper tube plate 225a are substantially parallel to each other, and is fixed to the side plate of the upper casing 229a. The upper heat insulator 227a has a plurality of holes formed therein corresponding to the number of cell stacks CS included in the electrolysis module 19. The diameters of the holes are set larger than the outer diameters of the cell stacks CS. The upper heat insulator 227a has oxygen discharge gaps 235b formed between the inner surfaces of the holes and the outer surfaces of the cell stacks CS inserted into the upper heat insulator 227a.

[0043] The upper heat insulator 227a separates the reaction chamber 215 from the oxygen discharge header 223, and prevents the atmosphere surrounding the upper tube sheet 225a from becoming too hot, thereby reducing its strength and increasing corrosion caused by oxidizers contained in the air. Furthermore, a metal material with high temperature resistance, such as a Ni-based alloy, may be used to prevent the upper tube sheet 225a and other components from being thermally deformed due to the temperature difference caused by exposure to the high temperature within the reaction chamber 215. The upper heat insulator 227a also guides the oxygen-enriched air that has passed through the reaction chamber 215 and been exposed to high temperatures through the oxygen discharge gap 235b to the oxygen discharge header 223.

[0044] According to this embodiment, the structure of the electrolysis module 19 described above allows water vapor and oxygen-enriched air to flow in opposite directions between the inside and outside of the cell stack CS. As a result, heat exchange occurs between the oxygen-enriched air and water vapor that passes through the inside of the base tube 14 of the cell stack CS and is supplied to the reaction chamber 215. The oxygen-enriched air is cooled to a temperature at which the upper tube plate 225a, etc., made of a metal material, will not undergo buckling or other deformation, and is then supplied to the oxygen discharge header 223. The water vapor is heated by heat exchange with the oxygen-enriched air discharged from the reaction chamber 215, and is supplied to the reaction chamber 215 by flowing through the inside of the base tube 14. As a result, water vapor that has been preheated to a temperature suitable for power generation can be supplied to the reaction chamber 215 without using a heater or the like.

[0045] The lower tube sheet 225b is fixed to the side plate of the lower casing 229b between the bottom plate of the lower casing 229b and the lower insulator 227b so that the lower tube sheet 225b, the bottom plate of the lower casing 229b, and the lower insulator 227b are approximately parallel to each other. The lower tube sheet 225b has a plurality of holes corresponding to the number of cell stacks CS included in the electrolysis module 19, and a cell stack CS is inserted into each of the holes. The lower tube sheet 225b airtightly supports the other ends of the plurality of cell stacks CS via either or both of a sealing member 237b and an adhesive member, and also isolates the hydrogen discharge header 219 from the air supply header 221.

[0046] The lower heat insulator 227b is disposed at the upper end of the lower casing 229b such that the lower heat insulator 227b, the bottom plate of the lower casing 229b, and the lower tube plate 225b are substantially parallel to each other, and is fixed to the side plate of the lower casing 229b. The lower heat insulator 227b has a plurality of holes formed therein corresponding to the number of cell stacks CS included in the electrolysis module 19. The diameters of the holes are set to be larger than the outer diameter of the electrolysis cells 10. The lower heat insulator 227b has an air supply gap 235a formed between the inner surface of the hole and the outer surface of the cell stack CS inserted through the lower heat insulator 227b.

[0047] The lower heat insulator 227b separates the reaction chamber 215 from the air supply header 221, and prevents the atmosphere around the lower tube sheet 225b from becoming too hot, resulting in a decrease in strength and increased corrosion due to oxidizers contained in the air. The lower tube sheet 225b and other components are made of a metal material that is resistant to high temperatures, such as Inconel, and this prevents the lower tube sheet 225b and other components from being thermally deformed due to increased temperature differences within the lower tube sheet 225b when exposed to high temperatures. The lower heat insulator 227b also guides the air supplied to the air supply header 221 through the air supply gap 235a to the reaction chamber 215.

[0048] According to this embodiment, the structure of the electrolysis module 19 described above allows hydrogen containing water vapor and air to flow in opposite directions inside and outside the cell stack CS. As a result, the hydrogen containing water vapor that passes through the inside of the base tube 14 of the cell stack CS and passes through the reaction chamber 215 exchanges heat with the air supplied to the reaction chamber 215, and is cooled to a temperature that does not cause deformation, such as buckling, of the lower tube plate 225b made of a metal material, and is supplied to the hydrogen discharge header 219. In addition, the air is heated by heat exchange with the hydrogen containing water vapor and is supplied to the reaction chamber 215. As a result, air heated to a temperature required for power generation can be supplied to the reaction chamber 215 without using a heater or the like.

[0049] Next, a description will be given of the control operation executed by the control device 80 of this embodiment at the start-up of the electrolysis module 19. Figures 4 and 5 are flowcharts showing the control operation at the start-up of the hydrogen generation system 100.

[0050] In step S101, the control device 80 performs control to start supplying air to the inside of the substrate tube 14 (hydrogen electrode 11) and the oxygen electrode 12. The control device 80 controls the adjustment unit 50 to open the air adjustment valve 54 and the air-side discharge amount adjustment valve 55 and to close the water vapor adjustment valve 51, the hydrogen adjustment valve 52, and the hydrogen adjustment valve (or gate valve) 53. The control device 80 also performs control to open the air adjustment valve 57 and close the hydrogen discharge valve 31 and the hydrogen supply valve 56.

[0051] The air supplied from the air supply unit 70 to the oxygen electrode 12 heats the oxygen electrode 12 and the entire electrolysis module 19 before being discharged to the outside. The air supply pipe (heating medium supply system) 72 is a system that supplies air from the air supply unit 70 to the hydrogen electrode 11. The air supplied from the air supply unit 70 through the air supply pipe 72 into the base tube 14 heats the base tube 14 and the entire electrolysis module 19 including the hydrogen electrode 11, and is then discharged to the outside through the air discharge pipe 73.

[0052] In step S102, the control device 80 determines whether the temperature Ta of the electrolysis module 19 detected by the temperature sensor 17 exceeds Temp1, and proceeds to step S103 if the temperature Ta exceeds Temp1. Temp1 is set to a temperature higher than the dew point of water vapor at the hydrogen electrode 11 so that water vapor does not become drain inside. Temp1 is, for example, a temperature not lower than 150°C and not higher than 200°C. Temp2, which will be described later, is set to a temperature higher than Temp1.

[0053] In step S103, the control device 80 starts to close the air regulating valve 54 from the open state so as to stop the supply of air from the air supply unit 70 to the inside of the substrate tube 14 (the hydrogen electrode 11). Subsequently, in step S104, the control device 80 starts to open the water vapor regulating valve 51 from the closed state so as to start the supply of water vapor from the water vapor supply unit 20 to the hydrogen electrode 11.

[0054] As described above, when the hydrogen generation system 100 is started, if the temperature Ta of the electrolysis module 19 exceeds Temp1, the control device 80 controls the adjustment unit 50 to transition from a state in which air is supplied from the air supply unit 70 into the substrate tube 14 and water vapor is not supplied from the water vapor supply unit 20 into the substrate tube 14 to a state in which air is not supplied into the substrate tube 14 and water vapor is supplied from the water vapor supply unit 20, thereby completing the oxygen purging on the hydrogen electrode 11 side.

[0055] In step S105, the control device 80 determines whether the temperature Ta of the electrolysis module 19 detected by the temperature sensor 17 exceeds Temp2, and if the temperature Ta exceeds Temp2, the process proceeds to step S106. Temp2 is a temperature lower than the temperature at which the metal components contained in the hydrogen electrode 11 oxidize. Temp2 is, for example, a temperature not lower than 350°C and not higher than 400°C. Temp2 is set lower than the temperature at which the rate at which the metal components contained in the hydrogen electrode 11 react with water vapor and oxidize increases significantly.

[0056] In step S106, the control device 80 starts supplying hydrogen from the hydrogen storage equipment 40 to the inside of the substrate tube 14 (hydrogen electrode 11), and switches the hydrogen regulating valve 52 and the hydrogen regulating valve (or gate valve) 53 from a closed state to an open state so that the hydrogen concentration at the inlet of the substrate tube 14 reaches a predetermined value.

[0057] Next, in step S107, the control device 80 adjusts the opening of the water vapor control valve 51 so that the water vapor concentration at the inlet of the substrate tube 14 becomes a predetermined value, thereby adjusting the amount of water vapor supplied from the water vapor supply unit 20 to the inside of the substrate tube 14 (hydrogen electrode 11).

[0058] As described above, when the temperature Ta of the electrolysis module 19 exceeds Temp2 during startup of the hydrogen generation system 100, the control device 80 controls the adjustment unit 50 to switch from a water vapor supply state to a state in which hydrogen, which is a reducing gas, is mixed. By switching from a water vapor supply state to a state in which hydrogen, which is a reducing gas, is mixed, the hydrogen electrode 11 is maintained in a reduced state, and water vapor oxidation of the hydrogen electrode by oxygen contained in the water vapor is prevented.

[0059] In step S108, the control device 80 determines whether the temperature Ta of the electrolysis module 19 detected by the temperature sensor 17 exceeds Temp3, and if the temperature Ta exceeds Temp3, the process proceeds to step S109. Temp3 is, for example, a temperature not lower than 300° C. and not higher than 500° C. Note that Temp3 is preferably set to the temperature of the hottest region in the reaction chamber 215, which is the space in which the oxygen electrode 12 is disposed.

[0060] In step S109, the control device 80 switches the hydrogen supply valve 56 from the closed state to the open state to start supplying hydrogen from the hydrogen storage facility 40 to the oxygen electrode 12. The hydrogen supplied to the oxygen electrode 12 of the electrolysis module 19 is combusted by the catalytic action of the oxygen electrode 12, and the temperature of the oxygen electrode 12 side of the electrolysis module 19 increases.

[0061] From the time when the supply of hydrogen to the oxygen electrode 12 is started in step S109 until the time when the supply of hydrogen to the oxygen electrode 12 is stopped in step S114, the control device 80 adjusts the amount of hydrogen supplied by controlling the opening degree of the hydrogen supply valve 56 of the hydrogen supply pipe 43 so that the hydrogen is at a concentration that does not ignite (below the lower flammable limit concentration) in the air supply header 221 before being supplied to the oxygen electrode 12.

[0062] Furthermore, the control device 80 adjusts the flow rate of the mixed gas and the hydrogen concentration by controlling the hydrogen supply amount and the air supply amount through the apertures of the hydrogen supply valve 56 and the air adjustment valve 57 so that the flame propagation speed of hydrogen supplied to the oxygen electrode 12 is lower than the flow speed of the mixed gas of air and hydrogen supplied to the oxygen electrode 12. Specifically, it is preferable that the flame propagation speed be lower than the flow speed of the gas (oxidizing gas containing water vapor) after catalytic combustion passing through the oxygen discharge gap 235b. Furthermore, the amount of hydrogen supplied to the oxygen electrode 12 may be set taking into account Joule heat generated by the application of current.

[0063] Note that the hydrogen concentration may be reduced by gradually decreasing the flow rate of hydrogen supplied to the oxygen electrode 12 after the supply of hydrogen is started in step S109 and reaches a predetermined hydrogen concentration, until the supply is stopped in step S114. For example, the hydrogen concentration may be reduced according to the temperature of the hottest region of the reaction chamber 215, which is the space in which the oxygen electrode 12 is disposed (e.g., a region near the vertical center of the reaction chamber 215). Furthermore, to prevent an abnormal temperature rise in the reaction chamber 215 while hydrogen is being supplied to the oxygen electrode 12, the flow rate of hydrogen supplied to the oxygen electrode 12 may be controlled by detecting the temperature of the coldest region of the reaction chamber 215, which is the space in which the oxygen electrode 12 is disposed (e.g., the temperature near the air supply gap 235a or the temperature near the vertical bottom of the reaction chamber 215), the temperature of the air supply header 221, or the temperature of the hydrogen discharge hole 231b, which is equivalent to the temperature of the air supply header 221.

[0064] In step S110, the control device 80 determines whether the temperature Ta of the electrolysis module 19 detected by the temperature sensor 17 exceeds Temp4 (first predetermined temperature), and if the temperature Ta exceeds Temp4, the process proceeds to step S111. Temp4 is a temperature lower than the ignition temperature of hydrogen (fuel gas), and is, for example, a temperature equal to or higher than 500°C and lower than 600°C.

[0065] The temperature sensor 17 that measures Temp4 detects the temperature of the lowest region in the reaction chamber 215 in which the electrolytic cell 10 is disposed. The lowest temperature region is, for example, the region near the air supply gap 235a. The control device 80 controls the power supply unit 18 to start supplying power to the electrolysis module 19 when the temperature of the lowest region in the space (reaction chamber 215) in which the electrolytic cell 10 is disposed exceeds Temp4. Alternatively, the temperature sensor 17 may detect the temperature of a region near the vertical center of the reaction chamber 215, and set Temp4 to a temperature corresponding to the temperature of the lowest region in the reaction chamber 215, for example, equal to or higher than 500°C and lower than 600°C.

[0066] In step S111, the control device 80 increases the amount of water vapor supplied from the water vapor supply unit 20 to the hydrogen electrode 11 so that the amount meets the electrolysis start conditions. The control device 80 adjusts the valve aperture of the water vapor adjustment valve 51, and also adjusts the aperture of the hydrogen adjustment valve 52, which controls the amount of hydrogen supplied from the hydrogen storage facility 40 to the hydrogen electrode 11, so that the inlet hydrogen concentration inside the substrate tube 14 (hydrogen electrode 11) meets the electrolysis start conditions.

[0067] In step S112, the control device 80 starts the power supply from the power supply unit 18 to the electrolysis module 19 and controls the power supply unit 18 to gradually increase the amount of current. When the power supply from the power supply unit 18 to the electrolysis module 19 starts, Joule heat is generated in the electrolysis cell 10, and the temperature of the reaction chamber 215 increases. The electrolysis module 19, which receives power from the power supply unit 18, starts producing hydrogen and oxygen by steam electrolysis.

[0068] In step S113, the control device 80 determines whether the temperature Ta of the electrolysis module 19 detected by the temperature sensor 17 exceeds Temp5 (a second predetermined temperature) or whether the amount of current supplied to the electrolysis module 19 exceeds a predetermined value, and if either of these conditions is met, the process proceeds to step S114. Temp5 is, for example, a temperature of 700°C or higher and 850°C or lower, which is set lower than the temperature at which the electrolysis module 19 operates at rated load.

[0069] In step S114 , the control device 80 switches the hydrogen supply valve 56 from the open state to the closed state so as to stop the supply of hydrogen from the hydrogen storage facility 40 to the oxygen electrode 12 .

[0070] The temperature sensor 17 that measures Temp5 detects the temperature of the hottest region in the reaction chamber 215 in which the electrolytic cell 10 is disposed. The hottest region is, for example, a region near the vertical center of the reaction chamber 215. The control device 80 controls the hydrogen supply valve 56 to stop the supply of hydrogen to the oxygen electrode 12 when the temperature of the hottest region in the space (reaction chamber 215) in which the electrolytic cell 10 is disposed exceeds Temp5.

[0071] Thereafter, in step S115, it is determined whether the amount of current supplied to the electrolysis module 19 has reached the rated value, and if the determination is YES, startup is completed at that point, and the electrolysis module 19 enters a rated operation state. Note that before the amount of current reaches the rated value, the control device 80 controls the water vapor regulation valve 51 and the hydrogen regulation valve 52 so that the amount of water vapor supplied to the hydrogen electrode 11 and the inlet hydrogen concentration in the substrate tube 14 (hydrogen electrode 11) meet the rated conditions. Here, the apertures of the water vapor regulation valve 51 and the hydrogen regulation valve 52 may be controlled as a function of the amount of current.

[0072] The following describes the actions and effects of the hydrogen generation system 100 of this embodiment. According to the hydrogen generation system 100 of this embodiment, even if the heat generated by the combustion of hydrogen due to the catalytic action of the oxygen electrode 12 is insufficient, the supply of power to the electrolysis module 19 is initiated when the temperature of the electrolysis module 19 exceeds Temp4 (first predetermined temperature), which is lower than the ignition temperature of hydrogen. Therefore, the Joule heat generated by the current flow can be used to appropriately increase the temperature of the electrolysis module 19, thereby shortening the start-up time.

[0073] According to the hydrogen generation system 100 of this embodiment, the concentration of hydrogen before being supplied to the oxygen electrode 12 is controlled to a level at which it will not ignite, thereby preventing the problem of hydrogen igniting in the area before being supplied to the oxygen electrode 12 and damaging the surrounding area.

[0074] According to the hydrogen generation system 100 of this embodiment, by setting Temp4 to 500°C or higher and lower than 600°C, it is possible to reliably prevent the problem of hydrogen ignition.

[0075] According to the hydrogen generation system 100 of this embodiment, the supply of power to the electrolysis module 19 is started when the temperature of the lowest region in the reaction chamber 215 in which the electrolysis cell 10 is placed exceeds Temp4. This allows the supply of power to the electrolysis module 19 to be started at an appropriate time, and the temperature of the electrolysis module 19 to be increased appropriately, thereby shortening the start-up time.

[0076] According to the hydrogen generation system 100 of this embodiment, the supply of hydrogen to the oxygen electrode 12 is stopped when the temperature of the electrolysis module 19 exceeds Temp5, which is higher than Temp4, and the temperature of the electrolysis module 19 can be appropriately increased by the heat generated by the combustion of hydrogen due to the catalytic action of the oxygen electrode 12.

[0077] According to the hydrogen generation system 100 of this embodiment, the supply of hydrogen to the oxygen electrode 12 is stopped when the temperature of the hottest area in the reaction chamber 215 in which the electrolysis cell 10 is placed exceeds Temp5, thereby making it possible to appropriately increase the temperature of the electrolysis module 19 using the heat generated by the combustion of hydrogen due to the catalytic action of the oxygen electrode 12.

[0078] According to the hydrogen generation system 100 of this embodiment, Temp5 is set lower than the temperature at which the electrolysis module 19 operates at rated load, so that the supply of hydrogen to the oxygen electrode 12 can be reliably stopped before the electrolysis module 19 operates at rated load.

[0079] According to the hydrogen generation system 100 of this embodiment, by setting Temp5 to 700°C or higher and 850°C or lower, it is possible to reliably stop the supply of hydrogen to the oxygen electrode 12 before the electrolysis module 19 is operated at rated load.

[0080] According to the hydrogen generation system 100 of this embodiment, the flame propagation speed of the hydrogen supplied to the oxygen electrode 12 is lower than the flow speed of the air supplied to the oxygen electrode 12, so that even if the hydrogen ignites, the flame can be prevented from propagating to the outside and causing damage to the outside.

[0081] According to the hydrogen generation system 100 of this embodiment, hydrogen generated by steam electrolysis is supplied to the oxygen electrode 12 as fuel gas, and the temperature of the electrolysis module 19 can be appropriately increased by the heat generated by the combustion of hydrogen due to the catalytic action of the oxygen electrode 12.

[0082] The hydrogen generation system (100) and the control method for the hydrogen generation system described in each of the above-described embodiments can be understood, for example, as follows: A hydrogen generation system according to a first aspect of the present disclosure includes an electrolysis module (19) including an electrolysis cell (10) having a hydrogen electrode, an oxygen electrode, and an electrolyte layer disposed between the hydrogen electrode and the oxygen electrode, and includes: a water vapor supply unit (20) that supplies the water vapor to the hydrogen electrode to generate hydrogen by steam electrolysis; an air supply unit (70) that supplies air to the oxygen electrode; a fuel gas system (43) that supplies a fuel gas to the oxygen electrode; a power supply unit (18) that supplies power to the electrolysis module; and a control unit (80) that controls the hydrogen generation system, wherein the control unit controls the power supply unit to start supplying power to the electrolysis module when the temperature of the electrolysis module exceeds a first predetermined temperature that is lower than the ignition temperature of the fuel gas.

[0083] According to the hydrogen generation system according to the first aspect of the present disclosure, even if there is an insufficient amount of heat generated by the combustion of fuel gas due to the catalytic action of the oxygen electrode, the supply of power to the electrolysis module begins when the temperature of the electrolysis module exceeds a first predetermined temperature that is lower than the ignition temperature of the fuel gas, thereby making it possible to appropriately increase the temperature of the electrolysis module and shorten the start-up time.

[0084] The hydrogen generation system according to a second aspect of the present disclosure is the same as the first aspect, and further includes the following configuration: Namely, the control unit controls the fuel gas system so that the fuel gas before being supplied to the oxygen electrode has a concentration that does not ignite.

[0085] According to the hydrogen generation system of the second aspect of the present disclosure, the fuel gas before being supplied to the oxygen electrode is controlled to a concentration that will not ignite, thereby preventing the fuel gas from igniting in the area before being supplied to the oxygen electrode and damaging the surrounding area.

[0086] The hydrogen generation system according to the third aspect of the present disclosure is the first or second aspect, further comprising the following configuration: the first predetermined temperature is equal to or higher than 500° C. and lower than 600° C. According to the hydrogen generation system according to the third aspect of the present disclosure, by setting the first predetermined temperature to be equal to or higher than 500° C. and lower than 600° C., it is possible to reliably prevent the problem of fuel gas ignition.

[0087] A hydrogen generation system according to a fourth aspect of the present disclosure is the first or second aspect, further comprising the following configuration: the control unit controls the fuel gas system to start supplying the fuel gas to the oxygen electrode in accordance with the temperature of the hottest region in the space in which the electrolysis cell is disposed.

[0088] According to the hydrogen generation system according to the fourth aspect of the present disclosure, the supply of fuel gas to the oxygen electrode can be started in accordance with the temperature of the hottest region in the space where the electrolysis cell is disposed.

[0089] A hydrogen generation system according to a fifth aspect of the present disclosure is the first or second aspect, further comprising the following configuration: the control unit controls the power supply unit to start supplying power to the electrolysis module when the temperature of the lowest region in the space in which the electrolysis cell is disposed exceeds the first predetermined temperature.

[0090] In the hydrogen generation system according to the fifth aspect of the present disclosure, the supply of power to the electrolysis module is started when the temperature of the lowest region in the space in which the electrolysis cell is placed exceeds a first predetermined temperature. This enables the supply of power to the electrolysis module to be started at an appropriate time, and the temperature of the electrolysis module to be increased appropriately, thereby shortening the start-up time.

[0091] A hydrogen generation system according to a sixth aspect of the present disclosure is the first or second aspect, further comprising the following configuration: the control unit controls the fuel gas system to stop the supply of the fuel gas to the oxygen electrode when the temperature of the electrolysis module exceeds a second predetermined temperature that is higher than the first predetermined temperature.

[0092] In the hydrogen generation system according to the sixth aspect of the present disclosure, the supply of fuel gas to the oxygen electrode is stopped when the temperature of the electrolysis module exceeds a second predetermined temperature that is higher than the first predetermined temperature, thereby making it possible to appropriately increase the temperature of the electrolysis module using heat generated by combustion of the fuel gas due to the catalytic action of the oxygen electrode.

[0093] A hydrogen generation system according to a seventh aspect of the present disclosure is the sixth aspect, further comprising the following configuration: the control unit controls the fuel gas system to stop the supply of the fuel gas to the oxygen electrode when the temperature of the hottest region in the space in which the electrolysis cell is disposed exceeds the second predetermined temperature.

[0094] According to the hydrogen generation system of the seventh aspect of the present disclosure, the supply of fuel gas to the oxygen electrode is stopped when the temperature of the hottest area in the space where the electrolysis cell is placed exceeds a second predetermined temperature, thereby making it possible to appropriately increase the temperature of the electrolysis module using the heat generated by the combustion of the fuel gas due to the catalytic action of the oxygen electrode.

[0095] A hydrogen generation system according to an eighth aspect of the present disclosure is the sixth aspect, further comprising the following configuration: the second predetermined temperature is set lower than the temperature at which the electrolysis module operates at rated load.

[0096] In the hydrogen generation system according to the eighth aspect of the present disclosure, the second predetermined temperature is set to be lower than the temperature at which the electrolysis module operates at rated load, and therefore the supply of fuel gas to the oxygen electrode can be reliably stopped before the electrolysis module operates at rated load.

[0097] A hydrogen generation system according to a ninth aspect of the present disclosure is the sixth aspect, further comprising the following configuration: the second predetermined temperature is equal to or higher than 700° C. and equal to or lower than 850° C. According to the hydrogen generation system according to the ninth aspect of the present disclosure, by setting the second predetermined temperature to be equal to or higher than 700° C. and equal to or lower than 850° C., it is possible to reliably stop the supply of fuel gas to the oxygen electrode before the electrolysis module is operated at rated load.

[0098] A hydrogen generation system according to a tenth aspect of the present disclosure is the first or second aspect, further comprising the following configuration: That is, the control unit controls the fuel gas system and the heating medium supply unit so that the flame propagation speed of the fuel gas supplied to the oxygen electrode is lower than the flow speed of air supplied to the oxygen electrode.

[0099] According to the hydrogen generation system of the tenth aspect of the present disclosure, the flame propagation speed of the fuel gas supplied to the oxygen electrode is lower than the flow speed of the air supplied to the oxygen electrode, so that even if the fuel gas ignites, the flame can be prevented from propagating to the outside and causing damage to the outside.

[0100] A hydrogen generation system according to an eleventh aspect of the present disclosure is the first or second aspect, further comprising the following configuration: the fuel gas system supplies hydrogen as the fuel gas to the oxygen electrode.

[0101] According to the hydrogen generation system according to the eleventh aspect of the present disclosure, hydrogen generated by steam electrolysis is supplied to the oxygen electrode as fuel gas, and the temperature of the electrolysis module can be appropriately increased by the heat generated by the combustion of hydrogen due to the catalytic action of the oxygen electrode.

[0102] A hydrogen generation system according to a twelfth aspect of the present disclosure is the eleventh aspect, further comprising the following configuration: Namely, the control unit controls the fuel gas system so as to gradually decrease the flow rate of hydrogen supplied to the oxygen electrode from the start of supply of the fuel gas to the oxygen electrode until the stop of supply of the fuel gas to the oxygen electrode.

[0103] A hydrogen generation system according to a thirteenth aspect of the present disclosure is the eleventh aspect, further comprising the following configuration: Namely, the control unit detects any one of the following temperatures during the period from when the supply of the fuel gas to the oxygen electrode is started to when the supply of the fuel gas to the oxygen electrode is stopped: the temperature of the lowest temperature region in the space in which the electrolysis cell is disposed, the temperature of an air supply header to which air is supplied from the air supply unit, and the temperature of a hydrogen discharge hole through which hydrogen generated by the electrolysis module is discharged; and controls the fuel gas system to adjust the flow rate of hydrogen supplied to the oxygen electrode.

[0104] In a control method for a hydrogen generation system according to a fourteenth aspect of the present disclosure, the hydrogen generation system includes an electrolysis module including an electrolysis cell having a hydrogen electrode, an oxygen electrode, and an electrolyte layer disposed between the hydrogen electrode and the oxygen electrode, the electrolysis module supplying water vapor to the hydrogen electrode to generate hydrogen by steam electrolysis, a water vapor supply unit supplying the water vapor to the hydrogen electrode, an air supply unit supplying air to the oxygen electrode, a fuel gas system supplying fuel gas to the oxygen electrode, and a power supply unit supplying power to the electrolysis module, and the method includes a control step of controlling the power supply unit to start supplying power to the electrolysis module in response to the temperature of the electrolysis module exceeding a first predetermined temperature that is lower than the ignition temperature of the fuel gas.

[0105] According to the control method for a hydrogen generation system according to the fourteenth aspect of the present disclosure, even if the heat generated by the combustion of fuel gas due to the catalytic action of the oxygen electrode is insufficient, the supply of power to the electrolysis module is initiated when the temperature of the electrolysis module exceeds a first predetermined temperature that is lower than the ignition temperature of the fuel gas, thereby making it possible to appropriately increase the temperature of the electrolysis module and shorten the start-up time.

[0106] REFERENCE SIGNS LIST 10 Electrolytic cell 11 Hydrogen electrode 11a Hydrogen electrode space 12 Oxygen electrode 12a Oxygen electrode space 13 Electrolyte layer 14 Base tube 17 Temperature sensor 18 Power supply unit 19 Electrolysis module 20 Water vapor supply unit 21 Water vapor supply pipe 30 Hydrogen separation equipment 31 Hydrogen discharge valve 32 Hydrogen booster 33 Hydrogen discharge pipe 40 Hydrogen storage equipment 41, 42, 43 Hydrogen supply pipe 50 Adjustment unit 51 Water vapor adjustment valve 52, 53 Hydrogen adjustment valve 54 Air adjustment valve 55 Air-side discharge amount adjustment valve 56 Hydrogen supply valve 57 Air adjustment valve 70 Air supply unit 72 Air supply pipe 73 Air discharge pipe 74 Air supply pipe 76 Oxygen discharge pipe 80 Control device (control unit) 100 Hydrogen generation system 215 Reaction chamber 217 Steam supply header 219 Hydrogen discharge header 221 Air supply header 223 Oxygen discharge header 225a Upper tube plate 225b Lower tube plate 227a Upper heat insulator 227b Lower heat insulator 227c Side heat insulator 229a Upper casing 229b Lower casing 231a Steam supply hole 231b Hydrogen discharge hole 233a Air supply hole 233b Oxygen discharge hole 235a Air supply gap 235b Oxygen discharge gap 237a, 237b Seal member

Claims

1. A hydrogen generation system comprising: an electrolysis module including an electrolysis cell having a hydrogen electrode, an oxygen electrode, and an electrolyte layer disposed between the hydrogen electrode and the oxygen electrode, the electrolysis module supplying water vapor to the hydrogen electrode to generate hydrogen by water vapor electrolysis; a water vapor supply unit supplying the water vapor to the hydrogen electrode; an air supply unit supplying air to the oxygen electrode; a fuel gas system supplying fuel gas to the oxygen electrode; a power supply unit supplying power to the electrolysis module; and a control unit that controls the hydrogen generation system, wherein the control unit controls the power supply unit to start supplying power to the electrolysis module in response to the temperature of the electrolysis module exceeding a first predetermined temperature that is lower than the ignition temperature of the fuel gas.

2. The hydrogen generation system according to claim 1, wherein the control unit controls the fuel gas system so that the fuel gas before being supplied to the oxygen electrode has a concentration that does not ignite.

3. A hydrogen generation system according to claim 1 or 2, wherein the first predetermined temperature is equal to or higher than 500°C and lower than 600°C.

4. A hydrogen generation system as described in claim 1 or claim 2, wherein the control unit controls the fuel gas system to start supplying the fuel gas to the oxygen electrode depending on the temperature of the hottest area in the space in which the electrolytic cell is placed.

5. A hydrogen generation system as described in claim 1 or claim 2, wherein the control unit controls the power supply unit to start supplying power to the electrolysis module when the temperature of the lowest area in the space in which the electrolysis cell is placed exceeds the first predetermined temperature.

6. A hydrogen generation system as described in claim 1 or claim 2, wherein the control unit controls the fuel gas system to stop the supply of the fuel gas to the oxygen electrode when the temperature of the electrolysis module exceeds a second predetermined temperature that is higher than the first predetermined temperature.

7. The hydrogen generation system described in claim 6, wherein the control unit controls the fuel gas system to stop the supply of the fuel gas to the oxygen electrode when the temperature of the hottest area in the space in which the electrolytic cell is placed exceeds the second predetermined temperature.

8. The hydrogen generation system according to claim 6, wherein the second predetermined temperature is set to be lower than the temperature at which the electrolysis module operates at a rated load.

9. The hydrogen generation system according to claim 6, wherein the second predetermined temperature is 700°C or higher and 850°C or lower.

10. A hydrogen generation system as described in claim 1 or claim 2, wherein the control unit controls the fuel gas system and the air supply unit so that the flame propagation speed of the fuel gas supplied to the oxygen electrode is lower than the flow speed of the air supplied to the oxygen electrode.

11. The hydrogen generation system according to claim 1 or 2, wherein the fuel gas system supplies hydrogen as the fuel gas to the oxygen electrode.

12. The hydrogen generation system described in claim 11, wherein the control unit controls the fuel gas system so as to gradually reduce the flow rate of hydrogen supplied to the oxygen electrode from the time when the supply of the fuel gas to the oxygen electrode starts until the time when the supply of the fuel gas to the oxygen electrode stops.

13. The hydrogen generation system described in claim 11, wherein the control unit detects any one of the following temperatures from the start of supplying the fuel gas to the oxygen electrode to the stop of supplying the fuel gas to the oxygen electrode: the temperature of the coldest area in the space in which the electrolysis cell is placed, the temperature of the air supply header to which air is supplied from the air supply unit, and the temperature of the hydrogen discharge hole from which hydrogen generated by the electrolysis module is discharged, and controls the fuel gas system to adjust the flow rate of hydrogen supplied to the oxygen electrode.

14. A control method for a hydrogen generation system, the hydrogen generation system comprising: an electrolysis module comprising an electrolysis cell having a hydrogen electrode, an oxygen electrode, and an electrolyte layer disposed between the hydrogen electrode and the oxygen electrode, the electrolysis module supplying water vapor to the hydrogen electrode to generate hydrogen by water vapor electrolysis; a water vapor supply unit supplying the water vapor to the hydrogen electrode; an air supply unit supplying air to the oxygen electrode; a fuel gas system supplying fuel gas to the oxygen electrode; and a power supply unit supplying power to the electrolysis module, the control method comprising a control step of controlling the power supply unit to start supplying power to the electrolysis module in response to the temperature of the electrolysis module exceeding a first predetermined temperature that is lower than the ignition temperature of the fuel gas.

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