Water vapor electrolysis device and water vapor electrolysis method

Abstract

To improve the safety of a water vapor electrolysis device.SOLUTION: A water vapor electrolysis device includes: an electrolysis cell stack which electrolyzes water vapor to generated hydrogen and oxygen; a heating furnace which includes a space for housing the electrolysis cell stack and heats the electrolysis cell stack; an oxygen meter which measures oxygen concentration in a region outside the electrolysis cell stack of the space; and a control device which controls the operation of the electrolysis cell stack according to the measured oxygen concentration.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a steam electrolysis device and a steam electrolysis method. [Background technology]

[0002] In recent years, the introduction of renewable energies such as solar, wind and geothermal energy has been promoted from the viewpoints of environmental issues such as the depletion of fossil fuels and global warming due to the release of carbon dioxide into the atmosphere, as well as energy security. In addition, hydrogen energy has attracted attention as a secondary energy source from the viewpoints of storage and transportation. Hydrogen energy is expected to be applied to, for example, fuel cell vehicles, and there is a demand for low-cost production and storage of high-quality hydrogen.

[0003] Currently, the mainstream method of producing hydrogen is to produce it by reforming fossil fuels from the viewpoints of cost and technology. However, producing hydrogen by reforming fossil fuels inevitably generates carbon dioxide during the production process. In contrast, it is known that producing hydrogen using renewable energy and water as a raw material does not generate carbon dioxide and has a small environmental impact. Known electrolysis devices that generate hydrogen by electrolyzing water or water vapor include PEM-type electrolysis devices that use a solid polymer electrolyte membrane (PEM) and SOEC-type electrolysis devices that use a solid oxide electrolysis cell (SOEC). Among them, SOEC-type electrolysis devices, in principle, require less electricity to produce hydrogen, and are expected to be the hydrogen production devices of the future.

[0004] An SOEC used in the electrolysis of water vapor to produce hydrogen has a hydrogen electrode support layer that passes electrons, a hydrogen electrode (active layer) that electrolyzes water, a solid oxide electrolyte layer that conducts oxygen ions, and an oxygen electrode that bonds the oxygen ions to form oxygen molecules. The electrolyte has oxygen ion conductivity and plays a role in separating hydrogen gas and oxygen gas. In addition to the function of passing electrons, the support layer is required to have gas permeability to supply water vapor to the active layer and strength to maintain the shape of the electrolysis cell.

[0005] Due to its mechanism, high-temperature steam electrolysis equipment generates hydrogen in a high-temperature furnace that houses an electrolysis cell stack, and the hydrogen is collected using metal piping, etc., but hydrogen leakage may occur due to aging and thermal cycles. Hydrogen leaking into a high-temperature furnace is extremely dangerous because it is above its ignition point and there is sufficient oxygen inside or outside the furnace, which may cause an explosion.

[0006] To address this issue, one possible method for detecting hydrogen leakage is to measure the hydrogen concentration in the atmosphere inside the furnace. However, this method has the problem that if the amount of leaked hydrogen is large, it can rapidly reach the explosion limit. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 5498191 [Patent Document 2] International Publication No. 2017 / 154138 Summary of the Invention [Problem to be solved by the invention]

[0008] The problem to be solved by the present invention is to improve the safety of a steam electrolysis device. [Means for solving the problem]

[0009] The water vapor electrolysis device of the embodiment includes an electrolysis cell stack that electrolyzes water vapor to produce hydrogen and oxygen, a heating furnace that has a space to accommodate the electrolysis cell stack and heats the electrolysis cell stack, an oxygen concentration meter that measures an oxygen concentration in a region of the space outside the electrolysis cell stack, and a control device that controls operation of the electrolysis cell stack in accordance with the measured oxygen concentration. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing a first configuration example of a water vapor electrolysis device according to an embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing a structural example of the electrolysis stack 1. [Diagram 3] FIG. 2 is a schematic diagram showing the relationship between the concentration of oxygen gas and the concentration of hydrogen gas in the region outside the electrolysis stack 1 of the space 20 and time. [Figure 4] FIG. 4 is a schematic diagram showing a second configuration example of the water vapor electrolysis device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments will be described with reference to the drawings. In each embodiment shown below, substantially the same components are denoted by the same reference numerals, and some of the descriptions thereof may be omitted. The drawings are schematic, and the relationship between thickness and planar dimensions, the thickness ratio of each part, etc. may differ from the actual ones.

[0012] In this specification, unless otherwise specified, "connect" may include not only a direct connection but also an indirect connection.

[0013] (First configuration example of the steam electrolysis device) Configuration examples of a steam electrolysis device according to an embodiment will be described. Fig. 1 is a schematic diagram showing a first configuration example of a steam electrolysis device according to an embodiment. The steam electrolysis device shown in Fig. 1 includes an electrolysis stack 1, a heating furnace 2, a gas supply source 3, a hydrogen collector 4, an oxygen collector 5, a power source 6, an oxygen concentration meter 7, and a control device 8. The steam electrolysis device according to the embodiment is, for example, a high-temperature steam electrolysis device.

[0014] The electrolysis stack 1 can generate hydrogen gas and oxygen gas by performing an electrolysis reaction using a supply gas containing water vapor, for example. Gases such as hydrogen gas and oxygen gas generated by the electrolysis stack 1 are also referred to as generated gases. The electrolysis stack 1 is connected to a pipe P1, a pipe P2, and a pipe P3 shown in FIG. 1. The pipe P1 can connect the electrolysis stack 1 to a gas supply source 3, for example. The pipe P1 has a function as a flow path through which the supply gas flows, for example. The pipe P2 can connect the electrolysis stack 1 to a hydrogen collector 4, for example. The pipe P2 has a function as a flow path through which the generated gas (hydrogen gas) flows, for example. The pipe P3 can connect the electrolysis stack 1 to an oxygen collector 5, for example. The pipe P3 has a function as a flow path through which the generated gas (oxygen gas) flows, for example. The pipes P1, P2, and P3 can be formed using, for example, a metal material. The water vapor electrolysis apparatus shown in FIG. 1 may have at least one of a pump, a valve, a pressure regulator, and a flow regulator in each of the pipes P1, P2, and P3.

[0015] FIG. 2 is a schematic cross-sectional view showing a structural example of the electrolysis stack 1. The electrolysis stack 1 shown in FIG. 2 has a hydrogen electrode 11, an oxygen electrode 12, an electrolyte 13, and a separator (partition plate) 14. FIG. 2 shows an X-axis, a Y-axis, and a Z-axis. The X-axis, the Y-axis, and the Z-axis perpendicularly intersect with each other. The Z-axis is along the thickness direction of the solid oxide electrochemical cell 10. FIG. 2 shows a part of an XZ cross section including the X-axis and the Z-axis. FIG. 2 shows a flat plate-type stack, but is not limited to a flat plate-type stack, and may be, for example, a cylindrical stack. FIG. 2 shows a plurality of hydrogen electrodes 11, a plurality of oxygen electrodes 12, a plurality of electrolytes 13, and a plurality of separators 14.

[0016] The hydrogen electrode 11, the oxygen electrode 12, and the electrolyte 13 are stacked to form a solid oxide electrochemical cell 10. The solid oxide electrochemical cell 10 can be operated at high temperatures, and the electrolytic reaction in the electrolysis stack 1 is carried out at a temperature of, for example, 500° C. to 1000° C. The temperature can be controlled by a heating furnace 2. The solid oxide electrochemical cell 10 has, for example, a catalyst that promotes the electrolytic reaction.

[0017] The electrolysis stack 1 includes, for example, a plurality of solid oxide electrochemical cells 10. The plurality of solid oxide electrochemical cells 10 are stacked with a separator 14 sandwiched therebetween. The plurality of solid oxide electrochemical cells 10 may be disposed, for example, between a plurality of supports (not shown). The number of stacked layers of the plurality of solid oxide electrochemical cells 10 is not particularly limited, but is, for example, eight or more layers.

[0018] The hydrogen electrode 11 is connected to a power source 6. The hydrogen electrode 11 can generate hydrogen gas and oxygen ions by, for example, an electrolytic reaction using water vapor. The hydrogen electrode 11 has, for example, a porous electric conductor. Examples of the porous electric conductor include a mixed sintered body (cermet) of a metal and a solid oxide. Examples of the mixed sintered body include yttria-stabilized zirconia and scandia-stabilized zirconia.

[0019] The hydrogen electrode 11 further includes, for example, a catalyst for promoting the electrolytic reaction. The catalyst includes, for example, at least one element selected from platinum (Pt), ruthenium (Ru), cerium (Ce), lanthanum (La), cobalt (Co), nickel (Ni), aluminum (Al), and copper (Cu). The catalyst is supported, for example, on the surface of an electric conductor. The catalyst may form a catalyst layer provided on the surface of the electric conductor.

[0020] The oxygen electrode 12 is connected to a power source 6. The oxygen electrode 12 can generate oxygen gas, for example, by an electrolytic reaction using oxygen ions. The oxygen electrode 12 has, for example, a porous electrical conductor. Examples of the porous electrical conductor include perovskite-type oxides and the like.

[0021] The electrolyte 13 is disposed, for example, between the hydrogen electrode 11 and the oxygen electrode 12. The electrolyte 13 may be provided in contact with each of the hydrogen electrode 11 and the oxygen electrode 12. The electrolyte 13 has, for example, an ion conductor that transmits oxygen ions but does not conduct electricity. Examples of the ion conductor include solid oxides such as stabilized zirconia, perovskite-type oxides, and molded bodies of ceria-based solid solutions.

[0022] The separator 14 is provided to separate the two solid oxide electrochemical cells 10. The separator 14 can, for example, isolate the atmospheres of the adjacent solid oxide electrochemical cells 10. The separator 14 can be formed using, for example, a material such as a metal, a carbon material, or a ceramic.

[0023] The separator 14 has a flow path 14a and a flow path 14b. The shapes of the flow paths 14a and 14b are not limited to those shown in FIG.

[0024] The flow path 14a is provided on the surface of the separator 14 on the hydrogen electrode 11 side, and faces the hydrogen electrode 11. The flow path 14a extends, for example, along the X-axis direction. The flow path 14a can pass a fluid including, for example, a supply gas and hydrogen gas. The flow path 14a has, for example, an inlet connected to a pipe P1 and an outlet connected to a pipe P2.

[0025] The flow path 14b is provided on the surface of the separator 14 on the oxygen electrode 12 side (opposite to the flow path 14a) and faces the oxygen electrode 12. The flow path 14b extends along the Y-axis direction, for example. The flow path 14b has an outlet connected to the pipe P3, for example. The flow path 14b may extend along the X-axis direction. The flow path 14b can pass a fluid including, for example, oxygen gas.

[0026] The electrolysis reaction in the electrolysis stack 1 is carried out, for example, as follows. A gas (supply gas) such as water vapor is supplied to the hydrogen electrode 11 side. Other gases may be supplied together with the water vapor. Examples of the other gases include nitrogen gas and air. The electrolysis reaction at the hydrogen electrode 11 can produce, for example, hydrogen and oxygen ions from the water vapor. Oxygen ions are supplied from the hydrogen electrode 11 side to the oxygen electrode 12 side via the electrolyte 13. The electrolysis reaction at the oxygen electrode 12 can produce oxygen.

[0027] The heating furnace 2 can accommodate, for example, the electrolysis stack 1. The heating furnace 2 can heat, for example, the accommodated electrolysis stack 1. The heating furnace 2 has a space 20 that accommodates the electrolysis stack 1 and an inner surface 21 that surrounds the space 20. The space 20 is preferably provided in the heating furnace 2 and sealed by the inner surface 21. The inner surface 21 is preferably formed of a heat insulating material. The space 20 may contain, for example, air containing oxygen different from the oxygen gas generated at the oxygen electrode 12. The space 20 is connected, for example, to a pipe P4.

[0028] The heating furnace 2 is, for example, an electric furnace. The heating furnace 2 has, for example, a heater. The heating furnace 2 is connected to a power source 6, and when power is supplied from the power source 6, the heater is heated, thereby heating the electrolysis stack 1.

[0029] The gas supply source 3 can supply a supply gas containing water vapor to the electrolysis stack 1, for example. The gas supply source 3 has, for example, a cylinder cabinet that stores the supply gas, and a mass flow controller that adjusts the flow rate of the supply gas flowing through a pipe P1 connected to the cylinder cabinet. The mass flow controller can be controlled by the control device 8. When the supply gas is a mixed gas containing water vapor and oxygen gas, the gas supply source 3 may have separate mass flow controllers for the water vapor and the oxygen gas, respectively.

[0030] The hydrogen collector 4 can collect, for example, a fluid containing hydrogen gas discharged from the electrolysis stack 1. The hydrogen collector 4 is connected to a pipe P2 shown in Fig. 1. The pipe P2 can connect the electrolysis stack 1 and the hydrogen collector 4.

[0031] The hydrogen collector 4 may, for example, purify hydrogen gas. The hydrogen collector 4 may, for example, have a tank capable of storing a fluid containing hydrogen gas, and a gas-liquid separator capable of separating hydrogen gas and water contained in the fluid from the electrolysis stack 1. The hydrogen collector 4 may have a gas separation membrane capable of separating gases other than hydrogen gas contained in the fluid containing hydrogen gas.

[0032] The oxygen collector 5 can collect, for example, a fluid containing oxygen gas discharged from the electrolysis stack 1. The oxygen collector 5 is connected to the pipe P3 shown in Figure 1. The pipe P3 can connect the electrolysis stack 1 and the oxygen collector 5.

[0033] The oxygen collector 5 may, for example, purify oxygen gas. The oxygen collector 5 may, for example, have a tank capable of accommodating a fluid containing oxygen gas, and a gas-liquid separator capable of separating oxygen gas and water contained in the fluid from the electrolysis stack 1. The oxygen collector 5 may have a gas separation membrane capable of separating gases other than oxygen gas contained in the fluid containing oxygen gas. The water vapor electrolysis device shown in FIG. 1 may supply purified oxygen gas to the gas supply source 3 and use it as a component of the supply gas.

[0034] The power supply 6 can supply power to, for example, each of the electrolysis stack 1 and the heating furnace 2. The dashed-dotted line shown in Fig. 1 indicates a power supply voltage or a power supply current. The power supply 6 is connected to, for example, the electrolysis stack 1 and the heating furnace 2 by wired or wireless connection. The power supply 6 may be connected to at least one of the gas supply source 3, the hydrogen collector 4, the oxygen collector 5, the oxygen concentration meter 7, and the control device 8, and supply power to the at least one of the above elements.

[0035] The oxygen concentration meter 7 is provided, for example, outside the heating furnace 2 and connected to the space 20 via a pipe P4. It is preferable that the pipe P4 is not connected to the electrolysis stack 1. Without being limited to FIG. 1, the oxygen concentration meter 7 may be provided, for example, in the middle of the pipe P4. The pipe P4 can be formed using, for example, a metal material.

[0036] The oxygen concentration meter 7 may be arranged, for example, in a region outside the electrolysis stack 1 in the space 20. The oxygen concentration meter 7 may be arranged, for example, on the inner surface 21. In this case, the water vapor electrolysis apparatus does not need to have the pipe P4.

[0037] The oxygen concentration meter 7 can directly or indirectly measure, for example, the oxygen concentration in a region outside the electrolytic stack 1 in the space 20. The oxygen concentration meter 7 can generate and output a detection signal by converting data indicating the measured oxygen concentration into an electrical signal. The dashed-dotted arrow in FIG. 1 indicates the detection signal.

[0038] The control device 8 can receive a detection signal from the oxygen concentration meter 7. The control device 8 can control the gas supply source 3 and the power source 6 using oxygen concentration data included in the detection signal. The control device 8 can generate and output control signals for controlling the states of the gas supply source 3 and the power source 6, respectively, in accordance with the measured oxygen concentration, for example. The dotted arrows shown in FIG. 1 indicate the respective control signals. The control device 8 is connected, for example, to each of the gas supply source 3, the power source 6, and the oxygen concentration meter 7, via a wired or wireless connection. The control device 8 may be connected to at least one of the hydrogen collector 4 and the oxygen collector 5 via a wired or wireless connection, and control the operation of at least one of the hydrogen collector 4 and the oxygen collector 5.

[0039] The control device 8 has hardware having an arithmetic unit such as a processor. Each operation may be stored as an operation program in a computer-readable recording medium such as a memory, and each operation may be executed by appropriately reading the operation program stored in the recording medium by the hardware.

[0040] Next, an example of a water vapor electrolysis method using the water vapor electrolysis device shown in Fig. 1 will be described. The water vapor electrolysis device starts operation by supplying gas from a gas supply source 3 and power from a power source 6 to the electrolysis stack 1 and the heating furnace 2, and produces hydrogen gas and oxygen gas by the above-mentioned electrolysis reaction. This operation can be controlled by a control device 8.

[0041] As described above, in the high-temperature steam electrolysis device, hydrogen gas may leak from the electrolysis stack 1 due to deterioration over time or due to thermal cycles. The leaked hydrogen gas leaks into the region outside the electrolysis stack 1 in the space 20 (the region between the electrolysis stack 1 and the inner surface 21).

[0042] A method for detecting leaked hydrogen gas using a hydrogen detector is known. However, since the leaked hydrogen gas reacts with oxygen gas contained in the air in space 20 to form water, and the amount of hydrogen gas does not increase unless the amount of oxygen gas that can react with hydrogen gas decreases to a certain value, it takes time for the amount of hydrogen gas to increase to a level that can be detected by the hydrogen detector.

[0043] 3 is a schematic diagram showing the relationship between time and the concentrations of oxygen gas and hydrogen gas in the region outside the electrolysis stack 1 in the space 20. As shown in FIG. 3, the concentration of oxygen gas in the space 20 at time T0 immediately after the start of operation of the water vapor electrolysis device is set to a reference value. The reference value is not particularly limited, but is, for example, 21%. Next, when hydrogen gas starts leaking at time T1, the leaked hydrogen gas reacts with oxygen gas to form water, causing the concentration of oxygen gas to decrease over time, and the concentration of hydrogen gas does not increase beyond an amount that cannot be detected by a hydrogen detector (detection limit).

[0044] When there is no oxygen gas capable of reacting with hydrogen gas in the space 20, at time T2, the hydrogen gas concentration in the space 20 starts to increase due to the hydrogen gas that continues to leak. Even if the hydrogen gas concentration increases slightly, there is a high possibility that the hydrogen gas will cause an explosion, so it is preferable to stop the operation of the electrolysis stack 1 as soon as possible. The lower limit of the hydrogen concentration in the explosion limit range in the above region is low at about 4.1%, and if the hydrogen concentration increases above this, there is a risk of explosion.

[0045] Therefore, the steam electrolysis device of the embodiment has an oxygen concentration meter 7 that measures the oxygen concentration in the region outside the electrolysis stack 1 in the space 20, and controls the operation of the electrolysis stack 1 according to the oxygen concentration measured by the oxygen concentration meter 7. For example, the oxygen concentration in the above region is monitored, and the operation of the electrolysis stack 1 can be stopped when the absolute value of the variation of the measured oxygen concentration from the reference value exceeds a threshold value (ΔTH) before the hydrogen concentration starts to increase, or when the value of the measured oxygen concentration falls below the threshold value (TH). The threshold value ΔTH and the threshold value TH can be set appropriately depending on, for example, the configuration and operating conditions of the steam electrolysis device, and are not particularly limited. The operation of the electrolysis stack 1 can be stopped, for example, by controlling the gas supply source 3 according to a control signal from the control device 8 to stop the supply of the supply gas to the electrolysis stack 1, and by controlling the power source 6 according to a control signal from the control device 8 to stop the supply of power to the electrolysis stack 1. The operation of the heating furnace 2 may also be stopped together with the electrolysis stack 1. The heating furnace 2 can be stopped, for example, by controlling the power source 6 according to a control signal from the control device 8 to stop the supply of power to the heating furnace 2. The control device 8 may include a determination circuit that monitors the measured oxygen concentration and determines whether or not to stop the operation of the electrolysis stack 1.

[0046] As described above, the steam electrolysis device of the embodiment can determine the presence or absence of hydrogen leakage before hydrogen gas leaks and the hydrogen concentration in the region outside the electrolysis stack 1 in the space 20 exceeds the explosion limit. Therefore, the operation of the electrolysis stack 1 can be stopped earlier than measuring the hydrogen concentration, thereby improving the safety of the steam electrolysis device.

[0047] (Second configuration example of the steam electrolysis device) Fig. 4 is a schematic diagram showing a second configuration example of a water vapor electrolysis device. The water vapor electrolysis device shown in Fig. 4 differs from the water vapor electrolysis device shown in Fig. 1 at least in that it includes an electrolysis unit 100. The following describes parts that differ from the first configuration example of the water vapor electrolysis device, and the description of the first configuration example of the water vapor electrolysis device can be used for other parts as appropriate.

[0048] The water vapor electrolysis apparatus shown in Fig. 4 includes multiple electrolysis units 100, a gas supply source 3, a hydrogen collector 4, an oxygen collector 5, a power source 6, an oxygen concentration meter 7, a control device 8, multiple pipes P1, multiple pipes P2, multiple pipes P3, multiple pipes P4, a pipe P20, a pipe P30, and a pipe P40. For convenience, the pipes P1, P2, P3, P4, P20, P30, and P40 are indicated by solid lines thicker than the solid line indicating the electrolysis stack 1 shown in Fig. 4.

[0049] Each of the multiple electrolysis units 100 includes an electrolysis stack 1, a heating furnace 2, a pipe P1, a pipe P2, a pipe P3, and a pipe P4. Each of the multiple electrolysis units 100 includes multiple electrolysis stacks 1, multiple heating furnaces 2, multiple pipes P1, multiple pipes P2, multiple pipes P3, and multiple pipes P4. For other descriptions of the electrolysis stack 1 and the heating furnace 2, the descriptions of the electrolysis stack 1 and the heating furnace illustrated in FIG. 1 can be cited as appropriate.

[0050] Each of the multiple pipes P1 is connected to the electrolysis stack 1 in the corresponding electrolysis unit 100. The multiple pipes P1 are connected to a gas supply source 3. For other descriptions of the pipes P1, the description of the pipes P1 illustrated in FIG. 1 can be cited as appropriate.

[0051] Each of the multiple pipes P2 is connected to the electrolysis stack 1 in the corresponding electrolysis unit 100. The multiple pipes P2 are connected to a pipe P20. The pipe P20 is connected to the hydrogen collector 4 and connects each pipe P2 to the hydrogen collector 4. For other descriptions of the pipe P2, the description of the pipe P2 illustrated in FIG. 1 can be cited as appropriate.

[0052] Each of the multiple pipes P3 is connected to the electrolysis stack 1 in the corresponding electrolysis unit 100. The multiple pipes P3 are connected to a pipe P30. The pipe P30 is connected to the oxygen collector 5 and connects each pipe P3 to the oxygen collector 5. For other descriptions of the pipe P3, the description of the pipe P3 illustrated in FIG. 1 can be cited as appropriate.

[0053] Each of the multiple pipes P4 is connected to a region outside the electrolysis stack 1 in the space 20 in the heating furnace 2 of the corresponding electrolysis unit 100. Each of the multiple pipes P4 is preferably not connected to the electrolysis stack 1 of the corresponding electrolysis unit 100. Each of the multiple electrolysis units 100 further includes a switching valve V1. In each of the multiple electrolysis units 100, the switching valve V1 is provided in the pipe P4. The water vapor electrolysis device illustrated in FIG. 4 includes multiple switching valves V1. Each of the multiple switching valves V1 is provided in the pipe P4 in the corresponding electrolysis unit 100. The multiple pipes P4 are connected to a pipe P40. The pipe P40 is connected to an oxygen concentration meter 7, and connects each pipe P4 to the oxygen concentration meter 7 via the switching valve V1. For other descriptions of the pipe P4, the description of the pipe P4 illustrated in FIG. 1 can be cited as appropriate.

[0054] The gas supply source 3 can supply a supply gas containing water vapor to the electrolysis stack 1 in each of the multiple electrolysis units 100. The gas supply source 3 has, for example, a cylinder cabinet that stores a supply gas, and a mass flow controller that adjusts the flow rate of the supply gas flowing through a pipe P1 connected to the cylinder cabinet. The mass flow controller can be controlled by the control device 8. The gas supply source 3 may have a mass flow controller for each electrolysis unit 100, and adjust the supply gas for each electrolysis unit 100 and supply it to the electrolysis stack 1. The gas supply source 3 is connected to the pipe P1 in each of the multiple electrolysis units 100. The description of the gas supply source 3 in FIG. 1 can be used as appropriate for other descriptions of the gas supply source 3.

[0055] The hydrogen collector 4 can collect, for example, a fluid containing hydrogen gas discharged from the electrolysis stacks 1 in the multiple electrolysis units 100. The hydrogen collector 4 is connected to the multiple pipes P2 via pipes P20. The hydrogen collector 4 may be provided separately for each of the multiple electrolysis units 100. For other descriptions of the hydrogen collector 4, the description of the hydrogen collector 4 illustrated in FIG. 1 can be cited as appropriate.

[0056] The oxygen collector 5 can collect, for example, a fluid containing oxygen gas discharged from the electrolysis stacks 1 in the multiple electrolysis units 100. The oxygen collector 5 is connected to the multiple pipes P3 via pipes P30. The oxygen collector 5 may be provided separately for each of the multiple electrolysis units 100. For other descriptions of the oxygen collector 5, the description of the oxygen collector 5 illustrated in FIG. 1 can be cited as appropriate.

[0057] The power supply 6 can supply power to, for example, each of the electrolytic stack 1 and the heating furnace 2 in each of the multiple electrolysis units 100. The dash-dotted line in FIG. 4 indicates a power supply voltage or a power supply current. The power supply 6 is connected to each of the electrolytic stack 1 and the heating furnace 2 in each of the multiple electrolysis units 100 via a wired or wireless connection. For other descriptions of the power supply 6, the description of the power supply 6 illustrated in FIG. 1 can be cited as appropriate.

[0058] The oxygen concentration meter 7 is connected to the space 20 shown in FIG 1 via, for example, a pipe P4 in each of the multiple electrolysis units 100. For other descriptions of the oxygen concentration meter 7, the description of the oxygen concentration meter 7 shown in FIG 1 can be cited as appropriate.

[0059] The control device 8 can receive a detection signal from the oxygen concentration meter 7 in each of the electrolysis units 100. The control device 8 can control the gas supply source 3 and the power source 6 by using data on the oxygen concentration included in the detection signal. The control device 8 can, for example, generate and output control signals for controlling the states of the gas supply source 3 and the power source 6 in accordance with the measured oxygen concentration. The dotted arrows in FIG. 4 indicate the control signals. The control device 8 may select one electrolysis unit 100 from the multiple electrolysis units 100 and control the opening and closing of the switching valve V1 in each of the multiple electrolysis units 100 so as to measure the oxygen concentration in the selected one electrolysis unit 100 by the oxygen concentration meter 7. The control device 8 is connected, for example, to each of the gas supply source 3, the power source 6, and the oxygen concentration meter 7 by wired or wireless connection. The control device 8 may be connected, for example, to the switching valve V1 by wired or wireless connection. In this way, the control device 8 can control the opening and closing of the switching valve V1 in each of the multiple electrolysis units 100 by the control signal. For other details of the control device 8, the description of the control device 8 shown in FIG. 1 can be used as appropriate.

[0060] Next, an example of a water vapor electrolysis method using the water vapor electrolysis device shown in Fig. 4 will be described. The water vapor electrolysis device starts operation by supplying gas from the gas supply source 3 and supplying power to the electrolysis stack 1 and the heating furnace 2 in each of the multiple electrolysis units 100, and generates hydrogen gas and oxygen gas by the above-mentioned electrolysis reaction. This operation can be controlled by the control device 8.

[0061] Furthermore, the second configuration example of the water vapor electrolysis device includes an oxygen concentration meter 7 that measures the concentration of oxygen gas in the space 20 of each electrolysis unit 100, and controls the operation of the corresponding electrolysis stack 1 in accordance with the oxygen concentration in each electrolysis unit 100 measured separately by the oxygen concentration meter 7. For example, the oxygen concentration in the above region is monitored, and the operation of the electrolysis stack 1 in the corresponding electrolysis unit 100 can be stopped when the absolute value of the amount of variation of the measured oxygen concentration from a reference value exceeds a threshold value (ΔTH) or when the value of the measured oxygen concentration falls below the threshold value (TH) before the hydrogen concentration starts to increase. The threshold value ΔTH and the threshold value TH can be set appropriately depending on, for example, the configuration and operating conditions of the water vapor electrolysis device. The operation of the electrolysis stack 1 can be stopped, for example, by controlling the gas supply source 3 according to a control signal from the control device 8 to stop the supply of the supply gas to the electrolysis stack 1, and by controlling the power source 6 according to a control signal from the control device 8 to stop the supply of power to the electrolysis stack 1. The operation of the heating furnace 2 may also be stopped together with the electrolysis stack 1. The heating furnace 2 can be stopped by, for example, controlling the power supply 6 according to a control signal from the control device 8 to stop power supply to the heating furnace 2. The control device 8 may control the multiple switching valves V1 to sequentially open the multiple switching valves V1, thereby sequentially measuring the oxygen concentration in each electrolysis unit 100. The control device 8 may include a determination circuit that monitors the measured oxygen concentration and determines whether to stop the operation of each electrolysis stack 1.

[0062] As described above, the second configuration example of the water vapor electrolysis device includes multiple electrolysis units 100. When hydrogen leakage occurs in any of the multiple electrolysis units 100, the presence or absence of hydrogen leakage can be determined before hydrogen gas leaks and the hydrogen concentration in the region in the space 20 outside the electrolysis stack 1 exceeds the explosion limit. Thus, operation of the problematic electrolysis stack 1 among the multiple electrolysis units 100 can be selectively stopped earlier than measuring the hydrogen concentration, thereby improving the safety of the water vapor electrolysis device.

[0063] The configurations of the above-mentioned embodiments can be applied in combination with each other, and some of them can be replaced. Although several embodiments of the present invention have been described here, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0064] 1...electrolysis stack, 2...heating furnace, 3...gas supply source, 4...hydrogen collector, 5...oxygen collector, 6...power supply, 7...oxygen concentration meter, 8...control device, 10...solid oxide electrochemical cell, 11...hydrogen electrode, 12...oxygen electrode, 13...electrolyte, 14...separator, 14a...flow path, 14b...flow path, 20...space, 21...inner surface, 100...electrolysis unit, P1...piping, P2...piping, P20...piping, P3...piping, P30...piping, P4...piping, P40...piping, P5...piping, T0...time, T1...time, T2...time, V1...switching valve.

Claims

1. an electrolysis cell stack for electrolyzing water vapor to produce hydrogen and oxygen; a heating furnace having a space for accommodating the electrolysis cell stack and for heating the electrolysis cell stack; an oxygen concentration meter for measuring an oxygen concentration in a region of the space outside the electrolysis cell stack; a control device that controls an operation of the electrolysis cell stack in response to the measured oxygen concentration; A steam electrolysis device comprising:

2. The control device shuts down the electrolysis cell stack in operation when a variation in the measured oxygen concentration from a reference value exceeds a threshold value. The steam electrolysis device according to claim 1 .

3. the controller shuts down the electrolysis cell stack in operation when the measured oxygen concentration value falls below a threshold value. The steam electrolysis device according to claim 1 .

4. Further comprising a power source; The control device controls the power supply to the electrolysis cell stack in response to the measured oxygen concentration. The steam electrolysis device according to claim 1 .

5. a gas supply source for supplying the water vapor-containing feed gas to the electrolysis cell stack; The control device controls the supply of the water vapor to the electrolysis cell stack in response to the measured oxygen concentration. The steam electrolysis device according to claim 1 .

6. a first electrolysis unit; and a second electrolysis unit; and Equipped with Each of the first and second electrolysis units comprises: the electrolysis cell stack; The heating furnace; Equipped with the oxygen concentration meter measures the oxygen concentration in the first electrolysis unit and the oxygen concentration in the second electrolysis unit; and the control device controls operation of the electrolytic cell stack in the first electrolysis unit in response to the oxygen concentration measured in the first electrolysis unit, and controls operation of the electrolytic cell stack in the second electrolysis unit in response to the oxygen concentration measured in the second electrolysis unit. The steam electrolysis device according to claim 1 .

7. the control device shuts down the electrolytic cell stack in the first electrolysis unit when an amount of variation of the oxygen concentration measured in the first electrolysis unit from a reference value exceeds a threshold, and shuts down the electrolytic cell stack in operation in the second electrolysis unit when an amount of variation of the oxygen concentration measured in the second electrolysis unit from a reference value exceeds a threshold. The steam electrolysis device according to claim 6.

8. the controller shuts down the electrolytic cell stack in the first electrolysis unit when the value of the oxygen concentration measured in the first electrolysis unit is lower than a threshold value, and shuts down the operating electrolytic cell stack in the second electrolysis unit when the value of the oxygen concentration measured in the second electrolysis unit falls below a threshold value. The steam electrolysis device according to claim 6.

9. Each of the first and second electrolysis units comprises: A first pipe connected to the space; and a switching valve provided in the middle of the first pipe; Further comprising: the control device selects one electrolysis unit from the first and second electrolysis units, and controls opening and closing of the switching valve in each of the first and second electrolysis units so as to measure the oxygen concentration in the selected one electrolysis unit by the oxygen concentration meter. The steam electrolysis device according to claim 6.

10. further comprising second piping connecting the first piping in each of the first and second electrolysis units to the oxygen concentration meter. The steam electrolysis apparatus according to claim 9.

11. A water vapor electrolysis method using a water vapor electrolysis device, comprising: The water vapor electrolysis device comprises: an electrolysis cell stack for electrolyzing water vapor to produce hydrogen and oxygen; a heating furnace having a space for accommodating the electrolysis cell stack and for heating the electrolysis cell stack; Equipped with The steam electrolysis method includes: measuring an oxygen concentration in a region of the space outside the electrolysis cell stack; controlling operation of the electrolysis cell stack in response to the measured oxygen concentration; Steam electrolysis method.

12. shutting down the electrolysis cell stack when the measured oxygen concentration varies from a reference value by more than a threshold value; The method for steam electrolysis according to claim 11.

13. shutting down the electrolysis cell stack when the measured oxygen concentration value is below a threshold value. The method for steam electrolysis according to claim 11.

14. controlling power supply to the electrolysis cell stack in response to the measured oxygen concentration; The method for steam electrolysis according to claim 11.

15. controlling the supply of the water vapor-containing feed gas to the electrolysis cell stack in response to the measured oxygen concentration. The method for steam electrolysis according to claim 11.

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