Steam electrolysis apparatus and its operating method

Abstract

The present invention provides a steam electrolysis apparatus capable of heating a cell stack to achieve a desired temperature distribution. [Solution] The steam electrolysis apparatus comprises a cell stack group 101G in which electrolytic cells consisting of a hydrogen electrode, an electrolyte, and an oxygen electrode are electrically connected via an interconnector, and a heating tube 3 for heating the cell stack group 101G. The heating tube 3 heats a portion of the cell stack group 101G with a high-temperature heat transfer medium and heats the other portion with a heat transfer medium at a lower temperature than the high-temperature heat transfer medium, so as to approach the target temperature distribution T1 of the cell stack group 101G.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a steam electrolysis apparatus and an operation method thereof. BACKGROUND ART

[0002] As a technology for realizing a low-carbon and decarbonized society, development of hydrogen production technology utilizing high-temperature thermal energy generated by a high-temperature gas reactor is underway. One of the hydrogen production methods that can utilize high-temperature thermal energy is SOEC (Solid Oxide Electrolysis Cell).

[0003] Patent Document 1 discloses that as a method of transferring nuclear heat of a high-temperature gas reactor to SOEC, a flow passage for flowing helium gas introduced from the high-temperature gas reactor is formed outside a cylindrical cell stack, so that each cell stack is heated individually. PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0004] PATENT DOCUMENT 1 Japanese Unexamined Patent Application Publication No. 2023-20282 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] However, in Patent Document 1, since the helium gas flow passage is provided for each cell stack, the structure may be complicated and the cost may be increased. In addition, since the helium flow mode is not clearly specified, the helium flow inside the cartridge is unregulated, and unexpected flows (such as circulating flows) may occur, which may fail to provide a desired temperature distribution to the cell stack.

[0006] Further, in SOEC, the temperature of the cell stack varies depending on the operating state (at the time of startup and shutdown, the amount of generated hydrogen, etc.), so it is preferable to perform appropriate heating in accordance with the temperature distribution.

[0007] This disclosure has been made in view of these circumstances and aims to provide a steam electrolysis apparatus and a method for operating the same that can heat a cell stack to a desired temperature distribution. [Means for solving the problem]

[0008] A steam electrolytic apparatus according to one aspect of the present disclosure comprises a cell stack in which electrolytic cells consisting of a hydrogen electrode, an electrolyte, and an oxygen electrode are electrically connected via an interconnector, and a heating unit for heating the cell stack, wherein the heating unit comprises a high-temperature section and a low-temperature section for heating the cell stack to approach a target temperature distribution.

[0009] A method for operating a steam electrolysis apparatus according to one aspect of the present disclosure is a method for operating a steam electrolysis apparatus comprising a cell stack in which electrolytic cells consisting of a hydrogen electrode, an electrolyte, and an oxygen electrode are electrically connected via an interconnector, and a heating unit for heating the cell stack, wherein the heating unit heats a portion of the cell stack with a high-temperature heat transfer medium to approach a target temperature distribution, and heats the other portion with a heat transfer medium at a lower temperature than the high-temperature heat transfer medium. [Effects of the Invention]

[0010] The cell stack can be heated to a desired temperature range. [Brief explanation of the drawing]

[0011] [Figure 1] This is a partially enlarged longitudinal cross-sectional view showing a portion of the cell stack of an SOEC according to one embodiment of the present disclosure. [Figure 2] This is a longitudinal cross-sectional view showing a SOEC cartridge according to one embodiment. [Figure 3] This diagram shows a schematic configuration for supplying heat from a high-temperature gas reactor to a heating tube. [Figure 4] This is a schematic diagram showing the flow direction of the heat transfer medium in the heating tube according to the first embodiment. [Figure 5]It is a perspective view of the main part of the cartridge showing the spirally formed heating tube. [Figure 6] Corresponding to FIG. 4, it is a schematic diagram showing Modification 1. [Figure 7] Corresponding to FIG. 4, it is a schematic diagram showing Modification 2. [Figure 8] Corresponding to FIG. 4, it is a schematic diagram showing Modification 3. [Figure 9] Corresponding to FIG. 4, it is a schematic diagram showing Modification 4. [Figure 10] Corresponding to FIG. 5, it is a schematic diagram showing Modification 5 in which the heating tube has a zigzag folded shape. [Figure 11] Corresponding to FIG. 5, it is a schematic diagram showing Modification 6 in which the heating tube has a header shape. [Figure 12] Corresponding to FIG. 5, it is a schematic diagram showing Modification 7 using a radiation panel. [Figure 13] It is a perspective view showing the radiation panel of FIG. 12. [Figure 14] It is a perspective view showing the modification of FIG. 13. [Modes for Carrying Out the Invention]

[0012] Hereinafter, one embodiment of the present disclosure will be described. A cylindrical solid oxide electrolysis cell will be described as an example of the cell stack of a solid oxide electrolysis cell (SOEC) constituting a steam electrolysis apparatus, but the present disclosure is not necessarily limited to this, and for example, a flat plate type cell stack may be used. The electrolysis cell is formed on a base, but an electrode (a hydrogen electrode or an oxygen electrode) may be formed thick instead of the base to also serve as the base. Hereinafter, one embodiment of the structure and material of the cylindrical solid oxide electrolysis cell according to the present disclosure will be described with reference to the drawings.

[0013] For convenience of explanation, the positional relationship of each component described using the expressions "upper" and "lower" with reference to the drawing sheet indicates the vertically upper side and the vertically lower side, respectively. In addition, in the present embodiment, for components that can achieve similar effects in the vertical direction and the horizontal direction, the vertical direction on the drawing sheet is not necessarily limited to the vertical up-down direction, and may correspond to, for example, a horizontal direction orthogonal to the vertical direction.

[0014] First, with reference to FIG. 1, a cylindrical cell stack using a base tube will be described as an example according to the present embodiment. When a base tube is not used, for example, the fuel electrode may be formed thick to double as the base tube, and the use of the base tube is not limited. Further, although the base tube in the present embodiment is described using a cylindrical shape, the base tube only needs to be tubular, and the cross section is not necessarily limited to a circular shape, and may be, for example, an elliptical shape. A cell stack such as a flat tubular obtained by vertically crushing the peripheral side surface of a cylinder may also be used. Here, FIG. 1 shows one aspect of the cell stack according to the embodiment. The cell stack 101 includes, as an example, a cylindrical base tube 103, a plurality of electrolysis cells 105 formed on the outer peripheral surface of the base tube 103, and an interconnector 107 formed between adjacent electrolysis cells 105. The electrolysis cell 105 is formed by laminating a hydrogen electrode 109, a solid electrolyte membrane 111, and an oxygen electrode 113. In addition, the cell stack 101 includes a lead film 117 electrically connected via an interconnector 107 to the oxygen electrode 113 of the electrolysis cell 105 formed at one outermost end in the axial direction of the base tube 103 among the plurality of electrolysis cells 105 formed on the outer peripheral surface of the base tube 103, and includes a lead film 117 electrically connected to the hydrogen electrode 109 of the electrolysis cell 105 formed at the other outermost end. The gas supplied to and discharged from the hydrogen electrode 109 often contains hydrogen in addition to the water vapor used for electrolysis, but in the following description, to avoid confusion, the supply gas containing hydrogen is referred to as "supply water vapor", and the hydrogen gas containing water vapor discharged from the hydrogen electrode is referred to as "generated hydrogen".

[0015] The base tube 103 is made of a porous material, and its main components are, for example, CaO-stabilized ZrO2 (CSZ), a mixture of CSZ and nickel oxide (NiO) (CSZ+NiO), Y2O3-stabilized ZrO2 (YSZ), or MgAl2O4. This base tube 103 supports the electrolytic cell 105, the interconnector 107, and the lead film 117, and also diffuses the supply water vapor supplied to the inner circumferential surface of the base tube 103 through the pores of the base tube 103 to the hydrogen electrode 109 formed on the outer circumferential surface of the base tube 103.

[0016] The hydrogen electrode 109 is composed of an oxide of a composite material of Ni and a zirconia-based electrolyte material, for example, Ni / YSZ is used. The thickness of the hydrogen electrode 109 is 50 μm to 250 μm, and the hydrogen electrode 109 may be formed by screen printing of a slurry. The solid electrolyte membrane 111 is primarily made of YSZ, which has airtightness that prevents gas from passing through and high oxygen ion conductivity at high temperatures. This solid electrolyte membrane 111 moves oxygen ions (O2-) generated at the hydrogen electrode to the oxygen electrode. The thickness of the solid electrolyte membrane 111 located on the surface of the hydrogen electrode 109 is 5 μm to 100 μm, and the solid electrolyte membrane 111 may be formed by screen printing of a slurry. The oxygen electrode 113 is composed of, for example, a LaSrMnO3-based oxide or a LaCoO3-based oxide, and the oxygen electrode 113 is applied as a slurry using screen printing or a dispenser. The oxygen electrode 113 can also have a two-layer structure. In this case, the oxygen electrode layer (oxygen electrode intermediate layer) on the solid electrolyte membrane 111 side is composed of a material that exhibits high ionic conductivity and excellent catalytic activity. The oxygen electrode intermediate layer may be composed of Sm-doped ceria that exhibits high ionic conductivity, and the oxygen electrode layer (oxygen electrode conductive layer) on the oxygen electrode intermediate layer may be composed of a perovskite-type oxide such as Sr and Ca-doped LaMnO3.

[0017] By applying a negative voltage to the hydrogen electrode 109 and a positive voltage to the oxygen electrode 113, the water vapor contained in the supplied water vapor at the hydrogen electrode 109 receives electrons and undergoes electrolysis to produce hydrogen molecules and oxygen ions (O2-) (see reaction equation (1) below). The generated hydrogen is removed to the outside along with the supplied water vapor. On the other hand, oxygen ions pass through the solid electrolyte membrane 111 due to the potential difference, move to the oxygen electrode 113, release electrons, and become oxygen molecules (see below). (See reaction equation (2)). The generated oxygen is discharged to the outside along with the oxidizing gas supplied to the oxygen electrode. H2O + 2e- → H2 + O2- ... (1) 2O2- → O2 + 4e- ···(2)

[0018] Oxidizing gases do not directly participate in the electrolytic reaction, but they supply the heat necessary for the electrolytic reaction (endothermic reaction) and dissipate excess heat generated during the electrolytic reaction. Typically, these gases contain approximately 15% to 30% oxygen, and air is the most suitable choice. However, other gases such as mixtures of combustion exhaust gas and air, mixtures of oxygen and air, and inert gases such as nitrogen can also be used.

[0019] The interconnector 107 is composed of conductive perovskite-type oxides such as SrTiO3-based M1-xLxTiO3 (where M is an alkaline earth element and L is a lanthanide element) or lanthanum chromite (LaCrO3), and is screen printed as a slurry. The interconnector 107 has a dense film to prevent mixing of the supplied water vapor and oxidizing gas. Furthermore, the interconnector 107 has stable durability and electronic conductivity under both oxidizing and reducing atmospheres. In adjacent electrolytic cells 105, the interconnector 107 electrically connects the oxygen electrode 113 of one electrolytic cell 105 to the hydrogen electrode 109 of the other electrolytic cell 105, thereby connecting adjacent electrolytic cells 105 in series.

[0020] The lead film 117 is required to possess electronic conductivity and have a thermal expansion coefficient close to that of the other materials constituting the cell stack 101. Therefore, it is composed of a composite material of Ni and zirconia-based electrolyte material such as Ni / YSZ, or M1-xLxTiO3 (where M is an alkaline earth element and L is a lanthanide element) such as SrTiO3. This lead film 117 applies the DC power necessary for the electrolytic reaction to the ends of the cell stack 101 to multiple electrolytic cells 105 connected in series by an interconnector 107. Furthermore, the surface on the oxidizing gas side may be protected with an airtight, oxidation-resistant material to prevent oxidation of the constituent materials such as Ni.

[0021] Next, the SOEC cartridge according to this embodiment will be described with reference to Figure 2. Here, Figure 2 shows one embodiment of the solid oxide electrolytic cell (SOEC) cartridge according to this embodiment.

[0022] As shown in Figure 2, the cartridge 203 comprises a plurality of cell stacks 101, a water vapor electrolysis chamber 215, a water vapor supply header 217, a generated hydrogen discharge header 219, an oxidizing gas (air) supply header 221, and an oxidizing gas discharge header 223. The cartridge 203 also comprises an upper tube sheet 225a, a lower tube sheet 225b, an upper insulator 227a, and a lower insulator 227b. In this embodiment, the water vapor supply header 217, the generated hydrogen discharge header 219, the oxidizing gas supply header 221, and the oxidizing gas discharge header 223 are arranged as shown in Figure 2, so that the supplied water vapor and oxidizing gas flow in opposition to each other on the inside and outside of the cell stack 101. However, this is not necessarily required, and for example, the gas may flow parallel to each other on the inside and outside of the cell stack 101, or the oxidizing gas may flow in a direction perpendicular to the longitudinal direction of the cell stack 101. The cartridge 203 is composed of one or more cartridges 203, insulation material, a storage container, etc., forming a module (not shown). The module is a device that maintains an operating state suitable for hydrogen production. Hereafter, the region formed by the water vapor supply header 217 and the oxidizing gas discharge header 223 at the top of the cartridge 203 will be referred to as the upper header 216a, and the region formed by the generated hydrogen discharge header 219 and the oxidizing gas supply header 221 at the bottom of the cartridge 203 will be referred to as the lower header 216b.

[0023] The steam electrolysis chamber 215 is a region formed between the upper insulator 227a and the lower insulator 227b. This steam electrolysis chamber 215 is the region where the electrolytic cells 105 of the cell stack 101 are located, and it is the region where water vapor is electrolyzed to produce hydrogen. The temperature near the center of the cell stack 101 in the longitudinal direction of this steam electrolysis chamber 215 may also be monitored by the temperature measurement unit 620 (such as a temperature sensor or thermocouple), and during steady-state operation, the atmosphere becomes high-temperature, approximately 700°C to 1000°C.

[0024] The steam supply header 217 is the region enclosed by the upper casing 229a and upper tube sheet 225a of the cartridge 203, and is connected to a steam supply branch pipe (not shown) by a steam supply pipe 231a provided on the upper part of the upper casing 229a. The multiple cell stacks 101 are joined together by the upper tube sheet 225a and the upper sealing member 237a, and the steam supply header 217 guides the steam supplied from the steam supply branch pipe (not shown) via the steam supply pipe 231a into the base pipe 103 of the multiple cell stacks 101 at a substantially uniform flow rate, thereby substantially equalizing the hydrogen generation performance of the multiple cell stacks 101.

[0025] The generated hydrogen discharge header 219 is the region enclosed by the lower casing 229b and lower tube sheet 225b of the cartridge 203, and is connected to a generated hydrogen discharge branch pipe (not shown) by a generated hydrogen discharge pipe 231b provided in the lower casing 229b. In addition, multiple cell stacks 101 are joined together by the lower tube sheet 225b and the lower sealing member 237b, and the generated hydrogen discharge header 219 collects the generated hydrogen that passes through the inside of the base tube 103 of the multiple cell stacks 101 and is supplied to the generated hydrogen discharge header 219, and guides it to the generated hydrogen discharge branch pipe (not shown) via the generated hydrogen discharge pipe 231b.

[0026] The oxidizing gas supply main pipe (not shown) branches off a predetermined flow rate of oxidizing gas corresponding to the operating temperature of the module to oxidizing gas supply branch pipes (not shown), supplying it to multiple cartridges 203. The oxidizing gas supply header 221 is the region surrounded by the lower casing 229b, lower tube sheet 225b, and lower insulator 227b of the cartridge 203, and is connected to an oxidizing gas supply branch pipe (not shown) by an oxidizing gas supply pipe 233a provided on the side of the lower casing 229b. This oxidizing gas supply header 221 guides the oxidizing gas supplied from the oxidizing gas supply branch pipe (not shown) via the oxidizing gas supply pipe 233a to the steam electrolysis chamber 215 via an oxidizing gas lower penetration section 235a, which will be described later.

[0027] The oxidizing gas discharge header 223 is the region enclosed by the upper casing 229a, upper tube sheet 225a, and upper insulator 227a of the cartridge 203, and is connected to an oxidizing gas discharge branch pipe (not shown) by an oxidizing gas discharge pipe 233b provided on the side of the upper casing 229a. This oxidizing gas discharge header 223 guides the exhaust oxidizing gas supplied from the steam electrolysis chamber 215 to the oxidizing gas discharge header 223 via the oxidizing gas upper penetration section 235b (described later) to an oxidizing gas discharge branch pipe (not shown) via the oxidizing gas discharge pipe 233b.

[0028] The upper tube sheet 225a is fixed to the side plate of the upper casing 229a between the top plate of the upper casing 229a and the upper insulator 227a, such that the upper tube sheet 225a, the top plate of the upper casing 229a, and the upper insulator 227a are substantially parallel to each other. The upper tube sheet 225a also has a number of holes corresponding to the number of cell stacks 101 provided in the cartridge 203, and each cell stack 101 is inserted into a hole. This upper tube sheet 225a airtightly supports one end of each of the cell stacks 101 via either or both of the upper sealing member 237a and the adhesive member, and also isolates the water vapor supply header 217 from the oxidizing gas discharge header 223.

[0029] The upper insulator 227a is positioned at the lower end of the upper casing 229a such that the upper insulator 227a, the top plate of the upper casing 229a, and the upper tube sheet 225a are substantially parallel, and is fixed to the side plate of the upper casing 229a. The upper insulator 227a is also provided with multiple holes corresponding to the number of cell stacks 101 provided in the cartridge 203. The diameter of these holes is set to be larger than the outer diameter of the cell stacks 101. The upper insulator 227a includes an oxidizing gas upper penetration portion 235b formed between the inner surface of these holes and the outer surface of the cell stacks 101 inserted into the upper insulator 227a.

[0030] The upper insulator 227a separates the steam electrolysis chamber 215 from the oxidizing gas discharge header 223, preventing the atmosphere around the upper tube sheet 225a from becoming too hot, which would reduce its strength and increase corrosion due to the oxidizing agent contained in the oxidizing gas. In addition, to suppress thermal deformation of the upper tube sheet 225a and other components due to temperature differences as they are exposed to the high temperatures inside the steam electrolysis chamber 215, high-temperature resistant materials such as Ni-based alloys may be used. The upper insulator 227a guides the exhaust oxidizing gas, which has passed through the steam electrolysis chamber 215 and been exposed to high temperatures, through the upper oxidizing gas penetration section 235b to the oxidizing gas discharge header 223.

[0031] According to this embodiment, the structure of the cartridge 203 described above causes the supplied steam and oxidizing gas to flow in opposition to each other on the inside and outside of the cell stack 101. As a result, the exhaust oxidizing gas exchanges heat with the steam supplied to the steam electrolysis chamber 215 through the inside of the base tube 103, and is cooled to a temperature at which the upper tube sheet 225a and other components made of the constituent materials can be prevented from being damaged by stress before being supplied to the oxidizing gas discharge header 223. In addition, the supplied steam is heated by heat exchange with the exhaust oxidizing gas discharged from the steam electrolysis chamber 215 and supplied to the steam electrolysis chamber 215. As a result, steam preheated to the temperature required for the electrolytic reaction can be supplied to the steam electrolysis chamber 215 without the use of heaters or the like.

[0032] 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, such that the lower tube sheet 225b, the bottom plate of the lower casing 229b, and the lower insulator 227b are substantially parallel to each other. The lower tube sheet 225b also has a number of holes corresponding to the number of cell stacks 101 provided in the cartridge 203, and each cell stack 101 is inserted into a respective hole. This lower tube sheet 225b airtightly supports the other end of each of the cell stacks 101 via either the lower sealing member 237b or the adhesive member, or both, and also isolates the generated hydrogen discharge header 219 from the oxidizing gas supply header 221.

[0033] The lower insulator 227b is positioned at the upper end of the lower casing 229b such that the lower insulator 227b, the bottom plate of the lower casing 229b, and the lower tube sheet 225b are substantially parallel, and is fixed to the side plate of the lower casing 229b. The lower insulator 227b is also provided with multiple holes corresponding to the number of cell stacks 101 provided in the cartridge 203. The diameter of these holes is set to be larger than the outer diameter of the cell stacks 101. The lower insulator 227b includes an oxidizing gas lower penetration portion 235a formed between the inner surface of these holes and the outer surface of the cell stacks 101 inserted through the lower insulator 227b.

[0034] The lower insulator 227b separates the steam electrolysis chamber 215 from the oxidizing gas supply header 221, preventing the atmosphere around the lower tube sheet 225b from becoming too hot, which would reduce its strength and increase corrosion due to the oxidizing agent contained in the oxidizing gas. In addition, to prevent thermal deformation of the lower tube sheet 225b and other components due to temperature differences when exposed to the high temperatures inside the steam electrolysis chamber 215, high-temperature resistant materials such as Ni-based alloys may be used. The lower insulator 227b guides the oxidizing gas supplied to the oxidizing gas supply header 221 through the lower oxidizing gas penetration section 235a to the steam electrolysis chamber 215.

[0035] According to this embodiment, the structure of the cartridge 203 described above causes the generated hydrogen and the oxidizing gas to flow in opposition to each other on the inside and outside of the cell stack 101. As a result, the generated hydrogen that has passed through the inside of the base tube 103 and through the steam electrolysis chamber 215 undergoes heat exchange with the oxidizing gas supplied to the steam electrolysis chamber 215, and is cooled to a temperature at which damage to the lower tube sheet 225b and other components made of the constituent materials can be prevented by stress before being supplied to the generated hydrogen discharge header 219. In addition, the oxidizing gas is heated by heat exchange with the generated hydrogen and supplied to the steam electrolysis chamber 215. As a result, the oxidizing gas heated to the temperature necessary for the electrolytic reaction can be supplied to the steam electrolysis chamber 215 without the use of heaters or the like.

[0036] Figure 3 schematically shows a configuration in which multiple cell stacks 101 (hereinafter referred to as "cell stack group 101G") provided on the cartridge 203 are heated from the outside. The cell stack group 101G is configured in which multiple cell stacks 101 are densely arranged in parallel, extending in the vertical direction as shown in Figure 2. Here, the case in which the cell stack group is composed of multiple cylindrical cell stacks is described, but the cell stack may also be made by stacking flat cylindrical or flat plate type cells other than cylindrical cells.

[0037] As shown in Figure 3, the cell stack group 101G is heated by the heating tube (heating section) 3 using the nuclear heat of the high-temperature gas reactor 5. The outer circumference of the cell stack group 101G and the heating tube 3 are spaced apart, and a predetermined space is formed between them.

[0038] The coolant (primary helium gas) of the high-temperature gas reactor 5 circulates between it and the intermediate heat exchanger 7. In the intermediate heat exchanger 7, heat exchange occurs between the coolant and the heat transfer medium (secondary helium gas), and the heat transfer medium circulates between the intermediate heat exchanger 7 and the heating tubes (heating section). Therefore, the heat transfer medium heated in the intermediate heat exchanger 7 flows through the heating tubes 3.

[0039] Between the downstream end of the heating tube 3 and the upstream end of the intermediate heat exchanger 7, there is a secondary heat utilization device 9 that further utilizes the heat from the heat transfer medium after heat utilization in the heating tube 3, and a circulator 11 that circulates the heat transfer medium.

[0040] The high-temperature gas reactor 5 is capable of generating thermal energy of 900°C or higher. Alternatively, a heliostat-type solar thermal concentrator may be used as a heat source instead of the high-temperature gas reactor 5. Furthermore, a heat storage device capable of storing high-temperature thermal energy may also be provided.

[0041] Figure 4 shows the flow direction of the heat transfer medium (secondary helium gas) circulating through the heating tube 3. The outer surface of the cell stack group 101G and the heating tube 3 are spaced apart, and a predetermined space is formed between them. The heating tube 3 is provided between the upper insulator 227a and the lower insulator 227b.

[0042] An inlet for the heat transfer medium is provided in the central part 3a of the heating tube 3 in the vertical direction (longitudinal direction of the cell stack 101 group), and outlets for the heat transfer medium are provided at the upper end 3b and lower end 3c of the heating tube 3. Therefore, the central part 3a of the heating tube 3 is the upstream position of the heat transfer medium, and the upper end 3b and lower end 3c are the downstream positions of the heat transfer medium. Consequently, the heat transfer medium is supplied from the central part 3a at a high temperature and discharged from the upper end 3b and lower end 3c at a reduced temperature.

[0043] The central portion 3a of the heating tube 3 is positioned near the center in the longitudinal direction of the cell stack group 101G, and the upper end 3b and lower end 3c of the heating tube 3 are positioned near the upper and lower ends in the longitudinal direction of the cell stack group 101G, respectively. Specifically, the upper end 3b of the heating tube 3 is lower than the lower surface of the upper insulator 227a, and the lower end 3c of the heating tube 3 is higher than the upper surface of the lower insulator 227b.

[0044] The cell stack group 101G is supported at its upper end by an upper tube sheet 225a and upper casing 229a, and at its lower end by an upper header 216a and lower header 216b, which consist of a lower tube sheet 225b and lower casing 229b. There is an allowable temperature that depends on the constituent material of the header. Therefore, it is necessary to maintain the temperature of the upper and lower ends of the cell stack group 101G below this allowable temperature. Furthermore, while a higher operating temperature of the cell stack reduces the internal resistance of the cells and improves electrolysis efficiency, on the other hand, in order to suppress electrode degradation, the maximum cell temperature during operation must be kept below the allowable temperature of the cells. Accordingly, as shown by the solid line in Figure 4, the temperature distribution T1 in the longitudinal direction of the cell stack group 101G during electrolysis should be kept below the allowable temperature at approximately the same temperature near both ends where the cell stack group 101G is supported by the upper header 216a and lower header 216b, and the heating state must be managed so that it is below the maximum allowable temperature of the cells. Similarly, for the same reasons, temperature control is also necessary for flat-plate stacked cell stacks that have headers above and below the cell stack.

[0045] Figure 4 shows an example of the cell temperature distribution (T0) when heating is not performed by a heating tube, indicated by a dashed line. The upper and lower parts of the cell stack are at almost the same temperature, the central part is the highest, and the temperature distribution is almost symmetrical vertically. The constituent materials of the upper header (216a) and lower header (216b), as well as the cell temperature in the central part, are sufficiently low to the allowable temperature. In this way, when the temperature of the constituent materials and cells has a margin of safety relative to the allowable values, supplying a high-temperature heat transfer medium from the central part of the cell stack group 101G allows for heating of the cell stack from the outside while suppressing the rise in the constituent temperature of the upper and lower header sections. By raising the cell temperature distribution to T1, the operating temperature of the entire cell is improved, enabling more efficient hydrogen production.

[0046] Figure 5 shows an example of a heating tube 3 through which a heat transfer medium flows, as shown in Figure 4. As shown in the figure, the cell stack group 101G is arranged with multiple cylindrical cell stacks 101 extending vertically so that the outer shape is approximately a rectangular parallelepiped. A single heating tube 3 is spirally arranged at a predetermined pitch so as to wind around the outer circumference (four sides in the figure) of the cell stack group 101G. The heat transfer medium flows in from the central part 3a and flows out from the upper end 3b and lower end 3c.

[0047] The cell stack group 101G is heated by radiation through a spiral heating tube 3 wound around its outer circumference. As a result, part of the heat required for the endothermic electrolytic reaction is supplied from the heating tube 3.

[0048] The flow rate of the heat transfer medium supplied to the heating tube 3 may be varied by the control unit so that the temperature of the constituent materials in the upper and lower header sections and the maximum cell temperature are both below an allowable value. For example, this can be controlled by changing the flow rate of the circulator 11 (see Figure 3).

[0049] According to this embodiment, the following effects and advantages are achieved. To achieve highly efficient steam electrolysis, it is preferable that the temperature in the steam electrolysis chamber 215, specifically between the lower surface of the upper insulator 227a and the upper surface of the lower insulator 227b, be as high as possible and below the allowable temperature of the cells. On the other hand, if the upper header 216a and lower header 216b are made of, for example, a metal material, a lower allowable temperature is set for the upper header 216a and lower header 216b than for the cells. For this reason, the heat transfer medium supply and discharge positions and the flow direction of the heat transfer medium of the heating tube 3 can be arbitrarily set to approach the target temperature distribution T1 of the cell stack group 101G. This makes it possible to maintain the maximum temperature of both the constituent materials of the upper and lower headers and the cells below the allowable value, while making the operating temperature of the cell stack group 101G a higher temperature distribution (T1) than the initial temperature distribution (TO).

[0050] By positioning the heating tube 3, through which the heat transfer medium flows, at a predetermined distance from the cell stack group 101G, the cell stack group 101G is heated by radiation. This prevents localized heating by the heat transfer medium and allows the cell stack to be heated uniformly.

[0051] The position near the center of the cell stack group 101G was designated as the upstream position of the heat transfer medium flow, and the positions corresponding to the upper and lower ends of the cell stack group 101G were designated as the downstream positions of the heat transfer medium flow. In other words, the area near the center of the cell stack group 101G was heated with a high-temperature heat transfer medium, and the upper and lower ends of the cell stack group 101G were heated with a heat transfer medium at a lower temperature than the center. According to the Stefan-Boltzmann law, the amount of heat transferred by radiation is proportional to the difference in the absolute temperatures of the surface of the object on the high-temperature side (heating tube 3 in this case) and the object on the low-temperature side (cell stack group 101G in this case). Therefore, this heating method is effective in increasing the overall operating temperature of the cell stack group 101G by heating with the heat transfer medium when the temperature of the central part of the cell stack group 101G has a margin above the maximum allowable temperature, and the temperatures of both the upper header 216a and the lower header 216b are below the allowable temperature, thereby improving the efficiency of hydrogen generation.

[0052] The heating tubes 3 are arranged in a spiral pattern surrounding the cell stack group 101G. This allows for effective heating of the entire cell stack group 101G with a simple structure.

[0053] <Example 1> This embodiment can be modified as shown in Figure 6. As shown in the same figure, the flow direction of the heat transfer medium shown in Figure 4 may be reversed. That is, a high-temperature heat transfer medium is supplied from the upper end 3b and lower end 3c of the heating tube 3, and a heat transfer medium with a lower temperature is discharged from the central part 3a. In this case, the heating tubes at the upper end 3b and lower end 3c become the hottest, and the temperature of the heating tube in the central part 3a decreases. This effectively raises the temperature of the upper and lower ends of the cell stack group 101G (specifically, the upper and lower regions of the steam electrolysis chamber 215). Such a heating method is effective, for example, when the temperature of the center of the cell stack group 101G during electrolysis operation is close to the maximum allowable temperature, and the temperature of the support parts of the upper and lower headers of the cell stack group 101G has sufficient margin over the allowable value, thereby raising the temperature of the entire cell stack group 101G while suppressing the rise in the maximum temperature of the cells. Furthermore, for example, during the heating process at startup, the upper and lower header sections with large heat capacity can be effectively heated, thereby shortening the startup time and reducing the temperature difference between the upper and lower parts of the cell stack group 101G.

[0054] <Modification 2> As shown in Figure 7, the heat transfer medium may be supplied from the upper end 3b and discharged from the lower end 3c. In this case, the central part 3a shown in Figure 4 is not used (the central part 3a is omitted in Figure 7). In this modified example, a heating tube without a central part 3a may be used, or the inflow and outflow of the heat transfer medium from the central part 3a may be closed off with a valve or the like. This modified example can be used when the temperature at the upper end of the cell stack group 101G is lower than the temperature at the lower end, as in the initial temperature distribution T0. For example, under operating conditions where the steam flow rate supplied from the upper end of the cell stack group 101G is large relative to the amount of hydrogen generated (low steam utilization rate), the upper end of the cell stack group 101G, which is the upstream end of the steam flow, tends to cool down easily, so the upper end is positioned upstream of the heat transfer medium flow. This raises the temperature on the upper end side of the cell stack group 101G, bringing the temperature of the upper header 216a closer to the allowable temperature, thereby increasing the temperature of the entire cell stack group 101G. Furthermore, for example, when heating an oxidizing gas during startup and supplying it from the lower supply header 221 to raise the module's temperature, supplying the heated heat transfer medium from the upper end 3b, where the temperature rises less easily, allows for uniform heating of the entire steam electrolysis chamber 215, thereby shortening the startup time.

[0055] <Variation 3> As shown in Figure 8, the heat transfer medium may be supplied from the lower end 3c and discharged from the upper end 3b, the opposite of Figure 7. This modified example can be used when the temperature at the lower end of the cell stack group 101G is lower than that at the upper end, as shown in the initial temperature distribution T0. For example, if the flow rate of the oxidizing gas supplied from the lower end of the cell stack group 101G is large relative to the amount of hydrogen generated, the lower end, which is the inlet for the oxidizing gas flow, will cool down easily, so the lower end is positioned upstream of the heat transfer medium flow. This increases the temperature at the lower end of the cell stack group 101G, bringing the temperature of the lower header 216b closer to the allowable temperature, and thus increasing the overall temperature of the cell stack group 101G.

[0056] <Modification 4> As shown in Figure 9, the flow paths of multiple heating tubes 3 may be independently provided from the top to the bottom of the cell stack group 101G. This allows for arbitrary heating amounts at each vertical position of the cell stack group 101G, reducing the temperature difference in the cell section of the electrolysis chamber while keeping the constituent materials of the upper and lower header sections below the allowable temperature, thereby bringing the temperature of the cell stack group 101G closer to the allowable temperature and improving electrolysis efficiency.

[0057] Furthermore, this embodiment (Figure 4) and modifications 1 to 4 may be arbitrarily combined to control the flow direction and flow rate of the heat transfer medium. For example, the control unit obtains an initial temperature distribution T0 using a temperature sensor, steam flow meter, air flow meter, etc. (not shown), and controls the flow direction and flow rate of the heat transfer medium to approach a target temperature distribution T1. This makes it possible to accommodate various operating modes.

[0058] <Modification 5> As shown in Figure 10, instead of the spiral heating tube 3 shown in Figure 6, the heating tube 3 may be in a zigzag shape. Specifically, as shown in Figure 10, the heating tube 3 is formed in a meandering, folded shape. One heating tube 3 may be provided on each of the four sides of the cell stack group 101G.

[0059] The heating tube 3 is formed by repeating units in a meandering manner within the same plane, each unit consisting of a first straight section 3d, a second straight section 3e parallel to the first straight section 3d, and a folded section 3f that connects one end of the first straight section 3d and the second straight section 3e. The direction in which the first straight section 3d and the second straight section 3e extend is perpendicular to the direction in which the cell stack 101 extends (up and down direction).

[0060] By making the heating tube 3 a zigzag shape in this way, the cell stack group 101G can be heated on a predetermined surface. Furthermore, since the heating tubes 3 are folded in a zigzag pattern and can be arranged on a flat surface, they offer excellent manufacturability and ease of installation, and make it easier to achieve manufacturing accuracy.

[0061] Furthermore, the winding heating tubes 3 do not need to be provided on all four sides of the cell stack group 101G; they only need to be provided on at least one side. Furthermore, in the winding heating tube 3, as in Figure 5, the heat transfer medium may be supplied or discharged from the central part of the heating tube, and discharged or supplied from the upper and lower ends.

[0062] <Variation 6> As shown in Figure 11, the heating tube 3 may be in a header shape instead of the zigzag shape shown in Figure 10. Specifically, the heating tube 3 comprises a first header 3g, a second header 3h provided parallel to the first header 3g, and a plurality of heat transfer tubes 3i provided between the first header 3g and the second header 3h, each arranged in parallel. The first header 3g and the second header 3h extend in the vertical direction, and each heat transfer tube 3i extends in a direction perpendicular to the first header 3g and the second header 3h (a direction perpendicular to the cell stack 101). The heat transfer medium may be supplied from the top of the first header 3g and discharged from the top of the second header 3h, or it may be discharged from the bottom of the second header 3h.

[0063] Both ends of the heat transfer tube 3i are connected to the first header 3g and the second header 3h, respectively, so that, for example, the heat transfer medium flows from the first header 3g through each heat transfer tube 3i to the second header 3h. Of course, the flow can also be in the reverse direction. The header-shaped heating tubes 3 may be provided one on each of the four sides of the cell stack group 101G.

[0064] The spacing (pitch) of each heat transfer tube 3i may be set arbitrarily according to the temperature distribution of the cell stack. For example, as shown in Figure 6, in the initial temperature distribution T0 where heating is not performed by the heating tubes, if the margin of the header temperature relative to the allowable value is sufficiently larger than the margin of the maximum cell temperature relative to the allowable value, the pitch at the ends may be narrower and the pitch in the center may be wider. Furthermore, as shown in Figure 7, in the initial temperature distribution T0 without heating by the heating tube, if the temperature of the constituent material of the upper header is significantly lower than the temperature of the constituent material of the lower header, the pitch of the upper header may be narrowed and the pitch of the lower header may be widened. Alternatively, the cell pitch may be kept constant, and flow rate adjustment orifices may be installed at the inlet or outlet of each heat transfer tube 3i to control the flow rate distribution of the heat transfer medium.

[0065] By shaping the heating tube 3 in this manner, the cell stack group 101G can be heated on a predetermined surface. Furthermore, since the heating tubes 3 are arranged in a header shape and can be placed on a flat surface, they offer excellent manufacturability and ease of installation, and it is easier to achieve high manufacturing accuracy.

[0066] Furthermore, the heating tubes 3, which are shaped like headers, do not need to be provided on all four sides of the cell stack group 101G; they only need to be provided on at least one side.

[0067] <Example 7> As shown in Figure 12, a radiant panel 13 may be used instead of the spiral heating tube 3 shown in Figure 10. The radiant panel 13 is, for example, a metal plate and is spaced apart from the cell stack group 101G at a predetermined interval. The radiant panel 13 is provided between the upper insulator 227a and the lower insulator 227b and is provided to cover all or part of one side surface of the cell stack group 101G. One radiant panel 13 may be provided on each of the four sides of the cell stack group 101G. Furthermore, the radiant panel may be installed on the part of one side surface that you want to heat intensively, and not on the part where you want to suppress the temperature rise. For example, as shown in Figure 8, if the initial temperature distribution T0 without heating by the heating tube is extremely low compared to the temperature of the constituent material of the lower header, a radiant panel may be provided only on the lower part.

[0068] Furthermore, by dividing the radiant panel and providing independent heat transfer fluid channels for each, as shown in Figure 9, it is possible to set any desired amount of heating at each vertical position of the cell stack group 101G. This allows the constituent materials of the upper and lower header sections to remain below the allowable temperature, while reducing the temperature difference in the cell section of the electrolysis chamber, bringing the average temperature closer to the allowable temperature and improving electrolysis efficiency.

[0069] As shown in Figure 13, the radiant panel 13 has a flow channel through which a heat transfer medium flows, and the radiant panel is heated by the heat from the heat transfer medium. The inner wall portion 13a faces the cell stack group 101G. The heat transfer medium flows through the heating channel as indicated by the arrows in the figure. However, the flow of the heat transfer medium may be reversed, or the heating channel may be in the horizontal direction. Alternatively, the structure can incorporate a heat transfer tube through which a heat transfer medium flows, instead of a heating channel. By using a heat transfer tube, the thickness of the inner wall portion 13a and the outer wall portion 13b can be reduced even when a high-pressure heat transfer medium flows through it.

[0070] According to this modified configuration, by using a radiant panel 13 as the heating element, the heating temperature of the entire surface of the radiant panel 13 is made uniform through heat conduction from the heat transfer tubes. This reduces the risk of localized heating and allows for more uniform transfer of radiant heat to the cell stack group 101G. Furthermore, since the radiant panel 13 is integrated as a panel structure, it is easy to attach to the cartridge 203.

[0071] As shown in Figure 14, the heating tube 3 may be formed in a zigzag pattern inside the radiant panel 13 to form a single flow path, resulting in one inlet and one outlet for the heat transfer medium. The direction of the heat transfer medium flow may be from top to bottom, as indicated by the arrows in the figure, or from bottom to top.

[0072] Alternatively, radiant heat in the rear direction may be suppressed by installing a reflector or insulating material on the back of the radiant panel 13.

[0073] The steam electrolysis apparatus and its operating method described in each embodiment above can be understood, for example, as follows.

[0074] A steam electrolytic apparatus according to a first aspect of the present disclosure comprises a cell stack (101G) in which electrolytic cells (105) consisting of a hydrogen electrode, an electrolyte, and an oxygen electrode are electrically connected via an interconnector (107), and a heating unit (3, 13) for heating the cell stack, wherein the heating unit (3, 13) heats a portion of the cell stack with a high-temperature heat transfer medium and heats the other portion with a heat transfer medium at a lower temperature than the high-temperature heat transfer medium in order to approach a target temperature distribution of the cell stack.

[0075] To approach the target temperature distribution of the cell stack, a high-temperature section and a low-temperature section were provided in the heating unit. This allows the temperature of the cell stack to be adjusted to any desired temperature distribution, thereby approaching the target temperature distribution.

[0076] A steam electrolytic apparatus according to a second aspect of the present disclosure, in the first aspect described above, is provided with header sections (216a, 216b) that supply or discharge steam and oxidizing gas to both ends of the cell stack, and the target temperature distribution is symmetrical in which both ends are below approximately the same allowable temperature of the header section, and the center between the two ends is below the allowable temperature of the electrolytic cell.

[0077] The header section has an allowable temperature that depends on the constituent materials. In contrast, the area between the two ends is preferably at a higher temperature than the allowable temperature of the support section in order to achieve highly efficient steam electrolysis. Therefore, the target temperature distribution of the cell stack was designed to be symmetrical, with the ends at approximately the same relatively low temperature and the center at a high temperature.

[0078] In the third aspect of the present disclosure, the steam electrolysis apparatus, in the first or second aspect described above, comprises a heating section (3) provided outside the cell stack (101G) at a predetermined interval, and through which a heat transfer medium flows.

[0079] By positioning the heating tubes through which the heat transfer medium flows at a predetermined distance from the cell stack, the cell stack is heated by radiation. This allows the cell stack to be heated uniformly.

[0080] In the steam electrolysis apparatus according to the fourth aspect of this disclosure, in any of the first to third aspects described above, the position corresponding to the center of the cell stack (101G) is set as the upstream position of the heat transfer medium flow, and the positions corresponding to both ends of the cell stack (101G) are set as the downstream positions of the heat transfer medium flow.

[0081] The position corresponding to the center of the cell stack is designated as the upstream position of the heat transfer fluid flow, and the positions corresponding to both ends of the cell stack are designated as the downstream positions of the heat transfer fluid flow. In other words, the center of the cell stack is heated with a high-temperature heat transfer fluid, and both ends of the cell stack are heated with a heat transfer fluid that is cooler than the center. This allows the overall temperature of the cell stack to be raised in accordance with the shape of the target temperature distribution. This heating method can effectively improve the hydrogen production efficiency, for example, when the temperature of the central part of the cell stack group is well above the maximum allowable temperature, and the temperatures of both the upper and lower tube sheets are below the allowable temperature. By heating with the heat transfer fluid, the overall operating temperature of the cell stack group is raised.

[0082] In the fifth aspect of the present disclosure, the steam electrolysis apparatus is configured such that, in any of the first to third aspects, the position corresponding to the center of the cell stack (101G) is the downstream position of the heat transfer medium flow, and the positions corresponding to both ends of the cell stack (101G) are the upstream positions of the heat transfer medium flow.

[0083] The position corresponding to the center of the cell stack is designated as the downstream position in the flow of the heat transfer medium, and the positions corresponding to both ends of the cell stack are designated as the upstream positions in the flow of the heat transfer medium. In other words, both ends of the cell stack are heated with a high-temperature heat transfer medium, and the center of the cell stack is heated with a heat transfer medium that is cooler than the ends. This allows the temperature at both ends of the cell stack to be raised as much as possible. This heating method can be used, for example, when the temperature in the center of the cell stack group is close to the maximum allowable temperature, and the temperatures at the upper and lower ends of the cell stack group are raised to close to the allowable temperature, thereby raising the average temperature of the entire cell stack group. Furthermore, during the heating process at startup, the upper and lower headers with large heat capacity can be heated effectively, shortening the startup time and reducing the temperature difference between the upper and lower parts of the cartridge.

[0084] In the steam electrolysis apparatus according to the sixth aspect of this disclosure, in any of the first to third aspects described above, the position corresponding to one end of the cell stack (101G) is set as the upstream position of the heat transfer medium flow, and the position corresponding to the other end of the cell stack (101G) is set as the downstream position of the heat transfer medium flow.

[0085] The position corresponding to one end of the cell stack is defined as the upstream position in the flow of the heat transfer medium, and the position corresponding to the other end of the cell stack is defined as the downstream position in the flow of the heat transfer medium. In other words, one end of the cell stack is heated with a high-temperature heat transfer medium, and the other end of the cell stack is heated with a heat transfer medium that is at a lower temperature than the first end. This allows the temperature distribution to be brought closer to the target temperature distribution even when the temperatures at both ends of the cell stack do not match. For example, if the steam flow rate supplied from one end of the cell stack is high, the upper end, which is upstream of the steam flow, will cool down more easily, so the upper end should be positioned upstream of the heat transfer medium flow. If the oxidizing gas flow rate supplied from the lower end of the cell stack is high, the other end, which is upstream of the oxidizing gas flow, will cool down more easily, so the other end should be positioned upstream of the heat transfer medium flow.

[0086] In the steam electrolysis apparatus according to the seventh aspect of this disclosure, in any of the first to sixth aspects described above, the heating tube (3) is provided with a plurality of flow paths from one end to the other end of the cell stack (101G).

[0087] A heating tube with multiple flow paths was provided from one end to the other of the cell stack. This allows for arbitrary heating levels at each position of the cell stack, enabling the temperature distribution to approach the target temperature.

[0088] The steam electrolysis apparatus according to the eighth aspect of the present disclosure comprises a cell stack group (101G) in which a plurality of the cell stacks are arranged in any of the first to seventh aspects described above, and the heating tube (3) is arranged in a spiral shape so as to surround the cell stack group.

[0089] By arranging the heating tubes in a spiral pattern around the cell stacks, the entire surface of the cell stacks can be heated efficiently.

[0090] The steam electrolysis apparatus according to the ninth aspect of the present disclosure, in any of the first to seventh aspects described above, comprises a cell stack group (101G) in which a plurality of the cell stacks are arranged, and the heating tube (3) has a zigzag shape formed by repeatedly serpentine units consisting of a first straight section (3d), a second straight section (3e) parallel to the first straight section, and a folded section (3f) that connects one end of the first straight section and the second straight section.

[0091] By making the heating section a zigzag shape, the cell stack group can be heated on a predetermined surface.

[0092] A steam electrolysis apparatus according to the tenth aspect of the present disclosure, in any of the first to seventh aspects described above, comprises a cell stack group (101G) in which a plurality of the cell stacks are arranged in a row, and the heating tube (3) has a header shape comprising a first header (3g), a second header (3h) provided parallel to the first header, and a plurality of heat transfer tubes (3i) provided between the first header and the second header and arranged parallel to each other.

[0093] By making the heating section a header shape, the cell stack group can be heated on a predetermined surface.

[0094] The steam electrolysis apparatus according to the eleventh aspect of this disclosure, in any of the first to seventh aspects described above, comprises a cell stack group (101G) in which a plurality of the cell stacks are arranged, and the heating section is a radiant panel (13) which is a plate-shaped body through which a heat transfer medium flows.

[0095] By using a plate-shaped radiant panel as the heating element, radiant heat can be efficiently transferred to the cell stack group.

[0096] A steam electrolysis apparatus according to the twelfth aspect of this disclosure, in any of the first to eleventh aspects described above, is provided with a flow direction changing means for changing the direction of the flow of the heat transfer medium through the heating section (3, 13).

[0097] By changing the direction of the heat transfer fluid flow, various operating modes can be accommodated.

[0098] A steam electrolysis apparatus according to the 13th aspect of this disclosure is provided with a flow rate adjustment means for adjusting the flow rate of the heat transfer medium flowing through the heating section (3,13) in any of the first to 12 aspects described above.

[0099] By adjusting the flow rate of the heat transfer medium, the amount of heating can be changed according to various operating modes.

[0100] A method for operating a steam electrolysis apparatus according to a first aspect of the present disclosure is a method for operating a steam electrolysis apparatus comprising a cell stack in which electrolytic cells consisting of a hydrogen electrode, an electrolyte, and an oxygen electrode are electrically connected via an interconnector, and a heating unit for heating the cell stack, wherein the heating unit heats a portion of the cell stack with a high-temperature heat transfer medium to approach a target temperature distribution, and heats the other portion with a heat transfer medium at a lower temperature than the high-temperature heat transfer medium. [Explanation of Symbols]

[0101] 3 Heating tube (heating part) 3a central part 3b Upper end 3c Lower end 3d 1st straight line 3e 2nd straight section 3f Turnaround section 3g 1st Header 3h Second Header 3i heat transfer tube 5. High-temperature gas reactor 7 Intermediate heat exchanger 9 Secondary heat utilization equipment 11 Circulation machine 13. Radiant Panel 13a Inner wall section 13b Outer wall 101 Cell Stack 101G Cell Stack Group 103 Base tube 105 Electrolytic Cells 107 Interconnector 109 Hydrogen electrode 111 Solid electrolyte membrane 113 Oxygen electrode 117 Lead film 203 Cartridge 215 Steam Electrolysis Room 216a Top Header 216b Bottom Header 217 Water vapor supply header 219 Hydrogen-generated emission header 221 Oxidizing gas supply header 223 Oxidizing gas emission header 225a Upper tube plate (support part) 225b Lower tube plate (support part) 227a Upper insulation 227b Lower insulation 229a Upper casing 229b Lower casing 231a Steam supply pipe 231b Hydrogen generated discharge pipe 233a Oxidizing gas supply pipe 233b Oxidizing gas exhaust pipe 235a Lower penetration for oxidizing gas 235b Upper penetration for oxidizing gas 237a Upper sealing member 237b Lower sealing member 620 Temperature measurement unit

Claims

1. A cell stack in which electrolytic cells consisting of a hydrogen electrode, an electrolyte, and an oxygen electrode are electrically connected via an interconnector, A heating unit for heating the cell stack, Equipped with, The heating section is a steam electrolysis apparatus that heats a portion of the cell stack with a high-temperature heat transfer medium and heats the other portion with a heat transfer medium at a lower temperature than the high-temperature heat transfer medium, in order to approach the target temperature distribution of the cell stack.

2. The cell stack is provided with header sections on both ends for supplying or discharging water vapor and oxidizing gases. The steam electrolysis apparatus according to claim 1, wherein the target temperature distribution has a symmetrical shape in which both ends are below the substantially same allowable temperature of the header portion and the center between the two ends is below the allowable temperature of the electrolytic cell.

3. The steam electrolysis apparatus according to claim 2, wherein the heating section is provided outside the cell stack at a predetermined interval and comprises heating tubes through which a heat transfer medium flows.

4. The position corresponding to the center of the cell stack is defined as the upstream position of the heat transfer medium flow. The steam electrolysis apparatus according to claim 3, wherein the positions corresponding to both ends of the cell stack are downstream positions in the flow of the heat transfer medium.

5. The position corresponding to the center of the cell stack is defined as the downstream position of the heat transfer medium flow. The steam electrolysis apparatus according to claim 3, wherein the positions corresponding to both ends of the cell stack are upstream positions in the flow of the heat transfer medium.

6. The position corresponding to one end of the cell stack is defined as the upstream position of the heat transfer medium flow. The steam electrolysis apparatus according to claim 3, wherein the position corresponding to the other end of the cell stack is a downstream position in the flow of the heat transfer medium.

7. The steam electrolysis apparatus according to claim 3, wherein the heating tube has a plurality of flow paths from one end to the other end of the cell stack.

8. The cell stacks are arranged in a group of multiple cell stacks, The steam electrolysis apparatus according to claim 3, wherein the heating tube is arranged in a spiral shape so as to surround the cell stack group.

9. The cell stacks are arranged in a group of multiple cell stacks, The steam electrolytic apparatus according to claim 3, wherein the heating tube has a zigzag shape formed by repeatedly serpentine units consisting of a first straight section, a second straight section parallel to the first straight section, and a folded section connecting one end of the first straight section and the second straight section, within the same plane.

10. The cell stacks are arranged in a group of multiple cell stacks, The steam electrolytic apparatus according to claim 3, wherein the heating tube has a header shape comprising a first header, a second header provided parallel to the first header, and a plurality of heat transfer tubes provided between the first header and the second header, each arranged in parallel.

11. The cell stacks are arranged in a group of multiple cell stacks, The steam electrolysis apparatus according to claim 2, wherein the heating section is a radiant panel in the form of a plate through which a heat transfer medium flows.

12. The steam electrolysis apparatus according to claim 2, further comprising a flow direction changing means for changing the direction of the flow of the heat transfer medium through the heating section.

13. The steam electrolysis apparatus according to claim 2, further comprising a flow rate adjustment means for adjusting the flow rate of the heat transfer medium flowing through the heating section.

14. A cell stack in which electrolytic cells consisting of a hydrogen electrode, an electrolyte, and an oxygen electrode are electrically connected via an interconnector, A heating unit for heating the cell stack, A method for operating a steam electrolysis apparatus equipped with, A method for operating a steam electrolysis apparatus, wherein the heating section heats a portion of the cell stack with a high-temperature heat transfer medium to approach a target temperature distribution, and heats the other portion with a heat transfer medium at a lower temperature than the high-temperature heat transfer medium.

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