Solid oxide electrolysis cell stack, electrolysis cell module, hydrogen production system, and method for operating solid oxide electrolysis cell stack

Abstract

To suitably generate a gas other than hydrogen.SOLUTION: The SOEC electrolyzes supplied water vapor to generate hydrogen. Provided are a cathode flow path 209 through which a steam-containing gas containing steam and nitrogen flows, an anode flow path 207 through which an oxidizing gas flows, a steam electrolysis chamber 215 into which the steam-containing gas flowing through the cathode flow path 209 and the oxidizing gas flowing through the anode flow path 207 are introduced and which electrolyzes the steam supplied from the cathode flow path 209 to generate hydrogen and discharges a mixed gas containing the generated hydrogen, and a lower heat exchange unit 213 that exchanges heat between the mixed gas discharged from the steam electrolysis chamber 215 and the oxidizing gas supplied to the steam electrolysis chamber 215. The lower heat exchange portion 213 is configured to have a predetermined temperature at which the mixed gas that exchanges heat with the oxidizing gas has a desired composition.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a solid oxide electrolysis cell stack, an electrolysis cell module, a hydrogen production system, and a method of operating a solid oxide electrolysis cell stack. [Background technology]

[0002] Water electrolysis, which produces hydrogen and oxygen by electrochemically decomposing water, is a hydrogen production method with excellent environmental properties that does not emit carbon dioxide. Examples of such methods include alkaline electrolysis, which electrolyzes liquid water, solid polymer electrolysis, and steam electrolysis, which electrolyzes water vapor. Among these, solid oxide electrolysis cells (SOECs), which electrolyze high-temperature water vapor, use ceramics with oxygen ion conductivity, such as yttria-stabilized zirconia, as the electrolyte. This allows for the use of thermal energy from high-temperature water vapor as part of the energy required for the electrolysis reaction, enabling more efficient hydrogen production than other electrolysis methods. Furthermore, co-electrolysis is also possible, in which a mixture of high-temperature water vapor and carbon dioxide (CO2) is supplied, and the hydrogen and carbon dioxide produced by electrolysis are reacted in the electrolysis cell to directly produce carbon monoxide (CO) and hydrocarbon compounds.

[0003] In such electrolytic cells, it is possible to produce gases other than hydrogen by reacting the produced hydrogen with other gases (for example, Patent Document 1). Patent Document 1 describes a system in which water vapor and a reducing medium are supplied to the hydrogen electrode side of the electrolytic cell, and the produced hydrogen and the reducing medium are further reacted to produce new hydrogen compounds. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-77464 Summary of the Invention [Problem to be solved by the invention]

[0005] In a hydrogen generation system equipped with an electrolytic cell, when generating gases other than hydrogen (e.g., ammonia, methane, etc.), a reactor for reacting the generated hydrogen with the other gas must be provided in addition to the electrolytic cell stack. However, providing a reactor for reacting hydrogen with the other gas in addition to the electrolytic cell stack increases equipment costs. To suppress the increase in equipment costs, it is possible to react the generated hydrogen with the other gas inside the same electrolytic cell stack and extract the gas other than hydrogen. In this way, the reactor for reacting the generated hydrogen with the other gas can be omitted or its capacity can be reduced, thereby suppressing the increase in equipment costs.

[0006] However, the electrolysis reaction temperature in an electrolytic cell is generally high (e.g., 750°C or higher), and when a gas other than hydrogen is produced in the same electrolytic cell, the reaction temperature becomes high, so there is a possibility that the desired gas other than hydrogen cannot be suitably produced in terms of the equilibrium composition.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide a solid oxide electrolysis cell stack, an electrolysis cell module, a hydrogen production system, and an operation method for a solid oxide electrolysis cell stack that can also suitably produce gases other than hydrogen. [Means for solving the problem]

[0008] In order to solve the above problems, the solid oxide electrolysis cell stack, electrolysis cell module, hydrogen production system, and solid oxide electrolysis cell operating method of the present disclosure employ the following measures. A solid oxide electrolysis cell according to one aspect of the present disclosure is a solid oxide electrolysis cell that produces hydrogen by electrolyzing supplied water vapor, and includes: a cathode flow path through which a water vapor-containing gas containing the water vapor and other gases flows; an anode flow path through which an oxidizing gas flows; an electrolysis unit into which the water vapor-containing gas that has flowed through the cathode flow path and the oxidizing gas that has flowed through the anode flow path are introduced, which electrolyzes the water vapor supplied from the cathode flow path to produce the hydrogen and discharges the produced mixed gas containing the hydrogen; and a heat exchange unit that exchanges heat between the mixed gas discharged from the electrolysis unit and the oxidizing gas supplied to the electrolysis unit, and the heat exchange unit is configured to maintain a predetermined temperature at which the mixed gas that exchanges heat with the oxidizing gas has a desired composition.

[0009] A method for operating a solid oxide electrolysis cell stack according to one aspect of the present disclosure is a method for operating a solid oxide electrolysis cell stack that produces hydrogen by electrolyzing supplied water vapor, the method comprising: a cathode flow path through which a water vapor-containing gas containing the water vapor and other gases flows; an anode flow path through which an oxidizing gas flows; an electrolysis unit into which the water vapor-containing gas that has flowed through the cathode flow path and the oxidizing gas that has flowed through the anode flow path are introduced, that electrolyzes the water vapor supplied from the cathode flow path to produce the hydrogen and discharges the produced mixed gas containing the hydrogen; and a heat exchange unit that exchanges heat between the mixed gas discharged from the electrolysis unit and the oxidizing gas supplied to the electrolysis unit, the method comprising the step of performing heat exchange in the heat exchange unit so that the mixed gas that is heat exchanged with the oxidizing gas has a predetermined temperature at which the mixed gas has a desired composition. [Effects of the Invention]

[0010] According to the present disclosure, gases other than hydrogen can also be suitably produced. [Brief explanation of the drawings]

[0011] [Figure 1] 1 illustrates an electrolysis cell stack according to a first embodiment of the present disclosure; FIG. [Figure 2]FIG. 1 is a diagram showing an electrolysis cell cartridge according to a first embodiment of the present disclosure. [Figure 3] 1 is a graph showing the temperature distribution of an electrolysis cell cartridge according to a first embodiment of the present disclosure. [Figure 4] 1 is a graph showing the relationship between the outlet equilibrium temperature and the amount of ammonia produced in the electrolytic cell cartridge according to the first embodiment of the present disclosure. [Figure 5] 1 is a graph showing the relationship between the pressure and the amount of ammonia produced in the electrolytic cell cartridge according to the first embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of a solid oxide electrolysis cell stack, an electrolysis cell module, a hydrogen production system, and an operating method of a solid oxide electrolysis cell stack according to the present disclosure will be described with reference to the drawings.

[0013] [First embodiment] A first embodiment of the present disclosure will be described with reference to Figures 1 to 5. A solid oxide electrolysis cell stack according to this embodiment is included in a hydrogen production system.

[0014] Although a cylindrical solid oxide electrolysis cell will be described as an example of a cell stack of a solid oxide electrolysis cell (SOEC), this is not necessarily the case and a flat cell stack may also be used. The electrolysis cell is formed on a substrate, but an electrode (hydrogen electrode or oxygen electrode) may be formed thickly and serve as the substrate instead of the substrate. An embodiment of the structure and materials of a cylindrical solid oxide electrolysis cell according to the present disclosure will be described below with reference to the drawings.

[0015] For ease of explanation, the positional relationships of the components described using the expressions "upper" and "lower" with respect to the plane of the paper indicate the vertically upper and lower sides, respectively. Also, in this embodiment, for components that can obtain similar effects in the vertical and horizontal directions, the vertical direction on the plane of the paper is not necessarily limited to the vertically upper and lower directions, but may correspond to, for example, a horizontal direction perpendicular to the vertical direction.

[0016] First, referring to FIG. 1, a cylindrical cell stack using a substrate tube will be described as an example according to this embodiment. When a substrate tube is not used, for example, the fuel electrode may be formed thick and used as the substrate tube, and the use of a substrate tube is not limited. Furthermore, although the substrate tube in this embodiment will be described as having a cylindrical shape, the substrate tube may be cylindrical and is not necessarily limited to a circular cross section, and may be, for example, elliptical. A flattened cylinder (Flat) in which the peripheral side of a cylinder is crushed vertically can be used. A cell stack such as a tubular cell may also be used.

[0017] 1 shows one aspect of a cell stack according to an embodiment. The cell stack 101 includes, for example, a cylindrical substrate tube 103, a plurality of electrolysis cells 105 formed on the outer peripheral surface of the substrate tube 103, and interconnectors 107 formed between adjacent electrolysis cells 105. The electrolysis cells 105 are formed by stacking a hydrogen electrode 109, a solid electrolyte membrane 111, and an oxygen electrode 113.

[0018] The cell stack 101 also includes a lead film 115 electrically connected via an interconnector 107 to the oxygen electrode 113 of the electrolytic cell 105 formed at one end of the electrolytic cell 105 at the extreme axial direction of the base tube 103 among the multiple electrolytic cells 105 formed on the outer peripheral surface of the base tube 103, and a lead film 115 electrically connected to the hydrogen electrode 109 of the electrolytic cell 105 formed at the other extreme 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 will be referred to as "supplied water vapor" and the gas containing water vapor discharged from the hydrogen electrode will be referred to as "mixed gas."

[0019] The substrate tube 103 is made of a porous material, and its main component is, for example, CaO-stabilized ZrO2 (CSZ), a mixture of CSZ and nickel oxide (NiO) (CSZ+NiO), Y2O3-stabilized ZrO2 (YSZ), or MgAl2O4. The substrate tube 103 supports the electrolytic cell 105, the interconnector 107, and the lead film 115, and also diffuses the supply steam supplied to the inner circumferential surface of the substrate tube 103 through the pores of the substrate tube 103 to the hydrogen electrode 109 formed on the outer circumferential surface of the substrate tube 103. The substrate tube 103 contains a metal component (nickel, etc.) that promotes the reaction of combining hydrogen and nitrogen.

[0020] The hydrogen electrode 109 is made of a composite oxide of Ni and a zirconia-based electrolyte material, for example, Ni / YSZ. The thickness of the hydrogen electrode 109 is 50 μm to 250 μm, and the hydrogen electrode 109 may be formed by screen printing a slurry.

[0021] The solid electrolyte membrane 111 is mainly made of YSZ, which has gas-tightness and high oxygen ion conductivity at high temperatures. The solid electrolyte membrane 111 is made of YSZ, which has gas-tightness and high oxygen ion conductivity at high temperatures. The solid electrolyte membrane 111 is made of YSZ, which has high oxygen ion conductivity at high temperatures and high oxygen ion conductivity at high temperatures. 2- The solid electrolyte membrane 111 located on the surface of the hydrogen electrode 109 has a thickness of 5 μm to 100 μm, and may be formed by screen printing a slurry.

[0022] The oxygen electrode 113 is made of, for example, a LaSrMnO3-based oxide or a LaCoO3-based oxide, and the oxygen electrode 113 is formed by screen printing or by applying a slurry using a dispenser. The oxygen electrode 113 may 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 made of a material that exhibits high ionic conductivity and excellent catalytic activity. The oxygen electrode intermediate layer may be made of Sm-doped ceria, which exhibits high ionic conductivity, and the oxygen electrode layer (oxygen electrode conductive layer) on the oxygen electrode intermediate layer may be made of a perovskite-type oxide such as Sr- and Ca-doped LaMnO3.

[0023] By applying a negative voltage to the hydrogen electrode (cathode) 109 and a positive voltage to the oxygen electrode (anode) 113, the water vapor contained in the supplied water vapor receives electrons at the hydrogen electrode 109 and is electrolyzed to produce hydrogen molecules and oxygen ions (O 2- ) is produced (see reaction formula (1) below). The produced hydrogen is extracted to the outside together with the supplied steam.

[0024] On the other hand, the 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 reaction formula (2) below). The generated oxygen is discharged to the outside together with the oxidizing gas supplied to the oxygen electrode. H2O+2e-→H2+O 2- ···(1) 2O 2- →O2+4e- (2)

[0025] The oxidizing gas is not directly involved in the electrolysis reaction, but supplies the heat necessary for the electrolysis reaction (endothermic) and discharges excess heat generated by the electrolysis reaction. It is usually a gas containing approximately 15% to 30% oxygen, and air is a typical example, but other gases that can be used include a mixture of combustion exhaust gas and air, a mixture of oxygen and air, and inert gases such as nitrogen.

[0026] The interconnector 107 is made of M such as SrTiO3. 1-x L x The interconnector 107 is made of a conductive perovskite oxide such as TiO3 (where M is an alkaline earth metal element and L is a lanthanoid element) or lanthanum chromite (LaCrO3), and is screen-printed as a slurry. The interconnector 107 is a dense film that prevents the supplied water vapor and oxidizing gas from mixing. The interconnector 107 also has stable durability and electronic conductivity in both oxidizing and reducing atmospheres. This interconnector 107 electrically connects the oxygen electrode 113 of one electrolytic cell 105 to the hydrogen electrode 109 of the other electrolytic cell 105, connecting the adjacent electrolytic cells 105 in series.

[0027] The lead film 115 is required to have electronic conductivity and a thermal expansion coefficient close to that of the other materials constituting the cell stack 101. Therefore, a composite material of Ni and a zirconia-based electrolyte material, such as Ni / YSZ, or an M material such as an SrTiO3-based material is used. 1-x L x It is made of TiO3 (M is an alkaline earth metal element, and L is a lanthanoid element). This lead film 115 applies DC power required for the electrolytic reaction to the end of the cell stack 101 to the multiple electrolytic cells 105 connected in series by the interconnectors 107. In addition, the surface on the oxidizing gas side may be protected with an airtight oxidation-resistant material to prevent oxidation of metal materials such as Ni.

[0028] The base tube 103 on which the slurry film of the hydrogen electrode 109, the solid electrolyte membrane 111, and the interconnector 107 is formed is co-sintered in the atmosphere at a sintering temperature of, for example, 1350°C to 1450°C. Next, the base tube 103 having the slurry film of the oxygen electrode 113 formed on the co-sintered base tube 103 is sintered in the atmosphere. The sintering temperature is, for example, 1100°C to 1250°C. The sintering temperature here is set to be lower than the co-sintering temperature after the base tube 103 to the interconnector 107 are formed.

[0029] Next, the SOEC cartridge according to this embodiment will be described with reference to Fig. 2. Here, Fig. 2 shows one embodiment of the solid oxide electrolysis cell (SOEC) cartridge according to this embodiment.

[0030] The cell stack 101 and the cartridge 203 are housed in a module container (not shown) of the SOEC. A plurality of cartridges 203 may be provided in the module container. As shown in Figure 2, the cartridge 203 includes multiple cell stacks 101, a water vapor electrolysis chamber (electrolysis section) 215, a water vapor-containing gas header 217, a mixed gas discharge header 219, an oxidizing gas (air) supply header 221, and an oxidizing gas discharge header 223.

[0031] Furthermore, cartridge 203 includes upper tube plate 225a, lower tube plate 225b, upper heat insulator 227a, and lower heat insulator 227b. In this embodiment, cartridge 203 has water vapor-containing gas header 217, mixed gas discharge header 219, oxidizing gas supply header 221, and oxidizing gas discharge header 223 arranged as shown in Fig. 2, so that supply water vapor and oxidizing gas flow in opposite directions inside and outside cell stack 101. However, this is not necessarily required, and for example, the flow may be parallel inside and outside cell stack 101, or the oxidizing gas may flow in a direction perpendicular to the longitudinal direction of cell stack 101.

[0032] The steam electrolysis chamber 215 is a region formed between the lower end of the upper insulator 227a and the upper end of the lower insulator 227b. This steam electrolysis chamber 215 is a region in which the electrolysis cells 105 of the cell stack 101 are arranged, and is a region in which hydrogen is produced by electrolyzing steam. The temperature near the center of the steam electrolysis chamber 215 in the longitudinal direction of the cell stack 101 may be monitored by a temperature measurement unit 620 (such as a temperature sensor or a thermocouple), and during steady-state operation of the cartridge 203, a high-temperature atmosphere of approximately 700°C to 1000°C is produced.

[0033] The water vapor-containing gas header 217 is an area surrounded by the upper casing 229a and upper tube plate 225a of the cartridge 203, and is connected to a water vapor-containing gas branch pipe (not shown) by a water vapor-containing gas supply pipe 231a provided at the top of the upper casing 229a. The multiple cell stacks 101 are joined to the upper tube plate 225a by an upper seal member 237a, and the water vapor-containing gas header 217 guides water vapor supplied via the water vapor-containing gas supply pipe 231a into the interiors of the base tubes 103 of the multiple cell stacks 101 at a substantially uniform flow rate, thereby substantially uniforming the hydrogen generation performance of the multiple cell stacks 101.

[0034] The mixed gas discharge header 219 is an area surrounded by the lower casing 229b and lower tube plate 225b of the cartridge 203, and is connected to a mixed gas discharge branch pipe (not shown) by a mixed gas discharge pipe 231b provided in the lower casing 229b. The multiple cell stacks 101 are joined to the lower tube plate 225b by a lower seal member 237b, and the mixed gas discharge header 219 collects the mixed gas that passes through the insides of the base tubes 103 of the multiple cell stacks 101 and is supplied to the mixed gas discharge header 219, and leads it to the mixed gas discharge branch pipe (not shown) via the mixed gas discharge pipe 231b.

[0035] An oxidizing gas supply header (not shown) supplies a predetermined flow rate of oxidizing gas to the plurality of cartridges 203 in accordance with the operating temperature of the module (not shown). The oxidizing gas supply header 221 is an area 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) via an oxidizing gas supply pipe 233a provided on the side surface of the lower casing 229b. The oxidizing gas supply header 221 guides a predetermined flow rate of 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 a lower oxidizing gas penetration 235a (described later).

[0036] The oxidizing gas discharge header 223 is an area surrounded by the upper casing 229a, upper tube plate 225a, and upper heat 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 surface of the upper casing 229a. The oxidizing gas discharge header 223 guides the exhaust oxidizing gas, which is supplied to the oxidizing gas discharge header 223 from the steam electrolysis chamber 215 via an oxidizing gas upper penetration 235b (described later), to the oxidizing gas discharge branch pipe (not shown) via the oxidizing gas discharge pipe 233b.

[0037] The upper tube plate 225a is fixed to the side plate of the upper casing 229a between the top plate of the upper casing 229a and the upper heat insulator 227a so that the upper tube plate 225a, the top plate of the upper casing 229a, and the upper heat insulator 227a are approximately parallel to each other. The upper tube plate 225a has a plurality of holes corresponding to the number of cell stacks 101 provided in the cartridge 203, and the cell stacks 101 are inserted into the holes. The upper tube plate 225a airtightly supports one end of the plurality of cell stacks 101 via either or both of an upper seal member 237a and an adhesive member, and separates the water vapor-containing gas header 217 from the oxidizing gas discharge header 223.

[0038] The upper heat insulator 227a is disposed at the lower end of the upper casing 229a so that the upper heat insulator 227a, the top plate of the upper casing 229a, and the upper tube plate 225a are substantially parallel to each other, and is fixed to the side plates of the upper casing 229a. The upper heat insulator 227a has a plurality of holes formed therein corresponding to the number of cell stacks 101 provided in the cartridge 203. The diameters of the holes are set larger than the outer diameters of the cell stacks 101. The upper heat insulator 227a has upper oxidizing gas penetration portions 235b formed between the inner surfaces of the holes and the outer surfaces of the cell stacks 101 inserted through the upper heat insulator 227a. The upper oxidizing gas penetration portions 235b are regions where heat exchange between the supply steam and the oxidizing gas takes place.

[0039] The upper heat insulator 227a separates the steam electrolysis chamber 215 from the oxidizing gas discharge header 223, and prevents the atmosphere surrounding the upper tube sheet 225a from becoming hot, thereby reducing its strength and increasing corrosion caused by the oxidizing agent contained in the oxidizing gas. Furthermore, a metal material with high temperature resistance, such as a Ni-based alloy, may be used to prevent the upper tube sheet 225a and other components from being thermally deformed due to the temperature difference caused by exposure to the high temperature inside the steam electrolysis chamber 215. The upper heat insulator 227a guides the exhaust oxidizing gas, which has been exposed to high temperatures after passing through the steam electrolysis chamber 215, through the upper oxidizing gas penetration 235b and into the oxidizing gas discharge header 223.

[0040] According to this embodiment, the structure of the cartridge 203 described above allows the supply water vapor-containing gas and the oxidizing gas to flow in opposite directions inside and outside the cell stack 101. As a result, the exhaust oxidizing gas exchanges heat with the water vapor-containing gas supplied to the steam electrolysis chamber 215 through the inside of the base tube 103, and is cooled to a temperature that prevents damage due to stress to the upper tube plate 225a made of a metal material, and is supplied to the oxidizing gas discharge header 223. The supply water vapor-containing gas is heated by heat exchange with the exhaust oxidizing gas discharged from the steam electrolysis chamber 215, and is supplied to the steam electrolysis chamber 215. As a result, a water vapor-containing gas preheated to a temperature required for the electrolysis reaction can be supplied to the steam electrolysis chamber 215 without using a heater or the like.

[0041] The lower tube plate 225b is fixed to the side plate of the lower casing 229b between the bottom plate of the lower casing 229b and the lower insulator 227b so that the lower tube plate 225b, the bottom plate of the lower casing 229b, and the lower insulator 227b are approximately parallel to each other. The lower tube plate 225b has a plurality of holes corresponding to the number of cell stacks 101 provided in the cartridge 203, and the cell stacks 101 are inserted into the holes. The lower tube plate 225b airtightly supports the other ends of the plurality of cell stacks 101 via either or both of a lower seal member 237b and an adhesive member, and also separates the mixed gas discharge header 219 from the oxidizing gas supply header 221.

[0042] The lower heat insulator 227b is disposed at the upper end of the lower casing 229b so that the lower heat insulator 227b, the bottom plate of the lower casing 229b, and the lower tube plate 225b are substantially parallel to each other, and is fixed to the side plate of the lower casing 229b. The lower heat insulator 227b has a plurality of holes formed therein corresponding to the number of cell stacks 101 provided in the cartridge 203. The diameters of the holes are set larger than the outer diameters of the cell stacks 101. The lower heat insulator 227b has lower oxidizing gas penetration portions 235a formed between the inner surfaces of the holes and the outer surfaces of the cell stacks 101 inserted through the lower heat insulator 227b. The lower oxidizing gas penetration portions 235a are regions where heat exchange occurs between the mixed gas discharged from the electrolysis section and the oxidizing gas.

[0043] The lower heat insulator 227b separates the steam electrolysis chamber 215 from the oxidizing gas supply header 221, and prevents the atmosphere surrounding the lower tube sheet 225b from becoming hot, thereby reducing its strength and increasing corrosion caused by the oxidizing agent contained in the oxidizing gas. Furthermore, a metal material with high temperature resistance, such as a Ni-based alloy, may be used to prevent thermal deformation of the lower tube sheet 225b and other components due to temperature differences when the lower tube sheet 225b and other components are exposed to high temperatures within the steam electrolysis chamber 215. The lower heat insulator 227b guides the oxidizing gas supplied to the oxidizing gas supply header 221 through the lower oxidizing gas penetration 235a to the steam electrolysis chamber 215.

[0044] According to this embodiment, the structure of the cartridge 203 described above allows the mixed gas and the oxidizing gas to flow in opposite directions between the inside and outside of the cell stack 101. As a result, the mixed gas discharged from the steam electrolysis chamber 215 through the interior of the base tube 103 exchanges heat with the oxidizing gas supplied to the steam electrolysis chamber 215, and is cooled to a temperature that prevents damage due to stress to the lower tube plate 225b made of a metal material, and is supplied to the mixed gas discharge header 219. The oxidizing gas is also heated by heat exchange with the mixed gas and is supplied to the steam electrolysis chamber 215. As a result, the oxidizing gas heated to a temperature required for the electrolysis reaction can be supplied to the steam electrolysis chamber 215 without using a heater or the like.

[0045] As shown in FIG. 2, the cartridge 203 according to this embodiment includes a steam electrolysis chamber 215, an upper heat exchanger 211 provided above the steam electrolysis chamber 215, and a lower heat exchanger (heat exchanger) 213 provided below the steam electrolysis chamber 215.

[0046] The steam electrolysis chamber 215 is a region formed between the lower end of the upper insulator 227a and the upper end of the lower insulator 227b. The steam electrolysis chamber 215 is a region where electrolysis cells 105 are mainly arranged in the substrate tubes 103 of the cell stack 101 (see FIGS. 1 and 2), and where hydrogen is produced by electrolyzing steam. The steam electrolysis chamber 215 is a high-temperature atmosphere of 700°C to 1000°C during steady-state operation.

[0047] The upper heat exchanger 211 is provided in a region formed between the lower end of the upper tube plate 225a and the lower end of the lower heat insulator 227b. The upper heat exchanger 211 is provided in a region (see FIG. 2) in which the electrolysis cells 105 are not arranged in the base tubes 103 of the cell stack 101. The upper heat exchanger 211 exchanges heat between a gas (a mixed gas of water vapor and nitrogen) flowing inside the base tubes 103 and a gas (oxidizing gas) flowing outside the base tubes 103 via the cell stack 101. Specifically, in the upper heat exchanger 211, the gas flowing inside the base tubes 103 is heated, and the gas flowing outside the base tubes 103 is cooled.

[0048] The lower heat exchange section 213 is provided in a region formed between the upper end of the lower heat insulator 227b and the upper end of the lower tube plate 225b. The lower heat exchange section 213 includes the lower heat insulator 227b and a part of the base tube 103 located in this region. The lower heat exchanger 213 is provided in a region of the base tube 103 of the cell stack 101 where no electrolysis cell 105 is disposed (see FIG. 2). The lower heat exchanger 213 exchanges heat between the gas flowing inside the base tube 103 and the gas (oxidizing gas) flowing outside the base tube 103 via the cell stack 101. Specifically, in the lower heat exchanger 213, the gas flowing inside the base tube 103 is cooled and the gas flowing outside the base tube 103 is heated.

[0049] The lower heat exchanger 213 is configured so that the gas flowing inside the base tube 103 is at a predetermined temperature. In other words, the lower heat exchanger 213 is designed so that the gas flowing inside the base tube 103 is at a predetermined temperature. The predetermined temperature may be a temperature at which the gas flowing inside the base tube 103 has a desired gas composition. The predetermined temperature may be, for example, a temperature at which nitrogen and hydrogen react favorably to produce ammonia. The predetermined temperature may also be, for example, 600°C or lower.

[0050] The lower heat exchange section 213 is designed to adjust the amount of heat exchange between the gas flowing inside the base tube 103 and the gas (oxidizing gas) flowing outside the base tube 103, so that the gas flowing inside the base tube 103 is at a predetermined temperature. The amount of heat exchanged in the lower heat exchange section 213 can be adjusted by changing the heat transfer area in the lower heat exchange section 213. Methods for changing the heat transfer area include, for example, changing the length of the base tube 103 in the lower heat exchange section 213 to adjust the length of the lower heat exchange section, and adjusting the outer diameter of the base tube 103 in the lower heat exchange section 213 to change the heat transfer area.

[0051] The amount of heat exchanged in the lower heat exchange section can also be adjusted by changing the heat transmission coefficient. One method for adjusting the heat transmission coefficient is to change the gap of the oxidizing gas lower through-holes 235a through which the oxidizing gas flows, thereby appropriately changing the flow rate of the oxidizing gas. For example, by reducing the through-hole diameter of the lower heat insulator 227b, the flow rate of the oxidizing gas can be increased, thereby improving the heat transmission coefficient of the heat exchange when passing through the oxidizing gas lower through-holes 235a. The heat transmission coefficient can also be increased by inserting a core into the base tube to increase the flow rate of the mixed gas flowing inside the base tube, or by providing a turbulence promoter. The temperature of the oxidizing gas supplied to the oxidizing gas supply header 221 (the supply temperature of the gas flowing outside the base tube 103) can also be adjusted.

[0052] Next, a description will be given of the flow of fluid inside the cartridge 203. In this embodiment, water vapor (H2O) and nitrogen (N2O) are supplied to the water vapor-containing gas header 217 via the water vapor-containing gas supply pipe 231a. 2: A mixed gas (water vapor-containing gas) containing water vapor and nitrogen (other gases) is supplied. The mixed gas of water vapor and nitrogen in the water vapor-containing gas header 217 flows into the cathode flow path 209 formed inside the cell stack 101. Hereinafter, the gas flowing through the cathode flow path will be referred to as the "mixed gas."

[0053] The mixed gas that has flowed into the cathode flow path 209 first flows through the upper heat exchanger 211. At this time, heat is exchanged with the high-temperature oxidizing gas discharged from the steam electrolysis chamber 215. In the upper heat exchanger 211, the mixed gas is heated by heat exchange with the high-temperature oxidizing gas (see FIG. 3). For example, the mixed gas is heated to about 400°C to 500°C.

[0054] The mixed gas that has flowed through the upper heat exchanger 211 flows into the steam electrolysis chamber 215. The mixed gas that flows through the cathode flow path 209 in the steam electrolysis chamber 215 is supplied to the hydrogen electrode 109 via the porous substrate tube 103. In the hydrogen electrode 109, the water vapor contained in the mixed gas is electrolyzed into hydrogen molecules and oxygen ions (O 2-) is produced (see reaction scheme (1) below). H2O+2e-→H2+O 2- ···(1)

[0055] On the other hand, oxygen ions (O 2- ) passes through the solid electrolyte membrane 111 due to the potential difference and moves to the oxygen electrode 113. The oxygen ions that move to the oxygen electrode 113 release electrons and become oxygen molecules (see reaction formula (2) below). The generated oxygen flows through the anode flow channel 207 and is discharged to the outside together with the oxidizing gas supplied to the oxygen electrode 113. 2O 2- →O2+4e- (2)

[0056] Furthermore, the reaction between hydrogen and nitrogen in the mixed gas flowing through the cathode flow path 209 in the water vapor electrolysis chamber 215 is accelerated by the catalytic action of metal components (e.g., nickel) contained in the hydrogen electrode 109 and the substrate tube 103. As a result, ammonia is produced (see reaction formula (3) below). 3H2+N2→2NH3 (3)

[0057] However, the mixed gas in the steam electrolysis chamber 215 is at a high temperature (for example, about 750°C to 900°C) suitable for the electrolysis reaction (see Figure 3), and the mixed gas in the steam electrolysis chamber 215 is at a high temperature that is not suitable for producing ammonia due to the chemical equilibrium of the mixed gas, so only a small amount of ammonia is produced in the steam electrolysis chamber 215.

[0058] The mixed gas that has flowed through the steam electrolysis chamber 215 flows into the lower heat exchanger 213. The mixed gas that flows into the lower heat exchanger 213 contains water vapor, nitrogen, hydrogen, and a small amount of ammonia. The mixed gas that flows through the cathode flow path 209 of the lower heat exchanger 213 exchanges heat with the oxidizing gas that flows into the steam electrolysis chamber 215. In the lower heat exchanger 213, the mixed gas exchanges heat with the low-temperature oxidizing gas, thereby cooling it to a predetermined temperature (see FIG. 3 ). The predetermined temperature may be a temperature at which the mixed gas has a desired composition. Specifically, the predetermined temperature may be a temperature at which the metal components contained in the substrate tube 103 exhibit catalytic activity, such as 600°C or lower. More specifically, the predetermined temperature may be approximately 400°C to 500°C. The predetermined temperature may also be a temperature at which the water vapor and ammonia contained in the mixed gas do not condense (e.g., 300°C or higher). The predetermined temperature may also be a temperature at which ammonia is suitably produced, for example.

[0059] The mixed gas that has circulated in the lower heat exchanger 213 is discharged to the outside of the cartridge 203 via the mixed gas discharge header 219 and the mixed gas discharge pipe 231b. At this time, the mixed gas contains water vapor, nitrogen, hydrogen, and ammonia.

[0060] According to this embodiment, the following advantageous effects are achieved. In this embodiment, a mixed gas is supplied from the steam electrolysis chamber 215 to the lower heat exchanger 213. In addition to hydrogen produced in the steam electrolysis chamber 215, the mixed gas contains nitrogen and ammonia gas formed by the combination of nitrogen and hydrogen. This embodiment also includes a lower heat exchanger 213 that exchanges heat between the mixed gas discharged from the steam electrolysis chamber 215 and the oxidizing gas supplied to the steam electrolysis chamber 215. This causes the mixed gas to be cooled in the lower heat exchanger 213. The composition of the mixed gas changes due to the catalytic action of the metal components contained in the base tube and due to cooling. At this time, the composition of the mixed gas depends on the temperature of the mixed gas.

[0061] In this embodiment, the lower heat exchanger 213 is configured to have a predetermined temperature at which the mixed gas has a desired composition. This allows the mixed gas to have the desired composition in the lower heat exchanger 213. Therefore, each gas contained in the mixed gas (such as hydrogen or ammonia gas formed by combining hydrogen and nitrogen) can be suitably produced. That is, in the SOEC (more specifically, in the cartridge 203 in the SOEC module container), not only hydrogen but also gases other than hydrogen (in this embodiment, ammonia gas) can be suitably produced.

[0062] In this embodiment, ammonia can be suitably produced by cooling the mixed gas discharged from the steam electrolysis chamber to a predetermined temperature through the action of the catalytic component contained in the substrate tube in the lower heat exchange section 213. Therefore, ammonia can be suitably produced in addition to hydrogen in the solid oxide electrolysis cell.

[0063] In this embodiment, the predetermined temperature may be a temperature equal to or lower than 600° C. This allows the lower heat exchange section 213 to suitably generate gases other than hydrogen.

[0064] The effect of increasing the amount of ammonia gas produced will be described in detail with reference to FIGS. First, the relationship between the amount of ammonia produced and temperature will be explained. Fig. 4 is a graph showing the relationship between the temperature of the mixed gas discharged from the lower heat exchange section 213 (hereinafter referred to as "outlet temperature") and the amount of ammonia produced in the lower heat exchange section 213, when the pressure of the mixed gas discharged from the lower heat exchange section 213 is set to 20 MPa. The amount of ammonia produced, shown on the vertical axis, is expressed as a ratio, with the amount of ammonia produced assuming that the temperature of the mixed gas at the outlet of the steam electrolysis chamber is 700°C, set to 1.

[0065] As shown in Figure 4, the lower the outlet temperature, the greater the amount of ammonia produced. In particular, the amount of ammonia produced significantly increases below 600°C. For example, the amount of ammonia produced at 600°C is 1.9 times greater than the amount produced when the outlet temperature is 700°C.

[0066] Next, the relationship between the amount of ammonia produced and pressure will be explained. Fig. 5 is a graph showing the relationship between the pressure of the mixed gas discharged from the lower heat exchange section 213 (hereinafter referred to as "outlet pressure") and the amount of ammonia produced in the lower heat exchange section 213 when the temperature of the mixed gas discharged from the lower heat exchange section 213 is set to 600°C. The amount of ammonia produced on the vertical axis shows the ratio, with the amount of ammonia produced when the outlet pressure is 5 MPa set to 1. As shown in Fig. 5, the amount of ammonia produced increases almost in proportion to the outlet pressure, and it is clear that high-pressure operation is suitable as an ammonia production condition.

[0067] [Second embodiment] Next, a second embodiment of the present disclosure will be described. The electrolysis system according to this embodiment differs from the first embodiment in the gas supplied to the cartridge 203 and the gas generated in the cartridge 203. The configuration of the lower heat exchanger 213 also differs from the first embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0068] The lower heat exchange section 213 according to this embodiment is configured so that the gas flowing inside the base tube 103 is at a predetermined temperature. The predetermined temperature may be, for example, a temperature at which hydrogen and carbon monoxide react favorably to produce methane.

[0069] The flow of gas inside the cartridge 203 according to this embodiment will be described. In this embodiment, water vapor (H2O) and carbon dioxide (CO2) are supplied to the water vapor-containing gas header 217 via the water vapor-containing gas supply pipe 231a. 2: The gas is supplied as a water vapor containing gas (and other gases). It may also contain carbon monoxide (CO) and methane (CH4). The water vapor-containing gas, which is a mixture of water vapor and carbon dioxide, in the water vapor-containing gas header 217 flows into the cathode flow channel 209 formed inside the cell stack 101. Hereinafter, the gas flowing through the cathode flow channel will be referred to as the "mixed gas."

[0070] The mixed gas that has flowed into the cathode flow path 209 first flows through the upper heat exchanger 211. At this time, heat is exchanged with the high-temperature oxidizing gas discharged from the steam electrolysis chamber 215. In the upper heat exchanger 211, the mixed gas is heated by heat exchange with the high-temperature oxidizing gas (see FIG. 3). Specifically, the mixed gas may be heated to approximately 600°C to 800°C.

[0071] The mixed gas that has passed through the upper heat exchanger 211 flows into the steam electrolysis chamber 215. The mixed gas that flows through the cathode flow path 209 in the steam electrolysis chamber 215 comes into contact with the hydrogen electrode 109 through the porous substrate tube 103. In the hydrogen electrode 109, the water vapor contained in the mixed gas is electrolyzed into hydrogen molecules and oxygen ions (O 2- ) is produced (see reaction formula (1) below). Carbon dioxide is also electrolyzed to produce carbon monoxide and oxygen ions (O 2- ) is produced (see reaction formula (4) below). H2O+2e-→H2+O 2- ···(1) CO2+2e-→CO+O 2- ···(4)

[0072] On the other hand, oxygen ions (O 2- ) passes through the solid electrolyte membrane 111 due to the potential difference and moves to the oxygen electrode 113 (see the arrow in FIG. 3). The oxygen ions that move to the oxygen electrode 113 release electrons and become oxygen molecules (see reaction formula (2) below). The generated oxygen flows through the anode flow channel 207 and is discharged to the outside together with the oxidizing gas supplied to the oxygen electrode 113. 2O 2- →O2+4e- (2)

[0073] Furthermore, the reaction between hydrogen and carbon monoxide in the mixed gas flowing through the cathode flow channel 209 in the steam electrolysis chamber 215 is promoted by the metal components (e.g., nickel) contained in the hydrogen electrode 109 and the substrate tube 103. This causes a methanation reaction to produce methane (see reaction formula (5) below). Furthermore, an aqueous shift reaction occurs between the steam and carbon monoxide (see reaction formula (6) below). CO + 3H2 → CH4 + H2O (5) H2O+CO→H2+CO2 (6)

[0074] However, the mixed gas in the steam electrolysis chamber 215 reaches a high temperature (for example, about 750°C to 900°C) due to the electrolysis reaction (see FIG. 5). As such, the mixed gas in the steam electrolysis chamber 215 is in a temperature condition that is not suitable for producing methane, and therefore only a small amount of methane is produced in the steam electrolysis chamber 215. In this embodiment, the catalyst does not include metal components (for example, nickel) that are contained in the hydrogen electrode and have catalytic properties.

[0075] The mixed gas that has passed through the steam electrolysis chamber 215 flows into the lower heat exchanger 213. The mixed gas that flows into the lower heat exchanger 213 is a mixed gas containing water vapor, carbon dioxide, hydrogen, carbon monoxide, and a small amount of methane.

[0076] The mixed gas flowing through the cathode flow path 209 of the lower heat exchanger 213 exchanges heat with the low-temperature oxidizing gas flowing into the steam electrolysis chamber 215. In the lower heat exchanger 213, the mixed gas exchanges heat with the low-temperature oxidizing gas, thereby cooling it to a predetermined temperature (see FIG. 3). Specifically, the mixed gas is cooled to a temperature at which the desired composition is achieved. Specifically, the predetermined temperature may be 600°C or lower. More specifically, the predetermined temperature may be approximately 400°C to 500°C. Alternatively, the predetermined temperature may be a temperature at which the water vapor and methane contained in the mixed gas do not condense (e.g., 300°C or higher). Alternatively, the predetermined temperature may be, for example, a temperature at which methane is suitably produced.

[0077] The mixed gas that has circulated in the lower heat exchanger 213 is discharged to the outside of the cartridge 203 via the mixed gas discharge header 219 and the mixed gas discharge pipe 231b. At this time, the mixed gas contains water vapor, carbon dioxide, hydrogen, carbon monoxide, and methane.

[0078] In this embodiment, similarly to the first embodiment, each gas contained in the mixed gas (hydrogen and methane gas formed by combining hydrogen and carbon monoxide) can be suitably produced. That is, in the SOEC, not only hydrogen but also gases other than hydrogen (methane gas in this embodiment) can be suitably produced.

[0079] The present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure. For example, in the above embodiment, an example was described in which the material forming the substrate tube 103 contains a catalytic component (such as nickel) that promotes the reaction between hydrogen and nitrogen, but the present disclosure is not limited to this. The catalytic component may be provided as a catalytic layer at a position that comes into contact with hydrogen. For example, a catalytic layer may be provided on the inner circumferential surface of the substrate tube 103. Furthermore, the catalyst that promotes the reaction between hydrogen and nitrogen may be other than nickel. For example, it may be a precious metal catalyst such as platinum.

[0080] Furthermore, although an example in which a catalyst is uniformly contained in the substrate tube 103 has been described, the present disclosure is not limited to this. For example, a catalyst layer may be provided only in the portion of the substrate tube 103 that is located in the steam electrolysis chamber 215, without providing a catalyst layer therein. In this configuration, the reaction occurs only in the lower heat exchanger 213, and the mixed gas can be more efficiently adjusted to the desired composition in the lower heat exchanger 213.

[0081] The amount and / or type of catalyst may be varied along the gas flow direction (extension direction of cell stack 101). For example, a platinum-based or copper-based catalyst that has catalytic activity even at low temperatures may be provided in the portion of lower heat exchanger 213 where low-temperature gas flows (i.e., downstream side of the gas flow), and a nickel-based or iron-based catalyst that has catalytic activity even at high temperatures may be provided in the portion where high-temperature gas flows (i.e., upstream side of the gas flow). Also, for example, catalyst layers may be provided from the upstream side (high-temperature side) to the downstream side (low-temperature side) so that the amount of catalyst is appropriate for the reaction rate.

[0082] In this configuration, it is more preferable that the lower heat exchange section 213 produces a gas (such as ammonia or methane) in which hydrogen is combined with another gas.

[0083] The solid oxide electrolysis cell stack, the electrolysis cell module, the hydrogen production system, and the method of operating the solid oxide electrolysis cell described in the above-described embodiments can be understood, for example, as follows. A solid oxide electrolysis cell according to a first aspect of the present disclosure is a solid oxide electrolysis cell (10) that generates hydrogen by electrolyzing supplied water vapor, and includes: a cathode flow path (209) through which a water vapor-containing gas containing the water vapor and other gases flows; an anode flow path (207) through which an oxidizing gas flows; an electrolysis unit (215) into which the water vapor-containing gas flowing through the cathode flow path (209) and the oxidizing gas flowing through the anode flow path (207) are introduced, which electrolyzes the water vapor supplied from the cathode flow path (209) to generate the hydrogen and discharges the generated mixed gas containing the hydrogen; and a heat exchanger (213) that exchanges heat between the mixed gas discharged from the electrolysis unit (215) and the oxidizing gas supplied to the electrolysis unit (215), and the heat exchanger (213) is configured to maintain a predetermined temperature at which the mixed gas that exchanges heat with the oxidizing gas has a desired composition.

[0084] In the above configuration, a mixed gas is supplied from the electrolysis unit to the heat exchange unit. In addition to hydrogen produced in the electrolysis unit, the mixed gas contains other gases, and gases formed by combining other gases with hydrogen. The above configuration also includes a heat exchange unit that exchanges heat between the mixed gas discharged from the electrolysis unit and the oxidizing gas supplied to the electrolysis unit. As a result, the equilibrium composition of the mixed gas changes in the heat exchange unit due to the action of the metal components contained in the substrate tube and cooling to a predetermined temperature. The composition of the mixed gas depends on the temperature of the mixed gas.

[0085] In the above configuration, the heat exchange unit is configured to maintain a predetermined temperature at which the mixed gas has a desired composition. As a result, the mixed gas has the desired composition in the heat exchange unit. Therefore, each gas contained in the mixed gas (hydrogen and a gas formed by combining hydrogen with another gas) can be suitably produced. In other words, in the solid oxide electrolysis cell, not only hydrogen but also gases other than hydrogen can be suitably produced.

[0086] Furthermore, in a solid oxide electrolysis cell stack according to a second aspect of the present disclosure, in the above-mentioned first aspect, the other gas contains nitrogen, and the mixed gas contains ammonia.

[0087] In the above configuration, the mixed gas contains ammonia, which is a combination of hydrogen and nitrogen. This allows ammonia to be suitably produced in the heat exchanger. Therefore, not only hydrogen but also ammonia can be suitably produced in the solid oxide electrolysis cell.

[0088] Furthermore, in the solid oxide electrolysis cell stack according to a third aspect of the present disclosure, in the first aspect, the other gas contains carbon dioxide, and the mixed gas contains methane.

[0089] In the above configuration, the mixed gas contains methane. This allows methane to be suitably produced in the heat exchange unit. Therefore, in the solid oxide electrolysis cell, not only hydrogen but also methane can be suitably produced.

[0090] Furthermore, in the solid oxide electrolysis cell stack according to a fourth aspect of the present disclosure, in any one of the first to third aspects, the predetermined temperature is a temperature of 600°C or less.

[0091] In the above configuration, the predetermined temperature is a temperature of 600° C. or less. This makes it possible to suitably generate gases other than hydrogen in the heat exchange section.

[0092] Furthermore, in the solid oxide electrolysis cell stack according to a fifth aspect of the present disclosure, in any one of the first to fourth aspects, the heat exchange section (213) has a catalyst that promotes a reaction between the other gas and the hydrogen.

[0093] In the above configuration, the heat exchanger includes a catalyst that promotes the reaction between the other gas and hydrogen, thereby enabling the heat exchanger to preferably generate a gas (e.g., ammonia or methane) in which the other gas and hydrogen are combined.

[0094] Furthermore, in a solid oxide electrolysis cell stack according to a sixth aspect of the present disclosure, in the above-described fifth aspect, the electrolysis section (215) is not provided with the catalyst that promotes the reaction between the other gas and the hydrogen.

[0095] In the above configuration, the electrolysis unit is not provided with a catalyst that promotes the reaction between other gases and hydrogen. As a result, the reaction temperature in the electrolysis unit is high enough for steam electrolysis, and even with a catalyst, the desired gas is only produced in small amounts due to chemical equilibrium. Therefore, the desired composition can be achieved by providing a catalyst only in the heat exchange unit.

[0096] Furthermore, a solid oxide electrolysis cell stack according to a seventh aspect of the present disclosure is the solid oxide electrolysis cell stack of the fifth or sixth aspect, wherein the amount and / or type of the catalyst in the heat exchange section (213) varies along the mixed gas flow direction.

[0097] In the above configuration, the amount and / or type of catalyst in the heat exchanger varies along the direction of flow of the mixed gas, which makes it possible to more effectively generate gases (e.g., ammonia and methane) in which hydrogen is combined with other gases in the heat exchanger.

[0098] An electrolysis cell module according to an eighth aspect of the present disclosure houses the solid oxide electrolysis cell stack according to any one of the first to seventh aspects in a container.

[0099] A hydrogen production system according to a ninth aspect of the present disclosure includes the electrolysis cell module according to the eighth aspect.

[0100] A method for operating a solid oxide electrolysis cell according to a tenth aspect of the present disclosure is a method for operating a solid oxide electrolysis cell (10) equipped with a heat exchanger so that a mixed gas produced by electrolyzing a supplied water vapor-containing gas is at a predetermined temperature at which the mixed gas has a predetermined composition, the solid oxide electrolysis cell (10) including a cathode flow path (209) through which a water vapor-containing gas containing water vapor and other gases flows, an anode flow path (207) through which an oxidizing gas flows, and an oxidizing gas flowing through the water vapor-containing gas and the anode flow path (209). an electrolysis section (215) into which the oxidizing gas that has flowed through the cathode flow path (207) is introduced, which electrolyzes the water vapor supplied from the cathode flow path (209) to generate the hydrogen and discharges a mixed gas containing the generated hydrogen; and a heat exchange section (213) that exchanges heat between the mixed gas discharged from the electrolysis section (215) and the oxidizing gas that is supplied to the electrolysis section (215), and the heat exchange section (213) includes a step of performing heat exchange in the heat exchange section (213) so that the mixed gas that is to be heat exchanged with the oxidizing gas has a predetermined temperature at which the mixed gas has a desired composition. [Explanation of symbols]

[0101] 101 Cell Stack 103 Base tube 105 Electrolysis Cell 107 Interconnector 109 Hydrogen electrode 111 Solid electrolyte membrane 113 Oxygen electrode 115 Lead Film 203 Cartridge 207 Anode flow path 209 Cathode flow path 211 Upper heat exchange section 213 Lower heat exchange section (heat exchange section) 215 Steam electrolysis chamber (electrolysis section) 217 Steam-containing gas header 219 Mixed Gas Discharge Header 221 Oxidizing gas supply header 223 Oxidizing gas discharge header 225a Upper tube plate 225b Lower tube sheet 227a Upper insulation 227b Lower insulation 229a Upper casing 229b Lower casing 231a Water vapor-containing gas supply pipe 231b Mixed gas exhaust pipe 233a Oxidizing gas supply pipe 233b Oxidizing gas exhaust pipe 235a Oxidizing gas lower penetration 235b Oxidizing gas upper penetration 237a Upper seal member 237b Lower seal member 620 Temperature measurement unit

Claims

1. A solid oxide electrolysis cell stack that generates hydrogen by electrolyzing supplied water vapor, a cathode flow path through which a water vapor-containing gas containing the water vapor and other gases flows; an anode flow path through which an oxidizing gas flows; an electrolysis unit into which the water vapor-containing gas flowing through the cathode flow channel and the oxidizing gas flowing through the anode flow channel are introduced, which electrolyzes the water vapor supplied from the cathode flow channel to generate the hydrogen, and which discharges a mixed gas containing the generated hydrogen; a heat exchange unit that exchanges heat between the mixed gas discharged from the electrolysis unit and the oxidizing gas supplied to the electrolysis unit, the heat exchange unit is configured to maintain a predetermined temperature at which the mixed gas that exchanges heat with the oxidizing gas has a desired composition.

2. the other gas comprises nitrogen; 10. The solid oxide electrolysis cell stack of claim 1, wherein the mixed gas comprises ammonia.

3. the other gas comprises carbon dioxide; 10. The solid oxide electrolysis cell stack of claim 1, wherein the mixed gas comprises methane.

4. 2. The solid oxide electrolysis cell stack according to claim 1, wherein the predetermined temperature is a temperature of 600°C or less.

5. The solid oxide electrolysis cell stack according to claim 1 , wherein the heat exchange section has a catalyst that promotes a reaction between the other gas and the hydrogen.

6. The solid oxide electrolysis cell stack according to claim 5 , wherein the electrolysis section is not provided with the catalyst that promotes the reaction between the other gas and the hydrogen.

7. The solid oxide electrolysis cell stack according to claim 5 , wherein the amount and / or type of the catalyst in the heat exchange section changes along the flow direction of the mixed gas.

8. An electrolysis cell module comprising a container that houses the solid oxide electrolysis cell stack according to any one of claims 1 to 7.

9. A hydrogen production system comprising the electrolysis cell module according to claim 8.

10. 1. A method for operating a solid oxide electrolysis cell stack that generates hydrogen by electrolyzing supplied water vapor, comprising: The solid oxide electrolysis cell stack comprises: a cathode flow path through which a water vapor-containing gas containing the water vapor and other gases flows; an anode flow path through which an oxidizing gas flows; an electrolysis unit into which the water vapor-containing gas that has flowed through the cathode flow channel and the oxidizing gas that has flowed through the anode flow channel are introduced, which electrolyzes the water vapor supplied from the cathode flow channel to generate the hydrogen, and which discharges a mixed gas containing the generated hydrogen; a heat exchange unit that exchanges heat between the mixed gas discharged from the electrolysis unit and the oxidizing gas supplied to the electrolysis unit, performing heat exchange in the heat exchange section so that the mixed gas that exchanges heat with the oxidizing gas has a predetermined temperature at which the mixed gas has a desired composition.

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