Electrolysis cell stack, electrolysis cell cartridge, electrolysis cell module, and method for producing electrolysis cell stack

Abstract

Provided are an electrolysis cell stack, an electrolysis cell cartridge, an electrolysis cell module, and a method for producing an electrolysis cell stack which make it possible to suppress a decrease in H2 / CO yield, even when a methanation catalyst is contained in a flow passage through which a generated gas generated by a hydrogen electrode via co-electrolysis flows. An electrolysis cell stack (101) according to the present disclosure comprises: an electrolysis cell (105) in which a hydrogen electrode (109), a solid electrolyte (111), and an oxygen electrode (113) are stacked, in this order; a flow passage (117) through which a generated gas generated by the hydrogen electrode flows; and a methanation suppression film (116) that covers the surface of a member (103), which defines the outer contour of the flow passage, on the side thereof on which the generated gas flows. The member defining the outer contour of the flow passage contains a methanation catalyst, and the methanation suppression film does not contain a methanation catalyst.

Description

Electrolytic cell stack, electrolytic cell cartridge, electrolytic cell module, and method for manufacturing electrolytic cell stack

[0001] This disclosure relates to an electrolytic cell stack, an electrolytic cell cartridge, an electrolytic cell module, and a method for manufacturing an electrolytic cell stack.

[0002] Water electrolysis, which electrochemically decomposes water to produce hydrogen and oxygen, is a hydrogen production method that does not emit carbon dioxide and has excellent environmental characteristics. Water electrolysis includes alkaline electrolysis and solid polymer electrolysis, which electrolyze liquid water, and steam electrolysis, which electrolyzes water vapor.

[0003] In particular, solid oxide electrolytic cells (SOECs), which electrolyze high-temperature steam, use ceramics with oxygen ion conductivity, such as yttria-stabilized zirconia, as the solid electrolyte. Because electrolytic cells using solid electrolytes can utilize the thermal energy of high-temperature steam as part of the energy required for the electrolytic reaction, they can produce hydrogen with higher efficiency compared to other electrolysis methods. Electrolytic cells using solid electrolytes can also be used for ammonia electrolysis.

[0004] Furthermore, in electrolytic cells, high-temperature water vapor and carbon dioxide (CO2) are used. ２ Co-electrolysis is also possible, in which a mixed gas (raw material gas) is supplied with ) and the hydrogen and carbon dioxide generated by electrolysis are reacted on the electrolytic cell to directly produce carbon monoxide (CO) or hydrocarbon compounds (see Patent Document 1).

[0005] Electrolytic cells using solid electrolytes use CO as a co-electrolytic agent. ２ / H ２ By simultaneously electrolyzing oxygen, the hydrogen necessary for synthesizing FT (Fischer-Tropsch), which is used in the production of synthetic fuels (e-fuels) such as sustainable aviation fuel (SAF), is produced. ２ This allows for the production of CO synthesis gas. This could potentially simplify the system compared to the production process using a reverse shift reaction from water electrolysis.

[0006] Japanese Patent Publication No. 2023-50701

[0007] In Patent Document 1, the electrode layer (hydrogen electrode) material contains Ni, and the metal support supporting the hydrogen electrode contains Fe. The Ni and Fe particles contained in the electrode layer and metal support act as catalysts (methanization catalysts) for the reaction in which methane is synthesized from hydrogen and carbon monoxide.

[0008] CO ２ / H ２ The product gas generated in the co-electrolysis of oxygen contains hydrogen and carbon monoxide. Therefore, when the product gas comes into contact with a structure containing a methanation catalyst, the methanation reaction proceeds.

[0009] In pressurized operation, which facilitates integration with FT synthesis, a methanation reaction occurs due to the action of a methanation catalyst, producing methane and H ２ One challenge is that the yield of CO decreases.

[0010] To prevent the methanation reaction, the methanation catalyst can be removed from the hydrogen electrode and metal support. However, Ni and Fe may serve purposes other than catalysis, such as controlling the coefficient of thermal expansion or adjusting porosity, so they cannot be easily removed.

[0011] This disclosure has been made in view of the above circumstances, and even if a methane catalyst is included in the flow path through which the product gas generated at the hydrogen electrode by co-electrolysis flows, H ２ The objective is to provide an electrolytic cell stack, an electrolytic cell cartridge, an electrolytic cell module, and a method for manufacturing an electrolytic cell stack that can suppress the decrease in CO yield.

[0012] To solve the above problems, the manufacturing methods for the electrolytic cell stack, electrolytic cell cartridge, electrolytic cell module, and electrolytic cell stack of this disclosure are employed as follows.

[0013] This disclosure provides an electrolytic cell stack comprising: an electrolytic cell in which a hydrogen electrode, a solid electrolyte, and an oxygen electrode are stacked in order; a flow passage through which a product gas generated at the hydrogen electrode flows; and a methanation suppression film covering the surface of a member defining the outer edge of the flow passage on the side through which the product gas flows, wherein the member defining the outer edge of the flow passage contains a methanation catalyst, and the methanation suppression film does not contain a methanation catalyst.

[0014] The present disclosure provides an electrolytic cell cartridge including the above-described electrolytic cell stack.

[0015] The present disclosure provides an electrolytic cell module including the above-described electrolytic cell cartridge.

[0016] The present disclosure relates to a method for manufacturing an electrolytic cell stack including an electrolytic cell in which a hydrogen electrode, a solid electrolyte, and an oxygen electrode are laminated in this order, and a flow path through which the product gas generated at the hydrogen electrode by co-electrolysis flows, the method including applying a material not containing a methanation catalyst to the surface on the product gas flow side of the member defining the outer contour of the flow path, and heating to form a methanation inhibition film.

[0017] According to the present disclosure, by covering the surface on the product gas flow side of the member defining the outer contour of the flow path with a methanation inhibition film, even when the flow path through which the product gas generated at the hydrogen electrode by co-electrolysis flows contains a methanation catalyst, the decrease in the yield of H ２ / CO can be suppressed.

[0018] It is an overall schematic cross-sectional view showing an example of an electrolytic cell stack according to the first embodiment. It is an enlarged view of the Z portion of the electrolytic cell stack of FIG. 1. It is a diagram showing the procedure of a method for manufacturing an electrolytic cell stack according to the first embodiment. It is an overall schematic cross-sectional view showing an example of an electrolytic cell stack according to the second embodiment. It is an overall schematic cross-sectional view showing an example of an electrolytic cell stack according to the third embodiment. It is a schematic diagram of a hollow tube. It is a diagram showing one aspect of an electrolytic cell cartridge including a cylindrical horizontally-striped electrolytic cell stack. It is a diagram showing one aspect of an electrolytic cell module including the electrolytic cell cartridge of FIG. 7. It is a schematic diagram of a flat-plate electrolytic cell. It is a schematic diagram of a cylindrical flat-plate electrolytic cell. It is a schematic diagram of a cylindrical vertically-striped electrolytic cell.

[0019] In the present embodiment, a cylindrical horizontally-striped electrolytic cell stack (hereinafter referred to as a cell stack) including a solid oxide electrolytic cell (SOEC), an electrolytic cell cartridge including the same, and an electrolytic cell module will be described with reference to the drawings.

[0020] For convenience of explanation, the positional relationships of the respective components described using the expressions "upper" and "lower" with reference to the paper surface indicate the vertically upper side and the vertically lower side, respectively. Further, in the present embodiment, for those in which the same effects can be obtained in the vertical direction and the horizontal direction, the vertical direction on the paper surface is not necessarily limited to the vertically up-and-down direction, and may correspond to, for example, the horizontal direction orthogonal to the vertical direction.

[0021] [First Embodiment] FIG. 1 is an overall schematic cross-sectional view showing an example of an electrolytic cell stack (hereinafter referred to as a cell stack). FIG. 2 is an enlarged view of the Z portion of the electrolytic cell stack of FIG. 1.

[0022] The cell stack 101 includes an electrolytic cell 105. In FIG. 1, supply pipes 122 for supplying gas into the cell stack 101 and discharge pipes 123 for discharging gas from the cell stack 101 are connected to both ends of the cell stack 101 via connection parts (120, 121).

[0023] The gas (raw material gas) supplied into the cell stack 101 flows from the left side to the right side of the paper surface and is electrolyzed in the electrolytic cell 105. A gas flow rate setting means (not shown) for stabilizing the introduction amount of the raw material gas may be connected to the supply pipe 122. The gas flow rate setting means can set the mixing ratio of carbon dioxide (CO ２ ) and water vapor (H ２ O) in the raw material gas to a predetermined value.

[0024] The gas (generated gas) generated by electrolysis (at the hydrogen electrode described later) is discharged to the outside from the discharge pipe 123 together with the un-electrolyzed raw material gas that did not contribute to the electrolysis reaction. Hereinafter, the gas discharged from the cell stack 101 to the outside is also called "generated gas" even when it contains un-electrolyzed raw material gas.

[0025] In the present embodiment, the cell stack 101 is divided into three areas along the axial direction. The area where the electrolytic cell 105 is formed is called an electrolysis part 130, the area on the upstream side of the gas flow from the electrolysis part 130 is called an upper lead part 131, and the area on the downstream side of the gas flow from the electrolysis part 130 is called a lower lead part 132. The generated gas flows through the base pipe 103 located in the lower lead part 132.

[0026] As shown in Figure 2, the cell stack 101 includes, for example, a cylindrical base tube 103, multiple electrolytic cells 105 formed on the outer surface of the base tube 103, and an interconnector 107 formed between adjacent electrolytic cells 105. The electrolytic cell 105 is formed by stacking a hydrogen electrode 109, a solid electrolyte membrane 111, and an oxygen electrode 113.

[0027] The cell stack 101 is equipped with a lead membrane (not shown) electrically connected via an interconnector 107 to the oxygen electrode 113 of an electrolytic cell 105 formed at one end (upper lead portion 131 side) in the axial direction of the base tube 103, and a lead membrane 115 electrically connected to the hydrogen electrode 109 of an electrolytic cell 105 formed at the other end (lower lead portion 132 side). In the axial direction of the cell stack 101 (base tube 103), the inner surface of the base tube 103 located at the lower lead portion 132 is covered with a methane suppression membrane 116.

[0028] The inner circumferential surface 104 of the base tube 103 defines the outer edge of the flow passage 117 through which the gas flows. In a cell stack where the hydrogen electrode 109 is formed thickly and also serves as the base tube, the inner circumferential surface of the hydrogen electrode 109 defines the outer edge of the flow passage.

[0029] The base tube 103 is made of a porous material, for example, CaO-stabilized ZrO ２ (CSZ), a mixture of CSZ and nickel oxide (NiO) (CSZ + NiO), or Y ２ O ３ Stabilized ZrO ２ (YSZ), or MgAl ２ O ４ These are considered to be the main components. The base tube 103 supports the electrolytic cell 105, the interconnector 107, and the lead film 115, and diffuses the raw material gas supplied to the inner circumferential surface 104 of the base tube 103 to the hydrogen electrode 109 formed on the outer circumferential surface of the base tube 103 through the pores of the base tube 103. The Ni particles contained in the base tube 103 can act as a methanation catalyst, but they are not added for the purpose of promoting methanation.

[0030] In the cell stack 101 shown in Figure 2, the electrolytic cell 105 is supported by a base tube 103. However, for example, the hydrogen electrode may be made thicker and serve as the base tube, and the use of a base tube is not limited to this configuration. Furthermore, although the base tube in this embodiment is described as being cylindrical, the base tube can be cylindrical, and its cross-section is not necessarily limited to a circle; for example, it may be elliptical. A cell stack of a flat tubular cylinder, for example, with the circumferential surface of a cylinder vertically flattened, may also be used.

[0031] 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.

[0032] The solid electrolyte membrane 111 is mainly 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 is made of oxygen ions (O) generated at the hydrogen electrode 109. ２－ This process moves the ) to the oxygen electrode 113. 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 a slurry.

[0033] The oxygen electrode 113 is, for example, LaSrMnO ３ LaCoO oxides, or LaCoO ３ Composed of a system oxide, the oxygen electrode 113 is coated using screen printing or a dispenser after being formed into a slurry. 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, which exhibits high ionic conductivity, and the oxygen electrode layer (oxygen electrode conductive layer) on the oxygen electrode intermediate layer may be Sr and Ca-doped LaMnO ３ It may be composed of perovskite-type oxides such as the following.

[0034] Oxidizing gases do not directly participate in the electrolytic reaction, but they supply the heat necessary for the electrolytic reaction (endothermic reaction) and discharge the waste heat from 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.

[0035] Interconnector 107 is SrTiO ３ M systems, etc. １－ｘ L ｘ TiO ３ (M is an alkaline earth metal element, L is a lanthanide element) and lanthanum chromite (LaCrO ３ The interconnector 107 is composed of a conductive perovskite-type oxide represented by ), and the slurry is screen printed. The interconnector 107 is a dense film that prevents the raw material gas and the oxidizing gas from mixing. The interconnector 107 also 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, and connects adjacent electrolytic cells 105 in series.

[0036] The lead film 115 needs to possess electronic conductivity and have a coefficient of thermal expansion similar to that of the other materials constituting the cell stack 101. Therefore, composite materials of Ni and zirconia-based electrolyte materials such as Ni / YSZ or SrTiO are suitable. ３ M systems, etc. １－ｘ L ｘ TiO ３ (M is an alkaline earth metal element, L is a lanthanide element). This lead film 115 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. 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.

[0037] The methanation-inhibiting film 116 does not contain a methanation catalyst. The methanation catalyst is particulate Ni, Fe, Co, Ru, etc. Note that Ni and Fe in alloys or other compounded states do not have catalytic activity. Ni and Fe in forms that do not have catalytic activity may be included in the methanation-inhibiting film.

[0038] The methanation-inhibiting film 116 may be a sintered body, specifically a dense low-temperature sintered body, a porous low-temperature sintered body, or a porous high-temperature sintered body. These will be explained in detail later.

[0039] The coefficient of linear expansion of the methanation-inhibiting membrane 116 is preferably close to that of the base tube 103. The difference in the coefficient of linear expansion between the methanation-inhibiting membrane 116 and the base tube 103 is 2 × 10⁻⁶. －６ It is preferable that the temperature be within / °C. The coefficient of linear expansion of the methanation-inhibiting film 116 is, for example, 8 × 10⁻⁶. －６ / ℃ to 12 × 10 －６ / ℃, preferably 10 × 10 －６ / ℃ to 11 × 10 －６ It is / ℃.

[0040] Materials that do not contain a methanation catalyst are selected from the group consisting of zirconia compounds, alumina, and forsterite. Examples of zirconia compounds include zirconium oxide, calcia-stabilized zirconia (CSZ), and yttria-stabilized zirconia (YSZ).

[0041] For materials that do not contain a methanation catalyst, commercially available heat-resistant ceramic adhesives may be used. For example, Resbond 989 (heat resistance temperature 1640°C, base component: alumina) and Resbond 904 (heat resistance temperature 2200°C, base component: zirconia) manufactured by Taiyo Kanami Co., Ltd. can be used.

[0042] Materials that do not contain a methanation catalyst may further contain a binder, a dispersant, or an additive.

[0043] The binder may be polyvinyl alcohol (PVA), polyvinyl butyral (PVB), methylcellulose derivatives, etc. The binder may be added in an amount of approximately 0.1% to 15% relative to the total amount of material that does not contain the methanation catalyst.

[0044] Dispersants include high molecular weight dispersants, low molecular weight dispersants, surfactant-type dispersants, and inorganic dispersants. Dispersants can be added in amounts ranging from 5% to 30% of the total amount of material that does not contain the methanation catalyst.

[0045] (Method for Manufacturing an Electrolytic Cell Stack) Figure 3 shows the procedure for manufacturing an electrolytic cell stack according to this embodiment. First, (S1) a slurry prepared from the porous material of the base tube 103 is extruded into a cylindrical shape. (S2) After forming films of the slurry of the hydrogen electrode 109, solid electrolyte membrane 111, and interconnector 107 on the outer surface of the cylindrical base tube (green body), (S3) co-sintering is performed in the atmosphere. The sintering temperature is, for example, 1350°C to 1450°C.

[0046] Next, (S4) a film of the slurry of the oxygen electrode 113 is formed on the solid electrolyte film 111 of the co-sintered base tube 103, and then (S5) sintering is performed in air. The sintering temperature is, for example, 1100°C to 1250°C. This sintering temperature is lower than the co-sintering temperature after the interconnector 107 is formed from the base tube 103.

[0047] Furthermore, (S6) the base tube 103 formed up to the oxygen electrode 113 is subjected to a reduction treatment. In the reduction treatment, for example, hydrogen gas is introduced into the base tube 103 at a temperature of 800°C to 1000°C. The NiO contained in the base tube 103 is reduced to Ni, thereby increasing the porosity of the base tube 103.

[0048] The methanation-inhibiting film 116 is formed by coating the inner surface of the substrate tube 103 with a material that does not contain a methanation catalyst and then heating it. For example, the material that does not contain a methanation catalyst is prepared as a slurry and then coated. The timing of coating and forming the methanation-inhibiting film differs depending on the type of methanation-inhibiting film (dense low-temperature sintered body, porous low-temperature sintered body, or porous high-temperature sintered body). Figure 3 shows an example of coating a dense low-temperature sintered body, with the coating timings for the porous low-temperature sintered body and porous high-temperature sintered body added as annotations.

[0049] (Dense Low-Temperature Sintered Body) In forming the dense low-temperature sintered body, (S7) after the reduction treatment in (S6) above, a slurry of a material that does not contain a methanation catalyst is applied to the inner surface of the base tube 103 of the lower lead portion 132. The green body of the applied methanation-inhibiting film is sintered by the heat generated when the electrolytic cell stack is started.

[0050] A dense low-temperature sintered body is formed by heating (sintering) a material that does not contain a methane catalyst at a low temperature of 100°C to 300°C.

[0051] The porosity of the dense low-temperature sintered body is 0% to 10%, preferably 5% to 10%. A film with a porosity of 10% or less is a dense film that is not permeable to gas.

[0052] The thickness of the dense low-temperature sintered body is 1 μm or more and 500 μm or less, preferably 50 μm or more and 300 μm or less, and more preferably 250 μm. A thickness of 1 μm or more makes it practically possible to apply the slurry. A dense film exceeding 500 μm is undesirable from the viewpoint of maintaining strength.

[0053] Porosity can be adjusted by controlling the particle size of the material without the methanation catalyst, the amount of binder and dispersant added, and other factors.

[0054] Materials used in dense low-temperature sintered bodies that do not contain a methanation catalyst include additives to lower the sintering temperature from 100°C to 300°C. These additives include silicates and phosphates. Silicates include sodium silicate, potassium silicate, and lithium silicate. Phosphates include aluminum phosphate and magnesium phosphate.

[0055] The additive can be added, for example, at a concentration of 5% to 10% relative to the total amount of material that does not contain the methanation catalyst. This enables sintering at low temperatures of 100°C to 300°C.

[0056] (Porous low-temperature sintered body) In forming the porous low-temperature sintered body, a slurry of a material that does not contain a methane catalyst is applied to the inner surface of the base tube 103 of the lower lead portion 132 at any of the following timings: between (S4) and (S5) (S7' in Figure 3), between (S5) and (S6) (S7'' in Figure 3), or after the reduction treatment in (S6) (S7 in Figure 3).

[0057] When applied between (S4) and (S5) above, the green body of the applied methanation-inhibiting film is sintered together with the oxygen electrode in (S5) above.

[0058] When applied between (S5) and (S6) above, the green body of the applied methane suppression film is sintered by the heat generated during the reduction treatment in (S6) or when the electrolytic cell stack is started.

[0059] When applied after the reduction treatment described in (S6) above, the green body of the applied methane-inhibiting film is sintered by the heat generated when the electrolytic cell stack is started.

[0060] Porous low-temperature sintered bodies are formed by heating (sintering) a material that does not contain a methane catalyst at a low temperature of 100°C to 300°C.

[0061] The porosity of the porous low-temperature sintered body is more than 10% and less than or equal to 40%, preferably 20% to 30%. Films with a porosity exceeding 10% allow for gas permeability. If the porosity becomes too high, it becomes difficult to maintain strength.

[0062] The thickness of the porous low-temperature sintered body is 500 μm or more and 4000 μm or less, preferably 700 μm or more and 1500 μm or less, and more preferably 1000 μm. A thickness of 500 μm or more reduces the amount of generated gas that reaches the inner surface of the substrate tube 103. A porous film exceeding 4000 μm is undesirable from the viewpoint of maintaining strength.

[0063] Porosity can be adjusted by controlling the particle size of the material without the methanation catalyst, the amount of binder and dispersant added, and other factors.

[0064] Materials used in porous low-temperature sintered bodies that do not contain a methanation catalyst include additives to lower the sintering temperature from 100°C to 300°C. These additives are similar to those used in dense low-temperature sintered bodies, such as silicates and phosphates.

[0065] The additive can be added, for example, at a concentration of 5% to 10% relative to the total amount of material that does not contain the methanation catalyst. This enables sintering at low temperatures of 100°C to 300°C.

[0066] (Porous high-temperature sintered body) In forming the porous high-temperature sintered body, a slurry of a material that does not contain a methane catalyst is applied to the inner surface of the base tube 103 of the lower lead portion 132 at either the timing between (S4) and (S5) (S7' in Figure 3) or between (S5) and (S6) (S7'' in Figure 3).

[0067] When applied between (S4) and (S5) above, the green body of the applied methanation-inhibiting film is sintered together with the oxygen electrode in (S5) above.

[0068] When applied between (S5) and (S6) above, the green body of the applied methane-inhibiting film is sintered by the heat generated during the reduction treatment in (S6) above.

[0069] Porous high-temperature sintered bodies are formed by heating (sintering) a material that does not contain a methanation catalyst. The sintering temperature of the material that does not contain a methanation catalyst is, for example, a high temperature of 1000°C or higher. The material that does not contain a methanation catalyst used in porous high-temperature sintered bodies does not contain additives to lower the sintering temperature from 100°C to 300°C.

[0070] Porous high-temperature sintered bodies allow for gas permeability. The porosity of porous high-temperature sintered bodies is greater than 10% and less than or equal to 40%, preferably between 20% and 30%. Films with a porosity exceeding 10% allow for gas permeability. If the porosity becomes too high, it becomes difficult to maintain strength.

[0071] The thickness of the porous high-temperature sintered body is 500 μm or more and 4000 μm or less, preferably 700 μm or more and 1500 μm or less, and more preferably 1000 μm. A thickness of 500 μm or more reduces the amount of generated gas that reaches the inner surface of the substrate tube 103. A porous film exceeding 4000 μm is undesirable from the viewpoint of maintaining strength.

[0072] Porosity can be adjusted by controlling the particle size of the material without the methanation catalyst, the amount of binder and dispersant added, and other factors.

[0073] The effects of the electrolytic reaction and the inclusion of a methanation-inhibiting membrane in the cell stack 101 described above will be explained.

[0074] The gas (raw material gas) supplied to the base tube 103 (hydrogen electrode 109) contains water vapor and carbon dioxide. The raw material gas may also contain hydrogen.

[0075] 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 raw material gas at the hydrogen electrode 109 receives electrons and undergoes electrolysis, producing hydrogen molecules and oxygen ions (O). ２－ ) is produced (see reaction equation (1) below). In addition, the carbon dioxide contained in the raw material gas accepts electrons and is electrolyzed to produce carbon monoxide molecules and oxygen ions (O). ２－ ) is produced (see reaction equation (2) below). H ２ O + 2e － →H ２ +O ２－ ... (1) CO ２ +2e － →CO+O ２－ ... (2)

[0076] Meanwhile, 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 equation (3) below). The generated oxygen is discharged to the outside along with the oxidizing gas supplied to the oxygen electrode 113. 2O ２－ →O ２ +4e － 　　　　 ... (3)

[0077] Electrolysis is an endothermic reaction, but if current is continuously passed through the electrolytic cell 105 for the electrolytic reaction, heat is generated due to electrical resistance. Therefore, the temperature of the electrolytic section 130, especially the axial central portion of the base tube 103, becomes higher than that of the upper lead portion 131. For example, if the upper lead portion 131 is 550°C, the axial central portion of the electrolytic section 130 will be 900°C to 950°C, and the lower lead portion 132 side of the electrolytic section 130 will be 850°C. On the other hand, the temperature of the lower lead portion 132 gradually decreases, and for example, the temperature near the opening on the lower lead portion 132 side will be around 550°C.

[0078] The product gas generated at the hydrogen electrode 109 by electrolysis can become a raw material for the methanation reaction as it flows through the substrate tube 103 containing the methanation catalyst (Ni particles). According to the inventors' simulation results, the methanation reaction proceeds most readily in the lower lead section 132, during the process of the temperature decreasing from high temperature (850°C) to low temperature (550°C).

[0079] By covering the inner surface of the base tube 103 located at the lower lead portion 132 with a methanation-inhibiting film 116, the opportunity for the generated gas to come into contact with the base tube 103 containing the methanation catalyst (Ni particles) can be reduced. This suppresses the methanation of the generated gas.

[0080] In this embodiment, the difference in the coefficient of linear expansion between the methanation suppression film 116 and the base tube 103 is 2 × 10 －６ Because it is within / °C, damage caused by differences in the coefficient of linear expansion during the manufacturing process or use can be suppressed.

[0081] Dense low-temperature sintered bodies and porous low-temperature sintered bodies can be sintered at low temperatures, making them suitable for coating after reduction treatment.

[0082] Porous low-temperature sintered bodies and porous high-temperature sintered bodies are porous, and therefore allow for easy aeration of reducing gases. Thus, even if applied before the reduction treatment, there is no risk of inhibiting the reduction of Ni-O in the oxygen electrode 113. In the reduction treatment, for example, the reducing gas is retained at 1200°C for 5 hours. Therefore, if a porosity of 10% or more is ensured, the reduction of the base tube 103 proceeds sufficiently. On the other hand, during normal use of the electrolytic cell stack, the temperature of the lower lead portion 132 is around 500°C, and the residence time is almost nonexistent. Therefore, if the methanation suppression film 116 has a porosity of 40% or less and a thickness of 500 μm or more, the methanation reaction that occurs when the generated gas comes into contact with the base tube 103 can be suppressed.

[0083] When a slurry of a material that does not contain a methane catalyst, used in porous low-temperature sintered bodies, is applied after (S5) oxygen electrode firing and before (S6) reduction treatment, the slurry is sintered at a medium temperature (800°C or higher but less than 1000°C). Therefore, the thermal effects associated with high-temperature processing can be avoided.

[0084] Because the porous high-temperature sintered body is sintered at high temperatures, it exhibits high adhesion to the base tube 103.

[0085] [Second Embodiment] The electrolytic cell stack according to this embodiment differs from the first embodiment in that the core is located inside the base tube at the lower lead portion. The following description of the configuration common to the first embodiment will be omitted.

[0086] Figure 4 shows a schematic cross-sectional view of the cell stack 141 according to this embodiment. Similar to Figure 2, the cell stack 141 is connected to a supply pipe 122 that supplies gas into the cell stack 141 and a discharge pipe 123 that discharges gas from inside the cell stack 141 via connection parts (120, 121).

[0087] A core 142 is positioned inside the cell stack 141 (base tube) at the lower lead portion 132, allowing the generated gas to flow through the base tube. One end of the core 142 is fixed to the connection portion 121 with ceramic adhesive.

[0088] The core 142 may be made of metal or nonmetal. The material of the core 142 may be, for example, a metal that has thermal conductivity and high corrosion resistance. In Figure 4, the core 142 is solid. For example, the core 152 may be a rod made of stainless steel.

[0089] The generated gas passes between the base tube and the core 142. By placing the core 142, the heat transfer coefficient of the inner surface of the base tube can be increased (by reducing the clearance between the base tube and the core 142 and increasing the convective heat transfer coefficient), thus promoting heat exchange of the supplied gas. If the core 142 is made of metal, the thermal conductivity of the core 142 itself increases, further promoting the cooling of the generated gas.

[0090] [Third Embodiment] The electrolytic cell stack according to this embodiment differs from the second embodiment in that a hollow tube is arranged inside the base tube located in the lower lead portion. The following description of the configuration common to the second embodiment will be omitted.

[0091] Figure 5 shows a schematic cross-sectional view of the cell stack 151 according to this embodiment. In Figure 5, a hollow tube 153 is arranged inside the cell stack 151 (base tube) located at the lower lead portion 132, and a core 152 is arranged inside the hollow tube 153.

[0092] In Figure 5, the hollow tube 153 is arranged coaxially with the base tube. One end of the hollow tube 153 is fixed to the connector 121 with ceramic adhesive.

[0093] In Figure 5, the hollow tube 153 is arranged over almost the entire area of ​​the lower lead portion 132, but this is not limited to this arrangement, and the hollow tube 153 may be partially arranged in a part of the lower lead portion 132. Also, the end of the hollow tube 153 may extend into the area of ​​the electrolytic section 130.

[0094] Figure 6 shows a schematic diagram of the hollow tube 153. Figure 6(a) is a front view, and Figure 6(b) is a side view. The outer diameter R of the hollow tube 153 is smaller than the inner diameter of the base tube.

[0095] In Figure 5, a clearance may exist between the hollow tube 153 and the base tube. This clearance is smaller than the inner diameter of the hollow tube 153. That is, the flow path cross-sectional area of ​​the clearance between the inner circumferential surface 104 of the base tube (or the surface of the methanation suppression film 116 where it is present) and the hollow tube 153 is smaller than the flow path cross-sectional area inside the hollow tube 153. The clearance is within a range that does not impose a physical load on the base tube due to the thermal expansion of the hollow tube 153 at the operating temperature of the cell stack 151. Within this range, a smaller clearance is preferable.

[0096] The hollow tube 153 does not contain a methane catalyst. The material of the hollow tube 153 may be a metal or nonmetal with heat resistance up to 500°C. The hollow tube 153 may be composed of a material with thermal conductivity and corrosion resistance. The material of the hollow tube 153 may be a metal such as SUS.

[0097] The coefficient of thermal expansion of the hollow tube 153 is less than or equal to that of the base tube. During operation of the cell stack 151, the hollow tube 153 does not expand more than the base tube. Preferably, the hollow tube 153 is made of a material whose coefficient of thermal expansion is approximately the same as that of the base tube (the member that defines the outer casing of the flow passage). Such a material for the hollow tube 153 is, for example, zirconia (ZrO ２ These are ceramics such as ). Here, "approximately equivalent" means that the difference in the coefficient of linear expansion is 2 × 10⁻⁶. －６ This means it is within / ℃.

[0098] In Figure 5, the core 152 is hollow and has open ends. The generated gas can flow through the hollow portion of the core 152.

[0099] In the cell stack 151 according to this embodiment, the pressure drop inside the hollow tube 153 is smaller than outside the hollow tube, so the generated gas is preferentially introduced into the hollow tube 153. This reduces the amount of generated gas that comes into contact with the low-temperature base tube, and as a result, the methane reaction becomes less likely to occur.

[0100] By making the linear expansion coefficient of the hollow tube 153 approximately the same as that of the base tube (the member that defines the outer perimeter of the flow passage), the outer diameter of the hollow tube 153 can be brought closer to the inner diameter of the base tube. If the outer diameter of the hollow tube 153 is larger, the clearance between the hollow tube 153 and the base tube becomes smaller, making it easier for the generated gas to be introduced into the hollow tube 153. This reduces the opportunities for the generated gas to come into contact with the methane catalyst.

[0101] If the material of the hollow tube 153 is made of a metal such as SUS, its high thermal conductivity can promote the cooling (cooling) of the generated gas passing through the base tube located at the lower lead portion 132. Lowering the temperature of the generated gas at the base tube outlet can reduce thermal damage to metal components that fix the base tube.

[0102] In the above embodiment, a configuration combining the core 152 and the hollow tube 153 was described, but the core 152 may be omitted. Even in that case, the effects and advantages of providing the hollow tube 153 can still be obtained.

[0103] [Fourth Embodiment] In this embodiment, an electrolytic cell cartridge and an electrolytic cell module equipped with an electrolytic cell stack will be described. Figure 7 is a diagram showing one aspect of the electrolytic cell cartridge. Figure 8 is a diagram showing one aspect of the electrolytic cell module.

[0104] The electrolytic cell stack (hereinafter simply referred to as the cell stack) 11 has the same configuration as in any of the first to third embodiments. In Figure 7, for the sake of simplicity, the methanation suppression membrane, core, and hollow tube are omitted from the description, but these are located between the lower end of the electrolytic cell 105, which is the most downstream in the base tube 103, and the lower end of the cell stack 11. The connection parts (120, 121) shown in Figures 2, 4, and 5 correspond to the downstream end of the base tube 103 in Figure 7. The outer circumferential surface of the lower end of the core or hollow tube is fixed to the inner circumferential surface of the base tube 103 by ceramic adhesive.

[0105] (Electrolytic Cell Cartridge) As shown in Figure 7, the cartridge 203 comprises a plurality of cell stacks 11, an electrolytic chamber 215, a raw material gas supply header 217, a generated gas 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 cartridge 203 is structured so that the raw material gas and oxidizing gas flow in opposition to each other on the inside and outside of the cell stack 11, with the raw material gas supply header 217, the generated gas discharge header 219, the oxidizing gas supply header 221, and the oxidizing gas discharge header 223 arranged as shown in Figure 7. 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 11, or the oxidizing gas may flow in a direction perpendicular to the longitudinal direction of the cell stack 11.

[0106] The electrolytic chamber 215 is a region formed between the upper insulator 227a and the lower insulator 227b. This electrolytic chamber 215 is the region where the electrolytic cells 105 of the cell stack 11 are located, and it is the region where the raw material gas is electrolyzed to produce product gases (hydrogen and carbon monoxide). The temperature near the center of the cell stack 11 in the longitudinal direction of this electrolytic chamber 215 may also be monitored by the temperature measurement unit 620 (temperature sensor, thermocouple, etc.), and during steady operation of the module 201, the atmosphere becomes high temperature of approximately 700°C to 1000°C.

[0107] The raw material gas 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 the raw material gas supply branch pipe 207a by the raw material gas supply pipe 231a provided on the upper part of the upper casing 229a. The multiple cell stacks 11 are joined together by the upper tube sheet 225a and the upper sealing member 237a, and the raw material gas supply header 217 guides the raw material gas supplied from the raw material gas supply branch pipe 207a via the raw material gas supply pipe 231a into the base pipe 103 of the multiple cell stacks 11 at a substantially uniform flow rate, thereby substantially equalizing the generated gas performance of the multiple cell stacks 11.

[0108] The generated gas 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 the generated gas discharge branch pipe 209a by a generated gas discharge pipe 231b provided in the lower casing 229b. The multiple cell stacks 11 are joined together by the lower tube sheet 225b and the lower sealing member 237b, and the generated gas discharge header 219 collects the generated gas that passes through the inside of the base tube 103 of the multiple cell stacks 11 and is supplied to the generated gas discharge header 219, and guides it to the generated gas discharge branch pipe 209a via the generated gas discharge pipe 231b.

[0109] The oxidizing gas supply main pipe (not shown) branches off a predetermined flow rate of oxidizing gas corresponding to the operating temperature of module 201 to oxidizing gas supply branch pipes (not shown) and supplies 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 SOEC 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 electrolysis chamber 215 via an oxidizing gas lower penetration section 235a, which will be described later.

[0110] The oxidizing gas discharge header 223 is an area surrounded 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 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.

[0111] 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 plurality of holes corresponding to the number of cell stacks 11 provided in the cartridge 203, and each cell stack 11 is inserted into a respective hole. This upper tube sheet 225a airtightly supports one end of each of the cell stacks 11 via either the upper sealing member 237a and / or the adhesive member, and also isolates the raw material gas supply header 217 from the oxidizing gas discharge header 223.

[0112] 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 11 provided in the cartridge 203. The diameter of these holes is set to be larger than the outer diameter of the cell stacks 11. 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 11 inserted through the upper insulator 227a.

[0113] The upper insulator 227a separates the electrolytic 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 prevent thermal deformation of the upper tube sheet 225a and the like due to temperature differences as the upper tube sheet 225a and the like are exposed to the high temperature inside the electrolytic chamber 215, a metal material with high temperature resistance, such as a Ni-based alloy, may be used. The upper insulator 227a guides the exhaust oxidizing gas, which has passed through the electrolytic chamber 215 and been exposed to high temperatures, through the upper oxidizing gas penetration section 235b to the oxidizing gas discharge header 223.

[0114] According to this embodiment, the structure of the cartridge 203 described above allows the raw material gas and the oxidizing gas to flow in opposition to each other on the inside and outside of the cell stack 11. As a result, the exhaust oxidizing gas exchanges heat with the raw material gas supplied to the electrolytic chamber 215 through the inside of the base tube 103, and is cooled to a temperature at which damage to the upper tube sheet 225a, etc., made of metal material, due to stress is prevented, before being supplied to the oxidizing gas discharge header 223. In addition, the raw material gas is heated by heat exchange with the exhaust oxidizing gas discharged from the electrolytic chamber 215 and supplied to the electrolytic chamber 215. As a result, the raw material gas, which has been preheated to the temperature necessary for the electrolytic reaction, can be supplied to the electrolytic chamber 215 without using a heater or the like.

[0115] 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 plurality of holes corresponding to the number of cell stacks 11 provided in the cartridge 203, and each cell stack 11 is inserted into a respective hole. This lower tube sheet 225b airtightly supports the other end of the plurality of cell stacks 11 via either the lower sealing member 237b or the adhesive member, or both, and also isolates the generated gas discharge header 219 from the oxidizing gas supply header 221.

[0116] 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 11 provided in the SOEC cartridge 203. The diameter of these holes is set to be larger than the outer diameter of the cell stacks 11. 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 11 inserted through the lower insulator 227b.

[0117] The lower insulator 227b separates the electrolytic 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 due to temperature differences when the lower tube sheet 225b is exposed to the high temperature inside the electrolytic chamber 215, a metal material with high temperature resistance, such as a Ni-based alloy, 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 electrolytic chamber 215.

[0118] According to this embodiment, the structure of the SOEC cartridge 203 described above causes the generated gas and the oxidizing gas to flow in opposition to each other on the inside and outside of the cell stack 11. As a result, the generated gas that has passed through the inside of the base tube 103 and through the electrolytic chamber 215 undergoes heat exchange with the oxidizing gas supplied to the electrolytic chamber 215, and is cooled to a temperature at which damage to the lower tube sheet 225b, etc., made of metal material, due to stress is prevented, and then supplied to the generated gas discharge header 219. The oxidizing gas is also heated by heat exchange with the generated gas and supplied to the electrolytic chamber 215. As a result, the oxidizing gas heated to the temperature necessary for the electrolytic reaction can be supplied to the electrolytic chamber 215 without the use of heaters or the like.

[0119] (Electrolytic Cell Module) As shown in Figure 8, the electrolytic cell module (module) 201 includes, for example, a plurality of cartridges (electrolytic cell cartridges) 203, a module container 205 that houses these plurality of cartridges 203, and an insulating material (not shown) provided inside the module container 205 to insulate the plurality of cartridges 203. The module 201 includes a raw material gas supply main pipe 207 and a plurality of raw material gas supply branch pipes 207a, and a generated gas discharge main pipe 209 and a plurality of generated gas discharge branch pipes 209a. The SOEC module 201 also includes an oxidizing gas supply main pipe (not shown) and a plurality of oxidizing gas supply branch pipes (not shown).

[0120] The raw material gas supply main pipe 207 is located inside the module container 205 and is connected to a raw material gas supply unit that supplies raw material gas of a predetermined gas composition and flow rate corresponding to the amount of raw material gas generated by the SOEC module 201. It is also connected to a plurality of raw material gas supply branch pipes 207a. This raw material gas supply main pipe 207 branches and guides the raw material gas supplied from the aforementioned raw material gas supply unit at a predetermined flow rate to a plurality of raw material gas supply branch pipes 207a. The raw material gas supply branch pipes 207a are connected to the raw material gas supply main pipe 207 and are also connected to the raw material gas supply pipes 231a of a plurality of cartridges 203. These raw material gas supply branch pipes 207a guide the raw material gas supplied from the raw material gas supply main pipe 207 to the plurality of cartridges 203 at a substantially equal flow rate, thereby substantially equalizing the electrolytic voltage of the plurality of cartridges 203.

[0121] The generated gas discharge branch pipe 209a is connected to the generated gas discharge pipes 231b of multiple cartridges 203 and is also connected to the generated gas discharge main pipe 209. This generated gas discharge branch pipe 209a guides the generated gas discharged from the cartridges 203 to the generated gas discharge main pipe 209. The generated gas discharge main pipe 209 is connected to the multiple generated gas discharge branch pipes 209a and a portion of it is located outside the module container 205. This generated gas discharge main pipe 209 guides the generated gas discharged from the generated gas discharge branch pipes 209a at a substantially uniform flow rate to the outside of the module container 205.

[0122] The module container 205 is operated at an internal pressure of several MPa from atmospheric pressure and a surface temperature of approximately 300°C from ambient temperature, and is preferably made of materials such as carbon steel from the viewpoint of cost reduction.

[0123] In this embodiment, a configuration in which multiple cartridges 203 are assembled and housed in a module container 205 has been described, but the embodiment is not limited to this, and for example, the cartridges 203 can be housed in the module container 205 without being assembled.

[0124] The DC power required for the electrolytic reaction is supplied to the module after the supplied power is converted to a predetermined voltage by a power conversion device such as a power conditioner. The power supplied to the module is distributed according to the number of series and parallel connections of each cartridge. In each cartridge 203, power is supplied to a power supply member (not shown) via a power supply plate (not shown), and after current is passed through lead films 115 made of Ni / YSZ or the like provided on multiple electrolytic cells 105 to near the ends of the cell stack 11, it is supplied to the electrolytic cells 105.

[0125] [Fifth Embodiment] In the above embodiment, cylindrical transverse striped electrolytic cell stacks 11, 101, 141, and 151 were described, but the shape of the electrolytic cell stack is not necessarily limited to these, and for example, a flat plate type cell stack may also be used. Although the electrolytic cell is formed on a substrate, the electrodes (hydrogen electrode or oxygen electrode) may be formed thickly instead of the substrate and serve as both the substrate and the electrodes. Below, flat plate type, cylindrical flat plate type, and cylindrical vertical striped type electrolytic cell stacks will be described.

[0126] (Planar electrolytic cell stack) A planar electrolytic cell stack has multiple planar electrolytic cells. The multiple electrolytic cells are stacked in a direction perpendicular to the surface of the plate with the largest surface area. Separators (interconnectors) are placed between the multiple electrolytic cells.

[0127] Figure 9 is a schematic diagram illustrating the structure of the electrolytic cell stack 160. The electrolytic cell 161 is made up of a flat hydrogen electrode 162, a solid electrolyte membrane 163, and an oxygen electrode 164 stacked in that order. The hydrogen electrode 162 faces the separator 165. The oxygen electrode 164 faces the separator 166. The electrolytic cell 161 may be of the electrolyte-supported, electrode-supported, or metal-supported type.

[0128] In the flat electrolytic cell stack 160, the raw material gas flows between the hydrogen electrode 162 and the separator 165, and the oxidizing gas flows between the oxygen electrode 164 and the separator 166. The raw material gas and the oxidizing gas are supplied in perpendicular directions. The hydrogen electrode 162 and the separator 165 facing the hydrogen electrode 162 define the outer perimeter of the flow path 167 for the generated gas produced at the hydrogen electrode 162.

[0129] In the flat electrolytic cell stack 160 shown in Figure 9, the hydrogen electrode 162 contains Ni. The methanation suppression film 168 is provided on the separator 165 side surface of the hydrogen electrode 162.

[0130] Furthermore, if the separator 165 that defines the flow path 167 for the generated gas produced at the hydrogen electrode 162 contains a methanation catalyst such as Ni or Fe, a methanation suppression film 168 is also provided on the surface of the separator 165 on the hydrogen electrode 162 side.

[0131] (Cylindrical flat plate electrolytic cell stack) A cylindrical flat plate electrolytic cell stack has multiple oval-shaped (rounded rectangle) electrolytic cells. The electrolytic cells are arranged in parallel.

[0132] Figure 10 is a schematic diagram illustrating the structure of the electrolytic cell stack 170. The electrolytic cell 171 includes a hydrogen electrode 172, a solid electrolyte membrane 173, an oxygen electrode 174, an interconnector 175, and a conductive support layer (substrate) 176. The substrate 176 contains a methanation catalyst such as Ni.

[0133] The substrate 176 has an oval shape, and multiple flow passages 177 through which the raw material gas passes are formed in parallel inside. The product gas generated at the hydrogen electrode 172 by co-electrolysis also passes through these flow passages 177. A methane suppression film 178 is provided on the inner circumferential surface of the flow passages 177.

[0134] A hydrogen electrode 172, a solid electrolyte membrane 173, and an oxygen electrode 174 are stacked in order on the outer surface of the substrate 176. The interconnector 175 is provided on the opposite side of the substrate 176 from the oxygen electrode 174 so that it can be connected to the oxygen electrode 174 located on the outer surface of an adjacent electrolytic cell 171.

[0135] In the electrolytic cell stack 170, the raw material gas flows inside the substrate 176 (flow passage 177), and the oxidizing gas flows outside the cylinder. The raw material gas and the oxidizing gas flow in parallel in the same direction.

[0136] (Cylindrical striped electrolytic cell stack) A cylindrical striped electrolytic cell stack has multiple cylindrical electrolytic cells. The electrolytic cells are arranged in parallel.

[0137] Figure 11 is a schematic diagram illustrating the structure of the electrolytic cell stack 180. The electrolytic cell 181 includes a cylindrical hydrogen electrode 182, a solid electrolyte membrane 183, an oxygen electrode 184, and an interconnector 185. The hydrogen electrode 182, the solid electrolyte membrane 183, and the oxygen electrode 184 are stacked in order from the outside to the inside. In the circumferential direction of the cylinder, there is a gap between the solid electrolyte membrane 183 and both ends of the hydrogen electrode 182. The interconnector 185 is stacked on the outer circumference of the oxygen electrode 184 to fill this gap.

[0138] In the cylindrical striped electrolytic cell stack 180, the oxidizing gas flows along the inner circumference of the cylinder, and the raw material gas flows along the outer circumference of the cylinder. The raw material gas and the oxidizing gas flow in parallel in the same direction.

[0139] In Figure 11, the outer surface of the hydrogen electrode 182 defines a portion of the outer periphery of the flow channel 186 through which the product gas generated at the hydrogen electrode 182 by co-electrolysis flows. The methanation suppression film 187 is provided on the outer surface of the hydrogen electrode 182.

[0140] <Note> The manufacturing methods for the electrolytic cell stack, electrolytic cell cartridge, electrolytic cell module, and electrolytic cell stack described above can be understood, for example, as follows.

[0141] An electrolytic cell stack (11, 101, 141, 151, 160, 170, 180) according to a first aspect of this disclosure comprises an electrolytic cell (105, 161, 171, 181) in which a hydrogen electrode (109, 162, 172, 182), a solid electrolyte (111, 163, 173, 183), and an oxygen electrode (113, 164, 174, 184) are stacked in order, and a generated gas produced at the hydrogen electrode The system comprises a flow passage (117, 167, 177, 186) through which the generated gas flows, and a methanation suppression film (116, 168, 178, 187) covering the surface of a member (103, 165, 166, 176, 182) defining the outer perimeter of the flow passage on the side through which the generated gas flows, wherein the member defining the outer perimeter of the flow passage contains a methanation catalyst, and the methanation suppression film does not contain a methanation catalyst.

[0142] The methanation-inhibiting film covering the surface of the member defining the outer perimeter of the flow passage on the side through which the generated gas flows, that is, the surface of the flow passage through which the generated gas produced at the hydrogen electrode flows, acts as a barrier to prevent the generated gas from directly contacting the flow passage surface. By providing a barrier, the opportunities for the generated gas to come into contact with the methanation catalyst are reduced, making it less likely for the methanation reaction of the generated gas flowing through the flow passage to occur. As a result, H ２ This can suppress the decrease in CO yield.

[0143] In the electrolytic cell stack according to a second aspect of this disclosure, the methanation suppression film is a sintered body, as described in the first aspect.

[0144] In the electrolytic cell stack according to the third aspect of this disclosure, the material of the methanation-suppressing film is selected from the group consisting of zirconia compounds, alumina, and forsterite, as described in the first or second aspect.

[0145] The methanation-inhibiting film made from the above-mentioned ceramics can become a sintered body usable in high-temperature environments.

[0146] In the electrolytic cell stack according to the fourth aspect of this disclosure, in any of the first to third aspects, the methanation suppression film is a low-temperature sintered body having a porosity of 0% or more and 10% or less, and containing an additive for reducing the sintering temperature of the material of the methanation suppression film to 100°C or more and 300°C or less.

[0147] The inclusion of the above-mentioned additives enables low-temperature sintering at temperatures between 100°C and 300°C. A methane-inhibiting film sintered at low temperatures can result in a sintered body with less thermal influence compared to a sintered body sintered at high temperatures.

[0148] A dense methane-inhibiting film with a porosity of 10% or less can firmly cover the surface of the component defining the outer perimeter of the flow path, even if it is thin. Lowering the porosity reduces the interconnection of pores, thereby reducing the opportunity for the generated gas to reach the surface of the component defining the outer perimeter of the flow path through the interconnected pores.

[0149] In the electrolytic cell stack according to the fifth aspect of this disclosure, the thickness of the methanation suppression film is 1 μm or more and 500 μm or less, as in the fourth aspect described above.

[0150] A dense methanation-inhibiting film with a porosity of 10% or less can block gas permeation if it is 1 μm thick. If the methanation-inhibiting film is too thick, it will not be able to maintain its strength. Therefore, the thickness of a dense methanation-inhibiting film with a porosity of 10% or less should be 500 μm or less.

[0151] In the electrolytic cell stack according to the sixth aspect of this disclosure, in any of the first to third aspects, the methanation suppression film is a low-temperature sintered body having a porosity of more than 10% and 40% or less, and containing an additive for lowering the sintering temperature of the material of the methanation suppression film from 100°C to 300°C.

[0152] The inclusion of the above-mentioned additives enables low-temperature sintering at temperatures between 100°C and 300°C. A methane-inhibiting film sintered at low temperatures can result in a sintered body with less thermal influence compared to a sintered body sintered at high temperatures.

[0153] Methanization-inhibiting films with a porosity of 10% or more allow gas to pass through in the film thickness direction. Because gas-permeable films do not interfere with the reduction process in the manufacturing of electrolytic cell stacks, there are many options for the timing of film formation, such as before the reduction process or during the sintering of the oxygen electrode. Strength can also be ensured if the porosity is 40% or less.

[0154] In the electrolytic cell stack according to the seventh aspect of this disclosure, the thickness of the methanation suppression film is 500 μm or more and 4000 μm or less, as described in the sixth aspect.

[0155] A methanation-inhibiting membrane with a porosity exceeding 10% can block gas permeation with a thickness of 500 μm. If the methanation-inhibiting membrane is too thick, it will not be able to maintain its strength. Therefore, the thickness of a methanation-inhibiting membrane with a porosity exceeding 10% should be 4000 μm or less.

[0156] In the electrolytic cell stack according to the eighth aspect of this disclosure, in the third aspect described above, the methanation suppression film is a high-temperature sintered body having a porosity of more than 10% and 40% or less, and is sintered at the sintering temperature of a material that does not contain the methanation catalyst.

[0157] Methanization-inhibiting films with a porosity of 10% or more allow gas to pass through in the film thickness direction. Because gas-permeable films do not interfere with the reduction process in the manufacturing of electrolytic cell stacks, there are many options for the timing of film formation, such as before the reduction process or during the sintering of the oxygen electrode. Strength can also be ensured if the porosity is 40% or less.

[0158] In the electrolytic cell stack according to the ninth aspect of this disclosure, in any of the first to eighth aspects, the difference in the coefficient of linear expansion between the member defining the outer casing of the flow path and the methanation suppression film is 2 × 10 －６ It is within / ℃.

[0159] By keeping the difference in the coefficient of linear expansion between the component defining the outer perimeter of the flow path and the methanation-inhibiting film within the above range, damage caused by differences in the coefficient of linear expansion during the manufacturing process or use can be reduced.

[0160] In the electrolytic cell stack according to the tenth aspect of the present disclosure, in any of the first to ninth aspects, the stack further comprises cores (142, 152) disposed within the flow passage so that the generated gas can flow through the flow passage.

[0161] The raw material gas supplied to the electrolytic cell stack is electrolyzed in the electrolytic cell. The gas produced at the hydrogen electrode (product gas containing hydrogen and carbon monoxide) is discharged to the outside through the flow passage. By placing a core, the heat transfer coefficient of the inner surface of the member defining the outer perimeter of the flow passage can be increased (by reducing the clearance between the member defining the outer perimeter of the flow passage and the core, the convective heat transfer coefficient is increased), thus promoting heat exchange of the product gas.

[0162] In the electrolytic cell stack according to the eleventh aspect of this disclosure, as in the tenth aspect, a hollow tube (153) is provided in the flow passage so that the generated gas can flow through the flow passage, and the core is provided in the hollow tube.

[0163] By placing the hollow tubes described above within the flow path, the generated gas preferentially flows into the hollow tubes, where the pressure drop is low. This reduces the opportunities for the generated gas to come into contact with the methanation catalyst contained in the flow path. As a result, the methanation reaction of the generated gas can be suppressed more reliably, and the amount of methane produced can be reduced. In such an electrolytic cell stack, H ２ The decrease in CO yield is suppressed.

[0164] The placement of hollow tubes within the flow path is straightforward. According to the above disclosure, the methanation reaction caused by the methanation catalyst downstream of the electrolytic cell can be suppressed by the simple operation of placing hollow tubes.

[0165] An electrolytic cell cartridge (203) according to the twelfth aspect of this disclosure comprises an electrolytic cell stack as described in any of the first to eleventh aspects.

[0166] An electrolytic cell module (201) according to the thirteenth aspect of this disclosure comprises the electrolytic cell cartridge of the twelfth aspect described above.

[0167] A method for manufacturing an electrolytic cell stack according to a fourteenth aspect of the present disclosure comprises an electrolytic cell in which a hydrogen electrode, a solid electrolyte, and an oxygen electrode are stacked in order, and a flow passage through which a product gas generated at the hydrogen electrode by co-electrolysis flows, wherein a member defining the outer edge of the flow passage contains a methanation catalyst, wherein a material that does not contain a methanation catalyst is applied to the surface of the member defining the outer edge of the flow passage on the side through which the product gas flows, and heated to form a methanation-inhibiting film.

[0168] In the method for manufacturing an electrolytic cell stack according to the 15th aspect of the present disclosure, in the 14th aspect, after sintering the oxygen electrode, Ni contained in the member defining the outer casing of the flow passage is subjected to a reduction treatment, after the reduction treatment, a material that does not contain the methanation catalyst is applied to the surface of the member defining the outer casing of the flow passage on the side through which the generated gas flows, and heated at a low temperature of 100°C to 300°C to form the methanation suppression film having a porosity of 0% to 10%, and the material that does not contain the methanation catalyst is a material that includes a substance selected from the group consisting of zirconia compounds, alumina and forsterite, and an additive for lowering the heating temperature to 100°C to 300°C.

[0169] In the method for manufacturing an electrolytic cell stack according to the 16th aspect of the present disclosure, in the 14th aspect, after the oxygen electrode is formed, after the oxygen electrode is sintered, or after the reduction treatment of Ni contained in the member defining the outer edge of the flow passage after the oxygen electrode has been sintered, a material that does not contain the methanation catalyst is applied to the surface of the member defining the outer edge of the flow passage on the side through which the generated gas flows, and heated at a low temperature of 100°C to 300°C to form the methanation suppression film having a porosity of 10% to 40%, wherein the material that does not contain the methanation catalyst is a material that includes a substance selected from the group consisting of zirconia compounds, alumina, and forsterite, and an additive for lowering the heating temperature to 100°C to 300°C.

[0170] In the method for manufacturing an electrolytic cell stack according to the 17th aspect of the present disclosure, in the 14th aspect, after the oxygen electrode is formed or after the oxygen electrode is sintered, a material that does not contain the methanation catalyst is applied to the surface of a member defining the outer casing of the flow passage on the side through which the generated gas flows, and the material is heated at the sintering temperature of the material that does not contain the methanation catalyst to form a methanation suppression film having a porosity of 10% or more and 40% or less, wherein the material that does not contain the methanation catalyst is selected from the group consisting of zirconia compounds, alumina, and forsterite.

[0171] 11, 101, 141, 151, 160, 170, 180 Cell stack (electrolytic cell stack) 103 Base tube (member defining the outer perimeter of the flow path) 104 Inner surface of base tube 105, 161, 171, 181 Electrolytic cell 107, 165, 166, 175, 185 Interconnector (separator) 109, 162, 172, 182 Hydrogen electrode 111, 163, 173, 183 Solid electrolyte membrane (solid electrolyte) 113, 164, 174, 184 Oxygen electrode 115 Lead membrane 116, 168, 178, 187 Methanation suppression membrane 117, 167, 177, 186 Flow path 120, 121 Connection part 122 Supply pipe 123 Discharge pipe 130 Electrolytic section 131 Upper lead section 132 Lower lead sections 142, 152 Core 153 Hollow tube 176 Conductive support layer (substrate, member defining the outer casing of the flow path) 201 Module 203 Cartridge 205 Module container 207 Raw material gas supply main pipe 207a Raw material gas supply branch pipe 209 Product gas discharge main pipe 209a Product gas discharge branch pipe 215 Electrolytic chamber 217 Raw material gas supply header 219 Product gas discharge header 221 Oxidizing gas supply header 223 Oxidizing gas discharge header 225a Upper tube sheet 225b Lower tube sheet 227a Upper insulator 227b Lower insulator 229a Upper casing 229b Lower casing 231a Raw material gas supply pipe 231b Gas discharge pipe 233a Oxidizing gas supply pipe 233b Oxidizing gas discharge pipe 235a Lower penetration for oxidizing gas 235b Upper penetration for oxidizing gas 237a Upper sealing member 237b Lower sealing member

Claims

1. An electrolytic cell stack comprising: an electrolytic cell in which a hydrogen electrode, a solid electrolyte, and an oxygen electrode are stacked in order; a flow passage through which the product gas generated at the hydrogen electrode flows; and a methanation-inhibiting film covering the surface of a member defining the outer edge of the flow passage on the side through which the product gas flows, wherein the member defining the outer edge of the flow passage contains a methanation catalyst, and the methanation-inhibiting film does not contain a methanation catalyst.

2. The electrolytic cell stack according to claim 1, wherein the methanation-inhibiting film is a sintered body.

3. The electrolytic cell stack according to claim 1, wherein the material of the methanation-suppressing membrane is selected from the group consisting of zirconia compounds, alumina, and forsterite.

4. The electrolytic cell stack according to claim 1, wherein the methanation-inhibiting film has a porosity of 0% or more and 10% or less, and is a low-temperature sintered body containing an additive for lowering the sintering temperature of the material of the methanation-inhibiting film to 100°C or more and 300°C or less.

5. The electrolytic cell stack according to claim 4, wherein the thickness of the methanation suppression film is 1 μm or more and 500 μm or less.

6. The electrolytic cell stack according to claim 1, wherein the methanation-inhibiting film has a porosity of more than 10% and 40% or less, and is a low-temperature sintered body containing an additive for lowering the sintering temperature of the material of the methanation-inhibiting film from 100°C to 300°C.

7. The electrolytic cell stack according to claim 6, wherein the thickness of the methanation suppression film is 500 μm or more and 4000 μm or less.

8. The electrolytic cell stack according to claim 3, wherein the methanation-inhibiting film has a porosity of more than 10% and 40% or less, and is a high-temperature sintered body sintered at the sintering temperature of the material of the methanation-inhibiting film.

9. The difference in the coefficient of linear expansion between the member defining the outer casing of the flow passage and the methanation suppression film is 2 × 10 －６ The electrolytic cell stack according to claim 1, wherein the temperature is within / ℃.

10. The electrolytic cell stack according to claim 1, further comprising a core disposed within the flow passage such that the generated gas can flow through the flow passage.

11. The electrolytic cell stack according to claim 10, comprising a hollow tube disposed within the flow passage so that the generated gas can flow through the flow passage, wherein the core is disposed within the hollow tube.

12. An electrolytic cell cartridge comprising the electrolytic cell stack according to any one of claims 1 to 11.

13. An electrolytic cell module comprising the electrolytic cell cartridge described in claim 12.

14. A method for manufacturing an electrolytic cell stack comprising: an electrolytic cell in which a hydrogen electrode, a solid electrolyte, and an oxygen electrode are stacked in order; and a flow passage through which a product gas generated at the hydrogen electrode by co-electrolysis flows, wherein a member defining the outer edge of the flow passage contains a methanation catalyst, the method for manufacturing an electrolytic cell stack comprising: applying a material that does not contain a methanation catalyst to the surface of the member defining the outer edge of the flow passage on the side through which the product gas flows, and heating to form a methanation-inhibiting film.

15. A method for manufacturing an electrolytic cell stack according to claim 14, wherein after sintering the oxygen electrode, Ni contained in the member defining the outer casing of the flow passage is subjected to a reduction treatment; after the reduction treatment, a material that does not contain the methanation catalyst is applied to the surface of the member defining the outer casing of the flow passage on the side through which the generated gas flows; and the material is heated at a low temperature of 100°C to 300°C to form the methanation suppression film having a porosity of 0% to 10%; and the material that does not contain the methanation catalyst is a material that includes a substance selected from the group consisting of zirconia compounds, alumina, and forsterite, and an additive for lowering the heating temperature to 100°C to 300°C.

16. A method for manufacturing an electrolytic cell stack according to claim 14, wherein, after the formation of the oxygen electrode, after the sintering of the oxygen electrode, or after the reduction treatment of Ni contained in the member defining the outer casing of the flow passage after the sintering of the oxygen electrode, a material that does not contain the methanation catalyst is applied to the surface of the member defining the outer casing of the flow passage on the side through which the generated gas flows, and the material is heated at a low temperature of 100°C to 300°C to form the methanation suppression film having a porosity of 10% to 40%, and the material that does not contain the methanation catalyst is a material that includes a substance selected from the group consisting of zirconia compounds, alumina, and forsterite, and an additive for lowering the heating temperature to 100°C to 300°C.

17. A method for manufacturing an electrolytic cell stack according to claim 14, wherein, after the oxygen electrode is formed or after the oxygen electrode is sintered, a material that does not contain the methanation catalyst is applied to the surface of a member defining the outer casing of the flow passage on the side through which the generated gas flows, and the material is heated at the sintering temperature of the material that does not contain the methanation catalyst to form a methanation suppression film having a porosity of 10% or more and 40% or less, and the material that does not contain the methanation catalyst is selected from the group consisting of zirconia compounds, alumina and forsterite.

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