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

Abstract

The present invention provides an electrolytic cell stack, an electrolytic cell cartridge, an electrolytic cell module, and a method for manufacturing an electrolytic cell stack, which can suppress the methane reaction of the generated gas even when a methane catalyst is present in the flow path through which the generated gas produced at the hydrogen electrode by co-electrolysis flows. [Solution] The electrolytic cell stack 101 according to this disclosure comprises an electrolytic cell 105 in which a hydrogen electrode 109, a solid electrolyte 111, and an oxygen electrode 113 are stacked in order, and a flow passage 117 through which the product gas generated at the hydrogen electrode 109 by co-electrolysis flows, and a structure 103 defining the outer edge of the flow passage 117 has a poisoned surface layer 119 containing a methane catalyst poisoned with S.

Description

[Technical Field]

[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. [Background technology]

[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. There are various types, including alkaline electrolysis and solid polymer electrolysis, which electrolyze liquid water, and steam electrolysis, which electrolyzes water vapor.

[0003] In particular, solid oxide electrolysis cells (SOECs), which electrolyze high-temperature steam, use oxygen ion conductive ceramics such as yttria-stabilized zirconia as a solid electrolyte. Because they 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. Electrolysis cells using solid electrolytes can also be used for ammonia electrolysis.

[0004] Furthermore, the electrolytic cell can also be supplied with a mixed gas of high-temperature steam and carbon dioxide (CO2) (raw material gas), and the hydrogen produced by electrolysis reacts with carbon dioxide on the electrolytic cell to directly produce carbon monoxide (CO) or hydrocarbon compounds in a co-electrolytic manner (see Patent Document 1).

[0005] Electrolytic cells using solid electrolytes can simultaneously electrolyze CO2 / H2O as a co-electrolysis to produce H2 / CO synthesis gas necessary for Fischer-Tropsch (FT) synthesis, which is used in the production of synthetic fuels (e-fuels) such as sustainable aviation fuel (SAF). This may simplify the system compared to production processes using reverse shift reactions from water electrolysis. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2023-50701 [Overview of the Initiative] [Problems that the invention aims to solve]

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

[0008] The product gas generated in the CO2 / H2O co-electrolysis 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 problem arises because the methanation reaction occurs due to the action of the methanation catalyst, producing methane and reducing the H2 / CO yield.

[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 these circumstances and aims 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 methane reaction of the generated gas even when a methane catalyst is included in the flow path through which the generated gas produced at the hydrogen electrode by co-electrolysis flows. [Means for solving the problem]

[0012] In order to solve the above problems, the electrolytic cell stack, electrolytic cell cartridge, electrolytic cell module, and method for manufacturing an electrolytic cell stack according to the present disclosure employ the following means.

[0013] The present disclosure provides 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 electrolysis flows, wherein a structure defining the outer contour of the flow path has a poisoned surface layer including a methanation catalyst poisoned by S.

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

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

[0016] The present disclosure provides 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 electrolysis flows, the method including exposing a surface of a structure defining the outer contour of the flow path to a poisoning fluid containing S and performing heat treatment in a reducing environment to poison a methanation catalyst contained in the surface of the structure defining the outer contour of the flow path with S to form a poisoned surface layer.

Advantages of the Invention

[0017] The methanation catalyst poisoned by S has a reduced catalytic ability. Thereby, even in a state containing a methanation catalyst, the methanation reaction of the product gas in the flow path through which the product gas generated at the hydrogen electrode by co-electrolysis flows can be suppressed. By suppressing the generation of methane as a by-product, a decrease in the H2 / CO yield can be prevented.

[0018] In the poisoning by S, the catalytic action of the methanation catalyst can be chemically suppressed, so additional fixtures or film formation are not required. Therefore, problems such as corrosion of fixtures and peeling of films do not occur.

Brief Description of the Drawings

[0019] [Figure 1] It is a diagram showing one aspect of a cylindrical electrolytic cell stack according to an embodiment. [Figure 2] It is a diagram showing the procedure of a manufacturing method of a cylindrical electrolytic cell stack according to an embodiment. [Figure 3] It is a schematic diagram explaining the procedure of poisoning treatment example 1. [Figure 4] It is a schematic diagram explaining the procedure of poisoning treatment example 2. [Figure 5] It is a schematic diagram explaining the procedure of poisoning treatment example 3. [Figure 6] It is a diagram showing the result of simulating the methane production amount (%) of an electrolytic cell stack manufactured by a conventional method. [Figure 7] It is a diagram showing one aspect of an electrolytic cell cartridge provided with a cylindrical electrolytic cell stack. [Figure 8] It is a diagram showing one aspect of an electrolytic cell module provided with the electrolytic cell cartridge of FIG. 7. [Figure 9] It is a schematic diagram of a flat plate type electrolytic cell. [Figure 10] It is a schematic diagram of a cylindrical flat plate type electrolytic cell. [Figure 11] It is a schematic diagram of a cylindrical vertically striped electrolytic cell.

MODE FOR CARRYING OUT THE INVENTION

[0020] In the present embodiment, a cylindrical electrolytic cell stack (hereinafter referred to as a cell stack) provided with a solid oxide type electrolytic cell (SOEC), an electrolytic cell cartridge provided with the same, and an electrolytic cell module will be described with reference to the drawings.

[0021] For the sake of convenience of explanation, the positional relationship of each component described using the expressions "upper" and "lower" based on the paper surface indicates the vertically upper side and the vertically lower side, respectively. Further, in the present embodiment, those having the same effect in the vertical direction and the horizontal direction are not necessarily limited to the vertically up-and-down direction on the paper surface, and may correspond to, for example, the horizontal direction orthogonal to the vertical direction.

[0022] (Electrolytic cell stack) 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.

[0023] The cell stack 101 comprises a plurality of electrolytic cells 105 formed on the outer circumferential surface of the base tube 103. The lead film 115 is electrically connected via an interconnector 107 to the oxygen electrode 113 of the electrolytic cell 105 formed at one end of the base tube 103 in the axial direction, and the lead film 115 is electrically connected to the hydrogen electrode 109 of the electrolytic cell 105 formed at the other end.

[0024] The raw material gas supplied to the hydrogen electrode 109 contains water vapor and carbon dioxide. The raw material gas may also contain hydrogen. The raw material gas is supplied to a flow passage 117 whose outer perimeter is defined by the inner surface 104 of the base pipe 103.

[0025] 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 accepts 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). H2O + 2e - →H2+O 2- ...(1) CO2+2e - →CO+O 2- ...(2)

[0026] On one hand, oxygen ions pass through the solid electrolyte membrane 111 due to the potential difference, move to the oxygen electrode 113, release electrons, and become oxygen molecules (see the following reaction formula (3)). The generated oxygen is discharged to the outside together with the oxidizing gas supplied to the oxygen electrode 113. 2O 2- →O2+4e - ···(3)

[0027] In the electrolytic cell stack 101 of FIG. 1, the electrolytic cell 105 is supported by the base tube 103. However, for example, the hydrogen electrode may be formed thickly to also serve as the base tube, and it is not limited to the use of the base tube. Also, although the base tube in this embodiment is described using a cylindrical shape, the base tube only needs to be tubular, and its cross-section is not necessarily limited to a circular shape. For example, an elliptical shape may also be used. A cell stack such as a flat tube (Flat tubular) obtained by vertically crushing the circumferential side surface of the cylinder may also be used.

[0028] The base tube 103 is made of a porous material. For example, CaO-stabilized ZrO2 (CSZ), a mixture of CSZ and nickel oxide (NiO) (CSZ + NiO), Y2O3-stabilized ZrO2 (YSZ), or MgAl2O4, etc. are used as the main components. This 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 peripheral surface 104 of the base tube 103 to the hydrogen electrode 109 formed on the outer peripheral surface of the base tube 103 through the pores of the base tube 103.

[0029] A poisoning surface layer 119 is formed on the inner peripheral surface 104 of the base tube 103 (the structure defining the outer contour of the flow passage 117). The poisoning surface layer 119 contains a methanation catalyst poisoned by S. The methanation catalyst is Ni, which is a component contained in the base tube material.

[0030] The form of "Ni poisoned with S" may be an adsorption type in which S is adsorbed onto Ni, or a reaction type in which nickel sulfide is formed by a chemical reaction between Ni and S. The reaction type is preferred for the form of "Ni poisoned with S". The thickness of the poisoned surface layer 119 should be 5 μm or more. Alternatively, the thickness of the poisoned surface layer 119 may be 100 μm or less.

[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 transfers 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 of a slurry.

[0033] The oxygen electrode 113 is composed of, for example, a LaSrMnO3-based oxide or a LaCoO3-based oxide, and the oxygen electrode 113 is applied as a slurry using screen printing or a dispenser. The oxygen electrode 113 can also have a two-layer structure. In this case, the oxygen electrode layer (oxygen electrode intermediate layer) on the solid electrolyte membrane 111 side is composed of a material that exhibits high ionic conductivity and excellent catalytic activity. The oxygen electrode intermediate layer may be composed of Sm-doped ceria that exhibits high ionic conductivity, and the oxygen electrode layer (oxygen electrode conductive layer) on the oxygen electrode intermediate layer may be composed of a perovskite-type oxide such as Sr and Ca-doped LaMnO3.

[0034] Oxidizing gases do not directly participate in the electrolytic reaction, but they supply the heat necessary for the electrolytic reaction (endothermic reaction) and dissipate excess heat generated during the electrolytic reaction. Typically, these gases contain approximately 15% to 30% oxygen, and air is the most suitable choice. However, other gases such as mixtures of combustion exhaust gas and air, mixtures of oxygen and air, and inert gases such as nitrogen can also be used.

[0035] Interconnector 107 is M for SrTiO3 series, etc. 1-x L x The interconnector 107 is composed of conductive perovskite-type oxides represented by TiO3 (where M is an alkaline earth metal element and L is a lanthanide element) or lanthanum chromite (LaCrO3), and the slurry is screen printed. The interconnector 107 has a dense film to prevent mixing of the source gas and the oxidizing gas. Furthermore, the interconnector 107 has stable durability and electronic conductivity under both oxidizing and reducing atmospheres. In adjacent electrolytic cells 105, the interconnector 107 electrically connects the oxygen electrode 113 of one electrolytic cell 105 to the hydrogen electrode 109 of the other electrolytic cell 105, thereby connecting adjacent electrolytic cells 105 in series.

[0036] The lead film 115 needs to possess electronic conductivity and have a thermal expansion coefficient close 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 M such as SrTiO3 are used. 1-x L x It is composed of TiO3 (where M is an alkaline earth metal element and 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] (Manufacturing method for electrolytic cell stacks) Figure 2 shows the procedure for manufacturing the electrolytic cell stack according to this embodiment. First, (S1) the 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) it is co-sintered in air. The sintering temperature is, for example, 1350°C to 1450°C.

[0038] 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 base tube 103 to interconnector 107 are formed.

[0039] 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. This reduces the NiO contained in the base tube 103 to Ni, thereby increasing the porosity of the base tube 103.

[0040] (S7) After the reduction treatment, the inside of the base tube 103 is exposed to the poisoned fluid in the same apparatus and heat-treated in a reducing environment to form the poisoned surface layer 119.

[0041] The poisoning fluid may be a poisoning gas containing sulfur or a poisoning solution containing sulfur.

[0042] The inner surface 104 of the base tube 103 is exposed to the poisoning fluid under conditions that a poisoned surface layer 119 of a predetermined thickness is formed. By calculating the amount of Ni contained in the surface portion from the inner surface 104 of the base tube 103 to a predetermined depth from the material composition of the base tube 103, the amount of S required to convert the obtained amount of Ni into a sulfur compound can be derived. By exposing the inner surface 104 of the base tube 103 to the derived amount of S, a poisoned surface layer 119 of a predetermined thickness can be formed.

[0043] The following describes the procedures for some specific examples of poisoning treatment. Here, assuming its use as an electrolytic cell stack, the base tube 103 is divided into three areas along its axial direction. The area where the electrolytic cell 105 is formed is called the electrolytic section 130, the area upstream of the raw material gas flow from the electrolytic section 130 is called the upper lead section 131, and the area downstream of the product gas flow from the electrolytic section 130 is called the lower lead section 132.

[0044] Poison treatment example 1: Poison gas Figure 3 is a schematic diagram illustrating the procedure for poisoning treatment example 1. In this treatment example, after placing the base tube 103, which has been reduced in (S6) above, into the electric furnace 120, a predetermined amount of poisoning gas is flowed into the base tube 103 for a predetermined time under high temperature.

[0045] The sulfur (S) contained in the poisoned gas supplied into the base tube 103 either adheres to the nickel (Ni) contained in the surface layer from the inner circumferential surface 104 of the base tube 103 to a predetermined depth, or reacts with the nickel to form nickel sulfide. Poisoning by sulfur reduces the catalytic activity of nickel, thereby suppressing methane production within the base tube 103.

[0046] The poisoned gas may be a mixture of sulfur gas such as H2S, SO2, or COS, and an inert balance gas such as N2 or a reducing balance gas such as H2. The sulfur gas concentration in the mixture is between 1 ppm and 10,000 ppm. The balance gas may be N2 or 3% H2 / N2. Permanent poisoning can be achieved by setting the sulfur concentration in the mixture to 1 ppm or higher. By setting the sulfur concentration in the mixture to less than 1 ppm, the Ni contained in the hydrogen electrode 109 can be prevented from being poisoned, and the electrolytic performance of the electrolytic cell 105 can be ensured.

[0047] The flow time and flow rate of the poisoning gas are set so that the amount of Ni contained in the surface layer of the inner circumferential surface 104 of the base tube 103, which is several tens of micrometers thick, is less than or equal to the amount of S required to poison it.

[0048] The temperature inside the electric furnace 120 is set to a temperature above the temperature at which sulfur (S) in the poisoned gas reacts thermodynamically with nickel (Ni). For example, for short-term processing of about one hour, the temperature inside the electric furnace (reduction temperature) is set to 900°C to 600°C.

[0049] The toxic gas should be supplied into the base tube 103 from the lower lead section 132. The sulfur (S) contained in the poisoned gas is consumed by a reaction with the nickel (Ni) contained in the inner circumferential surface 104 of the base tube 103 as it flows through the base tube 103. The S concentration of the poisoned gas supplied into the long base tube 103 decreases as it moves downstream. By supplying the poisoned gas from the lower lead section 132, a poisoned surface layer 119 can be preferentially formed on the surface of the flow passage 117 through which the product gas generated at the hydrogen electrode 109 by co-electrolysis flows, thereby reducing the impact of poisoning on other parts.

[0050] The following are examples of specific processing conditions when using H2S as the poisoning gas and forming a poisoned surface layer 119 to a depth of 100 μm from the surface of the substrate tube.

[0051] Base tube diameter 1.95cm Base tube wall thickness 0.01cm Base tube cross-sectional area 0.06cm 2 Base tube total length 30cm Base tube volume per cell stack: 1.8 m³ 3 Base tube porosity (oxidation): 26% by volume NiO content in base tube: 40% by volume NiO volume in base tube 0.54cm 3 NiO density 6.67g / cm 3 NiO weight 3.6g Ni moles = H2S mole amount 0.05 Required H2S 0.001Nm 3

[0052] H2S processing: Total flow rate: 7.2 NL / min H2S concentration 500 ppm (3% H2 / N2 balanced gas) H2S transit time: 5 hours Total H2S content: 0.001 Nm³ 3 Electric furnace internal temperature: 750℃

[0053] By reducing the molar amount of sulfur in the supplied poisoning gas to 1 / 10 or less of the molar amount of Ni contained in the base tube 103 (flow channel), the risk of poisoning the Ni in the electrolytic reaction field at the solid electrolyte membrane / hydrogen electrode interface of the electrolytic cell can be reduced. This allows the methane reaction to be inhibited without degrading the electrolytic performance.

[0054] Poisoning treatment example 2: Poisoning gas and poisoning gas introduction pipe Figure 4 is a schematic diagram illustrating the procedure for poisoning treatment example 2. In this treatment example, similar to poisoning treatment example 1, the base tube 103 that has been reduced in (S6) above is placed in an electric furnace, and then a predetermined flow rate of poisoning gas is flowed into the base tube 103 for a predetermined time under high temperature. At this time, a poisoning gas supply pipe 140 is inserted into the lower lead portion 132 side of the base tube 103, and the poisoning gas is supplied into the base tube 103 via the poisoning gas supply pipe 140, while an inert gas / reducing gas (for example, N2) is supplied into the base tube 103 from the upper lead portion 131 side.

[0055] The outer diameter of the poison gas supply pipe 140 is smaller than the inner diameter of the base pipe 103. When the poison gas supply pipe 140 is inserted into the base pipe 103, there is a gap between the outer surface of the poison gas supply pipe 140 and the inner surface of the base pipe 103 through which the poison gas can flow. The tip (opening) of the poison gas supply pipe 140 is preferably positioned at the end of the lower lead section 132 on the electrolytic section 130 side.

[0056] The flow rate of the poisoning gas is less than the flow rate of the inert gas / reducing gas supplied from the upper lead section 131. Other poisoning gas supply conditions may be the same as in poisoning treatment example 1.

[0057] The poisoned gas flowing out from the tip of the poisoned gas supply pipe 140 is redirected by the counterflow of inert gas / reducing gas supplied from the upper lead section 131, flows into the gap between the poisoned gas supply pipe 140 and the base pipe 103, and is discharged to the outside from the opening of the base pipe 103 on the lower lead section 132 side. As a result, only the inner surface of the base pipe 103 located at the lower lead section 132 is exposed to the poisoned gas. In other words, in this processing example, it is possible to form a poisoned surface layer 119 only on the inner surface 104 of the base pipe 103 located at the lower lead section 132.

[0058] Poisoning treatment example 3: Poisoning solution Figure 5 is a schematic diagram illustrating the procedure for poisoning treatment example 3. In this treatment example, the base tube 103, which has been reduced in (S6) above, is immersed in the poisoning solution 150 (see Figure 5(a) and (b)). This coats the inner surface of the base tube 103 with the poisoning substance S.

[0059] After a predetermined time has elapsed, the base tube 103 is removed from the poisoning solution 150, and any poisoning solution 150 adhering to parts of the base tube 103 that do not need to be poisoned, such as the outer surface, is wiped off (see Figure 5(c)).

[0060] After drying, the substrate tube 103 coated with the poisoning substance S is placed in a reducing environment such as an electric furnace and heat-treated at a high temperature (see Figure 5(d)). The heat treatment conditions may be the same as those in poisoning treatment example 1. The heat treatment after drying may also be performed by operating an electrolytic cell stack at a high temperature.

[0061] As shown in Figure 5, it is preferable to immerse only the lower lead portion 132 of the base tube 103 in the poisoning solution 150. This allows the poisoning substance S to be applied only to the base tube 103 located at the lower lead portion 132.

[0062] The poisoning solution 150 is a fluid containing sulfur. The poisoning solution 150 may be a solution of sulfate or sulfide dissolved in water, or an organic sulfur solution such as thiols or sulfides. Sulfates decompose under heat, generating SO2. The sulfate may be, for example, MnSO4.

[0063] The concentration of the toxic substance S in poisoning solution 150 is between 0.001 and 10.0 mol%.

[0064] The poisoning solution 150 should be adjusted to a viscosity of 0.1 to 1000 mPa·s at room temperature. This prevents the amount of poisoning substance S applied and prevents it from entering the base tube 103.

[0065] The time for which the poisoning gas is circulated and the flow rate of the poisoning gas are set so that the amount of Ni contained in the surface layer of the inner circumferential surface 104 of the base tube 103, which is several tens of micrometers thick, is less than or equal to the amount of S required to poison it.

[0066] Next, we will explain why it is preferable to provide a poisoned surface layer 119 on the inner circumferential surface of the base tube located at the lower lead portion 132.

[0067] Figure 6 shows the results of a simulation of the methane production amount (%) of an electrolytic cell stack manufactured by a conventional method. Figure 6(a) is a schematic cross-sectional view of the electrolytic cell stack, and Figure 6(b) shows the methane production amount during the equilibrium reaction. In Figure 6(b), the horizontal axis represents the outlet equilibrium temperature (°C) of the electrolytic cell stack, and the vertical axis represents the outlet methane concentration (%) of the electrolytic cell stack.

[0068] In the electrolytic cell stack shown in Figure 6(a), raw material gases (H2O and CO2) are supplied into the base tube 103 from the opening on the upper lead section 131 side and reach the electrolytic section 130. Co-electrolysis in the electrolytic cell 105 generates H2 and CO at the hydrogen electrode. In addition, at the Ni-containing hydrogen electrode, CO and H2O are generated by a reverse shift reaction between H2 and CO2. These gases (H2, CO, and H2O) and the raw material gases that did not contribute to the above reaction are discharged to the outside as product gas (H2O / CO2 / H2 / CO) from the opening on the lower lead section 132 side. When the product gas comes into contact with the inner surface of the Ni-containing base tube 103, the H2 and CO2 contained in the product gas undergo a methane reaction, producing methane (CH4).

[0069] According to Figure 6(b), the outlet methane concentration (%) was lowest at atmospheric pressure and tended to increase with increasing pressure. Furthermore, the lower the outlet equilibrium temperature (°C), the higher the outlet methane concentration (%). At atmospheric pressure, the outlet methane concentration (%) was over 12% at 550°C, but at 800°C, there was almost no outlet methane concentration (%).

[0070] 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.

[0071] Based on these findings, it can be said that the methane reaction proceeds most readily during the process of the temperature decreasing from a high temperature (850°C) to a low temperature (550°C), that is, in the lower lead section 132.

[0072] Whether the methanation reaction proceeds to equilibrium is greatly influenced by catalytic activity. If there is no catalyst or the catalytic activity is low, the outlet methane concentration (%) will not be as high as the result in Figure 6(b). Therefore, the formation of CH4 can be suppressed by poisoning the Ni contained in the inner surface of the base tube 103 located in the lower lead section 132 with S.

[0073] (Electrolytic cell cartridge) As shown in Figure 7, the cartridge 203 comprises a plurality of cell stacks 101, an electrolysis 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 101, as shown in Figure 7, but this is not necessarily required. For example, the gases may flow parallel to each other on the inside and outside of the cell stack 101, or the oxidizing gas may flow in a direction perpendicular to the longitudinal direction of the cell stack 101.

[0074] 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 101 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 101 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-state operation of module 201, the atmosphere becomes high-temperature, approximately 700°C to 1000°C.

[0075] 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. In addition, the multiple cell stacks 101 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 101 at a substantially uniform flow rate, thereby substantially equalizing the generated gas performance of the multiple cell stacks 101.

[0076] 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 the generated gas discharge pipe 231b provided in the lower casing 229b. In addition, the multiple cell stacks 101 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 101 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.

[0077] 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.

[0078] The oxidizing gas discharge header 223 is the region enclosed by the upper casing 229a, upper tube sheet 225a, and upper insulator 227a of the cartridge 203, and is connected to an oxidizing gas discharge branch pipe (not shown) by an oxidizing gas discharge pipe 233b provided on the side of the upper casing 229a. This oxidizing gas discharge header 223 guides the exhaust oxidizing gas supplied from the 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.

[0079] 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 multiple holes corresponding to the number of cell stacks 101 provided in the cartridge 203, and each cell stack 101 is inserted into one of these holes. This upper tube sheet 225a airtightly supports one end of each of the cell stacks 101 via either the upper sealing member 237a or an adhesive member, or both, and also isolates the raw material gas supply header 217 from the oxidizing gas discharge header 223.

[0080] The upper insulator 227a is positioned at the lower end of the upper casing 229a such that the upper insulator 227a, the top plate of the upper casing 229a, and the upper tube sheet 225a are substantially parallel, and is fixed to the side plate of the upper casing 229a. The upper insulator 227a is also provided with multiple holes corresponding to the number of cell stacks 101 provided in the cartridge 203. The diameter of these holes is set to be larger than the outer diameter of the cell stacks 101. The upper insulator 227a includes an oxidizing gas upper penetration portion 235b formed between the inner surface of these holes and the outer surface of the cell stacks 101 inserted into the upper insulator 227a.

[0081] The upper insulator 227a separates the electrolytic chamber 215 from the oxidizing gas exhaust 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 oxidizing agents in the oxidizing gas. In addition, to prevent thermal deformation of the upper tube sheet 225a and other components due to temperature differences when exposed to the high temperatures 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 exhaust header 223.

[0082] 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 101. 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 the use of heaters or the like.

[0083] The lower tube sheet 225b is fixed to the side plate of the lower casing 229b between the bottom plate of the lower casing 229b and the lower insulator 227b, such that the lower tube sheet 225b, the bottom plate of the lower casing 229b, and the lower insulator 227b are substantially parallel to each other. The lower tube sheet 225b also has a number of holes corresponding to the number of cell stacks 101 provided in the cartridge 203, and each cell stack 101 is inserted into a respective hole. This lower tube sheet 225b airtightly supports the other end of each of the cell stacks 101 via either the lower sealing member 237b or the adhesive member, or both, and also isolates the generated gas discharge header 219 from the oxidizing gas supply header 221.

[0084] The lower insulator 227b is positioned at the upper end of the lower casing 229b such that the lower insulator 227b, the bottom plate of the lower casing 229b, and the lower tube sheet 225b are substantially parallel, and is fixed to the side plate of the lower casing 229b. The lower insulator 227b is also provided with multiple holes corresponding to the number of cell stacks 101 provided in the SOEC cartridge 203. The diameter of these holes is set to be larger than the outer diameter of the cell stacks 101. The lower insulator 227b includes an oxidizing gas lower penetration portion 235a formed between the inner surface of these holes and the outer surface of the cell stacks 101 inserted through the lower insulator 227b.

[0085] 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 it is exposed to the high temperature inside the electrolytic chamber 215, a metal material with high temperature durability, 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.

[0086] 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 101. 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. In addition, the oxidizing gas is 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 using a heater or the like.

[0087] (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 also 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. Furthermore, the SOEC module 201 includes an oxidizing gas supply main pipe (not shown) and a plurality of oxidizing gas supply branch pipes (not shown).

[0088] 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 electrolysis voltage of the plurality of cartridges 203.

[0089] 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.

[0090] The module container 205 is operated at an internal pressure of atmospheric pressure to several MPa and a surface temperature of ambient temperature to approximately 300°C, and is preferably made of materials such as carbon steel from the viewpoint of cost reduction.

[0091] In this embodiment, a configuration in which multiple cartridges 203 are assembled and stored in a module container 205 has been described, but the embodiment is not limited to this, and for example, the cartridges 203 can be stored in the module container 205 without being assembled.

[0092] 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 101, it is supplied to the electrolytic cells 105.

[0093] In the above embodiment, a cylindrical transverse-striped electrolytic cell stack 101 was described, but the shape of the electrolytic cell stack is not necessarily limited to this, and for example, a flat-plate type cell stack may also be used. Although the electrolytic cells are formed on a substrate, the electrodes (hydrogen electrodes or oxygen electrodes) may be formed thickly instead of the substrate, and the substrate may also be used in conjunction with the electrodes. Below, flat-plate, cylindrical flat-plate, and cylindrical vertical-striped electrolytic cell stacks will be described.

[0094] (Flat plate 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.

[0095] Figure 9 is a schematic diagram of an electrolytic cell. The electrolytic cell 160 is made up of a flat hydrogen electrode 161, a solid electrolyte membrane 162, and an oxygen electrode 163 stacked in that order. The hydrogen electrode 161 faces the separator 164. The oxygen electrode 163 faces the separator 165. The electrolytic cell 160 may be of the electrolyte-supported, electrode-supported, or metal-supported type.

[0096] In a planar electrolytic cell stack, the source gas flows between the hydrogen electrode 161 and the separator 164, and the oxidizing gas flows between the oxygen electrode 163 and the separator 165. The source gas and the oxidizing gas are supplied in perpendicular directions. The hydrogen electrode 161 and the separator 164 facing the hydrogen electrode 161 define the outer perimeter of the flow path 166 for the generated gas produced at the hydrogen electrode 161.

[0097] In the planar electrolytic cell stack shown in Figure 9, the hydrogen electrode 161 contains Ni. The poisoned surface layer 167 is provided on the separator 164 side surface of the hydrogen electrode 161.

[0098] Furthermore, if the separator 164 that defines the flow path 166 for the generated gas produced at the hydrogen electrode 161 contains a methane catalyst such as Ni or Fe, a poisoned surface layer 167 is also provided on the surface of the separator 164 on the hydrogen electrode 161 side.

[0099] (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.

[0100] Figure 10 is a schematic diagram of an electrolytic cell. The electrolytic cell 170 includes a hydrogen electrode 171, a solid electrolyte membrane 172, an oxygen electrode 173, an interconnector 174, and a conductive support layer (substrate) 175. The substrate 175 contains a methane catalyst such as Ni.

[0101] The substrate 175 has an oval shape, and multiple parallel flow passages 176 through which the raw material gas passes are formed inside. The product gas generated at the hydrogen electrode 171 by co-electrolysis also passes through these flow passages 176. A poisoned surface layer 177 is provided on the inner circumferential surface of the flow passages 176.

[0102] A hydrogen electrode 171, a solid electrolyte membrane 172, and an oxygen electrode 173 are stacked in order on the outer surface of the substrate 175. The interconnector 174 is provided on the opposite side of the substrate 175 from the oxygen electrode 173 so that it can connect to the oxygen electrode 173 located on the outer surface of an adjacent electrolytic cell 170.

[0103] In the electrolytic cell 170, the raw material gas flows inside the substrate 175 (flow passage 176), and the oxidizing gas flows outside the cylinder. The raw material gas and the oxidizing gas flow in parallel in the same direction.

[0104] (Cylindrical striped electrolytic cell stack) A cylindrical striped electrolytic cell stack has multiple cylindrical electrolytic cells. The electrolytic cells are arranged in parallel.

[0105] Figure 11 is a schematic diagram of an electrolytic cell. The electrolytic cell 180 includes a cylindrical hydrogen electrode 181, a solid electrolyte membrane 182, an oxygen electrode 183, and an interconnector 184. The hydrogen electrode 181, the solid electrolyte membrane 182, and the oxygen electrode 183 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 182 and both ends of the hydrogen electrode 181. The interconnector 184 is stacked on the outer circumference of the oxygen electrode 183 to fill this gap.

[0106] In a cylindrical striped electrolytic cell stack, the oxidizing gas flows along the inner circumference of the cylinder, and the source gas flows along the outer circumference. The source gas and the oxidizing gas flow in parallel directions.

[0107] In Figure 11, the outer surface of the hydrogen electrode 181 partially defines the outer boundary of the flow channel 186 through which the product gas generated at the hydrogen electrode 181 by co-electrolysis flows. The poisoned surface layer 187 is provided on the outer surface of the hydrogen electrode 181.

[0108] <Note> The electrolytic cell stack, electrolytic cell cartridge, electrolytic cell module, and method for manufacturing the electrolytic cell stack described in the embodiments above can be understood, for example, as follows.

[0109] An electrolytic cell stack (101) according to a first aspect of the present disclosure comprises an electrolytic cell (105) in which a hydrogen electrode (109), a solid electrolyte (111), and an oxygen electrode (113) are stacked in order, and a flow passage (117) through which the product gas generated at the hydrogen electrode by co-electrolysis flows, wherein a structure (103) defining the outer casing of the flow passage has a poisoned surface layer (119) containing a methane catalyst poisoned with S.

[0110] A methanation catalyst poisoned with sulfur exhibits reduced catalytic activity compared to an untreated methanation catalyst. By providing a poisoned surface layer on the surface of the structure defining the outer perimeter of the flow channel, the methanation reaction of the gas flowing through the channel can be prevented. Suppressing methane production prevents a decrease in the H2 / CO yield.

[0111] In the electrolytic cell stack according to a second aspect of this disclosure, in the first aspect, the methanation catalyst poisoned by S is included in the poisoned surface layer as a sulfur compound.

[0112] Even the methanation catalyst can have its catalytic activity reduced simply by having sulfur adsorbed on it, but a permanent poisoning effect can be obtained by having sulfur present in the form of a sulfur compound in which the methanation catalyst and sulfur are chemically bonded.

[0113] An electrolytic cell stack according to a third aspect of the present disclosure, in the first or second aspect, comprises a support member (103) on one side that supports the electrolytic cell from the hydrogen electrode side, and the other side of the support member defines the outer casing of the flow passage.

[0114] In the fourth aspect of the present disclosure, the electrolytic cell stack, in the third aspect, is characterized in that the support member is a base tube, one of the surfaces is the outer surface of the base tube, and the configuration defining the outer periphery of the flow passage is the inner surface of the base tube.

[0115] An electrolytic cell cartridge (203) according to the fifth aspect of this disclosure comprises an electrolytic cell stack as described in any of the first to fourth aspects.

[0116] In the sixth aspect of the present disclosure, the electrolytic cell cartridge, in the fifth aspect, has a configuration that defines the outer casing of the flow passage and has the poisoned surface layer, which is placed in an environment in which the generated gas is cooled.

[0117] As the temperature of the generated gas decreases, the amount of methane produced as a by-product increases. By placing the poisoned surface in an environment where the generated gas is cooled, the effect of suppressing the methane reaction is greatly enhanced.

[0118] An electrolytic cell module (201) according to the seventh aspect of this disclosure comprises an electrolytic cell cartridge as described in the fifth or sixth aspect.

[0119] A method for manufacturing an electrolytic cell stack according to an eighth aspect of the present disclosure is 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 (S7) the surface of a structure defining the outer edge of the flow passage is exposed to a poisoned fluid containing S, heat-treated in a reducing environment, and the methanation catalyst contained in the surface of the structure defining the outer edge of the flow passage is poisoned with S to form a poisoned surface layer.

[0120] A method for manufacturing an electrolytic cell stack according to the ninth aspect of this disclosure, in the eighth aspect, is to obtain the molar amount of a methanation catalyst contained from the surface of a structure defining the outer edge of the flow passage to a predetermined depth, and to expose the surface of the structure defining the outer edge of the flow passage to a molar amount of S necessary to convert the molar amount of methanation catalyst into a sulfur compound.

[0121] By obtaining the amount of methanation catalyst contained up to a predetermined depth and setting the amount of S molars accordingly, the risk of poisoning the methanation catalyst in the electrolytic reaction field at the interface between the solid electrolyte and the electrode of the cell stack can be reduced. This allows the methanation reaction to be inhibited without degrading the electrolytic performance of the electrolytic cell.

[0122] When the amount of sulfur (S) in the poisoned gas is small, the methanation catalyst is poisoned via S adsorption. By obtaining the amount of methanation catalyst in moles and setting the amount of S in the poisoned gas accordingly, the methanation catalyst can be poisoned via S reaction. This makes permanent poisoning possible.

[0123] A method for manufacturing an electrolytic cell stack according to the tenth aspect of this disclosure, in the eighth or ninth aspect, wherein the poisoned fluid is a poisoned gas containing S.

[0124] A method for manufacturing an electrolytic cell stack according to an eleventh aspect of this disclosure, in the eighth or ninth aspect, wherein the poisoned fluid is a poisoned solution containing S, the flow passage is immersed in the poisoned solution, the solution on the surface of the flow passage is wiped off and dried, and then the heat treatment is performed. [Explanation of Symbols]

[0125] 101 Cell Stack 103 Base tube (structure that defines the outer casing) 104 Inner surface of the base tube 105, 160, 170, 180 electrolytic cells 107, 164, 165, 174, 184 Interconnectors (Separators) 109,161,171,181 Hydrogen electrodes 111,162,172,182 Solid electrolyte membrane 113,163,173,183 Oxygen electrodes 115 Lead film 117,166,176,186 Distribution path 119,167,177,187 Poisoned surface layer 120 Electric Furnaces 130 Electrolytic section 131 Upper lead section 132 Lower lead section 140 Poison gas supply pipe 150 Poisoning solution 175 Conductive support layer (substrate) 201 Modules 203 Cartridge 205 Module Container 207 Raw material gas supply main pipe 207a Raw material gas supply branch pipe 209 Generative gas discharge main pipe 209a Gas discharge branch pipe 215 Electrolysis chamber 217 Raw material gas supply header 219. Generated gas emission header 221 Oxidizing gas supply header 223 Oxidizing gas emission header 225a Upper tube plate 225b Lower tube sheet 227a Upper insulation 227b Lower insulation 229a Upper casing 229b Lower casing 231a Raw material gas supply pipe 231b Gas discharge pipe 233a Oxidizing gas supply pipe 233b Oxidizing gas exhaust pipe 235a Lower penetration for oxidizing gas 235b Upper penetration for oxidizing gas 237a Upper sealing member 237b Lower sealing member

Claims

1. An electrolytic cell in which a hydrogen electrode, a solid electrolyte, and an oxygen electrode are stacked in that order, A flow channel through which the generated gas produced at the hydrogen electrode flows, Equipped with, The structure defining the outer perimeter of the flow passage is an electrolytic cell stack having a poisoned surface layer containing a methane catalyst poisoned with S.

2. The electrolytic cell stack according to claim 1, wherein the methanation catalyst poisoned by S is contained in the poisoned surface layer as a sulfur compound.

3. On one side, the electrolytic cell is provided with a support member that supports it from the hydrogen electrode side, The electrolytic cell stack according to claim 1, wherein the other surface of the support member is configured to define the outer casing of the flow passage.

4. The support member is a base tube, The aforementioned one surface is the outer circumferential surface of the base tube, The electrolytic cell stack according to claim 3, wherein the structure defining the outer periphery of the flow passage is the inner circumferential surface of the base tube.

5. An electrolytic cell cartridge comprising an electrolytic cell stack according to any one of claims 1 to 4.

6. The electrolytic cell cartridge according to claim 5, wherein the configuration defining the outer casing of the flow passage and having the poisoned surface layer is arranged in an environment in which the generated gas is cooled.

7. An electrolytic cell module comprising the electrolytic cell cartridge described in claim 5.

8. An electrolytic cell in which a hydrogen electrode, a solid electrolyte, and an oxygen electrode are stacked in that order, A flow path through which the generated gas produced at the hydrogen electrode by co-electrolysis flows, A method for manufacturing an electrolytic cell stack comprising: A method for manufacturing an electrolytic cell stack, comprising exposing the surface of a component defining the outer casing of the flow passage to a poisoned fluid containing sulfur, heat-treating it in a reducing environment, and poisoning the methane catalyst contained in the surface of the component defining the outer casing of the flow passage with sulfur to form a poisoned surface layer.

9. A method for manufacturing an electrolytic cell stack according to claim 8, comprising obtaining the molar amount of a methanation catalyst contained from the surface of a structure defining the outer edge of the flow passage to a predetermined depth, and exposing the surface of the structure defining the outer edge of the flow passage to a molar amount of S necessary to convert the molar amount of methanation catalyst into a sulfur compound.

10. The method for manufacturing an electrolytic cell stack according to claim 8, wherein the poisoned fluid is a poisoned gas containing S.

11. The poisoning fluid is a poisoning solution containing S, A method for manufacturing an electrolytic cell stack according to claim 8, comprising immersing the flow passage in the poisoning solution, wiping off the solution from the surface of the flow passage and drying it, and then performing the heat treatment.

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