Electrolysis cell stack, electrolysis cell cartridge, electrolysis cell module and method for manufacturing an electrolysis cell stack

Abstract

Provided is an electrolysis cell stack capable of suppressing temperature rise of the cell stack and increasing the amount of electrolysis-based products. The electrolysis cell stack (101) according to the present invention includes: a hydrogen generation section (10) including an electrolysis cell (105) having a hydrogen electrode, an oxygen electrode, and a solid electrolyte membrane; a raw material gas supply port (11); a hydrogen gas discharge port (12); a raw material gas supply side heat exchange section (13); and a hydrogen gas discharge side heat exchange section (14), the raw material gas supply side heat exchange section and the hydrogen gas discharge side heat exchange section each being composed of a heat transfer section and a header section, and the heat transfer section of the hydrogen gas discharge side heat exchange section having a larger area than the heat transfer section of the raw material gas supply side heat exchange section.

Description

Technical Field

[0001] This invention relates to an electrolytic cell stack, an electrolytic cell box, 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 involve carbon dioxide emissions and has excellent environmental characteristics. It includes alkaline electrolysis or solid polymer electrolysis for liquid water, and steam electrolysis for water vapor.

[0003] Among them, the solid oxide electrolysis cell (SOEC: hereinafter referred to as "electrolysis cell") for electrolyzing high-temperature water vapor uses ceramics such as yttrium-stabilized zirconium oxide, which have oxygen ion conductivity, as electrolytes. It can utilize the thermal energy of high-temperature water vapor as part of the energy required for the electrolysis reaction. Therefore, compared with other electrolysis methods, it can produce hydrogen with high efficiency.

[0004] Patent Document 1 discloses a hydrogen generation system comprising a battery stack having multiple electrolytic cells arranged on a substrate tube, each having a hydrogen electrode, a solid electrolyte membrane, and an oxygen electrode. In the SOEC described in Patent Document 1, the hydrogen electrode is composed of an oxide of a composite material of Ni and a zirconium oxide-based electrolyte material.

[0005] Previous technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 7282968 Summary of the Invention

[0008] The technical problem to be solved by the invention

[0009] In SOEC, the goal is to increase the amount of hydrogen produced per cell.

[0010] Increasing the current flowing through SOEC promotes the electrochemical decomposition (electrolysis) of water, thereby increasing the amount of hydrogen produced. However, when increasing the electrolysis current to make the electrolysis voltage above the thermal neutral potential, the battery durability or the allowable temperature of the metal material must be considered for the following reasons.

[0011] By flowing current through the SOEC, Joule heating is generated due to the battery's internal resistance. However, water electrolysis is an endothermic reaction, and at low currents, the endothermic reaction dominates, thus preventing temperature rise. However, if operating at high currents above the thermal neutral potential, Joule heating accompanying the electrolysis reaction occurs, causing the battery temperature to rise. If the SOEC is exposed to high temperatures, the nickel in the hydrogen electrode sinters, gradually increasing the SOEC's internal resistance and making long-term stable electrolysis difficult. Therefore, it is necessary to manage the battery's maximum temperature below the permissible range.

[0012] In steam electrolysis of SOEC, to reduce the internal resistance of the cell, the temperature of the reaction section must be as uniform as possible, and the maximum temperature must be kept below the allowable temperature. In SOEC, to achieve thermal self-sufficiency of the cell stack, it typically operates at a high current above the thermal neutral point, higher than the operating current of the fuel cell, which is the reverse reaction. Consequently, the supply gas flow rate also increases, thus the gas temperature at the outlet side of the feed gas (steam) tends to rise. To ensure the operating temperature of the electrolyzer (reaction section) is as uniform as possible, to maintain the maximum temperature below the set temperature, and to suppress the exhaust gas temperature from the cell stack below the allowable temperature of the components located downstream of the cell stack, appropriate heat exchange sections need to be installed at the inlet and outlet sides.

[0013] On the other hand, the heat exchange section needs to be sealed to prevent the gas supplied to or discharged from the battery stack. Therefore, the heat exchange section is preferably made of a metal material with high-temperature durability and is designed to be integrated with the electrolytic cell. For example, in a flat-plate battery stack, the temperature of the gas discharged from the SOEC battery stack can be reduced by adopting a stacked structure in which a flat-plate heat exchanger consisting of a heat transfer section and a gas manifold section is integrated on top of and below the stacked electrolytic cells (reaction sections).

[0014] Furthermore, in a cylindrical SOEC stack, a stack structure can be formed where heat exchange sections are located on both sides of the electrolytic cell reaction section, which is constructed on the same substrate tube. However, at both ends of the stack, metal retaining components (sealing components) are required for gas sealing of the feed gas and oxidizing gas. If these retaining components are exposed to high temperatures for a long time, their durability will decrease due to oxidation and corrosion. Therefore, the electrolytic current flowing in the SOEC is limited to a range where the retaining component does not exceed the allowable temperature.

[0015] The present invention was made in view of this situation, and its object is to provide a method for manufacturing an electrolytic cell stack, an electrolytic cell box, an electrolytic cell module, and an electrolytic cell stack that can suppress the temperature rise of exhaust gas and gas sealing retaining member from the heat exchange section provided on the inlet and outlet sides of the SOEC battery stack within an allowable range and increase the hydrogen production based on electrolysis.

[0016] means for solving technical problems

[0017] To address the aforementioned issues, the manufacturing method of the electrolytic cell stack, electrolytic cell box, electrolytic cell module, and electrolytic cell stack of the present invention employs the following approach.

[0018] The present invention provides an electrolytic cell stack comprising: a hydrogen generation section having an electrolytic cell having a hydrogen electrode containing nickel, an oxygen electrode, and a solid electrolyte membrane sandwiched between the hydrogen electrode and the oxygen electrode; a feed gas supply port for supplying feed gas to the hydrogen electrode of the hydrogen generation section; a hydrogen discharge port for discharging hydrogen generated in the hydrogen generation section; a feed gas supply-side heat exchange section, on a side closer to the feed gas supply port than the hydrogen generation section, where the feed gas exchanges heat with an oxidizing gas discharged from the oxygen electrode side; and a hydrogen discharge-side heat exchange section, on a side closer to the hydrogen discharge port than the hydrogen generation section, where the hydrogen exchanges heat with an oxidizing gas supplied to the oxygen electrode side, wherein the feed gas supply-side heat exchange section and the hydrogen discharge-side heat exchange section are respectively composed of a heat transfer section and a manifold section, and the heat transfer section area of ​​the hydrogen discharge-side heat exchange section is larger than the heat transfer section area of ​​the feed gas supply-side heat exchange section.

[0019] The present invention provides an electrolytic cell box having the electrolytic cell stack described above.

[0020] The present invention provides an electrolytic cell module having the electrolytic cell box described above.

[0021] This invention provides a method for manufacturing an electrolytic cell stack, the electrolytic cell stack comprising: a hydrogen generation section having an electrolytic cell having a hydrogen electrode containing nickel, an oxygen electrode, and a solid electrolyte membrane sandwiched between the hydrogen electrode and the oxygen electrode; a raw material gas supply port for supplying raw material gas to the hydrogen electrode of the hydrogen generation section; a hydrogen discharge port for discharging hydrogen generated in the hydrogen generation section; a raw material gas supply-side heat exchange section, on a side closer to the raw material gas supply port than the hydrogen generation section, where the raw material gas exchanges heat with an oxidizing gas discharged from the oxygen electrode side; and a hydrogen discharge-side heat exchange section, on a side closer to the hydrogen discharge port than the hydrogen generation section, where the hydrogen exchanges heat with an oxidizing gas supplied to the oxygen electrode side. In the method for manufacturing the electrolytic cell stack, the raw material gas supply-side heat exchange section and the hydrogen discharge-side heat exchange section are each composed of a heat transfer section and a manifold section, and the heat transfer section area of ​​the hydrogen discharge-side heat exchange section is formed to be larger than the heat transfer section area of ​​the raw material gas supply-side heat exchange section.

[0022] Invention Effects

[0023] According to the present invention, by making the heat transfer section area of ​​the hydrogen emission side heat exchanger larger than the heat transfer section area of ​​the feed gas supply side heat exchanger, the cooling heat of the hydrogen generated in the hydrogen generation section can be increased. As a result, the temperature of the hydrogen emitted from the hydrogen emission port can be suppressed to a lower level than before.

[0024] The high-temperature steam used as feedstock for SOEC does not undergo an endothermic chemical reaction in the feedstock gas supply-side heat exchange section. Therefore, even if the heat transfer area of ​​the feedstock gas supply-side heat exchange section is reduced, the temperature will not decrease due to the endothermic reaction. The temperature of the feedstock gas rises due to heat exchange with the oxidizing gas, thus increasing the operating temperature of the electrolyzer stack. A higher operating temperature reduces the internal resistance of the cell, thereby reducing the power required to produce hydrogen per unit flow rate.

[0025] Even if the current density flowing through the hydrogen generation section increases, this type of electrolytic cell stack can suppress the maximum temperature of the stack within an acceptable range, and can control the hydrogen emitted from the electrolytic cell stack and the stack holding components to ensure that the temperature does not exceed the acceptable range. Attached Figure Description

[0026] Figure 1 This is a diagram illustrating one embodiment of a cylindrical electrolytic cell stack according to an embodiment of the present invention.

[0027] Figure 2 This is an enlarged cross-sectional schematic diagram of the end of the heat exchange section on the fuel supply side of the battery stack.

[0028] Figure 3 This is a diagram showing a cross-section of an electrolytic cell according to an embodiment of the present invention.

[0029] Figure 4 This is a diagram illustrating one embodiment of an electrolytic cell module according to an embodiment of the present invention.

[0030] Figure 5 This is a graph showing the relationship between the operating temperature of the battery stack and its IV characteristics.

[0031] Figure 6 This is a predicted temperature distribution diagram of the battery stack, supplied water vapor, and oxidizing gas in Example 1 and Comparative Example 1.

[0032] Figure 7 The figure shows the test conditions and simulation results of Examples 2 to 4, and Comparative Examples 2 and 3.

[0033] Figure 8 The figure shows the test conditions and simulation results of Examples 5 to 7, and Comparative Examples 4 and 5.

[0034] Figure 9The figure shows the test conditions and simulation results of Examples 8 to 10, and Comparative Examples 6 and 7.

[0035] Figure 10 The figure shows the test conditions and simulation results of Examples 11 to 13, and Comparative Examples 8 and 9.

[0036] Figure 11 The figure shows the test conditions and simulation results of Examples 14 to 16, and Comparative Examples 10 and 11.

[0037] Figure 12 The graph shows the amount of hydrogen generated by using the ratio of the length of the lower heat exchange section (L3) to the length of the heat transfer section of the upper heat exchange section (L1) (L3 / L1) as the horizontal axis. Detailed Implementation

[0038] Hereinafter, with reference to the accompanying drawings, one embodiment of the manufacturing method of the electrolytic cell stack, electrolytic cell box, electrolytic cell module and electrolytic cell stack according to the present invention will be described.

[0039] In this embodiment, "electrolysis" refers to "steam electrolysis".

[0040] For ease of explanation, the positional relationships of the constituent elements described below, using the terms "above" and "below" as a reference on the paper, refer to the vertically upper side and the vertically lower side, respectively. Furthermore, in this embodiment, where the same effect can be obtained in both the vertical and horizontal directions, the vertical direction on the paper is not necessarily limited to the vertical vertical direction; for example, it can correspond to the horizontal direction orthogonal to the vertical direction.

[0041] (Battery stack)

[0042] First, refer to Figure 1 , Figure 2 As an example of this embodiment, a cylindrical electrolyzer stack using a substrate tube will be described. In the absence of a substrate tube, for example, the hydrogen electrode can be thickened to serve as a substrate tube, and the method is not limited to using a substrate tube. Furthermore, while a cylindrical shape is used for the substrate tube in this embodiment, any cylindrical shape is acceptable; the cross-section is not necessarily limited to a circle, and for example, it can be elliptical. A flat tubular battery stack, formed by vertically crushing the circumferential side of a cylinder, is also possible. Additionally, a stacked structure consisting of multiple planar electrochemical single cells, separators, and planar heat exchange sections can also be used.

[0043] Figure 1This is a schematic diagram illustrating one embodiment of the battery stack (cylindrical electrolytic cell stack). The battery stack 101 has a hydrogen generation section 10 at its center along its length. The battery stack 101 has a feed gas supply port 11 and a hydrogen discharge port 12. The battery stack 101 has a feed gas supply side heat exchange section (hereinafter referred to as the upper heat exchange section) 13 and a hydrogen discharge side heat exchange section (hereinafter referred to as the lower heat exchange section) 14 that clamp the hydrogen generation section 10 from both sides along its length.

[0044] As the feed gas that can be supplied to and utilized at the hydrogen electrode of the battery stack 101, the gas used is water vapor, which serves as the hydrogen generation source in the hydrogen generation section 10 and does not produce an endothermic reaction in the upper heat exchange section 13 and the lower heat exchange section 14. The feed gas in this embodiment is water vapor. The gas supplied to the feed gas supply port 11 usually contains hydrogen in addition to the water vapor used in electrolysis. Furthermore, the gas discharged from the hydrogen discharge port 12 may contain the remaining water vapor from the feed gas in addition to the hydrogen generated in the hydrogen generation section 10. However, in the following description, to avoid confusion, the supply gas containing hydrogen is referred to as "supply water vapor", and the hydrogen containing the remaining water vapor is referred to as "generated hydrogen".

[0045] The upper heat exchange section 13 is located on the side of the feed gas supply port (water vapor supply port) 11 of the hydrogen generation section 10. The upper heat exchange section 13 is a region in which the water vapor supplied from the water vapor supply port 11 into the battery stack 101 exchanges heat with the oxidizing gas flowing outside the battery stack 101 before entering the hydrogen generation section 10. The upper heat exchange section 13 may include a lead portion (lead film 115 described later) electrically connected to the hydrogen generation section 10. Specifically, the upper heat exchange section 13 is the region from the end (outer end) of the electrolytic cell 105 formed on the side of the feed gas supply port (water vapor supply port) 11 of the battery stack 101 to the upper tube sheet 225a described later. In addition, the upper heat exchange section 13 does not include the area from the upper tube sheet 225a to the upper end of the battery stack 101. Furthermore, the upper heat exchange section 13 is not necessarily an integral part of the hydrogen generation section 10; it can also be a structure or heat exchanger that has the function of exchanging oxidizing gas with water vapor.

[0046] The upper oxidizing gas penetration section 235b, which will be used for heat exchange between the feed gas and the oxidizing gas in the upper heat exchange section 13, is designated as a heat transfer section (L1). The upper oxidizing gas penetration section 235b is a channel for the oxidizing gas formed between the outer surface of the battery stack 101 and the upper insulation body 227a (described later), and is the area where heat exchange between the feed gas and the oxidizing gas takes place. That is, the upper heat exchange section 13 is a region consisting of the area from the end (outer end) of the electrolytic cell 105 formed on the side of the feed gas supply port (water vapor supply port) 11 of the battery stack 101 to the upper oxidizing gas penetration section 235b (heat transfer section L1), the heat transfer section (L1), and a portion of the oxidizing gas discharge manifold 223.

[0047] The lower heat exchange section 14 is located on the side of the hydrogen emission port (generated hydrogen emission port) 12 of the hydrogen generation section 10. The lower heat exchange section 14 is a region where the hydrogen generated in the hydrogen generation section 10 exchanges heat with the oxidizing gas flowing outside the battery stack 101. The lower heat exchange section 14 may include a lead portion (lead film 115 described later) electrically connected to the hydrogen generation section 10. Specifically, the lower heat exchange section 14 is the region from the end (outer end) of the electrolytic cell 105 formed on the side of the hydrogen emission port (generated hydrogen emission port) 12 of the battery stack 101 to the lower tube sheet 225b described later. In addition, the lower heat exchange section 14 does not include the section from the lower tube sheet 225b to the lower end of the battery stack 101. Furthermore, the lower heat exchange section 14 is not necessarily a component integrally formed with the hydrogen generation section 10, and may also be a structure or heat exchanger with the function of exchanging heat between the oxidizing gas and the hydrogen (generated hydrogen).

[0048] The oxidizing gas lower penetration 235a, where heat exchange between hydrogen (generated hydrogen) and oxidizing gas occurs in the lower heat exchange section 14, is designated as a heat transfer section (L3). The oxidizing gas lower penetration 235a is a channel for oxidizing gas formed between the outer surface of the battery stack 101 and the lower insulation body 227b (described later), and is the area where heat exchange between hydrogen (generated hydrogen) and oxidizing gas occurs. In other words, the lower heat exchange section 14 is a region consisting of the area from the end (outer end) of the electrolytic cell 105 formed on the side of the hydrogen discharge port (generated hydrogen discharge port) 12 of the battery stack 101 to the inlet of the oxidizing gas lower penetration 235a, the heat transfer section (L3) in the oxidizing gas lower penetration, and the portion penetrating the oxidizing gas supply manifold 221.

[0049] The heat transfer area (S3) of the lower heat exchange section 14 (L3) is larger than the heat transfer area (S1) of the upper heat exchange section 13 (L1). (To be continued...) Figure 12In the middle, the ratio (S3 / S1) of the heat transfer area (S3) of the heat transfer section (L3) of the lower heat exchange section 14 to the heat transfer area (S1) of the heat transfer section (L1) of the upper heat exchange section 13 can be 2 or more, preferably 3 or more and 9 or less, and more preferably 3 or more and 7 or less.

[0050] Here, the effective area (S) of the battery stack 101 is the sum of the heat transfer area (S1) of the upper heat exchange section 13, the reaction area (S2) of the hydrogen generation section 10, and the heat transfer area (S3) of the lower heat exchange section 14.

[0051] The effective area (S) of the electrolytic cell stack = the heat transfer area of ​​the upper heat exchange section (S1) + the reaction area of ​​the hydrogen production section (S2) + the heat transfer area of ​​the lower heat exchange section (S3)

[0052] If the diameter of the base tube 103 is uniform, the heat transfer area can be replaced by the length.

[0053] The effective length (L) of the battery stack 101 is the sum of the lengths of the heat transfer section (L1) of the upper heat exchange section 13, the length (L2) of the hydrogen generation section 10, and the length (L3) of the heat transfer section (L3) of the lower heat exchange section 14.

[0054] The effective length (L) of the electrolytic cell stack = the length of the heat transfer section of the upper heat exchange section (L1) + the length of the hydrogen production section (L2) + the length of the heat transfer section of the lower heat exchange section (L3).

[0055] If the diameter of the base tube 103 is made uniform, the length (L3) of the heat transfer section of the lower heat exchange section 14 is greater than the length (L1) of the heat transfer section of the upper heat exchange section 13. The ratio (L3 / L1) of the length (L3) of the heat transfer section of the lower heat exchange section 14 to the length (L1) of the heat transfer section of the upper heat exchange section 13 can be 2 or more, preferably 3 or more and 9 or less, and more preferably 3 or more and 7 or less.

[0056] Figure 2 This is an enlarged cross-sectional view of the end of the hydrogen generation section of the battery stack. The hydrogen generation section 10 is formed on the outer peripheral surface of a cylindrical base tube 103. The diameter (outer and inner diameter) of the base tube 103 can be uniform along its length. The outer diameter of the base tube 103 is, for example, 10 mm to 50 mm. The total length of the base tube 103 is, for example, 500 mm to 3000 mm.

[0057] The hydrogen generation unit 10 includes a plurality of electrolytic cells 105 arranged axially in the base tube 103 and an interconnector 107 formed between adjacent electrolytic cells 105.

[0058] Electrolytic cell 105 is composed of a hydrogen electrode 109, a solid electrolyte membrane 111, and an oxygen electrode 113 stacked together. The solid electrolyte membrane 111 is sandwiched between the hydrogen electrode 109 and the oxygen electrode 113.

[0059] The battery stack 101 includes a lead film 115, which is electrically connected via an interconnect 107 to the oxygen electrode 113 of one of a plurality of electrolytic cells 105 formed on the outer peripheral surface of the substrate tube 103 at the axially furthest end of the electrolytic cell 105. The lead film 115 is also electrically connected to the hydrogen electrode 109 of the electrolytic cell 105 formed at the other furthest end. The outer end of the oxygen electrode 113 of the furthest electrolytic cell 105 becomes the end of the hydrogen generation section 10.

[0060] The substrate tube 103 is made of a porous material, such as CaO-stabilized ZrO2 (CSZ), a mixture of CSZ and nickel oxide (NiO) (CSZ+NiO), Y2O3-stabilized ZrO2 (YSZ), or MgAl2O4 as the main components. This substrate tube 103 supports the electrolytic cell 105, the interconnect 107, and the lead membrane 115, and allows the water vapor supplied to the inner circumferential surface of the substrate tube 103 to diffuse through the fine pores of the substrate tube 103 to the hydrogen electrode 109 formed on the outer circumferential surface of the substrate tube 103. The openings at both ends of the substrate tube 103 can serve as water vapor supply ports and hydrogen generation emission ports.

[0061] The hydrogen electrode 109 is composed of an oxide of a composite material of nickel and zirconium oxide electrolyte material, such as Ni / YSZ. The thickness of the hydrogen electrode 109 is 50 μm to 250 μm, and the hydrogen electrode 109 can be formed by screen printing paste.

[0062] The solid electrolyte membrane 111 primarily uses YSZ, which possesses excellent airtightness, preventing gas from passing through, and high oxygen ion conductivity at high temperatures. The solid electrolyte membrane 111 allows oxygen ions (O2) generated in the hydrogen electrode 109 to... 2- The hydrogen electrode 109 moves to the oxygen electrode 113. The solid electrolyte membrane 111 on the surface of the hydrogen electrode 109 has a thickness of 5 μm to 100 μm and can be formed by printing paste through a filter screen.

[0063] The oxygen electrode 113 is composed, for example, of LaSrMnO3-based oxides or LaCoO3-based oxides. The oxygen electrode 113 is coated with slurry using screen printing or a dispenser.

[0064] The oxygen electrode 113 can also be configured as a double-layer structure. In this case, the oxygen electrode layer (oxygen electrode intermediate layer) on the solid electrolyte membrane 111 side exhibits high ionic conductivity and is composed of a material with excellent catalyst activity. The oxygen electrode intermediate layer can be composed of cerium dioxide doped with Sm, which exhibits high ionic conductivity, and the oxygen electrode layer (oxygen electrode conductive layer) above the oxygen electrode intermediate layer can be composed of perovskite oxides such as LaMnO3 doped with Sr and Ca.

[0065] By applying a negative voltage to the hydrogen electrode 109 and a positive voltage to the oxygen electrode 113, water vapor contained in the supplied water vapor is electrolyzed by accepting electrons at the hydrogen electrode 109, thereby generating hydrogen molecules and oxygen ions (O2). 2- (Refer to the following reaction formula (1)). The generated hydrogen is extracted to the outside along with the supplied water vapor.

[0066] On the other hand, oxygen ions move to the oxygen electrode 113 through the solid electrolyte membrane 111 via the potential difference and release electrons to become oxygen molecules (refer to reaction formula (2) below). The generated oxygen, together with the oxidizing gas supplied to the oxygen electrode 113, is discharged to the outside.

[0067] H2O + 2e - →H2+O 2- ...(1)

[0068] 2O 2- →O2+4e - ...(2)

[0069] Oxidizing gases do not directly participate in the electrolysis reaction, but they supply the heat required for the electrolysis reaction (endothermic) or discharge the residual heat generated in the electrolysis reaction. Oxidizing gases are typically gases containing about 15% to 30% oxygen, with air being the most representative and preferred. However, in addition to air, mixtures of combustion exhaust gas and air, mixtures of oxygen and air, inert gases such as nitrogen, etc., can also be used.

[0070] Interconnector 107 is made of SrTiO3 series, etc. 1-x L x The slurry is composed of a conductive perovskite-type oxide represented by TiO3 (M being an alkaline earth metal element and L being a lanthanide element), and the slurry is screen-printed. The interconnect 107 is a dense film to prevent the water vapor supplied to the hydrogen electrode 109 from mixing with the oxidizing gas supplied to the oxygen electrode 113. Furthermore, the interconnect 107 possesses stable durability and conductivity under both oxidizing and reducing atmospheres. In adjacent electrolytic cells 105, the interconnect 107 electrically connects the oxygen electrode 113 of one electrolytic cell 105 to the hydrogen electrode 109 of another electrolytic cell 105, and connects adjacent electrolytic cells 105 in series.

[0071] The lead film 115 needs to have electronic conductivity and a coefficient of thermal expansion close to that of other materials constituting the battery stack 101. Therefore, it is made of a composite material of nickel such as Ni / YSZ and zirconium oxide electrolyte material or SrTiO3 such as M 1-x L x It is composed of TiO3 (M is an alkaline earth metal element, L is a lanthanide element). The lead film 115 supplies DC power to multiple electrolytic cells 105 connected in series through the interconnect 107. Furthermore, the surface on the oxidizing gas side can be protected with an airtight, oxidation-resistant material to prevent the oxidation of metal materials such as Ni.

[0072] A portion of the lead film 115 may be located on the upper heat exchange section 13 (or the lower heat exchange section 14). In this case, the upper heat exchange section 13 (or the lower heat exchange section 14) has the function of allowing current to flow.

[0073] Next, the manufacturing method of the battery stack will be explained.

[0074] The base tube 103 is formed, for example, by extrusion molding.

[0075] The outer circumferential surface of the base tube 103 is divided along the axial direction (length direction) into an upper heat exchange section, a hydrogen generation section, and a lower heat exchange section. The hydrogen generation section is located in the central part of the base tube 103 along the axial direction, the upper heat exchange section is located on the raw material gas supply port side of the hydrogen generation section, and the lower heat exchange section is located on the hydrogen generation emission port side of the hydrogen generation section.

[0076] The upper heat exchange section region and the lower heat exchange section region are set such that the heat transfer area (S3) of the lower heat exchange section is larger than the heat transfer area (S1) of the upper heat exchange section. The ratio (S3 / S1) of the heat transfer area (S3) of the lower heat exchange section to the heat transfer area (S1) of the upper heat exchange section is 2 or more, preferably 3 or more and 9 or less, and more preferably 3 or more and 7 or less.

[0077] When the diameter of the base tube 103 is uniform in the length direction, the "heat transfer (section) area" can also be converted into "length", and the length of the heat transfer section of the upper heat exchange section, the length of the hydrogen generation section, and the length of the heat transfer section of the lower heat exchange section can be set.

[0078] A hydrogen electrode paste is applied to the outer peripheral surface of the substrate tube 103 within the hydrogen generation region. Furthermore, a lead film paste is applied next to the hydrogen electrode paste applied at the very end. The lead film paste may span both the upper heat exchange region (or the lower heat exchange region) and the hydrogen generation region.

[0079] After applying the slurry for the hydrogen electrode, the slurry for the solid electrolyte membrane and the slurry for the interconnect are applied in sequence.

[0080] The substrate tube 103 of the slurry containing the hydrogen electrode 109, solid electrolyte membrane 111, interconnect 107, and lead wire membrane 115 is co-sintered in atmosphere. The sintering temperature is set, for example, to 1350°C to 1450°C.

[0081] Next, an oxygen electrode slurry is applied to the co-sintered substrate tube 103. The outer end of the oxygen electrode slurry applied to the outermost end becomes the end of the hydrogen generation region.

[0082] The substrate tube 103, which forms the film of the slurry with oxygen electrode 113, is sintered in atmosphere. The sintering temperature is set, for example, to 1100°C to 1250°C. Here, the sintering temperature is set to a lower temperature than the co-sintering temperature after the interconnect 107 is formed from the substrate tube 103.

[0083] Thus, a battery stack 101 in which the heat transfer area (S3) of the lower heat exchange section 14 is greater than the heat transfer area (S1) of the upper heat exchange section 13 can be obtained.

[0084] Next, refer to Figure 3 and Figure 4 The box (electrolytic cell box) and module (electrolytic cell module) involved in this embodiment will be described here. Figure 3 This describes one way of representing the box involved in this embodiment. Furthermore, Figure 4 A cross-sectional view showing one embodiment of the module involved in this implementation.

[0085] (SOEC box)

[0086] like Figure 3 As shown, the box 203 includes multiple battery stacks 101, a steam electrolysis chamber 215, a steam supply manifold 217, a hydrogen generation emission manifold 219, an oxidizing gas (air) supply manifold 221, and an oxidizing gas emission manifold 223. Furthermore, the box 203 includes an upper tube sheet 225a, a lower tube sheet 225b, an upper insulation body 227a, and a lower insulation body 227b. In this embodiment, the steam supply manifold 217, the hydrogen generation emission manifold 219, the oxidizing gas supply manifold 221, and the oxidizing gas emission manifold 223 are connected as follows... Figure 2 With such a configuration, the box 203 becomes a structure that supplies water vapor and oxidizing gas to flow oppositely to each other on the inside and outside of the battery stack 101, but it is not necessarily required to do so. For example, they can also flow parallel to each other on the inside and outside of the battery stack 101, or the oxidizing gas can flow in a direction orthogonal to the length direction of the battery stack 101.

[0087] exist Figure 3 In the battery stack 101, the upper heat exchange section 13 extends from the lower surface of the upper tube sheet 225a to the uppermost (outer end) of the electrolytic cell 105 among the plurality of electrolytic cells 105.

[0088] exist Figure 3 In the battery stack 101, the lower heat exchange section 14 extends from the lower end (outer end) of the lowest electrolytic cell 105 among the plurality of electrolytic cells 105 to the upper surface of the lower tube sheet 225b.

[0089] The steam electrolysis chamber 215 is the region formed between the upper insulation body 227a and the lower insulation body 227b. This steam electrolysis chamber 215 is the region of the electrolytic cell 105 where the battery stack 101 is disposed, and it is the region where steam is electrolyzed to generate hydrogen. Furthermore, the temperature near the central portion along the length of the battery stack 101 in the steam electrolysis chamber 215 can be monitored by a temperature measuring unit 620 (temperature sensor or thermocouple, etc.), and during stable operation of the electrolytic cell module 201, a high-temperature atmosphere of approximately 700°C to 1000°C is maintained.

[0090] The steam supply manifold 217 is the area surrounded by the upper housing 229a and the upper tube sheet 225a of the housing 203, and is connected to the steam supply branch pipe 207a via the steam supply pipe 231a located on the upper part of the upper housing 229a. Furthermore, the multiple battery stacks 101 are joined by the upper tube sheet 225a and the upper sealing member 237a. The steam supply manifold 217 guides the steam supplied from the steam supply branch pipe 207a via the steam supply pipe 231a into the interior of the base tube 103 of the multiple battery stacks 101 at a substantially uniform flow rate, thereby substantially homogenizing the hydrogen production performance of the multiple battery stacks 101.

[0091] The hydrogen generation emission manifold 219 is the area surrounded by the lower housing 229b and lower tube sheet 225b of the housing 203. It is located in the lower housing 229b and is connected to the hydrogen generation emission branch pipe 209a via the hydrogen generation emission pipe 231b. Furthermore, the multiple battery stacks 101 are joined by the lower tube sheet 225b and the lower sealing member 237b. The hydrogen generation manifold 219 collects the generated hydrogen supplied to the hydrogen generation manifold 219 from inside the base tube 103 of the multiple battery stacks 101 and guides it to the hydrogen generation emission branch pipe 209a via the hydrogen generation emission pipe 231b.

[0092] The oxidizing gas supply main pipe (not shown) distributes a specified flow rate of oxidizing gas to oxidizing gas supply branch pipes (not shown) corresponding to the operating temperature of module 201, and supplies it to multiple boxes 203. The oxidizing gas supply manifold 221 is the area surrounded by the lower housing 229b, lower tube sheet 225b, and lower insulation 227b of box 203, and is connected to the oxidizing gas supply branch pipe (not shown) through an oxidizing gas supply hole 233a provided on the side of the lower housing 229b. The oxidizing gas supply manifold 221 guides the specified flow rate of oxidizing gas supplied by the oxidizing gas supply branch pipe (not shown) via the oxidizing gas supply pipe 233a to the steam electrolysis chamber 215 through the lower oxidizing gas penetration 235a (described later).

[0093] The oxidizing gas exhaust manifold 223 is the area surrounded by the upper shell 229a, upper tube sheet 225a, and upper insulation 227a of the housing 203. It is connected to an oxidizing gas exhaust branch pipe (not shown) via an oxidizing gas exhaust pipe 233b located on the side of the upper shell 229a. The oxidizing gas supplied from the steam electrolysis chamber 215 via the oxidizing gas upper penetration 235b (described later) to the oxidizing gas exhaust manifold 223 is guided via the oxidizing gas exhaust pipe 233b to the oxidizing gas exhaust branch pipe (not shown).

[0094] The upper tube sheet 225a is fixed to the side plate of the upper housing 229a in a manner that makes the upper tube sheet 225a, the top plate of the upper housing 229a, and the upper heat insulation body 227a substantially parallel to each other, between the top plate of the upper housing 229a and the upper heat insulation body 227a. Furthermore, the upper tube sheet 225a has a plurality of holes corresponding to the number of battery stacks 101 included in the housing 203, and each battery stack 101 is inserted into one of these holes. The upper tube sheet 225a hermetically supports one end of the plurality of battery stacks 101 via either or both of the upper sealing member 237a and the adhesive member, and isolates the water vapor supply manifold 217 from the oxidizing gas emission manifold 223.

[0095] The upper heat insulation body 227a is arranged at the lower end of the upper housing 229a in a manner that makes the top plate of the upper housing 229a and the upper tube plate 225a substantially parallel, and is fixed to the side plate of the upper housing 229a. Furthermore, the upper heat insulation body 227a has a plurality of holes corresponding to the number of battery stacks 101 included in the housing 203. The diameter of these holes is set to be larger than the outer diameter of the battery stacks 101. The upper heat insulation body 227a has an oxidizing gas upper penetration portion 235b formed between the inner surface of the hole and the outer surface of the battery stacks 101 inserted through the upper heat insulation body 227a. The oxidizing gas upper penetration portion 235b is a region (heat transfer section L1) for heat exchange between supplied water vapor (raw material gas) and the oxidizing gas.

[0096] The upper insulation 227a separates the steam electrolysis chamber 215 from the oxidizing gas discharge manifold 223, and suppresses the increase in strength or corrosion caused by the oxidizing agent contained in the oxidizing gas due to the high temperature of the atmosphere surrounding the upper tube sheet 225a. Furthermore, to suppress thermal deformation of the upper tube sheet 225a and other components exposed to the high temperature within the steam electrolysis chamber 215 due to temperature differences, a high-temperature durable metal material such as a Ni-based alloy can be used. The upper insulation 227a guides the oxidizing gas exposed to high temperature through the steam electrolysis chamber 215 to the oxidizing gas discharge manifold 223 via the upper oxidizing gas penetration portion 235b.

[0097] When the oxidizing gas passes through the upper penetration section 235b (heat transfer section L1 of the upper heat exchange section), heat exchange occurs between the supplied water vapor and the oxidizing gas in the upper heat exchange section 13. In addition, heat exchange in the upper heat exchange section 13 is minimal in the area other than the heat transfer section L1 (the area from the end (outer end) of the electrolytic cell 105 formed on the side of the raw material gas supply port (water vapor supply port) 11 of the battery stack 101 to the upper penetration section 235b of the oxidizing gas and the portion passing through the oxidizing gas discharge manifold 223), and can therefore be ignored.

[0098] The thickness of the upper insulation 227a can be appropriately changed to keep the temperature of the upper tube sheet 225a below the allowable temperature. By increasing the thickness of the upper insulation 227a, the heat exchange can be increased. The volume of the oxidizing gas exhaust manifold 223 can be kept constant regardless of the area (length) of the heat transfer section of the upper heat exchange section 13.

[0099] According to this embodiment, through the structure of the box 203 described above, water vapor and oxidizing gas are supplied to flow oppositely inside and outside the battery stack 101. As a result, the oxidizing gas undergoes heat exchange with the water vapor supplied to the water vapor electrolysis chamber 215 through the interior of the base tube 103, and the upper tube plate 225a, etc., made of metal material, is cooled to a temperature capable of preventing damage caused by stress before being supplied to the oxidizing gas discharge manifold 223. Furthermore, the supplied water vapor is heated by heat exchange with the oxidizing gas discharged from the water vapor electrolysis chamber 215 and then supplied to the water vapor electrolysis chamber 215. Consequently, water vapor preheated to the temperature required for the electrolysis reaction is supplied to the water vapor electrolysis chamber 215 without the need for a heater or the like.

[0100] The lower tube sheet 225b is fixed to the side plate of the lower housing 229b between the bottom plate of the lower housing 229b and the lower insulation 227b, such that the lower tube sheet 225b, the bottom plate of the lower housing 229b, and the lower insulation 227b are substantially parallel. Furthermore, the lower tube sheet 225b has a plurality of holes corresponding to the number of battery stacks 101 included in the housing 203, and each battery stack 101 is inserted into one of these holes. The lower tube sheet 225b hermetically supports the other ends of the plurality of battery stacks 101 via either or both of the lower sealing member 237b and the adhesive member, and isolates the hydrogen emission manifold 219 from the oxidizing gas supply manifold 221.

[0101] The lower heat insulation body 227b is arranged in a manner that makes the bottom plate of the lower housing 229b and the lower tube plate 225b substantially parallel, and is fixed to the side plate of the lower housing 229b. Furthermore, the lower heat insulation body 227b has a plurality of holes corresponding to the number of battery stacks 101 included in the housing 203. The diameter of these holes is set to be larger than the outer diameter of the battery stacks 101. The lower heat insulation body 227b has an oxidizing gas lower penetration portion 235a (heat transfer portion L3) formed between the inner surface of the hole and the outer surface of the battery stacks 101 that penetrate the lower heat insulation body 227b. The oxidizing gas lower penetration portion 235a is a region (heat transfer portion L3) where heat exchange occurs between hydrogen (generated hydrogen) and the oxidizing gas.

[0102] The lower insulation 227b separates the steam electrolysis chamber 215 from the oxidizing gas supply manifold 221, and suppresses the increase in strength or corrosion caused by the oxidant contained in the oxidizing gas due to the high temperature of the atmosphere surrounding the lower tube sheet 225b. Furthermore, to suppress thermal deformation of the lower tube sheet 225b and other components exposed to the high temperature within the steam electrolysis chamber 215 due to temperature differences, a high-temperature durable metal material such as a Ni-based alloy can be used. The lower insulation 227b guides the oxidizing gas supplied to the oxidizing gas supply manifold 221 through the lower oxidizing gas penetration 235a to the steam electrolysis chamber 215.

[0103] When the oxidizing gas passes through the lower penetration section 235a (heat transfer section L3 of the lower heat exchange section), heat exchange occurs between the generated hydrogen and the oxidizing gas in the lower heat exchange section 14. In addition, the heat exchange in the lower heat exchange section 14 is minimal in the area other than the heat transfer section L3 (the area from the end (outer end) of the electrolytic cell 105 formed on the side of the generated hydrogen emission port (hydrogen emission port) 12 of the battery stack 101 to the lower penetration section 235a of the oxidizing gas and the portion passing through the oxidizing gas supply manifold 221), and therefore can be ignored.

[0104] The thickness of the lower insulation 227b can be appropriately changed to keep the temperature of the lower tube sheet 225b below the allowable temperature. By increasing the thickness of the lower insulation 227b, the heat exchange can be increased. The volume of the oxidizing gas supply manifold 221 can be kept constant regardless of the area (length) of the heat transfer section of the lower heat exchange section 14.

[0105] According to this embodiment, through the structure of the box 203 described above, generated hydrogen and oxidizing gas flow opposite each other inside and outside the battery stack 101. As a result, the generated hydrogen, passing through the interior of the base tube 103 and through the steam electrolysis chamber 215, exchanges heat with the oxidizing gas supplied to the steam electrolysis chamber 215. The lower tube sheet 225b, etc., made of metallic material, is cooled to a temperature capable of preventing damage caused by stress and supplied to the generated hydrogen discharge manifold 219. Furthermore, the oxidizing gas is heated through heat exchange with the generated hydrogen and supplied to the steam electrolysis chamber 215. Consequently, oxidizing gas heated to the temperature required for the electrolysis reaction is supplied to the steam electrolysis chamber 215 without the need for heaters or the like.

[0106] (SOEC module)

[0107] like Figure 4As shown, module (electrolyte module) 201 includes, for example, multiple boxes (electrolyte boxes) 203 and a module container 205 for housing these multiple boxes 203. Module 201 includes a steam supply main pipe 207, multiple steam supply branch pipes 207a, a hydrogen generation emission main pipe 209, and multiple hydrogen generation emission branch pipes 209a. Furthermore, module 201 includes an oxidizing gas supply main pipe (not shown) and multiple oxidizing gas supply branch pipes (not shown).

[0108] A steam supply main pipe 207 is disposed inside the module container 205, connected to a steam supply section that supplies steam with a specified gas composition and flow rate corresponding to the hydrogen production amount of module 201, and connected to multiple steam supply branch pipes 207a. The steam supply main pipe 207 branches off the specified flow rate of steam supplied from the steam supply section and guides it to the multiple steam supply branch pipes 207a. Furthermore, the steam supply branch pipes 207a are connected to the steam supply main pipe 207 and to steam supply pipes 231a of multiple boxes 203. The steam supply branch pipes 207a guide the steam supplied from the steam supply main pipe 207 to the multiple boxes 203 at approximately equal flow rates, thereby making the electrolysis voltage of the multiple boxes 203 approximately uniform.

[0109] A hydrogen generation emission branch pipe 209a is connected to hydrogen generation emission pipes 231b of multiple cartridges 203 and to a hydrogen generation emission main pipe 209. This hydrogen generation emission branch pipe 209a guides the generated hydrogen emitted from cartridges 203 to the hydrogen generation emission main pipe 209. Furthermore, the hydrogen generation emission main pipe 209 is connected to multiple hydrogen generation emission branch pipes 209a, and a portion of it is disposed outside the module container 205. This hydrogen generation emission main pipe 209 guides the generated hydrogen discharged from the hydrogen generation emission branch pipes 209a at approximately equal flow rates to the outside of the module container 205.

[0110] The module container 205 is used with an internal pressure of several MPa above atmospheric pressure and a surface temperature of about 300°C above atmospheric temperature. For example, from the point of view of cost reduction, carbon steel is preferred.

[0111] In this embodiment, the method in which multiple boxes 203 are gathered and stored in the module container 205 is described, but it is not limited to this. For example, it is also possible to configure the method in which the boxes 203 are not gathered but stored in the module container 205.

[0112] The DC power required for the electrolysis reaction is converted into a specified voltage by a power conversion device such as a power regulator and supplied to the module. The power supplied to the module is determined according to the number of series and parallel connections of each cell. In each cell 203, power is supplied to the power supply component (not shown) via a power supply board (not shown), and after being energized to the vicinity of the end of the battery stack 101 through lead films 115 made of Ni / YSZ or the like, which are disposed in multiple electrolytic cells 105, it is supplied to the electrolytic cells.

[0113] Next, the basis for setting the area (length) of the heat transfer section of the upper heat exchange section, the lower heat exchange section, and the hydrogen generation section will be explained.

[0114] (The relationship between the temperature and resistance of the battery stack)

[0115] Figure 5 The graph shows the relationship between the operating temperature of the battery stack and its IV characteristics. In this graph, the horizontal axis represents the electrolytic current (A) flowing through the battery stack, and the vertical axis represents the electrolytic voltage (V). The slope of each straight line represents resistance. The greater the slope, the greater the resistance. The "thermal neutral potential" is the potential at which the heat absorbed by the electrolytic reaction balances with the heat generated by the internal resistance of the electrolytic cell during the electrolytic reaction. To maintain a high energy efficiency in hydrogen conversion, a lower electrolytic voltage (close to the thermal neutral voltage) is generally preferred.

[0116] If the electrolysis current of the battery stack increases, the electrolysis voltage also increases. With the same electrolysis current, the lower the temperature of the battery stack, the higher the electrolysis voltage. That is, if the temperature of the battery stack is low, the internal resistance of the electrolytic cell increases, the battery voltage required to produce the same flow rate of hydrogen increases, and internal heat generation increases, thus reducing the energy efficiency of hydrogen conversion. Therefore, to increase hydrogen production and improve the energy efficiency of hydrogen conversion, it is necessary to increase the operating temperature of the battery stack, maintain the electrolysis voltage near the thermal neutral voltage, and increase the electrolysis current.

[0117] (Experiment 1)

[0118] Using the battery stack described in the above embodiments (Example 1) and the comparative battery stack (Comparative Example 1), the temperature distribution of the battery stack, the supplied water vapor, and the oxidizing gas when the same current flows through was predicted.

[0119] Here, the length (L2) of the hydrogen generation section in Example 1 and Comparative Example 1 is set to be the same. Furthermore, the length (L3) of the heat transfer section of the lower heat exchange section in Example 1 is set to be 9 times the length (L1) of the heat transfer section of the upper heat exchange section, and the length (L3) of the heat transfer section of the lower heat exchange section in Comparative Example 1 is set to be the same as the length (L1) of the heat transfer section of the upper heat exchange section.

[0120] Furthermore, in any calculation, the allowable temperature of the lower tube sheet is assumed to be 600°C, and the upper limit of the current value below the allowable value is determined, thereby calculating the amount of hydrogen generated.

[0121] The results are shown in Figure 6 In this figure, the solid line represents the predicted temperature distribution of the feed gas / product gas in Example 1, and the dashed line represents the predicted temperature distribution of the feed gas / product gas in Comparative Example 1. In Example 1, the temperature for hydrogen generation is highest at the hydrogen emission port side of the hydrogen generation section. This tendency was also confirmed in Comparative Example 1.

[0122] On the other hand, when the steam supply temperature of Example 1 and Comparative Example 1 is set to be the same, the lower tube sheet temperature (lower end temperature of L3) of Example 1 is lower than the lower tube sheet temperature (L3 lower end temperature) of Comparative Example 1. 3’ (Lower end temperature). Based on this result, it was confirmed that by making the heat transfer section length of the lower heat exchange section longer than the heat transfer section length of the upper heat exchange section, even the length of the hydrogen generation section (L2, L) is reduced. 2’ The combined length of the heat transfer sections of the upper and lower heat exchange sections is the same, which also helps to suppress the temperature rise of the lower tube sheet. Furthermore, both ends of the battery stack are held by retaining members (upper and lower tube sheets) made of a metal material with high-temperature durability. However, since the durability of these retaining members decreases due to oxidation caused by exposure to high temperatures, the length of the heat transfer section of the lower heat exchange section needs to be designed so that the retaining members do not exceed the allowable temperature, and the lower tube sheet is designed to be below the allowable temperature.

[0123] (Experiment 2)

[0124] Next, the impact of the ratio of the length of the heat transfer section of the upper heat exchange section to the length of the heat transfer section of the lower heat exchange section on the performance (hydrogen production) was evaluated for cases where the length of the hydrogen generation section (L2) relative to the effective length of the electrolyzer stack (L) was changed to 0.9, 0.8, 0.7, 0.6, and 0.5.

[0125] The diameter of the substrate tubes used in the battery stack is set to be uniform along its length, and the width of all the multiple electrolytic cells in the hydrogen generation section is set to be the same. Furthermore, the number of elements is set to be proportional to the length (L2) of the hydrogen generation section of the battery stack, and the amount of hydrogen generated is calculated based on the electrolysis current of the elements and the number of elements.

[0126] The temperature distribution of the lower tube sheet was predicted based on the heat balance calculation of the element resistance value of the hydrogen generation section at each temperature along the gas flow direction, the heat generated by the current, and the heat exchange in the upper and lower heat exchange sections. Similar to Experiment 1, the current value required for the lower tube sheet temperature to reach the allowable value (600℃) was determined. The calculation conditions are as follows.

[0127] Average electrolysis voltage: 1.5V

[0128] Maximum allowable temperature of battery stack: 950℃

[0129] Maximum allowable temperature of lower tube sheet: 600℃

[0130] The composition of the supplied water vapor is: 90% H2O; 10% H2

[0131] Water vapor utilization rate: 70%

[0132] Oxidizing gas utilization rate: 30%

[0133] Effective length of the battery stack (L = sum of L1, L2 and L3): 1 (constant)

[0134] For cases where the length (L2) of the hydrogen generation section is 0.9, 0.8, 0.7, 0.6, and 0.5, the ratio of the heat transfer section length (L1) of the upper heat exchange section to the heat transfer section length (L3) of the lower heat exchange section is changed, and the calculation results with performance prediction are shown below. Figures 7 to 11 Furthermore, the hydrogen production is shown in comparison with the hydrogen production when L3 / L1=1 in each case.

[0135] In Examples 2 to 16, the length (L3) of the heat transfer section of the lower heat exchanger is longer than the length (L1) of the heat transfer section of the upper heat exchanger. In Comparative Examples 2, 4, 6, 8, and 10, the length (L3) of the heat transfer section of the lower heat exchanger is equal to the length (L1) of the heat transfer section of the upper heat exchanger. In Comparative Examples 3, 5, 7, 9, and 11, the length (L3) of the heat transfer section of the lower heat exchanger is shorter than the length (L1) of the heat transfer section of the upper heat exchanger.

[0136] according to Figure 7 Examples 2 to 4 (L1 < L3), where the length of the heat transfer section of the lower heat exchanger is longer than that of the upper heat exchanger, have higher hydrogen generation rates than Comparative Examples 2 and 3 (L1 = L3). The larger the ratio (L3 / L1) of the length of the heat transfer section of the lower heat exchanger to that of the upper heat exchanger, the greater the hydrogen generation rate. Comparative Example 3 (L1 > L3), where the length of the heat transfer section of the upper heat exchanger is longer than that of the lower heat exchanger, has lower hydrogen generation rates than Comparative Example 2 (L1 = L3).

[0137] exist Figures 8 to 11 The same tendency is also shown in China.

[0138] according to Figures 7 to 11In embodiments where the ratio of the length of the heat transfer section (L3) of the lower heat exchange section to the effective length (L) of the battery stack is 0.07 or more and 0.45 or less, an increase in the amount of hydrogen generated per battery stack was confirmed.

[0139] according to Figures 7 to 11 In embodiments where the ratio (L3 / L1) of the length of the lower heat exchange section (L3) to the length of the upper heat exchange section (L1) is greater than 1 and less than 9, an increase in the amount of hydrogen generated per battery stack was confirmed.

[0140] If comparison Figures 7 to 11 As the length (L2) of the hydrogen generation section decreases, the current density increases. However, if the length of the hydrogen generation section decreases, the number of cells contained in the hydrogen generation section decreases. Therefore, considering the change in the number of cells, by shortening L2, the amount of hydrogen generated per cell stack decreases.

[0141] Figure 12 It will be Figures 7 to 11 The hydrogen generation amount calculated in the figure is set as 1 when the length of the hydrogen generating section (L2) is 0.9 and the ratio (L3 / L1) of the length of the heat transfer section of the lower heat exchange section to the length of the heat transfer section of the upper heat exchange section is 1. The figure is compiled based on the ratio (L3 / L1) of the length of the heat transfer section of the lower heat exchange section to the length of the heat transfer section of the upper heat exchange section.

[0142] according to Figure 12 It was confirmed that by setting the length (L3) of the lower heat exchange section to be longer than the length (L1) of the upper heat exchange section, the amount of hydrogen generated per battery stack increased compared to Comparative Example 2, which served as a baseline. When the ratio (L3 / L1) of the heat transfer section length (L3) of the lower heat exchange section to the heat transfer section length (L1) of the upper heat exchange section is 2 or more, the increase in hydrogen generation is greater, more preferably 3 or more and 9 or less, and even more preferably 3 or more and 7 or less.

[0143] The manufacturing methods of the electrolytic cell stack, electrolytic cell box, electrolytic cell module, and electrolytic cell stack described in the above-described embodiments can be understood as follows.

[0144] The electrolytic cell stack 101 according to the first aspect of the present invention includes: a hydrogen generation unit 10, which includes an electrolytic cell 105 having a hydrogen electrode 109 containing Ni, an oxygen electrode 113, and a solid electrolyte membrane 111 sandwiched between the hydrogen electrode and the oxygen electrode; a raw material gas supply port 11 for supplying raw material gas to the hydrogen electrode of the hydrogen generation unit; a hydrogen discharge port 12 for discharging hydrogen generated in the hydrogen generation unit; a raw material gas supply-side heat exchange unit 13, on the side closer to the raw material gas supply port than the hydrogen generation unit, where the raw material gas exchanges heat with an oxidizing gas supplied to the oxygen electrode side; and a hydrogen discharge-side heat exchange unit 14, on the side closer to the hydrogen discharge port than the hydrogen generation unit, where the hydrogen exchanges heat with an oxidizing gas supplied to the oxygen electrode side, wherein the raw material gas supply-side heat exchange unit and the hydrogen discharge-side heat exchange unit are respectively composed of a heat transfer section and a manifold section, and the heat transfer section area of ​​the hydrogen discharge-side heat exchange unit is larger than the heat transfer section area of ​​the raw material gas supply-side heat exchange unit.

[0145] By making the heat transfer area of ​​the hydrogen emission side heat exchanger larger than that of the feed gas supply side heat exchanger, heat exchange between the hydrogen generated in the hydrogen generation section and the supplied oxidizing gas can be promoted. Therefore, compared to setting the heat transfer areas of the feed gas supply side heat exchanger and the hydrogen emission side heat exchanger to be the same, the temperature of the hydrogen emitted from the hydrogen emission port can be kept lower.

[0146] The feed gas used for steam electrolysis is steam, and no endothermic chemical reaction occurs in the heat exchange section on the feed gas supply side. Therefore, unlike the case where the feed gas contains methane or similar gases, there is no temperature drop due to an endothermic reaction. Even though the heat transfer area of ​​the heat exchange section on the feed gas supply side is smaller than that on the hydrogen emission side, the temperature of the feed gas rises, thus maintaining the inlet temperature of the electrolysis section of the electrolytic cell stack. A higher operating temperature reduces the internal resistance of the cell, thereby lowering the electrolysis voltage and increasing the hydrogen production efficiency.

[0147] In the second aspect of the present invention, the ratio of the heat transfer area of ​​the hydrogen emission side heat exchange section to the heat transfer area of ​​the raw material gas supply side heat exchange section in the first aspect is 2 or more.

[0148] In electrolytic cell stacks where the ratio of the heat transfer area of ​​the hydrogen emission side heat exchanger to the heat transfer area of ​​the feed gas supply side heat exchanger is within the aforementioned range, the hydrogen production increases compared to conventional electrolytic cell stacks where the heat transfer areas of the hydrogen emission side heat exchanger and the feed gas supply side heat exchanger are equal.

[0149] In the third aspect of the present invention, the ratio of the heat transfer area of ​​the hydrogen emission side heat exchange section to the heat transfer area of ​​the raw material gas supply side heat exchange section in the electrolytic cell stack described in the first or second aspect is 3 or more and 9 or less.

[0150] In electrolytic cell stacks within the range of the ratio of the heat transfer area of ​​the heat exchange section on the hydrogen emission side to the heat transfer area of ​​the heat exchange section on the feed gas supply side, the increase in hydrogen production is particularly significant.

[0151] In any of the first to third embodiments described above, the ratio of the length of the heat transfer section of the hydrogen emission side heat exchange unit to the length of the heat transfer section of the raw material gas supply side heat exchange unit in the fourth embodiment of the present invention is 2 or more.

[0152] The electrolytic cell 203 according to the fifth aspect of the present invention includes the electrolytic cell stack described in any one of the first to fourth aspects.

[0153] The electrolytic cell module 201 according to the sixth aspect of the present invention includes the electrolytic cell box described in the fifth aspect above.

[0154] In the method for manufacturing an electrolytic cell stack according to the seventh aspect of the present invention, the electrolytic cell stack includes: a hydrogen generation section having an electrolytic cell having a hydrogen electrode containing Ni, an oxygen electrode, and a solid electrolyte membrane sandwiched between the hydrogen electrode and the oxygen electrode; a raw material gas supply port for supplying raw material gas to the hydrogen electrode of the hydrogen generation section; a hydrogen discharge port for discharging hydrogen generated in the hydrogen generation section; a raw material gas supply-side heat exchange section, on the side closer to the raw material gas supply port than the hydrogen generation section, where the raw material gas exchanges heat with an oxidizing gas supplied to the oxygen electrode side; and a hydrogen discharge-side heat exchange section, on the side closer to the hydrogen discharge port than the hydrogen generation section, where the hydrogen exchanges heat with an oxidizing gas supplied to the oxygen electrode side. In the method for manufacturing the electrolytic cell stack, the raw material gas supply-side heat exchange section and the hydrogen discharge-side heat exchange section are each composed of a heat transfer section and a manifold section, and the heat transfer section area of ​​the hydrogen discharge-side heat exchange section is formed to be larger than the heat transfer section area of ​​the raw material gas supply-side heat exchange section.

[0155] Symbol Explanation

[0156] 10-Hydrogen generation section, 11-Water vapor supply port (feed gas supply port), 12-Generated hydrogen emission port (hydrogen emission port), 13-Upper heat exchange section (feed gas supply side heat exchange section), 14-Lower heat exchange section (hydrogen emission side heat exchange section), 101-Battery stack (electrolyte stack), 103-Base tube, 105-Electrolyte, 107-Interconnector, 109-Hydrogen electrode (fuel electrode), 111-Solid electrolyte membrane, 113-Oxygen electrode, 115-Lead membrane, 201-Module (electrolyte module), 203-Box (electrolyte box), 205-Module container, 207-Water vapor supply main pipe, 207a-Water vapor supply branch pipe, 209-Generated hydrogen emission main pipe, 209a-Generated hydrogen emission branch pipe, 215-Water vapor electrolysis chamber, 217-Water vapor supply manifold, 219-Generated hydrogen emission manifold Pipes, 221-Oxidizing gas supply manifold, 223-Oxidizing gas exhaust manifold, 225a-Upper tube sheet, 225b-Lower tube sheet, 227a-Upper insulation, 227b-Lower insulation, 229a-Upper shell, 229b-Lower shell, 231a-Water vapor supply pipe, 231b-Hydrogen generation exhaust pipe, 233a-Oxidizing gas supply pipe, 233b-Oxidizing gas exhaust pipe, 235a-Lower osmotic gas penetration, 235b-Upper osmotic gas penetration, 237a-Upper sealing component, 237b-Lower sealing component, 620-Temperature measuring section, L1 (S1)-Heat transfer section (heat transfer section area) of the upper heat exchange section, L2 (S2)-Hydrogen generation section (hydrogen generation section reaction area), L3 (S3)-Heat transfer section (heat transfer section area) of the lower heat exchange section.

Claims

1. An electrolytic cell stack, comprising: A hydrogen generation unit, the hydrogen generation unit comprising an electrolytic cell having a hydrogen electrode containing nickel, an oxygen electrode and a solid electrolyte membrane sandwiched between the hydrogen electrode and the oxygen electrode; A raw material gas supply port supplies raw material gas to the hydrogen electrode of the hydrogen generation unit; A hydrogen emission port that discharges the hydrogen generated in the hydrogen generation unit; A heat exchange section on the feed gas supply side, located closer to the feed gas supply port than the hydrogen generation section, allows the feed gas to exchange heat with an oxidizing gas emitted from the oxygen electrode side; and The hydrogen emission side heat exchange section, located further from the hydrogen emission port than the hydrogen generation section, allows the hydrogen to exchange heat with the oxidizing gas supplied to the oxygen electrode side. The heat exchange section on the raw material gas supply side and the heat exchange section on the hydrogen emission side are respectively composed of a heat transfer section and a manifold section. The heat transfer area of ​​the heat exchange section on the hydrogen emission side is larger than the heat transfer area of ​​the heat exchange section on the raw material gas supply side.

2. The electrolytic cell stack according to claim 1, wherein, The ratio of the heat transfer area of ​​the hydrogen emission side heat exchanger to the heat transfer area of ​​the raw material gas supply side heat exchanger is 2 or more.

3. The electrolytic cell stack according to claim 1, wherein, The ratio of the heat transfer area of ​​the hydrogen emission side heat exchanger to the heat transfer area of ​​the raw material gas supply side heat exchanger is 3 or more and 9 or less.

4. The electrolytic cell stack according to claim 1, wherein, The ratio of the length of the heat transfer section of the hydrogen emission side heat exchanger to the length of the heat transfer section of the raw material gas supply side heat exchanger is 2 or more.

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

6. An electrolytic cell module comprising the electrolytic cell box as described in claim 5.

7. A method for manufacturing an electrolytic cell stack, the electrolytic cell stack comprising: A hydrogen generation unit, the hydrogen generation unit comprising an electrolytic cell having a hydrogen electrode containing nickel, an oxygen electrode and a solid electrolyte membrane sandwiched between the hydrogen electrode and the oxygen electrode; A raw material gas supply port supplies raw material gas to the hydrogen electrode of the hydrogen generation unit; A hydrogen emission port that discharges the hydrogen generated in the hydrogen generation unit; A heat exchange section on the feed gas supply side, located closer to the feed gas supply port than the hydrogen generation section, allows the feed gas to exchange heat with an oxidizing gas emitted from the oxygen electrode side; and The hydrogen emission side heat exchange section, located further from the hydrogen emission port than the hydrogen generation section, allows the hydrogen to exchange heat with the oxidizing gas supplied to the oxygen electrode side. In the method for manufacturing the electrolytic cell stack, the heat exchange section on the feed gas supply side and the heat exchange section on the hydrogen emission side are respectively composed of a heat transfer section and a manifold section. The heat transfer area of ​​the hydrogen emission side heat exchanger is made larger than the heat transfer area of ​​the raw material gas supply side heat exchanger.

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