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

Abstract

The present disclosure provides an electrolytic cell stack capable of increasing the amount of product generated by electrolysis while suppressing a temperature rise of the cell stack. An electrolytic cell stack (101) according to the present disclosure comprises: a hydrogen generation unit (10) provided with an electrolytic 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 unit (13); and a hydrogen gas discharge-side heat exchange unit (14). The raw material gas supply-side heat exchange unit and the hydrogen gas discharge-side heat exchange unit are each composed of a heat transfer unit and a header unit. The heat transfer unit area of the hydrogen gas discharge-side heat exchange unit is larger than the heat transfer unit area of the raw material gas supply-side heat exchange unit.

Description

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

[0001] The present disclosure relates to electrolysis cell stacks, electrolysis cell cartridges, electrolysis cell modules, and methods for manufacturing electrolysis cell stacks.

[0002] Water electrolysis, which produces hydrogen and oxygen by electrochemically decomposing water, is a hydrogen production method that does not involve carbon dioxide emissions and has excellent environmental properties. There are various methods, such as alkaline electrolysis and solid polymer electrolysis, which electrolyze liquid water, and steam electrolysis, which electrolyzes water vapor.

[0003] Among these, a solid oxide electrolysis cell (SOEC; hereinafter referred to as "electrolysis cell") that electrolyzes high-temperature steam uses ceramics having oxygen ion conductivity, such as yttria-stabilized zirconia, as an electrolyte, and can utilize the thermal energy of high-temperature steam as part of the energy required for the electrolysis reaction, making it possible to produce hydrogen more efficiently than other electrolysis methods.

[0004] Patent Document 1 discloses a hydrogen generation system equipped with a cell stack in which a plurality of electrolytic cells, each having a hydrogen electrode, a solid electrolyte membrane, and an oxygen electrode, are arranged on a substrate tube. In the SOEC described in Patent Document 1, the hydrogen electrode is made of a composite oxide of Ni and a zirconia-based electrolyte material.

[0005] Patent No. 7282968

[0006] In SOECs, it is desirable to increase the amount of hydrogen produced per unit cell. Increasing the current flowing through an SOEC promotes the electrochemical decomposition (electrolysis) of water, thereby increasing the amount of hydrogen produced. However, for the following reasons, when increasing the electrolysis current so that the electrolysis voltage exceeds the thermoneutral potential, consideration must be given to the durability of the cell and the allowable temperature of the metal material.

[0007] When a current is passed through an SOEC, Joule heat is generated due to the internal resistance of the cell. However, water electrolysis is an endothermic reaction, and at low currents, the endothermic reaction is dominant, so there is no problem of temperature rise. However, when an attempt is made to operate at a high current above the thermoneutral potential, the cell temperature rises due to heat generated by Joule heat associated with the electrolytic reaction. When an SOEC is exposed to high temperatures, the nickel in the hydrogen electrode sinters, gradually increasing the internal resistance of the SOEC and making stable electrolysis over long periods of time difficult. Therefore, it is necessary to control the maximum cell temperature below the allowable value.

[0008] In SOEC steam electrolysis, it is necessary to make the temperature of the reaction section as uniform as possible and maintain the maximum temperature below the allowable temperature to reduce the internal resistance of the cell. SOECs are typically operated at a high current above the thermal neutral point to ensure thermal self-sustainability of the cell stack, which is higher than the operating current of a fuel cell, which is the reverse reaction. As a result, the supply gas flow rate also increases, which tends to increase the gas temperature at the outlet of the raw gas (steam) flow. To make the operating temperature of the electrolytic cell (reaction section) as uniform as possible and maintain the maximum temperature below the set temperature while suppressing the exhaust gas temperature from the cell stack below the allowable temperature of the components installed downstream of the cell stack, it is necessary to install appropriate heat exchangers on the inlet and outlet sides.

[0009] On the other hand, the heat exchanger must seal the gas supplied to or discharged from the cell stack. Therefore, it is desirable that the heat exchanger be made of a metal material that is resistant to high temperatures and be integrated with the electrolysis cells. For example, in a planar cell stack, the temperature of the gas discharged from the SOEC cell stack can be reduced by using a stack structure in which flat plate heat exchangers consisting of a heat transfer section and a gas header section are integrated above and below the stacked electrolysis cells (reaction section).

[0010] Furthermore, a cylindrical SOEC stack can have a stack structure in which heat exchangers are provided on both sides of the electrolytic cell reaction section constructed on the same substrate tube. However, both ends of the cell stack require metal retaining members (sealing members) to seal between the source gas and the oxidizing gas. If these retaining members are exposed to high temperatures for a long time, their durability will be reduced due to oxidation corrosion. Therefore, the electrolytic current flowing through the SOEC is limited to a range that does not exceed the allowable temperature of these retaining members.

[0011] The present disclosure has been made in consideration of the above circumstances, and aims to provide an electrolysis cell stack, an electrolysis cell cartridge, an electrolysis cell module, and a method for manufacturing an electrolysis cell stack that can increase the amount of hydrogen produced by electrolysis while keeping the temperature rise of exhaust gases from heat exchangers provided on the inlet and outlet sides of the SOEC cell stack and of holding members for gas sealing within an acceptable range.

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

[0013] the hydrogen gas discharge port for discharging hydrogen gas generated in the hydrogen generation unit; a feed gas supply-side heat exchanger located closer to the feed gas supply port than the hydrogen generation unit and performing heat exchange between the feed gas and an oxidizing gas discharged from the oxygen electrode; and a hydrogen gas discharge-side heat exchanger located closer to the hydrogen gas discharge port than the hydrogen generation unit and performing heat exchange between the hydrogen gas and the oxidizing gas supplied to the oxygen electrode, wherein the feed gas supply-side heat exchanger and the hydrogen gas discharge-side heat exchanger are each composed of a heat transfer section and a header section, and the area of ​​the heat transfer section of the hydrogen gas discharge-side heat exchanger is larger than the area of ​​the heat transfer section of the feed gas supply-side heat exchanger.

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

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

[0016] the hydrogen gas discharge port for discharging hydrogen gas generated in the hydrogen generation unit; a feed gas supply-side heat exchanger located closer to the feed gas supply port than the hydrogen generation unit and performing heat exchange between the feed gas and an oxidizing gas discharged from the oxygen electrode; and a hydrogen gas discharge-side heat exchanger located closer to the hydrogen gas discharge port than the hydrogen generation unit and performing heat exchange between the hydrogen gas and the oxidizing gas supplied to the oxygen electrode, wherein the feed gas supply-side heat exchanger and the hydrogen gas discharge-side heat exchanger are each composed of a heat transfer section and a header section, and the area of ​​the heat transfer section of the hydrogen gas discharge-side heat exchanger is larger than the area of ​​the heat transfer section of the feed gas supply-side heat exchanger.

[0017] According to the present disclosure, by making the heat transfer area of ​​the hydrogen gas discharge side heat exchanger larger than the heat transfer area of ​​the feed gas supply side heat exchanger, the amount of heat for cooling the hydrogen gas generated in the hydrogen generation unit can be increased, thereby making it possible to keep the temperature of the hydrogen gas discharged from the hydrogen gas outlet lower than in the past.

[0018] High-temperature steam used as a raw material for SOEC does not undergo an endothermic chemical reaction in the heat exchange section on the raw gas supply side. Therefore, even if the heat transfer section area of ​​the heat exchange section on the raw gas supply side is reduced, there is no temperature drop due to an endothermic reaction. Because the temperature of the raw gas increases through heat exchange with the oxidizing gas, the operating temperature of the electrolytic cell stack can be increased. A high operating temperature reduces the internal resistance of the cell, allowing for a reduction in the power required to generate hydrogen per unit flow rate.

[0019] Such an electrolytic cell stack can keep the maximum temperature of the cell stack within an acceptable range even if the current density flowing through the hydrogen generation section increases, and can control the temperature of the hydrogen gas discharged from the electrolytic cell stack and the stack's holding members so that they do not exceed the acceptable temperature.

[0020] FIG. 1 is a diagram illustrating an embodiment of a cylindrical electrolysis cell stack according to an embodiment of the present disclosure. FIG. 2 is an enlarged cross-sectional schematic diagram of the end of a fuel supply-side heat exchanger of a cell stack. FIG. 3 is a diagram illustrating an embodiment of a cross-section of an electrolysis cell cartridge according to an embodiment of the present disclosure. FIG. 4 is a diagram illustrating an embodiment of an electrolysis cell module according to an embodiment of the present disclosure. FIG. 5 is a diagram illustrating the relationship between the operating temperature of a cell stack and IV characteristics. FIG. 6 is a diagram illustrating predicted temperature distributions of the cell stack, supplied steam, and oxidizing gas for Example 1 and Comparative Example 1. FIG. 7 is a diagram illustrating test conditions and simulation results for Examples 2 to 4 and Comparative Examples 2 and 3. FIG. 8 is a diagram illustrating test conditions and simulation results for Examples 5 to 7 and Comparative Examples 4 and 5. FIG. 9 is a diagram illustrating test conditions and simulation results for Examples 8 to 10 and Comparative Examples 6 and 7. FIG. 10 is a diagram illustrating test conditions and simulation results for Examples 11 to 13 and Comparative Examples 8 and 9. FIG. 11 is a diagram illustrating test conditions and simulation results for Examples 14 to 16 and Comparative Examples 10 and 11. １ ) to the length of the lower heat exchange section (L ３ ) ratio (L ３ / L １ ) on the horizontal axis.

[0021] Hereinafter, an embodiment of an electrolysis cell stack, an electrolysis cell cartridge, an electrolysis cell module, and a method for manufacturing an electrolysis cell stack according to the present disclosure will be described with reference to the drawings.

[0022] In this embodiment, "electrolysis" means "steam electrolysis."

[0023] In the following, for the sake of convenience, the positional relationship of each component described using the expressions "upper" and "lower" with respect to the plane of the paper indicates the vertically upper side and the vertically lower side, respectively. Also, in this embodiment, for components that can obtain similar effects in the vertical direction and the horizontal direction, the vertical direction on the plane of the paper is not necessarily limited to the vertically upper and lower directions, but may correspond to, for example, a horizontal direction perpendicular to the vertical direction.

[0024] (Cell Stack) First, referring to Figures 1 and 2, a cylindrical electrolysis cell stack using a substrate tube will be described as an example according to this embodiment. When a substrate tube is not used, for example, the hydrogen electrode may be formed thick and serve as the substrate tube, and the use of a substrate tube is not limited. Furthermore, although the substrate tube in this embodiment is described as having a cylindrical shape, the substrate tube may have any shape as long as it is cylindrical, and the cross section is not necessarily limited to a circular shape, and may be, for example, an elliptical shape. A cell stack such as a flat tubular cylinder in which the peripheral side surface of a cylinder is crushed vertically may also be used. Furthermore, a stack structure in which a plurality of flat-plate electrochemical single cells, separators, and flat-plate heat exchangers are stacked may also be used.

[0025] 1 is a schematic diagram showing one embodiment of a cell stack (cylindrical electrolysis cell stack) according to the present embodiment. The cell stack 101 includes a hydrogen generation unit 10 at the center in the longitudinal direction. The cell stack 101 has a raw material gas supply port 11 and a hydrogen gas discharge port 12. The cell stack 101 also includes a raw material gas supply-side heat exchange unit (hereinafter referred to as the upper heat exchange unit) 13 and a hydrogen gas discharge-side heat exchange unit (hereinafter referred to as the lower heat exchange unit) 14, sandwiching the hydrogen generation unit 10 from both sides in the longitudinal direction.

[0026] The raw material gas that can be supplied to the hydrogen electrode of the cell stack 101 and used is a gas that serves as a hydrogen generation source in the hydrogen generation unit 10 and does not cause an endothermic reaction in the upper heat exchange unit 13 or the lower heat exchange unit 14, and in this embodiment, the raw material gas is water vapor. The gas supplied to the raw material gas supply port 11 often contains hydrogen in addition to the water vapor used for electrolysis. Furthermore, the gas discharged from the hydrogen gas discharge port 12 may contain water vapor, which is the remainder of the raw material gas, in addition to the hydrogen gas generated in the hydrogen generation unit 10. However, in the following description, to avoid confusion, the supply gas containing hydrogen will be referred to as "supplied water vapor" and the hydrogen gas containing this remaining water vapor will be referred to as "produced hydrogen."

[0027] The upper heat exchange unit 13 is located on the source gas supply port (steam supply port) 11 side of the hydrogen generation unit 10. The upper heat exchange unit 13 is a region where supply steam supplied from the steam supply port 11 into the cell stack 101 exchanges heat with the oxidizing gas flowing outside the cell stack 101 before entering the hydrogen generation unit 10. The upper heat exchange unit 13 may include a lead portion (a lead film 115 described later) electrically connected to the hydrogen generation unit 10. Specifically, the upper heat exchange unit 13 is a region from the end (outer end) of the electrolysis cell 105 on the source gas supply port (steam supply port) 11 side formed in the cell stack 101 to an upper tube plate 225a described later. Note that the upper heat exchange unit 13 does not necessarily include the area from the upper tube plate 225a to the top end of the cell stack 101. Furthermore, the upper heat exchange unit 13 does not necessarily have to be molded integrally with the hydrogen generation unit 10, but may be a structure or a heat exchanger having a heat exchange function between the oxidizing gas and the supply steam.

[0028] In the upper heat exchange section 13, the upper oxidizing gas through-hole 235b, which will be described later and which performs heat exchange between the raw material gas and the oxidizing gas, is a heat transfer section (L １ The oxidizing gas upper penetration 235b is a passage for the oxidizing gas formed between the outer surface of the cell stack 101 and an upper heat insulator 227a (described later), and is a region where heat exchange between the raw material gas and the oxidizing gas takes place. That is, the upper heat exchange section 13 ... １) and the heat transfer section (L １ ) and the portion that penetrates the oxidizing gas discharge header 223 .

[0029] The lower heat exchange unit 14 is located on the hydrogen gas outlet (produced hydrogen outlet) 12 side of the hydrogen generation unit 10. The lower heat exchange unit 14 is a region where heat exchange occurs between the hydrogen gas (produced hydrogen) generated in the hydrogen generation unit 10 and the oxidizing gas flowing outside the cell stack 101. The lower heat exchange unit 14 may include a lead portion (a lead film 115 described below) electrically connected to the hydrogen generation unit 10. Specifically, the lower heat exchange unit 14 is a region from the end (outer end) of the electrolysis cell 105 on the hydrogen gas outlet (produced hydrogen outlet) 12 side formed in the cell stack 101 to a lower tube plate 225b described below. Note that the lower heat exchange unit 14 does not include the area from the lower tube plate 225b to the lower end of the cell stack 101. Furthermore, the lower heat exchange unit 14 does not necessarily have to be molded integrally with the hydrogen generation unit 10, but may be a structure or a heat exchanger having a heat exchange function between the oxidizing gas and the hydrogen gas (produced hydrogen).

[0030] The lower heat exchange section 14 includes a lower oxidizing gas penetration section 235a for exchanging heat between hydrogen gas (produced hydrogen) and oxidizing gas. ３ ) The oxidizing gas lower penetration 235a is a passage for oxidizing gas formed between the outer surface of the cell stack 101 and a lower heat insulator 227b described later, and is a region where heat exchange between hydrogen gas (produced hydrogen) and oxidizing gas takes place. In other words, the lower heat exchange section 14 is a region from the end (outer end) of the electrolysis cell 105 on the hydrogen gas discharge port (produced hydrogen discharge port) 12 side formed in the cell stack 101 to the inlet of the oxidizing gas lower penetration 235a, and a heat transfer section (L ３ ) and the portion that penetrates the oxidizing gas supply header 221 .

[0031] The heat transfer section (L ３ ) heat transfer area (S ３ ) is the heat transfer section (L １ ) heat transfer area (S １ ) is larger than the heat transfer section (L １) heat transfer area (S １ ) of the heat transfer portion (L ３ ) heat transfer area (S ３ ) ratio (S ３ / S １ ) is 2 or more, preferably 3 or more and 9 or less, and more preferably 3 or more and 7 or less.

[0032] Here, the effective area (S) of the cell stack 101 is the heat transfer area (S １ ), the reaction area of ​​the hydrogen generating unit 10 (S ２ ) and the heat transfer area of ​​the lower heat exchange section 14 (S ３ ) The effective area of ​​the electrolysis cell stack (S) = the heat transfer area of ​​the upper heat exchanger (S １ ) + reaction area of ​​the hydrogen generating section (S ２ ) + heat transfer area of ​​the lower heat exchange section (S ３ )

[0033] When the diameter of the substrate tube 103 is uniform, the heat transfer area may be considered as the length. The length (L) of the effective portion of the cell stack 101 is calculated by multiplying the length (L) of the heat transfer portion of the upper heat exchange section 13 by the length (L) of the effective portion of the cell stack 101. １ ), the length of the hydrogen generating section 10 (L ２ ) and the heat transfer section length (L ３ The effective length of the electrolysis cell stack (L) = the heat transfer length of the upper heat exchange section (L １ ) + length of hydrogen generating section (L ２ ) + the length of the heat transfer section of the lower heat exchange section (L ３ )

[0034] If the diameter of the substrate tube 103 is uniform, the heat transfer section length (L ３ ) is the heat transfer section length (L １ The heat transfer section length (L １ ) the heat transfer section length (L ３ ) ratio (L ３ / L １ ) is 2 or more, preferably 3 or more and 9 or less, and more preferably 3 or more and 7 or less.

[0035] 2 is an enlarged schematic cross-sectional view of the end of the hydrogen generation unit of the cell stack. The hydrogen generation unit 10 is formed on the outer peripheral surface of a cylindrical substrate tube 103. The diameter (outer diameter and inner diameter) of the substrate tube 103 may be uniform in the longitudinal direction. The outer diameter of the substrate tube 103 is, for example, 10 mm to 50 mm. The overall length of the substrate tube 103 is, for example, 500 mm to 3000 mm.

[0036] The hydrogen generation unit 10 includes a plurality of electrolytic cells 105 arranged in the axial direction of the substrate tube 103 and interconnectors 107 formed between adjacent electrolytic cells 105 .

[0037] The electrolysis cell 105 is formed by stacking a hydrogen electrode 109, a solid electrolyte membrane 111, and an oxygen electrode 113. The solid electrolyte membrane 111 is sandwiched between the hydrogen electrode 109 and the oxygen electrode 113.

[0038] The cell stack 101 includes a lead film 115 electrically connected via an interconnector 107 to the oxygen electrode 113 of the electrolytic cell 105 formed at one end of the electrolytic cell 105 at the extreme end in the axial direction of the base tube 103 among a plurality of electrolytic cells 105 formed on the outer peripheral surface of the base tube 103, and also includes a lead film 115 electrically connected to the hydrogen electrode 109 of the electrolytic cell 105 formed at the other extreme end. The outer end of the oxygen electrode 113 of the electrolytic cell 105 located at the extreme end becomes the end of the hydrogen generation section 10.

[0039] The substrate tube 103 is made of a porous material, for example, CaO stabilized ZrO ２ (CSZ), a mixture of CSZ and nickel oxide (NiO) (CSZ+NiO), or Y ２ O ３ Stabilized ZrO ２ (YSZ), or MgAl ２ O ４ The base tube 103 supports the electrolytic cell 105, the interconnector 107, and the lead film 115, and also diffuses the supplied water vapor supplied to the inner peripheral surface of the base tube 103 through the pores of the base tube 103 to the hydrogen electrode 109 formed on the outer peripheral surface of the base tube 103. Openings at both ends of the base tube 103 can serve as a water vapor supply port and a produced hydrogen discharge port.

[0040] The hydrogen electrode 109 is made of a composite oxide of nickel and a zirconia-based electrolyte material, such as Ni / YSZ, and has a thickness of 50 μm to 250 μm. The hydrogen electrode 109 may be formed by screen printing a slurry.

[0041] The solid electrolyte membrane 111 is mainly made of YSZ, which has gas-tightness that makes it difficult for gas to pass through and high oxygen ion conductivity at high temperatures. The solid electrolyte membrane 111 is made of YSZ, which has high oxygen ion conductivity at high temperatures and is suitable for absorbing oxygen ions (O ２－ ) to the oxygen electrode 113. The thickness of the solid electrolyte membrane 111 located on the surface of the hydrogen electrode 109 is 5 μm to 100 μm, and the solid electrolyte membrane 111 may be formed by screen printing a slurry.

[0042] The oxygen electrode 113 is made of, for example, LaSrMnO ３ based oxides, or LaCoO ３ The cathode 113 is made of a silicon dioxide-based oxide, and the slurry is applied to the cathode 113 by screen printing or by using a dispenser.

[0043] The oxygen electrode 113 may have a two-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 made of a material with excellent catalytic activity. The oxygen electrode intermediate layer may be made of Sm-doped ceria, which exhibits high ionic conductivity, and the oxygen electrode layer (oxygen electrode conductive layer) on the oxygen electrode intermediate layer may be made of Sr- and Ca-doped LaMnO ３ It may be composed of a perovskite oxide such as

[0044] By applying a negative voltage to the hydrogen electrode 109 and a positive voltage to the oxygen electrode 113, the water vapor contained in the supplied water vapor receives electrons at the hydrogen electrode 109 and is electrolyzed to form hydrogen molecules and oxygen ions (O ２－ (See reaction formula (1) below.) The hydrogen produced is extracted together with the supplied steam.

[0045] On the other hand, the oxygen ions pass through the solid electrolyte membrane 111 due to the potential difference, move to the oxygen electrode 113, release electrons, and become oxygen molecules (see reaction formula (2) below). The generated oxygen is discharged to the outside together with the oxidizing gas supplied to the oxygen electrode 113.

[0046] H ２ O + 2e － →H ２ +O ２－ ... (1) 20 ２－ →O ２ +4e － ...(2)

[0047] The oxidizing gas is not directly involved in the electrolytic reaction, but supplies the heat necessary for the electrolytic reaction (endothermic) and discharges excess heat generated by the electrolytic reaction. The oxidizing gas is usually a gas containing approximately 15% to 30% oxygen, and air is a typical example, but other gases that can be used include a mixture of combustion exhaust gas and air, a mixture of oxygen and air, and inert gases such as nitrogen.

[0048] The interconnector 107 is made of SrTiO ３ M such as １－ｘ L ｘ TiO ３ (M is an alkaline earth metal element, and L is a lanthanoid element), and a slurry is screen-printed. The interconnector 107 is a dense film that prevents the supply steam supplied to the hydrogen electrode 109 from mixing with the oxidizing gas supplied to the oxygen electrode 113. The interconnector 107 also has stable durability and electrical conductivity in both oxidizing and reducing atmospheres. This interconnector 107 electrically connects the oxygen electrode 113 of one electrolytic cell 105 to the hydrogen electrode 109 of the other electrolytic cell 105, connecting the adjacent electrolytic cells 105 in series.

[0049] The lead film 115 must have electronic conductivity and a thermal expansion coefficient close to that of the other materials constituting the cell stack 101. For this reason, a composite material of nickel and a zirconia-based electrolyte material, such as Ni / YSZ, or SrTiO ３ M such as １－ｘ L ｘ TiO ３(M is an alkaline earth metal element, and L is a lanthanoid element). The lead film 115 supplies DC power to a plurality of electrolysis cells 105 connected in series by interconnectors 107. 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.

[0050] A part of the lead film 115 may be 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 a function of allowing current to flow.

[0051] Next, a method for manufacturing the cell stack will be described. The base tube 103 is formed, for example, by extrusion molding. The outer peripheral surface of the base tube 103 is divided along the axial direction (longitudinal direction) into an upper heat exchanger region, a hydrogen generation region, and a lower heat exchanger region. The hydrogen generation region is located in the axial center of the base tube 103, the upper heat exchanger region is located on the raw material gas supply port side of the hydrogen generation region, and the lower heat exchanger region is located on the produced hydrogen outlet side of the hydrogen generation region.

[0052] The upper heat exchange area and the lower heat exchange area are the heat transfer area of ​​the lower heat exchange area (S ３ ) is the heat transfer area of ​​the upper heat exchanger (S １ The heat transfer area of ​​the upper heat exchanger (S １ ) the heat transfer area of ​​the lower heat exchanger (S ３ ) ratio (S ３ / S １ ) is 2 or more, preferably 3 or more and 9 or less, and more preferably 3 or more and 7 or less.

[0053] If the diameter of the substrate tube 103 is uniform in the longitudinal direction, the "heat transfer area" may be converted to "length" to set the heat transfer section length of the upper heat exchange section, the hydrogen generation section length, and the heat transfer section length of the lower heat exchange section.

[0054] A slurry for the hydrogen electrode is applied to the outer peripheral surface of the substrate tube 103 in the hydrogen generation region. A slurry for the lead film is applied adjacent to the slurry for the hydrogen electrode applied at the very end. The slurry for the lead film may straddle the upper heat exchange region (or the lower heat exchange region) and the hydrogen generation region.

[0055] After the slurry for the hydrogen electrode is applied, the slurry for the solid electrolyte membrane and the slurry for the interconnector are applied in this order.

[0056] The substrate tube 103 on which the slurry films of the hydrogen electrode 109, solid electrolyte film 111, interconnector 107 and lead film 115 are formed is co-sintered in the atmosphere at a sintering temperature of, for example, 1350°C to 1450°C.

[0057] Next, the slurry for the oxygen electrode is applied onto the co-sintered substrate tube 103. The outermost end of the slurry for the oxygen electrode that is applied to the outermost end becomes the end of the hydrogen generating region.

[0058] The base tube 103 on which the slurry film of the oxygen electrode 113 has been formed is sintered in the atmosphere at a sintering temperature of, for example, 1100° C. to 1250° C. The sintering temperature here is set to be lower than the co-sintering temperature after forming the interconnector 107 from the base tube 103.

[0059] As a result, the heat transfer area (S ３ ) is the heat transfer area of ​​the upper heat exchange section 13 (S １ ) is obtained.

[0060] Next, the cartridge (electrolysis cell cartridge) and module (electrolysis cell module) according to this embodiment will be described with reference to Figures 3 and 4. Here, Figure 3 shows one embodiment of the cartridge according to this embodiment, and Figure 4 shows a cross-sectional view of one embodiment of the module according to this embodiment.

[0061] 3, the cartridge 203 includes a plurality of cell stacks 101, a steam electrolysis chamber 215, a steam supply header 217, a produced hydrogen discharge header 219, an oxidizing gas (air) supply header 221, and an oxidizing gas discharge header 223. The cartridge 203 also includes an upper tube plate 225a, a lower tube plate 225b, an upper insulator 227a, and a lower insulator 227b. In this embodiment, the cartridge 203 has a structure in which the water vapor supply header 217, the produced hydrogen discharge header 219, the oxidizing gas supply header 221, and the oxidizing gas discharge header 223 are arranged as shown in Figure 2, so that the supply water vapor and the oxidizing gas flow in opposite directions inside and outside the cell stack 101. However, this is not necessarily required, and for example, the flow may be parallel inside and outside the cell stack 101, or the oxidizing gas may flow in a direction perpendicular to the longitudinal direction of the cell stack 101.

[0062] In Fig. 3 , the upper heat exchange section 13 of the cell stack 101 extends from the lower surface of the upper tube sheet 225a to the upper end (outer end) of the uppermost electrolytic cell 105 among the multiple electrolytic cells 105. In Fig. 3 , the lower heat exchange section 14 of the cell stack 101 extends from the lower end (outer end) of the lowermost electrolytic cell 105 among the multiple electrolytic cells 105 to the upper surface of the lower tube sheet 225b.

[0063] The steam electrolysis chamber 215 is a region formed between the upper insulator 227a and the lower insulator 227b. This steam electrolysis chamber 215 is a region in which the electrolysis cells 105 of the cell stack 101 are disposed, and is a region in which hydrogen is produced by electrolyzing steam. The temperature near the center of the steam electrolysis chamber 215 in the longitudinal direction of the cell stack 101 may be monitored by a temperature measurement unit 620 (such as a temperature sensor or a thermocouple). During steady-state operation of the electrolysis cell module 201, a high-temperature atmosphere of approximately 700°C to 1000°C is produced.

[0064] The water vapor supply header 217 is an area surrounded by the upper casing 229a and upper tube plate 225a of the cartridge 203, and is connected to the water vapor supply branch pipe 207a by a water vapor supply pipe 231a provided at the top of the upper casing 229a. The multiple cell stacks 101 are joined to the upper tube plate 225a by an upper seal member 237a, and the water vapor supply header 217 guides water vapor supplied from the water vapor supply branch pipe 207a via the water vapor supply pipe 231a into the interiors of the base tubes 103 of the multiple cell stacks 101 at a substantially uniform flow rate, thereby substantially uniforming the hydrogen generation performance of the multiple cell stacks 101.

[0065] The produced hydrogen discharge header 219 is an area surrounded by the lower casing 229b and lower tube plate 225b of the cartridge 203, and is connected to the produced hydrogen discharge branch pipe 209a by a produced hydrogen discharge pipe 231b provided in the lower casing 229b. The multiple cell stacks 101 are joined to the lower tube plate 225b by a lower seal member 237b, and the produced hydrogen discharge header 219 collects the produced hydrogen that passes through the insides of the base tubes 103 of the multiple cell stacks 101 and is supplied to the produced hydrogen discharge header 219, and guides it to the produced hydrogen discharge branch pipe 209a via the produced hydrogen discharge pipe 231b.

[0066] An oxidizing gas supply header (not shown) branches into oxidizing gas supply branch pipes (not shown) at a predetermined flow rate corresponding to the operating temperature of the module 201, and supplies the oxidizing gas to the plurality of cartridges 203. The oxidizing gas supply header 221 is an area surrounded by the lower casing 229b, lower tube plate 225b, and lower heat insulator 227b of the cartridge 203, and is connected to an oxidizing gas supply branch pipe (not shown) by an oxidizing gas supply pipe 233a provided on the side surface of the lower casing 229b. The oxidizing gas supply header 221 guides the oxidizing gas at a predetermined flow rate, supplied from the oxidizing gas supply branch pipe (not shown) via the oxidizing gas supply pipe 233a, to the steam electrolysis chamber 215 via a lower oxidizing gas penetration 235a (described later).

[0067] The oxidizing gas discharge header 223 is an area surrounded by the upper casing 229a, upper tube plate 225a, and upper heat insulator 227a of the cartridge 203, and is connected to an oxidizing gas discharge branch pipe (not shown) by an oxidizing gas discharge pipe 233b provided on the side surface of the upper casing 229a. The oxidizing gas discharge header 223 guides the exhaust oxidizing gas supplied to the oxidizing gas discharge header 223 from the steam electrolysis chamber 215 via an oxidizing gas upper penetration 235b (described later) to the oxidizing gas discharge branch pipe (not shown) via the oxidizing gas discharge pipe 233b.

[0068] The upper tube plate 225a is fixed to the side plate of the upper casing 229a between the top plate of the upper casing 229a and the upper insulator 227a so that the upper tube plate 225a, the top plate of the upper casing 229a, and the upper insulator 227a are approximately parallel to each other. The upper tube plate 225a has a number of holes corresponding to the number of cell stacks 101 provided in the cartridge 203, and the cell stacks 101 are inserted into the holes. The upper tube plate 225a airtightly supports one end of the multiple cell stacks 101 via either or both of an upper seal member 237a and an adhesive member, and also isolates the steam supply header 217 from the oxidizing gas discharge header 223.

[0069] The upper heat insulator 227a is disposed at the lower end of the upper casing 229a so that the upper heat insulator 227a, the top plate of the upper casing 229a, and the upper tube plate 225a are substantially parallel to each other, and is fixed to the side plate of the upper casing 229a. The upper heat insulator 227a is provided with a plurality of holes corresponding to the number of cell stacks 101 provided in the cartridge 203. The diameters of the holes are set to be larger than the outer diameters of the cell stacks 101. The upper heat insulator 227a is provided with an oxidizing gas upper penetration 235b formed between the inner surface of the hole and the outer surface of the cell stack 101 inserted through the upper heat insulator 227a. The oxidizing gas upper penetration 235b defines a region (heat transfer section L) where heat exchange between the supply steam (raw material gas) and the oxidizing gas takes place. １ )

[0070] The upper heat insulator 227a separates the steam electrolysis chamber 215 from the oxidizing gas discharge header 223 and prevents the atmosphere surrounding the upper tube sheet 225a from becoming hot, thereby reducing its strength and increasing corrosion caused by the oxidizing agent contained in the oxidizing gas. Furthermore, a metal material with high temperature resistance, such as a Ni-based alloy, may be used to prevent the upper tube sheet 225a and other components from being thermally deformed due to the temperature difference caused by exposure to the high temperature in the steam electrolysis chamber 215. The upper heat insulator 227a guides the exhaust oxidizing gas, which has been exposed to high temperatures after passing through the steam electrolysis chamber 215, through the upper oxidizing gas penetration 235b and into the oxidizing gas discharge header 223.

[0071] The heat exchange between the supply steam and the oxidizing gas in the upper heat exchange section 13 is performed through the upper oxidizing gas penetration section 235b (heat transfer section L of the upper heat exchange section). １ ) is passed through the upper heat exchanger 13. １ Heat exchange in areas other than this (the area from the end (outer end) of the electrolytic cell 105 on the raw material gas supply port (steam supply port) 11 side formed in the cell stack 101 to the oxidizing gas upper penetration 235b and the part penetrating the oxidizing gas discharge header 223) is slight and can be ignored.

[0072] The thickness of the upper heat insulating body 227a may be appropriately changed so that the temperature of the upper tube sheet 225a is below the allowable temperature, and by increasing the thickness of the upper heat insulating body 227a, the amount of heat exchanged can be increased. The volume of the oxidizing gas discharge header 223 may be constant regardless of the heat transfer section area (length) of the upper heat exchange section 13.

[0073] According to this embodiment, the structure of the cartridge 203 described above allows the supply steam and the oxidizing gas to flow in opposite directions between the inside and outside of the cell stack 101. As a result, heat exchange occurs between the exhaust oxidizing gas and the steam supplied to the steam electrolysis chamber 215 through the interior of the base tube 103, and the exhaust oxidizing gas is cooled to a temperature that prevents damage due to stress to the upper tube plate 225a, etc., made of a metallic material, and is then supplied to the oxidizing gas discharge header 223. The supply steam is also heated by heat exchange with the exhaust oxidizing gas discharged from the steam electrolysis chamber 215 and is then supplied to the steam electrolysis chamber 215. As a result, steam preheated to a temperature required for the electrolysis reaction can be supplied to the steam electrolysis chamber 215 without using a heater or the like.

[0074] 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 so that the lower tube sheet 225b, the bottom plate of the lower casing 229b, and the lower insulator 227b are approximately parallel to each other. The lower tube sheet 225b has a number of holes corresponding to the number of cell stacks 101 provided in the cartridge 203, and the cell stacks 101 are inserted into the holes. The lower tube sheet 225b airtightly supports the other ends of the multiple cell stacks 101 via either or both of a lower seal member 237b and an adhesive member, and also isolates the produced hydrogen discharge header 219 from the oxidizing gas supply header 221.

[0075] The lower heat insulator 227b is disposed at the upper end of the lower casing 229b so that the lower heat insulator 227b, the bottom plate of the lower casing 229b, and the lower tube plate 225b are substantially parallel to each other, and is fixed to the side plate of the lower casing 229b. The lower heat insulator 227b has a plurality of holes formed therein corresponding to the number of cell stacks 101 provided in the cartridge 203. The diameters of the holes are set to be larger than the outer diameters of the cell stacks 101. The lower heat insulator 227b has lower oxidizing gas penetrations 235a (heat transfer portions L) formed between the inner surfaces of the holes and the outer surfaces of the cell stacks 101 inserted through the lower heat insulator 227b. ３The oxidizing gas lower through-portion 235a is a region where heat exchange between hydrogen gas (produced hydrogen) and the oxidizing gas takes place (heat transfer portion L ３ )

[0076] The lower heat insulator 227b separates the steam electrolysis chamber 215 from the oxidizing gas supply header 221 and prevents the atmosphere surrounding the lower tube sheet 225b from becoming hot, thereby reducing its strength and increasing corrosion caused by the oxidizing agent contained in the oxidizing gas. Furthermore, a metal material with high temperature resistance, such as a Ni-based alloy, may be used to prevent the lower tube sheet 225b and other components from being thermally deformed due to the temperature difference caused by exposure to the high temperature within the steam electrolysis chamber 215. The lower heat insulator 227b guides the oxidizing gas supplied to the oxidizing gas supply header 221 through the lower oxidizing gas penetration 235a to the steam electrolysis chamber 215.

[0077] The heat exchange between the produced hydrogen and the oxidizing gas in the lower heat exchange section 14 is performed through the lower oxidizing gas penetration section 235a (the heat transfer section L of the lower heat exchange section). ３ ) is passed through the lower heat exchange section 14. ３ Heat exchange in areas other than this (the area from the end (outer end) of the electrolytic cell 105 on the side of the produced hydrogen outlet (hydrogen gas outlet) 12 formed in the cell stack 101 to the lower oxidizing gas penetration part 235a and the part penetrating the oxidizing gas supply header 221) is slight and can be ignored.

[0078] The thickness of the lower heat insulator 227 b may be changed as appropriate so that the temperature of the lower tube sheet is below the allowable temperature, and by increasing the thickness of the lower heat insulator 227 b, the amount of heat exchanged can be increased. The volume of the oxidizing gas supply header 221 may be constant regardless of the heat transfer section area (length) of the lower heat exchange section 14.

[0079] According to this embodiment, the structure of the cartridge 203 described above allows the product hydrogen and the oxidizing gas to flow in opposite directions between the inside and outside of the cell stack 101. As a result, the product hydrogen that passes through the interior of the base tube 103 and the steam electrolysis chamber 215 exchanges heat with the oxidizing gas supplied to the steam electrolysis chamber 215, and is cooled to a temperature that prevents damage due to stress to the lower tube plate 225b, which is made of a metal material, and is supplied to the product hydrogen discharge header 219. The oxidizing gas is also heated by heat exchange with the product hydrogen and is supplied to the steam electrolysis chamber 215. As a result, the oxidizing gas heated to a temperature required for the electrolysis reaction can be supplied to the steam electrolysis chamber 215 without using a heater or the like.

[0080] 4, the module (electrolytic cell module) 201 includes, for example, a plurality of cartridges (electrolytic cell cartridges) 203 and a module container 205 that houses the plurality of cartridges 203. The module 201 includes a water vapor supply header 207, a plurality of water vapor supply branch pipes 207a, a produced hydrogen discharge header 209, and a plurality of produced hydrogen discharge branch pipes 209a. The module 201 also includes an oxidizing gas supply header (not shown) and a plurality of oxidizing gas supply branch pipes (not shown).

[0081] The steam supply header 207 is provided inside the module container 205 and is connected to a steam supply unit that supplies steam at a predetermined gas composition and a predetermined flow rate corresponding to the amount of hydrogen produced by the module 201, and is also connected to multiple steam supply branch pipes 207a. This steam supply header 207 branches and guides the steam at a predetermined flow rate supplied from the steam supply unit to the multiple steam supply branch pipes 207a. Furthermore, the steam supply branch pipe 207a is connected to the steam supply header 207 and is also connected to steam supply pipes 231a of the multiple cartridges 203. This steam supply branch pipe 207a guides the steam supplied from the steam supply header 207 to the multiple cartridges 203 at a substantially uniform flow rate, thereby substantially uniforming the electrolysis voltage of the multiple cartridges 203.

[0082] The produced hydrogen discharge branch pipe 209a is connected to the produced hydrogen discharge pipes 231b of the multiple cartridges 203 and is also connected to the produced hydrogen discharge mother pipe 209. This produced hydrogen discharge branch pipe 209a guides the produced hydrogen discharged from the cartridges 203 to the produced hydrogen discharge mother pipe 209. The produced hydrogen discharge mother pipe 209 is also connected to the multiple produced hydrogen discharge branch pipes 209a and is partially disposed outside the module container 205. This produced hydrogen discharge mother pipe 209 guides the produced hydrogen discharged at a substantially uniform flow rate from the produced hydrogen discharge branch pipe 209a to the outside of the module container 205.

[0083] The module container 205 is operated with an internal pressure ranging from atmospheric pressure to several MPa and a surface temperature ranging from atmospheric temperature to approximately 300° C., and is preferably made of carbon steel, for example, from the viewpoint of cost reduction.

[0084] Here, in this embodiment, a configuration in which multiple cartridges 203 are grouped together and stored in a module container 205 is described, but this is not limited to this, and for example, a configuration in which the cartridges 203 are not grouped together but are stored in a module container 205 is also possible.

[0085] The DC power required for the electrolysis reaction is converted to a predetermined voltage by a power converter such as a power conditioner and then supplied to the module. The power supplied to the module is distributed according to the number of cartridges connected in series and in parallel. In each cartridge 203, power is supplied to a power supply member (not shown) via a power supply plate (not shown), and is then passed to the vicinity of the end of the cell stack 101 via lead films 115 made of Ni / YSZ or the like provided on the multiple electrolysis cells 105, before being supplied to the electrolysis cells.

[0086] Next, the basis for setting the heat transfer area (length) of the upper heat exchange section, the lower heat exchange section, and the hydrogen generation section will be described.

[0087] (Relationship between cell stack temperature and resistance value) Figure 5 shows the relationship between the operating temperature of the cell stack and the IV characteristics. In this figure, the horizontal axis represents the electrolysis current (A) flowing through the cell stack, and the vertical axis represents the electrolysis voltage (V). The slope of each line represents the resistance. The greater the slope, the greater the resistance. The "thermonutral potential" is the potential at which the amount of heat absorbed by the electrolysis reaction balances the amount of heat generated by the internal resistance of the electrolysis cell during the electrolysis reaction. To maintain high energy efficiency in hydrogen conversion, a low electrolysis voltage (close to the thermoneutral voltage) is generally preferable.

[0088] As the electrolysis current in the cell stack increases, the electrolysis voltage also increases. For the same electrolysis current, the lower the cell stack temperature, the higher the electrolysis voltage. In other words, when the cell stack temperature is low, the internal resistance of the electrolytic cell increases, and the cell voltage required to generate the same amount of hydrogen increases, resulting in increased internal heat generation and a decrease in the energy efficiency of hydrogen conversion. Therefore, in order to increase the amount of hydrogen produced and the energy efficiency of hydrogen conversion, it is effective to increase the operating temperature of the cell stack and increase the electrolysis current while maintaining the electrolysis voltage near the thermal neutral voltage.

[0089] (Test 1) Using the cell stack (Example 1) described in the above embodiment and a comparative cell stack (Comparative Example 1), the temperature distribution of the cell stack, supplied steam, and oxidizing gas when the same current was passed was predicted.

[0090] Here, the length (L ２ ) were used in common. In addition, the length of the heat transfer section of the lower heat exchange section in Example 1 (L ３ ) is the heat transfer length of the upper heat exchanger (L １ ) and the length of the heat transfer section of the lower heat exchange section in Comparative Example 1 (L ３ ) and the heat transfer section length of the upper heat exchange section (L １ ) were considered to be the same.

[0091] In addition, in all calculations, the allowable value of the lower tube sheet temperature was assumed to be 600° C., and the upper limit of the current value below the allowable value was determined, from which the amount of hydrogen produced was calculated.

[0092] The results are shown in Figure 6. In this figure, the solid line represents the predicted temperature distribution of the source gas / produced gas in Example 1, and the dashed line represents the predicted temperature distribution of the source gas / produced gas in Comparative Example 1. In Example 1, the temperature of the produced hydrogen was highest at the end of the hydrogen generation section on the side of the outlet for produced hydrogen. This tendency was also confirmed in Comparative Example 1.

[0093] On the other hand, when the steam supply temperature in Example 1 and Comparative Example 1 was the same, the lower tube sheet temperature (L ３ Lower end temperature) is the lower tube sheet temperature (L ３’ From this result, by making the heat transfer section length of the lower heat exchange section longer than that of the upper heat exchange section, the hydrogen generation section length (L ２ , L ２’ It was confirmed that the temperature rise of the lower tube plate can be suppressed even if the total length of the heat transfer section of the upper and lower heat exchange sections is the same. The cell stack is held at both ends by retaining members (upper and lower tube plates) made of high-temperature-resistant metal materials. However, because the durability of these retaining members decreases due to oxidation when exposed to high temperatures, it is necessary to design the length of the heat transfer section of the lower heat exchange section so that the retaining members do not exceed their allowable temperature and the lower tube plate remains below its allowable temperature.

[0094] (Test 2) Next, the length of the hydrogen generating portion (L) relative to the effective length (L) of the electrolysis cell stack was ２ ) was changed to 0.9, 0.8, 0.7, 0.6, and 0.5. For each case, the length of the heat transfer section of the upper heat exchanger (L １ ) and the length of the heat transfer section of the lower heat exchange section (L ３ The effect of the ratio of 100% CO₂ and 100% CO₂ on the performance (amount of hydrogen produced) of the electrolysis cell was evaluated.

[0095] The diameter of the substrate tube used in the cell stack was uniform in the longitudinal direction, and the width of the plurality of electrolytic cells in the hydrogen generating section was all the same. ２ ) and the amount of hydrogen produced was calculated from the electrolysis current of the element and the number of elements.

[0096] The temperature distribution in the lower tube sheet was predicted based on a heat balance calculation of the element resistance value of the hydrogen generation section at each temperature in the gas flow direction, the amount of heat generated by the current, and the amount of heat exchanged in the heat transfer sections of the upper and lower heat exchange sections, and the current value at which the lower tube sheet temperature reached the allowable value (600°C) was determined, as in Test 1. The calculation conditions were as follows:

[0097] Average electrolysis voltage: 1.5V Maximum allowable temperature of cell stack: 950°C Maximum allowable temperature of lower tube sheet: 600°C Supply steam composition: 90%H ２ O; 10% H ２ Water vapor utilization rate: 70% Oxidizing gas utilization rate: 30% Cell stack effective length (L = L １ , L ２ and L ３ Sum of ): 1 (= constant)

[0098] Length of hydrogen generating section (L ２ ) for each of the cases of 0.9, 0.8, 0.7, 0.6 and 0.5, the heat transfer section length of the upper heat exchange section (L １ ) and the heat transfer section length of the lower heat exchange section (L ３ 7 to 11 show the results of calculations in which the ratio of L ３ / L １ The amount of hydrogen produced at 1000 kJ / kg was expressed as a relative ratio.

[0099] In Examples 2 to 16, the length of the heat transfer section of the lower heat exchange section (L ３ ) is the heat transfer length of the upper heat exchange section (L １ In Comparative Examples 2, 4, 6, 8, and 10, the length of the heat transfer section of the lower heat exchange section (L ３ ) and the heat transfer section length of the upper heat exchange section (L １ In Comparative Examples 3, 5, 7, 9, and 11, the heat transfer section length (L ３ ) is the heat transfer length of the upper heat exchange section (L １ ) is shorter than

[0100] According to FIG. 7, the length of the heat transfer section of the lower heat exchange section is longer than the length of the heat transfer section of the upper heat exchange section in Examples 2 to 4 (L １ <L３ ) The amount of hydrogen produced is L １ =L ３ The ratio 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 (L ３ / L １ The amount of hydrogen generated increased as the heat transfer section length of the upper heat exchange section increased. １ >L ３ ) The amount of hydrogen produced is L １ =L ３ was lower than that of Comparative Example 2.

[0101] A similar tendency was observed in FIGS. 8 to 11.

[0102] 7 to 11, the length of the heat transfer section of the lower heat exchange section (L ３ In the examples where the ratio of 0.07 to 0.45 was 0.07 or more and 0.45 or less, an increase in the amount of hydrogen generated per cell stack was confirmed.

[0103] 7 to 11, the length of the upper heat exchange section (L １ ) to the length of the lower heat exchange section (L ３ ) ratio (L ３ / L １ In the examples where the value of β is greater than 1 and equal to or less than 9, an increase in the amount of hydrogen generated per cell stack was confirmed.

[0104] 7 to 11, the length of the hydrogen generating section (L ２ However, as the length of the hydrogen generating section becomes shorter, the number of cells included in the hydrogen generating section decreases. ２ By shortening the length, the amount of hydrogen generated per cell stack is reduced.

[0105] 12 shows the hydrogen generation amount calculated from FIGS. 7 to 11 as a function of the length of the hydrogen generating section (L ２ ) to 0.9, the length of the heat transfer section of the upper heat exchanger (L １ ) the heat transfer section length of the lower heat exchange section (L ３ ) ratio (L ３ / L １) is set to 1.0, the amount of hydrogen generated in Comparative Example 2 is set to 1, and the ratio 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 (L ３ / L １ ) is organized as follows.

[0106] According to FIG. 12, the overall length of the lower heat exchange section (L ３ ) is the length of the upper heat exchange section (L １ ), it was confirmed that the amount of hydrogen generated per cell stack increased compared to the reference comparative example 2. １ ) the heat transfer section length of the lower heat exchange section (L ３ The increase in the amount of hydrogen generated is large when the ratio (L3 / L1) of 1 to 2 is greater, more preferably 3 to 9, and even more preferably 3 to 7.

[0107] The methods for manufacturing the electrolytic cell stack, electrolytic cell cartridge, electrolytic cell module, and electrolytic cell stack described in the above-described embodiments can be understood, for example, as follows.

[0108] The electrolysis cell stack (101) according to the first aspect of the present disclosure includes a hydrogen generation unit (10) including an electrolysis 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 gas outlet (12) for discharging hydrogen gas generated in the hydrogen generation unit, and a hydrogen gas supply port (13) for discharging the raw material gas and the hydrogen gas generated in the hydrogen generation unit, the raw material gas and the hydrogen gas supply port being closer to the hydrogen generation unit than the hydrogen generation unit. The hydrogen gas discharge side heat exchanger is provided with a raw material gas supply side heat exchanger (13) which exchanges heat with an oxidizing gas supplied to the oxygen electrode side, and a hydrogen gas discharge side heat exchanger (14) which is located closer to the hydrogen gas outlet than the hydrogen generation section and which exchanges heat with the oxidizing gas supplied to the oxygen electrode side, the raw material gas supply side heat exchanger and the hydrogen gas discharge side heat exchanger each being composed of a heat transfer section and a header section, and the heat transfer section area of ​​the hydrogen gas discharge side heat exchanger is larger than the heat transfer section area of ​​the raw material gas supply side heat exchanger.

[0109] By making the heat transfer area of ​​the hydrogen gas discharge-side heat exchanger larger than that of the raw material gas supply-side heat exchanger, heat exchange between the hydrogen gas generated in the hydrogen generation unit and the supplied oxidizing gas can be promoted, and the temperature of the hydrogen gas discharged from the hydrogen gas outlet can be kept lower than when the heat transfer area of ​​the raw material gas supply-side heat exchanger and the heat transfer area of ​​the hydrogen gas discharge-side heat exchanger are the same.

[0110] The feed gas used for steam electrolysis is water vapor, which does not undergo an endothermic chemical reaction in the feed gas supply heat exchanger. Therefore, unlike when a feed gas containing methane or other gases is supplied, there is no temperature drop due to an endothermic reaction, and even if the heat transfer area of ​​the feed gas supply heat exchanger is smaller than that of the hydrogen gas discharge heat exchanger, the feed gas temperature rises, making it possible to maintain the inlet temperature of the electrolysis section of the electrolysis cell stack. A high operating temperature reduces the cell's internal resistance, which in turn reduces the electrolysis voltage and improves hydrogen generation efficiency.

[0111] An electrolysis cell stack according to a second aspect of the present disclosure is the above-described first aspect, wherein the ratio of the heat transfer area of ​​the hydrogen gas discharge side heat exchanger to the heat transfer area of ​​the raw material gas supply side heat exchanger is 2 or greater.

[0112] In an electrolytic cell stack in which the ratio of the heat transfer area of ​​the hydrogen gas discharge side heat exchanger to the heat transfer area of ​​the raw material gas supply side heat exchanger is within the above range, the amount of hydrogen produced is greater than in a conventional electrolytic cell stack in which the heat transfer area of ​​the hydrogen gas discharge side heat exchanger is equal to the heat transfer area of ​​the raw material gas supply side heat exchanger.

[0113] An electrolysis cell stack according to a third aspect of the present disclosure is, in the first or second aspect described above, wherein the ratio of the heat transfer area of ​​the hydrogen gas discharge 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.

[0114] In an electrolytic cell stack in which the ratio of the heat transfer area of ​​the hydrogen gas discharge side heat exchanger to the heat transfer area of ​​the raw material gas supply side heat exchanger falls within the above range, the increase in the amount of hydrogen produced is particularly large.

[0115] The electrolysis cell stack according to a fourth aspect of the present disclosure is any one of the first to third aspects, wherein the ratio of the heat transfer section length of the hydrogen gas discharge side heat exchange section to the heat transfer section length of the raw material gas supply side heat exchange section is 2 or more.

[0116] An electrolytic cell cartridge (203) according to a fifth aspect of the present disclosure includes the electrolytic cell stack according to any one of the first to fourth aspects.

[0117] An electrolysis cell module (201) according to a sixth aspect of the present disclosure includes the electrolysis cell cartridge according to the fifth aspect.

[0118] a hydrogen gas outlet port for discharging hydrogen gas generated in the hydrogen generation unit; a raw gas supply-side heat exchanger located closer to the raw gas supply port than the hydrogen generation unit and performing heat exchange between the raw gas and an oxidizing gas supplied to the oxygen electrode; and a hydrogen gas outlet-side heat exchanger located closer to the hydrogen gas outlet port than the hydrogen generation unit and performing heat exchange between the hydrogen gas and the oxidizing gas supplied to the oxygen electrode, wherein the raw gas supply-side heat exchanger and the hydrogen gas outlet-side heat exchanger are each composed of a heat transfer section and a header section, and the area of ​​the heat transfer section of the hydrogen gas outlet-side heat exchanger is larger than the area of ​​the heat transfer section of the raw gas supply-side heat exchanger.

[0119] REFERENCE SIGNS LIST 10 Hydrogen generation section 11 Steam supply port (raw material gas supply port) 12 Produced hydrogen outlet port (hydrogen gas outlet port) 13 Upper heat exchange section (raw material gas supply side heat exchange section) 14 Lower heat exchange section (hydrogen gas outlet side heat exchange section) 101 Cell stack (electrolysis cell stack) 103 Base tube 105 Electrolysis cell 107 Interconnector 109 Hydrogen electrode (fuel electrode) 111 Solid electrolyte membrane 113 Oxygen electrode 115 Lead film 201 Module (electrolysis cell module) 203 Cartridge (electrolysis cell cartridge) 205 Module container 207 Steam supply header 207a Steam supply branch pipe 209 Produced hydrogen outlet header 209a Produced hydrogen outlet branch pipe 215 Steam electrolysis chamber 217 Steam supply header 219 Produced hydrogen outlet header 221 Oxidizing gas supply header 223 Oxidizing gas discharge header 225a Upper tube plate 225b Lower tube plate 227a Upper heat insulator 227b Lower heat insulator 229a Upper casing 229b Lower casing 231a Steam supply pipe 231b Produced hydrogen discharge pipe 233a Oxidizing gas supply pipe 233b Oxidizing gas discharge pipe 235a Oxidizing gas lower penetration 235b Oxidizing gas upper penetration 237a Upper seal member 237b Lower seal member 620 Temperature measurement unit L １ (S １ ) Heat transfer area of ​​upper heat exchanger (heat transfer area) L ２ (S ２ ) Hydrogen generation section (hydrogen generation section reaction area) L ３ (S ３ ) Heat transfer area of ​​the lower heat exchanger (heat transfer area)

Claims

1. An electrolytic cell stack comprising: a hydrogen generation unit including an electrolytic cell having a nickel-containing hydrogen electrode, an oxygen electrode, and a solid electrolyte membrane sandwiched between the hydrogen electrode and the oxygen electrode; a raw material gas inlet for supplying a raw material gas to the hydrogen electrode of the hydrogen generation unit; a hydrogen gas outlet for discharging hydrogen gas generated in the hydrogen generation unit; a raw material gas supply-side heat exchanger, located on the raw material gas supply-side side of the hydrogen generation unit, for heat exchange between the raw material gas and an oxidizing gas discharged from the oxygen electrode side; and a hydrogen gas discharge-side heat exchanger, located on the hydrogen gas discharge-side side of the hydrogen generation unit, for heat exchange between the hydrogen gas and the oxidizing gas supplied to the oxygen electrode side, wherein the raw material gas supply-side heat exchanger and the hydrogen gas discharge-side heat exchanger are each composed of a heat transfer section and a header section, and the heat transfer section area of ​​the hydrogen gas discharge-side heat exchanger is larger than the heat transfer section area of ​​the raw material gas supply-side heat exchanger.

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

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

6. An electrolytic cell module comprising the electrolytic cell cartridge according to claim 5.

7. A method for manufacturing an electrolytic cell stack comprising: a hydrogen generation unit including an electrolytic cell having a nickel-containing hydrogen electrode, an oxygen electrode, and a solid electrolyte membrane sandwiched between the hydrogen electrode and the oxygen electrode; a raw material gas inlet for supplying a raw material gas to the hydrogen electrode of the hydrogen generation unit; a hydrogen gas outlet for discharging hydrogen gas generated in the hydrogen generation unit; a raw material gas supply-side heat exchanger, located on the raw material gas supply-side side of the hydrogen generation unit, for heat exchange between the raw material gas and an oxidizing gas discharged from the oxygen electrode side; and a hydrogen gas discharge-side heat exchanger, located on the hydrogen gas discharge-side side of the hydrogen generation unit, for heat exchange between the hydrogen gas and the oxidizing gas supplied to the oxygen electrode side, wherein the raw material gas supply-side heat exchanger and the hydrogen gas discharge-side heat exchanger are each composed of a heat transfer section and a header section, and the area of ​​the heat transfer section of the hydrogen gas discharge-side heat exchanger is formed larger than the area of ​​the heat transfer section of the raw material gas supply-side heat exchanger.

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