Electrochemical reaction module

Abstract

This suppresses the temperature drop in the electrochemical reaction cell stack. [Solution] The electrochemical reaction module comprises an electrochemical reaction cell stack, an auxiliary device, a fuel gas supply passage through which fuel gas supplied from the auxiliary device to the electrochemical reaction cell stack passes, a fuel gas discharge passage through which fuel gas discharged from the electrochemical reaction cell stack to the auxiliary device passes, an oxidant gas supply passage through which oxidant gas supplied from the auxiliary device to the electrochemical reaction cell stack passes, and an oxidant gas discharge passage through which oxidant gas discharged from the electrochemical reaction cell stack to the auxiliary device passes. The fuel gas supply passage, fuel gas discharge passage, oxidant gas supply passage, and oxidant gas discharge passage each have a portion arranged along the electrochemical reaction cell stack, and when the lengths of the portions of the oxidant gas supply passage and the oxidant gas discharge passage arranged along the electrochemical reaction cell stack are denoted as LO1 and LO2, LO1

Description

Technical Field

[0001] The technology disclosed in this specification relates to an electrochemical reaction module.

Background Art

[0002] A fuel cell module including a fuel cell stack, a combustor and a reformer disposed inside a housing provided independently of the fuel cell stack is known (see Patent Document 1). The fuel cell stack and the housing are connected by a pipe through which the gas used for power generation flows.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above SOFC, it is required to suppress a decrease in the power generation efficiency of the electrochemical reaction cell stack.

[0005] Such a problem is a common problem also in a module including an electrolysis cell stack including a plurality of electrolysis cell units which are constituent units of a solid oxide type electrolysis cell (SOEC) that generates hydrogen by utilizing an electrolysis reaction of water. Further, such a problem is a common problem not only in SOFC and SOEC but also in modules including other types of electrochemical reaction cell stacks.

Means for Solving the Problems

[0006] The technology disclosed in this specification can be realized, for example, in the following forms. (1) The electrochemical reaction module disclosed by this specification includes an electrochemical reaction cell stack including an electrochemical reaction cell, an auxiliary device that supplies a fuel gas and an oxidant gas to the electrochemical reaction cell stack, a fuel gas supply path through which the fuel gas supplied from the auxiliary device to the electrochemical reaction cell stack passes, a fuel gas discharge path through which the fuel gas discharged from the electrochemical reaction cell stack to the auxiliary device passes, an oxidant gas supply path through which the oxidant gas supplied from the auxiliary device to the electrochemical reaction cell stack passes, and an oxidant gas discharge path through which the oxidant gas discharged from the electrochemical reaction cell stack to the auxiliary device passes. The fuel gas supply path, the fuel gas discharge path, the oxidant gas supply path, and the oxidant gas discharge path each have a portion arranged along the electrochemical reaction cell stack. When the length of the portion of the oxidant gas supply path arranged along the electrochemical reaction cell stack is LO1 and the length of the portion of the oxidant gas discharge path arranged along the electrochemical reaction cell stack is LO2, LO1 < LO2 is satisfied.

[0007] According to the above configuration, a decrease in power generation efficiency due to a temperature drop of the electrochemical reaction cell stack is suppressed.

[0008] (2) In the electrochemical reaction module described in (1) above, when the length of the portion of the fuel gas supply path arranged along the electrochemical reaction cell stack is LF1 and the length of the portion of the fuel gas discharge path arranged along the electrochemical reaction cell stack is LF2, LF1 < LF2 may be satisfied.

[0009] According to the above configuration, a decrease in power generation efficiency due to a temperature drop of the electrochemical reaction cell stack is suppressed.

[0010] (3) In the gas chemical reaction module described in (1) or (2) above, the larger value of LF1 and LO1 may be smaller than the smaller value of LF2 and LO2.

[0011] With the above configuration, the decrease in power generation efficiency due to the temperature drop of the electrochemical reaction cell stack is further suppressed.

[0012] The technologies disclosed herein can be implemented in various forms, for example, in the form of an electrochemical reaction module and a method for manufacturing the same. [Brief explanation of the drawing]

[0013] [Figure 1] Perspective view showing the external configuration of the fuel cell stack of the embodiment. [Figure 2] A cross-sectional view showing the fuel cell stack of the embodiment, cut along the line II-II in Figure 1. [Figure 3] A cross-sectional view showing the fuel cell stack of the embodiment, cut along the line III-III in Figure 1. [Figure 4] A cross-sectional view showing two adjacent electrochemical reaction units in the fuel cell stack of the embodiment, cut at the same position as line II-II in Figure 1. [Figure 5] A cross-sectional view showing two adjacent electrochemical reaction units in the fuel cell stack of the embodiment, cut at the same position as line III-III in Figure 1. [Figure 6] Block diagram of the fuel cell module configuration of the embodiment. [Figure 7] Partially enlarged perspective view of the fuel cell module of the embodiment. [Figure 8] Perspective view showing the oxidizer gas supply piping of the embodiment. [Figure 9] Perspective view showing the oxidizer gas discharge piping of the embodiment. [Figure 10] Perspective view showing fuel gas supply piping of the embodiment [Figure 11] Perspective view showing the fuel gas exhaust piping of the embodiment [Modes for carrying out the invention]

[0014] (Embodiment) The embodiments will be described with reference to FIGS. 1 to 11. As shown in FIG. 6, the fuel cell module 1 (an example of an electrochemical reaction module) of the present embodiment includes a fuel cell stack 10 (an example of an electrochemical reaction cell stack) and an auxiliary device 400 provided outside the fuel cell stack 10.

[0015] The fuel cell stack 10 (an example of an electrochemical reaction cell stack) of the present embodiment is used in a solid oxide type fuel cell including an electrolyte layer 112 containing a solid oxide.

[0016] As shown in FIGS. 1 to 3, the fuel cell stack 10 includes a power generation block 100, a terminal separator 230, a first plate 232, a second plate 260, a first terminal plate 240, a second terminal plate 250, an insulating portion 220, a first end plate 210, a second end plate 270, and four gas passage members 280. The first end plate 210, the insulating portion 220, the terminal separator 230, the first terminal plate 240, the power generation block 100, the second terminal plate 250, the second plate 260, and the second end plate 270 have substantially the same rectangular outer shape and are arranged to overlap in this order in a predetermined arrangement direction (the vertical direction in FIG. 2).

[0017] As shown in FIG. 1, the fuel cell stack 10 has bolt holes BH penetrating from the first end plate 210 to the second end plate 270 near each of the four corners. Bolts B are inserted into each bolt hole BH. Nuts N are screwed to both ends of each bolt B. By these bolts B and nuts N, the members from the first end plate 210 to the second end plate 270 are integrally fastened. As shown in FIGS. 2 and 3, the first plate 232 is supported by the terminal separator 230, and the four gas passage members 280 are connected to the second end plate 270.

[0018] As shown in Figures 2 and 3, the power generation block 100 is composed of a plurality of electrochemical reaction units 100U (hereinafter sometimes abbreviated as "reaction unit 100U") arranged in a predetermined arrangement direction (up and down direction in Figure 2). In this embodiment, the power generation block 100 comprises seven reaction units 100U.

[0019] As shown in Figures 4 and 5, the electrochemical reaction unit 100U comprises a single cell 110 (an example of an electrochemical reaction cell), a single cell separator 120, an air electrode frame 130, a fuel electrode frame 140, a fuel electrode current collector 144, two interconnectors 190, and two IC separators 180. One IC separator 180, the air electrode frame 130, the single cell separator 120, the fuel electrode frame 140, and the other IC separator 180 are arranged in this order. The single cell 110 is supported by the single cell separator 120, the two interconnectors 190 are each supported by the two IC separators 180, and the fuel electrode current collector 144 is positioned between the single cell 110 and the interconnectors 190.

[0020] As shown in Figures 4 and 5, the IC separator 180 and interconnector 190 are shared by two adjacent reaction units 100U. However, as shown in Figure 2, one of the multiple reaction units 100U located at one end (the lower end in Figure 2) does not have an IC separator 180 and interconnector 190 adjacent to the fuel electrode frame 140, and the second terminal plate 250 is superimposed on the fuel electrode frame 140.

[0021] The single cell 110 comprises an electrolyte layer 112, an air electrode 114, and a fuel electrode 116. As shown in Figures 4 and 5, the air electrode 114, the electrolyte layer 112, and the fuel electrode 116 are arranged in this order, with a reaction prevention layer 118 interposed between the electrolyte layer 112 and the air electrode 114. The single cell 110 of this embodiment is a fuel electrode-supported single cell in which the other layers constituting the single cell 110 are supported by the fuel electrode 116.

[0022] The electrolyte layer 112 is a rectangular, flat member having one surface on which the air electrode 114 is located (the upper surface in Figures 4 and 5) and another surface parallel to the air electrode 116 (the lower surface in Figures 4 and 5). The electrolyte layer 112 contains a solid oxide such as YSZ (yttria-stabilized zirconia). The air electrode 114 is a layer having a rectangular shape smaller than the electrolyte layer 112. The air electrode 114 contains a perovskite-type oxide such as LSCF (lanthanum strontium cobalt iron oxide). The fuel electrode 116 is a layer having a rectangular shape approximately the same size as the electrolyte layer 112, and contains, for example, Ni (nickel), a cermet made of Ni and ceramic particles, a Ni-based alloy, etc. The reaction prevention layer 118 is a layer having a rectangular shape approximately the same size as the air electrode 114, and contains, for example, GDC (gadolinium-doped ceria). The reaction prevention layer 118 has the function of suppressing the reaction of elements diffused from the air electrode 114 with elements contained in the electrolyte layer 112, which would otherwise result in the formation of a highly resistive substance.

[0023] As shown in Figures 4 and 5, the single-cell separator 120 is a rectangular frame-shaped member having a substantially rectangular through-hole 121 near its center. The single-cell separator 120 is conductive and is made of a metal such as ferritic stainless steel. The thickness of the single-cell separator 120 is, for example, 0.05 mm or more and 0.2 mm or less. The peripheral edge of the through-hole 121 in the single-cell separator 120 is joined to the peripheral edge of the electrolyte layer 112 by a joint 124. The joint 124 is made of a brazing material such as silver brazing material.

[0024] As shown in Figures 4 and 5, the air electrode frame 130 is a rectangular frame-shaped member having a roughly rectangular through-hole 131 near the center, and is formed of an insulating ceramic such as mica. The thickness of the air electrode frame 130 is, for example, 0.5 mm to 5 mm.

[0025] As shown in Figure 5, the fuel electrode frame 140 is a rectangular frame-shaped member having a roughly rectangular through-hole 141 near its center. The fuel electrode frame 140 is conductive and is made of a metal such as ferritic stainless steel.

[0026] As shown in Figures 4 and 5, the IC separator 180 is a rectangular frame-shaped member having a through hole 181 near the center. The IC separator 180 is conductive and is made of a metal such as ferritic stainless steel. The thickness of the IC separator 180 is, for example, 0.05 mm or more and 0.2 mm or less.

[0027] As shown in Figures 4 and 5, the interconnector 190 comprises a rectangular flat plate portion 191, a plurality of plate-shaped air electrode current collector portions 192 protruding from one surface of the flat plate portion 191 toward the air electrode 114, and a coating layer 193. The flat plate portion 191 and the air electrode current collector portions 192 are conductive and are made of a metal such as ferritic stainless steel. The coating layer 193 is conductive and is made of a spinel-type oxide, for example. The coating layer 193 is arranged to cover the surface of the air electrode current collector portions 192 and the surface of the flat plate portion 191 on which the air electrode current collector portions 192 are arranged. The flat plate portion 191 is joined to the periphery of the through hole 181 in the IC separator 180, for example, by welding.

[0028] The fuel electrode current collector 144 is a member that connects the interconnector 190 and the fuel electrode 116, and is formed of a conductive material such as nickel, a nickel alloy, or stainless steel. As shown in Figures 4 and 5, the fuel electrode current collector 144 includes an interconnector-facing portion 146, an electrode-facing portion 145 parallel to the interconnector-facing portion 146, and a connecting portion 147 that connects the electrode-facing portion 145 and the interconnector-facing portion 146. The electrode-facing portion 145 is in contact with the fuel electrode 116, and the interconnector-facing portion 146 is in contact with the flat plate portion 191 of the interconnector 190.

[0029] As described above, the interconnector 190 is shared by two adjacent reaction units 100U. More specifically, as shown in Figures 4 and 5, the air electrode current collector 192 is joined to the air electrode 114 of a single cell 110 provided in one of the two adjacent reaction units 100U via a conductive bonding material 196 made of, for example, a spinel-type oxide, thereby electrically connecting to the air electrode 114. The flat plate portion 191 is electrically connected to the fuel electrode 116 of a single cell 110 provided in the other of the two adjacent reaction units 100U via a fuel electrode current collector 144. This ensures electrical conductivity between the two adjacent reaction units 100U.

[0030] However, as described above, the reaction unit 100U located at one end (the lower end of Figure 2) of the multiple reaction units 100U does not have an interconnector 190 on the fuel electrode 116 side. The fuel electrode 116 provided in this reaction unit 100U is connected to the second terminal plate 250 via a fuel electrode current collector 144.

[0031] A spacer 149, for example made of mica, is placed between the electrode facing portion 145 and the interconnect facing portion 146. As a result, the fuel electrode current collector 144 follows the deformation of the reaction unit 100U due to temperature cycles and reaction gas pressure fluctuations, and the electrical connection between the fuel electrode 116 via the fuel electrode current collector 144 and the interconnect 190 or second terminal plate 250 is maintained well.

[0032] As shown in Figures 4 and 5, the space partitioned by the single-cell separator 120 and single cell 110, the air electrode frame 130, the IC separator 180 and interconnector 190 faces the air electrode 114 and forms an air chamber 313 through which the oxidizer gas OG flows. The air electrode frame 130 partitions the air chamber 313 from the outside space around its entire circumference and seals the space between the single-cell separator 120 and the IC separator 180, preventing gas from leaking from the air chamber 313 into the outside space.

[0033] Furthermore, the space partitioned by the single-cell separator 120 and single cell 110, the fuel electrode frame 140, the IC separator 180 and interconnector 190 faces the fuel electrode 116 and forms a fuel chamber 323 through which fuel gas FG flows. The fuel electrode frame 140 partitions the fuel chamber 323 from the outside space around its entire circumference and seals the space between the single-cell separator 120 and the IC separator 180, preventing gas from leaking from the fuel chamber 323 into the outside space.

[0034] The single-cell separator 120 separates the air chamber 313 from the fuel chamber 323, suppressing cross-leakage of gas from the air electrode 114 to the fuel electrode 116, or from the fuel electrode 116 to the air electrode 114, around the single-cell 110. In addition, the IC separator 180 and interconnector 190 suppress gas leakage between adjacent reaction units 100U.

[0035] The first end plate 210 is a component formed by press-forming a single plate-shaped member. The first end plate 210 is made of a metal such as ferritic stainless steel. The thickness of the first end plate 210 is, for example, 0.5 mm or more and 3 mm or less. As shown in Figures 1-3, the first end plate 210 comprises a rectangular frame-shaped planar portion 211 having a through hole 212 near the center, and an outer projection 213 and an inner projection 214 that project from the planar portion 211 in the opposite direction to the insulating portion 220 (upwards in Figure 2). The planar portion 211 has holes that constitute the bolt holes BH described above. The outer projection 213 protrudes from the outer peripheral edge of the planar portion 211. The outer projection 213 is arranged around the entire circumference of the outer peripheral portion of the planar portion 211. The inner projection 214 protrudes from the inner peripheral edge of the planar portion 211. The inner projection 214 is arranged around the entire circumference of the inner peripheral portion of the planar portion 211.

[0036] The insulating portion 220 is a rectangular frame-shaped member with a through hole near the center, and is made of an insulating material. As shown in Figures 2 and 3, the insulating portion 220 is sandwiched between the first end plate 210 and the end separator 230, thereby ensuring insulation between the first end plate 210 and the end separator 230.

[0037] As shown in Figures 2 and 3, the end separator 230 is a rectangular frame-shaped member having a through hole 231 near its center. The end separator 230 is conductive and is made of a metal such as ferritic stainless steel.

[0038] The first plate 232 is a rectangular, flat member. The first plate 232 is conductive and is made of a metal such as ferritic stainless steel. As shown in Figures 2 and 3, the first plate 232 is joined to the peripheral portion of the through hole 231 in the end separator 230, for example, by welding. The end separator 230 and the first plate 232 separate the power generation block 100 from the external space of the fuel cell stack 10.

[0039] The first plate 232 is connected to an interconnector 190 provided on a reaction unit 100U located at the other end (upper end in Figure 2) of the multiple reaction units 100U that constitute the power generation block 100, via a connecting member with the same structure as the fuel electrode current collector 144. In this way, the reaction unit 100U and the first plate 232 are electrically connected.

[0040] As shown in Figures 2 and 3, the first terminal plate 240 is a rectangular frame-shaped member having a through hole 241 near its center. The first terminal plate 240 is conductive and made of a metal such as ferritic stainless steel. The thickness of the first terminal plate 240 is, for example, 0.2 mm or more and 3 mm or less. The first terminal plate 240 is electrically connected to the reaction unit 100U located at the other end (upper end in Figure 2) of the multiple reaction units 100U that constitute the power generation block 100, via the first plate 232 and the end separator 230. One end of the first terminal plate 240 (right end in Figure 2) protrudes laterally from the power generation block 100, and this protruding portion functions as the positive output terminal of the fuel cell stack 10.

[0041] The second terminal plate 250 is a rectangular plate-shaped member. The second terminal plate 250 is conductive and is made of a metal such as ferritic stainless steel. The thickness of the second terminal plate 250 is, for example, 0.2 mm or more and 3 mm or less. As described above, the second terminal plate 250 is connected to the fuel electrode 116 provided on the reaction unit 100U located at one end (the lower end in Figure 2) of the plurality of reaction units 100U via the fuel electrode current collector 144, thereby electrically connecting this reaction unit 100U and the second terminal plate 250. One end of the second terminal plate 250 (the right end in Figure 2) protrudes laterally from the power generation block 100, and this protruding portion functions as the negative output terminal of the fuel cell stack 10.

[0042] The second plate 260 is a rectangular, flat member made of an insulating material. As shown in Figures 2 and 3, the peripheral edge of the second plate 260 is sandwiched between the second terminal plate 250 and the second end plate 270, thereby ensuring insulation between the second terminal plate 250 and the second end plate 270.

[0043] The second end plate 270 is a component formed by press-forming a single plate-shaped member. The second end plate 270 is made of a metal such as ferritic stainless steel. The thickness of the second end plate 270 is, for example, 0.5 mm or more and 3 mm or less. As shown in Figures 2 and 3, the second end plate 270 comprises a rectangular frame-shaped planar portion 271 having a through hole 272 near the center, and an outer projection 273 and an inner projection 274 projecting from the planar portion 271 in the opposite direction to the second terminal plate 250 (downward in Figure 2). The outer projection 273 protrudes from the outer peripheral edge of the planar portion 271. The outer projection 273 is arranged around the entire circumference of the outer peripheral portion of the planar portion 271. The inner projection 274 protrudes from the inner peripheral edge of the planar portion 271. The inner projection 274 is arranged around the entire circumference of the inner peripheral portion of the planar portion 271.

[0044] As shown in Figures 1-3, the fuel cell stack 10 has four holes that penetrate from the power generation block 100 to the second end plate 270. The four holes are the oxidizer gas supply manifold 311, the oxidizer gas discharge manifold 312, the fuel gas supply manifold 321, and the fuel gas discharge manifold 322, respectively.

[0045] As shown in Figure 2, the oxidizer gas supply manifold 311 is a gas flow path that supplies oxidizer gas OG, introduced from outside the fuel cell stack 10, to the air chamber 313 of each reaction unit 100U. The oxidizer gas discharge manifold 312 is a gas flow path that discharges oxidizer off-gas OOG, discharged from the air chamber 313 of each reaction unit 100U, to the outside of the fuel cell stack 10. For example, air is used as the oxidizer gas OG.

[0046] As shown in Figure 3, the fuel gas supply manifold 321 is a gas passage that supplies fuel gas FG introduced from outside the fuel cell stack 10 to the fuel chamber 323 of each reaction unit 100U. The fuel gas discharge manifold 322 is a gas passage that discharges fuel off-gas FOG discharged from the fuel chamber 323 of each reaction unit 100U to the outside of the fuel cell stack 10. As the fuel gas FG, for example, hydrogen-rich gas obtained by reforming city gas is used.

[0047] As shown in Figure 2, the oxidizer gas supply manifold 311 and the oxidizer gas discharge manifold 312 are located on opposite sides of the air chamber 313. As shown in Figure 3, the fuel gas supply manifold 321 and the fuel gas discharge manifold 322 are located on opposite sides of the fuel chamber 323. In this embodiment, the oxidizer gas supply manifold 311 and the fuel gas discharge manifold 322 are located adjacent to each other on the same side with respect to the single cell 110. Also, the oxidizer gas discharge manifold 312 and the fuel gas discharge manifold 322 are located adjacent to each other on the opposite side of the single cell 110 from the oxidizer gas supply manifold 311 and the fuel gas discharge manifold 322.

[0048] As shown in Figures 2 and 3, the planar portion 271 of the second end plate 270 has four manifold holes 311EP, 312EP, 321EP, and 322EP, which are part of the four manifolds 311, 312, 321, and 322. The second end plate 270 further includes four retaining cylindrical portions 275 for holding each of the four gas passage members 280. Each of the four retaining cylindrical portions 275 is a cylindrical portion that extends outward from the respective edge of the four manifold holes 311EP, 312EP, 321EP, and 322EP, that is, away from the power generation block 100.

[0049] Each of the four gas passage members 280 comprises a main body portion 281 and a flange portion 282, as shown in Figures 1-3. The main body portion 281 is cylindrical with both ends open. The flange portion 282 is provided so as to protrude outward from one end of the main body portion 281 (the lower end in Figure 2). As shown in Figures 2 and 3, one end of the main body portion 281 is inserted into the interior of the retaining cylinder portion 275 and is joined to the retaining cylinder portion 275, for example, by welding. The internal space of the main body portion 281 provided in each of the four gas passage members 280 forms a gas passage 283 that communicates with the four manifolds 311, 312, 321, and 322, respectively.

[0050] The auxiliary unit 400 is a device for supplying fuel gas FG, obtained by reforming the raw fuel gas RFG, and air as oxidizer gas OG to the fuel cell stack 10. As shown in Figure 6, the auxiliary unit 400 comprises a housing 410, a combustor 420 and a reformer 430 located inside the housing 410, and an evaporator 440 located above the housing 410. In Figure 6, the flow of gas on the fuel electrode side (raw fuel gas RFG, fuel gas FG, and fuel off-gas FOG) is shown by a dashed line, the flow of gas on the air electrode side (oxidizer gas OG and oxidizer off-gas OOG) is shown by a solid line, and the flow of exhaust gas EG generated by the combustor 420 is shown by a dashed line.

[0051] As shown in Figure 6, the housing 410 is a double-walled container comprising an outer casing 411 and an inner casing 412 that is slightly smaller than the outer casing 411 and positioned inside the outer casing 411. The outer casing 411 and inner casing 412 are, for example, made of metal and are sealed box-shaped containers. The reformer 430 and the combustor 420 are housed inside the inner casing 412. The space between the outer casing 411 and the inner casing 412 serves as a heating channel 413, and heat transfer fins 414 are arranged inside the heating channel 413. The outer casing 411 is connected to an air supply pipe 451 that supplies oxidant gas OG into the heating channel 413, and an oxidant gas supply pipe 510 (an example of an oxidant gas supply path) that communicates with an oxidant gas supply manifold 311 via a gas passage member 280 and supplies the oxidant gas OG that has passed through the heating channel 413 to the fuel cell stack 10. The inner box 412 is connected to an exhaust gas relay pipe 481 for sending the exhaust gas EG generated by the combustor 420 to the evaporator 440.

[0052] The evaporator 440 is a device that evaporates the reformed water RW to generate steam, mixes this steam with the raw fuel gas RFG, and supplies it to the reformer 430. The evaporator 440 is connected to a reformed water supply pipe 471 for introducing the reformed water RW into it, a raw fuel gas supply pipe 461 for introducing the raw fuel gas RFG into it, a mixed gas supply pipe 462 that communicates with the internal space of the reformer 430 and supplies the mixed gas from the evaporator 440 to the reformer 430, and an exhaust gas discharge pipe 482 for discharging the exhaust gas EG, which has been used to heat the reformed water RW, to the outside.

[0053] The reformer 430 is a device for reforming the raw fuel gas RFG, which is supplied from the evaporator 440 and mixed with water vapor, to produce hydrogen-rich fuel gas FG. A catalyst to promote the reforming reaction may be placed inside the reformer 430. The reformer 430 is connected to a fuel gas supply pipe 530 (an example of a fuel gas supply line) which communicates with the fuel gas supply manifold 321 via a gas passage member 280 and supplies the fuel gas FG to the fuel cell stack 10.

[0054] The combustor 420 is a device for mixing and burning fuel off-gas FOG and oxidizer off-gas OOG, which are discharged without being used in the power generation reaction by the fuel cell stack 10, to generate exhaust gas EG, and for heating the reformer 430 and the fuel cell stack 10. A catalyst to promote the combustion of oxidizer off-gas OOG and fuel off-gas FOG may be placed inside the combustor 420. The combustor 420 is connected to an oxidizer gas discharge pipe 520 (an example of an oxidizer gas discharge route) which communicates with an oxidizer gas discharge manifold 312 via a gas passage member 280, and to a fuel gas discharge pipe 540 (an example of a fuel gas discharge route) which communicates with a fuel gas discharge manifold 322 via a gas passage member 280.

[0055] As shown in Figure 7, the fuel cell stack 10 is installed in a vertical orientation. A vertical orientation means that the arrangement direction of the multiple reaction units 100U, that is, the arrangement direction of the multiple single cells 110, is horizontal, and the planar portion 271 of the second end plate 270 is perpendicular to the ground. Note that in Figure 7, for the sake of readability, the outer protrusions 213 and inner protrusions 214 of the first end plate 210, the outer protrusions 273 and inner protrusions 274 of the second end plate 270, and the four gas passage members 280 are omitted. As shown in Figure 7, the housing 410 is positioned above the fuel cell stack 10. In the fuel cell stack 10, the four manifolds 311, 312, 321, and 322 all open to the outer surface of the planar portion 271, and this surface does not face the housing 410.

[0056] As shown in Figure 8, the oxidizer gas supply piping 510 comprises a main pipe section 511 and a connecting pipe section 517. The main pipe section 511 is the portion connected to the oxidizer gas supply manifold 311 via a gas passage member 280 and extends along the fuel cell stack 10 as shown in Figure 7. In this specification, "extending along the fuel cell stack 10" includes not only cases where the main pipe section 511 is in contact with the fuel cell stack 10, but also cases where the main pipe section 511 is positioned with a gap between it and the fuel cell stack 10.

[0057] As shown in Figures 7 and 8, the main pipe section 511 comprises a side pipe section 512 and an upper pipe section 513. The side pipe section 512 is an L-shaped bent square pipe arranged along the flat section 271. There is a gap between the flat section 271 and the side pipe section 512 equal to the length of the main body section 281 of the gas passage member 280. The side pipe section 512 has openings 514 and 515 at one end and the other end, respectively. The openings 514 and 515 open to the side of the side pipe section 512 facing the second end plate 270. One end of the side pipe section 512 is connected to the gas passage member 280 which is connected to the oxidizer gas supply manifold 311. More specifically, one end of the side pipe section 512 is welded to the flange section 282 such that the opening 514 aligns with the opening of the main body section 281. As a result, the internal space of the oxidizer gas supply piping 510 is connected to the oxidizer gas supply manifold 311 via the gas passage 283. The upper pipe section 513 is a straight rectangular pipe that extends from the opening edge of the opening 515 and is positioned between the fuel cell stack 10 and the housing 410. The upper pipe section 513 extends along the fuel cell stack 10 in the direction from the second end plate 270 toward the first end plate 210. The upper pipe section 513 has an opening 516 at its tip. The opening 516 is open to the side of the upper pipe section 513 that faces toward the housing 410.

[0058] The connecting pipe section 517 is a pipe that extends from the opening edge of the opening 516 toward the housing 410. The tip of the connecting pipe section 517 is connected to the outlet (not shown) of the heating channel 413 provided in the outer casing 411 of the housing 410.

[0059] As shown in Figure 9, the oxidizer gas discharge piping 520 comprises a main pipe section 521 and a connecting pipe section 527. The main pipe section 521 is the part connected to the oxidizer gas discharge manifold 312 via the gas passage member 280 and extends along the fuel cell stack 10 as shown in Figure 7. As shown in Figures 7 and 9, the main pipe section 521 comprises a side pipe section 522 and an upper pipe section 523. The configuration of the side pipe section 522, upper pipe section 523, and connecting pipe section 527 is the same as that of the side pipe section 512, upper pipe section 523, and connecting pipe section 517 provided in the oxidizer gas supply piping 510, except that they are of different lengths and the orientation of the L-shape is reversed, so a detailed explanation is omitted. The side pipe section 522 has an opening 524 at one end, and this opening 524 is aligned with the opening of the main body section 281 and connected to a gas passage member 280 that leads to the oxidizer gas discharge manifold 312. As a result, the internal space of the oxidizer gas discharge piping 520 is connected to the oxidizer gas discharge manifold 312 via the gas passage 283. The tip of the connecting pipe section 527 penetrates the outer walls of the outer casing 411 and the inner casing 412 and is connected to the combustor 420.

[0060] As shown in Figure 10, the fuel gas supply piping 530 comprises a main section 531 and a connecting section 537. The main section 531 is the part connected to the fuel gas supply manifold 321 via the gas passage member 280 and extends along the fuel cell stack 10 as shown in Figure 7. As shown in Figures 7 and 10, the main section 531 comprises a side section 532 and an upper section 533. The side section 532 is a straight rectangular pipe arranged along the flat section 271. There is a gap between the second end plate 270 and the side section 532 equal to the length of the main body 281 of the gas passage member 280. The side section 532 has openings 534 and 535 at one end and the other end, respectively. The openings 534 and 535 open to the side of the side section 532 that faces the second end plate 270. One end of the side pipe section 532 is connected to a gas passage member 280 that leads to the fuel gas supply manifold 321, such that the opening 514 aligns with the opening of the main body section 281. As a result, the internal space of the fuel gas supply piping 530 is connected to the fuel gas supply manifold 321 via the gas passage 283. The upper pipe section 533 is a straight rectangular pipe that extends from the opening edge of the opening 535 and is positioned between the fuel cell stack 10 and the housing 410. The upper pipe section 533 extends along the fuel cell stack 10 in the direction from the second end plate 270 toward the first end plate 210. The upper pipe section 533 has an opening 536 at its tip. The opening 536 is located on the side of the upper pipe section 533 that faces the housing 410.

[0061] The connecting pipe section 537 is a pipe that extends from the opening edge of the opening 536 toward the housing 410. The tip of the connecting pipe section 537 penetrates the outer walls of the outer casing 411 and the inner casing 412 and is connected to the reformer 430.

[0062] As shown in FIG. 11, the fuel gas discharge pipe 540 includes a main pipe portion 541 and a connecting pipe portion 547. The main pipe portion 541 is a portion connected to the fuel gas discharge manifold 322 via the gas passage member 280, and as shown in FIG. 7, it extends along the fuel cell stack 10. As shown in FIGS. 7 and 11, the main pipe portion 541 includes a side pipe portion 542 and an upper pipe portion 543. The configurations of the side pipe portion 542, the upper pipe portion 543, and the connecting pipe portion 547 are the same as those of the side pipe portion 512, the upper pipe portion 523, and the connecting pipe portion 517 provided in the oxidant gas supply pipe 510, except for the different lengths, so detailed description thereof is omitted. The side pipe portion 542 has an opening 544 at one end, and is connected to the gas passage member 280 continuous with the fuel gas discharge manifold 322 such that the opening 544 aligns with the opening of the main body portion 281. Thereby, the internal space of the fuel gas discharge pipe 540 communicates with the fuel gas discharge manifold 322 via the gas passage 283. The tip of the connecting pipe portion 547 penetrates the outer wall of the outer box 411 and the inner box 412 and is connected to the combustor 420.

[0063] When the length of the main pipe portion 511 of the oxidant gas supply pipe 510 is denoted as LO1 and the length of the main pipe portion 521 of the oxidant gas discharge pipe 520 is denoted as LO2, LO1 < LO2 is satisfied. As in this embodiment, when a portion of the oxidant gas supply path arranged along the electrochemical reaction cell stack has a bent shape or a shape in which two or more straight portions are connected, the length is the sum of the lengths of each straight portion constituting the portion of the oxidant gas supply path arranged along the electrochemical reaction cell stack. The same applies to the oxidant gas discharge path, the fuel gas supply path, and the fuel gas discharge path. In this embodiment, the length LO1 of the main pipe portion 511 is the sum of the lengths LO11 and LO12 of the two straight portions of the L-shaped bent side pipe portion 512 and the length LO13 of the upper pipe portion 513 (see FIG. 8). Similarly, the length LO2 of the main pipe portion 521 is the sum of the lengths LO21 and LO22 of the two straight portions of the L-shaped bent side pipe portion 522 and the length LO23 of the upper pipe portion 523 (see FIG. 9).

[0064] When the length of the main pipe portion 531 of the fuel gas supply pipe 530 is LF1 and the length of the main pipe portion 541 of the fuel gas discharge pipe 540 is LF2, LF1 < LF2 is satisfied. In the present embodiment, the length LF1 of the main pipe portion 531 is the sum of the length LF11 of the side pipe portion 532 and the length LF12 of the upper pipe portion 533 (see FIG. 10). Further, the length LF2 of the main pipe portion 541 is the sum of the lengths LF21 and LF22 of the two straight portions of the L-shaped side pipe portion 542 and the length LF23 of the upper pipe portion 543 (see FIG. 11).

[0065] Furthermore, the larger value of LF1 and LO1 is smaller than the smaller value of LF2 and LO2. In the present embodiment, LO1 is larger than LF1, and LO2 is smaller than LF2. And, LO1 is smaller than LO2.

[0066] Next, the operation of the fuel cell module 1 configured as described above will be described. As shown in FIG. 6, the oxidant gas OG supplied into the heating flow path 413 through the air supply pipe 451 flows through the heating flow path 413 while being heated by the combustion heat generated from the combustor 420, and is supplied to the oxidant gas supply manifold 311 through the oxidant gas supply pipe 510. Further, the raw fuel gas RFG (for example, city gas) is supplied to the evaporator 440 through the raw fuel gas supply pipe 461, and the reformed water RW is supplied through the reformed water supply pipe 471. Inside the evaporator 440, water vapor is generated by evaporation of the reformed water RW, and this water vapor is mixed with the raw fuel gas RFG. The raw fuel gas RFG mixed with the water vapor is supplied to the reformer 430 through the mixed gas supply pipe 462, and is steam reformed in the reformer 430, and as a result, a hydrogen-rich fuel gas FG is generated. The generated fuel gas FG is supplied to the fuel gas supply manifold 321 through the fuel gas supply pipe 530.

[0067] As shown in Figure 4, the oxidizer gas OG supplied to the oxidizer gas supply manifold 311 is supplied to the air chamber 313 of each reaction unit 100U. As shown in Figure 5, the fuel gas FG supplied to the fuel gas supply manifold 321 is supplied to the fuel chamber 323 of each reaction unit 100U.

[0068] When oxidant gas OG is supplied to the air chamber 313 of each reaction unit 100U and fuel gas FG is supplied to the fuel chamber 323, electricity is generated in the single cell 110 by an electrochemical reaction between the oxidant gas OG and fuel gas FG. This power generation reaction is an exothermic reaction. As described above, the interconnector 190 is shared by two adjacent reaction units 100U, and the interconnector 190 ensures conductivity between the two adjacent reaction units 100U. In other words, the multiple reaction units 100U included in the fuel cell stack 10 are electrically connected in series. Furthermore, the first terminal plate 240 is electrically connected to the reaction unit 100U located at one end (upper end of Figure 2), and the second terminal plate 250 is electrically connected to the reaction unit 100U located at the other end (lower end of Figure 2). As a result, the electrical energy generated in each reaction unit 100U is extracted from the second terminal plate 250, which functions as an output terminal of the fuel cell stack 10. Since SOFCs generate electricity at relatively high temperatures (for example, 700°C to 1000°C), the fuel cell stack 10 may be heated by a heater (not shown) after startup until the high temperature can be maintained by the heat generated by power generation.

[0069] The oxidant off-gas OOG, which is the oxidant gas discharged to the oxidant gas discharge manifold 312 after passing through the air chamber 313 of each reaction unit 100U, is supplied to the combustor 420 through the gas passage member 280 and the oxidant gas discharge pipe 520. Similarly, the fuel off-gas FOG, which is the fuel gas discharged to the fuel gas discharge manifold 322 after passing through the fuel chamber 323 of each reaction unit 100U, is supplied to the combustor 420 through the gas passage member 280 and the fuel gas discharge pipe 540. The oxidant off-gas OOG and fuel off-gas FOG are mixed and burned inside the combustor 420, and the heat generated at this time is used to heat the oxidant gas OG passing through the heating passage 413, the reformer 430, and the fuel cell stack 10. In addition, the high-temperature exhaust gas EG generated by combustion is supplied to the evaporator 440 through the exhaust gas relay pipe 481 and used to heat the reformed water RW to generate steam.

[0070] In this embodiment, as described above, the oxidizer gas supply manifold 311 and the fuel gas discharge manifold 322 are arranged adjacent to each other. The oxidizer gas discharge manifold 312 and the fuel gas discharge manifold 322 are arranged adjacent to each other on the opposite side of the single cell 110 from the oxidizer gas supply manifold 311 and the fuel gas discharge manifold 322. As a result, within the fuel cell stack 10, the direction of the flow of oxidizer gas OG from the oxidizer gas supply manifold 311 through the air chamber 313 to the oxidizer gas discharge manifold 312 and the direction of the flow of fuel gas FG from the fuel gas supply manifold 321 through the fuel chamber 323 to the fuel gas discharge manifold 322 are in opposite directions.

[0071] The oxidant gas OG passing through the oxidant gas supply pipe 510 is heated while passing through the heating channel 413, but it is at a lower temperature than the oxidant off-gas OOG that passes through the inside of the high-temperature fuel cell stack 10 and is discharged to the oxidant gas discharge pipe 520. Similarly, the fuel gas FG passing through the fuel gas supply pipe 530 is heated while being reformed by the reformer 430, but it is at a lower temperature than the fuel off-gas FOG that passes through the inside of the high-temperature fuel cell stack 10 and is discharged to the fuel gas discharge pipe 540. As a result, the temperature of the fuel cell stack 10 may decrease due to heat dissipation from the fuel cell stack 10 to the oxidant gas supply pipe 510 or the fuel gas supply pipe 530. In such cases, there is a concern that the power generation efficiency of the fuel cell stack 10 may decrease.

[0072] In this embodiment, the length LO1 of the main pipe section 511 of the oxidizer gas supply pipe 510, through which the relatively lower temperature oxidizer gas OG passes, is smaller than the length LO2 of the main pipe section 521 of the oxidizer gas discharge pipe 520, through which the relatively higher temperature oxidizer off-gas OOG passes. As a result, the temperature drop of the fuel cell stack 10 is suppressed compared to the case where LO1 is larger than LO2.

[0073] Similarly, the length LF1 of the main section 531 of the fuel gas supply pipe 530, through which the relatively lower-temperature fuel gas FG passes, is smaller than the length LF2 of the main section 541 of the fuel gas exhaust pipe 540, through which the relatively higher-temperature fuel off-gas FOG passes. As a result, the temperature drop of the fuel cell stack 10 is suppressed compared to the case where LF1 is larger than LF2.

[0074] Furthermore, the larger of LF1 and LO1 is smaller than the smaller of LF2 and LO2. By making the length of the main pipe sections 511 and 531 of the pipes 510 and 530 through which the relatively lower-temperature supply gas passes smaller than the length of the main pipe sections 521 and 541 of the pipes 520 and 540 through which the relatively higher-temperature exhaust gas passes, the temperature drop of the fuel cell stack 10 is further suppressed.

[0075] As described above, the fuel cell module 1 of the present embodiment includes a fuel cell stack 10 including single cells 110, an auxiliary device 400 that supplies a fuel gas FG and an oxidant gas OG to the fuel cell stack 10, a fuel gas supply pipe 530 through which the fuel gas FG supplied from the auxiliary device 400 to the fuel cell stack 10 passes, a fuel gas discharge pipe 540 through which a fuel off-gas FOG discharged from the fuel cell stack 10 to the auxiliary device 400 passes, an oxidant gas supply pipe 510 through which the oxidant gas OG supplied from the auxiliary device 400 to the fuel cell stack 10 passes, and an oxidant gas discharge pipe 520 through which an oxidant off-gas OOG discharged from the fuel cell stack 10 to the auxiliary device 400 passes. The oxidant gas supply pipe 510, the oxidant gas discharge pipe 520, the fuel gas supply pipe 530, and the fuel gas discharge pipe 540 each have main pipe portions 511, 521, 531, and 541 that are portions arranged along the fuel cell stack 10. When the length of the main pipe portion 511 of the oxidant gas supply pipe 510 is LO1 and the length of the main pipe portion 521 of the oxidant gas discharge pipe 520 is LO2, LO1 < LO2 is satisfied.

[0076] According to the above configuration, a decrease in power generation efficiency due to a temperature drop of the fuel cell stack 10 is suppressed.

[0077] In the present embodiment, when the length of the main pipe portion 531 of the fuel gas supply pipe 530 is LF1 and the length of the main pipe portion 541 of the fuel gas discharge pipe 540 is LF2, LF1 < LF2 is satisfied. According to such a configuration, a decrease in power generation efficiency due to a temperature drop of the fuel cell stack 10 is suppressed. [[ID=J]]

[0078] In the present embodiment, the larger value of LF1 and LO1 is smaller than the smaller value of LF2 and LO2. According to such a configuration, a decrease in power generation efficiency due to a temperature drop of the fuel cell stack 10 is further suppressed.

[0079] (Modification example) The technology disclosed in this specification is not limited to the above-described embodiment, and can be modified into various forms without departing from the gist thereof. For example, the following modifications are also possible. (1) In the above embodiment, the main pipe section 511 of the oxidizer gas supply pipe 510 was a square pipe, but the pipes constituting the oxidizer gas supply passage do not have to be square pipes, and may be round pipes, for example. The same applies to the oxidizer gas discharge passage, fuel gas supply passage and fuel gas discharge passage. (2) There are no particular restrictions on the shape of the oxidizer gas supply passage; for example, it may be straight or have curved sections. The same applies to the oxidizer gas discharge passage, fuel gas supply passage, and fuel gas discharge passage. (3) There are no particular restrictions on the orientation of the electrochemical cell stack when it is installed. For example, it may be installed horizontally with the stacking direction of multiple single cells 110 being vertical. (4) In an electrochemical cell stack, the side of the manifold that is open may face an auxiliary device. (5) The direction of the flow of the oxidizer gas and the direction of the flow of the fuel gas within the electrochemical cell stack may be in the same direction. (6) In the above embodiment, the fuel cell stack 10 was comprised of multiple flat-plate single cells 110, but the electrochemical reaction cell stack may be comprised of, for example, cylindrical or flat cylindrical single cells. (7) The above configuration can also be applied to cell stacks used in other types of fuel cells such as polymer electrolyte fuel cells (PEFCs), phosphoric acid fuel cells (PAFCs), and molten carbonate fuel cells (MCFCs), or to electrolytic cell stacks that have electrolytic cell units, which are constituent units of solid oxide electrolytic cells (SOECs), as single cells. [Explanation of symbols]

[0080] 1: Fuel cell module 10: Fuel cell stack 100: Power generation block 100U: Electrochemical reaction unit 110: Single cell 112: Electrolyte layer 114: Air electrode 116: Fuel electrode 118: Reaction prevention layer 120: Separator for single cell 121: Through hole 124: Joint 130: Air electrode frame 131: Through hole 140: Fuel electrode frame 141: Through hole 144: Fuel electrode current collector 145: Electrode opposing part 146: Interconnector opposing part 147: Connecting part 149: Spacer 180: Separator for IC 181: Through hole 190: Interconnector 191: Flat plate part 192: Air electrode current collector part 193: Coating layer 196: Conductive bonding material 210: First end plate 211: Flat part 212: Through hole 213: Outer protrusion 214: Inner protrusion 220: Insulating part 230: End separator 231: Through hole 232: First plate 240: First terminal plate 241: Through hole 250: Second terminal plate 260: Second plate 270: Second end plate 271: Flat part 272: Through hole 273: Outer protrusion 274: Inner protrusion 275: Retaining cylinder part 280: Gas passage member 281: Main body part 282: Flange part 283: Gas passage 311: Oxidizer gas supply manifold 311EP, 312EP, 321EP, 322EP: Manifold hole 312: Oxidizer gas discharge manifold 313: Air chamber 321: Fuel gas supply manifold 322: Fuel gas discharge manifold 323: Fuel chamber 400: Auxiliary device 410: Housing 411: Outer casing 412: Inner casing 413: Heating channel 414: Heat transfer fins 420: Combustor 430: Reformer 440: Evaporator 451: Air supply piping 461: Raw fuel gas supply piping 462: Mixed gas supply piping 471: Reformed water supply piping 481: Exhaust gas relay piping 482: Exhaust gas discharge piping 510: Oxidizer gas supply piping 511: Main section 512: Side section 513: Upper section 514, 515, 516: Opening 517: Connecting section 520: Oxidizer gas discharge piping 521: Main section 522: Side section 523: Upper section 524: Opening 527: Connecting section 530: Fuel gas supply piping 531: Main section 532: Side section 533: Upper pipe section 534, 535, 536: Opening 537: Connecting pipe section 540: Fuel gas discharge piping 541: Main pipe section 542: Side pipe section543: Upper pipe section 544: Opening 547: Connecting pipe section B: Bolt BH: Bolt hole EG: Exhaust gas FG: Fuel gas FOG: Fuel off-gas N: Nut OG: Oxidizer gas OOG: Oxidizer off-gas RFG: Raw fuel gas RW: Reformed water

Claims

1. An electrochemical reaction cell stack equipped with an electrochemical reaction cell, An auxiliary device for supplying fuel gas and oxidizer gas to the electrochemical reaction cell stack, A fuel gas supply path through which the fuel gas supplied from the auxiliary device to the electrochemical reaction cell stack passes, A fuel gas discharge passage through which the fuel gas discharged from the electrochemical reaction cell stack to the auxiliary device passes, An oxidizing gas supply path through which the oxidizing gas supplied from the auxiliary device to the electrochemical reaction cell stack passes, An oxidizing gas discharge passage through which the oxidizing gas discharged from the electrochemical reaction cell stack to the auxiliary device passes, Equipped with, The fuel gas supply passage, the fuel gas discharge passage, the oxidizer gas supply passage, and the oxidizer gas discharge passage each have a portion arranged along the electrochemical reaction cell stack. When the length of the portion of the oxidizing gas supply path that is arranged along the electrochemical reaction cell stack is denoted as LO1, and the length of the portion of the oxidizing gas discharge path that is arranged along the electrochemical reaction cell stack is denoted as LO2, LO1 < LO2 Satisfying Electrochemical reaction module.

2. The electrochemical reaction module according to claim 1, When the length of the portion of the fuel gas supply passage that is arranged along the electrochemical reaction cell stack is denoted as LF1, and the length of the portion of the fuel gas discharge passage that is arranged along the electrochemical reaction cell stack is denoted as LF2, LF1 < LF2 Satisfying Electrochemical reaction module.

3. An electrochemical reaction module according to claim 1 or claim 2, The larger of LF1 and LO1 is less than the smaller of LF2 and LO2. Electrochemical reaction module.

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