JP2016207270A - Fuel cell stack and power generation module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress gas leakage which occurs when contact pressure in a surface direction varies due to the difference in deformation of bolts caused by temperature difference of gas flowing through gas passages in a fuel cell stack.SOLUTION: A fuel cell stack fastened with a plurality of bolts comprises: a plurality of power generation units, each including an electrolyte layer, an air electrode and a fuel electrode, which are aligned in a first direction; and the plurality of bolts extending in the first direction. The plurality of bolts includes: a first bolt forming a gas passage through which gas is introduced from the outside of the fuel cell stack; and a second bolt forming a gas passage through which the gas is discharged to the outside of the fuel cell stack. A linear thermal expansion coefficient αof the first bolt and a linear thermal expansion coefficient αof the second bolt satisfy a relation of α<α.SELECTED DRAWING: Figure 11

Description

  The technology disclosed by the present specification relates to a fuel cell stack and a power generation module.

  A solid oxide fuel cell (hereinafter also referred to as “SOFC”) is generally used in the form of a fuel cell stack including a plurality of power generation units arranged in a predetermined direction (hereinafter also referred to as “array direction”). Is done. Here, the power generation unit is the minimum unit of power generation, and includes an electrolyte layer and an air electrode and a fuel electrode facing each other in the arrangement direction with the electrolyte layer interposed therebetween.

  For fastening the fuel cell stack, a plurality of bolts extending in the arrangement direction are used. In addition, a technique for forming a gas flow path (also referred to as a “manifold”) for flowing fuel gas or oxidant gas using this bolt is known (see, for example, Patent Document 1). In this technology, a space formed between the outer peripheral surface of the bolt shaft and the inner peripheral surface of the hole into which the bolt is inserted, or a space formed inside the bolt shaft is used as a gas flow path. Is done.

JP 2011-76762 A

  In the above conventional technique, there may be a difference between the temperature of the gas passing through the gas flow path formed by a certain bolt and the temperature of the gas passing through the gas flow path formed by another bolt. For example, since heat is generated in the power generation reaction in each power generation unit of the fuel cell stack, the temperature of the gas passing through the gas flow path for discharging the gas to the outside of the fuel cell stack is introduced from the outside of the fuel cell stack. Higher than the temperature of the gas passing through the gas flow path. As described above, in the conventional technique, each bolt forming each gas flow path is exposed to gases having different temperatures, and there is a case where a difference occurs in the deformation amount due to thermal expansion of each bolt. When the deformation difference due to thermal expansion of each bolt increases to some extent, the pressure (hereinafter also referred to as “contact pressure”) that holds the fuel cell stack in the arrangement direction in the surface direction of the fuel cell stack (the direction orthogonal to the arrangement direction). There is a risk of gas leaking from the inside of the fuel cell stack to the outside. Such a problem is not limited to SOFC, but is common to other types of fuel cells.

  In this specification, the technique which can solve the subject mentioned above is disclosed.

  The technology disclosed in the present specification can be realized as, for example, the following forms.

(1) A fuel cell stack according to one aspect disclosed in the present specification includes an electrolyte layer, an air electrode and a fuel electrode facing each other in a first direction with the electrolyte layer interposed therebetween, and the first A fuel cell stack comprising a plurality of power generation units arranged in a direction and a plurality of bolts extending in the first direction, wherein the plurality of bolts are the fuel cell stack A first bolt that forms a gas flow path through which gas is introduced from the outside of the fuel cell stack, and a second bolt that forms a gas flow path that discharges gas to the outside of the fuel cell stack. wherein a linear thermal expansion coefficient alpha ₁ of the bolt the second and the linear thermal expansion coefficient alpha ₂ of the bolt, and satisfies the alpha _{2 <alpha 1} relationship. In general, the gas temperature (T (A)) of the gas flow path into which gas is introduced from the outside of the fuel cell stack is equal to the gas temperature (T (B)) of the gas flow path for discharging the gas to the outside of the fuel cell stack. Lower (T (A) <T (B)). According to this fuel cell stack, the linear thermal expansion coefficient α1 of the _first bolt that forms the gas flow path through which the relatively low temperature (T (A)) gas flows has a relatively high temperature (T (B)). Since the linear thermal expansion coefficient α2 of the _second bolt that forms the gas flow path through which the gas flows is larger, the gas is discharged from the outside of the fuel cell stack to the gas flow path where the gas is introduced from the outside of the fuel cell stack. The difference in deformation amount of each bolt caused by the temperature difference of the gas flowing through each of the gas flow paths can be reduced, and the leakage of gas caused by variations in contact pressure in the surface direction can be suppressed. .

(2) In the fuel cell stack, the first coefficient of linear thermal expansion of the bolt alpha ₁ and linear thermal expansion coefficient alpha ₂ of the second bolt, a structure that satisfies α _{1 <1.7α 2} relationship Also good. According to this fuel cell stack, the linear thermal expansion coefficient α1 of the _first bolt is excessive with respect to the linear thermal expansion coefficient α2 of the _second bolt, and the difference in deformation amount between the bolts becomes rather large. It is possible to suppress gas leakage due to variations in contact pressure in the surface direction.

(3) In the fuel cell stack, each of the first bolt and the second bolt is formed of any one material of austenitic stainless steel, ferritic stainless steel, nickel-based alloy, and ceramics. It is good also as the structure currently made. According to this fuel cell stack, the linear thermal expansion coefficient α1 of the _first bolt is excessive with respect to the linear thermal expansion coefficient α2 of the _second bolt, and the difference in deformation amount between the bolts becomes rather large. It is possible to suppress gas leakage due to variations in contact pressure in the surface direction.

(4) In the fuel cell stack, the fuel cell stack is further provided at a position adjacent to at least one of the plurality of power generation units in the first direction, and is formed by the adjacent power generation unit and the first bolt. A heat exchanging section that exchanges heat with the gas discharged from the gas flow path, and the plurality of bolts have gas flow paths that carry the gas discharged from the heat exchanging section toward the power generation units. A third bolt to be formed may be included, and the linear thermal expansion coefficient α ₃ of the third bolt may satisfy the relationship of α ₂ <α ₃ <α ₁ . In general, the gas temperature (T (C)) of the gas flow path that carries the gas discharged from the heat exchange unit toward each power generation unit is the gas flow path in which the gas is introduced from the outside of the fuel cell stack described above. It is higher than the temperature (T (A)) and lower than the gas temperature (T (B)) of the gas flow path for discharging the gas to the outside of the fuel cell stack (T (A) <T (C) <T ( B)). According to this fuel cell stack, the linear thermal expansion coefficient α _{3 of} the third bolt that forms the gas flow path through which the medium temperature (T (C)) gas flows has a relatively low temperature (T (A)). Of the second bolt that forms a gas flow path that is smaller than the linear thermal expansion coefficient α1 of the _first bolt that forms the gas flow path through which the gas flows and that has a relatively high temperature (T (B)) gas flows. Since the coefficient of linear thermal expansion is larger than ₂ , the gas discharged from the heat exchange unit in addition to the gas flow path for introducing gas from the outside of the fuel cell stack and the gas flow path for discharging gas to the outside of the fuel cell stack The difference in the deformation amount of each bolt caused by the temperature difference of the gas flowing through each gas flow path can be reduced and the variation in contact pressure in the surface direction Gas leakage can be suppressed.

(5) The fuel cell stack may further include a nut fitted to the first bolt, and the linear thermal expansion coefficient α ₄ of the nut may satisfy a relationship of α ₄ <α ₁ . According to this fuel cell stack, the amount of deformation due to the thermal expansion of the nut can be suppressed from being excessive with respect to the amount of deformation due to the thermal expansion of the first bolt, and the occurrence of plastic deformation and creep can be suppressed. can do.

(6) In the fuel cell stack, each power generation unit may be a power generation unit of a solid oxide fuel cell or a molten carbonate fuel cell. According to this fuel cell stack, the amount of deformation of each bolt caused by the temperature difference of the gas flowing through each gas flow path when the temperature of the gas of the solid oxide fuel cell, the molten carbonate fuel cell, etc. is relatively high. In a fuel cell stack of a type of fuel cell in which the difference between the two is likely to be a problem, the difference in deformation amount of each bolt due to the temperature difference of the gas flowing through each gas flow path can be reduced, and the contact pressure in the surface direction can be reduced. Gas leakage caused by variation can be suppressed.

  The technology disclosed in this specification can be realized in various forms, for example, in the form of a fuel cell stack, a power generation module including the fuel cell stack, a fuel cell system including the power generation module, and the like. Is possible.

1 is an explanatory diagram schematically showing a configuration of a fuel cell stack 100 in a first embodiment. FIG. 1 is an explanatory diagram schematically showing a configuration of a fuel cell stack 100 in a first embodiment. FIG. 1 is an explanatory diagram schematically showing a configuration of a fuel cell stack 100 in a first embodiment. FIG. 1 is an explanatory diagram schematically showing a configuration of a fuel cell stack 100 in a first embodiment. FIG. 1 is an explanatory diagram schematically showing a configuration of a fuel cell stack 100 in a first embodiment. FIG. 1 is an explanatory diagram schematically showing a configuration of a fuel cell stack 100 in a first embodiment. FIG. 4 is an explanatory diagram showing a detailed configuration of a power generation unit 102. FIG. 4 is an explanatory diagram showing a detailed configuration of a power generation unit 102. FIG. 4 is an explanatory diagram showing a detailed configuration of a power generation unit 102. FIG. 4 is an explanatory diagram showing a detailed configuration of a power generation unit 102. FIG. It is explanatory drawing which shows roughly the planar structure of the upper side of the heat exchange part 103. FIG. It is explanatory drawing which shows the example of calculation of the difference D of deformation amount (DELTA) L of the volt | bolt 22. FIG. It is explanatory drawing which shows schematically the structure of the fuel cell hot module 10 in 2nd Embodiment. 3 is an explanatory diagram schematically showing a configuration of a power generation module 20. FIG. 3 is an explanatory diagram schematically showing a configuration of a power generation module 20. FIG. 3 is an explanatory diagram schematically showing a configuration of a power generation module 20. FIG. It is explanatory drawing which shows schematically the structure of the fuel cell stack 100b in 3rd Embodiment. It is explanatory drawing which shows schematically the structure of the fuel cell stack 100b in 3rd Embodiment.

A. First embodiment:
A-1. Constitution:
(Configuration of fuel cell stack 100)
1 to 6 are explanatory views schematically showing the configuration of the fuel cell stack 100 in the first embodiment. FIG. 1 shows an external configuration of the fuel cell stack 100, FIG. 2 shows a planar configuration of the upper side of the fuel cell stack 100, and FIG. FIG. 4 shows a cross-sectional configuration of the fuel cell stack 100 at the position IV-IV in FIGS. 1 to 3, and FIG. 5 shows a plan configuration in FIGS. A cross-sectional configuration of the fuel cell stack 100 at a position VV is shown, and FIG. 6 shows a cross-sectional configuration of the fuel cell stack 100 at a position VI-VI in FIGS. 1 to 3. In each figure, XYZ axes orthogonal to each other for specifying the direction are shown. In this specification, for the sake of convenience, the positive direction of the Z axis is referred to as the upward direction, and the negative direction of the Z axis is referred to as the downward direction. However, the fuel cell stack 100 is actually different from such an orientation. It may be installed. The same applies to FIG.

  The fuel cell stack 100 includes a plurality of (six in this embodiment) power generation units 102, a heat exchange unit 103, and a pair of end plates 104 and 106. The six power generation units 102 are arranged side by side in a predetermined arrangement direction (vertical direction in the present embodiment). However, among the six power generation units 102, the three power generation units 102 are arranged adjacent to each other, and the remaining three power generation units 102 are also arranged adjacent to each other, so that the three power generation units 102 and the remaining power generation units 102 are arranged. A heat exchanging unit 103 is disposed between the three power generation units 102. That is, the heat exchanging unit 103 is arranged near the center in the vertical direction in the assembly composed of the six power generation units 102 and the heat exchanging unit 103. The pair of end plates 104 and 106 are arranged so as to sandwich an assembly composed of the six power generation units 102 and the heat exchange unit 103 from above and below. The arrangement direction (vertical direction) corresponds to the first direction.

  A plurality of (eight in this embodiment) holes penetrating in the vertical direction are formed in the peripheral portions around the Z direction of each layer (power generation unit 102, heat exchange unit 103, end plates 104, 106) constituting the fuel cell stack 100. The corresponding holes formed in each layer communicate with each other in the vertical direction to form a communication hole 108 extending in the vertical direction from one end plate 104 to the other end plate 106.

  Bolts 22 extending in the vertical direction are inserted into the communication holes 108, and the fuel cell stack 100 is fastened by the bolts 22 and nuts 24 fitted on both sides of the bolts 22. 4 to 6, between the nut 24 fitted on one side (upper side) of the bolt 22 and the upper surface of the end plate 104 constituting the upper end of the fuel cell stack 100, and the bolt An insulating sheet 26 is interposed between the nut 24 fitted on the other side (lower side) of 22 and the lower surface of the end plate 106 constituting the lower end of the fuel cell stack 100. However, in a place where a gas passage member 27 described later is provided, an insulating sheet disposed between the nut 24 and the surface of the end plate 106 on the upper and lower sides of the gas passage member 27 and the gas passage member 27, respectively. 26 is interposed. The insulating sheet 26 is made of, for example, a mica sheet, a ceramic fiber sheet, a ceramic powder sheet, a glass sheet, a glass ceramic composite agent, or the like.

  The outer diameter of the shaft portion of each bolt 22 is smaller than the inner diameter of each communication hole 108. Therefore, a space is secured between the outer peripheral surface of the shaft portion of each bolt 22 and the inner peripheral surface of each communication hole 108. As shown in FIGS. 2 to 4, a bolt 22 (bolt 22 </ b> A) is located near one vertex (vertex on the Y-axis negative direction side and X-axis negative direction side) on the outer periphery around the Z direction of the fuel cell stack 100. The formed space functions as an oxidant gas introduction manifold 161 that is a gas flow path into which the oxidant gas OG is introduced from the outside of the fuel cell stack 100, and one side on the outer periphery of the fuel cell stack 100 around the Z direction. The space formed by the bolt 22 (bolt 22C) located near the midpoint of the two sides parallel to the Y-axis (the side on the X-axis positive direction side) is an oxidant discharged from the heat exchange unit 103. It functions as an oxidant gas supply manifold 163 that is a gas flow path that carries the gas OG toward each power generation unit 102. As shown in FIGS. 2, 3, and 5, one side of the outer periphery of the fuel cell stack 100 around the Z direction (the side on the negative X-axis side of the two sides parallel to the Y axis) The space formed by the bolts 22 (bolts 22B) located near the midpoint discharges the oxidant off-gas OOG, which is an unreacted oxidant gas OG discharged from each power generation unit 102, to the outside of the fuel cell stack 100. Functions as an oxidant gas discharge manifold 162. On the oxidant gas side, the bolt 22A that forms the oxidant gas introduction manifold 161 corresponds to the first bolt, and the bolt 22B that forms the oxidant gas discharge manifold 162 corresponds to the second bolt. The bolt 22C forming the gas supply manifold 163 corresponds to a third bolt. In the present embodiment, for example, air is used as the oxidant gas OG.

  2, 3, and 6, one side of the outer periphery of the fuel cell stack 100 around the Z direction (the side on the Y axis positive direction side of the two sides parallel to the X axis) In the space formed by the bolts 22 (bolts 22D) located near the midpoint, the fuel gas FG is introduced from the outside of the fuel cell stack 100 and the fuel gas FG is supplied to each power generation unit 102. The space formed by the bolt 22 (bolt 22E) located near the midpoint of the opposite side of the side (the side on the Y axis negative direction side of the two sides parallel to the X axis) is A fuel gas discharge manifold 172 that discharges unreacted fuel gas FG discharged from each power generation unit 102 and fuel off-gas FOG including gas after power generation of the fuel gas FG to the outside of the fuel cell stack 100. Functional. On the fuel gas side, the bolt 22D that forms the fuel gas introduction manifold 171 corresponds to the first bolt, and the bolt 22E that forms the fuel gas discharge manifold 172 corresponds to the second bolt. In the present embodiment, for example, hydrogen-rich gas obtained by reforming city gas is used as the fuel gas FG.

  As shown in FIGS. 4 to 6, the fuel cell stack 100 is provided with four gas passage members 27. Each gas passage member 27 has a hollow cylindrical main body portion 28 and a hollow cylindrical branch portion 29 branched from the side surface of the main body portion 28. The hole of the branch part 29 communicates with the hole of the main body part 28. A gas pipe (not shown) is connected to the branch portion 29 of each gas passage member 27. As shown in FIG. 4, the hole of the main body portion 28 of the gas passage member 27 arranged at the position of the bolt 22 </ b> A that forms the oxidant gas introduction manifold 161 communicates with the oxidant gas introduction manifold 161. As shown in FIG. 5, the hole of the main body portion 28 of the gas passage member 27 disposed at the position of the bolt 22 </ b> B that forms the oxidant gas discharge manifold 162 communicates with the oxidant gas discharge manifold 162. Further, as shown in FIG. 6, the hole of the main body portion 28 of the gas passage member 27 arranged at the position of the bolt 22D forming the fuel gas introduction manifold 171 communicates with the fuel gas introduction manifold 171 and the fuel gas The hole of the main body portion 28 of the gas passage member 27 disposed at the position of the bolt 22 </ b> E forming the discharge manifold 172 communicates with the fuel gas discharge manifold 172.

(Configuration of end plates 104 and 106)
The pair of end plates 104 and 106 are rectangular flat plate-shaped conductive members, and are formed of, for example, stainless steel. One end plate 104 is disposed on the upper side of the power generation unit 102 located on the uppermost side, and the other end plate 106 is disposed on the lower side of the power generation unit 102 located on the lowermost side. The plurality of power generation units 102 and the heat exchange unit 103 are held in a pressed state by a pair of end plates 104 and 106. The upper end plate 104 functions as a positive output terminal of the fuel cell stack 100, and the lower end plate 106 functions as a negative output terminal of the fuel cell stack 100.

(Configuration of power generation unit 102)
7 to 10 are explanatory diagrams showing the detailed configuration of the power generation unit 102. FIG. FIG. 7 shows a cross-sectional configuration of two power generation units 102 adjacent to each other at the same position as the cross section shown in FIG. 5, and FIG. 8 shows adjacent to each other at the same position as the cross section shown in FIG. 9 shows a cross-sectional configuration of the two power generation units 102. FIG. 9 shows a cross-sectional configuration of the power generation unit 102 at the position IX-IX in FIG. 7, and FIG. A cross-sectional configuration of the power generation unit 102 at the position X is shown.

  As shown in FIGS. 7 and 8, the power generation unit 102 that is the minimum unit of power generation includes a single cell 110, a separator 120, an air electrode side frame 130, an air electrode side current collector 134, and a fuel electrode side frame. 140, a fuel electrode side current collector 144, and a pair of interconnectors 150 constituting the uppermost layer and the lowermost layer of the power generation unit 102. A hole corresponding to the above-described communication hole 108 into which the bolt 22 is inserted is formed in the peripheral portion around the Z direction in the separator 120, the air electrode side frame 130, the fuel electrode side frame 140, and the interconnector 150.

  The interconnector 150 is a rectangular flat plate-shaped conductive member, and is formed of, for example, ferritic stainless steel. The interconnector 150 ensures electrical continuity between the power generation units 102 and prevents reaction gas from being mixed between the power generation units 102. In the present embodiment, when two power generation units 102 are arranged adjacent to each other, one interconnector 150 is shared by two adjacent power generation units 102. That is, the upper interconnector 150 in a power generation unit 102 is the same member as the lower interconnector 150 in another power generation unit 102 adjacent to the upper side of the power generation unit 102. Further, since the fuel cell stack 100 includes the pair of end plates 104 and 106, the power generation unit 102 located at the top in the fuel cell stack 100 does not include the upper interconnector 150 and is located at the bottom. The power generation unit 102 does not include the lower interconnector 150 (see FIGS. 4 to 6).

  The unit cell 110 includes an electrolyte layer 112, and an air electrode (cathode) 114 and a fuel electrode (anode) 116 that face each other in the vertical direction (the arrangement direction in which the power generation units 102 are arranged) with the electrolyte layer 112 interposed therebetween. The single cell 110 of the present embodiment is a fuel electrode-supported single cell that supports the electrolyte layer 112 and the air electrode 114 with the fuel electrode 116.

  The electrolyte layer 112 is a rectangular flat plate-shaped member. For example, YSZ (yttria stabilized zirconia), ScSZ (scandia stabilized zirconia), SDC (samarium doped ceria), GDC (gadolinium doped ceria), perovskite oxide, etc. The solid oxide is formed. The air electrode 114 is a rectangular flat plate-shaped member, and is formed of, for example, a perovskite oxide (for example, LSCF (lanthanum strontium cobalt iron oxide), LSM (lanthanum strontium manganese oxide), LNF (lanthanum nickel iron)). ing. The fuel electrode 116 is a rectangular flat plate-like member, and is formed of, for example, Ni (nickel), cermet made of Ni and ceramic particles, Ni-based alloy, or the like. Thus, the single cell 110 (power generation unit 102) of the present embodiment is a solid oxide fuel cell (SOFC) that uses a solid oxide as an electrolyte.

  The separator 120 is a frame-like member in which a rectangular hole 121 penetrating in the vertical direction is formed near the center, and is made of, for example, metal. The peripheral part of the hole 121 in the separator 120 is opposed to the peripheral part of the surface of the electrolyte layer 112 on the air electrode 114 side. The separator 120 is bonded to the electrolyte layer 112 (single cell 110) by a bonding portion 124 formed of a brazing material (for example, Ag brazing) disposed in the facing portion. The separator 120 divides the air chamber 166 facing the air electrode 114 and the fuel chamber 176 facing the fuel electrode 116, and gas leaks from one electrode side to the other electrode side in the peripheral portion of the single cell 110. It is suppressed. The single cell 110 to which the separator 120 is joined is referred to as a single cell with a separator.

  As shown in FIGS. 7 to 9, the air electrode side frame 130 is a frame-like member in which a rectangular hole 131 penetrating in the vertical direction is formed in the vicinity of the center, and is formed of an insulator such as mica, for example. ing. The air electrode side frame 130 is in contact with the peripheral edge portion of the surface of the separator 120 opposite to the side facing the electrolyte layer 112 and the peripheral edge portion of the surface of the interconnector 150 facing the air electrode 114. . The hole 131 of the air electrode side frame 130 forms an air chamber 166 that faces the air electrode 114. The pair of interconnectors 150 included in the power generation unit 102 is electrically insulated by the air electrode side frame 130. The air electrode side frame 130 has an oxidant gas supply communication hole 132 communicating the oxidant gas supply manifold 163 and the air chamber 166, and an oxidant gas communicating the air chamber 166 and the oxidant gas discharge manifold 162. A discharge communication hole 133 is formed.

  As shown in FIGS. 7, 8 and 10, the fuel electrode side frame 140 is a frame-like member in which a rectangular hole 141 penetrating in the vertical direction is formed near the center. For example, the fuel electrode side frame 140 is made of metal. Yes. The fuel electrode side frame 140 is in contact with the peripheral portion of the surface of the separator 120 facing the electrolyte layer 112 and the peripheral portion of the surface of the interconnector 150 facing the fuel electrode 116. In the present embodiment, the fuel electrode side frame 140 is welded to the separator 120 and the interconnector 150. The hole 141 of the fuel electrode side frame 140 forms a fuel chamber 176 that faces the fuel electrode 116. Further, the fuel electrode side frame 140 has a fuel gas supply communication hole 142 that connects the fuel gas introduction manifold 171 and the fuel chamber 176, and a fuel gas discharge communication hole 143 that connects the fuel chamber 176 and the fuel gas discharge manifold 172. And are formed.

  The air electrode side current collector 134 is disposed in the air chamber 166 as shown in FIGS. 7 to 9. The air electrode side current collector 134 is composed of a plurality of substantially quadrangular columnar conductive members arranged at predetermined intervals, and is made of, for example, ferritic stainless steel. The air electrode side current collector 134 is brought into contact with the surface of the air electrode 114 opposite to the side facing the electrolyte layer 112 and the surface of the interconnector 150 facing the air electrode 114, whereby the air electrode 114 and the interconnector 150 are electrically connected. The air electrode side current collector 134 and the interconnector 150 may be formed as an integral member.

  The fuel electrode side current collector 144 is disposed in the fuel chamber 176 as shown in FIGS. 7, 8 and 10. The fuel electrode side current collector 144 includes an interconnector facing portion 146, a plurality of electrode facing portions 145, and a connecting portion 147 that connects each electrode facing portion 145 and the interconnector facing portion 146. Or nickel alloy, stainless steel or the like. Specifically, as shown in the partially enlarged view in FIG. 10, the fuel electrode side current collector 144 is manufactured by cutting a rectangular flat plate-shaped member and bending the plurality of rectangular portions. The The bent rectangular portion becomes the electrode facing portion 145, the flat plate portion other than the bent raised portion becomes the interconnector facing portion 146, and the portion connecting the electrode facing portion 145 and the interconnector facing portion 146 is connected. Part 147. In addition, in the partial enlarged view in FIG. 10, in order to show the manufacturing method of the fuel electrode side collector 144, the state before the bending raising process of a part of several rectangular part is shown. Each electrode facing portion 145 contacts the surface of the fuel electrode 116 opposite to the side facing the electrolyte layer 112, and the interconnector facing portion 146 contacts the surface of the interconnector 150 facing the fuel electrode 116. To do. Therefore, the fuel electrode side current collector 144 electrically connects the fuel electrode 116 and the interconnector 150. Note that a spacer 149 made of, for example, mica is disposed between the electrode facing portion 145 and the interconnector facing portion 146. Therefore, the fuel electrode side current collector 144 follows the deformation of the power generation unit 102 due to the temperature cycle or reaction gas pressure fluctuation, and the fuel electrode 116 and the interconnector 150 are electrically connected via the fuel electrode side current collector 144. Maintained well.

(Configuration of heat exchange unit 103)
FIG. 11 is an explanatory diagram schematically showing a planar configuration on the upper side of the heat exchange unit 103. As shown in FIGS. 4 to 6 and FIG. 11, the heat exchanging portion 103 is a rectangular flat plate-like member, and is formed of, for example, ferritic stainless steel. As described above, eight holes constituting the communication hole 108 into which the bolt 22 is inserted are formed in the peripheral portion around the Z direction of the heat exchanging portion 103. Further, a hole 182 penetrating in the vertical direction is formed near the center of the heat exchanging portion 103. Further, the heat exchange unit 103 has a communication hole 184 communicating with the central hole 182 and the communication hole 108 forming the oxidant gas introduction manifold 161, and a communication forming the central hole 182 and the oxidant gas supply manifold 163. A communication hole 186 that communicates with the hole 108 is formed. The heat exchange unit 103 includes a lower interconnector 150 included in the power generation unit 102 adjacent to the upper side of the heat exchange unit 103 and an upper interconnector 150 included in the power generation unit 102 adjacent to the lower side of the heat exchange unit 103. And is sandwiched between. A space formed by the holes 182, the communication holes 184, and the communication holes 186 between these interconnectors 150 functions as a heat exchange channel 188 through which the oxidant gas OG flows for heat exchange described later.

A-2. Operation of the fuel cell stack 100:
As shown in FIG. 4, when the oxidant gas OG is supplied via a gas pipe (not shown) connected to the branch portion 29 of the gas passage member 27 provided at the position of the oxidant gas introduction manifold 161. The oxidant gas OG is supplied to the oxidant gas introduction manifold 161 through the branch portion 29 of the gas passage member 27 and the hole of the main body portion 28. As shown in FIGS. 4 and 11, the oxidant gas OG supplied to the oxidant gas introduction manifold 161 flows into the heat exchange channel 188 formed in the heat exchange unit 103, and the heat exchange channel 188. And is discharged to the oxidant gas supply manifold 163. Since the oxidant gas introduction manifold 161 is not in communication with the air chamber 166 of each power generation unit 102, the oxidant gas OG is supplied from the oxidant gas introduction manifold 161 to the air chamber 166 of each power generation unit 102. There is nothing. The oxidant gas OG discharged to the oxidant gas supply manifold 163 is communicated from the oxidant gas supply manifold 163 to the oxidant gas supply communication of each power generation unit 102 as shown in FIGS. 4, 5, 7 and 9. The air is supplied to the air chamber 166 through the hole 132.

  Further, as shown in FIGS. 6, 8, and 10, the fuel gas is connected via a gas pipe (not shown) connected to the branch portion 29 of the gas passage member 27 provided at the position of the fuel gas introduction manifold 171. When the FG is supplied, the fuel gas FG is supplied to the fuel gas introduction manifold 171 through the branch portion 29 of the gas passage member 27 and the hole of the main body portion 28, and the fuel of each power generation unit 102 is supplied from the fuel gas introduction manifold 171. The fuel is supplied to the fuel chamber 176 through the gas supply communication hole 142.

  When the oxidant gas OG is supplied to the air chamber 166 of each power generation unit 102 and the fuel gas FG is supplied to the fuel chamber 176, power is generated by an electrochemical reaction between the oxidant gas OG and the fuel gas FG in the single cell 110. Is called. This power generation reaction is an exothermic reaction. In each power generation unit 102, the air electrode 114 of the single cell 110 is electrically connected to one interconnector 150 via the air electrode side current collector 134, and the fuel electrode 116 is connected via the fuel electrode side current collector 144. The other interconnector 150 is electrically connected. In addition, the plurality of power generation units 102 included in the fuel cell stack 100 are electrically connected in series although the heat exchange unit 103 is interposed therebetween. Therefore, electrical energy generated in each power generation unit 102 is taken out from the end plates 104 and 106 that function as output terminals of the fuel cell stack 100. Since SOFC generates power at a relatively high temperature (for example, 700 ° C. to 1000 ° C.), the fuel cell stack 100 is heated by a heater (after the start-up until the high temperature can be maintained by the heat generated by the power generation. (Not shown).

  As shown in FIGS. 5, 7, and 9, the oxidant off-gas OOG that is the oxidant gas OG that has not been used for the power generation reaction in each power generation unit 102 passes from the air chamber 166 through the oxidant gas discharge communication hole 133. The gas is discharged to the oxidant gas discharge manifold 162 and further connected to the branch part 29 through the holes of the main body part 28 and the branch part 29 of the gas passage member 27 provided at the position of the oxidant gas discharge manifold 162. It is discharged to the outside of the fuel cell stack 100 through piping (not shown). Further, as shown in FIGS. 6, 8, and 10, the fuel off-gas FOG that is the fuel gas FG that has not been used in the power generation reaction in each power generation unit 102 passes through the fuel gas discharge communication hole 143 from the fuel chamber 176. Gas piping (shown in the figure) connected to the branching portion 29 through the holes of the main body portion 28 and the branching portion 29 of the gas passage member 27 that is discharged to the fuel gas discharge manifold 172 and further provided at the position of the fuel gas discharge manifold 172. Is not discharged to the outside of the fuel cell stack 100.

A-3. Temperature of gas flowing through each manifold:
As described above, the oxidant gas OG supplied to the oxidant gas introduction manifold 161 is discharged to the oxidant gas supply manifold 163 through the heat exchange channel 188 formed in the heat exchange unit 103. Here, the heat exchanging unit 103 is adjacent to the power generation unit 102 on the upper side and the lower side. The power generation reaction in the power generation unit 102 is an exothermic reaction. Therefore, when the oxidant gas OG passes through the heat exchange channel 188 in the heat exchange unit 103, heat exchange is performed between the oxidant gas OG and the power generation unit 102, and the temperature of the oxidant gas OG increases. To do. The oxidant gas OG discharged to the oxidant gas supply manifold 163 is supplied to each power generation unit 102 and then discharged to the oxidant gas discharge manifold 162. When the oxidant gas OG passes through each power generation unit 102, the temperature of the oxidant gas OG further increases due to heat generated by the power generation reaction. Therefore, the level relationship between the temperatures T (A), T (C), and T (B) of the gas flowing through the oxidant gas introduction manifold 161, the oxidant gas supply manifold 163, and the oxidant gas discharge manifold 162 is as follows. Equation (1) is obtained.
T (A) <T (C) <T (B) (1)

  For example, the temperature T (A) of the gas flowing through the oxidant gas introduction manifold 161 is about 350 ° C. to 450 ° C., and the temperature T (C) of the gas flowing through the oxidant gas supply manifold 163 is about 550 ° C. to 650 ° C. The temperature T (B) of the gas flowing through the oxidant gas discharge manifold 162 is about 700 ° C. to 800 ° C. In addition, the alphabet attached | subjected to the code | symbol showing each temperature respond | corresponds to the alphabet attached | subjected to the code | symbol of the volt | bolt 22 which forms each manifold. For example, the temperature of the gas flowing through the oxidant gas introduction manifold 161 formed by the bolt 22A is represented as T (A). The same applies to the flow path of the fuel gas FG.

In addition, the fuel gas FG supplied to the fuel gas introduction manifold 171 is supplied to each power generation unit 102 and then discharged to the fuel gas discharge manifold 172. When the fuel gas FG passes through each power generation unit 102, the temperature of the fuel gas FG rises due to heat generated by the power generation reaction. Therefore, the level relationship between the temperatures T (D) and T (E) of the gas flowing through the fuel gas introduction manifold 171 and the fuel gas discharge manifold 172 is expressed by the following equation (2).
T (D) <T (E) (2)

  For example, the temperature T (D) of the gas flowing through the fuel gas introduction manifold 171 is about 550 ° C. to 650 ° C., and the temperature T (E) of the gas flowing through the fuel gas discharge manifold 172 is about 700 ° C. to 800 ° C.

A-4. Linear thermal expansion coefficient α of each bolt 22:
As described above, since there is a difference in the temperature of gas flowing through each manifold, the bolts 22 forming each manifold are exposed to gases having different temperatures. Therefore, if the linear thermal expansion coefficient α (unit: 1 / ° C.) of each bolt 22 forming each manifold is equal to each other, there is a difference in the deformation amount ΔL due to thermal expansion of the length L of each bolt 22 (see FIG. 4). As a result, a difference occurs in the fastening force of each bolt 22. As a result, the contact pressure (pressure for pressing the fuel cell stack 100 in the arrangement direction) varies in the surface direction (the direction orthogonal to the arrangement direction of the power generation units 102), and there is a possibility that gas leaks from the inside of the fuel cell stack 100 to the outside. is there. Note that the axial deformation amount ΔL of the bolt 22 at T ° C. when the axial length L ₀ of the bolt 22 at 0 ° C. is used as a reference is calculated by the following equation (3).
ΔL = α · T · L ₀ (3)

Therefore, in this embodiment, the linear thermal expansion coefficient α of the bolts 22 forming each manifold is set in consideration of the temperature of the gas flowing through each manifold. Specifically, regarding the flow path of the oxidant gas OG, the linear thermal expansion coefficient α _{c1 of} the bolt 22A that forms the oxidant gas introduction manifold 161 and the linear thermal expansion of the bolt 22C that forms the oxidant gas supply manifold 163. The coefficient α _c3 and the linear thermal expansion coefficient α _{c2 of} the bolt 22B forming the oxidant gas discharge manifold 162 are set to satisfy the relationship of the following formula (4).
α _c2 <α _c3 <α _c1 (4)

That is, the linear thermal expansion coefficient α _c1 of the bolt 22A forming the oxidant gas introduction manifold 161 through which the coldest gas flows among the oxidant gas introduction manifold 161, the oxidant gas supply manifold 163, and the oxidant gas discharge manifold 162 is set. The linear thermal expansion coefficient α _c2 of the bolt 22B that forms the oxidant gas discharge manifold 162 through which the highest temperature gas flows is _minimized, and the oxidant gas supply manifold 163 through which the gas at the temperature between the two flows is formed. The linear thermal expansion coefficient α _c3 of the bolt 22C to be used is a value between the two. In this way, the difference in deformation amount ΔL of each bolt 22 caused by the temperature difference of the gas flowing through the oxidant gas introduction manifold 161, the oxidant gas supply manifold 163, and the oxidant gas discharge manifold 162 is reduced. It is possible to suppress gas leakage caused by variations in contact pressure in the surface direction.

  The bolt 22A for forming the oxidant gas introduction manifold 161 is formed of SUS304, which is austenitic stainless steel, and the bolt 22C for forming the oxidant gas supply manifold 163 is formed of SUS316, which is austenitic stainless steel. If the bolts 22B forming the manifold 162 are formed of SUS444, which is a ferritic stainless steel, the magnitude relationship of the linear thermal expansion coefficient α of each bolt 22 is as shown in the above formula (4). The material used for the bolt 22 can be selected from austenitic stainless steel, nickel-base alloy, ferritic stainless steel, and ceramics. For example, examples of the austenitic stainless steel include SUS201, SUS301, SUS305, SUS304, and SUS316. Examples of the nickel-based alloy include Inconel 600, Inconel 718, Incoloy 802, and the like. Examples of the ferritic stainless steel include SUS430, SUS434, SUS405, and SUS444. The material used for the bolt 22 is appropriately selected from these materials so as to satisfy the formula (4).

Theoretically, if the following expression (5) holds, the deformation amount ΔL of the bolt 22A and the deformation amount ΔL of the bolt 22B are the same. Therefore, for example, it is preferable that the following expression (6) is satisfied because the difference between the deformation amount ΔL of the bolt 22A and the deformation amount ΔL of the bolt 22B can be kept within a certain small range.
α _c2 = α _c1 · T (A) / T (B) (5)
0.9 · α _c1 · T (A) / T (B) <α _c2 <1.1 · α _c1 · T (A) / T (B) (6)

Similarly, theoretically, if the following expression (7) holds, the deformation amount ΔL of the bolt 22A and the deformation amount ΔL of the bolt 22C are the same. Therefore, for example, it is preferable that the following expression (8) is satisfied because the difference between the deformation amount ΔL of the bolt 22A and the deformation amount ΔL of the bolt 22C can be kept within a certain small range.
α _c3 = α _c1 · T (A) / T (C) (7)
0.9 · α _c1 · T (A) / T (C) <α _c3 <1.1 · α _c1 · T (A) / T (C) (8)

Similarly, in the present embodiment, on the fuel gas side, the linear thermal expansion coefficient α _{a1 of} the bolt 22D that forms the fuel gas introduction manifold 171 and the linear thermal expansion coefficient α _{a2 of} the bolt 22E that forms the fuel gas discharge manifold 172 However, the relationship of the following formula | equation (9) is satisfy | filled.
α _a2 <α _a1 (9)

That is, of the fuel gas introduction manifold 171 and the fuel gas discharge manifold 172, the fuel gas discharge through which higher temperature gas flows than the linear thermal expansion coefficient α _{a1 of} the bolt 22D that forms the fuel gas introduction manifold 171 through which lower temperature gas flows. The linear thermal expansion coefficient α _a2 of the bolt 22E forming the manifold 172 is reduced. By doing so, the difference in deformation amount ΔL of each bolt 22 caused by the temperature difference between the gas flowing through the fuel gas introduction manifold 171 and the fuel gas discharge manifold 172 can be reduced, and the contact pressure in the surface direction can be reduced. Gas leakage caused by variation can be suppressed.

  If the bolts 22D forming the fuel gas introduction manifold 171 are formed of SUS304 or SUS316, which are austenitic stainless steel, and the bolts 22E forming the fuel gas discharge manifold 172 are formed of SUS444, which is ferritic stainless steel, each bolt 22 The linear thermal expansion coefficient α is as shown in the above equation (9).

In theory, if the following expression (10) holds, the deformation amount ΔL of the bolt 22D and the deformation amount ΔL of the bolt 22E become the same. Therefore, for example, it is preferable that the following expression (11) holds, because the difference between the deformation amount ΔL of the bolt 22D and the deformation amount ΔL of the bolt 22E can be kept within a certain small range.
α _a2 = α _a1 · T (D) / T (E) (10)
0.9 · α _a1 · T (D) / T (E) <α _a2 <1.1 · α _a1 · T (D) / T (E) (11)

FIG. 12 is an explanatory diagram illustrating a calculation example of the difference D of the deformation amount ΔL of the bolt 22. Specifically, FIG. 12 shows the deformation amount ΔL ₁ (mm) of the bolt 22A forming the oxidant gas introduction manifold 161 and the deformation amount ΔL ₂ (mm) of the bolt 22B forming the oxidant gas discharge manifold 162. A calculation example of the difference D (= ΔL ₂ −ΔL ₁ ) is shown. As shown in FIG. 12, the deformation amount difference D in the example satisfying the relationship (α _c2 <α _c1 ) of the above equation (4) is larger than the deformation amount difference D in Comparative Examples 1 to 3 not satisfying the equation (4). small. Therefore, in this embodiment, it is possible to suppress gas leakage caused by variations in contact pressure in the surface direction as compared with the comparative examples.

The bolt 22B forming the oxidant gas discharge manifold 162 is exposed to a gas having a temperature higher than that of the bolt 22A forming the oxidant gas introduction manifold 161. Therefore, as shown in FIG. ΔL ₂ is larger than the deformation amount ΔL ₁ of the bolt 22A. However, when the linear thermal expansion coefficient alpha _c1 bolt 22A is too large, the magnitude relationship between the deformation amount [Delta] L ₂ of the deformation amount [Delta] L ₁ and the bolt 22B of the bolt 22A is reversed, also be larger deformation amount difference D Gakaette occur obtain. Therefore, the linear thermal expansion coefficient alpha _c2 of linear thermal expansion coefficient alpha _c1 and bolt 22B of the bolt 22A, it is preferable to satisfy the following relationship of equation (12).
α _c1 <1.7 α _c2 (12)

Satisfies the linear thermal expansion coefficient of the linear thermal expansion coefficient alpha _c1 and bolt 22B of the bolt 22A and alpha _c2 is the above formula 12, the gas temperature of the gas flow path described above (e.g., the oxidant gas inlet manifold 161 is about 450 ° C. from 350 ° C., at about 800 ° C.) from 700 ° C. for the oxidizing gas discharging manifold 162, the magnitude relationship between the deformation amount [Delta] L ₂ of the deformation amount [Delta] L ₁ and the bolt 22B of the bolt 22A is reversed Absent. If the bolt 22A that forms the oxidant gas introduction manifold 161 is formed of SUS304 or SUS316 that is austenitic stainless steel, and the bolt 22B that forms the oxidant gas discharge manifold 162 is formed of SUS444 that is ferritic stainless steel, each bolt 22 The magnitude relationship of the linear thermal expansion coefficient α satisfies the formula (12).

Similarly, the fuel gas side preferably satisfies the relationship of the following formula (13). If the bolt 22D that forms the fuel gas introduction manifold 171 is formed of SUS304 or SUS316 that is austenitic stainless steel, and the bolt 22E that forms the fuel gas discharge manifold 172 is formed of SUS444 that is ferritic stainless steel, the wire of each bolt 22 The magnitude relationship of the thermal expansion coefficient α satisfies the formula (13).
α _a1 <1.7 α _a2 (13)

Further, the technical idea disclosed in the present specification reduces the difference D in the deformation amount ΔL due to thermal expansion of each bolt 22 by appropriately setting the linear thermal expansion coefficient α of each bolt 22 forming each manifold. It is in point to let you. That is, as shown in the following formula (14), the difference D in the deformation amount ΔL due to the thermal expansion of each bolt 22 is the same material, and the linear thermal expansion coefficient α of each bolt 22 is equal to each other. It can be said that this is a technical idea that is smaller than the difference D ₀ of the deformation amount ΔL of each bolt 22 in the comparative example.
D <D ₀ (14)

In the comparative example in which the linear thermal expansion coefficient α _{c1 of} the bolt 22A forming the oxidant gas introduction manifold 161 and the linear thermal expansion coefficient α _{c2 of} the bolt 22B forming the oxidant gas discharge manifold 162 are equal, the deformation amount difference D ₀ is It is represented by the following formula (15).
D ₀ = α _c2 · T (B) · L ₀ −α _c2 · T (A) · L ₀ (15)

Further, the deformation amount difference D in the embodiment is expressed by the following equation (16).
D = | α _c2 · T (B) · L ₀ −α _c1 · T (A) · L ₀ | (16)

When equation (16) is solved from equation (14), equation (19) is derived as follows.
(If α _c2 · T (B) · L ₀ ≥ α _c1 · T (A) · L ₀ )
D = α _c2 · T (B) · L ₀ −α _c1 · T (A) · L ₀
From equation (14), α _c2 · T (B) · L ₀ −α _c1 · T (A) · L ₀ <α _c2 · T (B) · L ₀ −α _c2 · T (A) · L ₀
α _c2 <α _c1 (17)
(When α _c2 · T (B) · L ₀ <α _c1 · T (A) · L ₀ )
D = −α _c2 · T (B) · L ₀ + α _c1 · T (A) · L ₀
From equation (14) -α _c2 · T (B) · L ₀ + α _c1 · T (A) · L ₀ <α _c2 · T (B) · L ₀ -α _c2 · T (A) · L ₀
α _c1 <α _c2 · (2 · T (B) −T (A)) / T (A) (18)
From expression (17) and expression (18), α _c2 <α _c1 <α _c2 · (2 · T (B) −T (A)) / T (A) (19)

Thus, satisfies the relationship of the bolt 22A of the linear thermal expansion coefficient alpha _c1 and bolt 22B linear thermal expansion coefficient alpha _c2 Togashiki (19), the difference D of deformation amount ΔL due to thermal expansion of the bolt 22 in the embodiment It becomes smaller than the deformation amount difference D ₀ in the comparative example. The same applies to the bolts 22 forming other manifolds.

B. Second embodiment:
B-1. Constitution:
(Configuration of the fuel cell hot module 10)
FIG. 13 is an explanatory diagram schematically showing the configuration of a fuel cell hot module (hereinafter referred to as “hot module”) 10 in the second embodiment. In FIG. 13, in order to make the configuration of the hot module 10 easy to understand, a part of the configuration is shown transparently, or a part of the configuration is not shown. The hot module 10 includes a power generation module 20, a heat insulating container 30 that houses the power generation module 20, and various pipes 234 and 236 connected to the power generation module 20. The hot module 10 may include a heater (for example, a gas burner) that heats the power generation module 20 at the time of startup or the like.

(Configuration of heat insulation container 30)
The heat insulation container 30 has the structure by which the heat insulating material is arrange | positioned at the inner surface of the housing | casing formed, for example with stainless steel. By storing the power generation module 20 in the heat insulating container 30, the power generation module 20 is maintained at a high temperature when generating power.

(Configuration of power generation module 20)
14 to 16 are explanatory views schematically showing the configuration of the power generation module 20. FIG. 14 shows a cross-sectional configuration of the power generation module 20 at a position corresponding to the position of the cross section shown in FIG. 4 of the first embodiment, and FIG. 15 shows the cross section shown in FIG. 5 of the first embodiment. FIG. 16 shows a cross-sectional configuration of the power generation module 20 at a position corresponding to the position (position XV-XV in FIG. 13). FIG. 16 shows a position corresponding to the position of the cross section shown in FIG. The cross-sectional configuration of the power generation module 20 at the position XVI-XVI in FIG. 13 is shown. As shown in FIGS. 13 to 16, the power generation module 20 includes a fuel cell stack 100a and an auxiliary device 200 disposed below the fuel cell stack 100a. Since the configuration of the fuel cell stack 100a is the same as the configuration of the fuel cell stack 100 of the first embodiment described above, the description thereof is omitted by attaching the same reference numerals.

(Configuration of auxiliary device 200)
The auxiliary device 200 includes a substantially box-shaped auxiliary device main body 210 and four fixing portions 220 formed on the side surface of the auxiliary device main body 210. The auxiliary device 200 is made of, for example, stainless steel.

  Each fixing portion 220 is formed with a through-hole 208 penetrating in the vertical direction. The through holes 208 formed in the four fixing portions 220 are in communication with the communication holes 108 located near the midpoints of the four sides that form the outer periphery around the Z direction of the fuel cell stack 100a. The four bolts 22 inserted into these four communication holes 108 reach the through holes 208 of the fixing portions 220 at the corresponding positions, and the nuts 24 are fitted into these bolts 22, thereby the auxiliary device 200 and the fuel. The battery stack 100 is fixed.

  The interior of the auxiliary device main body 210 is divided into two primary partitioning chambers 212, a reforming chamber 214 disposed below the primary combustion chamber 212, and a secondary combustion disposed below the reforming chamber 214 by two partition walls 222. It is divided into chambers 216. The primary combustion chamber 212 is a chamber for mixing and burning the oxidant off-gas OOG and the fuel off-gas FOG discharged from the fuel cell stack 100a, and oxidant gas discharge through the through-hole 208 of the fixed portion 220. The manifold 162 and the fuel gas discharge manifold 172 communicate with each other. The secondary combustion chamber 216 is a chamber for further burning the oxidant off-gas OOG and the fuel off-gas FOG mixed and burned in the primary combustion chamber 212, and a flow path 218 that vertically penetrates the reforming chamber 214. And communicates with the primary combustion chamber 212. In one or both of the primary combustion chamber 212 and the secondary combustion chamber 216, a catalyst that promotes combustion of the oxidant off-gas OOG and the fuel off-gas FOG is disposed.

  The reforming chamber 214 is a chamber for reforming the mixed gas MG in which raw fuel gas (for example, city gas) and water vapor are mixed to generate a hydrogen-rich fuel gas FG. The fuel gas introduction manifold 171 communicates with the through hole 208. In the reforming chamber 214, a catalyst for promoting the reforming reaction is disposed.

(Configuration of various pipes 234, 236)
The auxiliary device 200 of the power generation module 20 is connected to a mixed gas introduction pipe 234 through which a mixed gas MG in which raw fuel gas and water vapor are mixed and an exhaust gas discharge pipe 236 through which exhaust gas EG is discharged. . More specifically, as shown in FIG. 16, the mixed gas introduction pipe 234 communicates with the reforming chamber 214 of the auxiliary device main body 210, and the exhaust gas discharge pipe 236 is connected to the secondary combustion of the auxiliary device main body 210. It communicates with the chamber 216.

B-2. Operation of the power generation module 20:
As shown in FIG. 14, the oxidant gas OG is passed through the branch portion 29 of the gas passage member 27 and the hole of the main body portion 28 provided at the position of the oxidant gas introduction manifold 161 as in the first embodiment. The oxidant gas introduction manifold 161 is supplied. As shown in FIGS. 14 and 15, the oxidant gas OG supplied to the oxidant gas introduction manifold 161 flows into the heat exchange channel 188 formed in the heat exchange unit 103, and the heat exchange channel 188. Then, the gas is discharged to the oxidant gas supply manifold 163 and supplied from the oxidant gas supply manifold 163 to the air chamber 166 of each power generation unit 102.

  As shown in FIG. 16, the mixed gas MG in which the raw fuel gas and the water vapor are mixed flows from the mixed gas introduction pipe 234 into the reforming chamber 214 of the auxiliary device main body 210 and is used for the reforming reaction. The The fuel gas FG generated in accordance with the reforming reaction in the reforming chamber 214 is supplied to the fuel gas introduction manifold 171 through the through hole 208 of the one fixed portion 220 of the auxiliary device 200, and each fuel gas FG is supplied from the fuel gas introduction manifold 171. It is supplied to the fuel chamber 176 of the power generation unit 102.

  When the oxidant gas OG is supplied to the air chamber 166 of each power generation unit 102 and the fuel gas FG is supplied to the fuel chamber 176, power generation is performed in each power generation unit 102 as in the first embodiment. As shown in FIG. 15, the oxidant off-gas OOG, which is the oxidant gas OG that has not been used for the power generation reaction in each power generation unit 102, passes through the oxidant gas discharge manifold 162 from the air chamber 166, and It is discharged into the primary combustion chamber 212. Further, the fuel off-gas FOG, which is the fuel gas FG that has not been used for the power generation reaction in each power generation unit 102, passes through the fuel gas discharge manifold 172 from the fuel chamber 176, as shown in FIG. It is discharged into the combustion chamber 212. The oxidant off-gas OOG and the fuel off-gas FOG discharged to the primary combustion chamber 212 are mixed and burned in the primary combustion chamber 212, and are guided to the secondary combustion chamber 216 via the flow path 218 for further combustion to emit exhaust gas. It is discharged outside the hot module 10 through the pipe 236. The reforming reaction in the reforming chamber 214 is promoted by the heat generated in the primary combustion chamber 212 and the secondary combustion chamber 216, and the power generation module 20 is maintained at a high temperature.

B-3. Temperature of gas flowing through each manifold and linear thermal expansion coefficient α of each bolt 22:
Also in the second embodiment, similarly to the first embodiment, the temperatures T (A) and T (C) of the gas flowing through the oxidant gas introduction manifold 161, the oxidant gas supply manifold 163, and the oxidant gas discharge manifold 162, respectively. ) And T (B) are in the relationship of the above formula (1) (T (A) <T (C) <T (B)), and the fuel gas introduction manifold 171 and the fuel gas discharge manifold 172 are The level relationship between the temperatures T (D) and T (E) of the flowing gas is the relationship (T (D) <T (E)) of the above equation (2).

Therefore, also in the second embodiment, as in the first embodiment, the linear thermal expansion coefficient α _{c1 of} the bolt 22A forming the oxidant gas introduction manifold 161 and the oxidant gas supply manifold 163 are formed on the oxidant gas side. the linear thermal expansion coefficient alpha _c3 bolts 22C to form a, a linear thermal expansion coefficient alpha _c2 bolt 22B forming the oxidizing gas discharging manifold 162, the relationship of the above formula _{(4) (α c2 <α} c3 <α _c1 ) is satisfied. Regarding the fuel gas side, the linear thermal expansion coefficient α _{a1 of} the bolt 22D forming the fuel gas introduction manifold 171 and the linear thermal expansion coefficient α _{a2 of} the bolt 22E forming the fuel gas discharge manifold 172 are expressed by the above formula ( 9) (α _a2 <α _a1 ) is satisfied. In this way, the difference in deformation amount ΔL of each bolt 22 caused by the temperature difference of the gas flowing through each manifold can be reduced, and gas leakage caused by variations in contact pressure in the surface direction is suppressed. can do.

B-4. Coefficient of linear thermal expansion α of the nut 24:
In the second embodiment, the fuel cell stack 100a is housed in the heat insulation container 30, and when the fuel cell stack 100a performs a power generation operation, the heat insulation container 30 is kept at a high temperature (for example, about 650 ° C. to 750 ° C.). Be drunk. Therefore, the nut 24 exposed on the outer surface of the fuel cell stack 100a is exposed to high temperature gas. On the other hand, the bolt 22A forming the oxidant gas introduction manifold 161 is exposed to a gas at a relatively low temperature (for example, about 350 ° C. to 450 ° C.). Therefore, if the linear thermal expansion coefficients of the bolt 22A and the nut 24 fitted to the bolt 22A are equal, the deformation due to the thermal expansion of the inner diameter dN (see FIG. 14) of the nut 24 is the heat of the outer diameter dB (see FIG. 14) of the bolt 22. The amount of deformation due to expansion becomes excessive, and plastic deformation and creep may occur.

Therefore, in the present embodiment, the linear thermal expansion coefficient α _{c1 of} the bolt 22A that forms the oxidant gas introduction manifold 161 and the linear thermal expansion coefficient α _{c4 of the} nut 24 fitted to the bolt 22A satisfy the relationship of the following equation (20). To meet. If the bolt 22A is made of SUS304, which is an austenitic stainless steel, and the nut 24 is made of SUS444, which is a ferritic stainless steel, the magnitude relationship between the linear thermal expansion coefficients is as shown in Expression (20). In this way, it is possible to suppress the deformation amount due to the thermal expansion of the nut 24 from being excessive with respect to the deformation amount due to the thermal expansion of the bolt 22, and to suppress the occurrence of plastic deformation and creep. it can.
α _c4 <α _c1 (20)

From the same point of view, the linear thermal expansion coefficient α _{c3 of} the bolt 22C forming the oxidant gas supply manifold 163 and the linear thermal expansion coefficient α _{c5 of the} nut 24 fitted to the bolt 22C satisfy the relationship of the following equation (21). The linear thermal expansion coefficient α _{a1 of} the bolt 22D forming the fuel gas introduction manifold 171 and the linear thermal expansion coefficient α _{a3 of the} nut 24 fitted to the bolt 22D satisfy the relationship of the following formula (22). preferable.
α _c5 <α _c3 (21)
α _a3 <α _a1 (22)

C. Third embodiment:
C-1. Constitution:
FIGS. 17 and 18 are explanatory views schematically showing the configuration of the fuel cell stack 100b in the third embodiment. FIG. 17 shows an external configuration of the fuel cell stack 100b. FIG. 18 shows a position corresponding to the position of the cross section shown in FIG. 5 in the first embodiment (position XVIII-XVIII in FIG. 17). A cross-sectional configuration of the fuel cell stack 100b is shown. Among the configurations of the fuel cell stack 100b in the third embodiment, the same configurations as those of the fuel cell stack 100 of the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted.

  The fuel cell stack 100b according to the third embodiment is different from the fuel cell stack 100 according to the first embodiment described above in that the heat exchange unit 103 is not provided. In this regard, the flow path configuration of the oxidant gas OG is also different. That is, in the third embodiment, the bolt located near the midpoint of one side (the X-axis positive direction side of the two sides parallel to the Y-axis) on the outer periphery around the Z-direction of the fuel cell stack 100b. A space formed by 22 (bolt 22A) functions as an oxidant gas introduction manifold 161 that is a gas flow path into which the oxidant gas OG is introduced from the outside of the fuel cell stack 100b.

C-2. Operation of the fuel cell stack 100b:
As in the first embodiment, the oxidant gas OG is supplied to the oxidant gas introduction manifold 161 via the branch part 29 of the gas passage member 27 provided at the position of the oxidant gas introduction manifold 161 and the hole of the main body part 28. Supplied. The oxidant gas OG supplied to the oxidant gas introduction manifold 161 is supplied to the air chamber 166 of each power generation unit 102. The subsequent flow of the oxidant gas OG is the same as in the first embodiment. Further, the flow of the fuel gas FG is the same as in the first embodiment. Also in the fuel cell stack 100b of the third embodiment, similarly to the first embodiment, power generation using the oxidant gas OG and the fuel gas FG is performed in each power generation unit 102, and the oxidant offgas OOG and the fuel offgas FOG are generated. It is discharged outside the fuel cell stack 100b.

C-3. Temperature of gas flowing through each manifold and linear thermal expansion coefficient α of each bolt 22:
In the third embodiment, as in the first embodiment, the level relationship between the temperatures T (A) and T (B) of the gas flowing through the oxidant gas introduction manifold 161 and the oxidant gas discharge manifold 162 is as follows. Equation (23) is obtained.
T (A) <T (B) (23)

Also in the fuel cell stack 100b of the third embodiment having such a configuration, the linear thermal expansion coefficient α _{c1 of} the bolt 22A forming the oxidant gas introduction manifold 161 and the oxidant gas discharge manifold are formed as in the first embodiment. The linear thermal expansion coefficient α _{c2 of} the bolt 22B forming 162 satisfies the relationship of the following formula (24). In this way, the difference in deformation amount ΔL of each bolt 22 caused by the temperature difference between the gas flowing through the oxidant gas introduction manifold 161 and the oxidant gas discharge manifold 162 can be reduced, and the contact pressure in the surface direction can be reduced. It is possible to suppress gas leakage caused by the variation of the gas.
α _c2 <α _c1 (24)

  In addition, the magnitude relationship of the linear thermal expansion coefficient α of the bolts 22 forming the fuel gas manifold is the same as that in the first embodiment, and thus the description thereof is omitted.

D. Variations:
The technology disclosed in the present 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 possible.

In the above embodiment, the magnitude relationship of the linear thermal expansion coefficient α is defined for both the bolt 22 forming each manifold through which the oxidant gas OG flows and the bolt 22 forming each manifold through which the fuel gas FG flows. However, if the magnitude relationship of the linear thermal expansion coefficient α described above is satisfied for at least one of them, the effect of suppressing gas leakage caused by variations in contact pressure in the surface direction is exhibited. Moreover, in the said embodiment, although it is supposed that Formula (4) ((alpha) _c2 <(alpha) _c3 <(alpha) _c1 ) is satisfy _| filled regarding the volt | bolt 22 which forms each manifold through which oxidizing gas OG flows, irrespective of the value of (alpha) _c3. If the relationship of at least α _c2 <α _c1 is satisfied, there is an effect of suppressing gas leakage caused by variations in contact pressure in the surface direction.

  The material for forming each bolt 22 described in the above embodiment is merely an example, and each bolt 22 may be formed of another material (for example, ceramics).

  In the above embodiment, the power generation module 20 includes the auxiliary device 200, but the power generation module 20 does not need to include the auxiliary device 200. Moreover, in the said embodiment, although the electric power generation module 20 is accommodated in the heat insulation container 30, it is not necessary for the power generation module 20 to be accommodated in the heat insulation container 30. FIG. Further, in the above embodiment, the auxiliary device 200 burns the gas discharged from the fuel cell stack 100, and the secondary combustion chamber 216 for further burning the gas burned in the primary combustion chamber 212. And a reforming chamber 214 that reforms the mixed gas MG in which the raw fuel gas and the water vapor are mixed and supplies the fuel cell stack 100 with the reformed gas FG. It suffices to have at least one of the primary combustion chamber 212 and the reforming chamber 214.

  In the above embodiment, the mixed gas introduction pipe 234 communicates with the reforming chamber 214 of the auxiliary body main body 210, and the exhaust gas discharge pipe 236 communicates with the secondary combustion chamber 216 of the auxiliary body main body 210. However, the arrangement and route of these pipes can be changed as appropriate.

  In the above embodiment, the number of power generation units 102 included in the fuel cell stack 100 is merely an example, and the number of power generation units 102 is appropriately determined according to the output voltage required for the fuel cell stack 100 or the like.

  Moreover, in the said embodiment, the position of the heat exchange part 103 in the arrangement direction of the fuel cell stack 100 is an example to the last, and the position of the heat exchange part 103 can be changed to arbitrary positions. However, the position of the heat exchanging unit 103 is a position adjacent to the power generation unit 102 having a higher temperature among the plurality of power generation units 102 included in the fuel cell stack 100, so that the heat in the arrangement direction of the fuel cell stack 100 is determined. It is preferable for the relaxation of the distribution. For example, when the power generation unit 102 near the center in the arrangement direction of the fuel cell stack 100 is likely to be hotter, the heat exchange unit 103 is provided near the center in the arrangement direction of the fuel cell stack 100 as in the above embodiment. preferable. Further, the fuel cell stack 100 may include two or more heat exchange units 103.

  In the above embodiment, the heat exchange unit 103 is configured to increase the temperature of the oxidant gas OG. However, the heat exchange unit 103 increases the temperature of the fuel gas FG instead of the oxidant gas OG. Alternatively, the temperature of the fuel gas FG may be increased together with the oxidant gas OG.

  In the above embodiment, the nuts 24 are fitted on both sides of the bolt 22, but the bolt 22 has a head, and the nut 24 is fitted only on the opposite side of the head of the bolt 22. Also good.

  In the above embodiment, the end plates 104 and 106 function as output terminals. However, instead of the end plates 104 and 106, separate members (for example, the end plate 104) connected to the end plates 104 and 106, respectively. , 106 and the power generation unit 102) may function as output terminals.

  Moreover, in the said embodiment, although the space between the outer peripheral surface of the axial part of each bolt 22 and the inner peripheral surface of each communicating hole 108 is utilized as each manifold, it replaces with this and the axis | shaft of each bolt 22 is used. An axial hole may be formed in the part, and the hole may be used as each manifold. In either case, each manifold is formed by each bolt 22.

  In the above embodiment, when two power generation units 102 are arranged adjacent to each other, one interconnector 150 is shared by two adjacent power generation units 102. Two power generation units 102 may be provided with respective interconnectors 150. In the above embodiment, the upper interconnector 150 of the uppermost power generation unit 102 in the fuel cell stack 100 and the lower interconnector 150 of the lowermost power generation unit 102 are omitted. These interconnectors 150 may be provided without being omitted.

  Further, in the above embodiment, the fuel electrode side current collector 144 may have the same configuration as the air electrode side current collector 134, and the fuel electrode side current collector 144 and the adjacent interconnector 150 are an integral member. It may be. Further, the fuel electrode side frame 140 instead of the air electrode side frame 130 may be an insulator. The air electrode side frame 130 and the fuel electrode side frame 140 may have a multilayer structure.

  Moreover, the material which forms each member in the said embodiment is an illustration to the last, and each member may be formed with another material.

  In the above embodiment, the city gas is reformed to obtain the hydrogen-rich fuel gas FG, but the fuel gas FG may be obtained from other raw materials such as LP gas, kerosene, methanol, gasoline, Pure hydrogen may be used as the fuel gas FG.

  Further, in the above embodiment, a reaction preventing layer formed of, for example, ceria is provided between the electrolyte layer 112 and the air electrode 114 so that zirconium or the like in the electrolyte layer 112 reacts with strontium or the like in the air electrode 114. An increase in electrical resistance between the electrolyte layer 112 and the air electrode 114 may be suppressed.

 In the above embodiment, the solid oxide fuel cell (SOFC) has been described as an example. However, the present invention can be applied to a solid polymer fuel cell (PEFC), a phosphoric acid fuel cell (PAFC), a molten carbonate type. It can also be applied to other types of fuel cells such as fuel cells (MCFC). Note that the present invention is a fuel cell of a type in which the difference in deformation amount of each bolt is likely to be a problem due to the temperature of the gas such as SOFC and MCFC being relatively high and the temperature difference of the gas flowing through each gas flow path. More preferred.

DESCRIPTION OF SYMBOLS 10: Fuel cell hot module 20: Electric power generation module 22: Bolt 24: Nut 25: Through-hole 26: Insulation sheet 27: Gas passage member 28: Main-body part 29: Branch part 30: Thermal insulation container 100: Fuel cell stack 102: Power generation unit DESCRIPTION OF SYMBOLS 103: Heat exchange part 104: End plate 106: End plate 108: Communication hole 110: Single cell 112: Electrolyte layer 114: Air electrode 116: Fuel electrode 120: Separator 121: Hole 124: Joining part 130: Air electrode side frame 131 : Hole 132: Oxidant gas supply communication hole 133: Oxidant gas discharge communication hole 134: Air electrode side current collector 140: Fuel electrode side frame 141: Hole 142: Fuel gas supply communication hole 143: Fuel gas discharge communication hole 144 : Fuel electrode side current collector 145: Electrode facing portion 146: A Counter connector facing portion 147: Connecting portion 149: Spacer 150: Interconnector 161: Oxidant gas introduction manifold 162: Oxidant gas discharge manifold 163: Oxidant gas supply manifold 166: Air chamber 171: Fuel gas introduction manifold 172: Fuel gas Discharge manifold 176: Fuel chamber 182: Hole 184: Communication hole 186: Communication hole 188: Heat exchange flow path 200: Auxiliary device 208: Through hole 210: Auxiliary device main body 212: Primary combustion chamber 214: Reforming chamber 216: Two Next combustion chamber 218: Flow path 220: Fixed part 222: Partition wall 234: Mixed gas introduction pipe 236: Exhaust gas discharge pipe

Claims (7)

A plurality of power generation units each including an electrolyte layer, and an air electrode and a fuel electrode facing each other in a first direction across the electrolyte layer, and arranged in the first direction; A plurality of bolts extending, and a fuel cell stack fastened with the plurality of bolts,
The plurality of bolts are:
A first bolt that forms a gas passage through which gas is introduced from the outside of the fuel cell stack;
A second bolt that forms a gas flow path for discharging gas to the outside of the fuel cell stack,
The first bolt and the linear thermal expansion coefficient alpha ₁ and the linear thermal expansion coefficient alpha ₂ of second bolt, and satisfies the alpha _{2 <alpha 1} relationship, the fuel cell stack. The fuel cell stack according to claim 1, wherein
The first bolt and the linear thermal expansion coefficient alpha ₁ and linear thermal expansion coefficient of the second bolt alpha _2, and satisfies the α _{1 <1.7α 2} relationship, the fuel cell stack. The fuel cell stack according to claim 1 or 2,
Each of the first bolt and the second bolt is formed of any one material of austenitic stainless steel, ferritic stainless steel, nickel-based alloy, and ceramics, Fuel cell stack. The fuel cell stack according to any one of claims 1 to 3, further comprising:
Gas exhausted from the gas flow path formed by the adjacent power generation unit and the first bolt provided at a position adjacent to the first direction with respect to at least one of the plurality of power generation units. A heat exchanging part that performs heat exchange of
The plurality of bolts include a third bolt that forms a gas flow path that carries the gas discharged from the heat exchange unit toward the power generation units,
The third bolt linear thermal expansion coefficient alpha ₃ is characterized by satisfying α _{2 <α 3 <α 1} relationship, the fuel cell stack. The fuel cell stack according to any one of claims 1 to 4, further comprising:
A nut fitted on the first bolt;
The fuel cell stack, wherein the nut has a linear thermal expansion coefficient α ₄ satisfying a relationship of α ₄ <α ₁ . In the fuel cell stack according to any one of claims 1 to 5,
Each of the power generation units is a power generation unit of a solid oxide fuel cell or a molten carbonate fuel cell. The fuel cell stack according to any one of claims 1 to 6,
An auxiliary device having at least one of a combustion chamber for burning the gas discharged from the fuel cell stack and a reforming chamber for reforming the raw fuel gas to generate fuel gas to be supplied to the fuel cell stack; With
A power generation module in which the fuel cell stack and the auxiliary device are fastened by the plurality of bolts.

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