JP6182289B1 - Fuel cell stack - Google Patents

Abstract

A fuel cell stack capable of sufficiently heating a member to be heated is provided. A fuel cell stack includes a fuel manifold, a fuel cell, and a porous member. The fuel cell 2 extends upward from the fuel manifold 1. The fuel battery cell 2 includes a support substrate, a gas flow path 22 extending in the vertical direction in the support substrate, and a power generation element unit disposed on the support substrate. The porous member 3 is disposed above the fuel cell 2 so as to cover the discharge side end of the gas flow path 22. As for the porous member 3, a side part is denser than an inside. [Selection] Figure 6

Description

  The present invention relates to a fuel cell stack.

  The fuel cell stack includes a fuel manifold and a plurality of fuel cells extending upward from the fuel manifold (see Patent Document 1). The fuel manifold distributes fuel gas to each fuel cell.

  Part of the fuel gas supplied to each fuel cell is discharged from each fuel cell in an unreacted state. By burning the discharged fuel gas, for example, a reformer or a member to be heated such as air flowing around can be heated.

JP 2004-319420 A

  In the fuel cell stack configured as described above, if the fuel gas utilization efficiency is improved, the fuel gas discharged from the upper end of each fuel cell decreases, and the member to be heated cannot be heated sufficiently. was there.

  Then, the subject of this invention is providing the fuel cell stack which can fully heat the member to be heated.

  A fuel cell stack according to an aspect of the present invention includes a fuel manifold, a fuel cell, and a porous member. The fuel cell extends upward from the fuel manifold. The fuel cell includes a support substrate, a gas flow path extending in the vertical direction in the support substrate, and a power generation element unit disposed on the support substrate. The porous member is disposed above the fuel cell so as to cover the discharge side end of the gas flow path. As for a porous member, a side part is denser than an inside.

  According to this structure, the fuel gas discharged | emitted from the gas flow path of a fuel cell and the air which flows through the outer surface of each fuel cell are supplied in a porous member. And since this fuel gas and air are mixed in a porous member, combustion of fuel gas turns into premixed combustion. For this reason, the fuel cell stack according to the present invention has improved combustion stability compared to conventional diffusion combustion, and can sufficiently heat the member to be heated. Further, since the side surface portion of the porous member is denser than the inside, it is possible to prevent the fuel gas and air supplied into the porous member from leaking to the side of the porous member. For this reason, the member to be heated can be heated more efficiently.

  Preferably, the porous member includes a plurality of flow paths extending in the vertical direction, a porous partition wall that partitions each flow path, and a resistance that is disposed in a part of the flow paths and serves as a resistance to a gas flow that flows upward. Part. According to this configuration, when the gas supplied to the flow path of the porous member reaches the resistance portion, it flows to the adjacent flow path via the partition wall. As a result, mixing of fuel gas and air in the porous member is promoted, and more stable combustion can be achieved.

  For example, it can be set as the structure where the porosity of the resistance part mentioned above is lower than the porosity of a partition.

  Preferably, the porous member has a resistance portion that serves as a resistance to the flow of gas flowing upward inside the porous member. According to this configuration, when the fuel gas or air flowing upward in the porous member reaches the resistance portion, the flow direction of the fuel gas or air is changed so as to avoid the resistance portion. As a result, mixing of fuel gas and air is promoted, and more stable combustion can be achieved.

  For example, it can be set as the structure where the porosity of a resistance part is lower than the porosity of the other part of a porous member.

  Preferably, the porous member is disposed below the member to be heated. The upper surface of the porous member has a facing region that faces the member to be heated and an outer region that is disposed outside the facing region. The outer region is preferably denser than the opposing region. According to this configuration, the member to be heated can be heated more efficiently.

  The porous member may be placed on the upper surface of the fuel battery cell.

  The porous member may be disposed at a distance from the upper surface of the fuel cell.

  The porous member has a recess opening downward, and the upper end of the fuel cell may be fitted in the recess of the porous member.

  According to the present invention, the member to be heated can be sufficiently heated.

The perspective view of a fuel cell stack. The perspective view of a fuel manifold. The perspective view of a fuel cell. The perspective view for demonstrating the operating state of a fuel cell. Sectional drawing of a fuel cell stack. 1 is a schematic diagram of a system including a fuel cell stack. Sectional drawing of a porous member. The top view of a porous member. Sectional drawing of the porous member which concerns on a modification. Sectional drawing of the porous member which concerns on a modification. The schematic diagram of the system containing the fuel cell stack concerning a modification. The schematic diagram of the system containing the fuel cell stack concerning a modification. The schematic diagram of the system containing the fuel cell stack concerning a modification.

[Fuel cell stack]
An embodiment of a fuel cell stack according to the present invention will be described with reference to the drawings.

[Fuel cell stack]
As shown in FIG. 1, the fuel cell stack 100 includes a fuel manifold 1, a plurality of fuel cells 2, and a porous member 3. A reformer (not shown) is disposed above the fuel cell stack 100.

[Fuel manifold]
As shown in FIG. 2, the fuel manifold 1 is configured to supply fuel gas to each fuel cell 2. The fuel manifold 1 is a rectangular parallelepiped housing having a longitudinal direction (z-axis direction). The fuel manifold 1 has a manifold body 11 and a support plate 12. The fuel manifold 1 also has an introduction pipe 13 for introducing fuel gas from the outside into the internal space of the fuel manifold 1.

  The manifold body 11 includes a bottom plate and a side plate and opens upward. The support plate 12 is disposed on the manifold body 11 and is configured to close the upper surface of the manifold body 11. The support plate 12 is configured to support the plurality of fuel cells 2. The support plate 12 has a plurality of insertion holes 14. Each insertion hole 14 is disposed along the longitudinal direction (z-axis direction) of the support plate 12 with a space between each other. The manifold body 11 and the support plate 12 are made of, for example, stainless steel.

  The introduction tube 13 is joined to the support plate 12. The introduction pipe 13 is also made of, for example, stainless steel. The introduction tube 13 is joined to the support plate 12 by welding, for example, in a state of being inserted into a through hole formed in the support plate 12.

[Fuel battery cell]
As shown in FIG. 1, each fuel cell 2 extends upward from the fuel manifold 1. As shown in FIG. 3, each fuel cell 2 includes a support substrate 20 and a plurality of power generation element portions 21. The respective power generation element portions 21 are arranged at intervals from each other along the longitudinal direction (x-axis direction) of the fuel cell 2. Each fuel cell 2 is a so-called horizontal stripe type solid oxide fuel cell (SOFC).

  The support substrate 20 has a flat plate shape having a longitudinal direction (x-axis direction). The support substrate 20 is made of a porous material that does not have electronic conductivity. A plurality of fuel gas passages 22 extending in the longitudinal direction are formed inside the support substrate 20. The fuel gas flow paths 22 are arranged at intervals in the width direction (y-axis direction). The support substrate 20 is made of CSZ (calcia stabilized zirconia), for example.

Each power generation element portion 21 is disposed on each of the main surfaces of the support substrate 20. Each power generating element portion 21 is a laminated fired body in which a fuel electrode, a solid electrolyte membrane, and an air electrode are laminated in this order. The fuel electrode is composed of, for example, NiO (nickel oxide) and YSZ (8YSZ) (yttria stabilized zirconia). The solid electrolyte membrane is made of, for example, YSZ (8YSZ) (yttria stabilized zirconia). The air electrode is made of, for example, LSCF = (La, Sr) (Co, Fe) O ₃ (lanthanum strontium cobalt ferrite). Hereinafter, the lowest temperature at which the fuel cell 2 can generate an electromotive force is referred to as an electromotive force generation temperature TA. The electromotive force generation temperature TA is, for example, 350 to 400 ° C.

As shown in FIG. 4, when a fuel gas (hydrogen gas or the like) is caused to flow in the fuel gas flow path 22 of the support substrate 20 and a gas (such as air) containing oxygen is caused to flow along each main surface of the support substrate 20. In each power generating element portion 21, an electromotive force is generated due to an oxygen partial pressure difference generated between the front and back surfaces of the solid electrolyte membrane (non-power generating state). When the fuel cell 2 in which the electromotive force is generated in this way is electrically connected to an electric circuit (closed circuit) including an external load, a power generation reaction represented by the following formulas (1) and (2) occurs, Current flows in the fuel cell 2 (power generation state). In this power generation state, electric power is taken out from the fuel cell 2. This power generation reaction is an exothermic reaction.
(1/2) · O ₂ + 2e ⁻ → O ²⁻ (where: air electrode) (1)
H ₂ + O ²⁻ → H ₂ O + 2e ⁻ (in the fuel electrode) (2)

  When the temperature of the fuel cell 2 is in the vicinity of the electromotive force generation temperature TA, the fuel cell 2 can generate an electromotive force, but the internal electric resistance of the fuel cell 2 is large. Therefore, a sufficient output cannot be taken out from the fuel battery cell 2. The internal electrical resistance of the fuel cell 2 decreases as the temperature of the fuel cell 2 increases. Further, the electromotive force generated by the fuel battery cell 2 hardly changes depending on the temperature. Therefore, as the temperature of the fuel cell 2 rises from the electromotive force generation temperature TA, the output that can be taken out from the fuel cell 2 increases. The temperature of the fuel cell 2 from which a sufficient output can be extracted from the fuel cell 2 is referred to as an operating temperature T1. The operating temperature T1 is, for example, 600 to 800 ° C. In the operation state of the fuel battery cell 2, the temperature of the fuel battery cell 2 is controlled so as to be maintained in the vicinity of the operating temperature T1. Thereby, a desired output can be stably taken out from the fuel cell 2. As described above, the planar fuel cell has been described as the fuel cell, but the fuel cell may be another type of fuel cell such as a cylindrical shape.

  As shown in FIG. 5, the lower end portion of each fuel cell 2 is inserted into the insertion hole 14 of the support plate 12. That is, each fuel cell 2 extends upward (x-axis positive direction) from the support plate 12. The fuel cells 2 are arranged at intervals from each other along the longitudinal direction (z-axis direction) of the fuel manifold 1. The upper end portion of each fuel cell 2 is a free end.

  Each fuel cell 2 is bonded to the support plate 12 by the first bonding material 4. The first bonding material 4 extends in an annular shape along the root portion of the fuel cell 2. The first bonding material 4 has a gas seal function. That is, the first bonding material 4 seals so that the fuel gas in the fuel manifold 1 does not leak from the gap between the fuel cell 2 and the support plate 12. The fuel gas flow path 22 of the fuel battery cell 2 communicates with the inside of the fuel manifold 1.

The first bonding material 4 is made of crystallized glass, for example. As the crystallized glass, for example, a SiO ₂ —B ₂ O ₃ system, a SiO ₂ —CaO system, or a MgO—B ₂ O ₃ system can be adopted, but a SiO ₂ —MgO system is most preferable.

  A current collecting member 5 is disposed between adjacent fuel cells 2. Specifically, the current collecting member 5 is disposed at the lower end of the fuel cell 2. The current collecting member 5 electrically connects adjacent fuel cells 2. Specifically, the current collecting member 5 electrically connects the fuel electrode of one fuel cell 2 and the air electrode of the other fuel cell 2. The current collecting member 5 is joined to each fuel cell 2 via the second joining material 6.

The current collecting member 5 is conductive and is made of, for example, a sintered body of oxide ceramics. Examples of such oxide ceramics include perovskite oxide and spinel oxide. Examples of the perovskite oxide include (La, Sr) MnO ₃ , (La, Sr) (Co, Fe) O _{3, and the} like. Examples of the spinel oxide include (Mn, Co) ₃ O ₄ , (Mn, Fe) ₃ O _{4, and the} like. For example, the current collecting member 302 does not have flexibility. In addition, the current collection member 5 may be comprised with the metal mesh etc., for example.

The second bonding material 6 is, for example, conductive and is formed of (Mn, Co) ₃ O ₄ -based conductive ceramics or a noble metal. Specifically, the second bonding material 6 is formed of at least one selected from the group consisting of (Mn, Co) ₃ O ₄ , (La, Sr) (Co, Fe) O ₃ , Pt, and Ag. The

  The power generating element portions 21 are electrically connected to each other by an electrical connection portion (not shown). In addition, on the upper end side of the fuel cell 2, the power generation element portion 21 formed on one surface of the support substrate 20 and the power generation element portion 21 formed on the other surface are electrically connected by the second current collecting member 7. Has been. In addition, each electric power generation element part 21 is connected in series.

[Porous member]
As shown in FIG. 6, the porous member 3 is disposed so as to cover the upper end portion of each fuel cell 2. In detail, the porous member 3 is arrange | positioned so that the discharge side edge part of the fuel gas flow path 22 of each fuel cell 2 may be covered.

  The porous member 3 is disposed above each fuel battery cell 2. The porous member 3 is placed on the upper surface of each fuel cell 2, for example. The porous member 3 may or may not be fixed to the upper surface of each fuel cell 2. A reformer 101 is disposed above the porous member 3. The reformer 101 and the fuel cell stack 100 are accommodated in a heat resistant container (not shown).

As shown in FIGS. 7 and 8, the porous member 3 includes a plurality of flow paths 31 extending in the vertical direction and porous partition walls 32 that partition the flow paths 31. For example, the porous member 3 has a honeycomb structure. The channel area of each channel 31 is smaller than the channel area of each gas channel 22 of the fuel cell 2. For example, the channel area of each channel 31 of the porous member 3 is about 1 to 25 mm ² , and the interval (pitch) between adjacent channels 31 is about 1 to 10 mm. The thickness (the dimension in the x-axis direction) of the porous member 3 is, for example, about 5 to 100 mm, and preferably about 3 to 30 mm.

  The partition wall 32 is made of, for example, a porous ceramic material. Examples of the porous ceramic material include silicon carbide, zirconia, alumina, cordierite, and the like. Is mentioned. In this case, the porosity of the porous ceramic material is 20 to 80% by volume.

The side part 33 of the porous member 3 is denser than the inside. Specifically, the side surface portion 33 of the porous member 3 is denser than the partition wall 32. For example, the side surface portion 33 may be made of the same material as the partition wall 32. In this case, the porosity of the side surface portion 33 is formed to be lower than the porosity of the partition wall 32. For example, the porosity of the side part 33 can be 5 to 70 volume%. Moreover, the side part 33 can also be comprised with a glass material. Examples of the glass material include crystallized glass such as SiO ₂ —MgO.

[Method of operation]
As shown in FIG. 6, the reformer 101 includes an inlet pipe 102 and an outlet pipe 103. The outlet pipe 103 is connected to the introduction pipe 13 of the fuel manifold 1. The reformer 101, the inlet pipe 102, and the outlet pipe 103 are made of a heat resistant metal. The reformer 101 contains a noble metal catalyst and a base metal catalyst for promoting a reaction for reforming a gas such as city gas.

Due to the presence of the noble metal catalyst or the like, specifically, a steam reforming reaction of methane occurs in the reformer 101 as shown in the following equation (3). By this reaction, fuel gas (hydrogen gas H ₂ ) used as fuel for the fuel cell 2 can be generated in the reformer 101.
CH ₄ + H ₂ O → CO + 3H ₂ (3)

  Hereinafter, the lowest temperature at which the steam reforming reaction can occur is referred to as the reforming temperature T2. When the temperature of the reformer 101 becomes equal to or higher than the reforming temperature T2, a steam reforming reaction occurs in the reformer 101. This steam reforming reaction is an endothermic reaction. Therefore, when the steam reforming reaction occurs, the reformer 101 absorbs heat.

  When the fuel cell stack 100 is in an operating state (that is, a state in which the temperature of the fuel cell stack 100 is maintained in the vicinity of the operating temperature T1), the reformer 101 has a temperature T3 that is higher than the reforming temperature T2 and lower than the operating temperature T1 (hereinafter referred to as the temperature T3). , Referred to as “operating temperature T3”). Thereby, the reformer 101 can stably generate the steam reforming reaction.

  The fuel gas generated by the reformer 101 is supplied to the gas flow path 22 of each fuel cell 2 through the introduction pipe 13 and the fuel manifold 1 and is used for power generation of each power generation element unit 21. Then, unreacted fuel gas that has not been used in each power generation element unit 21 is discharged from the upper end of each gas flow path 22.

  The fuel gas discharged from the gas flow path 22 of each fuel cell 2 is introduced into each flow path 31 of the porous member 3. In addition, air supplied between the fuel cells 2 is also introduced into the flow paths 31 of the porous member 3. The fuel gas and air introduced into each flow path 31 are mixed through the partition wall 32. For this reason, the combustion form of the fuel gas is premixed combustion, and stable combustion can be achieved. As a result, the reformer 101 can be sufficiently heated.

[Modification]
As mentioned above, although embodiment of this invention was described, this invention is not limited to these, A various change is possible unless it deviates from the meaning of this invention.

Modification 1
In the said embodiment, although each flow path 31 of the porous member 3 penetrated the up-down direction, it is not specifically limited to this. For example, as shown in FIG. 9, the porous member 3 may have a plurality of resistance portions 34. The resistance unit 34 is disposed in a part of the plurality of channels 31. The resistance portion 34 is configured to provide resistance to the flow of fuel gas that flows upward in the flow path 31. For example, the resistance portion 34 is made of cordierite, silicon nitride, crystallized glass, or the like. The porosity of the resistance portion 34 is lower than the porosity of the partition wall 32. According to this configuration, when the fuel gas or air flowing in the flow path 31 in which the resistance portion 34 is disposed reaches the resistance portion 34, the fuel gas or air flows to the adjacent flow path 31 via the partition wall 32. As a result, mixing of fuel gas and air can be further promoted.

Modification 2
In the said embodiment, although the porous member 3 had the honeycomb structure, the structure of the porous member 3 is not limited to this. For example, as shown in FIG. 10, the porous member 3 may have a sponge shape. In this case, the fuel gas flows upward in the porous member 3. The porous member 3 may have a resistance portion 34 that serves as a resistance of the fuel gas flowing upward. For example, the resistance part 34 of the fuel gas may be configured by making the porosity of a part of the porous member 3 lower than the porosity of the other part. According to this configuration, when the fuel gas or air flowing in the flow path 31 in which the resistance portion 34 is disposed reaches the resistance portion 34, the flow direction is changed. As a result, mixing of fuel gas and air can be further promoted.

Modification 3
As shown in FIG. 11, the upper surface of the porous member 3 may have a facing region 35 that faces the reformer 101 and an outer region 36 that is disposed outside the facing region 35. The outer region 36 does not face the reformer 101. The outer region 36 is denser than the facing region 35. For example, in the outer region 36, a dense film is formed and each flow path 31 is closed. As a result, fuel gas and air are not discharged from the outer region 36, and fuel gas and air are discharged only from the facing region 35. Therefore, the reformer 101 can be heated more efficiently.

Modification 4
Moreover, in the said embodiment, although the porous member 3 is mounted on each fuel cell 2, the arrangement | positioning method of the porous member 3 is not limited to this. For example, as shown in FIG. 12, the porous member 3 may have a plurality of recesses 37. Each recess 37 opens downward. The upper end portion of each fuel cell 2 is fitted in each recess 37.

  Further, as shown in FIG. 13, the porous member 3 may be disposed with a space from the upper surface of the fuel cell 2. In this case, the porous member 3 is supported by a support member (not shown).

Modification 5
In the above embodiment, the fuel cell stack 100 is heating the reformer 101 as a member to be heated, but the member to be heated of the fuel cell stack 100 is not limited to the reformer 101. For example, the air flowing around may be a member to be heated of the fuel cell stack 100.

1: Fuel manifold 11: Gas flow path 12: Support substrate 2: Fuel cell 20: Support substrate 21: Power generation element part 22: Gas flow path 3: Porous member 31: Flow path 32: Partition wall 33: Side part 34: Resistor 35: opposing region 36: outer region 100: fuel cell stack 101: reformer

Claims (9)

A fuel manifold;
A fuel cell having a support substrate, a gas flow path extending in the vertical direction in the support substrate, and a power generation element portion disposed on the support substrate, and extending upward from the fuel manifold;
A porous member disposed above the fuel cell so as to cover the discharge side end of the gas flow path;
With
The porous member has a side portion denser than the inside,
Fuel cell stack.
The porous member includes a plurality of flow paths extending in the vertical direction, a porous partition wall that divides the flow paths, and a resistance that is disposed in a part of the flow paths and serves as a resistance to a gas flow that flows upward. And having a part,
The fuel cell stack according to claim 1.
The porosity of the resistance portion is lower than the porosity of the partition wall,
The fuel cell stack according to claim 2.
The porous member has a resistance portion that serves as a resistance of a gas flow flowing upward in the porous member.
The fuel cell stack according to claim 1.
The porosity of the resistance portion is lower than the porosity of the other part of the porous member,
The fuel cell stack according to claim 4.
The porous member is disposed below the member to be heated,
The upper surface of the porous member has a facing region facing the heating target member, and an outer region disposed outside the facing region,
The outer region is denser than the opposing region;
The fuel cell stack according to any one of claims 1 to 5.
The porous member is placed on the upper surface of the fuel cell.
The fuel cell stack according to any one of claims 1 to 6.
The porous member is disposed at a distance from the upper surface of the fuel cell.
The fuel cell stack according to any one of claims 1 to 6.
The porous member has a recess opening downward,
The upper end portion of the fuel cell fits into the recess of the porous member,
The fuel cell stack according to any one of claims 1 to 6.

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