JP4512845B2 - Fuel cell manifold mechanism - Google Patents

Description

  The present invention relates to a fuel cell having a laminated structure, and more particularly to a fuel cell manifold mechanism with improved sealing performance.

  Solid oxide fuel cells (SOFC) are being developed as third-generation fuel cells for power generation. Currently, three types of solid oxide fuel cells have been proposed: a cylindrical type, a monolith type, and a flat plate type, all of which have a solid electrolyte layer made of an oxide ion conductor as an air electrode layer (cathode) from both sides. ) And the fuel electrode layer (anode). A plurality of power generation cells made of this laminate are alternately stacked with separators with a fuel electrode current collector and an air electrode current collector interposed therebetween to constitute a fuel cell stack.

For example, generally, the solid electrolyte layer is composed of stabilized zirconia (YSZ) or the like to which yttria is added, the fuel electrode layer is composed of a metal such as Ni or Co, or a cermet such as Ni—YSZ or Co—YSZ, and air. electrode layer is composed of LaMnO _3, LaCoO ₃ or the like, the fuel electrode current collector is composed of a sponge-like porous sintered metal plate such as Ni-base alloy, the air electrode current collector is spongy such as Ag-based alloy The separator is made of stainless steel or the like.

In the solid oxide fuel cell, an oxidant gas (oxygen) is supplied to the air electrode layer side and a fuel gas (H ₂ , CO, CH _4, etc.) is supplied to the fuel electrode layer side as a reaction gas. The air electrode layer and the fuel electrode layer are both porous so that the gas can reach the interface with the solid electrolyte layer.
Oxygen supplied to the air electrode layer passes through the pores in the air electrode layer and reaches the vicinity of the interface with the solid electrolyte layer, and receives electrons from the air electrode layer at this portion to receive oxide ions (O ²⁻ ). Is ionized. The oxide ions diffuse and move in the solid electrolyte layer toward the fuel electrode layer. Oxide ions that have reached the vicinity of the interface with the fuel electrode layer react with the fuel gas at this portion to generate reaction products (H ₂ O, CO _2, etc.), and discharge electrons to the fuel electrode layer. This electron can be taken out as an electromotive force in an external circuit of another route.

  By the way, in the fuel cell, a manifold is provided inside the fuel stack as a gas supply mechanism that introduces a reaction gas from the outside and distributes it to each of the stacked power generation cells. This manifold is a tubular body in which a ring member called a manifold ring is interposed between the separators and extends in the stacking direction while joining the separators. The manifold is composed of two systems for fuel gas introduction and oxidant gas introduction.

The reaction gas flowing through these manifolds is distributed at the junction with the separator for each stack, and is supplied to the electrode layer of the power generation cell through a gas passage provided in the separator. For this reason, the connecting portion between the manifold ring and the separator is required to have a high sealing performance (air tightness) that does not cause gas leakage. In order to prevent short circuit, individual manifold rings are required to have reliable electrical insulation.
Such a manifold mechanism is disclosed in Patent Document 1 and Patent Document 2, for example.
Japanese Patent Application Laid-Open No. 7-201353 JP-A-8-279364

  By the way, as described above, the manifold mechanism is required to have high sealing performance and reliable electrical insulation. Conventionally, as a means to ensure insulation between separators, a ceramic manifold ring has been used, and a mechanism that seals the joint with the separator with a glass material to prevent gas leakage has been adopted. Because there is a large difference in the coefficient of thermal expansion between this separator and this ceramic manifold ring, the stress caused by the difference in thermal expansion and the load generated by stacking during repeated heating (heating cycle) during fuel cell operation There is a problem that the ring is broken or the joint part is peeled off, and the sealing part has a problem in sealing performance because the liquid material is melted at the operating temperature of the fuel cell. Was leaving.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a fuel cell manifold mechanism having excellent durability and high gas sealability with respect to the thermal cycle of the fuel cell. .

That is, the present invention according to claim 1 is a fuel cell in which a power generation cell configured by arranging electrode layers on both surfaces of a solid electrolyte layer and a plurality of separators having a reaction gas passage inside are alternately stacked. A stack and an insulating manifold ring communicating with the gas passage through a gas introduction hole provided in the thickness direction of the separator are provided, and a reaction gas is supplied to each electrode layer through the gas passage of the separator. In the fuel cell manifold mechanism configured as described above, the manifold ring has a multiple structure in which a plurality of insulative ring members are concentrically combined and has a fine flow resistance at a surface portion in contact with the separator. grooves is characterized in that it is formed with a plurality of such.
In this configuration, by providing a multiple structure using a plurality of insulating ring members, electrical insulation between the separators can be obtained reliably, and even if some ring members are cracked, there is no other crack. Sealing performance is ensured by the ring member, and there is no fear of gas leakage. In addition, due to the differential pressure effect by the fine grooves, high gas sealability (air tightness) can be obtained at the contact portion between the separator and the manifold ring.

According to a second aspect of the present invention, in the fuel cell manifold mechanism according to the first aspect, the plurality of ring members constituting the manifold ring are all made of the same material. Yes.
By constituting a plurality of ring members with the same material, thermal expansion of each ring member can be eliminated. Thereby, the thermal stress at the time of a thermal cycle can be avoided and the crack of each ring member can be prevented.

Further, according to a third aspect of the present invention, there is provided the fuel cell manifold mechanism according to the first or second aspect, wherein the manifold ring is positioned on a surface portion of the separator in contact with the manifold ring. It is characterized by providing a concave portion.
Since the manifold ring can be positioned and arranged easily and accurately in the power generation cell stacking process, the assembly of the fuel cell stack is simplified, the number of assembly steps can be reduced, and the displacement of the manifold ring can be avoided. Battery performance degradation due to gas leakage can be prevented.

As described above, according to the invention described in claim 1, since the manifold ring has a multiple structure in which a plurality of insulating rings are concentrically combined, a part of the plurality of ring members is a ring member. Even if a crack occurs, the sealing performance of the manifold is reliably ensured by the presence of other ring members that are not cracked, and there is no risk of gas leakage. In addition, since a plurality of fine grooves are formed in the surface portion of the manifold ring in contact with the separator, a high sealing performance can be obtained at the contact portion between the separator and the manifold ring due to the differential pressure effect by the grooves.

  According to the invention of claim 2, since the plurality of ring members constituting the manifold ring are all made of the same material, the difference in thermal expansion of each ring member in the thermal cycle can be eliminated. Thus, it is possible to form a manifold ring that can prevent cracking of each ring member due to thermal stress and can withstand severe thermal cycles.

  According to the third aspect of the present invention, since the concave portion is provided in the surface portion of the separator that is in contact with the manifold ring, each manifold ring can be positioned easily and accurately during stacking. As a result, the assembly of the fuel cell stack can be simplified and the number of man-hours can be reduced, and the displacement of the manifold ring can be avoided, and the deterioration of the battery performance due to gas leakage can be prevented.

  Embodiments of a fuel cell according to the present invention will be described below with reference to the drawings.

  FIG. 1 is an exploded perspective view showing a configuration of a flat plate type solid oxide fuel cell stack to which the present invention is applied, and FIG. 2 is a sectional view taken along line II-II in FIG.

  As shown in FIG. 1, a fuel cell stack 1 includes a power generation cell 5 configured by disposing a fuel electrode layer and an air electrode layer on both sides of a solid electrolyte layer, and a fuel electrode current collector disposed outside the fuel electrode layer. 6, a single cell composed of an air electrode current collector 7 disposed outside the air electrode layer, and a separator 8 disposed outside each of the current collectors 6, 7. 15 and a large number of oxidant manifold rings 16 are stacked. In addition, each member which comprises a single cell can use the same thing as the past.

  Here, the separator 8 is composed of a square stainless steel plate having a thickness of about several millimeters (eg, a laminated structure of two stainless steel plates in this embodiment) having an Ag plating treatment for preventing oxidation. A fuel gas passage 9 through which the fuel gas flows and an oxidant gas passage 10 through which the oxidant gas flows are formed. However, as shown in FIG. 1, only the fuel gas passage 9 is formed for the separator 8 located at the lowermost portion, and only the oxidant gas passage 10 is formed for the uppermost separator 8.

One end of the fuel gas passage 9 communicates with a fuel gas introduction hole 13 provided at the center of the left end of the separator 8, and the other end communicates with a gas discharge hole 11 in the center of the separator facing the fuel electrode current collector 6. is doing. Further, one end of the oxidant gas passage 10 communicates with a fuel gas introduction hole 14 provided at the center of the right end of the separator 8, and the other end of the gas discharge at the center of the separator facing the air electrode current collector 7. It communicates with the hole 12. These gas introduction holes 13 and 14 have an elliptical shape.
Note that only the oxidant gas introduction hole 14 is formed in the uppermost separator 8, and the oxidant gas introduction hole 14 is opened only on the lower side. Each of the gas introduction holes 13 and 14 except for the upper and lower ends penetrates in the plate thickness direction.
The lowermost separator 8 has gas introduction passages 24 and 25 for introducing a reaction gas from the outside, and its thickness is thick. Among these, a fuel gas introduction passage through which fuel gas is supplied 25 communicates with the fuel gas introduction hole 13, and an oxidant gas introduction path 24 through which oxidant gas is supplied communicates with the oxidant gas introduction hole 14.

  A fuel manifold ring 15 through which fuel gas flows is disposed at the opening of the fuel gas introduction hole 13, and an oxidant manifold ring 16 through which oxidant gas flows through the opening of the oxidant gas introduction hole 14. Is arranged. By stacking single cells to form a stack, a large number of manifold rings 15 and 16 are connected in the vertical direction (stacking direction) via the gas introduction holes 13 and 14 of the separator 8 to form a tubular manifold. It is like that. However, the oxidant gas introduction hole 14 of the separator 8 located at the uppermost part is not a through hole, but has a hole structure that opens only on the lower side as described above. A fuel gas and an oxidant gas supplied from the outside flow through the two manifolds.

  Further, as shown in FIG. 2, elliptical recesses 17 for correctly positioning the manifold rings 15 and 16 on the separator surface are formed at the opening edges of the gas introduction holes 13 and 14, respectively. . By providing the concave portion 17, it is possible to arrange the gas introduction holes 13 and 14 and the manifold rings 15 and 16 without misalignment with each other, and stacking can be easily performed. By eliminating the misalignment, the sealing performance of the joint portion between the separator 8 and the manifold rings 15 and 16 is improved, and gas leakage can be completely prevented.

As shown in FIG. 3A, the fuel manifold ring 15 and the oxidant manifold ring 16 have an elliptical shape corresponding to the opening shape of the gas introduction holes 13 and 14, respectively.
The reason why each gas flow path is elliptical is that the length of the separator 8 is not extended and the volume of the gas flow path can be increased as compared to the case of a circular shape, and each gas with respect to the deviation or inclination when single cells are stacked. Of course, it is possible to unify all of them into a circular shape, for example, because the alignment between the introduction holes 13 and 14 and the manifold rings 15 and 16 can be made better.

  As shown in FIG. 3B, these manifold rings 15 (16) each have a triple structure ring structure in which a total of three ring members 15a to 15c (16a to 16c) are fitted concentrically. And, as the ring material, ceramic (for example, alumina) having a relatively low coefficient of thermal expansion and excellent in electrical insulation, thermal shock resistance and the like is used to ensure electrical insulation between the separators.

In addition, if there is a multiple ring structure, even if one or two of the ring members are cracked, the presence of the ring member that is not cracked ensures the sealing performance as the manifold ring 15 (16). Therefore, there is no concern that gas leaks out of the manifold from the cracks in the ring member where the cracks have occurred.
Further, by configuring all the ring members 15a to 15c (16a to 16c) with the same insulating material such as alumina, it is possible to eliminate the difference in thermal expansion of each ring member during the thermal cycle. The ring members 15a to 15c (16a to 16c) can be prevented from cracking due to thermal stress, and the manifold ring 15 (16) that can withstand severe thermal cycles can be configured.

Further, as shown in FIG. 4, in the manifold ring 15 (16) shown in FIG. 3, a large number of fine grooves 18 (the groove portions are emphasized in FIG. 4) are formed on the surface portion in contact with the separator 8. Good.
Since the fine groove 18 provided on the contact surface of the manifold ring 15 (16) has a large flow resistance, even if a reaction gas is introduced into each manifold, a differential pressure effect by the groove 18 causes the inside of the groove. The gas does not flow into the gas, the gas leakage at the contact surface between the separator 8 and each manifold ring 15 (16) is prevented, and the gas sealing performance at the contact portion is higher than when the smooth surfaces contact each other. Can be a thing.

  Next, FIG. 5 shows assembly of a fuel cell stack using the manifold mechanism of the present embodiment.

When assembling, the fuel manifold ring 15 is disposed at the opening of the fuel gas introduction hole 13 of the separator 8, and the oxidant manifold ring 16 is disposed at the opening of the oxidant gas introduction hole 14. Are stacked.
The assembled fuel cell stack 1 is supported at four corners by four fastening rods 22 inserted through mounting holes 23 provided at the corners of the separators 8 and tightened in the stacking direction by bolts or the like (not shown). A plurality of single cells are brought into close contact with each other and fixed together.
As a result, the manifold rings 15 and 16 are connected in the vertical direction (stacking direction) via the gas introduction holes 13 and 14 of the separator 8, respectively, so that two types of tubular manifolds for fuel gas and oxidant gas ( The connected state is not shown).

  In the assembly of the fuel cell described above, the positioning recesses 17 are provided at the opening edge portions of the gas introduction holes 13 and 14, respectively. Therefore, the arrangement of the manifold rings 15 and 16 when stacking single cells is easy. And it can arrange | position in the exact site | part on a separator surface, without both hole positions shifting | deviating.

Further, as described above, the fuel electrode current collector 6 and the air monopolar current collector 7 interposed between the separators are each composed of a sponge-like porous sintered metal. These sponge-like members are elastically deformed, and the manifold rings 15 and 16 are pressed and sandwiched between the upper and lower separators 8 with a certain degree of elasticity. The movement of the manifold rings 15 and 16 due to is restrained, and the manifold rings 15 and 16 can be prevented from being displaced after stack assembly.
Thus, in the present invention, there is no need for a special member for fixing the manifold rings 15 and 16 at the time of assembly, and the elastic fixing structure using the elastic deformation of the current collectors 6 and 7 by tightening is used. The stack assembly is further simplified.

In the fuel cell stack 1 having the above-described configuration, the fuel gas and the oxidant gas supplied from the outside are oxidized with the fuel gas introduction path 25 and the oxidation gas through the openings 25a and 24a provided in the side portions of the separator 8 located at the lowermost layer. They are individually introduced into the fuel gas manifold and the oxidant gas manifold via the agent gas introduction passage 24.
Although not shown, a fuel gas supply pipe for supplying fuel gas from the outside is connected to the opening 25a, and an oxidant gas supply pipe for supplying oxidant gas from the outside is connected to the opening 24a. It is assumed that The reaction gases introduced from the gas supply pipes are distributed from the gas introduction holes 13 and 14 of the respective layers (single cells) in the course of flowing through the pipes of the manifolds extending in the longitudinal direction. The gas is supplied to the electrode portion of each power generation cell 5 through each gas passage.

That is, the fuel gas in the fuel gas manifold is introduced into the fuel gas passage 9 from the fuel gas introduction hole 13 of each separator 8 and discharged from the fuel gas discharge hole 11 at the end of the passage to face the fuel electrode current collector 6. And pass through here while diffusing to reach the fuel electrode layer of the power generation cell 5.
On the other hand, the oxidant gas in the oxidant gas manifold is introduced into the oxidant gas passage 10 from the oxidant gas introduction hole 14 of each separator 8 and is discharged from the oxidant gas discharge hole 12 at the end of the passage to face the air. It is supplied to the polar current collector 7 and passes through here while diffusing and reaches the air electrode layer of the power generation cell 5.
Hereinafter, the electrochemical reaction in each single cell is as described in the section of the prior art, and the high temperature exhaust gas generated by this electrochemical reaction is discharged from the single cell to the outside of the stack through a predetermined exhaust route. Will be.

  Here, the manifold rings 15 and 16 constituting each manifold and the gas introduction holes 13 and 14 of the separator 8 are surely aligned with the positioning recesses 17 provided on the separator side, and The contact portion between the two has a high sealing performance due to the synergistic effect of the differential pressure due to the fine groove 18 on the contact surface, and there is no fear of gas leakage from the contact portion.

In addition, since each manifold ring 15 and 16 has a multiple structure, even if some of the ring members are cracked, damage is covered by other ring members that are not cracked. Is secured.
In this embodiment, each manifold ring 15 and 16 has a multiple structure of three ring members, but it is needless to say that the number is not limited to three.

1 is an exploded perspective view showing a configuration of a fuel cell stack according to the present invention. II-II sectional drawing of FIG. The manifold ring used for the fuel cell stack of this invention is shown, (a) is a perspective view, (b) is a longitudinal cross-sectional view. The side view of the manifold ring different from FIG. The perspective view which shows the assembly of the fuel cell stack to which this invention was applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell stack 5 Power generation cell 8 Separator 9 Fuel gas passage 10 Oxidant gas passage 13 Fuel gas introduction hole 14 Oxidant gas introduction hole 15 Fuel manifold ring 15a-15c Ring member 16 Oxidant manifold ring 16a-16c Ring member 17 Recess 18 Groove

Claims (3)

Provided in the thickness direction of the separator, a power cell constructed by arranging electrode layers on both surfaces of the solid electrolyte layer and a fuel cell stack constructed by alternately laminating a plurality of separators each having a reaction gas passage inside In a fuel cell manifold mechanism comprising an insulating manifold ring communicating with the gas passage through a gas introduction hole and configured to supply a reaction gas to each electrode layer through the gas passage of the separator.
The manifold ring has a multiple structure in which a plurality of insulative ring members are concentrically combined, and a plurality of fine grooves having a large flow resistance are formed in a surface portion in contact with the separator. A fuel cell manifold mechanism. 2. The fuel cell manifold mechanism according to claim 1, wherein the plurality of ring members constituting the manifold ring are all made of the same material. 3. The fuel cell manifold mechanism according to claim 1, wherein a concave portion for positioning the manifold ring is provided in a surface portion of the separator in contact with the manifold ring.

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