JP2006253047A - Fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable operation of a fuel cell formed by laminating a plurality of fuel cell units at a high fuel utilization factor without requiring a special sealing structure. <P>SOLUTION: This fuel cell has a fuel cell laminate 3, fuel gas manifolds 5a, 5b for supplying a fuel gas to a fuel gas passage, an oxidizer gas manifold for supplying an oxidizer gas to an oxidizer gas passage. The fuel gas manifold has a first fuel gas chamber 7, a second fuel gas chamber 13, and a third gas chamber 8 which extend in the laminated direction of fuel cell units. The fuel gas passage has a first fuel gas passage connected to the first fuel gas chamber 7 and the second fuel gas chamber 13, a second fuel gas passage connected to the second fuel gas chamber 13 and the third fuel gas chamber 8 and disposed in a surface different from the first fuel gas passage. The fuel gas supplied to the fuel cell passes through the first fuel gas chamber 7, the first fuel gas passage, the second fuel gas chamber 13, the second fuel gas passage, and the third fuel gas chamber 8 in this order, and is discharged to the outside of the fuel cell. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell, and more particularly to a fuel cell in which a plurality of fuel cells are stacked.

  A typical fuel cell is composed of a unit cell in which an electrolyte is sandwiched between two gas diffusion electrodes, and a plurality of fuel cells each having a fuel gas flow path and an oxidant gas flow path disposed in contact with the gas diffusion electrodes, respectively. And a gas manifold for supplying fuel and oxidant to the fuel gas flow path and the oxidant gas flow path. Then, a fuel such as hydrogen and an oxidant such as air are supplied to the fuel cell stack and reacted electrochemically to convert the chemical energy of the fuel directly into electrical energy and take it out.

  Here, by reducing the total amount of fuel that is not used in the reaction of the fuel cell and discharged outside the fuel cell with respect to the total amount of supplied fuel, the fuel utilization rate approaches 100%. It is possible to improve the energy conversion efficiency with respect to the total amount. However, as described above, the fuel cell stack is composed of a plurality of single fuel cells having a large number of fuel gas flow passages and oxidant gas flow passages, and a large amount of fuel flows due to the distribution unbalance of the fuel flowing through the fuel flow paths. The part and the part which flows with little fuel will occur. For this reason, if the fuel utilization rate is close to 100% as a whole, the fuel utilization rate partially reaches 100%, and the carbon material constituting the electrode substrate within the fuel cell alone due to local fuel shortage Corrosion may occur and the fuel cell itself may be damaged. Therefore, it is usually operated at a fuel utilization rate of about 80%.

As a solution to these problems, in general, in a fuel cell system composed of a plurality of fuel cells, fuel discharged from a fuel cell installed upstream of the fuel gas distribution path is used as fuel gas distribution. There is a method of increasing the fuel utilization rate of the entire system by using it again in another fuel cell installed on the downstream side of the path. Further, in a single fuel cell stack, the internal space of the fuel gas manifold is partitioned into a fuel inlet side manifold space and a fuel outlet side manifold space by a partition plate installed in parallel with the fuel cell unit, and the fuel inlet side manifold space There has been proposed a method in which fuel gas that has passed through an adjacent fuel cell unit and has not been used is again passed through a fuel cell unit adjacent to the fuel outlet side manifold space (see, for example, Patent Documents 1 and 2).
Japanese Patent Laid-Open No. 5-190195 (FIG. 1) Japanese Examined Patent Publication No. 62-23434 (Fig. 4)

  However, in the methods disclosed in Patent Documents 1 and 2, it is generally necessary to form a seal portion with the gas manifold partition plate on the side surface portion of the thin fuel cell alone, and the fuel cell stack and the gas manifold partition plate are formed. In order to ensure sufficient sealing performance at the contact surface of the fuel cell, either a thick plate spacer is laminated on the contact portion of the fuel cell stack facing the partition plate of the gas manifold to secure the seal width, or the fuel cell alone It is necessary to project a plate-like seal portion from the end portion of the gas pipe and seal it by sandwiching a sealing material between the tip thereof and the partition plate of the gas manifold or the inner wall of the gas manifold. In this case, as described above, there is a problem that it is necessary to install a special seal structure component.

  The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is a fuel cell in which a plurality of fuel cells are stacked without requiring a special seal structure. This is to enable operation at a high fuel utilization rate.

  In order to achieve the above object, the fuel cell of the present invention includes a unit cell in which both surfaces of a plate-like electrolyte are sandwiched between two plate-like gas diffusion electrodes, and a surface of the gas diffusion electrode. A fuel cell stack formed by laminating a plurality of single fuel cells each having a fuel gas flow path and an oxidant gas flow path configured to allow fuel gas and oxidant gas to flow, and the fuel gas flow path A fuel cell having a fuel gas manifold for supplying fuel gas to the oxidant gas flow passage and an oxidant gas manifold for supplying oxidant gas to the oxidant gas flow passage, wherein the fuel gas manifold is arranged in a stacking direction of the fuel cells alone. A first fuel gas chamber, a second fuel gas chamber, and a third fuel gas chamber extending respectively; and the fuel gas flow passage communicates with the first fuel gas chamber and the second fuel gas chamber, 3. The first fuel gas flow passage not connected to the fuel gas chamber, the first fuel gas flow passage connected to the second fuel gas chamber and the third fuel gas chamber, and not connected to the first fuel gas chamber. A second fuel gas flow passage disposed in a different plane from the first fuel gas chamber, wherein the fuel gas supplied to the fuel cell is a first fuel gas chamber, a first fuel gas flow passage, a second fuel gas chamber, The second fuel gas flow path and the third fuel gas chamber are sequentially passed through the fuel cell and discharged to the outside of the fuel cell.

  According to the present invention, it is possible to operate at a high fuel utilization rate by dividing the internal space of the fuel gas manifold without requiring a special seal structure, and sequentially flowing the fuel gas through these fuel gas spaces. A fuel cell can be provided.

  Hereinafter, various embodiments of a fuel cell according to the present invention will be described with reference to the drawings. Here, the same or similar components are denoted by common reference numerals, and redundant description is omitted.

[Embodiment 1]
Embodiment 1 of a fuel cell according to the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing the overall configuration of the fuel cell of Embodiment 1. FIG. However, the oxidant gas manifold (see FIG. 2) and the cooling water manifold are not shown in FIG. FIG. 2 is a plan view of this fuel cell.

  The fuel cell according to Embodiment 1 includes a fuel cell stack 3 in which a plurality of fuel cells 1 and fuel cells 2 are stacked, current collectors 4 installed above and below the fuel cell stack 3, fuel, and the like. Fuel gas manifolds 5a and 5b installed on the side surface of the battery stack 3 for supplying fuel gas to the fuel gas flow passage of the fuel cell, and an oxidant gas manifold 30 and a cooling water manifold (not shown). Is done.

  The fuel gas manifolds 5 a and 5 b are disposed on both sides of the fuel cell stack 3. An oxidant gas manifold 30 is disposed on both sides of the fuel cell stack 3 in a direction perpendicular to the direction in which the fuel gas manifolds 5a and 5b are arranged so that the oxidant is supplied to each fuel cell unit 1 and 2. It has become.

  As shown in FIG. 3, the fuel cell unit 1 includes a first fuel gas separator plate having a first fuel gas flow passage 10 disposed in contact with a unit cell 33 in which an electrolyte 31 is sandwiched between two gas diffusion electrodes 32. 11 and an oxidant gas separator plate 37 having an oxidant gas flow passage 36. Similarly, the fuel cell unit 2 includes a second fuel gas separator plate 15 having a second fuel gas flow passage 14 and an oxidant gas separator plate 37 having an oxidant gas flow passage 36 disposed in contact with the unit cells. . The adjacent first fuel gas separator plate 11 or the second fuel gas separator plate 15 and the oxidant gas separator plate 37 may be formed as an integral separator plate.

  The gas chamber inside the fuel gas manifold 5a is divided into a first fuel gas chamber 7 and a third fuel gas chamber 8 penetrating in the stacking direction by a partition plate 6 installed on the inner surface of the fuel gas manifold 5a. The first fuel gas chamber 7 and the third fuel gas chamber 8 are connected to external fuel supply means and fuel exhaust means (not shown) via fuel pipes 9a and 9b, respectively.

  Next, the first fuel gas separator plate 11 having the first fuel gas flow passage 10 will be described with reference to FIG. The first fuel gas separator plate 11 of Embodiment 1 is a gas-impermeable plate having a convex rib portion 11a on one side, and is arranged so that the flat unit cell and the rib portion 11a are in contact with each other. A space formed in a portion other than the rib portion 11 a of the first fuel gas separator plate 11 becomes the first fuel gas flow passage 10. Similarly, the second fuel gas separator plate 15 is also a gas-impermeable plate having a convex rib portion on one side, and is arranged so that the flat unit cell and the rib portion are in contact with each other. 2 A space (groove) formed in a portion other than the rib portion of the fuel gas separator plate 15 serves as a second fuel gas flow passage.

  Next, the configuration of the first fuel gas flow path 10, the first fuel gas chamber 7, the second fuel gas chamber 13, and the third fuel gas chamber 8 of the fuel gas manifolds 5a and 5b will be described with reference to FIG. FIG. 5 is a cross-sectional view of the fuel cell of FIG. 1 taken along the surface of the first fuel gas flow passage 10, and the first fuel gas separator plate 11 having the first fuel gas flow passage 10 and the fuel gas manifold 5a. 5b and the partition plate 6 are sealed with a sealing material 12 to form a first fuel gas chamber 7, a second fuel gas chamber 13, and a third fuel gas chamber 8, respectively. Here, no flow path is formed in a portion of the first fuel gas flow passage 10 in contact with the third fuel gas chamber 8 and the partition plate 6, and the first fuel gas flow passage 10 has the first fuel gas chamber 7 and the first fuel gas flow passage 10. Only the second fuel gas chamber 13 has an opening.

  Similarly, the configuration of the second fuel gas flow passage 14 and the first fuel gas chamber 7, the second fuel gas chamber 13, and the third fuel gas chamber 8 of the fuel gas manifolds 5a and 5b will be described with reference to FIG. FIG. 6 is a cross-sectional view of the fuel cell of FIG. 1 taken along the surface of the second fuel gas flow passage 14, and the second fuel gas separator plate 15 having the second fuel gas flow passage 14 and the fuel gas manifold 5a. 5b and the partition plate 6 are sealed with a sealing material 12 to form a first fuel gas chamber 7, a second fuel gas chamber 13, and a third fuel gas chamber 8, respectively. Here, no flow path is formed in a portion of the second fuel gas flow passage 14 in contact with the first fuel gas chamber 7 and the partition plate 6, and the second fuel gas flow passage 14 has the second fuel gas chamber 12 and Only the third fuel gas chamber 8 has an opening.

  Here, the sealing material 12 has a straight belt-like shape in accordance with the stacking method of the fuel cell stack, and the fuel cell stack 3 facing the seal portions of the gas manifolds 5a and 5b and the seal portion of the partition plate 6 of the gas manifold. Since there is no opening in the side surface of the gas manifold with respect to the internal space of the gas manifold, the sealing material 12 can be easily secured by sandwiching an elastic sealing material or a curable caulking material.

  Next, the flow of the fuel gas in the fuel cell according to this embodiment will be described. During operation of the fuel cell, the fuel gas supplied to the fuel cell from an external fuel supply means (not shown) enters the first fuel gas chamber 7 through the pipe 9a and passes through the first fuel gas flow passage 10 and is supplied to the fuel cell. The part is used for power generation of the fuel cell, and the exhaust gas not used for power generation is introduced into the second fuel gas chamber 13. Next, the fuel exhaust gas flowing into the second fuel gas chamber 13 moves in the stacking direction in the second fuel gas chamber 13 and is introduced into the second fuel gas flow passage 14. Similarly, the fuel exhaust gas flows through the second fuel gas flow passage 14. A part of the exhaust gas is used for power generation of the fuel cell, and the exhaust gas not used for power generation circulates in the third fuel gas chamber 8 and is exhausted to an external fuel exhaust means (not shown) via the fuel pipe 9b.

Here, Q is the total amount of fuel in the fuel gas supplied to the fuel cell, Q1 is the amount of fuel used in the first fuel gas flow passage 10, and Q2 is the amount of fuel used in the second fuel gas flow passage 14. Then, the fuel utilization rate Uf1 in the first fuel gas flow passage 10, the fuel utilization rate Uf2 in the second fuel gas flow passage 14, and the fuel utilization rate Uf of the entire fuel cell are:
Uf1 = Q1 / Q (1)
Uf2 = Q2 / (Q-Q1) (2)
Uf = (Q1 + Q2) / Q
= 1- (1-Uf1) * (1-Uf2) (3)
It becomes. If 44% of the total amount Q of fuel supplied to the fuel cell is consumed in the first fuel gas flow passage 10 and the second gas flow passage 14 respectively, the fuel in each gas flow passage and the entire fuel cell is consumed. The utilization rates are Uf1 = 44%, Uf2 = 78%, Uf = 88% from the formulas (1), (2), and (3), and the fuel utilization rate in each fuel gas flow path is 80% or less. Even so, the fuel utilization rate of the entire fuel cell reaches 88%.

  As described above, in this embodiment, the seal portion between the gas manifolds 5a and 5b and the fuel cell stack 3 and the seal portion between the partition plate 6 and the fuel cell stack 3 that divides the internal space of the gas manifold. Is installed vertically with respect to the single fuel cell, it is not necessary to install the partition plate 6 in the gas manifold horizontally with respect to the single fuel cell, and a special seal is provided when dividing the internal space of the gas manifold. Airtightness can be easily secured without adding structural parts.

In addition, since the exhaust fuel gas from the first fuel gas flow passage 10 is recirculated to the second fuel gas flow passage 14 and used for power generation, without increasing the fuel utilization rate of each fuel cell alone, The fuel utilization rate as a whole of the fuel cell stack can be increased.

  In the fuel cell of the first embodiment described above, the unit cells included in the single fuel cell 1 and the single fuel cell 2 are each optimized for the fuel gas composition passing through the first fuel gas flow passage 10. And the second unit cell optimized for the fuel gas composition passing through the second fuel gas flow passage 14.

  That is, part of the fuel gas that passes through the fuel gas flow passage of the fuel cell is used for power generation of the fuel cell during the passage, but the amount of components other than the fuel contained in the fuel gas does not change. Therefore, the amount of components other than the fuel contained in the fuel gas is relatively increased on the downstream side of the fuel flow passage as compared with the upstream side of the fuel flow passage. In addition, water vapor contained in the fuel gas is used for power generation of the fuel cell, and part of the generated water accompanying the power generation of the fuel cell is discharged to the fuel gas as water vapor, so the upstream and downstream sides of the fuel flow path Then, there is a difference in the amount of water vapor contained in the fuel gas. Further, when air is used as the oxidant gas of the fuel cell, a part of the nitrogen gas in the air diffuses from the oxidant gas flow passage to the fuel gas flow passage, so that the fuel gas is disposed downstream of the fuel gas flow passage. The nitrogen concentration inside becomes high.

  In addition, the amount of components contained in the fuel gas having the property of being adsorbed by the single fuel cell varies between the upstream side and the downstream side of the fuel flow passage. Therefore, the fuel gas composition and the fuel gas flow rate differ between the fuel gas flowing upstream of the fuel gas flow passage and the fuel gas flowing downstream of the fuel gas flow passage.

  Further, when the number of first unit cells and the number of second unit cells are different (see Embodiment 7), the first fuel gas flow passage 10 and the second fuel gas flow passage 14 of each unit cell are connected to each other. The flow rate of the flowing fuel gas also varies depending on the ratio of the number of first unit cells and second unit cells.

  Therefore, the first unit cell is optimized for the composition of the fuel gas flowing through the first fuel gas flow passage, and the second unit cell is optimized for the composition of the fuel gas flowing through the second fuel gas flow passage. To optimize. That is, the first unit battery and the second unit battery are not designed to have the same structure, and are designed by selecting electrode materials, porosity, water repellency, etc. according to the respective conditions. By optimizing the first unit cell and the second unit cell, respectively, higher efficiency or longer life of the fuel cell can be achieved than when the first unit cell and the second unit cell are the same unit cell. Can be realized.

  With this configuration, the first fuel gas flow passage corresponding to the upstream side and the downstream side of the fuel gas and the first fuel gas flow passage can be provided without installing horizontal partition plates in the gas manifold with respect to the single fuel cell. Two fuel gas flow passages can be provided, the first unit cell is optimized for the composition of the fuel gas flowing through the first fuel gas flow passage, and the second unit cell is placed in the second fuel gas flow passage. A high-performance fuel cell can be provided by optimizing the composition of the fuel gas to be distributed.

[Embodiment 2]
The configuration of Embodiment 2 of the fuel cell according to the present invention will be described with reference to FIGS. As shown in FIG. 7, in the fuel cell of the second embodiment, the first fuel gas flow passage 10 and the second fuel gas flow passage 14 are divided into an outward path and a return path, respectively. The gas chamber inside the fuel gas manifold 5a is divided into the first fuel gas chamber 7, the second fuel gas chamber 13, and the third fuel gas chamber 8 that penetrate in the stacking direction by partition plates 6a and 6b installed on the inner surface of the fuel gas manifold 5a. It is divided into and. The first fuel gas chamber 7 and the third fuel gas chamber 8 are respectively connected to external fuel supply means and fuel exhaust means (not shown) via a fuel pipe 9a and a fuel pipe 9b. Further, the gas chamber inside the fuel gas manifold 5b is divided into a fourth fuel gas chamber 16 and a fifth fuel gas chamber 17 penetrating in the stacking direction by a partition plate 6c installed on the inner surface of the fuel gas manifold 5b. FIG. 7 is the same as FIG. 1 in that the oxidizing agent is omitted from illustration such as the manifold.

  Next, referring to FIG. 8, the first fuel gas flow path 10, the first fuel gas chamber 7, the second fuel gas chamber 13, the third fuel gas chamber 8, and the fourth fuel gas chamber of the fuel gas manifolds 5a and 5b. The configuration of the fifth fuel gas chamber will be described. FIG. 8 is a cross-sectional view of the fuel cell of FIG. 7 taken along the surface of the first fuel gas flow passage 10. The first fuel gas separator plate 11 having the first fuel gas flow passage 10, the fuel gas manifolds 5a and 5b, and the partition plates 6a, 6b, and 6c are sealed by a sealing material 12, and each of the first fuel gas chambers is sealed. 7, the second fuel gas chamber 13, the third fuel gas chamber 8, the fourth fuel gas chamber 16, and the fifth fuel gas chamber 17 are formed.

  The first fuel gas flow path 10 is divided into a forward path 10a of the first fuel gas flow path and a forward path 10b of the first fuel gas flow path. The forward path 10 a of the first fuel gas flow passage has an opening only with respect to the first fuel gas chamber 7 and the fourth fuel gas chamber 16, and the return path 10 b of the first fuel gas flow path is the fourth fuel gas chamber 16. And has an opening only for the second fuel gas chamber 13.

  Similarly, referring to FIG. 9, the first fuel gas chamber 7, the second fuel gas chamber 13, the third fuel gas chamber 8, the fourth fuel gas chamber of the second fuel gas flow passage 14 and the fuel gas manifolds 5a and 5b. 16, the configuration of the fifth fuel gas chamber 17 will be described. FIG. 9 is a cross-sectional view of the fuel cell of FIG. 7 taken along the surface of the second fuel gas flow passage 14. A space between the second fuel gas separator plate 15 having the second fuel gas flow passage 14, the fuel gas manifolds 5a and 5b, and the partition plates 6a, 6b, and 6c is sealed by a sealing material 12, and each of the first fuel gas chambers. 7, the second fuel gas chamber 13, the third fuel gas chamber 8, the fourth fuel gas chamber 16, and the fifth fuel gas chamber 17 are formed.

  The second fuel gas flow path 14 is divided into a forward path 14a of the second fuel gas flow path and a forward path 14b of the second fuel gas flow path. The forward path 14 a of the second fuel gas flow passage has an opening only with respect to the second fuel gas chamber 13 and the fifth fuel gas chamber 17, and the return path 14 b of the second fuel gas flow passage is connected to the fifth fuel gas chamber 17. Only the third fuel gas chamber 8 has an opening.

  The sealing material 12 has a straight strip shape in accordance with the stacking method of the fuel cell stack, and the fuel cell stack facing the seal portions of the gas manifolds 5a and 5b and the seal portions of the partition plates 6a, 6b and 6c of the gas manifold. There is no opening on the side of the body relative to the internal space of the gas manifold. Therefore, as the sealing material 12, sealing performance is easily ensured by sandwiching an elastic sealing material or a curable caulking material.

  Next, the flow of the fuel gas in the fuel cell in the present embodiment will be described. During operation of the fuel cell, fuel gas supplied to the fuel cell from an external fuel supply means (not shown) enters the first fuel gas chamber 7 via the fuel pipe 9a, and passes through the forward path 10a of the first fuel gas flow passage. A part of the fuel passes through and is used for power generation of the fuel cell. The fuel gas that has not been used for power generation in the forward path 10a of the first fuel gas flow path is introduced into the return path 10b of the first fuel gas flow path via the fourth fuel gas chamber 16, and part of the fuel is in the fuel cell. Used for power generation. Again, the fuel gas that has not been used for power generation is introduced into the second fuel gas chamber 13.

  Next, the fuel exhaust gas flowing into the second fuel gas chamber 13 moves in the stacking direction in the second fuel gas chamber 13 and is introduced into the forward path 14a of the second fuel gas flow passage. Similarly, part of the fuel is used for power generation of the fuel cell in the forward path 14a of the second fuel gas flow path. The fuel gas that has not been used for power generation in the forward path 14a of the second fuel gas flow path is introduced into the return path 14b of the second fuel gas flow path via the fifth fuel gas chamber 17, and part of the fuel is in the fuel cell. Used for power generation. Here again, the exhaust gas that has not been used for power generation flows into the third fuel gas chamber 8 and is exhausted to an external fuel exhaust means (not shown) through the fuel pipe 9b.

  Here, when the first fuel gas flow passage 10 is divided into the forward passage 10a of the first fuel gas flow passage and the return passage 10b of the first fuel gas flow passage, the first fuel gas flow passage 10 of the first fuel gas flow passage 10 when not dividing the fuel flow passage. Compared to the full width of the fuel gas flow path near the outlet, the full width of the fuel gas flow path near the outlet of the return path 10b of the first fuel gas flow path becomes narrower. Therefore, when the flow rates of the fuel gas discharged from the first fuel gas flow passage 10 and the return passage 10b of the first fuel gas flow passage are the same, the flow rate of the fuel gas relative to the unit reaction area of the fuel cell becomes relatively large. Further, in the fourth fuel gas chamber 16, the exhaust gas from the forward path 10a of the first fuel gas flow path existing in the plurality of fuel cells alone is once mixed and redistributed to the return path 10b of each first fuel gas flow path. Since the fuel flow is made to flow, the fuel flow rate between the individual fuel cells is made uniform, so that there is no shortage of fuel due to the non-uniform fuel flow rate in a specific fuel cell.

  As described above, in this embodiment, the same effects as those of the first embodiment can be obtained, and even if the fuel utilization rate of each fuel cell alone is further increased, the fuel due to fuel shortage at the outlet portion of the fuel gas flow passage is also obtained. A fuel cell in which the battery is not damaged can be provided.

[Embodiment 3]
The configuration of Embodiment 3 of the fuel cell according to the present invention will be described with reference to FIGS. 10 and 11. The fuel cell according to the third embodiment is a modification of the fuel cell according to the first embodiment, and the flow paths of the first fuel gas flow passage 10 and the second fuel gas flow passage 14 are point-symmetric. That is, in the fuel cell of Embodiment 3, the first fuel gas separator plate 11 having the first fuel gas flow passage 10 and the second fuel gas separator plate 15 having the second fuel gas flow passage 14 have the same shape. When they are stacked as a fuel cell stack, the direction is rotated by 180 ° to use as the first fuel gas flow path or the second fuel gas flow path. The flow of the fuel gas during the fuel cell operation in the present embodiment is the same as that in the first embodiment.

  As described above, in this embodiment, the same effects as those of the first embodiment can be obtained, and the flow shapes of the first fuel gas flow passage 10 and the second fuel gas flow passage 14 are point-symmetric. A fuel gas separator plate having a fuel gas flow passage is manufactured in the same shape, and the first fuel gas flow passage 10 or the second fuel gas flow passage 14 is rotated by 180 ° when the fuel gas separator plate is stacked on the fuel cell stack. Therefore, it is not necessary to produce two types of fuel gas separator plates, and the production cost can be reduced.

[Embodiment 4]
The configuration of Embodiment 4 of the fuel cell according to the present invention will be described with reference to FIGS. The fuel cell according to the fourth embodiment is a modification of the fuel cell according to the second embodiment, and the fuel gas flow paths of the first fuel gas separator plate 11 and the second fuel gas separator plate 15 have a point-symmetric shape. That is, in the fuel cell of the fourth embodiment, the first fuel gas separator plate 11 having the forward path 10a and the return path 10b of the first fuel gas flow path and the second fuel gas having the forward path 14a and the return path 14b of the second fuel gas flow path. The separator plate 15 has the same shape, and when they are stacked as a fuel cell stack, the direction thereof is rotated by 180 ° to form the first fuel gas flow passage 10 or the second fuel gas flow passage 14. use. The flow of the fuel gas during the fuel cell operation in the present embodiment is the same as that in the second embodiment.

  As described above, in this embodiment, the same effects as those of the second embodiment can be obtained, and the flow path shapes of the first fuel gas separator plate 11 and the second fuel gas separator plate 15 are point symmetric. A fuel gas separator plate having a fuel gas flow passage is manufactured in the same shape, and the first fuel gas flow passage 10 or the second fuel gas flow passage 14 is rotated by 180 ° when the fuel gas separator plate is stacked on the fuel cell stack. Therefore, it is not necessary to produce two types of fuel gas separator plates, and the production cost can be reduced.

[Embodiment 5]
This embodiment is a modification of the first embodiment (FIGS. 1 to 6). As shown in FIGS. 14 and 15, the shapes of the first fuel gas flow passage 10 and the second fuel gas flow passage 14 are as follows. A serpentine shape with a bent portion in the middle is used. With such a configuration, the lengths of the first fuel gas flow passage 10 and the second fuel gas flow passage 14 can be increased.

[Embodiment 6]
This embodiment is a modification of the second embodiment (FIGS. 7 to 9). As shown in FIGS. 16 and 17, the shapes of the first fuel gas flow passage 10 and the second fuel gas flow passage 14 are changed. A serpentine shape with a bent portion in the middle is used. With such a configuration, the lengths of the first fuel gas flow passage 10 and the second fuel gas flow passage 14 can be increased as in the fifth embodiment.

[Embodiment 7]
The configuration of Embodiment 7 of the fuel cell according to the present invention will be described with reference to FIG. The fuel cell according to the seventh embodiment is a modification of the first embodiment, and includes a larger number of the fuel cell unit 1 having the first fuel gas flow passage 10 than the fuel cell unit 2 having the second fuel gas flow passage 14. Laminated.

  Here, as an example, the ratio (n1 / n2) of the number n1 of the fuel cell units 1 having the first fuel gas flow passage 10 and the number n2 of the fuel cell units 2 having the second fuel gas flow passage 14 is set to 5. The amount Q1 of fuel gas used in the first fuel gas flow passage 10 is 80% of the fuel Q supplied to the fuel cell, and the amount Q2 of fuel gas used in the second fuel gas flow passage 14 is the fuel. When 16% of the fuel Q supplied to the battery is used, Q1 / Q2 = 80/16 = 5, and the amount of fuel gas used for power generation in each single fuel cell having each fuel gas flow passage is Be the same. Furthermore, the fuel utilization rates of the respective gas flow passages and the entire fuel cell are Uf1 = 80%, Uf2 = 80%, Uf = 96% from the above-described equations (1), (2), and (3). Even if the fuel utilization rate in the gas flow path is limited to 80%, the fuel utilization rate of the entire fuel cell reaches 96%.

  The ratio n1 / n2 of the number n1 of the fuel cell units 1 having the first fuel gas flow passage 10 and the number n2 of the fuel cell units 2 having the second fuel gas flow passage 14 is not limited to 5, By laminating at least one fuel cell unit 1 having the first fuel gas flow passage 10 more than the fuel cell unit 2 having the second fuel gas flow passage 14, a corresponding effect can be obtained.

  In general, the fuel utilization rate of each fuel cell is designed to be as large as possible. Therefore, when Uf1 = Uf2, the following equation is obtained from equations (1), (2), and (3).

Q1 / Q2 = 1 / (1-Uf1) (4)
Uf = Uf1 (2-Uf1) (5)
Furthermore, since it is generally desirable that the amount of fuel used in each single fuel cell is made equal to maximize the amount of power generation, Q1 / Q2 is preferably the single fuel cell 1 having the first fuel gas flow passage 10. Is equal to the ratio n1 / n2 of the number n1 of the fuel cell unit 2 having the second fuel gas flow passage 14 and the number n2.

  Therefore, at this time, Expression (4) can be expressed as follows.

n1 / n2 = 1 / (1-Uf1) (6)
Here, since 0 <Uf1 <1, from Equation (6),
n1 / n2> 1 and
n1> n2.

In the above example, since Uf1 = 0.8, if this is substituted into equation (6),
n1 / n2 = 5 is obtained.

Further, from the equation (5), Uf = 0.96.

  As described above, in this embodiment, the same effects as those of the first embodiment can be obtained, and the exhaust fuel gas from the single fuel cell 1 having the plurality of first fuel gas flow passages 10 is converted into the first fuel gas flow passages. The fuel cell unit 2 having the number of the second fuel gas flow passages 14, which is smaller than the number of the fuel cell unit 1 composed of 10, is again distributed to the fuel cell unit 2 and used for power generation. Therefore, a sufficient amount of fuel gas can be secured from the second fuel gas flow passage 14 for each single fuel cell 2, and the fuel cell is damaged near the outlet of the second fuel gas flow passage 14 due to insufficient fuel. This can be prevented, and the fuel utilization rate of the fuel cell as a whole can be increased so that highly efficient operation can be performed.

[Embodiment 8]
FIG. 19 shows an embodiment in which the fuel cell unit 2 having the second fuel gas flow passage 14 is intensively stacked in the vicinity of the current collector plate 4 in the fuel cell of the seventh embodiment. The arrangement in the stacking direction of the second fuel gas flow passages 14 can be arranged at regular intervals or at irregular intervals as described above, and the arrangement is not limited to the above-described embodiment. Absent.

[Embodiment 9]
The configuration of the ninth embodiment of the fuel cell according to the present invention will be described with reference to FIG. The fuel cell of the ninth embodiment is a modification of the first embodiment, in which the fuel pipe 9c communicated with the second fuel gas chamber 13, the fuel pipe 9b, and the flow state of the fuel gas in the fuel pipe 9c are switched. Possible fuel supply / exhaust switching means 18a, 18b are provided.

  Next, the flow of the fuel gas in the fuel cell according to this embodiment will be described. In a normal fuel cell operation state, the fuel supply / exhaust switching means 18a is set to the fuel exhaust state, and the exhaust gas from the fuel cell is not shown outside via the fuel pipe 9b as shown by the solid line arrow 25. It is exhausted to the fuel exhaust means. Further, the fuel supply / exhaust switching means 18b is set in a fuel closed state, and there is no fuel circulation in the fuel pipe 9c. Therefore, the flow of the fuel gas inside the fuel cell is the same as that of the fuel cell of the first embodiment.

  Next, the flow of the fuel gas when the flow path of the fuel gas is switched will be described. In the fuel gas flow path switching state, fuel gas is supplied from an external fuel supply means (not shown) to the first fuel gas chamber 7 via the fuel pipe 9a, and the fuel supply / exhaust switching means 18a is set to the fuel supply state. As indicated by the dotted arrow 26, the fuel is directly supplied also from the external fuel supply means (not shown) to the third fuel gas chamber 8 through the fuel pipe 9b. Further, the fuel supply / exhaust switching means 18b is set in the fuel exhaust state, and the fuel exhaust gas that has passed through the first fuel gas flow passage 10 and the second fuel gas flow passage 14 and has not been used for power generation is indicated by a dotted arrow 27. As shown in FIG. 3, the fuel is exhausted to an external fuel exhaust means (not shown) through the fuel pipe 9c.

  As described above, in the present embodiment, the fuel gas flow state is switched by the fuel supply / exhaust switching means 18a, 18b, so that the fuel exhaust gas from the first fuel gas flow passage 10 is changed to the second fuel gas flow passage 14. The fuel gas can be discharged to the outside of the fuel cell without going through (see FIGS. 5 and 6, etc.), and the fuel gas can be supplied to the second fuel gas flow passage 14 without going through the first fuel gas flow passage 10. As a result, the flow path length and pressure loss from the fuel gas supply unit to the discharge unit can be reduced, and operation with reduced power required for fuel supply can be performed as necessary. Further, at the start of the power generation operation of the fuel cell, the fuel gas is quickly supplied to each of the fuel gas chambers 7, 13, 8 and the first gas flow passage 10 and the second gas flow passage 14, and the power generation operation of the fuel cell is performed. At the end of the operation, the purge gas such as inert gas is quickly introduced into each fuel gas chamber and the first gas flow passage 10 and the second gas flow passage 14 to replace the fuel gas with the inert gas, thereby deteriorating the performance of the fuel cell. Can be reduced.

[Other Embodiments]
Although various embodiments have been described above, these are merely examples, and the present invention is not limited thereto.

  For example, the ninth embodiment (FIG. 20) is an example in which a fuel pipe 9c, fuel supply / exhaust switching means 18a, 18b, and the like are added based on the first embodiment (FIGS. 1 to 6). It may be based on the second embodiment (FIGS. 7 to 9). In this case, it is conceivable to connect the fuel pipe to any two of the first to fifth fuel gas chambers.

  Further, in the description of the above embodiment, for convenience of explanation, each fuel cell unit is arranged so as to spread in the horizontal direction, and these fuel cell units are stacked in the vertical direction, but the direction is arbitrary. For example, each fuel cell unit may be vertically oriented.

  In the above embodiment, the fuel gas manifold and the oxidant gas manifold are arranged outside the fuel cell stack, but the separator plates are stacked by providing manifold holes near the outer periphery of each separator plate. Sometimes it is possible to configure the manifold holes to be a continuous manifold.

1 is a perspective view showing a fuel cell according to Embodiment 1 of the present invention. The top view of the fuel cell of FIG. FIG. 2 is a partial longitudinal sectional view of the fuel cell stack of FIG. 1. The perspective view which takes out and shows the fuel gas separator plate of the fuel cell of FIG. FIG. 2 is a horizontal sectional view showing a first fuel gas flow passage part of the fuel cell of FIG. 1. The horizontal sectional view which shows the 2nd fuel gas flow passage part of the fuel cell of FIG. The perspective view which shows the fuel cell of Embodiment 2 of this invention. FIG. 8 is a horizontal sectional view showing a first fuel gas flow passage portion of the fuel cell of FIG. 7. FIG. 8 is a horizontal sectional view showing a second fuel gas flow passage portion of the fuel cell of FIG. 7. The horizontal sectional view showing the 1st fuel gas flow passage part of the fuel cell of Embodiment 3 of the present invention. The horizontal sectional view showing the 2nd fuel gas flow passage part of the fuel cell of Embodiment 3 of the present invention. The horizontal sectional view showing the 1st fuel gas flow passage part of the fuel cell of Embodiment 4 of the present invention. The horizontal sectional view showing the 2nd fuel gas flow passage part of the fuel cell of Embodiment 4 of the present invention. The horizontal sectional view showing the 1st fuel gas flow passage part of the fuel cell of Embodiment 5 of the present invention. The horizontal sectional view showing the 2nd fuel gas flow passage part of the fuel cell of Embodiment 5 of the present invention. The horizontal sectional view showing the 1st fuel gas flow passage part of the fuel cell of Embodiment 6 of the present invention. The horizontal sectional view showing the 2nd fuel gas flow passage part of the fuel cell of Embodiment 6 of the present invention. The perspective view which shows the fuel cell of Embodiment 7 of this invention. The perspective view which shows the fuel cell of Embodiment 8 of this invention. The perspective view which shows the fuel cell of Embodiment 9 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell single-piece | unit 2 which has 1st fuel gas flow path 2 ... Fuel cell single-piece | unit 3 which has 2nd fuel gas flow path 3 ... Fuel cell laminated body 4 ... Current collector plate 5a, 5b ... Fuel gas manifold 6, 6a, 6b, 6c ... Partition plate 7 ... 1st fuel gas chamber 8 ... 3rd fuel gas chamber 9a, 9b ... Fuel piping 10 ... 1st fuel gas flow path 10a ... Outward path 10b of 1st fuel gas flow path ... 1st fuel gas flow path Return path 11 ... first fuel gas separator plate 11a ... rib portion 12 of first fuel gas separator plate ... sealing material 13 ... second fuel gas chamber 14 ... second fuel gas flow passage 14a ... outward path of the second fuel gas flow passage 14b ... Return path 15 of the second fuel gas flow passage ... Second fuel gas separator plate 16 ... Fourth fuel gas chamber 17 ... Fifth fuel gas chamber 18a, 18b ... Fuel supply / exhaust switching means 30 ... Oxidant gas manifold 31 ... Electrolyte 32 ... Gas expansion Electrodes 33 ... unit cell 36 ... oxidant gas flow passage 37 ... oxidant gas separator plate

Claims (11)

A unit cell in which both surfaces of a plate-like electrolyte are sandwiched by two plate-like gas diffusion electrodes, and a fuel gas configured such that fuel gas and oxidant gas flow along the surfaces of the gas diffusion electrodes, respectively. A fuel cell stack formed by stacking a plurality of fuel cells each having a flow path and an oxidant gas flow path;
A fuel gas manifold for supplying fuel gas to the fuel gas flow passage;
An oxidant gas manifold for supplying an oxidant gas to the oxidant gas flow passage;
In a fuel cell having
The fuel gas manifold has a first fuel gas chamber, a second fuel gas chamber, and a third fuel gas chamber respectively extending in the stacking direction of the fuel cells alone.
The fuel gas flow path is
A first fuel gas flow passage that communicates with the first fuel gas chamber and the second fuel gas chamber and does not communicate with the third fuel gas chamber;
A second fuel gas flow passage that communicates with the second fuel gas chamber and the third fuel gas chamber, does not communicate with the first fuel gas chamber, and is disposed in a different plane from the first fuel gas flow passage; ,
Have
The fuel gas supplied to the fuel cell passes through the first fuel gas chamber, the first fuel gas flow passage, the second fuel gas chamber, the second fuel gas flow passage, and the third fuel gas chamber in this order to the outside of the fuel cell. Configured to be discharged,
A fuel cell. The fuel gas manifold further includes a fourth fuel gas chamber extending in the stacking direction of the fuel cells alone,
The first fuel gas flow path is divided into a first fuel gas forward path and a first fuel gas return path in the same plane,
Fuel gas is configured to flow in the order of the first fuel gas forward path, the fourth fuel gas chamber, and the first fuel gas return path;
The fuel cell according to claim 1. The fuel gas manifold further includes a fifth fuel gas chamber extending in the stacking direction of the fuel cells alone,
The second fuel gas flow path is divided into a second fuel gas forward path and a second fuel gas return path in the same plane,
Fuel gas is configured to flow in the order of the second fuel gas forward path, the fifth fuel gas chamber, and the second fuel gas return path;
The fuel cell according to claim 1 or 2.   4. The fuel cell according to claim 1, wherein a flow path shape of at least one of the first fuel gas flow path and the second fuel gas flow path is point-symmetric.   5. The fuel cell according to claim 1, wherein the number of single fuel cells including the first fuel gas flow passage is greater than the number of single fuel cells including the second fuel gas flow passage. The fuel cell as described.   When the fuel utilization rate in each of the single fuel cells is Uf1, the number of the single fuel cells including the first fuel gas flow passage and the number of the single fuel cells including the second fuel gas flow passage The fuel cell according to claim 5, wherein the ratio is substantially equal to 1 / (1-Uf1).   Fuel supply / exhaust switching means is connected to any two or more of the first to third fuel gas chambers, which can switch the flow state of the fuel gas to any two or more states of supply, exhaust, and closed. The fuel cell according to any one of claims 1 to 6, wherein The flow state of the fuel gas can be switched to any one of two or more states of supply, exhaust, and closed for any one or more of the fourth gas chamber and the first to third gas chambers. Fuel supply / exhaust switching means is connected,
The fuel cell according to claim 2. The flow state of the fuel gas can be switched to any one of two or more states of supply, exhaust, and closed in any one or more of the fifth gas chamber and the first to fourth gas chambers. Fuel supply / exhaust switching means is connected,
The fuel cell according to claim 3.   The single fuel cell including the first fuel gas flow passage and the single fuel cell including the second fuel gas flow passage are designed to have different configurations according to the difference in the components of the fuel gas supplied to each. The fuel cell according to any one of claims 1 to 9, wherein the fuel cell is formed.   2. The fuel cell according to claim 1, wherein the single fuel cells are partitioned by a separator plate, and the first fuel gas flow passage and the second fuel gas flow passage are formed as grooves on the surface of the separator plate. The fuel cell according to any one of Items 10 to 10.

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