JP2000215904A - Fuel cell stack - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To make it possible to easily achieve higher lamination without deteriorating flow distribution, to reduce pressure loss, and to simplify the sealing structure. Provided is a fuel cell stack capable of increasing voltage. SOLUTION: The fuel cell system includes a cell laminated body 14 in which cells 4 are laminated with a separator 12 interposed therebetween, and a gas seal member 16 sandwiched between the separators. The separator has an anode gas internal manifold 12a hermetically sealed to the outside by a gas seal member, and the opposing sides 3a of the cathode 3 communicate with the outside on the opposite side via a gap between the separators. are doing. In addition, a cathode gas duct 20 is provided which hermetically surrounds the cell stack and supplies cathode gas from one side 3a of each cathode 3 via a gap between the separators and discharges the cathode gas from the other side. Further, a bypass resistor 22 is provided between the cell stack and the cathode gas duct to reduce a bypass flow other than a flow along the cathode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell stack in which cells are stacked via a separator.

[0002]

2. Description of the Related Art As shown schematically in FIG. 4A, a fuel cell (for example, a molten carbonate type fuel cell) comprises a thin flat electrolyte plate (tile) 1 and a fuel electrode (anode) 2 and air. A single cell 4 sandwiched between plate-like electrodes 3 of electrodes (cathodes);
A conductive bipolar plate (separator) 5. The separator 5 has a low voltage in the single cell 4 (0.8
V), these are stacked and used in multiple stages. Hereinafter, the stacked fuel cells are referred to as a fuel cell stack or simply a stack. As a means for supplying the process gas (anode gas and cathode gas) to each cell 4 in the stack 6, as shown in FIG. 4B, an external manifold system (a) for directly supplying the process gas from the side of the stack is used. )
And an internal manifold system (b) in which a vertical through manifold 8 is provided on the separator itself and process gas is supplied to each cell via this manifold.

In the external manifold system (a), since the process gas (anode gas and cathode gas) is supplied directly from the side of the stack, the structure of the separator is simplified.
In particular, it is suitable for a cross-flow type fuel cell in which the anode gas and the cathode gas are orthogonal. However, there is a drawback in that it is difficult to apply to a parallel flow system having excellent cell characteristics and to follow a change in height of the fuel cell stack due to a change in temperature or the like. on the other hand,
Since the internal manifold system (b) includes the through manifold 8 perpendicular to the separator itself, there is an advantage that it can be easily applied to a parallel flow system excellent in battery characteristics and can follow a change in stack height.

As described above, in an internal manifold type fuel cell, a separator is a partition plate for separating anode gas and cathode gas, a current collector connecting each cell, and a gas for supplying anode gas and cathode gas to each cell. It has multiple functions such as manifolds. In order to satisfy these functions, the separator is formed with a heat seal resistant to high temperatures of about 700 ° C. or more, a corrosion resistance resistant to molten carbonate, and a wet seal formed between the separators by an electrolyte plate (tile) containing molten carbonate. Flatness and flexibility, low electrical resistance that lowers the internal resistance of the battery, and the like are required. Meet these requirements,
In order to reduce costs, instead of the conventional precision machining, a corrugated separator having a corrugated plate in the channel portion and a press-type separator formed by press-forming each component have already been developed.

FIG. 5 is a schematic diagram of a conventional internal manifold parallel flow type fuel cell stack employing a press type separator. In this figure, (A) is a part of a plan view,
(B) is a cross-sectional view of the anode manifold, and (C) is a cross-sectional view of the cathode manifold. Separator 5
Is formed by pressing and joining a plurality of thin plates, sandwiching the cell 4 therebetween, flowing a fuel gas (anode gas) along the anode from the anode manifold 8a on one side to the opposite side, and oxidizing gas (cathode gas). Along the cathode from the cathode manifold 8c.

[0006]

However, the above-mentioned fuel cell stack of the parallel flow internal manifold type has the following problems. 1. Since it is necessary to provide an anode manifold and a cathode manifold adjacent to each other at positions facing each cell, gas sealing between them becomes difficult. In particular, as the size of the fuel cell increases, it becomes necessary to alternately arrange a plurality of manifolds, and the structure of the manifold section becomes complicated. 2. For fuel cell cooling,
Since the cathode gas needs to flow at least 10 times the anode gas, the size of the cathode manifold becomes larger than that of the anode manifold, making it difficult to distribute the anode gas uniformly on the reaction surface. 3. Since two types of manifolds are provided on the side surface of each cell, the size of the cathode manifold is limited, which limits the number of stacks in the stack. That is, if it is attempted to increase the voltage by forcibly increasing the number of layers, it is difficult to distribute the cathode gas uniformly in the direction of stacking, and the pressure loss due to gas branching in the manifold increases.

That is, the flow rate of the cathode gas used in the fuel cell stack is very large because it is supplied not only for the cell reaction but also for the purpose of cooling. Therefore, when the stack is stacked high, the size of the cathode manifold is restricted in the internal manifold type separator, so that the pressure loss increases due to gas branching in the manifold, the flow distribution of the cathode gas in the stacking direction deteriorates, and the manifold structure is There were problems such as complications. Therefore, there has been a problem that the increase in voltage due to the high stacking is limited to, for example, about 250 cells (about 200 V).

The present invention has been made to solve such a problem. That is, an object of the present invention is to make it possible to easily achieve higher lamination without deteriorating the flow distribution, to reduce the pressure loss, and to simplify the sealing structure. It is an object of the present invention to provide a fuel cell stack capable of generating a voltage.

[0009]

According to the present invention, a cell laminate (14) in which cells (4) are laminated via a separator (12), and a gas seal member (16) sandwiched between the separators. The separator has an anode gas internal manifold (12a) hermetically sealed to the outside by a gas seal member, and the opposite side (3a) of the cathode (3) via a gap between the separators. ) Are in communication with the outside on opposite sides, respectively.

According to the configuration of the present invention, the anode gas can be supplied to each cell from the anode gas internal manifold (12a), and the cathode gas can be supplied to each cell from the outside via the gap between the separators. Therefore, only the cathode side can be formed as an external manifold, and the adverse effects (increase in pressure loss and deterioration in flow distribution in the stacking direction) due to high stacking on the cathode side can be essentially solved. In addition, since the internal manifold is used only for the anode having a small flow rate, sealing by the gas seal member (16) is easy, and a plurality of manifolds can be freely arranged, so that uniform flow distribution on the anode side reaction surface is easy. Becomes

According to a preferred embodiment of the present invention, a holder member (18) for holding the cell stack is provided, and at least a part of the holder member is provided with the internal manifold (1).
An anode gas manifold (19) communicating with 2a) is provided. With this configuration, the holder member (18)
The cell stack (12) can be maintained so that the sealing characteristics and the battery characteristics are optimized, and anode gas is supplied to the anode side of each cell via the anode gas manifold (19) and the internal manifold (12a). Can be supplied and discharged.

Further, a cathode gas duct (20) for supplying a cathode gas from one side (3a) of each cathode (3) through a gap between the separators and exhausting the cathode gas from the other side through a gap between the separators. ). With this configuration, the opposed sides (3) of the cathode gas duct (20)
An inlet and an outlet are respectively provided corresponding to a), and only cathode gas is supplied from the inlet, and each cathode (3)
The cathode gas can be supplied uniformly and discharged from each cathode to the outlet. In addition, even if there is a cathode gas that bypasses the cathode and passes through the gap between the separators and the periphery of the cell stack, the cathode gas has a gas composition close to that of air, and the gap between the cathode gas and the anode gas is formed by the gas seal member (16). As long as it is sealed, there is no adverse effect, but it can be useful for cooling the fuel cell.

Further, it is preferable that a bypass resistor (22) for reducing a bypass flow other than a flow along the cathode is provided between the cell stack and the cathode gas duct. With such a bypass resistor, the flow other than the flow along the cathode (bypass flow) can be reduced, and the cathode gas can flow reliably along each cathode.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In each of the drawings, common portions are denoted by the same reference numerals, and redundant description will be omitted. FIG. 1 is a partial cross-sectional view of a fuel cell stack according to the present invention. As shown in this figure, a fuel cell stack 10 of the present invention includes a cell stack 14 (in the range of the arrow) in which cells 4 are stacked with a separator 12 interposed therebetween, and a gas seal member 16 sandwiched between the separators 12. Is provided. Although FIG. 2 schematically shows only the gas supply side of the fuel cell stack, the gas discharge side has the same configuration.

The cell 4 is, in this example, a central electrolyte plate 1.
, And an anode current collector 9a and a cathode current collector 9c sandwiching the anode 2 and the cathode 3. The current collectors 9 a and 9 b are, for example, perforated plates, and serve to protect the anode 2 and the cathode 3 and to pass generated current to the separator 12. Note that these current collecting plates 9a and 9b can be omitted.

The gas seal member 16 is sandwiched between the separators 12 at a position different from the cell 4. The gas sealing member 16 is made of a sealing material that is electrically insulating and has heat resistance and corrosion resistance that can withstand the operating state of the fuel cell. For example, a material that forms a so-called wet seal by wetting the electrolyte by infiltrating the electrolyte into ceramic powder, or a material containing a glass material that melts or softens at the operating temperature can be used as the sealing material.

In this example, the separator 12 is formed by pressing a plurality of thin plates and joining them.
Is configured to be held. The separator 12 has an anode gas internal manifold 12 a hermetically sealed from the outside by a gas seal member 16. Preferably, a plurality of the internal manifolds 12a are provided at positions opposed to each other across the cell 4 so as to communicate with the anode 2 of the cell 4. Further, the separator 12 is formed by a gap 3 between the separators formed by the gas seal member 16 and the opposing sides 3 a of the cathode 3.
Are arranged so as to communicate with the outside on the opposite side that faces each other with the cell 4 interposed therebetween.

The cell laminate 14 includes the above-described cell 4, the separator 12, and the gas seal member 16, and is formed by laminating these.

Further, as shown in FIG. 1, the fuel cell stack 10 of the present invention includes a holder member 18 for holding the cell stack 14. In this example, the holder member 18 includes an upper holder 18a and a lower holder 18b that sandwich the cell stack 14 from above and below. The separator 1 is attached to at least a part of the holder member 18 (in this example, the lower holder 18b).
2 is provided with an anode gas manifold 19 communicating with the internal manifold 12a of each of the cells 4 via the internal manifold 12a.
The anode gas (fuel gas) is supplied to the fuel cell and discharged from the manifold 19 on the opposite side.

FIG. 2 is an overall perspective view showing the whole fuel cell stack of FIG. 1 as a perspective view, and FIG. 3 shows a plan view (A) and a front view (B) of the cathode gas duct of FIG. It is a block diagram.

As shown in FIGS. 2 and 3, the fuel cell stack 10 of the present invention includes a cathode gas duct 20 that hermetically surrounds the cell stack 14. The duct 20 has a supply port 20a for supplying the cathode gas to the outside on the opposite side to which the opposite sides 3a of the cathode 3 communicate, and a discharge port 20b for discharging the cathode gas. By supplying the cathode gas from the supply port 20a of the duct 20, the separator 12
The cathode gas can be supplied from one side 3a of each cathode 3 and discharged from the other side 3a through the gap between the two.

Further, a bypass resistor 22 for reducing a bypass flow other than a flow along the cathode 3 is provided between the cell stack 14 and the cathode gas duct 20. The bypass resistor 22 is preferably made of a material having insulation and flexibility, for example, a heat insulating material.

According to the configuration of the present invention described above, the anode gas can be supplied to each cell from the anode gas internal manifold 12a, and the cathode gas can be supplied from the outside to each cell via the gap between the separators. Therefore, only the cathode side can be formed as an external manifold, and the adverse effects (increase in pressure loss and deterioration in flow distribution in the stacking direction) due to high stacking on the cathode side can be essentially solved. Further, since the internal manifold is used only for the anode having a small flow rate, sealing by the gas seal member 16 becomes easy, and a plurality of manifolds can be freely arranged, so that uniform flow distribution on the anode side reaction surface becomes easy. .

Further, by providing the holder member 18, the cell stack 12 can be held by the holder member 18 so that the sealing characteristics and the battery characteristics are optimized, and the anode gas manifold 19 and the internal manifold 12a
Anode gas is supplied to the anode side of each cell 4 via
Can be discharged.

Further, by providing the cathode gas duct 20, the cathode gas can be uniformly supplied to each cathode 3 and discharged from each cathode to the outlet 20b only by supplying the cathode gas from the inlet 20a.
In addition, even if there is a cathode gas that bypasses the cathode and passes through the gap between the separators 12 and the periphery of the cell stack 14, there is no adverse effect as long as the space between the anode gas and the anode gas is sealed, and it is useful for cooling the fuel cell. be able to.

Furthermore, the flow (bypass flow) other than the flow along the cathode of the bypass resistor 22 can be reduced, and the cathode gas can flow reliably along each cathode.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously changed without departing from the gist of the present invention.

[0028]

As described above, according to the fuel cell stack of the present invention, when the cathode manifold is an external manifold, the influence on the number of stacks is reduced, and the fuel cell stack is installed in a container. By using a cathode gas as the atmosphere gas in the container, the influence of gas leakage is small, and by using an external manifold, pressure loss on the cathode side can be reduced.

Therefore, the fuel cell stack of the present invention can easily achieve higher stacking without deteriorating flow distribution, can reduce pressure loss, and can simplify the sealing structure. Thereby, higher voltage than before can be achieved.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a fuel cell stack according to the present invention.

FIG. 2 is an overall perspective view of the fuel cell stack of FIG.

FIG. 3 is a configuration diagram of a cathode gas duct of FIG. 2;

FIG. 4 is an explanatory diagram of a conventional fuel cell.

FIG. 5 is a schematic diagram of a conventional internal manifold parallel flow type fuel cell stack.

[Explanation of symbols]

 Reference Signs List 1 electrolyte plate (tile) 2 fuel electrode (anode) 3 air electrode (cathode) 3a side part 4 cell (single cell) 5 bipolar plate (separator) 6 fuel cell stack 8 internal manifold 8a anode manifold 8c cathode manifold 10 fuel cell stack DESCRIPTION OF SYMBOLS 12 Separator 14 Cell laminated body 16 Gas seal member 18 Holder member 18a, 18b Holder 19 Anode gas manifold 20 Cathode gas duct 20a, 20b Inflow / outflow port 22 Bypass resistor

Claims (4)

[Claims] 1. A cell (4) via a separator (12)
And a gas seal member (16) sandwiched between separators, wherein the separator is hermetically sealed to the outside by a gas seal member. ), And the opposed sides (3a) of the cathode (3) communicate with the outside on the opposite side through a gap between the separators. 2. An anode gas manifold (19) communicating with the internal manifold (12a) is provided on at least a part of the holder member for holding the cell stack. The fuel cell stack according to claim 1, wherein: 3. One side (3) of each cathode (3) through a gap between separators surrounding the cell stack in an airtight manner.
3. The fuel cell stack according to claim 1, further comprising a cathode gas duct (20) for supplying the cathode gas from a) and discharging the gas from the other side. 4. The fuel according to claim 3, further comprising a bypass resistor (22) between the cell stack and the cathode gas duct for reducing a bypass flow other than a flow along the cathode. Battery stack.