JPH0624134B2 - Fuel cell - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a fuel cell using hydrogen as a fuel gas and oxygen or air as an oxidant gas, and more particularly to a fuel cell provided with a manifold for extending the life. .

[Technical background of the invention and its problems]

FIG. 1 is an exploded perspective view showing the structure of a conventional fuel cell. In the figure, the unit cell stack 1 is sandwiched by upper and lower reinforcing members 2, and a fuel inlet manifold 3 and a fuel outlet manifold 4 are provided on one side facing the unit cell stack 1 with a seal member 5 interposed therebetween. The fuel is supplied to and discharged from the unit cell stack 1. Further, an air inlet manifold 6 and an air outlet manifold 7 are respectively provided on the other side surface facing the unit cell stack 1 via a sealing material 5, and air is supplied to and discharged from the unit cell stack 1. It is like this. Further, these manifolds 3, 4, 6 and 7 are kept airtight, and all of them are housed in a closed container (not shown) filled with an inert gas such as nitrogen for operation.

By the way, the manifold in the above-mentioned fuel cell requires not only a structure capable of withstanding the movement of internal and external pressures, but is also used at an operating temperature of about 200 ° C., and the fuel cell is in operation or at the start / stop of operation. There is a risk that the material for the manifold structure will be corroded by the evaporation or scattering of phosphoric acid, which is the electrode quality of.

Therefore, recently, since there are few materials having sufficient resistance to high-temperature phosphoric acid, a method of using a metal for a pressure resistant structure and coating a fluorine resin (for example, polytetrafluoroethylene) on the inner surface thereof Has been adopted. However, even if the resin itself has strong heat resistance and chemical resistance, there is no one that can be used at 200 ° C. as a primer for coating material adhesion, and the linear expansion coefficient is 11.8 × 10 ⁻⁶ (1/1) of iron. ℃) for TFE is 1
It is different from 0 × 10 ^-5 by an order of magnitude and is weak against temperature changes, and when pressure and pressure are repeatedly applied due to the gas permeability of the resin itself, the gas reaching the resin adhesive surface expands during pressure reduction and the coating material The resulting coating material interferes with the uniform flow of gas and eventually stops the operation of the fuel cell.

[Object of the Invention]

The present invention has been made to solve the above problems, and an object of the present invention is to provide a fuel cell capable of preventing the resin film from peeling off due to pressure fluctuations to prolong the life and continue the operation. To provide.

[Outline of Invention]

In order to achieve the above object, the present invention provides a pair of manifolds for supplying and discharging a fuel gas through a gas supply / exhaust pipe on one side facing the unit cell stack, and supplying the pair of manifolds on the other side perpendicular to the manifold. In a fuel cell provided with a pair of manifolds for supplying and discharging an oxidant gas through a discharge pipe, the manifold is divided into a plurality of stacks in the unit cell stacking direction, and the inner surface of the manifold is a heat-resistant and chemical-resistant resin film. A gas vent pipe for exhausting the gas between the manifold and the resin film to the outside is attached to the divided manifold, and the gas supply / exhaust pipe and the gas vent pipe are, if necessary, It is assumed that they are connected via pressure holding means for holding the pressure at the same pressure.

Example of Invention

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 2 is a perspective view showing a configuration example of a manifold applied to the present invention, and shows a structure in which a plurality of parts (three parts in this example) are divided in the height direction, that is, the stacking direction of the unit cell stack 1. Become. The degree of division of the manifold 8 is determined by the height dimension of the fuel cell, and the mechanical strength and thermal expansion coefficient of the resin film that wraps the inner surface, that is, the degree to which the manifold 8 does not hang down and cut due to its own weight, is 1 per division.
It is preferably about m. It should be noted that there is no need to divide the small type.

FIG. 3 shows the unit cell stack 1 using the manifold 8 shown in FIG. 2 with a heat-resistant and phosphoric acid-resistant fluorine-based resin film 9.
3 shows a state in which the bolt 10 is attached to the side surface of the through the seal material 5 and the reinforcing material 2. The sealing material 5 is also inserted into the divided portion of the manifold 8, and the phosphoric acid resistant resin film 9 is pressed by the bolt 10 so as to wrap the metal material of the manifold. In addition, a gas vent pipe 11 that communicates to the outside through a small hole is attached to the substantially central portion of all the metal materials of the divided manifold. Then, the pipes 11 are grouped together so that a pressure difference does not occur. The gas vent pipe 11 prevents the gas that has permeated the resin film 9 during continuous operation from expanding and pushing up and deforming the resin film 9 during depressurization. On the other hand, one gas supply / exhaust pipe 12 is attached to the side surface of the unit cell stack 1.

FIG. 4 shows how the gas supply / discharge pipe 12 is joined to the manifold 8. In the figure, degassing pipe 1
The gas supply / exhaust pipe 1 is fixed to the inside of the manifold 8 having
It is only 2. With this structure, even if there is a pressure fluctuation on the gas side, the gas does not mix directly on both sides of the resin film 9.

FIG. 5 is a top view of the state in which the manifold 8 is attached to the unit cell stack 1. In the figure, bolt 1
The manifold 8 integrated with 0 is provided with a resin film 9 on its inner surface, and is attached to the side surface of the unit cell stack 1 via a seal material 5.

FIG. 6 shows a state of the joint portion of the divided manifold. In the drawing, the end portion of the metal material of the manifold is a joint portion of the marking wax system, and the lower manifold 8
A brim having a structure for pressing the sealing material 5 is attached to A, and the upper manifold 8B sandwiches the resin films 9A and 9B through the sealing material 5 and tightens them with bolts 10 and nuts 14. In FIGS. 5 and 6, depending on the nature of the resin film 9, a sealing material may be inserted between the manifold metal material and the resin film 9.

FIG. 7 shows the inner surface of the divided manifold metal material. In the figure, in order to surely remove the gas accumulated between the metal material and the resin film in a short time, a gas vent groove 15 is provided on the inner surface of the manifold metal material, and a gas vent pipe port 16 is provided.
If it is installed so that it gathers in, the resin film will be sucked into the gas vent piping port 16 due to an instantaneous pressure change,
The gas in other parts does not escape. Here, the gas vent groove 15 may have a width and a depth of about 2 mm.

In the fuel cell including the manifold configured as described above, even if the temperature rises and falls during operation, pressure is increased by gas supply, and pressure is decreased by gas discharge, the resin film 9
The gas that has permeated through the film does not expand to push up the film itself, the manifold structure material can be protected from corrosive phosphoric acid, and a long-life fuel cell can be obtained.

On the other hand, as the resin film 9 usable in the above, TFE, PFA, FEP and the like are used as the fluorine resin having heat resistance and chemical resistance.
In this case, if the structure of the manifold becomes complicated, it is difficult to process with TFE, and welding and realignment are required.
, FEP, etc. have fluidity when heated, so a free shape can be obtained using a film. Also, TFE and PFA are 2
60 ° C, FEP can withstand continuous use temperature at 200 ° C. Furthermore, the thickness of the film is preferably about 0.2 to 0.5 mm. Further, a film having a constant thickness can be obtained by performing thick coating with emulsion or powder on the premise of peeling.

Further, since the fuel cell is normally operated at a pressure of 4 to 5 kg / cm ² , if the end of the degassing pipe is exposed to the outside of the fuel cell body and opened to the atmosphere, it will correspond to the pressure difference. The gas passing through the resin film is released into the atmosphere. Further, the amount thereof is a minute amount and is not a problem, but there is a risk of ignition in the fuel side pipe. Therefore, as one method for preventing this, a valve that opens if necessary can be used. FIG. 8 schematically shows an embodiment thereof. In the figure, the gas supply / discharge pipe 12 connected to the manifold 8 is provided with a pressure detector 17 for detecting a pressure drop, and the valve 18 attached to the end of the gas vent pipe 11 is opened by the detection signal. By this, the shape of the resin film can be protected from being pushed up by the accumulated gas.

As another method, there is a method of maintaining the same pressure in the pipe, one example of which is shown in FIG. In FIG. 9, the gas vent pipe 11 and the gas supply / exhaust pipe 12 are connected through a filter 19 to keep the same pressure while preventing phosphoric acid from entering due to evaporation and scattering. Filter 1
Since 9 is mainly for degassing, the one having less gas resistance can cope with a sudden pressure decrease. The filter 19 may be a phosphoric acid adsorbent or a mist or dust separator. The filter 19 reduces the adsorbent for removing phosphoric acid if the entire fuel cell is placed in an inert gas closed system, and reduces the amount of phosphoric acid if the filter 19 is placed outside the closed system. It may be a simple pipe cooling unit for.

Furthermore, the first method for maintaining the same pressure in the pipe
There is an example of FIG. FIG. 10 shows the gas supply / exhaust pipe 12
A pressure adjusting portion 21 accommodating a flexible film 20 is provided between the gas vent pipe 11 and the gas venting pipe 11, and the material forming the film 20 is a softer material than the resin film 9 used inside the manifold, or rubber or the like. To use. It is also necessary to maintain the temperature around this room temperature outside this closed system.

Furthermore, another similar embodiment is shown in FIG. First
In FIG. 1, a pressure adjusting portion 21 having a piston 22 is provided between the gas supply / exhaust pipe 12 and the gas vent pipe 11. In addition to these membranes and pistons, bellows can be used to maintain the same pressure.

As described above, the manifold used in the present invention is particularly effective as an outlet manifold for fuel gas and oxidant gas, but if phosphoric acid scattering at the time of stoppage is also considered, degassing piping should also be provided for the inlet manifold. It is better to install the fuel cell for further prolonging the life of the fuel cell. FIG. 12 is a top view of the structure of an embodiment in which a gas vent pipe is attached to the gas supply pipe side. In the figure, the unit cell stack 1 has a fuel inlet manifold 3'on the left side, a fuel outlet manifold 4'on the right side, an air inlet manifold 6'on the lower side, and an air outlet manifold 7'on the upper side. Extraction piping 11-3 'and 11-4', 11
-6 'and 11-7' are connected on the way and are connected to the supply side pipes 12-3 'and 12-6' of each gal through a filter 19. In this case, since the pressure difference of the gas passing through the unit cell stack 1 is about several tens of mmHg, the resin film on the inner surface of the manifold is not particularly pushed up. Further, since the filter 19 is on the gas supply side, the performance deterioration due to the scattering of phosphoric acid is minimized, which is convenient for maintenance management. Further, the filter 19 may be the cooling unit or the pressure adjusting unit 21 as described in the other embodiments.

〔The invention's effect〕

As described above, according to the present invention, the manifold is
The unit cell stack is divided into a plurality of layers in the stacking direction, and the inner surface of the unit cell stack is wrapped with a heat-resistant and chemical-resistant resin film, and the divided manifold discharges gas between the manifold and the resin film to the outside. Since the gas vent pipe is attached, and if necessary, the gas supply / exhaust pipe and the gas vent pipe are connected through the pressure holding means for holding the internal pressure of the pipe at the same pressure, the resin due to pressure fluctuation It is possible to provide a highly reliable fuel cell capable of preventing the film from peeling and extending the life and continuing the operation.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a conventional fuel cell, FIG. 2 is a perspective view showing a manifold applied to the present invention, and FIG. 3 is a sectional view showing one side of a fuel cell provided with the manifold of the present invention. FIGS. 4, 5, 6, and 7 are partial configuration diagrams showing a manifold applied to the present invention, and FIGS. 8 to 12 are configuration diagrams showing another embodiment of the present invention. . 1 ... Unit cell stack, 3,4,6,7,8 ... manifold, 9 ... resin film, 11 ... gas venting pipe, 1
2 ... Gas supply / exhaust pipe, 15 ... Gas vent groove, 17 ...
Pressure detector, 18 ... Valve, 19 ... Filter, 21 ...
… Pressure regulator.

Claims (4)

[Claims] 1. A pair of manifolds for supplying and discharging a fuel gas through a gas supply / exhaust pipe are provided on one side facing the unit cell stack, and an oxidant gas is passed through a gas supply / exhaust pipe on the other side orthogonal to this. In a fuel cell provided with a pair of manifolds for supplying and discharging, the manifold is divided into a plurality in the stacking direction of the unit cell stack, and the inner surface of the manifold is covered with a heat-resistant and chemical-resistant resin film. The manifold
A fuel cell characterized in that a gas vent pipe for discharging gas between the manifold and the resin film to the outside is attached. 2. The fuel cell according to claim 1, wherein a gas vent groove communicating with a gas vent pipe is provided on the inner surface of the manifold. 3. The fuel cell according to claim 1, wherein the gas vent pipe is provided with a valve that is opened when the internal pressure of the gas supply and exhaust pipe drops. . 4. A pair of manifolds for supplying and discharging a fuel gas through a gas supply / exhaust pipe are provided on one side facing the unit cell stack, and an oxidant gas is passed through a gas supply / exhaust pipe for the other side orthogonal to this. In a fuel cell provided with a pair of manifolds for supplying and discharging, the manifold is divided into a plurality in the stacking direction of the unit cell stack, and the inner surface of the manifold is covered with a heat-resistant and chemical-resistant resin film. The manifold
A gas vent pipe for exhausting the gas between the manifold and the resin film to the outside is attached, and the gas supply and exhaust pipe and the gas vent pipe are connected via a pressure holding means for holding the internal pressure of the pipe at the same pressure. A fuel cell characterized by the above.