JPH0917439A - Solid polymer fuel cell - Google Patents

Abstract

PURPOSE: To lessen a necessary space for a substitution material with which a remaining gas of a fuel electrode is substituted at the time of operation stop or in an emergency and heighten space efficiency. CONSTITUTION: A substituting water tank 8 and a substituting water supplying pump 10 are connected with a discharge pipeline of a fuel electrode of a fuel cell main body 1 through a valve 14 and further a storage tank of a condensing tank 5 of a condenser 4 to condensed water in discharge gas is connected with the substituting water tank 8 through a condensed water turn back pump 9. At the time of operation stop or in an emergency, the valve 14 is opened and the substituting water supply pump 10 is started to supply a substituting water to the fuel electrode from the substituting water tank 8 and to substitute the remaining gas with the water. At the time of re-start, the used substituting water is sent back to the condensing tank 5 with a fuel gas, recovered to the substituting water tank 8 by the condensed water turn back pump 9, and then used for next substitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer electrolyte fuel cell, and more particularly to a structure for replacing fuel gas in a fuel electrode when the engine is stopped or in an emergency.

[0002]

2. Description of the Related Art In a polymer electrolyte fuel cell, unit cells having a fuel electrode and an oxidizer electrode are laminated on both sides of an ion exchange membrane of an electrolyte to form a fuel cell body, and hydrogen or monoxide is formed on the fuel electrode. Fuel gas such as carbon and oxidant gas such as air are supplied to the oxidant electrode to generate electricity by an electrochemical reaction.

FIG. 7 is a system diagram showing a basic structure of a main part of a reaction gas system of a conventional polymer electrolyte fuel cell. To the fuel electrode of the fuel cell body 1 schematically shown, the fuel gas humidified through the fuel gas humidifier 2 to secure the wettability of the polymer membrane of the electrolyte is supplied through the valve 11 in the open state. Similarly, the oxidant gas humidified through the oxidant gas humidifier 3 is supplied to one of the oxidant electrodes. The exhausted fuel gas, which causes an electrochemical reaction at the fuel electrode and contributes to power generation and is discharged, passes through the valve 12 in the open state to the condenser 4
And is taken out as dry exhaust gas from which water is condensed and removed. The water condensed in the condenser 4 is stored in the condensed water tank 5, and is appropriately taken out to the outside for use. Further, the fuel cell main body 1 is cooled by the water in the cooling water tank 6 circulated by using the cooling water pump 7 and kept at a constant temperature.

When the solid polymer fuel cell is stopped,
Alternatively, the valves 11 and 12 are closed in an emergency when an abnormality occurs in the fuel cell main body 1 or the fuel gas supply system during operation, and the valves 21 and 22 that are kept closed during operation are opened.
Measures are taken to ensure safety by supplying nitrogen gas to the fuel electrode and replacing the fuel gas remaining in the fuel gas system. The fuel gas is replaced while being mixed and diffused with the supplied nitrogen gas. When the power generation operation is started again, the replacement nitrogen gas in the fuel gas system is exhausted and the fuel gas is supplied.

[0005]

As described above, in the conventional polymer electrolyte fuel cell, the gas in the fuel gas system is replaced with nitrogen gas when the operation is stopped or in an emergency. Since it is a method, it is replaced while mixing and diffusing, so the amount of nitrogen gas required for replacement reaches several times the volume of the system to be replaced. In addition, a large compressor is required to recover the substituted nitrogen gas, which requires a large amount of equipment cost and is not economical, so it is customary to discharge the nitrogen gas into the atmosphere without recovering it. However, since it is not known when an emergency occurs and how many times it occurs, it is necessary to always hold the replacement nitrogen gas for several times during operation. Since this amount of holding is quite large, there is a problem that a wide space for that purpose must be secured.

The present invention has been made in view of the above problems, and has a high space efficiency in which the space required for the replacement material for replacing the residual gas in the fuel electrode is reduced when the operation is stopped or in an emergency. An object is to provide a polymer electrolyte fuel cell.

[0007]

In order to achieve the above object, in the present invention, (1) a unit cell in which an electrolyte composed of an ion exchange membrane is sandwiched between a fuel electrode and an oxidant electrode is laminated to form a fuel. Configure the battery body,
In a polymer electrolyte fuel cell that supplies fuel gas to the fuel electrode and oxidant gas to the oxidizer electrode to generate electricity by an electrochemical reaction, the fuel gas supply pipe to the fuel electrode and the discharge pipe from the fuel electrode A replacement water tank for storing replacement water to be sent to the fuel electrode is connected to either one via a valve that opens when the operation is stopped or in an emergency, and the fuel gas in the fuel electrode is replaced with water.

(2) Further, in the polymer electrolyte fuel cell of the above (1), the supply pipe for supplying the fuel gas to the fuel electrode is supplied from the inlet pipe having an opening in the humidified water and has an opening in the gas layer portion. In the one connected to the outlet pipe of the humidifier for humidifying the fuel gas by taking out from the outlet pipe, the humidifier is used as the above-mentioned replacement water tank, and the fuel gas in the fuel electrode is replaced with the humidifying water.

(3) Furthermore, in the polymer electrolyte fuel cell according to (2) above, fuel gas is supplied from the outlet pipe of the humidifier by valve operation when the operation is stopped or in an emergency, and the inlet pipe of the humidifier is supplied. By providing a pipe for connecting a supply pipe to the fuel electrode, the fuel gas in the fuel electrode is replaced with humidifying water. (4) Further, in the polymer electrolyte fuel cell of (1), (2), and (3) above, a condenser for condensing water contained in the fuel gas discharged from the fuel gas discharge pipe from the fuel electrode. The condensate water tank for storing the condensed water obtained in the condenser and the replacement water tank are connected via the condensed water return pump.

(5) Further, in the polymer electrolyte fuel cell according to the above (1), an exhaust pipe of the fuel gas from the fuel electrode is connected to a condenser for condensing water contained in the exhausted fuel gas. In this case, the fuel gas in the fuel electrode is replaced with the condensed water by using the condensed water tank for storing the condensed water obtained by the condenser as the replacement water tank. (6) Further, in the polymer electrolyte fuel cell according to (1) above, which is provided with a cooling water tank for storing cooling water for cooling the fuel cell main body and a cooling water pump for circulating the cooling water,
By using the cooling water tank as the replacement water tank, the fuel gas in the fuel electrode is replaced with the cooling water.

[0011]

As described above, if water is used to replace the fuel gas in the fuel electrode, water is a liquid and does not diffuse or mix with the fuel gas. The remaining fuel gas can be replaced by supplying approximately equal amounts of water. In particular, in the structure in which the fuel gas flows from the upper part to the lower part in the fuel electrode, if the water is supplied from the fuel gas outlet side of the fuel electrode to the inlet side, the fuel gas will flow from the lower part to the upper part. Since it is replaced without remaining, it is effectively replaced. Further, the water used for the replacement can be easily recovered, and it is possible to deal with the problem only by storing the replacement water for one time, and the space required for the replacement material is greatly reduced.

Further, if condensed water, humidifying water or cooling water is used as the replacement water, it is not necessary to newly provide a required space for replacement. In addition,
When water is used for substitution, the characteristics of the fuel cell that uses an aqueous solution as an electrolyte are degraded because the electrode is immersed in water or the electrolyte, but in the polymer electrolyte fuel cell, the wettability of the polymer membrane is maintained. Therefore, there is no risk of damaging the fuel cell body even if water is used for replacement because it is necessary to humidify.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram showing a basic configuration of a main part of a reaction gas system of a first embodiment of the polymer electrolyte fuel cell of the present invention. In the figure, components having the same functions as those of the conventional example shown in FIG. 7 are designated by the same reference numerals, and duplicated description will be omitted.

The feature of this embodiment is that, instead of the nitrogen gas supply and discharge system connected through the valves 21 and 22 used in the conventional example, the valve 1 is connected to the discharge pipe of the fuel electrode of the fuel cell body 1.
4, a replacement water supply pump 10 and a replacement water tank 8 serving as a replacement water tank are connected, and a condensed water tank 5 is connected to the replacement water tank 8 via a condensed water return pump 9. is there.

In the polymer electrolyte fuel cell of this embodiment, when the operation is stopped or in an emergency, the valves 11 and 12 are closed, the normally closed valves 13 and 14 are opened, and the replacement water supply pump 10 is operated. The replacement water stored in the replacement water tank 8 is supplied to the fuel electrode. The residual fuel gas is pressurized by the replacement water and is discharged from the valve 13 to be replaced. When restarting the operation, the replacement water supply pump 10 is stopped and the valves 13 and 1 are connected.
4 is closed and valves 11 and 12 are opened to supply the fuel gas to the fuel electrode. The replacement water discharged from the discharge pipe of the fuel electrode together with the supply of the fuel gas passes through the condenser 4 and is collected in the condensation tank 5. The replacement water collected in the condensing tank 5 is returned to the replacement water tank 8 again by the operation of the condensed water return pump 9, and is provided for the next use. As described above, in the configuration of the present embodiment, the replacement water can be collected and used many times, and the amount of the replacement water to be retained is only one. Therefore, the replacement space is significantly larger than the conventional one using nitrogen gas. Is reduced to.

Since the humidified fuel gas supplied to the fuel electrode is a mixture of gas and liquid containing water produced by the reaction at the fuel electrode, the gas inlet is connected to the gas inlet as schematically shown in FIG. It is customary to provide a gas outlet in the lower part in the upper part, and to form a flow path so as to flow from the upper part to the lower part. Therefore, when substituting the residual gas with the replacement water, it is effective to supply the replacement water from the lower portion, and in the embodiment of FIG. 1 also, in consideration of this, the replacement water is supplied from the discharge pipe side of the fuel electrode. Is configured to supply.

FIG. 3 is a system diagram showing the basic structure of the essential part of the reaction gas system of the second embodiment of the polymer electrolyte fuel cell of the present invention. A feature of this embodiment is that the fuel gas humidifier 2 is used as a replacement water tank instead of the replacement water tank 8 of the first embodiment, and the humidification water is used as replacement water. In this embodiment, the humidifying water is sent to the fuel electrode by the operation of the replacement water supply pump 10 to replace the residual gas. The humidifying water used for the replacement is collected in the condensing tank 5 and is again collected in the fuel gas humidifier 2 by the operation of the condensed water return pump 9. With this configuration, there is no need to provide a dedicated replacement water tank 8 as in the first embodiment, and it is effective in reducing the space.

FIG. 4 is a system diagram showing the basic structure of the essential part of the reaction gas system of the third embodiment of the polymer electrolyte fuel cell of the present invention. In the present embodiment, the humidifying water of the fuel gas humidifier 2 is used for replacement as in the second embodiment, and the route of the fuel gas flowing through the fuel gas humidifier 2 is changed by operating the valve. Thus, the feature is that the humidifying water is supplied to the fuel electrode when the operation is stopped or in an emergency. With this configuration, during normal operation, the valves 11 and 15 are opened,
Further, the valves 13 and 16 are kept closed to allow the fuel gas to flow through the valve 1.
It is supplied to the humidified water of the fuel gas humidifier 2 through 1 to be humidified, and is supplied to the fuel electrode through the valve 15. When the operation is stopped or in an emergency, the valves 11 and 15 are closed and the valves 13 and 1 are closed.
6 is opened and the fuel gas is supplied to the gas layer portion of the fuel gas humidifier 2 through the valve 16. The humidification water of the fuel gas humidifier 2 is pressure-fed to the fuel electrode through the valve 13 by the pressure of the supplied fuel gas and replaces the residual gas. In this configuration, since it is not necessary to provide the dedicated replacement water tank 8 and the replacement water supply pump 10 as in the first embodiment, the required space can be more effectively reduced.

FIG. 5 is a system diagram showing the basic structure of the essential parts of the reaction gas system of the fourth embodiment of the polymer electrolyte fuel cell of the present invention. The feature of the present embodiment is that the condensed water tank 5 is used as a replacement water tank, and the tank of the condensed water tank 5 is connected to a fuel gas supply pipe of a fuel electrode via a replacement water supply pump 10 and a valve 17. Is being done. In this configuration, when the operation is stopped or in an emergency, the valve 11 is closed, the valve 17 is opened, and the replacement water supply pump 10 is operated to supply the condensed water directly to the fuel electrode to replace the residual gas. In this configuration, since the exclusive replacement water tank 8 and the condensed water return pump 9 as in the first embodiment are not required, the required space can be reduced more effectively.

FIG. 6 is a system diagram showing the basic structure of the essential parts of the reaction gas system of the fifth embodiment of the polymer electrolyte fuel cell of the present invention. The feature of this embodiment is that the cooling water tank 6 that stores cooling water for cooling the fuel cell main body 1 to keep it at a constant temperature is used as a replacement water tank, and the cooling water tank 6 and the cooling water pump 7 are used. The cooling water system including the pipe is connected to the fuel gas supply pipe to the fuel electrode via the valve 18. With this configuration, at the time of operation stop or emergency,
The valve 11 is closed and the valve 18 is opened to supply a part of the cooling water to the fuel electrode to replace the residual gas. In this configuration, the dedicated replacement water tank 8, the condensed water return pump 9, and the replacement water supply pump 10 as in the first embodiment are not required, so that the required space is more effectively reduced.

[0021]

EFFECTS OF THE INVENTION As described above, according to the present invention, (1) in the polymer electrolyte fuel cell, the fuel gas is supplied to either one of the fuel gas supply pipe to the fuel electrode and the discharge pipe from the fuel electrode. Since the replacement water tank that stores the replacement water to be sent to the electrode is connected through a valve that opens when the operation is stopped or in an emergency, the fuel gas at the fuel electrode is replaced with water, so the volume of the fuel gas system is increased. It is possible to replace the remaining fuel gas by supplying an amount of water that is almost equal to, and the space required for the replacement material is greatly reduced compared to the conventional replacement with nitrogen gas. It has become possible to obtain a polymer electrolyte fuel cell.

(2) Further, a humidifier for humidifying the fuel gas by supplying the fuel gas to the fuel electrode from an inlet pipe having an opening in the humidified water and taking out from an outlet pipe having an opening in the gas layer portion. In the polymer electrolyte fuel cell connected to the outlet pipe of the above, if the humidifier is used as the replacement water tank and the fuel gas of the fuel electrode is replaced by the humidification water, a replacement water tank is installed separately. Since it is not necessary to do so, the space required for the replacement material is further reduced, and it is suitable as a polymer electrolyte fuel cell with high space efficiency.

(3) Furthermore, in the polymer electrolyte fuel cell of (2) above, fuel gas is supplied from the outlet pipe of the humidifier by valve operation when the operation is stopped or in an emergency, and the fuel is supplied to the inlet pipe of the humidifier. If a pipe for connecting the supply pipe to the pole is provided and the fuel gas in the fuel electrode is replaced with humidifying water, the humidifying water is pumped by the supplied fuel gas in the event of an operation stop or an emergency. Since it is not necessary to separately provide a pump for supplying replacement water, it is more suitable as a polymer electrolyte fuel cell with high space efficiency.

(4) Further, in the polymer electrolyte fuel cell of (1), (2) and (3) above, the water contained in the fuel gas discharged from the fuel gas discharge pipe is condensed. If the condensate tank for storing the condensed water obtained in the condenser and the replacement water tank are connected through the condensed water return pump, the replacement water used is Since the recovered water can be reused, the replacement water tank only needs to have a capacity for storing one replacement water, which is more suitable as a polymer electrolyte fuel cell with high space efficiency.

(5) Further, in a polymer electrolyte fuel cell in which a fuel gas discharge pipe from a fuel electrode is connected to a condenser for condensing water contained in the fuel gas discharged, If the condensed water tank that stores the condensed water is used as the replacement water tank and the fuel gas at the fuel electrode is replaced with the condensed water, the replacement water tank, the replacement water supply pump, and the condensed water return pump are also available. A polymer electrolyte fuel cell which is unnecessary and has extremely high space efficiency can be obtained.

(6) In a polymer electrolyte fuel cell provided with a cooling water tank for storing cooling water for cooling the fuel cell body and a cooling water pump for circulating the cooling water, the cooling water tank is used as a replacement water tank. If the fuel gas in the fuel electrode is replaced with cooling water, it is not necessary to separately install a replacement water tank, and thus it is suitable as a polymer electrolyte fuel cell with high space efficiency.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a basic configuration of a main part of a reaction gas system of a first embodiment of a polymer electrolyte fuel cell of the present invention.

FIG. 2 is a schematic diagram showing a general reaction gas flow path configuration of a unit cell of a polymer electrolyte fuel cell.

FIG. 3 is a system diagram showing a basic configuration of essential parts of a reaction gas system of a second embodiment of the polymer electrolyte fuel cell of the present invention.

FIG. 4 is a system diagram showing a basic configuration of a main part of a reaction gas system of a third embodiment of the polymer electrolyte fuel cell of the present invention.

FIG. 5 is a system diagram showing a basic configuration of a main part of a reaction gas system of a fourth embodiment of the polymer electrolyte fuel cell of the present invention.

FIG. 6 is a system diagram showing a basic configuration of a main part of a reaction gas system of a fifth embodiment of the polymer electrolyte fuel cell of the present invention.

FIG. 7 is a system diagram showing a basic configuration of a main part of a reaction gas system of a conventional polymer electrolyte fuel cell.

[Explanation of symbols]

 1 Fuel Cell Main Body 2 Fuel Gas Humidifier 3 Oxidizer Gas Humidifier 4 Condenser 5 Condensed Water Tank 6 Cooling Water Tank 7 Cooling Water Pump 8 Replacement Water Tank 9 Condensed Water Return Pump 10 Replacement Water Supply Pump 11, 12 Valve 13, 14 valves 15,16 valves 17,18 valves

Claims (6)

[Claims] 1. A fuel cell body is constructed by stacking unit cells in which an electrolyte composed of an ion exchange membrane is sandwiched between a fuel electrode and an oxidant electrode, and a fuel gas is formed in the fuel electrode and an oxidant gas is formed in the oxidant electrode. In a polymer electrolyte fuel cell that supplies electricity to generate electric power by an electrochemical reaction, the replacement water sent to the fuel electrode is stored in either the fuel gas supply pipe to the fuel electrode or the discharge pipe from the fuel electrode. A polymer electrolyte fuel cell characterized in that a replacement water tank is connected via a valve that opens when operation is stopped or in an emergency. 2. The polymer electrolyte fuel cell according to claim 1, wherein the fuel gas supply pipe to the fuel electrode is supplied from an inlet pipe having an opening in humidified water and an outlet pipe having an opening in a gas layer portion. A polymer electrolyte fuel cell, characterized in that it is connected to an outlet pipe of a humidifier for humidifying the fuel gas by taking it out further, and that the humidifier serves as the replacement water tank. 3. The polymer electrolyte fuel cell according to claim 2, wherein the fuel gas is supplied from the outlet pipe of the humidifier by valve operation when the operation is stopped or in an emergency, and the fuel electrode is supplied to the inlet pipe of the humidifier. A polymer electrolyte fuel cell comprising a pipe for connecting a supply pipe to the polymer electrolyte fuel cell. 4. The polymer electrolyte fuel cell according to claim 1, 2 or 3, wherein an exhaust pipe of the fuel gas from the fuel electrode is connected to a condenser for condensing water contained in the exhausted fuel gas. And a condensate tank for storing condensed water obtained by a condenser and the replacement water tank are connected via a condensed water return pump. 5. The polymer electrolyte fuel cell according to claim 1, wherein a discharge pipe for discharging the fuel gas from the fuel electrode is connected to a condenser for condensing water contained in the discharged fuel gas, and A polymer electrolyte fuel cell, wherein a condensed water tank for storing condensed water obtained by the condenser is used as the replacement water tank. 6. The polymer electrolyte fuel cell according to claim 1, further comprising a cooling water tank for storing cooling water for cooling the fuel cell main body and a cooling water pump for circulating the cooling water. A polymer electrolyte fuel cell, characterized in that a tank is used as the replacement water tank.