JP2001332281A - Solid polyelectrolyte fuel cell power generation system and its operation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid polyelectrolyte fuel cell power generation system, capable of reasonably drying the inside of the fuel cell and preventing it from freezing during its shut-down and having a simple system composition and operating sequence, and offer its operation method. SOLUTION: The solid polyelectrolyte fuel cell power generation system is equipped with the fuel cell main body 1 in charge of power generation by supplying the hydrogen-contained fuel gas 8 to the anode electrode and by supplying the air 7 as an oxidant gas to the cathode electrode and with a humidifier 2, in charge of humidifying the solid-polyelectrolyte film by humidifying the air 7. During shut-down, the humidification of the air 7 is first stopped and then an air, without being humidified is supplied to the cathode electrode for a prescribed time to stop the operation of the fuel cell power generation system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid polymer electrolyte fuel cell power generator and a method of operating the same.

[0002]

2. Description of the Related Art In general, the structure of a cell which is the minimum power generation unit of a solid polymer electrolyte fuel cell is shown in FIG. Membrane Ele (MEA: Membrane Ele)
Ctrode assembly is formed by bonding a catalyst layer 40 containing a noble metal (mainly platinum) to both surfaces of the electrolyte membrane 31. A porous diffusion layer 33 is provided outside the MEA.
There is a function to transmit a current to the outside while passing a fuel gas and an oxidizing gas as reaction gases.

[0003] Together with the porous diffusion layer 33 and the catalyst layer 40, the side through which the fuel gas flows is called the anode electrode, and the side through which the oxidizing gas flows is the cathode electrode. Further, the MEA in a broad sense may include a diffusion layer. A cell is formed by sandwiching the two electrodes between the separators 32 each having a fuel gas flow path and an oxidizing gas flow path. A stack of many of these cells is called a stack.

[0004] For the electrolyte membrane, a fluorine-based polymer material is most commonly used. Typical commercially available electrolyte membranes include
There is Nafion ^TM (trade name, manufactured by DuPont, USA). The features of these electrolyte membranes are that they have higher proton conductivity than other polymer electrolytes, and that the proton conductivity rapidly decreases when the electrolyte membrane dries. For this reason, in a solid polymer electrolyte fuel cell, it is required to always control the electrolyte membrane to an appropriate water-containing state. Usually, drying of the electrolyte membrane is prevented by humidifying the reaction gas.

[0005] Water for humidification is obtained by collecting and using produced water or supplied from outside. Since the electrolyte adsorbs metal ions, the water used for humidification must be free of metal ions by a method such as ion exchange. Further, additional equipment is required to collect and use the generated water.

[0006]

As described above, the electrolyte membrane of a solid polymer electrolyte fuel cell is a polymer ion exchange membrane, which must be kept wet during operation. Water is added to the gas by humidifying means. Water is also generated by the power generation of the fuel cell. Since a solid polymer electrolyte fuel cell is operated at a temperature equal to or lower than the boiling point of water at the operating pressure, such water is often present in a liquid state inside the cell.

In cold regions, the above-mentioned liquid water remaining inside the solid polymer electrolyte fuel cell freezes after the operation is stopped,
There is a possibility that the microstructure inside the catalyst layer or the diffusion layer is destroyed.

In order to cope with the above problem, in a solid polymer electrolyte fuel cell power generation apparatus of the type in which water is blown into a fuel gas as a reaction gas to generate a gas-liquid mixture and humidify the reaction gas when the fuel cell is stopped. A method of collecting water in a cooling water tank by water discharging means in a fuel cell provided with an air pump provided separately from an air blower, or collecting water in a cooling water tank by continuously operating only a fuel gas pump A method has been proposed (Japanese Unexamined Patent Publication No. 9-147).
No. 892).

However, Japanese Patent Application Laid-Open No. Hei 9-14789 discloses
The system described in Japanese Patent Publication No. 2 has a complicated system configuration and operating procedure as a whole.
In the former method, it is necessary to provide an air pump separately from the reaction air blower, and there is a problem that excess equipment is required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is an object of the present invention to provide an apparatus having a simple structure and operating procedure, and to obtain a reasonable dry state inside the battery when the power generator is stopped. An object of the present invention is to provide a solid polymer electrolyte fuel cell power generator and an operation method thereof.

[0011]

In order to solve the above-mentioned problems, according to the present invention, when the fuel cell power generation device terminates the electric output to the outside and enters a stop state, the fuel cell main body has a certain period of time. Supply dry gas to

It is convenient to use air as the drying gas. By stopping the humidification to the air, a gas having a sufficient drying effect can be obtained at the operating temperature of the battery. The method of stopping the humidification depends on the humidification means, but there is a method of stopping the supply of the humidification water, draining the water inside the humidification device, and bypassing the humidification device.

[0013] When air is used, the fuel cell keeps supplying power to the air supply device, so that it can be applied even to a small power generation device without system connection. In addition, when the system connection is made, it is possible to introduce air as a dry gas in a state where the power generation of the fuel cell body is completely stopped.

The time for supplying the drying gas can be set to an appropriate value in advance according to the flow rate of the drying gas.
It is also possible to determine the supply time of the dry gas by monitoring a decrease in the output voltage due to the drying of the electrolyte membrane. The reason for limiting the drying time in this way is that if the drying time is too long, the time required for restarting is increased.

[0015] Based on the above concept, the invention of claim 1 includes an anode electrode and a cathode electrode each comprising a catalyst layer and a porous diffusion layer disposed with a solid polymer electrolyte membrane interposed therebetween, and A fuel cell main body for generating electricity by supplying a fuel gas containing hydrogen to the electrode and supplying air as an oxidant gas to the cathode electrode, and a humidifier for humidifying the solid polymer electrolyte membrane by humidifying the air In the operation method of the solid polymer electrolyte fuel cell power generator including the above, when the operation is stopped, first the humidification of the air is stopped, and after the non-humidified air is supplied to the cathode electrode for a predetermined time, the fuel cell power generation is started. The operation of the device shall be stopped.

As described above, when the fuel cell is stopped, the humidification is stopped, and the reaction air blower is operated for a predetermined period of time (for example, about 3 minutes) which is preferable for drying the solid polymer electrolyte membrane. Since the object can be achieved, the configuration and the operation procedure are simplified.

Further, since the optimum drying state of the electrolyte membrane can be evaluated by the output voltage of the fuel cell as described above, the invention of claim 2 is preferable from the viewpoint of avoiding overdrying and wasted time. That is, in the operating method of the fuel cell power generator according to claim 1, the fuel cell main body is operated in a low load state by supplying non-humidified air to the cathode electrode instead of the predetermined time, and The operation of the fuel cell power generator is stopped when the output voltage of the fuel cell body drops to a predetermined value due to the drying.

Further, a solid polymer electrolyte fuel cell power generator for carrying out the method according to the first or second aspect of the present invention includes a catalyst layer provided with a solid polymer electrolyte membrane interposed therebetween and a porous diffusion layer. A fuel cell main body having an anode electrode and a cathode electrode comprising a layer, a fuel gas containing hydrogen supplied to the anode electrode, and air supplied as an oxidant gas to the cathode electrode to generate electric power; and A humidifier for humidifying the solid polymer electrolyte membrane by humidifying the fuel cell, and when the operation of the fuel cell power generator is stopped, first humidification of the air is stopped, and after supplying non-humidified air to the cathode electrode for a predetermined time, or A control device for stopping the operation of the fuel cell power generation device when the output voltage of the main body falls to a predetermined value is provided (the invention of claim 3).

As the embodiments of the humidifying device, the following inventions of claims 4 to 7 are preferable. That is, first, in the fuel cell power generator according to claim 3, the humidifying device for humidifying the air has a humidifying film, and has a space for storing water on one side of the main surface of the humidifying film, and the air on the other side. A space through which air flows is provided, and the humidification of the air is stopped by discharging stored water (the invention of claim 4).

Further, in the fuel cell power generator according to the third aspect, the humidifying device for humidifying the air diffuses the air into the water stored in the humidifying container and removes the air deaerated from the water. It has a configuration in which the air flows into the main body, and the humidification of the air is stopped by discharging the stored water (the invention of claim 5).

Further, in the fuel cell power generator according to claim 4 or 5, the humidifier is provided with a water storage tank separately provided with water stored on one side of the main surface of the humidifying film or water stored in the humidifying container. And the pump means comprises a flow direction switching means comprising at least four valves, and the control device, when the operation of the fuel cell power generation device is stopped, It is configured such that the stored water is discharged by switching the flow direction (the invention of claim 6).

Further, in the fuel cell power generator according to the fourth or fifth aspect, the humidifier further includes a bypass circuit for allowing non-humidified air to flow directly to the fuel cell body and a switching device for switching to the bypass circuit. The humidification of the air is stopped by switching the flow of the air to the bypass circuit (the invention of claim 7).

The embodiment of the humidifier can be properly used depending on the capacity of the fuel cell power generator and specifications based on customer needs. In particular, the invention according to claim 6 is suitable for simplifying the means and procedure for introducing and discharging humidifying water.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention.
1 shows a schematic system diagram according to the invention of FIG. The fuel cell power generator shown in FIG. 1 includes a fuel cell main body 1, a reformer 3 for supplying a hydrogen-rich reformed fuel gas 8 to the fuel cell main body, a blower 4 for supplying reaction air 7, A humidifier 2 for humidifying the solid polymer electrolyte membrane by humidifying the fuel cell, and when the operation of the fuel cell power generator is stopped, first, the humidification of the air is stopped, and after the non-humidified air is supplied to the cathode for a predetermined time or And a control device for stopping the operation of the fuel cell power generation device when the output voltage of the battery body drops to a predetermined value.

Further, the humidifier 2 introduces and discharges water stored on one side of the main surface of the humidifying film or water stored in the humidifying container from the separately provided water tank 6 by the pump means 5. And the pump means 5 is
A flow direction switching means comprising four valves 10 and 11;
The control device 20 is configured to discharge the water stored on one side of the humidifying film main surface or the water stored in the humidifying container when the operation of the fuel cell power generation device is stopped, by switching the flow direction. ing.

In FIG. 1, during normal operation, water flows from the tank 6 to the fuel cell main body 1 and the main body 21 of the humidifier 2 by the pump means 5, and flows back through the pipe 9. The pump means 5 can reverse the liquid sending direction by switching between the on-off valves 10 (two) and the on-off valves 11 (two). That is, when operating with the on-off valves 10 (two) open and the on-off valves 11 (two) closed,
The water in the tank 6 flows through the main body 21 of the humidifier 2.
Conversely, when operating with the on-off valves 10 (two) closed and the on-off valves 11 (two) open, the flow is in the opposite direction, and the water in the main body 21 of the humidifier 2 Is discharged to

The air supplied by the blower 4 is humidified by the humidifier 2 and then passes through the fuel cell body 1. Fuel gas 8
Passes through the fuel cell body 1 from the reformer 3, and the remainder returns to the reformer 3 and burns, and is used as heat for the reforming reaction.

The operation when the fuel cell power generation device is stopped is as shown in FIG. 2, for example. After stopping the power output to the outside,
Water is discharged from the inside of the main body of the humidifier 2 by reversing the liquid feeding direction of the pump means 5. At this time, the supply of the fuel gas and the air is continued, and the fuel cell main body 1 enters an operating state with a low load. By discharging the humidified water, the air is supplied to the battery body in a dry state, and the water inside the electrode is discharged. By drying the electrolyte membrane, the output voltage of the battery main body 1 is reduced at the same time. After an appropriate time has elapsed (for example, 3 minutes) or when the output voltage has dropped to a predetermined value,
The supply of fuel gas and air is stopped, and the fuel cell power generator shifts to a completely stopped state.

In the above embodiment, the fuel cell body 1 is in the low load operation state while the dry gas is being supplied.
It does not necessarily require that the battery body be in the operating state.

Next, an embodiment of the humidifier will be described with reference to FIGS.

The humidifier shown in FIG. 3 has a space 52 for storing water and a space 53 for flowing air with a humidifying film 51 interposed therebetween, and is configured to humidify the air via the humidifying film 51. Are shown. By discharging the stored water, the humidification of the air is stopped.

The humidifier shown in FIG. 4 diffuses air into water stored in a humidifying container 61 through a diffuser 62, and flows air deaerated from the water to the fuel cell body. Is shown. Also in this case, the humidification of the air is stopped by discharging the stored water.

The humidifying device shown in FIG. 5 further includes a bypass circuit 71 for allowing non-humidified air to flow directly to the fuel cell main body and a switching valve 72 as a switching device for switching to the bypass circuit, in addition to the humidifying device shown in FIG. Are shown. Stop humidification of air
This is performed by switching the flow of air to the bypass circuit 71. Note that a bypass circuit can be provided in the configuration shown in FIG.

[0035]

As described above, according to the present invention, there are provided an anode electrode and a cathode electrode each comprising a catalyst layer and a porous diffusion layer provided with a solid polymer electrolyte membrane interposed therebetween,
A fuel cell body that generates fuel by supplying a fuel gas containing hydrogen to the anode electrode and air as an oxidant gas to the cathode electrode, and humidifies the solid polymer electrolyte membrane by humidifying the air. In a method for operating a solid polymer electrolyte fuel cell power generator including a humidifier, when the operation is stopped, first stop the humidification of the air,
Thereafter, the operation of the fuel cell power generator is stopped after supplying non-humidified air to the cathode electrode for a predetermined time, so that the apparatus configuration and operation procedure are simple, and the ratio of the inside of the battery is reasonable when the power generator is stopped. It is possible to provide a solid polymer electrolyte fuel cell power generator capable of obtaining a dry state and a method of operating the same. By the above, the excess moisture present inside the electrode of the fuel cell is evaporated by the dry gas, so that the structure can be prevented from being destroyed due to freezing inside the electrode in cold weather, and the output voltage due to repeated start-stop in a cold region Can be suppressed over a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram of an embodiment of a fuel cell power generator according to the present invention.

FIG. 2 is a diagram showing an example of an operation procedure when the fuel cell power generator according to the present invention is stopped.

FIG. 3 is a conceptual diagram of a humidifying device having a humidifying film according to the present invention.

FIG. 4 is a conceptual diagram of a humidifying device provided with the humidifying container of the present invention.

FIG. 5 is a conceptual diagram of a humidifier having a bypass circuit with respect to the humidifier of FIG.

FIG. 6 is a perspective view showing a configuration of a cell of a solid polymer electrolyte fuel cell.

[Explanation of symbols]

1: fuel cell body, 2: humidifier, 3: reformer, 4:
Blower, 5: pump means, 6: tank, 7: air, 8:
Fuel gas, 10, 11: open / close valve, 20: control device, 3
1: electrolyte membrane, 32: separator, 33: diffusion layer, 4
0: catalyst layer, 51: humidifying film, 61: humidifying container, 71:
Bypass circuit.

Claims (7)

[Claims] An anode electrode and a cathode electrode each comprising a catalyst layer and a porous diffusion layer disposed with a solid polymer electrolyte membrane interposed therebetween, wherein a fuel gas containing hydrogen is supplied to the anode electrode; A solid polymer electrolyte fuel cell power generator comprising: a fuel cell main body that generates power by supplying air as an oxidant gas to a cathode electrode; and a humidifier that humidifies the air to humidify the solid polymer electrolyte membrane. In the operation method of the device, when the operation is stopped, first, the humidification of the air is stopped, and after the non-humidified air is supplied to the cathode electrode for a predetermined time, the operation of the fuel cell power generation device is stopped. A method for operating a polymer electrolyte fuel cell power generator. 2. The method of operating a fuel cell power generator according to claim 1, wherein the fuel cell main body is operated in a low load state by supplying non-humidified air to the cathode electrode instead of the predetermined time. A method for operating a solid polymer electrolyte fuel cell power generator, wherein the operation of the fuel cell power generator is stopped when the output voltage of the fuel cell body drops to a predetermined value due to drying of the membrane. 3. An anode and a cathode comprising a catalyst layer and a porous diffusion layer disposed with a solid polymer electrolyte membrane interposed therebetween, and a fuel gas containing hydrogen is supplied to the anode. A fuel cell main body that generates power by supplying air as an oxidant gas to the cathode electrode, a humidifier that humidifies the solid polymer electrolyte membrane by humidifying the air, and when the operation of the fuel cell power generator is stopped, A control device for stopping the humidification of the air and stopping the operation of the fuel cell power generation device after supplying the non-humidified air to the cathode electrode for a predetermined time or when the output voltage of the fuel cell main body falls to a predetermined value. A solid polymer electrolyte fuel cell power generator, comprising: 4. The fuel cell power generator according to claim 3, wherein the humidifying device for humidifying the air has a humidifying film, and has a space for storing water on one side of the main surface of the humidifying film, and the other side. A solid polymer electrolyte fuel cell power generator, wherein the humidification of the air is stopped by discharging stored water. 5. The fuel cell power generator according to claim 3, wherein the humidifier humidifies the air by diffusing the air into the water stored in the humidifying container and removing the air degassed from the water. A solid polymer electrolyte fuel cell power generator, characterized in that it has a configuration for flowing into a main body, and the humidification of the air is stopped by discharging stored water. 6. The fuel cell power generator according to claim 4, wherein the humidifying device separates water stored on one side of the humidifying film main surface or water stored in the humidifying container. And the pump means is configured to be introduced / discharged by a pump means. The pump means further includes a flow direction switching means including at least four valves, and the control device includes:
A solid polymer electrolyte fuel cell power generator, wherein the stored water is discharged by switching the flow direction when the operation of the fuel cell power generator is stopped. 7. The fuel cell power generator according to claim 4, wherein the humidifier further comprises a bypass circuit for directly flowing non-humidified air to the fuel cell body, and a switching device for the bypass circuit. The solid polymer electrolyte fuel cell power generator is characterized in that the humidification of the air is stopped by switching the flow of air to the bypass circuit.