JP2003197226A - Operating method of solid high polymer fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain stable power generating over a long period of time with respect to a solid high polymer fuel cell equipped with a humidity controller of a film humidifying type. <P>SOLUTION: With respect to the fuel cell equipped with a humidity controller, in which humidify controlling devices 1, which are constituted by arranging the ion exchange films 5 on both sides of the cooling-water separator 3, and further on these external surfaces, arranging the hydrogen gas separators 2 and the air separators 4, are connected in parallel, the power generating operation is performed while always supervising the resistance of the ion exchange film 5 by a milli-ohmmeter 6, and if the resistance rises beyond a regulation value, it stops power generation and takes a step of regeneration of the ion exchange films 5. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating a polymer electrolyte fuel cell equipped with a membrane humidification type humidity controller.

[0002]

2. Description of the Related Art In a polymer electrolyte fuel cell, when the electrolyte membrane is dried, the ionic conductivity is lowered and the electrolyte membrane and the electrode are not joined properly, resulting in a sharp drop in the cell output. Further, once dried, even if the electrolyte membrane is returned to a wet state, the defective joint between the electrolyte membrane and the electrode is not improved, and the battery output remains reduced. Therefore, in the polymer electrolyte fuel cell, it is necessary to always keep the electrolyte membrane in a constant wet state.

As a method of always keeping the electrolyte membrane in a constant wet state, the reaction gas immediately before flowing into the fuel cell is
The electrolyte membrane is made to flow through a gas passage separated from a water passage through an ion-exchange membrane having water permeability to moisturize and humidify, and the humidified and humidified raw material gas is supplied to a fuel cell. Is generally used. For example, Japanese Patent Application Laid-Open No. 9-35737 discloses a humidity control device including a plurality of humidification units for humidifying and controlling a gas by the above method (hereinafter, referred to as a film humidification method). The polymer electrolyte fuel cell of the type in which the gas conditioned by the humidity control device is supplied as a reaction gas to each unit cell is provided in the vicinity of the fuel cell stack.

[0004]

As described above, when the humidity control apparatus to which the membrane humidification method is applied is incorporated, the electrolyte membrane of each unit cell of the polymer electrolyte fuel cell is kept in a wet state. The decrease in ionic conductivity due to drying and the defective joint between the electrolyte membrane and the electrode are prevented, and the polymer electrolyte fuel cell can be operated for a long time.

However, even in the polymer electrolyte fuel cell incorporating such a humidity control device, when the operation is continued for a longer period of time, metal ions and gas contained in the humidification water flowing in the water flow path in contact with the ion exchange membrane are included. Since the cations contained in the reaction gas flowing in the flow channel cause a decrease in water permeability of the ion exchange membrane, there is a problem that the humidity of the reaction gas is insufficient and the battery characteristics are deteriorated.

The object of the present invention is to solve the above problems,
It is an object of the present invention to provide a method for operating a polymer electrolyte fuel cell, in which deterioration of the characteristics of the ion exchange membrane due to long-term operation is detected in advance, and proper power generation operation is maintained for a long time by appropriate measures.

[0007]

In order to achieve the above object, in the present invention, a reaction gas before being supplied to a fuel cell is circulated through a gas flow path separated from a water flow path through an ion exchange membrane. In a method of operating a polymer electrolyte fuel cell equipped with a membrane humidifying type humidity control device for controlling the humidity, (1) the resistance value of the ion exchange membrane used in the above humidity control device is constantly measured, When this resistance value exceeds the first specified value (for example, 1.2 times the initial resistance value), the fuel cell is stopped and the ion exchange membrane is regenerated. When the value becomes equal to or less than the second specified value, the operation of the fuel cell is restarted.

(2) In the operating method of (1) above,
The humidity control device is configured by a connected body of a plurality of humidity control devices in which the water flow path and the gas flow path are connected in series, and the resistance value of the ion exchange membrane of the humidity control device incorporated in the uppermost stream is constantly maintained. It will be measured. (3) Also, in the operating method of (1) or (2) above, the above-mentioned regeneration treatment of the ion exchange membrane is carried out by flowing an acid into the water channel or by exchanging it with a new one. .

When the water permeability of the ion exchange membrane decreases, the resistance of the ion exchange membrane increases. Therefore, the water permeability can be evaluated by measuring the resistance of the ion exchange membrane, and the humidity control state of the reaction gas can be known. Therefore, the above (1)
As described above, the resistance value of the ion exchange membrane is constantly measured, and when the resistance value becomes equal to or higher than the first specified value, the operation of the fuel cell is stopped to regenerate the ion exchange membrane, for example, (3) ), The fuel cell operation is restarted when the resistance value becomes equal to or lower than the second specified value by this regeneration measure, the deterioration of the cell characteristics is prevented, and It will be possible to operate stably over a long period of time.

Further, in the humidity control apparatus constituted by a connected body of a plurality of humidity control devices in which both the water flow path and the gas flow path are connected in series, the ion exchange of the most upstream humidity control device located at the inlet is performed. Since the membrane contributes most to the humidification of the reaction gas, its water permeability also drops the fastest. Therefore, according to the above (2), even in the fuel cell incorporating this type of humidity control device, the deterioration of the performance of the ion exchange membrane is effectively detected, and the deterioration of the cell characteristics is prevented in advance. It will be possible to operate stably over a long period of time.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for operating a polymer electrolyte fuel cell of the present invention will be described in detail with reference to Examples. <Example 1> FIG. 1 is a schematic diagram showing the basic structure of a fuel cell humidity control apparatus to which the method for operating a polymer electrolyte fuel cell of this example is applied. As shown in the figure, the humidity control apparatus includes three humidity control devices 1 in which air as an oxidant gas, hydrogen gas as a fuel gas, and cooling water as a humidifying water are all passed in parallel. It is composed of Also, 3
Each of the humidity control devices 1 has two ion exchange membranes 5 on both sides of a cooling water separator 3 through which cooling water flows, and a carbon resin having a hydrogen gas flow path on one of its outer surfaces. A hydrogen gas separator 2 made of a material is arranged, and an air separator 4 also made of a carbon resin material having an air flow path on the other outer surface is arranged. Also,
Of the three humidity control devices 1, the humidity control device 1 arranged at the right end portion in the drawing has a milliohm meter 6 for measuring the resistance between the hydrogen gas separator 2 and the air separator 4 incorporated therein. There is.

In this humidity control apparatus, when hydrogen is passed through the hydrogen gas separator, air is passed through the air separator and cooling water is passed through the cooling water separator, the hydrogen gas in the hydrogen gas separator and the air in the air separator are ion exchange membranes. It is humidified and conditioned by the cooling water that permeates and infiltrates 5 and is sent to the fuel cell stack. The flow of the conditioned reaction gas allows the electrolyte membrane of the fuel cell to be kept wet, so that predetermined cell characteristics can be obtained.

The polymer electrolyte fuel cell incorporating this humidity control apparatus was operated while constantly monitoring the resistance between the hydrogen gas separator 2 and the air separator 4 by the milliohm meter 6. The initial resistance value was 0.10 Ωm, but at 10000 hours after the start of operation, the resistance value increased by 20% and reached the specified value of 0.12 Ωm, so the power generation operation was stopped. 1 in the cooling water path of the cooling water separator 3
When pickling was carried out by flowing M sulfuric acid, the resistance value dropped to the specified value of 0.105 Ωm after 30 minutes, so the operation of the polymer electrolyte fuel cell was restarted. After that, the resistance value measured by the milliohm meter 6 is 0.12 Ω which is the specified value.
When it reaches m, the operation of the fuel cell is stopped and the ion exchange membrane 5 is regenerated by pickling, and the resistance value is 0.105Ω which is the specified value.
When it decreased to m, the power generation operation was continued by the method of stopping the pickling and restarting the operation of the fuel cell.

FIG. 3 shows the battery life characteristics when operated by the operation method of the present embodiment, in comparison with the characteristics when operated by the conventional operation method, that is, when the ion exchange membrane 5 is not regenerated. FIG. In the figure, the characteristic A indicated by the thick dotted line is the characteristic when the operating method of the first embodiment is used, and the characteristic C indicated by the thin solid line is the characteristic when the conventional operating method is used. When the conventional operating method was used, the generated voltage decreased at a constant speed with the lapse of operating time, whereas when the operating method of the present example was used, the decreasing speed of the generated voltage slowed down, and Operation above the voltage has become possible for a long time.

<Embodiment 2> FIG. 2 is a schematic diagram showing the basic construction of a fuel cell humidity control apparatus to which the method for operating a polymer electrolyte fuel cell of the second embodiment is applied. The humidity control apparatus used in the operation method of the present embodiment is also composed of three humidity control units, like the humidity control apparatus used in the operation method of the first embodiment shown in FIG. There is. The difference from the humidity control apparatus of FIG. 1 lies in the flow system of the reaction gas and the cooling water for humidification.
That is, in FIG. 1, air as an oxidant gas,
While the hydrogen gas as the fuel gas and the cooling water as the humidifying water were all passed through the three humidity controllers in parallel, the operation of the second embodiment shown in FIG. In the humidity control apparatus to which the method is applied, air, hydrogen gas, and cooling water are all passed in series through these three humidity control units. Further, the milliohm meter 6 for monitoring the deterioration of the ion exchange membrane 5 is incorporated in the humidity controller located at the uppermost stream where the decrease in water permeability is the fastest.

A polymer electrolyte fuel cell incorporating this humidity control device was operated while monitoring the resistance change of the ion exchange membrane 5 with a milliohm meter 6. Initial resistance is 0.10 Ωm
However, the resistance value reached the specified value of 0.12 Ωm (1.2 times the initial resistance value) at 5000 hours after the start of operation, so the power generation operation was stopped. After the operation was stopped, the ion exchange membrane 5 incorporated in the humidity controller located on the most upstream side of the humidity controller was replaced with an unused new one, and the fuel cell power generation operation was restarted. In this way, the life characteristics when the operation is continued by carrying out the regenerating procedure of exchanging the ion exchange membrane 5 with an unused new product every time when the resistance value reaches the specified value of 0.12 Ωm, the thick solid line is shown in FIG. It is like the characteristic B. Among the humidity controllers connected in series, the most upstream humidity controller in which the deterioration rate of the ion exchange membrane 5 is high is monitored, so that the deterioration is earlier than in the parallel-connected first embodiment. Since this is detected, the frequency of regeneration measures increases, but the drop in generated voltage is suppressed to a much smaller level, and a high voltage is obtained stably over a long period of time.

[0017]

As described above, according to the present invention, (1) a membrane for controlling the humidity by circulating a reaction gas before being supplied to a fuel cell in a gas channel separated from a water channel via an ion exchange membrane. A polymer electrolyte fuel cell equipped with a humidifying humidifier
Since the operation is performed by using the operation method as described in claim 1, deterioration of the ion exchange membrane used in the humidity control device is detected early, and regeneration treatment, for example, claim 3, is performed.
Alternatively, since the regenerating measures as described in 4 are adopted, stable battery characteristics can be obtained for a long period of time.

(2) If the polymer electrolyte fuel cell provided with this humidity control device is operated by using the operating method as defined in claim 2, the ion exchange membrane is deteriorated. Since it is detected earlier, it is suitable as an operating method that can obtain stable battery characteristics for a long period of time.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the basic configuration of a humidity control apparatus for a polymer electrolyte fuel cell to which the operating method of the first embodiment is applied.

FIG. 2 is a schematic diagram showing the basic configuration of a humidity control device for a polymer electrolyte fuel cell to which the operating method of the second embodiment is applied.

FIG. 3 is a characteristic diagram showing the battery life characteristics when operated by the operation method of the first embodiment and the operation method of the second embodiment in comparison with the characteristics when operated by the conventional method.

[Explanation of symbols]

1 Humidifier 2 Hydrogen gas separator 3 Cooling water separator 4 air separator 5 ion exchange membrane 6 Milliohm meter

Claims (5)

[Claims] 1. A solid polymer type provided with a humidity control device of a membrane humidification system for controlling the humidity by flowing a reaction gas before being supplied to a fuel cell in a gas flow passage separated from a water flow passage through an ion exchange membrane. In the method of operating a fuel cell, the resistance value of the ion exchange membrane used in the humidity control apparatus is constantly measured, and when the resistance value is equal to or higher than a first specified value, the operation of the fuel cell is stopped. A method for operating a polymer electrolyte fuel cell, comprising: taking a regenerating measure for the ion exchange membrane, and restarting the operation of the fuel cell when the resistance value becomes equal to or lower than a second specified value by the regenerating measure. 2. The method of operating a polymer electrolyte fuel cell according to claim 1, wherein the humidity control device is constituted by a connection body of a plurality of humidity control devices in which a water flow path and a gas flow path are both connected in series. The method for operating a polymer electrolyte fuel cell is characterized by constantly measuring the resistance value of the ion exchange membrane of the most upstream humidity controller. 3. The method for operating a polymer electrolyte fuel cell according to claim 1 or 2, wherein the ion exchange membrane is regenerated by flowing an acid into a water channel. Method of operating a polymer electrolyte fuel cell. 4. The method for operating a polymer electrolyte fuel cell according to claim 1 or 2, wherein the ion exchange membrane is regenerated by replacing it with a new polymer. Type fuel cell operating method. 5. The method for operating a polymer electrolyte fuel cell according to claim 1, wherein the first prescribed value of the resistance value is 1.2 times the initial resistance value. A method for operating a polymer electrolyte fuel cell, comprising: