JPH07288134A - Operation method for solid polymer electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To easily, stably start operation by maintaining the temperature of a humidifier in specified temperature difference based on the operation temperature of a solid polymer electrolyte fuel cell. CONSTITUTION:Temperature T1 of a fuel gas humidifier 12 is maintained in specified temperature difference to temperature T3 of a gas separator 17 of a cell through a temperature controller 11. Temperature T2 of an air humidifier 12A is maintained in specified temperature difference to temperature T4 of the gas separator 17 of the cell through the temperature controller 11. Vapor pressure for preventing drying of moisture from a solid polymer electrolyte is maintained, and excess drying or wetting of the solid polymer electrolyte is prevented, and movement from starting to steady-state operation is smoothly progressed.

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 solid polymer electrolyte fuel cell, and more particularly to a method for controlling the temperature of a humidifier.

[0002]

2. Description of the Related Art A solid polymer electrolyte fuel cell is formed by disposing an anode and a cathode, which are electrodes, on two main surfaces of a solid polymer electrolyte membrane. Each electrode of the anode or the cathode has an electrode catalyst arranged on an electrode substrate. The solid polymer electrolyte membrane uses polystyrene type cation exchange membrane with sulfonic acid group as cation conductive membrane, mixed membrane of fluorocarbon sulfonic acid and polyvinylidene fluoride, or trifluoroethylene grafted on fluorocarbon matrix. However, recently, a perfluorocarbon sulfonic acid membrane has been used to extend the life of the fuel cell.

The solid polymer electrolyte membrane has a proton (hydrogen ion) exchange group in the molecule, and when it is saturated with water, it exhibits a specific resistance of 20 Ω · cm or less at room temperature and functions as a proton conductive electrolyte. The saturated water content changes reversibly with temperature. The electrode base material is a porous body and functions as a reaction gas supply means or a reaction gas discharge means and a current collector of the fuel cell. At the anode (fuel electrode) or cathode (air electrode) electrode, a three-phase interface is formed and an electrochemical reaction occurs.

At the anode, the reaction of the formula (1) occurs. H ₂ = 2H ⁺ + 2e (1) At the cathode, the reaction of the formula (2) occurs. 1 / 2O ₂ + 2H ⁺ + 2e = H ₂ O (2) That is, at the anode, hydrogen supplied from the outside of the system produces protons and electrons. The generated protons move toward the cathode in the ion exchange membrane, and the electrons move to the cathode through an external circuit. On the other hand, in the cathode, oxygen supplied from the outside of the system reacts with protons moving from the anode in the ion exchange membrane and electrons moving from the external circuit to generate water.

FIG. 5 is a sectional view showing a solid polymer electrolyte fuel cell. The electrode 2 or 3 is constructed by laminating the electrode catalyst layer on the electrode base material. The electrodes 2 or 3 are arranged in close contact with both main surfaces of a solid polymer electrolyte membrane (also referred to as a solid polymer membrane or polymer membrane) 1 by hot pressing. The solid polymer electrolyte membrane 1 on which the electrodes are arranged is sandwiched by the gas separators 8 and 9 via the current collectors 4 and 5. Although not shown, the gas separators 8 and 9 are provided with cooling water passages for passing cooling water through the current collectors 4 and 5. Fuel gas is flown inside the current collector 4, and air that is an oxidant gas is flowed inside the current collector 5. The gas separators 8 and 9 separate the oxidant gas and the fuel gas from each other.

Such a solid polymer electrolyte fuel cell has a higher power density than a conventional phosphoric acid fuel cell because the solid polymer electrolyte has a high ionic conductivity. Further, since the steady operating temperature of this fuel cell is generally 60 to 100 ° C., the ionic conductivity near room temperature is not so low as that of other fuel cells, and the fuel cell can be operated under load from room temperature.

Since the solid polymer electrolyte membrane 1 contains water inside, it not only functions as an electrolyte, but also prevents cross-leakage in which fuel gas and oxidant gas are mixed with each other. However, in the conventional solid polymer electrolyte fuel cell as described above, the conductivity of the solid polymer electrolyte membrane is greatly influenced by the wettability of the membrane, and therefore the membrane will dry and become conductive when exposed to dry air. The sex becomes worse. That is, in this fuel cell, when a dry reaction gas is supplied, the characteristics of the fuel cell deteriorate due to the drying of the polymer film and the increase in internal resistance due to the decrease in ionic conductivity.

If the dry state is continued, the volume of the polymer film is reduced, so that the electrical contact between the polymer film and the electrode and between the electrode and the current collector becomes poor, and the characteristics of the fuel cell deteriorate. Therefore, the solid polymer electrolyte fuel cell employs a system for humidifying and supplying the reaction gas. FIG. 6 is a layout view showing a solid polymer electrolyte fuel cell including a conventional humidifier. This humidifier humidifies by passing a reaction gas into water. The temperature of the humidifier is controlled to a constant temperature, and the reaction gas having a predetermined saturated vapor pressure is supplied to the cells of the fuel cell.

FIG. 7 is a layout showing a conventional water spray type humidifier. Make-up water stored in the heating tank 14 is pump 1
5 is pumped up and sprinkled with water from the upper part of the humidifier 16. The reaction gas is humidified to a predetermined water vapor pressure and supplied to the fuel cell. For controlling the amount of humidification, conventionally, the temperature of the humidifier has been set to a predetermined temperature.

[0010]

However, in such a conventional humidifying method, for example, when the water temperature is controlled at 70 ° C., when the operation is raised from room temperature, the humidification amount is too high, so that the water vapor is condensed inside the cell, The catalyst in the electrode gets wet with water and the electrode reaction does not proceed smoothly. In addition, if the set temperature of the humidifier is set low to prepare for operation from room temperature, there will be no problem near room temperature, but if the temperature of the cell rises, the humidification amount of the reaction gas will be low and as a result dry gas will be supplied to the cell. However, there is a problem that the fuel cell cannot be started properly. The method of changing the set temperature of the humidifier according to the cell temperature was adopted, but the cell operation was very complicated.

The present invention has been made in view of the above points, and an object thereof is to improve the temperature control method of the humidifier in the operation of the solid polymer electrolyte fuel cell, thereby making it possible to start easily and stably. It is to provide a method of operating a fuel cell.

[0012]

According to the present invention, the above object is to provide a solid polymer electrolyte fuel cell having a solid polymer electrolyte body, an electrode and a gas separator, the fuel gas being humidified through a humidifier. In the method of operating a solid polymer electrolyte fuel cell, which supplies an oxidizer gas and an oxidant gas, respectively, it is achieved by maintaining the temperature of the humidifier at a predetermined temperature difference based on the operating temperature of the solid polymer electrolyte fuel cell. It

At this time, the operating temperature of the solid polymer electrolyte fuel cell is assumed to be the cell temperature of the solid polymer electrolyte fuel cell,
It shall be the temperature of the fuel exhaust gas of the solid polymer electrolyte fuel cell, the temperature of the oxidant exhaust gas of the solid polymer electrolyte fuel cell, or the cooling water outlet temperature of the solid polymer electrolyte fuel cell. It is effective to have it.

[0014]

[Operation] When the temperature of the humidifier is maintained at a predetermined temperature difference based on the operating temperature of the solid polymer electrolyte fuel cell, the vapor pressure required to prevent the water from drying out from the solid polymer electrolyte is constantly maintained. Excessive drying and wetting of the polymer electrolyte membrane is prevented, and the transition from the start of the fuel cell to the steady operation proceeds smoothly.

[0015]

Embodiments of the present invention will now be described with reference to the drawings. Example 1 FIG. 1 is a configuration diagram showing a solid polymer electrolyte fuel cell system according to an example of the present invention.

The temperature T ₁ of the humidifier 12 for the fuel gas is adjusted to the temperature T ₃ of the gas separator 17 of the cell via the temperature controller 11.
Is maintained at a predetermined temperature difference. The specified temperature difference is △
Letting T be T ₁ = T ₃ + ΔT ₁ . Where △
T ₁ is set within the range of 0 to + 10 ° C. As the cell temperature, in addition to the above gas separator, a current collector can be used.

At the anode (fuel electrode), depending on the cell temperature, electricity is generated.
In addition to evaporating water in the denaturation, the pro generated in the above formula (1)
Ton H⁺Is diffused toward the cathode (air electrode)
Since water moves with water molecules, water near the anode
Humidifier temperature T ₁Is the cell gas separator
Temperature T₃Higher than. The temperature controller turns on the heater.
I will When turning off the heater, fuel gas is
When evaporating, the latent heat of evaporation is removed to lower the temperature of the humidifier. cold
Introducing effluent allows more rapid temperature control. Normal
In this cell, the temperature change is gradual, so only the heater controls
Is enough.

The temperature T ₂ of the humidifier 12A for air is maintained at a predetermined temperature difference from the temperature T ₄ of the gas separator 17 of the cell via the temperature controller 11. The predetermined temperature difference is ΔT
Then, there is a relation of T ₂ = T ₄ + ΔT ₂ . Where ΔT
₂ is set within the range of 0 to -10 ° C. At the cathode, the water content of the electrolyte evaporates depending on the cell temperature, but since the protons H ⁺ accompanied by water molecules diffuse from the anode, the water content shortage due to the evaporation is compensated. Therefore, the water supply at the cathode may be slower than at the anode. This is the reason why the humidifier temperature T ₂ is set lower than the cell gas separator temperature T ₄ .

FIG. 4 is a connection diagram showing a temperature difference detecting method for the solid polymer electrolyte fuel cell system according to the embodiment of the present invention. A thermocouple is used for the temperature sensor. One terminal of the same polarity is connected to the two thermocouples of the humidifier and the gas separator, and the other terminal of the same polarity is input to the temperature difference controller. In this method, since the temperature difference is directly detected, it is possible to adjust the temperature of the humidifier by using an inexpensive temperature detector. Example 2 FIG. 2 is a configuration diagram showing a solid polymer electrolyte fuel cell system according to another example of the present invention.

[0020] The humidifier 12 of the fuel gas temperatures T ₁ and temperature T ₂ is the temperature T of each fuel exhaust air humidifier 12A
₅ and the temperature T _{6 of the} air exhaust gas. Since there is a temperature difference between the anode and the cathode and the temperature of the exhaust gas reflects the temperature of each electrode, the humidifier temperature can be controlled more precisely by using the exhaust gas temperature than when using the temperature of the gas separator. Embodiment 3 FIG. 3 is a constitutional view showing a solid polymer electrolyte fuel cell system according to still another embodiment of the present invention.

The fuel gas humidifier temperature T ₁ and the air humidifier temperature T ₂ are controlled using cooling water temperatures T ₇ and T ₈ , respectively. The cooling water is for cooling the heat generation during the operation of the solid polymer electrolyte fuel cell, and improves the temperature distribution in the cell. Therefore, the average temperature in the cell is displayed accurately.

[0022]

According to the present invention, the temperature of the humidifier is maintained at a predetermined temperature difference with respect to the operating temperature of the solid polymer electrolyte fuel cell, and the operating temperature is set to the cell temperature of the solid polymer electrolyte fuel cell. Since the exhaust gas temperature or the cooling water temperature is used, the water vapor pressure necessary to prevent the drying of the water from the solid polymer electrolyte is constantly maintained, and the excessive drying and wetting of the solid polymer electrolyte membrane is prevented, and the starting of the fuel cell is prevented. It is possible to obtain a solid polymer electrolyte fuel cell in which the transition to steady operation proceeds smoothly and starting is easy.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a solid polymer electrolyte fuel cell system according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a solid polymer electrolyte fuel cell system according to another embodiment of the present invention.

FIG. 3 is a configuration diagram showing a solid polymer electrolyte fuel cell system according to still another embodiment of the present invention.

FIG. 4 is a connection diagram showing a temperature difference detection method for a solid polymer electrolyte fuel cell system according to an embodiment of the present invention.

FIG. 5 is a sectional view showing a solid polymer electrolyte fuel cell.

FIG. 6 is a layout view showing a solid polymer electrolyte fuel cell including a conventional humidifier.

FIG. 7 is a layout view showing a conventional sprinkler type humidifier.

[Explanation of symbols]

 1 polymer film 2 electrode 3 electrode 4 current collector 5 current collector 6 fuel passage 7 air passage 8 gas separator 9 gas separator 10 cell 11 temperature controller 12 humidifier 12A humidifier 13 temperature difference controller 14 heating tank 15 pump 16 Humidifier 17 Gas separator

Front page continuation (72) Inventor Shinichi Maruyama 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd.

Claims (5)

[Claims] 1. A solid polymer electrolyte type fuel cell having a solid polymer electrolyte body, an electrode, and a gas separator, which supply a humidified fuel gas and an oxidant gas through a humidifier, respectively. In operating the fuel cell,
A method for operating a solid polymer electrolyte fuel cell, characterized in that the temperature of the humidifier is maintained at a predetermined temperature difference based on the operating temperature of the solid polymer electrolyte fuel cell. 2. The fuel cell according to claim 1, wherein the operating temperature of the solid polymer electrolyte fuel cell is the cell temperature of the solid polymer electrolyte fuel cell. 3. The fuel cell according to claim 1, wherein the operating temperature of the solid polymer electrolyte fuel cell is the temperature of the fuel exhaust gas of the solid polymer electrolyte fuel cell. battery. 4. The fuel cell according to claim 1, wherein the operating temperature of the solid polymer electrolyte fuel cell is the temperature of the oxidant exhaust gas of the solid polymer electrolyte fuel cell. Fuel cell. 5. The solid polymer electrolyte fuel according to claim 1, wherein the operating temperature of the solid polymer electrolyte fuel cell is a cooling water outlet temperature of the solid polymer electrolyte fuel cell. battery.