JPH06223850A - Operation protecting system for solid high polymer electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To provide an operation system for a fuel cell which allows indirect identification of the moisture condition of high polymer ion exchange membrane during operation of the fuel cell. CONSTITUTION:A hydrogen gas detector 15 is provided on the way of a residual oxygen agent discharge line 17 in a fuel cell. When high polymer ion exchange membrane as electrolyte 11 for a solid high polymer electrolyte fuel cell is short of moisture, the leakage of hydrogen gas from an anode 12 side to a cathode 13 side is detected to indirectly identify that the electrolyte 11 (the high polymer ion exchange membrane) comes short of moisture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an operation protection system for a solid polymer electrolyte fuel cell.

[0002]

[Prior art]

(1) Characteristics of Polymer Membrane for Solid Polymer Electrolyte Fuel Cell A polymer ion exchange membrane (for example, a fluororesin ion exchange membrane having a sulfonic acid group) used as an electrolyte of a solid polymer electrolyte fuel cell is an ion as an electrolyte. In addition to having to be permeable, it separates the fuel supplied to the anode and the oxidant supplied to the cathode, and both leak and
It must also function as a diaphragm to prevent mixing.

In order to maintain these functions while carrying out the fuel cell reaction, it is necessary to keep the polymer ion exchange membrane always in a sufficient water content state. This is because when the water content of the polymer ion-exchange membrane decreases, the ion permeability decreases and the electric resistance of the membrane increases, making it difficult for the battery reaction to occur. Further, if the water content of the membrane portion is reduced, the hydrogen gas in the fuel supplied to the anode electrode leaks directly to the cathode electrode side.

Usually, in order to keep the polymer ion-exchange membrane always in a sufficiently water-containing state, the fuel or oxidant is near the operating temperature of the fuel cell (about 40 ° C. to about 120 ° C.).
Moisture corresponding to the partial pressure of water vapor is given to the fuel cell. The moisture makes it possible to keep the polymer ion exchange membrane always in a water-containing state.

(2) Method of Operating Solid Polymer Electrolyte Fuel Cell As described above, in the operation of the solid polymer electrolyte fuel cell, the cell reaction is performed while confirming that the polymer ion exchange membrane is in a sufficiently water-containing state. However, until now there has been no means to know the water content of the polymer ion exchange membrane during operation.

(3) Power Generation Principle of Solid Polymer Electrolyte Fuel Cell FIG. 2 shows an example of a solid polymer electrolyte fuel cell. A fluororesin-based polymer ion exchange membrane (for example, a fluororesin-based ion exchange membrane having a sulfonic acid group) is used as the electrolyte 01, and catalyst electrodes 02 and 03 (for example, platinum) are attached to both sides with this as the center. An electrode assembly 06 is formed by sandwiching both surfaces of the porous carbon electrodes 04 and 05 in a sandwich shape. Hydrogen (H ₂ ) in the fuel supplied to the anode electrode side is 0% in the catalyst electrode (anode electrode).
2 is hydrogen-ionized, and the hydrogen ions move to the cathode side as H ⁺ · xH ₂ O in the electrolyte 01 under the presence of water. On the catalyst electrode (cathode electrode) 03, it reacts with oxygen (O ₂ ) in the oxidant and electrons flowing through the external circuit 07 to generate water, which is discharged to the outside of the fuel cell. At this time, the flow of electrons (e ⁻ ) flowing through the external circuit 07 can be used as DC electric energy. This reaction is shown in "Chemical Formula 1" below.

[0007]

[Chemical 1]

[0008]

By the way, a polymer ion exchange membrane which is an electrolyte of a solid polymer electrolyte fuel cell is
When the water content shortage occurs at any membrane part, the anode electrode becomes 0
The hydrogen gas in the fuel supplied to No. 2 leaks to the cathode 03 side. As a result, if hydrogen gas leaks to the cathode side, hydrogen and oxygen in the oxidant react suddenly to generate heat and eventually burn the fuel cell.

Therefore, it is desired to detect the water content of the polymer ion exchange membrane, which is the electrolyte of the solid polymer electrolyte fuel cell, during operation to prevent the above malfunction.

[0010]

The structure of the present invention for solving the above problems is to provide a hydrogen gas detector in a residual oxidant discharge passage arranged on the cathode side of a solid polymer electrolyte fuel cell,
Detects leakage of hydrogen gas due to deterioration of water content of polymer ion exchange membrane, which is an electrolyte, and also detects leakage of hydrogen gas to residual oxidant discharge passage arranged on cathode side by hydrogen gas detector. In this case, the fuel supplied to the fuel cell is shut off.

[0011]

[Function] The polymer ion exchange membrane, which is the electrolyte of the solid polymer electrolyte fuel cell, is designed so that the hydrogen gas in the fuel supplied to the anode leaks to the cathode when the water content is insufficient at any membrane site. become. By detecting this in the middle of the residual oxidant discharge line, the water content of the polymer ion exchange membrane can be indirectly confirmed.
Further, even when a defect (for example, a pore is generated) is generated in the polymer ion-exchange membrane, hydrogen gas leaks to the cathode side, so that it can be similarly detected. If hydrogen gas leaks to the cathode side, hydrogen and oxygen in the oxidant will react suddenly to generate heat and eventually burn the fuel cell. To do so. If the fuel supply is cut off immediately after the hydrogen leakage is detected, it is possible to prevent the fuel cell from burning.

[0012]

EXAMPLE An example of the present invention will be described below.

FIG. 1 shows an outline of a method for confirming the water content of a polymer ion exchange membrane and an operation protection system. In the figure, 11 is an electrolyte (ion exchange membrane), 12 is an anode pole, 13 is a cathode pole, 14 is a control unit, 15 is a hydrogen gas detector, 16 is a shutoff valve, 17 is a fuel supply line, and 18 is oxidation. An agent supply line, 19 is a residual fuel discharge line, and 20 is a residual oxidant discharge line.

In this embodiment, as shown in FIG. 1, a shutoff valve 16 is provided in the middle of the fuel supply line 17 and a hydrogen gas detector 15 is provided in the middle of the residual oxidant discharge line 20. The shut-off valve 16 is controlled by a detection signal via the control unit 14 so as to operate as soon as hydrogen gas is detected in the residual oxidant discharge line 20.

Next, the operating system will be described. As shown in FIG. 1, as a result of providing the hydrogen gas detector 12 in the middle of the residual oxidant discharge line 17 of the fuel cell, the polymer ion exchange membrane, which is the electrolyte 11 of the solid polymer electrolyte fuel cell, has a shortage of water content Generated from the anode 12 side to the cathode 1
It is possible to indirectly confirm that the electrolyte (polymer ion exchange membrane) 11 falls into a water-deficient state by detecting the leak of hydrogen gas to the 3 side.

When the fuel cell falls into the above-mentioned state, a shut-off valve 16 which is activated by a detection signal via the control unit 14 is provided in the middle of the fuel supply line 17 so that the fuel supply can be immediately shut off in order to protect the fuel cell. Installed to prevent fuel cell burnout.

[0017]

As described above, according to the present invention, the hydrogen gas detector is provided in the residual oxidant discharge line of the solid polymer electrolyte fuel cell, and the shutoff valve for shutting off the fuel supply by the detection signal is provided. As a result, (1) it became possible to confirm indirectly the water content of the polymer ion-exchange membrane during fuel cell operation, which was previously undetectable, and (2) due to hydrogen gas leaking to the cathode side. It is possible to prevent burnout and malfunction of the fuel cell.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a method for confirming the water content of a polymer ion exchange membrane and an operation protection system.

FIG. 2 is a schematic diagram of a power generation principle of a solid polymer electrolyte fuel cell.

[Explanation of symbols]

 11 Electrolyte 12 Anode 13 Cathode 14 Control Unit 15 Hydrogen Gas Detector 16 Shutoff Valve 17 Fuel Supply Line 18 Oxidant Supply Line 19 Residual Fuel Discharge Line 20 Residual Oxidant Discharge Line

Claims (1)

[Claims] 1. A hydrogen gas detector is provided in a residual oxidant discharge passage arranged on the cathode side of a solid polymer electrolyte fuel cell, and a hydrogen gas detector for hydrogen gas caused by a decrease in water content of a polymer ion exchange membrane, which is an electrolyte, is provided. In addition to detecting the leakage, when the hydrogen gas detector detects the leakage of the hydrogen gas into the residual oxidant discharge passage arranged on the cathode side, the fuel supplied to the fuel cell is shut off. Operation protection system for molecular electrolyte fuel cells.