JP2002093435A - Fuel cell unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the retention of leaked hydrogen in a case for storing a fuel cell stack. SOLUTION: The solid polymer electrolyte type fuel cell stack 1 is stored in the case 3. A hydrogen feed pipe 5, an oxygen feed pipe 7, a hydrogen exhaust pipe 13, and an air exhaust pipe 15 are connected to the fuel cell stack 1 respectively. Platinum 25 for catalytic combustion is formed in the upper inner wall 3a of the case 3 by plating. Micro hydrogen leaked from the fuel cell stack and shut-off valves 9 and 17 moves to the upper part of the case 3 and subjected to the catalytic combustion by the platinum 25 using the air in the case 3 to be converted into water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell unit in which a fuel cell body is accommodated in a case.

[0002]

2. Description of the Related Art In recent years, attention has been paid to a fuel cell technology capable of achieving clean exhaust and high energy efficiency with respect to environmental problems, in particular, air pollution caused by automobile exhaust gas and global warming caused by carbon dioxide. . 2. Description of the Related Art A fuel cell is an energy conversion system that supplies hydrogen or a hydrogen-rich reformed gas and air as a fuel to a polymer membrane-electrocatalyst composite to cause an electrochemical reaction to convert chemical energy into electric energy. . Among them, a solid polymer electrolyte fuel cell having a particularly high output density has attracted attention as a power source for mobile objects such as automobiles.

[0003] In these fuel cells, it is common to cover the outer periphery of the fuel cell with a case in order to protect the human body from a high voltage or to prevent outside dust and water droplets from being applied. On the other hand, in order to treat the unreacted hydrogen that did not contribute to the reaction among the hydrogen supplied to the fuel cell, a catalyst combustor filled with a catalyst such as platinum was installed, and the unreacted hydrogen discharged from the fuel cell was provided. Hydrogen and air are catalytically combusted and treated as combustion exhaust gas (water vapor) to prevent hydrogen from leaking from the inside of the case to the atmosphere (for example, see Japanese Unexamined Patent Publication No.
No. 84539).

[0004]

However, there is always a small amount of hydrogen leakage from the surface of the fuel cell or a valve on the hydrogen pipe for supplying hydrogen to the fuel cell. Treating unreacted hydrogen using does not result in treating leaked hydrogen. In addition, although the inside of the case is normally forcibly evacuated with a fan or the like to prevent the accumulation of trace hydrogen leaking from the fuel cell,
If the system stops, the fan will not run,
Hydrogen retention due to leakage of trace hydrogen cannot be prevented.
In particular, when the fuel cell system mounted on the vehicle is stopped, it is preferable that the fan is not operated in order to save power consumption of the fan motor.
Hydrogen stagnation in the case cannot be avoided.

[0005] Therefore, an object of the present invention is to prevent leakage hydrogen from accumulating in a case accommodating a fuel cell body.

[0006]

In order to achieve the above object, according to the present invention, a fuel cell main body in which air and hydrogen are supplied and power is generated is housed in a case, and the case is housed in the case. A precious metal for catalytic combustion for converting hydrogen leaking from the fuel cell body or the like into water by catalytic combustion is provided.

According to the fuel cell unit having such a configuration, hydrogen leaked from the fuel cell body or a valve on a hydrogen pipe connected to the fuel cell unit is catalyzed by the noble metal provided in the case to form water. And the stagnation of leaked hydrogen in the case is avoided.

[0008] A second aspect of the present invention is the configuration of the first aspect of the invention, wherein the noble metal is platinum.

According to the above configuration, the leaked hydrogen in the case is converted into water by catalytic combustion with platinum.

According to a third aspect of the present invention, in the configuration of the first or second aspect, the noble metal is formed by plating applied to the inner surface of the case.

[0011] According to the above configuration, hydrogen leaked from the case is converted into water by catalytic combustion in the plating of the noble metal applied to the inner surface of the case.

According to a fourth aspect of the present invention, in the configuration of the first or second aspect, the noble metal is formed by vacuum deposition on the inner surface of the case.

According to the above configuration, the noble metal formed on the inner surface of the case by vacuum evaporation converts the leaked hydrogen in the case.

According to a fifth aspect of the present invention, in the configuration according to any one of the first to fourth aspects, the noble metal is provided on an upper inner wall of the case.

According to the above structure, the lightweight hydrogen moves to the upper part of the case, where it is converted into water by catalytic combustion by the noble metal.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects of the present invention, water converted by the noble metal is absorbed by the water-absorbing substance.

According to the above configuration, the water converted from the leaked hydrogen by the noble metal is absorbed by the water-absorbing substance.

A seventh aspect of the present invention is the configuration of the sixth aspect of the invention, wherein the water-absorbing substance is a water-absorbing polymer sheet.

According to the above configuration, the water converted by the noble metal is absorbed by the water-absorbing polymer sheet.

According to an eighth aspect of the present invention, in the configuration of the seventh aspect, the end of the water-absorbent polymer sheet is drawn out of the case.

According to the above configuration, the water absorbed by the water-absorbing polymer sheet is discharged to the outside of the case.

[0022]

According to the first aspect of the present invention, a noble metal for catalytic combustion for converting leaked hydrogen into water by catalytic combustion is provided in the case in which the fuel cell main body is housed. Stagnation can be prevented.

According to the second aspect of the present invention, the leaked hydrogen in the case is catalytically burned by platinum and converted into water, thereby preventing the leaked hydrogen from staying in the case.

According to the third aspect of the present invention, stagnation of leaked hydrogen in the case can be prevented by plating the inner surface of the case with a noble metal.

According to the fourth aspect of the present invention, the noble metal is vacuum-deposited on the inner surface of the case, so that the leakage hydrogen can be prevented from staying in the case.

According to the fifth aspect of the present invention, since the noble metal is provided on the upper inner wall of the case, the lightweight hydrogen moving to the upper portion of the case can be converted into water by catalytic combustion by the noble metal provided on the upper portion. Can be.

According to the sixth aspect of the present invention, the water converted from the leaked hydrogen by the noble metal is absorbed by the water-absorbing substance, so that dripping of water from the noble metal can be prevented.

According to the seventh aspect of the present invention, since water converted by the noble metal is absorbed by the water-absorbing polymer sheet, dripping of water from the noble metal can be prevented.

According to the eighth aspect of the present invention, since the end of the water-absorbing polymer sheet is drawn out of the case, the water absorbed by the water-absorbing polymer sheet is discharged to the outside of the case, and is removed from the noble metal. Water can be reliably prevented from dripping.

[0030]

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

FIG. 1 is a sectional view showing the internal structure of the fuel cell unit according to the first embodiment of the present invention. The fuel cell stack 1 as a fuel cell body is housed in a case 3. The fuel cell stack 1 is a solid polymer electrolyte type suitable for a mobile body such as an automobile. One end of a hydrogen supply pipe 5 to which hydrogen is supplied as fuel and one end of an air supply pipe 7 to which air is supplied are connected to the left side of the fuel cell stack 1 in FIG. The other ends of the supply pipes 5 and 7 are drawn out of the case 3 and connected to respective supply sources. Further, shut-off valves 9 and 1 are provided in the supply pipes 5 and 7 in the case 3.
1 are provided.

On the right side of the fuel cell stack 1 in FIG. 1, a hydrogen discharge pipe 13 for discharging the unreacted portion of the supplied hydrogen and an unreacted portion of the supplied air are discharged. One end of each of the air discharge pipes 15 to be connected is connected. The other end of each of the discharge pipes 13 and 15 is drawn out of the case 3, the air discharge pipe 13 is opened to the atmosphere to release unreacted air into the atmosphere, and the hydrogen discharge pipe 15
For example, the unreacted hydrogen is connected to a catalytic combustor (not shown) and burned. The catalytic combustor for burning the unreacted hydrogen may be provided in the case 3. Further, a shut-off valve 1 is provided in each of the discharge pipes 13 and 15 in the case 3.
7, 19 are provided respectively.

An outside air introduction fan 21 for introducing outside air into the case 3 is provided on a lower side surface of the case 3 to which the hydrogen discharge pipe 13 and the air discharge pipe 15 are connected. An exhaust duct 23 for discharging the air in the case 3 to the outside is provided on the lower side surface.

On the upper inner wall 3a of the case 3 above the fuel cell stack 1, platinum 25 which is a noble metal for catalytic combustion for converting hydrogen to water by catalytic combustion is formed by plating. The formation of the platinum 25 is not limited to plating, but may be another method such as vacuum evaporation.

Next, the operation will be described. Hydrogen and air flowing from the hydrogen supply pipe 5 and the air supply pipe 7 respectively reach the fuel cell unit stack 1 through the shut-off valves 9 and 11 in an open state, and the electric power obtained by the reaction here is converted to an external power (not shown). Supplied to the circuit. Then, part of the hydrogen and air that did not contribute to the reaction is released from the hydrogen discharge pipe 13 and the air discharge pipe 15 to the atmosphere via shut-off valves 17 and 19 in an open state,
Hydrogen is supplied to a catalytic combustor (not shown) to be burned.

During operation of such a fuel cell system, the fuel cell stack 1, the shut-off valve 9,
17, or hydrogen supply pipe 5 and hydrogen discharge pipe 13
A small amount of hydrogen leaks from the connection to the fuel cell stack 1. The leaked hydrogen moves to the upper part in the case 3 because of its light weight, and the platinum 25 converts the leaked hydrogen into water by catalytic combustion using the air in the case 3.

The converted water is provided, for example, with a porous absorber as a base material of platinum 25, absorbed by the porous absorber, and then diffused into the case as water vapor. At this time, the radiation effect is enhanced by increasing the surface area of the porous absorber. The water vapor emitted into the case 3 is discharged to the outside of the case 3 through the exhaust duct 23 by the operation of the fan 21. As a result, dripping of water from the platinum 25 onto the fuel cell stack 1 can be avoided.

As described above, according to the above configuration, a small amount of hydrogen leaked from the fuel cell stack 1 in operation or the like is catalyzed by the platinum 25 and converted into water. Stagnation can be prevented. Also, in this case, even when the fuel cell system is stopped and the fan 21 is stopped, the leaked hydrogen in the case 3 is converted into water by the platinum 25, so that the staying of the leaked hydrogen in the case 3 is reduced. Can be suppressed.

FIG. 2 is a sectional view showing the internal structure of a fuel cell unit according to a second embodiment of the present invention. This embodiment is different from the first embodiment shown in FIG. 1 in that a water-absorbing polymer sheet 27 is provided on the upper inner wall 3a of the case 3, and hydrogen is converted into water by catalytic combustion on the water-absorbing polymer sheet 27. The platinum 25 which is a noble metal for catalytic combustion to be converted is formed by vacuum evaporation. In addition, this platinum 2
The formation of 5 is not limited to the vacuum deposition, but may be another method.

In the embodiment shown in FIG. 2, a small amount of hydrogen leaking from the fuel cell stack 1 and the shutoff valves 9 and 17 is converted into water by the platinum 25 using the air in the case 3 to perform catalytic combustion. The converted water is absorbed by the water-absorbing polymer sheet 27.

The water absorbed by the water-absorbing polymer sheet 27 is, for example, formed into a band shape such that a water concentration gradient is generated, and the end portion of the water-absorbing polymer sheet 27 is drawn out of the case 3. , And discharged to the outside as water droplets or water vapor. Thereby, dripping of water on the fuel cell stack 1 is reliably avoided.

In each of the above embodiments, the noble metal for catalytic combustion is not limited to platinum, and the fuel cell may be a phosphoric acid type, a molten carbonate type, or an alkaline type in addition to a solid polymer electrolyte type. You may.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an internal structure of a fuel cell unit according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing an internal structure of a fuel cell unit according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel cell stack 3 Case 3a Upper inner wall 25 Platinum (noble metal) 27 Water-absorbing polymer sheet

Claims (8)

[Claims] 1. A fuel cell main body in which air and hydrogen are supplied to generate electric power is housed in a case.
A fuel cell unit comprising a catalytic precious metal for converting hydrogen leaking from the fuel cell body or the like into water by catalytic combustion. 2. The fuel cell unit according to claim 1, wherein the noble metal is platinum. 3. The fuel cell unit according to claim 1, wherein the noble metal is formed by plating applied to the inner surface of the case. 4. The fuel cell unit according to claim 1, wherein the noble metal is formed by vacuum deposition on the inner surface of the case. 5. The fuel cell unit according to claim 1, wherein the noble metal is provided on an upper inner wall of the case. 6. The fuel cell unit according to claim 1, wherein the water converted by the noble metal is absorbed by a water-absorbing substance. 7. The fuel cell unit according to claim 6, wherein the water absorbing material is a water absorbing polymer sheet. 8. The fuel cell unit according to claim 7, wherein an end of the water-absorbent polymer sheet is drawn out of the case.