JPS62136774A - Heat insulating method for fuel cell stack - Google Patents

Abstract

PURPOSE:To keep cell temperature during off-operation more than a freezing point without requiring a separate power source, by letting fuel of methanol, natural gas, etc., available for a fuel cell as a heat source for hot insulation, react in contact combustion, and transmitting the produced heat to a cell stack via a heat-transfer body to be housed in a space in a hermetically sealed vessel. CONSTITUTION:A fuel cell stack 2 having a fuel inlet pipe 3a and its outlet pipe 3b, an air inlet pipe 4a and its outlet pipe 4b as well as a catalyzer inlet pipe 5a and its outlet pipe 5b at both sides respectively is housed in a hermetically sealed vessel 1 as projecting these pipes outside of the vessel 1. Next, a heat-transfer body 8 is set up at the lower side of the stack 2, situating this radiation fin 7 at the lower side of the stack 2, and the part not fitted with this fin 7 is projected outside of the vessel 1, surrounding it with a catalytic burner 9. In addition, a temperature sensor 12 is stuck to a surface of the stack 2 on the fin 7, while a valve 11 at the side of this burner 9 is operated via an interconnecting pipe 13, and when there is a fear of freezing, methanol out of a tank 10 is burned by the burner 9 and the stack 2 is warmed up via the fin 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field to which the Invention Pertains] The present invention relates to a heat retention method for preventing phosphoric acid from freezing, which tends to occur as the temperature decreases during suspension of operation of a phosphoric acid fuel cell.

[Prior art and its problems]

A longitudinal cross-sectional view of this type of phosphoric acid fuel cell is shown in Figure 1.
Let me explain this. 1 is a sealed container made of a heat insulating material, and a fuel cell stack 2 is housed in this container 1. This fuel cell stack 2 includes a fuel inlet pipe 3a and a fuel outlet pipe 3.
b, an air inlet pipe 4a, an air outlet pipe 4b, a heat medium inlet pipe 5a, and a heat medium outlet -g5b are attached and protrude to the outside through the container wall surface. Reference numeral 6 designates an electric heater as a heat source provided in the fuel cell stack 2 for heat retention, which will be described later. To operate this fuel cell stack 2, heating fluid flows in through the heat medium inlet pipe 5a to supply heat to the stack 2, and is discharged through the heat medium outlet pipe 5b to continue heating until the stack 2 reaches the operating temperature. . Thereafter, fuel containing hydrogen obtained by steam reforming metal is supplied to the stack 2 from the fuel inlet pipe 3a, and air is further supplied to the stack 21 from the air inlet pipe 4a to operate the stack 1 and generate electricity. Excess fuel and air not used for power generation and water vapor generated by power generation are discharged from the fuel outlet pipe 3b and the air outlet pipe 4a. Since the fuel cell stack 2 in the power generation state generates heat, in the phosphoric acid fuel cell,
In order to maintain the temperature during operation at about 200° C., a fluid serving as a refrigerant is introduced through a heating medium inlet pipe 5a to cool the stack 2, and the heated refrigerant is discharged through a heating medium outlet pipe 5b.

Generally, this heating medium is used for heating when starting up the fuel cell and for cooling during operation, and air, water, oil, etc. are used. This fuel cell stack 2 has a faster start-up time,
It is housed in a sealed container 1 made of a heat insulating material to keep it warm during suspension of operation.

In such a phosphoric acid fuel cell, when the temperature drops below room temperature during suspension of operation, the phosphoric acid, which is the electrolyte in the cell, freezes.
If the temperature falls below 30'C, the characteristics of the fuel cell may deteriorate. Frequently repeating operation and rest of a battery will cause a significant deterioration in its characteristics, so it is necessary to heat the battery to prevent the temperature of the battery from dropping during rest. 6 was added to stack 2 and heated. However, this method has the problem that the fuel cell cannot be stopped in a place where there is no separate power source for heating, and the fuel cell cannot be used as an independent power source at all.

[Purpose of the invention]

In view of the above-mentioned circumstances, it is an object of the present invention to provide a heat retention method using a heat source that does not require a separate power source to maintain the cell temperature above the freezing temperature of phosphoric acid during suspension of operation of a phosphoric acid fuel cell. .

[Key points of the invention]

In order to achieve the above object, this invention uses methanol, which is a fuel used in fuel cells as a heat source for heat retention.

A fuel cell such as natural gas undergoes a catalytic combustion reaction, and the generated heat is transferred to the fuel cell stack through a heat transfer body housed in a space inside a sealed container, thereby heating and maintaining the temperature of the stack.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the present invention, and the same parts as in FIG. 3 are designated by the same reference numerals and their explanation will be omitted. As a heat insulating device for this fuel cell, a plurality of heat dissipating fins 7 are provided in the inside C and one side of the sealed container, and the heat dissipating fin side of a heat transfer body 8 having no heat dissipating fins is housed on the other side. The other side of the container is made to penetrate the wall surface of the container and protrude to the outside. The heat transfer body 8 is made of a material with good thermal conductivity, such as aluminum or copper, and is formed into a rod or flat plate shape, and the part that protrudes from the sealed container is inserted into the contact W burner 9, which is made of alumina grains supporting a platinum catalyst. . Methanol is supplied to the catalytic burner 9 from a methanol tank 10 via a valve 11.

A temperature sensor 12 that utilizes thermal expansion of fluid is installed inside the fuel cell stack 2, and the temperature of the stack 1 is 40'0.
When the temperature reaches 45° or more, the valve stem (not shown) of the valve head lla is operated through the communication pipe 13 to open the valve 11, and when the temperature of the greenhouse reaches 45° or higher, the valve 11 is closed. While the fuel cell stack 2 is out of operation, the temperature is 40℃.
When the temperature drops below ゛C, methanol is supplied to the catalytic burner 9 and burned by the catalytic action, and the heat is transferred from the heat transfer body 8 to the heat dissipation fin 7.
The stack 2 is heated by convection heating the air in the space inside the sealed container 1, thereby preventing deterioration of the characteristics of the stack 2 due to freezing of the phosphoric acid. Further, when the temperature of the stack 2 becomes 45°C or more from heating, the supply of methanol to the catalytic burner 9 is stopped and the heating is automatically stopped.

FIG. 2 shows a heat transfer body 8 having radiation fins 7 in FIG. 1.
This is a modified example in which a heat transfer plate 17 is added to the tip of the heat transfer plate 18, and this heat transfer plate 17 is attached to the wall surface or inside of the stack 2 to directly heat it.

According to this heating method, the temperature of the heat transfer plate 17 becomes higher in the portion close to the catalytic burner 9, and a temperature difference occurs between the portions farther away. Therefore, the heat pipe type heat transfer method can eliminate this temperature difference.

In this embodiment, a method using methanol as the fuel was exemplified, but the fuel may be any fuel that can be catalytically combusted at low temperatures, such as hydrogen, ethanol, natural gas, etc.

〔Effect of the invention〕

A catalytic combustion method was adopted as the heat source for heat retention, and the method was used to heat the stack by directly transmitting the firing heat to the heat transfer body.
Not only is the thermal efficiency for heating good, but the combustion humidity is low, so the thermal efficiency is greatly improved in terms of less heat loss due to haiku air. Furthermore, since the degree of combustion is low, there is no risk of fire outbreak, and it is also excellent in terms of safety.

[Brief explanation of drawings]

FIG. 1 shows a fuel 1! example of the present invention. FIG. 2 is a side view showing a modification of the heat transfer body having radiation fins in FIG. 1, and FIG. 3 is a longitudinal sectional view of a conventional fuel cell. 1: Sealed container, 2: Fuel cell stack, 7: Release Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1) In a phosphoric acid fuel cell in which a fuel cell stack is housed in a heat-insulating sealed container; One side is accommodated in the space inside the sealed container, and the other side is made to penetrate the container wall surface and protrude to the outside, and a catalytic burner is brought into direct contact with this protruding heat transfer body. By supplying pre-reformed fuel and causing catalytic combustion, heat is guided to the heat transfer body, which heats the space inside the sealed container via the heat radiation fins of the heat transfer body to maintain the fuel cell stack within a predetermined temperature range. A method for keeping a fuel cell stack warm, characterized by: 2) A method for keeping a fuel cell stack warm as claimed in claim 1, wherein the fuel supply to the catalytic burner is automatically controlled by capturing the temperature of the fuel cell stack and using this signal. 3) In the heat retention method according to claim 2, a temperature sensor that utilizes thermal expansion of a liquid is used as a means for capturing the temperature of the fuel cell stack, and changes in the expansion of the liquid are used to control the temperature of the catalytic burner. A method for keeping a fuel cell stack warm, characterized by automatically controlling the opening and closing operations of a fuel supply valve.