JP2887346B2 - Fuel cell generator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a fuel cell power generation device, and more particularly, to a method for stopping operation of a fuel cell power generation device which can be safely and easily stopped in a mobile device. About.

[Conventional technology]

As is well known, a fuel cell forms a cell stack by stacking a plurality of unit cells each composed of a pair of fuel electrodes sandwiching an electrolyte and an oxidant electrode. A fuel gas containing hydrogen and air or oxygen are formed in the cell stack. The fuel cell generates electricity by supplying an oxidizing agent, and is classified into various types of fuel cells, such as a phosphoric acid type, an alkali type, and a molten carbonate type, depending on the electrolyte used and the operating temperature. On the other hand, when starting and stopping (including an emergency stop) these fuel cells, the supply and discharge system of the fuel gas including the fuel cell body is replaced with an inert gas, for example, nitrogen gas for safety operation. Has been generally performed conventionally. That is, when starting the fuel cell power generator in a stopped state, if a hydrogen-rich fuel gas is supplied while air or oxygen remains in the fuel system of the fuel cell power generator, a detonation is formed and an explosion occurs. When the fuel cell is stopped, if the fuel gas is left inside the fuel cell body, the pressure of the fuel gas drops due to the internal discharge of the fuel cell or a temperature change. Therefore, there is a possibility that air may enter the fuel side to form detonation air, so that the above-described gas replacement is performed to ensure safety.

[Problems to be solved by the invention]

By the way, in the conventional fuel cell equipment, in order to perform the above-described gas replacement, an inert gas is stored and managed in a storage tank such as a pressure cylinder separately from the fuel and oxidant supply systems, and the operation of the fuel cell is started and stopped. Each time is supplied from the storage tank to the reaction gas system of the fuel cell. However, in this method, apart from the fuel management, the amount of inert gas in the inert gas storage tank is constantly monitored for the inert gas, the inventory of the inert gas including spare parts, and the purchase and procurement are performed.
This is troublesome because it requires time-consuming management, and particularly in the case of mobile power supply equipment, a large inert gas storage tank must be mounted, which increases the size of the equipment.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of stopping the operation of a fuel cell power generation device which can easily replace the purge gas by solving the problems of the prior art.

[Means for solving the problem]

According to the present invention, there is provided a reformer for reforming a raw material, comprising a burner in which reformer fuel is supplied by a reformer fuel pump and air is supplied by an air supply device. A fuel cell body including a fuel electrode supplied with fuel gas reformed by the reformer and an air electrode supplied with air; a first valve, a second valve, a third valve, A fourth valve, the source supply pump, a source supply line through which the source is supplied to the reformer via the source supply pump and the first valve, and a source supply line via the second valve. A fuel gas supply pipe through which the fuel gas reformed by the reformer is supplied to the fuel cell main body; and a fuel off-gas discharged from the fuel cell main body through the third valve. Fuel gas line supplied as a heat source to the burner of the vessel, and connected to the fuel gas line And an air supply pipe through which air is supplied to the fuel electrode via the fourth valve, a portion between the second valve and the reformer in the fuel gas supply pipe, and a section in the fuel offgas pipe. A method for stopping operation of a fuel cell power generator, comprising: a relief valve disposed in a communication pipe communicating between a third valve and a burner; (1) First, a second valve and a third valve After closing the valve, after a predetermined time such that the internal pressure of the fuel electrode becomes lower than the atmospheric pressure, the fourth valve is gradually opened to supply air to the fuel electrode so that the internal pressure of the fuel electrode becomes the atmospheric pressure. After a predetermined time, the fourth valve is closed to seal the fuel electrode. (2) On the other hand, the pressure of the reformer increases due to the closing of the second valve and the third valve, and the predetermined operating pressure increases. After a predetermined time such that the pressure becomes equal to or higher than the operating pressure of the relief valve, the material supply pump is stopped. And closing said first valve.

[Action]

According to the present invention, when the operation of the fuel cell power generator is stopped, in the fuel cell body, the second valve (7) at the fuel gas inlet and the third valve (11) capable of sending off gas to the burner of the reformer. Is closed, the reformed fuel gas is no longer supplied to the fuel electrode of the fuel cell main body, so that the temperature of the fuel cell main body gradually decreases. As a result, the volume of the remaining fuel gas decreases due to the internal discharge, and the pressure of the remaining gas decreases. After a predetermined time such that the internal pressure of the fuel electrode becomes lower than the atmospheric pressure, a control device (not shown) outputs a signal for opening the fourth valve (14) to the fourth valve (14). 4th
When the valve is gradually opened, a small amount of air is supplied to the fuel electrode, and the air causes a gentle catalytic combustion reaction with the remaining fuel gas by the catalyst of the fuel electrode. By this catalytic combustion reaction, the combustible gas component in the fuel gas and the oxygen in the air are consumed, and hydrogen as the combustible gas in the fuel electrode is gradually converted to an inert gas. As described above, by gradually opening the fourth valve (14), a large amount of oxygen is not supplied to the fuel electrode at a stretch, so that the fuel gas is maintained at the atmospheric pressure without generating explosive gas. can do.

Subsequently, after a predetermined time such that the internal pressure of the fuel electrode becomes the atmospheric pressure, a control device (not shown) outputs a signal for closing the fourth valve (14) to the fourth valve (14). (14) is closed.

On the other hand, in the reformer, since the operation is continued even after the second valve (7) is closed, the pressure of the reformer increases and the relief valve (13) operates. After a predetermined time such that the pressure becomes a predetermined pressure at which the relief valve (13) operates, the raw material supply pump (2) is stopped, and a signal for closing the first (3) is output to output the signal to the reformer. Seal the inside.

〔Example〕

Hereinafter, the present invention will be described based on examples. FIG. 1 is a system diagram showing an embodiment of the present invention. In this example, a phosphoric acid fuel cell power generator using hydrogen as a raw material by steam reforming of methanol as a fuel gas is shown, and a reforming raw material in which methanol and water are mixed at a molar ratio of 1: 1.3 is supplied from a raw material inlet 1 to a pump 2. Through the first valve 3 to the reformer 4. Inside the reformer 4, there is a reforming tube 5, and the raw material is reformed into a hydrogen-rich fuel gas by the following reaction at about 250 ° C. by the catalyst filled in the tube.

This fuel gas is supplied to the fuel electrode of the fuel cell body 8 through the second valve 7. In the fuel cell main body 8, air is simultaneously supplied from the air intake port 9 to the air electrode, and power is generated by an electrochemical reaction. The fuel gas that has consumed hydrogen at the fuel electrode becomes an off-gas containing residual hydrogen and becomes the third gas.
Is supplied to the burner 6 of the reformer 4 through the valve 11 and simultaneously burned in the burner 6 together with the air supplied from the air inlet 12 to reduce the amount of heat required for the reaction of the above formula (1). Supply.

A relief valve 13 is disposed in a pipe connecting a fuel gas outlet of the reformer and a pipe inlet of the off gas to the burner 6, and this valve is set to a high operating pressure that does not operate during normal operation.

Next, a procedure for stopping the operation of the power generator will be described. First, when the second valve 7 and the third valve 11 are closed,
The temperature of the fuel cell body 8 from which the supply of the fuel gas is cut off is about 19
It gradually decreases from the operating temperature of 0 ° C. Accordingly, the pressure of the residual fuel gas in the fuel cell body decreases.
Then, after a predetermined time such that the internal pressure of the fuel electrode becomes lower than the atmospheric pressure, when the fourth valve 14 is gradually opened by a control device (not shown) and air is sucked in, the electrode catalyst reaction of the fuel cell main body causes the inside of the fuel electrode to react. The combustible gas contained in the gas can be converted to an inert gas. Since the flow rate of air sucked from the fourth valve 14 is very small according to the amount of reduction of the flammable gas, a large amount of oxygen is not sucked into the fuel electrode at a stretch, and the above-mentioned electrode catalytic reaction occurs. Even if
Since the cooling medium in the fuel cell is still flowed for cooling, the fuel cell is not overheated by the heat of reaction.

Further, since the flow rate of the air sucked from the fourth valve 14 is very small, the condition for generating the detonation air, that is, the volume ratio of hydrogen, which is a combustible gas, to oxygen does not reach around 2/1. Therefore, no explosive air is formed in the fuel cell body.

Subsequently, after a predetermined time such that the internal pressure of the fuel electrode becomes the atmospheric pressure, a signal to close the fourth valve 14 is output to the fourth valve 14 by a control device (not shown) to shut off the outside air.

On the other hand, the above-described relief valve 13 does not operate unless the pressure becomes equal to or higher than the set operating pressure higher than the atmospheric pressure. Therefore, the raw material is continuously supplied to the reformer 4 through the first valve 3 by the pump 2. Then, the pressure in the reforming pipe 5 increases, and finally the relief valve 13 operates to release the fuel gas toward the burner.

Then, after a predetermined time such that the pressure in the reformer becomes equal to or higher than the operating pressure of the relief valve 13 set to the predetermined operating pressure, the pump 2 for supplying the raw material is stopped, and the first valve 3 is turned off. Close and seal the reformer 4. Explaining that the pressure of the gas sealed in the reformer 4 decreases as the temperature decreases, the average temperature of the reformer is 250 ° C., and when the temperature decreases to 0 ° C., the reforming reaction proceeds. Proceeding as in the above equation (1), if H ₂ gas and CO ₂ gas are ideal gases, and if the pressure drops to the atmospheric pressure at 0 ° C., From equation (2), if the internal pressure before the reformer operation is stopped is 2.1 atm or more, the pressure does not drop to atmospheric pressure even if the temperature drops to 0 ° C., and the pressure setting of the relief valve 13 is 2.5 atm. The degree is good. If the pressure is set in this way, the internal pressure does not become lower than the atmospheric pressure even after the reformer shuts down and the temperature drops, so that air is sucked from the outside and a detonation is formed. Nor.

〔The invention's effect〕

As described above, according to the present invention, when the operation is stopped, the combustible gas component in the fuel gas and the oxygen in the air are consumed by the catalytic combustion reaction in the fuel cell main body due to the electrode catalytic action, and the fuel in the fuel cell main body is consumed. Conventionally, the flammable gas in the electrode is converted to non-flammable gas, the internal pressure is increased in the reformer, and the gas is sealed so that it does not fall below atmospheric pressure even if the temperature drops. The fuel cell power generator can be safely stopped without using a required inert gas such as nitrogen as a replacement gas. In particular, in the case of a mobile fuel cell power generation device, it is not necessary to provide a large storage tank for storing inert gas, and the device can be made compact. In addition, since the management of inert gas is not required, the operation management of the device is simplified. In addition, there is an advantage that the operation cost can be reduced because an inert gas such as nitrogen is not consumed.

[Brief description of the drawings]

FIG. 1 is a system diagram of a fuel cell power generator according to a method of an embodiment of the present invention. 3 ... first valve, 4 ... reformer, 7 ... second valve, 8 ...
... fuel cell body, 11 ... third valve, 13 ... relief valve,
14 The fourth valve.

Claims (1)

(57) [Claims] 1. A reformer for reforming a raw material, comprising: a burner in which reformer fuel is supplied by a reformer fuel pump and air is supplied by an air supply device; Fuel cell main body including a fuel electrode to which the supplied fuel gas is supplied and an air electrode to which air is supplied; a first valve, a second valve, a third valve, and a fourth valve; Pump, a raw material supply pipe line through which raw material is supplied to the reformer via the raw material supply pump and the first valve, and a raw material supply pipe line through which the raw material is reformed through the second valve. A fuel gas supply pipe through which the fuel gas is supplied to the fuel cell main body, and a fuel off gas discharged from the fuel cell main body are supplied as heat sources to the burner of the reformer via the third valve. A fuel off-gas line, and air connected to the fuel off-gas line via the fourth valve. An air supply line to be supplied to the fuel electrode, a second valve in the fuel gas supply line and a reformer, and a third valve and a burner in the fuel off gas line. A method for stopping operation of a fuel cell power generator comprising a relief valve disposed in a communication conduit, wherein (1) first, after closing a second valve and a third valve, an internal pressure of a fuel electrode is reduced. After a predetermined time such that the pressure becomes lower than the atmospheric pressure, the fourth valve is gradually opened to supply air to the fuel electrode, and after a predetermined time such that the internal pressure of the fuel electrode becomes the atmospheric pressure, the fourth valve is closed. (2) On the other hand, the pressure of the reformer rises by closing the second valve and the third valve and is equal to or higher than the operating pressure of the relief valve set to a predetermined operating pressure. After a predetermined time, the pump for supplying the raw material is stopped, and the first valve is closed. Shutdown method that a fuel cell power plant.