JPH04338101A - Method for starting fuel cell system - Google Patents

Abstract

PURPOSE:To exclude use of a heating means such as a burner in starting the steam reformer for a fuel cell system. CONSTITUTION:A gas of high hydrogen content is produced by the reforming reaction in a steam reformer 1 heated by a catalyzed combustion chamber 3, and the product gas is supplied to the hydrogen electrode 7 of a solid high molecular electrolyte-type fuel cell 6 to generate power by this fuel cell system. When the system is started, the hydrogen generated from a hydrogen storage 11 contg. a hydrogen storage alloy is supplied to the catalyzed combustion chamber 3 of the reformer 1.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for starting a fuel cell system using a catalytic fuel type steam reforming reactor.

0002

BACKGROUND OF THE INVENTION The practical application of a fuel cell system using a steam reforming reactor and a solid polymer electrolyte fuel cell has heretofore been studied. Here, the steam reforming reactor is
A raw material gas consisting of hydrocarbons and oxygen-containing hydrocarbons such as methane and methanol is decomposed into mainly hydrogen and carbon dioxide through a steam reforming reaction and a CO shift reaction. Furthermore, a solid polymer electrolyte fuel cell generates electricity by supplying hydrogen gas produced in a steam reforming reactor to a hydrogen electrode and also supplying air or oxygen to an air electrode.

[0003] In order to generate electricity with such a fuel cell system, the steam reformer must first be started. Known methods for starting a steam reformer include direct heating with a burner or a catalytic fuel method using hydrocarbons as a raw material.

0004

However, the direct heating method using a burner has the following drawbacks. ■
Because the temperature of the reaction tube wall locally increases to 800° C. or higher due to radiant heat, the material used becomes expensive. ■ In order to obtain a stable combustion state, measures against misfire such as a pilot burner are required, which inevitably complicates the structure of the combustor and the control system.

[0005] Furthermore, in the catalytic combustion method that uses hydrocarbons as raw materials, the catalytic activity at low temperatures (approximately 400°C or less) is extremely low, so it is necessary to raise the temperature of the combustion catalyst to 400°C or higher by heating with a burner or heater. There is. For this reason, burner heating has the disadvantages mentioned above, and heater heating has a high reforming reaction temperature (approximately 500°C or less), so ordinary sheath heaters have a significantly short lifespan and must be replaced every time the heater is stopped. There is a problem.

[0006] In view of these circumstances, it is an object of the present invention to provide a method for starting a fuel cell system that does not have the above-mentioned drawbacks.

[0007]

[Means for Solving the Problems] A method for starting a fuel cell system according to the present invention that achieves the above-mentioned object is a method for starting a fuel cell system according to the present invention, in which a catalytic combustion type steam reforming reactor is charged with hydrocarbons such as methane and methanol, or oxygen-containing hydrocarbons. When starting up a fuel cell system that supplies raw materials and produces gas with a high hydrogen concentration through a steam reforming reaction, and supplies the produced gas to a solid polymer electrolyte fuel cell to generate electricity, hydrogen containing a hydrogen storage alloy is used. The present invention is characterized in that hydrogen generated from the storage device is supplied to the steam reforming reactor and used as catalytic fuel.

[0008]

[Operation] With the above structure, hydrogen can be supplied from the hydrogen storage device to the combustion catalyst of the steam reforming reactor at startup, so that catalytic combustion can be performed at room temperature. Therefore, the burner or heater using hydrocarbon as a raw material becomes defective, and the structure of the steam reforming reactor becomes simple. In addition, catalytic combustion allows combustion outside the normal combustion range, making temperature control easy and preventing localized heating. Furthermore, since the combustion reaction occurs on the surface of the catalyst, the temperature rises faster than when heated by an external burner or heater.

[0009]

EXAMPLES The present invention will be explained below based on examples.

FIG. 1 shows an example of a fuel cell system according to the method of the present invention. In FIG. 1, 1 is a steam reforming reactor, to which is connected a raw material supply pipe 2 for introducing a mixture of methane gas and steam as raw materials. In addition, the steam reforming reactor 1 has a combustion catalyst chamber 3 which is a heat source necessary for the reforming reaction.
It is equipped with A pipe 4 is connected to the fuel catalyst chamber 3 for supplying methane, which is a raw material for the catalytic reaction during steady operation.

Methane and steam supplied to the steam reforming reactor 1 are mainly decomposed into hydrogen and carbon dioxide by a steam reforming reaction, and CO converts carbon monoxide into carbon dioxide.
It is sent to transformer 5.

In the figure, reference numeral 6 denotes a solid polymer electrolyte fuel cell (hereinafter referred to as a fuel cell), which has a hydrogen electrode 7 and an air electrode 8. Here, hydrogen gas converted into carbon dioxide and hydrogen in the CO shift converter 5 is introduced into the hydrogen electrode 7,
Furthermore, air is introduced into the air electrode 8 via a blower 9, and air is generated when the hydrogen gas introduced into the hydrogen electrode 7 and the air introduced into the air electrode 8 react.

Exhaust gas from the hydrogen electrode 7 of the fuel cell 6 is introduced into the combustion catalyst chamber 3 through a pipe 10, and a hydrogen storage device 11 is interposed in the middle of the pipe 10. The hydrogen storage device 11 is equipped with a hydrogen storage alloy and can temporarily store hydrogen, and is designed to store a certain amount of hydrogen during steady operation (during low load) or when stopped. When hydrogen is not being stored, the exhaust gas from the hydrogen electrode 7 is sent to the combustion catalyst chamber 3 via the bypass pipe 12. Note that air from the blower 9 is supplied to the combustion catalyst chamber 3 via an air supply pipe 13, and combustion exhaust gas from the combustion catalyst chamber 3 is discharged from a combustion exhaust gas exhaust pipe 14.

Next, a method of starting up the above-mentioned fuel cell system will be explained. First, during construction, the combustion catalyst is heated by supplying hydrogen from the hydrogen storage device 11 that stores hydrogen in advance or from outside to the combustion catalyst chamber 3 via the pipe 10. Then, when the temperature of the combustion catalyst reaches 500° C. or higher, methane is gradually supplied through the pipe 4 to switch from hydrogen to methane. After the steam reforming reactor 1 reaches a predetermined temperature, raw material methane gas and raw material steam are supplied into the steam reforming reactor 1 from the raw material supply pipe 2 to stabilize the system. Then, when the load is low or the system is stopped, hydrogen is stored in the hydrogen storage device 11 for the next startup,
During other operations, the exhaust gas from the hydrogen electrode 7 is transferred to the bypass pipe 1.
2 to the combustion catalyst chamber 3.

FIG. 2 shows the change in temperature of the combustion catalyst layer in the combustion catalyst chamber 3 over time in this embodiment. As shown in the figure, in this example, hydrogen was supplied from room temperature, but approximately 1
It was possible to switch from hydrogen to methane in a matter of hours.

On the other hand, conventionally, at startup, the temperature of the combustion catalyst layer is raised by heating with a burner using methane gas as a raw material, and then during steady operation, exhaust gas from the hydrogen electrode 7 is introduced into the combustion catalyst chamber to heat it. Ta. For comparison, FIG. 3 shows changes over time during startup due to such burner heating. As shown in the figure, in this case, the temperature of the tube wall rapidly rose to around 850°C due to radiant heat, but the internal combustion catalyst temperature rose slowly until methane could be introduced (until it reached about 500°C). It took about 2 hours.

[0017]

[Effects of the Invention] As explained above, according to the method of the present invention, catalytic combustion is possible from room temperature and local heating is prevented, so the steam reforming reactor can be made more compact and the material cost can be reduced. becomes. In addition, since startup is performed by a combustion catalyst, the combustion temperature can be easily controlled, stability is higher than that of a burner, and the temperature rises quickly, resulting in a short startup time.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a fuel cell system according to one embodiment.

FIG. 2 is an explanatory diagram showing a change in combustion catalyst temperature over time in an example.

FIG. 3 is an explanatory diagram showing a change in combustion catalyst temperature over time according to a comparative example.

[Explanation of symbols]

1 Steam reforming reactor 3 Combustion catalyst chamber 5 CO transformer 6 Fuel cell 7 Hydrogen electrode 8 Air electrode 11 Hydrogen storage device 12 Bypass piping

Claims (1)

[Claims] Claim 1: Supplying a raw material consisting of hydrocarbons or oxygen-containing hydrocarbons such as methane or methanol to a catalytic combustion type steam reforming reactor to produce gas with a high hydrogen concentration through a steam reforming reaction; When starting up a fuel cell system that supplies gas to a solid polymer electrolyte fuel cell to generate electricity,
A method for starting a fuel cell system, comprising supplying hydrogen generated from a hydrogen storage device containing a hydrogen storage alloy to the steam reforming reactor and using it as a catalytic fuel.