JP3062219B2 - Heat medium heating device of fuel reformer for fuel cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a heat transfer tube through which a heat medium for heating a reforming tube filled with a reforming catalyst of a fuel reformer flows. The present invention relates to a heat medium heating device for a fuel reforming tube for a fuel cell, which is heated by combustion of a burner comprising a combustion catalyst by air and exhaust air.

[Conventional technology]

The fuel reformer passes a reforming raw material consisting of an alcohol-based or hydrocarbon-based raw fuel through a reforming tube filled with a reforming catalyst,
The reforming tube is heated by a thermal catalyst to reform the reforming raw material into a gas rich in hydrogen, and the heating of the heat medium for heating the reforming tube is performed by using off-gas containing unused hydrogen from the fuel cell and unused gas. It is known to use a heating medium heating device which performs combustion by a burner comprising a combustion catalyst with exhaust air containing oxygen. FIG. 3 shows a conventional system of a fuel cell power generation system having such a heating medium heating device.

In FIG. 3, 1 is a heat exchanger, 2 is a fuel reformer, 3 is an air preheater, 4 is an off-gas preheater, 5 is a fuel cell, 6 is a starting heater, and 10 is a heating medium heating device.

The heat medium heating device 10 includes a burner 11 made of a combustion catalyst and a heat transfer tube provided in a combustion chamber 12 in which fuel is burned by the burner 11.
The heat medium for heating the reforming tube 14 filled with the reforming catalyst of the fuel reformer 2 flows through the heat transfer tube 15. Circulatory system 13
Circulates the heat medium between the heat transfer tube 15 and the fuel reformer 2.

The off-gas supply system 16 supplies off-gas from the fuel cell 5 to the burner 11 via the off-gas preheater 4. The exhaust gas from the fuel cell 5 is supplied to the off-gas supply system 16 by the air preheater 3.
An exhaust air supply system 17 for supplying the burner 11 to the burner 11 is connected to the system.

The start-up heater 6 heats the heat medium circulating in the circulation system 13 at the time of start-up, and comprises a burner 20 using raw fuel as a fuel and a heat transfer tube 21. The heat medium flowing through flows. The starting circulation system 22 is connected to the circulation system 13 with the heat transfer tube 21 inserted therein and the valve 23 of the circulation system 13 interposed therebetween. In addition,
24 and 25 are valves.

The start-up valve 23 of the fuel reformer 2 having such a configuration is closed, the valves 24 and 25 are opened, and the heat medium is circulated to the circulation system 13 and the start-up circulation system 22 by the heat medium circulation pump 25. The raw fuel is supplied to the burner 20 of the starting heater 6 and burned,
The heat medium flowing through the heat transfer tube 21 is heated and passed from the starting circulation system 22 to the fuel reformer 2 via the circulation system 13. The reformed pipe 14 disposed in the fuel reformer 2 is heated by the heated heat medium.
Is heated to a temperature at which the reforming reaction can be started.

After the temperature of the reforming catalyst in the reforming pipe 14 is raised as described above, the reforming raw material gas composed of the raw fuel and steam is supplied to the heat exchanger 1, where the heat medium heating device 10 is heated. The fuel gas is heated by the combustion exhaust gas discharged from the fuel tank to a high temperature, and flows through the reforming pipe 14 of the fuel reformer 2. The reforming raw material gas flowing through the reforming pipe 14 is heated by the heating medium heated by the starting circulation system 22 and the starting heater 6 circulating through the circulation system 13, and the reforming raw material gas is a hydrogen-rich gas. Is steam reformed.

The steam reforming reaction at this time, for example, when the raw fuel is methane, the following reaction occurs.

CH ₄ + 2H ₂ O → CO ₂ + 4H _{2 In} this reaction, a secondary carbon precipitation reaction also occurs, so in order to prevent carbon precipitation, excess water is added to carry out a steam reforming reaction. . Therefore, excess water is included in the reformed gas as it is. The water content is usually about 30%.

The above-mentioned reformed gas containing water passes through the air preheater 3 and the offgas preheater 4 to heat and raise the temperature of the offgas from the fuel cell 5 and the exhaust air, respectively, and is cooled to the operating temperature of the fuel cell 5 by itself. And supplied to the fuel cell 5.

On the other hand, the air taken in by the air blower 27 is supplied to the fuel cell 5, and a cell reaction is caused by the supplied reformed gas to generate power. In the battery reaction, 80% of the hydrogen in the reformed gas normally contributes to the battery reaction, and most of the water generated by the battery reaction is included in the exhaust air. The water content is usually about 20%.

Here, the off-gas and the exhaust air discharged from the fuel cell 5 flow through the off-gas supply system 16 and the exhaust air supply system 17, respectively, and are heated and heated by the reformed gas in the off-gas preheater 4 and the air preheater 3, respectively. The heat medium is supplied to a burner 11 made of a combustion medium in a heating medium heating device 10 and burned by the burner 11 to form a heat transfer tube 15.
Is heated and supplied to the fuel reformer 2, and the reforming tube 14 is heated to cause a steam reforming reaction.

When the burner 11 of the heat medium heating device 10 can burn with the off-gas from the fuel cell 5 and the exhaust air as described above, the combustion of the starting heater 6 is stopped, and the valve 23 is opened. Valve 24,2
5 is closed, and the heat medium flowing through the heat transfer tube 15 is heated by the heat medium heating device 10.

The reason for using a combustion catalyst for the burner 11 is that the combustion catalyst has a low calorific value, such as off-gas from the fuel cell 5, has a large load variation in the fuel cell, and stabilizes combustion when the variation in the off-gas amount is large. This is because there is no misfire.

[Problems to be solved by the invention]

As described above, the burner 11 composed of the combustion catalyst of the heat medium heating device 10 burns off-gas and exhaust air discharged from the fuel cell 5, but the equipment and piping at the beginning of the operation of the fuel cell power generation system. When the temperature is low, drainage is generated due to moisture contained in off-gas and exhaust air, and this drain flows into the combustion catalyst of the burner 11 and wets it.

In this case, the liquid drain covers the catalyst surface of the combustion catalyst with a water film, so that air and fuel cannot be brought into contact with each other, and the oxidation reaction of fuel on the combustion catalyst by air, that is, combustion cannot be performed. Therefore, there is a problem that unburned fuel is generated until these moistures evaporate, and unburned gas is generated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat medium for a fuel reformer for a fuel cell, which can completely burn off gas from a fuel cell by exhaust air in a burner comprising a combustion catalyst at the beginning of operation of a fuel cell power generation system. It is to provide a heating device.

[Means for solving the problem]

According to the present invention, in order to solve the above-described problems, a heating medium heating device having a burner including a combustion catalyst for heating by burning off gas containing unused hydrogen discharged from a fuel cell with exhaust air containing unused oxygen is provided. At the beginning of the operation of supplying the off gas and the exhaust air from the fuel cell to the burner, the apparatus is provided with heating means for heating the exhaust air to a temperature equal to or higher than the dew point of the moisture in the exhaust air or the off gas.

Further, as the heating means, a heat medium heated by a starting heater and a means for exchanging heat with the heat medium for heating a reforming tube filled with a reforming catalyst and the exhaust air is employed. I decided to.

Alternatively, an off-gas containing unused hydrogen discharged from the fuel cell is burned by exhaust air containing unused oxygen and heated to a heating medium heating device having a burner made of a combustion catalyst. At the beginning of the operation for feeding air, an electric heater for heating the burner above the dew point of moisture in exhaust air or off-gas is provided.

[Action]

At the beginning of the operation of the fuel cell power generation system, the drain in the exhaust air generated by the exhaust air discharged from the fuel cell passing through low-temperature equipment and pipes is discharged by the heat medium that heats the reforming pipe of the fuel reformer. The temperature is raised by a heating device for heating, and the solvent is evaporated and removed in a very short time. The high-temperature exhaust air flows into the burner of the heat medium heating device comprising the combustion catalyst, and the combustion catalyst can be heated to a temperature higher than the dew point of the off-gas discharged from the fuel cell. Does not occur, so that the combustion catalyst is not covered with the drain. Therefore, off-gas generated by the combustion catalyst at the beginning of operation is completely burned, and unburned gas is not generated.

Also, by disposing an electric heater in a burner made of a combustion catalyst, the electric heater is energized at the beginning of operation of the fuel cell power generation system, thereby heating the combustion catalyst and dew point of off-gas or exhaust air. The temperature can be set to the above temperature, so that the combustion catalyst is not covered with the drain.
Therefore, the off-gas is completely burned by the combustion catalyst at the beginning of the operation, and no unburned gas is generated.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram of a fuel cell power generation system including a heat medium heating device of a fuel reformer for a fuel cell according to an embodiment of the present invention. In FIG. 1 and FIG. 2 to be described later, the same parts as those in the conventional example of FIG. 3 are denoted by the same reference numerals, and the description thereof will be omitted. 1 is different from the conventional example in that an auxiliary air preheater 26 having a built-in heat transfer tube 25 is provided in an exhaust air supply system 17 downstream of the air preheater 3, and a heat medium supply system 27 connected to the heat transfer tube 25 is further provided. That is, the branching is provided downstream of the heat transfer tube 21 of the starting circulation system 22 and connected to the downstream of the heat transfer tube 15 of the circulation system 13.

With such a configuration, at the beginning of the operation of the fuel cell power generation system, the exhaust air containing moisture discharged from the fuel cell 5 is heated and heated by the air preheater 3, but at the beginning of the operation, the equipment and the piping are connected as described above. Is not heated sufficiently because of the low temperature, so that drainage occurs. The exhaust air containing the drain is further heated by the auxiliary air preheater 26 by the heating medium flowing from the starting circulation system 22 heated by the starting heater 6 to the heating medium supply system 27 to evaporate the drain in the exhaust air. Remove. Since the combustion catalyst is heated and heated to a temperature higher than the dew point of the off-gas by the high-temperature exhaust air containing no drain, even if the off-gas containing water is supplied to the burner 11 composed of the combustion catalyst, the combustion catalyst generates drain. And keep the combustion catalyst dry. For this reason, the off-gas is completely burned and does not generate any gas.

FIG. 2 is a system diagram of a fuel cell power generation system including a heat medium heating device according to another embodiment of the present invention. FIG. 2 is different from the conventional example of FIG.
That is, a plurality of electric heaters 30 are provided in the burner 11 made of the combustion catalyst.

With this configuration, at the beginning of the operation of the fuel cell power generation system, the electric heater 30 is energized to bring the combustion catalyst to a temperature equal to or higher than the dew point of the exhaust air or off-gas exhausted from the fuel cell. Since the water contained in the off-gas is removed by evaporation, and the combustion catalyst is in a dry state, the same effects as described above can be obtained.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, at the beginning of operation of the fuel cell power generation system, the exhaust air from the fuel cell is heated and heated to remove the drain contained therein, and this high-temperature exhaust air is used as a combustion catalyst. The temperature of the supplied combustion catalyst is set to a temperature equal to or higher than the dew point of the off-gas from the fuel cell. Therefore, even if the off-gas containing water flows into the combustion catalyst, no drain is generated.
The off-gas is completely burned and has an effect that no unburned gas is generated.

According to a third aspect of the present invention, an electric heater is disposed in a burner made of a combustion catalyst of a heat medium heating device, so that the electric heater is energized at the beginning of operation of the fuel cell power generation system so that the combustion catalyst is fueled. The temperature is higher than the dew point of the off-gas or exhaust air from the battery, so that even if the off-gas or exhaust air containing moisture flows into the combustion catalyst, no drain is generated, so the off-gas completely burns and no unburned gas is generated. effective.

[Brief description of the drawings]

FIG. 1 is a system diagram of a fuel cell power generation system provided with a heat medium heating device of a fuel reformer for a fuel cell according to an embodiment of the present invention, and FIG. 2 is a fuel reformer for a fuel cell according to a different embodiment of the present invention. FIG. 3 is a system diagram of a fuel cell power generation system provided with a heat medium heating device of a conventional fuel reformer for a fuel cell, and FIG. 2: Fuel reformer, 5: Fuel cell, 10: Heat medium heating device, 11: Burner, 15: Heat transfer tube, 26: Auxiliary air preheater, 30: Electric heat
Ta.

Claims (3)

(57) [Claims] 1. A heating medium heating device having a burner comprising a combustion catalyst for burning and heating off gas containing unused hydrogen discharged from a fuel cell by exhaust air containing unused oxygen, and from the fuel cell to a burner. A heat medium heating device for a fuel reformer, comprising: a heating means for heating the exhaust air to a temperature equal to or higher than the dew point of the moisture in the exhaust air or the off gas at the beginning of the operation for supplying the off gas and the exhaust air. 2. The heating means is a heat medium heated by a starting heater, and causes a heat exchange between the heat medium for heating a reforming tube filled with a reforming catalyst and the exhaust air. The heating medium heating device for a fuel reformer according to claim 1, wherein the heating medium is a means. 3. A heating medium heating device having a burner comprising a combustion catalyst for burning and heating off gas containing unused hydrogen discharged from a fuel cell with exhaust air containing unused oxygen, and from the fuel cell to a burner. An apparatus for heating a heating medium of a fuel reformer, comprising an electric heater for heating the burner above the dew point of the moisture in the exhaust air or the off-gas at the beginning of the operation for supplying the off-gas and the exhaust air.