JP2002289244A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system having a reformer with high energy efficiency. SOLUTION: A heat supply method for reforming is improved by setting the reformer on a combustion part by making the combustion part to burn surplus fuel and surplus oxidizer from a fuel battery module close to the fuel battery module adjacent to it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a fuel cell system having a reformer.

[0002]

2. Description of the Related Art In a conventional fuel cell, when it is necessary to reform a fuel and supply the reformed fuel to the fuel cell, as shown in FIG. After the power generation reaction, the surplus fuel and the surplus oxidant are discharged. The reforming reaction generally requires a temperature of several hundred degrees Celsius, and is an endothermic reaction. In the reformer 1, a fuel and an oxidizing agent are introduced and reforming is performed by a combustion means such as a burner or a fuel catalyst. The required amount of heat is supplied to reform the fuel for power generation. Further, in another conventional technique, as shown in FIG. 2, excess fuel and excess oxidant from the fuel cell module 3 are introduced into the reformer 1 so that the fuel is effectively used.

[0003]

However, the prior art shown in FIG. 1 has a problem that the energy efficiency of the system is low because fuel other than the power generation reaction is consumed in the reformer. In the prior art shown in FIG. 2, the fuel is effectively used by introducing excess fuel and excess oxidant from the fuel cell module into the reformer, but the combustion means such as a burner or a combustion catalyst is used. However, there is a problem that the cost is increased due to the necessity, and heat loss is caused by heat radiation until the surplus fuel and the surplus oxidant whose temperature has increased due to the power generation reaction are introduced into the reformer.

[0004] In view of the problems of the prior art, the present invention provides a fuel cell system having a reformer capable of reforming fuel by effectively utilizing surplus fuel and surplus oxidant from a fuel cell. The purpose is to provide.

[0005]

In order to solve the above-mentioned problems of the prior art, according to the fuel cell system of the first aspect, by installing the reformer in the combustion section,
The amount of heat of the surplus fuel and the surplus oxidant can be effectively used, and the energy efficiency can be increased.

[0006] According to the fuel cell system of the second aspect, since the reformer is provided with the heat transfer improving means, the amount of heat required for the reforming can be effectively supplied. The size can be reduced.

Further, according to the fuel cell system according to the third to fifth aspects, it is possible to consider the availability of the reforming catalyst, the installation property due to the shape of the reformer, the maintenance property, and the like. .

According to the fuel cell system of the present invention, since the reformer is divided into a reforming section reforming at a low temperature and a reforming section reforming at a high temperature, carbon deposition is suppressed. It becomes possible.

Further, according to the fuel cell system of the present invention, since the reformer has a portion not provided with a catalyst, carbon deposition can be suppressed.

Further, according to the fuel cell system of the present invention, since the catalyst provided in the reformer contains nickel as a main component, an inexpensive catalyst can be obtained.

Further, according to the fuel cell system of the ninth aspect, since the fuel cell is a molten carbonate type fuel cell or a solid oxide type fuel cell, the temperature of the combustion gas is high, and the surplus fuel is naturally discharged. The system can be ignited and burned, and a system that does not require a combustor such as a burner can be provided.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 3 is an example of a configuration diagram of a fuel cell system having a reformer according to the present invention.
And becomes a heat source for reforming the fuel in the reformer 1.

[0013] As the type of fuel, those which generate hydrogen or carbon monoxide by reforming, such as methanol and hydrocarbons, can be used. In addition, city gas having a fuel supply base can also be used by removing sulfur, which is poisoned by the catalyst. Air is generally used as the oxidizing agent.

The combustion of the excess fuel 5 and excess oxidant 6 in the fuel section 4 is performed by a combustion means such as a burner or a combustion catalyst, and when the ambient temperature is higher than the auto-ignition temperature and special combustion means is required. Sometimes it doesn't. In order for the ambient temperature to be equal to or higher than the auto-ignition temperature, the temperature of the fuel cell module 3 is high, and the excess fuel 5
Also, the excess oxidant 6 needs to be at a high temperature. Therefore, as a system that does not require a combustion means, it is desirable that the type of the fuel cell be a molten carbonate type or a solid oxide type whose operating temperature is about 700 ° C. or more. Further, it is desirable that the fuel cell module 3 and the combustion section 4 are close to or integrated with each other to reduce heat loss.

FIG. 4 shows an example of the structure of the reformer shown in FIG. In FIG. 4, when the combustion gas passes through the reformer 1, it supplies the reformer with the heat required for the reforming. However, since the reformer 1 is a heat exchanger equipped with a catalyst,
The heat transfer characteristics are improved by providing the above. It is common for general heat exchangers that the reformer can be reduced in size by providing the heat transfer improving means, but in a reformer of a fuel cell, if heat transfer characteristics are poor, Since there is a problem that the amount of heat required for reforming is insufficient and the rate of reforming is reduced, the need for heat transfer improving means is high. As the heat transfer improving means, in addition to the example shown in FIG. 4, irregularities for improving the heat transfer area, a structure in which fins are provided on the plate, and the like can be considered.

In FIG. 4, the flow path of the combustion gas is
The high-temperature reforming section 8 is disposed at a position where the temperature of the combustion gas is high, and the low-temperature reforming section 9 is disposed at a position where the high-temperature reforming section passes through the high-temperature reforming section and the temperature is lowered by the reforming. After entering, it enters the high temperature reforming section 9 and is reformed. This is because when the fuel supplied to the reformer contains a carbon compound, if the temperature of the reforming section is high, carbon may precipitate on the catalyst and degrade the catalyst performance. Although the reforming section has a separate structure, this structure is not always necessary depending on the temperature of the exhaust gas from the fuel cell. In addition, when the temperature of the combustion gas is high and when the reforming section is brought close to the above-described case where carbon deposition occurs as described above, the high temperature reforming section 8 in FIG. By lowering the temperature of the combustion gas passing through the installed low-temperature reforming section 9, carbon deposition can be suppressed. Having only a heat exchange function without such a catalyst can provide the same effect in other structures, and FIG. 5 shows an example thereof. FIG. 5 shows a fuel passage near the inlet of the combustion gas of the reformer 1 in which a fuel passage is provided inside the plate-type reformer and a combustion gas passage is provided outside the plate reformer. Is provided with a non-catalyst-installed part 11 in this part, and in this part, only the heat exchange is performed.

As for the type of the reforming catalyst installed in the reformer, it is desirable to use nickel as a main component in terms of cost. It is also conceivable to add ruthenium, rhodium, or the like to suppress carbon deposition. As in the examples shown in FIGS. 4 and 5 described above, the reformer has a structure for enlarging the heat transfer area, so that the flow path becomes complicated. There is. A general form that is commercially available and easily available is often a catalyst in the form of solid particles. However, when the flow path is narrow in the plate fin type reformer as shown in FIG. 5 and the solid catalyst cannot be filled, the reforming catalyst can be provided by coating the slurry catalyst. In addition, since the catalyst is formed in a fibrous form and installed in the reforming channel, it is highly convenient when replacing the catalyst.

Further, in the example of FIG. 3, the raw fuel is directly supplied to the reformer, but in the fuel cell, a part of the surplus fuel is recycled to the raw fuel line to recycle the fuel. In the present invention, a gas in which the surplus fuel and the raw fuel are mixed can also be supplied by having a means for returning a part of the surplus fuel before the reformer in the present invention.

[0019]

As described above, according to the fuel cell system of the present invention, by installing the reformer in the combustion section, the surplus fuel and the calorie of the excess oxidant can be effectively used. And energy efficiency can be increased. According to the fuel cell system of the present invention,
The reformer can be made compact and low-cost, and carbon deposition can be suppressed.

[Brief description of the drawings]

FIG. 1 shows an example of a conventional fuel cell system using a reformer.

FIG. 2 shows an example of a conventional fuel cell system using a reformer.

FIG. 3 is an example of an overall configuration diagram of a fuel cell system according to the present invention in which a reformer is installed in a combustion section.

FIG. 4 shows an example of a reformer according to the present invention.

FIG. 5 shows an example of a reformer according to the present invention.

[Explanation of symbols]

 1: Reformer 2: Reforming burner 3: Fuel cell module 4: Combustion unit 5: Excess fuel 6: Excess oxidizer 7: Combustion gas 8: High temperature reforming unit 9: Low temperature reforming unit 10: Fin 11: Non-catalyst installation section

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H026 AA05 AA06 BB04 CV10 5H027 AA05 AA06 BA01 BA09 BA10

Claims (9)

[Claims] A fuel cell module comprising a fuel cell having an anode and a cathode on both sides of an electrolyte; an oxidant supply unit for supplying an oxidant to the fuel cell module; A fuel supply unit for supplying fuel, a reformer including a reforming catalyst for reforming the fuel supplied from the fuel supply unit and supplying a reformed gas to the fuel cell module, and discharging from the fuel cell A fuel cell system comprising: a combustion unit for burning surplus fuel and excess oxidant; wherein the reformer is installed inside the combustion unit. 2. The fuel cell system according to claim 1, wherein the reformer includes a heat transfer improving unit. 3. The fuel cell system according to claim 1, wherein the reforming catalyst of the reformer is solid. 4. The fuel cell system according to claim 1, wherein the reforming catalyst of the reformer is a coating layer coated on the reformer. 5. The fuel cell system according to claim 1, wherein the reforming catalyst of the reformer is a fiber having catalytic performance. 6. The fuel cell according to claim 1, wherein the reformer is divided into a reformer for reforming at a low temperature and a reformer for reforming at a high temperature. system. 7. The fuel cell system according to claim 1, wherein the reformer partially has a portion not provided with a catalyst. 8. The fuel cell system according to claim 1, wherein a catalyst included in the reformer contains nickel as a main component. 9. The fuel cell system according to claim 1, wherein the fuel cell is a molten carbonate fuel cell or a solid oxide fuel cell.