Plant with high temperature fuel cells I

Details Plant with high temperature fuel cells I Plant with high temperature fuel cells I

1999-07-26

2001-08-14

Kalafut, Stephen (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Having magnetic field feature

C429S006000, C429S006000, C429S006000

Reexamination Certificate

active

06274260

ABSTRACT:

The invention relates to a power plant with high temperature fuel cells arranged with a reformer in a central cavity of a stack of the high temperature fuel cells characterized in that the heat required for the endothermic reforming processes is transferred at least partially by radiation from the fuel cells to the reformer.
BACKGROUND OF THE INVENTION
A plant of this kind comprises an apparatus such as is known from EP-A 0 780 917 (=P.6719). This apparatus contains a cell block with fuel cells which is surrounded by a heat insulating sleeve. An afterburner chamber is located between the sleeve and the cell block. A reformer for the treatment of a fuel gas (also called a pre-reformer) is arranged in the sleeve. It is connected to a heat exchanger, by means of which heat for the endothermic reforming process can be supplied to it from the exhaust gases.
In the reforming of the fuel gas, which consists mainly of methane in many applications, the latter is catalytically converted at least partially into CO and H
2
in the presence of H
2
O and with process heat being supplied. Instead of a gaseous fuel a liquid one can be provided, with it however being possible for the use of a liquid fuel to be connected with additional problems, in that the latter must be fed into the reformer in a suitable manner.
SUMMARY OF THE INVENTION
The object of the invention is to provide a plant with high temperature fuel cells in which the process heat which is required for the reforming of the fuel is won in a manner which is advantageous for the entire process and is supplied to the reforming.
The plant contains high temperature fuel cells that are arranged with planar design in a centrally symmetrical stack. A supply point is provided for a gaseous or liquid fuel. In a reformer following the supply point the fuel can be catalytically converted at least partially into CO and H
2
in the presence of H
2
O and with process heat being supplied. A central cavity is arranged along the stack axis. Fuel is treated in the reformer and fed into the fuel cells. The reformer is arranged in the central cavity and is designed in such a manner that the heat required for the endothermic reforming processes can be transferred at least partially via radiation from the fuel cells to the reformer.
The reformer of the plant in accordance with the invention is designated in the following as an integrated reformer.
Whereas the known reformer is arranged separately outside the cell blocks in known plants and is heated with exhaust gas, this separate one is replaced in the plant in accordance with the invention by the integrated, radiation-heated reformer. The heat for the reforming reactions is provided via radiation directly from the fuel cell stack. This means that the cells are cooled thereby, and indeed at the location at which they have the highest temperature is known plants. Through the heat sink in the cell stack the amount of cooling air required for the tempering of the stack can be reduced. Through the reduction of the amount of air both the electrical efficiency (lower blower power) and the total efficiency (lower exhaust gas losses) increase. Thanks to an increase of the exhaust gas temperature the size of a heat exchanger which is used for the utilization of waste heat can also be reduced.
Since the heat transfer through radiation grows in proportion to the fourth power of the absolute temperature and since the temperature is high (about 1150-1200 K), high heat flow densities result even at low temperature differences.


REFERENCES:
patent: 5079105 (1992-01-01), Bossel
patent: 5486428 (1996-01-01), Gardner et al.
patent: 266861 A1 (1988-05-01), None
patent: 0398111A1 (1990-11-01), None
patent: 0443241A1 (1991-08-01), None
patent: 0551054A1 (1993-07-01), None
patent: 0635896A1 (1995-01-01), None
patent: 0673074A1 (1995-09-01), None
patent: 0780917A1 (1997-06-01), None
patent: WO 95/10126 (1995-04-01), None
Patent Abstracts of Japan, vol. 011, No. 306 (E-546), Oct. 6, 1987 & JP 62 098567 A (Hitachi Ltd), May 8, 1987, Abstract.

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