Chemistry: electrical current producing apparatus – product – and – With pressure equalizing means for liquid immersion operation
Reexamination Certificate
1999-03-29
2001-10-23
Brouillette, Gabrielle (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
With pressure equalizing means for liquid immersion operation
C429S010000, C429S047000, C429S006000
Reexamination Certificate
active
06306535
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to powder for an electrolyte plate of a molten carbonate fuel cell, and a sheet and a molten carbonate fuel cell using it.
2. Description of Related Art
An existing molten carbonate fuel cell is constituted by stacking a plurality of unit cells through separators for forming flowing courses of reaction gases to the respective gas diffusing electrodes, and by connecting electrically the respective cells. Each of the unit cells comprises a pair of oppositely disposed gas diffusing electrodes, that is, a fuel electrode (anode) and an oxidant electrode (cathode), and an electrolyte plate which is interposed by these gas diffusing electrodes and carries an electrolyte of an alkali metal carbonate. The molten carbonate fuel cell is operated in such a manner that a carbonate is melted under high temperature, a fuel gas containing hydrogen and carbon monoxide is supplied to the fuel electrodes of the respective cells, and a gas mixture containing air and carbon dioxide is supplied to the oxidant electrodes.
An electrolyte plate is formed of an electrolyte consisting of an alkali metal carbonate, a carrying member for preventing the electrolyte, which becomes liquid under high temperature operation, from spilling, and a reinforcing member for preventing the crack from occurring during the rise and fall of temperature. And, as its manufacturing method, particles of the carrying member and reinforcing member, and an organic binder are dispersed in an organic solvent to prepare a slurry thereof, which is poured onto a carrier sheet, then, by use of a doctor blade, a green sheet is formed. Thereafter, the green sheet is degreased to form a sheet of a porous body having an appropriate pore structure (matrix sheet), then, to this sheet of a porous body, an alkali metal carbonate is impregnated. This is a prevailing manufacturing method.
Upon forwarding a larger capacity of a molten carbonate fuel cell, the mass-production and larger size of the electrolyte plate are demanded strong. However, in the aforementioned doctor blade method, since it takes a long time to evaporate the solvent, when large green sheets are being manufactured in large quantities, many doctor blade devices and long manufacturing time are necessary. Further, in the doctor blade method in which surfaces of the particles are covered by a binder in a slurry state to combine particles themselves, in order to form a sheet which is not cracked even after evaporation of the solvent, the binder is required to sufficiently fill the gaps between particles, that is, the addition of a large amount of the binder is required. Therefore, the cost goes up, and since a huge amount of hazardous gas is generated during degreasing of the huge amount of the binder, this is not recommended from an environmental point of view.
Thus, the doctor blade method, being slow in the manufacturing speed, is inadequate for making the size of the electrolyte plate larger and for mass-production thereof, moreover, since a huge amount of the binder is required, there are problems from the cost and environmental points of view.
SUMMARY OF THE INVENTION
This invention is disclosed in Japanese Patent Application No. 10-083103 filed on Mar. 30, 1998, and the entire disclosure thereof is incorporated herein by reference.
It is an object of the present invention to provide a powder for an electrolyte plate of a molten carbonate fuel cell which, by enhancing the manufacturing speed of the electrolyte plate for the molten carbonate fuel cell, can accomplish mass-production and the larger size thereof, and, at the same time, by reducing the amount of an organic binder used, can reduce the cost and environmental pollution, and a sheet and a molten carbonate fuel cell using it.
According to one aspect of the present invention, a powder for an electrolyte plate of a molten carbonate fuel cell comprises ceramic powder which has a binder layer on the surface thereof.
Such powder for an electrolyte plate by letting it pass between a pair of heat rollers while being interposed between plates of good thermal conductivity, can be formed easily and rapidly into a sheet for an electrolyte plate. Thereby, mass-production and larger size thereof can be easily attained. Further, compared with the doctor blade method, the amount of the binder used can be reduced, thereby, the cost reduction and suppression of generation of the hazardous gas during degreasing can be attained.
Therefore, according to another aspect of the present invention, a sheet for an electrolyte plate of a molten carbonate fuel cell includes ceramic powder which has a binder layer on the surface thereof and is formed into a sheet by adhering the ceramic powder to the binder layer.
According to a further aspect of the present invention, a molten carbonate fuel cell includes a pair of gas diffusing electrodes, and an electrolyte plate interposed between the gas diffusing electrodes. The electrolyte plate is formed by letting a carbonate electrolyte carry in a sheet including a ceramic powder which has a binder layer on the surface thereof which has been removed by degreasing.
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Akasaka Yoshihiro
Nakagawa Kazuaki
Ohzu Hideyuki
Tomimatsu Norihiro
Brouillette Gabrielle
Dove Tracy
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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