JPS62128456A - Molten carbonate type fuel cell - Google Patents

Abstract

PURPOSE:To improve corrosion resistance and electrical insulating ability, by intervening metal spacers of which surfaces are covered with alumina insulating films formed by a thermal treatment, between the sides of fuel cell body and surfaces which define wet seal portions on the surfaces of manifolds and between them and the sides of the fuel cell body. CONSTITUTION:Metal spacers of which surfaces are covered with alumina insulating films formed by a thermal treatment are intervened, between the sides of a fuel cell body 1 and surfaces which define wet seal portions on the surfaces of manifolds 9a-9d and between them and the sides of the fuel cell body. The spacers 8a-8d are, for example, formed by Fe-Cr-Al alloy which contains no less than 5w% of Al and is treated on 1,100 deg.C in the air not less than 5hr, and the gaps between the spacers 8a-8d and so-called flange portions of the manifolds 9a-9d are sealed by metallic O rings 10 in which there are coil springs. Thus, the corrosion of the manifolds can be prevented, and the corrosion resistance of the spacers themselves becomes favorable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a molten carbonate fuel cell that suppresses deterioration of characteristics over time.

[Technical background of the invention and its problems]

In recent years, molten carbonate fuel cells have been developed as next-generation fuel cells. A molten carbonate fuel cell is one in which an electrolyte made of carbonate is molten at high temperatures to cause an electric bridge reaction, and compared to other fuel cells such as phosphoric acid and solid electrolyte types, the M-pole reaction is faster. It has features such as easy generation, high heat generation efficiency, and no need for expensive precious metal catalysts.

By the way, in order to construct a high-output power generation plant using such a molten carbonate fuel cell, it is necessary to construct a fuel cell main body by stacking multiple unit cells in series and obtain the added output of each unit cell. There must be. For this reason, this type of fuel cell is usually configured as follows.

That is, each unit cell is composed of a pair of porous electrode plates and an electrolyte plate made of an alkali carbonate interposed between them. The separator has both the function of electrical connection between each unit cell and the function of forming mutually perpendicular reaction gas paths to each electrode plate.

Manifolds with the function of distributing and collecting reactive gases are placed on the four sides of the fuel cell, and one of these manifolds is supplied with oxidizing gas, while the adjacent manifold is supplied with fuel gas. The two gases are caused to flow crosswise through the fuel cell body, causing a reaction, and after obtaining a direct current output, the gases are discharged from the respective manifolds facing each other.

However, the fuel cell having such a structure has the following problems.

The above-mentioned fuel cell has a porous zirconia felt interposed between the manifold and the side surface of the fuel cell main body, and the zirconia felt is impregnated with molten carbonate to form a wet seal between the fuel cell main body and the manifold. We are trying to form a However, since carbonate is corrosive when melted at a wetness level, corrosion resistance of the contact area between the manifold and the carbonate becomes a problem. Therefore, conventionally, a corrosion-resistant layer was formed by plasma spraying oxide ceramic powder such as alumina or zirconia on the above-mentioned portion of the manifold.

However, the corrosion-resistant layer formed by the above method has a problem in that there are many fine pores, and molten carbonate penetrates into these fine pores and corrodes the base material. When the base material corrodes in this way, the corrosion-resistant layer peels off from the base material, and carbonate moves and escapes through minute gaps.

Also, if the oxide ceramic coating peels off, the electrical insulation between the manifold base material and the carbonate will be compromised. From this point of view, conventional molten carbonate fuel cells have had the problem of being subject to deterioration over time.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems, and its purpose is to improve the corrosion resistance and electrical insulation of the surface that forms the wet seal of the manifold, and thereby An object of the present invention is to provide a molten carbonate fuel cell with little deterioration.

[Summary of the invention]

The present invention provides a fuel cell main body formed by stacking a plurality of unit cells, and a molten carbon dioxide comprising a fuel cell main body formed by stacking a plurality of unit cells, and a manifold that is applied to each side of the fuel cell main body and allows a reactant gas to flow through the gas flow path of each of the unit cells. In the salt-type fuel cell, an alumina insulating coating is applied to the surface between the surface of the manifold and the side surface of the fuel cell body forming a wet seal portion and the side surface of the fuel cell body by heat treatment. It is characterized by the interposition of a metal spacer.

〔Effect of the invention〕

According to the present invention, since the spacer is interposed between the manifold and the side surface of the fuel cell main body, the manifold does not come into direct contact with the molten carbonate. Therefore, corrosion of the manifold can be effectively prevented. Furthermore, an alumina insulating film is formed on the surface of the spacer by heat treatment, and this film is very dense, so that the spacer itself has good corrosion resistance.

Therefore, according to the present invention, it is possible to provide a molten carbonate fuel cell that exhibits less deterioration over time.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, the fuel cell main body 2 includes an end plate 2
A plurality of unit batteries 3- are stacked between a and 2b with a separator 4 in between. The unit battery is constructed by interposing an electrolyte plate 6 between a pair of porous electrode plates 5a and 5b. The electrolyte plate 6 is formed, for example, by hot pressing a mixture of a mixed carbonate powder having a molar ratio of L 12 CO3 to 2 Co = 62/38 and a holding material of γ-lithium aluminate. A plurality of gas flow grooves 4a and 4b are formed on both surfaces of the separator 4 and extend in directions perpendicular to each other.

Square annular zirconia felts 7a, 7b, 7c are provided on each side of the fuel cell main body 1 constructed in this way.
, 7d, i and spacer 8a.

Manifold 9a via 8b, 8c, 8d.

9b, 9cy9d are polymerized, and these manifolds 9a
-9d are fixedly tightened by means not shown. The zirconia felts 7a to 7d have the function of impregnating them with molten carbonate and forming a wet seal with the spacers 8a to 8d. The spacers 8a to 8d are, for example, A
Fe containing 5W% or more of R! -Cr-Affi alloy treated at 1100° C. for 5 hours in 1 breath of air.

For example, a helicopterex (
It is sealed with a metal O-ring 10 containing a coil spring (trade name) or the like.

The fuel cell configured in this way was heated to 650°C,
While passing the oxidizing gas P from the manifold 9a side to the manifold 9C side, the manifold 9 b ll
Fuel gas Q was made to flow from l11 to the manifold 9d side, and the system was operated for 200 hours. Its flame, each manifold 9a
-9d was disassembled and its flange was examined, and no corrosion occurred on the flange, and no destruction of the airtight structure occurred.

By the way, when the zirconia felts 7a to 7d are interposed between the side surface of the fuel cell main body 1 and the manifolds 98 to 9d as in this embodiment, conventionally, the thickness of the zirconia felts 7a to 7d is increased and the fuel cell It was necessary to provide electrical insulation between the main body and the manifold. However, when the thickness of the zirconia felts 7a to 7d is increased, the amount of molten carbonate impregnated into the zirconia felts also increases, so that electrolyte movement occurs through the molten carbonate. As a result, there is a problem in that the output voltage decreases. However, if the above-mentioned spacers 8a to 8d are provided between the zirconia felts 7a to 7d and the manifolds 9a to 9d as in this embodiment, the necessary electrical insulation is ensured, so the zirconia felt 7a The thickness of ~7d is the minimum thickness necessary to simply form a wet seal. Therefore, in this case, the amount of electrolyte movement via the molten carbonate impregnated into the zirconia felts 7a to 7d can be suppressed to a minimum.

Note that the present invention is not limited to the embodiments described above. For example, as shown in FIG. 2, if a plurality of protrusions 17a and 17b are formed along the longitudinal direction on the contact surface of the spacer 16 with the zirconia felt, the contact between the spacer 16 and the zirconia felts 7a to 7b can be formed. The protrusions 17a and 17b are bonded by crimping to the zirconia felt 78.
~7d, further improving the sealing performance between the two.

Further, in the above embodiment, Fe-Cr is used as the metal spacer.
-Although heat-treated A4 alloy is used, SUS may also be aluminized.

Furthermore, if the 8203 layer is provided on the side in contact with the fuel cell main body, carbonate will be well repelled, and the sealing performance will be further improved.

Furthermore, by fixing the manifold and spacer in advance by brazing or other methods, assembly performance can be improved. Furthermore, if boric acid glass is impregnated into zirconia felt, the effect of preventing carbonate migration is further improved.

As described above, the present invention can be implemented with various modifications without departing from the gist thereof.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view showing the configuration of the main parts of a molten carbonate fuel cell according to an embodiment of the present invention, and FIG. 2 is a spacer of a molten carbonate fuel cell according to another embodiment of the present invention. FIG. 1- Fuel cell main body, 2a, 2b... End plate, 3... Unit cell, 4... Separator, 5a, 5
b... Porous electrode, 6... Electrolyte plate, 7a to 7d.
... Zirconia felt, 8a-8d, 16... Spacer, 98-9d... Manifold, 10... Metal O-ring, 17a, 17b... Projection, P... Oxidizing gas, Q ...Fuel gas.

Claims (3)

[Claims] (1) Molten carbonate comprising a fuel cell main body formed by stacking a plurality of unit cells, and a manifold that is applied to each side of the fuel cell main body and allows reaction gas to flow through the gas flow path of each unit cell. type fuel cell, an alumina insulating film is formed on the surface of the manifold by heat treatment between the surface of the manifold that forms a wet seal portion with the side surface of the fuel cell body and the side surface of the fuel cell body. A molten carbonate fuel cell characterized by having a metal spacer interposed therebetween. (2) between the metal spacer and the manifold;
The molten carbonate fuel cell according to claim 1, characterized in that a high-temperature metal seal ring is interposed. (3) The molten carbonate fuel cell according to claim 1, wherein the metal spacer is boronized on the side that contacts the side surface of the fuel cell main body.