JPH0565991B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel cell, and more particularly to a fuel cell capable of improving the thermal stress strength of an electrolyte plate of a molten carbonate fuel cell.

[Technical background of the invention and prior art]

The conventional molten carbonate fuel cell
There is one described in No. 154766, which is shown in FIGS. 2 to 6.

A unit cell of a fuel cell usually has a structure as shown in FIG. 2, and a plurality of these unit cells are stacked to form a fuel cell. The unit cell shown here has electrode plates (anode 2 and cathode 3) made of a porous material and to which a catalyst is added on both sides of an electrolyte plate 1 as a boundary, and further has electrode plates (anode 2 and cathode 3) on both sides of the electrolyte plate 1 as a boundary, and a rear surface of both electrode plates. A channel groove 5 formed by a plurality of parallel ribs that supplies fuel to the anode 2.
A separator plate 4 having an oxidant passage groove 6 formed by a plurality of parallel ribs for supplying an oxidant gas to the cathode 3 is laminated. FIG. 3 shows a cross-sectional view of the unit cell shown in FIG. 2. In the figure, there is a wet seal 7 between the separator 4 and the electrolyte plate 1.
is inserted. This is to seal the gas flowing inside the cell.

In the device having the above configuration, lithium aluminate powder (LiAlO ₂
A porous ceramic plate mixed with alumina fiber etc. is used as a reinforcing agent in the half), and a mixture of carbonates such as Li ₂ Co ₃ , K ₂ CO ₃ , NaCO ₃ etc. is used as the electrolyte. It is impregnated inside the board. This electrolyte is fixed at room temperature, but when the temperature exceeds approximately 490°C, it melts and flows to the interface between the electrode and separator groove, causing a chemical reaction and generating electricity. In addition, as electrode materials, Ni porous combusted material is used on the anode side and NiO porous material is used on the cathode side, and the material of the separator plate is austenitic stainless steel, such as SUS316, SUS304,
High-temperature corrosion-resistant materials such as SUS310 and SUS446 were used. This is because a reduction reaction due to hydrogen occurs on the anode side, and an oxidation reaction due to oxygen in the air occurs on the cathode side in an alkaline atmosphere, so austenitic steel with corrosion resistance is suitable.

The unit cells made of the above-mentioned constituent materials are stacked in a compressed state under a constant load in order to improve reaction performance and prevent gas from flowing out.
Furthermore, in this compressed lamination, since electricity is generated by a reaction at the electrode 2, the better the adhesion, the better the performance in terms of the electrical resistance between the electrode 2 and the separator 4.

FIG. 4a shows the temperature characteristics when the battery starts and stops. Before power generation, the temperature of the cell is raised to the rated temperature, and then fuel and oxidizer gas are introduced to generate power. When the system is stopped, the cell temperature is lowered after the gas is stopped.

Conventionally, fuel cells have been promising as a replacement for thermal power generation equipment, and in Japan, it is expected that nuclear power generation equipment will be used for base load operation and fuel cells will be used for daily load operation.

Therefore, it is necessary for the fuel cell to have excellent heat cycle properties that can withstand operation with frequent startup and shutdown operations.

Further, FIG. 4b shows changes in thermal elongation of various parts inside the fuel cell during startup and shutdown. As the temperature rises during startup, the separator plate and electrolyte plate of the battery elongate δ _S and δ _E , respectively, but the amount of elongation δ _S of the separator plate is larger than the amount of elongation δ _E of the electrolyte plate. There is. This is due to the fact that the linear expansion coefficient of the separator plate is larger than that of the electrolyte plate, as can be seen from the linear expansion characteristics shown in FIG. 6th
Figures a and b are schematic views of the elongated state of the battery main body viewed from the top and side.

When the temperature rises, the battery stretches in four directions from the center, but the amount of elongation δ _S of the separator plate is larger than the amount of elongation δ _E of the electrolyte plate, and the battery receives a compressive load F from the direction of the arrow in the figure, so the separator plate The electrolyte plate 1 tries to stretch due to the amount of elongation δ _S of the plate 4. Therefore, the electrolyte plate 1, which has a lower tensile strength than the separator plate 4, is subjected to tension and compression every time the battery is started or stopped (temperature rise or fall).

Therefore, it has been found that the ceramic material used as the electrolyte plate has high compressive strength but low tensile strength, so that fatigue strength during heat cycling becomes a problem.

When cracks occur in the electrolyte plate due to fatigue, hydrogen on the anode side mixes with air on the cathode, causing an oxidation reaction that generates water.
If this happens, the power generation reaction will be significantly reduced and heat will be generated, corroding the separator plates and electrodes and shortening the life of the battery body.

[Problem that the invention seeks to solve]

As described above, the conventional apparatus has a structure in which an electrolyte plate made of ceramic is sandwiched between separators made of austenite plates, and no consideration is given to thermal expansion.

[Purpose of the invention]

An object of the present invention is to provide a fuel cell of this type that is resistant to thermal elongation or heat cycling.

[Means for solving problems]

That is, the present invention provides a thin plate made of a metal material that covers the bottom and sides of the electrolyte plate and has a flange in a portion where the electrolyte plate is arranged, and the flange of the thin plate is sandwiched between separator plates. Further, in order to achieve the desired purpose, a large number of holes are provided in the thin plate located at the bottom of the electrolyte plate, and an electrically insulating member is interposed between the flange and the separator plate. This is what I did.

〔Example〕

Examples of the present invention will be described below.

FIG. 1 shows a longitudinal sectional view of an embodiment of a fuel cell according to the present invention. Components having the same configuration as the conventional example are designated by the same reference numerals.

In the figure, a thin plate 8 made of iron material, for example, is provided at a portion where the electrolyte plate 1 is arranged. thin plate 8
has a portion that covers the bottom and side portions of the electrolyte plate 1, and also has a flange portion 8b that is sandwiched between the separator plates 4.

When the thin plate 8 is formed in this way, the thin plate 8
A step is formed in the vicinity of the sealing portion, and can follow the difference in thermal expansion between the separator plate 4 and the thin plate 8. In other words, it has flexibility.

The electrolyte plate 1 may be sintered or not, and electrically insulating members 9 are provided at the cell ends located at both ends of the electrolyte plate 1 to prevent carbonate from leaking to the outside.
is inserted. This member 9 and separator plate 4
are integrated by heating the parts to extremely high temperatures through diffusion bonding, laser bonding, etc. Since the separator plate 4, electrode 2, and electrode 3 can be easily integrated under high-temperature reduction conditions, they are bonded in advance. Further, as shown in the figure, the thin plates 8 arranged in a grid pattern are provided with holes only inside the cells other than the seal portion 8a, that is, in the portion located at the bottom of the electrolyte. The size of the holes varies depending on the strength of the plate and the reaction rate of the cell.
As for the material of this thin plate, the same material as the separator plate 4, such as austenitic stainless steel, is suitable. Furthermore, since the inside of the cell is alkaline in nature, alkali corrosion-resistant surface treatment is required.

In the fuel cell formed in this way, the electrical insulating member 9 and the thin plate flange 8b are located between the ends of the separator plates 4, the electrolyte plate 1 is not sandwiched, and the thin plate is flexible. Therefore, even if the separator plate 4 is thermally expanded, the electrolyte plate 1 will not crack.

〔Effect of the invention〕

As described above, the present invention provides a thin plate made of a metal material that covers the bottom and sides of the electrolyte plate and has a flange in a portion where the electrolyte plate is arranged, and the flange of the thin plate. The electrolyte plate is sandwiched between separator plates, and the thin plate is provided with a large number of holes in the bottom portion of the electrolyte plate, and an electrically insulating member is interposed between the flange and the separator plate. Therefore, even if a difference in thermal expansion occurs between the separator plate and the electrolyte plate, the thermal expansion of the separator plate will not affect the electrolyte plate, thus obtaining this type of fuel cell that is resistant to thermal expansion, that is, heat cycle property. be able to.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention;
Fig. 2 is an inclined view of a conventional battery, Fig. 3 is a vertical cross-sectional view of a conventional battery, Fig. 4 a and b are illustrations of starting and stopping patterns of the battery, and Figs. 5 and 6 a and b are FIG. 2 is an explanatory diagram of linear expansion coefficient and elongation of a separator and an electrolyte plate. DESCRIPTION OF SYMBOLS 1... Electrolyte plate, 2... Anode, 3... Cathode, 4... Separator plate, 8... Thin plate, 8b...
...Brim portion, 9...Electrical insulating member.

Claims (1)

[Scope of Claims] 1. An electrolyte plate formed by impregnating an electrolyte inside a porous plate mixed with a reinforcing agent; a pair of electrodes disposed through the electrolyte plate;
a separator plate in which flow paths for fluid fuel and fluid oxidizer are formed by ribs formed in a direction perpendicular to each other on a surface facing each electrode; and the electrolyte. A thin plate made of a metal material that covers the bottom and sides of the electrolyte plate and has a flange is provided in the portion where the plate is arranged, and the flange of the thin plate is sandwiched between the separator plates, and further, A fuel cell characterized in that a plurality of holes are provided in a bottom portion of the thin electrolyte plate, and an electrically insulating member is interposed between the flange and the separator plate. 2. The fuel cell according to claim 1, wherein the thin plate made of the metal material is made of austenitic steel. 3. The fuel cell according to claim 2, wherein the thin plate made of the metal material has been subjected to an alkali corrosion-resistant surface treatment.