JPS625569A - Molten carbonate type fuel cell stack - Google Patents

Abstract

PURPOSE:To surely seal the periphery of unit cell and the space between a stack and a manifold by forming a side wall member which prevents leakage and mixing of reaction gasses with the same material as an electrolyte layer. CONSTITUTION:A conductive end plate is placed on the upper part of a fuel cell stack, and the fuel cell stack is fastened in a usual way, and manifolds 37a, 37b, 38a, and 38b for conducting reaction gasses are fixed to each side. Zirconium felt impregnated with molten carbonate having the same composition as electrolyte is placed between a frange of the manifold and the stack to serve as the sealant. The side of the fuel cell stack is covered with the electrolyte, and affinity between the stack and the manifold is improved. Since side walls 32a and 32b are formed with carbonate, they are corrosion-free and gas sealing is surely performed.

Description

DETAILED DESCRIPTION OF THE INVENTION C. Technical Field of the Invention The present invention relates to a molten carbonate fuel cell stack, and particularly to a fuel cell stack that is capable of improving reaction gas sealing performance.

[Technical uses of inventions and their problems]

In recent years, molten carbonate fuel cells have been developed as an energy conversion device for horse fat. A molten carbonate fuel cell is one in which an electrolyte made of alkali carbonate is molten at high temperatures to cause electrode reactions, and electrode reactions occur more easily than other fuel cells such as phosphoric acid and solid electrolyte types. It has great features such as not requiring expensive precious metal catalysts and high heat generation efficiency.

By the way, in order to construct a high-output power generation plant using molten carbonate fuel cells, since the output of the unit cells is weak, it is necessary to stack a plurality of unit cells in series to form a laminate.
It is necessary to obtain the summed output of each unit battery. For this reason, conventionally, molten carbonate fuel cells have been constructed in a stacked structure as shown in FIG.

That is, on each unit cell, a pair of porous electrodes 2a, 2
Electrolyte R3 consisting of b and carbonate interposed between them
It consists of These unit cells are laminated with conductive separators 4 interposed therebetween, which have both the function of electrical connection between the unit cells 1 and the function of forming passages for reaction gas to each electrode plate.

That is, the separator 4 includes a conductive separator plate main body 5 and two opposing surfaces on one side of the separator plate main body 5.
A side wall member 6a made of stainless steel is fixed, for example, by brazing, on the side portion, and a side wall member 6a made of stainless steel is fixed, for example, by brazing, on the other side of the separator plate main body 5, on two opposing sides in a direction orthogonal to the side wall member 6a. a stainless steel side wall member 6b;
A reaction gas passage A is formed by these side wall members 6a and 6b.

A corrugated plate 7a is fitted to B to separate the reaction gas.

7b.

Manifolds (not shown) having functions of distributing and collecting reactive gases are applied to the four sides of the fuel cell stack X configured in this manner. Then, oxidant gas P was supplied to one of these manifolds, and fuel gas Q was supplied to the adjacent manifold, and both gases contributed to the electrode reaction inside the fuel cell stack to obtain a DC output. Afterwards, the gas can be discharged from the respective opposing manifolds.

In the fuel cell configured in this way, each side wall member 6a,
A wet seal portion is formed between the electrolyte layer 6b and the electrolyte layer 3, and prevents the reaction gases P and Q from leaking or mixing into an unintended side of the fuel cell. Wet seals are also formed between each side surface of the fuel cell stack X and each manifold by impregnating ceramic felt with molten carbonate, for example.

However, in the case where a wet seal is formed by interposing ceramic felt or the like between the fuel cell stack X and the manifold, the gap between the stainless steel side wall members 6a, 6b and the felt is In addition to poor compatibility, there was a problem in that the sealing performance between the laminate X and the manifold deteriorated over time due to corrosion loss of the side wall members 6a and 6b due to molten carbonate.

In addition, the welding or brazing portion 15 between the side wall members 6a, 6b and the separator plate main body 5 may be affected by carbonate or the like moving on the surface of the side wall members 6a, 6b,
A gap is created between a, 6b and the separator plate main body 5. Such gaps have the problem of causing leakage and mixing of reactant gases, resulting in a decrease in power generation efficiency.

Further, when manufacturing the separator 4, a step of brazing or welding the side wall members 6a, 6b to the ends of the separator plate main body 5 is included, and further, the side wall members 6a, 6b are
The surface that corresponds to the manifold flange needs to be finished with sufficient machining accuracy from the viewpoint of gas tightness, which poses a problem of complicating manufacturing and reducing yield.

[Purpose of the invention]

The present invention has been made based on the above circumstances, and provides a molten carbonate fuel that can reliably seal the periphery of the unit cell and the seal between the stacked body and the manifold, and is easy to manufacture. The purpose is to provide a battery laminate.

[Summary of the invention]

The present invention includes stacking a plurality of unit cells each having a pair of porous electrode plates arranged on both sides of a carbonate electrolyte layer with conductive separator plates interposed therebetween. In the molten carbonate fuel cell stack, the side wall member is interposed between the side wall member and the side wall member to form a gas passage for guiding a reaction gas in a direction perpendicular to the stacking direction of the unit cells. It is characterized by being made of the same material as the electrolyte layer.

〔Effect of the invention〕

According to the present invention, the side wall member that prevents leakage and mixing of the reaction gas distributed between the peripheral edge of the electrolyte layer and the peripheral edge of the separator plate is formed of the same material as the electrolyte layer. Therefore, most of the portion appearing on the side surface of the fuel cell stack becomes N solute. Therefore, the fit between the fuel cell stack and the manifold is good, and since the side wall members are made of carbonate, there is no problem of corrosion, and gas sealing can be ensured.

Further, according to the present invention, the separator plate may be a simple plate-like body, there is no need to braze or weld the side wall members as in the conventional case, and the side wall members are not required to have a high surface area.

Therefore, the manufacturing efficiency is improved, and since there are no welded or brazed parts, the problem of the occurrence of gaps due to corrosion at those parts is also solved.

(Embodiments of the Invention) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Example> A fuel cell stack Y as shown in FIG. 1 was constructed.

A plurality of unit batteries 12 are stacked with separator plates 12 in between. The unit battery 12 has an anode 14a and a corrugated plate 15a on one side of an electrolyte layer 13 formed in a process described later.
are arranged in this order, and the cathode 14b and the corrugated plate 15b are placed on the other side.
are arranged in this order. The electrolyte layer 13 consists of two opposing surfaces on one side of the electrolyte plate 13a, which is the central reaction part.
A protrusion 13b serving as a side wall member is formed on the side part, and
On the other side, protrusions 13c, which also serve as side wall members, are protrudingly provided on two sides facing in a direction orthogonal to the protrusions 13b. This electrolyte layer 13 is composed of lithium aluminate/lithium carbonate/potassium carbonate -40:28:32 (w
%) mixed powder is filled into a mold, and pressed to about 300%
It was obtained by hot pressing at a pressure of Kg/i and a temperature of 460°C. The shape of the mold is such that the thickness of the electrolyte plate 13a is 2 m,
The thickness of the protrusions 131) and 13G was determined to be 6 m. The anode 14a is made of a porous nickel alloy,
It was fitted into the groove C formed by the protrusions 13a and 13b of the electrolyte 1113. The cathode 14b was formed of a porous nickel material and fitted into the groove formed by the protrusion 13c of the electrolyte layer 14b. Furthermore, two corrugated plates 15a for gas diversion are attached to the anode 14a and the cathode 14b, respectively.

15b was made of stainless steel. Also, unit battery 1
The separator plate 12 interposed between the ridges 15a of the electrolyte layer 13 is made of stainless steel (SUS316) with a thickness of 0.2 m and the same length and width as the electrolyte layer 13.
, 15b were in contact with each other, an alumina anti-corrosion layer 16 having a thickness of 1 mm was previously formed by plasma spraying.

After the fuel cell stack Y constructed in this manner was tightened in the usual manner by applying conductive end plates (not shown) from above and below, manifolds (not shown) for guiding reaction gas were pressed into contact with each side surface.

Note that, as in the conventional case, zirconia felt impregnated with molten carbonate having the same composition as the electrolyte was inserted into the peripheral flange of each manifold, and this was used as a sealing material.

The fuel cell constructed in this way is heated at 65°C by a normal method.
The temperature is raised to 0°C, and carbon dioxide gas is passed through as the oxidant gas Q and hydrogen gas is passed through as the fuel gas P.
Difference ΔF between F o and exhaust gas J21Ft (=F1−
Fo) to the supplied gas amount FD (decrease amount ΔF/F
O) was measured. At the same time, when the gas composition of the exhaust gas was examined to see the contribution of gas mixing between the oxidant gas side and the fuel side, no gas from the other pole was detected from either pole side. Therefore, it was decided that the amount of decrease was due to leakage from the manifold seal.

As a comparative example, the amount of leakage from the manifold seal was similarly measured using the conventional fuel cell stack X shown in FIG. The results are shown in the table below.

As is clear from the above results, in this example, the amount of reaction gas leaking from the manifold was reduced, and it was confirmed that the battery structure of this example was effective.

In addition, after operating both the fuel cells of the above example and comparative example for 200 hours, the temperature was lowered and the fuel cells were disassembled. In the comparative example, gaps due to corrosion of the welded parts between the side wall members 6a, 6b and the separator plate main body 5 were found. were observed at 3 locations per 10 cells, and the current-voltage characteristics of the three unit batteries with these gaps were 0.2 to 0.3 V lower than the other unit batteries immediately before the temperature fell. On the other hand, in the fuel cell stack Y according to the present example, no formation of gas leakage paths due to such corrosion was observed, and the variation in current-voltage characteristics between the unit cells 11 was within ±5%. was.

In addition, in this embodiment, the separator plate 12 is formed only of a metal flat plate, and the sealing side wall member 5 is different from the conventional sealing side wall member 5.
Manufacturability was extremely good because welding of parts a and 6b was not required.

As described above, the molten carbonate fuel cell stack Y of this example has good sealing performance and manufacturability, and can sufficiently suppress deterioration of performance over time.

Note that the present invention is not limited to the embodiments described above. For example, in the above example, the composition of the electrolyte layer is lithium aluminate/lithium carbonate/potassium carbonate-4.
0/28/32 (W%), but reinforcement 7 was added to the electrolyte layer.
To reduce cracking, lithiated alumina fibers or lithium zirconate fibers may be mixed. Alternatively, a small amount of an organic binder or plasticizer may be mixed in to impart flexibility to the electrolyte layer and improve manufacturability, and the organic binder or plasticizer may be volatilized during heating of the fuel cell stack. .

In addition, the electrolyte layer 13 is not formed by integrally forming the side wall members 21a and 21b, but as shown in FIG. It may also be formed by fixing it to the plate body 22 and volatilizing the organic adhesive while the temperature of the fuel cell is rising.

In addition, since the side wall member does not require ionic conductivity of carbonate ions (CO32-), it is necessary to use glass that exhibits plasticity at the fuel cell operating temperature and alumina Il as its support.
It is also possible to use a plate formed into a strip by mixing it with a strip.

Roughly speaking, in the above-described embodiment, the planar dimensions of the separator plate 12 and the electrolyte layer 13 were made the same, but the separator plate 12 may be slightly smaller than the electrolyte layer 13. Also,
The anti-corrosion treatment of the peripheral edge of the separator plate 12 is not limited to plasma spraying of alumina, but can also be done with a foil 25 of corrosion-resistant metal such as gold or aluminum-containing stainless steel, as shown in FIGS. 3 and 4. You can also cover it, like this.

In this case, FIG. 3 shows an example in which a corrugated plate 14a is used for current collection and gas diversion, and FIG. 4 shows an example in which a porous metal plate 26 with high porosity is used for gas diversion. .

In addition, as shown in FIGS. 5 and 6, the present invention allows the fuel gas P and the oxidizing gas Q to cross each other inside the fuel cell stack Z in a direction perpendicular to the stacking direction and in a diagonal direction. It can also be applied to devices in which the flow is caused to flow.

That is, crank-shaped grooves E and F are formed in the peripheral edges of both sides of the electrolyte plate main body 31 so that the fuel gas P and the oxidizing gas Q cross each other obliquely, and grooves E and F are formed in the same material as the electrolyte plate main body 31. Side wall member 32a formed in an L shape
, 32b are attached. In addition, the electrolyte plate main body 3
An anode 33a and a cathode 33b are arranged on both sides of the electrode 1 so as to fit into the grooves E and F, and a porous metal plate 34a having both a gas passage and a current collecting function is disposed on these electrodes.
, 34b are arranged. Unit battery 1 configured in this way
1 are laminated in plurality with conductive separator plates 36 interposed therebetween to form a fuel cell stack Z.

The manifolds 37a and 37b for supplying and discharging fuel gas are arranged on one side of the two opposing sides of the fuel cell stack Z constructed in this way, and the manifolds 37a and 37b for supplying and discharging oxidizing gas are arranged on the other side. A fuel cell is constructed by arranging the manifolds 38a and 38b.

It goes without saying that the effects of the present invention can be obtained even with a fuel cell having such a configuration.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of a molten carbonate fuel cell stack according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view showing another example of the structure of the electrolyte layer in the same fuel cell stack. Figures 1 and 5 are exploded side views showing other configuration examples of unit cells and separator plate anti-corrosion layers in the same fuel cell stack, respectively, and Figure 5 shows the configuration of a fuel cell stack in another embodiment of the present invention. FIG. 6 is a perspective view of a fuel N pond using the same fuel cell stack, and FIG. 7 is an exploded perspective view of a conventional molten carbonate fuel cell stack. 1.11.35... Unit battery, 2a, 2b-... Porous electrode plate, 3.13a, 13b... Electrolyte layer, 4...
・Separator, 5... Separator plate body, 6a, 6
b. 21 a, 21 b, 32 a, 32 b - side wall member,
7a, 7b, 15a, 15'o--corrugated plate, 12.3
6... Separator plate, 13a... Electrolyte plate main body, 1
3b. 13 G--Protrusion, 14a, 33a--Anode,
14'b, 33b... cathode, 16... anticorrosion layer,
25...Foil, 26.34a, 34b...Porous metal plate, 37a, 37b, 38a, 38b=-v nifold, A-F...groove, P...fuel gas, Q... Oxidizing gas. Applicant's representative Patent attorney Takehiko Suzue Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A plurality of unit cells each having a pair of porous electrode plates arranged on both sides of a carbonate electrolyte layer are stacked with conductive separator plates interposed therebetween, and between the peripheral part of the electrolyte layer and the peripheral part of the separator plate. A molten carbonate fuel cell stack comprising a side wall member interposed in the unit cell to form a gas passage for guiding a reaction gas in a direction perpendicular to the stacking direction of the unit cells,
A molten carbonate fuel cell stack, wherein the side wall member is made of the same material as the electrolyte layer.