JPH0358153B2 - - Google Patents

Description

[Detailed description of the invention]

[Object of the Invention] (Industrial Application Field) The present invention relates to a molten carbonate fuel cell, and particularly to a fuel cell in which a gas seal structure in a laminate in which a plurality of unit cells are stacked is improved. (Prior Art) Conventionally, fuel cells that obtain DC power by reacting easily oxidized gas such as hydrogen with oxidizing gas such as oxygen through an electrochemical reaction process have been widely known. It is being Fuel cells are broadly classified into phosphoric acid type, molten carbonate type, solid electrolyte layer, etc. depending on the electrolyte layer used. By the way, among the above-mentioned fuel cells, molten carbonate fuel cells are designed to operate at temperatures around 650°C, and their main parts are usually constructed as shown in Figure 1. There is. That is, on both sides of an electrolyte layer 1 formed by integrating a carbonate electrolyte such as lithium carbonate or potassium carbonate and a ceramic support material such as lithium aluminate into a flat plate, the vertical and horizontal dimensions of the electrolyte layer 1 are compared. A unit cell 3 is constructed by applying nickel alloy gas diffusion electrodes 2a and 2b, each of which is narrow in one dimension, so as to be orthogonal to each other. It is constructed as a laminate X which is laminated with a plate 4 interposed therebetween. Each bipolar separator 4 includes a stainless steel separator body 5 formed to have vertical and horizontal dimensions equal to the vertical and horizontal dimensions of the electrolyte layer 1, and a separator body 5 on both parallel sides of one surface of the separator body 5, respectively. A side wall member 6 made of stainless steel and forming a groove-shaped passage A through which fuel gas flows, as shown by a thick arrow P in the figure, between each side wall member 6, with the above-mentioned one surface being the inner surface of the bottom wall.
a, 6b, and the other surface of the separator body 5 and on both sides perpendicular to the side wall members 6a, 6b, and between each, the other surface is used as the inner surface of the bottom wall. As shown by the thick arrow Q, side wall members 7a and 7b made of stainless steel constitute a groove-like passage B through which the oxidant gas flows, and the side wall members 7a and 7b made of stainless steel constitute a groove-like passage B through which the oxidizing gas flows, and the gas flow is substantially controlled in the groove-shaped passages A and B. It is composed of a corrugated plate 8 made of stainless steel that is installed in a relationship to divide the flow into a plurality of parts. And the side wall member 6
The inner edges of a, 6b, 7a, and 7b have gas diffusion 2
Stopping step portions are formed for stopping both sides of a and 2b, respectively. That is, as shown in FIG. 2, the gas diffusion electrodes 2a and 2b are formed to have a thickness that is approximately equal to the so-called depth of the stop step 9.
Further, both sides thereof are engaged with the stopping step portion 9, and are formed in a width that can close the openings of the groove-shaped passages A and B. In addition, 10 in FIG. 2 indicates a ceramic anti-corrosion layer made of alumina, zirconia, etc. provided on the side wall member in order to prevent the portion of the side wall member that contacts the electrolyte layer 1 from being corroded by the electrolyte. There is. Therefore, in a molten carbonate fuel cell whose main part is constructed as described above, side wall members 6a, 6b, 7a, It is necessary to provide a gas seal between 7b and the end of the electrolyte layer 1 that comes into contact with it, but this sealing means is usually performed using the laminate X.
After forming the cell operating temperature (L1 ₂ CO ₃ /K ₂ CO ₃ 2
In the case of elemental electrolytes, the temperature is generally raised to 650℃),
The electrolyte melted by this temperature rise is used to seal. In other words, the electrolyte is in the process of heating up.
It melts at a eutectic temperature of 488° C., and this melt melts at the end of the electrolyte layer 1 and each side wall member 6a, 6b, 7a, 7b.
The gas enters the gap between the gas and the gas, thereby creating a gas seal. However, in the case of the molten carbonate fuel cell configured as described above and employing the gas seal method, the flat surface of the end of the electrolyte layer 1 and the side wall member 6a in contact with the flat surface of the end portion of the electrolyte layer 1, 6b, 7a,
Since gas sealing is performed with molten electrolyte between the flat surface of 7b, it is difficult for the electrolyte to enter the gap between the two flat surfaces, and as a result, the problem is that the seal is likely to be insufficient. It was hot. Note that if the sealing is insufficient, a water production reaction will occur on the side surface of the stack, impairing the effective use of the supplied gas. Therefore, in order to solve this problem, it is possible to widen the width of the side wall members 6a and 6b to widen the contact width with the electrolyte layer 1, but in this case, the effective reaction area of the electrolyte layer 1 is reduced. There is a problem that the space utilization rate decreases. (Problems to be Solved by the Invention) As described above, in the conventional technology, there is a problem in that the sealing is likely to be insufficient because the molten electrolyte is used to form a scum seal between the flat surface and the flat surface. Although it is conceivable to increase the width of the side wall members 6a and 6b in order to eliminate such a problem, in this case, there is a problem that the space utilization rate decreases. The present invention was made in view of the above circumstances, and its purpose is to expand the effective reaction area of the electrolyte layer while also ensuring reliable control from the low temperature region during heating. An object of the present invention is to provide a molten carbonate fuel cell having a laminated structure that can be sealed. [Structure of the Invention] (Means for Solving the Problems) The molten carbonate fuel cell according to the present invention has a molten carbonate electrolyte layer formed in a flat plate shape, on both sides of which there is a A plurality of unit cells are formed by applying a pair of gas diffusion electrodes in which only one dimension is narrow, and the vertical and horizontal dimensions are formed between each unit battery to be equal to the vertical and horizontal dimensions of the electrolyte layer, and both sides are formed. Bipolar separators each having a groove-shaped fuel gas passage and an oxidant gas passage whose openings are closed by fitting the gas diffusion electrode are interposed and laminated, and the bipolar separator plates A molten carbonate fuel cell in which a molten electrolyte is used to provide a gas seal between a side wall forming the groove-like gas passage and an end of the electrolyte layer that is in direct contact with the side wall of the bipolar gas passage. A groove is provided in the side wall of the separator that forms the groove-shaped gas passage in a portion that directly contacts the end of the electrolyte layer, and the groove has a eutectic temperature lower than the eutectic temperature of the electrolyte constituting the electrolyte layer. The electrolyte composition is set to , and a seal is attached that melts and integrates with the electrolyte layer when heated. (Function) When the sealing material installed as described above is heated, it melts and becomes integrated with the electrolyte layer, and spreads in the width direction of the groove while fully fitting into the inner surface of the groove in which no pressure is applied. Furthermore, since the sealing material installed in the groove is made of an electrolyte layer composition that has a eutectic temperature lower than the eutectic temperature of the electrolyte constituting the electrolyte layer, it is possible to reduce the temperature in the low temperature region during heating of the laminate. The sealant melts and acts as a sealant. (Example) Hereinafter, an example of the present invention will be described. FIG. 3 shows a bipolar separator 14 incorporated into the main part of the molten carbonate fuel cell according to the present invention, and the same parts as in FIG. 1 are designated by the same reference numerals. Therefore, the explanation of the overlapping parts will be omitted. The bipolar separator 14 in this embodiment has a separator body 5 to form groove-like gas passages A, B.
Side wall members 6a, 6b, 7a, 7b brazed to
Grooves 15 each having a width of 5 mm and a depth of 1.5 mm, for example, are formed on the surfaces that are in direct contact with the ends of the electrolyte layer 1. As shown in FIG. 1, when laminating the bipolar separator 14 between each electrolyte 1, an electrolyte layer 1
Sealing material with the same composition as the electrolyte composition, for example, lithium carbonate/potassium carbonate = 62 mol%/38 mol%
A mixture obtained by adding polytetrafluoroethylene fiber as a binder and ethyl alcohol as a viscosity adjusting solvent to the mixed powder is press-molded and cut into strings to form a sealing material 16 as shown in FIG. 5a. A laminate is formed in the attached state as shown in the figure, and after this laminate is tightened with a tightening bar etc., the laminate is heated to the battery operating temperature (650℃) by external heating.
Heat until. Due to this heating, the sealing material 16
is melted as shown in FIG. 5b, and finally becomes completely integrated with the electrolyte of the electrolyte layer 1 as shown in FIG. As shown in the figure, a sealed laminate is obtained by melting the sealing material 16. Reactant gas supply manifolds are attached to four sides of this laminate in a conventional manner to construct the final fuel cell. In order to check the sealing performance of the sealing part of the fuel cell configured as described above, hydrogen gas was flowed into each passage A and nitrogen gas was flowed through each passage B through the manifold, and nitrogen gas was supplied through each passage B. Confirm the sealing performance of passage A by measuring the hydrogen gas content in the gas with a catalytic combustion hydrogen meter,
In addition, conversely, flow hydrogen gas through passage B and nitrogen gas through each passage A, and measure the hydrogen gas content in the nitrogen gas passing through each passage A in the same manner to check the sealing performance of passage B. I tried it. Further, as a reference example, similar measurements were performed on a case in which the dimensions of each part and the number of steps were set to be the same, and the seal was made without using the groove 15 and the sealing material 16. As a result, Table 1
The data shown below were obtained.

【table】

Claims (1)

[Claims] 1 A plurality of units formed by applying a pair of gas diffusion electrodes formed in both sides of a molten carbonate electrolyte layer formed in a flat plate shape, in which only one dimension is narrower than the vertical and horizontal dimensions of the electrolyte layer. The battery is provided with grooves formed between each unit cell, the vertical and horizontal dimensions of which are equal to the vertical and horizontal dimensions of the electrolyte layer, and the openings of which are closed by fitting the gas diffusion electrodes on both sides. stacked with a bipolar separator having a fuel gas passage and an oxidant gas passage interposed therebetween;
A molten carbonate fuel cell, wherein a molten electrolyte is used to create a gas seal between a side wall forming the groove-like gas passage of the bipolar separator and an end of the electrolyte layer that is in direct contact with the side wall of the bipolar separator. A groove is provided in a side wall of the bipolar separator that forms the groove-shaped gas passage in a portion that directly contacts the end of the electrolyte layer, and the eutectic temperature of the electrolyte constituting the electrolyte layer is provided in the groove. A molten carbonate fuel cell characterized in that the electrolyte composition is set to a lower eutectic temperature and is equipped with a seal that melts and integrates with the electrolyte layer when heated.