JPH07254422A - Molten carbonate fuel cell - Google Patents

Abstract

PURPOSE:To provide a high gas-sealed fuel cell by composing an edge spring using flat ceramic plates for forming a constitution in which defects are hard to occur in the edge spring. CONSTITUTION:For an edge spring 20, both surfaces of a spring plate 21 of ceramic are held by support plates 22, and both outer sides of it are held by tightening plates 23 of ceramic. The plates 22 facing each other holding the plate 21 have rectangular cross sectional surfaces. and they are arranged at the same pitch on both sides, where their phases are deflected by half a pitch. Tightening force from the plates 23 press the spring plate 21 on both sides through the plates 22 to deform it by resiliency to be wavy. As a result, the spring 20 has such a resiliency as to contract in the height direction. These springs 20 are disposed on circumferential four sides of a current collector to be provided between an edge plate and a connector. Contact of the edge plate and carbonate matrix with each other is secured by reaction force when the spring 20 is contracted, thereby gas can be sealed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a unit cell in which a carbonate matrix is sandwiched between an anode (fuel electrode) and a cathode (air electrode), and a fuel gas is provided at the anode and an oxidant gas is provided at the cathode. The present invention relates to a molten carbonate fuel cell in which separators are alternately laminated.

[0002]

2. Description of the Related Art A fuel cell is a power generation system in which an electrochemical reaction occurring on an electrode is directly converted into an electric output. In order to carry out this reaction, a fuel gas and an oxidant gas face each other with an electrolyte matrix interposed therebetween. It must be supplied separately to the anode and the cathode. For this purpose, when a plurality of unit cells including an anode and a cathode are stacked to form a stacked fuel cell, a flow path for fuel gas and oxidant gas is formed, and adjacent unit cells are electrically connected to each other. The connecting separator is interposed.

Although the separator and the unit cell are in close contact, the fuel gas and the oxidant gas are kept airtight at the outer edge by their close contact. At this time, the unit cell is impregnated with a liquid electrolyte, and the contact surface gets wet with the electrolyte,
Airtightness is secured. When the separator and the unit cells are stacked, an edge spring is arranged at the outer edge of the separator in order to prevent contact failure at the outer edge. The edge spring has a function of contracting and pressing the outer edge of the separator against the unit cell by its reaction force.

A fuel cell using a molten carbonate as an electrolyte is called a molten carbonate fuel cell, and a matrix is impregnated with a carbonate as an electrolyte. One example of the molten carbonate fuel cell is extracted and shown in FIG. Moreover, what laminated | stacked the 2 cell of the AA cross section is shown in FIG. The unit cell 1 is composed of a carbonate matrix 2 and an anode 3 and a cathode 4 which are arranged in close contact with both surfaces of the carbonate matrix 2. The separator 5 is made of metal, and includes an interconnector 6, an anode edge plate 7, a cathode edge plate 8, an anode current collector plate 9, and a cathode current collector plate 10. The gas 11 and the oxidant gas 12 are introduced to the cathode. The anode 3 and the cathode 4 are called electrodes.

Although not shown in FIG. 3, the anode edge spring 13 and the cathode edge spring 14 ensure the contact between the edge plates 7 and 8 and the electrolyte matrix 2, so that the interconnector 6 and both edge plates 7 are provided. ,
It is arranged between eight. The position of the edge spring is shown in FIG. In this figure, the edge spring is in a contracted state.

By the way, the fuel gas 11 and the oxidant gas 12
Is supplied from the manifold to the anode and the cathode, respectively. The manifold is configured by connecting adjacent upper and lower separators with a manifold ring 15.

[0007]

As described above, since the edge spring constantly contracts to generate stress,
At 650 ° C., which is the operating temperature of the molten carbonate fuel cell, stress relaxation occurs and the reaction force of the spring decreases with time. Therefore, ceramics that are less likely to cause stress relaxation are used as the material of the edge spring (67A).
923043). However, ceramics have the drawback of being difficult to form. In particular, it is difficult to form a thin plate into a complicated shape, and defects are likely to occur in the thin plate. Such defects at points of stress concentration due to spring contraction broke the edge springs and impaired the gas's noll performance.

An example of the structure of a conventional ceramic edge spring is shown in FIG. It is configured by stacking thin plates formed in a corrugated shape. Defects are likely to occur in the bent part, causing damage. Therefore, it is an object of the present invention to provide a molten carbonate fuel cell having a structure in which an edge spring is less likely to have defects and, by extension, having a high gas sealing performance.

[0009]

An edge spring for pressing the outer edge portion of a separator against a unit cell to maintain the airtightness of the gas is constructed by using a flat plate made of ceramics.
In addition, an edge spring that presses the outer edge portion of the separator against the unit cell to maintain the airtightness of the gas is configured to bend the flat surface portion of the ceramic.

[0010]

Function: Molding ceramics into a complicated shape is likely to cause defects, but flat parts are less likely to have defects. The edge spring is less likely to be damaged by bending the flat portion of the ceramic to generate stress in the flat portion. As a result, it is possible to prevent the gas sealability from being impaired.

[0011]

Embodiments of the present invention will be described with reference to the drawings. Figure 1
FIG. 3 is a perspective view showing a part of an embodiment of the edge spring of the present invention. The edge spring 20 has a structure in which both sides of a ceramic spring plate 21 are sandwiched by support plates 22, and both outer sides thereof are sandwiched by ceramic tightening plates 23. The support plates 22 facing each other with the spring plate 21 interposed therebetween have a rectangular cross section and are arranged at the same pitch on both sides, but the phases are shifted by a half pitch. The tightening force from the tightening plate 23 presses the spring plate 21 from both sides via the support plate 22 to elastically deform it in a wave shape.
As a result, the edge spring 20 has elasticity that contracts in the height direction.

Like the conventional edge spring, the edge spring 20 is arranged on four sides around the current collector and is interposed between the edge plate and the interconnector. The reaction force when the spring contracted ensured the contact between the edge plate and the carbonate matrix and could seal the gas.

Although the spring plate 21, the support plate 22, and the tightening plate 23 are easily joined with an adhesive, the functions are the same even if they are not joined. Even if the support plate 22 and the tightening plate 23 are made of metal, the same effect can be obtained.

FIG. 2 is a perspective view showing another embodiment of the edge spring of the present invention. The edge spring 25 is formed by sandwiching the spring plate 21 with tightening plates 26 from both sides. A thin plate made of metal is pressed on the tightening plate 26 to form a protrusion 27, and the side having the protrusion 27 faces the spring plate. In the tightening plates 26 facing each other with the spring plate 21 sandwiched, the protrusions 27 are arranged at the same pitch on both sides, but the phases are shifted by a half pitch. The tightening force from the tightening plate 26 presses the spring plate 21 from both sides via the protrusion 27 to elastically deform it in a wave shape. As a result, the edge spring 25 has elasticity that contracts in the height direction.

This edge spring also had the same effect as the edge spring shown in FIG. As described above, in the edge spring configured to bend the ceramic flat plate, the spring plate is not likely to be defective and is hard to be damaged. Not only that, but also the manufacturing is easy and the cost can be reduced.

In order to increase the amount of contraction of the edge spring, a plurality of spring plates can be used in combination. For example, in the edge spring having the structure shown in FIG. 1, two spring plates are opposed to each other with a support plate having a certain pitch sandwiched therebetween, and support plates having the same pitch and a half-pitch offset are provided outside the both spring plates. Can be configured. In this case, the springs are connected in series, and the contraction amount is doubled with the same tightening pressure as compared with the case of one spring plate. Similarly, the edge spring shown in FIG. 2 may have a plurality of spring plates. Silicon nitride was used as the material of the spring plate. Since silicon nitride has high strength at high temperature and excellent spring characteristics, it was effective as a material for the edge spring.

[0017]

EFFECTS OF THE INVENTION By constructing the edge spring by using a flat plate made of ceramics, it becomes difficult for defects to enter into the ceramics, and damage to the edge spring can be prevented. As a result, good contact between the edge plate and the carbonate matrix could be maintained, and the performance of the molten carbonate fuel cell could be improved. At the same time, the manufacturing cost could be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of an edge spring in a molten carbonate fuel cell of the present invention.

FIG. 2 is a perspective view showing another embodiment of the edge spring in the molten carbonate fuel cell of the present invention.

FIG. 3 is an exploded perspective view of a molten carbonate fuel cell

FIG. 4 is a sectional view of a molten carbonate fuel cell.

FIG. 5 is a perspective view showing an edge spring in a conventional molten carbonate fuel cell.

[Explanation of symbols]

1 ... Single cell 2 ... Carbonate matrix 3 ... Anode
4 ... Cathode 5 ... Separator 6 ... Interconnector 7 ... Anode edge plate 8 ... Cathode edge plate 9 ...
Anode current collector 10 ... Cathode current collector 11 ... Fuel gas 12 ... Oxidizer gas 13 ... Anode edge spring 14 ... Cathode edge spring 20 ... Edge spring 21 ... Spring plate 22 ...
Support plate 23, 26 ... Tightening plate 27 ... Protrusion

Claims (4)

[Claims] 1. A unit cell in which a carbonate matrix is sandwiched between an anode and a cathode and a separator for guiding a fuel gas to the anode and a separator for guiding an oxidant gas to the cathode are alternately laminated to generate electric power. In a molten carbonate fuel cell, an edge spring that presses the outer edge portion of the separator against the unit cell to maintain airtightness of the gas,
A molten carbonate fuel cell, which is configured by using a flat plate made of ceramics. 2. A unit cell in which a carbonate matrix is sandwiched between an anode and a cathode and a separator for introducing a fuel gas to the anode and a separator for guiding an oxidant gas to the cathode are alternately laminated to generate electricity. In a molten carbonate fuel cell, an edge spring that presses the outer edge portion of the separator against the unit cell to maintain airtightness of the gas,
A molten carbonate fuel cell, characterized in that a flat portion of ceramics is bent. 3. The molten carbonate fuel cell according to claim 1, wherein the edge spring is configured by combining a metal member and a ceramic flat plate. 4. The molten carbonate fuel cell according to claim 1, wherein the ceramic member of the edge spring is made of silicon nitride.