JPS6037675A - Molten carbonate fuel cell - Google Patents

Abstract

PURPOSE:To improve reliability and maintainability in a long time of operation by installing a spring, comprising shape memory alloy, which expands and contracts in a stacked direction of a fuel cell stack. CONSTITUTION:Elasticity of a spring 20 is weak and fastening force applied to a fuel cell stack 11 is small at normal temperature. When the spring 20 reaches martensite transformation temperature by heat conducted from the cell through a fastening pressure and heat conducting rod 19, the spring expands to original shape, thereby fastening pressure is applied to the stack 11. When temperature is decreased, the spring 20 yields at martensite transformation temperature, and fastening force applied is released. When temperature of fuel cell stack is increased, proper fastening pressure is applied to absorb thickness change, and when temperature is decreased, fastening force is released. Therefore, breakage of electrolyte layer is prevented.

Description

[Detailed Description of the Invention] Electrolyte seeps into the gas side or surrounding area of the electrode. In addition, insufficient tightening may cause gas leakage problems. Furthermore, since carbonate, which is an electrolyte, is in a solid phase at room temperature during battery operation and in a liquid phase at operating temperature, pressure control is essential for tightening at each temperature due to the following two reasons.

The first reason is that the thickness of the electrolyte layer is small due to the transition from solid to liquid phase that occurs during the temperature rising process at startup. That is, the electrolyte is usually mixed with a ceramic mold-holding powder such as lithium oxide (LiAgO After the thickness decreases and the electrolyte transitions to a liquid phase, the electrolyte migrates to the porous electrode etc. provided in 7a and h'-, and the thickness of the electrolyte layer decreases.

Part 2 is that a so-called wet seal is constructed in order to prevent leakage in the electrolyte layer, which occurs during the transition from the solid phase to the solid phase during the temperature cooling process when the battery is stopped, and the pressure is stronger than in other parts. Since it is tightened with a gas-isolated electron conductive material (ink connector), stress is concentrated at the boundary of the wet seal part due to volumetric contraction due to the transition from liquid phase to solid phase.
This will cause cracks.

In this way (in a bi-molten carbonate fuel cell), it is necessary to ensure proper tightening force of the stack at each temperature.In other words, a large tightening displacement is required during the heating process from room temperature to operating temperature. At the same time, it is desirable that the tightening force be significantly reduced during the temperature-falling process.

However, when the fuel cell is housed in a pressure chamber and operated,
During the stoppage, that is, during the temperature raising and lowering processes, the work of opening the laminated lids becomes a large-scale operation. Therefore, when the fuel cell is stopped or when the temperature rises, there is no need to open the lid of the pressure vessel.
There was a desire for a mechanism that could apply appropriate tightening pressure at each stage during operation and during temperature drops.

[Purpose of the invention]

The present invention was made to solve the above-mentioned drawbacks, and it prevents the performance from decreasing due to a drop in the clamping pressure of the stack when the fuel cell temperature rises, and also reduces the clamping pressure by 14'r when the fuel cell temperature drops to 4A. The objective is to obtain a molten carbonate fuel cell that reduces the occurrence of cracks and improves reliability in long-term operation and maintainability.

[Summary of the invention]

In order to achieve the above object, in the present invention, clamping pressure is applied to the fuel cell stack by a shape memory alloy that expands and contracts in the stacking direction of the fuel cell stack, while 'ip')t?
/I/ 7-7 g, warm air, 7 capitulates 1
The force given by the spring by S:
゛・□・ This is to relieve the applied pressure.

[Embodiments of the invention]

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

The fuel cell stack 11, the supply plate 12.17, and the heat insulation plate 14
The tightening rod 15 is tightened by a tightening rod 15, and the tightening rod 15 is tightened by a fixing nut 22 extending from the bottom frame 16 of the pressure vessel 13.
to be fixed. A push plate 18 and a tightening pressure transmission/heat conduction adjustment rod 19 have already been assembled at the bottom of the stack. The spring 20 is assembled into the spring box 21 and attached to the lower plate 23 of the pressure vessel.

Cover the pressure vessel 13 and tighten with bolts. Then, a sealed gas of about 10 Kp/d is introduced into the pressure vessel 13.

At room temperature, the elasticity of the spring 20 is small, and the tightening force acting on the laminate 13 is small.As the temperature rises, the two rows of C2 are gradually tightened from the battery through the tightening pressure transmission and heat conduction adjustment rod 19. The pressure may be changed.

Also, when a bias spring is installed, a small amount of tightening pressure may remain even at room temperature.

Part of the heat insulating layer of the laminate may be replaced in order to prevent the temperature at the spring attachment location from becoming more than 60°C higher than the above-mentioned martensitic transformation point at the operating temperature of the 7i rechargeable battery. It is clear that the spring 20 may be located at the upper part of the pressure vessel, and that various mounting methods may be employed.

By configuring in this manner, the effects described below can be obtained.

(1) Appropriate tightening pressure can be applied by absorbing large thickness changes when the temperature of the fuel cell stack increases, and damage to the electrolyte layer can be prevented by releasing the tightening when the temperature drops.

(2) It is easy to keep the pressure vessel airtight.

(3) The pressure vessel can be passed through the pressure vessel from the outside to the inside (Effects of the Invention) According to the present invention, the clamping force of the molten carbonate fuel cell layer body becomes appropriate, and secondly, when the temperature rises, the gas There are no repeated leaks or increases in internal resistance due to insufficient contact pressure, allowing efficient operation, and no damage to the electrolyte layer due to excessive clamping pressure when stopped, allowing for long service life. A fuel cell with a long life is obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention. 11...Fuel cell stack x2. i7...Tighten plate 13...Pressure vessel 14...Insulation plate 15...Tighten it 16...Pressure vessel J frame 18...Insulation push plate work 9...Tighten Comes with a pressure transmission rod and heat conduction adjustment 20.
... Spring 21 ... Spring box 22 ... Fixing nut 23 ... Pressure vessel lower plate agent Go1) Management ±
111j Stone ;, -2ζ Ib (and 1 other person)

Claims (1)

[Claims] Using a molten carbonate fuel cell stack housed in a pressure vessel, when the fuel cell is operating at a rising temperature, the tightening pressure is applied to 4 areas, and when the fuel cell temperature stops cooling down, the applied tightening pressure is applied.