JPS63178455A - Free electrolyte type fuel cell - Google Patents

Abstract

PURPOSE:To increase the efficiency of a fuel cell and to make the fuel cell compact by installing an electrolyte chamber frame which surroundings a unit cell and has holes connecting with the electrolyte chamber of the unit cell in the upper and lower parts, constituting a cell stack by stacking unit cells via the electrolyte chamber frames, and putting the cell stack in the electrolyte in an electrolyte tank. CONSTITUTION:An electrolyte chamber frame 18 which surroundings a unit cell and has holes 18b, 18c connecting with the electrolyte chamber 2 of the unit cell in the upper part and the lower part is installed. Unit cells are stacked via the electrolyte chamber frame 18 to form a cell stack, and the cell stack is put in the electrolyte in an electrolyte tank 25. The power generation of a fuel cell is performed by reaction gasses supplied to the cell stack through reaction gas passages in the electrolyte chamber frame. The temperature of the electrolyte in the electrolyte chamber 2 is increased by heat generated by power generation, and the electrolyte forms rising flow and is discharged from the hole 18b. The temperature of the discharged electrolyte is decreased by heat radiation from the periphery of the electrolyte tank 25, and the electrolyte forms falling flow and is supplied from the hole 18c to the electrolyte chamber 2 to naturally circulate. Thereby, the fuel is made compact and steadily operated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a free electrolyte fuel cell that uses an alkaline aqueous solution or the like as an electrolyte.

[Conventional technology]

A free electrolyte fuel cell is a fuel cell 1 as shown in FIG.
, an electrolyte tank 5 , and a circulation pipe 10 for circulating the electrolyte between the electrolyte tank 5 and the electrolyte chamber 2 of the fuel cell 1 . The fuel cell 1 has an electrolyte chamber 2 in which an electrolyte such as an alkaline aqueous solution is circulated, and a fuel chamber 3 that supplies fuel gas to a fuel electrode (not shown), and an oxidizer that supplies oxidant gas to an oxidizer electrode (not shown). The chamber 4 is arranged and configured. Note that 12.13 is a supply pipe and a discharge pipe for supplying and discharging fuel gas to the fuel chamber 3, respectively, and 14.15 is a supply pipe and a discharge pipe for supplying and discharging oxidant gas to and from the oxidizer chamber 4, respectively. be.

The electrolyte tank 5 is equipped with an atmosphere release valve 11 and a liquid level gauge 6, and the electrolyte level accumulated in the electrolyte tank 5 is released to the atmosphere by opening the atmosphere release valve 11 to maintain a constant pressure at atmospheric pressure. In addition, a liquid level meter 6 is used as a monitoring means to monitor the level of the electrolytic solution and maintain the concentration of the electrolytic solution.

A circulation pipe 10 formed between the electrolyte tank 5 and the electrolyte chamber 2 of the fuel cell 1 is connected to a liquid supply pump 7 that connects the lower part of the electrolyte tank 5 and the inlet of the electrolyte chamber 2. The electrolyte supply pipe 8 and the outlet of the electrolyte chamber 2 and the electrolyte tank 5 provided
It consists of an electrolyte discharge pipe 18 connected to an upper space 17 above the electrolyte level. A bypass pipe 9 equipped with a regulating valve 9a is provided to connect the supply pipe 8 on the outlet side of the liquid sending pump 7 and the upper space 17 of the electrolyte tank 5, and the electrolyte can be adjusted by adjusting the regulating valve 9. The amount of electrolyte supplied to chamber 2 is adjusted.

With this configuration, the electrolyte is circulated through the circulation pipe 10 via the electrolyte chamber 2 by the liquid sending pump 7, the fuel gas is sent through the supply pipe 12 to the fuel chamber 3, and the oxidant gas is sent through the supply pipe 14. By supplying the oxidizer to the oxidizer chamber 4 through the oxidizer chamber 4, a cell reaction is caused and electricity is generated in the fuel cell.

[Problem that the invention seeks to solve]

If a free electrolyte fuel cell with an electrolyte circulation line as described above is operated for a long time, the seals at the joints of the circulation line, such as the connection between the electrolyte tank and the pipe, the pump and the pipe, etc., may deteriorate. As a result, the electrolyte leaks from this connection, and electrical components break down, causing problems in the operation of the fuel cell. In addition, since the electrolyte is delivered by a pump, an imbalance in the amount of delivered liquid may occur due to tax regulations such as abnormal rotation speed due to pump accidents, etc., and the reaction gas pressure due to the fuel gas and oxidant gas in the fuel cell and the electrolyte This disturbs the pressure equilibrium relationship with the liquid pressure. For this reason, the proper region of the three-phase interface where so-called battery reactions occur is disrupted, which adversely affects the catalyst layer of the electrode, resulting in a problem of shortening the life of the battery. Furthermore, since the circulation pipe is disposed outside, the fuel cell device becomes large and there is a problem of poor space efficiency.

In view of the above-mentioned points, an object of the present invention is to provide a free electrolyte fuel cell that is small in size, has a long life, and can operate stably over a long period of time.

[Means for solving problems]

In order to achieve the above object, according to the present invention, a liquid chamber frame is provided which surrounds the entire outer periphery of a unit cell and has holes in the upper and lower parts communicating with the electrolyte chamber of the unit cell. The cells were stacked together via a frame to form a cell stack, and this cell stack was placed in an electrolyte in an electrolyte tank.

[Effect]

A fuel cell generates electricity using a reactive gas that is supplied to the cell stack through a reactive gas passage in a liquid chamber frame.

At this time, the temperature of the electrolyte in the electrolyte chamber increases due to the heat generated during power generation, while the temperature of the electrolyte around the outer periphery of the cell stack decreases due to heat radiation from the outer periphery of the electrolyte tank.

As a result, the electrolyte in the electrolyte chamber flows upward due to its temperature and is discharged from the hole at the top of the chamber frame, and this discharged electrolyte decreases in temperature due to heat radiation from the outer circumference of the electrolyte tank and flows downward. Then, the electrolyte flows into the electrolyte chamber through the hole in the lower part of the electrolyte chamber frame, and in what is called natural circulation, the electrolyte in the electrolyte tank is circulated through the electrolyte chamber without the need for a pump.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings.

FIG. 4 is a system diagram of a free electrolyte fuel cell according to an embodiment of the present invention. In FIG. 4 and FIGS. 1 to 3, which will be described later, the same parts as those in the conventional example shown in FIG. What is different from the conventional example in FIG. 4 is that the fuel cell main body 1 is housed in an electrolyte tank 5, and an electrolyte such as an aqueous alkaline solution is filled until the upper part of the fuel cell 1 is completely buried. The entire outer circumference of each cell of the fuel cell 1 is surrounded by a frame-like liquid chamber frame, which will be described later, and the electrolyte flows into the electrolyte chamber 2 through holes provided in the upper and lower parts of the liquid chamber frame, respectively. In addition, in order to supply reaction gas to the fuel cell 1, a fuel gas supply pipe 32 and a discharge pipe 32a and an oxidizing gas supply pipe 33 and a discharge pipe 33a are connected to the side wall of the electrolyte tank 5, respectively. It penetrates through and connects to the fuel chamber 2 and oxidizer chamber 3 of the fuel cell.

Figure 1 is a partial sectional view of the free electrolyte fuel cell in the system diagram of Figure 4, Figure 2 is a sectional view taken along line A-A in Figure 1, and Figure 3 is a cross-sectional view of the single cell of the fuel cell in Figure 1. It is an exploded perspective view. 1st
Rectangular porous fuel electrode 3C as shown in Figures 3 and 3
The fuel electrode 3C and the oxidizer electrode 4C are arranged to face each other, and the electrolyte chamber 2 is defined by the fuel electrode 3C and the oxidizer electrode 4C. 19
is a gas-impermeable bipolar plate, with a fuel chamber 3 consisting of a plurality of concave grooves serving as a passage for supplying fuel gas to the fuel electrode 3C on one surface, and an oxidizer electrode 4C on the opposite surface. It has an oxidizing agent chamber 4 consisting of a plurality of concave grooves for supplying oxidizing gas. A frame-shaped fuel chamber gasket 21 faces the fuel chamber 3 of the bipolar plate 19.
The fuel electrode 3C faces the oxidizer chamber 4 via the frame-shaped oxidizer gasket 22 (see FIG. 3).
An oxidizer electrode 4C is arranged through the oxidizer electrode 4C. The unit cell 20 is composed of an electrolyte chamber 2, a fuel electrode 3C, an oxidizer electrode 4C, a fuel chamber 3, and an oxidizer chamber 4, which are arranged via a fuel chamber packing 21 and an oxidizer chamber packing 22, respectively. There is.

A wave-shaped liquid chamber spacer 2C is provided in the electrolyte chamber 2, and the liquid chamber spacer 2C is pressed against the bipolar plate 19 so that the fuel electrode 3C and the oxidizer electrode 4C are in close contact with each other.

A frame-shaped liquid chamber frame 18 is provided surrounding the entire periphery of the unit cell 20, and the liquid chamber frame 18 has a convex cross section, and the convex end 18a is inserted into the electrolyte chamber 2. And liquid chamber frame 1
The liquid chamber frame 1 is attached to the upper side and the lower side of the liquid chamber frame 1 with a collar 18a, respectively.
Holes 18b and 18c are provided that penetrate through the hole 8 and allow the electrolyte to flow therethrough. Note that a concave channel 18d is provided across the lower side of the liquid chamber frame 18, and the hole 18b is open to the channel 18d. Further, as shown in FIG. 2, one side of the collar 18a has a fuel gas supply manifold hole 31 as a passage.
d and an oxidant gas exhaust manifold hole 41f, and a fuel gas exhaust manifold hole 3 as a passage on the other side.
1f and an oxidant gas supply manifold hole 41d are provided, and these manifold holes are provided in the bipolar plate 19, the m41 chamber packing 21, and the oxidizing agent chamber packing 22, which constitute the ton battery, as shown in FIG. It communicates with the reactant gas flow path. That is, the bipolar plate 19 has a fuel supply manifold hole 3 having an inlet passage 3e opening on one side for supplying fuel gas to the fuel chamber 3.
d and an oxidizer discharge manifold hole 4f in which a discharge passage 4g for discharging oxidant gas from the oxidizer chamber 4 (not shown) opens, and a discharge passage 3g for discharging fuel gas from the fuel chamber 3 opens on the other side. A fuel gas discharge manifold hole 3f and an oxidant gas supply manifold hole 4d into which an artificial flow path 4e for supplying the oxidant to the oxidizer chamber 4 are provided. Further, the fuel chamber gasket 21 and the oxidizer chamber gasket 22 have holes 21d and 22d that communicate with the fuel gas supply manifold hole 3d, and an oxidizer gas discharge manifold hole 4, respectively.
A hole 21f22f that communicates with the fuel gas discharge manifold hole 3f, a hole not shown that communicates with the oxidant gas supply manifold hole 4d, and a hole not shown that communicates with the oxidizing gas supply manifold hole 4d are provided. And liquid chamber frame 18
A fuel gas supply manifold hole 31d, a discharge manifold hole 31f, and an oxidant gas supply manifold hole 4.
1d and exhaust manifold hole 41f are the fuel gas supply manifold hole 3d, fuel gas discharge manifold hole 3f, oxidant gas supply manifold hole 4d, and oxidant gas discharge manifold hole 4f of the bipolar plate 19, respectively. They communicate through holes 21d, 22d, etc.

The cell stack 22 is constructed by stacking unit cells 20 with liquid chamber frames 18 interposed therebetween, and a frame-shaped seal plate 23 made of Teflon is inserted between adjacent liquid chamber frames 18. Note that the electrolyte introduced into the seal plate 23 is in the fuel chamber 3.
This prevents the oxidizer from flowing into the oxidizer chamber 4, etc.

Current collector plates 15 are arranged on both end faces of the cell stack 220, and the liquid chamber frame 1 of the unit cell is in contact with the cell stack 22 side of the current collector plate 15.
The opposite side of the cell stack 22 is sandwiched by an outer edge plate 30 extending and protruding from the cell stack 22, and by an electrically insulating plate 16 on the opposite side of the cell stack 22. A clamping plate 12 is disposed in close contact with the electrical insulation terminals 1216 at both ends.

The electrolyte tank 25 has a bottom plate 26, and 4 holes surrounding the bottom plate 26.
Of the two side plates, two opposing side plates are used as the tightening plates 12. In addition, two different opposing side plates are made into side plates 28 having extendable bellows 27. Note that the bottom plate 26 is also provided with a bellows connected to the bellows 27.

The cell stack 22 is placed in the electrolyte tank 25 having such a structure with the flow path 18d of the liquid chamber frame 18 facing the bottom plate 26, and the cell stack is inserted through the clamping plate 12 through the electrical insulating plate 16. The fuel cell 1 is formed by tightening the recell stack with the four tightening studs 35. The tightening force at this time is adjusted by the disc spring 14.

At this time, the side plate 28 and bottom plate 26 of the electrolyte tank 25 contract at a portion of the tongue due to the tightening of the tightening stud 25.
This makes it easy to tighten the cell stack.

Also, the tightening plate 12. The fuel chamber 3 penetrates through the electrical insulating plate 16 etc.
A supply pipe 32 and a discharge pipe 32a are provided for supplying fuel gas to the oxidizer chamber 4, and a supply pipe 33 and a discharge pipe 33a for supplying oxidizer gas to the oxidizer chamber 4 are provided.

The electrolytic solution is filled into the electrolytic solution tank 25 to form a liquid level 17a, and the cell stack is housed below the liquid level 17a. Note that the current collector plate 15 and the outer edge plate 30 of the liquid chamber frame 18 that sandwich the current collector plate 15
The ends of the electrically insulating plate 16 protrude from the liquid surface 28, making it possible to extract electricity.

A lid 29 is provided on the top of the electrolyte tank 25, and a liquid level gauge 6 and an atmosphere release valve 11 having the same functions as in the prior art are provided.

With the above configuration, when fuel gas and oxidizing gas are supplied to the cell stack through the supply pipes 32 and 33, the fuel gas is supplied to the fuel gas supply manifold holes of the bipolar plate 19 and the liquid chamber frame 18, etc. The oxidizing agent is supplied to the fuel chamber 3 through a passage, and the oxidizing agent is supplied to the oxidizing agent chamber 4 through a passage such as an oxidizing gas supply manifold hole, where an electrochemical reaction occurs in the cell to generate electricity. At this time, since heat is generated with power generation, the temperature of the electrolyte in the electrolyte tank 25 increases. Therefore, the electrolyte in the electrolyte chamber 2 becomes an upward flow and flows out of the cell stack from the hole 18b as shown in FIG. The outflowing electrolyte is air-cooled through the outer wall of the electrolyte tank 25 to lower its temperature, and flows downward between the cell stack and the side wall of the electrolyte tank 25 as shown by the arrow, and flows into the passage of the liquid chamber frame 18. 18d, and the hole 18 of the liquid chamber frame 18.
It flows into the electrolyte chamber 2 from c. As described above, the temperature of the electrolytic solution that has flowed in increases and it rises again in the electrolytic solution chamber 2, so that so-called natural convection occurs, and the electrolytic solution in the electrolytic solution tank 25 is sent and circulated to the electrolytic solution chamber 2. At this time, heat generated by power generation is removed by natural circulation, and the temperature of the electrolyte in the electrolyte chamber 2 is maintained at the operating temperature.

Note that the fuel that does not contribute to the electrochemical reaction is the bipolar plate 19. The fuel gas discharge 72 from the liquid chamber frame 18, etc. is discharged to the outside from the discharge pipe 32a through passages such as two hold holes, and the oxidant gas is discharged to the outside from the discharge pipe 3a through passages such as oxidant gas discharge manifold holes. .

〔Effect of the invention〕

As is clear from the above explanation, a cell stack consisting of cells stacked together with a liquid chamber frame that surrounds the entire outer periphery of the cell is placed in the electrolyte in the electrolyte tank, and the cell stack is placed on the electrolyte in the electrolyte tank, and By causing natural convection of the electrolyte using the heat generated during power generation through the provided holes through which the electrolyte flows, the electrolyte in the electrolyte tank can be circulated through the electrolyte chamber of the fuel cell. This eliminates the need for pipes that circulate between the electrolyte tank and the electrolyte chamber as in the past, and also eliminates the pressure imbalance within the cell of reactant gas caused by the step-out of the pump attached to these. This eliminates leakage of the electrolyte, resulting in stable operation and long life of the fuel cell.

In addition, the power required for the pump is no longer required, which improves the efficiency of the fuel cell, and it also has the effect of being smaller.

[Brief explanation of the drawing]

Fig. 1 is a partial sectional view of a free electrolyte fuel cell according to an embodiment of the present invention, Fig. 2 is a sectional view taken along line AA in Fig. 1, and Fig. 3 is an exploded perspective view of the unit cell shown in Fig. 1. , FIG. 4 is a schematic diagram of the free electrolyte fuel cell shown in FIG. 1, and FIG. 5 is a structural circuit diagram of a conventional free electrolyte fuel cell. 1. Fuel cell Rinrin, 2. Electrolyte chamber, 3. Fuel chamber, 3C fuel electrode, 4. Oxidizer chamber 1.4C oxidizer electrode, 5, 25
Electrolyte tank, 15 Current collector plate, 16 Insulating plate, 18
Liquid chamber frame, 19 bipolar plate.

Claims (1)

[Claims] 1) In a free electrolyte fuel cell, which has a structure in which the electrolyte can freely circulate in the liquid chamber of the fuel cell defined between a pair of opposing porous electrodes, the upper part surrounds the entire outer periphery of the cell. A liquid chamber frame with a hole communicating with the electrolyte chamber of the battery is provided at the bottom of the cell, and a cell stack consisting of single cells is placed in the electrolyte tank via this liquid chamber frame. Characteristics of free electrolyte fuel cells.