JPH0423385B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field to which the Invention Pertains) The present invention is a cell stack in which unit batteries in which an electrolyte is supported on a porous matrix are stacked, and each unit battery has an electrolyte replenishment passage communicating with the matrix. The present invention relates to an electrolyte replenishment device for a matrix fuel cell, each of which is equipped with the following.

(Prior art and its problems) Matrix fuel cells have a structure in which the matrix constituting the unit cell supports an electrolyte, for example, in a phosphoric acid fuel cell, the matrix supports a liquid electrolyte of phosphoric acid, and the output of the fuel cell is In order to maintain the characteristics, it is desirable to be able to replenish electrolyte from outside not only at the beginning of operation but also during operation. In this case, it is required that electrolyte replenishment be carried out in the assembled state without disassembling the fuel cell.

Conventionally, the method of replenishing liquid electrolyte is to provide an electrolyte replenishment pipe that communicates with the matrix of each unit battery in a cell stack, connect this replenishment pipe to an electrolyte tank, and use gravity method or pump liquid supply method. There is a gravity method that sends electrolyte to the matrix of each unit cell and makes it supported. However, in the gravity method, the height becomes quite large in a cell stack with a large number of stacked unit cells, so when replenishing electrolyte, it is necessary to If a large hydraulic head is applied to the unit battery located at the top of the unit, the matrix, which has weak mechanical strength, may be damaged. On the other hand, in the pump liquid feeding system, the above-mentioned problems can be avoided by adjusting the pressure using a pressure regulating valve, etc., but the disadvantage is that the regulating valve, control circuit, etc. are required, resulting in a complicated structure. In addition, both the gravity method and the pump liquid delivery method have the disadvantage that a liquid junction occurs due to the electrolyte in the electrolyte replenishment path that commonly communicates with each unit battery, resulting in a decrease in the output of the unit battery and electrolytic corrosion of the constituent materials such as electrodes. be.

(Object of the Invention) In view of the above-mentioned drawbacks, the present invention provides a matrix fuel cell that can smoothly supply liquid electrolyte from the outside in a safe and simple manner to the matrix of unit cells constituting the cell stack of the matrix fuel cell. The purpose of the present invention is to provide an electrolyte replenishment device.

(Summary of the Invention) According to the present invention, this object is a cell stack in which unit cells in which an electrolyte is supported on a porous matrix are stacked, and a matrix type cell stack is provided in which electrolyte replenishment passages communicating with each of the matrices are respectively provided. In an electrolyte replenishment device for a fuel cell, a plurality of relay tanks are provided to which a plurality of replenishment pipes communicating with the replenishment passage are connected, and each of the relay tanks has an electrolyte supply pipe and a position lower than the opening of the replenishment pipe. an overflow pipe that opens at a position higher than the opening of the supply pipe and lower than the opening of the supply pipe, and is sequentially connected to the supply pipe of the lower relay tank; This is achieved by connecting a pressurizing means using gas to the supply pipe provided in the tank, or by connecting a depressurizing means to the electrolyte recovery port of the overflow pipe provided in the lowest relay tank. .

(Embodiments of the invention) Examples of the invention will be described below based on the drawings. FIG. 1 is a sectional view showing the structure of the electrolyte replenishment device of the present invention. FIGS. 2, 3, and 4 are cross-sectional views showing the main parts thereof, and from FIG. 1 onwards, the same parts as in FIG. 1 are given the same reference numerals. In FIG. 1, a unit cell 1 consists of a fuel electrode 1b and an air electrode 1c that sandwich a matrix 1a and have a groove for supplying a reaction gas, and a separate plate 1d is interposed between each unit cell. A cell stack 2 is constructed by stacking them. Further, in the unit battery 1, an electrolyte replenishment passage 3 having an electrolyte holding chamber 3a above the matrix 1a and communicating with the matrix 1a is formed, and one end thereof is open to the side surface of the unit battery.

A relay tank 4 is provided on the outside of the cell stack at a higher level than any of the matrices to which it supplies electrolyte. Relay tank 4
A supply pipe 5 having a supply port 5a is provided upward in the opening 4a of the upper plate, and the liquid electrolyte is supplied from the liquid electrolyte source to the relay tank 4 via the supply port 5a. Further, an overflow pipe 7 is provided above the side surface of the relay tank 4 and penetrates through an opening 4b, and communicates with a partition having an opening 7a near the bottom surface inside the relay tank. On the other hand, a supply pipe 6 made of an electrically insulating material is provided which penetrates the bottom surface of the relay tank 4 and connects with the supply passage 3, and the opening 6a in the relay tank 4 is connected to the opening 7a of the partition.
It opens upwards. In addition, since FIG. 1 shows a structure in which two matrices are supplied from the relay tank 4, two supply pipes 6 and 61 are shown as the supply pipes. Overflow pipe 7
is the opening 41 of the relay tank 41 installed in the lower stage.
It is connected to a supply pipe 51 penetrating at point a, and when the upper relay tank is replenished to a predetermined amount or more, the overflow electrolyte is supplied to the lower relay tank. Further, the structure of the relay tank 41 is the same as that of the relay tank 4, and the opening 41 on the side of the relay tank 41
The overflow pipe 71 passing through b is further connected to a lower relay tank, and the overflow pipe of the lowermost relay tank connected in this way is connected to an electrolyte recovery tank (not shown).

In the above-described structure, the electrolyte is supplied from the supply source via the supply pipe 5 to the relay tank 4 through the opening 4a while filling the supply pipe 5, and flows into the relay tank 4. At this time, the gas in the relay tank 4 is exhausted via the overflow pipe 7, the supply pipe 6, and the electrolyte supply passage 3. In this way, the electrolyte 8
is dripped as droplets 8a, and when the electrolyte 8 reaches the level of the opening 6a of the tube 6, the liquid electrolyte 8 is replenished from the opening 6a to the electrolyte replenishment passage 3 via the tube 6, from where it is fed into the matrix. It is impregnated and replenished. When the matrix is sufficiently replenished with electrolyte in this state, the interiors of the replenishment passage 3 and the replenishment pipe 6 are filled with electrolyte, and the electrolyte is supplied to the opening 6a of the replenishment pipe 6.
Therefore, it becomes impossible to flow into the supply pipe 6.

In this state, the liquid level of the electrolyte 8 rises within the relay tank 4, as shown in FIG. At this time, the supply pipe 5 is filled with the liquid electrolyte 8, the opening 4a of the relay tank 4 is closed with the electrolyte 8, and the pressure in the air chamber 4d above the liquid level increases due to the rise in the liquid level.
The liquid level in the partition communicating with the overflow pipe rises in proportion to the rise in pressure in the air chamber 4d, and reaches the liquid level B covering the lower surface of the top of the overflow pipe 7. That is, the difference between the liquid level A and the liquid level B in the relay tank 4 becomes a value commensurate with the pressure increase in the air chamber 4d. When the electrolyte 8 is further replenished dropwise, the electrolyte 8 is supplied to the overflow tube 7 while maintaining this pressure balance.
The liquid then flows into the relay tank 41 (see FIG. 1) installed in the lower stage.

Returning to FIG. 1, the electrolyte is replenished into the matrix in the relay tank 41 according to the same principle. When the electrolyte is replenished to each unit battery, the overflow pipe 71
It flows into a recovery tank (not shown) via the tank, and replenishment is completed. At this point, the supply of electrolyte from the supply pipe 5 is stopped, and the supply pipe 5 is pressurized with gas, or the recovery port 71 of the overflow pipe 71 is
When the pressure is reduced from b, a pressure difference occurs between the supply port 5a and the recovery port 71b, and the electrolyte remaining in the relay tank 4 overflows through the relay tank 4 from the opening 7a to the opening 4b based on the principle of a communicating pipe. It flows through the pipe 7 and is discharged into the lower relay tank 41 via the open end 41a. The liquid surface A in contact with the air chamber 4d shown in FIG. 3 is the opening 7 of the partition.
When the temperature drops to a, the discharge of the liquid electrolyte is completed, and the gas begins to be discharged to the relay tank 41 via the above-mentioned path. The electrolyte is also discharged from the relay tank 41 according to the same principle as described above, and when hollow chambers in which the electrolyte flow is discontinuous are formed in all the relay tanks, the electrolyte that has been discharged from the recovery port 71a is no longer discharged. In this state, as shown in FIG. 4, the electrolyte level in the relay tank is at the same level, and the level A is slightly lower than the opening 7a.

In the above replenishment work, at the time of replenishing electrolyte, the pressure of the electrolyte applied to each unit battery is as shown in Figure 1, and the pressure of the electrolyte applied to each unit battery is as shown in Figure 1. The difference in height between the pipe and the top of the tube is _H1 , which results in a positional hydraulic head, and by setting the value of _H1 appropriately, there is no risk of excessive hydraulic pressure being applied to the unit cells located at the bottom of the cell stack, unlike in the conventional system.

Furthermore, as shown in FIG. 4, after the replenishment is completed, the opening 6a of the replenishment pipe 6 made of electrically insulating material is located above the opening 7a of the partition, so there is a difference in height between the opening 6a and the liquid level A. becomes the pipe length l. Similarly, the supply pipe 61 that supplies other unit batteries from the relay tank 4 protrudes from the liquid level in the relay tank by a pipe length l, so the unit batteries connected to the supply pipes 6 and 61 have an electrically insulated length of 2 l. is ensured, the unit cells do not communicate with each other through the electrolyte, and leakage current flowing between the unit cells through the electrolyte can be prevented.

Furthermore, in this embodiment, supply pipes are connected from a plurality of unit batteries to the same relay tank 4, but even in this case, by setting the inner diameter and length of the supply pipe to appropriate values, it is possible to It is possible to reduce the leakage current value below the allowable value, and it is possible to replenish the electrolyte even while the fuel cell is in operation.

FIG. 5 shows a different embodiment of the invention,
In the relay tank, the overflow pipe 7 is extended into the relay tank so that the partition communicating with the overflow pipe has an opening 7a, and its function is the same as that described above.

(Effects of the Invention) As is clear from the above description, according to the present invention, when replenishing electrolyte to a matrix of unit batteries in a cell stack formed by stacking a large number of unit batteries, a relay for replenishment is provided for each plurality of unit batteries. Several tanks are provided, and a supply pipe is provided to replenish the electrolyte to this relay tank, and an overflow pipe is provided to overflow the electrolyte in excess of a predetermined amount supplied to the relay tank.
Connect this overflow pipe to the supply pipe of the lower relay tank, and connect the supply pipe from the relay tank to the supply passage inside the unit battery that leads to the matrix.
By replenishing electrolyte from the supply pipe of the top-tier relay tank, the replenishment electrolyte built into each stage of the relay tank is separated from the relay tanks of other stages and replenished into the matrix, and the replenishment electrolyte liquid is The pressure is the positional head due to the difference in height between the replenished matrix and the top of the overflow pipe. Therefore, by providing a relay tank so that the water head is below a permissible value, it is possible to prevent the matrix, which is weak in mechanical strength, from being damaged.

In addition, by opening the overflow pipe in the relay tank at a position lower than the opening of the replenishment pipe and connecting it to the lower relay tank via a position higher than the opening of this replenishment pipe, the overflow pipe can be opened after replenishment is completed. When draining more electrolyte, the electrolyte in the relay tank is drained to the level of the opening of the overflow tube, and the supply tube protrudes above the remaining electrolyte level. For this reason, the electrical insulation between unit batteries that are supplied from the same relay tank has a length that is twice the length of the supply pipe that protrudes from the liquid surface, and leakage current due to liquid junction between unit batteries is reduced. This has the effect of preventing a decrease in output due to this leakage current and preventing electrolytic corrosion of constituent materials such as electrodes.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing an embodiment of the present invention, Fig. 2 is a cross-sectional view showing a state in which the relay tank in Fig. 1 is replenished with electrolyte, and Fig. 3 is a cross-sectional view showing the electrolyte in Fig. 2 overflowing from the relay tank. FIG. 4 is a sectional view showing a state in which the electrolyte in FIG. 3 is recovered, and FIG. 5 is a sectional view showing a different embodiment of the relay tank. 1: unit battery, 1a: matrix, 3: supply passage, 4: relay tank, 5: supply pipe, 6: supply pipe, 7: overflow pipe.

Claims (1)

[Claims] 1. An electrolyte replenishment device for a matrix fuel cell, which is formed as a cell stack in which unit cells each having an electrolyte supported on a porous matrix are stacked, and each unit cell is provided with an electrolyte replenishment passage communicating with each of the matrices. , a plurality of relay tanks are provided to which a plurality of supply pipes communicating with the supply passage are connected, and each relay tank has an electrolyte supply pipe and an opening at a position lower than the opening of the supply pipe, and the supply pipe is connected to a plurality of relay tanks. an overflow pipe that extends to a position higher than the opening of the pipe and lower than the opening of the supply pipe and connected in sequence to the supply pipe of the lower relay tank; An electrolyte supply device for a matrix fuel cell, characterized in that a gas pressurizing means is connected to the supply pipe, or a depressurizing means is connected to the electrolyte recovery port of an overflow pipe provided in a lowermost relay tank. .