JPH0935727A - Electrolyte replenishing device of fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably replenish an electrolyte corresponding to the electrolyte scattering amount to each unit cell by installing a liquid leading part whose both ends are connected to a replenishing tank and a reservoir plate with rib, and which leads the electrolyte to the reservoir plate with rib. SOLUTION: Height of a liquid leading part 21 exposed to the liquid surface of an electrolyte reservoir 13 is lowered than suction height by capillary action as much as possible to smoothly transfer phosphoric acid. By lowering water head difference to a connection part 24 than the suction height by capillary action, cut of continued liquid flow is not generated, phosphoric acid holding factor depending on capillary action is held, and phosphoric acid is stably supplied to a reservoir plate with rib 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolyte replenishing device for replenishing the electrolyte in the matrix, which decreases during operation, from the outside in a matrix type fuel cell comprising a laminate of unit cells in which an electrolyte is held in a porous matrix. Regarding

[0002]

2. Description of the Related Art A matrix type fuel cell has a structure in which an electrolyte such as phosphoric acid is held in a matrix which constitutes a unit cell, and is provided with an electrolyte replenishing device for constantly replenishing an electrolyte which gradually decreases during power generation operation from the outside. Therefore, a matrix fuel cell configured to prevent a decrease in output power due to lack of electrolyte is known, and in this case, electrolyte replenishment can be continuously performed from the outside without disassembling the fuel cell. Is required.

FIG. 4 is a schematic cross-sectional view showing a conventional electrolyte replenishing device for a matrix type fuel cell. A matrix type fuel cell 1 comprises a matrix type unit cell 2 having a plurality of layers and a gas impermeable separator. It is configured as a laminated body (cell stack) with the plate 6. The unit cell 2 is formed by stacking a fuel electrode 4 and an air electrode 5 with a matrix 3 impregnated with, for example, a phosphoric acid solution 9 serving as an electrolyte in a porous insulating material, and is arranged in a direction orthogonal to each other. The reaction gas passages 4A and 5A are formed, and the fuel gas is supplied to the 4A side and the reaction air is supplied to the 5A side, whereby power generation based on the electrochemical electrode reaction is performed between the pair of electrodes 4 and 5.

The electrode reaction of a fuel cell is an exothermic reaction in which hydrogen and oxygen react with each other to generate electrons and water. In the case of a phosphoric acid fuel cell, the operation is carried out while maintaining the temperature at about 190 ° C. The generated water generated at that time becomes high-temperature steam, permeates the electrode, and is discharged to the outside through the reaction gas passage. Also, when water vapor permeates the electrodes, the matrix 3
A slight amount of the electrolyte 9 therein is dissolved in water vapor and scattered into the reaction gas, so that the amount of the electrolyte in the matrix 3 gradually decreases as the operation time elapses. Therefore, an electrolyte replenishing device 10 is added to the matrix fuel cell 1 to replenish the electrolyte 9 deficient in the matrix from the outside.

That is, an electrolyte replenishment passage 7 communicating with the matrix 3 is formed in both electrodes of each unit cell 2 of the matrix fuel cell 1 or in either one of the electrodes (fuel electrode 4 in the figure). An electrolyte replenishing device 10 including an electrolyte replenishing pipe 11 having a discharge end 11B communicating with the replenishing passage 7 and an electrolyte replenishing tank 12 connected to a suction end 11A side of the replenishing pipe 11 is provided in a matrix. Fuel cells configured to replenish the deficient electrolyte are known. In addition, in the replenishment tank 12, the electrolyte reservoirs 13A at different height positions corresponding to the replenishment pipe 11,
13B and the like are provided, and the electrolyte 9 supplied from the upper portion of the electrolyte tank 12 fills each electrolyte reservoir in the order of 13A and 13B and sequentially overflows, thereby increasing the liquid level of each electrolyte reservoir, A level difference of the height H is held between the height and the height of the matrix 3 of the unit cells communicating with this via the supply pipe.

Therefore, the supply pipe is bent in a siphon shape, and the electrolyte head 1 is utilized by utilizing the water head difference corresponding to the height difference H.
There is known a head difference type electrolyte replenishing device which is configured to transfer the electrolyte 9 in 3 to the replenishment passage 7 side. Also,
By filling the fiber 15 having hydrophilicity to the electrolyte over the entire length of the supply pipe 11 and transferring the electrolyte by utilizing the capillary phenomenon, the electrolyte 9 runs out of liquid in the supply pipe. There is also known an electrolyte replenishing device that prevents the above (Japanese Patent Laid-Open No. 61-107667).

Further, a hydrophilic fiber filler 15 as a liquid running-out preventing means in the replenishing pipe 11 is configured to be filled in the replenishing pipe, leaving a portion of the electrolyte reservoir 13 on the side of the replenishing pipe discharging lower than the liquid surface. At the rising portion of the siphon-shaped supply pipe, the electrolyte is transferred into the supply pipe 11 without causing liquid drainage due to the sucking action by the capillary action of the filled hydrophilic fibrous filler 15, and the fibrous filler is filled. There is also proposed an electrolyte replenishing device that transfers the electrolyte into the replenishment passage 7 with low resistance due to the difference in the water heads of the electrolyte that fills this falling portion near the discharge end 11B of the replenishment pipe (Japanese Patent Application Laid-Open No. Hei 10 (1999)). 6-36787).

[0008]

By filling the inside of the replenishment pipe with hydrophilic fibers, the water head difference method has the advantage that the liquid supply can be prevented and electrolyte replenishment can be stabilized. However, there is a problem in that the number of man-hours required to fill the entire length or a part of the multiple supply pipes communicating with each unit cell with the hydrophilic fiber increases, which hinders the cost reduction of the apparatus. Further, the amount of phosphoric acid as an electrolyte scattered from each unit cell 2 is affected by the temperature difference between the unit cells and the difference in the operating conditions, and it is extremely difficult to accurately grasp the amount. Adjustment is also impossible. For this reason, phosphoric acid is supplied to the unit cell in excess of the scattered amount, and the excess phosphoric acid may overflow into the reaction gas passage and hinder the normal flow of the reaction gas. There is also a problem that performance is degraded.

An object of the present invention is to provide a fuel cell provided with an electrolyte replenishing device having a simple structure capable of stably replenishing each unit cell with an electrolyte corresponding to the amount of scattered electrolyte.

[0010]

In order to achieve the above-mentioned object, the invention according to claim 1 is a unit cell composed of a matrix holding an electrolyte, a fuel electrode sandwiching the matrix and an air electrode. An electrolyte replenishing device for replenishing an electrolyte, which is lacking in the matrix during operation, from an electrolyte replenishing tank provided outside, which is provided in a fuel cell in which a plurality of layers are laminated with a separate plate interposed between cells, and each unit cell is A ribbed reservoir plate made of a porous carbon material laminated between a separate plate and holding an electrolyte, and a porous material having a capillary force similar to that of the ribbed reservoir plate, both ends of which are the replenishment tank. And a liquid guiding part which is connected to the ribbed reservoir plate and guides the electrolyte to the ribbed reservoir plate side.

According to a second aspect of the present invention, in the electrolyte replenishing device according to the first aspect, the ribbed reservoir plate and the liquid-conducting portion may both be made of a porous carbon material of the same material and manufacturing method. . Further, in the invention according to claim 3, in the electrolyte replenishing device for the fuel cell according to claim 1, it is preferable that at least a part of the liquid conducting portion has an insulating coating having moisture resistance.

Further, the invention according to claim 4 is, in the electrolyte replenishing device for a fuel cell according to claim 1, wherein the end of the liquid guiding part is inserted into the groove of the ribbed reservoir plate, and the liquid guiding property is provided. It is preferable to form the connecting portion.

[0013]

According to the first aspect of the invention, an electrolyte replenishing device for replenishing the matrix of each unit cell with an electrolyte from an electrolyte replenishing tank provided outside, is provided.
Porous carbon composed of a ribbed reservoir plate laminated between each unit cell and a separate plate and a liquid conducting part connecting the two, and the ribbed reservoir plate and the liquid conducting part have a similar capillary force Due to the material, the electrolyte sucked out from the electrolyte replenishment tank by the capillary force of the electrolyte is ribbed in the electrolyte retention rate (ratio of the weight of the electrolyte to the total weight of the electrolyte) of the electrolyte. Transferred toward the ribbed reservoir plate to equilibrate to a value approximately equal to the electrolyte retention of the reservoir plate. Therefore, the ribbed reservoir plate retains the electrolyte at an electrolyte retention rate determined by its capillary force, and during operation, the electrolyte lacking in the matrix of each unit cell permeates the hydrophilic portion formed on the electrode to form the matrix. Replenishment, and the replenishment amount is replenished from the replenishment tank via the liquid conducting section. In addition, when excessive electrolyte is generated in the ribbed reservoir plate due to changes in the fuel cell temperature, etc., an equilibrium action of sending excess electrolyte back to the replenishment tank via the liquid transfer part is also created, and therefore excessive ribbed reservoir plate is used. It is also possible to eliminate the inconvenience that the resulting electrolyte overflows into the reaction gas passage and hinders the normal flow of the reaction gas.

According to the second aspect of the present invention, the ribbed reservoir plate and the liquid-conducting portion are made of a porous carbon material of the same material and manufacturing method, so that the ribbed reservoir plate has the same capillary force. And the liquid conducting part can be easily obtained. Further, in the invention according to claim 3, since the liquid guiding part has an insulating coating having moisture resistance on at least a part thereof, the liquid guiding part can prevent moisture absorption of the electrolyte in the liquid guiding part and is also a conductor. A short-circuit accident caused by the mutual contact of the two is avoided. Furthermore, since the insulating coating prevents contact between the liquid-conducting portion and the outside air, the invasion of the outside air into the liquid-conducting portion is blocked, and the effect of adjusting the amount of electrolyte replenished to the ribbed reservoir plate by using the head difference is also provided. can get.

Further, according to the invention of claim 4, since the end portion of the liquid guiding portion is inserted into the groove of the ribbed reservoir plate to form the liquid conducting connecting portion, the connecting portion can be attached and detached. It is also possible to check whether or not the electrolyte retention rate of the ribbed reservoir plate is normal by removing the liquid conducting portion and weighing it to obtain the electrolyte retention rate.

[0016]

EXAMPLES The present invention will be described below based on examples. Since the members having the same reference numerals as those of the conventional example have the same functions as those of the conventional example, the description thereof will be omitted. FIG. 1 is a schematic sectional view showing an embodiment of an electrolyte replenishing device for a fuel cell according to the present invention. In the figure, an electrolyte replenishing device for replenishing the matrix 3 of each unit cell 2 with an electrolyte from a replenishment tank 12 of an electrolyte 9 provided outside the fuel cell is shown as an electrolyte replenishment tank 12, each unit cell 2 of a fuel cell, and a separate cell. The reservoir plate 23 with ribs laminated between the plate 6 and the liquid guide portion 21 connecting the reservoir plate 23 with ribs and the replenishment tank 12 are connected to each other.
One end of the replenishing tank 1 forms a connecting portion 24 which is in close contact with the ribbed reservoir plate for a certain length.
The electrolyte replenishing device 20 for the fuel cell is formed by inserting the second electrolyte reservoir 13 into the liquid electrolyte 9 from above the liquid surface.

Here, the ribbed reservoir plate 23 is made of a porous carbon material having a reaction gas passage 4A or 5A on the side in contact with the fuel electrode 4 or the air electrode 5 of the unit cell 2, and the liquid introducing portion 21 is also formed. Since the ribbed reservoir plate 23 is made of the same porous carbon material manufactured under the same manufacturing conditions as those of the ribbed reservoir plate 23, the ribbed reservoir plate 23 and the liquid transfer part 21 having substantially the same capillary force against phosphoric acid 9 can be easily formed. Is formed.

FIG. 2 is a characteristic diagram showing a comparison of the capillary forces of the ribbed reservoir plate member and the liquid guiding member in one embodiment of the present invention. One end of the test piece cut out from the base material in a strip shape is phosphorus. The test piece was vertically inserted into the acid solution at a constant depth, and the test piece was weighed at a constant standing time in a constant atmosphere temperature, and the phosphoric acid retention rate was determined from the weight change. In the figure, after the phosphoric acid solution permeates the part that was first inserted into the phosphoric acid solution and the phosphoric acid retention rate rises rapidly in both the reservoir plate and the liquid guiding member, it is exposed to the air due to capillary force over time. The phosphoric acid solution is sucked up by the above-mentioned portion, the phosphoric acid retention rate gradually increases, and both show a saturation characteristic that they reach a substantially constant saturation value at a certain point.

By the way, the capillary force of a thin tube is expressed by the suction height h which raises the liquid level in the capillary from the external liquid level when the end of the capillary is vertically inserted into the liquid. It is known that the capillary force h represented is proportional to the contact angle of the same liquid with the liquid and inversely proportional to the pore diameter of the porous body. Fig. 2 shows this suction height h by replacing it with the phosphoric acid retention rate. Since both curves are close,
It was demonstrated that the reservoir plate material and the liquid guiding member in the examples have substantially equal capillary forces. Further, from the above-described principle, the height of the liquid conducting portion 21 exposed on the liquid surface of the electrolyte reservoir 13 in FIG. 1 is kept as low as possible from the suction height h due to the capillary force, so that the phosphoric acid can be transferred smoothly. Be converted. Further, when the water head difference H with the connecting portion 24 is made larger than the suction height h due to the capillary force, the liquid conducting portion 2
1 causes the liquid to run out by sucking the outside air from the outer peripheral surface thereof. Therefore, by setting the water head difference H to be equal to or less than the suction height h due to the capillary force, the liquid will not run out.
Phosphoric acid is stably supplied to the ribbed reservoir plate 23 while maintaining the phosphoric acid retention rate determined by the capillary force.

In this embodiment, the ribbed reservoir plate 23
Since the liquid guiding part 21 is made of a porous carbon material having a similar capillary force, the liquid guiding part sucks the electrolyte from the electrolyte replenishing tank by the capillary force, and the electrolyte holding ratio of the liquid guiding part is ribbed. Since it is transferred toward the reservoir plate with ribs so as to equilibrate to a value that is almost equal to the electrolyte retention rate of the reservoir plate, unlike the conventional electrolyte replenishing device that uses the head difference, the liquid run-out at the liquid transfer part and excessive supply It is possible to stably supply the phosphoric acid corresponding to the scattered amount of phosphoric acid in each unit cell and to stably maintain the power generation performance of the fuel cell, without causing troubles such as a reaction gas flow failure due to. In addition, the liquid-conducting part has a simpler structure than the conventional refill tube filled with hydrophilic fibers, and does not require a labor-intensive process for filling the hydrophilic fibers, thus reducing the manufacturing cost. The effect of promoting is obtained.

Further, if the liquid introducing portion 21 is constructed so as to be provided with an insulating coating having moisture resistance, the replenishing tank 1 outside the fuel cell 1
In the vicinity of 2, the absorption of phosphoric acid caused by the contact of the liquid conducting portion with the atmosphere can be prevented, a high concentration of phosphoric acid can be supplied to the unit cell 2, and the liquid conducting portion 21 which is also a conductor comes into contact with each other. There is also an advantage that a short circuit accident can be avoided. In addition, since the insulating coating prevents the invasion of air or the like into the liquid-conducting portion, it becomes possible to replenish the electrolyte using the head difference H, and it is also possible to control the replenishment amount of the electrolyte by adjusting the head difference. Therefore, there is an advantage that the supply amount of the electrolyte can be controlled according to the difference in the scattering amount of phosphoric acid generated due to the difference in temperature between the unit cells and the difference in operating conditions.

FIG. 3 is an enlarged view of the essential parts showing a different embodiment of the electrolyte replenishing device for a fuel cell according to the present invention. In the figure, the difference between this embodiment and the embodiment shown in FIG.
Reaction gas passage 4A or 5A of the ribbed reservoir plate 23
The end of the liquid-conducting portion 21 is inserted into a part of the above to form a connecting portion having a liquid-conducting property. With such a configuration, the liquid guiding portion 21 can be attached and detached, and the liquid holding portion 21 is detached and weighed, and the electrolyte holding ratio thereof is obtained, whereby the electrolyte holding ratio of the ribbed reservoir plate 23 is increased. Since it can be checked whether it is normal or not, there is an advantage that the function of the electrolyte replenishing device which could not be conventionally checked without disassembling the fuel cell can be easily checked without disassembling the fuel cell.

In the above-mentioned embodiment, the case where the reservoir plate with ribs is provided on both the fuel electrode and the air electrode has been described as an example, but it is provided on only one of the electrode sides to simplify the structure of the apparatus. May be. Also, the case where a porous carbon material manufactured under the same material and manufacturing conditions is used for the ribbed reservoir plate and the liquid conducting part has been described as an example. However, if the mutual capillary forces are almost equal, the material is carbon fiber or carbon powder. Etc., and the liquid conducting portion may be a porous body made of a different material and having a manufacturing method.

[0024]

As described above, according to the present invention, the electrolyte replenishing device for replenishing the electrolyte from the replenishing tank outside the fuel cell to each unit cell uses the ribbed reservoir plate and the liquid conducting portion having substantially the same capillary force. Configured as as a result,
Since the ribbed reservoir plate and the liquid conducting section maintain an equilibrium state of electrolyte retention rate that is almost equal to each other and replenish the electrolyte shortage generated in the matrix due to the scattering of the electrolyte, there is a problem with the conventional electrolyte replenishment device of the water head difference method. It is possible to provide a fuel cell provided with an electrolyte replenishing device capable of stably supplying a shortage of the electrolyte without causing the flow of the reaction gas due to the exhaustion of the electrolyte and the excessive replenishment of the electrolyte. In addition, since the structure of the liquid guiding portion is simple and there is no need to perform processing such as filling the supply pipe with hydrophilic fibers, a fuel cell equipped with an electrolyte replenishing device that can stably supply a shortage of electrolyte is economically provided. The advantage that can be advantageously provided is obtained.

If the liquid-conducting portion is provided with a moisture-resistant insulating coating, the effect of preventing moisture absorption of the electrolyte and the effect of preventing short-circuiting between the liquid-conducting portions can be obtained, and the insulating coating has a function of shutting off the outside air. The effect of improving the function of the electrolyte replenishing device can be obtained such that the amount of electrolyte supply can be controlled by utilizing the difference. Furthermore, if the liquid guiding part is inserted into the reaction gas supply groove of the ribbed reservoir plate to form the connecting part, the liquid guiding part can be attached / detached, and the electrolyte of the ribbed reservoir plate can be removed by weighing the removed liquid guiding part. There is also an advantage that an electrolyte replenishing device having a check function for determining the retention rate can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing an embodiment of an electrolyte replenishing device for a fuel cell according to the present invention.

FIG. 2 is a characteristic diagram showing a comparison between the capillary force of a reservoir plate member with ribs and the liquid guiding member in one embodiment of the present invention.

FIG. 3 is an enlarged view of a main part showing a different embodiment of the electrolyte replenishing device for a fuel cell according to the present invention.

FIG. 4 is a sectional view schematically showing a conventional electrolyte replenishing device in a matrix fuel cell.

[Explanation of symbols]

 1 Fuel Cell 2 Unit Cell 3 Matrix 4 Fuel Electrode 5 Air Electrode 6 Separate Plate 7 Electrolyte Supply Channel 9 Electrolyte 10 Electrolyte Supply Device 11 Supply Pipe 12 Supply Tank 13 Electrolyte Reservoir 15 Hydrophilic Fiber (Filler) 20 Electrolyte Supply Device 21 Liquid transfer part 23 Reservoir plate with ribs 24 Connection part

Claims (4)

[Claims] 1. A unit cell comprising a matrix holding an electrolyte, a fuel electrode sandwiching the matrix, and an air electrode is provided in a fuel cell in which a plurality of layers are stacked with a separate plate interposed between the unit cells, and the operation is performed. In an electrolyte replenishing device for replenishing the electrolyte deficient in the matrix from an electrolyte replenishing tank provided outside, with ribs made of a porous carbon material laminated between the unit cells and the separate plate to hold the electrolyte. It consists of a reservoir plate and a porous material that has the same capillary force as this ribbed reservoir plate.
An electrolyte replenishing device for a fuel cell, characterized in that both ends thereof are connected to the replenishment tank and the ribbed reservoir plate, and a liquid conducting part for guiding the electrolyte to the ribbed reservoir plate side. 2. The electrolyte replenishing device for a fuel cell according to claim 1, wherein the ribbed reservoir plate and the liquid-conducting portion are both made of the same material and made of a porous carbon material. Supply device. 3. The electrolyte replenishing device for a fuel cell according to claim 1, wherein the liquid conducting portion has an insulating coating having moisture resistance on at least a part thereof. 4. The electrolyte replenishing device for a fuel cell according to claim 1, wherein an end portion of the liquid conducting portion is inserted into a groove of the ribbed reservoir plate to form a liquid conducting connecting portion. And a fuel cell electrolyte replenishing device.