JPH02278667A - How to repair a fuel cell stack - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides a method for repairing the entire fuel cell stack when a damaged unit cell occurs in a fuel cell stack consisting of a stack of unit cells mainly using cynic acid as an electrolyte. It relates to a method of restoring the product to a state capable of generating power without disassembling it.

[Conventional technology]

FIG. 6 is a schematic side view showing the general configuration of a fuel cell stack with one unit cell enlarged in the stacking direction;
This example shows a case where a unit cell called a grooved electrode method is used. The figure shows a fuel cell stack (hereinafter referred to as a stack) 10 in which unit cells 1 of the same number of membranes are laminated with senolate plates 7, 7 made of gas-impermeable carbon plates interposed on the laminated surface. unit cell 1
consists of a laminate including a matrix 2 holding a phosphoric acid solution as an electrolyte, an oxidizer electrode 3 arranged on both sides of the matrix 2, and a fuel electrode, and the picture electrodes 6 and 4 are made of carbon plates having gas permeability. The electrode catalyst layer 6A or 4A is supported on the surface opposite to the grooves of the grooved electrode base material 5, and the electrode catalyst layer is VJ! on the surface of the matrix 2. The grooves of the pair of grooved electrode base materials 5 are formed in directions perpendicular to each other and are in close contact with the separate plates, and the oxidizer passage 6A and the fuel passage 6F are arranged in directions perpendicular to each other. Can be formed. The stack of unit cells 1 thus configured is sandwiched between a pair of suppressing plates 8, 8 connected by connecting bolts (not shown) and a predetermined tightening load is applied to form a system stack 10. Hydrogen-rich fuel gas is supplied to the fuel passage 6F, and oxidant gas such as gas is supplied to the oxidizer passage 6A through a fuel gas manifold and an oxidizer manifold (not shown) that are airtightly attached to the side surface of the stack 10. A power generation reaction is performed by the fuel gas and the oxidant gas passing through the electrode base material 5 and being supplied to the electrode catalyst layer 4A or 3A.

In the power generation reaction of this type of fuel cell, the gas pressures of the oxidant gas and fuel gas supplied to the reaction gas passages 6A and 6F are maintained in pressure ranges close to each other and supplied to the electrode catalyst layer dripped with electrolyte. It is done by
In addition, in order to suppress the polarization phenomenon and efficiently extract the generated voltage and current of the unit cell, each unit cell is maintained at a predetermined operating temperature, for example, 190°C, and the electrode base material 5
Efforts are being made to maintain uniform and good gas permeability.

However, if an abnormality occurs in the reaction gas pressure and an excessive differential pressure is applied to the unit cell, or if an imbalance in operating conditions occurs such as an excessive flow rate difference or imbalance in gas supply amount between multiple unit cells. In some cases, the power generation reaction of a part of the unit cell has deteriorated, and the power generation voltage of a healthy unit cell is applied to the unit cell whose characteristics have deteriorated, and in severe cases, the unit cell whose characteristics have deteriorated has a reverse potential and the unit cell has deteriorated. A situation occurs in which damage to the material is accelerated.

When a damaged unit cell occurs, in the conventional technology, stack 1
0 and replace the damaged unit cell with a new unit cell, or connect a short circuit conductor to the damaged unit cell without disassembling the stack to form a bypass circuit for the generated current of the healthy unit cell. Usually, countermeasures are taken.

[Problem to be solved by the invention]

Among the conventional methods, the method of replacing damaged unit cells requires a lot of time and labor to disassemble and reassemble the stack, which has an extremely large impact on power generation operation and increases repair costs. There is a drawback. On the other hand, in the method of forming a bypass circuit, it is necessary to use a noble metal such as platinum to form a short-circuit conductor that can withstand highly corrosive phosphoric acid and bypass large currents, which causes economic disadvantage and It is necessary to stop the power generation reaction itself by blocking the reactant gas passage of the damaged unit cell, which requires a lot of time, and the problem arises that the reactant gas cannot be completely shut off.

An object of the present invention is to provide a simple and inexpensive method for repairing damaged unit cells, such as stopping power generation and forming current paths, without disassembling the stack.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, there is provided a method for repairing a fuel cell stack including a stacked body of a plurality of unit cells and including a damaged unit cell, the fuel gas passage and the oxidizer passage of the damaged unit cell. A low melting point metal is completely injected into the cell and solidified to provide mechanical reinforcement, and then a conductive spacing plate made of a gas-impermeable carbon plate having a thickness corresponding to the reinforced unit cell is inserted to form the reinforced unit. A method for repairing a fuel cell stack consisting of a stack of several unit cells and including a damaged unit cell, in which the cell is pushed out to the side and replaced with the conductive spacer plate, A gap is formed by cutting off the peripheral edge portion, and then a conductive spacing plate made of a gas-impermeable carbon plate having a thickness corresponding to the cut unit cell is pushed into the gap to surround the damaged unit cell. A conductive path that also serves as a seal is formed.

[Effect]

In the above method, after mechanically reinforcing the low melting point alloy material by injecting and solidifying it into the reaction gas passage of the damaged unit cell, the damaged unit cell reinforced with a gas-impermeable conductive spacer is pushed out laterally. By replacing the stack with a conductive spacer plate, the pressure plate can be used to completely eliminate the clamping load on the laminated surface, without having to disassemble the stack. It is possible to replace the conductive spacer plate with a conductive spacer plate, and the conductive spacer plate can form a conductive path with high corrosion resistance.

Additionally, a gap surrounding the failed unit cell is formed by cutting off the peripheral edge of the damaged unit cell to a predetermined width, and a conductive spacing plate made of a gas-impermeable carbon plate is inserted into this gap to form a seal. In the case of forming a conductive path that also serves as a conductive path, it is possible to simultaneously form a gas cutoff to the damaged unit cell and a current bypass path using a carbon plate with high gas sealing properties and corrosion resistance. Repairs can be performed easily, reliably, and inexpensively by avoiding the use of expensive connecting conductors.

〔Example〕

The present invention will be explained below based on examples.

1A and 1B are side views of a fuel cell stack showing different states of the embodiment method of the present invention,
This is an enlarged view of a damaged unit cell of a grooved electrode type unit cell in the entire stacking direction. In the figure, the damaged unit cell 1A of the stack 10, which is pressed between a pair of press plates 8 and 8 by a predetermined tightening load, is shown in FIG. 1A with a manifold (not shown) removed. By injecting the heated and melted low melting point alloy 11 into each of the oxidizer passage 6A and the fuel gas passage 6F, and cooling and solidifying it, the surfaces of the damaged unit cell 1A in contact with the separate plates 7.7 are mutually bonded. The grooves formed in the orthogonal directions are filled with a solidified low melting point alloy, and the electrode base material 5 made of a relatively flexible carbon material is mechanically reinforced to maintain gas permeability. The low melting point alloy used has a melting point of 10
A heat sink at a temperature of 0°C or lower or a low-flow solder material with a melting point of 100°C or lower is suitable, and the damaged unit cell is preheated by flowing a cooling medium at a temperature exceeding the above melting point through the illustrated cooling plate of the stack 10. The mechanical strength of the unit cell is improved by injecting the heated and melted low melting point alloy into the reaction gas passage and cooling and solidifying it. Therefore, the suppression plates 8, 8
By loosening the connecting bolts and reducing the load applied to one damaged unit cell to only the weight of the unit cell and suppression plate located above it, it becomes possible to push the reinforced damaged unit cell to the side.

In the embodiment method, as shown in FIG. 1B, a conductive spacing plate 12 made of a gas-impermeable carbon plate and having a thickness almost equal to that of the unit cell is divided into a plurality of strips in the extrusion direction of the damaged unit cell 1A. The spacer plates 12A and 12B are divided into a plurality of pieces to increase their rigidity, and with an adhesive containing a carbon-based filler applied to the end face, the spacer plate 12A is first pushed in while applying a load evenly in the extrusion direction, and then the spacer plate 12A is pushed in. The damaged unit cells are successively pushed out to the side by pushing the spacing plate 12B in, and replaced with a conductive spacing plate. In the stack 10 in which the damaged unit cells are replaced with the conductive spacer plates 12 in this way, a current path is formed by the conductive spacer plate 12 of the same quality as the separate plate 7, for example, without providing a bypass circuit using a short-circuit conductor. Since the adhesive layer 16 forms a hermetically bonded gas seal, reliable repairs can be easily made without disassembling the stack.

In addition, the damaged unit cell 1A is located at the lower part of the laminated body, and the load applied thereto is large, and the spacer plate 12A is in the form of a strip.

When it is difficult to extrude only with mechanical strength such as 12B,
The spacing plate 12A in contact with the damaged unit cell may be replaced with an extrusion jig made of a long metal plate, and the extrusion may be performed by applying a load to both ends of the extrusion jig. Since the load is only required to push itself into the gap, the replacement work can be simplified and simplified.

FIG. 2A is a side view showing a different embodiment of the invention, M2
Figure B is a plan view of the damaged unit cell portion in Figure 2A. In the figure, 1B is a defective cell whose peripheral edge part has been cut to a predetermined width, and the peripheral edge part can be cut out by a cutter that can cut the peripheral edge part of the unit cell to a width several times the thickness of the entire unit cell, for example, about 1ONn. etc. is used. In addition, in the gap after the peripheral portion has been cut off, there are trapezoidal (or strip-shaped) conductive spacer plates 15A, 15B, 15C, and 15 made of carbon plates made of the same material as that used in the previous embodiment.
D are inserted in a frame-like combination as shown in FIG. 2B, and their joint surfaces are airtightly adhered with an adhesive layer 16, forming a stack that is pressed and sandwiched between a pair of suppressing plates 8, 8. be done.

By carrying out the repair work in this manner, the damaged unit cell 1B after removal is gas-sealed at its peripheral edge by the frame-shaped conductive spacer plate 15, completely stopping the power generation reaction, and at the same time, the pair of separate plates 7 and 7 are conductively connected by the conductive spacer plate 15 to form a current bypass path, so that the generated current detours to the unit cell IB' where the electrodes are insulated by the matrix and passes through the conductive spacer plate 15. Due to the separation of the bypass passage, power generation can be performed without being affected by the remaining damaged unit cell 1B.

In addition, although the damaged unit cell 1B still contains electrolyte, since the conductive spacer plate 15 is made of the same carbon plate as the separate plate 7, etc., its conductive performance and seal are not corroded. performance can be maintained,
Therefore, reliable repair can be easily performed without disassembling the stack.

In addition, when the unit cell has a grooved separate plate, an oxidizing agent passage '-
! Alternatively, by forming the fuel gas passage in advance, repair can be performed without impairing the power generation performance of adjacent unit cells. In this case, it goes without saying that the end face of the damaged unit cell and the end face of the conductive spacer plate must be airtightly adhered to each other by the carbon adhesive layer 16.

〔Effect of the invention〕

As mentioned above, this invention is made by injecting and solidifying a low melting point alloy material into a damaged unit cell to mechanically strengthen it, and then inserting a conductive spacer made of a gas-impermeable carbon plate corresponding to the thickness of the damaged unit cell. It was configured to replace the unit cell. As a result, damaged unit cells can be eliminated without disassembling the stack, and a conductive path and gas seal can be formed using conductive spacing plates with excellent corrosion resistance, thus eliminating the need for a current bypass path using a platinum plate. At the same time, problems such as accelerated damage caused by incomplete blocking of the reaction gas passages are almost completely avoided, and therefore highly reliable 16-cycle operation can be carried out simply and economically.

In addition, a conductive spacing plate is inserted into the space left by cutting the entire peripheral edge of the damaged unit cell to a predetermined width to form a frame-shaped seal and a conductive path.As a result, the stack can be disassembled. This makes it possible to simultaneously and reliably shut off the gas to the damaged unit cell and bypass the current.
Highly reliable one-time recovery can be performed easily and reliably.

[Brief explanation of drawings]

1A and 1B are side views showing mutually different states of the embodiment of the method of the present invention, and FIGS. 2A and 2B are side views and plan views of essential parts of the different embodiments of the method of the present invention. 3 are schematic side views showing the general configuration of a fuel cell stack. 1...Unit cell, 1A...Damaged unit cell, 1B...
・Damaged unit cell with peripheral edge removed, 2... Matrix, 6, 4... Electrode, 6A, 6F... Reactant gas passage, 7... Separate plate, 10... Fuel cell stack , 11...Low melting point alloy, 12.15...Conductive spacing plate, 181a side UZA figure rod + jB figure challenge 2E figure/n 咋孕, ? 1st 9, v 7 Figure 3

Claims (1)

[Scope of Claims] 1) A method for repairing a fuel cell stack consisting of a stack of a plurality of unit cells and including a damaged unit cell, the method comprising injecting a low melting point metal into a fuel gas passage and an oxidant passage of the damaged unit cell. After solidifying and mechanically reinforcing, a conductive spacing plate made of a gas-impermeable carbon plate having a thickness corresponding to the reinforced unit cell is inserted to push the reinforced unit cell laterally. A method for repairing a fuel cell stack, the method comprising: replacing the electrically conductive spacer plate with the conductive spacer plate. 2) A method for repairing a fuel cell stack consisting of a laminate of a plurality of unit cells and including a damaged unit cell, the method comprising: cutting off a peripheral portion of the damaged unit cell to form a void, and then removing the removed unit cell. A fuel cell stack characterized in that a conductive spacer plate made of a gas-impermeable carbon plate having a thickness corresponding to the above is pushed into the gap to form a conductive path that also serves as a seal portion surrounding the damaged unit cell. How to repair.