JPH0831437A - Fuel cell and operation thereof - Google Patents

Abstract

PURPOSE:To reduce loss of electrolyte, and prolong a life of a fuel cell by lowering temperature at a specific part of a cooling plate of a fuel cell for decreasing temperature at an outlet part of reaction gas, and condensing the electrolyte vaporized and scattered into the reaction gas. CONSTITUTION:Fuel gas is supplied from an inlet hole 6 of an in/out manifold 2 to a cell, it returns in a return manifold 3, and it is discharged from an outlet hole 7. Oxidizer is supplied from an inlet hole 8 of an inlet manifold 4 to the cell, and it is discharged from an outlet hole 9 of an outlet manifold 5. Cooling medium under a saturation temperature is supplied from an inlet hole 10 of a cooling plate 1, and it is discharged through a cooling coil 12 form an outlet hole 11. When a cooling medium inlet temperature is set property, a temperature gradient can be provided at the part (diagonal line part) where a fuel gas outlet part and an oxidizer outlet part are combined with each other to set temperature of the cooling medium to be under the saturation temperature. Electrolyte in reaction gas can thus be recondensed to be recovered in a cell, thereby its loss can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell, and more particularly to a fuel cell without electrolyte replenishment and its operating method.

[0002]

2. Description of the Related Art A fuel cell is a power generation device that oxidizes a fuel by an electrochemical process in an electrolyte layer and directly converts the energy released by the oxidation reaction into electric energy, which is stored in the electrolyte layer. A small amount of electrolyte evaporates in the reaction gas during power generation and is carried away to the outside of the battery.Therefore, after long-term power generation operation, the electrolyte in the electrolyte layer decreased, and stable operation was impossible. .

[0003] In order to prevent such electrolyte deficiency of the fuel cell, it has been generally adopted to periodically replenish the electrolyte from the outside.
The operation of the battery had to be stopped for a long time, and it was surprisingly difficult to evenly distribute the electrolyte to a large number of stacked cells. Further, the electrolyte taken out of the battery adheres to downstream equipment, pipes, valves, instrumentation equipment, etc., and corrodes them.In addition, if it flows into the water recovery system, frequent maintenance of the water treatment equipment is required. There was a problem such as making it happen.

Therefore, a technique for reducing the electrolyte concentration in the reaction gas for the purpose of reducing the amount of electrolyte carried away to the outside of the cell has been proposed, for example, in JP-A-64-14876, "Fuel Cell Main Body Cooling System". However, the effect was insufficient because only the outlet of the oxidizer was cooled.

[0005]

As described above, the conventional fuel cell has a problem that the concentration of the electrolyte evaporated in the reaction gas is high and it is difficult to perform stable operation during the economically competing period. The present invention has been made to solve the above problems, and its purpose is to reduce the electrolyte concentration in the reaction gas and reduce the electrolyte carried away to the outside of the battery, thereby stabilizing the supply without electrolyte supply during an economically competing period. An object of the present invention is to provide a fuel cell that enables operation and a method of operating the fuel cell.

[0006]

In order to achieve the above-mentioned object, the first aspect of the present invention is to provide a unit cell composed of a cell composed of a pair of porous electrodes sandwiching an electrolyte layer impregnated with an electrolyte, A plurality of cooling cells for supplying and discharging a refrigerant to cool the battery are stacked inside each of the plurality of unit cells to form a square columnar cell stack, and a side surface of the cell stack is formed on a side surface of the cell stack. In a fuel cell composed of a laminated body in which a manifold for reaction gas supply / exhaust in which a reaction gas flow path is formed is arranged between one side of the reaction gas by lowering the temperature of a specific portion of the cooling plate. Alternatively, the temperature of both outlets is lowered so that the electrolyte that evaporates and scatters in the reaction gas is condensed.

According to a second aspect of the present invention, in the fuel cell according to the first aspect, a partition plate or the like is provided in the manifold for supplying and discharging the reaction gas, so that the flow path of the fuel is inverted at least once or more. It is characterized in that the outlet of the fuel gas is superposed on the outlet of the oxidant, and a refrigerant cooled to a saturation temperature is supplied to the superposed portion.

According to a third aspect of the present invention, in the fuel cell according to the second aspect, the refrigerant is water. According to claim 4 of the present invention, a unit cell composed of a cell composed of a pair of porous electrodes sandwiching an electrolyte layer impregnated with an electrolyte, and a plurality of unit cells each supplying and discharging a refrigerant inside A plurality of cooling plates for cooling the battery are stacked to form a rectangular column-shaped cell stack, and a reaction gas supply channel in which a reaction gas flow path is formed between the side surface of the cell stack and the side surface of the cell stack. In a method of operating a fuel cell, which is composed of a laminated body in which exhaust manifolds are arranged,
In order to make the temperature inside the fuel cell uniform over a wide range and to lower the temperature of a specific portion inside the fuel cell, a refrigerant cooled below the saturation temperature is supplied so that the outlet temperature of the reaction gas can be locally lowered. It is characterized by having done.

A fifth aspect of the present invention is the method for operating a fuel cell according to the fourth aspect, characterized in that the inlet temperature of the refrigerant is cooled to at least 10 ° C. or higher than the saturation temperature.

[0010]

It has been conventionally considered that the electrolyte of the fuel cell is scattered in the oxidant gas together with water produced by the electrochemical process and is lost to the outside of the cell. However, recent studies have found that the electrolyte concentration in the reaction gas is more strongly governed by the local cell temperature than the electrochemical process. That is, as shown in the characteristic diagram of FIG. 7 showing the relationship between the electrolyte concentration and the temperature, the logarithm of the electrolyte concentration in the reaction gas is almost proportional to the temperature near the average operating temperature of the fuel cell.

Therefore, according to the present invention, the temperature of the main reaction section of the battery is maintained at the main level in order to accelerate the electrochemical process and obtain a high voltage, and the cooling is locally enhanced only at the outlet section of the reaction gas. However, by lowering the temperature of the reaction gas in the part that contains the concentration of electrolyte that equilibrates with the temperature of the main reaction part of the battery (hereinafter referred to as the specific part), the electrolyte in the reaction gas is recondensed and collected in the battery. It is something that is done. In this way, by lowering the temperature of a specific part of the cooling plate, the temperature of one or both outlets of the reaction gas is decreased, and the electrolyte that evaporates and scatters in the reaction gas is condensed to reduce the loss of the electrolyte. Battery life can be extended.

[0012]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a partially cutaway plan view of a first embodiment of the present invention. As shown in the figure, in a fuel cell, a cooling plate 1 is provided for each unit cell composed of a pair of porous electrodes sandwiching an electrolyte layer impregnated with an electrolyte, and a plurality of the unit cells are stacked. Then, a rectangular column-shaped cell stack is formed, and a reaction gas inlet / outlet manifold is formed on a side surface of the cell stack. That is, the fuel gas is supplied to the cell through the fuel gas inlet hole 6 formed in the fuel inlet / outlet manifold 2, folded back inside the fuel return manifold 3, and discharged to the outside of the cell through the fuel gas outlet hole 7. The oxidant is supplied to the battery through an oxidant inlet hole 8 formed in the oxidant inlet manifold 4 so as to be orthogonal to the flow of the fuel gas, and is supplied to the battery through an oxidant outlet hole 9 formed in the oxidant outlet manifold 5. Is discharged to.

On the other hand, the refrigerant is supplied to the battery at a temperature cooled below the saturation temperature through a refrigerant inlet hole 10 formed in a corner of the cooling plate 1, and is heated by heat generated by an electrochemical reaction through a cooling spiral tube 12. And reaches the saturation temperature, and the cooling plate 1
It is discharged to the outside of the battery through the refrigerant outlet hole 11 formed in the other corner. Therefore, by appropriately setting the refrigerant inlet temperature, it is possible to provide a gradient such that the refrigerant temperature is equal to or lower than the saturation temperature in the portion where the fuel gas outlet portion and the oxidant outlet portion overlap (the hatched portion in the figure). it can. With such a temperature gradient, the temperature of the cooling plates in the superposed portions, and consequently the outlet temperature of the reaction gas, can be locally reduced, whereby the electrolyte in the reaction gas is recondensed and collected in the battery. By doing so, the loss of the electrolyte can be reduced.

FIG. 7 is a characteristic diagram showing the relationship between the electrolyte concentration and the reaction gas temperature. From this diagram, it is possible to reduce the electrolyte concentration by half by lowering the reaction gas temperature by 10 ° C. Therefore, the initial charge amount of the electrolyte and the electrolyte are It is possible to double the battery life determined by the evaporation concentration of.

As is apparent from the above description, the positional relationship between the fluids such as the fuel gas and the oxidizing agent and the supply position of the refrigerant are not limited to the present embodiment, and the following second to sixth embodiments are possible. With the configuration shown in the example, the same effect as that of the present embodiment can be obtained.

FIG. 2 is a partially cutaway plan view of the second embodiment of the present invention. This embodiment differs from the embodiment of FIG. 1 in that the method of supplying the refrigerant is one flexible tube 12 in the embodiment of FIG.
However, in this embodiment, two flexible tubes 12 and 15 are used. Along with this, refrigerant inlet holes 10 and 13 are formed at two corners of the cooling plate 1, and refrigerant outlet holes 11 and 14 are formed at the other corners of the cooling plate 1. Since other configurations are the same, the same reference numerals are given to the same portions and the description thereof will be omitted.

FIG. 3 is a partially cutaway plan view of the third embodiment of the present invention. The present embodiment is different from the embodiment of FIG. 2 in that the refrigerant supply method is two flexible pipes 12 and 15 in the embodiment of FIG. 2, but in this embodiment, two parallel pipes 16 and 15 are used.
17 is used. Along with this, one of the refrigerant inlet holes 13 provided at one corner of the cooling plate 1 and one of the refrigerant outlet holes 14 provided at the other corners of the cooling plate 1 is reversed. Since other configurations are the same, the same reference numerals are given to the same portions and the description thereof will be omitted.

FIG. 4 is a partially cutaway plan view of the fourth embodiment of the present invention. This embodiment is different from the embodiment of FIG. 1 in that the flow paths of the fuel gas and the oxidant are each turned back once.
That is, the outlet of the fuel gas is superposed on the outlet of the oxidant, and the refrigerant cooled to the saturation temperature is supplied to this portion.
Along with this, an oxidant inlet / outlet manifold 18 having an oxidant inlet 8 and an oxidant outlet 9 and an oxidant return manifold 19 are formed. Since other configurations are the same, the same reference numerals are given to the same portions and the description thereof will be omitted.

FIG. 5 is a partially cutaway plan view of the fifth embodiment of the present invention. The present embodiment is different from the embodiment of FIG. 1 in that the fuel gas flow path is folded back twice and the fuel gas outlet is overlapped with the oxidant outlet, and a refrigerant cooled to the saturation temperature is placed in this portion. The point of supply. Accordingly, the fuel inlet manifold 20 having the fuel inlet 6 and the fuel outlet 7 are provided.
A fuel outlet manifold 21 is provided.
Since other configurations are the same, the same reference numerals are given to the same portions and the description thereof will be omitted.

FIG. 6 is a partially cutaway plan view of the sixth embodiment of the present invention. This embodiment is different from the embodiment of FIG. 5 in that the fuel gas flow path is folded back twice and the oxidant flow path is changed to one.
The point is that the fuel gas outlet is folded back and overlapped with the outlet of the oxidant, and the refrigerant cooled to the saturation temperature is supplied to this portion. Accordingly, the oxidant inlet and outlet are configured as in the embodiment of FIG. That is, an oxidant inlet / outlet manifold 18 having an oxidant inlet 8 and an oxidant outlet 9 and an oxidant return manifold 19 are formed. Since other configurations are the same, the same reference numerals are given to the same portions and the description thereof will be omitted.

[0021]

As described above, according to the present invention,
While maintaining the temperature of the main reaction part of the battery at a level required to accelerate the electrochemical process to obtain a high voltage, the cooling is locally enhanced only at the outlet part of the reaction gas, and By lowering the temperature of the reaction gas containing an equilibrium concentration of electrolyte and then re-condensing the electrolyte in the reaction gas and collecting it in the cell, the loss of electrolyte is reduced and a long-life fuel cell is realized. it can. It also reduces the risk of the scattered electrolyte adhering to the equipment, pipes, valves, instrumentation, etc. downstream of the cell and corroding them, thus reducing the maintenance frequency and improving the operating rate of the entire fuel cell system. Is possible.

[Brief description of drawings]

FIG. 1 is a plan view of a first embodiment of the present invention.

FIG. 2 is a plan view of the second embodiment of the present invention.

FIG. 3 is a plan view of a third embodiment of the present invention.

FIG. 4 is a plan view of the fourth embodiment of the present invention.

FIG. 5 is a plan view of a fifth embodiment of the present invention.

FIG. 6 is a plan view of a sixth embodiment of the present invention.

FIG. 7 is a characteristic diagram showing the relationship between the temperature of the fuel cell and the electrolyte concentration.

[Explanation of symbols]

1 ... Cooling plate, 2 ... Fuel inlet / outlet manifold, 3 ... Fuel return manifold, 4 ... Oxidant inlet manifold, 5
... oxidant outlet manifold, 6 ... fuel inlet hole, 7 ... fuel outlet hole, 8 ... oxidant inlet hole, 9 ... oxidant outlet hole, 10,
13 ... Refrigerant inlet hole, 11, 14 ... Refrigerant outlet hole, 12, 1
5 ... Cooling pipes, 16, 17 ... Cooling pipes, 18 ... Oxidizing agent inlet / outlet manifold, 19 ... Oxidizing agent return manifold, 20 ... Fuel inlet manifold, 21 ... Fuel outlet manifold.

Claims (5)

[Claims] 1. A battery comprising a cell composed of a pair of porous electrodes sandwiching an electrolyte layer impregnated with an electrolyte, and a coolant is supplied to and discharged from each of the plurality of cells to cool the battery. A plurality of cooling plates are stacked to form a rectangular column-shaped cell stack, and a side face of the cell stack is provided with a reaction gas flow path between the side face and the side face of the cell stack. In a fuel cell composed of a laminated body in which manifolds are arranged, by lowering the temperature of a specific portion of the cooling plate, the temperature of one or both outlet portions of the reaction gas is lowered, and it is evaporated and scattered in the reaction gas. The fuel cell is characterized in that the electrolyte to be condensed is condensed. 2. The fuel cell according to claim 1, wherein a partition plate or the like is provided in the reaction gas supply / exhaust manifold so that the fuel flow path is inverted at least once and the fuel gas outlet is provided. A fuel cell characterized by being superposed on an outlet of an oxidant and supplying a refrigerant cooled to a saturation temperature to the superposed portion. 3. The fuel cell according to claim 2, wherein the refrigerant is water. 4. A unit cell composed of a cell composed of a pair of porous electrodes sandwiching an electrolyte layer impregnated with an electrolyte, and a coolant is supplied to and discharged from each of the plurality of unit cells to cool the battery. A plurality of cooling plates are stacked to form a rectangular column-shaped cell stack, and a side face of the cell stack is provided with a reaction gas flow path between the side face and the side face of the cell stack. In a method for operating a fuel cell composed of a laminate in which manifolds are arranged, in order to make the temperature inside the fuel cell uniform over a wide range and lower the temperature of a specific portion inside the fuel cell, a refrigerant cooled below the saturation temperature. Is supplied to locally lower the outlet temperature of the reaction gas. 5. The method of operating a fuel cell according to claim 4, wherein the inlet temperature of the refrigerant is at least 1 higher than the saturation temperature.
A method of operating a fuel cell, which is characterized in that it is cooled to 0 ° C. or more.