JPH08298131A - Fuel cell - Google Patents

Abstract

PURPOSE: To provide a fuel cell which is allowed to obtain a stable characteristic by setting each cooling plate at a uniform temperature so as to become uniform in flow distribution of cooling water. CONSTITUTION: In a pressure vessel 7 provided with a ventilating gas inlet 9 in a lower part and a ventilating gas outlet 10 in an upper part, a layer product 1 of laminating a plurality of cells 2 is formed. A cooling plate 3 for radiating heat of the cell 2 is arranged between each several sheets of unit cells 2. A gas manifold 6 of supplying fuel and air to the cell 2 is set up in a side surface of the layered product 1. Further in the upper/lower of the cooling plate 3 provided in the uppermost/lowermost in the layer product 1, a plurality of the cells 2 are laminated. A number of the cells 2, provided in the upper/ lower of the uppermost/lowermost cooling plate 3, is set to 3/4 or less 1/2 or more a number of the cells between the cooling plates 3. A gas non-permeable carbon plate 4 with a smooth surface is arranged in the upper/lower of the uppermost/lowermost cell 2, to be fixedly tightened by a fastening plate 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell which directly generates electric power by a chemical reaction between a fuel and an oxidant, and more particularly, by improving the laminated structure of a single cell, the stability of operation and the longevity are improved. The present invention relates to a fuel cell that has a long life.

[0002]

2. Description of the Related Art A fuel cell main body generates electric power by causing an electrochemical reaction between hydrogen and oxygen via an electrode and an electrolyte. Since this electrochemical reaction is an exothermic reaction at the same time,
The battery body generates heat due to its operation, but it is necessary to discharge surplus heat in order to maintain a constant temperature optimum for operation. If the excess heat generated in this way can be recovered and utilized, it will lead to effective use of energy.Therefore, a normal fuel cell is provided with a system for supplying / discharging a cooling medium to / from the main body, and the excess heat is supplied by this cooling medium. Collected.
In addition, when the reformed gas, the cathode exhaust air, the reformer exhaust gas, and the like contain excess heat, they can be recovered via the heat exchanger. The surplus heat thus recovered is used as steam or high-temperature water for heating, hot water supply, steam for industrial use, and in combination with an absorption refrigerator or heat pump as a heat source for cooling.

An example of such a fuel cell using cooling water as a cooling medium for the cell body is shown in FIGS. 5 and 6.
Will be described below. That is, a laminated body 1 in which a plurality of cells (unit cells) 2 are laminated is formed in a pressure vessel 7 having a ventilation gas inlet 9 in the lower part and a ventilation gas outlet 10 in the upper part. Cell 2 is a matrix (electrolyte layer)
Since the electrodes (fuel electrode, air electrode) are laminated with the cell sandwiched between them, and the output voltage per cell 2 is insufficient, by connecting a plurality of stacked bodies 1 in series as described above, It is being improved and used. A cooling plate 3 for radiating heat of the cells 2 is arranged between every several single cells 2.

A carbon plate 4 having a smooth surface and a gas impermeability is arranged at the uppermost lower part of the laminated body 1 for gas sealing (preventing gas leakage). Further, the upper and lower parts of the upper and lower carbon plates 4 are clamped and fixed by a tightening plate 5 for applying a necessary surface pressure to the laminated body 1. Further, a gas manifold 6 that supplies fuel and air to each cell 2 is installed on the side surface of the stack 1. The conventional example is a pressurized fuel cell in which the cell is operated at a pressure higher than atmospheric pressure in order to obtain high power generation efficiency, and the pressure vessel 7 is ventilated by a ventilation gas 8 containing nitrogen as a main component. Is.

The operation of the conventional example as described above is as follows. That is, during the operation of the fuel cell, the ventilation gas 8 is supplied into the pressure vessel 7 from the ventilation gas inlet 9 at the bottom of the vessel. The stimulating gas 8 is supplied at a temperature lower than the temperature of the cell 2, but is heated by the heat released from the cell 2 and rises,
It is discharged from the ventilation gas outlet 10 at the top of the container. Water, which is the cooling medium of the cell 2, is required to improve the cooling efficiency and take out the steam for reforming and heating / cooling. Therefore, as shown in FIG. In the state (single-phase flow), a method is adopted in which the outlet of the cooling water is a two-phase flow in which water and steam are mixed. In order for the cooling plate 3 to flow out such a two-phase flow, the amount of heat input from the cell 2 to the cooling plate 3 must be a certain value or more.

[0006]

However, in the prior art as described above, the heat input amount in the lowermost cooling plate 3 is only about half that of the other cooling plates 3. Therefore, as shown in FIG. 6, the lowermost cooling plate 3
In the above, since there is a single-phase flow that does not contain steam from the inlet to the outlet, the exhaust flow of the cooling water is not uniform throughout, the pressure loss differs for each cooling plate 3, and the characteristics of the fuel cell become unstable.

In the case of the uppermost cell 2, the ventilation gas 8 heated by each cell 2 reaches the cell 2, so that the temperature of the cell 2 is maintained at a certain temperature or higher. However, the evoked gas 8 is the ventilation gas inlet 9 below the pressure vessel 7.
Since the temperature is lower than the temperature of the cell 2 when supplied from, the temperature of the lowermost cell 2 is low and the output voltage is low. As described above, if there are cells 2 having different characteristics, the life may be deteriorated due to uneven distribution of current density.

The present invention has been proposed to solve the above-mentioned problems of the prior art, and its purpose is to:
It is an object of the present invention to provide a fuel cell in which cooling water is evenly distributed by making each cooling plate have a uniform temperature and stable characteristics can be obtained.

Another object of the present invention is to provide a fuel cell in which each unit cell has a uniform power generation capacity, so that operational safety and long life can be realized.

[0010]

In order to achieve the above object, the invention according to claim 1 is a unit cell in which a fuel electrode and an air electrode are laminated with a matrix impregnated with an electrolyte sandwiched therebetween, A plurality of stacked units are formed so that the unit cells are electrically connected to each other in series, and a cooling plate inserted for each of a predetermined number of unit cells in the stacked unit, and a fuel and an oxidizer In a fuel cell that generates electricity by chemical reaction,
Among the cooling plates in the stack, the unit cell is further stacked on the cooling plate arranged at the top and below the cooling plate arranged at the bottom.

According to a second aspect of the present invention, in the fuel cell according to the first aspect, the laminated body is housed in a pressure container capable of supplying and discharging ventilation gas, and the ventilation gas is supplied to a lower portion of the pressure container. A possible ventilation gas inlet is provided, a ventilation gas outlet capable of discharging ventilation gas is provided on the upper part of the pressure vessel, and the temperature of the evoked gas supplied from the ventilation gas inlet is
It is characterized in that the temperature between the cooling plates is set to be equal to or higher than the minimum temperature and equal to or lower than the maximum temperature of the unit cell.

According to a third aspect of the present invention, in the fuel cell according to the first aspect, the upper and lower portions of the laminated body are clamped and fixed by fastening plates, and heating means is provided on at least one of the upper and lower fastening plates. It is characterized by

According to a fourth aspect of the present invention, in the fuel cell according to the third aspect, temperature detecting means for detecting the temperature of the lowermost unit cell in the stack, and temperature detected by the temperature detecting means are used. And a control means for controlling the heating means.

[0014]

The operation of the present invention having the above construction is as follows. That is, in the invention according to claim 1, since the unit cells are further stacked above and below the lowermost cooling plate, the heat generation of these unit cells causes the uppermost cooling plate to be equivalent to other cooling plates. Heat input is obtained. Therefore, the cooling water flowing out from the outlet of the lowermost cooling plate 3 becomes a two-phase flow like the other cooling plates 3 and the drainage of the cooling water becomes uniform throughout.

According to the second aspect of the present invention, the ventilation gas supplied from the ventilation gas inlet at the bottom of the pressure vessel is controlled to be higher than or equal to the minimum temperature and lower than or equal to the maximum temperature of the unit cell between the cooling plates. As a result, the temperature of the lowest unit cell in the stack is overheated, and the unit cell between the cooling plates is kept at a temperature higher than the lowest temperature and lower than the highest temperature.

According to the third aspect of the present invention, since the heating means is provided on the lower clamping plate, the temperature of the lowermost unit cell is kept at the minimum value of the unit cells between the cooling plates by heating by the heating means. It is maintained above the temperature but below the maximum temperature.

In the invention according to claim 4, the temperature of the lowermost unit cell is measured by the temperature detecting means during heating by the heating means, and the measured value is not less than the minimum temperature and not more than the maximum temperature of the cell between the cooling plates. Therefore, the heating temperature of the heating means is controlled by the control means.

[0018]

EXAMPLES Examples of the fuel cell according to the present invention will be described below with reference to FIGS. The same members as those of the conventional technique shown in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted.

(1) First Embodiment An embodiment corresponding to the invention described in claims 1 and 2 will be described below as a first embodiment with reference to FIGS. 1 and 2. It should be noted that the present embodiment is a pressurized fuel cell in which the cell is operated at a pressure of atmospheric pressure or higher, and the pressure vessel is ventilated using a ventilation gas whose main component is nitrogen.

(A) Structure of the First Embodiment First, the structure of the present embodiment will be described. That is, in the present embodiment, as shown in FIG. 1, a plurality of cells (unit cells) 2 are further provided on the uppermost cooling plate 3 in the stack 1.
Are stacked. Further, a plurality of cells 2 are stacked below the lowest cooling plate 3 in the stack 1. Thus, the number of cells 2 provided above and below the lowermost cooling plate 3 is 3 / the number of cells stacked between the cooling plates 3.
4 or less and 1/2 or more. And the cell 2 of the lowermost layer
Further, carbon plates 4 are provided on the upper and lower sides of the carbon plate 4, and the laminated body 1 is clamped and fixed by clamping plates 5 from above and below the carbon plates 4.

(B) Operation of the first embodiment The operation of the present embodiment having the above-mentioned structure is as follows. That is, since the cells 2 are laminated on the uppermost and lowermost cooling plates 3, there is a heat input equivalent to that of the other cooling plates 3 due to the heat generation of these cells 2 during operation. Therefore, the cooling water at the outlet of the uppermost cooling plate 3 becomes a two-phase flow like the outlets of the other cooling plates 3.

Further, the temperature of the cells 2 in the lowermost layer is lower than the lowest temperature of the cells 2 between the cooling plates 3 as shown in FIG. 2A because of the heat radiation from the lower tightening plate 5. May be. Therefore, in this embodiment, the ventilation gas 8 is supplied to the ventilation gas inlet 9 by controlling the ventilation gas 8 to a temperature not lower than the minimum temperature and not higher than the maximum temperature of the cells 2 between the cooling plates 3. Then, the lower clamping plate 5 is heated by the ventilation gas 8,
The temperature of the lowermost cell 2 is maintained at the minimum temperature or higher and the maximum temperature or lower of the cells 2 between the cooling plates 3.

On the other hand, the ventilation gas 8 supplied as described above
Is heated by the heat radiation from each cell 2 while rising in the pressure vessel 7, the temperature is maintained at about the average temperature of each cell 2 as shown in FIG. 2B. Since such ventilation gas reaches the cell 2 stacked on the uppermost cooling plate 3, there is almost no heat radiation from the uppermost cell 2 to the ventilation gas, and the cell 2 is placed between the cooling plates 3. The temperature of the cell 2 is maintained above the minimum temperature and below the maximum temperature.

(C) Effects of First Embodiment The effects of this embodiment as described above are as follows. That is, since the flow on the outlet side of the lowermost cooling plate 3 becomes a two-phase flow like the other cooling plates 3, the distribution of the cooling water becomes uniform and the operation efficiency becomes stable.

Further, since the temperature of the cells 2 arranged at the uppermost lower part is higher than or equal to the lowest temperature and lower than or equal to the highest temperature of the cells 2 between the cooling plates 3, all cells 2 have a uniform temperature distribution. Therefore, each cell 2 can have a uniform power generation capability, and safety of operation and a long life can be realized.

(2) Second Embodiment An embodiment corresponding to the invention described in claims 1, 3 and 4 will be described below as a second embodiment with reference to FIGS. 3 and 4. To do. The heating means described in claim 3 is an electric heater, the temperature detection means described in claim 4 is a thermocouple, and the control means is a control circuit. The same members as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. Omit it. Further, the present embodiment is an atmospheric pressure type fuel cell in which the cell is operated at atmospheric pressure, and does not use ventilation gas.

(A) Configuration of the Second Embodiment First, the configuration of the present embodiment will be described. That is, in this embodiment, as shown in FIG. 3, the pressure vessel is not provided, and the electric heater 11 is attached to the lower fastening plate 5. Also,
The lowermost cell 2 is provided with a thermocouple 12. The electric heater 11 and the thermocouple 12 are connected to a control circuit (not shown), and according to the temperature measured by the thermocouple 12, so that the lowermost cell 2 is maintained in a certain temperature range.
The control circuit controls the heat generation of the electric heater 11.

(B) Operation of the second embodiment The operation of this embodiment having the above-mentioned structure is as follows. That is, since the cells 2 are stacked above and below the uppermost cooling plate 3, the heat generated by these cells 2 has the same heat input as that of the other cooling plates 3. Therefore, at the outlets of these lowermost cooling plates 3, a two-phase flow is formed, like the other cooling plates 3.

By heating the lower clamping plate 5 with the electric heater 11, the lowermost cell 2 is heated. At this time, as shown in FIG. 4, the temperature of the lowermost cell 2 is measured by the thermocouple 12 so that the temperature of the cell 2 becomes equal to or higher than the minimum temperature of the cells 2 between the cooling plates 3 and equal to or lower than the maximum temperature thereof. In addition, the heating temperature of the electric heater 11 is controlled by the control circuit.

(C) Effects of the Second Embodiment The effects of this embodiment as described above are as follows. That is, the flow on the outlet side of the lowermost cooling plate 3 becomes a two-phase flow like the other cooling plates 3, so that the cooling water is evenly distributed and the operation efficiency is stable as in the first embodiment. To do.

Further, since the temperature of the cell 2 arranged at the lowermost portion is higher than or equal to the lowest temperature and lower than or equal to the highest temperature of the cells 2 between the cooling plates 3, all cells have a uniform temperature distribution. Therefore, even in a normal-pressure fuel cell that does not have a pressure vessel and does not use ventilation gas, each cell 2 can have a uniform power generation capacity, and operational safety and a long life can be realized.

(3) Other Embodiments The present invention is not limited to the embodiments described above, and the quantity, type, etc. of each member can be changed appropriately. For example, the number of stacked cells can be freely increased or decreased according to a desired voltage, and the number of cooling plates can be increased or decreased accordingly. Further, the heating means and the temperature detecting means are not limited to the electric heater 11 and the thermocouple 12. For example, as the heating means, it is possible to provide a device for heating with steam flowing through the pipe. And the heating means is
It is possible to provide not only the lower tightening plate 5 but also the upper tightening plate 5. Furthermore, a computer can be used as well as a dedicated circuit as the control means.

[0033]

As described above, according to the present invention, by the constitution in which the unit cells are further stacked above and below the lowermost cooling plate,
Make each cooling plate a uniform temperature to make the distribution of cooling water uniform,
A fuel cell having stable characteristics can be provided.

Further, according to the present invention, by setting the temperature of the uppermost unit cell to be equal to or higher than the minimum temperature of the unit cell between the cooling plates and equal to or lower than the maximum temperature, each cell has a uniform power generation capacity and can be operated. It is possible to provide a fuel cell that can realize safety and a long life.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a fuel cell of the present invention.

FIG. 2 is a temperature distribution diagram (A) in a stacking direction and a temperature distribution diagram (B) in a stacking direction of a ventilation gas in the stacked body in the example shown in FIG.

FIG. 3 is a configuration diagram showing a second embodiment of the fuel cell of the present invention.

FIG. 4 is a temperature distribution diagram in the stacking direction of the stack in the example shown in FIG.

FIG. 5 is a configuration diagram showing an example of a conventional fuel cell.

6 is a cooling water temperature distribution diagram in a cooling plate in the conventional example shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laminated body 2 ... Cell (single cell) 3 ... Cooling plate 4 ... Carbon plate 5 ... Tightening plate 6 ... Gas manifold 7 ... Pressure vessel 8 ... Ventilation gas 9 ... Ventilation gas inlet 10 ... Ventilation gas outlet 11 ... Electric heater 12 ... Thermocouple

Claims (4)

[Claims] 1. A unit cell in which a fuel electrode and an air electrode are stacked with a matrix impregnated with an electrolyte sandwiched therebetween, and a stacked body in which a plurality of the unit cells are stacked so as to be electrically connected to each other in series. In a fuel cell that has a cooling plate inserted for each of a predetermined number of unit cells in the stack, and that generates power by a chemical reaction between a fuel and an oxidant, among the cooling plates in the stack, A fuel cell, wherein the unit cell is further stacked on the arranged cooling plate and below the arranged cooling plate. 2. The laminated body is housed in a pressure vessel capable of supplying and discharging ventilation gas, a ventilation gas inlet capable of supplying ventilation gas is provided at a lower portion of the pressure vessel, and an upper portion of the pressure vessel is provided. A ventilation gas outlet capable of discharging ventilation gas is provided, and the temperature of the arousal gas supplied from the ventilation gas inlet is set to a minimum temperature of the unit cells between the cooling plates or more and a maximum temperature or less. The fuel cell according to claim 1, wherein the fuel cell is a fuel cell. 3. The fuel cell according to claim 1, wherein the top and bottom of the stack are clamped and fixed by tightening plates, and heating means is provided on at least one of the upper and lower tightening plates. 4. A temperature detecting means for detecting the temperature of the lowermost unit cell in the stack, and a control means for controlling the heating means based on the temperature detected by the temperature detecting means are provided. The fuel cell according to claim 3, wherein: