JPS62139274A - Air cooling type fuel cell stack - Google Patents

Abstract

PURPOSE:To obtain an air cooling type fuel cell stack in which scatter of electrolyte is decreased, water produced is efficiently recovered, and maintenance is easy by mounting unit cells, a cell stack, inlet manifolds, and outlet manifolds. CONSTITUTION:Fuel gas inlet and outlet manifolds 6A, 6B and air inlet and outlet manifolds 51, 52 are mounted on four sides of a cell stack 20 comprising a plurality of unit cells. A common passage 51A for reaction air 80A and cooling air 80B is formed in the inlet manifold 51. A reaction air passage 52A partitioned with a partition 52C and a cooling air passage 52B is formed in the outlet manifoled 52. The cooling air 80B supplied from an inlet 11A of a cooling air chamber 11 is blocked so as not to enter the reaction air passage 52A by a partition 13 and supplied to the cooling air passage 52B. A reaction gas chamber formed in the back of the cooling air chamber 11 is connected to the reaction air passage 52A.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to, for example, an air-cooled matrix-type fuel cell stack using phosphoric acid as an electrolyte, and particularly to the structure of passages for reaction air and cooling air.

[Prior art and its problems]

FIG. 7 is a perspective view of a main part of a cell stack showing an example of the prior art, and FIG. 8 is a schematic horizontal sectional view of the cell stack.

In FIG. 7, 1 is an air electrode.

2 is a gas-impermeable carbon plate having fuel gas passages 6 and air passages 4 each formed of a plurality of grooves crossing each other at right angles on both sides; A cell stack 9 is formed by alternately stacking the matrix 1 and the separate plates 2.
As shown in the figure, a pair of manifolds 6A and 6B that communicate with the fuel gas passage 6 and a pair of manifolds 5A and 5B that communicate with the air passage 4 are airtightly fixed to two sets of opposing side surfaces of the cell stack 9, respectively. Then, supply fuel gas between manifolds 6A and 6B.

By supplying air to the manifolds 5A and 5B as shown by the arrows, the hydrogen in the fuel gas and the oxygen in the air react electrochemically to generate DC power.

By the way, in order to efficiently operate the fuel cell using the above-mentioned cynic acid as an electrolyte, the operating temperature of the fuel cell is usually set at 190℃.
It is operated while maintaining the temperature at around ℃. On the other hand, since fuel cells generate reaction heat corresponding to the energy of the generated electric power due to electrode reactions, in order to maintain the fuel cell at the operating temperature, it is necessary to cool the cell during operation. In this case, cooling is generally performed using water, gas, oil, or the like as a cooling medium. The most commonly used method is to separate the separate plates 2 and 2 as shown in Figure 8.
An excess amount of air, which is larger than the amount of reaction air required for the electrode reaction, is supplied to the air passage 4 by pipes 81 and 82 and the blower 71.
In this method, a part of the air volume is consumed for the electrode reaction, and at the same time, the heat generated in the stain pond is removed by passing the remaining surplus air.

By the way, electrolytes such as cynic acid, which are impregnated and retained in the matrix within a cell, evaporate during operation.

The electrolyte is scattered and carried out of the cell by the flow of the reaction gas, and the amount retained within the matrix gradually decreases, and the amount of electrolyte lost in this case increases in proportion to the flow rate of the reaction gas. Therefore, in the method of cooling the fuel cell by supplying air, which is a reactive gas, in excess as described above, a large amount of electrolyte is scattered and lost. Therefore, there is a problem in that troublesome operation management such as frequent replenishment of electrolyte during operation is required. In addition, the exhaust air containing the reaction product water of the unit cell 1 is transferred to the outlet side manifold 5B and the exhaust air piping 8.
4.87 and the flow rate regulating valve 72 in a steam/water separator (not shown) to condense and separate moisture and reuse the recovered water for, for example, reforming fuel, excess air for cooling Since the moisture in the exhaust air is diluted, there is a problem in that the recovery efficiency in the steam separator decreases. Therefore, a part of the exhaust air is returned to the intake side of the blower 71 via the circulation pipe 85 having the flow rate adjustment valve 76 and recirculated in the air passage 4 to increase the concentration of water vapor. A control method is implemented to increase the recovery efficiency in. By doing so, the water recovery efficiency can be increased, and the air taken in through the intake pipe 81 and the exhaust air are mixed, and the air on the inlet side of the cell stack 10 is used to cool the fuel cell. Can be maintained at a suitable temperature. However, if the exhaust air whose oxygen concentration has decreased due to the electrode reaction is recirculated within the air passage 4, a problem arises in that the electrode reaction of the cell stack is reduced. On the other hand, in systems that use cooling water, it is necessary to prevent electrical short circuits of the batteries due to the cooling medium, and to prevent the water piping from interfering with the manifold of the reaction gas supply system, including the water piping system. The structure of the cooling device becomes complicated. For this purpose, a structure is actually adopted in which a cooling plate is interposed between every few cells of each cell and a water cooling pipe is installed.In this method, the cells adjacent to the cooling plate have a strong cooling effect. In contrast, the cooling effect for cells that are far away from other cooling plates is low, and this creates a temperature difference between the cells that make up the cell stack, making it impossible to obtain proper battery cooling performance. There is a problem. In addition, air is used as a cooling medium instead of water, and a cooling air passage is installed in the cooling plate installed in the fuel cell cell stack every few cells. Japanese Patent Laid-Open No. 58-154181 discloses a method in which air is supplied, a part of which is supplied as a reaction gas to the electrodes of the single cell, and the remaining air flow is passed through the air passage of the cooling plate to strengthen the cooling of the battery. It is disclosed in the official gazette and is known. However, like the water-cooling method described above, this method also has the problem of creating a temperature difference between the cells that make up the cell stack, and the reaction air passage and cooling air passage are open in a common manifold. Therefore, it is difficult to adjust the distribution of the air flow rate between the two, and if the amount of air introduced into the manifold is increased to increase the amount of cooling air ventilation, the amount of air supplied to the reaction gas supply path will be increased at the same time. If the amount of electrolyte inevitably increases, resulting in an oversupply state that exceeds the amount required for the electrode reaction, the problem of increased scattering and loss of electrolyte will occur again.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and provides an air-cooled fuel cell stack in which scattering and loss of electrolyte is small, reaction product water can be easily separated and recovered, and the temperature of the cell stack can be controlled accurately. The purpose is to

[Key points of the invention]

In the present invention, a separate plate is divided into a fuel gas side and an air side, and the air side separate plate has a reaction air chamber on the side in contact with the air electrode and a cooling air chamber on the side opposite to the air electrode, each having a common inlet. The air chambers are formed so that they communicate with the inlet side manifold, and the partition walls arranged on the outlet sides of both air chambers form the outlet portions at different positions in the width direction of the seven barret plates. A reaction air passage and a cooling air passage are provided corresponding to the outlet of the chamber, and both air passages are connected to a known piping system, for example, the reaction air passage is connected to a steam separator system, and the cooling air passage is connected to an exhaust system and a circulation system. Due to the configuration in which the air is communicated with the system, the air supplied to the inlet manifold is separated into reaction air and cooling air at the inlets of both air chambers, and the size and position of the outlet are controlled by the partition wall. This allows appropriate amounts of reaction air and cooling air to be separately supplied to both air chambers.

[Embodiments of the invention]

The present invention will be explained below based on examples.

FIG. 1 is a horizontal sectional view and a piping system diagram showing an embodiment of the present invention, and is a horizontal sectional view passing through an air chamber of an air side separate plate. In the figure, reference numeral 20 denotes a cell stack consisting of a stacked assembly of a plurality of units.On the four sides of the cell stack, there are a pair of manifolds 6A and SB on the fuel gas inlet and outlet sides, and an air inlet. A pair of side and outlet side manifolds 51 and 5
2 is provided, and the inlet side manifold 51 is provided with reaction air 8.
A common passage 51A for cooling air 80A and cooling air 80B is formed in the outlet side manifold 52, and a reaction air passage 52A and a cooling air passage 52B partitioned by a partition wall 52C are formed. 1
Reference numeral 2 denotes an air-side separate plate made of a carbon plate or the like, and 11 is a cooling air chamber consisting of concave grooves connected in a lattice shape formed on one side of the separate plate 12. Cooling air flows in from the inlet portion 11A. 80B is the partition wall 13 arranged on the exit side
The reaction air is prevented from flowing into the reaction air passage 52A, and is configured to flow into the cooling air passage 52B via the outlet portion 11B. It is configured to communicate with the air passage 52A.

FIG. 2 is a perspective view of the main parts of the cell stack in the above-mentioned embodiment. A separate plate 16 having a groove-shaped fuel gas chamber 6, and a reaction air chamber 14 having grooves on both sides.
and an air side separate plate 12 having a cooling air chamber 11
are arranged to form a unit set 10, and a plurality of unit sets 10 are stacked to form a cell stack 20. On the outlet side of the reaction air chamber 14, there is an outlet part 14B whose position is regulated by a partition wall 15. However, there is a partition wall 13 on the outlet side of the cooling air chamber 11.
The outlet portions 11B, which are regulated in multiple positions, are formed to open at different positions in the width direction, and the reaction air chamber 14 and the cooling air chamber 11, which are formed by grooves, are in close contact with the cell 1 and the separate plate 13, respectively. Especially at the entrance,
Airtightness is maintained except for the outlet.

3 and 4 are horizontal sectional views showing the structure of the air chamber in the above-mentioned embodiment, and FIG.
The figures show the conditions of the reaction air chambers. In the figure, the cooling air chamber 11 and the reaction air chamber 14 are formed by lattice-shaped concave grooves that are substantially symmetrical to each other, and on the common passage 51A side of the inlet side manifold 51, there are inlet portions 11A and 14A of approximately the same number and size. An exit portion 1 is formed, and the location and number of exit portions are regulated by a partition wall 15 or 15 on the exit side.
1B and 14B are formed to form an air cooling air chamber 1.
1 is connected to the cooling air passage 52B of the outlet side manifold 52,
The reaction air chamber 14 is configured to communicate with the reaction air passage 52A, and by increasing the number of outlet portions 11B than the number of outlet portions 14B, the amount of cooling air 80B can be reduced to the amount of reaction air 80A. In addition to being able to reasonably increase the amount of air compared to the above, it is also possible to distribute air almost evenly to the air chambers of a plurality of unit sheets.

In the cell stack configured as described above, hydrogen-rich fuel gas 60 is supplied from the reformer 75 to the fuel gas chamber of the cell stack 20 via the pipe 94 and the manifold 6A.
By supplying A and sending air to the reaction air chamber 14 and the cooling air chamber 11 via the blower 71 and the inlet side manifold 51, power generation can be performed by the electrode reaction of the unit cell. Further, the fuel exhaust gas that has completed the reaction is sent to the combustion chamber of the reformer 75 via the manifold 6B and piping 95, where combustible gas components are burned and removed, and the thermal energy generated by the combustion is used as a heat source for reforming the fuel gas. used. On the other hand, the reaction air 80A whose oxygen concentration has decreased after the reaction is sent to the steam/water separator 73 via the reaction air passage 52A and piping 86, where the reaction product water is condensed and recovered, and the exhaust air is passed through the exhaust pipe 88. is released into the atmosphere,
Since the cooling air 80B is separated, the amount of excess air is reduced, the scattering and loss of electrolyte can be reduced, and the water concentration is increased, so that the recovery efficiency of produced water in the steam water separator 73 can be increased. Furthermore, the recovered water is used as water added to the raw material in a reformer 75 via a water treatment device 74. On the other hand, the cooling air 80B that has been warmed by passing through the cooling air chamber 11 passes through the cooling air passage 52B and piping 84, and a part of it passes through the exhaust air regulating valve 72. (by being released into the atmosphere via the exhaust pipe 87), new air corresponding to the amount of released air and the amount of air released via the steam separator 75 is supplied to the suction pipes 81, 82 . The cooling air is sent to the inlet side manifold 51 via the blower 71, and a portion of the cooling air is circulated to the intake side of the blower 71 via a circulation pipe 85 having a circulation air regulating valve 76. Therefore, the exhaust air regulating valve 72 is adjusted to control the amount of reaction air and the amount of cooling air discharged into the atmosphere, and at the same time, the circulating air regulating valve 76 is controlled.
By controlling the amount of circulating air mixed with the intake air,
It is possible to freely control the air temperature in the common passage 51A in the inlet side manifold 51. For example, by controlling the air temperature in accordance with the amount of power generation of the cell stack, the cell stack is suitable for power generation. The temperature can be maintained accurately at about 190°C. In addition, reaction air chamber 1
4 inlet section 14A and cooling air chamber 110 inlet section 11A
By configuring them so that they are opened in parallel to the common passage 51A, air controlled at a constant temperature can be separately supplied to the reaction air chamber and the cooling air chamber of each unit sheet 10. The temperature difference between the paper cells can be minimized, and therefore a fuel cell with high cooling performance and high power generation efficiency can be obtained.

5 and 6 are horizontal sectional views of cell stacks showing different embodiments, FIG. 5 shows the structure of the cooling air chamber, and FIG. 6 shows the structure of the reaction air chamber, respectively. .

In the figure, 22 is an air side separate plate, 21 is a cooling air chamber, 24 is a reaction air chamber, partition walls 26A, 23B are provided at both the entrance and exit of the cooling air chamber 21, partition walls 25A are provided at both the entrance and exit of the reaction air chamber 24, 25B are provided respectively, and the cooling air passages 5 of the outlet side manifold 52 are provided correspondingly.
The difference from the previous embodiment is that the cooling air chamber 21 and the reaction air passage 52A are separated from each other in that the inlet portions 21A and 24A of the inlet side manifold 51 are open to the common passage 51A. The air distributed to
Air flow is generated throughout the lattice-shaped grooves by diagonally crossing each air chamber made of the lattice-shaped grooves and being discharged from the outlet portions 21B and 24B to the respective passages 52A and 52B. As a result, the area effective for cooling can be increased, and heat transfer can be enhanced by the air flow colliding with the side surfaces of the concave grooves, so that a fuel cell with even better cooling performance can be obtained.

〔Effect of the invention〕

As described above, the present invention provides a reaction air chamber and a cooling air chamber consisting of concave grooves that communicate with each other and have partition walls on both sides of the air side separate plate that is separated into a fuel gas side and an air side and that have partition walls that regulate the outlet portion. An inlet side manifold having a common passage for supply air is provided on the inlet side of both air chambers.
An outlet side manifold was provided on the outlet side in which a reaction air passage and a cooling air passage were partitioned. As a result, since the cooling air passage is separated, only the reaction air suitable for supplying the oxygen necessary for the electrode reaction can be sent to the reaction air chamber. This eliminates various problems such as scattering and loss of electrolyte, replenishment of electrolyte, and reduction in efficiency of condensation and collection of reaction product water in the steam-water separator. It is possible to easily provide an air-cooled fuel cell stack, and by providing a partition wall on the outlet side of each of the reaction air chamber and the cooling air chamber, the amount of air required can be adjusted depending on the number and size of the outlet sections of both air chambers. The amount of air distributed to both air chambers is controlled with a difference corresponding to At the same time, the air controlled at a constant temperature is supplied to the common passage of the inlet side manifold, and the air controlled at a constant temperature is evenly distributed to each reaction air chamber and cooling air chamber through the inlet opening into the common passage. As a result, it is possible to prevent the reduction in power generation efficiency caused by the circulation of reaction air whose oxygen concentration has decreased due to the electrode reaction, which was a problem in the conventional technology, and also to maintain the cell stack at a temperature suitable for power generation. Since air can be sent into each air chamber at a constant temperature to maintain a constant temperature, for example, the incoming air temperature can be easily controlled according to the amount of heat generated by the cell stack, resulting in high cooling performance and power generation efficiency. It is possible to provide an air-cooled fuel cell stack having the following. Furthermore, by configuring the reaction air and cooling air to be supplied from a common air supply system on the inlet side, the air supply system can be simplified, and the reaction air chamber and cooling air chamber can be connected to both sides of one separate plate. By providing this, there is no problem even if a leak occurs between the two air chambers, and an advantage is obtained that the air side separate plate can be formed of an inexpensive carbon material.

Furthermore, dry cooling air that does not contain reaction product water is recirculated to cool the cell stack and control its temperature, which eliminates the increase in cell stack leakage current that was a problem with conventional water-cooled technology. This gives you the advantage of being able to prevent this.

In addition, by providing a cooling air chamber in the air-side separate plate of each unit set consisting of a unit cell and a pair of separate plates placed on both sides of the unit set, the conventional method of providing a cooling plate for each unit set has been improved. This technology has the advantage of eliminating technical problems such as an increase in temperature difference between cells, complication of cooling water piping, and mixing of reaction air and cooling air without complicating the structure of the cell stack.

[Brief explanation of drawings]

FIG. 1 is a horizontal sectional view showing an embodiment of the present invention, FIG. 2 is a perspective view of the main parts of the cell stack in the embodiment, and FIGS. 6 and 4 are views of the cooling air chamber and reaction air chamber in the embodiment. 5 and 6 are horizontal sectional views showing the structure of a cooling air chamber and a reaction air chamber in different embodiments. FIG. 7 is a horizontal sectional view showing the structure of a cell stack showing an example of the prior art. The perspective view and FIG. 8 are horizontal sectional views of a cell stack showing the prior art. DESCRIPTION OF SYMBOLS 1...Single cell, 2...Separate plate, 3...Fuel gas passage, 4...Air passage, 6A, 6B...Fuel gas side manifold, 5A, 51...Inlet side manifold ( air side), 51A...common passage, 5B, 52
...Outlet side manifold (air side), 9.20...
Cell stack, 10... Unit set, 11.21... Cooling air chamber, 12.22... Air side separate plate, 13
, 23° 25... Partition wall, 14... Reaction air chamber, 11
A, 14A, 21A, 24A... Entrance section, 11B, 1
4B, 21B, 24B... Outlet section, 52A... Reaction air passage, 52B... Cooling air passage, 71... Prower 172° 76... Regulating valve, 76... Steam water separator , 80... air, 81.82, 84.85.86...
·Piping. Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1) A unit cell consisting of a laminate of a fuel electrode, a matrix, and an air electrode, a separate plate having a groove-shaped fuel gas chamber disposed on the fuel electrode side of the unit cell, and an air electrode. A unit set consisting of an air-side separate plate having a reaction air chamber and a cooling air chamber, which are arranged on the side and have a partition wall that has concave grooves on both sides and regulates the outlet part, and a laminated assembly of a plurality of these unit sets. A cell stack, an inlet side manifold for common reaction air and cooling air disposed on the inlet side of both the air chambers, and a reaction air passage and a cooling air passage divided so as to correspond to the respective outlet portions of both the air chambers. An air-cooled fuel cell stack comprising an outlet side manifold. 2) The air-cooled fuel cell stack according to claim 1, wherein the reaction air passage and the cooling air passage of the outlet side manifold communicate with mutually different piping systems. 3) The air-cooled fuel cell according to claim 2, characterized in that the cooling passage communicates with an exhaust system having an exhaust air regulating valve and a circulation system having a circulating air regulating valve. cell stack.