JP2002170584A - Solid polymer type fuel battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an off-gas heating device excellent in humidification performance. SOLUTION: A humidifier comprising first and second humidification blocks 4 and 5 is connected to a fuel battery main body 7 through a spacer 6. The air, which is a reactive gas, is allowed to flow from a reactive gas 11 to the first humidification block 4 and further to the second humidification block 5, thus it is supplied to an air pole of the fuel battery main body. The off gas containing moisture discharged from the air pole is guided into the humidifier for flowing in the direction opposite to the reactive gas, then exhausted outside through a off gas outlet 14. The cooling water which becomes hot after passing a cooling mechanism of the fuel battery main body 7 is guided into the second humidification block 5, for heating the humidifier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer electrolyte fuel cell, and more particularly to a structure of a humidifier for a reaction gas supplied to a fuel cell body.

[0002]

2. Description of the Related Art When an electrolyte membrane (ion exchange membrane) used in a fuel cell body of a polymer electrolyte fuel cell is dried, its conductivity is reduced and the function as an electrolyte is lost. Therefore, in the polymer electrolyte fuel cell, it is necessary to keep the electrolyte membrane in a certain water-containing state. For this reason, a method is generally adopted in which a humidifier is attached to the fuel cell main body, and the reaction gas humidified by the humidifier is supplied to the fuel cell main body to keep the electrolyte membrane wet.

The humidifying method of the reaction gas includes a bubbling method in which the reaction gas is humidified by passing the reaction gas through hot water held in a humidification tank and bubbling the reaction gas. The membrane humidification method of contacting and humidifying the cooling water used in the method, and further, as disclosed in JP-A-6-132038, the reaction gas before flowing through the fuel cell main body and the fuel gas flowing through the fuel cell main body. There is an off-gas humidification method of humidifying the reaction gas by bringing the reacted gas, that is, the off-gas, into contact via a water vapor permeable membrane.
Of these, in the membrane humidification method and the off-gas humidification method, the fuel cell main body and the humidifier can be formed integrally, and can be configured separately. Since it is necessary to separately keep the connection portion warm, the connection portion is usually formed integrally.

If the off-gas humidification method is applied by integrating the fuel cell body and the humidifier, the water produced by the cell reaction contained in the off-gas and the reaction heat can be recycled into the reaction gas supplied to the fuel cell body. it can. Therefore, it is not necessary to supply water for humidification from the outside, and a large amount of heat of vaporization is not deprived during humidification. In other words, the off-gas humidifier can be regarded as a type of heat exchanger that transfers heat and water vapor at the same time, and the reaction gas supplied to the fuel cell body and the off-gas after the reaction flow inside the gas humidifier as a counter flow. If it comprises, humidification efficiency can be raised more.

FIG. 3 is an exploded perspective view showing a basic configuration example of a humidifying cell of a humidifier used in the above-described off-gas humidifying method. As shown in the figure, the humidifying cell has a structure in which a water vapor permeable membrane 1 having diffusion layers 3 disposed on both sides thereof is sandwiched between separators 2, and a humidifier is formed by stacking a plurality of humidifying cells having this structure. You. A flow path through which a reaction gas supplied to the fuel cell body flows is formed on one main surface of the separator 2, and a flow path through which an off-gas after the reaction flows is formed on the other main surface. 2 and a peripheral portion of the water vapor permeable membrane 1 are provided with three sets of introduction flow holes and discharge flow holes for introducing and discharging a reaction gas, an off gas, and cooling water for temperature control. . In this configuration, the reaction gas flows through one of the flow paths formed on the water vapor permeable membrane 1 side of the pair of separators 2 sandwiching the water vapor permeable membrane 1, and the reacted off gas flows through the other, The humidification of the reaction gas is performed.

[0006]

As described above, in the conventional polymer electrolyte fuel cell, the reaction gas supplied to the fuel cell body is humidified by an off-gas humidification method to be used in the fuel cell body. The electrolyte membrane is kept moist and conductive. The use of the off-gas humidification method does not require the introduction of cooling water from the outside as in the case of the film humidification method, so that the configuration is simplified and efficient in terms of heat utilization. The problem remains.

That is, since the amount of water vapor and the amount of heat contained in the off-gas used as a humidifying source in the off-gas humidification method are smaller than the cooling water used in the film humidification method, the humidification capacity of the off-gas humidification method is film humidification. Lower than the law. Therefore, in order to obtain humidification performance equivalent to that of the membrane humidification method, it is necessary to increase the area of the water vapor permeable membrane, and there is a disadvantage that the apparatus becomes large.

The present invention has been made in consideration of the current state of the art, and an object of the present invention is to more effectively humidify a reaction gas by an off-gas humidification method so that an electrolyte membrane of a fuel cell main body is formed. An object of the present invention is to provide a polymer electrolyte fuel cell which is kept wet and can obtain a predetermined humidifying performance without increasing the size of a humidifying device.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a fuel cell main body for generating electricity by an electrochemical reaction by introducing a fuel containing hydrogen and air, and supplying the fuel cell main body with the fuel cell main body. A solid polymer having a humidifier for humidifying the reaction gas by contacting at least one of the above-mentioned fuel and air with a reaction gas flowing through the fuel cell body through a water vapor permeable membrane; In the fuel cell, (1) at least a part of the humidifying device is configured to be heated by a refrigerant flowing through a cooling mechanism incorporated in the fuel cell main body. The device is composed of a laminate of a plurality of humidifying blocks,
A reaction gas is introduced from one end of this laminate and a plurality of humidification blocks are sequentially flowed to the other end opposite thereto, and the reacted gas is sequentially flowed through the plurality of humidification blocks in a direction opposite to the reaction gas, In addition, the refrigerant that has flowed through the cooling mechanism flows through at least one humidification block in the same direction as the flow direction of the gas after the reaction.

(3) Further, this humidifier is formed integrally with the fuel cell main body by disposing a humidifying block into which the gas after the reaction and the refrigerant flowing through the cooling mechanism are introduced, on the fuel cell main body side. It shall be. The reaction gas before flowing through the fuel cell body and the gas after reaction after flowing through the fuel cell body are brought into contact via a water vapor permeable membrane to humidify the reaction gas. The amount of water that permeates is proportional to the difference between the partial pressures of water vapor on both sides of the membrane, and decreases as the amount of water vapor contained in the gas on the humidification side approaches a saturated state. In addition, since the saturated steam amount decreases as the temperature of the humidifier decreases, if the temperature is too low, even if the gas on the humidifying side contains a large amount of moisture that causes condensation, the permeation of moisture through the steam permeable membrane will not increase. No longer occurs. Therefore, it is necessary to increase the temperature of the humidifier in order to enhance the humidification performance. On the other hand, in the fuel cell main body, the coolant is supplied to the built-in cooling mechanism to remove the heat generated by the electrochemical reaction and to maintain the operating temperature at a predetermined operating temperature. Is done. Therefore, if the off-gas humidifier is heated by the refrigerant flowing through the cooling mechanism of the fuel cell main body as in the above (1), the off-gas humidifier can be heated to a high temperature without introducing another heating means. It will be retained and high humidification performance will be obtained.

The off-gas humidifier generally comprises a laminated body of a plurality of humidifying blocks. At this time, as described in (2) above, the reaction gas for humidification is introduced from one end of the laminated body to form a relative gas. To the other end to be passed, the gas after the reaction for humidification is sequentially passed through a plurality of humidification blocks in a direction opposite to the reaction gas, and the refrigerant after flowing through the cooling mechanism is at least one humidification block. If it is made to flow in the same direction as the flow direction of the gas after the reaction, the amount of moisture contained in the gas after the reaction for humidification is smaller on the upstream side of the reaction gas for humidification, and is smaller on the downstream side. More. At the same time, the temperature of the humidification block is lower on the upstream side of the reaction gas for humidification, and higher on the downstream side. Therefore, the more downstream, the more effective the humidification, both in the amount of water contained in the humidification gas and in the temperature. In the off-gas humidifier of this configuration, the humidification performance is lower on the upstream side of the reaction gas for humidification than on the downstream side, but the reaction gas for humidification is closer on the upstream side to the inlet of the dried reaction gas. Contains a small amount of water and has a low partial pressure of steam.
Therefore, the reaction gas is effectively humidified even if the humidification performance is low. As the water vapor permeable membrane, an ion exchange membrane similar to the electrolyte membrane of the fuel cell body is usually used, but the water vapor permeability coefficient of this ion exchange membrane decreases as the water content decreases, and the humidification rate decreases as the temperature decreases. Is suppressed. Further, the humidification proceeds, the downstream side of the reaction gas, in which the amount of water contained increases and the partial pressure of water vapor increases, is humidified by high humidification performance. In the off-gas humidifier of this configuration,
As described above, since the humidification is effectively performed from the upstream side to the downstream side of the reaction gas, required humidification performance can be obtained without increasing the size of the apparatus.

Further, if the humidifier is formed integrally with the fuel cell main body as described in the above (3), not only loss of heat of the refrigerant from the fuel cell main body is suppressed to a very small amount, but also
Since the humidifying device is heated by heat conduction from the high temperature fuel cell main body, a device with high thermal efficiency can be obtained, and furthermore, the device can be made compact.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a flow chart showing a fuel cell body and a reaction gas system and a water system of a humidifier in an embodiment of a polymer electrolyte fuel cell according to the present invention. In this embodiment, the humidifying device is configured as a laminate of two blocks, a first humidifier block 4 and a second humidifier block 5, and a spacer 6 is provided on a fuel cell body 7 composed of a laminate of a plurality of battery cells. Are connected via

In the polymer electrolyte fuel cell of this embodiment, a method is adopted in which air supplied as a reaction gas is humidified by using off-gas from an air electrode, and the other fuel is supplied without humidification. . That is, air as a reaction gas is introduced from the reaction gas inlet 11 to the first humidification block 4 and further to the second humidification block 5, flows through the respective humidified gas flow paths, and then flows from the air supply port 12 to the fuel cell 12. It is sent to the main body 7. The reaction air is sent to the air electrode of each battery cell of the fuel cell body 7 and causes an electrochemical reaction together with the fuel sent to the fuel electrode to contribute to power generation. The air electrode off-gas discharged from the air electrode contains reaction product water generated during power generation, and the humidification of the second humidification block 5 and the first humidification block 4 from the fuel cell body 7 through the air off-gas discharge port 13. After being sent to the gas flow path and used to humidify the air flowing in the opposite direction through the humidification target gas flow path through the water vapor permeable membrane 1, the air is discharged from the off gas outlet 14. On the other hand, the fuel sent to the fuel electrode is introduced into the fuel cell main body 7 through the fuel supply port 15, flows through each battery cell, and is taken out of the fuel cell main body 7 through the fuel off-gas outlet 16. .

Further, in the configuration of the present embodiment, the cooling water discharged from the fuel cell main body 7 is sent to the second humidifying block 5 of the humidifying device and used for heating. That is, the cooling water that flows through the cooling mechanism inside the fuel cell body 7 from the cooling water inlet 17 and absorbs the heat generated by the electrochemical reaction and is heated to a high temperature passes through the cooling water outlet 18 to the second humidifier.
After being supplied to the humidification block 5 and contributing to the heating of the second humidification block 5, the first humidification block 5
The cooling water outlet 19 flows through the flow path in the peripheral portion of the humidifying block 4.
It is discharged to the outside. Therefore, the cooling water discharged from the fuel cell main body 7 is used only for heating the second humidification block 5 and is not directly used for heating the first humidification block 4.

FIG. 2 is an exploded cross-sectional view showing the basic structure of the humidifier of the embodiment shown in FIG. 1. FIG. 2 shows a reaction gas system and a water system at the same time. The structure of the humidifying cells constituting the first humidifying block 4 and the second humidifying block 5 is the same as that shown in FIG. 3 described above. The diffusion layer 3 to be formed is omitted. As described above, the water vapor permeable membrane 1 is an ion exchange membrane similar to the electrolyte membrane of the fuel cell body. The separator 2 is made of carbon having good thermal conductivity, and the diffusion layer 3 is also made of carbon paper. Further, the spacer 6 disposed between the second humidification block 5 of the humidifier and the fuel cell main body 7 is also formed of the same carbon as the separator 2.

In the configuration shown in FIG. 2, the first humidifying block 4 and the second humidifying block 5 each comprise two humidifying cells, and are connected by the separator 2 therebetween. Also, the first
In the humidification block 4, the water vapor permeable membranes 1 and the separators 2 are alternately arranged, whereas in the second humidification block 5, two separators 2 are arranged adjacent to each other and discharged from the fuel cell body 7 therebetween. A flow path for flowing the high-temperature cooling water is formed, and thereby the second humidification block 5 is heated.

In this embodiment, the humidifying device is constituted by two humidifying blocks each comprising two humidifying cells. However, the number of humidifying blocks constituting the humidifying device, and the humidifying units forming the respective humidifying blocks. The number of cells is not limited, and is selected according to the operating conditions of the polymer electrolyte fuel cell. In this embodiment, the humidifying gas is the air electrode off-gas, and the humidified gas is the reaction air.However, the present invention is not limited to this. It is possible to select any one of the reaction air and the fuel gas and to carry out in any combination.

[0019]

As described above, according to the present invention, a fuel cell main body that generates a fuel by an electrochemical reaction by introducing a fuel containing hydrogen and air, and removes heat generated by the reaction by flowing a refrigerant. A fuel cell body having a cooling mechanism, and an unreacted gas of at least one of the fuel and air before flowing through the fuel cell body and after a reaction after flowing through the fuel cell body. A solid polymer electrolyte fuel cell comprising a humidifier for humidifying unreacted gas by contacting said gas through a water vapor permeable membrane, as claimed in claim 1 or claim 2 or claim 3; As a result, the humidifier did not generate a portion having an insufficient amount of water vapor permeation, and the humidification of the reaction gas was performed more effectively, so that the electrolyte membrane of the fuel cell body was kept moist. Do not increase the size of the humidifier Both became the predetermined humidifying performance can be obtained a polymer electrolyte fuel cell obtained.

[Brief description of the drawings]

FIG. 1 is a flow chart showing a reaction gas system and a water system of a fuel cell main body and a humidifier in an embodiment of a polymer electrolyte fuel cell of the present invention.

FIG. 2 is an exploded cross-sectional view showing a basic configuration of the humidifier of the embodiment shown in FIG.

FIG. 3 is an exploded perspective view showing a basic configuration example of a humidifying cell of a humidifier using an off-gas humidification method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Water vapor permeable membrane 2 Separator 3 Diffusion layer 4 1st humidification block 5 2nd humidification block 6 Spacer 7 Fuel cell main body 11 Reactive gas inlet 12 Air supply port 13 Air off gas outlet 14 Off gas outlet 15 Fuel supply port 16 Fuel off gas outlet 17 Cooling water inlet 18 Cooling water outlet 19 Cooling water outlet

Claims (3)

[Claims] 1. A fuel cell body for generating electricity by an electrochemical reaction by introducing a fuel containing hydrogen and air, a reaction gas of at least one of the fuel and air supplied to the fuel cell body, and a fuel cell In a polymer electrolyte fuel cell comprising a humidifier for humidifying the reaction gas by contacting the gas after the reaction flowing through the main body through a water vapor permeable membrane, at least a part of the humidifier is a fuel cell main body. A polymer electrolyte fuel cell characterized by being configured to be heated by a refrigerant flowing through a cooling mechanism incorporated in the fuel cell. 2. The humidifier comprises a laminated body of a plurality of humidifying blocks, wherein the reaction gas is introduced from one end of the laminated body and flows through the plurality of humidifying blocks sequentially to the other end. The gas after the reaction flows sequentially through the plurality of humidification blocks in a direction opposite to the reaction gas, and the refrigerant after flowing through the cooling mechanism passes at least one humidification block through the gas after the reaction. The polymer electrolyte fuel cell according to claim 1, wherein the fuel cell is configured to flow in the flow direction. 3. The humidifying device according to claim 1, wherein the humidifying block into which the gas after the reaction and the refrigerant after flowing through the cooling mechanism is introduced is disposed on the fuel cell main body side, and is formed integrally with the fuel cell main body. The polymer electrolyte fuel cell according to claim 2, wherein: