Patent Application
20050074640
1. Field of the Invention
The present invention relates to a fuel cell system. More particularly, the present invention relates to a polymer electrolyte fuel cell system.
2. Description of the Related Art
In recent years, concern about environmental problems has been increasing on a global scale, under the influence of global warming, acid rain, and the like, due to carbon dioxide. So, in a field of power supply development, attention has been focused on a fuel cell system capable of energy change which is highly efficient and keeps the environment clean without emission of carbon dioxide. Among various fuel cell systems, particular attention has been paid to a polymer electrolyte fuel cell system that operates at a low temperature and has high output density, which is expected to be used as civil power supply, power supply for power-driven automobile, etc.
Now, an example of the conventional polymer electrolyte fuel cell system will be described with reference to the drawings.
Referring now to
Subsequently, an example of an operation of the conventional polymer electrolyte fuel cell system 300 will be described with reference to the drawings.
In the polymer electrolyte fuel cell system 300 constructed as shown in
For the purpose of temperature-increasing and humidifying an oxidizing gas to predetermined temperature and humidity, there has been proposed a method in which total enthalpy heat exchange is conducted between the oxidizing gas and cooling water exhausted from a fuel cell and having increased temperature (e.g., see Japanese Laid-Open Patent Application Publications Nos. 2002-231282 and 2000-3720).
In addition, for the purpose of removing impurities such as nitrogen oxide or sulfur oxide or other organic compounds, which may be contained in an oxidizing gas, there has been proposed a method in which filters or the like are provided at an inlet and an outlet of an air supply device to remove the impurities (e.g., see Japanese Laid-Open Patent Application Publication No. Hei. 8-138703).
By the way, recently, the use of the polymer electrolyte fuel cell system has been anticipated. And, in order to put the polymer electrolyte fuel cell system into practical use in applications of the civil power supply, power supply for power-driven automobile, and so on, it is important to improve power generation efficiency and cell life characteristic. In order to achieve these objects, inhibiting entry of the impurities such as nitrogen oxide or sulfur oxide or other organic compounds, which may be contained in the oxidizing gas, into the polymer electrolyte fuel cell, is effective.
However, if the filters are provided at the inlet and the outlet of the air supply device to remove the impurities such as the organic compounds from the oxidizing gas as described above, the air supply device and hence the polymer electrolyte fuel cell system will have intricate structures. Such a problem impedes reduction of cost of the polymer electrolyte fuel cell system, and consequently, makes it difficult for the polymer electrolyte fuel cell system to be put into practical use in the applications the civil power supply, the power supply for power-driven automobile, and so on.
The present invention has been developed under the circumstances, and an object of the present invention is to provide a polymer electrolyte fuel cell system which is inexpensive, is similar in construction to the conventional polymer electrolyte fuel cell system, and is capable of effectively removing impurities such as organic compounds from air to improve electric characteristic and life characteristic.
According to one aspect of the present invention, there is provided a polymer electrolyte fuel cell system comprising: a fuel cell configured to generate an electric power using a fuel gas and an oxidizing gas supplied to the fuel cell; and a total enthalpy heat exchanger configured to heat and humidify the oxidizing gas using heat and water exhausted from the fuel cell, wherein the total enthalpy heat exchanger is capable of removing impurities contained in the oxidizing gas from the oxidizing gas.
In such a construction, the oxidizing gas is increased in temperature and humidified concurrently with removal of impurities such as nitrogen oxide or sulfur oxide or other organic compounds. Consequently, it is possible to provide an inexpensive polymer electrolyte fuel cell system which is similar in construction to the conventional polymer electrolyte fuel cell system and achieves improved electric characteristic and life characteristic.
The total enthalpy heat exchanger may be equipped with a heater capable of decomposing or separating the removed impurities.
In such a construction, since the heater heats the total enthalpy heat exchanger, the impurities remaining in the interior of the total enthalpy heat exchanger are decomposed or separated to allow the impurity removing function of the total enthalpy heat exchanger to be restored. Consequently, it is possible to provide an inexpensive polymer electrolyte fuel cell system which is similar in construction to the conventional polymer electrolyte fuel cell system and achieves improved electric characteristic and life characteristic for a long time period.
The total enthalpy heat exchanger may have a total enthalpy heat exchange membrane configured to heat and humidify the oxidizing gas by total enthalpy heat exchange, and an impurity removal layer may be formed on one principal surface of the total enthalpy heat exchange membrane, which contacts the oxidizing gas, to remove the impurities.
Since the impurities such as nitrogen oxide or sulfur oxide or other organic compounds, which may be contained in air, can be removed by a simple construction, it is not necessary to provide a filter for removing the impurities.
The oxidizing gas supplied to the fuel cell may be heated and humidified using an oxidizing gas exhausted from the fuel cell.
Since the oxidizing gas exhausted from the fuel cell has heat and water sufficient to heat and humidify the oxidizing gas supplied to the fuel cell, it is possible to adjust the oxidizing gas supplied to the fuel cell to a predetermined state.
The oxidizing gas supplied to the fuel cell may be heated and humidified using cooling water exhausted from the fuel cell.
Since the heated cooling water exhausted from the fuel cell has heat and water sufficient to heat and humidify the oxidizing gas supplied to the fuel cell, it is also possible to adjust the oxidizing gas supplied to the fuel cell to a predetermined state.
The impurity removal layer may be formed of porous adsorbent.
Since such an impurity removal layer is capable of effectively removing the impurities such as nitrogen oxide or sulfur oxide or other organic compounds, which may be contained in air, the electric characteristic and life characteristic of the polymer electrolyte fuel cell system can be greatly improved.
The impurity removal layer may be formed of porous adsorbent carrying transition metal thereon.
Since such an impurity removal layer is capable of more effectively removing the impurities such as nitrogen oxide or sulfur oxide or other organic compounds, which may be contained in air, the electric characteristic and life characteristic of the polymer electrolyte fuel cell system can be further improved.
The transition metal may be at least one of platinum, palladium, rhodium, ruthenium, iridium, nickel, iron, copper, and silver.
Since these transition metals are available relatively easily, and relatively inexpensive, the impurity removal layer formed on the total enthalpy heat exchange membrane, and hence the total enthalpy heat exchange membrane can be produced in a relatively inexpensive manner.
The impurity removal layer may be formed of porous adsorbent carrying metal oxide thereon.
Since such an impurity removal layer is capable of more effectively removing the impurities such as nitrogen oxide or sulfur oxide or other organic compounds, which may be contained in air, the electric characteristic and life characteristic of the polymer electrolyte fuel cell system can be further improved.
The metal oxide may be at least one of aluminum oxide, silicon oxide, zinc oxide, manganese oxide, iron oxide, copper oxide, calcium oxide, and magnesium oxide.
Since these metal oxides are available relatively easily, and relatively inexpensive, the impurity removal layer formed on the total enthalpy heat exchange membrane, and hence the total enthalpy heat exchange membrane can be produced in a relatively inexpensive manner.
The impurity removal layer may be formed of porous adsorbent carrying zeolite thereon.
Since such an impurity removal layer is capable of more effectively removing the impurities such as nitrogen oxide or sulfur oxide or other organic compounds, which may be contained in air, the electric characteristic and life characteristic of the polymer electrolyte fuel cell system can be further improved.
The zeolite may be at least one of Mordenite, A-zeolite, MF-zeolite, B-zeolite, and Faujasite.
Since these zeolites are available relatively easily and relatively inexpensive, the impurity removal layer formed on the total enthalpy heat exchange membrane, and hence the total enthalpy heat exchange membrane can be produced in a relatively inexpensive manner.
The porous adsorbent may be made of active carbon or silica gel. Since the active carbon or silica gel are available easily and inexpensive, the impurity removal layer formed on the total enthalpy heat exchange membrane, and hence the total enthalpy heat exchange membrane can be produced in an inexpensive manner.
According to another aspect of the present invention, there is provided a method of operating a polymer electrolyte fuel cell system comprising a fuel cell configured to generate an electric power using a fuel gas and an oxidizing gas supplied to the fuel cell, and a total enthalpy heat exchanger configured to heat and humidify the oxidizing gas using heat and water exhausted from the fuel cell, the method comprising the steps of: removing impurities contained in the oxidizing gas from the oxidizing gas in the total enthalpy heat exchanger; heating the total enthalpy heat exchanger which has removed the impurities using a heater capable of decomposing or separating the impurities to decompose or separate the impurities, before the fuel cell starts or stops power generation; and discharging the decomposed or separated impurities from the total enthalpy heat exchanger.
In such a configuration, since the impurities remaining in the interior of the total enthalpy heat exchanger are decomposed or separated on a regular basis, the impurity removing function of the total enthalpy heat exchanger can be restored on a regular basis. Consequently, the polymer electrolyte fuel cell system has stable electric characteristic and life characteristic over a long time period.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
First of all, the construction of the polymer electrolyte fuel cell system according to the first embodiment of the present invention will be described with reference to the drawings.
Referring now to
The polymer electrolyte fuel cell system 100 further comprises a water storage tank 12 configured to store cooling water used for keeping the polymer electrolyte fuel cell 1 generating heat during an operation at a predetermined temperature, a cooling water pump 14 configured to circulate the cooling water stored in the water storage tank 12 to cause the cooling water to flow within the polymer electrolyte fuel cell 1, and a heat radiator 13 configured to radiate heat of the cooling water to outside of the polymer electrolyte fuel cell system 100.
In addition, as shown in
An operation principle and a construction of the impurity removal total enthalpy heat exchanger 15 which features the present invention will be described.
First, the operation principle of the impurity removal total enthalpy heat exchanger 15 will be described.
Referring now to
Subsequently, a construction of the total enthalpy heat exchanger 15 will be described.
As shown in
Subsequently, a basic operation of the polymer electrolyte fuel cell system 100 according to the first embodiment will be described with reference to the drawings.
As shown in
Meanwhile, the oxidizing gas supplied from the air supply device 6 flows into the introducing passage (not shown in
While generating an electric power, the polymer electrolyte fuel cell 1 is generating heat. Accordingly, in order to keep the polymer electrolyte fuel cell 1 at a constant temperature during power generation, the cooling water pump 14 operates to circulate the cooling water stored within the water storage tank 12 to cause the cooling water to flow through the cooling water passage 1a provided within the polymer electrolyte fuel cell 1. More specifically, the cooling water pump 14 operates so that the cooling water outflows from the water storage tank 12, then flows within the cooling water passage 1a provided within the polymer electrolyte fuel cell 1, and thereafter returns to the water storage tank 12. The cooling water which has increased in temperature due to heat generated by the polymer electrolyte fuel cell 1 and returned to the water storage tank 12, is cooled to a predetermined temperature in the heat radiator 13.
The polymer electrolyte fuel cell system 100 operates as described above, and a predetermined voltage is generated at an output terminal (not shown in
During the operation of the polymer electrolyte fuel cell system 100 constructed as described above, the oxidizing gas supplied from the air supply device 6 is increased in temperature and humidified to predetermined states by the impurity removal total enthalpy heat exchanger 15. Simultaneously, the impurities such as nitrogen oxide and sulfur oxide or other organic compounds, which may be contained in the oxidizing gas are effectively removed from the oxidizing gas. And, the oxidizing gas which has been increased in temperature and humidified to the predetermined states and does not substantially contain the impurities, is supplied to the polymer electrolyte fuel cell 1. In addition, the impurity removal layer recovery heaters 15e and 15f heat the impurity removal total enthalpy heat exchanger 15 as desired to cause the impurities remaining within the impurity removal total enthalpy heat exchanger 15 to be decomposed or separated, thus restoring an impurity removing function of the impurity removal total enthalpy heat exchanger 15 on a regular basis. In this case, the decomposed substances of the impurities or the separated impurities resulting from heating in the impurity removal total enthalpy heat exchanger 15 are discharged to outside of the polymer electrolyte fuel cell system 100 together with the oxidizing gas supplied from the air supply device 6 by switching the three-way valve 16 so that a supply destination of the oxidizing gas is outside the polymer electrolyte fuel cell system 100. In this construction, since the decomposed substances of the impurities or the separated impurities resulting from heating is inhibited from entering the polymer electrolyte fuel cell 1, it is possible to effectively avoid degradation of performance of the polymer electrolyte fuel cell 1 which would otherwise be caused by the decomposed substances of the impurities or the separated impurities. Consequently, it is possible to provide an inexpensive polymer electrolyte fuel cell system which is similar in construction to the conventional polymer electrolyte fuel cell system and can have improved electric characteristic and life characteristic for a long time period.
While in the first embodiment described thus far, the hydrogen-ion conductive polymer electrolyte membrane is employed as the total enthalpy heat exchange membrane, the total enthalpy heat exchange membrane employed in the fuel cell system of the present invention is not intended to be limited to this. Alternatively, a porous membrane may be employed so long as it functions as the total enthalpy heat exchange membrane. Further, in addition to the hydrogen-ion conductive electrolyte membrane or the porous membrane, any other membrane may be employed, so long as it functions as the total enthalpy heat exchange membrane. As used herein, “the membrane which functions as the total enthalpy heat exchange membrane” means a membrane which has a total enthalpy heat exchange function and does not degrade the quality of the oxidizing gas supplied to the polymer electrolyte fuel cell 1. More specifically, the membrane which functions as the total enthalpy heat exchange membrane is adapted to permit permeation of water and heat but not to permit permeation of chemical impurities or the like which may impede a power generation operation of the polymer electrolyte fuel cell, and allows a varying value of an oxygen partial pressure of the oxidizing gas supplied to the polymer electrolyte fuel cell to lie within a range in which power generation performance of the polymer electrolyte fuel cell is not substantially degraded, during total enthalpy heat exchange. Any membrane having such function can be employed as the total enthalpy heat exchange membrane, and by using such a membrane, the same effects as provided by the first embodiment can be obtained.
First of all, a method of manufacturing the polymer electrolyte fuel cell in the polymer electrolyte fuel cell system employed in the example 1 will be described.
In the polymer electrolyte fuel cell in the example 1, platinum particles having an average diameter of 30 Å was carried on ketjen black EC (produced by AKZO Chemie Co. Ltd, Holland) which is electrically conductive carbon particles having an average primary particle diameter of 30 nm in 50 wt % to produce cathode catalyst carrying particles. And, platinum particles and ruthenium particles each having an average diameter of 30 Å were carried on ketjen black EC in 25 wt % to produce anode catalyst carrying particles. Then, water was added to each catalyst carrying particles and ethanol dispersion solution (Flemion produced by Asahi Glass Co. Ltd) of hydrogen-ion conductive polymer electrolyte was mixed and agitated. The hydrogen-ion conductive polymer electrolyte was coated on the surface of each catalyst carrying particles, thereby creating a catalyst layer ink. As the hydrogen-ion conductive polymer electrolyte, an ethanol dispersion solution of perfluorocarbonsulfonic acid of 9 wt % concentration was used. And, the amount of the hydrogen-ion conductive polymer electrolyte with respect to the electrically conductive carbon particles carrying catalyst thereon was 80 wt %. The water was added in order to inhibit combustion of a solvent of the hydrogen-ion conductive electrolyte, which would be caused by the catalyst of the catalyst carrying particles. The water which enables the entire catalyst to become moist, is sufficient in amount as the added water, and the amount is not particularly limited. In the example 1, the water three times as much as the weight of the catalyst was added. And, the cathode and anode catalyst layer inks so created were adjusted so that weight of noble metal contained in a reaction electrode was 0.5 mg/cm2. Thereafter, these catalyst layer inks were coated on the surfaces of polytetrafluoroethylene bases by using a bar coater. The coated catalyst inks were thermally transferred to hydrogen-ion conductive polymer electrolyte membrane (Nafion 112 produced by Du Pont Co. Ltd) having a size of 20 cm×32 cm and further, subjected to thermal treatment at 140° C. for 10 min to adhere thereto. Through the above process, the hydrogen-ion conductive polymer electrolyte membrane having the catalyst layers was produced.
To produce the gas diffusion layer of the electrode, first, gas diffusion layer base was subjected to water-repellent treatment. More specifically, carbon paper (TGP-H-90 produced by TORAY Co. Ltd) which is a gas diffusion layer base having a size of 16 cm×20 cm and a thickness of 270 μm was impregnated in aqueous dispersion (Neoflon ND1 produced by Daikin Industries Co. Ltd) containing fluorocarbon polymers, and then dried. Further, the carbon paper was heated at 350° C. for 30 min to render the carbon paper water-repellent. And, water-repellent carbon layer ink containing a mixture of electrically conductive carbon powders (acethylene black produced by Denki Kagaku Co. Ltd) and an aqueous solution (D-1 produced by Daikin Industries Co. Ltd) with PTFE fine powders dispersed therein, was coated on one of surfaces of the water-repellent carbon paper by using a doctor blade, and further subjected to thermal treatment at 300° C. for 30 min, thereby producing the gas diffusion layer.
A membrane electrode assembly (hereinafter referred to as MEA) was manufactured in such a manner that two gas diffusion layers produced as described above were pressed against the hydrogen-ion conductive polymer electrolyte membrane having the catalyst layers under pressure from both sides by using a hot press with the other surfaces of the water-repellent carbon papers on which the water-repellent carbon ink layers were not coated in contact with the hydrogen-ion conductive polymer electrolyte membrane. In this case, pressing condition of the hot press was set to 120° C.-10 kg/cm2.
After manufacturing the MEA, gaskets were joined to outer peripheral portions of the hydrogen-ion conductive polymer electrolyte membrane of the MEA, and manifold holes were formed on the gaskets to allow cooling water, the fuel gas, and the oxidizing gas to flow therethrough. And, using two separators formed of resin-containing graphite plate having a size of 20 cm×30 cm, and a thickness of 2.0 mm, and provided with gas passages and cooling water passages having a depth of 1.0 mm, a unit cell was created. Specifically, the unit cell was created in such a manner that the separator provided with an oxidizing gas passage was joined to one of the surfaces of the MEA and the separator provided with a fuel gas passage was joined to the other surface of the MEA. Further, 100 unit cells were stacked and stainless current collecting plates and insulating plates made of electric-insulating material were provided on both ends thereof. The resulting stack was fastened by using end plates and fastening rod, thereby manufacturing the polymer electrolyte fuel cell. In this case, a fastening pressure of the fastening rod was 10 kg/cm2 per area of the separator.
Subsequently, a method of manufacturing the impurity removal total enthalpy heat exchanger in the polymer electrolyte fuel cell system employed in the example 1 will be described.
To manufacture the impurity removal total enthalpy heat exchanger, a fibrous phenol based active carbon sheet (Kuractive CH produced by Kuraray Co. Ltd) was used as an impurity removal layer. And, as the hydrogen-ion conductive polymer electrolyte membrane provided in the heat exchnager, a hydrogen-ion conductive polymer electrolyte membrane (Nafion 112 produced by Du Pont Co. Ltd) similar to that of the fuel cell was used. The active carbon sheet was joined to one of the surfaces of the hydrogen-ion conductive polymer electrolyte membrane by using the hot press. In this case, the press condition of the hot press was set to 100° C.-10 kg/cm2. And, the hydrogen-ion conductive electrolyte membrane having the impurity removal layer produced in this manner was sandwiched between separators provided with introducing passages and exhaust passages formed in predetermined shape on the resin-containing graphite plates, thereby manufacturing an impurity removal total enthalpy heat exchange unit. The impurity removal total enthalpy heat exchanger was manufactured by continuously stacking 40 impurity removal total enthalpy heat exchange units. Furthermore, the impurity removal layer recovery heaters were mounted to an entire outer periphery of the impurity removal total enthalpy heat exchanger. The impurity removal layer recovery heaters were energized to heat the impurity removal total enthalpy heat exchanger up to about 120° C. when the impurity removal layer adsorbed impurities of saturated adsorption amount or before the polymer electrolyte fuel cell system started or stopped a power generation operation. This heating decomposed the impurities contained in the impurity removal layer or separated the impurities therefrom. The decomposed substances of the impurities or the separated impurities were discharged to outside of the polymer electrolyte fuel cell system through the three-way valve. In this manner, impurity removing function of the impurity removal layer was restored. In addition, degradation of performance of the polymer electrolyte fuel cell, which would be caused by the separated impurities or the decomposed substances, was inhibited. The oxidizing gas supplied to the polymer electrolyte fuel cell was flowed through the introducing passage present on the side of the impurity removal layer formed on the hydrogen-ion conductive polymer electrolyte membrane, and the oxidizing gas exhausted from the fuel cell was flowed through the exhaust passage which directly contacted the hydrogen-ion conductive polymer electrolyte membrane.
In the cell life test of the polymer electrolyte fuel cell system according to the example 1, a polymer electrolyte fuel cell system constructed by using the polymer electrolyte fuel cell and the impurity removal total enthalpy heat exchanger manufactured as described above, and other desired components, and by piping and joining desired gas manifolds was employed. And, the cell life test was carried out under the condition in which a body of the polymer electrolyte fuel cell was kept at 75° C. by flowing cooling water within the fuel cell, the fuel gas was a simulated gas of a reformed gas (hydrogen concentration: 80%, carbon dioxide concentration: 20%, and carbon monoxide concentration: 20 ppm), the oxidizing gas was air (ambient air) supplied by using a blower, fuel gas utilization ratio (Uf) was 70%, and air utilization ratio (Uo) was 40%. From a test result shown in
In the example 2, in order to produce the impurity removal layer, powdery active carbon (Kuraray coal produced by Kuraray chemical Co. Ltd) and ethanol dispersion solution (Flemion produced by Asahi Glass Co. Ltd) of the hydrogen-ion conductive polymer electrolyte were mixed and agitated, and impurity removal layer ink was adjusted so that a composition of a weight of the hydrogen-ion conductive polymer electrolyte with respect to a weight of the powdery active carbon was 50 wt %. And, the impurity removal layer ink was coated on the polytetrafluoroethylene base by using the bar coater so that the weight of the powdery active carbon was adjusted to be 1.0 mg/cm2. Then, the impurity removal layer ink coated on the polytetrafluoroethylene base was thermally transferred to one surface of the hydrogen-ion conductive polymer electrolyte membrane (Nafion 112 produced by Du Pont Co. Ltd) and further, subjected to thermal treatment at 140° C. for 10 min to adhere thereto. In other process, the impurity removal total enthalpy heat exchanger was manufactured in the method described in the example 1. Using the polymer electrolyte fuel cell system of the example 2, the cell life test was carried out. From a test result shown in
In the example 3, in order to produce the impurity removal layer, powdery active carbon (Kuraray coal produced by Kuraray chemical Co. Ltd), Mordenite (HSZ-690HOA produced by TOSOH Co. Ltd), and ethanol dispersion solution (Flemion produced by Asahi Glass Co. Ltd) of the hydrogen-ion conductive polymer electrolyte were mixed and agitated, and impurity removal layer ink was adjusted so that a composition of a weight of Mordenite with respect to a weight of the powdery active carbon was 30 wt %, and a composition of a weight of the hydrogen-ion conductive polymer electrolyte with respect to a total weight of the powdery active carbon and Mordenite was 50 wt %. And, the impurity removal layer ink was coated on a polytetrafluoroethylene base by using the bar coater so that the total weight of the powdery active carbon and the Mordenite was adjusted to be 1.4 mg/cm2. Then, the impurity removal layer ink coated on the polytetrafluoroethylene base was thermally transferred to one surface of the hydrogen-ion conductive polymer electrolyte membrane (Nafion 112 produced by Du Pont Co. Ltd) and further, subjected to thermal treatment at 140° C. for 10 min to adhere thereto. In other process, the impurity removal total enthalpy heat exchanger was manufactured in the method described in the example 1. Using the polymer electrolyte fuel cell system of the example 3, the cell life test was carried out. From a test result shown in
In the example 4, the impurity removal layer was produced by a mixture containing powdery active carbon (Kuraray coal produced by Kuraray chemical Co. Ltd), platinum, and the hydrogen-ion conductive polymer electrolyte. Specifically, a chloroplatinic acid aqueous solution was dissolved in the aqueous solution with the powdery active carbon suspended therein, and alkaline reagent was added to this suspension for neutralization, thereby carrying Pt (OH)4 on the powdery carbon powder. Thus adjusted suspension was filtered and water-washed repeatedly to allow the impurities to be removed. Thereafter, the obtained powdery active carbon was heated in a reduction atmosphere such as hydrogen atmosphere, thereby carrying platinum particles on the powdery active carbon. Further, the powdery active carbon with the platinum fine powders carried thereon and the ethanol dispersion solution (Flemion produced by Asahi Glass Co. Ltd) of the hydrogen-ion conductive polymer electrolyte were mixed and agitated, and impurity removal layer ink was adjusted so that a composition of a weight of the hydrogen-ion conductive polymer electrolyte with respect to a weight of the powdery active carbon was 50 wt %. And, the impurity removal layer ink was coated on the polytetrafluoroethylene base by using the bar coater so that the weight of the powdery active carbon was adjusted to be 1.0 mg/cm2. Then, the impurity removal layer ink coated on the polytetrafluoroethylene base was thermally transferred to one surface of the hydrogen-ion conductive polymer electrolyte membrane (Nafion 112 produced by Du Pont Co. Ltd) and further, subjected to thermal treatment at 140° C. for 10 min to adhere thereto. In other process, the impurity removal total enthalpy heat exchanger was manufactured in the method described in the example 1. Using the polymer electrolyte fuel cell system of the example 4, the cell life test was carried out. From a test result shown in
(Embodiment 2)
In the second embodiment, as a fluid subjected to total enthalpy heat exchange with the oxidizing gas in the impurity removal total enthalpy heat exchanger 15, cooling water exhausted from the polymer electrolyte fuel cell 1 is used. Specifically, the pipe connecting portion c which is an upstream end of the exhaust passage D (see
In the polymer electrolyte fuel cell system 200 of the second embodiment constructed as described above, the oxidizing gas is subjected to total enthalpy heat exchange with the cooling water which has cooled the polymer electrolyte fuel cell 1 in the impurity removal total enthalpy heat exchanger 15. In this construction, since heat which has been generated during power. generation in the polymer electrolyte fuel cell 1 and recovered by the cooling water is used to heat the oxidizing gas, heat associated with power generation can be efficiently utilized.
In addition, since the cooling water sufficient to humidify the oxidizing gas exhausted from the polymer electrolyte fuel cell 1 is supplied to the impurity removal total enthalpy heat exchanger 15, total enthalpy heat exchange between the oxidizing gas supplied from the air supply device 6 and the cooling water is carried out more reliably.
While the impurity removal total enthalpy heat exchanger 15 and the polymer electrolyte fuel cell 1 are separate from each other in the first and second embodiments, the impurity removal total enthalpy heat exchanger 15 may alternatively be built in or mounted to the polymer electrolyte fuel cell 1. Such a construction can eliminate a pipe connecting the impurity removal total enthalpy heat exchanger 15 to the polymer electrolyte fuel cell 1. Consequently, the polymer electrolyte fuel cell system can be made smaller in size. Moreover, while the polymer electrolyte fuel cell system has been described in the first and second embodiments, the present invention is practicable in and applicable to other types of fuel cell systems.
Numerous modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of the foregoing description. Accordingly, the description is to be construed as illustrative only, and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and/or function may be varied substantially without departing from the spirit of the invention and all modifications which come within the scope of the appended claims are reserved.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-343328 | Oct 2003 | JP | national |
