JP2007257891A - Steam exchange film, humidifier, and fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steam exchange film used in a humidifier in which shortage of humidification of dry gas is improved. <P>SOLUTION: This is a steam exchange film 10 used in a humidifier 1 to carry out steam exchange between wet gas and dry gas, and a water absorption material 16 having a higher water absorption performance than the steam exchange film is dispersed in the steam exchange film. Since the water absorption material 16 is dispersed in the steam exchange film 10, moisture in the wet gas is absorbed and stored efficiently in the steam exchange film 10. On the other hand, the dry gas entered from the entrance into a dry gas passage 14 contacts the other face (dry gas passage 14 side) of the steam exchange film 10, and thereby moisture stored in the steam exchange film 10 is supplied to the dry gas. The wet gas is a fuel cell off-gas and the dry gas is a fuel cell supply gas. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a water vapor exchange membrane, and a humidifier and a fuel cell system using the same.

  There are various types of humidifiers such as a heating method, an ultrasonic method, a vaporization method, a bubbler method, and a water vapor exchange method. Among them, a humidifier using a water vapor exchange system absorbs moisture contained in a wet gas by a water vapor exchange membrane, which is a polymer membrane having fine pores, and supplies moisture to the dry gas. For example, humidity in a fuel cell It has been put to practical use as a humidifier to ensure

  In general, a fuel cell has an electrolyte membrane, a fuel electrode (anode electrode), an air electrode (cathode electrode), and an external circuit. When the fuel cell generates power, the fuel gas supplied to the fuel electrode is hydrogen gas, air electrode When the oxidizing gas supplied to the air is air, the fuel electrode side reacts with hydrogen ions and electrons, the hydrogen ions move through the electrolyte membrane to the air electrode side, and the electrons pass through the external circuit to the air electrode. In the air electrode side, hydrogen ions, electrons and oxygen react to generate water, and energy is released.

  In the fuel cell, it is necessary to appropriately humidify the electrolyte membrane in order to maintain ionic conductivity. Therefore, a humidifier is provided to humidify the fuel cell supply gas (meaning at least one of fuel gas and oxidizing gas) as a dry gas. Humidification of the fuel cell supply gas by the steam exchange type humidifier is, for example, a fuel cell off-gas as a wet gas containing moisture generated by a power generation reaction of the fuel cell (a fuel off-gas discharged by the fuel cell reaction, an oxidizing off-gas) The water content absorbed by the water vapor exchange membrane is supplied to the fuel cell supply gas as a dry gas.

  However, in the transition period from low load power generation to high load power generation of fuel cells, the water vapor exchange membrane used in conventional humidifiers (hereinafter referred to as “humidifiers”) has a low water absorption performance. The electrolyte membrane is dried due to insufficient humidification of the fuel cell supply gas by the humidifier against the increase in the supply amount of the fuel cell supply gas due to insufficient water absorption from the battery off gas, and the ionic conductivity of the electrolyte membrane There is a problem that the power generation performance is lowered without maintaining the power.

  On the other hand, in Patent Document 1, by providing a water retention layer on the surface of the water vapor exchange membrane used in the humidifier, moisture in the oxidizing offgas containing water is efficiently taken into the water vapor exchange membrane, and the oxidizing gas is absorbed. Humidifiers that humidify have been proposed.

JP 2004-55526 A

  However, in Patent Document 1, during the transition period from low load power generation to high load power generation of the fuel cell, the surface of the water vapor exchange membrane is covered with a water retention layer, which hinders the movement of moisture inside the water vapor exchange membrane. Therefore, there is a problem that the oxidizing gas is not sufficiently humidified.

  The present invention provides a water vapor exchange membrane for improving deficiency of dry gas in a water vapor exchange membrane used in a humidifier, and a humidifier and a fuel cell system using the same.

  The present invention is a water vapor exchange membrane used in a humidifier that performs water vapor exchange between a wet gas and a dry gas, and a water absorbent material having higher water absorption than the water vapor exchange membrane is provided inside the water vapor exchange membrane. It is dispersed.

  The wet gas is preferably a fuel cell off gas, and the dry gas is preferably a fuel cell supply gas.

  The present invention also provides a wet gas passage through which the wet gas passes, a dry gas passage through which the dry gas passes, and moisture from the wet gas that passes through the wet gas passage, and the moisture into the dry gas that passes through the dry gas passage. And a water vapor exchange membrane in which a water absorbing material having a higher water absorption than the water vapor exchange membrane is dispersed inside the water vapor exchange membrane.

  A fuel cell stack for generating power by supplying fuel cell supply gas and discharging fuel cell off gas; a wet gas passage for passing the fuel cell off gas; a dry gas passage for passing the fuel cell supply gas; and the wet gas passage. A fuel cell system comprising a humidifier having a water vapor exchange membrane that absorbs water from the fuel cell off-gas passing therethrough and supplies the water to the fuel cell supply gas passing through the dry gas passage, And a water vapor exchange membrane in which a water absorbing material having higher water absorption than the water vapor exchange membrane is dispersed.

  In the water vapor exchange membrane according to the present invention, the lack of humidification of the dry gas can be improved by dispersing the water absorbing material inside the water vapor exchange membrane.

  In the humidifier according to the present invention, by having the water vapor exchange membrane in which the water-absorbing material is dispersed inside the water vapor exchange membrane, dampening of the dry gas can be improved.

  In the fuel cell system according to the present invention, the lack of humidification of the fuel cell supply gas as the dry gas can be improved by having the water vapor exchange membrane in which the water absorbing material is dispersed in the water vapor exchange membrane.

  Embodiments of the present invention will be described below.

  FIG. 1 is a schematic cross-sectional view showing an example of a humidifier having a water vapor exchange membrane according to an embodiment of the present invention. The humidifier 1 includes a water vapor exchange membrane 10, a wet gas passage 12 through which one side of the water vapor exchange membrane 10 passes wet gas, and a dry gas through which the other side of the water vapor exchange membrane 10 passes. A dry gas passage 14 and an outer frame member 18 are provided. The wet gas passage 12 and the dry gas passage 14 are secured by forming grooves in the outer frame member 18. The grooves formed in the outer frame member 18 shown in FIG. 1 have a comb shape, but are not limited to this, and any groove can be used as long as the wet gas passage 12 and the dry gas passage 14 are secured. . Further, the water vapor exchange membrane 10 includes a water absorbing material 16 in the water vapor exchange membrane 10. Here, the wet gas is a gas containing more water vapor than the dry gas.

  With reference to FIG. 1, the function of water vapor exchange of the humidifier 1 having the water vapor exchange membrane 10 according to the embodiment of the present invention will be described. The wet gas that has entered the wet gas passage 12 from the inlet contacts one surface of the water vapor exchange membrane 10 (the wet gas passage 12 side), and moisture in the wet gas is absorbed into the water vapor exchange membrane 10. Since the water-absorbing material 16 is dispersed in the water vapor exchange membrane 10, the moisture in the wet gas is efficiently absorbed and stored in the water vapor exchange membrane 10. On the other hand, when the dry gas that has entered the dry gas passage 14 from the entrance contacts the other surface (the dry gas passage 14 side) of the water vapor exchange membrane 10, moisture stored in the water vapor exchange membrane 10 is dried. Supplied to the gas. Since the moisture is supplied to the dry gas, the moisture concentration in the water vapor exchange membrane 10 on the dry gas passage 14 side decreases and a concentration gradient is generated. Therefore, the water in the water vapor exchange membrane 10 in the direction indicated by the broken line arrow in FIG. And water vapor exchange is continuously performed between the wet gas and the dry gas.

  The water vapor exchange membrane 10 is not particularly limited as long as it can transmit water vapor from one side of the membrane to the other side, but heat resistance, strength resistance, chemical resistance and water absorption are not limited. A material that easily disperses the material 16 in the water vapor exchange membrane 10 is preferable. For example, a porous body of polyolefin resin such as polyethylene and polypropylene, a porous body such as polycarbonate, polystyrene, polyvinyl chloride, polyenevinylidene, polyester, and polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer And a porous body of a fluororesin such as polyvinyl fluoride and polyvinylidene fluoride, and a fluorine-based sulfonic acid polymer ion exchange membrane, for example, Goreselect (registered trademark) of Japan Gore-Tex Co., Ltd., DuPont (Du) (Pont) Nafion (registered trademark), a porous hollow fiber membrane and the like can be used.

  The average pore diameter of the fine pores of the water vapor exchange membrane 10 is not particularly limited as long as it can hold the water absorbing material 16. When the average pore diameter is small, it is difficult to disperse the water absorbent material 16, and when the average pore diameter is large, it may be difficult to hold the water absorbent material 16. If the average porosity is small, the moisture transfer efficiency in the water vapor exchange membrane 10 is lowered due to a decrease in moisture permeability, and if the average porosity is large, the strength of the water vapor exchange membrane 10 may be reduced. Further, when the film thickness is thin, the strength of the water vapor exchange membrane 10 is reduced, and when it is thick, the moisture transfer rate in the water vapor exchange membrane 10 may be reduced due to a decrease in moisture permeability.

  The water absorbing material 16 used in the present invention is not particularly limited as long as it has higher water absorption than the water vapor exchange membrane 10. Specific examples of the water-absorbing material 16 include one or more of a polyacrylic acid sodium crosslinked product, a methyl acrylate-vinyl acetate copolymer saponified product, a starch-acrylic acid graft polymer, and a starch-acrylonitrile graft polymer. It is preferable that it is a mixture.

  The outer frame member 18 is impervious to wet gas and dry gas, and is not particularly limited as long as it secures the wet gas passage 12 and the dry gas passage 14. , Metal plate, laminate film, resin and the like.

  The humidifier 1 is preferably one in which the water vapor exchange membrane 10 and the outer frame material 18 are integrally formed. Further, the humidifier 1 may be one cell and a plurality of layers may be laminated.

  By dispersing the water absorbing material 16 having higher water absorption than the water vapor exchange membrane 10 in the water vapor exchange membrane 10, moisture in the wet gas is efficiently taken into the water vapor exchange membrane 10, and moisture is supplied to the dry gas. It is possible to perform the steam exchange. The humidifier 1 having the water vapor exchange membrane 10 according to the present embodiment having such a function can be used for an apparatus that requires stable water vapor exchange even when the flow rate of the dry gas is rapidly increased. It is. For example, as described above, in order to maintain the ionic conductivity of the electrolyte membrane used in the fuel cell, it is necessary to appropriately humidify the fuel cell supply gas. During the transition period, the amount of fuel cell supply gas supplied to the fuel cell increases, and the conventional humidifier tends to cause insufficient humidification of the reaction gas, which causes a problem of reducing the power generation reaction due to drying of the electrolyte membrane. . However, by providing the fuel cell with the humidifier 1 having the water vapor exchange membrane 10 according to the embodiment of the present invention, the lack of humidification of the fuel cell supply gas that occurs during the transition from the low output of the fuel cell to the high output power generation is improved. can do.

  FIG. 2 shows an outline of an example of a fuel cell system provided with a humidifier having a water vapor exchange membrane according to an embodiment of the present invention, which will be described below.

  A fuel cell system 3 including a humidifier having a water vapor exchange membrane according to an embodiment of the present invention includes a fuel cell stack 20, a high pressure gas tank 22 (high pressure hydrogen tank), an air blower 28, humidifiers 2a and 2b, and piping. Have.

  The fuel cell stack 20 is formed by stacking one or a plurality of, for example, 100 fuel cells. The fuel cell is a solid polymer fuel cell having a solid polymer electrolyte membrane, an air electrode (cathode electrode) sandwiching the membrane, a fuel electrode (anode electrode), and a separator disposed outside each electrode. .

  As shown in FIG. 2, on the anode side of the fuel cell stack 20, the piping is a fuel gas supply path 24 a that connects the outlet of the high-pressure gas tank 22 and the gas supply port (not shown) of the humidifier 2 a, and the humidification A fuel gas supply path 24b connecting a gas discharge port (not shown) of the vessel 2a and a fuel gas inlet of the fuel cell stack 20, a fuel gas outlet of the fuel cell stack 20, and an off-gas supply port (not shown) of the humidifier 2a And a fuel gas discharge path 26b discharged from the off-gas discharge port (not shown) of the humidifier 2a to the outside of the fuel cell system 3. On the other hand, on the cathode electrode side of the fuel cell stack 20, an oxidizing gas supply path 30a connecting the discharge side of the air blower 28 and a gas supply port (not shown) of the humidifier 2b, and a gas discharge port (see FIG. (Not shown) and an oxidizing gas supply path 30b for connecting the oxidizing gas inlet of the fuel cell stack 20 to the oxidizing gas outlet of the fuel cell stack 20 and an off gas supply port (not shown) of the humidifier 2b. And an oxidizing gas discharge path 32b that is discharged out of the fuel cell system 3 from an off-gas discharge port (not shown) of the humidifier 2b.

  Next, the flow of the fuel cell supply gas during power generation of the fuel cell stack 20 will be described with reference to FIG. The fuel gas supplied from the high-pressure gas tank 22 passes through the fuel gas supply path 24a, is introduced into the humidifier 2a from the gas supply port, and is humidified by the humidifier 2a (a humidification method will be described later). Is discharged from the gas discharge port, supplied to the fuel cell stack 20 from the fuel gas inlet through the fuel gas supply path 24b, and used for power generation of the fuel cell stack 20. The remaining amount of the fuel gas used for power generation is discharged from the fuel gas outlet as fuel offgas, passes through the fuel gas discharge path 26a, and is introduced into the humidifier 2a from the offgas supply port. The water in the fuel off-gas introduced into the humidifier 2a is supplied to the fuel gas, and the fuel off-gas is discharged out of the fuel cell system 3 from the off-gas discharge port through the fuel gas discharge path 26b. On the other hand, the oxidizing gas supplied from the air blower 28 passes through the oxidizing gas supply path 30a, is introduced into the humidifier 2b from the gas supply port, and is humidified by the humidifier 2b (humidifying method). Is discharged from the gas discharge port, passes through the oxidizing gas supply path 30b, is supplied to the fuel cell stack 20 from the oxidizing gas inlet, and is used for power generation of the fuel cell stack 20. The remaining portion of the oxidizing gas used for power generation is discharged as an oxidizing off gas from the oxidizing gas outlet, passes through the oxidizing gas discharge path 32a, and is introduced into the humidifier 2b from the off gas supply port. Moisture in the oxidizing off gas introduced into the humidifier 2b is supplied to the oxidizing gas, and the oxidizing off gas is discharged out of the fuel cell system 3 through the oxidizing exhaust gas passage 32b from the off gas discharge port.

  The fuel cell system 3 including the humidifiers 2a and 2b having the water vapor exchange membrane according to the present embodiment is not limited to this. For example, the fuel off-gas is used again as a fuel gas by providing a circulation path. It may be. Further, for example, the oxidizing off-gas is preferably discharged out of the fuel cell system 3 through the oxidizing gas discharge path 32b, but the oxidizing off-gas passing through the oxidizing gas discharge path 32b is supplied to the air blower 28. It may be. Furthermore, it is not always necessary to provide both the humidifiers 2a and 2b, and either one may be provided.

  FIG. 3 shows an example of the humidifiers 2a and 2b used in the fuel cell system 3.

  The humidifiers 2a and 2b have the same structure as the humidifier 1 shown in FIG. 1, and include a water vapor exchange membrane 34 and a wet gas passage 36 through which the fuel cell off-gas passes through one surface of the water vapor exchange membrane 34. And a dry gas passage 38 through which the fuel cell supply gas passes through the other surface of the water vapor exchange membrane 34, and an outer frame member 42. The wet gas passage 36 and the dry gas passage 38 are secured by forming grooves in the outer frame member 42. The grooves formed in the outer frame member 42 shown in FIG. 3 have a comb shape, but are not limited to this, and any groove may be used as long as the wet gas passage 36 and the dry gas passage 38 are secured. . Further, the water vapor exchange membrane 34 has a water absorbing material 40 in the water vapor exchange membrane 34. The fuel cell supply gas means at least one of fuel gas and oxidizing gas, and the fuel cell off gas means at least one of fuel off gas and oxidizing off gas.

  Since water is generated by the power generation reaction in the fuel cell stack 20, the fuel cell off-gas passing through the fuel gas discharge path 26a and the oxidizing gas discharge path 32a is supplied to the humidifiers 2a and 2b in a state of containing moisture from the off-gas supply port. It is introduced into the wet gas passage 36. The introduced fuel cell off-gas comes into contact with the surface of the water vapor exchange membrane 34 (wet gas passage 36 side) provided inside the humidifiers 2a and 2b, and the water content in the fuel cell off-gas is absorbed by the water vapor exchange membrane 34. The fuel cell off-gas is discharged from the off-gas discharge port to the fuel gas discharge path 26b and the oxidizing gas discharge path 32b. Since the water absorbing material 40 is dispersed in the water vapor exchange membrane 34, the water in the fuel cell off-gas is efficiently absorbed and stored in the water vapor exchange membrane 34. On the other hand, the fuel cell supply gas passing through the fuel gas supply passage 24a and the oxidizing gas supply passage 30a is introduced into the dry gas passage 38 of the humidifiers 2a and 2b. The introduced fuel cell supply gas contacts the surface of the water vapor exchange membrane 34 (on the dry gas passage 38 side) provided inside the humidifiers 2a and 2b from the gas supply port, and is stored in the water vapor exchange membrane 34. The fuel cell supply gas humidified with moisture is discharged from the gas discharge port to the fuel gas supply passage 24b and the oxidizing gas supply passage 30b. The fuel cell supply gas humidified in this way is supplied to the fuel cell stack 20, and the ionic conductivity of the electrolyte membrane is maintained by humidifying the electrolyte membrane.

  The water vapor exchange membrane 34 is not particularly limited as long as it can transmit water vapor from one surface of the membrane to the other surface, and may be the same as the water vapor exchange membrane 10 described above.

  The average pore diameter of the micropores of the water vapor exchange membrane 34 is not particularly limited as long as the water-absorbing material 40 can be retained, and may be the same as the average pore size of the micropores of the water vapor exchange membrane 10. When the average pore diameter is small, it is difficult to disperse the water absorbent material 40, and when the average pore diameter is large, it may be difficult to hold the water absorbent material 40. Further, the average porosity may be the same as the average porosity of the water vapor exchange membrane 10, but if the average porosity is small, the moisture transfer in the water vapor exchange membrane 10 is caused by a decrease in moisture permeability. In some cases, it may be difficult to stably supply moisture to the fuel cell supply gas in the transition period from the low output of the fuel cell stack 20 to the high output power generation. Further, if the average porosity is large, the strength of the water vapor exchange membrane 34 is reduced, and if the water vapor exchange membrane 34 is broken, not only the functions of the humidifiers 2a and 2b are lowered, but also the power generation performance of the fuel cell stack 20 is achieved. May also interfere. Further, the film thickness may be the same as that of the water vapor exchange membrane 10, but particularly when used in the fuel cell system 3, if the film thickness is thin, the strength of the water vapor exchange membrane 34 decreases, and thus If the film thickness is thick, the moisture permeability may be lowered and the same problem as described above may be caused.

  The water-absorbing material 40 is not particularly limited as long as it has higher water absorption than the water vapor exchange membrane 34, and may be the same as the water-absorbing material 16, but is particularly used in the fuel cell system 3. In this case, it is necessary to stably supply moisture to the fuel cell supply gas even in the transition period from the low output power generation to the high output power generation of the fuel cell stack 20. The particle diameter of the water absorbent material 40 may be the same as that of the water absorbent material 16. Further, if the content of the water absorbing material 40 is small, efficient water absorption from the fuel cell off-gas is not performed, and if the content is large, the movement of moisture between the water vapor exchange membranes 34 is hindered. In the transition period from high power generation to high power generation, moisture cannot be stably supplied to the fuel cell supply gas.

  The outer frame member 42 is impermeable to the fuel cell supply gas and the fuel cell off gas, and is not particularly limited as long as the wet gas passage 36 and the dry gas passage 38 are secured. For example, a metal plate, a laminate film, resin, etc. are mentioned.

  The humidifiers 2 a and 2 b are preferably formed by integrating the water vapor exchange membrane 34 and the outer frame material 42. Further, the humidifiers 2a and 2b may be one cell and a plurality of cells may be stacked.

  As described above, the humidifier having the water vapor exchange membrane according to the embodiment of the present invention has the water vapor exchange membrane in which the water-absorbing material is dispersed in the water vapor exchange membrane, so that moisture in the wet gas is efficiently contained. Water is absorbed and stored in the water vapor exchange membrane, enabling stable water vapor exchange. In particular, when used in a fuel cell system, stable steam exchange can be performed even during a transition period from low output to high output power generation of the fuel cell, preventing insufficient humidification of the fuel cell supply gas, A decrease in power generation reaction of the fuel cell due to drying can be prevented.

  Further, the humidifier having a water vapor exchange membrane according to the above-described embodiments is, for example, for a fuel cell used as a small power source for mobile devices such as a mobile phone and a portable personal computer, a power source for automobiles, a household power source, etc. It can be used as a humidifier.

It is the schematic which shows an example of the humidifier which has a water vapor exchange membrane which concerns on embodiment of this invention. It is the schematic which shows an example of a structure of the fuel cell system provided with the humidifier which has the water vapor exchange membrane which concerns on embodiment of this invention. An example of the humidifiers 2a and 2b used in the fuel cell system 3 is shown.

Explanation of symbols

  1, 2a, 2b Humidifier, 3 Fuel cell system, 10, 34 Water vapor exchange membrane, 12, 36 Wet gas passage, 14, 38 Dry gas passage, 16, 40 Water absorbing material, 18, 42 Outer frame material, 20 Fuel Battery stack, 22 High pressure gas tank (high pressure hydrogen tank), 24a, 24b Fuel gas supply path, 26a, 26b Fuel gas discharge path, 28 Air blower, 30a, 30b Oxidative gas supply path, 32a, 32b Oxidative gas discharge path.

Claims (4)

A steam exchange membrane used in a humidifier that performs steam exchange between a wet gas and a dry gas,
A water vapor exchange membrane, wherein a water absorbing material having a higher water absorption than the water vapor exchange membrane is dispersed inside the water vapor exchange membrane.   The water vapor exchange membrane according to claim 1, wherein the wet gas is a fuel cell off-gas and the dry gas is a fuel cell supply gas. A wet gas passage for passing a wet gas, a dry gas passage for passing a dry gas, and a water vapor exchange membrane for absorbing moisture from the wet gas passing through the wet gas passage and supplying the moisture to the dry gas passing through the dry gas passage A humidifier comprising:
A humidifier comprising a water vapor exchange membrane in which a water absorbing material having a higher water absorption than the water vapor exchange membrane is dispersed inside the water vapor exchange membrane. A fuel cell stack that generates electric power by supplying a fuel cell supply gas and discharges the fuel cell off gas; a wet gas passage that passes the fuel cell off gas; a dry gas passage that passes the fuel cell supply gas; and the wet gas passage. A fuel cell system comprising a humidifier having a water vapor exchange membrane that absorbs moisture from the fuel cell off-gas passing therethrough and supplies the moisture to the fuel cell supply gas passing through the dry gas passage,
A fuel cell system comprising a water vapor exchange membrane in which a water absorbing material having higher water absorption than the water vapor exchange membrane is dispersed inside the water vapor exchange membrane.

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