JP2007207456A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system equipped with a humidifier capable of stably supplying humidified air even at low temperature. <P>SOLUTION: The humidifier 100 has a hollow fiber membrane module 10 consisting of a bunch of hollow fiber membranes coated with a resin layer 12, on an outer periphery of which 12, a metal outer wall layer 16 is put with a constant space set against the resin layer 12. Further, an air heat-insulating layer 14 is formed between the resin layer 12 and the metal outer wall layer 14. An offgas lead-in port 20a, a dry air lead-in port 22a, an offgas drain port 20b, and a humidified air drain port 22b are so made to penetrate the resin layer 12, the air heat-insulating layer 14, and the metal outer wall layer 16, that gas circulation between the outside and the hollow fiber membrane module 10 is possible. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system including a humidifier having strength against low temperature and strength against impact.

  As a fuel cell, for example, there is a solid polymer type fuel cell, and in this solid polymer type fuel cell, a humidifier that exchanges moisture of off-gas, which is a wet gas discharged from the fuel cell, with dry air is used. ing.

  In the conventional humidifier, as shown in FIG. 6, a hollow fiber membrane module 10 composed of a bundle of hollow fiber membranes is accommodated in a metal container 30, and dry air into which dry air is introduced into the container 30. An inlet 22a, an offgas inlet 20a for introducing wet offgas discharged from the fuel cell, an offgas outlet 20b for discharging dry offgas from which moisture has been separated and removed by the hollow fiber membrane module 10, and a hollow fiber A humidified air discharge port 22b for discharging humidified air humidified by the moisture supplied by the membrane module 10 is formed. Furthermore, both ends of the hollow fiber membrane module 10 are bundled and fixed by a bonding material 13. Further, the bonding material 13 separates the gas at the upper and lower ends of the container 30 from the gas at the intermediate portion of the container 30 and separates them.

  Further, in the humidifier 500 shown in FIG. 6, the wet off-gas discharged from the fuel cell is supplied from the off-gas inlet 20a to the space at the lower end of the container 30 partitioned by the bonding material 13. Further, the wet off gas is supplied into the hollow fiber membrane constituting the hollow fiber membrane module 10 whose end is exposed in the space at the lower end. Moisture in the off-gas is separated by the capillary action of the hollow fiber membranes constituting the hollow fiber membrane module 10, passes through the capillaries of the hollow fiber membranes, and moves to the outside of the hollow fiber membranes. The off-gas from which moisture has been separated is discharged from the off-gas outlet 20b as a dry off-gas. On the other hand, the dry air introduced from the dry air introduction port 22 a is supplied to an intermediate portion of the container 30 partitioned by the two bonding materials 13 and passes outside the hollow fiber membrane constituting the hollow fiber membrane module 10. The moisture separated from the wet off-gas has moved to the outside of the hollow fiber membrane, and the dry air is humidified by this moisture and discharged from the humidified air discharge port 22b. The exhausted humidified air is supplied into the fuel cell in order to prevent the solid polymer electrolyte membrane in the fuel cell from being dried and promote the movement of hydrogen ions in the solid polymer electrolyte membrane.

  However, the humidifier 500 shown in FIG. 6 is easily affected by the outside air temperature because the container 30 is made of metal and has good heat transfer properties. For this reason, moisture in the hollow fiber membrane easily freezes at low temperatures, especially in sub-freezing atmospheres, and clogging occurs due to ice. There is a possibility that the start-up time of the fuel cell may be prolonged due to a decrease in the amount of humidified air supplied to the fuel cell with a decrease in the humidity or a decrease in the humidification rate to the dry air.

  In Patent Document 1, a heat generating means for supplying heat to the hollow fiber membrane bundle in the humidifier is provided so that it can be suitably used in cold districts, and the entire fuel cell system including the humidifier is covered with a heat insulating material. The configuration is described.

JP 2001-202979 A

  However, in the configuration of Patent Document 1, since there is a heat generating means, it is necessary to supply further power, and it is difficult to manufacture a compact and economical fuel cell, and the entire fuel cell system is a heat insulating material. Therefore, the size of the fuel cell system itself is increased, which is not compatible with the recent trend toward compactness.

  The present invention has been made in view of the above problems, and provides a fuel cell system including a humidifier that can stably supply humidified air to a fuel cell even at low temperatures and suppresses the cost of measures against low temperatures. To do.

  The fuel cell system of the present invention has the following features.

  (1) The fuel cell system includes a humidifier that is provided with a heat insulating layer on the outer periphery, and is externally provided with a member having a higher strength than a humidifying element provided in the humidifier.

  Since the heat insulating layer is formed on the outer periphery, the humidifying element in the humidifier is not easily affected by the outside air temperature. Furthermore, since it becomes difficult to freeze the residual water in the humidifying element in the humidifier, it is possible to prevent the deterioration of the durability of the humidifying element due to repeated freezing / dissolving as in the prior art. Moreover, since it is armored by a member having higher strength than the humidifying element, it has durability against an impact applied to the humidifier from the outside.

  (2) In the fuel cell system according to (1), the heat insulating layer is an air heat insulating layer.

  Since air has a lower heat transfer property than metal, it is possible to obtain an inexpensive and sufficient heat insulating performance by using an air insulating layer as the heat insulating layer.

  (3) In the fuel cell system according to the above (1) or (2), the outside of the humidifying element is covered with a resin.

  Resin is less heat transferable than metal, so even if the outside air temperature is transmitted through the heat insulation layer, the heat transfer is hindered by the resin outside the humidifying element. It is hard to receive. Therefore, the humidifier can be stably operated even at a low temperature.

  (4) In the fuel cell system according to any one of (1) to (3), the humidifying element is a hollow fiber membrane.

  By making the humidifying element a hollow fiber membrane, water exchange can be performed efficiently.

(5) In a fuel cell system equipped with a humidifier, a hollow fiber membrane is provided inside the humidifier,
A heat insulating layer is provided outside the hollow fiber membrane.

  By using a hollow fiber membrane, not only can a humidifier with high water exchange performance be provided, but by providing a heat insulating layer on the outside of the hollow fiber membrane, the hollow fiber can be affected by the outside air temperature even at low temperatures. There is no fear that the moisture in the membrane will freeze, and humidified air can be discharged stably.

  According to the present invention, a fuel cell system provided with a humidifier that can stably provide humidified air without being affected by the outside air temperature as much as possible even at low temperatures, and that is also resistant to external impacts. Can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
An example of a fuel cell system according to a preferred embodiment of the present invention is as follows.

As shown in FIG. 5, the fuel cell 50 in the fuel cell system 110 is divided into a hydrogen electrode side and an oxygen electrode side with a solid polymer electrolyte membrane 44 interposed therebetween, and a platinum-based catalyst is included therebetween. An electrode is provided, and a hydrogen electrode 46 and an oxygen electrode 42 are formed. Further, hydrogen-rich fuel gas generated from the raw fuel flows through the hydrogen electrode side gas flow path 48, while humidified air humidified by the humidifier 100 as an oxidizing gas flows through the oxygen electrode side gas flow path 40. To do. The solid polymer electrolyte membrane 44 functions as a proton conducting electrolyte. Under the catalyst, protons generated by ionizing hydrogen at the hydrogen electrode 46 move through the solid polymer electrolyte membrane 44 and reach the oxygen electrode 42. . Then, the protons that reach the oxygen electrode 42 immediately react with oxygen ions generated from oxygen in the humidified air under the catalyst to generate water. The generated water is discharged from the oxygen electrode side of the fuel cell 50 as wet off gas which is wet gas together with humidified air. When hydrogen is ionized at the hydrogen electrode 46, the electrons e ⁻ reach the oxygen electrode 42 via an external load M such as a motor. The reason why the humidified humidified air is supplied as an oxidant gas to the fuel cell 50 is to prevent a decrease in power generation efficiency due to a decrease in proton conductivity due to the drying of the solid polymer electrolyte membrane 44. Here, although the fuel cell 50 has been described with a single cell structure, the fuel cell 50 is not limited to a single cell, and may have a stack structure in which a plurality of single cells are stacked.

  Next, the structure of the humidifier 100 will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the same component as the component demonstrated in the prior art, and the description is abbreviate | omitted.

  In the humidifier 100 of the present embodiment, the hollow fiber membrane module 10 composed of a bundle of hollow fiber membranes as a humidifying element is fixed at both ends by a bonding material 13 and entirely covered by a resin layer 12. Further, the bonding material 13 separates the gas at the upper and lower ends of the container 30 from the gas at the intermediate portion of the container 30 and separates them. Furthermore, a metal outer wall layer 16 is provided on the outer periphery of the resin layer 12 so as to open a certain space with respect to the resin layer 12. With the above configuration, the air heat insulating layer 14 is formed between the resin layer 12 and the metal outer wall layer 16. Further, the dry air introduction port 22a, the off gas introduction port 20a, the off gas discharge port 20b, and the humidified air discharge port 22b penetrate the resin layer 12, the air heat insulating layer 14, and the metal outer wall layer 16, and the outside and the hollow fiber membrane. It is arranged so as to allow gas flow with the module 10.

  Since air has a lower heat transferability than metal, by providing the air heat insulating layer 14 described above, it is possible to prevent the influence of the outside air temperature at the low temperature as much as possible. Thereby, there is no possibility that the moisture in the hollow fiber membrane will freeze at low temperatures, especially in an atmosphere below freezing point, and there is no possibility of clogging due to ice. In addition, since there is little possibility that the movement speed of moisture in the hollow fiber membrane module 10 decreases even at low temperatures, the humidification rate to the dry air can be kept constant, and a predetermined amount of humidification air is supplied to the fuel cell. Since it can supply stably, there is no possibility that the starting time of a fuel cell may become long.

  Here, water exchange in the humidifier will be described. In the humidifier 100 shown in FIG. 1, wet off-gas discharged from the fuel cell is supplied from the off-gas introduction port 20 a to the space at the lower end of the container 30 partitioned by the bonding material 13. Further, the wet off gas is supplied into the hollow fiber membrane constituting the hollow fiber membrane module 10 whose end is exposed in the space at the lower end. Moisture in the off-gas is separated by the capillary action of the hollow fiber membranes constituting the hollow fiber membrane module 10, passes through the capillaries of the hollow fiber membranes, and moves to the outside of the hollow fiber membranes. The off-gas from which moisture has been separated is discharged from the off-gas outlet 20b as a dry off-gas. On the other hand, the dry air introduced from the dry air introduction port 22 a is supplied to an intermediate portion of the container 30 partitioned by the two bonding materials 13 and passes outside the hollow fiber membrane constituting the hollow fiber membrane module 10. The moisture separated from the wet off-gas has moved to the outside of the hollow fiber membrane, and the dry air is humidified by this moisture and discharged from the humidified air discharge port 22b. The exhausted humidified air is supplied into the fuel cell in order to prevent the solid polymer electrolyte membrane in the fuel cell from being dried and promote the movement of hydrogen ions in the solid polymer electrolyte membrane. In the humidifier 100 described above, the configuration in which the wet off gas is introduced into the hollow fiber membrane and the dry air is allowed to pass through the outside of the hollow fiber membrane has been described. Water exchange may be performed by introducing dry air into the membrane and passing wet off-gas outside the hollow fiber membrane and utilizing the capillary action of the hollow fiber membrane. That is, a configuration may be adopted in which wet off-gas is supplied from the dry air introduction port 22a shown in FIG. 1, while dry air is introduced from the wet off-gas introduction port 20a. The same applies to the second, third, and fourth embodiments described later.

  The resin layer 12 is preferably a resin with high hardness such as an acrylic resin, an epoxy resin, or an alkyd resin. The metal outer wall layer 16 is preferably selected in consideration of durability against impact and workability, and for example, stainless steel, aluminum and alloys thereof are preferable. Moreover, the material of the metal outer wall layer 16 is preferably one having lower thermal conductivity than copper.

  The thickness of the air heat insulating layer 14 is 0.5 mm to 20 cm, preferably 1 mm to 10 cm. If the thickness is less than 0.5 mm, a sufficient heat insulation effect cannot be obtained, and if it exceeds 20 cm, the humidifier itself becomes large and a compact fuel cell system cannot be formed.

[Second Embodiment]
Another example of the humidifier in another fuel cell system 110 according to the preferred embodiment of the present invention will be described below with reference to FIG. In addition, the same code | symbol is attached | subjected to the component same as the component demonstrated in the prior art and the said 1st Embodiment, and the description is abbreviate | omitted.

  In the humidifier 200 of the present embodiment, the air heat insulating layer 14 of the humidifier 100 of the first embodiment shown in FIG. 1 is replaced with the porous heat insulating layer 34 of the first embodiment. The configuration is the same as that of the humidifier 100.

  The porous body has air in the air gap, and the heat transfer property decreases in the order of metal, porous body, and air. Therefore, heat insulation can be obtained by forming the porous heat insulating layer 34 inside the metal outer wall layer 16. Furthermore, the material of the porous body heat insulating layer 34 is a sponge-like porous resin such as urethane foam, and by setting the porosity to 50% or more, the heat transfer property can be lowered. Since the shock absorbing ability is also improved, the desired heat insulating property can be obtained and the shock absorbing ability can be exhibited even with a thickness thinner than that of the air heat insulating layer 14 shown in FIG. Further, the metal outer wall layer 16 is a metal exterior, and is made of a member having higher strength than the porous body heat insulating layer 34. Therefore, it is more difficult to be deformed with respect to an impact and the impact absorbing ability is high.

[Third Embodiment]
Another example of the humidifier in another fuel cell system 110 according to the preferred embodiment of the present invention will be described below with reference to FIG. In addition, the same code | symbol is attached | subjected to the component same as the component demonstrated in the prior art and the said 1st, 2nd embodiment, and the description is abbreviate | omitted.

  In the humidifier 300 of the present embodiment, the resin layer 12 in the humidifier 100 of the first embodiment shown in FIG. 1 is replaced with the metal inner layer 36, and the metal outer wall layer 16 of the humidifier 100 is the resin outer wall layer. The configuration is the same as that of the humidifier 100 according to the first embodiment except that 32 is used.

  In the humidifier 300 of the present embodiment, the outermost layer is the resin outer wall layer 32 made of resin. Since the resin has lower heat transferability than the metal, the humidifier 300 can suppress the heat conductivity from the outer wall layer. Furthermore, the air in the air heat insulation layer 14 has extremely low heat transferability compared to metals and resins. Therefore, in the humidifier 300, the resin outer wall layer 32 and the air heat insulating layer 14 have a sufficient heat insulating effect, and even if the outer periphery of the hollow fiber membrane module 10 is covered with the metal inner layer 36, the heat insulating property is sufficient. Can be secured. Further, by covering the hollow fiber membrane module 10 with the metal inner layer 36, the hollow fiber membrane module 10 can be sufficiently prevented from being damaged by an external impact.

  The resin outer wall layer 32 is preferably a resin with high hardness such as an acrylic resin, an epoxy resin, or an alkyd resin. The metal inner layer 36 is preferably selected in consideration of durability against impact and workability, and for example, stainless steel, aluminum and alloys thereof are preferable. Moreover, the material of the metal inner layer 36 is preferably one having lower thermal conductivity than copper.

[Fourth Embodiment]
Another example of the humidifier in another fuel cell system 110 according to the preferred embodiment of the present invention will be described below with reference to FIG. In addition, the same code | symbol is attached | subjected to the component same as the component demonstrated in the prior art and the said 1st, 2nd, 3rd embodiment, and the description is abbreviate | omitted.

  In the humidifier 400 of the present embodiment, the air heat insulating layer 14 of the humidifier 300 of the third embodiment shown in FIG. 3 is replaced with the porous heat insulating layer 34 of the third embodiment. The configuration is the same as that of the humidifier 300.

  As described above, the porous body has air in the air gap, and the heat transfer property decreases in the order of metal, porous body, and air. Therefore, by forming the porous heat insulation layer 34 inside the resin outer wall layer 32, more heat insulation can be obtained as compared with the humidifier 200 of the second embodiment. Furthermore, when the material of the porous body heat insulating layer 34 is a sponge-like porous resin such as urethane foam, the heat transferability can be lowered by setting the porosity to 50% or more. Since the shock absorbing ability is also improved, the desired heat insulating property can be obtained and the shock absorbing ability can be exhibited even with a thickness thinner than that of the air heat insulating layer 14 shown in FIG. Further, the resin outer wall layer 32 is made of a member having higher strength than the porous body heat insulating layer 34. Therefore, it is more difficult to be deformed with respect to an impact and the impact absorbing ability is high.

  As described above, the inner layer and the outer wall layer covering the hollow fiber membrane module 10 have been exemplified by the ones made of metal and resin, but are not limited to this, and either or both of the inner layer and the outer wall layer are ceramic. May be. Air transferability decreases in the order of metal, ceramic, porous body, and air. Therefore, it is preferable to appropriately use a ceramic material in consideration of heat insulation and the weight of the humidified humidifier.

  The fuel cell system of the present invention is effective for any application as long as it uses a fuel cell, but can be used particularly for a fuel cell for vehicles.

It is a schematic sectional drawing which shows the structure of the humidifier 100 of this Embodiment. It is a schematic sectional drawing which shows the structure of the humidifier 200 of this Embodiment. It is a schematic sectional drawing which shows the structure of the humidifier 300 of this Embodiment. It is a schematic sectional drawing which shows the structure of the humidifier 400 of this Embodiment. It is a figure which shows an example of the structure of the fuel cell system of this invention. It is a schematic sectional drawing which shows the structure of the conventional humidifier.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Hollow fiber membrane module, 12 Resin layer, 13 Bonding material, 14 Air heat insulation layer, 16 Metal outer wall layer, 20a Off-gas inlet, 20b Off-gas outlet, 22a Dry air inlet, 22b Humidified air outlet, 32 Resin outer wall Layer, 34 porous heat insulation layer, 36 metal inner layer, 40 oxygen electrode side gas flow path, 42 oxygen electrode, 44 solid polymer electrolyte membrane, 46 hydrogen electrode, 48 hydrogen electrode side gas flow path, 50 fuel cell, 100 , 200, 300, 400 Humidifier, 110 Fuel cell system.

Claims (5)

  A fuel cell system comprising a humidifier that is provided with a heat insulating layer on an outer periphery, and is externally provided with a member having higher strength than a humidifying element provided in the humidifier. The fuel cell system according to claim 1, wherein
The fuel cell system, wherein the heat insulation layer is an air heat insulation layer. The fuel cell system according to claim 1 or 2,
A fuel cell system in which an outside of the humidifying element is coated with a resin. In the fuel cell system according to any one of claims 1 to 3,
The fuel cell system, wherein the humidifying element is a hollow fiber membrane. In a fuel cell system equipped with a humidifier,
A hollow fiber membrane is provided inside the humidifier,
A fuel cell system in which a heat insulating layer is provided outside the hollow fiber membrane.

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