JP2007214062A - Fuel gas humidifying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel gas humidifying device capable of preventing condensed water from flowing into a fuel cell and efficiently humidifying a fuel gas. <P>SOLUTION: This fuel gas humidifying device is one in a fuel cell system S equipped with the fuel cell FC to generate power by reaction of a fuel gas and an oxidizer gas, a fuel tank to supply the fuel gas to the fuel cell FC, a circulation passage forming a passage to circulate an exhaust fuel gas exhausted from the fuel cell FC to the upstream side of the fuel cell, and a fuel gas mixing and circulating means to mix the fuel gas supplied from the fuel tank with the exhaust fuel gas and to circulate it in the circulation passage. The fuel gas humidifying device is equipped with a porous material in the inside of the circulation passage, the porous material holds condensed water in the circulation passage, and the fuel gas passing through the porous material is humidified by the condensed water. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a humidifier used in a fuel cell system, and more particularly to a humidifier that humidifies fuel gas (hereinafter also referred to as “hydrogen”).

  In recent years, research and development have been actively conducted on fuel cell systems mounted on fuel cell vehicles and the like. In a fuel cell system, in a fuel cell that is a main part of the fuel cell system, power generation is performed by an electrochemical reaction between hydrogen and an oxidant gas (oxygen in the air; hereinafter, also representatively referred to as “air”). In particular, in a polymer electrolyte fuel cell or the like, a device for humidifying the gas supplied to the fuel cell is required due to its characteristics.

  For this reason, many humidifiers that humidify the oxidant gas have been used in the past. However, with the recent increase in the temperature of fuel cells, a humidifier that humidifies the fuel gas has become necessary.

For example, Patent Document 1 discloses a technique for humidifying hydrogen supplied to a fuel cell using moisture (hydrogen discharged) immediately after being discharged from the fuel cell in a fuel cell system.
Japanese Patent Laying-Open No. 2004-111268 (paragraph 0013, FIG. 1)

However, the technique disclosed in Patent Document 1 has a problem that the condensed water generated in the fuel cell passes through the circulation path and flows into the fuel cell again.
In addition, moisture hardly accumulates in the hollow fiber membrane in the humidifying device, and moisture is immediately discharged out of the humidifying device together with the discharged hydrogen, which makes it impossible to efficiently humidify.

  Therefore, the present invention has been made in view of the above problems, and provides a fuel gas humidifier that can prevent the inflow of condensed water into the fuel cell and efficiently humidify the fuel gas. For the purpose.

  In order to solve the above-mentioned problems, a fuel gas humidifier according to the present invention according to claim 1 is a fuel cell that generates power by a reaction between a fuel gas and an oxidant gas, a fuel tank that supplies fuel gas to the fuel cell, a fuel A circulation path that is a path for circulating the exhaust fuel gas discharged from the battery upstream of the fuel cell, and a fuel gas mixing and circulation means that mixes the fuel gas supplied from the fuel tank with the exhaust fuel gas and circulates in the circulation path And a fuel gas humidifier in a fuel cell system. The fuel gas humidifier includes a porous material inside the circulation path, the porous material holds the condensed water in the circulation path, and humidifies the fuel gas passing through the porous material with the condensed water. .

According to the fuel gas humidifier of the present invention according to claim 1, since the porous material captures (and holds the condensed water in the circulation path), the inflow of the condensed water into the fuel cell is prevented. This improves the power generation stability and durability of the fuel cell.
Further, by holding condensed water in the porous material, the contact area between the fuel gas and moisture (condensed water) increases, and the fuel gas can be humidified efficiently.

  In the fuel gas humidifier of the present invention according to claim 2, the porous material is a hollow fiber membrane bundle including a plurality of moisture permeable hollow fiber membranes, and each hollow fiber membrane is curved in a U-shape. The U-shaped curved portion is arranged toward the downstream side of the fuel gas flow.

  According to the fuel gas humidifier of the present invention according to claim 2, the condensed water is captured at the curved portion of the U-shape in each hollow fiber membrane, so that the condensed water can be captured more reliably.

  The fuel gas humidifier of the present invention according to claim 3 is disposed in the middle of the supply pipe through which the fuel gas supplied from the fuel gas mixing and circulation means to the fuel cell passes.

According to the fuel gas humidifier of the present invention according to claim 3, the condensed water can be captured at the portion immediately before the fuel gas enters the fuel cell, so that the possibility of the condensed water flowing into the fuel cell is further increased. This can reduce the power generation stability and durability of the fuel cell.
In addition, by disposing the fuel gas humidifier at that position, the humidity of the fuel gas whose humidity has been reduced by being mixed with the fuel gas supplied from the fuel tank can be increased, and the fuel gas can be efficiently removed. Can be humidified.

  The fuel gas humidifier of the present invention according to claim 4 further includes a heating device for raising the temperature of the humidified fuel gas.

According to the fuel gas humidifier of the present invention according to claim 4, the temperature reduction of the fuel gas due to latent heat (heat of vaporization) accompanying the vaporization (evaporation) of the condensed water trapped in the porous material is suppressed, and the fuel cell Power generation stability can be improved.
In addition, by heating the fuel gas, the saturated water vapor amount of the fuel gas can be increased, thereby increasing the amount of water vapor supplied to the fuel cell, so that the power generation stability of the fuel cell can be further improved. .

  According to the fuel gas humidifier of the present invention, the inflow of condensed water into the fuel cell can be prevented, and the fuel gas can be humidified efficiently.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an overall configuration diagram of a fuel cell system S of the present embodiment. The fuel cell system S is mounted on, for example, a fuel cell vehicle.

As shown in FIG. 1, the fuel cell system S includes a hydrogen tank 1 (fuel tank), an ejector 2 (fuel gas mixing and circulation means), a humidifier 3 (fuel gas humidifier), a purge valve 4, a heater 5 and a temperature. A sensor T and a fuel cell FC are provided.
Actually, in addition to the purge valve 4, an on-off valve is provided at an appropriate position of the piping, and the on-off valve and the ejector 2 are controlled by an ECU (Electronic Control Unit), but these are not shown in the figure. is doing.

The hydrogen tank 1 is filled with high-purity hydrogen at a high pressure (for example, about 35 MPa), and supplies hydrogen as a fuel gas to the ejector 2 via a pipe.
The ejector 2 mixes the hydrogen supplied from the hydrogen tank 1 with the hydrogen circulated from the circulation pipe 13 (circulation path) and discharges it to the supply pipe 11 (circulation path).

The humidifier 3 is a device that humidifies the hydrogen supplied from the supply pipe 11 and discharges it to the supply pipe 12 (circulation path). Details will be described later with reference to FIGS.
The heating device 5 is a device for heating hydrogen passing through the humidifying device 3, and details thereof will be described later with reference to FIGS.
The temperature sensor T is provided in the supply pipe 12 and measures the temperature of hydrogen passing through the supply pipe 12. The temperature sensor T may be provided inside the humidifying device 3 instead of the supply pipe 12.

  For example, the ECU (not shown) controls the heating device 5 based on the temperature of hydrogen obtained from the temperature sensor T, so that the temperature of hydrogen flowing through the supply pipe 12 and flowing into the anode A is steady. It can be maintained at a temperature suitable for the operating temperature.

  The fuel cell FC has a configuration in which a cation exchange type solid polymer electrolyte membrane (hereinafter referred to as “electrolyte membrane”) P is sandwiched between an anode A and a cathode C. In FIG. 1, the fuel cell FC is shown as a single cell configuration, but in practice, the fuel cell FC has a configuration in which a plurality of single cells are connected in series.

  In the fuel cell FC, air (oxygen) as the oxidant gas is supplied to the cathode C, hydrogen as the fuel gas is supplied to the anode A, and power generation is performed by an electrochemical reaction between the hydrogen and oxygen. .

Exhaust hydrogen (exhaust fuel gas) discharged from the anode A of the fuel cell FC is sucked by the ejector 2 through the circulation pipe 13. The ejector 2 mixes hydrogen appropriately supplied from the hydrogen tank 1 with the discharged hydrogen, and discharges the mixed hydrogen to the supply pipe 11.
The purge valve 4 is controlled by an ECU (not shown) and appropriately opens to purge (discharge) hydrogen in the circulation pipe 13 to the outside.

  Next, a humidifier and a heating device will be described with reference to FIG. 2 (see FIG. 1 as appropriate). Fig.2 (a) is the figure which showed the structure of the humidifier and the heating apparatus, and FIG.2 (b) is AA sectional drawing of Fig.2 (a). In addition, the same code | symbol is attached | subjected about the same structure as FIG. 1, and duplication description is abbreviate | omitted suitably.

As shown in FIG. 2A, the humidifying device 3 includes a space portion 31, a hollow fiber membrane bundle 32, and a fixing portion 33.
The space part 31 is a sealed space except for the connection part with the supply pipe 12 and the opening part in the fixing part 33.

  The hollow fiber membrane bundle 32 is a porous material having a large number of holes, and here, is constituted by a plurality of hollow fiber membranes HF (Hollow Fiber). The hollow fiber membrane HF is, for example, a thread-like membrane formed of a polymer material such as polyimide, and has a large number of micropores with a diameter of several to several tens of nanometers that allow moisture and hydrogen to pass through the peripheral wall. .

  Each hollow fiber membrane HF is curved in a U-shape, and both ends thereof are fixed on substantially the same surface by fixing portions 33. The U-shaped curved portion of each hollow fiber membrane is arranged toward the downstream side of the hydrogen flow (left side in FIG. 2A).

  As shown in FIG. 2 (b), the hollow fiber membrane HF is in a state where the hollow is opened in the inner portion of the supply pipe 11 in the fixed portion 33, and other than the opened portion, gas, liquid Both are unable to pass.

  Returning to FIG. 2A, the heating device 5 is wound around the supply pipe 11 and heats hydrogen and condensed water passing through the supply pipe 11. Specifically, the heating device 5 has, for example, a tube shape in which a high-temperature gas such as an off-gas at the cathode C of the fuel cell FC or a cooling water for lowering the temperature of the fuel cell FC, What is necessary is just to heat by flowing a liquid. In addition, the heating device 5 may be one using a normal heating wire.

  As described above, the ECU (not shown) may control the heating device 5 using the temperature information from the temperature sensor T. If it does so, the humidified hydrogen which passes the supply piping 12 can be made into the predetermined temperature (for example, about 70 to 80 degreeC) convenient for the fuel cell FC.

  Next, the behavior of hydrogen and condensed water will be described. First, hydrogen and condensed water passing through the supply pipe 11 are heated by the heating device 5. Next, hydrogen and condensed water enter the inside of each hollow fiber membrane HF fixed to the fixing portion 33.

Since each hollow fiber membrane HF has a U shape, the condensed water is captured (and held at the tip of the U shape (both inside and outside the hollow fiber membrane HF). The same) and collect as water droplets.
The hydrogen that has entered the hollow fiber membrane HF escapes from the micropores of the hollow fiber membrane HF to the outside of the hollow fiber membrane HF, but is humidified by water droplets accumulated in the U-shape of the hollow fiber membrane HF, and becomes humidified hydrogen. It flows out from the supply pipe 12.

Thus, according to the humidifier 3 of this embodiment, the inflow of condensed water into the fuel cell FC can be prevented, and the fuel gas can be efficiently humidified.
That is, more specifically, according to the humidifying device 3 of the present embodiment, the hollow fiber membrane bundle 32, which is a porous material, captures the condensed water flowing in from the supply pipe 11 that is the circulation path. Condensed water can be prevented from flowing into the battery FC, and the power generation stability and durability of the fuel cell FC can be improved.

Further, by holding condensed water in the hollow fiber membrane bundle 32 which is a porous material, the contact area between hydrogen and moisture increases, and hydrogen can be efficiently humidified.
Furthermore, in the hollow fiber membrane bundle 32, each hollow fiber membrane HF is curved into a U shape, and the curved portion of the U shape is directed to the downstream side of the flow of hydrogen, so that the condensed water can be more reliably obtained. Can be captured.

Moreover, the possibility of the condensed water flowing into the fuel cell FC can be further reduced by arranging the humidifier 3 in the portion immediately before hydrogen enters the fuel cell FC.
Furthermore, by arranging the humidifier 3 at that position, it is possible to increase the humidity of hydrogen in the supply pipe 11 in which the humidity has decreased due to mixing with the hydrogen supplied from the hydrogen tank 1, and the fuel cell Hydrogen flowing into FC can be efficiently humidified.

Further, by providing the heating device 5 in the vicinity of the humidifying device 3, the temperature decrease of hydrogen due to latent heat (vaporization heat) accompanying the vaporization (evaporation) of the condensed water trapped in the hollow fiber membrane bundle 32 is suppressed, and the fuel The power generation stability of the battery FC can be improved.
Furthermore, by heating hydrogen, the amount of saturated water vapor of hydrogen can be increased, thereby increasing the amount of water vapor supplied to the fuel cell FC, so that the power generation stability of the fuel cell FC can be further improved. .

  In the embodiment according to FIG. 2, a hollow fiber membrane has been described as an example of the porous material. However, even if it is not a hollow fiber membrane, hydrogen and condensed water are allowed to pass therethrough, Other substances such as an ion exchange membrane may be used as long as they can be captured.

  Next, a first modification of the humidifying device and the heating device will be described with reference to FIG. 3 (see FIGS. 1 and 2 as appropriate). Fig.3 (a) is the figure which showed the structure of the humidification apparatus and heating apparatus of a 1st modification, and FIG.3 (b) is BB sectional drawing of Fig.3 (a). In addition, the same code | symbol is attached | subjected about the same structure as FIG. 2 (FIG. 2 (a) and FIG.2 (b): similarly), and duplication description is abbreviate | omitted suitably.

As shown to Fig.3 (a), the humidification apparatus 3a is provided with the space part 31, the fiber bundle 41, and the fixing | fixed part 33a. A heating device 5a is wound around the outer periphery of the humidifying device 3a.
The fiber bundle 41 need only be a porous material that can capture moisture, and may not be a hollow fiber membrane. Further, each fiber in the fiber bundle 41 does not have to be U-shaped like the hollow fiber membrane HF in FIG. 2A, and is in a somewhat dense state so that moisture can be captured. That's fine. The fiber bundle 41 is fixed to the fixing portion 33a.

The heating device 5a may be anything as long as it can heat the humidifying device 3a, such as the one using the off-gas of the cathode C, cooling water, or heating wire, like the heating device 5 in FIG.
Further, as shown in FIG. 3B, an inlet 42 for allowing hydrogen or condensed water to pass therethrough is provided in an inner portion of the supply pipe 11 in the fixed portion 33a. Both liquids cannot pass through. In addition, the arrangement | positioning location of the inflow port 42 may not be the center part of the supply piping 11, but another places, such as the lower part. Further, the number of inflow ports 42 may not be one, but two or more.

Next, the behavior of hydrogen and condensed water will be described. First, the hydrogen and condensed water that have passed through the supply pipe 11 enter the fiber bundle 41 via the inlet 42 of the fixed portion 33a.
Then, the condensed water is captured by the fiber bundle 41 and accumulates inside the fiber bundle 41 as water droplets. The hydrogen passing through the fiber bundle 41 is humidified by the water droplets accumulated in the fiber bundle 41, heated by the heating device 5a, and flows out from the supply pipe 12 as humidified hydrogen.

Thus, according to the humidification device 3a of the first modification, the inflow of condensed water into the fuel cell FC can be prevented, and the fuel gas can be efficiently humidified.
That is, more specifically, according to the humidifying device 3a of the first modified example, the fiber bundle 41, which is a porous material, captures the condensed water flowing in from the supply pipe 11 that is the circulation path. Condensed water can be prevented from flowing into the FC, and the power generation stability and durability of the fuel cell FC can be improved.

Further, by holding condensed water in the fiber bundle 41 which is a porous material, the contact area between hydrogen and moisture increases, and hydrogen can be efficiently humidified.
Further, by providing the heating device 5 on the outer periphery of the humidifying device 3a, the temperature drop of hydrogen due to the heat of vaporization due to the evaporation of the condensed water trapped in the fiber bundle 41 is more directly suppressed, and the power generation of the fuel cell FC Stability can be improved.

  In the embodiment according to FIG. 3, the fiber is described as an example of the porous material, but other materials such as various resins having porosity may be used as long as they can capture condensed water even if not a fiber. It may be a substance.

  Next, a second modification of the humidifying device and the heating device will be described with reference to FIG. 4 (see FIGS. 1 and 2 as appropriate). FIG. 4 is a diagram illustrating the structure of a humidifying device and a heating device according to a second modification. In addition, the same code | symbol is attached | subjected about the same structure as FIG. 2, and duplication description is abbreviate | omitted suitably.

  As shown in FIG. 4, the humidifying device 3b includes a space portion 31a, a fiber bundle 41a, a fixing portion 33b, and a heating device 5b. In addition, although the heating apparatus 5b is provided in the inside of the humidification apparatus 3b, it may be in direct contact with the fiber bundle 41a or not.

  The fiber bundle 41a only needs to be a porous material that can capture moisture, and may not be a hollow fiber membrane. Further, each fiber in the fiber bundle 41a does not have to be U-shaped like the hollow fiber membrane HF in FIG. 2 (a), and is in a somewhat dense state so that moisture can be captured. That's fine. The fiber bundle 41a is fixed to the fixing portion 33b.

  Further, the humidifier 3b is connected to the supply pipe 11 at the lower part (vertically downward part) and is connected to the supply pipe 12 at the upper part (vertical upward part). With this configuration, it is possible to reduce the possibility that condensed water that has flowed into the humidifying device 3b from the supply pipe 11 flows into the supply pipe 12, but the possibility that splashes of condensed water may flow into the supply pipe 12 is not possible. is there. Therefore, in order to further reduce the possibility, a fiber bundle 41a is provided.

  The heating device 5b may be anything as long as it can heat the humidifying device 3b, such as the one using the off-gas of the cathode C, cooling water, or heating wire, like the heating device 5 in FIG.

Next, the behavior of hydrogen and condensed water will be described. First, the hydrogen and condensed water that have passed through the supply pipe 11 enter the fiber bundle 41a fixed to the fixing portion 33b.
Then, the condensed water is captured by the fiber bundle 41a and accumulated in the fiber bundle 41 as water droplets. The hydrogen passing through the fiber bundle 41a is humidified by water droplets accumulated in the fiber bundle 41a, heated by the heating device 5b, and flows out from the supply pipe 12 as humidified hydrogen.

Thus, according to the humidifying device 3b of the second modified example, the inflow of condensed water into the fuel cell FC can be prevented and the fuel gas can be efficiently humidified.
That is, more specifically, according to the humidifying device 3b of the second modified example, the fiber bundle 41a, which is a porous material, circulates in addition to the configuration in which the condensed water hardly flows into the fuel cell FC originally. Since the condensed water flowing in from the supply pipe 11 as the route is captured, the possibility of the condensed water flowing into the fuel cell FC can be further reduced, and the power generation stability and durability of the fuel cell FC can be reduced. Can be improved.

  Further, by providing the heating device 5b inside the humidifying device 3b, the temperature drop of hydrogen due to the heat of vaporization due to the evaporation of the condensed water trapped in the fiber bundle 41a is more directly suppressed, and the power generation of the fuel cell FC Stability can be improved.

  The humidifiers 3, 3a, 3b shown in FIGS. 2 to 4 can be further modified in various ways. For example, the cross section of the fixing portion 33 of the humidifying device 3 illustrated in FIG. 2A may be, for example, as illustrated in FIG. 5 other than that illustrated in FIG. FIG. 5 is an AA cross-sectional view showing a modification of the fixing portion 33 of the humidifying device 3 shown in FIG.

As shown in FIG. 5, in the inner portion of the supply pipe 11 in the fixing portion 33 b which is a modified example of the fixing portion 33, the hollow fiber membrane HF is in a state where the hollow is opened, and hydrogen and condensed water are supplied. An inflow port 61 is provided for passage therethrough. In addition, the arrangement | positioning location of the inflow port 61 may not be a center part of the supply piping 11, but another places, such as the lower part. Further, the number of inflow ports 42 may not be one, but two or more.
Thus, by providing the inflow port 61, the pressure loss due to hydrogen passing through the fixed portion 33b can be reduced, and the burden on the ejector 2 (see FIG. 1) can be reduced.

  Next, a modification of the fuel cell system will be described with reference to FIG. FIG. 6 is an overall configuration diagram of a fuel cell system according to a modification. The fuel cell system S1 in FIG. 6 is different from the fuel cell system S in FIG. 1 in that the heating device 5 and the temperature sensor T are not provided. In addition, the same code | symbol is attached | subjected about the same structure as the fuel cell system S of FIG. 1, and duplication description is abbreviate | omitted suitably.

In the fuel cell system S1 shown in FIG. 6, the hydrogen passing through the humidifying device 3 is not heated. This can be realized, for example, by removing the heating device 5 from the configuration shown in FIG. The same applies to FIG. 3A and FIG.
That is, if the temperature of hydrogen supplied from the supply pipe 12 to the anode A is appropriately high even without the heating device 5 due to the overall structural characteristics of the fuel cell system S1, the heating device 5 ( And the temperature sensor T) can be omitted. Even in this case, the humidifier 3 can prevent the inflow of condensed water into the fuel cell FC and can appropriately maintain the humidity and temperature of the hydrogen gas supplied to the anode A.

  This is the end of the description of the embodiments, but the aspects of the present invention are not limited to these. For example, a catch tank for collecting condensed water may be provided in the circulation pipe 13 (see FIG. 1), and a certain amount of condensed water may be collected by the catch tank and discharged to the outside.

  Moreover, each humidification apparatus and heating apparatus in FIGS. 2-4 are not limited to this combination, Various other combinations are possible. Further, the fuel gas may not be hydrogen but may be other gas such as methane gas.

Further, in the fuel cell systems S and S1 of FIGS. 1 and 6, the humidifier 3 is arranged at a position downstream of the ejector 2 and upstream of the anode A, but may be arranged in the circulation pipe 13. .
In addition, about a concrete structure, it can change suitably in the range which does not deviate from the main point of this invention.

It is a whole block diagram of the fuel cell system of this embodiment. (A) is the figure which showed the structure of the humidification apparatus and the heating apparatus, (b) is AA sectional drawing of (a). (A) is the figure which showed the structure of the humidification apparatus and heating apparatus of a 1st modification, (b) is BB sectional drawing of (a). It is the figure which showed the structure of the humidification apparatus and heating apparatus of a 2nd modification. It is sectional drawing which shows the modification of the fixing | fixed part of the humidification apparatus shown to Fig.2 (a). It is a whole block diagram of the fuel cell system of the modification of this embodiment.

Explanation of symbols

FC fuel cell HF hollow fiber membrane 1 hydrogen tank 2 ejector 3, 3a, 3b humidifier 4 purge valve 5, 5a, 5b heating device 11, 12 supply pipe 13 circulation pipe 32 hollow fiber membrane bundle 33, 33a, 33b fixed Part 41, 41a Fiber bundle

Claims (4)

A fuel cell that generates electricity by a reaction between the fuel gas and the oxidant gas;
A fuel tank for supplying the fuel gas to the fuel cell;
A circulation path that is a path for circulating the exhaust fuel gas discharged from the fuel cell upstream of the fuel cell;
A fuel gas humidifying device in a fuel cell system comprising: a fuel gas mixing and circulating means for mixing the fuel gas supplied from the fuel tank with the exhausted fuel gas and circulating the fuel gas through the circulation path;
A porous material is provided inside the circulation path,
The porous gas retains condensed water in the circulation path, and humidifies the fuel gas passing through the porous material with the condensed water. The porous material is a hollow fiber membrane bundle including a plurality of moisture permeable hollow fiber membranes,
2. The fuel according to claim 1, wherein each of the hollow fiber membranes is curved into a U-shape, and the curved portion of the U-shape is disposed toward the downstream side of the flow of the fuel gas. Gas humidifier.   3. The fuel gas humidifier according to claim 1, wherein the fuel gas humidifier is disposed in a supply pipe through which the fuel gas supplied from the fuel gas mixing and circulation unit to the fuel cell passes.   The fuel gas humidifier according to any one of claims 1 to 3, further comprising a heating device that raises a temperature of the fuel gas to be humidified.

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