JP2002075418A - Humidifier for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance humidifying efficiency of gas supplied to a fuel cell by transforming moisture contained in exhaust air from the fuel cell into vapor in more volume to improve water recovery rate. SOLUTION: With the humidifying device AS1, a pressure control valve 5 is arranged at a downstream side of a channel for exhaust air Ae discharged from the fuel cell 1 and a humidifier 2 is arranged at a downstream side of the pressure control valve 5. In other words, the pressure control valve 5 is arranged at an upstream side of the humidifier 2. With this, the humidifier need not be put under high pressure even if the pressure of the fuel cell 1 is controlled by the pressure control valve 5, and therefore, moisture contained in the exhaust air can be transformed into vapor in more volume.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a humidifier for a fuel cell, and more particularly to a humidifier for a fuel cell having a high water recovery rate and excellent humidification efficiency.

[0002]

2. Description of the Related Art In recent years, fuel cells have attracted attention as power sources for electric vehicles. As this fuel cell, there is a so-called polymer electrolyte fuel cell. In this polymer electrolyte fuel cell, a humidifier for exchanging the moisture of off-gas, which is a humid gas discharged from the fuel cell, into a dry gas is used. A polymer electrolyte fuel cell equipped with such a humidifier is disclosed in, for example, JP-A-6-132.
No. 038 is disclosed. As shown in FIG. 5, the humidifier 50 in the solid polymer electrolyte fuel cell has a water vapor permeable membrane 51, and a humidified gas chamber 52 and a humidified gas chamber defined by the water vapor permeable membrane 51. 53. Humidifying gas chamber 52 of these
Is supplied with off-gas discharged from the oxidant passage in the fuel cell 54. In the humidified gas chamber 53,
Humidified gas is supplied from the reaction air blower 55. The humidified gas supplied to the humidified gas chamber 53 is humidified by the off gas supplied to the humidified gas chamber 52, and the fuel cell 54
Is supplied to the oxidant passage. A relief valve 56 for adjusting the pressure in the oxidizing agent passage of the fuel cell 54 is provided downstream of the humidified gas chamber 53.

[0003]

By the way, in this type of humidifier, it is desired to improve the humidification efficiency of the supply gas by increasing the recovery rate of the water contained in the off-gas and exchanging the water with the supply gas. . However, the humidified gas chamber 53 of the humidifying device 50 in the conventional solid polymer electrolyte fuel cell shown in FIG. For this reason, the amount of water vapor contained in the off-gas is small, and water that cannot be turned into water vapor condenses. Since the water that could not become water vapor cannot pass through the water vapor permeable membrane 51,
There was a problem that the water separation recovery rate was reduced. Also,
A humidifier using a hollow fiber membrane instead of using the water vapor permeable membrane 51 is also known. However, the hollow fiber membrane has a property that the humidification efficiency is reduced when a gas containing water vapor and condensed water flows therein. Therefore, it is desired to reduce condensed moisture.

[0004] Therefore, an object of the present invention is to improve the water recovery rate by converting as much as possible moisture contained in the off-gas discharged from the fuel cell into water vapor, thereby improving the humidification efficiency of the gas supplied to the fuel cell. To provide a humidifier for a fuel cell.

[0005]

According to a first aspect of the present invention which solves the above-mentioned problems, the present invention is directed to a method of flowing a supply gas supplied to a fuel cell and an exhaust gas discharged from the fuel cell. In the humidifying device for a fuel cell provided with a humidifier for humidifying the supply gas by exchanging moisture contained in the exhaust gas with the supply gas, a flow path of the exhaust gas discharged from the fuel cell is used. A humidifier for a fuel cell, wherein a first pressure control means for controlling an outlet pressure of the fuel cell is provided upstream of the humidifier.

In the invention according to the first aspect, the pressure control means is provided in the flow path of the exhaust gas discharged from the fuel cell and upstream of the humidifier. Therefore, the pressure in the fuel cell can be adjusted without excessively increasing the pressure in the humidifier. Therefore, dew condensation of water in the humidifier can be prevented, and the water recovery rate can be improved. Thus, the humidification efficiency of the gas supplied to the fuel cell can be increased.

According to a second aspect of the present invention, the exhaust gas flow path includes a second pressure control means for controlling an exhaust gas pressure in the humidifier downstream of the humidifier. The fuel cell humidifier according to claim 1, wherein the first pressure control means and the second pressure control means are controlled according to a humidification-related amount of a supply gas supplied to the fuel cell. is there.

According to the second aspect of the present invention, the second pressure control means for controlling the exhaust gas pressure in the humidifier is provided downstream of the humidifier. For this reason, since the pressure in the humidifier can be adjusted independently of the required pressure of the fuel cell, the humidification amount of the supply gas can be suitably controlled.
Note that the humidification-related amount of the supplied gas indicates the humidity, dew point, and the like of the supplied gas.

[0009]

Embodiments of the present invention will be specifically described below with reference to the drawings. Before describing the humidifier according to the present invention, an example of a fuel cell system having the humidifier will be described.

FIG. 1 is an overall configuration diagram of a fuel cell system including a humidifier according to the present invention, and FIG. 2 is an explanatory diagram schematically illustrating the configuration of a fuel cell. The fuel cell system FCS shown in FIG. 1 is a power generation system having the fuel cell 1 as a core, which includes a fuel cell 1, a humidifier AS1, a hydrogen supply device HS, and the like.

First, as shown in FIG. 2, the fuel cell 1
It is divided into a cathode electrode side (oxygen electrode side) and an anode electrode side (hydrogen electrode side) with the electrolyte membrane 1c interposed therebetween, and an electrode containing a platinum-based catalyst is provided on each side, and the cathode electrode 1b
And an anode electrode 1d. Electrolyte membrane 1c
For example, a solid polymer membrane, for example, a perfluorocarbon sulfonic acid membrane which is a proton exchange membrane is used. This electrolyte membrane 1c has many proton exchange groups in a solid polymer,
By containing saturated water, it exhibits a low specific resistance of 20 Ω-proton or less at room temperature and functions as a proton conductive electrolyte. The catalyst included in the cathode electrode 1b is a catalyst that generates oxygen ions from oxygen, and the catalyst included in the anode electrode 1d is a catalyst that generates protons from hydrogen.

Outside the cathode electrode 1b, there is provided a cathode side gas passage 1a through which supply air A, which is a supply gas as an oxidant gas, flows through the cathode electrode 1b.
Outside the anode electrode 1d, an anode electrode side gas passage 1e through which supply hydrogen H as a fuel gas flows to the anode electrode 1d is provided. The inlet and outlet of the cathode-side gas passage 1a are connected to a humidifier AS1, and the inlet and outlet of the anode-side gas passage 1e are connected to a hydrogen supply device HS. The fuel cell 1 shown in FIG.
Although the configuration is schematically represented as one single cell, the actual fuel cell 1 is configured as a stacked body in which about 200 single cells are stacked. Also, the fuel cell 1
Since a heat is generated by an electrochemical reaction during power generation, a cooling device (not shown) for cooling the fuel cell 1 is provided.

In the fuel cell 1, the supply air A flows through the cathode-side gas passage 1a,
When the supply hydrogen H is supplied to e, the hydrogen is ionized by the catalytic action at the anode electrode 1d to generate protons, and the generated protons move through the electrolyte membrane 1c and reach the cathode electrode 1b. Then, the protons that have reached the cathode electrode 1b immediately react with oxygen ions generated from oxygen of the supply air A in the presence of the catalyst to generate water. The supply air A containing the generated water and unused oxygen is discharged from the outlet on the cathode side of the fuel cell 1 as the discharge air Ae as the discharge gas (the discharge air Ae contains a large amount of moisture). The hydrogen in the anode electrode 1d electrons e when ionized ^- but is produced, the generated electrons e ^- reaches the cathode electrode 1b via the external load M such as a motor.

Next, as shown in FIG. 1, in addition to the humidifier 2, the humidifier AS1 according to the present invention includes an air cleaner 3, a compressor 4, and a pressure control valve 5 serving as first pressure control means.
And so on.

In the humidifier AS1, a humidifier 2 is disposed in the flow path of the supply air A in the fuel cell 1, upstream of the fuel cell 1, and a compressor 4 is disposed upstream of the humidifier 2. Have been. In addition, compressor 4
An air cleaner 3 is arranged upstream of the air cleaner. The flow path of the exhaust air Ae discharged from the fuel cell 1,
A pressure control valve 5 is disposed downstream of the fuel cell 1, and a humidifier 2 is disposed downstream of the pressure control valve 5. That is, the pressure control valve 5 is provided on the upstream side of the humidifier 2.

The humidifier 2 humidifies the air supplied from the air cleaner 3 and supplies the humidified air to the fuel cell 1. As the humidifier 2, a water permeable membrane type having the hollow fiber membrane module 21 shown in FIG. 3 can be used. The hollow fiber membrane module 21 has a housing 31, in which a hollow fiber membrane bundle 32 composed of thousands of hollow fiber membranes is housed. The hollow fiber membrane constituting the hollow fiber membrane bundle 32 is a hollow fiber having a diameter of 1 to 2 mm and a length of several tens cm having a hollow passage. Further, the hollow fiber membrane has a large number of fine capillaries having a diameter of several nanometers (nanometers) extending from the inside to the outside, and in the capillaries, the vapor pressure is reduced and moisture condensation easily occurs. The condensed water is sucked out by capillary action and passes through the hollow fiber membrane.

The housing 31 has a hollow cylindrical shape with both ends open, and has eight supply air inlets 3 for introducing supply air into the housing 31 at one end in the longitudinal direction.
Are formed to be spaced apart in the circumferential direction. On the other end side of the housing 31 in the longitudinal direction, eight supply air outlets 34, 34 serving as supply air outlets are formed so as to be circumferentially separated. The one end side and the other end side of the hollow fiber membrane bundle 32 are potted to form potting portions 35 and 36. The other end of the housing 31 has a discharge air inlet 37 for inflowing the discharge air Ae, and the one end of the housing 31 has a discharge air outlet 38 for discharging the discharge air Ae. ing.

The humidifier 2 includes two hollow fiber membrane modules 21 and 21 and two hollow fiber membrane modules 21 and 21.
And a switching means such as an electromagnetic valve or an electromagnetic valve controller for switching and using the two hollow fiber membrane modules according to the flow rate and humidity of the supply air A. Further, the humidifier 2 is switched by the switching means.
When the flow rate of the supply air A is small, the switching drive is performed so that only one hollow fiber membrane module is used. When the flow rate of the supply air A is large, the switching drive is performed so that both hollow fiber membrane modules are used. Is done. The switching drive is performed in this manner because the hollow fiber membrane module has the humidification characteristic that the humidification performance is reduced even if the flow rate of the supply air A and the discharge air Ae is too small or too large. The timing at which the hollow fiber membrane module is switched is determined by a detection signal from a flow rate sensor or humidity sensor (not shown).

The air cleaner 3 includes a filter (not shown) or the like, and filters air (supply air A) supplied to the cathode of the fuel cell 1 to remove dust contained in the supply air A.

The compressor 4 includes a supercharger (a positive displacement compressor) (not shown) and a motor for driving the supercharger. The compressor 4 sends out supply air A used as an oxidizing gas in the fuel cell 1 and sends it to the humidifier 2. Supply. The supply air A is sent to the cathode side of the fuel cell 1 through the humidifier 2 by the output power of the compressor 4, and after passing through the fuel cell 1, becomes the exhaust air Ae and passes through the pressure control valve 5 to the humidifier 2. Sent to

The pressure control valve 5 comprises a butterfly valve (not shown) and a stepping motor for driving the same, and adjusts the outlet pressure of the fuel cell 1. Also, by adjusting the outlet pressure of the fuel cell 1, the compressor 4
From the downstream side of the fuel cell 1 to the pressure upstream of the pressure control valve 5. The opening of the pressure control valve 5 is determined by the required pressure of the fuel cell 1.

On the other hand, as shown in FIG.
S comprises a hydrogen gas cylinder 11, a regulator 12, a hydrogen circulation pump 13, a three-way valve 14, and the like. The hydrogen gas cylinder 11 is composed of a high-pressure hydrogen container (not shown), and supplies hydrogen H introduced to the anode of the fuel cell 1.
Store. The supply hydrogen H to be stored is pure hydrogen, and the pressure is 15 to 20 MPaG (150 to 200 kg / cm ² G). The hydrogen gas cylinder 11 may be of a hydrogen storage alloy type that contains a hydrogen storage alloy and stores hydrogen at a pressure of about ¹ MPaG (10 kg / cm ² G).

The regulator 12 is a pressure control valve composed of a diaphragm, a pressure adjusting spring, and the like (not shown), and reduces the supply hydrogen H stored at a high pressure to a predetermined pressure so that the hydrogen can be used at a constant pressure. When the reference pressure input to the diaphragm is set to the atmospheric pressure, the regulator 12 can reduce the pressure of the supply hydrogen H stored in the hydrogen gas cylinder 11 to near the atmospheric pressure.

The hydrogen circulation pump 13 is composed of an ejector (not shown) or the like, and utilizes the flow of the supply hydrogen H toward the anode of the fuel cell 1 to supply hydrogen after being used as fuel gas in the fuel cell 1. H, that is, fuel cell 1
The exhausted hydrogen He discharged from the anode electrode side and flowing through the three-way valve 14 is sucked and circulated.

Next, the operation and action of the humidifier AS1 according to the present invention will be described. First, the flow of air in the humidifier AS1 will be described in order. By operating the compressor 4, the supply air A is sucked from the outside air via the air cleaner 3. The sucked supply air A is sent to the humidifier 2 arranged on the downstream side. In the humidifier 2, the inside of the housing 31 of the hollow fiber membrane module 21 of the humidifier 2 shown in FIG. 3 and the outside of the hollow fiber membrane constituting the hollow fiber membrane bundle 32 housed in the housing 31 pass through. Shed. At this time, moisture exchange is performed between the supply air A and the discharge air Ae passing through the hollow fiber membrane, and the supply air A is humidified. The humidified supply air A is discharged from the humidifier 2 and supplied to the fuel cell 1 to be used for power generation. Since the fuel cell 1 has generated water generated by power generation, the supply air A supplied into the fuel cell 1 absorbs the generated water, is humidified, and is discharged as exhaust air Ae. The exhaust air Ae discharged from the fuel cell 1 is sent to the humidifier 2 and flows through the inside of the hollow fiber membrane constituting the hollow fiber membrane bundle 32 shown in FIG. Provided for exchange. The exhaust air Ae that has left the humidifier 2 is discharged into the atmosphere.

Next, the humidifier A according to the present invention shown in FIG.
In S1, the humidifier 2 allows the supply air A supplied to the fuel cell 1 and the exhaust air Ae discharged from the fuel cell 1 to flow, and exchanges the moisture contained in the exhaust air Ae with the supply air. Then, the supply air A is humidified. The operation at this time will be described. The inside of the housing 31 in the hollow fiber membrane module 21 of the humidifier 2 shown in FIG.
Outside the hollow fiber membranes constituting the hollow fiber membrane bundle 32, supply air A sent from the compressor 4 flows. on the other hand,
The exhaust air Ae sent from the pressure control valve 5 flows inside the hollow fiber membranes constituting the hollow fiber membrane bundle 32. Water is extracted from the exhaust air Ae passing through the hollow fiber membrane by capillary action in the hollow fiber membrane. The extracted water is condensed, passes through the capillary in the hollow fiber membrane, is discharged to the outside of the hollow fiber membrane, and the discharged water is absorbed by the supply air A. In this way, moisture is exchanged between the discharge air Ae and the supply air A, and the supply air A is humidified.

In the humidifier AS1, the supply air circulating through the humidifier AS1 is controlled by the pressure control valve 5 in order to keep the pressure on the cathode side in the fuel cell 1 balanced with the pressure on the anode side. A and exhaust air Ae
Adjust pressure. For example, when the pressure on the anode side in the fuel cell 1 is 40 KPaG,
The pressure of the supply air A and the discharge air Ae circulating through the humidifier AS1 is adjusted by the pressure control valve 5 so that the pressure on the cathode side of the fuel cell 1 becomes 40 KPaG.

Here, in the humidifier AS1 according to the present invention, the humidifier 2 is disposed downstream of the pressure control valve 5,
In other words, the pressure control valve 5 is provided between the humidifier 2 and the fuel cell 1.
Is arranged. Since the pressure control valve 5 is disposed between the humidifier 2 and the fuel cell 1, the downstream side of the humidifier 2 immediately becomes the atmosphere, so that the pressure in the humidifier 2 is reduced. Specifically, for example, the outlet pressure of the fuel cell 1 is set to 40K.
When the pressure is maintained at PaG, the pressure in the humidifier 2 becomes 1
It becomes 0 KPaG. Therefore, in the humidifier 2,
The water contained in the exhaust air Ae is likely to evaporate into water vapor, and the water collection rate can be improved.

Next, a second embodiment of the present invention will be described. FIG. 4 is a configuration diagram of a humidifier according to the present invention. In the present embodiment, members having the same configurations as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. On the anode side of the fuel cell 1,
Although the hydrogen supply device HS shown in FIG. 1 is provided, its configuration is the same as that of the first embodiment, so that illustration and description thereof will be omitted.

As shown in FIG. 4, a humidifier AS2 according to the present embodiment is similar to the humidifier AS1 according to the first embodiment shown in FIG. In addition to the first pressure control valve 5 serving as pressure control means, a second pressure control valve 6 serving as second pressure control means is provided. Here, the second pressure control valve 6 used in the present embodiment has the same configuration as the first pressure control valve 5.

In the humidifier AS2, the humidifier 2 is disposed upstream of the supply air A in the fuel cell 1, and the compressor 4 is disposed upstream thereof. Further, an air cleaner 3 is arranged upstream of the compressor 4. Further, a first pressure control valve 5 is disposed downstream of the exhaust air Ae in the fuel cell 1, and a humidifier 2 is disposed downstream of the first pressure control valve 5. Further, a second pressure control valve 6 is disposed further downstream of the humidifier 2.

In the humidifier AS2 according to the present embodiment, the moisture is exchanged between the supply air A and the discharge air Ae in the humidifier 2 through the same process as in the first embodiment, and the supply air is supplied. A is humidified. At this time, the first
In the embodiment, only one pressure control valve 5 is provided, but in the present embodiment, the pressure control valve 5 is
Two pressure control valves 5, 6 are provided. Further, the required gas amount of the fuel cell 1 is controlled by the first pressure control valve 5, and the first pressure control means 5 controls the first pressure control means 5 so that the outlet pressure of the fuel cell 1 becomes a pressure corresponding to the required gas amount of the fuel cell. The opening is controlled. The required supply gas humidification related amount (humidity, dew point, etc.) of the fuel cell 1 is controlled by the second pressure control valve 6. By the way, the required supply air A of the fuel cell 1 has a humidity of 80% to 80%.
It is preferable to control to be between 95% and 80%
When it is less than the above, there is a concern that the humidification amount of the fuel cell 1 is reduced. Therefore, when the humidity of the supply air A is less than 80%, the first pressure control valve 5 is closed at a predetermined opening and the second pressure control valve 6 is opened at a predetermined opening. By performing such control, the pressure of the supply air A to the fuel cell 1 is controlled to a required value, and the pressure between the first pressure control valve 5 and the second pressure control valve 6 can be reduced. Therefore, since much of the water contained in the exhaust air Ae can be converted to steam, the water recovery rate can be increased, and the humidification performance of the humidifier 2 can be improved. On the other hand, the humidity is 95%
Is exceeded, the supply air A is in a state close to a saturated state. The water generated by the power generation of the fuel cell 1 is taken into the supply air A. However, since the supply air A is almost saturated, the amount of water that can be taken in is small. Supply air A
The generated water that has not been taken into the fuel cell may accumulate in the gas flow path of the fuel cell 1 and block the gas flow path. Therefore, when the humidity of the supply air A exceeds 95%, the first control valve is opened at a predetermined opening and the second pressure control valve 6 is closed at a predetermined opening. Then, the pressure in the humidifier 2 can be increased and the amount of water vaporized in the exhaust air Ae can be reduced, so that the amount of water recovered (the amount of humidification of the supply air A) can be suppressed.

Although not shown, in the first embodiment, a heat retaining means for keeping the pressure control valve 5 warm may be provided. By providing the heat retaining means for keeping the pressure control valve 5 warm, a decrease in the temperature of the exhaust air Ae supplied to the humidifier 2 via the pressure control valve 5 is prevented. Therefore, dew condensation of the exhaust air Ae in the humidifier 2 can be prevented, and the humidification efficiency of the supply air A can be improved.

Here, as the heat retaining means, a known means can be used as appropriate, and for example, a heat retaining material or a heater surrounding the pressure control valve 5 can be used. In addition, for example, cooling water which is heated in the fuel cell 1 and has a temperature of about 80 ° C. can be used.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, a hydrogen supply device is configured to supply hydrogen from a hydrogen tank to a fuel cell, but a liquid raw fuel such as methanol is reformed by a reformer to produce a hydrogen-rich fuel gas, which is then converted to a fuel cell. May be supplied. In addition, the present invention may be applied to the hydrogen supply device side irrespective of whether or not the discharged hydrogen is recycled. Furthermore, the water permeable membrane used for the humidifier is not limited to a hollow fiber membrane. Also, the compressor does not rotate the turbine like a supercharger or a turbocharger, but may be a reciprocating compressor. On the other hand, a hydrogen supply device that supplies hydrogen from a hydrogen tank to a fuel cell was used, but a liquid raw fuel such as methanol was reformed by a reformer to produce a hydrogen-rich fuel gas. This may be configured to be supplied to the fuel cell.

[0036]

As described above, claim 1 of the present invention
According to the invention, the pressure in the fuel cell can be adjusted without excessively increasing the pressure in the humidifier. Therefore, dew condensation of water in the humidifier can be prevented, and the water recovery rate can be improved. Thus, the humidification efficiency of the gas supplied to the fuel cell can be increased.

According to the second aspect of the present invention, the second pressure control means for controlling the exhaust gas pressure in the humidifier is provided downstream of the humidifier. For this reason, since the pressure in the humidifier can be adjusted independently of the required pressure of the fuel cell, the humidification amount of the supply gas can be suitably controlled.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a fuel cell system using a hollow fiber membrane module according to the present invention.

FIG. 2 is an explanatory diagram schematically illustrating a configuration of a fuel cell.

FIG. 3 (a) is a perspective view of a humidifying device accommodating a hollow fiber membrane module, and FIG. 3 (b) is a side sectional view thereof.

FIG. 4 is a configuration diagram showing a modified example of the humidifying device according to the present invention.

FIG. 5 is a configuration diagram of a conventional humidifier for a fuel cell.

[Explanation of symbols]

 Reference Signs List 1 fuel cell 2 humidifier 3 air cleaner 4 compressor 5 (first) pressure control valve (first pressure control means) 6 second pressure control valve (second pressure control means) 21 hollow fiber membrane module FCS fuel cell system AS1 , AS2 Humidifier HS Hydrogen supply device A Supply air Ae Discharge air

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tomohiro Tsuchiya 1-4-1 Chuo, Wako-shi, Saitama Pref. Inside Honda R & D Co., Ltd. (72) Hideo Numata 1-4-1 Chuo, Wako-shi, Saitama F-term in Honda R & D Co., Ltd. (reference) 5H026 AA06 5H027 AA06 KK01 KK31 MM01

Claims (2)

[Claims] 1. A supply gas supplied to a fuel cell and an exhaust gas discharged from the fuel cell are allowed to flow, and moisture contained in the exhaust gas is exchanged with the supply gas for moisture.
In a humidifier for a fuel cell, comprising a humidifier for humidifying the supply gas, wherein a flow path of exhaust gas discharged from the fuel cell,
A humidifier for a fuel cell, comprising a first pressure control means for controlling an outlet pressure of the fuel cell upstream of the humidifier. 2. A flow path for the exhaust gas, comprising a second pressure control means for controlling an exhaust gas pressure in the humidifier downstream of the humidifier, wherein the first pressure control means The humidifying device for a fuel cell according to claim 1, wherein the second pressure control means is controlled in accordance with a humidification-related amount of a supply gas supplied to the fuel cell.