KR20090128005A - Humidification system for fuel cell and fuel cell system using the same - Google Patents

Abstract

PURPOSE: A humidification system for a fuel cell is provided to minimize membrane fouling according to continuous use of a membrane humidifier and to improve durability of the membrane humidifier by suppressing the degradation of moisture transport function. CONSTITUTION: A humidification system for a fuel cell comprises a first filter(500) which removes impurities from moisture-containing unreacted gas discharged form a fuel cell(300); a membrane humidifier(100) for humidifying reaction gas supplied to the fuel cell using the moisture-containing unreacted gas from which impurities is removed. The first filter is installed to the membrane humidifier. The humidification system further comprises a second filter(400) for impurities from the reaction gas provided from the outside to the membrane humidifier.

Description

Humidification system for fuel cell and fuel cell system using same {Humidification System for Fuel Cell and Fuel Cell System using The Same}

The present invention relates to a humidification system for a fuel cell and a fuel cell system using the same. More specifically, durability is greatly improved by minimizing membrane contamination caused by continuous use of the membrane humidifier and minimizing degradation of the moisture transfer function of the membrane humidifier. A humidification system for a fuel cell and a fuel cell system using the same.

A fuel cell is a power generation type battery that generates electricity by combining hydrogen and oxygen. Unlike general chemical cells such as batteries and accumulators, fuel cells can continue to produce electricity as long as hydrogen and oxygen are supplied. Fuel cells have twice the efficiency of internal combustion engines due to no heat loss. In addition, pollutant emissions are low because chemical energy generated by the combination of hydrogen and oxygen is converted directly into electrical energy. Therefore, the fuel cell is not only environmentally friendly, but also has an advantage of reducing anxiety about resource depletion due to increased energy consumption.

These fuel cells can be classified into polymer electrolyte fuel cell (PEMFC), phosphate fuel cell (PAFC), molten carbonate fuel cell (MCFC), and solid oxide fuel cell depending on the type of electrolyte used. SOFC), alkaline fuel cell (AFC), and the like. Each of these fuel cells operates on essentially the same principle, but differs in the type of fuel used, operating temperature, catalyst, and electrolyte. Among them, the polymer electrolyte fuel cell is known to be most promising in transport systems as well as small stationary power generation equipment because it can operate at a lower temperature than other fuel cells and can be miniaturized due to its high power density.

One of the most important factors in improving the performance of a polymer electrolyte fuel cell is supplying a certain amount of water to a polymer electrolyte membrane (PEM) of a membrane-electrode assembly (MEA). This is to maintain the moisture content. This is because power generation efficiency is drastically reduced when the polymer electrolyte membrane is dried.

A method of humidifying a polymer electrolyte membrane includes 1) a bubbler humidification method in which water is supplied to a pressure vessel and a target gas is passed through a diffuser to supply moisture, and 2) the amount of water supplied for a fuel cell reaction is determined. And a direct injection method of supplying water directly to the gas flow pipe through the solenoid valve, and 3) a humidification method of supplying water to the fluidized bed of gas using a polymer membrane.

Among these, the humidification membrane system which humidifies by providing the polymer electrolyte membrane with water vapor in the exhaust gas using a membrane that selectively permeates only the water vapor contained in the exhaust gas is advantageous in that the humidifier can be reduced in weight and size.

The selective permeable membrane used in the humidification membrane system is preferably a hollow fiber membrane having a large permeation area per unit volume when forming a module. In other words, when manufacturing a humidifier using a hollow fiber membrane, high integration of the hollow fiber membrane with a large contact surface area is possible, so that the fuel cell can be sufficiently humidified even with a small capacity, low-cost materials can be used, and the fuel cell is discharged at a high temperature. The moisture and heat contained in the unreacted gas may be recovered and reused through a humidifier. The humidification membrane method using the hollow fiber membrane is mainly applied in automobiles using fuel cells as a power source.

Such a membrane humidifier has a problem that the outer surface of the hollow fiber membrane is contaminated when used for a long time. Contamination of the hollow fiber membranes results in a shortening of the replacement cycle of the membrane humidifier since the water transfer function of the hollow fiber membranes is drastically degraded.

The present invention was derived to solve the above problems, an object of the present invention is to minimize the membrane contamination caused by the continuous use of the membrane humidifier and to suppress the degradation of the moisture transfer function of the membrane humidifier as much as possible durability for fuel cells It is to provide a humidification system and a fuel cell system using the same.

As one aspect of the present invention for achieving the above object, the fuel cell humidification system of the present invention, the first filter for removing impurities from the moisture-containing unreacted gas discharged from the fuel cell; And a membrane humidifier for humidifying the reaction gas to be supplied to the fuel cell by using the moisture-containing unreacted gas from which the impurities are removed.

As another aspect of the present invention for achieving the above object, the fuel cell system of the present invention, the fuel cell; A first filter for removing impurities from moisture-containing unreacted gas discharged from the fuel cell; And a membrane humidifier for humidifying the reaction gas to be supplied to the fuel cell by using the moisture-containing unreacted gas from which the impurities are removed.

Preferably, the first filter is detachably mounted to the membrane humidifier by screwing or the like.

The first filter preferably has a woven structure in the form of a layer.

The membrane humidifier preferably comprises a porous membrane.

The fuel system humidification system may further include a second filter for removing impurities from the reaction gas to be provided to the membrane humidifier from the outside.

In addition, the fuel cell humidification system may further include a blower for providing a reaction gas from which impurities are removed by the second filter to the membrane humidifier.

The membrane humidifier, the housing; And a hollow fiber membrane fixed in the housing, wherein the hollow fiber membrane comprises: a tubular support; And a hydrophilic polymer membrane coated on the tubular support.

The hydrophilic polymer membrane may be made of Nafion, or may be a composite membrane including two or more of polyimide, polyphenylsulfone, polysulfone, polyamideimide, and polyimide.

According to the fuel cell humidification system and the fuel cell system of the present invention as described above, since the moisture-containing unreacted gas discharged from the fuel cell is provided to the membrane humidifier with impurities removed, membrane contamination caused by continuous use of the membrane humidifier. This is minimized.

Therefore, the durability of the membrane humidifier can be greatly improved by suppressing the degradation of the water transfer function of the membrane humidifier to the maximum.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the fuel cell humidification system and fuel cell system according to the present invention.

1 is a view schematically showing a humidifier for a fuel cell according to an embodiment of the present invention.

As shown in FIG. 1, the fuel cell humidifier 100 according to an embodiment of the present invention includes a housing 110 having a bundle of hollow fiber membranes 120. One side of the housing 110 is formed with a first inlet 111a through which the reaction gas to be supplied to the fuel cell is introduced, and on the other side of the housing 110, a first outlet 112a for supplying the reaction gas to the fuel cell. Is formed.

Both end portions of the bundle of hollow fiber membranes 120 are fixed to both sides of the housing 110 with adhesives 130, respectively. The adhesive 130 blocks the flow of air between the first inlet 111a and the first outlet 112a and the central portion of the housing 110, respectively.

On the other hand, since both ends of the hollow fiber membrane 120 bundle are open, the hollow portions of the hollow fiber membrane 120 bundle are in communication with the first inlet 111a and the first outlet 112a, respectively. Accordingly, the reaction gas introduced through the first inlet 111a may move to the other side of the housing 110 in which the first outlet 112a is formed through only the hollow portion of the hollow fiber membrane 120 for the humidifier.

On the other hand, the unreacted inflow into the central portion of the housing 110 through the second inlet 111b and the second inlet 111b through which the water-containing unreacted gas discharged from the fuel cell flows into the central portion of the housing 110. Second outlets 112b for discharging gas are respectively formed.

Looking at the operation of the fuel cell humidifier according to an embodiment of the present invention as described above in detail.

At the same time as the reaction gas to be supplied to the fuel cell is introduced through the first inlet 111a, the water-containing unreacted gas discharged from the fuel cell is introduced into the center of the housing 110 through the second inlet 111b. The reaction gas introduced through the first inlet 111a moves to the first outlet 112a through the hollow portions of the hollow fiber membrane 120 bundle.

While the reaction gas introduced through the first inlet 111a is in a dry state, the unreacted gas introduced into the center portion of the housing 110 through the second inlet 111b contains a large amount of water and thus a hollow fiber membrane ( 120) Humidity difference occurs inside and outside. Due to the difference in humidity inside and outside the hollow fiber membrane 120, moisture of the unreacted gas is selectively transmitted through the membrane to the hollow portion, and the reaction gas moves to the first outlet 112a side along the hollow portion of the hollow fiber membrane 120. The humidity will increase.

On the other hand, the unreacted gas from the fuel cell introduced into the center portion of the housing 110 through the second inlet 111b loses moisture and is gradually dried. The unreacted gas thus dried is the second outlet 112b. Is discharged through). As a result, by the operation of the humidifier of the present invention as described above, it is possible to supply the reaction gas having a higher humidity than the original reaction gas to the fuel cell.

According to an embodiment of the present invention, the second inlet 111b is formed at a portion adjacent to the first outlet 112a, and the second outlet 112b is formed at a portion adjacent to the first inlet 111a. It is preferable that this is to sufficiently permeate the moisture contained in the unreacted gas over the entire portion of the hollow fiber membrane located inside the housing 110.

That is, in the case of the reaction gas moving from the first inlet 111a to the first outlet 112a, the humidity is low at the first inlet 111a, but moisture is continuously supplied from the unreacted gas through the hollow fiber membrane 120. Therefore, the humidity increases toward the first outlet 112a. Accordingly, unreacted gas having a relatively low humidity contacts the hollow fiber membrane 120 positioned on the first inlet 111a and relatively close to the hollow fiber membrane 120 positioned on the first outlet 112a. By allowing unreacted gas of high humidity to contact, it is possible to achieve uniform moisture permeation over the entire hollow fiber membrane 120.

2 is a view showing a cross section of the hollow fiber membrane for a humidifier according to an embodiment of the present invention.

As shown in Figure 2, the hollow fiber membrane 120 for the humidifier according to an embodiment of the present invention is a tubular support 121 having a hollow portion 123, and the hydrophilic coating on the tubular support 121 The polymer film 122 is included. Since the partial pressure of oxygen contained in the air flowing into the fuel cell stack through the humidifier is maintained so that the fuel cell performance is not degraded, the polymer film 122 should be able to selectively permeate only moisture. A representative material of the hydrophilic polymer film 122 used in the hollow fiber membrane 120 for the humidifier is Nafion ^™ developed by Dupont, which has the following chemical structure.

<Chemical Structural Formula of Nafion>

In addition, a single membrane such as polysulfone, polyphenylsulfone, polyetherimide, polyamideimide, polyimide, or a composite membrane in which two or more thereof are mixed may be used as a humidification membrane for fuel cells.

Nafion membranes are preferred for the manufacture of membrane humidifiers because of their fast water transfer performance and excellent gas barrier effect, but they are expensive. Therefore, studies on low-cost, high-performance hollow fiber membranes are being actively conducted. For example, polyimide and polyphenylsulfone or polysulfone and polyphenylsulfone composite membranes are not only inexpensive but also about 80% of Nafion membranes. Indicates the performance. When the optimum design of the composite membrane, the membrane humidifier exhibiting the same humidification performance as the Nafion membrane on the same volume basis may be prepared.

However, unlike a Nafion membrane having a fine microstructure, a single membrane such as polyimide, polyphenylsulfone, polysulfone, polyamideimide, polyimide, or a composite membrane in which two or more thereof are mixed has a porous structure. Particularly vulnerable to contamination of the membrane surface.

In other words, the Nafion membrane having a dense microstructure selectively transmits moisture by chemical reaction, so that the influence of membrane contamination is relatively small. However, since the porous membrane selectively permeates moisture by physical reaction, pore due to contamination of its surface. If this blockage occurs, the degree of performance degradation is more severe than that of the Nafion membrane. Therefore, for membrane humidifiers employing porous membranes, it is very important to minimize membrane contamination over time.

3 is a view schematically illustrating a humidification system for a fuel cell according to an exemplary embodiment of the present invention for minimizing membrane contamination of a humidifier for a fuel cell.

As shown in FIG. 3, in the fuel cell humidification system of the present invention, external air (hereinafter referred to as 'reaction air') is supplied to the fuel cell 300 through the membrane humidifier 100 to supply oxygen to the fuel cell 300. 300). At this time, impurities contained in the reaction air may be introduced into the membrane humidifier 100 together with the reaction air to contaminate the outer surface of the hollow fiber membrane 120.

Accordingly, the fuel cell humidification system of the present invention includes a second filter 400 for removing impurities from the reaction gas to be provided to the membrane humidifier 100. The reaction gas from which impurities are removed by the second filter 400 is introduced into the membrane humidifier 100 by a blower 200. As a result, according to the present invention, it is possible to prevent contamination of the hollow fiber membrane 120 due to the reaction air flowing into the membrane humidifier 100.

However, simply removing impurities from the reaction air flowing into the membrane humidifier 100 only slows the contamination rate of the hollow fiber membrane 120, and can completely solve the contamination problem of the hollow fiber membrane 120 over time. Was not. Applicant proceeds research to determine the cause, moisture-containing unreacted gas from the fuel cell 300 introduced into the membrane humidifier 100 to supply moisture to the reaction gas contaminated hollow fiber membrane 120 It was found to be another cause.

Specifically, the solid polymer fuel cell 300 includes a membrane electrode assembly, and the membrane electrode assembly includes a gas diffusion layer for smooth diffusion of hydrogen and oxygen supplied thereto. This gas diffusion layer is mainly made of carbon fiber material. When such a fuel cell 500 is used for a long time, carbon powder is eluted out of the gas diffusion layer by an air flow, and the carbon powder is mixed with moisture-containing unreacted gas and introduced into the membrane humidifier 100, thereby hollow fiber membrane 120 ) Is contaminating.

Therefore, the humidification system for a fuel cell of the present invention further includes a first filter 500 for removing impurities from moisture-containing unreacted gas discharged from the fuel cell 300. Thus, since only the moisture-containing unreacted gas from which impurities are removed from the first filter 500 is introduced into the membrane humidifier 100 and used for humidification, contamination of the hollow fiber membrane 120 may be fundamentally prevented, and the membrane humidifier ( The lifetime of 100) is increased permanently.

Although the first filter 500 may be manufactured integrally with the membrane humidifier 100, the first filter 500 may be mounted on the membrane humidifier 100 so as to be detachable by screwing or the like. Since the convenience of replacement of the 1st filter 500 can be improved, it is preferable.

Meanwhile, the first filter 500 of the present invention is a metallic material such as stainless steel, monel, nickel, copper, titanium, aluminum, or polypropylene, teflon, brass fiber, or the like. It can be made of a polymer material.

Meanwhile, the first filter 500 of the present invention may be in the form of a nonwoven fabric or a mesh. However, when the first filter 500 is a nonwoven fabric, there is a disadvantage in that the pressure drop due to the air flow is large. Therefore, in order to minimize the pressure drop generated while the moisture-containing unreacted gas from the fuel cell 300 passes through the first filter 500, the first filter 500 preferably has a single layer or a water layer structure. Do.

According to a preferred embodiment of the present invention, the pressure drop through the first filter 500 to filter out impurities of 1 to 10 μm or less is about 0.1 bar based on 6,000 LPM (Liter Per Minute).

Hereinafter, the effects of the present invention will be described in more detail through specific examples and comparative examples. These examples are merely to aid the understanding of the present invention and do not limit the scope of the present invention.

<Example 1>

After the air filter was installed in the port of the humidifier connected to the air outlet of the stack, the 1 kW fuel cell system was operated for 1000 hours. The humidifier consists of 500 centimeters of Nafion hollow fiber of 15 centimeters, and after 1000 hours of operation, the humidifier was compared with the unused humidifier and the humidifier performance.

In order to evaluate the humidification performance, humid air having a temperature of 70 ° C. and a relative humidity of 90% is prepared and humidified with dry air having a temperature of 20 ° C. and a relative humidity of 10%. In the case of unused humidifiers, 500 LPM (liter per minute) of dry air was humidified with air having a temperature of 60 ° C and a relative humidity of 80%. Humidified with air.

<Example 2>

After the air filter was installed in the port of the humidifier connected to the air outlet of the stack, the 1 kW fuel cell system was operated for 1000 hours. The humidifier is composed of 500 centimeters of porous polysulfone hollow fiber of 15 centimeters. After 1000 hours of operation, the humidifier was compared with the unused humidifier and the humidification performance.

In order to evaluate the humidification performance, humid air having a temperature of 70 ° C. and a relative humidity of 90% is prepared and humidified with dry air having a temperature of 20 ° C. and a relative humidity of 10%. In the case of unused humidifiers, 500 LPM (liter per minute) of dry air was humidified with air having a temperature of 55 ° C and a relative humidity of 75%. Humidified with air.

<Example 3>

After the air filter was installed in the port of the humidifier connected to the air outlet of the stack, the 1 kW fuel cell system was operated for 1000 hours. The humidifier is composed of 500 centimeters of porous polyimide hollow fiber of 15 centimeters. After 1000 hours of operation, the humidifier was separated from the fuel cell system and compared with the unused humidifier.

In order to evaluate the humidification performance, humid air having a temperature of 70 ° C. and a relative humidity of 90% is prepared and humidified with dry air having a temperature of 20 ° C. and a relative humidity of 10%. In the case of unused humidifiers, 500 LPM (liter per minute) of dry air was humidified with air having a temperature of 59 ° C and a relative humidity of 79%. Humidified with air.

Comparative Example 1

The 1 kW fuel cell system was operated for 1000 hours without an air filter installed at the port of the humidifier connected to the air outlet of the stack. The humidifier consists of 500 centimeters of Nafion hollow fiber of 15 centimeters, and after 1000 hours of operation, the humidifier was compared with the unused humidifier and the humidifier performance.

In order to evaluate the humidification performance, humid air having a temperature of 70 ° C. and a relative humidity of 90% is prepared and humidified with dry air having a temperature of 20 ° C. and a relative humidity of 10%. In the case of unused humidifiers, 500 LPM (liter per minute) of dry air was humidified with air having a temperature of 60 ° C and a relative humidity of 80%. Humidified with air.

Comparative Example 2

The 1 kW fuel cell system was operated for 1000 hours without an air filter installed at the port of the humidifier connected to the air outlet of the stack. The humidifier is composed of 500 centimeters of porous polysulfone hollow fiber of 15 centimeters. After 1000 hours of operation, the humidifier was compared with the unused humidifier and the humidification performance.

In order to evaluate the humidification performance, humid air having a temperature of 70 ° C. and a relative humidity of 90% is prepared and humidified with dry air having a temperature of 20 ° C. and a relative humidity of 10%. In the case of unused humidifiers, 500 LPM (liter per minute) of dry air was humidified with air having a temperature of 55 ° C and a relative humidity of 75%. Humidified with air.

Comparative Example 3

After the air filter was installed in the port of the humidifier connected to the air outlet of the stack, the 1 kW fuel cell system was operated for 1000 hours. The humidifier is composed of 500 centimeters of porous polyimide hollow fiber of 15 centimeters. After 1000 hours of operation, the humidifier was separated from the fuel cell system and compared with the unused humidifier.

In order to evaluate the humidification performance, humid air having a temperature of 70 ° C. and a relative humidity of 90% is prepared and humidified with dry air having a temperature of 20 ° C. and a relative humidity of 10%. In the case of unused humidifiers, 500 LPM (liter per minute) of dry air was humidified with air having a temperature of 59 ° C and a relative humidity of 79%. Humidified with air.

1 is a view schematically showing a fuel cell membrane humidifier according to an embodiment of the present invention,

2 is a cross-sectional view of the hollow fiber membrane for a humidifier according to an embodiment of the present invention,

3 is a view schematically showing a humidification system for a fuel cell according to an embodiment of the present invention.

<Brief description of the symbols in the drawings>

100: fuel cell membrane humidifier 110: housing

111a: first inlet 111b: second inlet

112a: first outlet 112b: second outlet

120: hollow fiber membrane for the humidifier 130: adhesive

200: blower 300: fuel cell

400: second filter 500: first filter

Claims (13)

A first filter for removing impurities from moisture-containing unreacted gas discharged from the fuel cell; And And a membrane humidifier for humidifying the reaction gas to be supplied to the fuel cell by using the moisture-containing unreacted gas from which the impurities are removed. The method of claim 1, And the first filter is detachably mounted to the membrane humidifier. The method of claim 2, And said first filter is mounted to said membrane humidifier by screwing. The method of claim 1, The first filter has a weaving structure in the form of a layer, characterized in that the fuel cell humidification system. The method of claim 1, And the membrane humidifier comprises a porous membrane. The method of claim 1, And a second filter for removing impurities from the reaction gas to be provided to the membrane humidifier from the outside. The method of claim 6, And a blower for providing a reaction gas from which impurities are removed by the second filter to the membrane humidifier. The method of claim 1, wherein the membrane humidifier, housing; And Humidification system for a fuel cell, characterized in that it comprises a hollow fiber membrane fixed in the housing. The method of claim 8, wherein the hollow fiber membrane, Tubular support; And Humidification system for a fuel cell, characterized in that it comprises a hydrophilic polymer membrane coated on the tubular support. The method of claim 9, The hydrophilic polymer membrane is a fuel cell humidification system, characterized in that made of Nafion (Nafion). The method of claim 9, The hydrophilic polymer membrane is a fuel cell humidification system, characterized in that it comprises at least one of polyimide, polyphenylsulfone, polysulfone, polyamideimide, and polyimide. The method of claim 11, wherein The hydrophilic polymer membrane is a fuel cell humidification system, characterized in that the composite membrane containing two or more polymers. Fuel cell; A first filter for removing impurities from moisture-containing unreacted gas discharged from the fuel cell; And And a membrane humidifier for humidifying the reaction gas to be supplied to the fuel cell by using the moisture-containing unreacted gas from which the impurities are removed.

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