KR20040003656A - Apparatus for removing water film of fuel cell and the method thereof - Google Patents

Abstract

PURPOSE: An apparatus for removing a water film of a fuel cell and its preparation method are provided, to remove the water film formed on a cathode for maintaining the electric power generating performance to be constant. CONSTITUTION: The generator of a fuel cell comprises an anode where fuel is supplied through a fuel supply line(103), a cathode where air humidified at a humidifier is supplied through a air supply line(107), and a separator between the anode and the cathode, and the electricity is generated by the electrochemical reaction between the fuel and the humidified air. The method comprises the steps of detecting the output state of a generator, and directly supplying air inside the flow path of a cathode through a bypass line(118) which is set to go round a humidifier(111) if the detected value is below a set value, thereby removing the water film formed on the surface of a cathode.

Description

Water film removal device and method of fuel cell {APPARATUS FOR REMOVING WATER FILM OF FUEL CELL AND THE METHOD THEREOF}

The present invention relates to a fuel cell that generates electricity through an electrochemical reaction between fuel and air supplied from the outside, and more particularly, to prevent performance from being degraded by removing the water film formed on the cathode of the generator. A fuel cell water film removing apparatus and method thereof are provided.

In general, the fuel cell (FUEL CELL) is a device that directly converts the energy of the fuel into electrical energy, such a fuel cell system is usually attached to both the anode (ANODE) and the cathode (CATHODE) around the polymer electrolyte membrane At the anode (electrode or anode), electrochemical oxidation of hydrogen as a fuel, and at the cathode (reduction electrode or cathode), electrochemical reduction of oxygen as an oxidant occurs and electrical energy is generated by the movement of electrons generated at this time. .

Hydrogen supplied to such a fuel cell is purified by purifying only hydrogen (H ₂ ) from a hydrocarbon-based (CH-based) fuel such as LNG, LPG, CH ₃ OH, and gasoline through a desulfurization process → reforming reaction → hydrogen purification process. PEMFC (PROTON EXCHANGE MEMBRANE FUEL CELL) used in the form, and BFC (BORON FUEL CELL) which use BH ₄ ^- in the form of an aqueous solution and directly use it as fuel, are introduced.

A schematic configuration of a conventional BFC is illustrated in FIG. 1, which will be briefly described as follows.

As shown, the overall configuration of the fuel cell 1 is provided with a fuel tank 3 for storing BH ₄ ⁻ in an aqueous state on one side of the generator 2 that generates electricity, the fuel tank 3 The anode and the generator 2 are connected to the fuel supply line 4 and the fuel recovery line 5, and the fuel supply line 4 is provided with a fuel pump 6 for pumping fuel.

In addition, an air supply line 7 and an air discharge line 8 are installed at the cathode of the generator 2, and a filter for filtering the air supplied to the generator 2 is provided in the air supply line 7. 8), an air compressor 9 for pumping air and a humidifier 10 for humidifying the air are provided.

In addition, the humidifier 10 is connected to the water supply line 12 is connected to the water tank 11, the water supply line 12 is provided with a pump 13 and the valve 14 in sequence.

In addition, the air discharge line 8 is provided with a gas-liquid separator 15 for separating the water contained in the air discharged from the generator 2, the gas-liquid separator 15 is separated into the fuel tank The water recovery line 16 is provided so that it can supply to (3).

In addition, a power meter (POWER METER) 17 for detecting the power output from the generator 2 of the fuel cell 1 is provided at the output end of the generator 2, and the power provided as such A controller (not shown) for controlling the overall performance is provided separately with reference to the power value detected by the meter 17.

In the conventional fuel cell configured as described above, when the operation switch of the device is turned on, the fuel pump 6 pumps the BH ₄ ⁻ in the aqueous state stored in the fuel tank 3 to the generator through the fuel supply line 4. Air is supplied to the cathode of the generator 2 through the air supply line 7 by operating the air compressor 9 at the same time as supplying to the anode of (2), the air supplied in such a humidifier (10) It is supplied with sufficient humidification.

As described above, the BH ₄ ⁻ and the air in the aqueous solution state supplied to the generator 2 undergo the electrochemical oxidation of hydrogen at the anode of the generator 2, and the electrochemical reduction of oxygen occurs at the cathode. Electricity is generated due to the movement, and the generated electricity is collected at a current collecting plate (not shown) and used as an energy source.

The reaction formula at this time

BH ₄ ^- + 2O a _{2 → 2H 2 O + BO 2} E 0 = 1.64 V.

On the other hand, the electricity generated by the power generation of the generator 2 as described above is output to operate the load, the power output at that time is detected by the power meter 17, the detected power value is the controller ( In the case of deviation from the set value in comparison with the set value in (not shown), the operation of the fuel pump 6 or the air compressor 9 is adjusted so that the set power value is output.

However, in the conventional fuel cell 1 as described above, the air humidified by the humidifier 10 is supplied to the cathode of the generator 2 so that an active reaction proceeds and a water film is formed on the surface of the electrolyte membrane of the generator 2. In the event of flooding, the performance is reduced by inhibiting the reaction. In such a case, even when the air compressor 9 or the fuel pump 6 is operated, the amount of fuel or air supplied is adjusted. This had a problem that could not be improved satisfactorily.

An object of the present invention devised in view of the above problems is to provide a fuel cell water film removing apparatus and method suitable for removing the water film formed on the electrolyte membrane surface of the generator to improve the performance of the generator.

1 is a schematic configuration diagram showing a structure of a conventional fuel cell.

2 is a block diagram of a fuel cell equipped with a water film removing device of the present invention.

Figure 3 is a longitudinal sectional view showing a unit cell in the present invention.

Explanation of symbols on the main parts of the drawings

101: generator 103: fuel supply line

104: fuel recovery line 107: air supply line

108: air exhaust line 117: front three-way valve

117 ': rear three way valve 118: bypass line

In order to achieve the object of the present invention as described above, a fuel supply line for supplying fuel is connected to the inlet of the anode of the generator in which power generation is performed, and a fuel recovery line for recovering fuel after the reaction is connected to the outlet. The inlet of the cathode of the generator is connected to the air supply line for supplying air, the outlet is connected to the air discharge line for discharging the air after the reaction, the air supply line is a filter, air compressor In the fuel cell in which the humidifier is installed in order, the electricity is generated by the electrochemical reaction between the anode and the cathode inside the generator,

An air supply line before and after the humidifier is provided with a front and rear three-way valve that can adjust the opening degree, and bypasses the humidifier to supply air to remove the water film formed on the negative electrode inside the generator. Provided is a water film removing apparatus for a fuel cell, which is configured by installing a bypass line connecting a valve.

Hereinafter, with reference to the embodiment of the accompanying drawings, the water film removing apparatus and method of the fuel cell of the present invention configured as described above will be described in more detail.

2 is a block diagram of a fuel cell equipped with a water film removing device of the present invention.

As shown, the present invention is an aqueous solution state that is supplied to the anode (ANODE) of the generator 101 at a certain distance from the generator (101) in which electricity is generated by the electrochemical reaction of BH ₄ and air in the aqueous state The fuel tank 102 is installed to store the BH ₄ of the fuel tank 102, the lower portion of the fuel tank 102 and the anode (ANODE) inlet portion of the generator 101 to supply fuel fuel 103 Is connected to the outlet of the anode (ANODE) and the upper portion of the fuel tank 102 is connected to the fuel recovery line 104 to recover the fuel after the reaction, the fuel supply line (103) A fuel pump 105 for pumping fuel of the tank 102 is provided.

In addition, an air supply line 107 is installed at the inlet of the cathode 101 of the generator 101 so that air can be supplied, and the air after the reaction is discharged at the outlet of the cathode of the cathode CATHODE. An air discharge line 108 is provided, and the air supply line 107 is provided with a filter 109, an air compressor 110, and a humidifier 111.

In addition, the humidifier 111 is connected to the water supply line 113 so that water can be supplied from the water tank 112, the water supply line 113 is provided with a pump 114, the air The discharge line 108 is provided with a gas-liquid separator 115 for separating the water contained in the air so that the separated water can be recovered to the fuel tank 102 through the water recovery line 116.

In addition, the front and rear three-way valves 117 and 117 'are installed at the front and rear sides of the humidifier 111 installed in the air supply line 107, and the front and rear three-way valves are installed. Both ends are connected to (117) and (117 '), and a bypass line 118 is provided to bypass the humidifier 111, so that air can be supplied directly to the cathode when necessary.

In addition, a power meter 119 is provided at the output end of the generator 101 for detecting power, and a controller for adjusting performance by comparing the detected value detected by the power meter 119 with a set value (not shown). City) is provided.

3 shows a single cell structure of the generator 101. As shown in the drawing, a membrane electrode formed by bonding an anode 122 and a cathode 123 to diffuse gas to both sides of the electrolyte membrane 121 is illustrated. MEA (MEMBRANE-ELECTRODE ASSEMBLY) 124 and the membrane-electrode assembly 124 are assembled so as to be in close contact with each other, the flow path 125 of fuel gas and oxygen-containing gas at the anode 122 and the cathode 123. And a current collector plate 127 disposed on both sides of the separation plate 126 to form a collector electrode of the positive electrode 122 and the negative electrode 123.

The electrolyte membrane 121 of the membrane-electrode assembly 124 is an ion exchange membrane made of a polymer material. The electrolyte membrane 121 commercially available includes a Nafion membrane of DuPont, which serves as a carrier for hydrogen ions, The anode 122 and the cathode 123 serve as a support for supporting a catalyst layer made of a hydrogen storage alloy, and porous carbon paper or carbon cloth is formed on both sides of the electrolyte membrane 121. It is a structure joined to the.

The separating plate 126 is made of a dense carbon plate, and a plurality of flow path grooves 126a are formed at an inner side thereof so that fluid flows.

It is preferable that the current collector plate 127 is excellent in electrical conductivity, excellent in corrosion resistance, and does not generate hydrogen embrittlement.

In the fuel cell equipped with the water film removing apparatus of the present invention configured as described above, when the operation switch of the device is turned on, the fuel pump 105 pumps the BH ₄ in the aqueous state stored in the fuel tank 102 to the fuel. It is supplied to the anode 122 of the generator 101 through the supply line 103.

In the air compressor 110, air is supplied to the cathode 123 of the generator 101 through the air supply line 107. The BH ₄ in the aqueous solution state thus supplied is the electrolyte membrane 121. A gap flows along the flow path 125 formed on the outer surface of the anode 122, and air flows along the flow path 125 formed on the outer surface of the cathode 123, and diffuses the anode 122. In the electrochemical oxidation proceeds, the cathode 123 is electrochemical reduction is carried out to generate electricity by the movement of electrons, the electricity generated at that time is collected in the current collector plate 127 is used as a power source.

The reaction formula of the reaction generated in the generator 101 is

_{^{Anode: BH 4 - + 8OH -}} → BO 2 - + 6H 2 O + 8e - E 0 = 1.24 V

_{Cathode: 2O 2 + 4H 2 O} + 8e - → BOH - E 0 = 0.4 V

Total: BH ₄ ^- + 2O a _{2 → 2H 2 O + BO 2} E 0 = 1.64 V.

On the other hand, the output value detected by the power meter 119 when the power generation is generated in the generator 101 as described above is out of the set value compared to the set value in the controller (not shown), the air compressor 110 or the fuel pump ( By adjusting the operation of 105), the output is adjusted by adjusting the amount of air or fuel supplied.

In addition, when the output is not restored normally despite the operation of the air compressor 110 and the fuel pump 105 as described above, the front three-way valve 117 and the rear three-way installed in the air supply line 107. By adjusting the opening degree of the valve 117 'so that the air is directly supplied to the cathode 102 side of the generator 101 through the bypass valve 118 for a predetermined time, the air is inside the flow path 125 of the cathode 102. The water is purged to remove the water film attached to the side of the cathode 102.

After performing the water film removal as described above for a predetermined time, by adjusting the opening degree of the front and rear three-way valve 117 (117 ') again so that the air is humidified in the humidifier 111 is supplied to the generator 101, Even if a performance decrease due to water film formation occurs in the generator 101 of the device, prompt measures are taken to maintain constant performance at all times.

In the above embodiment, the case where the water film removing operation is performed through the bypass line 118 when the detection value detected by the power meter 119 is out of the setting value by comparing with the setting value is described as an example. It is also possible to periodically perform the water film removal operation so as to maintain constant performance at all times.

In addition, in the above embodiment, a case of BFC, which is a power generation method using BH ₄ ⁻ in an aqueous state as a fuel, has been described as an example. However, the present invention is not limited thereto, and the same type of PEMFC is used as the power generation method using hydrogen gas. In addition to maintaining the performance of the entire system at a certain level with the membrane removal device, it is possible to apply any number of other similar types of fuel cells without departing from the spirit and scope of the present invention.

As described above in detail, the water film removing device and method of the fuel cell of the present invention are provided with front and rear three-way valves at the front and rear of the humidifier installed in the air supply line, and both ends are provided at the front and rear three-way valves. By connecting a bypass line that bypasses the humidifier, if the detected value detected by the power meter installed at the output of the generator is out of the standard value, the opening and closing of the three-way valve is adjusted. By being supplied to the inside of the generator to be purged for a predetermined time, the water film formed on the negative electrode of the generator is removed, so that the power generation performance of the device is always maintained at a constant level.

Claims (5)

A fuel supply line for supplying fuel is connected to the inlet of the anode of the generator where power generation takes place, and a fuel recovery line for recovering fuel after the reaction is connected to the outlet of the generator. The air supply line for supplying the air is connected, and the outlet part is connected with the air exhaust line for discharging the air after the reaction, and the filter, the air compressor, the humidifier are installed in the air supply line in order, In a fuel cell in which electricity is generated by an electrochemical reaction between an anode and a cathode, The front and rear three-way valves for adjusting the opening degree are installed in the air supply lines before and behind the humidifier, and the air is supplied by bypassing the humidifier to remove the water film formed on the cathode inside the generator. A water film removing device of a fuel cell, characterized in that the bypass line is connected to both ends of the three-way valve and the rear three-way valve is installed. The apparatus of claim 1, wherein the generator is a BFC generator using BH ₄ ⁻ in an aqueous solution as a fuel. The apparatus of claim 1, wherein the generator is a PEMFC generator using hydrogen gas as a fuel. Fuel is supplied to the anode of the generator through the fuel supply line, and humidified air from the humidifier is supplied through the air supply line to the anode of the generator, and the anode and the cathode are interposed between the electrolyte membrane inside the generator. In a fuel cell in which electricity is generated by the electrochemical reaction of the fuel supplied to the humidified air, When the output state of the generator is detected and the detected value is less than or equal to the set value, constant performance is always maintained by directly supplying air to the inside of the flow path of the cathode through a bypass line provided to bypass the humidifier to remove the water film attached to the surface of the cathode. Method of removing water film of fuel cell. 5. The method of removing water film of a fuel cell according to claim 4, wherein the fuel cell is formed by a power meter provided at an output end of the generator for detecting the output state of the generator.