KR100689332B1 - Methanol supply apparatus for fuel cell and method thereof - Google Patents

Abstract

The fuel supply device of the fuel cell of the present invention supplies methanol mixed liquid 41 to the anode 22 and air to the cathode 23 to obtain electricity by an electrochemical reaction. In the mixed liquid storage tank 42 storing the mixed liquid 41, a concentration detecting sensor 51 for detecting the concentration of the methanol mixed liquid 41 is provided, and in accordance with the detected concentration value detected by the concentration detecting sensor 51. The water supply unit 52 for supplying the water 61 and the methanol supply unit 53 for supplying the methanol 71 are installed, and the concentration detection sensor 51 detects the concentration of the methanol mixed liquid 41, Stable power generation is achieved by supplying water 61 or methanol 71 and adjusting the concentration by logical operation using the data previously input to the controller 15.

Description

Fuel supply device of fuel cell and method thereof {METHANOL SUPPLY APPARATUS FOR FUEL CELL AND METHOD THEREOF}

1 is a schematic diagram showing an embodiment of a fuel supply device of a fuel cell of the present invention;

2 is a cross-sectional view showing a single cell of a fuel cell stack.

3 is a flow chart showing a control procedure according to an embodiment of the present invention.

Figure 4 is a schematic diagram showing another embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

10: stack 22: anode

23: cathode 41: methanol mixture

42: mixed liquid storage tank 43: liquid fuel supply line

51: concentration detection sensor 52: water supply unit

53: methanol supply portion 61: water

62: water storage tank 63: water supply line

64, 74, 82, 92: valve 71: methanol

72: methanol storage tank 73: methanol supply line

81: water refill line 91: methanol refill line

The present invention relates to a fuel cell for generating electricity through an electrochemical reaction of fuel and air supplied from the outside, and more particularly, to be able to automatically adjust the concentration of the fuel supplied for power generation of the fuel cell. A fuel supply device for a fuel cell and a method thereof are provided.

In general, a technique related to a fuel cell is known as a device for directly converting energy contained in a fuel into electrical energy, and such a fuel cell generally has a porous anode (ANODE) and a cathode (CATHODE) on both sides of a polymer electrolyte. Is attached, the electrochemical oxidation of hydrogen as a fuel occurs at the anode (anode or anode) and the electrochemical reduction of oxygen as an oxidant at the cathode (reduction electrode or cathode). Is generated.

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. It is used in the form of direct methanol fuel cell (DMFC), which is used in the form or uses liquid methanol as a direct fuel.

The direct methanol fuel cell is a reforming reaction at an electrode by directly supplying a methanol mixture of methanol and water in a predetermined ratio (about 10%: 90%) to a cathode of a stack, which is a power generator, without using a reformer. This has the big advantage that the reformer becomes unnecessary and can simplify the whole system.

However, in the fuel cell using the conventional methanol as described above, when the methanol mixture solution supplied directly to the stack is not mixed at an appropriate concentration or the concentration change occurs due to volatilization, it is not detected. It has often been a problem that the power generation efficiency is lowered by progressing.

An object of the present invention is to provide a fuel supply device for a fuel cell that does not have various problems as described above.

It is another object of the present invention to provide a fuel supply device and a method for a fuel cell suitable for maintaining the concentration of the methanol mixed liquid stored in the fuel storage tank at a constant concentration at all times.

In order to achieve the object of the present invention as described above to supply the methanol mixture through the liquid fuel supply line in the mixed liquid storage tank to the positive electrode of the stack to generate power, and to supply the air to the cathode to obtain the electromotive force from the chemical reaction fuel In the feeder,

A concentration detection sensor for detecting the concentration of the methanol mixture;

A water supply unit comprising a water storage tank, a water supply line, and a valve for storing water to supply water to the liquid fuel supply line to be supplied when the concentration value detected by the concentration detection sensor is higher than a reference value;

When the concentration value detected by the concentration detection sensor is lower than the reference value to supply the methanol to the liquid fuel supply line to control the concentration so that the methanol storage tank for storing the methanol and methanol supply line, comprising a methanol supply line, valve A fuel supply device for a fuel cell is provided.

In addition, in a fuel cell in which a methanol mixed liquid stored in a mixed liquid storage tank is supplied to a stack to generate electricity, the concentration of the methanol mixed liquid stored in the mixed liquid storage tank is detected, and the detected concentration value is compared with a reference value. As a result, when the detected measured value is more than the upper limit of the reference value, an additional water is supplied to the methanol mixture solution supplied to the stack, and below the lower limit, an additional methanol is supplied to control the concentration of the methanol mixture solution. .

BRIEF DESCRIPTION OF THE DRAWINGS To make the construction and operation of the present invention described above clearer, a preferred embodiment of the present invention will be described below.

1 is a schematic configuration diagram of a fuel cell in which a fuel detection apparatus according to the present invention is installed as an embodiment of the present invention.

As shown in the drawing, the overall configuration of the fuel cell 1 includes a stack of solid polymer type generating electricity, a liquid fuel supply means 11 for supplying a liquid fuel to the stack 10, and a stack ( Air line 12 for supplying air to 10), discharge line 13 for discharging CO ₂ and H ₂ O generated from the stack 10, and the concentration of liquid fuel supplied to the stack A concentration detecting sensor 51 for adjusting the concentration, a concentration adjusting means for adjusting to an appropriate concentration when the concentration detected by the concentration detecting sensor 51 deviates from the reference value, and an electronic control unit 15 for executing each type of control process. ).

The stack 10 may be a single cell in which an electrochemical reaction occurs or a plurality of single cells may be sequentially stacked and assembled into bolts. Referring to FIG. 2, a single cell structure will be described. A membrane-electrode assembly (MEA: MEMBRANE-ELECTRODE ASSEMBLY) 24 formed by bonding the anode 22 and the cathode 23 to diffuse gas on both sides of the membrane 21, and both sides of the membrane-electrode assembly 24. A separator 25 which is assembled so as to be in close contact with each other and forms a flow path of fuel gas and an oxygen-containing gas at the anode 22 and the cathode 23, and is disposed on both sides of the separator 25 and the anode 22. ) And current collector plates 26 and 27 serving as current collector electrodes of the cathode 23.

 The electrolyte membrane 21 of the membrane-electrode assembly 24 is an ion exchange membrane made of a polymer material, and an electrolyte membrane 21 commercially available includes a Nafion membrane of DuPont, which serves as a carrier for hydrogen ions, and contacts oxygen with hydrogen. The anode 22 and the cathode 23 serve as a support for the platinum (Pt) catalyst layer, and porous carbon paper or carbon cloth is bonded to both sides of the electrolyte membrane 21. Structure.

The separation plate 25 is formed of a dense carbon plate, and a plurality of ribs are formed to form a fuel gas flow path groove 31 on the surface of the anode 22 during assembly, and oxygen on the surface of the cathode 23. The containing gas flow path groove 32 is formed.                     

It is preferable that the current collector plates 26 and 27 have excellent electrical conductivity, excellent corrosion resistance, and do not generate hydrogen embrittlement. good.

The liquid fuel supply means 11 stacks a mixed liquid storage tank 42 in which a methanol mixed liquid 41 mixed with methanol and water is stored, and a methanol mixed liquid 41 of the mixed liquid storage tank 41. And a solenoid valve (44) mounted on the liquid fuel supply line (43) for supplying water to the liquid fuel supply line (43) to regulate the supply of the methanol mixed liquid (41) supplied to the stack (10). .

In addition, the liquid fuel supply line 43 is connected to the fuel gas flow path groove 31 of the stack 10, and the fuel gas flow path groove 31 is a discharge line connected to the outside of the stack 10 ( 13, and the air line 12 is connected to the oxygen-containing gas flow path groove 32.

On the other hand, the concentration control means 14 is a water storage tank for storing the water 61 to supply water to the liquid fuel supply line 43 when the concentration value detected by the concentration detection sensor 51 is higher than the reference value ( Methanol storage for storing methanol 71 so as to supply methanol to the liquid fuel supply line 43 when the water supply unit 52 and the water supply line 63 and the valve 64 are lower than the reference value. A methanol supply section 53 composed of a tank 72, a methanol supply line 73, and a valve 74 is provided.

In the figure, reference numeral 48 is a solenoid valve provided on the air line 12.

In the fuel cell equipped with the fuel supply device of the present invention configured as described above, when the operator operates the switch of the fuel cell 1, the air line 12 and the liquid fuel supply line according to a control program preset by the electronic controller 15 are provided. The solenoid valves 44 and 48 on the 43 are opened to allow the methanol mixed liquid 41 and air to be supplied to the stack 10.

As described above, the methanol mixed liquid 41 supplied to the stack 10 flows along the fuel gas flow path groove 31 and diffuses to the entire surface of the anode 22 of the membrane-electrode assembly 24 so that electrochemical oxidation of hydrogen proceeds. In addition, air flows along the oxygen-containing gas flow path groove 32 and diffuses across the cathode 23 of the membrane-electrode assembly 24 to cause electrochemical reduction of oxygen, and electricity is generated due to the movement of electrons generated therein. The electricity generated at this time is collected in the current collector plates 26 and 27 and used as an energy source.

At this time, the reaction formula and total reaction formula at each pole are as follows.

Anode _{(ANODE): CH 3 OH +} H 2 O → CO 2 + 6H + + 6e -

Cathode: 3 / 2O ₂ + 6H ⁺ + 6e ^_ → 3H ₂ O

Total Reaction: CH ₃ OH + 3 / 2O ₂ + H ₂ O → CO ₂ + 3H ₂ O

In addition, the methanol mixture liquid 41 supplied to the stack 10 as described above is supplied to the storage tank 42 in a state in which the mixture is mixed at a predetermined ratio in advance or supplied to the storage tank 42 at a predetermined ratio to adjust the mixing ratio. In general, when the concentration of methanol (CH ₃ OH) is high, the lifetime of the polymer electrolyte membrane 21 is reduced, and conversely, when the concentration is low, the power generation efficiency is lowered, so that the mixing is about 10%. In this case, in some cases, even after mixing at a constant mixing ratio or mixed at a constant mixing ratio, methanol is volatilized due to unused for a long time, so that the mixing ratio is varied. The concentration of the methanol mixture 41 supplied to 10) is adjusted and supplied.

The concentration control of the methanol mixture 41 as described above is performed after the predetermined time has elapsed after the start of the fuel cell 1, and as shown in FIG. 3, when the treatment is started, the mixture mixture storage tank 42 The concentration detection sensor 51 provided detects the concentration of the methanol mixed liquid 41, and the detected concentration value is judged by the electronic control unit 15 by logic circuit processing, and the measured value M ₁ is the upper limit value of the reference value. If greater than (a ₁ ), the amount of water 61 to be supplied is calculated to adjust the opening degree of the valve 64 installed on the water supply line 63 to the stack 10 through the fuel supply line 43. The methanol mixed liquid 41 to be supplied can be maintained at a proper concentration.

In addition, when the measured value (M ₁ ) of the concentration detected by the concentration detection sensor 51 is smaller than the lower limit (a ₂ ) of the reference value, the amount of methanol 71 to be supplied is calculated to calculate the amount of methanol on the methanol supply line 73. The concentration of the methanol mixed liquid 41 supplied to the fuel supply line 43 is adjusted by adjusting the opening degree of the valve 74 installed in the fuel supply line 43, and the concentration value detected by the concentration detection sensor 51 is the upper limit value (a ₁ ) of the reference value. When it is within the lower limit (a ₂ ) and the methanol mixed liquid 41 stored in the mixed liquid storage tank 42 is continuously supplied.

  The amount of water 61 or methanol 71 supplemented through the water supply line 63 or the methanol supply line 73 is changed in concentration when water 61 or methanol 71 is mixed with the methanol mixture 41. The relationship between the data and the data is input to the electronic control unit 15, and then the value detected by the concentration detection sensor 51 is logically processed by the electronic control unit 15 to supply water 61 or methanol. It is possible to calculate the amount of 71 and to adjust the opening degree of the valves 64 and 74 so that the water 61 or methanol 71 flows by the calculated amount.

Another embodiment of the present invention will be described.

4 is a schematic configuration diagram of a fuel cell according to another embodiment of the present invention. As shown in the drawing, in the state in which the configuration of the fuel cell 1 in the first embodiment is provided as it is (same parts are given the same numbers A water replenishment line 81 and a valve 82 are installed to replenish the water 61 from the water storage tank 62 to the mixed liquid storage tank 42. The mixed liquid storage tank is installed in the methanol storage tank 72. A methanol replenishment line 91 and a valve 92 are provided so as to replenish methanol 71 with 42.

According to another embodiment of the present invention configured as described above, when the concentration measurement value of the methanol mixed liquid 41 stored in the mixed liquid storage tank 42 deviates from the reference value, the methanol mixed liquid 41 supplied to the fuel supply line 43 is supplied. ), And the mixed liquid storage tank 42 by adjusting the opening degree of the valves 82 and 92 on the water replenishment line 81 or the methanol replenishment line 91 by controlling the concentration of the electronic control unit 15. It is possible to adjust the concentration of the methanol mixed liquid 41 stored in the.

 As described above in detail, the fuel supply device of the fuel cell of the present invention installs a concentration detection sensor in the mixed liquid storage tank in which the methanol mixed liquid is stored, installs a water storage tank, a water supply line and a valve, If the concentration value of the mixed liquid detected by the concentration detection sensor is higher than the reference value by installing a methanol supply line and a valve, adjust the opening degree of the valve installed in the water supply line to supply water to the methanol mixed liquid, and if the reference value is lower than the methanol supply line. By adjusting the opening degree of the valve installed in the supply of methanol to adjust the concentration of the methanol mixture, stable power generation is achieved.

Claims (3)

In the fuel supply device of a fuel cell that supplies a mixed methanol mixture through the liquid fuel supply line from the mixed liquid storage tank to the anode of the stack to generate power, and supplying air to the cathode to obtain electromotive force from the chemical reaction, A concentration detection sensor for detecting the concentration of the methanol mixed solution, a water storage tank for storing water to supply water to the liquid fuel supply line to be supplied when the concentration value detected by the concentration detection sensor is higher than the reference value, and A water supply unit comprising a water supply line connecting the water storage tank and the liquid fuel supply line, and a valve installed on the water supply line to control an amount of water supplied to the liquid fuel supply line; And A methanol storage tank for storing methanol and a methanol supply line connecting the methanol storage tank and the liquid fuel supply line to supply methanol to the liquid fuel supply line when the concentration value detected by the concentration detection sensor is lower than a reference value. And a methanol supply unit disposed on the methanol supply line and configured to control an amount of methanol supplied to the liquid fuel supply line. According to claim 1, wherein the water supply unit and the methanol supply unit further comprises a water supplement line and a methanol supplement line each provided with a valve to control the concentration of the methanol mixture by supplying water and methanol to the mixed liquid storage tank. A fuel supply device for a fuel cell. Detecting the concentration of the methanol mixture stored in the mixed liquid storage tank; Comparing the detected concentration value with a reference value; Additionally supplying water to the methanol mixture when the detected concentration value is equal to or higher than an upper limit of the reference value; And And supplying methanol to the methanol mixed solution when the detected concentration value is equal to or lower than a lower limit of the reference value.

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