KR100625693B1 - Methanol supply apparatus for fuel cell - 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. The light emitting sensor 45 and the light receiving sensor 45 'are disposed in the storage tank 42 storing the mixed liquid 41 so as to face each other, and the amount of ultraviolet light detected by the light receiving sensor 45' is controlled by the electronic control unit 46. By calculating the concentration value by the logical operation process using the data previously inputted in the) and display it on the display unit 47, when the operator sees this change and the change of the concentration is confirmed, the methanol or water is supplemented so that stable power generation can be achieved. do. In addition, the light emitting / receiving sensors 45 and 45 'are installed at a predetermined height inside the storage tank 42 so that the detection amount of ultraviolet light according to the change in absorbance when the sensor is in the mixed liquid and when the mixed liquid is exhausted and exposed. It is possible to detect the replenishment time or exchange time of the mixed solution.

Description

Fuel supply device of fuel cell {METHANOL SUPPLY APPARATUS FOR FUEL CELL}

1 is a schematic diagram showing the configuration of a fuel cell equipped with a fuel supply device of the present invention.

Figure 2 is a cross-sectional view showing a single cell structure of the stack according to the present invention.

Figure 3 is a longitudinal sectional view showing a storage tank in the present invention.

4 is a graph showing absorbance curves at specific wavelengths of liquid fuel;

Explanation of symbols on the main parts of the drawings

41: methanol mixed liquid 42: storage tank

45: light emitting sensor 45 ': light receiving sensor

46: electronic control unit 47: display unit

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 detect the concentration and exhaustion of the fuel supplied for the generation of fuel cells. The present invention relates to a fuel supply device for a fuel cell suitable for enabling a user to easily recognize a fuel replenishment time or replacement time.

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.

In addition, the exhausted state of the methanol mixture is such that the floating of the float installed inside the storage tank is indicated by the water level indicator on the outside of the storage tank so that the user can recognize the replacement time by visually confirming the change. There was a inconvenience in use because the water level indicator of the storage tank should be checked from time to time, and there was a problem that the power generation could not be made smoothly because the fuel could not be exchanged in a timely manner.

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.

Another object of the present invention is to provide a fuel supply device for a fuel cell suitable for detecting the concentration of the methanol mixed liquid stored in the fuel storage tank so that the methanol mixed liquid can maintain a proper concentration.                         

Still another object of the present invention is to provide a fuel supply device for a fuel cell suitable for detecting an exhausted state of fuel stored in a fuel storage tank so that the supply of fuel can be smoothly performed continuously at an appropriate time.

In order to achieve the object of the present invention as described above, in the fuel supply device of a fuel cell for supplying a liquid fuel to the electrode, and obtaining an electromotive force from the chemical reaction of the liquid fuel,

A fuel supply device for a fuel cell is provided, comprising absorbance detecting means for detecting a change in absorbance according to the concentration of the liquid fuel so as to detect a change in concentration and an exhausted state of the liquid fuel.

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 provided with a fuel detection device according to the present invention 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 ( An air line 12 for supplying air to the air 10, a secondary battery 13 for charging the electricity generated in the stack 10 to drive a load or operating a valve, and a stack 10 A discharge line 14 for discharging the generated CO ₂ and H ₂ O is provided.

The stack 10 may be a single cell (SINGLE CELL) or a plurality of single cells that are sequentially stacked and assembled into bolts. The single cell structure will be described with reference to FIG. 2. 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.

As shown in FIGS. 1 and 3, the liquid fuel supply means 11 includes a storage tank 42 in which a methanol mixed liquid 41 in which methanol and water are mixed at a predetermined ratio is stored, and the storage tank 41. ) Of the liquid fuel supply line 43 for supplying the methanol mixed liquid 41 of the present invention to the stack 10 and the methanol mixed liquid 41 supplied to the stack 10 by being mounted on the liquid fuel supply line 43. A solenoid valve 44 for controlling supply, a light emitter 45 installed on one side of the storage tank 42 to emit ultraviolet rays, and a light emitter 45 installed on the other side of the storage tank 42 corresponding to the light emitter 45; And a light receiver 45 'for receiving ultraviolet light emitted from the light emitter 45, an electronic controller 46 for performing various control processes, and a display unit 47 for displaying control results for the user to check. Equipped.

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 ( 28, and the air line 12 is connected to the oxygen-containing gas flow path groove 32.

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

The operation and effect of the fuel cell provided with the fuel supply device of the present invention configured as described above will be described.

When the operator operates the switch of the fuel cell 1, the solenoid valves 44 and 48 on the air line 12 and the liquid fuel supply line 43 are opened in accordance with a preset control program in the electronic control unit 46 to control the methanol mixed liquid. Allow 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 the 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 some cases, the methanol mixed liquid 41 is not mixed at a constant mixing ratio at the time of mixing, or even after being mixed at a predetermined mixing ratio, methanol is volatilized for long periods of unused, and the mixing ratio is changed. In this case, the storage tank 42 The electronic control unit 46 determines whether the ultraviolet light emitted from the light emitting sensor 45 installed at one side is received by the light receiving sensor 45 ', and whether the detected amount of the received ultraviolet light deviates from the specified value at a specific wavelength band by the electronic control unit 46. In the case where the mixing ratio of the methanol mixed liquid 41 is out of the prescribed value by making a mark, an operator additionally supplies methanol or water to the storage tank 42 to appropriately adjust the mixing ratio of the methanol mixed liquid 41.

As shown in the graph shown in FIG. 4, the concentration detection based on the degree of light reception of ultraviolet rays is performed by using the characteristic of the methanol mixed liquid 41 mixed at a certain concentration to absorb at a specific wavelength band. It is possible to detect the density value by inputting the data as data into the data (46) and performing a logical operation on the value detected by the light receiving sensor 45 'by the electronic controller 46.

Further, by appropriately disposing the light emitting sensor 45 and the light receiving sensor 45 'at a lower predetermined height inside the storage tank 42, the replenishment timing of the methanol mixed liquid 41 or replacement of the storage tank 42 itself. The timing is detected, which is similar to the case where the light emitting sensor 45 and the light receiving sensor 45 'installed at a predetermined height inside the storage tank 42 are exposed while the methanol mixed liquid 41 is exhausted. 41) The absorbance value in the case of exposure and the absorbance value in the case of exposure are made into the data in advance in the electronic control unit 46, and when there is a difference in absorbance, the state of exhaustion of the methanol mixed liquid 41, i.e., the replenishment timing or storage It is possible to detect the replacement timing of the tank 42.

As described above in detail, the fuel supply device of the fuel cell of the present invention is provided with a light emitting sensor for emitting ultraviolet light and a light receiving sensor for receiving ultraviolet light in a storage tank in which the methanol mixture is stored, and the difference in absorbance according to the concentration change of the mixed solution. Data is inputted to the electronic control unit, and the value detected by the light receiving sensor is logically processed by the electronic control unit so as to detect whether it is out of the prescribed value. The life of the membrane is not shortened and there is an effect that stable power generation is achieved.

In addition, the light emitting sensor and the light receiving sensor are installed at a predetermined height inside the storage tank, and when the methanol mixture is exhausted below the installation height of the sensor, the sensor is exposed so that the light absorbing value and the absorbance value when the light emitting / receiving sensor is in the mixed liquid are exposed. When the conductivity value data is input to the electronic control unit, the data detected by the sensor is logically processed by the electronic control unit to detect the exhausted state of the fuel. It can be effective.

Claims (2)

A fuel cell fuel supply apparatus for supplying liquid fuel to an electrode and obtaining electromotive force from a chemical reaction of the liquid fuel, And a light absorbance detecting means for detecting a difference in absorbance of the liquid fuel and detecting a change in concentration and exhaustion of the liquid fuel. According to claim 1, wherein the absorbance detection means is installed on the inner side of the storage tank is installed in the light emitting sensor for emitting ultraviolet light, and the light receiving for receiving the ultraviolet light emitted from the light emitter is installed on the other side corresponding to the light emitter A fuel supply device for a fuel cell comprising a sensor, an electronic controller for preliminarily inputting absorbance values detected by the light receiving sensor and a logic operation, and a display unit for displaying the processing result of the electronic controller. .

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