KR100810366B1 - Apparatus for fueling in direct methanol fuel cell - Google Patents

Abstract

The fuel electrode and the cathode are located on both sides of the electrolyte, and the fuel and air are supplied to the cells of the DMFC having a supply port and an outlet port for circulating and supplying fuel and air to the anode side and the cathode side, respectively. Provided is a fuel supply device having a structure for discharging carbon dioxide (CO ₂ ) exhaust gas. The fuel supply device includes a fuel supply port for discharging the stored fuel and an exhaust gas inlet for receiving gas discharged from the stack on one surface of the fuel tank for storing the fuel therein, the coupling part being sealingly coupled to the anode side of the fuel cell stack. And a gas discharge part having a membrane fixedly coupled to a portion of the outer surface of the fuel tank and discharging only the gas filled in the fuel tank to the outside of the tank by the pressure of the gas.

Fuel Cell, DMFC, CO2 Emissions, Methanol

Description

Fuel supply device for fuel cell {APPARATUS FOR FUELING IN DIRECT METHANOL FUEL CELL}             

1 shows a schematic diagram for explaining the principle of a direct methanol fuel cell;

2 is a cross-sectional view of a fuel supply apparatus of a fuel cell according to a preferred embodiment of the present invention.

<Code Description of Main Parts of Drawing>

20: fuel supply device, 22: fuel cell stack,

24: fuel tank, 26: fuel,

28: fuel supply port, 30: exhaust gas inlet,

32: fuel inlet, 34: gas-up area,

36: gas permeable membrane, 38, 40: membrane support.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply device for a fuel cell, and in particular, to supply fuel to a cell of a direct methanol fuel cell (hereinafter referred to as "DMFC") and to generate carbon dioxide (CO ₂ ) generated by a cell reaction. A fuel supply apparatus having a structure for discharging exhaust gas.

The fuel cell, as is well known, instead of directly burning hydrogen used as fuel and oxygen in the air, an electrochemical reaction in which only hydrogen ions move and electrons move through an electrolyte that can pass only ions. It refers to a high-efficiency power generation device that generates electricity by generating a. There are many kinds of such fuel cells, which are classified according to the material of the electrolyte formed between the two electrodes. For example, a polymer electrolyte fuel cell, in which an electrolyte is a solid polymer, is called a polymer electrolyte fuel cell, and a fuel cell using methanol mixed with water as a fuel without using hydrogen as a gas as a direct methanol fuel cell (Direct methanol fuel cell, DMFC). DMFC has a lower energy density than hydrogen, but it is easy to handle fuel and has a low operating temperature. Due to these advantages, DMFC has attracted attention as an optimal power source for replacing primary and secondary batteries. A schematic diagram of the structure and power generation principle of a direct methanol fuel cell is shown in FIG. 1.

1 is a schematic diagram illustrating the principle of a direct methanol fuel cell. Referring to FIG. 1, a polymer electrolyte layer 12 for use as an ion exchange membrane as a material of a polymer membrane is positioned at a central portion of a housing 10 of a fuel cell. The anode 14 and the cathode 16 are positioned at both sides of the electrolyte layer 12. Each of the anode 14 and the cathode 16 is made by attaching a catalyst layer of porous platinum / carbon, platinum + ruthenium / carbon, etc. on a porous conductive catalyst support such as carbon fiber paper. The fuel 18 mixed with methanol reacts electrochemically in the housing 10 (methanol is oxidized) to generate carbon dioxide, hydrogen ions, and electrons at the anode 14 as shown in Chemical Formula 1 below. Hydrogen ions generated in the anode 14 through the reaction as shown in Chemical Formula 1 move through the polymer electrolyte 12 to the cathode (anode) 16 to react with oxygen (usually from air) to generate water as shown in Equation 2 below. At this time, the electrons generated in the anode 14 move to the anode through an external circuit, resulting in a current flow. In the overall reaction of this process, methanol and oxygen react to produce water and carbon dioxide, as shown in Formula 3 below. In a practical system this reaction takes place in the presence of platinum based electrocatalyst material in the electrode.

Fuel electrode (cathode) reaction

Air electrode (anode) reaction

Overall reaction

As can be seen in the overall reaction of Chemical Formula 3, when 1 mol of methanol is reacted, 1 mol of carbon dioxide gas is generated. The volume of the liquid phase density of the methanol is 1 mol to about 0.786 g / m l is 40.64 ㎖, carbon dioxide gas of the vapor of methanol generated by the reaction has a volume of 22.4 ℓ under the same conditions. That is, carbon dioxide produced when 1 mol of liquid methanol is consumed The volume of gas reaches about 550 times.

The smooth supply of fuel in the chemical reaction of a fuel cell is the most basic requirement. Injecting fuel from DMFC using liquid fuel requires a fuel supply method different from the unit cell performance test or forced fuel supply method.

An apparatus for supplying fuel into a fuel cell in a DMFC is disclosed in US Pat. No. 5,759,712, which was invented by American “Robert G. Hockaday” and patented June 2, 1998. The fuel cell disclosed in the above patent discloses only a focus on the supply side of liquid fuel. For example, a technical configuration of supplying liquid fuel injected into a fuel bottle embedded in a plastic case of a fuel cell to a fuel cell through a fuel needle formed of a capillary tube. That is, the prior patent is a method of supplying the fuel filled in the fuel container to the fuel cell using a capillary phenomenon. However, the fuel supply apparatus disclosed in the above patent has a problem that the efficiency of the cell performance is not good due to the carbon dioxide exhaust gas generated in the fuel cell stack because the fuel container is sealed.

As described in Chemical Formulas 1, 2, and 3, DMFC has a volume expansion of about 550 times by the carbon dioxide gas generated when the liquid methanol is consumed. If the carbon dioxide gas is not removed smoothly, Interfering with the contact of the electrode is a cause of degradation of the electrode performance. In addition, if the fuel cell system is in a sealed form, not only the fuel contact of the electrode by the carbon dioxide gas generated in the fuel cell stack is disturbed, but also fuel leakage of the sealing portion due to the increase in pressure in the fuel container is concerned. If the fuel supply unit and the fuel cell stack are open to the outside, it is difficult to apply the portable power supply due to the possibility of the fuel leaking out, and in the case of methanol having high volatility, a loss due to evaporation occurs. Moreover, the loss of fuel due to evaporation is a more serious problem if the temperature of the system is increased by reaction.

Therefore, it is an object of the present invention to produce a stable and continuous operation of DMFC, The present invention provides a fuel supply device that enables smooth removal of gas and supply of fuel at the same time.

The present invention for achieving the above object has a fuel electrode and an air electrode located on both sides of the electrolyte, the supply port (exhaust port) and the exhaust port (exhaust port) for supplying fuel and air to the anode side and the cathode side A fuel cell having a fuel cell stack having a structure, the fuel cell stack having a fuel supply port for discharging stored fuel and an exhaust gas inlet for receiving gas discharged from the stack on one surface of a fuel tank for storing fuel therein; A connection portion sealingly coupled to the anode side of the fuel tank and having a membrane on the side of a portion of a gas up area in the fuel tank for discharging only the gas filled in the fuel tank to the outside of the tank by the pressure of the gas. Characterized in that the gas discharge portion is formed.

The fuel supply device of the present invention configured as described above is provided with a gas permeable membrane (Membrane) having a fine configuration of a constant size on the side of the gas up region portion of the tank, while supplying the fuel in the tank to the anode of the fuel cell stack The carbon dioxide gas generated by the reaction at the anode is selectively discharged to the outside of the apparatus.

Preferably, the gas permeable membrane is a resin of polyfluorine, polyalkene, cellulosics, polyvinyls, polysulfons, and polyamide resins. Good, Teflon (Teflon) can be used as the fluororesin fiber.

Fine pores (pores) formed in the gas permeable membrane preferably has a diameter of about 0.2 to 0.6 ㎛.

In addition, it is preferable that the membrane member is made of porous silicon fiber, and a plurality of holes are formed in the housing of the fuel tank on the outermost side of the gas discharge part.

Hereinafter, a process of supplying fuel to a fuel cell stack and a process of discharging exhaust gas generated from the anode to the outside of the fuel cell system according to the configuration of the fuel supply device of the DMFC according to a preferred embodiment of the present invention and the configuration thereof It will be described in detail with reference to. In addition, in describing the present invention, when it is determined that a detailed description of components that are too obvious to those skilled in the art may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. Will be.

It is to be understood that the above description and the accompanying drawings are intended to represent only preferred embodiments of the invention. It should be apparent to those skilled in the art that various modifications and variations of the present invention are apparent without departing from the scope and spirit of the invention as set forth in the appended claims.

2 is a cross-sectional view of a fuel supply apparatus of a fuel cell according to a preferred embodiment of the present invention. Referring to FIG. 2, the fuel supply device 20 according to the embodiment of the present invention is positioned in a sealed manner to the fuel cell stack 22. For example, while the fuel 26 injected into the fuel tank 24 is supplied to the anode side of the fuel cell stack 22 through the fuel supply port 28, the carbon dioxide gas generated by the reaction of the anode is supplied again through the drainage inlet 30. It is supposed to flow smoothly into 24. That is, the fuel supply port 28 and the exhaust gas inlet 30 are formed in the connection part 42 of the lower surface of the fuel tank 24, The fuel supply port 28 and the exhaust gas inlet 30 is formed in an appropriate number. The gas discharge part 44 is formed on the upper surface of the fuel tank 24. In the embodiment of the present invention, the gas outlet 44 is located on the upper side, but is preferably installed in the vicinity of the gas up area 34 where carbon dioxide gas can be best collected inside the fuel tank 24. Here, the gas up area 34 means a position where the carbon dioxide gas is best collected in the fuel tank 24. The gas up area 34 may be selected by appropriately designing the shape of the fuel tank 24. Also, the position can be appropriately selected. In an embodiment of the invention the gas outlet 44 is located on the upper side of the fuel tank 24. The gas outlet 44 is fitted with a membrane 36 sandwiched between sidewalls of the protruding region of the tank 24, and is positioned on the membrane supports 38 and 40 above and below the membrane 36. The outer wall of the fuel tank 24 positioned above the membrane support 36 has a plurality of exhaust holes 46 so that carbon dioxide gas in the tank can be smoothly discharged to the outside.

As the material of the membrane 36, a synthetic resin having micropores is used so that the aqueous methanol solution used as the fuel of the fuel cell does not pass, and only gaseous carbon dioxide gas can pass therethrough. For example, it is preferable to use resins of polyfluorine, polyalkene, cellulosics, polyvinyls poly sulfons, and polyamide resins. It is preferable to use Teflon as the fluororesin fiber. As the membrane supports 38 and 40, a silicon fiber made of a porous material may be used.

It should be noted that the fuel supply device as shown in FIG. 2 may be manufactured in an integrated form with a fuel cell stack or a separate type using a separate connection tool.

The operation of supplying fuel to the anode of the fuel cell stack using the fuel supply device according to the embodiment of the present invention and the operation of discharging carbon dioxide gas generated therefrom to the outside of the fuel cell system will be described in detail with reference to FIG. 2. do.

Now, when fuel is supplied through the fuel inlet 32 formed in the upper portion of the fuel tank 24 and the inside thereof is filled with methanol, which is an aqueous solution, the fuel cell stack through the fuel supply port 28 of the connection 42 with gravity and fuel pressing pressure. The fuel is supplied to the anode of 22. In this case, the fuel injection port 32 is made of a silicon rubber or the like, and the fuel supply in the fuel tank 24 is injected using a syringe or the like.

When the fuel is supplied to the fuel cell stack as described above, the carbon dioxide gas generated at the anode in the fuel cell stack 22 is smoothly introduced into the fuel tank 24 through the exhaust gas inlet 30 formed at the lower portion of the connection portion 42 as described above. At this time, the flow of the carbon dioxide gas and the fuel is reversed, as shown in FIG. 1, and the fuel cell stack 22 and the connection portion 42 of the fuel supply device 20 have a space large enough to not significantly affect the flow of each other. In addition, the fuel supply device 20 is preferably designed so that the generated carbon dioxide gas is smoothly collected where the membrane 36 is located.

When the carbon dioxide gas generated by the reaction of the fuel cell stack 22 is continuously collected in the gas up zone 34 through the exhaust gas inlet 30, and the reaction time is continued, the amount of carbon dioxide gas collected in the gas up zone 34 becomes large. The pressure increases within the defined space of 24. Increased pressure acts as a driving force, so that a plurality of vents formed in the membrane supporters 36 and 38 and the housing of the membrane 36 and the fuel tank 24 in which the carbon dioxide gas collected in the gas up zone 34 constitutes the gas outlet 44 It is discharged to the outside of the fuel cell system through the vent 46 formed in the.

Membrane supports 38 and 40 are fixedly positioned at the top and bottom of the membrane 36 to minimize physical deformation of the membrane 36. Membrane 36 used herein is chemically stable to methanol, and has a pore in the range of 0.2 to 0.5 μm, so that a liquid methanol aqueous solution does not pass therethrough and has a characteristic of selectively passing only carbon dioxide gas. As the material of the membrane 36, it is preferable to use a fluororesin fiber, polyalkene, celsus blade, polyvinyl, polysulfone, or a polyamide-based resin. Teflon may be used as the fluororesin fiber.

In the embodiment of the present invention, a plurality of vent holes 46 are formed in the outermost housing of the gas outlet 44 among the outer surfaces of the fuel tank 24, but if necessary, the membrane support 38 may be fixedly attached to the outermost part. Can have an effect. At this time, the membrane support 38 should be bonded correctly so as not to be separated from the fuel tank 24, or fixedly attached to the fuel tank 24 through grooves.                     

As described above, the fuel supply apparatus according to the embodiment of the present invention smoothly supplies fuel of the fuel cell stack and simultaneously discharges carbon dioxide gas of the stack generated by the reaction of the anode to the outside of the system through the fuel tank. It is possible to improve fuel leakage and improve contact between the fuel and the electrode, thereby making it possible to stably operate the fuel cell system.

In the above embodiment, a configuration of discharging carbon dioxide gas from a portion of the fuel tank has been described, but it should be noted that the present invention can be applied regardless of the shape of the tank. For example, when the shape of the fuel tank is cylindrical, the membrane and the membrane supporters may be formed in a cylindrical shape, and vent holes may be formed at appropriate positions of the fuel tank.

As described above, the present invention can smoothly remove carbon dioxide gas generated from the fuel cell stack and fuel supply to the DMFC system by installing a brain having a predetermined size range of pores on one side of the fuel tank. have. Therefore, smooth removal of the carbon dioxide gas produced by the electrode can be achieved to improve the contact between the fuel and the electrode can have a stable stack performance. In addition, by smoothly removing the carbon dioxide gas generated from the electrode, it is possible to prevent excessive pressure increase inside the system and to prevent fuel leakage due to weakening of the sealing portion, thereby achieving stable stack performance. In addition, it is possible to supply stable fuel by maintaining a constant pressure condition inside the system at all times, and it is possible to reduce the loss due to the volatilization of fuel caused by the temperature rise due to the fuel cell stack operation, thereby enabling long-term operation.

Claims (7)

A fuel cell having a fuel electrode stack having a fuel electrode and an air electrode positioned at both sides of an electrolyte, and having a supply port and a discharge port configured to circulate and supply fuel and air to the fuel electrode side and the air electrode side, respectively. A fuel supply port for discharging the stored fuel and an exhaust gas inlet for receiving the gas discharged from the stack are formed on one surface of the fuel tank storing the fuel therein, and a connection part sealingly coupled to the anode side of the fuel cell stack is formed. A gas discharge part having a gas-permeable membrane fixedly coupled to a portion of an outer surface of the fuel tank to discharge only the gas filled in the fuel tank to the outside of the tank by the pressure of the gas, And the gas discharge part includes a membrane supporter fixed to the outer surface of the fuel tank and positioned on both sides of the membrane to prevent a change in the shape of the membrane. The fuel supply device of claim 1, wherein the gas permeable membrane is a resin of any one of fluororesin fibers, polyalkenes, celsus vulcanis, polyvinyl, polysulfone, and polyamide-based resins. The fuel supply device for a fuel cell of claim 2, wherein the fluororesin fiber is Teflon. delete The fuel supply apparatus of claim 1, wherein the membrane support is a silicon fiber made of a porous material. The fuel supply apparatus according to claim 5, wherein a plurality of holes are formed in a housing of the fuel tank at the outermost side of the gas discharge part. The fuel supply device for a fuel cell according to any one of claims 1, 2, 3, 5, and 6, wherein the minute holes formed in the gas permeable membrane have a diameter of about 0.2 to 0.6 mu m.

Images