KR20060020024A - Fuel cell system and stack - Google Patents

Abstract

Fuel cell system according to the present invention, at least one electricity generating unit for generating electrical energy through the electrochemical reaction of hydrogen and oxygen; A fuel supply unit supplying a fuel containing hydrogen to the electricity generation unit; And an air supply unit supplying air to the electricity generation unit, wherein the electricity generation unit includes a membrane-electrode assembly (MEA), a separator disposed on both sides of the membrane-electrode assembly, and It is provided with a magnetic material connected to at least one separator.

Fuel cell, stack, MEA, separator, electrolyte membrane, hydrogen ion, moisture, magnetic material, magnetic force

Description

FUEL CELL SYSTEM AND STACK

1 is a schematic diagram showing an overall configuration of a fuel cell system according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of the stack shown in FIG. 1.

3 is a cross-sectional configuration diagram showing the electricity generating unit shown in FIG.

TECHNICAL FIELD The present invention relates to fuel cell systems, and more particularly, to stacks and separators used in fuel cell systems.

As is known, a fuel cell is a power generation system that converts chemical reaction energy of hydrogen and oxygen contained in hydrocarbon-based materials such as methanol, ethanol, and natural gas directly into electrical energy.

This fuel cell is classified into a phosphoric acid fuel cell, a molten carbonate fuel cell, a solid oxide fuel cell, a polymer electrolyte type or an alkaline fuel cell according to the type of electrolyte used. 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 these, the polymer electrolyte fuel cell (PEMFC, hereinafter referred to as PEMFC for convenience), which has been developed recently, has excellent output characteristics, low operating temperature, and fast start-up and response characteristics compared to other fuel cells. In addition to mobile power supplies such as automobiles, as well as distributed power supplies such as homes and public buildings and small power supplies such as for electronic devices has a wide range of applications.

Such a PEMFC basically includes a stack, a reformer, a fuel tank, a fuel pump, and the like to constitute a system. The stack forms the body of the fuel cell, and the fuel pump supplies the fuel in the fuel tank to the reformer. The reformer reforms the fuel to generate hydrogen gas and supplies the hydrogen gas to the stack. Thus, the PEMFC supplies fuel in the fuel tank to the reformer by operation of the fuel pump, reforming the fuel in the reformer to generate hydrogen gas, and electrochemically reacting the hydrogen gas and oxygen in the stack to generate electrical energy. Let's do it.

In the fuel cell as described above, the stack that substantially generates electricity is a stack of several to tens of cells of a unit consisting of a membrane-electrode assembly and a separator called bipolar plates in the art. Made of structure. The membrane-electrode assembly includes an anode electrode and a cathode electrode attached to both surfaces with an electrolyte membrane therebetween. The separator not only supplies hydrogen gas and oxygen necessary for the reaction of the fuel cell to the anode electrode and the cathode electrode of the membrane electrode assembly, but also functions as a conductor that connects the anode electrode and the cathode electrode of the membrane electrode assembly in series. do.                         

On the other hand, in the fuel cell, the stack is one of the important design for improving the efficiency of the fuel cell is to increase the hydrogen ion conductivity of the electrolyte membrane. In other words, in the membrane-electrode assembly, the ion conductivity of the electrolyte membrane that transfers hydrogen ions to the cathode electrode together with moisture becomes an important factor that determines the performance of the fuel cell.

Therefore, in order to improve the efficiency of the fuel cell system, it is important to improve the ionic conductivity of the electrolyte membrane by changing the chemical structure of the electrolyte membrane, which has not been specified in the past, which does not help to improve the efficiency of the fuel cell. I can't do it.

The present invention has been made in view of the above points, and an object thereof is to provide a fuel cell system and a stack having a structure capable of improving ion conductivity of an electrolyte membrane by magnetic force.

In order to achieve the above object, a fuel cell system according to the present invention comprises: at least one electricity generating unit generating electrical energy through an electrochemical reaction between hydrogen and oxygen; A fuel supply unit supplying a fuel containing hydrogen to the electricity generation unit; And an air supply unit supplying air to the electricity generating unit,

The electricity generating unit,

A membrane-electrode assembly (MEA), a separator disposed on both sides of the membrane-electrode assembly, and a magnetic material connected to the at least one separator are provided.

In the fuel cell system according to the present invention, the separator forms a hydrogen passage provided on the anode electrode side of the membrane-electrode assembly and an air passage provided on the cathode electrode side of the membrane-electrode assembly.

In the fuel cell system according to the present invention, it is preferable that the magnetic body is made of a plate type and placed in close contact with a surface opposite to a surface forming a passage of the separator.

In the fuel cell system according to the present invention, a plurality of the electric generators may be provided, and the magnetic body may be disposed between the separators of the electric generators adjacent to each other to form a stack having a stacked structure of the electric generators.

In addition, the fuel cell system according to the present invention may be installed between the stack and the fuel supply unit, a reformer for reforming the fuel supplied from the fuel supply unit to generate hydrogen gas is connected to the fuel supply unit and the stack.

In addition, in order to achieve the above object, the stack for a fuel cell system according to the present invention has a close structure by a membrane-electrode assembly (MEA) and a separator disposed on both sides of the membrane-electrode assembly. And a magnetic body provided with at least one electric generator, the magnetic body being provided to the electric generator and providing a predetermined magnetic force to the membrane-electrode assembly.

In the stack for a fuel cell system according to the present invention, the separator forms a hydrogen passage provided on the anode electrode side of the membrane-electrode assembly and an air passage provided on the cathode electrode side of the membrane-electrode assembly.

In addition, in the stack for a fuel cell system according to the present invention, the magnetic material may be connected to the at least one separator.

In addition, the stack for a fuel cell system according to the present invention may be installed between the separators in which the magnetic bodies are adjacent to each other.

In addition, in the stack for a fuel cell system according to the present invention, it is preferable that the magnetic body is made of a plate type and placed in close contact with a surface opposite to a surface forming a passage of the separator.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

1 is a schematic diagram showing an overall configuration of a fuel cell system according to an embodiment of the present invention.

Referring to FIG. 1, the system 100 generates a hydrogen gas by reforming a fuel containing hydrogen, and converts chemical energy generated by electrochemical reaction of the hydrogen gas and oxygen into an electrical energy directly. A fuel cell (Polymer Electrode Membrane Fuel Cell; PEMFC) method is adopted.

In the fuel cell system 100 according to the present invention, the fuel for generating electricity includes methanol, ethanol or natural gas.                     

However, the fuel described below is defined as a fuel consisting of a liquid phase for convenience.

In addition, the system 100 may use pure oxygen gas stored in a separate storage means as oxygen reacting with hydrogen contained in the fuel, or may use air containing oxygen as it is. However, the latter example is explained below.

The fuel cell system 100 basically includes a reformer 3 that generates hydrogen gas from the fuel, and at least one electricity generator 19 that generates electrical energy through an electrochemical reaction between the hydrogen gas and oxygen. ), A fuel supply unit (1) for supplying the fuel to the reformer (3), and an air supply unit (5) for supplying air to the electricity generating unit (19).

Alternatively, the fuel cell system 100 according to the present invention may employ a direct methanol fuel cell (DMFC) method capable of supplying the fuel directly to the electricity generating unit 19 to produce electricity. It may be. Such a direct methanol fuel cell fuel cell, unlike the polymer electrolyte fuel cell, does not require the reformer 3 shown in FIG. However, hereinafter, the fuel cell system 100 employing the polymer electrolyte fuel cell method is described as an example for convenience, and the present invention is not necessarily limited thereto.

The reformer 3 described above has a structure of a conventional reformer that generates hydrogen gas from the fuel through a chemical catalytic reaction by thermal energy and reduces the concentration of carbon monoxide contained in the hydrogen gas. In detail, the reformer 3 generates hydrogen gas from the fuel through a catalytic reaction such as steam reforming, partial oxidation, or autothermal reaction. As an example, the reformer 3 reduces the concentration of carbon monoxide contained in the hydrogen gas by a catalytic reaction such as a water gas conversion method, a selective oxidation method, or purification of hydrogen using a separation membrane.

The fuel supply unit 1 is connected to the reformer 3, and includes a fuel tank 9 for storing fuel and a fuel pump 11 connected to the fuel tank 9. The fuel pump 11 serves to discharge the liquid fuel stored in the fuel tank 9 by a predetermined pumping force.

The air supply unit 5 is connected to the stack 7, and has an air pump 13 that can suck air with a predetermined pumping force and supply the air into the stack 7.

The stack 7 which receives hydrogen gas through the fuel supply unit 1 and the reformer 3 and receives air from the air supply unit 5 electrochemically reacts hydrogen and oxygen to generate electrical energy and as a by-product. It is configured to generate heat and water.

FIG. 2 is an exploded perspective view of the stack shown in FIG. 1.

Referring to FIG. 2, the stack 7 applied to the present embodiment includes a plurality of electricity generating units generating electrical energy through an oxidation / reduction reaction of hydrogen gas and oxygen contained in the air through the reformer 3. It consists of (19). Each of the electricity generating units 19 is a minimum unit for generating electricity, and a membrane-electrode assembly (hereinafter referred to as "MEA") that oxidizes / reduces hydrogen gas and oxygen in the air. 21 and separators 23 and 25 arranged in close contact with both sides of the MEA 21.

The electricity generating unit 19 is centered on the MEA 21 and the separators 23 and 25 are arranged on both sides thereof to form a single stack, and the electricity generating unit 19 is provided in plural in this embodiment. To form a stack (7) of a laminated structure such as. And the outermost of the stack 7 may be a pressing plate 27 for close contact with the plurality of electricity generating unit 19 described above. However, the stack 7 according to the present invention excludes the pressure plate 27, so that the separators 23 and 25 positioned at the outermost sides of the plurality of electricity generating units 19 take the role of the pressure plate. Can be configured. In addition, the press plate 27 may be configured to have a unique function of the separators 23 and 25 in addition to the function of bringing the plurality of electricity generating units 19 into close contact.

According to the present embodiment, the electricity generating unit 19 configured as described above includes a magnetic material 29 that is substantially connected to the separators 23 and 25. In the stack 7 having a stack structure of the electricity generating units 19, the magnetic body 29 is interposed between the separators 23 and 25 of the electricity generating units 19 which are adjacent to each other, so as to generate a predetermined magnetic force. It is provided to the MEA 21 between the separators 23 and 25. In view of the fact that the separators 23 and 25 are generally rectangular, the magnetic body 29 is made of the same rectangular plate type as that of the separators 23 and 25. And the magnetic body 29 is preferably formed of a permanent magnet. The permanent magnet may be formed of various materials, and may be formed of ferrite, and may include transition elements such as Ni, Co, and Mn, and may also include a heater-based metal.

3 is a cross-sectional configuration diagram showing the electricity generating unit shown in FIG.

Referring to FIG. 3, the separators 23 and 25 are closely arranged with the MEA 21 interposed therebetween to form a hydrogen passage 15 and an air passage 17 on both sides of the MEA 21, respectively. The hydrogen passage 15 is located on the anode electrode 29 side of the MEA 21, and the air passage 17 is located on the cathode electrode 31 side of the MEA 21.

The hydrogen passage 15 and the air passage 17 are respectively disposed in a straight line at random intervals on the bodies 23a and 25a of the separators 23 and 25, and are formed by alternately connecting both ends thereof. It is becoming. Of course, the arrangement structure of the hydrogen passage 15 and the air passage 17 is not limited to this. At this time, the hydrogen passage 15 is formed on one surface of one separator 23, and the air passage 17 is formed on one surface of the other separator 25. The magnetic body 29 described above is in close contact with the surface opposite to the surface on which the passages 15 and 17 of the separators 23 and 25 are formed.

The MEA 21 interposed between the two separators 23 and 25 has an active region 21a having a predetermined area and undergoing an oxidation / reduction reaction. The anode electrode (A) is formed on both surfaces of the active region 21a. 29) and the cathode electrode 31, and the electrolyte membrane 33 between the two electrodes (29, 31). The MEA 21 has an inactive region 21b connected to an edge of the active region 21a. Here, in the non-active area 21b, a sealing material for sealing the edges of the contact surfaces of the separators 23 and 25 corresponding to the active area 21a, preferably, a gasket is formed (see FIG. 2).

The anode electrode 29 forming one surface of the MEA 21 is a portion receiving hydrogen gas containing water through a hydrogen passage 15 formed between the separator 23 and the MEA 21. Hydrogen gas is supplied to the catalyst layer through a gas diffusion layer (GDL) made of carbon paper or carbon cloth, and the hydrogen gas is oxidized in the catalyst layer to convert the converted electrons. The separator 25 moves to the cathode electrode 31, and hydrogen ions are transferred to the cathode electrode 31 through the electrolyte membrane 33. At this time, the electricity generating unit 19 generates a current by the flow of electrons.

In addition, the cathode electrode 31 from which the hydrogen ions generated from the anode electrode 29 are moved through the electrolyte membrane 33 is formed through the air passage 17 formed between the separator 25 and the MEA 21. Which is supplied with air, which also supplies air to the catalyst layer through a gas diffusion layer made of carbon paper or carbon cloth, wherein oxygen in the air and hydrogen ions and electrons transferred from the anode electrode 29 are transferred. The reaction is reduced to produce heat and water at a predetermined temperature.

The electrolyte membrane 33 is formed of a solid polymer electrolyte having a thickness of 50 to 200 μm, and enables ion exchange to transfer hydrogen ions generated in the catalyst layer of the anode electrode 29 to the catalyst layer of the cathode electrode 31 together with water. Let's do it.

According to the fuel cell system 100 according to the present invention configured as described above, a plurality of electricity generating units 19 formed by arranging the separators 23 and 25 on both sides with the MEA 21 as the center and While the magnetic bodies 29 are interposed between the separators 23 and 25 of the neighboring electricity generating units 19, the electrical generating units 19 are brought into close contact with each other through the pressing plate 27, and they are fastened together. The stack 7 is formed.

Therefore, the hydrogen gas containing water is supplied to the anode electrode 29 of the MEA 21 through the hydrogen passage 15 of the separator 23, and the air containing oxygen is supplied to the air passage 17 of the separator 25. When supplied to the cathode electrode 31 of the MEA 21 through, the anode 29 decomposes the hydrogen gas into electrons and hydrogen ions (protons) through an oxidation reaction. Here, the hydrogen ions are moved to the cathode electrode 31 through the electrolyte membrane 33 with moisture by a predetermined pressure acting from the fuel supply unit 1, and electrons are adjacent to the MEA through the separators 23 and 25. It moves to the cathode electrode 31 of 21, at which time current is generated by the flow of electrons. The cathode electrode 31 generates heat and moisture at a predetermined temperature through the reduced reaction of the transferred hydrogen ions, electrons, and oxygen.

In this process, the hydrogen ions pass through the electrolyte membrane 33 together with the water to move to the cathode electrode 31, and the magnetic material is separated between the separators 23 and 25 of the adjacent electricity generating units 19. Since 29 is provided, the above water is attracted to the magnetic body 29 by the magnetic force of the magnetic body 29. This principle is due to the fact that moisture has a polarity, and this polarity of moisture is due to the bonding state of the hydrogen atoms and oxygen atoms constituting the water molecules. That is, since the oxygen atoms attract more electron pairs than the hydrogen atoms, the shared electron pairs are biased toward the oxygen atom side, and the bonding angle between the oxygen atom and the hydrogen atom is 104.5 °. Negative charges, hydrogen atoms become positively charged, and water molecules become polar molecules.

Therefore, while the hydrogen ions pass through the electrolyte membrane 33 together with the moisture, the moisture is attracted to the cathode electrode 31 by the magnetic force of the magnetic body 29, thereby further improving the ion conductivity of the electrolyte membrane 33. You can.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the scope of the invention.

As described above, according to the fuel cell system according to the present invention, by providing a magnetic body that draws moisture passing through the electrolyte membrane together with hydrogen ions to the cathode electrode by magnetic force, the ion conductivity of the electrolyte membrane can be improved. Therefore, since the electrochemical reaction of the MEA can be further activated, the performance of the fuel cell can be improved. In addition, the electrochemical reaction of the MEA can be further activated by the magnetic material, thereby reducing the parasitic power consumed to supply hydrogen gas to the MEA, thereby further improving the energy efficiency of the system.

Claims (10)

At least one electricity generating unit generating electrical energy through an electrochemical reaction between hydrogen and oxygen; A fuel supply unit supplying a fuel containing hydrogen to the electricity generation unit; And Air supply unit for supplying air to the electricity generating unit Including; The electricity generating unit, A fuel cell system comprising a membrane-electrode assembly (MEA), a separator disposed on both sides of the membrane-electrode assembly, and a magnetic material connected to the at least one separator. The method of claim 1, The separator forms a hydrogen passage provided on the anode electrode side of the membrane-electrode assembly, and an air passage provided on the cathode electrode side of the membrane-electrode assembly. The method of claim 2, The magnetic body is formed of a plate type, and the fuel cell system is in close contact with the side opposite to the surface forming the passage of the separator. The method of claim 3, wherein And a plurality of the electricity generating units, wherein the magnetic bodies are disposed between the separators adjacent to each other to form a stack having a stacked structure of these electricity generating units. The method of claim 1, And a reformer for reforming the fuel supplied from the fuel supply unit to generate hydrogen gas between the stack and the fuel supply unit, the fuel cell system being connected to the fuel supply unit and the stack. At least one electricity generating unit comprising a membrane-electrode assembly (MEA) and a close contact structure formed by a separator disposed on both sides of the membrane-electrode assembly, And a magnetic body provided in the electricity generating unit to provide a predetermined magnetic force to the membrane-electrode assembly. The method of claim 6, And the separator forms a hydrogen passage provided on the anode electrode side of the membrane-electrode assembly and an air passage provided on the cathode electrode side of the membrane-electrode assembly. The method of claim 7, wherein And a stack of the magnetic material connected to the at least one separator. The method of claim 8, A stack for a fuel cell system, wherein the magnetic bodies are provided between the separators adjacent to each other in an electricity generating unit. The method of claim 9, The magnetic body is made of a plate type, and closely stacked on a surface opposite to a surface forming a passage of the separator.

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