KR100673746B1 - Seperator for fuel cell and, Stack and Fule cell system having thereof - Google Patents

Abstract

The present invention relates to a separator for a fuel cell and a fuel cell system employing the same, wherein a flow path for flowing a fuel containing hydrogen and an oxygen or oxygen containing oxidant is formed on each of the electrode-electrolyte composites. The flow paths are formed in a plurality of arrays of two or three arrays, and each of the flow paths is multi-refractive in the allocated area of the separator.

As a result, the hydrogen-containing fuel and the oxygen or the oxygen-containing oxidant are introduced to form an even flow over the entire area of the separator, and prevents overheating occurring at the inlet and adjacent portions of the conventional inlet, and evenly generates proper heat generation. As a result, the lifespan of the separator is extended compared to the prior art, and the even flow of the fuel and the oxidant is also uniformly supplied to the electrode-electrolyte composite, thereby reducing the life of the electrode-electrolyte composite by the conventional local supply. While being prevented, a small pump is used to reduce power consumption and noise.

 Fuel Cell, Separator, Stack, Bipolar Plate, Monopolar Plate

Description

Separator for fuel cell and, Stack and Fule cell system having

1 is a side view schematically showing a flow path formed in a conventional separator,

2 is a graph showing the amount of heat generated in the separator shown in FIG.

3 is a schematic view showing a fuel cell system according to a preferred embodiment of the present invention;

4 is an exploded perspective view schematically showing the stack shown in FIG. 3;

FIG. 5 is a side view schematically illustrating a flow path of the separator illustrated in FIG. 4;

FIG. 6 is a side view schematically showing the first modified example of FIG. 5;

FIG. 7 is a side view schematically showing the second modified example of FIG. 5.

<Description of Symbols for Main Parts of Drawings>

100 fuel cell system 200 stack;

220 ... electrode-electrolyte composite 220 ... separator,

222 ... inlet 224 ... outlet,

226 ... middle 230 ... Euro,

300 fuel tank 310, the first pump,

320 ... reformer 400 ... second pump.

The present invention relates to a fuel cell separator and a fuel cell system employing the same. More particularly, the flow path of the separator is changed to facilitate the flow of fuel or oxidant, and the fuel cell system is also applied to the fuel cell system.

In general, a fuel cell converts chemical energy into electrical energy by an electrochemical reaction that generates hydrogen and oxygen in air as fuels in a hydrocarbon-based material including methanol, ethanol or natural gas. It is a system made up of.

Such a fuel cell may artificially generate an electrochemical reaction between hydrogen and oxygen without a combustion process to generate electricity and heat as a by-product thereof.

In addition, the fuel cell may be a phosphoric acid fuel cell operating at around 150 to 200 ° C., a molten carbonate fuel cell operating at a high temperature of 600 to 700 ° C., and a solid oxide type operating at a high temperature of 1000 ° C. or higher, depending on the type of electrolyte used. It is classified into a fuel cell, a polymer electrolyte type and an alkaline type fuel cell operating at room temperature to 100 ° C or lower.

Each of these fuel cells operates on essentially the same principle, but is distinguished by the type of fuel, operating temperature, catalyst and electrolyte.

Among the various types of fuel cells, the polymer electrolyte fuel cell (PEMFC) has a high current density per unit area because there is no risk of corrosion or evaporation due to the electrolyte because the polymer is used as the electrolyte. Its output characteristics are much higher than other fuel cells and its operating temperature is low, so it can be used as a portable power source for automobiles, distributed power sources for homes and public buildings, and small power sources such as electronic devices. Development of this is being actively promoted.

Such an electrolyte fuel cell includes a stack (also called a fuel cell body), a fuel tank, a fuel pump for supplying fuel to the stack from the fuel tank, and an air pump for supplying air containing oxygen or oxygen. This is basically required, and includes a reformer for generating hydrogen gas by reforming the fuel in the process of supplying fuel stored in the fuel tank to the stack and supplying the hydrogen gas to the stack.

Therefore, in the polymer electrolyte fuel cell, the fuel stored in the fuel tank is supplied to the reformer by the pumping force of the fuel pump, and the reformer reforms the fuel to generate hydrogen gas and supply it to the stack. The hydrogen gas and the air pump By the electrochemical reaction of hydrogen gas and oxygen in the stack receiving oxygen or air at the same time is configured to produce electrical energy.

On the other hand, the fuel cell includes a direct methanol fuel cell (DMFC) having a configuration in which the reformer is excluded from the polymer electrolyte fuel cell.

This direct methanol fuel cell system excludes the reformer from the polymer electrolyte fuel cell as described above, and the other components and operation functions are the same.

In addition, according to the fuel and oxidant supply method in such a fuel cell system, it is divided into active type and passive type. The active type is configured to supply fuel and oxidant by a separate pump, and the passive type The mold is configured to supply fuel and oxidant without a separate supply pump.

The stack generating substantially electricity in the polymer electrolyte fuel cell and the direct methanol fuel cell includes an electrode-electrolyte assembly, and a separator called a bipolar plate or a monopolar plate in the art. It consists of a structure in which a plurality of cells of a unit are stacked.

In addition, the electrode-electrolyte composite includes an electrolyte membrane (Membrane), an anode electrode and a cathode electrode attached to both surfaces of the electrolyte membrane.

In order to supply fuel and oxidant to the electrode-electrolyte composite, a separator is mounted on the electrode-electrolyte composite, and the separator functions as a passage for the hydrogen-containing fuel and oxygen or the oxygen-containing oxidant for the reaction of the fuel cell. In addition, it simultaneously serves as a conductor connecting the anode electrode and the cathode electrode of each electrode-electrolyte composite in series.

Therefore, a fuel containing hydrogen is supplied to the anode electrode through the separator, and an oxidant containing oxygen or oxygen is supplied to the cathode electrode, whereby the fuel and the oxidant generate an electrochemical reaction in the electrode-electrolyte composite. Electric energy is generated.

In the separator 10, as illustrated in FIG. 1, a flow path 20 of a fuel or an oxidant is formed.

In general, the flow path 20 has a shape in which the inlet 22 and the outlet 24 are connected to both ends, and multiple refractions are formed at equal intervals over the entire surface of the separator 10. Of course, the flow path 20 is composed of one continuous groove.

Fuel or oxidant was forcibly supplied to the flow path 20 by a pump, and as a result, the closer to the inlet 22 side of the flow path 20, the more the load of fuel or oxidant was stagnated, which caused a heavy load. The heat generated by the load.

This calorific value is shown in the graph of FIG. 2, and when the calorific value is described with reference to FIG. 2, the calorific value is extremely partial, that is, a large amount of exothermic heat is generated at the inlet 22 and the region adjacent to the inlet 22. As it gradually moves away from the inlet 22 and reaches the outlet 24, the calorific value gradually decreases.

This phenomenon, in which the calorific value of each part of the separator 10 is caused by the fuel or the oxidant, causes local functional degradation in the catalyst layer of the electrode-electrolyte composite, thereby shortening the life of the catalyst layer, and overall, the electrode- There was a problem of adversely affecting the lifetime of the electrode-electrolyte composite by shortening the lifetime of the electrolyte composite.

The present invention devised in view of the above-described problems, since it is formed to be multi-refractive in the region in which a plurality of flow paths are allocated to the separator, the fuel containing hydrogen and the oxidant containing oxygen or oxygen flows into the entire area of the separator. With the formation of even flow, the overheating occurs in the inlet and adjacent areas, and the fuel and oxidant are evenly supplied to the electrode-electrolyte composite, preventing the shortened lifespan caused by the conventional local oversupply. It is an object of the present invention to provide a fuel cell separator and a fuel cell system employing the same, in which a pump is used to reduce power consumption and noise.

In the fuel cell separator according to the present invention for achieving the above object, the flow path for the flow of the fuel containing hydrogen and the oxygen-containing oxidant are formed on the mutually corresponding surface of the electrode-electrolyte composite. In addition, there are a plurality of flow paths, and each flow path is formed to be multi-refractive in the allocated area of the separator.

For example, the flow path has a two-array structure, and the separator is divided into an inlet and an outlet part so that one flow path is multi-refractive at the inlet part, and the other flow path is formed to be multi-refractive at the outlet part.

As another example, the flow path has a two-array structure, and the separator is divided into an inlet, an intermediate part, and an outlet part so that one flow path is formed to be multi-refractive at the inlet part and the outlet part, and the other flow path is formed at the middle part. It is formed to be refracted.

As another example, the flow path has a three-array structure, and the separator is divided into an inlet part, an intermediate part, and an outlet part so that each flow path is multi-refractive at the inlet part, the intermediate part, and the outlet part.

According to the present invention, a stack employing a separator having a plurality of flow paths includes an electrode-electrolyte composite in which electricity is generated by a mutual reaction between a hydrogen-containing fuel and oxygen or an oxygen-containing oxidant; and A flow channel for the flow of fuel and oxygen or an oxidant provided in the electrode-electrolyte composite is formed, the flow path being a plurality of separators connected to the same inlet and outlet at both ends and formed to be multi-refractive in the region to which each flow path is assigned; Is made.

For example, the flow path has a two-array structure, and the separator is divided into an inlet and an outlet part so that one flow path is multi-refractive at the inlet part, and the other flow path is formed to be multi-refractive at the outlet part.

As another example, the flow path has a two-array structure, and the separator is divided into an inlet part, an intermediate part, and an outlet part so that one flow path is formed to be multi-refractive at the inlet part and the outlet part, and the other flow path is formed at the middle part. It is formed to be refracted.

As another example, the flow path has a three-array structure, and the separator is divided into an inlet part, an intermediate part, and an outlet part so that each of the flow paths is multi-refractive at the inlet part, the intermediate part, and the outlet part.

In addition, a fuel cell system employing a separator having a plurality of flow paths according to the present invention includes a fuel pump for supplying fuel containing hydrogen; an oxidant pump for supplying oxygen or an oxidant containing oxygen; A fuel pump and an oxidant flowing from the fuel pump and the oxidant pump are respectively flowed through the flow path of the separator and reacted by the electrode-electrolyte composite to generate electricity; and a plurality of flow paths of the separator are included. The flow path is formed to be multi-refractive in other zones of the separator.

For example, the flow path has a two-array structure, and the separator is divided into an inlet and an outlet part so that one flow path is formed to be multi-refractive at the inlet part, and the other flow path is formed to be multi-refractive at the exit beam.

As another example, the flow path has a two-array structure, and the separator is divided into an inlet part, an intermediate part, and an outlet part so that one flow path is formed to be multi-refractive at the inlet part and the outlet part, and the other flow path is formed at the middle part. It is formed to be refracted.

As another example, the flow path has a three-array structure, and the separator is divided into an inlet part, an intermediate part, and an outlet part so that each of the flow paths is multi-refractive at the inlet part, the intermediate part, and the outlet part.

Hereinafter, a fuel cell separator and a fuel cell system employing the same according to the present invention will be described in detail with reference to the accompanying drawings.

3 is a configuration diagram schematically showing a fuel cell system according to a preferred embodiment of the present invention, Figure 4 is an exploded perspective view schematically showing the stack shown in FIG.

3 and 4, the fuel cell system 100 according to the present invention includes a stack 200 and a fuel tank 300 in which hydrogen gas and oxygen react electrochemically to convert chemical energy into electrical energy. Fuel containing hydrogen stored in the fuel supply unit configured to be supplied to the stack 200 by the first pump 310, and the oxidant containing oxygen and air is the stack 200 by the second pump 400 It consists of an oxidant supply unit configured to be supplied to.

In this case, the fuel supply unit further includes a reformer 320 configured to reform the fuel containing hydrogen to generate hydrogen-rich hydrogen gas and supply the hydrogen to the stack 200.

In addition, the fuel cell system 100 includes a direct current, an alternating current transformer and a control device for converting the direct current electricity generated from the stack 200 into alternating current electricity, and a heat dissipation device for dissipating heat generated during the power generation process. May be further included.

On the other hand, as shown in Figure 3, the fuel cell system 100 according to the present invention is a polymer electrolyte fuel cell (PEMFC) method including a reformer 320, but on the other hand A direct methanol fuel cell (DMFC) method in which the reformer 320 is excluded, that is, fuel is directly supplied to the stack 200 may be employed.

Hereinafter, in describing the present invention, a polymer electrolyte fuel cell will be described for convenience.

The reformer 320 generates a hydrogen gas from the fuel through a chemical catalytic reaction by thermal energy, and has a structure of a conventional reformer 320 that reduces the concentration of carbon monoxide contained in the hydrogen gas.

In more detail, the reformer 320 is, for example, made to generate hydrogen gas from the fuel through a catalytic reaction such as steam reforming, partial oxidation or autothermal reaction, and also a water gas conversion method, a selective oxidation method, and the like. It is made to reduce the concentration of carbon monoxide contained in the hydrogen gas by the same catalytic reaction or purification of hydrogen using a separation membrane.

In this case, the fuel includes a hydrocarbon-based fuel such as methanol, ethanol or natural gas.

As shown in FIG. 4, the stack 200 includes at least one unit cell 240 that receives hydrogen gas and oxygen contained in a fuel, induces oxidation and reduction reactions, and finally generates electrical energy. .

The unit cell 240 is a main part for generating electricity, an electrode-electrolyte assembly (MEA: 210) for oxidizing / reducing hydrogen gas and oxygen, and the electrode-electrolyte assembly (210). It refers to one unit cell consisting of at least one separator 220 for smooth supply of hydrogen gas and oxygen to the.

The electrode-electrolyte composite 210 is a structure of a conventional MEA in which an electrolyte membrane is interposed between an anode electrode and a cathode electrode, and the electrolyte membrane is a solid polymer electrolyte having a thickness of usually 50 to 400 μm, and the hydrogen ions from the supplied fuel. Only serves as a medium of ion exchange passing through.

The catalyst layer of the anode electrode converts hydrogen gas into electrons and hydrogen ions, and constitutes an anode electrode together with a gas diffusion layer (GDL) for smooth movement of electrons and hydrogen ions.

In addition, the catalyst layer of the cathode electrode is a layer that converts oxygen in the air into electrons and oxygen ions, and constitutes a cathode electrode together with a gas diffusion layer (GDL) for the smooth movement of electrons and oxygen ions.

Meanwhile, the stack 200 generates electricity, heat, and water according to the reaction shown in Scheme 1 below.

<Scheme 1>

Anode ^{_{reaction: H 2 → 2H + + 2e}} -

Cathode ^{_{reaction: 1 / 2O 2 + 2H +}} + 2e - → H 2 O

Total reaction: 2H ₂ + O ₂ → 2H ₂ 0 + Current + Heat

Referring to Scheme 1, hydrogen gas supplied to the anode electrode of the electrode-electrolyte composite 210 through the separator 220 and oxygen or oxygen-containing air supplied to the cathode electrode are supplied, and the hydrogen gas is As it flows through the anode, it is decomposed into electrons and protons (hydrogen ions). When the protons are transported through the electrolyte membrane, the electrons, oxygen ions, and transported protons at the cathode electrode combine with the help of a catalyst to generate water.

Herein, electrons generated by the anode electrode do not move through the electrolyte membrane but move to the cathode electrode through an external circuit.

Meanwhile, the separator 220 serves as a conductor that connects the anode electrode and the cathode electrode of the electrode-electrolyte composite 210 in series, and hydrogen required for the oxidation and reduction reaction of the electrode-electrolyte composite 210. It is made of a substantially rectangular carbon plate having the function of simultaneously serving as a passage for substantially supplying the contained fuel and oxygen and the oxidant containing oxygen.

In addition, the separator 220 refers to a monopolar plate when the fuel cell is passive, and refers to a bipolar plate when the fuel cell is active. This means that the separator 220 is irrelevant to whether a monopolar plate or a bipolar plate is selected.

The separator 220 is formed with a flow path 230 for the role of a passage, and the flow path 230 is formed of a plurality of each flow path 230 is formed to be multi-refractive on the allocated portion of the separator 220. . Of course, both ends of the flow path 230 should be connected to the inlet 222a and the outlet 224a.

The flow path 230 having such a structure is evenly distributed over the entire area of the separator 220 while preventing a phenomenon in which heat generated in the flow path 230 over the entire area of the separator 220 is concentrated on a part thereof is prevented. This is to allow flow. Of course, the calorific value may be the same over the entire area.

In order to form the flow path 230 as described above, examples of FIGS. 5, 6, and 7 are provided.

FIG. 5 is a side view schematically illustrating a flow path of the separator illustrated in FIG. 4.

Referring to FIG. 5, the flow path 230 of the separator 220 has a two-array structure. When the separator 220 is divided into the inlet part 222 and the outlet part 224, one flow path 231 is provided. ) Is formed to be multi-refractive at the inlet 222 of the separator 220, the other flow path 232 is formed to be multi-refractive at the outlet 224 of the separator 220.

FIG. 6 is a side view schematically showing the first modified example of FIG. 5.

Referring to FIG. 6, the flow path 230 of the separator 220 has a two-array structure. When the separator 220 is divided into an inlet part 222, an intermediate part 226, and an outlet part 224, the separator 220 is divided into three. The one flow path 233 is formed to be multi-refractive at the inlet part 222 and the outlet part 224 of the separator 220, and the other flow path 234 is formed at the middle part 236 of the separator 220. It is formed to be refractive.

FIG. 7 is a side view schematically showing the second modified example of FIG. 5.

Referring to FIG. 7, the flow path 220 of the separator 220 has a three-array structure. When the separator 220 is divided into an inlet part 222, an intermediate part 226, and an outlet part 224. The one flow path 235 is formed to be multi-refractive at the inlet 222 of the separator 220, the other flow path 236 is formed to be multi-refractive at the middle portion 226 of the separator 220, The other one flow path 237 is formed to be multi-refractive at the outlet 224 of the separator 220.

5 through 7, the flow paths 230 are separated into two and three arrays at the inlet 222a so that the inflow pressure to the inlet 222a is 1/2 and 1/3 as compared to the prior art. The amount of heat generated at the inlet 222 is reduced, and the fuel or oxidant is evenly distributed and flowed over the entire surface of the separator 220 through the flow paths 230, thereby evenly flowing into the electrode-electrolyte composite 210. Can be.

Here, the multi-refraction refers to a shape in which the flow path 230 is refracted adjacently at narrow intervals, and refers to a portion formed to actively introduce fuel or oxidant into the electrode-electrolyte composite 210 at this portion.

According to the present invention configured as described above, as the hydrogen-containing fuel and oxygen or oxygen-containing oxidant is introduced, even flow is formed with respect to the entire area of the separator, which causes the overheating phenomenon occurring at the conventional inlet and the adjacent portion. This prevents the heat generation of the separator and improves the lifetime of the separator as compared with the conventional one. Also, the electrode-electrolyte composite is evenly supplied to the electrode-electrolyte composite by the even flow of fuel and oxidant. The phenomenon that the life of the composite is shortened is prevented.

In addition, since the congestion at the inlet of the flow path is eliminated, the pumping capacity of the pump for supplying the same amount of fuel and oxidant may be reduced as well as a reduced volume pump may be used. The smaller the power consumption, the lower the noise generated by the pump.

Claims (12)

delete In the separator which is located on the mutually opposite surface of the electrode-electrolyte composite, the flow path for the flow of the fuel containing hydrogen and the oxidant containing oxygen, respectively, is formed, A plurality of flow paths are formed such that both ends thereof connect between the same inlet and outlet and are multi-refractive in the area to which each flow path is assigned; The flow path has a two-array structure, and the separator is divided into an inlet and an outlet part so that one flow path is formed to be multi-refractive at the inlet part, and the other flow path is formed to be multi-refractive at the outlet part. . In the separator which is located on the mutually opposite surface of the electrode-electrolyte composite, the flow path for the flow of the fuel containing hydrogen and the oxidant containing oxygen, respectively, is formed, A plurality of flow paths are formed such that both ends thereof connect between the same inlet and outlet and are multi-refractive in the area to which each flow path is assigned; The flow path has a two-array structure, and the separator is divided into an inlet part, an intermediate part, and an outlet part so that one flow path is formed to be multi-refractive at the inlet part and an outlet part, and the other flow path is formed to be multi-refractive at the middle part. A fuel cell separator characterized by the above-mentioned. In the separator which is located on the mutually opposite surface of the electrode-electrolyte composite, the flow path for the flow of the fuel containing hydrogen and the oxidant containing oxygen, respectively, is formed, A plurality of flow paths are formed such that both ends thereof connect between the same inlet and outlet and are multi-refractive in the area to which each flow path is assigned; The flow path has a three-array structure, and the separator is divided into an inlet part, an intermediate part, and an outlet part so that each of the flow paths is formed to be multi-refractive at the inlet part, the intermediate part, and the outlet part. delete An electrode-electrolyte composite in which electricity is generated by a mutual reaction of a hydrogen-containing fuel and an oxygen-containing oxidant; and In the stack made of a separator is located on the mutually opposite surface of the electrode-electrolyte composite and the flow path for the flow of the fuel containing hydrogen and the oxidant containing oxygen, respectively, A plurality of flow paths are formed such that both ends thereof connect between the same inlet and outlet and are multi-refractive in the area to which each flow path is assigned; The flow path has a two-array structure, and the separator is divided into an inlet and an outlet part so that one flow path is formed to be multi-refractive at the inlet part, and another flow path is formed to be multi-refractive at the exit beam. An electrode-electrolyte composite in which electricity is generated by a mutual reaction of a hydrogen-containing fuel and an oxygen-containing oxidant; and In the stack made of a separator is located on the mutually opposite surface of the electrode-electrolyte composite and the flow path for the flow of the fuel containing hydrogen and the oxidant containing oxygen, respectively, A plurality of flow paths are formed such that both ends thereof connect between the same inlet and outlet and are multi-refractive in the area to which each flow path is assigned; The flow path has a two-array structure, and the separator is divided into an inlet part, an intermediate part, and an outlet part so that one flow path is formed to be multi-refractive at the inlet part and an outlet part, and the other flow path is formed to be multi-refractive at the middle part. Featuring a stack. An electrode-electrolyte composite in which electricity is generated by a mutual reaction of a hydrogen-containing fuel and an oxygen-containing oxidant; and In the stack made of a separator is located on the mutually opposite surface of the electrode-electrolyte composite and the flow path for the flow of the fuel containing hydrogen and the oxidant containing oxygen, respectively, A plurality of flow paths are formed such that both ends thereof connect between the same inlet and outlet and are multi-refractive in the area to which each flow path is assigned; The flow path has a three-array structure, and the separator is divided into an inlet part, an intermediate part, and an outlet part, so that each of the flow paths is formed to be multi-refractive at the inlet part, the intermediate part, and the outlet part. delete A fuel pump for supplying fuel containing hydrogen; An oxidant pump for supplying oxygen or an oxygen containing oxidant; The fuel and oxidant flowing from the fuel pump and the oxidant pump is respectively flowed through the flow path of the separator and reacted by the electrode-electrolyte composite to generate electricity; In the fuel cell formed of a plurality of flow paths of the separator, both ends are connected to the same inlet and outlet, and formed so as to be multi-refractively in the area assigned each flow path, The flow path has a two-array structure, and the separator is divided into an inlet and an outlet part so that one flow path is formed to be multi-refractive at the inlet part, and the other flow path is formed to be multi-refractive at the exit beam. A fuel pump for supplying fuel containing hydrogen; An oxidant pump for supplying oxygen or an oxygen containing oxidant; The fuel and oxidant flowing from the fuel pump and the oxidant pump is respectively flowed through the flow path of the separator and reacted by the electrode-electrolyte composite to generate electricity; In the fuel cell formed of a plurality of flow paths of the separator, both ends are connected to the same inlet and outlet, and formed so as to be multi-refractively in the area assigned each flow path, The flow path has a two-array structure, and the separator is divided into an inlet part, an intermediate part, and an outlet part so that one flow path is formed to be multi-refractive at the inlet part and an outlet part, and the other flow path is formed to be multi-refractive at the middle part. A fuel cell characterized by the above-mentioned. A fuel pump for supplying fuel containing hydrogen; An oxidant pump for supplying oxygen or an oxygen containing oxidant; The fuel and oxidant flowing from the fuel pump and the oxidant pump is respectively flowed through the flow path of the separator and reacted by the electrode-electrolyte composite to generate electricity; In the fuel cell formed of a plurality of flow paths of the separator, both ends are connected to the same inlet and outlet, and formed so as to be multi-refractively in the area assigned each flow path, The flow path has a three-array structure, and the separator is divided into an inlet part, an intermediate part, and an outlet part, so that each of the flow paths is formed to be multi-refractive at the inlet part, the intermediate part, and the outlet part.

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