KR100599690B1 - Fuel cell system and stack of the same - Google Patents

Abstract

The present invention relates to a fuel cell system that prevents leakage of hydrogen gas and thereby prevents unstable reaction of hydrogen gas and oxygen.

A fuel cell system according to the present invention includes a fuel supply unit for supplying a fuel containing hydrogen; An air supply unit for supplying air containing oxygen; And first and second MEAs disposed on both sides of the MEA so as to generate electrical energy by electrochemically reacting hydrogen and oxygen supplied from the fuel supply unit and the air supply unit, respectively. A stack including at least one electricity generating unit including a separator, and includes a reinforcing member interposed between any one or more of the first separator and the MEA and between the second separator and the MEA.

Fuel cell, separator, stack, fuel passage, reinforcement member, air passage

Description

FUEL CELL SYSTEM AND STACK OF THE SAME

1 is a block diagram schematically showing the overall configuration of a fuel cell system according to the present invention.

2 is an exploded perspective view showing a stack according to the present invention.

3 is an exploded perspective view showing one electricity generating unit in the stack according to the present invention.

4 is a cross-sectional view taken along the line A-A in the state of assembling the electricity generating unit of FIG.

The present invention relates to a fuel cell system and a stack used in the fuel cell system.

In general, a fuel cell is a power generation that directly converts chemical energy into electrical energy by an electrochemical reaction generated from hydrogen contained in a hydrocarbon-based material such as methanol, ethanol or natural gas and oxygen in air as a fuel. System. In particular, the fuel cell is characterized in that it can simultaneously use the electricity generated by the electrochemical reaction of the fuel gas and the oxidant gas and heat by-products thereof without a combustion process.

Polymer electrolyte fuel cells (PEMFCs, hereinafter referred to as PEMFCs), which are being developed in recent years, have excellent output characteristics, low operating temperatures, and fast start-up and response characteristics compared to other fuel cells.

In order for the above PEMFC to basically have a system configuration, a fuel cell body (hereinafter referred to as a stack for convenience) called a stack, a fuel tank, and a fuel pump for supplying fuel from the fuel tank to the stack, etc. This is necessary. In the process of supplying the fuel stored in the fuel tank to the stack, a reformer for reforming the fuel to generate hydrogen gas and supplying the hydrogen gas to the stack is further needed. Therefore, PEMFC supplies the fuel stored in the fuel tank to the reformer by the pumping force of the fuel pump, generates hydrogen gas by reforming the fuel in the reformer, and produces electrical energy by electrochemically reacting hydrogen gas and oxygen in the stack. do.

On the other hand, the fuel cell may employ a direct methanol fuel cell (DMFC) method that can supply a liquid methanol fuel directly to the stack. This DMFC, unlike PEMFC, does not require a reformer.

In the fuel cell system as described above, the stack that substantially generates electricity includes an electric generator, namely, a unit cell comprising an electrode-electrolyte assembly (MEA) and a separator. It consists of a stacked structure of pieces to dozens.

This MEA consists of an anode electrode and a cathode electrode attached to both sides with an electrolyte membrane therebetween. Separators are disposed on both sides with the MEA interposed therebetween, acting as a passage for supplying oxygen gas and fuel gas for the reaction of fuel cells, and as a conductor for connecting the anode and cathode electrodes of each MEA in series. At the same time.

Therefore, a fuel gas containing hydrogen is supplied to the anode electrode by the separator, and air containing oxygen is supplied to the cathode electrode. In this process, an electrochemical oxidation reaction of fuel gas occurs at the anode electrode, and an electrochemical reduction reaction of oxygen occurs at the cathode electrode. At this time, electricity is generated by the movement of the generated electrons, and heat and water which are by-products are generated.

In general, since oxygen-containing air is supplied to the cathode and pure hydrogen gas is supplied to the anode, the cathode is supplied to the cathode in comparison with the amount of hydrogen gas supplied to the anode for efficient oxidation / reduction reaction at each electrode. It is desirable for the amount of air to be higher. To this end, the cathode electrode separator forms a plurality of air passages in a parallel straight line, ie, in a parallel type, to react the air supplied to one side in the MEA and discharge the unreacted air to the opposite side.

Accordingly, the cathode electrode side separator having the air passage closes to the anode electrode side separator having the hydrogen passage with the MEA interposed therebetween to constitute the electricity generating unit, where the MEA is firmly supported at the portion corresponding to the air passage. In this case, the state of excitation between both separators is maintained.

Due to this excited state, a gap is formed between the anode electrode side separator with the hydrogen passage and the MEA and between the cathode electrode side separator with the air passage and the MEA, whereby hydrogen gas leaks through the gap to cause unstable reaction with air. Will be raised.

The present invention has been made to solve the above problems, and an object thereof is to provide a fuel cell system and a stack thereof which prevent leakage of hydrogen gas and thereby prevent unstable reaction of hydrogen gas and oxygen.

In order to achieve the above object, the fuel cell system according to the present invention,

A fuel supply unit supplying a fuel containing hydrogen;

An air supply unit for supplying air containing oxygen; And

MEAs and first and second separators respectively disposed on both sides of the MEA so as to generate electrical energy by electrochemically reacting hydrogen and oxygen supplied from the fuel supply unit and the air supply unit, respectively, and having a fuel passage and an air passage, respectively. It includes a stack formed by having at least one electricity generating unit comprising a,

And a reinforcing member interposed between any one or more sides of the first separator and the MEA and between the second separator and the MEA.

In addition, the stack of the fuel cell system according to the present invention,

MEA, the first and second separators respectively disposed on both sides of the MEA, each having a fuel passage and an air passage to electrochemically react hydrogen and oxygen supplied from the fuel supply portion and the air supply portion to generate electrical energy. It is formed by having at least one electricity generating unit including;

And a reinforcing member interposed between any one or more sides of the first separator and the MEA and between the second separator and the MEA.

The first separator includes a plurality of fuel passages in a parallel and straight state.

The first separator includes a saddle stairway that saddles a reinforcing member on the inlet and outlet sides of the fuel passage.

The saddle stairs are formed at the inlet and outlet side ends of the fuel passage corresponding to the gasket portion of the MEA.

MEAs, reinforcing members, fuel passages, and first separators are sequentially formed and arranged at the inlet and outlet sides of the fuel passage.

The reinforcing member has a band shape so as to have a predetermined width at the inlet and outlet of the fuel passage.

The second separator includes a plurality of air passages in a parallel and straight state.

The second separator has a saddle step for saddle-reinforcing members on the inlet and outlet sides of the air passage.

The saddle stairs are formed at the inlet and outlet side ends of the air passage corresponding to the gasket portion of the MEA.

MEAs, reinforcing members, air passages, and second separators are sequentially formed and arranged at the inlet and outlet sides of the air passage.

The reinforcing member is formed in a band shape so as to have a predetermined width on the inlet and outlet of the air passage.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram schematically showing the overall configuration of a fuel cell system according to the present invention.

Referring to this drawing, a fuel cell system is described. The fuel cell system reforms a hydrocarbon-based fuel such as methanol, ethanol, or natural gas to generate a hydrogen-rich reformed gas, and generates the hydrogen gas and external air. It can be seen that the PEMFC method which converts chemical energy generated by chemical reaction directly into electrical energy is adopted.

The fuel cell system includes a fuel supply unit 10 for reforming and supplying the hydrocarbon-based fuel, an air supply unit 12 for supplying external air, and chemical energy according to a reaction of hydrogen gas and air supplied as described above. Consisting of a stack 14 for producing electricity by converting it into electrical energy.

The fuel supply unit 10 is configured to remove the reformer 16, unlike the PEMFC method, in the case of the DMFC method of supplying liquid fuel directly to the stack 14 to generate electricity. Hereinafter, the fuel cell system to which the PEMFC method is applied will be described as an example. However, the present invention is not necessarily limited thereto.

The fuel supply unit 10 includes a fuel tank 18 for storing liquid fuel containing hydrogen and a fuel pump 20 connected to the fuel tank 18 to discharge fuel stored in the fuel tank 18. ). The fuel tank 18 and the fuel pump 20 are connected to supply the fuel to the stack 14 via the reformer 16.

The air supply unit 12 includes an air pump 22 that sucks and blows external air with a pumping force, and the air pump 22 is connected to supply air to the stack 14.

In the fuel cell system of the present invention, the fuel includes a hydrocarbon-based fuel that is easy to mount and store, such as methanol, ethanol, natural gas, and the like. However, the fuel may be a mixture of water with methanol, ethanol or natural gas as described above, hereinafter, methanol, ethanol or natural gas is referred to as a liquid fuel for convenience.

The stack 14 receiving fuel and air from the fuel supply unit 10 and the air supply unit 12 oxidizes / reduces them to generate electricity.

Figure 2 is an exploded perspective view showing a stack according to the present invention, Figure 3 is an exploded perspective view showing one electric generator in the stack according to the present invention.

Referring to the stack 14 with reference to these figures, the stack 14 electrochemically reacts the reformed hydrogen gas or hydrogen gas supplied through the reformer 16 with the air supplied from the air supply 12. A plurality of electricity generating units 24 for generating electrical energy are provided. Each of the electricity generating units 24 refers to a cell of a unit generating electricity, and supplies the MEA 26 to oxidize / reduce hydrogen gas and air and the hydrogen gas and air to the MEA 26, respectively. It is formed of the first and second separators (also called bipolar plates) 28 and 29 disposed on both sides of the MEA 26. The electricity generating unit 24 may form a fuel cell as one, and constitute a fuel cell by a plurality of fuel cells arranged in succession.

The MEA 26 has a conventional structure in which an electrolyte membrane is interposed between the anode electrode and the cathode electrode forming both sides. The anode electrode is a hydrogen gas supplied through the first perlator 28, a catalyst layer for converting hydrogen gas into electrons and hydrogen ions by an oxidation reaction, and a gas diffusion layer for smooth movement of electrons and hydrogen ions. Layer) The cathode electrode, which is supplied with air through the second separator 29, is composed of a catalyst layer for converting oxygen into electrons and oxygen ions by a reduction reaction and a gas diffusion layer for smooth movement of electrons and oxygen ions. The electrolyte membrane is a solid polymer electrolyte having a thickness of 50 to 200 µm, and has an ion exchange function for transferring hydrogen ions generated in the catalyst layer of the anode electrode to the catalyst layer of the cathode electrode.

The electricity generating unit 24 configured as described above generates electricity, water, and heat according to the following reaction formula.

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

The cathode ^{_{reaction: O 2 + 2H + + 2e}} - → H 2 O

Total reaction: H ₂ + O ₂ → H ₂ O + current + heat

That is, hydrogen gas is supplied to the anode electrode of the MEA 26 through the fuel passage 30 of the first separator 28, and the cathode of the MEA 26 is provided through the air passage 32 of the second separator 29. Air is supplied to the electrode. This hydrogen gas flows to the anode electrode and decomposes into electrons and hydrogen ions in the catalyst layer. When the hydrogen ions are moved through the electrolyte membrane, electrons, oxygen ions and transferred hydrogen ions are combined at the cathode electrode with the help of a catalyst to generate water. In this case, the electrons generated by the anode electrode do not move through the electrolyte membrane but move to the cathode electrode through an external circuit, so that the electricity generator 24 generates electricity.

The stack 14 is configured such that fuel and air are supplied to one side thereof, and unreacted fuel and air are discharged to the other side thereof, while the fuel and air supplied to one side are respectively the first separator 28 and the second separator. A detailed configuration of how the supply is circulated in the separator 29 is omitted, and a configuration thereof may be known.

4 is a cross-sectional view taken along the line A-A in the state of assembling the electricity generating unit of FIG.

Referring to these drawings, the first and second separators 28 and 29 constituting the stack 14 will be described. The first separator 28 of the present invention includes a fuel passage 30. The fuel passage 30 is connected to the fuel supply unit 10 and is formed to supply fuel containing hydrogen therefrom. The second separator 29 has an air passage 32. The air passage 32 is connected to the air supply 12 to supply air containing oxygen therefrom. The first and second separators 28 and 29 form a fuel passage 30 and an air passage 32 on both sides thereof with the MEA 26 interposed therebetween.

The fuel passage 30 of the first separator 28 is a portion for supplying hydrogen gas to the MEA 26 side, and may be formed in a curve leading to a curved shape that is continuously reciprocated from one side to the other side, as shown in FIG. It may be formed in a straight state, and may be formed to be in parallel with other adjacent fuel passages 30.

The air passage 32 of the second separator 29 is a portion for supplying oxygen to the MEA 26 side, and may be formed in a curve leading to a curved shape that is continuously reciprocated from one side to the other side, respectively, as shown in a straight line state. It may be formed to be, and to be in parallel with the other adjacent air passages (32). When the air passage 32 is supplied with air, it is preferable that the air passage 32 is formed in a straight state unlike the fuel passage 30 so as to supply a larger amount of air than the amount of hydrogen supplied to the fuel passage 30. .

Reinforcement on either or both sides between the first separator 28 having the fuel passages 30 and the MEA 26 and between the second separator 29 having the air passage 32 and the MEA 26. The member 34 is interposed. The reinforcing member 34 may be provided on both sides or only one of the two sides, but when provided only on one side, the second separator 29 and the MEA 26 having the air passage 32. It is preferable to be provided in between. The reinforcing member 34 supports a portion of the MEA 26 that is not supported by the fuel passage 30 or the air passage 32, and prevents deformation of the MEA 26 at this portion to prevent both sides of the MEA 26. It will prevent the lifting from the. At this time, the reinforcing member 34 and the first and second separators 28 and 29 require a tighter and more rigid saddle.

To this end, the first separator 28 preferably has a saddle step 28a for saddle-reinforcing member 34 at the inlet 30a and outlet 30b side of the fuel passage 30. This saddle staircase 28a is formed at the tip of the inlet port 30a and the outlet port 30b of the fuel passage 30 corresponding to the gasket portion 26a of the MEA 26. The reinforcing member 34 reinforces and supports the corresponding MEA 26 gasket portion 26a at the inlet 30a and the outlet 30b of the fuel passage 30, so that the portion 26a is a fuel passage ( 30) to prevent deformation into the side, ie crooked. Therefore, the reinforcing member 34 is preferably formed in a band shape with a predetermined width so as to have sufficient rigidity not to be crushed between the inlet 30a and the outlet 30b of the MEA 26 and the fuel passage 30. Do.

Therefore, the MEA 26, the reinforcing member 34, the fuel passage 30, and the first separator 28 are sequentially formed and disposed at the inlet 30a and the outlet 30b of the fuel passage 30. This prevents the fuel passage 30 side of the MEA 26 from lifting. As a result, the discharge of hydrogen gas is prevented at the inlet port 30a and the outlet port 30b of the fuel passage 30.

In addition, the second separator 29 preferably includes a saddle staircase 29a that saddles the reinforcing member 34 on the inlet 32a and the outlet 32b of the air passage 32. This saddle step 29a is formed at the tip of the inlet 32a and the outlet 32b of the air passage 32 corresponding to the gasket portion 26a of the MEA 26. The reinforcing member 34 reinforces and supports the corresponding MEA 26 gasket portion 26a at the inlet 32a and outlet 32b of the air passage 32, so that the portion 26a is an air passage ( 32) Prevents crumpled into, deformed to the side. Therefore, the reinforcing member 34 is preferably formed in a band shape with a predetermined width so as to have sufficient rigidity that is not crushed between the inlet 32a and the outlet 32b of the MEA 26 and the air passage 32. Do.

Therefore, the MEA 26, the reinforcing member 34, the air passage 32, and the second separator 29 are sequentially formed and arranged at the inlet 32a and the outlet 32b of the air passage 32. This prevents the air passage 32 side of the MEA 26 from lifting. As a result, air is prevented from being discharged to the inlet 32a and the outlet 32b of the air passage 32.

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 present invention, a reinforcing member is provided at each inlet and outlet of one or both sides of the air passage and the fuel passage, and the reinforcing members provided at the inlet and the outlet of each passage and the corresponding MEA are in close contact with each other. In addition, by preventing the lifting phenomenon generated between the MEA and the separator to prevent the leakage of hydrogen gas from the fuel tank, thereby preventing the unstable reaction of hydrogen gas and oxygen.

Claims (17)

A fuel supply unit supplying a fuel containing hydrogen; An air supply unit for supplying air containing oxygen; And Membrane Electrode Assembly (MEA), each of which is disposed on both sides of the MEA so as to generate electrical energy by electrochemically reacting hydrogen and oxygen supplied from the fuel supply unit and the air supply unit, respectively and having a fuel passage and an air passage, respectively. It includes a stack formed by having at least one electricity generating unit including a first, second separator, And a reinforcing member interposed between any one or more sides of the first separator and the MEA and between the second separator and the MEA. The method of claim 1, The first separator includes a plurality of fuel passages in a parallel and straight state. The method of claim 1, The first separator has a saddle stairway to saddle the reinforcing member on the inlet and outlet side of the fuel passage. The method of claim 3, wherein The saddle stairs are formed at the inlet and outlet side ends of the fuel passage corresponding to the gasket portion of the MEA. The method of claim 1, And a MEA, a reinforcing member, a fuel passage, and a first separator are sequentially formed and arranged at the inlet and outlet sides of the fuel passage. The method of claim 1, The reinforcing member has a band shape so as to have a predetermined width at the inlet and outlet of the fuel passage. The method of claim 1, The second separator includes a plurality of air passages in a parallel and straight state. The method of claim 1, The second separator has a saddle staircase that saddles a reinforcing member on the inlet and outlet sides of the air passage. The method of claim 8, The saddle stairs are formed at the inlet and outlet side ends of the air passage corresponding to the gasket portion of the MEA. The method of claim 1, And a MEA, a reinforcing member, an air passage, and a second separator are sequentially formed and arranged at the inlet and outlet sides of the air passage. The method of claim 1, The reinforcing member is a fuel cell system having a band shape so as to have a predetermined width on the inlet and outlet sides of the air passage. Membrane Electrode Assembly (MEA), each having a fuel passage and an air passage respectively disposed on both sides of the MEA so as to generate electrical energy by electrochemically reacting hydrogen and oxygen supplied from the fuel supply unit and the air supply unit, respectively. At least one electricity generating unit including a second separator, And a reinforcing member interposed between any one or more sides of the first separator and the MEA and between the second separator and the MEA. The method of claim 12, The second separator is a stack of a fuel cell system having a plurality of parallel air passages in a straight line state. The method of claim 12, The second separator is a stack of a fuel cell system having a saddle step to saddle the reinforcing member on the inlet and outlet side of the air passage. The method of claim 14, The saddle staircase is a stack of fuel cell systems formed on the inlet and outlet side ends of the air passage corresponding to the gasket portion of the MEA. The method of claim 12, And a MEA, a reinforcing member, an air passage, and a second separator are sequentially formed and arranged at the inlet and outlet sides of the air passage. The method of claim 12, The reinforcement member is a stack of a fuel cell system formed in a band shape so as to have a predetermined width on the inlet and outlet side of the air passage.

Images