KR101127004B1 - Fuel cell stack with internal membrane humidifier - Google Patents

Abstract

The present invention relates to a fuel cell stack including an internal membrane humidifier, the fuel cell stack including a plurality of unit cells including a membrane electrode assembly and a separator plate disposed on both sides of the membrane electrode assembly, wherein the plurality of unit cells are stacked. At least one of the two separation plates positioned at the outermost part of the fuel cell stack has a flow passage that provides a flow path for the reaction gas therethrough, and the flow passage is disposed in the separation plate where the flow passage is formed. It includes an internal membrane humidifier for humidifying the reaction gas supplied to the fuel cell stack through the water exchange with the exhaust gas passing through, and reacts the reaction gas supplied to the fuel cell stack through the exhaust gas from the fuel cell stack, By increasing the relative humidity of the gas can improve the performance of the fuel cell.

Description

FUEL CELL STACK WITH INTERNAL MEMBRANE HUMIDIFIER}

The present invention relates to a fuel cell stack including an internal membrane humidifier. More particularly, the present invention relates to a fuel cell stack that further humidifies a reaction gas by using an exhaust gas generated in the fuel cell stack to further improve humidification efficiency.

A fuel cell is an electrochemical power generation facility that produces direct current by converting chemical energy of fuel directly into electrical energy. It is a high efficiency and high power that can simultaneously utilize power and heat from various energy sources such as natural gas, propane, naphtha, and methanol. It is an environmentally friendly next generation core power generation technology with features such as no pollution, no pollution and no noise.

The fuel cell system includes a fuel cell stack that largely generates electric energy, a fuel supply system for supplying fuel (hydrogen) to the fuel cell stack, an air supply system for supplying oxygen in the air, which is an oxidant for an electrochemical reaction, to the fuel cell stack, And a heat and water management system that removes the heat of reaction of the fuel cell stack out of the system and controls the operating temperature of the fuel cell stack.

In this configuration, the fuel cell system generates electricity by an electrochemical reaction between oxygen in the air and hydrogen as a fuel, and emits heat and water as reaction by-products.

Meanwhile, in a fuel cell system, humidification of reaction gases (hydrogen and air) is required for a smooth chemical reaction. Typically, the air is humidified by directly supplying water using a hollow fiber membrane or a film-type membrane or by exchanging moisture from the supersaturated humidified air discharged from the fuel cell stack with dry air, which is outside, and hydrogen is not reacted discharged from the fuel cell stack. It is humidified by recycling the hydrogen and mixing it with the incoming hydrogen.

FIG. 1 is a view showing a state in which a reaction gas is supplied by a conventional fuel cell humidification apparatus, and forcibly blows dry air from outside air into a blower 1 and passes the membrane humidifier 2 to a fuel cell. The supersaturated humidifying air containing the water discharged from the outlet of the stack 3 is passed through the membrane humidifier to humidify the dry air by exchanging water between the supersaturated humidifying air and the dry air, and the humidified air is used as a fuel cell stack. It is supplied to (3).

In addition, the unreacted humidified hydrogen passing through the outlet of the fuel cell stack 3 is forcedly blown through the recycle blower 4 and mixed with hydrogen supplied from the hydrogen tank 5, whereby the humidified hydrogen is fuel cell stack. It is supplied to the inlet of (3).

One of the factors that directly affect the performance of the fuel cell during operation is to supply a certain amount of moisture to the electrolyte membrane of the membrane electrode assembly (MEA), which is a key component of the fuel cell, and the ionomer in the catalyst layer. By maintaining the water content, the maximum performance of the ion conductivity possessed by the electrolyte membrane and the ionomer itself is obtained.

Here, the role of the membrane humidifier 2 is to supply the moisture and heat contained in the unreacted gas discharged at a high temperature from the fuel cell stack 3 to the dry reaction gas at room temperature supplied to the fuel cell stack through the membrane surface, To achieve humidification and temperature maintenance of the fuel cell stack.

Since both humidification of air using a conventional membrane humidifier or mixing of hydrogen with humidification through mixing with unreacted hydrogen is performed outside of the fuel cell stack, the temperature of humidified air and humidified hydrogen is determined by the exit of the fuel cell stack. It can only be lower than the temperature of the air and hydrogen discharged from it.

That is, the temperature of the reaction gas (hydrogen, air) that has undergone the above-mentioned humidification process is about 55 ° C. When the reaction gas enters the fuel cell stack maintaining the operating temperature of about 80 ° C, the relative humidity is increased due to the temperature increase. There is a problem that decreases by approximately 55%.

Accordingly, the present invention is to provide a fuel cell with improved performance by further increasing the relative humidity of the reaction gas by humidifying the reaction gas using the exhaust gas generated in the fuel cell stack.

The problem to be solved by the present invention is to further increase the relative humidity of the reaction gas flow by using an internal membrane humidifier installed inside the fuel cell stack, and at the same time suppress the flooding phenomenon generated in the fuel cell to further improve the performance of the fuel cell To provide a stack.

The present invention to achieve the above object,

A fuel cell stack comprising a plurality of unit cells including a membrane electrode assembly and separator plates disposed on both sides of the membrane electrode assembly,

At least one of the two separation plates located at the outermost portions of the plurality of stacked fuel cell stacks has a flow path for providing a passage for moving the reaction gas therethrough,

Provided is a fuel cell stack including an internal membrane humidifier disposed on the separation plate is formed through the flow passage, the internal membrane humidifier to humidify the reaction gas supplied to the fuel cell stack through the water exchange with the exhaust gas passing through the through-flow passage.

According to another embodiment of the present invention,

In a fuel cell stack comprising a plurality of unit cells including a central distributor having a reaction gas inlet and outlet, and a separator electrode disposed on both sides of the membrane electrode assembly and the membrane electrode assembly, on both sides of the central distributor.

At least one of the two separation plates positioned closest to the central distribution unit of the plurality of stacked fuel cell stacks has a flow path for providing a passage for moving the reaction gas therethrough,

A fuel including an internal membrane humidifier disposed between the separation plate and the central distribution unit through which the flow passage is formed and humidifies the reaction gas supplied to the fuel cell stack through water exchange with the exhaust gas passing through the flow passage. Provide a cell stack.

Here, the internal membrane humidifier, the reaction so that the humidification membrane and the reaction gas disposed on the opposite side facing the membrane electrode assembly of the separator provided with the passage formed flow path is supplied to the fuel cell stack while passing through the humidification membrane. It may include a humidifying port for guiding the gas.

In addition, the humidification film is preferably made of Nafion.

In addition, the humidification port may include a humidification passage part for providing a moving passage for the reaction gas in contact with the humidification membrane.

In addition, the reaction gas is air, and the discharge portion of the humidification port is preferably in communication with the air inlet of the fuel cell stack.

In addition, the reaction gas is hydrogen, the discharge portion of the humidification port is preferably in communication with the hydrogen inlet of the fuel cell stack.

In addition, the reaction gas is air and hydrogen, the internal membrane humidifier is provided in each of the two separation plates located at the outermost of the fuel cell stack, the discharge portion of the humidification port of the two internal membrane humidifiers the fuel cell It is preferred to communicate with the air inlet and the hydrogen inlet of the stack, respectively.

In addition, the reaction gas is air and hydrogen, the internal membrane humidifier is provided in each of the two separation plates located closest to the central distribution unit, the discharge portion of the humidification port of the two internal membrane humidifiers the fuel cell It is preferred to communicate with the air inlet and the hydrogen inlet of the stack, respectively.

The fuel cell stack according to the present invention humidifies the reaction gas supplied to the fuel cell stack by using the exhaust gas generated from the fuel cell stack using an internal membrane humidifier, thereby increasing the relative humidity of the reaction gas to improve the performance of the fuel cell. Can be improved.

In addition, since the internal membrane humidifier may absorb moisture generated in the fuel cell stack in the humidification process, it is possible to prevent the stack from deteriorating due to the flooding phenomenon.

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

2 (a) and 2 (b) are perspective views of a typical fuel cell stack, FIG. 3 (a) is an exploded perspective view thereof, and FIG. 3 (b) is a schematic sectional view of A-A.

The fuel cell stack 10 may be composed of a polymer electrolyte fuel cell (PEMFC) that receives electrical air and hydrogen as fuel to generate electrical energy by a reduction reaction of oxygen contained in the air. .

The fuel cell stack 10 is formed by stacking a plurality of unit cells including the membrane electrode assembly 11 and the separator 15. In addition, the fuel cell stack 10 includes a pair of end plates 16a and 16b. The fuel cell stack 10 generates electrical energy by chemical reaction of air supplied by an air supply means (not shown) and hydrogen supplied by a hydrogen supply means (not shown).

The inlet and outlet 40 of the reaction gas (hydrogen and air) is formed in the pair of end plates 16a and 16b as shown in FIG. 2 (a) or in the center located at the center of the fuel cell stack as shown in FIG. 2 (b). It may be formed in the distribution unit 18. In the fuel cell stack including the central distributor 18, a plurality of unit cells are stacked on both sides of the central distributor.

The fuel cell stack 10 is formed by alternately stacking the membrane electrode assembly 11 and the separator 15, and end plates 16a and 16b stacked on the outermost side of the fuel cell stack to be in close contact with each other. The fuel cell stack 10 may be press-bonded by inserting and fixing a fastening means such as a fastening rod 19 into the fastening hole 47.

Since the internal structure of the fuel cell stack 10 is substantially the same regardless of the arrangement position of the inlet and outlet of the reaction gas, the following description will be made based on the fuel cell stack shown in FIG.

The membrane electrode assembly 11 includes an electrolyte membrane 12 and a cathode electrode 13 and an anode electrode 14 formed on both surfaces of the electrolyte membrane 12, respectively. The cathode electrode 13 includes an air diffusion layer for supplying and diffusing air and a catalyst layer in which an oxidation / reduction reaction of air occurs. In addition, the anode electrode 14 includes a hydrogen diffusion layer for supplying and diffusing hydrogen and a catalyst layer in which an oxidation / reduction reaction of hydrogen occurs.

The separation plate 15 located inside the fuel cell stack includes a flow path 17 providing a moving passage of hydrogen or air on both sides thereof. In addition, the separator 15 is formed to include inlets 21 and 24 and outlets 23 and 26 through which hydrogen or air flow, and a coolant inlet 22 and a coolant outlet 25 through which coolant flows. The flow path 17 is formed to communicate with the inlets 21 and 24 and the outlets 23 and 26, and the air flow path for passing only the air supplied from the air supply port 41 and discharged to the air outlet 46 is passed through. Alternatively, only hydrogen supplied from the hydrogen supply port 44 and discharged to the hydrogen discharge port 43 may be a hydrogen flow path for passing. Here, the positions of the air supply port 41, the air discharge port 46, the hydrogen supply port 44, the hydrogen discharge port 43 is not limited to the above-described position, it is appropriate to those skilled in the art can be changed. Here, reference numerals 42 and 43, which are not described, refer to the cooling water supply port and the cooling water discharge port, respectively.

Meanwhile, since one side of the separator plate 15 positioned at the outermost side of the fuel cell stack 10 contacts the end plates 16a and 16b, one side of the separator plate 15 is different from the separator plate positioned inside the fuel cell stack 10. Only the flow path is formed.

The membrane electrode assembly 11 is also formed with inlets 31 and 34 through which hydrogen or air flows, and outlets 33 and 36, a coolant inlet 32 through which coolant flows, and a coolant outlet 35.

That is, the inlet, the outlet, the coolant inlet, and the coolant outlet are formed in the separator and the membrane electrode assembly to communicate with each other to form an air inlet, an air outlet, a hydrogen inlet, a hydrogen outlet, a coolant inlet, a coolant outlet, and these fuels Configure the manifold of the cell stack.

Since the outermost unit cell of the fuel cell stack 10 configured as described above is located too close or too far from the air supply port and the hydrogen supply port, hydrogen and air are not sufficiently supplied. Furthermore, in the outermost unit cell, the temperature is lowered due to the contact with the end plates 16a and 16b, thereby causing a flooding phenomenon in which moisture is easily generated. Therefore, the performance is severely degraded and the output is low. This flooding phenomenon occurs even when the inlet and outlet of the reaction gas is located in the center.

In the present invention, a membrane humidifier is provided between the outermost separator plate and the end plate of the fuel cell stack or between the central distributor having the reaction gas inlet and outlet and the separator closest to the fuel cell stack, thereby preventing the above-mentioned flooding phenomenon and simultaneously It is intended to humidify the reactant gases (hydrogen and air) supplied.

4 is a partially exploded perspective view of a fuel cell stack 100 provided with an internal membrane humidifier according to an embodiment of the present invention.

The internal membrane humidifier 50 according to the present invention may be disposed on at least one separation plate 15 ′ of two separation plates located at the outermost part of the fuel cell stack. 4 shows only one separation plate 15 ′ of the two separation plates located at the outermost side, but the inner membrane humidifier may be arranged symmetrically to that shown in FIG. 4 on the other separation plate.

That is, one internal membrane humidifier 50 may be disposed to humidify hydrogen or air in the reaction gases (hydrogen and air) used for the electrochemical reaction, and two internal membrane humidifiers for humidifying both hydrogen and air. Can be arranged.

Hereinafter, for convenience of description, an internal membrane humidifier for humidifying air in the reaction gas supplied to the fuel cell stack will be described as a reference. The internal membrane humidifier may be equally applicable to humidifying hydrogen, a reaction gas supplied to the fuel cell stack, and of course, may be applied to humidifying both air and hydrogen.

The outermost separating plate 15 ′ in which the inner membrane humidifier 50 is disposed has a passage 17 ′ formed therein for providing a moving passage of air therein. That is, heat and moisture exchange may be performed between fluids (reaction gas and exhaust gas) flowing through both sides of the separation plate 15 'by the flow path 17' formed through. Specific heat and moisture exchange process will be described later.

The internal membrane humidifier 50 includes a humidifying membrane 51 disposed on an opposite surface of the separator plate 15 ′ having a passage formed therethrough and facing the membrane electrode assembly 11, and a reaction gas passes through the humidifying membrane 51. And a humidifying port 52 for guiding the reaction gas to be supplied to the fuel cell stack.

The humidification membrane 51 is preferably made of a thin film having a size covering the flow path 17 'formed through the separation plate 15', and selectively selects moisture to humidify the reaction gas supplied into the fuel cell stack. It may be made of a material such as nafion having the property of permeation.

The humidification port 52 serves to humidify the air supplied to the fuel cell stack and to supply the air into the fuel cell stack. The humidification port 52 has a thickness capable of accommodating a predetermined volume of air, and the external shape thereof is substantially separated from the separator plate. The same is preferable. Therefore, when the humidification port 52 is disposed in the fuel cell stack, the humidification port 52 may be stacked in substantially the same form as the conventional fuel cell stack.

The humidification port 52 is a supply port 67 through which air is introduced into the fuel cell stack through an air supply means (not shown), and a discharge part for supplying humidified air passing through the humidification port to the manifold inside the fuel cell stack. And (61). Here, the discharge part 61 is formed in communication with the inlets 21 and 31 of the separator plate and the membrane electrode assembly, that is, the air inlet. In addition, the humidification port 52 is provided with inlets 64, outlets 63 and 66, cooling water inlet 62, and cooling water outlet 65 to form part of the manifold of the fuel cell stack.

Here, the shape of the humidification port 52 is not limited to the shape shown in FIG. 4, and any structure may be used as long as the incoming air passes through the humidification membrane and is supplied to the manifold of the fuel cell stack. In particular, the position of the supply port 67 and the discharge portion 61 of the humidification port may be appropriately changed according to the structure of the fuel cell stack to which the humidification port is applied.

In addition, the humidifying port 52 is formed to include a humidifying passage 68 for providing a moving passage for passing the air flowing from the outside through the supply port 67 in contact with the humidifying membrane 51. The humidifying channel part 68 can further improve the humidification efficiency by widening the contact area where air comes into contact with the humidifying membrane 51.

The humidifying passage 68 is formed including the humidifying passage 69. In FIG. 4, the humidifying passage 69 is formed by a plurality of partition walls 70 arranged in parallel to each other, but the configuration of the specific humidifying passage such as the size, position, and shape of the humidifying passage 69 is not limited thereto.

On the other hand, in order to prevent the temperature from falling during the heat and water exchange process between the reaction gas (air) and the exhaust gas (water or steam), the humidification port is made of a material having low thermal conductivity, for example, a ceramic material commonly used as a heat insulating material, etc. It is preferred to be prepared.

Using the internal membrane humidifier configured as described above, the process of humidifying the air inside the fuel cell stack will be briefly described as follows.

Moisture, which is the discharge gas generated while passing through the flow path 17 'of the separation plate 15', is adsorbed and permeated to the humidifying membrane 51. In this process, the flooding phenomenon generated in the separator may be reduced to some extent. In addition, since the moisture adsorbed and permeated to the humidifying membrane 51 is constantly maintained at the operating temperature (approximately 80 ° C.) of the fuel cell stack, the moisture acts as an isothermal heat source during the humidification process.

On the other hand, the air introduced from the supply port 67 of the humidification port 52 comes into contact with the humidifying membrane 51 through which the moisture is adsorbed and permeated while passing through the humidifying flow path 68. In this process, heat and moisture exchange are performed between the water and the air, and the air having the elevated temperature and humidity is moved to the inlet 21 of the separator 15 'through the discharge part 61 and into the fuel cell stack. Inflow.

The temperature change during the heat exchange process in the internal film humidifier according to the present invention is shown in Figure 5 (a), the temperature change during the heat exchange process in the conventional film humidifier is shown in Figure 5 (b).

Humidified air passing through the internal membrane humidifier is humidified with the exhaust gas having a temperature substantially equal to the operating temperature (T ₁ ) of the fuel cell stack. Can be supplied. In addition, since the temperature T ₁ of the humidified air passed through the internal membrane humidifier is substantially the same as the temperature inside the fuel cell stack, even if the humidified air flows into the fuel cell stack, it may be used for an electrochemical reaction without changing the relative humidity. have. At the same time, since the internal membrane humidifier absorbs water through the humidification membrane, it is possible to further prevent fuel flooding and further improve fuel cell performance.

On the other hand, in the case of the conventional membrane humidifier installed outside the fuel cell stack, since the temperature T ₂ of the humidified air is lower than the temperature inside the fuel cell stack, when the humidified air enters the fuel cell stack, the temperature As the relative humidity decreases, the humidification effect of the air is inevitably reduced.

6 is a schematic side view of a fuel cell stack 100 ′ according to another embodiment of the present invention, with two internal membrane humidifiers 50 installed.

As shown in FIG. 6, two inner membrane humidifiers 50 may be provided at the outermost side of the fuel cell stack to simultaneously humidify air and hydrogen, and in this case, newly introduced hydrogen is hydrogen and moisture as exhaust gas. Humidification occurs through exchange.

On the other hand, the internal membrane humidifier as described above can be equally applied to the case where the central distribution unit 18 in which the inlet and outlet of the reaction gas is formed is disposed in the center of the fuel cell stack.

7 is a schematic side view of a fuel cell stack 100 ″ in accordance with another embodiment of the present invention.

In this case, the internal membrane humidifier 50 including the humidification membrane 51 and the humidification port 52 only changes its arrangement position as the position of the inlet and outlet of the reaction gas changes. It is substantially the same as that shown.

At least one of the two separation plates 15 ′ positioned closest to the central distribution unit 18 of the fuel cell stack 100 ″ is provided with a flow path for providing a passage for moving the reaction gas.

In addition, an internal membrane humidifier 50 for humidifying the reaction gas supplied to the fuel cell stack through the water exchange with the exhaust gas passing through the passage formed therebetween is provided between the separation plate 15 ′ and the central distribution unit 18. It is arranged.

The internal membrane humidifier 50 may be provided at one side or both sides of the central distribution unit 180 to humidify the air and / or hydrogen as the reaction gas. In addition, the discharge portion of the internal membrane humidifier may be formed to communicate with the air inlet and / or the hydrogen inlet of the fuel cell stack, so that the reaction gas supplied to the fuel cell stack may enter the fuel cell stack through the internal membrane humidifier. .

For example, as shown in FIG. 7, air and hydrogen, which are reaction gases, may be introduced into the fuel cell stack through the internal membrane humidifier 50, and these may be formed again in the air outlet and hydrogen outlet formed in the central distribution unit 18. Is discharged out of the fuel cell stack.

As a result, the internal membrane humidifier according to the present invention may be provided at the inlet side of the reaction gas in the fuel cell stack to humidify the supplied reaction gas and prevent flooding at the same time, thereby greatly improving fuel cell performance.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

1 is a view showing a state in which a reaction gas is supplied by a conventional humidifier for fuel cells.

2 is a perspective view of a conventional fuel cell stack.

3 (a) is a partially exploded perspective view of a conventional fuel cell stack, and FIG. 3 (b) is a schematic cross-sectional view of A-A.

4 is a partially exploded perspective view of a fuel cell stack provided with an internal membrane humidifier according to the present invention.

Figure 5 (a) is a graph showing a temperature change inside the internal film humidifier according to the present invention, Figure 5 (b) is a schematic diagram showing a temperature change inside the conventional film humidifier.

6 is a side view of a fuel cell stack according to another embodiment of the present invention.

7 is a side view of a fuel cell stack according to another embodiment of the present invention.

Claims (10)

A fuel cell stack comprising a plurality of unit cells including a membrane electrode assembly and separator plates disposed on both sides of the membrane electrode assembly, At least one of the two separation plates located at the outermost portions of the plurality of stacked fuel cell stacks has a flow path for providing a passage for moving the reaction gas therethrough, A flow path is disposed in the through-plate separation plate, and includes an internal membrane humidifier for humidifying the reaction gas supplied to the fuel cell stack through the water exchange with the exhaust gas passing through the through-flow path, The internal membrane humidifier may be configured to supply a humidification membrane and a reaction gas disposed on an opposite surface of the separator plate having the passage formed therethrough to face the membrane electrode assembly, and supply the reaction gas to the fuel cell stack while passing through the humidification membrane. A fuel cell stack comprising a guide humidification port. In a fuel cell stack comprising a plurality of unit cells including a central distributor having a reaction gas inlet and outlet, and a separator electrode disposed on both sides of the membrane electrode assembly and the membrane electrode assembly, on both sides of the central distributor. At least one of the two separation plates positioned closest to the central distribution part of the plurality of stacked fuel cell stacks has a flow path for providing a passage for moving the reaction gas therethrough, A fuel including an internal membrane humidifier disposed between the separation plate and the central distribution unit through which the flow passage is formed and humidifies the reaction gas supplied to the fuel cell stack through water exchange with the exhaust gas passing through the flow passage. Battery stack. delete 3. The method of claim 2, The internal membrane humidifier may be configured to supply a humidification membrane and a reaction gas disposed on an opposite surface of the separator plate having the passage formed therethrough to face the membrane electrode assembly and supply the reaction gas to the fuel cell stack while passing through the humidification membrane. A fuel cell stack comprising a guide humidification port. The method according to claim 1 or 4, The humidification membrane is a fuel cell stack, characterized in that made of Nafion. The method according to claim 1 or 4, The humidification port includes a fuel cell stack, characterized in that it comprises a humidifying passage for providing a moving passage for the reaction gas in contact with the humidification membrane. The method according to claim 1 or 4, The reaction gas is air, And a discharge portion of the humidification port communicates with an air inlet of the fuel cell stack. The method according to claim 1 or 4, The reaction gas is hydrogen, And a discharge portion of the humidification port communicates with a hydrogen inlet of the fuel cell stack. The method of claim 1, The reaction gas is air and hydrogen, The inner membrane humidifier is provided in each of the two separation plates located at the outermost side of the fuel cell stack, And a discharge portion of the humidification port of the two inner membrane humidifiers is in communication with an air inlet and a hydrogen inlet of the fuel cell stack, respectively. 5. The method of claim 4, The reaction gas is air and hydrogen, The inner membrane humidifier is provided in each of the two separation plates that are located closest to the central distribution unit, And a discharge portion of the humidification port of the two inner membrane humidifiers is in communication with an air inlet and a hydrogen inlet of the fuel cell stack, respectively.

Images