KR102227608B1 - Fuel cell stack - Google Patents

Abstract

The present invention relates to a fuel cell stack, and more particularly, by forming a discharge path through which waste air and waste fuel is discharged and a supply path through which air and fuel are supplied as double pipes, high-temperature waste air and waste fuel and fuel The present invention relates to a fuel cell stack in which heat exchange occurs between fuel and air at room temperature supplied to the cell stack, and a temperature variation of the fuel cell stack is reduced.

Description

Fuel cell stack {FUEL CELL STACK}

The present invention relates to a fuel cell stack, and more particularly, by forming a discharge path through which waste air and waste fuel is discharged and a supply path through which air and fuel are supplied as double pipes, high-temperature waste air and waste fuel and fuel The present invention relates to a fuel cell stack in which heat exchange occurs between fuel and air at room temperature supplied to the cell stack, and a temperature variation of the fuel cell stack is reduced.

In general, a fuel cell is a power generation system that directly converts the chemical reaction energy of hydrogen contained in a hydrocarbon-based material and air containing oxygen or oxygen into electrical energy.

For example, a solid oxide fuel cell has a structure in which a plurality of electricity generation units including a unit cell and a separator for generating electricity through oxidation/reduction reactions of hydrogen and oxygen are stacked. The unit cell includes an electrolyte membrane, an anode (air electrode) disposed on one side of the electrolyte membrane, and a cathode (fuel electrode) disposed on the other side of the electrolyte membrane.

Accordingly, when oxygen is supplied to the anode and hydrogen is supplied to the cathode, oxygen ions generated by the reduction reaction of oxygen from the anode move to the cathode through the electrolyte membrane and then react with the hydrogen supplied to the cathode to generate water. At this time, electrons flow to an external circuit while electrons generated from the negative electrode are transferred to and consumed by the positive electrode, and the unit cell generates electrical energy by using the electron flow.

One unit cell and a separator located on both sides of the unit cell constitute one unit cell. These unit cells typically have an operating voltage of less than 1.0V, which is insufficient for industrial applications. Accordingly, the fuel cell forms a stack by stacking a plurality of unit cells electrically connected in series so as to increase the voltage.

Since the fuel cell having the above structure generates electricity by continuously supplying fuel and air in principle of operation, a passage for uniformly inducing the flow of fluid is formed in the separator, and fuel and air flow along the passage.

The electrochemical reaction occurring in a unit cell of a fuel cell converts some of the chemical energy of the fuel gas into electrical energy and at the same time converts some of it into thermal energy. In this case, the thermal energy is not generated evenly on the surface of the unit cell, but the amount of heat generated locally is different depending on the operating conditions of the unit cell and the direction of gas flow. In addition, the heat energy generated in this way tends to accumulate toward the flow of gas through convection caused by the flow of fluid. Accordingly, a hot spot, which is a point with the highest temperature on one unit cell, is formed on the front side of the unit cell at the outlet side of the air, and a cold spot, which is a relatively lowest temperature, is formed on the inlet side of air. As a result, there is a problem that a temperature gradient is formed in the flow direction of the fluid in each unit cell constituting the stack. This temperature non-uniformity affects performance and long-term durability, and at this time, when the temperature of the injected fluid is significantly lower than the operating temperature, this problem is further exacerbated.

Accordingly, there is a need for a fuel cell stack capable of improving the reliability of the stack and improving the performance and lifespan by minimizing the temperature gradient formed inside the stack without lowering the average temperature of the stack.

Korean Patent Registration No. 10-1407937

The present invention was conceived to solve the above-described problem, and an object of the present invention is that the discharge path and the supply path are formed as double pipes, so that the temperature of the fuel and air supplied to the fuel supply path and the air supply path is raised, The temperature of the waste fuel and waste air discharged through the fuel discharge path and the air discharge path is to provide a fuel cell stack in which temperature is reduced.

In addition, by forming a waste fuel/air chamber under the fuel cell stack, the fuel cell stack is provided to increase the temperature of the lower portion of the fuel cell stack to reduce the interlayer temperature gradient of the fuel cell stack.

A fuel cell stack according to an embodiment of the present invention includes a stack structure in which one or more unit cells are stacked; A fuel supply path (Fule inlet) for supplying fuel to the stacked structure; A fuel outlet for discharging waste fuel from the stacked structure; An air inlet supplying air to the stacked structure; And an air outlet for discharging waste air from the stacked structure, wherein at least one of the air discharge passage and the fuel discharge passage may include at least one of the fuel supply passage and the air supply passage It characterized in that it is formed of a double tube and

In one embodiment, the double pipe is characterized in that any one or more of the fuel and air supply paths form a contact surface on one or the other side of one or more of the air and fuel discharge paths.

In one embodiment, the double pipe is characterized in that any one of the fuel and air discharge paths is formed to surround the outside of any one or more of the fuel supply path and the air supply path.

In one embodiment, the double pipe is characterized in that the fuel and air discharge path is formed by being positioned to be spaced apart from the fuel supply path and the air supply path inside the fuel and air discharge path.

In one embodiment, the fuel cell stack further comprises a waste fuel/air chamber for storing at least one of the waste fuel and the waste air and supplying it to the double pipe, wherein the waste fuel/air chamber, It is characterized in that it is located in one of the fuel discharge passage, one side of the air discharge passage, and the lower portion of the stacked structure.

In one embodiment, the double pipe, the waste air and heat of the waste fuel discharged through the supply discharge passage and the fuel discharge passage is transferred to the fuel supply passage or the air supply passage, It is characterized by raising the temperature.

In one embodiment, temperatures of the fuel and air supplied through the fuel supply path and the air supply path are increased by 500°C or more.

In one embodiment, the fuel supply path is characterized in that it is formed in any one of a straight tube type, a spiral type, a coil type, and a fin type.

In one embodiment, the air supply path is characterized in that it is formed in any one of a straight tube type, a spiral type, a coil type, and a fin type.

In one embodiment, the fuel and air flow directions of the fuel supply path and the air supply path and the waste fuel and waste air flow directions to the fuel discharge path and the air discharge path are opposite directions.

According to the present invention, since the discharge path and the supply path are formed as double pipes, heat exchange occurs between the supplied fuel and air and the discharged waste air, and the hot and cold spots of the fuel cell stack become the same as the operating temperature of the fuel cell, thereby minimizing the temperature gradient. The effect is to occur.

In addition, according to the present invention, a stack capable of storing waste air and waste fuel is formed under the fuel cell stack, so that the temperature of the lower portion of the fuel cell stack is increased using the temperature of the waste air and waste fuel to increase the interlayer of the fuel cell stack. The effect of minimizing the temperature gradient occurs.

In addition, according to the present invention, since the temperature gradient of the fuel cell stack is minimized, the effect of reducing the deterioration rate of the fuel cell stack occurs.

In addition, according to the present invention, the difference in thermal expansion of each component is minimized, so that destruction of components or leakage of gas does not occur, so that the reliability of the stack is improved.

1 is a perspective view showing a fuel cell stack according to an embodiment of the present invention.
2 is a perspective view illustrating a fuel cell stack according to another embodiment of the present invention.
3 is a perspective view showing a fuel cell stack according to another embodiment of the present invention.
4 is a perspective view showing a fuel cell stack according to another embodiment of the present invention.
5 is a cross-sectional view illustrating a fuel cell stack according to another embodiment of the present invention.
6 is a perspective view showing a double pipe according to an embodiment of the present invention.
7(a) is a perspective view showing a double pipe according to another embodiment of the present invention, and FIG. 7(b) is a cross-sectional view of a double pipe according to another embodiment of the present invention.
8(a) is a perspective view showing a double pipe according to another embodiment of the present invention, and FIG. 8(b) is a cross-sectional view of a double pipe according to another embodiment of the present invention.
9 is a cross-sectional view showing a double pipe according to the present invention.

The present invention will be described in detail with reference to the accompanying drawings as follows. Here, repeated descriptions and detailed descriptions of known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted. Embodiments of the present invention are provided to completely explain the present invention to those with average knowledge in the art. Accordingly, the shapes and sizes of elements in the drawings may be exaggerated for clearer explanation.

Throughout the specification, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless specifically stated to the contrary.

Hereinafter, a preferred embodiment is presented to aid the understanding of the present invention. However, the following examples are only provided to more easily understand the present invention, and the contents of the present invention are not limited by the examples.

<Fuel cell stack>

1 to 5 are perspective views illustrating a fuel cell stack according to an embodiment of the present invention, and FIGS. 6 to 8 are diagrams illustrating double pipes 60, 60', and 60" according to an embodiment of the present invention. It is a perspective view and a cross-sectional view, and FIG. 9 is a cross-sectional view showing a double pipe according to the present invention.

The fuel cell stack according to the present invention may include a stacked structure 10, a fuel supply path 20, a fuel discharge path 30, an air supply path 40, and an air discharge path 50.

The stacked structure 10 according to the present invention is provided by stacking one or more unit cells, and may include a unit cell, a window frame, and an interconnector.

First, the unit cell can play a role of generating electricity in the fuel cell stack, and is composed of an electrolyte having oxygen ion conductivity, and a fuel electrode and an air electrode on both sides thereof. When fuel is supplied to the anode, the fuel is oxidized and electrons are released through an external circuit. When oxygen is supplied to the cathode, electrons are received from the external circuit and are reduced to oxygen ions. The reduced oxygen ions move to the anode through the electrolyte and react with the oxidized fuel to produce water. At this time, direct current electricity is produced by the flow of electrons from the anode to the cathode. The unit cell may have three structures: an electrolyte self-supporting membrane type, a negative electrode support type, and a porous support type.

The window frame prevents oxygen and hydrogen introduced through the cathode and anode interconnects from flowing into the unit cell, and prevents oxygen and hydrogen from being mixed with each other during the operation of the fuel cell stack. In addition, a flow path may be formed so that oxygen and hydrogen introduced through the cathode and anode interconnects flow inside the fuel cell stack.

The interconnector may be divided into a cathode interconnector supplied with air and an anode interconnector supplied with fuel. And, in the stacked structure 10 formed by stacking two or more unit cells according to the present invention, the interconnector serves to electrically connect the stacked two or more unit cells, and at the same time, the two or more unit cells are supplied to the anode and the cathode. A flow path may be formed so that the types of gases are not mixed and can be uniformly supplied to the unit cells.

The flow path formed in the cathode interconnector and the anode interconnect has an uneven structure and may be formed on one of the top and bottom surfaces of the cathode and anode interconnectors. In addition, it should be noted that the flow path formed in the cathode interconnect and the flow path formed in the anode interconnect are formed in a vertical direction and do not communicate with each other.

For example, when the air flow path is formed in a vertical direction, oxygen supplied through the cathode interconnect can be moved in the vertical direction of the cathode, and when the fuel channel is formed in a horizontal direction, the oxygen supplied through the anode interconnector Hydrogen can be moved in the horizontal direction of the anode.

In a fuel cell stack formed by stacking one or more unit cells, an interconnector positioned between the unit cell and the unit cell may serve as a separator.

The fuel supply path 20 is a path for supplying fuel gas to the cathode, and the fuel discharge path 30 is a path for discharging fuel gas that has not reacted with the cathode.

In addition, the air supply path 40 is a path for supplying air to the anode, and the air discharge path 30 is a path for discharging air that has not reacted with the anode.

For example, when the unit cell of the stacked structure 10 is a solid oxide fuel cell, hydrogen is supplied through the fuel supply path 20, hydrogen and the cathode react to generate electrons, and the generated electrons form an electrolyte. It moves to the anode through and can generate the current of the fuel cell. In addition, waste hydrogen gas that has not reacted with the cathode may be discharged through the fuel discharge path 30.

Furthermore, oxygen supplied through the air supply path 40 reacts with the anode to generate hydrogen ions, and the generated hydrogen ions move to the cathode through the electrolyte to generate a reaction product through a chemical reaction with the hydrogen ions that have lost electrons. can do. In addition, waste air that has not reacted with the reaction product and the anode may be discharged through the air discharge path 50.

At this time, the electrochemical reaction occurring in the unit cell may convert part of the chemical energy of the fuel gas into electrical energy and at the same time convert part of it into thermal energy. Therefore, the fuel and air supplied through the fuel and air supply paths 20 and 40 are discharged through the fuel and air discharge paths 30 and 50 after being in contact with the cathode and anode through the flow paths of the cathode and anode interconnectors. , Waste fuel and waste air may have an increased temperature.

Further, the fuel supply path 20, the fuel discharge path 30, the air supply path 40, and the air discharge path 50 according to the present invention may be formed of a double pipe 60.

In one embodiment, the air discharge path 50 may be positioned above and below the fuel supply path 20 to form the double pipe 60. Since the temperature of the air discharged through the air discharge path 50 is discharged at a higher temperature than the fuel supplied through the fuel supply path 20, heat exchange between the supplied fuel and the waste air may occur.

Since the fuel supply path 20 and the air discharge path 50 are formed as a double pipe 60, heat exchange occurs in the upper and lower portions of the fuel supply path 20, and the temperature of the fuel supplied within a short time is the operating temperature of the fuel cell. , It can be raised to about 500 ℃ or more. Accordingly, by providing a short pipe length of the fuel supply path 20, the fuel can be heated to a target temperature within a short time, thereby increasing space efficiency.

In addition, the temperature of the supplied fuel is raised, the temperature of the waste air is reduced to reduce the temperature difference between hot and cold spots generated in the fuel cell stack, and the temperature gradient formed inside the stack is reduced, so that each component of the fuel cell stack is reduced. The difference in thermal expansion of the elements is reduced, thereby preventing problems such as destruction of components or leakage of gas, thereby increasing the reliability of the stack.

The temperature of the waste air may be reduced by heat exchange between the supplied fuel and the waste air. However, since the minimum temperature to be reduced is above the operating temperature of the fuel cell, the average temperature of the fuel cell stack does not decrease, thus reducing the reaction speed of the fuel cell. Does not occur.

Referring to FIG. 2, the double pipe 60 of the fuel cell stack according to another embodiment of the present invention may be formed by having an air discharge path 50 positioned above and below the air supply path 40. Waste air may increase the temperature of the air supplied to the air supply path 40 to reduce the temperature gradient of the fuel cell stack. In addition, since the temperature of the waste air is decreased due to the structure of the double pipe 60, the temperature of the hot spot is reduced than the heat resistance temperature of all components of the fuel cell stack, but does not decrease below the operating temperature of the fuel cell, preventing a decrease in the reaction rate. can do.

And, referring to FIG. 3, in the fuel cell stack according to another embodiment of the present invention, the air discharge path 50 is positioned above and below the fuel and air supply paths 20 and 40, so that the double pipe 60 is Can be formed. For example, the double pipe 60 may be formed by stacking the air exhaust path 50, the fuel supply path 20, the air exhaust path 50, the air supply path 40, and the air exhaust path 50 in that order. have. That is, two double pipes 60 may be formed based on the fuel supply path 20 and the air supply path 40. By heating the fuel and air supplied to the fuel cell using the temperature of the waste air, no additional configuration is required to heat the fuel and air supply paths 20 and 40, and short fuel and air supply paths 20 and 40 ) To heat the fuel and air, it is possible to use the space efficiently.

At this time, the fuel cell stack according to the present invention is not limited to FIGS. 1 to 3, and a fuel discharge path 30 may be applied.

Further, the fuel supply path 20, the air supply path 30, the fuel discharge path 40, and the air discharge path 50 according to FIGS. 1 to 3 are formed on the top of the stacked structure 10, but the present invention The fuel supply path 20, the air supply path 30, the fuel discharge path 40, and the air discharge path 50 according to the above are not limited to the drawings, and may be formed under the stacked structure 10.

The double pipe of the fuel cell stack according to the present invention may be provided in various forms. First, referring to FIG. 6, the double pipe 60 according to an embodiment of the present invention is provided on one side and the other side of the fuel supply path 20. The air discharge path 50 may be located, and at this time, the fuel supply path 20 and the air discharge path 50 may form a contact surface. In addition, the double pipe 60 according to the present invention is not limited to FIG. 6, and a fuel discharge path is located on one side and the other side of the fuel supply path 20, or a fuel discharge path is located on one side and the other side of the air supply path. , Air discharge paths may be located on one side and the other side of the air supply path. In addition, the double tube 60 may be formed in any one of a straight tube type, a spiral type, a coil type, and a fin type. When the double pipe 60 is formed in any one of a spiral type, a coil type, and a fin type, a surface where the supply path and the discharge path are in contact with each other is increased than that of the straight tube type, so that a smoother heat exchange effect may occur.

Referring to FIG. 7, the double pipe 60 ′ according to another embodiment of the present invention may be formed in a form in which the air discharge path 50 surrounds the outside of the fuel supply path 20. Accordingly, the outer surface of the fuel supply passage 20 may form a contact surface with the waste air discharged through the air discharge passage 50. Here, the double pipe 60 ′ according to another embodiment of the present invention is not limited to FIG. 7, and a fuel discharge path is formed outside the fuel supply path 20, or an air discharge path 50 is formed outside the air supply path. Or, a fuel discharge path may be formed outside the air supply path.

Referring to FIG. 8, according to another embodiment of the present invention, the double pipe 60 ″ may be positioned so that the fuel supply path 20 and the air supply path 40 are spaced apart from the inside of the air discharge path 50. By discharging the waste air through the space spaced between the fuel supply path 20 and the air supply path 40, all outer surfaces of the fuel and air supply paths 20 and 40 can be in contact with the waste air. The double pipe 60" according to another embodiment of the present invention is not limited to FIG. 8, and the fuel and air supply paths 20 and 40 are spaced apart from each other, and the fuel discharge path is the fuel and air supply paths 20 and 40. ) Can be formed in a form surrounding.

In the double pipes 60' and 60" according to Figs. 7 and 8, the fuel and air supply paths 20 and 40 located inside the double pipes 60' and 60" are of a straight pipe type, a spiral type, a coil type, and a pin type. It can be provided in any one form. In the case of the spiral type, coil type, and fin type, the contact surface through which the fuel and air supplied to the fuel cell stack can be exchanged for heat exchange with the waste air and the waste fuel is increased compared to the straight tube type, thereby reducing the time for the supplied fuel and air to rise to the operating temperature. A reducing effect can occur.

In the double pipe according to the present invention, the flow direction of the fuel and air flowing through the fuel and air supply path, and the waste fuel and waste air flowing through the fuel and air discharge path may be opposite. Referring to FIG. 9, the double pipe 60 may be formed of a fuel supply passage 20 and an air discharge passage 50, and in this case, fuel and waste air may be introduced and discharged in opposite directions.

Accordingly, the temperature of the waste fuel and the waste air heat-exchanged with the fuel and air supplied to the fuel cell stack can always be provided under high temperature conditions. That is, the waste fuel and waste air, which have undergone heat exchange with the supplied fuel and air, flow in a direction opposite to the fuel and air to be discharged to the outside, and the fuel and air come into contact with the new waste fuel and waste air discharged from the fuel cell. Accordingly, the waste fuel and waste air heat-exchanged with the fuel and air supplied to the fuel cell stack maintain a constant temperature, and the time during which the supplied fuel and air is heated is reduced, so that the pipe length of the supply path can be shortened. . In addition, the temperature of the fuel and air supplied to the fuel cell stack is increased, so that the hot spot temperature of the fuel cell stack decreases below the heat resistance temperature of all components of the fuel cell stack, but does not decrease below the operating temperature of the fuel cell. Can prevent reduction.

The fuel cell stack according to the present invention may further include a waste fuel/air storage unit 70. The waste fuel/air stack 70 may serve to store at least one of waste fuel and waste air discharged from the fuel cell stack and then supply it to the double pipe 60. Accordingly, waste fuel and waste air can be constantly supplied to each of the discharge paths 50 positioned above and below the supply path 40 or inside and outside the supply path 40.

The waste fuel/air stack 70 may be located on one side of the double pipe 60 and on the lower portion of the stacked structure 10.

In one embodiment, referring to FIG. 4, the waste fuel/air stack 70 is located on one side of the double pipe 60 or the air discharge path 50, so that the waste air discharged through the air discharge path 50 is After storage, waste air may be constantly supplied to each of the air discharge paths 50 located above and below the fuel supply path 20 of the double pipe 60 formed on the other side of the waste fuel/air stack 70.

In another embodiment, referring to FIG. 5, the waste fuel/air stack 70 may be located under the stacked structure 10. Here, the air supply path 40 may supply air to the stacked structure through the inside of the waste fuel/air puck 70, and the air distribution path 50 conveys waste air to one side of the waste fuel/air stack 70. After being discharged, the waste air may be discharged to the double pipe 60 through the other side after raising the temperature of the waste fuel/air stack 70.

Since the waste fuel/air stack 70 is located under the stacked structure 10, the fuel cell stack is supplied with room temperature fuel and air through the lower layer to prevent the temperature of the lower part of the fuel cell stack from decreasing below the operating temperature. And, thus, reducing the temperature gradient of the fuel cell stack.

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art will variously modify and change the present invention within the scope not departing from the spirit and scope of the present invention described in the following claims. You will understand that you can do it.

10: laminated structure
20: fuel supply furnace
30: fuel discharge furnace
40: with air supply
50: with air exhaust
60, 60', 60": double tube
70: waste fuel/air reservoir

Claims (10)

A stacked structure in which one or more unit cells are stacked;
A fuel supply path (Fule inlet) for supplying fuel to the stacked structure;
A fuel outlet for discharging waste fuel from the stacked structure;
An air inlet supplying air to the stacked structure;
An air outlet for discharging waste air from the stacked structure; And
A waste fuel/air chamber located below the stacked structure, receiving and storing at least one of the waste fuel and the waste air, and crossing the fuel supply path and the air supply path therein, and
Any one of the fuel discharge path and the air discharge path,
It is located between the fuel supply path and the air supply path, and is formed of a double pipe having contact surfaces on one side and the other side of the fuel supply path and the air supply path,
The double pipe is characterized in that located on the side of the waste fuel / air chamber,
Fuel cell stack.
delete The method of claim 1,
The double pipe,
One of the fuel and air discharge paths, characterized in that formed in a shape surrounding the outside of at least one of the fuel supply path and the air supply path.
The method of claim 1,
The double pipe,
The fuel cell stack, characterized in that the fuel supply path and the air supply path are formed to be spaced apart from each other in the fuel and air discharge path.
delete The method of claim 1,
The double pipe,
The waste air and heat of the waste fuel discharged through the air discharge path and the fuel discharge path are transferred to the fuel supply path or the air supply path to raise the temperature of the fuel or the air, Fuel cell stack.
The method of claim 6,
The fuel cell stack, characterized in that the temperature of the fuel and the air supplied through the fuel supply path and the air supply path is increased by 500°C or more.
The method of claim 1,
The fuel supply path,
A fuel cell stack, characterized in that it is formed in any one of a straight tube type, a spiral type, a coil type, and a fin type.
The method of claim 1,
The air supply path,
A fuel cell stack, characterized in that it is formed in any one of a straight tube type, a spiral type, a coil type, and a fin type.
The method of claim 1,
The fuel cell stack, characterized in that the fuel and air flow directions of the fuel supply path and the air supply path and the waste fuel and the waste air flow directions of the fuel discharge path and the air discharge path are opposite directions.

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