KR102176558B1 - Thermal cascade system for fuel cell and management method thereof - Google Patents

Abstract

A thermal cascade system for fuel cells and its operating method are introduced.
Among them, the thermal cascade system for fuel cells generates an electromotive force through an electrochemical reaction using a fuel supply for fuel supply, a reformer that receives fuel from the fuel supply to generate fuel gas, and fuel gas generated in the reformer. An air preheating unit that preheats air and supplies the preheated air to the fuel cell stack using exhaust gas generated from the fuel cell stack, a catalytic oxidizer that oxidizes the unreacted gas discharged from the fuel cell stack, and , It may include a steam generator that generates steam using the exhaust gas generated from the catalytic oxidizer and provides the generated steam to the reformer.

Description

Thermal cascade system for fuel cells and its operation method {THERMAL CASCADE SYSTEM FOR FUEL CELL AND MANAGEMENT METHOD THEREOF}

The present invention relates to a thermal cascade system for a fuel cell and a method of operating the same.

A fuel cell is a device that converts chemical energy of a fuel into electrical energy through an electrochemical reaction, and is known to significantly reduce fuel consumption, pollutants and greenhouse gas emissions because the energy change efficiency is far higher than that of a heat engine.

In particular, a solid oxide fuel cell (SOFC) is composed of a porous positive electrode and a negative electrode, and an electrolyte having a dense structure between the two electrodes, air is supplied to the positive electrode, and hydrogen or fuel is supplied to the negative electrode. Since these single cells form a single solid oxide fuel cell stack through organic connection with each other using a connecting material, the system can be implemented in a wide range from several W to MW according to power demand, and can be applied from home to large-scale power generation. The range is wide.

However, in the case of conventional fuel cells, by configuring the system by separating the reformer, off-gas oxidizer, and heat exchanger, prioritizing the ease of maintenance rather than the viewpoint of thermal energy efficiency, heat loss is increased, and energy is reduced due to additional supply of external fuel. The efficiency is low.

In particular, when increasing the capacity of the battery stack through the additional arrangement of the unit stack, high-temperature red heat is generated in the central region in which the unit stack is arranged, so that the stack operation efficiency may decrease.

Accordingly, there is a need to optimize a process arrangement to minimize heat loss between element systems as well as to eliminate red heat due to multiple stack arrangements.

Korean Patent Publication No. 10-2013-0033824 (published on April 4, 2013)

Embodiments of the present invention provide a thermal cascade system for a fuel cell capable of efficient use of thermal energy by reusing the heat of chemical reaction and unreacted gas of a fuel cell stack for preheating of external air, steam production, and fuel reforming, and a method of operating the same. I want to.

A thermal cascade system for a fuel cell according to an embodiment of the present invention for achieving the above object includes: a fuel supply for supplying fuel; A reformer that receives fuel from the fuel supplier and generates fuel gas; A fuel cell stack generating electromotive force through an electrochemical reaction using the fuel gas generated in the reformer; A catalytic oxidizer for oxidizing unreacted gas discharged from the fuel cell stack; An air preheating unit that preheats air using exhaust gas generated from the catalytic oxidizer and supplies the preheated air to the fuel cell stack; And a steam generator that generates steam using the exhaust gas generated from the catalytic oxidizer and provides the generated steam to the reformer.

In this case, the present invention may further include an ejector positioned between the fuel supplier and the reformer and receiving the fuel from the fuel supplier and the steam from the steam generator using a pressure difference and providing the fuel to the reformer.

In addition, the present invention may further include a fuel bypass for bypassing the fuel of the fuel supplier to the catalytic oxidizer.

In addition, the present invention may further include an air bypass for bypassing the air preheated in the air preheating unit to the catalytic oxidizer.

In addition, the present invention may further include an unreacted gas loop for feeding back unreacted gas discharged from the fuel cell stack to the ejector.

In addition, the air preheating unit may include a latent heat recovery device for preheating the air supplied from the outside to exhaust gas of the catalytic oxidizer; And an air preheater for re-preheating the air preheated in the latent heat recovery device using exhaust gas of the catalytic oxidizer and then supplying the air to the fuel cell stack.

In addition, the fuel cell stack may include a plurality of battery stacks spaced apart from each other around the catalytic oxidizer; A main manifold receiving the fuel gas from the reformer; A plurality of sub-manifolds connecting between the main manifold and the plurality of battery stacks to supply the fuel gas in the main manifold to the plurality of battery stacks; And a connection manifold connecting the plurality of sub-manifolds and the catalytic oxidizer.

In addition, the main manifold may be provided in a ring shape, and a plurality of the sub-manifolds may be spaced apart from the upper surface along the circumferential direction.

A method of operating a thermal cascade system for a fuel cell according to an embodiment of the present invention includes: supplying fuel from a fuel supply; Generating fuel gas in a reformer using fuel supplied from a fuel supplier; Generating electromotive force in a fuel cell stack through an electrochemical reaction using fuel gas; Oxidizing the unreacted gas discharged from the fuel cell stack in a catalytic oxidizer; Preheating air using exhaust gas generated from the catalytic oxidizer, and then supplying the preheated air to the fuel cell stack; And generating steam using the exhaust gas generated in the catalytic oxidizer, and then providing the generated steam to the reformer.

At this time, the present invention may further include the step of bypassing the fuel of the fuel supplier to the catalytic oxidizer after the step of supplying the fuel to the fuel supplier.

In addition, the present invention may further include preheating air using exhaust gas generated from the catalytic oxidizer after oxidizing in the catalytic oxidizer, and then bypassing the preheated air to the catalytic oxidizer.

In addition, the present invention may further include a step of feeding back unreacted gas discharged from the fuel cell stack to a reformer after generating electromotive force in the fuel cell stack.

Embodiments of the present invention have the advantage of minimizing heat loss of the system and improving thermal energy efficiency by optimizing the urea process for heat energy production and distribution.

In addition, embodiments of the present invention have the advantage that fuel reforming in the reformer is possible without supplying an external heat source by using the heat of oxidation of the unreacted gas generated in the fuel cell stack as an endothermic reaction required for fuel reforming in the reformer. . Through this, process energy efficiency can be improved, and the device of the system can be compact.

In addition, embodiments of the present invention have the advantage of solving the problem of red heat occurring in the center of the battery stack when a plurality of fuel cell stacks are arranged through the optimization of the element process arrangement.

In addition, the embodiments of the present invention have the advantage that high-temperature off-gas can be repurified through non-powered power, so that high-temperature thermal energy can be directly utilized for fuel preheating and can be completely mixed with steam.

1 is a block diagram showing a thermal cascade system for a fuel cell according to the present invention.
2 is an exploded perspective view showing a thermal cascade system for a fuel cell according to the present invention.
3 is a combined perspective view showing a thermal cascade system for a fuel cell according to the present invention.
4 is a block diagram showing a method of operating a thermal cascade system for a fuel cell according to the present invention.

Hereinafter, a configuration and operation according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The following description is one of several aspects of the invention that are claimable, and the following description may form part of the detailed description of the invention. However, in describing the present invention, detailed descriptions of known configurations or functions may be omitted to clarify the present invention.

Since the present invention can make various changes and include various embodiments, specific embodiments will be illustrated in the drawings and described in the detailed description. However, this is not intended to limit the present invention to a specific embodiment, it is to be understood to include all changes, equivalents, or substitutes included in the spirit and scope of the present invention.

Further, terms including ordinal numbers such as first and second may be used to describe various elements, but the corresponding elements are not limited by these terms. These terms are only used for the purpose of distinguishing one component from another. When a component is referred to as being'connected' or'connected' to another component, it is understood that it may be directly connected or connected to the other component, but other components may exist in the middle. Should be. The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

1 is a block diagram showing a thermal cascade system for a fuel cell according to the present invention, FIG. 2 is an exploded perspective view showing a thermal cascade system for a fuel cell according to the present invention, and FIG. 3 is a fuel cell according to the present invention. It is a combined perspective view showing a thermal cascade system.

1 to 3, the fuel cell thermal cascade system 10 according to an embodiment of the present invention includes a fuel supply 100, an ejector 700, a reformer 200, and a fuel cell stack. It may include 300, a catalytic oxidizer 400, an air preheating unit 500, and a steam generator 600.

Specifically, the fuel supplier 100 may provide fuel to the reformer 200 through the ejector 700. The fuel supplier 100 may receive fuel from a fuel supply tank (not shown) to provide fuel to the ejector 700 or may provide fuel to the ejector 700 through a pipe in a state in which fuel is received.

In this embodiment, the fuel supplied to the ejector 700 through the fuel supplier 100 may be a hydrocarbon-based fuel, but is not limited thereto, and various types of fuel capable of generating electromotive force through the fuel electric stack are used. Of course it can be used.

The ejector 700 is located between the fuel supply unit 100 and the reformer 200, and may supply raw materials (fuel, steam, unreacted gas...) to the reformer 200. Since the ejector 700 provides a venturi structure therein, the raw material can be moved using a pressure difference (for example, a venturi effect) without a separate driving device.

Fuel from the fuel supply unit 100, steam from the steam generator 600, and unreacted gas from the fuel cell stack 300 may be introduced into the ejector 700, respectively. Fuel, steam, and unreacted gas introduced into the ejector 700 may be supplied to the reformer 200.

The reformer 200 may receive fuel from the fuel supplier 100 to generate fuel gas. In this case, the fuel gas may be understood as a gas including fuel, steam, and hydrogen generated by a heating reaction of unreacted gas through the reformer 200. For example, the reformer 200 may generate fuel gas by heating and reacting fuel, steam, and unreacted gas. The fuel gas generated by the reformer 200 may be supplied to the fuel cell stack 300.

The fuel cell stack 300 may generate electromotive force through an electrochemical reaction using the fuel gas of the reformer 200. For example, the fuel cell stack 300 may generate electromotive force by generating an electrochemical reaction using fuel gas and air supplied from the reformer 200. The maximum power value that can be generated in the fuel cell stack 300 may be affected by the amount of hydrogen supplied from the reformer 200.

The fuel cell stack 300 may include a cell stack 310, a main manifold 320, a sub manifold 330, and a connection manifold 340. Here, the battery stack 310 may be provided in a plurality that are spaced apart from each other around a predetermined space in which the catalytic oxidizer 400 is disposed.

In particular, when a plurality of battery stacks 310 are arranged in a plurality of unit stacks, a catalytic oxidizer 400, an ejector 700, and an air preheating unit 500 are located in a central region (a predetermined space) of the plurality of battery stacks 310. And since the steam generator 600 may be disposed, it is possible to prevent a decrease in stack operation efficiency due to high temperature red heat generated in the central region in which the unit stack is arranged.

The main manifold 320 may provide the fuel gas supplied from the reformer 200 by distributing it to the plurality of sub-manifolds 330. To this end, the main manifold 320 may be provided in a ring shape, and a plurality of sub-manifolds 330 may be spaced apart from each other in the circumferential direction on the upper surface of the main manifold 320.

In addition, the plurality of sub-manifolds 330 may be connected between the main manifold 320 and the plurality of battery stacks 310 to supply the fuel gas in the main manifold 320 to the plurality of battery stacks 310. have. The connection manifold 340 may connect the plurality of sub-manifolds 330 and the catalytic oxidizer 400.

The catalytic oxidizer 400 may oxidize unreacted gas discharged from the fuel cell stack 300. Since the catalytic oxidizer 400 corresponds to a conventional catalytic oxidizer capable of oxidizing unreacted gas, a detailed description thereof will be omitted.

The air preheating unit 500 is a heat exchanger capable of exchanging heat with exhaust gas, and may preheat air using exhaust gas generated from the catalytic oxidizer 400 and supply the preheated air to the fuel cell stack 300.

The air preheating unit 500 includes a latent heat recovery device 510 that preheats the air supplied from the outside to the exhaust gas of the catalytic oxidizer 400, and the air preheated in the latent heat recovery device 510 is the exhaust gas of the catalytic oxidizer 400. After re-preheating using, it may be configured with an air preheater 520 supplied to the fuel cell stack 300.

The steam generator 600 is a heat exchanger capable of exchanging heat with exhaust gas similar to the air preheating unit 500, and generates steam using exhaust gas generated from the catalytic oxidizer 400, and transfers the generated steam to the reformer 200. Can provide.

These latent heat recoverers 510, air preheaters 520, and steam generators 600 are a three-stage complex heat exchange that is continuously disposed in the central portion of the fuel cell stack 300, that is, in the central region of the plurality of battery stacks 310. It can be a flag.

As such, the latent heat recovery device 510, the air preheater 520, and the steam generator 600 preheat air using exhaust gas generated from the catalytic oxidizer 400, thereby minimizing heat loss of the system and Energy efficiency can be improved.

Meanwhile, the fuel of the fuel supplier 100 may be bypassed to the catalytic oxidizer 400 through the fuel bypass 710. The fuel bypass 710 may interconnect a pipe connecting the fuel supplier 100 and the ejector 700 and a pipe connecting the fuel cell stack 300 and the catalytic oxidizer 400. At this time, in order to bypass the fuel to the catalytic oxidizer 400, a separate control valve may be used.

In addition, the air preheated in the air preheating unit 500 may be bypassed to the catalytic oxidizer 400 through the air bypass 730. The air bypass 730 may interconnect between a pipe connecting the air preheater 520 and the fuel cell stack 300 and a pipe connecting the fuel cell stack 300 and the catalytic oxidizer 400. In this case, a separate control valve may be used to bypass air to the catalytic oxidizer 400.

In addition, the unreacted gas discharged from the fuel cell stack 300 may be fed back to the ejector 700 through the unreacted gas loop 720. The unreacted gas loop 720 may interconnect between the ejector 700 and a pipe connecting the fuel cell stack 300 and the catalytic oxidizer 400.

4 is a block diagram showing a method of operating a thermal cascade system for a fuel cell according to the present invention.

As shown in Figure 4, the operating method of the thermal cascade system for a fuel cell according to an embodiment of the present invention, the step of supplying fuel from the fuel supply (S100) and the step of generating fuel gas in the reformer ( S200), generating electromotive force in the fuel cell stack (S300), oxidizing in the catalytic oxidizer (S400), supplying air to the fuel cell stack (S500), and providing steam to the reformer It may include a step (S600).

In the step of supplying fuel from the fuel supplier (S100), fuel is supplied to the ejector through the fuel supplier. At this time, the fuel may be a hydrocarbon-based fuel. The fuel is transferred to the reformer through an ejector, but some of the fuel can be selectively transferred to the catalytic oxidizer through a fuel bypass.

In the step of generating fuel gas in the reformer (S200), fuel gas is generated in the reformer using the fuel supplied from the fuel supplier. The reformer may generate fuel gas by heating and reacting fuel, steam, and unreacted gas supplied through an ejector. The fuel gas generated by the reformer may be supplied to the fuel cell stack.

In the step of generating electromotive force in the fuel cell stack (S300), electromotive force is generated in the fuel cell stack through an electrochemical reaction using fuel gas. The unreacted gas discharged from the fuel cell stack may be fed back to the reformer through the unreacted gas loop.

In the step of oxidizing in the catalytic oxidizer (S400), unreacted gas discharged from the fuel cell stack is oxidized in the catalytic oxidizer.

In the step of supplying the air to the fuel cell stack (S500), air is preheated using exhaust gas generated from the catalytic oxidizer, and then the preheated air is supplied to the fuel cell stack. For example, exhaust gas generated from the catalytic oxidizer may preheat air through heat exchange in an air preheater and a latent heat recovery device. At this time, the preheated air may be moved to the fuel cell stack.

In the step of providing the steam to the reformer (S600), steam is generated using exhaust gas generated from the catalytic oxidizer, and then the generated steam is provided to the reformer. For example, the exhaust gas generated in the catalytic oxidizer may generate steam through heat exchange in the steam generator. At this time, the generated steam may be moved to the ejector.

As described above, the present invention optimizes the urea process for the production and distribution of thermal energy, thereby minimizing the heat loss of the system and improving the thermal energy efficiency, and reducing the heat of oxidation of the unreacted gas generated in the fuel cell stack to the fuel of the reformer. Since it can be used as an endothermic reaction required for reforming, it is possible to reform the fuel in the reformer without supplying an external heat source, and through the optimization of the arrangement of the urea process, the red heat generated in the center of the battery stack when multiple fuel cell stacks are arranged. The problem can be solved, and high-temperature off-gas can be repurified through non-powered power, so high-temperature thermal energy can be used directly for fuel preheating, and by optimizing the element process that can be completely mixed with steam for the production and distribution of thermal energy. In addition, it has the advantage of minimizing the heat loss of the system and improving the heat energy efficiency.

In addition, in the embodiments of the present invention, since the heat of oxidation of the unreacted gas generated in the fuel cell stack can be used as an endothermic reaction required for fuel reforming of the reformer, fuel reforming in the reformer is possible without supplying an external heat source. Consequently, there is an advantage that process energy efficiency can be improved, and the device of the system can be compact.

In addition, embodiments of the present invention have the advantage of solving the problem of red heat occurring in the center when a plurality of fuel cell stacks are arranged through optimization of the element process arrangement.

In addition, the embodiments of the present invention have the advantage that high-temperature off-gas can be repurified through non-powered power, so that high-temperature thermal energy can be directly utilized for fuel preheating and can be completely mixed with steam. And has excellent advantages.

Although the embodiments of the present invention have been described with reference to the accompanying drawings, those of ordinary skill in the art to which the present invention pertains can be implemented in other specific forms without changing the technical spirit or essential features. You can understand. For example, a person skilled in the art may change the material, size, etc. of each component according to the field of application, or combine or substitute embodiments to implement it in a form that is not clearly disclosed in the embodiments of the present invention. It does not go beyond the scope of Therefore, the embodiments described above are illustrative in all respects and should not be understood as limiting, and it should be said that these modified embodiments are included in the technical idea described in the claims of the present invention.

100: fuel supply 200: reformer
300: fuel cell stack 310: battery stack
320: main manifold 330: sub manifold
400: catalytic oxidizer 500: air preheating unit
600: steam generator 700: ejector
710: fuel bypass 720: unreacted gas loop
730: air bypass

Claims (12)

A fuel feeder for fuel supply;
A reformer that receives fuel from the fuel supplier and generates fuel gas;
A fuel cell stack generating electromotive force through an electrochemical reaction using the fuel gas generated in the reformer;
A catalytic oxidizer for oxidizing unreacted gas discharged from the fuel cell stack;
An air preheating unit that preheats air using exhaust gas generated from the catalytic oxidizer and supplies the preheated air to the fuel cell stack;
A steam generator for generating steam using exhaust gas generated from the catalytic oxidizer and providing the generated steam to the reformer;
An ejector positioned between the fuel supplier and the reformer, receiving the fuel from the fuel supplier and the steam from the steam generator using a pressure difference and providing the fuel to the reformer;
A fuel bypass for bypassing the fuel of the fuel supplier to the catalytic oxidizer; And
An air bypass for bypassing the air preheated in the air preheating unit to the catalytic oxidizer,
The air preheating unit
A latent heat recovery device for preheating the air supplied from the outside to exhaust gas of the catalytic oxidizer; And
An air preheater for re-preheating the air preheated in the latent heat recovery device using exhaust gas of the catalytic oxidizer and then supplying the air to the fuel cell stack,
The reformer, the air preheater, the steam generator, and the latent heat recoverer are heat-exchanged continuously by exhaust gas generated from the catalytic oxidizer. The method of claim 1,
The ejector is a thermal cascade system for a fuel cell that provides a venturi structure therein to move raw materials using a pressure difference. delete delete The method of claim 1,
The thermal cascade system for a fuel cell further comprising an unreacted gas loop for feeding back unreacted gas discharged from the fuel cell stack to the ejector. delete The method of claim 1,
The fuel cell stack
A plurality of battery stacks spaced apart from each other around the catalytic oxidizer;
A main manifold receiving the fuel gas from the reformer;
A plurality of sub-manifolds connecting between the main manifold and the plurality of battery stacks to supply the fuel gas in the main manifold to the plurality of battery stacks; And
A thermal cascade system for a fuel cell comprising a connection manifold connecting the plurality of sub-manifolds and the catalytic oxidizer. The method of claim 7,
The main manifold is
A thermal cascade system for a fuel cell provided in a ring shape and in which a plurality of the sub-manifolds are spaced apart from an upper surface along a circumferential direction. Supplying fuel to the fuel supplier;
Bypassing the fuel of the fuel supplier to the catalytic oxidizer;
Generating fuel gas in a reformer using fuel supplied from a fuel supplier;
Generating electromotive force in a fuel cell stack through an electrochemical reaction using fuel gas;
Feeding back the unreacted gas discharged from the fuel cell stack to the reformer;
Oxidizing the unreacted gas discharged from the fuel cell stack in a catalytic oxidizer;
Preheating air using exhaust gas generated from the catalytic oxidizer, and then bypassing the preheated air to the catalytic oxidizer;
Preheating air using exhaust gas generated from the catalytic oxidizer, and then supplying the preheated air to the fuel cell stack; And
After generating steam using the exhaust gas generated from the catalytic oxidizer, comprising the step of providing the generated steam to the reformer,
The exhaust gas generated from the catalytic oxidizer is a method of operating a thermal cascade system for a fuel cell in which the reformer, the air preheater, the steam generator, and the latent heat recovery unit according to claim 1 are continuously moved to exchange heat. delete delete delete

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