KR101093132B1 - Reformer using off gas, fuel cell system, and driving method thereof - Google Patents

Abstract

Fuel cell system according to the present invention, at least one electricity generating unit for generating electrical energy through the electrochemical reaction of hydrogen and oxygen to improve fuel utilization efficiency, and the hydrogen through a reforming reaction by a heat source A reformer for generating hydrogen gas from the fuel contained therein, a fuel supply source for supplying the fuel to the reformer, and an oxygen supply source for supplying the oxygen to the electricity generating unit, wherein the reformer includes a reforming catalyst and a flame therein. The reformed reaction unit and the combustion catalyst in which the space is generated are embedded, and the primary heating tube into which the unreacted fuel and air discharged from the stack are introduced, and the mixing tube in which the unreacted fuel and air heated in the primary heating tube are mixed. And a heating unit including a air mixed between the unreacted fuel heated between the reforming reaction unit and the heating unit. The injection hole through which is ejected is formed.

Fuel Cells, Stacks, Reformers, Unreacted Fuels

Description

Reformer using unreacted fuel discharged from fuel cell stack, fuel cell system employing same, and driving method of fuel cell system {REFORMER USING OFF GAS, FUEL CELL SYSTEM, AND DRIVING METHOD THEREOF}

The present invention relates to a fuel cell system, and more particularly, to a fuel cell system having an improved structure of a reformer using unreacted fuel.

As is known, a fuel cell is a power generation system that converts chemical reaction energy of hydrogen and oxygen contained in hydrocarbon-based materials such as methanol, ethanol, and natural gas directly into electrical energy.

This fuel cell is classified into a phosphoric acid fuel cell, a molten carbonate fuel cell, a solid oxide fuel cell, a polymer electrolyte type or an alkaline fuel cell according to the type of electrolyte used. Each of these fuel cells operates on essentially the same principle, but differs in the type of fuel used, operating temperature, catalyst, and electrolyte.

High-temperature fuel cells such as molten carbonate fuel cells (MCFCs) and solid oxide fuel cells (SOFCs) are fuel cells that operate at 600 ° C to 1000 ° C. It does not burn 100% and some fuel is discharged with the reactants. The unreacted fuel mixed with the reactants is a lean fuel with low concentration of hydrogen, so it is difficult to directly burn and use it as energy. As a method for increasing the energy utilization of the fuel, there is a method of adding fuel to a portion where an unreacted fuel is discharged and burning the fuel, and a method of increasing the utilization by installing a reactor using a catalyst. However, in the former case, there is a problem of significantly lowering the efficiency of the fuel cell, and in the latter case, since it is difficult to raise the temperature beyond the catalyst endurance temperature, there is a problem that utilization of thermal energy is very limited.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and an object thereof is to provide a fuel cell system having improved fuel use efficiency by using unreacted fuel.

The reformer of the fuel cell system according to the present invention for achieving the above object, the reforming reaction unit is a built-in reforming catalyst and the space is generated therein, and the combustion catalyst is embedded in the unreacted fuel discharged from the stack And a heating unit including a primary heating tube into which air is introduced and a mixing tube in which unreacted fuel heated in the primary heating tube and air are mixed, and an unreacted fuel heated between the reforming reaction unit and the heating unit. And injection holes through which air mixed with the air are ejected are formed.

The reforming reaction part includes a first wall forming a first space in which a reforming catalyst is embedded and a second wall formed in the first wall and communicating with the injection hole to form a second space in which a flame is formed. And the first wall and the second wall.

The second wall may have a heat transfer fin protruding toward the first wall, and the fuel supply pipe and the water supply pipe may be connected to the first wall. In addition, air is introduced into the outside of the mixing tube, and a heating body spaced apart from the outer surface of the mixing tube may be formed.

The lower portion of the mixing tube is open, the guide plate formed to be inclined with respect to the direction of the central axis of the primary heating tube in the space between the mixing tube and the primary heating tube,

The primary heating tube may be formed with a hole to discharge the unreacted fuel that did not react in the oxidation catalyst into the space between the primary heating tube and the mixing tube, the upper end of the primary heating tube Located below the injection hole may be formed of a conical projection.

The surface facing the protrusion in the mixing tube may be formed to be inclined parallel to the outer surface of the protrusion, the unreacted fuel introduced into the primary heating portion consumes only 10% to 30% in the combustion catalyst, the rest It may be introduced into the mixing tube.

According to an exemplary embodiment of the present invention, a fuel cell system includes at least one electricity generating unit generating electrical energy through an electrochemical reaction between hydrogen and oxygen, and hydrogen from a fuel containing hydrogen through a reforming reaction by a heat source. A reformer for generating a gas, a fuel supply source for supplying the fuel to the reformer, and an oxygen supply source for supplying the oxygen to the electricity generating unit, wherein the reformer includes a reforming catalyst and a space in which a flame is generated. The formed reforming reaction unit and the combustion catalyst are built-in, including a primary heating tube into which unreacted fuel and air discharged from the stack are introduced, and a mixing tube in which unreacted fuel and air heated in the primary heating tube are mixed. And an injection hole in which air mixed with the heated unreacted fuel is ejected between the reforming reaction part and the heating part. do.

The reforming reaction part includes a first wall that forms a first space in which a reforming catalyst is embedded and a second wall that is positioned inside the first wall and communicates with the injection hole to form a second space in which a flame is formed. The second wall may have a heat transfer fin protruding toward the first wall.

Air is introduced into the outside of the mixing tube, a heating body spaced apart from the outer surface of the mixing tube may be formed, the lower portion of the mixing tube is opened, the space between the mixing tube and the primary heating tube A guide plate inclined with respect to the direction of the central axis of the primary heating tube may be installed.

An upper end of the primary heating tube may be formed under the injection hole and a protrusion having a cone shape.

In a method of driving a fuel cell system according to an embodiment of the present invention, an unreacted fuel and an unreacted fuel are supplied to a primary heating tube having a combustion catalyst to supply an unreacted amount of air that is insufficient to completely burn the unreacted fuel. And mixing the unreacted fuel and air heated in the primary heating tube, mixing the heated unreacted fuel and injecting the reformed reaction unit with the reforming catalyst therein, and the fuel and water vapor. Reacting with the reforming catalyst to produce a reformed gas.

In the heating of the unreacted fuel, the unreacted fuel supplied to the primary heating tube may be consumed by reacting 10% to 30% of the supplied amount with the combustion catalyst.

According to the fuel cell system according to the present invention, it is possible to stably supply heat to a reformer by using a low-function, high-heating unreacted fuel by first catalytically heating unreacted fuel and then mixing the heated fuel with air to combust it. As such, the fuel utilization efficiency is improved by supplying heat to the reformer using unreacted fuel.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

1 is a schematic configuration diagram showing an overall configuration of a fuel cell system according to an embodiment of the present invention, Figure 2 is an exploded perspective view showing a stack of a fuel cell system according to an embodiment of the present invention.

Referring to this drawing, the fuel cell system 100 according to the present invention will be described. The fuel cell system 100 reforms a fuel containing hydrogen to generate reformed gas, and generates the reformed gas and air gas. It reacts chemically to generate electrical energy.

 In the fuel cell system 100, the fuel for generating electricity generally refers to a fuel made in a liquid or gaseous state such as methanol, ethanol, or natural gas.

In addition, the fuel cell system 100 may use oxygen gas stored in a separate storage means as air gas reacting with hydrogen gas, and may use air containing oxygen. However, the latter example is explained below.

The fuel cell system 100 according to the present invention basically generates an electric energy by generating an electric energy through an electrochemical reaction between hydrogen and oxygen, and the mixed fuel as described above to generate hydrogen gas. A reformer 20 for supplying the hydrogen gas to the electricity generation unit 11, a fuel supply source 50 for supplying the mixed fuel to the reformer 20, and oxygen to the electricity generation unit 11. And an oxygen source 70.

The electricity generating unit 11 has a separator (meaning 'bipolar plate' in the art) 16 on both sides thereof with the membrane-electrode assembly (MEA) 12 at the center thereof. Construct a fuel cell in the minimum unit that generates electricity. In the present embodiment, a plurality of electricity generating units 11 having the smallest unit as described above are provided, and as shown in FIG. 2, the stack 10, which is an aggregate structure of these electricity generating units 11, is formed.

In the stack 10, the membrane-electrode assembly 12 constituting the electricity generating unit 11 includes an anode electrode and a cathode electrode on both sides of the electrolyte membrane in the center thereof to oxidize / reduce hydrogen and oxygen. Is made of the structure of MEA. In addition to supplying hydrogen gas and oxygen-containing air to both sides of the membrane-electrode assembly 12, the separator 16 functions as a conductor that connects the anode electrode and the cathode electrode in series.

And the outermost of the stack 10 may be provided with a separate pressing plate 13 for close contact with the plurality of electricity generating unit 11 described above. However, the stack 10 according to the present invention may be configured such that the separator 16 positioned at the outermost portion of the electricity generating unit 11 may be substituted for the pressure plate 13 without the pressure plate 13 described above. . In addition to the function of bringing the pressure plates 13 into close contact with the plurality of electricity generating units 11, the pressure plate 13 may be configured to have a unique function of the separator 16 described later.

In addition, the pressurizing plate 13 supplies a first injection unit 13a for supplying the reformed gas generated from the reformer 20 to the electricity generation unit 11, and supplying air to the electricity generation unit 11. The second injection unit 13b for discharging, the first discharge unit 13c for discharging the unreacted fuel remaining after reacting in the electricity generating unit 11, and the reaction remaining with hydrogen in the electricity generating unit 11. A second discharge portion 13d for discharging air is formed.

Meanwhile, the reformer 20 applied to the fuel cell system 100 is configured to generate hydrogen gas from fuel through a chemical catalytic reaction by thermal energy. The structure of this reformer 20 will be further described later.

The fuel source 50 for supplying fuel to the reformer 20 as described above includes a tank for storing fuel as described above, and the oxygen source 70 sucks air with a predetermined pumping force to stack the air. And an air pump for supplying to (10). Oxygen is defined herein as a broad concept that includes pure oxygen and air containing oxygen.

The fuel supply source 50 and the reformer 20 are connected through the fuel supply pipe 91, and the oxygen supply 70 supplies air to the reformer through the first reformed air supply pipe 93 and the second reformed air supply pipe 94. Supply and supply air to the stack through the stack air supply pipe (95). Meanwhile, a recovery pipe 97 for delivering unreacted fuel to the reformer 20 is connected to the first discharge part 13c, and the reformed gas generated in the reformer 20 is stacked on the first inlet part 13a. The reformed gas supply pipe 96 which delivers to 10 is provided.

In addition, the fuel cell system 100 further includes a water supply source 60, and the water supply source 60 transmits water vapor to the reformer 20 through the water supply pipe 92.

3 is a cutaway perspective view showing a reformer according to an embodiment of the present invention, Figure 4 is a longitudinal cross-sectional view showing a reformer according to an embodiment of the present invention and Figure 5 is a reformer according to an embodiment of the present invention Figure is a cross-sectional view.

Referring to FIGS. 3 to 5, the reformer 20 according to the present embodiment is reformed from fuel through steam reforming (SR) catalytic reaction by a heat source (hereinafter also referred to as 'heat energy'). The reforming reaction part 22 which produces | generates a gas, and the heating part 24 which ignites and combusts unreacted fuel and produces | generates the said heat source are comprised.

The reforming reaction part 22 is formed in the form of a double cylindrical pipe forming the first space A and the second space B, which are independent of each other, and the first wall 21 and the first reforming catalyst 21a are provided. The second wall 23 is disposed inside the first wall 21 and the flame 29 is sprayed thereon. The first wall 21 is in the form of a circular pipe having a predetermined cross-sectional area and substantially closed at both ends. In this case, the first wall 21 may be formed of a conventional metal or non-metal insulating material having heat insulating properties.

The second wall 23 is in the form of a circular pipe having a cross-sectional area that is relatively smaller than that of the first wall 21. At this time, the outer peripheral surface of the second wall 23 and the inner peripheral surface of the first wall 21 are disposed in the direction of the inner center of the first wall 21 so as to be spaced apart by a predetermined interval.

With this structure, the reforming reaction part 22 according to the present embodiment forms the first space A between the first wall 21 and the second wall 23, and the second wall 23 is formed inside the second wall 23. The space B can be formed.

Therefore, a reforming gas rich in hydrogen is filled in the first space A between the first wall 21 and the second wall 23 by filling the reforming catalyst 21a with the reforming reaction of the fuel by the reforming catalyst 21a. In addition, the flame 29 may be formed in the second space B inside the second wall 23 to transfer heat energy to the reforming catalyst 21a.

In addition, a plurality of plate-shaped heat transfer fins 23a protruding toward the first wall 21 are formed in the second wall 23. The heat transfer fin 23a serves to efficiently transfer heat generated in the second space B to the reforming catalyst 21a.

The fuel supply pipe 91 to which fuel is supplied and the water supply pipe 92 into which steam is introduced are connected to the first wall 21 of the reforming reaction unit 22, and the steam and fuel introduced into the reforming reaction unit 22 are connected to each other. Is converted into hydrogen-rich reformed gas through the reforming catalyst 21a heated by the heat energy transferred from the heating section. The generated reformed gas is delivered to the stack 10 through the reformed gas supply pipe 96, and the combustion gas generated by the flame 29 is discharged to the outside through the exhaust pipe 98.

On the other hand, the heating unit 24 is disposed below the reforming reaction unit 22, the first reformed air supply pipe 93 is installed in the interior of the heating body 25 and the heating body 25 is installed connected to the inside The primary heating tube 28 provided with the combustion catalyst 28c, and the mixing tube 27 provided between the heating body 25 and the primary heating tube 28 are included. In the present description, the combustion catalyst 28c refers to a catalyst for oxidizing fuel.

The mixing tube 27 is spaced apart from the inner surface of the heating body 25 to form a space 25a, and the primary heating tube 28 is spaced apart from the inner surface of the mixing tube 27 to form a space 27a. As a result, the heating body 25, the mixing tube 27, the primary heating tube 28 has a triple cylindrical tube structure. At this time, the mixing tube 27 has a structure in which the lower end is opened, whereby the inner space 27a of the mixing tube 27 communicates with the space 25a formed by the heating body 25.

Under the primary heating tube 28, a recovery tube 97 for transferring unreacted fuel discharged from the stack 10 to the primary heating tube 28 is connected, and air is supplied to the primary heating tube 28. The second reformed air supply pipe 94 for supplying with is connected. In addition, a combustion catalyst 28c is installed inside the primary heating tube 28 to generate heat using unreacted fuel and air. In addition, a plurality of unreacted fuels oxidized by the combustion catalyst 28c and transferred to the space 27a between the primary heating tube 28 and the mixing tube 27 are disposed above the primary heating tube 28. The hole 28a is formed.

As a result, the unreacted fuel may be heated by the combustion catalyst 28c and moved to the mixing pipe 27. At this time, the amount of air delivered to the primary heating tube 28 through the second reformed air supply pipe 94 is supplied with a lean amount less than the amount that the unreacted fuel can be completely burned. Accordingly, the unreacted fuel supplied under the excess fuel reacts with only 10% to 30% of the fuel so that the heated unreacted fuel moves into the space 27a between the mixing tube 27 and the primary heating tube 28. .

On the other hand, the air introduced into the heating body 25 is introduced into the space (27a) between the mixing tube 27 and the primary heating tube 28 through the lower portion of the mixing tube 27, this primary heating In the space 27a between the tube 28 and the mixing tube 27, unreacted fuel and air are mixed and heated. An injection hole 26 is formed in the plate between the reforming reaction part 22 and the heating part 24. The unreacted fuel mixed with air is injected into the first space A through the injection hole 26. To form a flame (29). In this case, a spark plug or the like may be installed in the injection hole 29 to form a flame.

The primary heating tube 28 has a convex protrusion 28b formed at the top thereof so that the heated unreacted fuel can be easily transferred to the first space A through the injection hole 26. The spigot of 28b) is located below the injection hole 26. At the upper end of the mixing tube 27 is formed between the primary heating tube 28 and the mixing tube 27 formed of an inclined surface with a gradually decreasing internal cross-sectional area so that the surface facing the protrusion 28b is parallel to the protrusion 28b. Gas can be easily delivered to the injection hole (26). An igniter (not shown) may be installed in the injection hole 26.

On the other hand, the outer surface of the primary heating tube 28 is provided with a guide plate 28d for generating a swirl so that the air flowing into the mixing tube 27 can be easily mixed with the unreacted fuel. The guide plate 28d is formed to be inclined with respect to the direction of the central axis of the primary heating tube 28 so that the introduced air is obliquely introduced into the wall surface of the primary heating tube 28. Sloped air enters turbulence and mixes better with unreacted fuel.

After the lean unreacted fuel is heated to a high temperature by lean combustion by a combustion catalyst, a large amount of oxygen-rich air can be supplied to transfer a sufficient amount of heat to the reforming reaction unit.

Referring to the driving method of the fuel cell system 100 according to the present embodiment, first, an unreacted fuel and an unreacted amount of air that is insufficient to completely burn the primary heating tube having the combustion catalyst 28c ( 28) heating the unreacted fuel by supplying it to the mixture, mixing unreacted fuel and air heated in the primary heating tube 28, and combusting air mixed with the heated unreacted fuel to reform the catalyst 21a. Spraying the inside of the reforming reaction unit 22 having a built-in, and reacting fuel and water vapor with the reforming catalyst 21a to produce reformed gas.

In the step of heating the unreacted fuel, 10% to 30% of the unreacted fuel is consumed by reacting with the combustion catalyst 28c.

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.

1 is a schematic diagram illustrating an overall configuration of a fuel cell system according to an exemplary embodiment of the present invention.

2 is an exploded perspective view illustrating a stack of a fuel cell system according to an exemplary embodiment of the present invention.

3 is a cutaway perspective view showing a reformer according to an embodiment of the present invention.

4 is a longitudinal sectional view showing a reformer according to an embodiment of the present invention.

5 is a cross-sectional view showing a reformer according to an embodiment of the present invention.

<Description of reference numerals for main parts of the drawings>

100: fuel cell system 10: stack

11: electricity generator 12: membrane-electrode assembly

16: Separator 20: Reformer

21: first wall 21a: reforming catalyst

22: reforming reaction portion 23: the second wall

23a: heat transfer fin 24: heating part

25: heating body 26: injection hole

27: mixing tube 28: primary heating tube

28c: combustion catalyst 28d: guide plate

50: fuel source 60: water source

70: oxygen source

Claims (17)

A reforming reaction unit in which a reforming catalyst is embedded and a space in which a flame is generated is formed; And A heating unit having a combustion catalyst embedded therein and including a primary heating tube into which unreacted fuel and air discharged from the stack are introduced, and a mixing tube mixed with unreacted fuel and air heated in the primary heating tube; Including An injection hole is formed between the reforming reaction part and the heating part to eject air mixed with the heated unreacted fuel, The reforming reaction part includes a first wall forming a first space in which a reforming catalyst is embedded and a second wall formed in the first wall and communicating with the injection hole to form a second space in which a flame is formed. And the first wall and the second wall. delete The method of claim 1, A reformer of the fuel cell system in which the second wall has heat transfer fins protruding toward the first wall. The method of claim 1, The reformer of the fuel cell system, the fuel supply pipe and the water supply pipe is connected to the first wall. A reforming reaction unit in which a reforming catalyst is embedded and a space in which a flame is generated is formed; And A heating unit having a combustion catalyst embedded therein and including a primary heating tube into which unreacted fuel and air discharged from the stack are introduced, and a mixing tube in which unreacted fuel and air heated in the primary heating tube are mixed; Including An injection hole is formed between the reforming reaction part and the heating part to eject air mixed with the heated unreacted fuel, Reformer of the fuel cell system in which air is introduced into the outside of the mixing tube, the heating body spaced apart from the outer surface of the mixing tube and in communication with the mixing tube. The method of claim 1, And a guide plate inclined with respect to the direction of the central axis of the primary heating tube in a space between the mixing tube and the primary heating tube. The method of claim 1, And a hole formed in the primary heating tube so that unreacted fuel not reacted with the oxidation catalyst is discharged into the space between the primary heating tube and the mixing tube. The method of claim 1, A reformer of a fuel cell system having a protrusion formed in a conical shape on the upper end of the primary heating tube is located below the injection hole. The method of claim 1, The reformer of the fuel cell system formed in the mixing tube is inclined so as to be parallel to the outer surface of the protrusion. A stack including at least one electricity generating unit generating electrical energy through an electrochemical reaction of hydrogen and oxygen; A reformer for generating hydrogen gas from the hydrogen-containing fuel through a reforming reaction by a heat source; A fuel supply source for supplying the fuel to the reformer; And An oxygen supply source for supplying the oxygen to the electricity generating unit Including; The reformer, A reforming reaction unit having a reforming catalyst therein and having a space for generating a flame therein and a combustion catalyst therein, a primary heating tube into which unreacted fuel and air discharged from the stack are introduced, and an unheated primary heating tube. And a heating unit including a mixing tube in which a reaction fuel and air are mixed, and an injection hole is formed between the reforming reaction unit and the heating unit to eject air mixed with the heated unreacted fuel. 11. The method of claim 10, The reforming reaction part includes a first wall that forms a first space in which a reforming catalyst is embedded and a second wall that is positioned inside the first wall and communicates with the injection hole to form a second space in which a flame is formed. Fuel cell system. The method of claim 11, And a heat transfer fin protruding toward the first wall. 11. The method of claim 10, Air is introduced into the outside of the mixing tube, the fuel cell system formed with a heating body spaced apart from the outer surface of the mixing tube. 11. The method of claim 10, The lower portion of the mixing tube is opened, the fuel cell system is installed in the space between the mixing tube and the primary heating tube inclined with respect to the direction of the central axis of the primary heating tube. 11. The method of claim 10, A fuel cell system having a protrusion formed in a conical shape on the upper end of the primary heating tube is located below the injection hole. Heating the unreacted fuel by supplying an unreacted fuel and a lean amount of air insufficient to completely burn the unreacted fuel to a primary heating tube in which a combustion catalyst is embedded; Mixing unreacted fuel and air heated in the primary heating tube; Mixing with the heated unreacted fuel and injecting the reforming reaction unit into the reforming reaction unit; And Reacting fuel and water vapor with the reforming catalyst to produce reformed gas; Including, The reforming reaction unit includes a first wall forming a first space in which the reforming catalyst is embedded and a second wall formed in the first wall to communicate with the injection hole to form a second space in which a flame is formed. Including, The injecting of the fuel cell system may include injecting heated unreacted fuel and air into the second space and injecting the fuel into the first space. The method of claim 16, And the unreacted fuel supplied to the primary heating tube in the step of heating the unreacted fuel is consumed by reacting 10% to 30% of the supplied amount with a combustion catalyst.

Images