KR100774574B1 - Solid oxide fuel cell power generation system for apu and startup method thereof - Google Patents

Abstract

A solid oxide fuel cell generation system for an auxiliary power unit of vehicles, and a method for operating the solid oxide fuel cell generation system for an auxiliary power unit are provided to allow a fuel cell generation system to be operated effectively by providing standard operation method. A solid oxide fuel cell generation system comprises a fuel supply part(80); an air supply part(90); a fuel cell stack(20) which is provided with a fuel electrode and an air electrode to generate electricity by the chemical reaction of air and fuel; a reformer(30) which reforms the fuel of the fuel supply part to supply it to the stack; a rear burner(40) which mixes the gas after the reaction from the fuel electrode of the stack and the air from an air electrode and burns the mixture; a composite heat exchanger(50) which preheats the air supplied from the air supply part and receives the heat of the discharged gas; and a plurality of valves(60,61) and pipes which determines the supply direction of the air or reformed gas in a preheating process or the direction of the gas after the reaction from the stack.

Description

Solid Oxide Fuel Cell Power Generation System for APU and Startup method

1 is a conceptual diagram of power generation of a solid oxide fuel cell system.

2 is a schematic diagram of a solid oxide fuel cell power generation system for an auxiliary power unit according to an embodiment of the present invention;

3 is a schematic diagram of a high temperature chamber in a solid oxide fuel cell power generation system for an auxiliary power unit according to an embodiment of the present invention;

3A is a schematic diagram of a high temperature chamber of a solid oxide fuel cell power generation system for an auxiliary power unit according to an embodiment of the present invention separated from the system;

3B is a cross-sectional cutaway view of a reformer in a solid oxide fuel cell power generation system for an auxiliary power unit, according to an embodiment of the invention.

3C is a cross-sectional cutaway view of a post combustor in a solid oxide fuel cell power generation system for an auxiliary power unit according to one embodiment of the invention.

4 is a state diagram of a one-step start operation mode in a method of operating a solid oxide fuel cell power generation system for an auxiliary power unit according to an embodiment of the present invention.

FIG. 5 is a state diagram of a startup operation mode in two and three stages in a method of operating a solid oxide fuel cell power generation system for an auxiliary power unit according to an embodiment of the present invention. FIG.

6 is a state diagram of a four-step start operation mode in a method of operating a solid oxide fuel cell power generation system for an auxiliary power unit according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

10: high temperature room 20: fuel cell stack

21: fuel electrode 22: air electrode

30: reformer 31: nozzle unit

32: partial oxidation reactor 33: reformer catalyst

34 heat exchanger 35 reformer inlet

36: reformer outlet 40: after combustor

41: after-burner catalyst 42: after-burner inlet

43: after combustor outlet 44: three-dimensional mixing zone

45: after combustor heat exchanger 50: composite heat exchanger

60: valve 61: switching valve

62: splitter 70: room temperature room

80: fuel supply unit 90: air supply unit

The present invention relates to a solid oxide fuel cell power generation system for an auxiliary power unit and a method of starting the same.

Depending on the type of electrolyte used, the type of fuel cell includes phosphate (PAFC, Phosphoric Acid Fuel Cell), molten carbonate (MCFC, Molten Carbonate Fuel Cell), solid oxide type (SOFC, Solid Oxide Fuel Cell), and solid polymer type. (PEMFC, Proton Exchange Membrane Fuel Cell)

1 is a conceptual diagram of power generation of a solid oxide fuel cell system among the fuel cells.

As shown in the figure, a solid oxide fuel cell converts chemical energy of hydrogen and oxygen directly into electrical energy by an electrochemical reaction, and is a high efficiency, pollution-free power generation apparatus. The anode 21 is supplied with hydrogen to generate electricity by electrochemical reaction by reverse electrolysis of water.

The operation principle of the solid oxide fuel cell is to produce water by the oxygen ion generated by the reduction reaction of oxygen in the cathode moves to the anode through the electrolyte and reacts with hydrogen supplied to the anode again. In the air electrode, electrons are consumed, so when two electrodes are connected to each other, electricity flows.

Meanwhile, various methods have been proposed to commercialize the solid oxide fuel cell, and a method of using the same as a power source of a vehicle has been proposed. In order to be used as the main power source of a vehicle, a maximum output of about 50 kW is required, and the fuel cell system of this capacity is limited in weight or volume in order to be mounted in the engine room of the vehicle, and even considering the maximum power reported by the SOFC, It is true that there is a difficulty in commercialization since there must be a stacked stack.

In recent years, however, studies have been actively conducted to utilize an Auxiliary Power Unit (APU) before the solid oxide fuel cell is used as a main power source for automobiles. The fuel cell stack itself operates at very different temperatures, and instead of a solid polymer fuel cell (SOFC), which has the problem that it is necessary to maintain a thermal steady state at each stage for a complex multi-stage reforming system. There is a growing interest in systems using APU for APU.

In particular, the SOFC power generation system for APU enables independent operation of the transportation engine, and can be widely used in the transportation and non-transportation fields because it provides high efficiency power at the engine start and stop.

The advantages of SOFC's power generation system for APU are that it uses less reformed fuel and emits less pollutants, and it is easy to maneuver, power efficient, and various hydrocarbon fuels (gasoline, natural gas, diesel) because it requires cooling fast start and temporary operation. ) Is available. In addition, it has a relatively good durability against impurities such as sulfur, compared to other general fuel cells, does not require precious metal catalysts, uses dry electrolytes, and relatively simple unit operation for ceramic electrolytes, automotive engines and electrical systems. That is, it is possible to drive independently.

SOFC, the core technology of SOFC power generation system for APU, does not need complicated external reforming system compared to other fuel cells, does not use precious metal electrode catalyst such as platinum, and does not cause corrosion problems due to liquid electrolyte. It can minimize various operational problems that occur in the type fuel cell, and the electricity generation temperature is higher than 500 ℃, and it is possible to maintain the operating temperature through proper insulation, use various fuels, and have a wide operating temperature range. Also have.

However, while having these various advantages, most of the components are composed of ceramics and high-temperature metal materials, and because they are new electrochemical power generation technology operating at high temperatures, components of electrodes, electrolytes, connecting materials, etc. There are several technical problems involved.

In particular, the solid oxide fuel cell also has disadvantages such as phosphoric acid type, a low temperature fuel cell using an aqueous solution as an electrolyte, corrosion problems present in molten carbonate, expensive catalysts, electrolyte control, and reformer introduction.

As a result, reactions between materials due to the characteristics of solid oxide fuel cells, which are composed mostly of ceramics and operate at high temperatures of 700-1000 ° C, new materials development, electrode characteristics, stack manufacturing, heat-resistant components development and operation Research is being done on trial evaluation.

It is an object of the present invention to provide a power generation system using a solid oxide fuel cell for an auxiliary power source with improved initial starting capability.

In addition, it is an object to build a system that can be cold start independently without a heat source supplied from the outside.

And to provide a sequential power generation step through the reformer preheating, fuel cell stack preheating to start the solid oxide fuel cell power generation system.

The present invention relates to an operation method by a four-step operation mode that is sequentially performed at startup and to a power generation system for implementing the SOFC power generation system for APU having good instantaneous maneuverability.

The present invention provides a solid oxide fuel cell power generation system for an auxiliary power supply unit.

A fuel cell stack including a fuel supply unit for supplying a gas for fuel, an air supply unit for supplying air, a fuel electrode for supplying a reformed gas, and an air supply electrode for supplying air, and generate electricity by chemical reaction between air and fuel, wherein A reformer for reforming the fuel used in the anode of the fuel cell stack by receiving fuel from a fuel supply unit, a post combustor for mixing and combusting the gas after the reaction from the anode of the fuel cell stack with the air from the cathode, the air supply unit The complex heat exchanger that performs heat exchange in the system, such as preheating the air supplied from the air and receiving the heat of the exhaust gas discharged from the system, supplying air in the reformer preheating stage, and supplying the reformed gas from the reformer outlet. Determine the direction of the gas after reaction or from the stack It relates to auxiliary power units for a solid oxide fuel cell power system which comprises a plurality of valves and piping to give crystals.

The reformer includes a nozzle unit serving as an inlet including a preheated air passage, a fuel supply passage, and a gas passage after the reaction of the anode, a partial oxidation reactor including a catalyst, a self-heat exchanger, and a reformed gas as the anode of the fuel cell stack. It can be configured to include an outlet that can be reached, wherein the nozzle portion has the form of a triple tube, the innermost is supplied with preheated air, the fuel is supplied in the form of an annular liquid membrane around the air flow rate of the fuel It breaks the annular liquid film formed at the nozzle outlet at a faster flow rate and breaks it into small droplets. After the reaction, most of the gas generated from the anode flows into the after burner, but a part (about one third) is the outermost. It is configured to be fed back to the partial oxidation reactor through the gas passage after the circumferential reaction.

In addition, the post combustor is a three-dimensional mixing zone and a catalyst-coated ceramic honeycomb inside to mix well to prevent the combustion of post-reacted gas and unreacted fuel and air from the cathode before reaching the catalyst. It is configured to include an outlet for outflow of gas after overcombustion to a complex exchanger.

In the solid oxide fuel cell power generation system for an auxiliary power supply unit according to the present invention,

A reformer preheating step (first step) of preheating the reformer with hot air; Reformer operation step (second step) through reformer fuel supply; A fuel cell stack preheating step (3rd step) using afterburner operation and preheated air through a reformed gas supply to the afterburner; And a fourth step of supplying the reformed gas to the fuel cell stack via the switching valve and supplying the preheated air to the fuel cell stack. It relates to a starting method comprising a.

Here, the reformer preheating step (first step) is a step of preheating the after-burner by the hot air preheating the reformer is discharged through the after-combustor through the switching valve and the composite heat exchanger; The reformer operation step (second step) through the reformer fuel supply may further include a step of moving the reformed gas to a combustor after passing the reformed gas through a complex heat exchanger (34); It is also possible to include more.

In the fuel cell stack preheating step (third step), the air supplied from the air supply unit is transferred to the fuel cell stack through the heat exchanger and the valve, and thus the starting method may be preheated.

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

2 is a schematic view of a solid oxide fuel cell power generation system for an auxiliary power unit according to an embodiment of the present invention.

As shown in the figure, the reformed gas is supplied to the fuel electrode of the fuel cell stack 20 and air is supplied to the cathode, and the reformed gas passes through the reformer 30 and enters the stack 20.

However, in order for the fuel to be reformed, the reformer 30 must be above an appropriate temperature, so for this purpose, the reformer 30 must first be preheated as hot air, and the air is preheated through the electric heating preheater and then passed through the reformer 30. By doing so, it becomes possible.

Since the reformed gas and the preheated air are introduced into the fuel cell stack 20 through the reformer 30, power generation is possible, and the principle thereof is as described above. The post-reaction gas from the fuel electrode of the fuel cell stack 20 includes fuels that do not participate in the reaction, and gas and water vapor components after the reaction of the fuel cell. Most of these are introduced into the post-combustor to participate in the combustion reaction. Degree) can be sent back to the reformer inlet 35 to participate in the reforming reaction and then sent back to the stack 20 can be expected to improve the efficiency through the reforming catalyst protection and the conversion rate of the fuel cell.

In addition, the remaining part of the mixture is mixed with the gas after the cathode combustion, is burned in the post-combustor 40, and then the heat is recovered and then sent out.

The switching of the fuel and air supply direction is possible by the valve 60, which can be sent in one or two directions by the switching valve 61 and the splitter 62.

3 and 3A are schematic diagrams before and after separation in a high temperature chamber system in a solid oxide fuel cell power generation system for an auxiliary power unit according to an embodiment of the present invention, and FIGS. 3B and 3C are reformers and post-combustors. The cross-sectional incision of each is shown.

As shown in the figure, the fuel cell stack 20, the reformer 30, the after bunner 40 and the heat exchanger 50 are connected to the hot box 10 of the system. The fuel pump, the air compressor, the battery, the controller, and the like may be disposed in the room temperature chamber (cool box) 70 in close contact with the high temperature chamber 10.

The fuel cell stack 20 mounted in the high temperature chamber 10 is a stack of solid oxide fuel cells, in which air flows to the cathode 22 of each fuel cell, and a reformed gas flows to the anode 21. Can be generated.

The reformer 30 shown in FIG. 3B is specifically composed of a nozzle part 31, a partial oxidation reactor 32, and three parts of a heat exchanger 34 for supplying and injecting fuel and air. In particular, the nozzle unit 31 is configured in such a way as to be able to mix well with the gas after the reaction discharged from the fuel cell stack 20 while spraying fuel using the air preheated in the heat exchanger. That is, the overall shape of the nozzle part 31 has the form of a triple tube, and the preheated air is supplied from the innermost side, and the fuel is supplied in the form of the annular liquid film from the periphery thereof. And the passage of the gas after the reaction discharged from the anode 21 is in the form of being supplied directly to the partial oxidation reactor 32 as the last circumference. The partial oxidation reactor 32 is a structure for reforming fuel using the catalyst 33 and refers to a position located inside the reformer 30 in the drawing. The reformed gas may be supplied to the stack 20 in a warmed state while passing through the heat exchanger 50 of the reformer 30 itself.

For example, in the fuel cell system for an auxiliary power unit according to the present invention, assuming that the conversion rate of 1 kW diesel is 99% and the hydrogen selectivity is 85%, the amount of C ₁₆ H ₃₄ required is 0.914 liter / hr. The amount of air required is 2662 liters / hr. The flow rate of air at the nozzle is designed to be much faster than the flow rate of the fuel, which causes the rapid difference in velocity to break up the annular liquid film of the fuel formed at the nozzle exit and break it into small droplets.

The post-combustor 40 shown in FIG. 3c is for mixing and burning the post-reaction gas and unreacted fuel from the anode 21 of the fuel cell with the post-reaction gas from the cathode 22. (42) An independent three-dimensional mixing zone 44 is provided immediately below, and after the reaction from the cathode 22 / fuel electrode 21 in the three-dimensional mixing zone 44, the gas and unreacted fuel and air from the cathode are It is a three-dimensional spraying / mixing structure for mixing well to prevent some burning phenomenon before reaching the catalyst. After the reaction from the fuel electrode 21, the gas and the reaction after the reaction from the air electrode 22 are orthogonal to each other, and a strong mixing flow occurs in three dimensions, so that the mixing is very good. And it is possible to use a ceramic honeycomb coated with Pt-Pd catalyst 41 for the oxidation reaction, provided with a partial oxidation reactor. Gas combusted in the partial oxidation reactor is discharged through the combustor heat exchanger (50) through the combustor outlet (43). The heat exchanger 50 is used to preheat the air supplied to the cathode 22 of the fuel cell stack.

The composite heat exchanger 50 disposed in the high temperature chamber of FIGS. 3 and 3A preheats the air supplied from the air supply unit 90 and receives the heat of the exhaust gas discharged to perform overall heat exchange in the system. It plays a role. That is, after receiving heat from the air preheated by the first preheater, it becomes possible to operate a system that does not require the reformer preheating by the preheated air.

The valve 60 is a switching valve 61 and air from the composite heat exchanger 50 and the stack 20 and post-reaction gas which can smoothly switch the supply of the reformed gas and air coming from the reformer outlet 36. It is composed of a splitter 62 that can send the direction of in one or both directions. In addition, a pipe that is a supply passage of air and fuel is provided.

The fuel cell stack 20, the reformer 30, the after burner 40, and the composite heat exchanger 50 provided in the high temperature chamber 10 are illustrated in FIG. As shown in 3a, it is possible to pursue convenience in the configuration of the device by configuring in one piece.

Hereinafter, the starting method in the solid oxide fuel cell power generation system for the auxiliary power supply unit will be described in detail.

FIG. 4 is a state diagram showing a one-step start operation mode in a method of operating a solid oxide fuel cell power generation system for an auxiliary power unit according to an embodiment of the present invention.

As shown in the figure, the air introduced through the air compressor is warmed by a preheater and then passed through the composite heat exchanger 50 to preheat the reformer 30. As the preheater, a heater inside the reformer 30 and a preheater outside the reformer 30 are used. As a heater inside the reformer 30, an electric heater may be used as an EHC (Electric Heating Catalyst), a preheater outside the reformer 30, and other well-known heaters or heat sources may be used as a heater.

Only portions indicated by solid lines in the drawing indicate an activated state and portions indicated by dotted lines indicate inactive states.

In the first stage start-up operation mode, fuel is not supplied, and the air supplied through the air supply unit 90 is preheated in the preheater, and then supplied to the composite heat exchanger 50, and the air passed through the composite heat exchanger 50. Is introduced into the reformer 30 to preheat the reformer 30, and then again passes through the composite heat exchanger 50 and then passes through the combustor 40, and then again passes through the composite heat exchanger 50 to the outside. Discharged.

After the preheated air passes through the reformer 30, the position of the switching valve 61 may be adjusted to go in the direction of the composite heat exchanger 50.

FIG. 5 shows a state diagram of a start operation mode in two and three stages in the method of operating a solid oxide fuel cell power generation system for an auxiliary power unit according to an embodiment of the present invention.

As shown in the figure, the fuel supply is added in the two-stage start-up operation mode, but the reformed gas is not supplied to the stack 20 to operate normally. In the two-stage mode, fuel is supplied to introduce fuel into the reformer 30 to operate the reformer 30. The reformed gas is fed to the combustor 40 via the composite heat exchanger 50. The air supplied from the air supply unit 90 branches into two lines so that a part of the air is introduced into the reformer 30 through the composite heat exchanger 50 to maintain the reformer 30 temperature.

In the three-stage start-up operation mode, a part of the branched air passing through the composite heat exchanger 50 is sent to the stack 20 for preheating, and the reformed gas from the reformer outlet 36 is sent to the post combustor 40 and then The combustor 40 is operated. To this end, the switching valve 61 located at the reformer outlet 36 adjusts to send the reformed gas in the direction of the composite heat exchanger 50 rather than in the stack 20 direction.

 That is, in the two-stage and three-stage start-up operation mode, the reformer 30 is operated by supplying fuel to the reformer 30 (step 2), and the after-burner 40 is operated (step 3). It is not necessary to operate the preheater, etc. In addition, the time difference of 2-3 steps is about 2 minutes.

FIG. 6 is a state diagram showing a four-step start operation mode in a method of operating a solid oxide fuel cell power generation system for an auxiliary power unit according to an embodiment of the present invention.

The four-stage operation mode is a mode in which the internal temperature of the fuel cell stack 20 is preheated to about 650 to 700 degrees, and the SOFC power generation system for the APU of the present invention is normally operated.

As shown in the figure, the four-stage operation mode is the fuel cell stack 20 through the switching valve 61 to the reformed gas supplied to the combustor 40 after the complex heat exchanger 50 in the second and third stages ). In the fuel cell, the generated reformed fuel and air react with each other to generate power, and some of the generated water vapor and the reacted gas are branched back to the reformer 30, and the branched gas is reacted with the post combustor 40. After being introduced and burned, it is discharged to the exhaust unit through the composite heat exchanger (50).

As a result, the reformed gas is supplied to the fuel cell so that the reformer 30 operates normally to generate power.

What has been described above is only an embodiment of a solid oxide fuel cell power generation system for an auxiliary power unit and a method of starting the same according to the present invention, and the present invention is not limited to the above-described embodiment, and is claimed in the following claims. As described above, any person having ordinary knowledge in the field of the present invention without departing from the gist of the present invention will have the technical idea of the present invention to the extent that various modifications can be made.

According to the present invention it is possible to provide a solid oxide fuel cell that can be used for the auxiliary power source of the vehicle it is possible to provide a system capable of cold starting.

In addition, by providing a standard starting method for starting a solid oxide fuel cell for an auxiliary power supply, it is possible to provide an operation method that can efficiently use a fuel cell power generation system.

Claims (9)

A fuel cell stack including a fuel supply unit for supplying a gas for fuel, an air supply unit for supplying air, a fuel electrode for supplying a reformed gas, and an air supply electrode for supplying air, and generate electricity by chemical reaction between air and fuel, wherein A reformer that receives fuel from a fuel supply unit and reforms a fuel that can be used at the anode of the fuel cell stack, and a post combustor for mixing and combusting the gas after the reaction from the anode of the fuel cell stack with the air from the cathode. Complex heat exchanger which performs heat exchange in the system such as preheating the air supplied from the supply unit and receiving the heat of discharged exhaust gas, supply direction of air in the reformer preheating stage, and supply direction of reformed gas from the reformer outlet Of the gas after reaction or from the stack Auxiliary power unit for a solid oxide fuel cell power system which comprises a plurality of valves and piping to determine the flavor. The method of claim 1, The reformer includes a nozzle unit serving as an inlet including a preheated air passage, a fuel supply passage, and a gas passage after the reaction of the anode, a partial oxidation reactor including a catalyst, a self-heat exchanger, and a reformed gas as the anode of the fuel cell stack. A solid oxide fuel cell power generation system for an auxiliary power unit, characterized in that it comprises an outlet which can be reached. The method of claim 2, The nozzle portion has the form of a triple tube, the innermost preheated air is supplied, the fuel is supplied in the form of an annular liquid film around the annular liquid film of fuel formed at the nozzle outlet because the flow rate of air is faster than the flow rate of the fuel To break it into small droplets, and most of the post-reaction gas from the anode flows into the after burner, but is partially (about one third) recirculated to the partial oxidation reactor through the gas passage after the reaction, which is the outermost circumference. A solid oxide fuel cell power generation system for an auxiliary power unit, characterized in that the supply form. The method of claim 1, The post combustor is combusted with a three-dimensional mixing zone and a catalyst-coated ceramic honeycomb to mix well to prevent the combustion of post-reacted gas and unreacted fuel and air from the cathode before reaching the catalyst. A solid oxide fuel cell power generation system for an auxiliary power unit, characterized in that it comprises an outlet for outgoing gas to the complex heat exchanger. The method of claim 1, A fuel cell stack, a reformer, a post combustor and a complex heat exchanger are integrally formed. The solid oxide fuel cell power generation system for an auxiliary power unit. In the method of starting a solid oxide fuel cell power generation system for an auxiliary power supply unit, A reformer preheating step (first step) of preheating the reformer with hot air; Reformer operation step (second step) through reformer fuel supply; A fuel cell stack preheating step (3rd step) using afterburner operation and preheated air through a reformed gas supply to the afterburner; And a fourth step of supplying the reformed gas to the fuel cell stack via the switching valve and supplying the preheated air to the fuel cell stack. Method of starting a solid oxide fuel cell power generation system for an auxiliary power supply unit comprising a. The method of claim 6, The reformer preheating step (first step) includes a step of preheating the post combustor by discharging the hot air preheating the reformer through the post-combustor through the switching valve and the composite heat exchanger; Method of starting a solid oxide fuel cell power generation system for an auxiliary power unit further comprising a. The method of claim 6, The reformer operation step (second step) through the reformer fuel supply includes the step of moving the reformed gas to a post-combuster after passing the combined heat exchanger; Method of starting a solid oxide fuel cell power generation system for an auxiliary power unit further comprising a. The method of claim 6, In the fuel cell stack preheating step (third step), the air supplied from the air supply unit is transferred to the fuel cell stack through the heat exchanger and the valve to preheat the fuel cell stack. How to start.

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