Sofc / gt / sc02 hybrid power system based on cathode and anode recirculation

Abstract

The application discloses a SOFC / GT / SCO2 hybrid power system based on cathode and anode recirculation, which comprises a water pump, a first compressor, a second compressor, a reforming chamber, a SOFC, a post-combustion chamber, a second turbine, a fifth heat exchanger, an eighth heat exchanger and a supercritical CO2 circulation subsystem, wherein a part of gas flow at the anode outlet of the SOFC enters the reforming chamber to participate in a reforming reaction, a part of gas flow at the cathode outlet of the SOFC provides heat for the supercritical CO2 circulation and then returns to the cathode of the SOFC, and the remaining gas flow at the anode outlet and the cathode outlet of the SOFC enters the post-combustion chamber to burn, and the discharged gas provides required heat for the reforming reaction after work; the supercritical CO2 circulation subsystem forms a circulation to work by using the heat of the part of gas flow at the cathode outlet of the SOFC. The application realizes safe and efficient operation of the system by fully utilizing the waste heat of the SOFC operation to generate power under the premise of realizing SOFC constant-temperature operation.

Description

Technical Field

[0001] This invention relates to the field of battery and power device technology, and in particular to a SOFC / GT / SCO2 hybrid power system based on cathode and anode recirculation. Background Technology

[0002] SOFCs (Solid Oxide Fuel Cells) can directly convert chemical energy into electrical energy, are not limited by the Carnot cycle, and have high energy conversion efficiency. Currently, most SOFCs operate between 600-1000℃. Since the process of converting chemical energy into electrical energy is exothermic, it is necessary to consider how to ensure the safe operation of the SOFC within a certain temperature range. A common solution is to increase the airflow at the SOFC cathode to remove excess heat during operation. However, this process increases the energy consumption of the air compressor and reduces system efficiency.

[0003] Chinese patent CN105226314A discloses a method for heat recovery and temperature control of SOFC (SO2-fired power source) in underwater vehicles using a Stirling engine. The system consists of an SOFC, an insulated enclosure surrounding the SOFC, a cooling circuit, and a Stirling engine. Temperature control of the SOFC system and power generation from the waste heat of the SOFC are achieved by coupling one end of the Stirling engine to the interior of the insulated enclosure and the other end to the cooling circuit. However, currently, the output power and power density of Stirling engines are relatively low. Furthermore, since the heat source is external to the engine, heat transfer takes time, therefore the engine's output power cannot quickly change with variations in the heat source power. Summary of the Invention

[0004] To address the aforementioned deficiencies in the prior art, the present invention aims to provide a SOFC / GT / SCO2 hybrid power system based on cathode and anode recirculation, with the goal of controlling the SOFC operating temperature and improving system efficiency.

[0005] The technical solution of this invention is as follows: A SOFC / GT / SCO2 hybrid power system based on cathode and anode recirculation includes: a water pump, a first compressor, a second compressor, a reforming chamber, an SOFC, an afterburner, a second turbine, a fifth heat exchanger, an eighth heat exchanger, and a supercritical CO2 cycle subsystem. The water pump pressurizes water, and the first compressor pressurizes natural gas. The pressurized water and pressurized natural gas are heated and then enter the reforming chamber for reforming reaction. The outlet of the reforming chamber is connected to the anode of the SOFC to provide anode gas for the SOFC. Air is pressurized by the second compressor and heated before entering the cathode of the SOFC to provide cathode gas for the SOFC. A first portion of the airflow from the anode outlet of the SOFC enters the afterburner, and a second portion of the airflow from the anode outlet of the SOFC returns to the reforming chamber. A first portion of the airflow from the cathode outlet of the SOFC enters the afterburner, and a second portion of the airflow from the cathode outlet of the SOFC returns to the cathode of the SOFC through the eighth heat exchanger. The gas discharged from the afterburner is powered by the second turbine and then enters the fifth heat exchanger to provide the heat required for the reforming reaction in the reforming chamber.

[0006] The supercritical CO2 cycle subsystem includes a first turbine and a third compressor. The carbon dioxide pressurized by the third compressor is heated by the carbon dioxide that expands and does work through the first turbine before entering the eighth heat exchanger. It is then heated by the second part of the gas flow from the cathode outlet of the SOFC before entering the first turbine to expand and do work.

[0007] Furthermore, including a seventh heat exchanger, a first portion of the carbon dioxide pressurized by the third compressor, heated by the carbon dioxide that has undergone work expansion through the first turbine, enters the eighth heat exchanger and is heated by a second portion of the gas flow from the cathode outlet of the SOFC. The second portion of the carbon dioxide pressurized by the third compressor, heated by the carbon dioxide that has undergone work expansion through the first turbine, enters the seventh heat exchanger and is heated by a second portion of the gas flow from the anode outlet of the SOFC. The carbon dioxide heated by the seventh and eighth heat exchangers is combined and enters the first turbine to undergo work expansion.

[0008] Furthermore, the supercritical CO2 cycle subsystem includes a sixth heat exchanger, in which the carbon dioxide pressurized by the third compressor exchanges heat with the carbon dioxide that has undergone work by expansion through the first turbine.

[0009] Furthermore, the supercritical CO2 cycle subsystem includes a cooler connected between the sixth heat exchanger and the third compressor. The carbon dioxide that has undergone work by expanding through the first turbine is cooled by the sixth heat exchanger and then cooled by the cooler before entering the third compressor.

[0010] Furthermore, the third compressor employs a multi-stage compression stage cooling process.

[0011] Furthermore, it includes a first mixer and a fourth heat exchanger. The pressurized water and pressurized natural gas are mixed through the first mixer. The outlet of the first mixer is connected to the cold medium inlet of the fourth heat exchanger. The cold medium outlet of the fourth heat exchanger is connected to the reforming chamber. The outlet of the fifth heat exchanger is connected to the hot medium inlet of the fourth heat exchanger.

[0012] Furthermore, it includes a third heat exchanger, with the outlet of the second compressor connected to the cold medium inlet of the third heat exchanger, and the hot medium outlet of the fourth heat exchanger connected to the hot medium inlet of the third heat exchanger.

[0013] Furthermore, the system includes a second heat exchanger, wherein the outlet of the first compressor is connected to the cold medium inlet of the second heat exchanger, the cold medium outlet of the second heat exchanger is connected to the first mixer, and the hot medium outlet of the third heat exchanger is connected to the hot medium inlet of the second heat exchanger.

[0014] Furthermore, the system includes a first heat exchanger, with the outlet of the water pump connected to the cold medium inlet of the first heat exchanger, the cold medium outlet of the first heat exchanger connected to the first mixer, and the hot medium outlet of the second heat exchanger connected to the hot medium inlet of the first heat exchanger. The thermal energy of the gas discharged from the second turbine is utilized in a step-by-step manner through the first, second, third, fourth, and fifth heat exchangers, thereby improving the overall system efficiency.

[0015] Furthermore, it includes a second splitter, a third splitter, and a third mixer. The second splitter is used to divide the airflow at the anode outlet of the SOFC into a first part and a second part. The third splitter is used to divide the airflow at the cathode outlet of the SOFC into a first part and a second part. The third mixer is used to mix the pressurized and heated air with the second part of the airflow at the cathode outlet of the SOFC that has passed through the eighth heat exchanger and send it to the cathode of the SOFC.

[0016] The advantages of this invention compared to the prior art are:

[0017] (1) The heat generated during the operation of SOFC is carried out by the anode and cathode cycle and driven by the SCO2 cycle to generate electricity. This avoids the need to use a large flow of cathode gas to control the temperature of SOFC, and does not require increased power consumption and investment of air compressor. Under the premise of ensuring that the air inlet flow of air compressor remains unchanged, SOFC can be operated at constant temperature.

[0018] (2) The anode circulation is used to recirculate the large amount of water vapor carried by the tail gas at the anode outlet to the reforming chamber for water and methane reforming to produce hydrogen, which ensures the normal progress of the reforming reaction and can reduce the water flow required by the system.

[0019] (3) The waste heat of SOFC is collected by the SCO2 cycle and used to generate electricity, which avoids the waste of thermal energy and improves the system efficiency. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the SOFC / GT / SCO2 hybrid power system based on cathode and anode recirculation according to an embodiment of the present invention. Detailed Implementation

[0021] The present invention will be further described below with reference to embodiments. It should be understood that these embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention. After reading this description, any modifications of this description in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0022] Please combine Figure 1 As shown, the embodiment of the present invention relates to a SOFC / GT / SCO2 hybrid power system based on cathode and anode recirculation, where GT is a gas turbine and SCO2 is a supercritical carbon dioxide cycle. The system includes the following components: a water pump 1; a first compressor 2; a second compressor 3; a first heat exchanger 4; a second heat exchanger 5; a third heat exchanger 6; a first mixer 7; a fourth heat exchanger 8; a fifth heat exchanger 9; a second mixer 10; a reforming chamber 11; a third mixer 12; a first separator 13; a sixth heat exchanger 14; a cooler 15; a third compressor 16; a seventh heat exchanger 17; an SOFC 18; an eighth heat exchanger 19; a fourth mixer 20; a first turbine 21; a second separator 22; a third separator 23; an afterburner 24; and a second turbine 25.

[0023] The specific structure of the SOFC / GT / SCO2 hybrid power system based on cathode and anode recirculation includes a fuel reforming subsystem, an SOFC / GT hybrid power subsystem, and an SCO2 cycle subsystem.

[0024] The fuel reforming subsystem mainly includes a water pump 1, a first compressor 2, a first heat exchanger 4, a second heat exchanger 5, a first mixer 7, a fourth heat exchanger 8, a fifth heat exchanger 9, a second mixer 10, and a reforming chamber 11. The outlet of the water pump 1 is connected to the cold medium inlet of the first heat exchanger 4. The outlet of the first compressor 2 is connected to the cold medium inlet of the second heat exchanger 5. The cold medium outlets of both the first and second heat exchangers are connected to the inlet of the first mixer 7. The outlet of the first mixer 7 is connected to the cold medium inlet of the fourth heat exchanger 8. The cold medium outlet of the fourth heat exchanger 8 is connected to the inlet of the second mixer 10. The outlet of the second mixer 10 is connected to the reforming chamber 11. The outlet of the afterburner 24 is connected to the inlet of the second turbine 5. The outlet of the second turbine 25 is connected to the hot medium inlet of the fifth heat exchanger 9. The hot medium outlet of the fifth heat exchanger 9 is connected to the hot medium inlet of the fourth heat exchanger 8. The fifth heat exchanger 9 provides the necessary heat for the operation of the reforming chamber 11. The hot medium outlet of the fourth heat exchanger 8 is connected to the hot medium inlet of the third heat exchanger 6, the hot medium outlet of the third heat exchanger 6 is connected to the hot medium inlet of the second heat exchanger 5, the hot medium outlet of the second heat exchanger 5 is connected to the hot medium inlet of the first heat exchanger 4, and the hot medium outlet of the first heat exchanger 4 is discharged into the air.

[0025] The SOFC / GF hybrid power subsystem mainly includes a second compressor 3, a third heat exchanger 6, a third mixer 12, an SOFC 18, a second separator 22, a third separator 23, an afterburner 24, and a second turbine 25. The outlet of the second compressor 3 is connected to the cold medium inlet of the third heat exchanger 6, and the cold medium outlet of the third heat exchanger 6 is connected to the inlet of the third mixer 12. The cathode inlet of the SOFC 18 is connected to the outlet of the third mixer 12, and the anode inlet of the SOFC 18 is connected to the outlet of the reforming chamber 11. The cathode outlet of the SOFC 18 is connected via the third separator 23 to the hot medium inlets of the afterburner 24 and the eighth heat exchanger 19, respectively. The hot medium outlet of the eighth heat exchanger 19 is connected to the inlet of the third mixer 12. The anode outlet of the SOFC 18 is connected via the second separator 22 to the hot medium inlets of the afterburner 24 and the seventh heat exchanger 17, respectively. The hot medium outlet of the seventh heat exchanger 17 is connected to the inlet of the second mixer 10. A portion of the heat from the anode and cathode outlets of SOFC 18 is utilized through the seventh heat exchanger 17 and the eighth heat exchanger 19.

[0026] The SCO2 cycle subsystem mainly includes a first separator 13, a sixth heat exchanger 14, a cooler 15, a first turbine 21, an eighth heat exchanger 19, a fourth mixer 20, and a third compressor 16. The outlet of the third compressor 16 is connected to the cold medium inlet of the sixth heat exchanger 14. The cold medium outlet of the sixth heat exchanger 14 is connected to the cold medium inlets of the seventh heat exchanger 17 and the eighth heat exchanger 19 via the first separator 13. The cold medium outlets of the seventh heat exchanger 17 and the eighth heat exchanger 19 are combined via the fourth mixer 20 and connected to the inlet of the first turbine 21. The outlet of the first turbine 21 is connected to the hot medium inlet of the sixth heat exchanger 14. The hot medium outlet of the sixth heat exchanger 14 is connected to the inlet of the third compressor 16 via the cooler 15.

[0027] In this embodiment, the third compressor 16 employs a multi-stage compression interstage cooling process, with five compression stages. The separation ratio of the first separator 13 (the ratio of the cold medium inlet flow rate of the seventh heat exchanger 17 to the cold medium inlet flow rate of the eighth heat exchanger 19) is 2:3; the separation ratio of the second separator 22 (the ratio of the anode recirculated gas flow rate at the anode outlet of SOFC 18 to the gas entering the afterburner 24 at the anode outlet of SOFC 18) is 3:2; and the separation ratio of the third separator 23 (the ratio of the cathode recirculated gas flow rate at the cathode outlet of SOFC 18 to the gas entering the afterburner 24 at the cathode outlet of SOFC 18) is 3:2. The system uses methane as fuel, and the inlet air consists of oxygen and nitrogen in a molar ratio of 0.21:0.79.

[0028] The following describes in detail the working principle of the SOFC / GT / SCO2 hybrid power system based on cathode and anode recirculation provided in the embodiments of this application.

[0029] (I) Fuel Reforming Subsystem

[0030] Water is pressurized by water pump 1 and heated into steam by first heat exchanger 4. It is then mixed with natural gas (methane) that is pressurized by first compressor 2 and heated by second heat exchanger 5 in first mixer 7. The mixed gas is further heated by fourth heat exchanger 8 and then merged with the anode circulating gas of SOFC 18 that is cooled by seventh heat exchanger 17 in second mixer 10. The mixture then enters reforming chamber 11 to react and generate hydrogen-rich gas.

[0031] (II) SOFC / GT Hybrid Subsystem

[0032] Air is compressed by the second compressor 3 and heated by the third heat exchanger 6, then mixed with the SOFC 18 cathode recirculation gas cooled by the eighth heat exchanger 19 in the third mixer 12. The mixed gas enters the SOFC 18 cathode and undergoes an electrochemical reaction with the fuel gas entering the SOFC 18 anode from the reforming chamber 11, generating electricity. The SOFC 18 anode outlet gas is split into two paths by the second separator 22: one path enters the afterburner 24 for reaction, and the other path, as anode recirculation gas, is cooled by the seventh heat exchanger 17 and returns to the second mixer 10. The SOFC 18 cathode outlet gas is split into two paths by the third separator 23: one path enters the afterburner 24 to participate in the reaction, and the other path, as cathode recirculation gas, is cooled by the eighth heat exchanger 19 and returns to the third mixer 12. The high-temperature, high-pressure gas that burns in the afterburner 24 expands fully in the second turbine 25 to do work, and then enters the fifth heat exchanger 9 to heat the reforming chamber 11. Then, the mixture of gas, compressed air, pressurized natural gas (methane), and pressurized water in the first mixer 7 are further heated by the fourth heat exchanger 8, the third heat exchanger 6, the second heat exchanger 5, and the first heat exchanger 4, respectively, and finally discharged into the air.

[0033] (III) SCO2 Cyclic Subsystem

[0034] The carbon dioxide, compressed by the third compressor 16, is heated in the sixth heat exchanger 14 by the expanded carbon dioxide. It then enters the first separator 13, where it is separated into two streams. One stream passes through the seventh heat exchanger 17, where it is heated by the anode circulating gas before entering the fourth mixer 20. The other stream passes through the eighth heat exchanger 19, where it is heated by the cathode circulating gas before merging with the other stream in the fourth mixer 20. The resulting high-temperature, high-pressure gas expands in the first turbine 21, performs work, and then enters the sixth heat exchanger 14 to be cooled by the compressed carbon dioxide. The cooled carbon dioxide then enters the cooler 15 for further cooling before re-entering the third compressor 16 for compression, completing one cycle. The first turbine 21 and the second turbine 25 can drive a generator to produce electricity.

[0035] The following specific example further illustrates the feasibility of the present invention. The initial system conditions are shown in Table 1, and the system simulation results are shown in Table 2.

[0036] Table 1 System Initial Conditions

[0037] project Value project Value fuel flow 1mol / s airflow 10mol / s SOFC operating temperature 800℃ SOFC operating pressure 5atm Fuel efficiency 0.80 DC / AC conversion efficiency 0.97 Ambient temperature 25℃ Environmental pressure 1 atm Inlet water flow 1mol / s compressor isentropic efficiency 0.8 Compressor mechanical efficiency 0.98 Turbine isentropic efficiency 0.85 Turbine mechanical efficiency 0.98 Pump efficiency 0.8

[0038] Table 2 System Simulation Results

[0039]

[0040]

[0041] This hybrid power system can achieve a total power output of 626.53kW, a net power generation efficiency of 555.06kW, and a power generation efficiency of 69.18%, providing valuable guidance for the safe and efficient operation of SOFC / GT / SCO2 hybrid power systems.

Claims

1. A SOFC / GT / SCO2 hybrid power system based on cathode and anode recirculation, characterized in that, include: The system comprises a water pump, a first compressor, a second compressor, a reforming chamber, an SOFC (Sodium Air Fuel Cell), an afterburner, a second turbine, a fifth heat exchanger, a seventh heat exchanger, an eighth heat exchanger, and a supercritical CO2 cycle subsystem. The water pump pressurizes water, and the first compressor pressurizes natural gas. The pressurized water and pressurized natural gas are heated and then enter the reforming chamber for a reforming reaction. The outlet of the reforming chamber is connected to the anode of the SOFC to provide anode gas. Air is pressurized and heated by the second compressor and then enters the cathode of the SOFC to provide cathode gas. A first portion of the gas flow from the anode outlet of the SOFC enters the afterburner, and a second portion of the gas flow from the anode outlet of the SOFC returns to the reforming chamber. A first portion of the gas flow from the cathode outlet of the SOFC enters the afterburner, and a second portion of the gas flow from the cathode outlet of the SOFC returns to the cathode of the SOFC through the eighth heat exchanger. The gas discharged from the afterburner is powered by the second turbine and then enters the fifth heat exchanger to provide the heat required for the reforming reaction in the reforming chamber. The supercritical CO2 cycle subsystem includes a first turbine and a third compressor. The first portion of the carbon dioxide pressurized by the third compressor, after being heated by the carbon dioxide that expands and does work in the first turbine, enters the eighth heat exchanger and is heated by the second portion of the gas flow from the cathode outlet of the SOFC. The second portion of the carbon dioxide pressurized by the third compressor, after being heated by the carbon dioxide that expands and does work in the first turbine, enters the seventh heat exchanger and is heated by the second portion of the gas flow from the anode outlet of the SOFC. The carbon dioxide heated by the seventh and eighth heat exchangers is combined and enters the first turbine to expand and do work.

2. The SOFC / GT / SCO2 hybrid power system based on cathode and anode recirculation according to claim 1, characterized in that, The supercritical CO2 cycle subsystem includes a sixth heat exchanger, in which carbon dioxide pressurized by the third compressor exchanges heat with carbon dioxide that has undergone expansion and work by the first turbine.

3. The SOFC / GT / SCO2 hybrid power system based on cathode and anode recirculation according to claim 2, characterized in that, The supercritical CO2 cycle subsystem includes a cooler connected between the sixth heat exchanger and the third compressor. The carbon dioxide that has been expanded by the first turbine is cooled by the sixth heat exchanger and then cooled by the cooler before entering the third compressor.

4. The SOFC / GT / SCO2 hybrid power system based on cathode and anode recirculation according to claim 1, characterized in that, The third compressor employs a multi-stage compression interstage cooling process.

5. The SOFC / GT / SCO2 hybrid power system based on cathode and anode recirculation according to claim 1, characterized in that, It includes a first mixer and a fourth heat exchanger. The pressurized water and pressurized natural gas are mixed in the first mixer. The outlet of the first mixer is connected to the cold medium inlet of the fourth heat exchanger. The cold medium outlet of the fourth heat exchanger is connected to the reforming chamber. The outlet of the fifth heat exchanger is connected to the hot medium inlet of the fourth heat exchanger.

6. The SOFC / GT / SCO2 hybrid power system based on cathode and anode recirculation according to claim 5, characterized in that, It includes a third heat exchanger, the outlet of the second compressor is connected to the cold medium inlet of the third heat exchanger, and the hot medium outlet of the fourth heat exchanger is connected to the hot medium inlet of the third heat exchanger.

7. The SOFC / GT / SCO2 hybrid power system based on cathode and anode recirculation according to claim 6, characterized in that, The system includes a second heat exchanger, with the outlet of the first compressor connected to the cold medium inlet of the second heat exchanger, the cold medium outlet of the second heat exchanger connected to the first mixer, and the hot medium outlet of the third heat exchanger connected to the hot medium inlet of the second heat exchanger.

8. The SOFC / GT / SCO2 hybrid power system based on cathode and anode recirculation according to claim 7, characterized in that, It includes a first heat exchanger, the outlet of the water pump is connected to the cold medium inlet of the first heat exchanger, the cold medium outlet of the first heat exchanger is connected to the first mixer, and the hot medium outlet of the second heat exchanger is connected to the hot medium inlet of the first heat exchanger.

9. The SOFC / GT / SCO2 hybrid power system based on cathode and anode recirculation according to claim 1, characterized in that, It includes a second separator, a third separator, and a third mixer. The second separator is used to divide the airflow at the anode outlet of the SOFC into a first part and a second part. The third separator is used to divide the airflow at the cathode outlet of the SOFC into a first part and a second part. The third mixer is used to mix the pressurized and heated air with the second part of the airflow at the cathode outlet of the SOFC that has passed through the eighth heat exchanger and send it to the cathode of the SOFC.

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