SOFC / gt / SCO2 hybrid system based on cathode and anode recirculation

Abstract

To realize the safe and efficient operation of a system by fully utilizing the waste heat of operation of an SOFC to generate power on the premise of realizing the constant-temperature operation of the SOFC.SOLUTION: One part of gas flow at an anode outlet of an SOFC enters a reforming chamber to perform reforming reaction, and one part of gas flow at a cathode outlet of the SOFC returns to a cathode of the SOFC after providing heat for supercritical SCO2 circulation. The rest of gas flow at an anode outlet and the cathode outlet of the SOFC enters a post-combustion chamber, and exhausted gas provides required heat for reforming reaction after doing work. A supercritical SCO2 circulation subsystem forms circulation by utilizing the heat of a part of gas flow at the cathode outlet of the SOFC to do work.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the technical field of batteries and power plants, in particular to SOFC / GT / SCO2 hybrid systems based on cathode and anode recirculation. [Background technology]

[0002] SOFC (Solid Oxide Fuel Cell) can directly convert chemical energy into electrical energy, is not limited by the Carnot cycle, and has high energy conversion efficiency. Currently, most SOFCs operate in the range of 600-1000°C, and the process of converting chemical energy into electrical energy by SOFC is an exothermic process, so it is necessary to consider how to operate SOFC within a certain temperature range to ensure the system operates safely. The current common solution is to remove excess heat from SOFC operation by increasing the air flow of the SOFC cathode, but this process increases the energy consumption of the air compressor and reduces the efficiency of the system.

[0003] A Chinese patent with publication number CN105226314A discloses a system for heat recovery and temperature control of SOFC for underwater vehicles using a Stirling engine. The system is composed of a SOFC, an insulated container with the SOFC as the center, a cooling circuit, and a Stirling engine, and one end of the Stirling engine is coupled into the insulated container and the other end is coupled to the cooling circuit so as to realize temperature control of the SOFC system and power generation from the waste heat of the SOFC. However, currently, the output power and power density of the Stirling engine are low, and the heat source comes from outside the engine and takes time to transfer heat, so that the output power of the engine cannot be changed quickly with the change in the power of the heat source. Summary of the Invention

[0004] In view of the above technical deficiencies, the present invention aims to provide a SOFC / GT / SCO2 hybrid system based on the recirculation of cathode and anode, and to control the operating temperature of the SOFC to improve the efficiency of the system.

[0005] The technical solution of the present invention is as follows: A SOFC / GT / SCO2 hybrid system based on cathode and anode recirculation, comprising a water pump, a first compressor, a second compressor, a reforming chamber, a SOFC, a post-combustion chamber, a second turbo, a fifth heat exchanger, an eighth heat exchanger and a supercritical CO2 circulation subsystem, the water pump pressurizes water, the first compressor pressurizes natural gas, the pressurized water and the pressurized natural gas enter the reforming chamber after being heated to carry out reforming reaction, the outlet of the reforming chamber is connected to the anode of the SOFC to provide anode gas to the SOFC, and the air is compressed by the second compressor and then fed into the reforming chamber for reforming reaction. and enters the cathode of the SOFC to provide cathode gas to the SOFC, the gas flow of a first portion of the SOFC anode outlet enters the post-combustion chamber, the gas flow of a second portion of the SOFC anode outlet returns to the reforming chamber, the gas flow of a first portion of the SOFC cathode outlet enters the post-combustion chamber, the gas flow of a second portion of the SOFC cathode outlet returns to the SOFC cathode through the eighth heat exchanger, and the gas discharged from the post-combustion chamber enters the fifth heat exchanger after work by the second turbo to supply the amount of heat required for the reforming reaction to the reforming chamber.

[0006] The supercritical CO2 circulation subsystem includes a first turbo and a third compressor, and the carbon dioxide pressurized by the third compressor is heated by the carbon dioxide that has performed the expansion work by the first turbo, enters the eighth heat exchanger again, and is heated by the gas flow of the second portion at the outlet of the cathode of the SOFC, before further entering the first turbo to perform expansion work.

[0007] It further includes a seventh heat exchanger, and the carbon dioxide after being compressed by the third compressor and the first portion of the gas flow after being heated by the carbon dioxide that has performed the expansion work by the first turbo enters the eighth heat exchanger and is heated by the second portion of the gas flow at the outlet of the cathode of the SOFC, and the carbon dioxide heated by the third compressor and the second portion of the gas flow after being heated by the carbon dioxide that has performed the expansion work by the first turbo enters the seventh heat exchanger and is heated by the second portion of the gas flow at the outlet of the anode of the SOFC, and the carbon dioxide heated by the seventh heat exchanger and the eighth heat exchanger are combined and enter the first turbo to perform expansion work.

[0008] Further, the supercritical CO2 circulation subsystem includes a sixth heat exchanger, in which the carbon dioxide compressed by the third compressor and the carbon dioxide that has undergone expansion work by the first turbo exchange heat with each other.

[0009] Further, the supercritical CO2 circulation subsystem includes a cooler, which is connected between the sixth heat exchanger and the third compressor, and the carbon dioxide that has undergone expansion work by the first turbo is cooled by the sixth heat exchanger, and then cooled by the cooler and enters the third compressor.

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

[0011] The system further includes a first mixer and a fourth heat exchanger, wherein the pressurized water and the pressurized natural gas are mixed by the first mixer, an outlet of the first mixer is connected to a refrigerant inlet of the fourth heat exchanger, a refrigerant outlet of the fourth heat exchanger is connected to the reforming chamber, and an outlet of the fifth heat exchanger is connected to a heat medium inlet of the fourth heat exchanger.

[0012] The compressor further includes a third heat exchanger, the outlet of the second compressor being connected to a refrigerant inlet of the third heat exchanger, and the outlet of the heat medium of the fourth heat exchanger being connected to a heat medium inlet of the third heat exchanger.

[0013] The compressor further includes a second heat exchanger, the outlet of the first compressor being connected to a refrigerant inlet of the second heat exchanger, the refrigerant outlet of the second heat exchanger being connected to the first mixer, and the heat medium outlet of the third heat exchanger being connected to a heat medium inlet of the second heat exchanger.

[0014] The system further includes a first heat exchanger, an outlet of the water pump is connected to a refrigerant inlet of the first heat exchanger, a refrigerant outlet of the first heat exchanger is connected to the first mixer, and a heat medium outlet of the second heat exchanger is connected to a heat medium inlet of the first heat exchanger. The first, second, third, fourth, and fifth heat exchangers use the thermal energy of the gas discharged from the second turbo in stages, thereby increasing the efficiency of the entire system.

[0015] The eighth heat exchanger further includes a second flow divider, a third flow divider, and a third mixer, wherein the second flow divider is used to divide the gas flow at the outlet of the anode of the SOFC into a first part and a second part, the third flow divider is used to divide the gas flow at the outlet of the cathode of the SOFC into a first part and a second part, and the third mixer is used to mix the pressurized and heated air and the second part of the gas flow at the outlet of the cathode of the SOFC that has passed through the eighth heat exchanger, and send the mixed mixture to the cathode of the SOFC.

[0016] The present invention has the following advantages over the prior art.

[0017] (1) By utilizing the circulation of anodes and cathodes, heat is extracted during the operation of the SOFC, which drives the SCO2 circulation to generate electricity, avoiding the need to use a large amount of cathode gas to control the temperature of the SOFC, and there is no need to increase the power consumption and investment costs of the air compressor. Under the premise that the intake flow rate of the air compressor does not change, constant temperature operation of the SOFC is realized.

[0018] (2) By using the anode circulation, a large amount of water vapor carried by the exhaust gas at the anode outlet can be recirculated to the reforming chamber to reform water and methane to produce hydrogen, ensuring that the reforming reaction is carried out normally and reducing the water flow rate required for the system.

[0019] (3) Through SCO2 circulation, waste heat from the SOFC is collected to generate electricity, avoiding the waste of thermal energy and improving the efficiency of the system. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a structural schematic diagram of a SOFC / GT / SCO2 hybrid system based on cathode and anode recirculation according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Next, the present invention will be further described in conjunction with examples, and these examples are only for the purpose of illustrating the present invention and do not limit the scope of the present invention. It should be understood that after reading this description, modifications to this description in various equivalent forms by those skilled in the art are all within the scope limited by the claims attached to this application.

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

[0023] The specific structure of the SOFC / GT / SCO2 hybrid system based on the recirculation of the cathode and anode includes a fuel reforming subsystem, a SOFC / GT hybrid system and a SCO2 circulation 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 refrigerant inlet of the first heat exchanger 4, the outlet of the first compressor 2 is connected to the refrigerant inlet of the second heat exchanger 5, and the refrigerant outlet of the first heat exchanger 4 and the refrigerant outlet of the second heat exchanger 5 are both connected to the inlet of the first mixer 7. The outlet of the first mixer 7 is connected to the refrigerant inlet of the fourth heat exchanger 8, the refrigerant outlet of the fourth heat exchanger 8 is connected to the inlet of the second mixer 10, and the outlet of the second mixer 10 is connected to the reforming chamber 11. The outlet of the post-combustion chamber 24 is connected to the inlet of the second turbo 25, the outlet of the second turbo 25 is connected to the heat medium inlet of the fifth heat exchanger 9, and the heat medium outlet of the fifth heat exchanger 9 is connected to the heat medium inlet of the fourth heat exchanger 8. The fifth heat exchanger 9 provides the amount of heat required for the operation of the reforming chamber 11. The heat medium outlet of the fourth heat exchanger 8 is connected to the heat medium inlet of the third heat exchanger 6, the heat medium outlet of the third heat exchanger 6 is connected to the heat medium inlet of the second heat exchanger 5, the heat medium outlet of the second heat exchanger 5 is connected to the heat medium inlet of the first heat exchanger 4, and the heat medium outlet of the first heat exchanger 4 is discharged into the air.

[0025] The SOFC / GF hybrid subsystem mainly includes a second compressor 3, a third heat exchanger 6, a third mixer 12, a SOFC 18, a second separator 22, a third separator 23, a post-combustion chamber 24, and a second turbo 25. The outlet of the second compressor 3 is connected to the refrigerant inlet of the third heat exchanger 6, and the refrigerant 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 to the post-combustion chamber 24 and the heat medium inlet of the eighth heat exchanger 19 via the third separator 23, respectively, and the heat 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 to the post-combustion chamber 24 and the heat medium inlet of the seventh heat exchanger 17 via the second separator 22, and the heat medium outlet of the seventh heat exchanger 17 is connected to the inlet of the second mixer 10. A portion of the heat quantity at the anode outlet and the cathode outlet of the SOFC 18 is utilized by the seventh heat exchanger 17 and the eighth heat exchanger 19.

[0026] The SCO2 circulation subsystem mainly includes a first separator 13, a sixth heat exchanger 14, a cooler 15, a first turbo 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 refrigerant inlet of the sixth heat exchanger 14, the refrigerant outlet of the sixth heat exchanger 14 is connected to the refrigerant inlet of the seventh heat exchanger 17 and the refrigerant inlet of the eighth heat exchanger 19 through the first separator 13, respectively, the refrigerant outlet of the seventh heat exchanger 17 and the refrigerant outlet of the eighth heat exchanger 19 are combined and connected to the inlet of the first turbo 21 through the fourth mixer 20, the outlet of the first turbo 21 is connected to the heat medium inlet of the sixth heat exchanger 14, and the heat medium outlet of the sixth heat exchanger 14 is connected to the inlet of the third compressor 16 through the cooler 15.

[0027] In this embodiment, the third compressor 16 adopts a multi-stage compression interstage cooling process, and the compression stages are five. The separation ratio of the first separator 13 (the ratio of the flow rate of the refrigerant at the inlet of the seventh heat exchanger 17 to the flow rate of the refrigerant at the inlet of the eighth heat exchanger 19) is 2:3, the separation ratio of the second separator 22 (the ratio of the flow rate of the anode recirculation gas at the outlet of the anode of the SOFC 18 to the gas entering the post-combustion chamber 24 from the outlet of the anode of the SOFC 18) is 3:2, and the separation ratio of the third separator 23 (the ratio of the flow rate of the cathode recirculation gas at the outlet of the cathode of the SOFC 18 to the gas entering the post-combustion chamber 24 from the outlet of the cathode of the SOFC 18) is 3:2. The system burns methane, and the intake air is composed of oxygen and nitrogen, with a molar ratio of the two being 0.21:0.79.

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

[0029] (1) Fuel Reforming Subsystem Water is pressurized by a water pump 1 and heated by a first heat exchanger 4 to become steam. This steam is mixed in a first mixer 7 with natural gas (methane) that has been pressurized by a first compressor 2 and heated by a second heat exchanger 5. The mixed gas is further heated by a fourth heat exchanger 8 and joined in a second mixer 10 with the anode circulation gas of an SOFC 18 that has been cooled by a seventh heat exchanger 17, and then enters a reforming chamber 11 to react and produce a hydrogen-rich gas.

[0030] (2) SOFC / GT Hybrid Subsystem The air is compressed by the second compressor 3, heated by the third heat exchanger 6, and mixed in the third mixer 12 with the cathode circulation gas of the SOFC 18 cooled by the eighth heat exchanger 19. The mixed gas enters the cathode of the SOFC 18 and undergoes an electrochemical reaction with the fuel gas of the anode of the SOFC 18 that entered from the outlet of the reforming chamber 11 to generate electrical energy. The gas at the outlet of the anode of the SOFC 18 is separated into two flow paths by the second separator 22, one of which enters the post-combustion chamber 24 and reacts, and the other is cooled in the seventh heat exchanger 17 as the anode circulation gas and returns to the second mixer 10. The gas at the outlet of the cathode of the SOFC 18 is separated into two flow paths by the third separator 23, one of which enters the post-combustion chamber 24 and reacts, and the other is cooled in the eighth heat exchanger 19 as the cathode circulation gas and returns to the third mixer 12. The high-temperature, high-pressure gas that enters the post-combustion chamber 24 and is burned performs sufficient expansion work in the second turbo 25, then enters the fifth heat exchanger 9 to supply heat to the reforming chamber 11. After that, it further passes through the fourth heat exchanger 8, the third heat exchanger 6, the second heat exchanger 5, and the first heat exchanger 4 to heat the mixed gas in the first mixer 7, the compressed air, the pressurized natural gas (methane), and the pressurized water, respectively, and is finally discharged into the air.

[0031] (3) SCO2 Circulation Subsystem The carbon dioxide compressed by the third compressor 16 is heated by the carbon dioxide after expansion work in the sixth heat exchanger 14 and the temperature rises, then enters the first separator 13 and is divided into two flow paths, one of which is heated by the anode circulation gas in the seventh heat exchanger 17 and the temperature rises before entering the fourth mixer 20, and the other is heated by the cathode circulation gas in the eighth heat exchanger 19 and the temperature rises before joining the aforementioned gas in the fourth mixer 20. The mixed high-temperature and high-pressure gas performs expansion work in the first turbo 21 and enters the sixth heat exchanger 14 to be cooled by the carbon dioxide after compression, and the cooled carbon dioxide enters the cooler 15 to be further cooled, and then enters the third compressor 16 to be compressed, completing one circulation. The first turbo 21 and the second turbo 25 can drive a generator to generate electricity.

[0032] The following is a concrete example to further illustrate the feasibility of the present invention. Table 1 shows the initial requirements of the system, and Table 2 shows the simulation results of the system. [Table 1] [Table 2]

[0033] The hybrid system can achieve a total power generation of 626.53 kW, a net power generation efficiency of 555.06 kW and a power generation efficiency of 69.18%, which has good guiding value in realizing the safe and efficient operation of the SOFC / GT / SCO2 hybrid system.

Claims

【Request 1】 Water pump, first compressor, second compressor, reforming chamber, SOFC, post-combustion chamber, second turbo, fifth heat exchanger, eighth heat exchanger and supercritical CO ２ The circulation subsystem includes: the water pump pressurizes water; the first compressor pressurizes natural gas; the pressurized water and pressurized natural gas are heated and then enter a 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 and then enters the cathode of the SOFC to provide cathode gas for the SOFC; a first part of the gas flow at the outlet of the anode of the SOFC enters the post-combustion chamber; a second part of the gas flow at the outlet of the anode of the SOFC returns to the reforming chamber; a first part of the gas flow at the outlet of the cathode of the SOFC enters the post-combustion chamber; a second part of the gas flow at the outlet of the cathode of the SOFC returns to the cathode of the SOFC through the eighth heat exchanger; and the gas discharged from the post-combustion chamber enters the fifth heat exchanger after work by the second turbo to supply the reforming chamber with the amount of heat required for the reforming reaction; The supercritical CO ２ The SOFC / GT / SCO based on recirculation of cathode and anode is characterized in that the circulation subsystem includes a first turbo and a third compressor, and the carbon dioxide compressed by the third compressor is heated by the carbon dioxide that has undergone expansion work by the first turbo, enters the eighth heat exchanger, and is heated by the gas flow of the second portion at the outlet of the cathode of the SOFC, before further entering the first turbo to perform expansion work. ２ Hybrid system. 【Request 2】 The SOFC / GT / SCO based on recirculation of cathode and anode according to claim 1, further comprising a seventh heat exchanger, wherein the carbon dioxide compressed by the third compressor has a first portion of gas flow heated by the carbon dioxide having undergone expansion work by the first turbo, the first portion of gas flow entering the eighth heat exchanger and being heated by the second portion of gas flow at the outlet of the cathode of the SOFC, the carbon dioxide heated by the third compressor has a second portion of gas flow heated by the carbon dioxide having undergone expansion work by the first turbo, the second portion of gas flow entering the seventh heat exchanger and being heated by the second portion of gas flow at the outlet of the anode of the SOFC, and the carbon dioxide heated by the seventh heat exchanger and the eighth heat exchanger are combined and enter the first turbo to perform expansion work. ２ Hybrid system. 【Request 3】 The supercritical CO ２ The SOFC / GT / SCO based on recirculation of the cathode and the anode according to claim 1 or 2, characterized in that the circulation subsystem includes a sixth heat exchanger, and the carbon dioxide compressed by the third compressor and the carbon dioxide subjected to the expansion work by the first turbo exchange heat in the sixth heat exchanger. ２ Hybrid system. 【Request 4】 The supercritical CO ２ 4. The SOFC / GT / SCO based on recirculation of cathode and anode according to claim 3, wherein the circulation subsystem includes a cooler, the cooler is connected between the sixth heat exchanger and the third compressor, and the carbon dioxide subjected to the expansion work by the first turbo is cooled by the cooler after being heat-exchanged and cooled by the sixth heat exchanger and then enters the third compressor. ２ Hybrid system. 【Request 5】 The SOFC / GT / SCO based on cathode and anode recirculation as claimed in claim 1, characterized in that the third compressor adopts a multi-stage compression interstage cooling process. ２ Hybrid system. [Request 6] 2. The SOFC / GT / SCO based on recirculation of cathode and anode according to claim 1, further comprising a first mixer and a fourth heat exchanger, the pressurized water and the pressurized natural gas are mixed by the first mixer, an outlet of the first mixer is connected to an inlet of a refrigerant of the fourth heat exchanger, an outlet of the refrigerant of the fourth heat exchanger is connected to the reforming chamber, and an outlet of the fifth heat exchanger is connected to an inlet of a heat medium of the fourth heat exchanger. ２ Hybrid system. 【Request 7】 7. The SOFC / GT / SCO based on recirculation of cathode and anode according to claim 6, further comprising a third heat exchanger, wherein an outlet of the second compressor is connected to an inlet of the refrigerant of the third heat exchanger, and an outlet of the heat medium of the fourth heat exchanger is connected to an inlet of the heat medium of the third heat exchanger. ２ Hybrid system. 【Request 8】 8. The SOFC / GT / SCO based on recirculation of cathode and anode according to claim 7, further comprising a second heat exchanger, wherein an outlet of the first compressor is connected to an inlet of the refrigerant of the second heat exchanger, an outlet of the refrigerant of the second heat exchanger is connected to the first mixer, and an outlet of the heat medium of the third heat exchanger is connected to an inlet of the heat medium of the second heat exchanger. ２ Hybrid system. 【Request 9】 9. The SOFC / GT / SCO based on recirculation of cathode and anode as claimed in claim 8, further comprising a first heat exchanger, the outlet of the water pump being connected to the inlet of the refrigerant of the first heat exchanger, the outlet of the refrigerant of the first heat exchanger being connected to the first mixer, and the outlet of the heat medium of the second heat exchanger being connected to the inlet of the heat medium of the first heat exchanger. ２ Hybrid system. 【Request 10】 2. The SOFC / GT / SCO based on recirculation of cathode and anode according to claim 1, further comprising: a second flow divider, a third flow divider, and a third mixer, wherein the second flow divider is used for dividing the gas flow at the outlet of the anode of the SOFC into a first part and a second part, the third flow divider is used for dividing the gas flow at the outlet of the cathode of the SOFC into a first part and a second part, and the third mixer is used for mixing the pressurized and heated air and the second part of the gas flow at the outlet of the cathode of the SOFC that has passed through the eighth heat exchanger, and sending the mixed mixture to the cathode of the SOFC. ２ Hybrid system.

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