Dual-stream supercritical carbon dioxide system for solar combined heat and power and method of operation

Abstract

The application discloses a secondary flow supercritical carbon dioxide system and operation method for solar combined heat and power generation, which comprises a high-pressure turbine, a first generator, a low-pressure turbine, a second generator, a first molten salt-supercritical carbon dioxide printed board heat exchanger, a second molten salt-supercritical carbon dioxide printed board heat exchanger, a molten salt high-temperature heat storage tank, a molten salt low-temperature heat storage tank, a high-temperature regenerator, a low-temperature regenerator, a first main compressor, a second main compressor, a first re-compressor, a second re-compressor, a low-pressure heat network heat exchanger, a first high-pressure heat network heat exchanger, a second high-pressure heat network heat exchanger, a low-pressure pre-cooler, a high-pressure pre-cooler, a molten salt mixer, a supercritical carbon dioxide mixer, a hot water mixer, a plurality of three-way valves and control valves. The application builds a combined heat and power generation system with high power generation efficiency and adjustable heat supply on the basis of a conventional re-compression supercritical carbon dioxide cycle. The system can adjust the flow of supercritical carbon dioxide in the high-pressure and low-pressure heat network heat exchangers according to the relative demand of power generation and heat supply by controlling the three-way valves for twice flow distribution based on the difference in specific heat capacity of supercritical carbon dioxide under high-pressure and low-pressure conditions, so as to realize the purpose of flexibly adjusting the heat supply and power generation, and can simultaneously improve the flexibility and efficiency of the combined heat and power generation unit; the working modes of the system in the heating season and the non-heating season can be flexibly converted by controlling four valves.

Description

Technical Field

[0001] This invention belongs to the field of cogeneration technology for solar power plants, specifically relating to a secondary supercritical carbon dioxide diversion system and its operation method for solar cogeneration. Background Technology

[0002] To achieve sustainable energy development, developing new and renewable energy sources, optimizing the energy structure, and enhancing energy supply are currently the top priorities in energy transformation. Solar energy, due to its large total capacity, environmental friendliness, and low cost, has become a key focus of new energy development. However, it also exhibits intermittent and fluctuating characteristics. Currently, solar thermal power generation systems coupled with molten salt thermal storage integrate heat generation, heat transport, heat storage, and thermoelectric conversion, and can achieve stable energy supply through thermal storage technology, "peak shaving and valley filling," avoiding overload and power outages.

[0003] The supercritical carbon dioxide power cycle is a Brayton cycle using supercritical carbon dioxide as the working fluid. Because carbon dioxide has a density close to that of a fluid in its supercritical state, the volume of the cycle equipment is much smaller than that of a Rankine cycle using conventional steam as the working fluid. Furthermore, supercritical carbon dioxide has a viscosity close to that of a gas and a very small compressibility factor near the critical point. This results in lower power consumption within the compressor and a smaller pressure drop within the pipes. The supercritical carbon dioxide power cycle can employ extreme regenerative technology and advanced printed plate heat exchangers, making the energy recovery and utilization of exhaust steam simpler and more efficient than that of the traditional Rankine cycle.

[0004] Current research on supercritical carbon dioxide Brayton cycles primarily focuses on improving generator efficiency. Under conditions of an ambient temperature of 18°C, a maximum supercritical carbon dioxide temperature of 650°C, and a maximum pressure of 25 MPa, using existing single-pass recompression cycles, the power generation efficiency of 100 MW generator units can exceed 51%, higher than that of ultra-supercritical steam generator units under the same temperature conditions. In solar thermal power generation, commercially available tower solar thermal power plants coupled with nitrate thermal storage systems typically reach a maximum temperature of 565°C. To improve power generation efficiency, next-generation high-temperature molten salt thermal storage systems will exceed 700°C. In the high-temperature domain, the thermal efficiency advantage of supercritical carbon dioxide Brayton cycles will be even more pronounced; therefore, numerous domestic and international research findings support the supercritical carbon dioxide Brayton cycle as a power module for future high-efficiency solar thermal power plants.

[0005] Combined heat and power (CHP) can improve the overall energy efficiency of power plants through the cascade utilization of energy and the rational matching of user demand, and has always been an important development direction in the power generation field. Traditional steam power cycles use waste steam heat for heating, mainly divided into two types: back-pressure and extraction-condensing. Back-pressure heating loads are determined by the power supply load and cannot be adjusted according to user demand; while extraction-condensing uses a portion of steam for heating, achieving the goal of adjusting heating and electricity demand, but the heat exchange temperature difference is large, affecting the overall unit performance. Efficiency decreases due to the impact of heating demand. For conventional supercritical carbon dioxide cycles, the range of heat supply adjustment is limited by the use of extreme regeneration technology. Forcibly increasing the heat supply requires sacrificing some regeneration and will increase the heat transfer temperature difference during heating, which is detrimental to improving overall energy utilization. Research indicates that current research on supercritical carbon dioxide cycle cogeneration is relatively limited, and most studies focus on adjusting the heat supply or improving system processes during the heating and non-heating seasons. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and propose a secondary-diversion supercritical carbon dioxide system and its operation method for solar cogeneration; by proposing two system operation methods, one for power generation and one for heat supply, the cogeneration system is guaranteed to have high system efficiency under both operation methods. Efficiency; based on the relative proportions of heating and power generation demands, flexibly control power generation and heating supply, and maintain overall system efficiency. Efficiency should be kept as constant as possible.

[0007] This invention is achieved through the following technical solution:

[0008] A secondary supercritical carbon dioxide system for solar cogeneration includes a high-pressure turbine 1, a first generator 2, a low-pressure turbine 3, a second generator 4, a first-stage molten salt supercritical carbon dioxide printed plate heat exchanger 5, a second-stage molten salt supercritical carbon dioxide printed plate heat exchanger 6, a molten salt high-temperature heat storage tank 7, a molten salt low-temperature heat storage tank 8, a molten salt three-way valve 20, a low-temperature molten salt mixer 24, a high-temperature regenerator 13, a low-temperature regenerator 14, a first-stage main compressor 9, a second-stage main compressor 10, a first-stage recompressor 11, a second-stage recompressor 12, and a low-pressure heating network. The following components are connected as follows: heat exchanger 17, high-pressure primary heating network heat exchanger 18, high-pressure secondary heating network heat exchanger 19, low-pressure precooler 15, high-pressure precooler 16, low-pressure diversion three-way valve 21, high-pressure diversion three-way valve 22, low-temperature control valve 23, secondary heating pre-mixer 25, low-temperature pre-mixer 26, high-temperature regeneration pre-mixer 27, hot water supply mixer 28, low-pressure primary heating network heat exchanger control valve 29, low-pressure primary heating network heat exchanger bypass valve 30, high-pressure secondary heating network heat exchanger control valve 31, and high-pressure secondary heating network heat exchanger bypass valve 32.

[0009] The outlet of the molten salt high-temperature heat storage tank 7 is connected to the inlet of the molten salt three-way valve 20. One outlet of the molten salt three-way valve 20 leads to the hot-side inlet of the primary molten salt-supercritical carbon dioxide printed plate heat exchanger 5, and the other outlet leads to the hot-side inlet of the secondary molten salt-supercritical carbon dioxide printed plate heat exchanger 6. The hot-side outlets of the molten salt-supercritical carbon dioxide printed plate heat exchanger 5 and the molten salt-supercritical carbon dioxide printed plate heat exchanger 6 are simultaneously connected to the inlet of the low-temperature molten salt mixer 24. The outlet of the low-temperature molten salt mixer 24 is connected to the low-temperature molten salt storage tank 8. The cold-side outlet of the molten salt-supercritical carbon dioxide printed plate heat exchanger 5 is connected to the inlet of the high-pressure turbine 1, and the outlet of the high-pressure turbine 1 is connected to the inlet of the secondary molten salt-supercritical carbon dioxide printed plate heat exchanger 6. The cold-side inlet of the secondary molten salt supercritical carbon dioxide printed plate heat exchanger 6 is connected to the cold-side outlet of the secondary molten salt supercritical carbon dioxide printed plate heat exchanger 6, which is connected to the inlet of the low-pressure turbine 3. The outlet of the low-pressure turbine 3 is connected to the hot-side inlet of the high-temperature regenerator 13, and the hot-side outlet of the high-temperature regenerator 13 is connected to the hot-side inlet of the low-temperature regenerator 14. The cold-side outlet of the high-temperature regenerator 13 is connected to the cold-side inlet of the primary molten salt supercritical carbon dioxide printed plate heat exchanger 5, and the cold-side inlet of the high-temperature regenerator 13 is connected to the outlet of the high-temperature regenerator pre-mixer 27. The hot-side outlet of the low-temperature regenerator 14 is connected to the low-pressure diversion three-way valve 21. The outlet of the low-pressure diversion three-way valve 21 is divided into two paths: one path a2 is directly connected to the primary recompressor 11, and the other path a1 is connected in parallel to the low-pressure primary heating network. The heat exchanger control valve 29 and the low-pressure primary heat exchanger bypass valve 30 are connected. The primary heat exchanger control valve 29 is connected to the hot end inlet of the low-pressure heat exchanger 17. The outlet of the low-pressure primary heat exchanger bypass valve 30 and the hot end outlet of the low-pressure heat exchanger 17 are connected to the low-pressure precooler 15, which is connected to the primary main compressor 9. The outlet of the primary re-compressor 11 is connected to the high-pressure diversion three-way valve 22. One outlet a4 of the high-pressure diversion three-way valve 22 is directly connected to the secondary re-compressor 12, and the other outlet a3 passes through the high-pressure primary heat exchanger 18 and merges with the outlet of the primary compressor 9 before connecting to the secondary preheating mixer 25. The outlet of the secondary preheating mixer 25 is connected in parallel to the high-pressure secondary heat exchanger control valve 31 and the high-pressure secondary heat exchanger. Heat exchanger bypass valve 32; the outlet of high-pressure secondary heat exchanger control valve 31 is connected to the hot end inlet of high-pressure secondary heat exchanger 19, the outlet of high-pressure secondary heat exchanger bypass valve 32 and the hot end outlet of high-pressure secondary heat exchanger 19 are connected to low-temperature three-way control valve 23; the first outlet a6 of low-temperature three-way control valve 23 is directly connected to low-temperature pre-mixer 26, and the second outlet a5 is connected to the first outlet in low-temperature pre-mixer 26 after passing through high-pressure precooler 16; the outlet of low-temperature pre-mixer 26 is connected to the inlet of secondary main compressor 10, the outlet of secondary main compressor 10 is connected to the cold side inlet of low-temperature regenerator 14, and the cold side outlet of low-temperature regenerator 14 and the outlet of secondary re-compressor 12 are simultaneously connected to high-temperature regenerator pre-mixer 27 to complete one cycle;The outlet of the cold section of the high-pressure primary heat exchanger 18 connects to the inlet of the cold section of the high-pressure secondary heat exchanger 19. The outlet of the cold section of the low-pressure heat exchanger 17 merges with the outlet of the cold section of the high-pressure secondary heat exchanger 19 and connects to the hot water mixer 28.

[0010] The high-pressure turbine 1, the first generator 2, the first-stage main compressor 9, and the first-stage re-compressor 11 are arranged coaxially; the low-pressure turbine 3, the second generator 4, the second-stage main compressor 10, and the second-stage re-compressor 12 are arranged coaxially.

[0011] The operation method of the two-stage supercritical carbon dioxide diversion system for solar cogeneration is as follows:

[0012] During the heating season, the supercritical carbon dioxide at the hot end outlet of the low-temperature regenerator 14 is divided into two paths, a1 and a2, through the low-pressure diversion three-way valve 21. The low-pressure primary heating network heat exchanger bypass valve 30 is closed, and the low-pressure primary heating network heat exchanger control valve 29 is opened. The supercritical carbon dioxide in path a1 enters the low-pressure heating network heat exchanger 17 for heating, and the low-pressure precooler 15 cools the environment to room temperature. After compression in the primary main compressor 9, it flows into the secondary preheating mixer 25. The supercritical carbon dioxide in path a2 directly enters the primary re-compressor 11 for compression and then enters the high-pressure diversion... The three-way valve 22 divides the flow into two paths, a3 and a4. The supercritical carbon dioxide in path a4 is compressed to high pressure by the secondary recompressor 12 and flows into the high-temperature regenerative premixer 27. The high-pressure secondary heat exchanger bypass valve 32 is closed, and the high-pressure secondary heat exchanger control valve 31 is opened. The supercritical carbon dioxide in path a3 enters the high-pressure primary heat exchanger 18 and flows into the secondary premixer 25. The high-pressure secondary heat exchanger bypass valve 32 is then closed. The supercritical carbon dioxide in paths a1 and a3 mixes in the secondary premixer 25 and then enters the high-pressure secondary heat exchanger. 19. Heat is supplied, then split into two paths, a5 and a6, via a low-temperature three-way control valve 23. The supercritical carbon dioxide in path a5 is cooled by heat dissipation from the environment inside the high-pressure precooler 16 before flowing into the low-temperature premixer 26. The supercritical carbon dioxide in path a6 flows directly into the low-temperature premixer 26. The supercritical carbon dioxide in paths a5 and a6 mix in the low-temperature premixer 26, then enters the secondary main compressor 10 and is compressed to a circulating high pressure. It then enters the cold section of the low-temperature regenerator 14, absorbs heat, and heats up. There, it mixes with the supercritical carbon dioxide in path a4 in the high-temperature regenerator premixer 27, and so on. After absorbing heat and heating up in the cold section of the high-temperature regenerator 13 and the cold section of the first-stage molten salt supercritical carbon dioxide printed plate heat exchanger 5, the supercritical carbon dioxide from the outlet of the high-pressure turbine 1 outputs power to generate electricity. After absorbing heat and heating up in the cold section of the second-stage molten salt supercritical carbon dioxide printed plate heat exchanger 6, the supercritical carbon dioxide from the outlet of the high-pressure turbine 1 again enters the low-pressure turbine 3 to output power to generate electricity. The heating hot water is divided into two streams. One stream enters the high-pressure first-stage heating network heat exchanger 18 and the high-pressure second-stage heating network heat exchanger 19 in sequence to absorb heat, and the other stream enters the cold end of the low-pressure heating network heat exchanger 17 to absorb heat. After absorbing heat, the two streams of hot water are mixed in the hot water mixer 28 and then used for heating.

[0013] During non-heating season operation, the control valve 29 of the low-pressure primary heat exchanger and the control valve 31 of the high-pressure secondary heat exchanger are closed, while the bypass valve 30 of the low-pressure primary heat exchanger and the bypass valve 32 of the high-pressure secondary heat exchanger are open. Simultaneously, in the outlet of the high-pressure diversion three-way valve 22, passage a3 is closed and passage a4 is open. The a1 passage of the low-pressure diversion three-way valve 21 no longer supplies heat through the low-pressure heat exchanger 17, but directly enters the low-pressure precooler 15. After compression by the primary main compressor 9, it no longer supplies heat through the high-pressure secondary heat exchanger 19, but directly enters the low-temperature pre-three-way valve 23. The a3 passage of the high-pressure diversion three-way valve 22 is closed, no longer supplies heat through the high-pressure primary heat exchanger 18, and directly enters the secondary recompressor 12 for compression. The hot water supply path is completely cut off. Other processes are the same as the system operation mode during the heating season.

[0014] During the heating season, when heating is the primary function, the opening of the two outlets of the low-pressure diversion three-way valve 21 is adjusted to increase the outlet opening connected to passage a2 and decrease the outlet opening connected to passage a1. Simultaneously, the opening of the two outlets of the high-pressure diversion three-way valve 22 is adjusted to increase the outlet opening connected to passage a3 and decrease the outlet opening connected to passage a4. By adjusting the outlet openings of the two three-way valves, the overall flow rate of supercritical carbon dioxide through the cold end of the low-temperature regenerator 14 remains constant, while the flow rate of supercritical carbon dioxide through the high-pressure primary heat exchanger 18 is increased, and the flow rate of supercritical carbon dioxide through the low-pressure heat exchanger 17 is decreased, thereby increasing the heating capacity.

[0015] During the heating season, when power generation is the primary operation, the opening of the two outlets of the low-pressure diversion three-way valve 21 is adjusted to increase the outlet opening connected to passage a1 and decrease the outlet opening connected to passage a2. At the same time, the opening of the two outlets of the high-pressure diversion three-way valve 22 is adjusted to increase the outlet opening connected to passage a4 and decrease the outlet opening connected to passage a3. By adjusting the outlet openings of the two three-way valves, the overall supercritical carbon dioxide flow rate in the secondary heating pre-mixer 25 remains unchanged, the supercritical carbon dioxide flow rate through the primary re-compressor 11 is reduced, and the supercritical carbon dioxide flow rate through the primary main compressor 9 is increased, thereby achieving the goal of reducing the power consumption of compressing supercritical carbon dioxide and increasing power generation.

[0016] When the external ambient temperature rises, in order to ensure the efficient operation of the cogeneration unit, the opening of the two outlets of the low-temperature three-way control valve 23 is adjusted, increasing the outlet opening of the a6 passage and decreasing the outlet opening of the a5 passage, thereby increasing the inlet temperature of the secondary main compressor 10.

[0017] When the minimum temperature difference point inside the low-temperature regenerator 14 appears in the middle part of the low-temperature regenerator, in order to prevent thermal damage caused by the excessively small temperature difference in the low-temperature regenerator, the opening of the outlet of the low-pressure diversion three-way valve 21 connected to the a1 passage and the outlet of the high-pressure diversion three-way valve 22 connected to the a3 passage are increased. Overall, the supercritical carbon dioxide flow rate in the pre-mixer 25 of the secondary heating system is increased, so as to increase the supercritical carbon dioxide flow rate on the cold side of the low-temperature regenerator 14, balance the heat capacity difference at both ends, and transfer the minimum temperature difference point from the middle part of the low-temperature regenerator 14 to the inlet.

[0018] Compared with existing technologies, the present invention has the following advantages:

[0019] The present invention discloses a secondary supercritical carbon dioxide splitting system for solar cogeneration, which is based on a recompressed supercritical carbon dioxide broiler cycle. It further reduces the power consumption of compressing supercritical carbon dioxide by using a main compressor for staged compression and interstage cooling. Thermodynamic properties of supercritical carbon dioxide under different pressure and temperature conditions were analyzed. By flexibly adjusting the supercritical carbon dioxide flow rate through the low-pressure heat exchanger 17 and the high-pressure primary heat exchanger 18, and utilizing the characteristic that the specific heat capacity of carbon dioxide in the 8-10 MPa, 60-100℃ temperature range is generally more than twice that in the 7-8 MPa, 60-100℃ temperature range, the unit's heating capacity can be flexibly adjusted. Simultaneously, a low temperature difference in the heating network heat exchange can be maintained, further utilizing waste heat lost to the environment in the original cycle and increasing energy utilization efficiency. This ensures that the supercritical carbon dioxide flow rate on the cold side of the low-temperature regenerator 14 is within the high-efficiency range, preventing pinch-point problems in the cold-side low-temperature regenerator 14. This comprehensive adjustment strategy allows for highly flexible adjustment of the heating capacity, truly decoupling the unit's heating and power generation. The ratio of heating capacity per unit of working fluid to power generation can be flexibly adjusted between 30% and 90%, with minimal impact on the unit's power generation efficiency. Therefore, a high overall efficiency can be maintained simultaneously. Efficiency; When the ambient temperature changes, such as -10℃ in winter and 30℃ in summer, the opening of the two outlets of the low-temperature three-way control valve 23 can be adjusted to adjust the inlet temperature of the secondary main compressor 10 and reduce the power consumption of supercritical carbon dioxide compression in the secondary main compressor 10; Overall, the unit can maintain efficient operation under different heating and power supply requirements and different ambient temperatures; The main equipment of the system can be shared in both heating and non-heating seasons, and the process flow is switched only by the opening and closing of four control valves. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a secondary supercritical carbon dioxide diversion system and its operation method for solar cogeneration according to the present invention.

[0021] Among them, 1 is a high-pressure turbine, 2 is the first generator, 3 is a low-pressure turbine, 4 is the second generator, 5 is a first-stage molten salt supercritical carbon dioxide printed plate heat exchanger, 6 is a second-stage molten salt supercritical carbon dioxide printed plate heat exchanger, 7 is a molten salt high-temperature heat storage tank, 8 is a molten salt low-temperature heat storage tank, 9 is a first-stage main compressor, 10 is a second-stage main compressor, 11 is a first-stage recompressor, 12 is a second-stage recompressor, 13 is a high-temperature regenerator, 14 is a low-temperature regenerator, 17 is a low-pressure heat network heat exchanger, 18 is a high-pressure first-stage heat network heat exchanger, and 19 is a high-pressure second-stage heat exchanger. 15 is a low-pressure precooler, 16 is a high-pressure precooler, 20 is a molten salt three-way valve, 21 is a low-pressure diversion three-way valve, 22 is a high-pressure diversion three-way valve, 23 is a low-temperature control valve, 24 is a low-temperature molten salt mixer, 25 is a secondary heating premixer, 26 is a low-temperature premixer, 27 is a high-temperature regeneration premixer, 28 is a hot water supply mixer, 29 is a low-pressure primary heat exchanger control valve, 30 is a low-pressure primary heat exchanger bypass valve, 31 is a high-pressure secondary heat exchanger control valve, and 32 is a high-pressure secondary heat exchanger bypass valve. Detailed Implementation The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0022] See Figure 1 This invention discloses a secondary supercritical carbon dioxide system for solar cogeneration, comprising a high-pressure turbine 1, a first generator 2, a low-pressure turbine 3, a second generator 4, a first-stage molten salt supercritical carbon dioxide printed plate heat exchanger 5, a second-stage molten salt supercritical carbon dioxide printed plate heat exchanger 6, a molten salt high-temperature heat storage tank 7, a molten salt low-temperature heat storage tank 8, a molten salt three-way valve 20, a low-temperature molten salt mixer 24, a high-temperature regenerator 13, a low-temperature regenerator 14, a first-stage main compressor 9, a second-stage main compressor 10, a first-stage recompressor 11, and a second-stage recompressor. Compressor 12, Low-pressure heat exchanger 17, High-pressure primary heat exchanger 18, High-pressure secondary heat exchanger 19, Low-pressure precooler 15, High-pressure precooler 16, Low-pressure diversion three-way valve 21, High-pressure diversion three-way valve 22, Low-temperature control valve 23, Secondary heating premixer 25, Low-temperature premixer 26, High-temperature regeneration premixer 27, Hot water supply mixer 28, Low-pressure primary heat exchanger control valve 29, Low-pressure primary heat exchanger bypass valve 30, High-pressure secondary heat exchanger control valve 31, High-pressure secondary heat exchanger bypass valve 32.

[0023] The connection relationships of the above components are as follows:

[0024] The outlet of the molten salt high-temperature heat storage tank 7 is connected to the inlet of the molten salt three-way valve 20. One outlet of the molten salt three-way valve 20 leads to the hot-side inlet of the primary molten salt-supercritical carbon dioxide printed plate heat exchanger 5, and the other outlet leads to the hot-side inlet of the secondary molten salt-supercritical carbon dioxide printed plate heat exchanger 6. The hot-side outlets of the molten salt-supercritical carbon dioxide printed plate heat exchanger 5 and the molten salt-supercritical carbon dioxide printed plate heat exchanger 6 are simultaneously connected to the inlet of the low-temperature molten salt mixer 24. The outlet of the low-temperature molten salt mixer 24 is connected to the low-temperature molten salt storage tank 8. The cold-side outlet of the molten salt-supercritical carbon dioxide printed plate heat exchanger 5 is connected to the inlet of the high-pressure turbine 1, and the outlet of the high-pressure turbine 1 is connected to the inlet of the secondary molten salt-supercritical carbon dioxide printed plate heat exchanger 6. The cold-side inlet of the secondary molten salt supercritical carbon dioxide printed plate heat exchanger 6 is connected to the cold-side outlet of the secondary molten salt supercritical carbon dioxide printed plate heat exchanger 6, which is connected to the inlet of the low-pressure turbine 3. The outlet of the low-pressure turbine 3 is connected to the hot-side inlet of the high-temperature regenerator 13, and the hot-side outlet of the high-temperature regenerator 13 is connected to the hot-side inlet of the low-temperature regenerator 14. The cold-side outlet of the high-temperature regenerator 13 is connected to the cold-side inlet of the primary molten salt supercritical carbon dioxide printed plate heat exchanger 5, and the cold-side inlet of the high-temperature regenerator 13 is connected to the outlet of the high-temperature regenerator pre-mixer 27. The hot-side outlet of the low-temperature regenerator 14 is connected to the low-pressure diversion three-way valve 21. The outlet of the low-pressure diversion three-way valve 21 is divided into two paths: one path a2 is directly connected to the primary recompressor 11, and the other path a1 is connected in parallel to the low-pressure primary heating network. The heat exchanger control valve 29 and the low-pressure primary heat exchanger bypass valve 30 are connected. The primary heat exchanger control valve 29 is connected to the hot end inlet of the low-pressure heat exchanger 17. The outlet of the low-pressure primary heat exchanger bypass valve 30 and the hot end outlet of the low-pressure heat exchanger 17 are connected to the low-pressure precooler 15, which is connected to the primary main compressor 9. The outlet of the primary re-compressor 11 is connected to the high-pressure diversion three-way valve 22. One outlet a4 of the high-pressure diversion three-way valve 22 is directly connected to the secondary re-compressor 12, and the other outlet a3 passes through the high-pressure primary heat exchanger 18 and merges with the outlet of the primary compressor 9 before connecting to the secondary preheating mixer 25. The outlet of the secondary preheating mixer 25 is connected in parallel to the high-pressure secondary heat exchanger control valve 31 and the high-pressure secondary heat exchanger. Heat exchanger bypass valve 32; the outlet of high-pressure secondary heat exchanger control valve 31 is connected to the hot end inlet of high-pressure secondary heat exchanger 19, the outlet of high-pressure secondary heat exchanger bypass valve 32 and the hot end outlet of high-pressure secondary heat exchanger 19 are connected to low-temperature three-way control valve 23; the first outlet a6 of low-temperature three-way control valve 23 is directly connected to low-temperature pre-mixer 26, and the second outlet a5 is connected to the first outlet in low-temperature pre-mixer 26 after passing through high-pressure precooler 16; the outlet of low-temperature pre-mixer 26 is connected to the inlet of secondary main compressor 10, the outlet of secondary main compressor 10 is connected to the cold side inlet of low-temperature regenerator 14, and the cold side outlet of low-temperature regenerator 14 and the outlet of secondary re-compressor 12 are simultaneously connected to high-temperature regenerator pre-mixer 27 to complete one cycle;The outlet of the cold section of the high-pressure primary heat exchanger 18 connects to the inlet of the cold section of the high-pressure secondary heat exchanger 19. The outlet of the cold section of the low-pressure heat exchanger 17 merges with the outlet of the cold section of the high-pressure secondary heat exchanger 19 and connects to the hot water mixer 28.

[0025] The preferred rotating mechanical connection method of the present invention is as follows: the high-pressure turbine 1, the first generator 2, the first-stage main compressor 9, and the first-stage re-compressor 11 are arranged coaxially; the low-pressure turbine 3, the second generator 4, the second-stage main compressor 10, and the second-stage re-compressor 12 are arranged coaxially. Example:

[0026] During the heating season, the supercritical carbon dioxide at the hot end outlet of the low-temperature regenerator 14 is divided into two paths via the low-pressure diversion three-way valve 21. Figure 1In the a1 and a2 pathways shown, the bypass valve 30 of the low-pressure primary heat exchanger is closed, and the control valve 29 of the low-pressure primary heat exchanger is opened. Supercritical carbon dioxide in pathway a1 sequentially enters the low-pressure heat exchanger 17 for heating, and the low-pressure precooler 15 dissipates heat to the environment to cool to room temperature. After compression in the primary main compressor 9, it flows into the secondary pre-heating mixer 25. In the other pathway a2, supercritical carbon dioxide directly enters the primary re-compressor 11 for compression, and then enters the high-pressure diversion three-way valve 22, where it is divided into two paths, a3 and a4. Supercritical carbon dioxide in pathway a4... Carbon is compressed to circulating high pressure by the secondary recompressor 12 and flows into the high-temperature regenerator pre-mixer 27. The bypass valve 32 of the high-pressure secondary heat exchanger is closed, and the control valve 31 of the high-pressure secondary heat exchanger is opened. The supercritical carbon dioxide in path a3 enters the high-pressure primary heat exchanger 18 and flows into the secondary heating pre-mixer 25. The bypass valve 32 of the high-pressure secondary heat exchanger is closed. The supercritical carbon dioxide in paths a1 and a3 is mixed in the secondary heating pre-mixer 25 and then enters the high-pressure secondary heat exchanger 19 for heating. Afterward, it is divided into two paths by the low-temperature control valve 23. A5 and A6; the supercritical carbon dioxide in the A5 pathway is cooled by heat dissipation from the environment inside the high-pressure precooler 16 before flowing into the low-temperature premixer 26, while the supercritical carbon dioxide in the A6 pathway is directly introduced into the low-temperature premixer 26. After the supercritical carbon dioxide in the A5 and A6 pathways is mixed in the low-temperature premixer 26, it enters the secondary main compressor 10 and is compressed to the circulating high pressure. After entering the cold section of the low-temperature regenerator 14 to absorb heat and rise in temperature, it mixes with the supercritical carbon dioxide in the A4 pathway in the high-temperature regenerator premixer 27, and then enters the cold section of the high-temperature regenerator 13. After the cold section of the first-stage molten salt supercritical carbon dioxide printed plate heat exchanger 5 absorbs heat and heats up, it enters the high-pressure turbine 1 to output power for electricity generation. The supercritical carbon dioxide at the outlet of the high-pressure turbine 1 absorbs heat and heats up in the cold section of the second-stage molten salt supercritical carbon dioxide printed plate heat exchanger 6, and then enters the low-pressure turbine 3 to output power for electricity generation. The heating hot water is divided into two streams. One stream enters the high-pressure first-stage heating network heat exchanger 18 and the high-pressure second-stage heating network heat exchanger 19 in sequence to absorb heat, and the other stream enters the cold end of the low-pressure heating network heat exchanger 17 to absorb heat. After the two streams of hot water absorb heat, they are mixed in the hot water mixer 28 and then used for heating.

[0027] When the system operates under the following conditions: ambient temperature 18℃, circulating low temperature 32℃, circulating high temperature 710℃, circulating high pressure 25MPa, and circulating low pressure 7.6MPa, heating demand increases. Therefore, the outlet opening of the connecting a2 passage is increased, and the outlet opening of the connecting a1 passage is decreased. This increases the supercritical carbon dioxide flow rate through the a2 passage from 60% to 89%, and decreases the supercritical carbon dioxide flow rate through the a1 passage from 40% to 11%. Simultaneously, the opening of the two outlets of the high-pressure diverting three-way valve 22 is adjusted to increase the outlet opening of the connecting a3 passage and decrease the outlet opening of the connecting a1 passage. The outlet opening of passage 4 increases the supercritical carbon dioxide flow rate through passage a3 from 40% to 60%, and decreases the supercritical carbon dioxide flow rate through passage a1 from 60% to 40%. By adjusting the outlet opening of the two three-way valves, the overall supercritical carbon dioxide flow rate through the cold end of the low-temperature regenerator 14 remains unchanged, accounting for 70% of the total supercritical carbon dioxide flow rate. This increases the supercritical carbon dioxide flow rate through the high-pressure primary heat exchanger 18 and decreases the supercritical carbon dioxide flow rate through the low-pressure heat exchanger 17, thereby increasing the heat supply.

[0028] When the system operates under the conditions of a circulating high temperature of 710℃, a circulating high pressure of 25MPa, and a circulating low pressure of 7.6MPa, and the ambient temperature rises from 18℃ to 30℃ while the circulating low temperature needs to be increased from 32℃ to 45℃, in order to ensure the efficient operation of the cogeneration unit, the opening of the two outlets of the low-temperature three-way control valve 23 is adjusted. The outlet opening of the a6 passage is increased, and the outlet opening of the a5 passage is decreased. This increases the inlet temperature of the secondary main compressor 10 from 45℃ to 60℃, which can reduce the compression factor on the carbon dioxide compression path and further reduce the compression power consumption of the secondary main compressor 10.

[0029] To prevent heat exchange from deteriorating due to excessively small temperature differences in the low-temperature regenerator, the minimum temperature difference point is set at the inlet or outlet section in engineering practice. When the minimum temperature difference point inside the low-temperature regenerator 14 appears in the middle section, the opening of the outlet of the low-pressure diversion three-way valve 21 connecting to the a1 passage and the outlet of the high-pressure diversion three-way valve 22 connecting to the a3 passage are increased simultaneously. Overall, the supercritical carbon dioxide flow rate in the pre-mixer 25 of the secondary heating system is increased to increase the supercritical carbon dioxide flow rate on the cold side of the low-temperature regenerator 14, balance the product of specific heat capacity and mass flow rate at both ends, and shift the minimum temperature difference point from the middle section of the low-temperature regenerator 14 to the inlet.

[0030] During non-heating season operation, the control valve 29 of the low-pressure primary heat exchanger and the control valve 31 of the high-pressure secondary heat exchanger are closed, while the bypass valve 30 of the low-pressure primary heat exchanger and the bypass valve 32 of the high-pressure secondary heat exchanger are open. Simultaneously, in the outlet of the high-pressure diversion three-way valve 22, passage a3 is closed and passage a4 is open. The low-pressure diversion three-way valve a1 passage no longer supplies heat through the low-pressure heat exchanger but directly to the low-pressure precooler 15. After compression by the primary main compressor 9, it no longer supplies heat through the high-pressure secondary heat exchanger but directly to the low-temperature pre-three-way valve 23. The high-pressure diversion three-way valve a3 passage is closed, no longer supplies heat through the high-pressure primary heat exchanger, and directly enters the secondary re-compression compressor. The hot water supply path is completely cut off. Other processes are the same as the system operation mode during the heating season.

[0031] The methods described above for controlling the temperature and pressure at the inlet and outlet of valves and equipment are commonly used in engineering, and therefore will not be described in detail.

[0032] The above examples, under given ambient temperature and system maximum operating temperature conditions, provide specific opening control standards for several three-way valves, and elaborate on the purpose, technical solution, and implementation method of the present invention. However, it should be understood that the description of the above examples should not be considered as a limitation of the present invention. Various modifications and equivalent substitutions to the present invention by those who have read the above should be included within the scope of protection of the present invention, which is defined by the appended claims.

Claims

1. A secondary supercritical carbon dioxide diversion system for solar cogeneration, characterized in that: Includes a high-pressure turbine (1), a first generator (2), a low-pressure turbine (3), a second generator (4), a first-stage molten salt supercritical carbon dioxide printed plate heat exchanger (5), a second-stage molten salt supercritical carbon dioxide printed plate heat exchanger (6), a high-temperature molten salt storage tank (7), a low-temperature molten salt storage tank (8), a first-stage main compressor (9), a second-stage main compressor (10), a first-stage recompressor (11), a second-stage recompressor (12), a high-temperature regenerator (13), a low-temperature regenerator (14), a low-pressure precooler (15), a high-pressure precooler (16), a low-pressure heat network heat exchanger (17), and a high-pressure first-stage heat network heat exchanger. (18) High-pressure secondary heat exchanger; (19) Molten salt three-way valve; (20) Low-pressure diversion three-way valve; (21) High-pressure diversion three-way valve; (22) Low-temperature three-way control valve; (23) Low-temperature molten salt mixer; (24) Secondary heating pre-mixer; (25) Low-temperature pre-mixer; (26) High-temperature regeneration pre-mixer; (27) Hot water mixer; (28) Low-pressure primary heat exchanger control valve; (29) Low-pressure primary heat exchanger bypass valve; (30) High-pressure secondary heat exchanger control valve; (31) High-pressure secondary heat exchanger bypass valve; (32) The connection relationships of the above components are as follows: The outlet of the molten salt high-temperature heat storage tank (7) is connected to the inlet of the molten salt three-way valve (20). One outlet of the molten salt three-way valve (20) leads to the hot-side inlet of the first-stage molten salt-supercritical carbon dioxide printed plate heat exchanger (5), and the other outlet leads to the hot-side inlet of the second-stage molten salt-supercritical carbon dioxide printed plate heat exchanger (6). The hot-side outlet of the molten salt-supercritical carbon dioxide printed plate heat exchanger (5) and the hot-side outlet of the molten salt-supercritical carbon dioxide printed plate heat exchanger (6) are simultaneously connected to the inlet of the low-temperature molten salt mixer (24). The outlet of the low-temperature molten salt mixer (24) is connected to the low-temperature molten salt storage tank (8). The cold-side outlet of the molten salt-supercritical carbon dioxide printed plate heat exchanger (5) is connected to the inlet of the high-pressure turbine (1). The outlet of the flat (1) is connected to the cold side inlet of the secondary molten salt supercritical carbon dioxide printed plate heat exchanger (6), and the cold side outlet of the secondary molten salt supercritical carbon dioxide printed plate heat exchanger (6) is connected to the inlet of the low-pressure turbine (3); the outlet of the low-pressure turbine (3) is connected to the hot side inlet of the high-temperature regenerator (13), the hot side outlet of the high-temperature regenerator (13) is connected to the hot side inlet of the low-temperature regenerator (14), the cold side outlet of the high-temperature regenerator (13) is connected to the cold side inlet of the primary molten salt supercritical carbon dioxide printed plate heat exchanger (5), and the cold side inlet of the high-temperature regenerator (13) is connected to the outlet of the high-temperature regenerator pre-mixer (27); the hot side outlet of the low-temperature regenerator (14) is connected to the low-pressure diversion three-way valve (21), and the low-pressure diversion three-way valve... The outlet of valve (21) is divided into two paths. One path, a2, is directly connected to the first-stage recompressor (11). The other path, a1, is connected in parallel to the control valve (29) and bypass valve (30) of the low-pressure first-stage heat exchanger. The control valve (29) of the first-stage heat exchanger is connected to the hot end inlet of the low-pressure heat exchanger (17). The outlet of the bypass valve (30) and the hot end outlet of the low-pressure heat exchanger (17) are connected to the low-pressure precooler (15) and connected to the first-stage main compressor (9). The outlet of the first-stage recompressor (11) is connected to the high-pressure diversion three-way valve (22). One path, a4, of the outlet of the high-pressure diversion three-way valve (22) is directly connected to the second-stage recompressor (12). The other path, a3, is connected to the high-pressure first-stage heat exchanger (11). After 8), it merges with the outlet of the first-stage compressor (9) and is connected to the second-stage preheating mixer (25). The outlet of the second-stage preheating mixer (25) is connected in parallel to the high-pressure second-stage heat exchanger control valve (31) and the high-pressure second-stage heat exchanger bypass valve (32). The outlet of the high-pressure second-stage heat exchanger control valve (31) is connected to the hot end inlet of the high-pressure second-stage heat exchanger (19). The outlet of the high-pressure second-stage heat exchanger bypass valve (32) and the hot end outlet of the high-pressure second-stage heat exchanger (19) are connected together to the low-temperature three-way control valve (23). The first outlet a6 of the low-temperature three-way control valve (23) is directly connected to the low-temperature premixer (26). The second outlet a5 passes through the high-pressure precooler (16) and merges with the first outlet in the low-temperature premixer (26).The outlet of the low-temperature pre-mixer (26) is connected to the inlet of the secondary main compressor (10), the outlet of the secondary main compressor (10) is connected to the cold side inlet of the low-temperature regenerator (14), and the cold side outlet of the low-temperature regenerator (14) and the outlet of the secondary re-compressor (12) are simultaneously connected to the high-temperature regenerator pre-mixer (27) to complete one cycle; the cold section outlet of the high-pressure primary heat exchanger (18) is connected to the cold section inlet of the high-pressure secondary heat exchanger (19), and the cold section outlet of the low-pressure heat exchanger (17) and the cold section outlet of the high-pressure secondary heat exchanger (19) are connected to the hot water mixer (28); During the heating season: the control valve (29) of the low-pressure primary heat exchanger and the control valve (31) of the high-pressure secondary heat exchanger are open, and the bypass valve (30) of the low-pressure primary heat exchanger and the bypass valve (32) of the high-pressure secondary heat exchanger are closed. During non-heating season operation: the control valve (29) of the low-pressure primary heat exchanger and the control valve (31) of the high-pressure secondary heat exchanger are closed, the bypass valve (30) of the low-pressure primary heat exchanger and the bypass valve (32) of the high-pressure secondary heat exchanger are open, and at the same time, in the outlet of the high-pressure diversion three-way valve (22), the a3 passage is closed and the a4 passage is open.

2. The secondary supercritical carbon dioxide diversion system for solar cogeneration according to claim 1, characterized in that: The high-pressure turbine (1), the first generator (2), the first-stage main compressor (9), and the first-stage re-compressor (11) are arranged coaxially; the low-pressure turbine (3), the second generator (4), the second-stage main compressor (10), and the second-stage re-compressor (12) are arranged coaxially.

3. A secondary supercritical carbon dioxide diversion system for solar cogeneration according to claim 1, characterized in that: The method for controlling the maximum temperature of supercritical carbon dioxide is as follows: control the opening of the outlets on both sides of the molten salt three-way valve (20), adjust the flow rate of high-temperature molten salt flowing through the first-stage molten salt supercritical carbon dioxide printed plate heat exchanger (5) and the second-stage molten salt supercritical carbon dioxide printed plate heat exchanger (6) respectively, further control the heat exchange of the first-stage molten salt supercritical carbon dioxide printed plate heat exchanger (5) and the second-stage molten salt supercritical carbon dioxide printed plate heat exchanger (6), and finally achieve the purpose of controlling the supercritical carbon dioxide temperature at the outlet of the first-stage molten salt supercritical carbon dioxide printed plate heat exchanger (5) and the outlet of the second-stage molten salt supercritical carbon dioxide printed plate heat exchanger (6).

4. A secondary supercritical carbon dioxide diversion system for solar cogeneration according to claim 1, characterized in that: The heat supply control method is as follows: control the opening of the two outlets of the low-pressure diversion three-way valve (21) to adjust the supercritical carbon dioxide flow rate that directly enters the first-stage recompressor (11) for compression and sequentially passes through the low-pressure heat network heat exchanger (17) for heat supply, the low-pressure precooler (15) for heat dissipation to the environment, the first-stage main compressor (9) for compression, the high-pressure second-stage heat network heat exchanger (19) for heat supply, and the second-stage main compressor (10) for compression; control the opening of the two outlets of the high-pressure diversion three-way valve (22) to adjust the supercritical carbon dioxide flow rate that directly enters the second-stage recompressor (12) for compression and sequentially passes through the high-pressure first-stage heat network heat exchanger (18) for heat supply, the high-pressure second-stage heat network heat exchanger (19) for heat supply, and the second-stage main compressor (10) for compression, thereby controlling the heat supply.

5. A secondary supercritical carbon dioxide diversion system for solar cogeneration according to claim 1, characterized in that: The solution to the pinch problem of the low-temperature regenerator is to comprehensively control the outlet opening of the low-pressure diversion three-way valve (21) and the high-pressure diversion three-way valve (22) directly to the first-stage re-compressor (11) and the second-stage re-compressor (12), control the flow rate of high-pressure supercritical carbon dioxide on the cold side of the low-temperature regenerator (14), and reduce the difference in heat capacity of supercritical carbon dioxide at the cold and hot ends in the low-temperature regenerator (14).

6. A secondary supercritical carbon dioxide diversion system for solar cogeneration according to claim 1, characterized in that: The method for controlling the inlet temperature of the secondary main compressor (10) is as follows: control the opening of the two outlets of the low temperature control valve (23) to reduce or increase the supercritical carbon dioxide flow of the high pressure precooler (16) to achieve the purpose of reducing or increasing the inlet temperature of the secondary main compressor (10).

7. The method for operating a secondary supercritical carbon dioxide splitting system for solar cogeneration as described in any one of claims 1 to 6, characterized in that: During the heating season, the supercritical carbon dioxide at the hot end outlet of the low-temperature regenerator (14) is divided into two paths, a1 and a2, through the low-pressure diversion three-way valve (21). The bypass valve (30) of the low-pressure primary heat exchanger is closed, and the control valve (29) of the low-pressure primary heat exchanger is opened. The supercritical carbon dioxide in path a1 first enters the low-pressure heat exchanger (17) for heating, then dissipates heat to the environment through the low-pressure precooler (15), and is compressed by the primary main compressor (9) before flowing into the secondary preheating mixer (25). The supercritical carbon dioxide in the other path a2 directly enters the primary recompressor (11) for compression and then enters the high-pressure diversion three-way valve (21). The three-way valve (22) is divided into two paths, a3 and a4. The supercritical carbon dioxide in the a4 path is compressed to the circulating high pressure by the secondary recompressor (12) and flows into the high-temperature reheat pre-mixer (27). The high-pressure secondary heat exchanger bypass valve (32) is closed, and the high-pressure secondary heat exchanger control valve (31) is opened. The supercritical carbon dioxide in the a3 path enters the high-pressure primary heat exchanger (18) and flows into the secondary heating pre-mixer (25). The high-pressure secondary heat exchanger bypass valve (32) is closed, and the supercritical carbon dioxide in the a1 and a3 paths is mixed in the secondary heating pre-mixer (25) and then enters the high-pressure secondary heat exchanger. The heat is supplied by the heat exchanger (19), and then divided into two paths, a5 and a6, by the low-temperature three-way control valve (23). The supercritical carbon dioxide in the a5 path is cooled by the heat dissipation of the environment inside the high-pressure precooler (16) and then flows into the low-temperature premixer (26). The supercritical carbon dioxide in the a6 path is directly fed into the low-temperature premixer (26). After the supercritical carbon dioxide in the a5 and a6 paths is mixed in the low-temperature premixer (26), it enters the secondary main compressor (10) and is compressed to the circulating high pressure. After absorbing heat and rising in the cold section of the low-temperature regenerator (14), it is mixed with the supercritical carbon dioxide in the a4 path in the high-temperature regenerator premixer (27). The heat is absorbed and heated in the high-temperature regenerator (13) and the first-stage molten salt supercritical carbon dioxide printed plate heat exchanger (5) in sequence, and then enters the high-pressure turbine (1) to generate electricity. The supercritical carbon dioxide at the outlet of the high-pressure turbine (1) is heated in the second-stage molten salt supercritical carbon dioxide printed plate heat exchanger (6) in sequence, and then enters the low-pressure turbine (3) again to generate electricity. The hot water for heating is divided into two streams. One stream enters the high-pressure first-stage heat exchanger (18) and the high-pressure second-stage heat exchanger (19) in sequence to absorb heat, and the other stream enters the low-pressure heat exchanger (17) to absorb heat. After the two streams of hot water absorb heat, they are mixed in the hot water mixer (28) and then used for heating. During non-heating season operation, the control valve (29) of the low-pressure primary heat exchanger and the control valve (31) of the high-pressure secondary heat exchanger are closed, while the bypass valve (30) of the low-pressure primary heat exchanger and the bypass valve (32) of the high-pressure secondary heat exchanger are open. At the same time, in the outlet of the high-pressure diversion three-way valve (22), the a3 passage is closed and the a4 passage is open. The a1 passage of the low-pressure diversion three-way valve (21) no longer passes through the low-pressure heat exchanger (17) for heating, but is directly connected to the low-pressure precooler (15). After compression by the primary main compressor (9), it no longer passes through the high-pressure secondary heat exchanger (19) for heating, but is directly connected to the low-temperature pre-three-way valve (23). The a3 passage of the high-pressure diversion three-way valve (22) is closed, and it no longer passes through the high-pressure primary heat exchanger (18) for heating, but is directly connected to the secondary recompressor (12) for compression. The hot water supply path is completely cut off. The other processes are the same as the system operation mode during the heating season.

8. The operating method according to claim 7, characterized in that: During the heating season, when the heating is the main function, the opening of the two outlets of the low-pressure diversion three-way valve (21) is adjusted to increase the opening of the outlet connected to the a2 passage and decrease the opening of the outlet connected to the a1 passage; at the same time, the opening of the two outlets of the high-pressure diversion three-way valve (22) is adjusted to increase the opening of the outlet connected to the a3 passage and decrease the opening of the outlet connected to the a4 passage; by adjusting the opening of the two three-way valves, the supercritical carbon dioxide flow rate through the cold end of the low-temperature regenerator (14) remains unchanged, the supercritical carbon dioxide flow rate through the high-pressure primary heat exchanger (18) is increased, and the supercritical carbon dioxide flow rate through the low-pressure heat exchanger (17) is decreased, thereby achieving the purpose of increasing the heating supply. During the heating season, when the main operation is power generation, the opening of the two outlets of the low-pressure diversion three-way valve (21) is adjusted to increase the opening of the outlet connected to the a1 passage and decrease the opening of the outlet connected to the a2 passage; at the same time, the opening of the two outlets of the high-pressure diversion three-way valve (22) is adjusted to increase the opening of the outlet connected to the a4 passage and decrease the opening of the outlet connected to the a3 passage; by adjusting the opening of the two three-way valves, the supercritical carbon dioxide flow rate in the secondary heating pre-mixer (25) remains unchanged, the supercritical carbon dioxide flow rate through the primary re-compressor (11) is reduced, and the supercritical carbon dioxide flow rate through the primary main compressor (9) is increased, thereby achieving the purpose of reducing the power consumption of compressing supercritical carbon dioxide and increasing power generation.

9. The operating method according to claim 7, characterized in that: When the external ambient temperature rises, in order to ensure the efficient operation of the cogeneration unit, the opening of the two outlets of the low temperature three-way control valve (23) is adjusted, the outlet opening of the a6 passage is increased, and the outlet opening of the a5 passage is decreased, so as to increase the inlet temperature of the secondary main compressor (10).

10. The operating method according to claim 7, characterized in that: When the minimum temperature difference point inside the low-temperature regenerator (14) appears in the middle part of the low-temperature regenerator, in order to prevent thermal damage caused by the small temperature difference of the low-temperature regenerator, the opening of the outlet of the low-pressure diversion three-way valve (21) connected to the a1 passage and the outlet of the high-pressure diversion three-way valve (22) connected to the a3 passage are increased. Overall, the supercritical carbon dioxide flow rate in the premixer (25) before secondary heating is increased, so as to increase the supercritical carbon dioxide flow rate on the cold side of the low-temperature regenerator (14), balance the heat capacity difference at both ends, and transfer the minimum temperature difference point from the middle part of the low-temperature regenerator to the inlet.

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