Supercritical carbon dioxide Brayton cycle power generation system and method for recovering waste heat

Abstract

The present invention relates to a power generation system and method, specifically a supercritical carbon dioxide Brayton cycle power generation system and method for recovering waste heat. The present invention includes a heat source system, a supercritical carbon dioxide Brayton cycle system, a piston expansion linear generator waste heat power generation system, and a carbon dioxide pre-cooler; the working fluid side outlet of the heat source system is connected to the working fluid input end of the supercritical carbon dioxide Brayton cycle system; the working fluid side inlet of the heat source system is connected to the working fluid output end of the supercritical carbon dioxide Brayton cycle system; the working fluid circulation loop of the supercritical carbon dioxide Brayton cycle system is connected to the carbon dioxide pre-cooler; the piston expansion linear generator waste heat power generation system includes at least one single-stage piston expansion-linear generator waste heat recovery power generation subsystem. The present invention adopts several stages of piston expansion-linear generator waste heat recovery power generation subsystems to form a cascade waste heat recovery, making the entire system have the advantages of high efficiency, low cost, and a wide working range.

Description

Technical Field

[0001] The present invention relates to a power generation system and method, specifically a supercritical carbon dioxide Brayton cycle power generation system and method for recovering waste heat. Background Art

[0002] Continuously improving the efficiency of generator sets is an eternal theme and goal in the research of the power industry. For traditional energy conversion systems dominated by the steam Rankine cycle, the steam parameters need to be increased to 700 °C to reach an efficiency of about 50%. Therefore, it is necessary to spend high economic and time costs to develop new nickel-based superalloys. To break through the bottleneck of the traditional route, some new concept advanced power systems have received more and more attention. Supercritical working fluids have innate advantages such as high energy density, high heat transfer efficiency, and simple systems, which can significantly improve the thermal power conversion efficiency, reduce the equipment volume, and have high economy.

[0003] Carbon dioxide is considered a promising alternative working fluid due to its suitable critical pressure, stable characteristics, mature physical property research, non-toxicity, and low cost, etc. It can be applied in many advanced heat transfer and energy conversion systems, including new generation nuclear reactors that directly or indirectly utilize the supercritical carbon dioxide Brayton cycle; combined distributed energy supply systems for solar heating, power generation, and refrigeration using the supercritical carbon dioxide cycle, new air conditioners and heat pumps based on the carbon dioxide transcritical compression cycle, and so on. In particular, the supercritical carbon dioxide Brayton cycle coal-fired generator sets that have received extensive attention from many scholars in recent years can reach the efficiency of the conventional steam Rankine cycle at 700 °C within the temperature range of 620 °C, without the need to develop new high-temperature alloys, and have very good application prospects.

[0004] The supercritical CO2 Brayton cycle has also been widely concerned in the fields of solar thermal power generation, nuclear power, ship power, etc., and has become the most likely thermal cycle power generation system to replace the existing steam turbines. However, the supercritical CO2 Brayton cycle still has room for optimization and improvement. Due to the characteristics of the Brayton cycle, the heat release process of the supercritical CO2 Brayton cycle is not an isothermal process but a temperature reduction process, and the theoretical maximum heat release temperature is 80 - 90 °C. If the maximum heat release temperature is higher due to design requirements, it will undoubtedly cause waste if all is directly cooled by the cooling medium. It is entirely possible to recover and generate electricity using it as waste heat.

[0005] At present, there are also some low-temperature waste heat recovery power generation devices, the most common of which is the organic Rankine cycle (ORC) waste heat recovery power generation system. At present, these systems have some problems, making it difficult to promote and apply them on a large scale. The main problem is that due to the low temperature of the heat source, the efficiency of the ORC system is limited. The low efficiency makes the cost of the ORC system very high, and the investment recovery period of the system is very long, so many companies are reluctant to adopt it. The main reason is that, on the one hand, the scale of the waste heat source is often not large, and often encounters heat sources of the order of hundreds of kW or tens of kW. For heat sources of this order, the size of the turbine in the ORC system will become relatively small, otherwise it must use a high-speed motor with low efficiency and high cost. Under such conditions, the efficiency of the ORC turbine is often not high, which further limits the profit space of waste heat recovery power generation. At the same time, even if the turbine is designed at a speed of 3000rpm, the dynamic seal of the rotating machinery is a problem faced by the ORC system. The conventional shaft seal system cannot avoid zero leakage. Once there is a leak, it means the economic loss of the organic working fluid. If a more advanced sealing system is used, such as dry gas seal, the increase in cost will make the system face greater challenges. On the other hand, the current ORC system mostly uses centrifugal or axial flow turbines, and the processing cost of either turbine is very high. At the same time, in order to ensure the normal operation of the turbine, the turbine inlet and outlet need to maintain a relatively high pressure difference. The greater the pressure difference, the greater the expansion ratio of the turbine, the stronger the work capacity of the turbine, and the higher the thermal efficiency of the system. Therefore, the system must use pumps and other equipment for pressurization.

[0006] At the same time, most of the power generation equipment currently used in the field of low-temperature waste heat power generation has high costs and complex systems; in the development and utilization of new energy, rotary generators are obviously more suitable for high-speed motion, and because rotary generators cannot maintain high efficiency under relatively low-frequency motion conditions, ordinary turbines and ordinary generators cannot generate electricity in airflows with very low pressure differences and very low temperature differences, and there is a problem of being unsuitable for the field of low-temperature waste heat power generation. Therefore, the field of waste heat recovery power generation urgently needs a more cost-effective new technology to break the current dilemma faced by the ORC system. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a supercritical CO2 Brayton cycle power generation system and method for recovering waste heat discharged from the low-temperature end of the supercritical CO2 Brayton cycle for power generation, which can effectively improve the power generation power and thermal efficiency of the system, and has a reasonable design and low-cost waste heat recovery supercritical carbon dioxide Brayton cycle power generation system and method.

[0008] The present invention is achieved through the following technical solutions:

[0009] A supercritical carbon dioxide Brayton cycle power generation system for recovering waste heat, comprising a heat source system, a supercritical carbon dioxide Brayton cycle system, a piston expansion linear generator waste heat power generation system, and a carbon dioxide pre-cooler;

[0010] The working fluid side outlet of the heat source system is connected to the working fluid input end of the supercritical carbon dioxide Brayton cycle system; the working fluid side inlet of the heat source system is connected to the working fluid output end of the supercritical carbon dioxide Brayton cycle system;

[0011] A carbon dioxide pre-cooler is connected to the working fluid circulation loop of the supercritical carbon dioxide Brayton cycle system;

[0012] The piston expansion linear generator waste heat power generation system includes at least one single-stage piston expansion-linear generator waste heat recovery power generation subsystem; the single-stage piston expansion-linear generator waste heat recovery power generation subsystem includes a waste heat evaporator, a piston expansion-linear generator system, a condenser, and a liquid reservoir; the evaporation chamber outlet of the waste heat evaporator is connected to the inlet of the piston expansion-linear generator system; the outlet of the piston expansion-linear generator system is connected to the condensation chamber inlet of the condenser; the condensation chamber outlet of the condenser is connected to the circulating working fluid inlet of the liquid reservoir; the circulating working fluid outlet of the liquid reservoir is connected to the evaporation chamber inlet side of the waste heat evaporator;

[0013] The heating chamber inlet and outlet of the waste heat evaporator are respectively used as the CO2 side inlet and outlet of the piston expansion-linear generator waste heat power generation system, and are connected to the working fluid circulation loop of the supercritical carbon dioxide Brayton cycle system and are located on the working fluid inlet side of the carbon dioxide pre-cooler.

[0014] Furthermore, the supercritical carbon dioxide Brayton cycle system includes a turbine power generation system, a high-temperature recuperator, a low-temperature recuperator, a main compressor, and a recompressor;

[0015] The turbine inlet of the turbine power generation system is used as the working fluid input end of the supercritical carbon dioxide Brayton cycle system and is connected to the working fluid side outlet of the heat source system, and the turbine outlet of the turbine power generation system is connected to the heat release side inlet of the high-temperature recuperator;

[0016] The heat release side outlet of the high-temperature recuperator is connected to the heat release side inlet of the low-temperature recuperator, and the heat release side outlet of the low-temperature recuperator is respectively connected to the CO2 side inlet of the piston expansion linear generator waste heat power generation system and the inlet of the recompressor;

[0017] The CO2 side outlet of the piston expansion linear generator waste heat power generation system is connected to the working fluid side inlet of the carbon dioxide pre-cooler; the working fluid side outlet of the carbon dioxide pre-cooler is connected to the inlet of the main compressor; the outlet of the main compressor is connected to the heat absorption side inlet of the low-temperature recuperator; the heat absorption side outlet of the low-temperature recuperator and the outlet of the recompressor are both connected to the heat absorption side inlet of the high-temperature recuperator; the heat absorption side outlet of the high-temperature recuperator is used as the working fluid output end of the supercritical carbon dioxide Brayton cycle system and is connected to the inlet of the heat source system.

[0018] Furthermore, the piston expansion linear generator waste heat power generation system includes several single-stage piston expansion-linear generator waste heat recovery and power generation subsystems connected in series along the CO2 flow direction.

[0019] Even further, the heating chamber inlets and outlets of the waste heat evaporators of several single-stage piston expansion-linear generator waste heat recovery and power generation subsystems are connected in series in turn to form a series structure along the CO2 flow direction; the CO2 side inlet of the waste heat evaporator of the first-stage piston expansion-linear generator waste heat recovery and power generation subsystem and the CO2 side outlet of the waste heat evaporator of the last-stage piston expansion-linear generator waste heat recovery and power generation subsystem are respectively used as the CO2 side inlet and outlet of the piston expansion linear generator waste heat power generation system.

[0020] Furthermore, the piston expansion linear generator waste heat power generation system includes several single-stage piston expansion-linear generator waste heat recovery and power generation subsystems connected in series along the heat transfer direction of the circulating working fluid.

[0021] Even further, the refrigeration chamber of the condenser of the previous-stage piston expansion-linear generator waste heat recovery and power generation subsystem serves as the heating chamber of the waste heat evaporator of the next-stage piston expansion-linear generator waste heat recovery and power generation subsystem, and they are connected in series in turn to form a series structure along the heat transfer direction of the circulating working fluid.

[0022] Furthermore, the liquid level of the liquid circulating working fluid in the condenser is higher than the liquid level of the liquid working fluid in the waste heat evaporator.

[0023] A method for generating electricity by recovering waste heat using a supercritical carbon dioxide Brayton cycle, including,

[0024] While generating electricity using a supercritical carbon dioxide Brayton cycle system with the supercritical carbon dioxide working fluid provided by the heat source system, a piston expansion linear generator waste heat power generation system is used to recover and utilize the waste heat of the carbon dioxide working fluid in the working fluid circulation loop of the supercritical carbon dioxide Brayton cycle system;

[0025] When using the piston expansion linear generator waste heat power generation system to recover and utilize the waste heat of the carbon dioxide working fluid in the working fluid circulation loop of the supercritical carbon dioxide Brayton cycle system,

[0026] The waste heat of the carbon dioxide working fluid heats the circulating working fluid in the evaporation chamber through the heating chamber of the waste heat evaporator, and the carbon dioxide working fluid after releasing heat is connected back to the working fluid circulation loop; the circulating working fluid flows upward and gradually evaporates into a gas during the flow process and enters the expansion chamber of the piston expansion-linear generator system to do work on the piston; the piston drives the linear generator to generate electricity, and the return spring pushes the piston to reset and discharges the circulating working fluid after doing work into the condenser; the circulating working fluid entering the condenser flows downward and is cooled into a liquid state and then enters the liquid storage tank; the liquid circulating working fluid entering the liquid storage tank then enters the waste heat evaporator for cyclic operation.

[0027] Furthermore, when using the piston expansion-linear generator waste heat power generation system to recover and utilize the waste heat of the carbon dioxide working fluid in the working fluid circulation loop of the supercritical carbon dioxide Brayton cycle system,

[0028] The heating chambers of the waste heat evaporators of several single-stage piston expansion-linear generator waste heat recovery and power generation subsystems are connected in series to recover the waste heat of the carbon dioxide working fluid at multiple levels.

[0029] Even further, when using the piston expansion-linear generator waste heat power generation system to recover and utilize the waste heat of the carbon dioxide working fluid in the working fluid circulation loop of the supercritical carbon dioxide Brayton cycle system,

[0030] By using the refrigeration chamber of the condenser of the previous-stage piston expansion-linear generator waste heat recovery and power generation subsystem as the heating chamber of the waste heat evaporator of the next-stage piston expansion-linear generator waste heat recovery and power generation subsystem to form a series connection, the waste heat of the carbon dioxide working fluid recovered by the circulating working fluid of the first-stage piston expansion-linear generator waste heat recovery and power generation subsystem is recovered at multiple levels.

[0031] Compared with the prior art, the present invention has the following beneficial technical effects:

[0032] The supercritical carbon dioxide Brayton cycle power generation system and method for recovering waste heat of the present invention combines the piston expansion-linear generator waste heat recovery and power generation subsystem and the supercritical CO2 Brayton cycle power generation system, can recover the heat released at the low temperature end of the supercritical CO2 Brayton cycle to continue generating electricity, improves the system output power and thermal efficiency, and since the single-stage piston expansion-linear generator waste heat recovery and power generation subsystem itself is a system with relatively high efficiency and low cost and simplicity.

[0033] Furthermore, the present invention uses several piston expansion-linear generator waste heat recovery and power generation subsystems to form a cascaded waste heat recovery, making the entire system have the advantages of high efficiency, low cost, and wide working range. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic structural diagram of the waste heat recovery power generation subsystem of the single-stage piston expansion-linear generator of the present invention.

[0035] Figure 2 This is the schematic structural diagram described in the embodiment of the present invention.

[0036] In the figure: heat source system 1, supercritical carbon dioxide Brayton cycle system 2, turbine power generation system 21, high-temperature recuperator 22, low-temperature recuperator 23, main compressor 24, recompressor 25, piston expansion-linear generator waste heat power generation system 3, waste heat evaporator 31, piston expansion-linear generator system 32, condenser 33, liquid accumulator 34, carbon dioxide pre-cooler 4, first-stage waste heat-first-stage working fluid subsystem 1-1, first-stage waste heat-second-stage working fluid subsystem 1-2, second-stage waste heat-first-stage working fluid subsystem 2-1. Specific embodiments

[0037] The following further elaborates on the present invention in detail in conjunction with specific embodiments, which is an explanation rather than a limitation of the present invention.

[0038] As Figure 2 shown, the supercritical CO2 Brayton cycle power generation system for recovering waste heat of the present invention includes a heat source system 1, a supercritical carbon dioxide Brayton cycle system 2, a piston expansion-linear generator waste heat power generation system 3, and a carbon dioxide pre-cooler 4;

[0039] The supercritical carbon dioxide Brayton cycle system 2 includes a turbine power generation system 21, a high-temperature recuperator 22, a low-temperature recuperator 23, a main compressor 24, and a recompressor 25;

[0040] The turbine inlet of the turbine power generation system 21 is connected to the working fluid side outlet of the heat source system 1, the turbine outlet of the turbine power generation system 21 is connected to the heat release side inlet of the high-temperature recuperator 22, the heat release side outlet of the high-temperature recuperator 22 is connected to the heat release side inlet of the low-temperature recuperator 23, the heat release side outlet of the low-temperature recuperator 23 is respectively connected to the CO2 side inlet of the piston expansion-linear generator waste heat power generation system 3 and the inlet of the recompressor 25, the CO2 side outlet of the piston expansion-linear generator waste heat power generation system 3 is connected to the working fluid side inlet of the carbon dioxide pre-cooler 4, the working fluid side outlet of the carbon dioxide pre-cooler 4 is connected to the inlet of the main compressor 24, the outlet of the main compressor 24 is connected to the heat absorption side inlet of the low-temperature recuperator 23, the heat absorption side outlet of the low-temperature recuperator 23 and the outlet of the recompressor 25 are both connected to the heat absorption side inlet of the high-temperature recuperator 22, and the heat absorption side outlet of the high-temperature recuperator 22 is connected to the inlet of the heat source system 1.

[0041] As Figure 1As shown in the figure, in the single-stage piston expansion-linear generator waste heat recovery power generation subsystem, the waste heat of the carbon dioxide working fluid heats the circulating working fluid in the evaporation chamber through the heating chamber of the waste heat evaporator 31. After releasing heat, the carbon dioxide working fluid is connected back to the working fluid circulation loop; the circulating working fluid flows upward and gradually evaporates into a gas during the flow process and enters the expansion chamber of the piston expansion-linear generator system 32 to do work on the piston; the piston drives the linear generator to generate electricity, and the return spring pushes the piston to reset and discharges the circulating working fluid after doing work into the condenser 33; the circulating working fluid entering the condenser 33 flows downward and cools into a liquid state and then enters the liquid storage tank 34; the liquid circulating working fluid entering the liquid storage tank 34 then enters the waste heat evaporator 31 for cyclic operation. Among them, the liquid level of the liquid circulating working fluid in the condenser 33 is higher than the liquid level of the liquid working fluid in the waste heat evaporator 31.

[0042] The piston expansion linear generator waste heat power generation system 3 can adopt a multi-stage piston expansion-linear generator waste heat recovery power generation subsystem. The waste heat heat source is the heat released by the working fluid at the outlet of the heat release side of the low-temperature recuperator 23 in the supercritical carbon dioxide Brayton cycle system 2. In the overall waste heat recovery system, several single-stage piston expansion-linear generator waste heat recovery power generation subsystems are connected in series along the CO2 flow direction. The inlet and outlet of the heating chamber of the waste heat evaporator 31 of several single-stage piston expansion-linear generator waste heat recovery power generation subsystems are connected in series in turn to form a series structure along the CO2 flow direction; the CO2 side inlet of the waste heat evaporator 31 of the first-stage piston expansion-linear generator waste heat recovery power generation subsystem and the CO2 side outlet of the waste heat evaporator 31 of the last-stage piston expansion-linear generator waste heat recovery power generation subsystem are respectively used as the CO2 side inlet and outlet of the piston expansion linear generator waste heat power generation system 3. Among them, the number of stages of the piston expansion-linear generator waste heat recovery power generation subsystem is determined by factors such as the temperature of CO2 and the type of working fluid selected for the subsystem. Each single-stage piston expansion-linear generator waste heat recovery power generation subsystem recovers and utilizes the waste heat within a certain temperature range;

[0043] For the single-stage piston expansion-linear generator waste heat recovery power generation subsystem arranged at a relatively high temperature position, several piston expansion-linear generator waste heat recovery power generation subsystems can also be connected in series along the heat transfer direction of the circulating working fluid. The heat source of the subsequent stage subsystem is the waste heat released by the previous stage subsystem. The number of stages of the subsystem is determined by factors such as the temperature of the waste heat heat source and the type of working fluid selected for the subsystem. Each single-stage subsystem recovers and utilizes the waste heat within a certain temperature range. The refrigeration chamber of the condenser 33 of the previous-stage piston expansion-linear generator waste heat recovery power generation subsystem serves as the heating chamber of the waste heat evaporator 31 of the subsequent-stage piston expansion-linear generator waste heat recovery power generation subsystem, and they are connected in series in turn to form a series structure along the heat transfer direction of the circulating working fluid.

[0044] Taking the two-stage system as an example, such asFigure 2 As shown, two single-stage piston expansion-linear generator waste heat recovery power generation subsystems are connected in series along the working fluid flow direction at the outlet of the heat release side of the low-temperature recuperator 23 in the supercritical carbon dioxide Brayton cycle system 2. The outlet of the heat release side of the low-temperature recuperator 23 is connected to the CO2 side inlet in the waste heat evaporator 31 in the 1st stage waste heat-1st stage working fluid subsystem 1-1. The CO2 side outlet in the waste heat evaporator 31 in the 1st stage waste heat-1st stage working fluid subsystem 1-1 is connected to the CO2 side inlet in the waste heat evaporator 31 in the 2nd stage waste heat-1st stage working fluid subsystem 2-1. The CO2 side outlet in the waste heat heater 31 in the 2nd stage waste heat-1st stage working fluid subsystem 2-1 is connected to the working fluid side inlet of the carbon dioxide precooler 4; the condenser 33 in the 1st stage waste heat-1st stage working fluid subsystem 1-1 is the waste heat heater 31 in the 1st stage waste heat-2nd stage working fluid subsystem 1-2. The cycle working fluid in the 1st stage waste heat-1st stage working fluid subsystem 1-1 releases heat on the hot side of this heat exchanger, and the cycle working fluid in the 1st stage waste heat-2nd stage working fluid subsystem 1-2 absorbs heat on the cold side of this heat exchanger. The 1st stage waste heat-2nd stage working fluid subsystem 1-2 and the 2nd stage waste heat-1st stage working fluid subsystem 2-1 are the final-stage subsystems, and the cooling working fluid in their condensers 33 is cold air or cold water. The cold air or cold water cools the cycle working fluid in the condensation chamber of the final-stage subsystem through the corresponding refrigeration chamber.

[0045] The above specific implementation manners further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above is only the specific implementation manners of the present invention and is not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A supercritical carbon dioxide Brayton cycle power generation system for recovering waste heat, characterized in that It includes a heat source system (1), a supercritical carbon dioxide Brayton cycle system (2), a piston expansion linear generator waste heat power generation system (3), and a carbon dioxide pre-cooler (4); The working fluid side outlet of the heat source system (1) is connected to the working fluid input end of the supercritical carbon dioxide Brayton cycle system (2); the working fluid side inlet of the heat source system (1) is connected to the working fluid output end of the supercritical carbon dioxide Brayton cycle system (2); A carbon dioxide pre-cooler (4) is connected to the working fluid circulation loop of the supercritical carbon dioxide Brayton cycle system (2); The piston expansion linear generator waste heat power generation system (3) includes at least one single-stage piston expansion-linear generator waste heat recovery power generation subsystem; the single-stage piston expansion-linear generator waste heat recovery power generation subsystem includes a waste heat evaporator (31), a piston expansion-linear generator system (32), a condenser (33), and a liquid storage tank (34); the evaporation chamber outlet of the waste heat evaporator (31) is connected to the inlet of the piston expansion-linear generator system (32); the outlet of the piston expansion-linear generator system (32) is connected to the condensation chamber inlet of the condenser (33); the condensation chamber outlet of the condenser (33) is connected to the circulating working fluid inlet of the liquid storage tank (34); the circulating working fluid outlet of the liquid storage tank (34) is connected to the evaporation chamber inlet side of the waste heat evaporator (31); The heating chamber inlet and outlet of the waste heat evaporator (31) are respectively used as the CO2 side inlet and outlet of the piston expansion linear generator waste heat power generation system (3), and are connected to the working fluid circulation loop of the supercritical carbon dioxide Brayton cycle system (2) and are located on the working fluid inlet side of the carbon dioxide pre-cooler (4).

2. The supercritical carbon dioxide Brayton cycle power generation system for recovering waste heat according to claim 1, wherein The supercritical carbon dioxide Brayton cycle system (2) includes a turbine power generation system (21), a high-temperature recuperator (22), a low-temperature recuperator (23), a main compressor (24), and a recompressor (25); The turbine inlet of the turbine power generation system (21) is used as the working fluid input end of the supercritical carbon dioxide Brayton cycle system (2) and is connected to the working fluid side outlet of the heat source system (1), and the turbine outlet of the turbine power generation system (21) is connected to the heat release side inlet of the high-temperature recuperator (22); The heat release side outlet of the high-temperature recuperator (22) is connected to the heat release side inlet of the low-temperature recuperator (23), and the heat release side outlet of the low-temperature recuperator (23) is respectively connected to the CO2 side inlet of the piston expansion linear generator waste heat power generation system (3) and the inlet of the recompressor (25); The CO2 side outlet of the piston expansion linear generator waste heat power generation system (3) is communicated with the working fluid side inlet of the carbon dioxide pre-cooler (4); the working fluid side outlet of the carbon dioxide pre-cooler (4) is communicated with the inlet of the main compressor (24); the outlet of the main compressor (24) is communicated with the heat absorption side inlet of the low-temperature recuperator (23); the heat absorption side outlet of the low-temperature recuperator (23) and the outlet of the recompressor (25) are both communicated with the heat absorption side inlet of the high-temperature recuperator (22); the heat absorption side outlet of the high-temperature recuperator (22) serves as the working fluid output end of the supercritical carbon dioxide Brayton cycle system (2) and is communicated with the inlet of the heat source system (1).

3. The supercritical carbon dioxide Brayton cycle power generation system for recovering waste heat according to claim 1, characterized in that, The piston expansion linear generator waste heat power generation system (3) includes several single-stage piston expansion-linear generator waste heat recovery power generation subsystems connected in series along the CO2 flow direction.

4. The supercritical carbon dioxide Brayton cycle power generation system for waste heat recovery according to claim 3, wherein The heating chamber inlets and outlets of the waste heat evaporators (31) of several single-stage piston expansion-linear generator waste heat recovery power generation subsystems are connected in series in sequence to form a series structure along the CO2 flow direction; the CO2 side inlet of the waste heat evaporator (31) of the first-stage piston expansion-linear generator waste heat recovery power generation subsystem and the CO2 side outlet of the waste heat evaporator (31) of the last-stage piston expansion-linear generator waste heat recovery power generation subsystem are respectively used as the CO2 side inlet and outlet of the piston expansion linear generator waste heat power generation system (3).

5. The supercritical carbon dioxide Brayton cycle power generation system for recovering waste heat according to claim 1, wherein, The piston expansion linear generator waste heat power generation system (3) includes several single-stage piston expansion-linear generator waste heat recovery power generation subsystems connected in series along the heat transfer direction of the circulating working fluid.

6. The supercritical carbon dioxide Brayton cycle power generation system for recovering waste heat according to claim 5, wherein, The refrigeration chamber of the condenser (33) of the previous-stage piston expansion-linear generator waste heat recovery power generation subsystem serves as the heating chamber of the waste heat evaporator (31) of the next-stage piston expansion-linear generator waste heat recovery power generation subsystem, and they are connected in series in sequence to form a series structure along the heat transfer direction of the circulating working fluid.

7. The supercritical carbon dioxide Brayton cycle power generation system for recovering waste heat according to claim 1, wherein, The liquid level of the liquid circulating working fluid in the condenser (33) is higher than the liquid level of the liquid working fluid in the waste heat evaporator (31).

8. A supercritical carbon dioxide Brayton cycle power generation method for recovering waste heat, characterized in that, Based on the system described in any one of claims 1-7, including While generating electricity using the supercritical carbon dioxide Brayton cycle system (2) with the supercritical carbon dioxide working fluid provided by the heat source system (1), the piston expansion linear generator waste heat power generation system (3) is used to recover and utilize the waste heat of the carbon dioxide working fluid in the working fluid circulation loop of the supercritical carbon dioxide Brayton cycle system (2). When using the piston expansion linear generator waste heat power generation system (3) to recover and utilize the waste heat of the carbon dioxide working fluid in the working fluid circulation loop of the supercritical carbon dioxide Brayton cycle system (2), The waste heat of the carbon dioxide working fluid heats the circulating working fluid in the evaporation chamber through the heating chamber of the waste heat evaporator (31), and the carbon dioxide working fluid after releasing heat is connected back to the working fluid circulation loop; the circulating working fluid flows upward and gradually evaporates into a gas during the flow process and enters the expansion chamber of the piston expansion-linear generator system (32) to do work on the piston; the piston drives the linear generator to generate electricity, and the return spring pushes the piston to reset and discharges the circulating working fluid after doing work into the condenser (33); the circulating working fluid entering the condenser (33) flows downward and is cooled into a liquid state and then enters the liquid storage tank (34); the liquid circulating working fluid entering the liquid storage tank (34) then enters the waste heat evaporator (31) for cyclic operation.

9. The method for generating electricity by a supercritical carbon dioxide Brayton cycle for waste heat recovery according to claim 8, characterized in that, When the piston expansion linear generator waste heat power generation system (3) is used to recover and utilize the waste heat of the carbon dioxide working fluid in the working fluid circulation loop of the supercritical carbon dioxide Brayton cycle system (2), The heating chambers of the waste heat evaporators (31) of several single-stage piston expansion-linear generator waste heat recovery and power generation subsystems are connected in series to recover and utilize the waste heat of the carbon dioxide working fluid in multiple stages.

10. The method for generating electricity by a supercritical carbon dioxide Brayton cycle for recovering waste heat according to claim 9, characterized in that, When the piston expansion linear generator waste heat power generation system (3) is used to recover and utilize the waste heat of the carbon dioxide working fluid in the working fluid circulation loop of the supercritical carbon dioxide Brayton cycle system (2), By using the refrigeration chamber of the condenser (33) of the previous-stage piston expansion-linear generator waste heat recovery and power generation subsystem as the heating chamber of the waste heat evaporator (31) of the next-stage piston expansion-linear generator waste heat recovery and power generation subsystem to form a series connection, the waste heat of the carbon dioxide working fluid recovered by the circulating working fluid of the first-stage piston expansion-linear generator waste heat recovery and power generation subsystem is recovered and utilized in multiple stages.

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