A supercritical brayton cycle cascaded power generation system based on absorption system

Abstract

This invention discloses a supercritical Brayton cycle cascaded power generation system based on an absorption system, belonging to the field of multi-energy complementarity and energy storage technology. It includes a supercritical Brayton cycle unit and an ORC unit. The supercritical Brayton cycle unit generates electricity through the expansion of a first working fluid. The ORC unit includes an absorption subsystem and an ORC unit. The absorption subsystem acts as a cooler in the supercritical Brayton cycle unit, used to cool the first working fluid. The ORC unit uses the heat absorbed by the absorption subsystem during the cooling of the first working fluid as a heat source to heat its working fluid, and generates electricity through the expansion of the working fluid. This invention overcomes the cooling bottleneck of the supercritical Brayton cycle system at high temperatures by using the absorption subsystem to reach the critical temperature. Simultaneously, by using the heat absorbed by the absorption system as a heat source for the ORC subsystem, it significantly improves the overall energy utilization efficiency and the system's applicability in harsh environments.

Description

Technical Field

[0001] The technical field of this invention belongs to energy and power at the first level, and to multi-energy complementarity and new energy storage at the second level, specifically involving a supercritical Brayton cycle cascade power generation system based on an absorption system. Background Technology

[0002] Supercritical Brayton cycles are considered a promising technology for green energy conversion due to their high efficiency, compact structure, flexibility, and economic potential in the medium-to-high temperature range (e.g., 300–800°C). They are applicable to various heat sources, including nuclear power, solar thermal power, and industrial waste heat. However, the efficiency of supercritical Brayton cycles is highly sensitive to their cold-end temperature (i.e., the cycle's minimum temperature). In many promising applications, such as CSP power plants built in arid or desert regions, extreme environmental conditions, particularly high ambient air temperatures, severely limit the actual efficiency of supercritical Brayton cycle systems. Traditional cooling methods (such as air cooling) struggle to effectively cool the working fluid (e.g., CO2) to near its critical temperature (which is crucial for high efficiency) at high ambient temperatures, leading to an increase in the cycle's minimum temperature and a significant decrease in efficiency.

[0003] While using carbon dioxide-based mixtures as the working fluid can alleviate the cooling challenges in high-temperature environments to some extent by increasing its critical temperature, this does not completely solve the problem and typically cannot recover the large amount of heat dissipated during the cooling process. Furthermore, for utilizing industrial waste heat or low-temperature heat from other sources (e.g., below 150°C), the traditional Organic Rankine Cycle (ORC) also suffers from pinch point temperature difference limitations and low heat source utilization.

[0004] Therefore, there is an urgent need for an advanced thermal system that can not only efficiently utilize medium- and high-temperature heat sources, but also effectively address the challenges posed by high ambient temperatures to the cooling process in supercritical Brayton cycles. This system would allow supercritical Brayton cycles to operate close to their optimal cold-end temperature (critical temperature), while also recovering the heat released during cooling and other available low-grade heat to maximize overall energy conversion efficiency. This would enhance the feasibility and competitiveness of supercritical Brayton cycles (especially in fields such as CSP) under harsh environmental conditions. Summary of the Invention

[0005] In view of this, the present invention provides a supercritical Brayton cycle cascaded power generation system based on an absorption system. The absorption subsystem overcomes the cooling bottleneck of the supercritical Brayton cycle system at high temperatures to reach the critical temperature. At the same time, the heat absorbed by the absorption system is used as the heat source of the ORC subsystem, thereby significantly improving the overall energy utilization efficiency and the system's applicability in harsh environments.

[0006] This invention is achieved through the following technical solution:

[0007] A supercritical Brayton cycle cascaded power generation system based on an absorption system includes: a supercritical Brayton cycle unit and an AORC unit;

[0008] The supercritical Brayton cycle unit generates electricity by expanding its working fluid, which is called the first working fluid.

[0009] The AORC unit includes: an absorption subsystem and an ORC unit;

[0010] The absorption subsystem serves as a cooler in the supercritical Brayton cycle unit, used to cool the first working fluid.

[0011] The ORC unit uses the cooling heat absorbed by the absorption subsystem when cooling the first working fluid as a heat source to heat its working fluid, and generates electricity by expanding the working fluid.

[0012] Furthermore, the supercritical Brayton cycle includes: a heat source heat exchanger, a first expander, a high-temperature heat exchanger, a low-temperature heat exchanger, a main compressor, a re-compressor, and a heating unit;

[0013] The first working fluid discharged from the first expander passes sequentially through the primary side of a high-temperature heat exchanger and the primary side of a low-temperature heat exchanger. The first working fluid flowing out from the primary side of the low-temperature heat exchanger splits into two streams: one stream enters the absorption subsystem for cooling; the cooled first working fluid then enters the main compressor for compression and enters the secondary side of the low-temperature heat exchanger for preheating; the other stream of first working fluid enters the re-compressor from the primary side of the low-temperature heat exchanger for compression; the two streams of first working fluid merge at the outlet of the secondary side of the high-temperature heat exchanger, enter the secondary side of the high-temperature heat exchanger for preheating, and then enter the secondary side of the heat source heat exchanger for heating; the heated and pressurized first working fluid enters the first expander for expansion and work.

[0014] The heating unit transfers heat to the primary side of the heat source heat exchanger;

[0015] The absorption subsystem includes: a generator, a first condenser, a solution heat exchanger, a first valve, an absorber, a second pump, an evaporator, and a second valve;

[0016] The generator shell side is filled with a second working fluid, which absorbs heat from the evaporator tube side and evaporates to form a concentrated solution and water vapor. The concentrated solution enters the absorber shell side through the primary side of the solution heat exchanger and the first valve. The concentrated solution absorbs water vapor in the absorber shell side to become a dilute solution and releases heat. The dilute solution enters the generator shell side through the second pump and the secondary side of the solution heat exchanger.

[0017] The water vapor generated inside the shell of the generator enters the shell of the first condenser and condenses into condensate; the condensate enters the shell of the evaporator; the condensate absorbs heat from the tube side of the evaporator and evaporates into water vapor, releasing heat; the water vapor enters the shell of the absorber.

[0018] The ORC subsystem includes: a second expander, a second condenser, a first pump, and a preheating heat exchanger; the working fluid in the ORC subsystem is a third working fluid.

[0019] The third working fluid discharged from the second expander is cooled by the second condenser and then pressurized by the first pump before entering the secondary side of the preheating heat exchanger for preheating. The third working fluid enters the tube side of the absorber and the tube side of the condenser in sequence for heating, forming a three-stage temperature increase. The heated and pressurized third working fluid enters the second expander to expand and do work.

[0020] The first working fluid entering the AORC system passes through the tube side of the generator, the primary side of the preheating heat exchanger, and the tube side of the evaporator in sequence, undergoing three cooling processes, before flowing into the main compressor.

[0021] Furthermore, the heating unit includes: a solar collector mirror field, a fourth pump, a third valve, and a sixth valve;

[0022] The solar collector mirror field is sequentially connected to the third valve, the fourth pump, the primary side of the heat source heat exchanger, and the sixth valve, forming a closed loop;

[0023] When there is sunlight, the solar collector mirror field collects the heat generated by solar energy. The heat passes through the third valve and the fourth pump in sequence and is transferred to the primary side of the heat source heat exchanger.

[0024] The third valve and the sixth valve are used to control the heat transfer between the solar collector mirror field and the primary side of the heat source heat exchanger, respectively.

[0025] The fourth pump is used to provide power for the circulation of the heat transfer medium.

[0026] Furthermore, the heating unit also includes: an oil-salt heat exchanger, a heat storage tank, a cold storage tank, a fourth valve, and a fifth valve;

[0027] The outlet of the third valve is sequentially connected to the fourth valve, one side of the oil-salt heat exchanger, and the inlets of the fifth and sixth valves; the heat storage tank is sequentially connected to the other side of the oil-salt heat exchanger and the cold storage tank.

[0028] The fourth and fifth valves are used to control the heat transfer between one side of the oil-salt heat exchanger and the heat source heat exchanger.

[0029] When there is no light, the heat transfer medium in the heat storage tank flows into the cold storage tank through the other side of the oil-salt heat exchanger; the heat is transferred to the other side of the oil-salt heat exchanger through the heat transfer medium; the heat on one side of the oil-salt heat exchanger is transferred to the other side, and then sequentially through the fourth valve and the fourth pump to the primary side of the heat source heat exchanger to achieve heating.

[0030] Furthermore, the first working fluid of the supercritical Brayton cycle unit is supercritical carbon dioxide or a mixture containing carbon dioxide.

[0031] Furthermore, the second working fluid of the absorption subsystem is LiBr and water.

[0032] Furthermore, the third working medium of the ORC subsystem is an organic working medium.

[0033] Furthermore, a sprayer is provided inside the shell side of the generator for uniformly spraying the second working fluid that enters the shell side of the generator from the secondary side of the solution heat exchanger.

[0034] Furthermore, the absorber shell is equipped with a sprayer for uniformly spraying the second working fluid that enters the absorber shell from the primary side of the solution heat exchanger.

[0035] Furthermore, a sprayer is provided inside the shell side of the evaporator, and a third pump is provided between the shell side of the evaporator and the sprayer;

[0036] The sprayer is used to evenly spray the condensate inside the evaporator shell.

[0037] Beneficial effects:

[0038] (1) The present invention provides a supercritical Brayton cycle cascaded power generation system based on an absorption system, comprising: a supercritical Brayton cycle and an AORC unit. The absorption subsystem in the AORC unit acts as a cooler in the Brayton cycle unit. The absorption subsystem is based on the absorption refrigeration principle and is not affected by the ambient temperature. It effectively absorbs the cooling heat of the first working fluid in the supercritical Brayton cycle unit as needed. Even in high-temperature environments, it can cool the first working fluid to its optimal operating point close to its critical temperature, thereby ensuring that the supercritical Brayton cycle maintains a high-efficiency operating state. The ORC unit uses the heat of the first working fluid absorbed by the absorption subsystem as a heat source to heat its working fluid. It can effectively recover and utilize the heat energy that was originally discharged into the environment and convert the originally wasted heat energy into electrical energy to achieve secondary power generation, thereby improving the overall energy utilization rate. Through the coupling between the supercritical Brayton cycle unit and the AORC unit, the system can significantly improve the energy conversion efficiency, especially in the utilization of fluctuating energy (such as solar energy) and the recovery of industrial waste heat. It has both good economic and environmental benefits. The system has the flexibility of operating modes and the diversity of working fluid selection, and can adapt to a wider range of application scenarios.

[0039] (2) In the supercritical Brayton cycle cascade power generation system based on the absorption system of the present invention, the first working fluid entering the AORC system passes through the tube side of the generator, the primary side of the preheating heat exchanger, and the tube side of the evaporator in sequence, forming three cooling cycles; in particular, when the first working fluid passes through the tube side of the evaporator, the endothermic reaction in the shell side of the evaporator can effectively absorb the heat of the first working fluid, and is not affected by the ambient temperature, and can be cooled to the critical temperature even in a high-temperature environment; the third working fluid enters the secondary side of the preheating heat exchanger for preheating, and then enters the tube side of the absorber and the tube side of the condenser in sequence for heating, forming three heating cycles; the system can fully recover and utilize the heat from different links in the supercritical Brayton cycle and the absorption subsystem, thereby improving the overall energy utilization rate and thus improving the overall energy conversion efficiency.

[0040] (3) A supercritical Brayton cycle cascade power generation system based on an absorption system of the present invention includes a heating unit comprising: a solar collector mirror field, a fourth pump, a third valve and a sixth valve. When there is sunlight, the solar collector mirror field collects the heat generated by solar energy and transfers the heat to the primary side of the heat source heat exchanger, which can reduce the dependence on fossil fuels.

[0041] (4) The present invention provides a supercritical Brayton cycle cascade power generation system based on an absorption system. The heating unit further includes an oil-salt heat exchanger, a heat storage tank, a cold storage tank, a fourth valve, and a fifth valve. When there is no sunlight, the heat in the heat storage tank is transferred to the primary side of the heat source heat exchanger through the oil-salt heat exchanger, thereby realizing power supply at night or in cloudy conditions.

[0042] (5) The present invention provides a supercritical Brayton cycle cascade power generation system based on an absorption system, wherein the first working fluid is supercritical carbon dioxide or a mixture containing carbon dioxide, which can improve heat transfer efficiency.

[0043] (6) The present invention provides a supercritical Brayton cycle cascade power generation system based on an absorption system, wherein the second working fluid of the absorption subsystem is LiBr and water, which can be applied to different heat source conditions, effectively absorb and release heat, thereby improving the overall efficiency of the system.

[0044] (7) In the present invention, a supercritical Brayton cycle cascaded power generation system based on an absorption system is provided, wherein the third working medium of the ORC subsystem is an organic working medium, which can improve the system efficiency.

[0045] (8) A supercritical Brayton cycle cascade power generation system based on an absorption system of the present invention has a sprayer inside the generator, which can uniformly spray the second working fluid, increase the contact area between the second working fluid and the generator tube side, thereby improving the evaporation amount and evaporation efficiency of water in the second working fluid.

[0046] (9) A supercritical Brayton cycle cascade power generation system based on an absorption system of the present invention has a sprayer inside the shell side of the absorber, which can uniformly spray the second working fluid, increase the contact area between the second working fluid and the tube side of the absorber, and ensure that the concentrated solution of the second working fluid can fully contact the water vapor.

[0047] (10) A supercritical Brayton cycle cascade power generation system based on an absorption system of the present invention has a sprayer installed inside the shell side of the evaporator and a third pump installed between the shell side of the evaporator and the sprayer. The third pump can pump condensate into the sprayer. The sprayer can increase the contact area between the condensate and the tube side of the evaporator, thereby improving the evaporation amount and evaporation efficiency of the condensate. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of a supercritical Brayton cycle cascaded power generation system based on an absorption system according to the present invention.

[0049] Among them, 1-preheating heat exchanger, 2-generator, 3-first condenser, 4-solution heat exchanger, 5-second valve, 6-first valve, 7-absorber, 8-second pump, 9-third pump, 10-evaporator, 11-second expander, 12-first pump, 13-second condenser, 14-collector mirror field, 15-oil-salt heat exchanger, 16-third valve, 17-fourth valve, 18-fifth valve, 19-sixth valve, 20-fourth pump, 21-heat storage tank, 22-heat source heat exchanger, 23-cold storage tank, 24-first expander, 25-high temperature heat exchanger, 26-low temperature heat exchanger, 27-recompressor, 28-main compressor. Detailed Implementation

[0050] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0051] In this specification, the directions "up", "down", "left" and "right" mentioned are based on the positions shown in the attached drawings.

[0052] This embodiment provides a supercritical Brayton cycle cascaded power generation system based on an absorption system, such as... Figure 1 As shown, it includes: a supercritical Brayton cycle unit ( Figure 1 The upper and middle sections) and AORC (Absorption Organic Rankine Cycle) units ( Figure 1 (Lower middle section); The AORC unit acts as a cooler in the Brayton cycle, that is, the AORC unit is thermally coupled with the supercritical Brayton cycle unit, undertakes the cooling load of the supercritical Brayton cycle, and generates electricity using the absorbed heat.

[0053] In this embodiment, the supercritical Brayton cycle unit adopts a recompression Brayton cycle, including: a heat source heat exchanger 22, a first expander 24, a high-temperature heat exchanger 25, a low-temperature heat exchanger 26, a recompressor 27, a main compressor 28, a heating unit, and a generator A; the working fluid in the supercritical Brayton cycle unit is the first working fluid;

[0054] The outlet of the first expander 24 is connected to the primary side of the high-temperature heat exchanger 25. Figure 1 The upper middle side inlet and the primary side outlet of the high-temperature heat exchanger 25 are connected to the primary side inlet of the low-temperature heat exchanger 26. Figure 1 (Upper side), the primary side outlet of the low-temperature heat exchanger 26 is split into two paths, one of which is connected to the inlet of the main compressor 28 via the AORC unit, and the outlet of the main compressor 28 is connected to the secondary side of the low-temperature heat exchanger 26 (upper side). Figure 1 One path leads directly to the inlet of the recompressor 27 (lower side), and the outlet of the recompressor 27 merges with the secondary outlet of the low-temperature heat exchanger 26, and connects to the secondary outlet of the high-temperature heat exchanger 25. Figure 1 The secondary inlet of the high-temperature heat exchanger 25 (lower side) is connected to the secondary inlet of the heat source heat exchanger 22. Figure 1 (Right side of the middle section), the secondary outlet of the heat source heat exchanger 22 is connected to the inlet of the first expander 24; the generator A is driven by the first expander 24; the heating unit and the primary side of the heat source heat exchanger 22 form a closed loop;

[0055] Exhaust gas (i.e., the first working fluid) is discharged from the outlet of the first expander 24. The discharged first working fluid passes sequentially through the primary side of the high-temperature heat exchanger 25 and the primary side of the low-temperature heat exchanger 26. During this process, some of the heat of the first working fluid is recovered sequentially by the high-temperature heat exchanger 25 and the low-temperature heat exchanger 26 (i.e., the heat of the first working fluid in the primary side of the high-temperature heat exchanger 25 is transferred to the first working fluid in its secondary side, and the heat of the first working fluid in the primary side of the low-temperature heat exchanger 26 is transferred to the first working fluid in its secondary side). After flowing out from the primary side of the low-temperature heat exchanger 26, the first working fluid is divided into two paths, one of which enters... The AORC unit is cooled to form a low-temperature first working fluid (i.e., the temperature of the first working fluid reaches the critical temperature of the supercritical Brayton cycle unit); the low-temperature first working fluid enters the main compressor 28 for compression and then enters the secondary side of the low-temperature heat exchanger 26 for preheating; another first working fluid enters the re-compressor 27 directly from the primary side of the low-temperature heat exchanger 26 for compression; the two first working fluids merge at the secondary side outlet of the high-temperature heat exchanger 25 and enter together the secondary side of the high-temperature heat exchanger 25 for preheating, and then enter the secondary side of the heat source heat exchanger 22 for heating (i.e., the primary side of the heat source heat exchanger 22...). Figure 1The heat of the heat transfer medium in the left side is transferred to the first working medium in its secondary side, so that the first working medium in the secondary side of the heat source heat exchanger 22 forms a high temperature and high pressure first working medium; the high temperature and high pressure first working medium enters the first expander 24, and drives the generator A by expanding and doing work, and the generator A supplies power to the grid or load; the heat of the heat transfer medium in the primary side of the heat source heat exchanger 22 is provided by the heating unit.

[0056] The first working medium is supercritical carbon dioxide or a mixture containing carbon dioxide (e.g., a combination of carbon dioxide with any one of R1234yf, R32, R161, or propane, or a combination of carbon dioxide with any one of n-pentane, cyclopentane, or cyclohexane).

[0057] As an example, the heat transfer medium in the primary side of the heat source heat exchanger 22 is molten salt or heat transfer oil;

[0058] As an example, the heating unit uses solar energy as a heat source; the heating unit includes: a collector mirror field 14, a fourth pump 20, an oil-salt heat exchanger 15, a thermal storage tank 21, a cold storage tank 23, a third valve 16, a fourth valve 17, a fifth valve 18, and a sixth valve 19;

[0059] like Figure 1 As shown, the collector mirror field 14 is sequentially connected to the third valve 16, the fourth pump 20, the primary side of the heat source heat exchanger 22, and the sixth valve 19, forming a closed loop; the outlet of the third valve 16 is sequentially connected to the fourth valve 17, the left side of the oil-salt heat exchanger 15, the fifth valve 18, and the inlet of the sixth valve 19; the heat storage tank 21 is sequentially connected to the right side of the oil-salt heat exchanger 15 and the cold storage tank 23; the fourth pump 20 is used to provide power for the circulation of the heat transfer medium; the third valve 16 and the sixth valve 19 are respectively used to control the heat transfer between the collector mirror field 14 and the primary side of the heat source heat exchanger 22; the fourth valve 17 and the fifth valve 18 are used to control the heat transfer between the left side of the oil-salt heat exchanger 15 and the heat source heat exchanger 22;

[0060] The heating unit supplies heat to the heat source heat exchanger 22 in two ways: when there is sunlight and when there is no sunlight. When there is sunlight, the solar collector mirror field 14 collects the heat generated by solar energy. The heat is transferred to the primary side of the heat source heat exchanger 22 through the third valve 16 and the fourth pump 20. When there is no sunlight (night or cloudy), the heat transfer medium in the heat storage tank 21 flows into the cold storage tank 23 through the right side of the oil-salt heat exchanger 15. The heat is transferred to the right side of the oil-salt heat exchanger 15 through the heat transfer medium. The heat from the right side of the oil-salt heat exchanger 15 is transferred to its left side and then transferred to the primary side of the heat source heat exchanger 22 through the fourth valve 17 and the fourth pump 20, thereby achieving heating.

[0061] The AORC unit includes: an ORC subsystem and an absorption subsystem;

[0062] The absorption subsystem is used to absorb the heat (i.e., cooling heat) discharged during the cooling process of the first working fluid in the supercritical Brayton cycle unit. The absorbed heat is transferred to the ORC subsystem to generate electricity. Let the working fluid of the absorption subsystem be the second working fluid. In this embodiment, the second working fluid is: LiBr (lithium bromide) and water.

[0063] The absorption subsystem includes: generator 2, absorber 7, first condenser 3, evaporator 10, solution heat exchanger 4, first valve 6, second valve 5, and second pump 8, forming a flow path and a flow path between LiBr aqueous solution and vapor;

[0064] Let the shell side and tube side of generator 2 be the first shell side and the first tube side, respectively; the first shell side is provided with a liquid inlet / outlet and a water vapor outlet; let the shell side and tube side of first condenser 3 be the second shell side and the second tube side, respectively; the second shell side is provided with a water vapor inlet and a liquid outlet; let the shell side and tube side of evaporator 10 be the third shell side and the third tube side, respectively; the third shell side is provided with a water vapor outlet and a liquid inlet / outlet; let the shell side and tube side of absorber 7 be the fourth shell side and the fourth tube side, respectively; the fourth shell side is provided with a water vapor inlet and a liquid inlet / outlet.

[0065] LiBr flow path: The liquid outlet on the first shell side is connected to the primary side of the solution heat exchanger 4. Figure 1 The inlet (left side) of the solution heat exchanger 4 is connected to the liquid inlet on the fourth shell side of the absorber 7 via the first valve 6. The liquid outlet on the fourth shell side is connected to the secondary side of the solution heat exchanger 4 via the second pump 8. Figure 1 The inlet on the right side of the middle section is connected to the liquid inlet on the first shell side of the secondary side of the solution heat exchanger 4.

[0066] The first shell side contains a LiBr aqueous solution, which absorbs heat from the first tube side to form water vapor, thus concentrating the LiBr aqueous solution (hereinafter referred to as the concentrated solution). When the concentrated solution passes through the primary side of the solution heat exchanger 4, its heat is transferred to the secondary side. After entering the fourth shell side, the concentrated solution absorbs water vapor (from the third shell side of the evaporator 10) to become a dilute solution, releasing heat. At this time, the released heat is transferred to the fourth tube side. The dilute solution passes through the secondary side of the solution heat exchanger 4 and enters the first shell side.

[0067] In the LiBr flow path, the first valve 6 is used to regulate the flow rate of the concentrated solution flowing from the primary side of the solution heat exchanger 4 into the fourth shell side, thereby achieving throttling regulation and pressure control, and isolating the high-pressure zone (absorber 7) and the low-pressure zone (generator 2); the second pump 8 is used to allow the dilute solution to overcome the fluid pressure and flow smoothly through the solution heat exchanger 4 into the generator 2.

[0068] As an example, a sprayer is provided inside the first shell side of the generator 2. The sprayer is used to uniformly spray the dilute solution, increase the contact area between the dilute solution and the first tube side, thereby increasing the evaporation rate and evaporation efficiency of the water.

[0069] As an example, a sprayer is provided inside the fourth shell side of the absorber 7. The sprayer is used to uniformly spray the concentrated solution, increase the contact area between the concentrated solution and water vapor, and ensure that the concentrated solution can fully contact the water vapor.

[0070] LiBr aqueous solution and vapor flow path: the water vapor outlet on the first shell side is connected to the water vapor inlet on the second shell side, the liquid outlet on the second shell side is connected to the liquid inlet on the third shell side via the second valve 5, and the water vapor outlet on the third shell side is connected to the water vapor inlet on the fourth shell side.

[0071] In this process, water vapor formed in the first shell enters the second shell and condenses into condensate, releasing heat; the released heat is transferred to the second tube side; the condensate enters the third shell; the heat from the third tube side transfers heat to the condensate in the third shell, causing the condensate to evaporate and form water vapor; the water vapor enters the fourth shell, where the concentrated solution absorbs the water vapor to form a dilute solution.

[0072] In the LiBr aqueous solution and water vapor flow path, the second valve 5 is used to regulate the pressure and flow rate of the condensate flowing from the second shell side into the third shell side, thereby realizing throttling regulation and pressure control, and isolating the high-pressure zone (evaporator 10) and the low-pressure zone (first condenser 3);

[0073] As an example, a sprayer is provided inside the third shell side, and a third pump 9 is provided between the third shell side and the sprayer. Condensate is pumped into the sprayer through the third pump 9. The sprayer sprays the condensate evenly onto the third pipe side, thereby increasing the contact area between the condensate and the pipe side, and improving the evaporation rate and evaporation efficiency of the condensate.

[0074] The ORC subsystem includes: a second expander 11, a second condenser 13, a first pump 12, a preheating heat exchanger 1, and a generator B; the working fluid in the ORC subsystem is designated as the third working fluid, and the ORC subsystem constitutes the third working fluid flow path.

[0075] Third working fluid flow path: The outlet of the second expander 11 is connected to the primary side of the second condenser 13. Figure 1 The inlet (left side) and the primary outlet of the second condenser 13 are connected to the secondary side of the preheating heat exchanger 1 via the first pump 12. Figure 1 The inlet (right side) of the preheating heat exchanger 1 is connected to the inlet of the fourth tube side, the outlet of the fourth tube side is connected to the inlet of the second tube side, and the outlet of the second tube side is connected to the inlet of the second expander 11; the generator B is connected to the second expander 11 for drive.

[0076] The outlet of the second expander 11 discharges exhaust gas (i.e., the third working fluid); when the third working fluid passes through the primary side of the second condenser 13, heat is transferred to the secondary side, and the third working fluid condenses into a third working fluid (liquid); the third working fluid is pressurized by the first pump 12 and then enters the secondary side of the preheating heat exchanger 1. Figure 1 (Right side of the middle section) In the preheating heat exchanger 1, the heat of the first working fluid in the primary side is transferred to the third working fluid in the secondary side, achieving the first heating (preheating); the heated third working fluid enters the fourth tube side, and the heat in the fourth shell side is transferred to the third working fluid in the fourth tube side, achieving the second heating (heating); the heated third working fluid enters the second tube side, and the heat in the second shell side is transferred to the third working fluid in the second tube side, achieving the third heating (heating; at this time, the temperature of the third working fluid reaches the evaporation state and the superheated state, that is, forming a high-temperature and high-pressure steam third working fluid); at this time, the third working fluid enters the second expander 11; the third working fluid flows through the second expander 11, and drives the generator B by expanding and doing work, and the generator B supplies power to the grid or load, thereby realizing secondary power generation;

[0077] In this embodiment, the third working fluid is an organic working fluid (e.g., R245fa);

[0078] In a supercritical Brayton cycle, the primary side outlet of the low-temperature heat exchanger 26 is connected to the first tube side inlet, the first tube side outlet is connected to the primary side inlet of the preheating heat exchanger 1, and the primary side outlet of the preheating heat exchanger 1 is connected to the inlet of the third tube side.

[0079] The first working fluid flowing out of the low-temperature heat exchanger 26 enters the first tube side, and the heat of the first working fluid is transferred to the first shell side, achieving the first cooling. The cooled first working fluid enters the primary side of the preheating heat exchanger 1, and the heat of the first working fluid is transferred to the secondary side of the preheating heat exchanger 1, achieving the second cooling. The cooled first working fluid enters the third tube side, and the heat of the first working fluid is transferred to the third shell side, achieving the third cooling. After three cooling processes, the temperature of the first working fluid reaches the critical temperature of the supercritical Brayton cycle unit and enters the main compressor 28. As needed, the first tube side of the generator 2 and the primary side of the preheating heat exchanger 1 can be connected to external heat sources respectively.

[0080] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A supercritical Brayton cycle cascaded power generation system based on an absorption system, characterized by, include: Supercritical Brayton cycle unit and absorption cycle coupled organic Rankine cycle unit; The supercritical Brayton cycle unit generates electricity by expanding its working fluid, and the working fluid in the supercritical Brayton cycle unit is the first working fluid. The absorption-type cyclic coupled organic Rankine cycle unit includes: an absorption subsystem and an organic Rankine cycle unit; The absorption subsystem serves as a cooler in the supercritical Brayton cycle unit, used to cool the first working fluid. The organic Rankine cycle unit uses the cooling heat absorbed by the absorption subsystem when cooling the first working fluid as a heat source to heat the third working fluid, and generates electricity by doing work through the expansion of the third working fluid. The supercritical Brayton cycle unit includes: a heat source heat exchanger (22), a first expander (24), a high-temperature heat exchanger (25), a low-temperature heat exchanger (26), a main compressor (28), a re-compressor (27), and a heating unit; The first working fluid discharged from the first expander (24) passes sequentially through the primary side of the high-temperature heat exchanger (25) and the primary side of the low-temperature heat exchanger (26). The first working fluid flowing out from the primary side of the low-temperature heat exchanger (26) is divided into two paths. One path enters the absorption subsystem for cooling. The cooled first working fluid enters the main compressor (28) for compression and enters the secondary side of the low-temperature heat exchanger (26) for preheating. The other path of the first working fluid enters the re-compressor (27) for compression from the primary side of the low-temperature heat exchanger (26). The two paths of the first working fluid merge at the secondary side inlet of the high-temperature heat exchanger (25) and enter the secondary side of the high-temperature heat exchanger (25) for preheating. They then enter the secondary side of the heat source heat exchanger (22) for heating and temperature rise. The heated and pressurized first working fluid enters the first expander (24) for expansion and work. The heating unit transfers heat to the primary side of the heat source heat exchanger (22); The absorption subsystem includes: a generator (2), a first condenser (3), a solution heat exchanger (4), a first valve (6), an absorber (7), a second pump (8), an evaporator (10), and a second valve (5); The generator (2) contains a second working fluid in its shell side. The second working fluid absorbs heat from the tube side of the evaporator (10) and evaporates to form a concentrated solution and water vapor. The concentrated solution enters the shell side of the absorber (7) through the primary side of the solution heat exchanger (4) and the first valve (6). The concentrated solution absorbs water vapor in the shell side of the absorber (7) and becomes a dilute solution, releasing heat. The dilute solution enters the shell side of the generator (2) through the second pump (8) and the secondary side of the solution heat exchanger (4). The water vapor generated in the shell side of the generator (2) enters the shell side of the first condenser (3) and condenses into condensate; the condensate enters the shell side of the evaporator (10); the condensate absorbs the heat from the tube side of the evaporator (10) and evaporates into water vapor, releasing heat; the water vapor enters the shell side of the absorber (7). The organic Rankine cycle unit includes: a second expander (11), a second condenser (13), a first pump (12), and a preheating heat exchanger (1); the working fluid in the organic Rankine cycle unit is a third working fluid; The third working fluid discharged from the second expander (11) is cooled by the second condenser (13) and pressurized by the first pump (12) before entering the secondary side of the preheating heat exchanger (1) for preheating. The third working fluid enters the tube side of the absorber (7) and the tube side of the first condenser (3) in sequence for heating, forming a three-stage temperature rise. The heated and pressurized third working fluid enters the second expander (11) to expand and do work. The first working fluid entering the absorption-type cyclic coupled organic Rankine cycle unit passes through the tube side of the generator (2), the primary side of the preheating heat exchanger (1), and the tube side of the evaporator (10) in sequence, forming three cooling cycles, and then flows into the main compressor (28).

2. The supercritical Brayton cycle cascaded power generation system based on an absorption system as described in claim 1, characterized in that, The heating unit includes: a collector mirror field (14), a fourth pump (20), a third valve (16) and a sixth valve (19); The solar collector mirror field (14) is sequentially connected to the third valve (16), the fourth pump (20), the primary side of the heat source heat exchanger (22), and the sixth valve (19) to form a closed loop; When there is sunlight, the solar collector mirror field (14) collects the heat generated by the solar energy. The heat passes through the third valve (16) and the fourth pump (20) in sequence and is transferred to the primary side of the heat source heat exchanger (22). The third valve (16) and the sixth valve (19) are used to control the heat transfer between the collector mirror field (14) and the primary side of the heat source heat exchanger (22), respectively. The fourth pump (20) is used to provide power for the circulation of the heat transfer medium.

3. The supercritical Brayton cycle cascaded power generation system based on an absorption system as described in claim 2, characterized in that, The heating unit also includes: an oil-salt heat exchanger (15), a heat storage tank (21), a cold storage tank (23), a fourth valve (17), and a fifth valve (18). The outlet of the third valve (16) is connected in sequence to the fourth valve (17), one side of the oil-salt heat exchanger (15), the inlet of the fifth valve (18) and the sixth valve (19); the heat storage tank (21) is connected in sequence to the other side of the oil-salt heat exchanger (15) and the cold storage tank (23). The fourth valve (17) and the fifth valve (18) are used to control the heat transfer between one side of the oil-salt heat exchanger (15) and the heat source heat exchanger (22); When there is no light, the heat transfer medium in the heat storage tank (21) flows into the cold storage tank (23) through the other side of the oil-salt heat exchanger (15); the heat is transferred to the other side of the oil-salt heat exchanger (15) through the heat transfer medium; the heat on one side of the oil-salt heat exchanger (15) is transferred to the other side, and then transferred to the primary side of the heat source heat exchanger (22) through the fourth valve (17) and the fourth pump (20) in sequence, so as to achieve heating.

4. A supercritical Brayton cycle cascaded power generation system based on an absorption system as described in any one of claims 1-3, characterized in that, The first working fluid of the supercritical Brayton cycle unit is supercritical carbon dioxide or a mixture containing carbon dioxide.

5. A supercritical Brayton cycle cascaded power generation system based on an absorption system as described in claim 2 or 3, characterized in that, The second working fluid of the absorption subsystem is LiBr and water.

6. A supercritical Brayton cycle cascaded power generation system based on an absorption system as described in claim 2 or 3, characterized in that, The third working medium in the organic Rankine cycle unit is an organic working medium.

7. The supercritical Brayton cycle cascaded power generation system based on an absorption system as described in claim 1, characterized in that, The generator (2) is equipped with a sprayer inside the shell side for uniformly spraying the second working fluid that enters the generator (2) from the secondary side of the solution heat exchanger (4).

8. The supercritical Brayton cycle cascaded power generation system based on an absorption system as described in claim 1, characterized in that, The absorber (7) is equipped with a sprayer inside its shell for uniformly spraying the second working fluid that enters the shell side of the absorber (7) from the primary side of the solution heat exchanger (4).

9. The supercritical Brayton cycle cascaded power generation system based on an absorption system as described in claim 1, characterized in that, The evaporator (10) is equipped with a sprayer inside the shell side, and a third pump (9) is provided between the shell side of the evaporator (10) and the sprayer. The sprayer is used to evenly spray the condensate inside the shell side of the evaporator (10).

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