A supercritical carbon dioxide cycle system and method for recovering waste heat and flue gas carbon capture

Abstract

The application discloses a supercritical carbon dioxide cycle system and method for recycling waste heat and flue gas carbon capture, which comprises a coal gasification and carbon capture system, a working medium charging auxiliary system and a supercritical carbon dioxide Brayton cycle system, and the coal gasification and carbon capture system comprises a pre-drying device, a gasifier, a synthetic gas purification device, a flue gas purification device and a carbon capture device; the pre-drying device is connected with the gasifier, the gasifier is connected with the synthetic gas purification device, the synthetic gas purification device is connected with the supercritical carbon dioxide Brayton cycle system, the flue gas purification device is connected with the flue gas purification device, and the flue gas purification device is connected with the carbon capture device; the supercritical carbon dioxide Brayton cycle system and the carbon capture device are both connected with the working medium charging auxiliary system. The system integrates the functions of waste heat recovery and carbon capture, improves cycle efficiency, purifies, captures and supplements carbon dioxide in flue gas into the cycle system, simultaneously pre-dries coal powder by reducing pressure of part of dry working medium, so that the maximum energy cascade utilization efficiency is realized through system-level collaborative optimization.

Description

Technical Field

[0001] This invention relates to multiple fields such as waste heat recovery, flue gas carbon capture, and supercritical carbon dioxide cycle power generation, and specifically discloses a supercritical carbon dioxide cycle system and method for recovering waste heat and capturing flue gas carbon. Background Technology

[0002] Supercritical carbon dioxide Brayton cycle technology originated in the mid-20th century, but it only entered the engineering application stage in the early 21st century after breakthroughs in materials science and manufacturing processes. Compared with the traditional steam Rankine cycle, the supercritical carbon dioxide Brayton cycle has three significant advantages: First, in the supercritical state, carbon dioxide has a liquid-like high density and a gas-like low viscosity, allowing the system equipment size to be reduced to 1 / 10 of that of a steam system; second, its critical temperature is close to ambient temperature, significantly reducing cold-end losses; and most importantly, the theoretical system efficiency can be 5-8 percentage points higher than that of a steam cycle under the same parameters. Research at Sandia National Laboratories in the United States shows that when the turbine inlet temperature reaches 700°C, the efficiency of a simple regenerative sCO2 cycle can reach over 50%. In recent years, several supercritical carbon dioxide cycle test platforms have been built globally, such as the 50MW demonstration power plant of NET Power in the United States, which has verified the unique advantages of this technology in post-combustion carbon capture.

[0003] Compared to traditional post-combustion carbon capture, supercritical carbon dioxide recirculation systems have inherent advantages in carbon capture. When the system operating pressure exceeds 10 MPa, the partial pressure of carbon dioxide in the flue gas is relatively high, allowing for the collection of carbon dioxide from the flue gas with lower capture energy consumption through physical adsorption. Furthermore, in supercritical carbon dioxide recirculation systems, some of the captured liquid carbon dioxide can be partially recycled back into the recirculation as working fluid replenishment, forming a unique closed-loop carbon recirculation mechanism.

[0004] However, there is still room for optimization in the energy utilization of existing supercritical carbon dioxide cycle systems. After the carbon dioxide working fluid completes its work in the turbine, although some heat is recovered by the regenerator, it still needs to be cooled to near the critical point by the precooler before entering the compressor. The low-grade heat energy generated in this cooling process is not effectively utilized. Summary of the Invention

[0005] In addressing the problem in existing supercritical carbon dioxide cycle systems where the precooler lowers the temperature to near the critical point before entering the compressor, resulting in the ineffective utilization of low-grade heat energy generated during the cooling process, the present invention aims to provide a supercritical carbon dioxide cycle system and method for recovering waste heat and capturing carbon in flue gas. This system can integrate waste heat recovery and carbon capture functions to maximize energy cascade utilization efficiency through system-level synergistic optimization.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] A supercritical carbon dioxide cycle system for recovering waste heat and capturing carbon from flue gas includes a coal gasification and carbon capture system, a working fluid filling auxiliary system, and a supercritical carbon dioxide Brayton cycle system.

[0008] The coal gasification and carbon capture system includes a pre-drying device, a gasifier, a syngas purification device, a flue gas purification device, and a carbon capture device. The pre-drying device is connected to the gasifier, the gasifier is connected to the syngas purification device, the syngas purification device is connected to the supercritical carbon dioxide Brayton cycle system, the flue gas purification device is connected to the flue gas purification device, and the flue gas purification device is connected to the carbon capture device.

[0009] Both the supercritical carbon dioxide Brayton cycle system and the carbon capture device are connected to the working fluid filling auxiliary system.

[0010] Furthermore, the working fluid filling auxiliary system includes a liquid CO2 storage tank, a liquid pump, a heat exchanger, a vaporizer, and an expansion device; wherein, the carbon capture device is connected to the liquid CO2 storage tank, the liquid CO2 storage tank is connected to the liquid pump, the liquid pump outlet is divided into two paths, one connected to the heat exchanger and the other connected to the vaporizer inlet; the heat exchanger outlet is divided into two paths, one connected to the supercritical carbon dioxide Brayton cycle system and the other connected to the vaporizer, the vaporizer outlet is divided into two paths, one connected to the supercritical carbon dioxide Brayton cycle system and the supercritical carbon dioxide Brayton cycle system and the heat exchanger, the other vaporizer outlet is connected to the expansion device, and the expansion device is connected to the pre-drying device.

[0011] Furthermore, the supercritical carbon dioxide Brayton cycle system includes a boiler, a turbine, a regenerator, a precooler, a buffer tank, a compressor, a generator, and an electric motor; wherein, the precooler is connected to the buffer tank, the buffer tank is connected to the compressor, the electric motor is connected to the compressor, the generator is connected to the turbine, the compressor is connected to the turbine, and the compressor and turbine are all connected to the regenerator. The regenerator outlet is divided into three paths: one path is connected to the boiler, the second path is connected to the precooler, and the third path is connected to the working fluid charging auxiliary system. Both the regenerator and the precooler are connected to the heat exchanger, and the gasifier is connected to the buffer tank.

[0012] Furthermore, one outlet of the vaporizer is connected to the buffer tank via the third valve group, and the other outlet is connected to the expansion device via the fourth valve group.

[0013] Furthermore, one outlet of the regenerator is connected to the precooler via the fifth valve group, and the other outlet is connected to the heat exchanger via the sixth valve group.

[0014] Furthermore, one outlet of the liquid pump is connected to the heat exchanger via the first valve group, and another outlet of the liquid pump is connected to the vaporizer via the second valve group.

[0015] Furthermore, during the startup phase, the first, fourth, and sixth valve groups are closed, while the second, third, and fifth valve groups are opened to supply carbon dioxide working fluid into the circulation system. After the circulation stabilizes, the first, fourth, and sixth valve groups are opened again to preheat the working fluid.

[0016] A supercritical carbon dioxide recycling method for recovering waste heat and capturing carbon in flue gas involves transporting coal to a pre-drying device, where the pre-dried coal powder enters a gasifier while a gasifying agent is added. Under high-temperature conditions, the coal powder is converted into syngas rich in CO and H2. After multi-stage treatment in a syngas purification device, the syngas becomes clean fuel gas. The purified syngas is then transported to a boiler for combustion, where an oxidant is added. The released heat energy is used to heat the carbon dioxide on the working fluid side, achieving efficient energy utilization. The flue gas produced by combustion enters a flue gas purification device for further treatment. The high concentration of carbon dioxide in the purified flue gas is captured by a carbon capture device and converted into liquid through pressurization and cooling processes, ultimately stored in a liquid CO2 storage tank.

[0017] Furthermore, after liquid CO2 flows out of the liquid CO2 storage tank, it is pressurized to the required system pressure by a liquid pump, and then splits into two paths. One path directly enters the gasifier for phase change conversion, while the other path first flows through a heat exchanger to exchange heat with the waste heat of the carbon dioxide working fluid flowing out of the hot side outlet of the regenerator in the supercritical carbon dioxide Brayton cycle system. After recovering the system's waste heat, it enters the gasifier. After gasification in the gasifier, the working fluid is split into two paths. One path is sent to a buffer tank, and after pressure stabilization and regulation, it is continuously replenished to the supercritical carbon dioxide Brayton cycle system. The other path is sent to an expansion unit, where it is depressurized and cooled through an adiabatic expansion process, converting into dry carbon dioxide gas with reduced pressure. This gas is then sent to a pre-drying unit for efficient pre-drying of the raw coal.

[0018] Furthermore, the high-purity supercritical carbon dioxide working fluid from the buffer tank enters the compressor. After being pressurized to the required pressure, the working fluid first flows through the regenerator and is preheated by the supercritical carbon dioxide working fluid that has performed work, becoming a preheated high-pressure supercritical carbon dioxide working fluid. It then enters the working fluid side of the boiler, absorbing the high-temperature heat energy released from the combustion of syngas in the coal gasification system. The high-temperature, high-pressure supercritical carbon dioxide working fluid that has reached the design parameters enters the turbine to expand and perform work, driving the generator to rotate and generate electricity. After performing work, the working fluid first flows through the hot side of the regenerator. After passing through the regenerator, the working fluid is divided into two paths: one path goes directly to the precooler, and the other path flows through the heat exchanger. The two paths of working fluid finally converge at the inlet of the precooler, where the temperature is reduced to a suitable compression point by the cooling medium. The cooled working fluid enters the buffer tank for pressure regulation and buffering to ensure that the working fluid state is stable before re-entering the compressor to complete the cycle.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] This invention discloses a supercritical carbon dioxide circulation system for waste heat recovery and flue gas carbon capture. It utilizes the waste heat of the working fluid, which would otherwise be absorbed by the precooler, to preheat the supplementary working fluid, achieving cascaded utilization of thermal energy. Compared to traditional cooling systems, the auxiliary system energy consumption can be reduced by 5-10%. In this invention, the supercritical carbon dioxide circulation system is combined with a carbon capture system. Carbon dioxide from the flue gas generated by boiler combustion is purified and captured, and then the captured liquefied carbon dioxide is used as supplementary working fluid for reflux. This maintains the system's working fluid balance while achieving carbon circulation management. This invention adopts a modular design concept, coupling and connecting three subsystems: a coal gasification and carbon capture system, a working fluid filling auxiliary system, and a supercritical carbon dioxide Brayton cycle system. Each subsystem can be maintained independently. Combined with power circulation, carbon capture, and waste heat recovery, the system availability is improved, and dynamic matching enhances the system's variable load operating range. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a system flow diagram of a supercritical carbon dioxide recycling system for recovering waste heat and capturing carbon in flue gas, as described in Embodiment 1 of the present invention.

[0023] In the diagram, 1. Pre-drying device; 2. Gasifier; 3. Syngas purification device; 4. Flue gas purification device; 5. Carbon capture device; 11. Liquid CO2 storage tank; 12. Liquid pump; 13. Heat exchanger; 14. Gasifier; 15. Expansion device; 21. Boiler; 22. Turbine; 23. Regenerator; 24. Precooler; 25. Buffer tank; 26. Compressor; 27. Generator; 28. Electric motor; 31. Coal; 32. Gasifying agent; 33. Oxidizing agent; 41. First valve group; 42. Second valve group; 43. Third valve group; 44. Fourth valve group; 45. Fifth valve group; 46. Sixth valve group. Detailed Implementation

[0024] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0025] Furthermore, elements in this invention are referred to as being "fixed to" or "set on" another element, which may be directly on the other element or may also include an intervening element. When an element is considered to be "connected" to another element, it may be directly connected to the other element or may also include an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementations.

[0026] Example 1

[0027] like Figure 1 As shown, this embodiment provides a supercritical carbon dioxide cycle system for recovering waste heat and capturing carbon in flue gas, including a coal gasification and carbon capture system, a working fluid filling auxiliary system, and a supercritical carbon dioxide Brayton cycle system.

[0028] The supercritical carbon dioxide Brayton cycle system consists of a boiler 21, a turbine 22, a regenerator 23, a precooler 24, a buffer tank 25, a compressor 26, a generator 27, and a motor 28. The precooler 24 is connected to the buffer tank 25, the buffer tank 25 is connected to the compressor 26, the motor 28 is connected to the compressor 26, the generator 27 is connected to the turbine 22, the compressor 26 is connected to the turbine 22, and both the compressor 26 and the turbine 22 are connected to the regenerator 23. The outlet of the regenerator 23 is divided into three paths: one path is connected to the boiler 21, the second path is connected to the precooler 24, and the third path is connected to the working fluid charging auxiliary system.

[0029] Supercritical carbon dioxide working fluid is compressed by compressor 26 and flows into the cold side of regenerator 23. It flows from the cold side outlet of regenerator into the working fluid side of boiler 21, is heated, and then enters turbine 22 to generate electricity. After doing work, the working fluid flows into the hot side of regenerator 23 to recover some heat and then splits. The working fluid from the hot side outlet of regenerator 23 flows directly into precooler, and the other flows into precooler 24 for further cooling after heat exchange with working fluid charging auxiliary system through heat exchanger 13. Then it flows into buffer tank 25 for pressure stabilization and then into compressor 26 for a new cycle. Turbine 22 converts the energy output from doing work into electrical energy through generator 27. During the start-up phase, motor 28 drives compressor 26 to rotate.

[0030] The coal gasification and carbon capture system consists of a pre-drying device 1, a gasifier 2, a syngas purification device 3, a flue gas purification device 4, and a carbon capture device 5. The pre-drying device 1 is connected to the gasifier 2, the gasifier 2 is connected to the syngas purification device 3, the syngas purification device 3 is connected to the boiler 21, the boiler 21 is connected to the flue gas purification device 4, and the flue gas purification device 4 is connected to the carbon capture device 5.

[0031] After pre-drying, coal 31 enters gasifier 2 and reacts with gasifying agent 32 to generate syngas. The syngas outlet is connected to syngas purification device 3. The purified syngas enters boiler 21 for combustion and heat release. The flue gas generated after combustion passes through flue gas purification device 4 and carbon capture device 5 to become low-temperature liquid carbon dioxide, which flows into the working fluid filling auxiliary system for later use.

[0032] The working fluid filling auxiliary system consists of a liquid CO2 storage tank 11, a liquid pump 12, a heat exchanger 13, a vaporizer 14, and an expansion device 15. The carbon capture device 5 is connected to the liquid CO2 storage tank 11, which is connected to the liquid pump 12. The outlet of the liquid pump 12 is divided into two paths: one path is connected to the heat exchanger 13 via the first valve group 41, and the other path is connected to the inlet of the vaporizer 14 via the second valve group 42. The outlet of the heat exchanger 13 is divided into two paths: one path is connected to the precooler 24, and the other path is connected to the vaporizer 14. The outlet of the vaporizer 14 is divided into two paths: one path is connected to the buffer tank 25 via the third valve group 43, the buffer tank 25 is connected to the compressor 26, the compressor 26 is connected to the turbine 22, and both the compressor 26 and the turbine 22 are connected to the regenerator 23. The outlet of the regenerator 23 is divided into two paths: one path is connected to the heat exchanger 13 via the sixth valve group 46, and the other path is connected to the boiler 21. Another outlet of the vaporizer 14 is connected to the expansion device 15 via the fourth valve group 44, and the expansion device 15 is connected to the pre-drying device 1.

[0033] After liquid CO2 flows out of the liquid CO2 storage tank 11, it is pressurized by the liquid pump 12 and then split. One stream flows directly into the gasifier 14 for gasification, and the other stream exchanges heat with the waste heat in the supercritical carbon dioxide Brayton cycle system through the heat exchanger 13 before flowing into the gasifier 14 for gasification. The supercritical carbon dioxide flowing out of the gasifier 14 is split into two branches. One stream flows into the buffer tank 25 and then into the supercritical carbon dioxide Brayton cycle system. The other stream flows through the expansion device 15 for depressurization and cooling and then is injected into the pre-drying device 1 to pre-dry the coal 31. The low-temperature liquid carbon dioxide flows into the liquid CO2 storage tank 11.

[0034] In this embodiment 1, the working process of the coal gasification and carbon capture system is as follows: First, coal 31 is transported to the pre-drying device 1, where the coal powder is pretreated using the dry carbon dioxide gas flow from the expansion device 15 in the working fluid filling auxiliary system, achieving dehydration and drying of the coal powder while utilizing the system's waste heat resources; the pre-dried coal powder enters the gasifier 2, and gasifying agent 32 is added to the gasifier at the same time, converting the coal powder into syngas rich in CO and H2 under high temperature conditions. The gasification process generates a large amount of heat, which significantly increases the temperature of the syngas. This heat, along with the heat provided by the pre-drying, sustains the gasification reaction; after the high-temperature syngas undergoes multi-stage treatment by the syngas purification device 3, sulfides are removed. Impurities such as particulate matter and dust are removed, turning the syngas into clean fuel gas. The purified syngas is then transported to boiler 21 for combustion, while oxidant 33 is added to the boiler. The released heat energy is used to heat the carbon dioxide on the working fluid side, achieving efficient energy utilization. The flue gas produced by combustion enters the flue gas purification device 4 for deep treatment. Through desulfurization, denitrification, and high-efficiency dust removal processes, the emission indicators are ensured to meet environmental protection standards. The high concentration of carbon dioxide in the purified flue gas is captured by the carbon capture device 5 and converted into liquid through pressurization and cooling processes. Finally, it is stored in the liquid CO2 storage tank 11. This liquid carbon dioxide is ready for subsequent use, either as an industrial raw material for reuse or for geological sequestration, achieving carbon emission reduction.

[0035] In this embodiment 1, the working fluid filling auxiliary system operates as follows: After liquid CO2 flows out of the liquid CO2 storage tank 11, it is pressurized to the required system pressure by the liquid pump 12, and then divided into two paths. One path directly enters the gasifier 14 for phase change conversion, while the other path first flows through the heat exchanger 13, where it exchanges heat with the waste heat of the carbon dioxide working fluid flowing out of the hot side outlet of the regenerator 23 in the supercritical carbon dioxide Brayton cycle system. After recovering the system's waste heat, it enters the gasifier 14, improving the overall thermal efficiency of the system. After gasification in the gasifier 14, the working fluid is divided into two paths. The main branch is transported to the buffer tank 25, and after pressure stabilization and regulation, it is continuously replenished to the supercritical carbon dioxide Brayton cycle system to maintain a stable supply of the circulating working fluid. The auxiliary branch is guided to the expansion device 15, where it achieves pressure and temperature reduction through an adiabatic expansion process, converting into dry carbon dioxide gas with reduced pressure. This gas is then allocated to the pre-drying device 1 for efficient pre-drying of the raw coal 31.

[0036] In this embodiment 1, the workflow of the supercritical carbon dioxide Brayton cycle system is as follows: High-purity supercritical carbon dioxide working fluid from buffer tank 25 enters compressor 26. After being pressurized to the required system pressure, it first flows through regenerator 23 to be preheated by the supercritical carbon dioxide working fluid that has performed work, becoming preheated high-pressure supercritical carbon dioxide working fluid. It then enters the working fluid side of boiler 21, absorbing high-temperature heat energy released from the combustion of syngas in the coal gasification system, further increasing its temperature and pressure. The high-temperature, high-pressure supercritical carbon dioxide working fluid, reaching the design parameters, enters turbine 22 to expand and perform work, driving generator 27 to rotate and generate electricity, converting heat energy into electrical energy output. The working fluid still possesses considerable heat energy after performing work, therefore it first flows through regenerator 23. On the hot side of the regenerator 23, some of its heat is transferred to the working fluid on the cold side, realizing internal energy recovery. After passing through the regenerator, the working fluid is divided into two paths: the main path leads directly to the precooler 24, while the branch path flows through the heat exchanger 13, where it exchanges heat with the working fluid charging auxiliary system to further recover and utilize the system's waste heat. The two working fluid paths finally converge at the inlet of the precooler 24, where the temperature is reduced to a suitable compression operating point by the cooling medium. The cooled working fluid enters the buffer tank 25 for pressure regulation and buffering, ensuring that the working fluid state is stable before re-entering the compressor 26 to complete a complete cycle. During the startup phase, the compressor 26 is driven by the motor 28 to establish the initial cycle, and after the system reaches a stable operating condition, it switches to a self-sustaining operation mode.

[0037] In this embodiment 1, a first valve group 41 is installed on the first branch line after the liquid pump 12 to connect to the heat exchanger 13, and a second valve group 42 is installed on the second branch line to connect to the vaporizer 14; a third valve group 43 is installed on the main branch line after the vaporizer 14 to connect to the buffer tank 25, and a fourth valve group 44 is installed on the auxiliary branch line to connect to the expansion device 15; a fifth valve group 45 is installed on the main branch line after the regenerator 23 to connect to the precooler 24, and a sixth valve group 46 is installed on the branch line to connect to the heat exchanger 13.

[0038] In this embodiment 1, during the startup phase, the first valve group 41, the fourth valve group 44, and the sixth valve group 46 are closed, and the second valve group 42, the third valve group 43, and the fifth valve group 45 are opened to supply carbon dioxide working fluid into the circulation system. After the circulation stabilizes, the first valve group 41, the fourth valve group 44, and the sixth valve group 46 are opened again to preheat the working fluid to recover waste heat and to pre-dry the coal powder.

[0039] The circulation system of this invention integrates waste heat recovery and carbon capture functions, improves circulation efficiency, purifies and captures carbon dioxide in flue gas and replenishes it back into the circulation system, and at the same time pre-dries pulverized coal after depressurization of part of the drying working fluid, so as to maximize the energy cascade utilization efficiency through system-level synergistic optimization.

[0040] The above description is only of the preferred embodiment of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A supercritical carbon dioxide recycling system for recovering waste heat and capturing carbon in flue gas, characterized in that, This includes a coal gasification and carbon capture system, a working fluid filling auxiliary system, and a supercritical carbon dioxide Brayton cycle system. The coal gasification and carbon capture system includes a pre-drying device (1), a gasifier (2), a syngas purification device (3), a flue gas purification device (4), and a carbon capture device (5); the pre-drying device (1) is connected to the gasifier (2), the gasifier (2) is connected to the syngas purification device (3), the syngas purification device (3) is connected to the supercritical carbon dioxide Brayton cycle system, the flue gas purification device (4) is connected to the flue gas purification device (4), and the flue gas purification device (4) is connected to the carbon capture device (5); The supercritical carbon dioxide Brayton cycle system and the carbon capture device (5) are both connected to the working fluid filling auxiliary system; The working fluid filling auxiliary system includes a liquid CO2 storage tank (11), a liquid pump (12), a heat exchanger (13), a vaporizer (14), and an expansion device (15); wherein, the carbon capture device (5) is connected to the liquid CO2 storage tank (11), the liquid CO2 storage tank (11) is connected to the liquid pump (12), the outlet of the liquid pump (12) is divided into two paths, one path is connected to the heat exchanger (13), and the other path is connected to the inlet of the vaporizer (14); the outlet of the heat exchanger (13) is divided into two paths, one path is connected to the supercritical carbon dioxide Brayton cycle system, and the other path is connected to the vaporizer (14); the outlet of the vaporizer (14) is divided into two paths, one path is connected to the supercritical carbon dioxide Brayton cycle system, the supercritical carbon dioxide Brayton cycle system is connected to the heat exchanger (13), the other path of the vaporizer (14) outlet is connected to the expansion device (15), and the expansion device (15) is connected to the pre-drying device (1); The supercritical carbon dioxide Brayton cycle system includes a boiler (21), a turbine (22), a regenerator (23), a precooler (24), a buffer tank (25), a compressor (26), a generator (27), and a motor (28). The precooler (24) is connected to the buffer tank (25), the buffer tank (25) is connected to the compressor (26), the motor (28) is connected to the compressor (26), the generator (27) is connected to the turbine (22), the compressor (26) is connected to the turbine (22), and both the compressor (26) and the turbine (22) are connected to the regenerator (23). The outlet of the regenerator (23) is divided into three paths: one path is connected to the boiler (21), the second path is connected to the precooler (24), and the third path is connected to the working fluid charging auxiliary system. The regenerator (23) and the precooler (24) are both connected to the heat exchanger (13), and the gasifier (14) is connected to the buffer tank (25).

2. The supercritical carbon dioxide recycling system for waste heat recovery and flue gas carbon capture according to claim 1, characterized in that, One outlet of the vaporizer (14) is connected to the buffer tank (25) via the third valve group (43), and the other outlet is connected to the expansion device (15) via the fourth valve group (44).

3. The supercritical carbon dioxide recycling system for waste heat recovery and flue gas carbon capture according to claim 2, characterized in that, One outlet of the regenerator (23) is connected to the precooler (24) via the fifth valve group (45), and the other outlet is connected to the heat exchanger (13) via the sixth valve group (46).

4. The supercritical carbon dioxide recycling system for waste heat recovery and flue gas carbon capture according to claim 3, characterized in that, The outlet of the liquid pump (12) is connected to the heat exchanger (13) via the first valve group (41), and the outlet of the liquid pump (12) is connected to the vaporizer (14) via the second valve group (42).

5. The supercritical carbon dioxide recycling system for waste heat recovery and flue gas carbon capture according to claim 4, characterized in that, During the startup phase, close the first valve group (41), the fourth valve group (44), and the sixth valve group (46), and open the second valve group (42), the third valve group (43), and the fifth valve group (45) to supply carbon dioxide working fluid into the circulation system. After the circulation stabilizes, open the first valve group (41), the fourth valve group (44), and the sixth valve group (46) to preheat the working fluid.

6. A supercritical carbon dioxide recycling method for recovering waste heat and capturing carbon in flue gas based on the system described in claim 1, characterized in that, Coal (31) is transported to a pre-drying device (1). The pre-dried coal powder enters a gasifier (2), and a gasifying agent (32) is added to the gasifier. Under high temperature conditions, the coal powder is converted into syngas rich in CO and H2. After multi-stage treatment by a syngas purification device (3), the syngas becomes a clean fuel gas. The purified syngas is transported to a boiler (21) for combustion, and an oxidant (33) is added to the boiler. The released heat energy is used to heat carbon dioxide on the working fluid side, achieving efficient energy utilization. The flue gas generated by combustion enters a flue gas purification device (4) for deep treatment. The high concentration of carbon dioxide in the purified flue gas is captured by a carbon capture device (5). Through pressurization and cooling processes, it is converted into liquid and finally stored in a liquid CO2 storage tank (11).

7. The supercritical carbon dioxide recycling method for recovering waste heat and capturing carbon in flue gas according to claim 6, characterized in that, After liquid CO2 flows out of the liquid CO2 storage tank (11), it is pressurized to the required pressure by the liquid pump (12) and then divided into two paths. One path directly enters the gasifier (14) for phase change conversion, while the other path first flows through the heat exchanger (13) to exchange heat with the waste heat of the working fluid of carbon dioxide flowing out of the hot side outlet of the regenerator (23) in the supercritical carbon dioxide Brayton cycle system. After recovering the waste heat of the system, it enters the gasifier (14). After gasification in the gasifier (14), the working fluid is divided into two paths. One path is sent to the buffer tank (25) and continuously replenished to the supercritical carbon dioxide Brayton cycle system after pressure stabilization and regulation. The other path is sent to the expansion device (15) to achieve pressure and temperature reduction through the adiabatic expansion process, and is converted into dry carbon dioxide gas with reduced pressure. It is then sent to the pre-drying device (1) to perform efficient pre-drying treatment on the raw coal (31).

8. The supercritical carbon dioxide recycling method for recovering waste heat and capturing carbon in flue gas according to claim 6, characterized in that, The high-purity supercritical carbon dioxide working fluid from the buffer tank (25) enters the compressor (26). After the working fluid is pressurized to the required pressure, it first flows through the regenerator (23) and is preheated by the supercritical carbon dioxide working fluid that has done work, becoming a preheated high-pressure supercritical carbon dioxide working fluid. Then it enters the working fluid side of the boiler (21) to absorb the high-temperature heat energy released from the combustion of syngas in the coal gasification system. The high-temperature and high-pressure supercritical carbon dioxide working fluid that has reached the design parameters enters the turbine (22) to expand and do work, driving the generator (27) to rotate and generate electricity. After doing work, the working fluid first flows through the hot side of the regenerator (23). After passing through the regenerator, the working fluid is divided into two paths. One path goes directly to the precooler (24), and the other path flows through the heat exchanger (13). The two paths of working fluid finally converge at the inlet of the precooler (24) and the temperature is reduced to the appropriate compression condition point by the cooling medium. After cooling, the working fluid enters the buffer tank (25) for pressure regulation and buffering. After ensuring that the working fluid state is stable, it re-enters the compressor (26) to complete the cycle.

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