Compressed carbon dioxide energy storage system coupling low temperature molten salt with direct air carbon capture

Abstract

The application provides a compressed carbon dioxide energy storage system coupling low-temperature molten salt and direct air carbon capture, and relates to the field of energy storage, comprising: a carbon dioxide gas bag, the outlet gas of which is compressed by a carbon dioxide compressor unit, cooled by a subcooler to form liquid carbon dioxide, and sent to a high-pressure liquid carbon dioxide storage tank for storage, the compression heat generated in the carbon dioxide compression process is stored in a hot water tank in the form of hot water; the liquid carbon dioxide output by the high-pressure liquid carbon dioxide storage tank is sequentially passed through a preheater, a primary heater, a primary carbon dioxide turbine, a secondary heater, a secondary carbon dioxide turbine, and then the output carbon dioxide is cooled by a cooler and input into the carbon dioxide gas bag; an external molten salt device provides molten salt heat exchange for the heat conducting oil of the primary heater and the secondary heater; the outlet water of the hot water device provides heat for the regeneration process of a carbon capture device, and the outlet water of the carbon capture device is input into a cold water device. The application uses large-scale long-time energy storage technology to improve the heat utilization rate and peak capacity of a photothermal power station.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide energy storage, specifically to a compressed carbon dioxide energy storage system that couples cryogenic molten salt with direct air carbon capture. Background Technology

[0002] With the continuous development of new energy power generation technologies such as photovoltaics and wind power, the construction cycle of new energy projects is constantly shortening. However, due to the long construction cycle of grid supporting facilities, it is difficult to match the rapidly growing grid-connected capacity of new energy. In addition, new energy power generation has the characteristics of volatility and intermittency. Therefore, how to improve the grid's ability to absorb new energy power has become an urgent problem to be solved. As a technical approach to solving the grid absorption problem of new energy power, large-scale, long-term energy storage technology, such as compressed air energy storage, liquid air energy storage, pumped hydro storage, and flow batteries, has received much attention in recent years, and its construction scale is constantly increasing.

[0003] Among long-term energy storage technologies, compressed air energy storage technology has the advantages of large capacity, high efficiency, low investment, and short project construction time, and has been widely used in engineering applications in recent years. However, compressed air energy storage systems require natural salt caverns or artificial chambers as high-pressure air storage chambers, which are greatly limited by geographical conditions. If above-ground gas storage facilities are used, the construction cost is high and the system's economic performance is poor. Liquid air energy storage technology uses cryogenic processes to liquefy air for storage, which is not limited by geographical conditions. However, due to the greater energy loss in cryogenic processes, the efficiency of liquid air systems is lower than that of compressed air energy storage.

[0004] Compared to air, carbon dioxide has a higher critical point pressure and temperature (7.377 MPa, 30.98 ℃), while its critical temperature is close to room temperature. Using carbon dioxide instead of air as an energy storage medium allows for storage in the form of high-pressure liquid carbon dioxide on the high-pressure side, thus eliminating the construction costs of artificial chambers or cryogenic devices required in gas energy storage technologies. Furthermore, carbon dioxide is non-toxic, non-flammable, and chemically stable. Based on these characteristics, compressed carbon dioxide energy storage technology, which is similar to compressed air energy storage, has developed rapidly. Currently, engineering applications have gradually shifted from proof-of-concept and small-scale demonstrations to large-scale commercial operation, and compressed carbon dioxide energy storage systems under construction have already reached the megawatt level.

[0005] Carbon dioxide's heat capacity changes significantly near its critical temperature. It's difficult to fully recover the heat generated during carbon dioxide compression in the energy storage phase. This is because when carbon dioxide drops to near its critical temperature, the remaining low-grade heat needs to be transferred to the release phase at a considerable cost (the temperature change is minimal, requiring a huge amount of heat storage medium, resulting in extremely high investment costs). Ignoring this heat transfer means the high-quality heat stored in the storage phase needs to compensate for the heat loss near the critical temperature during the release phase. This prevents the gas expansion and power generation process in the release phase from heating the carbon dioxide to higher temperatures. Ultimately, the resulting compressed carbon dioxide energy storage system has a lower electricity-to-electricity conversion efficiency than compressed air energy storage technology, hindering its market adoption. Furthermore, due to equipment sealing issues, compressed carbon dioxide energy storage systems experience working fluid leakage during operation, requiring periodic replenishment to maintain storage capacity.

[0006] It is noted that the temperature of the molten salt in the cryogenic molten salt storage tank of a concentrated solar power (CSP) plant often needs to be higher than the system's anti-condensation temperature. This means that after the high-temperature molten salt passes through the molten salt steam generator, there is still a temperature range of heat that is not effectively utilized. CSP plants use solar radiation heat energy to heat steam to drive turbines for power generation, resulting in a fixed power output and poor peak capacity. At the same time, there are few residential areas or industrial parks around CSP plants, which provides conditions for the deployment of compressed carbon dioxide energy storage system gasbags. Summary of the Invention

[0007] This invention provides a compressed carbon dioxide energy storage system that couples cryogenic molten salt with direct air carbon capture, in order to solve at least one of the following problems: the current compressed carbon dioxide energy storage technology has problems such as low system efficiency and large annual replenishment volume, while solar thermal power plants have problems such as insufficient heat utilization and poor peak capacity.

[0008] To address the aforementioned technical problems, this invention discloses a compressed carbon dioxide energy storage system coupling cryogenic molten salt and direct air carbon capture, comprising: The carbon dioxide air bag has its outlet connected to the inlet of the carbon dioxide compressor unit, the outlet of the carbon dioxide compressor unit is connected to the carbon dioxide inlet of the subcooler, and the carbon dioxide outlet of the subcooler is connected to the inlet of the high-pressure liquid carbon dioxide storage tank. The preheater has its carbon dioxide inlet connected to the outlet of the high-pressure liquid carbon dioxide storage tank. The carbon dioxide inlet of the primary heater is connected to the outlet of the preheater. The carbon dioxide outlet of the primary heater is connected to the inlet of the primary carbon dioxide turbine. The outlet of the primary carbon dioxide turbine is connected to the carbon dioxide inlet of the secondary heater. The carbon dioxide outlet of the secondary heater is connected to the inlet of the secondary carbon dioxide turbine. The outlet of the secondary carbon dioxide turbine is connected to the carbon dioxide inlet of the cooler. The carbon dioxide outlet of the cooler is connected to the inlet of the carbon dioxide gasbag. The heat transfer oil outlets of the molten salt unit, the primary heater and the secondary heater are connected to the heat transfer oil inlet of the molten salt unit, and the high-temperature heat transfer oil outlet of the molten salt unit is connected to the heat transfer oil inlet of the primary heater and the secondary heater. The system includes a hot water unit and a carbon capture unit. The outlet of the hot water unit is connected to the inlet of the carbon capture unit, and the outlet of the carbon capture unit is connected to the inlet of the cold water unit.

[0009] Preferably, the carbon dioxide compressor unit includes: Low-pressure carbon dioxide compressor, medium-pressure carbon dioxide compressor, high-pressure carbon dioxide compressor; the inlet of the low-pressure carbon dioxide compressor is connected to the outlet of the carbon dioxide bladder; the outlet of the low-pressure carbon dioxide compressor is connected to the carbon dioxide inlet of the low-pressure stage aftercooler. The carbon dioxide outlet of the low-pressure stage aftercooler is connected to the inlet of the medium-pressure carbon dioxide compressor, and the outlet of the medium-pressure carbon dioxide compressor is connected to the carbon dioxide inlet of the medium-pressure stage aftercooler. The carbon dioxide outlet of the intermediate-pressure stage aftercooler is connected to the inlet of the high-pressure carbon dioxide compressor, the outlet of the high-pressure carbon dioxide compressor is connected to the carbon dioxide inlet of the high-pressure stage aftercooler, and the carbon dioxide outlet of the high-pressure stage aftercooler 7 is connected to the carbon dioxide inlet of the aftercooler.

[0010] Preferably, the heat transfer oil outlets of the primary heater and the secondary heater are connected to the inlet of the low-temperature heat transfer oil storage tank; The molten salt unit includes: a low-temperature heat transfer oil storage tank, the outlet of which is connected to the heat transfer oil inlet of the molten salt-heat transfer oil heat exchanger via a low-temperature oil pump; the heat transfer oil outlet of the molten salt-heat transfer oil heat exchanger is connected to the inlet of the high-temperature heat transfer oil storage tank; the outlet of the high-temperature heat transfer oil storage tank is connected to the inlet of the high-temperature oil pump; and the outlet of the high-temperature oil pump is connected to the heat transfer oil inlets of the primary heater and the secondary heater.

[0011] Preferably, the molten salt device includes: a low-temperature thermal oil storage tank, wherein the thermal oil outlets of the primary heater and the secondary heater are connected to the inlet of the low-temperature thermal oil storage tank; the outlet of the low-temperature thermal oil storage tank is connected to the thermal oil inlet of the molten salt-thermal oil heat exchanger via a low-temperature oil pump, the thermal oil outlet of the molten salt-thermal oil heat exchanger is connected to the inlet of the high-temperature thermal oil storage tank, the outlet of the high-temperature thermal oil storage tank is connected to the inlet of the high-temperature oil pump, and the outlet of the high-temperature oil pump is connected to the thermal oil inlets of the primary heater and the secondary heater.

[0012] Preferably, the hot water device includes: a hot water tank, the hot water outlet of the cooler is connected to the inlet of the hot water tank, and the outlet of the hot water tank is connected to the inlet of the hot water pump.

[0013] Preferably, the cooling water device includes: an air cooler, the water channel outlet of the air cooler being connected to the inlet of a cooling water tank, the outlet of the cooling water tank being connected to a cooling water pump, and the cooling water pump being connected to the cooling water inlet of the cooler.

[0014] Preferably, the carbon capture device includes: A solid amine adsorber with a heat exchange mechanism is provided, with the outlet of the hot water device connected to the inlet of the solid amine adsorber with a heat exchange mechanism, and the outlet of the solid amine adsorber with a heat exchange mechanism connected to the inlet of the cold water device. The fan's outlet is connected to the solid amine adsorber with heat exchange mechanism and the centrifugal pump's inlet. The centrifugal pump's outlet is also connected to the buffer tank inlet, and the buffer tank outlet is connected to the water cooler's air inlet. The water cooler has its inlet connected to the outlet of the hot water unit, and its outlet connected to the inlet of the cold water unit. The carbon dioxide compressor has its air inlet connected to the air outlet of the water cooler, its air outlet connected to the air inlet of the liquefier, and its liquid outlet connected to the liquid carbon dioxide storage tank. The refrigerant outlet of the cascade refrigeration unit is connected to the refrigerant inlet of the liquefier, and the refrigerant outlet of the liquefier is connected to the refrigerant inlet of the cascade refrigeration unit.

[0015] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention utilizes low-temperature molten salt to supplement the heat of the energy storage device, solving the problem of low system efficiency caused by the difficulty in recovering heat near the critical temperature of carbon dioxide during the operation of the energy storage device, greatly improving the system efficiency and facilitating the promotion of energy storage device applications.

[0017] 2. In the direct air carbon capture section of the present invention, solid amine is used as an adsorbent to adsorb carbon dioxide in the air. Since the regeneration temperature required by the solid absorption carbon capture technology is relatively low, the hot water generated during the energy storage stage can be used as a regeneration heat source. At the same time, the generated carbon dioxide can be used as a working fluid to supplement the system, reducing operation and maintenance costs and improving the system's energy utilization rate.

[0018] 3. Compared with traditional compressed carbon dioxide energy storage systems, the novel solution proposed in this invention has an additional high-temperature heat source. To improve system efficiency, depending on the remaining low-temperature molten salt or the range of temperatures that can be cooled, the number of compressor stages and interstage cooling in the energy storage stage can be increased to reduce energy storage power consumption; or a high-pressure fluid pump can be used to further pressurize the liquid carbon dioxide in the storage tank to increase the system's work potential.

[0019] 4. Based on the characteristics of the new solution, the remaining medium-to-high-quality heat can be used for absorption cooling, while the air after carbon dioxide removal is pressurized, thereby realizing the combined supply of cooling, heating, electricity and gas to the surrounding area of ​​the station, living area and office area, and improving the overall efficiency.

[0020] The new scheme reduces heat transfer losses and significantly improves system efficiency, helping energy storage devices to generate higher profits by taking advantage of peak-valley price differences. The added direct air carbon capture device effectively recovers low- to medium-grade heat generated by the system, reducing resource waste and producing high-value-added products. The liquid carbon dioxide produced in subsequent processes can serve as a byproduct, generating revenue during the operation of the new scheme, and can also be used as a working fluid to supplement the system, reducing operation and maintenance costs. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is an overall schematic diagram of the present invention; Figure 2 This is a schematic diagram of a traditional compressed carbon dioxide energy storage system.

[0022] In the diagram: 1. Carbon dioxide gasbag; 2. Low-pressure carbon dioxide compressor; 3. Low-pressure aftercooler; 4. Medium-pressure carbon dioxide compressor; 5. Medium-pressure aftercooler; 6. High-pressure carbon dioxide compressor; 7. High-pressure aftercooler; 8. Subcooler; 9. High-pressure liquid carbon dioxide storage tank; 10. Cold water tank; 11. Cold water pump; 12. Hot water pump; 13. Hot water tank; 14. Primary heater; 15. Primary carbon dioxide turbine; 16. Secondary heater; 17. Secondary stage heater. 18. Carbon dioxide turbine; 19. Preheater; 20. Cooler; 21. High-temperature heat transfer oil storage tank; 22. High-temperature oil pump; 23. Molten salt-heat transfer oil heat exchanger; 24. Low-temperature heat transfer oil storage tank; 25. Low-temperature oil pump; 26. Air cooler; 27. Fan; 28. Solid amine adsorber with heat exchange mechanism; 29. ​​Centrifugal pump; 30. Buffer tank; 31. Water cooler; 32. Carbon dioxide compressor; 33. Liquefaction unit; 34. Liquid carbon dioxide storage tank; 35. Cascade refrigeration unit. Detailed Implementation

[0023] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0024] Furthermore, in this invention, the use of terms such as "first" and "second" is for descriptive purposes only and does not specifically refer to any order or sequence, nor is it intended to limit the invention. They are merely used to distinguish components or operations described using the same technical terms and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions and features of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If a combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0025] The present invention provides the following embodiments: This invention provides a compressed carbon dioxide energy storage system that couples cryogenic molten salt with direct air carbon capture, such as... Figure 1 As shown, it includes: The carbon dioxide air bag 1 has its outlet connected to the inlet of the carbon dioxide compressor unit, the outlet of the carbon dioxide compressor unit is connected to the inlet of the supercooler 8, and the outlet of the supercooler 8 is connected to the inlet of the high-pressure liquid carbon dioxide storage tank 9. The preheater 18 has its inlet connected to the outlet of the high-pressure liquid carbon dioxide storage tank 9. The carbon dioxide inlet of the primary heater 14 is connected to the outlet of the preheater 18. The carbon dioxide outlet of the primary heater 14 is connected to the inlet of the primary carbon dioxide turbine 15. The outlet of the primary carbon dioxide turbine 15 is connected to the carbon dioxide inlet of the secondary heater 16. The carbon dioxide outlet of the secondary heater 16 is connected to the inlet of the secondary carbon dioxide turbine 17. The outlet of the secondary carbon dioxide turbine 17 is connected to the carbon dioxide inlet of the cooler 19. The carbon dioxide outlet of the cooler 19 is connected to the air inlet of the carbon dioxide gasbag 1. The heat transfer oil outlets of the primary heater 14 and the secondary heater 16 of the molten salt device are connected to the low-temperature heat transfer oil inlet of the molten salt device, and the high-temperature heat transfer oil outlet of the molten salt device is connected to the heat transfer oil inlet of the primary heater 14 and the secondary heater 16. The hot water device and the carbon capture device are connected. The outlet of the hot water device is connected to the inlet of the solid amine adsorber 27 with heat exchange mechanism of the carbon capture device. The outlet of the solid amine adsorber 27 with heat exchange mechanism of the carbon capture device is connected to the inlet of the cold water device.

[0026] Preferably, the carbon dioxide compressor unit includes: Low-pressure carbon dioxide compressor 2, medium-pressure carbon dioxide compressor 4, and high-pressure carbon dioxide compressor 6. The air inlet of low-pressure carbon dioxide compressor 2 is connected to the air outlet of carbon dioxide air bag 1, and the air outlet of low-pressure carbon dioxide compressor 2 is connected to the carbon dioxide air inlet of low-pressure stage aftercooler 3. The carbon dioxide outlet of the low-pressure stage aftercooler 3 is connected to the inlet of the medium-pressure carbon dioxide compressor 4, and the outlet of the medium-pressure carbon dioxide compressor 4 is connected to the carbon dioxide inlet of the medium-pressure stage aftercooler 5. The carbon dioxide outlet of the intermediate-pressure stage aftercooler 5 is connected to the inlet of the high-pressure carbon dioxide compressor 6, the outlet of the high-pressure carbon dioxide compressor 6 is connected to the carbon dioxide inlet of the high-pressure stage aftercooler 7, and the carbon dioxide outlet of the high-pressure stage aftercooler 7 is connected to the carbon dioxide inlet of the supercooler 8.

[0027] Preferably, the heat transfer oil outlets of the primary heater 14 and the secondary heater 16 are connected to the inlet of the low-temperature heat transfer oil storage tank 23; The molten salt device includes: a low-temperature heat transfer oil storage tank 23, the outlet of which is connected to the heat transfer oil inlet of the molten salt-heat transfer oil heat exchanger 22 via a low-temperature oil pump 24; the heat transfer oil outlet of the molten salt-heat transfer oil heat exchanger 22 is connected to the inlet of a high-temperature heat transfer oil storage tank 20; the outlet of the high-temperature heat transfer oil storage tank 20 is connected to the inlet of a high-temperature oil pump 21; and the outlet of the high-temperature oil pump 21 is connected to the heat transfer oil inlets of the primary heater 14 and the secondary heater 16.

[0028] Preferably, the molten salt device includes: a low-temperature heat transfer oil storage tank 23, the heat transfer oil outlets of the primary heater 14 and the secondary heater 16 are connected to the inlet of the low-temperature heat transfer oil storage tank 23; the outlet of the low-temperature heat transfer oil storage tank 23 is connected to the heat transfer oil inlet of the molten salt-heat transfer oil heat exchanger 22 via a low-temperature oil pump 24, the heat transfer oil outlet of the molten salt-heat transfer oil heat exchanger 22 is connected to the inlet of the high-temperature heat transfer oil storage tank 20, the outlet of the high-temperature heat transfer oil storage tank 20 is connected to the inlet of the high-temperature oil pump 21, and the outlet of the high-temperature oil pump 21 is connected to the heat transfer oil inlets of the primary heater 14 and the secondary heater 16.

[0029] Preferably, the hot water device includes: a hot water tank 13, the hot water outlet of the cooler 19 is connected to the inlet of the hot water tank 13, and the outlet of the hot water tank 13 is connected to the inlet of the hot water pump 12.

[0030] Preferably, the cooling water device includes: an air cooler 25, the water channel outlet of the air cooler 25 is connected to the water inlet of the cooling water tank 10, the water outlet of the cooling water tank 10 is connected to the cooling water pump 11, and the cooling water pump 11 is connected to the cooling water inlet of the cooler 19.

[0031] Preferably, the carbon capture device includes: The solid amine adsorber 27 with heat exchange mechanism is connected to the inlet of the solid amine adsorber 27 with heat exchange mechanism at the outlet of the hot water device, and the outlet of the solid amine adsorber 27 with heat exchange mechanism is connected to the inlet of the cold water device. Fan 26, the air outlet of fan 26 is connected to the air inlet of solid amine adsorber 27 and centrifugal pump 28, the air outlet of centrifugal pump 28 is also connected to the inlet of buffer tank 29, and the outlet of buffer tank 29 is connected to the air inlet of water cooler 30. Water cooler 30, the inlet of water cooler 30 is connected to the outlet of hot water device, and the outlet of water cooler 30 is connected to the inlet of cold water device. The carbon dioxide compressor 31 has its air inlet connected to the air outlet of the water cooler 30, the air outlet of the carbon dioxide compressor 31 connected to the air inlet of the liquefier 32, and the liquid outlet of the liquefier 32 connected to the liquid carbon dioxide storage tank 33. The refrigerant outlet of the cascade refrigeration unit 34 is connected to the refrigerant inlet of the liquefier 32, and the refrigerant outlet of the liquefier 32 is connected to the refrigerant inlet of the cascade refrigeration unit 34.

[0032] The energy storage / release process of compressed carbon dioxide energy storage technology is similar to that of traditional compressed air energy storage technology. The difference is that carbon dioxide cannot be obtained from the external environment at any time. Therefore, it is necessary to store atmospheric carbon dioxide in a gas bag for recycling. In the energy storage stage, the carbon dioxide compressor draws carbon dioxide from the gas bag and compresses it to a higher pressure through three stages: low, medium and high. The high-pressure carbon dioxide is cooled to below the critical temperature by a subcooler, thus achieving liquid storage in a high-pressure carbon dioxide storage tank. In the energy release stage, the high-pressure liquid carbon dioxide is heated and vaporized by the heat stored in the energy storage stage and superheated to a higher temperature by a heater. The shaft work generated by the expansion of the superheated gas drives the generator to generate electricity. After the gas expands to atmospheric pressure, it returns to the carbon dioxide gas bag for storage to await the next energy storage process.

[0033] The system flow diagram of the proposed compressed carbon dioxide energy storage device that couples cryogenic molten salt and direct air carbon capture (hereinafter referred to as the novel scheme) is shown below. Figure 1 As shown. The operating principle of the compressed carbon dioxide energy storage device remains unchanged. The difference lies in the energy release stage, where the hot water stored in the energy storage stage preheats the high-pressure liquid carbon dioxide. After its temperature exceeds the critical temperature and it vaporizes, the carbon dioxide is then superheated in the first and second stage superheaters using heat transfer oil before entering the expander for expansion. Due to the significant increase in the expander's inlet temperature, the expansion ratio remains unchanged, leading to a rise in the gas temperature at the expander outlet. The expansion of the carbon dioxide volume can easily cause the gas bladder to rupture, necessitating the addition of a cooler to cool the carbon dioxide gas at atmospheric pressure using circulating water. This device uses heat transfer oil to recover the heat from the low-temperature molten salt, avoiding significant modifications to the original design of the solar thermal power plant that could lead to safety issues.

[0034] The new design also incorporates a direct air carbon capture device, employing a solid absorption method. The adsorber is filled with solid amine material as the adsorbent for carbon dioxide. The operation process can be specifically divided into four stages: adsorption, purging, regeneration, and repressurization.

[0035] In the adsorption process, a blower blows air into an adsorber with a heat exchange structure, where carbon dioxide in the air is selectively adsorbed, and the air is then discharged into the external environment after the carbon dioxide is removed. During the purging process, after the adsorption process has been running for a period of time, the high-temperature hot water generated by the system during the energy storage stage is used to heat the adsorbent inside the adsorber to the regeneration temperature, and the partial pressure of carbon dioxide inside the adsorber increases. During the regeneration process, a high-temperature hot water flow rate is maintained to ensure that the adsorbent temperature in the adsorber is kept at the regeneration temperature. A vacuum pump is used to reduce the pressure in the adsorber tank. During this process, carbon dioxide is desorbed and drawn into the buffer tank. The repressurization process involves using a fan to restore the pressure inside the adsorber to its initial state, while circulating water continuously cools the adsorbent, thus completing the adsorbent regeneration process.

[0036] The carbon dioxide stored in the buffer tank is cooled by cooling water and pressurized by the carbon dioxide compressor to a three-phase pressure (0.517 MPa) or higher to prevent carbon dioxide from sublimating in subsequent cryogenic processes and generating dry ice that blocks the pipeline. The cryogenic refrigerant output from the cascade refrigeration unit cools and liquefies the carbon dioxide, which is then stored in storage tanks or transported to external users by tank truck.

[0037] The beneficial effects of the above technical solution are as follows: 1. This invention utilizes low-temperature molten salt to supplement the heat of the energy storage device, solving the problem of low system efficiency caused by the difficulty in recovering heat near the critical temperature of carbon dioxide during the operation of the energy storage device, greatly improving the system efficiency and facilitating the promotion of energy storage device applications.

[0038] 2. In the direct air carbon capture section of the present invention, solid amine is used as an adsorbent to adsorb carbon dioxide in the air. Since the regeneration temperature required by the solid absorption carbon capture technology is relatively low, the hot water generated in the energy storage stage can be used as a regeneration heat source. At the same time, the generated liquid carbon dioxide can be used as a working fluid to supplement the system, reducing operation and maintenance costs and improving the system energy utilization rate.

[0039] 3. Compared with traditional compressed carbon dioxide energy storage systems, the novel solution proposed in this invention has an additional high-temperature heat source. To improve system efficiency, depending on the remaining low-temperature molten salt or the range of temperatures that can be cooled, the number of compressor stages and interstage cooling in the energy storage stage can be increased to reduce energy storage power consumption; or a high-pressure fluid pump can be used to further pressurize the liquid carbon dioxide in the storage tank to increase the system's work potential.

[0040] 4. Based on the characteristics of the new solution, the remaining medium-to-high-quality heat can be used for absorption cooling, while the air after carbon dioxide removal is pressurized, thereby realizing the combined supply of cooling, heating, electricity and gas to the surrounding area of ​​the station, living area and office area, and improving the overall efficiency.

[0041] The new scheme reduces heat transfer losses and significantly improves system efficiency, helping energy storage devices to generate higher profits by taking advantage of peak-valley price differences. The added direct air carbon capture device effectively recovers low- to medium-grade heat generated by the system, reducing resource waste and producing high-value-added products. The liquid carbon dioxide produced in subsequent processes can serve as a byproduct, generating revenue during the operation of the new scheme, and can also be used as a working fluid to supplement the system, reducing operation and maintenance costs.

[0042] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A compressed carbon dioxide energy storage system coupling cryogenic molten salt and direct air carbon capture, characterized in that: include: The carbon dioxide air bag (1) has its outlet connected to the inlet of the carbon dioxide compressor unit, the outlet of the carbon dioxide compressor unit is connected to the carbon dioxide inlet of the supercooler (8), and the carbon dioxide outlet of the supercooler (8) is connected to the inlet of the high-pressure liquid carbon dioxide storage tank (9). The preheater (18) has its carbon dioxide inlet connected to the outlet of the high-pressure liquid carbon dioxide storage tank (9). The carbon dioxide inlet of the first-stage heater (14) is connected to the outlet of the preheater (18). The carbon dioxide outlet of the first-stage heater (14) is connected to the inlet of the first-stage carbon dioxide turbine (15). The outlet of the first-stage carbon dioxide turbine (15) is connected to the carbon dioxide inlet of the second-stage heater (16). The carbon dioxide outlet of the second-stage heater (16) is connected to the inlet of the second-stage carbon dioxide turbine (17). The outlet of the second-stage carbon dioxide turbine (17) is connected to the carbon dioxide inlet of the cooler (19). The carbon dioxide outlet of the cooler (19) is connected to the inlet of the carbon dioxide gasbag (1). The heat transfer oil outlets of the primary heater (14) and the secondary heater (16) of the molten salt device are connected to the low-temperature heat transfer oil inlet of the molten salt device, and the high-temperature heat transfer oil outlet of the molten salt device is connected to the heat transfer oil inlet of the primary heater (14) and the secondary heater (16). A hot water unit and a carbon capture unit are connected. The outlet of the hot water unit is connected to the inlet of the carbon capture unit, and the outlet of the carbon capture unit is connected to the inlet of the cold water unit. The molten salt device includes: a low-temperature heat transfer oil storage tank (23), whose outlet is connected to the heat transfer oil inlet of the molten salt-heat transfer oil heat exchanger (22) via a low-temperature oil pump (24); the heat transfer oil outlet of the molten salt-heat transfer oil heat exchanger (22) is connected to the inlet of the high-temperature heat transfer oil storage tank (20); the outlet of the high-temperature heat transfer oil storage tank (20) is connected to the inlet of the high-temperature oil pump (21); and the outlet of the high-temperature oil pump (21) is connected to the heat transfer oil inlets of the primary heater (14) and the secondary heater (16). The hot water device includes: a hot water tank (13), the hot water outlet of the cooler (19) is connected to the inlet of the hot water tank (13), and the outlet of the hot water tank (13) is connected to the inlet of the hot water pump (12); The cooling water device includes: an air cooler (25), the water channel outlet of the air cooler (25) is connected to the water inlet of the cooling water tank (10), the water outlet of the cooling water tank (10) is connected to the cooling water pump (11), and the cooling water pump (11) is connected to the cooling water inlet of the cooler (19). The carbon capture device includes: The solid amine adsorber (27) with heat exchange mechanism is connected to the inlet of the solid amine adsorber (27) with heat exchange mechanism and the outlet of the solid amine adsorber (27) with heat exchange mechanism is connected to the inlet of the cold water device. The outlet of the fan (26) is connected to the air inlet of the solid amine adsorber (27) with heat exchange mechanism and the centrifugal pump (28). The outlet of the centrifugal pump (28) is also connected to the inlet of the buffer tank (29). The outlet of the buffer tank (29) is connected to the air inlet of the water cooler (30). Water cooler (30), the inlet of water cooler (30) is connected to the outlet of hot water device, and the outlet of water cooler (30) is connected to the inlet of cold water device; The carbon dioxide compressor (31) has its inlet connected to the outlet of the water cooler (30), the outlet of the carbon dioxide compressor (31) is connected to the inlet of the liquefier (32), and the outlet of the liquefier (32) is connected to the liquid carbon dioxide storage tank (33). The refrigerant outlet of the cascade refrigeration unit (34) is connected to the refrigerant inlet of the liquefier (32), and the refrigerant outlet of the liquefier (32) is connected to the refrigerant inlet of the cascade refrigeration unit (34).

2. The compressed carbon dioxide energy storage system coupled with cryogenic molten salt and direct air carbon capture according to claim 1, characterized in that: The carbon dioxide compressor unit includes: Low-pressure carbon dioxide compressor (2), medium-pressure carbon dioxide compressor (4), high-pressure carbon dioxide compressor (6), the inlet of low-pressure carbon dioxide compressor (2) is connected to the outlet of carbon dioxide air bag (1), and the outlet of low-pressure carbon dioxide compressor (2) is connected to the carbon dioxide inlet of low-pressure stage aftercooler (3). The carbon dioxide outlet of the low-pressure stage aftercooler (3) is connected to the inlet of the medium-pressure carbon dioxide compressor (4), and the outlet of the medium-pressure carbon dioxide compressor (4) is connected to the carbon dioxide inlet of the medium-pressure stage aftercooler (5). The carbon dioxide outlet of the intermediate-pressure stage aftercooler (5) is connected to the inlet of the high-pressure carbon dioxide compressor (6), the outlet of the high-pressure carbon dioxide compressor (6) is connected to the carbon dioxide inlet of the high-pressure stage aftercooler (7), and the carbon dioxide outlet of the high-pressure stage aftercooler (7) is connected to the carbon dioxide inlet of the overcooler (8).

3. The compressed carbon dioxide energy storage system coupled with cryogenic molten salt and direct air carbon capture according to claim 1, characterized in that: The heat transfer oil outlets of the primary heater (14) and the secondary heater (16) are connected to the inlet of the low-temperature heat transfer oil storage tank (23).

4. The compressed carbon dioxide energy storage system coupled with cryogenic molten salt and direct air carbon capture according to claim 1, characterized in that: The solid amine adsorber with heat exchange mechanism (27) uses solid amine material filled inside as carbon dioxide adsorbent material, and realizes carbon dioxide adsorption and adsorbent regeneration through four processes including adsorption, purging, regeneration and repressurization. Adsorption process: The blower blows air into the solid amine adsorber (27) with heat exchange mechanism. Carbon dioxide in the air is selectively adsorbed by the solid amine material. The air after removing carbon dioxide is discharged to the outside environment. Purging process: After the adsorption process has been running for a period of time, the high-temperature hot water generated during the system's energy storage phase is used to heat the adsorbent inside the adsorber to the regeneration temperature, thereby increasing the partial pressure of carbon dioxide inside the adsorber. Regeneration process: Maintain high-temperature hot water flow to ensure that the adsorbent temperature in the adsorber is maintained at the regeneration temperature. Use a vacuum pump to reduce the pressure in the adsorber tank, so that carbon dioxide is desorbed and pumped into the buffer tank. Repressurization process: The blower is used to restore the pressure inside the adsorber to the initial state, while the circulating water continuously cools the adsorbent through the heat exchange structure, thus completing the adsorbent regeneration.

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