Coupling system for compressed carbon dioxide energy storage

Abstract

The invention belongs to the technical field of heat engine energy storage, and particularly relates to a coupling system for compressed carbon dioxide energy storage, trapped carbon dioxide is pressurized and cooled through a low-pressure compressor and a first heat exchange unit and then enters a high-pressure compressor, after the high-pressure compressor conducts secondary pressurization on the carbon dioxide, one part of the carbon dioxide is stored in an underground reservoir, and the other part of the carbon dioxide is stored in a second heat exchange unit; one part of carbon dioxide is primarily heated and stored in the high-pressure storage tank through the first-stage heat regenerator, the high-pressure storage tank heats the primarily heated carbon dioxide again through the second-stage heat regenerator and conveys the carbon dioxide to the high-pressure turbine, and the high-pressure turbine does work through heat expansion of the carbon dioxide to provide power for the generator to conduct first-stage power generation; after the temperature of the first heat exchange unit is increased again, the carbon dioxide enters the low-pressure turbine, and the low-pressure turbine does work through heat expansion of the carbon dioxide to provide power for the power generator for secondary power generation. Therefore, the utilization degree of heat energy of the system is improved through multi-stage heat exchange and waste heat recovery.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal engine energy storage, and in particular relates to a coupling system for compressed carbon dioxide energy storage. Background Art

[0002] With the rapid development of renewable energy and the transformation of traditional energy sources, large-scale energy storage systems have become a core component of the modern energy system, playing a vital role in balancing electricity supply and demand, improving energy utilization, enhancing grid resilience, and promoting carbon neutrality. Currently, mainstream energy storage technologies include battery storage and pumped hydroelectric storage, but these technologies are limited by cost, lifespan, and topographical factors, hindering their widespread adoption.

[0003] Compressed carbon dioxide energy storage (CCES) is a new energy storage technology that has garnered significant attention in recent years. Its core approach is to store and release energy through the compression and expansion of carbon dioxide. Combined with carbon capture and storage (CCS), it can directly utilize CO2 emissions from industries such as electricity, steel, and cement, achieving negative carbon emissions. During the charging process, gaseous CO2 is compressed to a supercritical state and stored in a high-pressure vessel. A portion of the high-pressure, low-temperature CO2 is then stored in an underground reservoir for storage. During the discharge process, the remaining high-pressure CO2 is heated and expanded to drive a turbine for power generation, completing a closed-loop "energy storage + carbon storage" system. Currently, existing CCS combined with CCS typically employs single-stage or two-stage compression. However, the heat exchange process typically uses a single stage, resulting in low thermal energy utilization and significant loss of high-quality thermal energy. For example, Chinese patent publication number CN118846752A provides a CCS system comprising an absorption tower, a desorption tower, and a CCS energy storage unit. The CCS energy storage unit includes a compressor, a first heat exchanger, a high-pressure gas storage device, a second heat exchanger, an expander, and a low-pressure gas storage device, forming an energy storage loop. On the one hand, the system uses industrial tail gas for carbon capture, and on the other hand, it uses industrial waste heat as a low-temperature heat source for auxiliary heating. However, the system adopts a single-stage heat exchange form. Since the specific heat capacity of carbon dioxide varies significantly with temperature, the single heat exchange path leads to low thermal energy utilization. The system's waste heat cannot be reasonably utilized, resulting in the loss of high-quality thermal energy. For example, the Chinese patent with publication number CN114673571B proposes a coupling system for carbon capture, utilization and storage and supercritical carbon dioxide energy storage technology. It uses two-stage compression to store excess energy in high-pressure supercritical carbon dioxide, and then transports and stores it in salt caverns, depleted oil and gas reservoirs, etc., to achieve full utilization of carbon dioxide. However, the system adopts a single-stage heat exchange and uses heat accumulators and cold accumulators to store heat storage working fluids. The system's thermal energy utilization rate is low, and the system's waste heat cannot be reasonably utilized, resulting in heat loss. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a coupled system for compressed carbon dioxide energy storage, which can effectively improve the recycling of system thermal energy, have high thermal energy utilization rate, and reduce heat loss.

[0005] The technical solution of the present invention is: A coupled system for compressed carbon dioxide energy storage, wherein the circulating medium is carbon dioxide, includes a low-pressure storage tank and a high-pressure storage tank, and further includes: The energy storage unit includes a low-pressure compressor and a high-pressure compressor connected in sequence, wherein the low-pressure compressor is connected to a low-pressure storage tank, and the high-pressure compressor is connected to a high-pressure storage tank; An energy release unit, comprising a high-pressure turbine and a low-pressure turbine connected in sequence, wherein the high-pressure turbine is connected to a high-pressure storage tank, and the low-pressure turbine is connected to a low-pressure storage tank, and both the high-pressure turbine and the low-pressure turbine are used to realize the conversion of thermal energy into mechanical energy; At least one heat exchange unit 1, used to replace the heat of the carbon dioxide output by the low-pressure compressor and apply it to the carbon dioxide flowing from the high-pressure turbine to the low-pressure turbine; The waste heat recovery and utilization unit includes: a first-level regenerator, whose low-temperature inlet is connected to the low-pressure storage tank, whose low-temperature outlet is connected to the low-pressure compressor, whose high-temperature inlet is connected to the high-pressure compressor, and whose high-temperature outlet is connected to the high-pressure storage tank, and which is used to replace the heat of the carbon dioxide delivered to the low-pressure compressor with the carbon dioxide flowing to the high-pressure storage tank for increasing the temperature; a second-level regenerator, whose low-temperature inlet is connected to the high-pressure storage tank, whose low-temperature outlet is connected to the high-pressure turbine, whose high-temperature inlet is connected to the low-pressure turbine, and whose high-temperature outlet is connected to the low-pressure storage tank, and which is used to replace the waste heat of the carbon dioxide output by the low-pressure turbine with the carbon dioxide flowing to the high-pressure turbine for increasing the temperature.

[0006] Preferably, the heat exchange unit 1 includes: a primary condenser, wherein a high-temperature side inlet thereof is connected to the low-pressure compressor, and a high-temperature side outlet thereof is connected to the high-pressure compressor; a primary cold salt storage tank, the outlet of which is connected to the low-temperature side inlet of the primary condenser; The first-stage hot salt storage tank has its inlet connected to the low-temperature side outlet of the first-stage condenser The high-temperature side inlet of the first-stage heater is connected to the outlet of the first-stage hot salt storage tank, and the high-temperature side outlet is connected to the inlet of the first-stage cold salt storage tank. The low-temperature side inlet of the first-stage heater is connected to the high-pressure turbine, and the low-temperature side outlet is connected to the low-pressure turbine.

[0007] Preferably, a second heat exchange unit is further provided between the low-pressure compressor and the high-pressure compressor, and the second heat exchange unit comprises: a secondary condenser, wherein the high-temperature side inlet is connected to the high-temperature side outlet of the primary condenser, and the high-temperature side outlet is communicated with the high-pressure compressor; a first-stage cold water storage tank, the outlet of which is connected to the low-temperature side inlet of the second-stage condenser; a first-stage hot water storage tank, the inlet of which is connected to the low-temperature side outlet of the second-stage condenser; The high-temperature side inlet of the secondary heater is connected to the outlet of the first-level hot water storage tank, and the high-temperature side outlet is connected to the inlet of the first-level cold water storage tank. The low-temperature side inlet of the secondary heater is connected to the high-pressure turbine, and the low-temperature side outlet is connected to the low-temperature side inlet of the first-level heater.

[0008] Preferably, a heat exchange unit three and a heat exchange unit four are also included. The heat exchange unit three has the same structure as the heat exchange unit one, and the heat exchange unit four has the same structure as the heat exchange unit two. The heat exchange unit three and the heat exchange unit four are both used to cool down and heat-exchange the carbon dioxide after being pressurized by the high-pressure compressor, and apply the displaced heat to the carbon dioxide flowing to the high-pressure turbine.

[0009] Preferably, the outlet of the high-pressure compressor is further connected to an underground reservoir, and the underground reservoir is used to store carbon dioxide overflowing from the high-pressure storage tank.

[0010] Preferably, a working fluid pump and a preheater are connected in sequence between the high-pressure storage tank and the secondary regenerator, the working fluid pump is connected to the high-pressure storage tank, and the preheater is connected to the secondary regenerator, and the preheater is used to preheat the carbon dioxide flowing to the secondary regenerator using the ambient temperature.

[0011] Preferably, a cooling and pressure reduction component is further provided between the low-pressure turbine and the low-pressure storage tank. The cooling and pressure reduction component includes a cooler. One end of the cooler is connected to the low-pressure turbine through the secondary heat regenerator, and the other end is connected to the low-pressure storage tank. The cooler is used to cool the carbon dioxide to ambient temperature and then transport it to the low-pressure storage tank for recycling.

[0012] Preferably, the low-pressure storage tank is connected to a carbon capture unit, which includes an absorption tower, a reaction tower and a gas-liquid separator. The raw material inlet of the absorption tower is used to be connected to the emission port of a high-emission industry, the rich liquid outlet of the absorption tower is connected to the rich liquid inlet of the reaction tower, the lean liquid inlet of the absorption tower is connected to the lean liquid outlet of the reaction tower, the gas-liquid outlet of the reaction tower is connected to the gas-liquid inlet of the gas-liquid separator, and the gas outlet of the gas-liquid separator is connected to the inlet of the low-pressure storage tank. The gas-liquid mixture enters the gas-liquid separator for separation to obtain pure carbon dioxide and store it in the low-pressure storage tank.

[0013] Preferably, it also includes a primary generator and a secondary generator, the input end of the primary generator is connected to the high-pressure turbine, the input end of the secondary generator is connected to the low-pressure turbine, and the output ends of the primary generator and the secondary generator are both used to connect to the power grid.

[0014] Preferably, it further includes a wind-solar power generation unit, which is used to supply power to the low-pressure compressor and the high-pressure compressor.

[0015] Compared with the prior art, the coupled system of compressed carbon dioxide energy storage of the present invention has the following beneficial effects: This system collects carbon dioxide emitted during the industrial production process into a low-pressure storage tank as a circulating working fluid for the carbon dioxide energy storage system. The carbon dioxide is first pressurized by a low-pressure compressor, and then the carbon dioxide output by the low-pressure compressor is heat exchanged by a heat exchange unit. The carbon dioxide entering the high-pressure compressor is cooled to a low temperature, and then pressurized again by the high-pressure compressor and enters the first-stage regenerator. At this time, the temperature of the high-pressure carbon dioxide entering the first-stage regenerator is lower than the temperature of the carbon dioxide entering from the low-temperature inlet due to the heat exchange effect of the heat exchange unit. Therefore, under the heat exchange effect of the first-stage regenerator, the high-pressure carbon dioxide is initially heated and then flows to the high-pressure storage tank for storage. The high-pressure storage tank then heats the heated carbon dioxide again through the secondary regenerator and transports it to the high-pressure turbine. The high-pressure turbine uses the heat expansion of the carbon dioxide to do work for generating electricity. The motor provides power for the first stage of power generation, and the carbon dioxide cooled and depressurized by the high-pressure turbine is transported to the low-pressure turbine. At the same time, the heat exchange unit 1 replaces the heat of the carbon dioxide output by the low-pressure compressor and applies it to the carbon dioxide flowing from the high-pressure turbine to the low-pressure turbine, so that the carbon dioxide entering the low-pressure turbine is heated again. The low-pressure turbine provides power for the generator through the thermal expansion of the carbon dioxide to perform secondary power generation. During this period, the secondary regenerator exchanges heat with the waste heat on the carbon dioxide output by the low-pressure turbine to achieve further heating of the carbon dioxide flowing to the high-pressure turbine. Therefore, with the cooperation of the heat exchange unit 1, the first-stage regenerator and the second-stage regenerator, the waste heat of the carbon dioxide circulating medium is utilized multiple times, effectively improving the recycling of the system's thermal energy, achieving high thermal energy utilization and reducing heat loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the system structure in Example 1 of the present invention; Figure 2 This is a schematic diagram of the system structure in Example 2 of the present invention.

[0017] Description of reference numerals: 1. Low-pressure storage tank; 2. Low-pressure compressor; 3. Primary condenser; 4. Secondary condenser; 5. High-pressure compressor; 6. Third-stage condenser; 7. Fourth-stage condenser; 8. Primary regenerator; 9. High-pressure storage tank; 10. Secondary cold water storage tank; 11. Secondary hot water storage tank; 12. Secondary cold salt storage tank; 13. Secondary hot salt storage tank; 14. Primary cold water storage tank; 15. Primary hot water storage tank; 16. Primary cold salt storage tank; 17. Primary hot salt storage tank; 18. Working fluid pump; 19. Secondary heat regenerator; 20. Fourth-stage heater; 21. Third-stage heater; 22. High-pressure turbine; 23. Second-stage generator; 24. Second-stage heater; 25. First-stage heater; 26. Low-pressure turbine; 27. First-stage generator; 28. Power grid; 29. Cooler; 30. Wind and solar power generation unit; 31. High-emission industry; 32. Absorption tower; 33. Reaction tower; 34. Gas-liquid separator; 35. Underground reservoir; 36. Preheater. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0019] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0020] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0021] Example 1 See also Figure 1 As shown, in order to effectively improve the recycling of the system's thermal energy, the thermal energy utilization rate is high and the heat loss is reduced. This embodiment provides a coupled system for compressed carbon dioxide energy storage, including a carbon capture unit, a low-pressure storage tank 1, a high-pressure storage tank 9, a low-pressure compressor 2, a high-pressure compressor 5, a high-pressure turbine 22, a low-pressure turbine 26, a first-stage regenerator 8, a second-stage regenerator 19 and at least one heat exchange unit. The low-pressure compressor 2 and the high-pressure compressor 5 serve as energy storage units, the high-pressure turbine 22 and the low-pressure turbine 26 serve as energy release units, and the first-stage regenerator 8 and the second-stage regenerator 19 serve as waste heat recovery units. The specific usage is as follows:

[0022] See also Figure 1As shown, carbon dioxide is provided as a circulating working fluid within the system primarily through a carbon capture unit. Specifically, the carbon capture unit includes an absorption tower 32, a reaction tower 33, and a gas-liquid separator 34. The raw material inlet of the absorption tower 32 is connected to the discharge port of the high-emission industry 31, and the absorbent in the absorption tower 32 absorbs carbon dioxide emitted during the industrial production process. The rich liquid outlet of the absorption tower 32 is connected to the rich liquid inlet of the reaction tower 33, and the lean liquid inlet of the absorption tower 32 is connected to the lean liquid outlet of the reaction tower 33. The absorbent rich liquid that has absorbed carbon dioxide reacts in the reaction tower 33, releasing a gas-liquid mixture containing carbon dioxide, and the remaining lean liquid is discharged back to the absorption tower 32. The gas-liquid outlet of the reaction tower 33 is connected to the gas-liquid inlet of the gas-liquid separator 34, and the gas-liquid mixture enters the gas-liquid separator 34 for separation to obtain pure carbon dioxide. The gas outlet of the gas-liquid separator 34 is connected to the inlet of the low-pressure storage tank 1, and the captured pure carbon dioxide is stored in the low-pressure storage tank 1 as the working fluid gas used by the system.

[0023] In the system, low-pressure storage tank 1 is connected to the low-temperature inlet of the primary regenerator 8. The low-temperature outlet of the primary regenerator 8 is connected to the inlet of low-pressure compressor 2. The outlet of low-pressure compressor 2 is connected to the inlet of high-pressure compressor 5. The outlet of high-pressure compressor 5 is connected to the high-temperature inlet of the primary regenerator 8, which in turn is connected to the inlet of high-pressure storage tank 9. High-pressure compressor 5 and low-pressure compressor 2 are connected to an external wind and solar power generation unit 30, which utilizes renewable electricity to convert electrical energy into high-quality thermal energy. The low-temperature inlet of the secondary regenerator 19 is connected to the outlet of high-pressure storage tank 9 via a working fluid pump 18. The inlet of high-pressure turbine 22 is connected to the low-temperature outlet of the secondary regenerator 19. The outlet of high-pressure turbine 22 is connected to the inlet of low-pressure turbine 26. The outlet of low-pressure turbine 26 is connected to the high-temperature inlet of the secondary regenerator 19. The high-temperature outlet of the secondary regenerator 19 is connected to the inlet of low-pressure storage tank 1 via a cooling and pressure reduction assembly. The output shafts of both the high-pressure turbine 22 and the low-pressure turbine 26 are connected to the rotating shaft of a generator, converting thermal energy into mechanical energy and providing power input for the generator. Preferably, the high-pressure turbine 22 is connected to the power grid 28 via a secondary generator 23, and the low-pressure turbine 26 is connected to the power grid 28 via a primary generator 27. Heat exchange unit 1 is positioned between the low-pressure compressor 2 and the high-pressure compressor 5 to displace heat from the carbon dioxide output by the low-pressure compressor 2 and apply it to the carbon dioxide flowing from the high-pressure turbine 22 to the low-pressure turbine 26. Furthermore, the outlet of the high-pressure compressor 5 is connected to an underground reservoir 35, which is used to store carbon dioxide that overflows from the high-pressure storage tank 9.

[0024] During operation, the carbon dioxide generated from the high-emission industry 31 is stored in the low-pressure storage tank 1 as the system operating working fluid. The low-pressure storage tank 1 transports the carbon dioxide to the low-pressure compressor 2 through the first-level regenerator 8. The carbon dioxide pressurized by the low-pressure compressor 2 enters the high-pressure compressor 5 after heat exchange and cooling treatment in the heat exchange unit 1. The high-pressure compressor 5 performs secondary pressurization on the low-temperature carbon dioxide to form high-pressure carbon dioxide. Part of the high-pressure carbon dioxide is stored in the underground reservoir 35, and part of it is stored in the high-pressure storage tank 9 through the first-level regenerator 8. Since the temperature of the high-pressure carbon dioxide entering the first-level regenerator 8 at this time is lower than the temperature of the low-pressure carbon dioxide flowing from the low-pressure storage tank 1 into the first-level heat exchanger 8 due to the cooling effect of the previous heat exchange unit 1, after the high-pressure carbon dioxide enters the first-level regenerator 8, the waste heat from the low-pressure carbon dioxide from the low-pressure storage tank 1 is replaced by the heat exchange effect of the first-level regenerator 8 and applied to the high-pressure carbon dioxide, thereby achieving preliminary heating of the high-pressure carbon dioxide and storing it in the high-pressure storage tank 9. Then, the high-pressure second-level regenerator in the high-pressure storage tank 9 is heated up by the working fluid pump 18. The carbon dioxide is heated again by the secondary regenerator 19 and transported to the high-pressure turbine 22. The high-pressure carbon dioxide input to the high-pressure turbine 22 expands by obtaining the heat of the carbon dioxide and does work to provide power for the secondary generator 23 to generate electricity. Subsequently, the high-pressure carbon dioxide is cooled and depressurized by the high-pressure turbine 22 and transported to the low-pressure turbine 26. At this time, the heat exchange unit 1 applies the displaced heat to the carbon dioxide flowing to the low-pressure turbine 26, so that the carbon dioxide flowing to the low-pressure turbine 26 is heated again and enters the low-pressure turbine 26. The low-pressure turbine 26 is heated again by the carbon dioxide. The thermal expansion of the carbon dioxide generates work that powers the primary generator 27, generating secondary electricity. After being cooled and depressurized by the low-pressure turbine 26, the carbon dioxide gas flows back to the secondary regenerator 19. The secondary regenerator 19 then displaces the residual heat from the carbon dioxide exiting the low-pressure turbine 26 and applies it to the carbon dioxide flowing to the high-pressure turbine 22, reusing the waste heat. After heat exchange in the secondary regenerator 19, the carbon dioxide is cooled to near ambient temperature by the pressure reduction assembly and then re-transferred to the low-pressure storage tank 1 for recycling. The power outlets of the primary generator 27 and the secondary generator 23 are connected to the power inlet of the power grid 28, converting the mechanical energy generated in the energy release unit into electrical energy and transmitting it to the grid 28 for transmission to the user. This coordinated effort among the heat exchange unit 1, the primary regenerator, and the secondary regenerator enables multi-stage heat exchange within the system, resulting in a higher waste heat utilization rate.

[0025] See also Figure 1As shown, further, in order to improve the utilization rate of the system heat, the heat exchange unit 1 includes a primary condenser 3, a primary cold salt storage tank 16, a primary cold salt storage tank 16, a primary hot salt storage tank 17 and a primary heater 25. The high temperature side inlet of the primary condenser 3 is connected to the outlet of the low pressure compressor 2, and the high temperature side outlet is connected to the inlet of the high pressure compressor 5. The outlet of the primary cold salt storage tank 16 is connected to the low temperature side inlet of the primary condenser 3, the inlet of the primary hot salt storage tank 17 is connected to the low temperature side outlet of the primary condenser 3, the high temperature side inlet of the primary heater 25 is connected to the outlet of the primary hot salt storage tank 17, the high temperature side outlet is connected to the inlet of the primary cold salt storage tank 16, the low temperature side inlet of the primary heater 25 is connected to the outlet of the high pressure turbine 22, and the low temperature side outlet is connected to the inlet of the low pressure turbine 26. In this way, through the circulation of molten salt among the first-stage condenser 3, the first-stage cold salt storage tank 16, the first-stage cold salt storage tank 16, the first-stage hot salt storage tank 17 and the first-stage heater 25, the heat of the carbon dioxide output by the low-pressure compressor 2 is replaced and applied to the carbon dioxide transported from the high-pressure turbine 22 to the low-pressure turbine 26, so that the heat is fully carried to the low-pressure turbine 26 through the carbon dioxide, thereby realizing full utilization of heat and thermal energy.

[0026] See also Figure 1 As shown, further, in order to improve the utilization rate of the system's thermal energy, a heat exchange unit 2 is provided between the heat exchange unit 1 and the high-pressure compressor 5. The heat exchange unit 2 includes a secondary condenser 4, a primary cold water storage tank 14, a primary hot water storage tank 15, and a secondary heater 24. The high-temperature side inlet of the secondary condenser 4 is connected to the high-temperature side outlet of the primary condenser 3, and the high-temperature side outlet is connected to the inlet of the high-pressure compressor 5. The outlet of the primary cold water storage tank 14 is connected to the low-temperature side inlet of the secondary condenser 4, and the inlet of the primary hot water storage tank 15 is connected to the low-temperature side outlet of the secondary condenser 4. The high-temperature side inlet of the secondary heater 24 is connected to the outlet of the primary hot water storage tank 15, and the high-temperature side outlet is connected to the inlet of the primary cold water storage tank 14. The low-temperature side inlet of the secondary heater 24 is connected to the outlet of the high-pressure turbine 22, and the low-temperature side outlet is connected to the low-temperature side inlet of the primary heater 25. In this way, after the molten salt heat is exchanged through a heat exchange unit, it is circulated again between the secondary condenser 4, the primary cold water storage tank 14, the primary hot water storage tank 15 and the secondary heater 24 through pressurized water. Therefore, through the cooperation between the molten salt and the hot water, the heat carried by the carbon dioxide output by the low-pressure compressor 2 can be more fully replaced and applied to the carbon dioxide transported from the high-pressure turbine 22 to the low-pressure turbine 26, so that the low-pressure turbine 26 is more efficient in doing work through heat expansion, thereby increasing the power generation of the first-stage generator 27.

[0027] See also Figure 1As shown, further, to improve the utilization rate of the system's thermal energy, heat exchange unit three and heat exchange unit four are sequentially arranged between the outlet of high-pressure compressor 5 and the first-stage heat exchanger. Heat exchange unit three has the same structure as heat exchange unit one, and heat exchange unit four has the same structure as heat exchange unit two. Heat exchange unit three and heat exchange unit four are sequentially arranged at the outlet of high-pressure compressor 5 to cool and heat the carbon dioxide pressurized by high-pressure compressor 5, and apply the displaced heat to the carbon dioxide on the inlet side of high-pressure turbine 22. Specifically, heat exchange unit three includes a third-stage condenser 6, a second-stage cold salt storage tank 12, a second-stage hot salt storage tank 13, and a third-stage heater 21. The outlet of the secondary cold salt storage tank 12 is connected to the low-temperature side inlet of the tertiary condenser 6, and the low-temperature side outlet of the tertiary condenser 6 is connected to the inlet of the secondary hot salt storage tank 13. The heat storage molten salt absorbs the heat of the high-temperature carbon dioxide in the tertiary condenser 6 and enters the secondary hot salt storage tank 13 after heating. The outlet of the secondary hot salt storage tank 13 is connected to the high-temperature side inlet of the tertiary heater 21, and the high-temperature side outlet of the tertiary heater 21 is connected to the inlet of the secondary cold salt storage tank 12. The high-temperature heat storage molten salt releases heat in the tertiary heater 21 and returns to the secondary cold salt storage tank 12 after cooling. The heat exchange unit 4 includes the quaternary condenser 7, the secondary cold water storage tank 10, the secondary hot water storage tank 11 and the quaternary heater 20. The outlet of the secondary cold water tank 10 is connected to the low-temperature inlet of the quaternary condenser 7, which in turn is connected to the inlet of the secondary hot water tank 11. The pressurized water undergoes a secondary heat exchange with the carbon dioxide in the quaternary condenser 7, then, after heating, enters the secondary hot water tank 11. The outlet of the secondary hot water tank 11 is connected to the high-temperature inlet of the quaternary heater 20, which in turn is connected to the inlet of the secondary cold water tank 10. The high-temperature pressurized water enters the quaternary heater 20, undergoes a secondary heat exchange with the carbon dioxide, and then, after cooling, returns to the secondary cold water tank 10. In this way, the heat released by the high-temperature heat storage molten salt in the tertiary heater 21 and the heat released by the high-temperature pressurized water in the quaternary heater 20 are further applied to the carbon dioxide entering the high-pressure turbine 22. This heat expansion causes the high-pressure turbine 22 to generate work that powers the secondary generator 23, thereby increasing power generation and achieving higher heat utilization efficiency.

[0028] See also Figure 1 As shown, further, the cooling and pressure reduction component includes a cooler 29, the high temperature side outlet of the secondary regenerator 19 is connected to the high temperature side inlet of the cooler 29, the high temperature side outlet of the cooler 29 is connected to the inlet of the low pressure storage tank 1, and the low temperature side inlet and outlet of the cooler 29 are connected to the atmospheric environment. The cooler 29 is used to cool the carbon dioxide to the ambient temperature and then transport it to the low pressure storage tank 1 for recycling.

[0029] See also Figure 1 As shown, the detailed working processes of heat exchange unit 1, heat exchange unit 2, heat exchange unit 3 and heat exchange unit 4 are as follows: Heat storage stage: the outlet of the first-level cold salt storage tank 16 is connected to the low-temperature side inlet of the first-level condenser 3, and the low-temperature side outlet of the first-level condenser 3 is connected to the inlet of the first-level hot salt storage tank 17. The heat storage molten salt exchanges heat with the high-temperature carbon dioxide in the first-level condenser 3 and enters the first-level hot salt storage tank 17 after heating. The outlet of the first-level cold water storage tank 14 is connected to the low-temperature side inlet of the second-level condenser 4, and the low-temperature side outlet of the second-level condenser 4 is connected to the inlet of the first-level hot water storage tank 15. The pressurized water performs a secondary heat exchange with carbon dioxide in the second-level condenser 4 and enters the first-level hot water storage tank after heating. 15; the outlet of the secondary cold salt storage tank 12 is connected to the low-temperature side inlet of the tertiary condenser 6, and the low-temperature side outlet of the tertiary condenser 6 is connected to the inlet of the secondary hot salt storage tank 13. The heat storage molten salt absorbs the heat of the high-temperature carbon dioxide in the tertiary condenser 6 and enters the secondary hot salt storage tank 13 after heating; the outlet of the secondary cold water storage tank 10 is connected to the low-temperature side inlet of the quaternary condenser 7, and the low-temperature side outlet of the quaternary condenser 7 is connected to the inlet of the secondary hot water storage tank 11. The pressurized water performs a secondary heat exchange with the carbon dioxide in the quaternary condenser 7 and enters the secondary hot water storage tank 11 after heating.

[0030] Heat release stage: the outlet of the first-level hot salt storage tank 17 is connected to the high-temperature side inlet of the first-level heater 25, and the high-temperature side outlet of the first-level heater 25 is connected to the inlet of the first-level cold salt storage tank 16. The high-temperature heat storage molten salt releases heat in the first-level heater 25 and returns to the first-level cold salt storage tank 16 after cooling; the outlet of the first-level hot water storage tank 15 is connected to the high-temperature side inlet of the second-level heater 24, and the high-temperature side outlet of the second-level heater 24 is connected to the inlet of the first-level cold water storage tank 14. The high-temperature pressurized water enters the second-level heater 24 for secondary heat exchange with carbon dioxide and returns to the first-level cold water storage tank after cooling. Tank 14; the outlet of the secondary hot salt storage tank 13 is connected to the high-temperature side inlet of the tertiary heater 21, and the high-temperature side outlet of the tertiary heater 21 is connected to the inlet of the secondary cold salt storage tank 12. The high-temperature heat storage molten salt releases heat in the tertiary heater 21 and returns to the secondary cold salt storage tank 12 after cooling; the outlet of the secondary hot water storage tank 11 is connected to the high-temperature side inlet of the quaternary heater 20, and the high-temperature side outlet of the quaternary heater 20 is connected to the inlet of the secondary cold water storage tank 10. The high-temperature pressurized water enters the quaternary heater 20 for secondary heat exchange with carbon dioxide, and returns to the secondary cold water storage tank 10 after cooling.

[0031] Heat utilization stage: the outlet of the high-pressure storage tank 9 is connected to the inlet of the working fluid pump 18, and the outlet of the working fluid pump 18 is connected to the low-temperature side inlet of the secondary regenerator 19. The high-pressure carbon dioxide that has been initially heated by the primary regenerator 8 is input into the secondary regenerator 19 through the working fluid pump 18. The initially heated high-pressure carbon dioxide undergoes heat exchange in the secondary regenerator 19 and is heated again; then the low-temperature side inlet of the secondary regenerator 19 is connected to the low-temperature side inlet of the fourth-stage heater 20, and the high-pressure carbon dioxide that has been heated twice enters the fourth-stage heater 20, and is heated for the first time using the high-temperature heat energy stored in the high-temperature pressurized water. The low-temperature side outlet of the secondary heater 24 is connected to the low-temperature side inlet of the tertiary heater 21, and the carbon dioxide enters the tertiary heater 21 and is heated for the second time using the heat energy stored in the molten salt; the low-temperature side outlet of the tertiary heater 21 is connected to the inlet of the high-pressure turbine 22, and the heated high-pressure carbon dioxide enters the high-pressure turbine 22, which does work by thermal expansion, drives the secondary generator 23 to generate electricity, and transmits the generated electricity to the power grid 28; the outlet of the high-pressure turbine 22 is connected to the low-temperature side inlet of the secondary heater 24, and the carbon dioxide cooled and depressurized by the high-pressure turbine 22 enters the secondary heater The heat exchanger 24 exchanges heat with the pressurized water to achieve a first-stage temperature increase; the low-temperature side outlet of the secondary heater 24 is connected to the low-temperature side inlet of the primary heater 25, and the carbon dioxide enters the primary heater 25 to exchange heat with the heat storage molten salt to achieve a second-stage temperature increase; the low-temperature side outlet of the primary heater 25 is connected to the inlet of the low-pressure turbine 26, and the heated low-pressure carbon dioxide enters the low-pressure turbine 26. The low-pressure turbine 26 performs work through thermal expansion, drives the first-stage generator 27 to perform work, and transmits the generated electrical energy to the power grid 28; the outlet of the low-pressure turbine 26 is connected to the high-temperature side inlet of the secondary regenerator 19, so that The exhaust gas from the low-pressure turbine 26 enters the secondary regenerator 19 to release waste heat; the secondary regenerator 19 replaces the waste heat and applies it to the carbon dioxide flowing to the high-pressure turbine 22 to achieve waste heat reuse, and the high-temperature side outlet of the secondary regenerator 19 is connected to the high-temperature side inlet of the cooler 29, that is, the carbon dioxide after heat exchange in the secondary regenerator 19 flows to the cooler 29, and the low-temperature side inlet and outlet of the cooler 29 are connected to the atmospheric environment to cool the carbon dioxide exhaust to a temperature close to the ambient temperature; the high-temperature side outlet of the cooler 29 is connected to the inlet of the low-pressure storage tank 1, and the cooled carbon dioxide is stored in the low-pressure storage tank 1 to complete the cycle.

[0032] High-emission industries 31 include steelmaking, chemical industry, thermal power generation and other industries; underground reservoirs 35 include depleted oil and gas fields, deep saline water layers, basalt formations and the like; the temperature of carbon dioxide injected into the underground reservoirs 35 is between 50°C and 80°C, and the pressure is between 10MPa and 15MPa.

[0033] The low-pressure compressor 2 and the high-pressure compressor 5 are screw compressors or centrifugal compressors, and the high-pressure turbine 22 and the low-pressure turbine 26 are axial-flow turbine expanders; the working pressure of the third-stage condenser 6, the fourth-stage condenser 7, the third-stage heater 21, the fourth-stage heater 20, the first-stage regenerator 8, and the second-stage regenerator 19 is greater than 3.5 MPa, and a printed circuit board type heat exchanger is used; the first-stage condenser 3, the second-stage condenser 4, the first-stage heater 25, the second-stage heater 24 and the cooler 29 work under low-pressure conditions and use a plate heat exchanger.

[0034] Example 2 like Figure 2 As shown, based on the system structure of Example 1, a preheater 36 is further provided between the outlet of the high-pressure storage tank 9 and the low-temperature inlet of the secondary regenerator 19. The inlet of the working fluid pump 18 is connected to the outlet of the high-pressure storage tank 9, the outlet of the working fluid pump 18 is connected to the low-temperature inlet of the preheater 36, the low-temperature outlet of the preheater 36 is connected to the low-temperature inlet of the secondary regenerator 19, and the high-temperature inlet and outlet of the preheater 36 are connected to the atmosphere. The working fluid pump 18 pumps low-temperature carbon dioxide into the preheater 36, where it is preheated using ambient temperature. The low-temperature outlet of the preheater 36 is connected to the low-temperature inlet of the secondary regenerator 19. The preheated carbon dioxide enters the secondary regenerator 19 and exchanges heat with the low-temperature carbon dioxide output by the low-pressure turbine 26, achieving recycling and improving the thermal energy utilization rate of the system.

[0035] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A coupled system for compressed carbon dioxide energy storage, wherein the circulating medium is carbon dioxide, characterized in that: It includes a low-pressure storage tank (1) and a high-pressure storage tank (9), and further includes: An energy storage unit comprises a low-pressure compressor (2) and a high-pressure compressor (5) connected in sequence, wherein the low-pressure compressor (2) is connected to the low-pressure storage tank (1), and the high-pressure compressor (5) is connected to the high-pressure storage tank (9); An energy release unit includes a high-pressure turbine (22) and a low-pressure turbine (26) connected in sequence, wherein the high-pressure turbine (22) is connected to the high-pressure storage tank (9), and the low-pressure turbine (26) is connected to the low-pressure storage tank (1), and both the high-pressure turbine (22) and the low-pressure turbine (26) are used to realize the conversion of thermal energy into mechanical energy; At least one heat exchange unit 1 is used to replace the heat of the carbon dioxide output by the low-pressure compressor (2) and apply it to the carbon dioxide flowing from the high-pressure turbine (22) to the low-pressure turbine (26); The waste heat recovery unit comprises: a first-stage regenerator (8), a low-temperature inlet connected to a low-pressure storage tank (1), a low-temperature outlet connected to a low-pressure compressor (2), a high-temperature inlet connected to a high-pressure compressor (5), and a high-temperature outlet connected to a high-pressure storage tank (9), for replacing heat from carbon dioxide delivered to the low-pressure compressor with carbon dioxide flowing to the high-pressure storage tank (9) for increasing the temperature; and a second-stage regenerator (19), a low-temperature inlet connected to a high-pressure storage tank (9), a low-temperature outlet connected to a high-pressure turbine (22), a high-temperature inlet connected to a low-pressure turbine (26), and a high-temperature outlet connected to the low-pressure storage tank (1), for replacing waste heat from carbon dioxide output from the low-pressure turbine (26) with carbon dioxide flowing to the high-pressure turbine (22) for increasing the temperature.

2. A coupled system for compressed carbon dioxide energy storage according to claim 1, characterized in that: The heat exchange unit 1 includes: a primary condenser (3), the high-temperature side inlet of which is in communication with the low-pressure compressor (2), and the high-temperature side outlet of which is in communication with the high-pressure compressor (5); A first-stage cold salt storage tank (16), the outlet of which is connected to the low-temperature side inlet of the first-stage condenser (3); The first-stage hot salt storage tank (17) has an inlet connected to the low-temperature side outlet of the first-stage condenser (3) The high-temperature side inlet of the first-stage heater (25) is connected to the outlet of the first-stage hot salt storage tank (17), and the high-temperature side outlet is connected to the inlet of the first-stage cold salt storage tank (16). The low-temperature side inlet of the first-stage heater (25) is connected to the outlet of the high-pressure turbine (22), and the low-temperature side outlet is connected to the inlet of the low-pressure turbine (26).

3. A coupled system for compressed carbon dioxide energy storage according to claim 2, characterized in that: A second heat exchange unit is further provided between the low-pressure compressor (2) and the high-pressure compressor (5), and the second heat exchange unit comprises: A secondary condenser (4), the high-temperature side inlet of which is connected to the high-temperature side outlet of the primary condenser (3), and the high-temperature side outlet is in communication with the high-pressure compressor (5); a first-stage cold water storage tank (14), the outlet of which is connected to the low-temperature side inlet of the second-stage condenser (4); a first-stage hot water storage tank (15), the inlet of which is connected to the low-temperature side outlet of the second-stage condenser (4); The secondary heater (24) has a high-temperature side inlet connected to the outlet of the primary hot water storage tank (15), and a high-temperature side outlet connected to the inlet of the primary cold water storage tank (14). The low-temperature side inlet of the secondary heater (24) is connected to the outlet of the high-pressure turbine (22), and the low-temperature side outlet is connected to the low-temperature side inlet of the primary heater (25).

4. A coupled system for compressed carbon dioxide energy storage according to claim 3, characterized in that: It also includes a heat exchange unit three and a heat exchange unit four. The heat exchange unit three has the same structure as the heat exchange unit one, and the heat exchange unit four has the same structure as the heat exchange unit two. The heat exchange unit three and the heat exchange unit four are both used to cool down and heat the carbon dioxide pressurized by the high-pressure compressor (5), and apply the replaced heat to the carbon dioxide flowing to the high-pressure turbine (22).

5. The coupled system for compressed carbon dioxide energy storage according to claim 1, characterized in that: The high-pressure compressor (5) is further connected to an underground reservoir (35), and the underground reservoir (35) is used to store carbon dioxide that overflows from the high-pressure storage tank (9).

6. A coupled system for compressed carbon dioxide energy storage according to claim 1, characterized in that: A working fluid pump (18) and a preheater (36) are also connected in sequence between the high-pressure storage tank (9) and the secondary regenerator (19). The working fluid pump (18) is connected to the high-pressure storage tank (9), and the preheater (36) is connected to the secondary regenerator (19). The preheater (36) is used to preheat the carbon dioxide flowing to the secondary regenerator (19) using the ambient temperature.

7. The coupled system for compressed carbon dioxide energy storage according to claim 1, characterized in that: A cooling and pressure reduction component is further provided between the low-pressure turbine (26) and the low-pressure storage tank (1). The cooling and pressure reduction component includes a cooler (29). One end of the cooler (29) is connected to the low-pressure turbine (26) through the secondary heat regenerator (19), and the other end is connected to the low-pressure storage tank (1). The cooler (29) is used to cool the carbon dioxide to ambient temperature and then transport it to the low-pressure storage tank (1) for recycling.

8. The coupled system for compressed carbon dioxide energy storage according to claim 1, characterized in that: The low-pressure storage tank (1) is connected to a carbon capture unit, which includes an absorption tower (32), a reaction tower (33) and a gas-liquid separator (34). The raw material inlet of the absorption tower (32) is used to be connected to the discharge port of the high-emission industry (31), the rich liquid outlet of the absorption tower (32) is connected to the rich liquid inlet of the reaction tower (33), the lean liquid inlet of the absorption tower (32) is connected to the lean liquid outlet of the reaction tower (33), the gas-liquid outlet of the reaction tower (33) is connected to the gas-liquid inlet of the gas-liquid separator (34), and the gas outlet of the gas-liquid separator (34) is communicated with the low-pressure storage tank (1).

9. The coupled system for compressed carbon dioxide energy storage according to claim 1, characterized in that: It also includes a primary generator (23) and a secondary generator (27), wherein the input end of the primary generator (23) is connected to the high-pressure turbine (22), the input end of the secondary generator (27) is connected to the low-pressure turbine (26), and the output ends of the primary generator (23) and the secondary generator (27) are both used to connect to the power grid (28).

10. The coupled system for compressed carbon dioxide energy storage according to claim 1, characterized in that: It also includes a wind-solar power generation unit (30), which is used to supply power to the low-pressure compressor (2) and the high-pressure compressor (5).

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