Liquid air energy storage and air separation deep coupling system and method

Abstract

The invention relates to the technical field of liquid air energy storage, air separation and the like, in particular to a liquid air energy storage and air separation deep coupling system and method.The system comprises an air compression unit, an air cooling unit, an air purification unit, an air pressurization unit, an air liquefaction unit, an air separation unit, an air expansion power generation unit, a cold storage unit and a heat storage unit; the first input end of the air compression unit is used for inputting ambient air, and the first output end of the air compression unit is connected with the first input end of the air cooling unit. According to the invention, key equipment for air separation circulation is shared, so that the liquid air energy storage investment cost is obviously reduced; in addition, the temperature gradient of the main heat exchanger is maintained through stream regulation and control of air separation circulation, so that the air liquefaction circulation channel is always in a standby state, and then quick response is achieved. Through multi-cycle collaborative design and dynamic load regulation and control, the energy utilization efficiency is improved, and meanwhile, the equipment cost is reduced.

Description

Technical Field

[0001] The present invention relates to technical fields such as liquid air energy storage and air separation, and in particular to a system and method for deep coupling of liquid air energy storage and air separation. Background Art

[0002] Liquid air energy storage is considered to be one of the most promising large-scale energy storage technologies due to its unique advantages such as high energy storage density, no geographical restrictions, long service life, and environmental friendliness. During the low electricity consumption period, electricity is stored in the form of liquid air, and at the same time, the compression heat generated during the air compression process is stored and used to improve the work capacity of the air expander when needed; during the high electricity consumption period, the liquid air is pressurized by a pressure pump, and after the low-temperature cold energy is recovered and stored, it drives the air expander to generate electricity.

[0003] As a core basic process in the industrial field, the cryogenic air separation technology consists of multiple key links such as compression, precooling, purification, boosting, refrigeration, heat exchange, and rectification. Its operating temperature range highly coincides with that of the liquid air energy storage system. The raw material of this technology is ambient air. Under the background of the gradual improvement of the time-of-use electricity price mechanism and the increasing expansion of the peak-valley electricity price difference, the electricity cost has become an important factor restricting the development of the industry. It is worth noting that integrating and innovating the liquid air energy storage technology with traditional air separation devices can bring significant synergistic benefits: on the one hand, the perfect matching of the refrigeration energy levels of the two technologies can achieve cascaded energy utilization; on the other hand, the liquid air energy storage system can share key equipment with the air separation system, which can not only significantly reduce the investment cost of the liquid air energy storage system but also significantly reduce the comprehensive electricity cost of air separation enterprises. This innovative solution provides a feasible path for industrial energy optimization and new energy consumption. Summary of the Invention

[0004] The purpose of the present invention is to solve the deficiencies existing in the prior art, and to propose a system and method for deep coupling of liquid air energy storage and air separation. By sharing the key equipment of the air separation cycle, the investment cost of liquid air energy storage is significantly reduced; in addition, through the flow control of the air separation cycle, the temperature gradient of the main heat exchanger is maintained, so that the air liquefaction cycle channel is always in a standby state, thereby achieving rapid response and being able to solve the pain point of the slow startup of the traditional liquid air energy storage system.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions: A system for deep coupling of liquid air energy storage and air separation includes an air compression unit, an air cooling unit, an air purification unit, an air boosting unit, an air liquefaction unit, an air separation unit, an air expansion power generation unit, a cold storage unit, and a heat storage unit; The first input end of the air compression unit is used to input ambient air. The first output end of the air compression unit is connected to the first input end of the air cooling unit. The second output end of the air compression unit is connected to the first input end of the heat storage unit. The first output end of the air cooling unit is connected to the first input end of the air purification unit. The first output end of the air purification unit is connected to the first input end of the air boosting unit. The air boosting unit is connected to the air liquefaction unit. The first output end of the air liquefaction unit is connected to the first input end of the air separation unit. The third output end of the air liquefaction unit is connected to the first input end of the air expansion power generation unit. The second output end of the air expansion power generation unit is connected to the second input end of the cold storage unit. The third output end of the air expansion power generation unit is connected to the second input end of the heat storage unit.

[0006] Preferably, the air compression unit includes a first compressor, a first cooler, a second compressor, a second cooler, a third compressor and a first three-way valve; The output end of the first compressor is connected to the first input end of the first cooler. The first output end of the first cooler is connected to the input end of the second compressor. The output end of the second compressor is connected to the first input end of the second cooler. The first output end of the second cooler is connected to the input end of the third compressor. The output end of the third compressor is connected to the air cooling unit. The first input end of the first three-way valve is connected to ambient air. The first output end of the first three-way valve is connected to the input end of the first compressor; The air compression unit is used to compress ambient air to obtain high-pressure air for subsequent air separation process and liquid air expansion power generation process.

[0007] By adopting the above technical solutions: High-temperature and high-pressure ratio compressors are selected here, taking into account both the compression power consumption and the thermal energy grade of the heat exchange fluid. A cooler is configured at the outlet of each stage of the compressor to reduce the air temperature at the inlet of the next stage of the compressor, thereby reducing the power consumption of the compressor. During the low electricity consumption period, by dynamically increasing the compressor load, compressed air is provided for the air liquefaction cycle to achieve efficient storage of liquid air.

[0008] The air cooling unit includes an air cooling tower, a first water pump, a water cooling tower, a second water pump and an electric refrigerator; The first input end of the air cooling tower is connected to the first output end of the air compression unit. The first output end of the air cooling tower is connected to the input end of the first water pump. The output end of the first water pump is respectively connected to the input end of the electric refrigerating machine and the first input end of the water cooling tower. The output end of the electric refrigerating machine is connected to the third input end of the air cooling tower. The second input end of the water cooling tower is connected to the first output end of the air purification unit. The first output end of the water cooling tower is connected to the input end of the second water pump. The output end of the second water pump is connected to the second input end of the air cooling tower. The second output end of the air cooling tower is connected to the input end of the air cooling unit. The second output end of the water cooling tower is discharged into the air. The air cooling unit cools the compressed air through the air cooling tower and the water cooling tower, facilitating the subsequent adsorption process.

[0009] By adopting the above technical solution: The air cooling tower indirectly exchanges heat with circulating water to initially reduce the temperature of the compressed air, reduce the cooling load of the subsequent water cooling tower, and improve the overall heat exchange efficiency. The water cooling tower further cools the air to make it close to the ambient wet bulb temperature, reduce the water content in the air, and prevent the subsequent molecular sieve purification system from failing due to excessive moisture. At the same time, the waste nitrogen generated by the air separation unit can provide cooling capacity for the water cooling tower.

[0010] The air purification unit includes an adsorption tower, a second three-way valve, and a desorption tower. The input end of the adsorption tower is connected to the first output end of the air cooling unit. The input end of the second three-way valve is connected to the seventh output end of the air pressurization unit. The input end of the desorption tower is connected to the output end of the second three-way valve and is discharged into the air as the second output end of the air purification unit. The air purification unit removes impurities such as water and carbon dioxide in the air through the adsorption tower, improves the air purity, and then proceeds with the subsequent process. After adsorption saturation, the waste nitrogen generated by the air separation unit is used to treat the desorption tower.

[0011] By adopting the above technical solution: The cooled air enters the adsorption tower to deeply remove carbon dioxide and moisture. The adsorption tower captures impurities at low temperature and provides clean air. During desorption, reverse purging is carried out using waste nitrogen, and nitrogen and water vapor are discharged into the atmosphere.

[0012] Preferably, the air pressurization unit includes a first separator, a first booster, a third cooler, a second separator, a second booster, and a fourth cooler. The input end of the first separator is connected to the first output end of the air purification unit. The first output end of the first separator is connected to the first input end of the air liquefaction unit. The second output end of the first separator is connected to the input end of the first booster. The output end of the first booster is connected to the input end of the third cooler. The output end of the third cooler is connected to the input end of the second separator. The first output end of the second separator is connected to the second input end of the air liquefaction unit. The second output end of the second separator is connected to the input end of the second booster. The output end of the second booster is connected to the input end of the fourth cooler. The output end of the fourth cooler is connected to the third input end of the air liquefaction unit; After the air pressurization unit pressurizes the air through a booster, it cools down and enters the main heat exchanger to participate in the subsequent air separation and expansion power generation processes.

[0013] Preferably, the air liquefaction unit includes a main heat exchanger, a first throttle valve, a first gas-liquid separator, a second throttle valve, a second gas-liquid separator, a cryogenic expander, a third three-way valve, and a fourth three-way valve; The first output end of the main heat exchanger is sequentially connected to the first input end of the air separation unit through the third three-way valve and the fourth three-way valve. The second output end of the main heat exchanger is connected to the input end of the cryogenic expander. The output end of the cryogenic expander is connected to the first input end of the air separation unit through the fourth three-way valve. The third output end of the main heat exchanger is connected to the input end of the second throttle valve. The output end of the second throttle valve is connected to the input end of the second gas-liquid separator. The first output end of the second gas-liquid separator is sequentially connected to the first input end of the air separation unit through the third three-way valve and the fourth three-way valve. The second output end of the second gas-liquid separator is connected to the second input end of the air separation unit. The fourth output end of the main heat exchanger is connected to the input end of the first throttle valve. The output end of the first throttle valve is connected to the input end of the first gas-liquid separator. The first output end of the first gas-liquid separator is connected to the fourth input end of the main heat exchanger. The second output end of the first gas-liquid separator is connected to the first input end of the air expansion power generation unit. The fifth input end of the main heat exchanger is connected to the second output end of the cold storage unit. The sixth input end of the main heat exchanger is connected to the first output end of the air separation unit. The seventh input end of the main heat exchanger is connected to the second output end of the air separation unit. The eighth input end of the main heat exchanger is connected to the third output end of the air separation unit. The fifth output end of the main heat exchanger is connected to the second input end of the cold storage unit. The seventh output end of the main heat exchanger is connected to the second input end of the air purification unit. The sixth output end and the eighth output end of the main heat exchanger are discharged into the environment; The air liquefaction unit performs pressure reduction and temperature reduction on air and then sends it to two gas-liquid separators for separation. A part of the liquid air participates in the expansion power generation process, and a part of the gas enters the rectification column to participate in the air separation process.

[0014] By adopting the above technical solutions: boosting raises the air to the working condition available for liquid air energy storage, and the flow divider distributes the flow rate of the flow stream to achieve the energy synergy of air separation and liquid air energy storage; by adjusting the gas volume of the booster, the load fluctuation is compensated; by sharing the key equipment of the air separation cycle, the investment cost of liquid air energy storage is significantly reduced; in addition, through the flow stream regulation of the air separation cycle, the temperature gradient of the main heat exchanger is maintained, so that the air liquefaction cycle channel is always in a standby state, thereby achieving rapid response.

[0015] Preferably, the air separation unit includes a rectification column and a liquid oxygen pump; The first output end of the rectification column is connected to the sixth input end of the main heat exchanger, the second output end of the rectification column is connected to the seventh input end of the main heat exchanger, the third output end of the rectification column is connected to the eighth input end of the main heat exchanger through the liquid oxygen pump, the first input end of the rectification column is connected to the sixth output end of the air liquefaction unit, and the second input end of the rectification column is connected to the seventh output end of the air liquefaction unit; The air separation unit separates air into nitrogen, oxygen and at the same time generates waste nitrogen through the rectification column, and the three gas streams return to the main heat exchanger and are discharged.

[0016] Preferably, the air expansion power generation unit includes a liquid air storage tank, a cryogenic pump, an evaporator, a first heater, a first expander, a second heater, a second expander, a third heater, a third expander, a fourth heater and a fourth expander; The input end of the liquid air storage tank is connected to the eighth output end of the air liquefaction unit, the output end of the liquid air storage tank is connected to the input end of the cryogenic pump, the output end of the cryogenic pump is connected to the first input end of the evaporator, the first output end of the evaporator is connected to the first input end of the first heater, the first output end of the first heater is connected to the input end of the first expander, the output end of the first expander is connected to the first input end of the second heater, the first output end of the second heater is connected to the input end of the second expander, the output end of the second expander is connected to the first input end of the third heater, the first output end of the third heater is connected to the input end of the third expander, the output end of the third expander is connected to the first input end of the fourth heater, the first output end of the fourth heater is connected to the input end of the fourth expander, and the output end of the fourth expander is connected to the second input end of the first three-way valve; The air expansion power generation unit drives a turbine to expand and do work for power generation by heating the stored liquid air through inter-stage heating, and the outlet air converges with the air compression unit.

[0017] Preferably, the cold energy storage unit includes a cold energy storage packed bed, a cold energy release circulation fan, and a cold energy storage circulation fan; The input end of the cold energy release circulation fan is connected to the first output end of the air liquefaction unit, the output end of the cold energy release circulation fan is connected to the second input end of the air expansion power generation unit, the input end of the cold energy storage circulation fan is connected to the second output end of the air expansion power generation unit, the output end of the cold energy storage circulation fan is connected to the fourth input end of the air liquefaction unit, the cold energy storage circulation fan is connected to the input end of the cold energy storage packed bed as the driving force for storing cold energy, and the cold energy release circulation fan is connected to the output end of the cold energy storage packed bed as the driving force for releasing cold energy; The cold energy storage unit stores the cold energy generated by gasifying the liquid air in the cold energy storage packed bed to provide cold energy for the air liquefaction unit.

[0018] Preferably, the heat energy storage unit includes a heat energy storage tank, a first circulating water pump, a normal temperature storage tank, and a second circulating water pump; The second output end of the air compression unit is connected to the input end of the heat energy storage tank, the output end of the heat energy storage tank is connected to the input end of the first circulating water pump, the output end of the first circulating water pump is connected to the third input end of the air expansion power generation unit, the third output end of the air expansion power generation unit is connected to the input end of the normal temperature storage tank, the output end of the normal temperature storage tank is connected to the input end of the second circulating water pump, and the output end of the second circulating water pump is connected to the second input end of the air compression unit; The heat energy storage unit receives the compression heat transmitted by the air compression unit to supply heat for the air expansion power generation unit.

[0019] Preferably, eight independent flow channels are provided inside the main heat exchanger, including a first flow channel, a second flow channel, a third flow channel, a fourth flow channel, a fifth flow channel, a sixth flow channel, a seventh flow channel, and an eighth flow channel; among them, the first flow channel, the second flow channel, and the third flow channel are used for the air liquefaction cycle, and the remaining fourth flow channel, fifth flow channel, sixth flow channel, seventh flow channel, and eighth flow channel are used for the air separation cycle. All channels jointly ensure that the two cycle systems do not interfere with each other and operate independently.

[0020] The present invention also provides a method for deeply coupling liquid air energy storage and air separation. This method is realized by the above-mentioned liquid air energy storage and air separation deep coupling system, including: During the low grid load period, the air liquefaction cycle and the air separation cycle operate jointly: Ambient air is cooled after three-stage compression and inter-stage cooling and then enters the air cooling unit to be further cooled. Then it enters the adsorption tower to remove water and carbon dioxide in the air. Subsequently, it is divided into two streams. One stream enters the main heat exchanger to be cooled and then enters the rectification column. The other stream is compressed to high pressure by an air booster, cooled by the third cooler, and then divided into two streams again. One stream directly enters the main heat exchanger. After preliminary cooling, part of the air expands and reduces pressure through a low-temperature expander and then enters the rectification column. The other part is deeply cooled and then cooled by the second throttle valve to the second gas-liquid separator where it is separated into gas and liquid and enters the rectification column respectively. The nitrogen, waste nitrogen, and oxygen separated by the rectification column return to the main heat exchanger in three streams and are discharged. During the high grid load period, the air power generation cycle and the air separation cycle operate jointly: The liquid air separated by the air liquefaction cycle is stored in a liquid air storage tank, pressurized to high pressure by a cryogenic pump, and then enters the evaporator to undergo a liquid-vapor phase change process. The latent cold energy of the phase change is recovered and stored in the cold storage packed bed through a pressurized fluid. The cold release circulation fan and the cold storage circulation fan act as the driving force for the gas in the packed bed. The gasified high-pressure air expands and generates electricity through four-stage expansion and inter-stage heating. Finally, the outlet air and the inlet air converge through the first three-way valve to reduce the overall power consumption of the system. During the flat grid load period, the air separation cycle operates independently: Ambient air is cooled after three-stage compression and inter-stage cooling and then enters the air cooling unit to be further cooled. Then it enters the adsorption tower to remove water and carbon dioxide in the air. Subsequently, it is divided into two streams. One stream enters the main heat exchanger to be cooled and then enters the rectification column. The other stream is compressed to high pressure by an air booster, cooled by the third cooler, and then divided into two streams again. One stream directly enters the main heat exchanger. After preliminary cooling, part of the air expands and reduces pressure through a low-temperature expander and then enters the rectification column. The other part is deeply cooled and then cooled by the second throttle valve to the second gas-liquid separator where it is separated into gas and liquid and enters the rectification column respectively. The nitrogen, waste nitrogen, and oxygen separated by the rectification column enter the main heat exchanger in three streams to provide cold energy and are discharged.

[0021] Among them, during the low grid load period, the air liquefaction cycle and the air separation cycle share the air separation unit, air cooling unit, air purification unit, air booster unit, and main heat exchanger. By sharing equipment, the investment cost of liquid air energy storage is significantly reduced. At the same time, a part of the compressor gas volume separated by the air separator is extracted as the raw material gas for the air liquefaction cycle, and liquid air is obtained by cooling through the main heat exchanger.

[0022] In addition, the high-purity expansion exhaust gas of the air expansion power generation unit is not directly discharged, but is connected back to the inlet of the first compressor of the air compression unit through the first three-way valve and converges with the ambient air, which can reduce the system power consumption.

[0023] By adopting the above technical solutions: during the low electricity consumption period, the air volume of the compressor in the air separation cycle is increased, and a part of the air volume is extracted as the raw material gas for the air liquefaction cycle; during the high electricity consumption period, the stored liquid air is heated and expanded in a cascade manner to output electric energy, and the expansion exhaust gas flows back to the inlet of the air separation cycle compressor, reducing the overall power consumption of the system.

[0024] Compared with the prior art, the present invention has the following beneficial effects: 1. During the low electricity consumption period, the present invention increases the air volume of the compressor in the air separation cycle, extracts a part of the air volume as the raw material gas for the air liquefaction cycle, and obtains liquid air through cooling in the main heat exchanger; during the high electricity consumption period, the stored liquid air is heated and expanded in a cascade manner to output electric energy, and the expansion exhaust gas flows back to the inlet of the air separation cycle compressor, reducing the power consumption of the entire system.

[0025] 2. By sharing the key equipment of the air separation cycle, the present invention significantly reduces the investment cost of liquid air energy storage. By sharing key equipment such as compressors and cold boxes, the investment cost is significantly reduced.

[0026] 3. Through the flow regulation of the air separation cycle, the present invention maintains the temperature gradient of the main heat exchanger, keeps the air liquefaction cycle channel in a standby state all the time, and thus realizes rapid response, solving the pain point of slow startup of the traditional liquid air energy storage system.

[0027] 4. Through the collaborative design of multiple cycles and dynamic load regulation, the present invention improves the energy utilization efficiency while reducing the equipment cost, providing an innovative idea for the application of liquid air energy storage systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 It is a schematic diagram of the structure of the air compression unit in the present invention; Figure 3 It is a schematic diagram of the structure of the air cooling unit in the present invention; Figure 4 It is a schematic diagram of the structure of the air purification unit in the present invention; Figure 5 It is a schematic diagram of the structure of the air boosting unit in the present invention; Figure 6 It is a schematic diagram of the structure of the air liquefaction unit in the present invention; Figure 7 It is a schematic diagram of the structure of the air separation unit in the present invention; Figure 8 It is a schematic structural diagram of the air expansion power generation unit in the present invention; Figure 9 It is a schematic structural diagram of the cold storage unit in the present invention; Figure 10 It is a schematic structural diagram of the heat storage unit in the present invention; Figure 11 It is a schematic diagram of the internal flow channel of the main heat exchanger in the present invention.

[0029] In the figure: 100 air compression unit, 101 first compressor, 102 first cooler, 103 second compressor, 104 second cooler, 105 third compressor, 106 first three-way valve, 200 air cooling unit, 201 air cooling tower, 202 first water pump, 203 water cooling tower, 204 second water pump, 205 electric refrigerating machine, 300 air purification unit, 301 adsorption tower, 302 second three-way valve, 303 desorption tower, 400 air pressurization unit, 401 first separator, 402 first booster, 403 third cooler, 404 second separator, 405 second booster, 406 fourth cooler, 500 air liquefaction unit, 501 main heat exchanger, 502 first throttle valve, 503 first gas-liquid separator, 504 second throttle valve, 505 second gas-liquid separator, 506 low-temperature expander, 507 third three-way valve, 508 third three-way valve, 600 air separation unit, 601 rectification column, 602 liquid oxygen pump, 700 air expansion power generation unit, 701 liquid air storage tank, 702 low-temperature pump, 703 evaporator, 704 first heater, 705 first expander, 706 second heater, 707 second expander, 708 third heater, 709 third expander, 710 fourth heater, 711 fourth expander, 800 cold storage unit, 801 cold storage packed bed, 802 cold release circulation fan, 803 cold storage circulation fan, 900 heat storage unit, 901 heat storage tank, 902 first circulating water pump, 903 normal temperature storage tank, 904 second circulating water pump. Detailed implementation manners

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings, so that those skilled in the art can better understand the advantages and features of the present invention, and thus more clearly define the protection scope of the present invention. The embodiments described in the present invention are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work belong to the protection scope of the present invention.

[0031] A liquid air energy storage and air separation deep coupling system, including an air compression unit 100, an air cooling unit 200, an air purification unit 300, an air boosting unit 400, an air liquefaction unit 500, an air separation unit 600, an air expansion power generation unit 700, a cold storage unit 800 and a heat storage unit 900; The first input end of the air compression unit 100 is used to input ambient air. The first output end of the air compression unit 100 is connected to the first input end of the air cooling unit 200. The second output end of the air compression unit 100 is connected to the first input end of the heat storage unit 900. The first output end of the air cooling unit 200 is connected to the first input end of the air purification unit 300. The first output end of the air purification unit 300 is connected to the first input end of the air boosting unit 400. The air boosting unit 400 is connected to the air liquefaction unit 500. The first output end of the air liquefaction unit 500 is connected to the first input end of the air separation unit 600. The third output end of the air liquefaction unit 500 is connected to the first input end of the air expansion power generation unit 700. The second output end of the air expansion power generation unit 700 is connected to the second input end of the cold storage unit 800. The third output end of the air expansion power generation unit 700 is connected to the second input end of the heat storage unit 900.

[0032] Specifically, the air compression unit 100 can adopt single-stage compression or multi-stage compression. When multi-stage compression is adopted, the air compression unit 100 includes a first compressor 101, a first cooler 102, a second compressor 103, a second cooler 104, a third compressor 105 and a first three-way valve 106; The output end of the first compressor 101 is connected to the first input end of the first cooler 102. The first output end of the first cooler 102 is connected to the input end of the second compressor 103. The output end of the second compressor 103 is connected to the first input end of the second cooler 104. The first output end of the second cooler 104 is connected to the input end of the third compressor 105. The output end of the third compressor 105 is connected to the air cooling unit 200. The first input end of the first three-way valve 106 is connected to ambient air. The first output end of the first three-way valve 106 is connected to the input end of the first compressor 101; The air compression unit 100 is used to compress ambient air to obtain high-pressure air, and then carry out the air separation process and the process of producing liquid air for expansion power generation.

[0033] In this embodiment, high-temperature and high-pressure ratio compressors are selected everywhere, taking into account both the compression power consumption and the thermal energy grade of the heat exchange fluid. A cooler is configured at the outlet of each stage of the compressor to reduce the inlet air temperature of the next stage of the compressor, thereby reducing the power consumption of the compressor. During the low electricity consumption period, by dynamically increasing the compressor load, compressed air is provided for the air liquefaction cycle to achieve efficient storage of liquid air.

[0034] The air cooling unit 200 includes an air cooling tower 201, a first water pump 202, a water cooling tower 203, a second water pump 204, and an electric refrigerator 205; The first input end of the air cooling tower 201 is connected to the first output end of the air compression unit 100. The output end of the air cooling tower 201 is connected to the input end of the first water pump 202. The output end of the first water pump 202 is respectively connected to the input end of the electric refrigerator 205 and the first input end of the water cooling tower 203. The output end of the electric refrigerator 205 is connected to the third input end of the air cooling tower 201. The second input end of the water cooling tower 203 is connected to the first output end of the air purification unit 300. The first output end of the water cooling tower 203 is connected to the input end of the second water pump 204. The output end of the second water pump 204 is connected to the second input end of the air cooling tower 201. The second output end of the air cooling tower 201 is connected to the input end of the air cooling unit 200. The second output end of the water cooling tower 203 is discharged into the air; The air cooling unit 200 cools the compressed air through the air cooling tower and the water cooling tower, facilitating the subsequent adsorption process.

[0035] In this embodiment, the air cooling tower uses circulating water for indirect heat exchange to initially reduce the temperature of the compressed air, reduce the cooling load of the subsequent water cooling tower, and improve the overall heat exchange efficiency. The water cooling tower further cools the air to make it close to the ambient wet bulb temperature, reduce the water content in the air, and prevent the subsequent molecular sieve purification system from failing due to excessive moisture. At the same time, the waste nitrogen generated by the air separation unit can provide cold energy for the water cooling tower.

[0036] The air purification unit 300 includes an adsorption tower 301, a second three-way valve 302, and a desorption tower 303; The input end of the adsorption tower 301 is connected to the first output end of the air cooling unit 200. The input end of the second three-way valve 302 is connected to the seventh output end of the air pressurization unit 400. The input end of the desorption tower 303 is connected to the output end of the second three-way valve 302 and is discharged into the air as the second output end of the air purification unit 300; The air purification unit 300 removes impurities such as water and carbon dioxide in the air through the adsorption tower, improves the air purity, and then proceeds with the subsequent process. After adsorption saturation, the waste nitrogen generated by the air separation unit is processed by the desorption tower, and the water pump provides power.

[0037] In this embodiment: The cooled air enters the adsorption tower to deeply remove carbon dioxide and moisture. At low temperature, the adsorption tower captures impurities to provide clean air. During desorption, the waste nitrogen is used for reverse purging, and the nitrogen and water vapor are discharged into the atmosphere.

[0038] Specifically, the air pressurization unit 400 includes a first separator 401, a first booster 402, a third cooler 403, a second separator 404, a second booster 405, and a fourth cooler 406; The input end of the first separator 401 is connected to the first output end of the air purification unit 300. The first output end of the first separator 401 is connected to the first input end of the air liquefaction unit 500. The second output end of the first separator 401 is connected to the input end of the first booster 402. The output end of the first booster 402 is connected to the input end of the third cooler 403. The output end of the third cooler 403 is connected to the input end of the second separator 404. The first output end of the second separator 404 is connected to the second input end of the air liquefaction unit 500. The second output end of the second separator 404 is connected to the input end of the second booster 405. The output end of the second booster 405 is connected to the input end of the fourth cooler 406. The output end of the fourth cooler 406 is connected to the third input end of the air liquefaction unit 500; The air pressurization unit 400 pressurizes the air through the booster and then cools it down before entering the main heat exchanger to participate in the subsequent air separation and expansion power generation processes.

[0039] In this embodiment, for the air pressurization unit 400: One stream of gas separated by the first separator 401 directly enters the main heat exchanger 501, and the other stream is cooled by the third cooler 403 after passing through the first booster 402. Then this stream is divided into two streams again through the second separator 404. One of them directly enters the main heat exchanger 501, and the other enters the second booster 405 for pressurization and is cooled by the fourth cooler 406 before entering the main heat exchanger 501.

[0040] Specifically, the air liquefaction unit 500 includes a main heat exchanger 501, a first throttle valve 502, a first gas-liquid separator 503, a second throttle valve 504, a second gas-liquid separator 505, a low-temperature expander 506, a third three-way valve 507, and a fourth three-way valve 508; The first output end of the main heat exchanger 501 is sequentially connected to the first input end of the air separation unit 600 through a third three-way valve 507 and a fourth three-way valve 508. The second output end of the main heat exchanger 501 is connected to the input end of the low-temperature expander 506. The output end of the low-temperature expander 506 is connected to the first input end of the air separation unit 600 through the fourth three-way valve 508. The third output end of the main heat exchanger 501 is connected to the input end of the second throttle valve 504. The output end of the second throttle valve 504 is connected to the input end of the second gas-liquid separator 505. The first output end of the second gas-liquid separator 505 is sequentially connected to the first input end of the air separation unit 600 through the third three-way valve 507 and the fourth three-way valve 508. The second output end of the second gas-liquid separator 505 is connected to the second input end of the air separation unit 600. The fourth output end of the main heat exchanger 501 is connected to the input end of the first throttle valve 502. The output end of the first throttle valve 502 is connected to the input end of the first gas-liquid separator 503. The first output end of the first gas-liquid separator 503 is connected to the fourth input end of the main heat exchanger 501. The second output end of the first gas-liquid separator 503 is connected to the first input end of the air expansion power generation unit 700. The fifth input end of the main heat exchanger 501 is connected to the second output end of the cold storage unit 800. The sixth input end of the main heat exchanger 501 is connected to the first output end of the air separation unit 600. The seventh input end of the main heat exchanger 501 is connected to the second output end of the air separation unit 600. The eighth input end of the main heat exchanger 501 is connected to the third output end of the air separation unit 600. The fifth output end of the main heat exchanger 501 is connected to the second input end of the cold storage unit 800. The seventh output end of the main heat exchanger 501 is connected to the second input end of the air purification unit 300. The sixth output end and the eighth output end of the main heat exchanger 501 are discharged into the environment; The air liquefaction unit 500 performs pressure reduction and temperature reduction treatment on air and then sends it to two gas-liquid separators for separation. A part of the liquid air participates in the expansion power generation process, and a part of the gas enters the distillation column to participate in the air separation process.

[0041] In this embodiment, the air liquefaction unit 500: After being preliminarily cooled, a part of the air from the main heat exchanger passes through the low-temperature expander 705 for expansion and pressure reduction and then enters the distillation column 601. Another part is deeply cooled and then cooled by the second throttle valve 504, and then is separated into gas and liquid by the second gas-liquid separator 505 and enters the distillation column respectively. Another stream of gas is separated by the first gas-liquid separator 503 after passing through the third throttle valve 502, and the liquid air enters the air expansion power generation unit 700.

[0042] By adopting the above technical solutions: pressurization raises air to the working conditions available for liquid air energy storage, and the flow divider distributes the flow rates of the streams to achieve the energy synergy between air separation and liquid air energy storage; by adjusting the air volume of the booster, the load fluctuation is compensated; by sharing the key equipment of the air separation cycle, the investment cost of liquid air energy storage is significantly reduced; in addition, through the flow control of the air separation cycle, the temperature gradient of the main heat exchanger is maintained, so that the air liquefaction cycle channel is always in a standby state, and thus a rapid response is achieved.

[0043] Preferably, the air separation unit 600 includes a rectification column 601 and a liquid oxygen pump 602; The first output end of the rectification column 601 is connected to the sixth input end of the main heat exchanger 501, the second output end of the rectification column 601 is connected to the seventh input end of the main heat exchanger 501, the third output end of the rectification column 601 is connected to the eighth input end of the main heat exchanger 501 through the liquid oxygen pump 602, the first input end of the rectification column 601 is connected to the sixth output end of the air liquefaction unit 500, and the second input end of the rectification column 601 is connected to the seventh output end of the air liquefaction unit 500; The air separation unit 600 separates air into nitrogen, oxygen and simultaneously generates waste nitrogen through the rectification column, and the three gases are respectively returned to the main heat exchanger and then discharged.

[0044] Preferably, the air expansion power generation unit 700 includes a liquid air storage tank 701, a cryogenic pump 702, an evaporator 703, a first heater 704, a first expander 705, a second heater 706, a second expander 707, a third heater 708, a third expander 709, a fourth heater 710 and a fourth expander 711; The input end of the liquid air storage tank 701 is connected to the eighth output end of the air liquefaction unit 500. The output end of the liquid air storage tank 701 is connected to the input end of the cryogenic pump 702. The output end of the cryogenic pump 702 is connected to the first input end of the evaporator 703. The first output end of the evaporator 703 is connected to the first input end of the first heater 704. The first output end of the first heater 704 is connected to the input end of the first expander 705. The output end of the first expander 705 is connected to the first input end of the second heater 706. The first output end of the second heater 706 is connected to the input end of the second expander 707. The output end of the second expander 707 is connected to the first input end of the third heater 708. The first output end of the third heater 708 is connected to the input end of the third expander 709. The output end of the third expander 709 is connected to the first input end of the fourth heater 710. The first output end of the fourth heater 710 is connected to the input end of the fourth expander 711. The output end of the fourth expander 711 is connected to the second input end of the first three-way valve 106; The air expansion power generation unit 700 drives the turbine to expand and do work to generate electricity by heating the stored liquid air in stages, and the outlet air converges with the air compression unit 100.

[0045] Among them, the evaporator 703 includes, but is not limited to, the following three evaporation cooling structures: direct evaporation cooling, indirect evaporation cooling, or dew point evaporation cooling.

[0046] In this embodiment, the cold storage form in the air expansion power generation unit is one or a combination of sensible heat cold storage or solid-liquid phase change cold storage. Pressurized fluid heat exchange is adopted, such as propane, air, carbon dioxide, etc. The stored medium can be sealed ice balls, sand, concrete, phase change materials, or pressurized fluid (both the heat exchange medium and the storage medium).

[0047] Among them, the heat storage form in the air expansion power generation unit is one or several of sensible heat, latent heat, or chemical reaction heat. The heat storage medium used can be water, paraffin, inorganic crystalline hydrates, molten salts, stones. The heat storage medium is stored in an adiabatic container; the fluid conveying equipment is a pump, a compressor, or a fan; the valve is a throttle valve or a three-way valve.

[0048] Specifically, the cold storage unit 800 includes a cold storage packed bed 801, a cold release circulation fan 802, and a cold storage circulation fan 803; The input end of the cold-release circulation fan 802 is connected to the first output end of the air liquefaction unit 500, the output end of the cold-release circulation fan 802 is connected to the second input end of the air expansion power generation unit 700, the input end of the cold storage circulation fan 803 is connected to the second output end of the air expansion power generation unit 700, the output end of the cold storage circulation fan 803 is connected to the fourth input end of the air liquefaction unit 500, the cold storage circulation fan 803 is connected to the input end of the cold storage packed bed 801 as the driving force for storing cold energy, and the cold-release circulation fan 802 is connected to the output end of the cold storage packed bed 801 as the driving force for releasing cold energy; The cold storage unit 800 stores the cold energy generated by vaporizing liquid air in the cold storage packed bed and provides cold energy for the air liquefaction unit.

[0049] Specifically, the heat storage unit 900 includes a heat storage tank 901, a first circulation water pump 902, a normal temperature storage tank 903, and a second circulation water pump 904; The second output end of the air compression unit 100 is connected to the input end of the heat storage tank 901, the output end of the heat storage tank 901 is connected to the input end of the first circulation water pump 902, the output end of the first circulation water pump 902 is connected to the third input end of the air expansion power generation unit 700, the third output end of the air expansion power generation unit 700 is connected to the input end of the normal temperature storage tank 903, the output end of the normal temperature storage tank 903 is connected to the input end of the second circulation water pump 904, and the output end of the second circulation water pump 904 is connected to the second input end of the air compression unit 100; The heat storage unit 900 receives the compression heat transmitted by the air compression unit 100 and supplies heat to the air expansion power generation unit.

[0050] Specifically, the main heat exchanger 501 is internally provided with eight independent flow channels, including a first flow channel 5011, a second flow channel 5012, a third flow channel 5013, a fourth flow channel 5014, a fifth flow channel 5015, a sixth flow channel 5016, a seventh flow channel 5017, and an eighth flow channel 5018; among them, the first flow channel 5011, the second flow channel 5012, and the third flow channel 5013 are used for the air liquefaction cycle, and the remaining fourth flow channel 5014, fifth flow channel 5015, sixth flow channel 5016, seventh flow channel 5017, and eighth flow channel 5018 are used for the air separation cycle. All the channels jointly ensure that the two cycle systems do not interfere with each other and operate independently.

[0051] A method for deeply coupling liquid air energy storage and air separation, which is realized by the above-mentioned liquid air energy storage and air separation deep coupling system, includes: During the low grid load period, the air liquefaction cycle and the air separation cycle operate in combination: Ambient air is compressed in three stages and cooled between stages to 5 bar, enters the air cooling unit 200 and is cooled to 15 °C, then enters the adsorption tower 303 to remove water and carbon dioxide from the air. Subsequently, it is divided into two streams. One stream enters the main heat exchanger 501, is cooled to -170 °C and then enters the rectification column 601. The other stream is compressed to 36 bar by the air booster 402, cooled to 40 °C by the third cooler 403 and then divided into two streams again. One stream directly enters the main heat exchanger 501. After preliminary cooling, a part of the air expands and reduces pressure to 5 bar through the low-temperature expander 506 and then enters the rectification column 601. The other part is deeply cooled and then cooled to the second gas-liquid separator 505 through the second throttle valve 504 and is divided into gas and liquid, which respectively enter the rectification column 601; 30% of the total air volume is extracted as the feed gas for the air liquefaction cycle, that is, the second output end of the second gas-liquid separator 404 passes through compression and cooling, then passes through the main heat exchanger 501, is throttled and cooled to 1 bar and -190 °C by the first throttle valve 502 and then enters the second gas-liquid separator 505. The separated liquid air is used for the air power generation cycle, and the liquefaction rate is 69.1%; the gaseous air returns to the main heat exchanger 501 to provide part of the cooling capacity and continues to participate in the cycle process. The nitrogen, waste nitrogen and oxygen separated by the rectification column 601 return to the main heat exchanger 501 in three ways and are discharged.

[0052] During the high grid load period, the air power generation cycle and the air separation cycle operate in combination: The liquid air separated by the air liquefaction cycle is stored in the liquid air storage tank 701, pressurized to 60 bar by the cryogenic pump 702, then enters the evaporator 703 to undergo a liquid-gas phase change process to 16 °C, and the phase change cooling energy is recovered and stored in the cold storage packed bed 801 through the pressurized fluid. The cold release circulation fan 802 and the cold storage circulation fan 803 serve as the driving forces for the gas in the packed bed. The gasified high-pressure air expands and generates electricity through four-stage expansion and inter-stage heating in sequence. Finally, the outlet air and the inlet air converge through the first three-way valve 106 to reduce the overall power consumption of the system.

[0053] During the flat grid load period, the air separation cycle operates independently: Ambient air is compressed in three stages and cooled between stages, then enters the air cooling unit 200 to be cooled, then enters the adsorption tower 303 to remove water and carbon dioxide from the air. Subsequently, it is divided into two streams. One stream enters the main heat exchanger 501, is cooled and then enters the rectification column 601. The other stream is compressed to a high pressure by the air booster 402, cooled by the third cooler 403 and then divided into two streams again. One stream directly enters the main heat exchanger. After preliminary cooling, a part of the air expands and reduces pressure through the low-temperature expander 506 and then enters the rectification column 601. The other part is deeply cooled and then cooled to the second gas-liquid separator 505 through the second throttle valve 504 and is divided into gas and liquid, which respectively enter the rectification column 601. The nitrogen, waste nitrogen and oxygen separated by the rectification column 601 enter the main heat exchanger in three ways to provide cooling capacity and are discharged.

[0054] In this embodiment, taking a 50MW liquid air energy storage system as an example, assuming the initial investment is 400 million yuan. Through research, by sharing the key equipment of the air separation cycle, the investment cost of the liquid air energy storage is significantly reduced to 160 million yuan. The round-trip efficiency of the liquid air energy storage system is 50%. The electricity price during peak hours is 0.9 yuan / kWh, and the electricity price during off-peak hours is 0.3 yuan / kWh. By calculating the initial investment, response time, and investment payback period indicators to compare traditional liquid air energy storage and the coupled system, it can be seen that the initial investment of the coupled system is reduced by 60%, and the investment payback period is reduced by 30%, as shown in Table 1: Table 1: Comparison results of technical and economic parameters of two energy storage systems

[0055] Among them, during the off-peak period of the power grid, the air liquefaction cycle and the air separation cycle share the air separation unit 100, air cooling unit 200, air purification unit 300, air pressurization unit 400, and main heat exchanger 501. By sharing the equipment, the investment cost of the liquid air energy storage is significantly reduced; at the same time, a part of the compressor gas volume separated by the air separator 404 is extracted as the raw material gas for the air liquefaction cycle, and liquid air is obtained through temperature reduction by the main heat exchanger.

[0056] In addition, the high-purity expansion exhaust gas of the air expansion power generation unit 700 is not directly discharged, but is connected back to the inlet of the first compressor of the air compression unit 100 through the first three-way valve 106 and merges with the ambient air, which can reduce the system power consumption.

[0057] To sum up, the present invention significantly reduces the investment cost of liquid air energy storage by sharing the key equipment of the air separation cycle; in addition, through the flow regulation of the air separation cycle, the temperature gradient of the main heat exchanger is maintained, so that the air liquefaction cycle channel is always in a standby state, thereby achieving rapid response and solving the pain point of slow startup of the traditional liquid air energy storage system. Through the collaborative design of multiple cycles and dynamic load regulation, the present invention improves the energy utilization efficiency while reducing the equipment cost, providing an innovative idea for the application of liquid air energy storage systems.

[0058] The descriptions and practices disclosed in the present invention are easy to think and understand for ordinary technical personnel in the technical field. And without departing from the principle of the present invention, several improvements and refinements can be made. Therefore, the modifications or improvements made without departing from the spirit of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A liquid air energy storage and air separation deep coupling system, characterized in that It includes an air compression unit (100), an air cooling unit (200), an air purification unit (300), an air boosting unit (400), an air liquefaction unit (500), an air separation unit (600), an air expansion power generation unit (700), a cold storage unit (800) and a heat storage unit (900); The first input end of the air compression unit (100) is used to input ambient air. The first output end of the air compression unit (100) is connected to the first input end of the air cooling unit (200). The second output end of the air compression unit (100) is connected to the first input end of the heat storage unit (900). The first output end of the air cooling unit (200) is connected to the first input end of the air purification unit (300). The first output end of the air purification unit (300) is connected to the first input end of the air boosting unit (400). The air boosting unit (400) is connected to the air liquefaction unit (500). The first output end of the air liquefaction unit (500) is connected to the first input end of the air separation unit (600). The third output end of the air liquefaction unit (500) is connected to the first input end of the air expansion power generation unit (700). The second output end of the air expansion power generation unit (700) is connected to the second input end of the cold storage unit (800). The third output end of the air expansion power generation unit (700) is connected to the second input end of the heat storage unit (900).

2. The liquid air energy storage and air separation deep coupling system according to claim 1, wherein The air compression unit (100) includes a first compressor (101), a first cooler (102), a second compressor (103), a second cooler (104), a third compressor (105) and a first three-way valve (106); The output end of the first compressor (101) is connected to the first input end of the first cooler (102). The first output end of the first cooler (102) is connected to the input end of the second compressor (103). The output end of the second compressor (103) is connected to the first input end of the second cooler (104). The first output end of the second cooler (104) is connected to the input end of the third compressor (105). The output end of the third compressor (105) is connected to the air cooling unit (200). The first input end of the first three-way valve (106) is connected to ambient air. The first output end of the first three-way valve (106) is connected to the input end of the first compressor (101); The air compression unit (100) is used to compress ambient air for subsequent air separation process and liquid air expansion power generation process; The air cooling unit (200) includes an air cooling tower (201), a first water pump (202), a water cooling tower (203), a second water pump (204) and an electric refrigerating machine (205); The first input end of the air cooling tower (201) is connected to the first output end of the air compression unit (100). The first output end of the air cooling tower (201) is connected to the input end of the first water pump (202). The output end of the first water pump (202) is respectively connected to the input end of the electric refrigerating machine (205) and the first input end of the water cooling tower (203). The output end of the electric refrigerating machine (205) is connected to the third input end of the air cooling tower (201). The second input end of the water cooling tower (203) is connected to the first output end of the air purification unit (300). The first output end of the water cooling tower (203) is connected to the input end of the second water pump (204). The output end of the second water pump (204) is connected to the second input end of the air cooling tower (201). The second output end of the air cooling tower (201) is connected to the input end of the air cooling unit (200). The second output end of the water cooling tower (203) is discharged into the air. The air cooling unit (200) cools the compressed air through the air cooling tower and the water cooling tower, facilitating the subsequent adsorption process. The air purification unit (300) includes an adsorption tower (301), a second three-way valve (302), and a desorption tower (303). The input end of the adsorption tower (301) is connected to the first output end of the air cooling unit (200). The input end of the second three-way valve (302) is connected to the seventh output end of the air boosting unit (400). The input end of the desorption tower (303) is connected to the output end of the second three-way valve (302) and is discharged into the air as the second output end of the air purification unit (300). The air purification unit (300) removes water and carbon dioxide impurities from the air through the adsorption tower, improves the air purity, and then proceeds with the subsequent process. After adsorption saturation, the waste nitrogen generated by the air separation unit is processed through the desorption tower.

3. The liquid air energy storage and air separation deep coupling system according to claim 1, wherein The air boosting unit (400) includes a first separator (401), a first booster (402), a third cooler (403), a second separator (404), a second booster (405), and a fourth cooler (406). The input end of the first separator (401) is connected to the first output end of the air purification unit (300). The first output end of the first separator (401) is connected to the first input end of the air liquefaction unit (500). The second output end of the first separator (401) is connected to the input end of the first booster (402). The output end of the first booster (402) is connected to the input end of the third cooler (403). The output end of the third cooler (403) is connected to the input end of the second separator (404). The first output end of the second separator (404) is connected to the second input end of the air liquefaction unit (500). The second output end of the second separator (404) is connected to the input end of the second booster (405). The output end of the second booster (405) is connected to the input end of the fourth cooler (406). The output end of the fourth cooler (406) is connected to the third input end of the air liquefaction unit (500); The air boosting unit (400) boosts the air through a booster and then cools it down before entering the main heat exchanger to participate in the subsequent air separation and expansion power generation processes.

4. A liquid air energy storage and air separation deep coupling system according to claim 1, characterized in that, The air liquefaction unit (500) includes a main heat exchanger (501), a first throttle valve (502), a first gas-liquid separator (503), a second throttle valve (504), a second gas-liquid separator (505), a low-temperature expander (506), a third three-way valve (507), and a fourth three-way valve (508); The first output end of the main heat exchanger (501) is sequentially connected to the first input end of the air separation unit (600) through a third three-way valve (507) and a fourth three-way valve (508). The second output end of the main heat exchanger (501) is connected to the input end of the low-temperature expander (506). The output end of the low-temperature expander (506) is connected to the first input end of the air separation unit (600) through the fourth three-way valve (508). The third output end of the main heat exchanger (501) is connected to the input end of the second throttle valve (504). The output end of the second throttle valve (504) is connected to the input end of the second gas-liquid separator (505). The first output end of the second gas-liquid separator (505) is sequentially connected to the first input end of the air separation unit (600) through a third three-way valve (507) and a fourth three-way valve (508). The second output end of the second gas-liquid separator (505) is connected to the second input end of the air separation unit (600). The fourth output end of the main heat exchanger (501) is connected to the input end of the first throttle valve (502). The output end of the first throttle valve (502) is connected to the input end of the first gas-liquid separator (503). The first output end of the first gas-liquid separator (503) is connected to the fourth input end of the main heat exchanger (501). The second output end of the first gas-liquid separator (503) is connected to the first input end of the air expansion power generation unit (700). The fifth input end of the main heat exchanger (501) is connected to the second output end of the cold storage unit (800). The sixth input end of the main heat exchanger (501) is connected to the first output end of the air separation unit (600). The seventh input end of the main heat exchanger (501) is connected to the second output end of the air separation unit (600). The eighth input end of the main heat exchanger (501) is connected to the third output end of the air separation unit (600). The fifth output end of the main heat exchanger (501) is connected to the second input end of the cold storage unit (800). The seventh output end of the main heat exchanger (501) is connected to the second input end of the air purification unit (300). The sixth output end and the eighth output end of the main heat exchanger (501) are discharged into the environment; The air liquefaction unit (500) performs pressure reduction and temperature reduction treatment on air and then sends it to two gas-liquid separators for separation. A part of the liquid air participates in the expansion power generation process, and a part of the gas enters the distillation column to participate in the air separation process.

5. The liquid air energy storage and air separation deep coupling system according to claim 4, wherein The air separation unit (600) includes a distillation column (601) and a liquid oxygen pump (602); The first output end of the rectifying column (601) is connected to the sixth input end of the main heat exchanger (501), the second output end of the rectifying column (601) is connected to the seventh input end of the main heat exchanger (501), the third output end of the rectifying column (601) is connected to the eighth input end of the main heat exchanger (501) through a liquid oxygen pump (602), the first input end of the rectifying column (601) is connected to the sixth output end of the air liquefaction unit (500), and the second input end of the rectifying column (601) is connected to the seventh output end of the air liquefaction unit (500); The air separation unit (600) separates air into nitrogen and oxygen through a rectifying column, and at the same time generates waste nitrogen. The three gases are respectively returned to the main heat exchanger and then discharged.

6. The liquid air energy storage and air separation deep coupling system according to claim 2, wherein, The air expansion power generation unit (700) includes a liquid air storage tank (701), a cryogenic pump (702), an evaporator (703), a first heater (704), a first expander (705), a second heater (706), a second expander (707), a third heater (708), a third expander (709), a fourth heater (710) and a fourth expander (711); The input end of the liquid air storage tank (701) is connected to the eighth output end of the air liquefaction unit (500), the output end of the liquid air storage tank (701) is connected to the input end of the cryogenic pump (702), the output end of the cryogenic pump (702) is connected to the first input end of the evaporator (703), the first output end of the evaporator (703) is connected to the first input end of the first heater (704), the first output end of the first heater (704) is connected to the input end of the first expander (705), the output end of the first expander (705) is connected to the first input end of the second heater (706), the first output end of the second heater (706) is connected to the input end of the second expander (707), the output end of the second expander (707) is connected to the first input end of the third heater (708), the first output end of the third heater (708) is connected to the input end of the third expander (709), the output end of the third expander (709) is connected to the first input end of the fourth heater (710), the first output end of the fourth heater (710) is connected to the input end of the fourth expander (711), and the output end of the fourth expander (711) is connected to the second input end of the first three-way valve (106); The air expansion power generation unit (700) drives a turbine to expand and do work for power generation by heating the stored liquid air between stages, and the outlet air converges with the air compression unit (100).

7. A liquid air energy storage and air separation deep coupling system according to claim 1, characterized in that The cold storage unit (800) includes a cold storage packed bed (801), a cold release circulation fan (802) and a cold storage circulation fan (803); The input end of the cold-release circulation fan (802) is connected to the first output end of the air liquefaction unit (500), the output end of the cold-release circulation fan (802) is connected to the second input end of the air expansion power generation unit (700), the input end of the cold-storage circulation fan (803) is connected to the second output end of the air expansion power generation unit (700), the output end of the cold-storage circulation fan (803) is connected to the fourth input end of the air liquefaction unit (500), the cold-storage circulation fan (803) is connected to the input end of the cold-storage packed bed (801) as the driving force for storing cold energy, and the cold-release circulation fan (802) is connected to the output end of the cold-storage packed bed (801) as the driving force for releasing cold energy; The cold-storage unit (800) stores the cold energy generated by gasifying liquid air in the cold-storage packed bed to provide cold energy for the air liquefaction unit.

8. A liquid air energy storage and air separation deep coupling system according to claim 1, characterized in that The heat-storage unit (900) includes a heat-storage tank (901), a first circulation water pump (902), a normal-temperature storage tank (903), and a second circulation water pump (904); The second output end of the air compression unit (100) is connected to the input end of the heat-storage tank (901), the output end of the heat-storage tank (901) is connected to the input end of the first circulation water pump (902), the output end of the first circulation water pump (902) is connected to the third input end of the air expansion power generation unit (700), the third output end of the air expansion power generation unit (700) is connected to the input end of the normal-temperature storage tank (903), the output end of the normal-temperature storage tank (903) is connected to the input end of the second circulation water pump (904), and the output end of the second circulation water pump (904) is connected to the second input end of the air compression unit (100); The heat-storage unit (900) receives the compression heat transmitted by the air compression unit (100) to supply heat to the air expansion power generation unit.

9. A liquid air energy storage and air separation deep coupling system according to claim 4, wherein The main heat exchanger (501) is internally provided with eight independent stream channels, which include a first stream channel (5011), a second stream channel (5012), a third stream channel (5013), a fourth stream channel (5014), a fifth stream channel (5015), a sixth stream channel (5016), a seventh stream channel (5017), and an eighth stream channel (5018); among them, the first stream channel (5011), the second stream channel (5012), and the third stream channel (5013) are used for the air liquefaction cycle, and the fourth stream channel (5014), the fifth stream channel (5015), the sixth stream channel (5016), the seventh stream channel (5017), and the eighth stream channel (5018) are used for the air separation cycle.

10. A method for deep coupling of liquid air energy storage and air separation, which is realized based on a liquid air energy storage and air separation deep coupling system according to any one of claims 1-9, characterized in that, Including: During the low grid load period, the air liquefaction cycle and the air separation cycle operate in combination: Ambient air is cooled after three-stage compression and inter-stage cooling and then enters the air cooling unit (200) to be cooled down. Then it enters the adsorption tower (303) to remove water and carbon dioxide in the air. Subsequently, it is divided into two streams. One stream enters the main heat exchanger (501) to be cooled down and then enters the distillation column (601). The other stream is compressed by the air booster (402) to a high pressure greater than 4 MPar, cooled by the third cooler (403), and then divided into two streams again. One stream directly enters the main heat exchanger. After preliminary cooling, a part of the air expands and reduces pressure through the low-temperature expander (506) and then enters the distillation column (601). The other part is deeply cooled and then cooled down to the second gas-liquid separator (505) through the second throttle valve (504) and is divided into gaseous and liquid states respectively and enters the distillation column (601). The other stream is compressed and cooled and then passes through the main heat exchanger (501), is throttled and cooled down by the first throttle valve (502) and then enters the second gas-liquid separator (505). The separated liquid air is used for the air power generation cycle, and the gaseous air returns to the main heat exchanger (501) to provide part of the cooling capacity and continue to participate in the cycle process. The nitrogen, waste nitrogen, and oxygen separated by the distillation column (601) are returned to the main heat exchanger (501) and discharged in three streams. During the high grid load period, the air power generation cycle and the air separation cycle operate in combination: The liquid air separated by the air liquefaction cycle is stored in the liquid air storage tank (701), pressurized by the cryogenic pump (702), and then enters the evaporator (703) to undergo a liquid-gas phase change process. The phase change cooling energy is recovered and stored in the cold storage packed bed (801) through the pressurized fluid. The cold release circulation fan (802) and the cold storage circulation fan (803) serve as the driving forces for the gas in the packed bed. The vaporized air expands and generates electricity through four-stage expansion and inter-stage heating expansion in sequence. Finally, the outlet air and the inlet air converge through the first three-way valve (106) to reduce the overall power consumption of the system. During the flat grid load period, the air separation cycle operates independently: Ambient air is cooled after three-stage compression and inter-stage cooling and then enters the air cooling unit (200) to be cooled down. Then it enters the adsorption tower (303) to remove water and carbon dioxide in the air. Subsequently, it is divided into two streams. One stream enters the main heat exchanger (501) to be cooled down and then enters the distillation column (601). The other stream is compressed by the air booster (402) to a high pressure greater than 4 MPar, cooled by the third cooler (403), and then divided into two streams again. One stream directly enters the main heat exchanger. After preliminary cooling, a part of the air expands and reduces pressure through the low-temperature expander (506) and then enters the distillation column (601). The other part is deeply cooled and then cooled down to the second gas-liquid separator (505) through the second throttle valve (504) and is divided into gaseous and liquid states respectively and enters the distillation column (601). The nitrogen, waste nitrogen, and oxygen separated by the distillation column (601) enter the main heat exchanger in three streams to provide cooling capacity and are discharged.

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