LNG cold energy utilization air separation process based on liquefied air energy storage

Abstract

The invention provides an LNG cold energy utilization air separation process based on liquefied air energy storage, and relates to the technical field of LNG cold energy utilization. According to the technology, when LNG is gasified and output, cold energy is stored in a cold storage type heat exchanger, in the valley electricity period, an air liquefaction device absorbs the cold energy from LNG storage through the cold storage type heat exchanger, air is liquefied and stored through low-price electric energy, liquid air is conveyed and gasified through a liquid air pump, and the cold energy is used for liquefaction of air separation oxygen and nitrogen products; the gasified liquid air and the air separation oxygen-nitrogen product are subjected to heat exchange and reheating and then are supplied to an air separation device as raw material air. According to the method, the problem that the stable production of the air separation device is influenced by cold output fluctuation caused by LNG consumption fluctuation can be relieved, a conventional air separation device does not need to be subjected to any technical transformation, conventional air separation products can be liquefied by utilizing LNG cold and low-price off-peak electricity, the liquefaction cost of the products of the air separation device is reduced, and the production efficiency of the air separation device is improved. And large-scale and distributed energy storage is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of LNG cold energy utilization, and in particular to an LNG cold energy utilization air separation process based on liquefied air energy storage. Background Art

[0002] Liquefied natural gas (LNG) inherently contains a significant amount of cold energy, and its recovery and utilization holds significant economic value. One primary method for recovering LNG cold energy is through integration with cryogenic air separation units (ASUs). These units absorb the cold energy from LNG vaporization, thereby reducing their own electrical energy consumption. However, ASUs utilizing LNG cold energy face a conflict during operation: the air separation unit requires stable operating parameters, while the LNG vaporization cold energy output is unstable. This creates a mismatch between the LNG cold energy output and the amount of cold energy absorbed by the ASU. If this issue is not addressed, the ASU will be unable to effectively utilize the cold energy from LNG vaporization and maintain stable ASU production. Summary of the Invention

[0003] In order to solve the technical problem of mismatch between LNG cold energy output and air separation absorption cold energy in the existing technology, the embodiment of the present invention provides an LNG cold energy utilization air separation process based on liquefied air energy storage. The technical solution is as follows:

[0004] An LNG cold energy utilization air separation process based on liquefied air energy storage, the process comprising:

[0005] S1. LNG from the LNG storage tank enters the LNG cold storage heat exchanger through the LNG pump, where the latent heat of vaporization and sensible heat are stored in the cold storage medium of the LNG cold storage heat exchanger. The natural gas then enters the natural gas pipeline system.

[0006] S2, after being compressed by the air compressor and purified by the air purifier, the air enters the air cold storage heat exchanger and the LNG cold storage heat exchanger in sequence, absorbs the cold energy and enters the air liquefaction device. The liquefied air is stored in the liquid air storage tank;

[0007] S3. The liquid air in the liquid air storage tank in step S2 is transported by a liquid air pump into the oxygen-nitrogen condensing heat exchanger, exchanges heat with oxygen and nitrogen in the oxygen-nitrogen condensing heat exchanger, and then enters the air cold storage heat exchanger to recover excess cold energy of the air, and then enters the air separation unit as feed gas for air separation;

[0008] S4. The product oxygen produced by the air separation device in step S3 is compressed and pressurized by the oxygen compressor and then enters the oxygen cooler. Then, it enters the gas heat exchanger to exchange heat with the oxygen and nitrogen from the oxygen-liquid separator and the nitrogen-gas-liquid separator, enters the oxygen-nitrogen condensing heat exchanger, and then enters the oxygen-liquid separator through the oxygen expander. The oxygen at the top of the oxygen-liquid separator is heated and restored in the gas heat exchanger before returning to the oxygen compressor inlet. The liquid oxygen at the bottom of the oxygen-liquid separator enters the liquid oxygen storage tank for storage as liquid oxygen product.

[0009] S5. The product nitrogen produced by the air separation device in step S3 is compressed and pressurized by the nitrogen compressor and then enters the nitrogen cooler. Then, it enters the gas heat exchanger to exchange heat with the oxygen and nitrogen from the oxygen-liquid separator and the nitrogen-gas-liquid separator, enters the oxygen-nitrogen condensing heat exchanger, and then enters the nitrogen-gas-liquid separator through the nitrogen expander. The nitrogen above the nitrogen-gas-liquid separator is heat exchanged and restored to its original temperature in the gas heat exchanger before returning to the nitrogen compressor inlet. The liquid nitrogen at the bottom of the nitrogen-gas-liquid separator enters the liquid nitrogen storage tank and is stored as liquid nitrogen product.

[0010] The process in step S1 is performed during both valley period and non-valley period.

[0011] The process in step S2 is performed during valley power period and stops during non-valley power period.

[0012] The amount of air liquefied by the air liquefaction device in step S2 satisfies the daily raw air requirement of the air separation system.

[0013] The processes in step S3, step S4 and step S5 are performed during both valley period and non-valley period.

[0014] In step S3, the oxygen and nitrogen come from gas heat exchangers respectively.

[0015] The air separation unit is a conventional air separation unit.

[0016] The systems that the process relies on include liquefied air energy storage system, air separation unit, air separation oxygen and nitrogen product liquefaction system and LNG cold storage and heat exchange system.

[0017] The liquefied air energy storage system includes an air compressor, an air purifier, an air liquefaction device and a liquid air storage tank;

[0018] The air separation oxygen and nitrogen product liquefaction system includes an oxygen compressor, a nitrogen compressor, an oxygen cooler, a nitrogen cooler, a gas heat exchanger, an oxygen expander, a nitrogen expander, an oxygen-liquid separator, a nitrogen-gas-liquid separator, a liquid oxygen storage tank, and a liquid nitrogen storage tank;

[0019] The LNG cold storage and heat exchange system includes an LNG storage tank, an LNG pump and an LNG cold storage heat exchanger.

[0020] The LNG storage tank is connected to the natural gas inlet of the LNG cold storage heat exchanger through an LNG pump, and the natural gas outlet of the LNG cold storage heat exchanger is connected to the natural gas pipeline network;

[0021] The air compressor inlet is connected to the ambient air, the air compressor outlet is connected to the air purifier, the air purifier outlet is connected to the air inlet I of the air cold storage heat exchanger, the air outlet I of the air cold storage heat exchanger is connected to the air inlet of the LNG cold storage heat exchanger, the air outlet of the LNG cold storage heat exchanger is connected to the air liquefaction device, and the air liquefaction device outlet is connected to the liquid air storage tank;

[0022] The outlet of the liquid air storage tank is connected to the air inlet of the oxygen-nitrogen condensing heat exchanger through a liquid air pump, the air outlet of the oxygen-nitrogen condensing heat exchanger is connected to the air inlet II of the air cold storage heat exchanger, and the air outlet II of the air cold storage heat exchanger is connected to the inlet of the air separation unit;

[0023] The oxygen outlet of the air separation unit is connected to the oxygen inlet of the oxygen cooler via the oxygen compressor, the oxygen outlet of the oxygen cooler is connected to the oxygen inlet I of the gas heat exchanger, the oxygen outlet I of the gas heat exchanger is connected to the oxygen inlet of the oxygen-nitrogen condensing heat exchanger, the oxygen outlet of the oxygen-nitrogen condensing heat exchanger is connected to the inlet of the oxygen-liquid separator via the oxygen expander, the upper gas outlet of the oxygen-liquid separator is connected to the oxygen inlet II of the gas heat exchanger, the oxygen outlet II of the gas heat exchanger is connected to the inlet of the oxygen compressor, and the liquid outlet at the bottom of the oxygen-liquid separator is connected to the liquid oxygen storage tank;

[0024] The nitrogen outlet of the air separation unit is connected to the nitrogen inlet of the nitrogen cooler via a nitrogen compressor, the nitrogen outlet of the nitrogen cooler is connected to the nitrogen inlet I of the gas heat exchanger, the nitrogen outlet I of the gas heat exchanger is connected to the nitrogen inlet of the oxygen-nitrogen condensing heat exchanger, the nitrogen outlet of the oxygen-nitrogen condensing heat exchanger is connected to the inlet of the nitrogen-liquid separator via a nitrogen expander, the upper gas outlet of the nitrogen-liquid separator is connected to the nitrogen inlet II of the gas heat exchanger, the nitrogen outlet II of the gas heat exchanger is connected to the inlet of the nitrogen compressor, and the liquid outlet at the bottom of the nitrogen-liquid separator is connected to the liquid nitrogen storage tank.

[0025] The above system does not require any technical transformation or change to the conventional air separation system.

[0026] The above oxygen compressor and nitrogen compressor can both be multi-stage compressed and intercooled.

[0027] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include at least:

[0028] The present invention combines an air liquefaction energy storage device with an air separation device utilizing LNG cold energy, that is, placing the liquefied air energy storage system between the LNG gasification system and the air separation system. The air liquefaction system absorbs the cold energy released by LNG, and the air liquefaction system provides the air separation system with a stable raw gas source and the cold energy required for liquefaction of air separation products. The LNG cold energy utilization air separation system obtains a stable operating environment and has a large-scale energy storage function. During the off-peak and non-off-peak power periods, the cold energy generated by LNG gasification is stored in the LNG cold storage and heat exchange device. During the off-peak power period, the liquefied air energy storage device absorbs the cold energy stored by LNG gasification and uses low-cost electricity to liquefy and store the air. The liquid air is vaporized after passing through the liquid air delivery pump and the cold energy is used to liquefy the oxygen and nitrogen products of the air separation. The vaporized liquid air and the air separation oxygen and nitrogen products are heat exchanged and reheated, and then supplied to the air separation device as raw air. The present invention does not require any technical modification to the air separation unit, and achieves a smooth combination of the volatility of LNG cold energy release and the stability of LNG cold energy absorption required by air separation. It also enables the LNG cold energy utilization air separation system to have a large-scale energy storage function, thereby effectively utilizing LNG cold energy and reducing the electricity cost of liquefying air separation products while achieving system operation stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 This is a flow chart of an air separation process for utilizing LNG cold energy based on liquefied air energy storage provided by an embodiment of the present invention.

[0031] Among them: 1- LNG storage tank; 2-LNG pump; 3-LNG cold storage heat exchanger; 4-air compressor; 5-air purifier; 6-air liquefaction unit; 7-liquid air storage tank; 8-liquid air pump; 9-oxygen and nitrogen condensing heat exchanger; 10-air separation unit; 11-gas heat exchanger; 12-oxygen compressor; 13-nitrogen compressor; 14-oxygen cooler; 15-nitrogen cooler; 16-oxygen expander; 17-nitrogen expander; 18-oxygen-liquid separator; 19-nitrogen-gas-liquid separator; 20-liquid oxygen storage tank; 21-liquid nitrogen storage tank; 22-air cold storage heat exchanger. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0033] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as an "exemplary" in the present invention should not be interpreted as being preferred or advantageous over other embodiments or designs. Rather, the use of the word "exemplary" is intended to present concepts in a concrete manner. Furthermore, in the embodiments of the present invention, "and / or" can mean both or either of the two.

[0034] In the embodiments of the present invention, sometimes a subscript such as W1 may be written as a non-subscript such as W1. When the difference is not emphasized, the meanings to be expressed are the same.

[0035] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0036] The embodiment of the present invention provides an air separation process for utilizing LNG cold energy based on liquefied air energy storage. Figure 1 The process flow chart of LNG cold energy utilization air separation based on air liquefaction energy storage is shown. The process may include the following steps:

[0037] S1, LNG from LNG storage tank 1 enters LNG cold storage heat exchanger 3 through LNG pump 2, stores latent heat of vaporization and sensible heat in the cold storage medium of LNG cold storage heat exchanger 3, and then enters the natural gas pipeline system;

[0038] S2, the air is compressed by the air compressor 4 and purified by the air purifier 5, and then enters the air cold storage heat exchanger 22 and the LNG cold storage heat exchanger 3 in sequence, absorbs the cold energy and enters the air liquefaction device 6, and the liquefied air is stored in the liquid air storage tank 7;

[0039] S3. The liquid air in the liquid air storage tank 7 in step S2 is transported by the liquid air pump 8 into the oxygen-nitrogen condensing heat exchanger 9. After heat exchange with oxygen and nitrogen in the oxygen-nitrogen condensing heat exchanger 9, the liquid air enters the air cold storage heat exchanger 22 to recover excess cold energy of the air, and then enters the air separation unit 10 as feed gas for air separation.

[0040] In step S4, the product oxygen produced by the air separation device 10 in step S3 is compressed and pressurized by the oxygen compressor 12 and then enters the oxygen cooler 14. The oxygen then enters the gas heat exchanger 11 to exchange heat with the oxygen and nitrogen from the oxygen-liquid separator 18 and the nitrogen-liquid separator 19, and then enters the oxygen-nitrogen condensing heat exchanger 9. The oxygen then enters the oxygen-liquid separator 18 through the oxygen expander 16. The oxygen at the top of the oxygen-liquid separator 18 is heated and restored in the gas heat exchanger 11 and then returns to the inlet of the oxygen compressor 12. The liquid oxygen at the bottom of the oxygen-liquid separator 18 enters the liquid oxygen storage tank 20 for storage as liquid oxygen product.

[0041] In step S5, the product nitrogen produced by the air separation device 10 in step S3 is compressed and pressurized by the nitrogen compressor 13 and then enters the nitrogen cooler 15. The nitrogen then enters the gas heat exchanger 11 for heat exchange with the oxygen and nitrogen from the oxygen-liquid separator 18 and the nitrogen-liquid separator 19, and then enters the oxygen-nitrogen condensing heat exchanger 9. The nitrogen then enters the nitrogen-liquid separator 19 through the nitrogen expander 17. The nitrogen above the nitrogen-liquid separator 19 is heat exchanged and restored to its original temperature in the gas heat exchanger 11 before returning to the inlet of the nitrogen compressor 13. The liquid nitrogen at the bottom of the nitrogen-liquid separator 19 enters the liquid nitrogen storage tank 21 for storage as liquid nitrogen product.

[0042] The process in step S1 is performed during both valley and non-valley periods.

[0043] The process in step S2 is performed during the valley period and stops during the non-valley period.

[0044] The amount of air liquefied by the air liquefaction device in step S2 meets the daily raw air demand of the air separation system.

[0045] The processes in step S3, step S4 and step S5 are performed in both valley period and non-valley period.

[0046] In step S3 , oxygen and nitrogen come from the gas heat exchanger 11 respectively.

[0047] The air separation unit is a conventional air separation unit.

[0048] The systems that the above-mentioned process relies on include liquefied air energy storage system, air separation unit, air separation oxygen and nitrogen product liquefaction system and LNG cold storage and heat exchange system.

[0049] The liquefied air energy storage system includes an air compressor 4, an air purifier 5, an air liquefaction device 6 and a liquid air storage tank 7;

[0050] The air separation oxygen and nitrogen product liquefaction system includes an oxygen compressor 12, a nitrogen compressor 13, an oxygen cooler 14, a nitrogen cooler 15, a gas heat exchanger 11, an oxygen expander 16, a nitrogen expander 17, an oxygen-liquid separator 18, a nitrogen-liquid separator 19, a liquid oxygen storage tank 20, and a liquid nitrogen storage tank 21;

[0051] The LNG cold storage and heat exchange system includes an LNG storage tank 1 , an LNG pump 2 and an LNG cold storage heat exchanger 3 .

[0052] The LNG storage tank 1 is connected to the natural gas inlet of the cold storage heat exchanger 3 through an LNG pump, and the natural gas outlet of the LNG cold storage heat exchanger 3 is connected to the natural gas pipeline network;

[0053] The inlet of the air compressor 4 is connected to the ambient air, the outlet of the air compressor 4 is connected to the air purifier 5, the outlet of the air purifier 5 is connected to the air inlet 1 of the air cold storage heat exchanger 22, the air outlet 1 of the air cold storage heat exchanger 22 is connected to the air inlet of the LNG cold storage heat exchanger 3, the air outlet of the LNG cold storage heat exchanger 3 is connected to the air liquefaction device 6, and the outlet of the air liquefaction device 6 is connected to the liquid air storage tank 7;

[0054] The outlet of the liquid air storage tank 7 is connected to the air inlet of the oxygen-nitrogen condensing heat exchanger 9 through the liquid air pump 8, the air outlet of the oxygen-nitrogen condensing heat exchanger 9 is connected to the air inlet II of the air cold storage heat exchanger 22, and the air outlet II of the air cold storage heat exchanger 22 is connected to the air inlet of the air separation unit 10;

[0055] The oxygen outlet of the air separation unit 10 is connected to the oxygen inlet of the oxygen cooler 14 via the oxygen compressor 12, the oxygen outlet of the oxygen cooler 14 is connected to the oxygen inlet I of the gas heat exchanger 11, the oxygen outlet I of the gas heat exchanger 11 is connected to the oxygen inlet of the oxygen-nitrogen condensing heat exchanger 9, the oxygen outlet of the oxygen-nitrogen condensing heat exchanger 9 is connected to the inlet of the oxygen-liquid separator 18 via the oxygen expander 16, the upper gas outlet of the oxygen-liquid separator 18 is connected to the oxygen inlet II of the gas heat exchanger 11, the oxygen outlet II of the gas heat exchanger 11 is connected to the inlet of the oxygen compressor 12, and the bottom liquid outlet of the oxygen-liquid separator 18 is connected to the liquid oxygen storage tank 20;

[0056] The nitrogen outlet of the air separation unit 10 is connected to the nitrogen inlet of the nitrogen cooler 15 through the nitrogen compressor 13, the nitrogen outlet of the nitrogen cooler 15 is connected to the nitrogen inlet I of the gas heat exchanger 11, the nitrogen outlet I of the gas heat exchanger 11 is connected to the nitrogen inlet of the oxygen-nitrogen condensing heat exchanger 9, the nitrogen outlet of the oxygen-nitrogen condensing heat exchanger 9 is connected to the inlet of the nitrogen liquid separator 19 through the nitrogen expander 17, the upper gas outlet of the nitrogen liquid separator 19 is connected to the nitrogen inlet II of the gas heat exchanger 11, the nitrogen outlet II of the gas heat exchanger 11 is connected to the inlet of the nitrogen compressor 15, and the bottom liquid outlet of the nitrogen liquid separator 19 is connected to the liquid nitrogen storage tank 21.

[0057] In the actual working process, during the off-peak period and the non-off-peak period, the LNG cold storage heat exchange system works, and the LNG from the LNG storage tank 1 enters the LNG cold storage heat exchanger 3 through the LNG pump 2, and the latent heat of vaporization and sensible heat are stored in the cold storage medium of the LNG cold storage heat exchanger 3, and then the natural gas enters the natural gas pipeline system.

[0058] During the off-peak period, the air is compressed by the air compressor 4 and purified by the air purifier 5, and then enters the air cold storage heat exchanger 22 and the LNG cold storage heat exchanger 3 in sequence. After absorbing the cold energy, it enters the air liquefaction device 6, and the liquefied air is stored in the liquid air storage tank 7. During the non-off-peak period, the air compressor, air purifier and air liquefaction device stop working and no air liquefaction is carried out.

[0059] During the valley power period and the non-valley power period, the liquid air in the liquid air storage tank 7 is transported by the liquid air pump 8 into the oxygen-nitrogen condensing heat exchanger 9. After heat exchange with oxygen and nitrogen in the oxygen-nitrogen condensing heat exchanger 9, it enters the air cold storage heat exchanger to recover the excess cold of the air, and then enters the air separation unit 10 as the raw gas for air separation. The air separation unit produces oxygen and nitrogen.

[0060] The produced oxygen is compressed and pressurized by the oxygen compressor 12 and cooled by the oxygen cooler 14 before entering the gas heat exchanger 11 for heat exchange with the oxygen and nitrogen from the oxygen-liquid separator 18 and the nitrogen-liquid separator 19. The oxygen then enters the oxygen-nitrogen condensing heat exchanger 9 for condensation and liquefaction. The oxygen then enters the oxygen-liquid separator 18 through the oxygen expander 16. The oxygen at the top of the oxygen-liquid separator 18 is heated and restored to its original temperature in the gas heat exchanger 11 before returning to the inlet of the oxygen compressor 12. The liquid oxygen at the bottom of the oxygen-liquid separator 18 enters the liquid oxygen storage tank 20 for storage as liquid oxygen product.

[0061] The produced nitrogen is compressed and pressurized by the nitrogen compressor 13 and cooled by the nitrogen cooler 15, then enters the gas heat exchanger 11 for heat exchange with the oxygen and nitrogen from the oxygen-liquid separator 18 and the nitrogen-liquid separator 19, and then enters the oxygen-nitrogen condensing heat exchanger 9 for condensation and liquefaction. After that, it enters the nitrogen-liquid separator 19 through the nitrogen expander 17. The nitrogen above the nitrogen-liquid separator 19 is heat-exchanged and rewarmed in the gas heat exchanger 11 and then returns to the inlet of the nitrogen compressor 13. The liquid nitrogen at the bottom of the nitrogen-liquid separator 19 enters the liquid nitrogen storage tank 21 for storage as liquid nitrogen product.

[0062] The implementation of the process of the present invention can form 40-50MW / 10,000 Nm 3 The energy storage power of oxygen air separation capacity is 360MWh / 10,000Nm 3 The energy storage scale of oxygen air separation production capacity. The electricity cost of oxygen and nitrogen liquefaction is significantly lower than that of conventional liquefaction equipment.

[0063] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. An LNG cold energy utilization air separation process based on liquefied air energy storage, characterized in that: The process comprises: S1. LNG from the LNG storage tank enters the LNG cold storage heat exchanger through the LNG pump, where the latent heat of vaporization and sensible heat are stored in the cold storage medium of the LNG cold storage heat exchanger. The natural gas then enters the natural gas pipeline system. S2, after being compressed by the air compressor and purified by the air purifier, the air enters the air cold storage heat exchanger and the LNG cold storage heat exchanger in sequence, absorbs the cold energy and enters the air liquefaction device. The liquefied air is stored in the liquid air storage tank; S3. The liquid air in the liquid air storage tank in step S2 is transported by a liquid air pump into the oxygen-nitrogen condensing heat exchanger, exchanges heat with oxygen and nitrogen in the oxygen-nitrogen condensing heat exchanger, and then enters the air cold storage heat exchanger to recover excess cold energy of the air, and then enters the air separation unit as feed gas for air separation; S4. The product oxygen produced by the air separation device in step S3 is compressed and pressurized by the oxygen compressor and then enters the oxygen cooler. Then, it enters the gas heat exchanger to exchange heat with the oxygen and nitrogen from the oxygen-liquid separator and the nitrogen-liquid separator, enters the oxygen-nitrogen condensing heat exchanger, and then enters the oxygen-liquid separator through the oxygen expander. The oxygen at the top of the oxygen-liquid separator is heat-exchanged and reheated in the gas heat exchanger before returning to the oxygen compressor inlet. The liquid oxygen at the bottom of the oxygen-liquid separator enters the liquid oxygen storage tank for storage as liquid oxygen product. S5. The product nitrogen produced by the air separation device in step S3 is compressed and pressurized by the nitrogen compressor and then enters the nitrogen cooler. Then, it enters the gas heat exchanger to exchange heat with the oxygen and nitrogen from the oxygen-liquid separator and the nitrogen-gas-liquid separator, enters the oxygen-nitrogen condensing heat exchanger, and then enters the nitrogen-gas-liquid separator through the nitrogen expander. The nitrogen above the nitrogen-gas-liquid separator is heat-exchanged and restored to its original temperature in the gas heat exchanger before returning to the nitrogen compressor inlet. The liquid nitrogen at the bottom of the nitrogen-gas-liquid separator enters the liquid nitrogen storage tank and is stored as liquid nitrogen product.

2. The LNG cold energy utilization air separation process based on liquefied air energy storage according to claim 1 is characterized in that: The process in step S1 is performed during both valley period and non-valley period.

3. The LNG cold energy utilization air separation process based on liquefied air energy storage according to claim 1 is characterized in that: The process in step S2 is performed during valley power period and stops during non-valley power period.

4. The LNG cold energy utilization air separation process based on liquefied air energy storage according to claim 1 is characterized in that: The amount of air liquefied by the air liquefaction device in step S2 satisfies the daily raw air requirement of the air separation system.

5. The LNG cold energy utilization air separation process based on liquefied air energy storage according to claim 1 is characterized in that: The processes in step S3, step S4 and step S5 are performed during both valley period and non-valley period.

6. The LNG cold energy utilization air separation process based on liquefied air energy storage according to claim 1 is characterized in that: In step S3, oxygen and nitrogen are respectively supplied to gas heat exchangers.

7. The LNG cold energy utilization air separation process based on liquefied air energy storage according to claim 1 is characterized in that: The air separation unit is a conventional air separation unit.

8. The LNG cold energy utilization air separation process based on liquefied air energy storage according to claim 1 is characterized in that: The systems that the process relies on include liquefied air energy storage system, air separation unit, air separation oxygen and nitrogen product liquefaction system and LNG cold storage and heat exchange system. The liquefied air energy storage system includes an air compressor, an air purifier, an air liquefaction device and a liquid air storage tank; The air separation oxygen and nitrogen product liquefaction system includes an oxygen compressor, a nitrogen compressor, an oxygen cooler, a nitrogen cooler, a gas heat exchanger, an oxygen expander, a nitrogen expander, an oxygen-liquid separator, a nitrogen-gas-liquid separator, a liquid oxygen storage tank, and a liquid nitrogen storage tank; The LNG cold storage and heat exchange system includes an LNG storage tank, an LNG pump and an LNG cold storage heat exchanger.

9. The LNG cold energy utilization air separation process based on liquefied air energy storage according to claim 8 is characterized in that: The LNG storage tank is connected to the natural gas inlet of the LNG cold storage heat exchanger through an LNG pump, and the natural gas outlet of the LNG cold storage heat exchanger is connected to the natural gas pipeline network; The air compressor inlet is connected to the ambient air, the air compressor outlet is connected to the air purifier, the air purifier outlet is connected to the air inlet I of the air cold storage heat exchanger, the air outlet I of the air cold storage heat exchanger is connected to the air inlet of the LNG cold storage heat exchanger, the air outlet of the LNG cold storage heat exchanger is connected to the air liquefaction device, and the air liquefaction device outlet is connected to the liquid air storage tank; The outlet of the liquid air storage tank is connected to the air inlet of the oxygen-nitrogen condensing heat exchanger through a liquid air pump, the air outlet of the oxygen-nitrogen condensing heat exchanger is connected to the air inlet II of the air cold storage heat exchanger, and the air outlet II of the air cold storage heat exchanger is connected to the inlet of the air separation unit; The oxygen outlet of the air separation unit is connected to the oxygen inlet of the oxygen cooler via the oxygen compressor, the oxygen outlet of the oxygen cooler is connected to the oxygen inlet I of the gas heat exchanger, the oxygen outlet I of the gas heat exchanger is connected to the oxygen inlet of the oxygen-nitrogen condensing heat exchanger, the oxygen outlet of the oxygen-nitrogen condensing heat exchanger is connected to the inlet of the oxygen-liquid separator via the oxygen expander, the upper gas outlet of the oxygen-liquid separator is connected to the oxygen inlet II of the gas heat exchanger, the oxygen outlet II of the gas heat exchanger is connected to the inlet of the oxygen compressor, and the liquid outlet at the bottom of the oxygen-liquid separator is connected to the liquid oxygen storage tank; The nitrogen outlet of the air separation unit is connected to the nitrogen inlet of the nitrogen cooler via a nitrogen compressor, the nitrogen outlet of the nitrogen cooler is connected to the nitrogen inlet I of the gas heat exchanger, the nitrogen outlet I of the gas heat exchanger is connected to the nitrogen inlet of the oxygen-nitrogen condensing heat exchanger, the nitrogen outlet of the oxygen-nitrogen condensing heat exchanger is connected to the inlet of the nitrogen-liquid separator via a nitrogen expander, the upper gas outlet of the nitrogen-liquid separator is connected to the nitrogen inlet II of the gas heat exchanger, the nitrogen outlet II of the gas heat exchanger is connected to the inlet of the nitrogen compressor, and the liquid outlet at the bottom of the nitrogen-liquid separator is connected to the liquid nitrogen storage tank.

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