Liquid air energy storage system coupled with LNG (Liquefied Natural Gas) cold energy Rankine cycle power generation

Abstract

The invention provides a liquefied air energy storage system coupled with LNG cold energy Rankine cycle power generation, and particularly relates to the technical field of liquefied air energy storage. During charging, an LNG cold source enters the first heat exchange side of the first LNG heat exchanger, the first heat exchange side of the third LNG heat exchanger and the second LNG heat exchanger, the first heat exchange side of the second LNG heat exchanger exchanges heat with air and cools the air, during discharging, the LNG cold source enters the first heat exchange side of the cold energy power generation condenser, and the second heat exchange side of the second LNG heat exchanger exchanges heat with the air and cools the air. Liquefied air in the cold energy power generation condenser and LNG jointly provide cold energy and generate power, the LNG cold source enters different heat exchangers for heat exchange during discharging and charging, the LNG cold source and the heat exchangers operate independently and do not interfere with each other, the utilization rate of LNG cold energy can be increased, and the efficiency of the liquid air energy storage system is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of liquefied air energy storage, and particularly to a liquefied air energy storage system coupled with an LNG cold energy Rankine cycle power generation system. Background Art

[0002] Liquefied air energy storage utilizes the conversion of air into liquid at low temperature to store energy. Liquefied air energy storage has the characteristics of large energy storage density, long operating life, high safety, and being not restricted by geographical conditions. It is one of the new large-scale long-duration energy storage technologies that have received much attention in recent years.

[0003] In the prior art, for example, a liquefied air energy storage system and method coupled with LNG cold energy disclosed in CN118463500A includes an air compression unit, an air purification unit, an air liquefaction unit, a liquefied air storage unit, a liquefied air boosting and gasification unit, an air expansion power generation unit, and an LNG cold energy storage and nitrogen heat exchange unit; the LNG cold energy storage and nitrogen heat exchange unit uses nitrogen as a circulating medium to absorb the cold energy at the low temperature end of LNG during the energy storage process to provide cold energy for air liquefaction in the air liquefaction unit, and during the energy release process, the cold energy at the low temperature end of LNG is used by the low-temperature nitrogen to precool the compressed air from the extraction of the expander in the air expansion power generation unit, and a process technology for recovering the cold energy of the evaporator in the liquefied air boosting and gasification unit is used to reliquefy and store the precooled compressed air; the LNG cold energy storage and nitrogen heat exchange unit uses an ethylene glycol aqueous solution as a circulating coolant to absorb the cold energy at the high temperature end of LNG for cooling system equipment. However, since both the charging and discharging processes of the liquefied air energy storage system are intermittent and the LNG cold energy is not required during the discharging process, this patent will cause waste of LNG cold energy. Summary of the Invention

[0004] In order to solve the problem of waste of LNG cold energy during the discharging process, the present invention proposes a liquefied air energy storage system coupled with an LNG cold energy Rankine cycle power generation system.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention proposes that a liquefied air energy storage system coupled with an LNG cold energy Rankine cycle power generation system includes an air liquefaction energy storage unit and an LNG cold energy utilization unit, wherein:

[0007] The air liquefaction energy storage unit includes a liquid air storage tank. The LNG cold energy utilization unit includes an LNG heat exchanger group and an LNG cold source. The LNG heat exchanger group includes a first LNG heat exchanger, a second LNG heat exchanger, and a third LNG heat exchanger disposed at the liquid inlet end of the liquid air storage tank, and a cold energy power generation condenser disposed at the liquid outlet end of the liquid air storage tank. Multiple branches of the LNG cold source are respectively connected to the first heat exchange side of the first LNG heat exchanger, the first heat exchange side of the second LNG heat exchanger, the first heat exchange side of the third LNG heat exchanger, the second heat exchange side of the second LNG heat exchanger, and the first heat exchange side of the cold energy power generation condenser and are connected to the outlet;

[0008] During the charging of the system, the LNG cold source enters the first heat exchange side of the first LNG heat exchanger, the first heat exchange side of the third LNG heat exchanger, the second heat exchange side of the second LNG heat exchanger, and the first heat exchange side of the second LNG heat exchanger respectively to provide cold energy for air liquefaction; during the discharging of the system, the LNG cold source enters the first heat exchange side of the cold energy power generation condenser and jointly provides cold energy with the liquid air entering the second heat exchange side of the cold energy power generation condenser for power generation. Further, the air liquefaction energy storage unit further includes a first air compressor, a second air compressor, and a liquid air turbine. The second heat exchange side of the first LNG heat exchanger is sequentially connected to the first air compressor, the third heat exchange side of the second LNG heat exchanger, the second air compressor, the second heat exchange side of the third LNG heat exchanger, the liquid air turbine, and the liquid air storage tank.

[0009] Further, the gas outlet of the liquid air storage tank is sequentially connected to the third heat exchange side of the third LNG heat exchanger, the fourth heat exchange side of the second LNG heat exchanger and is connected back to the second heat exchange side of the first LNG heat exchanger.

[0010] Further, the air liquefaction energy storage unit further includes a liquid air pump. The liquid outlet of the liquid air storage tank is sequentially connected to the liquid air pump and the second heat exchange side of the cold energy power generation condenser.

[0011] Further, a circulation unit is further included. The circulation unit includes a high-temperature water tank, a low-temperature water tank, a heat storage heat exchanger, a first heater, a second heater, and a third heater. The outlet end of the low-temperature water tank is sequentially connected to the first heat exchange side of the heat storage heat exchanger and the high-temperature water tank. The outlet end of the high-temperature water tank is respectively connected to the first heat exchange side of the first heater, the first heat exchange side of the second heater, and the first heat exchange side of the third heater and is connected back to the inlet end of the low-temperature water tank.

[0012] Further, it further includes an air expansion power generation unit, and the air expansion power generation unit further includes a first turbine expander, a second turbine expander, and a third turbine expander. The second heat exchange side of the cold energy power generation condenser is sequentially connected to the second heat exchange side of the first heater, the first turbine expander, the second heat exchange side of the second heater, the second turbine expander, the second heat exchange side of the third heater, and the third turbine expander.

[0013] Further, the air liquefaction energy storage unit further includes an air purifier, and the air purifier is connected to the second heat exchange side of the first LNG heat exchanger.

[0014] Further, the air liquefaction energy storage unit further includes an air filter and an air compressor. The air filter is sequentially connected to the air compressor, the second heat exchange side of the regenerative heat exchanger, and the air purifier.

[0015] Further, it further includes an LNG cold energy power generation unit. The LNG cold energy power generation unit includes a medium pump, an evaporator, and a power generation turbine. The outlet end of the power generation turbine is sequentially connected to the first heat exchange side of the evaporator, the power generation turbine, and the third heat exchange side of the cold energy power generation condenser, and is connected back to the inlet end of the power generation turbine.

[0016] Further, the evaporator is used for heat exchange with an external heat source.

[0017] Advantages of the present invention:

[0018] In the liquid air energy storage system coupled with LNG cold energy Rankine cycle power generation proposed by the present invention, during charging, the LNG cold source enters the first heat exchange side of the first LNG heat exchanger, the first heat exchange side of the second LNG heat exchanger, and the first heat exchange side of the third LNG heat exchanger respectively to exchange heat with air and cool the air. During discharging, the LNG cold source enters the first heat exchange side of the cold energy power generation condenser. The liquid air and the LNG cold source enter the cold energy power generation condenser to provide cold energy and generate electricity. During discharging and charging of the present application, the LNG cold source enters different heat exchangers for heat exchange respectively, and the two operate independently without interference, which can improve the utilization rate of LNG cold energy and further improve the efficiency of the liquid air energy storage system. Description of the drawings

[0019] Figure 1 It is a structural diagram of the liquid air energy storage system coupled with LNG cold energy Rankine cycle power generation of the present invention;

[0020] In the figure: 1: Air filter; 2: Air compressor; 3: Regenerative heat exchanger; 4: Air purifier; 5: First LNG heat exchanger; 6: First air compressor; 7: Second LNG heat exchanger; 8: Second air compressor; 9: Third LNG heat exchanger; 10: Liquid air turbine; 11: Liquid air pump; 12: Cold energy power generation condenser; 13: First heater; 14: First turbine expander; 15: Second heater; 16: Second turbine expander; 17: Third heater; 18: Third turbine expander; 19: Liquid air storage tank; 20: High-temperature water tank; 21: Low-temperature water tank; 22: Medium pump; 23: Evaporator; 24: Power generation turbine;

[0021] For the realization, functional features and advantages of the present invention, further explanations will be made with reference to the embodiments and the accompanying drawings. Detailed implementation manners

[0022] In order to more clearly and completely illustrate the technical solution of the present invention, the present invention will be further described below with reference to the accompanying drawings.

[0023] Please refer to Figure 1 , the present invention provides a liquid air energy storage system coupled with LNG cold energy Rankine cycle power generation, which includes an air liquefaction energy storage unit and an LNG cold energy utilization unit, wherein:

[0024] The air liquefaction energy storage unit includes a liquid air storage tank 19. The LNG cold energy utilization unit includes an LNG heat exchanger group and an LNG cold source. The LNG heat exchanger group includes a first LNG heat exchanger 5, a second LNG heat exchanger 7, and a third LNG heat exchanger 9 disposed at the liquid inlet end of the liquid air storage tank 19, and a cold energy power generation condenser 12 disposed at the liquid outlet end of the liquid air storage tank 19. Multiple branches of the LNG cold source are respectively connected to the first heat exchange side of the first LNG heat exchanger 5, the first heat exchange side of the second LNG heat exchanger 7, the first heat exchange side of the third LNG heat exchanger 9, the second heat exchange side of the second LNG heat exchanger 7, and the first heat exchange side of the cold energy power generation condenser 12 and are connected to the outlet;

[0025] During the charging of the system, the LNG cold source enters the first heat exchange side of the first LNG heat exchanger 5, the first heat exchange side of the third LNG heat exchanger 9, the second heat exchange side of the LNG heat exchanger, and the first heat exchange side of the second LNG heat exchanger 7 to provide cold energy for air liquefaction. During the discharging of the system, the LNG cold source enters the first heat exchange side of the cold energy power generation condenser 12 and jointly provides cold energy with the liquid air entering the second heat exchange side of the cold energy power generation condenser 12 for power generation.

[0026] In a specific embodiment, when storing electrical energy, the purified air passes through the first LNG heat exchanger 5, the second LNG heat exchanger 7, and the third LNG heat exchanger 9 for stepwise cooling and is converted into liquid air and stored in the liquid air storage tank 19. When discharging, the liquid air in the liquid air storage tank 19 is reheated and vaporized through the cold energy power generation condenser 12; the first branch of the four branches of the LNG cold source is connected to the first heat exchange side of the first LNG heat exchanger 5, the second branch is connected to the first heat exchange side of the second LNG heat exchanger 7, the third branch is connected to the first heat exchange side of the third LNG heat exchanger 9 and the second heat exchange side of the second LNG heat exchanger 7, and the four branches are connected to the first heat exchange side of the cold energy power generation condenser 12. Since the processes of storing electrical energy and discharging are both intermittent, when charging, the LNG cold source enters the first branch, the second branch, and the third branch to exchange heat with the air and cool / liquefy the air. When discharging, the LNG cold source enters the cold energy power generation condenser 12, and the liquid air and the LNG jointly provide cold energy for power generation. In this application, when discharging and charging, the LNG cold source enters different heat exchangers for heat exchange respectively, and the two do not interfere with each other, which can improve the utilization rate of the LNG cold energy.

[0027] Further, the air liquefaction energy storage unit further includes a first air compressor 6, a second air compressor 8, and a liquid air turbine 10. The second heat exchange side of the first LNG heat exchanger 5 is sequentially connected to the first air compressor 6, the third heat exchange side of the second LNG heat exchanger 7, the second air compressor 8, the second heat exchange side of the third LNG heat exchanger 9, the liquid air turbine 10, and the liquid air storage tank 19.

[0028] In a specific embodiment, the first compressor and the second compressor are used to compress air, and the liquid air turbine 10 is used to expand air. The air is successively subjected to multi-stage compression by the compressor and multi-stage cooling by the heat exchanger, and finally expands to the storage tank pressure and is converted into liquid air and stored in the liquid air storage tank 19.

[0029] In one embodiment, the number of compressors and LNG heat exchangers can be selected according to actual conditions, and a compressor is arranged at the outlet end of each LNG heat exchanger for compression.

[0030] Further, the gas outlet of the liquid air storage tank 19 is sequentially connected to the third heat exchange side of the third LNG heat exchanger 9, the fourth heat exchange side of the second LNG heat exchanger 7, and is connected back to the second heat exchange side of the first LNG heat exchanger 5.

[0031] In a specific embodiment, the air in the liquid air storage tank 19 that has not been converted into liquid flows out through the gas outlet, successively passes through the third heat exchange side of the third LNG heat exchanger 9 and the fourth heat exchange side of the second LNG heat exchanger 7 to recover cold energy, and then enters the branch connected to the second heat exchange side of the first LNG heat exchanger 5 again for re-cooling and liquefaction.

[0032] Further, it also includes an air expansion power generation unit, and the air expansion power generation unit further includes a liquid air pump 11. The outlet of the liquid air storage tank 19 is sequentially connected to the liquid air pump 11 and the second heat exchange side of the cold energy power generation condenser 12.

[0033] In the specific embodiment, the liquid air pump 11 is used to pressurize and convey liquid air, and the liquid air is conveyed to the second heat exchange side of the cold energy power generation condenser 12 through the liquid air pump 11 and is reheated into gaseous air.

[0034] Further, it also includes a circulation unit, and the circulation unit includes a high-temperature water tank 20, a low-temperature water tank 21, a heat storage heat exchanger 3, a first heater 13, a second heater 15, and a third heater 17. The outlet end of the low-temperature water tank 21 is sequentially connected to the first heat exchange side of the heat storage heat exchanger 3 and the high-temperature water tank 20. The outlet end of the high-temperature water tank 20 is respectively connected to the first heat exchange side of the first heater 13, the first heat exchange side of the second heater 15, and the first heat exchange side of the third heater 17 and is connected back to the inlet end of the low-temperature water tank 21.

[0035] In the specific embodiment, the low-temperature medium in the low-temperature water tank 21 enters the heat storage heat exchanger 3 to absorb the heat after air compression and is converted into a high-temperature medium. Then, it heats the air on the other side through the first heater 13, the second heater 15, and the third heater 17, and finally cools down and enters the low-temperature water tank 21 to complete the cycle, that is, the heat generated by air compression during energy storage is recovered to provide heat for the air during subsequent power generation.

[0036] Further, the air expansion power generation unit further includes a first turbine expander 14, a second turbine expander 16, and a third turbine expander 18. The second heat exchange side of the cold energy power generation condenser 12 is sequentially connected to the second heat exchange side of the first heater 13, the first turbine expander 14, the second heat exchange side of the second heater 15, the second turbine expander 16, the second heat exchange side of the third heater 17, and the third turbine expander 18.

[0037] In the specific embodiment, the first turbine expander 14, the second turbine expander 16, and the third turbine expander 18 are used to transmit electricity to the power grid. After the liquid air recovers cold energy through the cold energy power generation condenser 12, it enters the third turbine expander 18 for expansion and then enters the third heater 17 for inter-stage heating. Subsequently, it enters the second turbine expander 16, the second heater 15, the first turbine expander 14, and the first heater 13 for sequential expansion and inter-stage heating, so that the expander does work to input electricity to the power grid.

[0038] In one embodiment, the number of heaters and expanders can also be selected according to the actual situation, and a heater is arranged at the liquid outlet end of each expander for inter-stage heating.

[0039] Further, the air liquefaction energy storage unit further includes an air purifier 4, and the air purifier 4 is connected to the second heat exchange side of the first LNG heat exchanger 5.

[0040] In a specific embodiment, the air purifier 4 is used to absorb purified water and carbon dioxide in the air.

[0041] Further, the air liquefaction energy storage unit further includes an air filter 1 and an air compressor 2. The air filter 1 is sequentially connected to the air compressor 2, the second heat exchange side of the regenerative heat exchanger 3, and the air purifier 4.

[0042] In a specific embodiment, the filter is used to preliminarily filter impurities in the air. After the air is filtered by the filter to remove impurities, it is compressed by the air compressor 2 to appropriate temperature and pressure, generally medium-high pressure and high temperature. After the air is heated and pressurized, it recovers heat through the regenerative heat exchanger 3 and then enters the air purifier 4 to remove carbon dioxide and purified water, and finally enters the first LNG heat exchanger 5 for subsequent cooling / liquefaction steps.

[0043] Further, it further includes an LNG cold energy power generation unit. The LNG cold energy power generation unit includes a medium pump 22, an evaporator 23, and a power generation turbine 24. The outlet end of the power generation turbine 24 is sequentially connected to the first heat exchange side of the evaporator 23, the power generation turbine 24, and the third heat exchange side of the cold energy power generation condenser 12, and is connected back to the inlet end of the power generation turbine 24.

[0044] In a specific embodiment, the LNG cold energy power generation unit is used to convert cold energy into electric energy. The third heat exchange side of the cold energy power generation condenser 12, the intermediate medium pump 22, the evaporator 23, and the power generation turbine 24 form a Rankine cycle and operate during the air energy release stage to realize the conversion of cold energy into electric energy and improve the overall utilization rate of the system.

[0045] Further, the evaporator 23 is used to exchange heat with an external heat source.

[0046] In a specific embodiment, the external heat source can also be selected according to actual conditions, such as solar energy, waste heat, or connecting the second heat exchange side of the evaporator 23 to a circulation unit.

[0047] Certainly, the present invention can also have many other embodiments. Based on this embodiment, other embodiments obtained by those of ordinary skill in the art without any creative labor belong to the scope protected by the present invention.

Claims

1. A liquid air energy storage system coupled with LNG cold energy Rankine cycle power generation, characterized in that, It includes an air liquefaction energy storage unit and an LNG cold energy utilization unit, where: The air liquefaction energy storage unit includes a liquid air storage tank. The LNG cold energy utilization unit includes an LNG heat exchanger group and an LNG cold source. The LNG heat exchanger group includes a first LNG heat exchanger, a second LNG heat exchanger, and a third LNG heat exchanger disposed at the liquid inlet end of the liquid air storage tank, and a cold energy power generation condenser disposed at the liquid outlet end of the liquid air storage tank. Multiple branches of the LNG cold source are respectively connected to the first heat exchange side of the first LNG heat exchanger, the first heat exchange side of the second LNG heat exchanger, the first heat exchange side of the third LNG heat exchanger, the second heat exchange side of the second LNG heat exchanger, and the first heat exchange side of the cold energy power generation condenser and are connected to the outlet; During the charging of the system, the LNG cold source enters the first heat exchange side of the first LNG heat exchanger, the first heat exchange side of the third LNG heat exchanger, the second heat exchange side of the second LNG heat exchanger, and the first heat exchange side of the second LNG heat exchanger respectively to provide cold energy for air liquefaction. During the discharging of the system, the LNG cold source enters the first heat exchange side of the cold energy power generation condenser and jointly provides cold energy and generates electricity with the liquid air entering the second heat exchange side of the cold energy power generation condenser.

2. The liquid air energy storage system for coupling LNG cold energy Rankine cycle power generation according to claim 1, characterized in that, The air liquefaction energy storage unit further includes a first air compressor, a second air compressor, and a liquid air turbine. The second heat exchange side of the first LNG heat exchanger is sequentially connected to the first air compressor, the third heat exchange side of the second LNG heat exchanger, the second air compressor, the second heat exchange side of the third LNG heat exchanger, the liquid air turbine, and the liquid air storage tank.

3. The liquid air energy storage system for coupling LNG cold energy Rankine cycle power generation according to claim 2, wherein The gas outlet of the liquid air storage tank is sequentially connected to the third heat exchange side of the third LNG heat exchanger, the fourth heat exchange side of the second LNG heat exchanger, and is connected back to the second heat exchange side of the first LNG heat exchanger.

4. The liquid air energy storage system for coupling LNG cold energy Rankine cycle power generation according to claim 3, wherein The air liquefaction energy storage unit further includes a liquid air pump. The liquid outlet of the liquid air storage tank is sequentially connected to the liquid air pump and the second heat exchange side of the cold energy power generation condenser.

5. The liquid air energy storage system for coupling LNG cold energy Rankine cycle power generation according to claim 4, wherein, It further includes a circulation unit, which includes a high-temperature water tank, a low-temperature water tank, a heat storage heat exchanger, a first heater, a second heater, and a third heater. The outlet end of the low-temperature water tank is sequentially connected to the first heat exchange side of the heat storage heat exchanger and the high-temperature water tank. The outlet end of the high-temperature water tank is respectively connected to the first heat exchange side of the first heater, the first heat exchange side of the second heater, and the first heat exchange side of the third heater and is connected back to the inlet end of the low-temperature water tank.

6. The liquid air energy storage system for coupling LNG cold energy Rankine cycle power generation according to claim 5, characterized in that, It further includes an air expansion power generation unit, which further includes a first turbine expander, a second turbine expander, and a third turbine expander. The second heat exchange side of the cold energy power generation condenser is sequentially connected to the second heat exchange side of the first heater, the first turbine expander, the second heat exchange side of the second heater, the second turbine expander, the second heat exchange side of the third heater, and the third turbine expander.

7. The liquid air energy storage system for coupling LNG cold energy Rankine cycle power generation according to claim 5, characterized in that, The air liquefaction energy storage unit further includes an air purifier, which is connected to the second heat exchange side of the first LNG heat exchanger.

8. The liquid air energy storage system for coupling LNG cold energy Rankine cycle power generation according to claim 7, wherein The air liquefaction energy storage unit further includes an air filter and an air compressor. The air filter is sequentially connected to the air compressor, the second heat exchange side of the heat storage heat exchanger, and the air purifier.

9. The liquid air energy storage system for coupling LNG cold energy Rankine cycle power generation according to claim 1, characterized in that It further includes an LNG cold energy power generation unit, and the LNG cold energy power generation unit includes a medium pump, an evaporator, and a power generation turbine. The outlet end of the power generation turbine is sequentially connected to the first heat exchange side of the evaporator, the power generation turbine, and the third heat exchange side of the cold energy power generation condenser, and then connected back to the inlet end of the power generation turbine.

10. The liquid air energy storage system for coupling LNG cold energy Rankine cycle power generation according to claim 9, characterized in that, The evaporator is used for heat exchange with an external heat source.

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