Liquid air energy storage system coupled with lng cold energy rankine cycle power generation

Abstract

The application provides a liquid 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, LNG cold sources enter the first heat exchange side of a first LNG heat exchanger, the first heat exchange side of a third LNG heat exchanger and a second LNG heat exchanger, and the first heat exchange side of the second LNG heat exchanger, exchange heat with air and cool the air. During discharging, the LNG cold sources enter the first heat exchange side of a cold energy power generation condenser, and the liquid air and the LNG in the cold energy power generation condenser jointly provide cold energy and generate power. The LNG cold sources enter different heat exchangers for heat exchange during discharging and charging, and the two independently operate without interference, so that the utilization rate of the LNG cold energy is improved, and the efficiency of the liquid air energy storage system is further improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of liquefied air energy storage, and in particular to a liquefied air energy storage system coupled with LNG cold energy Rankine cycle power generation. BACKGROUND

[0002] Liquefied air energy storage is a new type of large-scale long-time energy storage technology that has attracted much attention in recent years, which uses air to be converted into liquid at low temperature to store energy. Liquefied air energy storage has the characteristics of high energy storage density, long service life, high safety, and no limitation on geographical conditions.

[0003] In the prior art, for example, CN118463500A discloses a liquefied air energy storage system and method coupled with LNG cold energy, which includes an air compression unit, an air purification unit, an air liquefaction unit, a liquefied air storage unit, a liquefied air pressure boosting and gasification unit, an air expansion power generation unit, and an LNG cold storage and nitrogen heat exchange unit. The LNG cold storage and nitrogen heat exchange unit uses nitrogen as a circulating medium to absorb the low-temperature end cold energy of LNG during the energy storage process to provide cold energy for air liquefaction of the air liquefaction unit, and during the energy release process, the low-temperature nitrogen uses the low-temperature end cold energy of LNG as a pre-cooling source for compressed air extracted from the expander of the air expansion power generation unit, and uses the process technology of recovering the cold energy of the evaporator of the liquefied air pressure boosting and gasification unit to re-liquefy and store the pre-cooled compressed air. The LNG cold storage and nitrogen heat exchange unit uses ethylene glycol water solution as a circulating coolant to absorb the high-temperature end cold energy of LNG for cooling of system equipment. However, since the charging and discharging processes of the liquefied air energy storage system are intermittent, the LNG cold energy is not needed during the discharging process, and therefore the patent causes waste of LNG cold energy. SUMMARY

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

[0005] The present application is achieved by the following technical solutions:

[0006] The present application provides a liquefied 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:

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

[0008] When the system is charging, 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 and the second heat exchange side of the second LNG heat exchanger and the first heat exchange side of the second LNG heat exchanger to provide cold energy for air liquefaction; when the system is discharging, the LNG cold source enters the first heat exchange side of the cold energy power generation condenser to provide cold energy together with liquid air entering the second heat exchange side of the cold energy power generation condenser and generate electricity. Further, the air liquefaction energy storage unit further comprises a first air compressor, a second air compressor and a liquid air turbine, and the second heat exchange side of the first LNG heat exchanger is sequentially connected to the first air compressor, a third heat exchange side of the second LNG heat exchanger, the second air compressor, a second heat exchange side of the third LNG heat exchanger, the liquid air turbine and the liquid air storage tank.

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

[0010] Further, the air liquefaction energy storage unit further comprises a liquid air pump, and a 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 circulating unit is further included, and the circulating unit comprises 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, a low-temperature water tank outlet end is sequentially connected to a first heat exchange side of the heat storage heat exchanger and a high-temperature water tank, and a high-temperature water tank outlet end is respectively connected to a first heat exchange side of the first heater, a first heat exchange side of the second heater and a first heat exchange side of the third heater and connected back to a low-temperature water tank inlet end.

[0012] Further, the air expansion power generation unit further comprises a first turbine expander, a second turbine expander and a third turbine expander, and the second heat exchange side of the cold energy power generation condenser is 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 in sequence.

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

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

[0015] Further, the LNG cold energy power generation unit comprises a medium pump, an evaporator and a power generation turbine, and the outlet end of the power generation turbine is 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 in sequence and 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 application:

[0018] The liquid air energy storage system coupled with the LNG cold energy Rankine cycle power generation provided in the present application can cool air by heat exchange between the LNG cold source and the air in 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 during charging, and can provide cold energy by heat exchange between the LNG cold source and the liquid air in the first heat exchange side of the cold energy power generation condenser during discharging. BRIEF DESCRIPTION OF DRAWINGS

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

[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] The purposes, functional features and advantages of the present application will be further illustrated with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

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

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

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

[0025] When the system is charging, 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; when the system is discharging, the LNG cold source enters the first heat exchange side of the cold energy power generation condenser 12 to provide cold energy together with the liquid air entering the second heat exchange side of the cold energy power generation condenser 12 and generate power.

[0026] In the specific embodiment, when storing electric energy, the purified air is gradually cooled and converted into liquid air for storage in the liquid air storage tank 19 through the first LNG heat exchanger 5, the second LNG heat exchanger 7 and the third LNG heat exchanger 9; when discharging, the liquid air in the liquid air storage tank 19 is 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 fourth branch is connected to the first heat exchange side of the cold energy power generation condenser 12. Since the processes of storing electric energy and discharging are intermittent, 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 during charging, and the LNG cold source enters the cold energy power generation condenser 12 during discharging, the liquid air and the LNG jointly provide cold energy and generate power. In the present application, the LNG cold source enters different heat exchangers during discharging and charging, and the two do not interfere with each other, which can improve the utilization rate of LNG cold energy.

[0027] Further, the air liquefaction energy storage unit further comprises a first air compressor 6, a second air compressor 8 and a liquid air turbine 10, and 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 the 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 sequentially compressed by multiple stages of compressors and cooled by multiple stages of heat exchangers, and finally expanded to the storage tank pressure to be 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 one 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 back to the second heat exchange side of the first LNG heat exchanger 5.

[0031] In the specific embodiment, the air in the liquid air storage tank 19 that has not been converted into liquid air flows out through the gas outlet, is sequentially cooled by 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, and then enters the branch connected to the second heat exchange side of the first LNG heat exchanger 5 again for cooling and liquefaction.

[0032] Further, the air expansion power generation unit further comprises a liquid air pump 11, and the outlet of the liquid air tank 19 is connected to the liquid air pump 11 and the second heat exchange side of the cold energy power generation condenser 12 in sequence.

[0033] In the specific embodiment, the liquid air pump 11 is used to pressurize and deliver the liquid air, and the liquid air delivered by the liquid air pump 11 is heated to become gaseous air at the second heat exchange side of the cold energy power generation condenser 12.

[0034] Further, the cycle unit comprises 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 connected to the first heat exchange side of the heat storage heat exchanger 3 and the high-temperature water tank 20 in sequence. The outlet end of the high-temperature water tank 20 is 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, respectively, and 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 is heated to become high-temperature medium in the heat storage heat exchanger 3, and then the high-temperature medium is used to heat the air on the other side in the first heater 13, the second heater 15, and the third heater 17, respectively, and finally the high-temperature medium is cooled and enters the low-temperature water tank 21 to complete the cycle, that is, the heat generated by the air compression during the energy storage is recovered to provide heat for the air during the subsequent power generation.

[0036] Further, the air expansion power generation unit further comprises 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 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 in sequence.

[0037] In the specific embodiment, the first turbine expander 14, the second turbine expander 16, and the third turbine expander 18 are used to deliver electric power to the power grid. After the liquid air is cooled by the cold energy power generation condenser 12, the liquid air enters the third turbine expander 18 to be expanded, and then enters the third heater 17 for inter-stage heating. Subsequently, the liquid air enters the second turbine expander 16, the second heater 15, the first turbine expander 14, and the first heater 13 for expansion and inter-stage heating in sequence, so that the expander does work to input electric power to the power grid.

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

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

[0040] In the 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 comprises an air filter 1 and an air compressor 2, wherein the air filter 1 is connected to the air compressor 2, the second heat exchange side of the heat storage heat exchanger 3 and the air purifier 4 in sequence.

[0042] In the specific embodiment, the filter is used to preliminarily filter impurities in the air, and after the air is filtered by the filter, the air is compressed to a suitable temperature and pressure, generally medium-high pressure and high temperature, by the air compressor 2, and after the air is heated and pressurized, the air is recovered by the heat storage 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, the LNG cold energy power generation unit further comprises a medium pump 22, an evaporator 23 and a power generation turbine 24, wherein the outlet end of the power generation turbine 24 is 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 in sequence, and is connected back to the inlet end of the power generation turbine 24.

[0044] In the specific embodiment, the LNG cold energy power generation unit is used to convert cold energy into electric energy, and 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, which operates in 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 the specific embodiment, the external heat source can also be selected according to actual conditions, for example, solar energy, waste heat or connecting the second heat exchange side of the evaporator 23 to the circulating unit.

[0047] Of course, the present application can have other various embodiments, and based on the embodiments, other embodiments obtained by those skilled in the art without any creative labor are within the scope of the present application.

Claims

1. A liquid air energy storage system coupled with LNG cold energy Rankine cycle power generation, characterized in that: It includes air liquefaction energy storage unit and LNG cold energy utilization unit, including: The air liquefaction energy storage unit includes a liquid air storage tank, and 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 arranged on the liquid inlet end of the liquid air storage tank, and a cold energy power generation condenser arranged 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; When the system is charging, 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 to provide cooling for air liquefaction; when the system is discharging, the LNG cold source enters the first heat exchange side of the cold energy power generation condenser, and together with the liquid air entering the second heat exchange side of the cold energy power generation condenser, provides cooling energy and generates electricity; The air liquefaction energy storage unit further includes a first air compressor, a second air compressor and a liquid-to-air turbine, wherein 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-to-air turbine and the liquid air storage tank; 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 then connected back to the second heat exchange side of the first LNG heat exchanger; The system further includes a circulation unit, the circulation unit including 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, wherein 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, and 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 then connected back to the inlet end of the low-temperature water tank; 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. The air liquefaction energy storage unit further includes an air purifier connected to the second heat exchange side of the first LNG heat exchanger.

2. The liquid air energy storage system coupled with LNG cold energy Rankine cycle power generation according to claim 1 is characterized in that: The air liquefaction energy storage unit further includes a liquid air pump, and 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.

3. The liquid air energy storage system coupled with LNG cold energy Rankine cycle power generation according to claim 1 is characterized in that: The air liquefaction energy storage unit further includes an air filter and an air compressor, wherein 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.

4. The liquid air energy storage system coupled with LNG cold energy Rankine cycle power generation according to claim 1 is characterized in that: It also includes an LNG cold energy power generation unit, which includes a medium pump, an evaporator and a power generation turbine. The outlet end of the power generation turbine is 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 in sequence, and is connected back to the inlet end of the power generation turbine.

5. The liquid air energy storage system coupled with LNG cold energy Rankine cycle power generation according to claim 4 is characterized in that: The evaporator is used for exchanging heat with an external heat source.

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