Liquefied air energy storage system coupled with LNG (Liquefied Natural Gas) cold energy

Abstract

The utility model discloses a liquid air energy storage system coupled with LNG (Liquefied Natural Gas) cold energy. The liquid air energy storage system comprises an air compression unit, an air purification unit, an air liquefaction unit, a liquid air storage unit, a liquid air boosting 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 cold energy of the low-temperature end of LNG in the energy storage process to provide cold energy for air liquefaction of the air liquefaction unit, and in the energy release process, the cold energy of the low-temperature end of the LNG is used for pre-cooling compressed air extracted by an expansion machine of the air expansion power generation unit through low-temperature nitrogen. The pre-cooled compressed air is re-liquefied and stored by adopting a process technology for recovering the cooling capacity of an evaporator of a liquid air boosting gasification unit; the LNG cold storage and nitrogen heat exchange unit uses an ethylene glycol aqueous solution as a circulating coolant to absorb the cold energy of the LNG high-temperature end for cooling system equipment. The device is low in power consumption and high in liquefaction rate and electricity-electricity energy storage efficiency after air throttling.

Description

Technical Field

[0001] The utility model relates to the technical field of liquid air energy storage, and in particular to a liquid air energy storage system coupled with LNG cold energy. Background Art

[0002] With the growth of the world's population and the acceleration of industrialization, energy demand continues to rise. Energy storage technology can improve the balance of energy supply and demand, reduce the gap between peak and valley energy consumption, and enhance the country's ability to resist energy crises. Liquid air energy storage technology based on new deep cooling technology has the characteristics of high energy storage density, long operating life, high safety, and is not restricted by geographical conditions. It is one of the new large-scale long-term energy storage technologies that has attracted much attention in recent years.

[0003] Although the liquid air energy storage system has great potential in improving energy utilization and coping with energy crises, the system has problems such as high compressor power consumption, insufficient system cooling capacity, low liquefaction rate and poor system flexibility when there is no cold source. At present, there is a method of coupling LNG cold energy to solve the problem of insufficient cooling capacity and low liquefaction rate of liquid air energy storage system, but the current liquid air energy storage system coupled with LNG cold energy does not take into account that the main component of LNG is methane. Once it leaks into the energy storage system during the heat exchange process, it will be dangerous and the system safety is poor. Utility Model Content

[0004] The technical problem to be solved by the utility model is to provide a liquid air energy storage system coupled with LNG cold energy, which not only has high system safety, but also has high air liquefaction rate and cold energy utilization rate, thus saving equipment manufacturing and system operation costs.

[0005] In order to solve the above technical problems, the technical solutions adopted by the present utility model are as follows.

[0006] A liquid air energy storage system coupled with LNG cold energy, comprising an air compression unit, an air purification unit, an air liquefaction unit, a liquid air storage unit, a liquid air boost gasification unit, an air expansion power generation unit, and an LNG cold storage and nitrogen heat exchange unit for completing the system energy storage process and energy release process;

[0007] The air compression unit, air purification unit, air liquefaction unit, liquid air storage unit, liquid air boosting and gasification unit and air expansion power generation unit are connected in sequence, and the air expansion power generation unit is also connected to the liquid air storage unit to achieve air compression, cooling, purification, liquefaction, storage, boosting, evaporation and gasification, reheating, expansion power generation and reliquefaction; the liquid air storage unit includes a liquid air storage tank 207, which is a Dewar storage tank or a cryogenic storage tank;

[0008] The LNG cold storage and nitrogen heat exchange unit is respectively connected to the air liquefaction unit, the liquid air boost gasification unit and the air expansion power generation unit and is connected to the external cold source LNG, and the LNG cold storage and nitrogen heat exchange unit uses nitrogen as a circulating medium to absorb the cold at the low temperature end of LNG during the energy storage process to provide cold for the air liquefaction unit to liquefy air, and during the energy release process, the low temperature end of LNG is used by the low temperature nitrogen to pre-cool the compressed air extracted from the expander of the air expansion power generation unit, and the process technology of recovering the cold of the evaporator of the liquid air boost gasification unit is used to re-liquefy and store the pre-cooled compressed air; the LNG cold storage and nitrogen heat exchange unit uses ethylene glycol aqueous solution as a circulating coolant to absorb the cold at the high temperature end of LNG for cooling the system equipment.

[0009] Preferably, the air liquefaction unit includes a main low-temperature heat exchanger, a low-temperature compressor unit, a subcooler, a hydraulic turbine and a second gas-liquid separator which are connected in sequence through a second air pipeline resistant to low temperature and high pressure, and the low-temperature compressor unit includes a first low-temperature compressor and a second low-temperature compressor; the main low-temperature heat exchanger is connected to the air purification unit and the LNG cold storage and nitrogen heat exchange unit respectively, and the second gas-liquid separator is connected to the liquid air storage unit through the second air pipeline; the low-temperature compressor unit is a single-stage or multi-stage low-temperature compressor, and the inlet and outlet air of each stage of the compressor passes through the main low-temperature heat exchanger.

[0010] Preferably, the liquid air pressurization gasification unit includes a cryogenic pump for pressurizing the low-temperature liquid air, an evaporator for gasifying the low-temperature liquid air, and a heat source heat exchanger for heating the gasified low-temperature air to normal temperature, which are connected in sequence through a second air pipeline resistant to low temperatures and high pressures; the cryogenic pump is connected to the liquid air storage unit through the second air pipeline; the heating medium used by the heat source heat exchanger is seawater, the heat source heat exchanger is connected to the seawater through a first heat source pipeline, and the heat source heat exchanger is connected to the air expansion power generation unit through a second air pipeline.

[0011] Preferably, the liquid air storage unit comprises a liquid air storage tank connected between the second gas-liquid separator and the cryogenic pump.

[0012] Preferably, the air expansion power generation unit includes a first air heater, a first power generation expander, a second air heater, a second power generation expander, a third air heater and a third power generation expander connected in sequence through a third air pipeline resistant to high temperature and high pressure; the first air heater is connected to a heat source heat exchanger; the first power generation expander, the second power generation expander and the third power generation expander constitute an air expansion power generation set, and the expansion power generation set is one-stage or multi-stage, which is consistent with the total compression stage of the air compression unit and the air liquefaction unit; the air outlet of the first power generation expander is also connected to a third gas-liquid separator through a third air pipeline branch pipeline resistant to high temperature and high pressure that is connected to the third air pipeline, and the third gas-liquid separator is connected between the inlet of the liquid air storage unit and the evaporator through a fourth air pipeline resistant to low temperature and high pressure, and the inlet of the third gas-liquid separator is provided with a valve connected between the third gas-liquid separator and the evaporator through a fourth air pipeline resistant to low temperature and high pressure.

[0013] Preferably, the LNG cold storage and nitrogen heat exchange unit comprises an LNG-nitrogen heat exchanger, a circulation fan, a nitrogen-ethylene glycol heat exchanger and a cold storage unit connected by an N2 circulation pipeline which is a closed circulation pipeline;

[0014] The LNG-nitrogen heat exchanger, the circulating fan and the cold storage unit are connected in sequence through the first N2 circulating pipeline of the N2 circulating pipeline, and the main low-temperature heat exchanger is also connected between the circulating fan and the cold storage unit through the first N2 circulating pipeline. The LNG-nitrogen heat exchanger and the cold storage unit are respectively connected to the external cold source LNG through the cold source pipeline; the first N2 circulating pipeline is used to use nitrogen as a circulating medium, and in the energy storage process, the cold capacity of the low-temperature end of LNG is transferred to the main low-temperature heat exchanger; the air outlet of the first power generation expander is connected to the cold storage unit through the third air pipeline branch pipeline, and the cold storage unit is connected to the LNG-nitrogen heat exchanger and the evaporator in sequence through the fourth air pipeline, so that in the energy release process, the low-temperature nitrogen uses the cold capacity of the low-temperature end of LNG to pre-cool the compressed air from the expander exhaust, and realizes that the exhaust after pre-cooling is cooled by the evaporator and the valve is reduced in pressure to liquefy into liquid air and stored in the liquid air storage unit; the cold storage unit is used to store excess LNG cold energy in the energy storage and energy release processes;

[0015] The nitrogen-ethylene glycol heat exchanger is connected between the main low-temperature heat exchanger and the cold storage unit through the second N2 circulation pipeline of the N2 circulation pipeline. The nitrogen-ethylene glycol heat exchanger uses ethylene glycol aqueous solution as a circulating coolant through the second circulating refrigeration pipeline to absorb the cold at the high-temperature end of LNG for cooling the system equipment.

[0016] Preferably, the air compression unit comprises a high-temperature compressor unit for compressing ambient air and a cooler for cooling the compressed air, which is connected to the air purification unit through a first air pipeline resistant to high temperature and high pressure.

[0017] Preferably, the system also includes a heat storage unit connected between the air compression unit and the air expansion power generation unit, which is used to recover and store heat energy generated by the air compression unit during the energy storage process and release heat energy during the energy release process to heat the gaseous air in the air expansion power generation unit; the heat storage unit includes a heat storage device, a first heat fluid transportation device and a second heat fluid transportation device, the heat storage device and the first heat fluid transportation device are connected through a first heat storage circulation pipeline which is a closed circulation pipeline and are connected to the cooler, the heat storage device and the second heat fluid transportation device are connected through a second heat storage circulation pipeline which is a closed circulation pipeline and are connected to the third air heater, the second air heater and the first air heater, and the heat storage device is also connected to the first air heater, the second air heater and the third air heater through a second heat storage circulation pipeline.

[0018] Preferably, the first air heater, the second air heater and the third air heater are connected in sequence through the second heat source pipeline, and the first air heater is also connected to an external heat source through the second heat source pipeline; the cooler is connected to a cold source through a third circulating refrigeration pipeline, and the cold source is an ethylene glycol aqueous solution.

[0019] Preferably, the air purification unit includes a cold source heat exchanger, a first gas-liquid separator and an air purification system which are connected in sequence through a first air pipeline resistant to high temperature and high pressure; the cold source heat exchanger is connected to the air compression unit, and the cold source heat exchanger is connected to a cold source through a first circulating refrigeration pipeline, and the cold source is a chilled water refrigerator or an ethylene glycol aqueous solution; the air purification system is a double-tower parallel or single-tower intermittent operation air purification system, and the air purification system is connected to the air liquefaction unit through a first air pipeline.

[0020] Due to the adoption of the above technical scheme, the technical progress achieved by the present invention is as follows.

[0021] The utility model realizes energy storage and LNG cold energy utilization by coupling liquid air energy storage and LNG cold energy, solves the problems of LNG cold energy waste and high energy consumption of liquid air energy storage, and can adapt to large fluctuations in LNG gasification transmission volume and temperature changes, and has better flexibility than cold energy air separation and power generation.

[0022] The utility model uses nitrogen as the intermediate circulation medium to achieve the transfer of LNG cold energy, avoids direct contact between LNG and the liquid air energy storage system, and further ensures the safety of the energy storage system. At the same time, ethylene glycol aqueous solution is used as the circulating coolant to absorb the low-grade cold energy at the high temperature end of LNG and then go to the compressor interstage cooler and the final stage cooler, and is used for cooling the motor and oil pump, etc., to achieve the cascade utilization of system cold energy and reduce operating energy consumption.

[0023] The utility model adopts coupled LNG cooling capacity, eliminates the booster turbine expander, greatly reduces the energy consumption and device complexity of the liquid air energy storage system, greatly improves the air liquefaction rate, greatly reduces the amount of reflux air, and greatly improves the electric-electric energy storage efficiency. At the same time, LNG is used to cool the compressor intake, which greatly reduces the compression heat and significantly improves the compressor efficiency.

[0024] The utility model adopts the process technology of recovering the cold energy of the evaporator to reliquefy the expanded machine exhaust gas, thereby improving the utilization rate of the system cold energy and saving the equipment manufacturing and system operation costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the structure of Example 1 of the utility model;

[0026] Figure 2 This is a schematic structural diagram of Example 2 of the present utility model.

[0027] Among them: 101. High temperature compressor unit, 102. Cooler, 103. Cold source heat exchanger, 104. First gas-liquid separator, 105. Air purification system, 201. Main low temperature heat exchanger, 202. First low temperature compressor, 203. Second low temperature compressor, 204. Subcooler, 205. Hydraulic turbine, 206. Second gas-liquid separator, 207. Liquid air storage tank, 301. Low temperature pump, 302. Evaporator, 303. Heat source heat exchanger, 304. First air heater, 305. First power generation expander, 306. Second air heater, 307. Second power generation expander, 308. Third air heater, 309. Third power generation expander, 310. Valve, 311. Third gas-liquid separator, 401. LNG-nitrogen heat exchanger, 402. Circulation Fan, 403. Nitrogen-ethylene glycol heat exchanger, 404. Cold storage unit, 501. Heat storage device, 502. First thermal fluid transport equipment, 503. Second thermal fluid transport equipment, A1. First air pipeline, A2. Second air pipeline, A3. Third air pipeline, A3-1. Third air pipeline branch pipeline, A4. Fourth air pipeline, P1. First air exhaust pipeline, P2. Second air exhaust pipeline, C1. First N2 circulation pipeline, C2. Second N2 circulation pipeline, E1. First circulation refrigeration pipeline, E2. Second circulation refrigeration pipeline, E3. Third circulation refrigeration pipeline, H1. First heat storage circulation pipeline, H2. Second heat storage circulation pipeline, L. Cold source pipeline, S1. First heat source pipeline, S2. Second heat source pipeline, M. Drive motor, G. Generator. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0029] A liquid air energy storage system coupled with LNG cold energy uses nitrogen as a circulating medium to absorb the cold energy at the low temperature end of LNG, providing cold energy for air liquefaction, replacing the conventional boost expansion refrigeration mode; uses ethylene glycol aqueous solution as a circulating coolant to absorb the cold energy at the high temperature end of LNG, and transfers it to the compressor interstage cooler or is used for cooling the system motor and oil pump, etc.; uses the process technology of recovering the cold energy of the evaporator to reliquefy and store the compressed air, replacing the conventional cold storage unit.

[0030] Example 1

[0031] like Figure 1 As shown, the system includes an air compression unit, an air purification unit, an air liquefaction unit, an LNG cold storage and nitrogen heat exchange unit, a liquid air storage unit, a liquid air boost and gasification unit, an air expansion power generation unit and a heat storage unit for completing the energy storage process and the energy release process of the system. Among them, the air compression unit, the air purification unit, the air liquefaction unit, the liquid air storage unit, the liquid air boost and gasification unit and the air expansion power generation unit are connected in sequence, and the air expansion power generation unit is also connected to the liquid air storage unit to realize air compression, cooling, purification, liquefaction, storage, boosting, evaporation and gasification, reheating, expansion power generation and reliquefaction; the LNG cold storage and nitrogen heat exchange unit is respectively connected to the air liquefaction unit, the liquid air boost and gasification unit and the air expansion power generation unit and is connected to the external cold source LNG, and the LNG cold storage and nitrogen heat exchange unit uses nitrogen as the circulating medium The cold energy of the low-temperature end of LNG is absorbed during the energy storage process to provide cold energy for the air liquefaction unit to liquefy the air. In the energy release process, the cold energy of the low-temperature end of LNG is used by low-temperature nitrogen to pre-cool the compressed air extracted from the expander of the air expansion power generation unit. The pre-cooled compressed air is cooled by the liquid air boosting and gasification unit and reduced in pressure by the throttle valve, then liquefied into liquid air and stored in the liquid air storage unit. The LNG cold storage and nitrogen heat exchange unit uses ethylene glycol aqueous solution as the circulating coolant to absorb the cold energy of the high-temperature end of LNG, and transfers it to the compressor interstage cooler or is used for cooling the system motor and oil pump, etc.

[0032] In the energy storage process, the air is compressed, cooled, and purified using renewable energy or off-peak electricity from the grid, and the compressed heat is recovered and stored. The compressed air then enters the air liquefaction unit, and nitrogen is used as the intermediate circulation medium to transfer the cold of LNG to the air liquefaction unit. The compressed air is further cooled, compressed, and expanded to obtain liquid air and store it. In the energy release process, the liquid air is pressurized, then evaporated and vaporized, heated to room temperature, and heated by the compressed heat, and then drives the air expansion power generation unit to generate electricity. At the same time, the process technology of recovering the cold of the liquid air boosting and gasification unit is used to reliquefy and store the compressed air extracted from the air expansion power generation unit; the dry and clean air discharged from the air expansion power generation unit is used for the regeneration air purification process and the cooling process.

[0033] The air compression unit includes a high-temperature compressor unit 101 and a cooler 102 connected by a first air pipeline A1 resistant to high temperature and high pressure, wherein the high-temperature compressor unit 101 is used to compress ambient air; the cooler 102 is used to cool the compressed air, and the cooler 102 is connected to the air purification unit through the first air pipeline A1. The high-temperature compressor unit 101 is a single-stage or multi-stage high-temperature compressor, the outlet pressure is between 0.3MPa and 2MPa, the exhaust temperature of the high-temperature compressor unit 101 is between 100℃ and 500℃, the exhaust of each stage of the high-temperature compressor passes through the cooler, and the number of coolers is consistent with the total number of stages of the high-temperature compressor unit.

[0034] The air purification unit includes a cold source heat exchanger 103, a first gas-liquid separator 104 and an air purification system 105 which are connected in sequence through a first air pipeline A1 resistant to high temperature and high pressure, wherein the cold source heat exchanger 103 is connected to the cooler 102 of the air compression unit, and the cold source heat exchanger 103 is connected to a cold source through a first circulating refrigeration pipeline E1, and the cold source is a chilled water refrigerator or an ethylene glycol aqueous solution, which is used to cool the compressed air entering the air purification unit; the air purification system 105 is a double-tower parallel or single-tower intermittent operation air purification system, and the air purification system 105 is used to remove CO2, water vapor and argon in the raw air, which are impurity gases that affect the normal operation of air compression, cooling and liquefaction equipment and the output of liquid air, and the air purification system 105 is connected to the air liquefaction unit through the first air pipeline A1.

[0035] The air liquefaction unit includes a main cryogenic heat exchanger 201, a cryogenic compressor unit (a first cryogenic compressor 202 and a second cryogenic compressor 203), a subcooler 204, a hydraulic turbine 205 and a second gas-liquid separator 206 which are connected in sequence through a second air pipeline A2 resistant to low temperature and high pressure, wherein the main cryogenic heat exchanger 201 is connected to the air purification system 105 of the air purification unit and the LNG cold storage and nitrogen heat exchange unit respectively; the cryogenic compressor unit is a single-stage or multi-stage cryogenic compressor with an outlet pressure between 1MPa and 8MPa, and the inlet and outlet air of each stage of the cryogenic compressor passes through the main cryogenic heat exchanger 201; the second gas-liquid separator 206 is connected to the liquid air storage unit through the second air pipeline A2.

[0036] The liquid air storage unit includes a liquid air storage tank 207 connected between the second gas-liquid separator 206 and the liquid air boosting and gasification unit. The liquid air storage tank 207 is a Dewar tank or a cryogenic storage tank. The tank pressure is 0.1-2 MPa. The liquid air is stored under normal pressure or under pressure.

[0037] The liquid air pressurization gasification unit includes a cryopump 301, an evaporator 302 and a heat source heat exchanger 303 which are sequentially connected through a second air pipeline A2 resistant to low temperature and high pressure. The cryopump 301 is connected to the liquid air storage tank 207 of the liquid air storage unit through the second air pipeline A2. The cryopump 301 is a reciprocating, centrifugal or hybrid type, and is used to pressurize the low-temperature liquid air to 3MPa to 25MPa. The evaporator 302 and the heat source heat exchanger 303 are of plate-fin type, coil-wound type, printed circuit board type, shell and tube type, plate type or hybrid type, wherein the evaporator 302 is used to vaporize liquid air, and utilizes the expansion exhaust after precooling to recover the evaporation gasification cooling capacity to reliquefy the precooled compressed air, and the expansion exhaust pressure of the air expansion power generation unit is between 0.3MPa and 5MPa; the heat source heat exchanger 303 is used to heat the vaporized low-temperature air to room temperature, and the heating medium used by the heat source heat exchanger 303 is seawater. The heat source heat exchanger 303 is connected to the seawater through the first heat source pipeline S1, so that the seawater is heated to room temperature by heat exchange with the pressurized and vaporized low-temperature air through the first heat source pipeline S1, and the heat source heat exchanger 303 is also connected to the air expansion power generation unit through the second air pipeline A2.

[0038] The air expansion power generation unit comprises a first air heater 304, a first power generation expander 305, a second air heater 306, a second power generation expander 307, a third air heater 308 and a third power generation expander 309 which are sequentially connected through a third air pipeline A3 resistant to high temperature and high pressure, wherein the first air heater 304 is connected to the heat source heat exchanger 303, and the first air heater 304, the second air heater 306 and the third air heater 308 are all plate-fin type, coil type, printed circuit board type, shell and tube type, plate type or hybrid type; the expansion power generation unit (the first power generation expander 30 5. The second power generation expander 307 and the third power generation expander 309 are single-stage or multi-stage, which is generally consistent with the total compression stage number of the air compression unit and the air liquefaction unit. The expansion generator sets are all piston type, axial flow type, centripetal type, screw type or mixed type. The intake temperature of the expansion generator set is between 100°C and 500°C. When the expansion generator set is multi-stage, multiple expanders are in coaxial series form or split-shaft parallel form. In the parallel form, each split shaft is dynamically connected to the main drive shaft, and the number of heater stages is consistent with the number of expansion generator sets. The output end of each heater is connected to the input end of the expansion generator in a one-to-one correspondence.

[0039] The air outlet of the first power generation expander 305 is also connected to a third gas-liquid separator 311 through a third air pipeline branch pipeline A3-1 connected to the third air pipeline A3 and resistant to high temperature and high pressure. By connecting the third gas-liquid separator 311 to the third air pipeline A3 of the air outlet of the first power generation expander 305, the air at the outlet of the first power generation expander 305 is divided into two streams, wherein one stream passes through the second air heater 306, the second power generation expander 307, and the third air heater 308 in sequence. The third gas-liquid separator 311 is connected to the inlet of the liquid air storage unit and the evaporator 302 through a fourth air pipeline A4 resistant to low temperature and high pressure. The inlet of the third gas-liquid separator 311 is provided with a valve 310 connected between the third gas-liquid separator 311 and the evaporator 302 through a fourth air pipeline A4. The valve 310 is a throttle valve or an angle valve.

[0040] The LNG cold storage and nitrogen heat exchange unit includes an LNG-nitrogen heat exchanger 401, a circulation fan 402, a nitrogen-ethylene glycol heat exchanger 403 and a cold storage unit 404 connected by a N2 circulation pipeline which is a closed circulation pipeline.

[0041] The LNG-nitrogen heat exchanger 401, the circulating fan 402 and the cold storage unit 404 are connected in sequence through the first N2 circulating pipeline C1 of the N2 circulating pipeline, and the main low-temperature heat exchanger 201 is also connected between the circulating fan 402 and the cold storage unit 404 through the first N2 circulating pipeline C1. The LNG-nitrogen heat exchanger 401 and the cold storage unit 404 are respectively connected to the LNG storage unit through the cold source pipeline L to transfer cold energy. Among them, the first N2 circulation pipeline C1 is used to use nitrogen as the circulation medium. During the energy storage process, the cold end of the LNG is transferred to the main low-temperature heat exchanger 201; the air outlet of the first power generation expander 305 is connected to the cold storage unit 404 through the third air pipeline branch pipeline A3-1, and the cold storage unit 404 is connected to the LNG-nitrogen heat exchanger 401 and the evaporator 302 in sequence through the fourth air pipeline A4. During the energy release process, the cold end of the LNG is used by the low-temperature nitrogen to pre-cool the compressed air from the expander exhaust. After pre-cooling, the expanded exhaust is cooled by the evaporator 302 and the valve 310 reduces the pressure to liquefy into liquid air and is stored in the liquid air storage unit.

[0042] During the energy storage and release process, the excess LNG cold energy is stored in the cold storage unit 404. The cold storage system 404 is one or a combination of sensible heat storage or solid-liquid phase change storage. The sensible heat storage medium used is one or more of sealed ice balls, sand and gravel, concrete, aluminum belt discs or other metal materials. The solid-liquid phase change storage medium is one or more of ammonia and its aqueous solution, salt aqueous solution, alkane, olefin substances and their compounds, alcohols and their aqueous solutions with a solid-liquid phase change temperature of 81K~273K. The cold storage medium is stored in an insulated container.

[0043] The nitrogen-ethylene glycol heat exchanger 403 is connected between the main low-temperature heat exchanger 201 and the cold storage unit 404 through the second N2 circulation pipeline C2 of the N2 circulation pipeline. The nitrogen-ethylene glycol heat exchanger 403 absorbs the cold energy of the high-temperature end of LNG through the second circulation refrigeration pipeline E2 using ethylene glycol aqueous solution as a circulating coolant, which is used for cooling system equipment, such as transferring it to the compressor interstage cooler or for cooling the system motor and oil pump, etc.

[0044] The heat storage unit is connected between the air compression unit and the air expansion power generation unit. The heat storage unit is used to recover and store the heat energy generated by the air compression unit during the energy storage process and to release the heat energy during the energy release process to heat the gaseous air in the air expansion power generation unit.

[0045] The heat storage unit includes a heat storage device 501, a first heat fluid transport device 502 and a second heat fluid transport device 503. The heat storage device 501 and the first heat fluid transport device 502 are connected through a first heat storage circulation pipeline H1 which is a closed circulation pipeline and are connected to the cooler 102. The heat storage device 501 and the second heat fluid transport device 503 are connected through a second heat storage circulation pipeline H2 which is a closed circulation pipeline and are connected to the third air heater 308, the second air heater 306 and the first air heater 304. The first heat storage circulation pipeline H1 and the second heat storage circulation pipeline H2 are both high temperature and high pressure resistant heat storage circulation pipelines. The heat storage form of the heat storage device 501 is one or more of sensible heat, latent heat or chemical reaction heat; the heat storage medium used is water, paraffin, biomass oil, inorganic crystalline hydrated salt, molten salt, metal and its alloy, organic fatty acid, stone, rock or concrete, and the heat storage medium is stored in an insulating container; the first thermal fluid conveying equipment 502 and the second thermal fluid conveying equipment 503 are both pumps, compressors or fans.

[0046] The system also includes a driving motor M and a generator G, wherein the driving motor M is fixedly connected to the transmission shafts of the high-temperature compressor unit 101 and the first low-temperature compressor 202 respectively; the high-temperature compressor unit 101 and the low-temperature compressor unit (the first low-temperature compressor 202 and the second low-temperature compressor 203) are connected in parallel with split shafts, and the first low-temperature compressor 202 and the second low-temperature compressor 203 are connected in series with a coaxial connection; the first power-generating expander 305, the second power-generating expander 307 and the third power-generating expander 309 are connected in series with a coaxial connection, and the generator G is fixedly connected to the transmission shaft of the three-stage expansion unit composed of the first power-generating expander 305, the second power-generating expander 307 and the third power-generating expander 309.

[0047] The third power generation expander 309 is connected to a first air exhaust pipeline P1 that is resistant to high temperature and high pressure, and the evaporator 302 is connected to a second air exhaust pipeline P2 that is resistant to low temperature and high pressure. The first air exhaust pipeline P1 and the second air exhaust pipeline P2 directly output air for air regeneration circulation or output cold energy and moist clean air through evaporative cooling.

[0048] The high temperature compressor unit 101 and the low temperature compressor unit (the first low temperature compressor 202 and the second low temperature compressor 203) are piston type, axial flow type, centrifugal type, screw type or mixed type. When the high temperature compressor unit 101 and the low temperature compressor unit are multiple compressors, the multiple compressors are in a coaxial series form or a split shaft parallel form; in the parallel form, each split shaft is dynamically connected to the main drive shaft. The cooler 102, the cold source heat exchanger 103, the main low temperature heat exchanger 201, the LNG-nitrogen heat exchanger 401, the nitrogen-ethylene glycol heat exchanger 403 and the subcooler 204 are plate-fin type, coil type, printed circuit board type, shell and tube type, plate type or mixed type. The high-temperature compressor unit 101, the first low-temperature compressor 202 and the second low-temperature compressor 203, the cooler 102, the cold source heat exchanger 103, the main low-temperature heat exchanger 201, the LNG-nitrogen heat exchanger 401, the nitrogen-ethylene glycol heat exchanger 403 and the subcooler 204 are all integrated with air purification and purification equipment for removing solid matter and impurity gases in the air.

[0049] During the energy storage process, the ambient air is compressed and cooled by the high-temperature compressor unit 101, the cooler 102 and the cold source heat exchanger 103, and then enters the air purification system 105 through the first gas-liquid separator 104 to remove CO2, water vapor and argon components in the raw air. At the same time, the heat storage device 501 is connected to the cooler 102 through the first heat storage circulation pipeline H1 to recover and store the compression heat generated by the high-temperature compressor unit 101. The system is provided with two-stage cryogenic compressors. The air at the outlet of the air purification system 105 enters the air liquefaction unit, and is cooled by the main cryogenic heat exchanger 201, compressed by the first cryogenic compressor 202, cooled by the main cryogenic heat exchanger 201, and compressed by the second cryogenic compressor 203. After the main cryogenic heat exchanger 201 is cooled, it is cooled and expanded by the subcooler 204 and the hydraulic turbine 205, and then enters the second gas-liquid separator 206; at the same time, the cold energy of the LNG cold source is transferred to the main cryogenic heat exchanger 201 through the intermediate circulation medium N2 of the LNG cold storage and nitrogen heat exchange unit to cool the air, and the low-grade cold energy at the high temperature end of the LNG is absorbed by the ethylene glycol aqueous solution and then goes to the cold source heat exchanger 103 before the air purification unit, or is used for cooling the motor and oil pump, etc. The gaseous air in the second gas-liquid separator 206 passes through the cooler 204 and returns to the main cryogenic heat exchanger 201 for heat exchange, and then mixes with the cooled compressed air stream and enters the first cryogenic compressor 202 to participate in the next cycle; the liquid air enters the liquid air storage tank 207 for storage.

[0050] During the energy release process, the low-temperature liquid air output from the liquid air storage tank 207 is pressurized to high pressure by the low-temperature pump 301 and then enters the evaporator 302, where it is heated by the exhaust gas of the first-stage power generation expander and converted from liquid phase to gas phase. It is then heated to room temperature by seawater through the heat source heat exchanger 303. The room-temperature high-pressure air enters the air expansion power generation unit, passes through the first air heater 304 and the first power generation expander 305, and the air at the outlet of the first power generation expander 305 is divided into two streams, of which one stream passes through the second air heater 306, the second power generation expander 307, the third air heater 308 and the third power generation expander 309 in sequence, and the compression heat in the heat storage device 501 is connected to the first heat storage circulation pipeline H2 through the second heat storage circulation pipeline H3. The air heater 304, the second air heater 306 and the third air heater 308 heat the air before entering the first power generation expander 305, the second power generation expander 307 and the third power generation expander 309, driving the first power generation expander 305, the second power generation expander 307 and the third power generation expander 309 to expand and generate electricity; the other stream is pre-cooled by the cold storage unit 404 and the LNG-nitrogen heat exchanger 401 in sequence, enters the evaporator 302 to recover the evaporator cold, cools and lowers the temperature, expands and depressurizes through the valve 310, and enters the third gas-liquid separator 311. The gaseous air in the third gas-liquid separator 311 is discharged after heat exchange in the evaporator 302, and the liquid air enters the liquid air storage tank 207 for storage. The exhaust gas at the outlet of the final third power generation expander 309 is directly output for air regeneration circulation, or outputs cold energy and moist clean air through evaporative cooling.

[0051] In general, the energy storage and energy release processes do not operate at the same time. During energy storage, the air compression unit, air purification unit, air liquefaction unit, LNG cold storage and nitrogen heat exchange unit and liquid air storage unit are working, the liquid air boost gasification unit and air expansion power generation unit are shut down, and the heat storage unit recovers and stores compression heat, compresses, cools, purifies, liquefies and stores the air. During energy release, the opposite is true. The air compression unit and air liquefaction unit are shut down, the air purification unit, liquid air storage unit, liquid air boost gasification unit, air expansion power generation unit and LNG cold storage and nitrogen heat exchange unit are working, and the heat storage unit releases heat energy, evaporates and gasifies the liquid air, expands it after reheating it, and generates electricity. The process technology of recovering the cold capacity of the evaporator is used to reliquefy and store the expanded air (compressed air).

[0052] Example 2

[0053] like Figure 2The example 2 of the utility model is a variation of the example 1. Based on the example 1, the heat storage unit and the first heat storage circulation pipeline H1 and the second heat storage circulation pipeline H2 are not included, but an external heat source, a second heat source pipeline S2 and a third circulation refrigeration pipeline E3 are introduced. Specifically, the first air heater 304, the second air heater 306 and the third air heater 308 are connected in sequence through the second heat source pipeline S2, and the first air heater 304 is also connected to the external heat source through the second heat source pipeline S2; the cooler 102 is connected to a cold source through the third circulation refrigeration pipeline E3, and the cold source is an ethylene glycol aqueous solution.

[0054] During the energy storage process, the exhaust gas of the high-temperature compressor unit 101 is cooled by an ethylene glycol aqueous solution; during the energy release process, the air before the inlet of the first power generation expander 305, the second power generation expander 307 and the third power generation expander 309 is heated by a heat source.

[0055] A liquid air energy storage method coupled with LNG cold energy includes two processes: an energy storage process and an energy release process, and the energy storage process and the energy release process are not operated at the same time.

[0056] During the energy storage process, the air compression unit, air purification unit, air liquefaction unit, LNG cold storage and nitrogen heat exchange unit and liquid air storage unit are working, the liquid air boost gasification unit and air expansion power generation unit are closed, and the heat storage unit recovers and stores compression heat. The energy storage process is as follows: the air enters the air liquefaction unit after being compressed, cooled, purified and pressurized, the compressed air is cooled to liquefaction by low-temperature nitrogen in the main low-temperature heat exchanger 201, and is further cooled to supercooling and expanded by the subcooler 204, and the unliquefied air refluxes to provide cooling capacity; the air out of the main low-temperature heat exchanger 201 is cooled to low temperature by low-temperature nitrogen, mixed with the unliquefied reflux air and enters the first low-temperature compressor 202 for compression.

[0057] During the energy release process, the air compression unit and the air liquefaction unit are closed, the air purification unit, the LNG cold storage and nitrogen heat exchange unit, the liquid air storage unit, the liquid air boost gasification unit and the air expansion power generation unit are working, and the heat storage unit releases the compression heat. The energy release process is as follows: the liquid air is pressurized by the cryogenic pump 301 and enters the evaporator 302 to exchange heat with the expander exhaust air, and is heated to room temperature by seawater. After being reheated by the heater, it enters the expander to generate power, and the process technology of recovering the cold capacity of the evaporator 302 is used to reliquefy and store the expanded exhaust air (compressed air). The dry and clean air discharged from the final power generation expander is used for the regeneration air purification process and the cooling process.

[0058] When the utility model is in use, compared with the liquid air energy storage system not coupled with LNG, the system utilizes the high-grade cold energy in the gasification process of LNG and liquid air, greatly reduces the power consumption of the compressor, eliminates the booster turbine expander, reduces the complexity of the system device, greatly improves the liquefaction rate after air throttling, greatly reduces the amount of reflux air, and greatly improves the efficiency of electric-electric energy storage. At the same time, considering that the main component of LNG is methane, it will be dangerous if it leaks into the energy storage system during the heat exchange process. Therefore, nitrogen is used as the intermediate circulation medium to realize the transfer of LNG cold energy, thereby avoiding direct contact between LNG and the liquid air energy storage system, and further ensuring the safety of the energy storage system. At the same time, ethylene glycol aqueous solution is used as the circulating coolant, and after absorbing the low-grade cold energy at the high-temperature end of LNG, it goes to the compressor interstage cooler and the final cooler, and is used for cooling motors and oil pumps, etc., to realize the cascade utilization of system cold energy and reduce operating energy consumption.

Claims

1. A liquid air energy storage system coupled with LNG cold energy, characterized in that: It includes an air compression unit, an air purification unit, an air liquefaction unit, a liquid air storage unit, a liquid air boost gasification unit, an air expansion power generation unit, and an LNG cold storage and nitrogen heat exchange unit for completing the system energy storage and release processes; The air compression unit, air purification unit, air liquefaction unit, liquid air storage unit, liquid air pressurization and gasification unit and air expansion and power generation unit are connected in sequence, and the air expansion and power generation unit is also connected to the liquid air storage unit, so as to realize air compression, cooling, purification, liquefaction, storage, pressurization, evaporation and gasification, reheating, expansion and power generation and reliquefaction; The LNG cold storage and nitrogen heat exchange unit is respectively connected to the air liquefaction unit, the liquid air boost gasification unit and the air expansion power generation unit and is connected to the external cold source LNG, and the LNG cold storage and nitrogen heat exchange unit uses nitrogen as a circulating medium to absorb the cold at the low temperature end of LNG during the energy storage process to provide cold for the air liquefaction unit to liquefy air, and during the energy release process, the low temperature end of LNG is used by the low temperature nitrogen to pre-cool the compressed air extracted from the expander of the air expansion power generation unit, and the process technology of recovering the cold of the evaporator of the liquid air boost gasification unit is used to re-liquefy and store the pre-cooled compressed air; the LNG cold storage and nitrogen heat exchange unit uses ethylene glycol aqueous solution as a circulating coolant to absorb the cold at the high temperature end of LNG for cooling the system equipment.

2. A liquid air energy storage system coupled with LNG cold energy according to claim 1, characterized in that: The air liquefaction unit comprises a main low-temperature heat exchanger (201), a low-temperature compressor unit, a subcooler (204), a hydraulic turbine (205) and a second gas-liquid separator (206) which are connected in sequence through a low-temperature and high-pressure resistant second air pipeline (A2), and the low-temperature compressor unit comprises a first low-temperature compressor (202) and a second low-temperature compressor (203); the main low-temperature heat exchanger (201) is connected to an air purification unit and an LNG cold storage and nitrogen heat exchange unit respectively, and the second gas-liquid separator (206) is connected to a liquid air storage unit through a second air pipeline (A2); the low-temperature compressor unit is a single-stage or multi-stage low-temperature compressor, and the inlet and outlet air of each stage of the compressor passes through the main low-temperature heat exchanger (201).

3. A liquid air energy storage system coupled with LNG cold energy according to claim 2, characterized in that: The liquid air pressurizing and gasifying unit comprises a low-temperature pump (301) for pressurizing low-temperature liquid air, an evaporator (302) for gasifying low-temperature liquid air, and a heat source heat exchanger (303) for heating the gasified low-temperature air to room temperature, which are connected in sequence through a second air pipeline (A2) resistant to low temperatures and high pressures; the low-temperature pump (301) is connected to the liquid air storage unit through the second air pipeline (A2); the heating medium used by the heat source heat exchanger (303) is seawater, the heat source heat exchanger (303) is connected to the seawater through a first heat source pipeline (S1), and the heat source heat exchanger (303) is connected to the air expansion power generation unit through the second air pipeline (A2).

4. A liquid air energy storage system coupled with LNG cold energy according to claim 3, characterized in that: The liquid air storage unit comprises a liquid air storage tank (207) connected between the second gas-liquid separator (206) and the cryogenic pump (301).

5. The liquid air energy storage system coupled with LNG cold energy according to claim 3, characterized in that: The air expansion power generation unit comprises a first air heater (304), a first power generation expander (305), a second air heater (306), a second power generation expander (307), a third air heater (308) and a third power generation expander (309) which are sequentially connected via a third air pipeline (A3) resistant to high temperature and high pressure; the first air heater (304) is connected to a heat source heat exchanger (303); the first power generation expander (305), the second power generation expander (307) and the third power generation expander (309) form an air expansion power generation set, and the expansion power generation set is one-stage or multi-stage, and is connected to the air compression unit The total number of compression stages of the air liquefaction unit is consistent; the air outlet of the first power generation expander (305) is also connected to a third gas-liquid separator (311) through a third air pipeline branch pipeline (A3-1) that is connected to the third air pipeline (A3) and is resistant to high temperature and high pressure; the third gas-liquid separator (311) is connected between the inlet of the liquid air storage unit and the evaporator (302) through a fourth air pipeline (A4) that is resistant to low temperature and high pressure; the inlet of the third gas-liquid separator (311) is provided with a valve (310) that is connected between the third gas-liquid separator (311) and the evaporator (302) through the fourth air pipeline (A4).

6. A liquid air energy storage system coupled with LNG cold energy according to claim 5, characterized in that: The LNG cold storage and nitrogen heat exchange unit comprises an LNG-nitrogen heat exchanger (401), a circulation fan (402), a nitrogen-ethylene glycol heat exchanger (403) and a cold storage unit (404) connected via a N2 circulation pipeline which is a closed circulation pipeline; The LNG-nitrogen heat exchanger (401), the circulating fan (402) and the cold storage unit (404) are connected in sequence through a first N2 circulating pipeline (C1) of the N2 circulating pipeline, and the main low-temperature heat exchanger (201) is also connected between the circulating fan (402) and the cold storage unit (404) through the first N2 circulating pipeline (C1), and the LNG-nitrogen heat exchanger (401) and the cold storage unit (404) are respectively connected to an external cold source LNG through a cold source pipeline (L); the first N2 circulating pipeline (C1) is used to use nitrogen as a circulating medium, and in the energy storage process, transfer the cold at the low-temperature end of the LNG to the main low-temperature heat exchanger (201); the first The air outlet of the power generation expander (305) is connected to the cold storage unit (404) through the third air pipeline branch pipeline (A3-1), and the cold storage unit (404) is connected to the LNG-nitrogen heat exchanger (401) and the evaporator (302) in sequence through the fourth air pipeline (A4), so that during the energy release process, the low-temperature nitrogen uses the cold energy at the low-temperature end of the LNG to pre-cool the compressed air from the expander exhaust, and the expanded exhaust after pre-cooling is cooled by the evaporator (302) and depressurized by the valve (310) to be liquefied into liquid air and stored in the liquid air storage unit; the cold storage unit (404) is used to store excess LNG cold energy during the energy storage and energy release process; The nitrogen-ethylene glycol heat exchanger (403) is connected between the main low-temperature heat exchanger (201) and the cold storage unit (404) through the second N2 circulation pipeline (C2) of the N2 circulation pipeline. The nitrogen-ethylene glycol heat exchanger (403) absorbs the cold energy of the high-temperature end of LNG through the second circulation refrigeration pipeline (E2) using ethylene glycol aqueous solution as a circulation coolant for cooling system equipment.

7. A liquid air energy storage system coupled with LNG cold energy according to claim 5, characterized in that: The air compression unit comprises a high-temperature compressor unit (101) for compressing ambient air and a cooler (102) for cooling the compressed air, which are connected via a first air pipeline (A1) resistant to high temperature and high pressure. The cooler (102) is connected to the air purification unit via the first air pipeline (A1).

8. A liquid air energy storage system coupled with LNG cold energy according to claim 7, characterized in that: The system also includes a heat storage unit connected between the air compression unit and the air expansion power generation unit, and used to recover the heat energy generated by the air compression unit during the energy storage process and release the heat energy during the energy release process to heat the gaseous air in the air expansion power generation unit; the heat storage unit includes a heat storage device (501), a first heat fluid transport device (502) and a second heat fluid transport device (503), the heat storage device (501) and the first heat fluid transport device (502) are connected via a first heat storage cycle which is a closed cycle pipeline. The loop pipeline (H1) is connected to the cooler (102), the heat storage device (501) and the second thermal fluid transport device (503) are connected to the third air heater (308), the second air heater (306) and the first air heater (304) through the second heat storage circulation pipeline (H2) which is a closed circulation pipeline, and the heat storage device (501) is also connected to the first air heater (304), the second air heater (306) and the third air heater (308) through the second heat storage circulation pipeline (H2).

9. The liquid air energy storage system coupled with LNG cold energy according to claim 7, characterized in that: The first air heater (304), the second air heater (306) and the third air heater (308) are connected in sequence via a second heat source pipeline (S2), and the first air heater (304) is also connected to an external heat source via the second heat source pipeline (S2); the cooler (102) is connected to a cold source via a third circulating refrigeration pipeline (E3), and the cold source is an ethylene glycol aqueous solution.

10. The liquid air energy storage system coupled with LNG cold energy according to claim 1, characterized in that: The air purification unit comprises a cold source heat exchanger (103), a first gas-liquid separator (104) and an air purification system (105) which are connected in sequence via a first air pipeline (A1) resistant to high temperature and high pressure; the cold source heat exchanger (103) is connected to an air compression unit, and the cold source heat exchanger (103) is connected to a cold source via a first circulating refrigeration pipeline (E1), wherein the cold source is a chilled water refrigerator or an ethylene glycol aqueous solution; the air purification system (105) is a double-tower parallel or single-tower intermittently operating air purification system, and the air purification system (105) is connected to an air liquefaction unit via the first air pipeline (A1).

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