A liquefied air energy storage system that indirectly utilizes the cold energy of LNG

Abstract

This invention provides a liquefied air energy storage system that indirectly utilizes the cold energy of LNG, comprising: an air circulation system, a water circulation system, a nitrogen cold storage circulation system, and an ethylene glycol solution circulation system. The air circulation system is used for pretreatment, pressurization, liquefaction, and expansion power generation of air. The water circulation system absorbs interstage heat from pretreatment and pressurization and releases it in the expansion power generation process. The nitrogen cold storage circulation system exchanges heat with LNG, absorbing and storing the cold energy of LNG. The nitrogen cold storage circulation system also releases the cold energy of LNG into the liquefaction process of the air circulation system. The ethylene glycol solution circulation system absorbs the cold energy of LNG stored in the nitrogen cold storage circulation system, cooling the ethylene glycol solution. The ethylene glycol solution circulation system also absorbs waste heat from the pretreatment and pressurization processes. This invention can safely, reliably, and fully utilize the high-grade cold energy of LNG and achieve efficient power storage and regeneration, helping to reduce electricity load and lower enterprise production costs.

Description

Technical Field

[0001] This invention belongs to the field of compressed air energy storage technology, and particularly relates to a liquefied air energy storage system that indirectly utilizes the cold energy of LNG. Background Technology

[0002] my country's natural gas imports are increasing daily, with more than half originating from LNG. Typically, cryogenic LNG needs to be heated to above 0°C before being piped into the pipeline system and ultimately reaching users. This process not only wastes a significant amount of high-grade cold energy but also consumes other energy resources used for LNG regasification.

[0003] Liquid air energy storage (LIFS), as a novel energy storage technology, can play a role in peak shaving and valley filling of electricity load. When electricity is plentiful, air is compressed and cooled into a liquid state for energy storage; when electricity demand is high, the liquid air is heated to undergo a Rankine cycle and expand to generate electricity. Large-scale application of this technology can not only meet its own electricity needs but also generate surplus electricity for grid connection, creating economic benefits. The liquefaction process requires a large amount of cold energy to cool the high-temperature compressed air, which is highly compatible with the energy consumption of LNG vaporization. However, LNG is a flammable and explosive medium, and contact with air poses a significant safety hazard. Therefore, providing a LIFS system that utilizes the cold energy of LNG without contacting air is a pressing issue that needs to be addressed. Summary of the Invention

[0004] To address the aforementioned technical problems in the existing technology, embodiments of the present invention provide a liquid air energy storage system based on the utilization of LNG cold energy.

[0005] The technical solution adopted in this embodiment of the invention is: a liquefied air energy storage system that indirectly utilizes the cold energy of LNG, comprising: an air circulation system, a water circulation system, a nitrogen cold storage circulation system, and an ethylene glycol solution circulation system;

[0006] The air circulation system is used for air pretreatment, pressurization, liquefaction, and expansion for power generation.

[0007] The water circulation system is used to absorb the interstage heat of the air in the air circulation system during the pretreatment and pressurization processes, and release the absorbed interstage heat in the expansion and power generation process of the air in the air circulation system.

[0008] The nitrogen cold storage circulation system is used to exchange heat with the LNG flowing in the LNG supply pipeline in order to absorb and store the cold energy of the LNG; the nitrogen cold storage circulation system is also used to release the cold energy of the stored LNG in the liquefaction process of the air circulation system, so as to liquefy the air in the air circulation system.

[0009] The ethylene glycol solution circulation system is connected to the nitrogen cold storage circulation system and is used to absorb the cold energy of the LNG stored in the nitrogen cold storage circulation system, so as to cool down the ethylene glycol solution in the ethylene glycol solution circulation system; the ethylene glycol solution circulation system is also used to absorb the interstage waste heat of the air in the air circulation system during the pretreatment and pressurization processes.

[0010] In an optional embodiment, the air circulation system includes a pretreatment unit, a pressurization unit, a liquefaction storage unit, and an expansion power generation unit connected sequentially along the air flow direction. The pretreatment unit is used to compress, cool, and filter the air. The pressurization unit is used to compress and cool the filtered and purified air. The liquefaction storage system is used to liquefy and store the compressed and cooled air. The expansion power generation unit is used to generate electricity using the liquid air stored in the liquefaction storage system.

[0011] In an optional embodiment, the pretreatment unit includes a purification device and multiple sets of compression cooling units, which are connected sequentially along the airflow direction. Each set of compression cooling units includes a compressor unit, a water cooler, and an ethylene glycol solution final cooler, all connected sequentially along the airflow direction. Air flows through the hot fluid side of the water cooler and the ethylene glycol solution final cooler, water from the water circulation system flows through the cold fluid side of the water cooler, and the ethylene glycol solution from the ethylene glycol solution circulation system flows through the cold fluid side of the ethylene glycol solution final cooler. The outlet of the hot fluid side of the downstream ethylene glycol solution final cooler in the multiple sets of compression cooling units is connected to the inlet of the purification device.

[0012] In an optional embodiment, the liquefaction storage unit includes a cold box, a hydraulic turbine, a gas-liquid separator, and a liquid air storage tank. The cold box has a first cold fluid side and a first hot fluid side. The first cold fluid side is connected in series in the nitrogen release circuit of the nitrogen cold storage circulation system. The inlet of the first hot fluid side is connected to the outlet of the booster unit of the air circulation system, the outlet of the first hot fluid side is connected to the inlet of the hydraulic turbine, the outlet of the hydraulic turbine is connected to the gas-liquid separator, and the liquid outlet of the gas-liquid separator is connected to the liquid air storage tank.

[0013] In an optional embodiment, the liquefaction storage unit further includes an expander, and the cold box also has a second cold fluid side and a second hot fluid side. The inlet of the second cold fluid side is connected to the outlet of the expander and the gas outlet of the gas-liquid separator, respectively. The outlet of the second cold fluid side is connected to the pipeline between the pretreatment unit and the pressurization unit of the air circulation system. The inlet of the second hot fluid side is connected to the outlet of the pressurization unit of the air circulation system, and the outlet of the second hot fluid side is connected to the inlet of the expander.

[0014] In an optional embodiment, the liquefied air energy storage system further includes a liquid air cold storage circulation system, which has an air release circuit and an air cold storage circuit;

[0015] The cold box also has a third cold fluid side, which is connected in series in the air release circuit of the liquid air cold storage circulation system.

[0016] In an optional embodiment, the expansion power generation unit includes an evaporator, multiple air heat exchangers, and multiple expansion generator sets. The number of air heat exchangers and expansion generator sets is the same, and one air heat exchanger is respectively installed upstream of each expansion generator set. The cold fluid side inlet of the evaporator is connected to the outlet of the liquid air storage tank, and the cold fluid side outlet of the evaporator is connected to the cold fluid side inlet of the upstreammost air heat exchanger. The hot fluid side of the evaporator is connected in series in the air cold storage loop of the liquid air cold storage circulation system. The cold fluid side outlet of each air heat exchanger is connected to the inlet of one of the expansion generator sets located downstream and adjacent to it, and the hot fluid side of the air heat exchanger is connected to the hot water pipeline of the water circulation system.

[0017] In an optional embodiment, the water circulation system includes a hot water storage tank, a cold water storage tank, a hot water pipeline, and a cold water pipeline; the cold fluid side of the water cooler is connected in series with the cold water pipeline, and one end of the cold water pipeline is connected to the cold water outlet of the cold water storage tank, and the other end of the cold water pipeline is connected to the hot water inlet of the hot water storage tank; the hot fluid side of the multiple air heat exchangers of the expansion power generation unit of the air circulation system is connected in series with the hot water pipeline, and one end of the hot water pipeline is connected to the hot water outlet of the hot water storage tank, and the other end of the hot water pipeline is connected to the cold water inlet of the cold water storage tank.

[0018] In an optional embodiment, the water circulation system further includes a regenerated gas heater, the inlet of which on the cold fluid side is connected to the outlet of the downstream expansion generator set, and the outlet of which on the cold fluid side is connected to the regenerated gas inlet of the purification device; the hot fluid side of which is connected in series with the hot water pipeline.

[0019] In an optional embodiment, the ethylene glycol solution circulation system includes an ethylene glycol solution tank, a buffer tank, and an ethylene glycol solution cooler. The hot fluid side of the ethylene glycol solution cooler is connected in series with the return pipeline between the ethylene glycol solution tank and the buffer tank, and the cold fluid side of the ethylene glycol solution cooler is connected in series with the nitrogen release circuit of the nitrogen storage circulation system.

[0020] The ethylene glycol solution circulation system also includes a regenerated gas cooler. The cold fluid side of the regenerated gas cooler is connected in series with the liquid delivery pipeline between the ethylene glycol solution tank and the buffer tank. The inlet of the hot fluid side of the regenerated gas cooler is connected to the outlet of the downstream expansion generator set, and the outlet of the hot fluid side of the regenerated gas cooler is connected to the regenerated gas inlet of the purification device.

[0021] In an optional embodiment, the nitrogen cold storage cycle system includes a first cold storage unit, a first nitrogen blower, and a second nitrogen blower. The cold storage inlet of the first cold storage unit is connected to one end of the nitrogen cold storage circuit, and the cold storage outlet of the first cold storage unit is connected to the other end of the nitrogen cold storage circuit. The cold release outlet of the first cold storage unit is connected to one end of the nitrogen cold release circuit, and the cold release inlet of the first cold storage unit is connected to the other end of the nitrogen cold release circuit. The first nitrogen blower is located on the nitrogen cold release circuit, and the second nitrogen blower is located on the nitrogen cold storage circuit. The hot fluid side of an LNG heat exchanger is also connected in series on the nitrogen cold storage circuit. The inlet of the cold fluid side of the LNG heat exchanger is connected to the LNG supply pipeline, and the outlet of the cold fluid side of the LNG heat exchanger is connected to the LNG pipeline. The first cold fluid side of the cold box is connected in series on the nitrogen cold release circuit.

[0022] In an optional embodiment, the liquid air cold storage circulation system includes a second cold storage unit, a first air blower, and a second air blower. The cold storage inlet of the second cold storage unit is connected to one end of the air cold storage circuit, the cold storage outlet of the second cold storage unit is connected to the other end of the air cold storage circuit, the cold release outlet of the second cold storage unit is connected to one end of the air cold release circuit, and the cold release inlet of the second cold storage unit is connected to the other end of the air cold release circuit. The first air blower is located on the air cold release circuit, and the second air blower is located on the air cold storage circuit.

[0023] Compared with the prior art, the beneficial effects of the embodiments of the present invention are as follows: the present invention can indirectly utilize the cold energy of LNG, can safely, reliably and fully utilize the high-grade cold energy of LNG, and realize the efficient storage and regeneration of electricity, which helps to reduce the power load and reduce the production costs of enterprises.

[0024] It should be understood that the foregoing general description and the following detailed description are exemplary and illustrative only, and are not intended to limit the invention.

[0025] The overview of various implementations or examples of the technology described in this invention is not a complete disclosure of the full scope or all features of the disclosed technology. Attached Figure Description

[0026] In drawings that are not necessarily drawn to scale, the same reference numerals may describe similar parts in different views. The drawings generally illustrate various embodiments by way of example rather than limitation and are used, together with the description and claims, to illustrate the disclosed embodiments. Where appropriate, the same reference numerals are used in all drawings to refer to the same or similar parts. Such embodiments are illustrative and not intended to be exhaustive or exclusive embodiments of the apparatus or method.

[0027] Figure 1 This is a schematic diagram of a liquid air energy storage system based on LNG cold energy utilization, according to an embodiment of the present invention.

[0028] Figure label:

[0029] 1-Compressor unit; 2-Water cooler; 3-Ethylene glycol solution final cooler; 4-Purification unit;

[0030] 5-First booster unit; 6-Second booster unit; 7-Booster cooler; 8-Booster terminal cooler; 9-Cold box; 10-Hydraulic turbine; 11-Gas-liquid separator; 12-Liquid air storage tank; 13-First cold fluid side; 14-Second cold fluid side; 15-Third cold fluid side; 16-First hot fluid side; 17-Second hot fluid side; 18-Expander; 19-JT valve; 20-Booster pump; 21-Evaporator; 22-Air heat exchanger; 23-Expander generator set; 24-Hot water storage tank; 25-Cold water storage tank; 26-Hot water pipeline; 27-Cold water pipeline; 28-Regenerated gas heater; 29-Regenerated gas cooler; 30-Ethylene glycol solution tank; 31-Buffer tank; 32-Ethylene glycol solution cooler; 33-Return liquid line; 34-Supply liquid line; 35-First accumulator; 36-First nitrogen blower; 37-Second nitrogen blower; 38-Nitrogen release circuit; 39-Nitrogen storage circuit; 40-Second accumulator; 41-First air blower; 42-Second air blower; 43-Air release circuit; 44-Air storage circuit; 45-LNG supply line; 46-NG line; 47-LNG heat exchanger. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0033] To keep the following description of the embodiments of the present invention clear and concise, detailed descriptions of known functions and known components are omitted.

[0034] This invention provides a liquefied air energy storage system that indirectly utilizes the cold energy of LNG. For example... Figure 1 As shown, the liquefied air energy storage system includes: an air circulation system, a water circulation system, a nitrogen cold storage circulation system, and an ethylene glycol solution circulation system.

[0035] The air circulation system is the main circulation system, running throughout the entire liquefied air energy storage system. It is used for air pretreatment, pressurization, liquefaction, and expansion for power generation. The air circulation system includes an energy storage phase and an energy release phase; pretreatment, pressurization, and liquefaction belong to the energy storage phase, while expansion for power generation belongs to the energy release phase.

[0036] The water circulation system employs heat and cold storage methods to absorb interstage heat from the air in the air circulation system during the pretreatment and pressurization processes, and releases this absorbed interstage heat during the air expansion and power generation process. In other words, the water circulation system includes both an energy storage stage and an energy release stage. The heat absorption during the pretreatment and pressurization processes of the air circulation system constitutes the energy storage stage, while the heat release during the expansion and power generation process constitutes the energy release stage.

[0037] The nitrogen cold storage cycle system is used to exchange heat with the LNG flowing within the LNG supply pipeline 45 to absorb and store the LNG's cold energy. It also releases the stored LNG's cold energy into the liquefaction process of the air circulation system, liquefying the air within it. In other words, the nitrogen cold storage cycle system includes both energy storage and energy release phases. The LNG's cold energy is stored using nitrogen circulation, and the stored cold energy is then transferred to the air circulation system via nitrogen, achieving indirect utilization of the high-grade cold energy of the LNG.

[0038] The ethylene glycol solution circulation system is connected to the nitrogen cold storage circulation system to absorb the cold energy of LNG stored in the nitrogen cold storage circulation system, thereby cooling the ethylene glycol solution in the ethylene glycol solution circulation system. In other words, the cold energy stored in the nitrogen cold storage circulation system is then transferred to the ethylene glycol solution loop via nitrogen to cool the ethylene glycol solution. The ethylene glycol solution circulation system also absorbs the interstage waste heat of air in the air circulation system during the pretreatment and pressurization processes; that is, the ethylene glycol solution circulation system assists the water circulation system in cooling the air in the air circulation system during the pretreatment and pressurization processes.

[0039] The liquefied air energy storage system for indirect utilization of LNG cold energy in this invention uses inactive gases such as nitrogen as an intermediate medium to transfer energy, thus achieving indirect utilization of LNG cold energy. This avoids contact between air and LNG, significantly reducing the possibility of fluid leakage during indirect heat exchange and safety accidents in locations involving highly hazardous media, such as receiving stations. It enables safe coupling of LNG cold energy and the liquefied air energy storage system, simultaneously meeting the operational requirements of LNG vaporization to above 0°C for pipeline network integration and air compression and cooling to a liquid state for storage. Furthermore, it regulates the power load during energy storage and release, reducing the burden on the power grid. The "shallow" coupling method of LNG makes the liquefied air energy storage system more coordinated and controllable, ensuring safe, coordinated, flexible, and full utilization of energy.

[0040] In some embodiments, the air circulation system includes a pretreatment unit, a pressurization unit, a liquefaction storage unit, and an expansion power generation unit connected sequentially along the air flow direction. The pretreatment unit compresses, cools, and filters the air, purifying it through pressure swing adsorption (PSA). The pressurization unit compresses and cools the filtered and purified air, increasing its pressure. The liquefaction storage system liquefies and stores the compressed and cooled air, reducing the high-pressure air to a low temperature and throttling it into a liquid state, which is then separated and stored. The expansion power generation unit generates electricity using the liquid air stored in the liquefaction storage system, by pumping out the liquid air, heating and vaporizing it, and then expanding it to generate electricity. This achieves the energy storage and release process of the air circulation system.

[0041] Furthermore, such as Figure 1As shown, the pretreatment unit includes a purification device 4 and multiple sets of compression cooling units connected sequentially along the airflow direction. Each compression cooling unit includes a compressor unit 1, a water cooler 2, and an ethylene glycol solution final cooler 3, all connected sequentially along the airflow direction. Air flows through the hot fluid side of the water cooler 2 and the ethylene glycol solution final cooler 3. Water from the water circulation system flows through the cold fluid side of the water cooler 2, and ethylene glycol solution from the ethylene glycol solution circulation system flows through the cold fluid side of the ethylene glycol solution final cooler 3. The outlet of the downstream ethylene glycol solution final cooler 3 (hot fluid side) is connected to the inlet of the purification device 4. Water and ethylene glycol solution are used as the medium for absorbing heat between the compression and boosting stages. The heat absorbed by the water is released for expansion power generation, and the heat absorbed by the ethylene glycol solution is released in the indirect LNG gasification stage, achieving full matching and utilization of heat and cold, thus improving system efficiency. The closed-loop circulation and clean, single medium reduce the requirements for equipment materials and lower investment costs.

[0042] It is understandable that both the water cooler 2 and the glycol solution final cooler 3 are heat exchangers and can employ the same or similar structures. The main difference lies in the different flowing media on their cold fluid sides. These two different flowing media correspond to different heat exchange temperature ranges. The water cooler 2 uses pressurized water, which can absorb heat from the relatively high-temperature air. This absorbed heat can be used to heat the air to a high temperature during power generation in the expansion generator unit of the air circulation system. The glycol solution final cooler 3 uses a solution of glycol (or other fluids) with a minimum temperature below 0°C, increasing the temperature difference between the two fluids. In this way, the heat of the compressed air can be fully recovered, thereby achieving stepped cooling of the air in the air circulation system.

[0043] In this invention, upstream and downstream refer to the direction of fluid flow, with the upstream being closer to the source and the flow gradually moving downstream.

[0044] like Figure 1 As shown, the pressurization unit includes a first pressurizer unit 5, a second pressurizer unit 6, a pressurizer cooler 7, and a pressurizer terminal cooler 8. The inlet of the first pressurizer unit 5 is connected to the outlet of the purification device 4. The outlet of the first pressurizer unit 5 is connected to the hot fluid side inlet of the pressurizer cooler 7. The hot fluid side outlet of the pressurizer cooler 7 is connected to the hot fluid side inlet of the pressurizer terminal cooler 8. The hot fluid side outlet of the pressurizer terminal cooler 8 is connected to the inlet of the second pressurizer unit 6. The cold fluid side of the pressurizer cooler 7 is connected in series with the cold water pipeline 27 of the water circulation system (the cold water pipeline 27 will be described below). The cold fluid side of the pressurizer terminal cooler 8 is connected in series with the liquid delivery pipeline 34 of the ethylene glycol solution circulation system (the liquid delivery pipeline 34 will be described below).

[0045] Continue to combine Figure 1The liquefaction storage unit includes a cold box 9, a hydraulic turbine 10, a gas-liquid separator 11, and a liquid air storage tank 12. The cold box 9 has a first cold fluid side 13 and a first hot fluid side 16. The first cold fluid side 13 is connected in series in the nitrogen release circuit 38 of the nitrogen cold storage cycle system. The inlet of the first hot fluid side 16 is connected to the outlet of the booster unit of the air circulation system, that is, the inlet of the first hot fluid side 16 is connected to the outlet of the second booster unit 6. The outlet of the first hot fluid side 16 is connected to the inlet of the hydraulic turbine 10, the outlet of the hydraulic turbine 10 is connected to the gas-liquid separator 11, and the liquid outlet of the gas-liquid separator 11 is connected to the liquid air storage tank 12. In this way, the nitrogen cold storage cycle system releases the stored LNG cold energy for air liquefaction, storing the LNG cold energy in the liquefied air.

[0046] A JT valve 19 (throttling valve) is installed on the pipeline between the outlet of the hydraulic turbine 10 and the inlet of the gas-liquid separator 11. A pressurized liquid air storage tank 12 is used to store the liquid air. The air, after expansion through the JT valve 19, is pressurized and balanced by the air liquefaction conversion curve, resulting in an increased liquefaction rate. More liquid air participates in the subsequent expansion and power generation, improving system efficiency. Furthermore, the pressurized return air increases the inlet pressure of the booster unit, reducing the pressure ratio required for boosting, decreasing power consumption, and further improving system efficiency.

[0047] Furthermore, the liquefaction storage unit also includes an expander 18. The cold box 9 also has a second cold fluid side 14 and a second hot fluid side 17. The inlet of the second cold fluid side 14 is connected to the outlet of the expander 18 and the gas outlet of the gas-liquid separator 11, respectively. The outlet of the second cold fluid side 14 is connected to the pipeline between the pretreatment unit and the pressurization unit of the air circulation system (that is, the outlet of the second cold fluid side 14 is connected to the inlet of the first pressurization unit 5). The inlet of the second hot fluid side 17 is connected to the outlet of the pressurization unit of the air circulation system (that is, the inlet of the second hot fluid side 17 is connected to the outlet of the second pressurization unit 6). The outlet of the second hot fluid side 17 is connected to the inlet of the expander 18. The air circulation system has a bypass in the liquefaction energy storage unit (the second hot fluid side 17 is equivalent to the bypass), so that the air pressurized by the pressurization unit is divided into two streams before entering the cold box 9. The air flows through the first hot fluid side 16 and the second hot fluid side 17 of the cold box 9, and is cooled to different states in the cold box 9. The air flowing through the first hot fluid side 16 is cooled into liquid, and the air flowing through the second hot fluid side 17 is cooled into a low-temperature gaseous state. The low-temperature gaseous air is further cooled after being expanded by the expander 18, and then mixed with the gas phase coming out of the gas outlet of the gas-liquid separator 11 and returned to the cold box 9. In the cold box 9, sufficient high-quality cooling capacity is provided for the air in the first hot fluid side 16 and the second hot fluid side 17 to facilitate the air liquefaction process.

[0048] The liquefaction process return gas from the air circulation system's liquefaction storage unit (including the gas phase from the gas-liquid separator 11 and the gas phase from the outlet of the expander 18) is not directly discharged from the system but instead mixes with the air processed by the pretreatment unit. The main reasons are: First, the liquid air storage tank 12 is a pressure tank, ensuring that the gas phase separated by the gas-liquid separator 11 is pressurized, making the pressure of the return gas comparable to the pressure of the air processed by the pretreatment unit, thus making the mixing of the two gases feasible; Second, the return gas is clean air (free of CO2 and water) and does not require further purification. It can directly enter the pressurization and liquefaction process, reducing the gas flow rate in the pressurization process before purification, reducing the power consumption of compressor unit 1, and helping to improve system efficiency; thirdly, it can balance the heat of interstage cooling (heat storage process) of the compressor in the energy storage process (including pretreatment, pressurization and liquefaction) and the heat of heating before the expansion power generation stage in the energy release process. Under the condition of keeping the power generation power unchanged, it can reduce the compressed air flow rate before purification, reduce the increase of compressed air temperature before purification, and avoid the increase of heat stored in water and ethylene glycol solution, which cannot be completely absorbed at the energy release point, resulting in energy loss and equipment damage.

[0049] The air on the first hot fluid side 16 and the air on the second hot fluid side 17 can be cooled to different states and temperatures. This can be achieved through the structural design of the cold box 9. For example, the lengths of the first hot fluid side 16 and the second hot fluid side 17 within the cold box 9 can be designed to be different. A longer heat exchange channel absorbs more cooling energy and is cooled to a lower temperature, while a shorter heat exchange channel absorbs less cooling energy and is cooled to a lower temperature. Of course, other design methods can also be used, such as different arrangements of the first hot fluid side 16 and the second hot fluid side 17.

[0050] In some embodiments, such as Figure 1 As shown, the liquefied air energy storage system also includes a liquid air cold storage circulation system, which has an air release circuit 43 and an air storage circuit 44. The cold box 9 also has a third cold fluid side 15, which is connected in series with the air release circuit 43 of the liquid air cold storage circulation system. By setting up the liquid air cold storage circulation system, the cold energy of the liquid air stored in the liquefied air energy storage unit of the air circulation system can be absorbed, and the absorbed cold energy can be used for air liquefaction within the cold box 9.

[0051] In some embodiments, continue to combine Figure 1The expansion power generation unit includes a booster pump 20, an evaporator 21, multiple air heat exchangers 22, and multiple expansion generator sets 23. The number of air heat exchangers 22 and expansion generator sets 23 is the same, and one air heat exchanger 22 is installed upstream of each expansion generator set 23. The inlet of the booster pump 20 is connected to the outlet of the liquid air storage tank 12, and the outlet of the booster pump 20 is connected to the cold fluid side inlet of the evaporator 21. The cold fluid side outlet of the evaporator 21 is connected to the cold fluid side inlet of the upstream air heat exchanger 22. The hot fluid side of the evaporator 21 is connected in series in the air storage loop 44 of the liquid air cold storage circulation system. The cold fluid side outlet of each air heat exchanger 22 is connected to the inlet of an expansion generator set 23 located downstream and adjacent to it, and the hot fluid side of the air heat exchanger 22 is connected to the hot water pipeline 26 of the water circulation system. The air in the liquid air cold storage circulation system absorbs the cold energy from the liquid air in the liquid air storage tank 12, causing the liquefied air in the air circulation system to vaporize and enter the expansion power generation unit for expansion power generation. The cold energy absorbed by the air in the liquid air cold storage circulation system can enter the cold box 9 for the liquefaction of the air in the air circulation system.

[0052] like Figure 1 As shown, the water circulation system includes a hot water storage tank 24, a cold water storage tank 25, a hot water pipeline 26, and a cold water pipeline 27. The cold fluid side of the water cooler 2 is connected in series with the cold water pipeline 27, and one end of the cold water pipeline 27 is connected to the cold water outlet of the cold water storage tank 25, while the other end of the cold water pipeline 27 is connected to the hot water inlet of the hot water storage tank 24. The hot fluid side of the multiple air heat exchangers 22 of the expansion power generation unit of the air circulation system is connected in series with the hot water pipeline 26, and one end of the hot water pipeline 26 is connected to the hot water outlet of the hot water storage tank 24, while the other end of the hot water pipeline 26 is connected to the cold water inlet of the cold water storage tank 25. Cold water is pumped out from the cold water storage tank 25 and distributed to various intercoolers (water cooler 2 and booster cooler 7) to cool the compressed hot air. The cold water is heated to become hot water and then flows into the hot water storage tank 24 for storage. During the expansion power generation process, the high-temperature water in the hot water storage tank 24 is pumped out and diverted to the air heat exchanger 22 to heat the air before expansion power generation.

[0053] Continue to combine Figure 1 The water circulation system also includes a regeneration gas heater 28. The inlet of the regeneration gas heater 28 on the cold fluid side is connected to the outlet of the downstream expansion generator set 23, and the outlet of the regeneration gas heater 28 on the cold fluid side is connected to the regeneration gas inlet of the purification device 4. The hot fluid side of the regeneration gas heater 28 is connected in series with the hot water pipeline 26. The clean air expanded at the end is heated by the hot water of the water circulation system in the regeneration gas heater 28 and used for purging and regeneration of the purification device 4 to remove impurities and restore the activity of the purification device 4.

[0054] like Figure 1As shown, the ethylene glycol solution circulation system includes an ethylene glycol solution tank 30, a buffer tank 31, and an ethylene glycol solution cooler 32. The hot fluid side of the ethylene glycol solution cooler 32 is connected in series with the return line 33 between the ethylene glycol solution tank 30 and the buffer tank 31, while the cold fluid side of the ethylene glycol solution cooler 32 is connected in series with the nitrogen release circuit 38 of the nitrogen storage circulation system. The ethylene glycol solution is diverted from the ethylene glycol solution tank 30 to the ethylene glycol solution final cooler 3 and the booster final cooler 8 for further cooling of the air, and then merges into the buffer tank 31. Under the action of a pump, it is transported to the ethylene glycol solution cooler 32, where it is reheated by the nitrogen in the nitrogen release circuit 38 of the nitrogen storage circulation system before returning to the ethylene glycol solution tank 30.

[0055] The ethylene glycol solution circulation system also includes a regeneration gas cooler 29. The cold fluid side of the regeneration gas cooler 29 is connected in series with the liquid delivery pipeline 34 between the ethylene glycol solution tank 30 and the buffer tank 31. The inlet of the hot fluid side of the regeneration gas cooler 29 is connected to the outlet of the downstream expansion generator set 23, and the outlet of the hot fluid side of the regeneration gas cooler 29 is connected to the regeneration gas inlet of the purification device 4. After the purification device 4 is regenerated using the clean gas expanded at the end of the expansion power generation process of the air circulation system, it uses the clean gas expanded at the end of the expansion power generation process of the air circulation system, which is cooled to a low temperature by the ethylene glycol aqueous solution, to enter the cooling packing of the purification device 4. This ensures the activity of the adsorption medium in the purification device 4, improves the purification quality and efficiency, and the semi-closed circulation and full utilization of cold and heat reduce additional investment costs.

[0056] like Figure 1 As shown, the nitrogen cold storage circulation system includes a first cold storage unit 35, a first nitrogen blower 36, and a second nitrogen blower 37. The cold storage inlet of the first cold storage unit 35 is connected to one end of the nitrogen cold storage circuit 39, the cold storage outlet of the first cold storage unit 35 is connected to the other end of the nitrogen cold storage circuit 39, the cold release outlet of the first cold storage unit 35 is connected to one end of the nitrogen cold release circuit 38, and the cold release inlet of the first cold storage unit 35 is connected to the other end of the nitrogen cold release circuit 38. The first nitrogen blower 36 is installed on the nitrogen cold release circuit 38, and the second nitrogen blower 37 is installed on the nitrogen cold storage circuit 39. The hot fluid side of the LNG heat exchanger 47 is also connected in series on the nitrogen cold storage circuit 39. The inlet of the cold fluid side of the LNG heat exchanger 47 is connected to the LNG supply pipeline 45, and the outlet of the cold fluid side of the LNG heat exchanger 47 is connected to the LNG pipeline 46. The first cold fluid side 13 of the cold box 9 is connected in series on the nitrogen cold release circuit 38.

[0057] The first cold storage unit 35 uses nitrogen as the circulating medium. First, the cold energy stored in the first cold storage unit 35 is released in the cold box 9 via the nitrogen release circuit 38 to liquefy the air, and then the ethylene glycol solution is cooled in the ethylene glycol solution cooler 32. After the heat exchange is completed, the circulating medium (nitrogen) is heated and then returns to the first cold storage unit 35 to store heat. The heat stored in the first cold storage unit 35 is released in the LNG heat exchanger 47 via the nitrogen cold storage circuit 39 to vaporize LNG, while absorbing the high-quality cold energy of LNG. In this way, the system can operate continuously and avoid the damage caused by frequent start-up and shutdown.

[0058] Continue to combine Figure 1 The liquid air cold storage circulation system includes a second cold storage unit 40, a first air blower 41, and a second air blower 42. The cold storage inlet of the second cold storage unit 40 is connected to one end of the air cold storage circuit 44, the cold storage outlet of the second cold storage unit 40 is connected to the other end of the air cold storage circuit 44, the cold release outlet of the second cold storage unit 40 is connected to one end of the air cold release circuit 43, and the cold release inlet of the second cold storage unit 40 is connected to the other end of the air cold release circuit 43. The first air blower 41 is installed on the air cold release circuit 43, and the second air blower 42 is installed on the air cold storage circuit 44.

[0059] The second cold accumulator 40 uses purified (carbon dioxide- and water-free) liquid air as the circulating medium. First, the cold energy stored in the second cold accumulator 40 is released in the cold box 9 via the air release circuit 43 to liquefy the air. After heat exchange, the circulating medium (liquid air) is heated and then returns to the second cold accumulator 40 to store heat. The heat stored in the second cold accumulator 40 is released in the evaporator 21 via the air storage circuit 44 to vaporize the liquid air, while absorbing the cold energy of the liquid air. This achieves continuous operation of the system and avoids damage caused by frequent start-up and shutdown.

[0060] The following is combined with Figure 1 The working principle of the liquefied air energy storage system that indirectly utilizes LNG cold energy according to an embodiment of the present invention will be explained as follows:

[0061] In the air circulation system (semi-closed circulation), the air undergoes energy storage and release processes. First, the air is compressed by compressor unit 1, and then cooled by water cooler 2 (interstage cooler) and ethylene glycol solution final cooler 3 before entering purification unit 4 (two units are configured, one for adsorbing and purifying the air, and the other for regeneration and impurity removal). The purified clean air mixes with the return air from the liquefaction process and enters the first booster unit 5 and the second booster unit 6 for pressurization. The interstage cooling between the two booster units is achieved by booster cooler 7 and booster final cooler 8. The pressurized air is then divided into two streams, entering the first hot fluid side 16 and the second hot fluid side 17 of the cold box 9 respectively. One stream of air entering the second hot fluid side 17 is cooled to a low-temperature gaseous state and enters the expander 18 for depressurization and cooling. The other stream of air entering the first hot fluid side 16 is liquefied and sent to the hydraulic turbine 10 and JT valve 19 for depressurization and cooling. The throttled gas-liquid mixture enters the gas-liquid separator 11. The separated gas mixes with the outlet gas of the expander 18 and enters the third cold fluid side 15 of the cold box 9 as a high-quality cold source. The separated liquid enters the pressurized liquid air storage tank 12 for storage, completing the liquefaction and energy storage part of the air. The liquid air is pressurized by the booster pump (cryogenic pump) 20 and sent to the evaporator 21 for vaporization. Then it enters the air heat exchanger 22 and the expander generator set 23 for alternating heating and expansion power generation, completing the energy release part. Part of the air from the final expansion stage is directly discharged into the atmosphere, and another part is first heated by the regeneration gas heater 28 and then enters the purification device 4 to regenerate the molecular sieve. Another part is cooled by the regeneration gas cooler 29 and then enters the purification device 4 to cool the molecular sieve, so that the purification adsorption of the purification device 4 is maintained at a high efficiency.

[0062] Nitrogen gas in the first cold storage unit 35 is sent to the LNG heat exchanger 47 by the second nitrogen blower 37 to extract the cold energy from the LNG, and then returns to the first cold storage unit 35 to transfer and store the low temperature. During cold release, the first nitrogen blower 36 circulates nitrogen gas, and the cold energy in the first cold storage unit 35 is carried by the nitrogen gas into the cold box 9 and the ethylene glycol solution cooler 32 for release. After being heated, it returns to the first cold storage unit 35 to store the higher temperature heat. Similarly, clean air in the second cold storage unit 40 is sent to the evaporator 21 by the second air blower 42 to extract the cold energy from the liquid air, and the cold energy is stored in the second cold storage unit 40. During cold release, the second air blower 42 circulates air to the cold box 9 and releases it to the air in the first hot fluid side 16 and the second hot fluid side 17. After being heated, it returns to the second cold storage unit 40 to store the higher temperature heat.

[0063] The liquid air energy storage system based on LNG cold energy utilization in this invention embodiment can utilize circulating nitrogen to transfer the cold energy of LNG, ensuring system safety and full utilization of cold energy. Employing two cold accumulators allows for the periodic storage and release of the cold energy from liquid air and LNG, meeting the system's peak-shaving and valley-filling alternating energy storage and release requirements. Using a closed-loop thermal storage cycle of water and ethylene glycol solutions improves the utilization rate of interstage compression heat and reduces system costs. Losses. By constructing a bypass loop, the source of high-grade cooling capacity is increased, effectively aiding air liquefaction and improving the overall system coordination and anti-interference capability. Using a pressurized liquid air storage tank 12 to store liquid air can improve the liquefaction rate, reduce power consumption and equipment investment during the pressurization stage, and even reduce the use of one compressor unit 1, significantly improving system efficiency and reducing costs. Employing a closed-loop thermal storage cycle of water and ethylene glycol solution, cascaded heat utilization, and conventional clean working fluid can improve system efficiency and reduce equipment and material costs.

[0064] The liquid air energy storage system that indirectly utilizes the cold energy of LNG in this invention can realize the transfer and conversion of energy in the forms of heat, cold, and electricity, and can save on LNG gasification costs, air liquefaction cooling costs, and peak electricity costs. While ensuring the safe and stable operation of the station, it significantly improves the overall energy utilization efficiency and achieves the dual goals of "gasification" and "liquefaction".

[0065] The above description is intended to be illustrative and not restrictive. Those skilled in the art can make variations, modifications, substitutions, and alterations to the above embodiments within the scope of this disclosure. Moreover, the above examples (or one or more of them) can be used in combination with each other, and these embodiments can be combined with each other in various combinations or arrangements.

Claims

1. A liquefied air energy storage system that indirectly utilizes the cold energy of LNG, characterized in that, include: Air circulation system, water circulation system, nitrogen cold storage circulation system and ethylene glycol solution circulation system; The air circulation system is used for air pretreatment, pressurization, liquefaction, and expansion for power generation. The water circulation system is used to absorb the interstage heat of the air in the air circulation system during the pretreatment and pressurization processes, and release the absorbed interstage heat in the expansion and power generation process of the air in the air circulation system. The nitrogen cold storage circulation system is used to exchange heat with the LNG flowing in the LNG supply pipeline in order to absorb and store the cold energy of the LNG; the nitrogen cold storage circulation system is also used to release the cold energy of the stored LNG in the liquefaction process of the air circulation system, so as to liquefy the air in the air circulation system. The ethylene glycol solution circulation system is connected to the nitrogen cold storage circulation system and is used to absorb the cold energy of LNG stored in the nitrogen cold storage circulation system so as to cool down the ethylene glycol solution in the ethylene glycol solution circulation system; the ethylene glycol solution circulation system is also used to absorb the interstage waste heat of air in the air circulation system during the pretreatment and pressurization processes. The air circulation system includes a pretreatment unit, a pressurization unit, a liquefaction storage unit, and an expansion power generation unit connected sequentially along the air flow direction. The pretreatment unit is used to compress, cool, and filter the air. The pressurization unit is used to compress and cool the filtered and purified air. The liquefaction storage system is used to liquefy and store the compressed and cooled air. The expansion power generation unit is used to generate electricity using the liquid air stored in the liquefaction storage system. The pretreatment unit includes a purification device and multiple sets of compressor cooling units, which are connected sequentially along the airflow direction. Each set of compressor cooling units includes a compressor unit, a water cooler, and an ethylene glycol solution final cooler, all connected sequentially along the airflow direction. Air flows through the hot fluid side of the water cooler and the ethylene glycol solution final cooler, water from the water circulation system flows through the cold fluid side of the water cooler, and ethylene glycol solution from the ethylene glycol solution circulation system flows through the cold fluid side of the ethylene glycol solution final cooler. The outlet of the hot fluid side of the downstream ethylene glycol solution final cooler in the multiple sets of compressor cooling units is connected to the inlet of the purification device. The liquefaction storage unit includes a cold box, a hydraulic turbine, a gas-liquid separator, and a liquid air storage tank. The cold box has a first cold fluid side and a first hot fluid side. The first cold fluid side is connected in series in the nitrogen release circuit of the nitrogen cold storage circulation system. The inlet of the first hot fluid side is connected to the outlet of the booster unit of the air circulation system, the outlet of the first hot fluid side is connected to the inlet of the hydraulic turbine, the outlet of the hydraulic turbine is connected to the gas-liquid separator, and the liquid outlet of the gas-liquid separator is connected to the liquid air storage tank. The liquefaction storage unit also includes an expander, and the cold box also has a second cold fluid side and a second hot fluid side. The inlet of the second cold fluid side is connected to the outlet of the expander and the gas outlet of the gas-liquid separator, respectively. The outlet of the second cold fluid side is connected to the pipeline between the pretreatment unit and the pressurization unit of the air circulation system. The inlet on the second hot fluid side is connected to the outlet of the booster unit of the air circulation system, and the outlet on the second hot fluid side is connected to the inlet of the expander. The ethylene glycol solution circulation system includes an ethylene glycol solution tank, a buffer tank, and an ethylene glycol solution cooler. The hot fluid side of the ethylene glycol solution cooler is connected in series with the return pipeline between the ethylene glycol solution tank and the buffer tank, and the cold fluid side of the ethylene glycol solution cooler is connected in series with the nitrogen release circuit of the nitrogen storage circulation system.

2. The liquefied air energy storage system for indirectly utilizing LNG cold energy according to claim 1, characterized in that, The liquefied air energy storage system also includes a liquid air cold storage circulation system, which has an air release circuit and an air cold storage circuit; The cold box also has a third cold fluid side, which is connected in series in the air release circuit of the liquid air cold storage circulation system.

3. The liquefied air energy storage system for indirectly utilizing LNG cold energy according to claim 2, characterized in that, The expansion power generation unit includes an evaporator, multiple air heat exchangers, and multiple expansion generator sets. The number of air heat exchangers and expansion generator sets is the same, and one air heat exchanger is installed upstream of each expansion generator set. The cold fluid side inlet of the evaporator is connected to the outlet of the liquid air storage tank, the cold fluid side outlet of the evaporator is connected to the cold fluid side inlet of the upstream air heat exchanger, and the hot fluid side of the evaporator is connected in series in the air cold storage loop of the liquid air cold storage circulation system; the cold fluid side outlet of the air heat exchanger is connected to the inlet of an expansion generator set located downstream and adjacent to it, and the hot fluid side of the air heat exchanger is connected to the hot water pipeline of the water circulation system.

4. The liquefied air energy storage system for indirectly utilizing LNG cold energy according to claim 3, characterized in that, The water circulation system includes a hot water storage tank, a cold water storage tank, a hot water pipeline, and a cold water pipeline; the cold fluid side of the water cooler is connected in series with the cold water pipeline, and one end of the cold water pipeline is connected to the cold water outlet of the cold water storage tank, and the other end of the cold water pipeline is connected to the hot water inlet of the hot water storage tank; the hot fluid side of multiple air heat exchangers of the expansion power generation unit of the air circulation system is connected in series with the hot water pipeline, and one end of the hot water pipeline is connected to the hot water outlet of the hot water storage tank, and the other end of the hot water pipeline is connected to the cold water inlet of the cold water storage tank.

5. The liquefied air energy storage system for indirectly utilizing LNG cold energy according to claim 4, characterized in that, The water circulation system also includes a regenerated gas heater. The inlet of the regenerated gas heater on the cold fluid side is connected to the outlet of the expansion generator set located at the downstream end. The outlet of the regenerated gas heater on the cold fluid side is connected to the regenerated gas inlet of the purification device. The hot fluid side of the regenerated gas heater is connected in series with the hot water pipeline.

6. The liquefied air energy storage system for indirectly utilizing LNG cold energy according to claim 5, characterized in that, The ethylene glycol solution circulation system also includes a regenerated gas cooler. The cold fluid side of the regenerated gas cooler is connected in series with the liquid delivery pipeline between the ethylene glycol solution tank and the buffer tank. The inlet of the hot fluid side of the regenerated gas cooler is connected to the outlet of the downstream expansion generator set, and the outlet of the hot fluid side of the regenerated gas cooler is connected to the regenerated gas inlet of the purification device.

7. The liquefied air energy storage system for indirectly utilizing LNG cold energy according to claim 1, characterized in that, The nitrogen cold storage circulation system includes a first cold storage unit, a first nitrogen blower, and a second nitrogen blower. The cold storage inlet of the first cold storage unit is connected to one end of the nitrogen cold storage circuit, and the cold storage outlet of the first cold storage unit is connected to the other end of the nitrogen cold storage circuit. The cold release outlet of the first cold storage unit is connected to one end of the nitrogen cold release circuit, and the cold release inlet of the first cold storage unit is connected to the other end of the nitrogen cold release circuit. The first nitrogen blower and the second nitrogen blower are located on the nitrogen cold storage circuit. The hot fluid side of an LNG heat exchanger is also connected in series on the nitrogen cold storage circuit. The inlet of the cold fluid side of the LNG heat exchanger is connected to the LNG supply pipeline, and the outlet of the cold fluid side of the LNG heat exchanger is connected to the LNG pipeline. The first cold fluid side of the cold box is connected in series on the nitrogen cold release circuit.

8. The liquefied air energy storage system for indirectly utilizing LNG cold energy according to claim 1, characterized in that, The liquid air cold storage circulation system includes a second cold storage unit, a first air blower, and a second air blower. The cold storage inlet of the second cold storage unit is connected to one end of the air cold storage circuit, and the cold storage outlet of the second cold storage unit is connected to the other end of the air cold storage circuit. The cold release outlet of the second cold storage unit is connected to one end of the air cold release circuit, and the cold release inlet of the second cold storage unit is connected to the other end of the air cold release circuit. The first air blower is located on the air cold release circuit, and the second air blower is located on the air cold storage circuit.

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