Flow adaptive type multi-temperature-level energy storage system and method based on LNG cold energy recovery

Abstract

The invention discloses a flow adaptive type multi-temperature-level energy storage system and method based on LNG cold energy recovery. The system comprises an LNG gasification module, a cold energy recovery and storage module and an electric compression refrigeration module. The LNG gasification module adopts a gasification mode of combining a multi-stage heat exchanger and a gasifier group, so that efficient gasification and cold energy release of LNG are realized; according to the cold energy recovery and storage system, the energy storage module serves as a core and is matched with the refrigeration house to form a cold energy storage and utilization channel, and the space-time limitation of cold energy utilization is broken through; and the electric compression refrigeration module and the cold energy recovery and storage module operate cooperatively to realize a cold supplementing function in a low ebb period. Through the collaborative design of the energy storage module and electric compression refrigeration, LNG flow fluctuation is flexibly adapted, the operation cost is reduced through low-price electricity cold supplement in the electricity consumption trough period, meanwhile, multi-temperature-level accurate energy storage is achieved through the pressure regulating valve, the beneficial effects of being high in cold energy utilization rate, good in operation economical efficiency, high in adaptability and the like are achieved, and the application range is wide. The system is suitable for cold energy resource utilization in multiple scenes such as LNG receiving stations and satellite stations.

Description

Technical Field

[0001] This invention relates to the field of liquefied natural gas (LNG) cold energy recovery and utilization technology, specifically to a flow-adaptive multi-temperature energy storage system and method based on LNG cold energy recovery. Background Technology

[0002] Liquefied natural gas (LNG), as a clean and efficient energy source, releases a large amount of high-grade cold energy during its gasification process. Its recovery and utilization is an important direction for energy conservation and emission reduction in the energy sector. With the continuous increase in the number and receiving capacity of LNG receiving terminals in my country, the demand for the resource utilization of LNG cold energy is becoming increasingly urgent. Currently, LNG cold energy recovery technology is mainly applied in scenarios such as power generation, liquefied air separation, and cryogenic cold storage. The core principle is to transfer the cold energy from LNG gasification to energy storage or consumption units through refrigerant circulation, achieving cascaded energy utilization and reducing cold energy waste and environmental impact.

[0003] Currently, LNG cold energy recovery and utilization technology still faces many practical bottlenecks in practical applications. The fixed layout of LNG receiving terminals and the concentrated timing of cold energy release make it difficult to overcome the spatial and temporal constraints of cold energy utilization, and it is impossible to achieve flexible allocation across regions and time periods. At the same time, the system lacks effective adaptive adjustment capabilities to fluctuations in LNG outflow. During peak periods, surplus cold energy leads to resource waste, while during off-peak periods, insufficient cold energy supply affects the continuity of cooling. In addition, LNG cold energy itself has a wide temperature range, but current processes generally suffer from problems such as excessive heat exchange temperature difference and insufficient cold energy recovery during cold energy recovery, resulting in a consistently low level of cold energy utilization and failing to fully realize the resource value of LNG cold energy.

[0004] In related technical fields, some improved solutions have emerged that focus on LNG cold energy recovery and integrate energy storage modules. Patent CN220669154U discloses an LNG cold energy recovery and storage system that uses a phase change storage skid to achieve long-distance cold energy transportation and solve the problem of cold energy spatial misalignment. However, it does not have a supplementary cooling module, which cannot guarantee the supply of cold energy during low flow periods. Furthermore, it lacks multi-temperature level control and cold energy surplus storage design, resulting in insufficient cold energy utilization and operational stability. Chinese invention patent CN117927858A discloses an LNG cold energy recovery and ice-making system that uses a cold storage tank to store cold energy and optimize the ice-making process. However, the cold energy is limited to use within the station and its surroundings and cannot be used across geographical areas. It also lacks flow fluctuation adaptation and supplementary cooling mechanisms, resulting in insufficient cold energy recovery over a wide temperature range. Summary of the Invention

[0005] To overcome at least one of the shortcomings and deficiencies of the existing technologies, this invention provides a flow-adaptive multi-temperature energy storage system based on LNG cold energy recovery. It aims to provide an LNG cold energy recovery and utilization solution with strong adaptability to operating conditions, high cold energy utilization rate, excellent operational economy, and the ability to overcome spatiotemporal constraints. This invention constructs a two-stage refrigerant circulation system, combining independent energy storage modules and an electric compression cooling device to form a collaborative mechanism of "cascaded cold energy recovery - cold energy storage - dynamic cooling supplementation." The operating mode is optimized, and differentiated control strategies are designed for LNG flow peaks and troughs. Simultaneously, a first pressure regulating valve is used to achieve multi-temperature energy storage. This solves the problems of spatiotemporal mismatch of cold energy, poor adaptability to flow fluctuations, and limited scenario coverage in traditional technologies, ensuring a continuous and stable supply of cold energy and significantly improving overall energy utilization efficiency and operational economic benefits.

[0006] To achieve the objectives of this invention, the present invention provides a flow-adaptive multi-temperature energy storage system based on LNG cold energy recovery, comprising an LNG vaporization module, a cold energy recovery and storage module, and an electric compression refrigeration module.

[0007] The LNG vaporization module includes a first vaporizer, an LNG storage tank, an LNG pump, a first heat exchanger, a second heat exchanger, and a second vaporizer. The output end of the LNG storage tank is connected to the input end of the LNG pump. The input end of the first vaporizer is connected in parallel with the tube-side input end of the first heat exchanger, and then connected to the output end of the LNG pump. The tube-side output end of the first heat exchanger is connected to the tube-side input end of the second heat exchanger, and the tube-side output end of the second heat exchanger is connected to the input end of the second vaporizer.

[0008] The cold energy recovery and storage module includes a third heat exchanger, a refrigerant storage tank, a refrigerant pump, an energy storage module, a cold storage, and a first pressure regulating valve. The shell-side output of the second heat exchanger, the shell-side output of the third heat exchanger, and the shell-side output of the fourth heat exchanger are connected in parallel and flow into the input of the refrigerant storage tank. The output of the refrigerant storage tank is connected to the input of the energy storage module and the input of the cold storage via the refrigerant pump. The output of the energy storage module and the output of the cold storage converge and are connected to the shell-side inputs of the second, third, and fourth heat exchangers via the first pressure regulating valve.

[0009] The electric compression refrigeration module includes a fourth heat exchanger, a throttle valve, a gas-liquid separator, a compressor, and a condenser. The output end of the gas-liquid separator, the compressor, the condenser, the throttle valve, the tube side of the fourth heat exchanger, and the input end of the gas-liquid separator are connected in sequence to form a circuit.

[0010] Furthermore, a first regulating valve and a second regulating valve are respectively installed between the branch where the first vaporizer and the first heat exchanger are located and the LNG storage tank to regulate and distribute the LNG flow rate and ensure the stability of LNG vaporization and external transmission. At the same time, a first shut-off valve is installed to control the on / off of the LNG cold energy recovery process.

[0011] Furthermore, the process system also includes a pressure regulator and a metering system. The output ends of the first vaporizer and the second vaporizer are both connected to the pressure regulator and the metering system. After the LNG vaporization and heating are regulated by pressure and the flow is counted, it enters the downstream pipeline network for supply.

[0012] Furthermore, the circulating refrigerant between the first heat exchanger and the third heat exchanger is ethane. The gaseous refrigerant ethane exchanges heat with LNG in the first heat exchanger to obtain cooling and liquefaction, and the liquid ethane enters the third heat exchanger to exchange heat with R32 for cooling and gasification.

[0013] Furthermore, the heat exchange medium in the second, third, and fourth heat exchangers is the same refrigerant R32. After being cooled in each heat exchanger, R32 flows into the refrigerant storage tank to supply cooling for the energy storage module and the cold storage.

[0014] Furthermore, a fifth regulating valve is provided between the first pressure regulating valve and the fourth heat exchanger to activate electric compression cooling when the LNG flow rate is low.

[0015] Furthermore, a seventh regulating valve and an eighth regulating valve are installed between the refrigerant storage tank and the energy storage module and the cold storage branch to achieve seamless switching of operating conditions. When the LNG flow rate is at its peak, the refrigerant flows into the two branches for cooling. When the LNG flow rate is at its low point, the refrigerant only flows through the energy storage module to prioritize energy storage needs.

[0016] Furthermore, the energy storage module uses a three-tube energy storage unit, which consists of three concentric tubes with diameters of 40-170-200 mm, namely, an outer tube, a middle tube, and an inner tube arranged coaxially. The phase change material is filled in the middle tube, and the heat exchange medium flows through the inner tube and the outer tube as a dual cold source.

[0017] Furthermore, the energy storage unit in the energy storage module is connected to the outside of the module through the upper quick connector and the side quick connector. At the same time, the energy storage unit tube bundle is fixed by the tube sheet, and the upper quick connector and the side quick connector are encapsulated and fixed in the outer insulation layer. The insulation layer plays a role in reducing the leakage of cold energy stored in the module and ensuring that the stored energy can be effectively utilized within a preset time.

[0018] Furthermore, a second pressure regulating valve is provided between the tube-side output end of the third heat exchanger and the shell-side input end of the first heat exchanger. The first and second pressure regulating valves are used to change the operating pressure of the secondary refrigerant R32 and the primary refrigerant ethane according to the temperature requirements of the energy storage module, thereby changing the gas-liquid phase change saturation temperature of the refrigerant, so that the main heat exchange temperature changes during refrigerant heat exchange, achieving the purpose of changing the energy storage temperature.

[0019] Furthermore, by adding a cold storage unit and a coupled electric compression system to the cold energy recovery and storage module, it is possible to effectively cope with LNG flow fluctuations and ensure reasonable distribution of cooling capacity.

[0020] This invention provides a flow-adaptive multi-temperature energy storage method based on LNG cold energy recovery, comprising the following steps:

[0021] S1. The LNG in the LNG storage tank enters the first heat exchanger via the LNG pump to exchange heat with the primary refrigerant. After vaporization and heating, it enters the second heat exchanger for further heating. Finally, after being regulated by the pressure regulator and metering system, it enters the downstream pipeline network.

[0022] S2. In the first heat exchanger, the primary refrigerant exchanges heat with LNG to obtain cooling, and then enters the third heat exchanger to exchange heat with the secondary refrigerant. The primary refrigerant heats up and returns to the first heat exchanger. In the second heat exchanger, LNG exchanges heat with the secondary refrigerant, and the secondary refrigerant is cooled.

[0023] S3. The cold energy recovery and storage module includes two operating conditions: peak LNG flow and off-peak LNG flow. When the LNG flow is at its peak, the electric compression refrigeration module does not need to be started. The fifth regulating valve and the sixth shut-off valve are closed. The secondary refrigerant is cooled by heat exchange and then flows into the refrigerant storage tank. It is then transported to the energy storage module and the cold storage to release cold energy. After heating up, it circulates for heat exchange. When the LNG flow is at its off-peak, the eighth regulating valve is closed, cutting off the refrigerant channel to the cold storage. The fifth regulating valve and the sixth shut-off valve are opened, and the electric compression refrigeration module is activated. The LNG flow is at its off-peak, which coincides with the electricity consumption off-peak. The compressor is driven by the low-cost electricity during the electricity consumption off-peak. The low-temperature refrigerant obtained by electric compression refrigeration exchanges heat with the secondary refrigerant in the fourth heat exchanger. After the secondary refrigerant is cooled by heat exchange, it flows into the refrigerant storage tank and is then transported to the energy storage module for recirculation and cooling.

[0024] Furthermore, in step S1, when the cold energy recovery and storage module malfunctions, the first shut-off valve is closed and the first regulating valve is opened to allow LNG to flow to the first vaporizer, ensuring stable LNG vaporization and external transmission.

[0025] Compared with the prior art, the present invention has the following advantages: 1. This invention, through the collaborative design of independent energy storage modules and cold storage, stores the cold energy released by LNG vaporization in phase change materials, breaking the time and space limitations of cold energy utilization, realizing flexible allocation of cold energy across regions and time periods, solving the contradiction between the waste of cold energy surplus and insufficient supply during peak demand periods in traditional technologies, and significantly improving the utilization rate of cold energy resources.

[0026] 2. This invention designs a differentiated operation mode for LNG flow peaks and off-peaks. During peak periods, it simultaneously supplies cooling to the energy storage module and cold storage. During off-peak periods, it shuts down the cold storage pipeline and activates the electric compression cooling system. With multiple sets of regulating valves, it achieves precise flow distribution, efficiently adapts to LNG flow fluctuations, and ensures the continuity of cold energy supply.

[0027] 3. This invention adjusts the operating pressure of the secondary refrigerant and the primary refrigerant by using the first pressure regulating valve and the second pressure regulating valve respectively, thereby changing their gas-liquid phase change saturation temperature and realizing multi-temperature energy storage and cooling. It can flexibly adapt to the differentiated cooling needs of different scenarios such as low-temperature cold storage and industrial refrigeration, breaking the limitation of single temperature level in traditional technology.

[0028] 4. This invention constructs a two-stage refrigerant circulation system. The first-stage refrigerant is adapted to the cryogenic temperature range of LNG to achieve cold energy capture, and the second-stage refrigerant recovers the excess cold energy after LNG vaporization, while completing the cold energy transfer and distribution. The two-stage heat exchange reduces the heat exchange temperature difference and reduces cold energy loss. In addition, the energy storage module adopts a three-tube energy storage unit, and the dual cold source heat exchange structure further improves the efficiency of cold energy storage and release.

[0029] 5. The electric compression refrigeration module and the cold energy recovery and storage module of the present invention share the same refrigerant, which improves the system coupling and heat exchange matching degree; the off-peak cooling supplementation strategy combined with peak-valley electricity pricing significantly reduces operating energy consumption costs; the fault redundancy design of the first vaporizer and multiple sets of shut-off valves ensures that LNG can be normally exported when the cold energy recovery and storage module fails, thereby improving the system's operational reliability and engineering practicality. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a flow-adaptive multi-temperature energy storage system based on LNG cold energy recovery, according to an embodiment of the present invention. Figure 2 This is a schematic diagram of LNG peak flow cold energy recovery according to an embodiment of the present invention; Figure 3 This is a schematic diagram of LNG flow off-peak cold energy recovery according to an embodiment of the present invention; Figure 4 This is a schematic diagram of an energy storage unit according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the internal structure of the energy storage module according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the thermal insulation structure of the energy storage module according to an embodiment of the present invention.

[0031] In the diagram: 1. First regulating valve; 2. First vaporizer; 3. LNG storage tank; 4. LNG pump; 5. First shut-off valve; 6. Second regulating valve; 7. First heat exchanger; 8. Second shut-off valve; 9. Second heat exchanger; 10. Third shut-off valve; 11. Fourth shut-off valve; 12. Second vaporizer; 13. Pressure regulator; 14. Metering system; 15. Third regulating valve; 16. Third heat exchanger; 17. Fourth regulating valve; 18. Fifth shut-off valve; 19. Fifth regulating valve; 20. Sixth shut-off valve; 21. Seventh shut-off valve; 22. Fourth heat exchanger; 23. Eighth shut-off valve. 24. Throttling valve; 25. Refrigerant storage tank; 26. Gas-liquid separator; 27. Ninth shut-off valve; 28. Compressor; 29. ​​Tenth shut-off valve; 30. Sixth regulating valve; 31. Condenser; 32. Refrigerant pump; 33. Seventh regulating valve; 34. Eleventh shut-off valve; 35. Energy storage module; 36. Twelfth shut-off valve; 37. Eighth regulating valve; 38. Cold storage; 39. First pressure regulating valve; 40. Second pressure regulating valve; 41. Energy storage unit; 42. Phase change cold storage material; 43. Tube sheet; 44. Top quick connector; 45. Side quick connector; 46. Insulation layer. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the following embodiments are only for explaining the invention and do not constitute any limitation on the scope of protection of this invention.

[0033] The ordinal numbers such as "first" and "second" used in the embodiments of this invention are only used to distinguish different technical features with the same or similar names in the description, and do not contain any implication or limitation regarding priority, hierarchy, or quantity. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, provided there are no logical contradictions or technical implementation obstacles, those skilled in the art can reasonably combine, substitute, or borrow the technical features described in the various embodiments of this invention. When such combination, substitution, or borrowing results in the technical solution being unachievable or creating contradictions, such combination should not be considered to be included within the scope of protection claimed by this invention.

[0034] Example 1 In a certain LNG regasification station, the gas supply was low from January to April, increased and stabilized from May to October, and then gradually declined after November. The peak gas consumption period was concentrated between 9:00 and 22:00, and the off-peak period was concentrated between 23:00 and 8:00. This example uses the peak gas consumption period as the benchmark for the operation process.

[0035] like Figure 1 , Figure 2 , Figure 3 As shown in the figure, this embodiment provides a flow-adaptive multi-temperature energy storage system based on LNG cold energy recovery, including an LNG vaporization module, a cold energy recovery and storage module, and an electric compression refrigeration module.

[0036] The LNG vaporization module includes a first vaporizer 2, an LNG storage tank 3, an LNG pump 4, a first heat exchanger 7, a second heat exchanger 9, and a second vaporizer 12. The heat exchange medium in the first heat exchanger 7 is ethane refrigerant, and the refrigerant used in the second heat exchanger 9 is R32. The output end of the LNG storage tank 3 is connected to the input end of the LNG pump 4. The input end of the first vaporizer 2 is connected in parallel with the tube-side input end of the first heat exchanger 7, and after the parallel connection, it is connected to the output end of the LNG pump 4. A first regulating valve 1 and a second regulating valve 6 are respectively installed on the two parallel branches to regulate and distribute the LNG flow and ensure the stability of LNG vaporization and external transmission. The second heat exchanger 9 and the second vaporizer 12 are sequentially installed on the parallel branch where the first heat exchanger 7 is located. A first shut-off valve 5 is installed between the output end of the LNG pump 4 and the second regulating valve 6. The working state is adjusted according to the LNG flow fluctuation and the operation of the cold energy recovery storage module. When the cold energy recovery storage module fails, the first shut-off valve 5 is closed and the first regulating valve 1 is opened to allow LNG to flow to the first vaporizer 2, ensuring the stability of LNG vaporization and external transmission.

[0037] The heat exchange medium in the second heat exchanger 9, the third heat exchanger 16, and the fourth heat exchanger 22 is the same refrigerant, preferably R32. Using the same refrigerant simplifies the system structure and reduces maintenance costs. A unified refrigerant reduces the need for specialized equipment such as refrigerant tanks, transfer pumps, and pipeline valves, eliminating the need for separate circulation systems for different refrigerants and significantly simplifying the overall system structure. It also reduces the costs of refrigerant procurement, storage, and replacement, as well as the complexity of equipment maintenance and troubleshooting. Using the same refrigerant ensures the accuracy of cascaded cold energy recovery: cascaded recovery of LNG cold energy is achieved through a two-stage refrigerant cycle. Ethane, as the primary refrigerant, captures the cold energy in the cryogenic temperature range of LNG, while R32, as the secondary refrigerant, completes the subsequent transfer and distribution of cold energy (the cooled R32 is used to supply cooling to energy storage module 35 and cold storage 38). The second, third, and fourth heat exchangers all serve as heat exchange carriers for the secondary refrigerant. Using R32 consistently ensures temperature consistency in the secondary refrigerant cycle, avoiding problems such as uncontrolled heat exchange temperature differences and increased cold energy loss due to different refrigerant types. Using the same refrigerant also improves system coupling. Sharing the same refrigerant allows for unobstructed circulation between modules, avoiding compatibility issues with heat exchange media and pipeline adaptation problems caused by different refrigerant types. This allows the cold energy recovery and storage module and the electric compression refrigeration module to form an organic whole, ensuring the continuity of cold energy transfer. In other embodiments, other refrigerants can be used depending on different operating conditions.

[0038] The cold energy recovery and storage module includes a third heat exchanger 16, a refrigerant storage tank 25, a refrigerant pump 32, an energy storage module 35, a cold storage 38, and a first pressure regulating valve 39. The refrigerant used in the third heat exchanger 16 is R32. The shell-side output terminals of the second heat exchanger 9, the third heat exchanger 16, and the fourth heat exchanger 22 are connected in parallel and flow into the input terminal of the refrigerant storage tank 25. A third shut-off valve 10, a fifth shut-off valve 18, and a sixth shut-off valve 20 are respectively installed on the three branches to ensure that the flow can be immediately cut off in case of a failure of any one of the heat exchangers, thus ensuring the safety and normal operation of the entire system. When the LNG flow is sufficient, the fourth heat exchanger 22 does not participate in providing cooling for the secondary refrigerant R32; therefore, the sixth shut-off valve 20 is closed at this time, cutting off the refrigerant passage for electric compression refrigeration. The refrigerant in the refrigerant storage tank 25 is drawn by the refrigerant pump 32, and its flow rate is regulated and distributed by the seventh regulating valve 33 and the eighth regulating valve 37, respectively flowing into the energy storage module 35 and the cold storage 38 to release cooling capacity. The output terminals of the energy storage module 35 and the cold storage 38 converge and are connected to the shell-side input terminals of the second heat exchanger 9, the third heat exchanger 16, and the fourth heat exchanger 22 respectively via the first pressure regulating valve 39. Similarly, the secondary refrigerant R32 after releasing cooling capacity does not flow into the fourth heat exchanger 22.

[0039] The electro-compression refrigeration module includes a fourth heat exchanger 22, a throttle valve 24, a gas-liquid separator 26, a compressor 28, and a condenser 31. The output end of the gas-liquid separator 26, the compressor 28, the condenser 31, the throttle valve 24, the tube side of the fourth heat exchanger 22, and the input end of the gas-liquid separator 26 are connected in sequence to form a loop. A shut-off valve is provided between every two devices, namely the ninth shut-off valve 27, the tenth shut-off valve 29, the eighth shut-off valve 23, and the seventh shut-off valve 21. This facilitates the disassembly and inspection of the equipment. In addition, if a module in the system malfunctions, the flow can be cut off in time through the shut-off valve to avoid safety accidents.

[0040] Among them, such as Figure 4 As shown, the energy storage unit 41 used in the energy storage module 35 is a three-tube energy storage unit, which includes three concentric tubes with diameters of 40-170-200 mm, defined as an outer tube, a middle tube, and an inner tube. The two walls of the middle tube are uniformly provided with eight fins with a length of 45 mm and a thickness of 1 mm. The phase change cold storage material 42 is selected as a sodium formate aqueous eutectic solution with a mass concentration of 17% and a eutectic temperature of -17.6 ℃, which is filled in the middle tube. The heat exchange medium flows through the inner tube and the outer tube as a dual cold source.

[0041] Among them, such as Figure 5 , 6 As shown, the inner volume of the energy storage module 35 is 2840 mm × 2330 mm × 2330 mm, and the distance between the outer walls of every two energy storage units 41 is 30 mm. A single energy storage module 35 can store up to 1525.55 MJ of cold energy. In this embodiment, the design is based on filling 12 energy storage modules 35 in 4 hours. The energy storage units 41 in the energy storage module 35 are connected to the outside of the module through the upper quick connector 44 and the side quick connector 45. At the same time, the tube bundle of the energy storage unit 41 is fixed by the tube sheet 43, and the upper quick connector 44 and the side quick connector 45 are encapsulated and fixed in the outer insulation layer 46.

[0042] This embodiment provides a flow-adaptive multi-temperature energy storage method based on LNG cold energy recovery, which can be implemented through the following steps: LNG from LNG storage tank 3 (S1) is pumped by LNG pump 4 at -162 ℃, 30 bar, and 9.4 t / h into the first heat exchanger 7. The LNG in the tube side exchanges heat with gaseous ethane at -35 ℃, 7.77 bar, and 15 t / h in the shell side. The gaseous ethane cools to -45 ℃ and liquefies before passing through the shell side into the third heat exchanger 16. The LNG in the first heat exchanger 7 vaporizes to -41 ℃ and then enters the second heat exchanger 9 for further cold energy recovery. In the second heat exchanger 9, the LNG exchanges heat with gaseous R32 at -17 ℃, 3.35 bar, and 1.03 t / h, raising its temperature to -24.6 ℃. It then passes through the second vaporizer 12 to be heated above 0 ℃, and after being regulated by the pressure regulator 13 and metering system 14, it enters the downstream pipeline network.

[0043] S2. In the shell side of the first heat exchanger 7, the gaseous refrigerant ethane is cooled and liquefied through heat exchange. After condensing to -45 ℃, it enters the third heat exchanger 16 to exchange heat with gaseous R32 at -17 ℃, 3.35 bar, and 17.3 t / h. The ethane vaporizes and heats up to -35 ℃ before returning to the first heat exchanger 7. The R32 is cooled to -30 ℃ and flows into the refrigerant storage tank 25. At the same time, the R32 in the second heat exchanger 9 also condenses to -30 ℃ and flows into the refrigerant storage tank 25 for use by downstream cooling modules.

[0044] S3. Liquid refrigerant R32 at -30 ℃ in refrigerant storage tank 25 is drawn by refrigerant pump 32 and distributed at a flow rate of 18.33 t / h through seventh regulating valve 33 and eighth regulating valve 37. It flows into energy storage module 35 and cold storage 38 respectively in a ratio of 1.95:1 for cooling. After heat exchange, R32 vaporizes to -17 ℃ and is distributed through third regulating valve 15 and fourth regulating valve 17. It flows into second heat exchanger 9 and third heat exchanger 16 respectively at the flow rates mentioned in S1 and S2 to continue to obtain cooling.

[0045] In this embodiment, the system recovers 6927.154 MJ of cold energy per hour, which can provide 1272 kW of cooling power to the energy storage module 35 and 652 kW of cooling power to the cold storage 38. The cold energy recovery efficiency is considerable and greatly alleviates the energy consumption pressure.

[0046] Example 2 This embodiment operates the system based on periods of low gas consumption, such as... Figure 3As shown in the figure, the flow-adaptive multi-temperature energy storage system based on LNG cold energy recovery provided in this embodiment includes three parts: LNG vaporization module, cold energy recovery and storage module, and electric compression refrigeration module. The LNG vaporization module includes a first vaporizer 2, an LNG storage tank 3, an LNG pump 4, a first heat exchanger 7, a second heat exchanger 9, and a second vaporizer 12. The specific connection method and component functions are the same as in Embodiment 1. The cold energy recovery and storage module includes a third heat exchanger 16, a refrigerant storage tank 25, a refrigerant pump 32, an energy storage module 35, a cold storage 38, and a first pressure regulating valve 39. In this embodiment, because the LNG flow rate is at a low point, the recoverable cold energy cannot meet the preset operating conditions of the energy storage module 35. Therefore, the eighth regulating valve 37 is completely closed to stop supplying cold energy to the cold storage 38. The electric compression refrigeration module includes a fourth heat exchanger 22, a throttle valve 24, a gas-liquid separator 26, a compressor 28, and a condenser 31. Because the cold energy recovery and storage module has insufficient cold energy, in this embodiment, the fifth regulating valve 19 and the sixth shut-off valve 20 will be opened to supplement the cold energy of the energy storage module 35.

[0047] This embodiment provides a flow-adaptive multi-temperature energy storage method based on LNG cold energy recovery, which can be implemented through the following steps: LNG from LNG storage tank 3 (S1) is pumped by LNG pump 4 at -162 ℃, 30 bar, and 5 t / h to the first heat exchanger 7. The LNG exchanges heat with gaseous ethane at -35 ℃, 7.77 bar, and 7.98 t / h in the tube side and shell side. The gaseous ethane cools to -45 ℃ and liquefies before entering the third heat exchanger 16. The LNG vaporizes to -41 ℃ and enters the second heat exchanger 9 for further cold energy recovery. In the second heat exchanger 9, the LNG exchanges heat with gaseous R32 at -17 ℃, 3.35 bar, and 0.55 t / h, raising its temperature to -24.6 ℃. It then passes through the second vaporizer 12 to be heated above 0 ℃, and after regulation by the pressure regulator 13 and metering system 14, it enters the downstream pipeline network.

[0048] S2. In the first heat exchanger 7, the gaseous refrigerant ethane is cooled and liquefied through heat exchange. After condensing to -45 ℃, it enters the third heat exchanger 16 to exchange heat with gaseous R32 at -17 ℃, 3.35 bar, and 9.2 t / h. The ethane vaporizes and heats up to -35 ℃ before returning to the first heat exchanger 7. The R32 cools down to -30 ℃ and flows into the refrigerant storage tank 25. At the same time, the R32 in the second heat exchanger 9 also condenses to -30 ℃ and flows into the refrigerant storage tank 25. At this time, due to insufficient LNG flow, the recoverable cooling capacity cannot meet the demand. Therefore, the electric compression refrigeration module is activated. Part of the secondary refrigerant R32 flows into the fourth heat exchanger 22, exchanges heat with the refrigerant produced by electric compression, and then flows into the refrigerant storage tank 25, maintaining the normal operating condition of the energy storage module 35.

[0049] S3. Liquid refrigerant R32 at -30 ℃ in refrigerant storage tank 25 is drawn by refrigerant pump 32 and flows only into energy storage module 35 for cooling. After heat exchange, R32 vaporizes to -17 ℃ and is regulated and distributed by third regulating valve 15, fourth regulating valve 17 and fifth regulating valve 19, flowing into second heat exchanger 9, third heat exchanger 16 and fourth heat exchanger 22 respectively to continue to obtain cooling.

[0050] In this embodiment, the refrigeration power provided by LNG cold energy recovery is 1023.54 kW, while the refrigeration power required by the energy storage module 35 under the preset operating conditions is 1272 kW. Therefore, the electric compression refrigeration module needs to be started to supplement the refrigeration power by 248.46 kW.

[0051] Example 3 This embodiment provides a flow-adaptive multi-temperature energy storage system based on LNG cold energy recovery, comprising three parts: an LNG vaporization module, a cold energy recovery and storage module, and an electro-compression refrigeration module. The LNG vaporization module includes a first vaporizer 2, an LNG storage tank 3, an LNG pump 4, a first heat exchanger 7, a second heat exchanger 9, and a second vaporizer 12. The cold energy recovery and storage module includes a third heat exchanger 16, a refrigerant storage tank 25, a refrigerant pump 32, an energy storage module 35, a cold storage 38, and a first pressure regulating valve 39. The electro-compression refrigeration module includes a fourth heat exchanger 22, a throttle valve 24, a gas-liquid separator 26, a compressor 28, and a condenser 31.

[0052] A second pressure regulating valve 40 is provided between the tube-side output end of the third heat exchanger 16 and the shell-side input end of the first heat exchanger 7. The output ends of the energy storage module 35 and the cold storage 38 are combined and then connected via the first pressure regulating valve 39 to the shell-side input ends of the second heat exchanger 9, the third heat exchanger 16, and the fourth heat exchanger 22, respectively.

[0053] In this embodiment, the first pressure regulating valve 39 and the second pressure regulating valve 40 are used to address the energy storage module 35 with different temperature requirements. The energy storage module 35 described in embodiments 1 and 2 is designed based on a solid-liquid phase change temperature of -17.6 ℃. When the required energy storage temperature is lower, such as when used as a cryogenic cold storage, the operating pressure of the circulating refrigerant can be reduced by adjusting the first pressure regulating valve 39 and the second pressure regulating valve 40, thereby reducing the refrigerant gas-liquid phase change temperature and changing the cold storage temperature. This achieves the function of the energy storage module 35 to address different temperature requirements. The specific pressure adjustment is made according to the required storage temperature.

[0054] The foregoing embodiments of the present invention address the problems of existing LNG cold energy utilization being limited by the location of the receiving station and the vaporization period, as well as poor adaptability to flow fluctuations. Through the coordinated design of energy storage modules and electric compression refrigeration, it flexibly adapts to LNG flow fluctuations, utilizes low-cost electricity during off-peak hours to supplement cooling and reduce operating costs, and achieves precise energy storage at multiple temperature levels through pressure regulating valves. It has the advantages of high cold energy utilization rate, good operating economy, and strong adaptability, and is suitable for cold energy resource utilization in multiple scenarios such as LNG receiving stations and satellite stations.

[0055] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A flow-adaptive multi-temperature energy storage system based on LNG cold energy recovery, characterized in that: It includes an LNG vaporization module, a cold energy recovery and storage module, and an electric compression refrigeration module; The LNG vaporization module includes a first vaporizer (2), an LNG storage tank (3), an LNG pump (4), a first heat exchanger (7), a second heat exchanger (9), and a second vaporizer (12). The input end of the first vaporizer (2) is connected in parallel with the tube-side input end of the first heat exchanger (7), and after being connected in parallel, it is connected to the output end of the LNG pump (4). The tube-side output end of the first heat exchanger (7) is connected to the tube-side input end of the second heat exchanger (9), and the tube-side output end of the second heat exchanger (9) is connected to the input end of the second vaporizer (12). The electric compression refrigeration module includes a fourth heat exchanger (22), a throttle valve (24), a gas-liquid separator (26), a compressor (28), and a condenser (31). The output end of the gas-liquid separator (26), the compressor (28), the condenser (31), the throttle valve (24), the tube side of the fourth heat exchanger (22), and the input end of the gas-liquid separator (26) are connected in sequence to form a loop. The cold energy recovery and storage module includes a third heat exchanger (16), a refrigerant tank (25), a refrigerant pump (32), an energy storage module (35), a cold storage (38), and a first pressure regulating valve (39). The shell-side output of the second heat exchanger (9), the shell-side output of the third heat exchanger (16), and the shell-side output of the fourth heat exchanger (22) are connected in parallel and flow into the input of the refrigerant tank (25). The output of the refrigerant tank (25) is connected to the input of the energy storage module (35) and the input of the cold storage (38) via the refrigerant pump (32). The output of the energy storage module (35) and the output of the cold storage (38) converge and are connected to the shell-side input of the second heat exchanger (9), the shell-side input of the third heat exchanger (16), and the shell-side input of the fourth heat exchanger (22) via the first pressure regulating valve (39).

2. The flow-adaptive multi-temperature energy storage system based on LNG cold energy recovery according to claim 1, characterized in that, A first regulating valve (1) and a second regulating valve (6) are respectively installed between the parallel branch where the first vaporizer (2) and the first heat exchanger (7) are located and the LNG storage tank (3) to regulate and distribute the LNG flow rate; and a first shut-off valve (5) is installed in the parallel branch where the first heat exchanger (7) is located to control the on / off of the LNG cold energy recovery process.

3. The flow-adaptive multi-temperature energy storage system based on LNG cold energy recovery according to claim 1, characterized in that, It also includes a pressure regulator (13) and a metering system (14), the output of the first vaporizer (2) and the output of the second vaporizer (12) are both connected to the pressure regulator (13) and the metering system (14).

4. The flow-adaptive multi-temperature energy storage system based on LNG cold energy recovery according to claim 1, characterized in that, The circulating refrigerant between the first heat exchanger (7) and the third heat exchanger (16) is ethane.

5. A flow-adaptive multi-temperature energy storage system based on LNG cold energy recovery according to claim 1, characterized in that, The heat exchange medium in the second heat exchanger (9), the third heat exchanger (16), and the fourth heat exchanger (22) is the same refrigerant.

6. A flow-adaptive multi-temperature energy storage system based on LNG cold energy recovery according to claim 1, characterized in that, A fifth regulating valve (19) is provided between the first pressure regulating valve (39) and the fourth heat exchanger (22) for use in electric compression to supplement cooling when the LNG flow rate is low.

7. A flow-adaptive multi-temperature energy storage system based on LNG cold energy recovery according to claim 1, characterized in that, A seventh regulating valve (33) is provided on the branch between the refrigerant storage tank (25) and the energy storage module (35), and an eighth regulating valve (37) is provided on the branch between the refrigerant storage tank (25) and the cold storage (38) to achieve seamless switching of operating conditions.

8. A flow-adaptive multi-temperature energy storage system based on LNG cold energy recovery according to claim 1, characterized in that, The energy storage module (35) includes an energy storage unit (41), which is a three-tube energy storage unit, including an outer tube, a middle tube and an inner tube arranged coaxially. The phase change cold storage material (42) is filled in the middle tube, and the heat exchange medium flows through the inner tube and the outer tube as a dual cold source.

9. A flow-adaptive multi-temperature energy storage system based on LNG cold energy recovery according to any one of claims 1-8, characterized in that, A second pressure regulating valve (40) is provided between the tube side output end of the third heat exchanger (16) and the shell side input end of the first heat exchanger (7). The first pressure regulating valve (39) and the second pressure regulating valve (40) are used to change the operating pressure of the secondary refrigerant and the primary refrigerant ethane respectively according to the temperature requirements of the energy storage module, thereby changing the gas-liquid phase change saturation temperature of the refrigerant and causing the energy storage temperature to change.

10. A flow-adaptive multi-temperature energy storage method based on LNG cold energy recovery, characterized in that, The system according to any one of claims 1-9 is used, and the method includes the following steps: S1. The LNG in the LNG storage tank (3) enters the first heat exchanger (7) via the LNG pump (4) to exchange heat with the primary refrigerant. After vaporization and heating, it enters the second heat exchanger (9) for further heating. S2. In the first heat exchanger (7), the primary refrigerant exchanges heat with LNG to obtain cooling capacity, and then enters the third heat exchanger (16) to exchange heat with the secondary refrigerant. The primary refrigerant heats up and returns to the first heat exchanger (7); in the second heat exchanger (9), LNG exchanges heat with the secondary refrigerant, and the secondary refrigerant obtains cooling capacity. S3. The cold energy recovery and storage module includes two operating conditions: peak LNG flow and off-peak LNG flow. When the LNG flow is at its peak, there is no need to start the electric compression refrigeration module. The secondary refrigerant is cooled by heat exchange and then flows into the refrigerant storage tank (25), and then is transported to the energy storage module (35) and the cold storage (38) to release cold energy. After heating up, it is circulated for heat exchange. When the LNG flow is at its off-peak, the refrigerant channel of the cold storage (38) is cut off and the electric compression refrigeration module is activated. The LNG flow is at its off-peak, which coincides with the electricity consumption off-peak. The compressor (28) is driven by the low-priced electricity during the electricity consumption off-peak. The low-temperature refrigerant obtained by compression refrigeration and the secondary refrigerant exchange heat in the fourth heat exchanger (22). After the secondary refrigerant is cooled by heat exchange, it flows into the refrigerant storage tank (25) and then is transported to the energy storage module (35) for circulated cooling.

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