LNG cold energy recovery device

Abstract

The present invention relates to an LNG cold energy recovery device, which utilizes energy storage and cold power generation technologies, combined with a gas turbine extraction and cooling liquefaction process, to efficiently recover the cold energy of LNG and realize cold power generation with low-grade cold energy. It can absorb photovoltaic power, wind power, or be used for valley shifting and peak filling in power systems, has the ability to provide combined cold and electricity, and is expected to have significant social and economic benefits.

Description

Technical Field

[0001] The present invention relates to an LNG cold energy recovery device (LNG is liquid natural gas, the same below), and in particular to an LNG cold energy recovery device that adopts energy storage and cold power generation technology. Background Art

[0002] As an important basic raw material for modern industry, gas products have a wide range of applications. Due to this wide range of applications, gas production and supply are generally considered to be the basic infrastructure of the industrial investment environment, just like power and water supply.

[0003] To facilitate large-scale storage and transportation, gases are typically liquefied to improve transportation and storage efficiency. Upon use, liquefied gases such as LNG, liquid nitrogen, liquid oxygen, liquid carbon dioxide, and liquid ammonia are converted back to room-temperature gases. This process releases a significant amount of usable cold energy. Currently, much of this cold energy is not effectively utilized, wasting a significant amount of valuable resources.

[0004] Large-scale, integrated utilization of LNG cold energy has yet to be achieved. The main technical challenge is the temporal and spatial mismatch between LNG vaporization operations and downstream users' use of cold energy. This temporal mismatch stems from the fact that the load at receiving stations must fluctuate based on downstream demand, primarily experiencing seasonal and diurnal fluctuations. Meanwhile, the demand for cold energy from users fluctuates with production processes and market demand. These two patterns operate in completely different ways, resulting in a fundamental mismatch. The spatial mismatch stems from the fact that receiving stations only require facilities like docks, LNG storage tanks, and vaporization facilities, occupying a relatively small footprint. However, downstream users, whether operating air separation, light hydrocarbon separation, waste tire cryogenic pulverization, dry ice, or cold storage, occupy significant space. Even if located as close to the receiving station as possible, cold energy transportation distances typically exceed 1 km. This creates two problems: First, safety and load regulation factors dictate that LNG vaporization operations must be fully controlled by the receiving station, making it impossible to distribute operations to multiple, distant users. Second, transporting such low-temperature cold energy over long distances results in significant cold losses, degrading its quality, and reducing economic benefits. If these two problems cannot be solved, it will be impossible to fully utilize the cold energy of LNG on a large scale. Other liquefied gas products also have similar problems as LNG.

[0005] Therefore, the efficient recovery of cold energy and energy-quality matching utilization in the high-grade section of liquefied natural gas gasification and supply process are worthy of in-depth study and are of great significance. Summary of the Invention

[0006] The present invention provides an LNG cold energy recovery device, which realizes the cold energy recovery process as follows:

[0007] A high-pressure liquid storage tank 5 is provided: a typical LNG distribution station generally stores LNG at near-normal pressure, which is convenient for transportation, use, and management. When in use, the LNG at near-normal pressure is vaporized into gaseous natural gas at near-normal pressure and room temperature for external supply, and a cold power generator is used to recover the cold energy from the LNG vaporization process for cold power generation. In the present invention, a high-pressure liquid storage tank 5 is provided, and the LNG in the low-pressure liquid storage tank 3 is pressurized by a high-pressure pump 4 and enters the high-pressure liquid storage tank 5. For example, photovoltaic power, wind power, or off-peak electricity with a large price difference between peak and off-peak electricity are used to drive the high-pressure pump 4, thereby realizing high-pressure LNG energy storage.

[0008] When releasing energy:

[0009] The LNG in the low-pressure liquid storage tank 3 or the high-pressure liquid storage tank 5 enters the No. 1 condenser 8, which absorbs the cold released by the transported LNG and liquefies the Rankine cycle gaseous working medium 15 discharged from the No. 1 gas turbine 13. The Rankine cycle gaseous working medium 15 is then vaporized by the No. 1 circulating pump 9 and the No. 1 evaporator 10. The formed gaseous working medium enters the No. 1 gas turbine 13 to expand and perform work, driving the No. 1 working device 14 (such as the No. 1 generator 14) to perform work or generate electricity. The Rankine cycle gaseous working medium 15 discharged from the No. 1 gas turbine 13 enters the No. 1 condenser 8 again to absorb cold and be liquefied, thereby forming a No. 1 working medium Rankine cycle working circuit; the high-pressure gaseous natural gas 16 coming out of the No. 1 condenser 8 enters the natural gas turbine 17 to expand and perform work, driving the gas turbine working device 18 (such as the gas turbine generator 18 ) to perform work or generate electricity, the exhaust gas of the natural gas turbine 17, namely the low-temperature gaseous natural gas 19, enters the No. 2 condenser 21 to release the cold energy and then is discharged to become the discharged natural gas 22. The discharged natural gas 22 can be used as an indirect cold source for cold storage or air-conditioning systems, etc.; the No. 2 condenser 21 absorbs the cold energy released by the low-temperature gaseous natural gas 19, liquefies the No. 2 Rankine cycle gaseous working medium 27, sends it to the No. 2 circulation pump 23 for pressure increase, and then is vaporized by the No. 2 evaporator 24. The formed gaseous working medium enters the No. 2 gas turbine 25 to expand and perform work, driving the No. 2 working device 26 (such as the No. 2 generator 26) to perform work or generate electricity. The No. 2 Rankine cycle gaseous working medium 27 discharged from the No. 2 gas turbine 25 enters the No. 2 condenser 21 again to absorb the cold energy and be liquefied, thereby forming a No. 2 working medium Rankine cycle power circuit.

[0010] The first working fluid in the first Rankine cycle power circuit and the second working fluid in the second Rankine cycle power circuit have boiling points less than -10°C at standard atmospheric pressure, making them both low-boiling-point working fluids. For example, CN2013100293794, a steam Rankine-low-boiling-point working fluid Rankine combined cycle power generation device, and CN2013100293775, an extraction-type steam Rankine-low-boiling-point working fluid Rankine combined cycle power generation device, provide further descriptions of low-boiling-point working fluids. In applications, propane can be used as the working fluid in both the first and second Rankine cycle power generation circuits.

[0011] Preferably, the No. 1 power generator 14, the turbine power generator 18, and the No. 2 power generator 25 are configured to select corresponding generators for recovering and converting the expansion work of the corresponding turbines.

[0012] The heating medium, such as the vaporizing medium 11, of the aforementioned No. 1 evaporator 10 can be selected from room temperature air or seawater. The liquid No. 1 working medium is heated in the No. 1 evaporator 10, causing it to vaporize. The cooled vaporized working medium 11, i.e., the cooling medium 12, exiting the No. 1 evaporator 10, can be used as a cooling source to supply cold storage or a cold energy seawater desalination system. The heating medium, such as the heat medium 30, of the aforementioned No. 2 evaporator 24 can be selected from room temperature air or seawater. The liquid No. 2 working medium is heated in the No. 2 evaporator 24, causing it to vaporize. The cooled heat medium 30, i.e., the cooling medium 31, exiting the No. 2 evaporator 24, can be used as a cooling source to supply cold storage or a cold energy seawater desalination system.

[0013] A low-pressure vaporizer 28 is provided: one end of the low-pressure vaporizer 28 is connected to the bottom liquid side of the low-pressure liquid storage tank 3 through a pipeline, and the other end is connected to the top gas side of the low-pressure liquid storage tank 3 through a pipeline; when the low-pressure and low-temperature LNG stored in the low-pressure liquid storage tank 3 releases energy, the pressure in the low-pressure liquid storage tank 3 decreases, and the low-pressure and low-temperature LNG in the low-pressure vaporizer 28 is heated to be vaporized and enter the top gas space of the low-pressure liquid storage tank 3, thereby maintaining the pressure in the low-pressure liquid storage tank 3 stable.

[0014] A high-pressure vaporizer 29 is provided: one end of the high-pressure vaporizer 29 is connected to the bottom liquid side of the high-pressure liquid storage tank 5 through a pipeline, and the other end is connected to the top gas side of the high-pressure liquid storage tank 5 through a pipeline; when the high-pressure and low-temperature LNG stored in the high-pressure liquid storage tank 5 releases energy, the pressure in the high-pressure liquid storage tank 5 decreases, and the high-pressure and low-temperature LNG in the high-pressure vaporizer 29 is heated to vaporize and enter the top gas space of the high-pressure liquid storage tank 5, thereby maintaining the pressure in the high-pressure liquid storage tank 5 stable.

[0015] The heater in the low-pressure vaporizer 28 or the high-pressure vaporizer 29 is made of metal coils or finned tubes, etc. The heating medium is preferably air, and the heating medium should contain less water to avoid ice clogging of the heater due to improper operation.

[0016] A pressure regulating pump 7 is provided: when the high-pressure and low-temperature LNG stored in the high-pressure liquid storage tank 5 releases energy, the pressure in the high-pressure liquid storage tank 5 decreases, and the output pressure is adjusted by the pressure regulating pump 7 to maintain the pressure of the high-pressure gaseous natural gas 16 stable. The pressure regulating pump 7 adopts a variable frequency speed regulation operation mode to maintain the stability of the output pressure.

[0017] When the high-pressure, low-temperature LNG in the high-pressure liquid storage tank 5 increases in pressure due to heat absorption, a gas release expansion cooling circuit is provided: the gaseous natural gas discharged from the high-pressure liquid storage tank 5 is expanded and works in the natural gas turbine 17 to reduce the pressure and temperature, and then enters the subsequent equipment to recover the cooling capacity before being discharged.

[0018] Two or three of the No. 1 gas turbine 13, the natural gas turbine 17 and the No. 2 gas turbine 25 can be coaxially arranged and combined with corresponding power generators (such as generators).

[0019] The first power plant 14 , the turbine power plant 18 and the second power plant 26 are mechanical energy conversion devices (such as traction fans, compressors, hydraulic pumps, etc.) or generators.

[0020] When the No. 1 working fluid in the No. 1 Rankine cycle power circuit and the No. 2 working fluid in the No. 2 Rankine cycle power circuit use the same working fluid, the corresponding circulating pump, evaporator, gas turbine, and gas turbine power device can be combined, and the gaseous working fluid coming out of the gas turbine enters the No. 1 condenser 8 and the No. 2 condenser 21 for liquefaction respectively, and the resulting liquid working fluid merges and enters the circulating pump, evaporator, and gas turbine, and the resulting gaseous working fluid enters the No. 1 condenser 8 and the No. 2 condenser 21 for liquefaction respectively, forming a composite Rankine cycle power circuit.

[0021] A No. 1 recooling liquefier 38 is provided: the natural gas turbine exhaust gas 37 (low-pressure natural gas) extracted from the natural gas turbine 17 absorbs the cold energy of the LNG delivered from the high-pressure liquid storage tank 5 through the No. 1 recooling liquefier 38, and the generated low-pressure liquid natural gas 41 is delivered to the low-pressure liquid storage tank 3, and the LNG delivered from the high-pressure liquid storage tank 5 enters the No. 1 condenser 8 through the No. 1 recooling liquefier 38.

[0022] A No. 2 recooling liquefier 39 is provided: the natural gas turbine exhaust 37 extracted from the natural gas turbine 17 passes through the No. 2 recooling liquefier 39 to absorb the cold energy of the exhaust gas of the natural gas turbine 17, and produces low-pressure liquefied natural gas 40 which returns to the low-pressure liquid storage tank 3, and the exhaust gas of the natural gas turbine 17 passes through the No. 2 recooling liquefier 39 and enters the No. 2 condenser 21.

[0023] When the LNG in the low-pressure liquid storage tank 3 and the high-pressure liquid storage tank 5 is replaced with liquid nitrogen, liquid oxygen, liquid argon, liquid nitrogen-enriched air or liquid oxygen-enriched air (nitrogen-enriched air means that the proportion of nitrogen components in the nitrogen-enriched air is higher than that in air; oxygen-enriched air means that the proportion of oxygen components in the oxygen-enriched air is higher than that in air), the cold energy recovery device of the present invention is also applicable.

[0024] Equipment and its systems, pipelines, instruments, valves, cold preservation, bypass facilities with regulating functions, etc. not described in the present invention are matched with reference to or in accordance with mature technologies in well-known traditional processes.

[0025] The equipment and pipelines in the present invention adopt necessary heat recovery, cooling recovery, mass recovery and other measures.

[0026] Parts not mentioned in the present invention, such as safety accessories, automatic control, etc., are equipped with existing well-known technologies, that is, existing mature, reliable and reasonable technical measures are applied to this device.

[0027] 1. Compared with existing LNG cold energy power generation technology (the supporting generator set recovers cold energy for cold power generation, which is actually just low-grade utilization of cold energy), this invention uses high-pressure liquid storage tanks to achieve the advantages of energy storage. At the same time, it uses the natural gas turbine extraction and cooling liquefaction process to recover the high-grade cold energy released by LNG and store it in the liquefied natural gas extracted and cooled. The cooling power generator set is then used to achieve low-grade utilization of natural gas cold energy, achieving energy-quality matching of cold energy recovery. Compared with traditional cold energy recovery technology, this is a high-efficiency cold energy recovery process.

[0028] 2. Compared with existing technologies, the present invention can combine the abundant surplus cold energy in the LNG cold energy recovery device to optimize large cold storage, central air conditioning, or seawater desalination systems using cold sources, or use it as a cold source for centralized cooling systems to achieve combined cooling and power generation.

[0029] 3. Compared with existing technologies, it can effectively absorb photovoltaic and wind power or use them for "shifting peaks and shifting valleys" to optimize operations;

[0030] 4. The LNG cold energy recovery device of the present invention is also applicable to the cold energy recovery of liquid nitrogen, liquid oxygen, liquid argon, liquid nitrogen-enriched air or liquid oxygen-enriched air. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The present invention is a process flow diagram of an LNG cold energy recovery device.

[0032] Figure 1Middle: 3- low-pressure liquid storage tank, 4- high-pressure pump, 5- high-pressure liquid storage tank, 6- pressure relief valve, 7- pressure regulating pump, 8- No. 1 condenser, 9- No. 1 circulating pump, 10- No. 1 evaporator, 11- gasification medium, 12- cooling medium, 13- No. 1 gas turbine, 14- No. 1 power plant (such as No. 1 generator), 15- Rankine cycle gaseous working medium, 16- high-pressure gaseous natural gas, 17- natural gas turbine, 18- No. 3 gas turbine power plant (such as gas turbine generator), 19- low-temperature gaseous natural gas, 20- pressure relief pipeline, 21- No. 2 condenser, 22- exhaust natural gas, 23- No. 2 circulating pump, 24- No. 2 evaporator, 25- No. 2 gas turbine, 26- No. 2 power plant (such as No. 2 generator), 27- No. 2 Rankine cycle gaseous working medium, 28- low-pressure gasifier, 29- high-pressure gasifier, 30 - Heating medium, 31 - Refrigerant, 37 - Natural gas turbine extraction, 38 - Recooling liquefier No. 1, 39 - Recooling liquefier No. 2, 40 - Low-pressure liquefied natural gas, 41 - Low-pressure liquid natural gas. Low-pressure liquefied natural gas 40 and low-pressure liquid natural gas 41 are used for differentiation only and are essentially the same. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. Example 1

[0034] like Figure 1 As shown, an LNG cold energy recovery device implements the following cold energy recovery process:

[0035] A high-pressure liquid storage tank 5 is provided: the LNG in the low-pressure liquid storage tank 3 is pressurized by a high-pressure pump 4 and enters the high-pressure liquid storage tank 5. For example, photovoltaic power, wind power, or off-peak electricity with a large price difference between peak and off-peak electricity are used to drive the high-pressure pump 4 to achieve high-pressure LNG energy storage;

[0036] When releasing energy:

[0037] The LNG in the high-pressure liquid storage tank 5 enters the No. 1 condenser 8, which absorbs the cold released by the transported LNG, liquefies the Rankine cycle gaseous working medium 15 discharged from the No. 1 gas turbine 13, and then vaporizes it through the No. 1 circulation pump 9 and the No. 1 evaporator 10. The formed gaseous working medium enters the No. 1 gas turbine 13 to expand and do work, driving the No. 1 generator 14 to generate electricity. The Rankine cycle gaseous working medium 15 discharged from the No. 1 gas turbine 13 enters the No. 1 condenser 8 again to absorb cold and liquefy, thereby forming a No. 1 working medium Rankine cycle power circuit; the high-pressure gaseous natural gas 16 coming out of the No. 1 condenser 8 enters the natural gas turbine 17 to expand and do work, driving the gas turbine generator 18 to generate electricity, and the natural gas The exhaust gas from the gas turbine 17, i.e., the low-temperature gaseous natural gas 19, enters the No. 2 condenser 21 to release the cooling energy before being discharged as the discharged natural gas 22. The discharged natural gas 22 can be used as an indirect cooling source for cold storage or air-conditioning systems, etc. The No. 2 condenser 21 absorbs the cooling energy released by the low-temperature gaseous natural gas 19, liquefies the No. 2 Rankine cycle gaseous working fluid 27, sends it to the No. 2 circulation pump 23 for pressure increase, and then vaporizes it in the No. 2 evaporator 24. The resulting gaseous working fluid enters the No. 2 gas turbine 25 to expand and perform work, driving the No. 2 generator 26 to generate electricity. The No. 2 Rankine cycle gaseous working fluid 27 discharged from the No. 2 gas turbine 25 then enters the No. 2 condenser 21 to absorb the cooling energy and liquefy it, thus forming a No. 2 working fluid Rankine cycle power circuit.

[0038] The first working fluid in the first Rankine cycle power circuit and the second working fluid in the second Rankine cycle power circuit have boiling points less than -10°C at standard atmospheric pressure, making them both low-boiling-point working fluids. For example, CN2013100293794, a steam Rankine-low-boiling-point working fluid Rankine combined cycle power generation device, and CN2013100293775, an extraction-type steam Rankine-low-boiling-point working fluid Rankine combined cycle power generation device, provide further descriptions of low-boiling-point working fluids. In applications, propane can be used as the working fluid in both the first and second Rankine cycle power generation circuits.

[0039] Preferably, the No. 1 power generator 14, the turbine power generator 18, and the No. 2 power generator 25 are configured to select corresponding generators for recovering and converting the expansion work of the corresponding turbines.

[0040] The heating medium, such as the vaporizing medium 11, of the aforementioned No. 1 evaporator 10 can be selected from room temperature air or seawater. The liquid No. 1 working medium is heated in the No. 1 evaporator 10, causing it to vaporize. The cooled vaporized working medium 11, i.e., the cooling medium 12, exiting the No. 1 evaporator 10, can be used as a cooling source to supply cold storage or a cold energy seawater desalination system. The heating medium, such as the heat medium 30, of the aforementioned No. 2 evaporator 24 can be selected from room temperature air or seawater. The liquid No. 2 working medium is heated in the No. 2 evaporator 24, causing it to vaporize. The cooled heat medium 30, i.e., the cooling medium 31, exiting the No. 2 evaporator 24, can be used as a cooling source to supply cold storage or a cold energy seawater desalination system.

[0041] A low-pressure vaporizer 28 is provided: one end of the low-pressure vaporizer 28 is connected to the bottom liquid side of the low-pressure liquid storage tank 3 through a pipeline, and the other end is connected to the top gas side of the low-pressure liquid storage tank 3 through a pipeline; when the low-pressure and low-temperature LNG stored in the low-pressure liquid storage tank 3 releases energy, the pressure in the low-pressure liquid storage tank 3 decreases, and the low-pressure and low-temperature LNG in the low-pressure vaporizer 28 is heated to be vaporized and enter the top gas space of the low-pressure liquid storage tank 3, thereby maintaining the pressure in the low-pressure liquid storage tank 3 stable.

[0042] A high-pressure vaporizer 29 is provided: one end of the high-pressure vaporizer 29 is connected to the bottom liquid side of the high-pressure liquid storage tank 5 through a pipeline, and the other end is connected to the top gas side of the high-pressure liquid storage tank 5 through a pipeline; when the high-pressure and low-temperature LNG stored in the high-pressure liquid storage tank 5 releases energy, the pressure in the high-pressure liquid storage tank 5 decreases, and the high-pressure and low-temperature LNG in the high-pressure vaporizer 29 is heated to vaporize and enter the top gas space of the high-pressure liquid storage tank 5, thereby maintaining the pressure in the high-pressure liquid storage tank 5 stable.

[0043] The heater in the low-pressure vaporizer 28 or the high-pressure vaporizer 29 is made of metal coils or finned tubes, etc. The heating medium is preferably air, and the heating medium should contain less water to avoid ice clogging of the heater due to improper operation.

[0044] A pressure regulating pump 7 is provided: when the high-pressure and low-temperature LNG stored in the high-pressure liquid storage tank 5 releases energy, the pressure in the high-pressure liquid storage tank 5 decreases, and the output pressure is adjusted by the pressure regulating pump 7 to maintain the pressure of the high-pressure gaseous natural gas 16 stable. The pressure regulating pump 7 adopts a variable frequency speed regulation operation mode to maintain the stability of the output pressure.

[0045] When the high-pressure, low-temperature LNG in the high-pressure liquid storage tank 5 increases in pressure due to heat absorption, a gas release expansion cooling circuit is provided: the gaseous natural gas discharged from the high-pressure liquid storage tank 5 is expanded and works in the natural gas turbine 17 to reduce the pressure and temperature, and then enters the subsequent equipment to recover the cooling capacity before being discharged.

[0046] Two or three of the No. 1 gas turbine 13, the natural gas turbine 17 and the No. 2 gas turbine 25 can be coaxially arranged and combined with corresponding power generators (such as generators).

[0047] The first power plant 14 , the turbine power plant 18 and the second power plant 26 are mechanical energy conversion devices (such as traction fans, compressors, hydraulic pumps, etc.) or generators.

[0048] When the No. 1 working fluid in the No. 1 Rankine cycle power circuit and the No. 2 working fluid in the No. 2 Rankine cycle power circuit use the same working fluid, the corresponding circulating pump, evaporator, gas turbine, and gas turbine power device can be combined, and the gaseous working fluid coming out of the gas turbine enters the No. 1 condenser 8 and the No. 2 condenser 21 for liquefaction respectively, and the resulting liquid working fluid merges and enters the circulating pump, evaporator, and gas turbine, and the resulting gaseous working fluid enters the No. 1 condenser 8 and the No. 2 condenser 21 for liquefaction respectively, forming a composite Rankine cycle power circuit.

[0049] A No. 1 recooling liquefier 38 is provided: the natural gas turbine exhaust gas 37 (low-pressure natural gas) extracted from the natural gas turbine 17 absorbs the cold energy of the LNG delivered from the high-pressure liquid storage tank 5 through the No. 1 recooling liquefier 38, and the generated low-pressure liquid natural gas 41 is delivered to the low-pressure liquid storage tank 3, and the LNG delivered from the high-pressure liquid storage tank 5 enters the No. 1 condenser 8 through the No. 1 recooling liquefier 38.

[0050] A No. 2 recooling liquefier 39 is provided: the natural gas turbine exhaust 37 extracted from the natural gas turbine 17 passes through the No. 2 recooling liquefier 39 to absorb the cold energy of the exhaust gas of the natural gas turbine 17, and produces low-pressure liquefied natural gas 40 which returns to the low-pressure liquid storage tank 3, and the exhaust gas of the natural gas turbine 17 passes through the No. 2 recooling liquefier 39 and enters the No. 2 condenser 21.

[0051] When the LNG in the low-pressure liquid storage tank 3 and the high-pressure liquid storage tank 5 is replaced with liquid nitrogen, liquid oxygen, liquid argon, liquid nitrogen-enriched air or liquid oxygen-enriched air (nitrogen-enriched air means that the proportion of nitrogen components in the nitrogen-enriched air is higher than that in air; oxygen-enriched air means that the proportion of oxygen components in the oxygen-enriched air is higher than that in air), the cold energy recovery device of the present invention is also applicable.

[0052] Parts not mentioned in the present invention, such as safety accessories, instruments, meters, automatic control, etc., are equipped with existing well-known technologies, and existing mature, reliable and reasonable technical measures can be applied to this device.

[0053] Although the present invention has been disclosed above with reference to preferred embodiments, these are not intended to limit the present invention. Any person skilled in the art will readily be able to make various changes or modifications without departing from the spirit and scope of the present invention, and these modifications are also within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims of this application.

Claims

1. An LNG cold energy recovery device, characterized in that: A high-pressure liquid storage tank (5) is provided: the LNG in the low-pressure liquid storage tank (3) is pressurized by a high-pressure pump (4) and then enters the high-pressure liquid storage tank (5), thereby realizing high-pressure LNG energy storage; When releasing energy: The LNG in the high-pressure liquid storage tank (5) enters the No. 1 condenser (8), and the No. 1 condenser (8) absorbs the cold released by the transported LNG, liquefies the Rankine cycle gaseous working medium (15) discharged from the No. 1 gas turbine (13), and then vaporizes it through the No. 1 circulation pump (9) and the No. 1 evaporator (10). The formed gaseous working medium enters the No. 1 gas turbine (13) to expand and perform work, driving the No. 1 power generator (14) to perform work or generate electricity. The Rankine cycle gaseous working medium (15) discharged from the No. 1 gas turbine (13) enters the No. 1 condenser (8) to absorb cold and liquefy, thereby forming the No. 1 working medium Rankine cycle power circuit; the high-pressure gaseous natural gas (16) coming out of the No. 1 condenser (8) enters the natural gas turbine (17) to expand and perform work, driving the turbine The power generator (18) performs work or generates electricity, and the exhaust gas of the natural gas turbine (17), i.e., the low-temperature gaseous natural gas (19), enters the No. 2 condenser (21) to release the cold energy and then is discharged to become the exhaust natural gas (22); the No. 2 condenser (21) absorbs the cold energy released by the low-temperature gaseous natural gas (19), liquefies the No. 2 Rankine cycle gaseous working medium (27), sends it to the No. 2 circulation pump (23) for pressure increase, and then is gasified by the No. 2 evaporator (24). The formed gaseous working medium enters the No. 2 gas turbine (25) to expand and perform work, driving the No. 2 power generator (26) to perform work or generate electricity. The No. 2 Rankine cycle gaseous working medium (27) discharged from the No. 2 gas turbine (25) enters the No. 2 condenser (21) again to absorb the cold energy and be liquefied, thereby forming the No. 2 working medium Rankine cycle power circuit; A low-pressure vaporizer (28) is provided: one end of the low-pressure vaporizer (28) is connected to the bottom liquid side of the low-pressure liquid storage tank (3) through a pipeline, and the other end is connected to the top gas side of the low-pressure liquid storage tank (3) through a pipeline; when the low-pressure and low-temperature LNG stored in the low-pressure liquid storage tank (3) releases energy, the pressure in the low-pressure liquid storage tank (3) decreases, and the low-pressure and low-temperature LNG in the low-pressure vaporizer (28) is heated to vaporize and enter the top gas space of the low-pressure liquid storage tank (3), thereby maintaining the pressure in the low-pressure liquid storage tank (3) stable; A high-pressure vaporizer (29) is provided: one end of the high-pressure vaporizer (29) is connected to the bottom liquid side of the high-pressure liquid storage tank (5) through a pipeline, and the other end is connected to the top gas side of the high-pressure liquid storage tank (5) through a pipeline; when the high-pressure and low-temperature LNG stored in the high-pressure liquid storage tank (5) releases energy, the pressure in the high-pressure liquid storage tank (5) decreases, and the high-pressure and low-temperature LNG in the high-pressure vaporizer (29) is heated to be vaporized and enter the top gas space of the high-pressure liquid storage tank (5), thereby maintaining the pressure in the high-pressure liquid storage tank (5) stable.

2. The LNG cold energy recovery device according to claim 1, characterized in that: A pressure regulating pump (7) is provided: when the LNG stored in the low-pressure liquid storage tank (3) or the high-pressure liquid storage tank (5) releases energy, the pressure in the low-pressure liquid storage tank (3) or the high-pressure liquid storage tank (5) decreases, and the output pressure is adjusted by the pressure regulating pump (7) to maintain the pressure of the high-pressure gaseous natural gas (16) stable.

3. The LNG cold energy recovery device according to claim 1, characterized in that: Two or three of the No. 1 gas turbine (13), the natural gas turbine (17) and the No. 2 gas turbine (25) are arranged coaxially.

4. The LNG cold energy recovery device according to claim 1, characterized in that: When the No. 1 working medium in the No. 1 working medium Rankine cycle power circuit and the No. 2 working medium in the No. 2 working medium Rankine cycle power circuit use the same working medium, the corresponding circulating pump, evaporator, gas turbine, and gas turbine power generator can be combined, and the gaseous working medium coming out of the gas turbine enters the No. 1 condenser (8) and the No. 2 condenser (21) for liquefaction respectively, and the generated liquid working medium merges and enters the circulating pump, evaporator, and gas turbine, and the generated gaseous working medium enters the No. 1 condenser (8) and the No. 2 condenser (21) for liquefaction respectively, thereby forming a composite Rankine cycle power circuit.

5. The LNG cold energy recovery device according to claim 1, characterized in that: The discharged natural gas (22) after the cooling capacity is released by the second condenser (21) is used as an indirect cooling source.

6. The LNG cold energy recovery device according to claim 1, characterized in that: The gasified fluid (11) with reduced temperature coming out of the No. 1 evaporator (10) is the cooling medium (12), which serves as a cooling source to supply cooling to the outside.

7. The LNG cold energy recovery device according to claim 1, characterized in that: The heat medium (30) with reduced temperature coming out of the No. 2 evaporator (24), i.e., the refrigerant (31), serves as a cold source to supply cooling to the outside.

8. The LNG cold energy recovery device according to claim 1, characterized in that: A No. 1 recooling liquefier (38) is provided: the natural gas turbine exhaust gas (37) extracted from the natural gas turbine (17) absorbs the cold energy of the LNG delivered from the high-pressure liquid storage tank (5) through the No. 1 recooling liquefier (38), and the generated low-pressure liquid natural gas (41) is delivered to the low-pressure liquid storage tank (3), and the LNG delivered from the high-pressure liquid storage tank (5) enters the No. 1 condenser (8) through the No. 1 recooling liquefier (38).

9. The LNG cold energy recovery device according to claim 1, characterized in that: A No. 2 recooling liquefier (39) is provided: the natural gas turbine exhaust gas (37) extracted from the natural gas turbine (17) absorbs the cold energy of the exhaust gas of the natural gas turbine (17) through the No. 2 recooling liquefier (39), generates low-pressure liquefied natural gas (40) and returns to the low-pressure liquid storage tank (3); the exhaust gas of the natural gas turbine (17) enters the No. 2 condenser (21) through the No. 2 recooling liquefier (39).

10. The LNG cold energy recovery device according to claim 1, characterized in that: When the LNG in the low-pressure liquid storage tank (3) and the high-pressure liquid storage tank (5) in the LNG cold energy recovery device is replaced with liquid nitrogen, liquid oxygen, liquid argon, liquid nitrogen-enriched air or liquid oxygen-enriched air, the cold energy recovery device is also applicable.

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