LNG (Liquefied Natural Gas) cold energy recovery device

Abstract

The invention relates to an LNG (liquefied natural gas) cold energy recovery device, which efficiently recovers the cold energy of LNG by utilizing the energy storage and cold power generation technology and combining with a gas turbine exhaust cold-returning liquefaction process, realizes the cold power generation of low-grade cold energy, can absorb photovoltaic power and wind power or be used for valley shifting and peak filling of an electric power system, has combined cooling and power supply capacity, and has obvious expected 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 using 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. Because of the wide application coverage of gas products, the production and supply of gas is generally regarded as the infrastructure of the industrial investment environment, just like power supply and water supply, and is regarded as the "lifeline" of the national economy and listed as a public utility industry.

[0003] In order to facilitate large-scale storage and transportation, gases are usually liquefied and turned into liquefied gases to improve the efficiency of transportation and storage. When used, liquefied gases such as LNG, liquid nitrogen, liquid oxygen, liquid carbon dioxide, liquid ammonia, etc. are converted into room temperature gases. In this process, a large amount of available cold energy is released. At present, most of this cold energy has not been effectively utilized, wasting a lot of precious resources. Take LNG as an example: At present, most of the LNG cold energy utilization projects in the world are single-user, and there are very few multi-user integrated projects. So far, only about 20% of LNG cold energy has been utilized; the cold energy utilization accounts for only about 8% of the total LNG cold energy. In the current utilization technology, except for the temperature of air separation utilization at -145 to -75℃, the cold temperature of other users mostly does not match the temperature distribution of cold energy from LNG gasification, that is, "high quality and low utilization", and the process has a large loss of available energy. For example, the current cold energy power generation is actually just a low-grade utilization of cold energy: such as the commonly used organic Rankine cycle power generation unit with propane as the working fluid, which is used to recover the cold energy released by converting liquefied natural gas near normal pressure into gaseous natural gas near normal pressure and temperature. The condensing temperature of the condenser is generally controlled at about -45℃, and the evaporating temperature of the evaporator is controlled at about 15℃. Considering the heat transfer temperature difference of about 10℃, the high-grade cold energy of -55 to -145℃ is not recovered and used in a matching way with energy quality.

[0004] It is estimated that by the middle of this century, if China consumes 5000*108m 3 / a, of which imported LNG 1000*108m 3 / a (equivalent to Japan's current import volume), the available cold energy is converted into electricity of 257*108kWh / a, which is equivalent to the annual power generation of a 600*104kW power station. Therefore, how to make breakthroughs in the utilization of LNG cold energy in terms of technology, management mechanism, market operation, etc., strive to make the utilization rate of LNG cold energy reach more than 70%, and the effective energy utilization rate strive to reach 40%, ranking among the top in the world. While achieving huge energy saving and economic benefits, promote the rapid development of large-scale cold energy industry chains including air separation and coal oxygen-enriched gasification, in order to contribute to the comprehensive realization of circular economy and conservation economy in my country. At the same time, the rapid development and model transformation of China's economy determine the absolute necessity of large-scale utilization of LNG cold energy, and provide a huge market for cold energy users. The cold energy of large-scale LNG receiving stations should first target large-scale markets such as large air separation, coal gasification, and light hydrocarbon separation. The traditional cold energy industry also needs to be integrated and utilized under the circular economy model. It should be pointed out that in addition to large LNG receiving stations, China will also have hundreds of small LNG satellite gasification stations for tank container transportation, as well as high-pressure natural gas pipelines throughout the country that use the energy of pressure difference when distributing to medium and low-pressure pipelines of various end users, and obtain cold energy through expanders or gas wave refrigeration. These are all precious energy and wealth, and the total amount of cold energy is not less than that of large LNG receiving stations, and should be planned and fully utilized.

[0005] LNG cold energy has not yet been used on a large scale. The main technical problem is the asynchrony between LNG gasification operation and the use of cold energy by downstream users in time and space. The asynchrony in time is due to the fact that the load of the receiving station must change according to the downstream demand, mainly seasonal and diurnal fluctuations; while the demand for cold energy load by cold energy users changes with the production process and market demand. The two have completely different rules and are basically asynchronous. The asynchrony in space is due to the fact that the receiving station only needs to consider the dock, LNG storage tanks, gasification facilities, etc., and the area occupied is not large; however, the downstream users of cold energy utilization, whether air separation, light hydrocarbon separation, or low-temperature crushing of waste tires, dry ice, cold storage, etc., occupy a large area. Even if they are arranged as close to the receiving station as possible, the cold energy transportation distance will usually exceed 1km. This creates two problems: first, factors such as safety and load regulation determine that the LNG gasification operation must be absolutely controlled by the receiving station, and it is impossible to distribute it to long-distance and multiple cold energy users; second, such long-distance transportation of low-temperature cold energy will cause greater cold loss, cold energy degradation, and reduced economic benefits. If these two problems cannot be solved, the comprehensive and full use of large-scale LNG cold energy is impossible. Other liquefied gas products have similar problems as LNG.

[0006] Therefore, the efficient recovery of cold energy and energy-quality matching utilization in the high-grade section of the liquefied natural gas gasification and supply process are worthy of in-depth study and are of great significance. Summary of the invention

[0007] The present invention provides an LNG cold energy recovery device, and the LNG cold energy recovery device realizes the cold energy recovery process as follows:

[0008] A high-pressure liquid storage tank 5 is provided: a common LNG transmission and 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 gasified into gaseous natural gas at near normal pressure and temperature for external supply, and a cold power generator set is used to recover the cold energy in the LNG gasification 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 valley electricity with a large price difference between peak and valley electricity are used to drive the high-pressure pump 4 to achieve high-pressure LNG energy storage;

[0009] When releasing energy:

[0010] The LNG in the low-pressure liquid storage tank 3 or 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 do work, and drives the No. 1 working device 14 (such as the No. 1 generator 14) to do 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 liquefy, 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 do work, and drives the gas turbine working device 18 (such as the gas turbine generator 18 ) to do work or generate electricity, 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 and then is discharged to become the discharged natural gas 22, which can be used as an indirect cold source for cold storage or air-conditioning systems, etc.; the No. 2 condenser 21 absorbs the cold 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 pressurization, 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 do work, and drives the No. 2 working device 26 (such as the No. 2 generator 26) to do 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 cold and be liquefied, thereby forming a No. 2 working medium Rankine cycle work loop.

[0011] The first working fluid in the first Rankine cycle power circuit and the second working fluid in the second Rankine cycle power circuit have a boiling point of less than -10°C under standard atmospheric pressure, and are both low-boiling-point working fluids, such as CN2013100293794 steam Rankine-low-boiling-point working fluid Rankine combined cycle power generation device, CN2013100293775 extraction type steam Rankine-low-boiling-point working fluid Rankine combined cycle power generation device, etc., which provide further descriptions of low-boiling-point working fluids. In the application, propane can be used as the working fluid of the first and second Rankine cycle power generation circuits.

[0012] Preferably, the first power generator 14, the turbine power generator 18 and the second power generator 25 select corresponding generators for recovering and converting the expansion work of the corresponding turbines.

[0013] The heating medium of the No. 1 evaporator 10, such as the gasification medium 11, can be selected from air or seawater at room temperature. The liquid No. 1 working medium is heated in the No. 1 evaporator 10 to be gasified. The gasification medium 11 with a reduced temperature coming out of the No. 1 evaporator 10, i.e., the cooling medium 12, can be used as a cold source to supply cold to a cold storage or a cold energy seawater desalination system. The heating medium of the No. 2 evaporator 24, such as the heat medium 30, can be selected from air or seawater at room temperature. The liquid No. 2 working medium is heated in the No. 2 evaporator 24 to be gasified. The heat medium 30 with a reduced temperature coming out of the No. 2 evaporator 24, i.e., the cooling medium 31, can be used as a cold source to supply cold to a cold storage or a cold energy seawater desalination system.

[0014] 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.

[0015] 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.

[0016] 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 preferably contains less water to avoid ice clogging of the heater due to improper operation.

[0017] 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.

[0018] When the high-pressure and 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 by the natural gas turbine 17 to reduce the pressure and temperature, and enters the subsequent equipment to recover the cold before being discharged.

[0019] 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).

[0020] 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.

[0021] 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 generated liquid working fluid merges and enters the circulating pump, evaporator, and gas turbine, and the generated 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.

[0022] A No. 1 recooling liquefier 38 is provided: the natural gas turbine exhaust 37 (low-pressure natural gas) extracted from the natural gas turbine 17 absorbs the coldness 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.

[0023] A No. 2 recooling liquefier 39 is provided: the natural gas turbine exhaust 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, and the exhaust gas of the natural gas turbine 17 enters the No. 2 condenser 21 through the No. 2 recooling liquefier 39.

[0024] 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.

[0025] 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.

[0026] The equipment and pipelines in the present invention adopt necessary heat recovery, cooling recovery, quality recovery and other measures.

[0027] Parts not mentioned in the present invention, such as safety accessories, automatic control, etc., are matched with existing well-known technologies, that is, existing mature, reliable and reasonable technical measures are applied to this device.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1. Compared with the 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), the present invention adopts high-pressure liquid storage tanks to achieve the advantages of energy storage, and uses the natural gas turbine exhaust cooling liquefaction process to recover the high-grade cold energy released by LNG and store it in the liquefied natural gas after exhaust cooling, and then drives the cold power generator set to realize the low-grade utilization of natural gas cold energy, realizing the energy-quality matching of cold energy recovery. Compared with the traditional cold energy recovery technology, this is a high-efficiency cold energy recovery process;

[0030] 2. Compared with the prior art, the present invention can combine the characteristics of abundant surplus cold energy in the LNG cold energy recovery device, optimize with large cold storage, central air conditioning or the system using cold source for seawater desalination, or use it as the cold source of the centralized cooling system to realize the cogeneration of cold and electricity;

[0031] 3. Compared with existing technologies, it can effectively absorb photovoltaic and wind power or use them to “shift valleys and fill peaks” to optimize operation;

[0032] 4. The LNG cold energy recovery device of the present invention is also suitable for cold energy recovery of liquid nitrogen, liquid oxygen, liquid argon, liquid nitrogen-enriched air or liquid oxygen-enriched air. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a process flow diagram of an LNG cold energy recovery device.

[0034] 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 work device (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 work device (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 circulation pump, 24-No. 2 evaporator, 25-No. 2 gas turbine, 26-No. 2 power generator (such as No. 2 generator), 27-No. 2 Rankine cycle gaseous working medium, 28-low-pressure vaporizer, 29-high-pressure vaporizer, 30-heat medium, 31-refrigerant, 37-natural gas turbine extraction, 38-No. 1 recooling liquefier, 39-No. 2 recooling liquefier, 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 only for distinction and are essentially the same. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Embodiment 1:

[0037] like Figure 1 As shown, an LNG cold energy recovery device implements the cold energy recovery process as follows:

[0038] 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 valley electricity with a large price difference between peak and valley electricity are used to drive the high-pressure pump 4 to realize high-pressure LNG energy storage;

[0039] When releasing energy:

[0040] 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 work loop; 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 of the gas turbine 17, i.e., the low-temperature gaseous natural gas 19, enters the No. 2 condenser 21 to release the cold 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 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 pressurization, 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 do work, driving the No. 2 generator 26 to 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 cold and liquefy, thereby forming a No. 2 working medium Rankine cycle work loop.

[0041] The first working fluid in the first Rankine cycle power circuit and the second working fluid in the second Rankine cycle power circuit have a boiling point of less than -10°C under standard atmospheric pressure, and are both low-boiling-point working fluids, such as CN2013100293794 steam Rankine-low-boiling-point working fluid Rankine combined cycle power generation device, CN2013100293775 extraction type steam Rankine-low-boiling-point working fluid Rankine combined cycle power generation device, etc., which provide further descriptions of low-boiling-point working fluids. In the application, propane can be used as the working fluid of the first and second Rankine cycle power generation circuits.

[0042] Preferably, the first power generator 14, the turbine power generator 18 and the second power generator 25 select corresponding generators for recovering and converting the expansion work of the corresponding turbines.

[0043] The heating medium of the No. 1 evaporator 10, such as the gasification medium 11, can be selected from air or seawater at room temperature. The liquid No. 1 working medium is heated in the No. 1 evaporator 10 to be gasified. The gasification medium 11 with a reduced temperature coming out of the No. 1 evaporator 10, i.e., the cooling medium 12, can be used as a cold source to supply cold to a cold storage or a cold energy seawater desalination system. The heating medium of the No. 2 evaporator 24, such as the heat medium 30, can be selected from air or seawater at room temperature. The liquid No. 2 working medium is heated in the No. 2 evaporator 24 to be gasified. The heat medium 30 with a reduced temperature coming out of the No. 2 evaporator 24, i.e., the cooling medium 31, can be used as a cold source to supply cold to a cold storage or a cold energy seawater desalination system.

[0044] 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.

[0045] 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.

[0046] 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 preferably contains less water to avoid ice clogging of the heater due to improper operation.

[0047] 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.

[0048] When the high-pressure and 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 by the natural gas turbine 17 to reduce the pressure and temperature, and enters the subsequent equipment to recover the cold before being discharged.

[0049] 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).

[0050] 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.

[0051] 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 generated liquid working fluid merges and enters the circulating pump, evaporator, and gas turbine, and the generated 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.

[0052] A No. 1 recooling liquefier 38 is provided: the natural gas turbine exhaust 37 (low-pressure natural gas) extracted from the natural gas turbine 17 absorbs the coldness 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.

[0053] A No. 2 recooling liquefier 39 is provided: the natural gas turbine exhaust 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, and the exhaust gas of the natural gas turbine 17 enters the No. 2 condenser 21 through the No. 2 recooling liquefier 39.

[0054] 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.

[0055] 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.

[0056] Although the present invention has been disclosed as above with preferred embodiments, they are not intended to limit the present invention. Anyone familiar with the art can make various changes or modifications without departing from the spirit and scope of the present invention, which also belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the definition of 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 first condenser (8), and the first condenser (8) absorbs the cold released by the transported LNG, liquefies the Rankine cycle gaseous working medium (15) discharged from the first gas turbine (13), and then vaporizes it through the first circulation pump (9) and the first evaporator (10). The formed gaseous working medium enters the first gas turbine (13) to expand and perform work, driving the first work unit (14) to perform work or generate electricity. The Rankine cycle gaseous working medium (15) discharged from the first gas turbine (13) enters the first condenser (8) to absorb cold and liquefy, thereby forming a No. 1 working medium Rankine cycle work circuit; the high-pressure gaseous natural gas (16) coming out of the first condenser (8) enters the natural gas turbine (17) to expand and perform work, driving the turbine The work unit (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 second condenser (21) to release cold energy and then is discharged to become the exhaust natural gas (22); the second condenser (21) absorbs the cold energy released by the low-temperature gaseous natural gas (19), liquefies the second Rankine cycle gaseous working medium (27), sends it to the second circulation pump (23) for pressure increase, and then is gasified by the second evaporator (24). The formed gaseous working medium enters the second gas turbine (25) to expand and perform work, driving the second work unit (26) to perform work or generate electricity. The second Rankine cycle gaseous working medium (27) discharged from the second gas turbine (25) enters the second condenser (21) again to absorb cold energy and be liquefied, thereby forming a second working medium Rankine cycle work loop.

2. The LNG cold energy recovery device according to claim 1, characterized in that: 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; Alternatively, 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.

3. 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.

4. 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 in a coaxial manner.

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

6. The LNG cold energy recovery device according to claim 1, characterized in that: The exhaust natural gas (22) after the second condenser (21) releases the cold energy is used as an indirect cold source.

7. The LNG cold energy recovery device according to claim 1, characterized in that: The gasified fluid (11) with reduced temperature coming out of the first evaporator (10), i.e., the cooling medium (12), serves as a cooling source to supply cooling to the outside.

8. 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.

9. The LNG cold energy recovery device according to claim 1, characterized in that: A first 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 first recooling liquefier (38), and the generated low-pressure liquid natural gas (41) is delivered to the low-pressure liquid storage tank (3); the LNG delivered from the high-pressure liquid storage tank (5) enters the first condenser (8) through the first recooling liquefier (38).

10. The LNG cold energy recovery device according to claim 1, characterized in that: A second 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 second 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 second condenser (21) through the second recooling liquefier (39).

11. 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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