Hydrate separation system, device and method for low temperature storage tank pre-cooled mixed gas

Abstract

The application relates to a hydrate separation system, device and method for mixed gas after precooling of a low-temperature storage tank, which is composed of an LNG storage tank, a hydrate reaction collector, a nitrogen gas cylinder, a nitrogen storage tank, a methane storage tank and a data acquisition processor. The application innovatively uses a hydrate method to efficiently separate the precooling mixed gas, improves the separation efficiency of the mixed gas, and ensures high gas absorption and high reaction efficiency by using a twisted-belt type spiral flow generator, a micro-bubble generator, a reaction accelerator bottle and a constant-temperature water bath in the hydrate reaction collector. The hydrate method is used to efficiently separate the mixed gas after precooling of the low-temperature storage tank, the system cold energy is fully utilized, the energy consumption is reduced, and the cost is lowered. Compared with general mixed gas recycling methods, the application adopts an automatic control system to realize intelligent control of hydrate generation, decomposition, separation gas collection and other steps, saves manpower cost and energy consumption, and has low investment and operation cost.

Description

Technical Field

[0001] The present invention belongs to the technical field of separation and recovery of mixed gases generated during the precooling process of cryogenic storage tanks, and in particular relates to a hydrate separation system, device and method for precooling mixed gases in liquid hydrogen storage tanks and LNG storage tanks. Background Art

[0002] With the increasing global demand for clean energy, the effective utilization of LNG has become a key issue in the domestic natural gas sector. Compared to other energy sources, LNG offers advantages such as cleanliness and efficiency, ease of transportation and storage, optimized energy structure, superior safety performance, and significant environmental benefits. The LNG industry chain primarily encompasses the liquefaction, storage, transportation, reception, and gasification of natural gas. LNG storage is a crucial link, and for LNG liquefaction plants and receiving terminals, LNG storage tanks are crucial to the storage process.

[0003] LNG storage tanks require pre-cooling before filling. During this process, liquefied nitrogen is injected in advance. Once the tank temperature drops to -162°C, LNG is injected into the tank. This process produces a mixture of methane and nitrogen. To ensure the purity of the LNG, the mixture must be discharged. The current treatment method is to directly ignite the discharged mixture. The methane in it burns to produce water and carbon dioxide, while nitrogen is non-combustible and does not participate in the reaction, so it is not treated. However, this treatment method not only leads to a large waste of resources, exacerbating the greenhouse effect and environmental pollution, but the heat energy and open flames generated by the combustion also pose safety risks to the tank area. At the same time, the cold energy carried by the mixture is also wasted. Summary of the Invention

[0004] In view of the above-mentioned drawbacks, the present invention proposes a hydrate separation system, device and method for pre-cooling mixed gas in a cryogenic storage tank. Since the discharged mixed gas contains usable methane gas, taking into account energy conservation and the characteristics of natural gas hydrates (natural gas hydrates are a non-stoichiometric, ice-like clathrate formed by water and methane under low temperature and high pressure), the methane in the mixed gas can be separated by forming natural gas hydrates. This not only reduces safety hazards, but also utilizes the cold energy contained in the mixed gas to recover methane and nitrogen, thereby achieving the goal of energy-saving and efficient resource recovery.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention provides a hydrate separation system for mixed gas after pre-cooling in a cryogenic storage tank, comprising a gas-liquid conveying system, a pre-cooling system, a hydrate reaction system, a separated gas collection system, and a data detection and collection system;

[0007] The gas-liquid delivery system is used for liquid nitrogen and LNG;

[0008] The pre-cooling system is connected to the gas-liquid delivery system and is used to pre-cool the liquid nitrogen and replace the nitrogen with LNG;

[0009] The hydrate reaction system is connected to the pre-cooling system to collect the nitrogen and methane mixed gas generated by the pre-cooling system and separate the nitrogen, methane and water;

[0010] The separated gas collection system is connected to the hydrate reaction system and the pre-cooling system respectively, and is used to receive the separated nitrogen, methane and water, and send the nitrogen to the pre-cooling system;

[0011] The data detection and collection system is connected to the hydrate reaction system and the separated gas collection system respectively, and is used to detect the nitrogen and methane pressures in the hydrate reaction system and the separated gas collection system, determine the pressure difference between each container, and control the recovery and utilization of nitrogen, methane and water.

[0012] The present invention also provides a hydrate separation device for mixed gas after pre-cooling in a cryogenic storage tank, which is used in the above-mentioned hydrate separation system for mixed gas after pre-cooling in a cryogenic storage tank, comprising an LNG storage tank, a hydrate reaction collector, a nitrogen cylinder, a nitrogen storage tank, a methane storage tank and a data acquisition processor;

[0013] The LNG storage tank is connected to the liquid inlet pipeline, the hydrate reaction collector is connected to the LNG storage tank, the nitrogen cylinder, nitrogen storage tank, and methane storage tank are respectively connected to the hydrate reaction collector, and the nitrogen storage tank is connected to the LNG storage tank. The data acquisition processor is respectively connected to the hydrate reaction collector, nitrogen storage tank, and methane storage tank through temperature and pressure sensors.

[0014] In order to achieve the purpose of energy saving and efficient resource recovery, the hydrate reaction collector includes a microbubble generator, a twisted ribbon spiral flow generator, a hydrate separator and a hydrate decomposition tank;

[0015] The microbubble generator is connected to the LNG storage tank, the twisted ribbon spiral flow generator is connected to the microbubble generator, the hydrate separator is connected to the twisted ribbon spiral flow generator and the hydrate decomposition tank respectively, and the hydrate decomposition tank is connected to the methane storage tank and the microbubble generator respectively.

[0016] Among them, as the core part of the hydrate reaction collector of the present invention, the microbubble generator is composed of a metal microporous tube with a diameter of 20-40 mm, a length of 100-300 mm, a minimum pore size of 0.3 μm, and an opening rate of 40-70%; the twisted ribbon spiral flow generator generates spiral flow by a twisted ribbon, and the twist rate of the twisted ribbon ranges from 4.3 to 8.8.

[0017] In order to facilitate the control of feed, the liquid inlet pipeline is connected to the LNG storage tank through multiple connecting pipelines, and each connecting pipeline is respectively provided with a first one-way valve, a second one-way valve, and a third one-way valve.

[0018] In order to facilitate the control of the mixed gas entering the hydrate reaction collector, a fourth one-way valve is provided on the connecting pipeline between the LNG storage tank and the hydrate reaction collector. In order to facilitate the control of the recovered nitrogen entering the LNG storage tank, a fifth one-way valve is provided on the connecting pipeline between the LNG storage tank and the nitrogen storage tank.

[0019] In order to facilitate the control of the temperature in the hydrate reaction collector and the addition of the reaction accelerator, the hydrate reaction collector is connected to a constant temperature water bath and a reaction accelerator bottle.

[0020] In order to facilitate the nitrogen recovered in the hydrate reaction collector to enter the nitrogen storage tank, a sixth one-way valve, a first compressor and a seventh one-way valve are provided on the connecting pipeline between the hydrate reaction collector and the nitrogen storage tank.

[0021] In order to facilitate the addition of methane recovered in the hydrate reaction collector to the methane storage tank, an eighth one-way valve, a second compressor and a ninth one-way valve are provided on the connecting pipeline between the hydrate reaction collector and the methane storage tank.

[0022] The present invention further provides a method for separating hydrates from mixed gas after pre-cooling in a cryogenic storage tank, based on the above-mentioned device for separating hydrates from mixed gas after pre-cooling in a cryogenic storage tank, comprising the following steps:

[0023] (1) Liquid nitrogen enters the LNG storage tank through the liquid inlet pipeline for pre-cooling;

[0024] (2) When the temperature of the storage tank drops to -162°C, LNG is introduced into the LNG storage tank through the liquid inlet pipeline to replace nitrogen with LNG. When the amount of LNG introduced into the tank reaches a certain level, LNG is continuously added into the tank through the liquid inlet pipeline. When the nitrogen concentration in the tank is lower than 5%, the replacement is stopped.

[0025] (3) The nitrogen-methane mixture generated during the replacement process enters the hydrate reaction collector. The temperature in the hydrate reaction collector is adjusted to 3-7°C by a constant temperature water bath, and the pressure is controlled by a high-pressure nitrogen cylinder at a pressure of 3 MPa. When the temperature and pressure are appropriate, a reaction promoter, sodium lauryl sulfate, is added to the hydrate reaction collector from the reaction promoter bottle;

[0026] (4) After the mixed gas enters the hydrate reaction collector, it enters the twisted ribbon spiral flow generator through the dosing port. Since the mixed gas has a certain amount of cooling capacity, under the action of appropriate temperature, pressure and promoter, the methane and water in the mixed gas generate natural gas hydrates in the twisted ribbon spiral flow generator, and the nitrogen does not react. The temperature and pressure sensor detects the pressure change in the hydrate reaction collector. If the pressure gradually decreases and then tends to be stable, it means that the reaction is completed. Then the substances in the twisted ribbon spiral flow generator enter the hydrate separator, and the nitrogen enters the nitrogen storage tank through the pipeline;

[0027] (5) The temperature and pressure sensor connected to the nitrogen storage tank detects the pressure of the nitrogen storage tank, and the data acquisition processor determines the pressure difference between the two containers. If the pressure in the hydrate reaction collector is greater than the pressure in the nitrogen storage tank, the one-way valve is opened to allow nitrogen to automatically enter the nitrogen storage tank through the pipeline. If the pressures of the two containers are similar or the pressure in the nitrogen storage tank is greater than the pressure in the hydrate reaction collector, the compressor is used to allow nitrogen to enter the nitrogen storage tank through the pipeline. The nitrogen in the nitrogen storage tank is cooled and returned to the pre-cooling pipeline in front of the LNG storage tank.

[0028] (6) The natural gas hydrate in the hydrate reaction collector is separated by the hydrate separator and enters the hydrate decomposition tank, where it is decomposed into water and methane. The water returns to the inlet of the hydrate reaction collector for recycling, and the methane enters the methane storage tank for recovery. The temperature and pressure sensor connected to the methane storage tank detects the pressure of the methane storage tank, and the data acquisition processor determines the pressure difference between the methane storage tank and the hydrate reaction collector. If the pressure in the hydrate reaction collector is greater than the pressure in the methane storage tank, the one-way valve is opened to allow methane to automatically enter the methane storage tank through the pipeline. If the pressures of the two containers are similar or the pressure in the methane storage tank is greater than the pressure in the hydrate reaction collector, the compressor is used to allow methane to enter the methane storage tank through the pipeline. At this point, the separation of the methane and nitrogen mixed gas is completed.

[0029] The beneficial effects of the present invention are:

[0030] ① The present invention innovatively utilizes the hydrate method to efficiently separate the pre-cooled mixed gas, thereby improving the separation efficiency of the mixed gas;

[0031] ②The hydrate reaction collector is composed of a twisted ribbon spiral flow generator, a microbubble generator, a reaction accelerator bottle, a constant temperature water bath, etc., which can ensure high aspiration volume and high reaction efficiency;

[0032] ③ The hydrate method is used to efficiently separate the mixed gas after pre-cooling the cryogenic storage tank, making full use of the system's cold energy, reducing energy consumption and lowering costs;

[0033] ④ Compared with the general mixed gas recovery and utilization method, the present invention adopts an automatic control system to realize intelligent control of hydrate formation, decomposition, separated gas collection and other steps, saving labor costs and energy consumption;

[0034] ⑤Low investment and operating costs;

[0035] ⑥ Select the appropriate type and concentration of kinetic promoter (5.56% molar fraction of tetrahydrofuran + 100 mg kg -1 Sodium dodecyl sulfate solution system), using chemical and physical enhancement methods to improve the hydrate formation efficiency and achieve maximum air intake. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic structural diagram of the hydrate separation system for mixed gas after pre-cooling in a cryogenic storage tank according to the present invention;

[0037] Figure 2 This is a schematic structural diagram of a hydrate separation device for mixed gas after pre-cooling in a cryogenic storage tank according to the present invention;

[0038] Figure 3 Schematic diagram of the structure of the hydrate reaction collector of the present invention;

[0039] Figure 4 Schematic diagram of the structure of the microbubble generator of the present invention. DETAILED DESCRIPTION

[0040] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more precise definition of the protection scope of the present invention.

[0041] Example 1:

[0042] like Figure 1 The hydrate separation system of the mixed gas after pre-cooling in a cryogenic storage tank shown in the figure includes a gas-liquid conveying system, a pre-cooling system, a hydrate reaction system, a separated gas collection system, and a data detection and collection system;

[0043] The gas-liquid delivery system is used to deliver liquid nitrogen and LNG;

[0044] The pre-cooling system is connected to the gas-liquid delivery system and is used to pre-cool the liquid nitrogen and replace the nitrogen with LNG;

[0045] The hydrate reaction system is connected to the pre-cooling system to collect the nitrogen and methane mixed gas generated by the pre-cooling system and separate the nitrogen, methane and water;

[0046] The separated gas collection system is connected to the hydrate reaction system and the pre-cooling system respectively, and is used to receive the separated nitrogen, methane and water, and send the nitrogen to the pre-cooling system;

[0047] The data detection and collection system is connected to the hydrate reaction system and the separated gas collection system respectively, and is used to detect the nitrogen and methane pressures in the hydrate reaction system and the separated gas collection system, determine the pressure difference between each container, and control the recovery and utilization of nitrogen, methane and water.

[0048] The gas-liquid transportation system first sends liquid nitrogen into the pre-cooling system for pre-cooling, and then sends LNG into the pre-cooling system to replace nitrogen. The mixed gas in the replacement process enters the hydrate reaction system, is separated by the hydrate reaction system, and is recovered by the separated gas collection system. The data detection and collection system detects the nitrogen and methane pressures in the hydrate reaction system and the separated gas collection system, determines the pressure difference between each container, and controls the reuse of nitrogen, methane, and water, thereby realizing intelligent control of hydrate formation, decomposition, separated gas collection and other steps, saving labor costs and energy consumption.

[0049] Example 2:

[0050] like Figure 2 The hydrate separation device shown is used for the hydrate separation system of the mixed gas after pre-cooling in the cryogenic storage tank, and includes an LNG storage tank 22, a hydrate reaction collector 21, a nitrogen cylinder 6, a nitrogen storage tank 23, a methane storage tank 17 and a data acquisition processor 9.

[0051] Specifically, the liquid inlet pipeline is connected to the LNG storage tank 22 through a plurality of connecting pipelines, and each connecting pipeline is respectively provided with a first one-way valve 1, a second one-way valve 2, and a third one-way valve 3. The hydrate reaction collector 21 is connected to the LNG storage tank 22, and a fourth one-way valve 4 is provided on the connecting pipeline. The nitrogen cylinder 6, the nitrogen storage tank 23, and the methane storage tank 14 are respectively connected to the hydrate reaction collector 21. The connecting pipeline between the hydrate reaction collector 21 and the nitrogen storage tank 23 is sequentially provided with a sixth one-way valve 11, a first compressor 12 and a seventh one-way valve 13. The connecting pipeline between the hydrate reaction collector 21 and the methane storage tank 17 is sequentially provided with an eighth one-way valve 14, a second compressor 15 and a ninth one-way valve 16. The connection between the hydrate reaction collector 21 and the nitrogen cylinder 6 is A tenth one-way valve 7 is provided on the pipe connection, a fifth one-way valve 20 is provided on the connecting pipe between the nitrogen storage tank 23 and the LNG storage tank 22, and an eleventh one-way valve 19 is provided on the connecting pipe between the nitrogen storage tank 23 and the inlet pipeline. The data acquisition processor 9 is connected to the hydrate reaction collector 21 through the first temperature and pressure sensor 8, connected to the nitrogen storage tank 23 through the second temperature and pressure sensor 10, and connected to the methane storage tank 17 through the third temperature and pressure sensor 18. In addition, the hydrate reaction collector 21 is connected to the constant temperature water bath 25 and the reaction accelerator bottle 24. A twelfth one-way valve 5 is provided on the connecting pipe between the hydrate reaction collector 21 and the reaction accelerator bottle 24. The reaction accelerator bottle 24 is filled with tetrahydrofuran with a molar fraction of 5.56% + 100 mg·kg -1 Sodium lauryl sulfate solution system.

[0052] Combine Figure 3 、 Figure 4 The hydrate reaction collector shown includes a micro bubble generator 28, a twisted ribbon spiral flow generator 29, a hydrate separator 31 and a hydrate decomposition tank 33;

[0053] The connection pipeline between the microbubble generator 28 and the LNG storage tank 22 is provided with a dosing port 26 and a thirteenth one-way valve 27. The microbubble generator 28 is composed of a metal microporous tube with a diameter of 20-40 mm and a length of 100-300 mm. The minimum pore size of the micropores 36 is 0.3 μm and the porosity is 40-70%. An air inlet 37 is provided at one end of the metal microporous tube. The twisted ribbon spiral flow generator 29 is connected to the microbubble generator 28. The hydrate separator 31 is connected to the hydrate separator 31. A fourteenth one-way valve 30 is provided on the connecting pipeline of the twisted ribbon spiral flow generator 29. The hydrate decomposition tank 33 is connected to the microbubble generator 28 and the methane storage tank 17 respectively. A fifteenth one-way valve 35 is provided on the connecting pipeline between the hydrate decomposition tank 33 and the microbubble generator 28. A sixteenth one-way valve 34 is provided on the connecting pipeline between the hydrate decomposition tank 33 and the methane storage tank 17. A seventeenth one-way valve 32 is provided on the connecting pipeline between the hydrate separator 31 and the hydrate decomposition tank 33.

[0054] The separation method of the hydrate separation device for the pre-cooled mixed gas of the low-temperature storage tank includes the following steps:

[0055] Liquid nitrogen enters the LNG storage tank 22 through the liquid inlet pipeline through the third one-way valve 3 for pre-cooling. When the temperature of the LNG storage tank 22 drops to -162°C, open the first one-way valve 1 to allow LNG to enter the LNG storage tank 22 through the liquid inlet pipeline, and replace the nitrogen with LNG. When the amount of LNG introduced into the tank reaches a certain scale, open the second one-way valve 2 to continue adding LNG into the tank through the liquid inlet pipeline. When the nitrogen concentration in the tank is lower than 5%, stop the replacement; the nitrogen and methane mixed gas generated during the replacement process passes through the fourth one-way valve 4 and enters the hydrate reaction collector 21 through the pipeline. The hydrate reaction collector 21 is connected to a temperature and pressure sensor 8. Open the constant temperature water bath 25 to adjust the temperature to 3-7°C. The pressure is controlled by the high-pressure nitrogen cylinder 6, and the pressure is 3MPa. When the temperature and pressure are The twelfth one-way valve 5 is opened appropriately, and the reaction promoter sodium lauryl sulfate is added to the hydrate reaction collector 21 through the reaction promoter bottle 24; after the mixed gas enters the hydrate reaction collector 21, it enters the microbubble generator 28 and the twisted ribbon spiral flow generator 29 through the dosing port 26. Since the mixed gas has a certain amount of cooling capacity, under the action of appropriate temperature, pressure and promoter, the methane and water in the mixed gas generate natural gas hydrates in the twisted ribbon spiral flow generator 29, and the nitrogen does not react; the temperature and pressure sensor 8 detects the pressure change in the hydrate reaction collector 21. If the pressure tends to be stable after gradually decreasing, it means that the reaction is completed, and then the material in the twisted ribbon spiral flow generator 29 enters the hydrate separator 31, and the nitrogen enters the nitrogen separator 31 through the pipeline. The temperature and pressure sensor 10 connected to the nitrogen storage tank 23 detects the pressure of the nitrogen storage tank 23, and the data acquisition processor 9 determines the pressure difference between the two containers. If the pressure in the hydrate reaction collector 21 is greater than the pressure in the nitrogen storage tank 23, the seventh one-way valve 13 is opened to allow nitrogen to automatically enter the nitrogen storage tank 23 through the pipeline; if the pressures of the two containers are similar or the pressure in the nitrogen storage tank 23 is greater than the pressure in the hydrate reaction collector 21, the sixth one-way valve 11 and the seventh one-way valve 13 are opened, and nitrogen is allowed to enter the nitrogen storage tank 23 through the pipeline through the first compressor 12. The nitrogen in the nitrogen storage tank 23 can be cooled and returned to the pre-cooling pipeline; the natural gas hydrate in the hydrate reaction collector 21 is separated by the hydrate separator 31 and then enters the hydrate decomposition The methane gas is decomposed into water and methane in the tank 33. The water is returned to the inlet of the microbubble generator 28 for recycling, while the methane enters the methane storage tank 17 through the sixteenth one-way valve 34 for recovery. The temperature and pressure sensor 18 connected to the methane storage tank 17 detects the pressure of the methane storage tank 17. The data acquisition processor 9 determines the pressure difference between the methane storage tank 17 and the hydrate reaction collector 21. If the pressure in the hydrate reaction collector 21 is greater than the pressure in the methane storage tank 17, the ninth one-way valve 16 is opened to allow the methane to automatically enter the methane storage tank 17 through the pipeline. If the pressures in the two containers are similar or the pressure in the methane storage tank 17 is greater than the pressure in the hydrate reaction collector 21, the eighth one-way valve 14 and the ninth one-way valve 16 are opened to allow the methane to enter the methane storage tank 17 through the pipeline via the second compressor 15.At this point, the separation of the mixed gas of methane and nitrogen is completed. ;

[0056] Finally, it should be noted that the above embodiments are only specific implementation methods of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above embodiments within the technical scope disclosed by the present invention, or replace some of the technical features therein with equivalents. Such modifications, changes or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A hydrate separation device for mixed gas after pre-cooling in a cryogenic storage tank, characterized by: Including LNG storage tanks, hydrate reaction collectors, nitrogen cylinders, nitrogen storage tanks, methane storage tanks and data acquisition processors; The LNG storage tank is connected to the liquid inlet pipeline, the hydrate reaction collector is connected to the LNG storage tank, the nitrogen cylinder, the nitrogen storage tank, and the methane storage tank are respectively connected to the hydrate reaction collector, and the nitrogen storage tank is connected to the LNG storage tank, and the data acquisition processor is respectively connected to the hydrate reaction collector, the nitrogen storage tank, and the methane storage tank via temperature and pressure sensors; The hydrate reaction collector includes a microbubble generator, a twisted ribbon spiral flow generator, a hydrate separator and a hydrate decomposition tank; The microbubble generator is connected to the LNG storage tank, the twisted ribbon spiral flow generator is connected to the microbubble generator, the hydrate separator is connected to the twisted ribbon spiral flow generator and the hydrate decomposition tank respectively, and the hydrate decomposition tank is connected to the methane storage tank and the microbubble generator respectively; The microbubble generator is composed of a metal microporous tube with a diameter of 20-40 mm, a length of 100-300 mm, a minimum pore size of 0.3 μm, and an opening rate of 40-70%. The twisted ribbon spiral flow generator generates a spiral flow by a twisted ribbon with a twist rate ranging from 4.3 to 8.

8. The liquid inlet pipeline is connected to the LNG storage tank through a plurality of connecting pipelines, and each connecting pipeline is respectively provided with a first one-way valve, a second one-way valve, and a third one-way valve; A fourth one-way valve is provided on the connecting pipeline between the LNG storage tank and the hydrate reaction collector, and a fifth one-way valve is provided on the connecting pipeline between the LNG storage tank and the nitrogen storage tank; The hydrate reaction collector is connected to a constant temperature water bath and a reaction accelerator bottle; The connecting pipeline between the hydrate reaction collector and the nitrogen storage tank is provided with a sixth one-way valve, a first compressor and a seventh one-way valve; An eighth one-way valve, a second compressor and a ninth one-way valve are provided on the connecting pipeline between the hydrate reaction collector and the methane storage tank.

2. A method for separating hydrates from mixed gas after pre-cooling in a cryogenic storage tank, based on the hydrate separation device for separating mixed gas after pre-cooling in a cryogenic storage tank as claimed in claim 1, characterized in that: The steps include: (1) Liquid nitrogen enters the LNG storage tank through the liquid inlet pipeline for pre-cooling; (2) When the temperature of the storage tank drops to -162°C, LNG is introduced into the LNG storage tank through the liquid inlet pipeline, and nitrogen is replaced by LNG. When the amount of LNG introduced into the tank reaches a certain scale, LNG is continued to be added into the tank through the liquid inlet pipeline. When the nitrogen concentration in the tank is lower than 5%, the replacement is stopped; (3) The nitrogen-methane mixture generated during the replacement process enters the hydrate reaction collector. The temperature in the hydrate reaction collector is adjusted to 3-7°C by a constant temperature water bath. The pressure is controlled by a nitrogen cylinder at 3 MPa. When the temperature and pressure are appropriate, the reaction promoter sodium lauryl sulfate is added to the hydrate reaction collector from the reaction promoter bottle. (4) After the mixed gas enters the hydrate reaction collector, it enters the twisted ribbon spiral flow generator through the dosing port. Since the mixed gas has a certain amount of cooling capacity, under the action of appropriate temperature, pressure and promoter, the methane and water in the mixed gas generate natural gas hydrates in the twisted ribbon spiral flow generator, and the nitrogen does not react. The temperature and pressure sensor detects the pressure change in the hydrate reaction collector. If the pressure gradually decreases and then tends to be stable, it means that the reaction is completed. Then the substances in the twisted ribbon spiral flow generator enter the hydrate separator, and the nitrogen enters the nitrogen storage tank through the pipeline; (5) The temperature and pressure sensor connected to the nitrogen storage tank detects the pressure of the nitrogen storage tank, and the data acquisition processor determines the pressure difference between the two containers. If the pressure in the hydrate reaction collector is greater than the pressure in the nitrogen storage tank, the seventh one-way valve is opened to allow nitrogen to automatically enter the nitrogen storage tank through the pipeline. If the pressures of the two containers are similar or the pressure in the nitrogen storage tank is greater than the pressure in the hydrate reaction collector, the nitrogen is allowed to enter the nitrogen storage tank through the pipeline through the first compressor. The nitrogen in the nitrogen storage tank is cooled and returned to the pre-cooling pipeline in front of the LNG storage tank. (6) The natural gas hydrate in the hydrate reaction collector is separated by the hydrate separator and then enters the hydrate decomposition tank, where it is decomposed into water and methane. The water returns to the inlet of the hydrate reaction collector for recycling, and the methane enters the methane storage tank for recovery. The temperature and pressure sensor connected to the methane storage tank detects the pressure of the methane storage tank, and the data acquisition processor determines the pressure difference between the methane storage tank and the hydrate reaction collector. If the pressure in the hydrate reaction collector is greater than the pressure in the methane storage tank, the ninth one-way valve is opened to allow methane to automatically enter the methane storage tank through the pipeline. If the pressures of the two containers are similar or the pressure in the methane storage tank is greater than the pressure in the hydrate reaction collector, the second compressor is used to allow methane to enter the methane storage tank through the pipeline. At this point, the separation of the mixed gas of methane and nitrogen is completed.

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