A resource comprehensive utilization system based on liquefied natural gas storage system and a control method thereof

Abstract

The application provides a resource comprehensive utilization system based on a liquefied natural gas storage system, which comprises an LNG storage tank, a buffer tank, a reflux pipeline, a pressure detection unit and a helium extraction unit, wherein the BOG outlet of the LNG storage tank is connected with the inlet of the buffer tank, the outlet of the buffer tank is connected with the helium extraction unit, tail gas generated in the helium extraction process of the helium extraction unit is converged to the reflux pipeline, the reflux pipeline is provided with two branches, the first branch is connected with the reflux port of the LNG storage tank through a compressor, the second branch is connected with the back port of the buffer tank, and the two branches are selectively conducted according to the detection result of the pressure detection unit. The application discloses a control method of the resource comprehensive utilization system based on the liquefied natural gas storage system, which comprises the following steps: a pressure balancing step, a helium extraction step and a mode judgment step. The application realizes the comprehensive target of safe operation reliability, energy recovery maximization and resource value maximization.

Description

Technical Field

[0001] This invention relates to the field of natural gas storage and comprehensive utilization technology, specifically to a resource comprehensive utilization system based on a liquefied natural gas storage system and its control method. Background Technology

[0002] As a clean energy source, liquefied natural gas (LNG) inevitably produces bloat gas (BOG) during storage and transportation due to the introduction of external heat. BOG's main component is methane, but it also contains nitrogen, hydrogen, and the extremely valuable rare gas helium. Failure to effectively manage BOG not only leads to energy waste and safety hazards but also results in the loss of its high-value helium resources.

[0003] Currently, the industry generally adopts two methods for handling BOG (Boiled Goods) at LNG receiving terminals or liquefaction plants: one is through flare combustion; the other is through recondensation to reliquefy the helium and return it to the storage tank. However, in the LNG process, because helium cannot be liquefied, it accumulates in the upper part of the storage tank over time, causing the BOG handling system load to continuously increase and the system operating pressure to rise. While flare combustion can achieve the purpose of pressure reduction, it leads to the loss of high-value helium resources. Recondensation cannot solve the problem of helium accumulation in the upper part of the storage tank. Therefore, traditional BOG handling methods actually result in a waste of resources through "low-value fuel utilization."

[0004] In recent years, the technology of extracting helium from BOG (Boiler Gas) has gradually gained attention. However, the technology faces several prominent challenges in engineering applications: First, the generation of BOG is discontinuous and unstable; its flow rate and pressure fluctuate drastically with the external environment and tank turnover, which greatly impacts the subsequent helium extraction system, which requires stable feed conditions, affecting separation efficiency and product purity. Second, the helium extraction process generates a large amount of tail gas (such as permeate from membrane separation and desorption waste gas from PSA), which still contains a considerable concentration of methane and has calorific value. Simply incinerating or venting these tail gases not only wastes energy but also increases carbon emissions, which is inconsistent with the concept of green and low-carbon development. Summary of the Invention

[0005] To address the technical problems existing in the background art, this invention proposes a resource comprehensive utilization system based on a liquefied natural gas storage system and its control method.

[0006] This invention proposes a resource comprehensive utilization system based on a liquefied natural gas (BOG) storage system, comprising: an LNG storage tank, a buffer tank, a return pipeline, a pressure detection unit for detecting the internal pressure of the LNG storage tank, and a helium extraction unit for extracting helium from BOG, wherein:

[0007] The LNG storage tank is equipped with a BOG outlet and a return port, and the buffer tank has an inlet, an outlet and a return port. The BOG outlet of the LNG storage tank is connected to the inlet of the buffer tank through an evacuation pipeline, and the outlet of the buffer tank is connected to the helium extraction unit through a helium extraction pipeline.

[0008] The exhaust gas generated during the helium extraction process in the helium extraction unit is collected in the return pipeline;

[0009] The return pipeline has a first branch and a second branch. The first branch is connected to the return port of the LNG storage tank via the compressor, and the second branch is connected to the return port of the buffer tank. The two branches are selectively connected based on the detection results of the pressure detection unit.

[0010] Preferably, it also includes a controller, which includes a control module, and the control module is configured to perform the following actions: when the pressure detection unit detects that the internal pressure of the LNG storage tank is greater than a preset value, it starts the venting pipeline; when the pressure detection unit detects that the internal pressure of the buffer tank reaches a set threshold, it starts the helium extraction unit.

[0011] Preferably, controller one further includes control module two, which is configured to perform the following actions when the helium extraction unit is started: when the pressure detection unit detects that the internal pressure of the LNG storage tank is greater than a preset value, it closes the first branch of the return pipeline and starts the second branch; when the pressure detection unit detects that the internal pressure of the LNG storage tank is less than a preset value, it closes the second branch of the return pipeline and starts the first branch.

[0012] Preferably, the venting pipeline includes a delivery pipeline connecting the BOG outlet of the LNG storage tank to the inlet of the buffer tank and a venting pump installed in the delivery pipeline; a pressure relief valve is provided on the top of the LNG storage tank, and the discharge port of the pressure relief valve is connected to an exhaust pipe, the output end of which is located between the outlet of the venting pump and the inlet of the buffer tank and is connected to the delivery pipeline.

[0013] Preferably, it also includes a second controller, which is configured to perform the following actions: when the pressure detection unit detects that the internal pressure of the LNG storage tank is greater than a preset value or the opening time of the pressure relief valve exceeds a preset time, the venting pipeline is started.

[0014] Preferably, the buffer tank includes a main chamber and a secondary chamber that are isolated from each other. The inlet and outlet of the buffer tank are both located in the main chamber, and the return port of the buffer tank is located in the secondary chamber.

[0015] Preferably, the pressure detection unit includes a first pressure sensor for detecting the internal pressure of the LNG storage tank, a second pressure sensor for detecting the internal pressure of the main chamber of the buffer tank, and a third pressure sensor for detecting the internal pressure of the auxiliary chamber of the buffer tank.

[0016] Preferably, the buffer tank is also provided with an air supply port; the air supply port is connected to an air supply pipeline, the output end of the air supply pipeline is divided into two lines, one of which is connected to the first branch in the return pipeline, and the other is connected to the downstream gas-using equipment; and there are two air supply ports, one of which is located in the main chamber and the other is located in the auxiliary chamber; the air inlet end of the air supply pipeline is connected to the two air supply ports respectively through two independently controlled on / off switches.

[0017] Preferably, the helium extraction unit includes a crude helium extraction unit, a catalytic dehydrogenation unit, a helium refining unit, and a filling unit connected in sequence by pipelines. The crude helium extraction unit is used to separate BOG to obtain crude helium gas rich in nitrogen, hydrogen, helium, and neon; the dehydrogenation unit is used to remove hydrogen from the crude helium gas and receive it after passing through the crude helium extraction unit; and the helium refining unit is used to remove nitrogen and neon from the dehydrogenated crude helium gas to extract helium gas.

[0018] This invention discloses a control method for a resource comprehensive utilization system based on a liquefied natural gas storage system, comprising the following steps:

[0019] Pressure balancing step: When the pressure detection unit detects that the internal pressure of the LNG storage tank is greater than the preset value, the venting pipeline is started to introduce the BOG in the LNG storage tank into the buffer tank.

[0020] Helium extraction procedure: When the pressure detection unit detects that the internal pressure of the buffer tank has reached the set threshold, the helium extraction unit is activated;

[0021] Mode determination steps: When the helium extraction unit is started, if the pressure detection unit detects that the internal pressure of the LNG storage tank is greater than the preset value, the first branch of the return pipeline is closed and the second branch is started to make the second branch conduct; if the pressure detection unit detects that the internal pressure of the LNG storage tank is less than the preset value, the second branch of the return pipeline is closed and the first branch is started to make the first branch conduct.

[0022] Preferably, it also includes an energy recovery step: when insufficient pressure is detected inside the LNG storage tank or downstream gas-using equipment has a gas demand, the gas supply port is opened and the gas supply pipeline is started, and the opening of the gas supply port follows a secondary chamber priority control strategy: the gas supply port of the secondary chamber is opened first to use the gas in the secondary chamber to meet the needs of the LNG storage tank and downstream gas-using equipment; when the pressure in the secondary chamber is insufficient, the gas supply port of the main chamber is opened to automatically supplement the gas in the main chamber.

[0023] This invention not only effectively controls the pressure of LNG storage tanks, ensuring the pressure safety and stable operation of the entire LNG storage system, but also recovers BOG (Bottle-Off Gas) as feedstock to extract high-purity helium. Furthermore, it comprehensively utilizes the methane-rich tail gas, a byproduct of helium extraction, achieving dual recovery of energy and scarce resources. This results in efficient helium extraction and complete cascade utilization of BOG energy, solving problems such as the contradiction between helium extraction and pressure maintenance, and wasteful tail gas emissions in traditional systems. Ultimately, it achieves the comprehensive goals of reliable safe operation, maximized energy recovery, and maximized resource value. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of a resource comprehensive utilization system based on a liquefied natural gas storage system proposed in this invention. Detailed Implementation

[0025] Reference Figure 1 This invention proposes a resource comprehensive utilization system based on a liquefied natural gas (BOG) storage system, comprising: an LNG storage tank 1, a buffer tank 2, a return pipeline, a pressure detection unit for detecting the internal pressure of the LNG storage tank 1 and the buffer tank 2, and a helium extraction unit for extracting helium from BOG, wherein:

[0026] LNG storage tank 1 is used to store cryogenic liquid natural gas (LNG), and it is equipped with a BOG outlet and a reflux port.

[0027] The buffer tank 2 is a pressure balancing and energy distribution unit. It is designed with a main chamber and a secondary chamber that are isolated from each other. The main chamber has an inlet and an outlet, and the secondary chamber has a return port.

[0028] The pressure detection unit includes a first pressure sensor P1 installed on the LNG storage tank 1 to detect the internal pressure of the LNG storage tank 1, a second pressure sensor P2 installed on the main chamber of the buffer tank 2 to detect the internal pressure of the main chamber, and a third pressure sensor P3 installed on the auxiliary chamber of the buffer tank 2 to detect the internal pressure of the auxiliary chamber.

[0029] The BOG outlet of LNG storage tank 1 is connected to the inlet of buffer tank 2 via evacuation pipeline 10, so that the main chamber of buffer tank 2 can specifically receive and temporarily store the raw BOG from LNG storage tank 1.

[0030] The outlet of buffer tank 2 is connected to the helium extraction unit via helium extraction pipeline 11, so that the helium extraction unit uses the BOG stored in the main chamber of buffer tank 2 as raw material gas for helium extraction.

[0031] The helium extraction unit mainly comprises a crude helium extraction unit 4, a catalytic dehydrogenation unit 5, a helium purification unit 6, and a filling unit 7, connected sequentially by pipelines. The crude helium extraction unit 4 includes a pressure regulator, a heater, a filter, a membrane separator, and a pressure swing adsorber (PSA), connected sequentially by pipelines. The pressure regulator, heater, and filter adjust the BOG from the buffer tank 2 to the pressure and temperature required for membrane separation, and remove particulate matter and droplets to protect downstream units. The membrane separator has a built-in polymer membrane selective for helium, which initially separates the pretreated gas into helium-rich gas and helium-lean permeate. The PSA consists of multiple adsorption towers filled with specialized adsorbents (such as activated carbon and zeolite molecular sieves). The crude helium extraction unit 4 separates crude helium rich in nitrogen, hydrogen, helium, and neon from the BOG through pressure regulation, heating, filtration, separation, and adsorption. The dehydrogenation unit 5 removes hydrogen from the crude helium. The helium purification unit 6 removes nitrogen and neon from the dehydrogenated crude helium to extract helium. In practical operation, the helium refining unit 6 adopts a low-temperature adsorption dual-tower switching method to ensure uninterrupted operation for industrial production. The filling unit 7 includes a helium storage tank for storing product helium, and the outlet pipeline of the helium storage tank is equipped with a purity analyzer and a product output control valve for quality inspection and sales control.

[0032] The exhaust gas generated during the helium extraction process of the helium extraction unit flows into the return pipeline 9. The return pipeline 9 has two branches, namely the first branch 9-1 and the second branch 9-2. Specifically, the tail gas recovery pipeline 9 is divided into the first branch 9-1 and the second branch 9-2 via a three-way valve. The first branch 9-1 is connected to the return port of the LNG storage tank 1 via the compressor 3, and the second branch 9-2 is connected to the return port of the buffer tank 2. The two branches are selectively activated based on the detection results of the pressure detection unit. Specifically, when the pressure detection unit detects that the internal pressure of the LNG storage tank 1 is greater than the preset value, the first branch 9-1 of the return pipeline 9 is closed and the second branch 9-2 is activated, so that the tail gas (mainly methane) generated during the helium extraction process is directly returned to the buffer tank 2 for temporary storage. When the pressure detection unit detects that the internal pressure of the LNG storage tank 1 is less than the preset value, the second branch 9-2 is closed and the first branch 9-1 is activated, so that the tail gas (mainly methane) generated during the helium extraction process is pressurized and liquefied by the compressor 3 and then transported back to the LNG storage tank 1.

[0033] In a further embodiment, a controller is also included, comprising a control module and a control module. The control module is configured to perform the following actions: when the pressure detection unit detects that the internal pressure of the LNG storage tank 1 is greater than a preset value, the evacuation pipeline 10 is activated; when the pressure detection unit detects that the internal pressure of the buffer tank 2 reaches a set threshold, the helium extraction unit is activated. The control module is configured to perform the following actions when the helium extraction unit is activated: when the pressure detection unit detects that the internal pressure of the LNG storage tank 1 is greater than a preset value, the first branch 9-1 of the return pipeline 9 is closed, and the second branch 9-2 is activated to make the second branch 9-2 conductive; when the pressure detection unit detects that the internal pressure of the LNG storage tank 1 is less than a preset value, the second branch 9-2 of the return pipeline 9 is closed, and the first branch 9-1 is activated to make the first branch 9-1 conductive.

[0034] Furthermore, the extraction pipeline 10 in this embodiment includes a delivery pipe connecting the BOG outlet of LNG storage tank 1 to the inlet of buffer tank 2, and an extraction pump installed in the delivery pipe. In this embodiment, the top of LNG storage tank 1 is equipped with a pressure relief valve 12. The discharge port of the pressure relief valve 12 is connected to an exhaust pipe 13. The output end of the exhaust pipe 13 is located between the outlet of the extraction pump and the inlet of buffer tank 2 and is connected to the delivery pipe. Under normal conditions, the extraction pump is not started, and the extraction pipeline 10 is in a closed state. The pressure balance inside LNG storage tank 1 is maintained solely by the pressure relief valve 12. That is, when the internal pressure of LNG storage tank 1 is greater than the starting pressure of the pressure relief valve 12, the pressure relief valve 12 is forced to start. Under the action of the internal pressure, the BOG in LNG storage tank 1 enters the discharge pipe through the pressure relief valve 12, and then enters the delivery pipeline, finally entering the buffer tank 2 through the delivery pipeline. When the pressure relief valve 12 continuously discharges for a longer than a preset time or the internal pressure of LNG storage tank 1 is greater than a preset value, the extraction pump starts, and the extraction pipeline 10 enters a conductive state.

[0035] In a further embodiment, a second controller is also included, configured to perform the following actions: when the pressure detection unit detects that the internal pressure of LNG storage tank 1 is greater than a preset value or the opening time of pressure relief valve 12 exceeds a preset time, the air pump is activated to open the air extraction pipeline 10. By adopting a dual judgment standard of "pressure" and "time", an intelligent safety protection system combining active and passive measures is constructed, namely: when the pressure of LNG storage tank 1 exceeds the starting pressure of pressure relief valve 12, the pressure relief valve responds immediately and passively performs rapid pressure relief to ensure safety; when the starting time of pressure relief valve exceeds the set time or the internal pressure of LNG storage tank 1 reaches a preset value (the starting pressure of pressure relief valve is often less than the preset pressure value of LNG storage tank 1), the system actively extracts air to relieve pressure. This design, which utilizes a pressure relief valve to provide a passive and rapid response when the pressure exceeds the limit, enabling immediate emergency pressure relief and ensuring basic safety, and also allows the system to actively activate a vacuum pump for forced pressure relief when the pressure relief valve remains open for too long or the pressure inside the tank approaches a higher upper limit, not only provides redundant safety barriers and greatly improves the reliability of the system, but also upgrades traditional passive protection to an active safety mode that can anticipate and handle abnormal operating conditions. This more comprehensively and effectively prevents overpressure risks and ensures the long-term stable operation of the LNG storage tank.

[0036] In a further embodiment, the buffer tank 2 is also provided with a gas supply port, which is connected to a gas supply pipeline 14. The gas supply pipeline 14 has two outputs, one of which is connected to the first branch 9-1 in the return pipeline 9, and the other is connected to the downstream gas-using equipment 8. When it is detected that the internal pressure of the LNG storage tank 1 is insufficient or the downstream gas-using equipment 8 has a gas demand, the gas in the buffer tank 2 is returned to the LNG storage tank 1 or the downstream gas-using equipment 8 through the gas supply pipeline 14.

[0037] Furthermore, there are two air supply ports, one located in the main chamber and the other in the auxiliary chamber. The air inlet of the air supply pipeline 14 is connected to the two air supply ports through two independently controlled on / off switches. During the return process, the auxiliary chamber gas is used first to meet the downstream demand. When the pressure in the auxiliary chamber is insufficient, the main chamber gas is automatically used to supplement the supply.

[0038] This invention proposes a control method for a resource comprehensive utilization system based on a liquefied natural gas storage system, comprising the following steps:

[0039] Pressure balancing step: When the pressure detection unit detects that the internal pressure of LNG storage tank 1 is greater than the preset value, the venting pipeline 10 is started to introduce the BOG in LNG storage tank 1 into buffer tank 2.

[0040] Helium extraction procedure: When the pressure detection unit detects that the internal pressure of buffer tank 2 has reached the set threshold, the helium extraction unit is started;

[0041] Mode determination steps: When the helium extraction unit is started, if the pressure detection unit detects that the internal pressure of LNG storage tank 1 is greater than the preset value, the first branch 9-1 of the return pipeline 9 is closed and the second branch 9-2 is started to make the second branch 9-2 conduct; if the pressure detection unit detects that the internal pressure of LNG storage tank 1 is less than the preset value, the second branch 9-2 of the return pipeline 9 is closed and the first branch 9-1 is started to make the first branch 9-1 conduct.

[0042] Energy recovery steps: When insufficient internal pressure is detected in LNG storage tank 1 or downstream gas-using equipment 8 has a gas demand, the gas supply port is opened and the gas supply pipeline 14 is started, so that the gas stored in the buffer tank 2 can be used as a gas source to supplement LNG storage tank 1 or as raw material gas to supply gas to downstream gas-using equipment 8.

[0043] In addition, safety monitoring steps are included: real-time monitoring of the pressure at all critical nodes of each unit; if the pressure at any point exceeds the safety threshold, an audible and visual alarm is immediately triggered, and a shutdown procedure is initiated as appropriate. At the same time, the overpressure gas is guided to be released to the flare system through the safety valve to ensure the absolute safety of the device.

[0044] As can be seen from the above, this invention can not only effectively control the pressure of LNG storage tanks and ensure the pressure safety and stable operation of the entire LNG storage system, but also recover BOG as feed gas to extract high-purity helium. It can also comprehensively utilize the by-product of helium extraction—methane-rich tail gas—achieving dual recovery of energy and scarce resources. This enables efficient extraction of helium resources and complete cascade utilization of BOG energy, solving problems such as the contradiction between helium extraction and pressure maintenance and waste of tail gas emissions in traditional systems. Ultimately, it achieves the comprehensive goals of reliable safe operation, maximized energy recovery, and maximized resource value.

[0045] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A resource comprehensive utilization system based on a liquefied natural gas storage system, characterized in that, include: LNG storage tank (1), buffer tank (2), return pipeline (9), pressure detection unit for detecting the internal pressure of LNG storage tank (1) and buffer tank (2), and helium extraction unit for extracting helium from BOG, wherein: The LNG storage tank (1) is equipped with a BOG outlet and a return port, and the buffer tank (2) has an inlet, an outlet and a return port. The BOG outlet of the LNG storage tank (1) is connected to the inlet of the buffer tank (2) through the evacuation pipeline (10), and the outlet of the buffer tank (2) is connected to the helium extraction unit through the helium extraction pipeline (11). The tail gas generated by the helium extraction unit during the helium extraction process is collected into the return pipeline (9). The return pipeline (9) is provided with a first branch (9-1) and a second branch (9-2). The first branch (9-1) is connected to the return port of the LNG storage tank (1) via the compressor (3), and the second branch (9-2) is connected to the return port of the buffer tank (2). The first branch (9-1) and the second branch (9-2) are connected according to the detection result of the pressure detection unit.

2. The resource comprehensive utilization system based on a liquefied natural gas storage system according to claim 1, characterized in that, It also includes controller one, which includes control module one. Control module one is configured to perform the following actions: when the pressure detection unit detects that the internal pressure of the LNG storage tank (1) is greater than the preset value, the gas extraction pipeline (10) is started; when the pressure detection unit detects that the internal pressure of the buffer tank (2) reaches the set threshold, the helium extraction unit is started.

3. The resource comprehensive utilization system based on a liquefied natural gas storage system according to claim 2, characterized in that, The controller also includes a control module 2, which is configured to perform the following actions when the helium extraction unit is started: when the pressure detection unit detects that the internal pressure of the LNG storage tank (1) is greater than the preset value, the first branch (9-1) of the return pipeline (9) is closed and the second branch (9-2) is started; when the pressure detection unit detects that the internal pressure of the LNG storage tank (1) is less than the preset value, the second branch (9-2) of the return pipeline (9) is closed and the first branch (9-1) is started.

4. The resource comprehensive utilization system based on a liquefied natural gas storage system according to claim 1, characterized in that, The extraction pipeline (10) includes a conveying pipeline connecting the BOG outlet of the LNG storage tank (1) to the inlet of the buffer tank (2) and an extraction pump installed in the conveying pipeline; the top of the LNG storage tank (1) is provided with a pressure relief valve (12), the outlet of the pressure relief valve (12) is connected to an exhaust pipe (13), the output end of the exhaust pipe (13) is located between the outlet of the extraction pump and the inlet of the buffer tank (2) and is connected to the conveying pipeline.

5. The resource comprehensive utilization system based on a liquefied natural gas storage system according to claim 4, characterized in that, It also includes controller two, which is configured to perform the following actions: when the pressure detection unit detects that the internal pressure of the LNG storage tank (1) is greater than the preset value or the opening time of the pressure relief valve (12) exceeds the preset time, the gas extraction pipeline (10) is started.

6. The resource comprehensive utilization system based on a liquefied natural gas storage system according to claim 1, characterized in that, The buffer tank (2) includes a main chamber and a secondary chamber that are isolated from each other. The inlet and outlet of the buffer tank (2) are both located in the main chamber, and the outlet of the buffer tank (2) is located in the secondary chamber. The pressure detection unit includes a first pressure sensor (P1) for detecting the internal pressure of the LNG storage tank (1), a second pressure sensor (P2) for detecting the internal pressure of the main chamber of the buffer tank (2), and a third pressure sensor (P3) for detecting the internal pressure of the secondary chamber of the buffer tank (2).

7. The resource comprehensive utilization system based on a liquefied natural gas storage system according to claim 6, characterized in that, The buffer tank (2) is also equipped with an air supply port; the air supply port is connected to an air supply pipeline (14), and the output end of the air supply pipeline (14) is divided into two paths, one of which is connected to the first branch (9-1) in the return pipeline (9), and the other is connected to the downstream gas-using equipment (8); and there are two air supply ports, one of which is located in the main chamber and the other is located in the auxiliary chamber; the air inlet end of the air supply pipeline (14) is connected to two air supply ports through two independent control switches.

8. The resource comprehensive utilization system based on a liquefied natural gas storage system according to claim 1, characterized in that, The helium extraction unit includes a crude helium extraction unit (4), a catalytic dehydrogenation unit (5), a helium refining unit (6), and a filling unit (7) connected in sequence by pipelines. The crude helium extraction unit (4) is used to separate BOG to obtain crude helium gas rich in nitrogen, hydrogen, helium, and neon. The dehydrogenation unit (5) is used to remove hydrogen from the crude helium gas and receive it after passing through the crude helium extraction unit (4). The helium refining unit (6) is used to remove nitrogen and neon from the dehydrogenated crude helium gas to extract helium gas.

9. A control method for a resource comprehensive utilization system based on a liquefied natural gas storage system as described in any one of claims 1-8, characterized in that, Includes the following steps: Pressure balancing step: When the pressure detection unit detects that the internal pressure of the LNG storage tank (1) is greater than the preset value, the venting pipeline (10) is started to introduce the BOG in the LNG storage tank (1) into the buffer tank (2); Helium extraction procedure: When the pressure detection unit detects that the internal pressure of the buffer tank (2) has reached the set threshold, the helium extraction unit is started; Mode judgment steps: When the helium extraction unit is started, when the pressure detection unit detects that the internal pressure of the LNG storage tank (1) is greater than the preset value, the first branch (9-1) of the return pipeline (9) is closed and the second branch (9-2) is started so that the second branch (9-2) is connected; when the pressure detection unit detects that the internal pressure of the LNG storage tank (1) is less than the preset value, the second branch (9-2) of the return pipeline (9) is closed and the first branch (9-1) is started so that the first branch (9-1) is connected.

10. The method according to claim 9, characterized in that, It also includes an energy recovery step: when the internal pressure of the LNG storage tank (1) is insufficient or the downstream gas-using equipment (8) has a gas demand, the gas supply port is opened and the gas supply pipeline (14) is started; and the opening of the gas supply port implements the secondary chamber priority control strategy: the gas supply port of the secondary chamber is opened first, and the gas in the secondary chamber is used to meet the needs of the LNG storage tank (1) and the downstream gas-using equipment (8); when the pressure in the secondary chamber is insufficient, the gas supply port of the main chamber is opened to automatically supplement the gas in the main chamber.

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