Intelligent gas filling system of LNG filling station

Abstract

The utility model discloses a kind of LNG gas station intelligent gas filling system, comprising: LNG liquid storage tank, LIN liquid nitrogen tank, LNG filling tank and control unit, the gas phase space of LNG liquid storage tank is communicated with the gas phase space of LNG filling tank by gas phase pipeline, the liquid phase space of LNG liquid storage tank is communicated with the liquid phase space of LNG filling tank by liquid phase pipeline, the liquid phase space of LIN liquid nitrogen tank is connected to the heat exchanger in the LNG filling tank by refrigeration pipeline, control unit includes PLC controller and control valve group, the PLC controller can switch gas filling system and work between BOG liquefaction condition and gas filling condition. By the above mode, the utility model can realize system BOG zero emission, both environmental protection and economic;Cancel submerged pump, system reliability improves, maintenance cost is greatly reduced, significantly improve station operating efficiency;Intelligent control is used simultaneously, automatically complete pressure balance, flow control, BOG management, vehicle communication and the like operation, improve security and efficiency.

Description

Technical Field

[0001] This utility model relates to the field of LNG refueling station technology, and in particular to an intelligent LNG refueling system for LNG refueling stations. Background Technology

[0002] Currently, LNG refueling stations generally suffer from high BOG (Boiler Gas) production and emissions. Traditional control schemes often rely on passive manual intervention, typically resorting to manual or simple automatic methods to release excess gas when system pressure is too high, resulting in significant energy waste and environmental pollution.

[0003] It is worth noting that the greenhouse effect of LNG-BOG can be up to 21 times that of carbon dioxide, making it a bottleneck restricting the environmental performance and operational efficiency of LNG refueling stations. Furthermore, existing LNG refueling stations generally use submersible pumps as transport equipment, and these pumps themselves are heat sources during operation; their return liquid flowing into the LNG storage tanks further exacerbates BOG formation.

[0004] With rising demand for refueling and the expansion of gas filling stations, the number of impeller stages in submersible pumps has evolved from the traditional two-stage pumps to four-stage pumps. Simultaneously, the required static positive head for these pumps has also increased. Under these circumstances, improper operation can easily lead to cavitation, causing pump damage. As the core dynamic equipment of a gas filling station, the failure or damage of the submersible pump will severely impact the normal operation of the station and result in high maintenance costs.

[0005] In addition, the current operation process of LNG refueling stations is complex, requiring manual judgment of pressure status and manual control of reflux. It relies heavily on the experience of operators, resulting in low overall operating efficiency and varying safety levels among individuals.

[0006] Therefore, how to achieve systematic and automated BOG control and equipment protection for LNG refueling stations has become an urgent technical challenge. Utility Model Content

[0007] The main technical problem solved by this utility model is to provide an intelligent LNG refueling system for LNG refueling stations, which can achieve zero BOG emissions, making it both environmentally friendly and economical; by eliminating the submersible pump, the system reliability is improved, maintenance costs are significantly reduced, and the station's operating efficiency is significantly improved; at the same time, intelligent control is adopted to automatically complete operations such as pressure balancing, flow control, BOG management, and vehicle communication, thereby improving safety and efficiency.

[0008] To solve the above-mentioned technical problems, the present invention adopts a technical solution as follows: providing an intelligent LNG refueling system for LNG refueling stations, including: an LNG storage tank, a LIN liquid nitrogen tank, an LNG filling tank and a control unit, wherein the gas phase space of the LNG storage tank is connected to the gas phase space of the LNG filling tank through a gas phase pipeline, for transporting the BOG generated by the LNG storage tank to the LNG filling tank. The liquid phase space of the LNG storage tank is connected to the liquid phase space of the LNG filling tank through a liquid phase pipeline, so that liquid LNG can be transferred between the two. The liquid phase space of the LIN liquid nitrogen tank is connected to a heat exchanger inside the LNG filling tank via a refrigeration pipeline, which is used to provide cooling to the LNG filling tank to liquefy its internal BOG. The control unit includes a PLC controller and a control valve group electrically connected to the PLC controller. The PLC controller is configured to switch the gas filling system between BOG liquefaction mode and gas filling mode.

[0009] In a preferred embodiment of the present invention, the heat exchanger is a condensation coil wound inside the LNG filling tank.

[0010] In a preferred embodiment of the present invention, a liquid filling pipeline and a gas return pipeline are further included: one end of the liquid filling pipeline is connected to the liquid phase space of the LNG storage tank, and the other end is connected to the liquid filling port of the vehicle storage tank; one end of the gas return pipeline is connected to the gas return port of the vehicle storage tank, and the other end is connected to the gas phase space of the LNG storage tank.

[0011] In a preferred embodiment of this utility model, both the LNG storage tank and the LNG filling tank are equipped with level sensors, and the level sensors are electrically connected to the PLC controller.

[0012] In a preferred embodiment of this utility model, pressure transmitters are provided on the LNG storage tank, LIN liquid nitrogen tank, LNG filling tank and return gas pipeline, and the pressure transmitters are electrically connected to the PLC controller.

[0013] In a preferred embodiment of the present invention, the control valve group includes a first pneumatic control valve, a second pneumatic control valve, a third pneumatic control valve, a fourth pneumatic control valve, a fifth pneumatic control valve, a sixth pneumatic control valve, a seventh pneumatic control valve, and an eighth pneumatic control valve.

[0014] In a preferred embodiment of the present invention, the first pneumatic control valve is located on the gas phase pipeline connecting the LNG storage tank and the LNG filling tank, and the second pneumatic control valve is located on the liquid phase pipeline connecting the LNG storage tank and the LNG filling tank.

[0015] In a preferred embodiment of the present invention, the LIN liquid nitrogen tank is provided with a first self-pressurization circuit, the first self-pressurization circuit including a first booster connected to the liquid phase space of the LIN liquid nitrogen tank, the outlet of the first booster being connected to the gas phase space of the LIN liquid nitrogen tank, and a third pneumatic control valve being provided on the first self-pressurization circuit.

[0016] In a preferred embodiment of the present invention, the LNG filling tank is provided with a second self-pressurization circuit, the second self-pressurization circuit including a second booster connected to the liquid phase space of the LNG filling tank, the outlet of the second booster being connected to the gas phase space of the LNG filling tank, and a fourth pneumatic control valve being provided on the second self-pressurization circuit.

[0017] In a preferred embodiment of this utility model, the fifth pneumatic control valve is located on the refrigeration pipeline between the LIN liquid nitrogen tank and the heat exchanger, the sixth pneumatic control valve is located on the return gas pipeline of the LNG storage tank, the seventh pneumatic control valve is located on the liquid filling pipeline of the LNG storage tank, a venting pipeline is also connected to the LIN liquid nitrogen pipeline, and the eighth pneumatic control valve is located on the venting pipeline.

[0018] The beneficial effects of this utility model are: Through intelligent monitoring and active pressure control, the pressure is always kept below the safety line. The structure is designed with a closed-loop recovery path for BOG reliquefaction, which can achieve zero emissions of BOG, meet environmental protection requirements, reduce fuel loss, and lower operating costs. The submersible pump has been eliminated, and the system's power source is solely the static pressure difference. With no high-speed rotating parts, all failure factors caused by the submersible pump have been fundamentally eliminated, enabling maintenance-free operation and significantly improving the station's operational efficiency. Through PLC controllers and automatic monitoring, an intelligent closed-loop control system is formed, which can automatically complete operations such as pressure balancing, flow control, BOG management, and vehicle communication. This frees operators from complex judgments and operations, reduces the risk of human error, and realizes standardized, efficient, and safe loading and unloading operations, laying the foundation for remote monitoring and digital management. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is a schematic diagram of a preferred embodiment of the intelligent LNG refueling system for LNG refueling stations according to this utility model; Figure 2This is a structural schematic diagram of Embodiment 2; The components in the attached diagram are labeled as follows: 1. LNG storage tank; 2. LNG filling tank; 201. Condensation coil; 3. LIN liquid nitrogen tank; 4. Gas phase pipeline; 5. Liquid phase pipeline; 6. Refrigeration pipeline; 7. Gas return pipeline; 8. Liquid filling pipeline; 9. First booster; 10. Second booster. 12. Liquid level sensor; 13. Pressure transmitter; 14. First pneumatic control valve; 15. Second pneumatic control valve; 16. Third pneumatic control valve; 17. Fourth pneumatic control valve; 18. Fifth pneumatic control valve; 19. Sixth pneumatic control valve; 20. Seventh pneumatic control valve; 21. Eighth pneumatic control valve. 21. Drainage pipe, 22. Flow meter, 23. Unloading port, 24. Liquid filling port, 25. Gas return port. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0022] This utility model relates to an intelligent LNG refueling system for LNG refueling stations. Through static pressure difference drive and intelligent collaborative control, it realizes safe, efficient and zero-emission refueling operations at LNG refueling stations, solving the problems of high BOG generation and emissions, high submersible pump failure rate, high maintenance costs, low level of intelligence, complex operation and varying safety levels among operators in current LNG refueling stations. Example 1:

[0023] Please see Figure 1 The intelligent LNG refueling system of the LNG refueling station includes an LNG storage tank 1, a LIN liquid nitrogen tank 3, an LNG filling tank 2, and a control unit.

[0024] The gas phase space of the LNG storage tank 1 is connected to the gas phase space of the LNG filling tank 2 via a gas phase pipeline 4. This gas phase pipeline forms a BOG (Booster Gas) transport channel, which can transport the BOG generated by the LNG storage tank 1 to the LNG filling tank 2 for processing and reliquefaction.

[0025] The liquid phase space of the LNG storage tank 1 is connected to the liquid phase space of the LNG filling tank 2 via a liquid phase pipeline 5. This liquid phase pipeline 5 enables bidirectional transfer of liquid LNG between the LNG storage tank 1 and the LNG filling tank 2, providing a liquid source for the LNG filling tank 2 and also allowing reliquefied LNG to be returned to the LNG storage tank 1.

[0026] When LNG filling tank 2 is not in refueling mode, it reliquefies the excess BOG to reduce the pressure of LNG storage tank 1; when LNG filling tank 2 is in refueling mode, it first pressurizes to implement the refueling function.

[0027] The LIN liquid nitrogen tank 3 is a cold medium tank that provides the system with the function of reliquefying BOG to reduce the system's gas phase pressure. Its liquid phase space is connected to the heat exchanger in the LNG filling tank 2 through the refrigeration pipeline 6.

[0028] In this embodiment, the heat exchanger is preferably a condenser coil 201 coiled inside the LNG filling tank 2. Liquid nitrogen flows into the condenser coil 201 through the refrigeration pipe 6, vaporizes and absorbs heat, providing the required cryogenic cooling capacity for the LNG filling tank 2, thereby liquefying the BOG therein.

[0029] The system is equipped with an unloading pipeline that connects to external storage and transportation equipment. During unloading, the LNG tanker truck connects to the LNG storage tank 1 through the unloading pipeline and unloading port 23, so that liquid LNG enters the liquid phase space of the storage tank and gaseous LNG flows to the gas phase space of the storage tank.

[0030] Furthermore, the system's external operations include a liquid filling pipeline 8 and a gas return pipeline 7. One end of the liquid filling pipeline 8 is connected to the liquid phase space of the LNG storage tank 1, and the other end is connected to the liquid filling port 25 of the vehicle's storage tank, for adding LNG to the vehicle's storage tank. A flow meter 22 is installed on this liquid filling pipeline 8. One end of the gas return pipeline 7 is connected to the gas return port 24 of the vehicle's storage tank, and the other end is connected to the gas phase space of the LNG storage tank 1, for recovering the gaseous medium from the vehicle's storage tank back into the system before refueling.

[0031] To ensure the operating pressure of LNG filling tank 2 and LIN liquid nitrogen tank 3, the system is also equipped with two self-pressurization circuits: a first self-pressurization circuit installed on the LIN liquid nitrogen tank 3 and a second self-pressurization circuit installed on the LNG filling tank 2.

[0032] The first self-pressurizing circuit includes a first booster 9 connected to the liquid phase space of the LIN liquid nitrogen tank 3. The outlet of the first booster 9 is connected to the gas phase space of the LIN liquid nitrogen tank 3. After part of the liquid nitrogen is vaporized by the first booster 9, it returns to the top of the tank, which can maintain the stable working pressure of the LIN liquid nitrogen tank 3.

[0033] The second self-pressurization circuit includes a second booster 10 connected to the liquid phase space of the LNG filling tank 2, and the outlet of the second booster 10 is connected to the gas phase space of the LNG filling tank 2. During refueling, activating the second booster 10 can vaporize a portion of the LNG and return it to the top of the filling tank 2, thereby providing the necessary driving force for refueling.

[0034] To achieve intelligent control, the system also includes a control unit, comprising a PLC controller and a control valve assembly electrically connected to the PLC controller. The control valve assembly consists of multiple pneumatic control valves, each electrically connected to the PLC controller and receiving signal commands from the PLC controller.

[0035] Furthermore, both the LNG storage tank 1 and the LNG filling tank 2 are equipped with a liquid level sensor 11, which is electrically connected to the PLC controller and is used to monitor the liquid level in the corresponding tank in real time.

[0036] Furthermore, each of the LNG storage tank 1, LIN liquid nitrogen tank 3, LNG filling tank 2 and return gas pipeline 7 is equipped with a pressure transmitter 12, which is used to monitor the pressure at the corresponding location in real time, and each pressure transmitter 12 is electrically connected to the PLC controller.

[0037] In this embodiment, the control valve group includes a first pneumatic control valve 13, a second pneumatic control valve 14, a third pneumatic control valve 15, a fourth pneumatic control valve 16, a fifth pneumatic control valve 17, a sixth pneumatic control valve 18, a seventh pneumatic control valve 19, and an eighth pneumatic control valve 20.

[0038] Specifically, the first pneumatic control valve 13 is installed on the gas phase pipeline 4 connecting the LNG storage tank 1 and the LNG filling tank 2, and is used to control the delivery of BOG; the second pneumatic control valve 14 is installed on the liquid phase pipeline 5 connecting the LNG storage tank 1 and the LNG filling tank 2, and is used to control the transmission and return of LNG.

[0039] The third pneumatic control valve 15 is located on the first self-pressurization circuit and is used to control the start and stop of self-pressurization of the LIN liquid nitrogen tank 3; the fourth pneumatic control valve 16 is located on the second self-pressurization circuit and is used to control the start and stop of self-pressurization of the LNG filling tank 2.

[0040] The fifth pneumatic control valve 17 is located on the refrigeration pipeline 6 between the LIN liquid nitrogen tank 3 and the heat exchanger, and is used to control the supply of liquid nitrogen cooling capacity.

[0041] The sixth pneumatic control valve 18 is located on the return gas pipeline 7 of the LNG storage tank 1 and is used to control the return gas operation; the seventh pneumatic control valve 19 is located on the liquid filling pipeline 8 of the LNG storage tank 1 and is used to control the liquid filling operation.

[0042] The LIN liquid nitrogen pipe 3 is also connected to a vent pipe 21, and the eighth pneumatic control valve 20 is installed on the vent pipe 21 for safe depressurization or venting of the system.

[0043] Based on the above structure, the system is configured to switch the entire gas filling system between BOG liquefaction mode and gas filling mode.

[0044] BOG liquefaction mode (non-gas filling condition): When pressure transmitter 12 detects that the pressure in LNG storage tank 1 exceeds the set upper limit, the PLC controller determines that it should enter BOG reliquefaction mode. The PLC controller opens the first pneumatic control valve 13, the second pneumatic control valve 14 and the fifth pneumatic control valve 17, and the BOG is introduced into the LNG filling tank 2 and liquefied under the cooling provided by liquid nitrogen. The liquefied LNG flows back to the LNG storage tank 1 through the liquid phase pipeline 5, thereby achieving system pressure maintenance and zero discharge.

[0045] Gas refueling mode: When a gas refueling command is received, the PLC controller first controls the sixth pneumatic control valve 18 to perform automatic gas return operation based on the signal from the pressure transmitter 12 on the return gas pipeline 7, so as to reduce the pressure of the vehicle storage tank to a safe range. Subsequently, the PLC controller closes the first pneumatic control valve 13 to stop BOG delivery, closes the fifth pneumatic control valve 17 to stop cooling, closes the second pneumatic control valve 14, and then opens the fourth pneumatic control valve 16 to start the self-pressurization of LNG filling tank 2. Once the pressure in LNG filling tank 2 reaches the set gas filling value, the seventh pneumatic control valve 19 is opened to perform the liquid filling operation. Example 2:

[0046] Please see Figure 2 This embodiment provides a specific implementation of an intelligent LNG refueling system for LNG refueling stations.

[0047] LIN liquid nitrogen tank 3 serves as the system's cold source, providing the system with the ability to reliquefy BOG to reduce the system's gas phase pressure. The control process is as follows: The pressure is monitored in real time by a second pressure transmitter PT2 installed in the gas phase space of the LIN liquid nitrogen tank 3. When PT2 detects that the pressure is lower than 0.5MPa, the PLC controller controls the third pneumatic control valve AOV3 to open, starting the first self-pressurization circuit. Liquid nitrogen is vaporized by the first booster 9 and returns to the top of the tank, causing the pressure to rise. When the pressure reaches 0.6MPa, the PLC controller controls the third pneumatic control valve AOV3 to close, stopping the pressurization. When PT2 detects that the pressure of LIN liquid nitrogen tank 3 reaches 1.4MPa, the PLC controller controls the eighth pneumatic control valve AOV8 to open, releasing excess nitrogen through the vent pipe 21. When the pressure drops to 1.0MPa, the PLC controller controls the eighth pneumatic control valve AOV8 to close.

[0048] Through the above closed-loop control, the working pressure of LIN liquid nitrogen tank 3 is intelligently maintained within a stable range of 0.5-1.4 MPa.

[0049] LNG filling tanks have two main functions: non-gas filling mode and gas filling mode.

[0050] When the system is not in refueling mode, it will reliquefy the excess BOG to depressurize LNG storage tank 1. The control process is as follows: The pressure of LNG storage tank 1 is monitored by the first pressure transmitter PT1. When the pressure reaches 0.85MPa, the PLC controller controls the fifth pneumatic control valve AOV5 to open. Liquid nitrogen in LIN liquid nitrogen tank 3 flows into the condenser coil 201 of LNG filling tank 2 through the refrigeration pipeline 6, causing partial liquefaction of the gas phase in LNG filling tank 2 and reducing the pressure in LNG filling tank 2 until it drops to about 0.5MPa (monitored by the third pressure transmitter PT3). At this point, the PLC controller controls the first pneumatic control valve AOV1 to open, allowing the high-pressure BOG in the LNG storage tank 1 to be released through the gas phase pipeline 4 into the low-temperature LNG filling tank 2. Under the action of the condenser coil 201, the liquefied LNG is rapidly liquefied. The liquefied LNG settles at the bottom of the filling tank until the pressure in the LNG storage tank 1 drops to 0.4 MPa. At this time, the PLC controller controls AOV1 and AOV5 to close, the BOG reliquefaction process ends, and the system enters the pressure holding standby state.

[0051] The system first pressurizes during gas refueling to implement the gas refueling function. The control process is as follows: When a gas supply signal is received, the PLC controller controls the opening and closing of the fourth pneumatic control valve AOV4 by detecting the data from the third pressure transmitter PT3. When the pressure is below 1.35MPa, the PLC controller controls the fourth pneumatic control valve AOV4 to open, pressurizing the LNG filling tank 2 until the pressure reaches 1.5MPa, at which point the PLC controller controls the fourth pneumatic control valve AOV4 to close. During this process, when the pressure rises to 1.4MPa, the PLC controller controls the seventh pneumatic control valve AOV7 to open and perform the gas filling operation; at the same time, by detecting the flow rate of the flow meter M1, the PLC controller controls the opening degree of the seventh pneumatic control valve AOV7 to keep the entire gas filling process at the optimal flow rate.

[0052] The entire workflow controls the liquid level in LNG filling tank 2 by detecting data from the second pressure transmitter PT2: When the liquid level is below 30%, the PLC controller controls the second pneumatic control valve AOV2 to open, and the liquid in LNG storage tank 1 flows into LNG filling tank 2 through liquid phase pipeline 5 to replenish the liquid until the liquid level reaches 70%. Then, the PLC controller controls the second pneumatic control valve AOV2 to close. During this process, by detecting the data from the first pressure transmitter PT1 and the third pressure transmitter PT3, the PLC controller determines and controls the opening and closing of the fifth pneumatic control valve AOV5 to reduce the pressure of the LNG filling tank 2. This ensures that the pressure of the LNG filling tank 2 is always more than 0.2 MPa lower than the pressure of the LNG storage tank 1 during the LNG transfer process. In this way, the liquid transfer can be completed safely and efficiently by utilizing the static pressure difference, without the need for an external transfer pump.

[0053] Based on the above system, the entire vehicle refueling process is automated, including gas return, pressurization, and refueling. Automatic return air: After the station's refueling gun and return air gun are connected to the vehicle's storage tank, the pressure in the vehicle's storage tank is monitored by the pressure transmitter PT4 on the return air pipeline 7. When the pressure is higher than 1.2 MPa, the PLC controller controls the sixth pneumatic control valve AOV6 to open, recovering the excess gas in the vehicle's storage tank to the LNG storage tank 1; when the pressure drops to 0.9 MPa, the PLC controller controls the sixth pneumatic control valve AOV6 to close, and the gas return is completed.

[0054] Pressurization of filling tank: After the return gas is completed, the PLC controller immediately enters the gas filling preparation and monitors the pressure of LNG filling tank 2 through pressure transmitter PT3: When the pressure is lower than 1.35MPa, the PLC controller controls the fourth pneumatic control valve AOV4 to open, start the second self-pressurization circuit, and return part of the LNG to the top of the tank for pressurization after vaporization. When the pressure reaches 1.5MPa, the PLC controller controls the fourth pneumatic control valve AOV4 to close.

[0055] Intelligent refueling: During the pressurization process, when the pressure rises to 1.4MPa, the PLC controller controls the seventh pneumatic control valve AOV7 to open and begin refueling the vehicle with LNG; Meanwhile, based on the real-time flow rate feedback from the flow meter M1, the opening of the seventh pneumatic control valve AOV7 is dynamically adjusted to ensure that the gas filling process is always maintained within the preset optimal flow rate range, achieving efficient and stable filling.

[0056] The beneficial effects of this utility model's intelligent LNG refueling system for LNG refueling stations are: By adopting intelligent prediction and reliquefaction modules, the pressure inside LNG storage tanks and filling tanks is effectively reduced, realizing closed-loop recycling of BOG and zero LNG emissions at the station. This not only significantly reduces energy waste and environmental pollution, but also greatly reduces the overall operating cost of the station. The system adopts a pump-free setup, fundamentally eliminating the submersible pump as the main heat source and point of failure, avoiding the BOG increase problem caused by pump body heat generation, improving the inherent reliability of the system, and completely eradicating all failure modes and maintenance costs caused by the submersible pump, thereby improving the operational efficiency and economic benefits of the site. The entire process is intelligently controlled, minimizing human judgment and intervention. The standardized and automated operation process significantly improves operational efficiency, eliminates safety risks caused by differences in personnel experience, and enhances the safety and stability of the station operation.

[0057] The above description is merely an embodiment of this utility model and does not limit the patent scope of this utility model. Any equivalent structural or procedural transformations made using the content of this utility model specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this utility model.

Claims

1. An intelligent LNG refueling system for LNG refueling stations, characterized in that, include: LNG storage tanks, LIN liquid nitrogen tanks, LNG filling tanks and control units, The gas phase space of the LNG storage tank is connected to the gas phase space of the LNG filling tank through a gas phase pipeline, which is used to transport the BOG generated by the LNG storage tank to the LNG filling tank. The liquid phase space of the LNG storage tank is connected to the liquid phase space of the LNG filling tank through a liquid phase pipeline, so that liquid LNG can be transferred between the two. The liquid phase space of the LIN liquid nitrogen tank is connected to a heat exchanger inside the LNG filling tank via a refrigeration pipeline, which is used to provide cooling to the LNG filling tank to liquefy its internal BOG. The control unit includes a PLC controller and a control valve group electrically connected to the PLC controller. The PLC controller is configured to switch the gas filling system between BOG liquefaction mode and gas filling mode.

2. The intelligent LNG refueling system for LNG refueling stations according to claim 1, characterized in that, The heat exchanger is a condensation coil coiled inside the LNG filling tank.

3. The intelligent LNG refueling system for LNG refueling stations according to claim 1, characterized in that, It also includes a liquid filling pipeline and a gas return pipeline: one end of the liquid filling pipeline is connected to the liquid phase space of the LNG storage tank, and the other end is connected to the liquid filling port of the vehicle storage tank; one end of the gas return pipeline is connected to the gas return port of the vehicle storage tank, and the other end is connected to the gas phase space of the LNG storage tank.

4. The intelligent LNG refueling system for LNG refueling stations according to claim 1, characterized in that, Both the LNG storage tank and the LNG filling tank are equipped with level sensors, which are electrically connected to the PLC controller.

5. The intelligent LNG refueling system for LNG refueling stations according to claim 3, characterized in that, Pressure transmitters are installed on the LNG storage tank, LIN liquid nitrogen tank, LNG filling tank and return gas pipeline, and the pressure transmitters are electrically connected to the PLC controller.

6. The intelligent LNG refueling system for LNG refueling stations according to claim 3, characterized in that, The control valve group includes a first pneumatic control valve, a second pneumatic control valve, a third pneumatic control valve, a fourth pneumatic control valve, a fifth pneumatic control valve, a sixth pneumatic control valve, a seventh pneumatic control valve, and an eighth pneumatic control valve.

7. The intelligent LNG refueling system for LNG refueling stations according to claim 6, characterized in that, The first pneumatic control valve is located on the gas phase pipeline connecting the LNG storage tank and the LNG filling tank, and the second pneumatic control valve is located on the liquid phase pipeline connecting the LNG storage tank and the LNG filling tank.

8. The intelligent LNG refueling system for LNG refueling stations according to claim 6, characterized in that, The LIN liquid nitrogen tank is equipped with a first self-pressurization circuit, which includes a first booster connected to the liquid phase space of the LIN liquid nitrogen tank. The outlet of the first booster is connected to the gas phase space of the LIN liquid nitrogen tank. The first self-pressurization circuit is equipped with a third pneumatic control valve.

9. The intelligent LNG refueling system for LNG refueling stations according to claim 6, characterized in that, The LNG filling tank is equipped with a second self-pressurization circuit, which includes a second booster connected to the liquid phase space of the LNG filling tank. The outlet of the second booster is connected to the gas phase space of the LNG filling tank. The second self-pressurization circuit is equipped with a fourth pneumatic control valve.

10. The intelligent LNG refueling system for LNG refueling stations according to claim 6, characterized in that, The fifth pneumatic control valve is located on the refrigeration pipeline between the LIN liquid nitrogen tank and the heat exchanger. The sixth pneumatic control valve is located on the return gas pipeline of the LNG storage tank. The seventh pneumatic control valve is located on the liquid filling pipeline of the LNG storage tank. The LIN liquid nitrogen tank is also connected to a vent pipeline, and the eighth pneumatic control valve is located on the vent pipeline.

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