CN113418135B - Novel self-pressurization gas supply system for marine LNG fuel and control method thereof - Google Patents

Abstract

The invention provides a novel self-pressurization gas supply system for marine LNG fuel. The invention further provides a control method of the novel self-pressurization air supply system for the marine LNG fuel. The invention optimizes the gas supply system of LNG fuel by adopting two key core technologies: the novel low-resistance and high-efficiency self-booster and the self-boosting system are adopted, so that the resistance of the self-boosting system is reduced from the perspective of improving the internal structure form of the self-booster and increasing the valve flow area of the self-boosting system, and the boosting effect of the self-boosting system is improved to optimize the LNG fuel gas supply system. Secondly, from the perspective of improving the system design and the control method thereof, the precision control of the air supply pressure is realized, the safety protection is cut off, and the actual problem of natural gas emission escape is solved.

Description

A new self-pressurized gas supply system for LNG fuel used in ships and its control method

Technical Field

The present invention relates to a novel gas supply system for ship LNG fuel and a control method thereof. The gas supply system uses the principle of self-pressurization of LNG liquid tank to increase the pressure of the liquid tank, and then gasifies and heats the LNG fuel to convert it into gas fuel for ship engines or other similar gas-consuming equipment.

Background Art

With increasingly stringent environmental protection requirements for ships, the use of clean energy liquefied natural gas (LNG) to replace traditional fuel has become one of the main directions for ship fuel. LNG is stored in liquid form on board, but it is very volatile and produces evaporation gas after being heated on board, forming a flammable and explosive dangerous environment. In order to avoid the spread of volatile gases from this type of alternative fuel, the International Maritime Organization allows the use of Type C fuel tanks (pressure vessel type) to store this type of low flash point fuel.

LNG liquid is stored in LNG liquid tanks that are vacuum insulated or covered with thermal insulation materials. When fuel needs to be supplied to ship engines or other gas-consuming equipment but the tank pressure is insufficient, an LNG vaporizer called a self-boosting device is usually used to increase the pressure of the low-temperature LNG liquid tank to the required value, and then heat the LNG liquid to room-temperature gas fuel, ensuring that the pressure, temperature, and flow rate of the gas fuel meet the technical requirements of ship engines or other similar gas-consuming equipment.

For the typical LNG tank self-pressurization system and principle, please refer to the publicly published paper: Gao Yun's paper "Design Optimization of Self-pressurization Device for Liquefied Natural Gas Cylinders for Vehicles" in Volume 43, Issue 9 of "Cryogenics and Superconductivity" in 2015. The paper introduces in detail the working principle of the self-pressurization system and its key component, the booster regulating valve. In the paper, the basic principle of the LNG tank self-pressurization system is shown in Figure 1, and the structure of the mechanical spring self-actuated booster regulating valve is shown in Figure 2.

When the mechanical spring self-acting booster valve shown in Figure 2 is traditionally used, the tightness of the spring changes accordingly with the pressure change of the LNG tank, thereby automatically adjusting the valve opening. The lower the pressure of the LNG tank, the larger the opening of the booster valve, and the higher the pressure of the LNG tank, the smaller the opening of the booster valve. When the set pressure of the boost is reached, the booster valve is completely closed. However, when the valve opening is small, the valve resistance will increase significantly, affecting the liquid inflow of the LNG booster (vaporizer); when the spring fails or the spring force fails to completely close the valve, the liquid will continue to flow into the LNG booster (vaporizer), resulting in continuous pressurization of the LNG tank, causing the risk of overpressure of the LNG tank.

Marine LNG vaporizers mainly use hot water, hot oil, steam and other media as heat sources. For typical marine LNG vaporizer solutions, please refer to the publicly published paper: Tian Yajie and Lin Wensheng from the Institute of Refrigeration and Cryogenics Engineering of Shanghai Jiaotong University published the paper "Comparison of Marine Spiral Wound LNG Vaporizer Solutions" in Volume 69, Issue S2 of the Journal of Chemical Industry in 2018. The structural form of the spiral wound LNG vaporizer in the paper is shown in Figure 3.

LNG self-superchargers on traditional ships usually use shell and tube heat exchangers with various media such as hot water, hot oil, steam, etc. as heat sources. The coils in the heat exchangers are usually made of spirally wound thin tubes. LNG self-superchargers belong to the large category of LNG vaporizers, but due to the particularity of their use occasions, the resistance of the LNG heat exchange tubes directly affects the actual effect of the LNG self-superchargers. LNG self-superchargers designed and manufactured in the form of traditional winding tube LNG vaporizers often have the problem of unclear self-supercharger effect in actual use, especially when the resistance of the LNG supercharger is too large, which will greatly affect the working efficiency of the LNG self-supercharger.

The technical solution for pressurizing a conventional ship LNG tank is shown in FIG4 , wherein 1 is an LNG tank, 2 is a mechanical spring self-actuated booster valve, and 3 is a spiral wound LNG self-boosting device.

LNG flows into the spirally wound LNG self-boosting machine 3 by its own weight through the height difference between the LNG liquid tank 1 and the spirally wound LNG self-boosting machine 3. Therefore, the internal resistance of the spirally wound LNG self-boosting machine 3 directly determines the liquid inflow amount of the LNG self-boosting machine and the boosting efficiency of the LNG self-boosting machine.

In order to maximize the heat exchange area and improve the heat exchange efficiency in a limited space, traditional LNG self-boosting devices often use one or more groups of small-diameter pipes in the form of spirally wound coils to compensate for the thermal expansion and deformation of the pipeline caused by the huge temperature difference between the inlet and outlet of the LNG self-boosting device.

This type of LNG self-boosting device often has insufficient boosting capacity or slow boosting when used in actual ship engineering applications. The reasons are:

First, since the liquid in the LNG tank 1 flows into the spiral-wound LNG self-boosting device 3 only by the deadweight generated by the liquid level height difference, especially when the LNG tank level is low, the net inlet pressure head generated by the height difference is small, and the power of LNG flowing into the spiral-wound LNG self-boosting device 3 is itself very small;

Secondly, during the process of liquid-to-gas conversion, the volume expands greatly, causing the flow rate to increase rapidly, thus causing the pipeline resistance to increase significantly. After the refrigerated liquid enters the spiral-wound LNG self-boosting machine 3, it is gasified. The spiral tube design causes the gas-liquid separation to be untimely, resulting in large resistance to gas-liquid mixed flow, and even gas backflow and reflux to blow the liquid out of the inlet, making it difficult for LNG to continue to flow into the spiral-wound LNG self-boosting machine 3;

Finally, the small-diameter spiral coil design in the spirally wound LNG self-boosting device 3 itself has too large a pipeline resistance. When its resistance offsets the net pressure head generated by the liquid level height difference at the inlet of the spirally wound LNG self-boosting device 3, the LNG self-boosting device will obviously have insufficient liquid inlet, resulting in a poor boosting effect, insufficient boosting capacity or a very slow boosting process.

The typical LNG fuel gas supply system with self-pressurized LNG vaporizer as the main equipment on the ship has the following patents (not limited to):

Authorization announcement number: CN 110886670A

Authorization announcement date: 2020.03.17

Patent name: Marine low-pressure air supply system capable of self-pressurizing air supply and self-pressurizing air supply method

In this patent, the first stage LNG vaporizer in the two-stage heating heat exchanger for LNG gasification and heating is used as a self-booster for pressurization, and a BOG self-operated pressure regulating valve is used for pressure reduction. The heat exchanger adopts a back-and-forth folding tube or winding tube form, and the gas supply system realizes the gas supply pressure regulation function through a self-operated pressure regulating valve, as shown in Figure 5.

Authorization announcement number: CN 213065523U

Authorization announcement date: 2021.04.27

Patent name: A marine liquefied natural gas low-pressure fuel supply system

In this patent, the first stage LNG vaporizer in the two-stage heating heat exchanger for LNG gasification and heating is used as a self-booster for pressurization, and the second stage NG heater is used as a heater for BOG decompression, and a BOG self-operated pressure regulating valve is used for decompression. See Figure 6 for details.

Authorization announcement number: CN 111550675A

Authorization announcement date: 2020.08.18

Patent name: A method and device for automatically pressurizing cryogenic liquid delivery

This patent is to control the opening of the remote control valve automatically through the pressure signal of the tank, and control the pressurization process by automatically adjusting the valve size. See Figure 7 for details.

Authorization announcement number: CN 104791602B

Authorization announcement date: 2018.06.05

Patent name: LNG gas fuel supply method and device with BOG priority utilization

This patent uses the self-supercharger as the main gasifier, and the BOG produced by the self-supercharger is used for both pressurizing the tank and being transported to the outside as fuel. See Figure 8 for details.

In the LNG fuel gas supply system for which the above patent is applied, various optimization schemes for the existing gas supply system are only proposed from the perspective of system principle. However, when the actual gas supply system is used, the LNG self-boosting device has excessive resistance itself, and the structural form of the pressure regulating valve forms a large valve resistance, which is the root cause of the unobvious self-boosting effect and unstable gas supply pressure. It cannot solve the problem of unsatisfactory self-boosting effect and inaccurate gas supply pressure regulation in principle and from the root. This patent improves the internal structure of the self-boosting device, increases the flow area of the valve of the self-boosting system, and realizes a new self-boosting system for ship LNG liquid tank pressurization through precise pressure regulation control methods. The LNG self-boosting device for LNG liquid tank pressurization and the LNG vaporizer for gas supply are designed as an integrated heat exchanger, and the gas supply system scheme is further optimized and improved.

Authorization announcement number: CN 108716441A

Authorization announcement date: 2018.10.30

Patent name: LNG gas supply system and natural gas powered ship

At the same time, referring to the above patent, when the ship's gas engine or other gas-consuming equipment uses gas fuel, it is also necessary to set up a set of double-walled pipe structure gas pipelines and a set of gas valve units (GasValves Unit, GVU) in the engine room where the gas engine is arranged. The above gas valve unit includes a fuel valve and a breathable valve that form an interlocking function and a closed container that accommodates the above interlocking valve. This prevents leakage of the gas pipeline and valve from causing gas to enter the engine room that accommodates the gas engine. However, setting up a set of gas valve units in the engine room to accommodate the above interlocking valve group will greatly increase the manufacturing difficulty and cost, and is not convenient for the operation, maintenance and repair of the valve.

Authorization announcement number: CN 205048157U

Authorization announcement date: 2015.09.08

Patent Name: Liquefied Natural Gas Storage Tank

When LNG liquid is added into the LNG tank, in order to prevent the LNG tank from being overfilled, a fullness valve is usually set at the maximum filling level of the tank. Whether the LNG tank is full is judged by whether LNG liquid or gas flows out when the fullness valve is opened. However, this measurement method will cause the LNG liquid or gas to be discharged into the atmosphere, which is not economical and environmentally friendly.

It can be seen from the above-mentioned publicly published papers and applied patents that in this type of system that uses a self-boosting device as the core equipment of the LNG fuel supply system, the efficiency of the operation of the self-boosting device and the self-boosting system is directly related to the quality of the entire LNG fuel supply system. It can also be seen from the paper that the resistance of the self-boosting system as a key factor directly affects the actual effect of self-boosting, which has attracted the attention of all parties and has been studied. However, the solutions proposed in the above-mentioned literature mainly propose optimization plans for the existing self-boosting system from aspects such as the direction layout of the liquid inlet pipeline and the installation layout of the valve. The patented LNG fuel supply system also mainly implements the differences between the gas supply systems through the mutual functional reuse changes between one or more LNG heat exchangers.

Summary of the invention

The technical problem to be solved by the present invention is that the existing technical solutions do not solve the practical problems of unsatisfactory effect of the supercharger, inaccurate pressure regulation and natural gas emission escape in principle and from the root.

In order to solve the above technical problems, a technical solution of the present invention is to provide a new type of self-pressurized gas supply system for marine LNG fuel, characterized in that it includes a low-temperature refrigerated liquid storage tank, which is connected to J sets of gas supply systems located inside the joint space, J≥1, each gas supply system supplies gas to K gas-consuming equipment, K≥1, and the gas-consuming equipment is located in the machine space, wherein:

The pressure signal acquisition unit acquires the pressure signal of the cryogenic liquid storage tank, and sends the acquired pressure signal to the controller located outside the joint; the cryogenic liquid storage tank has a liquid fuel outlet, a self-pressurized liquid outlet and a gas phase port;

Each gas supply system includes an integrated heat exchanger that integrates a self-boosting compressor and a vaporizer into one, and a gas buffer tank; the self-boosting compressor integrated in the integrated heat exchanger has a low-temperature freezing liquid inlet and a steam outlet for the low-temperature freezing liquid to be vaporized by heat; the vaporizer integrated in the integrated heat exchanger has a low-temperature fuel inlet and a normal-temperature gas fuel outlet; the integrated heat exchanger also has a heat source medium inlet and a heat source medium outlet; the low-temperature freezing liquid inlet of the integrated heat exchanger is connected to the self-boosting liquid outlet of the low-temperature freezing liquid storage tank via a low-temperature freezing liquid delivery pipe, and a switch-controlled remote-controlled self-boosting valve is provided on the low-temperature freezing liquid delivery pipe; the steam outlet of the integrated heat exchanger is connected to the gas phase port of the low-temperature freezing liquid storage tank via a steam delivery pipe; one end of the bypass pipe is connected to the steam delivery pipe, and the other end is connected to the low-temperature fuel delivery pipe. The bypass pipe is connected, and a switch-controlled remote-controlled gas fuel valve is provided on the bypass pipe; the low-temperature fuel delivery pipe is connected to the low-temperature fuel inlet of the integrated heat exchanger, and at the same time, the low-temperature fuel delivery pipe is also connected to the liquid fuel outlet of the low-temperature frozen liquid storage tank via the liquid fuel delivery pipe; a switch-controlled remote-controlled liquid fuel valve is provided on the liquid fuel delivery pipe; the normal temperature gas fuel outlet of the integrated heat exchanger is connected to the gas buffer tank via the normal temperature fuel delivery pipe, and the temperature signal of the gas in the normal temperature fuel delivery pipe is collected by the temperature signal acquisition unit 2, and the temperature signal is sent to the controller; the heat source medium inlet and the heat source medium outlet of the integrated heat exchanger are respectively connected to the heat source medium inlet interface and the heat source medium outlet interface located outside the joint; the gas buffer tank is connected to K gas-consuming equipment located outside the joint via the gas supply pipe.

Preferably, an overflow outlet is provided at the maximum filling level of the cryogenic liquid storage tank, and the cryogenic liquid storage tank also has an overflow return port;

Each air supply system also includes an overflow cylinder;

The overflow outlet of the low-temperature freezing liquid storage tank is connected to the overflow tube via the overflow outlet pipe, and the overflow tube is connected to the overflow return air port of the low-temperature freezing liquid storage tank via the overflow return air pipe; the temperature signal of the overflow tube is collected by the temperature signal acquisition unit 1, and the collected temperature signal is sent to the controller.

Preferably, the integrated heat exchanger comprises a shell and N straight heat exchange tubes arranged in the shell, N ≥ 1;

The housing has the heat source medium inlet and the heat source medium outlet;

N straight tube heat exchange tubes 1 are covered with M groups of spirally wound heat exchange tubes, M≥1, and the heat exchange tubes have independent low-temperature fuel inlets and normal-temperature gas fuel outlets for entering and exiting the shell; or there are M groups of straight tube heat exchange tubes 2 arranged side by side with the N straight tube heat exchange tubes 1, and the straight tube heat exchange tubes 2 have independent low-temperature fuel inlets and normal-temperature gas fuel outlets for entering and exiting the shell;

The low-temperature freezing liquid enters the straight tube heat exchange tube 1 through the low-temperature freezing liquid inlet, and the natural gas after the low-temperature freezing liquid is heated and vaporized exits the straight tube heat exchange tube 1 and then exits the integrated heat exchanger from the steam outlet; a bent pipe is provided between the low-temperature freezing liquid inlet and the straight tube heat exchange tube 1 and/or between the straight tube heat exchange tube 1 and the steam outlet to compensate for the deformation and expansion caused by thermal expansion and contraction.

Preferably, the shell and the straight tube heat exchange tube are arranged at a small angle to the horizontal direction, so that the heat source medium outlet is located at a low place and the heat source medium inlet is located at a high place, and the low-temperature freezing liquid inlet is located at a low place and the steam outlet is located at a high place, the low-temperature freezing liquid from the bottom of the low-temperature freezing liquid tank enters from the bottom of the integrated heat exchanger through the low-temperature freezing liquid inlet, and the vaporized steam passes through the top of the integrated heat exchanger through the steam outlet, thereby avoiding excessive resistance of the supercharger caused by gas-liquid mixed flow.

Preferably, the diameter of the low-temperature freezing liquid inlet is smaller than the inner diameter of the straight tube heat exchange tube one; an expansion joint is provided between the low-temperature freezing liquid inlet and the straight tube heat exchange tube one, and the inner diameter of the expansion joint is larger than the diameter of the low-temperature freezing liquid inlet. The low-temperature freezing liquid entering through the low-temperature freezing liquid inlet flows through the expansion joint and then enters the straight tube heat exchange tube one.

Another technical solution of the present invention is to provide a control method for the above-mentioned novel self-pressurized gas supply system of LNG fuel for ships, which is characterized by comprising the following contents:

When it is necessary to increase the pressure of the cryogenic liquid storage tank to supply gas, the pressure is increased, including the following steps:

The controller collects the pressure signal of the cryogenic liquid storage tank through the pressure signal acquisition unit; the controller compares the real-time collected pressure value with the target boost setting value pre-set in the controller, and controls the switch of the remote self-boosting valve to achieve the boost start and boost stop targets; during self-boosting, the switch controls the remote self-boosting valve to be in a fully open flow state with the largest flow area; the pressure of the cryogenic liquid storage tank can be freely modified in the controller according to the needs to achieve different degrees of boosting purpose;

When it is necessary to reduce the pressure of the cryogenic liquid storage tank to prevent the liquid tank from overpressure, the pressure reduction is carried out, including the following steps:

The controller collects the pressure signal of the cryogenic liquid storage tank through the pressure signal acquisition unit; the controller compares the real-time collected pressure value with the target pressure reduction setting value pre-set in the controller, controls the switch of the remote control gas fuel valve through the switch, and transmits the evaporated gas to the gas-consuming equipment as fuel to reduce the pressure of the cryogenic liquid storage tank, so as to achieve the pressure reduction start and pressure reduction stop goals; the pressure of the cryogenic liquid storage tank can be freely modified in the controller according to the needs. The target pressure reduction setting value to achieve different degrees of pressure reduction purposes;

When various accidents and emergencies occur, the controller forcibly stops the normal operation of the boosting or decompression function by forcibly cutting off the switch to control the remote self-pressurizing valve or the switch to control the remote gas fuel valve, thereby realizing the safety protection function of the gas supply system and avoiding the problem of natural gas escape caused by overpressure in cryogenic liquid storage tanks and pipelines.

Preferably, before the cryogenic liquid storage tank needs to be refilled with cryogenic liquid, the pressure of the cryogenic liquid storage tank is reduced as much as possible by lowering the target pressure reduction setting value of the controller using a pressure reduction method, thereby making it easier to inject the cryogenic liquid.

Preferably, the controller collects the operation signal of the gas-consuming equipment through the operation signal acquisition unit, and collects the temperature signal of the gas in the normal temperature fuel delivery pipe through the temperature signal acquisition unit 2, and controls the switch to control the remote control self-boosting valve based on the operation signal and temperature signal collected in real time: when it is judged based on the operation signal that the gas-consuming equipment is not operating or it is judged based on the temperature signal that the outlet temperature of the gasifier is too low, the switch controls the remote control self-boosting valve forcibly cut off, and automatically prohibits the self-boosting system from working to avoid the risk of freezing and cracking of the gasifier.

Preferably, the air supply pipe in the joint is connected with the air vent pipe; along the transmission direction of the gas fuel, a switch-controlled remote-controlled gas main fuel valve, a switch-controlled remote-controlled fuel valve and a pressure regulating valve are sequentially arranged on the air supply pipe; the air vent pipe is connected to the portion of the air supply pipe located between the switch-controlled remote-controlled gas main fuel valve and the switch-controlled remote-controlled fuel valve, and a switch-controlled remote-controlled fuel air vent valve and a check valve are arranged on the air vent pipe; the switch-controlled remote-controlled gas main fuel valve, the switch-controlled remote-controlled fuel valve, the switch-controlled remote-controlled fuel air vent valve, the check valve and the pressure regulating valve are all located in the joint; the switch-controlled remote-controlled gas main fuel valve, the switch-controlled remote-controlled fuel valve and the switch-controlled remote-controlled fuel air vent valve form an interlocking valve group: the switch-controlled When the switch-controlled remote-controlled gas main fuel valve and the switch-controlled remote-controlled fuel valve are closed, the switch-controlled remote-controlled fuel ventilation valve automatically opens; when the switch-controlled remote-controlled gas main fuel valve and the switch-controlled remote-controlled fuel valve are opened, the switch-controlled remote-controlled fuel ventilation valve automatically closes; when the switch-controlled remote-controlled gas main fuel valve, the switch-controlled remote-controlled fuel valve and the switch-controlled remote-controlled fuel ventilation valve are interlocked, a mode of immediately closing the valve and delaying opening the valve is set in the controller to avoid the simultaneous opening overlapping time of the interlock valve group composed of the switch-controlled remote-controlled gas main fuel valve, the switch-controlled remote-controlled fuel valve and the switch-controlled remote-controlled fuel ventilation valve, so as to avoid gas escape. The above valves are arranged inside the joint.

Preferably, the controller collects the temperature signal in the overflow tube through a temperature signal collection unit 1, and compares the collected real-time temperature with the target temperature setting value preset in the controller: when no overflow occurs, the overflow tube is in contact with the environment at room temperature; when overflow occurs, the temperature of the overflow tube is too low, and the controller generates a low-temperature overflow alarm, thereby determining whether the low-temperature frozen liquid storage tank is overfilled.

The present invention optimizes the LNG fuel gas supply system by adopting two core key technologies: first, a new type of low-resistance, high-efficiency self-supercharger and self-supercharger system is adopted to reduce the resistance of the self-supercharger system and improve the supercharging effect of the self-supercharger system from the perspective of improving the internal structure of the self-supercharger and increasing the flow area of the self-supercharger system valve to optimize the LNG fuel gas supply system. Second, from the perspective of improving the system design and its control method, the precision control of the gas supply pressure, the safety protection cut-off and the practical problem of natural gas emission escape are achieved.

Specifically, the present invention provides a novel self-pressurizing gas supply system for marine LNG fuel and a control method thereof to achieve a beneficial gas supply effect in the following manner:

(1) A new type of high-efficiency integrated heat exchanger is used to realize the functions of the self-boosting device and the vaporizer. The layout of the self-boosting device is inclined, and the inclination angle is generally within 30°. The heat exchange tubes inside the self-boosting device adopt a straight tube design method. This design type can realize gas-liquid separation in time inside the self-boosting device, and solve the problem that the spiral winding type cannot separate gas and liquid in time, the gas-liquid mixed flow resistance is large, and even the gas backflow blows the liquid out of the inlet. The straight tube diameter is also much larger than the same type of spiral winding coil. The pipeline flow rate is low, the resistance is small, and the liquid inlet is continuous, which greatly improves the boosting efficiency of the self-boosting device. The integrated design form will realize the functional integration of two LNG vaporizers, reduce the number of vaporizers, and improve the heat exchange efficiency.

(2) A switch-controlled remote-controlled booster valve is used to replace the traditional mechanical spring self-actuated booster valve. The controller collects the pressure signal of the LNG tank and compares it with the target pressure setting value set inside the controller to automatically control the switch of the booster valve to achieve the boosting target. During self-boosting, the booster valve is in a fully open flow state with the largest flow area, which greatly reduces the pipeline and valve resistance of the self-boosting system and increases the liquid intake and self-boosting efficiency.

(3) A switch-controlled remote-controlled gas fuel valve is used to replace the traditional mechanical spring self-acting pressure reducing valve. The controller collects the pressure signal of the LNG tank and compares it with the target pressure setting value set inside the controller to automatically control the switch state of the gas fuel valve, and the pressure of the LNG tank is reduced by delivering the evaporated gas to the engine as fuel. The pressure of the LNG tank can be freely modified in the controller 400 according to the needs to achieve different degrees of pressure reduction.

(4) Before the LNG tank needs to be refilled with LNG liquid, the pressure of the LNG tank needs to be reduced as much as possible to make it easier to inject LNG liquid. According to the method in point (3), the beneficial effect of reducing the pressure of the LNG tank and facilitating refilling can be achieved by lowering the pressure reduction setting value of the controller.

(5) The heat source required by the integrated heat exchanger comes from external hot water, but when there is insufficient hot water, the LNG liquid flowing into the integrated heat exchanger is prone to freezing and cracking, and the vaporizer outlet temperature is too low, causing low-temperature damage to the engine. The controller controls the self-pressurization valve by collecting the engine operation signal and the vaporizer outlet temperature signal. When the engine is not running or the vaporizer outlet temperature is too low, even if the LNG tank needs to be pressurized to increase the pressure, the self-pressurization valve is forcibly cut off, and the self-pressurization system is automatically prohibited from working to avoid the risk of vaporizer freezing and cracking.

(6) The traditional interlock valve group 3 is arranged in the engine room, near the machine. According to the ship specification requirements, in order to prevent valve leakage from causing gas fuel to enter the engine room, the interlock valve group needs to be installed in a closed container to form a complete gas valve group unit GVU, in which the gas pipeline of the gas valve group unit is connected to the inner pipe of the double-walled pipe, and the internal space of the pressure vessel is connected to the outer pipe of the double-walled pipe. By centrally arranging the interlock valve group inside the joint of the LNG tank and concentrating it with the pipeline valves of other gas supply systems, it is convenient for operation and maintenance and centralized monitoring of gas leakage, and the high-cost and high-requirement gas valve group unit GVU in the engine room is eliminated.

(7) By providing a check valve downstream of the remote-controlled fuel vent valve, which is one of the interlocking valves, it is prevented that air flows back into the gas pipeline after the vent valve is opened to form a dangerous source of air-gas mixture.

(8) When the traditional interlock valve group is switched, the valve action switches at the same time. Since the valve action has a switching travel time, there is a time period when the three interlock valves are simultaneously opened in an overlapping manner during the interlock valve switching period, which will cause the gas fuel (such as: gas buffer tank) in the equipment pipeline upstream and downstream of the interlock valve to escape through the remote control fuel vent valve during the overlapping time period. To solve the above hidden dangers, when the controller interlocks the interlock valve group, it sets the method of immediately closing the valve and delaying the opening of the valve in the controller to avoid the overlapping time of the interlock valve group opening at the same time, thereby avoiding the phenomenon of gas escape.

(9) An overflow outlet is set at the maximum filling level of the LNG tank. When the liquid level is too high, the liquid flows from the outlet into the overflow tube. The overflow tube is located below the overflow outlet. The liquid in the overflow tube is gasified and returns to the LNG tank through the overflow return port, thereby avoiding the problem of gas accumulation in the overflow tube that prevents the liquid from flowing in, and also avoiding the problem of LNG liquid or gas being discharged into the atmosphere. The temperature signal in the overflow tube is collected and sent to the controller, and compared with the target temperature setting value set inside the controller. When no overflow occurs, the overflow tube is in contact with the environment at normal temperature. When overflow occurs, the temperature of the overflow tube is too low, and the controller generates a low-temperature overflow alarm.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a diagram of the LNG tank self-pressurization system;

FIG2 is a schematic diagram of a mechanical spring self-acting boost regulating valve;

FIG3 is a schematic diagram of a coiled tube type LNG vaporizer;

Figure 4 is a schematic diagram of the self-pressurization principle of a conventional ship LNG tank;

FIG5 is a schematic diagram of the system disclosed in CN 110886670A;

FIG6 is a schematic diagram of a system disclosed in CN 213065523U;

FIG7 is a schematic diagram of the system disclosed in CN 111550675A;

FIG8 is a schematic diagram of a system disclosed in CN 104791602B;

FIG9 is a schematic diagram of a novel self-pressurizing gas supply system for LNG fuel for ships disclosed in an embodiment;

FIG10 is a side view of an integrated heat exchanger used in the embodiment;

FIG. 11 is a top view of an integrated heat exchanger used in the embodiment.

DETAILED DESCRIPTION

The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

The present embodiment discloses a novel self-pressurizing gas supply system for marine LNG fuel, as shown in FIG9 , including an LNG liquid tank 100 having a liquid fuel outlet 110, a self-pressurizing liquid outlet 111, a gas phase port 112, an overflow return gas port 113, and an overflow liquid outlet 114. The joint 101 is welded on the outer shell of the LNG liquid tank 100, and is a closed structure for accommodating the joint leakage of the LNG liquid tank 100. The material of the joint 101 is equivalent to the material of the LNG liquid tank 100 that can withstand LNG liquid. The joint 101 contains an integrated heat exchanger 102 that integrates the self-booster and the vaporizer, a gas buffer tank 103, and an overflow cylinder 104.

The pressure signal collecting unit 402 collects the pressure signal of the LNG liquid tank 100 and sends the collected pressure signal to the controller 400 located outside the joint location 101 .

The overflow outlet 114 of the LNG tank 100 is connected to the overflow cylinder 104 via the overflow outlet pipe, and the overflow cylinder 104 is connected to the overflow return gas port 113 of the LNG tank 100 via the overflow return gas pipe. The temperature signal of the overflow cylinder 104 is collected by the temperature signal collection unit 1 403, and the collected temperature signal is sent to the controller 400 located outside the joint 101.

The integrated heat exchanger 102 includes a group of straight heat exchange tubes 6 for realizing the self-boosting function of the self-boosting device and a group of wound coils 10 wound on the straight heat exchange tubes 6. The wound coils 10 are used to realize the function of heating the low-temperature fuel of the vaporizer to normal-temperature fuel. At the same time, the integrated heat exchanger 102 has an LNG liquid inlet 120 connected to the straight heat exchange tubes 6 and a steam outlet 121 after the LNG liquid is heated and vaporized; the integrated heat exchanger 102 also has a low-temperature fuel inlet 122 and a normal-temperature gas fuel outlet 123 connected to the wound coils 10; the integrated heat exchanger 102 also has a hot water or other heat source medium inlet 2 and a hot water or other heat source medium outlet 3.

The LNG liquid inlet 120 of the integrated heat exchanger 102 is connected to the self-pressurizing liquid outlet 111 of the LNG tank 100 via the LNG liquid delivery pipe, and a switch-controlled remote-controlled self-pressurizing valve 300 is provided on the LNG liquid delivery pipe. The steam outlet 121 of the integrated heat exchanger 102 is connected to the gas phase port 112 of the LNG tank 100 via the steam delivery pipe. One end of the bypass pipe is connected to the steam delivery pipe, and the other end is connected to the low-temperature fuel delivery pipe, and a switch-controlled remote-controlled gas fuel valve 302 is provided on the bypass pipe. The low-temperature fuel delivery pipe is connected to the low-temperature fuel inlet 122 of the integrated heat exchanger 102, and at the same time, the low-temperature fuel delivery pipe is also connected to the liquid fuel outlet 110 of the LNG tank 100 via the liquid fuel delivery pipe. A switch-controlled remote-controlled liquid fuel valve 301 is provided on the liquid fuel delivery pipe. The normal temperature gas fuel outlet 123 of the integrated heat exchanger 102 is connected to the gas buffer tank 103 via the normal temperature fuel delivery pipe. The temperature signal acquisition unit 2 404 acquires the temperature signal of the gas in the normal temperature fuel delivery pipe and sends the temperature signal to the controller 400 located outside the joint 101.

The hot water or other heat source medium inlet 2 and the hot water or other heat source medium outlet 3 of the integrated heat exchanger 102 are respectively connected to the heat source medium inlet interface 124 and the heat source medium outlet interface 125 located outside the joint location 101 .

The gas buffer tank 103 is connected to the gas engine 201 using gas fuel located outside the joint 101 via the gas supply pipe. The gas supply pipe in the joint 101 is connected to the ventilation pipe. Along the transmission direction of the gas fuel, the gas supply pipe is provided with a switch-controlled remote-controlled gas main fuel valve 303, a switch-controlled remote-controlled fuel valve 304 and a pressure regulating valve 307 in sequence. The ventilation pipe is connected to the part of the gas supply pipe located between the switch-controlled remote-controlled gas main fuel valve 303 and the switch-controlled remote-controlled fuel valve 304, and the ventilation pipe is provided with a switch-controlled remote-controlled fuel ventilation valve 305 and a check valve 306. The switch-controlled remote-controlled gas main fuel valve 303, the switch-controlled remote-controlled fuel valve 304, the switch-controlled remote-controlled fuel ventilation valve 305, the check valve 306 and the pressure regulating valve 307 are all located in the joint 101. The switch-controlled remote-controlled gas main fuel valve 303, the switch-controlled remote-controlled fuel valve 304, and the switch-controlled remote-controlled fuel ventilation valve 305 constitute an interlocking valve group: when the switch-controlled remote-controlled gas main fuel valve 303 and the switch-controlled remote-controlled fuel valve 304 are closed, the switch-controlled remote-controlled fuel ventilation valve 305 automatically opens; when the switch-controlled remote-controlled gas main fuel valve 303 and the switch-controlled remote-controlled fuel valve 304 are opened, the switch-controlled remote-controlled fuel ventilation valve 305 automatically closes.

The gas engine 201 is located in the machine room 200, and a double-walled gas pipeline 203 is provided in the machine room 200. The gas supply pipe is connected to the gas engine 201 via the inner pipe 202 of the double-walled gas pipeline 203. The gas engine 201 has an operation signal acquisition unit 401, and the operation signal acquisition unit 401 sends the collected operation signal of the gas engine 201 to the controller 400 located outside the joint room 101.

In this embodiment, the structure of the integrated heat exchanger 102 is shown in Figures 10 and 11, and includes a shell 1, and a hot water or other heat source medium inlet 2 and a hot water or other heat source medium outlet 3 are respectively provided at the front and rear ends of the shell 1. A straight tube heat exchange tube 6 is arranged in the shell 1. The shell 1 and the straight tube heat exchange tube 6 therein are arranged at a small angle to the horizontal direction, so that the hot water or other heat source medium outlet 3 is located at a low position and the hot water or other heat source medium inlet 2 is located at a high position, and the LNG liquid inlet 120 connected to the straight tube heat exchange tube 6 is located at a low position and the steam outlet 121 connected to the straight tube heat exchange tube 6 is located at a high position. The angle θ between the axis of the shell 11 and the axis of the straight tube heat exchange tube 6 and the horizontal plane is generally within 30°.

The LNG liquid entering through the LNG liquid inlet 120 is connected to the straight tube heat exchange tube 6 through the expansion joint 5 and the elbow 7-1 in turn. The vaporized steam exiting the straight tube heat exchange tube 6 exits the integrated heat exchanger 102 from the steam outlet 121 through the elbow 7-2. Assuming that the diameter of the LNG liquid inlet 120 is R1, the inner diameter of the expansion joint 5 is R2, the inner diameter of the straight tube heat exchange tube 6 is R3, the inner diameters of the elbows 7-1 and 7-2 are R4, and the diameter of the steam outlet 121 is R5, then: R1<R2, R2＝R3＝R4≤R5, the inner diameter R5 of the vaporized steam outlet pipe 121 can be further expanded according to actual needs to reduce resistance. The elbows 7-1 and 7-2 are used to compensate for thermal expansion and contraction. The connection between the expansion joint 5 and the elbow 7-1, between the elbow 7-1 and the straight heat exchange tube 6, and between the straight heat exchange tube 6 and the elbow 7-2 are all in the form of butt welding.

A group of wound coils 10 are sleeved outside the straight tube heat exchange tube 6. The wound coils 10 have independent low temperature fuel inlet 122 and normal temperature gas fuel outlet 123. It should be noted that the wound coils 10 can also adopt other structures and arrangements, for example, the wound coils 10 can adopt a straight tube structure and be arranged side by side with the straight tube heat exchange tube 6, etc., which will not be repeated here.

In this embodiment, the self-supercharger integrated in the integrated heat exchanger 102 achieves self-supercharging with low resistance and high supercharging efficiency by greatly reducing the resistance of the self-supercharging system, separating gas and liquid in time without mixing, and improving the liquid inlet efficiency of the self-supercharger. At the same time, the integrated heat exchanger 102 integrates the self-supercharger and the vaporizer into one, maximizes the use of the internal space of the heat exchanger, reduces the number of heat exchangers, and improves the heat exchange efficiency of the heat exchanger.

The control method of the self-pressurizing gas supply system of the new type of marine LNG fuel includes the following contents:

When the pressure of the LNG liquid tank 100 needs to be increased to supply gas, the pressure is increased, including the following steps:

The controller 400 collects the pressure signal of the LNG liquid tank 100 through the pressure signal acquisition unit 402. The controller 400 compares the real-time collected pressure value with the target boost setting value pre-set in the controller 400, and controls the switch of the remote control self-boosting valve 300 through the switch to achieve the boost start and boost stop targets. During self-boosting, the switch controls the remote control self-boosting valve 300 to be in a fully open flow state, with the largest flow area, which greatly reduces the pipeline and valve resistance of the self-boosting system and increases the liquid intake and self-boosting efficiency. The pressure of the LNG liquid tank 100 can be freely modified in the controller 400 according to the needs to achieve different degrees of boosting.

When it is necessary to reduce the pressure of the LNG tank 100 to prevent overpressure of the tank, the pressure reduction is performed, including the following steps:

The controller 400 collects the pressure signal of the LNG tank 100 through the pressure signal acquisition unit 402. The controller 400 compares the real-time collected pressure value with the target pressure reduction setting value pre-set in the controller 400, and controls the switch of the remote control gas fuel valve 302 by switching to reduce the pressure of the LNG tank 100 by delivering the evaporated gas to the engine 201 as fuel, so as to achieve the decompression start and decompression stop goals. The pressure of the LNG tank 100 can be freely modified in the controller 400 according to the needs to achieve different degrees of pressure reduction.

Before the LNG tank 100 needs to be refilled with LNG liquid, the pressure of the LNG tank 100 needs to be reduced as much as possible, so that the LNG liquid can be injected more easily. By lowering the target pressure reduction setting value of the controller 400, the pressure of the LNG tank 100 can be reduced by using the above pressure reduction method to facilitate the beneficial effect of refilling the LNG liquid.

When various accidents and emergencies occur, including but not limited to fire, gas leakage, abnormal hot water supply, low gasifier outlet temperature, etc., the controller 400 forcibly stops the normal operation of the pressurization or decompression function and stops the external transmission of low-temperature fuel by forcibly cutting off the switch-controlled remote-controlled self-pressurization valve 300 or the switch-controlled remote-controlled gas fuel valve 302 or the switch-controlled remote-controlled liquid fuel valve 301, thereby realizing the safety protection function of the gas supply system and avoiding the problem of natural gas escape caused by overpressure of the LNG liquid tank 100 and the pipeline.

The heat source required by the integrated heat exchanger 102 comes from external hot water, but when the hot water is insufficient, the LNG liquid flowing into the integrated heat exchanger 102 is prone to freezing and cracking, and the normal temperature gas fuel outlet 123 of the gasifier integrated in the integrated heat exchanger 102 is too low in temperature, resulting in low temperature damage to the engine 201. In order to solve this problem, in the technical solution disclosed in this embodiment, the controller 400 collects the operation signal of the engine 201 through the operation signal acquisition unit 401, and collects the temperature signal of the gas in the normal temperature fuel delivery pipe through the temperature signal acquisition unit 2 404. The switch controls the remote control self-pressurization valve 300 based on the real-time collected operation signal and temperature signal. Specifically, when it is judged that the engine 201 is not running based on the operation signal or the outlet temperature of the gasifier is too low based on the temperature signal, even if the LNG liquid tank 100 needs to be pressurized to increase the pressure, the switch controls the remote control self-pressurization valve 300 and automatically prohibits the self-pressurization system from working to avoid the risk of freezing and cracking of the gasifier.

When the conventional interlock valve group is switched, the switch action is performed simultaneously. Since there is a switch travel time for the valve action, there is a time period during which the three interlock valves are simultaneously in overlapping opening, which will cause the gas fuel (such as: gas buffer tank 103) in the equipment pipeline upstream and downstream of the interlock valve to escape through the switch-controlled remote-controlled gas fuel valve 302 during the overlapping time period. To solve the above hidden dangers, in this embodiment, when the controller 400 interlocks the switch-controlled remote-controlled gas main fuel valve 303, the switch-controlled remote-controlled fuel valve 304 and the switch-controlled remote-controlled fuel breathable valve 305, the controller 400 sets the mode of immediately closing the valve and delaying the opening of the valve in the controller 400 to avoid the overlapping time of the simultaneous opening of the interlock valve group composed of the switch-controlled remote-controlled gas main fuel valve 303, the switch-controlled remote-controlled fuel valve 304 and the switch-controlled remote-controlled fuel breathable valve 305, thereby avoiding the gas escape phenomenon.

An overflow outlet 114 is provided at the maximum filling level of the LNG tank 101. When the liquid level is too high, the liquid flows into the overflow cylinder 104 below the overflow outlet 114 by its own weight from the overflow outlet 114. An overflow return opening is provided at the top of the overflow cylinder 104 to communicate with the overflow return port 113 at the top of the LNG tank 101. After the liquid in the overflow cylinder 104 is vaporized, it returns to the LNG tank 101 through the overflow return port 113, thereby avoiding the problem of the liquid being unable to flow in due to the accumulation of air pressure in the overflow cylinder 104, and also avoiding the problem of LNG liquid or gas being discharged into the atmosphere when the overflow is full. The controller 400 collects the temperature signal in the overflow cylinder 104 through the temperature signal acquisition unit 403, and compares the collected real-time temperature with the target temperature setting value preset in the controller 400. When no overflow occurs, the overflow cylinder 104 is in contact with the environment at room temperature. When overflow occurs, the temperature of the overflow tube 104 is too low, and the controller 400 generates a low-temperature overflow alarm, thereby determining whether the LNG liquid tank 101 is overfilled.

The gas engine 201 can be one or more, or other gas-consuming equipment. It can include only one set of joints 101 welded on the LNG tank and its internal gas supply system, or multiple sets of independent joints 101 and their internal gas supply systems using the same gas supply principle. The controller 400 can have only one controller, and the controller 400 can have redundant functions or not, or it can be multiple independent controllers with process control and safety protection functions respectively. Each signal source collected by the controller 400 can be provided by one sensor, or it can be provided by multiple redundant or independent sensors. The heat source for LNG gasification is shown as hot water, or it can be various forms of heat sources such as hot oil, steam, ethylene glycol-water, or other antifreeze. The low-temperature medium of the LNG fuel gas supply system is shown as LNG, or it can be liquid nitrogen, liquefied petroleum gas, liquid hydrogen, liquid ammonia and other various low-temperature refrigeration liquids. The changes in the above-mentioned details, as long as the same or similar LNG fuel gas supply system design method is adopted, are all within the scope of protection of the present invention.

Claims (8)

1. Novel marine LNG fuel's self-pressurization gas supply system, its characterized in that includes low temperature freezing liquid storage tank, and low temperature freezing liquid storage tank is linked together with the gas supply system that J cover is located the junction inside, and J is greater than or equal to 1, and every gas supply system is K gas consumption equipment gas supply, and K is greater than or equal to 1, and gas consumption equipment is located the machine department, wherein:

The pressure signal acquisition unit acquires the pressure signal of the low-temperature frozen liquid storage tank and sends the acquired pressure signal to a controller positioned outside the joint; the low-temperature frozen liquid storage tank is provided with a liquid fuel outlet, a self-pressurizing liquid outlet and a gas phase port;

each set of air supply system comprises an integrated heat exchanger integrating the self-booster and the gasifier into a whole and a gas buffer tank; the self-booster integrated in the integrated heat exchanger is provided with a low-temperature frozen liquid inlet and a steam outlet after the low-temperature frozen liquid is heated and gasified; the gasifier integrated in the integrated heat exchanger is provided with a low-temperature fuel inlet and a normal-temperature gas fuel outlet; the integrated heat exchanger is also provided with a heat source medium inlet and a heat source medium outlet; the low-temperature frozen liquid inlet of the integrated heat exchanger is communicated with a self-pressurizing liquid outlet of the low-temperature frozen liquid storage tank through a low-temperature frozen liquid conveying pipe, and a switch control remote control self-pressurizing valve is arranged on the low-temperature frozen liquid conveying pipe; the steam outlet of the integrated heat exchanger is communicated with a gas phase port of the low-temperature frozen liquid storage tank through a steam conveying pipe; one end of the bypass pipe is communicated with the steam delivery pipe, the other end of the bypass pipe is communicated with the low-temperature fuel delivery pipe, and a switch control remote control gas fuel valve is arranged on the bypass pipe; the low-temperature fuel conveying pipe is communicated with the low-temperature fuel inlet of the integrated heat exchanger, and meanwhile, the low-temperature fuel conveying pipe is also communicated with the liquid fuel outlet of the low-temperature frozen liquid storage tank through the liquid fuel conveying pipe; a switch control remote control liquid fuel valve is arranged on the liquid fuel conveying pipe; the temperature signal acquisition unit II acquires a temperature signal of fuel gas in the normal temperature fuel conveying pipe and sends the temperature signal to the controller; the heat source medium inlet and the heat source medium outlet of the integrated heat exchanger are respectively communicated with a heat source medium inlet interface and a heat source medium outlet interface which are positioned outside the joint; the gas buffer tank is communicated with K gas consumption devices positioned outside the joint through a gas supply pipe;

an overflow liquid outlet is arranged at the maximum filling liquid level of the low-temperature frozen liquid storage tank, and the low-temperature frozen liquid storage tank is also provided with an overflow gas port;

each set of air supply system also comprises an overflow cylinder;

The overflow liquid outlet of the low-temperature frozen liquid storage tank is communicated with an overflow cylinder through an overflow liquid outlet pipe, and the overflow cylinder is communicated with an overflow air return port of the low-temperature frozen liquid storage tank through an overflow air return pipe; the first temperature signal acquisition unit acquires the temperature signal of the overflow cylinder and sends the acquired temperature signal to the controller;

the integrated heat exchanger comprises a shell and N straight pipe type heat exchange pipes I arranged in the shell, wherein N is more than or equal to 1;

The shell is provided with the heat source medium inlet and the heat source medium outlet;

M groups of spiral pipe type heat exchange pipes are sleeved outside the N straight pipe type heat exchange pipes, M is more than or equal to 1, and the heat exchange pipes are provided with the low-temperature fuel inlet and the normal-temperature gas fuel outlet which are independently communicated with the outer shell; or a first straight pipe type heat exchange pipe II which is formed by arranging M groups of straight pipe type heat exchange pipes and N straight pipe type heat exchange pipes side by side, wherein the first straight pipe type heat exchange pipe II is provided with the low-temperature fuel inlet and the normal-temperature gas fuel outlet which are independently communicated with the shell;

The low-temperature frozen liquid enters the straight pipe type heat exchange pipe I through the low-temperature frozen liquid inlet, and natural gas after being heated and gasified exits the straight pipe type heat exchange pipe I and then exits the integrated heat exchanger from the steam outlet; and bent pipes for compensating deformation expansion and contraction caused by thermal expansion and contraction are arranged between the low-temperature frozen liquid inlet and the straight pipe type heat exchange pipe I and/or between the straight pipe type heat exchange pipe I and the steam outlet.

2. The novel marine LNG fuel self-pressurization gas supply system according to claim 1, wherein the arrangement forms of the shell and the straight tube heat exchange tube are all arranged in a small angle inclination with the horizontal direction, so that the heat source medium outlet is located at a low position and the heat source medium inlet is located at a high position, the low-temperature freezing liquid inlet is located at a low position and the steam outlet is located at a high position, the low-temperature freezing liquid from the bottom of the low-temperature freezing liquid tank enters from the bottom of the integral heat exchanger through the low-temperature freezing liquid inlet, and the gasified steam is transmitted from the top of the integral heat exchanger through the steam outlet, thereby avoiding excessive resistance of the pressurizer due to mixed gas-liquid flow.

3. The novel self-pressurization gas supply system for marine LNG fuel as claimed in claim 2, wherein the diameter of the cryogenic liquid inlet is smaller than the inner diameter of the straight tube heat exchange tube one; an expanding joint is arranged between the low-temperature frozen liquid inlet and the straight pipe type heat exchange pipe I, the inner diameter of the expanding joint is larger than the diameter of the low-temperature frozen liquid inlet, and the low-temperature frozen liquid entering through the low-temperature frozen liquid inlet flows through the expanding joint and then enters the straight pipe type heat exchange pipe I.

4. A control method of a novel marine LNG fuel self-pressurization gas supply system according to claim 1, comprising the following steps:

when the pressure of the low-temperature frozen liquid storage tank needs to be increased for air supply, the pressure is increased, and the method comprises the following steps:

The controller collects pressure signals of the low-temperature frozen liquid storage tank through the pressure signal collecting unit; the controller compares the pressure value acquired in real time with a target boost set value which is set in the controller in advance, and controls the switch of the remote control self-boosting valve through the switch to realize the aims of boosting start and boosting stop; when self-pressurization is carried out, the switch controls the remote control self-pressurization valve to be in a full-open circulation state, and the flow area is maximum; the pressure of the low-temperature frozen liquid storage tank can freely modify the target boosting set value in the controller according to the requirement to achieve the purpose of boosting in different degrees;

When the pressure of the low-temperature frozen liquid storage tank needs to be reduced to prevent the overpressure of the liquid tank, the pressure is reduced, and the method comprises the following steps of:

The controller collects pressure signals of the low-temperature frozen liquid storage tank through the pressure signal collecting unit; the controller compares the pressure value acquired in real time with a target depressurization set value which is set in the controller in advance, and reduces the pressure of the low-temperature frozen liquid storage tank in a mode of conveying the evaporated gas to the gas consumption equipment as fuel by controlling the switch of a remote control gas fuel valve so as to realize the aim of depressurization starting and depressurization stopping; the pressure of the low-temperature frozen liquid storage tank can freely modify the target depressurization set value in the controller according to the requirement to achieve the depressurization purpose of different degrees;

When various accidents and emergency situations occur, the controller forcibly stops the normal operation of the pressurizing or depressurizing function by forcibly cutting off the switch to control the remote control self-pressurizing valve or the method for controlling the remote control gas fuel valve by the switch, thereby realizing the safety protection function of the gas supply system and avoiding the natural gas escape problem caused by the overpressure of the low-temperature frozen liquid storage tank and the pipeline.

5. The control method of claim 4, wherein the pressure in the cryogenic liquid storage tank is reduced as much as possible by reducing the target pressure reduction setting of the controller before the cryogenic liquid storage tank needs to be refilled with cryogenic liquid, thereby making it easier to inject the cryogenic liquid.

6. The control method according to claim 4, wherein the controller collects an operation signal of the gas consuming apparatus through the operation signal collection unit, and collects a temperature signal of the gas in the normal temperature fuel delivery pipe through the temperature signal collection unit two, and controls the on-off control of the remote control self-pressurizing valve based on the operation signal collected in real time and the temperature signal: when the gas consumption equipment is judged not to operate based on the operation signal or the outlet temperature of the gasifier is judged to be too low based on the temperature signal, the forced cut-off switch controls the remote control self-pressurization valve, and the self-pressurization system is automatically forbidden to work so as to avoid the risk of freezing and cracking of the gasifier.

7. The control method of claim 4, wherein the gas supply pipe in the junction is in communication with the gas permeable pipe; a switch control remote control gas main fuel valve, a switch control remote control fuel valve and a pressure regulating valve are sequentially arranged on the gas supply pipe along the transmission direction of the gas fuel; the gas vent pipe is connected with the gas supply pipe at the part between the switch control remote control gas main fuel valve and the switch control remote control fuel valve, and is provided with the switch control remote control fuel gas vent valve and the check valve; the switch control remote control gas main fuel valve, the switch control remote control fuel ventilation valve, the check valve and the pressure regulating valve are all positioned in the joint; the switch control remote control gas main fuel valve, the switch control remote control fuel valve and the switch control remote control fuel ventilation valve form an interlocking valve group: when the switch control remote control gas main fuel valve and the switch control remote control fuel valve are closed, the switch control remote control fuel ventilation valve is automatically opened; when the switch control remote control gas main fuel valve and the switch control remote control fuel valve are opened, the switch control remote control fuel ventilation valve is automatically closed; when the interlocking control switch controls the remote control gas main fuel valve, the switch control remote control fuel valve and the switch control remote control fuel ventilation valve, a mode of immediately closing the valve and opening the valve in a delayed manner is arranged in the controller, so that the overlapping time of opening the interlocking valve group consisting of the switch control remote control gas main fuel valve, the switch control remote control fuel valve and the switch control remote control fuel ventilation valve is avoided, the gas escape phenomenon is avoided, and the valves are all arranged in the joint.

8. The control method according to claim 4, wherein the controller collects the temperature signal in the overflow cylinder through the temperature signal collection unit one, and compares the collected real-time temperature with a target temperature set value preset in the controller: when overflow does not occur, the overflow cylinder is in normal temperature state in contact with the environment; when overflow occurs, the temperature of the overflow cylinder is too low, and the controller generates low-temperature overflow alarm, so that whether the low-temperature frozen liquid storage tank is overfilled or not is judged.