A method of pre-cooling, filling and exhaust gas treatment of an LNG fuelled ship

Abstract

This invention relates to the field of liquefied gas storage and distribution technology, specifically disclosing a pre-cooling, refueling, and exhaust gas treatment system for an LNG-fueled ship, comprising the following steps: Step S1: Pre-cooling the fuel tank of the LNG-fueled ship by connecting a liquid nitrogen tanker to a vaporization skid; Step S11: Low-temperature nitrogen / liquid nitrogen from the liquid nitrogen tanker is transported to the input pipeline via the vaporization skid, and the low-temperature nitrogen / liquid nitrogen is transported to the fuel tank via the input pipeline; Step S2: Vaporized natural gas is generated by connecting an LNG tanker to the vaporization skid to remove nitrogen from the fuel tank of the LNG-fueled ship, completing the LNG replacement of the fuel tank; Step S3: The LNG tanker achieves gas-phase pressurization via the vaporization skid, and LNG is transported to the fuel tank via the input pipeline, completing the LNG refueling of the fuel tank; Step S4: The LNG tanker achieves gas-phase pressurization via the vaporization skid and the refueling skid, and LNG enters the LNG submersible pump of the refueling skid, and LNG is transported to the fuel tank via the LNG submersible pump, completing the LNG refueling of the fuel tank.

Description

Technical Field

[0001] This invention relates to the field of liquefied gas storage and distribution technology, and in particular to methods for precooling, refueling and exhaust gas treatment of LNG-fueled ships. Background Technology

[0002] LNG, or liquefied natural gas, is typically stored at around -160°C. Due to its low temperature and volatile nature, it poses certain risks during the refueling and operation of ships powered by LNG. LNG-fueled ships generally require liquid nitrogen precooling and initial LNG refueling at the shipyard. Furthermore, the fuel tanks need to be precooled before the initial LNG refueling to ensure the temperature is suitable for storing LNG and to prevent safety issues and equipment damage caused by excessive temperature differences. Currently, the precooling, refueling, and exhaust gas treatment of LNG-fueled ships are handled by separate systems, lacking a complete integrated system. Therefore, there is an urgent need for a system that integrates nitrogen precooling, LNG refueling, and exhaust gas treatment for precooling and initial refueling of LNG-fueled ships at the shipyard. Summary of the Invention

[0003] In view of this, the present invention provides a method for precooling, refueling and exhaust gas treatment of LNG fuel ships to solve the technical problems in the background art mentioned above.

[0004] To achieve one, some, or all of the above objectives, or other objectives, the present invention proposes: a method for precooling, refueling, and exhaust gas treatment of an LNG-fueled ship, comprising: Step S1: Pre-cool the fuel tank of the LNG fuel ship by connecting a liquid nitrogen tanker to a vaporization skid. Step S1 specifically involves: Step S11: The cryogenic nitrogen / liquid nitrogen from the liquid nitrogen tanker is transported to the input pipeline via the vaporization skid, and the cryogenic nitrogen / liquid nitrogen is transported to the fuel tank via the input pipeline; Step S12: Low-temperature nitrogen / liquid nitrogen is exchanged for heat with the fuel tank and then sequentially transported to the heating skid and the long-burning flare system through the discharge pipeline for exhaust gas treatment and discharge; Step S2: Use an LNG tanker connected to a gasification skid to generate gasified natural gas to remove nitrogen from the fuel tank of the LNG-fueled ship, thus completing the LNG replacement of the fuel tank. Step S3: The LNG tanker truck uses a vaporization skid to pressurize the gas phase, and the LNG is transported to the fuel tank through the input pipeline, completing the LNG refueling of the fuel tank; Step S4: The LNG tanker achieves gas phase pressurization through the vaporization skid and the refueling skid. LNG enters the LNG submersible pump on the refueling skid and is then transported to the fuel tank through the LNG submersible pump, completing the LNG refueling of the fuel tank.

[0005] Preferably, step S11 includes: Step S110: The liquid nitrogen in the liquid nitrogen tanker is vaporized and heated by the ambient temperature vaporizer in the vaporization skid to form low-temperature nitrogen gas. Step S111: Cryogenic nitrogen is delivered to the fuel tank through the input pipeline.

[0006] Preferably, step S11 includes: Step S112: The liquid nitrogen tanker is pressurized by its own booster, creating a pressure difference between the liquid nitrogen tanker and the vaporization skid; Step S113: The cryogenic nitrogen or a small amount of liquid nitrogen in the liquid nitrogen tanker enters the input pipeline through the valve V104 (V104') of the vaporization skid under the action of pressure difference and is transported to the fuel tank.

[0007] Preferably, step S11 further includes: Step S114: A large amount of liquid nitrogen in the liquid nitrogen tanker enters the input pipeline and is transported to the fuel tank through the valve V103 (V103') of the vaporization skid under the action of pressure difference.

[0008] Preferably, step S3 includes: Step S31: After the LNG in the LNG tanker flows by gravity through the liquid phase valve of the tanker, it enters the ambient temperature vaporizer of the vaporization skid for vaporization and pressurization, and the LNG tanker is in gas phase. Step S32: Under the action of pressure difference, the LNG in the LNG tanker enters the input pipeline through the valve V103 (V103') of the vaporization skid and is transported to the fuel tank.

[0009] Preferably, step S3 further includes; Step S33: Under the action of pressure difference, the LNG in the LNG tanker enters the input pipeline through valve V103 (V103') of the vaporization skid. The LNG enters the LNG submersible pump through the input pipeline and valve V205. The LNG is then transported to the fuel tank by the LNG submersible pump.

[0010] Preferably, step S4 includes: Step S41: The LNG in the LNG tanker truck docked at the gasification skid enters the LNG submersible pump through the same circuit as in steps 31 and S32. Step S42: The LNG in the LNG tanker parked on the refueling skid flows by gravity through the tanker's liquid phase valve and enters the refueling skid's booster for vaporization and pressurization, and the LNG tanker is in the gas phase; the LNG in the LNG tanker enters the LNG submerged pump through valve V203 (V203') of the refueling skid under the action of pressure difference. Step S43: After mechanical pressurization by the LNG submersible pump, the LNG is transported to the bottom of the fuel tank through the input pipeline after passing through valve V207.

[0011] Preferably, in step S4: The DN40 return gas port of the LNG submersible pump is connected to the LNG tank truck through valve V206 to form return gas line one; The DN40 return gas port of the LNG submersible pump is connected to the discharge pipeline through valve V206' to form return gas line two.

[0012] Preferably, the heating skid is equipped with an electric heater for heating the exhaust gas returning from the fuel tank.

[0013] Preferably, the continuous torch system includes a torch combustion tower, a multi-stage burner, a continuous lamp, a torch ignition device, and electrical control equipment.

[0014] Implementing the embodiments of the present invention will have the following beneficial effects: After adopting the above solution, this invention uses a vaporization skid to achieve pre-cooling and replacement operations of the fuel tank in an LNG-fueled vessel. For short-distance, low-pressure LNG refueling operations, the LNG tanker can be parked at the vaporization skid, and the LNG refueling operation can be performed using the vaporization skid. For long-distance, high-pressure LNG refueling operations, the vaporization skid serves as a transfer fluid path for the LNG submersible pump of the refueling skid, providing LNG to the submersible pump, improving the pump's inlet efficiency, and thus completing the LNG refueling operation in the fuel tank. During pre-cooling and refueling operations, the fuel tank and heating skid are connected through an exhaust pipeline to heat the exhaust gas, and then the exhaust gas is safely discharged through a continuous flare system at the rear. In summary, this system integrates pre-cooling, refueling, and exhaust gas treatment into one unit. It achieves multiple operations such as pre-cooling, LNG replacement, LNG refueling, and auxiliary LNG refueling through a multi-functional vaporization skid, meeting the shipyard's requirements for the first refueling operation of an LNG-fueled vessel. The entire refueling process is more efficient, reliable, and safer. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] in: Figure 1 This is a flowchart illustrating the process in the embodiment; Figure 2 This is a schematic diagram of the overall circuit in the embodiment; Figure 3 This is a schematic diagram of the circuit of the vaporization skid in the embodiment; Figure 4 This is a schematic diagram of the circuit of the filling skid in the embodiment; Figure 5 This is a circuit diagram of the heating skid and the continuous torch system in the embodiment. Figure 6 This is a schematic diagram of the precooling line one in the embodiment; Figure 7 This is a schematic diagram of the precooling line two in the embodiment; Figure 8 This is a schematic diagram of the precooling line three in the embodiment; Figure 9 This is a schematic diagram of the first refueling line in the embodiment; Figure 10 This is a schematic diagram of the second refueling line in the embodiment; Figure 11 This is a schematic diagram of the refueling line three in the embodiment. Detailed Implementation

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings are used to distinguish different objects and not to describe a particular order.

[0018] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0019] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0020] As attached Figure 1-11 As shown, this embodiment of the invention provides a method for precooling, refueling, and exhaust gas treatment of an LNG-fueled ship, including: Step S1: Pre-cool the fuel tank of the LNG fuel ship by connecting a liquid nitrogen tanker to a vaporization skid. Step S1 is as follows: Step S11: The cryogenic nitrogen / liquid nitrogen from the liquid nitrogen tanker is transported to the input pipeline via the vaporization skid, and the cryogenic nitrogen / liquid nitrogen is transported to the fuel tank via the input pipeline; Step S12: Low-temperature nitrogen / liquid nitrogen is exchanged for heat with the fuel tank and then sequentially transported to the heating skid and the long-burning flare system through the discharge pipeline for exhaust gas treatment and discharge; Step S2: Use an LNG tanker connected to a gasification skid to generate gasified natural gas to remove nitrogen from the fuel tank of the LNG-fueled ship, thus completing the LNG replacement of the fuel tank. Step S3: The LNG tanker truck uses a vaporization skid to pressurize the gas phase, and the LNG is transported to the fuel tank through the input pipeline, completing the LNG refueling of the fuel tank; Step S4: The LNG tanker achieves gas-phase pressurization through the vaporization skid and the refueling skid. The LNG enters the LNG submersible pump on the refueling skid and is then transported to the fuel tank through the LNG submersible pump, completing the LNG refueling of the fuel tank. Step S1: To ensure the fuel tank temperature is suitable for storing liquefied natural gas and to avoid safety issues and equipment damage due to excessive temperature differences, pre-cooling is required before the initial refueling. The temperature reduction rate varies depending on the LNG fuel carrier model and can be adjusted as needed during actual operation. In this embodiment, the vaporization skid has two 1000 Nm³ ambient air vaporizers, which function as vaporizers and boosters during pre-cooling to provide nitrogen and liquid nitrogen at different temperatures. When the LNG tanker is parked at the vaporization skid, the ambient air vaporizers function as boosters to pressurize the LNG tanker. An emergency shut-off valve is installed on the main liquid pipe inside the vaporization skid, which can be controlled remotely or on-site using an emergency button. A pull-off valve is also installed at the connection point with the tank truck, allowing the tank truck to be driven away directly without disassembling the hose in case of an emergency. A flow meter and pneumatic valve are also installed at the gas outlet of the vaporization skid, which can monitor the output flow in real time and automatically open and close the start valve to prevent excessive flow from being output to the downstream end. At the same time, in accordance with the design principles of pressure pipelines, safety accessories such as safety valves, pressure and temperature monitoring instruments, and combustible gas detectors and alarms are provided. In order to ensure the requirements of use, the vaporization skid is also equipped with explosion-proof LED lights, mesh isolation doors, and other facilities.

[0021] Therefore, step S1 provides various precooling methods. Any one of the following precooling methods or a combination of several precooling methods can be selected according to actual needs. This embodiment describes the various precooling circuits one by one with reference to the accompanying drawings: Step S110: The liquid nitrogen in the liquid nitrogen tanker is vaporized and heated by the ambient temperature vaporizer in the vaporization skid to form low-temperature nitrogen gas. Step S111: Cryogenic nitrogen is delivered to the fuel tank through the input pipeline.

[0022] Specifically, the vaporization skid can vaporize and heat the liquid nitrogen in the liquid nitrogen tanker to form nitrogen gas at a temperature lower than ambient temperature. This gas is then transported via pipeline to the fuel tank of the LNG carrier for pre-cooling and purging. Figure 6 As shown in the pre-cooling circuit one, the liquid nitrogen tanker first increases its own pressure through the booster of its built-in pressurizer, creating a pressure difference between the liquid nitrogen tanker and the vaporization skid. Under the action of the pressure difference, the liquid nitrogen flows from valve V101 (V101') – valve V107 (V107') – ambient air vaporizer, where it is vaporized and heated – V105 (V105') – input pipeline – fuel tank, and then through internal heat exchange – discharge pipeline – heating skid, and finally through the continuous flare system to ensure safe discharge. The input pipeline includes at least an inlet valve V210, and the discharge pipeline includes at least an outlet valve V211. Furthermore, the temperature of the vaporized gas can be further controlled by adjusting the number of heat exchangers involved, the opening of the valve at the vaporizer inlet, and the pressure difference between the tanker and the system, referencing real-time temperature monitoring at the vaporizer's downstream end. For example, the outlet temperature of the vaporizer can be reduced by starting only one vaporizer, increasing the opening of the inlet valve, and increasing the pressure differential. At the same time, the gas outlet of the vaporizer skid is equipped with a flow meter to monitor the output flow rate. The pneumatic valve will also automatically open and close according to the real-time flow rate to ensure that no limit is exceeded. In addition, the outlet of the heating skid is equipped with a turbine flow meter and a temperature transmitter to monitor the amount of gas output to the flare system in real time. An alarm will be triggered when the limit is exceeded or approached. If the limit is exceeded to a certain extent, the gas supply to the entire system can be cut off. It should be noted that specific values ​​in this part can be set on site.

[0023] The vaporization skid can directly supply cryogenic gaseous nitrogen or a small amount of liquid nitrogen through a pre-set valve inside the skid, further enhancing the precooling effect, as detailed below: Step S112: The liquid nitrogen tanker is pressurized by its own booster, creating a pressure difference between the liquid nitrogen tanker and the vaporization skid; Step S113: The cryogenic nitrogen or a small amount of liquid nitrogen in the liquid nitrogen tanker enters the input pipeline through the valve V104 (V104') of the vaporization skid under the action of pressure difference and is transported to the bottom of the fuel tank.

[0024] like Figure 7The precooling line two shown here involves cryogenic nitrogen or a small amount of liquid nitrogen flowing from valve V104 (V104') through the input pipeline to the fuel tank, then through internal heat exchange, the discharge pipeline, and the heating skid. After heating, it reaches the continuous flare system, ensuring safe discharge. The amount of cryogenic nitrogen and the small amount of liquid nitrogen can be controlled by switching the gas-liquid valves on the liquid nitrogen tanker and adjusting the opening of valve V104 (V104'). For example, opening the liquid phase valve on the liquid nitrogen tanker and adjusting the opening of valve V104 (V104') can regulate the amount of liquid nitrogen input to the system (small quantity). Simultaneously, the gas outlet of the vaporization skid is equipped with a flow meter to monitor the output flow rate (mass data) in real time. The pneumatic valve will also automatically open and close based on the real-time flow rate to ensure no over-limit situations occur. Furthermore, the heating skid outlet is equipped with a turbine flow meter and a temperature transmitter to monitor the amount of gas output to the flare system in real time. An alarm will sound if the amount exceeds or approaches the limit, and exceeding the limit beyond a certain level can cut off the gas supply to the entire system (specific values ​​for this part can be set on-site).

[0025] When the final stage requires a large amount of liquid nitrogen, the vaporization skid can directly supply liquid nitrogen equivalent to the volume of liquid extracted from the liquid nitrogen tanker through a pre-set valve inside the skid, further improving the pre-cooling effect, as detailed below: Step S114: A large amount of liquid nitrogen in the liquid nitrogen tanker enters the input pipeline and is transported to the fuel tank through the valve V103 (V103') of the vaporization skid under the action of pressure difference.

[0026] like Figure 8 As shown in the pre-cooling line three, the liquid nitrogen tanker first increases its own pressure through its built-in booster, creating a pressure difference between the tanker and the downstream pipeline. Under this pressure difference, the liquid nitrogen flows from valve V103 (V103') through the input pipeline to the fuel tank, then through internal heat exchange, the discharge pipeline, and the heating skid. After heating, it reaches the continuous flare system to ensure safe discharge. The amount of liquid nitrogen can be controlled by adjusting the opening of valve V103 (V103'). Simultaneously, the heating skid outlet is equipped with a turbine flow meter and a temperature transmitter to monitor the amount of gas output to the flare system in real time. An alarm will sound if the amount exceeds or approaches the limit, and if it exceeds the limit to a certain extent, the gas supply to the entire system can be cut off (specific values ​​can be set on-site).

[0027] At this point, step S1 is complete, and the fuel tank has finished pre-cooling. After pre-cooling, the vaporization skid can also be used for LNG replacement in the fuel tank of an LNG-fueled ship, as in step S2: Gasified natural gas is generated by connecting the vaporization skid to an LNG tanker to remove nitrogen from the fuel tank of the LNG-fueled ship, completing the LNG replacement. Specifically... Figure 6As shown in the pre-cooling line one, the liquid nitrogen tanker is replaced with an LNG tanker. The LNG tanker is converted into vaporized natural gas by an ambient temperature vaporizer and enters the fuel tank through the input pipeline. Due to its density, the vaporized natural gas will push the nitrogen remaining in the fuel tank upwards. Finally, the mixture of vaporized natural gas and nitrogen is output to the heating skid through the discharge pipeline. After being heated, it is safely discharged to the long-burning flare system.

[0028] After the fuel tank is pre-cooled and LNG is replaced, the vaporization skid in this embodiment can also be used as a refueling skid. That is, LNG can be refueled into the fuel tank of an LNG-fueled ship by parking the LNG tanker at the vaporization skid, as detailed below: Step S31: After the LNG in the LNG tanker flows by gravity through the liquid phase valve of the tanker, it enters the ambient temperature vaporizer of the vaporization skid for vaporization and pressurization, and the LNG tanker is in gas phase. Step S32: Under the action of pressure difference, the LNG in the LNG tanker enters the input pipeline through the valve V103 (V103') of the vaporization skid and is transported to the fuel tank.

[0029] like Figure 9 As shown in the refueling line one, the LNG in the LNG tanker first flows by gravity through the tanker's pressurization liquid phase valve—valve V101 (V101')—to the ambient temperature vaporizer, where it is vaporized and pressurized—and then through valve V102 (V102') to the LNG tanker's gas phase, completing the pressurization. Then, the LNG in the tanker, under pressure differential, flows through valve V103 (V103')—to the input pipeline—to the fuel tank. It should be noted that the transmission distance, altitude, and pressure provided by refueling line one are relatively small compared to pump delivery, making it suitable for short-distance, low-altitude, and low-pressure refueling operations. Simultaneously, a turbine flow meter and temperature transmitter installed at the heating skid outlet monitor the amount of gas output to the flare system in real time. An alarm will sound if the amount exceeds or approaches the limit, and exceeding the limit beyond a certain level can cut off the gas supply to the entire system (specific values ​​for this part can be set on-site).

[0030] For situations where the requirements for transport distance, height, and pressure are high and the vaporization skid cannot meet these requirements, the vaporizer can transfer LNG from two LNG tank trucks to the inlet pipeline of the refueling skid (pump skid), thereby improving the inlet capacity of the LNG submersible pump. Specifically: Step S33: Under the action of pressure difference, the LNG in the LNG tanker enters the input pipeline through valve V103 (V103') of the vaporization skid. The LNG enters the LNG submersible pump through the input pipeline and valve V205. The LNG is then transported to the bottom of the fuel tank by the LNG submersible pump.

[0031] like Figure 10As shown in the second refueling route, LNG from the LNG tanker first flows by gravity through the tanker's pressurization liquid phase valve—valve V101 (V101')—to the ambient temperature vaporizer, where it is vaporized and pressurized—and then through valve V102 (V102')—to the LNG tanker's gas phase, completing the pressurization process. Then, the LNG in the tanker, under pressure differential, flows through valve V103 (V103')—the input pipeline—valve V205—to the LNG submersible pump, which then refuels the fuel tank. The combination of the vaporization skid and the refueling skid enables LNG refueling of the fuel tank under conditions requiring greater transport distance, altitude, and pressure. It also makes efficient use of the vaporization skid's piping, allowing for repeated use of the piping and improving work efficiency.

[0032] In addition to the pre-cooling, replacement, refueling, and auxiliary refueling operations of the aforementioned vaporization skid, this embodiment also provides a refueling skid, also known as a pump skid, primarily used to "pump" LNG from LNG tank trucks to the fuel tanks of LNG fuel carriers. The refueling skid is equipped with a cryogenic LNG submersible pump for pumping LNG, with a maximum head of 130 meters; a 300 cubic meter booster is used to pressurize the LNG tank truck and improve the pump skid's inlet efficiency; a 200 cubic meter EAG heater is used to release LNG for reheating; simultaneously, the main liquid pipe inside the skid is equipped with an emergency shut-off valve, which can be controlled remotely or on-site using an emergency button; a pull-off valve is also installed at the connection point with the tank truck, allowing the tank truck to be driven away directly without disassembling the hoses in case of an emergency; a flow meter and pneumatic valve are also installed at the output end of the refueling skid to monitor the output flow in real time and automatically adjust the output flow rate to prevent excessive flow from entering the downstream system. In accordance with the design principles of pressure pipelines, safety accessories such as safety valves, pressure and temperature monitoring instruments, and combustible gas detectors and alarms are provided. In order to ensure the requirements of use, explosion-proof LED lights, mesh isolation doors and other facilities are also installed.

[0033] The following route is specifically used for LNG bunkering on LNG-fueled ships. Step S41: The LNG in the LNG tanker truck docked at the gasification skid enters the LNG submersible pump through the loops of steps 210 and S212. Step S42: The LNG in the LNG tanker parked on the refueling skid flows by gravity through the tanker's liquid phase valve and enters the refueling skid's booster for vaporization and pressurization, and the LNG tanker is in the gas phase; the LNG in the LNG tanker enters the LNG submerged pump through valve V203 (V203') of the refueling skid under the action of pressure difference. Step S43: After mechanical pressurization by the LNG submersible pump, the LNG is transported to the bottom of the fuel tank through the input pipeline after passing through valve V207.

[0034] like Figure 11As shown in the third refueling route, the LNG in the LNG tanker parked on the vaporization skid first flows by gravity through the tanker's pressurization liquid phase valve—valve V101 (V101')—ambient air vaporizer, vaporization and pressurization—valve V102 (V102')—LNG tanker gas phase, completing the pressurization. Then, the LNG in the LNG tanker is pressurized by the pressure difference through valve V103 (V103')—input pipeline—valve V205—LNG submersible pump; Meanwhile, the LNG in the LNG tanker parked on the refueling skid flows by gravity through the tanker's pressurizing liquid phase valve—valve V201 (V201')—pressurizer, vaporizes and pressurizes—valve V202 (V202')—LNG tanker gas phase, completing the pressurization. Then, the LNG in the LNG tanker is pressurized by the pressure difference through valve V203 (V203')—LNG submersible pump; Then, the LNG submersible pump is mechanically pressurized—valve V207—input pipeline—fuel tank.

[0035] LNG submersible pumps require gas return and continuous gas return to ensure normal operation. There are two gas return lines: The DN40 return gas port of the LNG submersible pump is connected to the LNG tank truck through valve V206 to form return gas line one; The DN40 return gas port of the LNG submersible pump is connected to the discharge pipeline through valve V206' to form return gas line two; Among them, return gas line one is only suitable for situations where the tank truck pressure is not high and the liquid is plentiful. When the tank truck pressure is high and the liquid level is not high, the return gas will be obstructed. In this case, return gas line two can be selected.

[0036] Meanwhile, the pump skid outlet is equipped with a flow meter, which can monitor the output flow rate in real time. The pneumatic valve will also automatically open and close according to the real-time flow rate to ensure that no over-limit situations occur. In addition, the heating skid outlet is equipped with a turbine flow meter and a temperature transmitter, which can monitor the amount of gas output to the flare system in real time. An alarm will be triggered when the limit is exceeded or approached. If the limit is exceeded to a certain extent, the gas supply to the entire system can be cut off (the specific values ​​of this part can be set on site).

[0037] In this embodiment, an electric heater is installed inside the heating skid to heat the exhaust gas returning from the fuel tank. Specifically, the electric heater is a water bath type electric heater with a heating capacity of 2000 Nm³ / h. The electric heater heats the exhaust gas to ensure the temperature for subsequent emissions from the long-lasting flare system. The heater has a designed power of 90 kW and a minimum designed metal temperature of -196℃. Depending on the requirements of different projects, the reheating capacity of the electric heater can be set to be more than twice that of a conventional reheater. The electric heater adopts an explosion-proof design and has two modes: automatic and manual. The automatic mode enables temperature control operation, that is, it automatically starts and stops when the water temperature is between 50-60℃, starts heating when the water temperature is below 50℃, and stops heating when the water temperature is above 60℃. The manual mode keeps the heater in heating mode and requires personnel supervision. In addition, a combustible gas detector and alarm are installed according to the design principles of pressure pipelines; a turbine flow meter and a temperature transmitter are installed at the outlet of the heating skid to monitor the amount of gas output to the flare system in real time. An alarm will be triggered when the amount exceeds or approaches the limit, and the gas supply to the entire system can be cut off if the amount exceeds the limit to a certain extent (the specific value of this part can be set on site); in order to ensure the requirements of use, explosion-proof LED lights, mesh isolation doors and other facilities are also installed.

[0038] To ensure the safe emission of exhaust gases, this invention also includes an independent continuous flare system. This system comprises a flare combustion tower, multi-stage burners, continuous lamps, a flare ignition device, and electrical control equipment. In this embodiment, the flare combustion tower is a mobile modular design with a skid-mounted base, facilitating installation, disassembly, and transportation. The system uses a tower-like structure composed of ground-based flares approximately 10m high and 2.4m in diameter. Flare combustion is completed within a cylindrical ground-based steel flare cylinder, approximately 2.4m in diameter and 10m high. The combustion process is completely enclosed, with no visible flame, resulting in no light pollution, low heat radiation, and a flame height not exceeding that of the cylinder at full load. The cylindrical ground-fired furnace has an outer shell made of carbon steel, lined with refractory ceramic fiber, ceramic fiber compensation blanket, and ceramic fiber flat blanket. The total thickness of the 3 cm backing is no less than 170 mm, making it unaffected by rain or rapid temperature changes inside the furnace. It also possesses excellent sound absorption and noise reduction characteristics, ensuring that the outer surface temperature of the furnace shell remains ≤60℃ during prolonged full-load operation. The multi-stage burner employs a quincunx-shaped porous structure, which divides the large stream of flare gas into many smaller streams to facilitate mixing with air, increase the contact area, and achieve smokeless combustion. The mixing of air and flare gas is primarily achieved through the pressure of the flare gas itself and a specially designed burner. The quincunx-shaped porous burner is geometrically uniformly arranged within the cylindrical ground-fired furnace to fully utilize air. The burner is made of heat-resistant stainless steel to ensure its long service life. Two ignition lamps are installed inside the flare stack. These lamps remain constantly lit under normal conditions to ensure timely ignition of any flare gas emission, guaranteeing the absolute safety of the system. The continuous lighting lamps are equipped with automatic ignition devices, meaning they can be automatically relit when extinguished due to external factors, ensuring the reliability of ground flare ignition. All components of the continuous lighting lamps should be detachable for easy maintenance and replacement of vulnerable parts. The fuel gas consumption of each continuous lighting lamp should not exceed 5 Nm³ / h, ensuring stable safety, reliability, and good energy-saving performance. The flare should have a reliable and safe ignition device with strong self-cleaning capabilities, unaffected by gas pollution, resistant to oil, water, coking, and high temperatures, and characterized by safety, reliability, no pollution, and long lifespan. It should also have a simple, easy-to-operate, and reliable flame detection device capable of continuous monitoring of various combustion environments, and an independent local control cabinet for manual ignition. The electrical components include a local explosion-proof control cabinet and an explosion-proof box. The explosion-proof box is used for power distribution on the flare equipment, while the local explosion-proof control cabinet is used for all control operations of the flare system, featuring multiple functions such as field instrument display, buttons, indicator lights, alarms, and remote transmission. To enhance safety, anti-static grounding is implemented in the combustion tower and piping system. The unit's working ground, protective ground, lightning protection ground, and anti-static grounding devices are all connected together to form a common grounding network with a design grounding resistance of ≤1 ohm. Electrical equipment and cable supports are all equipped with lightning and anti-static grounding. Fuel gas process pipelines must be anti-static grounded. For the explosion-proof ignition control panel, the static grounding wire uses yellow-green insulated conductors with a diameter meeting specifications. The shielding layer of analog signal shielded cables must be grounded at one end.

[0039] In summary, this invention utilizes a vaporization skid to perform pre-cooling and purging operations on the fuel tanks of LNG-fueled vessels. For short-distance, low-pressure LNG refueling operations, the LNG tanker can be parked at the vaporization skid, and the skid can then be used to refuel the fuel tanks. For long-distance, high-pressure LNG refueling operations, the vaporization skid serves as a transfer path for the LNG submersible pump on the refueling skid, providing LNG to the submersible pump and improving its inlet efficiency, thereby completing the LNG refueling operation on the fuel tanks. During pre-cooling and refueling operations, the fuel tanks and heating skids are connected via an exhaust pipeline to heat the exhaust gas, which is then safely discharged through a continuous flare system at the rear. In general, this system integrates pre-cooling, refueling, and exhaust gas treatment, using a multi-functional vaporization skid to perform pre-cooling, LNG purging, LNG refueling, and auxiliary LNG refueling operations, meeting the shipyard's requirements for the first refueling operation of LNG-fueled vessels. The entire refueling process is more efficient, reliable, and safer.

[0040] Obviously, the embodiments described above are merely some embodiments of the present invention, not all embodiments. The accompanying drawings show preferred embodiments of the present invention, but do not limit the patent scope of the present invention. The present invention can be implemented in many different forms; rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the patent protection scope of this invention.

Claims

1. A method for precooling, refueling, and exhaust gas treatment of an LNG-fueled ship, characterized in that, include: Step S1: Pre-cool the fuel tank of the LNG fuel ship by connecting a liquid nitrogen tanker to a vaporization skid. Step S1 specifically involves: Step S11: The cryogenic nitrogen / liquid nitrogen from the liquid nitrogen tanker is transported to the input pipeline via the vaporization skid, and the cryogenic nitrogen / liquid nitrogen is transported to the fuel tank via the input pipeline; Step S12: Low-temperature nitrogen / liquid nitrogen is exchanged for heat with the fuel tank and then sequentially transported to the heating skid and the long-burning flare system through the discharge pipeline for exhaust gas treatment and discharge; Step S2: Use an LNG tanker connected to a gasification skid to generate gasified natural gas to remove nitrogen from the fuel tank of the LNG-fueled ship, thus completing the LNG replacement of the fuel tank. Step S3: The LNG tanker truck uses a vaporization skid to pressurize the gas phase, and the LNG is transported to the fuel tank through the input pipeline for LNG refueling. Step S4: The LNG tanker achieves gas phase pressurization through the vaporization skid and the refueling skid. LNG enters the LNG submersible pump on the refueling skid and is then transported to the fuel tank for LNG refueling.

2. The method for precooling, refueling, and exhaust gas treatment of an LNG-fueled ship according to claim 1, characterized in that, Step S11 includes: Step S110: The liquid nitrogen in the liquid nitrogen tanker is vaporized and heated by the ambient temperature vaporizer in the vaporization skid to form low-temperature nitrogen gas. Step S111: Cryogenic nitrogen is delivered to the fuel tank through the input pipeline.

3. The method for precooling, refueling, and exhaust gas treatment of an LNG-fueled ship according to claim 2, characterized in that, Step S11 includes: Step S112: The liquid nitrogen tanker is pressurized by its own booster, creating a pressure difference between the liquid nitrogen tanker and the vaporization skid; Step S113: The cryogenic nitrogen or a small amount of liquid nitrogen in the liquid nitrogen tanker enters the input pipeline and is transported to the fuel tank through valves V104 and V104' of the vaporization skid under the action of pressure difference.

4. The method for precooling, refueling, and exhaust gas treatment of an LNG-fueled ship according to claim 3, characterized in that, Step S11 further includes: Step S114: A large amount of liquid nitrogen in the liquid nitrogen tanker enters the input pipeline and is transported to the fuel tank through valves V103 and V103' of the vaporization skid under the action of pressure difference.

5. The method for precooling, refueling, and exhaust gas treatment of an LNG-fueled ship according to claim 1, characterized in that, Step S3 includes: Step S31: After the LNG in the LNG tanker flows by gravity through the liquid phase valve of the tanker, it enters the ambient temperature vaporizer of the vaporization skid for vaporization and pressurization. The pressurized gaseous natural gas is then returned to the LNG tanker. Step S32: Under the action of pressure difference, the LNG in the LNG tanker enters the input pipeline through valves V103 and V103' of the vaporization skid and is transported to the fuel tank.

6. The method for precooling, refueling, and exhaust gas treatment of an LNG-fueled ship according to claim 5, characterized in that, Step S3 also includes: Step S33: Under the action of pressure difference, the LNG in the LNG tanker enters the input pipeline through valves V103 and V103' of the vaporization skid. The LNG enters the LNG submersible pump through the input pipeline and valve V205. The LNG is then transported to the bottom of the fuel tank by the LNG submersible pump.

7. The method for precooling, refueling, and exhaust gas treatment of an LNG-fueled ship according to claim 6, characterized in that, Step S4 includes: Step S41: The LNG in the LNG tanker truck docked at the gasification skid enters the LNG submerged pump through the loops of steps S31 and S32. Step S42: The LNG in the LNG tanker parked on the refueling skid flows by gravity through the liquid phase valve of the tanker and enters the pressurizer of the refueling skid for vaporization and pressurization. The pressurized gaseous natural gas returns to the LNG tanker. Under the action of pressure difference, the LNG in the LNG tanker enters the LNG submerged pump through valves V203 and V203' of the refueling skid. Step S43: After mechanical pressurization by the LNG submersible pump, the LNG is transported to the bottom of the fuel tank through the input pipeline after passing through valve V207.

8. The method for precooling, refueling, and exhaust gas treatment of an LNG-fueled ship according to claim 7, characterized in that, In step S4: The return gas port of the LNG submersible pump is connected to the LNG tank truck through valve V206 to form return gas line one; The return gas port of the LNG submersible pump is connected to the discharge pipeline through valve V206' to form return gas line two.

9. The method for precooling, refueling, and exhaust gas treatment of an LNG-fueled ship according to claim 1, characterized in that, The heating skid is equipped with an electric heater for heating the exhaust gas returning from the fuel tank.

10. The method for precooling, refueling, and exhaust gas treatment of an LNG-fueled ship according to claim 1, characterized in that, The continuous torch system includes a torch combustion tower, a multi-stage burner, a continuous lamp, a torch ignition device, and electrical control equipment.

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