BOG dynamic balance treatment system for marine ship and land liquid cargo film tank

Abstract

The invention relates to a BOG dynamic balance treatment system for marine ship and land liquid cargo thin film tanks. The system comprises a first thin film tank and a second thin film tank, the first thin film tank is connected with the second thin film tank; the device further comprises a BOG cooling and pressure regulating mechanism. The system further comprises a liquid cargo processing mechanism. The BOG cooling and pressure regulating mechanism is connected with the second thin film tank; the liquid cargo processing mechanism is connected with the first thin film tank and the second thin film tank. And the BOG cooling and pressure regulating mechanism is connected with the liquid cargo treatment mechanism, so that the liquid cargo from the first thin film tank exchanges heat with the BOG from the second thin film tank. The first thin film tank is a ship thin film tank, and the second thin film tank is a land liquid cargo thin film tank; or the second film tank is a ship film tank, and the first film tank is a land liquid cargo film tank. Compared with the prior art, the problem that storage of compressed low-temperature liquefied gas such as LNG is affected due to the fact that the temperature of a land liquid cargo thin film tank (or a ship thin film tank) is increased due to the fact that the land liquid cargo thin film tank (or the ship thin film tank) is exposed to the sun and BOG generated by liquid cargo such as LNG is increased can be effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of BOG treatment of LNG membrane tanks, and in particular to a BOG dynamic balance treatment system for offshore ships and land liquid cargo membrane tanks. Background Art

[0002] Liquefied Natural Gas (LNG) has been the preferred energy source to replace oil for its advantages of being green, environmentally friendly and efficient, and has become one of the fastest growing energy industries in the world. The application and development of LNG has received more and more attention from all parties, and the demand for clean energy in society has grown rapidly.

[0003] LNG usually needs to rely on transportation equipment, such as ships and other marine equipment for transportation. The main components of an LNG receiving station are dock unloading, LNG storage, process processing and external transmission. Among them, the LNG storage tanks that undertake the storage task have the longest construction period, the most advanced technology, and the most difficulties in the construction process. They have always been managed as the key path of the entire project.

[0004] LNG has an extremely low temperature, which can be as low as -160℃. During storage, LNG will continuously absorb heat from the environment and evaporate flash gas (Boil Off Gas, BOG) which is stored in the LNG storage tank. At the same time, the BOG generated by LNG absorbing heat in other equipment and pipelines of the LNG station will eventually return to the LNG storage tank. The pressure in the LNG storage tank will gradually increase with the increase of BOG.

[0005] After the LNG ship arrives at the LNG receiving station, it is necessary to send LNG and other liquid cargoes in the LNG storage tanks of the sea vessels to the LNG storage tanks on land through pipelines. However, the temperature of the LNG storage tanks on land increases due to the sun and other reasons, and the BOG generated by LNG and other liquid cargoes increases. The increased tank pressure affects the storage of compressed low-temperature liquefied gases such as LNG. Therefore, it is necessary to deal with BOG in time to reduce the temperature and tank pressure in the land LNG storage tanks. In some cases, such as when ships are storing and transporting LNG, BOG will be generated in the tank due to the loss of cold energy on the surface of the LNG storage tank, so it is necessary to reduce the temperature and tank pressure in the ship's LNG storage tank.

[0006] CN119665136A discloses a LNG tank BOG liquefaction recovery system and a control method thereof. When the BOG in the LNG tank needs to be recovered, the BOG transported from the LNG tank is cooled and liquefied by a refrigerator and then returned to the LNG tank to achieve the recovery of the BOG gas in the LNG tank. During the BOG recovery process, when it is necessary to maintain the supercooling of the LNG tank, the LNG transported from the LNG tank is cooled by a refrigerator, and the cooled LNG is returned to the LNG tank and mixed with the LNG in the LNG tank to reduce the LNG temperature in the LNG tank to maintain the supercooling of the LNG tank. The system in CN119665136A is essentially a control process of a single LNG tank. Therefore, there is an urgent need for a processing system that can achieve dynamic balance between offshore ship LNG tanks and land LNG tanks, so as to be applicable to the LNG and other liquid cargo transportation process between offshore ship LNG tanks and land LNG tanks. Summary of the invention

[0007] The purpose of the present invention is to provide a BOG dynamic balance treatment system for marine vessels and land liquid cargo membrane tanks in order to overcome the defects of the above-mentioned prior art. Before the marine vessel membrane tank (or land liquid cargo membrane tank) is unloaded to the land liquid cargo membrane tank (or ship membrane tank), the BOG of the LNG in the land liquid cargo membrane tank (or ship membrane tank) is treated by utilizing the cold energy of the LNG in the ship membrane tank (or land liquid cargo membrane tank), so that the land liquid cargo membrane tank (or ship membrane tank) can be cooled by self-circulation, the double tanks can be circulated to recover BOG, and the tank pressure of the land liquid cargo membrane tank (or ship membrane tank) can be reduced. This can effectively solve the problem that the temperature of the land liquid cargo membrane tank (or ship membrane tank) increases due to the sun exposure, etc., and the BOG generated by liquid cargo such as LNG increases, resulting in an increase in tank pressure that affects the storage of compressed low-temperature liquefied gases such as LNG.

[0008] The purpose of the present invention can be achieved by the following technical solutions: The object of the present invention is to provide a BOG dynamic balance processing system for marine vessels and land liquid cargo film tanks, the system comprising a first film tank and a second film tank; the first film tank and the second film tank are connected by a pipeline; the system further comprises a BOG temperature reduction and pressure regulation mechanism, the BOG temperature reduction and pressure regulation mechanism is used for cooling and regulating the BOG in the second film tank; the system further comprises a liquid cargo processing mechanism, the liquid cargo processing mechanism is used for supercooling the liquid cargo in the first film tank; the BOG temperature reduction and pressure regulation mechanism is connected to the second film tank by a pipeline; the liquid cargo processing mechanism is respectively connected to the first film tank and the second film tank by pipelines; the BOG temperature reduction and pressure regulation mechanism is connected to the liquid cargo processing mechanism by a pipeline, so that the liquid cargo from the first film tank is heat exchanged with the BOG from the second film tank.

[0009] Furthermore, the first film tank and the second film tank are connected via a gas phase connecting hose; the first film tank and the second film tank are connected via a liquid phase connecting hose.

[0010] Optionally, when the cold energy of liquid cargo in a ship membrane tank is used to treat BOG of liquid cargo in a land liquid cargo membrane tank, the first membrane tank is a ship membrane tank, and the second membrane tank is a land liquid cargo membrane tank.

[0011] Optionally, when the cold energy of liquid cargo in a land liquid cargo membrane tank is used to treat the BOG of liquid cargo in a ship membrane tank, the second membrane tank is a ship membrane tank, and the first membrane tank is a land liquid cargo membrane tank.

[0012] Furthermore, the BOG temperature reduction and pressure regulation mechanism includes a heat exchange component and a compressor; the air intake end of the compressor is connected to the second membrane tank through a pipeline; the air outlet end of the compressor is connected to the inlet of the heat exchange component through a pipeline; the outlet of the heat exchange component is connected to the second membrane tank through a pipeline.

[0013] Furthermore, the heat exchange component includes a seawater heat exchanger and a low-temperature heat exchanger; the air intake end of the compressor is connected to the second membrane tank through a pipeline; the air outlet end of the compressor is connected to the inlet of the seawater heat exchanger through a pipeline; the outlet of the seawater heat exchanger is connected to the inlet of the low-temperature heat exchanger through a pipeline; the outlet of the low-temperature heat exchanger is connected to the second membrane tank through a pipeline, and a gas pressure regulating valve is provided on the pipeline between the outlet of the low-temperature heat exchanger and the second membrane tank (pressure regulation is achieved through a pressure regulating valve gas pressure regulating valve, which mainly reduces the fluid pressure to prevent damage to the atmospheric pressure membrane storage tank).

[0014] Furthermore, the seawater heat exchanger is a shell-and-tube heat exchanger, a coil-and-tube heat exchanger or a plate heat exchanger; and the low-temperature heat exchanger is a shell-and-tube heat exchanger, a coil-and-tube heat exchanger or a plate heat exchanger.

[0015] Furthermore, the liquid cargo handling mechanism includes a liquid cargo pump, a supercooling unit, and a gas-liquid spray cooling tank; the inlet of the liquid cargo pump is connected to the first film tank through a pipeline; the outlet of the gas-liquid spray cooling tank is connected to the inlet of the supercooling unit through a pipeline; the outlet of the supercooling unit is connected to the first film tank through a pipeline; the outlet of the supercooling unit is connected to the inlet of the gas-liquid spray cooling tank through a pipeline; the outlet of the gas-liquid spray cooling tank is connected to the second film tank through a pipeline; the outlet of the liquid cargo pump is connected to the inlet of the gas-liquid spray cooling tank through a pipeline; the outlet of the liquid cargo pump is connected to the second film tank through a liquid phase connecting hose.

[0016] Furthermore, the supercooling unit includes a supercooler.

[0017] Furthermore, the outlet of the liquid cargo pump is connected to the heat exchange component through a pipeline; the heat exchange component is connected to the inlet of the gas-liquid spray cooling tank through a pipeline; the air outlet end of the compressor is connected to the inlet of the supercooling unit through a pipeline; the air outlet end of the compressor is connected to the inlet of the gas-liquid spray cooling tank through a pipeline.

[0018] Furthermore, the outlet of the liquid cargo pump is connected to another inlet of the low-temperature heat exchanger through a pipeline, so that the liquid cargo from the first membrane tank is heat exchanged with the high-temperature BOG from the second membrane tank; the other outlet of the low-temperature heat exchanger is connected to the inlet of the gas-liquid spray cooling tank through a pipeline; the air outlet end of the compressor is connected to the inlet of the supercooling unit through a pipeline; the air outlet end of the compressor is connected to the inlet of the gas-liquid spray cooling tank through a pipeline.

[0019] Furthermore, a spray cooling pipeline and a spray filling pipeline are sequentially arranged on the top of the first film tank from top to bottom; The spray cooling pipeline and the spray filling pipeline are both arranged at a height higher than the liquid level of the liquid cargo in the first membrane tank.

[0020] Furthermore, the liquid cargo is cryogenic liquid such as liquefied natural gas or liquid ammonia.

[0021] Furthermore, valves are provided on the above pipelines.

[0022] Furthermore, the device can utilize the cold energy of the liquid cargo in the first membrane tank to treat the BOG in the liquid cargo in the second membrane tank, allowing the second membrane tank to self-circulate and cool down, the double tanks (the first membrane tank and the second membrane tank) to circulate and recover the BOG, and reduce the tank pressure of the second membrane tank.

[0023] Furthermore, the working method of the BOG dynamic balance treatment system of the marine vessel and the land liquid cargo membrane tank includes the following steps: The top temperature of the second film tank initially drops: The compressor extracts BOG from the land liquid cargo membrane tank and compresses it to obtain compressed gas, which then enters the seawater heat exchanger to cool the compressed gas to room temperature, and then enters the low-temperature heat exchanger to cool the BOG to about -20~0℃, and then cools the BOG to -80℃ after pressure regulation (0.65MPa), and circulates back to the land liquid cargo membrane tank (pressure regulation is to reduce the pressure of the fluid in the pipeline. The BOG in the tank needs to be pressurized by the compressor and then reduced to low temperature to liquefy, and then reduced to low pressure before entering the atmospheric pressure membrane tank) and then reduces the temperature in the land liquid cargo membrane tank to -160℃ and the pressure to atmospheric pressure, in preparation for the next step of reducing to a lower temperature; the ship membrane tank passes through the liquid cargo The pump supplies the liquid cargo to the low-temperature heat exchanger to exchange heat with the high-temperature BOG in the land-based liquid cargo membrane tank. The liquid cargo that absorbs heat will be vaporized. The vaporized liquid cargo enters the gas-liquid spray cooling tank and directly contacts with the liquid cargo spray cooling to cool down (the liquid cargo in the gas-liquid spray cooling tank comes from the liquid cargo transported by the liquid cargo pump in the ship's membrane tank, which is used as a direct heat exchanger to cool down the BOG; the compressor compresses and pressurizes the BOG, which will increase the temperature of the compressor). The low-temperature gaseous liquid cargo is pressurized to 0.65MPa by the compressor, and then mixed with the un-vaporized liquid cargo at the bottom of the gas-liquid spray cooling tank and passed into the supercooling unit to be cooled to -175℃ to obtain the liquefied liquid cargo. The liquefied liquid cargo is returned to the ship's membrane tank; The second membrane tank is further cooled down to below -165 degrees, in preparation for filling the second membrane tank with liquid cargo from the first membrane tank: The compressor extracts BOG from the land liquid cargo membrane tank and directly supplies it to the supercooling unit. The supercooling unit in S1 reduces the BOG temperature to a low temperature (-80°C) and then circulates the gas-liquid spray cooling tank for buffering and reduces the temperature to a low temperature of -160°C. The BOG reduced to a low temperature (-160°C) returns to the land liquid cargo membrane tank and continuously circulates the gas phase to gradually reduce the temperature in the land liquid cargo membrane tank to about -170°C, completing the cooling in the land liquid cargo membrane tank and reaching a supercooling temperature lower than the liquid cargo storage temperature. Subcooled liquid cargo spraying second membrane tank: Spray a certain amount of supercooled liquid cargo on the second film tank to be loaded, so that the main film shielding layer of the second film tank can adapt to the supercooled liquid cargo; First, the first membrane tank is loaded with liquid cargo through a liquid cargo pump and temporarily stored in a gas-liquid spray cooling tank. The liquid cargo is then sent to the supercooling unit through a circulating pump at the bottom of the gas-liquid spray cooling tank to be supercooled and gasified. The supercooled liquid cargo is then pumped into the second membrane tank and sprayed from the top of the second membrane tank until the second membrane tank reaches a low temperature state. The gas phase is connected to the second membrane tank through a gas phase connecting hose to achieve gas-liquid pressure balance. Carry out the filling process: the liquid cargo in the first membrane tank is transported into the second membrane tank through the liquid cargo pump and the liquid phase connecting hose.

[0024] Furthermore, during the filling process, part of the liquid cargo may be vaporized due to the friction between the liquid cargo and the pipeline, the loss of pipeline temperature, the cooling process of the pipeline, or the change in the temperature loss and pressure of the first and second membrane tanks. In order to ensure constant temperature and BOG stability, the BOG control of the second membrane tank is carried out: The liquid cargo stored in the first membrane tank is continuously transported into the second membrane tank through the liquid cargo pump and the liquid phase connecting hose. The BOG generated by gasification in the second membrane tank and the first membrane tank is pumped away by the compressor (the compression work is linked with the pressure of the zero membrane tank to ensure that the tank pressure is at normal pressure). The BOG generated by gasification in the second membrane tank and the first membrane tank first enters the gas-liquid spray cooling tank. The BOG is first directly cooled by the sprayed supercooled liquid cargo. The cooled BOG enters the compressor. The BOG compressed to 0.65MPa by the compressor is then mixed with the ungasified liquid cargo at the bottom of the gas-liquid spray cooling tank and enters the supercooling unit to complete the liquefaction of the BOG, thereby realizing the re-liquefaction and recovery of the BOG in this process.

[0025] Compared with the prior art, the present invention has the following beneficial effects: 1) The present invention provides a BOG dynamic balance processing system for marine vessels and land liquid cargo membrane tanks. Before the marine vessel membrane tank (or land liquid cargo membrane tank) is unloaded into the land liquid cargo membrane tank (or ship membrane tank), the BOG of the LNG in the land liquid cargo membrane tank (or ship membrane tank) is processed by utilizing the cold energy of the LNG in the ship membrane tank (or land liquid cargo membrane tank), so that the land liquid cargo membrane tank (or ship membrane tank) can be cooled by self-circulation, BOG can be recovered by double tank circulation, and the tank pressure of the land liquid cargo membrane tank (or ship membrane tank) can be reduced. This can effectively solve the problem that the temperature of the land liquid cargo membrane tank (or ship membrane tank) increases due to the sun exposure, etc., and the BOG generated by liquid cargo such as LNG increases, resulting in an increase in tank pressure that affects the storage of compressed low-temperature liquefied gases such as LNG.

[0026] 2) The present invention provides a BOG dynamic balance treatment system for marine vessels and land liquid cargo membrane tanks. The entire system has a simple structure and simple process operation.

[0027] 3) During the filling process, part of the LNG will be gasified due to friction between the LNG and the pipeline, temperature loss of the pipeline, cooling process of the pipeline, or temperature loss and pressure change of the membrane tank. The present invention provides a BOG dynamic balance processing system for marine vessels and land liquid cargo membrane tanks, which can ensure constant temperature and BOG stability during the filling process. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the overall structure of the BOG dynamic balance processing system for offshore vessels and land liquid cargo membrane tanks in an embodiment of the present invention.

[0029] Figure 2It is a partial schematic diagram of the BOG dynamic balance processing system for marine vessels and land liquid cargo membrane tanks in an embodiment of the present invention, to illustrate the BOG temperature reduction and pressure regulation mechanism.

[0030] Figure 3 It is a partial schematic diagram of the BOG dynamic balance processing system of the marine vessel and the land liquid cargo membrane tank in the embodiment of the present invention, to illustrate the liquid cargo processing mechanism and the ship membrane tank.

[0031] Figure 4 It is a partial schematic diagram of the BOG dynamic balance processing system of the offshore vessel and the land liquid cargo membrane tank in the embodiment of the present invention, to illustrate the gas phase connecting hose and the liquid phase connecting hose.

[0032] Figure 5 It is a partial schematic diagram of the BOG dynamic balance processing system of the marine vessel and the land liquid cargo membrane tank in the embodiment of the present invention, to illustrate the land liquid cargo membrane tank.

[0033] in: 1. Ship membrane tank, 2. Liquid cargo pump, 3. Subcooling unit, 4. Gas-liquid spray cooling tank, 5. Seawater heat exchanger, 6. Low-temperature heat exchanger, 7. Compressor, 8. Gas phase connecting hose, 9. Liquid phase connecting hose, 10. Land liquid cargo membrane tank, 11. Spray cooling pipeline, 12. Spray filling pipeline. DETAILED DESCRIPTION

[0034] The present invention is described in detail below in conjunction with specific embodiments, which are only used to illustrate the present invention and are not used to limit the scope of protection of the present invention. The features such as component models, material names, connection structures, control methods, etc. that are not clearly described in this technical solution are regarded as common technical features disclosed in the prior art.

[0035] Example 1

[0036] refer to Figure 1-Figure 5 The present invention provides a BOG dynamic balance processing system for marine ships and land liquid cargo membrane tanks, which can use the cold energy of liquid cargo in the ship membrane tank 1 to process the BOG of liquid cargo in the land liquid cargo membrane tank 10. The system includes a ship membrane tank 1 and a land liquid cargo membrane tank 10; the ship membrane tank 1 and the land liquid cargo membrane tank 10 are connected by a gas phase connecting hose 8; the ship membrane tank 1 and the land liquid cargo membrane tank 10 are connected by a liquid phase connecting hose 9.

[0037] The system further comprises a BOG temperature reduction and pressure regulation mechanism, which is used for reducing the temperature and regulating the pressure of BOG in the land liquid cargo film tank 10; the BOG temperature reduction and pressure regulation mechanism comprises a seawater heat exchanger 5, a low-temperature heat exchanger 6, and a compressor 7; the air intake end of the compressor 7 is connected to the land liquid cargo film tank 10 through a pipeline; the air outlet end of the compressor 7 is connected to the inlet of the seawater heat exchanger 5 through a pipeline; the outlet of the seawater heat exchanger 5 is connected to the inlet of the low-temperature heat exchanger 6 through a pipeline; the outlet of the low-temperature heat exchanger 6 is connected to the land liquid cargo film tank 10 through a pipeline, and a gas pressure regulating valve is provided on the pipeline between the outlet of the low-temperature heat exchanger 6 and the land liquid cargo film tank 10; the other inlet of the seawater heat exchanger 5 is connected to the seawater inlet pipeline; the other outlet of the seawater heat exchanger 5 is connected to the seawater outlet pipeline.

[0038] The system further comprises a liquid cargo handling mechanism, which is used for supercooling the liquid cargo in the ship's membrane tank 1; the liquid cargo handling mechanism comprises a liquid cargo pump 2, a supercooling unit 3, and a gas-liquid spray cooling tank 4; the inlet of the liquid cargo pump 2 is connected to the ship's membrane tank 1 through a pipeline; the outlet of the liquid cargo pump 2 is connected to another inlet of a low-temperature heat exchanger 6 through a pipeline, so that the liquid cargo from the ship's membrane tank 1 is heat-exchanged with the high-temperature BOG from the land liquid cargo membrane tank 10; the other outlet of the low-temperature heat exchanger 6 is connected to the inlet of the gas-liquid spray cooling tank 4 through a pipeline; the outlet of the gas-liquid spray cooling tank 4 is connected to the inlet of the supercooling unit 3 The outlet of the compressor 7 is connected to the inlet of the supercooling unit 3 through a pipeline; the outlet of the supercooling unit 3 is connected to the ship membrane tank 1 through a pipeline; the outlet of the supercooling unit 3 is connected to the inlet of the gas-liquid spray cooling tank 4 through a pipeline; the outlet of the gas-liquid spray cooling tank 4 is connected to the land liquid cargo membrane tank 10 through a pipeline; the outlet of the liquid cargo pump 2 is connected to the inlet of the gas-liquid spray cooling tank 4 through a pipeline; the outlet of the liquid cargo pump 2 is connected to the land liquid cargo membrane tank 10 through a liquid phase connecting hose 9; the outlet end of the compressor 7 is connected to the inlet of the gas-liquid spray cooling tank 4 through a pipeline.

[0039] The top of the ship's membrane tank 1 is provided with a spray cooling pipeline 11 and a spray filling pipeline 12 in sequence from top to bottom; the spray cooling pipeline 11 and the spray filling pipeline 12 are both arranged at a height higher than the liquid level of the liquid cargo in the ship's membrane tank 1 .

[0040] The seawater heat exchanger 5 may be a shell-and-tube heat exchanger, a coil-and-wind heat exchanger or a plate heat exchanger; the low-temperature heat exchanger 6 may be a shell-and-tube heat exchanger, a coil-and-wind heat exchanger or a plate heat exchanger.

[0041] The supercooling unit 3 includes a supercooler.

[0042] Liquid cargo is liquefied natural gas (LNG) or liquid ammonia (NH 3) and other low-temperature liquids.

[0043] A circulation pump is provided at the bottom of the gas-liquid spray cooling tank 4 .

[0044] Example 2

[0045] This embodiment provides a working method of the BOG dynamic balance processing system of the marine vessel and the land liquid cargo membrane tank in Embodiment 1, and the liquid cargo is LNG, and the method comprises the following steps: S1. Initial cooling of the top temperature of the land liquid cargo membrane tank 10: The compressor 7 extracts the BOG in the land liquid cargo membrane tank 10 and compresses it to obtain compressed gas, which then enters the seawater heat exchanger 5 to cool the compressed gas to room temperature, and then enters the low-temperature heat exchanger 6 to cool the BOG to about -20 to 0°C, and then cools the BOG to -80°C by pressure regulation (0.65MPa), and circulates back to the land liquid cargo membrane tank 10 (pressure regulation is to reduce the pressure of the fluid in the pipeline. The BOG in the tank needs to be pressurized by the compressor and then reduced to low temperature to liquefy, and then reduced to low pressure before entering the normal pressure membrane tank) and then reduces the temperature in the land liquid cargo membrane tank 10 to -160°C and the pressure to normal pressure, in preparation for the next step of reducing to a lower temperature; the ship membrane tank 1 passes through the liquid cargo pump 2 The liquid cargo is supplied to the low-temperature heat exchanger 6 for heat exchange with the high-temperature BOG in the land liquid cargo membrane tank 10. The liquid cargo that absorbs heat will be vaporized. The vaporized liquid cargo enters the gas-liquid spray cooling tank 4 and directly contacts with the liquid cargo for spray cooling and cooling (the liquid cargo in the gas-liquid spray cooling tank 4 comes from the liquid cargo transported by the liquid cargo pump 2 in the ship's membrane tank 1, which is used as the BOG to directly exchange heat with the BOG for cooling; the compressor 7 compresses and pressurizes the BOG, which will increase the temperature of the compressor 7). The low-temperature gaseous liquid cargo is pressurized to 0.65MPa by the compressor 7, and then mixed with the un-vaporized liquid cargo at the bottom of the gas-liquid spray cooling tank 4 and passed into the supercooling unit 3 to be cooled to -175°C to obtain the liquefied liquid cargo. The liquefied liquid cargo returns to the ship's membrane tank 1; S2, further cooling the land liquid cargo film tank 10, reducing the temperature inside the land liquid cargo film tank 10 to below -170°C, in preparation for filling the land liquid cargo film tank 10 with liquid cargo from the ship film tank 1: The compressor 7 extracts the BOG in the land liquid cargo film tank 10 and directly supplies it to the supercooling unit 3. In S1, the supercooling unit 3 reduces the BOG temperature to a low temperature (-80°C) and then circulates the gas-liquid spray cooling tank 4 for buffering and reduces the temperature to a low temperature of -160°C. The BOG reduced to a low temperature (-160°C) returns to the land liquid cargo film tank 10 and continuously circulates the gas phase to gradually reduce the temperature in the land liquid cargo film tank 10 to about -170°C, completing the cooling in the land liquid cargo film tank 10 and reaching a supercooling temperature lower than the liquid cargo storage temperature. S3, supercooled liquid cargo spraying land liquid cargo membrane tank 10: Spray the land liquid cargo membrane tank 10 to be loaded with a certain amount of supercooled liquid cargo (the reliquefaction device can supercool the liquid cargo delivered by the liquid cargo pump to -170°C for spraying to reduce the temperature) to allow the main film shielding layer of the land liquid cargo membrane tank 10 to adapt to the supercooled liquid cargo; First, the ship's membrane tank 1 is loaded with liquid cargo through the liquid cargo pump 2 and temporarily stored in the gas-liquid spray cooling tank 4. The liquid cargo is then sent to the supercooled liquid cargo in the supercooling unit 3 through the circulating pump at the bottom of the gas-liquid spray cooling tank 4 (the liquid cargo sprayed is not in the gas phase, the low-temperature BOG can be pre-cooled to -160°C in a cycle, and the liquid cargo sprayed is the supercooled liquid cargo at a low temperature of -170°C before filling). Then, the liquid cargo pump 2 sends the liquid cargo to the land liquid cargo membrane tank 10, and sprays from the top of the land liquid cargo membrane tank 10 until the land liquid cargo membrane tank 10 is filled. The inside reaches a low temperature state (the inside of the land liquid cargo film tank 10 is supercooled to -170°C and then filled with liquid cargo at -165°C, wherein -170°C is the supercooling temperature and -165°C is the normal liquid cargo temperature. Supercooling is to leave a margin temperature for the liquid cargo. The normal tank body will also heat up with the filling, rising to -165°C, and the tank body may rise to a temperature higher than -165°C), and the gas phase is connected to the land liquid cargo film tank 10 and the ship film tank 1 through the gas phase connecting hose 8 to achieve gas-liquid pressure balance; S4, performing the filling process: the liquid cargo in the ship's membrane tank 1 is transported into the land-based liquid cargo membrane tank 10 through the liquid cargo pump 2 and the liquid phase connecting hose 9.

[0046] Furthermore, during the filling process, part of the liquid cargo may be vaporized due to friction between the liquid cargo and the pipeline, temperature loss of the pipeline, cooling process of the pipeline, or temperature loss and pressure change of the ship membrane tank 1 and the land liquid cargo membrane tank 10. To ensure constant temperature and BOG stability, BOG control of the land liquid cargo membrane tank 10 is performed, including the following process: The liquid cargo stored in the ship's membrane tank 1 is continuously transported into the land-based liquid cargo membrane tank 10 through the liquid cargo pump 2 and the liquid phase connecting hose 9. The BOG generated by gasification in the land-based liquid cargo membrane tank 10 and the ship's membrane tank 1 is pumped away by the compressor 7 (the compression work is linked to the pressure of the filled membrane tank to ensure that the tank pressure is at normal pressure) (normally, when there is no excess BOG generated, there is no excessive gasification. The ship's membrane tank 1 and the land-based liquid cargo membrane tank 10 achieve pressure balance through the natural flow of the gas phase. When additional BOG is generated, it will cause the pressure to rise, and the compressor 7 needs to be turned on. The land-based liquid cargo membrane tank 1 0 and the BOG generated by gasification in the ship membrane tank 1 first enters the gas-liquid spray cooling tank 4, the BOG is first directly cooled by the sprayed supercooled liquid cargo (the liquid cargo comes from a small amount of liquid cargo diverted by the liquid cargo pump 2 during the filling process), the cooled BOG enters the compressor 7, the BOG compressed to 0.65MPa by the compressor 7 is then mixed with the ungasified liquid cargo at the bottom of the gas-liquid spray cooling tank 4 and enters the supercooling unit 3 to complete the liquefaction of the BOG (the liquefied BOG is then sent to the ship membrane tank 1 and / or the land liquid cargo membrane tank 10), realizing the reliquefaction and recovery of the BOG in this process.

[0047] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A BOG dynamic balance treatment system for marine vessels and land liquid cargo membrane tanks, characterized in that: The system includes a first membrane tank and a second membrane tank; The first membrane tank and the second membrane tank are connected; The system further comprises a BOG temperature reduction and pressure regulation mechanism, wherein the BOG temperature reduction and pressure regulation mechanism is used for reducing the temperature and regulating the pressure of the BOG in the second membrane tank; The system further comprises a liquid cargo handling mechanism, the liquid cargo handling mechanism being used for subcooling the liquid cargo in the first membrane tank; The BOG temperature reduction and pressure regulation mechanism is connected to the second membrane tank; The liquid cargo handling mechanism is connected to the first film tank and the second film tank respectively; The BOG temperature reduction and pressure regulation mechanism is connected to the liquid cargo processing mechanism so that the liquid cargo from the first membrane tank exchanges heat with the BOG from the second membrane tank.

2. The BOG dynamic balancing treatment system for marine vessels and land liquid cargo membrane tanks according to claim 1 is characterized in that: The first film tank and the second film tank are connected via a gas phase connecting hose (8); The first membrane tank and the second membrane tank are connected via a liquid phase connecting hose (9).

3. The BOG dynamic balancing treatment system for marine vessels and land liquid cargo membrane tanks according to claim 1 is characterized in that: The first film tank is a ship film tank (1); The second membrane tank is a land liquid cargo membrane tank (10).

4. The BOG dynamic balancing treatment system for marine vessels and land liquid cargo membrane tanks according to claim 1 is characterized in that: The second film tank is a ship film tank (1); The first membrane tank is a land liquid cargo membrane tank (10).

5. The BOG dynamic balancing treatment system for marine vessels and land liquid cargo membrane tanks according to claim 1 is characterized in that: The BOG temperature reduction and pressure regulation mechanism comprises a heat exchange component and a compressor (7); The air intake end of the compressor (7) is connected to the second membrane tank; The air outlet end of the compressor (7) is connected to the inlet end of the heat exchange component; The outlet of the heat exchange component is connected to the second membrane tank.

6. The BOG dynamic balancing treatment system for marine vessels and land liquid cargo membrane tanks according to claim 5 is characterized in that: The heat exchange component comprises a seawater heat exchanger (5) and a low-temperature heat exchanger (6); The air intake end of the compressor (7) is connected to the second membrane tank; The air outlet end of the compressor (7) is connected to the inlet end of the seawater heat exchanger (5); The outlet of the seawater heat exchanger (5) is connected to the inlet of the low-temperature heat exchanger (6); The outlet of the low-temperature heat exchanger (6) is connected to the second membrane tank.

7. The BOG dynamic balancing treatment system for marine vessels and land liquid cargo membrane tanks according to claim 5 is characterized in that: The liquid cargo handling mechanism comprises a liquid cargo pump (2), a supercooling unit (3), and a gas-liquid spray cooling tank (4); The inlet of the liquid cargo pump (2) is connected to the first membrane tank; The outlet of the gas-liquid spray cooling tank (4) is connected to the inlet of the supercooling unit (3); The outlet of the supercooling unit (3) is connected to the first film tank; The outlet of the supercooling unit (3) is connected to the inlet of the gas-liquid spray cooling tank (4); The outlet of the gas-liquid spray cooling tank (4) is connected to the second film tank; The outlet of the liquid cargo pump (2) is connected to the inlet of the gas-liquid spray cooling tank (4); The outlet of the liquid cargo pump (2) is connected to the second membrane tank.

8. The BOG dynamic balancing treatment system for marine vessels and land liquid cargo membrane tanks according to claim 7 is characterized in that: The outlet of the liquid cargo pump (2) is connected to the heat exchange component; The heat exchange component is connected to the inlet of the gas-liquid spray cooling tank (4); The air outlet end of the compressor (7) is connected to the inlet of the supercooling unit (3); The gas outlet end of the compressor (7) is connected to the inlet of the gas-liquid spray cooling tank (4).

9. The BOG dynamic balancing treatment system for marine vessels and land liquid cargo membrane tanks according to claim 1 is characterized in that: The top of the first film tank is provided with a spray cooling pipeline (11) and a spray filling pipeline (12) in sequence from top to bottom; The spray cooling pipeline (11) and the spray filling pipeline (12) are both arranged at a height higher than the liquid level of the liquid cargo in the first membrane tank.

10. The BOG dynamic balancing treatment system for marine vessels and land liquid cargo membrane tanks according to claim 1, characterized in that: The liquid cargo is liquefied natural gas or liquid ammonia.

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