CN114413567A - BOG reliquefaction system and method for ship and transport ship - Google Patents

BOG reliquefaction system and method for ship and transport ship Download PDF

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Publication number
CN114413567A
CN114413567A CN202210081320.9A CN202210081320A CN114413567A CN 114413567 A CN114413567 A CN 114413567A CN 202210081320 A CN202210081320 A CN 202210081320A CN 114413567 A CN114413567 A CN 114413567A
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China
Prior art keywords
bog
cooler
pipeline
lng
refrigerant
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CN202210081320.9A
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Chinese (zh)
Inventor
朱建鲁
李玉星
刘胜男
王武昌
胡其会
韩辉
刘翠伟
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China University of Petroleum East China
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China University of Petroleum East China
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Priority to CN202210081320.9A priority Critical patent/CN114413567A/en
Publication of CN114413567A publication Critical patent/CN114413567A/en
Pending legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/0002—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the fluid to be liquefied
    • F25J1/0022—Hydrocarbons, e.g. natural gas
    • F25J1/0025—Boil-off gases "BOG" from storages
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B25/00—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby
    • B63B25/02—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods
    • B63B25/08—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods fluid
    • B63B25/12—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods fluid closed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63J—AUXILIARIES ON VESSELS
    • B63J99/00—Subject matter not provided for in other groups of this subclass
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/003—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
    • F25J1/0047—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle
    • F25J1/005—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle by expansion of a gaseous refrigerant stream with extraction of work
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0203—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a single-component refrigerant [SCR] fluid in a closed vapor compression cycle
    • F25J1/0204—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a single-component refrigerant [SCR] fluid in a closed vapor compression cycle as a single flow SCR cycle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0228—Coupling of the liquefaction unit to other units or processes, so-called integrated processes
    • F25J1/0229—Integration with a unit for using hydrocarbons, e.g. consuming hydrocarbons as feed stock
    • F25J1/023—Integration with a unit for using hydrocarbons, e.g. consuming hydrocarbons as feed stock for the combustion as fuels, i.e. integration with the fuel gas system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0257—Construction and layout of liquefaction equipments, e.g. valves, machines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0257—Construction and layout of liquefaction equipments, e.g. valves, machines
    • F25J1/0275—Construction and layout of liquefaction equipments, e.g. valves, machines adapted for special use of the liquefaction unit, e.g. portable or transportable devices
    • F25J1/0277—Offshore use, e.g. during shipping
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J5/00—Arrangements of cold exchangers or cold accumulators in separation or liquefaction plants
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63J—AUXILIARIES ON VESSELS
    • B63J99/00—Subject matter not provided for in other groups of this subclass
    • B63J2099/001—Burning of transported goods, e.g. fuel, boil-off or refuse
    • B63J2099/003—Burning of transported goods, e.g. fuel, boil-off or refuse of cargo oil or fuel, or of boil-off gases, e.g. for propulsive purposes
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/62—Liquefied natural gas [LNG]; Natural gas liquids [NGL]; Liquefied petroleum gas [LPG]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2235/00—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams
    • F25J2235/60—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams the fluid being (a mixture of) hydrocarbons
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
    • F25J2240/60—Expansion by ejector or injector, e.g. "Gasstrahlpumpe", "venturi mixing", "jet pumps"
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
    • F25J2290/34—Details about subcooling of liquids

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Ocean & Marine Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Filling Or Discharging Of Gas Storage Vessels (AREA)

Abstract

The invention relates to a BOG reliquefaction system and method for a ship and a transport ship, and belongs to the technical field of BOG treatment. The system comprises a liquid cargo tank for placing LNG, wherein a gas phase outlet of the liquid cargo tank is communicated with an inlet of a BOG buffer tank through a first pipeline, a first outlet of the BOG buffer tank is communicated with a combustion unit of a ship through a second pipeline, and the system is characterized in that a second outlet of the BOG buffer tank is communicated with an inlet of an ejector through a third pipeline, an outlet of the ejector is communicated with the inside of the liquid cargo tank through a spray pipe, a liquid phase outlet of the liquid cargo tank is connected with an inlet of an LNG booster pump through a fourth pipeline, an outlet of the LNG booster pump is connected with a high-pressure port of the ejector through a first cooler, and the first pipeline, the second pipeline, the third pipeline and the fourth pipeline are provided with valves for controlling pipeline pipelines. The system solves the problem that BOG in the LNG transport ship liquid cargo tank can not be completely consumed by the gas combustion unit, so that the LNG transport ship can be kept at a lower pressure level no matter the LNG transport ship is underway or stopped.

Description

BOG reliquefaction system and method for ship and transport ship
Technical Field
The invention belongs to the technical field of BOG treatment, and particularly relates to a BOG reliquefaction system and method for a ship and a transport ship.
Background
The main component of natural gas is methane, which exists in a gaseous state at normal temperature and pressure, however, during the storage and transportation of natural gas, natural gas is generally required to be gasified into LNG and then stored and transported, LNG carriers are widely used for marine transportation of LNG, during long-distance transportation of LNG, heat leakage is inevitable due to environmental factors, which gasifies LNG in a cargo tank, thereby generating a large amount of BOG gas, which increases the pressure in an LNG cargo tank, which threatens the structural safety of the cargo tank, in order to maintain the cargo tank at an allowable pressure level, the generated BOG gas must be properly treated, and if the BOG is directly emptied, energy waste and economic loss are caused.
With the continuous improvement of the propulsion system and the BOG reliquefaction technology of the LNG carrier, the BOG is mainly processed by sending the BOG into the gas combustion unit to provide power fuel for the LNG carrier at present, the BOG of the medium-sized and large-sized LNG carriers cannot be completely processed by the gas combustion unit, redundant BOG gas needs to be reliquefied and then recycled into the liquid cargo tank, but the arrangement of the BOG reliquefaction system on the LNG carrier can improve the manufacturing cost of the LNG carrier, and the reliquefaction technology needs to consider the complexity, the investment cost factor and the power consumption problem of the reliquefaction system.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides a BOG reliquefaction system and method for a ship and a transport ship. The system solves the problem that BOG in the LNG transport ship liquid cargo tank can not be completely consumed by the gas combustion unit, so that the LNG transport ship can be kept at a lower pressure level no matter the LNG transport ship is underway or stopped.
The embodiment of the invention provides a BOG reliquefaction system for a ship, which comprises a liquid cargo tank for placing LNG, wherein a gas phase outlet of the liquid cargo tank is communicated with an inlet of a BOG buffer tank through a first pipeline, a first outlet of the BOG buffer tank is connected with a combustion unit of the ship through a second pipeline, a second outlet of the BOG buffer tank is connected with a gas port of an ejector through a third pipeline, an outlet of the ejector is communicated with the inside of the liquid cargo tank through a spray pipe, a liquid phase outlet of the liquid cargo tank is connected with an inlet of an LNG booster pump through a fourth pipeline, an outlet of the LNG booster pump is connected with a high-pressure port of the ejector through a first cooler, and valves for controlling the on-off of the pipelines are arranged on the first pipeline, the second pipeline, the third pipeline and the fourth pipeline.
The refrigerant circulating pipeline comprises a refrigerant storage tank, an outlet of the refrigerant storage tank is connected with a first inlet of the second cooler through a pipeline, a compressor assembly is arranged between the refrigerant storage tank and the first inlet of the second cooler, a first outlet of the second cooler is connected with a refrigerant inlet of the first cooler through a refrigerant expander, a refrigerant outlet of the first cooler is communicated with a second inlet of the second cooler, and a second outlet of the second cooler is communicated with the refrigerant storage tank.
Further, the compressor assembly comprises at least two compressors connected in series, wherein a first-stage seawater cooler is arranged between every two adjacent compressors, and a second-stage seawater cooler is arranged between the tail end compressor and the second cooler.
Furthermore, the refrigerant storage tank is provided with a refrigerant inlet port, and the refrigerant inlet port is connected with a refrigerant input pipe.
Further, the first cooler and the second cooler are identical in structure.
Further, the first cooler and the second cooler are a liquefaction cold box or a multi-stream heat exchanger.
Furthermore, the spraying ports of the spraying pipes form a net structure, and a plurality of nozzles are arranged on the net structure.
Further, the gas combustion unit comprises any one or any combination of a generator, a boiler, a main engine, a GVU valve box.
The embodiment of the invention also provides a liquefaction method of the BOG reliquefaction system for the ship based on any one of claims 1 to 8, which comprises the following steps:
when the ship body needs natural gas, a valve of the first pipeline is opened, BOG from the liquid cargo tank enters the BOG buffer tank, and enters the gas combustion unit through a first outlet of the BOG buffer tank so as to provide power for the ship;
when the ship body does not need the natural gas to provide power or the ship stops moving, the valve of the second pipeline is closed, the valve of the third pipeline is opened, the BOG that the liquid cargo hold comes out enters the ejector through the second outlet of the BOG buffer tank, meanwhile, the valve of the fourth pipeline is opened, the LNG that the liquid cargo hold flows out enters the LNG booster pump to be pressurized, the pressurized LNG enters the first cooler to be cooled, and after entering and mixing with the BOG in the ejector through the high pressure port of the ejector, the LNG is sprayed into the liquid cargo hold through the spray pipe.
An embodiment of the invention provides a transport ship, which comprises any one of the BOG reliquefaction systems for ships.
The invention has the following beneficial effects:
the BOG reliquefaction system for the ship provided by the invention can directly utilize the BOG from the liquid cargo tank as a combustion medium to provide power when the ship needs natural gas power for sailing, when the ship stops or does not need natural gas, the valve of the second pipeline can be closed, the valves of the third pipeline and the fourth pipeline are opened, the LNG in the liquid cargo tank can enter the LNG booster pump for pressurization and then enters the first cooler for cooling, then enters the ejector through the high-pressure port of the ejector to be mixed with the sucked BOG, so that the redundant BOG can be cooled and liquefied, and finally returns to the liquid cargo tank through the spray pipe, thereby solving the problem that the BOG in the liquid cargo tank of the LNG transport ship can not be completely consumed by the gas combustion unit, meanwhile, the BOG is liquefied again and then mixed with the supercooled LNG to be sprayed into the liquid cargo tank through the spray pipe, so that the temperature in the liquid cargo tank can be further reduced, and the gasification of the LNG is inhibited.
Drawings
Fig. 1 is a schematic diagram of a mechanism of a BOG reliquefaction system for a ship according to an embodiment of the invention.
In the figure: 1. the system comprises a first pipeline, a second pipeline, a third pipeline, a fourth pipeline, a second pipeline, a third pipeline, a second valve, a third valve, a second valve, a fourth valve, a second valve, a spray control valve, a second valve, a spray control valve, a second valve, a first-stage compressor, a first-stage seawater cooler, a second-stage compressor, a second-stage seawater cooler, a second-stage seawater cooler, a second-expansion device and a second-stage-cooling device.
Detailed Description
Referring to fig. 1, the embodiment of the present invention provides a BOG reliquefaction system for a ship, which mainly includes a BOG reliquefaction circulation loop and an LNG subcooling circulation loop, where the BOG reliquefaction circulation loop and the LNG subcooling circulation loop meet at an ejector 9.
Specifically, the BOG re-liquefaction circulation loop comprises a cargo tank 6 placed on a ship body for carrying LNG, wherein a gas phase outlet in the cargo tank 6 is connected with an inlet of a BOG buffer tank 7 through a first pipeline 1, a first valve 12 is arranged on the first pipeline 1, a first outlet of the BOG buffer tank 7 is connected with a gas combustion unit 8 on the ship body through a second pipeline 2, and a second valve 13 is arranged on the second pipeline 2, so that BOG gas generated in the LNG cargo tank 6 can be directly used as a power medium to power the ship.
A second outlet of the BOG buffer tank 7 is connected with a gas inlet of an ejector 9 through a third pipeline 3, the third pipeline 3 is provided with a third valve 14, an outlet of the ejector 9 is communicated with a cargo tank 6 of the LNG through a spraying pipeline 5, wherein the end part of the spraying pipeline 5 connected with the cargo tank 6 is a jet orifice, and the jet orifice is arranged inside the cargo tank 6.
The LNG supercooling circulation loop comprises an LNG transfer pump, a cargo tank 6, an LNG booster pump 10, a first cooler 11, an ejector 9 and the like, wherein the LNG transfer pump in the embodiment is connected with an inlet of a cargo pipeline in the cargo tank 6, an inlet of the LNG booster pump 10 is connected with a cargo outlet through a fourth pipeline 4, a fourth valve 15 is arranged on the fourth pipeline 4, an outlet of the LNG booster pump 10 is connected with a first inlet of the first cooler 11, a second valve 13 is arranged on the cargo pipeline, and a first outlet of the first cooler 11 is connected with a high-pressure port of the ejector 9 through a pipeline.
Therefore, the ship BOG reliquefaction system provided by this embodiment can directly use BOG coming out of the cargo tank 6 as a combustion medium to provide power when a ship needs natural gas power for sailing, when the ship stops or does not need natural gas, the valve of the second pipeline 2 can be closed, the valves of the third pipeline 3 and the fourth pipeline 4 are opened, LNG in the cargo tank 6 enters the LNG booster pump 10 to be pressurized and then enters the first cooler 11 to be cooled, then enters the ejector 9 through the high-pressure port of the ejector 9, high-pressure LNG flows through the nozzle in the ejector to form low pressure to suck BOG, the mixed fluid is mixed with BOG in the mixing chamber in the ejector, the redundant BOG after the mixed fluid passes through the diffuser section of the ejector is cooled and liquefied, finally returns to the cargo tank 6 through the spray pipe, and simultaneously the liquefied BOG is mixed with supercooled LNG and sprayed to the cargo tank 6 through the spray pipe, the temperature in the cargo tank 6 can be further reduced, thereby suppressing vaporization of the LNG.
The spray ports of the spray pipeline 5 in this embodiment are arranged at the upper part of the liquid surface in the cargo tank 6, the spray ports are in a mesh structure, a plurality of nozzles are arranged on the mesh structure, the supercooled LNG is sprayed into the interior through the nozzles, the temperature of the whole interior can also be reduced, and in order to control the on-off of the spray pipeline 5, a fifth valve is arranged on the spray pipeline 5.
In the embodiment, a spray control valve 16 is provided on the spray pipe 5, and the flow rate of the spray pipe 5 is adjusted by the control valve.
Specifically, referring to fig. 1, the BOG reliquefaction system in the present embodiment further includes a refrigerant circulation circuit, wherein the refrigerant circulation line includes a refrigerant buffer tank 17, a compressor part, a second cooler 22, and a refrigerant expander 23, which are connected in series.
Specifically, a first inlet of the refrigerant buffer tank 17 is communicated with a second outlet of the second cooler 22, an outlet of the refrigerant buffer tank 17 is communicated with a first inlet of the second cooler 22 through a pipeline, a compressor assembly is arranged on the pipeline, a first outlet of the second cooler 22 is connected with a second inlet of the first cooler 11 through a refrigerant expander 23, and a second outlet of the first cooler 11 is communicated with a second inlet of the second cooler 22, so that the refrigerant passes through the second inlet of the refrigerant buffer tank 17
Referring to fig. 1, the compressor assembly in this embodiment includes a first-stage compressor 18 and a second-stage compressor 20 connected in sequence, an inlet of the first-stage compressor 18 is communicated with an outlet of a refrigerant buffer tank 17, an outlet of the second-stage compressor 20 is communicated with a first inlet of a second cooler 22, wherein a first-stage seawater cooler 19 is disposed between the first-stage compressor 18 and the second-stage compressor 20, and a second-stage seawater cooler 21 is disposed between the second-stage compressor 20 and a first inlet of the second cooler 22, because the refrigerant generates a large amount of heat after being compressed, which affects the use effect of the compressors, and thus the refrigerant needs to be subjected to interstage cooling after being pressurized, so that the refrigerant can be compressed multiple times.
Of course, the compressor assembly of the present invention includes not only two-stage compressors, but also more than two stages, so that the amount of refrigerant to be cooled is determined, and a seawater cooler is required between two adjacent compressors.
The first outlet of the first cooler 11 is connected to the second inlet of the first cooler 11 through a refrigerant expansion valve, so that the refrigerant cooled by the first cooler 11 is further cooled, and the cooling effect is improved.
The first cooler 11 and the second cooler 22 in this embodiment are liquefaction cold tanks or multi-stream heat exchangers.
The refrigerant buffer tank 17 in this embodiment further comprises a second inlet connected to a refrigerant supplementary line through which refrigerant enters the refrigerant buffer tank 17.
Preferably, the gas combustion unit 8 in this embodiment comprises any one or any combination of a generator, a boiler, a main engine, and a GVU valve box.
The embodiment of the invention also provides a transport ship, which comprises the BOG reliquefaction system for the transport ship, the excess BOG gas in the liquid cargo tank 6 can be reliquefied by using a method of mixing LNG supercooling and BOG in the ejector 9, and the cooling capacity of the BOG before reliquefaction is not wasted, so that the load of a refrigeration system is reduced, and the operation cost is saved.
The following describes in detail a liquefaction process based on a BOG reliquefaction system for ships, which comprises the following processes:
when the ship needs natural gas during navigation, valves on the first pipeline 1 and the second pipeline 2 can be opened, and BOG from the LNG cargo tank 6 enters the buffer tank through the first pipeline 1 and then enters the gas combustion unit 8GCU through the second pipeline 2 to provide power for the ship;
when the ship is stopped or power is not required to be provided by natural gas, the valves on the second pipeline 2 are closed, the valves on the third pipeline 3 and the fourth pipeline 4 are opened, BOG coming out of the LNG cargo tank 6 enters the ejector 9 through the gas port of the ejector 9, meanwhile, LNG coming out of the LNG cargo tank 6 enters the LNG booster pump 10 through the liquid phase outlet to be pressurized and then enters the first cooler 11 to be cooled, the cooled liquid LNG enters the ejector 9 through the high pressure port of the ejector 9 to be mixed with the innermost BOG, the BOG is mixed, cooled and liquefied and then recycled into the LNG cargo tank 6, and then the BOG is mixed with subcooled LNG and sprayed into the LNG cargo tank 6 through the spraying pipe port of the spraying pipe after being re-liquefied, so that the temperature in the LNG cargo tank 6 can be further reduced, and vaporization of the LNG is inhibited.
In the refrigerant circulation pipeline, refrigerant enters the refrigerant buffer tank 17 through a refrigerant supplementary inlet, after the refrigerant flowing out of the refrigerant buffer tank 17 is primarily cooled by the two-stage compressor and the two-stage seawater cooler, the primarily cooled refrigerant enters the second cooler 22 to be crossed with the refrigerant which is expanded to provide cold energy for LNG, the refrigerant cooled by the second cooler 22 is further cooled by the refrigerant expander 23, the expanded and cooled refrigerant is crossed with the pressurized LNG in the first cooler 11 to achieve the purpose of supercooling the LNG flowing into the first cooler 11, then the LNG enters the first cooler EX1 to provide cold energy for the compressed refrigerant, and finally returns to the refrigerant buffer tank D2 to complete a cycle.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.

Claims (10)

1. The utility model provides a marine BOG reliquefaction system, including the cargo tank that is used for placing LNG, the gaseous phase export of cargo tank and the entry of BOG buffer tank are through first pipeline intercommunication, the first export of BOG buffer tank passes through the combustion unit of second tube coupling boats and ships, a serial communication port, the second export of BOG buffer tank passes through the gas mouth of third tube coupling sprayer, the export and the cargo tank of sprayer are inside to be passed through the shower and communicate, the liquid phase export of cargo tank passes through the entry linkage of fourth pipeline and LNG booster pump, the export of LNG booster pump is connected with the high-pressure port of sprayer through first cooler, first, second, three, four pipelines all are equipped with the valve of control pipeline break-make.
2. The marine BOG reliquefaction system according to claim 1, further comprising a refrigerant circulation line including a refrigerant storage tank, an outlet of the refrigerant storage tank being connected to a first inlet of the second cooler through a pipe, a compressor unit being provided between the refrigerant storage tank and the first inlet of the second cooler, the first outlet of the second cooler being connected to a refrigerant inlet of the first cooler through a refrigerant expander, a refrigerant outlet of the first cooler being in communication with a second inlet of the second cooler, and a second outlet of the second cooler being in communication with the refrigerant storage tank.
3. The marine BOG reliquefaction system according to claim 2, wherein the compressor assembly includes at least two compressors connected in series, wherein a first stage seawater cooler is provided between adjacent two of the compressors, and a second stage seawater cooler is provided between the final compressor and the second cooler.
4. The BOG reliquefaction system for ship according to claim 2, wherein the refrigerant storage tank is provided with a refrigerant inflow port connected to the refrigerant input pipe.
5. The marine BOG reliquefaction system according to claim 2, wherein the first cooler and the second cooler are identical in structure.
6. The marine BOG reliquefaction system according to claim 2, wherein the first cooler and the second cooler are both a liquefaction cold box or a multi-stream heat exchanger.
7. The BOG reliquefaction system of claim 1, wherein the spray ports of the spray pipes are formed in a mesh structure, and a plurality of nozzles are disposed on the mesh structure and are in communication with the spray pipes.
8. The marine BOG reliquefaction system according to claim 1, wherein the gas combustion unit includes any one or any combination of a generator, a boiler, a main engine, a GVU valve box.
9. The liquefaction method of a BOG reliquefaction system for a ship according to any one of claims 1 to 8,
when the ship body needs natural gas, valves of the first pipeline and the second pipeline are opened, BOG from the liquid cargo tank enters the BOG buffer tank, and enters the gas combustion unit through a first outlet of the BOG buffer tank to be combusted, so that power is provided for the ship;
when the ship body does not need the natural gas to provide power or the ship stops moving, the valve of the second pipeline is closed, the valve of the third pipeline is opened, the BOG that the liquid cargo hold comes out enters the ejector through the second outlet of the BOG buffer tank, meanwhile, the valve of the fourth pipeline is opened, the LNG that the liquid cargo hold flows out enters the LNG booster pump to be pressurized, the pressurized LNG enters the first cooler to be cooled, and after entering and mixing with the BOG in the ejector through the high pressure port of the ejector, the LNG is sprayed into the liquid cargo hold through the spray pipe.
10. A carrier vessel comprising a marine BOG reliquefaction system according to any one of claims 1 to 8.
CN202210081320.9A 2022-01-24 2022-01-24 BOG reliquefaction system and method for ship and transport ship Pending CN114413567A (en)

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