CN113503465B - BOG (boil off gas) processing system and method for LNG (liquefied natural gas) transport ship - Google Patents

BOG (boil off gas) processing system and method for LNG (liquefied natural gas) transport ship Download PDF

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Publication number
CN113503465B
CN113503465B CN202110768149.4A CN202110768149A CN113503465B CN 113503465 B CN113503465 B CN 113503465B CN 202110768149 A CN202110768149 A CN 202110768149A CN 113503465 B CN113503465 B CN 113503465B
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lng
compressor
nitrogen
cold box
outlet
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CN113503465A (en
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曾伟平
尹全森
李恩道
花亦怀
程昊
鹿来运
范明龙
刘淼儿
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CNOOC Gas and Power Group Co Ltd
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CNOOC Gas and Power Group Co Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C13/00—Details of vessels or of the filling or discharging of vessels
    • 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
    • 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
    • F25J1/006—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the refrigerant fluid used
    • F25J1/007—Primary atmospheric gases, mixtures thereof
    • F25J1/0072—Nitrogen
    • 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
    • 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
    • F25J1/0262—Details of the cold heat exchange system
    • F25J1/0264—Arrangement of heat exchanger cores in parallel with different functions, e.g. different cooling streams
    • F25J1/0265—Arrangement of heat exchanger cores in parallel with different functions, e.g. different cooling streams comprising cores associated exclusively with the cooling of a refrigerant stream, e.g. for auto-refrigeration or economizer
    • 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
    • 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
    • F25J1/0279—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc.
    • 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
    • F25J1/0279—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc.
    • F25J1/0285—Combination of different types of drivers mechanically coupled to the same refrigerant compressor, possibly split on multiple compressor casings
    • F25J1/0288—Combination of different types of drivers mechanically coupled to the same refrigerant compressor, possibly split on multiple compressor casings using work extraction by mechanical coupling of compression and expansion of the refrigerant, so-called companders
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
    • F17C2227/03—Heat exchange with the fluid
    • F17C2227/0337—Heat exchange with the fluid by cooling
    • F17C2227/0341—Heat exchange with the fluid by cooling using another fluid
    • F17C2227/0348—Water cooling
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
    • F17C2227/03—Heat exchange with the fluid
    • F17C2227/0367—Localisation of heat exchange
    • F17C2227/0388—Localisation of heat exchange separate
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2265/00—Effects achieved by gas storage or gas handling
    • F17C2265/03—Treating the boil-off
    • F17C2265/032—Treating the boil-off by recovery
    • F17C2265/033—Treating the boil-off by recovery with cooling
    • F17C2265/034—Treating the boil-off by recovery with cooling with condensing the gas phase
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2270/00—Applications
    • F17C2270/01—Applications for fluid transport or storage
    • F17C2270/0102—Applications for fluid transport or storage on or in the water
    • F17C2270/0105—Ships
    • 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
    • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/20—Integrated compressor and process expander; Gear box arrangement; Multiple compressors on a common shaft
    • 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

Abstract

The invention relates to a BOG (boil off gas) processing system and method for an LNG transport ship, which comprises the following components: the LNG storage system comprises a first LNG storage cabin and a cold box, wherein a liquid phase outlet of the first LNG storage cabin is connected with a first inlet of the cold box, and a first outlet of the cold box is connected with a spraying pipeline at the top of the first LNG storage cabin; a liquid phase outlet of the second LNG storage cabin is also connected with a first inlet of the cold box, and a first outlet of the cold box is also connected with a spraying pipeline at the top of the second LNG storage cabin; the expansion machine is connected with the second outlet of the cold box, the outlet of the expansion machine is connected with the third inlet of the cold box, the third outlet of the cold box is connected with the fourth inlet of the cold box, the fourth outlet of the cold box is connected with the inlet of the compressor, the outlet of the compressor is connected with the inlet of the cooler, and the outlet of the cooler is connected with the second inlet of the cold box. The BOG treatment system is integrally sledged, and is easy to arrange and install.

Description

BOG (boil off gas) processing system and method for LNG (liquefied natural gas) transport ship
Technical Field
The invention relates to a BOG (boil off gas) processing system and method for an LNG (liquefied natural gas) carrier, and belongs to the field of BOG recovery processing of LNG carriers.
Background
With the increase of energy demand, the overseas LNG (liquefied Natural Gas) trade becomes a new growing point in the world oil and Gas industry, and LNG carriers are adopted for the transportation of general LNG. Due to the low temperature of LNG, boil Off Gas (BOG) is generated during storage and transportation under the influence of external heat. In a traditional LNG transport ship, a steam turbine is mostly adopted for driving, and the generated BOG can be used as ship fuel after being compressed, so that the waste is reduced, but the steam turbine has low efficiency and large energy consumption, and is gradually replaced by a mainstream diesel-electric engine or a dual-fuel engine at present. Therefore, the BOG cannot be consumed by the hull itself, and a BOG recovery processing device needs to be installed on the LNG carrier. On the other hand, the LNG transportation process is influenced by factors such as cold insulation effect and transportation time, partial LNG can volatilize, and when the volatilization amount is larger than the demand of power fuel, redundant natural gas is required to be reliquefied, so most LNG transport ships are provided with reliquefaction devices. In addition, since the LNG tanker is affected by the nature of the operation, it is necessary to receive the BOG generated during the cold storage and replacement of the tanker during the refueling process, and to process the BOG gas generated by vaporization of the tanker during the waiting for the refueling operation, it is necessary to provide a small reliquefaction device for the LNG tanker.
Disclosure of Invention
In order to solve the outstanding problems, the invention provides a system and a method for processing BOG of an LNG transport ship.
In order to achieve the purpose, the invention adopts the following technical scheme:
a processing system of LNG carrier BOG is characterized by comprising the following components:
the LNG storage system comprises a first LNG storage cabin and a cold box, wherein a liquid phase outlet of the first LNG storage cabin is connected with a first inlet of the cold box, and a first outlet of the cold box is connected with a spraying pipeline at the top of the first LNG storage cabin;
a liquid phase outlet of the second LNG storage tank is also connected with the first inlet of the cold box, and a first outlet of the cold box is also connected with a spraying pipeline at the top of the second LNG storage tank;
the expansion machine comprises an expansion machine, a compressor and a cooler, wherein an inlet of the expansion machine is connected with a second outlet of the cold box, an outlet of the expansion machine is connected with a third inlet of the cold box, a third outlet of the cold box is connected with a fourth inlet of the cold box, a fourth outlet of the cold box is connected with an inlet of the compressor, an outlet of the compressor is connected with an inlet of the cooler, and an outlet of the cooler is connected with the second inlet of the cold box.
The processing system of the BOG of the LNG carrier preferably further includes a first LNG immersed pump and a second LNG immersed pump, the first LNG immersed pump is disposed in the first LNG tank, the second LNG immersed pump is disposed in the second LNG tank, and the first LNG immersed pump and the second LNG immersed pump are configured to deliver LNG in the first LNG tank and the second LNG tank to the cold box.
The LNG carrier BOG's processing system, preferably, the compressor includes nitrogen gas expansion compressor compression end, nitrogen gas compressor first grade and nitrogen gas compressor second grade, the cooler includes first cooler, second cooler and third cooler, the export of nitrogen gas expansion compressor compression end with the entry linkage of first cooler, the export of first cooler with the entry linkage of nitrogen gas compressor first grade, the export of nitrogen gas compressor first grade with the entry linkage of second cooler, the export of second cooler with the entry linkage of nitrogen gas compressor second grade, the export of nitrogen gas compressor second grade with the entry linkage of third cooler, the export of third cooler with the second entry linkage of cold box.
The processing system of LNG transport ship BOG, preferably, the expander with the expansion compressor compression end coaxial coupling, the expansion compressor compression end directly by the expander and first motor are jointly driven, the nitrogen compressor first-stage with the nitrogen compressor second grade is by the drive of second motor, the expander the compressor the first motor and the bearing of second motor all adopts electromagnetic bearing to reduce lubricating system configuration and area.
The processing system of the BOG of the LNG transport ship is characterized in that LNG spraying systems are arranged at the tops of the first LNG storage tank and the second LNG storage tank in the tank, and the LNG spraying systems are configured to enable supercooled LNG to enter the tank through liquid phase inlets of the first LNG storage tank and the second LNG storage tank to contact with the BOG for heat exchange, so that BOG condensation and recovery efficiency are improved.
Preferably, the cooler adopts a printed circuit board type heat exchanger, and closed circulating water is used as a cooling medium.
Based on the processing system of the BOG of the LNG transport ship, the invention also provides a processing method of the system, which comprises the following steps:
1) The first LNG storage cabin and the second LNG storage cabin generate a large amount of BOG due to absorption of ambient heat, and when the pressure in the cabin is higher than an operating pressure, LNG is conveyed to the cold box through the first LNG immersed pump and the second LNG immersed pump;
2) The nitrogen is compressed by the compressor to form nitrogen with the medium pressure of 25-30 bar, and then the nitrogen is cooled to 30-40 ℃ by the cooler;
3) The medium-pressure nitrogen entering the cold box exchanges heat with low-temperature nitrogen flowing back from the cold box, and the returned low-temperature nitrogen after heat exchange is reheated and enters the compressor; the medium-pressure nitrogen is cooled and then continuously enters the expansion machine, the medium-pressure nitrogen expands to reduce pressure and do work externally in the expansion machine, the expansion machine converts the pressure energy of the medium-pressure nitrogen into mechanical energy to cooperate with a motor to drive the compressor to run, the nitrogen is cooled to-175 to-179 ℃ after expansion and then enters the cold box, and the nitrogen returns to the compressor after reheating to complete a nitrogen compression cycle;
4) And the supercooled LNG enters the first LNG storage cabin and the second LNG storage cabin, and exchanges mass transfer and heat with BOG in the storage cabins to recondense the BOG into the LNG.
Due to the adoption of the technical scheme, the invention has the following advantages:
1. according to the invention, the LNG is sent into the cold box by using the original LNG immersed pump in the LNG storage cabin, and after the nitrogen supercooling treatment, the supercooled LNG recondenses the BOG in the storage cabin into the LNG by using the original feeding spraying system of the storage cabin, so that the equipment configuration and the transformation of the LNG storage cabin are not increased.
2. According to the invention, the LNG after the supercooling treatment is used for cooling the BOG in the LNG storage cabin, and an additional BOG compressor is not required.
3. The invention adopts nitrogen as a refrigerating medium, the system is quick to start and stop, and the adjustment is convenient.
4. The expansion compressor and the expansion machine are coaxial, the expansion machine and the motor are jointly driven, the number of equipment is reduced, the compressor, the expansion machine and the motor adopt magnetic bearings, a lubricating system is not needed, and the matching and the occupied area are reduced.
5. The BOG treatment system is integrally sledged, and is easy to arrange and install.
Drawings
Fig. 1 is a schematic diagram of a BOG processing system of an LNG carrier according to an embodiment of the present invention;
the respective symbols in the figure are as follows:
TK 1-a first LNG storage tank; TK 2-a second LNG storage tank; p1-a first LNG immersed pump; p2-a second LNG immersed pump; v1-a first valve; v2-a second valve; v3-third valve; v4-a fourth valve; v5-a fifth valve; v6-sixth valve; v7-seventh valve; v8-eighth valve; v9-ninth valve; v10-tenth valve; v11-eleventh valve; v12-twelfth valve; v13-a thirteenth valve; v14-fourteenth valve; v15-fifteenth valve; CB 1-cold box; c1-the compression end of a nitrogen expansion compressor; c2-1, a first stage of a nitrogen compressor; c2-2, a second stage of a nitrogen compressor; e1-a first cooler; e2-a second cooler; e3-a third cooler; TE 1-expander.
Detailed Description
To make the objects, technical solutions and advantages of the present invention clearer and more complete, the technical solutions of the present invention are described below clearly, and it is obvious that the described embodiments are some, not all embodiments of the present invention. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without making any creative efforts shall fall within the protection scope of the present invention.
Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs. The use of "first," "second," and similar terms in the present application do not denote any order, quantity, or importance, but rather the terms are used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that the element or item preceding the word comprises the element or item listed after the word and its equivalent, but does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect.
As shown in fig. 1, the present invention provides a processing system for BOG of LNG carrier, which includes the following components:
the LNG storage tank TK1 and the cold box CB1 are arranged, a liquid phase outlet of the first LNG storage tank TK1 is connected with a first inlet of the cold box CB1, and a first outlet of the cold box CB1 is connected with a spraying pipeline at the top of the first LNG storage tank TK 1;
the liquid phase outlet of the second LNG storage tank TK2 is also connected with the first inlet of the cold box CB1, and the first outlet of the cold box CB1 is also connected with a spraying pipeline at the top of the second LNG storage tank TK 2;
expander TE1, compressor and cooler, expander TE 1's entry and the second exit linkage of cold box CB1, expander TE 1's export and the third entry linkage of cold box CB1, the third export of cold box CB1 and the fourth entry linkage of cold box CB1, the fourth export of cold box CB1 and the entry linkage of compressor, the export of compressor and the entry linkage of cooler, the export of cooler and the second entry linkage of cold box CB1.
In a preferred embodiment of the present invention, a first LNG immersed pump P1 and a second LNG immersed pump P2 are further included, the first LNG immersed pump P1 is disposed in the first LNG tank TK1, the second LNG immersed pump P2 is disposed in the second LNG tank TK2, and the first LNG immersed pump P1 and the second LNG immersed pump P2 are configured to transfer LNG in the first LNG tank TK1 and the second LNG tank TK2 to the cold box CB1.
In a preferred embodiment of the invention, the compressor comprises a nitrogen expansion compressor compression end C1, a nitrogen compressor first stage C2-1 and a nitrogen compressor second stage C2-2, the coolers comprise a first cooler E1, a second cooler E2 and a third cooler E3, the outlet of the nitrogen expansion compressor compression end C1 is connected with the inlet of the first cooler E1, the outlet of the first cooler E1 is connected with the inlet of the nitrogen compressor first stage C2-1, the outlet of the nitrogen compressor first stage C2-1 is connected with the inlet of the second cooler E2, the outlet of the second cooler E2 is connected with the inlet of the nitrogen compressor second stage C2-2, the outlet of the nitrogen compressor second stage C2-2 is connected with the inlet of the third cooler E3, and the outlet of the third cooler E3 is connected with the second inlet of the cold box CB1.
In a preferred embodiment of the present invention, the expander TE1 and the compression end C1 of the expansion compressor are coaxially connected, the compression end C1 of the expansion compressor is directly driven by the expander TE1 and the first motor together, the first stage C2-1 of the nitrogen compressor and the second stage C2-2 of the nitrogen compressor are driven by the second motor, and electromagnetic bearings are adopted for the bearings of the expander TE1, the compressor, the first motor and the second motor, so as to reduce the configuration and the occupied area of the lubrication system.
In a preferred embodiment of the invention, LNG spraying systems are arranged at the top parts of the first LNG storage tank TK1 and the second LNG storage tank TK2, and the LNG spraying systems are configured to enable subcooled LNG to enter the tanks through liquid phase inlets of the first LNG storage tank TK1 and the second LNG storage tank TK2 to contact with BOG for heat exchange, so that condensation and recovery efficiency of the BOG are improved.
In a preferred embodiment of the invention, the cooler is a printed circuit plate heat exchanger, and closed circulating water is used as a cooling medium.
Based on the processing system of the BOG of the LNG transport ship, the invention also provides a processing method of the system, which comprises the following steps:
1) The first LNG storage tank TK1 and the second LNG storage tank TK2 generate a large amount of BOG due to the fact that ambient heat is absorbed, and when the pressure in the tank is higher than the operating pressure, LNG (60 m) is pumped by the first LNG immersed pump P1 and the second LNG immersed pump P2 3 H) conveying to a cold box CB1;
2) Compressing the nitrogen by a compressor to form medium-pressure nitrogen of 30bar, then cooling the nitrogen to 34 ℃ by a cooler, and finally precooling the nitrogen to-136.5 ℃ in a CB1 precooling section of a cold box;
3) After precooling, the nitrogen gas enters an expansion machine TE1 from a cold box CB1 and is expanded and depressurized to 6.6bar, after the nitrogen gas is expanded and cooled to-177 ℃, the nitrogen gas returns to a supercooling section of the cold box CB1 to provide cold energy for LNG, the LNG from a storage cabin is supercooled to-166 ℃, then the nitrogen gas forms low-temperature nitrogen gas and returns to a precooling section of the cold box CB1 to provide cold energy, and after reheating, the nitrogen gas returns to a compressor to complete a nitrogen gas compression cycle;
4) The subcooled LNG enters the first LNG storage tank TK1 and the second LNG storage tank TK2, and exchanges mass transfer and heat with BOG in the storage tanks, and the BOG is condensed into LNG again.
In the embodiment, in the step 3), the medium-pressure nitrogen gas entering the cold box exchanges heat with the low-temperature nitrogen gas flowing back from the cold box CB1, and the low-temperature nitrogen gas flowing back after heat exchange enters the compressor C1 after self reheating; and the medium-pressure nitrogen is cooled and then continuously enters the gas expander TE1, the medium-pressure nitrogen expands and reduces pressure in the gas expander TE1 to do work outwards, the gas expander TE1 converts the pressure energy of the medium-pressure nitrogen into mechanical energy to cooperate with a motor to drive the compressor C1 to run, and the nitrogen is cooled to-177 ℃ after expansion and then enters the cold box CB1.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (3)

1. A processing system of LNG carrier BOG is characterized by comprising the following components:
a first LNG storage tank (TK 1) and a cold box (CB 1), wherein a liquid phase outlet of the first LNG storage tank (TK 1) is connected with a first inlet of the cold box (CB 1), and a first outlet of the cold box (CB 1) is connected with a spraying pipeline at the top of the first LNG storage tank (TK 1);
a liquid phase outlet of the second LNG storage tank (TK 2) is also connected with a first inlet of the cold box (CB 1), and a first outlet of the cold box (CB 1) is also connected with a spraying pipeline at the top of the second LNG storage tank (TK 2);
an expander (TE 1), a compressor and a cooler, wherein the inlet of the expander (TE 1) is connected with the second outlet of the cold box (CB 1), the outlet of the expander (TE 1) is connected with the third inlet of the cold box (CB 1), the third outlet of the cold box (CB 1) is connected with the fourth inlet of the cold box (CB 1), the fourth outlet of the cold box (CB 1) is connected with the inlet of the compressor, the outlet of the compressor is connected with the inlet of the cooler, and the outlet of the cooler is connected with the second inlet of the cold box (CB 1);
a first LNG immersed pump (P1) and a second LNG immersed pump (P2), the first LNG immersed pump (P1) being disposed within the first LNG tank (TK 1), the second LNG immersed pump (P2) being disposed within the second LNG tank (TK 2), the first LNG immersed pump (P1) and the second LNG immersed pump (P2) being configured to transfer LNG within the first LNG tank (TK 1) and the second LNG tank (TK 2) to the cold box (CB 1);
the compressor comprises a nitrogen expansion compressor compression end (C1), a nitrogen compressor first stage (C2-1) and a nitrogen compressor second stage (C2-2), the coolers comprise a first cooler (E1), a second cooler (E2) and a third cooler (E3), an outlet of the nitrogen expansion compressor compression end (C1) is connected with an inlet of the first cooler (E1), an outlet of the first cooler (E1) is connected with an inlet of the nitrogen compressor first stage (C2-1), an outlet of the nitrogen compressor first stage (C2-1) is connected with an inlet of the second cooler (E2), an outlet of the second cooler (E2) is connected with an inlet of the nitrogen compressor second stage (C2-2), an outlet of the nitrogen compressor second stage (C2-2) is connected with an inlet of the third cooler (E3), and an outlet of the third cooler (E3) is connected with a second inlet of the cold box (1);
the LNG spraying systems are arranged at the top parts in the first LNG storage tank (TK 1) and the second LNG storage tank (TK 2) and are configured to enable supercooled LNG to enter the tank through liquid phase inlets of the first LNG storage tank (TK 1) and the second LNG storage tank (TK 2) to contact with BOG for heat exchange so as to improve BOG condensation and recovery efficiency;
expander (TE 1) with nitrogen gas expansion compressor compression end (C1) coaxial coupling, nitrogen gas expansion compressor compression end (C1) directly by expander (TE 1) and first motor drive jointly, nitrogen gas compressor first-stage (C2-1) with nitrogen gas compressor second level (C2-2) are by the drive of second motor, expander (TE 1) the compressor first motor and the bearing of second motor all adopt electromagnetic bearing to reduce lubricating system configuration and area.
2. The BOG treatment system for the LNG transport ship as claimed in claim 1, wherein the cooler is a printed circuit plate heat exchanger, and closed circulating water is used as a cooling medium.
3. A method of processing the LNG carrier BOG according to claim 1 or 2, comprising the steps of:
1) The first LNG storage tank (TK 1) and the second LNG storage tank (TK 2) generate a large amount of BOG due to absorption of ambient heat, and LNG is delivered to the cold box (CB 1) through the first LNG immersed pump (P1) and the second LNG immersed pump (P2) when the pressure in the tanks is higher than an operating pressure;
2) The nitrogen is compressed by the compressor to form nitrogen with the medium pressure of 25-30 bar, and then enters the cooler to be cooled to 30-40 ℃;
3) The medium-pressure nitrogen entering the cold box (CB 1) exchanges heat with the low-temperature nitrogen flowing back from the cold box (CB 1), and the low-temperature nitrogen flowing back after heat exchange enters the compressor after self reheating; the medium-pressure nitrogen is cooled and then continuously enters the expansion machine (TE 1), the medium-pressure nitrogen expands, reduces the pressure and does work outwards in the expansion machine (TE 1), the expansion machine (TE 1) converts the pressure energy of the medium-pressure nitrogen into mechanical energy to cooperate with a motor to drive the compressor to run, the nitrogen is cooled to-175 to-179 ℃ after expansion and then enters the cooling box (CB 1), and the nitrogen returns to the compressor after reheating to complete a nitrogen compression cycle;
4) And the subcooled LNG enters the first LNG storage tank (TK 1) and the second LNG storage tank (TK 2), and exchanges mass transfer and heat with BOG in the storage tanks, so that the BOG is condensed into LNG again.
CN202110768149.4A 2021-07-07 2021-07-07 BOG (boil off gas) processing system and method for LNG (liquefied natural gas) transport ship Active CN113503465B (en)

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CN104197635A (en) * 2014-09-17 2014-12-10 刘国满 Port staying re-liquefaction system and liquefaction method for LNG (liquefied natural gas) fuel powered ship
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CN109178286A (en) * 2018-08-24 2019-01-11 广东珠海金湾液化天然气有限公司 The pre-cooling technique of liquified natural gas carrier (LNGC) cabin
CN111630313A (en) * 2018-01-23 2020-09-04 气体运输技术公司 Method and system for treating gas in a gas storage facility of a gas tanker

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Publication number Priority date Publication date Assignee Title
CN103857955A (en) * 2011-10-20 2014-06-11 三菱重工业株式会社 Pressure rise suppression device for storage tank, pressure rise suppression system provided therewith, suppression method therefor, liquefied gas carrying vessel provided therewith, and liquefied gas storage facility provided therewith
CN202371968U (en) * 2011-12-02 2012-08-08 中国海洋石油总公司 Boil-off gas liquefaction recovery device for liquefied natural gas receiving station
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