EP1959217A2 - Apparatus and method for reliquefying boil-off gas capable of operating with variable refrigeration load - Google Patents

Apparatus and method for reliquefying boil-off gas capable of operating with variable refrigeration load Download PDF

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Publication number
EP1959217A2
EP1959217A2 EP07121837A EP07121837A EP1959217A2 EP 1959217 A2 EP1959217 A2 EP 1959217A2 EP 07121837 A EP07121837 A EP 07121837A EP 07121837 A EP07121837 A EP 07121837A EP 1959217 A2 EP1959217 A2 EP 1959217A2
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EP
European Patent Office
Prior art keywords
gas
boil
storage tank
refrigeration system
lng storage
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP07121837A
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German (de)
French (fr)
Other versions
EP1959217A3 (en
Inventor
Jin Yeol Yu
Bong Woon Park
Hyun Jin Kim
Hyun Ki Park
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hanwha Ocean Co Ltd
Original Assignee
Daewoo Shipbuilding and Marine Engineering Co Ltd
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Publication date
Application filed by Daewoo Shipbuilding and Marine Engineering Co Ltd filed Critical Daewoo Shipbuilding and Marine Engineering Co Ltd
Publication of EP1959217A2 publication Critical patent/EP1959217A2/en
Publication of EP1959217A3 publication Critical patent/EP1959217A3/en
Withdrawn legal-status Critical Current

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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
    • F17C7/00—Methods or apparatus for discharging liquefied, solidified, or compressed gases from pressure vessels, not covered by another 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
    • F25J1/02—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
    • F25J1/0244—Operation; Control and regulation; Instrumentation
    • F25J1/0245—Different modes, i.e. 'runs', of operation; Process control
    • F25J1/0249—Controlling refrigerant inventory, i.e. composition or quantity
    • F25J1/025—Details related to the refrigerant production or treatment, e.g. make-up supply from feed gas itself
    • 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
    • F25J1/0243—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.
    • F25J1/0281—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc. characterised by the type of prime driver, e.g. hot gas expander
    • F25J1/0284—Electrical motor as the prime mechanical driver
    • 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
    • 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.
    • F25J1/0298—Safety aspects and control of the refrigerant compression system, e.g. anti-surge control
    • 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
    • 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
    • F17C2265/035—Treating the boil-off by recovery with cooling with subcooling the liquid phase
    • 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
    • F25J2220/00—Processes or apparatus involving steps for the removal of impurities
    • F25J2220/60—Separating impurities from natural gas, e.g. mercury, cyclic hydrocarbons
    • F25J2220/62—Separating low boiling components, e.g. He, H2, N2, Air

Definitions

  • the present invention relates to an apparatus and a method for reliquefying boil-off gas, and more particularly, to an apparatus and a method for reliquefying boil-off gas in which refrigeration load can be changed during reliquefaction of the boil-off gas generated from a storage tank for storing natural gas in a liquid state.
  • LNG liquefied natural gas
  • LNG is likely to be vaporized even when the temperature of the LNG is slightly higher than -163°C at ambient pressure.
  • an LNG carrier having an LNG storage tank which is thermally-insulated, as heat is continually transmitted from the outside to the LNG in the LNG storage tank, the LNG is continually vaporized and boil-off gas is generated in the LNG storage tank during the transportation of LNG by the LNG carrier.
  • the boil-off gas generated in an LNG storage tank is reliquefied by the apparatus for reliquefying boil-off gas and then returned to the LNG storage tank so that a safe internal pressure of the LNG storage tank can be maintained.
  • the pressure in the LNG storage tank is increased, and when the pressure is higher than a set pressure, boil-off gas is discharged to the outside of the LNG storage tank through a safety valve.
  • This apparatus for reliquefying boil-off gas comprises a cold box, and the boil-off gas discharged from an LNG storage tank is reliquefied by passing through a cryogenic heat exchanger.
  • the cryogenic heat exchanger is connected to a refrigeration system for compressing and expanding nitrogen gas that is a refrigerant.
  • the refrigeration system comprises a multi-stage compressor, an expander, and a motor.
  • the conventional apparatus for reliquefying boil-off gas has another problem that a large amount of electricity is consumed during idle operation because the refrigeration load of the refrigeration system is fixed.
  • the idle operation indicates a state wherein only a refrigeration cycle is operated to remove the heat introduced from the outside without introducing boil-off gas into the apparatus for reliquefying boil-off gas, that is, without reliquefying boil-off gas in the apparatus for reliquefying boil-off gas.
  • the present invention provides an apparatus and a method for reliquefying boil-off gas in which the refrigeration load of a refrigeration system can be changed when the reliquefaction load of the apparatus for reliquefying boil-off gas is changed.
  • a boil-off gas reliquefaction apparatus which supercools and reliquefies the boil-off gas generated in an LNG storage tank by allowing the boil-off gas to pass through a cryogenic heat exchanger via a boil-off gas discharge line, and then to pass through a gas-liquid separator installed at a rear end of the cryogenic heat exchanger, so as to return the boil-off gas to the LNG storage tank, is characterized in that the cryogenic heat exchanger is connected to a refrigeration system for compressing and expanding a refrigerant, and in that the refrigerant system comprises a multi-stage compressor, an expander, and a motor, and that the motor is connected to an inverter.
  • a boil-off gas reliquefaction method which supercools and reliquefies the boil-off gas generated in an LNG storage tank by allowing the boil-off gas to pass through a cryogenic heat exchanger via a boil-off gas discharge line, and then to pass through a gas-liquid separator installed at a rear end of the cryogenic heat exchanger, so as to return the boil-off gas to the LNG storage tank, is characterized in that when the reliquefaction load of an apparatus for reliquefying boil-off gas is changed, the refrigeration load of a refrigeration system is changed by changing the rotational velocity of a motor of the refrigeration system which is connected to the cryogenic heat exchanger and which compresses and expands a refrigerant.
  • the refrigeration load of the refrigeration system according to the present invention can be changed when the reliquefaction load of the apparatus for reliquefying boil-off gas is changed. Accordingly, the present invention has advantages of minimizing the amount of nitrogen gas wasted to the atmosphere during low reliquefaction load operation of the apparatus for reliquefying boil-off gas, and also reducing electricity consumption during idle operation.
  • Fig. 1 is a schematic diagram of an apparatus for reliquefying boil-off gas according to the preferred embodiment of the present invention.
  • the apparatus for reliquefying boil-off gas according to the embodiment of the present invention comprises a cold box 10, and the boil-off gas discharged from an LNG storage tank 1 is reliquefied by passing through the cold box via a boil-off gas discharge line L1.
  • the cold box 10 includes a cryogenic heat exchanger 11 and a gas-liquid separator 13 installed at a rear end of the cryogenic heat exchanger 11.
  • a refrigeration system 20 for compressing and expanding nitrogen gas that is a refrigerant, is connected to the cryogenic heat exchanger 11.
  • the refrigeration system 20 comprises: a multi-stage compressor including first-, second-, and third-stage compressors 21 a, 21b, 21c, and first-, second-, and third-stage intermediate coolers 22a, 22b, 22c an expander 23; and a motor M.
  • Boil-off gas is supercooled and reliquefied by passing through the cryogenic heat exchanger 11, and divided into liquefied gas and non-liquefied gas by the gas-liquid separator 13, and then only the liquefied gas is returned to the LNG storage tank 1 through a reliquefied boil-off gas return line L2.
  • the refrigerant passing through the first-stage compressor 21a of the multi-stage compressor of the refrigeration system 20 has a relatively low pressure
  • the refrigerant passing through the second-stage compressor 21 b has an intermediate pressure
  • the refrigerant passing through the third-stage compressor 21c has a relatively high pressure
  • a transfer pump (not illustrated) is installed in the middle of each of the boil-off gas discharge line L1 and the reliquefied boil-off gas return line L2.
  • the boil-off gas discharge line L1 means a pipeline which is connected between a top portion of the LNG storage tank 1 and the cryogenic heat exchanger 11 and in which vaporized boil-off gas flows
  • the reliquefied boil-off gas return line L2 means a pipeline which is connected between the cryogenic heat exchanger 11 and a bottom portion of the LNG storage tank 1, and in which reliquefied boil-off gas flows.
  • An inverter 60 is connected to the motor M of the refrigeration system 20.
  • the inverter 60 plays a role of changing the rotational velocity of the motor M.
  • An end of a nitrogen gas supply line L4 for supplying nitrogen gas into the refrigeration system 20 is connected to a refrigerant conduit at front and rear portions of the multi-stage compressor of the refrigeration system 20.
  • a nitrogen generator 40 is installed at the other end of the nitrogen gas supply line L4. It is desirable to install the nitrogen generator in an engine room 3.
  • the nitrogen gas supply line L4 is connected to the refrigerant conduit at front and rear portions of the multi-stage compressor of the refrigeration system 20 through a nitrogen treating unit 50, and the nitrogen treating unit 50 comprises a nitrogen buffering tank 51, flow control valves 52a, 52b, and a nitrogen compressor 53.
  • the nitrogen buffering tank 51 which is a container for storing nitrogen, a refrigerant, so as to facilitate control of refrigeration load, is installed at the refrigerant conduit between a front end of the first-stage compressor 21a in which the refrigerant has a low pressure and a rear end of the third-stage compressor 21c in which the refrigerant has a high pressure.
  • the flow control valve 52a is installed at the refrigerant conduit between the nitrogen buffering tank 51 and the first-stage compressor 21 a
  • the flow control valve 52b is installed at the refrigerant conduit between the nitrogen buffering tank 51 and the third-stage compressor 21 c.
  • the flow control valve 52a installed at the refrigerant conduit between the nitrogen buffering tank 51 and the first-stage compressor 21 a having a low pressure is opened, and then the nitrogen in the nitrogen buffering tank 51 is introduced into a front end of the first-stage compressor 21a due to the pressure difference between the nitrogen buffering tank 51 and the first-stage compressor 21 a.
  • the flow control valve 52b installed at the refrigerant conduit between the nitrogen buffering tank 51 and the third-stage compressor 21 c having a high pressure is opened, and then part of the nitrogen is supplied from the third-stage compressor 21 c to the nitrogen buffering tank 51.
  • the nitrogen compressor 53 compresses the nitrogen generated from the nitrogen generator 40 so that the nitrogen can be introduced into the nitrogen buffering tank 51.
  • the operation of the nitrogen compressor 53 causes the pressure difference between the nitrogen compressor 53 and the nitrogen buffering tank 51, thereby introducing the nitrogen into the nitrogen buffering tank 51.
  • the condensed liquefied gas is not supercooled enough and part of it is in a gas state, thereby generating flash gas.
  • the gas-liquid separator 13 separates the liquefied gas from the flash gas which is a non-liquefied gas, and sends the liquefied gas to the LNG storage tank 1 through the reliquefied boil-off gas return line L2, and sends the flash gas to the LNG storage tank 1 or a gas combustion unit 70 through a flash gas discharge line L3.
  • the flash gas discharge line L3 has one end connected to a top portion of the gas-liquid separator 13 and the other end connected to the top portion of the LNG storage tank 1 or the gas combustion unit 70.
  • a flow control valve 15 for controlling the flow rate of the flash gas which is generated from the gas-liquid separator 13 and supplied to the LNG storage tank 1 or the gas combustion unit 70 is installed between the LNG storage tank 1 and the gas-liquid separator 13, that is, in the middle of the flash gas discharge line L3 so as to maintain the constant pressure of the gas-liquid separator 13.
  • a check valve 17 for preventing the backflow of the flash gas from the LNG storage tank 1 or the gas combustion unit 70 to the gas-liquid separator which may occur due to abnormal increase in the pressure of the LNG storage tank 1 or the gas combustion unit 70, is installed between the LNG storage tank 1 and the gas-liquid separator 13, that is, in the middle of the flash gas discharge line L3.
  • the flash gas When the amount of flash gas is small, the flash gas is sent to the LNG storage tank 1 and reliquefied, and when the amount of flash gas is large, the flash gas is sent to the gas combustion unit 70 and incinerated.
  • a three-way valve 71 is installed in the middle of the flash gas discharge line L3, and one way of the three ways of the three-way valve 71 is openably connected to the gas-liquid separator 13, and the other two ways of the three-way valve 71 are openably connected to the LNG storage tank 1 and the gas combustion unit 70 respectively.
  • the flash gas of the gas-liquid separator 13 is supplied to the LNG storage tank 1, and when the way of the three-way valve 71 toward the LNG storage tank 1 is closed and the way of the three-way valve 71 toward the gas combustion 70 is opened, the flash gas of the gas-liquid separator 13 is supplied to the gas combustion unit 70.
  • a method for reliquefying boil-off gas using the apparatus for reliquefying boil-off gas in which the refrigeration load of a refrigeration system can be changed during operation will be described below.
  • the refrigeration load of the refrigeration system 20 can be changed by changing the rotational velocity of the motor M of the refrigeration system 20 through the inverter 60.
  • the refrigeration load can readily be controlled by supplying nitrogen gas to the refrigeration system 20 through compressing and buffering steps.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Ocean & Marine Engineering (AREA)
  • Filling Or Discharging Of Gas Storage Vessels (AREA)
  • Separation By Low-Temperature Treatments (AREA)

Abstract

The invention relates to an apparatus and a method for reliquefying boil-off gas in which the refrigeration load of a refrigeration system (20) can be changed when the reliquefaction load of the apparatus for reliquefying boil-off gas is changed. The boil-off gas reliquefaction apparatus according to the present invention, which supercools and reliquefies the boil-off gas generated in an LNG storage tank (1) by allowing the boil-off gas to pass through a cryogenic heat exchanger (11) via a boil-off gas discharge line (L1), and then to pass through a gas-liquid separator (13) installed at a rear end of the cryogenic heat exchanger (11), so as to return the boil-off gas to the LNG storage tank (1), is characterized in that the cryogenic heat exchanger (11) is connected to a refrigeration system (20) for compressing and expanding a refrigerant, in that the refrigerant system (20) comprises a multi-stage compressor (21a, 21b, 21c, 22a, 22b, 22c), an expander, (23) and a motor (M), and in that the motor is connected to an inverter (60).

Description

    [Teehnical Field]
  • The present invention relates to an apparatus and a method for reliquefying boil-off gas, and more particularly, to an apparatus and a method for reliquefying boil-off gas in which refrigeration load can be changed during reliquefaction of the boil-off gas generated from a storage tank for storing natural gas in a liquid state.
    • [Background Art]
  • Generally, natural gas is turned into a liquefied natural gas (hereinafter called "LNG") in a liquefaction plant, and then transported over long distances to a destination by an LNG carrier.
  • As liquefaction of natural gas occurs at a cryogenic temperature of approximately -163°C at ambient pressure, LNG is likely to be vaporized even when the temperature of the LNG is slightly higher than -163°C at ambient pressure. In an LNG carrier having an LNG storage tank which is thermally-insulated, as heat is continually transmitted from the outside to the LNG in the LNG storage tank, the LNG is continually vaporized and boil-off gas is generated in the LNG storage tank during the transportation of LNG by the LNG carrier.
  • In an LNG carrier having an apparatus for reliquefying boil-off gas, the boil-off gas generated in an LNG storage tank is reliquefied by the apparatus for reliquefying boil-off gas and then returned to the LNG storage tank so that a safe internal pressure of the LNG storage tank can be maintained. In case there is a problem with a system for treating boil-off gas, the pressure in the LNG storage tank is increased, and when the pressure is higher than a set pressure, boil-off gas is discharged to the outside of the LNG storage tank through a safety valve.
  • This apparatus for reliquefying boil-off gas comprises a cold box, and the boil-off gas discharged from an LNG storage tank is reliquefied by passing through a cryogenic heat exchanger. The cryogenic heat exchanger is connected to a refrigeration system for compressing and expanding nitrogen gas that is a refrigerant. The refrigeration system comprises a multi-stage compressor, an expander, and a motor.
  • In a conventional apparatus for reliquefying boil-off gas, the refrigeration load of a refrigeration system is fixed. Consequently, even when the reliquefaction load of the apparatus for reliquefying boil-off gas is small because a small amount of boil-off gas is generated by unloading part of the LNG from an LNG storage tank and consequently reducing the amount of LNG in the LNG storage tank, the refrigeration load of the refrigeration system is the same as when the reliquefaction load of the apparatus for reliquefying boil-off gas is large. Accordingly, such a conventional apparatus for reliquefying boil-off gas has a problem that a large amount of nitrogen gas is wasted to the atmosphere during low reliquefaction load operation of the apparatus for reliquefying boil-off gas. Here, surplus nitrogen gas is discharged to the atmosphere through a vent master.
  • The conventional apparatus for reliquefying boil-off gas has another problem that a large amount of electricity is consumed during idle operation because the refrigeration load of the refrigeration system is fixed. Here, the idle operation indicates a state wherein only a refrigeration cycle is operated to remove the heat introduced from the outside without introducing boil-off gas into the apparatus for reliquefying boil-off gas, that is, without reliquefying boil-off gas in the apparatus for reliquefying boil-off gas.
    • [Disclosure] [Technical Problem]
  • To solve the above-mentioned problems posed by the prior art, the present invention provides an apparatus and a method for reliquefying boil-off gas in which the refrigeration load of a refrigeration system can be changed when the reliquefaction load of the apparatus for reliquefying boil-off gas is changed.
    • [Technical Solution]
  • To achieve the above-mentioned purpose, a boil-off gas reliquefaction apparatus according to the present invention, which supercools and reliquefies the boil-off gas generated in an LNG storage tank by allowing the boil-off gas to pass through a cryogenic heat exchanger via a boil-off gas discharge line, and then to pass through a gas-liquid separator installed at a rear end of the cryogenic heat exchanger, so as to return the boil-off gas to the LNG storage tank, is characterized in that the cryogenic heat exchanger is connected to a refrigeration system for compressing and expanding a refrigerant, and in that the refrigerant system comprises a multi-stage compressor, an expander, and a motor, and that the motor is connected to an inverter.
  • A boil-off gas reliquefaction method according to the present invention, which supercools and reliquefies the boil-off gas generated in an LNG storage tank by allowing the boil-off gas to pass through a cryogenic heat exchanger via a boil-off gas discharge line, and then to pass through a gas-liquid separator installed at a rear end of the cryogenic heat exchanger, so as to return the boil-off gas to the LNG storage tank, is characterized in that when the reliquefaction load of an apparatus for reliquefying boil-off gas is changed, the refrigeration load of a refrigeration system is changed by changing the rotational velocity of a motor of the refrigeration system which is connected to the cryogenic heat exchanger and which compresses and expands a refrigerant.
    • [Advantageous Effects]
  • As apparent from the above, the refrigeration load of the refrigeration system according to the present invention, can be changed when the reliquefaction load of the apparatus for reliquefying boil-off gas is changed. Accordingly, the present invention has advantages of minimizing the amount of nitrogen gas wasted to the atmosphere during low reliquefaction load operation of the apparatus for reliquefying boil-off gas, and also reducing electricity consumption during idle operation.
    • [Description of Drawings]
    • Figure 1 is a schematic diagram of an apparatus for reliquefying boil-off gas according to the preferred embodiment of the present invention.
    [Best Mode]
  • Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawing.
  • Fig. 1 is a schematic diagram of an apparatus for reliquefying boil-off gas according to the preferred embodiment of the present invention. The apparatus for reliquefying boil-off gas according to the embodiment of the present invention comprises a cold box 10, and the boil-off gas discharged from an LNG storage tank 1 is reliquefied by passing through the cold box via a boil-off gas discharge line L1. The cold box 10 includes a cryogenic heat exchanger 11 and a gas-liquid separator 13 installed at a rear end of the cryogenic heat exchanger 11. A refrigeration system 20 for compressing and expanding nitrogen gas that is a refrigerant, is connected to the cryogenic heat exchanger 11. The refrigeration system 20 comprises: a multi-stage compressor including first-, second-, and third- stage compressors 21 a, 21b, 21c, and first-, second-, and third-stage intermediate coolers 22a, 22b, 22c an expander 23; and a motor M. Boil-off gas is supercooled and reliquefied by passing through the cryogenic heat exchanger 11, and divided into liquefied gas and non-liquefied gas by the gas-liquid separator 13, and then only the liquefied gas is returned to the LNG storage tank 1 through a reliquefied boil-off gas return line L2.
  • The refrigerant passing through the first-stage compressor 21a of the multi-stage compressor of the refrigeration system 20 has a relatively low pressure, and the refrigerant passing through the second-stage compressor 21 b has an intermediate pressure, and the refrigerant passing through the third-stage compressor 21c has a relatively high pressure.
  • A transfer pump (not illustrated) is installed in the middle of each of the boil-off gas discharge line L1 and the reliquefied boil-off gas return line L2. Here, the boil-off gas discharge line L1 means a pipeline which is connected between a top portion of the LNG storage tank 1 and the cryogenic heat exchanger 11 and in which vaporized boil-off gas flows, and the reliquefied boil-off gas return line L2 means a pipeline which is connected between the cryogenic heat exchanger 11 and a bottom portion of the LNG storage tank 1, and in which reliquefied boil-off gas flows.
  • An inverter 60 is connected to the motor M of the refrigeration system 20. The inverter 60 plays a role of changing the rotational velocity of the motor M.
  • An end of a nitrogen gas supply line L4 for supplying nitrogen gas into the refrigeration system 20 is connected to a refrigerant conduit at front and rear portions of the multi-stage compressor of the refrigeration system 20.
  • A nitrogen generator 40 is installed at the other end of the nitrogen gas supply line L4. It is desirable to install the nitrogen generator in an engine room 3.
  • The nitrogen gas supply line L4 is connected to the refrigerant conduit at front and rear portions of the multi-stage compressor of the refrigeration system 20 through a nitrogen treating unit 50, and the nitrogen treating unit 50 comprises a nitrogen buffering tank 51, flow control valves 52a, 52b, and a nitrogen compressor 53.
  • The nitrogen buffering tank 51, which is a container for storing nitrogen, a refrigerant, so as to facilitate control of refrigeration load, is installed at the refrigerant conduit between a front end of the first-stage compressor 21a in which the refrigerant has a low pressure and a rear end of the third-stage compressor 21c in which the refrigerant has a high pressure. The flow control valve 52a is installed at the refrigerant conduit between the nitrogen buffering tank 51 and the first-stage compressor 21 a, and the flow control valve 52b is installed at the refrigerant conduit between the nitrogen buffering tank 51 and the third-stage compressor 21 c.
  • To increase the refrigeration load of the refrigeration system 20, the flow control valve 52a installed at the refrigerant conduit between the nitrogen buffering tank 51 and the first-stage compressor 21 a having a low pressure is opened, and then the nitrogen in the nitrogen buffering tank 51 is introduced into a front end of the first-stage compressor 21a due to the pressure difference between the nitrogen buffering tank 51 and the first-stage compressor 21 a.
  • To decrease the refrigeration load of the refrigeration system 20, the flow control valve 52b installed at the refrigerant conduit between the nitrogen buffering tank 51 and the third-stage compressor 21 c having a high pressure is opened, and then part of the nitrogen is supplied from the third-stage compressor 21 c to the nitrogen buffering tank 51.
  • The nitrogen compressor 53 compresses the nitrogen generated from the nitrogen generator 40 so that the nitrogen can be introduced into the nitrogen buffering tank 51. The operation of the nitrogen compressor 53 causes the pressure difference between the nitrogen compressor 53 and the nitrogen buffering tank 51, thereby introducing the nitrogen into the nitrogen buffering tank 51.
  • During the process of supercooling and reliquefying boil-off gas by allowing the boil-off gas to pass through the cryogenic heat exchanger 11, the condensed liquefied gas is not supercooled enough and part of it is in a gas state, thereby generating flash gas. The gas-liquid separator 13 separates the liquefied gas from the flash gas which is a non-liquefied gas, and sends the liquefied gas to the LNG storage tank 1 through the reliquefied boil-off gas return line L2, and sends the flash gas to the LNG storage tank 1 or a gas combustion unit 70 through a flash gas discharge line L3.
  • The flash gas discharge line L3 has one end connected to a top portion of the gas-liquid separator 13 and the other end connected to the top portion of the LNG storage tank 1 or the gas combustion unit 70.
  • A flow control valve 15 for controlling the flow rate of the flash gas which is generated from the gas-liquid separator 13 and supplied to the LNG storage tank 1 or the gas combustion unit 70 is installed between the LNG storage tank 1 and the gas-liquid separator 13, that is, in the middle of the flash gas discharge line L3 so as to maintain the constant pressure of the gas-liquid separator 13.
  • Also, a check valve 17 for preventing the backflow of the flash gas from the LNG storage tank 1 or the gas combustion unit 70 to the gas-liquid separator which may occur due to abnormal increase in the pressure of the LNG storage tank 1 or the gas combustion unit 70, is installed between the LNG storage tank 1 and the gas-liquid separator 13, that is, in the middle of the flash gas discharge line L3.
  • When the amount of flash gas is small, the flash gas is sent to the LNG storage tank 1 and reliquefied, and when the amount of flash gas is large, the flash gas is sent to the gas combustion unit 70 and incinerated.
  • A three-way valve 71 is installed in the middle of the flash gas discharge line L3, and one way of the three ways of the three-way valve 71 is openably connected to the gas-liquid separator 13, and the other two ways of the three-way valve 71 are openably connected to the LNG storage tank 1 and the gas combustion unit 70 respectively. Accordingly, when the way of the three-way valve 71 toward the LNG storage tank 1 is opened and the way of the three-way valve 71 toward the gas combustion 70 is closed, the flash gas of the gas-liquid separator 13 is supplied to the LNG storage tank 1, and when the way of the three-way valve 71 toward the LNG storage tank 1 is closed and the way of the three-way valve 71 toward the gas combustion 70 is opened, the flash gas of the gas-liquid separator 13 is supplied to the gas combustion unit 70.
  • It is desirable to install the gas combustion unit 70 at an upper end of the stern of the LNG carrier.
  • A method for reliquefying boil-off gas using the apparatus for reliquefying boil-off gas in which the refrigeration load of a refrigeration system can be changed during operation will be described below.
  • According to the boil-off gas reliquefaction method of the present invention, when the reliquefaction load of the apparatus for reliquefying boil-off gas is changed, the refrigeration load of the refrigeration system 20 can be changed by changing the rotational velocity of the motor M of the refrigeration system 20 through the inverter 60.
  • The refrigeration load can readily be controlled by supplying nitrogen gas to the refrigeration system 20 through compressing and buffering steps.
  • Although specific embodiments of the present invention have been described herein, it should be understood that various modification, variations or corrections may readily occur to those skilled in the art, and thus, the description and the drawing herein should be interpreted by way of illustrative purpose without limiting the scope and sprit of the present invention.

Claims (12)

  1. An apparatus for reliquefying boil-off gas in which boil-off gas generated in an LNG storage tank (1) is allowed to pass through a cryogenic heat exchanger (11) via a boil-off gas discharge line (L1), thereby being supercooled and reliquefied, and then to pass through a gas-liquid separator (13) installed at a rear end of the cryogenic heat exchanger (11), so as to be returned to the LNG storage tank (1), the apparatus being characterized in that a refrigeration system (20) for compressing and expanding a refrigerant is connected to the cryogenic heat exchanger (11), in that the refrigeration system (20) comprises a multi-stage compressor (21 a, 21 b, 21 c, 22a, 22b, 22c), an expander (23), and a motor( M), and in that an inverter (60) is connected to the motor (M).
  2. The apparatus according to claim 1, wherein the refrigeration system (20) uses nitrogen as a refrigerant, and one end of a nitrogen gas supply line (L4) for supplying nitrogen gas to the refrigeration system (20) is connected to a refrigerant conduit at front and rear portions of the multi-stage compressor (21 a, 21 b, 21 c, 22a, 22b, 22c) of the refrigeration system (20).
  3. The apparatus according to claim 2, wherein a nitrogen generator (40) is installed at the other end of the nitrogen gas supply line (L4).
  4. The apparatus according to claim 2 or 3, wherein the nitrogen gas supply line (L4) is connected to the refrigerant conduit at front and rear portions of the multi-stage compressor (21a, 21b, 21e, 22a, 22b, 22c) of the refrigeration system (20) through a nitrogen compressor (53) and a nitrogen buffering tank (51).
  5. The apparatus according to claim 1, wherein one end of a flash gas discharge line (L3) for discharging the flash gas generated from the gas-liquid separator (13) is connected to the gas-liquid separator (13).
  6. The apparatus according to claim 5, wherein the other end of the flash gas discharge line (L3) is connected to the LNG storage tank (1) or a gas combustion unit (70).
  7. The apparatus according to claim 6, wherein the other end of the flash gas discharge line (L3) is connected to the LNG storage tank (1) or the gas combustion unit (70) by means of a three-way valve (71).
  8. The apparatus according to claim 6, wherein a flow control valve (15) for controlling the flow rate of the flash gas which is generated from the gas-liquid separator (13) and supplied to the LNG storage tank (1) or the gas combustion unit (70) is installed in the middle of the flash gas discharge line (L3) so as to maintain the constant pressure of the gas-liquid separator (13).
  9. The apparatus according to claim 6, wherein a backflow prevention valve (17) is installed in the middle of the flash gas discharge line (L3) so as to prevent backflow of the flash gas from the LNG storage tank (1) or the gas combustion unit (70) to the gas-liquid separator (13) due to an abnormal increase in the pressure of the LNG storage tank (1) or the gas combustion unit (70).
  10. A method for reliquefying boil-off gas in which boil-off gas generated in an LNG storage tank (1) is allowed to pass through a cryogenic heat exchanger (11) via a boil-off gas discharge line (L1), thereby being supercooled and reliquefied, and then to pass through a gas-liquid separator (13) installed at a rear end of the cryogenic heat exchanger (11), so as to be returned to the LNG storage tank (1), the method being characterized in that when the reliquefaction load of an apparatus for reliquefying boil-off gas is changed, the refrigeration load of a refrigeration system is changed by changing the rotational velocity of a motor (M) of the refrigeration system (20) which is connected to the cryogenic heat exchanger (11) and which compresses and expands a refrigerant.
  11. The method according to claim 10, wherein nitrogen gas is supplied to the refrigeration system (20) through compressing and buffering steps.
  12. The method according to claim 10, wherein part of the nitrogen gas leaks from the refrigerant circuit of the refrigeration system (20).
EP07121837A 2007-02-13 2007-11-29 Apparatus and method for reliquefying boil-off gas capable of operating with variable refrigeration load Withdrawn EP1959217A3 (en)

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US20110203312A1 (en) * 2008-08-29 2011-08-25 Hamworthy Oil & Gas Systems As Method and system for optimized lng production
CN105927849A (en) * 2016-05-18 2016-09-07 西南石油大学 Remote well natural gas recovery device
US20170114960A1 (en) * 2014-05-19 2017-04-27 Hyundai Heavy Industries Co., Ltd. Liquefied gas treatment system
EP2464563A4 (en) * 2009-08-12 2017-11-29 Rondane Teknologi AS A plant comprising a tank for storing of liquid natural gas (lng) as marine fuel
US10267457B2 (en) 2013-09-27 2019-04-23 Excelerate Energy Limited Partnership Apparatus, system and method for the capture, utilization and sendout of latent heat in boil off gas onboard a cryogenic storage vessel
US10995910B2 (en) 2015-07-13 2021-05-04 Technip France Process for expansion and storage of a flow of liquefied natural gas from a natural gas liquefaction plant, and associated plant
CN113154797A (en) * 2020-01-23 2021-07-23 气体产品与化学公司 System and method for recondensing boil-off gas from a liquefied natural gas tank
US11561042B2 (en) 2016-02-26 2023-01-24 LGE IP Management Company Limited Method of cooling boil-off gas and apparatus therefor
US11578914B2 (en) 2017-04-20 2023-02-14 LGE IP Management Company Limited Method of cooling boil-off gas and apparatus therefor
US12044468B2 (en) 2019-08-23 2024-07-23 LGE IP Management Company Limited Method of cooling boil-off gas and apparatus therefor

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US20110203312A1 (en) * 2008-08-29 2011-08-25 Hamworthy Oil & Gas Systems As Method and system for optimized lng production
EP2464563A4 (en) * 2009-08-12 2017-11-29 Rondane Teknologi AS A plant comprising a tank for storing of liquid natural gas (lng) as marine fuel
US10267457B2 (en) 2013-09-27 2019-04-23 Excelerate Energy Limited Partnership Apparatus, system and method for the capture, utilization and sendout of latent heat in boil off gas onboard a cryogenic storage vessel
US20170114960A1 (en) * 2014-05-19 2017-04-27 Hyundai Heavy Industries Co., Ltd. Liquefied gas treatment system
US10995910B2 (en) 2015-07-13 2021-05-04 Technip France Process for expansion and storage of a flow of liquefied natural gas from a natural gas liquefaction plant, and associated plant
US11561042B2 (en) 2016-02-26 2023-01-24 LGE IP Management Company Limited Method of cooling boil-off gas and apparatus therefor
CN105927849B (en) * 2016-05-18 2018-07-17 西南石油大学 A kind of outlying well natural gas recycling device
CN105927849A (en) * 2016-05-18 2016-09-07 西南石油大学 Remote well natural gas recovery device
US11578914B2 (en) 2017-04-20 2023-02-14 LGE IP Management Company Limited Method of cooling boil-off gas and apparatus therefor
US12044468B2 (en) 2019-08-23 2024-07-23 LGE IP Management Company Limited Method of cooling boil-off gas and apparatus therefor
CN113154797A (en) * 2020-01-23 2021-07-23 气体产品与化学公司 System and method for recondensing boil-off gas from a liquefied natural gas tank
CN113154797B (en) * 2020-01-23 2022-11-11 气体产品与化学公司 System and method for recondensing boil-off gas from a liquefied natural gas tank

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