WO2019064347A1 - Structure flottante pour la production de gnl et procédé de maintenance de réservoir de gnl dans la structure flottante - Google Patents

Structure flottante pour la production de gnl et procédé de maintenance de réservoir de gnl dans la structure flottante Download PDF

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Publication number
WO2019064347A1
WO2019064347A1 PCT/JP2017/034766 JP2017034766W WO2019064347A1 WO 2019064347 A1 WO2019064347 A1 WO 2019064347A1 JP 2017034766 W JP2017034766 W JP 2017034766W WO 2019064347 A1 WO2019064347 A1 WO 2019064347A1
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WIPO (PCT)
Prior art keywords
lng
lng tank
bog
natural gas
gas
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PCT/JP2017/034766
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English (en)
Inventor
Kenichi Tadano
Naoki Watanabe
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Chiyoda Corporation
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Publication date
Application filed by Chiyoda Corporation filed Critical Chiyoda Corporation
Priority to PCT/JP2017/034766 priority Critical patent/WO2019064347A1/fr
Publication of WO2019064347A1 publication Critical patent/WO2019064347A1/fr

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/0002—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the fluid to be liquefied
    • F25J1/0022—Hydrocarbons, e.g. natural gas
    • 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
    • F17C6/00—Methods and apparatus for filling vessels not under pressure with liquefied or solidified gases
    • 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
    • F17C9/00—Methods or apparatus for discharging liquefied or solidified gases from vessels not under pressure
    • 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
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0228—Coupling of the liquefaction unit to other units or processes, so-called integrated processes
    • F25J1/0229—Integration with a unit for using hydrocarbons, e.g. consuming hydrocarbons as feed stock
    • F25J1/023—Integration with a unit for using hydrocarbons, e.g. consuming hydrocarbons as feed stock for the combustion as fuels, i.e. integration with the fuel gas system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0244—Operation; Control and regulation; Instrumentation
    • F25J1/0245—Different modes, i.e. 'runs', of operation; Process control
    • F25J1/0247—Different modes, i.e. 'runs', of operation; Process control start-up of the process
    • 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
    • F25J1/0248—Stopping of the process, e.g. defrosting or deriming, maintenance; Back-up mode or systems
    • 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
    • F25J1/0278—Unit being stationary, e.g. on floating barge or fixed platform
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B25/00—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby
    • B63B25/02—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods
    • B63B25/08—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods fluid
    • B63B25/12—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods fluid closed
    • B63B25/14—Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods fluid closed pressurised
    • 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
    • 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
    • F17C2265/037—Treating the boil-off by recovery with pressurising
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/40—Air or oxygen enriched air, i.e. generally less than 30mol% of O2
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/42—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
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/90—Processes or apparatus involving steps for recycling of process streams the recycled stream being boil-off gas from storage
    • 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
    • F25J2290/62—Details of storing a fluid in a tank

Definitions

  • the present invention relates to a floating structure for producing LNG and a maintenance method of an LNG tank in such a floating structure.
  • a floating structure known as LNG-FPSO (Floating Production, Storage and Off-loading) unit includes LNG production facilities and a plurality of LNG tanks for storing the produced LNG in the hull of the floating structure.
  • the LNG tanks are required to be inspected and repaired if necessary at predetermined intervals according to international regulations.
  • the LNG in the LNG tank is required to be removed by evaporating the residual LNG by heating the tank, purging the LNG gas in the LNG tank with inert gas, and purging the inert gas with the air.
  • the air in the LNG tank is purged by inert gas, the inert gas is then replace by hydrocarbon gas, and the LNG tank is cooled before supplying LNG to be stored in the LNG tank back into the LNG tank.
  • an LNG carrier has an LNG vaporizer that vaporizes LNG from another LNG carrier or an LNG receiving terminal/production plant, a high duty compressor that compresses natural gas vaporized from the own LNG tanks, and a warming up heater that heats the compressed natural gas.
  • the compressed and heated natural gas is supplied to the LNG tank which is to be subjected to maintenance work and the LNG in the LNG tank is vaporized.
  • the hydrocarbon gas vaporized by the LNG vaporizer is supplied to replace the inert gas with the hydrocarbon gas.
  • LNG-FPSO Since LNG-FPSO has LNG production facilities and LNG supply facilities, the space on the hull is limited. Therefore, it is difficult to find a space for arranging facilities used only for maintenance such as vaporizer and high duty compressor.
  • the present invention was made in view such a background, and has a primary object to provide a floating structure capable of omitting facilities that are used only for maintenance.
  • a second object of the present invention is to provide a method for performing a maintenance work for an LNG tank that does not need facilities used only for maintenance.
  • a floating structure (1) for producing LNG comprising: a dehydration system (11) for removing moisture from natural gas; a liquefaction system (3) for liquefying the natural gas from which moisture is removed to produce LNG; an LNG tank (4) for storing the LNG produced by the liquefaction system; a BOG compressor (66) for compressing BOG generated in the LNG tank; a first line (101) for connecting a downstream portion of the dehydration system with the LNG tank to supply the natural gas from which moisture has been removed to the LNG tank; and a second line (102) connecting the BOG compressor with the LNG tank to supply the compressed BOG to the LNG tank.
  • the natural gas from which moisture has been removed via the first line to the LNG tank
  • the BOG to the LNG tank via the second line.
  • at least one of the natural gas from which moisture has been removed and the BOG can be used to vaporize a part of the LNG remaining in the LNG tank during a maintenance work. Since the natural gas and the BOG supplied to the LNG tank do not contain moisture, they do not cause icing in the conduit or in the LNG tank. Because the BOG compressor and the dehydration system are already present in the floating structure as a part of the existing facilities, there is no need to add a new equipment to the floating structure. Therefore, equipment used only for maintenance such as an LNG vaporizer, a high duty compressor and a warming up heater provided in a conventional LNG tanker can be removed.
  • the floating structure may further comprise a first heat exchanger (58) provided in the first line to adjust a temperature of the natural gas from which moisture is removed by the dehydration system.
  • a first heat exchanger (58) provided in the first line to adjust a temperature of the natural gas from which moisture is removed by the dehydration system.
  • the floating structure may further comprise an NGL recovery system (12) connected between the dehydration system and the liquefaction system to remove heavy hydrocarbons from the natural gas from which moisture has been removed; wherein the first line connects a downstream portion of the NGL recovery system with the LNG tank.
  • NGL recovery system (12) connected between the dehydration system and the liquefaction system to remove heavy hydrocarbons from the natural gas from which moisture has been removed
  • the floating structure may further comprise a first heat exchanger (58) provided in the first line to adjust a temperature of the natural gas from which heavy hydrocarbons have been removed by the NGL recovery system.
  • a first heat exchanger (58) provided in the first line to adjust a temperature of the natural gas from which heavy hydrocarbons have been removed by the NGL recovery system.
  • the floating structure may further comprise a second heat exchanger (71) provided in the second line to cool the BOG compressed by the BOG compressor.
  • the floating structure may further comprise a fuel gas system (78) connected to the second line to burn the BOG compressed by the BOG compressor as a fuel.
  • a fuel gas system (78) connected to the second line to burn the BOG compressed by the BOG compressor as a fuel.
  • the amount of the BOG released to the air can be minimized.
  • the floating structure may further comprise a third line (103) for connecting the second line with the liquefaction system to supply the compressed BOG to the liquefaction system.
  • the excess BOG can be returned to the liquefaction system, the amount of the BOG released to the air can be minimized.
  • the floating structure may further comprise a flow control valve provided in each of the first line and the second line.
  • the present invention also provides a method for replacing LNG in an LNG tank with the air in a floating structure (1) including a dehydration system (11) for removing moisture from natural gas, a liquefaction system (3) for liquefying the natural gas from which moisture has been removed to produce LNG, an LNG tank (4) for storing the LNG produced by the liquefaction system, and a BOG compressor (66) for compressing BOG generated in the LNG tank, the method comprising: a first step of supplying the natural gas dehydrated in the dehydration system and/or the BOG compressed in the BOG compressor to the LNG tank to vaporize the LNG remaining in the LNG tank; a second step of supplying inert gas to the LNG tank to replace hydrocarbon gas remaining in the LNG tank with the inert gas following the first step; and a third step of supplying the air to the LNG tank to replace the inert gas with the air following the second step.
  • At least one of the natural gas from which moisture has been removed and the BOG can be used to vaporize the LNG remaining in the LNG tank during a maintenance work. Since the natural gas and the BOG supplied to the LNG tank do not contain moisture, they do not cause icing in the conduit or the LNG tank. Since the present invention uses the BOG compressor and the dehydration system that are essential system for the LNG production facility, it does not require the LNG vaporizer, the high duty compressor, and the warm up heater that were provided by the conventional LNG carrier.
  • the first step includes supplying the BOG compressed by the BOG compressor to the LNG tank when the dehydration system and the liquefaction system are not in operation, and supplying at least one of the natural gas dehydrated in the dehydration system and the BOG compressed by the BOG compressor to the LNG tank when the dehydration system and the liquefaction system are in operation.
  • the first step may include removing heavy hydrocarbons from the dehydrated natural gas, and supplying the natural gas from which the heavy hydrocarbons are removed to the LNG tank to vaporize the LNG remaining in the LNG tank.
  • the present invention also provides a method for refilling LNG to an LNG tank initially filled with the air in a floating structure (1) including a dehydration system (11) for removing moisture from natural gas, a liquefaction system (3) for liquefying the natural gas from which moisture has been removed to produce LNG, an LNG tank (4) for storing the LNG produced by the liquefaction system, and a BOG compressor (66) for compressing BOG generated in the LNG tank, the method comprising: a first step of supplying inert gas to the LNG tank to replace the air in the LNG tank with the inert gas; a second step of supplying the natural gas dehydrated in the dehydration system and/or the BOG compressed in the BOG compressor to replace the inert gas with hydrocarbon gas following the first step, and a third step of supplying the LNG produced in the liquefaction system or stored in other LNG tanks to the LNG tank following the second step.
  • At least one of the natural gas from which moisture has been removed and the BOG which is compressed by the BOG compressor can be used to replace the inert gas in the LNG tank with a hydrocarbon gas to return back to normal tank operation. Because the BOG compressor and the dehydration system are already present in the floating structure as a part of the existing facilities, there is no need to add a new equipment to the floating structure.
  • the second step may include supplying the BOG compressed by the BOG compressor to the LNG tank when the dehydration system and the liquefaction system are not in operation, and supplying at least one of the natural gas dehydrated in the dehydration system and the BOG compressed by the BOG compressor to the LNG tank when the dehydration system and the liquefaction system are in operation.
  • the present invention further provides a method for replacing and refilling LNG in an LNG tank in a floating structure (1) including a dehydration system (11) for removing moisture from natural gas, a liquefaction system (3) for liquefying the natural gas from which moisture has been removed to produce LNG, an LNG tank (4) for storing the LNG produced by the liquefaction system, and a BOG compressor (66) for compressing BOG generated in the LNG tank, the method comprising: a first step of supplying the natural gas dehydrated in the dehydration system and/or the BOG compressed in the BOG compressor to the LNG tank to vaporize the LNG remaining in the LNG tank; a second step of supplying inert gas to the LNG tank to replace hydrocarbon gas remaining in the LNG tank with the inert gas following the first step; and a third step of supplying the air to the LNG tank to replace the inert gas with the air following the second step; a fourth step of performing maintenance work inside the LNG tank following the third step; a fifth step of supplying inert gas to the LNG tank
  • At least one of the natural gas from which moisture has been removed and the BOG from which moisture has been removed can be used to vaporize the LNG remaining in the LNG tank, and to replace the inert gas in the LNG tank with a hydrocarbon gas during maintenance work. Since the natural gas and the BOG supplied to the LNG tank do not contain moisture, they do not cause icing in the conduit or the LNG tank. Because the BOG compressor and the dehydration system are already present in the floating structure as a part of the existing facilities, there is no need to newly add equipment to the floating structure.
  • FIG. 1 shows an LNG production facility constructed as a floating structure 1 known as FPSO (floating production storage and offloading) unit. Such a unit is also known as FLNG (floating liquefied natural gas) facilities.
  • FPSO floating production storage and offloading
  • FLNG floating liquefied natural gas
  • This floating structure 1 is configured to perform gas treatment, refining, liquefaction, storage and shipping of natural gas on a body of water.
  • the floating structure 1 is provided with a hull that floats on the body of water, and a topside facility on the hull contains a purification system 2 and a liquefaction system 3.
  • the hull contains a plurality of LNG tanks 4.
  • the purification system 2 includes an inlet facility 7 that accepts raw feed gas (natural gas), a mercury removal system 8 that removes mercury from the raw feed gas, an acid gas removal system 9 that removes acid gas from the raw feed gas, a dehydration system 11 for removing moisture from the raw feed gas and an NGL recovery system 12 for removing heavy hydrocarbons from the raw feed gas, which are arranged in that order from the upstream end of the feed flow.
  • the NGL recovery system 12 is optional for the present invention, and may be omitted if the contents of heavy hydrocarbons in the raw feed gas is low enough.
  • the dehydration system 11 removes moisture from the raw feed gas by contacting an adsorbent agent such as molecular sieve with the raw feed gas.
  • the NGL recovery system 12 liquefies and removes heavy hydrocarbons in the raw feed gas by lowering the temperature and the pressure of the raw feed gas.
  • the inlet facility 7 and the mercury removal system 8 are connected via a conduit 15, the mercury removal system 8 and the acid gas removal system 9 are connected via a conduit 16, the acid gas removal system 9 and the dehydration system 11 are connected via a conduit 17, and the dehydration system 11 and the NGL recovery system 12 are connected via a conduit 18.
  • the raw feed gas passes through the mercury removal system 8, acid gas removal system 9, dehydration system 11, NGL recovery system 12 in order, and is purified.
  • the purified natural gas contains methane as a main component.
  • Liquefaction system 3 liquefies the refined natural gas by cooling, and produces LNG.
  • the liquefaction system 3 may be based on known as mixed refrigerant process, a cascade process or any other liquefaction technologies.
  • An inlet of liquefaction system 3 is connected to an outlet of NGL recovery system 12 via a conduit 19.
  • the downstream end of the liquefaction system 3 is connected to an LNG rundown header 22 via a conduit 21.
  • the LNG rundown header 22 is connected to the plurality of LNG tanks 4 via respective conduits 23.
  • LNG in the liquefaction system 3 is supplied to each LNG tank 4 via the LNG rundown header 22.
  • Each of the conduits 23 is provided with a respective pressure control valves 24 to distribute equally to each LNG tank 4.
  • the plurality of LNG tanks 4 are connected to a gas header 27 via respective conduits 28 and are connected to an inert gas header 31 via respective conduits 32.
  • the plurality of conduits 28 are connected to the BOG header 33 via respective conduits 34. It is preferable that the end of the conduit 32 connected to the inert gas header 31 on the LNG tank 4 side is disposed at the bottom of the LNG tank 4.
  • Manual valves 36 are provided in each of the conduits 28 on the portion on the side of the gas header 27 from the connecting portion with the conduit 34.
  • Each of the conduits 32 is provided with a respective manual valve 37.
  • Each of the conduits 34 is provided with a respective manual valve 38.
  • Each LNG tank 4 is connected to an offloading header 40 via a corresponding conduit 39.
  • Each LNG tank 4 has a pump 43 which sends the LNG to the offloading header 40.
  • the offloading header 40 is connectable to an LNG tank of an LNG tanker existing around the floating structure 1 via an LNG offloading line 41.
  • the LNG offloading line 41 includes offloading facility.
  • the BOG header 33 is connectable to the LNG tank of the LNG tanker via an LNG tanker BOG return line 42.
  • the LNG stored in the LNG tank 4 of the floating structure 1 is supplied to the LNG tank of the LNG tanker via the offloading header 40, the LNG offloading line 41.
  • BOG generated in the LNG tank of the LNG tanker flows to the BOG header 33 through the LNG tanker BOG return line 42.
  • the LNG offloading line 41 and the LNG tanker BOG return line 42 may be configured as loading arms or floating hoses floating on the sea.
  • An isolation valve 44 is provided between the offloading header 40 and the LNG offloading line 41, and an isolation valve 45 is provided between the BOG header 33 and the LNG tanker BOG return line 42.
  • the conduit 18 between the dehydration system 11 and the NGL recovery system 12 and the conduit 19 between the NGL recovery system 12 and the liquefaction system 3 are connected to the inert gas header 31 via a conduit 47.
  • the conduit 47 includes a first upstream pipe part 51 connected at one end to the conduit 18, a second upstream pipe part 52 connected at one end to the conduit 19, a downstream pipe portion 53 connected to the other end of the first upstream pipe part 51 and the other end of the second upstream pipe part 52 at one end and connected to the inert gas header 31 at the other end.
  • the downstream pipe portion 53 of the conduit 47 is connected to the gas header 27 via a conduit 54.
  • a manual valve 56 is provided in the first upstream pipe part 51 and a manual valve 57 is provided in the second upstream pipe part 52.
  • the downstream pipe portion 53 provides a first heat exchanger 58, a flow control valve 61, and a manual valve 62 in order from the first upstream pipe part 51 side.
  • the flow control valve 61 is provided on the first upstream pipe part 51 side from the connection portion with the conduit 54 in the downstream pipe portion 53 and the manual valve 62 is provided in the downstream pipe portion 53 from the connection portion with the conduit 54, inert gas header 31 side.
  • the conduit 54 is provided with a manual valve 63.
  • the discharge port of the BOG compressor 66 is connected via a conduit 69 to the portion between the flow control valve 61 and the conduit 54 in the conduit 47.
  • the conduit 69 is provided with a second heat exchanger 71 and a flow control valve 72 in order from the BOG compressor 66.
  • the part between the second heat exchanger 71 and the flow control valve 72 of the conduit 69 is connected to the liquefaction system 3 via a conduit 74.
  • the conduit 74 is provided with a control valve 75.
  • the portion between the second heat exchanger 71 and the flow control valve 72 of the conduit 69 is connected to a fuel gas system 78 via a conduit 77.
  • the fuel gas system 78 consumes the BOG compressed by the BOG compressor 66 as a fuel, and may be an internal combustion engine that generates power.
  • the internal combustion engine may be a gas turbine, for example.
  • the conduit 77 is provided with a control valve 79.
  • the inert gas header 31 is connected to an inert gas generator 82 via a conduit 81.
  • the inert gas generator 82 may produce a flue gas, for example.
  • the inert gas generator 82 burns marine diesel oil or heavy fuel to produce inert gas with oxygen content of 2-4 %.
  • the conduit 81 is provided with a manual valve 83.
  • the portion between the inert gas generator 82 and the manual valve 83 in the conduit 81 is connected to the gas header 27 via a conduit 85.
  • the conduit 85 is provided with a manual valve 86.
  • the inert gas generated by the inert gas generator 82 is supplied to the LNG tank 4 via the inert gas header 31 during maintenance work to be described later, and hydrocarbon gas in the LNG tank 4 is purged with the inert gas.
  • the inert gas header 31 is connected to a vent system 92 via a conduit 91.
  • the conduit 91 is provided with a manual valve 93.
  • the portion between the vent system 92 and the manual valve 93 in the conduit 91 is connected to the gas header 27 via a conduit 95.
  • the conduit 95 is provided with a manual valve 96.
  • the vent system 92 discharges inert gas or air in the LNG tank 4 through the inert gas header 31 and the gas header 27 to the atmosphere.
  • the gas header 27 is connected to the flare system 111 via a conduit 110.
  • the conduit 110 is provided with a manual valve 112.
  • the portion between the flare system 111 and the manual valve 112 in the conduit 110 is connected to the inert gas header 31 via a conduit 116.
  • the conduit 116 is provided with a manual valve 117.
  • the portion between the flare system 111 and the manual valve 112 in the conduit 110 is connected to the BOG header 33 via a conduit 114.
  • the conduit 114 is provided with a manual valve 115.
  • the flare system 111 burns BOG and releases it into the atmosphere.
  • the inert gas generator 82 can also supply the air in addition to the inert gas.
  • the air is supplied from the inert gas generator 82 via conduit 81 to inert gas header 31 and is supplied to gas header 27 via conduit 85.
  • the air supplied to the gas header 27 is supplied to the upper part of the LNG tank 4 via a conduit 28.
  • the maintenance work of the LNG tank 4 in this case includes a preparatory process for enabling a worker to enter the LNG tank 4 so that the interior of the LNG tank may be inspected, and repaired if necessary.
  • the maintenance work also includes a restoration process for bringing the LNG tank 4 back into normal operation.
  • the preparatory process includes a vaporization step of vaporizing the LNG remaining in the target LNG tank 4 and raising the temperature of the LNG tank 4 at the same time, an inert gas replacement step of replacing the hydrocarbons in the LNG tank 4 with an inert gas (flue gas, for example), and an air replacement step of replacing the inert gas in the LNG tank 4 with the air, which are performed in this order.
  • a vaporization step of vaporizing the LNG remaining in the target LNG tank 4 and raising the temperature of the LNG tank 4 at the same time an inert gas replacement step of replacing the hydrocarbons in the LNG tank 4 with an inert gas (flue gas, for example), and an air replacement step of replacing the inert gas in the LNG tank 4 with the air, which are performed in this order.
  • the first line 101 includes the first upstream pipe part 51, the second upstream pipe part 52, the conduit 47, the inert gas header 31, the conduit 32, the conduit 54, the gas header 27 and the conduit 28.
  • the first line has the first heat exchanger 58 on the conduit 47.
  • the dry gas sequentially passes through the conduit 18, the conduit 47, the inert gas header 31 and the conduit 32 from the outlet of the dehydration system 11 and is supplied to the LNG tank 4. Also, the dry gas passes through the conduit 19, the conduit 47, the inert gas header 31, and the conduit 32 in order from the outlet of the NGL recovery system 12 and is supplied to the LNG tank 4.
  • the compressed BOG passes through the discharge port of the BOG compressor 66, the conduit 69, the conduit 47, the inert gas header 31, and the conduit 32, and is supplied to the LNG tank 4.
  • the conduit 69, the conduit 47, the inert gas header 31, and the conduit 32 configure a second line 102.
  • the second line 102 supplies compressed BOG to the LNG tank 4.
  • the dry gas is supplied to the LNG tank 4.
  • the compressed BOG is supplied to the LNG tank 4.
  • the selection between the dry gas and the compressed BOG can be made by suitably adjusting the flow control valve 72 and the flow control valve 61.
  • the compressed BOG is typically selected as the gas to be supplied to the LNG tank 4 at the time of terminating the production of LNG, or when the operation of the dehydration system 11 and the liquefaction system 3 is terminated.
  • one of the dry gas and the compressed BOG is selected as the gas to be supplied to LNG tank 4.
  • the dry gas is heated in the first heat exchanger 58 and the compressed BOG is cooled in the second heat exchanger 71.
  • the first heat exchanger 58 function as temperature regulators for adjusting the temperatures of the dry gas to values suitable for vaporizing the residual LNG and increasing the temperature of the LNG tank 4.
  • the second heat exchanger 71 uses cooling water or air as cooling medium, and the temperature of the compressed BOG will be near cooling medium condition which is close to ambient temperature. However, this temperature is enough warmer for vaporizing the residual LNG and increasing the temperature of the LNG tank 4 for maintenance purpose.
  • the inert gas generated by the inert gas generator 82 sequentially passes through the conduit 81, the inert gas header 31 and the conduit 32 and is supplied to the LNG tank 4 for maintenance purpose.
  • the BOG (hydrocarbon gas) in the LNG tank 4 is replaced with the inert gas, and the purged BOG sequentially passes through the conduit 28, the gas header 27, and the conduit 110 and flows to the flare system 111.
  • the air introduced from the inert gas generator 82 which is able to supply the air is supplied to the LNG tank 4 via the gas header 27, and the conduit 28 for maintenance purpose.
  • the inert gas in the LNG tank 4 is replaced by the air, and the purged inert gas sequentially passes through the conduit 32, the inert gas header 31, and the conduit 91 and flows to the vent system 92.
  • the restoration process includes an inert gas replacement step of replacing the air in the LNG tank 4 with an inert gas, a hydrocarbon replacement step of replacing the inert gas in the LNG tank 4 with a hydrocarbon gas, and an LNG filling step of filling LNG into the LNG tank, which are performed in that order.
  • At least one of the dry gas and the compressed BOG is selected and supplied to the LNG tank 4.
  • the dry gas supplied from the outlet of the dehydration system 11 or the outlet of the NGL recovery system 12 is forwarded to the LNG tank 4 via the first line 101.
  • the compressed BOG is supplied from the discharge port of the BOG compressor 66, and is forwarded to the LNG tank 4 via the second line 102.
  • the dry gas can be supplied to the LNG tank 4 via the first line 101, and the compressed BOG can be supplied to the LNG tank 4 via the second line 102.
  • the dry gas and the compressed BOG can be used to vaporize the remaining LNG in the LNG tank 4 during maintenance work. Since the BOG compressor 66 and the dehydration system 11 are conventionally provided in the floating structure 1, there is no need to add new facilities.
  • the dry gas adjusted to an appropriate temperature by the first heat exchanger 58 and the compressed BOG cooled to an appropriate temperature by the second heat exchanger 71 are supplied to the LNG tank 4 for maintenance work.
  • Such an appropriate temperature could be a temperature lower than the maximum design temperature of LNG tanks 4 or a temperature near cooling medium condition. This makes it possible to efficiently raise the temperature of the LNG tank in the vaporization step in the preparatory process.
  • the excess BOG can be supplied to the fuel gas system 78 or the liquefaction system 3 for reuse, the amount of the BOG released to the atmosphere or flared can be minimized, and the energy efficiency can be increased.
  • both the dry gas and the compressed BOG may be supplied to the same LNG tank.

Landscapes

  • 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)
  • Combustion & Propulsion (AREA)
  • Filling Or Discharging Of Gas Storage Vessels (AREA)

Abstract

La présente invention concerne une structure flottante apte à fournir un gaz hydrocarboné à un réservoir de GNL pendant des travaux de maintenance dudit réservoir de GNL en utilisant une installation essentielle pour la production de GNL. Une structure flottante (1) comprend un système de déshydratation (11), un système de liquéfaction (3), un réservoir de GNL (4), un compresseur de BOG (66), une première conduite (101) qui relie une partie aval du système de déshydratation au réservoir de GNL pour acheminer le gaz naturel dont l'humidité a été retirée vers le réservoir de GNL et une seconde conduite (102) qui relie le compresseur de BOG au réservoir de GNL afin d'acheminer le BOG comprimé vers le réservoir de GNL.
PCT/JP2017/034766 2017-09-26 2017-09-26 Structure flottante pour la production de gnl et procédé de maintenance de réservoir de gnl dans la structure flottante WO2019064347A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/JP2017/034766 WO2019064347A1 (fr) 2017-09-26 2017-09-26 Structure flottante pour la production de gnl et procédé de maintenance de réservoir de gnl dans la structure flottante

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/JP2017/034766 WO2019064347A1 (fr) 2017-09-26 2017-09-26 Structure flottante pour la production de gnl et procédé de maintenance de réservoir de gnl dans la structure flottante

Publications (1)

Publication Number Publication Date
WO2019064347A1 true WO2019064347A1 (fr) 2019-04-04

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2774546C1 (ru) * 2021-12-02 2022-06-21 Игорь Анатольевич Мнушкин Комплекс сжижения, хранения и отгрузки природного газа увеличенной производительности

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3374638A (en) * 1966-04-19 1968-03-26 Mcmullen John J System for cooling, purging and warming liquefied gas storage tanks and for controlling the boil-off rate of cargo therein
US20140366561A1 (en) * 2013-06-17 2014-12-18 Conocophillips Company Integrated cascade process for vaporization and recovery of residual lng in a floating tank application
KR20160129403A (ko) * 2015-04-30 2016-11-09 대우조선해양 주식회사 부유식 해양 구조물에서의 lng 하역 시스템 및 방법

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3374638A (en) * 1966-04-19 1968-03-26 Mcmullen John J System for cooling, purging and warming liquefied gas storage tanks and for controlling the boil-off rate of cargo therein
US20140366561A1 (en) * 2013-06-17 2014-12-18 Conocophillips Company Integrated cascade process for vaporization and recovery of residual lng in a floating tank application
KR20160129403A (ko) * 2015-04-30 2016-11-09 대우조선해양 주식회사 부유식 해양 구조물에서의 lng 하역 시스템 및 방법

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
EMI, HIROHIKO: "LNG carrier / LNG carrier technical document", 1991, SHIP TECHNOLOGY ASSOCIATION, pages: 91 - 94

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2774546C1 (ru) * 2021-12-02 2022-06-21 Игорь Анатольевич Мнушкин Комплекс сжижения, хранения и отгрузки природного газа увеличенной производительности

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