JP3610246B2 - LNG boil-off gas reliquefaction and air separation integrated device - Google Patents

LNG boil-off gas reliquefaction and air separation integrated device Download PDF

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JP3610246B2
JP3610246B2 JP30899898A JP30899898A JP3610246B2 JP 3610246 B2 JP3610246 B2 JP 3610246B2 JP 30899898 A JP30899898 A JP 30899898A JP 30899898 A JP30899898 A JP 30899898A JP 3610246 B2 JP3610246 B2 JP 3610246B2
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lng
nitrogen
gas
bog
compressor
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JP30899898A
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JP2000130926A (en
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稔 田窪
宗治 氏田
隆晃 朝倉
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Osaka Gas Co Ltd
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Osaka Gas Co Ltd
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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
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04333—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using quasi-closed loop internal vapor compression refrigeration cycles, e.g. of intermediate or oxygen enriched (waste-)streams
    • F25J3/04351—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using quasi-closed loop internal vapor compression refrigeration cycles, e.g. of intermediate or oxygen enriched (waste-)streams of nitrogen
    • F25J3/04357—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using quasi-closed loop internal vapor compression refrigeration cycles, e.g. of intermediate or oxygen enriched (waste-)streams of nitrogen and comprising a gas work expansion loop
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    • 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
    • F25J1/0012—Primary atmospheric gases, e.g. air
    • F25J1/0015—Nitrogen
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    • 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
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    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
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    • 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
    • F25J1/0032—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 the feed stream itself or separated fractions from it, i.e. "internal refrigeration"
    • F25J1/0035—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 the feed stream itself or separated fractions from it, i.e. "internal refrigeration" by gas expansion with extraction of work
    • F25J1/0037—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 the feed stream itself or separated fractions from it, i.e. "internal refrigeration" by gas expansion with extraction of work of a return stream
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    • 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
    • F25J1/0032—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 the feed stream itself or separated fractions from it, i.e. "internal refrigeration"
    • F25J1/0045—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 the feed stream itself or separated fractions from it, i.e. "internal refrigeration" by vaporising a liquid return stream
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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    • 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
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    • F25J1/0072—Nitrogen
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    • 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
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    • 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
    • F25J1/0221—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 the cold stored in an external cryogenic component in an open refrigeration loop
    • F25J1/0224—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 the cold stored in an external cryogenic component in an open refrigeration loop in combination with an internal quasi-closed refrigeration loop
    • 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
    • F25J1/0234—Integration with a cryogenic air separation unit
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    • 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
    • F25J1/0235—Heat exchange integration
    • F25J1/0236—Heat exchange integration providing refrigeration for different processes treating not the same feed stream
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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    • 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
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
    • F25J3/04187—Cooling of the purified feed air by recuperative heat-exchange; Heat-exchange with product streams
    • F25J3/04218—Parallel arrangement of the main heat exchange line in cores having different functions, e.g. in low pressure and high pressure cores
    • F25J3/04224—Cores associated with a liquefaction or refrigeration cycle
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    • 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
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04254—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using the cold stored in external cryogenic fluids
    • F25J3/0426—The cryogenic component does not participate in the fractionation
    • F25J3/04266—The cryogenic component does not participate in the fractionation and being liquefied hydrocarbons
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04406—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system
    • F25J3/04412—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system in a classical double column flowsheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column
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    • F25J2210/60—Natural gas or synthetic natural gas [SNG]
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    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/62—Liquefied natural gas [LNG]; Natural gas liquids [NGL]; Liquefied petroleum gas [LPG]
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  • Engineering & Computer Science (AREA)
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  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
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  • Oil, Petroleum & Natural Gas (AREA)
  • Separation By Low-Temperature Treatments (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は、液化天然ガス（以下「ＬＮＧ」と略称する）の有する冷熱を利用して、ＬＮＧを貯蔵するタンクで発生するボイルオフガス（以下「ＢＯＧ」と略称することがある）を再液化してＬＮＧタンクに戻し、また空気を液化して蒸留することによって成分に分離するＬＮＧのボイルオフガスの再液化および空気分離一体化装置に関する。
【０００２】
【従来の技術】
ＬＮＧは、たとえばＬＮＧタンカなどによって原産地から海上を輸送され、ＬＮＧタンクに貯蔵されて、需要先に供給される。貯蔵されるＬＮＧの温度は、−１６０℃程度で、常温に比べて極めて低いので、ＬＮＧタンク内では自然入熱等によってＢＯＧが発生する。このためＬＮＧタンク内圧力を一定範囲内に保持しておくためには、発生するＢＯＧを処理する必要がある。
【０００３】
ＢＯＧの処理としては、コンプレッサで昇圧して燃料として直接消費するために送出したり、コンプレッサによる昇圧後、再液化して、ＬＮＧタンク内に返送し、またはＬＮＧタンクから供給されるＬＮＧと混合させた後、消費のために送出したりしている。このようなＢＯＧの再液化についての先行技術は、本件出願人からも、たとえば特開平３−２３６５８８などとして開示している。この先行技術では、ＢＯＧの再液化のための冷熱源としても、ＬＮＧを利用している。
【０００４】
ＬＮＧの有する冷熱は、空気分離設備でも利用されている。空気分離設備では、沸点（−１８３〜−１９６℃）の差を利用して、空気から酸素（Ｏ２）、窒素（Ｎ２）、アルゴン（Ａｒ）などを分離・液化している。液化に必要な寒冷用のエネルギとして、圧縮機駆動用の電力とともに、ＬＮＧの冷熱が利用されている。本件出願人も、たとえば特願平７−２９５１８６などとして、ＬＮＧの冷熱を利用する空気分離についての先行技術を開示している。
【０００５】
【発明が解決しようとする課題】
従来のＢＯＧの再液化と空気分離とは、別々の設備として設置され、設備の管理も別々に行われている。この場合、ＢＯＧの再液化と空気分離とで、それぞれの需要に見合った量のＬＮＧが使用される。ＬＮＧの供給量に制約がある場合には、どちらかの能力を低下させる必要がある。ＬＮＧは、たとえば都市ガスの原料あるいは火力発電の燃料などとして大量に使用される。都市ガスや電力の需要は、昼間には多く夜間には少なくなる。したがって、ＬＮＧの使用量が多くなる昼間には、ＬＮＧの有する冷熱を利用してのＢＯＧの再液化や空気分離を充分に行うことができるが、夜間には利用可能な冷熱源が少なくなってしまう。ＢＯＧの発生は、断熱材を通過してくる外部からの入熱によって行われるので、昼間と夜間との温度差はＢＯＧの発生量にあまり影響がなく、夜間でもＢＯＧの再液化などの処理の必要性はほとんど変わらない。このため、ＬＮＧの使用量や消費量が減少して、ＢＯＧの再液化に使用することができる冷熱が不足する事態も生じ得る。ＢＯＧ自体を燃料として消費したり使用する場合であっても、その需要は夜間には少なくなり、再液化などによって処理する必要性は大きい。
【０００６】
ＢＯＧは、ＬＮＧ中のメタンが大部分を占め、他の成分も含むＬＮＧとは燃料としての特性が異なる。このため、ＢＯＧを単独あるいは主成分として、ＬＮＧの需要が減少している状態で、ＬＮＧの代わりに供給することは好ましくはない。
【０００７】
本発明の目的は、ＬＮＧの利用量が変動しても、ＢＯＧの再液化と空気分離とを効率的に行うことができるＬＮＧのボイルオフガス再液化および空気分離一体化装置を提供することである。
【０００８】
【課題を解決するための手段】
本発明は、ＬＮＧタンクから発生するボイルオフガスの再液化、および空気を液化して蒸留することによる成分への分離を、一体的に行う装置であって、 ボイルオフガスを圧縮するＢＯＧコンプレッサと、
空気から分離される窒素ガスを圧縮する窒素コンプレッサと、
圧縮された窒素ガスを膨張させる膨張タービン等と、
膨張タービン等によって膨張させた窒素ガス、窒素コンプレッサによって圧縮された窒素ガス、およびＢＯＧコンプレッサによって圧縮したボイルオフガス、およびＬＮＧをそれぞれ通過させて相互に熱交換させる熱交換器とを含むことを特徴とするＬＮＧのボイルオフガス再液化および空気分離一体化装置である。
【０００９】
本発明に従えば、ボイルオフガスはＢＯＧコンプレッサで圧縮される。空気から分離される窒素ガスは、窒素コンプレッサで圧縮される。圧縮された窒素ガスは膨張タービン等で膨張され、熱交換器を通過する。熱交換器には、ＢＯＧコンプレッサで圧縮されたボイルオフガスと、窒素コンプレッサで圧縮された窒素ガスと、ＬＮＧも通過させられ、相互に熱交換が行われる。この熱交換によって、ＬＮＧの冷熱を、ボイルオフガスの再液化のためにも、空気分離装置の窒素ガスの冷却のためにも利用することができる。ＬＮＧの使用量が少なくなる夜間などでは、窒素ガスの液化の割合を少なくし、優先的にＢＯＧを再液化するために使用する。ＬＮＧ利用量に充分余裕がある場合には、空気分離に使用する割合を増大させ、空気分離の需要と供給とのバランスを図る。また、空気分離用の窒素コンプレッサなどの能力に余裕を持たせておけば、電力の安価な夜間に空気分離設備の窒素ガスの液化量を減ずることなくＢＯＧの再液化を行うことが可能になる。
【００１０】
また本発明で前記窒素コンプレッサによって圧縮されて前記熱交換器を通過する窒素ガスの一部を、該熱交換器内で分岐させて前記膨張タービン等に供給し、該膨張タービン等によって膨張させて該熱交換器を通過させた窒素ガスを、該窒素コンプレッサの入側に戻す窒素循環用管路を備えることを特徴とする。
【００１１】
本発明に従えば、窒素コンプレッサによって圧縮される窒素ガスが、熱交換器を通過する途中で分岐して膨張タービン等に供給される。膨張タービン等によって膨張させた窒素ガスは、熱交換器を通過して窒素コンプレッサの入側に戻される。このような窒素循環用管路で窒素ガスを循環させて、圧縮と膨張とを繰返えすと、熱交換器が冷熱を供給し、ＬＮＧの冷熱だけでは不足する場合に、ＢＯＧの再液化用の冷熱源として利用することができる。
【００１２】
【発明の実施の形態】
図１は、本発明の実施の一形態としてのＬＮＧのＢＯＧ再液化・空気分離一体化装置の概略的な構成を示す。ＬＮＧは、ＬＮＧタンク１内に貯蔵される。ＬＮＧタンク１内に貯蔵されるＬＮＧは、ＬＮＧポンプ２によってＬＮＧタンク１内から取出され、熱交換器３のＬＮＧ通過層４を通って、都市ガスの原料や燃料などとしての利用のために送出される。都市ガスの原料や直接燃料として利用される際には、低温のＬＮＧではなく、常温の気化した天然ガス（ＮＧ）として供給する必要がある。ＬＮＧが熱交換器３のＬＮＧ通過層４を通過する際に、冷熱を供給する一方で、昇温および気化に必要な熱の少なくとも一部が供給される。
【００１３】
ＬＮＧの利用に伴って熱交換器３に供給される冷熱は、熱交換器３のＢＯＧ通過層５を通過するＢＯＧの再液化に使用される。また、熱交換器３に設けられる窒素膨張層６および窒素圧縮層７への冷熱供給のためにも使用される。熱交換器３は、プレートフィン（ＰＦ）形として構成され、ＬＮＧ通過層４、ＢＯＧ通過層５、窒素膨張層６および窒素圧縮層７の４つの層がそれぞれ分離され、かつ熱交換は相互に可能である。ＢＯＧ通過層５には、ＬＮＧタンク１から発生するＢＯＧが、ＢＯＧコンプレッサ８によって圧縮された後、供給される。ＢＯＧは、ＬＮＧ中に含まれるメタンがほとんど単一の成分として含まれ、圧縮と冷却とによって液化する。ＢＯＧが液化すると、ＬＮＧタンク１内に戻される。ＬＮＧタンク１、ＬＮＧポンプ２、ＢＯＧ通過層５およびＢＯＧコンプレッサ８は、ＢＯＧ再液化設備９を構成する。
【００１４】
熱交換器３の窒素膨張層６および窒素圧縮層７は、空気分離設備１０の一部を構成する。空気分離設備１０には、高圧蒸留塔１１、低圧蒸留塔１１’、窒素循環用管路１２および空気液化設備１３も含まれる。空気液化設備１３によって液化された液体空気１４は、高圧蒸留塔１１の底部に貯留される。高圧蒸留塔１１の上部では、液体空気１４から分離された窒素ガスが窒素コンプレッサ２０’で圧縮されて熱交換器３の窒素圧縮層７を通過する。
【００１５】
低圧蒸留塔１１’の上部で液体酸素１６から分離された窒素ガス１７は、窒素コンプレッサ２０で圧縮されて熱交換器３の窒素圧縮層７をも通過する。通過する窒素ガスの一部は、窒素循環用管路１２に設けられる膨張タービン２１に導かれて膨張させられる。膨張タービン２１へは、窒素圧縮層７の途中に接続される分岐管２２を介して分岐する。膨張タービン２１で膨張させられた窒素ガスは、熱交換器３の窒素膨張層６を通過し、合流管２３を介して窒素コンプレッサ２０の入側で、蒸留塔１１から供給される窒素ガスと合流する。合流管２３で合流した窒素ガスは、窒素コンプレッサ２０で圧縮された後、高圧蒸留塔１１の上部から導かれた窒素ガスと合流する合流管３０で合流した窒素ガスは、窒素コンプレッサ２０’から再び熱交換器３の窒素圧縮層７に入り、分岐管２２から分岐して膨張タービン２１で膨張され、熱交換器３の窒素膨張塔６を通って合流管２３で合流する。このような窒素循環用管路１２内を、窒素ガスを循環させることによって、熱交換器３に冷熱を供給することもできる。
【００１６】
窒素循環用管路１２で循環する窒素ガスを除いた他の窒素ガスは、低圧蒸留塔１１’から空気液化設備１３を経て窒素コンプレッサ２０に入り、熱交換器３の窒素膨張層６を通って、膨張弁２４から低圧蒸留塔１１’に還流液として戻る。また、膨張弁２４から、窒素タンク２５に供給して貯蔵するときは製品液体窒素となる。低圧蒸留塔１１’では、アルゴン１５および液体酸素１６もそれぞれ分離されるので、窒素タンク２５と同様にそれぞれ貯蔵して、製品として取出すようにすることができる。
【００１７】
高圧蒸留塔１１に液体空気１４を供給する空気液化設備１３では、原料となる空気を原料空気コンプレッサ２６で圧縮し、空気／窒素熱交換器２７を介して冷却し、液化させて液体空気１４として高圧蒸留塔１１の下部に供給する。空気／窒素熱交換器２７には、低圧蒸留塔１１’から冷却された窒素が供給され、空気を冷却する。
【００１８】
図１に示すような装置では、ＢＯＧ再液化のプロセスと空気分離のプロセスとを一体の設備として管理し、ＬＮＧが都市ガスなどの原料として、または直接燃焼用に送出されても、その有する冷熱を有効に利用し、またＬＮＧタンク１から発生するボイルオフガスを確実に再液化してＬＮＧタンク１に戻すことができる。本実施形態のＢＯＧ再液化および空気分離一体化装置では、次の図２に示すような考え方で、ＬＮＧの有する冷熱を有効に利用することができる。図２（ａ）は、ＬＮＧの送出量が大きくなる昼間での冷熱利用での冷熱の配分を示し、図２（ｂ）はＬＮＧ送出量が少なくなる夜間での冷熱の配分を示す。図２（ａ）に示すように、昼間ではＬＮＧの送出量が大きく、冷熱の利用量に充分余裕があるので、空気分離とＢＯＧ再液化とに充分な冷熱を割当てることができる。ＬＮＧ送出量が小さくなる夜間では、図２（ｂ）に示すように、ＬＮＧを利用して発生する冷熱をＢＯＧの再液化の方に優先的に割当てる。このため空気分離に割当てられる冷熱の相対的な割合は減少するけれども、ＬＮＧの冷熱は有効に利用することができる。特にＬＮＧを運搬するＬＮＧタンカなどが入船し、ＬＮＧがＬＮＧタンク１に補給される際などには、ボイルオフガスの発生量が増大する。このようなＬＮＧタンカの入船は、ＬＮＧ送出量が少なくなる夜間に行われ、発生するボイルオフガスの処理が困難となる場合が多いけれども、図２（ｂ）に示すよりもさらに冷熱のＢＯＧ再液化への割当て量を大きくし、一時的に空気分離による窒素ガスなどの生産量を減少させて、対応させることができる。
【００１９】
図３は、図１に示すようなＢＯＧ再液化および空気分離の一体化装置を利用して、ＬＮＧの冷熱を利用する他の考え方を示す。この考え方では、空気分離設備１０の窒素循環用管路１２に設けられる窒素コンプレッサ２０などの設備能力を、充分に余裕があるようにしておく。図３（ａ）に示すように、昼間では設備能力に余裕を持たせた状態で、空気分離を行う。すなわち、余裕分は休止させる。図３（ｂ）に示すように、夜間ではＢＯＧ再液化のための冷熱源が不足するので、昼間では余裕があって休止していた空気分離設備の能力をＢＯＧ再液化のためにも利用して、ボイルオフガスが再液化される際に必要となる冷熱の補給を行うことができる。ＢＯＧ再液化のための冷熱を窒素循環用管路１２を循環する窒素の冷熱サイクルで発生させるために窒素コンプレッサ２０を駆動する電力は、夜間電力を利用するので、昼間よりもコストが低く、経済的に空気分離とＢＯＧ再液化とを行うことができる。
【００２０】
【発明の効果】
以上のように本発明によれば、ＬＮＧの冷熱を利用するＢＯＧの再液化と空気分離の設備を一体的に管理することができるので、それぞれの設備の稼働率をＬＮＧ利用量に合わせてフレシキブルに調整することが可能になるとともに、設備コストの低減と効率的な一元管理とを図ることができる。たとえば、ＬＮＧ貯蔵タンクに入船したＬＮＧタンカから夜間にＬＮＧが補給されるときには特にＢＯＧの発生量が増大するけれども、空気分離の冷熱使用量を低減し、優先的にＢＯＧの再液化にＬＮＧの冷熱を振り向けることができる。また、空気分離の設備能力に余裕を持たせておいて、ＬＮＧの冷熱ではＢＯＧの再液化に不足が生じるときに、空気分離の設備から冷熱源を供給するようにすることもできる。
【００２１】
また本発明によれば、窒素循環用管路を用いて、窒素ガスを圧縮して膨張させることによる冷熱の発生量を増大させることができるので、ＢＯＧの再液化のための冷熱源として効率的に利用することができる。
【図面の簡単な説明】
【図１】本発明の実施の一形態のＢＯＧ再液化および空気分離一体化設備の概略的な構成を示す配管系統図である。
【図２】図１の実施形態で、昼間と夜間とでＬＮＧの冷熱利用割合を空気分離とＢＯＧ再液化とで変更する基本的な考え方を示す図である。
【図３】図１の実施形態で、空気分離設備１０の能力に余裕を持たせておき、ＬＮＧの送出量が減る夜間に空気分離設備からの冷熱量をＢＯＧ再液化にも利用する考え方を示す図である。
【符号の説明】
１ ＬＮＧタンク
３ 熱交換器
４ ＬＮＧ通過層
５ ＢＯＧ通過層
６ 窒素膨張層
７ 窒素圧縮層
８ ＢＯＧコンプレッサ
９ ＢＯＧ再液化設備
１０ 空気分離設備
１１ 高圧蒸留塔
１１’ 低圧蒸留塔
１２ 窒素循環用管路
１３ 空気液化設備
１７ 窒素ガス
２０，２０’ 窒素コンプレッサ
２１ 膨張タービン
２２ 分岐管
２３ 合流管
２５ 窒素タンク[0001]
BACKGROUND OF THE INVENTION
The present invention uses the cold heat of liquefied natural gas (hereinafter abbreviated as “LNG”) to reliquefy boil-off gas (hereinafter also abbreviated as “BOG”) generated in a tank that stores LNG. The present invention relates to an LNG boil-off gas re-liquefaction and air separation integrated device that returns to an LNG tank and liquefies and distills air into components.
[0002]
[Prior art]
LNG is transported from the place of origin by, for example, an LNG tanker, stored in an LNG tank, and supplied to a demand destination. The temperature of the stored LNG is about −160 ° C., which is extremely lower than the normal temperature. Therefore, BOG is generated in the LNG tank due to natural heat input or the like. For this reason, in order to keep the pressure in the LNG tank within a certain range, it is necessary to process the generated BOG.
[0003]
BOG processing is boosted by the compressor and sent out for direct consumption as fuel, or after being pressurized by the compressor, re-liquefied and returned to the LNG tank or mixed with LNG supplied from the LNG tank. After that, it is sent out for consumption. The prior art regarding such BOG reliquefaction is also disclosed by the present applicant as, for example, JP-A-3-236588. In this prior art, LNG is also used as a cold heat source for reliquefaction of BOG.
[0004]
The cold heat of LNG is also used in air separation equipment. In the air separation facility, oxygen (O 2 ), nitrogen (N 2 ), argon (Ar) and the like are separated and liquefied from the air by utilizing the difference in boiling points (−183 to −196 ° C.). As energy for cooling necessary for liquefaction, cold energy of LNG is used together with electric power for driving a compressor. The present applicant has also disclosed the prior art on air separation using the cold heat of LNG, for example, as Japanese Patent Application No. 7-295186.
[0005]
[Problems to be solved by the invention]
Conventional BOG reliquefaction and air separation are installed as separate facilities, and the management of the facilities is also performed separately. In this case, an amount of LNG commensurate with each demand is used for re-liquefaction of BOG and air separation. If there is a restriction on the amount of LNG supplied, it is necessary to reduce either capacity. LNG is used in large quantities, for example, as a raw material for city gas or fuel for thermal power generation. The demand for city gas and electricity is high during the day and low at night. Therefore, during the daytime when the amount of LNG used increases, BOG can be sufficiently liquefied and air separated using the cold heat of LNG, but the available cold heat source is reduced at night. End up. Since BOG is generated by external heat input that passes through the heat insulating material, the temperature difference between daytime and nighttime has little effect on the amount of BOG generated, and processing such as re-liquefaction of BOG is also possible at nighttime. The need is almost unchanged. For this reason, the usage-amount and consumption of LNG may reduce, and the situation which the cold which can be used for reliquefaction of BOG may run short may also arise. Even when the BOG itself is consumed or used as fuel, the demand is reduced at night, and there is a great need for treatment by reliquefaction or the like.
[0006]
BOG occupies most of methane in LNG, and is different in fuel characteristics from LNG including other components. For this reason, it is not preferable to supply BOG alone or as a main component in place of LNG while the demand for LNG is decreasing.
[0007]
An object of the present invention is to provide an LNG boil-off gas reliquefaction and air separation integrated device capable of efficiently performing BOG reliquefaction and air separation even when the amount of LNG used varies. .
[0008]
[Means for Solving the Problems]
The present invention is an apparatus that integrally performs re-liquefaction of boil-off gas generated from an LNG tank and separation into components by liquefying and distilling air, and a BOG compressor that compresses boil-off gas;
A nitrogen compressor that compresses nitrogen gas separated from the air;
An expansion turbine for expanding the compressed nitrogen gas,
And a heat exchanger that exchanges heat with each other by passing nitrogen gas expanded by an expansion turbine or the like, nitrogen gas compressed by a nitrogen compressor, boil-off gas compressed by a BOG compressor, and LNG, respectively. LNG boil-off gas reliquefaction and air separation integrated device.
[0009]
According to the invention, the boil-off gas is compressed with a BOG compressor. Nitrogen gas separated from air is compressed by a nitrogen compressor. The compressed nitrogen gas is expanded by an expansion turbine or the like and passes through a heat exchanger. The boil-off gas compressed by the BOG compressor, the nitrogen gas compressed by the nitrogen compressor, and LNG are also passed through the heat exchanger to exchange heat with each other. By this heat exchange, the cold heat of LNG can be used for reliquefaction of the boil-off gas as well as for cooling the nitrogen gas of the air separation device. At night, when the amount of LNG used is reduced, the rate of nitrogen gas liquefaction is reduced, and it is used to preferentially reliquefy BOG. When there is a sufficient margin in the amount of LNG used, the proportion used for air separation is increased to balance the demand and supply of air separation. In addition, if the capacity of a nitrogen compressor or the like for air separation is provided, it is possible to reliquefy BOG without reducing the amount of nitrogen gas liquefied in the air separation facility at night when power is inexpensive. .
[0010]
Further, in the present invention, a part of the nitrogen gas compressed by the nitrogen compressor and passing through the heat exchanger is branched in the heat exchanger, supplied to the expansion turbine or the like, and expanded by the expansion turbine or the like. A nitrogen circulation pipe is provided for returning the nitrogen gas passed through the heat exchanger to the inlet side of the nitrogen compressor.
[0011]
According to the present invention, the nitrogen gas compressed by the nitrogen compressor branches in the middle of passing through the heat exchanger and is supplied to the expansion turbine or the like. Nitrogen gas expanded by an expansion turbine or the like passes through the heat exchanger and is returned to the inlet side of the nitrogen compressor. When nitrogen gas is circulated in such a nitrogen circulation line and compression and expansion are repeated, the heat exchanger supplies cold heat, and when the cold heat of LNG alone is insufficient, the BOG is used for reliquefaction. It can be used as a cold heat source.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a schematic configuration of an integrated LNG BOG reliquefaction / air separation apparatus as one embodiment of the present invention. The LNG is stored in the LNG tank 1. The LNG stored in the LNG tank 1 is taken out from the LNG tank 1 by the LNG pump 2, sent through the LNG passage layer 4 of the heat exchanger 3 for use as a raw material or fuel of city gas. Is done. When used as a raw material for city gas or as a direct fuel, it is necessary to supply natural gas (NG) vaporized at room temperature, not LNG at low temperature. When LNG passes through the LNG passage layer 4 of the heat exchanger 3, while supplying cold, at least a part of heat necessary for temperature rise and vaporization is supplied.
[0013]
The cold supplied to the heat exchanger 3 along with the use of LNG is used for reliquefaction of BOG that passes through the BOG passage layer 5 of the heat exchanger 3. Further, it is also used for supplying cold heat to the nitrogen expansion layer 6 and the nitrogen compression layer 7 provided in the heat exchanger 3. The heat exchanger 3 is configured as a plate fin (PF) type, and the four layers of the LNG passage layer 4, the BOG passage layer 5, the nitrogen expansion layer 6 and the nitrogen compression layer 7 are separated from each other, and the heat exchange is mutually performed. Is possible. BOG generated from the LNG tank 1 is supplied to the BOG passage layer 5 after being compressed by the BOG compressor 8. BOG contains almost all of methane contained in LNG as a single component, and liquefies by compression and cooling. When the BOG is liquefied, it is returned to the LNG tank 1. The LNG tank 1, the LNG pump 2, the BOG passage layer 5, and the BOG compressor 8 constitute a BOG reliquefaction facility 9.
[0014]
The nitrogen expansion layer 6 and the nitrogen compression layer 7 of the heat exchanger 3 constitute a part of the air separation facility 10. The air separation facility 10 also includes a high pressure distillation column 11, a low pressure distillation column 11 ′, a nitrogen circulation pipe 12 and an air liquefaction facility 13. The liquid air 14 liquefied by the air liquefaction facility 13 is stored at the bottom of the high pressure distillation column 11. In the upper part of the high-pressure distillation column 11, the nitrogen gas separated from the liquid air 14 is compressed by the nitrogen compressor 20 ′ and passes through the nitrogen compression layer 7 of the heat exchanger 3.
[0015]
The nitrogen gas 17 separated from the liquid oxygen 16 at the top of the low-pressure distillation column 11 ′ is compressed by the nitrogen compressor 20 and also passes through the nitrogen compression layer 7 of the heat exchanger 3. Part of the passing nitrogen gas is led to an expansion turbine 21 provided in the nitrogen circulation pipe 12 to be expanded. The expansion turbine 21 branches through a branch pipe 22 connected in the middle of the nitrogen compression layer 7. The nitrogen gas expanded by the expansion turbine 21 passes through the nitrogen expansion layer 6 of the heat exchanger 3 and joins with the nitrogen gas supplied from the distillation tower 11 on the inlet side of the nitrogen compressor 20 via the merge pipe 23. To do. The nitrogen gas merged in the merge pipe 23 is compressed by the nitrogen compressor 20, and then the nitrogen gas merged in the merge pipe 30 that merges with the nitrogen gas introduced from the upper part of the high-pressure distillation column 11 is again supplied from the nitrogen compressor 20 ′. It enters into the nitrogen compression layer 7 of the heat exchanger 3, branches from the branch pipe 22, is expanded by the expansion turbine 21, passes through the nitrogen expansion tower 6 of the heat exchanger 3, and merges at the merge pipe 23. It is also possible to supply cold heat to the heat exchanger 3 by circulating nitrogen gas in the nitrogen circulation pipe 12.
[0016]
The other nitrogen gas excluding the nitrogen gas circulated in the nitrogen circulation pipe 12 enters the nitrogen compressor 20 from the low pressure distillation column 11 ′ through the air liquefaction equipment 13, passes through the nitrogen expansion layer 6 of the heat exchanger 3. Then, the refrigerant returns from the expansion valve 24 to the low-pressure distillation column 11 ′ as a reflux liquid. Further, when supplied from the expansion valve 24 to the nitrogen tank 25 and stored, it becomes product liquid nitrogen. In the low-pressure distillation column 11 ′, the argon 15 and the liquid oxygen 16 are also separated, so that they can be stored in the same manner as the nitrogen tank 25 and taken out as a product.
[0017]
In the air liquefaction facility 13 for supplying the liquid air 14 to the high-pressure distillation column 11, the raw material air is compressed by the raw material air compressor 26, cooled through the air / nitrogen heat exchanger 27, and liquefied to form the liquid air 14. A lower part of the high-pressure distillation column 11 is supplied. The air / nitrogen heat exchanger 27 is supplied with nitrogen cooled from the low-pressure distillation column 11 ′ to cool the air.
[0018]
In the apparatus as shown in FIG. 1, the BOG reliquefaction process and the air separation process are managed as an integrated facility, and even if LNG is sent as a raw material such as city gas or directly for combustion, the cold heat that it has The boil-off gas generated from the LNG tank 1 can be reliably liquefied and returned to the LNG tank 1. In the BOG reliquefaction and air separation integrated device of the present embodiment, the cold energy of LNG can be effectively utilized based on the concept as shown in FIG. FIG. 2 (a) shows the distribution of cold heat during daytime when the amount of LNG delivered increases, and FIG. 2 (b) shows the distribution of cold at night when the amount of LNG delivered decreases. As shown in FIG. 2 (a), since the amount of LNG delivered is large during the day and there is sufficient room for the amount of cold energy, sufficient cold energy can be allocated for air separation and BOG reliquefaction. At night when the amount of LNG delivered becomes small, as shown in FIG. 2B, the cold generated by using LNG is preferentially assigned to the re-liquefaction of BOG. This reduces the relative percentage of cold allocated to air separation, but allows the LNG cold to be used effectively. In particular, when an LNG tanker that transports LNG enters the ship and LNG is supplied to the LNG tank 1, the amount of boil-off gas generated increases. Such LNG tanker entry is performed at night when the amount of LNG delivered decreases, and it is often difficult to process the generated boil-off gas. However, the cold BOG reliquefaction is more than that shown in FIG. It is possible to cope with this by increasing the amount allocated to the gas and temporarily reducing the production amount of nitrogen gas or the like by air separation.
[0019]
FIG. 3 shows another concept of utilizing the cold heat of LNG using an integrated apparatus for BOG reliquefaction and air separation as shown in FIG. In this way of thinking, the facility capacity of the nitrogen compressor 20 provided in the nitrogen circulation pipe 12 of the air separation facility 10 is provided with a sufficient margin. As shown to Fig.3 (a), air separation is performed in the state which provided the allowance for equipment capacity at daytime. That is, the margin is paused. As shown in FIG. 3 (b), since there is a shortage of cold heat source for BOG reliquefaction at night, the capacity of the air separation facility that has been spared during the daytime can be used for BOG reliquefaction. Thus, it is possible to replenish the cold energy required when the boil-off gas is reliquefied. The electric power for driving the nitrogen compressor 20 to generate cold heat for BOG reliquefaction in the nitrogen cold cycle circulating through the nitrogen circulation line 12 uses nighttime power, so the cost is lower than the daytime and economical. Thus, air separation and BOG reliquefaction can be performed.
[0020]
【The invention's effect】
As described above, according to the present invention, the equipment for re-liquefaction of BOG and the air separation equipment using the cold heat of LNG can be managed in an integrated manner, so that the operation rate of each equipment is flexible according to the amount of LNG used. It is possible to make adjustments at the same time, and it is possible to reduce the equipment cost and perform efficient centralized management. For example, when LNG is replenished at night from an LNG tanker that has entered a LNG storage tank, the amount of BOG generated increases, but the amount of cold energy used for air separation is reduced, and LNG Can turn around. In addition, it is also possible to provide a cooling power source from the air separation facility when there is a shortage in the re-liquefaction of BOG due to the cold heat of LNG with a margin in the facility capacity of the air separation.
[0021]
Further, according to the present invention, the amount of cold generated by compressing and expanding nitrogen gas can be increased using the nitrogen circulation pipe, so that it is efficient as a cold source for re-liquefaction of BOG. Can be used.
[Brief description of the drawings]
FIG. 1 is a piping system diagram showing a schematic configuration of an integrated BOG reliquefaction and air separation facility according to an embodiment of the present invention.
FIG. 2 is a diagram showing a basic concept of changing the LNG cold heat utilization ratio between air separation and BOG reliquefaction between daytime and nighttime in the embodiment of FIG. 1;
FIG. 3 is an embodiment in which the capacity of the air separation facility 10 is given a margin in the embodiment of FIG. 1 and the cold energy from the air separation facility is also used for BOG reliquefaction at night when the amount of LNG delivered is reduced. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 LNG tank 3 Heat exchanger 4 LNG passage layer 5 BOG passage layer 6 Nitrogen expansion layer 7 Nitrogen compression layer 8 BOG compressor 9 BOG reliquefaction equipment 10 Air separation equipment 11 High pressure distillation tower 11 'Low pressure distillation tower 12 Pipe for nitrogen circulation 13 Air liquefaction equipment 17 Nitrogen gas 20, 20 ′ Nitrogen compressor 21 Expansion turbine 22 Branch pipe 23 Merge pipe 25 Nitrogen tank

Claims (2)

ＬＮＧタンクから発生するボイルオフガスの再液化、および空気を液化して蒸留することによる成分への分離を、一体的に行う装置であって、
ボイルオフガスを圧縮するＢＯＧコンプレッサと、
空気から分離される窒素ガスを圧縮する窒素コンプレッサと、
圧縮された窒素ガスを膨張させる膨張タービン等と、
膨張タービン等によって膨張させた窒素ガス、窒素コンプレッサによって圧縮された窒素ガス、およびＢＯＧコンプレッサによって圧縮したボイルオフガス、およびＬＮＧをそれぞれ通過させて相互に熱交換させる熱交換器とを含むことを特徴とするＬＮＧのボイルオフガス再液化および空気分離一体化装置。An apparatus for integrally performing re-liquefaction of boil-off gas generated from an LNG tank and separation into components by liquefying and distilling air,
A BOG compressor for compressing boil-off gas;
A nitrogen compressor that compresses nitrogen gas separated from the air;
An expansion turbine that expands the compressed nitrogen gas,
And a heat exchanger that exchanges heat with each other by passing nitrogen gas expanded by an expansion turbine or the like, nitrogen gas compressed by a nitrogen compressor, boil-off gas compressed by a BOG compressor, and LNG, respectively. LNG boil-off gas reliquefaction and air separation integrated device. 前記窒素コンプレッサによって圧縮されて前記熱交換器を通過する窒素ガスの一部を、該熱交換器内で分岐させて前記膨張タービン等に供給し、該膨張タービン等によって膨張させて該熱交換器を通過させた窒素ガスを、該窒素コンプレッサの入側に戻す窒素循環用管路を備えることを特徴とする請求項１記載のＬＮＧのボイルオフガス再液化および空気分離一体化装置。A part of the nitrogen gas compressed by the nitrogen compressor and passing through the heat exchanger is branched into the heat exchanger, supplied to the expansion turbine, etc., and expanded by the expansion turbine, etc. The LNG boil-off gas reliquefaction and air separation integrated apparatus according to claim 1, further comprising a nitrogen circulation conduit for returning the nitrogen gas that has passed through to the inlet side of the nitrogen compressor.
JP30899898A 1998-10-29 1998-10-29 LNG boil-off gas reliquefaction and air separation integrated device Expired - Fee Related JP3610246B2 (en)

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