CN103322769B - 一种基荷型天然气液化工厂的级联式液化系统 - Google Patents

一种基荷型天然气液化工厂的级联式液化系统 Download PDF

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CN103322769B
CN103322769B CN201210074603.7A CN201210074603A CN103322769B CN 103322769 B CN103322769 B CN 103322769B CN 201210074603 A CN201210074603 A CN 201210074603A CN 103322769 B CN103322769 B CN 103322769B
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propane
ethane
compressor
heat exchanger
knockout drum
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CN103322769A (zh
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唐令力
单彤文
陈杰
杨文刚
花亦怀
曾伟平
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China National Offshore Oil Corp CNOOC
CNOOC Gas and Power Group 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
    • 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
    • F25J1/0002—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
    • 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
    • F25J1/0052—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 vaporising a liquid refrigerant stream
    • 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
    • F25J1/006—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the refrigerant fluid used
    • F25J1/008—Hydrocarbons
    • F25J1/0082—Methane
    • 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
    • F25J1/008—Hydrocarbons
    • F25J1/0085—Ethane; Ethylene
    • 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
    • F25J1/008—Hydrocarbons
    • F25J1/0087—Propane; Propylene
    • 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
    • F25J1/0207—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 at least a three level SCR refrigeration cascade
    • 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
    • F25J2220/00—Processes or apparatus involving steps for the removal of impurities
    • F25J2220/60—Separating impurities from natural gas, e.g. mercury, cyclic hydrocarbons
    • F25J2220/64—Separating heavy hydrocarbons, e.g. NGL, LPG, C4+ hydrocarbons or heavy condensates in general

Abstract

本发明公开了一种基荷型天然气液化工厂的级联式液化系统，属于天然气液化技术领域。所述液化系统包括丙烷换热器、乙烷换热器、甲烷换热器、氮气换热器、丙烷预冷循环机构、乙烷制冷循环机构、甲烷深冷循环机构和氮气深冷循环机构；本发明具有以下有益效果：(1)具有传统阶式工艺不用配比混合冷剂等优点，同时结合了混合冷剂的优点；(2)有利于平衡天然气预冷、液化、过冷过程中各段的换热负荷，有利于设备的制造和板翅式换热器的应用；(3)平衡各段压缩机的负荷，可提高单线生产规模，有利于生产规模的扩大。

Description

一种基荷型天然气液化工厂的级联式液化系统
技术领域
本发明涉及一种基荷型天然气液化工厂的级联式液化系统，涉及天然气液化技术领域。
背景技术
目前国内常见天然气液化技术多为氮膨胀和单级混合冷剂循环制冷工艺，只能适用于规模较小的LNG装置。国外用于基荷型天然气液化工厂的液化技术中，乙烷预冷较多采用釜式或管壳式换热器，换热性能不佳，造成设备投资浪费，传统三级乙烷预冷系统功耗较大，深冷采用绕管换热器造成设备投资高昂，对进口设备依赖性高。
基荷型天然气液化工厂的液化技术中，压缩机和电机的设备制造能力影响着生产规模的大小，采用级联式工艺，有利于平衡天然气预冷，液化，过冷过程中各段的换热负荷，平衡各段压缩机的负荷，有利于生产规模的扩大。
发明内容
本发明的目的是提供一种操作方便、安全可靠，效率高、适应性强的基荷型天然气液化系统。
本发明提供的一种基荷型天然气液化工厂的级联式液化系统，包括丙烷换热器、乙烷换热器、甲烷换热器、氮气换热器、丙烷预冷循环机构、乙烷制冷循环机构、甲烷深冷循环机构和氮气深冷循环机构；
所述丙烷预冷循环机构包括三级压缩单元，所述三级压缩单元包括依次相连的丙烷压缩机a、丙烷压缩机b和丙烷压缩机c；所述三级压缩单元依次与丙烷气液分离罐a、丙烷气液分离罐b和丙烷气液分离罐c相连通；所述丙烷气液分离罐a、丙烷气液分离罐b和丙烷气液分离罐c的气相出口分别与所述丙烷压缩机a、丙烷压缩机b和丙烷压缩机c相连通，所述丙烷压缩机a、丙烷气液分离罐a、丙烷气液分离罐b和丙烷气液分离罐c之间均设有节流阀；所述丙烷压缩机a的出口与所述丙烷气液分离罐a之间设有丙烷压缩机末级冷凝器，该丙烷压缩机末级冷凝器设于所述节流阀的入口端；所述丙烷气液分离罐a、丙烷气液分离罐b和丙烷气液分离罐c均与所述丙烷换热器相连通；
所述乙烷制冷循环机构包括二级压缩单元，所述二级压缩单元包括依次相连的乙烷压缩机a和乙烷压缩机b；所述二级压缩单元依次与乙烷气液分离罐a和乙烷气液分离罐b相连通，且所述乙烷压缩机a通过管路与所述丙烷换热器相连通，并从所述丙烷换热器的顶部贯穿至其底部后引出，然后继续延伸与所述乙烷气液分离罐a相连通；所述乙烷气液分离罐a和乙烷气液分离罐b的气相出口分别与所述乙烷压缩机a和乙烷压缩机b相连通，所述乙烷压缩机a、乙烷气液分离罐a和乙烷气液分离罐b之间均设有节流阀；所述乙烷气液分离罐a和乙烷气液分离罐b均与所述乙烷换热器相连通；
所述甲烷深冷循环机构包括二级压缩单元，该二级压缩单元包括依次相连的一级甲烷压缩机、一级甲烷压缩机冷却器、二级甲烷压缩机和二级甲烷压缩机冷却器；所述二级甲烷压缩机冷却器的出口通过管路依次与甲烷经济器和乙烷换热器相连通，并从所述乙烷换热器的顶部贯穿至其底部后引出，该管路继续延伸至所述甲烷换热器并从所述甲烷换热器的顶部贯穿至其底部后引出，然后又与所述甲烷换热器的底部相连通，该连通处设有节流阀，所述管路继续延伸至所述甲烷换热器的顶部，然后从其顶部引出后与所述一级甲烷压缩机相连通；管路a与设于所述甲烷换热器内的管路相连通并从其侧部引出，然后所述管路a又与所述甲烷换热器的侧部相连通，该连通处设有节流阀，所述管路a继续延伸至所述甲烷换热器的顶部，然后从其顶部引出后依次与所述甲烷经济器和二级甲烷压缩机相连通；
所述氮气深冷循环机构包括依次连通的氮气膨胀压缩机、氮气压缩机和氮气压缩机冷却器；所述氮气压缩机冷却器的出口通过管路与丙烷换热器相连通，并从所述丙烷换热器的顶部贯穿至其底部后引出，该管路继续延伸至所述乙烷换热器并从其顶部贯穿至其底部后引出，然后依次与氮气经济器和氮气换热器相连通，该管路从所述氮气换热器的顶部引出后又依次与所述氮气经济器和氮气膨胀压缩机相连通。
上述的级联式液化系统，所述丙烷预冷循环机构还包括依次与所述丙烷压缩机c相连接的丙烷压缩机d和丙烷气液分离罐d，所述丙烷气液分离罐d与丙烷气液分离罐c相连通，该连通处设有所述节流阀，所述丙烷气液分离罐d与所述丙烷换热器相连通。
上述的级联式液化系统，所述乙烷制冷循环机构还包括与所述乙烷压缩机b相连接的乙烷压缩机c和乙烷气液分离罐c，所述乙烷气液分离罐c与乙烷气液分离罐b相连通，该连通处设有所述节流阀，所述乙烷气液分离罐c与所述乙烷换热器相连通。
上述的级联式液化系统，所述节流阀可为J/T阀。
本发明具有以下有益效果：
(1)具有传统阶式工艺不用配比混合冷剂等优点，同时结合了混合冷剂的优点；
(2)有利于平衡天然气预冷、液化、过冷过程中各段的换热负荷，有利于设备的制造和板翅式换热器的应用；
(3)平衡各段压缩机的负荷，可提高单线生产规模，有利于生产规模的扩大。
附图说明
图1为本发明提供的基荷型天然气液化工厂的级联式液化系统的结构示意图。
图中各标记如下：CB-1丙烷换热器、CB-2乙烷换热器、CB-3甲烷换热器、CB-4氮气换热器、C1-1丙烷压缩机a、C1-2丙烷压缩机b、C1-3丙烷压缩机c、C1-4丙烷压缩机d、V1-1丙烷气液分离罐a、V1-2丙烷气液分离罐b、V1-3丙烷气液分离罐c、V1-4丙烷气液分离罐d、C2-1乙烷压缩机a、C2-2乙烷压缩机b、C2-3乙烷压缩机c、V2-1乙烷气液分离罐a、V2-2乙烷气液分离罐b、V2-3乙烷气液分离罐c、C3-1一级甲烷压缩机、C3-2二级甲烷压缩机、C4-1氮气压缩机、C4-2氮气膨胀压缩机、E1-1丙烷压缩机末级冷凝器、E3-1一级甲烷压缩机冷却器、E3-2二级甲烷压缩机冷却器、E3-3甲烷经济器、E4-1氮气压缩机冷却器、E4-2氮气经济器、11，12，13，14，15，16，17，18，19J/T阀、2管路a。
具体实施方式
下面结合附图对本发明做进一步说明，但本发明并不局限于以下实施例。
本发明提供的级联式液化系统包括丙烷换热器CB-1、乙烷换热器CB-2、甲烷换热器CB-3、氮气换热器CB-2、丙烷预冷循环机构、乙烷制冷循环机构、甲烷深冷循环机构和氮气深冷循环机构；丙烷预冷循环机构包括四级压缩单元，四级压缩单元包括依次相连的丙烷压缩机a C1-1、丙烷压缩机b C1-2、丙烷压缩机c C1-3和丙烷压缩机d C1-4；该四级压缩单元依次与丙烷气液分离罐a V1-1、丙烷气液分离罐b V1-2、丙烷气液分离罐c V1-3和丙烷气液分离罐d V1-4相连通；丙烷气液分离罐a V1-1、丙烷气液分离罐b V1-2、丙烷气液分离罐c V1-3和丙烷气液分离罐d V1-4的气相出口分别与丙烷压缩机a C1-1、丙烷压缩机b C1-2、丙烷压缩机c C1-3和丙烷压缩机d C1-4相连通，丙烷压缩机a C1-1、丙烷气液分离罐a V1-1、丙烷气液分离罐b V1-2、丙烷气液分离罐c V1-3和丙烷气液分离罐d V1-4之间依次J/T阀11、12、13和14，丙烷压缩机a C1-1的出口与丙烷气液分离罐a V1-1之间设有丙烷压缩机末级冷凝器E1-1，该丙烷压缩机末级冷凝器E1-1设于J/T阀11的入口端；丙烷气液分离罐a V1-1、丙烷气液分离罐b V1-2、丙烷气液分离罐c V1-3和丙烷气液分离罐d V1-4均与丙烷换热器CB-1相连通；乙烷制冷循环机构包括三级压缩单元，该三级压缩单元包括依次相连的乙烷压缩机a C2-1、乙烷压缩机b C2-2和乙烷压缩机b C2-3；该三级压缩单元依次与乙烷气液分离罐a V2-1、乙烷气液分离罐b V2-1和乙烷气液分离罐c V2-3相连通，且乙烷压缩机a C2-1通过管路与丙烷换热器CB-1相连通，并从丙烷换热器CB-1的顶部贯穿至其底部后引出，然后继续延伸与乙烷气液分离罐a C2-1相连通；乙烷气液分离罐a V2-1、乙烷气液分离罐b V2-1和乙烷气液分离罐c V2-3的气相出口分别与乙烷压缩机a C2-1、乙烷压缩机b C2-2和乙烷压缩机b C2-3相连通，乙烷压缩机a C2-1、乙烷气液分离罐a V2-1、乙烷气液分离罐b V2-1和乙烷气液分离罐c V2-3之间依次J/T阀15、16和17；乙烷气液分离罐a V2-1、乙烷气液分离罐b V2-1和乙烷气液分离罐c V2-3均与乙烷换热器CB-2相连通；甲烷深冷循环机构包括二级压缩单元，该二级压缩单元包括依次相连的一级甲烷压缩机C3-1、一级甲烷压缩机冷却器E3-1、二级甲烷压缩机C3-2和二级甲烷压缩机冷却器E3-2；二级甲烷压缩机冷却器E3-2的出口通过管路依次与甲烷经济器E3-3和乙烷换热器CB-2相连通，并从乙烷换热器CB-2的顶部贯穿至其底部后引出，该管路继续延伸至甲烷换热器E3-3并从甲烷换热器E3-3的顶部贯穿至其底部后引出，然后又与甲烷换热器CB-3的底部相连通，该连通处设有J/T阀18，该管路继续延伸至甲烷换热器CB-3的顶部，然后从其顶部引出后与一级甲烷压缩机C3-1相连通；管路a2与设于甲烷换热器CB-3内的管路相连通并从其侧部引出，然后管路a2又与甲烷换热器CB-3的侧部相连通，该连通处设有J/T阀19，该管路a2继续延伸至甲烷换热器CB-3的顶部，然后从其顶部引出后依次与甲烷经济器E3-3和二级甲烷压缩机C3-2相连通；氮气深冷循环机构包括依次连通的氮气膨胀压缩机C4-2、氮气压缩机C4-1和氮气压缩机冷却器E4-1；氮气压缩机冷却器E4-1的出口通过管路与丙烷换热器相CB-1连通，并从丙烷换热器CB-1的顶部贯穿至其底部后引出，该管路继续延伸至乙烷换热器CB-2并从其顶部贯穿至其底部后引出，然后依次与氮气经济器E4-2和氮气换热器CB-4相连通，该管路从氮气换热器CB-4的顶部引出后又依次与氮气经济器E4-2和氮气膨胀压缩机C4-2相连通。
使用上述的级联式液化系统对海外某气田的原料天然气进行液化，原料气组分为95.86％甲烷，2.35％乙烷，丙烷0.52％，丁烷0.12％，异丁烷0.13％，氮气C5+组分0.02％，该装置年产LNG量为260万吨。主要实施步骤如下：
低温的丙烷进入丙烷压缩机经四段压缩至1.75MPaA后，经丙烷压缩机末级冷凝器E1-1冷凝至41℃，经过J-T阀11节流到约819kPaA后分成两股，一股进入丙烷换热器CB-1第一段蒸发提供预冷第一段所需的冷量，蒸发后的丙烷返回丙烷压缩机aC1-1入口；另一股经过J-T阀12节流到约475kPaA后又分为两股，一股进入丙烷换热器CB-1第二段蒸发以提供预冷第二段所需的冷量，蒸发后的丙烷返回丙烷压缩机bC1-2，另一股再经过J-T阀13节流到约253kPaA后又分为两股，一股进入丙烷换热器CB-1第三段蒸发以提供预冷第三段所需的冷量，蒸发后的丙烷再返回丙烷压缩机cC1-3，另一股液体丙烷再经过J-T阀14节流到约124kPaA后，又进入丙烷换热器CB-1第四段蒸发，以提供第四段预冷所需的冷量，蒸发后的丙烷返回到丙烷压缩机d C1-4，完成丙烷循环，丙烷循环利用四段不同压力的液态丙烷蒸发提供的冷量，将天然气和乙烷和氮气至-34℃进入乙烷换热器；低温的乙烷进入乙烷压缩机经三段压缩至1.5MPaA后，经过丙烷换热器冷却至-34℃后冷凝，然后依次经过J-T阀15节流到约495kPaA后分成两股，一股进入乙烷换热器CB-2第一段蒸发提供预冷第一段所需的冷量，蒸发后的乙烷返回乙烷压缩机a C2-1入口；另一股经过J-T阀16节流到约250kPaA后又分为两股，一股进入乙烷换热器第二段蒸发以提供预冷第二段所需的冷量，蒸发后的乙烷返回乙烷压缩机b C2-2入口，另一股再经过J-T阀17节流到约125kPaA，又进入乙烷换热器第三段蒸发，以提供第三段冷却所需的冷量，蒸发后的乙烷返回到乙烷压缩机c C2-3入口一段，完成乙烷循环，乙烷循环利用三段不同压力的液态乙烷蒸发提供的冷量，将天然气和甲烷和氮气至-81℃进入甲烷换热器；低温的甲烷进入甲烷压缩机经二段压缩至1.5MPaA后，经过甲烷经济器E3-3和乙烷换热器CB-2的冷却至-81℃，进入甲烷换热器CB-3冷却至-100℃抽出部分液体经过J-T阀19节流到约2360kPaA，提供第一段所需的冷量，然后经甲烷经济器E3-3加热后回到二级甲烷压缩机C3-2入口；剩余部分液体经甲烷换热器CB-3冷却至-140℃，经过J-T阀18节流换热后直接进入一级甲烷压缩机C3-1入口；天然气经过甲烷换热器CB-3冷却至约-140℃；低温的氮气进入氮气膨胀压缩机C4-2和氮气压缩机C4-1压缩至2.83MPaA后，水冷却到40℃，经过丙烷换热器CB-1的冷却至-34℃和乙烷换热器CB-2的冷却至-81℃，然后经氮气经济器E4-2冷却至-129℃膨胀到约600kPaA，给天然气提供过冷所需的冷量，然后经氮气经济器E4-2加热后回到氮气膨胀压缩机C4-2的入口；天然气经过氮气换热器冷却至约-155℃，过冷的天然气经过节流至-162℃进入LNG储罐。

Claims (4)

1.一种基荷型天然气液化工厂的级联式液化系统，其特征在于：所述液化系统包括丙烷换热器、乙烷换热器、甲烷换热器、氮气换热器、丙烷预冷循环机构、乙烷制冷循环机构、甲烷深冷循环机构和氮气深冷循环机构；
所述丙烷预冷循环机构包括三级压缩单元，所述三级压缩单元包括依次相连的丙烷压缩机a、丙烷压缩机b和丙烷压缩机c；所述三级压缩单元依次与丙烷气液分离罐a、丙烷气液分离罐b和丙烷气液分离罐c相连通；所述丙烷气液分离罐a、丙烷气液分离罐b和丙烷气液分离罐c的气相出口分别与所述丙烷压缩机a、丙烷压缩机b和丙烷压缩机c相连通，所述丙烷压缩机a、丙烷气液分离罐a、丙烷气液分离罐b和丙烷气液分离罐c之间均设有节流阀；所述丙烷压缩机a的出口与所述丙烷气液分离罐a之间设有丙烷压缩机末级冷凝器，该丙烷压缩机末级冷凝器设于所述节流阀的入口端；所述丙烷气液分离罐a、丙烷气液分离罐b和丙烷气液分离罐c均与所述丙烷换热器相连通；
所述乙烷制冷循环机构包括二级压缩单元，所述二级压缩单元包括依次相连的乙烷压缩机a和乙烷压缩机b；所述二级压缩单元依次与乙烷气液分离罐a和乙烷气液分离罐b相连通，且所述乙烷压缩机a通过管路与所述丙烷换热器相连通，并从所述丙烷换热器的顶部贯穿至其底部后引出，然后继续延伸与所述乙烷气液分离罐a相连通；所述乙烷气液分离罐a和乙烷气液分离罐b的气相出口分别与所述乙烷压缩机a和乙烷压缩机b相连通，所述乙烷压缩机a、乙烷气液分离罐a和乙烷气液分离罐b之间均设有节流阀；所述乙烷气液分离罐a和乙烷气液分离罐b均与所述乙烷换热器相连通；
所述甲烷深冷循环机构包括二级压缩单元，该二级压缩单元包括依次相连的一级甲烷压缩机、一级甲烷压缩机冷却器、二级甲烷压缩机和二级甲烷压缩机冷却器；所述二级甲烷压缩机冷却器的出口通过管路依次与甲烷经济器和乙烷换热器相连通，并从所述乙烷换热器的顶部贯穿至其底部后引出，该管路继续延伸至所述甲烷换热器并从所述甲烷换热器的顶部贯穿至其底部后引出，然后又与所述甲烷换热器的底部相连通，该连通处设有节流阀，所述管路继续延伸至所述甲烷换热器的顶部，然后从其顶部引出后与所述一级甲烷压缩机相连通；管路a与设于所述甲烷换热器内的管路相连通并从其侧部引出，然后所述管路a又与所述甲烷换热器的侧部相连通，该连通处设有节流阀，所述管路a继续延伸至所述甲烷换热器的顶部，然后从其顶部引出后依次与所述甲烷经济器和二级甲烷压缩机相连通；
所述氮气深冷循环机构包括依次连通的氮气膨胀压缩机、氮气压缩机和氮气压缩机冷却器；所述氮气压缩机冷却器的出口通过管路与丙烷换热器相连通，并从所述丙烷换热器的顶部贯穿至其底部后引出，该管路继续延伸至所述乙烷换热器并从其顶部贯穿至其底部后引出，然后依次与氮气经济器和氮气换热器相连通，该管路从所述氮气换热器的顶部引出后又依次与所述氮气经济器和氮气膨胀压缩机相连通。
2.根据权利要求1所述的级联式液化系统，其特征在于：所述丙烷预冷循环机构还包括依次与所述丙烷压缩机c相连接的丙烷压缩机d和丙烷气液分离罐d，所述丙烷气液分离罐d与丙烷气液分离罐c相连通，该连通处设有所述节流阀，所述丙烷气液分离罐d与所述丙烷换热器相连通。
3.根据权利要求1或2所述的级联式液化系统，其特征在于：所述乙烷制冷循环机构还包括与所述乙烷压缩机b相连接的乙烷压缩机c和乙烷气液分离罐c，所述乙烷气液分离罐c与乙烷气液分离罐b相连通，该连通处设有所述节流阀，所述乙烷气液分离罐c与所述乙烷换热器相连通。
4.根据权利要求1或2所述的级联式液化系统，其特征在于：所述节流阀为J/T阀。
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