WO2017093381A1 - Method of liquefying a contaminated hydrocarbon-containing gas stream - Google Patents

Method of liquefying a contaminated hydrocarbon-containing gas stream Download PDF

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Publication number
WO2017093381A1
WO2017093381A1 PCT/EP2016/079392 EP2016079392W WO2017093381A1 WO 2017093381 A1 WO2017093381 A1 WO 2017093381A1 EP 2016079392 W EP2016079392 W EP 2016079392W WO 2017093381 A1 WO2017093381 A1 WO 2017093381A1
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WO
WIPO (PCT)
Prior art keywords
stream
hydrocarbon
liquid
gaseous
enriched
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/EP2016/079392
Other languages
French (fr)
Inventor
Thijs Groenendijk
Raimo Edwin Gregor Poorte
Michiel Gijsbert VAN AKEN
Laurens Joseph Arnold Marie VAN CAMPEN
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Shell Internationale Research Maatschappij BV
Shell USA Inc
Original Assignee
Shell Internationale Research Maatschappij BV
Shell Oil Co
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Filing date
Publication date
Application filed by Shell Internationale Research Maatschappij BV, Shell Oil Co filed Critical Shell Internationale Research Maatschappij BV
Priority to AU2016363566A priority Critical patent/AU2016363566B2/en
Publication of WO2017093381A1 publication Critical patent/WO2017093381A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • F25J1/0032—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"
    • F25J1/004—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 flash gas recovery
    • 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
    • F25J1/0032—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
    • 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
    • F25J1/0032—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
    • 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
    • F25J1/0201—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 only internal refrigeration means, i.e. without external refrigeration
    • F25J1/0202—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 only internal refrigeration means, i.e. without external refrigeration in a quasi-closed internal 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
    • F25J1/0235—Heat exchange integration
    • F25J1/0237—Heat exchange integration integrating refrigeration provided for liquefaction and purification/treatment of the gas to be liquefied, e.g. heavy hydrocarbon removal from natural gas
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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
    • F25J3/06—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation
    • F25J3/0605—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation characterised by the feed stream
    • F25J3/061—Natural gas or substitute 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
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/06—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation
    • F25J3/063—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation characterised by the separated product stream
    • F25J3/0635—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation characterised by the separated product stream separation of CnHm with 1 carbon atom or more
    • 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
    • F25J3/06—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation
    • F25J3/063—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation characterised by the separated product stream
    • F25J3/0645—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation characterised by the separated product stream separation of CnHm with 3 carbon atoms or more
    • 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
    • F25J3/06—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation
    • F25J3/063—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation characterised by the separated product stream
    • F25J3/067—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation characterised by the separated product stream separation of carbon dioxide
    • 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
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/10—Processes or apparatus using other separation and/or other processing means using combined expansion and separation, e.g. in a vortex tube, "Ranque tube" or a "cyclonic fluid separator", i.e. combination of an isentropic nozzle and a cyclonic separator; Centrifugal separation
    • 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
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/20—Processes or apparatus using other separation and/or other processing means using solidification of components
    • 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
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/84—Processes or apparatus using other separation and/or other processing means using filter
    • 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
    • F25J2210/04—Mixing or blending of fluids with the feed 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
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/04—Recovery of liquid products
    • 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
    • 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
    • F25J2220/66—Separating acid gases, e.g. CO2, SO2, H2S or RSH
    • 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
    • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/30—Compression of the feed 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
    • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/60—Processes or apparatus involving steps for increasing the pressure of gaseous process streams the fluid being hydrocarbons or a mixture of hydrocarbons
    • 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
    • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
    • F25J2240/02—Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the 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
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/02—Recycle of a stream in general, e.g. a by-pass 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
    • 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
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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
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/04—Internal refrigeration with work-producing gas expansion loop
    • 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
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/88—Quasi-closed internal refrigeration or heat pump cycle, if not otherwise provided
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
    • Y02C20/00—Capture or disposal of greenhouse gases
    • Y02C20/40—Capture or disposal of greenhouse gases of CO2

Definitions

  • the present invention relates to a method of liquefying a hydrocarbon-containing gas stream, in particular a methane- containing gas stream such as natural gas.
  • hydrocarbon-containing gas stream is treated to remove one or more contaminants such as H20, C02, H2S and the like) which may freeze out during the liquefaction process.
  • W02014 /l 66925 describes a method of liquefying a
  • step (4) separating the partially liquefied stream 70 in a separator 5 thereby obtaining a gaseous stream 80 and a liquid stream 90; (5) expanding the liquid steam 90 obtained in step (4) thereby obtaining a multiphase stream 100, the multiphase stream 100 containing at least a vapour phase, a liquid phase and a solid phase;
  • step (10) combining the compressed gas stream 210 obtained in step (9) with the contaminated hydrocarbon-containing gas stream 20 provided in step (1) .
  • W02014 /l 66925 further describes and shows an optional methanol separator 17' .
  • the cooled contaminated hydrocarbon- containing stream 40 obtained in step (2) may be passed to the methanol separator 17' to separate methanol (as stream 50') that has been previously injected (e.g. into stream 20) to prevent hydrate formation.
  • An advantage of the method according to W02014/166925 is that it has a surprisingly simple design and can be
  • the application of the method is very flexible.
  • the method is in particular suitable for small scale operations (e.g. LNG production rate of about 0.1 mtpa) , but may also be applied at scale up to 4 mtpa.
  • liquid hydrocarbon product stream obtained in step (5) may have a different composition, e.g. containing more C02 (such as at least 250 ppm-mol) and more C5+ (such as above 0.1 mol%) than usual.
  • step (2) of WO2014166925 the contaminated
  • hydrocarbon-containing gas stream is cooled in a first heat exchanger thereby obtaining a cooled contaminated hydrocarbon-containing stream.
  • the heat exchanger is not particularly limited, but is preferably an indirect heat exchanger.
  • no solids are formed;
  • the cooled contaminated hydrocarbon-containing gas stream (40) is preferably free of solids.
  • the cooled contaminated hydrocarbon-containing gas stream is a gas stream possibly containing some liquid methanol, if previously injected.
  • the cooled contaminated hydrocarbon-containing stream obtained in step (2) has a temperature of at most -40°C, preferably at most -50°C, more preferably at most -60°C.
  • the exchanger is performed at a pressure that is higher than the cricondenbar .
  • the cricondenbar is the maximum pressure at which vapour and liquid phase can coexist. At higher
  • a method of liquefying a hydrocarbon-containing gas stream comprising at least the steps of:
  • the cooled hydrocarbon-containing stream (40) wherein the pressure of the cooled hydrocarbon-containing stream (40) is below the cricondenbar pressure of the mixture of hydrocarbons and contaminants, the cooled hydrocarbon- containing stream (40) being a liquid-vapour multiphase flow;
  • liquid bottom stream (50) being enriched in C3H— hydrocarbons ;
  • step (f) passing the liquid stream (90) obtained in step (e) to a pressure reduction and separation stage (91) to obtain one or more further gaseous streams (110, 180) and a liquid hydrocarbon stream (170) ,
  • step (g) passing the gaseous stream (80) obtained in step (e) through the first heat exchanger (3) thereby obtaining a heated gaseous stream (270) ;
  • step (i) combining at least part of the compressed gas stream (220) obtained in step (h) with the hydrocarbon-containing gas stream (20) provided in step (a);
  • step (j) passing the liquid bottom stream (50) being enriched in C3H—hydrocarbons obtained in step (c) to a NGL- fractionation stage to obtain a liquid product stream enriched in C3+ and one or more gaseous streams enriched in CI and/or C2;
  • step (k) compressing the one or more gaseous streams enriched in CI and/or C2 thereby obtaining one or more compressed gaseous stream enriched in CI and/or C2; (1) recycling the one or more compressed gaseous streams enriched in CI and/or C2 by adding at least part of the one or more compressed gaseous streams enriched in CI and/or C2 to the hydrocarbon-containing gas stream (20) provided in step (a) .
  • a system for liquefying a hydrocarbon-containing gas stream comprising:
  • a first heat-exchanger (3) arranged to receive the hydrocarbon containing gas stream from the feed conduit (20) and which is further arranged to cool the hydrocarbon- containing gas stream (20) and discharge a cooled
  • hydrocarbon-containing stream (40) wherein the pressure of the cooled hydrocarbon-containing stream (40) is below the cricondenbar pressure of the mixture of hydrocarbons and contaminants, the cooled hydrocarbon-containing stream (40) being a liquid-vapour multiphase flow;
  • a gas-liquid separator (17) arranged to receive the cooled hydrocarbon-containing stream (40) from the first heat exchanger (3) being arranged to separate the cooled
  • an expander (4) arranged to receive the gaseous top stream (60) and expand and thereby cool the gaseous top stream (60) thereby obtaining a partially liquefied stream (70) ;
  • a separator (5) arranged to receive the partially liquefied stream (70) and separate the partially liquefied stream (70) thereby obtaining a gaseous stream (80) and a liquid stream (90) ;
  • a pressure reduction and separation stage (91) arranged to receive the liquid stream (90) from the separator (5) further being arranged to obtain one or more further gaseous streams (110, 180) and a liquid hydrocarbon stream (170) from the liquid stream (90),
  • conduit (80) to pass the gaseous stream (80) obtained from the separator (5) to the first heat exchanger (3) and a conduit (270) to obtain a heated gaseous stream (270) from the first heat exchanger (3) ;
  • one or more compressors 13, 14 arranged to receive the heated gaseous stream (270) to obtain a compressed gas stream (220);
  • a combiner arranged to combine at least part of the compressed gas stream (220) with the hydrocarbon-containing gas stream (20) ;
  • system further comprises:
  • NGL-fractionation stage arranged to receive the liquid bottom stream (50) being enriched in C3H—hydrocarbons obtained from the gas-liquid separator (17), the NGL- fractionation stage being arranged to obtain a liquid product stream enriched in C3+ and one or more gaseous streams enriched in CI and/or C2 from the liquid bottom stream (50) being enriched in C3H—hydrocarbons;
  • one or more recycle conduits (330, 331) arranged to recycle the one or more gaseous streams enriched in CI and/or C2 to the one or more compressors (13, 14) .
  • the one or more gaseous streams enriched in CI and/or C2 are at least partially recycled by at least partially adding the one or more gaseous streams enriched in CI and/or C2 to the hydrocarbon-containing gas stream provided via feed conduit (20) .
  • the invention will be further illustrated by the following non-limiting drawing:
  • Fig. 6 schematically shows a phase-diagram of a typical mixture of hydrocarbons .
  • same reference numbers refer to same or similar components.
  • a single reference number will be used to identify a conduit or line as well as the stream conveyed by that line.
  • the embodiments described here disclose a method and system for liquefying a hydrocarbon-containing gas stream, in particular a methane-containing gas stream such as natural gas .
  • the method and system cool and liquefy a hydrocarbon- containing gas stream by expansion-cooling and self- refrigeration. Preferably, no use is made of refrigerant cycles.
  • the now proposed method and scheme allow separating the majority of the C3+-hydrocarbons from the hydrocarbon- containing gas stream within such a scheme.
  • Figures show systems and process schemes for performing a method of liquefying a hydrocarbon-containing gas stream.
  • the system and process scheme is generally referred to with reference number 1.
  • the process scheme 1 comprises a feed compressor 2, a heat exchanger 3 ("the first heat exchanger"), an expander 4, a first separator 5, a JT-valve 6, a second separator 7, a pump 8, a third (solid/liquid separator 9, an LNG storage tank 11, a C02 slurry heater 12, further compressors 13 and 14, a second heat exchanger 15, a second expander 16 and gas- liquid separator 17.
  • the process scheme may comprise further heat exchangers in addition to the first heat exchanger 3 and second heat exchanger 15.
  • the first heat exchanger in addition to the first heat exchanger 3 and second heat exchanger 15.
  • the first heat exchanger Preferably, the first heat
  • first heat exchanger 3 and second heat exchanger 15 are separate heat exchangers.
  • first heat exchanger 3 and second heat exchanger 15 are indirect heat exchangers in which the streams exchanging heat do not mix.
  • a hydrocarbon-containing gas stream 20 is provided (step a), which is cooled (step b) thereby creating a cooled hydrocarbon-containing stream 40 being a liquid-vapour multiphase flow.
  • the cooled hydrocarbon-containing stream 40 is separated to form a liquid bottom stream 50 and a gaseous top stream 60.
  • the liquid bottom stream 50 is enriched in C3+-hydrocarbons .
  • step (j) the liquid bottom stream enriched in C3H— hydrocarbons obtained in (c) is passed to a NGL-fractionation stage to obtain a liquid product stream enriched in C3+ and one or more gaseous streams enriched in CI and/or C2.
  • the liquid product stream enriched in C3+ can be passed to a suitable storage tank, can be sold separately or can be subject to further treatment and/or separation steps.
  • the storage tank may be a pressurized storage vessel.
  • the one or more gaseous streams enriched in CI and/or C2 can be recycled to be added to the hydrocarbon-containing gas stream (20) provided in step (a) .
  • Different embodiments will be described below with reference to Fig.'s 2 - 5.
  • a hydrocarbon dewpoint is achieved in stream 60 by operating a low temperature gas- liquid separator 17 to separate the cooled hydrocarbon- containing stream 40 in a liquid bottom stream 50 and a gaseous top stream 60 at a suitable pressure and temperature, i.e. gas-liquid separator 17 is operated at a pressure and temperature in the liquid-vapour regime of the phase
  • gas-liquid separator 17 is
  • a NGL-fractionation stage is operated at a suitable pressure and temperature to obtain a liquid product stream enriched in C3+ (liquid heavies stream) that satisfies the Reid Vapor Pressure specification (condensate sale product) .
  • the one or more gaseous streams enriched in CI and/or C2 obtained in step (j) are recycled back into the process preferably by integration with compressors already present in the process scheme.
  • the embodiments have the advantage that only the liquid bottom stream 50 enriched in C3H—hydrocarbons is let down in pressure in NGL-fractionation stage and only the one or more gaseous streams enriched in CI and/or C2 obtained in the NGL- fractionation stage need to be recompressed .
  • step (a) a hydrocarbon-containing gas stream (20) is provided, the hydrocarbon-containing gas stream comprising a mixture of hydrocarbons including CI, C2 and C3+- hydrocarbons , the mixture further comprising contaminants.
  • Ci refers to hydrocarbon molecules comprising i carbon atoms per molecule.
  • the hydrocarbon-containing gas stream is not particularly limited, it preferably is a methane-rich gas stream such as natural gas. According to a preferred
  • the hydrocarbon-containing gas stream comprises at least 50 mol% methane, preferably at least 80 mol%.
  • the hydrocarbon fraction of the hydrocarbon- containing gas stream comprises especially at least 75 mol% of methane, preferably at least 90 mol%.
  • the hydrocarbon fraction in the natural gas stream may suitably contain from between 0 and 10 mol% of C2+-hydrocarbons (i.e. hydrocarbons containing 2 or more carbon atoms per molecule) , preferably between 0 and 5 mol% of C2-C6 hydrocarbons, more preferably between 0.1 and 3 mol% of C2-C4 hydrocarbons, especially between 0.05 and 2 mol% of ethane.
  • the contaminant is also not particularly limited.
  • the contaminant is one or more of C02, H2S,
  • hydrocarbon-containing gas stream is suitably between 0.1 and 90 mol%, preferably above 0.5 mol% and preferably below 10 mol%.
  • the hydrocarbon-containing gas stream may have been treated.
  • the hydrocarbon-containing gas stream may be dehydrated to prevent hydrate formation in the subsequent cooling steps .
  • water e.g. more than 1 ppmv
  • methanol is injected into the hydrocarbon-containing gas stream to prevent the formation of hydrates.
  • the hydrocarbon-containing gas stream 20 as provided in step (a) has a pressure below the cricondenbar pressure of the mixture of hydrocarbons and contaminants, i.e. typically in the range of 60 - 100 bar.
  • the cricondenbar pressure Pc is defined as the maximum pressure at which vapour and liquid phase can coexist.
  • Fig. 6 schematically shows a phase-diagram of a typical mixture of hydrocarbons including CI, C2 and C3H—hydrocarbons, the mixture further comprising contaminants as provided in (a) .
  • the cricondenbar pressure Pc is indicated in Fig. 6.
  • Providing the hydrocarbon-containing gas stream 20 in step (a) may comprise compressing the hydrocarbon-containing gas stream to a pressure that does not exceed the
  • Providing the hydrocarbon-containing gas stream 20 in step (a) may comprise compressing the hydrocarbon-containing gas stream to a pressure such that the pressure of the cooled hydrocarbon-containing stream (40) is below the cricondenbar pressure of the mixture of hydrocarbons and contaminants
  • step (b) the hydrocarbon-containing gas stream (20) is cooled in a first heat exchanger (3) .
  • the heat exchanger is not particularly limited, but is preferably an indirect heat exchanger. This results in a cooled hydrocarbon- containing stream (40), wherein the pressure of the cooled hydrocarbon-containing stream (40) is below the cricondenbar pressure of the mixture of hydrocarbons and contaminants.
  • the cooling in the first heat exchanger 3 is controlled to ensure that the temperature of the cooled hydrocarbon-containing stream 40 is in the liquid-vapor regime. Consequently, substantially no solids are present in the cooled
  • hydrocarbon-containing stream 40 hydrocarbon-containing stream 40.
  • Controlling the cooling in the first heat exchanger 3 may for instance be done by controlling the flow rates of the streams entering the first heat exchanger 3 or when designing the first heat exchanger 3.
  • the pressure of the cooled hydrocarbon- containing stream (40) is at least 5 bar, preferably at least 10 bar below the cricondenbar pressure of the mixture of hydrocarbons and contaminants.
  • the pressure of the cooled hydrocarbon- containing stream is below 100 bar, preferably below 80 bar .
  • the method may comprise controlling the discharge pressure of the feed compressor 2 to ensure that the pressure of the cooled hydrocarbon-containing stream 40 is below the cricondenbar pressure. Controlling the discharge pressure of the feed compressor 2 may be done by a controller in response to a measured pressure of at least one of the cooled hydrocarbon-containing stream 40 is below the cricondenbar pressure. Controlling the discharge pressure of the feed compressor 2 may be done by a controller in response to a measured pressure of at least one of the cooled
  • hydrocarbon-containing stream 40 the hydrocarbon-containing gas stream 20 as provided in step (a) and the pressure inside gas-liquid separator 17.
  • step (a) comprises
  • hydrocarbon-containing gas stream (20) to provide the hydrocarbon-containing gas stream (20) at a pressure that is below the cricondenbar pressure of the mixture of
  • the temperature of the cooled hydrocarbon- containing stream 40 is selected and controlled such that the cooled hydrocarbon-containing stream 40 is in the liquid- vapour regime of the phase envelope.
  • the cooled hydrocarbon-containing stream 40 comprises more than 2 mol% liquid phase .
  • the cooled hydrocarbon-containing stream obtained in step (b) has a temperature of at most -40°C, preferably at most -50°C, more preferably at most -60°C.
  • the cooled hydrocarbon-containing stream (40) is a liquid-vapour multiphase flow.
  • the cooled hydrocarbon-containing stream (40) being a liquid-vapour multiphase flow obtained in (b) comprises a liquid fraction in the range of 1 - 10 massl.
  • the mass% is defined with respect to the cooled hydrocarbon- containing stream 40 representing 100%.
  • the liquid fraction is 5 mass%, pressure is below 80 bar and temperature is between -80°C and - 40°C.
  • step (c) the cooled hydrocarbon-containing stream (40) is separated in a liquid bottom stream (50) and a gaseous top stream (60), the liquid bottom stream (50) being enriched in C3H—hydrocarbons .
  • step (c) can be performed with any suitable gas-liquid separator, shown in the figures as gas- liquid separator 17.
  • the gas-liquid separator 17 may be a distillation column or a knock-out vessel, from which the liquid stream 50 is obtained as bottom stream and the gaseous stream 60 is obtained as top stream.
  • the liquid bottom stream 50 is enriched in C3H—
  • hydrocarbons and the gaseous top stream 60 is depleted in C3+ .
  • enriched is used to indicate that the mol fraction of the indicated component in the enriched stream is higher than the mol fraction of the indicated component in the stream from which the enriched stream is obtained.
  • deriched or depleted is used to indicate that the mol fraction of the indicated component in the deriched or depleted stream is lower than the mol fraction of the indicated component in the stream from which the
  • the cooled hydrocarbon- containing gas stream 40 may be subjected to a methanol separation step before being cooled in the expander in step
  • a vessel comprising a weir from which the gaseous stream 60 is obtained as top stream
  • the liquid bottom stream 50 is obtained downstream of the weir
  • a water-methanol is obtained upstream of the weir.
  • step (d) the gaseous top stream (60) is cooled in an expander (4) thereby obtaining a partially liquefied stream (70) .
  • step (e) the partially liquefied stream (70) is separated in a separator (5) thereby obtaining a gaseous stream (80) and a liquid stream (90) .
  • step (f) the liquid stream (90) is passed to a pressure reduction and separation stage to obtain one or more gaseous streams (110, 180) and a liquid hydrocarbon stream (170) .
  • Step (f) may be embodied in different ways. Below an example of step (f) will be described with reference to the figures, but it will be understood that alternative
  • step (f) can be implemented instead.
  • Step (f) may be embodied by the following
  • multiphase stream (100) containing at least a vapour phase, a liquid phase and a solid phase;
  • step (fl) the liquid stream obtained in step (e) is expanded thereby obtaining a multiphase stream 100.
  • Step (fl) may involve an expander, such as a (throttle) valve 6.
  • the multiphase stream 100 contains at least 20 mol% vapour.
  • the expander 6 as used in step (fl) is not particularly limited (and may include a JT valve an orifice, a liquid-expander, etc.), it is preferred that in the expander enthalpy is withdrawn from the cooled hydrocarbon- containing gas stream.
  • a suitable expander for withdrawing enthalpy whilst expanding is a liquid expander.
  • the cooled hydrocarbon-containing gas stream as fed into the expander 4 has a pressure of from 40 to 100 bara, more preferably from 60 to 80 bara.
  • the multiphase stream as removed from the expander 4 typically has a pressure of from 10 to 30 bara, preferably between 17 and 25 bara.
  • the multiphase stream obtained in step (fl) has a temperature of at most -100 °C (i.e. not warmer than - 100°C), preferably at most -120°C, more preferably at most - 140°C, most preferably at most -150°C.
  • step (f2) the multiphase stream is separated in a separator 7 thereby obtaining a gaseous stream 110 and a C02 slurry stream 120. It is preferred that the slurry stream 120 obtained in step (f2) is pressurized, e.g. using pump 8, before being separated in step (f3), to minimize vapour generation in the solid/liquid separator 9 in step (f3) .
  • pressurizing the slurry stream obtained in step (f2) prevents solids formation in a pressurized storage vessel (if any) in which the liquid hydrocarbon stream obtained in step (f3) is stored.
  • the slurry stream is pumped to at least 6 bara.
  • step (f3) the slurry stream 140 is separated in a solid/liquid separator 9 thereby obtaining a liquid
  • the concentrated slurry stream 140 is rich in contaminants.
  • the concentrated slurry stream 140 may comprise more than one contaminant.
  • the concentrated slurry stream 140 usually contains at least 20 mol% contaminant ( s ) and at most 80 mol% methane. If (one of) the contaminant ( s ) in the concentrated slurry stream is C02, then the concentrated slurry stream 140 preferably comprises at least 25 mol% C02.
  • the concentrated slurry stream 140 is heated to melt and/or evaporate the contaminant ( s ) .
  • the concentrated slurry stream 140 is melted (preferably in a heated vessel) to obtain a liquid contaminant stream 160 and a gaseous contaminant stream 150.
  • the gaseous contaminant stream 150 may still comprise some hydrocarbons, it may be recycled to be used as (part of) a fuel stream.
  • step (f) is an example and alternative pressure reduction and separation stages may be used.
  • a pressure reduction and separation stage may be used in which use is made of a direct contact heat exchanger to cool the liquid stream and obtain a multiphase stream comprising a liquid phase and a solid C02 phase, a solid liquid separator to obtain a C02 depleted liquid stream from the multiphase stream, a further cooling, pressure reduction and separation stage to generate a further C02 enriched slurry stream, in which at least part of the further C02 enriched slurry stream is passed to the direct contact heat exchanger to provide cooling duty to and mix with the - Il ⁇ liquid stream 90.
  • Upstream of direct contact heat exchanger may be a (throttle) valve.
  • multiphase stream (100) containing at least a liquid phase and a solid phase
  • a pressure reduction and separation stage may be used in which use is made of a crystallization chamber.
  • the pressure reduction and separation stage may comprise
  • step (fl'') expanding the liquid stream (90) obtained in step (e) thereby obtaining a multiphase stream (100), the multiphase stream (100) containing at least a vapour phase, a liquid phase and a solid phase;
  • step (g) the gaseous stream (80) obtained in step (e) is passed through the first heat exchanger (3) thereby obtaining a heated gaseous stream 270.
  • the heated gaseous stream 270 typically comprises at least 80 mol% methane and at most 20 mol% N2.
  • step (h) the heated gaseous stream 270 is compressed thereby obtaining a compressed gas stream 220. Compression is done by compressor 13.
  • step (i) at least part of the compressed gas stream 220 obtained in step (h) is combined with the hydrocarbon-containing gas stream 20 provided in step (a) . This may be done with a combiner, which may be embodied in any suitable manner, such as by T-piece or the like .
  • step (g) is compressed to a pressure equal to the pressure of the hydrocarbon-containing gas stream (20) provided in step (a), to allow combination of therewith.
  • An advantage of combining the (lean) heated gaseous stream with the hydrocarbon- containing gas stream 20 is that the contaminant level in stream 30 is lower than that in stream 20, allowing operating separator 5 at lower temperature, thus increasing the LNG yield.
  • the contaminated hydrocarbon-containing gas stream provided in step (a) has typically been compressed by feed compressor 2 before being cooled in step (b) and combined in step (i) .
  • the method further comprises cooling a part (240) of the compressed gas stream (220) obtained in step (h) through a second heat exchanger (15) thereby obtaining a cooled compressed gas stream (250);
  • Expansion of the cooled compressed gas stream 250 thereby obtaining an expanded gas stream 260 is done by a second expander 16.
  • the second expander 16 is not limited (and may include a JT valve, an orifice, an
  • the method further comprises
  • step (f) comprises: passing one of the gaseous streams (110) obtained in step (f) through the second heat exchanger (15) thereby obtaining a second heated gaseous stream (200); compressing the second heated gaseous stream (200) thereby obtaining a second compressed gas stream (210); and combining the second compressed gas stream (210) with the heated gaseous stream (270) obtained in step (g) .
  • Compressing the second heated gaseous stream 200 may be done by a compressor 14.
  • step (j) the liquid bottom stream (50) being enriched in C3H—hydrocarbons obtained in step (c) is passed to a NGL- fractionation stage to obtain a liquid product stream enriched in C3+ and one or more gaseous streams enriched in CI and/or C2.
  • NGL-fractionation stage refers to a Natural Gas
  • the NGL-fractionation stage can be embodied in different manners but serves to separate the majority of the C3+ molecules from the liquid bottom stream 50 to be discharged and to retrieve CI and/or C2 molecules from the liquid bottom stream 50 to be recycled.
  • the NGL-fractionation stage may comprise a single separator such as a distillation column (e.g. Fig.'s 2, 3) .
  • the NGL-fractionation stage may alternatively comprise a plurality of distillation columns positioned in series (e.g. Fig. 4, 5), each distillation column being arranged to separate a different Ci-molecule.
  • Such separators positioned in series are usually referred to as a demethanizer and a de-ethanizer .
  • one or more gaseous streams enriched in CI and/or C2 are obtained.
  • one distillation column typically one gaseous stream enriched in CI and C2 is obtained;
  • two distillation column in series typically one gaseous stream enriched in CI and one gaseous stream enriched in C2 are obtained .
  • step (k) the one or more gaseous streams enriched in CI and/or C2 are compressed, thereby obtaining one or more compressed gaseous stream enriched in CI and/or C2.
  • Compression may at least partially be done using further compressors 13 and 14, which are also used to compress
  • step (f) one or more of the gaseous streams (110, 180) obtained in step (f) .
  • step (1) the one or more compressed gaseous streams enriched in CI and/or C2 are recycled to be comprised in the hydrocarbon-containing gas stream (20) provided in step (a) .
  • Fig.'s 2 - 5 show different embodiments of embodying the
  • step (j) comprises
  • step (jl) passing the liquid bottom stream (50) being enriched in C3H—hydrocarbons obtained in step (c) through a pressure reduction device (300) and subsequently
  • a separator such as a distillation column or gravity based separator.
  • the pressure reduction device 300 is preferably a valve, such as a Joule Thomson valve.
  • the pressure reduction device 300 serves to control the Reid Vapour Pressure of the liquid product stream enriched in C3+ (340) .
  • step (j2) comprises obtaining the liquid product stream enriched in C3+ (340) as bottom stream from the separator (320) and obtaining a gaseous stream (330) enriched in CI and C2 as top stream from the separator (320) .
  • the gaseous stream 330 enriched in CI and C2 is recycled in an advantageous manner by adding this stream to the hydrocarbon-containing gas stream 20 which is passed to the first heat exchanger 3.
  • step (1) comprises recycling the gas stream (330) enriched in CI and C2 obtained in step (j2) by adding the gas stream (330) enriched in CI and C2 obtained in step (j2) to the second heated gaseous stream (200) .
  • This has the advantage that the C1/C2 can be recovered as LNG .
  • Fig. 4 and 5 show an alternative embodiment of embodying steps (j), (k) and (1), i.e. by providing a NGL-fractionation stage comprising two separators.
  • step (j2) comprises obtaining a gaseous stream (330') enriched in CI as top stream from the separator (320) and obtaining a liquid stream (323) as bottom stream from the separator (320), the method further comprising
  • distillation column or gravity based separator to obtain the liquid product stream enriched in C3+ (340) as bottom stream from the further separator (321) and obtaining a gaseous stream (331) enriched in C2 as top stream from the further separator (321) .
  • Fig. 4 further depicts an advantageous embodiment of recycling both the gaseous stream (330') enriched in CI and the gaseous stream (331) enriched in C2.
  • the advantage is that the operating pressure of separators 320 and 321 are matched to the suction pressures of compressors 13 and 14 already present in the system, respectively, as this
  • step (1) comprises
  • step (j2) adding the gaseous stream (330' ) enriched in CI obtained as top stream from the separator (320) in step (j2) to the second compressed gas stream (210), and
  • step (j4) adding the gaseous stream (331) enriched in C2 obtained as top stream from the further separator (321) in step (j4) to the second heated gaseous stream (200) .
  • Embodiments comprising a third heat exchanger are shown in Fig. 3 and 5, where Fig. 3 is a variation of Fig. 2 and Fig. 5 is a variation of Fig. 4.
  • step (j) comprises passing at least part of the liquid bottom stream (50) being enriched in C3H—hydrocarbons obtained in step (c) through a third heat exchanger (310) to obtain a cooled liquid bottom stream (50) being enriched in C3+-hydrocarbons .
  • the third heat exchanger 310 is preferably positioned upstream of the single separator
  • the cooled liquid bottom stream (50) being enriched in C3H— hydrocarbons is passed to the separator 320.
  • An example of such an embodiment is depicted in Fig. 3.
  • the third heat exchanger 310 is preferably positioned in the fluid
  • liquid stream 323 obtained as bottom stream from the separator 320 is passed to the third heat exchanger 310.
  • exchanger 310 is obtained from one of the processing streams and without introducing the need for a separate refrigerant and refrigerant cycle.
  • the method further comprises obtaining a split stream (81) from the gaseous stream (80) obtained in step (e) and pass the split stream (81) through the third heat exchanger (310) to provide cooling duty to the at least part of the liquid bottom stream (50) being enriched in C3H—hydrocarbons that is passed through the third heat exchanger .
  • the method may further comprise storing the liquid hydrocarbon stream 170 obtained in step (f) in a LNG storage tank 11, obtaining a boil-off gas stream 180 from the LNG storage tank 11 and combining the boil-off gas stream 180 with one of the one or more gaseous streams enriched in CI and/or C2 obtained from the NGL-fractionation stage. This may be part of step (f ) .
  • the boil-off gas stream 180 may be compressed separately and sent to a fuel system.
  • the operating pressure of the separators 320, 321 used in the NGL- fractionation stage are selected to match the suction pressures of the compressors 13, 14 used to compress heated gaseous stream (270) obtained in step (g) and second heated gaseous stream (200) obtained from the second heat exchanger 15.

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Abstract

The present invention provides a method for liquefying a hydrocarbon-containing gas stream, comprising cooling the hydrocarbon-containing gas stream (20) in a first heat exchanger (3), wherein the pressure of the cooled hydrocarbon-containing stream (40) is below the cricondenbar being a liquid-vapour multiphase flow and is separated in a liquid bottom stream (50) and a gaseous top stream (60). The gaseous top stream (60) is cooled in an expander (4) and separated in a separator (5) obtaining a gaseous stream (80) and a liquid stream (90). The liquid stream (90) is passed to a pressure reduction and separation stage (91) to obtain one or more further gaseous streams (110, 180) and a liquid hydrocarbon stream (170). The gaseous stream (80) is passed through the first heat exchanger (3) and a compressor obtaining a compressed gas stream (220). At least part of the compressed gas stream (220) obtained in step (h) is combined with the hydrocarbon-containing gas stream (20) provided in step (a). The liquid bottom stream (50) enriched in C3+-hydrocarbons is passed to a NGL-fractionation stage to obtain one or more gaseous streams enriched in C1 and/or C2 which are recycled to at least partially be combined with the hydrocarbon-containing gas stream (20).

Description

METHOD OF LIQUEFYING A CONTAMINATED HYDROCARBON- CONTAINING GAS STREAM
The present invention relates to a method of liquefying a hydrocarbon-containing gas stream, in particular a methane- containing gas stream such as natural gas.
Methods of liquefying hydrocarbon-containing gas streams are well known in the art. It is desirable to liquefy a hydrocarbon-containing gas stream such as natural gas stream for a number of reasons. As an example, natural gas can be stored and transported over long distances more readily as a liquid than in gaseous form, because it occupies a smaller volume and does not need to be stored at high pressures.
Typically, before being liquefied, the contaminated
hydrocarbon-containing gas stream is treated to remove one or more contaminants such as H20, C02, H2S and the like) which may freeze out during the liquefaction process.
W02014 /l 66925 describes a method of liquefying a
contaminated hydrocarbon-containing gas stream, a process scheme of which is schematically depicted in Fig. 1. The method comprising at least the steps of:
(1) providing a contaminated hydrocarbon-containing gas stream 20;
(2) cooling the contaminated hydrocarbon-containing gas stream in a first heat exchanger 3 thereby obtaining a cooled contaminated hydrocarbon-containing stream 40;
(3) cooling the cooled contaminated hydrocarbon- containing stream 40 in an expander 4 thereby obtaining a partially liquefied stream 70;
(4) separating the partially liquefied stream 70 in a separator 5 thereby obtaining a gaseous stream 80 and a liquid stream 90; (5) expanding the liquid steam 90 obtained in step (4) thereby obtaining a multiphase stream 100, the multiphase stream 100 containing at least a vapour phase, a liquid phase and a solid phase;
(6) separating the multiphase stream in a separator 7 thereby obtaining a gaseous stream 110 and a slurry stream 120 (comprising solid C02 and liquid hydrocarbons);
(7) separating the slurry stream 120 in a solid/liquid separator 9 thereby obtaining a liquid hydrocarbon stream 170 and a concentrated slurry stream 140;
(8) passing the gaseous stream 80 obtained in step (4) through the first heat exchanger 3 thereby obtaining a heated gaseous stream 200; and
(9) compressing the heated gaseous stream 200 thereby obtaining a compressed gas stream 210; and
(10) combining the compressed gas stream 210 obtained in step (9) with the contaminated hydrocarbon-containing gas stream 20 provided in step (1) .
W02014 /l 66925 further describes and shows an optional methanol separator 17' . The cooled contaminated hydrocarbon- containing stream 40 obtained in step (2) may be passed to the methanol separator 17' to separate methanol (as stream 50') that has been previously injected (e.g. into stream 20) to prevent hydrate formation.
The further elements of Fig. 1 will be discussed in more detail below with reference to Fig.'s 2 - 5.
An advantage of the method according to W02014/166925 is that it has a surprisingly simple design and can be
standardized to treat and liquefy a wide range of feed gas compositions. Further, there is relatively limited utility and chemicals requirement resulting in a significant OPEX and CAPEX reduction. Furthermore, the design is more robust with respect to trace contaminants such as rust and oil particles, compared to designs with amine treating systems.
As the method according to W02014 /l 66925 does not require connection to the grid (as the gaseous stream obtained in step (4) is combined with the contaminated hydrocarbon- containing stream provided in step (1)), the application of the method is very flexible. The method is in particular suitable for small scale operations (e.g. LNG production rate of about 0.1 mtpa) , but may also be applied at scale up to 4 mtpa.
An important aspect of W02014/166925 is that the liquid hydrocarbon product stream obtained in step (5) may have a different composition, e.g. containing more C02 (such as at least 250 ppm-mol) and more C5+ (such as above 0.1 mol%) than usual.
In step (2) of WO2014166925, the contaminated
hydrocarbon-containing gas stream is cooled in a first heat exchanger thereby obtaining a cooled contaminated hydrocarbon-containing stream. The heat exchanger is not particularly limited, but is preferably an indirect heat exchanger. Preferably, in step (2) no solids are formed;
hence, the cooled contaminated hydrocarbon-containing gas stream (40) is preferably free of solids. Typically, the cooled contaminated hydrocarbon-containing gas stream is a gas stream possibly containing some liquid methanol, if previously injected.
According to WO2014166925 the cooled contaminated hydrocarbon-containing stream obtained in step (2) has a temperature of at most -40°C, preferably at most -50°C, more preferably at most -60°C.
The process scheme according to WO2014166925 is operated such that the precooling in the first heat
exchanger is performed at a pressure that is higher than the cricondenbar . The cricondenbar is the maximum pressure at which vapour and liquid phase can coexist. At higher
pressures than the cricondenbar pressure, dense phase conditions occur.
This has the advantage that the precooling in the first heat exchanger operates with a single phase flow.
However, this has the drawback that all C3+-hydrocarbons (i.e. hydrocarbons containing 3 or more carbon atoms per molecule) end up in the LNG product stream thereby possibly leading to a (too) high Gross Heating Value (GHV) of the LNG product. This makes the process according to WO2014166925 unsuitable for processing relatively rich hydrocarbon- containing gas streams as this would result in off-spec LNG. The process according to WO2014166925 does not allow
controlling the composition of the LNG, hence its gross heating value.
So, it is an object to provide a method and system for liquefying a hydrocarbon-containing gas stream, in particular of the type described in WO2014166925, that i s bett e r suitable for treating rich hydrocarbon-containing gas streams comprising more C3H—hydrocarbons than are allowed in the LNG.
According to an aspect there is provided a method of liquefying a hydrocarbon-containing gas stream, the method comprising at least the steps of:
(a) providing a hydrocarbon-containing gas stream (20) , the hydrocarbon-containing gas stream comprising a mixture of hydrocarbons including CI, C2 and C3H— hydrocarbons;
(b) cooling the hydrocarbon-containing gas stream (20) in a first heat exchanger (3) thereby obtaining a
cooled hydrocarbon-containing stream (40) , wherein the pressure of the cooled hydrocarbon-containing stream (40) is below the cricondenbar pressure of the mixture of hydrocarbons and contaminants, the cooled hydrocarbon- containing stream (40) being a liquid-vapour multiphase flow;
(c) separating the cooled hydrocarbon-containing stream (40) in a liquid bottom stream (50) and a gaseous top stream
(60) , the liquid bottom stream (50) being enriched in C3H— hydrocarbons ;
(d) cooling the gaseous top stream (60) in an expander (4) thereby obtaining a partially liquefied stream (70) ;
(e) separating the partially liquefied stream (70) in a separator (5) thereby obtaining a gaseous stream (80) and a liquid stream (90) ;
(f) passing the liquid stream (90) obtained in step (e) to a pressure reduction and separation stage (91) to obtain one or more further gaseous streams (110, 180) and a liquid hydrocarbon stream (170) ,
(g) passing the gaseous stream (80) obtained in step (e) through the first heat exchanger (3) thereby obtaining a heated gaseous stream (270) ;
(h) compressing the heated gaseous stream (270) thereby obtaining a compressed gas stream (220) ; and
(i) combining at least part of the compressed gas stream (220) obtained in step (h) with the hydrocarbon-containing gas stream (20) provided in step (a);
wherein the method further comprises:
(j) passing the liquid bottom stream (50) being enriched in C3H—hydrocarbons obtained in step (c) to a NGL- fractionation stage to obtain a liquid product stream enriched in C3+ and one or more gaseous streams enriched in CI and/or C2;
(k) compressing the one or more gaseous streams enriched in CI and/or C2 thereby obtaining one or more compressed gaseous stream enriched in CI and/or C2; (1) recycling the one or more compressed gaseous streams enriched in CI and/or C2 by adding at least part of the one or more compressed gaseous streams enriched in CI and/or C2 to the hydrocarbon-containing gas stream (20) provided in step (a) .
According to a further aspect there is provided a system for liquefying a hydrocarbon-containing gas stream, the system comprising:
- a feed conduit (20) for providing a hydrocarbon- containing gas stream, the hydrocarbon-containing gas stream comprising a mixture of hydrocarbons including CI, C2 and C3H— hydrocarbons;
- a first heat-exchanger (3) arranged to receive the hydrocarbon containing gas stream from the feed conduit (20) and which is further arranged to cool the hydrocarbon- containing gas stream (20) and discharge a cooled
hydrocarbon-containing stream (40), wherein the pressure of the cooled hydrocarbon-containing stream (40) is below the cricondenbar pressure of the mixture of hydrocarbons and contaminants, the cooled hydrocarbon-containing stream (40) being a liquid-vapour multiphase flow;
- a gas-liquid separator (17) arranged to receive the cooled hydrocarbon-containing stream (40) from the first heat exchanger (3) being arranged to separate the cooled
hydrocarbon-containing stream (40) in a liquid bottom stream (50) and a gaseous top stream (60), the liquid bottom stream (50) being enriched in C3H—hydrocarbons;
- an expander (4) arranged to receive the gaseous top stream (60) and expand and thereby cool the gaseous top stream (60) thereby obtaining a partially liquefied stream (70) ;
- a separator (5) arranged to receive the partially liquefied stream (70) and separate the partially liquefied stream (70) thereby obtaining a gaseous stream (80) and a liquid stream (90) ;
- a pressure reduction and separation stage (91) arranged to receive the liquid stream (90) from the separator (5) further being arranged to obtain one or more further gaseous streams (110, 180) and a liquid hydrocarbon stream (170) from the liquid stream (90),
- conduit (80) to pass the gaseous stream (80) obtained from the separator (5) to the first heat exchanger (3) and a conduit (270) to obtain a heated gaseous stream (270) from the first heat exchanger (3) ; and
- one or more compressors (13, 14) arranged to receive the heated gaseous stream (270) to obtain a compressed gas stream (220); and
- a combiner arranged to combine at least part of the compressed gas stream (220) with the hydrocarbon-containing gas stream (20) ;
wherein the system further comprises:
- a NGL-fractionation stage arranged to receive the liquid bottom stream (50) being enriched in C3H—hydrocarbons obtained from the gas-liquid separator (17), the NGL- fractionation stage being arranged to obtain a liquid product stream enriched in C3+ and one or more gaseous streams enriched in CI and/or C2 from the liquid bottom stream (50) being enriched in C3H—hydrocarbons;
- one or more recycle conduits (330, 331) arranged to recycle the one or more gaseous streams enriched in CI and/or C2 to the one or more compressors (13, 14) .
This way the one or more gaseous streams enriched in CI and/or C2 are at least partially recycled by at least partially adding the one or more gaseous streams enriched in CI and/or C2 to the hydrocarbon-containing gas stream provided via feed conduit (20) . Hereinafter the invention will be further illustrated by the following non-limiting drawing:
Fig.'s 2 - 5 schematically show process schemes
according to different embodiments,
Fig. 6 schematically shows a phase-diagram of a typical mixture of hydrocarbons .
For the purpose of this description, same reference numbers refer to same or similar components. Furthermore, a single reference number will be used to identify a conduit or line as well as the stream conveyed by that line. The embodiments described here disclose a method and system for liquefying a hydrocarbon-containing gas stream, in particular a methane-containing gas stream such as natural gas . The method and system, as will be explained in more detail further below, cool and liquefy a hydrocarbon- containing gas stream by expansion-cooling and self- refrigeration. Preferably, no use is made of refrigerant cycles. The now proposed method and scheme allow separating the majority of the C3+-hydrocarbons from the hydrocarbon- containing gas stream within such a scheme.
Different embodiments are shown in and will be described in detail below with reference to Figures 2 - 5. These
Figures show systems and process schemes for performing a method of liquefying a hydrocarbon-containing gas stream. The system and process scheme is generally referred to with reference number 1.
The process scheme 1 comprises a feed compressor 2, a heat exchanger 3 ("the first heat exchanger"), an expander 4, a first separator 5, a JT-valve 6, a second separator 7, a pump 8, a third (solid/liquid separator 9, an LNG storage tank 11, a C02 slurry heater 12, further compressors 13 and 14, a second heat exchanger 15, a second expander 16 and gas- liquid separator 17. The process scheme may comprise further heat exchangers in addition to the first heat exchanger 3 and second heat exchanger 15. Preferably, the first heat
exchanger 3 and second heat exchanger 15 are separate heat exchangers. Preferably, the first heat exchanger 3 and second heat exchanger 15 are indirect heat exchangers in which the streams exchanging heat do not mix.
A hydrocarbon-containing gas stream 20 is provided (step a), which is cooled (step b) thereby creating a cooled hydrocarbon-containing stream 40 being a liquid-vapour multiphase flow. The cooled hydrocarbon-containing stream 40 is separated to form a liquid bottom stream 50 and a gaseous top stream 60. The liquid bottom stream 50 is enriched in C3+-hydrocarbons .
In step (j) the liquid bottom stream enriched in C3H— hydrocarbons obtained in (c) is passed to a NGL-fractionation stage to obtain a liquid product stream enriched in C3+ and one or more gaseous streams enriched in CI and/or C2.
The liquid product stream enriched in C3+ can be passed to a suitable storage tank, can be sold separately or can be subject to further treatment and/or separation steps. The storage tank may be a pressurized storage vessel.
The one or more gaseous streams enriched in CI and/or C2 can be recycled to be added to the hydrocarbon-containing gas stream (20) provided in step (a) . Different embodiments will be described below with reference to Fig.'s 2 - 5.
Compared to WO2014 /l 66925 a hydrocarbon dewpoint is achieved in stream 60 by operating a low temperature gas- liquid separator 17 to separate the cooled hydrocarbon- containing stream 40 in a liquid bottom stream 50 and a gaseous top stream 60 at a suitable pressure and temperature, i.e. gas-liquid separator 17 is operated at a pressure and temperature in the liquid-vapour regime of the phase
envelope .
It is noted that the gas-liquid separator 17 is
different from the optional methanol separator 17' described in W02014/166925. It will be understood that a separate methanol separator (not shown) may still be provided or a three-phase separator 17 may be provided, as described in more detail below.
Furthermore, a NGL-fractionation stage is operated at a suitable pressure and temperature to obtain a liquid product stream enriched in C3+ (liquid heavies stream) that satisfies the Reid Vapor Pressure specification (condensate sale product) .
The one or more gaseous streams enriched in CI and/or C2 obtained in step (j) are recycled back into the process preferably by integration with compressors already present in the process scheme.
The embodiments have the advantage that only the liquid bottom stream 50 enriched in C3H—hydrocarbons is let down in pressure in NGL-fractionation stage and only the one or more gaseous streams enriched in CI and/or C2 obtained in the NGL- fractionation stage need to be recompressed .
The different steps will now be described in more detail .
In step (a) a hydrocarbon-containing gas stream (20) is provided, the hydrocarbon-containing gas stream comprising a mixture of hydrocarbons including CI, C2 and C3+- hydrocarbons , the mixture further comprising contaminants.
The terms CI, C2 etc. are known to the skilled person. Ci refers to hydrocarbon molecules comprising i carbon atoms per molecule.
Although the hydrocarbon-containing gas stream is not particularly limited, it preferably is a methane-rich gas stream such as natural gas. According to a preferred
embodiment, the hydrocarbon-containing gas stream comprises at least 50 mol% methane, preferably at least 80 mol%.
Preferably, the hydrocarbon fraction of the hydrocarbon- containing gas stream comprises especially at least 75 mol% of methane, preferably at least 90 mol%. The hydrocarbon fraction in the natural gas stream may suitably contain from between 0 and 10 mol% of C2+-hydrocarbons (i.e. hydrocarbons containing 2 or more carbon atoms per molecule) , preferably between 0 and 5 mol% of C2-C6 hydrocarbons, more preferably between 0.1 and 3 mol% of C2-C4 hydrocarbons, especially between 0.05 and 2 mol% of ethane.
The contaminant is also not particularly limited.
Typically, the contaminant is one or more of C02, H2S,
H20, C6+ hydrocarbons, aromatic compounds, but is in
particular C02.
The amount of contaminant in the contaminated
hydrocarbon-containing gas stream is suitably between 0.1 and 90 mol%, preferably above 0.5 mol% and preferably below 10 mol%.
Before cooling in step (b) , the hydrocarbon-containing gas stream may have been treated. As an example, if the hydrocarbon-containing gas stream contains water (e.g. more than 1 ppmv) , then the hydrocarbon-containing gas stream may be dehydrated to prevent hydrate formation in the subsequent cooling steps . As the person skilled in the art is familiar with dehydration of gas streams (e.g. using adsorption by desiccants) this is not further discussed here. Preferably, methanol is injected into the hydrocarbon-containing gas stream to prevent the formation of hydrates.
According to the embodiments, the hydrocarbon-containing gas stream 20 as provided in step (a) has a pressure below the cricondenbar pressure of the mixture of hydrocarbons and contaminants, i.e. typically in the range of 60 - 100 bar.
The cricondenbar pressure Pc is defined as the maximum pressure at which vapour and liquid phase can coexist. Fig. 6 schematically shows a phase-diagram of a typical mixture of hydrocarbons including CI, C2 and C3H—hydrocarbons, the mixture further comprising contaminants as provided in (a) . The cricondenbar pressure Pc is indicated in Fig. 6.
Providing the hydrocarbon-containing gas stream 20 in step (a) may comprise compressing the hydrocarbon-containing gas stream to a pressure that does not exceed the
cricondenbar pressure.
Providing the hydrocarbon-containing gas stream 20 in step (a) may comprise compressing the hydrocarbon-containing gas stream to a pressure such that the pressure of the cooled hydrocarbon-containing stream (40) is below the cricondenbar pressure of the mixture of hydrocarbons and contaminants
In step (b) the hydrocarbon-containing gas stream (20) is cooled in a first heat exchanger (3) . The heat exchanger is not particularly limited, but is preferably an indirect heat exchanger. This results in a cooled hydrocarbon- containing stream (40), wherein the pressure of the cooled hydrocarbon-containing stream (40) is below the cricondenbar pressure of the mixture of hydrocarbons and contaminants. The cooling in the first heat exchanger 3 is controlled to ensure that the temperature of the cooled hydrocarbon-containing stream 40 is in the liquid-vapor regime. Consequently, substantially no solids are present in the cooled
hydrocarbon-containing stream 40.
Controlling the cooling in the first heat exchanger 3 may for instance be done by controlling the flow rates of the streams entering the first heat exchanger 3 or when designing the first heat exchanger 3. Preferably, the pressure of the cooled hydrocarbon- containing stream (40) is at least 5 bar, preferably at least 10 bar below the cricondenbar pressure of the mixture of hydrocarbons and contaminants.
Typically, the pressure of the cooled hydrocarbon- containing stream is below 100 bar, preferably below 80 bar .
The method may comprise controlling the discharge pressure of the feed compressor 2 to ensure that the pressure of the cooled hydrocarbon-containing stream 40 is below the cricondenbar pressure. Controlling the discharge pressure of the feed compressor 2 may be done by a controller in response to a measured pressure of at least one of the cooled
hydrocarbon-containing stream 40, the hydrocarbon-containing gas stream 20 as provided in step (a) and the pressure inside gas-liquid separator 17.
According to an embodiment step (a) comprises
controlling a feed compressor (2) which provides the
hydrocarbon-containing gas stream (20) to provide the hydrocarbon-containing gas stream (20) at a pressure that is below the cricondenbar pressure of the mixture of
hydrocarbons and contaminants.
Additionally, the temperature of the cooled hydrocarbon- containing stream 40 is selected and controlled such that the cooled hydrocarbon-containing stream 40 is in the liquid- vapour regime of the phase envelope. Preferably the cooled hydrocarbon-containing stream 40 comprises more than 2 mol% liquid phase .
Preferably, the cooled hydrocarbon-containing stream obtained in step (b) has a temperature of at most -40°C, preferably at most -50°C, more preferably at most -60°C.
Consequently, the cooled hydrocarbon-containing stream (40) is a liquid-vapour multiphase flow. Preferably, the cooled hydrocarbon-containing stream (40) being a liquid-vapour multiphase flow obtained in (b) comprises a liquid fraction in the range of 1 - 10 massl. The mass% is defined with respect to the cooled hydrocarbon- containing stream 40 representing 100%. Typically the liquid fraction is 5 mass%, pressure is below 80 bar and temperature is between -80°C and - 40°C.
In step (c) the cooled hydrocarbon-containing stream (40) is separated in a liquid bottom stream (50) and a gaseous top stream (60), the liquid bottom stream (50) being enriched in C3H—hydrocarbons .
The separation in step (c) can be performed with any suitable gas-liquid separator, shown in the figures as gas- liquid separator 17.
The gas-liquid separator 17 may be a distillation column or a knock-out vessel, from which the liquid stream 50 is obtained as bottom stream and the gaseous stream 60 is obtained as top stream.
The liquid bottom stream 50 is enriched in C3H—
hydrocarbons and the gaseous top stream 60 is depleted in C3+ .
The term enriched is used to indicate that the mol fraction of the indicated component in the enriched stream is higher than the mol fraction of the indicated component in the stream from which the enriched stream is obtained. The term deriched or depleted is used to indicate that the mol fraction of the indicated component in the deriched or depleted stream is lower than the mol fraction of the indicated component in the stream from which the
deriched/depleted stream is obtained.
If desired, preferably if methanol has been injected upstream to avoid hydrate formation, the cooled hydrocarbon- containing gas stream 40 may be subjected to a methanol separation step before being cooled in the expander in step
(d) .
This may be done by providing a separate methanol separator (not shown) or by providing a three-phase separator 17 that has three outlets for a gaseous product, a liquid hydrocarbon product, and a water/methanol product
respectively, such as a vessel comprising a weir from which the gaseous stream 60 is obtained as top stream, the liquid bottom stream 50 is obtained downstream of the weir, and a water-methanol is obtained upstream of the weir.
In step (d) the gaseous top stream (60) is cooled in an expander (4) thereby obtaining a partially liquefied stream (70) .
In step (e) the partially liquefied stream (70) is separated in a separator (5) thereby obtaining a gaseous stream (80) and a liquid stream (90) .
In step (f) the liquid stream (90) is passed to a pressure reduction and separation stage to obtain one or more gaseous streams (110, 180) and a liquid hydrocarbon stream (170) .
Step (f) may be embodied in different ways. Below an example of step (f) will be described with reference to the figures, but it will be understood that alternative
embodiments of step (f) can be implemented instead.
Step (f) may be embodied by the following
steps :
(fl) expanding the liquid stream (90) obtained in step
(e) thereby obtaining a multiphase stream (100), the
multiphase stream (100) containing at least a vapour phase, a liquid phase and a solid phase;
(f2) separating the multiphase stream (100) in a
separator (7) thereby obtaining a gaseous stream (110) and a slurry stream (120); (f3) separating the slurry stream (120) in a solid/liquid separator (9) thereby obtaining a liquid hydrocarbon stream (170) and a concentrated C02 slurry stream (140) .
In step (fl), the liquid stream obtained in step (e) is expanded thereby obtaining a multiphase stream 100. Step (fl) may involve an expander, such as a (throttle) valve 6.
Typically, the multiphase stream 100 contains at least 20 mol% vapour.
Although the expander 6 as used in step (fl) is not particularly limited (and may include a JT valve an orifice, a liquid-expander, etc.), it is preferred that in the expander enthalpy is withdrawn from the cooled hydrocarbon- containing gas stream. A suitable expander for withdrawing enthalpy whilst expanding is a liquid expander. Preferably, the cooled hydrocarbon-containing gas stream as fed into the expander 4 has a pressure of from 40 to 100 bara, more preferably from 60 to 80 bara. The multiphase stream as removed from the expander 4 typically has a pressure of from 10 to 30 bara, preferably between 17 and 25 bara.
Preferably, the multiphase stream obtained in step (fl) has a temperature of at most -100 °C (i.e. not warmer than - 100°C), preferably at most -120°C, more preferably at most - 140°C, most preferably at most -150°C.
In step (f2), the multiphase stream is separated in a separator 7 thereby obtaining a gaseous stream 110 and a C02 slurry stream 120. It is preferred that the slurry stream 120 obtained in step (f2) is pressurized, e.g. using pump 8, before being separated in step (f3), to minimize vapour generation in the solid/liquid separator 9 in step (f3) .
Also, pressurizing the slurry stream obtained in step (f2) prevents solids formation in a pressurized storage vessel (if any) in which the liquid hydrocarbon stream obtained in step (f3) is stored. Preferably the slurry stream is pumped to at least 6 bara.
In step (f3), the slurry stream 140 is separated in a solid/liquid separator 9 thereby obtaining a liquid
hydrocarbon stream 170 and a concentrated slurry stream 140. Typically, the concentrated slurry stream 140 is rich in contaminants. The concentrated slurry stream 140 may comprise more than one contaminant. The concentrated slurry stream 140 usually contains at least 20 mol% contaminant ( s ) and at most 80 mol% methane. If (one of) the contaminant ( s ) in the concentrated slurry stream is C02, then the concentrated slurry stream 140 preferably comprises at least 25 mol% C02. Preferably, the concentrated slurry stream 140 is heated to melt and/or evaporate the contaminant ( s ) . Preferably, the concentrated slurry stream 140 is melted (preferably in a heated vessel) to obtain a liquid contaminant stream 160 and a gaseous contaminant stream 150. As the gaseous contaminant stream 150 may still comprise some hydrocarbons, it may be recycled to be used as (part of) a fuel stream.
As indicated above, the above description of step (f) is an example and alternative pressure reduction and separation stages may be used.
For instance, a pressure reduction and separation stage may be used in which use is made of a direct contact heat exchanger to cool the liquid stream and obtain a multiphase stream comprising a liquid phase and a solid C02 phase, a solid liquid separator to obtain a C02 depleted liquid stream from the multiphase stream, a further cooling, pressure reduction and separation stage to generate a further C02 enriched slurry stream, in which at least part of the further C02 enriched slurry stream is passed to the direct contact heat exchanger to provide cooling duty to and mix with the - Il ¬ liquid stream 90. Upstream of direct contact heat exchanger may be a (throttle) valve.
According to such an embodiment the pressure reduction and separation stage may comprise
(fl') expanding the liquid steam (90) obtained in step
(e) thereby obtaining a multiphase stream (100), the
multiphase stream (100) containing at least a liquid phase and a solid phase;
(f2') cooling the multiphase stream (100) in a direct contact heat exchanger obtaining a multiphase stream
containing at least a liquid phase and a solid C02 phase; separating the multiphase stream in a solid-liquid separator (202) obtaining a C02 depleted liquid stream; passing the C02 depleted liquid stream to a further cooling, pressure reduction and separation stage to generate a further C02 enriched slurry stream; passing at least part of the further C02 enriched slurry stream to the direct contact heat exchanger to provide cooling duty to and mix with the liquid stream .
According to a further example, a pressure reduction and separation stage may be used in which use is made of a crystallization chamber. According to such an embodiment, the pressure reduction and separation stage may comprise
(fl'') expanding the liquid stream (90) obtained in step (e) thereby obtaining a multiphase stream (100), the multiphase stream (100) containing at least a vapour phase, a liquid phase and a solid phase;
(f2'') separating the multiphase stream (100) in a separator thereby obtaining a gaseous stream and a slurry stream;
(f3' ' ) feeding the slurry to a crystallization chamber comprising C02 seed particles, obtaining a concentrated slurry 140 from the crystallization chamber, removing the concentrated slurry from the crystallization chamber by means of an extruder, thereby obtaining solid C02 ; obtaining a feedback stream from the solid C02 comprising C02 seed particles preferably having an average size greater than 100 micron and passing the feedback stream into the
crystallization chamber 91 to provide the C02 seed particles.
In step (g) the gaseous stream (80) obtained in step (e) is passed through the first heat exchanger (3) thereby obtaining a heated gaseous stream 270. The heated gaseous stream 270 typically comprises at least 80 mol% methane and at most 20 mol% N2.
In step (h) the heated gaseous stream 270 is compressed thereby obtaining a compressed gas stream 220. Compression is done by compressor 13. In step (i) at least part of the compressed gas stream 220 obtained in step (h) is combined with the hydrocarbon-containing gas stream 20 provided in step (a) . This may be done with a combiner, which may be embodied in any suitable manner, such as by T-piece or the like .
Typically, the heated gaseous stream obtained in step
(g) is compressed to a pressure equal to the pressure of the hydrocarbon-containing gas stream (20) provided in step (a), to allow combination of therewith. An advantage of combining the (lean) heated gaseous stream with the hydrocarbon- containing gas stream 20 is that the contaminant level in stream 30 is lower than that in stream 20, allowing operating separator 5 at lower temperature, thus increasing the LNG yield.
The contaminated hydrocarbon-containing gas stream provided in step (a) has typically been compressed by feed compressor 2 before being cooled in step (b) and combined in step (i) . According to an embodiment, the method further comprises cooling a part (240) of the compressed gas stream (220) obtained in step (h) through a second heat exchanger (15) thereby obtaining a cooled compressed gas stream (250);
expanding the cooled compressed gas stream (250) thereby obtaining an expanded an expanded gas stream (260); and combining the expanded gas stream (260) with the gaseous stream (80) obtained in step (e) .
Expansion of the cooled compressed gas stream 250 thereby obtaining an expanded gas stream 260 is done by a second expander 16. Although the second expander 16 is not limited (and may include a JT valve, an orifice, an
expander) , it is preferred that a rotating equipment type expander is used.
According to an embodiment, the method further
comprises: passing one of the gaseous streams (110) obtained in step (f) through the second heat exchanger (15) thereby obtaining a second heated gaseous stream (200); compressing the second heated gaseous stream (200) thereby obtaining a second compressed gas stream (210); and combining the second compressed gas stream (210) with the heated gaseous stream (270) obtained in step (g) .
Compressing the second heated gaseous stream 200 may be done by a compressor 14.
In step (j) the liquid bottom stream (50) being enriched in C3H—hydrocarbons obtained in step (c) is passed to a NGL- fractionation stage to obtain a liquid product stream enriched in C3+ and one or more gaseous streams enriched in CI and/or C2.
The term NGL-fractionation stage refers to a Natural Gas
Liquid-fractionation stage. The NGL-fractionation stage can be embodied in different manners but serves to separate the majority of the C3+ molecules from the liquid bottom stream 50 to be discharged and to retrieve CI and/or C2 molecules from the liquid bottom stream 50 to be recycled.
Different embodiments of the NGL-fractionation stage will be described in more detail below. The NGL-fractionation stage may comprise a single separator such as a distillation column (e.g. Fig.'s 2, 3) . The NGL-fractionation stage may alternatively comprise a plurality of distillation columns positioned in series (e.g. Fig. 4, 5), each distillation column being arranged to separate a different Ci-molecule. Such separators positioned in series are usually referred to as a demethanizer and a de-ethanizer .
From the one or more separators one or more gaseous streams enriched in CI and/or C2 are obtained. When one distillation column is used, typically one gaseous stream enriched in CI and C2 is obtained; when two distillation column in series are used, typically one gaseous stream enriched in CI and one gaseous stream enriched in C2 are obtained .
In step (k) the one or more gaseous streams enriched in CI and/or C2 are compressed, thereby obtaining one or more compressed gaseous stream enriched in CI and/or C2.
Compression may at least partially be done using further compressors 13 and 14, which are also used to compress
- the gaseous stream (80) obtained in step (e) and
- one or more of the gaseous streams (110, 180) obtained in step (f) .
In step (1) the one or more compressed gaseous streams enriched in CI and/or C2 are recycled to be comprised in the hydrocarbon-containing gas stream (20) provided in step (a) .
Fig.'s 2 - 5 show different embodiments of embodying the
NGL-fractionation stage, in particular of embodying steps ( ) , (k) and (1) . According to the embodiments depicted in Fig. 2 - 5 step (j) comprises
(jl) passing the liquid bottom stream (50) being enriched in C3H—hydrocarbons obtained in step (c) through a pressure reduction device (300) and subsequently
(j2) into a separator (320), such as a distillation column or gravity based separator.
The pressure reduction device 300 is preferably a valve, such as a Joule Thomson valve. The pressure reduction device 300 serves to control the Reid Vapour Pressure of the liquid product stream enriched in C3+ (340) .
According to the embodiments depicted in Fig.'s 2 and 3 step (j2) comprises obtaining the liquid product stream enriched in C3+ (340) as bottom stream from the separator (320) and obtaining a gaseous stream (330) enriched in CI and C2 as top stream from the separator (320) .
The gaseous stream 330 enriched in CI and C2 is recycled in an advantageous manner by adding this stream to the hydrocarbon-containing gas stream 20 which is passed to the first heat exchanger 3.
According to the embodiment shown in Fig.'s 2 and 3, step (1) comprises recycling the gas stream (330) enriched in CI and C2 obtained in step (j2) by adding the gas stream (330) enriched in CI and C2 obtained in step (j2) to the second heated gaseous stream (200) . This has the advantage that the C1/C2 can be recovered as LNG .
Fig. 4 and 5 show an alternative embodiment of embodying steps (j), (k) and (1), i.e. by providing a NGL-fractionation stage comprising two separators.
According to this embodiment, step (j2) comprises obtaining a gaseous stream (330') enriched in CI as top stream from the separator (320) and obtaining a liquid stream (323) as bottom stream from the separator (320), the method further comprising
(j3) passing the bottom stream from the separator (320) obtained in (j2) through a further pressure reduction device (324) and subsequently
(j4) into a further separator (321), such as a
distillation column or gravity based separator, to obtain the liquid product stream enriched in C3+ (340) as bottom stream from the further separator (321) and obtaining a gaseous stream (331) enriched in C2 as top stream from the further separator (321) .
Fig. 4 further depicts an advantageous embodiment of recycling both the gaseous stream (330') enriched in CI and the gaseous stream (331) enriched in C2. The advantage is that the operating pressure of separators 320 and 321 are matched to the suction pressures of compressors 13 and 14 already present in the system, respectively, as this
minimizes the compression power required.
According to this embodiment, step (1) comprises
- adding the gaseous stream (330' ) enriched in CI obtained as top stream from the separator (320) in step (j2) to the second compressed gas stream (210), and
- adding the gaseous stream (331) enriched in C2 obtained as top stream from the further separator (321) in step (j4) to the second heated gaseous stream (200) .
Further efficiency can be obtained by providing a third heat exchanger 310 to the NGL-fractionation stage to provide cooling duty. This has the advantage that separation can be achieved with a smaller pressure reduction. Consequently, less compression duty is needed to recycle the one or more compressed gaseous streams enriched in CI and/or C2 by adding the one or more compressed gaseous streams enriched in CI and/or C2 to the hydrocarbon-containing gas stream (20) provided in step (a) .
Embodiments comprising a third heat exchanger are shown in Fig. 3 and 5, where Fig. 3 is a variation of Fig. 2 and Fig. 5 is a variation of Fig. 4.
According to such an embodiment step (j) comprises passing at least part of the liquid bottom stream (50) being enriched in C3H—hydrocarbons obtained in step (c) through a third heat exchanger (310) to obtain a cooled liquid bottom stream (50) being enriched in C3+-hydrocarbons .
In the embodiments in which the NGL-fractionation stage comprises a single separator (320), the third heat exchanger 310 is preferably positioned upstream of the single separator
320 and downstream of the pressure reduction device 300. The cooled liquid bottom stream (50) being enriched in C3H— hydrocarbons is passed to the separator 320. An example of such an embodiment is depicted in Fig. 3.
In the embodiments in which the NGL-fractionation stage comprises a two separators (320, 321), the third heat exchanger 310 is preferably positioned in the fluid
connection between the separator 320 and the further
separator 321, preferably upstream of the further separator
321 and the further pressure reduction device 324. In this embodiment the liquid stream 323 obtained as bottom stream from the separator 320 is passed to the third heat exchanger 310.
Advantageously, cooling duty for the third heat
exchanger 310 is obtained from one of the processing streams and without introducing the need for a separate refrigerant and refrigerant cycle.
According to an embodiment the method further comprises obtaining a split stream (81) from the gaseous stream (80) obtained in step (e) and pass the split stream (81) through the third heat exchanger (310) to provide cooling duty to the at least part of the liquid bottom stream (50) being enriched in C3H—hydrocarbons that is passed through the third heat exchanger .
The method may further comprise storing the liquid hydrocarbon stream 170 obtained in step (f) in a LNG storage tank 11, obtaining a boil-off gas stream 180 from the LNG storage tank 11 and combining the boil-off gas stream 180 with one of the one or more gaseous streams enriched in CI and/or C2 obtained from the NGL-fractionation stage. This may be part of step (f ) .
Alternatively, the boil-off gas stream 180 may be compressed separately and sent to a fuel system.
According to an advantageous embodiment, the operating pressure of the separators 320, 321 used in the NGL- fractionation stage are selected to match the suction pressures of the compressors 13, 14 used to compress heated gaseous stream (270) obtained in step (g) and second heated gaseous stream (200) obtained from the second heat exchanger 15.
The person skilled in the art will readily understand that many modifications may be made without departing from the scope of the invention.

Claims

C L A I M S
1. Method of liquefying a hydrocarbon-containing gas stream, the method comprising at least the steps of:
(a) providing a hydrocarbon-containing gas stream (20), the hydrocarbon-containing gas stream comprising a mixture of hydrocarbons including CI, C2 and C3H— hydrocarbons;
(b) cooling the hydrocarbon-containing gas stream (20) in a first heat exchanger (3) thereby obtaining a cooled hydrocarbon-containing stream (40), wherein the pressure of the cooled hydrocarbon-containing stream (40) is below the cricondenbar pressure of the mixture of hydrocarbons and contaminants, the cooled hydrocarbon-containing stream (40) being a liquid-vapour multiphase flow;
(c) separating the cooled hydrocarbon-containing stream
(40) in a liquid bottom stream (50) and a gaseous top stream (60), the liquid bottom stream (50) being enriched in C3H— hydrocarbons ;
(d) cooling the gaseous top stream (60) in an expander (4) thereby obtaining a partially liquefied stream (70);
(e) separating the partially liquefied stream (70) in a separator (5) thereby obtaining a gaseous stream (80) and a liquid stream (90) ;
( f) passing the liquid stream (90) obtained in step (e) to a pressure reduction and separation stage (91) to obtain one or more further gaseous streams (110, 180) and a liquid hydrocarbon stream (170),
(g) passing the gaseous stream (80) obtained in step (e) through the first heat exchanger (3) thereby obtaining a heated gaseous stream (270) ; and
(h) compressing the heated gaseous stream (270) thereby obtaining a compressed gas stream (220); and (i) combining at least part of the compressed gas stream (220) obtained in step (h) with the hydrocarbon-containing gas stream (20) provided in step (a);
wherein the method further comprises:
(j) passing the liquid bottom stream (50) being enriched in C3H—hydrocarbons obtained in step (c) to a NGL- fractionation stage to obtain a liquid product stream enriched in C3+ and one or more gaseous streams enriched in CI and/or C2;
(k) compressing the one or more gaseous stream enriched in CI and/or C2 thereby obtaining one or more compressed gaseous streams enriched in CI and/or C2 (330; 331) ;
(1) recycling the one or more compressed gaseous streams enriched in CI and/or C2 by adding at least part of the one or more compressed gaseous streams enriched in CI and/or C2 to the hydrocarbon-containing gas stream (20) provided in step (a) .
2. The method according to claim 1, wherein the pressure of the cooled hydrocarbon-containing stream (40) is at least 5 bar, preferably at least 10 bar below the cricondenbar pressure of the mixture of hydrocarbons and contaminants.
3. Method according to any one of the preceding claims, wherein step (a) comprises controlling a feed compressor (2) which is involved in providing the hydrocarbon-containing gas stream (20) to provide the hydrocarbon-containing gas stream (20) at a pressure that is below the cricondenbar pressure of the of the mixture of hydrocarbons and contaminants.
4. Method according to any one of the preceding claims, wherein the cooled hydrocarbon-containing stream (40) being a liquid-vapour multiphase flow obtained in (b) comprises a liquid fraction in the range of 1 - 10 massl.
5. Method according to any one of the preceding claims, wherein (f) comprises
(fl) expanding the liquid steam (90) obtained in step
(e) thereby obtaining a multiphase stream (100), the
multiphase stream (100) containing at least a vapour phase, a liquid phase and a solid phase;
(f2) separating the multiphase stream (100) in a separator (7) thereby obtaining a gaseous stream (110) and a slurry stream (120);
(f3) separating the slurry stream (120) in a
solid/liquid separator (9) thereby obtaining a liquid hydrocarbon stream (170) and a concentrated slurry stream
(140) .
6. The method according to any one of claims 1-5, further comprising: cooling a part (240) of the compressed gas stream (220) obtained in step (h) through a second heat exchanger
(15) thereby obtaining a cooled compressed gas stream (250); expanding the cooled compressed gas stream (250) thereby obtaining an expanded an expanded gas stream (260); and combining the expanded gas stream (260) with the gaseous stream (80) obtained in step (e) .
7. The method according to claim 6, further comprising:
passing one of the gaseous streams (110) obtained in step (f) through the second heat exchanger (15) thereby obtaining a second heated gaseous stream (200); compressing the second heated gaseous stream (200) thereby obtaining a second compressed gas stream (210); and combining the second compressed gas stream (210) with the heated gaseous stream (270) obtained in step (g) .
8. Method according to any one of the preceding claims, wherein step (j) comprises
(jl) passing the liquid bottom stream (50) being enriched in C3H—hydrocarbons obtained in step (c) through a pressure reduction device (300) and subsequently
(j2) into a separator (320), such as a distillation column or gravity based separator .
9. Method according to claim 8, wherein step (j2) comprises obtaining the liquid product stream enriched in C3+ (340) as bottom stream from the separator (320) and obtaining a gaseous stream (330) enriched in CI and C2 as top stream from the separator (320) .
10. Method according to claim 7 and 9, wherein step (1) comprises recycling the gas stream (330) enriched in CI and C2 obtained in step (j2) by adding the gas stream (330) enriched in CI and C2 obtained in step (j2) to the second heated gaseous stream (200) .
11. Method according to claim 8, wherein step (j2) comprises obtaining a gaseous stream (330') enriched in CI as top stream from the separator (320) and obtaining a liquid stream (323) as bottom stream from the separator (320), the method further comprising
(j3) passing the bottom stream from the separator (320) obtained in (j2) through a further pressure reduction device (324) and subsequently
(j4) into a further separator (321), such as a
distillation column or gravity based separator, to obtain the liquid product stream enriched in C3+ (340) as bottom stream from the further separator (321) and obtaining a gaseous stream (331) enriched in C2 as top stream from the further separator (321) .
12. Method according to claim 7 and 11, wherein (1)
comprises
- adding the gaseous stream (330' ) enriched in CI obtained as top stream from the separator (320) in step (j2) to the second compressed gas stream (210), and
- adding the gaseous stream (331) enriched in C2 obtained as top stream from the further separator (321) in step (j4) to the second heated gaseous stream (200) .
13. Method according to any one of the preceding claims, wherein step (j) comprises passing at least part of the liquid bottom stream (50) being enriched in C3H—hydrocarbons obtained in step (c) through a third heat exchanger (310) to obtain a cooled liquid bottom stream (50) being enriched in C3H—hydrocarbons.
14. Method according to claim 13, wherein the method further comprises obtaining a split stream (81) from the gaseous stream (80) obtained in step (e) and pass the split stream (81) through the third heat exchanger (310) to provide cooling duty to the liquid bottom stream (50) being enriched in C3H—hydrocarbons.
15. Method according to any one of the preceding claims, wherein the method comprises storing the liquid hydrocarbon stream (170) obtained in step (f) in a LNG storage tank 11, obtaining a boil-off gas stream (180) from the LNG storage tank 11 and combining the boil-off gas stream (180) with one of the one or more gaseous streams enriched in CI and/or C2 obtained from the NGL-fractionation stage.
16. System for liquefying a hydrocarbon-containing gas stream, the system comprising:
- a feed conduit (20) for providing a hydrocarbon- containing gas stream, the hydrocarbon-containing gas stream comprising a mixture of hydrocarbons including CI, C2 and C3H— hydrocarbons;
- a first heat-exchanger (3) arranged to receive the hydrocarbon containing gas stream from the feed conduit (20) and which is further arranged to cool the hydrocarbon- containing gas stream (20) and discharge a cooled
hydrocarbon-containing stream (40) , wherein the pressure of the cooled hydrocarbon-containing stream (40) is below the cricondenbar pressure of the mixture of hydrocarbons and contaminants, the cooled hydrocarbon-containing stream (40) being a liquid-vapour multiphase flow;
- a gas-liquid separator (17) arranged to receive the cooled hydrocarbon-containing stream (40) from the first heat exchanger (3) being arranged to separate the cooled
hydrocarbon-containing stream (40) in a liquid bottom stream (50) and a gaseous top stream (60) , the liquid bottom stream (50) being enriched in C3H—hydrocarbons;
- an expander (4) arranged to receive the gaseous top stream (60) and expand and thereby cool the gaseous top stream (60) thereby obtaining a partially liquefied stream (70) ;
- a separator (5) arranged to receive the partially liquefied stream (70) and separate the partially liquefied stream (70) thereby obtaining a gaseous stream (80) and a liquid stream (90) ; - a pressure reduction and separation stage (91)
arranged to receive the liquid stream (90) from the separator (5) further being arranged to obtain one or more further gaseous streams (110, 180) and a liquid hydrocarbon stream (170) from the liquid stream (90) ,
- conduit (80) to pass the gaseous stream (80) obtained from the separator (5) to the first heat exchanger (3) and a conduit (270) to obtain a heated gaseous stream (270) from the first heat exchanger (3) ; and
- one or more compressors (13, 14) arranged to receive the heated gaseous stream (270) to obtain a compressed gas stream (220) ; and
- a combiner arranged to combine at least part of the compressed gas stream (220) with the hydrocarbon-containing gas stream (20) ;
wherein the system further comprises:
- a NGL-fractionation stage arranged to receive the liquid bottom stream (50) being enriched in C3H—hydrocarbons obtained from the gas-liquid separator (17) , the NGL- fractionation stage being arranged to obtain a liquid product stream enriched in C3+ and one or more gaseous streams enriched in CI and/or C2 from the liquid bottom stream (50) being enriched in C3H—hydrocarbons;
- one or more recycle conduits (330, 331) arranged to recycle the one or more gaseous streams enriched in CI and/or C2 to the one or more compressors (13, 14) .
PCT/EP2016/079392 2015-12-03 2016-12-01 Method of liquefying a contaminated hydrocarbon-containing gas stream Ceased WO2017093381A1 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US12392549B2 (en) 2020-06-03 2025-08-19 Chart Energy & Chemicals, Inc. Gas stream component removal system and method

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030089125A1 (en) * 2000-03-15 2003-05-15 Fredheim Arne Olay Natural gas liquefaction process
EP2789957A1 (en) * 2013-04-11 2014-10-15 Shell Internationale Research Maatschappij B.V. Method of liquefying a contaminated hydrocarbon-containing gas stream

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030089125A1 (en) * 2000-03-15 2003-05-15 Fredheim Arne Olay Natural gas liquefaction process
EP2789957A1 (en) * 2013-04-11 2014-10-15 Shell Internationale Research Maatschappij B.V. Method of liquefying a contaminated hydrocarbon-containing gas stream

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US12392549B2 (en) 2020-06-03 2025-08-19 Chart Energy & Chemicals, Inc. Gas stream component removal system and method

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