WO2014173598A2 - Procédé et appareil de production d'un flux d'hydrocarbure liquéfié - Google Patents

Procédé et appareil de production d'un flux d'hydrocarbure liquéfié Download PDF

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Publication number
WO2014173598A2
WO2014173598A2 PCT/EP2014/055959 EP2014055959W WO2014173598A2 WO 2014173598 A2 WO2014173598 A2 WO 2014173598A2 EP 2014055959 W EP2014055959 W EP 2014055959W WO 2014173598 A2 WO2014173598 A2 WO 2014173598A2
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WO
WIPO (PCT)
Prior art keywords
stream
vapour
fraction
refrigerant
gas
Prior art date
Application number
PCT/EP2014/055959
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English (en)
Other versions
WO2014173598A3 (fr
Inventor
Jan Van Amelsvoort
Original Assignee
Shell Internationale Research Maatschappij B.V.
Shell Oil Company
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Filing date
Publication date
Application filed by Shell Internationale Research Maatschappij B.V., Shell Oil Company filed Critical Shell Internationale Research Maatschappij B.V.
Publication of WO2014173598A2 publication Critical patent/WO2014173598A2/fr
Publication of WO2014173598A3 publication Critical patent/WO2014173598A3/fr

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/003—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"
    • F25J1/0042—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 liquid 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"
    • F25J1/0045—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using the feed stream itself or separated fractions from it, i.e. "internal refrigeration" by vaporising a liquid return stream
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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    • F25J1/003—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
    • F25J1/0047—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle
    • F25J1/0052—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle by vaporising a liquid refrigerant stream
    • F25J1/0055—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle by vaporising a liquid refrigerant stream originating from an incorporated cascade
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    • F25J1/0211—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a multi-component refrigerant [MCR] fluid in a closed vapor compression cycle
    • F25J1/0214—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a multi-component refrigerant [MCR] fluid in a closed vapor compression cycle as a dual level refrigeration cascade with at least one MCR cycle
    • F25J1/0215—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a multi-component refrigerant [MCR] fluid in a closed vapor compression cycle as a dual level refrigeration cascade with at least one MCR cycle with one SCR cycle
    • F25J1/0216—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a multi-component refrigerant [MCR] fluid in a closed vapor compression cycle as a dual level refrigeration cascade with at least one MCR cycle with one SCR cycle using a C3 pre-cooling cycle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0228—Coupling of the liquefaction unit to other units or processes, so-called integrated processes
    • F25J1/0229—Integration with a unit for using hydrocarbons, e.g. consuming hydrocarbons as feed stock
    • F25J1/023—Integration with a unit for using hydrocarbons, e.g. consuming hydrocarbons as feed stock for the combustion as fuels, i.e. integration with the fuel gas system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
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    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0244—Operation; Control and regulation; Instrumentation
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    • F25J1/0255—Operation; Control and regulation; Instrumentation controlling particular process parameter, e.g. pressure, temperature controlling the composition of the feed or liquefied gas, e.g. to achieve a particular heating value of natural gas
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    • 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
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    • F25J1/0257—Construction and layout of liquefaction equipments, e.g. valves, machines
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    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0257—Construction and layout of liquefaction equipments, e.g. valves, machines
    • F25J1/0262—Details of the cold heat exchange system
    • F25J1/0264—Arrangement of heat exchanger cores in parallel with different functions, e.g. different cooling streams
    • F25J1/0265—Arrangement of heat exchanger cores in parallel with different functions, e.g. different cooling streams comprising cores associated exclusively with the cooling of a refrigerant stream, e.g. for auto-refrigeration or economizer
    • F25J1/0267—Arrangement of heat exchanger cores in parallel with different functions, e.g. different cooling streams comprising cores associated exclusively with the cooling of a refrigerant stream, e.g. for auto-refrigeration or economizer using flash gas as heat sink
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    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
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    • F25J1/0274—Retrofitting or revamping of an existing liquefaction unit
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    • F25J1/0281—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc. characterised by the type of prime driver, e.g. hot gas expander
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    • F25J2230/20—Integrated compressor and process expander; Gear box arrangement; Multiple compressors on a common shaft
    • 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
    • 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
    • F25J2235/00—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams
    • F25J2235/60—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams the fluid being (a mixture of) hydrocarbons
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
    • F25J2240/30—Dynamic liquid or hydraulic expansion with extraction of work, e.g. single phase or two-phase turbine
    • 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
    • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
    • F25J2240/40—Expansion without extracting work, i.e. isenthalpic throttling, e.g. JT valve, regulating valve or venturi, or isentropic nozzle, e.g. Laval
    • 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
    • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
    • F25J2240/80—Hot exhaust gas turbine combustion engine
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/02—Recycle of a stream in general, e.g. a by-pass 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
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/90—Processes or apparatus involving steps for recycling of process streams the recycled stream being boil-off gas from storage
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2260/00—Coupling of processes or apparatus to other units; Integrated schemes
    • F25J2260/60—Integration in an installation using hydrocarbons, e.g. for fuel purposes
    • 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
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/12—External refrigeration with liquid vaporising 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
    • F25J2280/00—Control of the process or apparatus
    • F25J2280/02—Control in general, load changes, different modes ("runs"), measurements

Definitions

  • the present invention relates to a method and apparatus for producing a liquefied hydrocarbon stream.
  • Liquefied natural gas forms an economically important example of such a cryogenic hydrocarbon stream.
  • Natural gas is a useful fuel source, as well as a source of various hydrocarbon compounds. It is often desirable to liquefy natural gas in a liquefied natural gas plant at or near the source of a 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 pressure .
  • WO 2006/120127 describes an LNG separation process and installation.
  • Liquefied natural gas in liquid form is sent to a separation unit, wherein a stream of LNG purified of nitrogen, and a nitrogen-enriched vapour are produced.
  • the separation unit employs two columns.
  • An LNG stream which has been liquefied in a liquefier is first separated in a first column operating at about 1.25 bar producing a nitrogen-depleted liquid and an overhead gas stream.
  • the overhead gas stream is recompressed to about 4 bar and passed to a second column, where any remaining methane is recondensed.
  • the recondensed methane is withdrawn as liquid from the second column and mixed with the nitrogen-depleted liquid from the first column to form the stream of LNG purified of nitrogen.
  • Gaseous nitrogen is withdrawn from the top of the second column, allowing for the nitrogen contained in the natural gas to be utilized at commercial purity.
  • the refrigeration or said recondensing of the methane in the second column is provided by a nitrogen cycle independent of the liquefier, which employs a refrigerant fluid is of which the nitrogen content is greater than 80 mol%.
  • a drawback of this LNG separation process is that an independent refrigeration cycle is required which involves both capital expenditure as well as operational expenditure. Moreover, as the recondensed methane is added to the purified LNG stream, it becomes increasingly demanding to maintain the nitrogen level in the purified LNG stream below the specification required for
  • the present invention provides a method of producing a liquefied hydrocarbon stream, comprising:
  • cryogenic hydrocarbon composition comprising nitrogen and a methane-containing liquid phase at an initial pressure of between 1 and 2 bar absolute;
  • composition in an end flash separator at a first separation pressure of between 1 and 2 bar absolute, into a vaporous reject stream and a liquid stream; - discharging the liquid stream from the end flash separator in the form of the liquefied hydrocarbon stream;
  • the present invention provides an apparatus for producing a liquefied hydrocarbon stream, comprising :
  • a liquefier comprising a refrigerant circuit for cycling a refrigerant stream, said refrigerant circuit comprising a refrigerant compressor coupled to a
  • refrigerant compressor driver arranged to compress the refrigerant stream, and a cryogenic heat exchanger arranged to establish an indirect heat exchanging contact between a hydrocarbon stream and the refrigerant stream of the refrigerant circuit, whereby a raw liquefied stream is formed out of the hydrocarbon stream comprising a subcooled hydrocarbon stream;
  • a pressure reduction system arranged downstream of the cryogenic heat exchanger in fluid communication therewith to receive the raw liquefied stream and to reduce its pressure;
  • a rundown line fluidly connecting the pressure reduction system with the cryogenic heat exchanger to establish fluid communication for the raw liquefied stream to pass from the cryogenic heat exchanger to the pressure reduction system;
  • an end-flash separator arranged downstream of the pressure reduction system and in fluid communication therewith to receive a cryogenic hydrocarbon composition from the pressure reduction system;
  • a liquid hydrocarbon product line fluidly connected to a bottom part of the end-flash separator to discharge a liquid stream in the form of the liquefied hydrocarbon stream from the end-flash separator;
  • vapour reject line fluidly connected to an overhead part of the end-flash separator to discharge a vaporous reject stream from the end-flash separator;
  • an end-flash compressor arranged in the vapour reject line to compress the vaporous reject stream, thereby obtaining a compressed vapour stream;
  • a condenser arranged in the vapour reject line downstream of the end-flash compressor, arranged to receive the compressed vapour stream and to form a partially condensed intermediate stream from the
  • said partially condensed intermediate stream comprising a condensed fraction and a vapour fraction, which condenser is arranged to establish indirect heat exchanging contact between at least part of the compressed vapour stream and an auxiliary refrigerant stream;
  • an auxiliary refrigerant return line extending between the condenser and the refrigerant circuit of the liquefier arranged to return the auxiliary refrigerant containing heat from the compressed vapour stream back to the liquefier;
  • a gas/liquid separator arranged downstream of the condenser and arranged to receive the condensed fraction and vapour fraction
  • vapour fraction discharge line fluidly connected with an overhead part of the gas/liquid separator arranged to receive the vapour fraction from the
  • a combustion device other than a gas turbine fluidly connected with the gas/liquid separator by means of the vapour fraction discharge line to receive and combust the discharged vapour fraction;
  • a condensed fraction discharge line fluidly connected with a bottom part of the gas/liquid separator arranged to receive the condensed fraction from the gas/liquid separator;
  • a revaporizer arranged in the condensed fraction discharge line between the gas/liquid separator and the gas turbine and arranged to transform the condensed fraction into a fully vaporized stream prior to
  • Fig. 1 schematically represents a process flow scheme representing a method and apparatus according to an embodiment of the invention
  • Fig. 2 schematically represents an embodiment of a pressure reduction system for use in the invention
  • FIG. 3 schematically represents a process flow scheme representing a method and apparatus according to another embodiment of the invention.
  • FIG. 4 schematically represents a process flow scheme representing a method and apparatus according to still another embodiment of the invention.
  • Fig. 5 schematically represents a process flow scheme wherein the embodiment of Fig. 3 is applied in
  • Fig. 6 schematically represents a process flow scheme wherein the embodiment of Fig. 4 is applied in
  • Fig. 7 schematically represents a process flow scheme wherein the embodiment of Fig. 4 is applied with a specific type of end-flash separator.
  • a cryogenic hydrocarbon composition obtained by subjecting a raw liquefied hydrocarbon stream to a pressure reduction step, is first separated into a vaporous reject stream and a liquid stream.
  • the liquid stream is discharged in the form of the liquefied hydrocarbon stream.
  • the vaporous reject stream is recompressed, partially condensed by indirectly heat exchanging the compressed vapour stream against an auxiliary refrigerant stream, and separated.
  • the condensed fraction is revaporized and combusted in a gas turbine.
  • the vapour fraction which generally has a higher nitrogen content and a lower heating value than the condensed fraction, is combusted in a combustion device other than a gas turbine.
  • the auxiliary refrigerant stream is advantageously formed by a slip stream of the cycled refrigerant stream from the liquefier. No high degree of separation between the methane and the nitrogen in the intermediate
  • vapour fraction does not have to be free from methane while the condensed fraction is bound to less stringent requirements for its nitrogen content than if it would be added to the liquefied hydrocarbon stream.
  • the proposed method and apparatus thus do not require a full nitrogen rejection unit, since a combustible fuel gas stream is produced instead of a ventable nitrogen stream .
  • the proposed method and apparatus can be any known method and apparatus.
  • the raw liquefied stream comprises in the range of from 1 mol% to 7 mol% nitrogen.
  • the raw liquefied stream comprises more than 3 mol% of nitrogen, as in such cases a relatively high flow rate of vaporous reject gas is generated in order to maintain the liquid stream from which the liquefied hydrocarbon stream is derived within specification with regard to maximum content of lower boiling constituents such as nitrogen in commercially tradable liquefied natural gas.
  • the high flow rate of vaporous reject gas generally contains too much nitrogen for use as fuel in gas turbines, and it usually exceeds plant fuel
  • More than 30 mol% of the vaporous reject stream and/or more than 30 mol% of the partially condensed intermediate stream may consist of nitrogen. Such nitrogen content would be too high to meet the fuel gas requirements of most gas turbines.
  • the proposed method and apparatus may then be advantageously employed to recondense a fraction of the vaporous reject stream, to obtain a condensed fraction of which less than 30 mol% consists of nitrogen so that, after revaporization, it can be used to fuel a gas turbine. If the nitrogen content is still too high for the selected gas turbine, the condensed fraction (preferably after revaporization) may be blended with other fuel gas to bring the fuel on specification. In such cases the invention provides the benefit that the blending
  • the revaporized condensed fraction may have to be subjected to compression in order to meet a pre- determined gas turbine fuel gas pressure specification.
  • the condensed fraction may be pressurized, e.g. by means of a liquid pump, before revaporizing so that the condensed fraction can be revaporized at a pressure that is already sufficiently high to meet the fuel pressure specification of the gas turbine in which the revaporized condensed fraction will be combusted.
  • the slip stream for the auxiliary refrigerant stream is preferably formed of a part of the cycled refrigerant stream against which the hydrocarbon stream is subcooled. This is generally the refrigerant stream that within the liquefier is adapted to extract heat from the hydrocarbon stream at the lowest temperature range. This makes it the most suitable cycled refrigerant stream that is available in the liquefier for the purpose of partly condensing the vaporous reject stream.
  • FIG. 1 illustrates an embodiment of the invention.
  • a liquefier 100 is provided to produce a raw
  • the liquefier 100 comprises a refrigerant circuit 101 for cycling a refrigerant.
  • the refrigerant circuit 101 comprises a refrigerant compressor 160 coupled to a refrigerant compressor driver 190 in a mechanical driving engagement.
  • the refrigerant compressor 160 is arranged to compress a spent
  • At least one reject heat exchanger 124 is normally provided in the compressed refrigerant line 120 of the refrigerant circuit 101.
  • the exchanger 124 is arranged to reject heat from the pressurized refrigerant stream carried in the compressed refrigerant line 120 to the ambient, either to the air or to a body of water such as a lake, a river, or the sea.
  • the liquefier 100 typically comprises a refrigerant refrigerator arranged to refrigerate the pressurized refrigerant from the compressed refrigerant line 120 from which heat has been rejected in the reject heat exchanger 124.
  • a refrigerated refrigerant stream is obtained in a refrigerated refrigerant line 131.
  • the liquefier 100 further comprises a cryogenic heat exchanger 180 connected to the refrigerant compressor 160 discharge outlet via the compressed refrigerant line 120.
  • the cryogenic heat exchanger 180 also fulfils the function of the
  • the cryogenic heat exchanger is generally arranged to establish an indirect heat exchanging contact between a hydrocarbon stream 110 and the refrigerant of the refrigerant circuit 101.
  • a main refrigerant return line 133 establishes fluid communication between the refrigerated refrigerant line 131 and a cold side of the cryogenic heat exchanger 180.
  • the hydrocarbon stream 110 flows through a warm side of the cryogenic heat exchanger 180.
  • the cold side and the warm side are in heat
  • a main refrigerant control valve 134 is configured in the main refrigerant return line 133.
  • refrigerant return line 133 is in fluid communication with the spent refrigerant line 150, via said cold side and in heat exchanging arrangement with the hot side.
  • a spent refrigerant line 150 connects the cryogenic heat exchanger 180 with a main suction end of the refrigerant compressor 160.
  • the cryogenic heat exchanger 180 receives the refrigerant stream in a depres surized condition from the main refrigerant return line 133 via the main refrigerant control valve 134, and discharges into the refrigerant compressor 160.
  • the cryogenic heat exchanger 180 forms part of the refrigerant circuit 101.
  • the cryogenic heat exchanger 180 may be provided in any suitable form, including a printed circuit type, a plate fin type, optionally in a cold box configuration, or a tube-in-shell type heat exchanger such as a coil wound heat exchanger or a spool wound heat exchanger.
  • a pressure reduction system 5 is arranged in a rundown line 1 downstream of the cryogenic heat exchanger 180 and the liquefier 100 and in fluid communication therewith to receive the raw liquefied stream and to reduce its pressure.
  • An end-flash separator 50 is arranged downstream of the pressure reduction system 5, and in fluid communication therewith, to receive a cryogenic cryogenic hydrocarbon composition 8 from the pressure reduction system 5.
  • the pressure reduction system 5 may comprise a dynamic unit, such as an expander turbine, a static unit, such as a Joule Thomson valve, or a combination thereof.
  • Joule Thomson valve 7 in series with an expander turbine 6 is shown in Fig. 2. If an expander turbine is used, it may optionally be drivingly connected to a power
  • the end flash separator 50 may be provided in the form of a simple drum which separates vapour from liquid phases in a single equilibrium stage (such as depicted in Fig. 1), or a more sophisticated distillation column.
  • a simple drum which separates vapour from liquid phases in a single equilibrium stage (such as depicted in Fig. 1), or a more sophisticated distillation column.
  • Non- limiting examples of possibilities are disclosed in US Patents 5,421,165; 5,893,274; 6,014,869; 6,105,391; and pre-grant publication US 2008/0066492.
  • a liquid hydrocarbon product line 90 is fluidly connected to a bottom part of the end-flash separator 50.
  • the liquid hydrocarbon product line 90 connects the end- flash separator 50 to a cryogenic storage tank 210.
  • An optional cryogenic pump (not shown) may be present in the liquid hydrocarbon product line 90, to assist the transport of any liquid hydrocarbon product that is being discharged from the end-flash separator 50 to the cryogenic storage tank 210.
  • a vapour reject line 64 is fluidly connected to an overhead part of the end-flash separator 50.
  • An end- flash compressor 260 is arranged in the vapour reject line 64, to compress the vaporous reject stream from the end-flash separator 50.
  • a condenser 35 is arranged in the vapour reject line 64, downstream of the end-flash compressor 260. This part of the vapour reject line will be referred to as compressed vapour stream line 70.
  • the condenser 35 is arranged to receive the
  • the condenser is arranged to establish indirect heat exchanging contact between at least part of the compressed vapour stream, and an auxiliary refrigerant stream .
  • An aftercooler 69 may be provided in the compressed vapour stream line 70 between the end-flash compressor 260 and the condenser 35.
  • the aftercooler is arranged to reject heat from the compressed vapour to the ambient (for instance by heat exchanging against an ambient air stream or an ambient water stream) .
  • Such an aftercooler is recommended in embodiments where the temperature of the compressed vapour stream as it is discharged from the end-flash compressor exceeds the temperature of the ambient air and/or ambient water so that at least part of the heat added to the vapour in the end-flash compressor can be rejected to the ambient.
  • a cold recovery heat exchanger 65 may optionally be provided in the vapour reject line 64 resulting in that the reject vapour is fed into the end flash compressor 260 at an end-flash compressor suction temperature that is higher than the temperature at which the reject vapour is discharged from the end-flash separator 50 into the vapour reject line 64.
  • the cold vested in the reject vapour in vapour reject 64 is preserved in a cold recovery stream 66, by heat exchanging against the cold recovery stream 66 prior to compressing the reject vapour to the end-flash compressor 260.
  • the cold recovery stream 66 may comprise or consist of a side stream sourced from the hydrocarbon stream 110 in the liquefier 100.
  • the resulting cooled side stream may for instance be combined with the cryogenic hydrocarbon composition in the cryogenic feed line 8.
  • the cold recovery heat exchanging in the cold recovery heat exchanger 65 supplements the production rate of the cryogenic
  • the cold recovery stream 66 may comprise or consist of a refrigerant stream being cycled in the liquefier 100 whereby the refrigerant stream (or a slipstream thereof) is condensed or sub- cooled.
  • a slip stream of the compressed refrigerant can be drawn from the compressed refrigerant line 120 and be refrigerated by vapour reject line 64.
  • the cold recovery stream 66 may comprise or consist of the aftercooled reject vapour in the compressed vapour stream line 70,
  • the auxiliary refrigerant stream is supplied from an auxiliary refrigerant feed line 132 that extends between the refrigerant circuit 101 of the liquefier 100 and the condenser 35.
  • An auxiliary refrigerant return line 138 extends between the condenser 35 and the refrigerant circuit 101 of the liquefier 100, and is arranged to return the auxiliary refrigerant containing heat from the compressed vapour stream back to the liquefier 100.
  • An auxiliary refrigerant control valve 135 is arranged in the auxiliary refrigerant feed line 132.
  • the refrigerated refrigerant line 131 is split into the auxiliary
  • the auxiliary refrigerant return line 138 on an upstream end thereof, fluidly connects with the auxiliary refrigerant feed line 132 via the condenser 35. On a downstream end thereof, the auxiliary refrigerant return line 138 ultimately connects with the spent refrigerant line 150.
  • a gas/liquid separator 33 is arranged downstream of the condenser 35.
  • a vapour fraction discharge line 80 is fluidly connected with an overhead part of the gas/liquid separator 33 and a condensed fraction discharge line 40 is fluidly connected with a bottom part of the gas/liquid separator 33.
  • a gas turbine 320 is fluidly connected with the gas/liquid separator, by means of the condensed fraction discharge line 40.
  • a combustion device 220 other than a gas turbine is fluidly connected with the gas/liquid separator by means of the vapour fraction discharge line 80.
  • the combustion device 220 may comprise multiple combustion units. It may include, for example, one or more of a furnace, a boiler, an incinerator, a dual fuel diesel engine, or cross-combinations thereof. A boiler and a duel fuel diesel engine may advantageously be coupled to an electric power generator.
  • a revaporizer 285 is arranged in the condensed fraction discharge line 40, between the gas/liquid separator 33 and the gas turbine 320.
  • the revaporizer is arranged to bring the condensed fraction in the condensed - In ⁇ fraction discharge line 40 in indirect heat exchanging contact with a heating fluid 286 whereby during operation heat is transferred from the heating fluid 286 to the condensed fraction in the condensed fraction discharge line 40.
  • a fuel gas compressor 360 is arranged in the condensed fraction discharge line 40 between the revaporizer 285 and the gas turbine 320.
  • a cold recovery heat exchanger 85 may optionally be provided in the vapour fraction discharge line 80 to recover cold vested in the vapour fraction prior to combusting it in the combustion device 220.
  • the cold recovery heat exchanger 85 is arranged to bring the vapour fraction in the vapour fraction discharge line 80 in indirect heat exchanging contact with a cold recovery stream 86. During operation heat is transferred from the cold recovery stream 86 to the vapour fraction in the vapour fraction discharge line 80.
  • This cold recovery heat exchanger 85 may be referred to as second cold recovery heat exchanger in embodiments wherein the cold recovery heat exchanger 65 is provided in the vapour reject line 64. In such embodiments, the cold recovery heat exchanger 65 in the vapour reject line 64 may be referred to as first cold recovery heat exchanger.
  • the apparatus described above may be used in a method described as follows.
  • a refrigerant is cycled in the refrigerant circuit 101 of the liquefier 100. Cycling comprises driving the refrigerant compressor 160, and compressing the
  • a hydrocarbon stream 110 is condensed and subcooled.
  • the condensing and subcooling involves indirectly heat exchanging the hydrocarbon stream 110 against the refrigerant in the liquefier 100.
  • the thus formed subcooled liquefied hydrocarbons stream is referred to as raw liquefied stream.
  • the raw liquefied stream is formed out of the hydrocarbon stream by condensing and subsequently subcooling the hydrocarbon stream.
  • the hydrocarbon stream 110 in any of the examples disclosed herein may be obtained from natural gas or petroleum reservoirs or coal beds.
  • the cryogenic hydrocarbon composition 8 may also be obtained from another source, including as an example a synthetic source such as a Fischer-Tropsch process.
  • the cryogenic hydrocarbon stream 110 comprises at least 50 mol% methane, more preferably at least 80 mol% methane.
  • the resulting liquid hydrocarbon product conveyed in the liquid hydrocarbon product line 90 and/or stored in the cryogenic storage tank 210 is preferably liquefied natural gas (LNG) .
  • LNG liquefied natural gas
  • the hydrocarbon stream 110 may contain varying amounts of components other than methane and nitrogen, including one or more non- hydrocarbon components other than water, such as C0 2 , Hg, H 2 S and other sulphur compounds; and one or more
  • hydrocarbons heavier than methane such as in particular ethane, propane and butanes, and, possibly lesser amounts of pentanes and aromatic hydrocarbons.
  • Hydrocarbons with a molecular mass of at least that of propane may herein be referred to as C3+ hydrocarbons
  • hydrocarbons with a molecular mass of at least that of ethane may herein be referred to as C2+ hydrocarbons.
  • the hydrocarbon stream 110 may have been pre-treated to reduce and/or remove one or more of undesired components such as C0 2 and H 2 S, or have
  • composition of the hydrocarbon stream 110 thus varies depending upon the type and location of the gas and the applied pre-treatment (s) .
  • the raw liquefied stream is discharged in the rundown line 1 from the liquefier 100.
  • the raw liquefied stream may comprise in the range of from 1 mol% to 7 mol% nitrogen and more than 81 mol% of methane.
  • a cryogenic hydrocarbon composition 8 is obtained from the raw liquefied stream by passing the raw liquefied stream through a pressure reduction step in pressure reduction system 5, whereby reducing the pressure from the
  • Flash vapour is usually generated during such pressure reduction step.
  • the cryogenic hydrocarbon composition 8 comprises a nitrogen- and methane-containing liquid phase, and is usually at a temperature lower than -130 °C.
  • the temperature of the raw liquefied stream in the rundown line 1 may be in the range of from -160 °C to -145 °C. Within this more narrow range the cooling duty needed in the liquefaction system 100 is lower than when lower temperatures are desired, while the amount of sub-cooling at the pressure of above 15 bara is sufficiently high to avoid excessive production of flash vapours upon reducing the pressure to the initial pressure of between 1 and 2 bara.
  • the cryogenic hydrocarbon composition 8 is
  • a vaporous reject stream 64 subsequently phase separated, at a first separation pressure of between 1 and 2 bar absolute, into a vaporous reject stream 64 and a liquid stream 90.
  • this phase separating is performed in the end-flash separator 50.
  • the vaporous reject stream 64 comprises a majority of, preferably all of, any flash vapour that has been generated during the pressure reduction step.
  • the liquid stream 90 is discharged in the form of the liquefied hydrocarbon stream, which may be a liquefied natural gas stream provided that the methane content is at least 81 mol%.
  • the liquid stream 90 is typically conveyed to the cryogenic storage tank 210.
  • the vaporous reject stream 64 is discharged from the end-flash separator 50, and subsequently compressed in the end-flash compressor 260 to a pressure of above 2 bar absolute, thereby obtaining a compressed vapour stream 70.
  • the compressed vapour stream 70 is passed to the condenser 35. If an aftercooler 69 is provided in the compressed vapour stream line 70, the compressed vapour stream 70 is passed through the aftercooler 69 as it is being passed to the condenser 35. In the aftercooler 69, heat is rejected from the compressed vapour to the ambient (for instance by heat exchanging against an ambient air stream or an ambient water stream) .
  • the compressed vapour 70 is discharged from the optional aftercooler 69 at an aftercooled temperature that is close to ambient temperature, for instance 2 °C above ambient temperature. Ambient temperature is considered to be the temperature of the ambient medium (air or water) to which the heat is rejected.
  • the partially condensed intermediate stream comprises a condensed fraction 40 and a vapour fraction 80.
  • the partially condensing comprises indirect heat exchanging of the compressed vapour stream 70 against an auxiliary refrigerant stream 132, formed by a slip stream of the cycled refrigerant from the liquefier 100. During the indirect heat exchanging, heat passes from, at least part of, the compressed vapour stream 70 to the auxiliary refrigerant stream 132.
  • the condensed fraction 40 is then separated from the vapour fraction 80 in the gas/liquid separator 33, at a second separation pressure.
  • the vapour fraction and the condensed fraction co-exist in the gas/liquid separator 33, and are separated in a single thermodynamic equilibrium state between said vapour fraction and the condensed fraction residing inside the gas/liquid separator 33. This can generally be achieved if the gas/liquid separator 33 is embodied in the form of simple drum with no gas/liquid contacting internals such as trays or packing, thus essentially representing one single theoretical stage.
  • the vapour fraction 80 is discharged from the gas/liquid separator 33, typically as a vapour phase in its dew point.
  • the vapour fraction 80 as it is being discharged from the gas/liquid separator 33, has a first heating value.
  • the vapour fraction 80 is combusted in the combustion device 220.
  • the condensed fraction 40 is also discharged from the gas/liquid separator 33, but as liquid phase at its bubble point.
  • the condensed fraction 40 is subsequently revaporized in revaporizer 285.
  • the revaporizing comprises bringing the condensed fraction 40 in indirect heat exchanging contact with the heating fluid 286, whereby heat is transferred from the heating fluid 286 to the condensed fraction 40.
  • the condensed fraction 40 is transformed into a fully vaporized stream having a second heating value.
  • the condensed fraction 40 is fully in vapour phase.
  • the fully vaporized stream resulting from the condensed fraction 40 is combusted in a gas turbine
  • the auxiliary cooling duty transferred by the auxiliary refrigerant stream 132 in the condenser 35 can be altered by manipulating the auxiliary refrigerant control valve 135.
  • the auxiliary refrigerant control valve 135 is functionally coupled to an optional level controller 37 arranged in the gas/liquid separator 33 to establish a constant liquid level in gas/liquid separator 33 by regulating the amount of partial condensation of the compressed vapour 70 that occurs in the condenser 35.
  • Another example involves the auxiliary refrigerant control valve 135 is functionally coupled to an optional temperature sensor (not shown) arranged between the condenser 35 and the gas/liquid separator 33 to establish a constant temperature of the partially condensed intermediate stream.
  • Set point for the temperature sensor can be derived from a desired nitrogen content of the condensed fraction 40 that is consisted with the fuel gas composition specification of the gas turbine 320.
  • the remaining nitrogen stays in the vapour fraction.
  • the rundown temperature of raw liquefied stream in the rundown line 1 can be regulated such as to ensure that the total available heating power in the reject vapour 64 and/or the partially condensed intermediate stream meets the combined fuel gas requirement of the combustion device (s) 220 and the gas turbine (s) 320. For instance, if there is too much heating power in the reject vapour 64, the rundown temperature can be lowered to reduce the amount of methane that is flashed in the pressure reduction step in pressure reduction system 5.
  • the partitioning of the nitrogen over the vapour fraction 80 and the condensed fraction 40 is regulated by the auxiliary cooling duty.
  • the nitrogen content of the liquid stream 90 may be kept within specification over the range of rundown temperatures anticipated during operation by the correct choice and dimensioning of the end-flash separator 50 at the design stage.
  • the first and second heating values define the amount of heat that can be released by combustion of a mole of the fuel gas. This can be either the so-called “high” heating value as the "low” heating value as long as the same conditions are used for comparing the two heating values. Preferably the "low” heating value is used to compare the two heating values, as this is the closest to the combustion conditions used in the invention.
  • the heating value may be determined using ASTM D3588-98 applied regardless of the composition of the vapour fraction 80 and/or the condensed fraction 40.
  • the second heating value (belonging to the condensed fraction 40) is higher than the first heating value (belonging to the vapour fraction 80) .
  • the partially condensed intermediate stream essentially consists of two components, methane and nitrogen
  • the first and second heating values uniquely map onto nitrogen content of the vapour fraction 80 and the condensed fraction 40, respectively.
  • the vapour fraction 80 is combusted the combustion device 220 preferably at a first fuel gas pressure that is not higher than the second separation pressure. This way a compressor can be avoided as the pressure in the vapour fraction 80 does not have to be increased.
  • the vapour fraction 80 is combusted in the combustion device at a pressure of between 2 and 15 bara, more preferably at a pressure of between 2 and 6 bara.
  • the condensed fraction 40 may have to be pressurized to a second fuel gas pressure that is higher than the second separation pressure. If a fuel gas compressor 360 is arranged in the condensed fraction discharge line 40 between the revaporizer 285 and the gas turbine 320, the fully vaporized stream may optionally be compressed in such fuel gas compressor 360 to the second fuel gas pressure before combusting the fully vaporized stream in the gas turbine 320.
  • the second fuel gas pressure is generally higher than the second separation pressure, and preferably adapted to meet fuel gas pressure requirements imposed by the selected gas turbine 320.
  • a pressure reduction valve 245 may optionally be arranged in the condensed fraction discharge line 40 between the gas/liquid separator 33 and the revaporizer 285. This allows for flashing some of the condensed fraction 40 prior to passing the condensed fraction 40 through the revaporizer 285, by first passing the condensed fraction 40 through the pressure reduction valve 245 and subsequently performing the indirectly heat exchanging of the condensed fraction 40 against the heating fluid 286.
  • a lower temperature of the heating fluid 286 can be achieved when it is discharged from the revaporizer 285 and/or more of the cold vested in the condensed fraction 40 can be recovered into the heating fluid 286.
  • the pressure reduction valve 245 controls the discharge temperature of the vaporized stream being discharged from the revaporizer 285.
  • the pressure reduction valve 245 may suitably be functionally coupled to a first temperature sensor 247, arranged in the condensed fraction discharge line 40 downstream of the revaporizer 285, whereby the valve setting is controlled in response to a first temperature signal generated in the first temperature sensor 247.
  • the first temperature sensor is suitably arranged in the condensed fraction discharge line 40 between the revaporizer 285 and the optional fuel gas compressor 390.
  • a first target temperature setting for this control loop may be set at a few degrees below, e.g. 2 °C below, the temperature of the heating fluid 286 at the inlet of the revaporizer 285.
  • the temperature of the condensed fraction 40 at the outlet of the revaporizer is between ambient temperature and 10 °C below ambient temperature to effectively obtain the most benefit from the cold vested in the condensed fraction 40.
  • the second separation pressure is preferably higher than the first separation pressure.
  • separation pressure may suitably be between 2 and 22 bara, preferably between 5 and 22 bara, more preferably between 5 and 15 bara.
  • a second separation pressure in the higher end of the range of 2 to 22 bara helps the partial condensation of the compressed stream 70 and to provide clearance for a higher pressure drop in the optional pressure reduction valve 245 and/or to maintain a higher pressure even after the pressure reduction valve 245, which saves on fuel gas compression duty in the optional fuel gas compressor 360.
  • the lower end of the range helps the separation efficiency in the gas/liquid separator 33 and causes less over compressing of the vapor fraction 80 which is to be combusted in the combustion device 220 at a relatively low pressure of typically less than 15 bara.
  • the proposed range of between 5 and 15 bara for the second separation pressure strikes a proper balance between the beneficial and the adverse effects summarized earlier in this paragraph.
  • the second separation pressure is in the range of from 5 to 8 bara, which pressure most often meets the requirements of a low-pressure fuel gas stream suitable for conveying the vapour fraction 80 to the combustion device 220 without need for further compression.
  • a higher pressure may be selected if the combustion device 220 is at a relatively large distance from the first gas/liquid phase separator and/or when the vapour fraction 80 is intended to pass through one or more cold recovery heat exchangers 85. In such
  • the second separation pressure is about 6.5 bara.
  • the gas turbine 320 in which the condensed fraction 40 is ultimately combusted is the refrigerant compressor driver 190 that is in driving engagement with the refrigerant compressor 160.
  • the gas turbine 320 may drive the refrigerant compressor 160.
  • suitable liquefaction systems can represent any suitable hydrocarbon liquefaction system and/or process, in particular any natural gas liquefaction process producing liquefied natural gas, and the invention is not limited by the specific choice of liquefaction system.
  • suitable liquefaction systems employ single refrigerant cycle processes (usually single mixed refrigerant - SMR - processes, such as PRICO described in a paper by K R
  • refrigerant such as for instance the BHP-cLNG process also described in the afore-mentioned paper by Johnsen and Christiansen) ; double refrigerant cycle processes
  • LIQUEFIN process such as described in for instance the paper entitled “LIQUEFIN: AN INNOVATIVE PROCESS TO REDUCE LNG COSTS” by P-Y Martin et al, presented at the 22 nd World Gas Conference in Tokyo, Japan (2003) .
  • Other suitable three-cycle processes include for example US
  • 100 is selected to be a coil wound heat exchanger, comprising a warm side comprising all the tubes,
  • the cold side is formed by the shell side of the cryogenic heat exchanger 180.
  • At least one refrigerated hydrocarbon pre-cooling heat exchanger 115 may be provided in the hydrocarbon stream line 110, upstream of the cryogenic heat exchanger 180.
  • the main refrigerant in the present embodiment is a mixed refrigerant.
  • the refrigerant circuit 101 comprises a spent refrigerant line 150, connecting the cryogenic heat exchanger 180 (in this case a shell side 186 of the cryogenic heat exchanger 180) with a main suction end of the refrigerant compressor 160, and a compressed
  • refrigerant line 120 connecting the refrigerant
  • compressor 160 discharge outlet with an MR separator 128.
  • One or more heat exchangers are provided in the
  • the compressed refrigerant line 120 including in the present example at least one reject heat exchanger 124.
  • the MR separator 128 is in fluid connection with the lower LMR tube bundle 183 via a light refrigerant fraction line 121, and with the HMR tube bundle via a heavy refrigerant fraction line 122.
  • the at least one refrigerated hydrocarbon pre-cooling heat exchanger 115 and the at least one refrigerated main refrigerant pre-cooling heat exchanger 125 are
  • pre-cooling refrigerant via lines 127 and 126, respectively.
  • pre-cooling refrigerant via lines 127 and 126, respectively.
  • refrigerant may be shared from the same pre-cooling refrigerant cycle. Moreover, the at least one
  • refrigerated hydrocarbon pre-cooling heat exchanger 115 and the at least one refrigerated main refrigerant pre- cooling heat exchanger 125 may be combined into one pre- cooling heat exchanger unit (not shown) .
  • the HMR tube bundle 185 is in fluid connection with an HMR line 141.
  • the HMR line 141 is in fluid communication with the shell side
  • first HRM return line 143 is fluidly connected to the spent refrigerant line 150.
  • the LMR tube bundle 184 is in fluid connection with the refrigerated refrigerant line 131.
  • a main refrigerant return line 133 establishes fluid communication between the refrigerated refrigerant line 131 and the shell side 186 of the cryogenic heat exchanger 180.
  • a main refrigerant control valve 134 is configured in the main refrigerant return line 133.
  • the main refrigerant return line 133 is in fluid communication with the spent refrigerant line 150, via said shell side 186 and in heat exchanging
  • each one of the LMR tube bundles 183 and 184, and the HMR tube bundle 185 is identical to each one of the LMR tube bundles 183 and 184, and the HMR tube bundle 185.
  • the refrigerated refrigerant line 131 is split into the auxiliary refrigerant feed line 132 and the main refrigerant return line 133.
  • the auxiliary refrigerant return line 138 on an upstream end thereof, fluidly connects with the auxiliary refrigerant feed line 132 via the condenser 35.
  • the auxiliary refrigerant return line 138 on a
  • the refrigerant is cycled in the refrigerant circuit 101, whereby spent refrigerant 150 is compressed in the refrigerant compressor 160 to form a compressed
  • MR separator 128 into a light refrigerant fraction 121 consisting of the vaporous constituents of the partially condensed compressed refrigerant, and a heavy refrigerant fraction 122 consisting of the liquid constituents of the partially condensed compressed refrigerant.
  • the light refrigerant fraction 121 is passed via successively the lower LMR bundle 183 and the upper LMR bundle 184 through the cryogenic heat exchanger 180, while the heavy refrigerant fraction 122 is passed via the HMR bundle 185 through the cryogenic heat exchanger
  • hydrocarbon stream 110 passes through the cryogenic heat exchanger 180 via successively the lower hydrocarbon bundle 181 and the upper hydrocarbon bundle 182 and is being liquefied evaporating heavy refrigerant fraction and sub-cooled against the evaporating light refrigerant fraction .
  • the auxiliary refrigerant stream is formed by a slip stream of the main refrigerant stream, more specifically by a slip stream of the light refrigerant fraction. This latter case is illustrated in Figures 5 and 6.
  • a slip stream may conveniently be passed back into the main refrigerant circuit via the shell side 186 of the cryogenic heat exchanger 180, where it may still assist in withdrawing heat from the stream in the upper and/or lower tube bundles.
  • a contemplated composition of the auxiliary refrigerant contains between 25 mol% and
  • auxiliary refrigerant contains at least 95% of these constituents and/or the total of nitrogen and methane is at least 65 mol%.
  • a composition within these ranges is may be readily available from the main
  • refrigerant circuit if a mixed refrigerant is employed for sub-cooling of the liquefied hydrocarbon stream.
  • Employing a slip stream from the main refrigerant stream has as advantage that the amount of additional equipment to be installed is minimal. For instance, no additional auxiliary refrigerant compressor and auxiliary refrigerant condenser would be needed, which would be the case if a separate independent auxiliary refrigerant cycle would be proposed.
  • the vaporizer 285 is arranged in the compressed vapour line 70 between the end-flash
  • end flash compressor 260 and the optional fuel gas compressor 360 may share a single compressor driver 290.
  • These compressors may be embodied as two separate compressor casings on a common drive shaft, or they may actually be two compressor stages within a single casing.
  • Figure 4 shows a special group of embodiments wherein a stream splitter 75 is provided in the compressed vapour stream line 70, whereby the compressed vapour stream line 70 is divided over a first branch 71 and a second branch 72.
  • the first branch 71 is arranged to convey a first compressed vapour part stream to the gas/liquid separator 33
  • the second branch 72 is arranged to convey a second compressed vapour part stream to the same
  • the stream splitter 75 merely divides the incoming compressed vapour stream 70 into two part streams of equal composition and phase.
  • the stream splitter 75 may be a pipe junction in the form a simple T-junction, preferably in conjunction with a split ratio control valve 76 in one of the first and second branches.
  • the condenser 35 is arranged in the first branch 71.
  • the optional cold recovery heat exchanger 85 is also arranged in the first branch 71 such that the first compressed vapour part stream is employed as the cold recovery fluid 86 generally referenced in Figure 1.
  • the revaporizer 285 may be arranged in the second branch 72, such that the second compressed vapour part stream is employed as the heating fluid 286 generally referenced in
  • compressed vapour stream 70 is split into a first compressed vapour part stream and a second compressed vapour part stream.
  • the first compressed vapour part stream is discharged from the stream splitter 75 into and conveyed to the gas/liquid separator 33 in the first branch 71, while the second compressed vapour part stream is discharged from the stream splitter 75 into and conveyed to the gas/liquid separator 33 in the second branch 72.
  • the first compressed vapour part stream and second compressed vapour part stream both have the same composition and phase as the compressed vapour 70.
  • the part of the compressed vapour stream 70 from which heat is passed to the auxiliary refrigerant stream 132 is formed by the first compressed vapour part stream.
  • the first compressed vapour part stream is indirectly heat exchanged against the vapour fraction 80 from the gas/liquid separator 33 in the cold recovery heat exchanger 85. Downstream of this heat exchanging, the vapour fraction 80 is warmer than between the gas/liquid separator 33 and the cold recovery heat exchanger 85. It may then be combusted in the combustion device 220 as explained hereinbefore.
  • intermediate stream that is fed into the gas/liquid separator 33 is formed by the combination of the first and second compressed part streams.
  • the splitting of the compressed vapour is preferably performed with an adjustable split ratio.
  • the split ratio corresponds to the quotient of mass flow rates in the second branch 71 and the compressed vapour line 70.
  • the split ratio may be adjusted in response to a
  • temperature signal representative of the temperature of the vapour fraction 80 from the gas/liquid separator 33 being discharged from the cold recovery heat exchanger 85 before being combusted.
  • This temperature is preferably maintained at a pre-determined target value by adjusting the split ratio, and this way it will be possible to achieve a certain degree of cold recovery from the vapour fraction 80 regardless of variations in the flow rate of the vapour fraction 80.
  • a second temperature sensor 77 may be provided in the vapour fraction line 80 between the cold recovery heat exchanger 85 and the combustion device 220, which is electronically coupled to the split ratio control valve 76 such that the valve setting of the split ratio control valve 76 is controlled using the signal representative of the temperature generated in the second temperature sensor 77.
  • a second target temperature setting for this control loop may be set at a few degrees below, e.g. 2 °C below, the temperature of the cold recovery fluid 86 at the inlet of the cold recovery heat exchanger 85. If the temperature of the vapour fraction 80 at the outlet of the cold recovery heat exchanger 85 is still lower than the second target temperature, the split ratio may be adjusted to be increased (for instance by reducing the flow opening in the split ratio control valve 76) .
  • the temperature of the vapour fraction 80 at the outlet of the cold recovery heat exchanger 85 is between ambient temperature and at most 10 °C below ambient temperature, to obtain the most cold recovery out of the vapour fraction 80.
  • separator 50 in this case comprises a gas/liquid
  • the cold recovery stream 66 consists of a side Table 1 (low pressure case)
  • cryogenic hydrocarbon composition 8 is assumed to consist of the cold recovery stream 66 and the raw liquefied stream 1 coming from the pressure reduction system 5.
  • the remainder of Figure 7 corresponds to Figure 4.
  • vapour bypass control valve 77, vapour recycle control valve 88, recycle valve 14, and external stripping vapour flow control valve 73 are closed and in no-flow condition.
  • C2+ indicates all hydrocarbons having a mass corresponding to that of ethane, and upward.
  • C2+ consists mostly of ethane .
  • Tables 1 and 2 correspond to one calculation wherein the second separation pressure falls in the range of from 4 to 8 bara.
  • a low quality fuel gas is discharged from the cold recovery heat exchanger 85 at a pressure of 5.00 bara and a temperature of 28 °C; and a revaporized condensed fraction that is discharged from the revaporizer 285 at a pressure of 3.00 bara and a temperature of 25 °C.
  • the latter may be utilized as high quality fuel gas .
  • the ultimate composition of the liquefied hydrocarbon inventory as stored in the cryogenic storage tank 210 is 0.82 mol% nitrogen; 98.75 mol% methane and 0.43 mol% C2+.
  • the liquefied hydrocarbon stream being passed through the main product line 91 to the cryogenic storage tank 210 has slightly more nitrogen than the liquefied hydrocarbon inventory as stored in the cryogenic storage tank 210.
  • a preferred range of liquefaction pressure, at which raw liquefied stream is discharged in the rundown line 1 from the liquefier 100 is from 15 bara to 120 bara, more preferably from 15 bara to 90 bara or from 45 bara to 120 bara.
  • a preferred temperature range for the raw liquefied stream in the rundown line 1 may be from -165 °C to -120 °C.
  • the vapour fraction 80 is envisaged to contain in the range of from 30 mol% to 90 mol% of nitrogen, preferably in the range of from 30 mol% to 80 mol% of nitrogen or in the range of from 45 mol% to 90 mol% of nitrogen, preferably in the range of from 45 mol% to 80 mol% of nitrogen, most preferably from 50 mol% to 80 mol% of nitrogen.
  • a content of nitrogen of between 50 mol% and 80 mol% such as about
  • the condensed fraction 40 generally contains up to 30 mol% of nitrogen, and not less than 5 mol%, preferably not less than 10 mol%. Striving for lower values would cost more auxiliary cooling duty whereas that is not needed for typical gas turbines and particularly not for aero derivative gas turbines.
  • any refrigerant compressor including refrigerant compressor 160 may be driven by any type of suitable compressor driver 190, including any selected from the group consisting of gas turbine; steam turbine; and electric motor; and inter combinations thereof. This generally applies also to refrigerant compressor driver 190.
  • the gas turbine may be selected from the group of so-called industrial gas turbines, or the group of so-called aeroderivative gas turbines .
  • the group of aeroderivative gas turbines includes: Rolls Royce Trent 60, RB211, or 6761, and General Electric LMS100TM, LM6000, LM5000 and
  • LM2500 and variants of any of these (e.g. LM2500+) .
  • the second fuel gas pressure is selected in a range between 15 and 75 bara, more preferably in a range of between 45 and 75 bara.
  • industrial gas turbines is between around 15 and around 25 bara, on average.
  • the latest generation of industrial gas turbine requires relatively high pressure fuel gas, such as in the range of from 35 to 45 bara.
  • the range of between 45 and 75 bara is recommended to meet fuel gas pressure requirements of typical
  • the auxiliary refrigerant stream 132 preferably has a bubble point under standard conditions at a lower temperature than the bubble point of the compressed vapour stream 70 under standard conditions (ISO 13443 standard: 15 °C under 1.0 atmosphere absolute pressure) .
  • the auxiliary refrigerant may contain between 5 mol% and 75 mol% of nitrogen.
  • the auxiliary refrigerant may contain between 5 mol% and 75 mol% of nitrogen.
  • auxiliary refrigerant contains between 5 mol% to 40 mol% of nitrogen, more preferably between 25 mol% and 40 mol%.
  • auxiliary refrigerant consists of methane with the proviso that the total content of methane and nitrogen does not exceed 100 mol%.
  • the majority of or the entire balance may consist of ethane and/or ethylene.
  • the amount of nitrogen in the liquid hydrocarbon stream 90 is between 0.5 and 1 mol%, preferably as close to 1.0 mol% as possible yet not exceeding said maximum of about 1.1 mol%.
  • boil-off gas results from thermal evaporation caused by heat added to the liquefied product, for instance in the form of heat leakage into storage tanks, LNG piping, and heat input from plant LNG pumps.
  • boil-off gas may
  • vapour reject line 64 optionally be injected into the vapour reject line 64, either upstream or downstream of the end-flash compressor 260 to be subject to the phase separation in the
  • gas/liquid separator 33 This may suitably comprise collecting boil-off gas from the cryogenic storage tank 210, possibly via a boil-off gas supply line 230 as is illustrated for example in Figure 5.
  • Boil-off gas results from adding heat to at least part of the liquefied hydrocarbons, whereby a part of the methane- containing liquid phase in the liquefied hydrocarbons evaporates to form said boil-off gas.

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Abstract

Une composition d'hydrocarbure cryogénique, obtenue par l'exposition d'un flux d'hydrocarbure liquéfié brut à une étape de réduction de pression, est d'abord séparée en un flux de rejet sous forme de vapeur et en un flux liquide. Le courant liquide est déchargé sous la forme du flux d'hydrocarbure liquéfié. Le flux de rejet sous forme de vapeur est recomprimé, partiellement condensé par échange thermique indirect du flux de vapeur comprimé avec un flux de réfrigérant auxiliaire, et séparé. La fraction condensée est revaporisée et brûlée dans une turbine à gaz. La fraction de vapeur, qui présente généralement une teneur en azote plus élevée et un pouvoir calorifique inférieur à celui de la fraction condensée, est brûlée dans un dispositif de combustion autre qu'une turbine à gaz. Le flux de réfrigérant auxiliaire est formé par l'écoulement glissant du flux de réfrigérant recyclé provenant du liquéfacteur.
PCT/EP2014/055959 2013-04-22 2014-03-25 Procédé et appareil de production d'un flux d'hydrocarbure liquéfié WO2014173598A2 (fr)

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US4746342A (en) * 1985-11-27 1988-05-24 Phillips Petroleum Company Recovery of NGL's and rejection of N2 from natural gas
DE10119761A1 (de) * 2001-04-23 2002-10-24 Linde Ag Verfahren und Vorrichtung zur Verflüssigung von Erdgas
DE10121339A1 (de) * 2001-05-02 2002-11-07 Linde Ag Verfahren zum Abtrennen von Stickstoff aus einer Stickstoff-entaltenden Kohlenwasserstoff Fraktion
AU2009319191B2 (en) * 2008-11-03 2013-05-02 Shell Internationale Research Maatschappij B.V. Method of rejecting nitrogen from a hydrocarbon stream to provide a fuel gas stream and an apparatus therefor
RU2554736C2 (ru) * 2009-07-21 2015-06-27 Шелл Интернэшнл Рисерч Маатсхаппий Б.В. Способ очистки многофазного углеводородного потока и предназначенная для этого установка

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