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US3400547A - Process for liquefaction of natural gas and transportation by marine vessel - Google Patents

Process for liquefaction of natural gas and transportation by marine vessel Download PDF

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Publication number
US3400547A
US3400547A US654935A US65493567A US3400547A US 3400547 A US3400547 A US 3400547A US 654935 A US654935 A US 654935A US 65493567 A US65493567 A US 65493567A US 3400547 A US3400547 A US 3400547A
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United States
Prior art keywords
natural gas
nitrogen
site
refrigerant
methane
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Expired - Lifetime
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US654935A
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Virgil C Williams
Omar H Simonds
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Williams
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Priority to US59149666A priority Critical
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Priority to US654935A priority patent/US3400547A/en
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Publication of US3400547A publication Critical patent/US3400547A/en
Anticipated expiration legal-status Critical
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used)
    • F25J1/003Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
    • F25J1/0032Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) 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"
    • F25J1/004Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) 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
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B63SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63BSHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
    • B63B25/00Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby
    • B63B25/02Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods
    • B63B25/08Load-accommodating arrangements, e.g. stowing, trimming; Vessels characterised thereby for bulk goods fluid
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17STORING OF DISTRIBUTING GASES OR LIQUIDS
    • F17CVESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C9/00Methods or apparatus for discharging liquefied or solidified gases from vessels not under pressure
    • F17C9/02Methods or apparatus for discharging liquefied or solidified gases from vessels not under pressure with change of state, e.g. vaporisation
    • F17C9/04Recovery of thermal energy
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used)
    • F25J1/0002Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) characterised by the fluid to be liquefied
    • F25J1/0012Primary atmospheric gases, e.g. air
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used)
    • F25J1/0002Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) characterised by the fluid to be liquefied
    • F25J1/0012Primary atmospheric gases, e.g. air
    • F25J1/0015Nitrogen
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used)
    • F25J1/0002Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) characterised by the fluid to be liquefied
    • F25J1/0022Hydrocarbons, e.g. natural gas
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used)
    • F25J1/003Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
    • F25J1/0032Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) 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"
    • F25J1/0042Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) 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
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used)
    • F25J1/003Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
    • F25J1/0047Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) 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
    • F25J1/0052Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) 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
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used)
    • F25J1/006Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) characterised by the refrigerant fluid used
    • F25J1/008Hydrocarbons
    • F25J1/0087Propane; Propylene
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used)
    • F25J1/02Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) 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
    • F25J1/0203Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) requiring the use of refrigeration, e.g. of helium or hydrogen Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a single-component refrigerant [SCR] fluid in a closed vapor compression cycle (not used)
    • F25J1/0204Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) requiring the use of refrigeration, e.g. of helium or hydrogen Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a single-component refrigerant [SCR] fluid in a closed vapor compression cycle (not used) as a single flow SCR cycle
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used)
    • F25J1/02Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) 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
    • F25J1/0221Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) requiring the use of refrigeration, e.g. of helium or hydrogen Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using the cold stored in an external cryogenic component in an open refrigeration loop
    • F25J1/0223Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) requiring the use of refrigeration, e.g. of helium or hydrogen Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using the cold stored in an external cryogenic component in an open refrigeration loop in combination with the subsequent re-vaporisation of the originally liquefied gas at a second location to produce the external cryogenic component
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used)
    • F25J1/02Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) 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
    • F25J1/0221Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) requiring the use of refrigeration, e.g. of helium or hydrogen Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using the cold stored in an external cryogenic component in an open refrigeration loop
    • F25J1/0224Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) requiring the use of refrigeration, e.g. of helium or hydrogen Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using the cold stored in an external cryogenic component in an open refrigeration loop in combination with an internal quasi-closed refrigeration loop
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used)
    • F25J1/02Processes or apparatus for liquefying or solidifying gases or gaseous mixtures (not used) 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
    • F25J1/0243Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0279Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc.
    • F25J1/0292Refrigerant compression by cold or cryogenic suction of the refrigerant gas
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17STORING OF DISTRIBUTING GASES OR LIQUIDS
    • F17CVESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2265/00Effects achieved by gas storage or gas handling
    • F17C2265/05Regasification
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00Processes characterised by the type or other details of the feed stream
    • F25J2210/06Splitting of the feed stream, e.g. for treating or cooling in different ways
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00Processes characterised by the type or other details of the feed stream
    • F25J2210/40Air or oxygen enriched air, i.e. generally less than 30mol% of O2
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00Processes characterised by the type or other details of the feed stream
    • F25J2210/42Nitrogen
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00Processes characterised by the type or other details of the feed stream
    • F25J2210/62Liquefied natural gas [LNG]; Natural gas liquids [NGL]; Liquefied petroleum gas [LPG]
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2230/00Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/08Cold compressor, i.e. suction of the gas at cryogenic temperature and generally without afterstage-cooler
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2230/00Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/20Integrated compressor and process expander; Gear box arrangement; Multiple compressors on a common shaft
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2230/00Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/30Compression of the feed stream
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2230/00Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/40Processes or apparatus involving steps for increasing the pressure of gaseous process streams the fluid being air
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2230/00Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/42Processes or apparatus involving steps for increasing the pressure of gaseous process streams the fluid being nitrogen
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2235/00Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams
    • F25J2235/42Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams the fluid being nitrogen
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2235/00Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams
    • F25J2235/60Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams the fluid being (a mixture of) hydrocarbons
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2240/00Processes or apparatus involving steps for expanding of process streams
    • F25J2240/02Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream
    • F25J2240/12Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream the fluid being nitrogen
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2270/00Refrigeration techniques used
    • F25J2270/14External refrigeration with work-producing gas expansion loop
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2270/00Refrigeration techniques used
    • F25J2270/14External refrigeration with work-producing gas expansion loop
    • F25J2270/16External refrigeration with work-producing gas expansion loop with mutliple gas expansion loops of the same refrigerant
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25JLIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2290/00Other details not covered by groups F25J2200/00 - F25J2280/00
    • F25J2290/62Details of storing a fluid in a tank

Description

Sept. 10, 1968 v, c. w L s ETAL 3,400,547

PROCESS FOR LIQUEFACTION OF NATURAL GAS AND TRANSPORTATION BY MARINE VESSEL Filed July 20, 1967 6 Sheets-Sheet 2 I E 5 I 220 I80 00 -60 -20 O 20 60 I09 TEMP F TEMP. "F

60 I00 1/0 I30 140 I P ps in.

mu/n/rozs: wee/1. C. w/LLmMs, OMAR H.5/HOND5,

Sept. 10, 1968 v, c. WILLIAMS ETAL 3,400,547 PROCESS FOR LIQUEFACTION OF NATURAL GAS AND TRANSPORTATION BY MARINE VESSEL Filed July 20, 1967 6 Sheets-Sheet 5 F/ELD SITE METHANE psz'a.

IN CYc LE ATTORNEYS Sept. 10. 1968 v. c. WILLIAMS E AL 3,400,547 PROCESS FOR LIQUEFACTION OF NATURAL GAS AND TRANSPORTATION BY MARINE VESSEL Filed July 20, 1967 6 Sheets-Sheet 6 llb C soa /fa 1am- L766 150 MAKE-UP 162 Paws? v 7 w= 67 w=l06 N: 1360 flfi' V k r MARKET SITE PRocEss x Z N M DIAGRAM 405 L z IEPSIA +05/-' 174176175 2-8? '60 i: 5 {80 V llb cu 1595M sat Zz 258F 7 /.05 26 IV; Sat ziq- 32oF I5'PSIA MARKET SITE I-IEAT EXCHANGE/Q5 7 32.12.

/80 I45 -I00 60 2o m 200 EACH TANK Co/vmuvs [MIT/ALLY 0.00525 Cu FT 4 H 2 /LIQ NITROGEN 0.262 LB LIQ NITROGEN EAo-I TANK HALF FULL MAREEI FIELD 1.05 1.6 NITROGEN ILB NITROGEN EACH TANK CONTAINS INITIAL-LYO-OI CU FT 2 3 5. :/LIQ METHANE, 0-262 L8 L/Q METHANE 4 H TANK: FULL INVENTORs:

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FIELD AgKET 5v/.74L/4,E?M azuwmw I 1.6 METHANE 202 1-05 LB METHANE HTTOPNEYS United States Patent .s

3,400,547 PROCESS FOR LIQUEFACTION OF NATURAL GAS AND TRANSPORTATION BY MARINE VESSEL Virgil C. Williams, 104 Frontenac Forest, St. Louis, Mo. 63131, and Omar H. Simonds, Essex Fells, N.J.; said Simonds assignor of thirty-five percent to said Williams Continuation-impart of application Ser. No. 591,496, Nov. 2, 1966. This application July 20, 1967, Ser. No. 654,935

23 Claims. (Cl. 62-55) ABSTRACT OF THE DISCLOSURE Natural gas liquefaction and transportation from a field site to a market site is accomplished by transporting liquid nitrogen or liquid air by ship from the market place to the field site where it is used to liquefy the natural gas. The availability of the cold or refrigeration in the liquid nitrogen or air reduces the equipment required at the field site. Liquid natural gas is pumped into the holds of the same cryogenic tanker ship used to transport the liquid nitrogen or air and the liquefied natural gas is returned to the market site. Regasification of the liquid natural gas is carried out to use the cold or refrigerant effect therein to liquefy nitrogen or air, which is then charged to the returning tanker to the field site. The process is a repetition of liquid nitrogen or liquid air. from the market site to the field site and there used to liquefy natural gas, which is then shipped from the field to the market where the liquid natural gas is gasified and in the process liquefies nitrogen or air for return to the field. The cycle employs about 1.0 to 2.1 pounds of nitrogen to 1.05 pounds of methane. In the process of both the field site and the market site, various cycles employing expansion of the various high pressure streams for cooling is employed and the work is matched against compression of other streams and subsequent expansion for efficiency in the system and minimization of power requirement.

CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of our application Ser. No. 591,496, filed Nov. 2, 1966 and now abandoned.

BACKGROUND OF THE INVENTION There is an economic use for the great quantities of unused natural gas in areas remote from the worlds markets. There are two classes of natural gas: (a) gas produced from gas wells and (b) natural gas produced in association with crude oil. Much of this gas production occurs in vast fields in the developing countries and cannot be transported economically by pipepline to these world markets. Because of this, only a fraction of the worlds natural gas resources are at present usefully consumed.

It is one thing to flare or release natural gas at great pressure, it is another to reduce it to manageable proportions, transport it, store it, and sell it in competition with other fuels.

One way to deal with a large volume of gas is to liquefy it. However, natural gas, which is largely methane, cannot be liquefied by simply increasing the pressure, as has been the case with heavier hydrocarbons used for energy purposes. The critical temperature of methane is -1l6.5 R, which is the temperature above which it is impossible to liquefy methane regardless of the pressure applied. At atmospheric pressure, the liquefied methane will be at its normal boiling point of -258 F. Hence, the techniques of liquefying and handling natural gas are within the scope of the field of cryogenic technology.

3,400,547, Patented Sept. 10, 1968 The liquefaction of natural gas requires the removal of energy in the form of sensible and latent heat. This process can be accomplished by mechanical refrigeration where heat is transferred by a series of refrigerants to a reject ambient temperature-level heat sink. This method uses what is referred to as a cascade cycle or process.

Another method is that of compressing and expanding the gas, using turbine-expanders. This is known as an expander cycle.

The most widely used cycle is the cascaded vapor compression system. This cycle, based on refrigeration principles, uses commercially available refrigerants whose thermodynamic and physical properties are fairly wellknown. Storage of large volumes of natural gas is most economical in its liquefied form. As a liquid, natural gas will occupy approximately of its gaseous volume under standard conditions (625 cu. ft. of gas at standard temperature and pressure=1 cu. ft. liquid at normal boiling point). Two areas of interests show need for storage of liquefied natural gas.

The first area of interest lies in transporting gas from energy-rich to energy-poor areas in insulated tankers, whereby storage depots at both the field site and the market site are required. In such base-load operations, the storage facility is essentially a surge tank smoothing out the nonuniform base-load demand and fuel delivery operations. In this case, it is not necessary to preserve the liquefied natural gas in the tank for long periods, since it is passed on to distribution within a short period of time.

The second area of interest is in the continued growth and expansion of the natural gas industry which has resulted in the need for storage of large volumes of gas near metropolitan areas to meet winter peak-loads. In this case, liquefied natural gas is stored for relatively long periods of time and used during only a few days of the winter. Consequently, heat influx must be held to a minimum.

A great deal of research is at present being devoted to finding and refining industrial processes which will make continuous use of the very large amounts of cold available. The main possibilities here lie in the development of major industrial applications such as the production by air rectification of liquid oxygen, nitrogen, etc.

Ideally, to make the maximum use of cold potential, it is necessary that such use should show a considerable reduction in capital investment and operating costs compared with conventional processes for making some saleable commodity.

The cold should replace low-temperature refrigeration which is very expensive compared to mild refrigeration (e.g. the low temperatures needed in the production of cryogenic liquids). The overall cost of refrigeration in the liquefaction of the natural gas is a major part of the final sales price.

There is, however, another manner of approaching the use of the available cold. This would be to consider the cold as an inherent part of the process thus making it the commodity; not selling it or something derived from it, but building its use into the process technology to reduce the investment and operating costs and thus' to increase the profitability of a natural gas distribution venture.

SUMMARY OF THE INVENTION By means of this invention, a process has been devised for liquefaction of nitrogen at the market site against the evaporating liquefied natural gas and returning the liquid nitrogen in the insulated transport tanks in the marine vessel to the field site where it is employed in liquefaction of the natural gas, which is then loaded on the marine vessel for shipment to the market. The availability of the cold in the liquid nitrogen reduces greatly the equipment required at the field site. The cycle is a constant repetition of these two factors, namely, shipping liquid gas to the market and returning liquid nitrogen back to the field, and using the refrigeration effect at both the field and the market sites of the liquefied gas shipped to the site to liquefy the gas shipped from the site. Nitrogen may be separated from air at the market site by air rectification, thus producing oxygen gas, which at the market, is of great use in the chemical and metallurgical industries. No auxiliary liquefaction means are needed at the field site and all of the energy necessary for liquefaction of the natural gas is provided through the liquid nitrogen shipped from the market site to the field site.

It is also possible to employ liquid air because of its major proportion of nitrogen instead of liquid nitrogen in this cycle for shipment to the field site. Air, because of its high percentage of nitrogen, has substantially similar thermal characteristics to nitrogen. In this case the liquid storage tanks would require purging with nitrogen to remove the oxygen containing atmosphere to avoid possible explosive mixtures of natural gas and air. This purged nitrogen is obtainable from an auxiliary supply or from fractionation of the liquid air either at the field site or the market site.

The large refrigeration complexes required to liquefy the natural gas at the field site are thus obviated, and economy-wise the capital equipment located in the foreign field site is reduced to a very minimum. The process is initiated for each ship by sending outbound from market site to field site one cargo of liquid nitrogen which can be accumulated by any economical means in the market site.

The above features are objects of this invention and further objects will appear in the detailed description which follows, and will be otherwise apparent to those skilled in the art.

For the purpose of illustration, there are shown in the accompanying drawings examples of the process of this invention. It is to be understood that these drawings are for the purpose of example only and that the invention is not limited thereto.

In the drawings:

FIGURE 1 is a flow sheet showing a typical field site process for liquefaction of natural gas;

FIGURE 2 is a flow sheet showing a typical market site process for the liquefaction of nitrogen;

FIGURE 3 is a graph showing the heat transfer in the field site exchanger;

FIGURE 4 is a graph showing the heat transfer in the market site heat exchanger;

FIGURE 5 is a graph showing a typical pressure relationship at the field site for the proportion of nitrogen to methane needed for liquefaction;

FIGURE 6 is a graph showing the vapor pressure curves for nitrogen and methane;

FIGURE 7 is a flow sheet of a modified process employing higher pressures and showing a typical field site process for liquefaction of natural gas;

FIGURE 8 is a block diagram showing the arrangement of the equipment employed in the fiow sheet of FIGURE 7;

FIGURE 9 is a graph illustrating the flow of heat in the field site exchangers;

FIGURE 10 is a flow sheet of the modified example employing higher pressures and showing a typical market site process;

FIGURE 11 is a block diagram showing the arrangement of the equipment for the market site process of FIGURE 10;

FIGURE 12 is a graph showing the flow of heat in the market site heat exchangers of FIGURE 10; and

FIGURE 13 is a schematic view of the tankers employed in the transfer of liquid nitrogen from the market site to the field site and the return tanker shipment transferring liquefied natural gas from the field site to the market site.

DISCLOSURE Natural gas, which is comprised principally of methane with small percentages of ethane, propane, butane, and minimal percentages of carbon dioxide and nitrogen, is available in many places in the world, but in most cases the markets for this gas are in industrial countries remote from the field sites. In many situations pipe lines are used to transport the gas from the source to the market. However, there are circumstances where pipe line transportation is technically and economically unfeasible. Such cases are, for example, the transportation of Arabian or Algerian gas to England or Germany, and Venezuelan or Mexican gas to Florida or the each coast of the United States, or the North Sea area. It has been proposed to liquefy natural gas at the field site and take it by barge or ship to the market site. At the market site it would be re-gasified and pumped into the distribution system.

In the instant invention the great refrigeration available in the liquid natural gas is employed to liquefy nitrogen at the market site by evaporating the natural gas in heat exchange relation with the nitrogen. The liquid nitrogen is then returned to the transport tanks in insulated marine vessels, although it will be understood that other insulated carriers, such as trucks, railroad tank cars and the like, may be employed, for transport to the field site. At the field site the liquefied nitrogen returned in the tanker, or other vessel, is employed in liquefying the natural gas, which is then returned in the tanker to the market. By this invention the marine vessel is not deadheaded when it is returned from the market site back to the field site, and the cycle is a constant repetition of taking the liquid natural gas to market and then the liquid nitrogen back to the field.

Nitrogen is separated from air at the market site, such as by air rectification, and oxygen gas is produced as a byproduct, which is of great use in the chemical and metallurgical industries. The oxygen then becomes a valuable by-product and a premium factor for the cycle of this invention.

In considering the illustration of the invention, it will be assumed that an insulated marine tanker is employed, although as above stated other insulated carriers, such as railroad tank cars, truck carriers, and the like, may be used.

Example 1 The unit basis chosen for illustration of this invention is the receipt at the market site of one pound of methane, which is the major constituent of natural gas and for practical purposes is considered in calculations demonstrating this process and the two terms may be used interchangeably. In the air rectification at the market site the input may be, as an example, 2.775 pounds of air, which will produce 2.1 pounds of nitrogen and 0.675 pound of purity oxygen. The market site process for nitrogen liquefaction obtained through heat exchange relation with the methane by evaporation from the liquefied gas is carried out on the basis of the use of one pound of methane to 1.0-2.1 pounds of nitrogen. The methane vaporizes and moves or is compressed into the market pipe lines for distribution. The liquid nitrogen produced is put into the insulated storage tanks of the tanker and is taken back to the field site. In this transportation about five percent of the nitrogen is lost by evaporation, thereby delivering about 95% of the nitrogen liquefied at the market site to the field site.

The field site cycle evaporates the liquefied nitrogen against condensing methane and the liquid methane is then put into the insulated storage tanks of the tanker. This cycle uses about 1.0 to 2.1 pounds of nitrogen to 1.05 pounds of methane. The lower ratio, i.e., 1 pound of nitrogen to 1 pound of methane represents the optimum for ship construction but requires a greater pressure of methane employed at the field site. In the limit for tank filling storage capacity on the shipping vessel, about 2 pounds of nitrogen can be carried per 1.0 pound of methane. As the pressure is reduced at the field site, representing economies in compression, the ratio of nitrogento methane is increased which deviates from optimum values for ship construction. FIGURE 5 shows a typical curve for the cycles shown in FIGURES 1 and 2 for the effect of pressure on the nitrogenzmethane relationship. The methane on being returned to the market in the tanker loses about 5% by evaporation, so 1.0 pound is delivered to the market site Where it is evaporated in heat exchange relation with nitrogen to produce liquid nitrogen for shipment of the liquefied nitrogen in the same tanker. back to the field. The program and process consists of repetition of these basic cycles. Some intermediate storage may be employed at both the market and the field sites for transfer purposes through insulated tanks employed to prevent loss of refrigeration.

In the field site flow sheet of FIGURE 1 and the market site flow sheet of FIGURE 2, the cycles employed at these two sites are disclosed. In the field site it will be noted that the features employed use liquefied nitrogen in heat exchange relationship with the natural gas, followed by expansion and consequent cooling of the nitrogen, after which the nitrogen is again used in heat exchange relation with the natural gas to obtain the fullest possible effect of refrigeration available. The nitrogen may be vented to the atmosphere upon the completion of the field site process or used in any other fashion desired. In the market site process the fullest possible effect of refrigeration from the liquefied natural gas is employed by sending compressed nitrogen in heat exchange relation with the liquefied naturalgas and then expanding a major portion of this to reduce the pressure and cool the nitrogen to liquefaction. A portion of the nitrogen stream is drawn off and used in heat exchange relation with the nitrogen stream before expansion and then compressed and fed back into the introduction line for the nitrogen before it is passed into heat exchange relation with the liquefied natural gas. In this manner a highly eificient use of refrigeration is made available to liquefy the nitrogen.

At the field site, the liquid nitrogen is pumped out of the storage tanks of the tanker, or other carrier, and is replaced with liquid methane.It is a significant phenomenon of the two substances, nitrogen and methane, in the process of this invention, that the quantities demanded for flow in the heat exchange stages on a mass basis for heat balance are also in acceptable balance on a liquid volume basis.

The design of the various elements in the cycles of this invention is in accordance with the thermodynamic properties of the individual materials. The data given in the examples are dealt with graphically to satisfy the requirements of the first and second laws of thermodynamics and also to have real significant temperature differences that permit of economic design of the heat exchangers.

FIELD SITE PROCESS The field site process of Example 1 is shown in FIG- URE 1 and graphically shown for the field site exchanger heat flow values in FIGURE 3.,In the field site process, liquefied nitrogen at atmospheric pressure is returned by the insulated tanker from the market site to the field site, and is pumped to working pressure by a liquid pump. The cold nitrogen heat exchanges countercurrently against warm methane gas, which thus is brought to a condensed liquid state at atmospheric pressure. This liquid methane is then put into the tanker for shipping to the market site. To make one pound of methane available at the market site, 1.05 pounds is shipped from the field and 0.05 pound is lost through vaporization or may be vented or used as fuel in an engine or other purposes while in transit.

In the process of FIGURE 1, liquid nitrogen is charged to an intermediate insulated storage tank 10. From the insulated tank 10, 1.7 pounds of liquefied nitrogen is charged at 320 F. and atmospheric pressure, i.e., 14.7 p.s.i.a. to pump 18 where it is compressed to 800 p.s.i.a., for purpose of example, to 310 F. The still liquid nitrogen is then charged through line 20 to heat exchanger 22, where it passes in countercurrent relationship to natural gas. The nitrogen passes through the heat exchanger in pass 24 and leaves at 55 F. and about 800 p.s.i.a. where it is expanded through a turbine expander 26 to p.s.i.a. and l80 F. The nitrogen under these conditions is charged through line 28 to pass 29 in the heat exchanger, and in the process is heated at at 50 p.s.i.a. and is vented in line 30. The natural gas from the field site in the amount of 1.05 pounds at 80 F. and at 800 p.s.i.a. is charged into the heat exchanger in line 32. It goes through the heat exchanger in pass 34 and leaves as liquefied natural gas at atmospheric pressure at 260 F. The thus liquefied natural gas is charged in line 36 to insulated storage tank 12 and from it can be charged to the carrier such as a marine tanker or the like. In the process, the turbine expander delivers 99 B.t.u. of work, which must be absorbed and the heat exchanger transfers 385 B.t.u. In many cases the field site natural gas pressure is below 800 p.s.i.a. and the turbine work may be conveniently used in a compressor to raise the natural gas pressure to 800 p.s.i.a. As an example of alternate pressures and quantities of nitrogen employed in the process, 1.4 pounds of nitrogen may be employed at 1500 p.s.i.a., in which case the turbine expanders will deliver 89 B.t.u. of work and the heat exchanger will transfer 375 B.t.u.

MARKET SITE PROCESS The market site process of Example 1 is shown schematically in FIGURE 2, while FIGURE 4 shows the heat transfer between the methane and the nitrogen by way of a graph. In the market site process, 1 pound of liquefied natural gas is taken from the carrier in line 40 and charged to the intermediate tank 14. One pound of liquefied natural gas is taken from the storage tank through line 42 and charged to the heat exchanger 44 at 260 F. and atmospheric pressure. The liquefied natural gas passes through pass 46 in the heat exchanger and in heat exchange relation with the nitrogen leaves in line 47 at F. where it can be passed to distribution systems or storage tanks or the like for ultimate use and sale at the market site. The nitrogen employed in this system can be obtained from air rectification, as will be well understood in the art, and this process leaves available oxygen for industrial purposes. Nitrogen in the amount of 1.78 pounds is employed, since this provides 1.7 pounds at the field site since there is 5% loss of nitrogen in shipping back to the field through evaporation or the like. This nitrogen is charged through the line 48 at F. and at 250 p.s.i.a. through pass 50 in the heat exchanger, where it is cooled to 255 F. To this is added .725 pound of a compressed flash stream of nitrogen, so that in line 52, 2.505 pounds of nitrogen are obtained. The nitrogen is cooled and condensed to liquid at 255 F. while the methane vaporizes at 260 F. and superheats to +60 F. at 15 p.s.i.a.

The liquid nitrogen in line 52 is subcooled from 255 F. to -310 F. against 0.725 pound of flash gas which warms from 320 F. to 260 F. in line 54. This process is effected in heat exchanger 56. The flash gas slip stream is then compressed from 15 p.s.i.a. at260 F. in compressor 58 to 250 p.s.i.a. at 80 F., and is added in line 60 to the feed stream of 1.78 pounds of nitrogen, which originally enters the process through line 48. The pull off from the separator bottle 62 in line 64 provides 1.78 pounds of liquid nitrogen at atmospheric pressure and at temperature of 320 F. The liquefied nitrogen is charged from line 64 to the intermediate storage tank 16 or directly to the insulated marine tanker or other insulated carrier as provided in this process. The compression work for the slip stream gas is 58 B.t.u.

FIGURE 6 is a vapor pressure curve listing the vapor pressures for methane and nitrogen.

To summarize the example process, and to provide for the loss in transit, 1.05 pounds of liquefied natural gas is charged 'at the field site to the tanker to provide 1.0 pound of liquefied natural gas at the market site. At the market site 1.78 pounds of nitrogen is provided -for shipment in the tanker to provide 1.70 pounds of liquefied nitrogen at the field site.

Example 2 In this example a high pressure system is employed for the field site process and market site process initially described in Example 1. Utilization is made in the full of work provided for the expansion of the various gases to be used in compressing other streams to utilize full efiiciency and economies in the process. The field site process is disclosed in FIGURES 7, 8 and 9, while the market site process is disclosed in FIGURES 10, 11 and 12.

FIELD SITE PROCESS The field site process of Example 2 is shown schematically in FIGURE 7 and in block diagram in FIG- URE 8. The graph of FIGURE 9 shows the heat transfer between the methane and nitrogen. In this process one pound of liquid nitrogen is charged at 320 F. and atmospheric pressure, which, for purpose of illustration, is taken at 15 p.s.i.a. in line 100 to a pump 102. In the pump the liquid nitrogen is pressured to 2000 p.s.i.a. at -300 F. The shaft work is provided through 'a turbine expander (impulse or reaction type) 104 in the methane stream as will be further described. From the pump, the nitrogen is charged through heat exchanger 106 in counter-current relation with methane stream heat exchanger 108. The nitrogen refrigerant is then charged through heat exchanger 110, which along with heat exchanger 112, 114 and 116, all used in the nitrogen refrigerant stream as will be later described, are in heat exchange relationship with the methane heat exchanger 118. From the heat exchanger 110 the nitrogen at 'a temperature of 0 F. passes through a turbine expander 120 to a reduced pressure of 300 p.s.i.a. and a reduced temperature of 190 F. The turbine expander 120 is matched with a compressor 122 which is employed to compress the methane in the feed stream as will be later described. The nitrogen refrigerant from the turbine expander 120 then is passed through heat exchanger 112 in further heat exchange relation with the methane heat exchanger 118 from which it is then introduced to another turbine expander 124 where the pressure is reduced to 30 p.s.i.a and the temperature is reduced to about 190 F. The turbo expander 124 is matched with a compressor 126 in the nitrogen stream, which later compresses the downstream nitrogen as will be further described.

From the turbine expander 124, the nitrogen stream is introduced into heat exchanger 114 in heat exchange relation with the methane heat exchanger 118 in the same fashion as the previous streams. From the heat exchanger 114, the nitrogen refrigerant is introduced to the compressor 126 where it is compressed and then cooled in aftercooler 128. An additional compressor 130 is also employed to further increase the pressure and work is provided through turbine expander 132, which will be further described in the nitrogen stream. From the compressor 130, further cooling is effected in cooling unit 133 after which the nitrogen stream is passed through heat exchanger 134 to obtain a temperature of F. The nitrogen is then introduced at 200 p.s.i.a. to the turbine expander 132 where it is expanded to 18 p.s.i.a. and 190 F. This nitrogen is then passed through the last heat exchanger 116 in heat exchange relation with the methane heat exchanger 118. The nitrogen refrigerant leaving heat exchanger 116 then passes through heat exchanger 136, and is exhausted through line 138 for any eventual desired usage at 18 p.s.i.a. and F.

The incoming methane stream is introduced into the field site process through line 140 at 800 p.s.i.a. and in an amount for the process shown of 1.05 pounds methane. The methane is further compressed in the compressor 122 with work being provided through the nitrogen turbine expander 120, as previously described. Auxiliary refrigeration is provided through cooler 142 and the methane is then introduced at 10 F. and at a pressure of 1500 p.s.i.a. into the methane heat exchanger 118. After leaving the heat exchanger 118, with the consequent cooling by the four nitrogen refrigerant heat exchange units 110, 112, 114 and 116, the methane is passed through heat exchanger 108 for a final phase of heat exchanger cooling in heat exchange relation with the methane heat exchanger 106. The methane is then passed through the turbine expander 104 for further reduction in pressure to 15 p.s.i.a. and a temperature of -258 F. to provide the 1.05 pounds of methane in liquefied form. The work provided in the turbine expander 104 is used to drive the pump 102, as previously described.

FIGURE 8 shows the field site process in block diagram with a matching of the compressors and turbine expanders in simplified form. It further shows the heat transfer in the various heat exchange units and the work provided in the matched turbine expanders and compressor pairs. The graph of FIGURE 9 illustrates the following of the second law of thermodynamics in the field site process by having real temperature differences with the refrigerant nitrogen stream always at a lower temperature than the methane stream from which the nitrogen is abstracting heat The compressors employed may be diaphragm cooled machines with a ratio of isothermal to isentropic ideal works of 0.748 but corrected to actual work by the multiplier 1.175. The isentropic work is calculated at 83% efficiency.

MARKET SITE PROCESS The market site process of Example 2 is shown in FIGURES 10, 11 and 12. FIGURE 10 is a schematic diagram and flow sheet of the nitrogen refrigerant and methane streams, while FIGURE 11 is a block diagram illustrating the work output and input matching of the turbine expanders and compressors to provide for efficiency and economy in the process. FIGURE 12 is a graph showing the heat transfer between the nitrogen and methane to provide a real temperature difference between these streams and illustrates the colder temperature of the methane for abstraction of heat from the nirogen stream. The figures in the market site process are based on 1.05 of nitrogen feed at 1 atmosphere pressure and 85 F. against 1.0 pound of methane in liquefied form, which is being vaporized and processed.

At the market site the liquid methane is vaporized and delivered into the pipe line grid at 600 p.s.i.a. The heat required for this vaporization is used to condense nitrogen gas or (liquid air) which is then returned to the field as a source of refrigeration to liquefy the natural gas. Of the two cycles, the field site and the market site, the latter is the more difiicult to analyze. There are several workable cycles, among them being mixed gas (nitrogen and methane) heat pumping, straight heat pumping (as shown in this example), nitrogen heat pumping, all of which are novel in the invention as described herein. With air employed there is also the possibility for fractionation Within the cycle to deliver liquid nitrogen and oxygen gas for an added economic benefit. The amount of oxygen in a plant size installation would be quite considerable and could support a satellite chemical or metallurgical enterprise.

In the process as shown in FIGURES l0 and 11, 1.05 pound of methane in saturated liquid form at 15 p.s.i. and -258 F. is introduced in the process through line where it is split into a first stream in line 152 and a second stream in' line 154. The first stream in the amount of 0.385 pound methane is passed through heat exchanger 156, which is in heat exchange relation with nitrogen heat exchangers 158 and 160, as will be later described. The methane stream, after passing through heat exchanger 156, is at a temperature of 245 F. when it is introduced into compressor 162 where it is compressed to 600 p.s.i.a. and a temperature of 110 F. in stream 164. The compressor 162 is matched with a turbine expander 165,.which 'is provided in the second stream of methane as will be more clearly described below. This matching provides that the work output from the turbo expander 166 is supplied to the compressor 162 for part of the power required. Stream 164 is combined in final output stream 166 with a second stream output to provide 1.0 pound methane at 600 p.s.i. and 120 F.

The second liquid methane stream in an amount of 0.615 pound methane is pressured by pump 168 to 1500 p.s.i.a. and a'temperature of 245 F. Part of the work required for thepump is provided through turbine e-xpander 170 in the nitrogen stream, as will be more clearly described below. The liquid methane pumped by the pump 168 is introduced through line 172 to methane heat exchanger 174, which is in heat exchange relation with nitrogen heat exchangers 176 and 178, as will more clearly be described below in the discussion of the nitrogen stream flow. The methane from heat exchanger 174 is introduced at a temperature of 60 F. to superheater exchanger 176 where it is heated to a temperature of 260 F. The exhaust gas from a makeup power source, which may be used for the compressor 180 in the nitrogen stream, to be later described, may be used as a source of heat in the superheater exchanger. The methane from the superheater exchanger is introduced to the turbine expander 165, previously described, for exhaust to 600 p.s.i.a. at a temperature of 120 F. where it is then introduced to the final output stream 166 for distribution to the natural gas system and the ultimate pipeline grid at 600 p.s.i.a.

The nitrogen is introduced into the process through line 179 in the amount of 1.05 pounds nitrogen at 15 p.s.i.a. and 85 F. This stream is passed through heat exchanger 176 where with recycled nitrogen it is introduced in line 182 to compressor 180. The nitrogen in line 182 is at 15 p.s.i.a and 240 F. and is compressed by the compressor to 265 p.s.i.a. and a temperature of 85 F. The total stream of the nitrogen introduced into the system and the recycled nitrogen is in the amount of 1.316 pounds nitrogen. This combined stream in line 184 is passed to the heat exchanger 178, and is then passed through heat exchange-rs 160 and 186 for further cooling. The nitrogen is then passed through the turbine (impulse or reaction) [170 for reduction in pressure and further cooling and introduced into separator 188. From the separator liquefied nitrogen in the amount of 1.05 pounds is withdrawn in stream 190 at a pressure of 15 p.s.i.a. and 320 F. for delivery to the tanker bound for the field site.

A recycle nitrogen stream is taken from the separator 188 in line 192' and passed through recycle heat exchangers 194 and 158 for combination with the initial feed nitrogen in line 182, as previously described. This provides further cooling for the process.

FIGURE 12 graphically shows the real temperature differences in the system with the refrigerant nitrogen and methane streams employed in the process always being colder than the nitrogen stream from which the heat is being abstracted.

In the process the compressors utilized in the cycle may be coldsuction high gas density centrifugal machines. Efficiencies are high in this equipment, particularly for the axial flow machines and can be taken as 0.85 (isentropic). The net power supply to the market site process may be in the form of a makeup machine which may be a gas turbine for the compressor 180 with, as previously mentioned, the exhaust gas being used as a heat source in the superheater exchanger 176. The heat exchanger unit 156, 158 and 160 may be a multipass condenser evaporator. The maximum pressure of 265 p.s.i.a. used in these units allow the use of so-called low pressure type exchangers. The heat exchangers 186 and 194 used for subcooling the nitrogen may also be of this type, while the higher pressure heat exchangers 174, 176 and 178 may be of the wound mandrel type.

Heat exchanger 176, the low pressure gaseous nitrogen (or air) heat exchanger may be installed in duplicate form with the matching amount of heat transfer surface from heat exchanger 174 to act as a water and carbon dioxide knockout surface for the incoming low pressure nitrogen or air. Thus, when one of the duplicate surfaces is rimed the heat exchanger surface is switched to the other duplicate in the method called switch heat exchangers in the cryogenic industry, while the rimed surface is heated and derimed preparatory to the next switching. By this means an expensive drying system on the feed nitrogen (or air) is obviated.

SHIPPING STAGE The shipment of the nitrogen refrigerant and natural gas is on a 1:1 mass basis. For analysis on the basis of 1 pound of methane and nitrogen there would be shipped from the market site to the field 1.05 pounds liquid nitrogen (or liquid air) in the outbound vessel, which would provide 0.021 cubic foot of liquid. The receipt at the field site, allowing for some evaporation, is considered as 1.00 pound of liquid nitrogen. In the reverse shipment from the field site to the market site, 1.05 pounds of liquid methane would be provided on the outbound vessel, which would constitute 0.040 cubic foot of liquid since the density of liquid methane is about one-half of the liquid nitrogen. At the market site there would be received, after allowing for evaporation, about 1.00 pound of liquid methane or natural gas.

In FIGURE 13 the-re is shown a schematic diagram illustrating the aforementioned shipment considerations which may be used in both Examples 1 and 2. The outbound vessel from the market site to the field site carrying the liquid nitrogen is indicated by the reference numeral 200, while the return vessel from the field site to the market site carrying the liquefied methane is indicated by the reference numeral 202.

After arrival from the market site at the field site with all four hold tanks only one-half full in the vessel 200, hold tank No. 1, containing 0.25 pound liquid nitrogen, would be pump transferred to a field site land storage tank. Hold tank No. 2 liquid nitrogen would be pumped into methane liquifier process and 0.262 pound of liquid methane, representing one-fourth of the total charge of 1.05 pounds, would be put into empty hold tank No. No. 1. This process would be repeated for each hold tank in turn and then finally the 0.25 pound of liquid nitrogen in the field site land storage tank would go into the methane liquefier process to deliver the 0.262 pound liquid methane representing the last quarter charge of liquefied methane to hold tank No. 4. The ship is then filled with the 1.05 pound liquid methane, used as a base for purpose of example, for its trip from the field site to the market site.

It is to be noted that the minimal land storage requirement, which assumes no field site turn around lost time for the liquid nitrogen, is 0.005 cubic foot (0.00525/). This is one-eighth the volumetric equivalent of the full liquid methane ship load of four hold tanks at 0.01 cubic foot each or 0.04 cubic foot total. If desired, double strength tanks could be built for the No. 2 and No. 3 hold tanks in the middle of the vessel and they could then be filled with liquid nitrogen for the trip to the field site, while tanks No. 1 and No. 4 would ride empty or deadhead on this trip..

The purging of the vessel or hold storage tanks at both the field site and the marked site deserves consideration. At the field site a tank which contained liquid air over which the equilibrium vapor associated with that liquid air is maintained will, when empty of all of that liquid air, have a vapor of 95% nitrogen content at one atmosphere pressure. According to known flammability limits, this 95% nitrogen, which would have oxygen vapor admixed, would with any amount of methane be nonflammable. Thus, for the field site, no special purging conditions are required on refilling the tanks with liquid methane when they are emptied of liquid air providing the above conditions are satisfied.

At the market site, the liquid methane after removal from the vessel tanks will leave a hold full of methane vapor. Since the hold is relatively warm (minus 258 F.) compared to the charge of liquid air (minus 318 F.), the cool down of the hold tank would initially vaporize some of the liquid air charge and this path would direct itself across the tip of the flammable region. Accordingly, it would be necessary to perform the tank cool down with liquid nitrogen at the market site.

Alternatively, as the liquid methane is pumped from the ship tanks at the market, the overlaying methane vapor can be displaced with nitrogen vapor to maintain an essentially nitrogen vapor space. So long as the pumped out tank has a methane content of less than 12% in the methane-nitrogen vapor mixture, liquid air can be pumped in directly and have the tank space in the non-flammable region.

Various changes and modifications may be made within this process as will be readily apparent to those skilled in the art. As an example, air, which, of course, is principally composed of nitrogen, can be used in this process instead of nitrogen, and when speaking of nitrogen it is to be understood that other gases such as air in which the major constituent is nitrogen can be employed where the thermal characteristics of the gas are similar to nitrogen. Such changes and modifications are within the scope and teaching of this invention as defined by the claims appended hereto.

What is claimed is:

1. A method for transportation of natural gas from a field site to a market site which comprises liquefying natural gas at the field site by heat exchange with a liquid refrigerant which is evaporated to obtain available refrigeration effect, said refrigerant being composed principally of nitrogen, transferring the liquefied natural gas to an insulated transport carrier for shipment to the market site, transferring liquefied refrigerant from an insulated transport carrier which is also used as a carrier for liquefied natural gas to the field site for use in said aforementioned step of liquefying natural gas at the field site, said liquefied refrigerant being obtained by evaporating liquefied natural gas in heat exchange relation with refrigerant gas to liquefy the refrigerant, said liquid refrigerant being compressed before it is passed in heat exchange relation with the natural gas and after said heat exchange being expanded to a lower pressure and lower temperature andpassing the so-cooled refrigerant in a second heat exchange stage into heat exchange relation with the natural gas.

2. The method of claim 1 in which the liquid refrigerant transported from the market site to the field site is in the ratio of about 1.0 pound to 2.1 pounds for 1.05 pounds of liquefied natural gas transferred from the field site to the market site.

3. A method for transportation of natural gas from a field site to a market site which comprises liquefying natural gas at the field site by heat exchange with a liquid refrigerant composed principally of nitrogen, transferring the liquefied natural gas to an insulated transport carrier for shipment to the market site, transferring liquefied refrigerant from an insulated transport carrier, which is also used as a carrier for liquefied natural gas to the field site, for use in said aforementioned step of liquefying natural gas at the field site, said liquid refrigerant being compressed before it is passed in heat exchange relation with the natural gas and after said heat exchange being expanded to a lower pressure and lower temperature and passing the so-cooled refrigerant in a second heat exchange stage into heat exchange relation with the natural gas.

4. The method of claim 3 in which the expansion of the refrigerant is carried out in a turbine expander.

5. A method for transportation of natural gas from a field site to a market site which comprises liquefying natural gas at the field site by heat exchange with a liquid refrigerant composed principally of nitrogen, transferring the liquefied natural gas to an insulated transport carrier for shipment to the market site, transferring liquefied refrigerant from an insulated transport carrier, which is also used as a carrier for liquefied natural gas, to the field site for use in said aforementioned step of liquefying natural gas at the field site, said refrigerant being compressed atthe market site and then being passed into heat exchange relation with liquefied natural gas, said refrigerant being further cooled in a main stream by reducing its pressure and being split into a liquefied product stream and a recycle stream.

6. The method of claim 5 in which the recycle stream is passed in heat exchange relation with the main stream of refrigerant before the pressure is reduced and is then compressed and added to the refrigerant gas passed in heat exchange relation with the liquefied natural gas to form the main stream of refrigerant.

7. A method for transportation of natural gas from a field site to a market site which comprises liquifying compressed natural gas at the field site by heat exchange with a liquid refrigerant which is evaporated to obtain available refrigeration effect, said refrigerant being composed principally of nitrogen, transferring the liquefied natural gas to an insulated transport carrier for shipment to the market site, using the liquefied natural gas to liquefy refrigerant and returning the liquefied refrigerant to the field site in an insulated transport carrier for use in said aforementioned step of liquefying natural gas at the field site, said liquid refrigerant being compressed before it is passed in heat exchange relation with the natural gas and after said heat exchange being expanded to a lower pressure and lower temperature and passing the so-cooled refrigerant in a second heat exchange stage into heat exchange relation with the natural gas.

8. The method of claim 7 in which the liquefied refrigerant is charged to the carrier at the market site in the ratio of about 1.0 pound to 2.1 pounds for 1.05 pounds of liquefied natural gas charged to the carrier at the field site to provide about 1 pound of natural gas at the market site and to compensate for loss by evaporation of natural gas in the transportation stage, said refrigerant being compressed at the market site and then being passed into heat exchange relation with liquefied natural gas, said refrigerant being further cooled in a main stream by reducing its pressure and being split into a product stream and a recycle stream.

9. A method for transportation of natural gas from a field site to a market site which comprises liquefying natural gas at the field site by heat exchange with a liquid refrigerant composed principally of nitrogen, transferring the liquefied natural gas to an insulated transport carrier for shipment to the market site, transferring liquefied refrigerant from an insulated transport carrier which is also used as a carrier for liquefied natural gas to the field site for use in said aforementioned step of liquefying natural gas at the field site, said liquid refrigerant being compressed before it is passed in heat exchange relation with the natural gas and after said heat exchange being expanded to a lower pressure and lower temperature, said natural gas being compressed at the field site before it is passed in heat exchange relation with the refrigerant and after said heat exchange being expanded to a lower pres- 13 sure, the work provided in the expansion of the natural gas being used in the compression of the refrigerant and the work provided in the expansion of the refrigerant being used in the compression of the natural gas.

' 10. The method of claim 9 in which the refrigerant is passed in heat exchange relation with the natural gas in a multiplicity of passesfrom substantially the same temperature.

11. The method of claim 9 in which the refrigerant after initial expansion is passed in heat exchange relation with the natural gas in at least one additional pass at a reduced temperature obtained by additional expansion of the gas to a lower pressure.

12L'The method of claim in which the refrigerant after initial expansion is passed in heat exchange relation with the natural gas in at least one additional pass at a reduced temperature obtained by additional expansion of the gas to -a lower pressure.

13. A method for transportation of natural gas from a field site to a market site which comprises liquefying natural gas at the field site by heat exchange with a liquid refrigerant composed principally of nitrogen, transferring the liquefied natural gas to an insulated transport carrier for shipment to the market site, transferring liquefied refrigerant from an insulated transport carrier which is also used as a carrier for liquefied natural gas to the field site for use in said aforementioned step of liquefying natural gas at the field site, said refrigerant being passedat the market site in heat exchange with cold natural gas, compressed and cooled by passing in heat exchange with liquefied natural gas, said refrigerant being further cooled in a main streamtby expansion to a lower pressure and splitting it into a liquefied product stream and a recycle stream.

, 14. A method for transportation of natural gas from a field site to a market site which comprises liquefying natural gas at the field site by heat exchange with a liquid refrigerant composed principally of nitrogen, transferring the liquefied natural gas to an insulated transport carrier for shipment to'the market site, transferring liquefied refrigerant from an insulated transport carrier which is also used as a carrier for liquefied natural gas to the field site for use in said aforementioned step of liquefying natural gas at the field site, said liquefied natural gas being split at the market site into first and second streams, said first stream being passed in heat exchange relation with the refrigerant and subsequently compressed for discharge in a natural gas product stream, said second stream being compressed and passed in heat exchange relation with the refrigerant, said second stream being subsequently expanded to a lower pressure and combined in the natural gas product stream.

15. The method of claim 14 in which the work provided in the expansion of the second stream of natural gas is used in the compression of the first stream.

-16. A method for transportation of natural gas from a field site to a market site which comprises liquefying natural gas at the field site by heat exchange with a liquid refrigerant composed principally of nitrogen, transferring the liquefied natural gas to an insulated transport carrier for shipment to the market site, transferring liquefied refrigerant from an insulated transport carrier, which is also used as a carrier for liquefied natural gas to the field site, for use in said aforementioned step of liquefying natural gas at the field site, said refrigeratnt being passed at the market site in heat exchange with cold natural gas, compressed and cooled by passing in heat exchange with liquefied natural gas, said refrigerant being further cooled in a main stream by expansion to a lower pressure and splitting it into a liquefied product stream and a recycle stream, said liquefied natural gas being split at the market site into first and second streams, said first stream being passed in heat exchange relation with the refrigerant and subsequently compressed for discharge in a natural gas product stream, said second stream being compressed and passed in heat exchange relation with the refrigerant, said second stream being subsequently expanded to a lower pressure and combined in the natural gas product stream.

17. The method of claim 16 in which the work pro vided in the expansion of the refrigerant is used in the compression of the second stream.

18. 'The method of claim 16 in which the work provided in the expansion of the refrigerant is used in the compression of the second stream and the work provided in the expansion of the second stream of natural gas is used in the compression of the first stream.

19. A method for transportation of natural gas from a field site to a market site which comprises liquefying natural gas at the field site by heat exchange with a liquid refrigerant composed principally of nitrogen, transferring the liquefied natural gas to an insulated transport carrier for shipment to the market site, transferring liquefied refrigerant from an insulated transport carrier which is also used as a carrier for liquefied natural gas to the field site for use in said aforementioned step of liquefying natural gas at the field site, said liquid refrigerant being compressed before it is passed in heat exchange relation with the natural gas and after said heat exchange being expanded to a lower pressure and lower temperature, said natural gas being compressed at the field site before it is passed in heat exchange relation with the refrigerant and after said heat exchange being expanded to a lower pressure, the work provided in the expansion of the natural gas being used in the compression of the refrigerant and the work provided in the expansion of the refrigerant being used in the compression of the natural gas, said refrigerant being passed at the market site in heat exchange with cold natural gas, compressed and cooled by passing in heat exchange with liquefied natural gas, said refrigerant being further cooled in a main stream by expansion to a lower pressure and splitting it into a liquefied product stream and a recycle stream.

20. A method for transportation of natural gas from a field site to a market site which comprises liquefying natural gas at the field site by heat exchange with a liquid refrigerant composed principally of nitrogen, transferring the liquefied natural gas to an insulated transport carrier for shipment to the market site, transferring liquefied refrigerant from an insulated transport carrier which is also used as a carrier for liquefied natural gas to the field site for use in said aforementioned step of liquefying natural gas at the field site, said liquid refrigerant being compressed before it is passed in heat exchange relation with the natural gas and after said heat exchange being expanded to a lower pressure and lower temperature, said natural gas being compressed at the field site before it is passed in heat exchange relation with the refrigerant and after said heat exchange being expanded to a lower pressure, the work provided in the expansion of the natural gas being used in the compression of the refrigerant and the work provided in the expansion of the refrigerant being used in the compression of the natural gas, said liquefied natural gas being split at the market site into first and second streams, said first stream being passed in heat exchange relation with the refrigerant and subsequently compressed for discharge in a natural gas product stream, said second stream being compressed and passed in heat exchange relation with the refrigerant, said second stream being subsequently expanded to a lower pressure and combined in the natural gas product stream.

21. A method for transportation of natural gas from a field site to a market site which comprises liquefying natural gas at the field site by heat exchange with a liquid refrigerant composed principally of nitrogen, transferring the liquefied natural gas to an insulated transport carrier for shipment, to the market site, transferring liquefied refrigerant from an insulated transport 15 carrier which is also used as a carrier for liquefied natural gas to the field site for use in said aforementioned step of liquefying natural gas at the field site, said liquid refrigerant being compressed before it is passed in heat exchange relation with the natural gas and after said heat exchange being expanded to a lower pressure and lower temperature, said natural gas being compressed at the field site before it is passed in heat exchange relation with the refrigerant and after said heat exchange being expanded to a lower pressure, the work provided in the expansion of the natural gas being used in the compression of the refrigerant and the work provided in the expansion of the refrigerant being used in the compression of the natural gas, said refrigerant being passed at the market site in heat exchange with cold natural gas, compressed and cooled by passing in heat exchange with liquefied natural gas, said refrigerant being further cooled in a main stream by expansion to a lower pressure and splitting it into a liquefied product stream and a recycle stream, said liquefied natural gas being split at the market site into first and second streams, said first stream being passed in heat exchange relation with the refrigerant and subsequently compressed for discharge in a natural gas product stream, said second stream being compressed and passed in heat exchange relation with the refrigerant, said second stream being subsequently expanded to a lower pressure and combined in the natural gas product stream.

22. A method for transportation of natural gas from a field site to a market site which comprises liquefying natural gas at the field site by heat exchange with a liquid refrigerant composed principally of nitrogen, transferring the liquefied natural gas to an insulated transport carrier for shipment to the market site, transferring liquefied refrigerant from an insulated transport carrier which is also used as a carrier for liquefied natural gas to the field site for use in said aforementioned step of liquefying natural gas at the field site, said liquid refrigerant being compressed before it is passed in heat exchange re- 1 lation with the natural gas and after said heat exchange being expanded to a lower pressure and lower temperature, said natural gas at the field site being passed in heat exchange relation with the refrigerant and after said heat exchange being expanded to a lower pressure, the work provided in the expansion of the natural gas being used in the compression of the refrigerant and the work provided in the expansion of the refrigerant being used in part for the compression of the natural gas, said refrigerant being passed at the market site in heat exchange with cold natural gas, compressed and cooled by passing in heat exchange with liquefied natural gas, said refrigerant being further cooled in a main stream by expansion to a lower pressure and splitting it into a liquefied product stream and a recycle stream, said liquefied natural gas being split at the market site into one or more streams, which are passed in heat exchange relation with the refrigerant, one of said streams being compressed and passed in heat exchange relation withthe refrigerant, and subsequently expanded to a lower pressure and combined in the natural gas product stream.

23. The method of claim 7 in which said refrigerant is compressed at the market site and is passed into heat exchange relation with liquefied natural gas, said refrigerant being further cooled in a main stream by reducing its pressure and being split into a product stream and a recycle stream, said recycle refrigerant stream being compressed and recombined in the refrigerant stream passed into heat exchange relation with the liquefied natural gas.

References Cited UNITED STATES PATENTS 2,975,604 3/1961 McMahon 6255 X 3,018,632 1/1962 Keith 6255 X 3,034,309 5/1962 Muck 6255 3,302,416 2/1967 Proctor et al 62-55 3,324,670 6/1967 Van Kleef 62-55 ROBERT A. OLEARY, Primary Examiner.

US654935A 1966-11-02 1967-07-20 Process for liquefaction of natural gas and transportation by marine vessel Expired - Lifetime US3400547A (en)

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BE705963D BE705963A (en) 1966-11-02 1967-10-31
IL28868A IL28868A (en) 1966-11-02 1967-10-31 Process for liquefaction of natural gas and transportation by marine vessel
ES346651A ES346651A1 (en) 1966-11-02 1967-10-31 A method for transporting natural gas from a production site to a retail location.
OA53092A OA2527A (en) 1966-11-02 1967-11-02 A method of liquefaction and transportation of a natural gas.
NO170364A NO124796B (en) 1966-11-02 1967-11-02
JP7028067A JPS535321B1 (en) 1966-11-02 1967-11-02
NL6714932A NL6714932A (en) 1966-11-02 1967-11-02
GB49800/67A GB1170329A (en) 1966-11-02 1967-11-02 Method of Transporting Natural Gas from a Field Site to a Market Site
FR126820A FR1542232A (en) 1966-11-02 1967-11-02 A method of liquefaction and transportation of a natural gas

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US3768271A (en) * 1971-01-19 1973-10-30 L Denis Method and plant for storing and transporting a liquefied combustible gas
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IL28868A (en) 1971-06-23
BE705963A (en) 1968-04-30
GB1170329A (en) 1969-11-12
FR1542232A (en) 1968-10-11
JPS535321B1 (en) 1978-02-25
NO124796B (en) 1972-06-05
ES346651A1 (en) 1969-03-16
NL6714932A (en) 1968-05-03
OA2527A (en) 1970-05-05

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