EP0990108B1 - Cycle de refrigeration en deux etapes utilisant un frigorigene a plusieurs constituants - Google Patents

Cycle de refrigeration en deux etapes utilisant un frigorigene a plusieurs constituants Download PDF

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Publication number
EP0990108B1
EP0990108B1 EP98928467A EP98928467A EP0990108B1 EP 0990108 B1 EP0990108 B1 EP 0990108B1 EP 98928467 A EP98928467 A EP 98928467A EP 98928467 A EP98928467 A EP 98928467A EP 0990108 B1 EP0990108 B1 EP 0990108B1
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EP
European Patent Office
Prior art keywords
condensate
refrigeration cycle
vapour
refrigerant
low pressure
Prior art date
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EP98928467A
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German (de)
English (en)
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EP0990108A1 (fr
Inventor
Wieslaw Henryk Isalski
David Thomas Linnett
John Terence Lavin
Philip Boustead
Adrian Joseph Finn
Terence Ronald Tomlinson
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BOC Group Ltd
Costain Oil Gas and Process Ltd
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BOC Group Ltd
Costain Oil Gas and Process Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—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
    • 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"
    • F25J1/004—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
    • F25J1/003—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
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/003—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
    • F25J1/0047—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle
    • F25J1/0052—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle by vaporising a liquid refrigerant stream
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/003—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
    • 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
    • F25J1/0211—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
    • F25J1/0212—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 single flow MCR 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
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0279—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc.
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0279—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc.
    • F25J1/0291—Refrigerant compression by combined gas compression and liquid pumping
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0279—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc.
    • F25J1/0296—Removal of the heat of compression, e.g. within an inter- or afterstage-cooler against an ambient heat sink
    • 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
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/80—Processes or apparatus using separation by rectification using integrated mass and heat exchange, i.e. non-adiabatic rectification in a reflux exchanger or dephlegmator
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/02—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/62—Ethane or ethylene
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2220/00—Processes or apparatus involving steps for the removal of impurities
    • F25J2220/60—Separating impurities from natural gas, e.g. mercury, cyclic hydrocarbons
    • F25J2220/62—Separating low boiling components, e.g. He, H2, N2, Air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2220/00—Processes or apparatus involving steps for the removal of impurities
    • F25J2220/60—Separating impurities from natural gas, e.g. mercury, cyclic hydrocarbons
    • F25J2220/64—Separating heavy hydrocarbons, e.g. NGL, LPG, C4+ hydrocarbons or heavy condensates in general
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
    • F25J2290/32—Details on header or distribution passages of heat exchangers, e.g. of reboiler-condenser or plate heat exchangers

Definitions

  • This invention relates to refrigeration cycles using a mixed refrigerant.
  • low pressure vapour is compressed and the compressed vapour is thereafter cooled and condensed and the high pressure condensed stream expanded back to the low pressure to form a returning low pressure refrigerant stream which is vaporised to re-form the low pressure vapour stream for return to the compressor.
  • the final cooling and condensation of the compressed vapour is effected in indirect counter-current heat exchange with the vaporising low pressure stream. Cooling of the material to be refrigerated is by heat exchange with the vaporising low pressure stream.
  • the refrigerant stream is made up of a plurality of components having differing boiling points.
  • the compressed vapour thus condenses over a range of temperatures and likewise the condensed refrigerant boils over a range of temperatures.
  • Such a refrigeration cycle is known from US-A-5,613,373.
  • This invention provides an improvement to the mixed refrigerant refrigeration cycles
  • a refrigeration cycle utilizing a multi-component refrigerant wherein the compression of low pressure refrigerant vapour is effected in at least two stages of compression with cooling, partial condensation and separation from the uncondensed vapour of the entire condensate formed after each of at least two of the said stages thereby providing two or more condensate streams of different compositions and at different pressures and wherein at least two of said condensate streams are expanded and injected into the returning low pressure refrigerant at different temperatures of said low pressure refrigerant.
  • At least one of the said condensate streams is sub-cooled prior to the said expansion.
  • at least two of said streams are sub-cooled to the same temperature; alternatively, however, they may be sub-cooled to different temperatures. It is to be understood, however, that even if sub-cooled to the same temperature at least two of the said condensate streams must be injected into the returning low pressure refrigerant at different temperatures.
  • vapour recovered from the last stage of compression is subjected to two or more steps of cooling and partial condensation with separation of condensate from uncondensed vapour after each step and each separated condensate is thereafter expanded and injected into returning low pressure refrigerant.
  • at least one of the separated condensates is sub-cooled.
  • One or more of these cooling steps may be effected by indirect countercurrent heat exchange with returning low pressure refrigerant.
  • a refluxing exchanger is employed in the generation and separation of condensate from uncondensed vapour in one or more of the vapour/liquid separation steps in the cycle.
  • the use of a refluxing exchanger in the generation and separation of condensate from uncondensed vapour in a refrigeration cycle utilizing a multi-component refrigerant and including at least one step of cooling and partially condensing compressed vapour and separating the condensate so formed from uncondensed vapour is the subject of GB patent application 9712301.2 filed on 12 June 1997.
  • Figure 1 of the drawings which provides a flow sheet of a known mixed refrigerant refrigeration cycle for the liquefaction of natural gas
  • the natural gas which is to be liquefied is supplied at an elevated pressure to a heat exchanger 4 through line 2 and the liquefied product is recovered through line 6.
  • the details of the arrangement for recovering the liquefied product are not relevant to the invention and many variants are possible but in the embodiment illustrated the gas is first cooled and partially condensed to recover a heavy hydrocarbon fraction.
  • the condensate is separated from uncondensed gas in liquid/vapour separator 8.
  • Condensate is recovered in line 10 and the uncondensed gas is returned to a cooler section of the heat exchanger in line 12 for a further step of cooling and partial condensation with the further condensate being separated from the uncondensed gas in liquid/vapour separator 14.
  • the uncondensed gas is again returned to the heat exchanger, this time to the cold end, in line 16 for final cooling and condensation after which it is recovered, expanded to an intermediate pressure through valve 18 and supplied to liquid/vapour separator 20 for separation of any uncondensed gas.
  • Condensate recovered from the separator 20 in line 22 is further expanded to its final pressure in expansion valve 24 and supplied to liquid/vapour separator 26 from which the liquefied gas is recovered in line 6 as mentioned above.
  • Uncondensed gas from separator 20 is returned via line 30 to be reheated in heat exchanger 4 and is then combined with condensed liquid in line 32 from separator 14 which has been expanded through valve 34.
  • the combined stream is further warmed in heat exchanger 4 and then recovered therefrom in line 36. It is thereafter joined by the cold uncondensed gas from separator 26 in line 38.
  • the cooling and liquefaction of the natural gas is effected in heat exchanger 4 by indirect countercurrent heat exchange with a vaporising mixed refrigerant stream in line 40.
  • the mixed refrigerant preferably comprises a mixture of nitrogen and C 1 to C 5 hydrocarbons.
  • the low pressure vaporised stream recovered from the heat exchanger in line 40 is recycled for recompression in a two stage compressor having first and second stages 42, 44.
  • the vapour is transferred via line 46 for cooling in inter-cooler 48 and then passed via line 50 to vapour/liquid separator 52 for the separation of condensate formed by the cooling in the inter-cooler.
  • the uncondensed vapour is recovered in line 54 and transferred to the second stage 44 of the compressor, the compressed vapour therefrom being collected in line 56 for transfer to after cooler 58 where it is cooled and partially condensed.
  • the partially condensed high pressure stream is recovered in line 60.
  • Condensate formed as a result of cooling in the inter-cooler 48 is recovered from vapour/liquid separator 52 in line 64, pumped up to the same pressure as the stream in line 60 by pump 66, and combined with that stream for supply to the vapour/liquid separator 62.
  • Uncondensed vapour from vapour/liquid separator 62 is recovered overhead in line 68.
  • Condensate recovered in line 70 is pumped by pump 72 to rejoin the overhead vapour via line 74.
  • the combined stream is then passed through heat exchanger 4 in line 76 where the vapour is cooled and condensed in indirect countercurrent heat exchange with the vaporising refrigerant stream in line 40 and thereafter expanded through valve 78 into the low pressure line 40 to form the returning low pressure refrigerant stream.
  • condensate formed in inter-cooler 48 and separated from uncondensed vapour in vapour/liquid separator 52 is recovered in line 102, in which it is directed into heat exchanger 4 at the warm end thereof and wherein it is sub-cooled by indirect countercurrent heat exchange with vaporising returning low pressure refrigerant in line 40, expanded to substantially the same pressure as said returning low pressure refrigerant in valve 104 and injected through line 106 into said low pressure refrigerant in line 40 at a higher temperature than that at which the condensate in line 94 is injected.
  • the condensate in line 102, which was formed in the inter-cooler will be at a lower pressure than that in line 90 which was formed in the aftercooler.
  • the condensate in line 102 is injected into the returning vaporising low pressure refrigerant stream at a higher temperature than that at which the condensate in line 90 is injected because the condensate in line 102 will have a higher boiling range than that in line 90.
  • the heavier liquid condensed in the compressor interstage cooler 48 is used as a separate refrigerant stream from the liquid condensed in the aftercooler 58.
  • the interstage liquid is subcooled separately and is injected into the returning stream 40 at a higher temperature level than the liquid from the aftercooler. This in effect creates a complete-additional refrigerant stage. This results in lower power consumption and/or a reduction in heat exchanger size due to the following:
  • a further benefit of the refrigeration cycle according to the invention is that it permits greater operational flexibility to cope with variation in gas composition, temperature and/or pressure and in changes in ambient conditions.
  • the invention is also applicable to three or more stages of compression in which case any two or more of the condensate streams so obtained may be expanded and injected into the returning low pressure refrigerant.
  • at least one is sub-cooled to an appropriate temperature before expansion.
  • two or more steps of cooling and separation of condensate may be effected after each stage of compression. It will be understood that the resultant condensate streams will be at substantially the same pressure although of different composition.
  • Figure 4 is a modification of the arrangement of Figure 3 wherein two stages of after cooling are provided.
  • the compressed refrigerant stream recovered from final compressor stage 44 in line 56 is cooled and partially condensed in first after-cooler 58A and the partially condensed stream is conveyed via line 60A to a first vapour/liquid separator 62A condensate from which is recovered in line 90A, subcooled in heat exchanger 4 in indirect countercurrent heat exchange with returning vaporising low pressure refrigerant in line 40, expanded in expansion valve 92A to substantially the pressure of said low pressure refrigerant and injected into it through line 94A.
  • the uncondensed vapour from liquid/vapour separator 62A is further cooled and partially condensed in second after cooler 58B and the condensate formed therein is separated from uncondensed vapour in liquid/vapour separator 62B. recovered in line 90B and likewise sub-cooled, expanded (through expansion valve 92B) and injected (via line 94B) into the returning low pressure refrigerant stream. It will be understood that the condensate streams in lines 90A and 90B will be of different composition but at substantially the same pressure which will be a higher pressure than that of the condensate in line 102 which has been formed in inter-cooler 48.
  • FIG. 5 is a modification of the arrangement of Figure 3 and where all pipelines and apparatus components common with Figure 3 are accorded the same reference numerals.
  • the after cooler 58 and liquid/vapour separator 62 of the arrangement of Figure 2 are replaced by a reflux exchanger 120.
  • the compressed refrigerant recovered from the final stage 44 of compression is directed via line 56 to reflux exchanger 120 where it is cooled and partially condensed while being directed upwardly through the exchanger.
  • Uncondensed vapour is recovered from the top of the exchanger through line 68 while condensate formed in the exchanger travels back down through the exchanger in direct countercurrent contact with the rising vapour and is collected from the bottom of the exchanger in line 90.
  • the concentration of light components in the condensate in line 90 can be minimised thus enabling the condensate to be subcooled to a temperature where little or no flash occurs on expansion into the returning low pressure refrigerant. This greatly reduces the complexity and cost of equipment necessary for achieving good two-phase distribution.
  • condensate may also be recovered at one or more points in the course of the cooling of the compressed refrigerant by indirect countercurrent heat exchange with the low pressure refrigerant in heat exchanger 4.
  • FIG. 6 is a modification of the arrangement of Figure 5 and wherein pipelines and apparatus components common with Figure 5 are accorded the same reference numerals.
  • the compressed refrigerant vapour recovered overhead from the refluxing exchanger 120 in line 68 and passed through heat exchanger 4 in line 76 is withdrawn from heat exchanger 4 at an intermediate point where it is not fully condensed.
  • the condensate is separated from uncondensed vapour in liquid/vapour separator 202, subcooled in line 204 in indirect countercurrent heat exchange with vaporising returning low pressure refrigerant, expanded through expansion valve 206 to about the same pressure as said low pressure refrigerant and thereafter injected into it.
  • condensate formed in the compressed refrigerant may be recovered from it close to its dewpoint and then re-injected into returning low pressure refrigerant stream close to its boiling point, thereby further improving heat transfer efficiency and reducing the heat exchanger duty.
  • a refluxing condenser is shown as replacing the compressor after cooler and associated vapour/liquid separator, it will be understood that it may also be employed, additionally or alternatively, to replace a compressor inter-cooler such as inter-cooler 48 and associated vapour/liquid separator, such as separator 50, and possibly also even in the generation and separation of other condensate streams in the refrigeration cycle by partial condensation of compressed refrigerant.
  • Each refluxing exchanger may also be used to provide less than all the cooling and thus used in series with a conventional inter-cooler or after cooler as well as a total replacement therefor.
  • One or more of the expansion valves employed for the expansion of condensate in any part of the refrigeration cycle may, if desired, be replaced by devices in which expansion is effected with performance of external work, e.g. a turbine expander.
  • heat exchanger 4 is shown as being a single heat exchanger, its overall function may be supplied by a plurality of exchangers.
  • At least any heat exchanger employed in the indirect counter-current heat exchange of compressed refrigerant with returning low pressure refrigerant to be a multi-stream plate fin type heat exchanger because such heat exchangers provide greater flexibility to efficiently process a multiplicity of different streams.
  • any suitable combination of two or more refrigerants may be used in the mixed refrigerant cycle and the choice will depend upon the composition of the material to be refrigerated and the temperature to which it is to be cooled.
  • suitable refrigerants include nitrogen, low boiling halogenated hydrocarbons, eg. chlorofluorocarbons, and low boiling hydrocarbons.
  • the mixed refrigerant will usually comprise two or more of nitrogen and C 1 -C 5 hydrocarbons.
  • one or more of the condensate streams formed in the refrigeration cycle of the invention may be divided into at least two sub-streams having the same composition and the said sub-streams may each be expanded and injected into the returning low pressure refrigerant stream at different temperatures of the returning low pressure refrigerant. This enables the evaporation characteristics of the low pressure refrigerant to be changed progressively to better match the combined cooling curve of the high pressure streams, thereby still further improving the efficiency of the refrigeration cycle.
  • the use of the mixed refrigerant refrigerator cycle of the present invention is found to give improved efficiency.
  • the total power consumed in the first experiment is 53784 KW while that second according to the invention is only 52860 KW, a saving of nearly 1MW (1.7%).
  • the total UA 1 was also measured in both cases.
  • the value was 34.99 MW/°C while in the experiment in accordance with the invention the value was 34.92 MW/°C.
  • This value is a measure of heat exchanger surface area and shows that the experiment in accordance with the invention gives a similar surface area for a reduced power consumption. This results in a similar capital cost for this item of plant.
  • the reduced capital cost for the refrigerant compression thus gives a net cost benefit.

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Abstract

L'invention concerne un cycle de réfrigération utilisant un frigorigène à plusieurs constituants. Selon cette invention, la compression de la vapeur à basse pression du frigorigène est effectuée au cours d'au moins deux étapes de compression (42, 44) consistant à refroidir (48, 58), condenser partiellement et séparer (52, 62) le condensat, formé après chacune de ces deux étapes minimales, de la vapeur non condensée. Ceci permet d'obtenir au minimum deux courants (64, 70) de condensat de compositions différentes et de pressions différentes. Au moins deux desdits courants de condensat subissent une détente et sont injectés dans le frigorigène (40) à basse pression de retour et ce, à des températures différentes de celle dudit frigorigène (40) à basse pression.

Claims (12)

  1. Cycle de réfrigération utilisant un réfrigérant multi-composants dans lequel la compression de la vapeur du réfrigérant à basse pression est effectuée en au moins deux étapes de compression (48, 58) avec refroidissement, condensation partielle et séparation entre la vapeur non condensée et la totalité du condensat formé après chacune des deux dites étapes, créant ainsi au moins deux courants de condensats (90, 102) de différentes compositions et à différentes pressions, et dans lequel au moins deux desdits courants de condensats subissent une détente et sont injectés dans le réfrigérant à basse pression de retour (40) à différentes températures dudit réfrigérant à basse pression.
  2. Cycle de réfrigération selon la revendication 1, dans lequel au moins l'un desdits courants de condensats est sous-refroidi avant ladite détente.
  3. Cycle de réfrigération selon la revendication 1, dans lequel au moins deux desdits courants de condensats sont sous-refroidis à la même température avant ladite détente.
  4. Cycle de réfrigération selon la revendication 1, dans lequel au moins deux desdits courants de condensats sont sous-refroidis à des températures différentes avant ladite détente.
  5. Cycle de réfrigération selon l'une quelconque des revendications précédentes, dans lequel la vapeur récupérée à la dernière étape de compression est soumise à au moins deux étapes de refroidissement et de condensation partielle avec séparation entre le condensat et la vapeur non condensée après chaque étape, chaque condensat séparé étant ensuite détendu et injecté dans le réfrigérant de retour à basse pression.
  6. Cycle de réfrigération selon la revendication 5, dans lequel la compression après refroidissement est effectuée par étapes avec séparation du condensat formé à chaque étape pour former au moins deux condensats avec différentes compositions à essentiellement la même pression, lesdits condensats étant séparément sous-refroidis, détendus et injectés dans le réfrigérant de retour à basse pression.
  7. Cycle de réfrigération selon la revendication 5 ou 6, dans lequel au moins l'un desdits condensats séparés est sous-refroidi avant ladite détente.
  8. Cycle de réfrigération selon l'une quelconque des revendications précédentes, dans lequel un échangeur de reflux est utilisé pour la génération et la séparation entre le condensat et la vapeur non condensée dans au moins l'une des étapes de refroidissement, de condensation partielle et de séparation entre le condensat et la vapeur non condensée.
  9. Cycle de réfrigération selon la revendication 8, dans lequel un échangeur de reflux est utilisé pour la génération et la séparation entre le condensat et la vapeur comprimée récupérée à la dernière étape de compression.
  10. Cycle de réfrigération selon l'une quelconque des revendications précédentes, utilisé pour la liquéfaction de gaz naturel.
  11. Cycle de réfrigération selon l'une quelconque des revendications précédentes, dans lequel le réfrigérant comprend un mélange contenant toute combinaison de deux ou plusieurs hydrocarbures C1 à C5 et d'azote.
  12. Cycle de réfrigération selon l'une quelconque des revendications précédentes, dans lequel un ou plusieurs échangeurs de chaleur multi-courants à plaques sont utilisés pour le refroidissement et la condensation partielle du réfrigérant comprimé.
EP98928467A 1997-06-12 1998-06-12 Cycle de refrigeration en deux etapes utilisant un frigorigene a plusieurs constituants Expired - Lifetime EP0990108B1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GBGB9712304.6A GB9712304D0 (en) 1997-06-12 1997-06-12 Refrigeration cycle using a mixed refrigerant
GB9712304 1997-06-12
PCT/GB1998/001720 WO1998057108A1 (fr) 1997-06-12 1998-06-12 Cycle de refrigeration en deux etapes utilisant un frigorigene a plusieurs constituants

Publications (2)

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EP0990108A1 EP0990108A1 (fr) 2000-04-05
EP0990108B1 true EP0990108B1 (fr) 2002-09-18

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EP98928467A Expired - Lifetime EP0990108B1 (fr) 1997-06-12 1998-06-12 Cycle de refrigeration en deux etapes utilisant un frigorigene a plusieurs constituants

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EP (1) EP0990108B1 (fr)
AU (1) AU8029698A (fr)
DE (1) DE69808087T2 (fr)
GB (1) GB9712304D0 (fr)
WO (1) WO1998057108A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9441877B2 (en) 2010-03-17 2016-09-13 Chart Inc. Integrated pre-cooled mixed refrigerant system and method
US10480851B2 (en) 2013-03-15 2019-11-19 Chart Energy & Chemicals, Inc. Mixed refrigerant system and method
US10663221B2 (en) 2015-07-08 2020-05-26 Chart Energy & Chemicals, Inc. Mixed refrigerant system and method
US11408673B2 (en) 2013-03-15 2022-08-09 Chart Energy & Chemicals, Inc. Mixed refrigerant system and method
US11428463B2 (en) 2013-03-15 2022-08-30 Chart Energy & Chemicals, Inc. Mixed refrigerant system and method

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6065305A (en) * 1998-12-30 2000-05-23 Praxair Technology, Inc. Multicomponent refrigerant cooling with internal recycle
US6041620A (en) * 1998-12-30 2000-03-28 Praxair Technology, Inc. Cryogenic industrial gas liquefaction with hybrid refrigeration generation
DE102009016046A1 (de) * 2009-04-02 2010-10-07 Linde Aktiengesellschaft Verfahren zum Verflüssigen einer Kohlenwasserstoff-reichen Fraktion
WO2016026533A1 (fr) * 2014-08-21 2016-02-25 Statoil Petroleum As Système de pompe à chaleur
FR3043451B1 (fr) * 2015-11-10 2019-12-20 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Methode pour optimiser la liquefaction de gaz naturel
FR3043452B1 (fr) * 2015-11-10 2019-12-20 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Procede de liquefaction de gaz naturel a l'aide d'un circuit de refrigeration en cycle ferme

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Publication number Priority date Publication date Assignee Title
FR2540612A1 (fr) * 1983-02-08 1984-08-10 Air Liquide Procede et installation de refroidissement d'un fluide, notamment de liquefaction de gaz naturel
US5329774A (en) * 1992-10-08 1994-07-19 Liquid Air Engineering Corporation Method and apparatus for separating C4 hydrocarbons from a gaseous mixture
FR2703762B1 (fr) * 1993-04-09 1995-05-24 Maurice Grenier Procédé et installation de refroidissement d'un fluide, notamment pour la liquéfaction de gaz naturel.
FR2725503B1 (fr) * 1994-10-05 1996-12-27 Inst Francais Du Petrole Procede et installation de liquefaction du gaz naturel

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9441877B2 (en) 2010-03-17 2016-09-13 Chart Inc. Integrated pre-cooled mixed refrigerant system and method
US10502483B2 (en) 2010-03-17 2019-12-10 Chart Energy & Chemicals, Inc. Integrated pre-cooled mixed refrigerant system and method
US10480851B2 (en) 2013-03-15 2019-11-19 Chart Energy & Chemicals, Inc. Mixed refrigerant system and method
US11408673B2 (en) 2013-03-15 2022-08-09 Chart Energy & Chemicals, Inc. Mixed refrigerant system and method
US11428463B2 (en) 2013-03-15 2022-08-30 Chart Energy & Chemicals, Inc. Mixed refrigerant system and method
US10663221B2 (en) 2015-07-08 2020-05-26 Chart Energy & Chemicals, Inc. Mixed refrigerant system and method
US11408676B2 (en) 2015-07-08 2022-08-09 Chart Energy & Chemicals, Inc. Mixed refrigerant system and method

Also Published As

Publication number Publication date
DE69808087T2 (de) 2003-05-28
WO1998057108A1 (fr) 1998-12-17
GB9712304D0 (en) 1997-08-13
DE69808087D1 (de) 2002-10-24
AU8029698A (en) 1998-12-30
EP0990108A1 (fr) 2000-04-05

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