EP0340465B1 - Hydrocarbon separation process - Google Patents

Hydrocarbon separation process Download PDF

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Publication number
EP0340465B1
EP0340465B1 EP89105944A EP89105944A EP0340465B1 EP 0340465 B1 EP0340465 B1 EP 0340465B1 EP 89105944 A EP89105944 A EP 89105944A EP 89105944 A EP89105944 A EP 89105944A EP 0340465 B1 EP0340465 B1 EP 0340465B1
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EP
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Prior art keywords
column
residual gas
rescrubbing
fed
fraction
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EP89105944A
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German (de)
French (fr)
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EP0340465A2 (en
EP0340465A3 (en
Inventor
Heinz Dr. Rer. Nat. Dipl.-Phys. Bauer
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Linde GmbH
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Linde GmbH
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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
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
    • F25J3/0252—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of hydrogen
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G5/00—Recovery of liquid hydrocarbon mixtures from gases, e.g. natural gas
    • C10G5/06—Recovery of liquid hydrocarbon mixtures from gases, e.g. natural gas by cooling or compressing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/0204—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the feed stream
    • F25J3/0219—Refinery gas, cracking gas, coke oven gas, gaseous mixtures containing aliphatic unsaturated CnHm or gaseous mixtures of undefined nature
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
    • F25J3/0233—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of CnHm with 1 carbon atom or more
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
    • F25J3/0238—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of CnHm with 2 carbon atoms or more
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/04—Processes or apparatus using separation by rectification in a dual pressure main column 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
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/70—Refluxing the column with a condensed part of the feed stream, i.e. fractionator top is stripped or self-rectified
    • 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
    • F25J2200/78—Refluxing the column with a liquid stream originating from an upstream or downstream fractionator column
    • 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
    • F25J2200/90—Details relating to column internals, e.g. structured packing, gas or liquid distribution
    • 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
    • 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
    • F25J2205/04—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum in the feed line, i.e. upstream of the fractionation step
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/12—Refinery or petrochemical off-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
    • F25J2235/00—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams
    • F25J2235/60—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams the fluid being (a mixture of) hydrocarbons
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/02—Recycle of a stream in general, e.g. a by-pass stream
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/02—Internal refrigeration with liquid vaporising loop
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/08—Internal refrigeration by flash gas recovery loop
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/90—External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration

Definitions

  • the invention relates to a process for the separation of hydrocarbons from a gas stream containing light and heavy hydrocarbons and possibly components which boil lighter than methane, in which the gas stream under increased pressure is cooled, partially condensed and separated into a liquid and a gaseous fraction and in which the liquid fraction is broken down by rectification into a product stream containing essentially high-boiling components and a residual gas stream containing predominantly lower-boiling components, and the gaseous fraction separated off after the partial condensation is fed to a backwash column in which residual gas obtained in the rectification after its partial condensation high-boiling hydrocarbons are washed out of the gaseous fraction and the liquid fraction obtained in the bottom of the backwash column is fed to the rectification.
  • Such processes are primarily used to remove ethane and propane from hydrocarbon gas mixtures, such as natural gas or refinery waste gases. These processes are also suitable for the removal of analog unsaturated hydrocarbons such as ethylene and propylene. Refinery exhaust gases contain such hydrocarbons, which has made their work-up interesting due to increased market prices for C3 / C4 hydrocarbon mixtures.
  • DE-OS 3511636 a method of the type mentioned is described, which is used to separate C2+ or C3+ hydrocarbons from a gas mixture.
  • a raw gas stream is partially condensed in countercurrent to process streams to be heated and separated into a liquid and a gaseous fraction.
  • the liquid fraction which consists essentially of the high-boiling hydrocarbon components C2+ or C3+, is passed into a rectification column in which the low-boiling components are removed from this fraction.
  • a residual gas fraction which, after its partial condensation, is passed into a backwash column in order to wash out high-boiling components from the gaseous fraction of the separator.
  • the bottom fraction obtained in the backwash column is also fed into the rectification column.
  • the backwashing serves to increase the yield of the process, since this measure can be used to obtain C2+ or C3+ components that cannot otherwise be obtained both from the gaseous fraction of the separator and from the residual gas from the rectification column.
  • a disadvantage of the above method is that the required process temperature must be generated by means of a refrigeration system, possibly a refrigeration cascade. For this purpose, the cold-performing expansion of at least part of the residual gas flows is provided.
  • the invention is therefore based on the object of further improving a method of the type mentioned, in particular a costly generation of cold should be avoided while at the same time maintaining high pressures of the residual gas flows.
  • This object is achieved in that the residual gas obtained in the rectification is separated into a gaseous and a liquid fraction after its partial condensation and before it is fed to the backwash column, and the liquid fraction is at least partially expanded to provide cooling, and is warmed against partially condensing residual gas from the rectification column and the residual gas stream of the rectification is mixed again, while the remaining part of the liquid fraction is fed to the backwash column.
  • the renewed admixing of the part of the liquid fraction of the residual gas stream used as the cooling medium to the top product of the rectification column has the effect that the total amount circulating is greater than the actual top product amount. In this way, the cooling capacity of the branched-off part of the condensed residual gas stream can be used to cool further process streams.
  • the backwash column and the rectification column are operated under increased pressure.
  • the pressure of the residual gas which is fed to the backwash column is adjusted to the pressure of the backwash column.
  • the ethane-rich top product of the backwash column contributes significantly to achieving a sufficient level Joule-Thompson effect in the downstream H2 cleaning.
  • the invention provides that, before the cold-cooling relaxed fraction is mixed with the residual gas from the rectification, the two streams are equalized and the mixture stream is adjusted to the pressure of the backwash column.
  • the pressures of the two streams can be equalized on the one hand by relieving one of the two to the pressure of the other, or, in the opposite case, by increasing the pressure of the one stream.
  • the pressure is then adjusted to the pressure of the backwash column. This is usually done by compressing the mixture flow, since the pressure level of the backwash column is above that of the rectification column.
  • the quantitative ratio of the part of the liquid fraction which is relaxed with respect to the cold to the part which is fed to the backwash column is as 0.43-2.3: 1.
  • the inventive method is particularly suitable for the combination of different separation steps of H2 and hydrocarbon-containing gas mixtures, which work with high inlet pressures.
  • any combination of two separation steps consisting of C5+, C3+, C2+ and H2 separation, can be operated in a particularly energy-saving and efficient manner.
  • a raw gas stream under increased pressure is introduced via line 1, partially condensed by indirect heat exchange in heat exchanger E1 and separated into a liquid and a gaseous fraction in separator D1.
  • the liquid fraction is drawn off via line 3 and, after heating in heat exchanger E1, expanded into a central region of the rectification column T.
  • the gaseous fraction of the separator is fed via line 2 and after further cooling in heat exchanger E2 into the lower region of the backwash column R, in which further components are obtained by washing out of the gaseous fraction.
  • the liquid fraction obtained is drawn off via lines 7 and 8.
  • the part in line 7 is expanded directly into the upper region of the rectification column T, while the part of the bottom product in line 8 is initially in the heat exchangers E2 and E1 is warmed before it is released into a central area of the rectification column.
  • a product fraction is obtained in the bottom of the rectification column and is withdrawn via line 10. Part of it is branched off via branch line 11, heated in heat exchanger E3 and fed back as a boiling stream into the bottom of the rectification column T.
  • a residual gas stream is obtained which still contains desired heavy components.
  • this current is drawn off partially condensed in the heat exchangers E1 and E2 and separated into a gaseous and a liquid fraction in separator D3.
  • the liquid fraction is fed via line 14 to the upper region of the backwash column R for backwashing.
  • the fraction of line 14 is branched off in a branch-cold manner to reduce the pressure, heated in heat exchangers E2 and E1 against streams of lines 1 to be cooled (raw gas) and 12 (residual gas stream from the rectification column) and after compression in compressors C1 and C2 and reheating in the heat exchangers E4 and E5 mixed with the top residual gas stream of the rectification column T.
  • the residual gas obtained at the top of the backwash column R consisting of low-boiling components, is at least partially condensed in heat exchanger E6 after removal by means of line 4.
  • Separator D2 then separates them into gaseous and liquefied components.
  • the gaseous fractions are withdrawn in line 6, while the liquefied fractions are withdrawn from the system via line 5, together with the gaseous fraction of the separator D3 from line 13.
  • the flows 9 of the heat exchanger E1 are auxiliary circuits for the refrigeration.
  • a raw gas stream under increased pressure is passed via line 1, after cooling and partial condensation by indirect heat exchange in heat exchanger E1, to separator D, where it is separated into a liquid and a gaseous fraction.
  • the liquid fraction is drawn off via line 3, decompressed and, after heating in heat exchanger E1, passed into a central region of the rectification column T.
  • the gaseous fraction of the separator is fed into line 2, after further cooling in heat exchange E2, into the lower region of the backwash column R.
  • the liquid fraction obtained is drawn off from the bottom of the backwash column via lines 5 and 6.
  • the liquid fraction of line 5 is expanded, heated in heat exchanger E2 and fed to a central area of the rectification column T, while the portion in line 6 is expanded directly into an upper area of the rectification column.
  • the liquid fraction obtained in the bottom of the rectification column is removed via line 7. After heating in heat exchanger E3, a part is returned to the bottom of the rectification column as a boiling stream, the rest of the stream is compressed P and released
  • the top product of the rectification column T drawn off by means of line 8, is first warmed up in E1, expanded and mixed with the compressed and heated stream of line 9, after which the mixture is further compressed in line 10 into compressor C2, and heating in the heat exchanger ES takes place .
  • the flow of the line 10 is washed back into the separation chamber column R relaxed.
  • the separation room is arranged in the upper area of the backwash column R and separated from the actual backwash room by a chimney tray.
  • a gaseous fraction is released via line 4 and, after heating, is drawn off in E2 and E1.
  • the liquid fraction accumulating on the chimney floor is drawn off by means of line 9 and partly fed in as a return to the upper area of the backwashing room.
  • the remaining portion, after relaxation and heating in E2 and E1, is compressed by compressor C1, further heated in heat exchanger E4 and mixed with the relaxed top product of the rectification column T.
  • the flows 11 of the heat exchanger E1 are auxiliary circuits for the refrigeration.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Separation By Low-Temperature Treatments (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Description

Die Erfindung betrifft ein Verfahren zur Abtrennung von Kohlenwasserstoffen aus einem leichte und schwere Kohlenwasserstoffe und gegebenenfalls leichter als Methan siedende Komponenten enthaltenden Gasstrom, bei dem der unter erhöhtem Druck stehende Gasstrom abgekühlt, partiell kondensiert und in eine flüssige und eine gasförmige Fraktion getrennt wird und bei dem die flüssige Fraktion durch Rektifikation in einen im wesentlichen schwersiedende Komponenten enthaltenden Produktstrom und einen überwiegend leichter siedende Komponenten enthaltenden Restgasstrom zerlegt wird, und die nach der partiellen Kondensation abgetrennte gasförmige Fraktion einer Rückwaschkolonne zugeführt wird, in der mit bei der Rektifikation gewonnenem Restgas nach dessen teilweiser Kondensation schwersiedende Kohlenwasserstoffe aus der gasförmigen Fraktion ausgewaschen werden und die im Sumpf der Rückwaschkolonne anfallende flüssige Fraktion der Rektifikation zugeführt wird.The invention relates to a process for the separation of hydrocarbons from a gas stream containing light and heavy hydrocarbons and possibly components which boil lighter than methane, in which the gas stream under increased pressure is cooled, partially condensed and separated into a liquid and a gaseous fraction and in which the liquid fraction is broken down by rectification into a product stream containing essentially high-boiling components and a residual gas stream containing predominantly lower-boiling components, and the gaseous fraction separated off after the partial condensation is fed to a backwash column in which residual gas obtained in the rectification after its partial condensation high-boiling hydrocarbons are washed out of the gaseous fraction and the liquid fraction obtained in the bottom of the backwash column is fed to the rectification.

Derartige Verfahren dienen vor allem der Entfernung von Ethan und Propan aus Kohlenwasserstoffgasgemischen, wie Erdgas oder Raffinerieabgasen. Ebenso ist eine Eignung dieser Verfahren für die Abtrennung von analogen ungesättigten Kohlenwasserstoffen wie Ethylen und Propylen gegeben. Raffinerieabgase enthalten derartige Kohlenwasserstoffe, womit ihre Aufarbeitung aufgrund gestiegener Marktpreise für C₃/C₄-Kohlenwasserstoffgemische interessant geworden ist.Such processes are primarily used to remove ethane and propane from hydrocarbon gas mixtures, such as natural gas or refinery waste gases. These processes are also suitable for the removal of analog unsaturated hydrocarbons such as ethylene and propylene. Refinery exhaust gases contain such hydrocarbons, which has made their work-up interesting due to increased market prices for C₃ / C₄ hydrocarbon mixtures.

In der DE-OS 3511636 ist ein Verfahren der eingangs genannten Art beschrieben, das der Abtrennung von C₂₊- bzw. C₃₊-Kohlenwasserstoffen aus einem Gasgemisch dient. Eine Rohgasstrom wird dabei im Gegenstrom zu anzuwärmenden Verfahrensströmen partiell kondensiert und in eine flüssige und eine gasförmige Fraktion geschieden. Die flüssige Fraktion, die im wesentlichen aus den schwersiedenden Kohlenwasserstoffkomponenten C₂₊ bzw. C₃₊ besteht, wird in eine Rektifiziersäule weitergeleitet, in der die leichtsiedenden Komponenten aus dieser Fraktion entfernt werden. Dabei fällt am Kopf der Rektifiziersäule eine Restgasfraktion an, die nach ihrer partiellen Kondensation in eine Rückwaschsäule geleitet wird, um dort aus der gasförmigen Fraktion des Abscheiders schwersiedende Komponenten auszuwaschen. Die in der Rückwaschsäule hierbei anfallende Sumpffraktion wird ebenfalls in die Rektifiziersäule eingespeist.In DE-OS 3511636 a method of the type mentioned is described, which is used to separate C₂₊ or C₃₊ hydrocarbons from a gas mixture. A raw gas stream is partially condensed in countercurrent to process streams to be heated and separated into a liquid and a gaseous fraction. The liquid fraction, which consists essentially of the high-boiling hydrocarbon components C₂₊ or C₃₊, is passed into a rectification column in which the low-boiling components are removed from this fraction. At the top of the rectification column there is a residual gas fraction which, after its partial condensation, is passed into a backwash column in order to wash out high-boiling components from the gaseous fraction of the separator. The bottom fraction obtained in the backwash column is also fed into the rectification column.

Die Rückwaschung dient der Ausbeuteerhöhung des Verfahrens, da durch diese Maßnahme sowohl aus der gasförmigen Fraktion des Abscheiders wie aus dem Restgas der Rektifiziersäule sonst nicht gewinnbare C₂₊- bzw. C₃₊-Komponenten erhalten werden können.The backwashing serves to increase the yield of the process, since this measure can be used to obtain C₂₊ or C₃₊ components that cannot otherwise be obtained both from the gaseous fraction of the separator and from the residual gas from the rectification column.

Nachteilig ist bei obigem Verfahren, daß die benötigte Prozeßtemperatur mittels einer Kälteanlage, gegebenenfalls einer Kältekaskade erzeugt werden muß. Dafür ist die kälteleistende Entspannung wenigstens eines Teiles der Restgasströme vorgesehen.A disadvantage of the above method is that the required process temperature must be generated by means of a refrigeration system, possibly a refrigeration cascade. For this purpose, the cold-performing expansion of at least part of the residual gas flows is provided.

Ist beabsichtigt, die anfallenden Restgasströme weiter zu verarbeiten müssen hohe Drücke beibehalten werden. Die Kälteerzeugung geschieht in diesem Fall mit in geschlossenen Kreisläufen geführten Arbeitsmedien. Diese Prozeßvariante hat jedoch den Nachteil, daß sie außerordentlich aufwendig ist.If the intention is to process the residual gas flows further, high pressures must be maintained. In this case, the cold is generated with working media in closed circuits. However, this process variant has the disadvantage that it is extremely complex.

Der Erfindung liegt daher die Aufgabe zugrunde, ein Verfahren der eingangs genannten Art weiter zu verbessern, wobei insbesondere eine aufwendige Kälteerzeugung vermieden werden soll unter gleichzeitiger Beibehaltung hoher Drücke der Restgasströme.The invention is therefore based on the object of further improving a method of the type mentioned, in particular a costly generation of cold should be avoided while at the same time maintaining high pressures of the residual gas flows.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß das bei der Rektifikation gewonnene Restgas nach seiner teilweisen Kondensation und vor seiner Zufuhr zur Rückwaschkolonne in eine gasförmige und eine flüssige Fraktion getrennt wird, und die flüssige Fraktion mindestens teilsweise kälteleistend entspannt, gegen partiell kondensierendes Restgas der Rektifiziersäule angewärmt und dem Restgasstrom der Rektifikation wieder zugemischt wird, während der verbliebene Teil der flüssigen Fraktion der Rückwaschsäule zugeführt wird.This object is achieved in that the residual gas obtained in the rectification is separated into a gaseous and a liquid fraction after its partial condensation and before it is fed to the backwash column, and the liquid fraction is at least partially expanded to provide cooling, and is warmed against partially condensing residual gas from the rectification column and the residual gas stream of the rectification is mixed again, while the remaining part of the liquid fraction is fed to the backwash column.

Durch die Abzweigung eines Teils des kondensierten Restgasstroms, dessen Verwendung als Kältemedium und erneute Zumischung zum Restgasstrom der Rektifikation, kann unter Beibehaltung der hohen Restgasdrücke eine aufwendige Kältekaskade vermieden werden.By branching off part of the condensed residual gas stream, using it as a cooling medium and re-admixing it to the residual gas stream of the rectification, an expensive cooling cascade can be avoided while maintaining the high residual gas pressures.

Die erneute Zumischung des als Kältemedium verwendeten Teils der flüssigen Fraktion des Restgasstromes zum Kopfprodukt der Rektifiziersäule bewirkt, daß die umlaufende Gesamtmenge größer ist als die eigentliche Kopfproduktmenge. Auf diese Neise kann die Kälteleistung des abgezweigten Teils des kondensierten Restgasstroms der Abkühlung weiterer Prozeßströme dienen.The renewed admixing of the part of the liquid fraction of the residual gas stream used as the cooling medium to the top product of the rectification column has the effect that the total amount circulating is greater than the actual top product amount. In this way, the cooling capacity of the branched-off part of the condensed residual gas stream can be used to cool further process streams.

Um die Drücke der einzelnen Restgasströme hoch zuhalten, beispielsweise für nachfolgende Trennschritte dieser Ströme, werden die Rückwaschkolonne sowie die Rektifiziersäule unter erhöhtem Druck betrieben.In order to keep the pressures of the individual residual gas streams high, for example for subsequent separation steps of these streams, the backwash column and the rectification column are operated under increased pressure.

In Ausgestaltung der Erfindung wird dafür der Druck des Restgases, welches der Rückwaschsäule zugeführt wird, dem Druck der Rückwaschkolonne angeglichen.In an embodiment of the invention, the pressure of the residual gas which is fed to the backwash column is adjusted to the pressure of the backwash column.

Damit wird sichergestellt, daß der über Kopf der Rückwaschsäule anfallende Restgasstrom unter erhöhtem Druck gewonnen wird, dessen Bereich zweckmäßig bis zum Rohgasdruck reicht. Das erhaltene Kopfprodukt kann somit ohne Verluste weiterer Abtrennung zugeführt werden.This ensures that the residual gas stream occurring at the top of the backwash column is obtained under increased pressure, the range of which expediently extends to the raw gas pressure. The top product obtained can thus be fed in without further losses.

Im Falle einer Kombination von H₂/C₃₊-Abtrennung trägt das ethanreiche Kopfprodukt der Rückwaschsäule wesentlich zur Erzielung eines ausreichenden Joule-Thompson-Effekts in der nachgeschalteten H₂-Reinigung bei.In the case of a combination of H₂ / C₃₊ separation, the ethane-rich top product of the backwash column contributes significantly to achieving a sufficient level Joule-Thompson effect in the downstream H₂ cleaning.

Die Erfindung sieht darüber hinaus vor, daß vor der Vermischung von kälteleistend entspannter Fraktion mit dem Restgas der Rektifikation eine Druckangleichung beider Ströme stattfindet und der Gemischstrom dem Druck der Rückwaschkolonne angeglichen wird.In addition, the invention provides that, before the cold-cooling relaxed fraction is mixed with the residual gas from the rectification, the two streams are equalized and the mixture stream is adjusted to the pressure of the backwash column.

Die Angleichung der Drücke beider Ströme kann einerseits dadurch geschehen, daß einer von beiden auf den Druck des anderen entspannt wird, oder im entgegengesetzten Fall eine Erhöhung des Druckes des einen Stromes stattfindet.The pressures of the two streams can be equalized on the one hand by relieving one of the two to the pressure of the other, or, in the opposite case, by increasing the pressure of the one stream.

In beiden Fällen wird jedoch im Anschluß daran eine Angleichung des Druckes an den Druck der Rückwaschsäule vorgenommen. Dies geschieht in der Regel durch Komprimierung des Gemischstromes, da das Druckniveau der Rückwaschkolonne über dem der Rektifiziersäule liegt.In both cases, however, the pressure is then adjusted to the pressure of the backwash column. This is usually done by compressing the mixture flow, since the pressure level of the backwash column is above that of the rectification column.

Weiterhin wird erfindungsgemäß vorgeschlagen, daß das Mengenverhältnis des kälteleistend entspannten Teils der flüssigen Fraktion sich zu dem Teil, welcher der Rückwaschsäule zugeführt wird, wie 0.43-2.3: 1 verhält.Furthermore, it is proposed according to the invention that the quantitative ratio of the part of the liquid fraction which is relaxed with respect to the cold to the part which is fed to the backwash column is as 0.43-2.3: 1.

Mit diesem Verhältnis wird einerseits weiterhin eine effiziente Rückwaschung in der Rückwaschkolonne sichergestellt und gleichzeitig genügend Kältemedium zur Verfügung gestellt.With this ratio, on the one hand, efficient backwashing in the backwash column is ensured and at the same time sufficient refrigerant is made available.

Das erfindungsgemäße Verfahren eignet sich besonders für die Kombination unterschiedlicher Trennschritte von H₂ und Kohlenwasserstoffe enthaltenden Gasgemischen, welche mit hohen Eingangsdrücken arbeiten. So können beispielsweise beliebige Kombination zweier Trennschritte, bestehend aus C₅₊-, C₃₊-, C₂₊- und H₂-Abtrennung, in besonders energiesparender und effizienter Weise betrieben werden.The inventive method is particularly suitable for the combination of different separation steps of H₂ and hydrocarbon-containing gas mixtures, which work with high inlet pressures. For example, any combination of two separation steps, consisting of C₅₊, C₃₊, C₂₊ and H₂ separation, can be operated in a particularly energy-saving and efficient manner.

Das erfindungsgemäße Verfahren sei weiterhin beispielhaft anhand der Figuren beschrieben.The method according to the invention is further described by way of example with reference to the figures.

Figur 1: Figure 1 :

Ein unter erhöhtem Druck stehender Rohgasstrom wird über Leitung 1 herangeführt, durch indirekten Wärmetausch in Wärmetauscher E1 partiell kondensiert und in Abscheider D1 in eine flüssige und eine gasförmige Fraktion getrennt. Die flüssige Fraktion wird über Leitung 3 abgezogen und nach Anwärmung in Wärmetauscher E1 in einen mittleren Bereich der Rektifikationssäule T entspannt. Die gasförmige Fraktion des Abscheiders wird mittels Leitung 2 und nach weiterer Abkühlung in Wärmetauscher E2 in den unteren Bereich der Rückwaschkolonne R eingespeist, in der weitere Komponenten durch Auswaschung aus der gasförmigen Fraktion gewonnen werden. Am Sumpf der Rückwaschkolonne wird über die Leitungen 7 und 8 die anfallende flüssige Fraktion abgezogen. Der Teil in Leitung 7 wird direkt in den oberen Bereich der Rektifikationssäule T entspannt, während der Teil des Sumpfprodukts in Leitung 8 zunächst in den Wärmetauschern E2 und E1 angewärmt wird, bevor er in einen mittleren Bereich der Rektifiziersäule entspannt wird. Im Sumpf der Rektifiziersäule fällt eine Produktfraktion an, welche über Leitung 10 abgezogen wird. Über Stichleitung 11 wird davon ein Teil abgezweigt, in Wärmetauscher E3 erwärmt und als Aufkochstrom in den Sumpf der Rektifiziersäule T zurückgeleitet. Am Kopf der Kolonne T fällt ein Restgasstrom an, welcher noch erwünschte schwere Komponenten enthält. Mittels Leitung 12 wird dieser Strom abgezogen in den Wärmetauschern E1 und E2 partiell kondensiert und in Abscheider D3 in eine gasförmige und eine flüssige Fraktion geschieden. Über Leitung 14 wird die flüssige Fraktion nach Kompression in Pumpe P zur Rückwaschung dem oberen Bereich der Rückwaschsäule R zugeführt. Vor der Kompression wird der Fraktion der Leitung 14 über Stichleitung 15 ein Teil abgezweigt kälteleistend entspannt, in den Wärmetauschern E2 und E1 gegen abzukühlende Ströme der Leitungen 1 (Rohgas) und 12 (Restgasstrom der Rektifiziersäule) erwärmt und nach Verdichtung in den Kompressoren C1 und C2 und erneuter Anwärmung in den Wärmetauschern E4 und E5 dem Kopfrestgasstrom der Rektifiziersäule T wieder zugemischt. Das am Kopf der Rückwaschsäule R anfallende Restgas, bestehend aus leichtersiedenden Komponenten, wird nach Abzug mittels Leitung 4 mindestens teilweise in Wärmetauscher E6 partiell kondensiert. In Abscheider D2 erfolgt daraufhin eine Trennung in gasförmige und veflüssigte Anteile. Die gasförmig gebliebenen Anteile werden in Leitung 6 abgezogen, während die verflüssigten Anteile über Leitung 5, zusammen mit der gasförmigen Fraktion des Abscheiders D3 aus Leitung 13, aus dem System abgezogen werden. Die Ströme 9 des Wärmetauschers E1 sind Hilfskreisläufe für die Kälteerzeugung.A raw gas stream under increased pressure is introduced via line 1, partially condensed by indirect heat exchange in heat exchanger E1 and separated into a liquid and a gaseous fraction in separator D1. The liquid fraction is drawn off via line 3 and, after heating in heat exchanger E1, expanded into a central region of the rectification column T. The gaseous fraction of the separator is fed via line 2 and after further cooling in heat exchanger E2 into the lower region of the backwash column R, in which further components are obtained by washing out of the gaseous fraction. At the bottom of the backwash column, the liquid fraction obtained is drawn off via lines 7 and 8. The part in line 7 is expanded directly into the upper region of the rectification column T, while the part of the bottom product in line 8 is initially in the heat exchangers E2 and E1 is warmed before it is released into a central area of the rectification column. A product fraction is obtained in the bottom of the rectification column and is withdrawn via line 10. Part of it is branched off via branch line 11, heated in heat exchanger E3 and fed back as a boiling stream into the bottom of the rectification column T. At the top of column T, a residual gas stream is obtained which still contains desired heavy components. By means of line 12, this current is drawn off partially condensed in the heat exchangers E1 and E2 and separated into a gaseous and a liquid fraction in separator D3. After compression in pump P, the liquid fraction is fed via line 14 to the upper region of the backwash column R for backwashing. Before the compression, the fraction of line 14 is branched off in a branch-cold manner to reduce the pressure, heated in heat exchangers E2 and E1 against streams of lines 1 to be cooled (raw gas) and 12 (residual gas stream from the rectification column) and after compression in compressors C1 and C2 and reheating in the heat exchangers E4 and E5 mixed with the top residual gas stream of the rectification column T. The residual gas obtained at the top of the backwash column R, consisting of low-boiling components, is at least partially condensed in heat exchanger E6 after removal by means of line 4. Separator D2 then separates them into gaseous and liquefied components. The gaseous fractions are withdrawn in line 6, while the liquefied fractions are withdrawn from the system via line 5, together with the gaseous fraction of the separator D3 from line 13. The flows 9 of the heat exchanger E1 are auxiliary circuits for the refrigeration.

Figur 2: Figure 2 :

Ein unter erhöhtem Druck stehender Rohgasstrom wird mittels Leitung 1, nach Abkühlung und partieller Kondensation durch indirekten Wärmetausch in Wärmetauscher E1, zum Abscheider D geleitet und dort in eine flüssige und eine gasförmige Fraktion getrennt. Die flüssige Fraktion wird über Leitung 3 abgezogen, entspannt und nach Anwärmung in Wärmetauscher E1 in einen mittleren Bereich der Rektifiziersäule T geleitet. Die gasförmige Fraktion des Abscheiders wird mittels Leitung 2, nach weiterer Abkühlung in Wärmetausch E2, in den unteren Bereich der Rückwaschkolonne R eingespeist. Vom Sumpf der Rückwaschkolonne wird über die Leitungen 5 und 6 die anfallende flüssige Fraktion abgezogen. Die flüssige Fraktion der Leitung 5 wird entspannt, in Wärmetauscher E2 angewärmt und einem mittleren Bereich der Rektifiziersäule T aufgegeben, während der Anteil in Leitung 6 direkt in einen oberen Bereich der Rektifiziersäule entspannt wird. Die im Sumpf der Rektifiziersäule anfallende flüssige Fraktion wird über Leitung 7 entfernt. Ein Teil wird nach Anwärmung in Wärmetauscher E3 als Aufkochstrom in den Sumpf der Rektifiziersäule zurückgeleitet, der übrige Strom wird komprimiert P und nach Erwärmung in E1 abgegeben.A raw gas stream under increased pressure is passed via line 1, after cooling and partial condensation by indirect heat exchange in heat exchanger E1, to separator D, where it is separated into a liquid and a gaseous fraction. The liquid fraction is drawn off via line 3, decompressed and, after heating in heat exchanger E1, passed into a central region of the rectification column T. The gaseous fraction of the separator is fed into line 2, after further cooling in heat exchange E2, into the lower region of the backwash column R. The liquid fraction obtained is drawn off from the bottom of the backwash column via lines 5 and 6. The liquid fraction of line 5 is expanded, heated in heat exchanger E2 and fed to a central area of the rectification column T, while the portion in line 6 is expanded directly into an upper area of the rectification column. The liquid fraction obtained in the bottom of the rectification column is removed via line 7. After heating in heat exchanger E3, a part is returned to the bottom of the rectification column as a boiling stream, the rest of the stream is compressed P and released after heating in E1.

Das Kopfprodukt der Rektifiziersäule T, mittels Leitung 8 abgezogen, wird zunächst in E1 angewärmt, entspannt und mit dem komprimierten und erwärmten Strom der Leitung 9 vermischt, wonach in Leitung 10 das Gemisch weiter verdichtet wird in Kompressor C2, und eine Anwärmung im Wärmetauscher ES erfolgt. Nach Abkühlung und partieller Kondensation in den Wärmetauschern E1 und E2 wird der Strom der Leitung 10 in den Abscheideraum der Rückwasch kolonne R entspannt. Der Abscheideraum ist im oberen Bereich der Rückwaschkolonne R angeordnet und vom eigentlichen Rückwaschraum durch einen Kaminboden getrennt. Am Kopf des Abscheideraumes wird über Leitung 4 eine gasförmige Fraktion abgegeben und nach Anwärmung in E2 und E1 abgezogen. Die am Kaminboden anfallende flüssige Fraktion wird mittels Leitung 9 abgezogen und teilweis als Rücklauf auf den oberen Bereich des Rückwaschraumes aufgegeben. Der übrige Anteil wird, nach Entspannung und Anwärmung in E2 und E1, durch Kompressor C1 verdichtet, im Wärmetauscher E4 weiter erwärmt und mit dem entspannten Kopfprodukt der Rektifiziersäule T vermischt. Die Ströme 11 des Wärmetauschers E1 sind Hilfskreisläufe für die Kälteerzeugung.The top product of the rectification column T, drawn off by means of line 8, is first warmed up in E1, expanded and mixed with the compressed and heated stream of line 9, after which the mixture is further compressed in line 10 into compressor C2, and heating in the heat exchanger ES takes place . After cooling and partial condensation in the heat exchangers E1 and E2, the flow of the line 10 is washed back into the separation chamber column R relaxed. The separation room is arranged in the upper area of the backwash column R and separated from the actual backwash room by a chimney tray. At the top of the separation chamber, a gaseous fraction is released via line 4 and, after heating, is drawn off in E2 and E1. The liquid fraction accumulating on the chimney floor is drawn off by means of line 9 and partly fed in as a return to the upper area of the backwashing room. The remaining portion, after relaxation and heating in E2 and E1, is compressed by compressor C1, further heated in heat exchanger E4 and mixed with the relaxed top product of the rectification column T. The flows 11 of the heat exchanger E1 are auxiliary circuits for the refrigeration.

Nachfolgend ist das erfindungsgemäße Verfahren anhand eines zahlenmäßigen Beispiels unter Einbeziehung der Numerierung der Figur 2 dargestellt.

Figure imgb0001
The method according to the invention is shown below using a numerical example including the numbering in FIG. 2.
Figure imgb0001

Claims (4)

1. A process for separating hydrocarbons from a gas stream containing light and heavy hydrocarbons and possibly components which are lower boiling than methane, wherein the gas stream, which is under increased pressure, is cooled, partially condensed and divided into a liquid and a gaseous fraction, and wherein the liquid fraction is separated by rectification into a product stream which substantially contains high boiling components and into a residual gas stream which predominantly contains lower boiling components and wherein the gaseous fraction, which has been separated following the partial condensation, is fed to a rescrubbing column in which, with the residual gas obtained by the rectification, after the partial condensation thereof, high boiling hydrocarbons are scrubbed out of the gaseous fraction and the liquid fraction occurring in the sump of the rescrubbing column is fed to the rectification stage, characterised in that the residual gas obtained by the rectification, following its partial condensation and before it is fed to the rescrubbing column, is divided into a gaseous and a liquid fraction, and the liquid fraction is at least partially expanded with the production of cold, is heated in the presence of partially condensing residual gas from the rectifier column, and is remixed with the residual gas stream of the rectification stage, whilst the remaining part of the liquid fraction is fed to the rescrubbing column.
2. A process as claimed in Claim 1, characterised in that the pressure of the residual gas which is fed to the rescrubbing column is adjusted to the pressure of the rescrubbing column.
3. A process as claimed in Claim 1, characterised in that before the liquid fraction, which has been expanded with the production of cold, is mixed with the residual gas of the rectification stage, a pressure adjustment of the two streams takes place and the mixed stream is adjusted to the pressure of the rescrubbing column.
4. A process as claimed in Claim 1 to 3, characterised in that the quantity ratio of that part of the liquid fraction which is expanded with the production of cold to that part which is fed to the rescrubbing column is 0.43-2.3: 1.
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AU613180B2 (en) 1991-07-25
ES2027431T3 (en) 1992-06-01
AU3371789A (en) 1989-11-02
EP0340465A2 (en) 1989-11-08
US4966612A (en) 1990-10-30
EP0340465A3 (en) 1990-03-21
DE3814294A1 (en) 1989-11-09

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