Classifications

• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D5/00—Condensation of vapours; Recovering volatile solvents by condensation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
• • 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
  • F25J3/0209—Natural gas or substitute natural gas
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
  • F25J3/02—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
  • 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
  • F25J3/0242—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 3 carbon atoms or more
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J5/00—Arrangements of cold exchangers or cold accumulators in separation or liquefaction plants
• • 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
  • C10G2400/00—Products obtained by processes covered by groups C10G9/00 - C10G69/14
  • C10G2400/20—C2-C4 olefins
• • 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
  • F25J2200/02—Processes or apparatus using separation by rectification in a single 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
  • F25J2200/30—Processes or apparatus using separation by rectification using a side column in a single pressure 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
  • F25J2200/80—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
  • 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
  • F25J2210/06—Splitting of the feed stream, e.g. for treating or cooling in different ways
• • 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
  • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
  • F25J2240/02—Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2270/00—Refrigeration techniques used
  • F25J2270/12—External refrigeration with liquid vaporising loop
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2270/00—Refrigeration techniques used
  • F25J2270/60—Closed external refrigeration cycle with single component refrigerant [SCR], e.g. C1-, C2- or C3-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
  • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
  • F25J2290/40—Vertical layout or arrangement of cold equipments within in the cold box, e.g. columns, condensers, heat exchangers 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
  • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
  • F25J2290/42—Modularity, pre-fabrication of modules, assembling and erection, horizontal layout, i.e. plot plan, and vertical arrangement of parts of the cryogenic unit, e.g. of the cold box
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
  • Y02C20/00—Capture or disposal of greenhouse gases
  • Y02C20/20—Capture or disposal of greenhouse gases of methane

Definitions

• This invention relates to a process and apparatus for the separation of a gas containing hydrocarbons.
• the applicants claim the benefits under Title 35, United States Code, Section 119(e) of prior U.S. Provisional Application Number 61/186,361 which was filed on June 11, 2009.
• the applicants also claim the benefits under Title 35, United States Code, Section 120 as a continuation-in-part of U.S. Patent Application No. 12/750,862 which was filed on March 31, 2010, and as a continuation-in-part of U.S. Patent Application No. 12/717,394 which was filed on March 4, 2010, and as a continuation-in-part of U.S. Patent Application No. 12/689,616 which was filed on January 19, 2010, and as a continuation-in-part of U.S. Patent Application No. 12/372,604 which was filed on February 17, 2009.
• Assignees S.M.E. Products LP and Ortloff Engineers, Ltd. were parties to a joint research agreement that was in effect before the invention of this application was made
• Ethylene, ethane, propylene, propane, and/or heavier hydrocarbons can be recovered from a variety of gases, such as natural gas, refinery gas, and synthetic gas streams obtained from other hydrocarbon materials such as coal, crude oil, naphtha, oil shale, tar sands, and lignite.
• Natural gas usually has a major proportion of methane and ethane, i.e., methane and ethane together comprise at least 50 mole percent of the gas.
• the gas also contains relatively lesser amounts of heavier hydrocarbons such as propane, butanes, pentanes, and the like, as well as hydrogen, nitrogen, carbon dioxide, and other gases.
• the present invention is generally concerned with the recovery of ethylene, ethane, propylene, propane, and heavier hydrocarbons from such gas streams.
• a typical analysis of a gas stream to be processed in accordance with this invention would be, in approximate mole percent, 90.3% methane, 4.0% ethane and other C 2 components, 1.7% propane and other C 3 components, 0.3% iso-butane, 0.5% normal butane, and 0.8% pentanes plus, with the balance made up of nitrogen and carbon dioxide. Sulfur containing gases are also sometimes present.
• Patent No. 33,408; and co-pending application nos. 11/430,412; 11/839,693; 11/971,491; and 12/206,230 describe relevant processes (although the description of the present invention in some cases is based on different processing conditions than those described in the cited U.S. Patents).
• a feed gas stream under pressure is cooled by heat exchange with other streams of the process and/or external sources of refrigeration such as a propane compression-refrigeration system.
• liquids may be condensed and collected in one or more separators as high-pressure liquids containing some of the desired C 2 + components.
• the high-pressure liquids may be expanded to a lower pressure and fractionated. The vaporization occurring during expansion of the liquids results in further cooling of the stream. Under some conditions, pre-cooling the high pressure liquids prior to the expansion may be desirable in order to further lower the temperature resulting from the expansion.
• the expanded stream comprising a mixture of liquid and vapor, is fractionated in a distillation (demethanizer or deethanizer) column.
• the expansion cooled stream(s) is (are) distilled to separate residual methane, nitrogen, and other volatile gases as overhead vapor from the desired C 2 components, C 3 components, and heavier hydrocarbon components as bottom liquid product, or to separate residual methane, C 2 components, nitrogen, and other volatile gases as overhead vapor from the desired C 3 components and heavier hydrocarbon components as bottom liquid product.
• the feed gas is not totally condensed (typically it is not), the vapor remaining from the partial condensation can be split into two streams.
• One portion of the vapor is passed through a work expansion machine or engine, or an expansion valve, to a lower pressure at which additional liquids are condensed as a result of further cooling of the stream.
• the pressure after expansion is essentially the same as the pressure at which the distillation column is operated.
• the combined vapor-liquid phases resulting from the expansion are supplied as feed to the column.
• the remaining portion of the vapor is cooled to substantial condensation by heat exchange with other process streams, e.g., the cold fractionation tower overhead.
• Some or all of the high-pressure liquid may be combined with this vapor portion prior to cooling.
• the resulting cooled stream is then expanded through an appropriate expansion device, such as an expansion valve, to the pressure at which the demethanizer is operated. During expansion, a portion of the liquid will vaporize, resulting in cooling of the total stream.
• the flash expanded stream is then supplied as top feed to the demethanizer.
• the vapor portion of the flash expanded stream and the demethanizer overhead vapor combine in an upper separator section in the fractionation tower as residual methane product gas.
• the cooled and expanded stream may be supplied to a separator to provide vapor and liquid streams.
• the vapor is combined with the tower overhead and the liquid is supplied to the column as a top column feed.
• the residue gas leaving the process will contain substantially all of the methane in the feed gas with essentially none of the heavier hydrocarbon components and the bottoms fraction leaving the demethanizer will contain substantially all of the heavier hydrocarbon components with essentially no methane or more volatile components.
• this ideal situation is not obtained because the conventional demethanizer is operated largely as a stripping column.
• the methane product of the process therefore, typically comprises vapors leaving the top fractionation stage of the column, together with vapors not subjected to any rectification step.
• the preferred processes for hydrocarbon separation use an upper absorber section to provide additional rectification of the rising vapors.
• One method of generating a reflux stream for the upper rectification section is to use the flash expanded substantially condensed stream to cool and partially condense the column overhead vapor, with the heated flash expanded stream then directed to a mid-column feed point on the demethanizer.
• the liquid condensed from the column overhead vapor is separated and supplied as top feed to the demethanizer, while the uncondensed vapor is discharged as the residual methane product gas.
• the heated flash expanded stream is only partially vaporized, and so contains a substantial quantity of liquid that serves as supplemental reflux for the demethanizer, so that the top reflux feed can then rectify the vapors leaving the lower section of the column.
• U.S. Patent No. 4,854,955 is an example of a process of this type.
• the present invention employs a novel means of performing the various steps described above more efficiently and using fewer pieces of equipment. This is accomplished by combining what heretofore have been individual equipment items into a common housing, thereby reducing the plot space required for the processing plant and reducing the capital cost of the facility.
• the more compact arrangement also significantly reduces the power consumption required to achieve a given recovery level, thereby increasing the process efficiency and reducing the operating cost of the facility.
• the more compact arrangement also eliminates much of the piping used to interconnect the individual equipment items in traditional plant designs, further reducing capital cost and also eliminating the associated flanged piping connections. Since piping flanges are a potential leak source for hydrocarbons (which are volatile organic compounds, VOCs, that contribute to greenhouse gases and may also be precursors to atmospheric ozone formation), eliminating these flanges reduces the potential for atmospheric emissions that can damage the environment.
• hydrocarbons which are volatile organic compounds, VOCs, that contribute to greenhouse gases and may also be precursors to atmospheric ozone formation
• C 2 recoveries in excess of 86% can be obtained.
• C 3 recoveries in excess of 99% can be obtained while providing essentially complete rejection of C 2 components to the residue gas stream.
• the present invention makes possible essentially 100% separation of methane (or C 2 components) and lighter components from the C 2 components (or C 3 components) and heavier components at lower energy requirements compared to the prior art while maintaining the same recovery level.
• the present invention although applicable at lower pressures and warmer temperatures, is particularly advantageous when processing feed gases in the range of 400 to
• FIGS. 1 and 2 are flow diagrams of prior art natural gas processing plants in accordance with United States Patent No. 4,854,955;
• FIG. 3 is a flow diagram of a natural gas processing plant in accordance with the present invention.
• FIGS. 4 through 6 are flow diagrams illustrating alternative means of application of the present invention to a natural gas stream.
• the molar flow rates given in the tables may be interpreted as either pound moles per hour or kilogram moles per hour.
• the energy consumptions reported as horsepower (HP) and/or thousand British Thermal Units per hour (MBTU/Hr) correspond to the stated molar flow rates in pound moles per hour.
• the energy consumptions reported as kilowatts (kW) correspond to the stated molar flow rates in kilogram moles per hour.
• FIG. 1 is a process flow diagram showing the design of a processing plant to recover C 2 + components from natural gas using prior art according to U.S. Pat. No. 4,854,955.
• inlet gas enters the plant at 110°F [43°C] and 915 psia [6,307 kPa(a)] as stream 31.
• the sulfur compounds are removed by appropriate pretreatment of the feed gas (not illustrated).
• the feed stream is usually dehydrated to prevent hydrate (ice) formation under cryogenic conditions. Solid desiccant has typically been used for this purpose.
• the feed stream 31 is divided into two portions, streams 32 and 33.
• Stream 32 is cooled to -34°F [-37 0 C] in heat exchanger 10 by heat exchange with cool residue gas stream 42a, while stream 33 is cooled to -13°F [-25 0 C] in heat exchanger 11 by heat exchange with demethanizer reboiler liquids at 52°F [11°C] (stream 45) and side reboiler liquids at -49°F [-45 0 C] (stream 44).
• Streams 32a and 33a recombine to form stream 31a, which enters separator 12 at -28°F [-33 0 C] and 893 psia [6,155 kPa(a)] where the vapor (stream 34) is separated from the condensed liquid (stream 35).
• Stream 36 containing about 27% of the total vapor, is combined with the separator liquid (stream 35), and the combined stream 38 passes through heat exchanger 13 in heat exchange relation with cold residue gas stream 42 where it is cooled to substantial condensation.
• the resulting substantially condensed stream 38a at -135°F [-93°C] is then flash expanded through expansion valve 14 to slightly above the operating pressure (approximately 396 psia [2,730 kPa(a)]) of fractionation tower 18. During expansion a portion of the stream is vaporized, resulting in cooling of the total stream.
• the expanded stream 38b leaving expansion valve 14 reaches a temperature of -138°F [-94 0 C] before entering heat exchanger 20.
• the flash expanded stream is heated and partially vaporized as it provides cooling and partial condensation of column overhead stream 41, with the heated stream 38c at -139°F [-95 0 C] thereafter supplied to fractionation tower 18 at an upper mid-column feed point.
• the temperature of stream 38b/38c drops slightly as it is heated, due to the pressure drop through heat exchanger 20 and the resulting vaporization of some of the liquid methane contained in the stream.
• the remaining 73% of the vapor from separator 12 enters a work expansion machine 15 in which mechanical energy is extracted from this portion of the high pressure feed.
• the machine 15 expands the vapor substantially isentropically to the tower operating pressure, with the work expansion cooling the expanded stream 39a to a temperature of approximately -95 °F [-71 0 C].
• the typical commercially available expanders are capable of recovering on the order of 80-85% of the work theoretically available in an ideal isentropic expansion.
• the work recovered is often used to drive a centrifugal compressor (such as item 16) that can be used to re-compress the heated residue gas stream (stream 42b), for example.
• the partially condensed expanded stream 39a is thereafter supplied as feed to fractionation tower 18 at a lower mid-column feed point.
• the column overhead vapor (stream 41) is withdrawn from the top of demethanizer 18 and cooled from -136°F [-93 0 C] to -138°F [-94 0 C] and partially condensed (stream 41a) in heat exchanger 20 by heat exchange with the flash expanded substantially condensed stream 38b as previously described.
• the operating pressure in reflux separator 21 (391 psia [2,696 kPa(a)]) is maintained slightly below the operating pressure of demethanizer 18. This provides the driving force which causes overhead vapor stream 41 to flow through heat exchanger 20 and thence into the reflux separator 21 wherein the condensed liquid (stream 43) is separated from the uncondensed vapor (stream 42).
• the liquid stream 43 from reflux separator 21 is pumped by pump 22 to a pressure slightly above the operating pressure of demethanizer 18, and stream 43a is then supplied as cold top column feed (reflux) to demethanizer 18.
• This cold liquid reflux absorbs and condenses the C 2 components, C 3 components, and heavier components in the vapors rising through the upper region of absorbing section 18a of demethanizer 18.
• the demethanizer in tower 18 is a conventional distillation column containing a plurality of vertically spaced trays, one or more packed beds, or some combination of trays and packing.
• the demethanizer tower consists of two sections: an upper absorbing (rectification) section 18a that contains the trays and/or packing to provide the necessary contact between the vapor portion of expanded stream 39a rising upward and cold liquid falling downward to condense and absorb the C 2 components, C 3 components, and heavier components; and a lower stripping (demethanizing) section 18b that contains the trays and/or packing to provide the necessary contact between the liquids falling downward and the vapors rising upward.
• the demethanizing section 18b also includes reboilers (such as the reboiler and the side reboiler described previously) which heat and vaporize a portion of the liquids flowing down the column to provide the stripping vapors which flow up the column to strip the liquid product (stream 46) of methane and lighter components.
• the liquid product stream 46 exits the bottom of the tower at 77 0 F [25°C], based on a typical specification of a methane to ethane ratio of 0.010:1 on a mass basis in the bottom product.
• Vapor stream 42 from reflux separator 21 is the cold residue gas stream.
• FIG. 2 is a process flow diagram showing one manner in which the design of the processing plant in FIG. 1 can be adapted to operate at a lower C 2 component recovery level. This is a common requirement when the relative values of natural gas and liquid hydrocarbons are variable, causing recovery of the C 2 components to be unprofitable at times.
• the process of FIG. 2 has been applied to the same feed gas composition and conditions as described previously for FIG. 1. However, in the simulation of the process of FIG. 2, the process operating conditions have been adjusted to reject nearly all of C 2 components to the residue gas rather than recovering them in the bottom liquid product from the fractionation tower.
• inlet gas enters the plant at 110°F [43 °C] and
• Cooled stream 31a enters separator 12 at 15°F [-9 0 C] and 900 psia [6,203 kPa(a)] where the vapor (stream 34) is separated from the condensed liquid (stream 35).
• Stream 36 containing about 28% of the total vapor, is combined with the separator liquid (stream 35), and the combined stream 38 passes through heat exchanger 13 in heat exchange relation with cold residue gas stream 42 where it is cooled to substantial condensation.
• the resulting substantially condensed stream 38a at -114°F [-81°C] is then flash expanded through expansion valve 14 to slightly above the operating pressure (approximately 400 psia [2,758 kPa(a)]) of fractionation tower 18. During expansion a portion of the stream is vaporized, resulting in cooling of the total stream.
• the expanded stream 38b leaving expansion valve 14 reaches a temperature of -137°F [-94°C] before entering heat exchanger 20.
• the flash expanded stream is heated and partially vaporized as it provides cooling and partial condensation of column overhead stream 41, with the heated stream 38c at -107°F [-77 0 C] thereafter supplied to fractionation tower 18 at an upper mid-column feed point.
• the column overhead vapor (stream 41) is withdrawn from the top of deethanizer 18 and cooled from -102 0 F [-74 0 C] to -117 0 F [-83 0 C] and partially condensed (stream 41a) in heat exchanger 20 by heat exchange with the flash expanded substantially condensed stream 38b as previously described.
• the partially condensed stream 41a enters reflux separator 21, operating at 395 psia [2,723 kPa(a)], where the condensed liquid (stream 43) is separated from the uncondensed vapor (stream 42).
• the liquid stream 43 from reflux separator 21 is pumped by pump 22 to a pressure slightly above the operating pressure of deethanizer 18, and stream 43a is then supplied as cold top column feed (reflux) to deethanizer 18.
• the liquid product stream 46 exits the bottom of the tower at 223 °F [ 106°C] , based on a typical specification of a ethane to propane ratio of 0.050:1 on a molar basis in the bottom product.
• the cold residue gas (vapor stream 42 from reflux separator 21) passes countercurrently to the incoming feed gas in heat exchanger 13 where it is heated to -25 0 F [-31 0 C] (stream 42a) and in heat exchanger 10 where it is heated to 105°F [41 0 C] (stream 42b) as it provides cooling as previously described.
• the residue gas is then re-compressed in two stages, compressor 16 driven by expansion machine 15 and compressor 23 driven by a supplemental power source.
• stream 42d is cooled to HO 0 F [43°C] in discharge cooler 24, the residue gas product (stream 42e) flows to the sales gas pipeline at 915 psia [6,307 kPa(a)].
• FIG. 2 Stream Flow Summary - Lb. Moles/Hr [kg moles/Hr]
• FIG. 3 illustrates a flow diagram of a process in accordance with the present invention.
• the feed gas composition and conditions considered in the process presented in FIG. 3 are the same as those in FIG. 1. Accordingly, the FIG. 3 process can be compared with that of the FIG. 1 process to illustrate the advantages of the present invention.
• inlet gas enters the plant as stream 31 and is divided into two portions, streams 32 and 33. The first portion, stream 32, enters a heat exchange means in the upper region of feed cooling section 118a inside processing assembly 118.
• This heat exchange means may be comprised of a fin and tube type heat exchanger, a plate type heat exchanger, a brazed aluminum type heat exchanger, or other type of heat transfer device, including multi-pass and/or multi-service heat exchangers.
• the heat exchange means is configured to provide heat exchange between stream 32 flowing through one pass of the heat exchange means and a distillation vapor stream arising from rectifying section 118b inside processing assembly 118 that has been heated in a heat exchange means in the lower region of feed cooling section 118a.
• Stream 32 is cooled while further heating the distillation vapor stream, with stream 32a leaving the heat exchange means at -29°F [-34 0 C].
• This heat and mass transfer means may also be comprised of a fin and tube type heat exchanger, a plate type heat exchanger, a brazed aluminum type heat exchanger, or other type of heat transfer device, including multi-pass and/or multi-service heat exchangers.
• the heat and mass transfer means is configured to provide heat exchange between stream 33 flowing through one pass of the heat and mass transfer means and a distillation liquid stream flowing downward from an absorbing means above the heat and mass transfer means in stripping section 118d, so that stream 33 is cooled while heating the distillation liquid stream, cooling stream 33a to -10 0 F [-23°C] before it leaves the heat and mass transfer means.
• the heat and mass transfer means provides continuous contact between the stripping vapors and the distillation liquid stream so that it also functions to provide mass transfer between the vapor and liquid phases, stripping the liquid product stream 46 of methane and lighter components.
• Streams 32a and 33a recombine to form stream 31a, which enters separator section 118e inside processing assembly 118 at -23°F [-31 0 C] and 900 psia [6,203 kPa(a)], whereupon the vapor (stream 34) is separated from the condensed liquid (stream 35).
• Separator section 118e has an internal head or other means to divide it from stripping section 118d, so that the two sections inside processing assembly 118 can operate at different pressures.
• Stream 36 containing about 29% of the total vapor, is combined with the separated liquid (stream 35, via stream 37), and the combined stream 38 enters a heat exchange means in the lower region of feed cooling section 118a inside processing assembly 118.
• This heat exchange means may likewise be comprised of a fin and tube type heat exchanger, a plate type heat exchanger, a brazed aluminum type heat exchanger, or other type of heat transfer device, including multi-pass and/or multi-service heat exchangers.
• the heat exchange means is configured to provide heat exchange between stream 38 flowing through one pass of the heat exchange means and the distillation vapor stream arising from rectifying section 118b inside processing assembly 118, so that stream 38 is cooled to substantial condensation while heating the distillation vapor stream.
• the resulting substantially condensed stream 38a at - 135°F [-93 °C] is then flash expanded through expansion valve 14 to slightly above the operating pressure (approximately 388 psia [2,675 kPa(a)]) of rectifying section 118b and absorbing section 118c (an absorbing means) inside processing assembly 118. During expansion a portion of the stream may be vaporized, resulting in cooling of the total stream. In the process illustrated in FIG. 3, the expanded stream 38b leaving expansion valve 14 reaches a temperature of -139°F [-95 0 C] before it is directed into a heat and mass transfer means inside rectifying section 118b.
• This heat and mass transfer means may also be comprised of a fin and tube type heat exchanger, a plate type heat exchanger, a brazed aluminum type heat exchanger, or other type of heat transfer device, including multi-pass and/or multi-service heat exchangers.
• the heat and mass transfer means is configured to provide heat exchange between the distillation vapor stream arising from absorbing section 118c flowing upward through one pass of the heat and mass transfer means and the expanded stream 38b flowing downward, so that the distillation vapor is cooled while heating the expanded stream. As the distillation vapor stream is cooled, a portion of it is condensed and falls downward while the remaining distillation vapor continues flowing upward through the heat and mass transfer means.
• the heat and mass transfer means provides continuous contact between the condensed liquid and the distillation vapor so that it also functions to provide mass transfer between the vapor and liquid phases, thereby providing rectification of the distillation vapor.
• the condensed liquid is collected from the bottom of the heat and mass transfer means and directed to absorbing section 118c.
• the flash expanded stream 38b is partially vaporized as it provides cooling and partial condensation of the distillation vapor stream, and exits the heat and mass transfer means in rectifying section 118b at -140°F [-96 0 C]. (Note that the temperature of stream 38b drops slightly as it is heated, due to the pressure drop through the heat and mass transfer means and the resulting vaporization of some of the liquid methane contained in the stream.)
• the heated flash expanded stream is separated into its respective vapor and liquid phases, with the vapor phase combining with the vapor arising from absorbing section 118c to form the distillation vapor stream that enters the heat and mass transfer means in rectifying section 118b as previously described.
• the liquid phase is directed to the upper region of absorbing section 118c to join with the liquid condensed from the distillation vapor stream in rectifying section 118b.
• the remaining 71% of the vapor from separator section 118e enters a work expansion machine 15 in which mechanical energy is extracted from this portion of the high pressure feed.
• the machine 15 expands the vapor substantially isentropically to the operating pressure of absorbing section 118c, with the work expansion cooling the expanded stream 39a to a temperature of approximately -93 0 F [-70 0 C].
• the partially condensed expanded stream 39a is thereafter supplied as feed to the lower region of absorbing section 118c inside processing assembly 118 to be contacted by the liquids supplied to the upper region of absorbing section 118c.
• Absorbing section 118c and stripping section 118d each contain an absorbing means consisting of a plurality of vertically spaced trays, one or more packed beds, or some combination of trays and packing.
• the trays and/or packing in absorbing section 118c and stripping section 118d provide the necessary contact between the vapors rising upward and cold liquid falling downward.
• the liquid portion of the expanded stream 39a commingles with liquids falling downward from absorbing section 118c and the combined liquid continues downward into stripping section 118d.
• the vapors arising from stripping section 118d combine with the vapor portion of the expanded stream 39a and rise upward through absorbing section 118c, to be contacted with the cold liquid falling downward to condense and absorb most of the C 2 components, C 3 components, and heavier components from these vapors.
• the vapors arising from absorbing section 118c combine with the vapor portion of the heated expanded stream 38b and rise upward through rectifying section 118b, to be cooled and rectified to remove most of the C 2 components, C 3 components, and heavier components remaining in these vapors as previously described.
• the liquid portion of the heated expanded stream 38b commingles with liquids falling downward from rectifying section 118b and the combined liquid continues downward into absorbing section 118c.
• the volatile components are stripped out of the liquid continuously, reducing the concentration of the volatile components in the stripping vapors more quickly and thereby improving the stripping efficiency for the present invention.
• the present invention offers two other advantages over the prior art in addition to the increase in processing efficiency.
• the compact arrangement of processing assembly 118 of the present invention replaces eight separate equipment items in the prior art (heat exchangers 10, 11, 13, and 20, separator 12, reflux separator 21, reflux pump 22, and fractionation tower 18 in FIG. 1) with a single equipment item (processing assembly 118 in FIG. 3). This reduces the plot space requirements, eliminates the interconnecting piping, and eliminates the power consumed by the reflux pump, reducing the capital cost and operating cost of a process plant utilizing the present invention over that of the prior art.
• VOCs volatile organic compounds
• the present invention offers significant efficiency advantages over the prior art process depicted in FIG. 2.
• the operating conditions of the FIG. 3 process can be altered as illustrated in FIG. 4 to reduce the ethane content in the liquid product of the present invention to the same level as for the FIG. 2 prior art process.
• the feed gas composition and conditions considered in the process presented in FIG. 4 are the same as those in FIG. 2. Accordingly, the FIG. 4 process can be compared with that of the FIG. 2 process to further illustrate the advantages of the present invention.
• inlet gas stream 31 enters a heat exchange means in the upper region of feed cooling section 118a inside processing assembly 118.
• the heat exchange means is configured to provide heat exchange between stream 31 flowing through one pass of the heat exchange means and a distillation vapor stream arising from rectifying section 118b inside processing assembly 118 that has been heated in a heat exchange means in the lower region of feed cooling section 118a.
• Stream 31 is cooled while further heating the distillation vapor stream, with stream 31a leaving the heat exchange means and thereafter entering separator section 118e inside processing assembly 118 at 15°F [-9 0 C] and 900 psia [6,203 kPa(a)], whereupon the vapor (stream 34) is separated from the condensed liquid (stream 35).
• Stream 36 containing about 28% of the total vapor, is combined with the separated liquid (stream 35, via stream 37), and the combined stream 38 enters a heat exchange means in the lower region of feed cooling section 118a inside processing assembly 118.
• the heat exchange means is configured to provide heat exchange between stream 38 flowing through one pass of the heat exchange means and the distillation vapor stream arising from rectifying section 118b inside processing assembly 118, so that stream 38 is cooled to substantial condensation while heating the distillation vapor stream.
• the resulting substantially condensed stream 38a at - 114 0 F [-81 °C] is then flash expanded through expansion valve 14 to slightly above the operating pressure (approximately 393 psia [2,710 kPa(a)]) of rectifying section 118b and absorbing section 118c inside processing assembly 118. During expansion a portion of the stream may be vaporized, resulting in cooling of the total stream, hi the process illustrated in FIG. 4, the expanded stream 38b leaving expansion valve 14 reaches a temperature of -138°F [-94 0 C] before it is directed into a heat and mass transfer means inside rectifying section 118b.
• the heat and mass transfer means is configured to provide heat exchange between the distillation vapor stream arising from absorbing section 118c flowing upward through one pass of the heat and mass transfer means and the expanded stream 38b flowing downward, so that the distillation vapor is cooled while heating the expanded stream. As the distillation vapor stream is cooled, a portion of it is condensed and falls downward while the remaining distillation vapor continues flowing upward through the heat and mass transfer means.
• the heat and mass transfer means provides continuous contact between the condensed liquid and the distillation vapor so that it also functions to provide mass transfer between the vapor and liquid phases, thereby providing rectification of the distillation vapor.
• the condensed liquid is collected from the bottom of the heat and mass transfer means and directed to absorbing section 118c.
• the flash expanded stream 38b is partially vaporized as it provides cooling and partial condensation of the distillation vapor stream, then exits the heat and mass transfer means in rectifying section 118b at -104 0 F [-75°C] and is separated into its respective vapor and liquid phases.
• the vapor phase combines with the vapor arising from absorbing section 118c to form the distillation vapor stream that enters the heat and mass transfer means in rectifying section 118b as previously described.
• the liquid phase is directed to the upper region of absorbing section 118c to join with the liquid condensed from the distillation vapor stream in rectifying section 118b.
• the remaining 72% of the vapor from separator section 118e enters a work expansion machine 15 in which mechanical energy is extracted from this portion of the high pressure feed.
• the machine 15 expands the vapor substantially isentropically to the operating pressure of absorbing section 118c, with the work expansion cooling the expanded stream 39a to a temperature of approximately -60 0 F [-51 0 C].
• the partially condensed expanded stream 39a is thereafter supplied as feed to the lower region of absorbing section 118c inside processing assembly 118 to be contacted by the liquids supplied to the upper region of absorbing section 118c.
• Absorbing section 118c and stripping section 118d each contain an absorbing means.
• Stripping section 118d also includes a heat and mass transfer means beneath its absorbing means which is configured to provide heat exchange between a heating medium flowing through one pass of the heat and mass transfer means and a distillation liquid stream flowing downward from the absorbing means, so that the distillation liquid stream is heated. As the distillation liquid stream is heated, a portion of it is vaporized to form stripping vapors that rise upward as the remaining liquid continues flowing downward through the heat and mass transfer means.
• the heat and mass transfer means provides continuous contact between the stripping vapors and the distillation liquid stream so that it also functions to provide mass transfer between the vapor and liquid phases, stripping the liquid product stream 46 of methane, C 2 components, and lighter components.
• the resulting liquid product (stream 46) exits the lower region of stripping section 118d and leaves processing assembly 118 at 221°F [105 0 C].
• FIG. 4 Stream Flow Summary - Lb. Moles/Hr [kg moles/Hr]
• FIG. 4 embodiment of the present invention provides the same advantages related to the compact arrangement of processing assembly 118 as the FIG. 3 embodiment.
• the FIG. 4 embodiment of the present invention replaces seven separate equipment items in the prior art (heat exchangers 10, 13, and 20, separator 12, reflux separator 21, reflux pump 22, and fractionation tower 18 in FIG. 2) with a single equipment item (processing assembly 118 in FIG. 4). This reduces the plot space requirements, eliminates the interconnecting piping, and eliminates the power consumed by the reflux pump, reducing the capital cost and operating cost of a process plant utilizing this embodiment of the present invention over that of the prior art, while also reducing the potential for atmospheric releases that can damage the environment.
• Some circumstances may favor supplying liquid stream 35 directly to stripping section 118d via stream 40 as shown in FIGS. 3 through 6.
• an appropriate expansion device such as expansion valve 17
• the resulting expanded liquid stream 40a is supplied as feed to stripping section 118d above the absorbing means, above the heat and mass transfer means, or to both such feed points (as shown by the dashed lines).
• Some circumstances may favor combining a portion of liquid stream 35 (stream 37) with the vapor in stream 36 to form combined stream 38 and routing the remaining portion of liquid stream 35 to stripping section 118d via streams 40/40a.
• Some circumstances may favor combining the expanded liquid stream 40a with expanded stream 39a and thereafter supplying the combined stream to the lower region of absorbing section 118c as a single feed.
• FIGS. 3 and 5 in lieu of the first portion (stream 36) of vapor stream 34 to form stream 38 flowing to the heat exchange means in the lower region of feed cooling section 118a.
• first portion (stream 36) of vapor stream 34 to form stream 38 flowing to the heat exchange means in the lower region of feed cooling section 118a.
• only the cooled first portion (stream 32a) is supplied to separator section 118e (FIG. 3) or separator 12 (FIG. 5), and all of the resulting vapor stream 34 is supplied to work expansion machine 15.
• separator 12 can be used to separate cooled feed stream 31a into vapor stream 34 and liquid stream 35.
• the cooled feed stream 31a entering separator section 118e in FIGS. 3 and 4 or separator 12 in FIGS. 5 and 6 may not contain any liquid (because it is above its dewpoint, or because it is above its cricondenbar).
• Feed gas conditions, plant size, available equipment, or other factors may indicate that elimination of work expansion machine 15, or replacement with an alternate expansion device (such as an expansion valve), is feasible.
• an alternate expansion device such as an expansion valve
• individual stream expansion is depicted in particular expansion devices, alternative expansion means may be employed where appropriate.
• conditions may warrant work expansion of the substantially condensed portion of the feed stream (stream 38a).
• the use of external refrigeration to supplement the cooling available to the inlet gas from the distillation vapor and liquid streams may be employed, particularly in the case of a rich inlet gas.
• a heat and mass transfer means may be included in separator section 118e (or a collecting means in such cases when the cooled feed stream 31a contains no liquid) as shown by the dashed lines in FIGS. 3 and 4, or a heat and mass transfer means may be included in separator 12 as shown by the dashed lines in FIGS. 5 and 6.
• This heat and mass transfer means may be comprised of a fin and tube type heat exchanger, a plate type heat exchanger, a brazed aluminum type heat exchanger, or other type of heat transfer device, including multi-pass and/or multi-service heat exchangers.
• the heat and mass transfer means is configured to provide heat exchange between a refrigerant stream (e.g., propane) flowing through one pass of the heat and mass transfer means and the vapor portion of stream 31a flowing upward, so that the refrigerant further cools the vapor and condenses additional liquid, which falls downward to become part of the liquid removed in stream 35.
• a refrigerant stream e.g., propane
• the heat and mass transfer means in stripping section 118d may include provisions for providing supplemental heating with heating medium as shown by the dashed lines in FIGS. 3 and 5.
• another heat and mass transfer means can be included in the lower region of stripping section 118d for providing supplemental heating, or stream 33 can be heated with heating medium before it is supplied to the heat and mass transfer means in stripping section 118d.
• the multi-pass and/or multi-service heat transfer device will include appropriate means for distributing, segregating, and collecting stream 32, stream 38, and the distillation vapor stream in order to accomplish the desired cooling and heating.
• the type of heat and mass transfer device selected for the heat and mass transfer means in rectifying section 118b may allow combining it with the heat exchange means in the lower region of feed cooling section 118a (and possibly with the heat exchange means in the upper region of feed cooling section 118a as well) in a single multi-pass and/or multi-service heat and mass transfer device.
• the multi-pass and/or multi-service heat and mass transfer device will include appropriate means for distributing, segregating, and collecting stream 38, stream 38b, and the distillation vapor stream (and optionally stream 32) in order to accomplish the desired cooling and heating.
• a less preferred option for the FIGS. 3 and 5 embodiments of the present invention is providing a separator vessel for cooled first portion 31a and a separator vessel for cooled second portion 32a, combining the vapor streams separated therein to form vapor stream 34, and combining the liquid streams separated therein to form liquid stream 35.
• Another less preferred option for the present invention is cooling stream 37 in a separate heat exchange means inside feed cooling section 118a (rather than combining stream 37 with stream 36 to form combined stream 38), expanding the cooled stream in a separate expansion device, and supplying the expanded stream either to the heat and mass transfer means in rectifying section 118b or to the upper region of absorbing section 118c.
• the relative amount of feed found in each branch of the split vapor feed will depend on several factors, including gas pressure, feed gas composition, the amount of heat which can economically be extracted from the feed, and the quantity of horsepower available. More feed above absorbing section 118c may increase recovery while decreasing power recovered from the expander and thereby increasing the recompression horsepower requirements. Increasing feed below absorbing section 118c reduces the horsepower consumption but may also reduce product recovery. [0072]
• the present invention provides improved recovery of C 2 components, C 3 components, and heavier hydrocarbon components or of C 3 components and heavier hydrocarbon components per amount of utility consumption required to operate the process. An improvement in utility consumption required for operating the process may appear in the form of reduced power requirements for compression or re-compression, reduced power requirements for external refrigeration, reduced energy requirements for supplemental heating, reduced energy requirements for tower reboiling, or a combination thereof.

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