WO2024197232A2 - Système et procédé pour améliorer la récupération de propane et le rejet d'éthane dans un système gsp/expanseur - Google Patents

Système et procédé pour améliorer la récupération de propane et le rejet d'éthane dans un système gsp/expanseur Download PDF

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Publication number
WO2024197232A2
WO2024197232A2 PCT/US2024/021085 US2024021085W WO2024197232A2 WO 2024197232 A2 WO2024197232 A2 WO 2024197232A2 US 2024021085 W US2024021085 W US 2024021085W WO 2024197232 A2 WO2024197232 A2 WO 2024197232A2
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stream
fractionation column
feed
column
condenser
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WO2024197232A3 (fr
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Rayburn C. Butts
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BCCK Holding Co
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BCCK Holding Co
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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
    • F25J3/0204—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
    • F25J3/0209—Natural gas or substitute natural gas
    • F25J3/0214—Liquefied 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
    • F25J3/0228—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
    • 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
    • F25J2200/74—Refluxing the column with at least a part of the partially condensed overhead 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
    • 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
    • F25J2210/62—Liquefied natural gas [LNG]; Natural gas liquids [NGL]; Liquefied petroleum gas [LPG]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/62—Ethane or ethylene
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/64—Propane or propylene
    • 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
    • F25J2270/02—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
    • F25J2270/12—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
    • F25J2280/00—Control of the process or apparatus
    • F25J2280/02—Control in general, load changes, different modes ("runs"), measurements
    • 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.

Definitions

  • This invention relates to a system and method for separation of natural gas liquid (NGL) components from natural gas streams processed through NGL extraction methods, such as a modified gas subcooled/expander process (GSP/expander process or simply GSP), in an ethane rejection mode with enhanced propane recovery.
  • NGL natural gas liquid
  • NGL extraction techniques including the GPS process
  • the economics associated with ethane in NGL product streams have varied over time and by geographic location.
  • Many facilities in operation today operate in ethane rejection mode (reducing the amount of ethane in the NGL product stream and increasing the amount of ethane in the residue gas stream) because an operator could lose up to $0.10 for each gallon of ethane in the NGL product stream. This adds up to significant revenue loss, making it desirable to improve upon rejection methods to reduce the amount of ethane in the NGL product stream and increase the amount of ethane in the residue stream.
  • propane is significantly more profitable in the NGL product stream than in the residue gas stream, so it is advantageous to increase propane recovery.
  • a prior art GSP process is disclosed in U.S. Patent No. 4,157,904.
  • a cooled feed stream is separated into a vapor stream and a liquid stream in a separator.
  • a lean feed stream comprising around 5.5% ethane in the example in the ‘904 patent
  • a first portion of the vapor stream is mixed with the entirety of the liquid stream and the mixed stream is subcooled through heat exchange with an overhead stream from a fractionation column (a demethanizer or deethanizer column) and then expanded.
  • the subcooled, expanded stream (or GSP stream) then feeds into an upper level of the GSP fractionation column as a reflux stream.
  • a second portion of the vapor stream is expanded through a turboexpander before feeding into a mid-level of the fractionation column.
  • the fractionation column separates these streams into the overhead stream (which becomes the residue gas stream) and a bottoms stream (which is the NGL stream).
  • the ‘904 patent discloses splitting the liquid stream as shown in FIG. 5 of the ‘904 patent.
  • a first portion of the liquid stream is combined with the first portion of the vapor stream prior to subcooling, with the combined stream being subcooled and expanded to form the GSP stream that feeds into an upper level of the fractionation column.
  • a second portion of the liquid stream is expanded and then feeds into a mid to lower level of the GSP fractionation column.
  • the feed stream in a GSP process is cooled prior to the feed stream entering the separator, typically through heat exchange with the fractionation column overhead stream and a side stream withdrawn from a lower level of the fractionation column.
  • Prior art GSP processes may be used in either an ethane recovery or ethane rejection mode; however, its fundamental thermodynamic limitations during ethane rejection cause it to lose significant volumes of valuable propane. When operated in full rejection mode, GSP processes can lose between 5% to 15% of the propane. It is most desirable to recover that propane in the NGL stream.
  • the GSP stream that feeds into an upper level of the fractionation column in prior art GSP systems typically comprises around 27% of the total ethane and around 33% of the total propane that feeds into fractionation column 17 from the primary fractionation column feeds in an ethane rejection mode for a lean feed stream comprising around 5% ethane.
  • FIG. 1 The GSP system shown in FIG. 1 has been modified from the original ‘904 patent to show modifications made by industry from the time of introduction of the technology.
  • the purpose of FIG. 1 is to provide a typical and modem GSP system where the new technology according to preferred embodiments of the invention is to be applied.
  • the prior art GSP system is modified by adding column (117), by combining all of the separator bottoms stream with a part of the separator overhead stream to form the sub-cooled, expanded GSP stream (36b) which is diverted to feed into column 117 (rather than fractionation column 17 as it would normally in operation of the prior art GSP system), and by not feeding a portion of the separator bottoms stream (38a) into a lower tray location of the fractionation column 17.
  • the overhead stream (39) from the fractionation column (17, operated as a deethanizer at a pressure of around 402 psi) is also fed into the add-on column (117) to allow for heat and mass transfer between streams (36b and 39) through direct contact in the add-on column (117).
  • the overhead stream (151 ) from the add-on column (17) is then processed as the fractionation column overhead stream would normally be processed in a GSP system to become the residue gas stream.
  • the bottoms stream (152) from the add-on column (17), which contains around 40-45% of the total propane the primary fractionation column feed streams (152a and 37a), is then fed into an upper level of the fractionation column (17) as the highest fractionation column feed stream.
  • the bottom stream from the fractionation column is the NGL product stream.
  • the addition of the add-on column results in ethane recovery in the NGL stream of around 0.92% and propane recovery of around 99.65% (around 3% higher than the prior art process of FIG. 2 in the ‘428 patent) for a lean feed stream comprising around 4% ethane.
  • the operating pressure of the fractionation column in this example was 402 psi and the residue gas compression requirement for this example is 5,565 HP.
  • the ‘118 patent also discloses more complex embodiments of the add-on column (117) compared to the column in the ‘428 patent.
  • the add-on column (as shown in FIG. 8 for example) has a heat exchange section, a heat and mass transfer section, and absorbing section, and a separation section all in a single piece of equipment.
  • the ‘118 patent does not involve heat and mass transfer of the sub-cooled, expanded GSP stream (36b) and fractionation column overhead stream (39) fed in the add-on column (117).
  • the sub-cooled, expanded GSP stream (36b) passes through a heat exchanger housed inside add-on column 117 to exchange heat with stream 151 a, which is either a portion of the overhead stream (153) from the add-on column (117, as in FIG. 7) or a portion of the overhead stream (39) from the fractionation column (17, as in FIG. 9).
  • Exiting stream 36c is combined with the bottoms stream (154) from the add-on column to form a feed stream (155) that feeds into a top of the fractionation column (17).
  • the overhead stream (39) from the fractionation column (17) feeds into the add-on column (117).
  • the overhead stream (153) from the add-on column (117), or a portion of that overhead stream, is processed as the fractionation column overhead stream would normally be processed in a GSP system to become the residue gas stream.
  • the subcooled GSP stream (36a) passes through a heat exchanger housed inside add-on column 117 to exchange heat with rising vapors inside add-on column 117, exiting as cooled and substantially condensed stream 151 a (as shown in FIG. 8).
  • Stream 115a is then expanded through expansion valve 23 to become stream 151 b (at a temperature of around -140 F), which feeds into add-on column 117 for heat and mass transfer with the fractionation column overhead stream (39).
  • Stream 151 b is similar to the sub-cooled, expanded stream 36b in a normal GSP operation except that it has undergone an additional heat exchange inside add-on column 117 prior to being expanded and it contains all of the separator (11) bottoms stream (33), rather than only a portion.
  • the bottoms stream (154) from the add-on column feeds into a top of the fractionation column (17), which is operated at a pressure of around 344 psia.
  • the overhead stream (39) from the fractionation column (17) feeds into the add-on column (117).
  • the overhead stream (153) from the add-on column (117) is processed as the fractionation column overhead stream would normally be processed in a GSP system to become the residue gas stream. According to the example of FIG.
  • the addition of the add-on column results in ethane recovery in the NGL stream of around 0.6% and propane recovery of around 99.91 % for a lean feed stream comprising around 8.5% ethane.
  • a rich feed stream generally contains more than 10% ethane and a corresponding increase in propane and heavier components.
  • the operating pressure of the fractionation column in this example was 344 psia and the residue gas compression requirement for this example is 11 ,656 HP.
  • the ‘428 and ‘118 patents can achieve very low ethane recoveries of ⁇ 1 % and high propane recoveries of 98.46-99.91 %. These results are around 5.5-10% more propane recovery than in the GSP systems. While the ‘428 and ‘118 patents can achieve high propane recovery in ethane rejection mode, the add-on columns in these patents are relatively expensive and complex pieces of equipment.
  • Systems and methods disclosed herein facilitate the economically efficient rejection of ethane in NGL product streams with enhanced propane recovery by modifying a prior art NGL extraction systems with an add-on system that acts as a reflux system for a fractionation column in the NGL extraction system and changes in certain process flows from the NGL extraction system to incorporate the add-on system.
  • Preferred embodiments of an add-on system may be integrated into an existing NGL extraction system or may be incorporated into a newly built NGL extraction system, as will be understood by those of ordinary skill in the art.
  • the add-on systems and methods are particularly useful with a GSP system and the parameters discussed herein are primarily directed to use with such a system; however, those of ordinary skill in the art will understand that the add-on system and method can also be used with other NGL extraction systems and methods.
  • References herein to the GSP system, fractionation column in the GSP system, specific streams in the GSP system, and the GSP stream (or similar wording) may be substituted with references to other NGL extraction systems, a fractionation column in such other NGL extraction systems, corresponding or similar specific streams in the NGL extraction systems, and a subcooled expanded stream that feeds into the fractionation column in such other NGL extraction systems as will be understood by those of ordinary skill in the art.
  • an add-on system comprises a heat exchanger and a condenser as separate pieces of equipment from each other and external to a fractionation column used in the GSP system.
  • At least a first portion of a separator overhead stream and a fractionation column overhead stream are preferably diverted from the GSP system to the add-on system to pass through the addon system heat exchanger.
  • the first portion of the separator overhead stream is warmed through heat exchange with the overhead stream from the fractionation column, which is cooled.
  • the warmed stream then feeds into the fractionation column, preferably at an upper level of the column below the top feed location.
  • the cooled stream then feeds into the add-on system condenser, where it is separated into a condenser overhead stream and a condenser bottoms stream.
  • the condenser overhead stream is then returned to the GSP system for heat exchange with other process streams (in the same manner as the fractionation column overhead stream would normally be processed in the GSP system) and for compression to become the residue gas stream.
  • the condenser bottoms stream is also returned to the GSP system to feed into the fractionation column as a top feed reflux stream.
  • the fractionation column bottoms stream is the NGL product stream.
  • the add-on system further comprises a first pump to pump the condenser bottoms stream to the top of the fractionation column.
  • the first portion of the separator overhead stream is a subcooled expanded GSP stream (or “GSP stream”).
  • GSP stream passes through a heat exchanger in the GSP system (for heat exchange with the add-on condenser overhead stream) and then an expansion valve in the GSP system prior to passing through the add-on heat exchanger.
  • an add-on system comprises a heat exchanger, a condenser, and a reflux column. Most preferably, each of these are separate pieces of equipment from each other and external to the fractionation column used in the GSP system. At least a first portion of a separator overhead stream and a fractionation column overhead stream are preferably diverted from the GSP system to the add-on system. The first portion of the separator overhead stream passes through the add-on system heat exchanger, where it is warmed through heat exchange with an overhead stream from the reflux column, which is cooled. The warmed stream then feeds into the fractionation column, preferably at an upper level of the column.
  • the cooled stream then feeds into the add-on system condenser, where it is separated into a condenser overhead stream and a condenser bottoms stream.
  • the condenser overhead stream is then returned to the GSP system for heat exchange with other process streams (in the same manner as the fractionation column overhead stream would normally be processed in the GSP system) and compression to become the residue gas stream.
  • the condenser bottoms stream feeds into a top level of the reflux column and the fractionation column overhead stream feeds into a bottom level of the reflux column.
  • the fractionation column bottoms stream is the NGL product stream.
  • the add-on system further comprises a first pump to pump the condenser bottoms stream to the top of the reflux column and a second pump to pump the reflux column bottoms stream to the top of the fractionation column.
  • the reflux column comprises 0 to 5 theoretical stages.
  • a first portion of a separator bottoms stream in the GSP system is not mixed with the first portion of the separator overhead stream prior to heat exchange in the GSP system or prior to feeding into the fractionation column.
  • the first portion of the bottoms stream and first portion of the overhead stream both pass through a heat exchanger in the GSP system as separate streams for heat exchange with the add-on condenser overhead stream to cool the separator streams.
  • the cooled first portion of the bottoms stream then feeds into a top level of the fractionation column.
  • an add-on system also further comprises an expansion valve for expanding the cooled first portion of the bottoms stream prior to feeding into the fractionation column.
  • a second portion of the separator overhead stream is expanded in a turboexpander prior to feeding into the fractionation column, preferably at an upper-mid level of the column.
  • the turbo-expanded stream feeds into the fractionation column at the same level as the warmed first portion of the separator overhead stream returning from the add-on system.
  • a second portion of the separator bottoms stream is expanded through a valve before feeding into the fractionation column, preferably at a mid to upper-mid level of the column lower than the turboexpanded second portion of the separator overhead stream and lower than the warmed first portion of the separator overhead stream.
  • the add-on systems further comprise various components necessary to connect the equipment in the add-on systems to components of a typical GSP system to allow for flow of process streams between the two systems.
  • the first portion of the separator overhead stream (or the subcooled expanded GSP stream) does not feed into the reflux column.
  • the first portion of the separator overhead stream (or the subcooled expanded GSP stream) only enters an add-on system for indirect heat exchange with either the fractionation column overhead stream or the reflux column overhead stream and there is no mass transfer between the first portion of the separator overhead stream and any other process streams in the add-on system or GSP system prior to that stream feeding into the fractionation column.
  • the first portion of the separator overhead stream (or the subcooled expanded GSP stream) only undergoes mass transfer inside the fractionation column.
  • Add-on systems and methods according to preferred embodiments operated in ethane rejection mode have the advantage of limiting the total amount of propane (in MMSCFD or Ibmol/hr) that feeds into a top or an upper level of the GSP fractionation column.
  • the amount of propane feeding into a top level of fractionation column 17 is preferably around 1 -20% of the amount of propane in the feed stream, more preferably around 2-10%, and most preferably around 3-6%. This is an improvement over prior art systems that feed around 30% or more of the propane from the feed stream into a top or upper level of the GSP fractionation column.
  • Add-on systems and methods according to preferred embodiments operated in ethane rejection mode also have the advantage of increasing the percentage of total ethane and propane in the primary fractionation column feed streams that feed into the top/upper level of the GSP fractionation column.
  • the amount of propane feeding into a top level of fractionation column 17 is preferably around 3-7% of total amount of propane in the primary fractionation column feed streams and the amount of ethane feeding into a top level of fractionation column 17 is preferably around 25-35% of total amount of ethane in the primary fractionation column feed streams.
  • Add-on systems and methods according to preferred embodiments operated in an ethane rejection mode are capable of minimizing the amount of ethane in the NGL product stream, with ethane recoveries of around 8% or less, more preferably 6% or less, while increasing propane recoveries to at least 97%, more preferably at least 98%, and most preferably at least 99% of the propane from the feed stream. Even lower ethane recoveries of around 1 to 2% are achievable with add-on systems and methods according to preferred embodiments, while still achieving a propane recovery of 95% or more.
  • Add-on systems and methods according to preferred embodiments operated in an ethane rejection mode are also capable of reducing power requirements compared to a typical GSP system operated without an add-on system.
  • the primary power use for the base GSP system (such as in FIG. 1 ) is in the amount of recompression required to compress the residue gas stream up the desired pressure level to be injected into a gas pipeline.
  • the use of the add-on system reduces the amount of vapor, by nature of the recovered propane and so the amount of compression HP is reduced accordingly.
  • the propane is reliquefied in the add-on system condenser or reflux column and fed back into the upper section of the tower (preferably at tray or stage 1 , which is the same feed location as the liquid streams from the GSP section separator that is upstream of the fractionation column) as the reflux stream.
  • heavier components C3+
  • C3+ lighter components
  • That leaner overhead stream serves as a feed stream to the add-on system condenser or reflux column, resulting in the reflux stream that gets recycled back to feed the top of the fractionation column.
  • the add-on system provides a more efficient separation of ethane and propane components, allowing for more propane to exit the fractionation column as liquid and hence, increasing the overall propane recovery.
  • FIG. 1 is a process flow diagram illustrating principal processing stages of a GSP system without an add-on system according to an embodiment of the invention
  • FIG. 2 is a process flow diagram illustrating principal processing stages of a preferred embodiment of an add-on system and method according to the invention incorporated into the embodiment of a GSP system of FIG. 1 ;
  • FIG. 3 is a process flow diagram illustrating principal processing stages of another preferred embodiment of an add-on system and method according to the invention incorporated into the embodiment of a GSP system of FIG. 1 .
  • GSP system 110 is similar to FIG. 5 of the ‘904 patent except for differences in feed stream cooling upstream of the separator and that the first portion of the liquid bottoms stream from the separator is not combined with the first portion of the overhead vapor stream; rather, those streams separately pass through the subcooler heat exchanger 12.
  • the separate cooled streams also separately pass through expansion valves 21 , 25 prior to feeding into the fractionation column 17.
  • the feed stream 31 is preferably split into a first portion 31 a and a second portion 31 b for different heat exchange treatment prior to being separated in separator 11 .
  • Stream 31 a passes through heat exchanger 13, where it is cooled through heat exchange with an overhead stream 39a from a fractionation column 17, exiting as stream 31 d.
  • Stream 31b passes through heat exchanger 22T, which is a tube side of a shell and tube type heat exchanger disposed internally to fractionation column 17 in a mid-lower section of the column, with the column 17 acting as the shell side of the heat exchanger (although 22T is shown in FIG. 1 as external to column 17).
  • stream 31 b is cooled through heat exchange with cold fluid internal to the fractionation column 17. This aids in cooling this portion of the feed stream and in adding heat to a lower section of column 17.
  • Stream 31 b exits heat exchanger 22T as stream 31 c.
  • a side stream may be withdrawn from fractionation column 17 to pass through a heat exchanger comprising 22T and a shell side that is external to column 17, with the side stream returning to column 17 after exchanging heat with stream 31 b.
  • Streams 31 c and 31 d are preferably mixed in mixer 24 to form stream 31 e, which is then further cooled in heat exchanger 26T through heat exchange with an external refrigerant, preferably propane, exiting as stream 31f.
  • Stream 31f is then separated in separator 11 into overhead stream 32 and bottoms stream 38.
  • Splitters 46 and 19 split those streams into streams 36 and 37 and streams 38a and 38c, respectively.
  • separator overhead stream 32 is split into a first portion stream 36 and a second portion stream 37, with at least 60% of the flow from stream 32 being sent to stream 37, more preferably at least 65% of the flow from stream 32 being sent to stream 37.
  • bottoms stream 38 is preferably split into a first portion stream 38c and a second portion stream 38a, with at least 95% of the flow from stream 38 being sent to stream 38a, more preferably at least 98% of the flow from stream 38 being sent to stream 38a.
  • the first portion 38c of bottoms stream 38 is diverted to pass through heat exchanger or subcooler 12, along with the first portion of the separator overhead stream 36. These streams are cooled, exiting as streams 38d and 36a, respectively.
  • An overhead stream 39 from fractionation column 17 also passes through heat exchanger 12, exiting as stream 39a, which then passes through heat exchanger 10.
  • the first portion of the separator overhead stream and first portion of the separator bottoms streams would be mixed together prior to passing through the subcooler, with the combined subcooled stream then being expanded in a single expansion valve before feeding into an upper level of fractionation column 17.
  • they are preferably kept separate, both streams 38c and 36 passing separately through subcooler 12.
  • Stream 38d is expanded in expansion valve 25 before feeding into a top level of fractionation column 17 as stream 38e.
  • Stream 38e in system 110 feeds into a top level or stage of fractionation column 17 and is the only stream feeding into the column at that location.
  • Stream 36a is expanded in valve 21 before feeding into an upper level of fractionation column 17 as stream 36b.
  • Stream 36b in system 110 feeds in lower than stream 38e, at around stage or tray 5 as shown in FIG. 1 (although this location may be varied as will be understood by those of ordinary skill in the art).
  • a second portion 37 of overhead stream 32 is expanded through a turboexpander 14 with expanded stream 37a feeding into a mid-upper level of the GSP fractionation column 17, at around stage or tray 7 (although this location may be varied as will be understood by those of ordinary skill in the art).
  • Stream 37a in system 110 feeds fractionation column 17 at a location lower than stream 36b.
  • a second portion 38a of bottoms stream 38 is expanded in valve 16 with exiting expanded stream 38b feeding into a mid-level or slightly higher stage or tray of GSP fractionation column 17, such as around stage or tray 10 as shown in FIG. 1 (although this location may be varied as will be understood by those of ordinary skill in the art).
  • Stream 38b in system 110 feeds fractionation column 17 at a location lower than stream 37a.
  • Streams 38e, 36b, 37a, and 38b are the primary feed streams into fractionation column 17 in system 110.
  • Vapor stream 41 from reboiler 18 also feeds into column 17 as a returning stream but is not considered a primary feed stream.
  • the GSP stream 36b in system 110 typically comprises substantially more of the total amount of ethane and propane that feed into fractionation column 17 from primary fractionation column feed streams as compared to the top feed stream 38e, but the majority of the ethane and propane that are in the primary fractionation column feed streams are contained in streams 37a and 38b that feed lower than the GSP stream but still in the upper half of the fractionation column 17 in system 110.
  • GSP fractionation column 17 separates streams 38e, 36b, 37a, and 38a (and returning reboiler stream 41 ) into an overhead stream 39 and a bottoms stream 42 (NGL product stream).
  • Overhead stream 39 is warmed in subcooler 12, with stream 39a then being further warmed in heat exchanger 13.
  • Stream 39b is then compressed in compressor 15 to become stream 39c, which is further cooled in another heat exchanger (preferably an air cooler) 74 to form the residue gas stream 39d.
  • Stream 39d may be further compressed to meet pipeline specifications.
  • GSP system 110 may have an additional or different separator and additional heat exchange components as will be understood by those of ordinary skill in the art.
  • Fractionation column 17 in GSP system 110 does not have a condenser, but does have a reboiler 18 to provide an ascending vapor stream 41 , with GSP stream 36a and stream 38e providing reflux.
  • a GSP system 110 operated in ethane rejection mode will result in a propane recovery in the NGL stream of less than 92% and an ethane recovery of less than 6%.
  • System 120 for use with a GSP system, such as system 110, is shown.
  • the primary components of system 120 are shown in the dashed line box and may be added onto any existing GSP system (such as 110) with a few modifications to the process flows for the existing GSP system or included as part of a newly built GSP system to operate the GSP system in an ethane rejection with enhanced propane recovery mode.
  • System 120 preferably comprises an expansion valve 125, heat exchanger 130, a condenser 155, and a pump 199.
  • System 120 also preferably comprises a reboiler 18 for fractionation column 17 and mixers, valves, piping, and other connectors as further described and needed to connect system 120 to GSP system 110.
  • Heat exchanger 130 is preferably a shell and tube type heat exchanger, but other types of heat exchangers such as a plate-fin heat exchanger may also be used. Heat exchanger 130 is preferably external to fractionation column Condenser 155 is preferably external to fractionation column.
  • system 120 involves a few modifications to the stream flows in the typical GSP system 110.
  • the GSP stream 36b is diverted to system 120.
  • stream 36b would normally feed into an upper level of GSP fractionation column 17 as a reflux stream, but is instead diverted to pass through heat exchanger 130.
  • Stream 36b passes through heat exchanger 130, exiting as warmed stream 36c.
  • Stream 36c feeds into an upper level of fractionation column 17.
  • stream 36c will feed into column 17 at the same stage or tray location as stream 36b would normally feed into column 17 in GSP system 110 (such as around stage or tray 5).
  • fractionation column overhead stream 39 is also diverted to system 120.
  • overhead stream 39 would normally pass through the GSP subcooler 12 and then be further processed as the residue gas stream in GSP system 110, but is instead diverted to pass through heat exchanger 130.
  • overhead stream 39 is cooled in heat exchanger 130 through heat exchange with stream 36b, exiting as stream 39a.
  • Stream 39a feeds into condenser 155, where it is separated into a condenser overhead stream 152 and a condenser bottoms stream 154.
  • Overhead stream 152 is then returned to GSP system 110 and processed as fractionation column overhead stream 39 would normally be processed in GSP system 110 (such as shown in FIG. 1 ).
  • Overhead stream 152 passes through GSP subcooler 12, exiting as stream 152a.
  • Stream 152a then passes through heat exchanger 13, exiting as stream 152b.
  • Stream 152b is then compressed in compressor 15 (preferably part of a turboexpander unit combining expander 14 and compressor 15) to form stream 152c, cooled in cooler 74 to form stream 152d, which is the residue gas stream.
  • Stream 152d may be further compressed as needed to meet pipeline specifications.
  • turboexpanded stream 37a (a second portion of separator 11 overhead stream 32) preferably feeds into fractionation column 17 at a location slightly higher than it would in system 110.
  • the turboexpanded stream 37a feeds below the feed location of subcooled expanded GSP stream 36b.
  • stream 37a preferably feeds higher in the fractionation column, most preferably at the same stage as stream 36c.
  • fractionation column 17 utilizes condenser 155 to provide an additional reflux stream 154a.
  • the primary fractionation column feed streams with use of system 120 comprise streams 38e, 154a, 36c, 37a, and 38b.
  • Vapor stream 41 from reboiler 18 also feeds into column 17 as a returning stream but is not considered a primary fractionation column feed stream.
  • Streams 38e and 154a preferably feed into a top level of fractionation column 17. . Most preferably, this is around stage or tray 1 as shown in FIG. 2 (although this location may be varied as will be understood by those of ordinary skill in the art).
  • Streams 38e and 154a preferably feed into fractionation column 17 at the same stage or tray level.
  • Streams 37a and 36c preferably feed into an upper level of fractionation column 17, but lower than the feed location of streams 38e and/or 154a. Most preferably, this is around stage or tray 5 as shown in FIG. 2 (although this location may be varied as will be understood by those of ordinary skill in the art).
  • Streams 37a and 36c preferably feed into fractionation column 17 at the same stage or tray level.
  • Stream 38b preferably feeds into fractionation column 17 at a mid-level or slightly higher stage or tray, but lower than the feed level of streams 37a and/or 36c. Most preferably, this is around stage or tray 10 as shown in FIG. 2 (although this location may be varied as will be understood by those of ordinary skill in the art).
  • a GSP system with system 120 operated in ethane rejection mode will result in a propane recovery in the NGL stream of at least 97%, more preferably between 99-99%, and an ethane recovery of less than 6%. This is substantially more propane recovery and around the same ethane recovery compared to system 110 operated without system 120.
  • FIG. 3 another preferred embodiment for an add-on system 220 for use with a GSP system, such as system 110, is shown.
  • the primary components of system 120 are shown in the dashed line box and may be added onto any existing GSP system (such as 110) with a few modifications to the process flows for the existing GSP system or included as part of a newly built GSP system to operate the GSP system in an ethane rejection mode with enhanced propane recovery mode.
  • System 220 is similar to system 120 with the addition of a couple of pieces of equipment and some process flow changes.
  • System 220 preferably comprises a reflux column 250 and a second pump 258.
  • Reflux column 250 is preferably a distillation column that comprises 2 to 5 theoretical stages.
  • GSP stream 36b from separator 11 is diverted to system 220 to pass through heat exchanger 130 but is warmed through heat exchange with an overhead stream 251 from reflux column 250. Warmed stream 36c then feeds into an upper level of fractionation column 17, preferably around stage or tray 5 and preferably at the same location as stream 37a. Cooled overhead stream 251a exits heat exchanger 130 to feed into condenser 155. Condenser overhead stream 152 returns to GSP system 110 to be processed into the residue gas stream, like in system 120.
  • overhead stream 39 from fraction column 17 is also diverted to system 220, but feeds into a bottom level of reflux column 250 as an ascending vapor stream in system 220.
  • Condenser bottoms stream 154 is pumped in pump 199, with stream 154a feeding into a top of column 250 as a reflux stream.
  • Column 250 separates streams 39 and 154a into overhead stream 251 and bottoms stream 256.
  • Bottoms stream 256 is then pumped in pump 258, with stream 256a feeding into a top of fractionation column 17, preferably in the same location as previously described for stream 154a in system 120.
  • fractionation column 17 utilizes reflux column 250 to provide an additional reflux stream 256a.
  • the primary fractionation column feed streams with use of system 220 comprise streams 38e, 256a, 36c, 37a, and 38b.
  • Vapor stream 41 from reboiler 18 also feeds into column 17 as a returning stream but is not considered a primary fractionation column feed stream.
  • Streams 38e and 256a preferably feed into a top level of fractionation column 17. Most preferably, this is around stage or tray 1 as shown in FIG. 3 (although this location may be varied as will be understood by those of ordinary skill in the art).
  • Streams 38e and 256a preferably feed into fractionation column 17 at the same stage or tray level.
  • Streams 37a and 36c preferably feed into an upper level of fractionation column 17, but lower than the feed location of streams 38e and/or 256a. Most preferably, this is around stage or tray 5 as shown in FIG. 3 (although this location may be varied as will be understood by those of ordinary skill in the art).
  • Streams 37a and 36c preferably feed into fractionation column 17 at the same stage or tray level.
  • Stream 38b preferably feeds into fractionation column 17 at a mid-level or slightly higher stage or tray, but lower than the feed level of streams 37a and/or 36c. Most preferably, this is around stage or tray 10 as shown in FIG. 3 (although this location may be varied as will be understood by those of ordinary skill in the art).
  • a GSP system with system 220 operated in ethane rejection mode will result in a propane recovery in the NGL stream of at least 98%, more preferably at least 99%, and an ethane recovery of less than 6%.
  • This is substantially more propane recovery and around the same ethane recovery compared to system 110 operated without system 220 and is an improvement of at least around 0.5% propane recovery compared to system 120.
  • Preferred parameters for the various streams in a GSP system 110 (without systems 120 or 220), with add-on system 120, or with add-system 220 with add-on system 220 operated in ethane rejection mode in various examples based on a computer simulation are shown in the table below.
  • the flow rates, temperatures and pressures of various flow streams referred to in connection with the discussion of systems 110 (as shown in FIG. 1 , for example), 110 with add-on system 120 (as shown in FIG. 2, for example), or 110 with add-on system 220 (as shown in FIG. 3, for example) and their methods according to preferred embodiments of the invention are for a feed stream 31 having the parameters indicated below when operated in ethane rejection mode.
  • feed stream 31 and remixed feed stream 31f are identical in each of the systems 110, 120, and 220.
  • stream number e.g., 31 and 31 f
  • the streams will be identified by a stream number followed by a dash and the system number (for example, stream 31 d-110 refers to stream 31 d in system 110, as shown in FIG. 1 for example; 31 d-120 refers to stream 31 d in system 120, as shown in FIG. 2 for example).
  • Stream 36c is only in systems 120 and 220, but the composition of stream 36c is the same in both systems 120 and 220. There is no stream 36c in system 110.
  • Stream 36c is only in systems 120 and 220, but the composition of stream 36c is the same in both systems 120 and 220. There is no stream 36c in system 110.
  • Stream 37a in system 110 preferably feeds into fractionation column 17 at a lower stage or tray location than GSP stream 36b; however, with use of systems 120 or 220, stream 37a preferably feeds into column 17 at the same location or level as stream 36c, which is higher than 37a would normally feed into column 17 in system 110.
  • System 120 and 220 achieve these results by altering the feeds into the fractionation column 17 in several key ways: (1 ) stream 36c in systems 120 and 220 feeds into column 17 at a temperature range of -70 to -90 °F, more preferably -75 to -85 °F, which is significantly warmer than stream 36b feeds into column 17 at a temperature range of - 130 to -140 °F; (2) less than 10% and more preferably less than 5% of the total methane in the primary column feed streams is fed into the top stage/tray location in systems 120 and 220, which is significantly less than the 45%-55% in system 110; and (3) the percentage of the total amount of ethane and total amount of propane in in the primary column feed streams that feeds into the top stage/tray location in systems 120 and 220 is significantly higher than in system 110.
  • reflux stream 154a in system 120 and reflux stream 256a in system 220 aids in increasing the amounts of these components fed higher in the column as compared to system 110 without an add-on system.
  • systems 120 and 220 preferably around 25-35%, more preferably around 27- 30%, of the total ethane in the primary fractionation column feed streams feeds into the top of the column, whereas less than 1 % feeds into the top of the column in system 110.
  • systems 120 and 220 preferably around 2-7%, more preferably around 3-6%, of the total propane in the primary fractionation column feed streams feeds into the top of the column, whereas less than 1 % feeds into the top of the column in system 110.
  • systems 120 or 220 aids in increasing the amounts of both ethane and propane fed into a top level of fractionation column 17, allowing more propane to be recovered than when GSP system 110 is operated without add-on systems 120 or 220 without significant change in the ethane recovery.
  • stream 152a in Example 4 feeds the fractionation column at the highest level of all fractionation column feed streams and contains 112 Ibmol/hr propane, based on a feed stream (stream 31 ) flow rate of 13,726 Ibmol/hr containing 1.7% propane (and 3.98% ethane).
  • Stream 152a feeds into an upper level of fractionation column 17 in the ‘428 patent, which appears to be below the top level (around tray 5), but the specific level for the example is not stated.
  • the total amount of propane fed into the top level of fractionation column 17 in system 120 is 39.45 Ibmol/hr and in system 220 is 59.59 Ibmol/hr, both based on an example having a feed stream (stream 31 ) flow rate of 24,155.6 Ibmol/hr containing 4.34% propane (and 16.9% ethane).
  • This is both a higher feed flow rate and higher percentages of propane and ethane compared to the ‘428 patent, but the resulting amount of propane in Ibmol/hr feeding into the top of column 17 is substantially reduced by around 45-65%. This data is shown in Table 10 below.
  • the amount of propane (in MMSCFD or Ibmol/hr) feeding into a top level of fractionation column 17 is preferably around 1-20% of amount of propane in the feed stream, more preferably around 2-10%, and most preferably around 3-6%, when the feed stream is a rich stream comprising at least 10% ethane and 5% propane. For leaner feeds, these amounts will be further reduced.
  • a preferred method for processing a feed stream in an ethane rejection mode in a GSP system (preferably system 110) modified with add-on components, preferably an add-on system 120 comprises the following steps: (1 ) separating the feed stream in a separator into a separator overhead stream and a separator bottoms stream; (2) splitting the separator overhead stream into a first portion and a second portion; (3) splitting the separator bottoms stream into a first portion and a second portion; (4) separating a plurality of fractionation column feed streams into a fractionation column overhead stream and a fractionation column bottoms stream in a fractionation column; (5) separating the fractionation overhead stream into a condenser overhead stream and a condenser bottoms stream in a condenser; (6) cooling at least a first part of the feed stream in a first heat exchanger through heat exchange with the condenser overhead stream prior to feeding the first part of the feed stream into the separator; (7) cooling a first part
  • the fractionation column feed streams preferably comprises the primary fractionation column feed streams and stream recycled from a reboiler.
  • the primary fractionation column feed streams preferably comprise: (a) the condenser bottoms stream; (b) the first part of the separator bottoms stream after expansion in step 10; (c) the first part of the separator overhead stream after the heat exchange in step 9; (d) the second part of the separator overhead stream after expansion in step 11 ; and (e) the second part of the separator bottoms stream after expansion in step 12.
  • Primary fractionation column feed streams (a) and (b) preferably feed into a top level of the fractionation column; streams (c) and (d) preferably feed into an upper level of the fractionation column, but preferably lower than the top feed level, and stream (e) to a mid-to-upper level of the fractionation column.
  • the stream that feeds into the condenser in step 9 is the fractionation column overhead stream.
  • the fractionation column bottoms stream is the NGL stream and the condenser overhead stream is the residue gas stream.
  • Another preferred method for processing a feed stream in an ethane rejection mode in a GSP system (preferably system 110) modified with add-on components, preferably an add-on system 220 according to a preferred embodiment of the invention, comprises the following steps: steps 1 -12 above with the following modification to step 5: (5-i) separating the fractionation column overhead stream and a condenser bottoms stream into a reflux column overhead stream and a reflux column bottoms stream in a reflux column and (5-ii) separating the reflux column overhead stream into a condenser overhead stream and a condenser bottoms stream in a condenser.
  • the primary fractionation column feed streams preferably comprise: (a) the reflux column bottoms stream; (b) the first part of the separator bottoms stream after expansion in step 10; (c) the first part of the separator overhead stream after the heat exchange in step 9; (d) the second part of the separator overhead stream after expansion in step 11 ; and (e) the second part of the separator bottoms stream after expansion in step 12.
  • Fractionation column feed streams (a) and (b) preferably feed into a top level of the fractionation column; streams (c) and (d) preferably feed into an upper level of the fractionation column, but preferably lower than the top feed level, and stream (e) to a mid-to-upper level of the fractionation column.
  • the stream that feeds into the condenser in step 9 is the reflux column overhead stream.
  • the fractionation column bottoms stream is the NGL stream and the condenser overhead stream is the residue gas stream.
  • the method also preferably comprises the following steps: (13) splitting the feed stream into the first part and a second part; (14) cooling the second part of the feed stream through heat exchange with streams preferably internal to a lower portion of the fractionation column (although a withdrawn stream external to the fractionation column may also be used); (15) mixing the first part and the second part of the feed stream after heat exchange in steps 6 and 14; (16) cooling the mixed feed stream from step 15 in a feed stream heat exchanger with external refrigeration and prior to feeding the cooled, mixed stream into the separator for separation in step 1 ; (17) compressing the condenser overhead stream after heat exchange in step 6; and (18) further cooling the condenser overhead stream after compression in step 17, preferably with an air cooler.
  • the condenser overhead stream may be further processed, including additional compression, as needed to meet pipeline or end use specifications.
  • the source of feed gas stream 31 is not critical to the systems and methods of the invention; however, natural gas drilling and processing sites with flow rates of 20 to 300 MMSCFD and containing up to 25% ethane and 15% propane are particularly suitable. Where present, it is generally preferable for purposes of the present invention to remove as much of the water vapor, carbon dioxide, and other contaminants from feed stream 31 prior to processing with systems GSP system 110 and add-on system 120 or 220Methods for removing water vapor, carbon dioxide, and other contaminants are generally known to those of ordinary skill in the art and are not described herein. This type of pretreatment would normally be done with any of these GSP systems even without using an add-on system and is not a special requirement of using add-on system 120 or 220.
  • Embodiment 1 A propane recovery system for increasing propane recovery in an NGL stream produced from a feed stream comprising methane, ethane, and propane in a GSP system operated in an ethane rejection mode, the GSP system comprising (1 ) a separator to separate the feed stream into a separator overhead stream and a separator bottoms stream and (2) a fractionation column to separate a plurality of fractionation column feed streams into a fractionation column overhead stream and a fractionation column bottoms stream, the plurality of fractionation column feed streams comprising (a) a first stream comprising a subcooled expanded first part of the separator overhead stream, (b) a second stream comprising a subcooled expanded first part of the separator bottoms stream, (c) a third stream comprising an expanded second part of the separator overhead stream, and (d) a fourth stream comprising an expanded second part of the separator bottoms stream; the propane recovery system comprising: a first heat exchanger to warm the first stream through heat exchange with a first set of streams
  • Embodiment 2 The propane recovery system of embodiment 1 wherein the first set of streams comprises the fractionation column overhead stream and wherein the condenser feed stream comprises the fractionation column overhead stream after passing through the first heat exchanger.
  • Embodiment 3 The propane recovery system of embodiment 1 wherein the first set of streams consists of the fractionation column overhead stream and wherein the condenser feed stream consists of the fractionation column overhead stream after passing through the first heat exchanger.
  • Embodiment 4 The propane recovery system of any one of embodiments 1 -3 wherein the feed stream comprises 10% or more ethane.
  • Embodiment 5 The propane recovery system of any one of embodiments 1 -4 wherein the plurality of fractionation column feed streams further comprises the condenser bottoms stream, which feeds into a top level of the fractionation column.
  • Embodiment 6 The propane recovery system of any one of embodiments 1 -5 further comprising a reflux column for separating the fractionation column overhead stream and the condenser bottoms stream into a reflux column overhead stream and a reflux column bottoms stream, wherein the reflux column has 0 to 5 theoretical stages.
  • Embodiment 7 The propane recovery system of embodiment 6 wherein the first set of streams comprises the reflux column overhead stream and wherein the condenser feed stream comprises the reflux column overhead stream after passing through the first heat exchanger.
  • Embodiment 8 The propane recovery system of embodiment 6 wherein the first set of streams consists of the reflux column overhead stream and wherein the condenser feed stream consists of the reflux column overhead stream after passing through the first heat exchanger.
  • Embodiment 9 The propane recovery system of any one of embodiments 1 -8 wherein the feed stream comprises 10% or more ethane.
  • Embodiment 10 The propane recovery system of any one of embodiments 6-9 wherein the plurality of fractionation column feed streams further comprises the reflux column bottoms stream, which feeds into a top level of the fractionation column.
  • Embodiment 11 A method for increasing propane recovery in an NGL stream produced from a feed stream comprising methane, ethane, and propane in a GSP system operated in an ethane rejection mode, the method comprising: (1 ) separating the feed stream in a separator into a separator overhead stream and a separator bottoms stream; (2) splitting the separator overhead stream into a first portion and a second portion; (3) splitting the separator bottoms stream into a first portion and a second portion;
  • Embodiment 12 The method for increasing propane recovery of embodiment 11 wherein the first set of streams in step 9 comprises the fractionation column overhead stream and wherein the condenser feed stream comprises the fractionation column overhead stream after heat exchange in step 9.
  • Embodiment 13 The method of increasing propane recovery of any one of embodiments 11 -12 wherein the first set of streams in step 9 consists of the fractionation column overhead stream and wherein the condenser feed stream consists of the fractionation column overhead stream after heat exchange in step 9.
  • Embodiment 14 The method of increasing propane recovery of any one of embodiments 11 -13 wherein the feed stream comprises 10% or more ethane.
  • Embodiment 15 The method of increasing propane recovery of any one of embodiments 11-14 wherein the plurality of fractionation column feed streams further comprises the condenser bottoms stream.
  • Embodiment 16 The method of increasing propane recovery of any one of embodiments 11 -15 further comprising: (13) separating the fractionation column overhead stream and the condenser bottoms stream into a reflux column overhead stream and a reflux column bottoms stream in a reflux column, wherein the reflux column has 0 to 5 theoretical stages.
  • Embodiment 17 The method of increasing propane recovery of embodiment 16 wherein the first set of streams in step 9 comprises the reflux column overhead stream and wherein the condenser feed stream comprises the reflux column overhead stream after heat exchange in step 9.
  • Embodiment 18 The method of increasing propane recovery of embodiment 16 wherein the first set of streams in step 9 consists of the reflux column overhead stream and wherein the condenser feed stream consists of the reflux column overhead stream after heat exchange in step 9.
  • Embodiment 19 The method of increasing propane recovery of any one of embodiments 11 -18 wherein the feed stream comprises 10% or more ethane.
  • Embodiment 20 The method of increasing propane recovery of any one of embodiments 16-19 wherein the plurality of fractionation column feed streams further comprises the reflux column bottoms stream. [0089] Embodiment 20. The method of increasing propane recovery of any one of embodiments 11 -20 using the propane recover system of any one of embodiments 1 - 10.
  • ethane rejection mode refers to processing a natural gas stream operated in a specific method to decrease the amount of ethane recovered from the feed stream in the NGL product stream, while still maximizing the amount of propane and heavier hydrocarbons in the NGL product stream.
  • the systems and methods according to preferred embodiments of the invention are configured to recover less than 10%, preferably less than 8%, and most preferably less than 6% of the ethane from the feed stream in the NGL product stream, while preferably still recovering 96% or more, preferably 98% or more, and most preferably 99% or more of the propane from the feed stream in the NGL product stream.
  • Heat exchangers as described herein and shown in the figures are preferably a single heat exchanger in which all streams shown in the figures simultaneously pass through so that certain stream(s) are cooled and other stream(s) are warmed through heat exchange between the passing streams. Most preferably, only the streams shown on the figures pass through any particular heat exchanger and no other streams undergo heat exchange with that set of streams in any particular heat exchanger. Although other heat exchange configurations and multiple heat exchangers may be used to achieve the heat exchange described herein, most preferably the heat exchange is specifically limited as shown in the figures, with the heat exchange shown being the only heat exchange between given streams prior to or after various processing equipment.
  • streams 36, 38c, and 152 are preferably the only streams that pass through heat exchanger 12 and all of these streams preferably pass simultaneously through a single heat exchanger 12; with stream 38e not undergoing any other heat exchange with other process streams or external refrigeration or heat sources between separator 11 and fractionation column 17; with stream 36 not undergoing any other heat exchange with other process streams or external refrigeration or heat sources between separator 11 and heat exchanger 130; and with stream 152 not undergoing any other heat exchange with other process streams or external refrigeration or heat sources between condenser 155 and heat exchanger 13. Any change in temperature of a stream while flowing through piping from one piece of equipment to another piece of equipment as a result of a differential between the temperature of the stream and the ambient air temperature surrounding the piping, without more, is not considered heat exchange for purposes of the invention.
  • All numerical values indicated as a percentage being “at least” X means the range of X% to 100% and value indicates as percentage being “less than” X means the range of 0% to X%. All numerical values herein indicated as a range (including as “at least” or “less than”) include each individual value or ratio within those ranges and any and all subset combinations within ranges, including subsets that overlap from one preferred range to a more preferred range. Any operating parameter, step, process flow, or equipment indicated as preferred or preferable herein may be used alone or in any combination with other preferred/preferable features.

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Abstract

L'invention concerne un système et un procédé pour améliorer la récupération de propane dans un système GSP fonctionnant selon un mode de rejet d'éthane à l'aide d'un système complémentaire comprenant un échangeur de chaleur et un condenseur et éventuellement une colonne de reflux comportant 0 à 5 étages théoriques. Un flux de tête provenant d'une colonne de fractionnement de GSP et un flux de GSP expansé sous-refroidi sont déviés du traitement GSP typique pour être traités dans le système complémentaire afin de fournir un flux de reflux supplémentaire qui augmente la quantité d'éthane et de propane alimentant un niveau supérieur de la colonne de fractionnement de GSP. Dans le mode de rejet d'éthane, le système complémentaire conduit à un flux de produit GNL comprenant de préférence moins de 6 % de l'éthane et au moins 97 % du propane provenant du flux d'alimentation de GSP.
PCT/US2024/021085 2023-03-22 2024-03-22 Système et procédé pour améliorer la récupération de propane et le rejet d'éthane dans un système gsp/expanseur Ceased WO2024197232A2 (fr)

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US18/124,795 US20240318910A1 (en) 2023-03-22 2023-03-22 System and method for improving propane recovery and ethane rejection in a gsp/ expander system
US18/124,795 2023-03-22

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