GB2415201A - Enhanced LPG Recovery Process - Google Patents
Enhanced LPG Recovery Process Download PDFInfo
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- GB2415201A GB2415201A GB0411808A GB0411808A GB2415201A GB 2415201 A GB2415201 A GB 2415201A GB 0411808 A GB0411808 A GB 0411808A GB 0411808 A GB0411808 A GB 0411808A GB 2415201 A GB2415201 A GB 2415201A
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- Prior art keywords
- stream
- separator
- deethaniser
- liquid
- column
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
- F25J3/0242—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
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- 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
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
- C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
- C10L3/10—Working-up natural gas or synthetic natural gas
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
- C10L3/12—Liquefied petroleum gas
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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
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
- F25J3/0233—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
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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
- F25J2200/00—Processes or apparatus using separation by rectification
- F25J2200/04—Processes or apparatus using separation by rectification in a dual pressure main column system
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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
- 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
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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
- 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
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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
- F25J2205/00—Processes or apparatus using other separation and/or other processing means
- F25J2205/02—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J2205/00—Processes or apparatus using other separation and/or other processing means
- F25J2205/02—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum
- F25J2205/04—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum in the feed line, i.e. upstream of the fractionation step
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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
- F25J2235/00—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams
- F25J2235/60—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams the fluid being (a mixture of) hydrocarbons
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Separation By Low-Temperature Treatments (AREA)
Abstract
A process for the recovery of propane and heavier hydrocarbons from a feed stream of raw natural gas, which comprises providing <SL> <LI>(A) a separator operating to produce a gas stream rich in methane and a liquid stream; <LI>(B) a liquid petroleum gas recovery column operating at a temperature lower than the temperature of separator(A) and at a pressure lower than the pressure of separator(A) to produce a gas stream rich in methane and a liquid stream; and <LI>(C) a deethaniser column operating at a pressure lower than the pressure of the liquid petroleum gas recovery column(B) to produce a gas stream rich in ethane and a liquid stream rich in propane and heavier hydrocarbons; and carrying out the following steps: <SL> <LI>(i) supplying a feed stream of cooled liquid petroleum gas to separator(A); <LI>(ii) passing at least part of the liquid stream from separator(A) to the deethaniser column(C); <LI>(iii) passing at least part of the gas stream from separator(A) to the liquid petroleum gas recovery column(B); <LI>(iv) passing at least part of the liquid stream from the liquid petroleum gas recovery column(B) to the deethaniser column(C); <LI>(v) passing at least part of the partially condensed gas stream from the deethaniser column(C) to the liquid petroleum gas recovery column(B); <LI>(vi) discharging or collecting the exit gas stream(s) from the process; and <LI>(vii) collecting the liquids stream from the deethaniser column(C). </SL> </SL>
Description
241 520 1 Enhanced LPG Recovery Process The present invention relates to
an enhanced LPG recovery process.
LPG plants operate to separate the feed into its various constituents. Ideally, the vapours leaving the plant will contain almost all of the methane and ethane found in the feed, while the higher (C3+) hydrocarbons will be removed separately as a liquid stream. A conventional LPG plant may for example be configured as follows. Feed gas comprising a mix of hydrocarbons is cooled, then sent to a first stage separator which operates at relatively high temperature and pressure. Gases from this separator are expanded to an LPG recovery column, while liquids from this separator are sent, after cooling in a heat exchanger, to act as a reflux in the LPG recovery column. Gases from the LPG recovery column are either discharged or collected, while liquids are sent, after warming in a heat exchanger, to a deethaniser column.
Liquids, consisting primarily of propane and heavier hydrocarbons (C3+), are collected from the deethaniser.
It is, however, a disadvantage of this conventional method of operation that a certain proportion of the C3+ hydrocarbons, primarily propane, is inevitably lost to the discharge gas streams which comprise primarily methane and/or ethane.
US 4,507,133 discloses an improved process for the separation and recovery of propane and heavier hydrocarbon components.
In this process, a feedstream is cooled and separated into a first vapour fraction and a first liquid fraction, and the first liquid fraction is distilled in a deethanizer. The process comprises expanding and transferring said first vapour fraction to the lower portion of a direct heat exchanger, cooling said second vapour fraction to form a substantially liquefied stream, transferring at least a portion of said liquefied stream to the upper portion of said direct heat exchanger whereby said liquefied stream contacts said first vapour fraction to form a third vapour fraction and a third liquid fraction, returning said third liquid fraction to said deethanizer, and removing said third vapour fraction from said direct heat exchanger. In all embodiments of the process of US 4,507,133, the first liquid fraction and the third liquid fraction are passed to the deethanizer by pumping.
We have now found a new and simplified process which is capable of a very high level of recovery of C3+ hydrocarbons from an LPG feed stream.
Accordingly, the present invention provides a process for the recovery of propane and heavier hydrocarbons from a feed stream of raw natural gas, which comprises providing (A) a separator operating to produce a gas stream rich in methane and a liquid stream) (B) a liquid petroleum gas recovery column operating at a temperature lower than the temperature of separator(A) and at a pressure lower than the pressure of separator(A) to produce a gas stream rich in methane and a liquid stream; and (C) a deethaniser column operating at a pressure lower than the pressure of the liquid petroleum gas recovery column(B) to produce a gas stream rich in ethane and a liquid stream rich in propane and heavier hydrocarbons; and carrying out the following steps: (i) supplying a feed stream of cooled raw natural gas to separator(A); (ii) passing at least part of the liquid stream from separator(A) to the deethaniser column(C); (iii) passing at least part of the gas stream from separator(A) to the liquid petroleum gas recovery column(B)) (iv) passing at least part of the liquid stream from the liquid petroleum gas recovery column(B) to the deethaniser column(C); (v) passing at least part of the partially condensed gas stream from the deethaniser column(C) to the liquid petroleum gas recovery column(B)) (vi) discharging or collecting the exit gas stream(s) from the process) and (vii) collecting the liquids stream from the deethaniser column(C).
It is a key advantage of the process of the invention that, by ensuring that within the process system comprising units (A), (B) and (C), the pressure is progressively reduced from one unit to the next, the liquid streams are able to flow without pumping) i.e., steps (ii) and (iv) are carried out without pumping.
Separator(A) provides a first cut separation of the feed stream into a gas stream rich in methane and ethane and a liquid stream rich in C3+ hydrocarbons. This separator is operated under conditions which optimise this separation, typically at a temperature in the range of from -30 F to -5 F, preferably from -20 F to -15 F, and preferably at a pressure of from 900 to 1300 psig.
Preferably the liquid stream from separator(A) is passed directly to the deethaniser(C) via a heat exchanger, without passage via any other separator.
The LPG recovery column(B) provides a second and cleaner cut into a gas stream rich in methane and a liquid stream rich in C2+ hydrocarbons. The LPG recovery column(B) is operated at a temperature lower than that of separator column(A), and under conditions which optimise the required separation, preferably at a temperature in the range of from -125 F to -90 F, preferably from -115 F to -100 F. This low temperature may be achieved by expanding the gas stream from separator(A) through an expander. The pressure of the LPG column(B) must be lower than the pressure of separator(A).
Typically, the pressure in the LPG recovery column(B) is in the range of from 250 to 350 psig, preferably from 275 to 325 psig. Preferably, the pressure differential between separator(A) and LPG recovery column (B) is at least 600 psi.
The deethaniser column(C) is constructed and operated under conditions which optimise separation of the input into the deethaniser into a liquid stream comprising mainly C3+ hydrocarbons and a gas stream comprising mainly C1 and C2 hydrocarbons and other light gases such as nitrogen and carbon dioxide. These conditions also need to be compatible with those of separator(A) to ensure that no pumping of the liquid stream from the separator is required, and with those of the LPG recovery column(B) to ensure that no pumping of the liquid stream from the LPG recovery column is required.
Typical conditions are a temperature in the range of from -70 F to -40 F at the top tray and +100 F to +150 F at the bottom, preferably -55 F to -45 F at the top and +115 F to +125 F at the bottom, and a pressure in the range of from 160psig to 230psig, preferably 190 psig to 210psig.
Preferably the pressure differential between separator(A) and the deethaniser(C) is at least 700psig, preferably at least 850psig, while the pressure differential between the LPG recovery column(B) and the deethaniser(C) is at least 50psig, preferably at least lOOpsig.
The optimal process conditions will naturally depend upon many factors; for example, ambient temperature at the location of the plant together with the exact nature and composition of the feed stream available may have a significant effect on local operating conditions.
The feed stream into separator(A) is a stream of raw natural gas, which may have undergone certain pre-treatments. It is typically a stream rich in hydrocarbons, including C3+ hydrocarbons, which should be sweet (negligible hydrogen sulphide) and dry (negligible water vapour). Hydrogen sulphide and water may be removed in a series of pre- treatment steps, for example by treatment over molecular sieves. The feed may also contain other components, for example carbon dioxide and nitrogen.
The deethaniser(C) requires the introduction of a liquid reflux stream at the top and a vapour input stream at the bottom in order to maximise efficiency. In a preferred embodiment of the process of the invention, the liquid reflux stream is provided by an additional separator(D) which is located at the gas exit of the deethaniser(C), and at least part of the gas stream exiting the deethaniser is passed, after cooling in a heat exchanger, to this additional separator(D). At least part of the liquid stream from the additional separator(D) is recycled back to the deethaniser.
This liquid stream provides the reflux for the deethaniser.
A vapour feed to the bottom of the deethaniser(C) is preferably provided by a reboiler at the base of the deethaniser.
Similarly, the LPG recovery column(B) requires the introduction of a liquid reflux stream at the top. In a further preferred embodiment of the process of the invention, at least part of the gas stream from the deethaniser(C) is cooled in a heat exchanger before being passed to an additional separator(E). The gas stream from the additional separator(E) is discharged or collected, and at least part of the liquid stream is passed to the LPG recovery column (B) to act as liquid reflux, if necessary after pumping to raise its pressure.
In an especially preferred embodiment of the process according to the invention, both the additional separators (D) and (E) mentioned above are present in the system, with the gaseous stream from additional separator(D) providing the feed to the additional separator(E). In this preferred embodiment, two heat exchangers are required as well as two additional separators, and preferably the cooling stream for a first heat exchanger associated with additional separator(D) is provided by the liquid stream from the LPG recovery column(B) prior to this stream being passed to the deethaniser(C); and the cooling stream for a second heat exchanger associated with additional separator(E) may be provided by the gas stream from the LPG recovery column(B) prior to this stream being discharged or collected.
Thus, an especially preferred embodiment of the process of the invention also includes: (D) providing a first additional separator; (E) providing a second additional separator; and carrying out the following steps: (viii) passing at least part of the gas stream exiting the deethaniser(C), to a first heat exchanger and subsequently to the additional separator(D) ; (ix) recycling at least part of the liquid stream from the additional separator(D) back to the top of the deethaniser(C)i (x) passing at least part of the gaseous stream from the additional separator(D) to a second heat exchanger and subsequently to the additional separator(E); (xi) passing the liquid stream from the additional separator(E) to the top of the liquid petroleum gas recovery column(B); and optionally (xii) using at least part of the liquid stream from the liquid petroleum gas recovery column(B) as the cooling stream for said first heat exchanger; and optionally (xiii) using at least part of the gas stream from the liquid petroleum gas recovery column(B) as the cooling stream for said second heat exchanger.
In a further preferred embodiment of the process of the invention, the energy requirements of the system can be optimised by efficient use of input and exit streams. Thus, one or more of the gas exit streams from the LEG recovery column(B) or the deethaniser(C), and/or the additional separators(D) and/or (E) if present, may be recycled for use as cooling streams for the hydrocarbon input stream to the process. Thus, a particularly preferred embodiment of the process of the invention includes all of steps (i) to (xi) above, optionally one or both of steps (xii) and (xiii), and also one or both of the following steps: (xiv) passing at least part of the gas stream from the liquid petroleum gas recovery column(B) to a heat exchanger to act as coolant for the feed stream of raw natural gas to the process; (xv) passing at least part of the gas stream from the additional separator(E) to a heat exchanger to act as coolant for the feed stream of raw natural gas to the process.
The use of such a system obviates the need for the expensive provision of an external cooling system which is required, for example, in heat exchangers (22) and (50) of US 4,507,133.
The process according to the present invention allows a very high level of C3+ recovery from the feed. In addition, compared with certain known systems, the load on the deethaniser is reduced. The system is significantly simplified over that described in US 4,507,133, with a requirement for fewer pumping operations and also fewer heat exchange operations, with a corresponding increase in efficiency and decrease in cost. Loss levels of C3+ hydrocarbons are significantly reduced over those reported in US 4,507,133: it is believed that the high recovery levels reported in US 4,507,133 would only be achievable using the more complex flow schemes as shown in either Fig. 2 or Fig. 3 of that document, which utilise an additional separator (100) and pump (32).
The invention will now be further illustrated by reference to the accompanying drawings, in which Figures 1 and 2 illustrate flow schemes representing preferred processes according to the invention.
In Figure 1, a feedstream 1 is passed via a heat exchanger 20, which reduces the temperature from around ambient temperature to a suitable operating temperature, to a separator 21 operating at a temperature in the range of from -30 F to -5 F and a pressure in the range of from 900 to 1300 psig. The liquid stream 2 from separator 21 is passed to the upper half of deethaniser 22 operating at a temperature in the range of from -70 F to - 40 F at the top tray and +100 F to +150 F at the bottom, and a pressure in the range of from 160 to 230psig. The gas stream 3 from separator 21 is passed via an expander 30 to an LPG recovery column 23 operating at a temperature in the range of from -125 F to -90 F and a pressure in the range of from 250 to 350psig. The liquid stream 4 from the LPG recovery column 23 is passed via a heat exchanger 24 to a higher part of deethaniser 22.
The gas stream 5 from the deethaniser 22 is passed via heat exchanger 24 to a first additional separator 25. The liquid stream 6 from the first additional separator 25 is passed via a pump 26 to the top of deethaniser 22 to provide the liquid reflux stream. A vapour feed to the bottom of the deethaniser is provided by a reboiler unit at the bottom of the deethaniser (not shown).
The gas stream 7 from the first additional separator 25 is passed via a heat exchanger 27 to a second additional separator 28. The liquid stream 8 from the second additional separator 28 is passed via a pump 29 to the LPG recovery column 23.
The gas stream 9 from the LPG recovery column 23 is passed to heat exchanger 27, from whence exit stream 10 is discharged or collected.
The gas stream 11 from the second additional separator 28 is discharged or collected.
The liquid stream 12 from the deethaniser 22 comprises C3+ hydrocarbons and is collected.
In Figure 2, the scheme of Figure 1 is optimised to make more efficient use of the various liquid and gas streams.
Feedstream 1 is passed to separator column 21 via a heat exchanger system 20 comprising heat exchangers in parallel.
The liquid stream 2 from separator 21 is passed to the upper half of deethaniser 22 via the heat exchanger system 20.
The gas stream 9 from the LEG recovery column 23 is passed to heat exchanger 27, from whence exit stream 10 is passed to act as coolant for heat exchanger system 20, prior to being discharged or collected in exit stream 12, via compressor 31 associated with expander 30.
The gas stream 11 from the second additional separator 28 is passed to act as coolant for heat exchanger system 20 prior to being discharged or collected via compressor 32 and exit stream 12.
Other units and steps are as described in Figure 1.
In the operation of a process using a flow scheme as described in Figure 2 above, loss levels of propane of less than 1% and as low as 0.2%, have been recorded.
Claims (12)
11 Case 10093 ( 1) Claims 1. A process for the recovery of propane and
heavier hydrocarbons from a feed stream of raw natural gas, which comprises providing (A) a separator operating to produce a gas stream rich in methane and a liquid stream; (B) a liquid petroleum gas recovery column operating at a temperature lower than the temperature of separator(A) and at a pressure lower than the pressure of separator(A) to produce a gas stream rich in methane and a liquid stream; and (C) a deethaniser column operating at a pressure lower than the pressure of the liquid petroleum gas recovery column(B) to produce a gas stream rich in ethane and a liquid stream rich in propane and heavier hydrocarbons; and carrying out the following steps: (i) supplying a feed stream of cooled liquid petroleum gas to separator(A) ; (ii) passing at least part of the liquid stream from separator(A) to the deethaniser column(C); (iii) passing at least part of the gas stream from separator(A) to the liquid petroleum gas recovery column(B); (iv) passing at least part of the liquid stream from the liquid petroleum gas recovery column(B) to the deethaniser column(C); (v) passing at least part of the partially condensed gas stream from the deethaniser column(C) to the liquid petroleum gas recovery column(B); (vi) discharging or collecting the exit gas stream(s) from the process; and (vii) collecting the liquids stream from the deethaniser column(C).
2. A process according to claim 1, in which separator(A) is operated at a temperature in the range of from -30 F to -5 F, preferably from -20 F to 15 F, and a pressure of from 900 to 1300 psig.
3. A process according to either claim 1 or claim 2, in which the liquid stream from separator(A) is passed directly to the deethaniser(C) via a heat exchanger, without passage via any other separator.
4. A process according to any one of claims 1 to 3, in which the LPG recovery column(B) is operated at a temperature in the range of from 125 F to -90 F, preferably from -115 F to -100 F, and a pressure in the range of from 250 to 350 psig, preferably from 275 to 325 psig.
5. A process according to any one of claims 1 to 4, in which the pressure differential between separator(A) and LPG recovery column(B) is at least 600psi.
6. A process according to any one of claims 1 to 5, in which the deethaniser column(C) is operated at a temperature in the range of from 70 F to -40 F at the top tray and +100 F to +150 F at the bottom, preferably -55 F to -45 F at the top and +115 F to + 125 F at the bottom, and a pressure in the range of from 160psig to 230psig, preferably 190 psig to 210psig.
7. A process according to any one of claims 1 to 6, in which the pressure differential between separator(A) and the deethaniser(C) is at least 700psig, preferably at least 850psig, and the pressure differential between the LPG recovery column(B) and the deethaniser(C) is at least 50psig, preferably at least lOOpsig.
8. A process according to any one of claims 1 to 7, in which a vapour feed to the bottom of the deethaniser(C) is provided by a reboiler at the base of the deethaniser(C).
9. A process according to any one of claims 1 to 8, in which at least part of the gas stream exiting the deethaniser is passed, after cooling in a heat exchanger, to an additional separator(D), and at least part of the liquid stream from the additional separator(D) is recycled back to the deethaniser(C).
10. A process according to any one of claims 1 to 9, in which at least part of the gas stream from the deethaniser(C) is cooled in a heat exchanger and subsequently passed to an additional separator(E); the gas stream from the additional separator(E) is discharged or collected) and at least part of the liquid stream from the additional separator(E) is passed to the LPG recovery column(B) to act as liquid reflux.
11. A process as claimed in any one of claims 1 to 8, which also includes: (D) providing a first additional separator; (E) providing a second additional separator) and carrying out the following steps: (viii) passing at least part of the gas stream exiting the deethaniser(C), to a first heat exchanger and subsequently to the additional separator(D) ; (ix) recycling at least part of the liquid stream from the additional separator(D) back to the top of the deethaniser(C); (x) passing at least part of the gaseous stream from the additional separator(D) to a second heat exchanger and subsequently to the additional separator(E); (xi) passing the liquid stream from the additional separator(E) to the top of the liquid petroleum gas recovery column (B); and optionally (xii) using at least part of the liquid stream from the liquid petroleum gas recovery column(B) as the cooling stream for said first heat exchanger; and optionally (xiii) using at least part of the gas stream from the liquid petroleum gas recovery column(B) as the cooling stream for said second heat exchanger.
12. A process as claimed in claim 11, which also includes one or both of the following steps: (xiv) passing at least part of the gas stream from the liquid petroleum gas recovery column(B) to a heat exchanger to act as coolant for the feed stream of raw natural gas to the process) (xv) passing at least part of the gas stream from the additional separator(E) to a heat exchanger to act as coolant for the feed stream of raw natural gas to the process.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0411808A GB2415201A (en) | 2004-05-26 | 2004-05-26 | Enhanced LPG Recovery Process |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0411808A GB2415201A (en) | 2004-05-26 | 2004-05-26 | Enhanced LPG Recovery Process |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB0411808D0 GB0411808D0 (en) | 2004-06-30 |
| GB2415201A true GB2415201A (en) | 2005-12-21 |
Family
ID=32671130
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0411808A Withdrawn GB2415201A (en) | 2004-05-26 | 2004-05-26 | Enhanced LPG Recovery Process |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2415201A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007110331A1 (en) * | 2006-03-24 | 2007-10-04 | Shell Internationale Research Maatschappij B.V. | Method and apparatus for liquefying a hydrocarbon stream |
| US10852060B2 (en) | 2011-04-08 | 2020-12-01 | Pilot Energy Solutions, Llc | Single-unit gas separation process having expanded, post-separation vent stream |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110823749B (en) * | 2019-11-26 | 2022-07-05 | 陕西延长石油（集团）有限责任公司 | Multifunctional high-pressure reaction evaluation device and method |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4507133A (en) * | 1983-09-29 | 1985-03-26 | Exxon Production Research Co. | Process for LPG recovery |
| EP0272391A2 (en) * | 1986-12-19 | 1988-06-29 | The M. W. Kellogg Company | Process for separation of hydrocarbon gases |
-
2004
- 2004-05-26 GB GB0411808A patent/GB2415201A/en not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4507133A (en) * | 1983-09-29 | 1985-03-26 | Exxon Production Research Co. | Process for LPG recovery |
| EP0272391A2 (en) * | 1986-12-19 | 1988-06-29 | The M. W. Kellogg Company | Process for separation of hydrocarbon gases |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2007110331A1 (en) * | 2006-03-24 | 2007-10-04 | Shell Internationale Research Maatschappij B.V. | Method and apparatus for liquefying a hydrocarbon stream |
| AU2007229546B2 (en) * | 2006-03-24 | 2010-04-29 | Shell Internationale Research Maatschappij B.V. | Method and apparatus for liquefying a hydrocarbon stream |
| US8434326B2 (en) | 2006-03-24 | 2013-05-07 | Shell Oil Company | Method and apparatus for liquefying a hydrocarbon stream |
| US10852060B2 (en) | 2011-04-08 | 2020-12-01 | Pilot Energy Solutions, Llc | Single-unit gas separation process having expanded, post-separation vent stream |
Also Published As
| Publication number | Publication date |
|---|---|
| GB0411808D0 (en) | 2004-06-30 |
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| Date | Code | Title | Description |
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| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |