EP4244557B1 - Method for extracting ethane from an initial natural gas stream and corresponding plant - Google Patents

Method for extracting ethane from an initial natural gas stream and corresponding plant Download PDF

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Publication number
EP4244557B1
EP4244557B1 EP21810002.2A EP21810002A EP4244557B1 EP 4244557 B1 EP4244557 B1 EP 4244557B1 EP 21810002 A EP21810002 A EP 21810002A EP 4244557 B1 EP4244557 B1 EP 4244557B1
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Prior art keywords
stream
natural gas
flow
gas
separation column
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EP21810002.2A
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German (de)
French (fr)
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EP4244557A1 (en
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Sylvain Vovard
Benoit LAFLOTTE
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Technip Energies France SAS
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Technip Energies France SAS
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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    • 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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    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/0002—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the fluid to be liquefied
    • F25J1/0022—Hydrocarbons, e.g. natural gas
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    • F25J1/003—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
    • F25J1/0032—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using the feed stream itself or separated fractions from it, i.e. "internal refrigeration"
    • F25J1/004—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using the feed stream itself or separated fractions from it, i.e. "internal refrigeration" by flash gas recovery
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    • F25J1/0032—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using the feed stream itself or separated fractions from it, i.e. "internal refrigeration"
    • F25J1/0042—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using the feed stream itself or separated fractions from it, i.e. "internal refrigeration" by liquid expansion with extraction of work
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    • F25J1/0229—Integration with a unit for using hydrocarbons, e.g. consuming hydrocarbons as feed stock
    • F25J1/0231—Integration with a unit for using hydrocarbons, e.g. consuming hydrocarbons as feed stock for the working-up of the hydrocarbon feed, e.g. reinjection of heavier hydrocarbons into the liquefied gas
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    • 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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    • F25J2215/62—Ethane or ethylene
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    • F25J2260/20—Integration in an installation for liquefying or solidifying a fluid stream

Definitions

  • Such a process is intended in particular to extract ethane and C3+ hydrocarbons from a starting natural gas, while producing a natural gas treated under pressure, which is then liquefied before being expanded for storage.
  • Ethylene, ethane, propylene, propane and heavier hydrocarbons can be extracted from gases such as natural gas, refinery gas and synthetic gases obtained from other hydrocarbon sources such as coal, crude oil, naphtha.
  • Natural gas typically contains a majority of methane and ethane (e.g., methane and ethane constitute at least 50 mol% of the gas). Natural gas may also contain in lesser amounts heavier hydrocarbons such as propane, butanes, pentanes, and also hydrogen, nitrogen, and carbon dioxide.
  • the invention described herein relates more particularly to the recovery of ethane, propane and heavier hydrocarbons from natural gas.
  • natural gas such as ethane, propane and butane
  • the heavy hydrocarbons present in natural gas can be highly valorized by marketing them separately with high purity, they risk condensing during transport or freezing in the liquefaction exchangers (for the heaviest of them).
  • WO 96/14547 A1 describes a method according to the preamble of claim 1 and an apparatus according to the preamble of claim 15.
  • US 6,578,379 describes a highly efficient process for recovering ethane and propane from a natural gas stream. Such a process generally operates very efficiently, particularly to achieve very high extraction (e.g. greater than 99 mol%) of the ethane contained in the feed natural gas, while minimizing energy consumption.
  • a recirculation stream is taken from the recompressed gas from the top of the methane and ethane separation column.
  • the recirculation stream is cooled countercurrent to the gas from the top of the column and is then expanded to form the main reflux introduced at the top of the column.
  • the quality of the main reflux is likely to deteriorate in temperature and/or composition.
  • An aim of the invention is to provide a flexible and highly efficient process for extracting ethane and C3+ hydrocarbons from a starting natural gas stream, in which the ethane extraction rate is not or only slightly affected when fluctuations in the quality of the separation column head occur.
  • a first ethane extraction installation 10 according to the invention is shown in the figure 1 .
  • This installation 10 is intended for the simultaneous production, from a starting natural gas stream 12, of an ethane-rich stream 14, of a bottom stream 16 rich in C3+ hydrocarbons, of a relaxed liquefied natural gas 18, and of a fuel stream 20, advantageously intended to be reused in the installation 10.
  • installation 10 comprises an ethane extraction unit 22, a liquefaction unit 24, and a liquefied natural gas flash and storage unit 26.
  • the extraction unit 22 comprises first and second upstream heat exchangers 28, 30, a separator tank 32, and a column 34 for separating methane and C2+ hydrocarbons.
  • the column 34 is here equipped with a bottom reboiler 35.
  • the unit 22 further comprises a dynamic expansion turbine 36 coupled to a first compressor 38, a second compressor 40, each compressor 38, 40 being provided downstream with a cooler 42, 44.
  • the unit 22 further comprises a bottom pump 46, a fractionation column 48, provided with a bottom reboiler 50 and a reflux system 52, the reflux system 52 comprising a cooler 54, a reflux drum 56, and a reflux pump 58.
  • the natural gas liquefaction unit 24 is a known unit, notably of the C3MR or DMR type.
  • the flash and storage unit 26 comprises an expansion member 60, here a dynamic expansion turbine, a flash tank 62, and a pump 64 for conveying liquefied natural gas to a storage 66.
  • the expansion member 60 is a static expansion valve.
  • Storage 66 is for example a thermally insulated storage tank.
  • the flash and storage unit 26 further comprises in this example a downstream heat exchanger 68, possibly a suction tank 70, and a compression device 72 comprising a plurality of compressors 74 mounted in series, separated from each other by coolers 76.
  • the starting natural gas forming stream 12 is advantageously a desulfurized, dry and at least partially decarbonated natural gas.
  • At least partially decarbonated means that the carbon dioxide content in the starting natural gas stream 13 is advantageously less than or equal to 50 ppmv.
  • the water content is less than 1 ppmv, preferably less than 0.1 ppmv.
  • the content of sulfur elements, including hydrogen sulfide, is less than 10 ppmv and advantageously less than or equal to 4 ppmv.
  • the molar fraction of methane in the starting natural gas stream 12 is between 75 mol% and 95 mol%
  • the molar fraction of C2 hydrocarbons is between 3 mol% and 12 mol%
  • the molar fraction of C3+ hydrocarbons is between 1 mol% and 8 mol%.
  • the flow rate of the starting natural gas stream 12 is for example greater than 2000 kmol/h and is for example between 2000 kmol/h and 70000 kmol/h, in particular equal to 55,000 kmol/h.
  • the starting natural gas stream 12 has a temperature close to ambient temperature, in particular between 0° and 40°C, here equal to 21.5°C and a pressure advantageously greater than 35 bars, in particular greater than 70 bars, in this example equal to 81 bars.
  • the starting natural gas 12 is introduced into the first heat exchanger 28 to be cooled there. It forms a stream 80 of cooled natural gas.
  • the starting natural gas 12 is here supercritical, it is therefore simply cooled. In a variant, it is not supercritical and it is at least partially condensed in the first heat exchanger 28.
  • It has a temperature below -20°C, and in particular between -25°C and -45°C, in particular equal to -37°C.
  • the stream 80 is then introduced into the separator tank 32, to be separated there into a liquid stream 82, recovered at the foot of the separator tank 32, and a gas stream 84 recovered at the top of the separator tank 32.
  • the flow rate of the liquid stream 82 may be zero, in particular when the cooled natural gas stream 80 is supercritical.
  • the liquid flow 82 passes through a static expansion valve 86, to form a relaxed mixed phase 88.
  • the pressure of the relaxed mixed phase 88 is less than 50 bars, in particular less than 30 bars, and is for example equal to 28.7 bars.
  • the relaxed mixed phase 88 is introduced at a bottom level N1 of the separation column 34.
  • the gas flow 84 is divided into a main turbine feed stream 90 and a secondary reflux stream 92.
  • the molar flow rate of the turbine feed stream 90 is greater than the molar flow rate of the reflux stream 92, and in particular between 5% and 25% of the molar flow rate of the reflux stream 92.
  • the turbine feed stream 90 is introduced into the dynamic expansion turbine 36 to be expanded there to a pressure less than 50 bars, in particular less than 30 bars, for example equal to 28.7 bars.
  • the dynamic expansion of the 90 current allows the recovery of more than 10,000 kW of energy, for example 10,865 kW of energy.
  • the temperature of the cooled and expanded stream 94 coming from the dynamic expansion turbine 36 is for example less than -70°C, in particular less than -80°C, for example equal to -80.8°C.
  • the cooled and expanded stream 94 is then introduced into the separation column 34 at a level N2 located above the level N1.
  • the reflux stream 92 is introduced into a static expansion valve 96 to be expanded there to a pressure lower than 50 bars, in particular lower than 30 bars, in particular equal to 28.7 bars. It is cooled in the second upstream heat exchanger 30 to a temperature lower than -80°C, in particular lower than -90°C, in particular equal to -95.8°C.
  • the expanded and cooled reflux stream is introduced into separation column 34 at a level N3 located above level N2 at the head of column 34.
  • the pressure of the separation column 34 is preferably between 10 bars and 40 bars, in particular between 20 bars and 40 bars, for example substantially equal to 28.5 bars.
  • the separation column 34 produces a head stream 98.
  • the head stream 98 is reheated in the second upstream heat exchanger 30, then in the first upstream heat exchanger 28 in counter-current with the starting natural gas 12 to form a reheated head stream 100.
  • the temperature of the heated head stream 100 is greater than 0°C, in particular greater than 15°C, and is for example equal to 17.6°C.
  • the heated head stream 100 is then compressed in the compressor 38 coupled to the turbine 36, then is cooled in the cooler 42, to obtain a stream at a pressure greater than 30 bars, in particular equal to 34.6 bars.
  • the compressed purified natural gas stream 102 has a pressure greater than 60 bars, in particular greater than 80 bars, for example equal to 91 bars. It has a temperature greater than 0°C, in particular greater than 10°C, in particular equal to 21.5°C.
  • the coolers 42, 44 are here supplied by a cooling flow with a temperature lower than 10°C, in particular equal to 7°C.
  • This cooling flow may in particular be air or water.
  • the compressed purified natural gas stream 102 is rich in methane. It has a methane content greater than 99.0 mol%, in particular equal to 99.1 mol%. It has a low nitrogen content, in particular less than 1.0 mol%, and a low C2+ hydrocarbon content, in particular a content of less than 0.5 mol% in ethane, substantially equal to 0.2 mol% in ethane.
  • the separation column 34 produces at the bottom a bottom stream 106 rich in C2+ hydrocarbons.
  • This stream 106 contains for example more than 95 mol% of the ethane contained in the starting natural gas 10, and 100 mol% of the C3+ hydrocarbons contained in this stream.
  • the bottom stream 106 has a temperature greater than 10°C, in particular between 20°C and 30°C, for example equal to 23.2°C. It contains less than 1000 ppmv of carbon dioxide, preferably between 200 ppmv and 500 ppmv of carbon dioxide, for example 313 ppmv of carbon dioxide. It has a methane content of less than 5 mol%, for example between 0 mol% and 3 mol%, in particular less than 1 mol%.
  • a first lateral reboiling stream 108 is extracted from the separation column 34, at a level N5 lower than the level N1, for example located at the 20th stage from the top of the separation column 34.
  • the first reboiling liquid stream 108 is brought to the first heat exchanger 28, to be reheated in this exchanger 28 by heat exchange in particular with the starting natural gas 12, up to a temperature above 0°C, in particular equal to 8.25°C.
  • the reboiling stream 108 is then reintroduced into the separation column 34 at a level N6 located below the level N5, for example at the 21st stage starting from the top of the column 34.
  • a second liquid reboiling stream 110 is extracted from the separation column 34 at a level N7 lower than the level N6, for example from the 22nd stage starting from the top of the separation column 34, to be brought to the bottom reboiler 35 in order to be reheated there to a temperature greater than 0°C, for example equal to 10.7°C.
  • the second reboiling liquid stream 110 is then returned to the separation column 34 at a level N8 located below the level N7.
  • This level N8 is for example located on the 23rd floor from the top.
  • the bottom stream 106 is pumped into the pump 46 to be introduced at an intermediate level P1 of the fractionating column 48.
  • the fractionation column 48 produces at the top a top stream 112 containing less than 1 mol% of C3+ hydrocarbons, in particular less than 1 mol% of propane.
  • the overhead stream 112 is partially condensed in the cooler 54, then is separated in the reflux drum 56 to form at the top, the ethane-rich stream 14, and at the bottom, a liquid reflux stream 114 reintroduced at the top of the fractionation column 48, after pumping by the reflux pump 58.
  • Ethane-rich stream 14 contains more than 96 mol% of the ethane contained in starting natural gas 12. It contains more than 97 mol% ethane.
  • the ethane-rich stream 14 is here gaseous. Alternatively (not shown), the ethane-rich stream 14 is a liquid taken from the liquid stream 114.
  • the C3+ hydrocarbon stream contains less than 500 ppmv ethane, particularly less than 100 ppmv ethane.
  • the compressed purified natural gas stream 102 is fed into the liquefaction unit 24 which produces in a known manner a pressurized liquefied natural gas stream 120.
  • the pressurized natural gas stream has a pressure greater than 20 bars, in particular between 20 bars and 90 bars, advantageously equal to 73 bars. It has a temperature lower than -120°C, in particular lower than -130°C, and advantageously equal to -136.8°C.
  • the compressed liquefied natural gas 120 is introduced into the expansion member 60, here in a dynamic expansion turbine. It is expanded to a pressure lower than 5 bars, in particular lower than 2 bars, for example equal to 1.25 bars to form a stream of flashed liquefied natural gas 122.
  • the flashed liquefied natural gas stream 122 is introduced into a flash tank 62 to be separated therein into a relaxed liquefied natural gas stream 124 and a first flash gas stream 126.
  • the expanded liquefied natural gas stream 124 is pumped into the storage 66 using the pump 64 to form the expanded liquefied natural gas 18.
  • the first flash gas flow 126 is recovered at the top of the flash tank 62. It is introduced into the downstream heat exchanger 68 to be reheated there in counter-current to a portion of the compressed purified natural gas 102, which is reintroduced into the stream of flashed liquefied natural gas 122, upstream of the flash tank 62.
  • the flow of reheated flash gas 130 thus formed has a temperature greater than -60°C, and in particular substantially equal to 5°C. It has a very high methane content, for example greater than 80 mol%, for example greater than 85 mol%, in particular greater than 90 mol%. This content is advantageously greater than 95 mol% in methane, in particular greater than 96 mol% in methane, for example equal to 96.46 mol% in methane.
  • It has a nitrogen content of less than 20 mol%, for example less than 15 mol%, in particular less than 10 mol%. This content is advantageously less than 5 mol%, in particular less than 4 mol%, for example substantially equal to 3.54 mol% of nitrogen.
  • the reheated flash gas stream 130 has an ethane content of less than 50 ppmv, in particular less than 10 ppmv, for example equal to 5 ppmv.
  • the flow of heated flash gas 130 is compressed in the compression device 72 to a pressure greater than 25 bars, in particular greater than 30 bars, and for example equal to 60 bars to produce a flow of compressed flash gas 132.
  • the compressed flash gas stream 132 is separated into the fuel stream 20 and a recycle stream 134.
  • the fuel stream 20 is intended to be sent to the fuel gas network of the installation 10 to supply, for example, gas turbines of the natural gas liquefaction unit 24 or those of an electric current generation unit intended, for example, to supply the compressor 40 or other equipment of the installation 10.
  • the recycling stream 134 has a pressure greater than 30 bars, in particular greater than 50 bars, for example equal to 58.5 bars.
  • first heat exchanger 28 It is conveyed successively into the first heat exchanger 28, then into the second heat exchanger 30 to be cooled there to a temperature below -80°C, in particular below -90°C, for example equal to -95.5°C.
  • This recycling stream 134 is then expanded in a static expansion valve 136 to a pressure less than 50 bars, in particular less than 30 bars, for example equal to 28.7 bars, to be introduced into the separation column 34 at a head level N9 of the column 34, for example at the first stage starting from the top of the column 34.
  • the level N9 is located above the level N3 of introduction of the expanded and cooled reflux stream.
  • the recycle stream 134 from the flash gas stream 126 is very rich in methane, since the ethane remains in the liquefied natural gas 18, or is successively extracted in the separation column 34, then in the fractionation column 48.
  • composition of the reflux introduced at the top of the separation column 34 remains very rich in methane, whatever the fluctuations in the quality of the top stream 98 of the separation column 34.
  • the heated overhead stream 100 is compressed at the outlet of the compressor 38 coupled to the turbine 36 in a compression machine comprising two compression stages of the same power, the total power being equal to that of the compressor 40.
  • the compression machine comprises an intercooler cooling the gas between the compression stages. The arrangement thus obtained provides a power saving of 5.8 MW.
  • a second installation 140 intended for the implementation of a second method according to the invention is shown in the figure 2 .
  • the second method according to the invention is similar to the first method according to the invention. It differs from the first method according to the invention in that it comprises a step of withdrawing, from the compressed purified natural gas stream 102, a recirculation stream 142.
  • the molar flow rate of the recirculation stream 142 is advantageously lower than the molar flow rate of the residual compressed purified natural gas stream 102, after collection of the recirculation stream 142, upon its introduction into the liquefaction unit 22.
  • the recirculation stream 142 has a pressure greater than 50 bars, in particular greater than 80 bars, for example equal to 90 bars. It is introduced successively into the first heat exchanger 28, then into the second heat exchanger 30 to be cooled there to a temperature lower than -90°C, preferably lower than -95°C and for example substantially equal to -95.4°C.
  • the recirculation stream 142 is expanded to a pressure lower than 50 bars, in particular lower than 30 bars, in particular equal to 28.7 bars and is introduced into the separation column 34 between the recycling stream 134 and the reflux stream 92.
  • a third installation 150 intended for the implementation of a third method according to the invention is shown in the figure 3 .
  • the installation 150 differs from the first installation 10 in that it comprises a system 152 for collecting and recompressing the evaporation gases formed in the storage 66.
  • the collection system 152 comprises a protection balloon 154, and a compression apparatus 156 comprising a plurality of compression stages 158, spaced two by two by a cooler 160.
  • a second flash gas flow 162 resulting from the evaporation of the liquefied natural gas in the storage 66 is collected at the head of the storage 66, then is introduced into the compression apparatus 156 to be compressed there to a pressure greater than 25 bars, in particular between 26 bars and 70 bars, for example equal to 60 bars.
  • the second compressed flash gas stream 164 thus produced is separated into the fuel stream 20 and the recycle stream 134, which is reintroduced into the separation column 34, after cooling in the heat exchangers 28, 30 and expansion in the expansion valve 136.
  • the installation 150 is devoid of an expansion member 60.
  • the compressed liquefied natural gas 120 from the liquefaction unit 24 is directly introduced into the liquefied natural gas storage 66 and is flashed in the storage 66.
  • a fourth installation 170 intended for the implementation of a fourth method according to the invention is shown in the figure 4 .
  • the fourth installation 170 differs from the first installation 10 in that the storages 66 are equipped, like the third installation 150, with a system 152 for collecting evaporation gases.
  • the first compressed flash gas stream 132 and the second compressed flash gas stream 164 are mixed, before the mixture is separated into the fuel stream 20, and the recycle stream 134.
  • the recycling stream 134 is reintroduced into the separation column 34 after passing through the heat exchangers 28, 30, then expansion in the static expansion valve 136.
  • a fifth installation 200 for implementing a fifth method according to the invention is illustrated by the figure 5 .
  • the fifth method differs from the second method shown in the figure 2 in that the entire gas flow 84 recovered from the balloon 32 forms the turbine feed stream 90 sent to the dynamic expansion turbine 36, without separation.
  • This process is therefore both simple and effective for maintaining a constant ethane extraction content, without increasing investment costs or operating costs.
  • the total power consumed in the presence of a reflux generated from the recycling stream 134 significantly decreases the power consumed and the specified power brought back to the start of liquefied natural gas produced by the installation.

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Description

La présente invention concerne un procédé d'extraction d'éthane dans un courant de gaz naturel de départ, comportant les étapes suivantes :

  • refroidissement du courant de gaz naturel de départ dans au moins un premier échangeur thermique amont, pour former un courant de gaz naturel refroidi ;
  • séparation du courant de gaz naturel refroidi en un flux liquide et en un flux gazeux ;
  • détente du flux liquide et introduction d'au moins un courant issu du flux liquide dans une colonne de séparation du méthane et des hydrocarbures en C2+, à un premier niveau ;
  • formation d'un courant d'alimentation de turbine à partir du flux gazeux ;
  • détente du courant d'alimentation de turbine dans une turbine de détente dynamique et introduction du courant détendu issu de la turbine de détente dynamique dans la colonne de séparation à un deuxième niveau,
  • récupération et compression d'au moins une partie d'un courant de tête issu de la colonne de séparation pour former un courant de gaz naturel purifié comprimé ;
  • liquéfaction du courant de gaz naturel purifié comprimé dans une unité de liquéfaction pour former un courant de gaz naturel liquéfié sous pression ;
  • détente flash du courant de gaz naturel liquéfié sous pression et récupération de gaz naturel liquéfié détendu dans un stockage ;
  • récupération d'au moins un flux de gaz de flash issu de la détente du courant de gaz naturel liquéfié sous pression ;
  • compression du ou de chaque flux de gaz de flash.
The present invention relates to a process for extracting ethane from a starting natural gas stream, comprising the following steps:
  • cooling the starting natural gas stream in at least one first upstream heat exchanger, to form a cooled natural gas stream;
  • separation of the cooled natural gas stream into a liquid stream and a gaseous stream;
  • expansion of the liquid flow and introduction of at least one stream from the liquid flow into a column for separating methane and C2+ hydrocarbons, at a first level;
  • formation of a turbine feed stream from the gas flow;
  • expansion of the turbine feed stream in a dynamic expansion turbine and introduction of the expanded stream from the dynamic expansion turbine into the separation column at a second level,
  • recovering and compressing at least a portion of an overhead stream from the separation column to form a compressed purified natural gas stream;
  • liquefying the compressed purified natural gas stream in a liquefaction unit to form a pressurized liquefied natural gas stream;
  • flash expansion of the pressurized liquefied natural gas stream and recovery of expanded liquefied natural gas in storage;
  • recovery of at least one flash gas stream from the expansion of the pressurized liquefied natural gas stream;
  • compression of the or each flash gas flow.

Un tel procédé est destiné notamment à extraire l'éthane et les hydrocarbures en C3+ d'un gaz naturel de départ, tout en produisant un gaz naturel traité sous pression, qui est ensuite liquéfié avant d'être détendu en vue de son stockage.Such a process is intended in particular to extract ethane and C3+ hydrocarbons from a starting natural gas, while producing a natural gas treated under pressure, which is then liquefied before being expanded for storage.

L'éthylène, l'éthane, le propylène, le propane et les hydrocarbures plus lourds peuvent être extraits de gaz tels que le gaz naturel, le gaz de raffinerie et les gaz synthétiques obtenus à partir d'autres sources hydrocarbonées telles que le charbon, l'huile brute, le naphta.Ethylene, ethane, propylene, propane and heavier hydrocarbons can be extracted from gases such as natural gas, refinery gas and synthetic gases obtained from other hydrocarbon sources such as coal, crude oil, naphtha.

Le gaz naturel contient généralement une majorité de méthane et d'éthane (par exemple, le méthane et l'éthane constituent au moins 50% molaire du gaz). Le gaz naturel peut également contenir en quantités plus négligeables des hydrocarbures plus lourds tels que le propane, les butanes, les pentanes et aussi, de l'hydrogène, de l'azote et du dioxyde de carbone.Natural gas typically contains a majority of methane and ethane (e.g., methane and ethane constitute at least 50 mol% of the gas). Natural gas may also contain in lesser amounts heavier hydrocarbons such as propane, butanes, pentanes, and also hydrogen, nitrogen, and carbon dioxide.

L'invention ici décrite concerne plus particulièrement la récupération d'éthane, de propane et d'hydrocarbures plus lourds à partir de gaz naturel. Outre le fait que les hydrocarbures lourds présents dans le gaz naturel, tels que l'éthane, le propane et le butane peuvent être fortement valorisés en les commercialisant de façon séparée avec une pureté élevée, ils risquent de condenser au cours du transport ou de geler dans les échangeurs de liquéfaction (pour les plus lourds d'entre eux).The invention described herein relates more particularly to the recovery of ethane, propane and heavier hydrocarbons from natural gas. In addition to the fact that the heavy hydrocarbons present in natural gas, such as ethane, propane and butane, can be highly valorized by marketing them separately with high purity, they risk condensing during transport or freezing in the liquefaction exchangers (for the heaviest of them).

Cela peut provoquer des incidents, tels que l'arrivée de bouchons liquides dans des installations de transport ou des arrêts de l'usine de liquéfaction pour déboucher les échangeurs gelés.This can cause incidents, such as liquid plugs entering transport facilities or shutdowns of the liquefaction plant to unclog frozen exchangers.

WO 96/14547 A1 décrit un procédé selon le préambule de la revendication 1 et un appareil selon le préambule de la revendication 15. WO 96/14547 A1 describes a method according to the preamble of claim 1 and an apparatus according to the preamble of claim 15.

US 6 578 379 décrit un procédé très efficace pour récupérer l'éthane et le propane à partir d'un courant de gaz naturel. Un tel procédé fonctionne généralement de manière très performante, notamment pour obtenir une extraction très poussée (par exemple supérieure à 99% molaire) de l'éthane contenu dans le gaz naturel de charge, tout en minimisant la consommation énergétique. US 6,578,379 describes a highly efficient process for recovering ethane and propane from a natural gas stream. Such a process generally operates very efficiently, particularly to achieve very high extraction (e.g. greater than 99 mol%) of the ethane contained in the feed natural gas, while minimizing energy consumption.

Pour obtenir de tels rendements d'extraction, il est connu d'utiliser en reflux principal, à savoir pour le reflux le plus haut de la colonne de séparation du méthane et de l'éthane, un flux très appauvri en éthane.To obtain such extraction yields, it is known to use in the main reflux, namely for the highest reflux of the methane and ethane separation column, a flow very depleted in ethane.

A cet effet, un courant de recirculation est prélevé dans le gaz recomprimé issu de la tête de la colonne de séparation du méthane et de l'éthane. Le courant de recirculation est refroidi à contre-courant du gaz issu de la tête de colonne, puis est détendu pour former le reflux principal introduit en tête de colonne.For this purpose, a recirculation stream is taken from the recompressed gas from the top of the methane and ethane separation column. The recirculation stream is cooled countercurrent to the gas from the top of the column and is then expanded to form the main reflux introduced at the top of the column.

Toutefois, dans certaines conditions opératoires, la qualité du reflux principal est susceptible de se détériorer en température ou/et en composition.However, under certain operating conditions, the quality of the main reflux is likely to deteriorate in temperature and/or composition.

Par exemple si le reflux principal s'appauvrit en méthane, le taux de séparation d'éthane dans la colonne diminue, et la qualité du courant de tête produit en tête de colonne se détériore encore, aggravant l'appauvrissement en méthane du reflux principal. Un effet « boule de neige » se produit, engendrant une diminution significative du taux d'extraction d'éthane. Cela peut être le cas notamment en cas d'entrainement de liquide sur les plateaux supérieurs de la colonne.For example, if the main reflux becomes depleted in methane, the ethane separation rate in the column decreases, and the quality of the overhead stream produced at the top of the column deteriorates further, aggravating the methane depletion of the main reflux. A "snowball" effect occurs, causing a significant decrease in the ethane extraction rate. This can be the case in particular in the event of liquid entrainment on the upper plates of the column.

Un but de l'invention est de disposer d'un procédé flexible et très efficace d'extraction d'éthane et d'hydrocarbures en C3+ d'un courant de gaz naturel de départ, dans lequel le taux d'extraction d'éthane n'est pas ou peu affecté lorsque des fluctuations de la qualité de la tête de colonne de séparation se produisent.An aim of the invention is to provide a flexible and highly efficient process for extracting ethane and C3+ hydrocarbons from a starting natural gas stream, in which the ethane extraction rate is not or only slightly affected when fluctuations in the quality of the separation column head occur.

À cet effet, l'invention a pour objet un procédé du type précité, caractérisé par les étapes suivantes :

  • introduction d'un courant de pied riche en hydrocarbures en C2+ récupéré de la colonne de séparation dans une colonne de fractionnement, et récupération, à partir de la colonne de fractionnement, d'un flux d'éthane ;
  • séparation du flux de gaz de flash comprimé en un courant de combustible et er un courant de recyclage ;
  • refroidissement et détente au moins partielle du courant de recyclage, puis introduction du courant de recyclage refroidi et détendu à un étage de tête de la colonne de séparation.
For this purpose, the invention relates to a method of the aforementioned type, characterized by the following steps:
  • introducing a bottom stream rich in C2+ hydrocarbons recovered from the separation column into a fractionation column, and recovering, from the fractionation column, an ethane stream;
  • separation of the compressed flash gas stream into a fuel stream and a recycle stream;
  • cooling and at least partial expansion of the recycling stream, then introduction of the cooled and expanded recycling stream into a head stage of the separation column.

Le procédé selon l'invention peut comprendre une ou plusieurs des caractéristiques suivantes, prise(s) isolément ou suivant toute combinaison techniquement possible :

  • la teneur en méthane du courant de recyclage est supérieure à 90% molaire, notamment supérieure à 95% molaire ;
  • l'introduction du courant de recyclage s'effectue à un premier étage en partant du haut de la colonne de séparation ;
  • le courant de recyclage est introduit et refroidi dans le premier échangeur thermique par échange thermique avec le courant de tête issu de la colonne de séparation ;
  • il comporte la séparation du flux gazeux en le courant d'alimentation de turbine, introduit dans la turbine de détente dynamique, et en un courant de reflux, introduit dans la colonne de séparation, plus bas que le courant de recyclage, après refroidissement dans un deuxième échangeur thermique amont et détente statique du courant de reflux ;
  • le refroidissement du courant de recyclage comporte le passage du courant de recyclage dans le deuxième échangeur thermique ;
  • la détente du courant de recyclage comporte le passage du courant de recyclage dans une vanne de détente statique ;
  • au moins une partie du gaz naturel de tête purifié comprimé est placé en relation d'échange thermique avec le flux de gaz de flash dans un échangeur thermique aval ;
  • il comporte le prélèvement dans le courant de gaz naturel purifié comprimé, en amont de l'unité de liquéfaction, d'un courant de recirculation, le courant de recirculation étant refroidi, détendu, et introduit dans la colonne de séparation ;
  • le courant de gaz naturel liquéfié sous pression est détendu dans un organe de détente dynamique ou statique, puis est introduit dans un ballon de flash, pour être séparé en le gaz naturel liquéfié détendu introduit dans le stockage, et en un flux de gaz de flash ;
  • au moins un flux de gaz de flash est formé dans le stockage, lors de l'introduction du gaz naturel liquéfié détendu dans le stockage ;
  • le courant de gaz naturel liquéfié sous pression est introduit directement dans le stockage, sans passage par un ballon de flash ;
  • la compression du courant de tête issu de la colonne de séparation s'effectue dans au moins un premier compresseur couplé à la turbine de détente dynamique puis dans une machine de compression comprenant successivement un deuxième compresseur, un refroidisseur du gaz comprimé dans le deuxième compresseur, et un troisième compresseur, pour former le courant de gaz naturel purifié comprimé ;
  • un flux de tête issu de la colonne de fractionnement est refroidi et partiellement condensé, puis est introduit dans un ballon de tête, le flux d'éthane étant récupéré en tête du ballon de tête, le pied du ballon de tête étant réintroduit en reflux dans la colonne de fractionnement ;
  • la totalité du flux gazeux issu de la séparation du courant de gaz naturel refroidi forme le courant d'alimentation de turbine qui est envoyé vers la turbine de détente dynamique sans séparation.
The method according to the invention may comprise one or more of the following characteristics, taken in isolation or in any technically possible combination:
  • the methane content of the recycling stream is greater than 90 mol%, in particular greater than 95 mol%;
  • the introduction of the recycling stream takes place at a first stage starting from the top of the separation column;
  • the recycling stream is introduced and cooled in the first heat exchanger by heat exchange with the overhead stream from the separation column;
  • it involves the separation of the gas flow into the turbine feed stream, introduced into the dynamic expansion turbine, and into a reflux stream, introduced into the separation column, lower than the recycle stream, after cooling in a second upstream heat exchanger and static expansion of the reflux stream;
  • cooling of the recycling stream involves passing the recycling stream through the second heat exchanger;
  • the expansion of the recycling stream involves the passage of the recycling stream through a static expansion valve;
  • at least a portion of the compressed purified overhead natural gas is placed in heat exchange relationship with the flash gas stream in a downstream heat exchanger;
  • it involves the collection from the stream of compressed purified natural gas, upstream of the liquefaction unit, of a recirculation stream, the recirculation stream being cooled, expanded, and introduced into the separation column;
  • the stream of liquefied natural gas under pressure is expanded in a dynamic or static expansion device, then is introduced into a flash tank, to be separated into the expanded liquefied natural gas introduced into the storage, and into a stream of flash gas;
  • at least one flash gas flow is formed in the storage, upon introduction of the expanded liquefied natural gas into the storage;
  • the pressurized liquefied natural gas stream is introduced directly into the storage, without passing through a flash tank;
  • the compression of the overhead stream from the separation column is carried out in at least a first compressor coupled to the dynamic expansion turbine then in a compression machine successively comprising a second compressor, a cooler of the compressed gas in the second compressor, and a third compressor, to form the compressed purified natural gas stream;
  • an overhead stream from the fractionation column is cooled and partially condensed, then introduced into a head drum, the ethane stream being recovered at the top of the head drum, the bottom of the head drum being reintroduced as reflux into the fractionation column;
  • The entire gas stream from the separation of the cooled natural gas stream forms the turbine feed stream which is sent to the dynamic expansion turbine without separation.

L'invention a également pour objet une installation d'extraction d'éthane à partir d'un courant de gaz naturel de départ, comprenant :

  • au moins un premier échangeur thermique amont propre à refroidir le courant de gaz naturel de départ, pour former un courant de gaz naturel refroidi ;
  • un séparateur pour séparer le courant de gaz naturel refroidi en un flux liquide et en un flux gazeux ;
  • un organe de détente du flux liquide ;
  • une colonne de séparation du méthane et des hydrocarbures en C2+ et un ensemble d'introduction d'au moins un courant issu du flux liquide détendu dans la colonne de séparation, à un premier niveau ;
  • un ensemble de formation d'un courant d'alimentation de turbine à partir du flux gazeux ;
  • une turbine de détente dynamique propre à détendre le courant d'alimentation de turbine et un ensemble d'introduction du courant détendu issu de la turbine de détente dynamique dans la colonne de séparation à un deuxième niveau ;
  • un ensemble de récupération et compression d'au moins une partie d'un courant de tête issu de la colonne de séparation pour former un courant de gaz naturel purifié comprimé ;
  • une unité de liquéfaction du courant de gaz naturel purifié comprimé propre à former un courant de gaz naturel liquéfié sous pression ;
  • un ensemble de détente flash du courant de gaz naturel liquéfié sous pression et un stockage de récupération de gaz naturel liquéfié détendu ;
  • un ensemble de récupération d'au moins un flux de gaz de flash issu de la détente du courant de gaz naturel liquéfié sous pression ;
  • un ensemble de compression du ou de chaque flux de gaz de flash,
    caractérisé par: - une colonne de fractionnement, un ensemble d'introduction d'un courant de pied riche en hydrocarbures en C2+ issu de la colonne de séparation dans la colonne de fractionnement, et un ensemble de récupération, à partir de la colonne de fractionnement, d'un flux d'éthane ;
  • un ensemble de séparation du flux de gaz de flash comprimé en un courant de combustible et en un courant de recyclage ;
  • un ensemble de refroidissement et détente au moins partielle du courant de recyclage, et d'introduction du courant de recyclage refroidi et détendu à un étage de tête de la colonne de séparation.
The invention also relates to an installation for extracting ethane from a starting stream of natural gas, comprising:
  • at least one first upstream heat exchanger capable of cooling the initial natural gas stream, to form a cooled natural gas stream;
  • a separator for separating the cooled natural gas stream into a liquid stream and a gaseous stream;
  • a liquid flow relaxation organ;
  • a column for separating methane and C2+ hydrocarbons and an assembly for introducing at least one stream from the liquid flow expanded in the separation column, at a first level;
  • an assembly for forming a turbine feed stream from the gas flow;
  • a dynamic expansion turbine suitable for expanding the turbine feed stream and an assembly for introducing the expanded stream from the dynamic expansion turbine into the separation column at a second level;
  • an assembly for recovering and compressing at least part of a head stream from the separation column to form a stream of compressed purified natural gas;
  • a unit for liquefying the compressed purified natural gas stream capable of forming a stream of liquefied natural gas under pressure;
  • a flash expansion assembly for the pressurized liquefied natural gas stream and a storage facility for recovering the expanded liquefied natural gas;
  • a recovery assembly for at least one flash gas flow resulting from the expansion of the pressurized liquefied natural gas stream;
  • a compression assembly of the or each flash gas flow,
    characterized by: - a fractionation column, an assembly for introducing a bottom stream rich in C2+ hydrocarbons from the separation column into the fractionation column, and an assembly for recovering, from the fractionation column, an ethane stream;
  • a set for separating the compressed flash gas flow into a fuel stream and a recycle stream;
  • a cooling and at least partial expansion assembly for the recycling stream, and for introducing the cooled and expanded recycling stream into a head stage of the separation column.

L'invention sera mieux comprise à la lecture de la description qui va suivre, donnée uniquement à titre d'exemple, et faite en se référant aux dessins annexés, sous lesquels :

  • [ Fig 1 ] La figure 1 est un schéma synoptique représentant une première installation pour la mise en oeuvre d'un premier procédé d'extraction d'éthane selon l'invention ;
  • [ Fig 2 ] La figure 2 est un schéma analogue à celui de la figure 1, d'une deuxième installation pour la mise en oeuvre d'un deuxième procédé d'extraction d'éthane selon l'invention ;
  • [ Fig 3 ] La figure 3 est un schéma analogue à celui de la figure 1, d'une troisième installation pour la mise en oeuvre d'un troisième procédé d'extraction d'éthane selon l'invention ;
  • [ Fig 4 ] La figure 4 est un schéma analogue à celui de la figure 1, d'une quatrième installation pour la mise en oeuvre d'un quatrième procédé d'extraction selon l'invention ;
  • [ Fig 5 ] La figure 5 est un schéma analogue à celui de la figure 2, d'une cinquième installation pour la mise en oeuvre d'un cinquième procédé d'extraction selon l'invention.
The invention will be better understood from reading the following description, given solely by way of example, and made with reference to the appended drawings, in which:
  • [ Fig 1 ] There figure 1 is a block diagram representing a first installation for implementing a first ethane extraction process according to the invention;
  • [ Fig 2 ] There figure 2 is a diagram similar to that of the figure 1 , of a second installation for implementing a second ethane extraction process according to the invention;
  • [ Fig 3 ] There figure 3 is a diagram similar to that of the figure 1 , of a third installation for implementing a third ethane extraction process according to the invention;
  • [ Fig 4 ] There figure 4 is a diagram similar to that of the figure 1 , of a fourth installation for implementing a fourth extraction method according to the invention;
  • [ Fig 5 ] There figure 5 is a diagram similar to that of the figure 2 , of a fifth installation for implementing a fifth extraction method according to the invention.

Dans tout ce qui suit, on désignera par une même référence un flux de liquide et la conduite qui le véhicule, les pressions considérées sont des pressions absolues, et les pourcentages considérés sont des pourcentages molaires.In all that follows, a liquid flow and the pipe which carries it will be designated by the same reference, the pressures considered are absolute pressures, and the percentages considered are molar percentages.

Les procédés décrits ont été modélisés sur un simulateur de procédés. Des rendements de 82% polytropique pour les compresseurs et de 86% adiabatique pour les turbines ont été définis.The processes described were modeled on a process simulator. Polytropic efficiencies of 82% for compressors and 86% adiabatic for turbines were defined.

Une première installation 10 d'extraction d'éthane selon l'invention est représentée sur la figure 1.A first ethane extraction installation 10 according to the invention is shown in the figure 1 .

Cette installation 10 est destinée à la production simultanée, à partir d'un courant de gaz naturel de départ 12, d'un flux riche en éthane 14, d'un courant de pied 16 riche en hydrocarbures en C3+, d'un gaz naturel liquéfié détendu 18, et d'un courant de combustible 20, avantageusement destiné à être réutilisé dans l'installation 10.This installation 10 is intended for the simultaneous production, from a starting natural gas stream 12, of an ethane-rich stream 14, of a bottom stream 16 rich in C3+ hydrocarbons, of a relaxed liquefied natural gas 18, and of a fuel stream 20, advantageously intended to be reused in the installation 10.

En référence à la figure 1, l'installation 10 comporte une unité 22 d'extraction d'éthane, une unité 24 de liquéfaction, et une unité 26 de flash et de stockage de gaz naturel liquéfié.In reference to the figure 1 , installation 10 comprises an ethane extraction unit 22, a liquefaction unit 24, and a liquefied natural gas flash and storage unit 26.

L'unité d'extraction 22 comporte des premier et deuxième échangeurs thermiques amont 28, 30, un ballon séparateur 32, et une colonne 34 de séparation du méthane et des hydrocarbures en C2+. La colonne 34 est ici munie d'un rebouilleur de fond 35.The extraction unit 22 comprises first and second upstream heat exchangers 28, 30, a separator tank 32, and a column 34 for separating methane and C2+ hydrocarbons. The column 34 is here equipped with a bottom reboiler 35.

L'unité 22 comporte en outre une turbine de détente dynamique 36 couplée à un premier compresseur 38, un deuxième compresseur 40, chaque compresseur 38, 40 étant muni en aval d'un refroidisseur 42, 44.The unit 22 further comprises a dynamic expansion turbine 36 coupled to a first compressor 38, a second compressor 40, each compressor 38, 40 being provided downstream with a cooler 42, 44.

L'unité 22 comporte en outre une pompe de fond 46, une colonne de fractionnement 48, munie d'un rebouilleur de fond 50 et d'un système de reflux 52, le système de reflux 52 comportant un refroidisseur 54, un ballon de reflux 56, et une pompe de reflux 58.The unit 22 further comprises a bottom pump 46, a fractionation column 48, provided with a bottom reboiler 50 and a reflux system 52, the reflux system 52 comprising a cooler 54, a reflux drum 56, and a reflux pump 58.

L'unité de liquéfaction du gaz naturel 24 est une unité connue, notamment de type C3MR ou DMR.The natural gas liquefaction unit 24 is a known unit, notably of the C3MR or DMR type.

Dans l'exemple de la figure 1, l'unité de flash et de stockage 26 comporte un organe de détente 60, ici une turbine de détente dynamique, un ballon de flash 62, et une pompe 64 de convoyage de gaz naturel liquéfié vers un stockage 66. En variante, l'organe de détente 60 est une vanne de détente statique.In the example of the figure 1 , the flash and storage unit 26 comprises an expansion member 60, here a dynamic expansion turbine, a flash tank 62, and a pump 64 for conveying liquefied natural gas to a storage 66. Alternatively, the expansion member 60 is a static expansion valve.

Le stockage 66 est par exemple une cuve de stockage isolée thermiquement.Storage 66 is for example a thermally insulated storage tank.

L'unité de flash et de stockage 26 comporte en outre dans cet exemple un échangeur thermique aval 68, éventuellement un ballon d'aspiration 70, et un appareil de compression 72 comportant une pluralité de compresseurs 74 montés en série, séparés entre eux par des refroidisseurs 76.The flash and storage unit 26 further comprises in this example a downstream heat exchanger 68, possibly a suction tank 70, and a compression device 72 comprising a plurality of compressors 74 mounted in series, separated from each other by coolers 76.

Un premier procédé selon l'invention, mis en oeuvre dans l'installation 10, va maintenant être décrit.A first method according to the invention, implemented in the installation 10, will now be described.

Le gaz naturel de départ formant le courant 12 est avantageusement un gaz naturel désulfuré, sec et au moins partiellement décarbonaté.The starting natural gas forming stream 12 is advantageously a desulfurized, dry and at least partially decarbonated natural gas.

Le terme « au moins partiellement décarbonaté » signifie que la teneur en dioxyde de carbone dans le courant de gaz naturel de départ 13 est avantageusement inférieure ou égale à 50 ppmv.The term “at least partially decarbonated” means that the carbon dioxide content in the starting natural gas stream 13 is advantageously less than or equal to 50 ppmv.

De même, la teneur en eau est inférieure à 1 ppmv, avantageusement inférieure à 0,1 ppmv.Similarly, the water content is less than 1 ppmv, preferably less than 0.1 ppmv.

La teneur en éléments soufrés, incluant le sulfure d'hydrogène est inférieure à 10 ppmv et avantageusement inférieure ou égale à 4 ppmv.The content of sulfur elements, including hydrogen sulfide, is less than 10 ppmv and advantageously less than or equal to 4 ppmv.

Un exemple de composition molaire du courant de gaz naturel de départ 12 est donné dans le tableau ci-dessous. [Table 1] Fraction molaire en % Azote 0,19 Méthane 90,62 Ethane 6,56 Propane 2,05 i-butane 0,25 n-butane 0,23 C5+ 0,09 An example of the molar composition of the starting natural gas stream 12 is given in the table below. <b>[Table 1]</b> Molar fraction in % Nitrogen 0.19 Methane 90.62 Ethane 6.56 Propane 2.05 i-butane 0.25 n-butane 0.23 C5+ 0.09

Plus généralement, la fraction molaire en méthane dans le courant de gaz naturel de départ 12 est comprise entre 75% molaire et 95% molaire, la fraction molaire en hydrocarbures en C2 est comprise entre 3% molaire et 12% molaire, et la fraction molaire en hydrocarbures en C3+ est comprise entre 1 % molaire et 8% molaire.More generally, the molar fraction of methane in the starting natural gas stream 12 is between 75 mol% and 95 mol%, the molar fraction of C2 hydrocarbons is between 3 mol% and 12 mol%, and the molar fraction of C3+ hydrocarbons is between 1 mol% and 8 mol%.

Le débit du courant de gaz naturel de départ 12 est par exemple supérieur à 2000 kmol/h et est par exemple compris entre 2000 kmol/h et 70000 kmol/h, notamment égal à 55 000 kmol/h.The flow rate of the starting natural gas stream 12 is for example greater than 2000 kmol/h and is for example between 2000 kmol/h and 70000 kmol/h, in particular equal to 55,000 kmol/h.

Le courant de gaz naturel de départ 12 présente une température voisine de la température ambiante, notamment comprise entre 0° et 40°C, ici égale à 21,5°C et une pression avantageusement supérieure à 35 bars, notamment supérieure à 70 bars, dans cet exemple égale à 81 bars.The starting natural gas stream 12 has a temperature close to ambient temperature, in particular between 0° and 40°C, here equal to 21.5°C and a pressure advantageously greater than 35 bars, in particular greater than 70 bars, in this example equal to 81 bars.

Le gaz naturel de départ 12 est introduit dans le premier échangeur thermique 28 pour y être refroidi. Il forme un courant 80 de gaz naturel refroidi. Le gaz naturel de départ 12 est ici supercritique, il est donc simplement refroidi. Dans une variante, il n'est pas supercritique et il est au moins partiellement condensé dans le premier échangeur thermique 28.The starting natural gas 12 is introduced into the first heat exchanger 28 to be cooled there. It forms a stream 80 of cooled natural gas. The starting natural gas 12 is here supercritical, it is therefore simply cooled. In a variant, it is not supercritical and it is at least partially condensed in the first heat exchanger 28.

Il présente une température inférieure à -20°C, et notamment comprise entre -25°C et -45°C, en particulier égale à -37°C.It has a temperature below -20°C, and in particular between -25°C and -45°C, in particular equal to -37°C.

Le courant 80 est ensuite introduit dans le ballon séparateur 32, pour y être séparé en un flux liquide 82, récupéré au pied du ballon séparateur 32, et un flux gazeux 84 récupéré en tête du ballon séparateur 32. Le débit du flux liquide 82 peut être nul, notamment lorsque le courant de gaz naturel refroidi 80 est supercritique.The stream 80 is then introduced into the separator tank 32, to be separated there into a liquid stream 82, recovered at the foot of the separator tank 32, and a gas stream 84 recovered at the top of the separator tank 32. The flow rate of the liquid stream 82 may be zero, in particular when the cooled natural gas stream 80 is supercritical.

Le flux liquide 82 passe dans une vanne de détente statique 86, pour former une phase mixte détendue 88. La pression de la phase mixte détendue 88 est inférieure à 50 bars, notamment inférieure à 30 bars, et est par exemple égale à 28,7 bars. La phase mixte détendue 88 est introduite à un niveau N1 de fond de la colonne de séparation 34.The liquid flow 82 passes through a static expansion valve 86, to form a relaxed mixed phase 88. The pressure of the relaxed mixed phase 88 is less than 50 bars, in particular less than 30 bars, and is for example equal to 28.7 bars. The relaxed mixed phase 88 is introduced at a bottom level N1 of the separation column 34.

Le flux gazeux 84 est divisé en un courant principal d'alimentation de turbine 90 et en un courant secondaire 92 de reflux.The gas flow 84 is divided into a main turbine feed stream 90 and a secondary reflux stream 92.

Le débit molaire du courant d'alimentation de turbine 90 est supérieur au débit molaire du courant de reflux 92, et notamment compris entre 5% et 25% du débit molaire du courant de reflux 92.The molar flow rate of the turbine feed stream 90 is greater than the molar flow rate of the reflux stream 92, and in particular between 5% and 25% of the molar flow rate of the reflux stream 92.

Le courant d'alimentation de turbine 90 est introduit dans la turbine de détente dynamique 36 pour y être détendu à une pression inférieure à 50 bars, notamment inférieure à 30 bars, par exemple égale à 28,7 bars.The turbine feed stream 90 is introduced into the dynamic expansion turbine 36 to be expanded there to a pressure less than 50 bars, in particular less than 30 bars, for example equal to 28.7 bars.

L'expansion dynamique du courant 90 permet de récupérer plus de 10 000 kW d'énergie, par exemple 10 865 kW d'énergie.The dynamic expansion of the 90 current allows the recovery of more than 10,000 kW of energy, for example 10,865 kW of energy.

La température du courant refroidi et détendu 94 issu de la turbine de détente dynamique 36 est par exemple inférieure à -70°C, notamment inférieure à -80°C, par exemple égale à -80,8°C.The temperature of the cooled and expanded stream 94 coming from the dynamic expansion turbine 36 is for example less than -70°C, in particular less than -80°C, for example equal to -80.8°C.

Le courant refroidi et détendu 94 est alors introduit dans la colonne de séparation 34 à un niveau N2 situé au-dessus du niveau N1.The cooled and expanded stream 94 is then introduced into the separation column 34 at a level N2 located above the level N1.

Le courant de reflux 92 est introduit dans une vanne de détente statique 96 pour y être détendu à une pression inférieure à 50 bars, notamment inférieure à 30 bars, notamment égale à 28,7 bars. Il est refroidi dans le deuxième échangeur thermique amont 30 à une température inférieure à -80°C, notamment inférieure à -90°C, en particulier égale à -95,8°C.The reflux stream 92 is introduced into a static expansion valve 96 to be expanded there to a pressure lower than 50 bars, in particular lower than 30 bars, in particular equal to 28.7 bars. It is cooled in the second upstream heat exchanger 30 to a temperature lower than -80°C, in particular lower than -90°C, in particular equal to -95.8°C.

Le courant de reflux détendu et refroidi est introduit dans la colonne de séparation 34 à un niveau N3 situé au-dessus du niveau N2 à la tête de la colonne 34.The expanded and cooled reflux stream is introduced into separation column 34 at a level N3 located above level N2 at the head of column 34.

La pression de la colonne de séparation 34 est de préférence comprise entre 10 bars et 40 bars, notamment entre 20 bars et 40 bars, par exemple sensiblement égale à 28,5 bars.The pressure of the separation column 34 is preferably between 10 bars and 40 bars, in particular between 20 bars and 40 bars, for example substantially equal to 28.5 bars.

La colonne de séparation 34 produit un courant de tête 98. Le courant de tête 98 est réchauffé dans le deuxième échangeur thermique amont 30, puis dans le premier échangeur thermique amont 28 à contre-courant avec le gaz naturel de départ 12 pour former un courant de tête réchauffé 100.The separation column 34 produces a head stream 98. The head stream 98 is reheated in the second upstream heat exchanger 30, then in the first upstream heat exchanger 28 in counter-current with the starting natural gas 12 to form a reheated head stream 100.

La température du courant de tête réchauffé 100 est supérieure à 0°C, notamment supérieure à 15°C, et est par exemple égale à 17,6°C.The temperature of the heated head stream 100 is greater than 0°C, in particular greater than 15°C, and is for example equal to 17.6°C.

Le courant de tête réchauffé 100 est ensuite comprimé dans le compresseur 38 couplé à la turbine 36, puis est refroidi dans le refroidisseur 42, pour obtenir un courant à une pression supérieure à 30 bars, notamment égale à 34,6 bars.The heated head stream 100 is then compressed in the compressor 38 coupled to the turbine 36, then is cooled in the cooler 42, to obtain a stream at a pressure greater than 30 bars, in particular equal to 34.6 bars.

Il est ensuite recomprimé dans le compresseur 40, puis refroidi dans le refroidisseur 44 afin de produire un courant de gaz naturel purifié comprimé 102 destiné à l'unité de liquéfaction 24.It is then recompressed in the compressor 40, then cooled in the cooler 44 in order to produce a stream of compressed purified natural gas 102 intended for the liquefaction unit 24.

Le courant de gaz naturel purifié comprimé 102 présente une pression supérieure à 60 bars, notamment supérieure à 80 bars, par exemple égale à 91 bars. Il présente une température supérieure à 0°C, notamment supérieure à 10°C, en particulier égale à 21,5°C.The compressed purified natural gas stream 102 has a pressure greater than 60 bars, in particular greater than 80 bars, for example equal to 91 bars. It has a temperature greater than 0°C, in particular greater than 10°C, in particular equal to 21.5°C.

Les refroidisseurs 42, 44 sont ici alimentés par un flux de refroidissement de température inférieure à 10°C, notamment égale à 7°C. Ce flux de refroidissement peut être notamment de l'air ou de l'eau.The coolers 42, 44 are here supplied by a cooling flow with a temperature lower than 10°C, in particular equal to 7°C. This cooling flow may in particular be air or water.

Le courant de gaz naturel purifié compressé 102 est riche en méthane. Il comporte une teneur en méthane supérieure à 99,0% molaire, notamment égale à 99,1% molaire. Il présente une teneur faible en azote, notamment inférieure à 1,0 % molaire, et une teneur faible en hydrocarbures en C2+, en particulier une teneur inférieure à 0,5% molaire en éthane, sensiblement égale à 0,2% molaire en éthane.The compressed purified natural gas stream 102 is rich in methane. It has a methane content greater than 99.0 mol%, in particular equal to 99.1 mol%. It has a low nitrogen content, in particular less than 1.0 mol%, and a low C2+ hydrocarbon content, in particular a content of less than 0.5 mol% in ethane, substantially equal to 0.2 mol% in ethane.

La colonne de séparation 34 produit en fond un courant de fond 106 riche en hydrocarbures en C2+. Ce courant 106 contient par exemple plus de 95% molaire de l'éthane contenu dans le gaz naturel de départ 10, et 100% molaire des hydrocarbures en C3+ contenus dans ce courant.The separation column 34 produces at the bottom a bottom stream 106 rich in C2+ hydrocarbons. This stream 106 contains for example more than 95 mol% of the ethane contained in the starting natural gas 10, and 100 mol% of the C3+ hydrocarbons contained in this stream.

Le courant de fond 106 présente une température supérieure à 10°C, notamment comprise entre 20°C et 30°C, par exemple égal à 23,2°C. Il contient moins de 1000 ppmv de dioxyde de carbone, de préférence entre 200 ppmv et 500 ppmv de dioxyde de carbone, par exemple 313 ppmv de dioxyde de carbone. Il présente une teneur en méthane inférieure à 5% molaire, par exemple comprise entre 0% molaire et 3% molaire, notamment inférieure à 1% molaire.The bottom stream 106 has a temperature greater than 10°C, in particular between 20°C and 30°C, for example equal to 23.2°C. It contains less than 1000 ppmv of carbon dioxide, preferably between 200 ppmv and 500 ppmv of carbon dioxide, for example 313 ppmv of carbon dioxide. It has a methane content of less than 5 mol%, for example between 0 mol% and 3 mol%, in particular less than 1 mol%.

Le tableau ci-dessous illustre un exemple de composition du courant de fond 106. [Table 2] Fraction molaire en % Azote 0,0 Méthane 0,21 Ethane 70,5 Propane 22,8 i-butane 2,8 n-butane 2,6 C5+ 0,97 The table below illustrates an example of the composition of the 106 undercurrent. <b>[Table 2]</b> Molar fraction in % Nitrogen 0.0 Methane 0.21 Ethane 70.5 Propane 22.8 i-butane 2.8 n-butane 2.6 C5+ 0.97

Un premier courant de rebouillage latéral 108 est extrait de la colonne de séparation 34, à un niveau N5 inférieur au niveau N1, par exemple situé au 20ème étage à partir du haut de la colonne de séparation 34.A first lateral reboiling stream 108 is extracted from the separation column 34, at a level N5 lower than the level N1, for example located at the 20th stage from the top of the separation column 34.

Le premier courant liquide de rebouillage 108 est amené au premier échangeur thermique 28, pour y être réchauffé dans cet échangeur 28 par échange thermique notamment avec le gaz naturel de départ 12, jusqu'à une température supérieure à 0°C, notamment égale à 8,25°C. Le courant de rebouillage 108 est ensuite réintroduit dans la colonne de séparation 34 à un niveau N6 situé sous le niveau N5, par exemple au 21ème étage en partant du haut de la colonne 34.The first reboiling liquid stream 108 is brought to the first heat exchanger 28, to be reheated in this exchanger 28 by heat exchange in particular with the starting natural gas 12, up to a temperature above 0°C, in particular equal to 8.25°C. The reboiling stream 108 is then reintroduced into the separation column 34 at a level N6 located below the level N5, for example at the 21st stage starting from the top of the column 34.

De même, un deuxième courant liquide de rebouillage 110 est extrait de la colonne de séparation 34 à un niveau N7 inférieur au niveau N6, par exemple à partir du 22ème étage en partant du haut de la colonne de séparation 34, pour être amené au rebouilleur de fond 35 afin d'y être réchauffé à une température supérieure à 0°C, par exemple égale à 10,7°C. Une énergie supérieure à 1 MW par exemple égale à 4MW est fournie au deuxième courant liquide de rebouillage 110.Similarly, a second liquid reboiling stream 110 is extracted from the separation column 34 at a level N7 lower than the level N6, for example from the 22nd stage starting from the top of the separation column 34, to be brought to the bottom reboiler 35 in order to be reheated there to a temperature greater than 0°C, for example equal to 10.7°C. Energy greater than 1 MW, for example equal to 4 MW, is supplied to the second liquid reboiling stream 110.

Le deuxième courant liquide de rebouillage 110 est ensuite renvoyé dans la colonne de séparation 34 à un niveau N8 situé sous le niveau N7. Ce niveau N8 est par exemple situé au 23ème étage en partant du haut.The second reboiling liquid stream 110 is then returned to the separation column 34 at a level N8 located below the level N7. This level N8 is for example located on the 23rd floor from the top.

Le courant de fond 106 est pompé dans la pompe 46 pour être introduit à un niveau intermédiaire P1 de la colonne de fractionnement 48.The bottom stream 106 is pumped into the pump 46 to be introduced at an intermediate level P1 of the fractionating column 48.

La colonne de fractionnement 48 produit en tête un flux de tête 112 contenant moins de 1 % molaire d'hydrocarbures en C3+, en particulier moins de 1% molaire de propane.The fractionation column 48 produces at the top a top stream 112 containing less than 1 mol% of C3+ hydrocarbons, in particular less than 1 mol% of propane.

Le flux de tête 112 est partiellement condensé dans le refroidisseur 54, puis est séparé dans le ballon de reflux 56 pour former en tête, le flux riche en éthane 14, et en pied, un flux liquide de reflux 114 réintroduit en tête de la colonne de fractionnement 48, après pompage par la pompe de reflux 58.The overhead stream 112 is partially condensed in the cooler 54, then is separated in the reflux drum 56 to form at the top, the ethane-rich stream 14, and at the bottom, a liquid reflux stream 114 reintroduced at the top of the fractionation column 48, after pumping by the reflux pump 58.

Le flux riche en éthane 14 contient plus de 96% molaire de l'éthane contenu dans le gaz naturel de départ 12. Il contient plus de 97% molaire d'éthane.Ethane-rich stream 14 contains more than 96 mol% of the ethane contained in starting natural gas 12. It contains more than 97 mol% ethane.

Le flux riche en éthane 14 est ici gazeux. En variante (non représentée), le flux riche en éthane 14 est un liquide prélevé à partir du flux liquide 114.The ethane-rich stream 14 is here gaseous. Alternatively (not shown), the ethane-rich stream 14 is a liquid taken from the liquid stream 114.

Le courant d'hydrocarbures en C3+ contient moins de 500 ppmv d'éthane, en particulier moins de 100 ppmv d'éthane.The C3+ hydrocarbon stream contains less than 500 ppmv ethane, particularly less than 100 ppmv ethane.

Le courant de gaz naturel purifié comprimé 102 est amené dans l'unité de liquéfaction 24 qui produit d'une manière connue un courant de gaz naturel liquéfié sous pression 120.The compressed purified natural gas stream 102 is fed into the liquefaction unit 24 which produces in a known manner a pressurized liquefied natural gas stream 120.

Le courant de gaz naturel sous pression présente une pression supérieure à 20 bars, notamment comprise entre 20 bars et 90 bars, avantageusement égale à 73 bars. Il présente une température inférieure à -120°C, notamment inférieure à -130°C, et avantageusement égale à -136,8°C.The pressurized natural gas stream has a pressure greater than 20 bars, in particular between 20 bars and 90 bars, advantageously equal to 73 bars. It has a temperature lower than -120°C, in particular lower than -130°C, and advantageously equal to -136.8°C.

Le gaz naturel liquéfié comprimé 120 est introduit dans l'organe de détente 60, ici dans une turbine de détente dynamique. Il est détendu à une pression inférieure à 5 bars, notamment inférieure à 2 bars, par exemple égale à 1,25 bars pour former un courant de gaz naturel liquéfié flashé 122.The compressed liquefied natural gas 120 is introduced into the expansion member 60, here in a dynamic expansion turbine. It is expanded to a pressure lower than 5 bars, in particular lower than 2 bars, for example equal to 1.25 bars to form a stream of flashed liquefied natural gas 122.

Le courant de gaz naturel liquéfié flashé 122 est introduit dans un ballon de flash 62 pour y être séparé en un courant de gaz naturel liquéfié détendu 124 et en un premier flux de gaz de flash 126.The flashed liquefied natural gas stream 122 is introduced into a flash tank 62 to be separated therein into a relaxed liquefied natural gas stream 124 and a first flash gas stream 126.

Le courant gaz naturel liquéfié détendu 124 est pompé dans le stockage 66 à l'aide de la pompe 64 pour former le gaz naturel liquéfié détendu 18.The expanded liquefied natural gas stream 124 is pumped into the storage 66 using the pump 64 to form the expanded liquefied natural gas 18.

Le premier flux de gaz de flash 126 est récupéré en tête du ballon de flash 62. Il est introduit dans l'échangeur thermique aval 68 pour y être réchauffé à contre-courant d'une partie du gaz naturel purifié comprimé 102, laquelle est réintroduite dans le courant de gaz naturel liquéfié flashé 122, en amont du ballon de flash 62.The first flash gas flow 126 is recovered at the top of the flash tank 62. It is introduced into the downstream heat exchanger 68 to be reheated there in counter-current to a portion of the compressed purified natural gas 102, which is reintroduced into the stream of flashed liquefied natural gas 122, upstream of the flash tank 62.

Après échange thermique dans l'échangeur thermique aval 68, le flux de gaz de flash réchauffé 130 ainsi formé présente une température supérieure à -60°C, et notamment sensiblement égale à 5°C. Il présente une teneur très élevée en méthane, par exemple supérieure à 80% molaire, par exemple supérieure à 85% molaire, notamment supérieure à 90% molaire. Cette teneur est avantageusement supérieure à 95% molaire en méthane, notamment supérieure à 96% molaire en méthane, par exemple égale à 96,46% molaire en méthane.After heat exchange in the downstream heat exchanger 68, the flow of reheated flash gas 130 thus formed has a temperature greater than -60°C, and in particular substantially equal to 5°C. It has a very high methane content, for example greater than 80 mol%, for example greater than 85 mol%, in particular greater than 90 mol%. This content is advantageously greater than 95 mol% in methane, in particular greater than 96 mol% in methane, for example equal to 96.46 mol% in methane.

Il présente une teneur en azote inférieure à 20% molaire, par exemple inférieure 15% molaire, notamment inférieure à 10% molaire. Cette teneur est avantageusement inférieure à 5% molaire, notamment inférieure à 4% molaire, par exemple sensiblement égale à 3,54% molaire d'azote.It has a nitrogen content of less than 20 mol%, for example less than 15 mol%, in particular less than 10 mol%. This content is advantageously less than 5 mol%, in particular less than 4 mol%, for example substantially equal to 3.54 mol% of nitrogen.

Le flux de gaz de flash réchauffé 130 présente une teneur en éthane inférieure à 50 ppmv, notamment inférieure à 10 ppmv, par exemple égale à 5 ppmv.The reheated flash gas stream 130 has an ethane content of less than 50 ppmv, in particular less than 10 ppmv, for example equal to 5 ppmv.

Après passage éventuel dans un ballon d'aspiration 70, le flux de gaz de flash réchauffé 130 est comprimé dans l'appareil de compression 72 jusqu'à une pression supérieure à 25 bars, notamment supérieure à 30 bars, et par exemple égale à 60 bars pour produire un flux de gaz de flash comprimé 132.After possibly passing through a suction tank 70, the flow of heated flash gas 130 is compressed in the compression device 72 to a pressure greater than 25 bars, in particular greater than 30 bars, and for example equal to 60 bars to produce a flow of compressed flash gas 132.

Le flux de gaz de flash comprimé 132 est séparé en le courant de combustible 20 et en un courant de recyclage 134.The compressed flash gas stream 132 is separated into the fuel stream 20 and a recycle stream 134.

Le courant de combustible 20 est destiné à être envoyé au réseau de gaz combustible de l'installation 10 pour alimenter par exemple des turbines à gaz de l'unité de liquéfaction de gaz naturel 24 ou celles d'une unité de génération de courant électrique destinée par exemple à alimenter le compresseur 40 ou d'autres équipements de l'installation 10.The fuel stream 20 is intended to be sent to the fuel gas network of the installation 10 to supply, for example, gas turbines of the natural gas liquefaction unit 24 or those of an electric current generation unit intended, for example, to supply the compressor 40 or other equipment of the installation 10.

Le courant de recyclage 134 présente une pression supérieure à 30 bars, notamment supérieure à 50 bars, par exemple égale à 58,5 bars.The recycling stream 134 has a pressure greater than 30 bars, in particular greater than 50 bars, for example equal to 58.5 bars.

Il est convoyé successivement dans le premier échangeur thermique 28, puis dans le deuxième échangeur thermique 30 pour y être refroidi à une température inférieure à - 80°C, notamment inférieure à -90°C, par exemple égale à -95,5°C.It is conveyed successively into the first heat exchanger 28, then into the second heat exchanger 30 to be cooled there to a temperature below -80°C, in particular below -90°C, for example equal to -95.5°C.

Ce courant de recyclage 134 est ensuite détendu dans une vanne de détente statique 136 jusqu'à une pression inférieure à 50 bars, notamment inférieure à 30 bars, par exemple égale à 28,7 bars, pour être introduit dans la colonne de séparation 34 à un niveau de tête N9 de la colonne 34, par exemple au premier étage en partant du haut de la colonne 34. Le niveau N9 est situé au-dessus du niveau N3 d'introduction du courant de reflux détendu et refroidi.This recycling stream 134 is then expanded in a static expansion valve 136 to a pressure less than 50 bars, in particular less than 30 bars, for example equal to 28.7 bars, to be introduced into the separation column 34 at a head level N9 of the column 34, for example at the first stage starting from the top of the column 34. The level N9 is located above the level N3 of introduction of the expanded and cooled reflux stream.

Comme indiqué plus haut, le courant de recyclage 134 issu du flux de gaz de flash 126 est très riche en méthane, puisque l'éthane reste dans le gaz naturel liquéfié 18, ou est extrait successivement dans la colonne de séparation 34, puis dans la colonne de fractionnement 48.As indicated above, the recycle stream 134 from the flash gas stream 126 is very rich in methane, since the ethane remains in the liquefied natural gas 18, or is successively extracted in the separation column 34, then in the fractionation column 48.

Ainsi, la composition du reflux introduit en tête de la colonne de séparation 34 reste très riche en méthane, quelles que soient les fluctuations de qualité du courant de tête 98 de la colonne de séparation 34.Thus, the composition of the reflux introduced at the top of the separation column 34 remains very rich in methane, whatever the fluctuations in the quality of the top stream 98 of the separation column 34.

La présence de ce nouveau reflux fournit également une flexibilité opératoire lors de la mise en oeuvre du procédé, mais également en phase de conception.The presence of this new reflux also provides operational flexibility during the implementation of the process, but also in the design phase.

Il est ainsi possible d'optimiser globalement la consommation énergétique entre l'unité d'extraction d'éthane 22 et l'unité de liquéfaction 24 pour régler les paramètres des deux unités 22, 24, afin de sélectionner au mieux les compresseurs et leur mode d'entrainement requis dans les deux unités 22, 24. Ceci diminue significativement les coûts d'investissement, et également les coûts opératoires comme on le verra dans l'exemple décrit plus bas.It is thus possible to globally optimize the energy consumption between the ethane extraction unit 22 and the liquefaction unit 24 to adjust the parameters of the two units 22, 24, in order to best select the compressors and their drive mode required in the two units 22, 24. This significantly reduces the investment costs, and also the operating costs as will be seen in the example described below.

En variante (non représentée), le courant de tête réchauffé 100 est comprimé en sortie du compresseur 38 couplé à la turbine 36 dans une machine de compression comprenant deux étages de compression de même puissance, la puissance totale étant égale à celle du compresseur 40. La machine de compression comporte un refroidisseur intermédiaire refroidissant le gaz entre les étages de compression. L'arrangement ainsi obtenu fournit une économie de puissance de 5,8 MW.Alternatively (not shown), the heated overhead stream 100 is compressed at the outlet of the compressor 38 coupled to the turbine 36 in a compression machine comprising two compression stages of the same power, the total power being equal to that of the compressor 40. The compression machine comprises an intercooler cooling the gas between the compression stages. The arrangement thus obtained provides a power saving of 5.8 MW.

Une deuxième installation 140 destinée à la mise en oeuvre d'un deuxième procédé selon l'invention est représentée sur la figure 2.A second installation 140 intended for the implementation of a second method according to the invention is shown in the figure 2 .

Le deuxième procédé selon l'invention est analogue au premier procédé selon l'invention. Il diffère du premier procédé selon l'invention en ce qu'il comprend une étape de prélèvement, dans le courant de gaz naturel purifié comprimé 102, d'un courant de recirculation 142.The second method according to the invention is similar to the first method according to the invention. It differs from the first method according to the invention in that it comprises a step of withdrawing, from the compressed purified natural gas stream 102, a recirculation stream 142.

Le débit molaire du courant de recirculation 142 est avantageusement inférieur au débit molaire du courant de gaz naturel purifié comprimé 102 résiduel, après prélèvement du courant de recirculation 142, à son introduction dans l'unité de liquéfaction 22.The molar flow rate of the recirculation stream 142 is advantageously lower than the molar flow rate of the residual compressed purified natural gas stream 102, after collection of the recirculation stream 142, upon its introduction into the liquefaction unit 22.

Le courant de recirculation 142 présente une pression supérieure à 50 bars, notamment supérieure à 80 bars, par exemple égale à 90 bars. Il est introduit successivement dans le premier échangeur thermique 28, puis dans le deuxième échangeur thermique 30 pour y être refroidi à une température inférieure à -90°C, de préférence inférieure à -95°C et par exemple sensiblement égale à -95,4°C.The recirculation stream 142 has a pressure greater than 50 bars, in particular greater than 80 bars, for example equal to 90 bars. It is introduced successively into the first heat exchanger 28, then into the second heat exchanger 30 to be cooled there to a temperature lower than -90°C, preferably lower than -95°C and for example substantially equal to -95.4°C.

Puis, le courant de recirculation 142 est détendu à une pression inférieure à 50 bars, notamment inférieure à 30 bars, notamment égale à 28,7 bars et est introduit dans la colonne de séparation 34 entre le courant de recyclage 134 et le courant de reflux 92.Then, the recirculation stream 142 is expanded to a pressure lower than 50 bars, in particular lower than 30 bars, in particular equal to 28.7 bars and is introduced into the separation column 34 between the recycling stream 134 and the reflux stream 92.

Une troisième installation 150 destinée à la mise en oeuvre d'un troisième procédé selon l'invention est représentée sur la figure 3.A third installation 150 intended for the implementation of a third method according to the invention is shown in the figure 3 .

L'installation 150 diffère de la première installation 10 en ce qu'elle comporte un système 152 de collecte et de recompression des gaz d'évaporation formés dans le stockage 66.The installation 150 differs from the first installation 10 in that it comprises a system 152 for collecting and recompressing the evaporation gases formed in the storage 66.

Le système de collecte 152 comprend un ballon de protection 154, et un appareil de compression 156 comportant une pluralité d'étages de compression 158, espacés deux à deux par un refroidisseur 160.The collection system 152 comprises a protection balloon 154, and a compression apparatus 156 comprising a plurality of compression stages 158, spaced two by two by a cooler 160.

Un deuxième flux de gaz de flash 162 résultant de l'évaporation du gaz naturel liquéfié dans le stockage 66 est collecté en tête du stockage 66, puis est introduit dans l'appareil de compression 156 pour y être comprimé à une pression supérieure à 25 bars, notamment comprise entre 26 bars et 70 bars, par exemple égale à 60 bars.A second flash gas flow 162 resulting from the evaporation of the liquefied natural gas in the storage 66 is collected at the head of the storage 66, then is introduced into the compression apparatus 156 to be compressed there to a pressure greater than 25 bars, in particular between 26 bars and 70 bars, for example equal to 60 bars.

Le deuxième flux de gaz de flash comprimé 164 ainsi produit est séparé en le courant de combustible 20 et en le courant de recyclage 134, qui est réintroduit dans la colonne de séparation 34, après refroidissement dans les échangeurs thermiques 28, 30 et détente dans la vanne de détente 136.The second compressed flash gas stream 164 thus produced is separated into the fuel stream 20 and the recycle stream 134, which is reintroduced into the separation column 34, after cooling in the heat exchangers 28, 30 and expansion in the expansion valve 136.

Avantageusement, dans l'exemple représenté sur la figure 3, l'installation 150 est dépourvue d'organe de détente 60. Le gaz naturel liquéfié comprimé 120 issu de l'unité de liquéfaction 24 est directement introduit dans le stockage 66 de gaz naturel liquéfié et est flashé dans le stockage 66.Advantageously, in the example shown in the figure 3 , the installation 150 is devoid of an expansion member 60. The compressed liquefied natural gas 120 from the liquefaction unit 24 is directly introduced into the liquefied natural gas storage 66 and is flashed in the storage 66.

Une quatrième installation 170 destinée à la mise en oeuvre d'un quatrième procédé selon l'invention est représentée sur la figure 4.A fourth installation 170 intended for the implementation of a fourth method according to the invention is shown in the figure 4 .

La quatrième installation 170 diffère de la première installation 10 en ce que les stockage 66 sont équipés, comme la troisième installation 150, d'un système 152 de collecte des gaz d'évaporation.The fourth installation 170 differs from the first installation 10 in that the storages 66 are equipped, like the third installation 150, with a system 152 for collecting evaporation gases.

Lors de la mise en oeuvre du quatrième procédé selon l'invention, le premier flux de gaz de flash comprimé 132 et le deuxième flux de gaz de flash comprimé 164 sont mélangés, avant que le mélange ne soit séparé en le courant de combustible 20, et en le courant de recyclage 134.When implementing the fourth method according to the invention, the first compressed flash gas stream 132 and the second compressed flash gas stream 164 are mixed, before the mixture is separated into the fuel stream 20, and the recycle stream 134.

Comme précédemment, le courant de recyclage 134 est réintroduit dans la colonne de séparation 34 après passage dans les échangeurs thermiques 28, 30, puis détente dans la vanne de détente statique 136.As previously, the recycling stream 134 is reintroduced into the separation column 34 after passing through the heat exchangers 28, 30, then expansion in the static expansion valve 136.

Une cinquième installation 200 pour la mise en oeuvre d'un cinquième procédé selon l'invention est illustrée par la figure 5.A fifth installation 200 for implementing a fifth method according to the invention is illustrated by the figure 5 .

Le cinquième procédé diffère du deuxième procédé représenté sur la figure 2 en ce que la totalité du flux gazeux 84 récupéré du ballon 32 forme le courant d'alimentation de turbine 90 envoyé vers la turbine de détente dynamique 36, sans séparation.The fifth method differs from the second method shown in the figure 2 in that the entire gas flow 84 recovered from the balloon 32 forms the turbine feed stream 90 sent to the dynamic expansion turbine 36, without separation.

Grâce à l'invention qui vient d'être décrite, il est possible de maintenir une composition sensiblement constante du reflux de la colonne de séparation 34, ce qui évite l'effet boule de neige qui se produit lors de fluctuations de composition du courant de tête 98 extrait de la colonne de séparation 34, en l'absence d'apport du courant de recyclage 134.By means of the invention which has just been described, it is possible to maintain a substantially constant composition of the reflux from the separation column 34, which avoids the snowball effect which occurs during fluctuations in the composition of the overhead stream. 98 extracted from the separation column 34, in the absence of supply of the recycling stream 134.

Ce procédé est donc à la fois simple et efficace pour maintenir une teneur constante d'extraction en éthane, sans augmenter les coûts d'investissement ou les coûts d'opération.This process is therefore both simple and effective for maintaining a constant ethane extraction content, without increasing investment costs or operating costs.

La consommation énergétique du procédé est détaillée dans le tableau suivant. [Table 3] Etat de la technique Figure 1 Figure 2 Figure 3 Taux de récupération d'éthane (%) 97 97 97 97 Puissance compresseur 36 (MW) 48,105 49,175 49,261 49,397 Puissance compresseurs unité 26 (MW) 197,471 159,230 172,732 174,874 Puissance compresseur 72 (MW) 2,856 38,012 22,929 Pas de compresseur 72 Puissance compresseur 156 (MW) 3,129 3,127 3,129 25,978 Débit GNL produit au bac (ton/h) 778,486 778 ,702 778,616 778,482 Puissance totale consommée (MW) 251,563 249,544 248,051 250,250 Puissance spécifiée (kWh/ton) 323,1 320,5 318.8 321,5 The energy consumption of the process is detailed in the following table. <b>[Table 3]</b> State of the art Figure 1 Figure 2 Figure 3 Ethane recovery rate (%) 97 97 97 97 Compressor power 36 (MW) 48,105 49,175 49,261 49,397 Compressor power unit 26 (MW) 197,471 159,230 172,732 174,874 Compressor power 72 (MW) 2,856 38,012 22,929 No compressor 72 Compressor power 156 (MW) 3,129 3,127 3,129 25,978 LNG flow rate produced in the tank (ton/h) 778,486 778,702 778,616 778,482 Total power consumed (MW) 251,563 249,544 248,051 250,250 Specified power (kWh/ton) 323.1 320.5 318.8 321.5

Comme indiqué dans ce tableau, la puissance totale consommée en présence d'un reflux engendré à partir du courant de recyclage 134 diminue significativement la puissance consommée et la puissance spécifiée ramenée au début de gaz naturel liquéfié produit par l'installation.As shown in this table, the total power consumed in the presence of a reflux generated from the recycling stream 134 significantly decreases the power consumed and the specified power brought back to the start of liquefied natural gas produced by the installation.

Claims (15)

  1. A method for extracting ethane from a stream of initial natural gas (12), comprising the following steps:
    - cooling the stream of initial natural gas (12) in at least one first upstream heat exchanger (28), to form a stream of cooled natural gas (80);
    - separating the stream of cooled natural gas (80) into a liquid flow (82) and a gas flow (84);
    - expanding the liquid flow (82) and introducing at least one stream originating from the liquid flow (82) into a methane and C2+ hydrocarbon separation column (34) at a first level (N1);
    - forming a turbine feed stream (90) from the gas flow (84);
    - expanding the turbine feed stream (90) in a dynamic expansion turbine (36) and introducing the expanded stream (94) originating from the dynamic expansion turbine (36) into the separation column (34) at a second level (N2),
    - recovering and compressing at least a part of a head stream (98) originating from the separation column (34) to form a stream of compressed purified natural gas (102);
    - liquefying the stream of compressed purified natural gas (102) in a liquefier (24) to form a stream of pressurized liquefied natural gas (120);
    - flash expanding the stream of pressurized liquefied natural gas (120) and recovering the expanded liquefied natural gas (18) in storage (66);
    - recovering at least one flow of flash gas (126; 162) originating from the expansion of the stream of pressurized liquefied natural gas (120);
    - compressing the or each flow of flash gas (126; 162), characterized by the following steps: - introduction of a bottom stream rich in C2+ hydrocarbons recovered from the separation column into a fractionation column (48), and recovering a flow of ethane (14) from the fractionation column (48);
    - separating the flow of compressed flash gas (132; 164) into a fuel stream (20) and a recycle stream (134);
    - at least partially cooling and expanding the recycle stream (134), then introducing the cooled and expanded recycle stream at a head stage of the separation column (34).
  2. The method according to claim 1, wherein the methane content of the recycle stream (134) is greater than 90 mol%, in particular greater than 95 mol%.
  3. The method according to any one of claims 1 or 2, wherein the recycle stream (134) is introduced at a first stage starting from the top of the separation column (34).
  4. The method according to any one of the preceding claims, wherein the recycle stream (134) is introduced and cooled in the first heat exchanger (28) by heat exchange with the head stream (98) originating from the separation column (34).
  5. The method according to any one of the preceding claims, comprising separating the gas flow (84) into the turbine feed stream (90) introduced into the dynamic expansion turbine (36), and into a reflux stream (92) introduced into the separation column (34), lower than the recycle stream (134), after cooling the reflux stream in a second upstream heat exchanger (30) and static expansion of the reflux stream (92), the cooling of the recycle stream (134) optionally including passing the recycle stream (134) through the second heat exchanger (30).
  6. The method according to any one of the preceding claims, wherein the expansion of the recycle stream (134) comprises passing the recycle stream (134) through a static expansion valve (136).
  7. The method according to any one of the preceding claims, wherein at least a part of the compressed purified head natural gas (102) is placed in heat exchange with the flow of flash gas (126) in a downstream heat exchanger (68).
  8. The method according to any one of the preceding claims, comprising removing a recirculation stream (142) from the stream of compressed purified natural gas (102) upstream of the liquefaction unit (24), the recirculation stream (142) being cooled, expanded and introduced into the separation column (34).
  9. The method according to any one of the preceding claims, wherein the stream of pressurized liquefied natural gas (120) is expanded in a dynamic or static expander (60), then introduced into a flash drum (62), to be separated into the expanded liquefied natural gas (124) introduced into the storage (66), and a flow of flash gas (126).
  10. The method according to any one of the preceding claims, wherein at least one flow of flash gas (162) is formed in the storage (66) when the expanded liquefied natural gas is introduced into the storage (66).
  11. The method according to claim 10, wherein the stream of pressurized liquefied natural gas (120) is introduced directly into the storage (66), without passing through a flash drum (62).
  12. The method according to any one of the preceding claims, wherein the compression of the head stream (98) originating from the separation column (34) takes place in at least one first compressor (38) coupled to the dynamic expansion turbine (36) and then in a compression machine successively comprising a second compressor, a cooler for the gas compressed in the second compressor, and a third compressor, to form the stream of compressed purified natural gas.
  13. The method according to any one of the preceding claims, wherein a head stream (112) from the fractionation column (48) is cooled and partially condensed, then introduced into a head drum (56), the flow of ethane (14) being recovered at the head of the head drum (56), the bottom of the head drum (56) being reintroduced as reflux into the fractionation column (48).
  14. The method according to any one of the preceding claims, wherein the turbine feed stream (90) that is sent to the dynamic expansion turbine (36) without separation is formed from the entire gas flow (84) originating from the separation of the stream of cooled natural gas (80).
  15. An ethane extraction installation for extracting ethane from a stream of initial natural gas (12), comprising:
    - at least one first upstream heat exchanger (28) for cooling the stream of initial natural gas (12) to form a stream of cooled natural gas (80);
    - a separator for separating the stream of cooled natural gas (80) into a liquid flow (82) and a gas flow (84);
    - a liquid flow expander (82);
    - a methane and C2+ hydrocarbon separation column (34) and an assembly for introducing at least one stream originating from the expanded liquid flow (82) into the separation column (34), at a first level (N1);
    - an assembly for forming a turbine feed stream (90) from the gas flow (84);
    - a dynamic expansion turbine (36) for expanding the turbine feed stream (90) and an assembly for introducing the expanded stream (94) originating from the dynamic expansion turbine (36) into the separation column (34) at a second level (N2),
    - an assembly for recovering and compressing at least a part of a head stream (98) originating from the separation column (34) to form a stream of compressed purified natural gas (102);
    - a liquefier for liquefying the stream of compressed purified natural gas (102) capable of forming a stream of pressurized liquefied natural gas (120);
    - a flash expander of the stream of pressurized liquefied natural gas (120) and storage (66) for recovering the expanded liquefied natural gas (18);
    - an assembly for recovering at least one flow of flash gas (126; 162) originating from the expansion of the stream of pressurized liquefied natural gas (120);
    - an assembly for compressing the or each flow of flash gas (126; 162), characterized by: - a fractionation column, an assembly for introducing a C2+ hydrocarbon-rich bottom stream originating from the separation column into the fractionation column, and an assembly for recovering a flow of ethane from the fractionation column;
    - an assembly for separating the flow of compressed flash gas (132; 164) into a fuel stream (20) and a recycle stream (134);
    - an assembly for at least partially cooling and expanding the recycle stream (134), and for introducing the cooled and expanded recycle stream at a head stage of the separation column (34).
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020095246A2 (en) * 2018-11-08 2020-05-14 Saipem S.P.A. Process for the ri—liquefaction and simultaneous reduction of nitrogen content in the bog for self-frigerated absorption

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4435198A (en) * 1982-02-24 1984-03-06 Phillips Petroleum Company Separation of nitrogen from natural gas
US5615561A (en) * 1994-11-08 1997-04-01 Williams Field Services Company LNG production in cryogenic natural gas processing plants
DZ2535A1 (en) * 1997-06-20 2003-01-08 Exxon Production Research Co Advanced process for liquefying natural gas.
FR2817766B1 (en) 2000-12-13 2003-08-15 Technip Cie PROCESS AND PLANT FOR SEPARATING A GAS MIXTURE CONTAINING METHANE BY DISTILLATION, AND GASES OBTAINED BY THIS SEPARATION
US6526777B1 (en) * 2001-04-20 2003-03-04 Elcor Corporation LNG production in cryogenic natural gas processing plants
CN105074370B (en) * 2012-12-28 2017-04-19 林德工程北美股份有限公司 Integrated process for NGL (natural gas liquids recovery) and LNG (liquefaction of natural gas)

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020095246A2 (en) * 2018-11-08 2020-05-14 Saipem S.P.A. Process for the ri—liquefaction and simultaneous reduction of nitrogen content in the bog for self-frigerated absorption

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