GB2582815A - Process for producing liquefied natural gas - Google Patents

Process for producing liquefied natural gas Download PDF

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Publication number
GB2582815A
GB2582815A GB1904818.0A GB201904818A GB2582815A GB 2582815 A GB2582815 A GB 2582815A GB 201904818 A GB201904818 A GB 201904818A GB 2582815 A GB2582815 A GB 2582815A
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United Kingdom
Prior art keywords
stream
gas
heat exchanger
outlet
expander
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GB1904818.0A
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GB201904818D0 (en
Inventor
Frederick Skinner Geoffrey
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Gasconsult Ltd
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Gasconsult Ltd
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Priority to GB1904818.0A priority Critical patent/GB2582815A/en
Publication of GB201904818D0 publication Critical patent/GB201904818D0/en
Publication of GB2582815A publication Critical patent/GB2582815A/en
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • 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"
    • F25J1/0035—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 gas expansion with extraction of work
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • 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"
    • F25J1/0035—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 gas expansion with extraction of work
    • F25J1/0037—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 gas expansion with extraction of work of a return stream
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0201—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using only internal refrigeration means, i.e. without external refrigeration
    • F25J1/0202—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using only internal refrigeration means, i.e. without external refrigeration in a quasi-closed internal refrigeration loop
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0244—Operation; Control and regulation; Instrumentation
    • F25J1/0254—Operation; Control and regulation; Instrumentation controlling particular process parameter, e.g. pressure, temperature
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/06—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation
    • F25J3/063—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation characterised by the separated product stream
    • F25J3/064—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation characterised by the separated product stream separation of CnHm with 2 carbon atoms or more
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/62—Ethane or ethylene
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2220/00—Processes or apparatus involving steps for the removal of impurities
    • F25J2220/60—Separating impurities from natural gas, e.g. mercury, cyclic hydrocarbons
    • F25J2220/64—Separating heavy hydrocarbons, e.g. NGL, LPG, C4+ hydrocarbons or heavy condensates in general
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/02—Recycle of a stream in general, e.g. a by-pass stream

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Separation By Low-Temperature Treatments (AREA)

Abstract

A process for producing LNG and liquid ethane comprising: providing streams of feed and recycle gas, 1, 3, at 40 to 120 bar, mixing the feed gas with a first part 4 of the recycle gas; passing the resulting mixture to a first gas expander C; cooling the first expander outlet stream 7 in a first heat exchanger D to form a mixture of vapour and a condensed liquid 9; passing the cooled first expander outlet stream into a first separator E provided with a reboiler F, said first separator having an ethane-rich outlet liquid product stream 9 and a vapour stream 10; reheating and compressing said vapour stream to form a first part 21 of the recycle gas, cooling a second part of the recycle gas 14, then passing it into a second gas expander J wherein it is partly liquefied; separating the outlet stream 16 from said second gas expander into a methane-rich liquid stream 17 and a second vapour stream 18; depressurising the methane-rich liquid stream to form LNG product 19, and returning the second vapour stream to form a second part of the recycle gas.

Description

Description
Process for Producing Liquefied Natural Gas
Field of the Invention
The present invention relates to a method for producing liquid methane and liquid ethane from natural gas
Background
WO 201 2/1 722 81 discloses a process for liquefying natural gas or other methane-rich gas comprising -cooling feed natural gas, generally at a pressure of 40 to 100 bar, to a temperature of -50 to -80°C by means of a heat exchanger and a first gas expander, the heat exchanger receiving the feed natural gas and having an outlet temperature higher than the outlet temperature of the expander; -reheating the expander outlet stream in a first cold passage of said heat exchanger to just below the inlet temperature of the feed natural gas to said heat exchanger, compressing and recycling, -passing all or part of the cold outlet stream from said heat exchanger into a second expander in which it is partly liquefied; -separating the outlet stream of said second expander into vapour and liquid fractions; -collecting the liquid fraction for use as LNG product, -reheating the vapour fraction in a second cold side passage of said heat exchanger to just below the inlet temperature of the feed natural gas to said heat exchanger; -recycling the said reheated vapour fraction after compression in part to the said first expander and in part to the said heat exchanger.
Many sources of natural gas contain up to 10 mol% or more of ethane. In the production of liquefied natural gas the separation of a significant part of the ethane content of such gases may be necessary in order to moderate the ethane content of the LNG product. In other circumstances there may be a commercial or economic incentive for recovery of ethane from the natural gas prior to liquefaction. In current practice such recovery usually would require a separate ethane recovery operation upstream of the LNG production facility.
Summary of the Invention
According to the invention there is provided a process for producing liquid methane and liquid ethane according to Claim 1.
The invention comprises a modification of methane expander based LNG processes, and particularly of the dual methane expander process described in WO 2012/172281. In this modification, a mixture of the feed gas with a methane-rich recycle gas is admitted to the first gas expander. The outlet stream from said first gas expander is then cooled by means of a heat exchanger, in which the desired quantity of ethane is condensed. The outlet stream from said heat exchanger flows to a separator device -a reboiled absorber -from which an ethane rich stream is withdrawn as the liquid product.
Application of the invention typically allows separation and recovery of a high proportion of the ethane content of a wide range of natural gases with only a moderate additional of equipment -said heat exchanger and said reboiled absorber column -to the dual expander liquefaction process described in WO 2012/172281.
Optionally: -the mixture of feed gas and part of the recycle gas may be cooled in a second heat exchanger before admission to the first gas expander, so as to increase the amount of condensate formed in said first heat exchanger.
-said second heat exchanger may supply heat to the reboiler of said reboiled absorber column; -a gas/liquid separator may be interposed between the outlet of said first expander and said reboiled absorber, the liquid outlet stream from said gas/liquid separator forming the liquid feed to said reboiled absorber, thereby facilitating operation of said reboiled absorber at a lower pressure than the outlet pressure of said first gas expander, or at a higher pressure than the outlet pressure of said first gas expander by means of a pump.
Description of Preferred Embodiment
The invention will be further described with reference to the accompanying drawing, in which Figure 1 represents a flow diagram illustrating a process in accordance with the invention.
The exact flow sheet will depend upon the feed gas specification, but will generally contain these basic elements. Where pressures are stated anywhere in this application as "bar", these are bar absolute.
The feed natural gas (1) is passed through a pretreatment stage (A) in which components such as acid gases, water vapour and mercury may be removed to produce a pre-treated gas (2).
The pre-treated gas is mixed with a first part (4) of a recycle gas (3), described below, comprising typically 20% to 60% of the total recycle gas flow on a molar basis. In the resulting mixture the ratio of the molar flow of the recycle gas to the molar flow of feed gas is typically in the range of 1.5 to 2.5. The resulting mixture (5) flows to a first gas expander C at a pressure of between 40 and 120 bar, more typically between 60 and 100 bar.
The outlet from expander C (7) has a pressure of 3 to 50 bar, and more typically between 10 to 30 bar. Stream 7 is further cooled in first heat exchanger D (stream 8) to a temperature of -80 to -120 degC, such that a condensate containing ethane is formed.
The partially condensed stream (8) flows to the top of absorber column E containing mass transfer packing or trays, and provided with reboiler F. The heat input for reboiler F may optionally be provided by heat exchanger B. The liquid outlet (9) from column E is the ethane-rich product stream from the process.
The vapour (10) from column E is reheated in a first cold passage of heat exchanger D (Stream 11) and then first cold passage (12) of second heat exchanger G. The reheated vapour (12) compressed in compressor H (13) and then cooled in cooler I to form a first constituent of the aforementioned recycle gas (3).
A second part (14) of the recycle gas (3) is cooled to a temperature of between -20 degC and -80 degC (15) in a hot passage of heat exchanger G and is then passed into a second gas expander J, from which the outlet (16) is at a pressure of between 5 and 20 bar, such that a liquid phase consisting mainly of methane is formed. Stream 16 flows to separator K, having a methane rich liquid outlet (17) and a vapour outlet (18). Stream 17 may be depressurised in a valve or turbine L to produce an LNG product (19).
The vapour (18) from separator K is typically reheated in a second cold passage of heat exchanger D (20) and then further reheated in a second cold passage of heat exchanger G. The reheated vapour (21) compressed in compressor H to a pressure of 40 to 120 bar (13) and then cooled in cooler to form a second constituent of the aforementioned recycle gas (3).
Optionally the mixture (5) of feed gas and recycle gas is cooled in a third heat exchanger (B) before passing to first gas expander (C).
Optionally the heat requirement of reboiler F is supplied at least in part by said third heat exchanger (B).
An example of the process is given in the following Table 1.
Table 1 Stream
No. 2 3 4 5 6 7 8 9 10 11 mol 0.005 0.122 0.122 0.085 0.085 0.085 0.085 0.000 0.086 0.086 fraction N2 CH4 0.940 0.875 0.875 0.895 0.895 0.895 0.895 0.050 0.908 0.908 C2H6 0.050 0.004 0.004 0.018 0.018 0.018 0.018 0.843 0.007 0.007 C3H8 0.004 0.000 0.000 0.001 0.001 0.001 0.001 0.075 0.000 0.000 C4H10 n- 0.001 0.000 0.000 0.000 0.000 0.000 0.000 0.012 0.000 0.000 C4H10 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.009 0.000 0.000 C5H12 n- 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.005 0.000 0.000 C5H12 n- 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.005 0.000 0.000 C6H14 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.002 0.000 0.000 °C 30.0 30.0 30.0 29.9 11.0 -65.5 -101.6 -4.6 -101.3 -78.6 bar abs 90.1 90.1 90.1 90.1 89.8 25.0 24.7 24.8 24.6 24.5 kmol/h 398.9 2244.0 854.8 1254.0 1254.0 1254.0 1254.0 17.8 1236.0 1236.0 vapour fraction 1.00 1.00 1.00 1.00 1.00 1.00 0.84 0.00 1.00 1.00 Stream No. 12 13 14 15 16 17 18 19 20 21 mol 0.0858 0.1217 0.122 0.122 0.122 0.027 0.174 0.027 0.174 0.174 fraction N2 CH4 0.908 0.875 0.875 0.875 0.875 0.963 0.826 0.963 0.826 0.826 C2H6 0.007 0.004 0.004 0.004 0.004 0.010 0.000 0.010 0.000 0.000 C3H8 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 C4H10 n- 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 C4H10 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 C5H12 n- 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 C5H12 n- 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 C6H14 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 °C 16.8 60.4 30.0 -66.1 -128.3 -128.9 -128.9 146.0 -78.6 16.8 bar abs 24.3 91.1 90.1 89.8 10.0 9.7 9.7 3.5 9.4 9.1 kmol/h 1236.0 2244.0 1389.0 1389.0 1389.0 491.8 897.3 491.8 897.3 897.3 vapour fraction 1.00 1.00 1.00 1.00 0.64 0.00 1.00 0.15 1.00 1.00

Claims (3)

  1. Claims 1 A process for liquefying methane-rich gases comprising - providing a stream (2) of feed methane-rich gas containing ethane at a pressure of from 40 to 120 bar; - providing a stream (3) of methane-rich recycle gas at a pressure of from to 120 bar; - dividing the recycle gas into first (4) and second (14) parts; - mixing the feed gas with the first part (4) of the recycle gas; -passing the resulting mixture (5) to a first gas expander (C) having a outlet pressure of between 3 bar and 50 bar; - passing the first expander outlet stream (7) to a first heat exchanger (D) and cooling said stream (7) to a temperature of between -80 degC and -120 degC to form a mixture (8) of vapour and a condensed liquid containing ethane; - passing said mixture (8) into a first separator (E) provided with a reboiler (F), said first separator having an outlet ethane-rich liquid stream (9) and an outlet vapour stream (10); - removing the separated liquid stream (9) from the process as ethane-rich product; - reheating said vapour stream (10) in a first cold passage (11) of first heat exchanger (D) and a first cold passage (12) of a second heat exchanger (G); - compressing said vapour stream (12) after said reheating to a pressure of from 40 to 120 bar to form a first constituent of the above-said recycle gas (3); - passing the second part (14) of the recycle gas to a hot passage of second heat exchanger (G) and cooling the second part of the recycle gas to a temperature of between -20 degC and -80 degC; - passing said cooled second part of the recycle gas (15) into a second gas expander (J) having an outlet pressure of between 5 bar and 20 bar to form a second gas expander outlet stream comprising a mixture of vapour and a condensed liquid containing methane; - passing the second expander outlet stream (16) into a second separator (K) having an outlet liquid stream containing methane (17) and a vapour stream (18); - depressurizing said outlet stream (17) to form a liquid methane stream (19) which is removed from the process as LNG product; - reheating said vapour stream (18) in a second cold passage of first heat exchanger (D) and a second cold passage of second heat exchanger (G); and then - compressing the resulting vapour stream (21) to a pressure of from 40 to 120 bar to form a second constituent of the above-said recycle gas (3).
  2. 2 A process according to Claim 1 in which the mixture (5) of feed gas and recycle gas is cooled in a third heat exchanger (B) before passing to first gas expander (C).
  3. 3 A process according to Claim 2 in which the heat requirement of reboiler F is supplied at least in part by said third heat exchanger (B).
GB1904818.0A 2019-04-05 2019-04-05 Process for producing liquefied natural gas Withdrawn GB2582815A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2596297A (en) * 2020-06-22 2021-12-29 Equinor Us Operations Llc Hydrocarbon gas recovery methods

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5390499A (en) * 1993-10-27 1995-02-21 Liquid Carbonic Corporation Process to increase natural gas methane content
WO2012172281A2 (en) * 2011-06-15 2012-12-20 Gasconsult Limited Process for liquefaction of natural gas

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5390499A (en) * 1993-10-27 1995-02-21 Liquid Carbonic Corporation Process to increase natural gas methane content
WO2012172281A2 (en) * 2011-06-15 2012-12-20 Gasconsult Limited Process for liquefaction of natural gas

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2596297A (en) * 2020-06-22 2021-12-29 Equinor Us Operations Llc Hydrocarbon gas recovery methods
US11725154B2 (en) 2020-06-22 2023-08-15 Energy And Environmental Research Center Foundation Hydrocarbon gas recovery methods

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