WO2015110779A2 - Lng production process - Google Patents

Lng production process Download PDF

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Publication number
WO2015110779A2
WO2015110779A2 PCT/GB2015/000006 GB2015000006W WO2015110779A2 WO 2015110779 A2 WO2015110779 A2 WO 2015110779A2 GB 2015000006 W GB2015000006 W GB 2015000006W WO 2015110779 A2 WO2015110779 A2 WO 2015110779A2
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WO
WIPO (PCT)
Prior art keywords
stream
gas
heat exchanger
bar
mpa
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Application number
PCT/GB2015/000006
Other languages
French (fr)
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WO2015110779A3 (en
Inventor
Anthony Dwight Maunder
Geoffrey Frederick Skinner
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Gasconsult Limited
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Publication date
Application filed by Gasconsult Limited filed Critical Gasconsult Limited
Publication of WO2015110779A2 publication Critical patent/WO2015110779A2/en
Publication of WO2015110779A3 publication Critical patent/WO2015110779A3/en

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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
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/04—Internal refrigeration with work-producing gas expansion loop
    • F25J2270/06—Internal refrigeration with work-producing gas expansion loop with multiple gas expansion loops

Definitions

  • This invention relates to a process for liquefying a methane-rich gas and more particularly but not exclusively relates to a method of producing liquefied natural gas (LNG) comprising a gas expander and a liquid pressure reduction machine or turbine.
  • LNG liquefied natural gas
  • a market is emerging for small-scale liquefaction of natural gas for local use, for instance as a transportation fuel, especially for heavy goods vehicles.
  • step 2 3) dividing the gas stream from step 2 into at least first and second parts, 4) passing said first part through a gas expansion machine or turbine having an outlet pressure of from 3 bar to 20 bar (0.3 MPa to 2MPa) and an outlet temperature of from -70 to -130°C,
  • step 5) passing the outlet stream from step 4) successively through a second heat exchanger and the first heat exchanger, and
  • step 3) the second part from step 3) is cooled in the second heat exchanger to a temperature in the range -70 to -130°C, at which it is substantially condensed,
  • the methane-rich gas stream in Step 1 ) typically has a temperature of from -10 to 60°C.
  • the process optionally includes the steps of 10) passing the outlet vapour stream from step 9) successively through the second heat exchanger and first heat exchanger, and optionally
  • the present invention describes a natural gas liquefaction process comprising a step of expanding a methane rich gas in an expansion machine or turbine and a second step of reducing the pressure of a methane rich liquid through a pressure reduction machine or turbine, thereby materially reducing the compression power required per unit of LNG produced compared with a process comprising a gas expansion machine or turbine alone.
  • the resulting mixture (2) is cooled by at least 10°C in a passage of a first heat exchanger (A). For instance, if the first heat exchanger inlet temperature is 42°C, the corresponding outlet from the exchanger would be around -7°C, if the inlet temperature is 0°C the outlet would be around -20°C and if -10°C the outlet would be around -24°C. Thus as the feed plus recycle temperature drops, so does the duty of the first heat exchanger.
  • the cooled mixture (3) is then divided.
  • One part (4) is admitted to an expansion machine or turbine (B), having outlet pressure typically between 3 bar and 20 bar (0.3 MPa and 2 MPa) and outlet temperature typically between -80 and -110°C.
  • This stream (5) is reheated in a first cold passage of a second heat exchanger (C) and then further reheated (6) in a first cold passage of heat exchanger (A).
  • the reheated stream (7) having a temperature close to the temperature of the inlet gas stream to the first heat exchanger (2) is mixed with compressed flash gas (21 ) described below and flows (8) to a recycle compressor (D).
  • the compressor outlet stream (9) is cooled (10) in a recycle cooler (E) to form the above mentioned recycle gas.
  • the feed gas (1 ) may be introduced by mixing with stream (8) or at an intermediate pressure in compressor (D);
  • the recycle gas (10) may be cooled separately from the feed gas (1) in a second hot passage in heat exchanger (A) and then divided, one part flowing to expansion turbine (B) and another part being combined with the cooled feed gas (3);
  • any part or all of the feed and/or compressor suction and/or recycle streams may be cooled separately, or after mixing (2), typically to a temperature of between 10 to -20°C before entering heat exchanger A, by means of an absorption chiller or a mechanical refrigeration cycle or a combination thereof.
  • Another part (11) of the above mentioned cooled mixture (3) is cooled in a passage of second heat exchanger (C), emerging as a condensed liquid or cooled supercritical fluid at a temperature (12) typically between -80°C and - 110°C.
  • This stream flows to a pressure reduction machine or turbine (F), emerging (13) at a pressure between 1 bar and 10 bar (0.1 MPa and 1.0 MPa).
  • This two-phase stream flows to vapour/liquid separator (G).
  • the vapour (15) is reheated in a second cold passage of heat exchanger (C) and then is further reheated (16) in a second cold passage of heat exchanger (A) emerging (17) at a temperature close to the temperature of the mixture of feed gas and recycle gas (2).
  • Stream (17) may optionally be discharged from the process (18), for instance for use as a fuel, or compressed all or in part (19) in a flash gas compressor (H).
  • the compressed stream (20) is cooled (21) in a flash gas cooler (I) and mixed with recycle gas (7) as described above.
  • the liquid phase (14) may comprise the liquefied methane rich product from the process.
  • This liquefied methane stream may be further depressurised in a valve or expansion machine or turbine, for instance into an atmospheric pressure storage tank.
  • the resulting low pressure flash gas may be reheated in a third cold passage of heat exchanger (C) and then further reheated in a third cold passage of heat exchanger (A) emerging at a temperature close to the temperature of the mixture of feed gas and recycle gas (2).
  • the aforementioned first and second heat exchangers may be combined into a single heat exchange unit such as a brazed aluminium plate-fin core construction, such single heat exchange unit containing internal streams corresponding to streams 3), 6), 11) and 16) in Fig. 1 with a stream
  • a typical set of values of pressure and temperature for streams in Figure 1 are as below.
  • any part or all of the feed (1), recycle gas (10), mixture thereof (2) and/or compressor suction streams may be cooled by means of external refrigeration system, such as an absorption refrigeration cycle or a mechanical refrigeration cycle.
  • external refrigeration system such as an absorption refrigeration cycle or a mechanical refrigeration cycle.
  • the heat requirement of the refrigeration system may be supplied by the exhaust heat of a gas engine or a gas turbine, such gas engines or turbines typically being used for supplying power to the process compressors.
  • the said cooling of either feed and/or recycle streams and/or compressor suction streams by means of an external refrigeration system may be combined with removal of carbon dioxide and/or other impurities from the feed gas.

Abstract

A process comprising: cooling a methane rich gas stream in a first heat exchanger, dividing the cooled stream into at least two parts, passing the first part into a gas expander, reheating the expander outlet stream in a first cold passage of a second heat exchanger and in a first cold passage of the first exchanger, at least partially compressing and recycling said reheated expander outlet stream, cooling the second part in the second heat exchanger to form a condensed stream, passing said condensed stream to a pressure reduction turbine, separating the outlet stream from the pressure reduction turbine into liquid and vapour fractions, reheating the vapour fraction in a second cold passage of the second heat exchanger and in a second cold passage of the first exchanger, at least partially compressing and recycling said reheated vapour fraction, collecting the liquid fraction for use as product.

Description

Description
LNG Production Process Field of the Invention
This invention relates to a process for liquefying a methane-rich gas and more particularly but not exclusively relates to a method of producing liquefied natural gas (LNG) comprising a gas expander and a liquid pressure reduction machine or turbine.
Background to the Invention
A market is emerging for small-scale liquefaction of natural gas for local use, for instance as a transportation fuel, especially for heavy goods vehicles.
As these small liquefaction units are usually required to operate without the presence of an attendant, liquefaction processes requiring evaporation and storage of liquid hydrocarbon refrigerants are not very suitable, particularly on grounds of safety.
Consequently, liquefaction processes based on use of methane or nitrogen gas expanders have been preferred for these small unmanned liquefiers. However such gas expander liquefaction processes based on use of a methane or nitrogen expander generally have a low thermal efficiency, requiring substantially more compression power per unit of LNG produced when compared with large base-load LNG plants.
Summary of the Invention According to the present invention there is provided a process for the production of a methane-rich liquid which comprises
1 ) providing a methane-rich gas stream having a pressure of from 40 bar to 120 bar (4 MPa to 12 MPa),
2) cooling said gas stream in a first heat exchanger by at least 10°C,
3) dividing the gas stream from step 2 into at least first and second parts, 4) passing said first part through a gas expansion machine or turbine having an outlet pressure of from 3 bar to 20 bar (0.3 MPa to 2MPa) and an outlet temperature of from -70 to -130°C,
5) passing the outlet stream from step 4) successively through a second heat exchanger and the first heat exchanger, and
6) at least partially recycling said stream from step 5), wherein:
7) the second part from step 3) is cooled in the second heat exchanger to a temperature in the range -70 to -130°C, at which it is substantially condensed,
8) passing the liquid fraction of the cooled gas stream from the second heat exchanger through a pressure reduction machine or turbine having an outlet pressure in the range 1 bar to 20 bar (0.1 MPa to 2 MPa),
9) separating the two phase stream from said pressure reduction machine or turbine into a methane-rich liquid product and a vapour. The methane-rich gas stream in Step 1 ) typically has a temperature of from -10 to 60°C.
The process optionally includes the steps of 10) passing the outlet vapour stream from step 9) successively through the second heat exchanger and first heat exchanger, and optionally
1 1 ) at least partially recycling said stream from step 10). The present invention describes a natural gas liquefaction process comprising a step of expanding a methane rich gas in an expansion machine or turbine and a second step of reducing the pressure of a methane rich liquid through a pressure reduction machine or turbine, thereby materially reducing the compression power required per unit of LNG produced compared with a process comprising a gas expansion machine or turbine alone.
Small scale LNG production units frequently are required to deliver the liquefied product at above atmospheric pressure, and accordingly the invention described herein produces liquid typically at a pressure of around 3 bar (0.3MPa). The invention may however be adapted to produce LNG product at nearer to atmospheric pressure, as outlined in the Description below. Where pressures are referred to, these are absolute values. Description of Preferred Embodiments Reference is made to the accompanying Figure!
A feed stream of methane rich gas (1 ) with acid gases and water vapour substantially removed, a pressure typically between 40 bar and 120 bar (4 MPa and 12 MPa) and a temperature generally between -20 and 60°C, typically between 10 and 50°C, is mixed with a recycle gas (10) described below. The resulting mixture (2) is cooled by at least 10°C in a passage of a first heat exchanger (A). For instance, if the first heat exchanger inlet temperature is 42°C, the corresponding outlet from the exchanger would be around -7°C, if the inlet temperature is 0°C the outlet would be around -20°C and if -10°C the outlet would be around -24°C. Thus as the feed plus recycle temperature drops, so does the duty of the first heat exchanger.
The cooled mixture (3) is then divided. One part (4) is admitted to an expansion machine or turbine (B), having outlet pressure typically between 3 bar and 20 bar (0.3 MPa and 2 MPa) and outlet temperature typically between -80 and -110°C. This stream (5) is reheated in a first cold passage of a second heat exchanger (C) and then further reheated (6) in a first cold passage of heat exchanger (A). The reheated stream (7) having a temperature close to the temperature of the inlet gas stream to the first heat exchanger (2) is mixed with compressed flash gas (21 ) described below and flows (8) to a recycle compressor (D). The compressor outlet stream (9) is cooled (10) in a recycle cooler (E) to form the above mentioned recycle gas.
Some variations of the above described flow scheme are foreseen, as instances:
1. the feed gas (1 ) may be introduced by mixing with stream (8) or at an intermediate pressure in compressor (D);
2. the recycle gas (10) may be cooled separately from the feed gas (1) in a second hot passage in heat exchanger (A) and then divided, one part flowing to expansion turbine (B) and another part being combined with the cooled feed gas (3);
3. if the feed gas (1 ) has a significant content of C3+ hydrocarbon, this may in part be removed by a separator typically provided downstream of heat exchanger (A); 4. where a external demand exists for medium pressure fuel gas, this may be extracted from streams (7) or (8);
5. any part or all of the feed and/or compressor suction and/or recycle streams may be cooled separately, or after mixing (2), typically to a temperature of between 10 to -20°C before entering heat exchanger A, by means of an absorption chiller or a mechanical refrigeration cycle or a combination thereof.
Another part (11) of the above mentioned cooled mixture (3) is cooled in a passage of second heat exchanger (C), emerging as a condensed liquid or cooled supercritical fluid at a temperature (12) typically between -80°C and - 110°C. This stream flows to a pressure reduction machine or turbine (F), emerging (13) at a pressure between 1 bar and 10 bar (0.1 MPa and 1.0 MPa).
This two-phase stream flows to vapour/liquid separator (G). The vapour (15) is reheated in a second cold passage of heat exchanger (C) and then is further reheated (16) in a second cold passage of heat exchanger (A) emerging (17) at a temperature close to the temperature of the mixture of feed gas and recycle gas (2). Stream (17) may optionally be discharged from the process (18), for instance for use as a fuel, or compressed all or in part (19) in a flash gas compressor (H). The compressed stream (20) is cooled (21) in a flash gas cooler (I) and mixed with recycle gas (7) as described above. The liquid phase (14) may comprise the liquefied methane rich product from the process. This liquefied methane stream may be further depressurised in a valve or expansion machine or turbine, for instance into an atmospheric pressure storage tank. The resulting low pressure flash gas may be reheated in a third cold passage of heat exchanger (C) and then further reheated in a third cold passage of heat exchanger (A) emerging at a temperature close to the temperature of the mixture of feed gas and recycle gas (2).
The aforementioned first and second heat exchangers may be combined into a single heat exchange unit such as a brazed aluminium plate-fin core construction, such single heat exchange unit containing internal streams corresponding to streams 3), 6), 11) and 16) in Fig. 1 with a stream
corresponding to stream 4) taken out of the heat exchange unit at an intermediate point as also shown in Fig.1.
A typical set of values of pressure and temperature for streams in Figure 1 are as below.
Name 1 2 3 4 5 6
Pressure (bar) 65.0 65.0 64.6 64.6 12.0 11.9 Temperature (C) 45.0 42.5 -6.9 -6.9 -90.6 -32.9
Name 7 8 9 10 11 12
Pressure (bar) 11.7 11.7 65.3 65.0 64.6 64.4 Temperature (C) 39.5 39.8 80.3 42.0 -6.9 -88.6
Name 13 14 15 16 17 18
Pressure (bar) 3.00 3.00 3.00 2.98 2.95 2.95 Temperature (C) -147.1 147.1 147.1 -32.9 39.5 39.5
Name 19 20 21
Pressure (bar) 2.95 11.8 11.7
Temperature (C) 39.5 98.0 42.0
Any part or all of the feed (1), recycle gas (10), mixture thereof (2) and/or compressor suction streams may be cooled by means of external refrigeration system, such as an absorption refrigeration cycle or a mechanical refrigeration cycle. In the case of an absorption refrigeration cycle, the heat requirement of the refrigeration system may be supplied by the exhaust heat of a gas engine or a gas turbine, such gas engines or turbines typically being used for supplying power to the process compressors. The said cooling of either feed and/or recycle streams and/or compressor suction streams by means of an external refrigeration system may be combined with removal of carbon dioxide and/or other impurities from the feed gas.

Claims

Claims
1 . A process for the production of a methane-rich liquid which comprises 1) providing a methane-rich gas stream (1) having a pressure of from 40 bar to 120 bar (4 MPa to 12 MPa),
2) cooling said gas stream (1 ) in a first heat exchanger (A) by at least 10°C, 3) dividing the gas stream (3) from step 2) into at least first (4) and second (11) parts,
4) passing said first part (4) through a gas expansion machine or turbine (B) having an outlet pressure of from 3 bar to 20 bar (0.3 MPa to 2MPa) and an outlet temperature of from -70 to -130°C,
5) passing the outlet stream (5) from step 4) successively through a second heat exchanger (C) and the first heat exchanger (A), and 6) at least partially recycling said stream (7) from step 5), wherein:
7) the second part (1 1) from step 3) is cooled in the second heat exchanger (C) to a temperature in the range -70 to -130°C, at which it is substantially condensed, 8) passing the liquid fraction of the cooled gas stream (12) from the second heat exchanger through a pressure reduction machine or turbine (F) having an outlet pressure in the range 1 bar to 20 bar (0.1 MPa to 2 MPa), 9) separating the two phase stream (13) from said pressure reduction machine or turbine into the methane-rich liquid product (1 ) and a vapour (15).
2. A process as claimed in Claim 1 in which the temperature of the gas stream (1) in step 1) is in the range from -10 to 60°C.
3. A process as claimed in Claim 1 or Claim 2 in which the stream (7) from step 5) is compressed and mixed with the stream from step 1 ).
4. A process as claimed in Claim 1 or Claim 2 in which the stream (7) from step 5) is mixed with a gas stream that is compressed to provide the stream of step 1).
5. A process as claimed in Claim 1 or Claim 2 in which the stream from step 5) is compressed and then cooled separately from the gas stream in step 2) in the first heat exchanger and then divided into two parts; a first part passing to the gas expansion machine or turbine of step 4) and a second part being combined with said second part of step 3).
6. A process as claimed in any preceding claim in which the gas stream of step 1) comprises a significant content of Cs+ hydrocarbon which is removed from the gas stream downstream of the first heat exchanger.
7. A process as claimed in any preceding claim in which at least a part of the gas stream (7) from step 5) is used as fuel gas.
8. A process as claimed in Claim 7 in which the gas stream (7) from step 5) is discharged from the process and/or compressed and recycled.
9. A process as claimed in any preceding claim in which the vapour fraction (15) from step 9) is passed successively through the second heat exchanger (C) and the first heat exchanger (A).
10. A process as claimed in any preceding claim in which part of the vapour stream (15) from step 9) is used as fuel gas.
1 1. A process as claimed in any preceding claim in which the said first exchanger (A) cold outlet temperature is in the range of 0°C to -30°C.
12. A process as claimed in any preceding claim in which the said second exchanger cold outlet temperature is in the range of -80°C to -110°C.
13. A process as claimed in any preceding claim in which the said gas expansion machine or turbine (B) has outlet pressure in the range 3 bar to 20 bar (0.3 MPa to 2 MPa) and an outlet temperature of from -80°C to -110°C.
1 . A process as claimed in any preceding claim in which any part or all of the feed and/or compressor suction and/or recycle streams is cooled by means of an external refrigeration cycle.
15. A process as claimed in any preceding claim in which the heat requirement for an absorption refrigeration system is supplied by gas engine or gas turbine exhaust heat, such gas engines or turbines which may be used for supplying power to the process compressors.
16. A process as claimed in any preceding claim wherein such cooling of either feed and/or compressor suction and/or recycle streams is combined with removal of carbon dioxide and/or other impurities.
PCT/GB2015/000006 2014-01-22 2015-01-12 Lng production process WO2015110779A2 (en)

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GB1401073.0A GB2522421B (en) 2014-01-22 2014-01-22 LNG production process

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WO2017162566A1 (en) 2016-03-21 2017-09-28 Shell Internationale Research Maatschappij B.V. Method and system for liquefying a natural gas feed stream
CZ308591B6 (en) * 2019-10-04 2020-12-16 Siad Macchine Impianti S.P.A. Natural gas processing equipment

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GB2539955A (en) * 2015-07-03 2017-01-04 Frederick Skinner Geoffrey Process for producing liquefied natural gas
GB2541464A (en) * 2015-08-21 2017-02-22 Frederick Skinner Geoffrey Process for producing Liquefied natural gas
CN105674686B (en) * 2016-01-15 2018-09-14 成都赛普瑞兴科技有限公司 A kind of liquefied method and device of swell refrigeration high methane gas
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IT202100020159A1 (en) 2021-07-28 2023-01-28 Saipem Spa BOG RECONDENSATION PROCESS THROUGH REFRIGERATION OF CRYOGENIC LIQUIDS COGENERATED IN THE LNG VAPORIZATION PROCESS

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Publication number Priority date Publication date Assignee Title
WO2017162566A1 (en) 2016-03-21 2017-09-28 Shell Internationale Research Maatschappij B.V. Method and system for liquefying a natural gas feed stream
CZ308591B6 (en) * 2019-10-04 2020-12-16 Siad Macchine Impianti S.P.A. Natural gas processing equipment

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