Enhanced NGL recovery utilizing refrigeration and reflux from LNG plants

• US 6,401,486 B1
• Filed: 12/08/2000
• Issued: 06/11/2002
• Est. Priority Date: 05/18/2000
• Status: Expired due to Term

• Current Assignee: Conocophillips Company (ConocoPhillips)
• Original Assignee: Phillips Petroleum Company (ConocoPhillips)
• Inventors: Yao, Jame, Elliot, Douglas G., Lee, Rong-Jwyn, Chen, Jong Juh
• Primary Examiner(s): DOERRLER, WILLIAM CHARLES
• Application Number:
  US09/733,533
• Time in Patent Office: 550 Days
• Field of Search: 626/11, 626/12, 626/13, 626/14, 626/19, 626/20, 626/30, 626/23
• US Class Current: 62/630
• CPC Class Codes: F25J 1/0022 Hydrocarbons, e.g. natural gas
• CPC Class Codes: F25J 1/0035 by gas expansion with extraction of work
• CPC Class Codes: F25J 1/004 by flash gas recovery F25J1/0267 takes precedence
• CPC Class Codes: F25J 1/0052 by vaporising a liquid refrigerant stream
• CPC Class Codes: F25J 1/0055 originating from an incorporated cascade
• CPC Class Codes: F25J 1/0087 Propane; Propylene
• CPC Class Codes: F25J 1/0212 as a single flow MCR cycle
• CPC Class Codes: F25J 1/0216 using a C3 pre-cooling cycle
• CPC Class Codes: F25J 1/0219 in combination with an internal quasi-closed refrigeration loop, e.g. using a deep flash recycle loop
• CPC Class Codes: F25J 1/0231 for the working-up of the hydrocarbon feed, e.g. reinjection of heavier hydrocarbons into the liquefied gas
• CPC Class Codes: F25J 1/0238 Purification or treatment step is integrated within one refrigeration cycle only, i.e. the same or single refrigeration cycle provides feed gas cooling (if present) and overhead gas cooling
• CPC Class Codes: F25J 1/0262 Details of the cold heat exchange system constructional details F25J5/00, construction of cold-exchangers in general F28
• CPC Class Codes: F25J 1/0265 comprising cores associated exclusively with the cooling of a refrigerant stream, e.g. for auto-refrigeration or economizer
• CPC Class Codes: F25J 1/0267 using flash gas as heat sink
• CPC Class Codes: F25J 1/0283 Gas turbine as the prime mechanical driver
• CPC Class Codes: F25J 1/0291 Refrigerant compression by combined gas compression and liquid pumping
• CPC Class Codes: F25J 1/0292 Refrigerant compression by cold or cryogenic suction of the refrigerant gas
• CPC Class Codes: F25J 1/0294 Multiple compressor casings/strings in parallel, e.g. split arrangement
• CPC Class Codes: F25J 2200/02 in a single pressure main column system
• CPC Class Codes: F25J 2200/04 in a dual pressure main column system
• CPC Class Codes: F25J 2200/50 : using multiple (re-)boiler-condensers at different heights of the column
• CPC Class Codes: F25J 2200/72 : Refluxing the column with at least a part of the totally condensed overhead gas
• CPC Class Codes: F25J 2200/74 : Refluxing the column with at least a part of the partially condensed overhead gas
• CPC Class Codes: F25J 2200/76 : Refluxing the column with condensed overhead gas being cycled in a quasi-closed loop refrigeration cycle
• CPC Class Codes: F25J 2200/78 : Refluxing the column with a liquid stream originating from an upstream or downstream fractionator column
• CPC Class Codes: F25J 2205/04 : in the feed line, i.e. upstream of the fractionation step
• CPC Class Codes: F25J 2210/06 : Splitting of the feed stream, e.g. for treating or cooling in different ways
• CPC Class Codes: F25J 2215/62 : Ethane or ethylene
• CPC Class Codes: F25J 2220/60 : Separating impurities from natural gas, e.g. mercury, cyclic hydrocarbons
• CPC Class Codes: F25J 2230/08 : Cold compressor, i.e. suction of the gas at cryogenic temperature and generally without afterstage-cooler
• CPC Class Codes: F25J 2230/60 : the fluid being hydrocarbons or a mixture of hydrocarbons
• CPC Class Codes: F25J 2240/02 : Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream
• CPC Class Codes: F25J 2260/02 : Integration in an installation for exchanging heat, e.g. for waste heat recovery
• CPC Class Codes: F25J 2270/12 : External refrigeration with liquid vaporising loop
• CPC Class Codes: F25J 2270/60 : Closed external refrigeration cycle with single component refrigerant [SCR], e.g. C1-, C2- or C3-hydrocarbons
• CPC Class Codes: F25J 2270/66 : Closed external refrigeration cycle with multi component refrigerant [MCR], e.g. mixture of hydrocarbons
• CPC Class Codes: F25J 2270/88 : Quasi-closed internal refrigeration or heat pump cycle, if not otherwise provided
• CPC Class Codes: F25J 2280/02 : Control in general, load changes, different modes ("runs"), measurements
• CPC Class Codes: F25J 2290/12 : Particular process parameters like pressure, temperature, ratios
• CPC Class Codes: F25J 2290/32 : Details on header or distribution passages of heat exchangers, e.g. of reboiler-condenser or plate heat exchangers
• CPC Class Codes: F25J 3/0209 : Natural gas or substitute natural gas
• CPC Class Codes: F25J 3/0233 : separation of CnHm with 1 carbon atom or more
• CPC Class Codes: F25J 3/0238 : separation of CnHm with 2 carbon atoms or more
• CPC Class Codes: F25J 3/0242 : separation of CnHm with 3 carbon atoms or more

Abstract

The present invention is directed to methods and apparatus for improving the recovery of the relatively less volatile components from a methane-rich gas feed under pressure to produce an NGL product while, at the same time, separately recovering the relatively more volatile components which are liquified to produce an LNG product. The methods of the present invention improve separation and efficiency within the NGL recovery column while maintaining column pressure to achieve efficient and economical utilization of the available mechanical refrigeration. The methods of the present invention are particularly useful for removing cyclohexane, benzene and other hazardous, heavy hydrocarbons from a gas feed. The benefits of the present invention are achieved by the introduction to the NGL recovery column of an enhanced liquid reflux lean on the NGL components. Further advantages can be achieved by thermally linking a side reboiler for the NGL recovery column with the overhead condenser for the NGL purifying column. Using the methods of the present invention, recoveries of propane and heavier components in excess of 95% are readily achievable.

Claims

1. A process for recovering the relatively less volatile components from a methane-rich gas feed under pressure to produce an NGL product while rejecting the relatively more volatile components which are subsequently liquified to produce LNG, comprising the steps of:

cooling at least a portion of a gas feed in one or more heat exchangers by means of a mechanical refrigeration cycle;

introducing said gas feed into an NGL recovery column at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components and a first liquid stream primarily comprising relatively less volatile components;

introducing said first liquid stream into an NGL purifying column at one or more feed stages to produce an NGL product stream comprising desirable less volatile components from the bottom and a second gas stream comprising more volatile components from the overhead of said NGL purifying column;

cooling said second gas stream and thereafter introducing said cooled, second gas stream to the top portion of said NGL recovery column as an overhead reflux to enhance recovery of desirable less volatile components; and

liquefying said first gas stream to produce a pressurized LNG stream, wherein at least one mechanical refrigeration cycle is used in the cooling of said second gas stream and in the liquefying of said first gas stream.

2. The process of claim 1 wherein the step of cooling and introducing said gas feed into the NGL recovery column further comprises:

separating said cooled gas feed into a cooled vapor portion and a cooled liquid portion comprising condensed components, if any;

dividing said cooled vapor portion into a first vapor portion and a second vapor portion;

further cooling said first vapor portion to substantial condensation and thereafter introducing said substantially condensed first vapor portion into an upper portion of said NGL recovery column as a middle reflux; and

introducing the remaining portion of said cooled gas feed comprising said second vapor portion and said cooled liquid portion into said NGL recovery column at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components rich in methane and a first liquid stream primarily comprising relatively less volatile components.

3. The process of claim 1 or 2 wherein said mechanical refrigeration cycle includes a refrigerant selected from the group consisting of single-component refrigerants and multi-component refrigerants.

4. The process of claim 1 or 2 wherein a refrigeration stream is withdrawn from said NGL recovery column to provide at least a portion of the refrigeration in said first cooling step.

5. The process of claim 4 wherein said refrigeration stream is partially vaporized as a result of said cooling and further comprising separating said partially vaporized refrigeration stream into a first gas phase which is re-introduced into said NGL recovery column and a first liquid phase.

6. The process of claim 1 or 2 wherein said second gas stream is cooled to partial condensation with the condensed liquid being introduced to a top portion of said NGL purifying column as an overhead reflux and the remaining vapor being introduced to a top portion of said NGL recovery column as an overhead reflux after further cooling.

7. The process of claim 6 wherein said second gas stream is cooled by a refrigeration stream withdrawn from said NGL recovery column.

8. A process for recovering the relatively less volatile components from a methane-rich gas feed under pressure to produce an NGL product while rejecting the relatively more volatile components which are subsequently liquified to produce LNG, comprising the steps of:

cooling at least a portion of a gas feed in one or more heat exchangers by means of a mechanical refrigeration cycle;

introducing said gas feed into an NGL recovery column at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components and a first liquid stream primarily comprising relatively less volatile components;

introducing said first liquid stream into an NGL purifying column at one or more feed stages to produce an NGL product stream comprising desirable less volatile components from the bottom and a second gas stream comprising more volatile components from the overhead of said NGL purifying column;

cooling said second gas stream and thereafter introducing said cooled, second gas stream to the top portion of said NGL recovery column as an overhead reflux to enhance recovery of desirable less volatile components;

liquefying said first gas stream to produce a pressurized LNG stream;

expanding said pressurized LNG stream in one or more expanding stages to produce an LNG stream suitable for storage; and

producing a portion of said overhead reflux from a portion of the flashed vapor generated in one or more of said expanding stages.

9. A process for recovering the relatively less volatile components from a methane-rich gas feed under pressure to produce an NGL product while rejecting the relatively more volatile components which are subsequently liquified to produce LNG, comprising the steps of:

cooling at least a portion of a gas feed in one or more heat exchangers by means of a mechanical refrigeration cycle;

introducing said gas feed into an NGL recovery column at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components and a first liquid stream primarily comprising relatively less volatile components;

introducing said first liquid stream into an NGL purifying column at one or more feed stages to produce an NGL product stream comprising desirable less volatile components from the bottom and a second gas stream comprising more volatile components from the overhead of said NGL purifying column;

compressing and then cooling said second gas stream;

introducing said compressed, cooled, second gas stream to the top portion of said NGL recovery column as an overhead reflux to enhance recovery of desirable less volatile components; and

liquefying said first gas stream to produce a pressurized LNG stream.

10. A process for recovering the relatively less volatile components from a methane-rich gas feed to produce an NGL product while rejecting the relatively more volatile components which are subsequently liquified to produce LNG, comprising the steps of:

cooling at least a portion of a gas feed in one or more heat exchangers by means of a mechanical refrigeration cycle;

further cooling a portion of said cooled gas feed with mechanical refrigeration to substantial condensation and thereafter introducing said substantially condensed gas feed into the top of an NGL recovery column as an overhead reflux;

introducing the remaining portion of said cooled gas feed into said NGL recovery column at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components rich in methane and a first liquid stream primarily comprising relatively less volatile components;

introducing said first liquid stream into an NGL purifying column at one or more feed stages to produce an NGL product stream comprising desirable less volatile components from the bottom and a second gas stream comprising more volatile components from the overhead of said NGL purifying column; and

liquefying said first gas stream utilizing at least one mechanical refrigeration cycle to produce a pressurized LNG stream.

11. The process of claim 10 wherein the step of cooling and introducing said gas feed into the NGL recovery column further comprises:

separating said cooled gas feed into a cooled vapor portion and a cooled liquid portion comprising condensed components, if any;

dividing said cooled vapor portion into a first vapor portion and a second vapor portion;

further cooling said first vapor portion with mechanical refrigeration to substantial condensation and thereafter introducing said substantially condensed first vapor portion into an upper portion of said NGL recovery column as an overhead reflux; and

introducing the remaining portion of said cooled gas feed comprising said second vapor portion and said cooled liquid portion into said NGL recovery column at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components rich in methane and a first liquid stream primarily comprising relatively less volatile components.

12. The process of claim 10 or 11 wherein a refrigeration stream is withdrawn from said NGL recovery column to provide at least a portion of the refrigeration in said first cooling step.

13. The process of claim 12 wherein said refrigeration stream is partially vaporized as a result of said cooling and further comprising separating said partially vaporized refrigeration stream into a first gas phase which is re-introduced into said NGL recovery column and a first liquid phase.

14. The process of claim 10 wherein said mechanical refrigeration cycle includes a refrigerant selected from the group consisting of single-component refrigerants and multi-component refrigerants.

15. A process for recovering the relatively less volatile components from a methane-rich gas feed to produce an NGL product while rejecting the relatively more volatile components which are subsequently liquified to produce LNG, comprising the steps of:

cooling at least a portion of a gas feed in one or more heat exchangers by means of a mechanical refrigeration cycle;

separating said cooled gas feed into a cooled vapor portion and a cooled liquid portion comprising condensed components, if any;

dividing said cooled vapor portion into a first vapor portion and a second vapor portion;

further cooling said first vapor portion with mechanical refrigeration to substantial condensation and thereafter introducing said substantially condensed first vapor portion into an NGL recovery column as a reflux;

introducing the remaining portion of said cooled gas feed comprising said second vapor portion and said cooled liquid portion into said NGL recovery column at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components rich in methane and a first liquid stream primarily comprising relatively less volatile components;

introducing said first liquid stream into an NGL purifying column at one or more feed stages to produce an NGL product comprising desirable less volatile components from the bottom and a second gas stream comprising more volatile components from the overhead of said NGL purifying column;

liquefying said first gas stream utilizing at least one mechanical refrigeration cycle to produce a pressurized LNG stream; and

introducing at least a portion of said pressurized LNG stream to the top of said NGL recovery column as an overhead reflux to enhance recovery of relatively less volatile components.

16. A process for recovering the relatively less volatile components from a methane-rich gas feed under pressure to produce an NGL product while rejecting the relatively more volatile components which are subsequently liquified to produce LNG, comprising the steps of:

cooling at least a portion of a gas feed in one or more heat exchangers by means of a mechanical refrigeration cycle;

introducing said cooled gas feed into an NGL recovery column at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components and a first liquid stream primarily comprising relatively less volatile components;

introducing said first liquid stream into an NGL purifying column at one or more feed stages to produce an NGL product stream comprising desirable less volatile components from the bottom and a second gas stream comprising more volatile components from the overhead of said NGL purifying column;

liquefying said first gas stream to produce a pressurized LNG stream;

expanding said pressurized LNG stream in one or more stages to a lower pressure to produce an LNG stream suitable for storage and at least one flashed vapor stream; and

compressing and cooling at least a portion of said flashed vapor stream to substantial condensation and thereafter introducing said substantially condensed, flashed vapor stream to a top portion of said NGL recovery column as an overhead reflux to enhance recovery of desirable less volatile components.

17. The process of claim 16 wherein the step of cooling and introducing said gas feed into the NGL recovery column further comprises:

separating said cooled gas feed into a cooled vapor portion and a cooled liquid portion comprising condensed components, if any;

dividing said cooled vapor portion into a first vapor portion and a second vapor portion;

further cooling said vapor portion to substantial condensation and thereafter introducing said substantially condensed first vapor portion into an upper portion of said NGL recovery column as a reflux; and

introducing the remaining portion of said cooled gas feed comprising said second vapor portion and said cooled liquid portion into said NGL recovery column at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components rich in methane and a first liquid stream primarily comprising relatively less volatile components.

18. The process of claim 17 wherein said mechanical refrigeration cycle includes a refrigerant selected from the group consisting of single-component refrigerants and multi-component refrigerants.

19. The process of claim 17 wherein a refrigeration stream is withdrawn from said NGL recovery column to provide at least a portion of the refrigeration in said first cooling step.

20. The process of claim 19 wherein said refrigeration stream is partially vaporized as a result of said cooling and further comprising separating said partially vaporized refrigeration stream into a first gas phase which is re-introduced into said NGL recovery column and a first liquid phase.

21. The process of claim 17 wherein said second gas stream is cooled to partial condensation with the condensed liquid being introduced to a top portion of said NGL purifying column as an overhead reflux and the remaining vapor being introduced to a top portion of said NGL recovery column as an overhead reflux after further cooling.

22. The process of claim 21 wherein said second gas stream is cooled by a refrigeration stream withdrawn from said NGL recovery column.

23. Apparatus for recovering the relatively less volatile components from a methane-rich gas feed under pressure to produce an NGL product while rejecting the relatively more volatile components which are subsequently liquified to produce LNG, comprising:

a heat exchanger for cooling at least a portion of a gas feed by means of a mechanical refrigeration cycle;

an NGL recovery column for receiving said cooled gas feed at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components and a first liquid stream primarily comprising relatively less volatile components;

an NGL purifying column for receiving said first liquid stream at one or more feed stages to produce an NGL product stream comprising desirable less volatile components from the bottom and a second gas stream comprising more volatile components from the overhead of said NGL purifying column;

a heat exchanger for cooling said second gas stream with mechanical refrigeration;

means for introducing said cooled, second gas stream to the top portion of said NGL recovery column as an overhead reflux to enhance recovery of desirable less volatile components; and

means for liquefying said first gas stream utilizing at least one mechanical refrigeration cycle to produce a pressurized LNG stream, wherein said heat exchangers can be the same or different.

24. The apparatus of claim 23 further comprising:

a first separator for separating said cooled gas feed into a cooled vapor portion and a cooled liquid portion comprising condensed components, if any;

means for dividing said cooled vapor portion into a first vapor portion and a second vapor portion;

a heat exchanger for further cooling said first vapor portion to substantial condensation, wherein said heat exchanger can be the same or different from said other heat exchangers;

means for introducing said substantially condensed, cooled, first vapor portion into said NGL recovery column as a reflux; and

means for introducing said second vapor portion and said cooled liquid portion into said NGL recovery column at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components rich in methane and a first liquid stream primarily comprising relatively less volatile components.

25. The apparatus of claim 23 wherein said mechanical refrigeration cycle includes a refrigerant selected from the group consisting of single-component refrigerants and multi-component refrigerants.

26. The apparatus of claim 23 further comprising means for expanding said pressurized NGL stream in one or more stages to a lower pressure to produce an NGL stream suitable for storage and means for directing at least a portion of the flashed vapor generated in one or more expanding stages to said NGL recovery column as said overhead reflux.

27. Apparatus for recovering the relatively less volatile components from a methane-rich gas feed under pressure to produce an NGL product while rejecting the relatively more volatile components which are subsequently liquified to produce LNG, comprising:

a heat exchanger for cooling at least a portion of a gas feed by means of a mechanical refrigeration cycle;

an NGL recovery column for receiving said cooled gas feed at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components and a first liquid stream primarily comprising relatively less volatile components;

an NGL purifying column for receiving said first liquid stream at one or more feed stages to produce an NGL product stream comprising desirable less volatile components from the bottom and a second gas stream comprising more volatile components from the overhead of said NGL purifying column;

a compressor for compressing said second gas stream prior to cooling to substantial condensation;

a heat exchanger for cooling said second gas stream;

means for introducing said cooled, second gas stream to the top portion of said NGL recovery column as an overhead reflux to enhance recovery of desirable less volatile components; and

means for liquefying said first gas stream to produce a pressurized LNG stream, wherein said heat exchangers can be the same or different.

28. Apparatus for recovering the relatively less volatile components from a methane-rich gas feed to produce an NGL product while rejecting the relatively more volatile components which are subsequently liquified to produce LNG, comprising:

a heat exchanger for cooling at least a portion of a gas feed by means of a mechanical refrigeration cycle;

means for further cooling a portion of said cooled gas feed with mechanical refrigeration to substantial condensation;

an NGL recovery column;

means for introducing said condensed gas feed into the top of said NGL recovery column as an overhead reflux;

means for introducing the remaining portion of said cooled gas feed into said NGL recovery column at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components rich in methane and a first liquid stream primarily comprising relatively less volatile components;

an NGL purifying column for receiving said first liquid stream at one or more feed stages to produce an NGL product stream comprising desirable less volatile components from the bottom and a second gas stream comprising more volatile components from the overhead of said NGL purifying column; and

means for liquefying said first gas stream utilizing at least one mechanical refrigeration cycle to produce a pressurized LNG stream.

29. The apparatus of claim 28 further comprising:

a first separator for separating said cooled gas feed into a cooled vapor portion and a cooled liquid portion comprising condensed components, if any;

means for dividing said cooled vapor portion into a first vapor portion and a second vapor portion;

means for further cooling said first vapor portion with mechanical refrigeration to substantial condensation;

means for introducing said substantially condensed, cooled, first vapor portion into said NGL recovery column as an overhead reflux; and

means for introducing said second vapor portion and said cooled liquid portion into said NGL recovery column at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components rich in methane and a first liquid stream primarily comprising relatively less volatile components.

30. Apparatus for recovering the relatively less volatile components from a methane-rich gas feed to produce an NGL product while rejecting the relatively more volatile components which are subsequently liquified to produce LNG, comprising:

one or more heat exchangers for cooling at least a portion of a gas feed by means of mechanical refrigeration cycle;

an NGL recovery column for receiving said cooled gas feed at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components and a first liquid stream primarily comprising relatively less volatile components;

an NGL purifying column for receiving said first liquid stream at one or more feed stages to produce an NGL product comprising desirable less volatile components from the bottom and a second gas stream comprising more volatile components from the overhead of said NGL purifying column;

means for liquifying said first gas stream to produce a pressurized LNG stream; and

means for introducing at least a portion of said pressurized LNG stream to the top of said NGL recovery column as an overhead reflux to enhance recovery of relatively less volatile components.

31. The apparatus of claim 30 further comprising:

a first separator for separating said cooled gas feed into a cooled vapor portion and a cooled liquid portion comprising condensed components, if any;

means for dividing said cooled vapor portion into a first vapor portion and a second vapor portion;

means for further cooling said first vapor portion to substantial condensation;

means for introducing said substantially condensed, cooled, first vapor portion into said NGL recovery column as a middle reflux; and

means for introducing said second vapor portion and said cooled liquid portion into said NGL recovery column at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components rich in methane and a first liquid stream primarily comprising relatively less volatile components.

32. Apparatus for recovering the relatively less volatile components from a methane-rich gas feed under pressure to produce an NGL product while rejecting the relatively more volatile components which are subsequently liquified to produce LNG, comprising:

a first heat exchanger for cooling at least a portion of a gas feed by means of a mechanical refrigeration cycle;

an NGL recovery column for receiving said cooled gas feed at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components and a first liquid stream primarily comprising relatively less volatile components;

an NGL purifying column for receiving said first liquid stream at one or more feed stages to produce an NGL product stream comprising desirable less volatile components from the bottom and a second gas stream comprising more volatile components from the overhead of said NGL purifying column;

means for liquifying said first gas stream to produce a pressurized LNG stream;

means for expanding said pressurized LNG stream in one or more stages to a lower pressure to produce an LNG stream suitable for storage and at least one flashed vapor stream;

means for compressing and cooling at least a portion of said flashed vapor stream to substantial condensation; and

means for introducing said substantially condensed, flashed vapor stream to a top portion of said NGL recovery column as an overhead reflux to enhance recovery of desirable less volatile components.

33. The apparatus of claim 32 wherein said mechanical refrigeration cycle includes a refrigerant selected from the group consisting of single-component refrigerants and multi-component refrigerants.

34. A process for recovering the relatively less volatile components from a methane-rich gas feed under pressure to produce an NGL product while rejecting the relatively more volatile components which are subsequently liquified to produce LNG, comprising the steps of:

cooling at least a portion of a gas feed in one or more heat exchangers by means of a mechanical refrigeration cycle;

introducing said gas feed into an NGL recovery column at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components and a first liquid stream primarily comprising relatively less volatile components;

introducing said first liquid stream into an NGL purifying column at one or more feed stages to produce an NGL product stream comprising desirable less volatile components from the bottom and a second gas stream comprising more volatile components from the overhead of said NGL purifying column;

cooling said second gas stream and thereafter introducing said cooled, second gas stream to the top portion of said NGL recovery column as an overhead reflux to enhance recovery of desirable less volatile components; and

introducing said first gas stream directly to a next cooling step for liquefying said first gas stream to produce a pressurized LNG stream.

35. The process of claim 34 further comprising compressing said first gas stream prior to introduction to said next cooling step.

36. The process of claim 34 wherein the step of cooling and introducing said gas feed into the NGL recovery column further comprises:

separating said cooled gas feed into a cooled vapor portion and a cooled liquid portion comprising condensed components, if any;

dividing said cooled vapor portion into a first vapor portion and a second vapor portion;

further cooling said first vapor portion to substantial condensation and thereafter introducing said substantially condensed first vapor portion into an upper portion of said NGL recovery column as a reflux; and

introducing the remaining portion of said cooled gas feed comprising said second vapor portion and said cooled liquid portion into said NGL recovery column at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components rich in methane and a first liquid stream primarily comprising relatively less volatile components.

37. The process of claim 34 or 36 wherein said mechanical refrigeration cycle includes a refrigerant selected from the group consisting of single-component refrigerants and multi-component refrigerants.

38. The process of claim 34 or 36 wherein a refrigeration stream is withdrawn from said NGL recovery column to provide at least a portion of the refrigeration in said first cooling step.

39. The process of claim 38 wherein said refrigeration stream is partially vaporized as a result of said cooling and further comprising separating said partially vaporized refrigeration stream into a first gas phase which is re-introduced into said NGL recovery column and a first liquid phase.

40. The process of claim 34 or 36 wherein said second gas stream is cooled to partial condensation with the condensed liquid being introduced to a top portion of said NGL purifying column as an overhead reflux and the remaining vapor being introduced to a top portion of said NGL recovery column as an overhead reflux after further cooling.

41. The process of claim 40 wherein said second gas stream is cooled by a refrigeration stream withdrawn from said NGL recovery column.

42. Apparatus for recovering the relatively less volatile components from a methane-rich gas feed under pressure to produce an NGL product while rejecting the relatively more volatile components which are subsequently liquified to produce LNG, comprising:

a heat exchanger for cooling at least a portion of a gas feed by means of a mechanical refrigeration cycle;

an NGL recovery column for receiving said cooled gas feed at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components and a first liquid stream primarily comprising relatively less volatile components;

an NGL purifying column for receiving said first liquid stream at one or more feed stages to produce an NGL product stream comprising desirable less volatile components from the bottom and a second gas stream comprising more volatile components from the overhead of said NGL purifying column;

a heat exchanger for cooling said second gas stream;

means for introducing said cooled, second gas stream to the top portion of said NGL recovery column as an overhead reflux to enhance recovery of desirable less volatile components; and

a heat exchanger for liquefying said first gas stream to produce a pressurized LNG stream, said first gas stream being directly received by said heat exchanger without prior heating and wherein said heat exchangers can be the same or different.

43. The apparatus of claim 42 further comprising a compressor for compressing said first gas stream prior to liquefaction in said heat exchanger.

44. The apparatus of claim 42 further comprising:

a first separator for separating said cooled gas feed into a cooled vapor portion and a cooled liquid portion comprising condensed components, if any;

means for dividing said cooled vapor portion into a first vapor portion and a second vapor portion;

a heat exchanger for further cooling said first vapor portion to substantial condensation wherein said heat exchanger can be the same or different from said other heat exchangers;

means for introducing said substantially condensed, cooled, first vapor portion into said NGL recovery column as a reflux; and

means for introducing said second vapor portion and said cooled liquid portion into said NGL recovery column at one or more feed stages for separation into a first gas stream primarily comprising relatively more volatile components rich in methane and a first liquid stream primarily comprising relatively less volatile components.

45. The apparatus of claim 42 wherein said mechanical refrigeration cycle includes a refrigerant selected from the group consisting of single-component refrigerants and multi-component refrigerants.

46. The apparatus of claim 42 further comprising means for expanding said pressurized NGL stream in one or more stages to a lower pressure to produce an NGL stream suitable for storage and means for directing at least a portion of the flashed vapor generated in one or more expanding stages to said NGL recovery column as said overhead reflux.

47. The apparatus of claim 42 further comprising a compressor for compressing said second gas stream prior to cooling to substantial condensation.