Integrated high pressure NGL recovery in the production of liquefied natural gas

• US 6,662,589 B1
• Filed: 04/16/2003
• Issued: 12/16/2003
• Est. Priority Date: 04/16/2003
• Status: Expired due to Term

• Current Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Original Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Inventors: Roberts, Mark Julian, Rowles, Howard Charles
• Primary Examiner(s): Bennett, Henry
• Assistant Examiner(s): Drake, Malik N.
• Application Number:
  US10/414,735
• Time in Patent Office: 244 Days
• Field of Search: 626/18, 626/20, 626/24, 626/25
• US Class Current: 62/425
• CPC Class Codes: F25J 1/0022 Hydrocarbons, e.g. natural gas
• CPC Class Codes: F25J 1/005 by expansion of a gaseous refrigerant stream with extraction of work
• CPC Class Codes: F25J 1/0052 by vaporising a liquid refrigerant stream
• CPC Class Codes: F25J 1/0072 Nitrogen
• CPC Class Codes: F25J 1/0087 Propane; Propylene
• CPC Class Codes: F25J 1/0217 as at least a three level refrigeration cascade with at least one MCR cycle
• CPC Class Codes: F25J 1/0218 with one or more SCR cycles, e.g. with a C3 pre-cooling cycle
• 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 1/0241 wherein the overhead cooling comprises providing reflux for a fractionation step
• CPC Class Codes: F25J 1/0271 Inter-connecting multiple cold equipments within or downstream of the cold box
• CPC Class Codes: F25J 1/0292 Refrigerant compression by cold or cryogenic suction of the refrigerant gas
• CPC Class Codes: F25J 2200/02 in a single pressure main column system
• CPC Class Codes: F25J 2200/74 Refluxing the column with at least a part of the partially condensed overhead gas
• CPC Class Codes: F25J 2200/92 Details relating to the feed point
• CPC Class Codes: F25J 2205/30 using a washing, e.g. "scrubbing" or bubble column for purification purposes
• CPC Class Codes: F25J 2205/50 using absorption, i.e. with selective solvents or lean oil, heavier CnHm and including generally a regeneration step for the solvent or lean oil
• CPC Class Codes: F25J 2215/64 Propane or propylene
• CPC Class Codes: F25J 2215/66 Butane or mixed butanes
• CPC Class Codes: F25J 2220/62 Separating low boiling components, e.g. He, H2, N2, Air
• CPC Class Codes: F25J 2245/02 Recycle of a stream in general, e.g. a by-pass stream
• 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 2290/50 : Arrangement of multiple equipments fulfilling the same process step in parallel
• 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 3/0242 : separation of CnHm with 3 carbon atoms or more
• CPC Class Codes: F25J 3/0247 : separation of CnHm with 4 carbon atoms or more

Abstract

Process for the recovery of components heavier than methane from natural gas, wherein the process comprises (a) cooling a natural gas feed to provide a cooled natural gas feed and introducing the cooled natural gas feed into an absorber column at a first location therein; (b) withdrawing from the absorber column a first overhead vapor stream depleted in components heavier than methane and a bottoms stream enriched in components heavier than methane; (c) introducing a methane-rich reflux stream at a second location in the absorber column above the first location; (d) separating the bottoms stream into a stream enriched in methane and one or more streams enriched in components heavier than ethane; and (e) introducing an absorber liquid comprising components heavier than ethane into the absorber column at a location between the first location and the second location.

Claims

1. A process for the recovery of components heavier than methane from natural gas, wherein the process comprises

(a) cooling a natural gas feed to provide a cooled natural gas feed and introducing the cooled natural gas feed into an absorber column at a first location therein;

(b) withdrawing from the absorber column a first overhead vapor stream depleted in components heavier than methane and a bottoms stream enriched in components heavier than methane;

(c) introducing a methane-rich reflux stream at a second location in the absorber column above the first location;

(d) separating the bottoms stream into a stream enriched in methane and one or more streams enriched in components heavier than ethane; and

(e) introducing an absorber liquid comprising components heavier than ethane into the absorber column at a location between the first location and the second location.

2. The process of claim 1 which further comprises combining all or a portion of any of the one or more streams enriched in components heavier than ethane in (d) with the methane-rich reflux stream in (c).

3. The process of claim 1 which further comprises withdrawing all or a portion of any of the one or more streams enriched in components heavier than ethane in (d) as a product stream.

4. The process of claim 1 wherein the natural gas feed is at a pressure above 600 psia.

5. The process of claim 1 wherein the absorber liquid comprises components obtained from any of the one or more streams enriched in components heavier than ethane in (d).

6. The process of claim 1 wherein the absorber liquid contains greater than 50 mole % of hydrocarbons containing five or more carbon atoms.

7. The process of claim 1 wherein the absorber liquid contains greater than 50 mole % of hydrocarbons containing four or more carbon atoms.

8. The process of claim 1 wherein the absorber liquid contains greater than 50 mole % of hydrocarbons containing three or more carbon atoms.

9. The process of claim 1 wherein the absorber liquid is cooled by indirect heat exchange with a vaporizing recirculating refrigerant prior to being introduced into the absorber column.

10. The process of claim 9 wherein the vaporizing recirculating refrigerant is propane.

11. The process of claim 1 which further comprises cooling and partially condensing the first overhead vapor stream to form a two-phase stream, separating the two-phase stream to provide a second overhead vapor stream and the methane-rich reflux stream in (c).

12. The process of claim 11 wherein the second overhead vapor stream is recovered as a product stream depleted in components heavier than methane.

13. The process of claim 11 which further comprises combining all or a portion of any of the one or more streams enriched in methane in (d) with the first overhead vapor stream prior to separating the two-phase stream.

14. The process of claim 11 wherein refrigeration for cooling and partially condensing the first overhead vapor stream is provided by indirect heat exchange with a vaporizing refrigerant.

15. The process of claim 14 wherein the vaporizing refrigerant is a multi-component refrigerant.

16. The process of claim 11 which further comprises cooling, condensing, and subcooling the second overhead vapor stream to provide a liquefied natural gas product.

17. The process of claim 16 wherein all or a portion of the refrigeration required to cool, condense, and subcool the second overhead vapor stream is provided by indirect heat exchange with a vaporizing refrigerant.

18. The process of claim 17 wherein the vaporizing refrigerant is a multi-component refrigerant.

19. The process of claim 16 wherein all or a portion of the refrigeration required to cool, condense, and subcool the second overhead vapor stream is provided by indirect heat exchange with a cold refrigerant provided by work expansion of a compressed refrigerant comprising nitrogen.

20. The process of claim 16 which further comprises cooling, condensing, and subcooling the stream enriched in methane in (d) to provide a liquefied methane-rich product.

21. The process of claim 20 wherein all or a portion of the refrigeration required to cool, condense, and subcool the stream enriched in methane is provided by indirect heat exchange with the vaporizing refrigerant.

22. The process of claim 20 wherein all or a portion of the refrigeration required to cool, condense, and subcool the stream enriched in methane is provided by indirect heat exchange with a cold refrigerant provided by work expansion of a compressed refrigerant comprising nitrogen.

23. The process of claim 20 wherein the liquefied methane-rich product is combined with the liquefied natural gas product.

24. The process of claim 1 wherein all or a portion of the cooling of the natural gas feed is provided by indirect heat exchange with one or more streams of vaporizing refrigerant.

25. The process of claim 24 wherein the vaporizing refrigerant is propane.

26. The process of claim 1 which further comprises providing a portion of the cooling of the natural gas feed by indirect heat exchange with a liquid bottoms stream from the absorber column, thereby providing a vaporized bottoms stream, and introducing the vaporized bottoms stream into the absorber column to provide boilup vapor.

27. A system for recovery of components heavier than methane from natural gas, wherein the system comprises

(a) an absorber column for separating natural gas into a methane-rich stream and a stream enriched in components heavier than methane;

(b) cooling means to cool a natural gas feed to provide a cooled natural gas feed and means for introducing the cooled natural gas feed into the absorber column at a first location therein;

(c) means for withdrawing from the absorber column a first overhead vapor stream depleted in components heavier than methane and a bottoms stream enriched in components heavier than methane;

(d) means for introducing a methane-rich reflux stream at a second location in the absorber column above the first location;

(e) separation means for separating the bottoms stream into a stream enriched in methane and one or more streams enriched in components heavier than ethane; and

(f) means for introducing an absorber liquid comprising components heavier than ethane into the absorber column at a location between the first location and the second location.

28. The system of claim 27 which further comprises means for cooling and partially condensing the first overhead vapor stream to form a two-phase stream and means for separating the two-phase stream to provide a second overhead vapor stream and the methane-rich reflux stream.

29. The system of claim 28 which further comprises a main heat exchanger having flow passages therein for cooling and partially condensing the first overhead vapor stream by indirect heat exchange with a vaporizing multi-component refrigerant, having flow passages therein for cooling a compressed multi-component refrigerant, pressure reduction means for reducing the pressure of the multi-component refrigerant to yield the vaporizing multi-component refrigerant, and means for distributing the vaporizing multi-component refrigerant in the main heat exchanger.

30. The system of claim 29 which further comprises additional flow passages in the main heat exchanger for cooling and at least partially condensing the second overhead vapor stream to provide a liquefied natural gas product.

31. The system of claim 30 which further comprises a product heat exchanger wherein the liquefied natural gas product is further cooled by indirect heat exchange with a cold refrigerant provided by work expansion of a compressed refrigerant comprising nitrogen.