SYSTEM FOR ENHANCED GAS TURBINE PERFORMANCE IN A LIQUEFIED NATURAL GAS FACILITY

• US 20100058801A1
• Filed: 08/28/2009
• Published: 03/11/2010
• Est. Priority Date: 09/09/2008
• Status: Active Grant

• Current Assignee: Conocophillips Company (ConocoPhillips)
• Original Assignee: Conocophillips Company (ConocoPhillips)
• Inventors: Meher-Homji, Cyrus B., Masani, Karl D.
• Granted Patent: US 9,841,230 B2
• Time in Patent Office: Days
• US Class Current: 62/611
• CPC Class Codes: F01D 15/005 Adaptations for refrigeration plants
• CPC Class Codes: F02C 7/143 before or between the compressor stages
• CPC Class Codes: F25J 1/0022 Hydrocarbons, e.g. natural gas
• 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 1/0085 Ethane; Ethylene
• CPC Class Codes: F25J 1/0087 Propane; Propylene
• CPC Class Codes: F25J 1/021 using a deep flash recycle loop
• CPC Class Codes: F25J 1/0236 providing refrigeration for different processes treating not the same feed stream
• CPC Class Codes: F25J 1/0242 Waste heat recovery, e.g. from heat of compression
• CPC Class Codes: F25J 1/0283 Gas turbine as the prime mechanical driver
• CPC Class Codes: F25J 2220/64 Separating heavy hydrocarbons, e.g. NGL, LPG, C4+ hydrocarbons or heavy condensates in general
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft

Abstract

A system for liquefying natural gas that includes a process and apparatus for enhancing the performance of one or more gas turbines. Gas turbine power output can be stabilized or even enhanced using the interstage cooling system configured according to one or more embodiments of the present invention. In one embodiment, partially compressed air from a lower compression stage of a gas turbine is cooled via indirect heat exchange with a primary coolant before being returned to a higher compression stage of the same gas turbine. Optionally, the interstage cooling system can employ one or more secondary coolants to remove the rejected heat from the primary coolant system.

Claims

1. A process for liquefying a natural gas stream, said process comprising:

(a) cooling at least a portion of said natural gas stream via indirect heat exchange with a first refrigerant in a first refrigeration cycle to thereby produce a cooled natural gas stream;

(b) further cooling at least a portion of said cooled natural gas stream via indirect heat exchange with a second refrigerant in a second refrigeration cycle to thereby provide a further cooled natural gas stream; and

(c) cooling a partially compressed air stream via indirect heat exchange with a primary coolant to thereby provide a cooled partially compressed air stream, wherein said partially compressed air stream is withdrawn from an intermediate compression stage of a gas turbine used to drive at least one refrigerant compressor associated with said first and/or said second refrigeration cycle.

2. The process of claim 1, wherein said cooling of step (c) results in a warmed primary coolant stream;

further comprising cooling at least a portion of said warmed primary coolant stream via indirect heat exchange with a secondary coolant stream to thereby provide a cooled primary coolant stream and using at least a portion of said cooled primary coolant stream to accomplish at least a portion of said cooling of step (c).

3. The process of claim 2, wherein said primary coolant stream comprises water, wherein said secondary coolant stream comprises at least a portion of said first and/or said second refrigerant.

4. The process of claim 2, wherein said primary coolant stream comprises water, wherein said secondary coolant stream comprises air.

5. The process of claim 1, wherein said first and second refrigerants are each comprised predominately of hydrocarbons.

6. The process of claim 1, wherein said first refrigerant is comprised predominately of propane, propylene, ethane, or ethylene.

7. The process of claim 1, wherein said first refrigerant is comprised predominately of propane.

8. The process of claim 7, wherein said second refrigerant is a mixed hydrocarbon refrigerant.

9. The process of claim 7, wherein said second refrigerant is comprised predominately of ethane, ethylene, methane, or nitrogen.

10. The process of claim 1, wherein said cooling of step (c) cools said partially compressed air stream to a temperature that is at least 1°

C. cooler than the temperature of an uncompressed air stream being supplied to the inlet of said gas turbine.

11. The process of claim 1, further comprising cooling an uncompressed air stream via indirect heat exchange with said first and/or second refrigerant to thereby provide a cooled inlet air stream and introducing said cooled inlet air stream into the inlet of said gas turbine.

13. The process of claim 1, wherein said gas turbine is dual-shaft or triple-shaft gas turbine.

14. The process of claim 13, wherein said gas turbine is a triple-shaft gas turbine.

15. The process of claim 14, wherein said first refrigerant is predominately comprised of propane, wherein said second refrigerant is a mixed hydrocarbon refrigerant.

16. The process of claim 15, further comprising cooling at least a portion of said further cooled natural gas stream in a third refrigeration cycle, wherein said third refrigeration cycle comprises a nitrogen refrigeration cycle.

17. The process of claim 1, further comprising cooling at least a portion of said further cooled natural gas stream in a third refrigeration cycle, wherein said third refrigeration cycle comprises an open-loop methane refrigeration cycle.

18. The process of claim 1, further comprising, intermediate to step (b), separating at least a portion of said cooled natural gas stream in a heavies removal column to thereby provide a predominantly methane overhead product and a heavies-rich bottom product, wherein said further cooled natural gas stream comprises at least a portion of said predominantly methane overhead product.

19. The process of claim 1, wherein said first and said second refrigerants are pure-component refrigerants, wherein said first and second refrigerants have different compositions.

12. The process of claim 12, wherein said partially compressed air stream and said uncompressed air stream are cooled in a common heat exchanger.

20. A process for liquefying a natural gas stream, said process comprising:

(a) compressing a first refrigerant stream in a first refrigerant compressor to thereby provide a first compressed refrigerant stream, wherein said first refrigerant compressor is at least partially driven by a first gas turbine;

(b) cooling a first air stream via indirect heat exchange with at least a portion of said first refrigerant in a first heat exchanger to thereby provide a first cooled air stream; and

(c) introducing at least a portion of said first cooled air stream into said first gas turbine.

21. The process of claim 20, wherein said first air stream is a partially compressed air stream withdrawn from a low compression stage of said first gas turbine.

22. The process of claim 21, further comprising cooling a second air stream via indirect heat exchange with said first refrigerant to thereby provide a second cooled air stream and introducing said second cooled air stream into said first gas turbine, wherein said second air stream is an uncompressed air stream, wherein said second cooled air stream is introduced into said low compression stage of said first gas turbine.

23. The process of claim 21, further comprising cooling a second air stream via indirect heat exchange with said first refrigerant to thereby provide a second cooled air stream and introducing said second cooled air stream into a second gas turbine used to power a second refrigerant compressor operable to compress a second refrigerant stream.

24. The process of claim 23, wherein said first and said second refrigerant streams have different compositions.

25. The process of claim 24, wherein said first and said second refrigerant streams are comprised predominantly of hydrocarbons.

26. The process of claim 23, wherein said first refrigerant stream comprises predominantly propane, wherein said second refrigerant stream comprises predominantly ethylene, ethane, nitrogen, or methane.

27. The process of claim 26, further comprising using at least a portion of said first and said second refrigerant streams to cool said natural gas stream to thereby provide a cooled natural gas stream and further cooling said cooled natural gas stream via indirect heat exchange with a third predominantly methane refrigerant.

28. The process of claim 23, wherein said first refrigerant is comprised predominately of propane, wherein said second refrigerant is a mixed hydrocarbon refrigerant.

29. The process of claim 20, wherein said cooling of step (b) cools said first air stream by no more than 25°

C., wherein none of said cooling of step (b) is accomplished via direct heat exchange.

30. The process of claim 20, wherein said first gas turbine is a multi-shaft gas turbine.

31. A liquefied natural gas (LNG) facility, said LNG facility comprising:

a first refrigeration cycle comprising a first refrigerant compressor, a first refrigerant chiller, and a first gas turbine, wherein said first refrigerant compressor is operable to produce a compressed first refrigerant stream and said first refrigerant chiller is operable to cool a natural gas stream via indirect heat exchange with said compressed first refrigerant stream to thereby produce a cooled natural gas stream, wherein said first compressor is driven by said first gas turbine, wherein said first gas turbine is a multi-stage, multi-shaft gas turbine comprising a first low compression stage and a first high compression stage; and

a first heat exchange zone operable to cool a first partially compressed air stream withdrawn from said first low compression stage via indirect heat exchange with a first coolant to thereby produce a first cooled air stream, wherein said first high compression stage is configured to receive said first cooled air stream.

32. The facility of claim 31, further comprising a second refrigeration cycle comprising a second refrigerant compressor operable to produce a compressed second refrigerant stream and a second refrigerant chiller operable to cool said cooled natural gas stream via indirect heat exchange with said compressed second refrigerant stream, wherein said second compressor is driven by a second multi-stage, multi-shaft gas turbine, wherein said second gas turbine comprises a second low compression stage and a second high compression stage, said first heat exchange zone further operable to cool a second partially compressed air stream withdrawn from said second low compression stage via indirect heat exchange with said first coolant to thereby produce a second cooled air stream, wherein said second high compression stages is operable to receive said second cooled air stream.

33. The facility of claim 31, wherein said first refrigeration cycle comprises a closed-loop propane refrigeration cycle, wherein said second refrigeration cycle comprises a mixed refrigerant cycle.

34. The facility of claim 31, wherein said first refrigeration cycle comprises a closed-loop propane refrigeration cycle, wherein said second refrigeration cycle comprises a closed loop refrigeration cycle, wherein said second refrigeration comprises predominantly ethane, ethylene, or nitrogen.

35. The facility of claim 31, wherein said first heat exchange zone comprises a single heat exchanger.

36. The facility of claim 31, wherein said multi-stage, multi-shaft first gas turbine is a triple-shaft gas turbine.