NITROGEN REJECTION AND LIQUIFIER SYSTEM FOR LIQUIFIED NATURAL GAS PRODUCTION

• US 20120067079A1
• Filed: 03/22/2011
• Published: 03/22/2012
• Est. Priority Date: 03/25/2010
• Status: Abandoned Application

• Current Assignee: Linde AG (Linde Plc)
• Original Assignee: Linde AG (Linde Plc)
• Inventors: SETHNA, Rustam H., PAGES, Guillaume
• Application Number:
  US13/053,809
• Publication Number:
  US 20120067079A1
• Time in Patent Office: Days
• US Class Current: 62/611
• CPC Class Codes: C10L 3/105 of nitrogen
• 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 1/0055 originating from an incorporated cascade
• 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 1/0258 vertical layout of the equipments within in the cold box
• CPC Class Codes: F25J 1/0259 Modularity and arrangement of parts of the liquefaction unit and in particular of the cold box, e.g. pre-fabrication, assembling and erection, dimensions, horizontal layout "plot"
• 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 1/0264 Arrangement of heat exchanger cores in parallel with different functions, e.g. different cooling streams F25J1/0272 takes precedence
• CPC Class Codes: F25J 1/0279 Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc.
• CPC Class Codes: F25J 1/0291 Refrigerant compression by combined gas compression and liquid pumping
• CPC Class Codes: F25J 2205/60 using adsorption on solid adsorbents, e.g. by temperature-swing adsorption [TSA] at the hot or cold end
• CPC Class Codes: F25J 2210/06 Splitting of the feed stream, e.g. for treating or cooling in different ways
• CPC Class Codes: F25J 2210/66 Landfill or fermentation off-gas, e.g. "Bio-gas"
• CPC Class Codes: F25J 2220/62 Separating low boiling components, e.g. He, H2, N2, Air
• CPC Class Codes: F25J 2230/30 Compression of the feed stream
• CPC Class Codes: F25J 2245/02 Recycle of a stream in general, e.g. a by-pass stream
• CPC Class Codes: F25J 2245/90 the recycled stream being boil-off gas from storage
• 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 2290/62 Details of storing a fluid in a tank
• CPC Class Codes: Y02E 50/30 : Fuel from waste, e.g. synthetic alcohol or diesel

Abstract

A method for recovering liquefied natural gas from a gas mixture containing natural gas and impurities by subjecting the natural gas to a series of steps beginning with feeding a natural gas stream containing impurities to a nitrogen rejection unit; feeding the purified natural gas stream to a liquefier heat exchanger; expanding the liquefied natural gas and feeding the expanded liquefied natural gas to a flash vessel; flashing the liquid natural gas and separating the liquefied natural gas from the flash gas; and feeding the liquefied natural gas to storage and the flash gas to the nitrogen rejection unit.

Claims

1. A method for recovering liquefied natural gas comprising the steps:

feeding a natural gas stream containing impurities to a nitrogen rejection unit;

feeding the purified natural gas stream to a liquefier heat exchanger;

expanding the liquefied natural gas and feeding the expanded liquefied natural gas to a flash vessel;

flashing the liquid natural gas and separating the liquefied natural gas from the flash gas; and

feeding the liquefied natural gas to storage and the flash gas to said nitrogen rejection unit.

2. The method as claimed in claim 1 wherein said impurities are selected from the group consisting of water, carbon dioxide, non-methane organic compounds and sulfur compounds.

3. The method as claimed in claim 1 wherein nitrogen is recovered from said nitrogen rejection unit.

4. The method as claimed in claim 1 wherein the pressure in said liquefier heat exchanger range from 6 to 30 bar.

5. The method as claimed in claim 1 wherein said liquefied natural gas is expanded to a pressure of 1 to 5 bar.

6. The method as claimed in claim 1 wherein said flash gas is richer in nitrogen than natural gas.

7. The method as claimed in claim 1 wherein said natural gas stream is selected from the group consisting of landfill gas and biogas.

8. The method as claimed in claim 1 wherein said flash gas is recycled to said natural gas feed.

9. The method as claimed in claim 1 wherein flash pressure is lower than storage pressure.

10. The method as claimed in claim 1 wherein said nitrogen rejection unit is a vacuum swing adsorption unit.

11. The method as claimed in claim 1 wherein said recovered natural gas is fed to a storage unit.

12. The method as claimed in claim 1 wherein said storage unit is situated horizontally.

13. A method for recovering liquefied natural gas comprising the steps:

feeding a natural gas stream containing impurities to a nitrogen rejection unit;

feeding the purified natural gas stream to a liquefier heat exchanger;

expanding the liquefied natural gas and feeding the expanded liquefied natural gas to a flash vessel;

flashing the liquid natural gas and separating the liquefied natural gas from the flash gas;

recovering refrigeration from said flash gas; and

feeding the liquefied natural gas to storage and the flash gas to said nitrogen rejection unit.

14. The method as claimed in claim 13 wherein said impurities are selected from the group consisting of water, carbon dioxide, non-methane organic compounds and sulfur compounds.

15. The method as claimed in claim 13 wherein nitrogen is recovered from said nitrogen rejection unit.

16. The method as claimed in claim 13 wherein the pressure in said liquefier heat exchanger range from 6 to 30 bar.

17. The method as claimed in claim 13 wherein said liquefied natural gas is expanded to a pressure of 1 to 5 bar.

18. The method as claimed in claim 13 wherein said flash gas is richer in nitrogen than natural gas.

19. The method as claimed in claim 13 wherein said natural gas stream is selected from the group consisting of landfill gas and biogas.

20. The method as claimed in claim 13 wherein said flash gas is recycled to said natural gas feed.

21. The method as claimed in claim 13 wherein flash pressure is lower than storage pressure.

22. The method as claimed in claim 13 wherein said nitrogen rejection unit is a vacuum swing adsorption unit.

23. The method as claimed in claim 13 wherein said recovered natural gas is fed to a storage unit.

24. The method as claimed in claim 13 wherein said storage unit is situated horizontally.

25. The method as claimed in claim 13 wherein said recovered refrigeration provides cooling to a heat exchanger.

26. The method as claimed in claim 13 wherein said heat exchanger is in thermal contact with the liquefier feed.

27. An apparatus comprising a nitrogen rejection unit, a liquefier heat exchanger and a flash vessel.

28. The apparatus as claimed in claim 27 wherein said nitrogen rejection unit is a vacuum swing adsorption unit.

29. The apparatus as claimed in claim 27 wherein said liquefier heat exchanger is in thermal communication with said flash vessel.

30. The apparatus as claimed in claim 27 wherein said nitrogen rejection unit is in thermal communication with said liquefier heat exchanger.

31. The apparatus as acclaimed in claim 27 wherein said flash vessel is in fluid communication with a storage tank.

32. The apparatus as claimed in claim 27 further comprising a second heat exchanger.