US2012067079A1PendingUtilityA1

Nitrogen rejection and liquifier system for liquified natural gas production

39
Individually held — no corporate assignee on recordPriority: Mar 25, 2010Filed: Mar 22, 2011Published: Mar 22, 2012
Est. expiryMar 25, 2030(~3.7 yrs left)· nominal 20-yr term from priority
Inventors:Rustam H. SethnaGuillaume Pages
F25J 2220/62F25J 1/0279C10L 3/105F25J 2230/30F25J 1/0291F25J 2245/90F25J 1/0264F25J 2210/66F25J 2290/62F25J 1/0022F25J 1/0219F25J 2245/02F25J 1/0259F25J 2205/60F25J 1/0258F25J 1/0055F25J 2210/06F25J 1/004F25J 2290/32F25J 1/0262Y02E50/30
39
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Claims

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

exact text as granted — not AI-modified
Having thus described the invention, what we claim is: 
     
         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.

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