Natural gas liquefaction

Abstract

The invention relates to a method for liquefying a hydrocarbon-rich feed fraction, preferably natural gas, against a nitrogen refrigeration cycle. A feed fraction is cooled against gaseous nitrogen that is to be warmed, and liquefied against liquid nitrogen that is to be vaporized. The feed fraction is cooled and liquefied in an at least three-stage heat-exchange process. In the first section of the heat-exchange process, the feed fraction is cooled against superheated gaseous nitrogen to the extent that an essentially complete separation of the relatively heavy components is achievable. In the second section, the feed fraction freed from relatively heavy components is partially liquefied against gaseous nitrogen that is to be superheated. In the third section, the feed fraction is liquefied against nitrogen that is to be partially vaporized.

1 . A method for liquefying a hydrocarbon-rich feed fraction against a nitrogen refrigeration cycle, comprising:
 cooling said wherein feed fraction against gaseous nitrogen that is to be warmed, and liquefying said feed fraction against liquid nitrogen that is to be vaporized,   wherein
 said feed fraction is cooled and liquefied in an at least three-stage heat-exchange process (E 1   a -E 1   c ), 
 in the first section of said heat-exchange process (E 1   a ), said feed fraction ( 1 ) is cooled against superheated gaseous nitrogen ( 9 ) to the extent that an essentially complete separation (D 2 ) of relatively heavy components ( 2 ′) is achievable, 
   in the second section of said heat-exchange process (E 1   b ), the feed fraction ( 2 ) freed from relatively heavy components is partially liquefied against gaseous nitrogen that is to be superheated ( 9 ), and
 in the third section of said heat-exchange process (E 1   c ), the feed fraction ( 2 ) is liquefied against nitrogen that is to be partially vaporized ( 8 ). 
   
     
     
         2 . The method according to  claim 1 , wherein said hydrocarbon-rich feed fraction is natural gas. 
     
     
         3 . The method according to  claim 1 , wherein said three-stage heat-exchange process (E 1   a -E 1   c ) is performed in one heat exchanger. 
     
     
         4 . The method according to  claim 2 , wherein said three-stage heat-exchange process (E 1   a -E 1   c ) is performed in one heat exchanger. 
     
     
         5 . The method according to  claim 1 , wherein said three-stage heat-exchange process (E 1   a -E 1   c ) is performed in more than one heat exchanger. 
     
     
         6 . The method according to  claim 2 , wherein said three-stage heat-exchange process (E 1   a -E 1   c ) is performed in more than one heat exchanger. 
     
     
         7 . The method according to  claim 1 , wherein the condensation pressure of the feed fraction ( 2 ) freed from relatively heavy components is adjusted (V 2 ) to a value of 1-15 bara. 
     
     
         8 . The method according to  claim 7 , wherein the condensation pressure of the feed fraction ( 2 ) freed from relatively heavy components is adjusted (V 2 ) to a value of 1-8 bara. 
     
     
         9 . The method according to  claim 1 , wherein the boiling pressure of the gaseous nitrogen that is to be superheated ( 9 ) is adjusted (V 4 ) to a value of 5-30 bara. 
     
     
         10 . The method according to  claim 9 , wherein the boiling pressure of the gaseous nitrogen that is to be superheated ( 9 ) is adjusted (V 4 ) to a value of 10-20 bara.