Method of liquefying a hydrocarbon-rich fraction

Abstract

For liquefying a hydrocarbon-rich fraction, in particular natural gas, the hydrocarbon-rich fraction which is to be liquefied is merely cooled and liquefied against a coolant mixture, and the coolant mixture, before its cooling, is separated into a gas phase and a liquid phase, and wherein the gas ( 5 ) and the liquid phases ( 6 ) are cooled (E) separately and not until after cooling (E) has been performed are they expanded (a, b) and recombined ( 8 ).

1 . A method comprising liquefying a hydrocarbon-rich fraction, in particular natural gas, wherein the hydrocarbon-rich fraction which is to be liquefied is cooled and liquefied against a coolant mixture, and the coolant mixture, before cooling, is separated in a separator (D) into a gas phase ( 5 ) and a liquid phase ( 6 ), the improvement wherein the gas phase ( 5 ) and the liquid phase ( 6 ) are cooled (E) separately and not until after cooling (E) has been performed are they expanded (a, b) and recombined. 
   
   
       2 . A method according to  claim 1 , wherein the expanded gas ( 5 ) and liquid ( 6 ) phases are recombined before or after warming (E) thereof against the hydrocarbon-rich fraction ( 1 ) which is to be liquefied. 
   
   
       3 . A method according to  claim 1 , comprising a preceding step of separating a fraction rich in heavy hydrocarbons from the hydrocarbon-rich fraction which is to be cooled. 
   
   
       4 . A method according to  claim 1 , wherein the coolant mixture comprises nitrogen, methane, ethane, ethylene, propane, butane and/or pentane. 
   
   
       5 . A method according to  claim 3 , wherein at least some of the hydrocarbon-rich fraction ( 1 ) which is to be cooled, the fraction rich in relatively heavy hydrocarbons and has been separated off, and/or the resultant liquefied hydrocarbon-rich fraction ( 2 ) is added to the coolant mixture. 
   
   
       6 . A method according to  claim 1 , wherein the resultant liquefied hydrocarbon-rich fraction is stored temporarily in a storage vessel, characterized in that recycle gas in the storage vessel is at least in part added to the coolant mixture. 
   
   
       7 . A method according to  claim 1 , wherein the coolant mixture is compressed to a final pressure in at least two stages, wherein liquid fraction(s) formed at an intermediate pressure after the cooling of the compressed coolant mixture is or are pumped to the final pressure of compression (V) and fed to the separator (D) for separating the coolant mixture. 
   
   
       8 . A method according to  claim 2 , wherein the expanded gas and liquid phases are recombined before said warming. 
   
   
       9 . A method according to  claim 2 , wherein the expanded gas and liquid phases are recombined after said warming. 
   
   
       10 . A method according to  claim 5 , wherein at least some of the methane is replaced. 
   
   
       11 . A method according to  claim 6 , wherein at least some of the nitrogen is replaced. 
   
   
       12 . A method according to  claim 6 , wherein the coolant mixture is compressed to a final pressure in at least two stages, wherein liquid fraction(s) formed at an intermediate pressure after the cooling of the compressed coolant mixture is or are pumped to the final pressure of compression (V) and fed to the separator (D) for separating the coolant mixture.