Method for liquefaction of a stream rich in hydrocarbons

Abstract

A method for liquefying a hydrocarbon-rich stream is disclosed. In an embodiment, the hydrocarbon-rich stream is liquefied in a heat exchanger countercurrent to a three component refrigerant mixture. The refrigerant mixture is compressed in a two stage compressor. The refrigerant mixture is separated into a higher boiling fraction and a lower boiling fraction. A fluid fraction is recovered from a partial stream of the lower boiling fraction. The fluid fraction is supercooled and expanded to a pressure of the higher boiling fraction and the fluid fraction is provided to a compressor stage to which the higher boiling fraction is taken.

1 - 7 . (canceled) 
     
     
         8 . A process for liquefying a hydrocarbon-rich stream, specifically a natural gas stream, wherein:
 liquefaction of the hydrocarbon-rich stream takes place in heat exchange countercurrent to a three or more component refrigerant mixture;   one of the components is a part of the hydrocarbon-rich stream to be liquefied;   one of the components is propane, propylene or a C 4  hydrocarbon;   one of the components is C 2 H 4  or C 2 H 6 ;   compression of the refrigerant mixture is carried out by means of an at least two-stage compression;   before cooling and expansion of the refrigerant mixture to provide refrigeration, separation of the refrigerant mixture into a higher boiling and a lower boiling refrigerant fraction takes place;   the higher boiling and the lower boiling refrigerant fractions following their expansion to provide refrigeration are taken at a hot end of the heat exchange at different pressures for compression; and   at least one partial stream of the lower boiling refrigerant fraction is partially condensed and a fluid fraction recovered is supercooled and expanded;   wherein the fluid fraction recovered is expanded to a pressure of the higher boiling fraction and taken to a compressor stage to which the higher boiling fraction is also taken.   
     
     
         9 . The process according to  claim 8 , wherein the refrigerant mixture is a three-component refrigerant mixture. 
     
     
         10 . The process according to  claim 8 , wherein the refrigerant fractions are cooled separately, expanded separately to provide refrigeration and heated separately countercurrent to the hydrocarbon-rich stream to be liquefied. 
     
     
         11 . The process according to  claim 8 , wherein a further component of the refrigerant mixture is nitrogen. 
     
     
         12 . The process according to  claim 8 , wherein at least one C 4  to C 6  hydrocarbon is used as an additional component of the refrigerant mixture. 
     
     
         13 . The process according to  claim 8 , wherein a second fluid fraction is recovered and supercooled, is expanded to a pressure of the lower boiling fraction and taken to a compressor stage to which the lower boiling fraction is also taken. 
     
     
         14 . The process according to  claim 8 , wherein the liquefaction of the hydrocarbon-rich stream takes place countercurrent to the refrigerant mixture in a plate heat exchanger. 
     
     
         15 . The process according to  claim 14 , wherein the plate heat exchanger is a single plate heat exchanger. 
     
     
         16 . A method for liquefying a hydrocarbon-rich stream, comprising the steps of:
 liquefying the hydrocarbon-rich stream in a heat exchanger countercurrent to a three component refrigerant mixture;   compressing the refrigerant mixture in a two stage compressor;   separating the refrigerant mixture into a higher boiling fraction and a lower boiling fraction;   recovering a fluid fraction from a partial stream of the lower boiling fraction;   supercooling and expanding the fluid fraction to a pressure of the higher boiling fraction; and   providing the fluid fraction to a compressor stage to which the higher boiling fraction is taken.   
     
     
         17 . The method according to  claim 16 , wherein the lower boiling fraction is taken to a first stage of the compressor. 
     
     
         18 . The method according to  claim 17 , wherein the higher boiling fraction is taken to a second stage of the compressor. 
     
     
         19 . The method according to  claim 16 , wherein the fluid fraction is supercooled in the heat exchanger. 
     
     
         20 . The method according to  claim 16 , wherein the fluid fraction is expanded in an expansion valve external to the heat exchanger. 
     
     
         21 . The method according to  claim 16 , wherein the fluid fraction is recovered in a separator. 
     
     
         22 . The method according to  claim 16 , wherein the partial stream of the lower boiling fraction is taken from the lower boiling fraction in the heat exchanger. 
     
     
         23 . The method according to  claim 16 , wherein after the step of expanding the fluid fraction, the fluid fraction is provided to the heat exchanger. 
     
     
         24 . The method according to  claim 21 , wherein the fluid fraction is drawn off from a bottom of the separator. 
     
     
         25 . The method according to  claim 24 , wherein a gaseous fraction of the partial stream of the lower boiling fraction is drawn off at a head of the separator. 
     
     
         26 . The method according to  claim 24 , wherein the gaseous fraction is provided to the heat exchanger. 
     
     
         27 . The method according to  claim 26 , wherein the gaseous fraction is provided to the lower boiling fraction.