Method for treating a hydrocarbon stream

Abstract

The present invention relates to a method for treating a natural gas feed stream, containing >10 mole % CO 2 , the method at least comprising the steps of separating the feed stream ( 10 ) in a first ( 2 ) or a second ( 3 ) gas/liquid separator, removing from the top of the second gas/liquid separator ( 3 ) a gaseous stream ( 60 ), partially condensing it by heat exchanging against a cold stream ( 120 ) and feeding it ( 70 ) into a third gas/liquid separator ( 4 ) thereby obtaining a liquid stream ( 80 ) and a gaseous stream ( 90 ) and feeding the liquid stream ( 80 ) having a temperature above the freezing point of CO 2 at the prevailing conditions, into the second gas/liquid separator ( 3 ) removing from the bottom of the second gas/liquid separator ( 3 ) a liquid stream ( 100, 100 a ).

1 . Method for treating a hydrocarbon stream containing >10 mole % CO 2 , the method at least comprising the steps of:
 (a) supplying a partly condensed feed stream containing >10 mole % CO 2  to a first gas/liquid separator;   (b) separating the feed stream in the first gas/liquid separator into a gaseous stream A and a liquid stream;   (c) expanding the liquid stream obtained in step (b) and feeding it into a second gas/liquid separator at a first feeding point;   (d) expanding the gaseous stream obtained in step (b), thereby obtaining an at least partially condensed stream, and subsequently feeding it into the second gas/liquid separator at a second feeding point, the second feeding point being at a higher level than the first feeding point;   (e) removing from the top of the second gas/liquid separator a gaseous stream, partially condensing it and feeding it into a third gas/liquid separator;   (f) separating the stream fed in the third gas/liquid separator in step (e) thereby obtaining a liquid stream and a gaseous stream;   (g) feeding the liquid stream obtained in step (f), having a temperature above the freezing point of CO 2  at the prevailing conditions, into the second gas/liquid separator at a third feeding point, the third feeding point being at a higher level than the second feeding point; and   (h) removing from the bottom of the second gas/liquid separator a liquid stream;
 wherein the gaseous stream removed from the second gas/liquid separator in step (e) is partially condensed by heat exchanging against a cold stream, which is selected such that the partially condensed stream obtained in step (e) has a temperature greater than or equal to −60° C. and wherein all streams being fed into the second gas/liquid separator fully originate from the feed stream. 
   
     
     
         2 . Method according to  claim 1 , wherein the cold stream is selected such that the partially condensed stream obtained in step (e) has a temperature above the freezing point of CO 2  at the prevailing conditions. 
     
     
         3 . Method according to  claim 1 , wherein the temperature of the liquid stream obtained in step (f) is at or above −60° C. near the third feeding point. 
     
     
         4 . Method according to  claim 1 , wherein the cold stream is obtained from a separate source of liquefied natural gas (LNG). 
     
     
         5 . Method according to  claim 1 , wherein >75% by weight of the propane present in the partially condensed feed stream is recovered in the liquid stream obtained in step (h). 
     
     
         6 . Method according to  claim 1 , wherein the partially condensed feed stream contains >15 mole % CO 2 . 
     
     
         7 . Method according to  claim 1 , wherein the partially condensed feed stream has a pressure >20 bar. 
     
     
         8 . Method according to  claim 1 , wherein the pressure in the second gas/liquid separator is in the range from 10 to 50 bar. 
     
     
         9 . Method according to  claim 1 , wherein the gaseous stream obtained in step (f) is sent to a gas network. 
     
     
         10 . Method according to  claim 1 , wherein the gaseous stream obtained in step (f) is liquefied thereby obtaining a liquefied hydrocarbon stream. 
     
     
         11 . Method according to  claim 1 , wherein the liquid stream removed from the bottom of the second gas/liquid separator is subjected to distillation thereby obtaining two or more distilled streams. 
     
     
         12 . Method according to  claim 1 , wherein the partially condensed feed stream has been previously cooled against a cold stream. 
     
     
         13 . Method according to  claim 1 , wherein the temperature of the liquid stream obtained in step (f) is at or above −55° C. near the third feeding point. 
     
     
         14 . Method according to  claim 1 , wherein the cold stream is selected such that the partially condensed stream obtained in step (e) has a temperature from −60° C. to −40° C. 
     
     
         15 . Method according to  claim 1 , wherein the cold stream is selected such that the partially condensed stream obtained in step (e) has a temperature greater than or equal to −55° C. 
     
     
         16 . Method according to  claim 2 , wherein the temperature of the liquid stream obtained in step (f) is at or above −60° C. near the third feeding point. 
     
     
         17 . Method according to  claim 2 , wherein the cold stream is obtained from a separate source of liquefied natural gas (LNG). 
     
     
         18 . Method according to  claim 3 , wherein the cold stream is obtained from a separate source of liquefied natural gas (LNG). 
     
     
         19 . Method according to  claim 2 , wherein >75% by weight of the propane present in the partially condensed feed stream is recovered in the liquid stream obtained in step (h). 
     
     
         20 . Method according to  claim 3 , wherein >75% by weight of the propane present in the partially condensed feed stream is recovered in the liquid stream obtained in step (h).