Method and apparatus for separating a fraction rich in c2+ from liquefied natural gas

Abstract

A process and apparatus for separating a fraction rich in C 2+ from liquefied natural gas (LNG) is disclosed. In an embodiment, partial evaporation of the liquefied natural gas occurs in a heat exchanger. The partially evaporated natural gas is separated into a first gas fraction rich in C 1 and a first liquid fraction rich in C 2+ . In a separation column, rectification separation of the first liquid fraction rich in C 2+ into a second gas fraction rich in C 1 and a second liquid fraction rich in C 2+ occurs. The first gas fraction rich in C 1 is re-liquefied in the heat exchanger. At least one sub-stream of the re-liquefied gas fraction rich in C 1 is fed as a reflux to the rectification separation.

1 - 10 . (canceled) 
   
   
       11 . A process for separating a fraction rich in C 2+  from liquefied natural gas (LNG), comprising the steps of:
 a) partial evaporation of the liquefied natural gas;   b) separation of the partially evaporated natural gas into a first gas fraction rich in C 1  and a first liquid fraction rich in C 2+ ;   c) rectification separation of the first liquid fraction rich in C 2+  into a second gas fraction rich in C 1  and a second liquid fraction rich in C 2+ ;   d) re-liquefaction of the first gas fraction rich in C 1 ; and   e) feeding of a least one sub-stream of the re-liquefied gas fraction rich in C 1  as a reflux to the rectification separation.   
   
   
       12 . The method according to  claim 11 , wherein the re-liquefaction of the first gas fraction rich in C 1  takes place in an exchange of heat with the liquefied natural gas. 
   
   
       13 . The method according to  claim 11 , wherein the rectification separation takes place at a higher pressure than the separation of the partially evaporated natural gas into the first gas fraction rich in C 1  and the first liquid fraction rich in C 2+ . 
   
   
       14 . The method according to  claim 13 , wherein the separation of the partially evaporated natural gas into the first gas fraction rich in C 1  and the first liquid fraction rich in C 2+  takes place in a pressure range between 15 and 25 bar and the rectification separation takes place in a pressure range between 30 and 40 bar. 
   
   
       15 . The method according to  claim 11 , wherein a sub-stream of the re-liquefied gas fraction rich in C 1  which is not taken as the reflux to the rectification separation is combined with the second gas fraction rich in C 1  obtained in the rectification separation. 
   
   
       16 . The method according to  claim 11 , wherein the second gas fraction rich in C 1  obtained in the rectification separation is at least partially re-liquefied by an exchange of heat with the liquefied natural gas. 
   
   
       17 . The method according to  claim 11 , wherein a cooling of process streams which result from a separation of the second liquid fraction rich in C 2+  takes place countercurrent to the first liquid fraction rich in C 2+  and/or countercurrent to at least one fluid fraction which is drawn off from the rectification separation below a feed of the first fluid fraction rich in C 2+ . 
   
   
       18 . The method according to  claim 11 , wherein the second liquid fraction rich in C 2+  undergoes C 2 /C 3  rectification separation, wherein a head condensation of the C 2 /C 3  rectification separation takes place in a lateral boiler countercurrent to at least one liquid fraction which is drawn off from the rectification separation below a feed for the first fluid fraction rich in C 2+ , 
   
   
       19 . The method according to  claim 11 , wherein the second liquid fraction rich in C 2+  undergoes C 2 /C 3  rectification separation, wherein a gas fraction rich in C 2 /C 3  obtained in the C 2 /C 3  rectification separation is cooled in an exchange of heat countercurrent to the first liquid fraction rich in C 2+  and cooled to a pressure-free storage temperature. 
   
   
       20 . The method according to  claim 11 , wherein the separation of the partially evaporated natural gas into the first gas fraction rich in C 1  and the first liquid fraction rich in C 2+  takes place in a separator or a rectifier column. 
   
   
       21 . A process for separating a fraction rich in C 2+  from liquefied natural gas (LNG), comprising the steps of:
 partial evaporation of the liquefied natural gas in a heat exchanger;   separation of the partially evaporated natural gas into a first gas fraction rich in C 1  and a first liquid fraction rich in C 2+ ;   rectification separation of the first liquid fraction rich in C 2+  into a second gas fraction rich in C 1  and a second liquid fraction rich in C 2+ ;   re-liquefaction of the first gas fraction rich in C 1  in the heat exchanger; and   feeding of a sub-stream of the re-liquefied gas fraction rich in C 1  as a reflux to the rectification separation process.   
   
   
       22 . The process according to  claim 21 , wherein the step of re-liquefaction of the first gas fraction rich in C 1  in the heat exchanger includes the step of refrigeration of the first gas fraction rich in C 1  by the liquefied natural gas which is heated up to a boiling point. 
   
   
       23 . The process according to  claim 21 , wherein the first gas fraction rich in C 1  is re-liquefied in the heat exchanger countercurrent to a stream of the liquefied natural gas. 
   
   
       24 . An apparatus for separating a fraction rich in C 2+  from liquefied natural gas (LNG), comprising:
 a heat exchanger, wherein the liquefied natural gas is partially evaporated in the heat exchanger;   a separator coupled to the heat exchanger, wherein the partially evaporated natural gas is separated in the separator into a first gas fraction rich in C 1  and a first liquid fraction rich in C 2+ ; and   a separator column coupled to the separator, wherein rectification separation of the first liquid fraction rich in C 2+  into a second gas fraction rich in C 1  and a second liquid fraction rich in C 2+  occurs in the separator column;   wherein the first gas fraction rich in C 1  is re-liquefied in the heat exchanger and wherein a sub-stream of the re-liquefied gas fraction rich in C 1  is fed as a reflux to the separation column.   
   
   
       25 . The apparatus according to  claim 24 , wherein the re-liquefaction of the first gas fraction rich in C 1  in the heat exchanger includes refrigeration of the first gas fraction rich in C 1  by the liquefied natural gas which is heated up to a boiling point. 
   
   
       26 . The apparatus according to  claim 24 , wherein the first gas fraction rich in C 1  is re-liquefied in the heat exchanger countercurrent to a stream of the liquefied natural gas.