Method for cryogenically separating a natural gas stream

Abstract

A method for cryogenically separating a natural gas supply stream into a gas containing the most volatile compounds of the supply stream, and a liquid product containing the heaviest compounds at least including the following. Introducing an at least partially condensed stream into an absorption column at an introduction stage in the lower part of said absorption column, thus producing, at the top, a gaseous stream that contains the most volatile compounds and, the bottom, a liquid product. Introducing the liquid product into a fractionation column in order to obtain, in the bottom of the fractionation column, a liquid product that contains the heaviest compounds of the supply stream and, at the top of the fractionation column, a distillate that is at least partially condensed in a second heat exchanger system

1 .- 5 . (canceled) 
     
     
         6 . A process for the cryogenic separation of a natural gas feed stream into a gas containing the most volatile compounds of the feed stream and into a liquid product containing the heaviest compounds of the feed stream, comprising at least the following stages:
 Stage a): at least partial condensation of a natural gas feed stream in a first heat-exchange system;   Stage b): introduction of the at least partially condensed stream resulting from stage a) into an absorption column at an introduction level located in the lower part of said absorption column, said absorption column producing, at the top, a gas stream containing the most volatile compounds and, at the bottom, a liquid product;   Stage c): introduction of the liquid product resulting from stage b) into a fractionation column in order to obtain, in the fractionation column bottom, a liquid product containing the heaviest compounds of the feed stream and, at the fractionation column top, a distillate, at least partially condensed in a second heat-exchange system;   Stage d): introduction, at a level located in the upper part of the absorption column, of the gas phase of the condensed distillate resulting from stage c) as feed stream of the absorption column;   wherein the gas stream produced at the absorption column top resulting from stage b) is employed in order to condense, in the second heat-exchange system, the distillate resulting from the top of the fractionation column.   
     
     
         7 . The process according to  claim 6 , further comprising a stage, prior to stage d), of condensation of the distillate resulting from the top of the fractionation column in a third heat-exchange system. 
     
     
         8 . The process as claimed in  claim 6 , wherein all of the gas stream produced at the absorption column top resulting from stage b) is employed in order to condense, in the second heat-exchange system, the distillate resulting from the top of the fractionation column. 
     
     
         9 . The process as claimed in  claim 6 , wherein the gas stream produced at the absorption column top resulting from stage b) is separated into several streams, at least one of which is employed in order to condense, in the second heat-exchange system, the distillate resulting from the top of the fractionation column. 
     
     
         10 . The process as claimed in  claim 6 , wherein the liquid phase of the condensed distillate resulting from stage c) is used as reflux at the top of the fractionation column.