Bath-type vaporiser-condenser for a method of cryogenically separating a natural gas stream

Abstract

A method of cryogenically separating a natural gas supply stream into a gas which contains the most volatile compounds of the supply stream, and a liquid product which contains the heaviest compounds of the supply stream, including the following steps: at least partially condensing a natural gas supply stream in a first heat exchanger system; introducing the liquid product into a fractionation column in order to obtain, in the bottom of the fractionation column, a liquid produce 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; introducing, at a stage in the upper part of the absorption column, the gaseous phase of the condensed distillate as a supply stream for the absorption column; where the distillate is condensed in a bath-type vaporizer-condenser installed in a casing mounted on the fractionation column.

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, an at least partially condensed distillate;   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 distillate resulting from stage c) is condensed in a bath vaporizer-condenser installed in a shell surrounding the fractionation column.   
     
     
         7 . The process as claimed in  claim 6 , wherein the bath vaporizer-condenser contains at least one heat exchanger fed with refrigerating fluid by the liquid product resulting from stage b). 
     
     
         8 . 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. 
     
     
         9 . The process as claimed in  claim 6 , wherein no pump is necessary for setting up said reflux. 
     
     
         10 . A unit for the cryogenic separation of a natural gas feed stream utilizing the process as defined in  claim 6 , wherein a pipe connects the top of the fractionation column to a heat exchanger surmounting said fractionation column, which heat exchanger is itself placed in a shell provided for a bath formed predominantly of hydrocarbons.