Method for separating heavy hydrocarbons from a hydrocarbon-rich fraction

Abstract

Disclosed is a method for separating heavy hydrocarbons, in particular C6+ hydrocarbons and/or aromatic hydrocarbons, such as benzene, from a hydrocarbon-rich fraction to be liquefied, in particular from natural gas, the hydrocarbon-rich fraction being precooled prior to separation of the heavy hydrocarbons. One or a plurality of C5 hydrocarbon-rich fractions are mixed into the hydrocarbon-rich fraction prior to the pre-cooling thereof and/or into the separation column used for separating the heavy hydrocarbons at least in such a quantity, preferably in liquid form, that freezing of the heavy hydrocarbons to be separated is prevented.

1 . A method of separating heavy hydrocarbons, from a hydrocarbon-rich fraction to be liquefied, where the hydrocarbon-rich fraction is precooled before the heavy hydrocarbons are separated off, characterized in that a C 5 -hydrocarbon-rich fraction is added to the hydrocarbon-rich fraction before the latter is precooled or upstream of the removal column serving to separate off the heavy hydrocarbons at least in such an amount, that freezing-out of the heavy hydrocarbons to be separated off is avoided. 
     
     
         2 . The method as claimed in  claim 1 , characterized in that the C 5 -hydrocarbon-rich fraction to be added is at least partly formed from the hydrocarbon-rich fraction to be liquefied. 
     
     
         3 . The method as claimed in  claim 1 , characterized in that the content of C 2+ -hydrocarbons in the hydrocarbon-rich fraction to be liquefied is less than 15 mol %. 
     
     
         4 . The method as claimed in  claim 1 , characterized in that the C 5 -hydrocarbon-rich fraction to be added contains from 50 to 100% by volume of i- and/or n-pentane. 
     
     
         5 . The method as claimed in  claim 4 , characterized in that the C 5 -hydrocarbon-rich fraction to be added additionally contains propane, butane, hexane and/or higher hydrocarbons. 
     
     
         6 . The method as claimed in  claim 1 , characterized in that a substream of the hydrocarbon-rich fraction which has not been precooled is fed as heating medium into the removal column. 
     
     
         7 . The method as claimed in  claim 1 , characterized in that the C 5 -hydrocarbon-rich fraction fed to the removal column is cooled to a temperature in the range from −100 to −130° C. and is fed into the removal column above the feed point for the hydrocarbon-rich fraction to be liquefied. 
     
     
         8 . The method as claimed in  claim 1 , characterized in that a substream of the hydrocarbon-rich fraction which has been freed of heavy hydrocarbons and has been liquefied is fed as runback into the removal column. 
     
     
         9 . The method as claimed in  claim 1 , characterized in that the hydrocarbon-rich fraction to be liquefied is precooled to a temperature in the range from −25 to −55° C. before the heavy hydrocarbons are separated off. 
     
     
         10 . The method as claimed in  claim 1 , wherein the heavy hydrocarbons are C 6+ -hydrocarbons and/or aromatic hydrocarbons. 
     
     
         11 . The method as claimed in  claim 11 , Wherein the heavy hydrocarbons are benzene. 
     
     
         12 . The method as claimed in  claim 1 , wherein the hydrocarbon-rich fraction is natural gas. 
     
     
         13 . The method of  claim 1  wherein the heavy hydrocarbons are separated off in liquid form.