Method for recovering helium

Abstract

A method for recovering a helium product fraction ( 6 ) from a nitrogen- and helium-containing feed fraction ( 3 ) is described, wherein the nitrogen- and helium-containing feed fraction ( 3 ) is partially condensed (E 1 ), separated into a first helium-enriched fraction ( 5 ) and a first nitrogen-enriched fraction ( 8 ) and the former is cleaned again in an adsorptive manner. According to the invention, the separation is carried out in a separation column (T), which is supplied with the first nitrogen-enriched fraction ( 8 ) as return flow and with a sub-flow of the second nitrogen-enriched fraction as stripping gas ( 12 ), wherein the stripping gas quantity ( 12 ) is set such that a third nitrogen-enriched fraction ( 20 ), which contains at least 30% of the nitrogen contained in the first nitrogen-enriched fraction ( 8 ), can be recovered in the separation column (T).

1 . A method for recovering a helium product fraction from a nitrogen- and helium-containing feed fraction, wherein
 the nitrogen- and helium-containing feed fraction is partially condensed and separated into a first helium-enriched fraction and a first nitrogen-enriched fraction,   the first helium-enriched fraction is subjected to an adsorptive cleaning process and the helium-enriched fraction recovered therefrom represents the helium product fraction,   the first nitrogen-enriched fraction is separated into a second helium-enriched fraction and a second nitrogen-enriched fraction, and   the second helium-enriched fraction is preheated against the nitrogen- and helium-containing feed fraction to be partially condensed, condensed and admixed to the nitrogen- and helium-containing feed fraction to be partially condensed,   
       characterized, in that
 the separation of the first nitrogen-enriched fraction into a second helium-enriched fraction and a second nitrogen-enriched fraction is implemented in a separation column, to which the first nitrogen-enriched fraction is supplied as return flow, 
 a sub-flow of the second nitrogen-enriched fraction evaporates and the separation column is supplied as stripping gas, 
 at least a sub-flow of the second nitrogen-enriched fraction is evaporated against the nitrogen- and helium-containing feed fraction to be partially condensed under a pressure of less than 5 bar, 
 a third nitrogen-enriched fraction is removed from the separation column, 
 wherein the stripping gas quantity is set such that the third nitrogen-enriched fraction contains at least 30% of the nitrogen contained in the first nitrogen-enriched fraction, and 
 the third nitrogen-enriched fraction serves at least partially to cool the nitrogen- and helium-containing feed fraction to be partially condensed. 
 
     
     
         2 . The method according to  claim 1 , characterized in that the third nitrogen-enriched fraction is at least partially work-performing expanded. 
     
     
         3 . The method according to  claim 1 , characterized in that the separation column is operated under a pressure of 7 to 20 bar. 
     
     
         4 . The method according to  claim 1 , characterized in that the third nitrogen-enriched fraction contains at least 50% of the nitrogen contained in the first nitrogen-enriched fraction. 
     
     
         5 . The method according to  claim 1 , characterized in that at least a sub-flow of the second nitrogen-enriched fraction is evaporated against the nitrogen- and helium-containing feed fraction to be partially condensed under a pressure of less than 3 bar. 
     
     
         6 . The method according to  claim 1 , characterized in that the adsorptive cleaning process is a (V)PSA and/or TSA process. 
     
     
         7 . The method according to  claim 3 , characterized in that the separation column is operated under a pressure of 10 to 15 bar.