Recovery Of Helium From Nitrogen-Rich Streams

Abstract

Overall power consumption in a cryogenic distillation process for recovering helium from nitrogen-rich gases comprising helium may be reduced if the feed to the distillation column system is at least substantially condensed by indirect heat exchange against a first bottoms liquid at first pressure, and a second bottoms liquid at a second pressure that is different from the first pressure.

1 . Apparatus for recovering helium from a nitrogen-rich feed gas comprising helium, said apparatus comprising:
 a distillation column system for operation at an elevated operating pressure to separate at least partially condensed feed gas into helium-enriched overhead vapor and nitrogen-enriched bottoms liquid(s);   an overhead condenser for partially condensing helium-enriched overhead vapor by indirect heat exchange to produce helium-enriched vapor as product and liquid for reflux in the column system;   a first heat exchange system for cooling feed gas by indirect heat exchange with a first nitrogen-enriched bottoms liquid to produce cooled feed gas and vapor for the column system;   a first pressure reduction device for reducing the pressure of a second nitrogen-enriched bottoms liquid to produce reduced pressure bottoms liquid;   a second heat exchange system for cooling said cooled feed gas by indirect heat exchange against said reduced pressure bottoms liquid to produce at least partially condensed feed gas and vaporized bottoms liquid; and   a second pressure reduction device for reducing the pressure of said at least partially condensed feed gas to produce at least partially condensed feed gas at reduced pressure for use as said feed to the distillation column system.   
     
     
         2 . The apparatus of  claim 1  comprising a third pressure reduction device for reducing the pressure of a third nitrogen-enriched bottoms liquid to produce reduced pressure bottoms liquid for vaporization by indirect heat exchange in said overhead condenser to produce nitrogen-enriched vapor. 
     
     
         3 . The apparatus of  claim 2  comprising an expander for expanding said nitrogen-enriched vapor to produce expanded nitrogen-enriched vapor for warming by indirect heat exchange in said overhead condenser to produce warmed nitrogen-enriched vapor. 
     
     
         4 . The apparatus of  claim 2  comprising a fourth pressure reduction device for reducing the pressure of a fourth nitrogen-enriched bottoms liquid to produce reduced pressure bottoms liquid for vaporization by indirect heat exchange in said overhead condenser to produce nitrogen-enriched vapor. 
     
     
         5 . The apparatus of  claim 1  comprising an expander for expanding said vaporized bottoms liquid to produce expanded nitrogen-enriched vapor for warming by indirect heat exchange in said overhead condenser to produce warmed nitrogen-enriched vapor. 
     
     
         6 . The apparatus of  claim 5  comprising:
 a fourth pressure reduction device for reducing the pressure of a fourth portion of said nitrogen-enriched bottoms liquid to produce reduced pressure bottoms liquid; and 
 a storage vessel for storing said reduced pressure bottoms liquid. 
 
     
     
         7 . Apparatus substantially as hereinbefore described with reference to the accompanying examples and/or drawings.