Method and System for Treating an Oxygen-Rich Liquid Bath Collected at the Foot of a Cryogenic Distillation Column

Abstract

Methods and apparatus for treating a liquid bath of oxygen. A liquid bath of at least 70 mol % of oxygen is located at the base of a cryogenic distillation column. The bath is continuously boiled by an aluminum reboiler. A portion of the liquid bath is purged to prevent a build up of inflammable impurities in the bath. A portion of the purge is sent to a second reboiler, which is less inflammable than the first reboiler. Oxygen boiled by the second reboiler is sent back to the column, and a portion of the oxygen rich liquid bath treated by the second reboiler is also purged. The invention also relates to an apparatus of carrying out this method.

1 - 10 . (canceled) 
   
   
       11 . A method which may be used for treating a liquid bath of oxygen, said method comprising:
 a) providing a liquid bath in the bottom of a cryogenic distillation column or a column element, wherein:
 1) said liquid bath comprises at least about 70 mol % oxygen; and 
 2) said column or column element forms part of a system of columns that are used for the separation of air; 
   b) boiling continuously a portion of said liquid bath with at least one first reboiler, wherein said first reboiler is made of aluminum;   c) purging a portion of said liquid bath, wherein said purging prevents an excessive build up of inflammable impurities in said bath;   d) sending said purged portion to at least one second reboiler, wherein said second reboiler is less inflammable than said first reboiler;   e) sending oxygen boiled by said second reboiler back to said column; and   f) purging a portion of the oxygen rich liquid bath treated by said second reboiler.   
   
   
       12 . The method of  claim 11 , wherein said purged portion sent to said second reboiler is at least about 0.5 mol % of the total air stream feeding said system of distillation columns. 
   
   
       13 - 14 . (canceled) 
   
   
       15 . The method of  claim 11 , wherein said purged portion of said oxygen rich liquid bath treated by said second reboiler is less than about 1% of the total air stream feeding said system of distillation columns. 
   
   
       16 . The method of  claim 15 , wherein said purged portion of said oxygen rich liquid bath treated by said second reboiler is less than about 0.2% of said total air stream feeding said distillation columns. 
   
   
       17 . An apparatus which may be used for the cryogenic distillation of air, said apparatus comprising:
 a) a cryogenic distillation column or column element, wherein said column comprises a sump;   b) at least one first aluminum reboiler for treating an oxygen rich liquid bath, wherein said first aluminum reboiler is located in said sump;   c) a first purge, wherein:
 1) said first purge sends at least a portion of said bath into at least one second reboiler; and 
 2) said second reboiler is less inflammable than said first reboiler 
   d) a conduit which sends oxygen vaporized by said second reboiler back into said column; and   e) a second purge, wherein said second purge purges a portion of said bath in said second reboiler.   
   
   
       18 . The apparatus of  claim 17 , wherein said second reboiler is located at the bottom of a heat exchanger outside of said column. 
   
   
       19 . The apparatus of  claim 17 , further comprising a partition located in said column, wherein:
 a) said partition divides said sump into a first compartment and a second compartment;   b) said first reboiler is located in said first compartment;   c) said second reboiler is located in said second compartment; and   d) said partition has a height such that said second compartment is fed oxygen rich liquid by overflow from said first compartment.   
   
   
       20 . (canceled) 
   
   
       21 . The apparatus of  claim 17 , wherein:
 a) said column comprising said sump is a low pressure column of a double column;   b) said double column comprises both said low pressure column and a medium pressure column;   c) said low pressure and said medium pressure columns are thermally coupled to each other by said first reboiler;   d) said first reboiler is warmed by a nitrogen enriched gas from said medium pressure column.   
   
   
       22 . The apparatus of  claim 21 , wherein said second reboiler is warmed by a nitrogen enriched gas from said medium pressure column. 
   
   
       23 . An apparatus which may be used for cryogenic distillation of air, said apparatus comprising:
 a) a low pressure column, wherein said low pressure column comprises a sump;   b) at least one first aluminum reboiler for treating an oxygen rich liquid bath, wherein said first aluminum reboiler is located in said sump;   c) a medium pressure column, wherein said medium pressure column is thermally coupled to said low pressure column by said first aluminum reboiler;   d) at least one partition located in said sump;   e) at least one second reboiler, wherein:
 1) said second reboiler is located in said sump; 
 2) said partition separates said first reboiler and said second reboiler; and 
 3) said second reboiler is less inflammable than said first reboiler 
   f) a first purge, wherein said first purge sends at least a portion of said oxygen rich liquid bath to said second reboiler;   g) a conduit which sends oxygen vaporized by said second reboiler back into said low pressure column;   h) a second purge, wherein said second purge purges at least a portion of said oxygen rich liquid bath in said second reboiler; and   i) a nitrogen conduit connecting said medium pressure column with said first reboiler.