Apparatus And Method For Separating Air By Cryogenic Distillation

Abstract

An apparatus and to a method for producing krypton and xenon by separating air by cryogenic distillation and in particular to a method for separating gasses from air using internal compression (in which the gaseous oxygen is produced by vaporization under pressure in the exchange line) where a krypton/xenon mixture is extracted is provided.

1 - 15 . (canceled) 
     
     
         16 . A method for producing krypton and xenon by separation of air by cryogenic distillation in a double column comprising a medium pressure column and a low pressure column, said method comprising:
 i) sending cooled and purified compressed gaseous air to a first level of the medium pressure column;   ii) sending cooled and purified compressed liquid air to a second level of the medium pressure column, wherein said second level is above the first level;   iii) withdrawing a liquid, enriched in oxygen, krypton and xenon from the bottom of the medium pressure column;   iv) withdrawing a liquid from the medium pressure column, at a level between the first and second levels, and sent to the low pressure column;   v) partially vaporizing the liquid enriched in oxygen, krypton and xenon in order to form an intermediate gas and an intermediate liquid;   vi) withdrawing a first liquid stream rich in oxygen from a third level of the low pressure column;   vii) sending the intermediate liquid from the vaporizer to the low pressure column at an intermediate level of the low pressure column, lower than the third level, and   viii) a second oxygen-rich liquid stream is tapped from the low pressure column at a fourth level, lower than the third level, and, lower than the intermediate level.   
     
     
         17 . The method of  claim 16 , wherein the vaporized intermediate gas is sent to the low pressure column at a level higher than the intermediate level. 
     
     
         18 . The method of  claim 16 , wherein the liquid enriched in oxygen, krypton and xenon is vaporized by heat exchange with a gas tapped from the medium pressure column. 
     
     
         19 . The method of  claim 18 , wherein the gas tapped from the medium pressure column is tapped from above the first level. 
     
     
         20 . The method of  claim 16 , wherein the intermediate liquid is sent from the vaporizer to an intermediate level of the low pressure column, lower than the third level. 
     
     
         21 . The method of  claim 20 , wherein the second oxygen-rich liquid stream is withdrawn from the low pressure column at a fourth level, lower than the intermediate level. 
     
     
         22 . The method of  claim 16 , wherein the intermediate liquid is mixed with a second oxygen-rich liquid stream. 
     
     
         23 . An apparatus for separation of air by cryogenic distillation comprising a double column constituted by a medium pressure column and a low pressure column and a vaporizer comprising:
 i) means for sending cooled and purified compressed gaseous air to a first level of the medium pressure column   ii) means for sending cooled and purified compressed liquid air to a second level of the medium pressure column, above the first level   iii) means for tapping a liquid, enriched in oxygen, krypton and xenon from the bottom of the medium pressure column   iv) means for tapping a liquid from the medium pressure column, at a level between the first and second levels, and it is sent to the low pressure column   v) means for sending at least a portion of the liquid enriched in oxygen, krypton and xenon to the vaporizer where it is partially vaporized to form an intermediate gas and an intermediate liquid   vi) means for tapping a first liquid stream rich in oxygen from a third level of the low pressure column   vii) means for sending the intermediate liquid from the vaporizer to the low pressure column at an intermediate level of the low pressure column or for mixing it with a second liquid stream rich in oxygen and   viii) means for tapping a/the second oxygen-rich liquid stream from the low pressure column at a fourth level, lower than the third level, and lower than the intermediate level.   
     
     
         24 . The apparatus of  claim 23 , further comprising means for sending the intermediate gas from the vaporizer to the low pressure column at a level higher than the intermediate level. 
     
     
         25 . The apparatus of  claim 23 , further comprising means for sending a gas tapped from the medium pressure column to the vaporizer. 
     
     
         26 . The apparatus of  claim 25 , further comprising means for tapping the gas from the medium pressure column from above the first level. 
     
     
         27 . The apparatus of  claim 23 , further comprising means for pressurizing and vaporizing the first oxygen-rich stream, 
     
     
         28 . The apparatus of  claim 27 , wherein said means for pressurizing and vaporizing the first oxygen-rich stream is by heat exchange with the air to be distilled. 
     
     
         29 . The apparatus of  claim 23 , further comprising means for sending the intermediate liquid from the vaporizer to an intermediate level of the low pressure column, lower than the third level. 
     
     
         30 . The apparatus of  claim 29 , further comprising means for tapping the second oxygen-rich liquid stream from the low pressure column at a fourth level, lower than the intermediate level. 
     
     
         31 . The apparatus of  claim 23 , further comprising means for mixing the intermediate liquid with a second oxygen-rich liquid stream.