Apparatus and method for separating air by cryogenic distillation

Abstract

The invention relates to equipment for separating air that includes a first average pressure distillation column, a second low-pressure distillation column, a third low-pressure distillation column, a first condenser-vaporizer, a second condenser-vaporizer arranged in the tank of the second column, a pipe for supplying air to the first column, a pipe for supplying a nitrogen-enriched liquid from the head of the first column to the head of the third column, at least one pipe for supplying the liquid from the tank of the third column to the first condenser-vaporizer, a pipe for supplying a liquid of the tank from the first column to the third column, a pipe for supplying the liquid from the first condenser-vaporizer to the second column, a pipe for supplying gas from the head of the second column to the tank of the third column, wherein the first, second, and third columns are arranged side by side.

1 - 14 . (canceled) 
     
     
         15 . An apparatus for separating air comprising;
 a) a first distillation column, comprising a head and a bottom, capable of operating at a first pressure,   b) a second distillation column, comprising a head and a bottom, capable of operating at a second pressure,   c) a third distillation column, comprising a head and a bottom, capable of operating at a third or at the second pressure,   d) a first condenser-vaporizer,   e) a second condenser-vaporizer arranged in the bottom of the second column,   f) a pipe for supplying air at least to the first column,   g) a pipe for supplying a nitrogen-enriched liquid from the head of the first column to the head of the third column,   h) at least one pip for supplying liquid from the bottom of the third column to the first condenser-vaporizer,   i) a pipe for supplying a liquid from the bottom of the first column to the third column,   j) a pipe for supplying liquid from the first condenser-vaporizer to the second column, and   k) a pipe for supplying overhead gas from the second column to the bottom of the third column, the first, second and third columns being arranged side-by-side   
     
     
         16 . The apparatus of  claim 15 , wherein the first, second and third columns are all arranged on a floor surface. 
     
     
         17 . The apparatus of  claim 15 , wherein a liquid oxygen vaporizer capable of operating at a cryogenic temperature, is arranged below one of the columns and wherein the two other columns and the liquid oxygen vaporizer are placed directly on the floor surface. 
     
     
         18 . The apparatus of  claim 17 , comprising a means for pressurization connected to the bottom of the second column and to the liquid oxygen vaporizer. 
     
     
         19 . The apparatus of  claim 15 , wherein the first condenser-vaporizer is above the first column and is connected to the head of the first column to permit reboiling by a gas from the first column. 
     
     
         20 . The apparatus of  claim 15 , further comprising a single pump connected to two of the columns. 
     
     
         21 . The apparatus of  claim 20 , wherein the pump is connected to the two pipes for supplying liquid from the bottom of the second column to the first condenser-reboiler. 
     
     
         22 . The apparatus of  claim 15 , further comprising a gas pipe connecting the first condenser-reboiler to the bottom of the third column. 
     
     
         23 . The apparatus of  claim 15 , wherein the head of the second column and/or the third column is at a lower level than the first condenser-reboiler and the packing densities in the first column may be lower than the packing densities of the second column and/or of the third column. 
     
     
         24 . The apparatus of  claim 23 , wherein the head of the second column and/or the third column is lower than the head of the first column. 
     
     
         25 . The apparatus of  claim 15 , wherein the third column does not contain a condenser-reboiler. 
     
     
         26 . The apparatus of  claim 15 , wherein the second column also contains a third condenser-reboiler in addition to means for exchanging heat and material arranged above the third condenser-reboiler. 
     
     
         27 . The apparatus of  claim 15 , wherein the pipe for supplying overhead gas from the second column to the bottom of the third column is connected to a pipe for gas vaporized in the first condenser-reboiler. 
     
     
         28 . The apparatus of  claim 15 , wherein the liquid oxygen vaporizer is arranged below the third column. 
     
     
         29 . A method for separating air using an apparatus as claimed in  claim 15 , wherein the difference in pressure between the operating pressure of the first column and the pressure of at least one of the second and third columns is less than 3 bar. 
     
     
         30 . The method of  claim 29 , wherein the difference in pressure between the operating pressure of the first column and the pressure of at least one of the second and third columns is 2.5 bar. 
     
     
         31 . The method of  claim 30 , wherein the difference in pressure between the operating pressure of the first column and the pressure of at least one of the second and third columns is 2 bar 
     
     
         32 . The method for separating air using an apparatus as claimed in  claim 15 , wherein the difference in pressure between the operating pressure of the top of the second column and the bottom of the third column is less than 1 bar. 
     
     
         33 . The method of separating air of  claim 32 , wherein the difference in pressure between the operating pressure of the top of the second column and the bottom of the third column is less than 0.5 bar. 
     
     
         34 . The method of separating air of  claim 33 , wherein the difference in pressure between the operating pressure of the top of the second column and the bottom of the third column is less than 0.2 bar.