Process and apparatus for the separation, by rectification, of a gas mixture containing at least three components

Claim 1

A PROCESS FOR OBTAINING THE VOLATILE CONSITITUENT FREE FROM ANY CONSTITUENT OF INTERMEDIATE VOLATILITY FROM A GASEOUS MIXTURE CONTAINING THREE COMPONENTS WITH DIFFERENT BOILING POINTS BY SUCCESSIVE FRACTIONATION AT LOW TEMPERATURES IN TWO SUCCESSIVE RECTIFYING COLUMNS, COMPRISING CONDENSING AT THE TOP OF THE COLUMN OPERATING UNDER A PRESSURE HIGHER THAN THAT OF THE LAST COLUMN, A FIRST LIQUID RICH IN THE MOST VOLATILE COMPONENT, INTRODUCING SAID FIRST LIQUID INTO THE LAST COLUMN AS THE FINAL REFLUX LIQUID, WITHDRAWING FROM THE COLUMN IN WHICH THE FIRST LIQUID IS CONDENSED A SECOND LIQUID RICH IN THE LEAST VOLATILE COMPONENT AND INTRODUCING IT INTO THE LAST COLUMN AT A LOW ELEVATION, WITHDRAWING FURTHER FROM THE COLUMN IN WHICH THE FIRST LIQUID IS CONDENSED AT THE POINT OF MAXIMUM CON-CENTRATION OF CONSTITUENT OF INTERMEDIATE VOLATILITY A THIRD LIQUID AND INTRODUCING IT IN TO THE LAST COLUMN AT AN INTERMEDIATE POINT AS A WASH LIQUID.