Separation of closely boiling fractions from a binary mixture

Claim 1

AN IMPROVED METHOD OF SEPARATING AND RECOVERING FRACTIONS HAVING A LOW RELATIVE VOLATILITY FROM A BINARY MIXTURE, WHICH COMPRISES, COOLING SAID MIXTURE AND SUBSEQUENTLY INTRODUCING THE COOLED MIXTURE AT A RELATIVELY LOW FRACTIONATING PRESSURE TO A FRACTIONATING AND SEPARATING ZONE, FRACTIONATING SAID MIXTURE IN SAID ZONE IN THE PRESENCE OF A COLD REFLUX STREAM OF THE LOWER BOILING FRACTION WHICH IS OBTAINED AS HEREINAFTER DESCRIBED, DISCHARGING THE HIGHER BOILING FRACTION FROM THE LOWER PORTION OF THE FRACTIONATING ZONE, WITHDRAWING A STREAM OF THE LOWER BOILING FRACTION FROM THE UPPER PORTION OF SAID FRACTIONATING ZONE, COMPRESSING THE LATTER FRACTION TO SUBSTANTIALLY HIGHER SUPERATMOSPHERIC PRESSURE AND EFFECTING THE HEATING THEREOF, PASSING THE RESULTING COMPRESSED STREAM IN INDIRECT HEAT EXCHANGE WITH THE LIQUID PHASE IN THE LOWER PORTION OF THE FRACTIONATING ZONE AND REBOILING LIQUID THEREIN WHILE SIMULTANEOUSLY COOLING AND CONDENSING THE COMPRESSED STREAM, REDUCING THE PRESSURE ON THE RESULTING CONDENSED STREAM OF THE DESIRED LIGHTER FRACTION TO EFFECT A FURTHER TEMPERATURE REDUCTION AND INTRODUCTING THE SAME TO A RECEIVING ZONE MAINTAINED AT THE REDUCED PRESSURE AND THEREIN SEPARATING GAS FROM LIQUID, WITHDRAWING RESULTING SUBSTANTIALLY PURE LIQUID FRACTION FROM THE LOWER PORTION OF THE RECEIVING ZONE AND RETURNING A PORTION THEREOF TO THE FRACTIONATING AND SEPARATING ZONE AS SAID REFLUX STREAM AND PASSING ANOTHER PORTION THEREOF IN INDIRECT HEAT EXCHANGE WITH SAID MIXTURE UNDERGOING COOLING AS AFORESAID.