Distillation of low-boiling components

Claim 1

IN A PROCESS FOR SEPARATING A LOWER BOILING COMPONENT OF A DISTILLABLE MIXTURE FROM A HIGHER-BOILING COMPONENT THEREOF, COMPRISING FEEDING SAID MIXTURE TO A FRACTIONATION ZONE OPERATED AT A PRESSURE AT WHICH SAID HIGHERBOILING COMPONENT IS CONDENSIBLE AT A TEMPERATURE OBTAINABLE BY COOLING WATER IN THE SURROUNDINGS, WITH DRAWING AN OVERHEAD VAPOR PRODUCT COMPRISING SAID LOWERBOILING COMPONENT AND WITHDRAWING A BOTTOMS LIQUID PRODUCT COMPRISING SAID HIGHER BOILING COMPONENT, WHEREIN UPFLOWING VAPORS ARE GENERATED BY HEATING BELOW THE FEED POINT TO A TEMPERATURE SUBSTANTIALLY ABOVE ATMOSPHERIC IN ORDER TO KEEP THE CONCENTRATION OF LOWER-BOILING COMPONENT IN THE BOTTOMS LIQUID PRODUCT BELOW A SET MAXIMUM, AND WHEREIN REFRIGERATION MEANS IS USED TO SUPPLY TOP REFLUX AT A LOWER TEMPERATURE THAN IS NATURALLY OBTAINABLE IN THE SURROUNDINGS IN ORDER TO KEEP TO CONCENTRATION OF HIGHER-BOILING COMPONENT IN THE OVERHEAD VAPOR PRODUCT BELOW A SET MAXIMUM; THE IMPROVEMNT FOR MINIMIZING THE REFRIGERATION WORK, WHICH COMPRISES: WITHDRAWING ALL UPFLOWING VAPOR FROM THE FRACTIONATION ZONE AT A POINT ABOVE THE FEED POINT WHERE THE TEMPERATURE IS SUBSTANTIALLY ABOVE ATMOSPHERIC, PARTIALLY CONDENSING THE WITHDRAW VAPOR AT A TEMPERATURE OBTAINABLE BY COOLING WATER IN THE SURROUNDINGS, PASSING ONLY THE UNCONDENSIBLE PORTION OF THE WITHDRAWN VAPOR TO A RECTIFICATION SECTION OF SAID FRACTIONATION ZONE ABOVE THE POINT OF VAPOR WITHDRAWAL FOR COUNTERCURRENT CONTACT THEREIN WITH DOWNFLOWING TOP REFLUX SUPPLIED BY SAID REFRIGERATION MEANS, AND RETURNING THE RESULTING CONDENSED PORTION OF THE WITHDRAWN VAPOR TO THE FRACTIONATION ZONE BETWEEN THE FEED POINT AND THE POINT OF VAPOR WITHDRAWAL.