Fractionation process and apparatus

Claim 1

IN A FRACTIONATION PROCESS, THE STEPS WHICH COMPRISES HEATING A FEED STREAM TO BE FRACTIONATED, INTRODUCING THE MAJOR PORTION OF THE HEATED FEED STREAM INTO A FRACTIONATION ZONE AND THEREIN SEPARATING IT INTO A KETTLE PRODUCT AND AN OVERHEAD PRODUCT, INTRODUCING THE REMAINING SMALL PART OF THE FEED STREAM INTO A CONTROL VESSEL WHEREIN A LIQUID LEVEL IS MAINTAINED, PASSING LIQUID FROM SAID VESSEL INTO SID FRACTIONATION ZONE AT A REGION CLOSELY ADJACENT THE REGION OF FEED INTRODUCING, CONTINUOUSLY WITHDRAWING VAPOR FROM SAID CONTROL VESSEL INTO A LOW PRESSURE REGION OF SAID FRACTIONATION ZONE, ESTABLISHING A LIQUID LEVEL IN SAID CONTROL VESSEL AT A HIGHT DETERMINED BY THE VAPOR PRESSURE DIFFERENCE BETWEEN THE CONTROL VESSEL AND THE FEED INTRODUCTION REGION OF THE FRACTIONATION ZONE, DECREASING THE HEAT SUPPLIED IN SAID HEATING STEP WHEN SAID LIQUID LEVEL FALLS BELOW ITS ESTABLISHED VALUE AND INCREASING THE HEAT SUPPLIED WHEN SAID LIQUID LEVEL RISES ABOVE ITS ESTABLISHED VALUE, WHEREBY THE FEED ENTERING SAID FRACTIONATION ZONE IS MAINTAINED AT A PREDETERMINED TEMPERARURE WITH RESPECT TO ITS BUBBLE POINT AT THE PRESSURE PREVENTING AT SAID REGION OF FEED INTRODUCTION.