Controlling a distillation operation to maintain specified product purities with optimum feed enthalpy

Claim 1

IN A PROCESS WHEREIN A MULTICOMPONENT FEED STREAM IS HEATED AND INTRODUCED INTO A DISTILLATION COLUMN FOR SEPARATION THEREIN INTO A DISTILLATE PRODUCT STREAM AND A BOTTOM PRODUCT STREAM EACH OF WHICH POSSESS A SPECIFIED PURITY, A COLUMN OVERHEAD VAPOR STREAM IS PRODUCED AND AT LEAST PARTIALLY CONDENSED, SOME OF SAID CONDENSED OVERHEAD IS RECYCLED TO SAID COLUMN AS AN EXTERNAL REFLUX STREAM, OF SAID COLUMN OVERHEAD STREAM IS YIELDED AS A DISTILLATE PRODUCT STREAM HAVING A SPECIFIED PURITY, WHEREIN HEAT IS SUPPLIED TO SAID COLUMN TO EFFECT SAID SEPARATION, AN IMPROVED CONTROL METHOD FOR DETERMINING THE OPTIMUM ENTHALPY OF THE HEATED FEED STREAM INTRODUCED INTO SAID COLUMN NECESSARY TO PRODUCE SAID PURITIES WHILE MINIMIZING THE INPUT OF HEAT TO SAID COLUMN, SAID METHOD COMPRISING THE STEPS OF MEASURING A PROCESS VARIABLE INDICATIVE OF THE FLOW RATE OF FEED TO SAID COLUMN; PRODUCING A SIGNAL REPRESENTATIVE OF THE FLOW OF FEED TO SAID COLUMN; ANALYZING SAID FEED TO DETERMINE THE CONCENTRATIONS OF COMPONENTS PRESENT IN SAID FEED; PRODUCING SIGNALS REPRESENTATIVE OF THE CONCENTRATION OF SAID COMPONENTS IN SAID FEED; COMBINING SAID SIGNALS IN AN OPERATIONS COMPUTER IN A MANNER BASED ON THE FOLLOWING EXPRESSION: