Control of internal reflux in a fractional distillation process and system

Claim 1

IN A FRACTIONATION SYSTEM THAT INCLUDES A FRACTIONATION COLUMN, MEANS TO INTRODUCE A FEED MIXTURE TO BE SEPARATED INTO SAID COLUMN, FIRST CONDUIT MEANS CONNECTED TO SAID COLUMN TO REMOVE A VAPOR STREAM FROM THE UPPER REGION OF SAID COLUMN, COOLING MEANS CONNECTED TO SAID FIRST CONDUIT MEANS TO CONDENSE AT LEAST A PORTION OF THE VAPOR STREAM REMOVED FROM SAID COLUMN, AND SECOND CONDUIT MEANS CONNECTED BETWEEN SAID FIRST CONDUIT MEANS AND SAID COLUMN TO RETURN A PORTION OF THE RESULTING CONDENSATE TO SAID COLUMN AS EXTERNAL REFLUX, A CONTROL SYSTEM COMPRISING FIRST TEMPERATURE SENSING MEANS POSITIONED TO SENSE THE TEMPERATURE TO OF SAID VAPOR REMOVED FROM SAID COLUMN; SECOND TEMPERATURE SENSING MEANS POSITONED TO SENSE THE TEMPERATURE TR OF SAID CONDENSATE RETURNED TO SAID COLUMN AS EXTERNAL REFLUX; MEANS RESPONSIVE TO SAID FIRST AND SECOND TEMPERATURE SENSING MEANS TO ESTABLISH A FIRST SIGNAL REPRESENTATIVE OF 1+K$T, WHERE K IS A CONSTANT EQUAL TO TH SEPCFIC HEAT OF SAID EXTERNAL REFLUX DIVIDED BY THE HEAT OF VAPORIZATION OF LIQUID IN THE TOP OF SAID COLUMN AND $T IS TO -TR; SIGNAL MULTILYING MEANS HAVING FIRST AND SECOND IMPUTS AND AN OUTPUT; MEANS TO APPLY SAID FIRST AND SECOND INPUTS; CONTROLLER MEANS HAVING A SIGNAL INPUT AND A SET POINT INPUT WITH THE SIGNAL APPLIED TO SAID SET POINT INPUT BEING REPRESENTATIVE OF THE DESIRED VALUE OF INTERNAL REFLUX; MEANS CONNECTING SAID OUTPUT OF SAID MULTIPLYING MEANS TO SAID SIGNAL INPUT OF SAID CONTROLLER MEANS, SAID CONTROLLER MEANS BEING ADAPTED TO COMPARE THE SIGNAL APPLIED TO ITS SET POINT INPUT WITH THE SIGNAL APPLIED TO ITS SIGNAL INPUT AND PRODUCE RESPONSIVE TO SUCH COMPARISON AN OUTPUT SIGNAL REPRESENTATIVE OF THE VALUE OF EXTERNAL REFLUX NECESSARY TO MAINTAIN THE INTERNAL REFLUX SUBSTANTIALLY EQUAL TO SAID DESIRED VALUE; MEANS INDEPENDENT OF THE ACTUAL FLOW OF EXTERNAL REFLUX TO APPLY THE OUTPUT SIGNAL OF SAID CONTROLLER MEANS TO SAID SECOND INPUT OF SAID MULITPLYING MEANS; AND MEANS RESPONSIVE TO SAID OUTPUT SIGNAL OF SAID CONTROLLER MEANS TO REGULATE THE RATE OF FLOW OF SAID EXTERNAL REFLUX THROUGH SAID SECOND CONDUIT MEANS.