Process control by gas chromatography

Claim 1

IN A METHOD OF CONTROLLING A PROCESS HAVING A MANIPULATED PROCESS VARIABLE, WHEREIN A SAMPLE OF GAS MIXTURE IS OBTAINED FROM SAID PROCESS AND ANALYZED BY GAS CHROMATOGRAPHY WHEREIN A SAMPLE OF SAID GAS MIXTURE IN A STREAM OF INERT CARRIER GAS IS INTRODUCED ONTO A PACKED CHROMATOGRAPHIC COLUMN, SAID SAMPLE IS ELUTED BY CONTINUING THE PASSAGE OF SAID STREAM OF CARRIER GAS INTO SAID COLUMN TO CAUSE THE SEPARATION OF AT LEAST ONE SAMPLE COMPONENT OF INTEREST, AND A STREM OF CARRIER GAS CONTAINING AT LEAST ONE SEPARATED SAMPLE COMPONENT OF INTEREST IS WITHDRAWN AS EFFLUENT FROM SAID COLUMN, THE IMPROVEMENT COMPRISING PASSING SAID STREAM OF CARRIER GAS THROUGH THE REFERENCE ZONE OF A CHROMATOGRAPHIC DETECTOR INTO AND THROUGH SAID COLUMN AND THEN INTO AND THROUGH THE SENSING ZONE OF SAID DETECTOR, SUBSQUENT TO THE COMMENCEMENT OF PASSAGE OF CARRIER GAS THROUGH SAID SENSING ZONE INTRODUCING SAID SAMPLE INTO SAID STREAM OF CARRIER GAS AT A POINT UPSTREAM OF SAID REFERENCE ZONE AND PASSING SAID STREAM OF CARRIER GAS CONTAINING SAID SAMPLE THROUGH SAID REFERENCE ZONE PRIOR TO PASSING THE SAME ONTO SAID COLUMN AND PASSING EFFLUENT FROM SAID COLUMN THROUGH SAID SENSING ZONE OF SAID DETECTOR WHILE CONTINUING THE PASSAGE OF CARRIER GAS THROUGH SAID REFERENCE ZONE AND INTO SAID COLUMN TO PROVIDE AT A FIRST POINT OF TIME ONLY CARRIER GAS IN SAID SENSING ZONE AND CARRIER GAS PLUS SAID SAMPLE IN SAID REFERENCE ZONE AND AT A SECOND SUBSEQUENT POINT OF TIME ONLY CARRIER GAS IN SAID REFERENCE ZONE AND CARRIER GAS PLUS SAID SEPARATED COMPONENT IN SAID SENSING ZONE, DETECTING AT SAID FIRST POINT OF TIME A CHANGE IN A SELECTED PROPERTY OF SAID CARRIER GAS PASSING THROUGH SAID REFERENCE ZONE DUE TO THE PRESENCE OF SAID SAMPLE OF GAS MIXTURE AND ESTABLISHING A FIRST SIGNAL REPRESENTATIVE OF THE THUS DETECTED CHANGE, ESTABLISHING AND STORING A SECOND SIGNAL REPRESENTATIVE OF THE INTEGRAL OF SAID FIRST SIGNAL, AND DETECTING AT SAID SECOND POINT OF TIME A CHANGE IN SAID SELECTED PROPERTY OF THE CARRIER GAS PASSING THROUGH SAID SENSING ZONE DUE TO THE PRESENCE OF SAID SEPARATED COMPONENT THEREIN AND ESTABLISHING A THIRD SIGNAL REPRESENTATIVE OF THE THUS DETECTED CHANGE, ESTABLISHING AND STORING A FOURTH SIGNAL REPRESENTATIVE OF THE INTEGRAL OF SAID THIRD SIGNAL, ESTABLISHING RESPONSIVE TO SAID STORED SECOND AND FOURTH SIGNALS A FIFTH SIGNAL REPRESENTATIVE OF THE RATIO OF SAID SECOND AND FOURTH SIGNALS AND THUS REPRESENTATIVE OF THE CONCENTRATION OF SAID COMPONENT IN SAID SAMPLE, ESTABLIHSING A SIXTH SIGNAL REPRESENTATIVE OF A PREDETERMINED DESIRED CONCENTRATION OF SAID COMPONENT IN SAID GAS MIXTURE, COMPARING SAID FIFTH AND SIXTH SIGNALS AND ESTABLISHING A SEVENTH SIGNAL REPRESENTATIVE OF THE DIFFERENCE BETWEEN SAID FIFTH AND SIXTH SIGNALS AND CONTROLLING SAID PROCESS VARIABLE RESPONSIVE TO SAID SEVENTH SIGNAL.