Method to control dosage of additive into treatment process and automatic device therefor

Abstract

Abstract A METHOD FOR CONTROLLING, BY A NOVEL FEEDFORWARD-FEEDBACK ADAPTIVE SYSTEM, A CONTINUOUS PROCESS OF TREATING A FLUID, CONTAINING AN INGRIEDENT, THAT INCLUDES INCORPORATING A DOSAGE OF ADDITIVE IN THE FLOWING FLUID SO AS TO CHANGE THE INGRIDIENT. DURING THE OPERATION OF THE PROCESS, WITHOUT THE USE OF THE CONTROL METHOD, THERE CAN BE UNPREDICTABLE VARIATIONS AFFECTING THE EFFICIENCY OF THE TREATMENT SO AS TO REQUIRE CORRECTION OF THE DOSAGE OF ADDITIVE TO AN UNPREDICTABLE EXTENT. A DEVICE FOR THIS SYTEM PROVIDES FOR AUTOMATIC CONTROL OF DOSAGE OF THE ADDITIVE. IN THE PROCESS THERE IS A NONLINER RELATIONSHIP BETWEEN THE AMOUNT OF ADDITIVE AND THE DEGREE OF TREATMENT. THIS RELATIONSHIP CAN BE EXPRESSED AS A MONOTONIC CURVE WITHIN THE RANGE OF CONCENTRATION OF THE INGREDIENT IN THE FLUID AND THE RANGE OF DOSAGE REQUIRED FOR THE DESIRED EXTENT OF TREATMENT. THE CONTROL METHOD COMPRISES: A FEEDFORWARD CONTROL PROCESS INCLUDING (1) MONITORING THE FLOWING FLUID TO SENSE A PROPERTY OF THE FLUID RELEVANT TO THE TREATMENT OF THE FLUID BY THE ADDITIVE, AND (2) GENERATING A FIRST SIGNAL PROPORTIONAL TO THE MAGNITUDE OF THE SENSED PROPERTY OF THE FLUID TO BE TREATED, A FEEDBACK CONTROL PROCESS INCLUDING (1) MONITORING A PRODUCT OF THE TREATMENT PROCESS TO SENSE A PROPERTY OF THAT PRODUCT RELEVANT TO THE DESIRED RESULT OF THE TREATMENT PROCESS, (2) GENERATING A SECOND SIGNAL PROPORTIONAL TO THE DESIRED MAGNITUDE OF THE SENSED PROPERTY OF THE PRODUCT, (3) GENERATING A THIRD SIGNAL PROPORTIONAL TO THE MAGNITUDE OF THE ACTUAL SENSED PROPERTY OF THE PRODUCT, AND (4) COMPARING THE SECOND AND THIRD SIGNALS TO PROVIDE AN ERROR SIGNAL INDICATING THE DIFFERENCE BETWEEN THE ACTUAL AND DESIRED SENSED PROPERTY OF THE PRODUCT, AN ADAPTIVE CONTROL PROCESS INCLUDING (1) SUPERIMPOSING THE FIRST SIGNAL ON THE ERROR SIGNAL BY DIVIDING THE LATTER BY THE FORMER TO PROVIDE A FOURTH SIGNAL, (2) INTEGRATING THE FOURTH SIGNAL OVER A LONG PERIOD OF TIME TO PROVIDE A FIFTH SIGNAL, AND (3) MULTIPLYING THE FIRST SIGNAL BY THE FIFTH SIGNAL TO OBTAIN A SIXTH SIGNAL THAT INCLUDES THE VARIABLE GAIN FOR THE FIRST SIGNAL BY THE EXTENT OF THE FIFTH SIGNAL, AND USING THE SIXTH SIGNAL TO ADJUST THE DOSAGE OF ADDITIVE INTO THE FLUID. THE DEVICE FOR AUTOMATICALLY CONTROLLING THE DOSAGE OF ADDITIVE PERFORMS THE THREE BASIC CONTROL FUNCTIONS DESCRIBED ABOVE FOR THE PROCESS. THUS THE PART OF THE DEVICE THAT PROVIDES A SIGNAL REPRESENTING A COMPARISON OF ACTUAL AND DESIRED PROPERTY OF A PRODUCT OF THE TREATMENT IS THE FEEDBACK SYSTEM THAT IS USED TO ADJUST DOSAGE WITH THE ADJUSTMENT TIME BEING MADE THROUGH AN INTERGRATOR TO REDUCE THE STEADY STATE ERROR TO ZERO. THE SIGNAL PROPORTIONAL TO THE MAGNITUDE OF THE PROPERTY OF THE FLUID TO BE TREATED IS THE FEEDFORWARD SIGNAL THAT PROVIDES ESSENTIALLY INSTANTANEOUS CORRECTIVE RESPONSE WHILE THE OTHER SYSTEM IS VERY SLOW. THE CONTROL OF THE FEEDFORWARD SYSTEM TO CHANGE WITH VARIATION IN ONE OR MORE PROCESS CONDITIONS, E.G., EFFICIENCY, IS DETERMINED BY THE FEEDBACK SYSTEM THAT ADJUSTS THE GAIN OF THE FEEDFORWARD SYSTEM.

Inventors

• 👤 Carl J Zaander
• 👤 Veljko Milenkovic
• 👤 Bernard A Johnson

Bibliographic Details