Modeling and Control of pH Process for Weak Acid-Weak Base System

Abstract

This paper studies the model and control of pH neutralization process of waste watersystem using different control schemes. An experimental investigation was conducted forthe dynamic behavior of neutralization process of waste water in a continuous stirred tankreactor (CSTR).A dynamic model for pH neutralization process in a continuous stirred tank reactor(CSTR) is described by a first order plus dead time (FOPDT).The pH value is calculated by solving the charge balance of the mixture. Good agreementis obtained between the simulated and experimental responses. However, a smalldifferences between the responses due to the error in the measurements.The conventional feedback control was studies in this work and the controllerparameters was tuned by Ziegler-Nichols reaction curve method to find the best values ofproportional gain (Kc), integral time (t I) and derivative time (t D). Artificial NeuralNetwork Model Predictive Control (ANN MPC) was used as another strategy to comparewith above strategy.The ANN controller was compared with conventional controller and it was found thatANN controller provides better control for the set point changes with low settling timeand lower overshoot. Whereas the conventional controller provides sluggish behavior inset point change. Also it was found that the ANN controller provides better response toregulated change than the conventional controllers where the PI and PID controllersprovide sluggish disturbance responses because the approximate FOPTD model hasrelatively small time delay. As non-linear process the conventional feedback controllerwas unable to control this system adequately.