A NEW CONTROL ALGORITHM FOR CONCENTRATION CONTROL IN THREE EFFECT FALLING FILM EVAPORATORS

Falling film evaporators have been given great attention due to their wide applications in industrial processes. In these processes, due to large time delay and disturbances the tight exact and proper control of product concentration is difficult. In this study, a nonlinear dynamic model has been considered for modeling and simulation of a three-effect falling film evaporator. The basic structure of the model is composed of heat and mass conservation equations coupled with thermodynamics as well as auxiliary correlations for prediction of physical properties. Also, a triple loop cascade control is proposed and tuned for control of this process. The proposed algorithm consists of three conventional loops. Results obtained from this proposed algorithm are compared with results of conventional PID control. It is shown that the regulatory and servo responses can be significantly improved by the proposed control algorithm.