Conceptual Model and Referential Reaction Methods applied to Binary Batch Distillation

ESPINOSA, JOSÉ; LUIS MARCHETTI, JACINTO

Rio de Janeiro

Congreso; 4th Mercosur Congress on Process Systems Engineering; 2005

Abstract: This contribution discusses the combination of a conceptual modeling method to describe a quasi-optimal trajectory for batch distillation of a binary mixture, with the use of the referential reaction method to adjust the feedback controller tracking the desired conditions. The proposed trajectory is derived from pinch theory leading to minimum energy expenses during the operation of a batch distillation column conditioned for recovering most of the light component at a pre-fixed purity. Once the desired trajectory is obtained from the conceptual model, a simple open-loop ratio controller associated to the condenser-drum level control gives a reasonable performance of the plant rigorously simulated in MATLAB. However, this control strategy is not enough to protect the light-component purity from unfavorable disturbances.The referential reaction method is an extension of the classical process reaction curve to empirically determine reduced-order models for designing and tuning feedback controllers dedicated to tracking non-stationary conditions in batch processes. Defining a feedback control system for a batch distillation implies first the selection of an appropriate tray temperature evolution. Then, the dynamics associated to the manipulated variable, which in this case is the distillate flow rate, is isolated from the main time-variable behavior desired for the operation, and used with available tuning rules for integrating systems. The effectiveness of this procedure is illustrated by using a nonlinear model of a binary distillation column where high purity light component is recovered.