Composition control in batch distillation: Binary and multicomponent mixtures

A strategy is proposed for the control of constant-distillate- composition operations of batch distillation columns. The proposed control law is derived in the framework of Nonlinear Internal Model Control. The distillate composition is estimated from selected tray temperature measurements by an observer. The same observer provides the estimate of the system states that are necessary for the computation of the control algorithm. Results are provided for binary and multicomponent separations of ideal and nonideal systems. Several sources of process/model mismatch are considered in order to provide a realistic test scenario for the proposed procedure. It is shown that the proposed controller ensures fast and smooth transition from the startup phase to the production phase, and tight composition control until the end of the operation. Moreover, the tuning of the controller is performed very easily. Finally, the on-line computation of the control law is straightforward, which is a promising result toward practical implementation of the proposed method.