Modelling and Control Analysis of Dividing Wall Distillation Columns

Abstract

This work aims to study the behavior of fluid mixtures in the dividing wall column, particularly from a controllability point of view. It covers the aspects of design, modeling, and control. A ternary mixture of benzene, toluene, and o-xylene (BTX) is selected as a case study. A controllability analysis for determining and screening the candidate control combinations of the manipulated variables is carried out with the aid of a linearized model using the concept of relative gain array (RGA). The manipulated variables are the reflux (L), the distillate (D), the side stream (S), the bottom (B) and the boilup (V). Based on RGA criterion, two of the candidate combinations are selected to control the column due to the low interaction between control loops. In each combination the manipulated variables are used to control the top level, the bottom level, the top composition, the middle composition and the bottom composition. Finally, the performance of these two combinations is examined and found to be successful in resisting the disturbances.