Controllability Features of Dividing-Wall Columns

Abstract

The dividing wall columns have they renascence, however, there is lack of comprehensive investigation of column with upper and lower positioned walls. Previous work presented the energy efficiencies of dividing wall columns compared to common and energy integrated column structures.
This paper presents a comprehensive study of controllability features based on frequency dependent controllability indices and their aggregation in the so called “desirability function”.
Conventional distillation column sequences and dividing-wall columns are selected for the study. A total of six different distillation arrangements are considered separating three ternary alcohol mixtures with different eases of separation. Rigorous simulations are carried out using Aspen Plus and Aspen Dynamics. Linear state-space representations of the studies systems are obtained using the Control Design Interface. Frequency dependent controllability indices, MRI, CN and RGAno, are calculated by MATLAB. Based on open-loop responses, discrete frequencies are chosen to determine characteristic indices of the systems. Evaluation of the results is supported by the desirability function. The results show that the separated mixtures influence the controllability features. However, from the different results of our work, we select that if indirect separation structure is recommended, DWC with lower partition shows considerable enhancement in controllability properties.