Control and dynamic optimization of a BTX dividing-wall column

This work presents simulation results of the control and dynamic optimization of a dividing-wall column (DWC) used for the separation of a benzene-toluene-xylene (BTX) ternary mixture. Rigorous simulations were carried out in Aspen Plus and Aspen Dynamics. Several conventional control structures based on PID control loops (DB/LSV, DV/LSB, LB/DSV, LV/DSB) were used as a control basis. These control structures were enhanced by adding an extra loop controlling the heavy component composition in the top of the prefractionator, by using the liquid split as an additional manipulated variable, thus implicitly achieving minimization of energy requirements. The results of the dynamic simulations show short settling times and low overshooting especially for the DB/LSV and LB/DSV control structures.