Analysis of different control possibilities for the divided wall column:: feedback diagonal and dynamic matrix control

This work addresses the control of the divided wall column (DWC) as a basic issue to be considered when this kind of distillation arrangement is used to take profit of its potential to reduce energy consumption. Different control structures of diagonal feedback control are compared using multiple input multiple output (MIMO) linear analysis tools in the frequency domain. A controllability analysis of the process is done for the separation of different mixtures and for different operating conditions, including optimal operation. As a result, it is seen that a trade off appears between energy minimisation and controllability. As an alternative, application of dynamic matrix control (BMC) to the DWC is also evaluated. Through simulation, the ability of DMC for disturbance rejection and setpoint tracking is studied and compared with that of the feedback diagonal control. Important limitations of using DMC for the composition control of the DWC are finally highlighted. Q 2001 Elsevier Science Ltd. All rights reserved.