Experimental investigation of conventional control strategies for a heterogeneous azeotropic distillation column

In this work, a laboratory scale sieve plate distillation column was constr ucted to investigate the conventional control strategies of an isopropyl al cohol (IPA), cyclohexane (CyH) and water (H2O) heterogeneous azeotropic dis tillation column. Steady state process analysis showed that the optimal ope ration point should be located at a critical reflux, a transition point at which the distillation path switches from a route that passes through IPA H2O azeotrope to one that passes through IPA + CyH azeotrope. At this crit ical reflux, a high purity IPA product can be obtained with minimum energy consumption and maximum product recovery. However, the steady state is extr emely sensitive to feed disturbances. A good control strategy must be able to maintain a steady column temperature profile that shows a plateau near 7 0 degrees C to ensure passage around IPA + CyH azeotrope. In this study, an inverse double loop control strategy is recommended. Through experimental testing, the proposed control strategy was demonstrated to keep the product IPA purity at the desired high-purity level under all feed disturbance cha nges while other conventional control strategies fail. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.