A robust PI control configuration for a high-purity ethylene glycol reactive distillation column

The control problem of an ethylene glycol reactive distillation column is studied in this work. The control objective is to regulate the ethylene glycol composition in the product by manipulating the reboiler boil-up ratio. A preliminary input/output bifurcation analysis reveals the existence of an unique equilibrium point at low reboiler heat inputs and three equilibrium points (two stable and one unstable) at high reboiler heat inputs. Moreover, the existence of input multiplicities at moderate and high product purity is also revealed. A first-order output-feedback compensator is designed which is shown to be equivalent to a PI controller. Tuning issues in terms of two-lime constants are given, and the ability of the controller to regulate the product composition in the face of sampled/delayed measurements is shown via numerical simulations on a full dynamical model. (C) 2000 Elsevier Science Ltd. All rights reserved.