ISA transactions

Dynamic simulation and nonlinear control of a rigorous batch reactive distillation.

PMID 19815199


This work deals with the dynamics and control of a high-purity batch distillation column with chemical reaction. A heterogeneous esterification reaction between the acetic acid and butanol takes place to produce butyl acetate. The process model is formulated considering variable liquid holdup, UNIQUAC model for thermodynamic property predictions, nonlinear Francis weir formula for tray hydraulics, pseudohomogeneous model to represent the reaction kinetics and rigorous energy balance. A structured and simple iterative approach is devised to compute the vapor flows with the fast convergence, under the rigorous energy balance. The representative column is treated with a distillate policy based on which, the lightest product, water is removed as distillate at the starting of production phase. As a consequence, the column gets progressively richer with the main product, butyl acetate. In addition, almost complete conversion of the limiting reactant is achieved. In order to maintain the product purity at the top, a nonlinear generic model controller (GMC) in two different forms has been proposed. Finally, a comparative closed-loop performance is addressed. It is shown that the control scheme, along with the effective distillate strategy, leads to almost complete conversion of ingredients and high-purity products.