Rigorous dynamic modelling and identification of distillation column using Aspen Plus

Abstract

Knowledge of dynamic behavior of process plants is essential in designing, commissioning and operating process plants. Several advanced model based technologies require explicit dynamic models of the process plant. However, even the development of the dynamic model of a simple unit operation is very daunting, costly and time-consuming. This paper presents a rigorous dynamic simulation using Aspen Plus. The data from the dynamic simulation is then used to develop transfer function model of the column. This case study considers a distillation column with an ethanol-water feed. A 2×3 distillation column transfer function model is developed from step responses of the Aspen plus dynamic simulation, i.e. with feed valve opening %, reflux flow rate and reboiler duty as input and top and the bottom compositions as an output. A separate SISO transfer function from condenser duty to column pressure is also developed.