Modelling and Dynamics of an Extractive Distillation Column

Much of the published research literature on distillation column dynamics and control has been focussed on binary systems or on multicomponent systems in which key components are used to define the operations. This paper presents both non-linear mass and energy balance models and experimental results for an extractive distillation system separating acetone from methanol using a water solvent. The system comprises a 15 cm diameter bubblecap column with 13 trays and the solvent is used to break the acetone-methanol azeotrope. Fitted transfer function models are compared with simulation models describing the transient responses of the system to changes in the inlet feedrates and composition. The system is controlled by a VAX 11/750 process computer with a DPM-23 distributed front-end using on-line temperature and composition measurements.