Modelling and Optimisation of Middle Vessel Batch Distillation

Abstract

This contribution demonstrates that middle vessel batch distillation can be conveniently studied using commercial process engineering software such as Aspen Plus and Aspen Dynamics. A steady-state model is initially developed in Aspen Plus, in order to obtain the starting point for the batch operation – total reflux operation. The model is exported to Aspen Dynamics as flow-driven or pressure-driven simulations. After the relevant controllers are added, the dynamic simulation model predicts the evolution of products composition. The optimal operation strategy can be easily found (for example, the setpoints of temperature and flow controllers which achieve the required product purities, while minimizing the energy requirements). This approach has significant advantages: rigorous distillation models including mass and energy balances; tray hydraulics calculations; temperature-dependent physical properties available from an extensive library; built-in models for other process units and control elements; robust numerical algorithms, including dynamic optimization.