A rigorous and efficient distillation column model for engineering and training simulators

Abstract

A comprehensive dynamic distillation column model has been developed and implemented in the commercial simulator package ProSim. The effectiveness and robustness of the model has been proven through several deliveries of operator training simulators as well as engineering simulators to the process industry. The present paper describes the main model equations and the applied solution method. The implemented algorithm allows the column model to be combined with a large number of other process and instrumentation models in simulators running in real-time or faster, with a time step of typically one second. Rigorous equations are used for material and energy balances on each tray, together with hydraulic correlations describing internal liquid and vapour flows. Liquid flows along the column are determined by a single pass semi-implicit method where flow influences on liquid levels at the tray below are approximately taken into account. Internal vapour flows are calculated simultaneously with the solution of mass and energy balance equations. The method used is a multi pass shooting algorithm where the bottom pressure is adjusted to obtain a given overhead vapour flow.