High-purity liquefied gases: Aspen Dynamics simulation of a purification process in a middle-vessel batch distillation column

Abstract

The paper explores the use of Aspen Plus and Aspen Dynamics for simulating and optimising a high-precision process of liquefied gases high purification in a middle-vessel packed distillation column. The example studied involves the removal of lower- and higher- boiling impurities from the upper- and lower rectifying sections and maintaining the purified product in the middle vessel. Total reflux operation is studied in the pressure range between the normal boiling point of the purified product and the critical point. Among the considered aspects are the column design and sizing, hydrodynamics study (flooding calculations), the effect of operating pressure and temperature on the thermodynamics of vapour-liquid equilibrium and mass-transfer kinetics in a wide range of operating conditions. The paper demonstrates that the effects and dependencies observed previously through the experiments and by using user-developed custom models are adequately reproduced in the commercial simulator (Aspen Plus) by setting up a fictitious steady-state continuous process with rigorous built-in models. The optimised flowsheet can be converted to Aspen Dynamics as a pressure-driven process where a rigorous dynamic simulation gives a realistic dynamic response, and alternative control structures can be explored.