Simulation and optimisation of extractive distillation with water as solvent

Acetone–methanol, methyl acetate–methanol and methanol–chloroform binary extractive single column distillation systems were simulated with the HYSYS software platform, to investigate the effects of solvent feed entry stages, solvent split stream feed and solvent condition on the separation. Water was used in all of the simulations as the solvent. The simulations supported data and findings from experimental column studies of the same systems. A rigorous simulation of the acetone–methanol system including a secondary stripping column and recycle loop was established to simulate an industrially relevant situation. This simulation enabled an economic evaluation of the process to be made. It was found for feed mixtures containing 25, 50 and 75 mol% methanol, the optimum reflux ratios were found to be 3.5, 3.5 and 4.2, respectively. As a consequence one column design could separate binary feed of varying composition between 25 and 75% methanol. The optimum number of ideal stages for the primary column for an equimolar binary feed was determined to be 73. When maintaining a constant solvent flow, the distance between the split feed entry stages had no effect on the economic potential (EP) of the system.