BACKGROUNDDiffusion distillation process was used for separation of ethanol-water mixtures of azeotropic composition. Experimental results were compared with a Stefan-Maxwell equations based mathematical model by assuming point behavior of the process. RESULTSThe performance of a diffusion distillation column for anhydrous ethanol production has been investigated by extending the point behavior to an integral column under process relevant operating conditions. New modeling results are in better agreement with the experimental data than old modeling results. The maximum variation in selectivity is obtained at lowest flow rate (0.05molm(-1)s(-1)). CONCLUSIONSThe diffusion distillation column should be operated at the lowest possible feed rate and the highest possible vaporization temperature to minimize the column length requirement for anhydrous ethanol production. The effect of selectivity on enrichment of ethanol is negligible in long diffusion distillation columns and flux to flow ratio is more important for determination of enrichment. (c) 2014 Society of Chemical Industry