In this paper we introduce a novel operation policy for the separation of zeotropic mixtures via batch distillation. The novel policy is based on feasibility studies of a batch distillation column provided with a side withdrawal. The process is illustrated via computer-based simulations of the purification of an intermediate-boiling component (1-propanol) from a mixture containing a low boiler (ethanol) and a-high boiler (1-butanol). Furthermore, the effects of the most important process and design parameters are investigated in detail. A comparison to the middle vessel column is provided at the end of the paper. (C) 2004 Elsevier Ltd. All rights reserved.