The study of the dynamics of a simple batch distillation usually assumes the equilibrium between the liquid and vapour phases. In contrast to that approach, this work considers the analysis of the dynamic behaviour of a nonequilibrium simple batch distillation. A simple batch distillation device is similar to an evapouration unit because no reflux is employed. A mathematical model and their singular points are analysed through the usual technique of linearization followed by the eigenvalues analysis. The stability nature of those points is presented for ideal solutions. Phase plane plots are made to show the occurrence of some unexpected behaviours such as 'dynamic azeotropic points' and 'inversion of the distillation order'. The dependence of these phenomena on the vapour withdrawal flowrate is established for simple batch distillation. (C) 2002 Elsevier Science B.V. All rights reserved.426475485