Design of side-stream azeotropic distillation columns

Side-stream distillation columns can provide an interesting choice for the separation of ternary mixtures. Potential advantages include a lower number of reboilers, condensers and distillation shells than sequences based on conventional distillation columns. When azeotropic mixtures are to be separated, the design task is more complicated than for the case of ideal or near-ideal mixtures, and a proper method is needed to provide the tray structure for such complex columns. In this paper, a method for the design of side-stream columns for the separation of azeotropic mixtures is presented. While typical methods for the design of conventional azeotropic columns base the location of the feed tray on the intersection of the operating profiles, the proposed method uses a minimization of the difference between tray and feed compositions as an alternative criterion. The results from several case studies show that the proposed method can provide better designs than the use of an alternative method based on the intersection of operating profiles for the feed tray.