Distillation is important that it is still the first separation process to be considered for liquid mixtures separation in petroleum, petrochemical, and chemical industries. Some unique and interesting characteristics of this process such as tray arrangement, packing structure, handling of azeotropic mixtures make distillation still be full of challenge in design, control, and operation. The full acknowledge of the existence of azeotropic point and properties of a mixture would be very advantageous to design the apparatus and control systems for separating this mixture. In this study, a prediction methodology was proposed for determining the possible azeotropes of binary and ternary mixtures. This prediction procedure was based on the rigorous thermodynamic consideration and the parameter-free activity coefficient models of Scatchard-Hildebrand, UNIQUAC, Vetere-NRTL, and Ash-Wilson. The mathematical techniques of pseudo-archlength continuation and homotopy were used to locate the azeotropic compositions and temperatures of mixtures. About 262 azeotropic mixtures obtained from the work of Horsley (1973) were grouped into 8 categories and tested by the present prediction method. In this study, the vapor-liquid equilibrium experiments of the binary mixtures of isobutanol-n-pentanol, isobutanol-n-hexane, and n-pentanol-n-hexane were conducted and correlated by UNIQUAC, NRTL, and Wilson models. Then the predicted azeotropic behavior of these three mixtures by the proposed method was compared to the experimental data. The results of this study showed that the proposed method was about 97% success in predicting azeotrope for mixtures obtained from literature and from our experiments.
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JOURNAL OF THE CHINESE INSTITUTE OF CHEMICAL ENGINEERS
