The presence of azeotropic points in the vapor-liquid equilibria of some solutions is a limiting factor in separation operations by distillation. Knowledge of azeotropy is based on understanding its origins and behavior in relation to the different variables that modulate phase equilibria, and can be used to control the appearance of these singular points. This work studies the phenomenon of azeotropy and presents a practical view based on the study of ester-alkane binary solutions. After considering the principles of vapor-liquid thermodynamics and the special cases of azeotropic points, a detailed description is given of the experimental techniques used to determine these points and also for their thermodynamic verification. Two different but complementary modeling approaches are proposed: the correlation of experimental data and the prediction of azeotropic variables. The first is required to achieve a rigorous design of apparatus and installations, while the second is useful in preliminary design stages. Finally, alternatives to the separation process are studied by simulation. For a practical perspective on these aspects, each section is accompanied by data for ester-alkane solutions, and references are made to applications in the chemical, food and pharmaceutical industries.
The design of processes containing information on phase equilibria must be carried out through a series of steps, experimentation ↔ verification ↔ modeling ↔ simulation. Each of these steps should be rigorously performed to guarantee a good representation of the behavior of the system under study, whose adequate modeling could be used to simulate the corresponding process. To carry out the different previous tasks, two representative systems, extracted from known database, are used. The quality checking of experimental data series is certified through several thermodynamic consistency methods. The modeling is done by applying a multi-objective optimization procedure, which allows to define a solution front (Pareto front) for different sub-models that are established in this work. The fitness of trade-off solutions, obtained from the efficient front, on the design of distillation processes is analyzed through a simulation.
Part of the book: Distillation