INVITED LECTURE: MARCELO S. ZABALOY: Equation of State Description of the Phase Equilibria of Asymmetric Systems

MARTÍN CISMONDI; S. BELÉN RODRIGUEZ-REARTES; GERARDO PISONI; JUAN M. MILANESIO; PAPA M. NDIAYE; LUCIO CARDOZO-FILHO; MARCELO S. ZABALOY

Algarve. Praia da Rocha, Portugal

Conferencia; VIII IBEROAMERICAN CONFERENCE ON PHASE EQUILIBRIA AND FLUID PROPERTIES FOR PROCESS DESIGN – EQUIFASE 2009; 2009

Laboratory of Separation and Reaction Engineering/ Laboratory of Catalysis and Materials – Faculdade de Engenharia da Universidade do Porto.

Asymmetric systems under medium to high pressure arise in several applications such as the extraction of oils from grounded seeds using condensed gases as solvents, or the encapsulation of materials within a polymeric matrix. The effect of pressure on the phase behavior of asymmetric systems is typically accounted for by using models of the Equation of State (EOS) type. The structure of such models makes them basically able to describe the properties of gases, liquids and supercritical fluids. Several issues are related to EOS type models. The chosen EOS model has to be flexible but also consistent. Mathematical flexibility, if not handled carefully, may lead to unacceptable qualitative behavior when considering wide ranges of conditions. Having available a model with the required features is not enough to carry out the modeling work: we also need reliable algorithms able to unveil the reality within the universe of the model, i.e., we need algorithms that can detect all the different phase equilibrium regions under the constraints that the user sets. In this presentation, we will describe part of the work on modeling the phase behavior of asymmetric systems under current development in the Group of Process Thermodynamics of PLAPIQUI/UNS/CONICET. We will highlight the consideration of flexibility, consistency and of model behavior in wide ranges of conditions. With regard to flexibility and consistency, we discuss here the features of mixing rules which have a cubic dependence with respect to mole fraction. The distinguishing feature of such cubic mixing rules is that they make it possible to fit ternary data while leaving invariant the description of the binary subsystems. In particular, the effect of ternary parameters on the size of ternary immiscibility regions will be shown. We will also stress the usefulness of using numerical continuation methods for generating many kinds of phase equilibria hyperlines, and of keeping a global perspective both, when fitting model parameters and when computing phase equilibria. Besides, our strategy for calculating and modeling solid-fluid equilibria will be discussed. New phase equilibria modeling results will be presented for asymmetric binary and ternary fluid systems, and also for binary systems under conditions of solid fluid equilibrium.