INVESTIGADORES
MILANESIO Juan Manuel
congresos y reuniones científicas
Título:
New Models and Algorithms for the Phase Equilibria of Complex Systems in Wide Ranges of Conditions
Autor/es:
MARTÍN CISMONDI; SABRINA BELÉN RODRÍGUEZ REARTES; GERARDO PISONI; JUAN MANUEL MILANESIO; JUAN IGNACIO RAMELLO; MARCELO SANTIAGO ZABALOY
Lugar:
Mar del Plata, Buenos Aires, Argentina
Reunión:
Congreso; VI CONGRESO ARGENTINO DE INGENIERÍA QUÍMICA; 2010
Institución organizadora:
Asociación Argentina de Ingeniería Química (AAIQ)
Resumen:
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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.
Asymmetric systems exhibit a complex phase behavior. The effect of pressure on
the phase equilibria 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. This includes the computation
of binary solid-fluid-fluid equilibrium lines of different types, and of
complex isopleths, with liquid-vapor, liquid-liquid, solid-vapor and
solid-liquid segments and with presence of one or more critical points and/or
one or more solid-fluid-fluid points. 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.