CALCULATION OF CONSTANT OVERALL COMPOSITION PHASE DIAGRAMS INVOLVING FLUID AND SOLID PHASES

SABRINA BELÉN RODRIGUEZ REARTES; MARCELO SANTIAGO ZABALOY

Buenos Aires

Congreso; VIII CONGRESO ARGENTINO DE INGENIERÍA QUÍMICA; 2015

Asociación Argentina de Ingenieros Químicos

The phase behavior of binary systems made of CO2 and an organic compound having a relatively high molecular weight is of interest in varied applications, e.g, Refs (Giufrida, Rodriguez-Reartes et al. 2011; Rodriguez-Reartes, Cismondi et al. 2011; Pinto, Rodriguez-Reartes et al. 2013). Within the ranges of conditions of interest, these systems may present fluid-fluid (FFE), solid-fluid (SFE), liquid-liquid-vapor (LLVE) and solid-fluid-fluid (SFFE) equilibria. Typically, transition pressures (temperatures) are measured at set temperature (pressure), and set overall composition (isopleths), through the synthetic method, covering a temperature (pressure) range. The result is a set of measured segments of isopleth phase envelopes, eventually together with segments of three-phase equilibrium lines in the pressure-temperature space. Appropriate models for these complex systems may be useful to interpolate and extrapolate experimental information, and to study possible patterns of phase behavior. One such model has been used in Refs (Giufrida, Rodriguez-Reartes et al. 2011; Rodriguez-Reartes, Cismondi et al. 2011; Pinto, Rodriguez-Reartes et al. 2013). In particular, in Ref (Pinto, Rodriguez-Reartes et al. 2013) the calculated isopleths included the phase envelope and the appropriate segments of a SFFE line, for the system carbon dioxide + medroxyprogesterone acetate; while in Ref (Giufrida, Rodriguez-Reartes et al. 2011), for the system CO2 + Mitotane, only phase envelopes were computed. In both cases (Rodriguez-Reartes, Cismondi et al. 2011; Pinto, Rodriguez-Reartes et al. 2013), the phase envelopes included SFE and FFE segments. The systems in Refs (Giufrida, Rodriguez-Reartes et al. 2011) and (Pinto, Rodriguez-Reartes et al. 2013) present retrograde behavior. A more complete characterization of the contribution of the SFE to isopleths can be done by computing lines of constant solidified fraction. Thus, the objective of the present work is to study the heterogeneous region of computed solid-fluid equilibrium isopleths of binary asymmetric systems, by resorting to calculated constant solidified-fraction curves. The computed constant solidified fraction curves reveal a phase behavior more complex than the one that could be imagined from just looking at the isopleth phase envelope and at the appropriate parts of three-phase lines. Giufrida, W. M., S. B. Rodriguez-Reartes, et al. (2011).Journal of Chemical & Engineering Data 56: 4333-4341. Pinto, L. F., S. B. Rodriguez-Reartes, et al. (2013). Fluid Phase Equilibria 349(0): 1-11. Rodriguez-Reartes, S. B., M. Cismondi, et al. (2011). The Journal of Supercritical Fluids 57(1): 9-24.