(AI-71) Efficient flash computation of continuous sets of solid-liquid-vapor equilibria directly related to laboratory data obtained through the synthetic method

M.J. MOLINA; J.V. MATTOS; S.B. RODRIGUEZ-REARTES; L. CARDOZO-FILHO; M.S. ZABALOY

Los Cocos

Conferencia; VI Iberoamerican Conference on Supercritical Fluids (ProSCiba 2023); 2023

Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales

Often in the laboratory the set goal is to measure solid-fluid equilibria for systems made of CO2(1), a drug(3) and an organic solvent(2), at supercritical conditions, by using a variable volume equilibrium cell. Frequently, it is decided to proceed as follows: a known amount of a known-composition binary liquid solution of components 2 and 3 is fed into the cell, followed by feeding a known amount of the antisolvent CO2(1). In this way, the global composition becomes known. Then, at set temperature (T), by moving the cell piston, a high enough pressure (P) is found, at which the system is a homogeneous fluid (F). Next, P is lowered up to the appearance of an incipient solid (S) phase [fluid-solid (FS) equilibrium]. Sometimes, already at the maximum operating pressure of the apparatus, solid-fluid coexistence (no homogeneity) is found, and hence the lowering of the pressure leads to the detection of an incipient vapor (V) phase in the presence of a solid phase and of a fluid phase, each of finite size (solid-liquid-vapor (SLV) equilibrium). In this case, at the end of the experiment, the only known information to be recorded is: T, the global composition, and the pressure P of SLV equilibrium where the V phase is the only incipient one [1]. If an isothermal set of such experiments covers a range of global amount of CO2 (same liquid solution fed), then, the experimentalist essentially obtains a curve of SLV equilibrium pressure versus, e.g., global CO2 mole fraction, at set T and set global drug/solvent ratio. We recognize that the right type of computation corresponding to a point of such curve is a ternary solid-liquid-vapor flash at zero vapor-phase mole fraction and set temperature T (Duhem’s Theorem), being the predicted P just one of the outcomes of the calculation. Notice that none of the SLV phase compositions is experimentally known. The purpose of this work is to develop an efficient algorithm for computing curves as the previously described, each in a single computer run. (and continues)