CONICET | Buscador de Institutos y Recursos Humanos

Often in the literature the calculation of solid-fluid and fluid-fluidequilibria for binary systems is limited to the ranges of conditions of theexperimental data on which the model parameters rely. However, a deeperunderstanding of the possible qualitative behavior of the system under studycan be achieved by performing calculations at conditions well beyond those ofthe experimental data. Due to the highly non-linear nature of some phasecoexistence boundaries, such as some isoplethic lines, the algorithms forcarrying out the calculations over a wide range of conditions should have theability of selecting, among the variables involved, the optimum one, i.e., thevariable that should be specified for calculating the next point on the curve.This is a feature of the so called path-following methods. Such methods areuseful for calculating several types of phase equilibrium lines (critical, liquidliquid-vapor, azeotropic, solid-fluid-fluid, isoplethic, isothermal, etc.). Threephase lines are particularly important since they set limits of existence forisothermal and/or isobaric and/or isoplethic hyper-lines. A given hyper-linemay meet more than one stable three-phase line. This implies that a hyper-line,e.g., an isopleth, may be made of a number of segments of varying nature. Inthis work, we couple a model applicable to fluid-fluid and solid-fluidequilibria to a set of path-following methods, to study the rich phase behaviorof the binary system made of CO2 and n-Eicosane (C20H42). This system isrepresentative of the most complex binary systems that can be found. Themodel assumes a solid phase only formed by the pure heavy component. Thefluid phases were described through the Peng-Robinson equation of state (PREOS).The model is relatively simple but it can generate a wide variety ofphase behaviors.

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