Description of solid-fluid equilibrium through a solid solution model (T280)

A.F. PORRAS GIRALDO; S. BELÉN RODRIGUEZ-REARTES; MARCELO S. ZABALOY

Nova Friburgo

Congreso; X Congresso Brasileiro de Termodinâmica Aplicada (CBTermo 2019); 2019

Universidade do Estado do Rio de Janeiro (UERJ)

Solids are present in numerous industrial processes in which the knowledge of the conditions of their appearance can be used either to promote their formation or to avoid it. In previous works, for describing the solid-fluid equilibria (SFE) of binary systems, over wide ranges of conditions, we employed a modelling approach which uses an equation of state (EoS) to represent the fluid phases, coupled to a pure-component solid fugacity expression (SFugE) for the component selected to precipitate as a pure solid. The SFugE uses, as a reference, the fugacity of the pure component in a hypothetical (metastable) liquid state. The SFugE can be parameterized, with relative ease, to guarantee a proper relative stability between the pure solid and the pure liquid at any PT conditions. For multicomponent systems, precipitation in pure state is strictly inconsistent. To overcome this drawback, we extended, in this work, the SFugE to the case of solid solutions (SS). From the expression of the SS fugacity it is possible to find the expressions for the component fugacities in the SS. Part of the pure-component parameters are obtained from experimental information on the melting curve and on density (in solid and liquid states). Modelling results are shown for the binary systems Ar+CH4 and CH4+n-C20H42 in wide ranges of conditions. They illustrate the capacity of the SS-FugE to properly capture the SFE patterns observed in the laboratory. The tangent plane distance (tpd) analysis was used to verify the global stability of the calculated equilibria.