Precipitation of pure solids in fluid mixtures: A calculation procedure based on Gibbs energy minimization

Abstract

The possibility of phase equilibria involving solid phases is often ignored in the popular phase-equilibrium calculation tools although one possible way of accounting for the potential presence of solid phases is to assume that solids precipitate as pure compounds. Using this assumption, multicomponent systems may contain a number of pure solid phases equal to the number of components. Predicting the correct number of coexisting solid and fluid phases then becomes a challenge. In this work, the Gibbs energy minimization technique is used. The cases of fluid (vapor or liquid) + solid(s) phase equilibrium and multi-fluid + solid(s) (i.e., 1 or 2 liquid phases and/or vapor phase + solid phases) equilibrium are both described. The effectiveness of the proposed approach is demonstrated by applications to several examples. A Python code is provided to illustrate the proposed algorithms.