Convex envelope method for T, p flash calculations for mixtures with an arbitrary number of components and arbitrary aggregate states

TL;DR

This paper extends the convex envelope method to include vapor and solid phases, enabling comprehensive phase equilibrium calculations for mixtures with any number of components and phases, useful for chemical process simulation.

Contribution

The work introduces an extension of the convex envelope method to handle vapor and solid phases, allowing phase equilibrium calculations across the entire composition space for complex mixtures.

Findings

Successfully applied to mixtures with up to four components.

Demonstrated use for parameter fitting of $g^E$-models.

Showcased potential integration with machine learning for property prediction.

Abstract

$T, p$ flash calculations determine the correct number of phases at phase equilibrium and their compositions for fixed temperature and pressure. They are essential for chemical process simulation and optimization. The convex envelope method (CEM) is an existing approach that employs the tangent plane criterion to determine liquid phase equilibria for mixtures with an arbitrary number of components without providing the number of phases beforehand. This work extends the CEM to include also vapor and solid phases. Thus, any phase equilibrium of a given mixture with an arbitrary number of components and phases can be calculated over the whole composition space. The CEM results are presented for various vapor-liquid and solid-liquid phase equilibria examples of up to four components. We show how the CEM can be used for parameter fitting of $g^E$-models. As an outlook, we demonstrate how the CEM can be combined with a machine learning-based tool for property prediction to construct phase equilibria.