Three thermodynamic paths to describe solid fugacity: Application to sulphur precipitation from supercritical natural gas

In a previous work [P. Cezac, J.-P. Serin, J. Mercadier, G. Mouton, Modelling solubility of solid sulphur in natural gas, Chem. Eng. J. 133 (1–3) (2007) 283–291], we established a model able to estimate the solubility of a solid in a supercritical fluid. For this kind of systems, the description of the phase equilibrium is a key point. In this work, a new expression of solid fugacity is established and compared with previous expressions. For sulphur precipitation in supercritical natural gas application, the three approaches to characterize the solid fugacity lead to similar qualitative description of the system behaviour. However, a sensitive analysis demonstrated that the choice of the fugacity expression influences the calculated amount of sulphur plugging.