A further discussion on solid-liquid equilibrium in complex synthetic paraffinic systems with the effects of solid-solid transition

A predictive thermodynamic model for the prediction of wax precipitation in paraffinic mixtures is developed, on the basis of the wax prediction model (RSFV-IRSW) established by Yang et al. (2016), where the liquid phase is described by the combination of regular solution model and Flory free-volume equation, and the solid phase is modelled by the combination of improved regular solution model and Wilson equation. Advancements are adopted in the present work: 1. The influence of transition enthalpy between disorder and order solid phases on liquid-solid fugacity ratio of pure component is considered; 2. A method for the precise calculation of fusion enthalpy and transition enthalpy is suggested; 3. The boundary condition to decide whether one component would precipitate out to form the solid phase is added. The predictive model, RSFV-IRSW, predictive Wilson and regular solution model are tested against the experimental data of complex synthetic paraffinic systems. Results show that the predictive model behaves the best with high prediction accuracy in terms of the characteristics of wax precipitation curve and the composition of solid phase.