Evaluation of Activity Coefficient Models in Prediction of Wax Appearance Temperature

Abstract

Abstract In order to prevent wax formation phenomenon, it is essential to be able to predict the cloud point temperature by using a reliable thermodynamic model. The description of the solid phase non-ideality is the main obstacle in the modeling of the solid-liquid equilibrium of hydrocarbons. In this work, 25 combinations of five models (regular solution theory, UNIFAC, predictive UNIQUAC, predictive Wilson and ideal solution model) for the description of solid and liquid phases have been surveyed to get the best results near the experimental data without using any adjustable parameters. For validating the models, ternary, quaternary and multi-component systems as the experimental data have been used. The results show that for the C14-C15-C16 ternary and multi-component systems, the best models are predictive Wilson-regular solution and predicitve Wilson-predictive UNIQUAC, respectively, for the description of non-ideality behavior of solid and liquid phase. For the C18-C19-C20 ternary and quaternary systems the best models are predictive UNIQUAC-UNIFAC and predictive UNIQUAC-regular solution, respectively, for the description of solid and liquid phase behavior. These models, in comparison with multi-solid models, show better agreement with the experimental data.