determining thermodynamic conditions for petroleum wax formation using activity models in solid-liquid and solid-gas equilibria

The deposition of paraffinic and heavy hydrocarbons in pipelines is a major challenge in the petroleum industry during production and transportation of oil products. in this paper, the wax appearance temperature (wat) in solid-liquid equilibria is calculated based on solid-liquid phase models for binary hydrocarbon systems under high-pressure operational conditions. these models, rooted in won’s framework for liquid-solid equilibria, employ the ideal activity coefficient to compute fugacity in the liquid phase and the wilson activity model for the solid phase. the developed model accurately describes solid-phase equilibria in hydrocarbon systems across a wide pressure range (atmospheric to high pressures). for systems where operational temperatures exceed the critical temperature of the light component, forming solid-gas equilibria, the model assumes negligible solubility of the light component in the solid phase (zero concentration). the model predicts wat for binary mixtures of light and heavy hydrocarbons with high precision, demonstrating an average absolute error of 1.64% and 1.19% across 13 tested systems (617 experimental data points).