A new combinatorial thermodynamics model for asphaltene precipitation

In past, the Flory–Huggins model has been modified to predict the phase behavior of asphaltene precipitation phenomenon. This paper introduce a new thermodynamics model to predict amount of precipitated asphaltene. It was shown that the proposed model is comparable with experimental data and available models. The initial structure of proposed model is based on combination of two models, the Flory–Huggins model and one of the local composition models, None Random Two Liquid (NRTL). The Gibbs energy for mixture (oil+solvent) is expressed as a sum of two terms: (1) combinatorial contribution and (2) residual contribution. In the combinatorial contribution, the Flory–Huggins model, some physical properties such as volume and shape are important while in the residual contribution, the NRTL model, physical interactions are considered. Accuracy of this combinatorial model for predicting asphaltene precipitation is investigated using two crude oil samples, some precipitants such as n-C5, n-C6 and n-C7 at different temperatures.