Application of a sequential multi-solid-liquid equilibrium approach using PC-SAFT for accurate estimation of wax formation

Abstract

Several existing thermodynamic models for Wax precipitation use cubic EOS and average properties for petroleum fractions. To improve predictions, this work introduces a thermodynamic model using a multi-solid framework in a sequential equilibrium calculation procedure. The PC-SAFT EOS is used to predict liquid phase properties. Binary interaction coefficients and difference of heat capacities between solid and liquid are adjusted to minimize the deviations caused by the employment of averaged relations for properties of hydrocarbon cuts. Three groups of oil samples are chosen for verification. First, the Wax precipitation data of three synthetic mixtures from Pauly et al. [1] are estimated, and the modeling results are compared to the predicted results of Dalirsefat and Feyzi [2] and Schou Pedersen et al. [3]. Also, two crude oil samples with Paraffin, Naphthene, and Aromatic (PNA) content from Pan et al. [4] are used for evaluation. Finally, the suggested model is used to calculate weight percent of precipitated Wax and Wax appearance temperature (WAT) of six crude oil samples from North Sea [3]. The calculated predictions of the suggested model are compared to the works of Schou Pedersen et al. [3], Lira‐Galeana et al. [5], and Bagherinia et al. [6]. The deviations for WATs and precipitation amounts from experimental data are lower compared to previous studies. The average absolute deviation for precipitated Wax weight of the North Sea samples is 0.19 in comparison to 0.61, 0.33, and 0.4 of Schou Pedersen et al. [3], Lira‐Galeana et al. [5], and Bagherinia et al. [6], respectively.