Thermodynamics of wax precipitation in petroleum mixtures

Abstract

A thermodynamic framework is developed for calculating wax precipitation in petroleum mixtures over a wide temperature range. The framework uses the experimentally supported assumption that precipitated wax consists of several solid phases; each solid phase is described as a pure component or pseudocomponent that does not mix with other solid phases. Liquid‐phase properties are obtained from an equation of state. Calculated wax‐precipitation data are in excellent agreement with experimental results for binary and multicomponent hydrocarbon mixtures, including petroleum.

Cloud Points: Can We Measure or Model Them?

“…(Erickson et al, 1993;Coutinho et al, 2001) or may be described using a free energy model (Won, 1986;Hansen et al, 1988;Coutinho et al, 1996;Lira-Galena et al, 1996). For high pressure systems (live oils), on the other hand, the liquid phase is generally described using an Equation of State (Lira-Galena et al, 1996;Pan et al, 1997;Pauly et al, 2000).…”

“…Either the authors assume that the solid phase is a sum of independent pure components or pseudo-components Lira-Galena et al, 1996;Pan et al, 1997) or that it is made up of a solid solution, stable or not, of all the materials that crystallize. Some authors that consider the formation of a solid solution assume it being ideal (Erickson et al, 1993;Coutinho et al, 2001;Won, 1986;Hansen et al, 1988;Coutinho et al, 1996).…”

Experimental study and a proposed new approach for thermodynamic modeling of wax precipitation in crude oil using a PC-SAFT model

“…Also, a new approach for investigating the PC-SAFT EOS parameters of wax in the crude oil was proposed in this work. In order to examine the performance of the PC-SAFT model, the wax precipitation experimental data reported in the literature were correlated using the above-mentioned models such as the Ji model (Ji et al 2004) from the solid solution (SS) category and the LiraGaleana model (Lira-Galeana et al 1996) from the multisolid (MS) phase category.…”

“…The performance of the proposed model for correlating the wax precipitation of the experimental data reported in the literature was compared to those obtained using the Ji model (Ji et al 2004) from solid solution (SS) category and Lira-Galeana model (Lira-Galeana et al 1996) from multi-solid (MS) phase category. The absolute deviation of the correlated WAT values obtained for the studied models from their experimental values was calculated by the following relation:…”

“…In fact, an EOS is used directly for vapor-liquid equilibrium, and solid phase is described indirectly from the EOS by fugacity ratio. The multi-solid (MS) phase model assumes that each pure or pseudo-component precipitate constitutes a separate solid phase which is not miscible with other solid phases (Lira-Galeana et al 1996;Pan and Firoozabadi 1997;Nichita et al 2001;Escobar-Remolina 2006;Dalirsefat and Feyzi 2007). The thermodynamic models are developed based on complex properties, such as interaction coefficient, critical properties, acentric factor, solubility parameter, and molecular weight.…”