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Prediction and computation of phase equilibria in polar and polarizable mixtures using theory-based equations of state Al-Saifi, Nayef Masned

Abstract

The purpose of this dissertation is to contribute to the development of the predictive theory-based equation of state. The specific objectives are threefold: first, to improve the predictive capability of theory-based EOS in studying multiphase equilibrium in water-alcohol-hydrocarbon mixtures by taking into account long-ranged electrostatic interactions. The second objective is to develop a general treatment of polar-polarizable mixtures for any theory-based equation of state; and the third is to develop robust and reliable computational methods that conduct and simplify multiphase and stability calculations for theory-based equations of state. The long-ranged electrostatic interactions considered in this thesis are dipole-dipole, quadrupole-quadrupole and polarization. The electrostatic interactions are incorporated into the statistical association fluid theory (SAFT) using different polar approaches. The polar SAFT is utilized to predict multiphase equilibrium of water-alcohol-hydrocarbon mixtures. The results are compared to experimental data. Excellent prediction of multiphase equilibrium is obtained without adjusting experimental data including difficult mixtures such as water-hydrocarbons. This dissertation also presents a general treatment of polar-polarizable systems for theory-based equation of state for non-spherical molecules by the use of the self-consistent mean field theory proposed originally by Carnie and Patey (1982). The treatment is applicable for any kind of polarization arising from polar molecules including ions induced interactions. The theory is tested against simulation data and is applied to the statistical association fluid theory. The general theory is compared to simulation data and is shown to give excellent agreement. The developments in this dissertation also contribute to the subject of theory-based equations of state by developing a reliable and robust multiphase and stability testing method. The developed algorithm computes multiphase and stability simultaneously. The new algorithm is tested extensively on complex mixtures including water-hydrocarbon mixtures. Furthermore, the calculations of phase equilibrium from theory-based equations of state are significantly simplified by the use of the complex-step derivative approximation which computes derivatives numerically.

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