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UBC Theses and Dissertations

Prediction of gas hydrate equilibrium Amir-Sardary, Babak


This thesis studies the application of Statistical Association Fluid Theory (SAFT) in the prediction of hydrate formation conditions. The main objective is to develop a robust, reliable and purely predictive model for calculating the formation of single hydrates former gases. The current study is based on the use of the algorithm proposed by Englezos et al. (1991). Simplified SAFT (Fu & Sandler 1995) was employed to model the vapor and liquid phases as well as the van der Waals-Platteew model to represent the hydrate phase. The predictive ability of the model was investigated on single hydrate formers in the presence of inhibitors. With this end in mind, the inhibiting effects of methanol and ethylene glycol on methane, ethane, propane and carbon dioxide incipient hydrate forming were studied. The calculated results were compared to the experimental data obtained from the literature. A deviation of less than 10% in pressure or 1℃ in temperature was desired. Additionally, the phase equilibria of water-methanol, methanol-methaen, methanol-ethane and methanol-propane were also studied. Excellent results were obtained from incipient hydrate calculations and the SAFT equation of state was found to be highly capable of tackling non-ideal mixtures such as water-alcohol and water-alcohol-hydrocarbon systems. Estimation of the SAFT pure component parameters and the temperature range over which the SAFT parameters are estimated was found to be crucial. To overcome this issue, several parameters were estimated over various different temperature ranges, and the one which provided the smallest average absolute deviation was selected.

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