Prediction of Gas Hydrate Forming Conditions by Using PR Equation of State and Different Mixing Rules

فاقد چكيده

In this work, the ability of different mixing rules for prediction of hydrate formation pressure, are compared. For this purpose, by using Van der Waals–Plauteeuw model for solid hydrate phase and PR equation of state for calculation of fugasity of components in gas and liquid phases, the pressure of hydrate formation in different mixtures have been calculated by four different mixing rules Van der Waals, Danesh, GNQ and Wong- Sandler, then by comparison of calculated results with experimental data, determined the accuracy of mixing rules. Studied systems contain binary mixtures CH4, C2H6, C3H8, i-C4H10, CO2, and H2S with water in hydrate forming conditions. The interaction parameters in each mixture have been optimized by using two phase equilibrium data ( ) W VL and then the optimized parameters have been used for three phase equilibrium (VL H) W calculations. Comparison of the calculated pressure of hydrate forming with experimental pressure shows that for most of mixtures in studied temperature and pressure ranges, GNQ mixing rule with average percent of error 6% has more accuracy than three other mixing rules Van der Waals, Danesh and WS. According to obtained results for methane equilibrium concentrations in liquid phase, it seems that Danesh mixing rule is more efficient for prediction mole concentrations of components. Since Danesh rule consider the polarity of water molecule, has more precision for predicting the equilibrium fractions.