Prediction of Gas Hydrate Dissociation Point by Using Different Equations of State and Mixing Rules in binary systems

In this work, the ability of different equation of states and mixing rules for prediction of hydrate formation pressure, are compared. For this purpose, by using Van der Waals–Plauteeuw model forsolid hydrate phase and six equation of states for calculation of fugacity of components in gas andliquid phases, the pressure of hydrate formation in different mixtures have been calculated by three different mixing rules Van der Waals, Danesh and GNQ, then by comparison of calculated resultswith experimental data, determined the accuracy of mixing rules and EOSs. Studied systemscontain binary mixtures CH4, C2H6, C3H8, i-C4H10, N2, CO2, and H2S with water in hydrate forming conditions. The interaction parameters in each mixture have been optimized by using two phase equilibrium data and then the optimized parameters have been used for three phaseequilibrium calculations. Comparison of the calculated pressure of hydrate forming with experimental pressure shows that for most of binary mixtures in studied temperature and pressureranges, GNQ mixing rule with average percent of error 7% has more accuracy than three other mixing rules Van der Waals and Danesh, and among of EOSs, SRK equation of state is better than others and using from YU-LU equation of state be not suggested.

Keywords:

Mixing rules , Equation of state , Gas hydrate , Three Phase equilibria , Formation Pressure