Application of Electrolyte Cubic Square-Well Equation of State for Prediction of the Gas Hydrate Formation in the Presence of Electrolyte Solutions

Electrolyte Cubic Square-Well Equation of State, eCSW EOS, [Haghtalab, A.; Mazloumi, S.H.; Fluid Phase Equilib. 2009, 285, 96-104] is based upon cubic-square-well equation of state. This equation of state is composed of the attractive term that is based on the square-well potential, the van der Waals repulsive part and the mean spherical approximation theory (MSA) for electrostatic contribution. In this work, eCSW EOS is coupled with the van der Waals-Platteuw model and applied to compute the conditions of gas hydrate formation. The H-L-V equilibrium calculation is performed to optimize the Langmuir constants against temperature for N2, CH4, C2H6, C3H8, i- C4H10, n-C4H10 and CO2 hydrates using the experimental data in literature. Also, using eCSW EOS the interaction parameters of CO2-water and electrolyte-water are obtained. The equilibrium hydrate formation pressures of single gas hydrates are predicted and the results compared with the calculated values using SRK and PR EOSs. Also, predicting equilibrium hydrate formation pressures of various hydrate formers in the presence of electrolytes such as NaCl, KCl and CaCl2 are performed. The results of prediction at the different cases are in good agreement with the experiments.