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Abstract
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In this study, a new thermodynamic model is presented for prediction of hydrate formation conditions of different hydrate formers in solutions containing an electrolyte, alcohol and their mixtures. The developed model is based on the c–u approach
for modeling the phase behavior. The theory of van der Waals–Platteeuw and the Valderama–Patel–Teja equation of state coupled with non-density dependent mixing rules were used to describe the hydrate and vapor phase, respectively. Also, the nonelectrolyte Wilson, non-random factor local composition model and Margules equation were adopted to determine the water activity in solutions containing electrolyte and alcohol, respectively.
The effects of solubility of the components in the liquid and vapor phases were considered
for prediction of hydrate formation conditions. The model was applied to a number of
hydrate forming compounds and mixtures in different electrolyte and methanol solutions,
including NaCl, KCl and CaCl2 and their mixtures, and results are compared with
experimental data and/or existing models. It was found that hydrate formation conditions
are better predicted by this model compared to existing models, especially for ethane and
propane in electrolyte solutions, and C1/CO2/C3 gas mixture in solutions containing
electrolyte and alcohol. The solubility of components in the liquid and vapor phases was
found to have a considerable effect on the model predictions.
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