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Abstract
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In this paper, a new predictive model is proposed for prediction of gas hydrate formation conditions in
the presence of single and mixed electrolytes and solutions containing both electrolyte and a polar inhibitor
such as monoethylene glycol (MEG), diethylene glycol (DEG) and triethylene glycol (TEG). The proposed
model is based on the c–u approach, which uses modified Patel–Teja equation of state (VPT EOS)
for characterizing the vapor phase, the solid solution theory by van der Waals and Platteeuw for modeling
the hydrate phase, the non-electrolyte NRTL-NRF local composition model and Pitzer–Debye–Huckel
equation as short-range and long-range contributions to calculate water activity in single electrolyte
solutions. Also, the Margules equation was used to determine the activity of water in solutions containing
polar inhibitor (glycols). The model predictions are in acceptable agreement with experimental data. For
single electrolyte solutions, the model predictions are similar to available models, while for mixtures of
electrolytes and mixtures of electrolytes and inhibitors, the proposed model gives significantly better
predictions. In addition, the absolute average deviation of hydrate formation pressures (AADP) for 144
experimental data in solutions containing single electrolyte is 5.86% and for 190 experimental data in
mixed electrolytes solutions is 5.23%. Furthermore, the proposed model has an AADP of 14.13%, 5.82%
and 5.28% in solutions containing (Electrolyte MEG), (Electrolyte DEG) and (Electrolyte TEG),
respectively.
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