Considering multiple occupancy of cavities in clathrate hydrate phase equilibrium calculations

One of the major assumptions of the original van der Waals-Platteeuw (vdWP) model is the single occupancy of hydrate cavities. In this work, the vdWP model is modified to also account for multiple occupancies of hydrate cavities by small molecules. The developed model is evaluated by calculating the hydrate equilibrium conditions with either oxygen or nitrogen as guest molecules in pure form, as well as mixtures of nitrogen and propane (molecules of these pure gases and those in (nitrogen + propane) have double occupancy in large cavities of structure II up to a certain concentration of propane). The results of this modified model show good agreement with the experimental data reported in the literature. (C) 2011 Elsevier Ltd. All rights reserved.