A Fugacity Approach for Prediction of Phase Equilibria of Methane Clathrate Hydrate in Structure H

In this communication, a thermodynamic model is presented to predict the dissociation conditions of structure H (sH) clathrate hydrates with methane as help gas. This approach is an extension of the Klauda and Sandler fugacity model (2000) for prediction of phase boundaries of sI and sII clathrate hydrates. The phase behavior of the water and hydrocarbon system is modeled using the Peng-Robinson equation of state (PR-EoS) with Wong-Sandler mixing rule, while the excess Gibbs free energy of the mixture is calculated using the UNIFAC activity model. The van der Waals-Platteeuw (vdWP) solid solution theory is used to model the hydrate phase. Results are compared with the results of the models proposed by Mehta and Sloan (1996) and Chen et al. (2003) for prediction of dissociation conditions of structure H hydrates. According to the results, the overall average absolute deviation of dissociation temperatures between experiments and predictions are 0.18 (K), depending on the promoter, and the accuracy of the model proposed in this study is found to be better than the accuracies of the aforementioned models.