Modeling the Phase Equilibrium Behavior of Gas Hydrates by the Thermodynamic Model
Date Issued
2011
Date
2011
Author(s)
Yeh, Yen-Ting
Abstract
In this study, the simple hydrate thermodynamic model including van der Waals and Platteuw model (vdWP) model and Peng-Robinson-Stryjek-Vera Equation of State (PRSV EoS) is developed to calculate the phase equilibrium of pure gas hydrates (CH4, C2H6, C3H8, CO2, N2). Moreover, it can be extended to predict the phase behaviors of gas hydrate systems in the presence of inhibitors e.g. methanol, ethanol, ethylene glycol, diethylene glycol and glycerol, and mixed hydrates systems. The PRSV EoS is incorporated with the van der Waals (vdW) mixing rules and the modified Huron-Vidal (MHV1) mixing rules, and the UNIQUAC and the COSMO-SAC models are used to determine the activity coefficient in the MHV1 mixing rules. The COSMO-SAC model is the completely predictive model without any fitting binary interaction parameters, and the results obtained by using the COSMO-SAC model are comparable to those derived from vdW mixing rules and the UNIQUAC model containing fitting parameters in this work. For the C2H6 + H2O and C3H8 + H2O hydrate systems, the AADP (%) are 1.93 % and 2.61 % (MHV1+COSMO-SAC), 1.96 % and 2.63 % (vdW), and 1.94% and 2.62 % (MHV1+UNIQUAC). The model parameters are fitted to experimental data for pure gas hydrates, and the phase equilibria for the hydrate systems with inhibitors and mixed hydrate systems can be predicted successfully without any additional parameters.
Subjects
gas hydrates
inhibitors
Type
thesis
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