Institute of Petroleum Engineering

Centre for Gas Hydrate Research Publications

Abstract 118
Hydrate Phase Equilibria in Aqueous Solutions of Salt and Methanol using a Combined Equation of State and Activity based Model
Mohammadi, A.H., and Tohidi, B.
The 5th International Conference on Gas Hydrates, Trondheim, Norway, June 13-16 (2005).
In this communication, a thermodynamic model based on combination of the Valderrama modification of the Patel-Teja equation of state with non-density dependent mixing rules and a modification of a Debye-Hückel electrostatic term is extended by taking into account interaction of all species in the aqueous solution and by correcting the properties of the aqueous phase such as dielectric constant, density and molecular weight in order to predict hydrate formation conditions in the presence of salt and organic inhibitor. A linear mixing rule is used for determination of dielectric constant of salt-free mixture by introducing an interaction parameter, which is tuned using the freezing point data of the aqueous phase containing salt and organic inhibitor. The binary interaction parameter between salt and inhibitor is adjusted using the bubble point (i.e., aqueous solution vapour pressure) data due to the presence of salt and organic inhibitor. The predicted hydrate dissociation conditions are in good agreement with the experimental data, demonstrating the capability of the model used in this work.

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