Prediction of hydrate phase equilibria in aqueous solutions of salt and organic inhibitor using a combined equation of state and activity coefficient-based model

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 to systems containing salt and organic inhibitor by correcting the properties of the aqueous phase such as dielectric constant, density and molecular weight. A linear mixing rule is used for determining the dielectric constant of salt-free mixture by introducing an interaction parameter (in dielectric constant mixing rule), which is tuned using the freezing point data of aqueous solutions containing salt and organic inhibitor. The binary interaction parameter between salt and organic inhibitor is adjusted using water vapour pressure data in the presence of salt and organic inhibitor. The predicted hydrate dissociation conditions are in acceptable agreement with the experimental data, demonstrating the reliability of the model developed in this work.