Prediction of gas hydrate formation condition in the presence of thermodynamic inhibitors with the Elliott–Suresh–Donohue Equation of State

Elliott–Suresh–Donohue (ESD) equation of state (EOS) which is based on thermodynamic perturbation theory and uses the Wertheim association contribution to account for association interactions, is applied to predict hydrate formation conditions in the presence and absence of thermodynamic inhibitors. The ESD EOS is coupled with the van der Waals–Platteuw model. Methane, ethane, propane, nitrogen, carbon dioxide, n-butane and iso-butane are considered as gas components and methanol, ethanol, and mono-ethylene glycol (MEG) are thermodynamic inhibitors considered to be present in the aqueous phase. Different cases of single gas and gas mixtures in pure water and in a solution of water and an inhibitor are considered. To achieve more accurate results, binary interaction coefficients are adjusted as a linear function of temperature. Generally, with regard to the results obtained in various cases, it is shown that the application of the ESD EOS in predicting hydrate formation conditions leads to accurate and acceptable results.

Research Highlights
► In this work the ability of Elliot-Suresh-Donohue (ESD) equation of state in predicting gas hydrate formation conditions in the presence of thermodynamic inhibitors is examined.
► Two phase flash calculation by the φ-φ approach is employed.
► The gases considered are pure methane, ethane, propane, nitrogen, carbon dioxide, n-butane and iso-butane and some mixtures of them.
► The inhibitors that are used for the evaluation of the model are methanol, ethanol, and mono-ethylene glycol.
► Since ESD EoS takes the association interactions explicitly into account, reliable and accurate predictions are observed.