An insight into the role of the association equations of states in gas hydrate modeling: a review

Encouraged by the wide spectrum of novel applications of gas hydrates, e.g., energy recovery, gas separation, gas storage, gas transportation, water desalination, and hydrogen hydrate as a green energy resource, as well as CO2 capturing, many scientists have focused their attention on investigating this important phenomenon. Of course, from an engineering viewpoint, the mathematical modeling of gas hydrates is of paramount importance, as anticipation of gas hydrate stability conditions is effective in the design and control of industrial processes. Overall, the thermodynamic modeling of gas hydrate can be tackled as an equilibration of three phases, i.e., liquid, gas, and solid hydrate. The inseparable component in all hydrate systems, water, is highly polar and non-ideal, necessitating the use of more advanced equation of states (EoSs) that take into account more intermolecular forces for thermodynamic modeling of these systems. Motivated by the ever-increasing number of publications on this topic, this study aims to review the application of associating EoSs for the thermodynamic modeling of gas hydrates. Three most important hydrate-based models available in the literature including the van der Waals–Platteeuw (vdW–P) model, Chen–Guo model, and Klauda–Sandler model coupled with CPA and SAFT EoSs were investigated and compared with cubic EoSs. It was concluded that the CPA and SAFT EoSs gave very accurate results for hydrate systems as they take into account the association interactions, which are very crucial in gas hydrate systems in which water, methanol, glycols, and other types of associating compounds are available. Moreover, it was concluded that the CPA EoS is easier to use than the SAFT-type EoSs and our suggestion for the gas hydrate systems is the CPA EoS.