Compositional data calculation of vapor–aqueous–hydrate systems in batch operations by a new algorithm

• Three phase gas-aqueous-hydrate calculation is performed by a new methodology.
• The results are compared with the available compositional data in literature.
• The convergence ability of the method over the existing algorithms is examined.
• Much better convergence is observed by the new methodology.

Separation of gaseous mixtures by gas hydrate formation process is one of the promising methods in the gas separation industry. In this regard, calculation of compositional data of the hydrate forming systems is an important issue. For this purpose, an accurate and trustable three phase calculation algorithm is proposed in this work. Valderrama modification of the Patel-Teja (VPT) equation of state (Valderrama, 1990) combined with non-density dependent mixing rules (NDD) (Avlonitis et al., 1994) is used to model the gaseous and liquid phases, and ideal solid solution theory is applied to model the hydrate phase. Since pressure and composition of the gaseous phase is changed during hydrate formation, a dynamic algorithm should be applied. Equilibrium compositions of each component, phase fractions of the coexisting phases and final conditions of the hydrate forming system, are estimated in a batch hydrate forming process. Different gaseous mixtures are considered to validate the calculation procedure. The results are compared with experimental and calculated values obtained by CSMGem and HWHYD thermodynamic prediction softwares reported in literature. The superior feature of the proposed algorithm is its convergence ability compared with similar procedures.