Applying the Fowler-Guggenheim Adsorption Model to the vdWP Hydrate Model to Consider Guest-Guest Interactions of Methane-Ethane Hydrate Systems

The accurate thermodynamic modeling of hydrate equilibrium systems has crucial importance in gas separation/storage-based technologies. One of the most-used hydrate thermodynamic models is the vdWP model. There are various studies on developing empirical corrections and regression of the parameter set for the vdWP model in order to keep the model performance satisfactory in different binary and mixed hydrate systems, which shows that the vdWP model needs serious modification in its primary assumptions in order to turn into a more comprehensive form. The comprehensiveness of the model would lead to the accurate determination of different aspects of the hydrate lattice including dissociation condition, hydrate occupation fraction, dissociation enthalpy, and incipient structure in both mixed and simple hydrate systems without needing to use different model parameter sets for each hydrate system. In the present study, the guest-guest interactions were included in the theoretical framework of the vdWP model through substitution of the ideal adsorption model used in its original derivation. The generalized Langmuir adsorption model was replaced by the Fowler-Guggenheim model in order to consider the nonidealities existing in the hydrate lattice. The interaction coefficients of the proposed model were regressed using equilibrium dissociation condition and structure type at several compositions of methane in the C1-C2 hydrate system. The proposed model was evaluated in the case of different isotherms of the C1-C2 hydrate system, and its performance was satisfactory in the determination of complex structure transition phenomenon in the mentioned hydrate system.