Consistent Enthalpies of the Hydrate Formation and Dissociation Using Residual Thermodynamics

Abstract

Kinetics of the hydrate phase transition is implicit functions of the free-energy change of the phase transition and the related dynamics of associated mass and heat transport. The enthalpy change of any phase transition is trivially coupled to the free-energy change of the phase transition. We propose a consistent scheme for calculating the free-energy change, as well as the associated enthalpy change, using residual thermodynamics for every component in all phases, this includes the hydrate phase. The proposed method does not have any limitations to pure components, although we focus on pure CH4 and pure CO2 hydrates in this work. One reason is that there are some experimental data for these components. But the main reason is that the work presented here is a part of a project related to the use of CO2 for simultaneous production of CH4 from natural gas hydrates and safe long-term storage of CO2 in the form of hydrate. A fast mechanism for this exchange entails the formation of a new carbon dioxide (CO2...