A robust and highly efficient phase boundary method for determining the thermodynamic equilibrium conditions of bulk gas hydrate systems

Abstract

The phase equilibrium conditions of gas hydrate systems play a fundamental and essential role in establishing the feasibility of the various hydrate based technological applications. Although the classical isochoric and isothermal pressure search methods can provide accurate and reliable gas hydrate phase equilibrium data, these methods require researchers to devote tremendous time towards achieving each data point. Herein, we extend the phase boundary (PB) method for bulk hydrate systems and demonstrate it to be robust and highly efficient. The PB method involves a controlled pressure drop of the hydrate system to initiate the automatic trace of the pressure and temperature region upon dissociation of the hydrates. Three-phase equilibrium data for four different gas hydrate systems, namely pure methane (CH4), mixed CH4/1,3-dioxolane (DIOX), mixed hydrogen (H2)/DIOX, and mixed carbon dioxide (CO2)/DIOX, have been obtained using the PB method. Independent measurements made using the isochoric pressure search method have been obtained to validate the accuracy and reliability of the data obtained using the PB method.