Experimental Measurement and Thermodynamic Modeling of Hydrate Dissociation Conditions for the Argon + TBAB + Water System

Abstract

Gas hydrate (clathrate hydrate) dissociation data at low to moderate pressures are necessary for practical applications, e.g., for gas separation. However, it is often known or recognized that the separation conditions encountered exist at high pressures and low temperatures. One solution to this problem is the application of the quaternary ammonium salts (QAS) semiclathrate hydrates such as tetra-n-butyl ammonium bromide (TBAB) which can moderate the hydrate dissociation conditions. The addition of TBAB to the solution enables a shift in the pressure-temperature diagrams to lower pressures and higher temperatures. In this study, the isochoric pressure search method1,4,13,28,34−37 was used to measure hydrate dissociation conditions for the argon + TBAB + water system. The measurement of hydrate dissociation conditions were performed at various TBAB concentrations, namely, (0, 0.05, 0.10, 0.20, and 0.30) mass fraction. The experiments were performed in the temperature range of (274 to 293.6) K and pressures ranging from (0.34 to 12.32) MPa. Results indicate that TBAB has a significant promotion effect on argon hydrate formation. In addition, increasing the TBAB concentration increases its promotion effect. A thermodynamic model was developed to predict the hydrate dissociation conditions for the system of argon + TBAB + water. The results show good agreement between the experimental measurements and model results.