Measuring and modelling the rate of decomposition of gas hydrates formed from mixtures of methane and ethane

Abstract

The rate of decomposition of gas hydrates formed from mixtures of methane and ethane was measured in a semi-batch stirred-tank reactor. The experimental apparatus was the same as that used by Clarke and Bishnoi (Chem. Eng. Sci. 55 (2000) 4869; Can. J. Chem. Eng. (2000) accepted for publication) to measure the kinetics of decomposition of hydrates formed from pure ethane and methane. Experiments were conducted with methane/ethane mixtures ranging from 25% methane to 75% methane and at temperatures and pressures between 274 and 278 K and 6.39 to 14.88 bar , respectively. The model of Clarke and Bishnoi was extended to hydrates that are formed from gas mixtures. For hydrates that were known to form structure I, no new parameters were needed and the model was found to accurately predict the data. For the structure II hydrates, it was assumed that the rate constant of ethane was independent of structure because ethane only occupies the large cavities. The intrinsic rate constant and activation energy for methane in structure II were determined to be 8.06×10 3 mol/ m 2 Pa s and 77.33 kJ/ mol , respectively.