Matthew A. Clarke

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

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 278K and 6.39 to 14.88bar, 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 8.06×103mol/m2Pas and 77.33kJ/mol, respectively.

Development of an implicit least squares optimisation scheme for the determination of Kihara potential parameters using gas hydrate equilibrium data

Abstract An implicit optimisation scheme is formulated to find the Kihara potential parameters for methane and ethane, using experimental hydrate formation data from both pure methane and ethane hydrates and hydrates formed from mixtures of methane and ethane. In this method, all three Kihara potential parameters, for both methane and ethane, are allowed to be adjustable parameters. Phase equilibria calculations, using the new Kihara potential parameters, exhibit a transition from structure I to structure II in hydrates formed from methane/ethane mixtures. This is consistent with experimentally observed behaviour. The use of Microsoft® Excel, an easily available tool, is illustrated for the determination of the Kihara potential parameters by implementing the formulated implicit optimisation scheme using gas hydrate equilibrium data.

Determination of the Intrinsic Rate of Gas Hydrate Decomposition Using Particle Size Analysis

Abstract: An experimental technique to determine the intrinsic kinetics of gas hydrate decomposition is presented and a new mathematical model is developed. The experimental technique uses an on‐line particle size analyzer. The new mathematical model accounts for the distribution of particle sizes in the hydrate phase when determining the intrinsic rate constant of decomposition. Results from an experiment for the decomposition of ethane gas hydrates are presented.