Experimental study of mixed CH4/CO2 hydrate formation kinetics and modeling

The gas hydrate formation process from CH4/CO2 gas mixtures was experimentally investigated in a 5.3L stirred reactor under isothermal-isochoric conditions in a feed pressure of 3.5MPa at the temperature ranging from 0.0 to 4.0 degrees C and CH4 mole fraction in the feed gas ranging from 0.2 to 0.8. The composition changes of the gas phase were determined by gas chromatography, and a simplified kinetic model was used to calculate the gas composition changes in the hydrate phase. The results showed that the initial gas consumption rates and the total gas consumptions of each gas species were remarkably enhanced as the temperature decreased. The gas consumptions can be well described by the kinetic model with an overall average absolute deviation of 5.2%. In addition, the hydrate formation from CH4/CO2 gas mixtures exhibited a good selectivity for CO2 capture in the early stage of hydrate crystallization, especially at high temperatures. Increased CO2 concentration in the feed gas could also efficiently accelerate the hydrate formation. It was suggested that CO2 played a key function in stabilizing hydrate structure in the newly formed hydrate nuclei. (c) 2014 Curtin University of Technology and John Wiley & Sons, Ltd.