A Simplified Approach to Modeling the Rate of Formation of Gas Hydrates Formed from Mixtures of Gases

摘要

Experiments were conducted in a semibatch stirred tank reactor, equipped with an in situ particle size analyzer, to study the rate of formation of hydrates from mixtures of carbon dioxide and methane. Two gas mixtures of CO_2(1) + CH_4 (2), one with X_1 = 0.4 and the other with X_1= 0.6, were used in the current study. The experimental temperature ranged from 274 to 276 K and the experimental pressure ranged from 20 to 27 bar absolute. The range of temperatures was bounded by the freezing point of water and the temperature at which the CO_2 vapor pressure curve intersects the methane hydrate curve. Initially, the results were analyzed using the kinetic model of Englezos et al. (Chan. Eng. Set 1987, 42, 2659-2666). After a careful re-examination of the model of Englezos et al., it was realized that the mathematical model for gas hydrate formation from gas mixtures could be simplified by directly incorporating the hydrate phase stoichiometry. The new approach has the added advantage that the intrinsic rate constant of gas hydrate formation is required for only a single component. Thus, a new approach was proposed to model the kinetics of gas hydrate formation from a mixture of gases, and the results from these predictions were compared to the results obtained using the model of Englezos et al. The root-mean squares of the relative errors between the experimental results and the predictions of the new model and the model of Englezos et al. were found to be 2.70% and 4.29%, respectively.