Abstract
Gas hydrate growth kinetics was studied at a pressure of 90 bars to investigate the effect of temperature, initial water content, stirring rate, and reactor size in stirred semi-batch autoclave reactors. The mixing energy during hydrate growth was estimated by logging the power consumed. The theoretical model by Garcia-Ochoa and Gomez for estimation of the mass transfer parameters in stirred tanks has been used to evaluate the dispersion parameters of the system. The mean bubble size, impeller power input per unit volume, and impeller Reynold’s number/tip velocity were used for analyzing observed trends from the gas hydrate growth data. The growth behavior was analyzed based on the gas consumption and the growth rate per unit initial water content. The results showed that the growth rate strongly depended on the flow pattern in the cell, the gas-liquid mass transfer characteristics, and the mixing efficiency from stirring. Scale-up effects indicate that maintaining the growth rate per unit volume of reactants upon scale-up with geometric similarity does not depend only on gas dispersion in the liquid phase but may rather be a function of the specific thermal conductance, and heat and mass transfer limitations created by the limit to the degree of the liquid phase dispersion is batched and semi-batched stirred tank reactors.
Highlights
Gas hydrate formation has been an important subject in the petroleum industry, because when gas hydrate forms in oil and gas pipelines and processing equipment, it plugs them
We have conducted experiments in two (141.4 mL and 318.1 mL) geometrically similar, semi-batch autoclave reactors to study the effect of temperature, water content, stirring rate, and reactor scale-up on gas hydrate growth rate
Higher water content led to a decrease in hydrate growth rate due to unfavorable hydrodynamic effects, suggesting that higher hydrate growth rates can be obtained by applying techniques that increase the gas–liquid contact area by reducing bubble and droplet size
Summary
Gas hydrate formation has been an important subject in the petroleum industry, because when gas hydrate forms in oil and gas pipelines and processing equipment, it plugs them. Compared with building new pipelines and railway systems for transportation, which are expensive and labor-intensive, or storing the gas as compressed natural gas (CNG, requiring very high pressures; 20–25 MPa) and liquefied natural gas (LNG, requiring cryogenic temperatures below −161 ◦ C), which are capital-intensive and have a very high safety demand [35], CO2 capture and sequestration would contribute to a greener environment, while gas hydrates as an energy source will play a significant role in the transition to cleaner energy sources To implement these gas-hydrate-related technologies at an industrial scale so that they can compete with existing technologies, emphasis must be placed on forming hydrates in a fast and efficient manner.
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