| Summary: | This thesis studies the formation and decomposition of methane hydrate crystal in an unconsolidated bed of silica sand particles. Hydrate processes were visualized by taking advantage of the ¹H magnetic resonance imaging technique, and the integrated intensity of magnetic resonance images was used to quantify the rate and kinetics. For all of the experiments, the initial pressure was 8 MPa and the temperature was kept constant at 1℃. Beds composed of 2 grams of sand were saturated with different amounts of water (0.44, 0.33, 0.22 and 0.11 mL) in order to examine the effect of water content of the bed on the kinetics of hydrate formation in porous media. Also, the effect of particle size was investigated by forming hydrate in beds with different particle size ranges (210-297, 125-210, 88-177 and <74 µm). It was found that the hydrate formation process in a bed of silica sand particles can be divided into three stages: induction time, non-uniform growth and uniform growth. During the first stage, methane molecules dissolved and diffused in water. After formation of the first crystals of hydrate at the end of the induction period (nucleation point), hydrate formation proceeded through a combination and competition between nucleation and growth, and multiple nucleation occurred. During the last stage, no obvious nucleation was observed and hydrate formation continued only through the growth of the crystals which had already been formed during the previous stages. The rate of hydrate formation was found to be faster in beds with smaller particles and lower water content. Applied Science, Faculty of Chemical and Biological Engineering, Department of Graduate
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