ABSTRACT:

Dissociation behavior of methane gas hydrate in ethylene glycol and silicone oil was investigated experimentally. Pellet shaped hydrate samples were prepared using artificial fine methane hydrate powder. These pellets were soaked in ethylene glycol or silicone oil in highpressure optical vessel, and dissociation reaction was induced by depressurizing the system pressure. The dissociation rates were measured under several isothermal-isobaric conditions, and the reaction surface was directly observed. Obtained dissociation rates were discussed with mathematical model that is based on one-dimensional thermal conductivity. From these approaches some characteristic aspects of dissociation behavior of methane hydrate in ethylene glycol and silicone oil is discussed.

INTRODUCTION

Natural gas hydrate is crystalline compounds that can contain large amount of natural gas in it. Some ocean transportation or storage systems of natural gas using gas hydrate are investigated. In these systems it is advantageous that gas hydrate is treated as slurry medium. Therefore, gas hydrate is prospected to soak in cooling medium or viscous fluid. It is also advantageous that such fluids have functions of preventing or promoting the dissociation reaction of gas hydrate to control the dissociation rate. Therefore, the dissociation behavior of gas hydrate in such fluid is required basic data. In this study, dissociation behavior of methane gas hydrate in ethylene glycol and silicone oil was investigated experimentally. Pure methane hydrate powder was synthesized from ice and pure methane gas using " Ice-Gas Interface Method". With these powders, pellet shaped hydrate samples were prepared. These pellets were soaked in ethylene glycol or silicone oil in high-pressure optical vessel, and dissociation reaction was induced by depressurizing the system pressure. The dissociation rates were measured under several isothermal-isobaric conditions, and the reaction surface was directly observed. Obtained dissociation rates were discussed with mathematical model that is based on one-dimensional thermal conduction.

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