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International Conference on Gas Hydrates (ICGH) (6th : 2008)

DISSOCIATION HEAT OF MIXED-GAS HYDRATE COMPOSED OF METHANE AND ETHANE Hachikubo, Akihiro; Nakagawa, Ryo; Kubota, Daisuke; Sakagami, Hirotoshi; Takahashi, Nobuo; Shoji, Hitoshi


Enormous amount of latent heat generates/absorbs at the formation/dissociation process of gas hydrates and controlls their thermal condition themselves. In this paper we investigated the effect of ethane concentration on dissociation heat of mixed-gas (methane and ethane) hydrate. It has been reported by researchers that a structure II gas hydrate appears in appropriate gas composition of methane and ethane. We confirmed by using Raman spectroscopy that our samples had the following three patterns: structure I only, structure II only and mixture of structures I and II. Dissociation heats of the mixed-gas hydrates were within the range between those of pure methane and ethane hydrates and increased with ethane concentration. In most cases two peaks of heat flow appeared and the dissociation process was divided into two parts. This can be understood in the following explanation that (1) the sample contained both crystal structures, and/or (2) ethane-rich gas hydrate formed simultaneously from dissociated gas and showed the second peak of heat flow.

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