Experimental Study on Self-preservation Property of Gas Hydrate for Natural Gas Sea-borne Transport

抄録

Gas hydrate is generally formed at comparatively high pressure or low temperature. But, in recent years, some researchers reported that CH₄ hydrate remains meta-stable even under some conditions outside its stability region. If the meta-stable property of gas hydrate can be utilized economically, it is possible to store and transport stranded natural gas at higher temperature, compared to conventional LNG method.
Although the‘self-preservation’property of gas hydrate has been gradually clarified, its mechanism has been still poorly understood. There is a disparity among the obtained experimental data, and the reason for the data gap has not been still elucidated. In order to understand the‘genuine’self-preservation property of gas hydrate, we made gas hydrate samples from small ice particles and CH₄ with hydrate particle size controlled and with no pelletization processed, and experimentally examined their self-preservation property at 0.1 MPa. We compared the results with our previous data obtained for both‘non-pelletized’and‘pelletized’CH₄ hydrate samples, and pointed out that there was a possibility that we observed such the data gap mainly owing to several factors of differences in both manufacturing method and thermal history of the hydrate samples, besides influence of pelletization process.