| Abstract
| - An attempt has been made to form continuously either a structure-I or a structure-H hydrateusing methane as the common guest substance and methylcyclohexane as the second guest forthe structure-H hydrate. The experimental technique we tested was to spray water into a high-pressure chamber charged with methane gas. In the experiments to form the structure-I hydrate,water droplets sprayed from a single nozzle at the top of the chamber coalesced into a water poolunderlying the methane gas phase. In the experiments to form the structure-H hydrate, the waterdroplets fell onto a methylcyclohexane layer superposed on a pool of water then merged with thepool. Water was continuously drained from the bottom of the chamber and circulated back throughthe spray nozzle. During this circulation, the water passed through a heat exchanger outsidethe chamber to release the heat generated by hydrate formation. The pressure in the chamberwas maintained at a prescribed level (typically 2.5−3.7 MPa) by supplying methane gas througha port at the top of the chamber. The rate of methane flowing into the chamber was continuouslymeasured to determine the instantaneous rate of hydrate formation in the chamber. The resultsof the measurements indicate that comparable methane-storing rate may be obtained forstructure-H and structure-I hydrates, but with the structure-H hydrate formed at lower pressures.The process of hydrate formation was observed visually through a pair of glass windows in thechamber wall, alternatively using a digital video camera and a microscope connected to a high-speed video-recording system. This paper discusses the mechanisms of hydrate formation revealedby these observations and by the measurements of the rate of hydrate formation.
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