Release:
2017, Vol. 3. №1About the authors:
Anatoliy A. Kislitsin, Dr. Sci. (Phys.-Math.), Professor, Department of Applied and Technical Physics, School of Natural Sciences, University of Tyumen, Tyumen, Russia; a.a.kislicyn@utmn.ru, https://orcid.org/0000-0003-3863-0510Abstract:
In this work stability of metastable dry water methane hydrate contained residual unreacted water at a supercooled state below 0°C and supercooled unreacted water stability was studied. Gas hydrates which did not contain unreacted water could exist at a temperature below 0°C as a metastable phase at the pressure range that meant the field between the ice-hydrate-gas and supercooled liquid-hydrate-gas equilibrium lines. The experiments were carried out in the high pressure reactor. Phase transformations in the reactor were observed by the pressure and temperature monitoring and using differential thermal analysis (DTA). It was established dissociation probability of dry water methane hydrate contained in the metastable field at temperature below 0°C might be significantly higher than probability of ice nucleation in unreacted supercooled water contained in the gas hydrate samples. Thus wise, the induction time of methane hydrate dissociation was even more than one-tenth of the average existence time of supercooled unreacted water at the temperature of –5°C and at pressure less than the equilibrium pressure 15%. It was observed that the increase of fumed silica nanoparticle concentration in “dry water” used for its preparing led to decrease of metastable dry water gas hydrate stability contained unreacted supercooled water. It was shown that at a temperature below 0°C the increase of fumed silica nanoparticle concentration from 5 to 10 wt% led to rapidly decrease of the induction time of metastable gas hydrate dissociation. Specifically, the decrease of the induction time almost 20 times was noticed at the temperature of –5°C and the pressure of 2000 kPa.
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