Effects of Micro-bubbles on the Nucleation and Morphology of the Gas Hydrate Crystals
Gas hydrate is usually regarded as a huge potential energy resource as well as its promising industrial application for gas separation, storage and transportation. Previous researches have shown that gas hydrate phase transition is mainly controlled by heat and mass transfer, while limited work concerns the mass transfer effects of gas micro-bubbles on the hydrate crystallization. In this study, variations in microscopic morphology of hydrate crystals growth in a liquid-gas interface have been observed using a microscope imaging system. The results indicate that the nucleation of hydrate firstly tends to occur at a bubble surface. And the cooling rates increase exponentially with the crystal growth rates and play an important role in the morphology of hydrate crystal growth. In addition, the hydrate crystals tend to grow in the direction of the bubbles affected by the Ostwald ripening effects, which suggests that the bubbling is an efficient measure to promote the application of hydrate-based technologies. In turn, reducing the concentration of bubbles on the surface of hydrate and inhibiting its generation and enhancing the process of gas mass transfer in water around the hydrate surface are also conducive to further accelerate the decomposition of hydrate, which may provide some guidance for the resource exploitation of gas hydrate.