Synergistic effect of ultrasound combined with bubble enhanced rapid nucleation and growth of methane hydrate

Abstract

The synergistic effect between ultrasound and bubbles serves to amplify the nucleation-enhancing effect of bubbles, effectively addressing the crucial challenges of limited gas–liquid interface and intricate nucleation. Based on this, this study proposed a new method of ultrasound combined with microbubbles and bubbling to enhance hydrate nucleation and growth. A visualization experimental system for the growth of methane hydrates enhanced by ultrasound combined with bubbles was developed. The optimal conditions for ultrasound-enhanced methane hydrate nucleation were quantitatively determined. Subsequently, the enhancement effects of ultrasound combined with microbubbles and bubbling systems were systematically analyzed. Under the influence of ultrasound, the nucleation induction period was reduced from 860 min to 7.5 min, and the complete reaction time was shortened to less than 100 min, resulting in a 3.2-fold increase in methane gas conversion. The combination of ultrasound and microbubble method reduced the nucleation induction time to 6.7 min and increased the growth rate by 10.6%. Furthermore, the combination of ultrasound and bubbling method, by fragmenting large nuclei into smaller ones and inducing secondary nucleation, enhanced mass transfer and increased the growth rate of hydrates by 4.4–5.2 times, with a gas conversion increase of 77.5 %–80 %. A novel finding was made in this study, where under the combined effect of ultrasound and bubbling, the stable formation of slurry hydrates was discovered, providing a new idea for the promotion of high-efficiency energy storage technology for hydrates.