Experimental investigation of methane hydrate formation on suspended water droplets

The formation of methane hydrate films at the surface of suspended water droplets has been experimentally investigated using a novel experimental apparatus. Experiments were performed at a temperature between 273.35 and 275.15 K and a pressure between 4.01 and 6.65 MPa. The observed morphology of hydrate films showed that the growth rate of methane hydrate formed at the droplet surface is significantly increased as the supersaturation (Δμ/kT) is increased and the droplet size is reduced. The induction time of hydrate nucleation is influenced by the degree of supersaturation. A longer induction time was obtained at a lower supersaturation. The measured induction times were correlated to an induction time model developed based on the nucleation theory. A high value of kinetic constant and a low value of effective surface energy were obtained. The results indicated that heterogeneous nucleation of methane hydrate was occurring at the suspended water droplets. The diffusion resistance in the hydrate film was increased as the temperature was decreased and the hydrate film thickened.

► Growth morphology of methane hydrate films formed at the surface of suspended water droplets is experimentally investigated.
► Growth rate of methane hydrate films on suspended droplets is significantly increased by increasing the driving force (Δμ/kT) and reducing the droplet size.
► Heterogeneous nucleation of methane hydrate occurs at the surface of suspended water droplets.
► Methane hydrate nucleation on suspended droplets is diffusion controlled.
► Diffusion resistance in hydrate films is increased by decreasing the temperature or thickening the hydrate films.