Study of CO2 hydrate formation on the surface of residue shell from dissociated CH4 hydrate

Abstract

The use of hydrates to store CO2 is considered an effective method that can be implemented. However, the problems of interfacial hydrate film formation and low mass transfer efficiency when forming CO2 hydrate under static conditions still need to be solved. This study compared the growth modes of CH4 hydrate and CO2 hydrate under static conditions and believed that the wall-climbing growth mode of CH4 hydrate can be used to generate CO2 hydrate. It is proposed to use the residual shell of CH4 hydrate as a water-absorbing medium to change the mode in which CO2 hydrate is preferentially generated in the main body of the liquid phase. In this method, CO2 hydrate shows a faster formation rate and almost no induction time, which is attributed to the larger gas-liquid contact area provided by the shell, the residual ring in decomposed water on the surface, and the crystal structure inside the shell. When sodium dodecanoate (SD) is used as a promotor for CH4 hydrate to regenerate CO2 hydrate, the observation of the hydrate growth morphology shows that CO2 hydrate can grow on the CH4 hydrate shell. It does not have the wall climbing height of CH4 hydrate but grows toward the center of the reactor. When SDS is combined with SD to regenerate CO2 hydrate as an accelerator in the CH4 hydrate generation process, filamentous growth of CO2 hydrate can be observed.