| 초록 |
Replacement occurring in natural gas hydrates (NGHs) has been considered as a promising method for both CO2 storage and CH4 recovery without weakening sediments. NGHs exist in three different structures (sI, sII, and sH) that have been discovered through previous explorations. Among these structures, sI hydrates are the most abundant in the deep ocean sediments. However, it has been revealed that the sII hydrates are also deposited around the world, so the replacement in each structure should be studied to examine their exact mechanism. In this study, the guest exchange in sII hydrate – CO2 + N2 was investigated to elucidate the influence of feed gas compositions. The replacement efficiency was measured via gas chromatography. Structural transformation before and after replacement was confirmed via 13C NMR and PXRD analyses. The experimental results demonstrated that CO2 was more selectively enclathrated than N2, and a replacement efficiency and structural transition from sII to sI were more significant with feed gas in higher CO2 concentration. The findings of this study would be helpful for understanding the replacement mechanism in sII hydrates using flue gas injection. |
