| 초록 |
Recently, the CH4-CO2 replacement using CO2 injection into natural gas hydrates has been considered as a promising gas production technology. In this study, structure I and H hydrates which were formed with methane and methane + methylcyclopentane (MCP), respectively, were replaced with pure CO2 gas. To identify the effect of the replacement pressure on the replacement behavior, the injecting pressure of CO2 was controlled within pressure ranges where pure CO2 hydrate is thermodynamically stable. To observe the replacement efficiency of each experiment, the compositions of hydrate phase were measured by gas chromatography. Additionally, Raman spectroscopy, 13C NMR, and powdered X-ray diffraction were used to examine the occupancy changes of guest molecules and structural information. For sI hydrate, the replacement efficiency was found to be about 70 % irrespective of the CO2 injecting pressure. However, for sH hydrate, the replacement efficiency was increased up to 80% with increasing the CO2 injecting pressure, which was attributed to a larger portion of a structural transition to sI hydrate. |
