Recovering methane from quartz sand-bearing hydrate with gaseous CO2

183 This figure is the schematic of the guest molecule's fugacity on gas phase and hydrate phase during the recovering CH4 from CH4 hydrate. The blue dots represent CO2 molecules on gas phase, and red dots indicate methane molecules on hydrate phase. The hexagon and pentagon show respectively the large and small cages of hydrate, while the green dots inside the cages represent water molecules. fi,g and fi,H are used to indicate the fugacity of i guest molecules on gas phase and hydrate phase respectively. The arrows on the left side illustrate the entrance of CO2 gas, and the opposite arrows state that the mix gas of CO2 and CH4 exits to outside.