Formation characteristics of synthesized natural gas hydrates in meso- and macroporous silica gels.

Phase equilibria and formation kinetics of the natural gas hydrate in porous silica gels were investigated using the natural gas composition in the Korean domestic natural gas grid. The hydrate-phase equilibria in the porous media are found to shift to the inhibition area than that in the bulk phase. The measured phase equilibrium data, combined with the Gibbs-Thomson equation, were used to calculate the hydrate-water interfacial tension. The value was estimated to be 59.74 +/- 2 mJ/m(2) for the natural gas hydrate. In addition, the inhibition effect is observed to be more significant in the meso-sized pore than the macro-sized one. In the formation kinetics, it was found that the hydrate formation reached the steady-state in a short period of time without mechanical stirring. Furthermore, the formation rate was found to be faster at 275.2 K than 273.2 K even though the driving force at 273.2 K is larger than that of 275.2 K. Even though the porous silica gels have smaller volume than other methods for gas storage, the gas consumption was found to be significantly enhanced in this study (for example, 120 vol/vol for the silica gels and 97 vol/vol for wet activated carbon). In this regard, using porous silica gels can be a potential alternative for gas storage and transportation as a nonmechanical stirring method. Although this investigation was performed with the natural gas composition in the Korean domestic grid, the results can also be expanded for designing or operating any hydrate-based process using various gas compositions.