Investigation of the kinetics of mixed methane hydrate formation kinetics in saline and seawater

Solidified Natural Gas (SNG) technology for storing methane/natural gas in clathrate hydrates is gaining prominence due to its promising advantages of being extremely safe, relatively greener, more economical and offering a compact mode of long-term reliable storage in comparison to prevalent technologies. Recently, we demonstrated a faster method to store methane in seawater and saline water via mixed sII hydrates in an unstirred reactor configuration. In this study, we investigate in detail the macroscopic kinetics of mixed hydrate formation in presence of saline (3 wt% or 1.1 mol% NaCl) water, artificial and natural seawater. The effect of driving force on the kinetics of mixed hydrate formation was studied by performing hydrate formation experiments at three different pressures of 3.0, 5.0 and 7.2 MPa at 283.2 K. Characteristic difference in the formation kinetics was observed at lower driving force (3.0 MPa and 5.0 MPa) experiments of saline water in comparison to the experiment without salt. Further, effect of amino acids (leucine and arginine) on mixed hydrate formation starting from saline water at moderate pressure of 5.0 MPa have been studied. 200 ppm leucine was found to be enhancing the mixed methane hydrate formation kinetics in saline water under studied experimental conditions. These findings highlight the promise of employing seawater for SNG technology to store methane (natural gas) on a large scale suited for long-term storage.