Morphology Study on the Effect of Thermodynamic Inhibitors during Methane Hydrate Formation in the Presence of NaCl

In this study, we investigate the morphology of methane hydrate formation and growth in the presence of well-known thermodynamic inhibitors, monoethylene glycol (MEG) and methanol (MeOH) in a quiescent system. Morphology changes observed during the growth of methane hydrate while employing 5 wt % MEG and MeOH solutions in the presence and absence of NaCl are presented. When 5 wt % of MEG or MeOH was present in an aqueous solution individually, hydrate grew predominantly within the bulk solution featuring a "ridge"-shaped formation above the interface. In the presence of 3.5 wt % NaCl, an enhanced inhibition was observed for methane hydrates formed from 5 wt % MEG solution with limited hydrate growth in the bulk solution and above the gas-liquid interface. In contrast, 5 wt % MeOH solution in the presence of 3.5 wt % NaCl resulted in an increased hydrate growth in bulk (compared to the system without NaCl) and on the reactor wall above the gas liquid interface, implying a weak promotion rather than the inhibition. Further, the effect of subcooling (Delta T) on the morphology of methane hydrates in the presence of MeOH/NaCl and MEG/NaCl was examined.