Rapid and efficient methane hydrate conversions by utilising the water molecules confined in intra- and inter-granular space of silica powders.

This study reports methane (CH4) gas storage capacity along with TetraHydroFuran (THF) as guest molecules in mixed hydrates. This process has been studied in two reactors of 100 and 400 mL capacity, having 4.5 and 7.5 cm internal diameter respectively, in non-stirred configuration. Experiments were conducted in each reactor at constant initial gas pressure (7.5 MPa) and by increasing the height of the solution from 1 to 8 cm, resulting in volume scale-up factor of 5. The total CH4 gas uptake (moles) passes through a maximum at around 50% volume of the reactor indicating a transition from gas-rich to solution rich conditions. Observed variations in gas uptake are within ±20% of the maximum, upon different solution volume from 35% to 70% of reactor’s volume. Another set of experiments were conducted keeping the amount of the solution constant and increasing gas pressure in the range of 0.5–11.0 MPa. The gas uptake increased upon an increase in the gas pressure, but this is at least 40% less compared to the theoretical estimate. The stirring of solution or addition of promoter (Sodium Dodecyl Sulfate, SDS) is also not effective in increasing the gas consumption. Kinetics of gas uptake, in both stirred and non-stirred conditions, are quicker and 90% of gas consumption occurs in an hour after the hydrate nucleation event.

Coal bed methane is an emerging and prosperous unconventional energy source, encompassing highly variable (10-70%) mole fractions of methane gas along with other higher hydrocarbon and nonhydrocarbon gases. The gas pressure at the source is typically low, posing technical constraints in the gas separation process. In particular, separation of methane gas from this source is a topic of wider scientific interest. The present study demonstrates the ability of hydrate-based technology in trapping methane gas, in nitrogen (N 2 ) + methane (CH 4 ) gas mixture, using tetrahydrofuran (THF)-based hydrate-forming system at lower operating pressures (1.0 MPa). It is observed that the gas trapping is efficient and rapid. All the experiments were conducted at non-stirred condition, which is technically easy to achieve. Mole fraction of CH 4 was increased in proportion with N 2 , and it was found that methane gas uptake capacity in hydrate cages, increased progressively with increasing CH 4 concentration. Gas uptake kinetics was also found to be extremely fast and 90% of the gas consumed in hydrates within 50-60 min from hydrate nucleation.

Immense gas hydrate reservoirs have been reported in the Krishna-Godavari Basin, India. They mostly constitute methane gas and could serve as an alternative energy source. For efficient exploitation of methane from hydrates, it is crucial to know the region's stability conditions. The present study reports the stability and equilibrium conditions of methane hydrates, synthesized with seawater obtained from the Krishna-Godavari Basin. At Station MD161/02/GH, the water samples are collected at depths ranging from 500 to 1,500 m. The influence of salinity on methane hydrate formation and dissociation in the presence of seawater is established. The hydrate dissociation patterns in seawater and saline water (4 wt% NaCl) are similar and follow the phase equilibrium around 6 wt% NaCl. The identical dissociation behavior of the two systems ascertains seawater to have ~4 wt% salinity. The salinity concentration varies little with depth because the hydrate dissociation temperatures are the same for all the samples collected at the three depths. Using the Clausius-Clapeyron equation, dissociation enthalpies are calculated. The dissociation enthalpy in saline systems is about 6% higher. The hydrate growth kinetics is marginally faster in the saline system.