Kinetic and thermodynamic study of CO2 storage in reversible gellan gum supported dry water clathrates

Abstract

The effects of "Dry Gel" on the carbon dioxide hydrate formation and storage capacity were studied. Gel-supported dry water (Dry Gel) was prepared by mixing gelling agents, hydrophobic silica nanoparticles, water, and air in a high-speed blender. The kinetic parameters of carbon dioxide hydrate formation such as mole of consumed gas, induction time, gas uptake rate, storage capacity, final conversion of water to hydrate, and apparent rate constant were investigated in the presence of dry gel with different gel strength (0 to 15 wt.%) at two silica ratios (5 and 10 wt.%). The experiments of hydrate formation were performed using a 200 cc stainless-steel vessel with and without stirring under the initial condition of 21 bars and 15 °C. Meanwhile, the thermodynamic recyclability of both dry water and dry gels over multiple hydrate cycles were studied. Besides, we utilized the diffusion-reaction kinetics model of Englezos and Bishnoi for calculating the apparent rate constant of hydrate growth. The van der Waals-platteeuw model, through a reversed micelle approach, was used to obtain hydrate phase equilibrium conditions. Results revealed that the amount of gas uptake increased significantly in both dry water and dry gel systems compared to pure water. It was found that dry gel with 15 wt.% gellan gum could substantially improve the storage and recyclability of CO2 hydrate by decreasing the decay percent from 68.8 to 5.1 over repeating seven hydrate cycles.Moreover, the more Nano-silica content, the better the storage repeatability was observed. It was also shown that the equilibrium hydrate formation conditions were approximately stable in the presence of dry gels. Mixing seemed to be critical for multiple freezing-thawing hydrate cycles since it could reduce the reaction and induction time significantly. Finally, the dry water and dry gel can be used as a promising platform for carbon dioxide capturing using clathrate through the recyclability of hydrate formation.