Effect of PVA contained in ice on methane hydrate formation and gas storage

In this study, the kinetics of methane hydrate formation synthesized from frozen powdered polyvinyl alcohol (PVA) solutions was investigated. PVA with different molecular weights and hydrolysis degrees and also industrial PVA from different manufacturers were used to prepare the experimental samples. The influence of the hydrolysis degrees (87-100%) and molecular weights (31-186.10(3) Da) on the methane hydrate formation rates and gas storage capacity were studied. The higher methane hydrate formation rates and gas consumptions are observed in powdered samples prepared using frozen solutions of low molecular weight PVA. All investigated powdered samples prepared from frozen PVA solutions are observed to be more effective in methane hydrate formation than powdered ice with analogous particle sizes of 80-140 mu m. The work also reports the effect of particle sizes on the water to methane hydrate conversion ratio for dispersed ice and ice containing PVA was studied. By nuclear magnetic resonance (NMR) relaxometry the changes in the solutions/gels PVA under repeated freezing/thawing cycles were determined. Moreover, it was shown that the additives of technical grade PVA in a concentration of 3 wt% has a positive effect on resistance to sintering of dispersed ice while maintaining high methane consumption after prestorage the samples of powdered ice modified by PVA for 2, 5, 7, and 14 days at a negative temperature. Obtained results might be useful in the application of powdered PVA systems for hydrate based technologies of natural gas storage and transport.

Automated summary

This study investigates the kinetics of methane hydrate formation from frozen powdered polyvinyl alcohol (PVA) solutions. The results show that powdered samples prepared using frozen solutions of low molecular weight PVA have higher methane hydrate formation rates and gas consumption. All powdered samples prepared from frozen PVA solutions are more effective in methane hydrate formation than powdered ice.