Methane hydrate stability in the presence of water-soluble hydroxyalkyl cellulose

The effect of low-dosage water-soluble hydroxyethyl cellulose (approximate M-W similar to 90,000 and 250,000) as a member of hydroxyalkyl cellulosic polymer group on methane hydrate stability was investigated by monitoring hydrate dissociation at pressures greater than atmospheric pressure in a closed vessel. In particular, the influence of molecular weight and mass concentration of hydroxyethyl cellulose (HEC) was studied with respect to hydrate formation and dissociation. Methane hydrate formation was performed at 2 degrees C and at a pressure greater than 100 bar. Afterwards, hydrate dissociation was initiated by step heating from -10 degrees C at a mild pressure of 13 bar to -3 degrees C, 0 degrees C and 2 degrees C. With respect to the results obtained for methane hydrate formation/dissociation and the amount of gas uptake, we concluded that HEC 90,000 at 5000 ppm is suitable for long-term gas storage and transportation under a mild pressure of 13 bar and at temperatures below the freezing point.