Effect of the concentration and carbon chain length of a sulfate-based surfactant on hydrate formation kinetics
Résumé
This paper reports an experimental study on the effect of the concentration and the carbon chain length of surfactants on the formation kinetics of gas hydrates in a quiescent CO2/CH4/water system. Sodium alkyl sulfates with different carbon chain length (C8, C10, C12, C14, C16 and C18) were tested at different concentrations. The experiments were conducted in a batch configuration, at a temperature of 275 K and with an initial gas pressure of about 3.3 MPa. For each system studied, hydrate crystallization was triggered by suddenly injecting a small amount of THF (4,000 ppm) directly into the surfactant solution in contact with the gas-hydrate-former phase at
275 K and 3.3 MPa. The long induction time for hydrate formation usually observed for these systems at the pressure and temperature conditions used in this study was thus eliminated. The experimental results show that, of the six surfactants tested, only the sodium dodecyl (C12) sulfate efficiently promotes the formation of CO2-CH4 binary hydrate under quiescent conditions. A minimum concentration of 500 ppm of the C12 surfactant was however necessary to obtain a beneficial effect on hydrate formation, and the rate of hydrate crystallization was observed to level off for the surfactant concentrations higher than 3,000 ppm. For the systems containing the C8 and C10 surfactants, which have a Krafft temperature lower than 275 K, the presence or absence of micelles in the surfactant solution does not have any effect on the hydrate formation kinetics.
Origine : Fichiers produits par l'(les) auteur(s)
Loading...