Effect of Sodium Dodecyl Sulphate on Gas Hydrate Formation Kinetics of Methane and Ethane Mixtures

Abstract

In this study, the effects of sodium dodecyl sulphate (SDS) on gas hydrate formation kinetics of methane and ethane mixture has been investigated experimentally and also the thermodynamic natural path has been used for modeling of the hydrate formation rate in a constant volume process. Different mole fractions of methane 0.1, 0.2, 0.3, 0.5, 0.68 and 0.8 have been studied. All experiments have been carried out at a constant temperature of 277.15 K, approximately initial pressure of 3.6 MPa and a stirrer speed of 800 rpm, with and without the presence of SDS with concentration of 500 ppm. The results show that SDS increases the hydrate formation rate by means of decreasing the gas liquid surface tension, so that the initial rate of hydrate formation and the model kinetic parameter of Ar/RT are increased about 3 and 1.2 times, respectively. Besides, SDS transforms two-step process of methane-ethane hydrate formation to one-step of that. This surfactant also promotes the hydrate growth in the liquid phase and increases the moles of gas consumed, so that the highest amount of gas consumption for hydrate formation belongs to the mixture with 0.3 mole fraction of methane.