Kinetics of Gas Hydrate Formation and Dissociation

A consistent method was developed to monitor the rate of formation and dissociation of hydrates. The method consisted of monitoring pressure and temperature over time, and visually documenting the presence of hydrates inside a fixed volume high pressure cell and extracting hydrate samples from the cell. The effect of various types and concentrations of surfactants and foaming agents on the formation and dissociation of gas hydrates was investigated. The surfactants tested were sodium dodecyl sulfate, cetyl trimethyl ammonium bromide (CTAB) and Aerosol AY. Foaming appeared to have a limited effect on the rate of hydrate formation. Some surfactants appeared to significantly increase the rate of hydrate formation and decrease nucleation time. This would be beneficial in any process that required purposefully producing gas hydrates. Hydrates produced with surfactants were much more homogeneous than those formed with gas and water alone, and appeared to grow from the edge of the cell inwards rather than randomly. Two surfactants, CTAB and Aerosol AY, appeared to act as hydrate inhibitors at relatively low concentrations, suggesting they could be used to prevent hydrate formation in pipes and equipment. Hydrate nucleation time appeared to be a stochastic process, and there was no significant evidence that trials with numerous “freeze periods” had decreased nucleation time, or significantly altered hydrate formation.