Insights into carbon dioxide hydrate formation, fluid type, and agglomeration in the system with or without tween-80

Abstract

In this work, the flow of carbon dioxide (CO2) hydrate slurry is systematically investigated by analyzing its rheological behavior, apparent viscosity, and crystal shape. The results show that blocking is easy to occur in the pure water system, while no blockage is observed from the system containing Tween-80. Besides, we confirm that the hydrate slurry formed in the pure water system is a dilatant fluid with shear-thickening behavior. However, that obtained from the system containing Tween-80 are pseudoplastic fluids with shear-thinning behavior. The time development of hydrate slurry flow in the system with or without Tween-80 showed that the shear-thinning behavior is a key factor in preventing the hydrate slurry from blockage. In addition, in the presence of Tween-80, hydrates will form on the surface of the bubble. These hydrates are easily dispersed on top of the liquid phase and will not adhere to the top wall of the pipeline. However, in pure water, a dense adhesive layer is observed on the top of the pipeline, which will reduce the flow area in the pipeline, increasing the flow resistance. Overall, the main role of Tween-80 in preventing hydrates from aggregation includes two aspects, (1) changing the type of fluid from dilatant to pseudoplastic; (2) providing bubbles for hydrate formation. The addition of defoamer(BK601) will reduce the Tween-80′s effects in preventing hydrates by reducing shear-thinning behavior and the amount of bubbles.