Search

• Morphology and rheological behavior of CO 2 hydrate slurry in flow-loop are studied. • Tween-80′s effect in flow assurance depends greatly on shear-thinning behavior and bubble. • Defoamer(BK601) has negative effects in preventing hydrates aggregation. • The mechanism of Tween-80 in preventing hydrates aggregation is summarized. In this work, the flow of carbon dioxide (CO 2) 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. [ABSTRACT FROM AUTHOR]

[Display omitted] • Typical flue gas components all play inhibitory roles for Cd species adsorption. • HCl, CO 2 , and H 2 O have mild inhibitory effects on Cd species removal. • O 2 , NO, and SO 2 strongly exclude the adsorption of Cd species. • The adsorption selectivity of Cd species decreases with the increased temperature. Removal of cadmium (Cd) pollutants from waste incineration (MSW) flue gas by modified activated carbon (AC) is of great potential, yet the influence of flue gas composition on their interaction mechanism is still unclear. Thus, density functional theory and thermodynamic analyses were combined to explore the effects of typical flue gas compositions (O 2 , HCl, NO, SO 2 , CO 2 , and H 2 O) on Cd species capture over the Fe/AC and Mn/AC surfaces. All flue gas compositions inhibit the adsorption of Cd species, wherein their inhibitory effects are mainly divided into two categories, i.e., one with moderate inhibition (HCl, CO 2 , and H 2 O), and the other with significant inhibition (O 2 , NO, and SO 2). For the first category, HCl forms new active sites after adsorption on the surface, while CO 2 and H 2 O have weak competitiveness with Cd species, resulting in mild inhibitory effects. Nevertheless, O atoms of O 2 /SO 2 and N atoms of NO are highly effortless to bond with Fe/Mn atoms, and strongly exclude the Cd adsorption on the active sites, greatly weakening their binding strength. According to thermodynamic analysis, the fixation of Cd species by Fe/AC and Mn/AC spontaneously proceeds with the interference of flue gas components, while the selectivity to Cd species decreases with the increased temperature. In summary, it is instrumental to adjust the operating parameters and AC injection location to attenuate the negative effects of O 2 , SO 2 , NO, and high temperature on Cd capture by Fe/AC and Mn/AC. [ABSTRACT FROM AUTHOR]