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Slug flow in tubular membrane in which air and activated sludge flow: A CFD study
Yang, Jixiang
2023-10-01
摘要Air bubbles have been widely applied to alleviate membrane fouling of tubular membranes in membrane bioreactors. However, the impact of the air bubbles on the flow at the membrane surface as well as the removal of membrane foulant are not well understood. Therefore, a theoretical computational fluid dynamics model was established to address this. In the model, air and activated sludge flowed at the superficial velocities of 0.7 m/s and 0.3 m/s, respectively. Furthermore, sludge concentrations were 5 g/L and 10 g/L, respectively. The model showed that the activated sludge did not flow downwards in the film zone and eddies were not observed in the zone below the tail of a bubble. The viscosity of sludge varied significantly in the film zone. Mass transfer capacities at membrane surface gradually decreased from the nose to the end of a bubble. Moreover, a lower sludge concentration resulted in a higher mass transfer capacity. The highest shear stress at membrane surface was 14 and 11 Pa, which were significantly higher than the shear stress achieved in submerged membranes being aerated. Microparticles (3-10 mu m) at membrane surface could be shifted towards the filtrated bulk solution and sucked at the membrane surface alternatively when a gas slug flowed nearby. Furthermore, the bubbles are not effective in shifting microparticles (<3 mu m) toward a bulk solution.
关键词CFD Tubular membrane Slug Sludge Mass transfer
DOI10.1016/j.jece.2023.110764
发表期刊JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING
ISSN2213-2929
卷号11期号:5页码:6
通讯作者Yang, Jixiang(jixiang.yang@cigit.ac.cn)
收录类别SCI
WOS记录号WOS:001068459900001
语种英语