摘要
The effects of baffles on the operation and mass-transfer characteristics in novel hollowfiber membrane contactor used in distillation were investi-gated.Hollowfiber membranes,coated with a 7μm polydimethyl-siloxane,were operated as structural packing in the separation of ethanol-water solutions.The parallelflow mode was chosen for separation due to the stronger driving force of the concentration difference,in which liquidflows through the lumens of thefibers and vaporflows countercurrent-wise outside thefibers.Two baffles were installed on the shell side of the membrane contactors to enhance separation,which had a round shape with a semi-lunar hole.The results show that both baffled and unbaffled membrane contactors gave better,more produc-tive separations than traditional packing in distillation,such as the excellent Sulzer Gauze BX structured packing.The baffled membrane contactors performed better than unbaffled ones,especially at high vapor velocities.The minimal HTU of membrane contactor with baffles could reach as low as 4.5 cm,and almost all the contactors could work well above the limit whereflooding normally occurs in conventional cases.Theoretical analysis predicted that baffles helped membrane module to obtain a higher mass-transfer coefficient and a smaller mass-transfer resistance.Finally,theoretical mass-transfer coefficient and experi-mental value were compared as well as the contribution of each individual mass-transfer coefficients among liquid,gas and membrane.
基金
funded by the Research Fund of the National Natural Science Foundation of China(Grants Nos.20476096,20776133)
Other financial support came from the Research Fund from the Bureau of Education(Key Discipline of Environmental Engineering grants 56310503014).
