Effects of baffles on separation of aqueous ethanol solution with hollow fibers |
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Authors: | Zhihong YANG Guoliang ZHANG Lan LIN Danping REN Qin MENG Hongzi ZHANG |
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Affiliation: | (1) College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou, 310014, China;(2) College of Materials Science and Chemical Engineering, Zhejiang University, Hangzhou, 310027, China |
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Abstract: | The effects of baffles on the operation and mass-transfer characteristics in novel hollow fiber membrane contactor used in
distillation were investigated. Hollow fiber membranes, coated with a 7 μm polydimethyl-siloxane, were operated as structural
packing in the separation of ethanol-water solutions. The parallel flow mode was chosen for separation due to the stronger
driving force of the concentration difference, in which liquid flows through the lumens of the fibers and vapor flows countercurrent-wise
outside the fibers. 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
productive 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
where flooding normally occurs in conventional cases. Theoretical analysis predicted that baffles helped membrane module to
obtain a higher masstransfer coefficient and a smaller mass-transfer resistance. Finally, theoretical mass-transfer coefficient
and experimental value were compared as well as the contribution of each individual mass-transfer coefficients among liquid,
gas and membrane. |
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Keywords: | hollow fiber membrane contactor baffle mass-transfer ethanol-water |
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