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The ultrasonic-enhanced factor of mass-transfer coefficient in the supercritical carbon dioxide extraction

Science China(Physics,Mechanics & Astronomy) 2008年第10期51卷 1496-1504页

作者： LUO BenYi LU YiGang School of Physics South China University of TechnologyGuangzhou 510640China

Based on several hypotheses about the process of supercritical carbon dioxide extraction, the onflow around the solute granule is figured out by the Navier-Stocks equation. In combination with the Higbie’s solute infiltration model, the link be-tween the mass-transfer coefficient and the velocity of flow is found. The mass-transfer coefficient with the ultrasonical effect is compared with that without the ultrasonical effect, and then a new parameter named the ultrasonic-enhanced fac-tor of mass-transfer coefficient is brought forward, which describes the mathe-matical model of the supercritical carbon dioxide extraction process enhanced by ultrasonic. The model gives out the relationships among the ultrasonical power, the ultrasonical frequency, the radius of solute granule and the ultrasonic-enhanced factor of mass-transfer coefficient. The results calculated by this model fit well with the experimental data, including the extraction of Coix Lacryma-jobi Seed Oil (CLSO) and Coix Lacryma-jobi Seed Ester (CLSE) from coix seeds and the extrac-tion of Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) from the alga by means of the ultrasonic-enhanced supercritical carbon dioxide extraction (USFE) and the supercritical carbon dioxide extraction (SFE) respectively. This proves the rationality of the ultrasonic-enhanced factor model. The model provides a theoretical basis for the application of ultrasonic-enhanced supercritical fluid extraction technique.

关键词： ultrasonic enhance mass-transfer coefficient supercritical fluid extraction

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Performance of rotating jet bed——A new Higee

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化工进展 2011年第S2期30卷 254-257页

作者： LI Yuming,WANG ying,LI Xiaohua,XU Zhichao,JI Jianbing (Zhejiang Province Key Laboratory of Biofuel,College of Chemical Engineering and Materials Science, Zhejiang University of Technology,Hangzhou 310014,Zhejiang,China)

The rotating jet bed(RJB) has been developed by Zhejiang University of Technology,as a noveler type of gas-liquid mass-transfer unit than rotating zigzag bed(RZB).The rotor of RJB is composed of perforated concentric baffles fixed to a rotating disc.The top of the baffles is in the grooves of the stationary disc,preventing short cut of the gas.Experiments of total reflux distillation with RZB and two types of RJB were carried out with ethanol-water systems at atmospheric pressure.The two types of RJB are with rotor of mesh baffles and of shutter baffles,respectively.The results showed that the number of theoretical plates per meter of RJB,lower than that of RZB,increased with increasing rotational speed,and increased firstly and then decreased with increasing gas superficial F-factor.The maximum number of theoretical plates per meter is 40.7 for RJB with rotor of mesh baffles and 40.0 for RJB with rotor of shutter baffles.The specific pressure drop of RJB was far less than that of RZB.The gas phase film volumetric mass-transfer coefficients of RJB with rotor of mess baffles and shutter baffles were correlated with the Reynolds number,Grashof number and Schmidt number.The calculated value agreed well with the experimental value,and the average deviation was less than 15%.

关键词： distillation rotating jet bed mass-transfer specific pressure drop

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Effects of baffles on separation of aqueous ethanol solution with hollow fibers

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Frontiers of Chemical Science and Engineering 2009年第1期3卷 68-72页

作者： Zhihong YANG Guoliang ZHANG Lan LIN Danping REN Qin MENG Hongzi ZHANG College of Biological and Environmental Engineering Zhejiang University of TechnologyHangzhou 310014China College of Materials Science and Chemical Engineering Zhejiang UniversityHangzhou 310027China

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.

关键词： hollowﬁber membrane contactor bafﬂe mass-transfer ethanol-water

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