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为了建立振动筛板萃取塔传质模型,用单液滴萃取装置测定了氯仿萃取咖啡因过程的传质系数。通过双膜理论分析得知,滴外传质是萃取过程的控制步骤。采用Krishna关联式估算的液滴终端速度与测量值符合较好,平均相对误差为1.69%。当分散相的Reynolds数在308.1～365.4范围时,内环流液滴的滴外传质系数测量平均值为1.30×10-4m.s-1,与Garner-Tayeban和Trybal关联式计算得出的传质系数平均相对误差分别为6.89%和8.93%。结果表明上述关联式可以用于萃取塔的设计和放大。
In order to establish the mass transfer model of vibrating plate extraction column, the mass transfer coefficient of chloroform extraction caffeine was determined by a single droplet extraction device. Through the double membrane theory analysis, it is known that the mass transfer outside the droplet is the control step of the extraction process. The Krishna correlation estimates of the drop velocity agree well with the measured values, with an average relative error of 1.69%. When the Reynolds number of the disperse phase ranged from 308.1 to 365.4, the average droplet mass transfer coefficient of the inner-loop droplets was 1.30 × 10-4m · s-1, which was calculated according to the Garner-Tayeban and Trybal correlations The average relative error of the quality coefficient were 6.89% and 8.93% respectively. The results show that the above correlation can be used for the design and amplification of extraction column.