摘要
针对微尺度液-液混合体系,考察了流量对膜分散萃取过程的影响,并根据传质过程方程,计算了各种条件下的传质系数和传质速率;采用现有的传质模型分别计算分散相和连续相的分传质系数,然后根据传质阻力的加合性得到总传质系数;应用理论传质系数计算传质效率,与实验值进行了比较.研究结果表明,在微尺度混合条件下,直接影响传质系数的因素是停留时间和液滴直径,传质系数随着停留时间的减小而增大.膜分散萃取的传质系数可以达到1.2×10-4 m*s-1,比传统的萃取方式大10～100倍;不能像塔式萃取设备一样,用简单地忽略某一相的传质阻力或用总体平均的简化计算公式来计算微尺度混合的传质性能;考虑滴内滴外传质系数,并考虑时间的影响,利用现有公式分别计算滴内滴外传质系数,并采用阻力加合,可以较为准确地计算微混合条件下的总传质系数,计算值与实验值符合很好.
The effect of total flow rate on membrane dispersion extraction efficiency was studied for liquid-liquid micromixing systems. Mass transfer coefficient and mass transfer rate were obtained from the experimental results for the micromixing process. In order to predict mass transfer performance of the micromixing process, some traditional mathematical models were tested. Total and individual mass transfer coefficients were calculated, and compared with the experimental results. The results showed that main factors affecting mass transfer coefficients were residence time and droplets size, and mass transfer coefficients increased with the reduction of residence time. Mass transfer coefficients in the micromixing process could reach as much as 1.2×10-4 m·s-1, which was about 10-100 times higher than that in a traditional column extraction process. The mass transfer performance in the micromixing process could be predicted neither with the model in which mass transfer resistance of any one phase was ignored, nor with the simplified average equations. So mass transfer performance in the micromixing process was much different from the traditional column extraction process. The authors' results showed that mass transfer coefficients could be predicted with the full traditional two-phase resistance model by considering both steady and non-steady states, and the calculated values were in good agreement with the experimental values.
出处
《化工学报》
EI
CAS
CSCD
北大核心
2005年第3期435-440,共6页
CIESC Journal
基金
国家教育部博士点基金项目 (20040003032).~~
关键词
萃取
传质模型
传质系数
微混合
Curve fitting
Liquid membranes
Mass transfer
Mathematical models
