液-液微分散萃取传质模型的研究

Research and Analysis of Mass Transfer Model for Liquid-Liquid Phase Dispersion Extraction

以H3PO4/H2O/TBP+煤油为实验体系,考察了流量、磷酸浓度、稀释剂含量、液滴直径及停留时间对液-液微分散萃取过程的影响,找出适宜操作条件。结果表明,萃取效率随磷酸质量分数、停留时间的增加而增加,随稀释剂含量的减小而增加,随流量的增加呈现先增加后减小的趋势。适当增大磷酸质量分数,减小稀释剂含量,缩短停留时间可以提高传质系数;液滴直径越小,传质系数越大,最高可达1.997×10?4 m?s?1。对微分散状态下的液-液萃取过程进行了分析,根据扩散传质理论,建立了液滴内浓度分布的数学模型,为微分散萃取的优越性找到了理论依据,将实验值与理论值比较,萃取效率、传质系数的误差在20%以内,说明模型是合理的,为微分散萃取的工业设计和操作提供了实验依据。

The system of water/phosphoric acid/TBP＋kerosene was used to study the effects of flow rate, phosphate content, the content of diluent, droplet diameter and residence time on the liquid-liquid phase micro extraction, and to find out the suitable operation conditions. Results show that the extraction efficiency tends to increase with increasing mass fraction of phosphoric acid and residence time, and increases with the decrease of diluent content, while the extraction efficiency increases at first and then decreases with increasing flow rate. Reasonably increasing the mass fraction of phosphoric acid, decreasing diluent content and shorten the residence time can enhance mass transfer coefficient. The smaller the droplet diameter, the larger the mass transfer coefficient, its highest value can up to 1.997×10^4m·s^-1. Micro disperse state of liquid-liquid extraction process was analyzed. According to the laws of diffusion and mass transfer, a mathematical model of concentration distribution inside the liquid drop was established, and a formula for calculating the extraction efficiency was proposed. The errors between the results calculated by the proposed model and the experimental data keep well within 20%. The experimental results of this study can be served as the guidance for the industrial design and operation of micro extraction.