膜萃取处理水溶液中镉、锌离子的传质模型

通过测量中空纤维膜器管程和壳程RTD曲线,发现对于中低装填密度的膜器,管程的实际流动与理想层流有较大差异,而壳程的流动与理想层流符合较好,膜器管程和壳程流动RTD曲线的平均停留时间的实验值与理论值相差很小,停留时间相对偏差小于±5%.通过计算,得出与实际RTD曲线符合较好的速度分布公式,依据镉离子传质数据,提出了较为准确的低流速下的传质系数预测关联式,并用此关联式预测锌离子的出口浓度,预测值与实验值符合较好,相对偏差在±25% 以内.

Mass Transfer Model of Membrane Extraction for Recovery of Cadmium Ion and Zinc Ion

By measuring the residence time distribution(RTD) curve of shell side and tube side of hollow fiber modules, it was found that the flow status in hollow fiber module with moderate or low packing density was complicated. For tube side, there were deviation between the experimental RTD curves and the theoretical laminar flow ones, which indicated that the flow status in tube side was between laminar flow and turbulent flow. For shell side, the experimental RTD curves agreed well with the laminar flow ones. The deviations as low as ±5% between the experimental average residence times and the theoretical ones suggested that there was no apparent non-ideal flow in the hollow fiber module with medium packing density. Based on the comparison between the experimental results and some typical correlations, a new velocity profile was purposed to describe the flow status in hollow fiber modules. According to the results of cadmium transport, the individual mass transfer coefficient correlations were developed. The zinc outlet concentrations predicted by the new correlations agreed relatively well with the experimental results, the relative deviation was among ±25%.