带转动挡板的搅拌萃取塔连续相停留时间分布研究

Study on residence time distribution of continuous phase in a stirred extraction column with rotating baffles

为获取带转动挡板的搅拌萃取塔内部流体流动状况,采用脉冲示踪法对塔内连续相停留时间分布(RTD)进行研究,并结合轴向返混模型得到了连续相的返混系数。结果表明,随着连续相体积流量、总流量或连续相与分散相体积流量比值的增大,连续相RTD曲线收窄、峰值明显增大、连续相停留时间和返混系数均减小;改变分散相体积流量,连续相RTD以及返混系数基本不变。此外,改变搅拌转速对连续相RTD影响较小。将返混系数与操作条件和物性参数进行关联,关联式最大偏差为19.8%、平均偏差为7.7%,表明关联式可用于带转动挡板的搅拌萃取塔的连续相轴向返混程度的评估。

In order to obtain flow profiles in a stirred extraction column with rotating baffles,the residence time distribution(RTD)of continuous phase was studied by a pulse tracer method,and the back mixing coefficients of continuous phase were obtained by axial back mixing model.The results show that with the increase of continuous phase flow rate,total flow rate or flow ratio of continuous phase to dispersed phase,the continuous phase RTD is narrowed and the peak value is increased significantly,while the mean residence time and back mixing coefficient of continuous phase are decreased.The continuous phase RTD and back mixing coefficient of continuous phase are unchanged with the change of dispersed phase flow rate.Moreover,stirring speed has little effect on the continuous phase RTD.Correlating back mixing coefficient with operating parameters and physical properties,the maximum deviation between estimated back mixing coefficient calculated by the correlation and experimental value was 19.8%and the average deviation was 7.7%.These results indicate that the correlation can be used for the evaluation of axial back mixing degree of continuous phase in the column.