无挡板搅拌槽中液－固体系的分散特性

在内径0.3 m、高0.45 m的无挡板搅拌槽内，采用直径0.15 m的三叶70o下推斜叶透平桨(PBTD, Pitched Blade Turbine Downflow)进行水-二氧化硅两相体系液固分散特性的研究. 应用PC-6A粉体浓度测量仪对体系中颗粒局部浓度进行测定. 考察了颗粒平均相含率为0.005的条件下，不同搅拌转速、搅拌桨离底高度对颗粒局部浓度分布的影响. 结果表明，采用较高搅拌转速、较低的搅拌桨离底高度有利于固体颗粒的悬浮. 本实验中，在搅拌转速为173 r/min、搅拌桨离底高度为0.08 m的操作条件下，颗粒悬浮效果最好.

Dispersion Characteristics of Solid-Liquid Suspension in an Unbaffled Stirred Tank

The dispersion characteristics of water-silica two-phase system in an unbaffled stirred tank with diameter of 0.3 m, and height 0.45 m, equipped with a 0.15 m diameter 3-blade 70o PBTD (pitched blade turbine downflow) were studied. The profile of local solid concentrations was measured using a PC-6A fiber optic reflection probe. The effects of impeller speed from 113 to 173 r/min and impeller off-bottom clearance height from 0.08 to 0.16 m on particle concentration distribution were examined when the average particle phase holdup was set as 0.005(j). The results show that the suspension of solid particles in the stirred tank can be improved by increasing the impeller speed and decreasing impeller off-bottom clearance height. In the present experiment, solid particles reached the best suspension under the impeller speed of 173 r/min and impeller off-bottom clearance height of 0.08 m.