Investigation On Immiscible Liquid-liquid Dispersion Characteristics In Stirred Tanks Using A Novel Multi-blade Composite Agitator

The dispersion ability of the novel multi-blade composite agitator in an immiscible liquid-liquid system with lager dispersed phase viscosity was investigated.The effect of the operating conditions(such as the stirring speed,power consumption)and,the submergence of the agitator and the agitator clearance on the the critical rotational speed for the dispersed phase and,the drop size distribution and mean drop size.The dispersing mechanism of this immiscible liquid-liquid system were studied in a flat-bottomed vessel too.The dispersion characteristics of an agitator in the heterogeneous system could be investigated by thhe dispersion of the dispersed phase,and the dispersed phase dispersibility are mainly reflected in the dispersed droplet size and its distribution law.So the technique which can measure the drop size distribution and mean drop size accurately is crucial.The planar laser induced fluorescence(PLIF)method combined with a refractive index matching technique was used in this paper to photo the dispersed situation of the droplets in the vertical middle plane of the immiscible liquid-liquid system,and we can get the droplet diameter data by processing the pictures with the Image-Pro Plus.By statistical and calculate the data of the droplets diameter to get the drop size distribution and the Sauter Mean Diameter.This method has the advantages of the non-intrusive measuring techniques which is without interference flow field,high measuring accuracy,and equipment set up easily,and at the same time it can improve the measurement accuracy by ruled out the overlapping of the dispersed droplets.The effects of the impeller submergence depth,clearance of the impeller off the tank bottom,and the liquids system height on the dispersion of the dispersed phase have been investigated in detail with the photographic method.The best location for the agitator is C=20mm,S=50mm,and the height of the liquids system is set as H=300 mm,by comparing the dispersed phase dispersing pictures with controlling variables method taken by the camera.The power consumption and power number(NP)were calculated by measure the stirring shaft torque when the agitator installation location and the height of the liquids system were determined.The effect of impeller speed,dispersed phase volume fraction and viscosity on the power consumption per unit volume(P/V),and Reynolds number on power number have been studied.The effect of the dispersed phase physical parameters and operating conditions such as the agitation speed,volume fraction and viscosity of the dispersed phase on the critical dispersion rotational speed,the drop size distribution and Sauter Mean Diameter have been investigated by this new measurement method.