Mixing Characteristics Investigation In The Stirred Tank With Long-Short Blades(LSB) Agitator

The mixing characteristics of the LSB agitator have been investigated. Firstly the power consumption characteristics of the LSB agitator have been studied. The effects of impeller design (blade shape and blade dimension), the height of liquid level, and the location of the agitator and baffles on the liquid mixing have been critically analyzed. The results show that the power consumption per unit volume of the agitator growing with the increase of the HIT and N; for the LSB agitator(LB-1, β=0°), when H/T<1.4, the effects of short blades on unit power consumpution satified the following relationship:CSB< SB-2<SB-1. When H/T≥1.4, CSB≥SB-2≥SB-1. The location of the baffles also has many effects on the power consumption. The effect of the C (the clearance between the bottom of the tank and the agitator) on the power consumption was more significant than the baffles, with the increasing of the C, the power number gradually decreased.The mixing time experiment of the LSB agitator was carried out using the Planar Laser Induced Fluorescence (PLIF) technology. The effects of the rotation speed of the impeller (N), the liquid level (H) and the location of the baffles on the mixing performance were investigated. We compared the mixing process of the LSB agitator with the standard Rushton DT. The results show that when the liquid level is low (H=T), at different baffles’location there was no obvious difference between the mixing time, the larger the space between the baffles and the wall of the tank the smaller of the mixing time. When HIT=1.5, △C=5 mm, the mixing process of the LSB agitator compared with standard Rushton DT, it was found that the LSB agitator has better mixing efficienyThe flow pattern of the high viscosity fluid in the stirred tank was also studied. In the study following factors have been researched:the height of the liquid level (H), the shape parameters of the impeller, the shape parameters of the stirred tank. The results show that a certain distance (AC=0.057) between the baffles and the wall of the tank can enhance the mixing of high viscosity fluid, on the contrary when the distance was △C=0.1T, it will hindering the mixing process. The flow pattern of the fluid in the tank was axial flow when H=T. With the increase of the liquid level, the fluid in the tank forming the mixed flow (the combination of axial flow and radial flow). When C/T≈0.25-0.33, we can obtain better flow pattern with the height of liquid level H/T=1.5.