Effects of surface vortex on the drawdown and dispersion of floating particles in stirred tanks

Publication date: Available online 27 June 2019Source: ParticuologyAuthor(s): Wentao Xu, Yangbo Tan, Meng Li, Jianglong Sun, De Xie, Zeng LiuAbstractThe effects of surface vortex on the drawdown and dispersion of floating particles in stirred tanks were investigated. Particle distribution and power consumption were analyzed by experiments and numerical simulations in both baffled and unbaffled tanks agitated by a Rushton impeller. In unbaffled tanks, a non-aggregation rule was applied and the average dispersion index was found to serve as a reasonable prediction of the full drawdown of floating particles. The critical impeller speeds in an unbaffled tank were higher than those in a tank with vertical baffles. At each immersion depth in a baffled tank, particles distributed more uniformly and more power was consumed. Comparison of snapshots of the baffled and unbaffled tanks shows that the surface vortex increases the drawdown speed while it decreases the particle distribution uniformity and power consumption. Therefore, the use of baffles to suppress the surface vortex provides for a more uniform particle distribution in stirred tanks.Graphical abstract

Source: Particuology - June 28, 2019 Category: Science Source Type: research