Experimental Investigation of Particles Dynamics and Solid-Liquid Mixing Uniformity in a Stirred Tank

Particle suspension and deposition dynamics are significant factors affecting the level of mixing quality in solid-liquid two-phase stirring processes. In general, the ability to increase the suspension rate and minimize deposition effects is instrumental in improving the uniformity of particle mixing, accelerating the reaction of involved solid-liquid two-phase, and improving the efficiency of production operations. In this work, suspension and deposition indicator based on the Betti number and a uniformity indicator are introduced and obtained by means of image analysis. The influence of the blade type, rotation speed, blade diameter and blade bottom height on the particle suspension/deposition characteristics and mixing uniformity are carefully investigated. The experimental results show that the two-phase motion region can be divided into three local regions, including a bottom motion along the wall, a low-degree suspension region under the blade and a high suspension region above the blade. The best degree of particle suspension is attained by the double-inclined blade paddle at a speed of 270 r/min, a paddle diameter ratio of 0.414, and a height-diameter ratio of 0.086. The double-inclined blade paddle has a better effect on promoting particle suspension and solid-liquid two-phase mixing uniformity.