(723a) Particle Motion in Vertical Bladed Mixers

Vertical axis mixers are common particle-particle mixers in industry. Particle motion in vertical axis mixers is similar to other equipment utilized in industry, including high shear granulators in pharmaceutical applications and filter dryers in food processing. The motion of individual particles within industrial equipment is subject to competing mechanisms of mixing including diffusion, convection, and shear mixing. In spite of the importance of particle mixing in industry, understanding the mixing fundamentals is still challenging. For example, mixing processes can lead to particle segregation under certain operating conditions, and in some instances, mixing and segregation occur simultaneously but in different regions.

In order to study the mixing process it is imperative to study the motion of individual particles under different mixing mechanisms arising from blade movement. In this study, experiments were performed in a transparent 15.2 cm ID acrylic cylinder fitted with two 45^o blades and filled with particles of varying diameter and density. Tagged particles were loaded in different positions and image analysis techniques were employed to follow the trajectories of the tagged particles. Observations were obtained for tagged particle initial location at the free surface as well as along the transparent walls. Particle Tracking Velocimetry (PTV) techniques were used to obtain the particle position, orientation, and velocity. The effects of particle size, density, initial location, and impeller speed on the trajectory and final location of the tagged particles are reported.