(208f) Segregation of Non-Spherical Particles in Vibrated Packed Bed Mixers

The effect of the shape of particles on mixing and segregation is studied in a vibrated packed bed mixer. Binary mixtures (unequal sized) of four types of non-spherical glass particles (prolate, oblate, rectangular, and elongated needle) with different aspect ratios are used alongside spherical particles. The overarching goal is to explore the effect of non-sphericity of granules (particles > 2 mm) used in the pharmaceutical and food industries. The total amount of energy added to the binary mixture of particles through vibrations depends on two independent operating parameters: frequency and amplitude of vibrations that are combined as a single feature defined by vibration strength. The results show the existence of a critical vibration strength below which there is little mixing. In addition, the axial segregation index value (SI) is also significantly correlated to the random monodisperse packing fraction of coarse particles. The axial segregation index follows the decreasing trend: Cube > sphere > oblate > prolate > elongated needle. Similarly, increasing the angularity of fine particles, the axial segregation is reduced. Furthermore, binary particle mixing is also affected by particle size ratio, the varying fine mass fraction, and the column’s geometry. When the particle size ratio (between fine and coarse particles) it leads to reduction in segregation. The initial proportion of fines added to the system also plays an important role in determining the extent of segregation. As the proportion of the fines decreases in the initial fill - segregation decreases. In addition, the column's geometry causes a decrease in segregation when it’s changed from cylindrical to rectangular.

Future work would involve using better tools like radioactive particle tracking and high-speed camera studies to make even more accurate predictions.