STUDY OF SEGREGATION IN A VIBRATED PACKED BED SYSTEM FOR NONSPHERICAL PARTICLES

Abstract

The effect of particle properties that include shape, size, and density in a vibrated packed bed mixer for multi-component granular mixtures is investigated and mixing is characterized using segregation index (57) and subdomain mixing index (SMI). Granular materials exhibit a unique set of challenges during their handling and transport. One of the most important of the se challenges is to maintain the uniformity of the blend of particles which naturally segregate and are influenced by system parameters and differences in particle properties. This natural segrega- tion directly affects product quality and process efficiency. Comprehensively understanding and accurately predicting the amount of the mixing and complex dynamic flow behavior of granular materials is important for both scientific theory and direct industrial applications. The focus of this dissertation is to characterize segregation in a vibrated packed bed. The significant results can be divided into three parts: the first two parts are an experimental study and last part is primarily a computational study. First, the experimental work investigates the parameters affecting the segregation of binary mixtures in a vibrated packed bed. These param- eters include system parameters such as vibration frequency, amplitude, columns" geometry. and bed fill height, as well as physical properties of the particles, including shape and size. The purpose of this dissertation is to explore the effect of the non-sphericity of granules (particles>1 mm) on the mixing process using experiments. Initially, four different sensitivity studies are performed to fix the base case, which includes the initial configuration of particles, the total time vibration study, the sampling section width study, and the bed fill height study. Following that, the experimental studies analyze the mixing behavior based on the particle (shape and size) and system (frequency and amplitude) parameters. The results show the existence of a critical vibration intensity (T = 4.64) below which there is little mixing. In addition, the axial segrega- tion index (57) value is significantly correlated to the random monodisperse packing fraction of coarse particles and the angularity of the fine particles. As the random monodisperse packing solid density increases from cubes to elongated needles, the axial segregation index follows a decreasing trend for the coarse particles: Cube > Sphere > Oblate > Prolate > Elongated Nee- dle. Cube gives the worst mixing, whereas elongated needle gives the best mixing. Similarly,