Dynamics of rate-based separation methods for granular materials and the solid-liquid interaction

摘要

Processing of granular materials is a costly endeavor that spans across a variety of industries ranging from pharmaceutical, food, and cosmetics to construction and metal extraction. Devices commonly used in granular processing however, lack a fundamental understanding of granular behavior - implementing outdated technologies based on heuristics. Separation units for dry mixture, in particular, are highly energy intensive and environmentally unfriendly. For wet or damp mixtures, less is understood about the liquid-solid particle interactions that govern mixture behavior, which has limited development of advanced separation units for wet mixtures in industry. ududThe work herein implements discrete element method (DEM) simulations along with experimental work to present two energy-efficient (green), granular separation unit prototypes, designed to rationally exploit the properties of particulate materials that naturally result in segregation. This work also describes an analytical method that yielded a deeper and novel characterization of solid-liquid interactions among two- or three-particles simultaneously. Taken together, the work presented in this dissertation seeks to advance the current state of knowledge of solid-solid and solid-liquid interactions, and has furthered the development of rationale separation systems with applications in industry. ududHerein, segregation of granular mixtures with two newly developed systems was successfully demonstrated. Each prototype potentiates the effects of physical differences among particles to achieve separation via a kinetic differential, known as rate-based separation. In the first case, a passive separation system – analogous to sieving – was developed to successfully induce segregation among size-disperse granular mixtures, without being encumbered by issues with material accumulation or fouling. In the second case, separation of density-disperse mixtures was successfully demonstrated using a fluid coated vibrating system. The unique features of these systems make each an attractive option for further development as a unit operation in manufacturing settings, particularly given the rising interest in green technology. ududFurther study of the rupture forces of complex liquid bridges is presented to advance the understanding of liquid-solid interactions in particle processing. Using a custom-built micromechanical force microscope, the rupture force of bridges conjoining two or three particles were analytically measured. Direct characterization of three-particle interactions in the funicular regime is a novel achievement. Results indicate that the maximum force and rupture distance are the effect of surface characteristics, straining mechanism and effective liquid volume. These insights may encourage new solutions to achieve wet mixture separation.ududThis work utilizes powerful computational simulations and experimental methods to reveal novel insights of granular behavior, which drive innovation of new, rational separation devices that are attractive to industry applications.ud