The objective of this work is to advance the fundamental understanding of mixing
and segregation of cohesive granular materials. Cohesion can arise from a variety of
sources: van der Waals forces, electrostatic forces, liquid bridging (capillary) forces.
These forces may play a significant role in the processing of fine and/or moist powders
in many industries, from pharmaceuticals to materials synthesis; however, despite its
prevalence, there is only limited information available in the literature on processing
of cohesive materials. Instead, the vast majority of work has been directed at the
study of non-cohesive (i.e., free-flowing) particles, and a wealth of information has
been learned about the behavior of cohesionless materials. With growing emphasis on
controlling the structure of materials at increasingly small length-scales (even tending toward the nano-scale), understanding the effects of particle interactions - which tend
to dominate at smaller length-scales - on processing operations has become more
important than ever.
This project focuses on the effects of cohesion on mixing and segregation in simple,
industrially-relevant, granular flows. In particular, the paradigm cases of a slowly
rotated tumbler and the flow in a simple shear cell are examined. We take a novel approach to this problem, placing emphasis on microscopic (particle-level), discrete modeling so as to take as its staring point the well understood interaction laws governing cohesion (capillary, van der Waals, etc.), and build to the view of the macroscopic flow via experiment and Particle Dynamics Simulation. We develop and use discrete
characterization tools of cohesive behavior in order to construct a simple theory
regarding the mixing and segregation tendency of cohesive granular matter. This theory allows us to analytically determine a phase diagram, showing both mixed and segregated phases, and agrees both quantitatively and qualitatively with experiment. These results have implications for industrial mixing/separation processes as well as novel particle production methods (e.g., engineered agglomerates with precisely
prescribed compositions).
Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-11172005-201553 |
Date | 01 February 2006 |
Creators | Li, Hongming |
Contributors | Patrick Smolinski, Sachin S Velankar, Robert Enick, Joseph J. McCarthy |
Publisher | University of Pittsburgh |
Source Sets | University of Pittsburgh |
Language | English |
Detected Language | English |
Type | text |
Format | application/pdf |
Source | http://etd.library.pitt.edu/ETD/available/etd-11172005-201553/ |
Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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