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Li, Hongming (2006) IMPACT OF COHESION FORCES ON PARTICLE MIXING AND SEGREGATION. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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The objective of this work is to advance the fundamental understanding of mixingand segregation of cohesive granular materials. Cohesion can arise from a variety ofsources: 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 powdersin many industries, from pharmaceuticals to materials synthesis; however, despite itsprevalence, there is only limited information available in the literature on processingof cohesive materials. Instead, the vast majority of work has been directed at thestudy of non-cohesive (i.e., free-flowing) particles, and a wealth of information hasbeen learned about the behavior of cohesionless materials. With growing emphasis oncontrolling the structure of materials at increasingly small length-scales (even tending toward the nano-scale), understanding the effects of particle interactions - which tendto dominate at smaller length-scales - on processing operations has become moreimportant 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 slowlyrotated 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 discretecharacterization tools of cohesive behavior in order to construct a simple theoryregarding 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 preciselyprescribed compositions).


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairMcCarthy, Joseph Jmccarthy@engr.pitt.eduJJMCC
Committee MemberSmolinski, Patrickpatsmol@pitt.eduPATSMOL
Committee MemberEnick,
Committee MemberVelankar, Sachin
Date: 1 February 2006
Date Type: Completion
Defense Date: 20 June 2005
Approval Date: 1 February 2006
Submission Date: 17 November 2005
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Chemical Engineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Capillary force; Cohesion; Granular material; Interparticle forces; Liquid-bridge; Mixing/segregation; Particle dynamics; van der Waals force
Other ID:, etd-11172005-201553
Date Deposited: 10 Nov 2011 20:05
Last Modified: 15 Nov 2016 13:51


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