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Electrostatic instabilities, charging and agglomeration in flowing granular materials
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Electrostatic instabilities, charging and agglomeration in flowing granular materials
Name
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LaMarche
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Keirnan R.
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Keirnan R. LaMarche
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Cuitino
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Alberto
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Advisory Committee
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Alberto Cuitino
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chair
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Pedersen
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Henrik
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Advisory Committee
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Henrik Pedersen
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Glasser
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Benjamin
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Advisory Committee
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Benjamin Glasser
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internal member
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Michniak-Kohn
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Bozena
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Advisory Committee
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Bozena Michniak-Kohn
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outside member
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Rutgers University
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Graduate School - New Brunswick
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theses
OriginInfo
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2008
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2008-05
Language
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English
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electronic
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application/pdf
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text/xml
Extent
xii, 174 pages
Abstract
The unpredictable behavior of granular materials is one of the largest stumbling blocks on the way to satisfactory design and control of many manufacturing processes. There are many factors which contribute to the complex behavior of granular materials, however, the effect of electrostatic forces is both one of the least studied aspects of granular materials as well as one of the most important. Electrostatics can cause agglomeration of otherwise free flowing powders, the adhesion of grains to equipment surfaces, and particles of differing composition or size to segregate. In addition, electrostatic discharges can ignite dangerous dust explosions. With a better understanding of the effects of electrostatics, as well as the processes at work during the charging of particulate flows, some of these issues can begin to be addressed. To these ends, we examine the charge and agglomeration of grains and investigate how flows of particles charge, and in turn, how they are affected by those charges.
In this work, we show that the behavior of flows of uncharged grains through chutes can be approximated by simple models, but when charging takes place the behaviors change dramatically, replacing fluid-like flow instabilities with significant agglomeration, making the flow much more difficult to model. To understand and predict these transitions from relatively simple flow to a more complex/agglomerated state requires that the distribution of charge amongst the particles, as well as the effect of large electric fields, produced by either charged surfaces or particles, be investigated.
It was found that highly nonuniform distributions of charge could be generated by flowing particles. This distribution can result in significantly different forces acting on charged and uncharged grains and suggests that many of the problems commonly encountered during powder handling may be due to a small fraction of the particles.
Lastly, significant agglomeration was observed when particles were subjected to nonuniform electric fields. Nonuniform electric fields, which are produced as particles charge, cause polarization of the particles and attraction between grains. The resulting forces acting on the particles (referred to as dielectrophoretic forces) were large enough to produce both large agglomerates of powder, as well as adhesion to equipment surfaces. These forces may also be utilized to control particle behavior as this adhesion depends on the presence of an easily controlled external electric field.
In this work, we show that the behavior of flows of uncharged grains through chutes can be approximated by simple models, but when charging takes place the behaviors change dramatically, replacing fluid-like flow instabilities with significant agglomeration, making the flow much more difficult to model. To understand and predict these transitions from relatively simple flow to a more complex/agglomerated state requires that the distribution of charge amongst the particles, as well as the effect of large electric fields, produced by either charged surfaces or particles, be investigated.
It was found that highly nonuniform distributions of charge could be generated by flowing particles. This distribution can result in significantly different forces acting on charged and uncharged grains and suggests that many of the problems commonly encountered during powder handling may be due to a small fraction of the particles.
Lastly, significant agglomeration was observed when particles were subjected to nonuniform electric fields. Nonuniform electric fields, which are produced as particles charge, cause polarization of the particles and attraction between grains. The resulting forces acting on the particles (referred to as dielectrophoretic forces) were large enough to produce both large agglomerates of powder, as well as adhesion to equipment surfaces. These forces may also be utilized to control particle behavior as this adhesion depends on the presence of an easily controlled external electric field.
Note
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Ph.D.
Note
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Includes bibliographical references (p. 158-173).
Subject
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Topic
Chemical and Biochemical Engineering
Subject
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Topic
Electrostatics
Subject
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Topic
Granular materials
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Graduate School - New Brunswick Electronic Theses and Dissertations
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rucore19991600001
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http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.17342
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ETD_862
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doi:10.7282/T3TM7BGT
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ETD doctoral
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The author owns the copyright to this work.
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Copyright protected
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Open
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Keirnan LaMarche
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Copyright holder
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Rutgers University. Graduate School - New Brunswick
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Non-exclusive ETD license
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Author Agreement License
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I hereby grant to the Rutgers University Libraries and to my school the non-exclusive right to archive, reproduce and distribute my thesis or dissertation, in whole or in part, and/or my abstract, in whole or in part, in and from an electronic format, subject to the release date subsequently stipulated in this submittal form and approved by my school. I represent and stipulate that the thesis or dissertation and its abstract are my original work, that they do not infringe or violate any rights of others, and that I make these grants as the sole owner of the rights to my thesis or dissertation and its abstract. I represent that I have obtained written permissions, when necessary, from the owner(s) of each third party copyrighted matter to be included in my thesis or dissertation and will supply copies of such upon request by my school. I acknowledge that RU ETD and my school will not distribute my thesis or dissertation or its abstract if, in their reasonable judgment, they believe all such rights have not been secured. I acknowledge that I retain ownership rights to the copyright of my work. I also retain the right to use all or part of this thesis or dissertation in future works, such as articles or books.
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