The Fluidlike Behavior of Fine and Ultrafine Powders Fluidized by Gas
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Fine powders traditionally have been classified as Group C materials according to Geldart’s classification scheme. They are not capable of being fluidized by a gas because interparticle forces are exceedingly large compared to particle weight, which causes cohesive aggregation. Consequently, when Group C powders are subjected to a gas flow, they tend to rise as a slug of solids or to form channels through which the gas will escape rather than being distributed through the bulk. Typical examples are talc, flour and starch. In this chapter, we review observations on a different class of fine powders which exhibit a completely diverse gas-fluidization behavior resembling the nonbubbling fluid-like behavior shown by most noncohesive granular materials when fluidized by liquids.
KeywordsHurst Exponent Interparticle Force Tensile Yield Stress Toner Particle Interparticle Attractive Force
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