Thermally induced agglomeration in fluidized beds.
Item
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Title
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Thermally induced agglomeration in fluidized beds.
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Identifier
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AAI9009724
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identifier
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9009724
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Creator
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Compo, Peter C.
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Contributor
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Advisers: Gabriel Tardos | Robert Pfeffer
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Date
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1989
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Language
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English
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Publisher
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City University of New York.
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Subject
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Engineering, Chemical | Engineering, General
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Abstract
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The surfaces of particulate solids can become cohesive at temperatures as low as 40% of the material's absolute melting point. This "high temperature cohesion", frequently described as being due to sintering, occurs in a number of industrial fluidized bed systems and is in general a nuisance to be avoided. Siegell (1976) showed that dilatometry could be used to predict the temperature of incipient cohesion. In the present work, this technique is broadened so as to apply to a number of industrially important particle types and other materials which had not been previously tested. It is concluded that the surfaces of particles in the high temperature range exhibit liquid-like behavior which allows for instantaneous interparticle bonding of some strength. The minimum sintering temperatures of numerous materials are reported and the relative minimum sintering temperature is shown to decrease with the material's degree of ionic bonding.;Fluidized bed agglomeration is proposed to occur according to a survival mechanism in which the state of agglomeration is determined by the strength and nature of both the interparticle attraction and the breaking forces in the bed. It is shown that Geldart type "C" fluidization is a limiting case of agglomeration where the agglomerate structures are porous and very weak. The mechanism deviates from the two body models of agglomeration because two body models do not discriminate between agglomerate configurations. The minimum fluidization velocity and defluidization of agglomerating systems at high temperatures are also discussed.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
