THE STRUCTURE AND OPERATING CHARACTERISTICS OF HIGH VELOCITY FLUIDIZED BEDS.
Item
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Title
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THE STRUCTURE AND OPERATING CHARACTERISTICS OF HIGH VELOCITY FLUIDIZED BEDS.
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Identifier
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AAI8508717
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identifier
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8508717
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Creator
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MELLER, MENACHEM M.
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Contributor
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Herbert Weinstein
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Date
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1985
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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
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Abstract
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An experimental investigation of the parameters that determine local solids holdup in a transported gas-solid fluidized bed is reported. Knowledge of the local solids holdup is necessary both to predict the axial pressure gradient in the fluid bed as well as to evaluate the performance of the fluidized bed for a particular process. Such information is essential to assure smooth operation of the equipment, good contact between gas and solid, and have some measure of the system power consumption.;The experimental system consists of an 8.5 meter high, 15.2 cm. I.D. recirculating bed. Two different silica-alumina cracking catalysts were used, which differ mainly by a density ratio of 1.4. Gas velocities ranged from 0.65 to about 6.0 m/s and solid rates approached 150 Kb/m('2) sec for the heavier catalyst. Axial solid density profiles were measured using a series of differential manometers. A method for measuring radial solid profiles using X-ray absorption was explored. The radial density distribution measurement was based on inverting side-on absorption data using a chordal absorption technique.;The axial solid fraction profile often exhibits, for either solid, a variation from a relatively high value in the bottom section of the bed (dense phase) through a transition region in the middle of the bed which contains an inflection point, to a low value (dilute phase) in the top section of the bed. The position of the point of inflection is shown to depend upon the pressure drop imposed across the bed as well as gas and solid rates. Raising the imposed pressure drop, raising the solid rate or decreasing the gas rate all have the effect of raising the inflection point in the density profile.;Experiments have shown x-rays to be suitable for nondisruptive solid density variation measurements. These experiments confirm the existence of a core-annular radial density profile. Preliminary experiments indicate that this type of profile applies for both turbulent and fast fluidization. The X-ray images at three axial positions in the fast fluidized bed, corresponding to the dense phase, dilute and inflection point positions show relative agreement with the densities determined from the axial pressure gradient.
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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.
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Program
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Engineering
