RADIAL AND AXIAL VARIATION IN VOIDAGE IN HIGH VELOCITY FLUIDIZED BEDS.
Item
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Title
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RADIAL AND AXIAL VARIATION IN VOIDAGE IN HIGH VELOCITY FLUIDIZED BEDS.
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Identifier
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AAI8629736
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identifier
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8629736
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Creator
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SHAO, MANJUN.
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Contributor
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Herbert Weinstein
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Date
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1986
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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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High velocity gas fluidization is a transported gas-solid fluidization which includes turbulent fluidization, fast fluidization and dense phase and dilute phase transport. The major advantages of high velocity fluidization are high throughput of gas and solid, intimate contact between gas and solid, controlled residence time of both phases and smooth operation.;An experimental investigation of the parameters that determine local radial and axial cross-sectional void fraction in high velocity fluidized beds is reported. It is shown that a dilute core and a dense wall region are characteristic of the local radial variation of bed voidage in the various high velocity fluidization regimes, and that s-shape profiles are characteristic of the axial variation of cross-sectional average bed voidage for fast fluidization.;The experimental system consisted of an 8.5 m high, 15.2 cm I.D. recirculating fluidized bed. A cracking catalyst HFZ-33 (59 (mu)m in mean particle diameter and 1.46 K(,g)/m('3) in particle density) was fluidized by ambient air. An x-ray system was used to measure the radial and axial solid fraction profiles, and the axial pressure gradient profiles were also measured with pressure taps. The x-ray system also was used for real-time flow visualization which illustrated the dynamics of the solid-gas flow. In this work, superficial gas velocities ranged from 1.0 m/s to 6.0 m/s. Solid circulation rate were controlled from 10 K(,g)/m('2)-s to 154 K(,g)/m('2)-s. Two system inventories I(,s) = 2.0 m and I(,s) = 2.5 m were used.;The superficial gas velocity, solid circulation rate and system inventory are important flow operating conditions in high velocity fluidized beds. These parameters not only affect slip velocity and the profiles of bed voidage, but also the characteristics structure of the fluidized bed. Different radial and axial profiles of bed voidage illustrate the characteristic structure of various fluidization regimes: bubbling fluidization, fast fluidization and dense phase and dilute phase transport.
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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
