Impulsive fluidization: A mechanism for particle segregation in dense suspensions

Book · Sat Dec 31 00:00:00 EST 1994

OSTI ID:110059

Schiaffino, S; Kytoemaa, H K ^[1]

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1. Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Mechanical Engineering

Unsteady fluidization is investigated as a method in obtain sizes-dependent particle segregation in concentrated suspensions. A uniformly mixed binary bed of spheres is impulsively fluidized in a rectangular test section. The fines are in the range of 200--400 {micro}m and the coarse particles are in the range of 2--4 mm. From rest, a positive displacement pump impose a constant fluid velocity that is greater than the fine particle minimum fluidization velocity, but smaller than that of the coarse particles. Different values of particle sizes, bed heights and liquid flow rates are studied. The dependence of the segregation velocity on the particle density is also assessed for different materials. This variable controls the segregation speed and is therefore of significant practical interest. This can be useful to evaluate the opportunity to improve particle separation at high solid loading by controlling induced body forces -- e.g. centrifugal forces in a rotating environment. The initial upward motion of the packed bed forms a void at the bottom of the bed, through which coarse particles rain down to form a fines-free region. The void progresses upward and the fines remain in this region until it comes close to the top of the bed and the fines suddenly break through to the surface. A bed of coarse particles that is free of fines is left behind. In this process, the formation and upward motion of the void is essential for segregation to occur. The quality of segregation is improved with larger liquid flows but it also results in higher bed expansions, and possible related difficulties confining the particle mixture.

• DOE Contract Number: FG02-85ER13331
• OSTI ID: 110059
• Report Number(s): CONF-940659-; ISBN 0-7918-1369-X; TRN: IM9543%%361
• Resource Relation: Conference: 1994 American Society of Mechanical Engineers (ASME) Fluids Engineering Division summer meeting, Lake Tahoe, NV (United States), 19-23 Jun 1994; Other Information: PBD: 1994; Related Information: Is Part Of Industrial and environmental applications of fluid mechanics 1994. FED Volume 186; Morrow, T.B.; Horii, K.; Elger, D.F.; Marshall, L.R. [eds.]; PB: 203 p.
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
42 ENGINEERING NOT INCLUDED IN OTHER CATEGORIES
FLUIDIZED BEDS
PERFORMANCE
PARTICULATES
SEPARATION PROCESSES
PARTICLE SIZE CLASSIFIERS
UNSTEADY FLOW
PARTICLE SIZE
SORTING
BINARY MIXTURES
CERAMICS
HAZARDOUS MATERIALS
POWDER METALLURGY
CALIBRATION
FLOW VISUALIZATION
EXPERIMENTAL DATA