Effects of interparticle forces in fluidized beds

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1987

OSTI ID:6105293

Ells, T S

The object of this work was to study the effects of interparticle forces in fluidized beds. Geldart (1) type A powders were mixed with Type C powders to prepare powder systems with varying degrees of cohesiveness. The dense phase and the bubble phase were studied separately in terms of particle interactions. Powder cohesiveness was measured directly by measuring the tensile strength of a powder compact in a split-cell device. A comprehensiveness parameter has been introduced to relate powder cohesiveness to the fluidization characteristics of the emulsion phase. The transition from particulate to aggregative fluidization was predicted by a simple model which describes the propagation of a shock wave. A shock wave will arise in a fluidized bed when the propagation velocity of a void is greater than the velocity of an elastic wave. The criterion takes into account interparticle and hydrodynamic effects. Agreement with the reported data was much improved over previous models that only consider hydrodynamic effects. An unobtrusive fiber optic probe was developed for measuring bubble frequency and interfaced to a computerized data acquisition system. The probe was shown to accurately record the passage of a bubble. The data were analyzed statistically using a power spectral density function. No correlation was observed between the cohesiveness of a powder and the bubble size using video photography and the bubble frequency measured with the fiber optic probe. Visual observations in a two-dimensional bed indicated deviations from the typical spherical cap bubble with the addition of fine cohesive powder.

• Research Organization: West Virginia Univ., Morgantown, WV (USA)
• OSTI ID: 6105293
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
421000* -- Engineering-- Combustion Systems
ADHESION
BUBBLES
DATA ACQUISITION
FIBER OPTICS
FLOW MODELS
FLUID MECHANICS
FLUIDIZATION
FLUIDIZED BEDS
FUNCTIONS
HYDRODYNAMICS
MATHEMATICAL MODELS
MECHANICAL PROPERTIES
MECHANICS
MIXING
PHOTOGRAPHY
POWDERS
PROBES
SHOCK WAVES
SPECTRAL DENSITY
SPECTRAL FUNCTIONS
TENSILE PROPERTIES
WAVE PROPAGATION