Study of solids motion, mixing, and heat transfer in gas fluidized beds
Knowledge on solids motion, mixing, and their relation to chemical reaction, heat and mass transfer in a gas-fluidized bed is of critical importance in the design of large scale fluidized bed combustors and reactors for desulfurization of solid fuels. The mean solids velocity and the particulates density for a range of superficial gas velocities and particle sizes were determined using a single radioactive tracer particle, dynamically identical to the bed particles. Gross circulation patterns and density distributions were in agreement with previously reported measurements. The cross correlations and Lagrangian autocorrelations of the solids fluctuating velocities were evaluated from the instantaneous and mean solids velocity. Root-Mean-Square (RMS) velocities, Lagrangian integral time scales, and the solids dispersion coefficients were inferred from the autocorrelations. Turbulent shear and normal stresses experienced by the particulates were also obtained. Solids mixing was investigated both experimentally and numerically. A multi-particle tracking technique was devised to experimentally study the mixing process in a fluidized bed. A transient convection-diffusion model was employed for the numerical simulation of the process. The influence of the solids hydrodynamics on the local heat transfer from immersed tubes was examined by measurement of the local time-averaged heat transfer coefficients from horizontal internals simulating tube banks at several locations of a fluidized bed along with measurements of the local mean solids velocity and density for a range of superficial gas velocities.
- Research Organization:
- Illinois Univ., Urbana (USA)
- OSTI ID:
- 5924093
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
014000* -- Coal
Lignite
& Peat-- Combustion
BUBBLES
CHEMICAL REACTIONS
COMBUSTORS
DENSITY
DESULFURIZATION
ENERGY TRANSFER
FLOW RATE
FLUID FLOW
FLUID MECHANICS
FLUIDIZED-BED COMBUSTORS
GAS FLOW
HEAT TRANSFER
HYDRODYNAMICS
ISOTOPE APPLICATIONS
MATHEMATICAL MODELS
MECHANICS
MIXING
PARTICLE SIZE
PARTICLES
PARTICULATES
PHYSICAL PROPERTIES
SIZE
SOLIDS
TRACER TECHNIQUES
TURBULENT FLOW