HOLDUP OF GAS BUBBLES AND LONGITUDINAL DISPERSION COEFFICIENT OF SOLID PARTICLES IN FLUID-BED CONTACTORS FOR GAS-SOLID SYSTEMS

摘要

References(18) Cited-By(15) Holdup of gas bubbles and longitudinal dispersion coefficient of solid particles were measured in 3.2, 7.9, 12.0 and 19.5cm inside-diameter fluid beds of F.C.C. particles. Holdup of gas bubbles based on the emulsion bed height (Le) was dependent on superficial gas velocity (uf) and bed diameter (DT). Le was determined as the bed height obtained by extrapolating the constant rate sedimentation curve to zero time. In the range of Uf ?? 2 cm/sec, Le did not vary with uf and DT, and it was about 9% larger than the completely settled bed height for the particles used in this experiment. The experimental and literature data of the longitudinal dispersion coefficient of F.C.C.particles based on the mean density of fluidizing bed (E*s) were correlated with Peclet number (Pe=uf DT/E*s), Froude number (Fr=uf/√gDT ) and (DT+0.23), and the following empirical equation was obtained for bed diameter ranging from 0.032 to 1.5 m. Pe=19(DT+0.23)Fr/(1+6.5Fr0.8)where the unit of DT is meters.