Bed height and material density effects on local timeâ??average gas hold â??up in Fluidized bed Reactor

Abdelsalam Efhaima, and Muthanna H. Al Dahhan, Department of Chemical and Biological
Engineering, Missouri University of Science and Technology, 143 schrenk Hall, 400 W. 11 th
.Rolla, MO 65409,USA, Email ayed67@mst.edu
The hydrodynamic behavior of fluidized bed reactors is complicated due to complex interaction phenomena among the gas and solids phases. The hydrodynamic must be understood to improve fluidized bed operations and process efficiencies. Gas hold-up is one of the most important parameters with minimum fluidization velocity. Gas hold-up describes the volumetric fraction of gas present within the bed materials, characterizes the fluidization quality, and is also useful in estimating the interfacial area between the dense and dilute phases that would be useful in heat and mass transfer calculation. Local time-averaged gas holdup was determined by using a
0.14 m diameter and 1.82 m height Plexiglas cylindrical fluidized bed column, two different
Geldart type -B particles were used, glass bead and copper particle with material density of 2500,
5300 Kg/m3 respectively with the same size particle 210 micrometer. Three different bed height to diameter ratios were investigated H/D = 0.286, 0.644 and 1.6 at specific superficial gas velocity Ug = 0.25 m/s by using non-invasive Technique Computed Tomography (CT). Results show that local time â??average gas hold-up increases by increasing (H/D) ratio, decreasing the bed density increasing the gas hold-up in the bed.

Keywords: Fluidized beds, hydrodynamics, Computed Tomography(CT), Gas holdup.