The
influence of the packing size on the mean bubble diameter in a flooded
bed reactor packed with glass spheres of three different diameters
(1.9, 4.0, and 9.3 mm) was investigated. The gas saturation and interfacial
area were respectively measured by electrical capacitance tomography
and chemical absorption of oxygen. It is observed that the presence
of packing has greatly reduced the bubble diameter and increased the
gas saturation compared with a bubble column. To explore the underlying
relationship between the bubble diameter and packing size, the packing
size featured by the pore diameter was utilized as a reference. It
shows that the bubble diameter is 2–3 times the pore for the
1.9 and 4.0 mm packings, while they are approached for the packing
of 9.3 mm. An empirical correlation was proposed for the mean bubble
diameter prediction with a discrepancy of less than 25% from the measurements.
Films and rivulets are the two basic forms of dynamic liquid in a three-phase fixed bed (trickle bed), which determines the wetting efficiency of the catalyst. This paper is devoted to the conflicting wetting performance observed between non-porous glass beads and porous alumina pellets, and a parallel zone model is applied to resolve the complex liquid flow texture. This shows that in the case of glass beads, the wetting efficiencies of the catalyst along with the liquid flow rate in increasing and decreasing branches are different, especially when the gas flow rate is low. In comparison, there is almost no wetting difference for the alumina pellets with respect to liquid flow rate increasing or decreasing. The dynamic liquid is significantly more uniformly distributed over the cross-section in the Al2O3 bed than in the glass one.
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