LDV measurements of particle velocity distribution and annular film thickness in a turbulent fluidized bed

Local particle velocity and annular film, thickness in a 4.8 m-high, 0.15 m-ID turbulent fluidized bed (TFB) were determined with a Laser Doppler Velocimeter (LDV) at several axial heights. The effects of superficial gas velocities (0.47-0.94 m/s), initial bed heights (03-0.5 m), and particle sizes (mean diameter is 164 pm and 89 pm, respectively) on particle velocity and annular film thickness were investigated at ambient conditions. When superficial gas velocity or initial bed height was increased, the radial profile of particle velocity became significantly non-uniform. Additionally, the core-annulus flow pattern was observed in TFB. The annular film layer narrowed along the axis, but widened with the increase of initial bed height or superficial gas velocity. When compared particles with diameter of 164 pm, the smaller particles were more sensitive to the change of operating conditions. The particles with diameter of 89 pm showed more non-uniform radial profiles of particle velocity and a wider annulus. Based on effects of operating conditions, measurement height, and particle sizes, a new correlation was developed to predict the annular film thickness in turbulent fluidized bed. A good agreement was obtained between the predicted results and experimental data. (C) 2016 Elsevier B.V. All rights reserved.