Experimental investigation of monodisperse solids drying in a gas-fluidized bed

Fluidized bed drying is an unsteady process where particle and gas properties evolve in time. The bed hydrodynamics and its interplay with mass and heat transfer changes in time. In this study, experiments in a pseudo-2D fluidized bed setup are performed to obtain insight in this complex behavior. A coupled particle image velocimetry infrared thermography technique provides solids velocity and temperature fields in the bed. Significant hydrodynamic changes due to the evaporation of water from the porous γ-Al₂O₃ material for three superficial velocities were observed. The 1.25 u_mf case resulted in an fixed bed state, but after drying for 580 s a bed inversion took place. The 1.50 and 1.75 u_mf experiments showed an increase in bed expansion over time. Furthermore, clear asymmetrical solids volume fluxes were observed for the wet material that became more symmetrical over time when the material dried.