Analysis of the Influence of Dimensionless Vibration Number on the Drying of Pastes in Vibrofluidized Beds

Abstract

The purpose of this work is to evaluate the operation of a vibrofluidized bed of inert particles in the transient and steady-state regimes for water evaporation and for drying of domestic sewage sludge. The feeding rate was initially set on 10 mL/min and this value has been gradually raised at 4 mL/min increments until saturated moist conditions were obtained at the bed exit. The bed was operated at 80 and 100°C, with inlet air velocities 20 and 40% above the minimum fluidization velocity. The dimensionless vibration numbers (Γ) were 0.00 and 4.00, the latter one with amplitudes of 0.003 and 0.015 m. For the conditions investigated, the effect of Γ on the drying dynamics was observed to depend on the amplitude and frequency of vibration. The use of vibration with lower amplitude and higher frequency provided the highest powder production. For paste feeding rates from 14 to 38 mL/min, the moisture content of the dried sewage sludge powder varied from around 5 to 10% on a wet basis, tending to increase with the increase of paste feeding rates.

Keywords:

• Drying of pastes
• Transient drying period
• Vibrofluidized bed

ACKNOWLEDGMENTS

The authors thank the Brazilian funding agencies FAPESP, CAPES, and CNPq for their financial support.