Experimental Investigation on Drying of Forest Biomass Particles in a Mechanically Stirred Fluidized Bed

Abstract

This chapter reflects a review of the results obtained in several investigations on the fluidization process of wet biomass particles in a mechanically stirred fluidized bed equipment. For the experimental purposes, an experimental equipment with a drying column of 300 mm in diameter is used. Using the Ergun equation, the fluodynamic behavior of the bed is analyzed to obtain, from the measurements of pressure drops in the bed and imposed velocities, the specific gas-particle contact surface; such interfacial surface varies between 5758 and 7317 m2 m–3 for dry particles and between 2774 and 4444 m2 m–3 for high humidity particles. Subsequently, the phenomena of heat and mass transfer by convection between the fluidizing gas and the biomass particles during the drying process are studied. The gas-particle heat and mass transfer coefficients are determined, considering stirrer rotation speeds between 1 and 2 rev s–1. The convective coefficients vary between 13 and 25.7 W m–2 K–1 for heat transfer and between 6 x 10–3 and 20 x 10–3 m s–1 for mass transfer; thus, correlations have been obtained between the Nusselt and Reynolds numbers and between the Sherwood and Reynolds numbers, respectively, valid in the Reynolds number range between 102 and 257.