Analysis of The Fluidized Bed Drying of Wood Particles

Michael R. Milota, James B. Wilson


Engineering parameters necessary to design an industrial, continuous fluidized-bed dryer for wood particles were examined using a 0.21-m square batch fluidized-bed dryer. Parameters of main interest were gas velocity and drying curves, but bed voidage, particle elutriation, and distributor plate design also were considered. For unscreened (mixed sizes) hammermilled wood and sawdust, the minimum gas velocities for fluidization were 1.03 and 0.55 m/s, respectively. These values increased with increasing moisture content, decreasing sphericity, and increasing particle diameter. Current methods of adjusting batch drying curves so that they can be applied to a commercial continuous dryer were shown to be inadequate for some wood particle sizes. To predict drying curves for all particle sizes, a new method was developed that accounts for both internal and external resistances to drying. The new method was confirmed experimentally.


Drying curves;moisture content;heat transfer;mass transfer;design parameters

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