Js. Qi et C. Krishnan, MATHEMATICAL-MODELING OF CONTINUOUS CROSS-FLOW DIFFUSION-CONTROLLED DRYERS, Chemical Engineering Science, 51(21), 1996, pp. 4769-4780
A mathematical model has been developed for continuous cross-dow dryer
s operating in diffusion-controlled regime. In the model, a cross-dow
dryer is treated as a series of gas-solid contact stages, each purged
by a stream of drying gas while wet solids are passing through. By ana
lyzing the gas-solid interactions in each stage, boundary conditions f
or intra-particle diffusion were established and model equations obtai
ned. The model correlates the amount of moisture removed to a number o
f process variables (diffusivity, partition coefficient, particle size
, residence time, total number of stages, solids loading, drying gas h
umidity and purge rate) and allows effects of these variables on dryin
g to be studied. For drying fine powders, the effect of reduced mass t
ransfer efficiency due to particle agglomeration and gas channeling is
taken into account in the model by factoring an efficiency parameter
into the Fourier number. Model predictions of product moisture concent
ration based on laboratory-measured partition coefficient, diffusivity
, and efficiency factor were found to closely match data from a commer
cial cross-dow HDPE powder dryer. Copyright (C) 1996 Elsevier Science
Ltd