Based on the single stage dryer model (Qi, 1996), a model for a multi-
stage diffusion-controlled pneumatic-conveying dryer train was develop
ed. The model consisted of a set of algebraic equations describing the
relationship between the moisture level in solids and major process p
arameters (i.e., diffusivity, partition coefficient, particle size, nu
mber of stages, solids loading, residence time, etc.). The effects of
these parameters on drying were studied using the model. Equilibrium a
nd other special or asymptotical conditions (e.g., infinitesimal injec
tion of drying gas, uniform partition coefficient and Fourier numbers,
etc.) were analyzed. Model calculations have been shown to compare ve
ry well with data from an actual plant HDPE drying process.