MATHEMATICAL-MODELING OF MULTISTAGE DIFFUSION-CONTROLLED PNEUMATIC-CONVEYING DRYER TRAIN

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.