Drying of polymer powder in fluidized bed: Modeling of multizone dryer

The process of drying of porous polymer powder (polypropylene) intended to remove the solvent (heptane) is analyzed. The dryer consists of two stages (apparatus) with multizone fluidized bed. The mathematical model of the process in multizone fluidized bed is proposed. The rate-limiting step, depending on diameter of polymer particles, is determined. It was found that in relatively large particles (>200 ?m) the rate of drying is limited by intraparticle diffusion. A way to decrease the energy consumption in drying has been also discussed and verified in experiments.