Characteristics for the growth of particles in drying of orthophosphate solution have been studied in a 7.8 cm I.D. Χ94 cm high fluidized bed.
Preheated air was used as fluidizing gas and drying was operated in the semi-batch mode by the 4-kW external heater. Initial bed materials are STPP (sodium tripolyphosphate) with a mean size of 0.190 mm and glass beads of 0.415 mm in volume-surface mean diameter, respectively. Liquid feed was introduced into the fluidized bed through the air atomizing nozzle.
Mean particle sizes in the bed are measured with concentration of liquid feed (25-50 wt.%), bed temperature (250-380℃), gas velocity (Ug/Umf=2.0-4.0) and NAR value (526-900).
Growth of particles in the bed was dominated by the agglomeration of particles, and growth rate of particles for glass beads is larger than that for STPP. Mean particle size in the bed increased with a increase of the concentration of liquid feed, while it decreased with increase of bed temperature, gas velocity and NAR value.
Growth rate constant was measured from the result of glass beads, and correlation equation was obtained to predict the growth rate constant.
