Using experimental design to optimize the process parameters in fluidized bed granulation

In this study many parameters were screened for a small-scale granulation p rocess for their effect on the yield of granules between 75 and 500 mum and the geometrical granule mean size (d50). First a Plackett-Burman design wa s applied to screen the inlet air temperature, the inlet flow rate, the spr ay rate, the nozzle air pressure, the nozzle spray diameter; and the nozzle position. The Plackett-Burman design showed that the key process parameter s were the inlet flow rate and the spray rate and probably also the inlet a ir temperature. Afterward a fractional factorial design (2(5-2)) was applie d to screen the remaining parameters plus the nozzle aircap position and th e spraying time interval. The functional factorial design showed that the n ozzle air pressure was also important As the target values for the granule yield (between 75 and 500 mum) and the geometric mean granule size (between 300 and 500 mum) were reached during the screening experiments, further op timization was not considered necessary.