The application of factorial design to evaluate granular formation in a fluidized-bed granulator

A two-way factorial design was employed to examine the effects of severa1 processing variables, including air volume, inlet air temperature, nozzle size, spraying air pressure, and spraying rate, on the formation of lactose granules in a fluidized-bed granulator. Subsequently, the influence of PVP concentration and two processing variables on granular size were also examined. A quantitative equation for each experimental design based on a reduced quadratic model was deduced by a stepwise method using REG procedure of the SAS program with both SLENTRY and SLSTAY equal to F = 0.1. In the first experiment, all individual factors were found to significantly affect granule size. The two-factor interaction terms found to be significant included air volume with either inlet air temperature, spraying air pressure, or spraying rate, inlet air temperature with nozzle size, and inlet air temperature with spraying air pressure. In the second study, PVP concentration was the only one factor term found to significantly affect granule size. A combined effect of PVP concentration with inlet air temperature as well as PVP concentration raised to second power with spraying rate were found to be significant.