Using experimental design to optimize the process parameters in fluidized bed granulation on a semi-full scale

A face-centered central composite design was applied in order to optimize t he granulation process on a semi-full scale (30-kg batch) for the geometric mean granule size. The granulation process variables investigated were: in let air temperature, inlet airflow rate, spray rate and inlet air humidity. Based on the process variables, the theoretical powder bed moisture conten t after the spraying process and a measure for the droplet size were determ ined. Multiple regression modeling was used to develop two models for the g ranule size: an empirical model, based on the four process parameters. and a fundamental model, based on the balance between the granule growth affect ed by the theoretical powder bed moisture content and the droplet size and the breakage effect of the airflow rate. These regression models were used to optimize the granulation process to obtain a granule size between 300 an d 500 mum. Additional experiments confirmed that these models were valid. O ther granule properties, namely the geometric standard deviation, the Hausn er index. the angle of repose and the moisture content, were evaluated at t he optimal operation conditions. (C) 2001 Elsevier Science B.V. All rights reserved.