Fluidized bed drying of a pharmaceutical powder: A parametric investigation of drying of dibasic calcium phosphate

A parametric analysis of four fluidized bed dryer operating parameters—initial moisture content, material loading, heating air temperature, and air flux—was carried out using two factorial experimental designs. Two different dryer scales, the Glatt GPCG-1 and MiniGlatt, with chamber volumes of 23 and 3 L, respectively, were used to dry dibasic calcium phosphate powders. According to a Pareto analysis, initial moisture content and air flux were the most significant variables. For the larger GPCG-1, the four variables used in the factorial tests were found to be independent. For the smaller MiniGlatt, the interaction of the initial moisture content and the air flow rate was also significant. From the parametric analysis, it was observed that drying is dominated by the constant drying stage, and zero-order kinetics, for the mild drying conditions (appropriate for many pharmaceutical products) we considered in this work. A comparison of the two dryers and an evaluation of energy efficiency were also carried out. It was found that drying should be carried out with relatively low temperatures and high air fluxes for both the large- and small-scale dryers in order to maximize the energy efficiency.