• drying;
  • powder technology;
  • unit operations;
  • physical characterization;
  • particle sizing;
  • agitated filter-dryer;
  • parametric study;
  • heat transfer coefficient;
  • calorimetry (DSC);
  • powder diffraction


A systematic experimental investigation of contact drying operation was carried out in an agitated Charles Thompson filter-dryer. In this study, the effect of process parameters (wall temperature, impeller speed, fill level) on the drying performance in the filter-dryer is quantified as a function of bed temperature and solvent concentration. In addition, the impact of drying conditions on the particle size distribution was also examined. It was found that in the range of parameters investigated, drying rate increased with wall temperature and reduced bed depth. The effect of impeller speed was variable where favorable drying conditions were strongly dependent on the particle properties. Moreover, decrease in the particle size was evident with an increase in impeller speed and decrease in the bed depth due to increased collision frequency and reduction in the fill volume both leading to particle attrition respectively. Besides, the average wall to solid heat transfer coefficient is also estimated for variable operating conditions. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:2198–2213, 2013