Abstract

Among various methods for drying pharmaceutical granules in the pharmaceutical industry, fluidized bed drying is commonly used due to its high rate of moisture removal, excellent performance in solids mixing, and heat and mass transfer. As pharmaceutical powders are typically organic materials with high resistivity, they can easily be charged due to repeated collision and separation of particles, along with particle-wall friction, in a fluidized bed dryer. This phenomenon, called “tribocharging”, could adversely affect the process performance. Effects of drying air temperature and drying air velocity on drying performance as well as electrostatic charge generation during the drying process were investigated in this project. In order to elucidate the effect of moisture content (ranging from approximately 30 wt. % to 1.8 wt. %) on tribocharging behaviour, the specific charge of granules was measured in a rotary device and apparent volume resistivity was investigated in a self-designed resistivity testing cell. Limited drying data was available in the literature for drying pharmaceutical granules. Therefore, experimental work also was conducted to investigate drying kinetics under different operating conditions of relevance to industry processes.