Electrostatic measurements on a miniaturized fluidized bed

In the pharmaceutical industry fluidization is often used in drying, coating and granulation processes. During fluidization powder particles contact other particles as well as the walls of the vessel and this leads to generation of electric charges. These charges may result in sparks, dust explosions, fires, reduced process efficiency and particle accumulation on the walls. However, the mechanism of the charging is not well understood. In this paper, an inductive method for charge generation measurement is presented. The system consists of an electrostatic ring probe, which allows charge scanning across the miniaturized fluidized bed without disturbing the fluidization process. The charge coupling from the system to the probe has been modelled and the experimental data have been simulated using an advanced field solving software. Experiments on lactose monohydrate, microcrystalline cellulose and glass beads have been performed and these results are presented.