Dispersion and transport of cohesive lactose powder using travelling wave field technique

Abstract

The main objective of this research was to study transport phenomena of cohesive powders using the travelling wave field technique. In the literature only limited attention has been paid to the transport of cohesive powder materials using this technique, although it has been successfully used with non-cohesive powders. Cohesive powders are generally much more difficult to transport due to short range molecular forces as well as electrostatic forces. Such forces usually cause agglomeration and adhesion of particles which may significantly impede the flow. In this study, an optimisation process is presented for selecting an appropriate electrode arrangement for levitation and transportation of a given powder. Computer modeling was used to establish how the shape and geometry of the electrodes influence the transport of a particle having a given size and charge-to-mass ratio. Based on the modelling results a flat-bed travelling wave panel with optimised strip electrodes arrangement was constructed and used in the experimental study. Cohesive lactose powder (150 mesh, D 4.3 = 80 μm) was successfully dispersed and transported using this panel arrangement. Particle trajectories were examined using a CCD camera with telemicroscopic lenses interfaced with a computer controlled image grabbing system.