Influence of electrode geometry on transport and separation efficiency of powders using travelling wave field technique

In this paper the separation processes of powders using 3-phase travelling wave field were studied theoretically and experimentally. The separation properties of the nonuniform travelling wave field was investigated by studying the amplitude of its spatial harmonics. The finite element software was used to model the spatial distribution of electric field created by the electrodes with different shapes, It was established that cylindrical, square and stripe electrodes produce the most optimised field distribution. Based on the modelling results several flat-bed travelling wave panels with stripe and cylindrical electrodes were constructed and tested. The separation characteristics of the panels were assessed by examining the direction of transport of a two powder mixture with different size distributions for the frequencies of AC potential up to 300 Hz. It was discovered that for the majority of panels successful powder separation could be achieved for two frequency bands. The position of the bands depended mainly on electrode geometry (i.e. pitch and width). In order to further understand transport phenomena in both separation bands particles trajectories were examined using a CCD camera with telemicroscopic lenses interfaced with computer controlled image grabbing system.