Numerical modelling of conductive particle trajectories in roll-type electrostatic separators

Several attempts have already been made to simulate particle trajectories in roll-type electrostatic separators. However, the predictive value of the results is limited by an excessive number of simplifying assumptions regarding the electric field distribution, as well as particle charging and discharging mechanisms. The present work is aimed at improving the existing models by taking into account: (i) the non-uniformity of the electric field in the active zone of the separator; (ii) the effect of spark discharges occuring between the electrodes. Based on previous observations, the conductive particles were assumed to lift-off when no longer exposed to corona discharge. The numerical simulations were performed for particles of various sizes. The electric field was computed in each point of the trajectory using a finite element program. It was found that: (i) some of the smaller particles impact the static electrode and are deviated to the middling compartment of the collector; (ii) field annealing which accompanies spark discharges significantly affect the trajectories of conductive particles. The results of this study could guide the design of new electrostatic separation applications.