Electrostatic separation of insulating and conductive particles from granular mixes

Electrostatic separation is extensively used for the selective sorting of granular mixtures, by means of the electric forces which act on charged or polarized bodies. The roll-type separator with combined corona-electrostatic field has been proved to be the most advantageous solution when the purpose is to isolate conductive particles from non-conductive ones. The paper presents the contributions of the High intensity Electric Fields Laboratory of the Technical University of Cluj-Napoca to the development of this solution for various industrial applications. The first chapter is devoted to the theoretical analysis of the phenomena and points out the multitude of factors which influence the efficiency of the separation process. A special attention is paid to the study of the corona charging conditions of insulating particles. In the second and third cahpters, the authors show how the results of numerical modeling guided the design of new equipment and the optimization of their operating conditions. Laboratory and pilot plant tests described in the forth chapter brought evidence of the effectiveness of the proposed technologies. The presentation of several applications in the recycling industry concludes the paper.