Electric Separation of Finely Divided Particles in Gaseous Stream or in Vacuo

Selective charging of solid particles can be obtained in various ways. Frictional electrification of powdered minerals for beneficiation purposes is one very interesting aspect and can be effectively achieved by using a suitable surface as charge exchanger, on which particles are made to slide or impinge with sufficiently strong contact forces. The validity of the process is theoretically and experimentally demonstrated by the results of a comprehensive basic research which allowed to determine the influence of the main variables involved, by means of the band model of semiconducting solids. It is shown that a satisfactory separation efficiency is obtained with apparatus of original design in which high energy contacts are produced in centrifugal fields.