Tribocharging of Insulating Powders in the Annular Ducts of Pneumatic Devices

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The aim of the experiments reported in this paper was to evaluate the tribocharging phenomena that might occur in the annular ducts specific to the cyclonelike aspiration unit of a suction-type dilute-phase pneumatic transport system. The experiments were carried out with two types of powders, on two models of ducts, having the same geometrical characteristics but being built of different materials. It was found that the charge acquired by the particles strongly depends on the nature of the material of the annular ducts. This triboelectric effect might be effectively employed for the selective charging and electrostatic separation of granular or pulverulent mixtures of insulating materials.