Triboelectric Phenomena in Suction-Type Dilute-Phase Pneumatic Transportation Systems for Granular Plastics

The triboelectric phenomena related to particle-to-particle and particle-to-wall impacts are known to affect the efficiency of suction-type dilute-phase transport systems. The aim of this paper is to evaluate the effects of two factors: the granular material feed rate and the aspirating air flow rate. The study was conducted with mm-size ABS and HIPS particles, two granular materials originating from genuine information technology (IT) wastes. The tribocharging processes in polyvinyl chloride (PVC) and aluminum pipes were modeled using the response surface method of experimental design. An induction-type sensor connected to an electrometer has been employed for the measurement of the charge imparted to a well-defined section of the duct, which is equal to the charge transferred to the particles passing through that section of the pneumatic transport system. The measured data were processed by a virtual instrument developed in LabVIEW and then analyzed using commercial software (MODDE 5.0, Umetrics, Sweden). Under the specific conditions of the experiments described in this paper, the charge/mass ratio of the processed particles was found to increase with the aspirating air speed, but was less affected by the granular material feed rate. It was concluded that the appropriate design of the transport system might provide an effective precharging of the granular mixtures of insulating materials that are processed in standard triboelectrostatic separators.