Triboelectrostatic Separation For Granular Plastic Waste

Plastic products can be found everywhere in people’s daily life. Withthe consistent growth of plastic consumption, more and more plastic wasteis generated. Considering the stable chemical and physics characteristics ofplastic, regular solid waste management methods are not suitable for therecycling economic strategic of our country, which has become a seriousenvironmental problem. Recycling plastic waste is considered to be one ofthe best way to treat it, because it can not only deduce the waste but alsosave the energy to produce new virgin plastic. As a mechanical separationmethod utilizing the difference of surface properties of materials,triboelectrostatic separation is strongly recommended for plastic separationas it can preserve the original properties of plastic and has little secondarypollution. However, the researchers in the world focus little on the realplastic waste particles; it is still controversial about the humidity impact ontriboelectrostatic separation; there is also little research on numericalsimulation of particle trajectory in inclined electric field. This dissertationaims to study the charging properties of plastic waste granules, design andmake the separation equipment, simulate particle trajectory in inclinedelectrode electric field with computational method.Plastic granules are generated by crushing plastic waste in wasteelectric and electronic equipment. The tribocharging properties of plasticwaste were studied by vibrating tribocharging and cyclone tribocharging. The triboelectric series obtained by vibrating tribocharging was(-)-PE-PS-PC-PVC-ABS(white)-ABS(black)-PP(grey)-(+), while thetriboelectric series obtained by cyclone tribocharging was(-)-PE-PS-PC-PVC-ABS(white)-ABS(black)-PP(grey)-(+). By comparisonexperiments, cyclone charging was found to be more effective and stablethan vibrating charging. The impact factors experiments showed that smallparticle was easier separated than bigger particle. High relative humiditywas found to impede charging.The simulating trajectory model of plastic particles in inclinedelectrode electric field was established by MATLAB programming.Different trajectories of different particle characteristics and differentelectric field characteristics were simulated. Results showed that goodseparation need the charge-mass ratio of particles up to5nC/g. The lowerthe initial velocity of particles was, the better they could be separated.Higher applied voltage was found to be more effective in separation.Smaller inclined angle had better electric filed distribution and largerinclined angle were favorable as it could avoid rebounding effect. Smalldistance between electrodes was recommended for separation.A self-designed separation device was established. There are specialdesigns in the feeder, the separation zone as well as the collection system.Separation of different mixed plastic particles was studied. The results ofseparation pure virgin plastic particles showed that the separation efficiencycould be improved by increasing applied voltage. The separation effect wasimpeded by the friction between particles and wall of charger so that simplyincreasing residence time was not good for separation. Separation results for real plastic waste particles showed that triboelectrostatic separation was aneffective way to recycle plastic waste. Little increase of humidity (40%-60%)was found to approve separation by decreasing the impact of wall ofcharger.