Experimental Modeling and Optimization of the Tribo-Electrostatic Separation of PET Fibers From End-of-Life Tires

The recycling of end-of-life tires involves their shredding followed by grinding and electromagnetic separation, which leads to a mixture composed of agglomerates of textile (mainly Polyethylene Terephthalate - PET) fibers and rubber granules. The objective of this study was to validate the possibility of using a new patent-pending tribo-electrostatic separator to sort the constituents of this mixture. The tribo-electrostatic separator is made up of a triboelectric charger and two pairs of cylindrical rotating electrodes connected to two HV sources of opposite polarity. The mixture to be treated is introduced inside the triboelectric charger consisting of a sieve cylinder rotating at speeds ranging from 5 rpm to 50 rpm. The electrodes on the left and on the right are connected to two HV sources (+/- 30 kV) of positive and negative polarities respectively. The electrodes can move horizontally and vertically allowing the test of several geometric configurations of the electrodes and tribocharger system. Thus, the charging zone is also a separation zone so that when the fibers or the gums are sufficiently charged, they are attracted by the electrodes of opposite polarities. The tests were carried out by varying the voltage from +/- 5 kV up to +/- 20 kV in steps of +/- 5 kV. Each test lasted 3 min with a maximum rotation speed of the tribocharger. The comparison between the electrode configurations was made by measuring the mass of the fibers collected at the electrodes.