Mechanism\nStudy of Removing Sealing Aluminum Contaminates from Waste Packaging\nHigh-Density Polyethylene by Eddy Current Separation

Recycling of high-density polyethylene (HDPE) packaging\nwaste plastics is necessary for ending white pollution. Existing recycling\ntechnologies generally require high purity of polymers before treatment.\nHowever, the sealing aluminum film contamination in crushed bottle\nflakes hinders recycling works. Eddy current separation (ECS) was\nfirst applied for the removal of aluminum-containing flakes from crushed\nHDPE bottles in this study. Through finite element analysis, the formation\nof rotating magnetic fields, eddy currents, and Lorentz forces are\nanalyzed. It reveals, different from the traditional theory of eddy\ncurrent forces, that the factors influencing the flake trajectories\nare attributed to the Lorentz force, whose horizontal component aligns\nwith the tangential direction of the rotor’s rotation, while\nits vertical component is directed upward. The magnitude of the Lorentz\nforce is affected by the magnetic field intensity and the spatial\npositioning of the flakes. The variation cycle of the force is primarily\ninfluenced by the size of the magnetic poles. This model accounts\nfor the unique motion behaviors observed during the separation process.\nAfter parameter optimization, the removal efficiency of aluminum foil\nwas 97.38 wt %. This study enhances the mechanical theoretical framework\nof the ECS process and extends the application scope of the ECS technologies.