Development of a New Gravity Separator for Plastics —a Hybrid-Jig—

Abstract

The development of mechanical methods for plastic-plastic separation is important for recycling of scrapped plastics of office/home appliances and cars. This paper proposes a Hybrid-Jig as a new method for plastic-plastic separation. The Hybrid-Jig was developed based on jigging and flotation, where air bubbles are introduced into the particle bed during jigging to modify the apparent specific gravity of the particles by the attachment of air bubbles to the particles so that particles having different surface properties can be separated by jigging even if their specific gravities are similar.To demonstrate the performance of the Hybrid-Jig, a laboratory scale TACUB jig was modified to induce air bubbles through the screen under the particle bed, and separation experiments of plastic particle mixtures were carried out under various displacements and frequencies of water pulsation. Feed samples were particle mixtures of two plastics chosen from eight kinds of plastics (3 of polyvinyl chloride (PVC), 4 of polyethylene (PE), and 1 of polyethylene terephthalate (PET)). The particles were cylindrical of 2-3 mm length and diameter, and their specific gravities were 1.05-1.55.In normal jig operation (without air bubbles), plastic particles with similar specific gravities were difficult to separate, but they were easily separated by the Hybrid-Jig, when air bubbles adsorbed on the surface of the more hydrophobic plastics, and the plastic particles with air bubbles were recovered as top product due to the decrease in apparent specific gravity. Because the differences in the hydrophobicity of the plastics cause the selective bubble attachment, high grade plastic products over 99.9 mass% were recovered by the Hybrid-Jig even for plastic mixtures having the same specific gravity.

Glass Waste3: A Preliminary Study for a New Industrial Recovery Processing

“…The pulses are repeated until the grains retained by the fixed sieve reached a good separation on the base of their density. Unlike previous researches [18][19][20], where flotation is the separation methodology, the jig concentrator is more environmentally friendly working only with fluid motion without the dangerous use of additives and collectors.…”

Jig separation of crushed automobile shredded residue and its evaluation by float and sink analysis

“…This jig is a candidate for further treatment of ASR. Tsunekawa et al have reported that this jig is useful to separate relatively low-density particles such as plastics [7][8][9], and it has also been demonstrated that highly efficient jig separation of different types of plastic components in waste office automation equipment recycling is possible in pilot-scale tests [10].…”

Reverse jig separation of shredded floating plastics — separation of polypropylene and high density polyethylene

“…Dr. Tsunekawa (one of the authors, professor of Hokkaido University) has modified the TACUB jig for plastic-plastic separation in the recycling of used products containing plastics and reported that the RETAC jig (modified TACUB jig) is very efficient in separating relatively low density particles such as plastics Tsunekawa et al, 2005 because precise control of the operation is possible. To further improve the separation efficiency, a 'hybrid jig' (RETAC jig with air bubbler under the particle bed) which can separate plastics having similar specific gravities using differences in wettability produced by a pretreatment, has been developed by the authors Hori et al, 2009 and these techniques expanded the possibilities of separation of a wide variety of types of plastics.…”