Shredder Practice for Preparation of Nonmetallic Concentrates and Potential for Particle Sorting of these Concentrates

The remaining hulk is flattened for transport to a shredder where, in a matter of seconds, it is reduced to fist-sized pieces. Next, steel is removed by magnets and nonmetals are separated by eddy-current rotor separators. The resulting nonmagnetic metal concentrate enables profitable shipment of that concentrate from the shredder to the metal sorter, and thus the recovery of nonmagnetic metals from the residue.
Preparation of concentrates of plastic-rubber and of precursors for residue-derived fuel (RDF) will be necessary to enable profitable shipment of these concentrates to plastic and rubber recyclers and to producers of RDF for waste-to-energy incinerators, cement kilns and metal smelters that use RDF as fuel or reducing agents. The Basel Convention bans trans-boundary shipment of wastes, but by concentrating the recyclables in the concentrate, waste can be converted to an article of commerce that is allowed to travel across boundaries and between continents. Shredded-scrap-derived Al, dense metal mix, mixed metal grain, and nonmagnetic metal concentrate (NMMC) are now routinely sold in US and Europe for export to Asia. Since industrial plastic scrap is already sold for export, there is no reason for the Basel Convention to ban transport of shredder-scrap-sourced plastic and rubber concentrates for recycling. The Convention requires local disposal of the non-recyclable residue fraction. This paper discusses the preferred composition and size specifications for these concentrates, and preferred practices and technologies for their production. It then explores the potential for further upgrading of these concentrates by downstream recyclers by sensor based particle sorting to either recycle plastics or prepare intermediate fractions for further size reduction, wet cleaning and wet sorting.
The sorting of metal, plastic, rubber and RDF and how it can be accomplished using already industrially applied sensors and data processing techniques is discussed.
The paper concludes with a discussion of the remaining shredder residue (SR), which is dominated by fines, and what can be done to extract the substances of concern (SOCs) and residual metals and organics.