Eddy current separation removes non-ferrous metals based on conductivity, and is a well proven and established technology for resource recovery in garbage sorting station/MRF. Although there are a number of different configurations, a design type known as the Rotating Disk Separator will be used in the waste sorting plant. The Rotating Disk Separator involves the materials “free falling” between parallel rotating magnetic disks, which are composed of permanent magnetic plates. The opposing magnetic fields create high magnetic fluxes that generate electrical currents within the non-ferrous metals. The electrical (eddy) currents in the non-ferrous materials cause them to be deflected when faced by an opposing magnetic field. The conductivity of the metal determines the strength of the eddy current that can be produced. Since aluminum has a low density relative to its conductivity, it is easily extracted using eddy current separation.
This technology can potentially be used to separate a wide range of additional metals that have value such as lead, copper, silver, gold and titanium. However, the only non-ferrous metal that is targeted by the most city’s recycling program is aluminum. Aluminum is the most common non-ferrous metal in municipal solid waste, accounting for about 90 percent of all nonferrous metals. If other non-ferrous metals are targeted in the future, the sorting system could be adjusted with additional separation processes such as flotation to further separate among these metals. The removal of lead for example would be environmentally beneficial before disposal.