| Description |
Metals are essential, reusable resources. The reusable nature of metal contributes to the sustainability of its use through recycling, which will reduce landfill disposal and encourage recovery of valuable materials and reuse of components. Legislation and high cost of disposal also encourage recycling. Magnetic separators have been used for many years to recover ferrous metal from scrap. However in the process of recovery, a mixture of nonferrous metallic and nonmetallic material remains. Several methods were investigated for the recovery of these nonferrous metals. The eddy current separation technique is the best known for this purpose, and was mostly confined to the recovery of aluminum. Recently this technique has been applied for other metals like copper and zinc. This study investigates the applicability of a novel concept in high frequency eddy current separation to various nonferrous metals. Previous patents involved the use of solenoids, moving mechanical parts with permanent magnets or a ramp embedded with permanent magnets for the generation of electromagnetic field. These methods are limited in the frequencies that can be achieved. The high frequency eddy current separation uses high frequency AC currents for this purpose, meaning more freedom in generating higher frequencies, and is thus applicable to wide variety of metals and sizes. The variables involved in the setup are the capacitance, number of turns on the core, iv width of air gap on the core, core material characteristics and size of metal granules. The ratio of specific conductivity to specific gravity is also a governing parameter. The efficiency of separation was tested on metals like copper, aluminum, and zinc in sizes 1.0 to 6.0 mm. The results were very promising. A case study involving industrial scrap sample containing very fine non ferrous metal is also discussed. The proposed high frequency eddy current separation holds promise for foundries, smelters, electronic scrap and dry cell battery recycling operations. |
