| Description |
Magnetic separation technology has been utilized for many years in the scrap sorting industry. Ferrous metal scrap is easily sorted using magnetic separation while sorting nonferrous scrap is a tricky process. Currently available technology to sort nonferrous material using mechanical eddy current sorters have limitations in terms of the capability to sort material larger than a quarter inch. Moving parts are subjected to wear and tear and they are also incapable of sorting different nonferrous metals and alloys like aluminum, aluminum alloys, copper, copper alloys, titanium, and so forth, from one another. The research work presented in this thesis reveals various nonferrous metals and alloy sorting test results using solid state, variable-frequency eddy current technology. The setup for this technology consists of a ferrite core with a V-shaped cut for the air gap wound with wire to produce an alternating magnetic field in the gap when supplied with alternating current. Nonferrous particles, when fed into the gap, interact with the external magnetic field which induces eddy currents into the material, and based on Lenz’s law, material tends to deflect away from the source of external magnetic field. Frequency determination for the selective sorting of material from the mixture of nonferrous material was done based on the ejection velocity experiments performed on size, ranging 4mm to 12mm at a frequency range of 1kHz - 8 kHz on aluminum, copper, brass, and titanium. Ejection velocity results were used to determine an optimal strategy and sorting experiments of nonferrous metals and alloy mixtures were conducted using a double stacked core of ferrite material having a 2mm inner gap and 33 mm outer gap. Also, experiments were conducted to sort zorba scrap using a larger size NiZn ferrite core with a 10mm inner gap and 20 mm outer gap. The pendulum experiment showed a trend of increasing ejection velocity with respect to increasing frequency, but the magnitude of velocity for different materials differ at a particular frequency is not the same, this allowed for an optimal frequency to be determined for optimal sorting. Nonferrous materials were sorted very well using both single and double stacked ferrite cores, but grade and recovery was slightly better when the double core was used. Promising results were also achieved for aluminum alloy sorting. All the results strongly indicate that capability for the solid state eddy current sorting technique is to be used to sort various nonferrous metals and alloys when operated at the optimal frequency. |
