Numerical modeling & microwave roasting of refractory gold ore
AuthorHonaganahalli, Puttanna S.
Mining & Metallurgical Engineering
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Microwave roasting of refractory ores is an attractive alternate to conventional thermal roasting. Temperature measurements and hence temperature control is a major problem which is obstructing the introduction of this new technology to mineral processing. This thesis presents a mathematical model of determining temperature continuously and suggests control of temperature as a function of time of roasting. The mathematical model was applied to two types of refractory gold ores viz. carbonaceous and sulfidic gold ores. The model was tested for three different power levels of 133, 298 and 531 kW/sq.m . The temperatures predicted by the model and the transient temperature plots which enable control of temperature are presented here. The temperatures for sulfidic ore was always found to far higher than that for carbonaceous ore for a given input power and time of irradiation. Power absorption efficiency for sulfidic ores was at 55% while for carbonaceous ore it was a dismal 20%. Steady state was achieved very rapidly in all cases and irradiation beyond this time would only lead to dissipation losses of energy. Preliminary investigations qualitatively confirmed the theoretical results. The recovery of gold with sulfidic ore was higher because it got roasted at the limited power levels that was applied. Scanning electron microscope studies showed size reduction of the ore particles which suggested capabilities of improved mass transfer of the lixiviant and promise of enhanced recoveries.
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