Dephosphorization of high-phosphorous manganese ores from Andhra Pradesh and southern Orissa, India, by roasting

Abstract

Because conventional (physical) methods of ore dressing are not suitable for reducing the phosphorus contents of high-phosphorous manganese ores fr-om Andhra Pradesh (AP) and rite adjoining area in southern Orissa, India, the adaption of chemical methods becomes imperative. Art attempt was therefore made to reduce the phosphorus content of partially beneficiated manganese ores from AP by roasting with sodium carbonate and then leaching with hot water. However, due to the higher phosphorus contents of the manganese ores from Nishikhal mines in southern Orissa, and because of their apparent resistance to dephosphorization by roasting with Na2CO3 alone, a mixture of Na2CO3 and NaCl was found to be necessary to reduce the phosphorus content to below 0.15%. Free-energy calculations at 700 degrees C and above indicated that Na2CO3 (or Na2O as the active component) is a more active reagent than NaCl. Various process parameters, such as the temperature and time of roasting, the amount of sodium carbonate and rite temperature and rime of leaching, were studied to an-ive at the optimum conditions for dephosphorization.