Thermal beneficiation of low-grade chrome ore from Kankauli deposits, Ratnagiri district, Maharashtra

A low grade chrome ore from Kankauli deposit of Ratnagiri District, Maharashtra with a chemical composition of 34.72% Cr2O3, 21.5% FeO, 14.74% Al2O3, 9.6% SiO2, 17.21% MgO, 2.0% CaO was subjected to thermal beneficiation consisting of preferential reduction by the iron oxide constituent and its subsequent removal by acid leaching. Concentrate of the ore obtained by tabling was found to be a better starting material for the process than the original ore. Various factors studied include the effect of temperature and period of reduction, particle size of the reactants for reduction as well as particle size of the reduced product, amount of acid and period for leaching. The results indicate that a table concentrate of the ore with an initial Cr:Fe ratio of 1.6:1 could be upgraded to a Cr:Fe ratio higher than 10:1 with more than 85% chromium recovery. It was also possible to upgrade the ore up to Cr:Fe ratio of 3:1 with almost full chromium recovery under controlled leaching conditions. (Mr. R.N. Misra, Senior Scientific Officer and Mr. P.P. Bhatnagar, Assistant Director, National Metallurgical Laboratory)