Thermal beneficiation of low-grade chrome ore from Vagda deposits, Ratnagiri District, Maharashtra

A low grade chrome ore from Vagda deposits, Ratnagiri dist., Maharashtra, which could not be upgraded to the desired Cr : Fe ratio, by conventional physical methods of beneficiation , was successfully beneficiated to yield a metallurgical grade by preferential roast reduction and acid leaching. A table concentrate of the ore containing 44.93% Cr2O3, 15.39% total iron, 14.9% Al2O3, 8.9% MgO, 2.3% SiO2, 1.1% CaO and an initial Cr: Fe ratio of 1.53:1 was reduced with varying quantities of solid reducing agent, at different temperatures and iron leached with dilute sulphuric acid. The Cr:Fe ratio thereby increased to 3:1 with more than 87% chromium recovery by preferential reduction of -72 mesh (B.S.S) size ore with the -170 mesh (B.S.S) size coke at 1250°C for a period of 2½ hours and subsequent leaching with dilute sulphuric acid. It has been observed that chromium dissolution can be suppressed appreciably by controlled leaching with restricted amount of sulphuric acid, to yield a metallurgically suitable beneficiated chrome ore. (Miss Shipra Samanta, Senior Scientific Assistant and Messrs R. N. Misra and P.P. Bhatnagar, Scientists, National Metallurgical Laboratory, Jamshedpur)