Thermal beneficiation of low grade Chrome ores: Part I- Gaseous Reduction

The paper outlines known reserves of chromes ores in India and stresses the importance of the beneficiation of low grade chrome ores. The low grade Indian chromites with Cr:Fe ratio less than 3:1 cannot be upgrade by the conventional ore-dressing treatments as iron occurs in a chemically combined state with the chrome spinal. The process described consists of preferential gaseous reduction of iron oxide in crushed low grade ore (Cr:Fe as 1.66:1)at 950°C-1150°C followed by sulphuric acid leaching of the reduced product to remove soluble iron. Various factors studied included particle size of the ore, temperature, time of roasting, rate of flow of the gaseous reductant, effect of preheated gas, pre-oxidation of the ore and magnetic separation before acid leaching. Effect of particle size and kinetics of the leaching have also been recorded in the paper.