Thermal beneficiation of low grade Chrome ores Part 2- Solid state Reduction

Abstract

The present paper is in contribution of an earlier publication by the authors and discusses the preferential elimination of iron from Chrome ores by thermal reduction with solid reducing agents followed by acid leaching. A low grade chrome ore from Tagadur area of Mysore with an initial Cr: Fe ratio of 1.01 has been beneficiation to give a Cr/Fe ratio of 3 or higher by reduction -100 mesh size ore with -100 mesh (B.S.S) size coke in briquetted at 1300° for a period of 3 hours and subsequent leaching with dilute sulphuric acid. Various factors studied include the effects of temperature, kinetics of reduction, ore/coke ratio, particle size of reactants, and briquetting pressures etc. The effects of particle size reduced ore, temperature, strength and quantity of sulphuric acid on the leaching characteristics of the reduction ore have also been studied .It has been observed that use of less acid than is required to dissolved all the soluble iron helps in complete recovery of chromium. This paper also records the results of thermodynamical considerations for the preferential reduction of iron alone and it has been shown that maintaining desired CO/CO2 ratio at a particular temperature can prevent the reduction of chromium to the soluble form. Based on the laboratory scale experiments a flow sheet for the Pilot Plant has also been recommended.