Utilization of waste coconut shells in the reduction roasting of overburden from iron ore mines

Abstract

The reduction of iron ore using biomass-based reductants has opened up a new chapter because of its contribution to energy conservation and emission reduction. In this connection, the application of waste coconut shells (CS) as the reductant in the reduction roasting-magnetic separation of an iron ore overburden sample is explored. Characterization studies on the overburden having 49% Fe suggest that the sample is mostly a goethitic ore containing kaolinite as themajor gangue mineral. A concentratewith 63.2% Fe at an iron recovery of 66.2% has been obtained fromthe low-intensity magnetic separation of the overburden roasted at a temperature of 800 °C, time of 60 min and a CS to feed ratio of 0.2. Characterization studies indicate the formation ofmagnetite and hematite under these optimum conditions, whereas roasting at a temperature of 900 °C and a reductant to feed ratio of 0.3 is found to form feebly magnetic phases like wustite, fayalite and complex iron aluminosilicates resulting in poor iron recovery. The thermo-gravimetric analysis studies explain the disintegration of the biomass and reduction of the iron ore thereby validating the reduction sequence as predicted using the characterization studies.