Comparative study on reduction behaviors of low- and high-grade fired hematite iron ore pellets in coal

Abstract

The reduction behaviors of fired Ramallakota (low-grade) and Bolani (high-grade) iron ore pellets were studied isothermally at temperatures of 1123, 1173 and 1223 K in non-coking coal. The degree of reduction progressed with the rise in reduction temperature and time. Ramallakota iron ore pellets exhibited relatively higher reduction rates than Bolani iron ore pellets reduced under identical conditions due to their higher porosity and gangue contents. Comparison of XRD patterns confirmed almost complete reduction in Ramallakota iron ore pellets at all the studied reduction temperatures in a much shorter period. Fayalite and hercynite formations were observed in both the types of reduced iron ore pellets with higher intensities in the pellets of Ramallakota iron ore. SEM images revealed relatively more growth of iron whiskers in reduced Bolani high-grade iron ore pellets. The apparent activation energy values for the reduction of studied iron ore pellets by coal were calculated to be in the range 14–20 kJmol−1, while pellets reduced in coal char under identical conditions exhibited relatively higher values owing to their slower reduction rates.