Kinetic Studies on the Reduction of Iron Oxides in Low-Grade Chromite Ore by Coke Fines for Its Beneficiation

In a novel method of beneficiation of low-grade chromite ore, nuggets, 25 mm in diameter and 10 mm long, made of chromite ore and coke fines, are subjected to partial reduction. A significant degree of reduction of iron oxide is observed at temperatures of 1373–1523 K up to a reduction time of 240 min, and subsequent magnetic separation is found to enrich the low-grade chromite ore. In the kinetic studies performed on the partial reduction of chromite ore, nucleation and growth model NG1 (Avrami–Erofeev eq.; \(n=1\)) is found to be the rate-controlling regime. However, during the early phase of the reaction, particularly at lower temperature up to 1423 K, the nucleation and growth model NG2 (Avrami–Erofeev eq., \(n = 2\)) predicts the reduction behaviour better. At higher conversion, particularly at a higher temperature of 1523 K, diffusion plays a significant role. The average apparent activation energy of reaction, based on the NG1 model over the entire reaction period, is estimated to be 38.52 kJ/mol.