Optimization of Reduction Parameters of Quenched Titaniferous Magnetite Ore by Boiler Grade Coal Using Box–Behnken Design

Abstract

To improve the reducibility of titaniferous magnetite ore (TMO), a technique of high-temperature heating followed by water quenching has been adapted. This quenching technique imparts cracks into the dense TMO which in turn leads to the enhancement of reducibility during carbothermal reduction using boiler grade coal. A major problem associated with TMO is that the reducibility of the ore is very less as compared to haematite owing to its compact dense interlocking structure with polymetallic elements. In this context, a method of effective pre-treatment, i.e., heating at high temperature followed by rapid quenching using water has been used to impart cracks and fissures in the TMO lump to increase the extent of reduction. The quenching parameters, namely quenching temperature (1323, 1373 and 1423 K), quenching time (5, 10 and 15 min) and number of quenching (1, 2 and 3), have been optimized using Box–Behnken design (3-factors, 3-levels) with extent of reduction as the response. A maximum extent of reduction of 81.57% has been achieved at the following optimized conditions: quenching temperature—1373 K, quenching time—15 min and number of quenching—3. Under the identical conditions of reduction for untreated TMO, the extent of reduction is only 56.6%. This confirms the novelty of the repeated heating and quenching process of TMO prior to reduction.