Optimal Recovery of Iron Values from a Low Grade Iron Ore using Reduction Roasting and Magnetic Separation

A low grade iron ore containing 51.6% Fe, 17.6% SiO2, 4.3% Al2O3, and 3.8% LOI was subjected to reduction roasting followed by low intensity magnetic separation studies. The phase transformation of hematite into magnetite and fayalite due to reduction roasting was investigated using reflected microscope and X-ray diffraction (XRD) techniques. The effects of reduction variables such as reduction time (40-175 min), temperature (750-1000 degrees C), and reductant dosage (3-11%) using activated charcoal were studied. The process was optimized by using central composite rotatable design (CCRD) and response surface methodology. Iron grade from 59-66% with recovery of 9.5-87% was achieved using CCRD experiments. Model equations were developed both for Fe grade and recovery and then optimized within the bounds of experimental conditions. The program predicted 63.3% Fe with 79% recovery with the following optimum conditions: temperature: 950 degrees C, time: 53.04 min, and reductant: 3%.