Rotary Kiln Reduction of Titano-Magnetite Concentrate

Abstract

A series of reduction test runs were carried out in a laboratory rotating tube using -3mm concentrate, which was magnetically separated from a titano-magnetite ore, and high ash thermal coal supplied from Mozambique. The effect of temperature, residence time and coal to concentrate ratio (C/Fe stoichiometric ratio) on the degree of iron metallisation was studied during the runs and the results indicated that above 70% high level metallisation degree could be obtained under the conditions of 1.5 times stoichiometric coal addition at 1150 °C for 2 hours. Following the success of bench scale tests, pilot plant (semi-industry scale) operation were conducted in a Φ1500×12500 (mm) rotary kiln for direct reduction of iron (DRI). A total of 78t concentrate was processed in a 17 day campaign. Although various problems occurred during the first few days trial, the operation of rotary kiln gradually turned relatively stable, and metallisation degree of DRI reached 50%~60% in the stable stage with fuel and reductant coal addition of the amount of concentrate is 50% (about 1.5 times of stoichiometry). The pilot plant test achieved satisfactory direct reduction of mixed -3mm titano-magnetite concentrate and high ash thermal coal without pelletizing process, with kiln operating parameters of 1150 ~1200°C temperature and not less than 3 hours residence time in hot zone.