EFFECT OF GAS COMPOSITION AND TEMPERATURE ON REDUCTION CHARACTERISTIC IN RED MUD-COAL COMPOSITE PELLETS

The disposal of red mud, which is the by-product obtained from alumina production, has brought about environmental pollution because of its caustic nature as well its metal and alkaline contents. Red mud-coal composite pellets were directly reduced to deal with red mud. The influences of reduction temperature and gas composition on the reaction were studied. Experiment results indicated that the optimum reaction parameters were a temperature of 1100 degrees C and an H-2 atmosphere. Reduction degrees in H-2 and CO atmospheres were significantly higher than those in N-2 atmosphere. Reduction did not strictly follow the Fe2O3 -> Fe3O4 -> FeO -> Fe sequence in N-2 atmosphere, and this phenomenon did not occur in H-2 atmosphere. This gas solid combination reduction process is appropriatefor recovering Fefrom Bayer red mud. Meanwhile, the microstructure and phase transformation of the reduction process were investigated via scanning electron microscopy and X-ray diffraction.