ORALS

The drying process of iron ore pellets in the travelling grate pelletizing furnace is carried out through the transfer of heat from the hot gas by convection, with gaseous flows that initially occur upwards and then downwards, through the bed of pellets. The furnaces are designed according to the characteristics of the iron ores. However, over time, changes occur in the iron ore mineralogical characteristics that strongly affected the process kinetics, making the process inefficient. At Samarco, after the exhaustion of the Germano mine, the hydrated iron ore were incorporated into the process, mainly with the mineral goethite, demanding a greater input of thermal energy. In addition to removing the free moisture in the pellets, it was also necessary promote the thermal decomposition of goethite. With the aim of improving the drying process of iron ore pellets, especially in older furnaces, studies were carried out evaluating the effects of microwave irradiation in the drying process. Initially, laboratory experiments were carried out with homemade equipment (frequency of 2450 MHz and power of 1,000 W) for small samples of pellets, and then in a semi-industrial equipment (frequency of 915 MHz and power of 18 kW) for a greater mass of pellets. The study investigates the use of microwaves in the iron ore drying process and the effect on the green pellets quality.