Abstract
Ferronickel alloys are produced by pyrometallurgical processes from nickel-bearing hydrous magnesium silicates occurring in the saprolite in laterite deposit of the Serra de Onça-Puma/Pará-Brazil. The ore is treated by RKEF process. It consists of drying, calcination and reduction, however, the processing of lateritic nickel ore is quite difficult since the Ni-bearing minerals are finely disseminated in the ore bodies. In this work was studied the influence of thermal treatment between 25°C and 1100°C in nickel lateritic ore, evaluated through thermal analysis (Tg/DTA) and x-ray diffraction (XRD). The XRD analyses of raw samples without thermal treatment showed that they are mixture of serpentine, smectite and chlorite. After starting thermal treatment, the curves of Tg/DTA revealed to have two endothermic peaks at 60°C to180°C and 594°C to 613°C due to release the adsorbed and crystalline water, respectively, followed by an exothermic peak at 820ºC which can be attributed to the change in crystal structure and consequent formation of a new mineral phases. Weight differences can be observed when the adsorbed water removed, without phase changes in the range of 60°C to 180°C, indicated stability of nickel ore. Phase changes and weight loss were observed at 594°C to 613°C with clear crystalline breaking of the serpentines and smectite forming amorphous substances. Above this temperature new phases are crystallized until 820°C, when is formed forsterite (trevorite), enstatite and hematite, remaining unchanged quartz. On the analyzed conditions might infer that the pyrometallurgical to iron nickel production through this type of laterite ore effectively corresponds to RKEF process.
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