New Evidence of the Effect of Post-Combustion During Roasting/Reduction of Nickel-Bearing Lateritic Ores

The roasting/reduction process is one of the fundamental stages of Caron technology, ensuring the adequate transformation of lateritic ore, with post-combustion air feed being one of the main variables considered. In this study, new evidence is presented that justifies the negative effect that post-combustion air has on Ni extractions in H-6 of the furnace. With this objective, three air feed levels were evaluated, measuring the hearth temperature from 495 °C without post-combustion to 780 °C for the maximum post-combustion level analyzed. The evaluation was carried out in a conventional multi-hearth furnace at pilot scale using atomic absorption spectrometry, XRD, SEM, and particle size analysis as the main analytical techniques for the characterization of lateritic ore before and after the reduction process. Increasing the temperature of H-6 resulted in a significant decrease in Ni extractions by 1.68% for every 57 °C increase in hearth temperature, which was due to the resulting decrease in the reaction rate constant and the significant increase in the average particle size of the reduced ore. This research emphasizes the importance of controlling post-combustion air inflow as a technological alternative to optimize Ni extraction and reduce delays in the control of diffusive processes.