Caracterização tecnológica de materiais estéreis com elevado teor de PPC e P da Mina de Alegria da Samarco Mineração S.A.

Abstract

Samarco holds a reserve of 3.08 billion tons, the iron formation being cut into ore and waste. Iron formations presenting P and LOI contents lower than 0.097% and 7.7%, respectively, are considered ore. Contents higher than those levels characterize the material as waste. This study addressed the possibility of generating information to support Samarco´s decision on the future concentration of materials presenting high contents of LOI and P, currently considered as wastes, representing approximately 90 million tons of Alegria North and South mines. The work samples are "ores" presenting P grade above 0.097% and LOI content between 6% and 7.7%. Technological characterization tests were performed, simulating at bench scale the beneficiation processes at Samarco. The results were compared with those achieved with a reference sample. It was observed that the samples under investigation required higher energy consumption in the primary grinding, resulting in lower productivity. The recovery levels in desliming and conventional flotation were lower. However, the flotation kinetics was good and the liberation degree of quartz in all size fractions was higher than 90%. The productivity in the secondary grinding was low and the particles size was too coarse to meet the Blaine currently practiced. It was impossible to reach the final specification of silica in the concentrate after regrinding. The settling tests indicated no future problems in the stages of slimes, tailings, and concentrate thickening. The product of primary grinding and the desliming underflow were also submitted to wet high intensity magnetic separation using a Minimag apparatus aiming at improving the concentration. The magnetic separation applied to the Alegria North and South samples indicated that the materials present paramagnetic behavior. According to the results, introducing a magnetic separation stage after the primary grinding might enrich significantly the flotation feed, besides roughing a significant amount of silica.