Influência da perda por calcinação na sedimentação de concentrados de minério de ferro da Samarco Mineração S.A.

Abstract

An increase in the goethite content in the ores processed by flotation at Samarco´s concentrator is a concern for impacting either on the current process or on future expansions. The percentage of the mineral goethite is highly correlated with the loss on ignition (LOI). Due to the fact that LOI is easily determined, this characteristic is widely used by the concentrator operational staff. The thickening stage plays a fundamental role on Samarco´s process. It increases the solids content of the slurry to be pumped and is also responsible for recovering a good quality water to be reused in the process. The ore quality variations strongly affect the particles settling. This study aimed at evaluating the influence of goethite content on the concentrate particles settling, supernatant clarification, and compactation, as well as searching for alternatives to enhance the sedimentation characteristics, using as comparison parameter the loss on ignition (LOI) instead of the goethite content itself. For the settling laboratory experiments, laboratory flotation concentrates were produced, from samples selected in the mine, having as target LOI contents 1.5%,2.5%, and 3.5%. The LOI contents of the concentrates reached figures close to the target, 1.53%, 2.65%, and 3.73%, respectively, SiO2 grades in the range 1% and 2%, and percentage passing 0.044 mm between 87% and 89%. It was characterized that the samples were similar, except regarding the LOI content. There is a trend of settling velocity decrease, especially in the case of the concentrate presenting LOI content 3.73%, and a gradual increase in the supernatant turbidity when the LOI content increases. The non ionic flocculant, currently used in Samarco´s process, was the reagent presenting the best performance as an aid for the concentrates settling.