Flotação direta de minério de ferro itabirítico

Abstract

The present work has evaluated the hematite direct flotation, through bench scale tests, with the natural - 150m fraction of an itabiritic ore of low iron content (26.0%) from the iron quadrangle in Minas Gerais, Brasil. The collecting reagents in the investigation were the oleic acid and an industrial vegetal oil and the commercial reagents Flotin FS-1 and Flotin - FS-2. The work considered the investigation of sodium silicate action as gangue depressor and two commercial reagents as a frother and dispersing respectively. Other investigated variables were the reagents dosage and time of conditioning and also the agitation intensity and pulp solids percentage during the flotation. After the accomplishment of the preliminary tests that targeted to establish the flotation best conditions, the use of oleic acid without the addition of a frother or a depressor, was selected for the results optimization. The rougher concentrate produced in the final tests was submitted to several cleaner stages in such a way that, for two cleaner stages, a Gaudin selectivity index of 31.2 was achieved. The silica content in the concentrate was 1.67%, the iron content in the tailings was 3.77% and the iron recovery was 90.85%.for three cleaner stages a Gaudin selectivity index of 40.0 was achieved. The silica content in the concentrate was 0.95, the iron content in the tailings was 4.04% and the iron recovery was 90.09%. These final results show the viability of producing adequate concentrates for blast furnaces as well as direct reduction concentrates. The high flotation selectivity index had as a consequence a superior iron recovery. This result demonstrates the technical viability for the direct flotation of low iron content ores occurring in the iron quadrangle region and also indicates a great potential for the flotation operational costs reduction.