Flotação fracionada: aumento do rendimento da flotação através da divisão da alimentação em duas frações granulométricas

Abstract

The motivation for the present investigation was to evaluate the differences in an iron ore flotation process when the feed is treated globally or splitted in two size ranges. In both cases the top size was 0.150 mm. In the preliminary study the cut size was 0.038 mm and in the final study the cut size was 0.044 mm. The full investigation was planned with the aid of the statistical method known as factorial design. Pairs of variables for each factor and fraction (-0.150 +0.038 mm and - 0.038 +0,010 mm in the preliminary study and -0.150 +0.044 mm and -0.044 +0,010 mm in the final study) and also for the control experiment, global sample -0.150 +0,010 mm. Optimized variables pairs were established for the flotation of each fraction. In the preliminary study laboratory tests were performed with a sample collected in the Vargem Grande concentrator flotation feed, consisting of predominantly hematite ore.The final study was carried out with a representative sample of an itabirite ore from Conceição do Mato Dentro and in another exploratory test a hematite ore was used. The results of the preliminary study reached the target of showing the difference between the flotation of the global sample and of the two size fractions individually. The flotation of the global sample requires specific reagents dosages that are not idealfor any of the two fractions. The results of the final study showed increases in weight recovery from 47.3% to 50.9% and in metallurgical recovery from 81.9 to 87.3%, decrease in the silica content in the concentrate from 0.75% to 0.53% and increase in Gaudin´s selectivity index from 23 to 32. Another finding of the study was that splitting the flotation feed at 0.044 mm, the concentrate achieved with the fine fraction will not require further grinding prior to transportation via pipeline.