Estudo da influência do tamanho de bolha na flotação em coluna para diferentes granulometrias de apatita

Abstract

Flotation is a concentration process based on the selective separation of the constituents through the difference between the surface properties of the substances involved in the operation. One of its applications is in the fertilizer industry, in which the process aims to separate the minerals of interest from the gangue components. Given the strong demand for agricultural products, associated to the high dependence on fertilizer imports, a study that provides a better knowledge of the flotation process is important, since this is an operation that promotes mineral concentration from a complex and low-grade mineral exploration, economically and with good yields. The main mechanism of flotation process is bubble-particle interaction, which is strongly dependent on particle size and bubble size distribution (BSD). In order to promote a more efficient process, different particle sizes require various BSDs. Knowing that air bubbles are responsible for collecting and transporting the hydrophobic particles from the pulp to the foam, controlling the size and distribution of the bubbles generated is essential to promote greater bubble-particle interaction. The aim of this study was to verify the influence of the bubble size on apatite flotation performance of different sizes: fine (d3,2 = 13,95 m), intermediate (d3,2 = 50,86 m) and coarse (d3,2 = 108,96 m). Therefore, initially the influence of the addition of the mineral particle in the flotation column was investigated and it was verified a considerable decrease in bubble size (2.1 to 3.2 times lower in relation to the bubbles measured in the air-water system), thereby it was defining that the bubbles would be measured during mineral flotation. In the analysis of the bubble size influence on flotation, for each particle size range studied, the conditions of pulp conditioning that favored the best flotation performance were determined and the results were evaluated from the obtained images and the values for recovery and P2O5 content. The results allowed to identify bands of bubble diameter that favored a better performance for each particle size range studied. The intermediate particles presented the best results for the entire distribution of bubble diameter studied. The fine particles obtained a better flotation performance when using medium-sized bubbles (800-1000 m). And the coarse particles showed a better performance for large bubbles, but due to their high detaching rate, low recovery values were observed in the flotation of this particles range.