Flotation is one of the main concentration processes being employed for many classes of minerals (sulfides, oxides, silicates, phosphates, for example) at different particle sizes. In the iron ore industry, reverse quartz flotation has been successfully employed for particle sizes below ISOfim after the desliming process. The high demand for iron ore products has made flotation the main process for concentration in this industry, thus a better understanding of its mechanisms and the effect of the particle sizes in the process has become imperative. Flotation tests were carried out with three different size fractions of an itabirite iron ore, obtained using cyclone classification after desliming. The results showed distinct behaviors of the different size ranges. Higher etheramine dosages are required when coarse and fine fractions are floated separately and also this procedure is more sensitive to variations in etheramine dosages and pH values. The differences in particle size distributions and the specific surface area may explain the different flotation behavior of the distinct size fractions. The split flotation circuits for coarse and fine particles indicated an increase of 3% points in the metallurgical recovery with reduction of SiO2 content in final concentrate, increase of etheramine dosage and reduction of corn starch dosage. Economic feasibility analysis indicated a positive net present value of 50 million of dollars with split circuits for coarse and fine particles, considering a production of 10 million tons per year of pellet feed.
Iron ore flotation; particle size ranges; flotation reagents
