Kinetic Response of Industrial Flotation Banks: Effect of Particle Size and Mineralogy

One of the main problems in current flotation plants and new projects is the significant decrease in feed grades and changes in the mineral composition, which has an important effect on the mineral liberation and associations. Additionally, flotation plants usually operate with a feed throughput higher than the original design, which has a significant impact on the feed particle size. All these conditions affect the metallurgical performance, and they must be evaluated and addressed by improving the control strategies for the optimization of banks. For this purpose, the flotation of valuable minerals along the circuits requires better understanding, considering the compromise between performance and selectivity in flotation circuits. This paper presents a characterization of the different minerals recovered along industrial flotation circuits. Plant sampling campaigns, performed in a copper industrial concentrator in Chile, provided the data for the study. Two rougher flotation banks consisting of cells of 130 m(3) and 300 m(3), were evaluated. All the samples from the industrial surveys were analysed by screening and mineralogy, and the mineral recovery along the circuits was evaluated per particle size class, liberation class, type of associations, and others. Additionally, operating data on froth depth profiles complemented the evaluation of the mineral composition of concentrate streams along the circuit. The results allowed for identifying and quantifying the main factors that affect the copper recovery and concentrate grade along the flotation banks. We found that minerals with liberation lower than 50% have a significant impact on the recovery. On the other hand, the decrease in the Cu grade in concentrates along the flotation circuits is mainly due to the relative increase of middling minerals (less liberated), non-valuable floatable minerals, such as free pyrite, and gangue entrainment. The characterization of the gangue entrainment flowrate along the flotation banks showed a strong relationship with froth depth, which becomes more critical towards the last cells of the banks.