This communication presents a model structure for the flotation recovery of middling particles (10–90% liberation). Fourteen datasets from the literature were studied (galena flotation), which involved different flotation systems and operating conditions. The flotation responses allowed the model flexibility to be evaluated under a range of recovery profiles. The modelling results showed that galena recovery can be characterized by the interaction between a linear function and a concave function (e.g., Gamma model), to account for the liberation and particle size effects, respectively. Liberation also impacts the location and dispersion of the recovery dependence on particle size. The proposed model structure showed there was adequate flexibility with five parameters, leading to adjusted coefficients of determination ranging from 0.863 to 0.998 for the studied datasets. Thus, an alternative approach for modelling the recovery of middling particles is proposed, which represents the liberation and particle size dependence with a few parameters.

The aim of this work was to study the true flotation process and entrainment contamination along flotation banks. For this purpose, a new approach for characterizing the recovery and grade profiles down the industrial flotation banks was developed and tested in two industrial rougher banks, of nine 130 m³ and six 250 m³ cells. The procedure consisted of feed, top-of-froth (TOF) and concentrate grades measurement together with mineralogical analysis down the bank. These data are useful for the assessment of liberation and association of floatable particles recovered into the concentrate (true flotation) and gangue entrainment. Results allowed for the quantification of the decrease of Cu grade in concentrates and TOF samples along the banks, due to the relative increase of middling minerals and gangue entrainment. The liberation coefficient of Cu sulfides significantly decreased down the banks, because of preferential flotation of middling particles after exhaustion of the free Cu sulfide minerals. The main difference between concentrate and TOF samples was the entrainment content, while the composition of floatable minerals was similar. Therefore, the TOF measurement and mineralogical analysis provides a simpler way to assess the flotation process down the industrial flotation banks. This knowledge is relevant for process diagnosis and for selecting control strategies for flotation banks operation and optimization (e.g., froth depth and gas flowrates profiles).

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 m³ and 300 m³, 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.

In flotation cells, especially in large flotation units, froth management is a crucial variable that should be considered during the design phase or optimized to improve the performance of existing flotation circuits. This paper presents a simulation evaluation of the effect of launder design on the metallurgical performance of an industrial flotation circuit consisting of five TankCell^® e630 (630 m³) cells in a Cu rougher duty. This analysis was carried out using a new industrial simulator that includes novel metallurgical and hydrodynamic models, developed from a wide database collected from many industrial concentrators. This tool is currently incorporated into HSC Chemistry^® software and allows evaluating the effect of launder design on mineral froth recovery, water recovery, entrainment, and other variables. The industrial flotation circuit was evaluated under different launder design scenarios, considering an actual flotation circuit that includes TankCell^® e630 cells for calibration and as a reference (baseline). Firstly, two different designs were evaluated in the full circuit: a standard launder design and a new launder technology. It was found that the new launder technology enabled improvement of the mineral recovery along the circuit, mainly for coarse particles, due to the improvement in froth mineral recovery. Next, a partial upgrade of the launder design along the circuit was analysed. Thus, the new launder technology was evaluated in the first and the last two cells of the bank. The results showed that upgrading the launders in different cells along the circuit delivered an increase in the final recovery with respect to the baseline, with a partial impact on the concentrate grade. However, these changes are less than those when evaluating the full upgrade scenario. A partial launder upgrade either in the first or last two cells of the bank showed similar final recoveries, but the latter enabled a slightly higher concentrate grade (about 1% higher) to be achieved. Finally, the evaluation of launder design using the industrial simulator made it possible to estimate its effect on variables that are not commonly obtained from plant surveys, including superficial gas rates at the froth surface level, froth recovery per particle size, collection recovery per particle size and liberation, gangue entrainment, and bubble loading grade.