Omid VandGhorbany

A detailed test work was carried out with an industrial semi-autogenous (SAG) mill in a copper plant in close and open circuits to specify the effects of ore characteristics and operational parameters on mill performance. In addition, the shape of mill product particles was studied to monitor breakage events as a function of ore strength. For this purpose, the strength properties of the SAG mill feed and product were specified by different techniques, including the point load index, impact breakage parameters (A x b), abrasion index (t(a)), and Bond ball mill work index (W-i). Experimental studies showed that an increase in ore hardness is linked with an increase in point load index and Bond work index and a decline in impact breakage parameter (A x b). Hard ore grinding resulted in finer products, compared to the soft ore milling. The softer ore is ground chiefly via the impact breakage whereas the stronger ore is subjected to abrasion and attrition events where the media impact could not sufficiently break the stronger particles. The main reason for the decrease of circuit throughput was changes in breakage mechanisms. The results displayed that the highest aspect ratio and the lowest circularity of mill product are achieved by soft ore milling. As ore strength changes, differences in shape can be attributed to the different breakage mechanisms operated in the mill. In addition, the particle shape characteristics provide a convenient way to quantify changes in SAG mill as a function of the ore properties and the kind of breakage action used.

In this paper, the main and interaction effects of chemical reagent (collector and frother) dosages on the copper flotation performance using response surface methodology in design expert software were examined and the optimized dosage of reagents were specified. Then, in order to increase copper grade and recovery at industrial rougher flotation cells of the Miduk copper concentrator, Iran, distribution patterns of chemical reagents in suggested optimum conditions were investigated. A central composite design with three levels and five variables was employed to model and optimize the laboratory batch scale flotation process. The effect of dosages of Z11 (0–10 g/t), Flomin C4132 (14–34 g/t), A3477 (5–15 g/t) as collectors, AF65 (5–15 g/t) and MIBC (4–12 g/t) as frothers was studied. Forty-eight batch rougher flotation experiments (pH 11.5) for Miduk porphyry copper ore consisting of 0.9% Cu were conducted at different conditions using a bench scale Denver flotation cell with 3 L capacity. Second order response functions were generated for both the Cu grade and recovery models, as metallurgical indicators. These model equations were optimized using quadratic programming so as to maximize Cu grade and recovery within the experimental range studied. The main effect of all reagents dosages and the interaction of the Z11-Flomin C4132, Z11-A3477, and A3477-MIBC dosages had a significant impact on both recovery and grade. The optimum reagents dosages were found to be 5 g/t Z11, 34 g/t C4132, 5 g/t A3477, 15 g/t AF65, and 8 g/t MIBC. Maximum recovery of 91.4% and grade 8.13 were achieved under optimal conditions. Additionally, verification experiments at optimum conditions proposed by the models were carried out to specify the validity and adequacy of the predicted models. Based on the industrial rougher circuit tests results, distribution patterns of 75%-0%-25% and 50%-25%-25% were selected as the best distributions of collectors and frothers in mentioned conditions, respectively. The copper recovery and grade improved about 2% and 1.8%, respectively, via the use of optimized stage addition of reagents.

Obtaining high recovery in copper flotation plants has been always under investigation in recent years. Misreported copper into tailing dramatically declines copper recovery. This study aims to find the possible reasons of copper loss to tailing and present the methods to improve the performance of the Sarcheshmeh copper plant flotation circuit. This work was performed in two phases. In the first stage, two surveys were carried out in an industrial plant for evaluation of floatability of two different types of copper ore (sulfide and mixed copper ores comprising sulfide and oxide minerals) and investigation of misreported copper into tailing. In the second stage, influence of particle size distribution in different levels, the collector (Z11 + R407), and sulfidisation agent (NaHS) dosages were investigated on the floatability of mixed copper ore, and possible improvement of copper recovery ores was evaluated by a series of batch flotation experiments. Almost 95% of overall copper loss in final tailing took place in the rougher circuit. The overall recovery of mixed copper ores was obtained 8% less than the other survey. It was found that an important factor of recovery reduction was due to increasing oxide copper proportion in rougher feed. Results of size-by-size recovery analysis showed that the highest sulfide copper loss occurred in coarse particles (>74 µm) and the highest oxide copper loss happened in fine particles (74 μm) of rougher tailing and then their flotation have significant effect on increasing overall recovery from 79.3% to 82.2%. Experimental studies showed that the use of the proposed methods with considering the optimized conditions in the plant can be led to an increase in copper recovery from 79% to 87% without any decrease in grade.