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Since the start-up of the Sossego copper concentrator, located in the Carajás Mineral Province in the southeast of Para State, Brazil, the low-grade ore (~0.34% Cu) has been stockpiled, as defined in the long-term mine plan, to be reclaimed at the end of the mine life. Given this imminent need to process around 40 Mt of this low-grade ore, questions have been raised related to the extent of oxidation that might have occurred in this stockpiled ore. In this context, a study was designed to characterize the stockpiled ore and assess the effect of the ore oxidation on its flotation response. A sampling campaign of the stockpiled ore was carried out to analyze the main variables that could influence the level of oxidation, and, consequently, copper recovery, such as stockpiling time, depth, and particle size. The results showed that there are two main factors negatively impacting the copper recovery of the low-grade stockpiled ore: the surface oxidation and the level of liberation of the copper mineral. Depth and period of stockpiling were not found to influence the level of oxidation, nor the flotation response. An empirical model was proposed for the copper recovery in the rougher stage, which resulted in a predicted value of 90.7%, which was lower than that for the fresh (and higher copper content) ore fed to the plant (93%). [ABSTRACT FROM AUTHOR]

Comminution is an essential step in processing itabirite ores, given the need to liberate silica and other contaminants from the iron minerals for downstream concentration and then pellet feed production. In general, these ores in Brazil are not particularly hard to crush and grind, but both capital (CAPEx) and operating (OPEx) expenditures in this stage of preparation can be critical for the project, in particular due to uncertainties in iron ore prices. Several circuits have been designed and are in operation for this type of ore in Brazil; however, it is not yet clear which technologies are more cost-effective and in which configuration they should be applied. This work critically analyzes four comminution circuits for an undisclosed case study. For these circuits, CAPEx, OPEx, and some environmental sustainability indices, as well as qualitative technical criteria, were used in the comparisons. This work concludes that two of these process routes, especially those based on more energy-efficient technologies (and one of these still rarely explored even at bench-scale), have demonstrated to be very attractive from multiple standpoints. [ABSTRACT FROM AUTHOR]

• Relationships appeared between iron ore concentrates composition and breakage characteristics in 150–45 μm sizes. • Single-particle compression tests discriminated well iron ore concentrate characteristics. • Energy utilization appeared as a good measure to discriminate between materials amenability for breakage at such fine sizes. • Higher efficiency for rigidly-mounted roll mill and piston-and-die, followed by lab-HPGR and ball mill. Production of iron ore pellets typically requires regrinding of the iron ore concentrates. Although these concentrates are produced following close control of chemical composition, substantial differences may exist in their response to the size reduction operations that are used prior to pellet formation in the pelletizing disc or drum. Establishing relationships between some intrinsic characteristics of these concentrates and their response to size reduction is, therefore, worthwhile. Single-particle breakage testing has long been used to characterize the material intrinsic response to comminution. However, application of traditional breakage tests to iron ore concentrates is not possible, given their fine sizes. The present work analyzes the application of recent single-particle testing methods that are suitable for particles in the –150 µm size range to characterize breakage of four iron ore concentrates from Brazil. The response of particles when assembled in beds is then analyzed in great detail through piston-and-die testing, as well as by comminution tests in a bench-scale ball mill and high-pressure grinding rolls. Relationships between the results in the various devices, which represent the different levels of particle interaction, have been analyzed in light of their energy utilization. Furthermore, implications of differences in particle characteristics on the differences observed in breakage response are also analysed. [ABSTRACT FROM AUTHOR]

• Strength at coarse sizes directly related to vertical position in deposit. • Limited correlation between strength at coarse sizes and grindability. • Evidence of gangue concentration in intermediate sizes for selected ore types. Low-grade iron ore deposits in Brazil are typically represented by rocks called itabirites. These deposits contain ores with different characteristics, which present varying degrees of weathering, with direct implications in iron contents, liberation characteristics and comminution response. This work analyzes the five main ore types or lithologies contained in the Serra do Sapo deposit, as part of the Minas-Rio mining complex (near the city of Conceição do Mato Dentro, Brazil). Besides detailed chemical and mineralogical composition, liberation characteristics of the ore types have been analyzed by scanning electron microscopy and QEMSCAN. Samples were also subjected to point-load and abrasiveness tests as well as batch grinding tests. It is evident that at coarse sizes the ore types present significantly different strengths and abrasiveness, with values decreasing, as expected, with increasing degree of weathering. However, such differences partially disappeared as comminution progressed to finer sizes. Amenability of the different ores to slimes generation also varied, with weathered ores presenting significantly higher values. Grade by size deportment results show that selected ore types offer opportunity for early gangue (silica) rejection prior to the grinding stage. [ABSTRACT FROM AUTHOR]