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Cone crushers have a central role in the processing of quarry rocks, besides coarser ore preparation in several mineral processing plants. This is particularly true in the case of Itabirite iron ore preparation plants in Brazil, so optimizing their performance is of central importance for reaching maximum productivity of the circuit. The work presents results of modeling the HP500 cone crusher in operation in an industrial plant in Brazil (Minas Rio), from surveys carried out over a few years with different feeds and crushing conditions. A version of the Andersen–Whiten cone crusher model was implemented in the Integrated Extraction Simulator featuring a non-normalizable breakage response and a fit-for-purpose throughput model. The results demonstrate the good ability of the model to predict crusher performance when dealing with different closed-side settings and feed size distributions. [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]

High-pressure grinding rolls (HPGR) have gained great popularity in the mining industry in the last 25 years or so. One of the first successful applications of the technology has been in iron ore pressing prior to pelletization. Piston-and-die tests can provide good insights on the material response in an HPGR. This work analyzed confined bed breakage of four iron ore concentrates under different conditions. Saturation in breakage of particles contained in the top size in the tests was observed to occur at specific energies of about 2 kWh/t, whereas full saturation in breakage, with no additional increase in specific surface area of the material, occurred at energies above about 6 kWh/t. An expression was proposed to characterize the propensity of a material to break under confined bed conditions. The phenomenology involved in confined bed breakage of such materials was then analyzed in light of the results. [ABSTRACT FROM AUTHOR]

High-pressure grinding rolls have an important role in several iron ore pellet feed preparation circuits. Modeling and simulation are potentially useful tools to improve their performance, but the applicability of mathematical models from the literature in this particular application has not yet been demonstrated, although the model by Torres and Casali has been identified as having good potential. The present work relies on several surveys on four HPGRs with variable diameters (1.4 to 2.25 m) and aspect ratios (0.88 to 1.45) operating in pelletizing plants to test the model originally proposed by Torres and Casali, as well as modifications proposed to it. Inadequacies have been found in the original model, which gave poor predictions of power, throughput and product size distribution along the roll's length. Modification of the power equation, incorporating a machine-dependent correction factor for the nip angle, as well as several modifications to the throughput model, including an expression meant to account for the ejection of material from the edge of the rolls and extrusion, resulted in very good agreement between data from surveys and the model. Finally, incorporation of an empirical correction equation to account for saturation and a more general expression for the roll profile led to good agreement between measured and predicted product size distributions, including their variation along the roll's length. [Display omitted] • Torres and Casali model presented poor results in HPGRs for pellet feed. • Modifications in model resulted in improved predictions of power and throughput. • Trapezoidal axial profile observed on the product described well with new equation. • A modification incorporating saturation resulted in improved prediction of product size. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effects of solids content, pH, slurry temperature, coagulant and surfactant dosage were studied. • Ceramic filtration performance of iron ore slurries analyzed through cake moisture and thickness and capacity. • Solids content has the greatest effect on the system studied. • Coagulant addition improved capacity at low solids content. Although ceramic capillary filtration is a novel technology, it is proving rapidly to be an attractive alternative for dewatering slurries in the minerals industry. For instance, it has demonstrated great potential for application to iron ore slurries. However, the current understanding of effects of its variables on the performance of the process is still limited. The present work investigates the effects of solids content, pH, slurry temperature, and coagulant and surfactant dosage on ceramic filtration performance of iron ore slurries. The experiments were conducted both varying one variable at a time and following a response surface approach (Box-Behnken design), being carried out either in batch or pilot-scale. The results show that solids content is the variable with the greatest impact on ceramic filtration and that addition of a coagulant increased capacity of the filtration system at lower solids content. Furthermore, it is concluded that the addition of neither of the surfactants studied is recommended for ceramic filtration of the ore in question due to significant reduction in productivity of the plates. [ABSTRACT FROM AUTHOR]

Various approaches have been used over the years to describe quantitatively ball milling, with different levels of success. The present work presents the application and validation of a mechanistic model to describe ball milling of iron ore pellet feed. The approach started by estimating selected parameters describing the ore characteristics by back-calculation from batch grinding tests, followed by validation of the model in batch grinding as well as continuous open-circuit ball milling at a pilot-scale operating at a variety of solids concentrations, both with overflow and grate discharge. An industrial ball mill was then laser scanned and surveyed, including measurements of residence time distribution. Simulations using the discrete element method were then conducted and the model was applied to simulate closed-circuit operation, resulting in good agreement between measured and predicted size distributions and circulating load ratio. [Display omitted] • Mechanistic ball mill model applied to grinding iron ore pellet feed. • Particle breakage parameters back-calculated from bench-scale ball mill tests. • Model predictions validated for other batch milling conditions. • Open-circuit pilot-scale tests predicted with good accuracy. • Application to simulation to full-scale milling circuit provided valid results. [ABSTRACT FROM AUTHOR]

[Display omitted] • An energy-based ball mill model was applied to describe two industrial-scale operations that use large-diameter mills. • Very distinct breakage and selection functions appeared when comparing PGMs and itabirite iron ores. • Reduction in ball size increased the breakage rates of fine particles in PGM ores, at the expense of a reduction in the rates of coarser particlesItabirite iron ore showed higher ameneability to breakage compared to the PGMs even though minimal differences were noted at finer sizes. • Calibration of the model based on batch-grinding data showed ability to describe industrial grinding. Phenomenological models of ball milling are routinely used to optimize size reduction operations. A usual method adopted in the minerals industry relies on batch-grinding tests to calibrate models in a population balance model formulation describing the breakage behaviour and then scale-up the breakage parameters using an energy-based relationship. Despite the important advances and application of these methods, their application in describing grinding in large-diameter (>7.5 m) mills has not been widely demonstrated. The work demonstrates the calibration of industrial-scale ball mill model parameters from laboratory milling tests on Platinum Group Metals (PGM) and Itabirite iron ores. Minor fine-tunning of a single model parameter was required to simulate the large-diameter industrial mills, demonstrating the validity of the approach for ores as distinct as PGM and Itabirite iron ores. Estimation of the Arbiter Flow Number below 4.1 showed a regular slurry transport for all mills studied. This model can then be used in optimization of the ball mill performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Modified Torres and Casali model applied as an online digital assistant coupled with real-time information. • An elegant model was used to describe the relationship between operating pressure and operating gap. • Simulation case study showed feasibility to reduce process disturbance and increase energy utilization. • HPGR showed potential ability absorbing a coarser feed size distribution and providing a homogenous product. Besides the recent advances in high-pressure grinding rolls (HPGR) technology, the good track record demonstrates the potential growth in its applications in the future. In this regard, challenges are emerging driven by technology improvements and the increasing demand for a proper understanding of the operation and optimization of the grinding process in different scenarios. To fill this gap, new dynamic modeling and simulation approaches have been evolving to capture information of the process in real-time using online tools. However, proper application of these models as online digital assistants is still missing. The present work applies the online modeling approach proposed by the authors in the first part of this series as a digital assistant. The digital assistant receives real-time information of an industrial-scale HPGR pressing of iron ore concentrates and uses the Modified Torres and Casali model to predict the main HPGR performance variables. At first, a quantitative description of the HPGR hydro-pneumatic pressurizing system is calibrated and validated describing the relationship between hydraulic pressure and gap in the industrial machine. Feasibility of applying the online model as a digital assistant was demonstrated from two simulation case studies by providing setpoints of hydraulic pressure based on real-time changes in HPGR feed BSA, with the aim of reducing the variabilities of the HPGR product BSA and absorbing a coarser feed BSA. [ABSTRACT FROM AUTHOR]

[Display omitted] • Modified Torres and Casali model applied as an online model coupled with real-time information. • A new method was proposed to circumvent the model limitations when describing HPGR operating with worn rolls. • Model demonstrated ability on capturing variabilities of the process in real-time to predict HPGR power, throughput and product BSA. • Use of bench-scale data to improve description of size reduction in industrial-scale is demonstrated. High-pressure grinding rolls reached great popularity for pressing iron ore concentrates since its first application in the 1990s. For this particular application, mathematical models describing HPGR performance on the basis of operating conditions and feed characteristics have successfully been used by the authors to map industrial-scale operations under controlled conditions. Despite these important advances, this modeling approach has only been used so far offline and under steady-state conditions. The present work applies the Modified Torres and Casali model proposed by the authors as a novel online model coupled with real-time information from an industrial-scale HPGR pressing iron ore concentrates. The model is demonstrated to be able to predict throughput, power and product size distribution on the basis of data available online from the process. Results showed capability of the model to map the operation giving a realistic description of the process. A new method was proposed to circumvent the model limitations when describing HPGR operating with worn rolls, and bench-scale data was used to improve description of the size reduction in industrial-scale. [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]

• Poor predictions when applying directly Torres and Casali model to data. • Modifications to the model have been proposed. • Modifications in capacity and power equations have been successfully implemented. • Use of non-normalizable breakage function led to improved product size distribution. • Comparisons showed benefit of edge recycle in comparison to single and double-stage. The roller press, also called high-pressure grinding rolls (HPGRs), has been successfully used for over 25 years in increasing the surface area of iron ore concentrates for pellet feed production prior to green pellet formation. In spite of the long track record of application, there have been no systematic mathematical modeling studies of that operation in pellet feed production. The paper initially analyzes the direct application of Torres and Casali model to data from roller pressing of iron ore concentrate fines at a pilot-scale facility. Inadequacies have been identified and modifications for improved prediction of power, throughput and product size distribution for the case in question have been proposed. Parameters from two of the submodels (power and breakage) were amenable to fitting on the basis of data from a single experiment. Simulation results with the modified version of the model agreed well with experiments. Finally, different strategies of operation of the roller press in pellet feed pressing, namely single pass, double-stage pressing and single-stage with recycle of the edge product were then analyzed on the basis of experiments and simulations, demonstrating the benefit of edge recycling. [ABSTRACT FROM AUTHOR]

• Throughput drops as specific force increases. • A parabolic profile appears in Blaine and %-45 µm along the rolls. • Moister feeds led to smaller operating gaps and higher energy absorption. • Moister feeds led to a more limited edge effect. • Efficiency dropped for higher velocities and finer feeds. Much practical experience has been gathered along the nearly thirty years of application of high-pressure grinding rolls (HPGRs), also called roller presses, in size reduction of iron ore concentrates prior to pelletization. In spite of this, relatively limited experimental data exists from tests conducted under controlled conditions in a large enough scale that allows understanding the influence of several of the process variables on the comminution performance. The paper analyzes tests with an iron ore concentrate sample carried out over a range of pressures, roll velocities, feed size distributions and moisture contents in a pilot-scale facility. It is observed that specific throughput drops as the operating pressure is increased, a parabolic profile appears along the rolls regarding both Blaine specific surface area (BSA) and percent passing 0.045 mm, and also that operation at higher moistures resulted in smaller gaps, higher specific energy absorption and higher BSA. The ratio between the surface area created and the energy consumption was generally found to be relatively constant for different operating conditions, only reducing for higher roll speeds and finer feeds. A model for estimating BSA on the basis of the size distributions has also been successfully fitted. [ABSTRACT FROM AUTHOR]