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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]

[Display omitted] • Breakage of coke, iron ore lump, sinter, briquette and pellet studied. • Sinter and lump have low breakage strength; coke and pellet have high. • Coke and pellet suffer limited weakening and surface breakage. • High fines generation from simulation of degradation with briquette and lump ore. • Low fines generation from simulation of degradation with coke and pellet. Mechanical degradation of steelmaking materials can have significant economic and environmental implications. Such degradation typically occurs as result of impacts during transportation and handling from their production site to the steelmaking furnace, in operations that include transfers in chutes, ship loading, stockpiling, reclaiming, wagon loading and discharging, etc. Predicting the extent of such degradation and attempting to prevent it, is worthwhile. Fortunately, mechanical degradation during such operations can now be predicted using different approaches, but a proper breakage model is required. The work presents results from single-particle breakage tests of iron ore lump, sinter, briquette, and pellet samples, besides coke, followed by fitting parameters of the Tavares UFRJ Breakage Model. These are then used to simulate degradation in a hypothetical handling circuit. Predictions demonstrate the high susceptibility of iron ore lump and briquette to fines generation, when compared to the other materials, and the occurrence of conditioning for briquettes and sinter, which is the increase in strength of particles surviving handling. Iron ore pellets and coke remained comparatively unaffected by the handling operations simulated, which is explained by their greater resistance to either body or surface breakage. [ABSTRACT FROM AUTHOR]

In a recent study by the authors, green pellets motion behavior and interactions among themselves and with the equipment during classification were successfully modeled through simulations with the discrete element method using the Hertz-Mindlin with JKR contact model. The present work initially deals with a parametric simulation study of five important variables in a roller screening operation, namely, gap between the rolls for removal of undersize, rolls rotational frequency, rolls diameter, deck angle, and throughput. The effect of the individual variables and their interactions are analyzed through factorial simulation experiments. Following these initial simulations, a response surface methodology coupled to the application of multiobjective optimization was used to identify a setting of the various variables that would allow improving classification performance. Such results led to a proposition of a new configuration for the roller screen, which consisted in a significant reduction in roll diameter and deck slope, an increase in rolls rotational frequency and a reduction in undersize gap. Simulations predicted, for the studied material, an increase in fines removal efficiency from 91.4% for the base case configuration to 97.1% for the optimized case, with a reduction to one-third the contamination of the on-size material, and a moderate increase in the efficiency of properly sized material reporting to the on-size product. Although at the expense of a modest increase in loss of properly sized pellets to the oversize, such optimized configuration is also predicted to be significantly more robust to surges in the feed than the base case. [ABSTRACT FROM AUTHOR]

Mechanical degradation of green iron ore pellets prior to induration is a concern and can result in return of material to discs or drums or contamination of the feed to the induration furnace during pelletization. The work investigates the effects of pellet size, drop height, impact angle and type of surface on the response of pellets to multiple impacts, analyzing not only the critical condition for appearance of a surface crack, but also for their disintegration. It also analyzes the effect of deformation velocity during compression, showing that stiffness of green iron ore pellets remains relatively constant while pellet fracture energies significantly increase. It is observed that the effect of pellet size is limited, while the effects of drop height, velocity, angle and type of surface significantly influence degradation of such pellets. Finally, the effect of weakening due to repeated drops on the strength of pellets after firing is demonstrated. Unlabelled Image • Energy to crack green iron ore pellets varies with deformation velocity. • Green pellets are more amenable to breakage by double than single impact. • Proportion of green pellets broken varies as a function of cumulative drop height. • Strength of green pellets is not significantly influenced by pellet size. • Damage of green pellets reduced the strength of fired pellets. [ABSTRACT FROM AUTHOR]

Slow compression tests are routinely used both in quality control of fired iron ore pellets during production and in negotiating commercial contracts. In spite of their widespread use, such tests represent stressing conditions consistent with those experienced by pellets during transportation in ships, wagons and conveyor belts, as well as when they are stored in silos and hoppers. However, operations that are most likely to damage pellets occur during transfers in chutes, screening, ship and wagon loading, stockpiling and reclaiming, where they are subjected to rapid loading. The present work compares the mechanical behavior of individual pellets subjected to slow compression and rapid loading, this later in an impact load cell device. Besides pellet strength, fracture energy and also stiffness of the pellets are analyzed, demonstrating that pellets present significantly higher stiffness when subjected to impact, with only marginally higher pellet strengths and no clear trend regarding fracture energy. These strain rates differences are then discussed and their potential effect on deformation behavior and wave propagation in the pellets are analyzed. Unlabelled Image • Strength, fracture energy and stiffness reduced with increase in pellet size. • The same general trend was found for (double) impact and slow compression. • A ratio of 104 in strain rates was used in the experiments. • Significant differences between impact and slow compression for stiffness. • Marginally higher strengths for impact in comparison to slow compression. [ABSTRACT FROM AUTHOR]

Degradation that results from transportation and handling can have an important economic impact in steelmaking materials, given the lower value of the finer material that is generated. In spite of their higher strength when compared to lump iron ores, fired iron ore pellets also undergo some degradation, which increases with severity of the handling operations that occur from the pelletizing plant to the end user. Such degradation can occur in the form of fine debris lost from the surface of the pellet, in a mechanism of surface breakage, or as result of complete loss of integrity of the pellet (fracture), generating a wide range of fragments in size. The work deals with this second mechanism of breakage, describing the probability of fracture of pellets under impact conditions, the amenability of pellets to break under repeated impacts, besides the size distribution of the progeny for selected iron ore pellets, proposing appropriate experimental methods and models to describe them quantitatively. [ABSTRACT FROM AUTHOR]

The fracture load of iron ore pellets in the 12.5 to 16-mm size range is routinely measured in pellet plants following the ISO 4700 standard. The analysis of such data, however, seldom goes beyond averages and standard deviations of the load required for fracturing each pellet. Iron ore pellets are produced in the range from approximately 8 to 19 mm, so the entire distribution of fracture strengths over the range of sizes produced is relevant. This study analyzed in great detail the variability and the size-scale effect on the strength of five industrial iron ore pellets. The fracture strength data of pellets contained in five size ranges were analyzed on the basis of 12 probability distributions, as well as different parameter estimation methods. Further, other measures collected from compression tests, that is, pellet stiffness and specific pellet fracture energy, were also analyzed as a function of pellet size. Results show that the Weibull distribution provided comparably good fitting to pellet strength data. Fracture energy data could be described well using the normal distribution with square root transformation, although the Gumbel distribution was identified as the best fit-for-purpose distribution describing the data. The maximum likelihood parameter estimation method was demonstrated to be marginally more capable of fitting the data than the least-squares technique. It was also shown that the fracture strength of pellets increases with a reduction in pellet size. This size effect on strength was found to be more pronounced than that predicted using Weibull theory on the basis of variability in pellet strengths. [ABSTRACT FROM AUTHOR]

The increase in production of steel in electric arc furnaces in recent years influenced directly the world production of direct reduction iron (DRI). Amongst the most widely used technologies for DRI production is the MIDREX® process. The behavior of the metallic charge used in these furnaces, mainly made up of iron ore pellets, influences directly their productivity. Fines contained in the feed are typically removed by screening, in order to prevent them from impacting negatively the productivity of the furnace. However, fines still may be generated inside the furnace as a result of the collisions amongst pellets and between them and internals of the furnace as they move downwards from the feed to the discharge of the shaft furnace. Predicting and preventing such mechanical degradation is critical in the furnace operation. The present work deals with the prediction of degradation of iron ore pellets during reduction in a MIDREX furnace. Collision energies involved in the vertical flow of pellets along a MINIMOD® MIDREX direct reduction furnace were estimated using the discrete element method. Using this technique along with a model of degradation that considered assumptions based on information from the literature it was possible to estimate the proportion of fines generated inside the reactor, which was consistent with plant practice. Finally, it was predicted that the generation of fines in the reduction zone of the furnace would vary from 3.4 % to 4.6 % as the throughput of the furnace increased in 50 %. [ABSTRACT FROM AUTHOR]

Abstract: Degradation of steelmaking materials during handling causes a significant economic impact, given the higher prices achieved by lump ore in comparison to finer products. It is relevant to model the amenability of ores to degradation, since it may be used to simulate the response of ores to different sequences of handling and transportation events from mine to port. The paper presents a mechanistic model to describe degradation caused by transfers and drops of particulate materials. The model is based on damage mechanics and the distribution of fracture energies of the original particles, using data collected in impact load cell and tumbling tests. This model, which is capable of predicting the proportion of particles broken and the entire size distribution resulting from any sequence of drops, has been validated at a preliminary level using data from drop tests of a Brazilian iron ore. [Copyright &y& Elsevier]

Abstract: Degradation of steelmaking materials during handling causes a significant economic impact, given the higher prices achieved by lump ore in comparison to finer products. It is relevant to model the amenability of ores to degradation, since it may be used to simulate the response of ores to different sequences of handling and transportation events from mine to port. The paper presents a mechanistic model to describe degradation caused by transfers and drops of particulate materials. The model is based on damage mechanics and the distribution of fracture energies of the original particles, using data collected in impact load cell and tumbling tests. This model, which is capable of predicting the proportion of particles broken and the entire size distribution resulting from any sequence of drops, has been validated at a preliminary level using data from drop tests of a Brazilian iron ore. [Copyright &y& Elsevier]

Simulation of breakage embedded in the discrete element method (DEM) has evolved significantly in recent years, taking advantage of both greater computing power and novel approaches that have become available in both commercial and open-source packages. This work analyzes in detail the simulation of breakage using the discrete breakage model (DBM) in the commercial software Ansys Rocky. Breakage of iron ore pellets under slow compression was studied. After the selection of suitable contact parameters for the pellets, described as polyhedral particles, the model is used to describe their breakage considering fully resolved fragments from the beginning of the simulation. The effects of contact model, time step and number of elements on the ability of the model to represent average breakage response of iron ore pellets under compression is analyzed. An approach was then used to account for the variability in the breakage characteristics of the pellets, which provided a valid description when applied to another pellet sample, also showing capability to describe the size-scale effect on the breakage energy of pellets when applied to pellets of different sizes. [Display omitted] • The discrete breakage model with polyhedral particles examined. • Approach proposed to calibrate model parameters for simulation. • Expressions proposed to vary number of elements in meta-particles with no model recalibration. • Model parameters capable of describing size-scale effects on iron ore pellet breakage. • Predictions insensitive to deformation rates below about 1.7 m/s. [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]

• Particle replacement model was implemented in a DEM commercial code. • Breakage of particle beds by compression and impact was studied. • Fragmentation of iron ore pellets was modeled and simulated. • PR model calibrated on the basis of analytical models and experiments. • PR model validated by comparison with experiments. The present work introduces a particle replacement model implemented in the commercial software EDEM to describe breakage of particles. Several model parameters were initially estimated on the basis of single-particle breakage tests on iron ore pellets. The model was then used to simulate breakage of particle beds by both slow compression and impact. Model predictions were compared to experiments in terms of compressive force versus packing density, breakage probability of the particles versus compressive force applied to the bed, and the product size distribution in compression and impact. The model showed the expected trends as well as some agreement with the measured product size distributions both from confined and unconfined stressing conditions of the bed of particles, being a simple and effective approach to describe breakage in systems where particles are stressed as assemblies. [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]

Mechanical degradation of iron ore pellets can have important economic and environmental implications. The work initially describes a pneumatic gun device that has been developed for characterizing breakage of pellets, by impacting them one-by-one against a target at controlled velocities, angles and against different types of surfaces. It shows that body breakage probability was only a function of the normal component of the impact and that pellets presented higher resistance and lower variability when subjected to impact than to slow compression. Mass loss due to surface breakage was well described using a model that accounts for the energy dissipated in the impact, including both normal and shear components. Parameters capturing their amenability to break either catastrophically or only undergoing surface breakage were estimated from data and the model has been validated on the basis of data from different sequences of impacts, also being used to predict the phenomenon of stabilization. Unlabelled Image • Impact device developed for studying breakage of fired iron ore pellets. • Breakage probability defined exclusively by normal component of impact energy. • Body breakage progeny distribution well described using a t10-based model. • Surface breakage model responsive to impact energy and impact angle. • Model capable of predicting fragment size distribution under different impacts. [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]

• A pseudo-dynamic screen/rod milling circuit model was calibrated. • Mill model was validated with industrial survey data. • Long-term circuit operation predicted with qualitative agreement to plant experience. • Significant reduction in product variability by changing mill speed to compensate for charge wear. • Substantial reduction in number of stops for replacing rod charge by increasing initial rod charge and diameter. One important application of rod milling is in size reduction of coke breeze, which is used as solid combustible in iron ore sintering plants. The work applies modeling and simulation of an industrial circuit comprised of a flip-flow screen and a rod mill to predict the circuit response in long-term operation, following the strategy used in the plant of replacing the rod charge only when it reaches the end of its life. Initially, the model for rod wear has been calibrated and the mill fillings estimated. Then the mill model has been validated with data from several industrial surveys, showing good agreement between the two. A long-term (approximately three-month) pseudo-dynamic simulation was then carried out to mimic the strategy normally used in plant operation. Additional simulations were then carried out to compare different scenarios of operation, demonstrating the benefit of increasing the rod charge and diameter, in particular when associated with operation of the mill at lower speed in the beginning of the charge life and progressive increase thereafter, besides partially replacing worn rods in their midlife. For instance, simulations showed that an increase in initial mill filling from 15 to 20 %, progressive increase in fraction of critical speed from 0.40 to 0.65 in contrast to operation at constant speed and gradual reduction of throughput from 60.0 to 40.2 t/h resulted in 56 % increase in charge lifetime, 35 % reduction in variability in product quality and 12 % reduction in cost of operation per ton of coke breeze produced. [ABSTRACT FROM AUTHOR]

• Breakage function of coke breeze exhibited non-normalizable response. • Very good agreement of size-mass balance model for batch tests operated under different conditions. • Reduction of breakage rates with increase in moisture. • Good agreement between model predictions and full-scale rod mill surveys. Limited to less than 5 m in diameter and, as such, no longer found in large-scale circuits, rod mills remain popular in medium- and small-scale plants, primarily owing to their ability to prevent overgrinding. One successful application of rod milling is in size reduction of coke breeze, a material generated from mechanical degradation of coke during handling which is used as solid combustible in iron ore sintering. The work investigates the grinding response of coke breeze in a laboratory rod mill, through experiments conducted with narrow-size feeds under a range of conditions. Data has been described using the size-mass balance model, which demonstrated that coke exhibits non-normalizable breakage response, with an inflexion point at 0.27 mm. The model showed very good ability to predict grinding of different narrow sizes after being fitted form a single test. The validity of the Austin-Klimpel-Luckie scale-up relationship, incorporating an additional correction term for moisture, has then been demonstrated by comparing results from experiments with different rod sizes, mill fillings, interstitial fillings and moisture contents to predictions, with very good agreement. Finally, predictions of product size of an industrial mill operating at different throughputs were also in good agreements to data collected in plant surveys, demonstrating the great potential of the model in optimizing full-scale operations. [ABSTRACT FROM AUTHOR]

Abstract Surface breakage or attrition occurs when iron ore pellets are subjected to handling stages in which the stressing level is insufficient to cause their massive fracture. This breakage mechanism has been investigated for five types of industrial iron ore pellets from impacts against a steel target, leading to a model that accounts for the effect of pellet size, impact energy and angle. The model is then validated on the basis of two different tests. First, a tumbling test on a small drum (0.305 m diameter) is used to demonstrate the validity of the model to describe surface breakage by motion of the pellets at comparatively low velocities, such as those that are found during flow in hoppers and silos. The model is also validated on the basis of simulations of a RO-TAP® sieve shaker. It is demonstrated that it is able to predict with confidence results from the tests, proving to be a powerful tool when used in combination with simulations using the discrete element method, to predict mechanical degradation due to surface breakage during handling. Graphical abstract Unlabelled Image Highlights • Surface breakage of pellets is analyzed using drop tests. • Mass loss by attrition follows upper-truncated lognormal distribution. • Attrition varied with impact energy, angle and pellet size. • Modified model of Ghadiri and Zhang applied successfully. • Model was validated using tumbling and sieving experiments. [ABSTRACT FROM AUTHOR]

Bed permeability is a critical parameter in induration of green iron ore pellets in travelling grate furnaces. Its control and optimization must be pursued in order to achieve higher productivity, lower fuel consumption and higher quality and uniformity of fired pellets. One important method of improving bed permeability is to strictly control the size distribution of green pellets prior to feeding the induration furnace. Given the limited control that exists in the sizes of pellets that leave pelletizing drums or discs during balling, size classification by screening becomes of central importance. The work analyzes the performance of the main type of screen used in classification of green iron ore pellets, the roller screen, through simulations using the discrete element method. Recognition of the sticky nature of the material led to the choice of the Hertz-Mindlin model with JKR cohesion to describe the contacts. Material characterization tests were conducted that resulted in the estimation of detailed material and contact parameters for simulation. Finally, simulations using the discrete element method were used to analyze the sensitivity of the roller screen performance to selected material and operating variables. [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]

Tata Steel handles yearly several million tons of sinter for ironmaking. At present, a significant amount of the sinter produced becomes fines during handling and needs to be recycled. These fines are generated mainly during handling of sinter from the plant to the blast furnace, in particular inside transfer chutes. Repeated impact loading of particles against each other and against wall surfaces lead to their surface and body breakage and, thus, fines generation. The present work describes the calibration of a detailed breakage model of a sinter product, followed by model validation through simulation using the Discrete Element Method (DEM) in a simple laboratory handling system, besides a 14 m high, complex industrial-scale chute system. The full-scale validation consisted of comparing the final size distribution of material at the discharge belt of the transfer chute from the simulation using a commercial software (Altair EDEM) to results from an industrial survey, demonstrating reasonable agreement. In-depth analysis of the simulations made it possible to locate the problematic areas for the existing chute design, demonstrating the value of DEM not only to predict flow in chute systems, but also breakage and fines generation during sinter handling. [Display omitted] • Significant amount of the sinter becomes fines during handling and needs to be recycled. • Calibration of a breakage model and validation using DEM simulation. • Simple drop tests validated Breakage Model with good confidence. • Values were found to also be consistent with similar material in the literature. • Survey results showed reasonable match with results from DEM with UFRJ Breakage Model. [ABSTRACT FROM AUTHOR]

Abstract: The appropriate choice of contact parameters is of great importance, particularly when simulations using the discrete element method (DEM) are run with the aim of capturing quantitative information on collision events that occur among the individual particles, as what happens during handling of iron ore pellets. The paper analyzes the use of tests conducted with single pellets for estimating material and contact parameters that are required in DEM simulations using the no-slip Hertz–Mindlin model. Tests included impact load cell, tribometer, drop tests and a simple test in which the rolling angle of individual pellets is measured. It is concluded that, provided particle shapes are described appropriately, DEM simulations provide reasonably realistic predictions of pellet motion in assemblies from contact parameters measured on the basis of single-particle tests. In this case the physical significance of the contact parameters is maintained. However, if pellets are described in a simplistic way as spheres, then the DEM simulation of their flow no longer matches the experimental results, requiring fitting some of the contact parameters in order to match the observed global flow, so that much of the physical meaning of the parameters is lost. [Copyright &y& Elsevier]

[Display omitted] • DEM-MBD-PRM coupling simulations predicted key variables of pilot-scale HPGRs. • Material, contact and simulation parameters were calibrated with a step-by-step procedure. • Density of the scaled DEM particles was estimated from experimental flake density. • Very good agreement between measured and predicted HPGR throughput and power. • Tavares PRM was able to predict well qualitatively variation of product PSD. In spite of the important developments in mathematical modeling of high-pressure grinding rolls (HPGRs) in the last decade or so, predicting their performance for a wide range of geometries, wear conditions of the rolls and types of containment remains a challenge. Simulation using DEM coupled to multibody dynamics (MBD) of the floating roll appears as a viable alternative, but studies that demonstrate its validity are very scarce. Pilot-scale HPGRs, one with cheek plates and other with flanges, were tested in size reduction of iron ore pellet feed. Both have been simulated using DEM-MBD with a novel particle replacement model (PRM) in EDEM™. Simulations matched the throughput and the power demanded by the machines with very good accuracy. The predicted product size variations with operating conditions and along the axial roll position were in very good agreement with experiments, but only qualitatively, owing to the coarser sizes of particles simulated in comparison to those in the feed to the tests. [ABSTRACT FROM AUTHOR]

As soon as fired iron ore pellets suffer their first breakage event, fragments are created. During handling from the pelletizing plant to the steelmaker furnace, several stages of handling occur, so that if a well-formed and nearly spherical pellet breaks early in the handling chain, its fragments may also end up undergoing breakage. This is particularly important if one wishes to predict breakage during all handling stages. Unfortunately, no study in the past analyzed breakage of fragments of fired iron ore pellets, which will likely differ in comparison to the nearly spherical pellets owing to the irregular shapes of fragments. This work investigates breakage of fragments of iron ore pellets by impact using a pneumatic gun device, investigating the effect of fragment history and impact velocity on the breakage probability, the generation of fines by surface breakage as well as the fragment size distribution from body breakage. Results show that fragments are more amenable to surface breakage than well-formed pellets and also that their strength increases as fragment sizes reduce. [Display omitted] • Fragments of iron ore pellets tested by impact using a pneumatic gun device. • Breakage probability increases monotonically as fragment size increases. • Fragments are more amenable to breakage by repeated impacts than pellets. • Fragments are more amenable to surface breakage (attrition) than pellets. • Fragmentation pattern of fragments was different from that of well-formed pellets. [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]

• 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]