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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]

Advances in high-pressure grinding roll (HGPR) technology since its first commercial application in the cement industry include new roll wear protection techniques and new confinement systems. The latter contribute to reductions in the edge effects in an attempt to reach a more homogenous product size along the rolls. Additional advances in this technology have been made in recent years, while modeling and simulation tools are also reaching maturity and can now be used to subject such novel developments to detailed scrutiny. This work applies a hybrid approach combining advanced simulations using the discrete element method, the particle replacement model and multibody dynamics to a phenomenological population balance model to critically assess two recent advances in HPGR technology: spring-loaded cheek plates and the offset roller press. Force and torque controllers, included in the EDEM 2022.1 software, were used to describe the responses of the geometries in contact with the granular material processed. Simulations showed that while the former successfully reduced the lateral bypass of the material by as much as 65% when cheek plates became severely worn, the latter demonstrated lower throughput and higher potential wear but an ability to generate a finer product than the traditional design. [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]

Breakage occurs in several particulate systems that are simulated using the discrete element method (DEM), namely crushing and grinding as well as inadvertently in several others that include transportation, handling, mixing, separation and geotechnical applications. Different approaches may be used to describe particle breakage using DEM, but in cases in which particle breakage influences significantly the flow behaviour of the material, imbedding the breakage description in DEM provides the only valid alternative. This study describes the implementation of a detailed breakage model based on particle replacement with spheres in the commercial software EDEM. It accounts for variability and size-dependency in particle fracture energies, weakening of particles by unsuccessful stressing events, as well as addressing several reported shortcomings in sphere replacement schemes. The model is verified in great detail on the basis of single-particle breakage information and validated using measurements in unconfined particle beds of mineral ores. [Display omitted] • A particle replacement scheme involving spherical particles is proposed. • A detailed breakage model has been implemented in EDEM as an API. • Model involves three classes of particles: resolved breakable, resolved unbreakable and dummy. • The model has been properly verified on the basis of single-particle breakage. • The model has been validated on the basis of unconfined particle bed experiments. [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]

Several approaches have been proposed over the years that may be used to predict the performance of industrial rod mills. Unfortunately, studies that allow comparing the accuracy in their predictions are very scarce. The work compares four methods for predicting size reduction in an industrial rod mill. These were the Bond work index method (BW) and the Callcott–Lynch (CL) model, both originally proposed for rod mills, besides the Herbst–Fuerstenau (HF) and the Austin–Klimpel–Luckie (AKL) models, first proposed for ball mills, but here adapted and applied to rod milling. A total of 10 industrial surveys were conducted of the industrial mill in dry grinding of coke breeze, covering operation under a variety of conditions, all of which at lower fillings than commonly used in industry (<15%). Since most conditions surveyed were not within the typical operating range for rod mills, simulations using the Discrete Element Method were used to predict the mill power, used as input in both BW and HF models. At first, the fidelity of methods that allow predicting full-scale mill performance solely from bench-scale information, namely BW, HF, and AKL, is compared. Results showed that they all presented high biases in their estimates of product fineness, with AKL predicting finer products whereas BW and HF predicting coarser products. Using then data from a single industrial survey for model calibration (base case), in addition to the bench-scale test results, a comparison of the four approaches became possible. Taking the absolute deviations between measured and predicted P80 values, it became evident that the HF provided the highest fidelity in the predictions, with mean deviations of 12.8%, AKL with 15.3%, with both BW and CL presenting deviations above 18%. The work thus shows that size-mass balance models that rely on fitting most model parameters from bench-scale tests (HF and AKL) can provide predictions with good confidence when data from an industrial base case are additionally used in fine-tuning the model, even when applied to describing rod milling under unusually low fillings. [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]

The HPGR is properly regarded as one of the most important recent developments in the field of size reduction. This success is mainly associated to its improved energy efficiency, grinding capacity, lower sensitivity to grindability variations and higher metal recovery in downstream processes compared with conventional grinding technologies such as ball mills and cone crushers. It comprises two counter-rotating rolls mounted on a sturdy frame, one of which is allowed to float and is positioned using hydraulic springs. Comminution in the HPGR is largely determined by the pressure exerted on the bed of particles by the hydraulic system. The paper describes how the coupling of the multi-body dynamic simulation with the discrete element method can be effectively used to describe the performance of the HPGR. The model considers important variables, including the HPGR rolls geometry and design, the hydraulic spring system start-up parameters and the material loading response, to describe key operational outputs as material throughput, operating gap and roller pressure distribution. The preliminary version of the model has been used to demonstrate qualitatively the effect of material properties on the operating gap, the pressure and the energy consumption of a laboratory-scale HPGR. Predictions using the model have been compared to those from phenomenological models, showing good agreement, but also limitations in the DEM approach with the current simple particle replacement model to predict the working gap at high initial nitrogen pressures. [ABSTRACT FROM AUTHOR]

It has been known that the performance of high-pressure grinding rolls (HPGR) varies as a function of the method used to laterally confine the rolls, their diameter/length (aspect) ratio as well as their condition, if new or worn. However, quantifying these effects through direct experimentation in machines with reasonably large dimensions is not straightforward, given the challenge, among others, of guaranteeing that the feed material remains unchanged. The present work couples the discrete element method (DEM) to multibody dynamics (MBD) and a novel particle replacement model (PRM) to simulate the performance of a pilot-scale HPGR grinding pellet feed. It shows that rotating side plates, in particular when fitted with studs, will result in more uniform forces along the bed, which also translates in a more constant product size along the rolls as well as higher throughput. It also shows that the edge effect is not affected by roll length, leading to substantially larger proportional edge regions for high-aspect ratio rolls. On the other hand, the product from the center region of such rolls was found to be finer when pressed at identical specific forces. Finally, rolls were found to have higher throughput, but generate a coarser product when worn following the commonly observed trapezoidal profile. The approach often used in industry to compensate for roller wear is to increase the specific force and roll speed. It has been demonstrated to be effective in maintaining product fineness and throughput, as long as the minimum safety gap is not reached. [ABSTRACT FROM AUTHOR]

The Discrete Element Method (DEM) is a numerical method that is able to simulate the mechanical behavior of bulk solids flow using spheres or polyhedral elements, offering a powerful tool for equipment design and optimization through modeling and simulation. The present work uses a Particle Replacement Model (PRM) embedded in the software EDEM® to model and simulate operation of a laboratory-scale jaw crusher. The PRM was calibrated using data from single particle slow compression tests, whereas simulations of the jaw crusher were validated on the basis of experiments, with very good agreement. DEM simulations described the performance of the crusher in terms of throughput, product size distribution, compressive force on the jaws surface, reduction ratio, and energy consumption as a function of closed side setting and frequency. [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]

Important advances have been made in understanding ball milling during the last 25 years or so, a great part of it owing to the widespread application of the discrete element method (DEM), which is now an integral part of several advanced ball mill models. These models, however, must rely on assumptions regarding the mill mechanical environment that can help make the problem more manageable. The paper analyzes the validity of some assumptions that have been the basis of several advanced ball mill models by conducting DEM simulations of dry batch mills including both grinding media and particles. The validity of the assumption of perfect mixing of grinding media and particles, as well as of simulating exclusively the grinding media in order to collect the collision energy information for prediction of breakage and, thus, saving computational effort, are analyzed in great detail. It is concluded that the assumption of perfect mixing in the radial direction is generally valid, except for mill frequencies that are unusually high and exceedingly large ratios of mean ball and particle sizes being ground. It is also observed that a fraction of the number of collisions inside the mill do not involve particles, so that an empirical expression that is based on the ratio of surface areas of the ball and particle charge is proposed to estimate such proportion of unsuccessful collisions. Finally, a model from the authorś laboratory, that assumes that each collision in the mill will involve a monolayer bed of particles, is tested, demonstrating reasonable agreement when compared to simulations. [ABSTRACT FROM AUTHOR]

Abstract: In spite of its relative operational simplicity and earlier attempts to model its performance, the Vertical shaft impact (VSI) crusher is still lacking a comprehensive mathematical description that allows predicting its performance accurately. One of the reasons is the limited knowledge of particle interaction and solids flow inside the machine. The paper deals with the application of the discrete element method (DEM) in the prediction of solids flow within a pilot-scale VSI crusher operating under different conditions. A large amount of data has been generated and used to calculate the collision energy spectra, as well as the residence time distributions of rock particles that are fed to the machine. It is shown that the collision energy distribution and frequency change significantly if rock or a ring of steel anvils is used as the target and also if a cascading flow of material bypasses the rotor directly into the crushing chamber. Finally, it is discussed how these data, along with models that describe breakage and damage of single particles, can serve as the basis for the development of a fully-predictive model of comminution in this machine in the future. [Copyright &y& Elsevier]

Abstract: Mathematical models of grinding mills and crushers are undergoing significant advances in recent years, demanding ever more detailed information characterizing ore response to the mechanical environment. In a mechanistic model of a comminution machine, the type of characterization data used should cover, as much as possible, the conditions found inside the size reduction machines. This applies to the particle size, the stressing energy and rates that particles are subject to, the breakage mechanism and the level of interaction of the particles during stressing, which all must be described appropriately. Whereas, a very large number of experimental techniques and published data exist that allows understanding and quantitatively describing the response of single particles to stressing, comparatively little information exists on the breakage of particles contained in beds. The present work investigates breakage of particle beds impacted by a falling steel ball in unconstrained conditions, such as those that are likely to be found in tumbling mills. The influences of particle size, impact energy, ball size and bed configuration are investigated for selected materials and a mathematical model is proposed that describes the influence of all these variables. The key element of this model is that it allows predicting breakage in monolayer unconfined particle beds with a combination of single-particle breakage data and functions that describe energy partition and volume of material captured in the bed. This model has been calibrated and validated using data from quartz, granulite, limestone and a copper ore, with good agreement. [Copyright &y& Elsevier]

• DEM-MBD-PRM coupling simulations used to study roll skewing. • Uneven feed regarding rate, top size and fracture energy causing skewing were studied. • When uneven feed to the HPGR no longer occurs, simulations show that skewing ceases. • Simulations show the application of differential pressure on the pistons to reduce skewing. • Heterogeneity in force profile is higher when skewing is disabled. Roll skewing is an integral part of the operation of most HPGR designs presently used and is the result of the system attempting to compensate for uneven reaction from the particle bed along the length of the rolls to the applied forces. Several studies in recent years have simulated HPGR performance using the discrete element method (DEM). However, even when coupled to multi-body dynamics (MBD), these simulations have been limited to the description of one-dimensional motion of the rolls. The present work uses a combination of DEM and MBD to describe two-dimensional motion of the floating roll, making predictions of HPGR operation under skewing possible. Simulation case studies were carried out of a pilot-scale HPGR considering the case of uneven feeding, besides cases in which the feed is segregated with respect to particle size and also strength, represented by different median particle fracture energies, fed to each section of the rolls. Results show that the force profile along the bed and the product fineness along the length of the rolls become more uniform if skewing is allowed in the presence of uneven feed. [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] • Size-dependent fracture energy distribution and progeny size distribution characterized by uniaxial slow compression tests. • An energy-based model describing single-particle breakage by slow compression is proposed. • Energy absorbed by single particles during compression is modeled as function of particle thickness. • Model able to capture changes in particle fracture energy, stiffness, shape and breakage intensity. • Model validity demonstrated by predicting progeny distribution and energy consumption in double roll crusher. Compression of particles to a fixed final gap is the mode of application of stresses in many crushing devices. Understanding and modelling this particle fracture process is indispensable for comminution operations. The present work is based on detailed compression tests conducted with a polymetallic ore to different applied deformation ratios to characterize the size-dependent fracture energy distribution and progeny size distribution. An energy-based model is then proposed that accounts explicitly for particle thickness and maximum deformation to define if the particle is classified for breakage (classification function), the likelihood that the classified particle is sufficiently nipped to break (breakage probability) and the extent of breakage the particle will undergo (breakage distribution). Expressions that allow calculation of the energy absorbed by the particle in both primary and secondary breakage regimes are proposed. The validity of the model is demonstrated by accurately predicting, without any fitting, the progeny and energy consumption of compression using fixed gaps and breakage in a double roll crusher. The advantage of the approach not only lies in its ability to accurately predict the product size distribution, but also the energy demanded in the operation. [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]

The planetary mill is one of the most commonly used mills for ultrafine grinding in the laboratory, given its ability to reach higher intensity of the collisions as the result of increase in rotational frequency and ball acceleration without the undesired centrifugation of the grinding charge. Several attempts have been made in the literature to develop a predictive model of this mill, with limited success. The work applies the mechanistic UFRJ mill modeling approach to predict the size distribution in a laboratory planetary mill, on the basis of single-particle slow compression data obtained using a micro compression tester, besides simulations using the discrete element method. At first, careful verification of the Hertz-Mindlin contact parameters was conducted using a video recording system that moves along with the jar during milling. Grinding tests were conducted with hematite for the mill operating at frequencies that varied from 150 to 300 rpm, resulting in generally very good agreement between model and experiments. However, agreement between the two was found to reduce for the highest rotational frequency studied. This was attributed to the reduction in grinding efficiency in the experiments that was not observed in the simulations, which resulted in predicted values overestimating fineness of the product. Finally, simulations were compared to experiments for quartz, silicon carbide and blast furnace slag under identical conditions and it was shown that the model provided very good predictions, with the exception of quartz. Overview of application of UFRJ Mechanistic Mill Model to predict planetary milling. [Display omitted] • Media motion in a planetary mill recorded using special video recording system. • Fine particle breakage data used to model key breakage parameters. • Good ability of mechanistic model in predicting planetary milling of hematite. • Predictions were optimal at lower mill frequencies. • Very good predictions for other materials at 200 rpm, with minimal model fit. [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]

Vertical Shaft Impact (VSI) crushers have been used as interesting alternatives to cone crushers, particularly in the production of aggregates for the construction industry, not only due to their good energy efficiency but also to their ability to generate more isometric and tougher particles, which is highly desirable in cement mortars and concrete applications. Several mathematical models for the VSI crusher have been proposed in the last two decades or so. The Whiten crusher model, originally developed for cone crushers, has served as the basis of several approaches to model VSI crushers. In the present work, the Andersen/Awachie/Whiten model has been used as the basis for modeling a VSI crusher operating in an industrial plant in Brazil, processing quarry rock to product manufactured sand. Nineteen industrial experiments, covering a range of feed rates, rotor speeds, feed distributor types and feed size distributions, have been carried out. The approach demonstrated to be capable of providing satisfactory estimates of the VSI performance, being able to predict the product size distribution and the specific energy consumption with confidence over a wide range of operating conditions. Since it uses a model that is already available in commercial plant simulators, it may be used, with additional expressions, in simulating any desired circuit. Model parameters such as K 3 and T 10 were found to be particularly influenced by key operational variables such as feed rate and rotor frequency. The significant effect of feed rate on the performance of the VSI crusher studied has been discussed on the basis of simulations of the material flow pattern inside its feed distributing system, simulated using the discrete element method. According to these simulations, it has been inferred that change in the behavior of VSI from lower to higher feed rates may be related to the transition from material being fed predominantly to the rotor, to the increasing contribution of the cascading effect. [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]

[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]