Comminution Of Ore Research Articles

Predictive modeling of crushing power in cone crushers with the discrete element method

In the mineral processing industry, crushers are relevant machines used for the comminution of ore. One method that has been used to model mining equipment is the discrete element method (DEM), which has proven to be an excellent tool for predicting the behavior of mineral processing machines. This paper presents a DEM model of a laboratory cone crusher with two versions: full and simplified. The simplified version — developed for simulation using fewer computer resources — is compared with the full model to analyze its usefulness. Complete and rigorous parameter calibration was performed, and the results obtained in both models were validated with experimental testing of crushing power, mass flow rate, and product size distribution; errors of less than 15% were obtained in all tests. In addition, a detailed analysis of the loads on the crusher mantle was performed using a polar coordinate representation of the crusher mantle.

Influence of ore size on the production of micro-sized ore particles by high-pressure gas rapid unloading

Comminution of ore is a critical and energy-intensive process in mineral resource utilization. High-pressure gas rapid unloading (GRU) has emerged as a promising ore grinding technique, wherein high-pressure gas is injected into the ore and is unloaded at high speed to induce tensile failure inside the ore. Although the GRU is capable to achieve more efficient ore comminution with lower energy consumption compared to conventional methods, it is still in the early stages of development. The pulverization effect of different size ores is a crucial question needing to be revealed before the GRU industrial application. This study explores the impact of ore size on ore pulverization by GRU, using kaolin as an experimental material. Specifically, we discuss the following: 1. the impact of ore size on high-pressure gas infiltration, 2. the effect of infiltration time on ore pulverization, and 3. the effect of ore size on GRU-pulverized ore. The results indicate that the GRU pulverization method is highly applicable to kaolin, and different ore sizes have minimal effects on ore pulverization. Finally, we explain the insignificant size effect of GRU-pulverized ore by discussing the ore material length scale, deformation scale, and ore size. The conclusion may provide a basis for extending the GRU method from the experimental lab scale to a larger one. It may also provide a reference for applying GRU in kaolin comminution.

Part Two - Extraction, comminution, classification, and beneficiation of iron ore

Part Two - Extraction, comminution, classification, and beneficiation of iron ore

A novel technology of high-voltage pulse discharge for comminution of galena ore

An innovative technology of high-voltage pulse discharge (HVPD) was proposed to investigate the comminution characteristics of galena ore. The optimal experiment parameters were determined as follows: spark gap spacing of 25 mm, pulse number of 120, and voltage of 25 kV. The mass fraction with size <0.074 mm in ground products was improved by the HVPD. Meanwhile, the relative grindability declined with the increase of the grinding time, which indicated that the superiority of HVPD was weakened. The ground products of HVPD were distributed more homogeneously than those of mechanical crushing. The liberation of breakage products was improved by 24.57% via the HVPD. Moreover, the Brunauer–Emmett–Teller (BET) specific surface area, pore volume, and average pore size were increased via the HVPD. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses suggested that obvious grain-boundary breakage and several stomatal traces were observed in the HVPD products.

Modeling comminution of iron ore concentrates in industrial-scale HPGR

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.

Simulation of the comminution process in a high-speed rotor mill based on the feed’s macroscopic material data

In this paper, we present a method that allows for the quick and efficient simulation of the comminution process in high-speed rotor mills. The method requires only the feed’s macroscopic material data and the geometry of the machine. Consisting of two stages, the method couples Computational Fluid Dynamics (CFD) with the Discrete Element Method (DEM) to obtain the collisional velocities and angles of a representative group of particles passing through the machine. Due to this coupling, any mill which relies on fluid forces acting on the ore particles can be simulated. After obtaining these values, the second stage commences wherein a single ore particle consisting of DEM elements collides against a rigid surface. The data obtained from this stage is then used to determine the minimum required working parameters of the chosen machine to achieve proper ore comminution. The proposed methodology was applied to analyse the novel concept of using beater mills for the comminution of copper ore.

Comminution of Copper Ores with the Use of a High-Pressure Water Jet

The article presents research on the comminution of copper ore in a self-constructed mill using high-pressure water jet energy to investigate the usefulness of such a method for comminuting copper ore. As a result, ore particles are obtained that are characterized by appropriate comminution and a significant increase in their specific surface, in turn allowing for potential further processing of the mineral. A comparative analysis of the efficiency of copper ore comminution, primarily taking into account the unit energy consumption and the efficiency of the milling process, clearly indicates that the energy absorption of hydro-jet material comminuting is lower than during mechanical grinding, e.g., in a planetary ball mill. The applicability of the technique depends on the brittle nature of the host rock, e.g., it is especially appropriate for sandstone and shale ores.

Effects of microwave irradiation on impact comminution and energy absorption of magnetite ore

The severe mechanical wear and high-energy consumption in the comminution process of high hardness iron ore have always restricted the efficient and economic development of an enterprise. On the basis of the basic principle that microwave irradiation can induce rock damage, the magnetic ore specimens were subjected to microwave heating treatment with different heating paths and cooling paths; the uniaxial impact comminution test was conducted by the drop hammer impact equipment. This study analyzed the effect of the heating and cooling paths on the crack propagation process, dynamic mechanical strength, and energy consumption of magnetite ore. The results show that microwave irradiation causes obvious microwave-induced cracks in ore, and in the subsequent impact cracking process, the new cracks gradually penetrate the microwave-induced cracks and form the macroscopic fracture surface. With the increase of irradiation power and time, the ore dynamic strength decreased, and the absorption energy increased. Therefore, increasing the total output energy of microwave can effectively alleviate the mechanical wear and enhance the comminution effect of ores. Among the factors that affect the mechanical properties and absorption energy of ore, power has a higher priority than time. With the increase in the heat exchange rate between the ore and the external environment, the ore comminution becomes more intense, leading to the best comminution effect of ores. The research results have an important reference for the practical application of microwave irradiation technology in hard rock comminution.

Two-stage method for the simulation of the comminution process in a high-speed beater mill

The paper presents a two-stage simplified method for the simulation of comminution process which takes place in a beater mill. The first stage of the proposed method is a simulation of the flow of gas and ore particles through a mill based on a two-phase continuous-discrete model. It allows to capture the interaction between the fluid flow and embedded particles, to determine trajectories of their motion and average velocities and frequencies of their collisions against the flywheel and the mill's walls. The second stage of the proposed method is a discrete element method simulation of the process of comminution of a single ore particle. It allows to determine the size distribution of created smaller particles in terms of normal velocity and angle of impact and to estimate the global efficiency of the comminution process. The proposed simulation methodology is applied for the verification of the innovative concept of the application of high–speed beater mill for the comminution of the copper ore.

Two-stage method for the simulation of the comminution process in a high-speed beater mill

The paper presents a two-stage simplified method for the simulation of comminution process which takes place in a beater mill. The first stage of the proposed method is a simulation of the flow of gas and ore particles through a mill based on a two-phase continuous-discrete model. It allows to capture the interaction between the fluid flow and embedded particles, to determine trajectories of their motion and average velocities and frequencies of their collisions against the flywheel and the mill's walls. The second stage of the proposed method is a discrete element method simulation of the process of comminution of a single ore particle. It allows to determine the size distribution of created smaller particles in terms of normal velocity and angle of impact and to estimate the global efficiency of the comminution process. The proposed simulation methodology is applied for the verification of the innovative concept of the application of high–speed beater mill for the comminution of the copper ore.

Use of the attainable region approach to determine major trends and optimize particle breakage in a laboratory mill

In this paper, we apply the Attainable Region (AR) method to laboratory data in order to find ways of reducing the overall grinding time required to achieve a specific result, and also of maximizing the amount of material in a size class of interest. No work on using the AR technique to improve comminution of a gold ore, specifically targeting optimizing powder filling (U), is available as yet. Results obtained here prove that the AR technique could be successfully applied to determine major trends and also recognize opportunities for improving recovery in milling operations. For different experiments on silica and gold ores investigated, a total of 83% (varying J) and 46% (varying U) time saving were obtained respectively. Further applying the AR method to experiments done on the gold ore varying U from 0.5 to 1.75, a value of 1.0 was confirmed to be optimal.

Numerical simulation of high voltage electric pulse comminution of phosphate ore

Numerical simulation of the electrical field distribution helps in-depth understanding of the mechanisms behind the responses and the benefits of the high voltage pulse comminution. The COMSOL Multiphysics package was used to numerically simulate the effect of ore compositions in this study. Regarding phosphate ore particles shape and composition, the effects of mineral composition, particle size, particle shape and electrodes distance were investigated on the electrical field intensity and distribution. The results show that the induced electrical field is significantly dependent on the electrical properties of minerals, the feed particle size and the location of conductive minerals in ores. The angle of material contact surface with the discharge electrode is also an important factor in the intensity of electrical field. Moreover, it is found that the specific liberation effect at the disintegration of phosphate ore by electrical pulses is due to the locality of the electrical field at the interface of mineral components of the phosphate ore aggregates with different permittivities. However, the intensity of the electrical field increases with sharpening the contact angle. Besides, the electrical discharge in the samples is converted to the electrohydraulic discharge across the surrounding water by changing the distance between the discharge electrode and sample surface.

LINE WEAR SENSOR DESIGN

In the mineral processing industry, tumbling mills are used in the size reduction or comminution of ore to a target size distribution. The tumbling mill environment is characterised by frequent and violent interactions all of which are associated with wear either of the steel media or the mill liners. Liner profiles are monitor periodically using manual measurements. In this paper, the design and development of a liner wear sensor is investigated. The thin-film sensor operates within a mill, measuring liner wear while protecting the shell. Also, it is designed to avoid failure modes due to the operating environment. A prototype sensor was built and tested in dry and wet laboratory conditions. The results of the grind test show the feasibility of using the sensor in an industrial machine.

EXPLORING THE DESIGN AND DEVELOPMENT OF AN "ON-THE-SHELL" TUMBLING MILL ACOUSTING MONITORING SYSTEM

In the mineral processing industry, tumbling mills are used in the size reduction or comminution of ore to a target size distribution. As the tumbling mill environment is quite violent it is difficult to monitor mill charge motion. One way is to develop an “on-the-shell” acoustic system. This system will be used in the determination of the charge toe angle of an operating tumbling mill. The instrument, microphone system with the appropriate data acquisition system, collects the acoustic data. An analysis of the signal determines the location of the toe. The results of this development along with some trial data are presented.

INSTRUMENTED BALL DESIGN AND DEVELOPMENT

In the mineral processing industry, tumbling mills are used in the size reduction or comminution of ore to a target size distribution. As the tumbling mill environment is quite violent it is difficult to monitor mill charge motion let alone single ball or particle motion. An effort was initiated to investigate the development of an instrumented ball that includes data collection capabilities. A variety of sensors, including accelerometers and gyros, form the instrument package. The data collected by the instruments allow the calculation of a number of dynamic and kinematic quantities as a function of time. Using instrumented ball data, the error model of the instrument can be found. Finally, the importance of the data with respect to ball mills is discussed along with the relationship between the instrumented ball data and charge motion simulation results is discussed.

Investigation on grinding wear behaviour of austempered ductile iron as media material during comminution of iron ore in ball mills

An attempt has been made to assess the grinding wear behaviour of austempered ductile iron (ADI) as media material in comminution of Kudremukh haematite iron ore in a ball mill. Spheroidal graphite (S.G) iron balls were austenitised at 900°C for one hour and austempered at 280°C and 380°C for different time durations. These materials were characterized by measuring hardness, carrying out X-ray diffraction analysis, studying microstructures using scanning electron microscope (SEM). Grinding wear behaviour of ADI was assessed during wet grinding at different pH of the mineral slurry. The wear resistance of ADI was compared with that of forged En 31 steel balls under similar grinding conditions. It was found that ADI balls austempered at 280°C for 30 minutes which contains lower bainite registered superior wear resistance. It was also noted that the wear resistance of ADI was more at higher pH range of the slurry.

Large-volume platinum ore deposits in zonal mafic-ultramafic complexes of the Ural-Alaskan type and the outlook for their development

The results of mineralogical-technological studies of PGM mineralization in zonal mafic-ultramafic complexes of the Ural-Alaskan type are given. All studied massifs in the Urals and Kamchatka are characterized by similar evolution of mineral assemblages. The chromite (platinum-chromitite-dunite) and dunite (platinum-pegmatoid dunite) geological-economic types of small platinum deposits and occurrences are separate enriched sites (ore shoots) of large-volume platinum ore deposits. These are rather thick and extended zones of recrystallized dunites with attributes of high-temperature structural deformations and intense fluid reworking. Low Pt grade in ore (<0.5 gpt) is determined by fine and very fine (grain size class — 80 μm) euhedral PGM crystals distributed rather uniformly in ore mass. The high and occasionally anomalous Pt contents (up to 1 kgpt and higher) are related to large xenomorphic segregations of PGM, which concentrate largely in the marginal parts of separate chromite segregations. The significant part of productive Pt-bearing mineralization is hosted in olivine matrix of igneous rocks, so that recovery of platinum cannot be associated only with separation of chromite ore. The direct gravity concentration of platinum ore without preliminary separation of chromite concentrate is recommended as the main technique of platinum recovery. The technological scheme provides for two-stage comminution of ore with between-cycle separation of coarse the PGM fraction into the concentrate as a commodity product. The results obtained allow us to regard the aforementioned mineralization as a new geological and economic type of lode platinum deposits, whose potential is comparable with active platinum reserves in the complex Cu-Ni ores of the Noril’sk district.

Multistage mill with flow-through classification for selective comminution of sylvinite ore

The process of sylvinite ore comminution in a multistage flow-through mill is analyzed. The potential applications of the mill in preliminary treatment of the sylvinite ore to prepare it for flotation are considered.

Micromechanics of a model heterogeneous material system under compressive loading

Compressive loading is often encountered in mining and mineral processes during the comminution of ore bearing minerals, or alternatively, in the wear-resistant materials used in the comminution circuit. A common thread joining many of the engineered materials used predominantly under compressive loading is the presence of a high modulus secondary phase, either fiber or particulate, embedded within a lower modulus matrix phase (i.e., a brittle heterogeneous material). To improve their toughness, an imperfect or a less-than-coherent interface is often strived for in the manufacture of many heterogeneous materials. To better understand the complex behavior of these materials, a model heterogeneous material system was developed by the U.S. Bureau of Mines and the Idaho National Engineering Laboratory. In this work, moire interferometry was used to map the micromechanical displacements on the surface of the model system. Uniaxial and biaxial compressive loading was applied to a model system consisting of a PMMA (polymethylmethacrylate) plate having a precision ground steel rod as the cylindrical reinforcement. Moire patterns revealed that two dominant phenomena occur along the interface: (1) frictional slip/stick and (2) a form of semi-cohesive bonding or mechanical locking. These observations were subsequently confirmed by nonlinear finite-element simulations of the model heterogeneous system. Experimental and numerical results show that the imperfect interface plays an important role in the micromechanical behavior of these model systems.

Electrical Disintegration of Rock

Abstract Mechanical compressive and impactive disintegration of rock by metallic devices or by water shock waves consumes a disproportionally high amount of energy and are of low efficiency for liberating mineral aggregates in ores. The tensile loading of the rock, which results in significant saving of energy and decreases the cost of maintenance of equipment and substantially improves the mineral liberation, cannot be achieved in mechanical crushers. Electrical disintegration by high voltage pulses results from the tensile failure of rock and can be carried out in inexpensive light weight non-metallic containers. The plasma explosion, generated by pulses inside the rock fragments, is induced by development of the treelike conductive capillaries which result from application of an electrical field which exceeds the dielectric strength of the rock. The explosion takes place on return of the streamers bridging the two electrodes. Tests on continuous comminution of complex apatite-nepheline ore, gold bearing quartzites, emerald bearing pegmatites, diamond bearing kimberlites and other ores show high liberation results from the electrical disintegration technique. Efficiency of electrical disintegration depends on the right match of voltage and energy of pulses with mechanical strength of rock and desirable size of fragments, and is directly proportional to the rate of build up of voltage across the rock. Electrical disintegration of rock consumes substantially less energy than compressive mechanical crushing and enhances effect of liberation of mineral constituents of rock aggregates.