Minerals

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4 pages, 191 KiB

Open AccessEditorial

Editorial for Special Issue “Comminution in the Minerals Industry”

by Luís Marcelo Tavares

Minerals 2021, 11(5), 445; https://doi.org/10.3390/min11050445 - 22 Apr 2021

Cited by 3 | Viewed by 1865

Abstract

Size reduction processes, which encompass crushing and grinding, represent a significant part of the capital as well as the operating cost in ore processing [...] Full article

(This article belongs to the Special Issue Comminution in the Minerals Industry)

Research

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20 pages, 8068 KiB

Open AccessEditor’s ChoiceArticle

Industrial Vertical Stirred Mills Screw Liner Wear Profile Compared to Discrete Element Method Simulations

by Priscila M. Esteves, Douglas B. Mazzinghy, Roberto Galéry and Luís C. R. Machado

Minerals 2021, 11(4), 397; https://doi.org/10.3390/min11040397 - 10 Apr 2021

Cited by 16 | Viewed by 6951

Abstract

Vertical stirred mills have been widely applied in the minerals industry, due to its greater efficiency in comparison with conventional tumbling mills. In this context, the agitator liner wear plays an important role in maintenance planning and operational costs. In this paper, we [...] Read more.

Vertical stirred mills have been widely applied in the minerals industry, due to its greater efficiency in comparison with conventional tumbling mills. In this context, the agitator liner wear plays an important role in maintenance planning and operational costs. In this paper, we use the discrete element method (DEM) wear simulation to evaluate the screw liner wear. Three different mill rotational velocities are evaluated in the simulation, according to different scale-up procedures. The wear profile, wear measurement, power consumption, and particle contact information are used for obtaining a better understanding of the wear behavior and its effects on grinding mechanisms. Data from a vertical stirred mill screw liner wear measurement obtained in a full-scale mill are used to correlate with simulation results. The results indicate a relative agreement with industrial measurement in most of the liner lifecycle, when using a proper mill velocity scale-up. Full article

(This article belongs to the Special Issue Comminution in the Minerals Industry)

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12 pages, 2500 KiB

Open AccessArticle

Fit-for-Purpose VSI Modelling Framework for Process Simulation

by Simon Grunditz, Gauti Asbjörnsson, Erik Hulthén and Magnus Evertsson

Minerals 2021, 11(1), 40; https://doi.org/10.3390/min11010040 - 31 Dec 2020

Cited by 4 | Viewed by 2246

Abstract

The worldwide shortage of natural sand has created a need for improved methods to create a replacement product. The use of vertical shaft impact (VSI) crushers is one possible solution, since VSI crushers can create particles with a good aspect ratio and smooth [...] Read more.

The worldwide shortage of natural sand has created a need for improved methods to create a replacement product. The use of vertical shaft impact (VSI) crushers is one possible solution, since VSI crushers can create particles with a good aspect ratio and smooth surfaces for use in different applications such as in construction. To evaluate the impact a VSI crusher has on the process performance, a more fit-for-purpose model is needed for process simulations. This paper aims to present a modelling framework to improve particle breakage prediction in VSI crushers. The model is based on the theory of energy-based breakage behavior. Particle collision energy data are extracted from discrete element method (DEM) simulations with particle velocities, i.e., rotor speed, as the input. A selection–breakage approach is then used to create the particle size distribution (PSD). For each site, the model is trained with two datasets for the PSDs at different VSI rotor tip speeds. This allows the model to predict the product output for different rotor tip speeds beyond the experimental configurations. A dataset from 24 different sites in Sweden is used for training and validating the model to showcase the robustness of the model. The model presented in this paper has a low barrier for implementation suitable for trying different speeds at existing sites and can be used as a replacement to a manual testing approach. Full article

(This article belongs to the Special Issue Comminution in the Minerals Industry)

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17 pages, 7094 KiB

Open AccessArticle

Comminution Effects on Mineral-Grade Distribution: The Case of an MVT Lead-Zinc Ore Deposit

by Gabriele Baldassarre, Oliviero Baietto and Paola Marini

Minerals 2020, 10(10), 893; https://doi.org/10.3390/min10100893 - 9 Oct 2020

Cited by 1 | Viewed by 3655

Abstract

Every mining operation is followed by a beneficiation process aimed at delivering quality materials to the transformation industry. Mainly, in order to separate valuable minerals from gangue in mineral processing, the crushing and grinding of extracted ore are crucial operations for the following [...] Read more.

Every mining operation is followed by a beneficiation process aimed at delivering quality materials to the transformation industry. Mainly, in order to separate valuable minerals from gangue in mineral processing, the crushing and grinding of extracted ore are crucial operations for the following separation steps. Comminution is the most energy-consuming operation in mining, and the quality of the results is strictly related to the characteristic of the material under treatment, the type of equipment used in comminution, and the circuit design adopted. A preliminary study was performed in order to understand the crushing behavior under different comminution forces of a high-grade mixed Zn-Pb sulfide ore sample, collected in a Mississippi-Valley Type (MVT) deposit, and the distribution of the target minerals among the products of the process. Ore samples were examined and characterized through thin section observation and SEM analyses for the determination of grain size and texture features, while X-ray powder diffraction (XRPD) quantitative analyses were performed for the definition of target mineral concentrations of comminuted product samples. The selected crushing and grinding circuit comprised lab-scale equipment. For each stage of the process, products below the estimated free-grain size threshold were collected, and particle size analyses were carried out. Comminution products were divided into size distribution classes suitable for further separation operations, and XRPD analyses showed a mineral-grade distribution varying with the dimensions of the products. Characterization of the ore material after crushing and grinding force applications in terms of the distribution of target minerals among different-sized classes was achieved. The important trends highlighted should be considered for further investigation related to an efficient separation. Full article

(This article belongs to the Special Issue Comminution in the Minerals Industry)

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18 pages, 13482 KiB

Open AccessArticle

Fracture Analysis of α-Quartz Crystals Subjected to Shear Stress

by Giovanni Martinelli, Paolo Plescia, Emanuela Tempesta, Enrico Paris and Francesco Gallucci

Minerals 2020, 10(10), 870; https://doi.org/10.3390/min10100870 - 30 Sep 2020

Cited by 5 | Viewed by 3525

Abstract

This study assesses the correlations between the intensity of stress undergone by crystals and the morphological characteristics of particles and fracturing products. The effects of the fractures on the microstructure of quartz are also studied. Alpha quartz, subjected to shear stress, is quickly [...] Read more.

This study assesses the correlations between the intensity of stress undergone by crystals and the morphological characteristics of particles and fracturing products. The effects of the fractures on the microstructure of quartz are also studied. Alpha quartz, subjected to shear stress, is quickly crushed according to a fracturing sequence, with a total fracture length that is correlated to the stress rate. The shear stress generates a sequence of macro and microstructural events, in particular localized melting phenomena, never highlighted before on quartz and the formation of different polymorphs, such as cristobalite and tridymite together with amorphous silica. Full article

(This article belongs to the Special Issue Comminution in the Minerals Industry)

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10 pages, 466 KiB

Open AccessArticle

An LSTM Approach for SAG Mill Operational Relative-Hardness Prediction

by Sebastian Avalos, Willy Kracht and Julian M. Ortiz

Minerals 2020, 10(9), 734; https://doi.org/10.3390/min10090734 - 20 Aug 2020

Cited by 8 | Viewed by 4287

Abstract

Ore hardness plays a critical role in comminution circuits. Ore hardness is usually characterized at sample support in order to populate geometallurgical block models. However, the required attributes are not always available and suffer for lack of temporal resolution. We propose an operational [...] Read more.

Ore hardness plays a critical role in comminution circuits. Ore hardness is usually characterized at sample support in order to populate geometallurgical block models. However, the required attributes are not always available and suffer for lack of temporal resolution. We propose an operational relative-hardness definition and the use of real-time operational data to train a Long Short-Term Memory, a deep neural network architecture, to forecast the upcoming operational relative-hardness. We applied the proposed methodology on two SAG mill datasets, of one year period each. Results show accuracies above 80% on both SAG mills at a short upcoming period of times and around 1% of misclassifications between soft and hard characterization. The proposed application can be extended to any crushing and grinding equipment to forecast categorical attributes that are relevant to downstream processes. Full article

(This article belongs to the Special Issue Comminution in the Minerals Industry)

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16 pages, 9201 KiB

Open AccessArticle

DEM Simulation of Laboratory-Scale Jaw Crushing of a Gold-Bearing Ore Using a Particle Replacement Model

by Gabriel Kamilo Barrios, Narcés Jiménez-Herrera, Silvia Natalia Fuentes-Torres and Luís Marcelo Tavares

Minerals 2020, 10(8), 717; https://doi.org/10.3390/min10080717 - 14 Aug 2020

Cited by 14 | Viewed by 6098

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Comminution in the Minerals Industry)

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14 pages, 5603 KiB

Open AccessArticle

Development of a More Descriptive Particle Breakage Probability Model

by Murray M. Bwalya and Ngonidzashe Chimwani

Minerals 2020, 10(8), 710; https://doi.org/10.3390/min10080710 - 12 Aug 2020

Cited by 13 | Viewed by 2961

Abstract

Single-particle breakage test is becoming increasingly popular, as researchers seek to understand fracture response that is purely a function of the material being tested, instead of that which is based on the performance of the comminution device being used. To that end, an [...] Read more.

Single-particle breakage test is becoming increasingly popular, as researchers seek to understand fracture response that is purely a function of the material being tested, instead of that which is based on the performance of the comminution device being used. To that end, an empirical breakage probability model that builds on previous work was proposed. The experimental results demonstrate the significance of both energy input and the number of repeated breakage attempts. Four different materials were compared, to gain a better insight into the breakage response. This modelling work goes further from previous research of the authors, by showing that not only does size related threshold energy and repeated impacts characterize particle breakage properties, but each material exhibits unique trends in terms of how its threshold energy and its rate of deterioration varies with particle size and each impact, respectively. This behaviour can be attributed to the different mechanical characteristics of the material and their flaw distribution. The importance of these aspects was highlighted. Full article

(This article belongs to the Special Issue Comminution in the Minerals Industry)

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15 pages, 5178 KiB

Open AccessArticle

Confined Bed Breakage of Fine Iron Ore Concentrates

by Túlio M. Campos, Gilvandro Bueno and Luís Marcelo Tavares

Minerals 2020, 10(8), 666; https://doi.org/10.3390/min10080666 - 27 Jul 2020

Cited by 6 | Viewed by 3407

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Comminution in the Minerals Industry)

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15 pages, 1882 KiB

Open AccessArticle

Grinding Behaviors of Components in Heterogeneous Breakage of Coals of Different Ash Contents in a Ball-and-Race Mill

by Jin Duan, Qichang Lu, Zhenyang Zhao, Xin Wang, Yuxin Zhang, Jue Wang, Biao Li, Weining Xie, Xiaolu Sun and Xiangnan Zhu

Minerals 2020, 10(3), 230; https://doi.org/10.3390/min10030230 - 3 Mar 2020

Cited by 8 | Viewed by 2874

Abstract

Coals used for power plants normally have different ash contents, and the breakage of coals by the ball-and-race mill or roller mill is an energy-intensive process. Grinding phenomena in mill of power plants is complex, and it is also not the same with [...] Read more.

Coals used for power plants normally have different ash contents, and the breakage of coals by the ball-and-race mill or roller mill is an energy-intensive process. Grinding phenomena in mill of power plants is complex, and it is also not the same with ideal grinding tests in labs. The interaction among various coals would result in changes of grinding behaviors and energy consumption characterization if compared with those of single breakage. In this study, anthracite and bituminous coal of different ash contents were selected to be heterogeneously ground. Quantitation of components in products was realized using the relation between sulfur content of the mixture and mass yield of one component in the mixture. Product fineness t₁₀ of the component was determined, and split energy was calculated on the premise of specific energy balance and energy-size reduction model by a genetic algorithm. Experimental results indicate that breakage rate and product fineness t₁₀ of the mixture decrease with the increase of hard anthracite content in the mixture. Unlike the single breakage, t₁₀ of anthracite in heterogeneous grinding is improved dramatically, and bituminous coal shows the opposite trend. The interaction between components results in the decrease of the specific energy of the mixture if compared with the mass average one of components in single breakage. Breakage resistance of hard anthracite decreases due to the addition of soft bituminous coal, and grinding energy efficiency of anthracite is also improved compared with that of single grinding. Full article

(This article belongs to the Special Issue Comminution in the Minerals Industry)

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19 pages, 6664 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Quantitative Microstructural Analysis and X-ray Computed Tomography of Ores and Rocks—Comparison of Results

by Oleg Popov, Irina Talovina, Holger Lieberwirth and Asiia Duriagina

Minerals 2020, 10(2), 129; https://doi.org/10.3390/min10020129 - 31 Jan 2020

Cited by 22 | Viewed by 5075

Abstract

Profound knowledge of the structure and texture of rocks and ores as well as the behavior of the materials under external loads is essential to further improvements in size reduction processes, particularly in terms of liberation size. New analytical methods such as computer [...] Read more.

Profound knowledge of the structure and texture of rocks and ores as well as the behavior of the materials under external loads is essential to further improvements in size reduction processes, particularly in terms of liberation size. New analytical methods such as computer tomography (CT) were adopted to improve the understanding of material characteristics in rocks and ores relevant to mineral processing, particular the crushing and grinding and the modelling/simulation thereof. Results obtained on the texture and structure of identical samples of rather different rocks and ores (copper ore, granodiorite, kimberlite) are compared by CT with quantitative results from traditional optical microscopy obtained by quantitative microstructural analysis (QMA). While the two approaches show a good agreement of the results in many areas, the measurements with the two different methods also exhibit remarkable differences in other areas, which are discussed further. In conclusion, both methods have their specific advantages starting from sample preparation to the accuracy of information obtained concerning certain parameters of mode and fabric. While sample preparation is faster with CT and information on special distribution of metal minerals is more reliable, the information on mode, grain size and clustering seem to be more precise with QMA. Based on the results, it can be concluded that both methods are comparable in many areas, but in in the field of spatial distribution, they are merely complementary. Full article

(This article belongs to the Special Issue Comminution in the Minerals Industry)

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16 pages, 4433 KiB

Open AccessArticle

Effects of Ball Size on the Grinding Behavior of Talc Using a High-Energy Ball Mill

by Hyun Na Kim, Jin Woo Kim, Min Sik Kim, Bum Han Lee and Jin Cheul Kim

Minerals 2019, 9(11), 668; https://doi.org/10.3390/min9110668 - 31 Oct 2019

Cited by 32 | Viewed by 11470

Abstract

The properties and preparation of talc have long been investigated due to its diverse industrial applications, which have expanded recently. However, its comminution behavior is not yet fully understood. Therefore, having better control of the particle size and properties of talc during manufacturing [...] Read more.

The properties and preparation of talc have long been investigated due to its diverse industrial applications, which have expanded recently. However, its comminution behavior is not yet fully understood. Therefore, having better control of the particle size and properties of talc during manufacturing is required. In this study, we investigate the effect of the ball size in a high-energy ball mill on the comminution rate and particle size reduction. High-energy ball milling at 2000 rpm produces ultrafine talc particles with a surface area of 419.1 m²/g and an estimated spherical diameter of 5.1 nm. Increasing the ball size from 0.1 mm to 2 mm increases the comminution rate and produces smaller talc particles. The delamination of (00l) layers is the main comminution behavior when using 1 mm and 2 mm balls, but both the delamination and rupture of (00l) layers occurs when using 0.1 mm balls. The aggregation behavior of ground talc is also affected by the ball size. Larger aggregations form in aqueous solution when ground with 0.1 mm balls than with 1 mm or 2 mm balls, which highlights the different hydro-phobicities of ground talc. The results indicate that optimizing the ball size facilitates the formation of talc particles of a suitable size, crystallinity, and aggregation properties. Full article

(This article belongs to the Special Issue Comminution in the Minerals Industry)

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Review

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23 pages, 5917 KiB

Open AccessReview

Methods of Ore Pretreatment for Comminution Energy Reduction

by Sefiu O. Adewuyi, Hussin A. M. Ahmed and Haitham M. A. Ahmed

Minerals 2020, 10(5), 423; https://doi.org/10.3390/min10050423 - 9 May 2020

Cited by 33 | Viewed by 9697

Abstract

The comminution of ores consumes a high portion of energy. Therefore, different pretreatment methods of ores prior to their comminution are considered to reduce this energy. However, the results of pretreatment methods and their technological development are scattered in literature. Hence, this paper [...] Read more.

The comminution of ores consumes a high portion of energy. Therefore, different pretreatment methods of ores prior to their comminution are considered to reduce this energy. However, the results of pretreatment methods and their technological development are scattered in literature. Hence, this paper aims at collating the different ore pretreatment methods with their applications and results from published articles, conference proceedings, and verified reports. It was found that pretreatment methods include thermal (via oven, microwave, or radiofrequency), chemical additive, electric, magnetic, ultrasonic, and bio-milling. Results showed that the chemical pretreatment method has been used at an industrial scale since 1930, mainly in cement production. The microwave pretreatment results showed positive improvements at pilot scale mining applications in 2017. The results of ore pretreatment using electric and ultrasonic methods showed up to 24% and 66% improvement in energy consumption, respectively. The former and the latter have been piloted for gold and carbonate ore, respectively. Findings also showed that magnetic, radiofrequency, and bio-milling methods have not led to significant reductions in comminution energy. Based on energy reduction, safety, costs, stage of application, and downstream benefits, microwave and electrical pretreatment methods may be focused for applications in the mining industry. Full article

(This article belongs to the Special Issue Comminution in the Minerals Industry)

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