Editorial

3 pages, 161 KiB

Open AccessEditorial

Editorial for Special Issue “Comminution and Comminution Circuits Optimisation”

by Ngonidzashe Chimwani

Minerals 2023, 13(1), 81; https://doi.org/10.3390/min13010081 - 05 Jan 2023

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Comminution is the size reduction of rock particles from blasting during the mining stage to crushing and milling during the mineral processing stage [...] Full article

(This article belongs to the Special Issue Comminution and Comminution Circuits Optimisation)

Research

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13 pages, 2926 KiB

Open AccessArticle

A Kinetic Model for Size Reduction in a Pilot Scale Tower Mill: Model Verification

by Leonard G. Austin and Claudio L. Schneider

Minerals 2022, 12(6), 679; https://doi.org/10.3390/min12060679 - 27 May 2022

Cited by 3 | Viewed by 1598

Abstract

Mark Duffy produced a complete set of grinding data on a pilot-scale tower mill. Here these data are analyzed in terms of grinding kinetics. The results show that the data can be fitted with a simple first-order breakage model, which is not normally [...] Read more.

Mark Duffy produced a complete set of grinding data on a pilot-scale tower mill. Here these data are analyzed in terms of grinding kinetics. The results show that the data can be fitted with a simple first-order breakage model, which is not normally observed in any grinding system, including other types of grinding machines such as tumbling ball mills and rod mills. The model has only two parameters, making it possible to determine the parameters using simple search methods. The results show that larger particles break faster than smaller particles, as is usually observed in all mills. Statistical analysis of the data showed that one of the parameters could be fixed for seven of the nine tests. Full article

(This article belongs to the Special Issue Comminution and Comminution Circuits Optimisation)

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25 pages, 16108 KiB

Open AccessArticle

Using Process Mineralogy as a Tool to Investigate Blending Potential of the Pentlandite-Bearing Ores at the Nkomati Ni Mine in South Africa

by Thomas Dzvinamurungu, Derek Hugh Rose, Ngonidzashe Chimwani and Fanus Viljoen

Minerals 2022, 12(5), 649; https://doi.org/10.3390/min12050649 - 20 May 2022

Cited by 2 | Viewed by 2191

Abstract

The mineralogy and texture of Ni-sulfide ores at the Nkomati nickel mine are highly variable, and this results in often erratic nickel recovery at the mine. The variability of the ore presents an opportunity to study the influence of grind size on the [...] Read more.

The mineralogy and texture of Ni-sulfide ores at the Nkomati nickel mine are highly variable, and this results in often erratic nickel recovery at the mine. The variability of the ore presents an opportunity to study the influence of grind size on the flotation-based recovery of Ni in highly heterogeneous sulfide ores, which would be applicable to this ore type at many other mines worldwide. In view of this, a process mineralogy investigation was conducted on thirteen mineralogically and texturally different nickel-sulfide ores from the Nkomati Nickel Mine, with a view on the influence of grind size on the flotation performance of pentlandite. Ore types presented include medium- and high-grade variants of the bleb, disseminated, massive, semi-massive, and net-textured sulfide ores of the Main Mineralized Zone (MMZ), as well as disseminated chromite-rich nickel sulfide ore and massive chromitite ore of the Peridotitic Chromitite Mineralized Zone (PCMZ). Laboratory scale metallurgical test work, comprising of sequential grinding and bench-top flotation testing of the ores, was conducted in combination with quantitative mineralogical investigation of the flotation feed and associated flotation products, using a FEI 600F Mineral Liberation Analyzer. The ore types under consideration require a variety of grind sizes (i.e., milling times) in order to attain optimal recovery of nickel through flotation. This is predominantly controlled by ore texture, and also partly by the abundance of the major constituent minerals in the ore, being pyroxenes, base metal sulfides, and chromite. Liberation of pentlandite is directly correlated with grind size (milling time), which is also positively correlated with the level of nickel recovery through flotation. A grind size of P80 at 75 µm results in the highest concentrate nickel grades of 7.5–8.1% in the PCMZ ores’ types which is the current grind for the PCMZ ores at Nkomati. A grind size of P77 at 75 µm yields the best overall pentlandite liberation, Ni recoveries of 84–88% and grades of 5.3–5.6% in the MMZ ores. This holds the potential to produce the best overall pentlandite liberation, nickel grades, recoveries from blending the MMZ and PCMZ ore types, and milling the composite ore at a target grind of P80 at 75 µm. Full article

(This article belongs to the Special Issue Comminution and Comminution Circuits Optimisation)

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14 pages, 6662 KiB

Open AccessArticle

Heating Pre-Treatment of Copper Ores and Its Effects on the Bond Work Index

by Nataly Cisternas, Pablo Tobosque, Daniel Sbarbaro, Carlos Munnier, Willy Kracht and Claudia Carrasco

Minerals 2022, 12(5), 593; https://doi.org/10.3390/min12050593 - 07 May 2022

Cited by 2 | Viewed by 1660

Abstract

Comminution is the stage with the largest energy consumption in the mining process. Therefore, several pre-treatments have been proposed to reduce the energy requirements of this stage. This work analyzed the effect of a heating pre-treatment on the Bond index. A conventional heating [...] Read more.

Comminution is the stage with the largest energy consumption in the mining process. Therefore, several pre-treatments have been proposed to reduce the energy requirements of this stage. This work analyzed the effect of a heating pre-treatment on the Bond index. A conventional heating pre-treatment was applied to a Chilean copper ore. The ore was heated to temperatures from 300 to 600 °C using a conventional furnace, resulting in a reduction of 19% in the Bond work index. Due to the pre-treatment, the mineral cracked in several areas. Microfracture and composition analyses of these areas confirmed that crack generation in the ore is due to the thermal stress produced by the pre-treatment. The fracture analysis explains the reduction in the Bond work index, since crack generation started at similar temperatures to those at which the reduction in the Bond work index was observed. In addition, the analysis also shows that micro-cracks occur between and through different phases, which may have an impact on mineral liberation. These results also show that, under a moderate high temperature, an important reduction in energy consumption can be obtained. Full article

(This article belongs to the Special Issue Comminution and Comminution Circuits Optimisation)

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24 pages, 17853 KiB

Open AccessArticle

An Improved Capacity Model of the Cone Crushers Based on the Motion Characteristics of Particles Considering the Influence of the Spatial Compound Motion of the Mantle

by Zilong Zhang, Tingzhi Ren, Jiayuan Cheng and Jianxu Zhu

Minerals 2022, 12(2), 235; https://doi.org/10.3390/min12020235 - 11 Feb 2022

Cited by 2 | Viewed by 2075

Abstract

Capacity is the important indicator of the cone crushers, which is determined by the motion characteristics of particles. The spatial compound motion of the mantle, which rotates both around the central axis of the cone crusher and its central axis, was analyzed to [...] Read more.

Capacity is the important indicator of the cone crushers, which is determined by the motion characteristics of particles. The spatial compound motion of the mantle, which rotates both around the central axis of the cone crusher and its central axis, was analyzed to develop motion characteristic equations of particles. The velocity distribution of particles with different motion characteristics was determined by solving the motion characteristic equations of particles using the coordinate system transformation matrix. An improved capacity model of the cone crushers based on the motion characteristics of particles considering the influence of the spatial compound motion of the mantle was established by analyzing the velocity of particles in the upward and downward direction zones of the choke-level and the influence of circumferential deflection of particles on the velocity in the radial direction. A reduced-scale cone crusher with various rotational speeds was used to simulate cone crushers with different motion characteristics of the particles passing through the choke-level. The average error between the capacity calculated by the improved capacity model and the capacity determined according to the experimental data was 5.96%. Therefore, the accuracy of the improved capacity model was verified. The improved capacity model was used in the capacity calculation of the ZS200MF cone crusher; the error was 7.4% compared with the measured value at the production site; thus, the applicability of the improved capacity model is proved. The influences of four typical parameters of the cone crusher on capacity were investigated based on the improved capacity model, which provides theoretical support for the development of new high-efficiency cone crusher and the optimization of existing equipment. Full article

(This article belongs to the Special Issue Comminution and Comminution Circuits Optimisation)

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12 pages, 6633 KiB

Open AccessArticle

Numerical Simulation of a Single and Double-Rotor Impact Crusher Using Discrete Element Method

by Murray M. Bwalya and Ngonidzashe Chimwani

Minerals 2022, 12(2), 143; https://doi.org/10.3390/min12020143 - 25 Jan 2022

Cited by 6 | Viewed by 2795

Abstract

The Discrete element method (DEM) is an invaluable tool for studying comminution as it provides detailed information that can help with process analysis as well as trying out new equipment designs before the equipment is physically built. The DEM was used to analyse [...] Read more.

The Discrete element method (DEM) is an invaluable tool for studying comminution as it provides detailed information that can help with process analysis as well as trying out new equipment designs before the equipment is physically built. The DEM was used to analyse previous experimental work to gain some insight into the comminution process in an impact crusher with a single impeller. Further DEM simulations were done on a crusher with a second impeller installed. The energy spectra and threshold energy levels calculated from the drop-weight test were used as the basis of comparison. The simulations indicate that even at much lower speeds, the performance of a double impeller impact crusher is exceedingly superior. However, the energy associated with the double impeller impact crusher is much higher and energy intensification, rather than energy efficiency, is the main gain of the double impeller design. The double impeller also offers more operational flexibility, such as spacing between the impellers, which can be tailored to the particle size range being handled. Full article

(This article belongs to the Special Issue Comminution and Comminution Circuits Optimisation)

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16 pages, 2390 KiB

Open AccessEditor’s ChoiceArticle

Optimization of Aggregate Production Circuit through Modeling of Crusher Operation

by Tomasz Gawenda and Daniel Saramak

Minerals 2022, 12(1), 78; https://doi.org/10.3390/min12010078 - 09 Jan 2022

Cited by 4 | Viewed by 2331

Abstract

The paper concerns investigation of the effect of impact crusher operation on selected qualitative characteristics of mineral aggregate products. Qualitative characteristics of crushing products in terms of size reduction ratio and fine particles contents were analyzed from the point of view of operational [...] Read more.

The paper concerns investigation of the effect of impact crusher operation on selected qualitative characteristics of mineral aggregate products. Qualitative characteristics of crushing products in terms of size reduction ratio and fine particles contents were analyzed from the point of view of operational parameters of the impact crusher. An investigative program was carried out on a plant scale and two primary parameters of the impactor were analyzed: velocity of the crusher rotor and the width of the outlet gap. The models of the crushing device operation were built separately for each type of the tested material, as well as for general conditions. Full article

(This article belongs to the Special Issue Comminution and Comminution Circuits Optimisation)

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Review

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23 pages, 4669 KiB

Open AccessReview

A Review of the Milestones Reached by the Attainable Region Optimisation Technique in Particle Size Reduction

by Ngonidzashe Chimwani

Minerals 2021, 11(11), 1280; https://doi.org/10.3390/min11111280 - 18 Nov 2021

Cited by 3 | Viewed by 1630

Abstract

The attainable region (AR) is an optimization method adopted for use in comminution to achieve different objective functions, which all converge to optimising the production of the desired particle size distributions for downstream processes. The technique has so far mostly been used to [...] Read more.

The attainable region (AR) is an optimization method adopted for use in comminution to achieve different objective functions, which all converge to optimising the production of the desired particle size distributions for downstream processes. The technique has so far mostly been used to optimise the breakage of particles in tumbling mills. It achieved the desired purpose by unveiling all possible outcomes derived from a combination of operational parameters that are bound by trajectories showing the limitations of a system. The technique has given the scientific community lenses to see the behaviour of different parameters in ball mills otherwise known as the black boxes due to their concealing nature. Since its inception, the AR technique has been applied to data obtained from the laboratory tests and simulated industrial mills and the results sometimes contradict or confirm the conventional milling practices in the industry. This makes the already conservative mining industry sceptical about its adoption. This review thus assesses the milestone covered as far as the AR development in comminution is concerned. It also helps to clarify the sources of the discrepancies between the AR results and the conventional knowledge concerning the optimisation of ball mill operational parameters. Full article

(This article belongs to the Special Issue Comminution and Comminution Circuits Optimisation)

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