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By T. H. Yang, Q. K. Wang, T. Song, J. W. Zhou

The grinding circuit can be one of the most important mineral processing circuits in plants. Along with the application of large-scale milling machines, the design and optimisation of the operation strategy for grinding circuits is more complicated. An in-house grinding process simulation tool was developed to mass balance, model fit and simulate crushing, grinding and classification circuits. An industrial grinding and classification circuit in a copper mine was modelled, and the modelling parameters were verified by a particular group of plant survey data. To justify the prediction ability of the fitted models, the model predictions under different operation conditions were compared with another group of plant survey data. Then the model predicted the effects on the circuit of changing operating conditions. Circuit analysis of the comminution process for water feed to a SAG mill, water feed to sump, the rolling speed of a SAG mill and the percentage of ball filling in a SAG mill was put into practise, based on the simulation results. The simulation results can be used to help plant operators understand the features of the comminution process and may help to build a knowledge library for process control. Keywords: Process modelling, grinding, comminution, circuit analysis

Jan 1, 2020

By A. Tosun

Muckpile fragmentation formed by blasting depends on the specific charge factor, the discontinuities in the rock mass, and the rock strength. Determination of the discontinuity characteristics and rock strength is a long and difficult process. These two parameters are directly associated with the rock drilling speed. Therefore, it is the drilling speed of the machine used for the blast-hole, rather than the blasthole discontinuity characteristics and rock strength parameters, that is used in the prediction of muckpile fragmentation before blasting. Primarily, it has been suggested that the muckpile fragmentation values can be correctly determined by establishing correlations between the efficiency of the loader and muck pile fragmentation, since fragmentation is directly correlated with the former parameter. Subsequently, a correlation predicting the drilling speed of the drill machine was developed according to the discontinuity characteristics of the blasting surface and the rock strength. Finally, a correlation was developed predicting muckpile fragmentation according to the specific charge factor and the drilling speed of the drill machine The data was obtained by conducting blasting tests in two different limestone quarries.

Nov 30, 2022

By S. O. Bada

Coal is a complex mixture of organic and mineral constituents and is the most abundant resource of fossil energy in the world. In recent years, significant research into dry coal beneficiation has gained much attention, primarily due to the need to improve grades and reduce the environmental contaminants in coal without the use of water, and to achieve this in as cost-effective manner as possible, relative to wet beneficiation processes. This paper seeks to review the application of various electrostatic separators with their process principles, to draw comparisons between different dry beneficiation techniques with specific emphasis on the tribo-electrostatic separation method, and finally to report the results of tribo electrostatic separation conducted on various South African coals. Previous research conducted on Indian, European and American coals has indicated that this technique is likely to lead to significant economic benefit through the reduction of ash content, NOx and more specifically Sox by separating out the liberated Fe-S-bearing minerals prior to utilization. The removal of the latter suite of minerals is also likely to significantly reduce or eliminate the emissions of associated trace elements, including mercury and arsenic. The research results reported in this paper indicate that the rotary tribo-electrostatic process has the potential for significant upgrading of high ash pulverized South African coal. The impact of various operational parameters was investigated and key factors established for the optimum recovery of low ash and low sulphur fine coal.

Jan 1, 2010

By А. А. Vasiliev, Y. G. Seredkin, А. V. Aksenov, А. Y. Senchenko

Refractory gold-containing concentrates usually contain gold enclosed in sulphides as well as in rock-forming minerals. Another difficulty is that gold often occurs as very fine inclusions of several micrometres, and even smaller than 1 micrometre, or can be part of the mineral composition at the structure level. Processing of such concentrates is a challenge. Ultrafine grinding and further oxidation are applied for gold liberation. The paper deals with the results from the study of gold deportment using Qemscan, and atmospheric oxidation testwork involving Albion Process™ on a gold-containing concentrate with a high content of refractory gold in sulphides and gangue minerals. Albion process testing was performed at Institute TOMS with the participation of Glencore Technology Pty Ltd (Australia). Additionally, conventional cyanidation testwork was carried out for the concentrate processing. As an alternative technology of gold liberation, oxidising roasting with arsenic stabilisation was used. The results from the study make it possible to assess the efficiency of the above-mentioned methods of gold liberation, and applicability of Albion technology to recover gold from the refractory concentrate. Key words: Gold, refractory concentrate, Albion Process, atmospheric oxidation, oxidising roasting, leaching

Jan 1, 2020

By J. Hadjigeorgiou, G. Knox

There is a considerable wealth of information on the behaviour of rockbolts under axial loading conditions both in situ and under controlled laboratory conditions. However, there is comparably less data on the behaviour of rockbolts in shear. Several authors have contributed to the understanding of the behaviour of conventional rockbolts’ performance under shear loading. Much of this data have been gathered through experimental programmes conducted on sections of the rockbolt. Considering the continuous coupling between the rockbolt and borehole interface, the approach is justified. Due to the design premise of energy-absorbing rockbolts with discrete couplings, full scale testing is required to quantify the behaviour of the rockbolts. This paper reviews published results obtained from two testing facilities, which are the SINTEF rockbolt pull test rig in Trondheim, Norway and the Epiroc Combinations Shear and Tensile test rig in Johannesburg, South Africa, both capable of conducting full scale testing of rockbolts. Based on this high-quality database it was possible to identify three distinct responses of rockbolts in shear. The behaviour under load is controlled by the presence or absence of an encapsulation medium (resin/cement grout), the reinforcement mechanism, and whether the rockbolt is continuously or discretely captured. As a reference the results are compared to the performance in shear of conventional grouted rockbolts.

Nov 24, 2025

By A. R. Javadi

Pyrite (FeS2), chalcopyrite (CuFeS2), sphalerite (ZnS) and galena (PbS) generate hydrogen peroxide (H2O2) when placed in water, with pyrite generating the most amount of H2O2. The order of these minerals for generating H2O2 in water is: pyrite > chalcopyrite > sphalerite > galena. In previous research, the methods of generation of H2O2 in the grinding mill were studied. In this study, data from experiments were included by using MODDE 9 software for six parameters composed of water, grinding media, particle size; adding collector to the grinding, and adding depressant and pH. Finally the optimal condition was achieved. According to the results, most of the recovery is related to the particle 75 μ size and when using processed water, adding 100% collector and without depressant and pH 10. The most recovery of lead in the case of the use of fresh water is in the case of 100% collector, without depressant, pH 10 and 150 μ particle size. Maximum recovery in fraction size 45 μ in the case of water process is 100% collector, without depressant and pH 10. Maximum depressant of pyrite will be the fraction size 75 μ, distilled water, without collector, 100 depressant. Keywords: Sulfide mineral, hydrogen peroxide, flotation, oxidation

Jan 1, 2020

By C. J. Badenhorst

The primary focus of management today is safety, or preventing negative, generally irreversible, events of acute duration. The outcomes of safety-related events are usually visible and can evoke strong emotions if the results are severe. Experts now see that occupational illness and disease also result in significant emotional and financial toll to workers, their families and communities, and to their employers. Effective health and safety management must include acknowledging the importance of occupational health hazards and the proportionate application of resources to address those issues. Improvement in workplace conditions and decrease or elimination of illness and disability are due to actions within the workplace and result from the implementation of risk prevention and control measures. However, success may only be visible months or years later and may require interventions that have to be maintained over prolonged periods. This demands continuous, co-ordinated effort to ensure sustainability of diverse occupational health programmes and the relevant management systems. Too often occupational health is not seen as being part of the general management of business, but rather the function of a medical practitioner somewhere off site in a clinic. Integration of occupational health management systems with other management systems within an organization is essential for its success.

Jan 1, 2004

By C. Dorfling, M. Tadie, S. Grobbelaar

The physicochemical properties of the complex electrolytes used in direct copper electrowinning are an important consideration for the development of a high-fidelity model of the process. Direct electrowinning electrolytes typically contain a high background of metallic impurities. The effect of metallic ions on the properties and accompanying change in the limiting-current density for copper reduction have been the subject of several studies. Although various empirical correlations have been published for describing the physicochemical properties of electrowinning electrolytes, the correlations are only applicable to a limited range of conditions and cannot be extrapolated without further validation. Consequently, in this paper we validated existing physicochemical property correlations for the full range of operating conditions applicable to direct copper electrowinning and developed a new correlation for predicting the associated limitingcurrent density for copper deposition. Following, we evaluated the benefit of using the validated correlations as a component of a dynamic electrowinning model.

Jan 1, 2023

By T. Szendrei, S. Tose

The generally accepted view in rock blasting is that the sources of energy for the fracture and movement of rock reside in the shock wave and gas action resulting from the explosion, and yet the mechanisms by which these sources interact with the rock have remained unclarified. It has also been noted that up to 50% of the work capacity of an explosive released in a blast cannot be accounted for by field measurements of energy partitioning. In this study, we describe a physical model that details the response of rock to both shock wave and gas action. An analytical model based on momentum conservation is derived to describe the dynamics of shock-driven expansion of the blasthole. Radial expansion of the hole is the key parameter that permits the derivation of the following characteristics of rock response to shock loads: hole expansion time; volume of displaced rock; energy consumed per unit volume; expansion energy efficiency; stress wave pulse length; gas pressure in enlarged hole. Soon after the completion of hole expansion, the shock wave degenerates to an elastic stress wave that runs through the burden. Blasthole expansions of between 50% and 300% of diameter are completed in under 1 ms and, depending on rock properties, consume 32% to 42% of the detonation energy or about 55% of the available mechanical (Gurney) energy. Gas pressure in the enlarged holes in five rock types is between 35 MPa and 650 MPa, and drives the mass movement of burden rock.

Oct 9, 2024

By U. Atici, R. Comakli

"Understanding rock properties is of vital importance in mining and civil engineering. Rock properties are generally determined through laboratory tests, which require a large number of uniformly shaped samples and technicians who use indirect methods to determine rock properties. The texture coefficient (TC), which represents various textural parameters including the size, shape, orientation, and relative proportions of grains and the matrix, is an efficient means for indirectly evaluating the mechanical behaviour of rocks. In this study, 12 different rocks (ten granites, one diorite, and one gabbro) were collected and their engineering properties. including specific gravity, porosity, P- and S-wave velocities, Schmidt rebound hardness, uniaxial compressive strength, and elasticity modulus, were investigated. Relationships between TC and these measured properties were assessed. Statistically significant (at the 95% confidence level) correlations were found between the TC and compressive strength, elasticity modulus, sound velocity (both compression and shear waves for dry and saturated samples), but no significant correlation was found with Schmidt rebound hardness. The results suggest that it is possible to use the relationships between TC and the mechanical properties of rocks in rock classification. IntroductionIn every aspect of rock engineering, knowing rock properties is essential for determining and predicting the behaviour of rocks and rock masses. Mechanical properties of rocks are important parameters in mining, geology, and engineering, and they are affected by textural characteristics such as grain size, grain shape, cement type, degree of cementation, mineral content, and the ratio of the grain area to the matrix area. The effects of textural properties on the physical and mechanical properties of rocks have been investigated for a long time, and previous studies revealed close relationships between single parameters related to rock texture and mechanical properties of rocks (Akesson et al. 2001; Gunsallus and Kulhawy 1984; Merriam, Rieke, and Kim, 1970: Onodera and Kumara 1980; Prikryl 2006; Ulusay, Tureli, and Bider, 1994; Tugrul and Zarif 1998). Rock properties are usually determined using mechanical tests, which require uniformly shaped and relatively large samples. However, it is not always possible to obtain such samples. Furthermore, rocks with similar textural and structural properties may exhibit different mechanical behaviour. Howarth and Rowlands (1987) developed a texture coefficient (TC) that expresses all the main textural parameters of a rock in a single dimensionless quantity based primarily on statistical assessment. The TC makes it possible to understand the effects of a rock’s textural properties on its mechanical properties using thin sections instead of large, uniform samples. Ersoy and Waller (1995) investigated the relationship between strength and TC for limestone, sandstone, and siltstone; they also examined the effect of rock properties and TC on drilling performance. Ozturk, Nasuf, and Bilgin (2004) explored the relationship between rock quality and TC by evaluating the uniaxial compressive strength (UCS) values of limestone, basaltic andesite, and tuff. Gupta and Sharma (2012) evaluated TCs as well as the petrophysical and mechanical properties of quartzite from the lower and higher Himalayas and found a strong relationship between TC and UCS. Similarly, Ozcelik, Bayram, and Yasitli (2013) investigated the relationship between TC and various parameters in marble by applying the statistical analyses developed by Ozturk, Nasuf, and Kahraman (2014)."

Jan 1, 2019

By H. Zhong, S. Wang, Q. Sun

The flotation performance of 2-(benzylthio)-acetohydroxamic acid (BTHA) to diaspore was first evaluated by micro-flotation tests. The adsorption mechanism was further investigated through adsorption experiments, molecular dynamics simulation, zeta potential and X-ray photoelectron spectroscopy (XPS). The results demonstrated that BTHA had a stronger ability to collect diaspore in comparison with another diaspore collector, benzohydroxamic acid (BHA), especially under the condition of weak alkalinity, the flotation recovery can reach 90%. The more negative interaction energy (ΔE) between BTHA and diaspore from molecular dynamics simulation results revealed that BTHA had an easier adsorption ablity onto diaspore than BHA, which matched with adsorption results. The zeta potential and XPS revealed that Al atoms might bond with -C(=O)NHOH by formation of Al-O bonds. Keywords: Diaspore, flotation; adsorption; 2-(benzylthio)-acetohydroxamic acid

Jan 1, 2020

By W. Ferreira

Steel is produced in a basic oxygen furnace from hot metal obtained from a blast furnace. A sintered iron ore with good hightemperature properties (strength and permeability) should be used as feed to the blast furnace. The quality of this sintered ore depends on the reactivity of the iron ore used as feed to the sinter plant during the lime assimilation step in the sintering process. The penetration test is the standard method for evaluating the reactivity of iron ore with lime. It is, however, difficult to determine the exact depth of penetration from the standard test. A new test method is proposed that allows automatic evaluation of iron ores in terms of lime assimilation with increasing temperature. A comparison of the coefficients of variation for the new and standard methods for each ore type demonstrates that the results of the new test are more reproducible and more precise than those of the standard method. The test is also less time-consuming and easier to implement.

Jan 1, 2014

By C. Birch

"Mineral reserve statements as well as optimizing mine planning require a block model with grades for each mining block. A cut-off grade is determined by considering the mining costs as well as the expected revenue for each block. These grades are estimated using various techniques, but in reality there is uncertainty in the grade values. These uncertainties result in two types of error. A type I error is where material is classified as ore and mined, but the true value is below the cut-off grade and the material is therefore waste. This material constitutes dilution. The type II error is where material is estimated to be below the cut-off grade and is classified as waste, whereas the true grade is actually above the cut-off grade. This material is not mined and the value is lost.This research considers the value of the lost ore and the costs of dilution under various degrees of uncertainty. Simulation using @Risk and mixed integer linear programing (Excel Solver) is used in a financial optimizer model to maximize either profit or net present value. This is applied to four Witwatersrand tabular gold deposits to investigate the impact of block grade uncertainty on cut-off grades.When optimizing for profit, value may be added by adjusting the cutoff grade slightly downwards. When optimizing for NPV, value may be added by lowering the cut-off grade significantly for the lower discounting rates. At higher discount rates, the lowering of the cut-off grades should be reduced, and in some cases an increase in cut-off grade may be required. Each mine reacted differently to the optimization and thus there is no single rule that can be applied across all tabular Witwatersrand gold deposits."

Jan 1, 2017

By F. Navarro, F. Soto, G. Díaz, E. Jélvez, G. Morales, N. Morales

The increasing availability of tools on the web provides a great opportunity for the research community to boost investigation by accessing computational resources from all over the world. For example, data analytics libraries implemented in languages like Python can be accessed through many open and commercial platforms, therefore providing researchers with a common set of tools or shared datasets. Unfortunately, that is not the case with research in resource assessment and mine planning, where the most standardised tools are commercial applications designed to work on the desktop, but there are not many standard platforms for research. As a result, researchers from different groups often need to start from scratch in order to develop their work, and rarely share implementations details. Similarly, apart from a few publicly available examples, there is a lack of common datasets that are validated and can be used to compare results between different approaches. In this paper, we introduce a platform that provides tools for resource assessment and mine planning, which can be accessed remotely utilising Jupyter Notebooks. In its current version, the platform provides (i) definition and implementation of basic structures for managing samples and models (loading, saving, adding or removing columns, etc.), (ii) definition of experimental and modelled variograms for spatial continuity analysis, (iii) definition of standard interpolation methods in resource evaluation (inverse distance and kriging), (iv) definition of standard problems in mine planning (ultimate pit and precedence constrained production scheduling), (v) generation of 2D standard graphs like grade distribution, conditional means, tonnage-grade, and production plans (vi) a set of datasets, which can be used for case studies, and (vii) a set of notebooks with examples and documentation. In this paper, we introduce the platform and show some examples that illustrate some of the possibilities that it has for research and education in the area of resource assessment and mine planning.

Sep 1, 2021

By M. S. Shishvan, S. Klerkx, J. Sattarvand

The inaccurately drilled blastholes from the planned locations cause changes in the spatial distribution of explosive energy; some areas of the blast may receive a surplus of explosive energy, while others see a reduction. This results in less uniform fragmentation, reduces the efficiency of mining operations and increases costs. Additionally, it can lead to slope stability issues, flyrock, and uneven benches. To mitigate these problems, this study attempts to reduce differences in the explosive energy distribution (EED) through an optimization approach that adjusts the height of explosive columns in blastholes. Two optimization algorithms, the Genetic Algorithm (GA) and Tabu Search (TS), are tested. The latter is preferred for its local search neighbourhood strategy that gives superior computation times. Applications on different blast patterns result in improvements of 0.53–1.54%, or 2.14–3.94% when only the affected blocks are considered.

Sep 1, 2021

By J. F. Brand, J. C. van Dyk, F. B. Waanders

"Syngas from Africary’s Theunissen underground coal gasification (UCG) project will be used for power production and synthesis of liquid fuels and commodity chemicals. However, some of the coal components, especially condensable water, oils, tars, inorganic trace elements, and a small fraction of fly ash and particulate matter, make their way to the surface via the production well and can cause adverse impacts on downstream processes. Africary’s standard design incorporates a cold gas clean-up system that relies on relatively mature techniques based on highly effective wet scrubbers and acid gas removal (AGR) systems such as Rectisol®, but with the downside of low energy efficiency and waste water generation. In this paper, novel technologies for removing contaminants and species separation from the hot (T > 300°C) raw syngas are compared. Comparisons are made between supersonic gas separation (SGS), Ranque–Hilsch vortex tube (RHVT), vortex gradient separation (VGS), and inertia vacuum filtering (IVF), and a vortex-based gas separation concept is proposed for UCG applications. IntroductionImpurities in gasification feedstock (coal, biomass, waste, etc.), especially sulphur, nitrogen, chlorine, and inorganic mineral matter, often end up in the syngas and can cause adverse impacts on downstream processes. Africary’s standard design incorporates a cold gas clean-up system that relies on relatively mature techniques based on highly effective wet scrubbers and acid gas removal (AGR) systems such as RectisolR, SelexolR or aMDEAR; but with the downside of low energy efficiency and waste water generation.Hot (T > 300°C) gas clean-up technologies are attractive because they avoid cooling and reheating of the syngas stream. Some available warm gas cleaning technologies include traditional particulate removal devices such as cyclones, candle filters, membranes, and molecular sieves. The warm gas desulphurization process technology developed by RTI LLC (2018) requires hot syngas to remove sulphur and has become commercially ready. Many other hot gas cleanup systems are still under development, given the technical difficulties caused by extreme environmental and operating conditions."

Jan 1, 2018

By Turgay Gurun

"Digital simulation can be used as an analytical tool to optimize the design of crushing plants without need for large-scale experimental programs.General mathematical description of a crushing operation permits the simulation of a crushing plant flowsheet under various operating conditions. The process model encompasses multistage open- and closed-circuit crushing of hard and soft rock. Crushing balances are analyzed in the light of crusher and screen performance and a comparison of different closed-circuit arrangements is made in terms of process and layout criteria.The simulation model allows comparison of process alternatives to be made in terms of equipment selection and capital and operating cost estimation. It thus provides the pertinent practical information to maximize plant efficiency, and to minimize expenditures in such items as equipment, structures, power consumption, and so on."

Jan 1, 2014

By Y. Jeong, K. Kim

Excess water can lead to instability and even failure in tailings storage facilities (TSFs). Simply reducing the amount of water in TSFs could be the best way to ensure the safety of nearby communities. In this case study we investigated the effects of reducing the water content in tailings slurry at a copper-cobalt-zinc mine in Mexico. An environmentally friendly polymer was used as a drag reduction agent (DRA) to offset the increase in solids percentage. The potential effects of the increased solids concentration on the tailings transportation system were also assessed. A series of ‘what if’ studies was conducted to assess whether adding the polymer would allow the solids concentration to be increased without changing the pressure loss in the tailings pipeline. The studies entailed conducting pipe loop tests to investigate these changes under various solids/ polymer concentrations and then constructing a computational fluid dynamics (CFD) simulation model using the test results. The validated model was used to determine the optimal polymer percentages needed to maintain the same pressure loss under baseline (30% solids) conditions, and to assess the potential risks (clogging, increased erosion rates) to the pipelines. The potential water savings were found to be significant, varying from about 1.852 Mm3/a at 35% solids to 3.915 Mm3/a at 45% solids.

Dec 13, 2023

By G. Song, S. Yang

"SynopsisThe development of techniques and equipment for single-pass high-seam longwall mining in China is reviewed. Some methods used to obtain the fractured zone height are discussed. The boundary between the caved and fractured zones is generally not clear, but one important difference that distinguishes the two zones is that horizontal compressional forces exist only between blocks of fractured zone. Based on this, a theoretical method is presented to investigate the destabilizing modes of the main roof (by sliding or rotation) and is used to determine if the main roof is in the caved or fractured zone. This method considers the mining height, immediate roof thickness, bulking factor, main roof thickness, main roof strength, main roof periodic weighting interval, and vertical stress in the overlying strata. To verify the method, a representative physical model of Wangzhuang coal mine is developed. The movement of overlying strata and fractured zone height are thus obtained. According to the results, the total collapsed height of the strata reaches about 70 m above the coal floor; the first main roof bending interval is 45 m and periodic bending distance is 10–15 m; the maximum strata subsidence is around 62 mm; and the presence of a three-hinged arch causes the fluctuation of subsidence in the same stratum level. Based on the theoretical and experimental analysis, the middle of the main roof is considered the boundary between caved and fractured zone; the caved and fractured zone heights are about 21 and 49 m respectively.IntroductionThick coal seams (>3.5 m) account for about 44% of the coal rescource/reserves and more than 40% of the total annual production in China (Zhao 2004; Wang 2009). Three mining methods – slice mining, top coal caving, and single-pass high-seam longwall mining – are frequently used in underground thick-seam operations. Compared with slice mining and top coal caving, high-seam single-pass longwall mining significantly simplifies the mining processes, reduces roadway excavation, and improves coal production, productivity, and recovery. The favourable economics, high production, and technical simplicity make high-seam single-pass longwall mining one of the most popular underground mining methods for thick coal seams in China."

Jan 1, 2015

The two methods for calibrating the parameters K and (alpha) for use in Gy’s equation for the Fundamental Sampling Error (FSE)–, Duplicate Sampling Analysis (DSA) and Segregation Free Analysis (SFA)–, are described in detail. A case study using identical broken reef material from a Witwatersrand-type orebody was calibrated using the DSA and SFA methods and the results compared. Classically, the form of Gy’s equation for the FSE raises the nominal size of fragments given by dN to the power of 3. A later modification of Gy’s formula raises dN to the power (alpha), the latter term being calibrated with the coefficient K in the DSA and SFA methods. The preferred value of for low-grade gold ores used by sampling practitioners in the mining industry is 1.5. A review of calibration experiments for low-grade gold ores using the DSA and SFA methods has produced values of K that vary between 70 and 170 and values of in the range 0.97 to 1.30. The average value for is shown to be 1, rather than 3 as originally proposed in the classic form of Gy’s equation or the industry-preferred 1.5. It is suggested that for low-grade gold-bearing ores the equation for the FSE should raise dN to a power of 1. Such an equation for the variance of the FSE greatly simplifies the characterization of gold ores, now requiring only the calibration of K for a given mass and established fragment size. The implications of the simplified equation for the heterogeneity test are that, provided the fragments have been screened to within a narrow size range, any particular size will return a value for K that is acceptable for use in the sampling nomogram.

Jan 1, 2017