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By W. W. de Graaf, M. J. Ntsekhe

Klipspruit Colliery is experiencing coal losses, which leads to a negative impact on coal production and subsequently loss in revenue. This study aimed to identify the possible causes of coal losses in the No. 4 upper and lower seams. The objectives were to identify potential sources of coal losses through a literature survey, to identify areas where the coal losses occurred, to determine factors affecting coal losses, and to identify the most cost-effective methods to reduce coal losses. Highwall losses, top-of-coal losses, and coal edge losses were identified as the major areas of coal loss at Klipspruit. These losses were mostly attributed to the drilling and blasting practises of the pre-split, interburden waste, and the coal seams. Recommendations include re-visiting the current pre-split design and the tolerances adopted for the interburden and coal seam drilling and blasting design. It is furthermore recommended that Klipspruit implement a continuous improvement plan for the drilling and blasting and refresher training for the blasting crew and operators.

Jun 10, 2024

By R. G. Diale, H. R. Chauke, T. M. Ledwaba, P. E. Ngoepe

FeCo alloys play an important role in soft magnetic materials with a wide range of technological applications due to their high saturation magnetization and Curie temperature. However, these alloys have low ductility at room temperature. The ductility can be improved by the ternary addition of elements such as V. A density functional theory supercell approach was used to generate B2 Fe50Co50-xVx (0 ≤ x ≤ 50) structures and the properties were evaluated at different atomic percentage compositions to determine the ductility at room temperature. The structures were fully optimized to obtain better equilibrium ground-state properties such as lattice parameters and thermodynamic properties for both binary and ternary systems. The stability of Fe50Co50- xVx was evaluated from the heats of formation, elastic properties, and phonon dispersion curves. Furthermore, magnetic strength was evaluated from magnetic moments. It was found that all structures are thermodynamically stable due to the negative heats of formation. The calculated Pugh’s ratio and Poisson’s ratio confirm that alloying with V effectively improved the ductility. It was also found that Fe50Co50-xVx showed a positive shear modulus for the entire concentration range investigated, in agreement with phonon dispersion curves. The ternary addition of V to the FeCo system resulted in reduced magnetic strength due to a decrease in magnetic moments. These findings reveal that B2 FeCo-V alloys can be used as components and actuators for the automotive industry.

Jun 10, 2024

By B. A. Obadele, R. Machaka, M. L. Raganya, M. E. Makhatha, N. A. Moshokoa

The influence of solution treatment on the phase evolution and tensile properties of Ti-Mo alloys was investigated to assess their potential use in biomedical applications. Phase formation and microstructural evolution were studied using X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The mechanical properties were characterized by means of tensile tests and bending strength. XRD analysis showed that solution treatment increased the volume fraction of β phase and supressed the α" phase. The microstructures of the as-cast alloys consisted of β equiaxed grains with sub-grain structures of different sizes, while the solution treated alloys comprised β equiaxed grains only except for Ti- 10.02Mo, which comprised needle-like α" structures. EBSD showed an increase in the volume fraction of the ω and α" phases in all the alloys after solution treatment. The elastic modulus and UTS of all the alloy significantly decreased after solution treatment, except for Ti-15.05Mo,whereas the elongation significantly increased. The fracture surfaces of all the alloys after solution treatment indicated more ductile behaviour than brittle

Jun 10, 2024

By L. Zhou, J. Qiu, M. Tang, J. Wang, G. Dai

Coal spontaneous combustion in longwall gobs is a major concern in coal mines. In comparison to other hazards, this phenomenon is difficult to detect. Fifteen factors influencing coal spontaneous combustion in longwall gobs were identified from the literature. The logical relationships between these factors were evaluated and quantified by decision-making trial and evaluation laboratory (DEMATEL) and interpretive structural modelling (ISM) methods. A four-level hierarchical structure model was established. The research shows that combining DEMATEL and ISM can reveal the key factors that influence coal spontaneous combustion in longwall gobs and establishthe interactions and relationships among these factors. The results can provide the basis for preventing and controlling coal spontaneous combustion in longwall gobs.

Jun 10, 2024

By M. Grozdanovic, D. Marjanovic, M. Ilic

We present a framework for solving the problem of functional compatibility between process control equipment in control centres at underground mines and operator capabilities. The equipment incorporates displays of current ventilation, gas, and fire hazard data, status of alarm and early warning systems, a voice communication subsystem, and facilities for recording and printing ofdata and reports. The layout of the existing control panel is compared with a recommended design. The basic principles of ergonomic design and arrangement of the controls and indicators, as well as ease of use, type of operations carried out with these controls, and operators’ viewing angles are discussed. The objective is to improve the usability of control panels, display boards, and graphic screens so as to enhance the functioning of control centres and optimize control of technological processes in coal mines.

Jun 10, 2024

By S. Moolla, R. Lynch, S. Brijraj

A reliable method to locate microseismic evets is an important objective for routine mine seismic monitoring. We developed an algorithm that can automatically and reliably locate an event from a single uniaxial trace. Signals created by microseismic events are recorded as seismograms that consist of direct P- and S-waves as well as the waves reflected off the underground excavations. We take advantage of the extra complexity these reflections introduce as they make the signal more unique. In our investigation we cross-correlated unaltered synthetic seismograms against trial waveforms created from a linear combination of appropriate waveforms from a library of numerically calculated strain Green’s tensors. We use a single uniaxial synthetic seismogram to invert for the source location, six moment tensor components, and frequency. The resulting cost functions are constructed as maximal correlations at each node in the mine grid through the true source x-planes. This function is maximized by differential evolution to simultaneously yield the source parameters. Sensitivity tests such as shifting the mine plans and altering the background velocities of the media are investigated to test the robustness of the method. We contaminate the data with 40% white noise to test the resolution against simulated real recorded seismograms. The method is demonstrated using synthetic data calculated with a realistic underground 3D velocity model.

Jun 10, 2024

By Edward Holloway

The basis for the selection of the ultimate pit for an open-pit mining operation is generally opaque. Some form of value-based analysis will generally guide the final decision; however, the value will often gradually plateau while the ultimate pit size continues to increase. There is no established framework to guide specialists in the selection of the ultimate pit, with such decisions regularly made on a somewhat arbitrary basis. The key component that is missing from the analyses typically used to select the size of the ultimate pit is risk. Once risk is quantified within the analysis framework, the decision-mak-ing range is significantly reduced and the process for select-ing the ultimate pit becomes more consistent, replicable and defensible. The technique outlined in this paper provides an approach to including risk in the process used to select the ultimate pit.

Jun 1, 2024

By C. Nesbit, N. Duru

During the cyanide leaching process of gold and silver, ores that come from the transition zones which typically con-tains low levels of sulfide may produce one or more of the following reduced sulfur species: sulfide (HS ), polysulfides (Sn ), thiocyanate (SCN ), thiosulfate (S2O3 ), trithionate (S3O6 ), tetrathionate (S4O6 ), pentathionate (S5O6 ) and hexathionate (S6O6 ). The actual speciation of the reduced sulfur species in the circuits will primarily depend on the re-dox potential, pH, cyanide levels and existing sulfur species in recycled process water, as well as the presence of other reac-tive metal species. Development of an accurate analytical method for sul-fur species in cyanide leaching units of gold ores where sul-fur speciation occurs has an important role in explaining the metal recovery deviations. This study presents the speciation of sulfur species and development of an ion chromatography method to analyze the reduced sulfur species thiocyanate, thio-sulfate, trithionate and tetrathionate in cyanide leaching circuits for gold ores. The method developed has resulted in the precise quantification of target sulfur species in leach solutions.

Jun 1, 2024

By Yaxiong An, Jianwen Yu, Yuexin Han, Peng Gao

This paper presents an industrial verification test, adding a high pressure grinding roll and magnetic separation operation after the third-stage fine crushing operation to reduce the particle size of ball mill feed and improve the processing capacity of grinding operation. The optimal process parameters of high pressure grinding roll and magnetic separation were determined to be a 10 mm of roller surface spacing, a 10.5 Mpa of roller surface pressure, a 14 r/min of roller surface speed, a particle feed size to the magnetic separator of P100 3 mm, and a 3000 Oe of magnetic field intensity. Under the above optimized conditions, the iron grade of magnetic pre-enriched concentrate increased significantly from 28.27% to 36.30%, and the iron recovery was 87.59%. Meanwhile, the yield of coarse tailings was 36.16%, which significantly reduced the amount of ore entering the subsequent ball mill-magnetic separation operation. The ball mill Bond work index Wib of raw materials and the pre-enriched concentrate were 11.76 kW•h/t and 10.46 kW•h/t, respectively. The relative grindability of the pre-enriched concentrate was increased by 34%.

May 31, 2024

By Lida Sun, Na Wu, Mengyang Huang, Xingxiang Fan, Yan Jiang, Shasha He, Kunbin Yang, Yang Cao

The separation of lead (Pb) and mercury (Hg) from copper (Cu) smelting acid sludge using the carbonization and acidleaching total hydrometallurgical process was investigated. The effects of the excess coefficient of sodium carbonate, excess coefficient of nitric acid, conversion time, conversion temperature, dissolution time, and dissolution temperature on the separation efficiency of Pb and Hg were studied. The test results indicated that when the dosage of sodium carbonate was 2.0 times the stoichiometric ratio, the conversion time was 1.5 h, the conversion temperature was 75 ℃, and the amount of nitric acid was 1.8 times the stoichiometric ratio. Additionally, the dissolution time was 1.0 h, the dissolution temperature was 60 ℃, the ratio of liquid–solid was 5:1, and the separation efficiency of Pb and Hg was 98.72%. This study demonstrated the advantages of a short, simple, and environmentally friendly process for separating Pb and Hg from Cu smelting acid sludge, providing complete separation and introducing a new technology.

May 30, 2024

By Prashant Dixit, Akhil Singh, Asim Kumar Mukherjee, Sudipta Patra, Veerendra Singh

Phosphorous is an undesired element present in iron ore used in the steel making process. It leads to an increase in overall production cost as well as deteriorated steel quality. The desired phosphorus content in iron ores used in steel making is < 0.1%. Numerous beneficiation studies are mentioned in the literature; however, there is no commercial scale technology established to beneficiate high phosphorous iron. The major phosphorous bearing minerals are apatite (Ca5(PO4)(Cl/F/OH), wavellite (Al3(PO4)2(OH)3·5(H2O)), senegalite (Al2(PO4)(OH)3(H2O), barrandite ((Fe,Al)PO4·2H2O), etc. Ultrafine grinding is required to liberate phosphorous minerals from iron ore minerals and subsequently subject it to flotation, acid leaching, and bioprocessing. The selective flotation of iron ore could successfully reduce the phosphorous content from 0.82% to < 0.20% with the combination of grinding, magnetic separation, and carbothermic reduction. Acid leaching processes are also able to remove ~80% (0.85%→0.16%) of phosphorus; however, these are relatively costly and complex processes. The mechanism of bio-extraction for phosphorous removal is reported as one of the most successful processes. This process is capable of removing more than 80% of the total phosphorous and significantly reducing the phosphorous content from 1.06% to 0.16%. The main disadvantage of this process is that it occurs at a much slower pace. In today’s scenario, ultrafine grinding followed by froth flotation seems to be the most feasible solution for the beneficiation of high phosphorous iron ore in which the concentrate obtained can be utilized for pellet making and ultimately used for steel making processes. Development of additives for leaching, roasting, and bioprocessing can be explored further to make these processes more effective and economically viable.

May 28, 2024

By Aaron Noble, Mahmud Esad Uluer

Respirable coal mine dust (RCMD) is one of the biggest occupational health hazards for underground coal miners. Dusty mining environments can cause long-term health problems, including pneumoconiosis and progressive massive fibrosis. The Mine Safety and Health Administration (MSHA) has recently revised regulations promoting enhanced dust mitigation technologies, which have sparked renewed interest in the development of dust mitigation technologies. The flooded bed dust scrubber (FBS) is one of the most widely used technologies; however, it is limited by technical challenges, the most notable being the potential to clog. Recent studies have shown that applying vibration to filter mesh can improve the overall efficiency of the scrubber and that the system can be readily integrated to existing continuous mining equipment using an energy harvesting approach. In this follow-up study, the impact of mesh design and surface modification on system efficiency was examined using different vibrating liquid-coated stainless-steel mesh panels in a laboratory-scale FBS. Based on the two-way interaction data from a multi-factor experimental design, the results show that the performance of the system can be optimized by using hydrophilic 20- or 30-layer filters and by excitation frequencies between 67 and 134 Hz. This laboratory study suggests that a 20-layer mesh screen with hydrophilic surface applications and optimized vibration parameters can perform similar to that of a 30-layer static mesh, which is typically used in industrial units.

May 23, 2024

By Giovanni Rubinich Moraes, Giorgio de Tomi, Irfan Ullah

The study examines productive and unproductive hours in four underground mine shifts: 6 h, 8 h, 10 h, and 12 h. Moreover, two sub-scenarios of single or two blasts examined the effect on mine utilization regarding effective working hours in underground mines. Cuiabá Mine data, the Brazilian’s largest and deepest underground gold mine, was used in both sub-scenarios. Under the first sub-scenario, which assumes two blasts per day, the 6-h shift had an effective work time (EWT) of 13 h and 30 min or 56.3% of the day. The EWT was 15 h and 20 min, 63.9% of the day, in the 8-h shift scenario. The 15-h, 30-min EWT took 64.6% of the day in both 10/12-h shifts. The 6-h scenario had an EWT of 16 h and 15 min (67.7%) in the second sub-scenario with a single blast daily. The 8-h scenario boosted EWT to 18 h and 25 min (76.7%) daily. An EWT of 18 h and 35 min daily (77.4%) was found in 10/12-h shifts. Comparisons of both sub-scenarios show that EWT positively correlates with shift length. Sub-scenario 1 has a 7.6% incremental step from 6 to 8 h, while sub-scenario 2 has 9%. EWT increases from 8-h to 10/12-h shifts by 0.7% for single and two blasts daily. Compared to the two sub-scenarios, halting operations for blasting once daily improves the EWT average by 12.5%. Reducing blasting and changing underground mining shift duration might boost economic viability.

May 21, 2024

By Emily Sarver, August Greth, Cigdem Keles, Setareh Ghaychi Afrouz

The characterization of respirable dust on the basis of constituent fractions and particle sizes is increasingly of concern for evaluating exposure hazards. For high-resolution particle analysis, scanning electron microscopy with energy dispersive X-ray (SEM-EDX) can be an effective tool. However, it requires particles to be deposited on a smooth, uniform substrate such as a polycarbonate (PC) filter for optimal results. While direct sampling onto PC is possible, this is not the standard approach in many situations. For example, in coal mines, respirable dust samples have typically been collected onto polyvinyl chloride (PVC) filters because they are intended for gravimetric and/or infrared spectroscopy analysis. Such fibrous substrates are not ideal for SEM-EDX (or other microscopy), but an effective method to recover and redeposit the dust particles could render such samples suitable for the additional analysis. Here, we present a simple method and compare SEM-EDX results for paired samples analyzed directly on PC and following recovery from PVC and redeposition on PC. Both laboratorygenerated dust samples (n = 10 pairs) and field samples of respirable coal mine dust (n = 44 pairs) are included in this study. Although some changes in particle size distributions were observed between samples analyzed directly and those that were recovered and redeposited prior to analysis, the results indicate the dust recovery method generally yields a representative sample in terms of mineral constituents. That said, results also highlighted the effects of high particle loading density on individual particle analysis. Considering all sample pairs, those with similar loading density between the directly analyzed and recovered sample tended to exhibit similar mineralogy distributions. This was generally the case for the lab-generated sample pairs, and the Freeman-Halton exact test of independence indicated that the samples in just three (of 10) pairs were in disagreement in terms of their mineralogy distributions. On the other hand, for the field samples, the directly analyzed sample often had higher loading density than the recovered sample; and the Freeman-Halton test showed that 25 (of 44) pairs were in disagreement. However, the effect of possible particle agglomeration on the directly analyzed samples cannot be ruled out—and exploration of this factor was beyond the scope of the current study.

May 17, 2024

By Shankar Kumar, Arvind Kumar Mishra, Chitranjan Prasad Singh

Formulating a predictive model for blast-induced ground vibration (BIGV) has always been challenging due to the complex non-linear relationship between the BIGV and its influencing factors. Researchers have used empirical, artificial intelligence methods and numerical modelling methods to predict BIGV. In a dragline bench blasting, a massive quantity of explosives is used compared to other loading machinery, and the height of the bench depends on the size of the dragline. For effective utilization of explosives energy, decking is used to reduce the hazardous effects of blasting. In this paper, an attempt has been made for effective prediction of BIGV, and its mitigation on dragline bench blasting considering a deck length, stiffness ratio, hole spacing to burden ratio, hole depth to burden ratio, the distance of monitoring PPV from blasting site, Schmidt hammer rebound number of the bench to be blasted, and maximum charge per hole to total charge per blast. So artificial neural network (ANN) model and random forest (RF) model have been developed considering the parameters mentioned above. For the statistical performance of the predictive model, the coefficient of determination (R2) value is 0.8895, MSE is 22.84 for the ANN model, and the random forest (RF) model whose R2 is 0.8165 and MSE is 27.18. The sensitivity analysis results show that stiffness ratio, deck length, and Schmidt hammer rebound number are more influential parameters out of the selected parameters. The reduction of ground vibration with the introduction of decking led to a 3 to 15% reduction in ground vibration.

May 15, 2024

By C. Allen, H. Zhang, L. Falk

Shock loss occurs when there is a change in the area of a drift or airflow direction. These shock losses accumulate throughout the ventilation system and will increase the mine resistance as underground development deepens or becomes more complex. Hence, shock losses should be carefully considered when establishing the resistance through a series of branches as they can be a significant contributor to the estimated mine resistance. Using computer software to simulate a ventilation system is common but applying reasonable shock loss factors in the software is not a simple or direct process. Determining shock loss values includes the consideration of historical measurements, application of factors and formulas from literature based on the geometry and complexity of junctions, and the geometry variation at different locations. For example, the shock loss at the bottom of a ventilation raise can be comprised of a 90° bend and a sudden area change. This paper presents an approach for estimating shock loss factors near raise junctions using computational fluid dynamics. Current and future work will also be compared with field measurements. Results from this approach are compared with software defaults as well as classical techniques in published literature and standards.

May 14, 2024

By Taghi Sherizadeh, Samuel Nowak, Kutay Karadeniz, Paul Brooks, Alper Kirmaci, Mina Esmaeelpour, Dogukan Guner, Gunnar Wurst

As mines continue to deepen and become more expansive, active monitoring of larger volumes of rock mass will become more critical to calibrate numerical simulations and to ensure the safety of underground workers. Monitoring larger volumes of rock mass requires low-cost sensors which are simple in construction and installation. In this study, a novel hybrid optical fiber cable (HOFC) designed for use in distributed optical fiber sensing (DOFS) via grouted boreholes was employed to monitor a bulk mining operation in an underground metal mine. The HOFC was successfully used to monitor approximately 2.7 × 103 m3 of rock mass above excavations surrounding a pillar removal area in which six large pillars were removed simultaneously. A total of six measurement boreholes (maximum depth of 22 m) were used to measure strain along the optical fiber during the pillar removal operation using the HOFC, allowing for 70 individual strain measurement points, which were constructed for under one US dollar each. Monitoring of the excavation area took place over a 44-day period after pillar removal. Extensional strains were noted in the areas closest to the removed pillars, while areas of compression were noted directly above the remaining pillar in the area. The results of the case study demonstrate that a low-cost optical fiber strain sensing network can be rapidly installed in a large excavation area and can provide highly sensitive strain measurements in a manner that would be cost-prohibitive via other methods.

May 13, 2024

By Tahereh Rostami, Behnam Khoshandam

In the present paper, the recovery of mixed spent cathodes is evaluated and performed through a hydrogen reduction process. Firstly, the lithium is isolated by the hydrogen reduction process as LiOH at 600 ◦C for 15 min with 10% H2 with a flow rate of 350 ml/min. In the second step, 98.37% Li is recovered through water-leaching of hydrogen reduction products at 100 ◦C for 90 min with 50 ml/g. The filtration residual is reduced by using a carbothermic reduction process and a hydrogen reduction method. The first one is performed under an Ar atmosphere at 900 ◦C for 210 min and the second one is conducted at 800 ◦C for 150 min. The purer products are achieved using the hydrogen reduction method at lower temperatures and shorter holding times compared to a carbothermic reduction process with recovery percentages of 100%, 99.06%, and 70% for Ni, Co, and Mn, respectively. Given the importance of reducing the emission of toxic gases, the hydrogen reduction process is also a promising method for metal recycling. The obtained results also demonstrated that Li, Co, Ni, and Mn can be effectively separated from the mixed cathode material through the hydrogen reduction process as a sustainable and environmentally friendly recycling process. This study provides an impressive understanding of the hydrogen reduction process and valuable guidance for a larger-scale hydrogen reduction process.

May 3, 2024

By Ebrahim F. Salmi, Tan Phan, Ewan J. Sellers, Thomas R. Stacey

Extension of ore pass length has become increasingly critical for optimising energy-efficient underground mining operations. Long and ultra-long ore passes, spanning from 300 to 700 m, can significantly improve the functionality and viability of underground mass mining operations though suboptimal performance has an extremely adverse impact on production. The public domain lacks substantial information regarding the primary engineering, geological, and geotechnical risks and challenges associated with the design, implementation, operation, and maintenance of such long ore passes. Therefore, the aggregation of past experiences and the insights of experts assume paramount significance. An innovative methodology is introduced to address this evident data deficiency and to establish comprehensive guidelines for the resilient design of such lengthy ore passes — combining gap analysis with expert elicitation techniques. This equips design engineers with the necessary tools to formulate and adapt strategies for assessing the numerous challenges and uncertainties that invariably accompany their projects. Expert elicitation techniques are summarised, and a gap analysis is conducted with subject matter experts, from various countries, collating their extensive ore pass design experience, to create a comprehensive list of effective parameters and key risks that must be considered. Quantitative analysis of the survey results enabled the identification and ranking of the numerous factors affecting the design, operation, and maintenance of long and ultra-long ore passes and highlights the complex technical challenges (substantial damage from rock particle impact, increased dynamic mining stresses leading to failure, air-blasts and back blasts, dust, preferential flow, turbulent and dynamic material flow) that are uncommon in shorter ore passes. Additionally, increasing length heightens the probability of intersecting weak rock or discontinuities, leading to a higher risk of structural failure and instabilities. Faulting, folding, and large-scale structures are also critical geological factors to be considered in the design of such structures. The key geotechnical factor is also the rock type surrounding the pass. Experts highlighted the lack of clear guidelines for decision-making, resilient design, and construction so this work suggests future investigations to determine the complex interaction between the effective parameters, using approaches like the rock engineering system, discovery of cascading hazards, and optimal controls.

May 3, 2024

By Étienne Yvenou, Martin Désilets

Le procédé d’électroaffinage du Cu est nécessaire pour atteindre les niveaux de pureté requis pour les applications les plus courantes telles que son utilisation comme conducteur électrique ou thermique.

May 2, 2024