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By B. S. Agbenuvor, R. Morrison, V. Jokovic, C. Antonio

Body breakage usually involves breakage of particles by compression between two surfaces or impacted against a rigid surface, with the latter of interest in this current study. This mode of breakage has been identified to be the most elementary size reduction process and the most effective breakage process in comminution devices. It has been found in the literature that the progenies produced from this form of breakage possess a residual velocity at which they move, after the breakage event. In the pursuit of efficiently utilising applied comminution energy, a laboratory-scale breakage device has been developed to deliver precise specific impact breakage using the concept of a fast-moving hammer and a slow-moving particle to effect breakage. The residual velocities of the progenies from the breakage event may be used to generate secondary breakage without further addition of energy if the particle encounters a stiff obstacle such as a steel plate at right angles to its path. To measure the extent of secondary breakage, the steel wall of the device was lined with a rubber material to suppress the second set of breakage events. The performance of the new device is analysed, based on calculated t10 values and measured residual velocities of the moving daughter particles. Testing involving anvils showed a much finer PSD and higher t10 compared to the test involving rubber lining. This finding is corroborated by the measured residual velocities of the progenies. The resulting energies calculated from the measured residual velocities of the progeny were found to be approximately 42-88% of the primary specific impact energy. This retained energy was found to be sufficient for secondary breakage. Keywords: Impact breakage, residual velocity, secondary breakage, energy utilisation

Jan 1, 2020

By M. Rudolph, A. D. Renno, H. Wu

In this study, synthetic pure cassiterite and cassiterite doped with Fe were successfully produced by sintering. Their crystal structure and chemical compositions are characterised by optical microscopy, X-ray powder diffraction (XRD) as well as scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) based chemical composition analysis. The electrostatic behaviour of synthetic and natural cassiterite was studied by electrophoretic measurements. Their floatability was studied by microflotation with two types of anionic collectors. Results show that the cassiterite floatability with these collectors behaves differently and lead to two opposite results: Natural cassiterite (enriched with Fe) > undoped pure SnO2 by using sulfosuccinamate (Aerosol® 22) Undoped pure SnO2 > Fe3+ doped > natural cassiterite (enriched with Fe) by using styrene phosphonic acid (SPA). Keywords: Synthetic cassiterite, lattice impurities, flotation, zeta potential, Aerosol® 22, styrene phosphonic acid

Jan 1, 2020

By G. C. Lindeque

"A downward trend in tyre life on haul trucks at an open pit iron ore mine prompted an investigation into the current tyre management strategy in order to improve tyre life. ‘Best practice’ was compared to the current tyre management strategy at the mine to determine aspects that could be improved. Aspects that showed significant room for improvement included employee tyre awareness, tyre pressure maintenance, and road conditions. For each of these aspects a plausible alternative was suggested.A new tyre management strategy was formulated as a step-by-step guide on how to implement the proposed changes. Each step introduces new initiatives but at the same time builds on the previous step’s success. A sensitivity analyses was performed to determine the impact of the proposed changes, with the variables being the reduction in the percentage of premature tyre failure, and the reduction of the site wear rate.The ‘most likely’ scenario showed an increase in tyre life of 41% for the Komatsu 730 trucks and 105% for the CAT 777 trucks if the entire tyre management model is implemented. This would result in a possible annual saving related to tyre usage of R9.2 million. OverviewThe study focused on the tyre life on the main haul fleet at an open pit iron ore mine. The haul fleet consisted of 17 Komatsu 730 (180 t) haul trucks and 12 CAT 777 (90 t) haul trucks.The haulage operation consists entirely of tyre-based haul trucks. Five per cent of the total mining budget is related to tyre costs. Since 2012 there has been a steady decrease in tyre life as measured in operating hours (Figure 1) due to the high percentage of tyres that fail prematurely. In 2014 a total of 41% of all tyres failed prematurely and 61% were classified as ‘worn out’."

Jan 1, 2016

By and M. V Roper, H. N. Engelbrecht

Quality control interventions emanate from process upsets and trends that move product quality beyond the natural variation expected in a stable process. The ability to detect upset conditions and react in an effective manner protects both resource utilisation and compliance to specifications. Product quality control on coal processing plants traditionally relies on the reference (combined sampler and laboratory) system to measure product qualities. The introduction of online analyser (OA) technology, applied in different configurations, creates a second source of measurement information for control decision making. The case study was done on the primary sample stream of the final product stream at Exxaro’s GG7 and 8 plants, part of the Grootegeluk complex. It explores the OLA system’s ability to meet the OEM performance guarantee, perform equally to the reference system without analytical delay time, and assesses the effort to achieve this performance in a by-line analyser (BLA) configuration. In the paper, a conceptual comparison of the two measurement systems is done and the theoretical and practical comparison of measurement performance is discussed. Results demonstrate that the OA outperformed the OEM’s performance guarantee and achieved similar levels of performance to the reference system without the response delay. Keywords: Online analyser (OLA), by-line analyser (BLA), coal quality measurement, measurement performance

Jan 1, 2020

By M. Bryson, G. Marap, M. Ntlhane, M. D. Hlahane

This study investigated flotation of phosphate from a low-medium grade 8-12% P2O5, 65-73% SiO2 sedimentary phosphate ore from Kropz Elandsfontein (herein referred to as Elandsfontein) in South Africa. Quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) was used to determine apatite grain size distribution, liberation and mineral association in the F2 horizon sample. The mineralogy indicated that apatite was liberated and for the Elandsfontein plant to operate at the design throughput, the flotation feed has to be milled to a coarse grind ranging between 300 μm and 425 μm. Reverse flotation process routes using varying reagent dosages, and flotation feed top sizes that could possibly yield a final product of 31% P2O5,10% SiO2 at a reasonable +70% P2O5 recovery were investigated. Based on the results, a split circuit of coarse (-300+212μm) flotation and fine (-212+20μm) flotation, was mostly preferred as compared to treating the whole ore. A final combined concentrate of 31% P2O5 and 10% SiO2 with P2O5 recovery of 84% could be produced from the reverse split circuit. The robustness of reverse flotation for both coarse and fine fractions was further investigated. Reverse flotation of the fines fraction was found to be robust and produced a final product of 31% P2O5. It was however more challenging to achieve the required product grade and recoveries on the coarser fraction (-425+212μm), suggesting that reverse circuit was not adequately robust at fractions coarser than 300μm. Keywords: Phosphate, sedimentary, reverse flotation, particle size

Jan 1, 2020

By C. O’Donova, E. Adam, L. A. Torres-Cruz

High-profile failures of tailings dams illustrate the significant safety challenge they pose. The decant pond of such facilities plays an important role in their mechanical stability. This study investigates the feasibility of using public multispectral data collected by the Sentinel-2 satellite mission to monitor the area of the decant pond. The Sentinel-2 mission has a revisit time of 5 days and the data used herein has a spatial resolution of 10 m/pixel. We considered two water-detection metrics: the normalized difference water index (NDWI) and the near-infrared (NIR) reflectance. Implementation of the method at a South African platinum tailings dam illustrates the capabilities and limitations. Public, sub-metre resolution true-colour imagery served as validation data. There is good agreement between pond area measurements based on Sentinel-2 and the validation imagery. These results suggest the feasibility of using Sentinel-2 data to supplement the monitoring of the decant pond.

Apr 2, 2022

By Z. Luo, W. Chen, Y. Zhao, Y. Fu, L. Dong

The gas-solid dense-phase fluidised bed includes a complex multiphase fluid-particle system; different complex exchanges significantly affect the stability of the fluidised bed. To elucidate the characteristics of fluidisation in a gas-solid dense-phase fluidised bed, this study used experimental performance tests to obtain the static density characteristics, and the attachment and flow characteristic of the dense medium. The results indicate that the bulk density of the dense medium increases first and then decreases with the increase of particle size. The airflow rate difference is used to quantify the wall attachment characteristics of dense medium and the average pressure gradient in the axial direction of the bed is approximately 20 Pa/mm under the fluidisation results. At the same settlement location, with the decrease of fluidisation number, the settlement velocity of large and small particles becomes slower, the boundaries of settlement displacement and location probability are gradually disrupted, and the falling velocity of particles with a radius of 20 mm is faster than that of materials with a radius of 15 mm. This work also established a theoretical basis for regulating the stability and separation characteristics of gas-solid dense-phase fluidised bed. Keywords: Fluidised bed, different size particles, fluidisation characteristics, flotation bubbles, settling motion

Jan 1, 2020

By D. F. Malan, P. J. Le Roux

Almost no work has been published on the strength of pillars in mines exploiting the LG6/LG6A chromitite bands in the Western Bushveld Complex. The strength of these pillars is unknown, and the hard rock industry still uses the Hedley and Grant formula. Numerical modelling, using inelastic constitutive models, may be of some value in estimating the pillar strength, but this approach is difficult and prone to errors as many assumptions are made. This paper explores the alternative approach of the back-analysis of actual LG6/LG6A mining layouts, using displacement discontinuity codes to simulate the average pillar stresses on a mine-wide scale. From this, and underground observations, a ‘minimum’ pillar strength (K-value in the pillar strength formula) can be estimated. The codes TEXAN and Map3D are both used in the paper to simulate the actual pillar shapes and sizes in an LG6/LG6A mine. The results are encouraging as the two codes produced similar APS values for a complex pillar geometry. An estimated K-value of 77 MPa was determined for the LG6/LG6A pillars in this particular area. This is more or less similar to earlier work done for the UG2 chromitite seam, but higher than the K-value of 39 MPa for a linear formula obtained by other workers for LG6/LG6A pillars. Caution should therefore be exercised before using this higher value for all areas. The effect of element sizes and explicitly simulating the effect of the surface for shallow pillars is illustrated in the manuscript using both codes. The need for actual pillar observations and an iterative design process, which cycles between modelling and observations, is also emphasized.

Nov 27, 2024

By I. Wigden

This paper discusses system integration and installation of High-Tec systems in underground mines. ABB has the capability to be a System Integrator and co-operates with partners in different areas of technology. Today it is difficult to find one Company that is responsible for the complete Automation System. The design of the system is also dependent on the caving procedure that is currently being used in mines. Most of the engineering must be done during the feasibility study and the design phase. Any mistakes made during these phases will be costly to rectify in the commissioning phase. The paper will also include a presentation of the benefit of using Automation in an Underground Mine, and the importance of integration with the people component. Most of the experience and discussions in this paper are from different technologies that have been developed in Scandinavia and adopted from LKAB in Kiruna. The author of this paper was responsible for the Automation projects in Kiruna Mine during1994 - 1999. These projects include: • Broadband communication of data, audio and compressed video in one data stream. • Control System for Haulage -1045m • Automation of Load Haulage and Dumping machines (LHD) • Control of Production Drilling Rigs from a Central Control Room.

Sep 1, 2001

Sampling In The Coal Industry Exploration, Mine, Met and Environmental Sampling EMMES 2005 3, 4 November 2005

Jan 1, 2005

By G. E. Blight

Several aspects of the behaviour and properties of backfills consisting of cemented cyclone underflow tailings are illustrated by means of examples, and guidelines are given on the optimization of the performance of cemented fills. The stretch characteristics of the geofabric used to contain freshly placed backfill are described, as well as the relationship between these characteristics and the forces acting on retaining barricades. The properties required to achieve a self-supporting, stable free face in cemented backfill are explored, and a graphic relationship between stable height and shear strength is presented and compared with that for uncemented (classified) tailings. After a description of the characteristics of Witwatersrand quartzite gold-tailings backfill and commonly used cements, the process of drainage and air entry into backfill is outlined. Following this, the early-age gain in strength and the shear-strength characteristics, as well as the compressibility characteristics of cemented backfill, are described. Two phenomena that are potentially damaging to cemented backfill are seismic effects (or blasting acceleration) and the closure that takes place during the curing of cement. Investigations show that neither of these phenomena is actually significantly deleterious to gold-tailings backfill: liquefaction does not Occur as a result of seismicity, and hydration of cemented fill is not significantly impeded by closure.

Jan 1, 1996

By B. Oladipo, E. Govender-Opitz, T. V. Ojumu

Bioleaching, one of the several important processes of biohydrometallurgy is an accepted technique for the extraction of desired metals from sulphide ores. Although the mechanism is well understood, the slow metal extraction rate due to passivating layer and ferric ion precipitation, especially in a typical chalcopyrite leaching, impact negatively on the overall efficiency of the process. Iron precipitates are common in many biohydrometallurgical operations and these precipitates represent the exit route for undesired iron, alkali ions or sulphate ion from the processing circuit. While there have been reports on approaches to slow the formation of these precipitates by manipulation of various operating conditions such as pH, redox potential and temperature, the precipitates become highly significant over the long term in the continuous operation of bioleaching and may render heap impermeable. Although there is evidence supporting the nature of the passivation to be precipitates of iron, their scavenging mode of reducing extraction efficiency is still not well understood. This paper thus discusses iron precipitation in biohydrometallurgical processes, including its formation and significance on bioleach processes. The paper also details the associated passivating species identified with heap bioleaching of sulphide minerals and provides some insight into sorption mechanism that limits metal recovery in a typical bioleach operation. Keywords: Iron precipitation, bioleaching, chalcopyrite, passivation, jarosite, metal sorption

Jan 1, 2020

By L. A. Balzan, M. Kalicinski, F. Nieuwenhuys

GEOSCANs on belt analysers have been widely utilised in iron ore for nearly two decades. Since the first installations in 2003, the availability of accurate and reliable grade data has become standardised across iron ore mines in the Northern Cape, where various streams are monitored continuously to ensure the optimal functioning of plants. Assmang Khumani has been at the forefront of technology adoption and has implemented 19 GEOSCANs at various locations throughout the plant, monitoring run-of-mine, stockyard feed, beneficiation plant feeds, and products. Over the years, collaborative advances in the technology have allowed for numerous benefits and gains to be made. In recent times, there has been a concerted effort on the development of analysis for phosphorus in the material flows, and based on Scantech's experience in the phosphate industry, this element has now been calibrated to achieve statistically acceptable and repeatable accuracies for real time analysis of this element on many of Khumani's GEOSCAN analysers. This paper provides an overview of GEOSCAN use at Khumani, while focusing on the development of phosphorus analysis. A case study of analysis results is presented for a range of analysers that have been calibrated for this element, as well as a discussion on the benefits obtained as a result of this analysis. Keywords: Online analysis, real-time, process control

Jan 1, 2020

By J. D. Swanepoel, S. Horn, C. J. Badenhorst

Diesel particulate matter (DPM) is the particulate component of diesel exhaust, which includes diesel soot and aerosols. When released into the atmosphere, DPM can take the form of individual particles or chain aggregates, with most in the invisible sub-micrometer range of 100 nanometres. The main particulate fraction of diesel exhaust consists of fine particles and because of their small size, inhaled particles may easily penetrate deep into the lungs. The rough surfaces of these particles make it easy for them to bind with other toxins in the environment, thus increasing the hazards of particle inhalation. DPM is a significant health hazard in underground mining operations, where the use of dieselpowered equipment in confined spaces can lead to high levels of exposure among people working in these environments. Classified as a carcinogen by the International Agency for Research on Cancer (IARC), DPM has been linked to severe health effects, including respiratory and cardiovascular diseases, as well as an increased risk of lung cancer. Effective management of DPM is essential not only for protecting people’s health but also for ensuring regulatory compliance, maintaining operational efficiency, and safeguarding the long-term viability of mining companies.

Mar 5, 2025

By T. Tamenti

The purpose of the project was to conduct a feasibility study to determine if the current operating bottom dump trucks that haul coal should be replaced with rear dump trucks. The engineering availability of the bottom dump trucks was lower than targeted while the operating costs are the highest of all coal haulers within the Anglo Coal opencasts. To determine if it is feasible to replace the current bottom dump trucks with rear dump trucks, a production profile simulation was conducted to determine the number of rear dump trucks that would be required to meet the annual coal hauling requirements. The total capital and operating costs of these rear dump trucks were also determined using a total cost of ownership model. These were compared with the current costs of the bottom dump trucks to determine if it is financially feasible to replace the bottom dump trucks with rear dump trucks. Having considered the capital outlay that would be required to replace the bottom dump trucks with rear dump trucks as well as their respective operating costs, it was concluded that the current bottom dump trucks should be replaced with rear dump trucks. Other factors were considered in coming to this conclusion.

Jan 1, 2007

By N. D. Fernandes

Labour-intensive narrow reef stoping, as traditionally practised in South African gold and platinum mines, is almost unique in the modern first-world mechanized mining environment. Shortcomings of the system include the ever increasing cost of labour, a cap on achievable productivity and a poor safety record, particularly in the field of rock-related accidents. In the absence of sustainable alternative technologies, the South African mining industry has spent millions of rands improving the present system, focusing on improving workplace safety. This paper details the changes to stope support at Impala Platinum?s Rustenburg operations, and the impact on rock-related safety performance. Keywords Stope panel support, narrow reef stoping, improving workplace safety.

Jan 1, 2011

The following comment has been received from Mr A. D. Osche* on the above paper, which was published in the Journal in October 1977 (vol. 78, no. 3, pp. 51-62). Obituary: T. K. Prentice The Institute records with deep regret the death on 30th January of its senior surviving Past President, Mr Thomas Kennedy Prentice, at the age of 83. Book reviews R. A. Rich, H. D. Holland, and U. Petersen. Hydrothermal uranium deposits. (Developments in Economic Geology, vol. 6). Amsterdam, Elsevier Scientific Publishing Co., 264 pp. with 77 illustrations and diagrams, 30 tables. U.S. $34,75. M. David. Geostatistical ore reserve estimation. Amsterdam, Elsevier Publishing Company, 1977. 364 pp. World mineral industry The Australasian Institute of Mining and Metallurgy is celebrating its sesquicentenary in 1979. A conference will be held in Perth from 13th to 18th August, 1979, as part of the celebrations, the theme being 'Australia's Role in the World Mineral Industry'. Engineering teaching staff UNESCO has extended its technical assistance to the Venezuelan government in the training of engineers to suit the rapidly developing economy of the country. UNESCO vacancy Vacancy for a post of expert under the UNDP. (1) Title of post: Expert in metallurgical engineering. (2) Duty station: Instituto Universitario Politecnico of Ciudad Guyana (Venezuela). Shell Design Awards The annual Shell Design Awards, organized by the Design Institute and sponsored by Shell South Africa (Pty) Ltd, focus attention on achievements in South African design.

Jan 1, 1978

By T. Tamenti

The purpose of the project was to conduct a feasibility study to determine if the current operating bottom dump trucks that haul coal should be replaced with rear dump trucks. The engineering availability of the bottom dump trucks was lower than targeted while the operating costs are the highest of all coal haulers within the Anglo Coal opencasts. To determine if it is feasible to replace the current bottom dump trucks with rear dump trucks, a production profile simulation was conducted to determine the number of rear dump trucks that would be required to meet the annual coal hauling requirements. The total capital and operating costs of these rear dump trucks were also determined using a total cost of ownership model. These were compared with the current costs of the bottom dump trucks to determine if it is financially feasible to replace the bottom dump trucks with rear dump trucks. Having considered the capital outlay that would be required to replace the bottom dump trucks with rear dump trucks as well as their respective operating costs, it was concluded that the current bottom dump trucks should be replaced with rear dump trucks. Other factors were considered in coming to this conclusion.

Jan 1, 2007

By S. K. Murphy

A partial shaft pillar extraction project was embarked on at a mine in the West Wits mining region in South Africa. Prior to the extraction, a rock engineering assessment was conducted with the main objective being to establish which areas of the shaft pillar could be extracted without unduly affecting the stability of major infrastructure within the shaft pillar. Standard numerical modelling methods were used to conduct this assessment and several areas were identified for extraction. However, during the extraction process, it was found that the infrastructure was affected more than was originally predicted by linear elastic modelling. In addition to this, several large events resulted in far more large aftershocks than would normally be predicted. In order to gain an understanding of this phenomenon, seismic data was integrated with numerical modelling as follows: > The seismic data in the form of displacements was integrated in 3D space within the model to assess the effect of static stress changes associated with seismic activity > Data from large events was integrated onto specific structures, where displacements associated with large events were integrated onto the plane of structure in question. This paper describes the methodology and results obtained from each of the above processes and include insights into the mining process that were previously unfathomable using standard linear elastic numerical modelling. The way forward for this rock engineering assessment of partial shaft pillar extraction is also discussed.

Jan 1, 2012

Metso Minerals Cisa have developed VisiofrothTM - a system which calculates parameters of the froth surface using vision from remote cameras mounted about individual flotation cells. The parameters calculated from this system can be utilised within process control strategies to achieve stabilisation or optimisation of the flotation process. As part of a JKMRC AMIRA P9 field campaign, froth vision was collected from various cells operated at different air rates and froth depths within Rio Tinto's Northparkes copper roughing and scavenging circuit. At the same time, samples were collected to determine the cell metallurgical performance at each operating condition. These froth images have been processed using the VisiofrothTM system with froth velocity, bubble size, froth collapse rate and various froth colour parameters calculated. These parameters have been compared to the measured concentrate flow and concentrate grade produced at each condition. This analysis shows that the concentrate tonnage flow is strongly correlated with froth velocity whereas the concentrate grade is best correlated using froth velocity in combination with a bubble stability parameter which affects the bubble size distribution on the top surface of the froth. This paper summarises the results from this analysis as well as an overview of the VisiofrothTM system and the parameters that are measured by the software.

Jan 1, 2007