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By Y. Cao, C. Li, A. Song

Bubble size plays a key role in determining flotation efficiency. Bubbles can be formed by passing air through pores. Bubble detachment from a pore is driven by lifting forces including buoyancy force and momentum force. Enhancing the momentum force is the key to accelerate bubble detachment and to minimise bubble size. Recent studies show that replacing steady air with oscillatory air supply could significantly decrease bubble size by enhancing the momentum force. To date, the underlying mechanism for the improved momentum force with oscillatory air supply is not yet clear. This work, for the first time, developed a qualitative model for the momentum force as a function of frequency, on/off time ratio and gas flow rate. It was found that the momentum force was positively correlated with the frequency as well as the air flow rate, and was negatively related to the on/off time ratio. The relation between bubble size and these operating parameters was also investigated. Keywords: Flotation, bubble size, momentum force, modelling, oscillatory air supply

Jan 1, 2020

By J. Hadjigeorgiou, Y. Potvin

In a benchmarking paper published in the SAIMM Journal, Potvin and Hadjigeorgiou (2008) reviewed ground control strategies to manage large deformations in underground hard rock mines. Significant differences were identified in the design and acceptable tolerance between civil and mining engineering practice for squeezing ground conditions. Variations were also noted in ground support strategies between Australian and Canadian mines. In this paper we review progress in design methodology and ground support practice since 2008, including the availability of more effective deformation monitoring, new design tools, greater access to yielding ground support elements, and better installation practices. An improved understanding of technical and practical issues associated with squeezing conditions has led to the development of ground support guidelines for a range of squeezing ground conditions in hard rock mines.

Jul 5, 2023

By P. K. Hofmeyr

Traditional fire assay dates back over 3000 years and has changed very little over that time. The only improvement is to replace the gravimetric finish with dissolution of the Precious Metal bead followed by AA or ICP analysis of the solution. The newly developed FIP A (Fast In-line Fire Assay) method allows full automation of the fire assay process from sample preparation to spark analysis of the Pb button. This results in fully quantitative analyses for Pt, Pd, Rh, Ru, lr, Au and Ag in typically less than an hour after a sample is entered into the system. Detection limits are theoretically Pt 0.08 ppm, Pd 0.002 ppm, Rh 0.002 ppm, Au 0.08 ppm and Ag 0.002 ppm but in practice the lower measurable limits are about double these figures. Few opportunities have been available to present data obtained using the FIFA system as all FIFA laboratories have been in the domain of a Pt mining company which prefers to keep all Pt analytical matters confidential. However, IMP has recently participated in the round robin exercise to establish recommended values for a new series of Merensky Reef and UO-2 Layer reference materials produced by African Mineral Standards. The precision of the results was excellent being on average Pt 2.05%, Pd 1.25%, Rh 4.08% and Ru 4.94% being expressed as Relative Standard Deviation. The excellent precision is a reflection of the efficient collection of POEs in the Pb buttons and the homogeneity of the Pb buttons. However, the accuracy was not as good. The poorer accuracy is interpreted as the calibration of the spectrometer not being as good as desired due to the difficulty in acquiring a suitable range of standards with reliable recommended values for the PGEs. The most recent spectrometer was calibrated with the greatest care and produced slightly better results for Pt, Pd and Rh and slightly worse for Ru.

Jan 1, 2014

By W. Gabryk

A large new underground platinum mining project required that all different mining options were investigated during an option study before proceeding to the prefeasibility stage of the project. The capital project team identified 21 different options requiring investigation. These options considered 10 different access methods and 4 different mining methods. Each of the 21 options required a mine design, a valid production schedule, and the associated economics in order to facilitate a comparison on project Net Present Value (NPV) and other metrics. The project sponsors required this work to be completed in 3 months and therefore the project team decided to adopt an object-oriented modelling approach as implemented by Cyest Corporation. This would allow all 21 options to be valuated within the tight time frame due to the generation and re-use of templates. Standard objects were configured into templates containing the mine layout, design, and scheduling logic. These templates could then be assembled into a model to represent the option being investigated. The adoption of rules-based design and production scheduling then allowed for the rapid generation of a valid production schedule for each option with different iterations of varying production ramp-up and mining efficiency assumptions. The activity-based operating costs, labour, and capital were also linked to the standard templates such as a half level or barrel, which were then replicated to represent the overall mine structure for each option under consideration. Using this approach for each option, a full production schedule was produced per mining activity, the operating costs were calculated using activity-based costing, an infrastructure capital expenditure estimate was determined, the development capital requirements costed, and an overall NPV determined. This options study was completed in an unprecedented 10 weeks and a recommendation was put through to the Business to take three of the options to the next study phase.

Jan 1, 2012

By K. M. Uderstadt, G. C. Howell, L. de Villiers

This paper highlights the advantages of developing tailings storage facility-specific water balances. A case study illustrates how such focused analysis provides clearer insights into water storage and release, supporting improved conservation, regulatory compliance, and enhanced stability of tailings storage facilities. A robust water balance informed by up-to-date hydraulic data is essential for long term management. It is proposed that tailings storage facility-specific water balances should be regarded as standard practice in mining.

Apr 8, 2026

A powerful, interactive metallurgical process simulator for use on micro- computers has been developed in the Department of Metallurgy and Materials Engineering at the University of the Witwatersrand. MICROSIM presently allows simulation of all ore-dressing flowsheets and a selection of hydrometallurgical unit operations, and is extendable to all such processes. MICROSIM is written in Pascal. This modern language provides very versatile data structures which can be effectively used to solve the major problem in generalised simulation programs, namely storage and transmission of data relating to liquid and solid phases. Dynamic memory allocation allows optimal utilisation of computer storage space. The simulator utilises very efficient precalculation algorithms that determine the tear streams for optimal sequential modulator calculation convergence. Microcomputer graphics simplifies flowsheet specification, and form-filling data capture with supplied default values eliminate most common input errors.

Jan 1, 1987

By L. M. Tavares, H. A. Petit, P. P. Cavalcanti

Iron ore pellets experience degradation during handling due low energy impacts and stresses. These impacts lead to volume or surface breakage of the pellets, creating fine particles that accumulate along the process. Some of the particles are in contact with the air and are dragged as dust into the workplace or into the atmosphere. The aerodynamic size of the particles allows them to be potentially inhaled by the workers or to be carried to nearby communities. Dust emission becomes critical at specific locations, such as transfer chutes and stockpiles. This work models the dust generation that occurs in an iron ore pellet stockyard using a methodology that combines experiments to quantify the degradation of the pellets to mathematical modelling of the dust emission mechanisms in the stockyard. First, laboratory tests were used to characterise the amount of mass and the particle size distribution of the dust generated by degradation under controlled conditions. Second, the flow over a stockpile of an iron ore pellet company was simulated with the aid of computational fluid dynamics (CFD) simulations. Third, semiempirical equations linked the data generated by simulations and laboratory tests to estimate the dust emission in the stockyard. Finally, results were validated with measured field data, obtained with a novel online measurement tool. Results suggest that the approach is able to predict dust emission with sufficient accuracy and can be used for further implementation in the management of operations and decision making in order to reduce the environmental impact of the process. Keywords: Iron ore pellets, abrasion, dust emission, mathematical modelling

Jan 1, 2020

By K. Woodward, Y. Potvin, B. McFadyen, M. Grenon

Open stoping has become a popular mining method in hard rock mines, not only due to the safety of the method as a non-entry approach, but also because of the high extraction rate and low costs. At mine sites, stope performance is evaluated by calculating stope overbreak using the stability chart. However, limitations of the stability chart regarding the precision of the predictions, nonconsideration of factors such as the influence of blasting, and the exclusion of underbreak have led to non-optimal designs. The capabilities of today's computers have increased the amount of data being collected and the power of models being built. This article presents a step towards a new stope design approach where stope overbreak and underbreak are measured and georeferenced using octrees at an approximately cubic metre resolution and predicted using multivariate statistical models (partial least square, linear discriminant analysis, and random forest). Results show that overbreak and underbreak location along the design surface and their magnitude are predicted with good precision using a random forest model. These predictions are used to build the expected geometry of the open stope. The resolution of the data and the use of multivariate analysis has enabled the prediction of variation in stope performance along the design surface, going well beyond the simple qualitative per stope face prediction provided by a traditional stability chart approach.

Jun 5, 2023

By E. L. Forner, G. M. Miller, J. Scheepers, A. J. du Toit

"The sizing, designing, and costing of copper electrowinning circuits requires an in-depth understanding of the fundamental relationships between circuit parameters and the practical operation requirements. The aim of this investigation was to optimize total copper electrowinning project cost by mapping the operating limits of key mechanical equipment. The model was compiled by mapping various cellhouse layouts in terms of number of cathodes per cell, crane productivity, stripping machine productivity, and rectifier–transformer (rectiformer) sizing using data tables for sensitivity analysis. These parameters were then collated and evaluated on a cost by size basis. The model provides an optimum band of operation for cellhouse productivity and project capital cost for a typical range of production throughputs, from 10 kt/a to 200 kt/a cathode copper. The information may be used as a high-level selection guide to assist with identifying a costeffective copper electrowinning circuit design for a specific production rate. The data was validated and compared with existing copper electrowinning cellhouses around the world that typically install no more than 84 cathodes per cell. IntroductionThe sizing, designing, and costing of copper electrowinning (EW) circuits require an indepth understanding of the fundamental parameters as well as the practical requirements to optimize cellhouse productivity and capital cost. Although a significant amount of work has been done designing new copper electrowinning circuits, an in-depth evaluation of world operating data reveals that the number of cathodes per cell, which affects cellhouse layout and productivity, is not consistent for a specific production rate (Anderson et al., 2009; Robinson et al., 2003, 2013). Based on this premise, Kafumbila (2017) suggested that there are unanswered questions, such as ‘why are the numbers of cathodes per cell different for copper production rates of 20 kt/a and 40 kt/a?’In this paper, data tables are employed to map the operating limits and costs of key Cu EW equipment. An overall Cu EW project cost map is then compiled by collating optimum cellhouse layout (number of cathodes per cell), optimum crane productivity, optimum"

Nov 1, 2018

By S. Andika, O. A. Putri

Maintaining fleet productivity, which consists of balancing loader and truck performance, has always been a challenging task. An automatic dispatching system (ADS) is implemented to help monitoring fleet condition and assign trucks to a designated loader. Integrated data from real time Global Positioning System, Vehicle Health Monitoring System, and other production related data are acquired to support the ADS. However, the abnormal truck cycle has been the main culprit which resulted in unnecessary loader hanging time and trucks queuing time. Hanging and queuing time accounted for 2.34 and 2.07 minutes respectively per loading cycle or equal to 2,861 loose cubic metres per fleet per day production losses. Using integrated dispatching system data, the authors conducted research to study a truck’s hauling cycle that affects fleet productivity. The data is modelled to obtain the arrival rate pattern in a front loading area by adopting the queue theory algorithm. This paper aims to understand the potential pattern of a truck’s cycle abnormality and to resolve its occurrence.

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 L. A. Jagger

The world?s second largest producer of platinum, Impala Platinum Ltd, approved two new twin shaft projects at the end of September 2004, Nos. 16 and 20 Shafts. Both shaft projects are stand-alone entities and are being sunk from surface. Previously Impala had embarked on a strategy of extending the life of its third generation shafts by means declines. No. 16 Shaft is the first of a new fourth generation shaft complex, while No. 20 Shaft is the last of the third generation type shafts in the so-called shallow to intermediate mining zone. This paper details the basic designs of each project and covers the initial implementation. Although both projects are twin shaft systems, the access methods from the shafts to the reef horizon differ. Initiatives implemented to speed up the projects are also briefly covered.

Jan 1, 2006

By S. Mohanta, B. C. Melkap

"SynopsisDry beneficiation of coal by air dense medium fluidized bed is an emerging trend. It is widely believed that the particle size of the medium has a significant effect on the separation efficiency. This investigation demonstrates that medium particle size has a major effect on separation efficiency. Experimental results show that different size fractions of the same feed respond differently to the same size fraction of medium solids. Furthermore, a particular size fraction of feed coal responds differently with different size fractions of medium solids. The Ep values and overall metallurgical performance parameters, obtained from experimental results, clearly indicate the superior performance of an air dense medium fluidized bed separator when using –150+106 µm magnetite powder as the fluidizing medium. These observations reinforce the importance of sizing the medium particle size for the air dense medium fluidized bed.IntroductionIn an air dense medium fluidized bed (ADMFB), a fluidizing bed of a particular density is created by suspending solid particles in an upward air flow. A feed containing coal particles of different densities is introduced into this fluidizing bed. The particles with relative density less than the bed density float on the top of the bed, while particles denser than the bed density sink through it. Since there is a general correlation between ash content and density of coal particles, it is possible to remove ash-forming impurities from a raw coal to the required level by regulating the density of the fluidizing bed. Recently, the ADMFB process has received significant attention world-wide for its specific advantages of low operating cost and less restrictive for small capacities (Luo and Chen, 2001; Houwelingen and de Jong, 2004; Dwari and Hanumantha Rao, 2007; Sahu et al., 2009; Mohanta et al., 2012). This process is not recognized as a well-established industrial practice because of the availability of efficient wet processing technology. However, with the revival of interest in dry beneficiation of coal in general, and ADMFB in particular, there is a concerted effort to improve the efficiency of the ADMFB process, and successive improvements have made the process a competitive and viable option for beneficiating coal."

Jan 1, 2015

By K. Cole, D. Mesa, P. Brito-Parada, M. R. van Heerden

Turbulence in mechanical flotation cells, achieved via an impeller, plays a key role in keeping particles in suspension, dispersing air bubbles, and promoting particle-bubble collision. However, studying the hydrodynamics of a flotation cell is not a simple task, due to the complex nature of flotation systems which are opaque, turbulent, multiphase and polydisperse in terms of particle and bubble sizes. In this paper we study the impact of impeller design modifications on the hydrodynamics of a continuously overflowing bench-scale flotation tank. To this end, two different impeller designs, with and without a stator, were assessed using Positron Emission Particle Tracking (PEPT). This allowed the authors to determine, for the first time, the effect of an impeller design on the behaviour of both hydrophobic and hydrophilic particle tracers. It was experimentally observed that the use of a stator modifies the hydrodynamics within the flotation cell, distorting the lower mixing loop that is characteristic of axial impellers. The role of the stator in dissipating turbulence results in reduced particle velocities outside of the impeller-stator region. These results have important implications for flotation cell design and are discussed in the context of the impact that different designs have on particle movement, flotation hydrodynamics and, ultimately, flotation performance. The data set generated is also extremely valuable for modelling and validation purposes. Keywords: Flotation, flotation tank, impeller design, rotor, stator, PEPT, hydrodynamics

Jan 1, 2020

By S. Nana, M. B. Cortie

Duplex stainless steels containing high levels of manganese and copper and lower-than-normal levels of nickel were produced and evaluated. The experimental alloys containing 3 per cent copper by mass could not be successfully hot-rolled. Alloys containing less than 2 per cent copper could be hot- and cold-rolled without difficulty. The wrought experimental alloys that contained copper were found to offer some advantages over the 2205- type duplex stainless steel in sulphuric acid at 52°C. Resistance to pitting attack was governed primarily by the chromium, molybdenum, and nitrogen contents, and one of the experimental alloys was superior to the 2205-type alloy in the ferric chloride test. It is concluded that manganese is a useful substitute for nickel in duplex alloys, but that further work is required before the present alloys, or variations of them, could be commercially viable.

Jan 1, 1993

By C. Bergmann, V. Ross

The concept of underground ore processing, in which valuable ore and waste are separated at a coarse particle size to improve the economics of operations and minimise the environmental impact, seems attractive from a sustainability perspective. Perceived benefits of such an operation include energy and cost savings due to a reduced hoisting load, a reduced footprint of surface operations, and using material for backfill that has not been contaminated by process chemicals. Progress in the South African mining industry in this area has however been below expectation, and opportunities for underground processing in deep, narrow reef operations were therefore explored by an Excel-based simulation with sensor-based sorting (SBS) as concentration technology. Various PGM mining scenarios incorporating factors such as the mining rate, depth of operation, and effects of dilution and particle size on the metallurgical efficiency, were compared. Whilst these initial results can be regarded as indicative only, they have shown that the economics of such an operation are driven by selective mining at significantly higher rates than achievable with conventional methods. Also, the cost of preparing, conveying and placing rock backfill will need to be lower than that of hoisting waste and depositing it on a surface dump. Another aspect to be addressed is whether ore sorting machines would be able to operate under harsh conditions underground and what provision would need to be made to ensure their efficient operation. Further investigations should focus on refining costs, incorporating environmental considerations in the modelling of economics and sustainability, and compare greenfields with brownfield scenarios. Keywords: Ore sorting, hoisting, backfill, mining rate, economics simulation

Jan 1, 2020

By T. Bezuidenhout, J. D. Visagie

In recent years the requirements for a barrier system between the waste body of tailings storage facilities (TSFs) and the natural ground (NG) has necessitated the use of HDPE-lined TSFs in South Africa and other countries. The addition of an HDPE liner creates an interface between, inter alia, the tailings and surrounding soils on the footprint of the TSF. It is known that low-strength materials beneath slopes can cause slope instability. One method which can theoretically mitigate this instability of a lined TSF is the addition of stability bunds along the footprint of the TSF. Altering the profile of the footprint to include slope changes which oppose the direction of the failure creates passive slices in a limit equilibrium analysis. The passive slices actively oppose the movement of active slices, resisting the mobilization of tailings, thus greater active slice forces are required to develop a failure surface running along the liner interface. Two scenarios are presented and compared. The first scenario retains the ground profile unaltered and the second scenario includes stability bunds along the ground profile. An in-depth assessment is made of the interslice forces and the interface shear stresses for each scenario. The theoretical background is discussed in greater detail to determine the mechanisms of reinforcement provided by the bunds.

Jun 2, 2022

By G. J. McTeer, D. J. Rioux

Teck Metals Ltd operates an integrated zinc-lead complex at Trail, British Columbia, Canada. Since 1997, KIVCETTM flash smelting technology has been utilized for the treatment of zinc plant residues and lead concentrates. Trail Operations’ furnace uses four water-cooled jackets for bullion tapping. This paper provides an overview of KIVCET bullion tapping for the past 16 years, and discusses successes and challenges encountered with respect to operations, training, and monitoring.

Jan 1, 2014

By H. D. Mtegha

The Southern African Development Community (SADC) aims to harmonize mineral policies and regulatory regimes in the minerals sector. This paper provides a review of the progress made towards harmonization of mineral regimes in the region. It singles out only the mining fiscal environment, as this is normally one of the key issues of interest to potential investors as well as the host state. Indications are that the region is slowly progressing towards a more harmonized approach, and there is evidence that the ?race to the bottom? has been prevented, which is the basis for an integrated mineral sector that the region aspires to.

Jan 1, 2011

By C. Kirmanli

The purpose of this paper is to develop an expert system for hydraulic excavator and truck selection in surface mining. Hydraulic excavators and trucks are finding increasing applications in mining operations. Hydraulic excavators are extensively used especially when bringing electricity to rural areas is difficult and for small-scale mining. This paper describes an expert system, which selects the optimum hydraulic excavator truck configuration such that unit production cost is minimized and technical constraints such as geological, geotechnical and mining constraints are satisfied. The system has four modules: user interface, rules and an methods, databases and output module. The expert system in this study is developed within KappaPC shell. It supports object-orientated technology for the MS Windows environment. The software provides a very useful tool to practitioners, saving time and cost. Equipment selection is a recurring and expensive problem of mine planning and often involves interdisciplinary experts from different fields. It is very difficult and expensive to bring together all these experts. The capabilities of the expert system developed are illustrated in the paper. The software overcomes the difficulties of selecting the proper equipment for surface mining operations, which is very important, and results in substantial savings. Equipment databases for hydraulic excavators with 15-59 yd3 capacities and trucks with 35-360 tons are constructed and these databases are used to select the proper configuration. A case study is carried out for Soma Surface Coal mines in Turkey. Keywords: surface mining, expert systems, equipment selection, hydraulic excavators, diggability

Jan 1, 2009