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By L. G. Austin

The paper summarizes the current state of development of simulation models for SAG and FAG mills, and gives the results of recent investigations of the physical processes occurring in autogenous grinding. The breakage process is treated as the sum of three regions of breakage actions: normal breakage caused by nipping of particles between media (steel balls or pebbles); abnormal breakage caused by media when the particle or lump is too big in relation to the media to be readily nipped; and self-breakage resulting from the chip¬ping fracture and abrasion of the tumbling action of rock lumps. Each region of breakage action has associated specific rates of breakage and primary progeny fragment distributions. A simplified form of the model was used to predict the performance of an 8 m diameter SAG mill with L/D = 0.5 grinding a copper ore, and predicted maximum capacity and minimum kWh/ton at about 6% ball load at 25% total filling. Two FAG mills of L/D = 2 were necessary to give the same capacity, and the simulations indicated a lower kWh/ton for these mills. For this ore, both systems were technically feasible.

Jan 1, 1987

By S. K. Mahata, P. G. Suresh Kumar, B. B. Singh

Improvement of post tap hole practices is achievable by mechanized handling of melt during the production of Ferro Chrome, resulting in higher recovery of chromium. The paper deals with modern practices adopted in the production of ferro-chrome since past two decades. The methods and practices deal with various areas : a) Improved method of operating the tap hole by selection of right quality of refractory to maintain the life of tap hole. b) Collection of melt in different types of receptacles like refractory brick lined mild steel ladles, cast steel ladles, cast iron pans being chosen for cost effective and efficient handling. c) Separation of slag and metal, casting of metal, crushing, sizing and stock piling etc. d) Slag disposal and recovery of entrapped metal. The drive behind the above development is continuous improvement, which results in higher chromium recovery and reduces loss of metal in slag by completely mechanized method so as to be at the same level with producers of ferro-chrome in other advanced countries , in the emerging global economy.

Jan 1, 2007

By F. M. Russell

Scheduling the extraction and rates of production for an underground mining operation is a common task carried out during the life of a mine, from the initial feasibility study through to the final production phase. The scheduling process can be complex when several requirements have to be satisfied, for example, match mill capacity and maximize net present value while constrained by mining sequence and availability of resources. Many mines have computer programs relevant to their operation but because they are site-specific they need considerable reprogramming to be adapted to other operations. Other methods currently in use also suffer drawbacks: manual spreadsheets are laborious, computerized spreadsheets cannot handle sufficient constraints, and operations research techniques require a complex mathematical model to be set up. The use of network analysis techniques has been proposed previously but the unavailability, until recently, of easily used computer programs has not allowed this approach to be developed. There are now many programs which can be used; however, the particular program which has been adapted to mine scheduling is Metier's 'Artemis-PC' running on IBM-XT or compatible machine. The use of network analysis offers many advantages, including the use of a logical mining sequence; activities can be as detailed as required; related activities can be readily incorporated, and costs can be easily extracted. A heuristic approach is necessary to optimize the schedule, but the ease and speed of program execution enables this to be readily achieved, while leaving the mining engineer in full control. The paper discusses the problems encountered in mine scheduling and current solutions. It then details the use of network analysis techniques and the application of the Artemis-PC program to solve mine scheduling problems.

Jan 1, 1987

By R. G. B. Pickering

The South African narrow reef hard rock mining industry has been stuck in a time warp with relatively little change in the mining process in the last century. This paper presents a methodology on how to implement change in narrow reef hard rock mining. It then explores a number of technologies that have been introduced into this mining industry and the impact that they have had on the mining process. The author then presents his view on whether the defined change process has been followed and sets out to identify the most critical aspect of ensuring that change is successfully implemented. Future demand will also be speculated on.

Jan 1, 2007

By J. L. Gaigher

A simple mineralogical regression model is described, which was devised in order to help the flotation plant cope with rapidly changing headgrades and feed mineralogy. Minerals in the feed were determined by means of quantitative X-ray diffraction and compared with plant performance parameters and flotation reagent consumption rates, using regression analysis. A mineralogical regression model for predicting recovery served to motivate flotation plant personnel and also set standards whereby flotation performance could be measured. The reagent consumption model indicated in which direction any or all of five flotation consumption rates should be altered. All practically measurable parameters, even those showing poor or no correlation, were included in the model, provision being made for the continuous update of a batch of data of 30 lines. Compared with the method of multiple linear regressions, the r2 is poorer at 0,41 (versus 0,50), but the mean standard error of estimate for both methods is identical at ± 6,6 units. The regression model is simpler than the method of multiple linear regressions, and although the accuracy of prediction is not high (41%), the mineralogical regression model proved to be successful in practice. Flotation efficiency, as measured by the mean ratio of head to tails grade, for the 9 month period after the mineralogical regression model was implemented on an hourly basis, improved from 2,8 to 3,2, which is equivalent to an improvement in average flotation recovery of 5% relative.

Jan 1, 1987

By H. L. Zimba

Flotation involves the selective levitation of mineral and its transfer from cell to launder. The flotation rate is the rate of this transfer. It may be defined by the slope of a recovery-time curve for any cell in a bank or at any time in a batch operation. The objective in flotation rate study is an equation expressing the rate in terms of some measurable property of the pulp. This can be either the concentration of floatable mineral in weight per unit volume or a relative concentration, which will be a function of the recovery. A rate equation for an actual flotation pulp will contain at least two constants, both to be determined from the collected data. The data used in this paper were collected from bench-scale flotation tests on Konkola primary mill cyclone overflow at various pulp densities and pre-flotation thickener underflow at a pulp density of 35% solids by weight.

Jan 1, 2009

By C. Botha

The South African democratically-elected government instituted policies and legislation that are intended to bring about change and transformation in the country and have drastically affected different industries, among others, the mining industry. The Mineral and Petroleum Resources Development Act 28 of 2002 (MPRDA) and the Broad-based Socio-economic Empowerment Charter (Mining Charter) were introduced in order to redress previous inequalities and to promote women's employment in the mining industry. This research evaluates the practical implementation of the MPRDA and the Mining Charter with specific reference to women in underground mining. A quantitative research paradigm was used. Data were collected through a process of a face-to-face interview surveys utilizing a structured questionnaire. The research setting was limited to the platinum-mining industry in the area of Rustenburg in the North West Province. The study population consisted of 195 available women working undergound at the mine. It is clear from the findings that mining companies are facing major challenges in their attempt to incorporate women in underground mining activities. Company policies regarding these issues must be firmly in place; however, the challenge lies in the translation of these policies into practice. In this regard, managers will have to play a leading role in the successful phasing in of women into the underground mining arena.

Jan 1, 2012

By K. Tobór-Osadnik, M. Wyganowska, A. Manowska

"The behaviour of employees is an essential issue in the field of occupational health and safety. Safe behaviour is to a large extent determined by, apart from motivation and preventive actions, an employee’s attitude towards hazard. Thus, attention should be given to defining employees’ attitudes, and following that, to the possibility of correcting and shaping these attitudes in relation to hazard and obeying occupational health and safety regulations. The authors have focused on the analysis of employee attitudes to health and safety regulations in Polish coal mining companies, taking into consideration earlier research on the behaviour of selected employees. The paper presents the methods used to identify Z-type (passive) behaviour. Next, this behaviour is analysed to identify differences between a Z-type employee (enslaved) and other employees. To conclude, the paper presents a list of possible motivational tools that may be used to encourage occupational health and safety in Z-type employees. IntroductionThe technical state of equipment and conditions in the workplace greatly influence occupational safety. However, the deciding factor influencing the rate of accidents in the workplace is the frequency with which employees practise risky behaviour. Factors such as the social conditioning of conduct and motivation for organizing safe work conditions have been included in the notion of creating a positive culture of work safety. This notion has been approved as one of the main goals in management (Studenski, 1996).Safe behaviour is to a large extent, apart from motivation and preventive actions, determined by an employee’s attitude towards hazard. All actions undertaken in the field of occupational health and safety, including training, motivational systems, or imitation of behaviour resulting from a high culture of occupational safety in a given work environment, will not bring about the desire effects if workers have an inappropriate attitude towards occupational health and safety regulations."

Jan 1, 2017

By R. H. Matjie, J. R. Bunt, C. A. Strydom

"A number of conventional and advanced analytical techniques (proximate and ultimate analysis, low-temperature oxygen-plasma ashing, X-ray diffraction, X-ray fluorescence spectrometry, coal petrography, and lightelement electron microprobe analysis) have been integrated and crosschecked to provide detailed characterization of coals from the Highveld coalfield in South Africa, as a basis for better understanding of the mineralogical and chemical properties of the individual coal sources that are blended as feedstocks for combustion and carbon conversion processes. The techniques included methods to quantify the abundance and composition of the mineral matter (minerals and non-mineral inorganic elements), and also the abundance and chemical composition of the individual macerals in the individual coals concerned.Kaolinite is the most abundant of the minerals in the coals studied, with lesser but still significant proportions of quartz, mica and/or illite, dolomite, calcite, and pyrite. Small but variable proportions of anatase, goyazite, and siderite are present in some coal samples. Electron microprobe analysis, based on a special configuration for light-element study, shows that the vitrinite contains less carbon and more oxygen, and has significantly higher concentrations of nitrogen and organic sulphur, than the inertinite macerals in the same samples. Minor proportions of organically-associated inorganic elements, including titanium, were also identified in some of the maceral components.A comprehensive knowledge of the minerals and non-mineral inorganic elements in the coals used for feedstock preparation, obtained by integration of data from these advanced analytical techniques with more conventional analyses, may be of benefit in understanding the processes that take place during coal utilization, and also in avoiding or ameliorating some of the operational and environmental problems that may occur in different sectors of the coal utilization industry."

Jan 1, 2016

By K. A. Annan

The last seven hot rolling passes of the ferritic stainless steel AISI430 were simulated on a Gleeble-1500D® thermo-mechanical simulator to investigate the effect of temperature, strain rate, and interpass time on the texture. The compression tests were carried out over a wide range of strain rates (0.1 s-1 to 5 s-1) and temperatures (1100°C to 820°C) with different interpass times (2, 10, 20, and 30 seconds). The dynamic recrystallization to dynamic recovery transition temperature was determined from examining the relationship between the mean flow stress and the inverse of the deformation temperature in multi-pass tests. It was found that the texture in the central layer of the compressed sample is a strong recrystallization-type. The through-thickness textural and microstructural banding, to a large extent, were found to be weakened by hot deformation in the two-phase (a+ ?) region, as opposed to the single-phase (a) region.

Jan 1, 2013

By P. J. Foster

This paper summarizes a behavioural safety project undertaken in seven quarries in the UK in order to investigate its applicability as a means of raising the standards of health and safety in the UK quarrying industry. A behavioural safety methodology was developed and trialed at two quarry sites in the UK. During the study the number of unsafe acts and minor accidents had decreased and at one of the quarries there was a 95% reduction in the number of working days lost. It was then introduced at a further five sites of varying sizes and within this focused specifically on lone workers as well as behaviours that affected quality and environmental issues. Positive improvements were noted in most of these operations. The project also looked at the effectiveness of health and safety performance indicators. Here, the common lead and trailing indicators for both safety and health that are commonly used by industry were identified. In consultation with the UK quarrying industry these were then used to identify specific performance measurement criteria that can be used by the quarrying sector to measure performance. Following on from this, a quarry specific health and safety management system specification was developed for large and small quarries.

Jan 1, 2008

By R. M. Kear

The Mine Planning Department of Rio Tinto Management Services South Africa has installed an interactive graphic work station to assist with the long- term mine planning of Palabora. Previously, the planning was drafted manually after which digitised areas were fed to the computerised ore reserve system. This method was slow, tedious, prone to error and was becoming incapable of meeting new planning parameters. To assist the planning engineer an interactive graphic system was developed, and subsequently a rewrite of the ore reserve reporting system was incorporated. The work station has reasonable computing power and, when not utilised for graphics, has been found suitable for the evaluation of various non- graphical applications, a recent example of which was the in-pit crusher investigation. This project, in contrast to similar studies, was not based on a fixed system throughput but rather on a well designed system which would be operated at its own optimum capacity. In order to determine the probable throughput a simple simulator was designed to model the crushing and conveying system. This paper describes the investigation into the specifications for the work station, the selection of hardware, operating system and languages. An over- view is then given of the graphic planning system. The in-pit crushing simulation has been included as an example of how the work station has been applied to other, non graphical, applications.

Jan 1, 1987

By J. Githiria, C. Musingwini

"Cut-off grade is a decision-making criterion often used for determining the quantities of material (ore and waste) to be mined, ore processed, and saleable product. It therefore directly affects the cash flows from a mining operation and the net present value (NPV) of a mining project. A series of different cut-off grades that are applied over the life of mine (LOM) of an operation defines a cut-off grade policy. Due to the complexity of the calculation process, previous work on cut-off grade calculation has mostly focused on deterministic approaches. However, deterministic approaches fail to capture the uncertainty inherent in input parameters such as commodity price and grade-tonnage distribution. This paper presents a stochastic cut-off grade optimization model that extends Lane’s deterministic theory for calculating optimal cut-off grades over the LOM. The model, code-named ‘NPVMining’, uses realistic grade-tonnage realizations and commodity price distribution to account for uncertainty. NPVMining was applied to a gold mine case study and produced an NPV ranging between 7% and 186% higher than NPVs from deterministic approaches, thus demonstrating improved project value from using stochastic optimization approaches. Background on cut-off grade calculation and optimizationCut-off grade is a decision-making criterion that is generally used in mining to distinguish ore from waste material. Consequently, it is used to determine the quantities of material (ore and waste) to be mined, ore processed, and saleable product. A series of different cutoff grades that are applied over the life-ofmine (LOM) of a mining operation defines the cut-off grade policy for that particular operation. The cut-off grade therefore directly affects the cash flows to be produced and the net present value (NPV) of a project at the mine planning or feasibility study stage."

Mar 1, 2019

By L. A. Sandham

Environmental impact assessment (EIA) in South Africa is administered by the Department of Minerals and Energy (DME) for the mining industry, and the Department of Environmental Affairs and Tourism (DEAT) for all other sectors. Thus far, EIA research has focused on the process under the auspices of DEAT but none has focused on the EIA process that has been mandatory in the South African mining industry since 2004. Using the Lee and Colley(Lee et al.13) review package as a basis, a review model specifically tailored to the needs of the mining industry was applied to review the quality of a sample of 20 environmental impact reports (EIRs)approved by the DME. Results reveal that 85% of the EIRs are of a satisfactory quality. Presentational and descriptive components generally achieved higher quality grades than the analytical components such as impact magnitude and alternatives. The results show that in spite of some areas of weakness, and in spite of being conducted in terms of different legislation, EIR quality in the mining sectors appears to conform to the overall standard of quality of EIRs in other sectors in South Africa, and is also on a par with quality abroad. Hence, despite the criticism that DME is usurping the role of DEAT, it is concluded that EIRs of comparable standard are being produced, and that the quality of EIRs in the mining sector do not provide supporting evidence for this criticism. However, EIR quality is only a single aspect of EIA effectiveness, others including action and implementation of EIA proposals and mitigation measures.

Jan 1, 2008

By V. Matou?ek

The paper addresses pipe flows of aqueous medium-sand slurries at velocities lower than the deposition-limit velocity. Laboratory test results including measurements of particle concentration distributions are used in order to describe a flow with a (pseudo-) linear concentration gradient above a stationary bed. Particle dispersion within the flow is evaluated and a stratification-ratio equation is formulated, estimating a portion of contact load in the flow. The formula is incorporated in the proposed predictive model for the hydraulic gradient for a medium-sand flow above a stationary bed.

Jan 1, 2007

By P. K. Van Manen

Anglo Platinum?s Polokwane Smelter is situated outside Polokwane, in the Limpopo Province in South Africa. A single 168 MVA six-in-line rectangular furnace smelts dry concentrates containing platinum group metals (PGMs). Furnace energy consumption since commissioning is presented, showing that energy efficiency improves as capacity utilization increases. An energy balance for the furnace is outlined, indicating the measured or calculated energy losses from the hearth and side-wall cooling, the copper coolers, the upper furnace walls and roof, and the energy losses in off-gas, matte, and slag. From the energy balance, the potential to improve energy efficiency by controlling the slag temperature, the slag level, and the off-gas volume is derived. Furthermore, the impact on the energy balance of different concentrate types is discussed, as well as the potential impact of replacing all upper waffle coolers by plate cooler panels.

Jan 1, 2009

By Mark Craddock, Johan Swanepoel

In this paper we present The Ultimate Flotation Cell, a newly developed flotation cell that is proving very popular in the industry. All flotation cells have only one purpose and that is the recovery of the required product, the patented impeller and disperser system of the Ultimate Flotation Cell allows total flexibility in order to achieve the optimal recovery. This ability to tune the cell performance provides the optimization of the ?capture? (collection) stage, all existing models address the need for a wide bubble size distribution (100µm-2 mm) to obtain a better flotation size-by-size, Yoon, 1999,Yoon 2000, Franzidis and Manlapig, 1999. The Ultimate Flotation Cell provides flexible performance optimization. This ability to optimize the flotation regime particular to a specific ore is achieved by the following factors: ? The impeller allows vastly improved air induction rates compared to conventional and sparged cells. This ability to induce and disperse large quantities of air, in a controlled manner, allows the cells to be tuned to give the optimal Sb by varying the rotational speed via a VSD which every cell is fitted with. ? The patented impeller gives a very constant and stable air induction rate, which ensures that the cell?s circulation pattern is constant, giving a very stable surface, allowing optimal froth depth. ? Although conventional dart valve, level control can be offered, great success has been achieved with a simple draft tube/sand relief device. ? The cells have a inlet design similar to the old Denver ?Cell-to-Cell? design, which guarantees the at lease one pass through the mixing zone in each cell. Actual plant performance data will be presented from two plants, one in Zambia and the other in the DRC.

Jan 1, 2007

By C. Botha

The South African democratically-elected government instituted policies and legislation that are intended to bring about change and transformation in the country and have drastically affected different industries, among others, the mining industry. The Mineral and Petroleum Resources Development Act 28 of 2002 (MPRDA) and the Broad-based Socio-economic Empowerment Charter (Mining Charter) were introduced in order to redress previous inequalities and to promote women?s employment in the mining industry. This research evaluates the practical implementation of the MPRDA and the Mining Charter with specific reference to women in underground mining. A quantitative research paradigm was used. Data were collected through a process of a face-to-face interview surveys utilizing a structured questionnaire. The research setting was limited to the platinum-mining industry in the area of Rustenburg in the North West Province. The study population consisted of 195 available women working undergound at the mine. It is clear from the findings that mining companies are facing major challenges in their attempt to incorporate women in underground mining activities. Company policies regarding these issues must be firmly in place; however, the challenge lies in the translation of these policies into practice. In this regard, managers will have to play a leading role in the successful phasing in of women into the underground mining arena.

Jan 1, 2012

By O. Tshifungat, A. Luzanga, N. Goel, S. Sandoval

"Tenke Fungurume Mining Company (TFM), located in Katanga Province, Democratic Republic of Congo (DRC), began production of copper cathode and cobalt hydroxide in March 2009. Copper production capacity was 115 000 t/a utilizing a semi-autogenous grinding, agitated leach, countercurrent decantation process followed by solvent extraction and electrowinning (SX-EW). Cobalt production capacity (as cobalt hydroxide) was 8000 t/a utilizing a three-stage purification/precipitation process treating raffinate from the copper SX-EW process. Recently a phase II expansion was completed, in which copper electrowinning capacity was doubled and four stages were added to the SX plant. Corresponding enhancements were made to mining, milling, and processing to bring production to 195 kt/a copper and 15 kt/a cobalt. An additional sulphuric acid plant is currently being constructed, adding 1400 t/d sulphuric acid to bring total acid production to 2250 t/d for use in leaching at TFM.Initial copper electrowinning results were satisfactory, but cathode quality and current efficiency decreased as copper production increased. The Freeport-McMoRan (FCX) Technology Centre and TFM personnel began operation of two bench-scale copper electrowinning cells in the tankhouse to diagnose chemistry effects on the cathode and anode. The results indicated an excellent electrolyte chemistry, producing finely crystalline copper at 430 A/m2 current density with 98% current efficiency. Attention next turned to the physical factors of the electrowinning cells, including electrode insulator geometry and performance. A demonstration cell was selected in the tankhouse and was operated with varying cathode and anode insulator geometries. Operation of the demonstration cell with a three-side cathode edge strip, A-style anode insulators, and an improved cell furniture design increased current efficiency from 77% to 89% at 400 A/m2 current density. Cathode quality improved correspondingly. TFM is now operating at 92% current efficiency."

Jan 1, 2016

A number of issues relating to the computational aspects of pillar design are addressed in this paper. The computation of average pillar stress values is important when attempting to establish criteria for pillar design and in the analysis of the stability of tabular pillar layouts. One of the default ?classic? numerical methods that are used to determine pillar stresses is the displacement discontinuity method. In many instances it is not clearly understood that this approach does suffer from some limitations, particularly in relation to the fact that in coarse element simulations, the simulated average pillar stress (APS) can depend on the chosen mesh size. The nature of this error is highlighted in this paper and some strategies are suggested to bound the magnitude of these errors. It is demonstrated as well that the popular linear stiffness approximation to pillar or seam compressibility does appear to allow reasonably accurate estimates of the average pillar stress when either the pillar height is varied or when the seam modulus differs from the host rock modulus. A practical implication of this study is that if the seam modulus is noticeably lower than that of the host rock, such as for coal seams, it is important to use a linear stiffness constitutive model for the pillars rather than a ?rigid? pillar assumption. This added complexity seems unnecessary, however, when simulating hard rock pillars in mines where the seam modulus is very similar to that of the surrounding rock.

Jan 1, 2011