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By D. H. Batchelor

Efficient modern-day mining operations are turning increasingly to technology to combat rising operating costs in an adverse economic climate for the industry. Computerised truck dispatching is one such technological advance that has enhanced the efficiency of the mining operation at Palabora. The economic incentives, basic operation and general system benefits of Palabora's computerised truck dispatching system are considered.

Jan 1, 1987

By F. P. Greyling

The aspect of sustainability of ferroalloy processes has long been a serious matter for consideration in many of the world?s industrialized countries. A number of countries can be named where ferroalloy plants that were once flourishing, have all but disappeared. One of the most important factors playing a role in this type of occurrence is the cost and availability of quality raw materials. Given that all natural resources will be depleted with time, users are compelled to develop new processes that are sustainable in the changing environment. The DC arc smelting furnace is one such process that has proved itself, and has gained increasing popularity over the past two decades. This process, amongst other benefits, directly addresses the use of more readily available and more affordable raw materials in ferroalloy production. Since early in the new millennium, GLPS has been involved in various studies for different clients of furnaces for the production of ferroalloys. Two of these recent studies have culminated in the design, construction and commissioning of DC arc furnaces for the production of ferrochrome. One of these furnaces is a 10 MW unit at Mogale Alloys, and the other a 60 MW unit at the Middelburg plant of Samancor Chrome. This paper discusses the approach taken in the design and construction of these two furnaces, which, although varying significantly in size and capacity, are very similar in many other aspects of their design. Keywords Furnace, DC arc, and ferrochrome.

Jan 1, 2010

By K. Lomberg

In this paper the process of sampling and assaying as it relates in particular to the platinum group elements (PGEs) is presented. A discussion of the geology of PGE deposits is included to provide an understanding of the mineralization that is considered necessary prior to sampling, as this has a direct bearing on the mineral resource estimate and also the selection of an appropriate mining cut. The discussion includes the selection of the sampling technique (drilling or face sampling), the size of the sample relating to the requirements of the laboratory, the potential mining cut, as well as a reference to sampling theory. The selection of an assay technique that is appropriate and will yield the optimal result based on sample turnaround, precision, accuracy, and cost is then considered. Examples are drawn from work undertaken on the Bushveld Complex (Merensky Reef, UG2 Chromitite Layer, Platreef) and Great Dyke (Main Sulphide Zone). A discussion of the appropriate QA/QC programme includes the chain of custody, CRM selection and the QA/QC process. Keywords sampling, assaying, QA/QC, platinum group elements.

Jan 1, 2014

Mill relining is a major contributor to overall plant downtime. Reducing the number of mill liner pieces removed from and replaced in the mill has a direct impact on the overall reline time and in turn, mill availability. To improve the mill availability of Ridgeway Operations' 32 foot SAG mill, a number of initiatives were implemented in terms of liner design. These included the conversion of the shell from 40 to 30 rows, reducing the number of pieces from 80 to 60 each shell reline and reducing the number of pieces from 48 to 32 per feed end reline. In addition, modifications were made to the discharge end of the mill to extend the life of the outer pulp lifter and discharge cone, thereby reducing the frequency of change out. The standard radial outer pulp lifter was converted to an angled design. The discharge cone was converted to the BullnoseTM design supplied by Bradken. This paper discusses the design changes made and the expected benefits to the Ridgeway Operations in terms of mill availability improvements.

Jan 1, 2007

Grains are subject to contamination by mycotoxins which are metabolic by-products of various fungi. The fungal infestations produce local concentrations of the mycotoxins thousands of times higher than the average. These facts make the sampling of the grain for assessment of the mean mycotoxin levels potentially very difficult. In the context of sampling theory, this morphology of the infestations creates a very high distributional and intrinsic heterogeneity of the grain shipment. The distributions of mycotoxin concentrations in seaborne shipments that exist at loading and the number and intensity of infestations that develop under shipping conditions are unknown. All grain shipments carry spores that may give rise to mycotoxin-producing colonies; moisture and temperature determine the final extent of the problem. This paper develops the value of the sampling constant with respect to intrinsic heterogeneity based on data on observed Ochratoxin A (OTA) concentrations in individual wheat kernels. A useful relationship between the distribution of mycotoxin concentrations on a kernel to kernel basis and the distribution of concentration over subsamples is developed.

Jan 1, 2009

By Kedikilwe Oageng

Effective perimeter control during drilling and blasting is critical not only to blasting results but also to the overall stability of the pit over its entire life span. A pit where perimeter control is not given enough attention when conducting drilling and blasting operations, often experiences over-break or back break beyond final pit wall limits, and therefore has a relatively high probability of failure. Such a pit also becomes unsafe, sometimes not easily accessible, has increased loading costs due to production of oversize, longer cycle times and often problems are encountered when blasting subsequent benches. All these are undesirable consequences, which have negative cost implications. Specialised blasting techniques such as trim blasting and pre-splitting have over the years proved to be effective perimeter control measures. However, the success of these techniques is directly attributable to the time and effort given to the processes. This paper presents results of a project undertaken to monitor, review and optimize the trim blasting and pre-splitting processes at Orapa Diamond Mine in Botswana. The project was specifically incepted to improve the final wall conditions, which continued to deteriorate due to persistent over-break during blasting. The paper also analyses the results obtained against a benchmark of results taken prior to project implementation. Specific blast design parameters which are critical to blasting results were identified as problem areas after auditing of the pre-implementation drilling and blasting practices. These include drill-hole depth, spacing, splitting factor for pre-splits and timing of trim blasts. The impact of different rock types on the results was also studied, and recommendations were made at different phases of the project and results obtained after implementation analysed until optimum results were achieved.

Jan 1, 2008

Mixed integer programming (MIP) has been used for optimizing production schedules of mines since the 1960s. The major problem in the long-term production scheduling for an entire orebody is that the number of integer variables needed to formulate an MIP model is too large to solve the formulation. This number may reach well over one hundred thousand. To overcome this difficulty, this paper presents two new algorithms to reduce the size of the problem. These algorithms assign an earliest and latest possible start date for each machine placement, eliminating the integer variables that correspond to machine placement before its early start date and after its late start date. A case study based on Kiruna Mine, the second largest underground mine in the world, is summarized in the paper. It shows substantial improvement in the solution time required using the new algorithms. This increased efficiency in the solution time of the MIP model allows it to be applied to Kiruna Mine, with the potential to increase substantially the net present value (NPV) of the project.

Jan 1, 2008

By J. J. Taute, G. Chisakuta, P. Bwando, G. Mitshabu

"BASF Mining Solutions have developed a new generation of copper solvent-extraction reagents that offer significant benefits over the existing reagents available to the industry today. Initial laboratory studies and pilot-plant trials have shown that these new reagents offer the benefits of a dramatic increase in resistance to degradation and are nitration-proof. This paper details a recent pilot-plant campaign at a commercial solvent-extraction plant. The main focus was to evaluate the copper/iron selectivity, copper recovery and net transfer of the new reagent compared with the conventional oxime reagents. The new reagent displays similar copper recovery and net transfer capabilities from typical agitation leach solutions. The pilot-plant results show a step change improvement in copper/iron selectivity in comparison with the existing modified and non-modified hydroxyoxime reagents used on the commercial plant. INTRODUCTION Copper solvent extraction (SX) from an acidic aqueous solution is typically accomplished using a hydroxyoxime extractant (Jergensen, 1999; Kordosky, 2000; Szymanowski, 1993). There are three hydroxyoximes from which all standard formulations are derived: 5-nonyl salicylaldoxime (NSAO), 5-dodecyl salicylaldoxime (DSAO) and 2-hydroxy-5-nonyl acetophenone oxime (HNAO). In the case of NSAO, it is necessary to use equilibrium modifiers in order to increase the copper stripped from the extractant (Kordosky & Virnig, 2003). Blends of DSAO, NSAO and HNAO are used to cover a wide spectrum of conditions (Kordosky, 2008). Use of modified aldoximes and reagent blends over the last 30 years has influenced the way copper producers and equipment manufacturers have approached the operation of copper plants. Existing solvent-extraction reagents cater for typical pregnant leach solutions (PLS) of copper mining systems which do not have significant effects on the reagent. Table I illustrates the range of copper concentration, pH values, temperature and iron concentrations for different leaching operations. As conditions become increasingly aggressive (i.e., higher PLS temperatures in primary sulfide leach or high iron content), current reagents become less capable of functioning according to expectations. One example is the effect of high iron (Fe3+) concentration in PLS and operating SX to achieve high copper recoveries. The ferric is partially chemically extracted and is transferred to elctrowinning (EW) during the stripping stage. To avoid a build-up of iron in electrolyte, which negatively affects current efficiency, a bleed of electrolyte is required. This bleed leads to excessive consumption of reagents, such as cobalt added to the EW process, and thus increases operational cost."

Jan 1, 2015

By B. Talbot

How this simple plant generates a large revenue stream. The concept behind the Tailings Scavenging Plant (TSP) is simple: it is a non-complicated modular plant which is designed to be more stable than upstream plants. This, plus the use of ?high energy?, enables the plant to recover any metal missed by the upstream operation. Impala Platinum?Mineral process started pilot plant exercises in June 2003. The pilot plant ran for one year before the capital for the full-scale plant was approved. This year was used to motivate, design and cost a full-scale plant. The metal produced during the pilot and feasibility study enabled this part of the project to run at a small profit. The scale-up to full-scale was relatively simple as the pilot plant had a capacity of 180 m3/hrand the full-scale plant was designed for a capacity of 550 m3/h. The design for the full scale plant was completed in May 2003, with ground breaking taking place on 19 May 2003. The construction phase of the project went well with the commissioning of the first two modules taking place on 22 October 2003. The remaining two modules were commissioned two weeks later. The plant was at full capacity by the 20 November 2003. A review of the plants performance for the first 5 production months is as follows: the plant has required only a few minor modifications and additions, it has run well in excess of 95%availability with no major wear apparent. In addition to this, the plant has produced 3 times the metal forecast.

Jan 1, 2004

By E. Keskinkilic

In this study, sulfide-type inclusion morphologies of a Ca-treated hot-rolled wheel steel, Grade-X, were investigated. The specimens taken from the hot-rolled products of Grade-X heats were studied. The size and distribution of elongated sulfide inclusions were examined for the heats of different S levels. Elongated sulfide inclusions were either not observed or rarely encountered when ladle analysis S content was below 50 ppm. The size and relative abundance of sulfide inclusions were reported to increase markedly when the S composition was greater than or equal to 70 ppm and the Ca/S ratio was less than 0.50. The effect of Ti addition (0.010?0.020% Ti) on sulfide-type inclusion morphologies was then investigated for heats having a sulfur content higher than 50 ppm. Addition of Ti was found to have a partial effect on decreasing the size of sulfide-type inclusions under real steelmaking conditions. Keywords Sulfide inclusions, Ca-treatment, titanium.

Jan 1, 2011

By H. Rosen

The pump is the heart of most industrial and mining plants, providing the energy to separate valuable minerals from process feed. The actual effect of the pump, both in terms of production costs and overall process efficiency, is often assumed or misunderstood by engineers due to insufficient pump performance data. Pump performance can be understood and corrected, where required, through continuous performance monitoring, leading to dramatic improvements in both pump life cycle costs and system efficiencies. The performance of every pumping application is subject to variation and the main contributing factors are as follows: ?Unavoidable deviations from pump supplier curves ?Pump wear ?Pump curve derating factors for slurry pumping ?System curve variation ?Deviation from basic principles of centrifugal pump operation. These are discussed in detail through case studies and the author?s personal experiences. This paper shows ways to minimize the effect of these variations, thereby reducing performance loss and preventing damage to the pump. The paper discusses the benefits of efficient pump operation, the requirements of pump performance monitoring, and its practical application to pump operation in the slurry and water environments. The cost of remedial actions is explored and compared against the savings in both power and plant reliability, resulting in a reduced life cycle cost of the pump.

Jan 1, 2010

A brief overview is given of the issues regarding the processing of waste electrical and electronic equipment (WEEE). The printed circuit board component of WEEE is an exceptionally complex feed to possible recycling processes. Scrap printed circuit boards were selectively smelted at 1 200°C to produce a metallic alloy. Iron and aluminium were found not to be part of the alloy. The alloy was characterized by SEM-EDS, and three phases were identified: alpha and delta bronzes, and a lead-rich phase. Calculations show that about 56 mass per cent of the alloy is the alpha phase, 35 per cent delta phase and 9 per cent lead phase. A simplified approach using appropriate binary phase diagrams was used to derive a phase composition for the alloy. This was further backed by FactSage calculations, which showed that the simplified approach was appropriate for this alloy. The experimental findings and theory were found to agree well.

Jan 1, 2009

By D. Van Dyk

Horizontal rotating mills are being used all over the world in different mineral and power generation industries. David Brown South Africa, with over 140 years of experience in gear manufacture and design, has been supplying these industries with innovative designs at exceptional quality. The gearing systems associated with these industries are challenged daily with operating conditions that are not always fully understood. Failures are therefore experienced, over time in the industry, which cannot always be fully explained. David Brown South Africa has developed a gear monitoring system, the Intelligent Gearing System, in association with Transmission Dynamics (UK), in order to monitor and analyse these operating conditions in real time. The system has been designed on the principles of Six Sigma, incorporating Design for Six Sigma. The purpose with this system design is to monitor the operating conditions on the pinion, record the information and analyse the data in relation to the rate of fatigue damage to the girth gear and pinion. This is done in real time and unattended. The output from the Intelligent Gearing System can be fed back into the operating system of the mill user, in order to display an alarm for operating conditions exceeding the design criteria as well as information on the rate of fatigue damage due to these operating conditions. When the mill operating and the effect on the fatigue life of the mill gearing components, conditions are better understood, mill users can forecast critical spare holding levels with an increased accuracy. The Intelligent Gearing System also allows early actions to remove reasons for system overloads.

Jan 1, 2006

The Namakwa Sands heavy mineral deposit is located along the West Coast of South Africa and the mine is a world class producer of high quality zircon, ilmenite and rutile concentrates from essentially unconsolidated marine and aeolian sands of Cainozoic age. The objective of this study was to characterize rutile with respect to distribution, grain size, textures, colour and mineral chemistry within the Namakwa Sands orebody with the aim to explain its overall poor recovery. A representative suite of heavy mineral concentrates from various sections of the orebody and stages in the recovery circuit has been investigated microscopically and by means of SEM-EDS and LA-ICP-MS. The rutile grain size distribution displays a wide range and is directly related to its variable chemistry and consequently density. In placer deposits such as Namakwa Sands, mineral sorting is a function of hydraulic equivalence, and high density grains are smaller than the lighter grains when deposited under similar conditions. Grain size is also a function of sediment maturity, and the highly mature red aeolians and (RAS) component of the deposit has a coarser grain size than the less mature orange feldspathic marine sands (OFS). The above primary characteristics of rutile are responsible for the loss of the coarse-grained fraction during screening and, given the empirically determined relationship that increased substitution elements reduce conductivity, also during electrostatic separation. Provenance studies using geothermometry have shown that the heavy mineral suite has been sourced mainly by the proximal medium-to high-grade Namaqualand Metamorphic Complex. The positive relationship between substitution elements and temperature of formation explains their high concentration in rutile of this deposit. The heterogeneity of rutile, produced by the combination of a high temperature primary source and the typical marine-aeolian placer genesis is deposit specific and unfortunately not conducive to high recovery levels in the current Namakwa Sands beneficiation circuit.

Jan 1, 2010

By Karl-H. Daum

Over many decades, numerous feasibility studies have demonstrated, that the production of sulphuric acid remains the most viable option of sulphur recovery from smelter off gas and abatement of SO2 emissions to the atmosphere. This is particularly more pronounced as smaller but more concentrated off-gas flows are to be treated from smelters, and enhanced sulphuric acid processes be-come available. Off-gas handling systems represent a significant capital and operating cost burden to the metallurgical operation. Modern pyrometallurgical smelter processes for sulphide ores based on the use of oxygen-enriched air, produce relatively small off-gas flows with high SO2 concentrations in the smelter gas of 30?60 %-vol. of SO2. This is a prerequisite for substantial cost reductions in the smelter off-gas handling and treatment system. As an alternative to sulphuric acid production, numerous scrubbing concepts with alkali or dual-alkali combinations as well as organic absorbents have been proposed. Also the reduction of the SO2 to elemental sulphur has frequently been studied. Very few of those alternative processes have been built in industrial scale, but all were generally characterized by none sustainable operation due to cost reasons, problems with issues related to chemicals used and by-products or poor availability. Thus the traditional concept of converting the SO2 to sulphuric acid is most common, although regarded as un-economic, but is at least a proven, environmentally sustainable and reliable way of sulphur gas processing. With the high acid price levels these days, operating companies are even able to generate significant revenue with their otherwise ?fatal? acid.

Jan 1, 2009

A method is proposed for the evaluation of the influence of grout prestressing systems on the support resistance offered by timber packs. It is shown that, in order not to reduce the load-carrying capacity of timber packs, grout prestressing systems need to be at least as stiff as a single timber rise. The method was used to establish strength specifications for the grout prestressing systems to be used under non-seismic and seismic conditions. For non-seismic requirements, the 24-hour grout strength needs to be at least 1,7 MPa, and the 7-day grout strength 4,9 MPa. The investigation showed that the proposed strength specification is realistic in the light of current grout-strength capabilities. For seismic requirements, the grout strength needs to be at least 4 MPa and 8 MPa to prevent extensive damage to the grout during seismic events with a peak velocity of 1m/s 3 m/s respectively.

Jan 1, 1996

By Peter N. Calder, Alan Bauer

The complexity of modem open pit load-haul-dump systems is described, and the need for realistic working models is pointed out. Both standard and probabilistic simulation procedures are discussed, probabilistic simulation being indicated as the more powerful and practical technique. Acquisition of the necessary pit operating data required for simulator construction and general modelling procedures are described. Finally, results from a typical open pit simulator are used to indicate the scope of the technique.

Jan 1, 2014

By A. J. Rogers

The KX36 kimberlite was discovered using a high-resolution gradient aeromagnetic survey, with follow-up detailed ground geophysics and deflation soil sampling used to assess and prioritize the geophysical anomalies identified from the initial aeromagnetic survey. Prospect drilling intersected kimberlite in the first hole drilled on the KX36 anomaly. Preliminary evaluation has shown that KX36 is diamondiferous, and a more detailed evaluation and sampling programme is currently underway. The area around KX36 has been prospected by numerous companies over the last few decades, with sporadic kimberlite indicator mineral (KIM) recoveries in regional deflation sampling indicating the possible presence of kimberlites, but without sufficient resolution to ?home in? on specific targets. Previous (lower resolution) aeromagnetic surveys and soil sampling campaigns also did not define anomalies with sufficient detail to guide prospect drilling effectively. The discovery of KX36 highlights the prospectivity of areas of Botswana under deep Kalahari cover that have been explored previously. Keywords kimberlite exploration, central Kalahari, overburden, high resolution aeromagnetics, deflation sampling, KIM.

Jul 1, 2013

By J. McPherson

In order to add value to South Africa?s gold reserves AuTEK, a joint venture between Mintek and Anglogold-Ashanti, was started in 2000 with the aim of developing new industrial uses for gold. Accordingly gold catalysts are being made in kilogram quantities by Project AuTEK and sold toend users and other interested parties under the trade name AUROliteTM. Although these materials are optimized for use in CO oxidation applications, demonstration of appropriate activity, selectivity and durability in both liquid- and other gas-phase reactions has been shown1. The review below highlights the recent use of these materials, and other gold catalysts, in reactions of commercial interest.

Jan 1, 2009

EMMES Sampling Conference BACKGROUND & INTRODUCTION ?Impala acquires toll material to supplement production from ROM ?Toll material consists of filter cake, slurry and catalysts ?Samples are collected to determine the commercial values of the lots ?Slurry deliveries projected to remain relatively constant at 120tons dry solids per month, whereas filter cake deliveries set to increase five-fold to 800 tons dry solids per month ?Due to projected increase in toll material, new sampling and offloading facility presently under construction at Impala ?Presentation will cover two projects aimed at reducing the uncertainty associated with sampling of toll deliveries ?i.e. slurries and filter cake.

Jan 1, 2005