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By C. Chongo, F. X. Paquot, C. Ngulube

"Over the last six years, the Kansanshi copper-gold mine has continued to process significant quantities of complex transitional mixed ores. Initially, the ore treated came predominantly from accumulated stockpiles. Subsequently, the feed source shifted primarily to freshly mined ore that generally showed less tarnish with better flotation kinetics, but with the downside of lower concentrate grades. A number of changes were made to improve the efficiency of the rougher circuit and quality of concentrate produced. These changes were as a result of initial mineralogical studies and laboratory flotation test work that were discussed at length in a previous paper1. Salient among the recommendations adopted as a result of previous work were increased circuit capacity and a modified configuration to increase the residence time and the number of sulphidization stages. These modifications were completed and commissioned in 2011. This, however, resulted in significantly low rougher concentrate grades and a below-specification final concentrate product. This was due primarily to higher mass pulls from the extended rougher bank with multiple concentrate discharge streams, and which necessitated an enlarged cleaning capability. The extra cleaning capacity came on stream in 2014. Of note was the development of a recovery model, based on the strong correlation between the total copper and acid-soluble copper ratio, as a tool for monitoring plant performance. IntroductionThe Kansanshi mine, the largest copper mine in Africa, is 80% owned by Kansanshi Mining plc, a subsidiary of First Quantum Minerals. The remaining 20% is owned by the state through the parastatal Zambia Consolidated Copper Mines Ltd (ZCCM). The mine is located approximately 10 km north of the town of Solwezi and 180 km to the northwest of the Copperbelt town of Chingola. The mine has been in commercial operation since 2005."

Jan 1, 2016

By P. J. D. Lloyd

An account is given of the development of a process to concentrate gold and other valuable minerals and to produce a discardable waste. In this process, the ore is coarsely milled, a bulk flotation concentrate is prepared, and the flotation tailing is scavenged in a hydrocyclone, which returns coarse gangue, moderately coarse valuable minerals, and locked valuable minerals back to the mill. The engineering developments required by this circuit in order that it will fit underground, and the progress made towards the achievement of those requirements, are reviewed. If the waste is to be suitable for use as a backfill in a deep-level, flat tabular excavation, it should be capable of being placed hydraulically, and should have both low voidage and high rates of drainage. Such a material could be prepared by the fine screening of the overflow from the cyclone in the proposed circuit. Possible methods for the handling of the concentrate and the recovery of its valuable constituents are described. The paper concludes with a discussion of the possible benefits from the use, in deep-level Witwatersrand mines, of a system involving concentration underground, extensive backfilling using the tailings from the concentration process, and hydraulic hoisting of the concentrate.

Jan 1, 1979

"Chairman: Dr R. E. ROBINSON Rapporteur: Dr R. P. COLBORNPapers:The simulation of crushing plants by W. J. WhitenSimulation of multi-component flotation plants by B. K. Loveday and G. R. MarchantComputer control of flotation at the Ecstall concentrator by M. P. Amsden C. Chapman and M. G. ReadingModel for the design and control of flotation plants by R. P. KingIn presenting his paper Dr W. J. Whiten outlined the basic concepts on which the control model was based and emphasized the fact that empirical models based as much as possible on theory were used to simulate each unit of the crushing plant. The final parameters of each model were computed using data collected from the plant. Unfortunately, the system did not permit accurate extrapolation but was successful when operating in the region from which the parameters were calculated.He concluded from the results of the test work that the crusher amperage was a critical parameter and that the utilization of the model gave a 15 per cent increase in the plant output. This was because the model predicted that a marginally fine grind would provide a significant increase in throughput. Dr Whiten elaborated on what constituted the multiple spline regression, explaining that it was a least-squares curve-fitting technique in one or more dimensions, where the calculation of coefficients in analytic expressions was replaced by the calculation of typical points on a very smooth curve called a spline function. The emphasis was placed on the shape and value of the curve or curves instead of on the coefficients as in analytic regression. A spline function was the line drawn between all points constituting the data set.Dr B. K. Loveday commented that the simulation was unusual in that the optimum throughput was considered to be the maximum throughput, which, surely, was limited by the crusher size. He also emphasized the importance of the interaction between both crushing and grinding circuits and added that in practice the optimum operating conditions were inter-dependent. Dr Whiten replied that in the case of the plant under consideration, the crushing process was not, in fact, the limiting operation.Mr C. E. Clifford indicated that the model was being used to simulate a number of crushing and grinding circuits at Mount Isa Mines. He reported that the model simulated the circuit satisfactorily for primary and secondary gap settings of 0,625 in. to 0,375 in., but that adjustment had to be made to the model parameters for gap settings of 0,250 in. to 0,125 in.In reply to a question from Dr D. M. Hawkins, Dr Whiten said that he preferred to use low-order splines with smaller segments rather than high-order spline functions with large segments."

Jan 1, 2014

By C. Montoya

This paper shows, through a case study, the impact of multivariate grade modelling upon mine design and mine planning. A deposit explored by drill holes is considered, in which the grades of five elements (copper, silver, molybdenum, arsenic, and antimony) are of interest. Forty alternative models of the deposit are constructed by fitting the joint correlation structure of the grade variables and using conditional cosimulation. In addition, a reference model, obtained by averaging the alternative models, is also considered. The study shows that the resulting mine design (final pit characteristics and production schedules) is sensitive to the grade model under consideration, and that the design based on the reference model may not be optimal when compared to the alternative models based on cosimulation. However, when assuming a given long-term plan and extraction sequence, the grades and net present value (NPV) calculated on the reference model are unbiased with respect to those calculated on the alternative models with the same extraction sequence. The latter allow assessing the possible dispersion of the actual grades and NPV around their expected values, and are useful for the planner in order to determine the probability of meeting given production targets and of exceeding or falling short of given threshold grades. Additionally, unlike cosimulation, the separate simulation of each grade variable leads to unrealistic resource models and to biased results in mine design and mine planning. This approach should therefore be avoided, unless the grade variables are spatially uncorrelated.

Jan 1, 2012

By J. Rowe

The attrition of activated carbon, and the loss of gold associated with it, is of significant economic importance to the operation of a CIP/CIL circuit The focus of this study was on activated carbon recovered from an elution circuit which was deemed too fine for reuse. Results of cyclosizer and laser particle size analysis identified that most of the carbon was contained in the larger size fraction suggesting formation by abrasion. Digestion and AAS analysis of the individual size fractions identified a disproportionate concentration of gold in the finer size fractions which was identified by scanning electron microscopy to be due to the presence of fine metallic gold formed as a result of the acid washing process. Attempts to strip the remaining gold using sodium hydroxide or sodium sulphide based solutions proved unsuccessful due to poor elution efficiencies and re adsorption of gold. Upgrading of the material by froth flotation was also investigated using various conventional flotation reagents which had some success in concentrating the free metallic gold, however, grade and/or recoveries were considered less than desirable. Greater success was ultimately found in the transfer of gold from the fine carbon material onto coarser virgin activated carbon using a caustic cyanide solution. Sodium sulphide, sodium chloride and ammonium chloride based solutions were also trialled but proved less successful owing to their inability to mobilise metallic gold or gold cyanide species. Repetition of the transfer process proved capable of stripping 97% of the gold contained on the carbon fines for abed volume ratio of 6:1.

Jan 1, 2009

The kinetics of cyanide loss were found to be first order under any given set of conditions, allowing rate constants to be easily determined. At room temperature and in the absence of activated carbon, some cyanide is lost by hydrolysis to hydrogen cyanide, but this does not occur to any significant extent at pH values higher than about 10. A higher rate of hydrolysis occurs when air agitation is used. When activated carbon is present, an additional carbon-catalysed oxidation reaction is responsible for a fairly high loss of cyanide. The evidence indicates a reaction mechanism that consumes oxygen and produces cyanate ion. Some of the cyanate thus produced decomposes to form a mixture of ammonia, carbonate, and urea, depending on the solution conditions. Additional cyanide is lost as a result of the adsorption of sodium cyanide by the activated carbon. At high temperatures, an additional hydrolysis reaction, which involves the formation of ammonium formate as an intermediate, occurs an/j is responsible for. a high loss of cyanide, leading ultimately to the formation of ammonia, hydrogen, and carbon dioxide. The presence of activated carbon has no effect on the rate of this reaction.

Jan 1, 1990

By M. Helm

Over the last 40 years, numerous investigations have focussed on the preg-robbing capacity of carbonaceous material during gold ore processing. Various techniques have been applied to characterize the physical and chemical properties of the carbonaceous material in efforts to predict its preg-robbing capacity. The present study, which forms part of an ongoing investigation, is specifically designed to increase the understanding of preg-robbing in ores containing carbonaceous material. In excess of 100 samples from 13 gold mines located in major gold provinces of the world have been incorporated into the present study. These samples were characterized using industry standard metallurgical techniques and were shown to have gold adsorption capacities ranging from a few grams to many hundreds of grams of gold per ton of ore. Further analysis showed that the crystalline nature of the carbonaceous material, which is related to its geological history, is important in determining the preg-robbing capacity of an ore. This finding builds on the common understanding that the preg-robbing behaviour of an ore is related to the amount (or abundance) of carbonaceous material present in that ore. In this study, Raman spectroscopy was used to evaluate the physical nature of carbonaceous material. This is a tool which has been successfully applied by researchers for the characterisation of carbon materials, with respect to crystallite size and lattice defects. Raman analysis of the samples included in this study showed varying degrees of disorder in the carbonaceous materials from the different deposits. Comparison of the Raman spectra with the gold loading capacities of the samples indicated a direct relationship between the structure of the carbonaceous material and its capacity to preg-rob gold. From this, a simple and robust method has been developed based on the Raman spectra of the sample and carbonaceous material content to predict the preg-robbing capacity of an ore. The potential exists to develop a predictive tool using Raman spectroscopy for characterising the preg-robbing capacity of an ore. Such a tool would have potential application in projects ranging from the early stage of exploration through to more detailed feasibility studies and mining operations. The result of applying the predictive method outlined in this paper would be the effective and proactive management of the deleterious influence of carbonaceous material on gold recovery in mining operations.

Jan 1, 2009

By P. Lloyd

Perceptions of disaster caused by burning fossil fuels have reached such a pitch that they seriously threaten the very future of the industry. Coal is a dirty word. A leader in Business Day(January 192009) claimed ?There is no disputing that renewable and non-polluting energy sources are preferable to the country?the true cost of so-called cheap coal-fired power stations is neither reflected nor accounted for by Eskom?the true and immediate but unacknowledged cost of continued coal mining is apparent in the catastrophic level of acidification from mining runoff of all significant natural water resources in the country?and their waters have been rendered unfit for human consumption. Air quality is in a similar state with?increases in pulmonary disease causing workforce absenteeism and compromised childhood development, among many other health problems recorded in areas polluted by coal mining.? The upshot is that our latest coal-fired power station, Kusile, is being required to use flue gas desulphurization. The costs are considerable, and the benefits minimal. Meanwhile, exports are being threatened by EU directives and an assumption that South African coal gives off excessive quantities of SOx and NOx when burned. The industry needs to arm itself with clear responses to these and similar misconceptions, and to communicate those responses loudly and clearly, if it is to survive.

Jan 1, 2011

By H. Wagner

The discovery of the gold-rich Main Reef Group of reefs on the farm Langlaagte in 1886 marked the opening of the richest and most extensive goldfield in history. Mining of the narrow reefs progressed from the outcrops to more than 3,5 km, and has made South Africa the foremost mining country in the world. Changes in the political and socio-economic climate create a new challenge to the gold-mining industry. The most significant of these is the emergence of Black trade unions, with their demands for higher wages, improved safety, job advancement, and abolition of discriminatory legislation. Industrial conflicts on gold mines have risen significantly in the past ten years, and are likely to continue in the future, although the causes of these conflicts may change. Events largely outside the control of the gold-mining industry, such as the improved dollar price for gold and the depreciation of the value of the rand relative to major currencies, have enabled the industry to meet the demands for higher wages and to narrow the wage gap. However, labour productivities have improved insignificantly and are a cause of major concern for the future development of the industry. Continued pressure in the industrial-relations area, the inflation of working costs, and the extension of mining operations to greater depths and more difficult areas create major challenges to mine managements and mining engineers. Significant improvements in mining technology, environmental control, and safety will have to be made to ensure the long-term survival of the industry. The unavoidable introduction in deep gold mines of mechanization on a larger scale to meet the requirements of higher labour productivities and a better and safer underground environment will have a major impact on the cost and management structure of these mines. Engineering will assume a more important role on deep gold mil1es, and management styles and structures will have to be adapted to accommodate these changes. The supply of suitably qualified engineers, technicians, and artisans will be a crucial factor controlling the rate of technological change. The industry is well-geared through its Group system to meet these challenges, and to benefit from the experience gained in the operation of highly mechanized mines. However, changes take time to implement and there is very little time left.

Jan 1, 1986

By F. G. Hill

The paper reviews the restrictions imposed by the Department of Mines (now the Department of Mineral and Energy Affairs) on the surface use of ground that has been undermined at shallow depths (down to a depth of244m). The reasons for the restrictions are discussed, with special reference to the early records kept by the Department of Mines on subsidence and fracture of the surface. A discussion of the nature of the strata overlying the ore-body, and the effect of undermining, is followed by a detailed account of investigational work, particularly since 1970, on the stability of shallowly undermined ground. The significance of the data collected during the investigations is considered next, with special reference to the social and economic implications. These are so farreaching, that it is proposed that the already flexible approach of the Department of Mineral and Energy Affairs in considering what structures may be built on undermined ground should become even more flexible. To this end, the appointment of a Commission is proposed to collect as much information as possible on the stability of ground undermined at shallow depth, and to revise the current overrestrictive conditions or guide lines that are in use.

Jan 1, 1981

For practical reasons all basic input data for the gold mines of the Anglovaal Group conform to a regular grid of averages of sample values within 25-ft squares in the plane of the ore body; individual sample values with their metric co-ordinates are input and converted by a computer program to the basic 25-ft square averages. At the Prieska copper mine the bore- hole data are forced on to a regular grid of 15-m squares corresponding to the coordinates of the grid points nearest to the actual borehole intersections. As for the gold mines the Prieska ore body, although some 3 to 30 m thick, is also dealt with on a two-dimensional basis (Krige, 1973). On the gold mines the data subjected to geostatistical analysis cover: gold values (in cm g/t), uranium values (cm kg/t), and channel widths (cm). The gold and uranium values are normalised on the basis of log (value plus constant) and all the geostatistical analyses are performed on these transformed values. The channel widths usually conform reasonably well to the normal distribution and are, therefore, not transformed. At Prieska the metal grades analysed cover the two main products, copper and zinc, as well as the impurities lead and bismuth; in addition the specific gravity values and the hanging- and foot-wall deviations from a projection plane are also handled. These were all previously used on an untransformed basis but because of problems associated with the proportional effect the lognormal-de Wijsian model is now used for some of the grade variables. The key computer pro- grams can be summarised briefly as follows:

Jan 1, 1981

By Keith Rowley, Neal Harries, David Noon

The management of risks associated with slope instability is an essential process in the safe and economic operation of open cut mines. The ?slope stability radar? (SSR) has been developed to better manage those risks. The SSR remotely scans rock slopes to continuously measure any surface movement and can be used to detect and alert users of wall movements with sub-millimetre precision. The high level of movement precision and broad area coverage of the rock face can allow for a better understanding of the geomechanics of slope deformation, including magnitude of potential failures and additional warning time of impending instability. Additionally, radar waves adequately penetrate through rain, dust and smoke to give reliable measurements, 24 hours a day. SSR systems have been deployed in many mines in Australia, Indonesia, South Africa, Zambia, Chile and the United States. Greater than 70 rock falls and waste dump failures (from several to millions of tonnes) have been monitored, and on every occasion precursor ?warning? movements were recorded by the SSR. This technology enables a radical change in the management of risks in open cut mining. This paper will present recent case studies of the SSR operation in coal and metalliferous mines.

Jan 1, 2006

By T. Orupold

This paper covers the commercial development of gravity separation of fine particles using a Lamella High Shear Rate REFLUX? Classifier (REFLUX? Classifier), focusing primarily on coal applications. The REFLUX? Classifier is a fluidized bed device that incorporates a system of closely spaced parallel inclined channels located above the fluidized bed. These channels make it possible to achieve a significant suppression of the effects of particle size, resulting in a highly effective separation on the basis of density. The improved gravity separation performance is shown to be remarkably high, with a significant reduction in the variation of separation density with particle size, and a significant reduction in the change in Ecart probable error (Ep) with size. The first full commercial-sized units of the REFLUX? Classifier were field-tested in late 2009 in coal applications. More recently, the technology has been applied in fine particle separation in minerals applications and there are a number of full-sized units operating in chrome applications in South Africa. Initially, pilot-scaled units (typically the RC?300) were trialled in iron ore, mineral sands, and manganese plants amongst other minerals, typically after other technologies failed to achieve the desired results. Currently a number of laboratories globally are carrying out more testing in minerals applications. More than 50 RC? units are now operating in coal and minerals applications. This paper introduces the REFLUX? Classifier technology, identifies commercial applications, and gives some commercial results.

Jan 1, 2014

By R. O. Heckroodt

After a brief review of the characteristics of clay minerals and their origin, a summary is given of the industrial uses of different types of clay materials. The mining and beneficiation of clays are discussed, with special reference to the upgrading of certain types of materials. The occurrence and resources of the more important varieties of clays are dealt with in some detail, viz residual kaolin derived from granite and sediments, brickmaking clays, refractory clays, bentonite, and palygorskite. The Republic of South Africa is well endowed with a wide spectrum of clay materials, with one important exception. Kaolin suitable for paper coating is not known to occur in the Republic, and efforts to beneficiate and treat local materials to achieve the desired properties have so far been unsuccessful.

Jan 1, 1991

By J. Tikka, E. Bäcklund, N. -O. Lindfors

Tornados are the most violent weather events in the world, and we have all seen the forces and phenomena created by tornados in nature. Airgrinder AB has been working with a material treatment technology, which most easily could be described as an artificial tornado. The process consists principally of one air fan providing a high-velocity airstream that enters a mechanical cyclone. When the gas enters the cyclone, an outer vortex is created. This outer vortex rotates next to the cyclone wall, and at the bottom of the cyclone funnel the gas stream is turned and an inner vortex is created. The control of the air flow is tuned by a special device on top of the cyclone. The gas outlet is at the top of the cyclone and the material outlet at the bottom. The material is fed through a feeding device into the air stream channel prior to the inlet into the cyclone. The process is basically an improved grinding and dehydrating system, which is very efficient and environmentally friendly and can even be employed with very sticky materials. Also due to its rotating comminution, the material particles become rounded during grinding, hence more free flowing and easier to handle. MEFOS has already tested more than 30 different applications in the pilot equipment. The materials tested range from metallurgical slags containing 2?3% moisture to sludges with up to70% moisture. This technology has a potentially strong impact on mineral beneficiation, including the drying of sticky fine-grained materials, improved and selective gas scrubbing and the manufacture of free flowing powders.

Jan 1, 2007

By P. van der Westhuyzen

Gone are the days of stock-standard diamond beneficiation and final recovery circuits that could, with minor modifications, be adapted to treat any diamond-bearing ore source. A new era has dawned, offering the opportunity to streamline existing diamond processing operations or develop simpler, more efficient, and economical diamond processing plants, with the focus on more efficient comminution, beneficiation, and final recovery. This change in scene has been brought about by: ? The introduction, rapid development, and maturation of multiple comminution, sorting, and recovery technologies ? The need to adapt to a new standard of project approach post the commodity super-cycle phase, where optimizing existing operations and developing scalable, ?fit for purpose? new mines are fast becoming the norm in diamond processing plants in both primary and alluvial operations ? The quest for energy efficiency and lower labour costs ? More remote and inaccessible reserves (under lakes, tops of mountains etc.). This paper serves to identify some technology advances and demonstrates how these could be considered as replacements for or in combination with conventional technologies to arrive at an optimum techno-economic solution. To name a few applications/technologies: ? Comminution: conventional cone crusher, modified/specialized cone crusher, and the high-pressure grinding roll (HPGR). Although significant advances have been made in recent years, this paper only briefly covers comminution within the beneficiation circuit design ? Waste sorting: NIR (near-infrared) sorting, optical (colour) sorting, XRF (X-ray fluorescence) ? Primary concentration by combining dense media separation (DMS) with either XRT (X-ray transmissive), pulsed X-ray, jigs, or pan plants depending on the application, scale, and economics ? Final recovery of diamonds with either conventional X-ray technology, pulsed X-ray technology, or XRT. From recent studies, it can be concluded that there is no longer a standard solution, but rather the ?right? or appropriate solution. Through combining a sound knowledge of the ore source (ore dressing studies or onmine data gathering) and leveraging off the advances in technologies, one is able, through trade-off studies, to arrive at the ultimate techno-economic configuration, the ?right? solution. Emphasis is placed on maximizing diamond recoveries through appropriate technology selection and minimizing the associated costs in an effort to de-bottleneck or improve efficiencies of existing diamond processing plants, or to arrive at the ideal new diamond process plant design..

Jan 1, 2014

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 G. Mitchell

Much debate has ensued over the past few years on the speed of transformation in the mining industry. By transformation is meant the degree to which the industry has met the requirements of the Mining Charter. In response to this, the Department of Mineral Resources (DMR) commissioned a research study in 2009 to ascertain the degree of industry compliance. The mining industry in response made a presentation to the Minerals Portfolio Committee in Parliament in 2011, during which it released aggregated figures on industry compliance to the Mining Charter. The conclusions of both of the studies are widely divergent. It is argued in this paper that both processes are flawed. The government-sponsored research is empirically and methodologically weak and the results therefore have to be taken with a great degree of caution. The Chamber of Mines figures, on the other hand, while faithful to the reporting of the Chamber member companies, do not represent the entire span of the industry but only the larger mining companies. It is further argued that in order to ascertain a true reflection of the industry an independent audit be undertaken using recognized social scientific survey methods.

Jan 1, 2013

A wide range of drill holes and process streams are sampled for resource estimation, grade control and contractual purposes in the minerals industry. However, despite the availability of training courses, conferences and both national and international standards on correct sampling practices, it is still surprising how often little attention is given to ensuring that representative samples are collected for analysis. The reason for this is that the responsibility for sampling is often entrusted to personnel who do not appreciate the significance and importance of sampling, with cost being the main driving force rather than whether the sample is representative of the material from which it was extracted. This seriously undermines the precision and accuracy of the analyses subsequently generated and can render the analysis process a total waste of time and money and expose mining companies to serious, potential, financial losses. Company management needs to reverse this situation and ensure that sampling is given the attention it deserves to generate representative samples for analysis.

Jan 1, 2009

By D. J. Hallbom

A new graphical method termed the ?Design Curve Diagram? (DCD) has been developed to analyse non-Newtonian pipe flow data by relating the plastic Karman number to the plastic Reynolds number. Since the plastic Karman number is directly proportional to the pressure loss gradient and the plastic Reynolds number is directly proportional to the velocity, the DCD is essentially a non-dimensional pipe flow curve. This makes the DCD conceptually easier than the commonly used Hedström-Moody diagram. While, the DCD was developed for the analysis of yield plastic fluids (e.g., Bingham plastics), it is equally applicable to Newtonian fluids.

Jan 1, 2007