Search Documents

By R Linares

For centuries, diamond's superlative properties have earned it a reputation as the 'dream' material for mankind in its search to create advanced applications. Until recently, this dream has been realized only in the use of diamond for gemstones and abrasive applications where several tons of diamonds are now used on an annual basis. The vision of having large, high quality diamond as part of a broad engineering tool-kit for many diverse high tech industries is now becoming a reality however, with the advent of early stage commercial availability of single crystal and poly crystalline CVD diamond.

Jan 1, 2010

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 R. I. Klintworth

The multi-reef area of Cooke 3 Shaft provides a unique mining challenge on account of the very thin middlings between the pay bands and the marginal values of the reef. It is uneconomic or impractical, because of the excessive heights, to mine the middlings using conventional stoping methods. The development of suitable mining methods is discussed with particular emphasis on the control of water inflow and the policy of not jeopardizing or sterilizing other reef horizons by the mining method implemented. No definite solution is currently available, but with the aid of instrumentation, computer analyses and mechanized mining equipment, the mine continues to attempt to maximize extraction and profits.

Jan 1, 1988

By S. M. Bradshaw

In order to assess the requirements for online matching when using a transverse electric field (E-field) applicator to treat mineral ores continuously, the effect of varying load properties on matching has been investigated by simulation. The effective permittivity of the ore to be treated is expected to show variation on both short (< 1 s ) and long (minutes) time scales. By modelling the ore as a series of slices with alternating effective permittivity values, it was shown that permittivity variations on the scale of the expected particle size are attenuated significantly and matching is not required. For variations in permittivity on the length scale of the free-space wavelength, variations in reflected power are at most within ±10% of the mean. This is not considered operationally significant, as extreme permittivity variation over this length scale is unlikely, given the expected distribution of ore particle sizes to be treated. At typical ore transport speeds through the applicator, these variations occur on a time scale an order of magnitude shorter than the response time of typical industrial online matching equipment. This implies that online matching is neither required nor possible for short time scale variation. Long-term variations in dielectric properties can be adequately compensated for by current matching technologies. It is concluded that the transverse E-field applicator is robust to changes in the dielectric properties of crushed ores within the expected range of their variation.

Jan 1, 2012

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 C. Hey

The cycloned gravitated tailings backfill system, also referred to as a soft or low density fill, has been implemented at Vaal Reefs. Inhibiting the success of the system was the problem of shrinkage after placement. The problem was overcome by a pressure fill technique which eliminated settlement, contained costs and allowed remote placement. The technique involves the preinstallation of disposable pipes which are filled cyclically until a residual pressure of 0,5 bar of active support is generated in the filled paddock.

Jan 1, 1988

By R. Kosmicki

Wet end components of centrifugal slurry pumps used in the hydraulic transport of solids are subject to substantial erosive wear. Accurate prediction of the casing wear rate and location for a particular duty is beneficial for correct pump selection and design, maintenance planning, and elimination of emergency shutdowns. CFD multiphase simulation using the Eulerian-Eulerian approach is being applied successfully to determine the velocity fields and solids concentration in the centrifugal pump, allowing for accurate predictions of casing wear patterns resulting from sliding abrasive wear. Simulation results for various single domain and multi-domain (multistage) multiphase simulations are discussed. Emphasis is placed on results from a 3-dimensional, multi-stage transient, multiphase simulation and comparison to field data.

Jan 1, 2007

By M. Guarascio

Microseismic monitoring of mining areas is a developing technique, described here for the Belvedere Spinello Mine, southern Italy, where dissolution cavities in the mining area have proved problematic. The preliminary condition for locating seismic impulses has been found to be a reliable seismic ground model. Ground signals are continuously recorded by means of data from piezometric wells, for sinkhole data, and linked gephones, for microseismic data. A computer system has been implemented to collect, analyse and interpret the incoming signals consequently, identification and classification of hypocentres of activity is facilitated, with advantages in terms of safety, preventing harmful side-effects, including rock bursts, and for environmental conservation.

Jan 1, 1987

By J H. Sullivan

Contents Background information Locality of Kumba?s Iron Ore Mines Sishen?s Product Specifications Geological Description of boreholes Sample Preperation Block delineations Production Geology Process Laboratory information Turnover times reached Inter Laboratory Comparisons Quality control activities in lab Purpose of laboratory Results attained Standard samples Monitoring of processes with QA/QC standards Mean paired difference of duplicates Duplicate samples Conclusion

Jan 1, 2005

By J. T. M. Amphlett, C. A. Sharrad, M. D. Ogden, R. I. Foster

"A renewed interest in nuclear power around the world in order to reduce greenhouse gas emissions is going to increase demand for uranium as fuel. This will result in more uranium being mined, which will in turn increase associated environmental pressures, such as fresh water use. A move to lower quality waters containing impurities such as chloride would help alleviate these pressures. In this work, we determined the uptake characteristics of weakly basic anion exchange resin Ps-EDA towards uranium from saline solutions in a dynamic flow column. Breakthrough curves were produced, with suppression of uptake being observed for chloride concentrations above 5 g L-1. Calculated resin saturation capacities at zero and 5 g L-1 chloride are comparable with literature values for strong-base anion exchange resins, and exceed those published for weak-base resins up to 20 g L-1 chloride. Data has been fitted to multiple breakthrough models, with the modified dose-response model most effectively predicting uranium recovery. The results show that the ethylenediamine functionality could be suitable for use in future uranium processing flow sheets where a high-saline lixiviant is used. IntroductionIon exchange (IX) is a key technology in the uranium mining industry and is well established for the extraction of uranium from both acidic and alkaline leach liquors (Edwards and Oliver, 2000). It was first employed in 1952 at the West Rand mine in South Africa (Ford, 1993; Taylor, 2016). H2SO4 and Na2CO3 are the most commonly employed lixiviants used to solubilize uranium in acidic and alkaline leach conditions respectively. The chemistry of these systems causes uranium to form anionic sulphate or carbonate complexes, which can be taken advantage of by anion exchange resins.Another major technology for the extraction and purification of uranium from leach liquors is solvent extraction (SX). This technique involves the extraction of uranium from the aqueous phase into an immiscible organic layer. Although this is a commonly used method, there are major drawbacks to it, including the use of large volumes of flammable solvents, solvent loss, phase disengagement, third phase formation, and the production of problematic degradation products (Veliscek-Carolan, 2016). These problems can be circumvented through the use of IX resins."

Dec 1, 2018

By H. Wagner

It is a great privilege for me to have been asked to present the closing address to this most successful symposium on backfill in the South African mining industry. When I accepted this invitation I did not fully appreciate the tremendous progress made on most aspects of backfilling in the last few years. The number and quality of papers presented at this symposium bear testimony to the mining industry&apos;s determination and success in introducing backfill in underground mines to improve strata control and environmental conditions, and to provide better protection to mineworkers against the hazards of rockbursts and rockfalls. Many contributions demonstrated that these benefits can be achieved at a reasonable cost, and in some instances improved grade and higher rate of face advance result in improved economics. In my closing address I will attempt to summarize the progress made in the various aspects of backfilling underground workings and to identify those areas which, in my opinion, require further attention and effort. I will undertake this review under the following main headings: ? fundamentals of backfilling; ? design of backfill systems; ? operation of backfill systems; ? control of backfill systems; and other aspects of backfill systems.

Jan 1, 1988

By P. W. J. van Rensburg

COLLOQUIUM AND GENERAL MEETING A General Meeting and Colloquium on comminution was held on March 13th, 1974, at Kelvin House, Johannesburg. Mr P. W. J. van Rensburg (President) was in the chair. The Colloquium was attended by 140 delegates and was opened by the President at 9.15 a.m. MINUTES The minutes of the general meeting held on November 14th, 1973, as published in the December issue of the Journal, were confirmed.

Jan 5, 1974

By G. Voiloshnikov, P. Koblova, Ye. Musin

Preg-robbing activity of the carbonaceous matter negatively impacts the process of precious metals recovery from gold-bearing ores and concentrates. In this paper, ore heap leaching (HL) using a blinding agent which inhibits ‘preg-robbing’ is a promising method. A carbonaceous ‘preg-robbing’ gold ore with head gold grade of 1.92 g/t from a Russian deposit was studied. Corg was 1.12%. In accordance with the Irgiredmet technique, preg-robbing activity was 65.3%. Surfactant reagent DN was used as the blinding agent. Column tests on the ore HL were conducted using two options. They were: a conventional flow sheet (Column 1) and a flow sheet with the reagent addition (Column 2). Gold recovery in Column 1 was 55.39% while gold recovery in Column 2 was 68.48%. The test results confirmed the efficiency of reagent DN. Keywords: Carbonaceous ore, organic blanking, preg-robbing, recovery

Jan 1, 2020

By Q. G. Reynolds

The dual-electrode DC arc furnace, an alternative design using an anode and cathode electrode instead of a hearth anode, was studied at small scale using computational modelling methods. Particular attention was paid to the effect of two key design variables, the arc length and the electrode separation, on the furnace behaviour. It was found that reducing the arc length to brush arc conditions was a valid means of overcoming several of the limitations of the dual-electrode design, namely high voltages and arc deflection.

Jan 1, 2012

By D. Borman

The location of underground positions in mines has usually fallen to their survey department&apos;s. Their usual tasks include: ? installation of a high-precision peg network like the National Survey grid as beacons ? offset measurements to the sidewalls, and sometimes hangingwall and footwalls, of development tunnels and excavations ? offsetting of stoping panels for the calculation of face ? advance and the square meterage of area removed. Other departments build their observations into the plans produced by the surveyors. If more precision is required, they ask the surveyors to `elevate&apos; their points with a theodolite. Apart from the survey peg network and `elevations&apos; these measurements are usually planer measurements suitable for producing plans, sections and projection sheets. When the only representation medium was a sheet of paper or transparency, this was perfectly suitable. However the development of CAD models of the workings has changed all this. Full 3D representation is not properly catered for in the tool sets in current use, and needless hours are spent converting analogue-type observations into digital form. The basic survey models need to be augmented by the observations of other disciplines that are also required to locate positions underground. These include: ? the need for geologists to plott their mapping and ? borehole logs into 3D space ? the need for samplers to position their sample points accurately because the geostatistical models are biased and inaccurate ? the need for stoping width recorders to position their thickness observations to prevent errant evaluation and bonuses ? the need for rock engineers to place their mappings into 3D to build true geotechnical models to manage geotechnical stresses ? the need for production officials to receive updated face ? positions during the month so that they can manage the ? production and utilize their resources properly. This paper covers a new method of positioning profiling points to a suitable degree of accuracy. I believe the method is sufficiently simple and cheap for all to use. Historical methods Platinum and gold orebodies, especially in South Africa, are generally narrow tabular deposits. This made them suitable for depicting on a 2D medium like paper. The determination of stoping or face widths was not a problem, as the ore is removed in a single stoping process. Such 2D representations could be easily positioned using tape offsetting between survey pegs or points tied in from survey pegs. Problems of dip were handled by using &apos;Stope Sheets&apos; which chose a best fit projection for the whole area depicted or by using true dip section sheets for inclined tunnels. Rolling reef and potholes were the common areas of difficulty. Most mines now model their orebody and plan the extraction in computer graphics. This means that the representation of the current workings has to change to support this trend. It now becomes a truly 3D problem. Mining officials find it inconvenient to have their actual workings in single-line depictions while their orebody is depicted with top and bottom contacts and the planned tunnels in 3D shapes. Geological models which form the basis for the resource model and planning process are often out of date, as the updating process is slow. The geological mapping has to be plotted onto sections and plans. These are then digitized into graphics by a draughtsman and checked by the geologist. Only then does the interpretation and model update take place. Potential methods to create 3D &apos;Actuals&apos; Global positioning systems (GPS) Surface mines have been blessed by the advent of GPS technology. These simple-to-operate pieces of equipment and compatible software make it possible for all types of mine employees to locate themselves, and therefore to locate their observations. GPS are often inexpensive and give an acceptable degree of accuracy. Only in deep pits or close to the highwalls are observations hindered. Such technology cannot however, work underground. Ground penetrating radar (GPR) GPR is reported to be very useful for estimating the positions of potholes and faults. However it is still considered as providing an estimate, not a definite measurement. GPR is good for seeing into solid rock, not into open spaces. Inertia reading devices Experiments with inertia reading devices have been conducted on the mines. They were the forerunners of GPS for military guidance systems, and were even used for city navigation in the early 70s. They do however work best with heavy or fast-spinning gyros. Anglogold Ashanti&apos;s attempt to use them were discontinued in the mid-90s when the developers asked for an additional few million rand for a device that would weigh more than 12 kg and have a limited operational life.

Jan 1, 2006

By L. S. Linda, P. G. H Pistorius

Ferritic stainless steel is utilized to fabricate automotive exhaust systems using a ferritic weld metal. Ductility of the weld metal is higher if its microstructure contains a significant proportion of equiaxed grains. The formation of equiaxed (rather than columnar) grains is favoured by a higher titanium weld metal content. In this study, the Ti content of ferritic stainless steel weld metal was changed by using Tifree (Type 436) and Ti-containing (441) ferritic stainless steel as base metals. The metal-cored welding consumable contained 0.4% Ti. Gas–tungsten arc welding and gas–metal arc welding processes were compared. The weld metal Ti content ranged from zero to 0.5% Ti, as determined from scanning electron microscopy supplemented by inductively coupled plasma optical emission spectroscopy. Cross-sections of the weld beads were subjected to point counting (to estimate the fraction of equiaxed grains) and image analysis (to estimate the average grain size). Point counting proved to be more reliable. The fraction of equiaxed grains was sensitive to the Ti content, but not to the welding process. Below 0.4% Ti, the fraction of equiaxed grains gradually increased with an increase in the weld metal Ti content; above 0.4% Ti, the fraction of equiaxed grains rapidly increased with increasing Ti content. The transition in behaviour at 0.4% Ti corresponded to a Ti content at which Ti-rich precipitates became stable at the estimated liquidus temperature of the weld metal.

Jul 2, 2022

By G. A. Bezuidenhout

Lonmin Platinum installed a concentrated mode dual-alkali scrubber at the smelter in Marikana in 2002. The dual-alkali scrubber was the technology of choice at that time as a sulphur fixation plant, due to the perceived benefits of handling both the high SO2 concentrations of converter off-gas and the swings in SO2 concentration that are linked to Peirce-Smith operation. Owing to current and impending legislative requirements for air quality and waste, Lonmin is currently considering additions to the dual-alkali plant, but is also evaluating alternative technologies for sulphur fixation. This paper reviews the decision of Lonmin to install a concentrated mode dual-alkali scrubber and presents plant performance achieved. It also describes the important control variables and sensitivities of the plant, and the final product that is produced by the operation of the plant. The legislative requirement that drives the Lonmin technology evaluation is also discussed.

Jan 1, 2012

By R. W. O. Kersten

Backfilling is one of the options available to the mining engineer in mine design. The decision as to the type of backfill is dependent on the purpose for which it will be used. For example, in a situation where high-grade, steeply dipping multiple reefs are to be mined, the purpose would be the following: ? to facilitate maximum extraction; a ? to minimize loss of fines; ? to allow closely spaced multiple reefs to be mined; and a ? to create a working platform. The physical properties required which will satisfy the abovementioned requirements can then be defined; the design of the fill plant, as well as the transport of the fill, will be governed by these considerations. The same procedure is also adopted in deciding on backfill in single- reef gold mines. The first question to be asked is the purpose of the fill. It may be to reduce the energy release rate, for environmental reasons, to reduce timber usage, to improve productivity, to reduce stoping costs, to obtain higher mining extraction, and so on. Only after one, or a combination, of these factors has been selected, can the specifications for the fill be decided on, and the plant designed accordingly. The introduction of backfill at Sheba Gold Mine will be used to illustrate the procedure adopted by Anglovaal in determining the type of fill required.

Jan 1, 1988

By R. B. Khumalo, F. K. Mulenga

Sampling in a continuous flotation plant is always a challenge as these plants are meant for production and not research work. The continuous flotation operation used in this work produced three sets of data: the first was based on overall plant performance, done by sampling the feed, concentrate, and tails; the second was based on the roughers row cell-by-cell; the third set of results came from the cleaners/recleaners row cell-by-cell. The highest recovery results in all sets of data obtained lie in the particle size ranges of 40 μm and 100 μm, which is in agreement with results by other researchers in the same field. King’s theoretical (model) recovery proved to be able to fit the experimental data but there is still room for improvement as the sum of squared error ranged between 400– 1200. Data obtained in continuous flotation operation could be used with batch flotation test-work to characterize scale-up of flotation cells.

Jan 1, 2023

By F. E. Steffens

The application of kriging in assessing the area rainfall in a weather modification experiment is complicated by the presence of many zero rainfall recordings on a given day, and the fact that the variograms seem to be quite different for the rainfall on different days. Indicator variograms are shown to be directly related to two sets of conditional probabilities. Probability kriging is used in estimating the probability of rainfall amounts above any cutoff at any point

Jan 1, 1987