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By R. Altındag, D. Akbay

The point load index is a simple, fast, and inexpensive method for determining rock strength and can be applied both in the field and in the laboratory. There are, however, some disadvantages and limitations to the method, and the test results can be affected by the person carrying out the test, the rock characteristics, or the test device. In this study we describe an investigation into how the point load index value is affected by the shape of the conical platens used in the test. Point load index tests were carried out using different devices fitted with conical platens of different spherical radii, and on a modified device which circumvented the limitations/disadvantages. It was seen that the point load index value increased as the platen radius increased, as expected. In the case of testing using non-standard conical platens, an equation is proposed to normalize the point load index value with respect to the standard spherical radius value.

Nov 1, 2021

By L. Stamenov, A. Grigoryan, M. Nolte, E. Ayvazov, K. Evtiminova

Dundee Precious Metals Inc. (DPM) owns and operates the Ada Tepe gold mine and processing facility (previously referred to as the Krumovgrad Gold Project) located in south-western Bulgaria. The Ada Tepe mine became the first green filed project in past 40 year in Balkans and one of the few in Europe when it was commissioned during the first half of 2019. The plant produces a high-grade gold silicate concentrate generated through its comminution circuit and staged floatation reactors (SFR’s) while depositing its tailings in a state-of-the-art Integrated Mine Waste Facility (IMWF). This paper presents the successful commissioning, ramp-up and optimization of the Ada Tepe processing plant and how the various challenges, including that of an inexperienced front-line workforce, were overcome. More specifically addressing how the implemented modern processing technologies and the operational readiness program, supported the people and process to achieve the design parameters safely and consistently. Keywords: Commissioning, Optimization, Innovation, Gold mine, Digital mine

Jan 1, 2020

By C. M. Rule, A. K. Anyimadu, L. Knopjes

Ongoing development work on ultra-fine grinding for various applications at the Group?s concentrators has been conducted by Anglo Platinum over the last few years. Current potential applications for mainstream grinding and concentrate grinding are the subject of a group-wide research and development programme. The first 10 000-litre 2.6 MW IsaMill was jointly developed by Anglo Platinum, Xstrata Technology and Netszch for installation at the Western Limb Tailings Re-treatment project in Rustenburg, South Africa. The unit was commissioned in late 2003/early 2004, and has operated in an intermediate concentrate regrind application successfully since. This paper describes the operational performance to date, as compared with the original duty specifications and objectives. The first mainstream M10 000 IsaMill with a 3 MW drive will be operational in November2006 at the Potgietersrus Platinum (PPL) ?Platreef? Sandsloot Concentrator in South Africa?s Limpopo Province. Key Words: Western Limb Tailings Re-treatment Plant, IsaMilling, Platreef, Platinum, Palladium, PGMs, tailings.

Jan 1, 2006

By N. B. Strydom

Die bedryfsfisioloog en lugbesoedeling N. B. STRYDOM, Ph.D. (Phys.) (Illinois) (Genoot) Although the industrial physiologist can still be regarded as a rarity in South African industry, it is obvious that he could make a positive contribution to the control of air pollution. For the past twenty-two years, the gold-mining industry has invoked the aid of industrial physiologists in solving various problems that continually crop up in the more effective and safer utilization of man-power. Air pollution is only one facet that has received attention. It can be stated emphatically that other industries could gain many advantages from the employment of this type of specialist. Because of inadequate opportunities for academic training, however, the industrial physiologists available might not be enough to fill all the possible posts in industry at present, but confidence is expressed that interested persons will soon be able to follow a full university course in this field of study.

By A. L. Hinde, A. A. Bradley, K. H. Stanton, P. J. D. Lloyd, G. K. Schymura

As part of its programme to develop methods for concentrating minerals underground, the Chamber of Mines of South Africa in conjunction with Lurgi evolved and tested a I MW centrifugal mill. The machine is capable, in the autogenous mode, of grinding more than 25 t/h of minus 75 plus 44 mm hard quartzite to a minus 3 mm product containing over 50 per cent minus 75 µm material, and as a ball mill of grinding more than 60 t/h of minus 19 mm quartzite to a minus 3 mm product containing over 35 per cent minus 75 µm material. Extrapolation of computer models of the process suggests that these limits can be comfortably exceeded. Long-term continuous testing is in hand, aimed at proving that this I m in diameter by I m long mill is in every respect the equivalent of a conventional 4 m by 6 m ball mill.

Jan 1, 1982

By L. A. Vermeulen

Electronic circuits were developed and successfully utilized to record, store, and continuously transmit to a remote station physical information relating to the impacts of pebbles on the shell liners of an industrial pebble mill, and of electrical conduction in the mineral pulp. The information was obtained by the instrumentation of some of the bolts that are used to clamp the liner blocks and litter bars to the mill shell. The features associated with the impact and conduction signals have been interpreted, and it is shown that such signals can lead to continuous measurements of the volume of the load in an industrial mill. Information is given regarding the angular distribution of direct impacts of the pebbles onto the shell liners, the power required to promote impacts, the amount of material in flight, the impact velocity, and the average number of direct impacts with the shell liner that any given pebble undergoes in unit time in the given mill.

Jan 1, 1984

The treatment of gold-plant tailings with ferrous sulphate to remove the cyanide is currently in use, on several gold plants. In some cases there is scope for optimization the process. The present work provides a detailed study of the reaction between cyanide and ferrous sulphate. Optimal conditions for the removal of total cyande required a ph of 5,.5 to 6,5 and an Fe:CN molar ratio of 0,5. Ferrocyanide ion is shown to be unstable In aqueous acidic solution, with rapid oxidation to ferricyanide, (Fe(CN) 6 ), and formation .of Fe(CN)5H2O3- at pH values below 4, The precipitate from the reaction between cyanide and ferrous sulphate consists mainly 01 Insoluble Prussian blue, Fe4[Fe(CNI&!.3,and IS shown to be unstable in the presence of alkaline solution, since it decomposes rapidly at pH values above 7 to form ferrocyanide, (Fe(CN)6 ), in solution and various insoluble iron oxides,

Jan 1, 1992

In Chapter 1 we mentioned that up to three components are considered to represent the variability of regionalized variables : a deterministic component, a correlated component, and a random component. In Chapter 2 we considered some of the models based on the assumption of randomly distributed values: the random component was assumed to be the only one present. In Chapters 3 to 11, more general but also more complex models were described, based on the assumption that the values were correlated with the possible presence of random noise. In this chapter we introduce a model used to analyse non- stationary data, for which a deterministic component (or drift) must be assumed. This model will be used for estimation purposes, and the corresponding optimal linear estimation procedure is known as universal kriging. The theory of universal kriging is much more complex than the theory of kriging. Fortunately, in the majority of mine valuation problems the drift can be ignored and the simpler form of kriging can be used.

Jan 1, 1978

By V. P. Kolosyuk, A. M. Bryukhanov

Occurrences of hazardous events (explosions of methane or coal dust, fires, outbursts) have been investigated and presented as a flow of events in time. It has been shown that flows of hazardous events in a long time span are homogeneous, stationary and no-after effect flows and can be considered as stationary Poisson flows. A flow of CH4/coal dust explosions that had happened for the last 27 years in Ukraine was analyzed. The explosions have been statistically processed. Practicability of agreement of statistical and theoretical data on mathematical expectation and mean square deviation of time interval between explosion and the explosion intensity has been stated. Probability of an emergency event in time is expressed through an exponential function, while mathematical expectation of an accident and mean square deviation of time interval between successive explosions are in inverse proportion to the accident intensity. Accident probability for practical purposes can be determined as a product of accident intensity by calculated time interval.

Jan 1, 2003

By G. C. Howell, H. A. D. Kirsten

The mining-induced effects around narrow tabular stopes have traditionally been evaluated in terms of elastic continuum analyses. An understanding of the phenomenological behaviour of the rock surrounding deep-level gold mines has accordingly been developed on the basis of such analyses. However, elastic analyses do not afford reliable representations of the behaviour of rock in which failure may occur on discontinuities. This paper describes investigations that show how the stress and stiffness characteristics of a rockmass are affected under such circumstances for representative ranges of values for the relevant parameters (depth, span, support stiffness, field stress ratio, and discontinuity strength). These investigations afford a substantially different understanding of the mechanical behaviour of rock that is subject to failure. Instead of forming an arch across the abutments, the rock in the hangingwall bears directly across the stope onto the footwall and, instead of being subjected to tension, the nether hangingwall is clamped in compression in the horizontal direction.

Jan 1, 1993

By M. Faure

The experiment with backfill at Harmony was mainly an attempt to improve the ground conditions in a particularly tricky section of the mine. A deslimed tailings system was selected for financial reasons, ease of installation, ease of operation and its low level of mechanization. The design of the system has three aspects: firstly, to define the parameters of the backfill material itself; secondly, to design a reliable plant which could consistently produce the desired material in sufficient quantities; and, thirdly, to design a fill distribution system for maximum reliability in the shaft, minimum pipe line velocity, pressure and cost in the horizontal sections and consistency and reliability at the delivery end. The system was successfully constructed and commissioned in a short space of time at a relatively low cost. It has now reached its full potential, and very encouraging results have been achieved with regard to cost savings, ground conditions, ventilation and accident statistics.

Jan 1, 1988

By Y. C. Kim

The estimation of local recoverable reserves using the widely spaced exploration drill hole information in an open-pit mine is probably one of the most difficult tasks in ore reserve estimation. The difficulty of this problem is magnified if the grade distribution is highly skewed, such as in a gold deposit. This paper describes the results of performance comparison of three different kriging techniques in an open-pit gold - silver deposit. The three different kriging techniques compared in their local recoverable reserve estimation capabilities are: (1) lognormal kriging, (2) indicator kriging, and (3) probability kriging. For performance comparison, the predictions are compared with the actual recoverable reserves determined from blast hole information. Based on the results from one test bench, both indicator and probability kriging performed better than lognormal kriging, perhaps owing to samples not being truly lognormal. Between indicator and probability kriging, probability kriging results were definitely superior to indicator kriging results.

Jan 1, 1987

By G. T. G. Emere

The Johannesburg Branch of The South African Institute of Mining and Metallurgy was officially inaugurated at a General Meeting held in Kelvin House on Monday, 18th January, 1988. In addition to nominating committee members, Mr G. T.G. Emere delivered a presentation on the Barbrook gold-mining project, which is currently in the development phase some 40 km east of Barberton.

Jan 1, 1988

By M. J. King, W. K. B. Loftus, H. S. Simpson

SYNOPSIS The history of the early diamond fields and primitive methods of diamond recovery are traced, giving a brief description of the improvements made in final diamond recovery processes and techniques up to the present day. In particular the emphasis is on the effect of improved equipment in reducing final hand sorting time and labour, better security and greater recovery of fine diamonds.

By R. J. Davidson, M. V. Nkosi, V. Veronsee

When activated carbon is used for the recovery of gold and silver from Witwatersrand gold-plant solutions, severe fouling of the carbon by calcium carbonate is experienced. Also, difficulty is encountered in the retention of the adsorbed silver on the carbon because it is displaced by gold. The acidification of plant pregnant solutions before they are contacted with carbon was therefore investigated as a means of overcoming these shortcomings. The results from batch laboratory experiments on the effect of pH on gold adsorption from plant solutions and from synthetic solutions of high ionic strength indicated reaction rate optima in the region of pH 5 and below pH I. The effect of pH on the equilibrium capacity constant for gold adsorption onto activated carbon was also studied, using both a plant solution and a synthetic solution of high ionic strength. In the case of the plant solution, the results suggested only a marginal change in carbon capacity for gold in the pH range 12 to 6, with significant increases in capacity at lower pH values. In the case of the synthetic solution of high ionic strength, the capacity constant was found to increase steadily as the pH was lowered from 12 to I. It was also found that the gold adsorption capacity of the carbon was significantly better for the synthetic solution. No precipitation of gold from the pregnant solution (gold content approximately 6 g/t) was noted as the pH was decreased to values as low as ,. However, about 25 per cent of the 0,6 g/t silver content was found to have precipitated when a pH value of 3,0 was attained. Further substantial precipitation of silver took place as the pH was lowered further. The investigation was extended by the passing of suitably acidified gold-plant solutions through one or more columns containing activated carbon. Preliminary results showed that the particle size of the carbon had a significant effect on the rate of gold adsorption. No displacement of adsorbed silver by gold was observed to take place at an influent pH of 5. In a typical continuous 'merry-go-round' operation involving three columns in which gold was eluted from the lead column every 48 hours, effluent values averaging 0,001 g/t gold could be consistently achieved under simulated plant-operating conditions. The results were obtained at relatively high velocities of influent solution, resulting in very little hold-up of gold in the carbon-recovery circuit. More than 99,9 per cent of the gold and more than 99,8 per cent of the silver was recovered in the adsorption circuit, while the elution data indicated an average elution recovery of 99,8 per cent of the adsorbed gold and 98,2 per cent of the adsorbed silver. Elution of the carbon was carried out at 91 QC. This involved pretreatment of the carbon with a sodium cyanide solution, followed by elution with deionized water. At a loading flowrate of 66 bed volumes per hour, the indicated take-up of metals on the carbon in the lead column was as follows; 53 k g/t gold, 6 k g/t silver, 57 k g/t copper, 14 k g/t nickel, and I k g/t zinc. Only a trace of cobalt was adsorbed. At an elution rate of 1,7 bed volumes per hour, the lead column was found to be completely stripped in under 5 hours, with concentrations of gold in the eluate reaching 6 to 7 g/l. Besides the excellent adsorption and elution results obtained when acidified pregnant solution was used, no fouling of the carbon was indicated, and the pressure drop across the three columns was considered to be well within practical limits. When compared with conventional zinc precipitation, the carbon process would appear to have considerable economic merit, with strong indications that significant savings would be possible both in capital and operating costs. Further pilot-plant experiments, preferably on a gold plant, would be required before a meaningful cost comparison could be made with the existing process.

Jan 1, 1979

By W. J. Jordaan

The ability of soils to retain and hold cations is called the cation exchange capacity (CEC). Adsorbed cations, however, can be replaced by other cations through the process of cation exchange. Heavy mineral deposits contain a significant portion of slimes including the very fine clay minerals. In most circuits the slimes fraction hampers efficiency and has to be removed during early stages of the process. Being a nonvaluable process stream, the processing of the slimes is a costly exercise. In thickening applications it might be possible to manipulate the ability of clay minerals to retain and hold positively charged cations in order to optimize flocculation and therefore reduce flocculation costs. The CEC value of the slimes could be a measure of this possibility. To investigate this hypothesis, different slimes samples were characterized for size, chemical composition and clay minerals present. The CEC value of each sample was determined and explained in terms of the mineral phases present. Settling tests were conducted and an attempt was made to explain the CEC characteristics of the clay minerals in terms of settling rate. The scope of this investigation was to test the hypothesis and should not be seen as an in-depth study of the subject matter. A greater number of samples and detailed analyses to identify and quantify minerals and phases present would be required to investigate further the relationships between clay minerals in the deposit, CEC and settling rates. Location and geological setting Exxaro KZN Sands is mining a heavy minerals deposit at Hillendale mine located at Richards Bay, South Africa. The orebody consist of a dune some 8 km inland from the coast to the north of eSikhawini. A geological synopsis undertaken by Botha1 concluded that the Hillendale mining area represents a coastal dune sequence that accumulated north of the Tugela River. The northward movement of sediment by long shore drift currents result in a high sand budget on the beaches north of the river youth and is the dominant contributing factor to the accretion of the coastline and development of parallel dune systems along the coastal zone in this area. Beach swash zone processes and enrichment of the fine sand fraction occurs during wind transport off the beach by ascending parabolic dunes that form the coastal barrier dunes. This process results in heavy mineral concentration on the windward dune face and localized enrichment parallel to the dune forms. The aeolian sedimentary facies processes result in the primary concentration of higher grades in the upper silt-enriched reddish brown horizons of the profile. The synopsis by Botha1 further showed that an additional component of heavy mineral concentration can be ascribed to the post-depositional relative enrichment of heavy minerals due to weathering. Therefore, it is likely that the Hillendale orebody protolith was pedogenically weathered to form the homogeneous, silt-enriched, clayey reddish brown to dark red, palaeosol profile that grades downwards into yellowish brown, less clay-enriched sand. Slimes characterization Samples The Hillendale orebody was divided into geochemically discretized zones based on the concentration of ilmenite and other specific minerals and/or phases. Six composite samples were made up from exploration samples taken from Zone 9, Zone 11 and Zone 12. The red and orange horizons within these composite samples were separated and test samples were prepared to conduct test work and analyses. The test samples were submitted for preparation and analysis to characterize the slimes properties. Each test sample was deslimed at 45 µm representing the slimes fraction (-45 µm) and dried at 40°C. The -45 µm slimes samples were then split to conduct size analysis, chemical analysis, XRD and to determine the CEC. Size analysis The size distribution of the composite samples is shown in Table I. The size analysis shows that there is a difference in size distribution between the orange and red horizons of each zone. The orange horizons contain less 850 µ material as well as less slimes (-45 µm). The red horizons contain yore slimes (-45 µm). The size distribution of the slimes fraction (-45 µm) was determined using Malvern size analysis. The cumulative particle size distribution of the slimes is shown in Figure 1. The red horizons of the different zones show similar size distributions. The orange horizons show some differences. However, there is a difference in size distributions between the red and orange horizons.

Jan 1, 2007

By L. Ziyuan, S. Chunbao, K. Jue, H. Yang, S. Tichang

In this study, potassium ferrocyanide, a non-toxic cyanide precursor in dark and diffuse reflection environments, was applied as a reagent for the leaching of gold. The free cyanide ions were gradually released from the potassium ferrocyanide solution under the ultraviolet light. Orthogonal leaching experiments were performed in gold ore to analyse the effect of solution pH, potassium ferrocyanide dosage, and temperature in potassium ferrocyanide solution system under UV light. Response surface methodology (RSM) was applied to explore the role of potassium ferrocyanide in gold leaching, Optimised results showed that the gold recovery reached 67.74% in a high-alkaline environment at a 12.6 pH, 3.8 kg/t potassium ferrocyanide dosage, 62°C, and irradiance of 10mW/cm-2. The gold leaching kinetics was monitored by quartz crystal microbalance with dissipation (QCM-D) of potassium ferrocyanide solution. The results indicate that the gold extraction process consists of two processes: adsorption and leaching, and a rigid adsorption layer formed on the reaction surface. Furthermore, Xray photoelectron spectroscopy (XPS) analysis of the gold sensor surface after leaching reaction showed that -C≡N appears on the gold sensor surface, and the gold is oxidised to form AuCN complexes. Keywords: Gold leaching, potassium ferrocyanide, UV light, QCM-D, AuCN complexes

Jan 1, 2020

By A. Yañez, J. Yianatos, P. Vallejos, R. Grau

This paper presents an evaluation of the effect that the mineral feed characteristics have on the metallurgical performance in an industrial flotation circuit. Variables such as mineralogy, particle size, solid content and mineral grade were evaluated using a flotation simulator, which was previously developed and validated using industrial data from different concentrators. The metallurgical performance was evaluated not only from the point of view of recovery and concentrate grade, but also by analysing less common variables such as froth carrying rate, froth and collection recovery, water recovery and others. Then, new data from the industrial flotation circuit was used to complement this analysis and evaluate the simulator predictability by comparing simulated and measured data. The results allowed for the quantification of the significant effect that mineralogy and particle size have on recovery and/or concentrate grade. Therefore, the grinding stage and flotation cells design become important factors to avoid a significant loss in metallurgical performance when feed mineral characteristics change in an industrial operation. In this context, an evaluation of cells design and arrangement should be performed to compensate the loss in recovery and concentrate grade in order to find an optimal operating condition. Keywords: Flotation circuits, mineral feed, modelling, particle size, liberation, mineralogy

Jan 1, 2020

Plurigaussian simulation allows constructing lithofacies or rock type models that reproduce the contacts between facies in accordance with the geologist?s interpretation. Its implementation requires inferring the local facies proportions, but the uncertainty in the true proportions is not accounted for. The simpler model with constant facies proportions may not yield realistic results, due to the possibility of obtaining facies at locations where it is geologically unlikely to find them. This article presents a variation of the plurigaussian model, in which the facies proportions are represented by random fields. The realizations can be made conditional to soft geological informati onto account for local changes in the facies proportions. The model is illustrated via a case study of a porphyry copper deposit where four Gaussian random fields are simulated conditionally to drill hole data and to constraints on the probability of finding a given facies at specific locations (control points) in the deposit. Then the first two fields are truncated using the random thresholds defined by the last two, generating a three-facies model. The proposed random proportion model proves to be simple to use and to account for spatial variations of the geological characteristics and for the uncertainty in the facies proportions. Keywords: categorical variable; lithofacies; truncated plurigaussian simulation; regionalized proportions

Jan 1, 2008

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