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By R. Jacobs, R. E. L. Pobe

The Moab Khotsong Metallurgical Complex comprises a gold recovery circuit (Noligwa Gold Plant) and a uranium recovery circuit (South Uranium Plant). The metallurgical complex employs the reverse leach technology for the recovery of uranium; specifically, uranium extraction prior to gold using acid leaching processing. The inherent uranium species in the ore are uraninite, coffinite and brannerite. The slurry that has been subjected to the uranium leach is further subjected to solid-liquid separation to separate the uranium in a solution through counter-current decantation and the solids (solids carrying all the gold), which are repulped and returned to the gold plant for gold processing. The uranium leaching process is critical to the uranium playing a pivotal role as a value adding by-product to the gold operation. The benefit of adopting this reverse leach process, for improved gold recovery, is that it exposes gold particles occluded within the uranium matrices and avails them for cyanidation. However, the drive for operational efficiency in uranium extraction must be weighed against the incremental operating cost against the backdrop of depressed spot uranium market prices. Over the years, efforts were directed at maintaining the benefit of extracting uranium to enhance gold recovery and simultaneously, optimising the operating cost model for the uranium operation to remain relevant to the gold operation. The aim of this paper and the corresponding presentation is to give an account of the uranium processing optimisation journey embarked on over the years; namely, the operational tradeoffs made in the process of ensuring that uranium continues to add value to the gold operation. These challenges were faced while striking a fine balance between processing cost and operational efficiencies against the prevailing depressed uranium spot market prices. Mineralogical- and laboratory tests conducted form the support basis for the results and observations articulated in the paper. Keywords: By-products, gold extraction, reverse leach benefit, uranium extraction

Jan 1, 2020

By D. Vogt

A brief summary of the propagation characteristics of rock provides the necessary understanding to design effective radar surveys. Measurements of the electrical properties of the major Bushveld platinum-bearing horizons and their host rocks show that radar is an excellent tool for both short -and longer-range mapping. Experimental work confirms the performance predictions. High frequency, 500 MHz ground-penetrating radar (GPR) is a first-rate tool for mapping features in the hangingwall of the orebody, locally known as a ?reef?, for the purposes of determining hangingwall stability. The triplet chromitites above the UG2 have been clearly mapped, as has the Leader Seam above the UG2. Borehole radar at lower frequencies has been used over longer ranges to map reef elevation. Potholes in the UG2 are clearly distinguished in range and elevation to within metre accuracy. The nature of the slump in the various footwall horizons is also apparent. In future, as GPR is routinely applied, it is likely to become used for other purposes. Borehole radar is being developed to operate at higher frequencies, which will allow it to be deployed from boreholes that are within 5 m of the target horizon. Keywords: GPR, borehole radar, Bushveld Complex, UG2, Merensky, pothole, triplet

Jan 1, 2005

By P. N. Erasmus, M. Heyns, M. J. Pretorius

The characteristic of stope supports plays a vital role in the design of the supports. This paper deals with the characterisation of both cellular lightweight concrete and timber supports since both supports absorb and dissipate the energy in different ways. The behaviour of the support and hence its performance is simulated for different loading conditions by constructing a model consisting of various mechanical components like springs, dampers and blow-off valves. When the force exerted by the stope support increases significantly during deformation of the support, the stresses in the hangingwall could exceed values where failure of the hangingwall may occur. There is a need to understand this phenomena and the work presented in this paper is a first attempt to start with the characterisation of the stope support. Les caractéristiques des supports de taille jouent un rôle vital dans la conception des supports. L’étude présente traite de la caractérisation des supports cellulaires en béton léger et en bois, puisque ces deux types absorbent et dissipent l’énergie de façons différentes. Le comportement du support et par conséquent sa performance est simulée pour des conditions différentes de chargement en construisant un modèle qui consiste en des organes mécaniques variés tels que ressorts, registres et valves d’échappement. Quand la force exercée par le support de taille augmente considérablement pendant la déformation du support, les contraintes dans le toit peuvent dépasser des valeurs qui pourraient entraîner la défaillance du toit. Il est nécessaire de comprendre ce phénomène et l’étude ici présentée constitue un premier essai dans la caractérisation du support de taille. Die Charakteristika der Strossenunterstützung spielt im Design von Unterstützungen eine vitale Rolle. Diese Arbeit befaßt sich mit der Charaketerisierung sowohl der porösen Leichtgewichtbeton- als auch mit der Holzunterstützung, da beide Unterstützungen Energien auf verschiedene Art und Weise absorbieren und auflösen. Das Verhalten der Unterstützung und folglich seine Leistung wird für unterschiedliche Ladezustände simuliert, indem ein Model konstruiert wird, welches verschiedene mechanische Komponenten wie Federn, Dämpfer und Ausblaseventile enthält. Wenn die von Strossenunterstützung während einer Unterstützungsdeformation aufgebotene Kraft signifikant ansteigt, könnten die Spannungen im Bereiche des Stollenfirstes Werte überschreiten wo ein Versagen des Stollenfirstes eintreten kann. Es besteht die Notwendigkeit dieses Phänomen zu verstehen, und die Arbeit, die in diesem Elaborat dargestellt wird, ist ein erster Versuch, mit der Charaketerisierung der Strossenunterstützung zu beginnen.

Jan 1, 2003

By L. Morgan, M. Le Roux, Q. P. Campbell

Dry coal processing is becoming increasingly favoured as a fine coal beneficiation technique. The decline in suitable good-quality coal, as well as the ongoing decrease in usable process water, makes dry beneficiation of the fine coal fraction even more crucial. Dry fine coal beneficiation is a relatively young process with most of the methods still in the developmental phase. Additionally, many of the dry processing options available are better suited for coarser (+6 mm) and easy-to-beneficiate coal. Air winnowing for fine particles has been established in both agricultural and pharmaceutical industries, which indicates that the method can be used to separate smaller particles on a density basis and therefore, may prove effective in the coal industry as well. A proof of concept study was conducted using both computer-based simulations (which do not form part of this paper) and physical experiments. The initial winnowing unit consisted of a closed box with a horizontal air stream flowing through the top section. Coal particles were injected into the air stream and displaced horizontally across a distance (x), depending on the particle size and density, thus actuating a separation based on these two parameters. For this study particle sizes of 6, 4 and 2 mm were used all with a density ranging from 1200 kg·m-3 to 2000 kg·m-3. The simulation in Star CCM+ confirmed the findings of the mathematic behavioural model and provided a virtual representation of the separation using streamlines and particle tracks. The coal tests prove that size separation can be achieved at an airflow velocity of 21 m·s-1 and the density cut-point can also be predicted by using the prediction matrices constructed as part of this study. The results show efficiency values (EPM) of 0.11 and 0.09 at density cut-points of 1400 kg·m-3 and 1500 kg·m-3 respectively. The data obtained from the study indicates that air winnowing can be used to separate fine coal particles based on both size and density. However, in order to achieve an efficient density separation, a narrow size range is required. With some improvements to the model, simulation, method and design, the separation efficiency can also be improved. The next phase of testing will include the upscaling of the process to a demonstration plant, optimising the separation unit and testing the method on different qualities of coal. Keywords: Dry processing, fine coal, winnowing, simulation, tracers, demonstration plant

Jan 1, 2020

The effect of composition on electrical conductivity (resistivity), viscosity and liquidus temperature of the slags encountered in electric smelting of PGM containing suphide concentrates is reviewed, along with the relationsip between slag composition, slag-matte separation and metal losses to slag. Optimization of slag composition at furnace temperature is attempted on the basis of opposite and parabolic trends of the viscosity-conductivity relationships of the slags. The importance of surface tension of slags is emphasized using available and estimated information which are grouped into a useful correlation. These values are coupled with or incorporated into slag viscosity plots to illustrate the correlation between the two factors, which influence slag-matte separation as well as refractory attack. The electrode in the slag-resistance furnace is the central factor in the design and operation of the furnace by its role of conveying the smelting power. The obvious parameters are the size and positioning in the slag bath, which are defined by slag resistively, furnace resistance, cell constant and power input. The flow of heat generated by the electrode current determines the energy distribution and furnace dimensions creating viscosity profiles, which in turn affect flow conditions. Thus the flow of slag and matte are discussed in conjunction with the furnace geometry, stirring action of the electrodes, buoyancy and electromagnetic effects. The action of the electric furnace as a settler is discussed. The rectangular furnace is considered as a channel reactor in this analysis, and the action of the electrodes is described to indicate a balanced settling rate in the area of electrode action. Discussion of the design and production capacity of the electric furnace, with reference too perating current, power input, furnace dimensions and electrode size, are based on considerations derived mainly from slag properties such as its resistively, viscosity and liquidus temperature.

Jan 1, 2004

By A. Chryss

Tailings management aims to dispose of tailings at the minimum cost consistent with meeting or exceeding imposed standards, including legislative obligations. This simple business objective requires managing the tailings storage facility (TSF) risks associated with surface water, groundwater, dust, sustainable closure, and potential catastrophic failure. The individual nature of every orebody and specific site topography ensures that no one size fits all. It has been suggested that paste and thickened tailings (P&TT) provides the ability to tailor the production and transportation of tailings to suit the deposition site, rather than the traditional approach of accepting that the deposition site has to accommodate tailings of high variability. While the traditional approach can be made to work, it is directly linked to the catastrophic failures of tailings impoundments, where large volumes of decant water have triggered failures due to overtopping, piping or slope instability, or saturated tailings have simply liquefied. P&TT offers an ability to mitigate these risks, and when implemented into new projects with variable tailings streams there are significant benefits to be realized. This paper identifies the interdependencies between the various tailings disposal processes, such as thickening, pumping, and deposition. It demonstrates that there are benefits in taking a more integrated approach to the design and operation of tailings disposal facilities. A collaborative industry project to tackle this challenge is described.

Jan 1, 2012

By F. Qunfei, W. Laijun, X. Lyu, A. Cosmos, L Huijuan, Z. Jinggang, G. Yao

In this paper, four cyanide-utilising bacteria strains were isolated from a gold mine tailings pond, in the Hexi gold mine (Shandong), China. Based on the analysis of 16S rRNA gene sequence, four strains were identified as Aeromonas hydrophila strain C1, Bacillus mojavensis strain C3, Shewanella oneidensis strain C2, and Aeromonas media strain C4. Based on the cyanide detoxification efficiencies results of the four strains, Bacillus mojavensis C3 had the highest detoxification rate and was selected to assess its efficiency to detoxify cyanide in gold mine tailings at different pH (9.5, 10.5, and 11.6) using cyanide as the sole carbon and nitrogen sources. Strain C3 was capable of detoxifying 46.5mg/L of cyanide-containing gold mine tailings at all tested pH ranges at 30oC, 196 rpm after 15 d. The amounts of cyanide detoxified were 87.5%, 84.1%, and 73.5% at initial pH 9.5, 10.5, and 11.6, respectively. The highest cyanide detoxification was observed at pH 9.5. The viable cells growths in the samples were 5.7E+09CFU/mL, 4.9E+09CFU/mL, and 2.7E+09CFU/mL at pH 9.5, 10.5, and 11.6, respectively. Free ammonia concentrations were observed as a byproduct of the biodetoxification process. The residual ammonia concentration in the sample was observed at 0.35 mg/L, 0.33 mg/L, and 0.62 mg/L at pH 9.5, 10.5, and 11.6, respectively. The highest residual ammonia concentration was noticed at pH 11.6. The amount of cyanide removed by mixed culture strains C3 and C4 was 94.6% and showed a residual free ammonia concentration of 2.6mg/L, as biodetoxification byproduct after 120 h. The pure culture Bacillus mojavensis strain C3 and its mixed culture strains exhibited higher potential to detoxify cyanide-containing gold mine tailings at alkaline pH values and could be cultivated to detoxify gold mine effluents at large-scale. Keywords: Bacteria strain, cyanide, detoxification efficiency, gold mine tailings

Jan 1, 2020

By J. Searra, M. Aboagye

"For new mining projects or for medium- to long-term areas of existing mines, drilling data is invariably on a relatively large grid. Direct estimates for selective mining units (SMUs), and also for much larger block units, will then be smoothed due to the information effects and the high error variance.The difficulty is that ultimately, during mining, selection will be done on the basis of SMUs on the final close-spaced data grid (grade control), which will then be available, i.e. the actual selection will be more efficient, with fewer misclassifications. However, this ultimate mining position is unknown at the project feasibility stage and therefore has to be estimated. This estimation is required because any cash flow calculations made on the basis of the smoothed estimates will obviously misrepresent the overall economic value of the project, i.e. the average grade of blocks above cut-off will be underestimated and the tonnage overestimated for cut-off grades below the average grade of the orebody. Similarly, unsmoothed estimates will be conditionally biased and will give even worse results, particularly in local areas of short- and medium-term planning or mining.This paper presents a case study of indirect post-processing and proportional modelling of recoverable resources designed for mediumand long-term mine planning at the Gold Fields’ Tarkwa Mine in Ghana. The case study compares long-term indirect recoverable mineral resource estimates based on typical widely spaced feasibility data to the corresponding production grade control model as well as the mine production. The paper also proposes certain critical regression slope and kriging efficiency control limits to avoid inefficient medium- to longterm recoverable estimates, and highlights the danger of accepting block estimates that have a slope of regression less than 0.5."

Jan 1, 2015

By P. van Dorssen

In South African metalliferous mines, stoping operations are largely confined to narrow, tabular orebodies making mechanization extremely difficult. Limited flexibility in terms of stope width has necessitated drilling by means of handheld, pneumatic rock drills at most of our operations. As the largest producer of platinum in the world, we drill in excess of forty million stope blast holes per annum. Cleaning of the broken ore is also done by conventional means?utilizing scrapers and scraper winches. Conventional methods such as these carry high costs in terms of risk exposure as well as labour intensity. The purpose of this paper is to describe the development of a long hole stoping system suitable for the narrow platinum reefs. The new system had to be substantially safer and more cost effective than conventional mining. We selected a site that was conducive to mechanized mining and set out the parameters that we considered would meet our requirements. We then conducted a feasibility study to evaluate the conceptualized long hole stoping system in terms of specific goals. An analysis of the proposed system identified the Key Performance Indicators (KPIs). One of the most critical goals was to be able to create a man-free stope. This would mitigate the safety risk associated with normal stoping operations, as well as the inefficiency cost previously referred to.

Jan 1, 2002

By P. Valicek, M. Farren, R. G. B. Pickering, G. Harrison, P. van Dorssen, W. Joubert, H. J. van Rensburg

Introduction In South African metalliferous mines, stoping operations are largely confined to narrow, tabular orebodies making mechanization extremely difficult. Limited flexibility in terms of stope width has necessitated drilling by means of hand held, pneumatic rock drills at most of our operations. As the largest producer of platinum in the world, we drill in excess of forty million stope blast holes per annum. Cleaning of the broken ore is also done by conventional means—utilizing scrapers and scraper winches. Conventional methods such as these carry high costs in terms of risk exposure as well as labour intensity. The purpose of this paper is to describe the development of a long hole stoping system suitable for the narrow platinum reefs. The new system had to be substantially safer and more cost effective than conventional mining. We selected a site that was conducive to mechanized mining and set out the parameters that we considered would meet our requirements. We then conducted a feasibility study to evaluate the conceptualized long hole stoping system in terms of specific goals. An analysis of the proposed system identified the Key Performance Indicators (KPIs). One of the most critical goals was to be able to create a man-freestope. This would mitigate the safety risk associated with normal stoping operations, as well as the inefficiency cost previously referred to. Other challenges included setting targets for long hole accuracy, stoping width reduction and specific blasting system performance for long hole stoping. We also modelled a critical span that we considered to be inherently safe and to ensure hangingwall stability, throw-blastcleaning and overall system productivity. Anglo Platinum Research and Development and Sandvik Tamrock entered into an agreement for the supply of a specialized long hole-drilling machine. The system was implemented and tested by the mine with the support of the other participants. The results achieved met our expectations. It was demonstrated that with this method of mining it is possible to have a man-free/support-free stope face and to achieve a reduction in shaft head cost per ton whilst reducing dilution. Key performance indicators assessed during the trial •Safety targets •Mining layout •Drill rig •Production targets •Support requirement •Explosives requirement •Services requirement •Ore removal and cleaning requirement •Training requirement Safety targets All persons involved with the project had to adhere to the mine’s safety programme including the zero-tolerance campaign, and were required to report all hazards observed immediately. Mine personnel and Tamrock carried out a full risk assessment on the drill rig before transporting underground. A further risk assessment was carried out when the machine was in position underground. Mining layout See Figure 1 and Figure 2 for a detailed description. Drill rig The drill rig was a combination of a Secoma P-Low LC 10long hole feed and an Axera low profile carrier. The choice of this equipment was made through consultation with Tamrock Sandvik. All relevant design perimeters of the area to be mined were taken into consideration. Production targets

Sep 1, 2001

By Siyabonga Malevu

Chemical Initiatives? Umbogintwini plant is the production facility of Chemical Initiatives? business. Umbogintwini?s J Plant manufactures sulphuric acid. The plant was designed and built by Simon Carves, and was commissioned in 1974. The plant was designed to produce 500 tons/day of Sulphuric acid (H2SO4) at maximum rates. The Sulphuric acid manufacturing is through the famous contact process whereby liquid Sulphur is injected through dried air in a burner operating at 1000 °C to form sulphur dioxide (10.5% SO2). The SO2 gas is then cooled in waste heat boiler no. 1 before being fed to a four pass converter which provides 99.5% SO2 conversion to sulphur trioxide (SO3). The SO3 gas is the absorbed by 98.5% H2SO4 through the inter-pass & final tower to make more concentrated acid and dilute it with water back to 98.5% H2SO4 in acid pump tanks and dispatched to storage tanks. The manufactured Sulphuric acid is supplied to a variety of industrial manufacturing customers includes Pulp & Paper industry, Mining industry, Chemical manufacturing industry etc.

Jan 1, 2009

By B. J. Vorster

AngloGold South Africa region currently consists of twelve gold plants. These plants use a combined total of $20 million of cyanide per annum. Of this, the major portion (60%) is consumed at two Ergo dump retreatment plants. Historically the primary motivation for cyanide control at Ergo has been one of leach/cost optimization. However, more recently, with the increased public awareness of cyanide in the environment, a secondary but increasingly important motivation for control has been to ensure that only the minimum amount of cyanide is added to the process whilst not compromising leach performance. Following a brief overview of the Ergo process, the methodology in determining the amount of cyanide to be added is described. The paper then traces the developments in cyanide control from very basic manual systems to the current automated control system. In line with the increasingly sophisticated control systems, developments also took place in regards to the method of cyanide analysis. The development of these analysers is also discussed. Whilst cyanide is one of the major drivers, if not the major driver of gold dissolution, it cannot be viewed in isolation particularly with respect to the relationship between cyanide and oxygen as ascertained from the Elsner?s well-known equation. Consequently, in order to control cyanide addition, knowledge of the relative cyanide/oxygen profiles is necessary. Various means investigated at Ergo for pulp oxygenation have therefore been included for the sake of completeness. Finally a comparison is made of the control achieved from the current system compared to the original manual system. The knowledge and experience gained at Ergo is now being used to draw up guidelines for the installation and optimization work at the other AngloGold plants. The net effect of this will be reduced cyanide consumption for the region, which also, apart from the obvious economic benefit, translates into a reduced environ-mental risk.

Jan 1, 2001

By C. Righi, R. Carli

In modern steel continuous casting technologies mould fluxes are well-known to assure lubrication required by tribological system of mould-solidifying strand shell, and to provide crystalline phase solid film, contributing to control heat extraction between strand and mould wall. Actual cooling rates during normal continuous casting mould operations are far higher than critical cooling rate of the liquid slag. Indeed, DTA measurements point out that even relatively small cooling rates of 30?50 K/min are high enough to give exiguous formation of crystals. In this paper, contribution of devitrification in defining crystalline phase formation of industrial basic mould slag, used in continuous casting of crack-sensitive steel grades, has been investigated by means of non-isothermal experiments study. Devitrification has proved to play a major role in mould flux crystallization in a working environment explaining the higher amount of crystalline phase formed in plant sample in comparison with lab sample from DTA analysis with typical cooling rate of 5?20 K/min. The amount of crystalline phases formed ranks as follow: Cuspidine > Combeite > Gehlenite. Kinetic analysis of DTA non-isothermal experiments has provided kinetic parameters through Kissinger and Ozawa methods, as Avrami constant resulting to be n ?2 and activation energy of Cuspidine crystallization resulting to be EC= 315 kJ/mole. The effect of addition to the parent material of oxides as MnO, TiO2, ZrO2, Al2O3 and Fe2O3near to saturation point has proved to affect, in certain cases, crystallization behaviour of mold flux. In particular, MnO, TiO2, ZrO2oxides produce a relevant dump of crystallization of Combeite and Gehlenite phases, while Al2O3and Fe2O3do not appreciably affect crystallization. Key words: Mould flux, crystallization, devetrification, DTA non-isothermal analysis, Kissinger and Ozawa methods.

Jan 1, 2004

By H. S. Marshall

Optimum Colliery is an opencast strip mine producing 18Mt of bituminous coal per annum for the export and inland markets as well as for domestic power generation at the Hendrina PowerStation. Coal is exposed by four 60m3 and four 11m3 walkingdraglines and transported from the open cuts to the processing plants by twelve 130 ton coal haulers. Overburden and interburden areas are drilled by nine 250mm-diameter rotary drill rigs. Until 1997 all surveying tasks were conducted by electronictotal stations requiring accurate control points from which line-of-sight XYZ readings could be taken. In 1997 a GPS system was introduced which consisted of a fixed base station and two rovers. The rovers were able to perform most of the survey tasks assigned to total stations. In addition, two overburden drills were equipped with blasthole drill navigation systems, which includes the drill monitoring and material (strata) recognitions system. The rest of the drilling fleet will also be equipped with GPS systems. Blasthole positions are designed in the office based on survey and geological/geophysical information and transmitted via radio link to an industrial PC on the drills. Together with GPS positional data, both the planned and actual drill positions are displayed on an LCD screen. This eliminates the need for surveyed hole positions to be staked before drilling, and for actual hole positions to be surveyed after drilling. As holes are drilled, performance and rock property data transmitted back to the office. Future applications will include GPS monitoring of dragline positions and pad elevations. GPS receivers on the draglines will utilize the existing base station to calculate and transmit XYZ co-ordinates. Another application will be locating of boreholes in the field prior to the pumping of specified explosive charges into the blastholes. Charging instructions for each blasthole will be loaded into the computer on the explosives truck which will be equipped with a GPS system for hole identification.

Jan 1, 1998

By K. C. Naidoo

There are two main types of densifying cyclones currently available in the market, namely polyeurethane (PU) and ceramic. The PU densifying cyclones are currently used throughout the Grootegeluk complex and coal beneficiation in general. It has been identified that PU densifiers wear relatively fast depending on the operating pressure and need to be replaced frequently as a result. The motivation for this paper is to achieve an increase in the densifying cyclone lifetime through less wear and an increase in efficiency resulting in the ability to build higher relative densities (RD) more quickly. This will allow for a reduction in downtimes due to replacing densifying cyclones as well as building RD and a reduction in the operating costs associated with replacing worn densifying cyclones. Some of the major findings of the study indicated that the ceramic cyclone theoretically undergoes less wear than the PU cyclone, but since wear is application-specific and was evaluated, the wear on the polyurethane cyclone was found to be minimal. The RD differential is higher on the PU cyclones than the ceramic cyclones, showing that the PU cyclones perform better in a densifying application. This is the first test conducted on this application and type of cyclones. It should therefore be noted that having the PU cyclone significantly outperform the ceramic cyclone was not expected, due to the only change being the material of construction. This is an indication to take the material of construction into account when selecting cyclones as it can have a significant impact on the cyclone performance in specific applications. Keywords: Ceramic, cyclone, densifying, density, dense medium, polyurethane, wear

Jan 1, 2020

By J. C. van Dyk, F. B. Waanders, J. Brand, C. A. Strydom

"Underground coal gasification (UCG) is a fast-emerging, in situ mining technology that provides access to low-cost energy through the utilization of coal reserves that are currently not technically or economically exploitable by conventional mining methods.Groundwater monitoring for conventional coal mining in South Africa is well established, with SANS, ASTM, and ISO standards for the specific environment, location, and purposes. South Africa’s groundwater is a critical resource that provides environmental benefits and contributes to the well-being of the citizens and economic growth. Groundwater supplies the drinking water needs of large portions of the population, and in some rural areas it represents the only source of water for domestic use. Implementation of, and adherence to, groundwater monitoring standards are thus non-negotiable.The groundwater quality management mission, according to the Department of Water and Sanitation in South Africa, is set in the context of the water resources mission and reads as follows:‘To manage groundwater quality in an integrated and sustainable manner within the context of the NationalWater Resource Strategy and thereby to provide anadequate level of protection to groundwater resources and secure the supply of water of acceptable quality.’ (SABS, 2016).In this paper we propose fit-for-purpose groundwater monitoring standards for a commercial UCG operation. It is important to proactively prevent or minimize potential impacts on groundwater through long-term protection and monitoring plans. Scope of study / standard proposal The purpose of this paper is to set out a National Standard Proposal to emphasize groundwater monitoring as one of the five strategies of the ‘Policy and Strategy for Groundwater Quality Management in South Africa’ (Department of Water Affairs and Forestry, 2000) and to align it with the National Water Act, Act no. 36 of 1998 (Republic of South Africa, 1998).The focus of this standard is directed solely towards groundwater monitoring during underground coal gasification (UCG). Groundwater in this context refers to water as sampled from dedicated monitoring wells around the targeted site, which will include the shallow aquifer referred to as groundwater, and water flow at the level of the underground gasifier, referred to as ‘coal water’."

Oct 1, 2018

By J. A. Maritz, D. F. Malan

Pillar strength is affected by pillar shape, but this has largely been ignored in past research studies. Bord-and-pillar layouts are typically designed using empirical strength equations developed for square pillars. Owing to the poor quality of pillar cutting, many hard-rock pillars have an irregular shape and it is not clear how this affects pillar strength. Furthermore, the strength of rectangular pillars in comparison with square pillars is also difficult to quantify. The ‘perimeter rule’ is widely adopted for rectangular pillars, but its applicability for pillars with irregular shapes has never been tested. We used numerical modelling in this study to investigate the effect of pillar shape on strength. An analytical limit equilibrium model of a square and a strip pillar also provided useful insights. For slender pillars, the strength of a long rib pillar is essentially similar to that of a square pillar. In contrast, for rib pillars with a large width to height ratio, there is a substantial increase in strength. The study found that the perimeter rule should not be used for irregularly shaped pillars. Displacement discontinuity modelling, using a limit equilibrium approach, is proposed as an alternative to determine the strength of these pillars.

May 3, 2023

By C. Marais

The use of machine vision in the monitoring and control of metallurgical plants has become a very attractive option in the last decade, especially since computing power has increased drastically in the last few years. The use of cameras as a non-intrusive measurement mechanism not only holds the promise of uncomplicated sampling but could provide more consistent monitoring, as well as assistance in decision making and operator and metallurgist training. Although the very first applications of machine vision were in the platinum industry, no automated process control has been developed for platinum group metals (PGMs) as yet. One of the reasons is that to date froth features could not be related to key performance indicators, such as froth grade and recovery. A series of laboratory experiments was conducted on a laboratory-scale platinum froth flotation cell in an effort to determine the relationship between the platinum grade and a combined set of image features and process conditions. A fractional factorial design of experiments was conducted, investigating 6 process conditions, namely air flow rate (x1), pulp level (x2), collector dosage (x3), activator dosage (x4), frother dosage (x5) and depressant dosage(x6), each at levels. Videos were recorded and analysed to extract 20 texture features from each image. By using artificial neural networks (ANN), the nonlinear relationship between the image variables and process conditions and the froth flotation grades could be established. Positive results indicate that the addition of image features to process conditions could be used as sufficient input into advanced model based control systems for flotation plants. Keywords Flotation, machine vision, image analysis, neural networks.

Jan 1, 2011

By B. Erdem

This article introduces a computer model, which emphasizes panel design for draglines deployed in direct side-casting mode. The study covers flat and inclined coal-seam conditions with the dragline operating along the strike-line. Two casting methods are embedded in the model: material is placed in the open set adjacent to the one on which the dragline is located (the DNS method) and material is placed in the open set adjacent to the one the dragline excavates (the DND method). While in the first method the unproductive walking time is reduced as the set is enlarged, in the second method the cycle time is lessened as the dragline swings along an acute angle. The side-casting model is shaped so as to provide several panel configurations instead of a single one to conform to the characteristics for an opencast mine. This is achieved by assigning the pit width an interval of values ranging from a minimum to a maximum. The model includes solutions to other critical design parameters such as: set length, swing angles at key cut and main cut positions, and required dragline reach at key cut and main cut positions. The model outcomes reveal the following: the stripping operation is largely affected when the coal-seam is inclined. The downhill spoiling mode should be applied wherever possible. The DNS pattern allows wider pit width intervals as well as longer sets and longer reaches.

Jan 1, 2004

By Q. X. Yun

This paper provides a new approach to optimize the production planning in underground mines by means of evolutionary algorithms. Firstly, genetic algorithm is used to reach the global optimization in planning. Then, evolutionary programming is employed to obtain the partial optimization for each year. The application proves that the new approach is reasonable and useful. Keywords: Evolutionary algorithm, Genetic algorithm, Evolutionary programming, Optimization, Mining engineering.

Jan 1, 2003