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By K. L. Morton, R. .. J. Connelly, P. C. Bouw

Uncertainties in the forecasting of the volume of groundwater likely to enter underground workings present difficulties for mine management in planning and costing the water-related activities of mining. This paper describes a technique that was developed to assess future inflows into a gold mine in the Orange Free State. The approach employed was based on the interactive operation of two separate computer models: a regional-flow model and an inflow model. As a first stage, a regional finite-element model of groundwater flow was set up and calibrated. Predictive runs were made to establish the influence of mining on the water levels from base-line conditions. This step was necessary since observations of the regional water levels were sparse. The predicted water levels were transferred to the inflow model, and the future flowrates were calculated. Both models were calibrated by trial and error until a satisfactory match was obtained between historical records and the values predicted by modeling. In this way, an improved monitoring system to record regional water levels and pressure heads within a mine was established. By the use of information, the initial model predictions can be refined as mining progresses. The models used are based on a non-linear relationship between the area mined and the inflows. A phased behaviour in the rates of inflow increase was noted. In conclusion, the modeling approach can provide mine management with guidelines for dewatering requirements. The confidence levels depend upon the records that have been collected during the mine's history.

Jan 1, 1988

By G. S. Harper

Noise in general and drilling noise in particular have received increasing attention within the South African mining industry during the last 10?15 years. The Mine Health and Safety Committee1, during their 2003 annual summit, established two significant milestones to be met by December 2008 and December 2013. The 2008 milestone target is that of no more than ten per cent deterioration in hearing among occupationally exposed individuals, whereas the 2013 milestone target is that of less than 110 dB sound pressure levels at any place in the workplace. While these targets relate to general noise within the mining industry, it is widely believed that the most significant source of noise contributing to noise induced hearing loss (NIHL) among the underground workforce, is that of pneumatic rock drills. Data pertaining to the noise emission level of any machine is generally reported as either a sound pressure level or a sound power level of a single machine measured under free field conditions as defined in Appendix 3 of SABS-ISO 37442. However, rock drills are seldom used in isolation and underground conditions cannot be considered as free field. A methodology for the selection of rock drills on the basis of total operating cost has been developed. However, this paper focuses on the noise elements of the generic methodology and provides a model for the prediction of the composite sound pressure level and the equivalent noise exposure levels of groups of individuals from machines, used singly and in combination in an underground environment based on the sound pressure level determined according to SABS-ISO 3744 under free field conditions. The methodology includes provision for the consideration of the effect of hearing protection devices and the use of multiple machines in combination and provides an indication of the potential costs of hearing compensation.

Jan 1, 2006

By Q. P. Campbell

Activated carbons used in the precious metals extraction industry are characterized by large internal surface areas and a great affinity for metal ions. The purpose of this research is to prepare activated carbon from a South African bituminous coal by physical activation that is suitable and cost-effective for use in the extraction of metals. The quality of the coal-based activated carbon may not prove to be as good as activated carbon produced from other traditional sources, but the production costs involved may make South African coal a feasible alternative feedstock. The activated carbons produced were characterized by Brunauer, Emmett, and Teller (BET) surface area, activated carbon pH, and phenol adsorption studies and the results compared to the results from a commercially available activated carbon, Norit RO 0.8 (control sample). Bituminous coals from various sources including Witbank Seam 4 and Free State coal were used in this study. The preparation method chosen was physical activation using superheated steam. The effects of process variables such as activation time (1-3 h) and temperature (600-800°C) were studied in order to optimize those parameters. The activated carbon surface area was characterized by means of nitrogen adsorption isotherms at 77K. BET surface area analysis showed that Witbank Seam 4 coal activated at a temperature of 800°C and activation time of 3 hours resulted in a surface area of 340 m2/g. Quality control of each sample was performed by measuring the pH of a known amount of the prepared activated carbon in distilled water over time. Results showed that the pH of some of the prepared activated carbons reached a value of 11. Phenol adsorption results for the different activated carbons prepared corresponded well to the results obtained for the Norit RO 0.8 activated carbon sample.

Jan 1, 2012

By L. R. Nelson

The efficiency and cost-effectiveness of the aluminothermic reduction process in the production of ferro-alloys and 'pure' metals depends strongly on appropriate balancing of the process energy required. Insufficient energy results in a poor metal yield, while over-supply can result in excessive fuming and possibly even ejection of the reactor contents in a potentially dangerous 'thermite bomb' reaction. This situation becomes even more critical when the suitability of limited quantities of oxide from new sources must be evaluated, dictating smaller-scale testwork. The resulting higher relative heat losses from the system complicates control of the energy balance, and usually requires the addition of thermal boosters or reactant preheating in order to sustain an autothermic process. This often detracts from the quality of the metal product, and adds to the hazards of batch aluminothermic- reduction testing. The development of a small-scale method (producing less than 2,5 kg of metal) for the plasma-assisted aluminothermic reduction of chromium oxide that overcomes such difficulties is described. The technique involves the use of a sealed 50 kVA plasma-arc furnace to provide controlled electrical ignition and supplementary energy to the reactants contained in a water-cooled copper crucible. The application of the method to the evaluation of the aluminothermic production of pure chromium metal from a unique chromic oxide source is reported.

Jan 1, 1996

The newly implemented mineral law framework exacerbated the need to clarify the roles and responsibilities of mine and land surveyors in the preparation and registration of plans and diagrams. The main concern is that survey tasks may be performed by persons who are not considered competent under the different laws. The methodology used was to analyse historic and present legislation on the issue in order to formulate a narrow interpretation of the current requirements. The major findings are tabulated to present a summary of who is responsible for which areas of survey.

Jan 1, 2010

By A. R. Barnes, C. W. P. Finn

The prereduction and smelting characteristics of UG-2 ore were studied and compared with those of Winterveld chromite ore. The UG-2 ore proved more reducible, and substantial prereduction (over 70 per cent reduction after 30 minutes at 1250oC) was obtained. No difficulty was experienced in the production oh high-carbon ferrochromium alloy containing 48 to 50 per cent chromium. Calculations of the energy balance show that UG-2 chromite has lower total energy requirements (both on the basis of unit of ferrochromium produced and of total chromium content). More than 50 per cent of the energy required for reduction can be supplied outside the smelting furnace.

Jan 1, 1983

By J. A. Maritz

Since the dawn of mining, pillars have been used as primary support to ensure stable workings. Early designs were based on trial and error, after which more scientific means developed over time. A vast amount of progress has been made, especially in soft-rock room-and-pillar design methodologies, from which hard-rock design theories developed with minor changes to constant parameter values. The commonly used Hedley and Grant method for hard rock and Salamon and Munro methodology for soft rock draw on the tributary area associated with the pillar, the width-toheight ratio of the pillar, and a back-analysed strength reduction factor. In these methods, only the vertical stress, or stress normal to the pillar influences the load applied to the pillar. This investigation considers the possible influence of shear stresses on pillars in a room-and-pillar layout in single reef planes and multi-reef environments, based on elastic numerical modelling methods. The possible shear stress poses a safety and financial risk to the design process, whereby an undersized pillar would lead to unstable working conditions, whereas oversized pillars could lead to an under-utilized ore resource.

Jan 1, 2014

By P. G. Gresse

The Orange-Vaal River system is known to be the primary secondary source for alluvial diamond deposits in the northern Cape and along the west coast of Namaqualand. The higher order sources for diamonds contained within this system are still not defined entirely to satisfaction, but certainly include kimberlite pipes exposed in the catchment regions of these rivers. The focus of alluvial diamond mining along the Orange-Vaal system recently changed from the traditional areas in the upper catchment regions?the Barkly West, Christiana, Bloemhof, Wolmaranstad, Schweizer-Reineke region, and the lower regions near the mouth of the Orange River at Baken, Alexander Bay and Oranjemund, to the area between Douglas and Prieska?the so-called mid-Orange region (Figure 1).

Jan 1, 2003

By I. M. W. Preston

A new shaft system was required to replace stope face for the North Section of Harmony Mine and to allow for systematic opening up of the North Eastern Section. Owing to the economic circumstances at the time the project started, it became vital to alter the original planning and to sink the service shaft first. The MATLA coal-sinking headgear, a novel presinking arrangement, allowed sinking to continue to 108 m concurrently with the erection of the permanent sinking headgear and sinking winders. It is estimated that this arrangement resulted in a saving of two months on the overall project.

Jan 1, 1983

By G. Wu, S. Liu

In view of the singleness of traditional methods about international petroleum (Brant) price forecast, ten main factors that affect international petroleum price are fully analysed. Based on time series method and multivariate linear regression method, the simulation model with the theory and idea of system simulation is firstly established. And this forecasting system realizes visual operation under the environment of MATLAB/SIMULINK. So this article tries a new way for further exploring petroleum price’s running law and guiding its forecasting practice. Keywords: Petroleum price forecast, system simulation, residual error, physical flows information flows

Jan 1, 2003

By B. R. Broekman, D. W. Penman

SYNOPSIS This paper traces the developments in flotation practice at Anglovaal's Prieska Copper Mine, with em¬phasis on the depression/deactivation of lead and zinc. A depressant system was devised to accept feed material that was once regarded as untreatable. Of particular interest is the long-term downward trend of concentrator working costs in real terms. This trend follows the classic Experience Curve, which relates production costs to cumulative experience. It is felt that the experience-curve concept has important implications for the mining industry in general.

Jan 1, 1991

By B. R. Broekman, D. W. Penman

Discussion by P.J Lloydt Broekman and Penman describe (J.S. Afr. Inst. Min. Metal., vol. 91, Aug. 1991, p. 261) the addition of sodium cyanide and zinc sulphate to the flotation feed at Prieska. They note that for 'safety sake, lime was added to the rod mil to raise the pH to 9,5', and that 'personnel working in the vicinity of the rod mil were required to wear gas masks'. Author reply to P.J. Lloyd We thank Dr Lloyd for his interesting contribution. As he correctly points out, the Prieska float had run with cyanide solutions at pH values of 6,4. In fact, it ran safely for extended period with the pH slightly below 6.

Jan 1, 1991

By E. Arghavani, S. H. Amiri, S. Zare, F. Sepehri, M. Ramezanizadeh

Mineral processing plants include different stages like crushing, grinding, classification and concentration, all of which have partially affect the final product. To identify and solve the related problems of each stage, process audition should be carried out continuously to find the major solutions of improving product and decreasing the maintenance and operating costs. The Iranian Gohar-Zamin iron ore beneficiation plant consists of equipment such as gyratory and cone crushers, high pressure grinding rolls (HPGR), ball mill, dry and wet double-deck vibrating screens, hydrocyclones cluster, magnetic drum separators, thickener and horizontal vacuum belt filters. The defects of initial design as well as current non-standard operating conditions of equipment were monitored and detected and the opportunities for process optimisation were presented as follows: establishing the control loop of power draw for cone crushers, the modification of feeding chute in cone crushers to minimise the non-uniform wear of parts, removing segregation in the fresh feed bin and screen’s circulating load chute in order to provide the proper feed to HPGR, reducing wear rate on HPGR rolls surfaces, decreasing the amount of rejected materials in screen, equalising the solid content and particle size distribution (PSD) of feed in all magnetic drum separators and equalising the PSD of hydrocyclones overflow. This paper provides a guideline for the mineral processing industry to focus its efforts on process design to deliver the efficiency with minimum capital costs. Keywords: Process audition, gyratory crusher, cone crusher, HPGR, screening, hydrocyclones, magnetic drum separators

Jan 1, 2020

Assuming that a gold ore has been effectively ground to ensure maximum economic liberation of gold, the circuits that will have the most effect on the successful operation of a gold plant will be that of the leaching and carbon-in-pulp circuit (CIP). The reagent and utilities operating costs associated with leaching, adsorption, elution and regeneration would typically make up some 15% of total operating cost, whilst the capital costs associated with these areas is about 16% of the total. Although not largest (capital and operating costs associated with comminution are generally dominant) these items represent a significant proportion of capital and operating cost. Much more importantly, these plant areas represent the primary gold recovery process and their technical and operational efficiencies will have a significant impact on overall plant efficiency. The objective during process design of these sections is thus to develop a design which provides maximum technical and economic efficiency and which is robust to potential changes in ore throughput, mineralogical characteristics and head-grade. Experience has shown that, particularly for longer life and higher-grade projects typical of the South African underground gold mining industry, small changes in recovery and efficiency have a significant value over the life of the project.

Jan 1, 1999

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

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

Jan 1, 2009

Scrap printed circuit boards were selectively smelted at 1 200°C to produce a metallic alloy having three phases. These phases were identified as a lead-rich phase, a low tin content alpha bronze phase, and a high tin delta phase. Electrochemical leaching studies on this alloy were done in 1 mol/dm3 sulfuric acid or in 2 mol/dm3 hydrochloric acid (adjusted to an ionic strength of 3 mol/dm3). The lead rich phase was more strongly passivated in sulfate media, and in this medium the high tin content delta bronze was more resistant to corrosion than the lower tin alpha bronze phase. In chloride medium the lead phase and both bronze phases corroded readily, but with current densities about an order of magnitude lower than in sulfate medium (static conditions) for the bronze phases. The high tin delta bronze phase was found to form a passivating layer in sulfate media. A similar layer was not seen in chloride medium. The leaching studies in sulfate medium also showed the existence of an alpha bronze phase of lower tin content in the centres of the alpha phase grains. This phase was quite resistant to leaching in sulfate medium.

Jan 1, 2009

By P J. Grobler

The current commodity boom is depleting the ore bodies at a rate not seen in the past. As the existing ore bodies get depleted, only the more inferior bodies are left for exploitation. This places an emphasis on beneficiation to upgrade the lower grade ore to high-grade feedstock for downstream processes. This paper discusses the role of dense medium separation in this quest for high-grade feedstock for the future. It covers the production and utilization of ferrosilicon and gives a future perspective of the technology. It concludes about the way ahead and the challenges facing the processing fraternity and mining industry.

Jan 1, 2006

By D. M. Meyer, K. Auerswald

The production of electrolytic manganese in South Africa by M. HARRIS, Pr. Eng., B.Se. (Eng.) (Fellow), D. M. MEYER, Pr. Eng., B.Se. (Meeh. Eng.) (Visitor), and K. AUERSWALD (Visitor) The decision to construct the first electrolytic manganese plant in South Africa was important and farreaching. After evaluating the results of the pilot plant operation, the first South African producer, Electrolytic Metal Corporation (Emcor), established a plant in Krugersdorp. Initially, there were many process problems that had to be InvestIgated, and, after these had been solved and many operating parameters had been established, manganese was successfully produced. When the Delta Manganese plant in Nelspruit was planned, cognizance was taken of the fact that, if peak efficiencies were to be maintained, the process must be operated between fairly narrow parameters. Instrumentation was therefore installed to control the process automatically wherever possible. The main features of the Delta Manganese operation are outlined, with a brief description of each stage of the process from ore milling through to electrowinning and packing of the metal. It is concluded that much benefit can be obtained from further research work into process improvements and into the exact effect of certain variables on plant and current efficiency.

Jan 2, 1977

By E. H. van Niekerk

The production of high-strength Iow-alloy (HSLA) steels containing either niobium or vanadium as the principal micro-alloying element is discussed, including recent developments in steelmaking practice that have had a great effect on the development of HSLA steels; strengthening mechanisms, as well as the principles of thermomechanical treatment during controlled rolling on a hot-strip mill; and the results of production heats with various amounts of micro-alloying elements.

Jan 1, 1984