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By M. J. Nicol

The kinetics of the dissolution of colloidal silver in aerated cyanide solutions has been investigated with the aim of developing a relatively rapid and convenient method for monitoring the ?leaching power? of solutions typically used in the cyanidation process. Experimental results obtained are consistent with an electro-chemical model, in which the mixed potential is set up in the active region of the polarization curve for the anodic dissolution of silver, giving rise to a rate of dissolution which is controlled by the rate of mass transport of either cyanide or oxygen to the surface of the silver. The rate of dissolution of colloidal silver was found to respond to variations in the reactant concentrations in a similar manner to gold (and silver) in a typical free-milling ore. The use of this technique for the monitoring and control of the cyanide leach process is discussed.

Jan 1, 1998

By I. Benning

Since the dismal performance of the Rand Mines management was called to account by its shareholders in 1994, the waves of change have continued to ripple across the South African mining industry .The number of listings on the gold board of the Johannesburg Stock Exchange, that once numbered 40 or 50-odd, have now dwindled to no more than a handful as unprecedented restructuring has taken place. The redefining of the industry has not been limited to the gold sector, but across the base metal, coal, diamond, platinum and industrial mineral sectors as well. At the same time the Mining Houses began to reconsider their funding strategies. Originally established in the early part of the century to ensure the long-term sustainability of their group mining operations by providing substantial financial muscle and technical support, the Mining Houses were faced with a rapidly changing political environment, which proved to be a critical catalyst in giving momentum to the change. Furthermore, the significant development costs and increasing risk profile for new projects, coupled with pressure from shareholders demanding respectable returns, opened the door to opportunities for banks to begin providing external debt by the way of project finance. However, the provision of long-term debt to the South African mining industry had generally not been common since mining companies had financed new projects with equity, or with the cash flows from existing operations. Those banks that had the appetite for exposure to the perceived high risks of the mining sector rapidly built up specialist resource banking divisions capable of addressing the increasing demands of the industry. The application of project finance, the principles of which were developed in the 1970s specifically for infrastructure projects and privatization, is now commonly applied in the financing of greenfield and brownfield mining projects. This paper outlines the approach that lending banks would typically adopt when arranging or providing mining project finance, their usual areas of concern and the way in which the finance is structured to mitigate the many inherent risks.

Jan 1, 2000

By L. R. C. Cairncross

In this study, the general case of semi-batch precipitation of nickel hydroxide, Ni(OH)2, is modelled. In practical terms, this precipitation may occur at high ionic strengths, and therefore the model for solution chemistry requires a thermodynamic model that is applicable for these non-ideal systems. The activity coefficient model used is the ELEC-NRTL. The simulation of the solution chemistry is performed using AspenPlusTM, which is a steady-state process simulation program. This allows for rigorous evaluation of the solution speciation, and hence the degree of supersaturation which dictates the precipitation kinetics. The solution chemistry provides the basis for predicting the formation of solids. The model consists of a solution chemistry part and a solids formation part. The inputs to the model include the initial concentrations of the streams entering the reactor, kinetic parameters for the precipitation processes, and a particle size distribution obtained from experiments. The solids formation part of the model employs the method of moments for the evaluation of the population balance. The population balance accounts for total particle number, and the formation and increase in size of particles across the entire particle size range. This balance requires kinetic parameters for the processes of nucleation, growth and agglomeration. Using optimization routines inherent in AspenPlusTM, parameters for the rate of nucleation, growth and agglomeration may be extracted from experimental particle size distributions. These are then used in the model to extrapolate to other conditions. Once an understanding of the kinetics of the precipitation processes is gained, the model provides a predictive tool for optimization of these kinetics, in order to increase the overall particle size and therefore improve solid-liquid separation. The work is deemed to be significant as it sheds some light on solids formation processes involved in precipitation?including nucleation, growth and aggregation?and develops a predictive modelling tool applicable to solutions of high ionic strength. We argue that this dewatering of suspensions is affected significantly by particle size distribution and surface properties of the solids formed by precipitation. This modelling tool should facilitate the design of solids formation processes where downstream dewatering is enhanced.

Jan 1, 1997

By T. Celik, B. Genc, C. Musingwini

"Mine planning software continues to be an important factor when it comes to the development of the South African mining industry. To contribute to this development, a new methodology to define and measure mine planning software utilization in the South African coal mining sector within an evolving data-set framework was developed. An initial data-set showing the mine planning software providers, their corresponding software solutions, as well as the software capabilities and information on the number of licences was collected and compiled in 2012 in an online database for software utilized in the South African mining industry. Details of the database development and implementation were published in the Journal of the Southern African Institute of Mining and Metallurgy in 2013. In 2014 the data-set was updated with additional and new information.In this paper, using the 2012 and 2014 time-stamps, a methodology for estimating the software utilization is developed. In this methodology, three variables: commodity, functionality, and time factor are used to define and measure the software utilization in order to ultimately inform decision making strategies for software utilization. Utilization in the coal sector was measured according to six different functionalities, namely Geological Data Management, Geological Modelling and Resource Estimation, Design and Layout, Scheduling, Financial Valuation and Optimization. The methodology is useful for stakeholders reviewing existing software combinations or intending to purchase new software in the near future and wanting to estimate the comparative attractiveness of a certain software package. These stakeholders include mining companies, consulting companies, educational institutions, and software providers. The work presented in this paper is part of a PhD research study in the School of Mining Engineering at the University of the Witwatersrand."

Jan 1, 2016

By H. G. Oltmann

The equilibrium nitrogen solubility in the CaO-SiO2system was studied by a slag-gas equilibration technique, in graphite crucibles at 1823K under a CO-N2 atmosphere. The nitrogen content of the slags was determined by the Kjeldahl method. A reliable technique was used to obtain an initial nitrogen content in the master slags, from the addition and pre-melting of silicon nitride. Reduction of silica by graphite was found to occur during the equilibration experiments, resulting in compositional changes of the slags. The results were extrapolated to equilibrium by kinetic evaluation of the data. The nitrogen solubility showed good agreement with the result of Suito and Sano, while Fruehan?s results were lower. However, the results of the present study do not support the maximum nitrogen solubility values found by Sano.

Jan 1, 1999

By V. Ross

"Bench-scale flotation tests play a major role in the geometallurgical process value chain. Despite their apparent simplicity, these tests pose pitfalls in terms of operation, as well as the interpretation and modelling of results. In this paper we highlight key aspects to consider in generating accurate and reproducible experimental results, and critically review some assumptions relating to the estimation of entrainment and froth recovery. We subsequently focus on first-order equations to model kinetics and propose a method that accounts more realistically for the decay in kinetics over the duration of a float, and the contributions of froth stability and hence mass pull. The method was applied to three case studies on platinum group metal (PGM) ores and matched or outperformed first-order, two-component models. Also, it allows for a deeper analysis of the integrity of the bench-scale flotation results. IntroductionGeometallurgy is a structured, multidisciplinary approach that integrates key data from the geological, mining, mineralogical, and metallurgical aspects of the value chain to construct spatial models of an ore deposit such that the overall economic benefit and sustainability of an operation can be optimized. Process geometallurgy is aimed primarily at enhancing metallurgical efficiency and plant throughput by the application of appropriate mining and processing strategies, as well as supporting production planning and operational strategies to reduce the impact of highly variable ores. With flotation being the dominant concentrating process in the mineral value chain, the bench-scale flotation test is an important characterization tool – a relatively cheap, simple, and rapid way to obtain key information about the ore and its amenability to economic extraction of valuable minerals. This includes the evaluation of different ore types and the implications of mineralogical composition and texture for comminution and floatability, the effect of the grinding environment on the liberation of minerals, the electrochemical environment in the pulp (Bradshaw et al., 2006), the screening of reagents to improve floatability (Ekmekci et al., 2003), and the role of hydrodynamics in the recovery of valuables and the entrainment of gangue (Amini et al., 2016; Wang et al., 2016). It is also a critical tool in auditing the performance of a flotation plant by hot floats, paving the way for concept and feasibility studies and providing essential data on kinetics for the purposes of scale-up, optimization, and simulation of flotation circuits."

Mar 1, 2019

By B. J. Madden

Over 206 million tons of hard coal were mined in South African collieries in 1996. Some 132.5 millions tons came from underground operations and approximately 120 million tons came from bord-and-pillar workings resulting in between 100 000 and 150 000pillars being formed. Coal pillar design remains a significant feature of South African mining. This paper reviews South African coal pillar design procedures in the light of 90 pillar collapses that have occurred since 1904. It shows that, while the current pillar strength formula is still valid within the original empirical range of Salamon1,cognisance must be taken of local conditions. Current South African coal pillar research is attempting to account for the variations in local conditions with the emphasis on the effect of discontinuities and pillar deterioration. It is suggested that a more holistic approach to pillar design be adopted to include a design methodology that examines the stability of the roof, pillar and floor of the underground workings. Using this approach, deviations from the empirical database used by Salamon and Munro will be incorporated into the design methodology resulting in more stable underground workings.

Jan 1, 1998

By J. Roodt

Paper written on project work carried out in partial fulfilment of B. Eng (Metallurgical Engineering) degree This work was done to characterize the leaching of a uranium containing pulp processed by a South African producer to identify parameters that could be adjusted to increase the extraction of uranium in the existing circuit. Batch leach tests were used to characterize the leach properties and especially the influence of the oxidant concentration on the leaching achieved. It was found that relatively high extraction could be obtained even at room temperature by using a high liquid-to-solids ratio and that increasing the oxidant concentration significantly improved the leaching of the uranium minerals.

Jan 1, 2003

The paper deals with the importance of design and of codes of practice in ensuring safe working conditions in mines. The design principles involved in the design process are dealt with, and the importance of a logical design process is emphasized. The links between the requirements for developing a code of practice, embodied in the existing guidelines for the preparation of such a code, and the design principles and process are considered in some detail. Finally, suggestions are included, which may provide improvements to the code and hence, ultimately, lead to further improvement in safe working conditions.

Jan 1, 2004

The reality of rising electrical power costs and the haunting prospect of decreasing electrical power availability are a threat to the growth of new projects and expansion programmes that could negatively affect the sustainability of mining operations. These threats require the adoption of effective power saving measures aimed at three principal objectives: the elimination of wastage, the reduction of power usage particularly during peak demand periods and, more importantly, improving the efficiency of high power-demand processes. It is reasonable to assume that the greatest impact will be achieved by concentrating on those processes that are large electrical power consumers. For Anglo Platinum operations, mine ventilation and, currently to a lesser extent, mine cooling are two continuous processes that fall in this category. It is estimated that these may consume fifteen to thirty-five per cent of the power delivered to the shaft head-depending on the shaft's design. Mine ventilation systems suffer from inherent, historical inefficiencies that lead to excessive power consumption. Air cooling systems are designed to be energy-wise in terms of modulating refrigeration plant operation to meet the underground requirements while maximizing use of 'free' cooling from surface conditions. Currently about ninety-five per cent of the refrigeration capacity used in Anglo Platinum mines is dedicated to surface bulk air coolers. The net thermal efficiency of these systems is compromised as mines expand in depth and on strike. Looking to the future, this practice will be complemented by more energy demanding underground cooling tactics requiring considerably higher electrical power consumption per unit ton produced. To counter this increase in power consumption, more energy-efficient systems and advantageous transient strategies such as thermal storage and the use of ice-on surface and possibly even underground-are being considered. This paper describes work currently undertaken and planned by Anglo Platinum operations to reduce power consumption by main fans during off-shift periods, the associated efforts currently introduced to reduce underground air leakage, the possibility of introducing more efficient auxiliary ventilation systems, the feasibility of thermal storage, and a brief look at energy recovery system as a means of countering the anticipated power demand associated with underground cooling. Keywords Mine ventilation, mine air cooling, energy efficiency, chilled service water, energy recovery, air wastage, fan selection.

Jan 1, 2011

By T. E. Pogue

This paper traces the co-operative initiative undertaken by South Africa?s gold mining companies through the Chamber of Mines Research Organization (COMRO) in development of hydraulic technologies. After a brief description of the structure of these technologies? development under COMRO?s stewardship, the paper turns to an overview of the structure of innovation within which these hydraulic technologies were developed. A central focus of this paper is systematic review on whether similar technologies are likely to emerge in the present system of innovation and the role played by innovation policy.

Jan 1, 2006

The validity of a steady state assumption made by Adams and Nicol (1986) in the modelling of the elution of gold from activated carbon was investigated. It is shown that the accuracy of the steady state approximation is dependent, not only on the magnitudes of the solution flow rate and reactor volume, but also on the lumped elution rate constant. Under the experimental conditions used by Adams and Nicol (1986) the steady state assumption was inaccurate. This could be circumvented in this instance by applying a rigorous general model which accounts for unsteady state behaviour in the solution and in the activated carbon to the experimental data.

Jan 1, 1997

By D. P. Roberts

The stoping of platinum orebodies in the Bushveld has in the past been accomplished by using in-stope pillars to ensure stability of the workings. In the future, the use of continuous mining machines to mine the platinum orebodies is probable. It is not envisaged that such machines will cut in-stope pillars. This paper describes the alternative support systems that will replace the pillars and the stope geometries that will be required for this type of mining. The paper describes how the support resistance provided by in-stope pillars in current mining was determined and then evaluates support systems that can substitute for these pillars. Conceptual layouts based on existing breast mining layouts are presented. The layouts consist of panels of up to 100 m face length between rigid strike stabilizing pillars. A number of design charts are then proposed that allow for the design of appropriate support systems.

Jan 1, 2005

By R. P. Mohring

The South African Coal Industry had its beginnings in the Eastern Cape in 1859 when coal was mined to satisfy the fledgling settlements in the Eastern Cape. The growth in the industry was relatively slow up to the early 1970s when, firstly, the export business was expanded coupled with a major increase in the quantity of coal converted to liquid fuels and utilized for power generation. To meet this increased demand the industry developed many new operations employing the latest mining technology and systems. Coal production in South Africa reached 204 million tons in 1996 and revenue from exports reached R8 billion making it the second-largest foreign exchange earner after gold. In his address Rick P. Mohring describes the role coal plays in the international energy scene and outlines South Africa?s position as a producer and consumer of coal, and the challenges facing the industry. A wide range of steam-coals are produced to satisfy both the local market (power generation, coal conversion and the metallurgical industry) and the export steam-coal market. South Africa is in a unique position regarding the export market as it is still a relatively low-cost producer and is geographically well-placed to play in both the European and Far East markets. There are, however, a number of challenges facing the industry. To retain our competitiveness in the international market, ways of minimizing the cost pressures caused by high-cost inflation, increased environmental protection obligations and a decreasing quality resource base need to be sought. Locally the coal mining industry has a major role to play in Eskom?s goal of reducing the real cost of electricity by 15% in the next three years. Safety and health, productivity and the adaptation of the latest technology are issues being addressed by the industry to maintain its dominant position within the South African economy.

Jan 1, 1997

By R. Banda

This paper describes the decision to implement and then the implementation itself, through trials, of electronic ?Smartdets? over previously used shock tubes. It concludes that Mufulira Mine has become the first mine in Zambia to convert 100% of its stoping to ?Smartdets?, because the Mine?s management was prepared to look beyond the unit cost of product and were ready to look at the broader picture of cost effectiveness and increased productivity.

Jan 1, 2005

By Masanobu Masukawa, Toshio Shiota

The shaft-type ferromanganese smelting furnace (SF) at Mizushima Ferroalloy Co., Ltd. has been in operation since startup in 1985 and is continuing to perform smoothly. Production has been increased from the original design capacity of 270t/d to 350t/d by various operational improvements. As a productivity index of the shaft-type furnace, production of 350t/d is equivalent to productivity of 0.9t/m3/d (daily production/cubic capacity of furnace). Recently, various operational improvements were implemented to achieve productivity of 1.0t/m3/d or higher, including oxygen enrichment operation, increased tapping frequency, maintenance of the throat profile, and operation with small lump coke. The target productivity of 1.0 t/m3/d was achieved in January 2005. This report describes the improvements introduced as part of this high productivity technology.

Jan 1, 2007

By A. Hammel

This paper summarizes indigenous mining methods used to collectmetal ores in pre-colonial southern Africa, south of 15°S. These methods, for the purposes of discussion, are divided into sections inorder of increasing organizational complexity, from scavenging,which only required basic equipment and a relatively minimal division of labour, to underground mines, which necessitated complex planning to overcome obstacles such as the need for illumination and ventilation. Examples concerning the pre-colonial exploitation of iron, copper, tin, and gold have been taken from the archaeological literature. This review paper provides an introduction to the technology that was available to and used by miners in the past, illuminates some of the factors limiting their operations, and supports the claim to the indigenous nature of this activity

Jan 1, 2000

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 D. H. Diering

The paper deals with the technologies required for opening up anew idealized ultra-deep level mine. First the overall philosophy of accessing ore at ultra depths is discussed. Then the individual technologies which will be required are explored. Finally a detailed overview on one of the key technologies, namely tunnel support, is given. Because this project is still in its infancy, few definitive answers are provided; instead each of the envisaged technologies are briefly discussed, with emphasis on those which require the element of speed for rapidly accessing the ore body.

Jan 1, 1997

By F. M. L. Mulaudzi

Metal dusting is a corrosion phenomenon that occurs in strongly carburizing gas atmospheres at elevated temperatures. Reaction kinetics and product characterizations of Alloys 602CA and 800 were examined by scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX) and X-ray diffraction (XRD).The results showed that Alloy 602CA is more resistant to metal dusting than Alloy 800. Visual examination and SEM surface analysis showed that Alloy 800 suffered metal dusting attack after a relatively short exposure period. The amount of coke deposits increased on Alloy 800 with increased exposure from 96 to 336 hours. X-ray diffraction on the reacted surfaces identified graphite and austenite in both alloys and some iron oxides/spinel for Alloy 800.

Jan 1, 2012