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By E. Minnaar, P. J. Cilliers, M. Bellino, L. M. Roux, R. Dye

The classic technique to remove impurities in a cobalt stream is selective precipitation. This is usually followed by re-leaching to produce an advanced electrolyte for cobalt electrowinning. Although this technique ensures an adequate cobalt concentration in the electrowinning circuit, some of the consequences include unwanted losses through the numerous selective precipitation steps resulting in lower recoveries. One plant that currently utilizes selective precipitation is the Luilu Metallurgical Plant (Luilu) in the Democratic Republic of the Congo. This paper evaluates the benefits of using solvent extraction technology as a purification step in the Luilu Process with the aim of further increasing the overall cobalt recovery and to ensure that a suitable cobalt concentration in the advanced electrolyte is achieved. The implementation of a solvent extraction-electrowinning process is found to be beneficial in terms of achieving improved recoveries and cobalt cathode quality, however there are many other factors that impact the success of converting from the classic precipitation process used at Luilu.

Jan 1, 2007

The special mixing requirements for backfilling are discussed, and the problems associated with the mixing of coarse and deslimed slurries, as well as the tailings from the gold plant are outlined. The mixing of binders which are used to strengthen backfill and the parameters for the scale-up of mixer pilot plant work are also discussed

Jan 1, 1988

By M. Mpofu, B. Maphalala, S. Khan, S. Ngobese, D. Roberts

This paper details an assessment of stemming practices at a South African opencast coal mine and their influence on ground vibration and air blast. Quantitative and qualitative analysis methods were used for the study. The parameters assessed for the quantitative analyses included stemming length, stemming material type, blast-hole depth, burden, and spacing. Pre-blast data from the mine was analysed to determine the deviation between actual and mine design stemming parameters. Mine design stemming length was also compared to the rule-of-thumb stemming lengths. Peak particle velocity (ground vibration) and air blast data from seismograph stations around the mine was analysed to determine the correlation between stemming length and excessive ground vibration and air blast. The qualitative analysis involved observations of blasting procedures at the mine to determine compliance with mine procedures. Some level of non-compliance of actual stemming parameters to design stemming parameters was found, which initially suggested that non-compliance may have contributed to excessive air blast. However, further analysis of the seismograph results indicated no direct correlation between stemming length and excessive air blast and ground vibration. Since stemming parameters are interrelated, it is crucial that all blasting procedures, including stemming, are executed in accordance with best practice, and recorded accurately. There is a need for digital systems for capturing on-bench blasting parameters, as the currently used manual data recording and reporting systems are inefficient and prone to error. Improvements to blast designs are possible through efficient and accurate data recording and reporting systems.

Jan 1, 2021

Rock fall accidents continue to be the main causes of fatalities in the mining industry. The occurrence of rock falls in supported stopes implies a failure of the support system. The failure of the support system in turn implies a failure in design. In this paper, ethical issues associated with engineering design are discussed, with particular relevance to stope support design. A risk approach is introduced that will allow designs to be carried out that are compatible with the acceptable risk defined by the mining company management. The implementation of this approach would overcome the ethical shortcomings of current support design practices.

Jan 1, 2007

By R. G. Votteler, A. C. Brent

"The first in this series of two papers, on the potential of renewable electricity sources for mining operations in South Africa, investigated the internal structure of mining corporations to evaluate feasible alternative electricity sources that were identified as through earlier research. The purpose of this paper is to combine current knowledge about the external macroeconomic and the internal environments to produce a clear picture of how renewable sources of electricity could perform from the perspective of mining corporations in South Africa. The multi-attribute value theory (MAVT) approach was adapted to structure the research and results. The model was fed with real-time data provided from five different energy companies and four mining corporations operating in South Africa. The results show that the performance of hybrid versions of the currently used electricity sources (diesel generators and Eskom grid connection) with solar PV and onshore wind is favourable compared with the current sources alone. The advantage of diesel generators is significantly greater than that of the Eskom grid connection. By combining the macroeconomic influences with the MAVT results, hybrid solar PV versions are identified as having the greatest potential. In second place are hybrid wind solutions, which have the shortcoming that good wind conditions occur only in coastal regions where there are fewer mining activities. Geothermal hybrid versions are the least favourable owing to the lack of service infrastructure and high initial investment costs.IntroductionRecent developments in the macroeconomic environment necessitate an investigation of the internal structure of mining corporations to evaluate possible alternative electricitygenerating sources (Roehrl and Riahi, 2000). To be able to combine current knowledge of macroeconomic factors and the internal structure of mining corporations, the research process is presented in two papers. The first paper (Votteler and Brent, 2016) investigated the internal structure and argued that a strategic tool should be used to evaluate electricity sources from the perspective of mining corporations. The multi-criteria decision analysis (MCDA) approach was selected as the most appropriate strategic tool. Based on a literature review of previous similar MCDA approaches in energy planning, it was concluded that no adaptation of MCDA methods could be found from a corporate, mining, or South African perspective. Finally, the paper investigated the internal evaluation structure in collaboration with mining corporations, by identifying the criteria they use to evaluate electricity sources."

Jan 1, 2017

By M. Rudolph, R. Tolosana-Delgado, E. Schach, M. Buchmanna, G. van den Boogaart, U. Peuker

The multidimensional characterisation of processes based on various particle properties is a key requirement for a detailed prediction on certain process streams. To access the relevant particle properties (e.g. particle size, particle density and mineral content) automated mineralogy (i.e. Mineral Liberation Analyser) is applied. The kernel density estimation is used to transfer the received discrete particle data into continuous distributions without the necessity of binning the information and the related loss of information. From these continuous distributions, multidimensional separation curves are estimated. The uncertainty of these representations is tracked via bootstrap resampling. For the evaluation of the separation efficiency of the multidimensional separation curves, the statistical entropy is calculated. The statistical entropy represents a local (for each property combination) as well as a global (for the investigated property range) measure of separation efficiency and can be weighted with various property distributions (e.g. mass or mineral mass distribution) to allow for a comparison of different parameter settings and processes. With the help of a case study of a dry magnetic separation of a cassiterite bearing skarn ore from the Erzgebirge (Germany), the methodology is presented and the results are discussed in detail. Keywords: Multidimensional, magnetic separation, kernel density estimation, mineral liberation, statistical entropy

Jan 1, 2020

By D. Seke

Metal inventories are usually reported in financial statements of mining companies. However, the value of these inventories can be reliable only if the metals in stock are measured within acceptable tolerances. Reliable metal balancing requires accurate mass measurement, sampling, and chemical analysis. Many mining companies are usually unable to validate the accuracy of metals in inventories at the end of their financial year. This is mainly due to poor mass measurement, sampling, and chemical analysis practices. This has an adverse impact on metallurgical accounting and metal valuation. In addition, it puts a lot of stress on external auditors, who have the duty to recommend the approval of the financial statements to the board of directors. Although a full value chain of metal reconciliation includes the accuracy of Mineral Reserve definition and grade control at the mine, this paper discusses the implementation of best practices for mass measurement, sampling, and chemical analysis at processing plants. This is an important aspect of sampling and reconciliation that is required in order to improve the reporting of inventories in the financial statements of public mining companies. Keywords metallurgical accounting, corporate governance, sampling, analysis.

Jan 1, 2014

In the wake of the financial crisis that affected world markets in 2002, there has been an increasing international focus on corporate governance. Various corporate governance codes of practice have been introduced, such as the Sarbanes-Oxley legislation in the USA, the Combined Code in the UK, and King III in South Africa. This focus on corporate governance has increased since the most recent financial crisis in 2008, the effects of which are still being felt world-wide. In the mining and minerals industry, reliable metal accounting is essential to sound corporate governance and is also becoming a focus of increased attention and concern, particularly as the figures generated by the metal accounting system feed directly into the financial accounts of mining companies. Mass measurement, sampling, and analysis provide the input data for the metal accounting system and sound corporate governance requires that the procedures used are based on best practice and that the data generated is accurate and handled correctly, transparently, and consistently to produce the accounting reports. The AMIRA Code of Practice for Metal Accounting has been widely adopted in the industry as a means to achieve this, and the compilers of the Code have conducted numerous metal accounting audits at operations, both in South Africa and abroad. These audits have shown that there is a real need for such a code of practice. Keywords metal accounting, AMIRA Code, corporate governance, risk management.

Jan 1, 2014

By John Taylor

?Introduction to Black Mountain ?Historical metal accounting practice ?Metal accounting audit ?Feed measurement ?Sample precision ?Concentrate measurment ?Current metal accounting practice ?Further refinements to the metal accounting practice

Jan 1, 2005

By R. Venter

Uranium in the tetravalent state has very low solubility in acid and alkaline solutions and needs to be oxidized to the hexavalent state to become soluble. In acid leaching of uranium the uranium is oxidized by ferric iron, which in turn is reduced to ferrous iron. The reduced iron needs to be oxidized to the ferric form to allow the uranium dissolution reaction to proceed. This paper considers the known and proven oxidants used in acid leaching of uranium. These include manganese dioxide, sodium chlorate, hydrogen peroxide, ferric iron, oxygen and sulphur dioxide/air (oxygen). The reaction chemistry of each oxidant as well as the practical applications are considered and discussed. All the oxidants discussed work adequately in acid leaching of uranium and it is possible to engineer solutions for the use of the oxidants in acid leaching on plant scale. The availability and supply of the oxidant as well as the cost and environmental impact of the oxidant plays a major role in the selection of a suitable oxidant. The location of the plant will also have an impact on these issues.

Jan 1, 2009

By Jonty Tshipa

The Mine Site Technologies, MST BlastPED ST is a wireless/remote blasting system used in more than sixty (60) mines (including two mines in Zambia and one in Tanzania) since its release in 2002. The system consists of a controller and signal tube initiator which communicate wirelessly using spread spectrum frequency. This technique ensures a robust and secure wireless link between the controller and the signal tube initiator. The configuration of the system ensures ease of use with all the instructions for initiating the blast printed on the equipment. This means little or no formal training is required to use the system. The technology enables you to have your blasting point at a distance of up to 4 km, line of sight (LOS), as opposed to the traditional distance of 500m from the blast. This ensures the blast takes place from a safer and secure location. The paper and presentation will provide the audience with the benefit of many years of international mining know-how in this technology as well as more recent local African experiences. There will be references to demonstration blasts done in South Africa, current users in Africa and elsewhere. Practical Return on Investment (ROI) calculations and references to safe blasting practice will also be included.

Jan 1, 2008

By R. V. Ramani

Managers need quality information for effective decision making. This demand, at the present time, is being fulfilled by the increased use of computers via information systems, decision support systems and management information systems. The idea of incorporating intelligence into computers to aid decision-makers has been evolving for over two decades. In recent years, significant progress is reported on applications to business and sciences. In engineering functions, the Artificial Intelligence approach that seems to have great potential is the application of Knowledge Based Systems. The primary objective of this paper is to identify domains in mining engineering where application of knowledge based systems could be beneficial. In- corporation of the expertise required during the analysis and interpretation stages of an engineering design problem through knowledge based systems is recognized as an area of significant benefit. To this end, the components of knowledge based systems for mine ventilation and strata control design are described. The potential applications and limitations of knowledge based systems are outlined.

Jan 1, 1987

By J. Rowe

The attrition of activated carbon, and the loss of gold associated with it, is of significant economic importance to the operation of a CIP/CIL circuit The focus of this study was on activated carbon recovered from an elution circuit which was deemed too fine for reuse. Results of cyclosizer and laser particle size analysis identified that most of the carbon was contained in the larger size fraction suggesting formation by abrasion. Digestion and AAS analysis of the individual size fractions identified a disproportionate concentration of gold in the finer size fractions which was identified by scanning electron microscopy to be due to the presence of fine metallic gold formed as a result of the acid washing process. Attempts to strip the remaining gold using sodium hydroxide or sodium sulphide based solutions proved unsuccessful due to poor elution efficiencies and re adsorption of gold. Upgrading of the material by froth flotation was also investigated using various conventional flotation reagents which had some success in concentrating the free metallic gold, however, grade and/or recoveries were considered less than desirable. Greater success was ultimately found in the transfer of gold from the fine carbon material onto coarser virgin activated carbon using a caustic cyanide solution. Sodium sulphide, sodium chloride and ammonium chloride based solutions were also trialled but proved less successful owing to their inability to mobilise metallic gold or gold cyanide species. Repetition of the transfer process proved capable of stripping 97% of the gold contained on the carbon fines for abed volume ratio of 6:1.

Jan 1, 2009

By A. D. Pienaar

The aqueous chemistry of niobium and tantalum compounds with hydrofluoric acid is a mature field of investigation. In contrast, very little attention has been paid to reactions of these compounds in non-aqueous environments. Similarly, reactions of elemental fluorine with niobium and tantalum compounds have received little more than cursory attention in literature. This work discusses the isothermal reaction kinetics derived from thermogravimetry, using a less redundant approach than is currently the standard. We also discuss the most likely kinetic models for this reaction.

Jan 1, 2012

While some of the practical details of ilmenite smelting are not well documented, there is a substantial body of literature on the principles of ilmenite smelting, and the behaviour of solidified titania slag. This information is summarized, focusing on the basic reactions, departure from equilibrium, the behaviour of impurities, and reactions of solidified slag. The emphasis is on the South African operations.

Jan 1, 2007

By G. P. A. Howe

"A computer model of the rutile, ilmenite and zircon industry was developed jointly by Associated Minerals Consolidated and Consolidated Gold Fields for exploring marketing strategies and making predictions over a ten-year period. The industry is described briefly and the reasons for modelling it and choosing a deterministic approach explained. The economic structure of the model and its level of complexity are discussed. The necessity and techniques for convenient input and clear output, the team composition and the method of work are discussed.The reasons for the choice of FORTRAN, large computers, remote batch terminals and the vital importance of fast turn-round are discussed.Costs in staff time and computing are given, with an assessment of the reasons for the success of the model. The model is used on a regular basis to aid management decisions."

Jan 1, 2014

By J. Martinovic

The large proportion of gangue minerals present in platinum bearing ores in South Africa provides challenges to the flotation and down stream processes. In order to take effective measures to reduce their recovery in flotation an understanding of the mechanisms and factors influencing their behaviour is needed. Typical gangue minerals are pyroxene, feldspar, quartz, chromite and talc. Of these, talc is a naturally hydrophobic mineral and although it is present in relatively small quantities, it has a disproportionate effect as it has a strong froth stabilizing effect, increasing the recovery of other gangue minerals by entrainment. Talc recovery is effectively reduced with the addition of polymeric depressants. Although the other gangue minerals are assumed to be hydrophilic and their recovery by entrainment is expected to follow the water recovery, there is some evidence that they may be activated by the typical reagent suites used. Reagents such as copper sulphate, added as an activator, and collectors are used to selectively induce hydrophobicity on the sulphides. It has been shown that some of these gangue minerals can be activated. This research work investigates whether inadvertent copper activation is mineral specific and evaluates the mechanisms and factors affecting the reversal of activation with the addition of the depressants using electrokinetic measurements, adsorption and microflotation tests. Results are presented that show that the selected minerals do respond differently and that the reversal of activation is dependent on mineral type, depressant type, dosage and ionic strength of the electrolyte.

Jan 1, 2004

Acid heap leaching has been extensively applied to the processing of copper oxide ores, with recovery of copper by solvent extraction and electrowinning. Heap leaching has also been extended to the treatment of secondary sulphide copper ores, where oxidative conditions are generated in aerated heaps by the bacterially-assisted oxidation of ferrous iron to ferric iron. The treatment of low-grade chalcopyrite ores has recently been the focus of research, with Mintek playing a prominent role. When processing chalcopyrite ores, more complex column test work is performed, which incorporates the prediction and simulation of temperature behaviour in pyrite-containing heaps. Mintek has devised a trade-marked column leaching apparatus (SmartColumn?) for the simulation of the natural temperature profile development in pyrite-containing heaps. As heap leach applications are becoming more complex, the parameters that need to be built into the design and operation of heap leach plants are growing in number, and the amount of data to be collected and processed, and the number of decisions to be taken daily, are also increasing. Mintek has therefore developed the HeapStar® administrative advisory software, as a guidance system to ensure that the correct protocols are implemented at various stages of the leach cycle.

Jan 1, 2012

By L. A. Cramer

There are a couple of dozen junior platinum mining companies coming into existence in Southern African and most intend to mine, concentrate the PGM?s in a flotation product and sell the concentrate to one of the major producers in South Africa. The price they will receive for their product and hence the return they achieve for their investment will depend upon the large number of factors that influence the market for such a product. Unfortunately the number of buyers is severely limited as it is dominated by the two major local producers, Impala Platinum and Anglo Platinum. Furthermore the current smelting technology has limited capacity for UG2 concentrates and high nickel concentrates will quickly fill any available base metal refining capacity. Few if any overseas buyers can compete for the bulky flotation concentrate produced. This paper will explore those factors such as metal recoveries, metal prices, operating costs, capacity constraints, deleterious elements, transport issues, metal premiums and discounts that are in play, types of flotation concentrates, processing capital costs, PGM grades, etc and their impact up on what smelters and refiners might be prepared to pay for such PGM concentrates. Ultimately simple graphs and equations can be developed for probably payment terms for such concentrates. Those who negotiate well will move to the higher return section of the envelope and those who use the concentrator facilities to produce the most saleable combination of flotation concentrates will enhance their returns. A deep and firm understanding of the issues surrounding this market is necessary in order to negotiate the best possible price for the seller.

Jan 1, 2008

The variety and sources of sampling errors have been studied since the late 1800s, but the pioneering work of Pierre Gy in the 1950s provided insights into sampling as an error generating process. Total sampling variance is a measure of the total sampling error, but disaggregating the variance into its component parts is problematical. Ten sources of error and error generating processes have been identified, some of which can be eliminated through rigorous application of the principle of correct sampling. Others can only be minimized but never eliminated. Three principal questions relating to the appropriate mass of a sample, the fragment size of the sample and the size of the associated error are addressed. These questions relate principally to the Fundamental Error (FE), the only error that can be estimated before the sampling event. Aspects of constitutional and distributional heterogeneity are examined, as are the essential components of Gy?s formula including the shape factor (?), the granulometric factor (g), the mineralogical composition factor (c), and the liberation factor, l. Applications of Gy?s equation to the problems of sampling in the minerals industry are explained using real-life examples. The approach to sampling taken by Pierre Gy provides an excellent inferential relationship between the mass of material to be sampled, the size of the fragments being sampled, and the relative variance of the sampling error. It also provides solutions for three of the main problems associated with the Theory of Sampling.

Jan 1, 2007