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By S. Stuurman

Inorganic acids such as sulphuric acid have found use together with certain reducing agents in leaching of copper-cobalt oxide ores. These reagents are not ideal due to the adverse effect the inorganic acids generally have on the environment and the high costs of the reducing agents. In this study a copper-cobalt oxide ore from the Central African Copperbelt was leached in two different environments; sulphuric acid in conjunction with hydrogen peroxide as a reducing agent and tartaric acid. The effects of acid concentration, reducing agent concentration, and temperature were independently determined for both leaching environments. The sulphuric acid concentration was varied between 0.4 M and 1.2 M and the concentration of hydrogen peroxide between 4.0 M and 6.5 M, while the tartaric acid concentration was varied between 0.15 M and 0.35 M. The temperature was varied between 20°C and 50°C. The results showed that the extraction of both copper and cobalt increased with sulphuric acid concentration, reaching a peak at approximately 0.8 M and then decreasing at higher acid concentrations. A similar increase and decrease in metal extraction was observed when the reducing agent was increased. In leaching with tartaric acid, the extraction of cobalt was much higher than that of copper, although extraction of both metals increased with acid concentration. Additions of small amounts of hydrogen peroxide were found to increase cobalt extraction in tartaric acid but had a minimal effect on copper. An increase in the solution temperature had a significant effect in the organic acid environment, with the effect on cobalt extraction being much more pronounced than on copper.

Jan 1, 2014

By N. E. K. Schuttler

Experience with Mars pumping of underground water by N. E. K. SCHUTTLER (Visitor) As the result of a planned increase in production, Vaal Reefs Exploration & Mining Company Limited increased the hoisting capacity of their existing equipment to its fullest extent and installed Mars pumps and a washing plant. The layout of the installation is described, and details are given of the modifications made to overcome its weaknesses. Plans to change the present four-stage system to a seven-stage system are outlined.

Jan 3, 1977

By C. Hartford, T. Holmes

Bulk-solids handling systems are often the most over-looked component and thereby weakest links in a processing plant’s value chain. Since their performance can dictate that of the entire operation, they actually deserve special attention. When designing a liquid handling plant, density and viscosity are well known and commonly used as design parameters. Bulk solids however, differ. While the design process is similar, the relevant parameters in handling bulk solids are instead friction, cohesive strength, compressibility, and permeability. These then vary depending on the mineralogy, particle size distribution and shape, moisture content, storage time-at-rest, temperature, and consolidation pressure. With so many variables, it becomes important to characterize each individual bulk solid across the full range of representative process conditions within the handling system, plant wide – or if you are not very lucky, suffer the consequences of poor material flow. Measuring flow properties and applying them correctly in bulk solid handling system design reduces project risk, saves significant capital, and drastically increases throughput, especially when done in the early stages of a project. Keywords: Flow Properties, Bulk Solids, Process Conditions, System Design

Jan 1, 2020

By C. Gatschlhofer, A. Krammer, H. Raupenstrauch, T. Hochsteiner, A. Holzer, L. Wiszniewski

The rising demand for lithium-ion batteries, coupled with international climate targets, emphasises the need for circular economy and zero-waste recycling approaches. However, so far, no industrial-scaled solutions are available that fulfil global recovery targets. Therefore, a novel pyrometallurgical reactor was developed at the Chair of Thermal Processing Technology at Montanuniversitaet Leoben to avoid lithium slagging and recover volatile elements via the gas phase. Nevertheless, previous results show that several impact factors, including interfering elements or pre-treatment steps, strongly limit the recycling efficiency of black mass. To simulate the black mass and provide feedback on possible influences of pre-treatment steps, cathode material from production with additives of interfering elements was analysed regarding melting behaviour. The results show that formation of a further processable alloy was increased by almost 50% when pretreatment steps were excluded, indicating pre-treatment steps as a major influence to be considered within this specific recycling route.

Jan 1, 2023

By J. D. T. Steyl, G. B. Grobbelaar

Two examples are presented to show how first-principles – physical-dynamic, here termed behavioural modelling, is used to build digital twins of unit processes or plant sections. A digital twin equips the metallurgist, engineer, or manager with a powerful tool to conduct model-based design, solve process problems and improve operations. It is particularly relevant in the metallurgical industry where plant behaviour is highly integrated, rates respond to particle dynamics in complicated ways and mineral flows across flowsheet boundaries are variable. The two examples used to illustrate the behavioural modelling methodology are 1) a flotation column unit block and 2) a multi-compartment pressure oxidation (POX) autoclave. It simultaneously accounts for the causality of material and heat flow, takes care of mineral particle dynamics, physical and chemical reaction rates, the plant control system behaviour and operating heuristics. The basic modelling building blocks are briefly reviewed to show how the behavioural modelling attributes constrain the mass and heat flow dynamics to physically realistic values. This is the key aspect that allows project value to be created with minimal input data. Behavioural modelling is especially valuable where the process dynamics are poorly understood or controlled, where data-driven models fail to cope with complex and highly integrated plant behaviour, where quality data is lacking or limited funds are available to generate the data required to fill all the knowledge gaps. The paper uses the flotation column example to show how behavioural modelling and simulation can be used to optimise plant performance, while the multi-compartment POX autoclave model shows how it can be used to diagnose process problems. It also provides a solid basis to add a data-driven component – in other words, it makes a strong case for a hybrid first-principle– data-driven approach to solve process problems, especially where microscopic-level understanding is poor. Keywords: Digital twin, behavioural modelling, simulation, flotation column, pressure oxidation

Jan 1, 2020

By S. J. van Wyk, A. S. H. Haagner, A. Abraha

Opencast coal mining is responsible for the greatest area of land disturbance across all of the commodity types in South Africa. Many thousands of hectares have been rehabilitated to date and, although rehabilitation performance is not always measured or reported, a significant database, spanning 24 years, has now been analysed to identify the main shortcomings holding back rehabilitation sustainability across the industry. Data from 48 different collieries with rehabilitation performance scores measured from 2000-2024 were analysed. A standardised assessment framework was implemented at all 48 collieries, focusing on aspects of land capability, soil fertility, landscape form and drainage, vegetation species composition and basal cover, implementation of maintenance programmes, and prevalence of invasive alien plants. The findings show that, although invasive species management, plant species composition, and plant basal cover are often adequate, the implementation of aftercare and maintenance programmes (influencing soil fertility) and deficiencies in overall landform design and drainage systems are most significant in preventing overall rehabilitation progression and self-sustainability. Integrating these during design and rehabilitation execution, followed by intensive maintenance (especially in the first five years post-topsoiling and seeding) will be key for the overall industry performance to improve to acceptable levels. The database is biased towards collieries that actually do undertake rehabilitation and that do measure it, hence the actual industry performance is likely worse than what is presented. Due to the substantial hectarages involved and the main post-mining land uses being grazing and crop production, the industry cannot afford to keep perpetuating deficiencies in achieving the foundational aspects of rehabilitation that would pave the way for sustained economic future use.

Apr 25, 2025

By A. S. Geldenhuys, L. S. Leal Filho, D. A. Deglon, T. C. Souza Pinto

The Brucutu iron ore mine (Minas Gerais, Brazil), is Vale`s largest iron producing operation achieving around 21 million tons by flotation of iron ore pellet feed per annum. The run of mine is mainly composed of hematite (70%) and quartz (30%). After preparation (comminution and sizing), the slurry is submitted to reverse cationic flotation of quartz under basic conditions (pH=10.5). Corn starch (500g/t) is used to depress Fe-bearing minerals and alkyl (C10) ether amine is the collector for quartz. The flotation circuit is arranged in a “coarse” section utilizing dated 28m3 square Wemco cells, and a “fine” section utilizing modern 160m3 tank cells. The “coarse” flotation circuit treats material from the deslime cyclone underflow while the “fine” circuit treats material from the deslime cyclone overflow and the pulp product from the “coarse” circuit scavenger 2 bank. Evaluation of process performance is of high importance as even small gains can lead to large improvements for this high throughput plant. Cell-by-cell samples of the froth products, selected feed and pulp-products were analyzed for flow-rate, overall chemical composition, and particle size distribution. Bank-by-bank samples of the feed, froth and pulp products were analyzed on an assay-by-size basis. In addition, the flotation cells were hydrodynamically characterized and gas dispersion parameters assessed. The detailed experimental program resulted in a thorough characterization of the process and enough information to produce a calibrated floatability component model. Longer mainline residence time results in significant Fe2O3 losses while yielding little benefit in terms of SiO2 grade. Scavenger 2 has twice the residence time of scavenger 1 while having to treat only 10% of the SiO2; resulting in high Fe2O3 recoveries to the froth and poor separation. In addition, it is shown that the Fe2O3 exhibits true flotation behavior resulting in increased Fe2O3 losses. The detailed data collection campaign coupled with in depth data analysis and modelling gives unprecedented information and highlights avenues for optimization that was previously unknown. Keywords: Froth Flotation, Process modelling, Process evaluation, Metallurgical survey

Jan 1, 2020

By G. C. Lindeque

"A downward trend in tyre life on haul trucks at an open pit iron ore mine prompted an investigation into the current tyre management strategy in order to improve tyre life. ‘Best practice’ was compared to the current tyre management strategy at the mine to determine aspects that could be improved. Aspects that showed significant room for improvement included employee tyre awareness, tyre pressure maintenance, and road conditions. For each of these aspects a plausible alternative was suggested.A new tyre management strategy was formulated as a step-by-step guide on how to implement the proposed changes. Each step introduces new initiatives but at the same time builds on the previous step’s success. A sensitivity analyses was performed to determine the impact of the proposed changes, with the variables being the reduction in the percentage of premature tyre failure, and the reduction of the site wear rate.The ‘most likely’ scenario showed an increase in tyre life of 41% for the Komatsu 730 trucks and 105% for the CAT 777 trucks if the entire tyre management model is implemented. This would result in a possible annual saving related to tyre usage of R9.2 million. OverviewThe study focused on the tyre life on the main haul fleet at an open pit iron ore mine. The haul fleet consisted of 17 Komatsu 730 (180 t) haul trucks and 12 CAT 777 (90 t) haul trucks.The haulage operation consists entirely of tyre-based haul trucks. Five per cent of the total mining budget is related to tyre costs. Since 2012 there has been a steady decrease in tyre life as measured in operating hours (Figure 1) due to the high percentage of tyres that fail prematurely. In 2014 a total of 41% of all tyres failed prematurely and 61% were classified as ‘worn out’."

Jan 1, 2016

By F. K. Crundwell

The rate of dissolution of sulphide minerals is frequently interpreted in terms of the passivating behaviour of a layer of material on the surface. This interpretation has driven research to identify and possibly remove this layer from the surface, and thus yield higher rates of dissolution. The identification of such layers has proved difficult, with different researchers claiming different compositions for possible layers. An alternative framework has been pursued by the author and co-workers, who have argued that the rate of dissolution is governed by the electronic structure of the minerals which give rise to their semiconducting properties. Researchers sceptical of this approach have argued that semiconducting properties are only important in highly pure substances. In this paper, we review the electronic and semiconducting properties and discuss how they impact dissolution behaviour. These properties affect their colour and dissolution properties even though the minerals are not high purity substances. Keywords: Dissolution, leaching, passivation, semiconductor, chalcopyrite

Jan 1, 2020

Council and Standing Committees, 1978-1979 President: Dr M. G. Atmore. Vice-Presidents: D. A. Viljoen and Dr P. R. Jochens. Honorary Treasurer: J. K. E. Douglas. Immediate Past President: P. A. von Wielligh. Members of Council: J. D. Austin, A. N. Brown, H. E. James, Prof. R. P. King, Dr D. G. Krige, Prof. F. Q. P. Leiding, D. G. Malan, C. S. McPhail, J. C. Mostert, G. Y. Nisbet, H. G. M. Rose, W. T. Ruhmer, G. C. Thompson, R. A. von Maltitz. Chairman, Witbank-Middelburg Branch: T. S. Wilmot. Chairman, Orange Free State-Klerksdorp Branch: H. M. W. Eschenburg. Past Presidents Serving on Council: R. J. Adamson, H. Britten, J. K. E. Douglas, Prof. D. D. Howat, Dr J. P. Hugo, D. G. Maxwell, Prof. R. P. Plewman, Dr R. E. Robinson, Dr M. D. G. Salamon, P. W. J. van Rensburg. Standing Committee Chairmen: Membership, Dr P. R. Jochens ; Technical Programme - Metallurgy, Prof. R. P. King ; Technical Programme - Mining, H. G. M. Rose; Vacation School - Metallurgy, J. C. Mostert; Vacation School - Mining, D. G. Malan/J. D. Austin; Awards, P. A. von Wielligh; Excursions, D. A. Viljoen; Adjudication, P. A. von Wielligh; Constitution, Rules and Policy, P. A. von Wielligh; Monograph Series, Dr R. E. Robinson; Professional and Technician Train¬ing Committee, Dr M. D. G. Salamon; Career Guidance, D. G. Malan; Phoenix National Committee, Dr R. E. Robinson; 1982 World Congress, Dr M. G. Atmore; Witbank Coal Colloquium, Dr P. R. Jochens; Mines and Works, P. A. von Wielligh.

Jan 1, 1979

By M. Rudolph, A. D. Renno, H. Wu

In this study, synthetic pure cassiterite and cassiterite doped with Fe were successfully produced by sintering. Their crystal structure and chemical compositions are characterised by optical microscopy, X-ray powder diffraction (XRD) as well as scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) based chemical composition analysis. The electrostatic behaviour of synthetic and natural cassiterite was studied by electrophoretic measurements. Their floatability was studied by microflotation with two types of anionic collectors. Results show that the cassiterite floatability with these collectors behaves differently and lead to two opposite results: Natural cassiterite (enriched with Fe) > undoped pure SnO2 by using sulfosuccinamate (Aerosol® 22) Undoped pure SnO2 > Fe3+ doped > natural cassiterite (enriched with Fe) by using styrene phosphonic acid (SPA). Keywords: Synthetic cassiterite, lattice impurities, flotation, zeta potential, Aerosol® 22, styrene phosphonic acid

Jan 1, 2020

By B. Oladipo, E. Govender-Opitz, T. V. Ojumu

Bioleaching, one of the several important processes of biohydrometallurgy is an accepted technique for the extraction of desired metals from sulphide ores. Although the mechanism is well understood, the slow metal extraction rate due to passivating layer and ferric ion precipitation, especially in a typical chalcopyrite leaching, impact negatively on the overall efficiency of the process. Iron precipitates are common in many biohydrometallurgical operations and these precipitates represent the exit route for undesired iron, alkali ions or sulphate ion from the processing circuit. While there have been reports on approaches to slow the formation of these precipitates by manipulation of various operating conditions such as pH, redox potential and temperature, the precipitates become highly significant over the long term in the continuous operation of bioleaching and may render heap impermeable. Although there is evidence supporting the nature of the passivation to be precipitates of iron, their scavenging mode of reducing extraction efficiency is still not well understood. This paper thus discusses iron precipitation in biohydrometallurgical processes, including its formation and significance on bioleach processes. The paper also details the associated passivating species identified with heap bioleaching of sulphide minerals and provides some insight into sorption mechanism that limits metal recovery in a typical bioleach operation. Keywords: Iron precipitation, bioleaching, chalcopyrite, passivation, jarosite, metal sorption

Jan 1, 2020

By T. Song, X. Wang, X. O. Xia, X. J. Luo, B. Chen

Interparticle breakage is the main crushing mode of an inertia cone crusher according to its working principle and feeding condition. In this paper the breakage behaviour of an inertia cone crusher is investigated, based on energy controlled compression combined with the vibration theory, rather than geometry controlled compression (form conditioned) which plays a major role in conventional eccentric cone crushers. The effect of feeding and operating conditions on breakage behaviour was described quantitatively from the perspective of energy consumption and product size distribution. The influence of feeding conditions, discharge size settings and vibration exciter speeds on the crushing process and product quality has been studied according to the results of laboratory crushing experiments. The results of the experiments show that the particle size of broken products becomes finer with the decrease of a discharge gap within the gap range selected by the experiment. The product size increases significantly when the gap approaches the upper limit of 6 mm. The variation of eccentric speed has a more prominent effect on reducing the product size compared with the change of discharge gap. The change in product size is not apparent when the eccentric speed rises to a certain level. The throughput of an inertia cone crusher is sensitive to the change of discharge gap, which increases linearly with the discharge gap and decreases with the eccentric speed. The change of feeding conditions has little influence on the crusher throughput. Keywords: Inertia cone crusher, interparticle breakage, energy consumption, product size distribution

Jan 1, 2020

A powerful, interactive metallurgical process simulator for use on micro- computers has been developed in the Department of Metallurgy and Materials Engineering at the University of the Witwatersrand. MICROSIM presently allows simulation of all ore-dressing flowsheets and a selection of hydrometallurgical unit operations, and is extendable to all such processes. MICROSIM is written in Pascal. This modern language provides very versatile data structures which can be effectively used to solve the major problem in generalised simulation programs, namely storage and transmission of data relating to liquid and solid phases. Dynamic memory allocation allows optimal utilisation of computer storage space. The simulator utilises very efficient precalculation algorithms that determine the tear streams for optimal sequential modulator calculation convergence. Microcomputer graphics simplifies flowsheet specification, and form-filling data capture with supplied default values eliminate most common input errors.

Jan 1, 1987

By M. Seerane, R. Machaka, P. Ndlangamandla

"Metal injection moulding (MIM) is a near-net-shaping powder metallurgy technique suitable for the cost-effective mass production of small and complex components. In this paper, the effects of the metal powder particle size on the final properties of 17-4 PH stainless steel are reported. Three different particle sizes (d50 33.0, 7.91 and 4.04 µm) were used to prepare the injectable MIM feedstocks using a CSIR-developed wax-based binder system at a fixed solids loading of 60 vol.%. The distribution slope parameter and the rheological flow index behaviour were used to predict the flowability of the feedstocks. The effects of the particle size on MIM products were established. The results are discussed in terms of the subsequent microstructural and mechanical properties of MIM 17-4 PH stainless steel against the established MPIF Standard 35. IntroductionMetal injection moulding (MIM) is a near-netshape manufacturing process established as an alternative to produce complex small-tomedium shaped components that were previously fabricated by conventional methods at higher costs (Attia and Alcock, 2011; Todd and Sidambe, 2013).Although recent advances in micromanufacturing (mainly machining and electrodeposition-based) have enabled the fabrication of complex micro-size geometries directly into miniaturized parts, these processes are generally neither routine nor easily accessible at present (Attia and Alcock, 2011).Typically, the MIM process consists of four steps: mixing, injection moulding, debinding and sintering. Mixing involves blending of the desired metal powder composition with carefully selected multicomponent organic binders at the right proportion. This mixture, which is called feedstock, is then injected into a mould of a required shape to form a ‘green part’. Debinding is the removal of the binders by chemical, thermal, or catalytic means while maintaining the shape of the part. Finally, the debound part is sintered to a full or near-full density part (Sotomayor, Varez and Levenfeld, 2010). The MIM process is essentially a combination of plastic injection moulding with conventional powder metallurgy technologies."

Jan 1, 2016

By N. V. Nemchinova, A. A. Kozlov, A. V. Epiforov

The gold dissolution in sulfuric acid media during industrial oxidative leaching test of sulfide gold-copper flotation concentrates has been achieved. The reason for this was using technological water containing thiocyanates and cyanides, which can dissolve gold under these conditions. The carbon in column (CIC) process for gold recovery from these solutions was proposed. However, significant amounts of copper and iron were adsorbed onto the carbon during CIC technology industrial tests. This resulted in a decrease of the gold content in the loaded carbon up to 0.5 kg/t. Further development of the technology was conducted by optimisation of gold and impurities stripping and implementation of carbon reactivation. It was shown, that the copper extraction from the loaded carbon during cyanide treatment was about 95%. The copper content in the stripped carbon after cyanide treatment was 1.76 kg/t. The gold recovery during high-pressure elution by caustic solution was 98%. The hydrochloric acidic treatment with thermal pre-treatment (reactivation) for removing iron and calcium from gold-free carbon was proposed. In this case, the iron and calcium extractions from carbon were 40-45 and 50-55% respectively. These tests showed that for carbon recycling the sequence operations of ‘cyanide treatment, gold elution, thermal pre-treatment, hydrochloric acidic treatment’ can be used. Keywords: Thiocyanate leaching, recovery of gold, carbon adsorption, gold elution, copper stripping, thermal reactivation of carbon, activated carbon, carbon-in-column

Jan 1, 2020

By D. F. Malan, D. Ile

This study explores the use of backfill in hard rock bord-and-pillar mines to increase the pillar strength and extraction ratio at depth. The use of backfill will also minimize the requirement for tailings storage on surface and the risk of environmental damage. A literature survey indicated that backfill is extensively used in coal mines, but rarely in hard rock bord-and-pillar mines. To simulate the effect of backfill confinement on pillar strength, an extension of the limit equilibrium model is proposed. Numerical modelling of an actual platinum mine layout is used to illustrate the beneficial effect of backfill on pillar stability at greater depths. The magnitude of confinement exerted by the backfill on the pillar sidewalls is unknown, however, and this needs to be quantified using experimental backfill mining sections equipped with suitable instrumentation.

May 3, 2023

What is the role of The South African Institute of Mining and Metallurgy at a time when so much is developing and changing in South Africa? The minerals industry is represented through employers, employees, government, education, research, public views, and even pure political interests. The role of the Institute is to represent the mining and metallurgical profession. In this role the Institute has aligned itself with Associated Scientific and Technical Societies, the Council of Scientific Societies and the Engineering Association. The Institute is also active on the Engineering Council of South Africa.

Jan 1, 1996

By N. B. Strydom, P. L. Jooste, H. F. Kotze, W. H. Van Der Walt

Note: A revised method of heat acclimatization by N. B. STRYDOM, W. H. VAN DER WALT, P. L. JOOSTE, and H. F. KOTZE INTRODUCTION Climatic-room acclimatization was introduced in the gold-mining industry in 1965 and was rapidly adopted by all mines because it reduced the number of days required for heat acclimatization from 12 to 8. The method has been adequately described in previous papers1, 2 but, briefly, requires four hours of heat exposure per day while the work rate is progessively increased from 35 W on Day 1 to 70 W on Days 7 and 8. Several attempts to shorten

Jan 6, 1976

By Y. Cao, C. Li, A. Song

Bubble size plays a key role in determining flotation efficiency. Bubbles can be formed by passing air through pores. Bubble detachment from a pore is driven by lifting forces including buoyancy force and momentum force. Enhancing the momentum force is the key to accelerate bubble detachment and to minimise bubble size. Recent studies show that replacing steady air with oscillatory air supply could significantly decrease bubble size by enhancing the momentum force. To date, the underlying mechanism for the improved momentum force with oscillatory air supply is not yet clear. This work, for the first time, developed a qualitative model for the momentum force as a function of frequency, on/off time ratio and gas flow rate. It was found that the momentum force was positively correlated with the frequency as well as the air flow rate, and was negatively related to the on/off time ratio. The relation between bubble size and these operating parameters was also investigated. Keywords: Flotation, bubble size, momentum force, modelling, oscillatory air supply

Jan 1, 2020