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By W. Banda

Paper written on project work carried out in partial fulfilment of Phd. (Process Engineering) degree* The recovery of cobalt and copper from waste slag was studied in a plasma DC-arc furnace in reducing conditions. Three fluxes, CaO,CaF2, and TiO2, were investigated for their influence on selective recovery of cobalt into an iron-rich alloy. A further investigation on the influence of furnace power on the reduction of slag to recover cobalt to the alloy showed that a change in power setting had an unexpected effect on the recovery of metals to the alloy, in that selectivity of base metal recovery over iron recovery decreased at an increased power level. Keywords: DC-furnace, reduction, nonferrous, slags

Jan 1, 2004

By M. D. Mwema

Copper oxide ores deposits in the Katanga province of the Democratic Republic of Congo (DRC) contain at variable level cobalt oxide minerals. In contrast to copper oxide minerals which readily dissolve in the sulphuric acid solution, the cobalt oxide bearings are difficult to dissolve, especially if cobalt is present in the third oxidation state (Co2O3). This species become soluble after reduction of Co+3in Co+2. In practice, the use of reducing agent is therefore necessary in order to transform the insoluble minerals into soluble cobalt sulphate species. The following reducing agents are currently used at the Shituru plant: ferrous ions, which are present in leach solutions, pulverised copper or sodium meta bisulphite (MBS). Due to the high consumption of reducing agents (0,8 t MBS/t of solubilized Co; 1,2 t Cu/t-Co), cobalt production is expensive. The use of sulphur dioxide as reducing agent was then investigated in order to reduce operating cost. This reagent also presents the advantage of sulphuric acid production during the leaching process. It has been added in the leaching vessel (tank). From the laboratory and industrial tests, selective leaching of cobalt (78%) has been performed. The cobalt leaching kinetic depend on sulphur dioxide dosage. Dissolution of copper, iron and manganese remained very low. No emanation of SO2 gas was observed during the process.

Jan 1, 2002

To the members of The South African Institute of Mining and Metallurgy We have audited the annual financial statements of The South African Institute of Mining and Metallurgy set out on pages 451 to 460 for the year ended 30 June 2002. These financial statements are the responsibility of the Institute?s Council. Our responsibility is to express an opinion on these financial statements based on our audit. Scope We have conducted our audit in accordance with statements of South African Auditing Standards. Those standards require that we plan and perform the audit to obtain reasonable assurance that the financial statements are free of material misstatement. An audit includes: ?examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements, ?assessing the accounting principles used and significant estimates made by management, and ?evaluating the overall financial statement presentation. We believe that our audit provides a reasonable basis for our opinion. Audit opinion In our opinion, the financial statements fairly present, in all material respects, the financial position of the Institute at 30 June 2003 and the results of its operations and cash flows for the year then ended in accordance with South African Statements of Generally Accepted Accounting Practice. Auditors 29 July 2003 Council?s approval of the annual financial statements The annual financial statements for the year ended 30 June 2003 set out on page 451 to 460 were approved by the Council on 26 July 2002 and are signed on its behalf by:

Jan 1, 2003

By S. Ngidi

Palabora Mining Company operates a low grade underground copper mine situated in the Limpopo Province, South Africa. Full production was first reached in May 2005 after a successful transition from an open pit operation to an underground block cave operation. The operation faces a number of technical and operational challenges, not the least being fragmentation of a competent rock mass and external dilution. The cave is subdivided into three main sectors being the east, the west and the central sectors. Caving was initiated from the weaker central sector, which has the majority of its drawpoints located directly under the open pit bottom currently filled with about 130 million tons of waste material from the pit wall failure incurred in 2004. About 48% of the ore reserve has to be extracted from the western sector, which has a much courser fragmentation compared to the other two sectors and only 25% from the central sector with the finest fragmentation. The main constraint during the ramp-up stage has been secondary breaking of drawpoint blockages. Ground-breaking secondary breaking and cave management initiatives and practices have made it possible for Palabora to realize and sustain high production rates.

Jan 1, 2007

By A. A. Smithen

There is an increasing awareness of the importance of including an assessment of environmental liabilities in the preparation of bankable feasibility documents. This means that environmental assessments of proposed, existing and decommissioned mine sites have to be undertaken for the purposes of quantifying environmental liabilities and assessing potential risks. This paper examines the need for considering environmental liabilities before describing the approach adopted in undertaking due diligence studies for the preparation of bankable feasibility documents and some of the difficulties experienced. Finally, some concluding remarks are made and the implications for the mining industry are discussed.

Jan 1, 1999

By H. G. Denkhaus

Please allow me the temerity to reply to your reply to my contribution as follows: A fracture is brittle if plastic deformation is absent or, conversely a fracture is ductile if plastic deformation is present. Consequently, brittleness is specified by the degree of plastic deformation at fracture. This is the generally accepted definition. If other material properties (e.g. the quorient or the product of the uniaxial compressive and tensile strengths) under certain conditions are influenced by brittleness, or brittleness by them, these should not be called brittleness. If the one or the other author does that, he simply uses imprecise language. Even your remark, that ?Inyang and Pitt (1990) stated that the ratio of the compressive strength (sc/st) is directly proportional to brittleness?, confirms that the two quantities are not considered the same. For example:? The well known definition that a material is linear?elastic if the strain is directly proportional to the stress?does not mean that stress (measured in MPa) and strain (measured in %) are the same thing.

Jan 1, 2003

By M. B. C. Brandt

Focal depths of 15 tectonic earthquakes and 9 mine-related events were determined for South Africa using data recorded by the South African National Seismograph Network. These earthquakes and events were relocated by means of the Hypocenter program using direct P-waves (Pg) , critically refracted P-waves (Pn) , and first-arrival S-waves for the magnitude range 3.6 ?? ML ?? 4.4. Focal depths were first determined by means of the minimum root mean square (RMS) of the differences between the measured travel times and those predicted using the velocity model. The depths for tectonic earthquakes had a 2 km ?? D ?? 10 km range and an average depth and standard deviation of 6.9 ± 2.3 km. Depths for minerelated events ranged over 0 km ?? D ?? 7 km, averaging 3 ± 2.3 km. Next, arrival times for the additional regional depth phases sPn , PmP, sPmP, and SmP were measured. Focal depths were re-determined for the relocated epicentres, with the minimum variance (i.e. spread) of the differences between the measured travel times and travel times predicted by means of the Wentzel, Kramer, Brillouin, and Jeffreys (WKBJ) method for synthetic waveform modelling. Depth ranges were 4 km ?? D ?? 7 km (average 5.9 ± 1.2 km) and 1 km ?? D ?? 4 km (average 2.4 ± 1.2 km) for tectonic and mine-related events, respectively. The derived depths were verified for one tectonic earthquake with synthetic-to-recorded-waveform fits using the WKBJ synthetic seismogram software for the abovementioned regional phases. The focal mechanism parameters for this earthquake source were obtained from the National Earthquake Information Centre. Focal depths were estimated for nine stations by visually comparing synthetic waveform phases with recorded waveforms, ranging from 5 km to 8 km.

Jan 1, 2014

By B. Amadei, F. Tonon

Rock stress measurement is cast in the more general context of the determination of boundary conditions for rock engineering. A study on the effect of elastic anisotropy on underground excavations reveals that this effect is actually controlled by the imposed boundary conditions. Applications to tunneling and to the Underground Research Laboratory (URL), Canada, exemplify a procedure for boundary condition estimation formerly developed by the authors. The procedure displayed fast convergence despite the complex geometry, and the high degree of non-linearity of the models. In the URL application, the 3-D model was able to completely reproduce the complex measured stress pattern, and the 90° rotation of the principal in situ stresses with depth. In order to reliably estimate the boundary conditions reproducing the current in situ state of stress, response measurements of the rock mass to current disturbances are necessary as input data. La mesure des contraintes in situ tombe dans le domaine général de la détermination des conditions aux limites pour les problèmes de mécanique des roches. Une étude sur le rôle de l’anisotropie élastique sur les excavations souterraines montre que ce rôle est contrôlé par les conditions aux limites qui sont imposées. L’application aux tunnels et au Laboratoire Souterrain de Recherche (URL) au Canada, nous permet de présenter une méthode de détermination des conditions aux limites. La méthode converge rapidement bien que le géométrie soit complexe et que le problème soit non-linéaire. Pour le URL, le modèle 3D est capable de reproduire la distribution des contraintes qui ont été mesurées ainsi que la rotation de 90 degrés des contraintes in situ avec la profondeur. Afin de déterminer avec précision les conditions aux limites responsables pour la distribution actuelle des contraintes, la réponse du massif rocheux doit être connue et mesurée. In der Felsentechnik sind die Spannungsmessungen in Gestein an die Bestimmung der Randbedingungen gebunden. Eine Studie legt dar, dass der Effekt elastischer Anisotropie in unterirdischen Aushoehlungen von den Randbedingungen kontrolliert ist. Eine von den Authoren entwickelte Methode zur Bestimmung der Randbedingungen wird an Beispielen im Tunnelbau und im Underground Research Laboratory (URL) in Kanada illustriert. Auch bei komplexer Geometrie und einem hohen Grad an Nicht-Linearitaet zeigt diese Methode ein schnelles Konvergenzverhalten. Ein 3D-Model und dessen 90° Drehung der lokalen Hauptspannungen mit der Tiefe, kann bei einer URL Anwendung vollstaendig reproduziert werden. Um mit dieser Methode die Randbedingungen zuverlaessig abschaetzen zu koennen, werden der gegenwaertige lokale Spannungszustand sowie die Antwort des Gesteins und die resultierenden Stoerungen als Eingabedaten benoetigt.

Jan 1, 2003

The 102nd Annual General Meeting of The South African Institute of Mining and Metallurgy was held in the Gold Room, Transvaal Automobile Club, 60 5th Street, Lower Houghton, Johannesburg on Wednesday, 18th August, 1999. Obituaries The President announced the death, during the year, of the following members: Honorary Life Fellows and Past Presidents D.D. Howat Life Fellows O. Deane, J.S. van Zijl Fellow A.A. Hejja Retired Fellows A.L. Forder, C.B. Parker, A.C. Petersen, F.W.J. Ross Members J.S. Stanko, D.H. Gray Retired Member P.K. Bredell Retired Associate I.S. van Eyssen In memory of the deceased and in sympathy with the bereaved, all rose and observed a moment of silence.

Jan 1, 1999

By A. J. Lynch

Mineral processing models have been discussed for many years but it was not until digital computers became available about 1960 that serious attempts at circuit simulation could be carried out. Even then the work was primarily academic until PCs could be used by engineers in plants and design offices in the mid-1980s. Since then simulation has moved quickly and it is now at the point that most processes can be simulated reasonably accurately for purposes of design and optimization. There are still some significant deficiencies, notably in dry grinding and separation, and in the chemical interactions in flotation. Future work will involve: ?improvements of existing models ?dynamic simulation for automatic control and, in particular ,for training which is a weak link ?using advanced simulation models to predict liberation and separation from data acquired from SEM-based liberation analysers. Eventually mineral processes models will be part of total simulation systems which will incorporate mining and downstream processes including all environmental impacts.

Jan 1, 1999

The gold concentration profiles which develop inside the activated carbon particles during the adsorption process were measured, so as to obtain additional direct proof of intra-particle mass transfer rate-control and to determine how individual carbon particles in a population vary in their gold uptake behaviour. The observed gold concentration profiles inside the activated carbon particles were typical of situations where an intra-particle mass transfer mechanism is rate-controlling. Gold di-cyanide penetrated the carbon particles with a wave-like front until it was uniformly distributed throughout the particle. This corresponds with the profiles predicted by the film and surface diffusion model. However, the rate with which gold di-cyanide was transported inside the individual carbon particles varied within the population of carbon particles. This variation was characterized by a lognormal distribution in surface diffusivity. Because the estimated variances of these surface diffusivity distributions were small, the dynamic adsorption behaviour of the carbons used in the present study did not deviate significantly from that predicted by a model based on film mass transfer and a single surface diffusivity. Van Deventer (1984, 1985 and 1986a) reported data that could not be adequately described by a model based on film mass transfer and a single surface diffusivity. In this study a model based on film mass transfer and a wide lognormal distribution of surface diffusivity values was applied to his data. It was shown that a population of carbon particles with a wide distribution in surface diffusivity values could offer an alternative explanation to the mechanism proposed by Van Deventer which was based on film mass transfer, with partitioning of the carbon into micro- and macropores with surface diffusion in the macropores and slow mass transfer into the micropores.

Jan 1, 1997

By R. C. D. Phillis

Conventional stoping in hard rock mining is largely considered an operational environment. This paper suggests that stoping falls within the realm of a project management environment typified by uncertainty, variation, and large numbers of interdependencies. Stoping was then equated to a micro-project with many simultaneous activities that had to be executed accurately using finite resources within limited shift durations in order to reach specific goals. Critical chain project management (CCPM) principles were applied to the stoping activities, and the results showed that the number of blasts per panel can be significantly increased by successfully moving the distribution of work as close as possible to the start of shift. Critical chain principles also assisted in facilitating re-focusing and teamwork among stoping crews as well as between day- and night-shift crews. The main recorded success was in managing inherent protective capacities/local contingencies/fat/buffers that are found in all projects. The impact on mine health and safety (MHS) was significant as individual operators and crews became convinced that they could perform all stoping tasks (activities) without compromising accuracy or speed.

Jan 1, 2011

By P. M. Cole

An unprecedented expansion of the global zinc industry is currently under way. While most new projects and plant upgrades remain committed to traditional processing technologies, recent advances in zinc solvent extraction (SX) have created opportunities for new process routes for both primary and secondary materials. The first commercial plant to use zinc SX for the mainstream processing of a low-grade ore is under construction and promises to become one of the lowest cost zinc producers. Several other oxide and sulphide projects in various stages of feasibility are considering the inclusion of SX in their process flowsheet. Zinc SX has also proved advantageous in the reprocessing of secondary materials, particularly for the treatment of zinc residues and furnace dusts. This review focuses on recent installations and projects underdevelopment that feature zinc SZ as the key separation step.

Jan 1, 2002

Ongoing rockpass problems on mines within the South Africa region, prompted AngloGold Ashanti to embark on a risk assessment of major rockpasses. This commenced with the collection of relevant data to identify gaps in the available knowledge and identify existing problems. This was followed by an assessment of rockpass layouts to determine existing and potential interactions with other excavations. An initial risk assessment has been completed and the rockpasses have been ranked in terms of their risk profile. The lack of geological data and an easy and reliable method of surveying rockpasses have been identified as problem areas. Shortcoming is terms of rockpass management procedures have also been identified. Further work is required to quantify the risk in terms of probability of occurrence and consequences.

Jan 1, 2005

By S. V. Rungan

Since 1994, South Africa has been the subject of international attention, especially in regard to its transformation initiatives, which aim to redress the post-apartheid imbalances. Mining, as a major employer and one of the major industries in South Africa, has been the focus of the government?s Black Economic Empowerment initiative with the introduction of the Minerals and Petroleum Resources Development Act and the Broad?Based Socio?Economic Empowerment Charter for the South African Mining Industry. The historical background to South Africa?s transformation and the role of the mining industry are pivotal to an appreciation of certain aspects of the Minerals and Petroleum Resources Development Act and the Broad?Based Socio?Economic Empowerment Charter for the South African Mining Industry. The issues around Black Economic Empowerment and the enabling of a smooth transition to the South African mining industry of the future are explored in this paper.

Jan 1, 2005

By H. Appiah

Small scale mining (SSM) has been going on for a long time in Ghana. SSM was legalized by the PNDC Law 218, 1989. Since then there have been numerous gains from the SSM industry. The SSM is organized locally by the concession owner who engages people to work for the gold which he buys. Small scale miners (SSMs) use crudely made sluices in Ghana and, therefore, their production falls below what is expected. The SSMs work in groups and not as cooperatives, as they do in Brazil and other Latin American countries. Legalization of SSM has curbed gold smuggling considerably because a gold marketing entity is available. SSM poses certain environmental problems like pollution of water bodies and soils by mercury and indiscriminate digging of pits.

Jan 1, 1998

By J. Maiti

This study examined the group differences in accident susceptibility among underground coal mine workers accounting for their personal and workplace characteristics. A logistic regression model was used for this purpose. Data were collected from five underground coal mines for a period of four years. The case study results revealed that different age and experience groups of workers bear no significant differences in their accident susceptibility; however, the workplace location and occupation groups show significant differences in their risk of injuries. It is inferred based on the logistic model results that among the three occupation groups, the face workers are more susceptible towards accidents/injuries compared to the haulage and other workers. Key Words: Mine Safety, Accident Susceptibility, Group Differences, and Logistic Regression.

Jan 1, 2001

By B. C. Viljoen

"SynopsisCommencement of the next phase of the Lesotho Highlands Water Project is a year or so away from becoming reality. Some 50 km of tunnels in the form of access adits, shafts, diversion tunnels, and main waterways will be constructed. Sprayed concrete will form an integral part of the temporary and permanent rock support systems that will be installed. Furthermore, the use of sprayed concrete as a final tunnel lining solution was proposed as a viable alternative to concrete linings in the feasibility studies that preceded the forthcoming implementation phase.The aim of this paper is to make the reader aware of all the sprayed concrete related issues that engineers tend to grapple with during the design and construction of tunnel projects and other underground works. Primarily, these issues would include selection of applicable design parameters, technical specifications, construction application methods, quality control and, most importantly in the context of final or permanent linings, the durability of sprayed concrete.The International Tunnelling Association (ITA) Working Group (WG) 12 has been tasked specifically to publish a set of recommendations on the Quality and Control of the Application of Sprayed Concrete and the Testing of Sprayed Concrete for Durability. These tasks were also further explored at the recent World Tunnel Congress (WTC 2015) that was held in Dubrovnik, Croatia at the end of May 2015.IntroductionSprayed concrete is presented in a variety of shapes, designs, forms, application methods and accompanying terminologies including shotcrete, gunite, pneumatically applied concrete, and the like. The International Tunnelling Association (ITA) decided to standardize on a single terminology, namely ‘sprayed concrete’, in order to simplify specification, interpretation of guidelines, and codes of practice."

Jan 1, 2015

This is an abstract from Environmental Service and Technology (Vol 32 No 20 1998) which will be o finterest to South African Mining and Metallurgical Scientists, involved in chromium mining and Metallurgical processing. Maybe the scourge of our dams and reservoirs?the water hyacinth can be put to good use! The novel technology of phytoremediation embraces plant accumulation processes for the cleanup of toxic heavy metals and organic chemicals. Several plant species have been identified that are excellent hyperaccumulators of a number of heavy metals, e.g., Brassica juncea (Indian mustard) and Thlaspe caerulescens (Alpine pennycress). Other speciesincluding Myriophyllum brasiliense(Parrot?s feather), Salixsp. (willow), and Popullussp. (poplar) have also demonstrated phytoremediating abilities.

Jan 1, 1999

By B. M. Nyombolo

Mintek has been involved in the development of bioleach technology for many years, initially for refractory gold extraction, and more recently also for base metals extraction. Mintek, in collaboration with its Australian technology partner (BacTech), is the technology provider for the Beaconsfield refractory gold bioleach plant. At present Mintek, BacTech and Peñoles are constructing a demonstration bioleach plant for copper-zinc concentrate treatment. Bioleach liquors produced in all applications have to be neutralized. In the copper-zinc case, neutralization is required for bleeding iron from the circuit and for adjusting the pH value ahead of solvent extraction. In the refractory gold bioleach circuit, neutralization is required for producing a stable iron-arsenic residue. Some of the challenges encountered in each of these neutralization applications are discussed, and examples of results obtained are presented.

Jan 1, 2000