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By John M. L Lewis, Antoine F. Mulaba-Bafubiandi

In the irradiation of ore particles by microwave energy preferential absorption of this energy occurs in minerals having specific dielectric properties (Bradshaw, 1999). This leads to a selective heating of the various components of within the ore particle matrix. The result is a differential thermal expansion of such components and the resulting induced stresses become ideally concentrated at mineral grain boundaries (Kingman et al., 2000). Dependent upon the relative composition of absorbent, opaque and reflective components this may lead to enhancement of the inter-granular fracture of the ore particles in the initial comminution process (Fandrich et al., 1997). The potential is thus a greater proportion of free mineral grain within the fractured ore particle that may lead to improvement in subsequent mineral separation processes. As the composition of the ore dictates the result of such a treatment (Kingman et al., 2000) it is essential to evaluate the response of each ore sample on an individual basis. This paper reports on results obtained from two ore samples: the one being the zinc ore from the Black Mountain mine (South Africa) and the other a pre-concentrated sample of handpicked cobalt?copper mixed oxide ore from the Gecamines (DRC). The equipment and methods used to simulate the comminution of the samples and evaluate the level of the value liberation will be described along with the results obtained. Using King (1975), Kanellopoulous and Ball (1975), and Gungor and Atalay (1998), a comparison between the behaviour upon microwave irradiation of sulphide and mixed oxide ores leads to conclude that while the technique (i.e. microwave irradiation) is appropriate to the zinc sulphide ore, it does not seem to lead to exceptional results for the oxide.

Jan 1, 2005

By D. E. Ng?andu

The experience of Mufulira concentrator, of the Zambia Consolidated Copper Mines Limited, with underground mine drainage water, which is used in milling operations is discussed. It is shown that the underground mine water has a deleterious effect on flotation performance. The adverse effect of the underground water was successfully negated by adding lime into the primary ball mills and increasing the pH of the slurry, from a ?natural? pH of 8 to the flotation pH of 10.5. Traditionally, the pH modifier, quicklime, had been added downstream of the milling. Changing the lime addition point further reduced lime consumption by 50%,?a key issue as lime accounted for over 60% of the Mufulira flotation reagent costs. The nature of the effect of the underground water at Mufulira, particularly the sensitivity of the flotation to the pH at which the milling was conducted, characterized galvanic interaction. A large-scale plant situation is presented in which the desired electro-chemical response in the flotation was achieved, by a deliberate manipulation of the milling environment. The experience provides practical testimony of a more fundamental role for the milling process, other than the mere physical preparation, i.e. size reduction and liberation, of mineral particles prior to flotation.

Jan 1, 2001

By S. E. Olsen, M. Tangstad

The main source of Mn in raw materials for SiMn production is Mn-ore and Mn-rich slag from the high carbon FeMn production. The amount of slag per tonne of SiMn metal is mainly determined by the ore/slag ratio. Increasing share of FeMn slag at expense of Mn-ore will lead to larger slag/metal ratio in the SiMn process. High volume of slag leads to an increased consumption of energy and probably to higher losses of metal inclusions in the final slag. Excavation of a SiMn furnace has shown that only modest pre-reduction of Mn-ore with CO gas seems to be obtained. Nearly all reduction of MnO was finished at the top of the cokebed. Dissolution and reduction of quartz obviously takes place in the cokebed zone after the main reduction of manganese oxide is finished. Probably the ?pick up? of Si in the metal is quite fast and takes place as the metal trickles down through the cokebed towards the metal bath. The distribution of Si between SiMn alloys and multicomponent MnO-SiO2-CaO-Al2O3-MgO slags is mainly determined by the process temperature, the silica content of the slag and its R-ratio = (CaO+MgO)/Al2O3. As an example, the equilibrium content of Si in the alloy will increase by about 6 % if the R-ratio is reduced from 2 to 1, provided constant temperature and silica content. The effect of temperature is also considerable. The equilibrium content of silicon will increase by approximately 6 % per 50°C in the temperature range 1550°C to 1700°C. The equilibrium content of MnO in SiMn slags depends first of all on the temperature and secondly on the silica content of the slag. At 1600°C the MnO content decreases from about 9 % at silica saturation to a minimum of about 3-4% when the silica content is reduced to about 40-45%.

Jan 1, 2004

By C. Balci

Specific energy is defined as the amount of work required to break a unit volume of rock and is used to predict the performance of mechanical miners. It is obtained from full-scale rock cutting experiments, which require large block samples, experienced personnel and expensive equipment found in only a few research centres in the world. Estimation of the optimum specific energy, at which a given geological formation is excavated at optimum cutting geometry in the most energy efficient manner, from mechanical rock properties to predict the performance/efficiency of roadheaders is the basic aim of this study. The mechanical rock property tests require only core samples, which are easier to obtain and to test. In this context, full-scale rock cutting tests are performed on 23 different rock, mineral and ore samples including sandstone, claystone, tuffite, chromite, trona and copper collected from some operating mines in Turkey. The optimum specific energy values are obtained for each sample. Physical and mechanical property tests are performed on the core samples obtained from the same samples to determine uniaxial compressive strength, indirect (Brazilian) tensile strength, static and dynamic elasticity moduli, Schmidt hammer rebound values, density, and Cerchar abrasivity index. The relationships between the optimum specific energy and the mechanical rock properties are analysed using statistical methods. The results indicate strong relationships between the optimum specific energy and the mechanical rock properties. The strongest relationships are found by using uniaxial compressive strength and tensile strength. The performance models developed in this study are in good agreement with the empirical models previously developed for roadheaders and can be used reliably for prediction purposes. Keywords: Mechanical excavation, roadheader, performance prediction, rock cutting, optimum specific energy, mechanical properties of rocks.

Jan 1, 2004

In ilmenite smelting, the FeO content of the feed material (nominally FeO.TiO2) is decreased by reduction with carbon. In a parallel reaction, a significant amount of the TiO2 is reduced toTi2O3. One of the striking features of these reactions is a consistent relationship between the extents of FeO and TiO2 reduction; this relationship is independent of furnace size. It was recently proposed that this relationship follows from the solidification behaviour of the slag, where the final slag composition corresponds to the minimum melting point (?eutectic groove?) in the FeO-TiO2-Ti2O3 phase system; the hypothesis is that solidification equilibrium with the freeze lining stabilizes the slag composition. If this is the case, the system of slag and freeze lining must be capable of correcting two types of disturbances: thermal and compositional. Thermal disturbances result from incorrect power input, for the feed rates of ilmenite and reductant. For example, excessive power input will tend to overheat the slag, causing the freeze lining to melt partially, establishing a new steady-state heat loss from the furnace. Compositional disturbances result from an incorrect reductant input for the given power and ilmenite input. In this work, the dynamic response of the slag and freeze lining to different inputs (flow rates of ilmenite and reductant, and power input) is modelled. The model is based on solidification equilibria, and quantified heat loss through the freeze lining. The conclusion is that the solidification equilibrium cannot constrain the composition to the eutectic groove for typical operating conditions. Keywords: ilmenite smelting, freeze lining, solidification, high-titanium slag

Jan 1, 2004

By J. H. Potgieter

The method used to assess the reactivity of lime was evaluated to gauge it usefulness as a quality control tool. The effect of particle sizes, different lime and water masses for a fixed s:l ratio and the same for various s:l ratios on the reactivity values obtained, were investigated. An attempt to introduce the amount of grit produced during the slaking reaction as an additional measure of limeís quality and reactivity, proved to be unsuccessful. It was also found that the relative amount of lime slaked during the different tests was independent of the reactivity value of the lime. The investigation confirmed the usefulness of the accepted test procedure as are liable method to measure the reactivity of lime, despite various reservations expressed from a theoretical point of view.

Jan 1, 2002

By S. J. Ramokgopa

The development of the modern State and the growth of capitalism involves a complex process of interaction between cross-cutting structural dimension: first between politics and economics and, second, between market and hierarchy. Central to such developments are political economies of scale. Mineral specialization in the Third World developed within the framework of an international extension on oligopolistic structure of the advanced capitalist economies of Western Europe and North America. Up to the late 1960s, the world mineral and metallurgical industry was closely controlled by a handful of Western mining and industrial groups. To the extent that, foreign control of the mining sector was seen in the Third World producing countries both as the essence of foreign domination and as its major symbol. In some newly industrializing countries, the State took a more direct role in tying the economy and society together. Central to this process was the growth of large-scale finance capital. From early 1959to the mid-1970s, metal consumption in industrial countries expanded well beyond their domestic mineral endowments. And a free access to Third World minerals was a major element of the economic dynamism of these countries throughout that period. With the change in the characteristics of international investment, Africa has become less important as an outlet for capital exports of European countries. Actually, the African continent now receives only a very minor share of direct foreign investments of Western enterprises. International political economy is concerned first of all with the relationship between the economic and political domains across territorial boundaries. Second, attention should be drawn to the role of the State as the focus of decision-making in a system of competitive States, that is in turn, interdependent with a trans-national market economy in which mining and metallurgy are essential activities that affect the politics of the State, and how this in turn, rebounds on the politics of the international system. Understanding the role of the State must go beyond the glib pronouncements on the ?national interest?. How, and whose interest, the ?national interest? is determined, is precisely the problem. This implies a third theoretical problem that must be addressed: the linkage between the domestic and international domains (or levels of analysis), given that political-economic processes clearly cut across the lines of political decision-making constituted by the institutional structures of the State. Situating the State and economic interests within this vast ?state-society? complex that we call the global order will be a crucial problem for any theoretical approach that involves mining and metallurgy.

Jan 1, 2002

By H. Simonsen

Risk assessment consists of a search for the answers to: ?What can happen? ?How likely it is that it can happen? ?What are the consequences if it does happen? Perhaps the most important aim of risk analysis is to predict the likelihood that a planned profit will be achieved over a given period of time. A typical risk model employed for this purpose includes a stochastic connection between the dependent variable of an expression that describes a process and independent variables represented as random quantities. The output will be a probabilistic distribution. The uncertainties in a planned mining operation include: ?Commodity market characteristics, particularly price ?Ore reserves and mineralogical composition ?Mining method ?Process performance ?Capital and operating costs ?Schedule duration ?Economic environment effects. The processes employed in the probabilistic estimation of a project?s outcome include both Monte Carlo simulations and simulations where variable correlation is considered important. The risk model, once developed and tested, provides a framework for a rational approach to risk analysis and the testing of alternatives.

Jan 1, 1999

By J. Bongardt

Ecologically acceptable techniques are described for the handling of waste materials from the fabrication industry. New production methods and the recycling of sludges from grinding and other waste materials are suggested.

Jan 1, 1997

By M. A. W. Bryson

Platinum group metals are extracted almost exclusively in South Africa from three very different zones in the Bushveld Igneous Complex, called the Plat, Merensky, and the UG-2 reefs. The Plat reef is currently being exploited only by Anglo American Platinum, whereas the Merensky reef is exploited by them, Impala Platinum, Northam, and Lonplats. The UG-2 reef, on the other hand, is also processed by these producers, but Kroondal and Barplats have operations that exclusively treat ore from this reef. At present the extraction of pgms from ores in South Africa follows the traditional route of upgrading to a concentrate in a minerals processing circuit, further upgrading to a matte in a smelter, and final upgrading and separation of the individual metals in a refinery. Thus all operations that extract pgms require a minerals processing circuit, the design and performance of which is a topic of much interest, as it is a poorly understood and not a very efficient process in relative terms, compared to the other processes. Recoveries across the minerals processing circuit of between 75 and 90% are the norm.

Jan 1, 2004

By H. G. Denkhaus

Comment on ?The evaluation of rock brittleness concept on rotary blast hole drills? in the Journal of SAIMM, vol 102. no. 1. pp. 61?66 Comment on ?Correlation of specific energy with rock brittleness concepts on rock cutting? in the Journal of SAIMM, vol 103. no. 3. pp. 163?171by R. Altindag Foreword Some thirty years ago it was almost customary that articles in South African technical and scientific journals were followed up by discussions in which the reader(s) expressed criticism and/or added to the information contained in the article. This custom has obviously died out, be it that the articles are nowadays of such a high standard that nothing can be added or be it that the receivers of the Journal suffer from an information inflation and do not read the articles anymore. I now have the temerity to offer a discussion to an article that recently appeared in the journal, namely ?The evaluation of rock brittleness concept on rotary blast hole drills? by R. Altindag (J.S. Afr. Inst. Min. Metall., vol, 102(2002), pp. 61?66.

Jan 1, 2003

1. A statistical approach to some mine valuation and allied problems on the Witwatersrand. Unpublished Master?s Thesis, University of the Witwatersrand ? 1951. (Separate) 2. A statistical approach to some basic mine valuation problems on the Witwatersrand - J. of the Chem. Metall. and Min. Soc. of S.A., December, 1951 - discussions and replies March, May, July and August 1952. (Vol. 1?.1). Also: J. of the Institute of Mine Surveyors of S.A. December 1952, March 1953. (Vol. 1?2) 3. A statistical analysis of some of the borehole values of the Orange Free State goldfield - J. of the Chem. Metall. and Min. Soc. of S.A., September, 1952 - discussions and reply November 1952, and February 1953. (Vol. 1?3). 4. A study of the relationship between development values and recovery grades on the South African goldfields - J.S.A.I.M.M, January 1959, - discussion and reply April and October 1959. (Vol. 1?6) 5. On the departure of ore value distributions from the lognormal model in South African gold mines. J.S.A.I.M.M., November 1960, January and August 1961. (Vol. 1?8) 6. Developments in the valuation of gold mining properties from borehole results - Seventh Commonwealth Mining and Metallurgical Congress, 1961. (Vol. 1?9) 7. Effective pay limits for selective mining. J.S.A.I.M.M., January and August 1962. (Vol. 1?10)

Jan 1, 2014

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 L. M. Sekhukhune

The atmospheric leaching of copper-bearing matte by acidic ferric chloride solution was studied at the laboratory scale. The aim was to achieve maximum copper and nickel recovery by investigating the mechanisms of leaching, as well as identifying the effect of temperature, and concentration of ferric chloride and oxygen. Djurleite (Cu1.96S), hazelwoodite (Ni3S2), and Ni alloy were the primary phases detected in the matte. The quantitative composition of the matte was Cu 31%, Ni 50%, S 13%. Fe and Co constituted 2%, with platinum group metals (PGMs) accounting for 0.5%. A maximum nickel extraction of 98% was achieved using two-stage oxidative leaching at 90°C and 11 g/L Fe3+ as compared to 65% under non-oxidative conditions. A copper extraction of 99% was achieved in the first 45 minutes using two-stage non-oxidative leaching, and copper was recovered from solution by cementation. Three processes took place simultaneously throughout the leaching process, namely: dissolution, cementation/ metathesis, and oxidation. The leaching process was found to be diffusioncontrolled.

Jan 1, 2014

By P. L. Duncanson, J. D. Toth

Since 1995, when "freeze lining" refractory systems were introduced to the ferroalloy industry, they have gained in popularity, due to the freeze lining?s reputation for reliability, safety, and the contribution it makes to profitability. As with many popular and effective technologies, however, the freeze lining has spawned low-cost pretenders that claim the "freeze lining" name. On the surface they appear to contain some of the components of the technology, such as thermally conductive materials, but they fail to incorporate all of the principles that define a true Freeze Lining. The term "freeze lining" refers to the refractory system?s ability to maintain a temperature profile that is low enough to freeze a layer of process material on its hot face, which insulates the refractory and prevents direct contact with molten metal and slag. In doing so, the common wear mechanisms found in the submerged arc furnace - chemical attack, erosion, and thermal stress - can be prevented. These wear mechanisms are all related to high temperature; thus, they are prevented by maintaining low temperatures. Certain refractory properties and design concepts are absolutely necessary for the lining system to function as a true Freeze Lining. The paper explains these requirements and why they are important - the Truth of freeze linings - and further explains why systems that ignore one or more of these requirements cannot claim to be freeze linings, thereby exposing the Myths.

Jan 1, 2004

By W. P. Nel

The introduction of the Higher Education Qualifications Framework (HEQF) and the updated Higher Education Qualifications Sub-Framework (HEQSF) has caused many South African university departments to rethink their programme qualification mixes (PQMs). In addition to the requirements stated in the HEQSF, a number of other factors have to be taken into consideration by a university department. These factors include, for example, the standards generated by the Engineering Standards Generating Body (ESGB) and subsequently approved by the Engineering Council of SA (ECSA) and the need to prepare students for various categories of professional registration with ECSA. This means that a university department has to choose the correct mix of Learning Programmes (LPs) from the HEQSF menu (which consists of 13 types of LPs). Preparing students for ECSA registration is aligned with the mission of universities, which is to teach and undertake research. However, research and the LPs associated with research go beyond the requirements for current ECSA registration. Assuming that universities offering engineering LPs would elect to prepare students for both ECSA registration and teach them to produce research outputs, which is mostly done at Master and Doctorate levels (NQF Levels 9 and 10), then it follows that academics are more interested in NQF Level 5 to 10 pathways (abbreviated as ?L5-10?) rather than the shorter pathways required towards professional registration. (For example, ECSA requires an NQF L5-L7 pathway for registration as a candidate professional technologist. This specific pathway may consist, for example, of two LPs, namely the 360-credit Diploma and the Advanced Diploma.) A L5-L10 pathway is a combination of LPs that will prepare the learner with a NSC (or equivalent qualification at level 4) to Doctoral level (level 10). Universities may choose at least four major pathways from the HEQSF menu in order to educate and develop students from NQF Level 5 to 10. However, various pathways towards registration in the category of candidate with ECSA are also embedded into these four NQF L5-L10 pathways, where each consist of a unique combination of LPs. Each of these pathways has an opportunity cost, and economic reality means that smaller departments may have to choose between the four pathways. Of all the many factors involved in PQM decision-making, the focus of this paper is on the HEQSF requirements, ECSA standards, and ECSA registration and how these, together with the various qualifications and educational LPs provided for by the HEQSF may impact on the PQM decision taken by engineering departments and schools at South African universities. The proposed four NQF L5-L10 ?pathway tool? for PQM decision-making may be useful for pointing out the advantages, disadvantages, and applications of the various pathways and combinations of pathways. Rather than deciding from a menu of thirteen qualifications and associated LPs, this article proposes that decision-making be undertaken on the basis of a menu of four main articulated ?NQF L5-L10? pathways (which also include one or more of the ECSA?s pathways for professional registration). The proposed ?NQF L5-L10 pathway? tool is an attempt to move one step closer to the aim of achieving a structured decision-making approach for designing a PQM at departmental level.

Jan 1, 2014

By J. A. Kinnaird, B. J. Youlton, K. L. Youlton

Methods for treating and processing refractory gold ores are well established. However, what is less well understood is how the formation of the gold-bearing deposits affects gold processing and extraction. In order to evaluate the effect of ore genesis on gold extraction a number of South African gold deposits were studied. These included complex Pilgrim’s Rest samples as well as refractory Fairview, Barbrook, and Consolidated Murchison samples. We found the refractory nature of gold ores is controlled by a limited number of well-understood mineralogical factors. Solid solution gold is linked to low temperature and pressure conditions in fine-grained sedimentary lithologies, while reactive pyrrhotite can form from hydrothermal fluids associated with mafic magmatic rocks. These formational controls can be used to identify and avoid complex deposits at a desktop study phase, or address and reduce complications further along the pipeline using early mineralogical studies.

Jun 1, 2021

By N. Mutemeri, T. -L. Field, M. Chuma

The categorization of artisanal and small-scale mining has a significant impact on perception and understanding of the sector, particularly from a livelihood perspective. Several developing countries classify different types of artisanal and small-scale mining based on legal status. Given the nature such activities, the tragedy of the commons theory has been applied to understand the inevitable environmental, economic, sociocultural, safety, and health negative externalities – which are products of informality and illegality. Consequently, formalization is a panacea to sustainability. This article aims to offer a conceptual organization and foundational knowledge for characterization of artisanal and small-scale mining. It seeks to identify existing literature on the subject to avoid replication and acknowledge other scholars. Moreover, the article aims to place the study within the context of existing literature, establishing relationships with other studies and why the research is necessary. This paper pinpoints gaps left from other studies in so far as the characterization of artisanal and small-scale mining is concerned. Thus, reviewing literature abetted in finding similarities and differences on how artisanal and small-scale mining is defined from a scholarly and legal basis. The paper ascertains major claims made by earlier research on this topic, such as environmental impacts, the lack of adequate regulatory framework, and presents querying and probing questions lacking from other studies.

Jul 10, 2024

By J. J. Geldenhuys

A colloquium on 'Developments in the Mechanization of Mining Operations' was held in, conjunction with the 1984 Electra Mining Exhibition, at the Milpark Holiday Inn in Johannesburg on 19th September, 1984. An attendance of close on 200 delegates was testimony to the popularity of the subject. The delegates included a number of visitors from abroad, including senior members of the management of foreign companies and a member of the Council of the Institution of Mining and Metallurgy, United Kingdom. Both the local and foreign press was also represented.

Jan 1, 1985