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By N. F. Dawson

Recovery of a chromite concentrate from UG2 flotation tailings streams, of a grade suitable for further pyrometallurgical treatment for the production of ferrochrome, has certain specific challenges not only by virtue of the decoupled nature of the primary PGM recovery process and secondary gravity based chromite recovery circuits, but also because of intrinsic variations in the nature of the ore and its mineral composition. Variability in the ore, together with upstream process dynamics, creates a challenging environment in which to achieve optimal recovery of a gravity concentrate with accurate grade control. This paper examines certain inter-relational aspects between the ore gangue and chromite mineral types, the influence of the primary PGM extraction circuit and secondary chromite extraction activity as applied specifically to UG2 ore against a background of actual plant experiences and circuit configurations applied in order achieve a suitable quality of chromite concentrate.

Jan 1, 2010

By A. L. Bleloch, A. M. Starfield

This paper is concerned with heat flow in the plane of a typical cross-section of a deep underground airway. A new algorithm, called the quasi-steady method, is presented for the calculation of rock temperatures in that plane. The algorithm is used in the computation of heat and moisture transfer rates from the rock to the ventilating air for an airway that is wet on part of its circumference and dry elsewhere. The speed and accuracy of the new method are demonstrated on a microcomputer, and it is argued that this method offers a considerably more versatile and physically meaningful alternative to previous methods for the prediction of increases in air temperature along mine airways. The algorithm is also used to explore the concept of a uniformly wet airway that is equivalent to a partly wet airway in terms of its effect on the ventilating air. The concept is shown to be reasonable, but more complex than one might have anticipated. Finally, several useful extensions and applications of the new method are suggested.

Jan 1, 1983

The results of small-scale resin-in-pulp pilot-plant investigations at Grootvlei Proprietary Mines Ltd, President Brand Gold Mining Co. Ltd, and Western Areas Gold Mine Co. Ltd are reported. At each mine, a pulp was fed simultaneously to a carbon-in-pulp plant, allowing a direct comparison of the metallurgical performance of the two processes. With the Grootvlei pulp, gold was extracted more efficiently by resin than by carbon owing to the Iow concentration of competing base-metal cyanide complexes in solution. With the Western Areas pulp, the reverse was true because of the high concentrations of copper and nickel in solution. Finally, with the President Brand pulp, resin-inpulp was significantly superior to carbon-in-pulp owing mainly to the inherently slow rate of gold extraction from calcine by activated carbon. Results are presented that show the efficiency of the elution of gold and other elements with a variety of reagents from the loaded resins arising from these three campaigns. At Western Areas, a detailed investigation enabled a preliminary cost evaluation to be made of three techniques for the elution of strong-base resins.

Jan 1, 1984

By M. Gericke

Over the past few decades the commercial application of heap bioleaching technology for the extraction of base metals has become increasingly important, due mainly to the depletion of high-grade ore reserves. Heap bioleaching is widely used for the extraction of copper from secondary copper sulphide ores. The design and engineering aspects of the process have received considerable attention, but issues related to the microbiology of the process have been subjected to less rigorous scrutiny. The major role of micro-organisms in bioleaching processes is to catalyse the regeneration of ferric iron and protons, from ferrous iron and by sulphur oxidation respectively. It is accepted that even the most carefully engineered heaps are heterogeneous in terms of temperature, pH, the presence of anaerobic pockets, irrigation efficiency, and dissolved solutes. Since interactions between solution chemistry, mineralogy, and microbial populations exist in heaps, a better understanding of the correlation between microbial numbers and types with changes in these chemical and physical profiles with time would be beneficial during process design and operation of heaps, and could result in faster start-up times and higher metal recoveries. This paper reviews the role of microbiology in heap bioleaching processes. Aspects such as microbial diversity, identification and monitoring of cultures, inoculation strategies, colonization behaviour, and tolerance to metals and salts are discussed, and the potential contribution of the knowledge to the improvement of the operation and design of heap bioleach processes assessed. Conclusions are drawn with respect to the role of genetic engineering, heap inoculation practises, and remaining areas for future heap bioleaching research and development.

Jan 1, 2012

By C. Birch, J. Perold

"Due to the challenging geological environment of the Postmasburg Manganese Field (PMF), a study was conducted to determine if any benefits would derive from the inclusion of resistivity data during threedimensional (3D) modelling of the manganese resource. This was achieved by estimating manganese resources from 2011/2012 drilling data and comparing them with manganese resources estimated from the same drilling data and resistivity data collected during 2013 and 2017.Both models were adjusted to limit their extent to the same 3D modelling space. Significant volume and tonnage differences were observed for all lithological units. The greatest differences were noted in the manganiferous zones of alteration – 7.200 Mt for the geological model versus 3.700 Mt for the geoelectric model.This study showed that the inclusion of resistivity data can reduce exploration costs significantly, as a direct consequence of the resistivity data allowing more accurate siting of boreholes. This decreases the number of boreholes, samples, and analyses required due to the 3D electrical delineation of mineralized areas prior to drilling.An additional benefit is the ability to more correctly forecast the net present value of an operation due to more accurate estimation of manganese resources and stripping ratios. This is clearly demonstrated by the estimated gross profit estimation of R409 million for the geological resource model versus R264 million for the geoelectric resource model.The addition of resistivity data can, therefore, reduce exploration costs and can increase confidence in geological and financial modelling. It would be reasonable to conclude that this approach could also be used for karsthosted massive sulphide deposits. IntroductionAccording to Corathers (2014) and Gajigo, Mutambatsere. and Adjei (2011), South Africa holds between 75–80% of global manganese reserves, followed by Ukraine (10%), Australia (3%), India (3%), and Gabon (2%). The known, land-based, manganese resources located elsewhere are estimated at 2%.The majority of economically important sedimentary manganese ore deposits in South Africa are situated in the Northern Cape Province (Gutzmer, 1996). Manganese ores of the Postmasburg Manganese Field (PMF) were discovered in 1922, and the Kalahari Manganese Field (KMF) in 1940. According to Astrup and Tsikos (1998) and Gutzmer (1996), mining of manganese ore from the PMF ceased during 1989 in favour of the superior quality of manganese ore from the KMF."

Mar 1, 2019

By A. M. Bauristhene

Ti-64, which accounts for more than 50% of the worldwide titanium tonnage, has found commercial importance in industries requiring components with high specific strength and resistance to corrosion. Investment casting is the preferred production method due to the difficult machinability of the alloy. This study was aimed at investigating the mechanism and the extent of alpha case formation on Ti-64 components cast using the investment casting method with YFSZ (yttria fully-stabilized zirconia) shell moulds after vacuum induction melting. The extent of the reaction between the mould hot face and the molten metal has been studied by varying parameters such as soaking temperature and mould hot face composition, and examining their effects on the reaction with the mould. An increase in the soaking temperature had an effect on the alpha case, both in appearance and hardness, but had no effect on contamination levels by carbon, oxygen, and nitrogen. The depth of alpha case increased with soaking temperature, increasing from 35 µm to 161 µm with an increase in temperature from 1200°C to 1400°C. The micro-hardness profiles provided insight into the effect of the alpha case on the mechanical properties of the Ti-64 alloy by displaying hardness values of 1000 HV0.1 and above, but could not be solely utilized to determine the alpha case penetration depth due to microstructural differences in the unaffected Ti-64, in particular the martensitic microstructure that formed with a fast cooling rate from a higher temperature. Levels of expected contaminants such as Zr, Y, 0, and C were low. The addition of the colloidal zirconia binder affected the interfacial reactions. YFSZ proved to be a thermodynamically stable refractory material, with the alpha case possibly forming as a result of segregation.

Jan 1, 2013

By N. A. Sithole, S. A. C. Hockaday, P. J. A. Bezuidenhout

The Northern Cape Province in South Africa has high levels of annual direct normal solar irradiance and reserves of zinc (Zn) ores. The question arises as to the benefits of integrating renewable solar energy into the beneficiation routes of these reserves. The paper evaluates a novel flowsheet for the production and beneficiation of Zn in this region, maximising localised solar energy as a source for both electricity and process heat. Solar variability is discussed and the cost and benefits of thermal storage in the flowsheets are evaluated by its influence on the levelised costs of electricity and process energy over the project life-time at a possible implementation site. The results of the developed scoping model showed that solar photovoltaic integration to provide electricity for electrowinning without battery storage can lead to more than 10% cost saving on electricity over the lifetime of the project. Additional savings potential was identified when battery storage was included to enable the solar PV system to supply electricity during peak tariff periods. The solar thermal case showed the most promise with savings of 70% on heating costs for casting, while solar PV electricity without storage resulted in a 16% cost saving on heating for casting over the lifetime of the project. Solar PV electricity generation resulted in the avoidance of more than 20% of CO2 emissions from grid electricity use. Solar thermal heating can avoid up to 80% of the CO2 emissions associated with grid electricity use for remelting of Zn cathodes for casting. The CO2 emissions are indirect and not subject to South African carbon tax. Keywords: Solar process energy, zinc beneficiation, flowsheet evaluation

Jan 1, 2020

By D. Saramak, T. Gawenda, A. Stempkowska, Z. Naziemiec

The aim of the paper is to discuss the possibility of producing aggregates with an increased content of regular particles, as well as to present a method of aggregate production which has not previously been used in the industry. Traditional aggregate production circuits require the application of three or four grinding stages (depending on the particle size of the feed), but for fine particle fractions of aggregates, irregular grains occur on average with a content of 10%. The innovative technological circuit can produce the aggregates with the content below 3%, even in a single- or two-stage crushing circuit. Downstream jig beneficiation of such prepared material results in higher separation sharpness, lower probable error index (Ep) and imperfection (I). Keywords: Aggregate production, jig beneficiation, mineral processing, raw materials

Jan 1, 2020

By S. K. Lahiri, K. C. Ghanta

Design of industrial slurry pipelines is usually performed by applying semi-empirical procedures, requiring a significant experimental study for each project. The mechanisms of suspension flow are not yet completely understood and existing predictive models cover only some aspects of uniform or closely graded particle slurry flows. This paper presents a computational technique for prediction of the velocity and concentration profile in slurry pipelines based on computational fluid dynamics. This model gives numerical solutions for the concentration and velocity distributions in the pipeline cross-section. The model prediction and experimental concentration and velocity profiles were found to be in good agreement. Keywords: pressure drop; concentration profile; particle diffusivity; slurry flow.

Jan 1, 2007

By R. Sun, R. G. Gillies, R. S. Sanders, J. Schaan

The pipeline transport of paste, backfill or thickened tailings slurries is an important component of the tailings disposal process in many mines around the world. These mixtures contain significant fractions of fine (clay) and coarse (sand) particles, causing them to exhibit non-Newtonian flow behaviour and high frictional pressure gradients. There is often economic incentive to operate these pipelines in the laminar flow regime. Irrefutable evidence has shown that coarse particle settling can occur during the laminar flow of these slurries even when static settling tests show no indication of such behaviour. Previously, a ?rule-of-thumb? minimum frictional pressure gradient of ~1.5 to 2 kPa/m was suggested to ensure effective sand transport, based on the results of tests conducted using viscous Newtonian oils. In this paper, we examine the results of laminar flow tests of non-Newtonian, coarse-particle laden slurries conducted with pipeline loops of 50, 100, 150 and 250 mm in diameter. The results indicate that the ratio of the mean wall shear stress to the mean surficial particle stress is abetter indicator of laminar flow settling tendency than frictional pressure gradient.

Jan 1, 2007

By R. Trammell, O. Eterigho-Ikelegbe, S. O. Bada

In response to the enormous amounts of coal discard generated during coal mining and preparation, the development of an efficient and sustainable strategic use of this resource is essential. Furthermore, the rising urban population over the next decades is confronted with the depletion of quality raw materials for building components. To this end, this study reports new information on the morphology, water absorption, and flexural strength properties of ceramic composites produced from three different coal discards and polysiloxane pre-ceramic polymer (PCP) resin. In addition, test results relating to the continuous operating temperature, chemical resistance, and efflorescence potential of the composites are presented. The results show that the water absorption and flexural strength of the coal composites, up to 1.94% and 36.46 MPa respectively, exceed the requirements for ceramic and clay roof tiles. The continuous operating temperature of composites is found to be more thermally stable than conventional roofing tiles (concrete and ceramic) between ambient temperature and 600°C. In addition, the excellent chemical resistance of the composites (94.43%−99.98%) compared to conventional roofing tiles (67.82%−99.97%) eliminates the need for additional external coatings. The interesting results documented so far suggest that this technique could be used to produce low-temperature application building products such as bricks, panels, roofing tiles, etc. This new recycling technique offers an excellent opportunity to eliminate enormous volumes of coal discard and to advance the circular economy in the coal industry.

Aug 2, 2022

By T. Feroze, B. Genc

"Blind headings in room and pillar coal mines are a major source of methane and coal dust. Most methane and coal dust explosions therefore occur in the blind headings. The primary cause of these explosions is the disruption of the local ventilation system. Line brattice (LB) ventilation systems are used to ventilate blind headings by directing air from the last through road (LTR) into the heading. The amount of air available to ventilate the face of the empty heading depends on the heading dimension, settings of the LB, and velocity of air in the LTR. LBs are commonly installed by underground supervisory staff based on work experience, which may result in ineffective ventilation. The correct installationof LBs remains a challenge. In this study, a validated computational fluid dynamics (CFD) model has been used to analyse the effect of the LB ventilation system variables on the air flow rates close to the face of the empty heading. Full-scale three-dimensional models with various heading heights, heading depths, LB settings, and LTR velocities were simulated. The air flow rates and patterns at various locations inside the heading were analysed. A comparative study was carried out to quantify the effect of each of these system variables on the flow rates close to the face of the heading. Based on the findings, a user-friendly numerical model was formulated that can be used to estimate the flow rate close to the face of an empty heading for different practical settings of the system variables. This model can help the supervisory staff to swiftly implement the ventilation plan according to the regulations and the mine standards. The model can also serve as part of the curriculum for educating future mining engineers."

Jan 1, 2017

By T. Feroze, B. Genc

"Blind headings in room and pillar coal mines are a major source of methane and coal dust. Most methane and coal dust explosions therefore occur in the blind headings. The primary cause of these explosions is the disruption of the local ventilation system. Line brattice (LB) ventilation systems are used to ventilate blind headings by directing air from the last through road (LTR) into the heading. The amount of air available to ventilate the face of the empty heading depends on the heading dimension, settings of the LB, and velocity of air in the LTR. LBs are commonly installed by underground supervisory staff based on work experience, which may result in ineffective ventilation. The correct installation of LBs remains a challenge.In this study, a validated computational fluid dynamics (CFD) model has been used to analyse the effect of the LB ventilation system variables on the air flow rates close to the face of the empty heading. Full-scale three-dimensional models with various heading heights, heading depths, LB settings, and LTR velocities were simulated. The air flow rates and patterns at various locations inside the heading were analysed. A comparative study was carried out to quantify the effect of each of these system variables on the flow rates close to the face of the heading. Based on the findings, a user-friendly numerical model was formulated that can be used to estimate the flow rate close to the face of an empty heading for different practical settings of the system variables. This model can help the supervisory staff to swiftly implement the ventilation plan according to the regulations and the mine standards. The model can also serve as part of the curriculum for educating future mining engineers."

Jan 1, 2017

By N. Wagner, P. den Hoed, J. D. Steenkamp, S. Soqinase

In pyrometallurgical processes, metal oxides are reduced from molten slag through carbothermic reduction. It is of interest to evaluate the reactivity of the carbonaceous materials towards substances such as slag. Characterization techniques such as coal petrography can provide insight into the influence of feed coal properties and how they potentially dictate reductant performance. This study aimed to compare the petrographically determined organic composition of coal to reductant reactivity. Two South African medium-rank C bituminous coals and one anthracite sample were investigated together with high-carbon ferromanganese industrial slag. The reductant reactivity tests were conducted at 1500°C in a muffle furnace to assess the potential of carbonaceous reductant in reacting with the main slag components. SEM-EDS was applied to understand the extent of MnO (and to a lesser extent, SiO2) reduction from the slag. Coal 2, consisting of a greater proportion of vitrinite (59.5 vol% on a mineral matter-free basis and 54.7 vol% including mineral matter) was the most reactive reductant. The anthracite sample, with the highest inert maceral proportions (71.8 vol% including mineral matter and 76.8 vol% on a mineral matter-free basis), was the least reactive reductant.

Feb 6, 2023

When designing coal mine roof support, it is necessary to account for the uncertainties and variability that inherently exist within the rock mass and support elements. The performance of a support system is affected by these uncertainties, which are not taken into account in the current deterministic design methodologies used in South Africa. The key to the design of a roof support system is a better understanding of roof behaviour and uncertainties that can been countered during extraction. This paper sets out to develop a method that takes all uncertainties that exist within the rock mass and the mining process into account and provides a quantitative risk-based design methodology.

Jan 1, 2009

By R. L. Castro

Currently, in several caving operations, the spacing between the drawpoints is determined by consulting Laubscher's design guide (Laubscher 1994, 2000), a methodology based on the gravity flow characteristics of the caved rock. Laubscher's methodology is based upon the height of interaction between adjacent flow zones, but does not allow calculation of primary recovery for a given layout. In this paper the authors present a technical and economic methodology based on the flow that occurs near the drawpoint and the associated development costs to estimate the optimal spacing. The flow model at the drawpoint was validated at the El Teniente mine, which extracts coarse caved rock. To validate the flow model, small-scale simulations using drawpoint clusters were conducted and results compared to extracted grades, marker recovery, and drill holes to determine ore remnants that are part of the production control programme at the mine. The results indicate that primary recovery depends on the height of interaction, which varies with the friction angle of the caved rock and the spacing between adjacent drawpoints. Primary recovery estimations indicate values from 85 per cent to 97 per cent depending on the drawpoint spacing used. Extrapolations were then conducted to estimate the primary recovery for different drawpoint configurations planned to be used in the New Mine Level of the mine. The results indicate that the optimal drawpoint spacing is 32 m x 20 m with a through length of 18 m. The methodology developed may be used to estimate optimal drawpoint spacing for block caving mines under different metal prices and mine cost conditions.

Jan 1, 2012

By N. C. Joughin

A simplified economic model is derived for the financial return from a new gold mining project. The model is used to analyze the effects of changes in the mining rate, capital costs, working costs, value of the reef and the stoping width. The most effective avenues for improving the return from a new project are indicated. It is shown that those technological innovations which would improve the return significantly, and therefore make it possible to open more mines, are the use of smaller mines, means for improving the mining rate to capital costs ratio for smaller mines, planning and control of mines by computer simulation, an improved mine valuation procedure and means for mining at a decreased stope tramming width.

Jan 1, 2014

It is perhaps somewhat unusual for a contributor to comment on the authors' reply to his critique. However, I should like to return to a specific comment made by the authors. Award to Bob Laburn The Federation of Societies of Professional Engineers (FSPE) is pleased to announce that the 1984 FSPE Award for Services to the Engineering Profession was presented to Dr R. J. (Bob) Laburn at a function held on 14th February, 1984.

Jan 1, 1984

By J. M. Stewart

The purpose of my few comments is to try to create a healthy perspective to constructively link considerations of the sessions to follow to those of the earlier sessions. I propose to do this by considering some of the issues and priorities related to the development of backfill systems and technology for South African gold mines.

Jan 1, 1988

By Y. P. Shoupletsov

ABSTRACT. A retrospective analysis of some geomechanical classifications for rock masses is presented. It is shown that estimates of rock mass strength according to geomechanical classifications developed, e.g., for construction of tunnels and for ore mines can differ very much. Development of specifically oriented classifications for rock masses with certain geomechanical properties is required. ZUSAMMENFASSUNG. Es wurde eine retrospektive Analyse einiger geomechanoschen Klassifikationen von Gesteinsmassiven durchgefuhrt. Es idt aufgezeigt worden, dass die Bes-timmung der Festigkeit des Massivs nach geomechanischen Klassifikationen, die z.B. fur den Bau von Tunnelen und fur Erzbergwerke entwickelt wurden, sich um etliche Male unterscheiden kann. Es ist eine Entwicklung von spezialisierten Klassifikationen fur Gesteinsmassive mit bestimmten geomechanischen Eigenschaften erforderlich. RESUME. Il a ete fait l’analyse retrospective de certaines classifications geomecaniques des massifs de roche. Il a ete montre que les estimations de solidite du massif suivant les classifications geomecaniques etudiees, par exemple, pour la construction des tunnels et pour les puits de minerai peuvent differer en quelques fois. Il est donc necessaire d’etudier les classifications specialisees pour les massifs aux proprietes geomecaniques particulieres.

Jan 1, 2003