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By H. Yilmaz

Tensile strength testing has been one of the most common physical property testing methods of thin spray-on liner (TSL) products worldwide. However, the variety of products tested has been insufficient for comparison purposes. Specimen preparation procedures and test parameters such as curing time and loading rate are not reported well. Comprehensive tensile strength testing on 20TSL products and one plain shotcrete brand was performed over 28days of curing period. Detailed information on the test procedures with particular attention on the important aspects during sample preparation and test execution are provided. As expected, the tensile strength increases with increasing curing period. The test results make the categorization and comparison of liner products possible.

Jan 1, 2010

By H A. Myburgh

The beneficiation of heavy metal oxides, such as iron ore, is usually performed with heavy medium separation in cyclones, static baths and lately with Larcodems. Atomized ferrosilicon is most suitable as a heavy medium at densities above 3600 kg/m3 whereas a mixture of milled and atomized ferrosilicon is suitable at densities below 3600 kg/m3. When operating a beneficiation plant at densities higher than 3600 kg/m3 the quality of the ferrosilicon particles is an important factor that influences the control of the beneficiation process. Therefore, it is important to know how the rheology would be affected by the ferrosilicon quality as it also influences the control of the process at these elevated densities. Background The Kumba Resources Sishen Iron Ore Mine in South Africa produces 26.5 Mt iron ore per annum from its beneficiation plant. The ore body consists mainly of laminated and massive type hematite ore that is crushed down to ?90mm before being beneficiated by means of a combination of Wemco drums, Larcodem and dense medium cyclone separators. The need for higher densities When the percentage of high-density gangue2 is higher than normal in the run-of-mine (ROM), a higher separation density is necessary to produce a product to specification. Certain ore types of this quality in the Sishen reserves require a separating density higher than 4000 kg/m3, whereas densities would normally average 3600 kg/m3 when beneficiating ores of normal high-density gangue content. Sink and float tests conducted on the ROM material at Sishen revealed some interesting characteristics. In the waste fraction, (density < 3600 kg/m3) it was found that the %Fe was <21% (Fig. 1). Similarly, for the product fraction (density >3000 kg/m3), the percentage Fe varied between 35% and 67.2%. The bulk of the material (88%) actually had a density greater than 4000 kg/m3 and a Fe content that varied between 63% and 67.2%. At a density interval of 3600 to 4000 kg/m3, the Fe content varied from 37% to 60% with an average of 45%.

Jan 1, 2006

By N. P. Mahumapelo

This paper is based on a study to determine the potential beneficiation opportunities for marble from Griekwastad in the Northern Cape Province. The marble was characterized mineralogically by X-ray diffraction. Major and trace elements were determined using inductively coupled plasma-optical emission spectroscopy. The sample was crushed, and the crushed material beneficiated by tumbling and polishing. The resulting beads were incorporated into a variety of jewellery and other decorative items. It is concluded that the beneficiation of Griekwastad marble presents a good opportunity for value addition and job creation, provided that an effective marketing strategy for the products can be developed..

Jan 1, 2014

By D. Lusinga

Hydrocyclones are a common feature in almost all mining operations in the world, serving mainly as classifiers. Some of their advantages include low capital costs, low space requirements and their ability to reduce residence time in closed circuit grinding processes. Although an extensive body of literature exists for hydrocyclones, these devices are still inherently inefficient, and more research is currently being undertaken, particularly in the field of modelling. In the vast body of hydrocyclone literature published so far, there has been little or no effort devoted to analysing the effect of the cone force ratio on the performance of hydrocyclones. The cone force ratio is defined as the ratio of the spigot to the vortex finder diameter (Shah, 2005). In this study a total of 44 tests was carried out in a custom-built rig at the University of Cape Town. These tests were aimed at evaluating the effect of the cone force ratio on the performance of as mall diameter hydrocyclone. The cut size and water split were used as the criterion for evaluating the performance of the hydrocyclone. Results from the tests showed that the cut size decreased with an increase in the cone force ratio. The cut size also appeared to decrease as the calculated locus of zero vertical velocity (LZVV) shifted inwards. The water recovery to the underflow appeared to increase with an increase in the cone force ratio. The effect on the cut size of adjusting the cone force ratio was found to be higher for a coarser feed than it was for a finer feed.

Jan 1, 2009

By S. M. Rupprecht

Transportation accounts for some 26% of all mine accidents in South Africa. Although this figure may not be as prolific as fall of grounds accidents or accidents caused by seismic events, the enormity of transportation accidents demands attention, especially as many of these accidents are avoidable. This paper investigates vertical (i.e. shaft), horizontal (i.e. haulages), and in-stope transportation systems and their function as it applies to safety. Recent transportation accidents are discussed looking at current trends within the three transportation areas. In the shaft area, discussions will focus on handling of material cars, loading and off-loading of the workforce and management of shaft orepass systems. The horizontal component will focus on personnel transportation, safety around trains and hoppers, and handling of material in the cross-cut. The discussion on in-stope transportation will focus on the general congestion of the stope environment and how it affects the overall movement of personnel, material, and rock. Of concern are the large numbers of material handling and scraper winch accidents that occur and which will be discussed in some detail. The paper will conclude with a section on proposed guidelines within the three above-mentioned systems for mine engineers to consider in mine design and life of mine planning and scheduling. Keywords Underground logistics, safety in material handling.

Jan 1, 2011

By B. K. Loveday, N. V. Ramlall

A study was carried out to evaluate various batch flotation models for the recovery of minerals in a UG2 platinum ore. The major minerals in a UG2ore can be grouped as platinum group minerals, chromite, and siliceous gangue. This study also examined the entrainment of minerals during flotation. The models were ranked using statistical methods and an analysis of model-fit residuals. Entrainment parameters obtained from model fitting were evaluated for logic using a simple mineral-to-water ratio versus time plot. The foremost conclusion from the study was the importance of entrainment modelling. The measurement of water recovery increased the size of the data-set, and the inclusion of a simple entrainment model was statistically significant. The overall fit to the data was improved, and the entrainment model provided logical information on the recovery of gangue minerals that were not considered to be floatable.

Jan 1, 2015

By B. Leong, H. Joubert

Keywords: Pyrometallurgy, furnace, auxiliary equipment, copper slag launders Pyromet has designed copper launders for tapping slag. What makes Pyromet?s launder design innovative and safe is that it does not have any cooling water channels underneath the launder runner, whilst achieving effective cooling of the runner. If matte burn-throughs were to occur through the launder runner, the risk of damaging water channels and the risk of explosions are reduced. In addition, since the cooling water channels are not harmed, the launder is easily repairable and reusable. Pyromet makes use of Finite Element Analysis to optimize the launder geometry to ensure that sufficient energy is removed from the centre of the launder. Factors considered during the launder design include the suitability of the geometry to the client?s needs, experience from existing installations, and ease of fabrication. Pyromet goes so far as to develop procedures for fabricators to ensure that fabrication issues do not compromise the functionality of the launder. When launder orders are received by Pyromet, the entire fabrication process and the functioning of the launders during operations are monitored to ensure that the launder designs are continuously improving with every installation.

Jan 1, 2006

By F. R. Camisani-Calzolari

Surface defects on continuously cast slabs require treatment by grinding. This extra phase in the process causes lower throughput of final product and extra energy costs. The elimination of slab treatment after casting implies that slabs can be direct rolled or hot charged, resulting in higher throughput and lower energy costs. To increase the number of slabs that can be direct rolled or hot charged, defects have to be predicted before a slab has completed the casting process. Transversal and longitudinal cracking, casting powder entrapment and other inclusions, bleeders, deep and uneven oscillation marks, stop marks and depressions are the defects thatare considered for prediction. A structure with two models is proposed. The first model describes the effect of mould level, water inlet temperature and casting speed (MV?manipulated variables) on 38 thermocouple temperatures (IV?intermediate variable). Casting speed is a manipulated variable while mould level and water inlet temperature are treated as measured disturbances. This model is known as the MV to IV model, and is used to control the occurrence of defects. The second model describes the effect of the thermocouple temperatures on the defects at different positions and locations on the slabs (OV?output variables). This model is known as the IV to OV model and is the predictor of defects. The models are determined using time-series methods in the form of auto regression with exogenous input using data of approximately 500 slabs cast over a period of 6 months. The models are validated using plant data from 44 slabs gathered three years later, with good results. As an example, published results give a sensitivity and specificity of 61.5 per cent and 75 per cent respectively for longitudinal cracks on validation data, while the presented method gives 63.6 per cent and 93.5 percent, respectively. The IV to OV model is used in an inversion to determine the optimal thermocouple temperatures for each slab width. Keywords: Continuous casting, model, defect, prediction, direct rolling, hot charging, goodness-of-fit, correlation, time-series, soft sensor, ARX.

Jan 1, 2003

By O. Celep, T. Uslu, Savas

This study investigates the enrichment of a low-grade colemanite concentrate (-3 mm) using a Knelson centrifugal gravity concentrator. Due to its low boron content, the concentrate is unsaleable and has to be stored under appropriate conditions to avoid potential environmental problems. The low-grade colemanite concentrate was comminuted to size fractions of-1 mm, -0.5 mm, and -0.15 mm before treatment in the Knelson Concentrator. The effects of particle size, fluidizing water velocity, and bowl speed on the enrichment process were examined. The B2O3content of the concentrate was increased from 33.96% to a maximum of 45.52%. B2O3recovery increased with increasing bowl speed and particle size, and decreased with increasing fluidizing water velocity. The enrichment process also rejected arsenic and iron to some extent, with a maximum reduction of arsenic from 1360 g/t to 765 g/t and iron from 0.88% to0.33%.

Jan 1, 2015

The estimation of the spatial variation of the b-value of the Gutenberg- Richter relationship is important for both the general interpretation of the mechanism of rock mass response and seismic hazard assessment. The interpretation of b-value as a parameter of rock mass response is discussed in this paper. The methods applied to evaluate the spatial variation of b-value and the algorithm for obtaining the magnitude of completeness and b-value for subsets of data are presented with some verification analyses. The algorithms presented enable the automation of a spatial evaluation of b-value.

Jan 1, 2014

By D. F. Malan

In deep level hard rock mining the rheological behaviour of the rock is important as time-dependent aseismic processes can lead to a stable dissipation of energy thus reducing violent outbursts. Underground closure measurements, observations of time-dependent fracture formation and siesmic data indicate that the rock in deep South African gold mines shows significant time-dependent behaviour. The objective of this work is to quantify the time-dependent rock behaviour for laboratory specimens and underground conditions. Laboratory experiments indicated that lava and quartzite specimens undergo measurable creep strain at stress magnitudes below the failure stress. Quartzite is however prone to more significant creep at lower stress levels. A viscoelastic analysis showed that laboratory creep results can not fully explain the behaviour observed underground. The in situ behaviour is governed mainly by the rheological behaviour of the fracture zone and the resulting time-dependent formation of new fractures. A viscoplastic discontinuity model implemented in a boundary element program is used to simulate this behaviour.

Jan 1, 1997

By M. A. Kujoana

Following on the design of good mining layouts and regional support systems, and the implementation of sound strata control practices, stope support is the ultimate strategy to combat the hazards of rockfalls and rockbursts. The primary function of stope support in intermediate and deep level mines is to stabilize the rock mass immediately surrounding stoping excavations, that is, the zone of fractured rock which behaves in elastically around stopes. Support design is a process resulting in a support system which is both practical and meets or exceeds by a factor of safety the requirements for a particular geotechnical environment. The aim of this project was to design a support system, which accommodates the factors of rockfalls and rockbursts. The pack support unit must be easily handled, less costly and can be used in stopes without any significant convergence. The project tested the structural stability of packs to their expected deformation, in order to design a height to width ratio for stopes where little convergence is expected.

Jan 1, 2009

By D. J. Fourie

During the production of pure TiO2for the pigment industry, ilmenite, containing 35?60% TiO2, is reduced to high titania slag, containing 70?95% ?TiO2? and pig iron. The high titania slag produced, consists mainly of titanium in different oxidation states and FeO in equilibrium with liquid iron. To predict the phase and chemical reaction equilibria in a furnace, a suitable solution model is required with accurately determined binary interaction parameters, as slag melts tend to behave very non-ideally. This paper investigates two popular slag models, namely, modified quasi-Chemical (MQC) model and the cell model and provides the binary interaction parameters based on recently published data of the ternary system and critically assessed published unary and binary data. Very few modelling results have been published on the ternary Ti-Fe-O system pertaining to high titanium slags. The solution models, with their regressed interaction parameters, can subsequently be implemented in commercial software of the slag-metal phase equilibria to predict how much and which type of solids will precipitate for a given bulk slag chemistry and operating temperature or, alternatively, above which temperature should a furnace be operated to avoid excessive solids precipitation.

Jan 1, 2005

By V. Brabie, S. Jansson, L. Bohlin

The rate of dissolution of solid MgO-C and doloma into liquid in CaO-Al2O3-SiO2-MgO slag at different temperatures was studied under conditions of forced convection by rotating cylindrical refractory specimens in a stationary crucible containing the molten slag. The corrosion rate was calculated from the change in diameter of the cylindrical specimens. Refractory specimens were 13 mm in diameter and 70 mm long. The specimens were rotated for15 to 120 minutes at speeds of 100 to 400 rpm in the molten slag. The rate of corrosion increased with temperature and with the rotating speed of the rod, and decreased when the slag was nearly saturated with MgO. The experimental results confirm the assumption that the diffusion of magnesium oxide through the slag phase boundary layer controls the corrosion process. The corrosion mechanism seems to be the dissolution of the refractory materials into the slag, followed by penetration of pores and grain boundaries and dispersion of the grains in the slag. Keywords: MgO-C refractory, doloma refractory, molten slag, corrosion rate, corrosion mechanism

Jan 1, 2004

A201 aluminium alloy is a high strength casting alloy with a nominal composition of Al-4.6Cu-0.3Mg-0.6Ag. It is strengthened by the O(Al2Cu) phase and the ??(Al2Cu) phase during heat treatment. Further strengthening of this alloy system can be obtained through the addition of transition elements, but care must be taken as other elements might have adverse effects on the mechanical properties. The objective of this study is to determine the influence of Mn on the tensile properties of rheo-processed Al-Cu-Mg-Ag alloy A201. ThermoCalc software was used to predict the different phases that can be expected in the alloys, and scanning electron microscopy(SEM) with energy dispersive spectroscopy (EDS) was used to investigate the actual phases that formed. The influence of these phases on tensile properties is quantified. SEM and ThermoCalc revealed that there is an increased amount of the Al20Cu2Mn3 with increasing Mn. The tensile properties showed that high amounts of Mn do have adverse effects on the tensile properties of alloy A201, especially the ductility. Keywords Semi-solid metal (SSM) forming, alloy A201, intermetallics, Al20Cu2Mn3

Jan 1, 2011

By L. Mabiza

Keywords: Pyrometallurgy, circular furnace, PGM, platinum, Peirce-Smith converter, Zimbabwe The Zimplats Smelter, located on the northern part of the Great Dyke, at the Selous Metallurgical Complex, is the only PGM smelter in Zimbabwe. Zimplats? operations currently consist of the Ngezi Platinum Mine, which is a 1.5 Mt/a open-cast and 0.7 Mt/a underground mine, and a Concentrator and Smelter to which ore is transported 80 km by road. The final converter matte product is transported to Impala Refining Services in South Africa for refining and marketing. The Zimplats Smelter operations consist of a concentrate filtration plant, a Drytech flash dryer, a modified Elkem / Hatch 13.5 MVA circular furnace, two 10? x 15? Peirce-Smith converters, and a matte granulation plant. The Zimplats smelter uses a three-field electrostatic precipitator, supplied by ELB-Brandt, for removal of particulates in the gas streams from both the converter and furnace. Construction of the smelter commenced in 1995, under the BHP / Delta Gold of Australia joint venture. The furnace was lined mid-1996, and smelting operations commenced in 1997. Due to design challenges, the Elkem furnace was modified by Hatch in 1998, and the smelter had not reached full capacity when operations were suspended in 1999. Re-commissioning took place in January 2002.

Jan 1, 2006

By W. S. Steinberg

In 1963, the full-scale engineering study for the development of an iron, steel, and vanadium plant was initiated. This was the birth of Evraz Highveld and its process flow as it is known today. Highveld started out as a steelworks that produced steel and vanadium-bearing slag from a titaniferous magnetite iron ore mined from its own mine site near Steelpoort. The process utilized co-current rotary kilns for prereduction, and submerged-arc furnaces for the production of pig iron with approximately 1.15% vanadium. Because of various technical challenges that the submerged-arc furnaces experienced over the years, a decision was taken in 2004 to convert the furnaces to open slag bath (OSB) operation, in order to enable the maximum production of iron and vanadium while improving the control over operational parameters. The conversion proved to be highly successful and, since 2005, three furnaces have been converted to OSB operation. The fourth furnace will be converted in the first half of 2011. The conversion to OSB furnaces not only yields higher vanadium recovery to the metal at the iron plant, but also improves the overall throughput of the steel plant. This is the result of the higher carbon content of the liquid iron from the OSB furnaces, eliminating the need for anthracite addition to the shaking ladle process. This reduces the blowing time by approximately 60%. The conversion of the furnaces to OSB configuration is seen as an enabling technology change and a prerequisite to the implementation of other plant improvements that are envisaged. The long-term vision of EHSV is to convert five furnaces to OSB mode, and permanently decommission the two remaining submerged-arc furnaces. This will allow EHSV to maintain current steel and vanadium production but at a significantly improved overall efficiency.

Jan 1, 2011

By A. Kale

A chlorination pilot plant having capacity to produce 5?10 kg/hr of titanium tetrachloride is in operation at the chlorination facility in Mintek. The bubbling fluid bed chlorination plant can be operated in batch and/or continuous process to study the chlorination kinetics of various feedstocks. The chlorination of titaniferrous ores to produce titanium tetrachloride (TiCl4) was carried out during the commissioning of the pilot plant and also as part of the titanium programme carried out at Mintek. TiCl4 is a basic raw material for producing commercial titanium dioxide pigment and titanium metal. This paper discusses the challenges faced during the commissioning and operation of the chlorination pilot plant. It also discusses the effect on the auxiliary facilities and instrumentation as a result of the harsh operating conditions of +1000°C and use of corrosive gases like chlorine and titanium tetrachloride. It discusses the effect of physico-chemical properties of the titanium tetrachloride and iron chlorides. The effect on the chlorinator refractory lining due to heating and cooling of the chlorinator is also discussed. Besides the special provisions made during the design of the chlorinator, this paper also discusses the operational experience and possible solutions to be implemented in future. Keywords Fluid bed chlorination, titanium ore chlorination, titanium tetrachloride (TiCl4) production using fluid bed technology.

Jan 1, 2011

By M. I. Mthenjane

"BackgroundThe paper discusses post-mining land use however, the essence of the topic is the emotional motivation behind the decisions related to mining investment and development. Therefore this is not a typical SAIMM technical paper about the science and techniques of post-mining land use. There are already numerous papers written and conferences held on this aspect of post-mine land use; the science is well understood, but the evidence of the practical application of the (environmental, social, and economic) science is sparse. At a recent conference held in November 2017 on the theme of ‘Science, Business, Society Dialogue – linking science, society, business and policy for the sustainable use of abandoned mines in the SADC region’, it was demonstrated through the delivery of several papers on the possible viable options of post-mine land use. The conference was structured in nine sessions, covering the following relevant topics:? Sessions 1 and 2: Nature and magnitude of the problem: raising awareness? Sessions 3 and 4: International experiences in remediation: case studies? Sessions 5, 6 and, 7: Technological solutions: converting liabilities into assets? Session 8: Implementing solutions: social and legal aspects? Session 9: Wrap up, lessons learned: conference resolution.Summaries of the key outcomes of the sessions are available for reference.The aim of this paper, accompanied by the video speech, is to provide a visualization of the possibilities of post-mine land use. Mining contributes approximately 7% to South Africa’s GDP - this is the lowest it has ever been and is attributable to both a diversifying economy and to poor mining and investment policy which has resulted in reduced investment in the sector. The objective of the paper is to highlight the opportunities, for succeeding and diversifying economic activity following mining and mineral extraction which can continue to sustain the livelihoods and wellbeing of communities and societies beyond mining.During mining, very few alternative and local economies develop. Dependence on mining and its value chain prevails until mining ceases. This idea is conveyed in Figures 1a and b."

Jul 1, 2019

By K. Schwerdtfeger

Data are presented on the effect of iron oxide on the electrical conductivity of CaO-SiO2-FeO-Fe2O3melts, and on limiting current and impedance in direct current or alternating current charge transfer at iron electrodes. The strong influence of iron oxide content can be utilized for in situ determination of total iron oxide content and Fe3+/Fe2+ratio. The possible probe designs are presented and the principles and procedures of the measurements are explained. Keywords: in situ probe for iron oxide determination in steelmaking slags, electrical conductivity of CaO-SiO2-FeO-Fe2O3slags, direct current over voltage and alternating current impedance at iron/slag electrodes.

Jan 1, 2004