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By S. Vorberg, J. Preussner, B. Fischer, U. Glatzel, R. Völkl, M. Wenderoth

Pt-Al-X alloys have shown good mechanical properties and adequate oxidation resistance. Starting from a promising Pt-Al-Cr alloy, the influence of Ni additions was investigated. After ageing finely dispersed precipitates are observed. Nb, Ta, Ti and Re increase strength when added as partial substitute for Al. Minor additions of B increase creep resistance and rupture time remarkably, owing to strengthening of the grain boundaries. The evolution of the alloy development programme as well as selected properties of the multi-component Pt-base alloys are presented.

Jan 1, 2006

Significant advances have been made in the design of centrifugal slurry pumps that are used for pumping high-density viscous and paste slurries. This paper presents the results of a series of centrifugal pump performance tests that were conducted using an FLSmidth 6 x 4 Krebs millMAX centrifugal pump. The pump was fitted with a dry mechanical seal to prevent dilution of the slurry from gland service water, as the theology of the slurry is sensitive to small changes in slurry density. Tests were done using paste kaolin slurry with Bingham yield stress values between 578-1 120 Pa and plastic viscosities between 728 and 1491 mPa.s. The viscous properties of the paste during each pump test were measured using a rotational viscometer. Pump head and efficiency de-rating were measured and compared to the correlations of Walker and Goulas (1984). The test data shows the pump's best-efficiency point (BEP) changes and shifts to the left of the performance curve. The pump efficiency decreases as the slurry yield stress increases. The head de-rating data shows more head de-rating at the low flow rates compared to the high flow rates for the high viscosity slurry, which is in line with the findings of Walker and Goulas (1984). This paper demonstrates that it is possible to pump very viscous, high yield stress slurries with limited head and efficiency de-rating using centrifugal pumps, provided that positive suction conditions are maintained at all times.

Jan 1, 2012

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Jan 1, 2009

By J. D. Steenkamp

In a paper presented at the Heavy Minerals Conference 2001 a laboratory scale investigation on the beneficiation of an ilmenite containing waste stream by magnetizing roasting was reported1.This waste stream contained a high concentration of ilmenite, which was contaminated by chromite and other gangue minerals. Interpretation of the results of the investigation was based on the assumption that during magnetizing roasting of an ilmenite concentrate, under the oxidizing conditions, the magnetic properties of the chromite would remain constant. In this article the following hypothesis was tested: The magnetic susceptibility of chromite would remain constant during magnetizing roasting of an ilmenite concentrate under the oxidizing conditions reported by Gouws and Van Dyk1. The results of this study indicated that the hypothesis is not true. The increase in the magnetic susceptibility is not significant though and it is expected that it will not influence the final ilmenite quality to a large extent. Based on the assumptions that the bulk magnetic susceptibility of the waste stream samples represents that of the ilmenite in the waste stream, and the bulk magnetic susceptibility of UG1 chromite that of the chromite in the waste stream, the results also served to confirm that the waste stream with a high chromite content should be roasted under oxidizing conditions, in a reactor with a well-defined retention time distribution (i.e. a fluidized bed reactor), at a roasting temperature of 750°C (rather than the higher temperature ranges of 800°C and 850°C).

Jan 1, 2003

By S-L. Weeber

Ash fusion temperature is the temperature at which the mineral matter in coal begins to soften, flow and fuse. It is an important parameter relating to coal utilization. Optimum ash fusion temperatures derived from coal in the Witbank Coalfield region are approximately 1400°C, and higher, although temperatures above1300°C may be deemed acceptable. This study attempted to determine which factors, mineralogical or inorganic-chemical, influence variations in the ash fusion temperatures in certain coals. Coal was sampled from the Number 2 coal seam at opencast and underground workings at New Clydesdale Colliery, Witbank Coalfield, South Africa. The samples represented known low and high ash fusion temperature coal. Analyses performed included proximate analyses, calorific value determination, percentage sulphur, ash fusion temperatures, ash analyses (composition of ash), X-ray diffraction, scanning electron microscopy and petrographic studies. Results show that although a complex relationship exists between ash fusion temperature and the various geological and coal parameters, some positive correlative results were obtained. These indicate a possible relationship between low ash fusion temperatures and i) finer size fractions, ii) an increase in iron content present in the form of pyrite and iii) the form in which pyrite is present, namely cleats. High ash fusion temperatures tend to correlate with i) the absence of pyrite or ii) pyrite present as framboids.

Jan 1, 2000

By L. Hekkala, J. Ollila, J. Keihäs, P. Mäkelä

The Outokumpu Steel Belt Sintering (SBS) Technology is used for manufacturing chromite pellets that are charged into a smelting furnace for ferrochromium production. One of the main elements in successful furnace operation is the control of gas flows inside the furnace, giving improved temperature distribution in the bed during the process. Computational Fluid Dynamics (CFD) gives excellent opportunities for studying these phenomena. An investigation using CFD can be performed relatively fast. For example, implications of different configurations can be studied within a day and an optimum design chosen. Therefore, Outokumpu Technology has developed a Steel Belt Sintering Model (SBSM), which takes advantage of a commercial CFD code. Each main physicochemical event occurring in a steel belt sintering furnace is incorporated independently in the SBS model as a sub-model, enabling every event to be studied separately. The commercial CFD code solves mass, momentum, species and energy equations for determination of the gas flow, composition and temperature. In addition, the Outokumpu SBSM takes into account the moving pellet bed, drying of pellets interms of water content, coke combustion, oxidation and reduction of chromite and the decomposition of carbonates and silicates. During the development of the model, numerous laboratory-scale tests were performed. The sub-models were validated against the laboratory tests. The reliability of the Outokumpu Steel Belt Sintering Model was validated against a pilot-scale batch-sintering furnace by comparing the modelling results against measurements. The aim of this paper is to give a brief presentation of the Outokumpu steel belt sintering model by showing some general modelling examples. Emphasis has been placed on demonstrating some of the main features of the model.

Jan 1, 2007

By P. Marinos, G. Tsiambaos, H. Saroglou

Anisotropy is a characteristic of intact foliated metamorphic rocks (slates, gneisses, phyllites, schists). ?esting was used to establish the anisotropic behaviour of selected gneissic rocks. The effect of anisotropy on various mechanical properties (strength, deformation) and dynamic properties (wave velocity) was examined. The rock samples were also tested at successively higher confining pressures in order to evaluate the effect of anisotropic behaviour at high overburden pressures. L’ anisotropie characterise les roches foliées (schistes, gneiss, phyllades). Dans ce travail des essais en laboratoire ont été exécutés afin de déterminer le comportement anisotropique des roches gneissiques. L’ effet de l’anisotropie a été examiné par rapport aux propriétés méchaniques (résistance, deformation) et propriétés dynamiques (vélocité ultrasonique). En outre des essais des roches ont été exécutés a des compressions latérales successivement plus grandes afin de déterminer le comportement des roches sous grands charges. Anisotropie ist eine Eigenschaft der geschieferten Gesteine (TonSchiefer, Gneis, Phyllit, Marmor). Versuche wurden durchgeführt, um anisotrope Verhalten von gneis Gesteinen zu ermitteln. Der Einfluss von Anisotropie auf mechanische (Festigkeit, Dehnung) und dynamische Eigenschaften (Wellegeschwindigkeit) wurde bestimmt. Die Dreiaxialversuche wurden unter grossem allseitigen Drücken entnommen, um das anisotrope Verhalten auf grösse herrschende Spannung zu bestimmen.

Jan 1, 2003

The November General Meeting of the Branch was held at the S1. Helena Club on Friday, 15th November, 1968. Mr. J. G. Kirchner (Chairman of the O.F.S. Branch) was in the chair. There were also present: President: Mr R. C. J. Goode. Eighteen Members: Mr A. E. Gilfillan (Council Member), Messrs T. Zadkin, J. N. Saunders, N. A. Honnet, D. D. Waterman, C. R. Netscher, (Committee Members), Messrs G. Thorburn, Z. Lombard, H. V. Henwood, C. J. Isaac, S. L. S. Swart, J. D. McNamara, H. H. Schellhorn, J. W. Wilson, G. C. P. Labuschagne, L. J. Thorne, R. C. Espley-Jones, J. Handley. Seventeen Associate Members: Messrs H. J. Reeders, R. Campbell, P. A. Hoffman, D. E. Couperthwaite, M. D. de Lange, G. J. C. Young, G. W. Futcher, U. Visser, F. H. De Groot, E. Schmid, K. G. Pearce, D. A. Viljoen, H. W. M. Eschenburg, R. Still, W. B. Howe, A. H. Edwards, R. H. Drake. Three Graduates: Messrs T. R. Stromsoe, J. G. Cockburn, T. A. Ward. One Affiliate: Mr O. A. Huss. Twenty-three visitors. Total present: 64. Apologies were reseived from Messrs L. O. W. Leimer, V. C. Barnes and A. Louw. WELCOME TO VISITORS The Chairman declared the meeting open and extended a special welcome to the following: Mr R. C. J. Goode, President of the S.A. Institute of Mining and Metallurgy; Mr A. E. Gilfillan, Member of Council and Mr D. A. Viljoen, all from Johannesburg. Also to Mr J. D. McNamara, the guest speaker for the evening who had made the trip from Oranjekrag. MINUTES OF PREVIOUS GENERAL MEETINGS The minutes of two meetings, viz., the General Meeting held on 26th June, 1968 together with those of the Annual General Meeting held on 14th August, 1968 were taken as read and their adoption moved by Messrs T. Zadkin and D. D. Waterman. MATTERS ARISING FROM THE MINUTES There were no matters arising from the minutes. ADDRESS BY PRESIDENT OF COUNCIL, MR R. C. J. GOODE With regard to the 75th Anniversary of the Institute, the President called upon those present to bear the following two dates in mind, viz.: 21st March, 1969-Banquet at the Wanderers' Club, to which ladies are invited. 24th March, 1969-General Meeting at Kelvin House at 9.30 a.m., the speakers being the President of the Institute, the President of the Chamber of Mines and Dr H. J. van Eck.

By Q. G. Reynolds

The presence of dust and fume suspended in the freeboard region is a common feature of the operation of direct current (DC) plasma smelting furnaces. This occurs primarily as a result of the use of fine feed materials together with the open-arc, open-bath operation of such smelters, and is exacerbated by the high velocities and turbulent mixing of the gas in the vicinity of the arc jet. Dust and fume losses into the furnace off-gas system can be significant in some cases and may have economic, operational, and environmental impacts on the process. A computational modelling study is presented in which the concentration of dust material was considered as a continuous field subject to a governing partial differential equation. Settling behaviour was calculated as a function of particle size, local gas/plasma temperature, and other physical properties. Development of the coupling between the concentration field and a magnetohydrodynamic description of the arc is shown, and the resulting models were used to compute various aspects of the behaviour of the concentration field in the arc region for a variety of furnace conditions. Time-averaged as well as transient models of the arc were used to generate the results presented. Qualitative case studies produced several practical suggestions for furnace operation, including increased dust capture by the bath when feed ports are located closer to the electrode, and the possible effects of feed segregation in the furnace freeboard based on dust particle size and density.

Jan 1, 2015

Heavy mineral deposits are becoming more complex in terms of their compositional variation, particle mineralogy and size distributions, and present challenges for the operation of separation equipment to achieve the required grades and recoveries. Changes in equipment design and concepts potentially provide new opportunities for the beneficiation of heavy mineral sands deposits. The development of a framework for the fundamental understanding of separator performance issues is a first step to develop new machines. This paper will present a first step analysis of electro-static and magnetic separation machines with their application to real separation scenarios.

Jan 1, 2010

By Hao Li, Allan Moss, Richard K. Brummer

At the Palabora Mine, the transition to caving 400 m below the bottom of the 800 m deep pit resulted in a slope failure of the North wall that began in 2003, and is still mobile. This failure can be explained by the daylighting into the cave zone of a prominent joint set. The failure was modelled by the 3-dimensional code 3DEC, which is capable of modelling the nonlinear behaviour of discontinuum materials with large displacement.

Jan 1, 2006

Interest in the potential use of high-density, thickened tailings has recently increased significantly. Reasons for considering this new technology vary across projects, but commonly include the need to conserve water, perceived lower risk of catastrophic failure, potential easier closure, or even reduced overall costs. As with any new technology, there has been some tendency to overstate its potential benefits. This paper reflects on whether or not the potential benefits that have been attributed to paste and thickened tailings have been realized. Using a grading system, thirteen benefits that were ascribed to the new technology some years ago are evaluated. Data is taken from case studies, and it is suggested that the key proven benefits appear to be reduced operating costs in some cases, reduced wall-building costs, and reductions in water consumption. One key potential benefit that has not been universally achieved is a reduction in the footprint of the tailings facility. Reports in the literature highlight the sometimes confusing nature of trade-off studies. Unless full life-of-mine costs are considered, these studies can be misleading and incorrect. The need to establish a consistent basis for comparative studies is discussed.

Jan 1, 2012

By Y. I. Yang, Y. -B. Tang, D. -J. Ma

Chlorine-containing minerals are commonly present in coal. Associated minerals such as pyrite can undergo exothermic reactions. Consequently, it is of great significance to study the effect of inorganic chloride on the spontaneous combustion of coal. In this study, the effects of five inorganic chlorides (sodium chloride, magnesium chloride, potassium chloride, calcium chloride, and zinc chloride) on the spontaneous oxidation of coal were investigated. Analysis of the gaseous products of coal oxidization at low temperatures (323K to 453K) showed that the presence of inorganic chlorine in coal markedly decreases O2 consumption and the generation of CO and CO2. Samples of raw coal and chlorine-loaded coal were oxidized for 36 hours under the same experimental conditions. Infrared diffuse reflectance spectroscopy results showed that inorganic chloride can inhibit the oxidative decomposition of some functional structure components (methyl, methylene, methine, and hydroxy) in the coal. The influence of inorganic chloride on the oxidation characteristics of the functional groups in coal during spontaneous combustion was investigated using benzyl alcohol and 1-phenylpropanol as model compounds, which were tested under the same experimental conditions as the coal samples. The oxygen consumption of model compounds with and without the addition of inorganic chloride further suggested that inorganic chloride may hinder the oxygenolysis of these structures during low-temperature oxidation. This phenomenon can be attributed to the radical reaction from the perspective of radical chemistry. It can therefore be concluded that inorganic chlorides play an inhibitory role in the spontaneous combustion of coal.

Jan 1, 2015

By C. C. Pretorius

3D seismic surveys have become a well-accepted method of imaging sub-surface geology in the Bushveld Basin. Because both the seismic sources and receivers are placed at surface, most surveys are limited to imaging faults with >=7 m throw. However, some areas such as shaft infrastructure can benefit from the ability to detect smaller structures prior to shaft sinking. Borehole radar and logs such as the acoustic televiewer can identify these structures in the shaft barrel, but not within -200 m from the shaft. Therefore, Anglo Platinum has developed the method of high-resolution 3D vertical seismic profiles (VSPs) for structural sterilization of shaft sites prior to shaft sinking. VSPs utilize a surface source and sub-surface receivers deployed down a borehole. This means that seismic energy goes through the near surface only once, and therefore suffers less frequency loss than when both source and receivers are on surface. Furthermore, VSPs can record 3 component (3C) data which comprises P wave, Sh (horizontal) and Sv (vertical) wavemodes. Because S waves travel at about 0.6 of the velocity of a P wave, shorter wavelengths and therefore higher resolutions are possible using S wave data. VSPs were first used in their one dimensional, zero offset, mode to correlate borehole geology with seismic stratigraphy within seismic surveys. This showed that VSPs record -30% higher frequencies than surface seismic surveys. The program then applied two dimensional VSPs to the problem of imaging geological structure close to a borehole. 2D VSPs confirmed that high frequency results could be achieved, and that this enabled a more accurate image of the Merensky Reef than could be achieved by surface seismic data. Finally, the program has achieved the successful recording and processing of 3D VSP data, with both compressional and shear wavemodes giving a high resolution structural result. Although P wave data gives -30% frequency improvement over surface seismic surveys, S wave data can give as much as 80% improvement, further improving the structural image achieved. The high fixed costs of VSP surveys mean that they should ideally be run in multi-client batches, which can reduce the per borehole cost by up to 50%. Their application is anticipated to be on high value capital infrastructure with a geological risk from faults which are not imaged by surface seismics-generally in the sub-7 m range. Keywords VSP, 3D seismic, bushveld, platinum, resolution, imaging, shear waves, shaft sinking.

Jan 1, 2011

By E. S. Schubert

Keywords: co-generation, furnace CO-gas cleaning, disintegrator scrubber, Theisen In a closed, electric, reduction furnace, no oxygen enters the furnace from the surrounding environment. The off-gases are thus not ?burnt? and therefore contain a considerable amount of CO and H2. Traditionally these gases have been captured and burnt in a flare stack. Recent developments have led operators of such furnaces to revise this strategy and to consider utilising these gases as a fuel for gas-fired generator sets to produce electricity, thus becoming more energy efficient. On 31 March 2010 the new emission standards, in accordance with the Air Quality Act, Act 39 of 2004, were promulgated. The minimum emission standards according to the act require that the particulate matter emissions from the primary fume-capture systems on closed furnaces for ?new plants? in ferroalloy and calcium carbide production not exceed 50 mg/Nm³ and 25 mg/Nm³, respectively. By implementing co-generation, the producer automatically complies with the new environmental emission standards for an off-gas. As much as 30% of the electrical power cost, which is set to double in the near future, can be saved by partly generating one?s own electrical power. In December 2010, the National Treasury published a discussion paper for public comment, one entitled ?Reducing greenhouse gas emissions: The carbon tax option?. Irrespective of how the tax is finally implemented, it will result in an increase of production costs in affected industries. This paper focuses on the characteristics of a furnace-off-gas cleaning system for closed ferroalloy smelters, characteristics that meet the requirements of both reducing solid-matter emissions and operating a safe and reliable gas plant.

Jan 1, 2011

By F. T. Wang, Y. Yuan, S. H. Tu, X. G. Zhang

Hydraulic support instability (HSI) is one of the most common causes of disasters in underground coal mining, posing a threat to the safety of mine workers and normal operation of the equipment. It is prone to occur in fully-mechanized mining faces with a large mining height (FMMLMH), especially when the dip angle of the coal seam is large. The key to controlling HSI is to deduce its mechanism and employ effective control techniques. This paper focuses on the analysis of HSI types, the key parameters and techniques to control HSI in FMMLMH, the establishment of a model of HSI in FMMLMH, and a multi-parameter sensitivity mechanical model of different HSI forms in the no. 7219 longwall face in Xutuan Coal Mine, Huaibei Mining Group, by using sensitivity analysis . The results show that HSI mainly presents in three forms: hydraulic support gliding (HSG), hydraulic support tilting (HST), and hydraulic support tail twisting (HSTT). The occurrence of the above three forms depends mainly on support anti-instability capability. In the no. 7219 longwall face, HSG and HST are the main two forms of HSI. The dip angle of the working face and the friction coefficient between floor and hydraulic support are the sensitive parameters for HSG, while HST is strongly dependent on the dip angle of the working face and the friction coefficient between roof and hydraulic support. By the applications of measures such as the oblique layout of the working face, cutting the floor into a step pattern, moving the support under pressure, and raising the setting load, the support stability was controlled effectively.

Jan 1, 2015

By W. P. Erasmus

This paper will focus on the use of the ?wet-mix? steel fibre re-in forced shotcrete as a permanent lining in deep shafts, assessing gold bearing reef. It will cover all aspects relating to the choice of this material covering the geological conditions through to the final quality control. All procedures are in line with ISO 9001,as JCI projects who manage the project, are an approved company therof.

Jan 1, 2001

By W. D. Northrop

This paper gives an account of the development of a technique whereby the vertical limits of geological horizons may be identified by the use of vertical variograms on the mineral of economic interest. This information may supplement or guide the correct subdivision of the individual horizons into meaning full data sets by diligent geological observation. This process then improves the quality of the variance modelling of the gold distribution in the plane of the individual layers and therefore enables better estimates to be made into the grids or blocks of the mine model. The technique is explained by an account of the development work, which was performed, on duplicate superimposed reef horizons in the Kimberley formations. The paper then shows how the correct approach was developed to evaluate the mineralized layers in a multiple stacked conglomerate layer sequence in the Elsburg reefs of the Witwatersrand Rand System at the Target deposit. The method of categorization of resources according to confidence in the estimate is also explained. The feasibility processes carried out on the three-dimensional model, in accordance with the SAMREC code are also described. An example of the development of a reconciliation process utilizing chip sampling is also explained.

Jan 1, 2003

Following a short review of selected literature, a back analysis of stress measurements of stress regeneration in a closed mini-longwall is shown. The agreement is good, lending confidence to the parameters used in the proposed numerical model. Foundation yielding was modelled in the absence of total stope closure. A ?Prandtl? wedge was formed, coinciding with the yield point of the pillar/foundation system. Some theoretical work is used as a starting point for the formulation of a new design methodology for strike or dip stabilizing pillar/foundation systems in deep level goldmines. The existing guideline for the stability of foundations (APS< 2.5UCS) is critically examined. Finally, the advantages of the new approach, and the work required to substantiate the proposed new design methodology, are outlined.

Jan 1, 1998

By D. F. Malan

This paper presents an overview of work conducted over several years to investigate the continuous stope closure profiles recorded in tabular excavations and the use of this data as a hazard indicator. In spite of the brittle nature of the rock, measurements in gold mines and intermediate depth platinum mines revealed a significant time-dependent closure component. Various approaches to simulate the time-dependent closure have been investigated. Viscoelastic theory is able to simulate the time-dependent closure behaviour, but there are subtle problems with the use of this theory as it cannot simulate the failure processes in the rock. To overcome these problems, continuum and discontinuum elasto-viscoplastic models were developed by the authors. Discontinuum models have the advantage of being able to simulate the creep behaviour of prominent discontinuities. Development of these models has led to useful insights into rock mass deformation and has made the numerical simulation of parameters, such as rate of mining, possible for the first time. A number of practical applications for the mining industry have been developed from this study. Among these are the delineation of geotechnical areas using closure data, use of the data as a hazard indicator and to give warning of large collapses in the platinum mines, identification of areas to be preconditioned in the gold mines, measurement of the effectiveness of preconditioning and improved da

Jan 1, 2007