Search Documents

A physical modelling study has been carried out to simulate the slag-metal dispersion induced by a high-strength bottom gas injection. Water and kerosene were utilized to simulate metal and slag respectively. A water model of CLU (Creusot-Loire Uddeholm)vessel was used with three different nozzle orientations, namely, off-centre, triangular off-centre and centre. The gas flow rates changed from 0.00599 m3/s to 0.01081 m3/s. Height of heavy and light phases was kept fixed at 0.23 m and 0.02 m respectively. The dispersed phase hold-up was determined at various axial and radial distances, gas flow rates, and tuyere configurations. The observations revealed that at a fixed gas injection rate, as the vertical distance increased in the centerline, straight off-centre orientation resulted in greater dispersed phase hold-up values than those of the centre configuration and the triangular off-centre orientation. The dispersed phase hold-up was found to increase with gas injection rate and decreased with axial distance. The variation of the dispersed phase hold-up with the dimensionless axial distance and the gas injection rate was correlated by using the modified Froude number. The experimental values of the dispersed phase hold-up were found to be in reasonable agreement with the correlated values obtained from the modelling equations. The findings of the present study may be utilized in the ferroalloy refining vessels in terms of designing tuyere locations for optimum processing conditions.

Jan 1, 2004

By A. A. B. Douglas

In this paper the origins of the mortar intruded concrete concept and its development and application in the construction of watertight bulkheads in South Africa are described. The events leading to the commissioning and execution of the West Driefontein Experimental Plug and the Virginia/Merriespruit Boundary Plugs, and their roles in the proving of the technique, follow. The development of the first Transvaal and Orange Free State Chamber of Mines Code of Practice for Mortar Intrusion Concrete for Underground Plugs and Bulkheads, Johannesburg, November 1962,is explained. The saga of the October 1968 flood and subsequent salvage of the West Driefontein Gold Mine is recounted. The paper concludes with mention of the validation programme carried out for the Placer Dome Western Areas Joint Venture and their South Deep water barrier programme.

Jan 1, 2006

By M. G. Wimberger

The Merensky Reef zone, as developed on Impala Platinum?s Rustenburg Operations, displays a gradational mineralized zone, with grades decreasing from the Merensky Pegmatoid Unit into the footwall and hanging wall. A system of identifying a manageable method of defining the mining cut is introduced, termed the grade profile attenuation cut-off grade. Although horizontal grade selectivity is not applied in the mining of the Merensky Reef zone, low extraction of the orebody, due to manageable and non-manageable factors, can contribute to a reduction in revenue, even losses, due to fixed cost contributions in the mining and beneficiation of the ore. A model is proposed that integrates all variables affecting the revenue of the mining operation, including the grade profile attenuation cut-off grade, the extraction factors, commodity prices and exchange rates, utilizing numerical simulation techniques in a PC-based environment. A breakeven extraction factor for a specific cut-off grade is delivered for a range of market conditions. The breakeven extraction factor is a useful guide when designing mining layouts in structurally complex and low metal content areas. Incorporating distribution functions for individual commodity prices and exchange rates into the model provides mineral resource managers with a risk profile for individual mining areas. Shaft areas have varying grade profiles and each area should have individual models run, to prevent generalizations being made about acceptable risk levels on mining areas.

Jan 1, 2004

By J. Nell

An overview is given of the matte melting process used for the beneficiation of South African platinum group metal (PGM) ores. Most producers use six-electrode furnaces to melt the concentrate and Pierce Smith converters to oxidize excess iron sulphide from the furnace matte. Concentrates from two reef types (the so-called Merensky and UG-2 reefs) dominate the feedstock supply. Concentrate from the Merensky Reef is low in chromium and does not pose significant melting problems. Concentrates from the UG-2reef contain much higher levels of chromium, which results in the formation of chromium-rich spinels during melting. This is attributed to the low solubility of chromium in furnace slag under typical operating conditions (an oxygen partial pressure of 10-8?10-9bar at temperatures of 1550°C to 1600°C). During the converting process, care is needed to avoid excessively oxidizing conditions, which result in cobalt, nickel and copper losses to the slag. High nickel losses result in the formation of Fe2NiO4 (trevorite), which often forms solid solutions with FeCr2O4and Fe3O4. In future, the main challenge in the processing of South African PGM ores will be to cope with ever-increasing levels of chromium in the concentrate. A short-term solution to the problem would be to melt the concentrate under slightly reducing conditions to promote the formation of CrO, which is more soluble in the slag than Cr2O3.A longer-term solution to the problem would be to abandon the current matte-smelting process in favour of an alloy-based process, which would offer total flexibility with respect to the amount of chromium that can be tolerated in the feed. Keywords: Merensky, UG-2, furnace, slag, matte, converting, spinel, chromium

Jan 1, 2004

By M. M. D. S. Vemba

Paper written on project work carried out in partial fulfilment of B.Sc. Eng (Mining Engineering) degree Engineering refers to the application of mathematics and other sciences to logically develop solutions to problems. However, in opencast mining, due to the randomness of operations, the use of mathematics is often neglected. Instead, practices that have proven successful elsewhere tend to apply. At the other end of the scale, mathematical models have been developed to identify and quantify all the operational parameters involved in the loading and haulage of ore. These are then used to optimize the operation. Optimization in this context, refers to the reduction of cost through effective utilization of the available time and resources. Considering these mathematical models, the loading and transport system at SMC (Catoca Mining Society) will be assessed with a view to its optimization. The discussion will be introduced by considering the mine background and other general information, which will highlight the main operational variables.

Jan 1, 2004

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

By M. J. Lukhele

Paper written on project work carried out in partial fulfilment of B. Tech (Mining Engineering) degree A number of high wall mining methods were developed over the years to mine coal reserves exposed on the high walls created during surface mining. The auger mining system was initially developed in the early 1940s in the United States of America. High wall mining is a method of recovering coal from seam exposed either by mechanical excavation methods or natural erosions. This is usually associated with strip-mining (opencast) where the stripping ratio is high and uneconomical to mine using the opencast mining method. This paper discusses the surface auger mining as deployed at Rietspruit Mine Services Proprietary Limited.

Jan 1, 2002

By E. Munnik

The Chambishi Metals Cobalt Plant in Zambia has recently installed a novel oxidation/precipitation pressure leach process as part of the COSAC (CObalt from Slag And Copper as by-product) Project. Aniron-cobalt-copper alloy, produced by the carbothermic reduction of slag, is atomized and pumped to the COSAC Leach Plant, where cobalt and copper are recovered as dissolved sulphate salts, andiron is rejected primarily as hematite. Cobalt and copper are subsequently recovered as cathode metal in the existing Chambish ioperation by conventional electrowinning. This paper examines the challenges faced during the design and subsequent successful commissioning of the COSAC Leach Plant. The challenges discussed include alloy handling, autoclave design, autoclave cooler design, residue liquor recovery and the water balance design. Keywords: Chambishi, Avmin, COSAC, Zambia, Copperbelt, cobalt, copper, alloy handling, pressure leach, autoclaves, cooling, filtration.

Jan 1, 2003

By M. Kumral

Raw material fed into a processing or refining plant is required to be uniform in composition for several reasons. When the mined ore is highly variable in quality the only way to ensure consistency is to homogenize the ore prior to the process. The problem is more complicated in the case of multiple ore sources. The idea behind the research is that theoretical blending ratios can serve not only to meet predefined specific criteria but also to reduce grade fluctuations of variables under consideration. In this paper, the problem is formulated as a quadratic programming problem, whose objective function is in quadratic form and constraints are linear. A case study was conducted on a data set from an iron orebody to demonstrate the technique. The objective was to minimize the blend variability in terms of each variable (in this study, iron, silica, alumina and lime) grade of ores extracted in three different production faces. The stockpile capacity, lower and upper limits of each variable satisfying operational requirements and non-negativity were constrained to the model. A modified simplex method developed by Wolfe was used for solving the blending and homogenization problem. The promising results can be used as apart of the stacking and reclaiming design. Keywords: blending and homogenization problem, quadratic programming, Wolfe method.

Jan 1, 2005

By Deur T. A. M. Saayman

Die sesde jaarlikse Ingenieursimposium is in September by YSKOR, Vanderbijlpark gehou. Rierdie simposium, wat deur Ingenieurs-in-Opleiding georganiseer word, bied aan die Ingenieurs-in-Opleiding die geleentheid om referate te lewer oor projekte wat gedurende hul drie jaar opleidingsperiode uitgevoer word. Continuing education courses The following courses are to be given in the near future in The Netherlands. Coal trade, transportation, and handling . The 4th Coal Trade, Transportation and Handling Conference and Exhibition, CoalTrans '86, will take place the Rai Congress Centre, Amsterdam, from 10th to 12th June, 1986.

Jan 1, 1986

By O. Gunaydin

Performance measurements of large-diameter circular saws were conducted on eight different carbonate rocks in marble factories located in some areas of Turkey. Rock samples were collected from these factories for laboratory tests. Uniaxial compressive strength, tensile strength and impact strength were determined in the laboratory. The brittleness of B3 (the ratio of compressive strength minus tensile strength to compressive strength plus tensile strength), the brittleness of B5 (the product of percentage fines in the impact strength test and compressive strength) and the brittleness of B8 (half of the product of compressive strength and tensile strength) were calculated from the test results. Hourly slab productions were correlated with brittleness indexes. It was concluded that sawability of carbonate rocks can best be predicted from the brittleness of B8.

Jan 1, 2004

By B. Elevli

The aim of this paper is to demonstrate the implementation of multicriteria analysis in selection of the most suitable underground ore transport system for a chromite mine in Turkey. The related problem includes five possible ore transport systems and six criteria to evaluate them. The adopted evaluation and ranking method for this study is PROMETHEE. PROMETHEE I revealed a partial order of alternatives where incomparability exists. PROMETHEE II gave the absolute ordering of alternatives. The results have shown that the PROMETHEE method can be successfully used in solving mining engineering problems. Keywords: multi-objective, decision analysis, mining, ore transport system

Jan 1, 2004

By D. W. Dew

Billiton Process Research has carried out extensive research over the past four years to develop new process technology using bioleaching for extraction of copper and nickel from their sulphide concentrates. Continuous pilot scale and laboratory batch testwork has been carried out with adapted mesophile bacterial cultures at40°C?45°C, moderate thermophile cultures at 50°C?55°C and thermophile cultures at 65°C?85°C. Pilot scale work has demonstrated the commercial viability of mesophile cultures for bioleaching of secondary copper sulphide and nickel sulphide concentrates. Moderate thermophiles offer benefits in terms of reduced cooling requirements for commercial reactors and, in the case of bioleaching of nickel concentrates, some selectivity over bioleaching of pyrite. Continuous pilot scale testwork has shown that thermophiles achieve efficient bioleaching of primary copper sulphide and nickel sulphide concentrates, giving much higher recoveries than achieved by bioleaching with a mesophile or moderate thermophile culture.

Jan 1, 2000

Council for 1999/2000 President M.H. Rogers President Elect Dr L.A. Cramer Vice Presidents Senior A.A.B. Douglas Immediate Past President J.R. Dixon Junior S.J. Ramokgopa Honorary Treasurer J.A. Cruise

Jan 1, 2000

By A. V. Aleksandrov, T. N. Aleksandrova, N. V. Nikolaeva

Using complex thermal analysis methods, flotation concentrates were classified depending on what the organic and nonorganic carbon form is. The possibility of ultrafine particles of valuable components (noble metals and diamonds) extraction using physical actions of different genesis in the processing of ‘unconventional’ mineral raw materials is considered in the paper. Electromagnetic treatment is one of new technologies in the field of mineral processing. The features of the electromagnetic effect on substances include uniform heating throughout of the volume, high speed and low inertia of heating, as well as the possibility of selective heating. A selection of studies including gravity, flotation and extraction methods of enrichment using energy effects, as well as thermal analysis was conducted to establish the availability and possibility of extracting valuable components. Due to microwave and high-temperature exposure, minerals and gas-liquid inclusions are decremented, and crystal-chemical water is released, resulting in additional defects. As a result, self-cleaning of sulphide minerals from atoms of scattered gold occurs by distilling it into peripheral parts of grains and intergranular space, where ultradispersed individuals are formed. Keywords: Refractory gold-bearing ores, physico-chemical properties, ore preparation, flotation, modelling, simulation, selection

Jan 1, 2020

By P. A. Olubambi

The leaching of zinc and copper from Nigerian bulk sulphide ore with sulphuric acid in the presence of hydrogen peroxide was studied. The aim of the study was to investigate the effectiveness of hydrogen peroxide as an oxidant for the sulphuric acid leaching of zinc and copper from a complex sulphide ore. Distribution of elementals within the various particle sizes was initially determined by ICP-OES and XRF to provide a basis for explaining the dissolution process. The effects of concentration of hydrogen peroxide, particle size, stirring speed, and leaching time at a constant temperature of 298K were studied. There were variations in elemental and mineralogical composition within the different sizes. The concentrations of zinc and copper reduced as particle size decreased while silica, sulphur, iron and lead contents increased. Dissolution results showed that the leaching rate of copper was lower than that of zinc. The highest recoveries of zinc and copper were obtained at a leaching time of 180 minutes, stirring speed of 160 rpm, particle size of 75 µm and a concentration of 1M H2SO4/1MH2O2. It was observed that the leaching rate of zinc and copper increased with increasing hydrogen peroxide concentration. Increased stirring speed had a negative leaching effect as it promotes hydrogen peroxide decomposition. Keywords: Nigerian sulphide ore, zinc, copper, hydrometallurgy, sulphuric acid, hydrogen peroxide.

Jan 1, 2006

By P. A. Olubambi

The leaching of zinc and copper from Nigerian bulk sulphide ore with sulphuric acid in the presence of hydrogen peroxide was studied. The aim of the study was to investigate the effectiveness of hydrogen peroxide as an oxidant for the sulphuric acid leaching of zinc and copper from a complex sulphide ore. Distribution of elementals within the various particle sizes was initially determined by ICP-OES and XRF to provide a basis for explaining the dissolution process. The effects of concentration of hydrogen peroxide, particle size, stirring speed, and leaching time at a constant temperature of 298K were studied. There were variations in elemental and mineralogical composition within the different sizes. The concentrations of zinc and copper reduced as particle size decreased while silica, sulphur, iron and lead contents increased. Dissolution results showed that the leaching rate of copper was lower than that of zinc. The highest recoveries of zinc and copper were obtained at a leaching time of 180 minutes, stirring speed of160 rpm, particle size of 75 µm and a concentration of 1M H2SO4/1MH2O2. It was observed that the leaching rate of zinc and copper increased with increasing hydrogen peroxide concentration. Increased stirring speed had a negative leaching effect as it promotes hydrogen peroxide decomposition. Keywords: Nigerian sulphide ore, zinc, copper, hydrometallurgy, sulphuric acid, hydrogen peroxide.

Jan 1, 2006

By M. S. M. Aljuhani

In this paper, one of the human factors that affect productivity in an underground gold mine in Saudi Arabia was investigated and analysed for the purpose of improving productivity. The human factor that was investigated is labour utilization and labour productivity. In the selected mine, labourer?s performances were measured carefully. It was found that in this mine, workers spend only 65% of the shift time in a productive work, and they spend 35% of the shift time in non-productive activities. As a result, recommendations were presented to enhance productivity in the selected underground gold mine by enhancing labour utilization.

Jan 1, 2002

By G. Bacon

The past decade has witnessed unprecedented growth in the development and implementation of solvent extraction technology in the extractive metallurgy of nickel and cobalt. Solvent extraction is proving to be a powerful tool, opening new opportunities for simpler, more cost efficient and environmentally sound metal refining processes. These advances, however, could not have been possible without the cooperative efforts between the nickel industry and the people and organizations involved with reagents, materials and equipment development and supply as well as solvent extraction research, aided by the accumulated knowledge and practical experience from the copper and uranium solvent extraction operations. This paper provides an overview of these developments and some of the challenges ahead.

Jan 1, 2002

Leinster Nickel Operations, located in Western Australia, consists of an underground and three open pit mines in relatively adverse ground conditions. This paper reviews our ground control practices in the open pits, covering aspects of ground support, wall control and monitoring. These methods have been effective in allowing mining operations to continue beneath unstable slopes. In particular, the use of Ground probe?s slope stability radar has enabled the Harmony open pit to safely operate for months following indication of failure from traditional methods. This case study highlights the benefits of investing in appropriate slope stability monitoring systems.

Jan 1, 2006