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By M. B. Cortie

The historical development of materials engineering in the mining industry Is briefly reviewed, and some of the factors currently influencing the industry in South Africa are discussed. Material usages in various parts of the mining operation are surveyed. The predominant mechanisms in the degradation of materials in mines are wear, corrosion, and fatigue. The issue of corrosion-abrasion Is considered, but it Is concluded that abrasive wear predominates in most rock-handling and comminution applications and that, in general, little economic benefit Is to be gained in those applications by the use of existing corrosion-resistant alloys. However, alloys with a measure of corrosion resistance find profitable application elsewhere in the mining environment. The use of other engineering materials such as polymers, ceramics, al1l1inium, and various ferrous alloys may be economically viable in a variety of niche situations. Identification of the most cost-effective material in each case calls for a systematic approach and some patience.

Jan 1, 1996

By M. H. Moys, K. S. Liddell

The dynamics of the ball load within a wet-grinding mil are examined, using measurements of torque and load position, The test equipment provided an accurate torque measurement, and the toe and shoulder positions of the load were measured by the use of a conductivity probe mounted in the mill shell. Both the variables tested-mil filing and rotational speed-influence the position of the load, and hence the torque, and have interactive effects on both the torque and the load position, An increase in mil speed and filing causes the torque to increase to a maximum value, after which further increases in speed or filing cause the torque to decrease. The position of the load toe is influenced only by the filing up to speeds of approximately 80 per cent of critical, whereas the speed and filing both cause the load shoulder to rise as their magnitudes are increased, The power drawn by the mill is predicted by the use of published equations, and these values are compared with the measured power draw.

Jan 1, 1988

By C. Musingwini, M. Woodhall

An often overlooked factor in the analysis of mine layouts and schedules is technical operating flexibility, mainly due to its nebulous nature. If one glosses over technical operating flexibility the resultant mine layouts and schedules tend to be sub-optimal. The need to incorporate technical operating flexibility into the analysis and comparison of mine layouts and schedules is increasing in importance. This paper illustrates the nature of technical operating flexibility, reviews previous work on valuing operating flexibility and proposes how technical operating flexibility can be quantified for tabular reef mines by using a platinum reef deposit as a case study. Once technical operating flexibility is quantified it becomes possible to explore its incorporation into the analysis of mine layouts and schedules and subsequent optimization processes. The work described in this paper is part of a current PhD study at the University of the Witwatersrand. Keywords: mine plans, layouts, schedules, technical operating flexibility, ore availability.

By B. Gamble

Solid Energy's project evaluation process utilises a standard staged gate approach, with five levels leading ultimately to project execution (level 6). For a project to progress through each level, specific financial criteria need to be satisfied. Solid Energy primarily use value based (discounted cash flow) metrics to support investment decisions. Within this approach Solid Energy utilise a number risk-based techniques to quantify project uncertainty. This includes the use of risk-based probabilistic analysis using Monte Carlo simulation and probability-based scenario analysis. Figure 1 shows the net present value (NPV) cumulative probability. Project risks are identified through comprehensive risk workshops. The output of these workshops (list of key risks, ranges of uncertainty and probability of occurrence), is quantified within the financial models. Incorporating this risk information on a probabilistic basis allows an investment decision to be made with a robust knowledge of the range of possible project outcomes along with the likelihood (probability) of those outcomes occurring, for example 80 per cent confidence that the project value will be greater than NZ$10 M, 50 per cent confident it will be greater than NZ$50 M and ten per cent confident it will be greater than NZ$70 M. Incorporating risk implicitly into the financial analysis allows the business to easily evaluate/measure projects with different risk profiles. The detailed risk analysis does away with the complexity of arbitrary risk-based hurdle (discount) rates, as projects can be evaluated based on their specific risk characteristics. Whether a project will progress to the next level of investment and ultimately into implementation depends firstly on the value assessment in comparison with the associated risk/uncertainty, and secondly matching this with the businesses appetite for risk. At Solid Energy standard criteria are used for specific project evaluations, but in addition projects are considered on a portfolio or strategic basis also. Solid Energy attempts to maintain a mix of low risk (low value) projects with some high risk (high value) opportunities. The mix of projects must remain in line with the shareholders' risk appetite. One of the keys to a successful investment decision is ensuring that the appropriate information is available to decision-makers so that they may proceed with a comprehensive understanding of the risks and impacts associated with the decision.

Jan 1, 2007

By S. Ganguly

Slag samples taken from adjacent to the furnace wall of a submerged arc ferromanganese smelting furnace have been found to contain high concentrations of K2O. To characterize the phase equilibria relevant to these slags experimental studies have been carried out to determine pseudo-ternary sections of the form ?MnO?-CaO-(SiO2+Al2O3) with a fixed Al2O3/SiO2 weight ratio of 0.65 and 6.0 wt% K2O for temperatures in the range 1523-1673 K. In the pseudo-ternary section investigated the primary phase fields are found to be mullite, 3Al2O3?2SiO2; corundum, Al2O3; spinel, MnO?Al2O3; manganosite solid solution, (Mn,Ca)O; dicalcium silicate,2CaO?SiO2; gehlenite 2CaO?Al2O3?SiO2; anorthite CaO?Al2O3?2SiO2; kalsilite KAlSiO4 and leuciteKAlSi2O6. It was found that the presence of K2O in the slag decreases liquidus temperature in the anorthite and gehlenite primary phase fields. The manganosite primary phase field is expanded in the direction of increased (Al2O3+SiO2) and the liquidus temperatures in the manganosite primary phase field are increased significantly with the presence of K2O in the slag.

Jan 1, 2007

By H. Scott-Russell

Much of the technology and methodology extensively employed in current mining operations is in the mature phase of its lifecycle and, consequently, subject to the principle of diminishing returns. It is probable that future gains in productivity and safety of the magnitude essential for the sustained economic viability of the industry will be derived only from a determined technological development programme. The history of trackless mechanized mining, which represented a radical change in methodology in deep-level gold mines, is reviewed. The benefits and obstacles to the realization of the full potential are highlighted. Similarly, an overview is given of alternative mechanization developments in South Africa. In addition to the development and application of advanced technology, an envelope of operating parameters relevant to each methodology must be engineered to facilitate the site-specific selection of the most appropriate. Furthermore, a mechanism for the evaluation of cost effectiveness is essential to the decision-making process. The narrow, tabular orebodies of relatively low dip that are encountered in the South African hard-rock mining industry make the design and manufacture of a comprehensive range of stoping equipment extremely difficult. The machinery that has been available to date has demonstrated only limited site-specific success. The development of suitable machinery must necessarily be initiated and driven by the South African mining industry in collaboration with the major equipment manufacturers in the world.

Jan 1, 1993

By A. O. Filmer

In the mining and metals industry, business strategy demands that leaders extract more from any set of capital assets. This improvement is achieved through a combination of continuous improvement and upgrading of the assets. Continuous Improvement involves a series of incremental changes in the workplace to stabilize the process, remove waste, and test the limits of process capability. Enhanced Technology involves the replacement of an existing as set with a different process or equipment, to achieve a similar function in a more efficient and effective manner. The paper compares and contrasts the two methodologies and outlines the key business considerations which dictate how and when to select one or other improvement method. The paper also addresses the implications for these two improvement methods for those undertaking R&D in support of the mining and metals business.

Jan 1, 2009

By R. Rubin, P. A. Laxen, G. S. M. Becker

An account is given of developments in the use of activated carbon for the recovery of gold from cyanide solutions. The carbon-In-pulp process employed at the Homestake Mine is described, and its various applications in South Africa and their effectiveness are discussed. Probable future work on the carbon-in-pulp process and other possible applications of carbon for the recovery of gold are outlined.

Jan 1, 1979

By J. H. Bulloch

A study of fatigue-crack growth in a rail steel and an associated weld metal showed that fatigue cracks in the deformed rail steel had slightly higher growth rates than in undeformed rail steel. The crack growth in the weld metal was appreciably faster than either and exhibited plateaux that were above the upper bound reported for rail steels, The cyclic-life curves showed that, over an indicated service period of 8 years, both the deformed and the undeformed rail steels should not be prone to fatigue failures under the defined mechanical conditions, For the weld metal, the cyclic-life curves indicated the possibility of premature fatigue failures but, as al the input parameters represented a 'worst case' situation, this assessment could wel be ultra-conservative. In the rail steels at low levels, the extension of the fatigue cracks occurred by ductile striated growth. At a Kmax level of 35 MPa .J/n, cleavage facets formed initially on the surface of the fatigue fractures, and their incidence increased with Kmax until the onset of fast failure, The microstructure of the deformed rail steel exhibited cleavage facets at a slightly lower Kmaxvalue, and contained more cleavage facets at a given K level, than the microstructure of the undeformed rail steel. The average size of the cleavage facets agreed well with the pearlite nodule dimensions of 60 to 100 ILm. The microstructure of the weld metal was much coarser and contained columnar grains. At al f.K levels, the dominant fracture mode was cleavage, with small isolated regions of ductile striated fatigue cracks. The size of the cleavage facets varied from 150 to 600 ILm, and such a variation may be explained by the fact that cracking generally occurs in association with the pro-eutectoid ferite phase, and that this phase is distributed along some boundaries of prior austenite grains and the boundaries of the coarser columnar grains.

Jan 1, 1987

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 D. P. Venter

When Oryx Mine down-scaled in 1994, focus was placed on development, with the primary aim being the exposure and proving of ore reserves. In order to achieve this aim, development ends had to be advanced to reef at the maximum possible rate. This in turn called for support methods which could keep up with the advancing faces, taking up minimum space and time for installation, while providing on the face a real coverage and effective long-term support. In the majority of the development ends which were located in fairly competent ground, the grouted rod development support proved to be adequate until such time as secondary support in the form of meshing and lacing could be installed. The ends developing towards the eastern boundary of the mine, especially in the ?C? block, encountered extremely adverse ground conditions due to the presence of smectite zones within the footwall quartzites. Smectites are a group of montmorillonite clay materials, mainly composed of hydrous aluminosilicates. They occur as minute platy crystals in the rock mass and are especially notable for their ability to absorb liquids. Generally, the zones are found in between the bedding planes of the host rock, and may vary considerably in thickness over short distances. Wherever the smectites were exposed by the development blasting, the rockwalls weathered as the smectites absorbed water and the condition of the tunnel rockwalls deteriorated rapidly. When the smectites were left exposed and allowed to weather, it became almost impossible to install secondary permanent support such as meshing and lacing at a later stage. To minimise the exposure time and subsequent deterioration of the smectite zones, it was recommended that all development ends encountering smectites be shotcreted as soon as possible after blasting. In developing a shotcreting support methodology, both a drycreting and wetcreting system were investigated. The situation at the time ruled out the use of a wetcreting system on the basis of the extensive and costly infrastructure required, as well as its limited manoeuverability. Instead, it was decided to opt for as maller scale but more manoeuverable drycreting system. The system utilized a number of portable drycrete machines with pre-bagged cement, which could support several development ends in close proximity. Initial trials using normal 30 MPa shotcrete on 19level proved successful and the system was implemented.

Jan 1, 1998

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

Jan 1, 2014

By B. Rezai, Z. Pourkarimi, M. Noaparast, S. Chehreh Chelgani

Nanobubbles (NBs) flotation separation can be an indicator for improving the efficiency of fine particles through the conventional process. Since flotation reagents such as frothers can reduce bubble size, they can potentially be used for the generation of NBs and develop a selective NB flotation separation. This study explored the flotation separation of fine phosphate particles from their associated minerals in the presence of NBs, which were generated by using a phosphate flotation reagent (Flo-YS: collector-frother). The results of flotation tests showed that in the presence of NBs, the flotation efficiency was significantly improved. However, in the presence of NBs, surface chemistry analyses (Fourier Transform Infrared Spectroscopy and High-Performance Liquid Chromatography) illustrated that the collector adsorption on the surface of phosphate particles decreased. A comparison between outcomes of various phosphate flotation conditions indicated that increasing the flotation efficiency in the presence of NBs may be due to the aggregation of fine particles by the generated NBs, and also selective adsorption of NBs (hydrophobisation) on the surface of particles. In other words, generating NBs by selective collectors may increase efficiency and decrease the collector consumption of a flotation process. Keywords: Phosphate, selective separation, fine particles, collector-frother, efficiency, mechanical flotation cell

Jan 1, 2020

By M. Lange

The postulation that primary platinum group metal (PGM) matte will chemically react with magnesia-chrome bricks when temperatures exceed 1500°C was tested. Magnesia-chrome brick samples were heated in contact with matte at 1300°C to 1750°C for 30 minutes, after which the refractory samples were analysed using reflected light microscopy and scanning electron microscopy. The samples were all completely penetrated by matte. As the temperature increased the matte also penetrated the fused aggregate grains and disintegrated them. The chromium concentration of the matte inside the refractory samples was found to be slightly higher than that of the bulk matte. At temperatures of 1500°C and higher, MgO, FeO, and magnesium-rich silicate crystals could be identified in the matte directly adjacent to the refractorymatte interface. Phase relations clearly indicated that chemical reactions take place between primary PGM matte and the magnesiachrome refractory material at temperatures above 1500°C, but that these reactions are more complex than expected from FactSAGE® calculations.

Jan 1, 2014

Dr R. E. Robinson, Pr. Eng., obtained a B.sc. (Chem. Eng.) cum laude from the University of the Witwatersrand in 1950 and a Ph.D. (Eng.) from the same University in 1953, where he was awarded the Haikes Memorial Medal for Industrial Chemistry. Professor G. G. Garrett was appointed Professor of Physical and :Fabrication Metallurgy in the Department of Metallurgy at the University of the Witwatersrand in June 1980, and in January 1984 he became Head of the Department. Mr P. A. van Wielligh, Pr. Eng., climbed the mining ladder in the hard way, starting as a Mine Surveyor in 1936 and working his way up as Chief Surveyor, Underground Manager, Mine Manager, and Consulting Engineer, to Executive Director, including the intermediate steps. Mr H. E. James, Pr. Eng., is a graduate in Chemical Engineering from the University of the Witwatersrand. Both his B.sc. degree (1961) and his M.sc. degree (1964) were obtained on bursaries, the former from Gold Fields of South Africa and the latter from the Atomic Energy Board. Mr G. Pienaar, Pr. Eng., obtained a B.Eng. (Met) in 1967 and an M.Eng. in 1973, both from the University of Pretoria. Dr A. K. Haines, Pr. Eng., obtained all his degrees from the University of Natal, finishing with a. Ph.D. in 1971. Mr B. C. Alberts, Pr. Eng., obtained his academic training at the University of Pretoria, where he was awarded B.sc. degrees in both agricultural engineering (1963) and mining engineering (1965). Mr H. C. van Zyl, Pr. Eng., holds B.sc. degrees in mining engineering (1968) and civil engineering (1972), both from the University of Pretoria.

Jan 1, 1984

By J. W. Wilson, J. G. Taylor

The mechanization of haulage drilling in the gold mines of Anglo American Corporation by J. w. WILSON, Ph. D., C.Eng., M.AIME, F.!.Min.E., F.I.M.M. (Fellow), and J. G. TAYLOR, A.C.S.M., C.Eng., M.!.M.M. (Visitor) Some one-thousand kilometres of tunnels are mined annually in the gold mines of South Africa. Until two years ago, mechanized drilling on South African gold mines was not an economic proposition because of the availability of inexpensive labour and the fact that mechanized equipment developed for other mining markets could not perform satisfactorily in the tough, abrasive quartzites of theWitwatersrand System. A project team from the Technical Development Services Organisation of the Anglo American Corporation, in collaboration with various manufac turers of drill rigs and drill steel, has been concerned with the development of suitable equipment for mechanized main-haulage drilling. After two-and-a-half years of extensive testing and development of drifters, drill steels, and bits, many of the problems encountered have been sotved, and gradually jumbos mounting pneumatically and hydraulically powered drifters are being phased into production on various gold mines of the Group. A description of the development work is given, and actual operating results are recorded, together with details of the drilling and blasting techniques used.

Jan 1, 1975

By M. Akyüzlü

The equilibrium between carbon-saturated Fe-Cr-Si-C alloys and SiO2-CaO-MgO-A2O3-CrO2-FeOy slags was studied under atmospheres of argon and carbon monoxide at temperatures of 1500 and 1600°C. The equilibrium distribution of chromium, silicon, and iron between the slag and the metal phases was determined for different compositions of both phases under different atmospheres and temperatures. It is shown that silicon transfer from the slag to the metal increases with increasing temperature, decreasing carbon monoxide partial pressure, decreasing carbon content of the metal, increasing chromium-to-iron ratio of the metal, increasing silica content of the slag, and decreasing lime-to-alumina ratio of the slag. Some activity calculations were made for the experiments conducted at 1600OC in a carbon monoxide atmosphere. It is also shown that a decrease in the iron content and an increase in the slag basicity decrease the chromium content of the slag. A major proportion of the chromium present in the slag was found to be in the divalent state under the highly reducing conditions prevailing in the experiments. The chromous capacities of these slags were calculated and were found to decrease with increasing basicity.

Jan 1, 1992

By A. Mainza, I. Govender, Elbasher M. E. Ahmed

A mechanistic description of axial segregation in rotating drum flows remains an open question. Consequently, optimal mixing of grinding balls and rocks for efficient breakage, maximum production of fines, and slurry transport is seldom achieved. Experimental and numerical studies of granular mixtures in rotating drums identify alternating axial bands that eventually coarsen in the long-term limit. Most models of axial segregation are limited to binary mixtures and cannot always predict the logarithmic coarsening effects observed experimentally. A key missing factor is a robust description of the axial free surface profile that is valid across a wide range of flow regimes. We present a practical model of the axial free surface profile by linking it to readily-derived geometric features of the cross-sectional S-shaped free surface profile. A parametric study shows good agreement with experimental measurements reported in the literature and heuristically valid trends.

May 1, 2021

By S. M. Spottiswoode, A. J. Jager, N. C. Gay, J. A. Ryder

The South African mining industry is at present planning to extract orebodies at depths of up to 4 km. To do this cost effectively and, at the same time, ensure safe working conditions for mining, the personnel will require both the development of new strategies and the implementation of current rock-engineering technological developments on a wide scale. This paper covers most of the technological developments likely to be required for mining at very high stresses, but it is clear that improved regional support systems will need to be developed to ensure defective stability of the rockmass during mining operations. Similarly, it is clear that improved strategies for mining in large-scale geologically disturbed areas, where slip on faults or dykes can result in wide-spread rockburst damage, will have to be addressed

Jan 1, 1995

By M. Z. Emad, S. Raza, K. Jalil, M. A. Raza, M. U. Khan, S. A. Saki

Dimension stone mining is Increasing because of growing demand from the building and construction industries. Diamond wire saw cutting is a popular dimension stone mining technique around the world. Estimation of the production cost for this method is critical for these operations. n this research a production cost model was developed for the mining of granite using a diamond wire saw. Cost and production data were collected from a granitic dolerite operation in Pakistan for a 4.5-year period, and analysed to identify the cost components. Fuel (34%), labour (15%), consumables (40%), and maintenance (5%) were found to be the four major cost components in this operation. A regression-based dimension stone production cost model incorporating statistically significant variables was developed. The data presented a strong correlation of production cost with fuel, labour, and consumables costs. Finally, a production cost model based on the consumption cost of diamond wire is presented. The model was verified using actual production cost data, which indicated 95% (R2 = 0.95) variance in the data between the predicted and actual production cost values. The model may help field engineers in computing their dimension stone operational cost during the cutting phase.

Nov 6, 2023