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By K. I. Afewu, L. C. Woollacott

The design of in-pulp adsorption vessels in the gold industry has, for the most part, been seen as a problem involving the suspension of fine particles o ore in a slurry. The need for the vessel to be designed as a mass-transfer contactor has received insufficient attention. The current series of papers addresses this need The previous paper considered the question of the scale dependence of the film transfer coefficient. This paper examines the mixing considerations that are relevant. A review of the literature and an examination of a limited set of data provide some insight into the mixing conditions needed for the dispersion of the particles of adsorbent. The mixing requirements for the suspension of the ore particles are also considered, and conclusions are drawn in regard to the design of mechanically agitated vessels for gold in-pulp adsorption circuits.

Jan 1, 1995

By L. A. Vermeulen

Electronic circuits were developed and successfully utilized to record, store, and continuously transmit to a remote station physical information relating to the impacts of pebbles on the shell liners of an industrial pebble mill, and of electrical conduction in the mineral pulp. The information was obtained by the instrumentation of some of the bolts that are used to clamp the liner blocks and litter bars to the mill shell. The features associated with the impact and conduction signals have been interpreted, and it is shown that such signals can lead to continuous measurements of the volume of the load in an industrial mill. Information is given regarding the angular distribution of direct impacts of the pebbles onto the shell liners, the power required to promote impacts, the amount of material in flight, the impact velocity, and the average number of direct impacts with the shell liner that any given pebble undergoes in unit time in the given mill.

Jan 1, 1984

Book review HOEK, E., and BRAY, J. Rockslope engineering. London, The Institution of Mining and Metallurgy, 1974. £5. NIM reports Report no. 1625 The determination of uranium and thorium by the use of delayed neutrons. Report no. 1626 Formation constants of zinc chlorocomplexes in perchlorate medium. Report no. 1629 The thermodynamics of the formation of complexes of silver with some substituted pyridines. Report no. 1630 An electrochemical investigation of the dissolution of copper, nickel, and copper-nickel alloys in ammonium carbonate solutions. Report no. 1640 A semi-automatic titrimeter for cyanide analyses. Report no. 1644 Prospects for the recovery of minerals from the sea. 1974 A.S. & T.S. National Award Professor D. C. Midgley, President of the Associated Scientific and Technical Societies of South Africa, today announced the winner of the 1974 A.S. & T.S. National Award. 1974 G.W. en T.V. Nasionale Toekenning Professor D. C. Midgley, President van die Geassosieerde Wetenskaplike en Tegniese Verenigings van Suid- Afrika het vandag die wenner van die 1974 G.W. & T.V. Nasionale Toekenning aangekondig.

Jan 9, 1974

By A. Hinde, M. H. Moys

Tailings from metallurgical plants, when deslimed with hydrocyclones, provide a valuable source of material for the backfilling of mines. The effectiveness of this material as a support medium is a sensitive function of its particle- size distribution and water content. It is therefore important that the hydrocyclone-classification plants used to prepare the backfill are operated efficiently, and that the effects of feed disturbances on the composition of the backfil are minimized. This paper addresses the problem of the design, control, and optimization of classification plants to satisfy this need. The development of a computer program to simulate the dynamic behaviour of a hydrocyclone circuit of any given configuration is described. The use of the simulator to investigate the relative performance of conventional and innovative control strategies for single-stage and two-stage circuits is discussed in depth. The results of simulation studies are presented that indicate there is considerable scope for improving the performance and cost-effectiveness of backfill-classification plants.

Jan 1, 1991

By H. S. Eisner, J. -P. Leger

Published South African fatality and injury statistics for mine accidents are investigated. Where possible, the South African statistics are compared with those of other countries. Commonly held attitudes to the South African accident experience are also examined. Analysis reveals that the published accident rates present a more favourable picture than the rates actually experienced by underground workers. In addition, fatality rates in South African underground gold and coal mines do not differ significantly and have remained stable over the past decade, although the injury rates have decreased rapidly. No evidence was found that this is due to improved safety, and a comparison with international fatality and injury data suggests that it is not. The underground fatality rate for South African coal mining is, on average, eight times that of the UK, four times that of all EEC coal mines taken together, and over double that of the USA. Despite the unreliability of the injury rates, much has been made in South Africa of their rapid decline, an emphasis that appears to be misplaced.

Jan 1, 1988

By R. B. MacGillivray

The No. 2 Seam at Van Dyks Drift Colliery was found to be made up of six easily recognizable bands or plies of differing qualities. Not only did the plies differ from one another in quality, but their thickness and quality varied laterally across the mine. The economic production of a Iow-ash blendcoking coal for supply to the Japanese Steel Mills called for the mining of different portions of the seam. The portions that could be extracted economically varied in thickness and position within the No. 2 Seam across the mine. A unique system of selective mining had to be developed involving the dispatch of two separate streams of coal out of the mine. Conventional American mechanized pillarand-stall mining was used, and the productivity was improved by the installation of twin conveyor belts into a double-header section. The method of grade control that was instituted to ensure efficient extraction of the available coal reserves is described.

Jan 1, 1985

By G. Panopoulos, R. P. King, A. H. Juckes

The flotation characteristics of two South African coals were investigated: one from the Dumacol Colliery in Natal, and the other from Landau Colliery in the WitbankCoal Field. Samples of fine coal (smaller than 1 mm)were studied, the Dumacol coal showing significantly better ash-liberation characteristics than the Landau coal. Neither coal was found to produce satisfactory flotation concentrates, except at very fine sizes. The poor flotation performance can be ascribed to the non-selective flotation of unliberated particles that may contain considerable quantities of ash. Flotation recoveries were greatest for particles between 100 and 200 µ m, and fell of rapidly as the size increased above 200 µ m. Very fine particles were found to float adequately, and acceptable concentrates can be made at comparatively high yields from materials smaller than 75 µ m. The flotation of ultrafine coal was demonstrated successfully in a continuous pilot plant. This result opens the way to a potentially viable industrial process for the beneficiation of ultrafines from the Witbank No. 2 seam, which for decades has been regarded as non-floatable.

Jan 1, 1986

By G. Rebel

Owing to the helical construction of the wires and strands in a triangular-strand rope, a torque is generated when the rope is restrained and tensioned. When a rope is suspended vertically, there is a load differential along its length due to the self weight of the rope. This load differential gives rise to an initial torque differential m the rope. Since the rope is constrained only at the conveyance and sheave wheel, the torque along its length must be constant ID order to maintain equilibrium, a variation in lay length occurs so that the lay length at the conveyance end decreases, and the lay length at the sheave end increases, from the manufactured state. The tension-torsion testing of steel-wire ropes is discussed, and it is shown how the results of the tests can be used to predict static in-shaft torsional behaviour. The expected changes in strand lay length in very deep shafts (deeper than 2500 m) are calculated, and the associated problems and of severe changes m lay length on rope endurance and safety are discussed. Examples of current in-service rope distortions such as kinks and corkscrews are shown.

Jan 1, 1996

By N. C. Gay

During the past two to three years, there have been some significant Improvements to the quality of the support systems being used on South African gold mines, and the Implementation of these new developments, together with more worker awareness has been instrumental in reducing rock-related accidents, particularly in deep mines. This paper provides guidelines to mine and group personnel on how to monitor the ongoing Implementation of new technologies and so ensure the benefits that will accrue in terms of mine safety and profitability. Particular attention is given to the establishment of auditing procedures that will enable management to assess the benefits obtained from new technologies, as well as providing Improved maintenance procedures and procedures for the optimum utilization of seismic data. The areas that receive most attention include support systems for stopes and tunnels, such as hydraulic props, backfill, and rockburst-resistant tunnel support; stope and regional support layouts; mine standards; and staffing of the rock-engineering department. The paper includes a draft audit form and a hypothetical example of an audit report

Jan 1, 1997

By D. Limpitlaw

As coal mining often results in the generation of acid mine drainage (AMD), careful planning and management of the water on such mines is required. A colliery in Mpumalanga recently sponsored independent research into the pollution-ameliorating potential of a natural wetland that has been receiving AMD for at least two decades. Samples of the sediment collected in the wetland were subjected to nine stages of sequential extraction in a determination of the distribution of the metal species present. The samples were then analysed for aluminium, iron, and manganese. The concentrations of sulphate-reducing bacteria (SRB) were also determined. The SRB concentration was found to increase with distance downstream (away from the source of pollution). An analysis of the sediment speciation data indicated that metal immobilization may be optimal in areas where the organic adsorption of metals is at its greatest. The analysis also provided evidence of the biogeochemical improvement of the water quality as the AMD passed through the wetland environment. The metal species present did not correlate strongly with the SRB populations; nor did the soluble species correlate with the species formed over long periods of time.

Jan 1, 1996

By S. M. Spottiswoode

A simple method for the application of excess shear stress (ESS) analysis to the mining of planar reefs is examined. The potential for seismicity associated with mining is expressed as the calculated increase in ESS on a regular grid of points 50 m above the reef, and is compared with observed seismicity around a deep-level, relatively geologicaly-undisturbed gold mine. Thirty regions were studied, involving over 2000 seismic events with magnitudes greater than 1,5 on the Richter scale and associated with almost 2 million square metres of stoping. The total seismicity, measured either as the number of seismic events or as the total radiated energy, corelated more closely with changes in ESS than with ERR. The incidence of rockbursts also favoured the ESS model. Corelation coeficients of around 0,8 for seismicity and ESS indicated that the assumptions inherent in the method used are collectively reasonable. The total seismicity in each region was found not to be strongly controlled by the presence of dykes and faults, although numerous individual seismic events were located close to such features.

Jan 1, 1988

By N. Birtek, R. P. King

The washability characteristics of fine South African coals were measured and were found to be well characterized by an M-curve having the equation Z = aQb exp(cQ) x dQ, where Z is the ash content per 100 units of total feed and 0 is the mass yield. Parameters a, b, c, and d were determined for 23 different samples of coal from important coal seams in the main South African coalfields in the size range 0,0025 to 1 mm. The relationship between ash content and relative density was determined and correlated by means of two linear relationships. This characteristic behaviour was explained in terms of the liberation of macerals and the different association between the mineral mater and the two major macerals vitrinite and inertinite. The results obtained in this study can be used to calculate the expected performance of an ideal separation process, and can also be used as input for the simulation of real beneficiation plants. An example is worked through in detail to illustrate the method of calculation.

Jan 1, 1990

By J. D. Salter

Most diamonds are liberated from their ores by crushing. Diamond and other coarse grained mineral ores require carefully optimised crushing circuits. Recent advances in computer technology have made possible the on-line capture of crushing plant performance data and, hence, the accurate empirical modelling of the crushing process. Such models are used in simulation studies to determine the optimum operating conditions for a given plant. A system is described which allows operating data from mineral treatment processes to be logged. Up to 16 channels of data may be recorded simultaneously at sampling rates in the kiloHertz range per channel. A data storage and analysis procedure is described which allows the system to make full use of its sampling capabilities.

Jan 1, 1987

Edward J. Stephenson. Extractive metallurgy. Recent advances. Park Ridge (New Jersey), Noyes Data Corporation. James L. McCall and P. M. French (eds.). Interpretive techniques for microstructural analysis. 1977. Institution of Mining and Metallurgy. Prospecting in areas of glaciated terrain. London, the Institution, 1977. £16 ($D.S. 30). NIM reports Report no. 1928 A liquid-nitrogen monitor for lithium-drifted germanium detectors. (21st Nov., 1977). Report no. 1931 The equilibrium between the slag and the metal in the production of low-carbon ferromanganese. (14th Nov., 1977). Report no. 1934 The spectrometric analysis of chromium-bearing materials with particular reference to ferrochromium slags and chromite ores. (30th Nov., 1977). Report no. 1935 The construction and testing of a small mixer-settler for use in the laboratory. (30th Nov., 1977). Report no. 1933 The determination of trace elements by thin-film X-rayfluorescence spectrometry, and its application to zirconium. (30th Nov. 1977). Report no. 1942 The accuracy of assays for platinum -group metals and gold. (30th Nov., 1977). Courses on geostatistics In view of the continuing demand, the University of Leeds will offer two further courses on geostatistics in 1978, each covering ten working days (3rd to 14th April, and 3rd to 14th July).

Jan 1, 1978

By R. H. C. Andrew

With the advent in recent years qf mechanization in deep-level gold and platinum mines, large quantities of rubber was are being used on both production and support vehicles. Conditions in these types of mines are extremely harsh and, as a result, we performance is significantly lower than in other types of mining such as open-cast base metal mining, where more favourable conditions prevail. Various options are available to the user to reduce tyre costs, including the use of retreads, the filing of tyres, and the repair of damaged tyres. While these methods may be generally successful in open-cast conditions, their use in deep-level mining needs to be carefully evaluated for each particular set of conditions. A basic requirement for any evaluation of we costs is the availability of reliable data on tyre performance and, for this reason, it is essential that proper tyre records are maintained This paper reviews the performance of tyres in deep-level gold and platinum mines in Johannesburg Consolidated Investment Company, Limited (JCI) over a period of about 8 years, and shows how the costs of retreading and tyre filing can be evaluated in practice. It also discusses the cost implications of repairing damaged tyres.

Jan 1, 1994

By D. G. Krige

Recent publications have demonstrated the important role that can be played by a priori information of the grade levels, variability, and spatial patterns in adjacent or nearby areas in improving the quality of grade estimates for virgin or sparsely drilled areas. A research project was therefore conducted involving the collection and analysis of extensive sampling and borehole data from 7 reefs on some 30 Witwatersrand mines. This paper shows that the 'equivalent' log variance for the two-parameter lognormal model provides a good basis for the study and comparison of the levels and behaviour of relative variances. The trends of these against the corresponding log areas were found to form distinctive patterns, which are useful for these purposes. The patterns for the Basal, Vaal, Carbon Leader, and Main Reef Series form a reasonably close group, whereas those for the V.C.R.(particularly where the facies are mixed), B Reef, and Kimberley-Elsburg Reefs (particularly for narrow channel widths) do not always conform. The patterns shown by underground chip samples are also compared with those obtained from borehole cores. It is shown how this information can be used to improve the borehole valuation of new mines and of virgin areas in existing mines.

Jan 1, 1993

By P. M. Swash

A mineralogical investigation of the main causes of refractoriness of some metalurgicaly complex gold ores in South Africa is reported. It is shown that this refractoriness is related to the presence of submicroscopic gold, carbonaceous material, pyrhotite, and base-metal sulphides. Gold ores can be classified according to their content of these components. Electron-microprobe analysis shows that gold occurs in arsenopyrite and pyrite, the gold contents of which can be up to 2700 gft. The gold and arsenic contents of these minerals are closely corelated. Furthermore, within zoned arsenopyrite grains, the concentration of gold closely folows that of arsenic. Mossbauer spectroscopy caried out on samples of concentrate from the Barberton area indicates that the submicroscopic gold within the sulphides is in a non-metalic form. The mineralogical examination of beneficiation products is important, since it sheds light on some fundamental aspects of the behaviour of the ore and gangue components during milling and flotation. Such basic information will lead ultimately to a better understanding of the problems in the beneficiation of these ores. Investigations have shown that the overmiling of the auriferous arsenopyrite and the disseminated nature of the sulphide mineralization are the main problems during beneficiation.

Jan 1, 1988

The structural design of a pavement relates to the ability of the road to carry the imposed loads without the need for excessive maintenance or rehabilitation. Current techniques for the structural design of haulage roads are empirical and based primarily on the previous experience of personnel assigned to pavement design, both in terms of the strength of the structure and the quality of the wearing course material. This has the potential for unwarranted expenditure on too thick a structure or, conversely, premature deformation leading to the need for excessive expenditure on maintenance. Furthermore, the effect of larger haulage vehicles on the structural performance of a pavement cannot be predicted. Thus, there is a need to develop a portable and practical method of structural design. This paper presents an overview of structural design methods for mine haulage roads and, through an analysis and quantification of the structural performance of existing pavements, recommends the mechanistic design procedure, together with a revised structural design and associated limiting design criteria. It is concluded that the application of the mechanistic method to a design project can reduce the costs of haulage roads construction and accrue additional benefit in terms of reduced operating and maintenance costs.

Jan 1, 1996

By L. Hermansson

Trackless mining at LKAB, Sweden by L HERMANSSON (Visitor) Because the usual means of transporting men and material to the working sites was time-wasting and uneconomical, inclined subways were installed in the Kiirunavaara Mine that permitted the access of rubber-wheeled vehicles to all underground working sites. Men and material could now be transported direct to the working site with no reloading. An increase of 8 to 12 per cent in underground productivity has been obtained by the use of this new transportation system. Rubber-wheeled vehicles are also used in development, production drilling, and loading. In December 1958, the management of the Luossavaara Mine decided to cut the costs of waste-rock haulage. The system of waste transport was the conventional one of shuttle car, rail haulage, and skip hoisting. After consideration of other methods, it was decided to re-equip the mine completely for a system of trackless transport. Results show that mining costs per ton of ore were reduced by 27 per cent, and mining costs per ton of waste were reduced by a spectacular 80 per cent. The new system has proved to be more flexible, and ore grading has been simplified since there is no longer any mixing in ore passes and chutes.

By C. Van Rhee

In dredging practice sand is eroded at very high flow velocities using water jets. The existing pick-up functions overestimate erosion. By taking the permeability into account conventional pick-up functions can be made suitable for high velocity erosion. This can be achieved by modifying the critical Shields parameter. The procedure is demonstrated using the pick-up function of Van Rijn. The theory is compared with experiments and agreement is good.

Jan 1, 2007