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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 B. G. Fordyce, W. B. Parker

A description is given of the methods used in management planning, pit-equipment selection and maintenance operator training, and formal organization of mining personnel.

Jan 1, 1979

By P. G. Henderson, G. C. Thompson

The organization and mechanized colliery management of a large by G. C. THOMPSON, B.Sc. (Min. Eng.) (Witwatersrand), M.B.L. (Member), and P. G. HENDERSON, B.Sc. (Min. Eng.) (Pretoria), M.B.A. (Member). Usutu Collieries Limited, at present the largest single producer of coal in South Africa, supplies Cam den power station. and produces 435 000 tonnes per month by conventional mechanized methods from bord-and-pillar workings in three mines. The thickness of the seams averages 2 metres, and the depth below surface varies from 15 to 150 metres. Each mine depends to a different extent on certain common facilities and services. Two of the mines are located on the same coalfield, and their rationalization would possibly be advantageous. Production policy is one of productivity with flexibility. The double-loader system is widely used, and one section at each mine is worked on single shift. Pillar extraction is practised where possible. In addition to lubrication and inspections, planned maintenance of mining equipment consists of sub-assembly replacements and overhauls. Conveyor and tractor/trailer transport is used underground. but trolley-wire locomotive haulage is being considered. The organization is such that co-ordination is relatively difficult, and certain changes could possibly improve the functioning of the engineering and mining departments. Technical and management training is carried out. Long-term planning will make use of a computer programme and will involve the investigation of other mining methods. Five-year and twelve-month plans are prepared, the planning of coal quality being based on the view that the mine and the power station together constitute a system. Control information systems make use of a remote computer terminal located at the mine. An improved integrated system is being investigated.

Jan 3, 1975

1. New Publications Tin and its uses no. 140. Greenford (England), International Tin Research Institute, 1984. Catalogue. English translations of German standards 1984. Berlin, Beuth Verlag GmbH, 1984. Mining and mineral processing operations in Canada 1983. Ottawa, Canadian Government Publishing Centre, 1984. $6.00. Canadian mineral deposits not being mined in 1983. Ottawa, Canadian Government Publishing Centre, 1984. $6.00. 2. Mintek Publications Report M42D The recovery of tantalite and cassiterite from a bulk sample of pegmatite supplied by Falconbridge Explorations Limited. (First issued 1982.) Report M46D Tests on the nature and reduction of the chlorine in fluorspar concentrate from the western Transvaal. (First issued 1982.) Report M58D An electrochemical process for the recycling of tungsten carbide scrap. (First issued 1982.) Report M59D Testwork on samples of oxidized ore from the Potgietersrus Prospect. (First issued 1982.) Report M60D The production of electrolytic manganese dioxide from furnace sludge. (First issued 1983.) Report M64D Isotope-source neutron-activation analysis for the determination of manganese in bulk samples. (First issued 1982.) Report M128 The determination of cyanide in hydrometallurgical process solutions and effluents by ion chromatography. Report M132 Mineralogical parameters influencing the acid-bacterial leachability of low-grade nickel ores. Report Ml34 The NIMROC reference materials: revised values for thorium, yttrium, lanthanum, and the rare-earth elements. ReportM140 The effect of physical and chemical factors on the corrosivity of a synthetic mine water. Report Ml44 The development of standard procedures for the evaluation of magnetite for use in heavy-medium separation. Report M145 A preliminary study of the mineralogy of the nickel occurrence at Mabilikwe Hill, northern Transvaal.

Jan 1, 1984

By S R Grano

A fundamental model, which considers the subprocesses of particle collection by bubbles in flotation, is applied to two comprehensive flotation surveys in the rougher stages of C3 concentrator, PT Freeport Indonesia. The flotation surveys focused on the collection of: ? cell-by-cell and size-by-size metallurgical, ? cell hydrodynamic, and ? pulp and surface chemistry information. The two surveys were conducted at significantly different feed tonnages, giving rise to significantly different feed particle size distributions, pulp densities and mean pulp residence times. A series of model simulations are performed with the aim of quantifying changes in copper recovery, on both a size-by-size and unsized basis, with changes in values of the hydrodynamic parameters and hydrophobicity of the copper sulfide mineral. This was carried out in an effort to identify the most promising route to increase overall copper recovery in roughing. It was found that by increasing the hydrophobicity of the copper sulfide mineral surfaces it became possible to optimise cell hydrodynamics, which targeted increased fine (-12 µm) copper sulfide mineral recovery but without adversely affecting coarse (+150 µm) copper sulfide mineral recovery.

Jan 1, 2007

By N. R. Shoko, J. Chirasha

Refractory design remains the most fundamental factor in furnace construction. Refractory design details and proven technology consideration is of paramount importance to come up with an optimum furnace life and to maintain productivity in the life span of the furnace lining. The failure to produce a technically or operationally durable refractory design lining could give rise to pre-mature deterioration of the refractory lining and furnace shell. The premature failure of the furnace lining will lead to extensive heat losses, furnace bath shift, change in taphole orientation and alteration of the Pitch Circle Diameter. A combination of these were experienced at Zimbabwe Alloys? new high carbon ferrochrome furnace. The Zimbabwe Alloys experience has shown an excellent furnace performance in the first two years of operation although signs of an anomaly showed within the first six months of the new furnace. Production slowed down due to induced problems from refractory failure causing furnace distortions impacting on the availability of the furnace and smelting capacity. This paper presents the lessons learnt, measures taken to deal with the premature failure and constraints within which the situation was managed.

Jan 1, 2007

By M. U. Özbay

A series of blasting experiments was carried out in an up-dip stope of a gold mine using short-perioddelay electric detonators. The main object of the investigation was to show the interactive effects of short-delay blasting. The delay range over which observations were made was restricted to between 10 and 200 ms. To quantify the blast results, data were collected on fragmentation, throw, position of muckpile, and ground vibration. For comparative purposes, blasting parameters for conventional pyrotechnic sequential firing were also measured. The paper describes the most relevant parts of the study and gives the experimental results. The interactive effects of short-delay blasting are analysed, and some aspects of the breaking mechanism are discussed.

Jan 1, 1985

By J. Kitagawa

The principal objectives of a metallurgical test programme for a 'grass roots' mining project are twofold. The first requirement is to establish the metallurgical viability of the project by demonstrating that acceptable results can be obtained by processing of the ore. The second goal is to obtain essential supporting data to determine whether the project is economically feasible. This involves several functions, which include the establishment of a workable flowsheet, the obtaining of design criteria for the commercial plant, and the collection of the evidence necessary to convince management, and often a third-party expert, that the metallurgy predicted for the ore can be achieved in a full-scale operation. The latter task is facilitated if a coherent overall picture is presented considering the geology of the orebody, the mining plan, and the mineralogy and metallurgy of the ore. The purpose of this paper is to provide guidance in the establishment of a test programme to meet the above objectives.

Jan 1, 1978

By H. Van Aswegen, C. V. B. 0unningham

The need for the more accurate measurement of blasting results has increased substantially with the proliferation of the types of explosives available to mining operations in South Africa. The primary object of blasting is the production of broken rock of a specific size distribution. A method for the measurement of size distribution, more popularly known as fragmentation, is being developed at Sishen Iron Ore Mine, and the object of this paper is to describe the method briefly and so encourage an exchange of views on reliable methods. Once the fragmentation of broken rock can be assessed reliably, meaningful conclusions can be drawn from blasting trials. It will then be possible for equipment productivity to be related to muckpile properties, with the accompanying advantages.

Jan 1, 1986

By T. T. Matuludi

Kleinkopje Colliery has five Wemco drums that were installed and commissioned in 1978. Over the years, there have been remarkable changes in mining and geological conditions at the colliery. First, an increase in the percentage of fines was recorded, which resulted in an uneven split or an imbalance in silo levels between material feeding the cyclone (-12 mm) and Wemco drum (+12 mm) sections respectively. This problem was solved by doing modifications around the banana screens to allow finer material to the drums. The imbalance challenge was then followed by spontaneous combustion that takes place in situ and results in low product yield. The results obtained from efficiency tests indicate that although there is a limit in the percentage of -6 mm material in the feed, Wemco drums are still very efficient and applicable to the current mining conditions. These results also suggest that it is essential to lower the throughput when the drums are treating low yielding coal.

Jan 1, 2010

By M. Splaine, M. A. Field, S. J. Browner

In the field of operational control, Shewhart Control Charts and Cusum Charts have long been available to management. These techniques provide help by detecting rogue values of a control variable and changes in the underlying mean of that variable respectively. This paper describes a new technique for identifying changes in the trend of a control variable, particularly when that variable is subject to large inherent variance.

Jan 1, 1983

By C. L. de Jongh

Fracturing of the rock caused considerable difficulties during the boring of a deep-level tunnel in hard rock. A pilot bore was suggested as a possible means of reducing the effect of the fracturing, and this possibility was investigated theoretically by means of a three-dimensional elastic stress analysis. Failure criteria were applied to the results of this analysis, and it was found that fractures predicted by the use of a simple criterion of limiting tensile macrostrain criterion agreed remarkably well with in situ observation. It was concluded that fracture could not be avoided and that a pilot bore was likely to aggravate tunnelling conditions.

Jan 1, 1978

By X. M. Prevost

A computer system to store, retrieve and process coal borehole and analytical data together with other geological, geographical or topographical information is described. As a result of the large volume and variety of data stored since its inception in 1979, as well as the basic versatility of the system, the National Coal Data Base has been performing a number of new tasks for which it was not originally designed. As considerable sets of data are used on almost every project, the use of statistical application programs has become an important processing tool.

Jan 1, 1987

By J. C. Zachariades, D. M. Fraser

The leaching of pyrolusite in acidic ferous sulphate solution was studied so that the important factors governing the kinetics of the reaction could be determined. The reaction is very rapid, and was monitored by continuous measurement and logging of the redox potential in solution by use of a microcomputer. The relationship between redox potential and manganese extraction was established empiricaly for each set of conditions by the use of a technique in which a calibration run was conducted in paralel with each leaching run. The study involved a number of batch leaching runs, and demonstrated that, of the variables investigated, only the initial ferous ion concentration and the reaction temperature afect the rate of manganese extraction. The final extraction did not vary. The reaction was modeled from the results by use of the shrinking-core model and Britan's activation-energy model. The later was found to provide a significantly better fit to the data.

Jan 1, 1991

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 G. Lyman

The cross-belt sampler is a device that is very widely used even though it has not been ratified by the Standards associations. This paper is concerned with the bias testing of two cross-belt sampler designs against stopped belt samples and a cross-stream cutter at the belt end. The bias analysis is carried out using size distribution as the analyte and conventional t-testing and the Hotelling T squared test, which are compared for their effectiveness. The paper considers the issue of detectable bias and the statistical planning of bias tests.

Jan 1, 2009

By K. Bryan, O&apos

A 10-year program to integrate crushing and screening models into daily flowsheet design practice has proven successful. A Circuit Analysis Program (CAP) is used worldwide to design and evaluate new and existing crushing flowsheets. To gain user acceptance of CAP and maximize effectiveness, model development, simulation flexibility, ease of use, and developing international access are key issues. These issues have been resolved effectively resulting in flowsheet simulations to assist in justifying increased capital investment. CAP is presently utilized in Canada, United States, and South Africa with intentions to expand to Europe and Asia.

Jan 1, 1987

This paper illustrates the application of numerical modeling methods, in conjunction with limit-equilibrium techniques, to the location of critical slip surfaces in slope-stability problems. Initially, the Spencer slice-based method of analysis is introduced, together with a dynamic-programming algorithm for slip-surface location. This limit-equilibrium method is assessed critically through the use of an illustrative problem. The technique is then extended to locate the critical slip surface for a similar slope, but with more complex constitutive and yield relationships for the material comprising the slope. To this end, the use of the stress field generated from a finite-difference program, together with a dynamic-programming search routine, is presented as an advanced technique of slope-stability analysis for engineers.

Jan 1, 1993

An evaluation was made of the wear and performance characteristics of liter bars, and the cost-life effectiveness of backing materials for rotary-mil liners. In a large run-of-mine mil in which the liter bars were mounted on grid liners of austenitic manganese steel (AMS), the liners had an average life that was five to six times that of equivalent unprotected liners. For a single mil, this is equivalent to annual savings in the cost of materials of up to R320 000, and to a downtime of 100 hours. Of the five materials tested in a large pebble mil grinding quartzitic ore, AMS grids and 'white iron' blocks performed best on a cost-life basis, with possibly improved performance from a real white cast iron. (The 'white iron' was shown by microstructural analysis to contain flake raphite and pearlite, being in reality a grey cast iron.) The high-chromium white iron had by far the longest predicted life, with mild steel a surprising second. Rubber was shown to last well in this type of mil. The wear rates of liners change during their lifetimes. The protective effect of liter bars was clearly illustrated by the reduction of over 40 per cent in the wear rates of the liners when the lifter bars were renewed to a height of 80 mm from a fully worn height of 35 mm.

Jan 1, 1991

By N. C. Joughin

Progress during the last two years in the Chamber of Mines programme for the development of mechanized stoping methods is reviewed, and advances in the basic technology are outlined. Specifically. advances in the understanding of rock fracture around stope faces. in rockbreaking techniques, in rockhandling techniques, and in engineering are described. The state of development reached with mining systems based on cutting, impacting. and blasting is also described.

Jan 1, 1978