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By T. Szendrei, S. Tose

The fracturing and movement of rock that occurs in the vicinity of a stemmed borehole charge in open pit mining operations are described by examining the effects of the emitted stress waves – shock and elastic – and the expansion of high-pressure detonation product gases. Three principal modes of momentum transfer to fractured rock are identified, all linked to gas expansion work. This work can be delivered radially (burden), axially (stemming), and in the collar zone (cratering). Flyrock is generated under unusual combinations of blast parameters and rock properties. Although infrequent and seldom predictable, the generation of flyrock can nonetheless be interpreted and modelled in terms of the principal mechanisms of rock projection described in this study. The physical processes underlying these principal mechanisms are identified and will permit the development of predictive models for flyrock velocities.

Dec 13, 2023

By M. Loots, E. Van Der Lingen, S. Grobbelaar

The increased adoption of unmanned aerial vehicles (UAVs) may improve the productivity and costeffectiveness of remote sensing in the mining industry. This review’s objective is to enable stakeholders to identify possible application adoption, improvement, and innovation opportunities. The review merges a building block strategy and practical screening criteria to identify possible avenues of research to answer the review questions. After the screening process, 72 documents were included in the review. Papers were classified into four categories: exploration, development, exploitation, and reclamation. Fifteen applications were identified, the majority of which were in the exploration phase. The most often researched applications were topographic surveys, reclamation monitoring, and slope management. From the two UAV types identified, multi-rotor vehicles were the most favoured for all applications. From the eight remote sensing techniques identified, photogrammetry was the one most often used. Other techniques were limited because of complexity, cost, or the incompatibility of sensors and UAVs. The review was limited to published papers in academic journals. Future studies could aim to include empirical data on the latest UAV applications used in the mining industry.

Jul 2, 2022

By P. J. D. Lloyd

An account is given of the development of a process to concentrate gold and other valuable minerals and to produce a discardable waste. In this process, the ore is coarsely milled, a bulk flotation concentrate is prepared, and the flotation tailing is scavenged in a hydrocyclone, which returns coarse gangue, moderately coarse valuable minerals, and locked valuable minerals back to the mill. The engineering developments required by this circuit in order that it will fit underground, and the progress made towards the achievement of those requirements, are reviewed. If the waste is to be suitable for use as a backfill in a deep-level, flat tabular excavation, it should be capable of being placed hydraulically, and should have both low voidage and high rates of drainage. Such a material could be prepared by the fine screening of the overflow from the cyclone in the proposed circuit. Possible methods for the handling of the concentrate and the recovery of its valuable constituents are described. The paper concludes with a discussion of the possible benefits from the use, in deep-level Witwatersrand mines, of a system involving concentration underground, extensive backfilling using the tailings from the concentration process, and hydraulic hoisting of the concentrate.

Jan 1, 1979

By J. W. Oberholzer

The use of computers in the South African coal mining industry has increased during the 1980s. Applications at mine level commenced in the financial and personnel areas of payroll systems, mine accounting procedures and staff record keeping. More use is made now on mines of technical programs for purposes such as mine planning and mine survey calculations. The Coal Mining Laboratory of the Chamber of Mines Research Organization has provided, for a number of years, a service to Chamber member collieries in regard to the application of technical computer programs. Programs presently in use for simulating production procedures and conveyor belt transport systems are described. In addition, reference is made to the collection, storage and analysis of data concerning the performance of continuous miners over a period of eight years. More recently a computer program for the simulation of the cutting action of continuous miner cutting drums has been developed. The use of this program to assist with drum design is explained. The fact that many requests to make use of the programs are received from collieries is an indication of their acceptance by industry. Their interest in running the programs themselves on their own desktop computers has led to the need to convert the software for microcomputers.

Jan 1, 1987

By A. Koning

Pressure hydrometallurgy operations require vessels to be lined with an impermeable membrane for corrosion protection and one or more courses of refractory or ceramic brick. Examples of unit operations that utilize composite lining systems include pressure oxidation autoclaves, sulphide precipitation autoclaves, chloride leach reactors, flash vessels, cyclone separators, and direct contact condensers (heater vessels and quench vessels). The refractory lining must satisfy multiple requirements: it must thermally insulate the membrane from process fluid, be structurally stable, provide erosion resistance, be chemically compatible with process fluid, and provide an economic service life. New hydrometallurgical processes are pushing the pressure, and temperature with each new generation of plants. A fundamental understanding of all factors affecting the mechanical stability of the lining system is essential as lining designs move further away from the industry?s experience base. The method of designing a refractory lined vessel is examined taking into account the impact of irreversible chemical swell, operating factors, design factors, and installation factors. The effect of geometry and incorporating additional degrees of freedom to the analysis is explored using two-dimensional and three-dimensional finite element analysis (FEA). The effect of these additional degrees of freedom on the results of the one-dimensional model are discussed. Keywords refractory lining design,autoclave, finite element analysis.

Aug 1, 2013

By C. L. E. Swartz, I. J. Barker, J. H. Schubert

A dynamic simulator of the leaching and adsorption cascades of a gold plant was developed and used to compare the effect of various disturbances on the overall efficiency of the plant. These comparisons show which disturbances most critically need to be controlled to optimize plant performance. The simulator was based on an existing gold plant. Dynamic and steady-state data were collected on the plant and were used in the modeling of the process. Simple dual-rate models are used to describe the leaching and adsorption processes. Mole-balances of various species take into account the changes of concentrations in the leach, and also the movement of pulp and carbon up and down the adsorption cascade. Fluctuations in the flow rate, density, and cyanide concentration of the feed to the leach have a negative effect on the efficiency of the leach, while carbon attrition was found to be an important factor in decreasing the efficiency of the carbon-in-pulp (GIP) section. Badly regulated transfers contribute towards the decreased efficiency of the GIP section, but overflows and carbon leakage have only a limited long-term effect. Various carbon profiles and transfer schemes were studied, and the results indicated that a slightly heavier loading at the bottom of the cascade is beneficial, while the type of transfer is relatively unimportant.

Jan 1, 1993

Project evaluation is completed through individual studies covering technical and financial aspects of the mine to market. These studies are completed at various levels of detail depending on where the project evaluation is in the project's life cycle. The competency of the studies varies in relation to the quality of data, level of the skills employed, control, management and reporting structure. The focus of this paper is managing elements of the study, looking at the cost of opportunity to influence the project, against the value added. Selection of the study manager and study teams is central to getting an integrated project evaluation addressing the correct issues completed on time. Retention of key personnel can reduce rework which, in turn, can reduce time and cost impacts. It is important to have a work breakdown structure at the outset so that the study teams have a common numbering and naming system that will integrate areas, equipment, budgets estimates and accounts. Having set up the evaluation groups and provided training in the study procedures, understanding the scope and schedule are vital elements in producing a project evaluation that addresses the opportunities and the risks of the final project. Arriving at an accurate capital budget requires integration of the research controlled through common systems. Project evaluation process must also address how the project is to be delivered.

Jan 1, 2007

By T. A. Silva, A. C. Bragança

Lime has been added to the iron ore slurry transported by the Samarco pipeline since its operation start-up in 1977.Initially, internal corrosion was the main concern therefore the reagent was used only for pH correction. Over the last ten years, though, transport of more complex slurries demanded a significantly higher dosage of lime to guarantee adequate rheology control. Several other reagents have been tested for the same purpose yet none has proven to be as effective regarding technical performance, environmental impact and cost. However, an alternative was sought so that the slurry rheology could still be controlled in case lime addition became impracticable. The objective of this paper is to present a technical solution for this matter, which takes into account environmental aspects. It consists of adding soda for pH correction and an organic coagulant as a rheology modifier. The latter is a quaternary ammonium salt which affected the slurry transport properties in the same manner as lime when tested in a laboratory. It showed no plug formation and allowed solid particles to settle, forming a loose sediment after rest. These results indicate a low probability of plug occurrence in the pipeline and the formation of a readily reslurryable sediment upon shutdown of the pumping system. Industrial tests should be performed in order to validate the laboratory results.

Jan 1, 2007

By P. Lloyd

Perceptions of disaster caused by burning fossil fuels have reached such a pitch that they seriously threaten the very future of the industry. Coal is a dirty word. A leader in Business Day(January 192009) claimed ?There is no disputing that renewable and non-polluting energy sources are preferable to the country?the true cost of so-called cheap coal-fired power stations is neither reflected nor accounted for by Eskom?the true and immediate but unacknowledged cost of continued coal mining is apparent in the catastrophic level of acidification from mining runoff of all significant natural water resources in the country?and their waters have been rendered unfit for human consumption. Air quality is in a similar state with?increases in pulmonary disease causing workforce absenteeism and compromised childhood development, among many other health problems recorded in areas polluted by coal mining.? The upshot is that our latest coal-fired power station, Kusile, is being required to use flue gas desulphurization. The costs are considerable, and the benefits minimal. Meanwhile, exports are being threatened by EU directives and an assumption that South African coal gives off excessive quantities of SOx and NOx when burned. The industry needs to arm itself with clear responses to these and similar misconceptions, and to communicate those responses loudly and clearly, if it is to survive.

Jan 1, 2011

By M. H. Dehghanpoor, M. Zivdar, M. Torabi

"A hydrometallurgical route was developed to extract metals such as gold, silver, copper, and selenium from anode slime from Sarcheshmeh Copper Complex in Iran. For the extraction of copper by leaching, the anode slime was heated and stirred with 4 M sulphuric acid in the presence of oxygen. Optimal conditions for recovery of copper were temperature 80°C, mixing time 5 hours, and oxygen flow rate 2 L/min, resulting in a copper recovery of 94.47%. Silver and selenium were dissolved by leaching anode slime from which the copper had been removed with nitric acid. For gold extraction, anode slime was heated with aqua regia at 90°, and the gold then extracted with 2-ethyl-hexanol at a concentration of 0.5 M and phase ratio of 4. The extract was then stripped with soda solution at pH=10.5 and a phase ratio of 5. Finally, gold was recovered by precipitation with oxalic acid at a ratio of mass to volume 10 g/L. Total gold recovery was 80%. IntroductionDuring the electrorefining of copper, some metals are accumulated in the byproduct anode slime, which is an important source for recycling and recovery of these metals (Petkova, 1994). In this paper, a hydrometallurgical route is described for the recovery of precious metals from copper anode slime of Sarcheshmeh Copper Complex, which is located in southeastern Iran .Copper anode slime is black or gray powder with a particle size less than 200 mesh. Approximately 2 to 20 kg of anode slime is produced per ton of copper cathode. The slime is characterized by higher amount of Ag, Se, Pb, and Cu compared to other metals and a very low Au content (Khaleghi and Ghader, 2013).The copper anode slimes are composed of 11.69% selenium, 3.93% copper, 5.26% silver, 0.13% gold, and 45% barite, plus lead, tellurium, antimony, sulphur, and silica with small amounts of nickel, iron, zinc, and bismuth. Gold is one of the most important noble metals due to its wide applications in industry and economic importance, so recovery of gold from slime is more appealing than that of other metals. According to the World Gold Council (2013), the demand for gold has increased during the last decade. This increase is due not only to the increasing demands of the jewellery market, but also to the increasing demand for gold in industrial as well as medical applications (Ranjbar et al., 2014)."

Jan 1, 2016

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 C. Musingwini, C. Beaumont

"Kansanshi mine, located in northwestern Zambia, uses conventional openpit mining to produce primarily copper, with gold as a by-product. The ore is extracted from a deposit with highly complex mineralogical suites that are difficult to process, sometimes leading to poor recoveries. The mine was using an ore classification system called ‘Mat-Type’, which classified various ore types into 22 different quality categories, ranging from poor to good quality. Ore with poor recovery was classified as ’poor quality’ ore and directed to long-term stockpiles. Due to a lack of proper integration between the technical and functional areas forming the mine value chain, Mat-Type unintentionally misclassified ore. A geometallurgical analysis was therefore undertaken to review Mat-Type and a new geometallurgical ore classification system, called ‘OXMAT ’, was developed to replace Mat- Type.When implemented, OXMAT eliminated nine of the 22 ore categories and the remaining 13 ore categories could now be more accurately and consistently defined, leading to a significant change in the quantity of ore being mined. OXMAT demonstrated that within a defined test volume of the geological model, waste tonnes could be reduced by 19% while ore tonnes could be increased by 17%. This paper therefore demonstrates the value created through integrated geometallurgical modelling. IntroductionKansanshi mine is located in northwestern Zambia, approximately 10 km north of the provincial capital Solwezi and about 160 km west of Nchanga mine in the Central African Copperbelt (Broughton and Hitzman, 2002). The location of Kansanshi mine relative to other major copper deposits in the Copperbelt is indicated in Figure 1.Kansanshi mine uses conventional openpit mining methods to exploit copper- and gold-bearing veins hosted in a structurallycontrolled mineral deposit. Mining is carried out in two areas of the deposit, the Northwest and Main pits. A third area of the deposit, called Southeast Dome, is currently not being exploited (Figure 2)."

Mar 1, 2019

1. New books Australian Institute of International Affairs. Uranium - energy source of the future? Canberra, thelnstitute (Box E181, P.O., Canberra, A.C.T. 2600, Australia), 1979. 202 pp. A$4,95 (postage 50c). Euroeconomics. The steel industry in Western Europe.. industrial and financial indicators. Paris, Eurofinance (9 Avenue Hoche, 75008 Paris, France), 1979. 167 pp. FF4,500 (Available in English and French.) M. B. Piggott. Load-bearing composite materials. Oxford, Pergamon Press, 1979. $15,00. J. H. E. Olaf. Automation and remote monitoring and control in mines. Essen (West Germany), Verlag Gliickauf GmbH, 1979. 200 pp. DM36. (In English.) J. P. Jenkins and E. T. Brown (eds). KWIC index of rock mechanics literature. Oxford, Pergamon, 1979. 742 pp. £60. R. J. Wakeman (ed.). Progress in filtration and separation 1. Amsterdam, Elsevier, 1979. 346 pp. Dfl.llO,OO. 2. New journal As from 1980, Coal Calendar is being published as a separate monthly periodical. 3. Proceedings L. E. St Pierre and G. R. Brown (eds). Future sources of organic raw materials. Oxford, Pergamon, 1979. 612 pp. £22,50. P. Haasen, V. Gerold, and G. Kostorz (eds). Strength of metals and alloys. Oxford, Pergamon, 1979. 3 vols., 1800 pp. $200. K. J. Miller and R. F. Smith (eds). Mechanical behaviour of materials. Oxford, Pergamon, 1979. 3 vols., 1800 pp. U.S.$200. 4. Tax relief? The Publishers' Association of Great Britain recently issued a circular to a number of professional bodies drawing their attention to a court decision in favour of tax allowances on the purchase of textbooks. In January Electroheat The International Union for Electroheat, which com. prises a score of highly industrialized countries, every four years organizes a congress at which experts discuss the technicalities and economics of the latest applications of electroheat in industry and other sectors. Corrigenda: March issue The following amendments should be made to Table II of the paper 'Commodity analysis:

Jan 1, 1980

By J. H. Viljoen, C. H. Graan, N. B. Strydom, J. S. Greyson

M J Martinson (Fellow) There is everywhere a lamentable dearth of quantitative information on occupational factors affecting the health and safety of mineworkers, and as the authors point out in their introduction underground lighting is one of the factors which has received little attention in South Africa prior to this welcome paper. Since the authors are to some extent pioneering, it is perhaps inevitable that the paper should raise more questions than it answers, but nevertheless it provides a provisional yardstick against which the need for, and success of, remedial action may be judged. Before commenting in detail on a few aspects of the paper it may be worthwhile to summarize the statutory provisions relating to underground lighting, contained in Chapter 15 of the Regulations promulgated in terms of the Mines and Works Act 27 of 1956. Chapter 15 is entitled `Lighting, Safety Lamps and Contraband', but in the context of the present paper only four simple regulations need be noted: firstly, no person shall work or travel in an unilluminated part of a mine unless he carries a light ; secondly, adequate stationary lights shall be provided at stations and certain other localities in shafts, winzes and places used for winding; thirdly, mechanically propelled conveyances shall be provided with an effective bright light shining in the direction of travel; and fourthly, moving machinery to which personnel have access shall be illuminated so as to be clearly visible. In all four regulations the standard of lighting to be provided is wholly subjective, and under these circumstances the wide inter- and intra-mine variations in light intensity disclosed by the study are hardly unexpected. Nevertheless the data presented in the authors' Table I raise three points (1) Is there any evidence that the 19 mines visited during the survey are representative of the 45-50 large gold mines in South Africa, or that the shafts selected are representative of the respective mines? Mine managers would scarcely be human were they not to offer better lit working places for the survey; perhaps the use of a scaling factor (e.g. tonnes or transit mineworkers per shift, kilowatts, etc.) for each working place might have helped to put the figures in perspective. (2) Looking at two of the more numerous - and probably important - of the ten working places included in the survey, i.e. stations and tips, one is struck by the marked. skewness of both intensity distributions (with higher frequencies at the lower intensities) and the abrupt cut-off in both cases just short of pitch darkness. Thus, of the 45 meaned readings recorded at 26 tips no less than 19 fall in the lowest range of 0,1-0,9 1m/ft2, with but one tip in total darkness; of 46 readings on 26 stations, 7 fall in the lowest range and none is in total dark-'1 ness. Although a light with an intensity in the range 0,1-0,9 1m/ft2 may satisfy the regulations, it is certainly arguable that in some situations it may be safer to have no light at all. (3) In view of the skewness referred to above, one wonders how meaningful are the `total average light intensities for (the gold mining) industry' quoted in Table I, which the authors compare with illumina¬tion levels found in other countries. Looking at tips again, one notes that 34 out of 45 meaned intensity readings fall below the `total average' for tips, and only 10 exceed it. From this it may be concluded that a few well-lit working places included in a `total average' may conceal a plethora in Stygian gloom. In their discussion the authors make fleeting reference to the effect of underground lighting on productivity and accident rates, without however quoting any South African experience in this regard. Intuitively it seems highly likely that better lighting (in the widest sense) would improve productivity and reduce accidents, and of course it is in these areas that the mining industry might seek economic justification for providing better lighting. It is all the more regrettable therefore that these factors were not studied simultaneously with the present investigation, especially at the Psychological Division of the Human Sciences Laboratory has recently published a study on underground accidents in the gold mining industry without making any reference whatsoever to lighting as a causal factor. In the event neither of the two studies enables us to make an economic appreciation of the situation, and this seems to be a classic example of a situation where some dovetailing of research effort would have greatly increased the useful return. On the effect of lighting on accidents, it may be noted that in 1939 Mickel presented some very interesting statistics to the Mine Managers Association of the Transvaal2, on the improvement in accident rates which followed the random issue of electric cap lamps to native mineworkers in the Hercules Section of E.R.P.M. the previous year. Based on a 12 month trial period in which 250 000 shifts were worked with carbide lamps and (contemporaneously) 307 000 shifts with cap lamps, the incidence of major accidents (at least one day in hospital among men using carbide lamps was 1,15 accidents per 1000 shifts, while the incidence of minor accidents (requiring dressing only) was 11,52 per 1 000 shifts. The corresponding figures for men using cap lamps were 0,79 and 7,31 accidents per 1 000 shifts respectively, representing a reduction of over 30 per cent in both major and minor accidents. While these figures are obviously dated - only men using cap lamps were issued with hard hats, for instance - they do indicate a need for similar research today.

Jan 1, 1971

Proceedings of the Ninth International Symposium on Techniques for Decision-Making in the Mineral Industry, Montreal, June 1970. The Ninth International Symposium on Techniques for Decision-Making in the Mineral Industry was sponsored by The Canadian Institute of Mining and Metallurgy, McGill University and Ecole Poly technique. The programme included 71 papers on various topics, as follows: Market Analysis and Logistics Planning; Quantification of Geological Variables; Blending; Capital Investment Decisions; Mining; Financial and Economic Analysis; Search for Mineral Deposits; Market Forecasting and Strategies; Operations Research in Process Modelling; Ore Reserve Estimation; Management Information Systems; Optimization and Control of Mineral Processes. In addition to general sessions, a special feature of the Symposium was Executives' Day, which was held to provide top and middle management with a broad understanding of the usefulness of decision-making techniques and their role in the mining organization. Panel Discussions and two keynote speakers provided a review, in non-technical terms, of the areas in which decision-making techniques have proven valuable. The present volume contains 65 papers submitted for publication, along with a complete account of the Executives' Day discussion. It is broadly divided according to the above subject headings. Approximately 550 pages, illustrated. Price: $15.00; $12.00 to students, plus 50 cents for handling costs. Order now from CIM headquarters: Canadian Institute of Mining and Metallurgy, 906-1117 Ste. Catherine St. W. Montreal 110, Quebec.

British Mining Fields, by J. E. Metcalf. Published by the Institution of Mining and Metallurgy, London, 1969. Price 50s. (Students, 30s.). A 100 years or so ago Britain's mining industry led the world in the production of coal and base metals. Although she still maintains a sizeable-and, under the circumstances, remarkably progressive-coal mining industry, her production of most other base minerals has long since been dwarfed by mining fields in the Americas Africa, Australia and the U.S.S.R. Nevertheless the story of mining in Britain is of wider interest than the present scale of operations there might suggest, if only because the domestic British mining industry has in terms of finance, technology and manpower been the fons et origo of many highly productive mining fields outside Britain, including the Witwatersrand goldfields. British Mining Fields was published by the Institute of Mining and Metallurgy to give delegates attending the Ninth Commonwealth Mining and Metallurgical Conference a succinct account of mining in Britain. The main emphasis is on underground mining of base minerals-treated regionally-with separate chapters on coal and gypsum. The author strikes an admirable balance between historical aspects, geological origin and environment of ore deposits, mining methods and economic factors, and provides a few key references for those who wish to make deeper studies. This is exactly the sort of booklet one often wishes were available on South African mining.

By Z. Nzimande

The Constitution of the Republic of South Africa advocates the importance of sustainable economic development and justifiable environmental consciousness by business. The government needs to ensure that every citizen of the Republic has access to an environment that is protected, pollution free, and sustainable by enacting certain regulations. However, there are more than 5 700 derelict and unrehabilitated mines of all types in South Africa. Former asbestos operations were among the first to be targeted for clean-up under the programme instituted by the Department of Mineral Resources (DMR), owing to the proven direct impact of asbestos pollution on health. This paper seeks to investigate the challenges faced by the coal sector as far as mine rehabilitation and closure is concerned. For the purpose of this paper rehabilitation is defined as per the Chamber of Mines Rehabilitation Guidelines publication, which defines rehabilitation as putting the land impacted by mining activities back to a sustainable and usable condition. Some of the current rehabilitation challenges are technical skills (know-how), leadership focus, poor planning, cost saving initiatives, and the government's lack of capacity to enforcement rehabilitation requirements. It is imperative that mining companies identify rehabilitation as a critical strategic pillar that directly influences license to operate. The case study evidence indicates that relevant policies, appointment of accountable people, sufficient leadership support, and the correct choice of rehabilitation equipment can assist to improve the rehabilitation and land management challenge.

Jan 1, 2012

By M. Kilfoil

Many minerals processing operations result in crushed rock being mixed with a liquid. Sometimes, the rock particles have to be dried before the next process begins and there may be a considerable distance between the equipment carrying out these processes. Bateman Engineered Technologies (BET) developed, patented and commercialized a method of simultaneous pneumatic conveying and drying. A joint project to assist with optimizing the process is under-way. Part of it is a numerical simulation of the process. The simulation is done using a dedicated program written in MATLAB, (commercial software which is widely used in engineering). It accounts for heat and mass transfer as well as particle transport. The main part of the program consists of a loop containing a series of equations which are evaluated sequentially. During any particular iteration, the properties are changed one at a time. Since the properties are changing relatively slowly, this method gives good results. The outputs of the simulation are consistent with the operational experience of BET’s engineers. The output is very comprehensive and all numerical. Since the program is currently being used for research purposes, flexibility is very important. Thus the output is converted into a spreadsheet file. Variations in the output quantities are displayed graphically using MS Excel. Some simulation could have been done using computational fluid dynamics (CFD) software. The advantages and disadvantages (technical, financial and skills requirements) of the two approaches for this particular type of simulation are compared briefly. Keywords: Pneumatic conveying, Heat and mass transfer, Computer model

Jan 1, 2003

Iron ore pellets with or without additives are commonly used as alternate charge material in both conventional and newer ironmaking processes. The performance characteristics of these pellets are normally assessed on the basis of their reducibility values, reduction strength and resistance to clustering. These properties depend mainly on the type and amount of additives and on the sintering phenomena of the pellets during firing. In the case of composite pellets (ore-coal pellets), reduction and sintering of the iron ore fines occur simultaneously. The thermodynamic and reaction mechanisms of the processes involved in the reduction of iron ore pellets with and without reductants, additives, etc., may not necessarily be identical. The reduction and sintering characteristics of pellets greatly influence the reaction mechanism and the surface morphology of the reduced pellets. The approaches in the literature to the analysis of these reduction and sintering phenomena are broadly categorized as follows: (i) empirical models, (ii) models based on kinetics, and (ill) models based on morphological changes. The relative merits and de-merits of these models are illustrated by their application to the reduction of fluxed ore-coal composite pellets. A critical analysis of the investigations that have been conducted on the reduction and sintering behaviour of such pellets is given. It is shown that, although elegant empirical models and kinetic equations have theoretical significance and can be usefully employed in elucidating the reaction mechanisms of iron ore lumps, they are sometimes not directly applicable to fluxed ore-coal composite pellets. In studies of the latter, the approach should be to correlate the morphological changes with the reduction mechanism. The paper also gives a brief account of an investigation on the reduction and sintering aspects of fluxed composite reduced iron pellets.

Jan 1, 1996

By H. A. D. Kirsten

Mining-induced seismicity is usually evaluated in terms of continuum elastic analyses, and is quantified in terms of energy release rate as state parameter and excess shear stress along particular features on which failure may be induced. Although both of these quantities are representative measures of potential seismic activity, elastic analyses do not enable the associated stresses and displacements in the rock in which failure occurs to be evaluated reliably. The paper compares the effect of depth, span, support stf1Jhess, field stress ratio, and discontinuity strength on mining induced seismicity determined from elastic analyses and from analyses in which discontinuities in the rock are allowed to fall. It is, accordingly, shown that the incidence and magnitudes of potential seismic events and the net excess shear as representative state parameter cannot be determined reliably from elastic analyses that do not account for the failure of ubiquitous discontinuities. The magnitudes of seismic events in rock in which ubiquitous discontinuities are allowed to fail are very considerably overestimated in elastic analyses. The extent of the seismic source region and the associated seismicity do not increase with depth, which, together with the improved containment of the concomitant rockburst damage by backfill is reassuring for mining at greater depth in future. For conventional support, the magnitude of potential seismicity increases for an increase in span in elastic rock, but remains unaffected in non-elastic rock. For backfill, the magnitude of potential sesmicity decreases substantially in elastic and non-elastic rock for an increase in span. Increases infield stress ratio very significantly reduce potential seismicity irrespective if the type if analysis, but effect the distribution if potential seismic events very differently in elastic and non-elastic rock.

Jan 1, 1994