Search Documents

High pressure grinding roll (HPGR) technology is used in an increasingly diverse range of applications, predominantly iron ore , gold and diamonds. KHD Humboldt Wedag HPGRs are applied world-wide, and consistently prove to be well designed and reliable operating units, with their performance meeting the pre-set standards. This publication summarizes some of the features and experiences for recent applications in treatment of copper ore, coarse iron ore, and gold ore. Summary data of roll surface wear life and operating data are given, together with operational observations. In addition, effects of feed segregation and truncated feed are discussed, as well as the implications of a product recycle flow sheet.

Jan 1, 2012

By P. R. Jochens, D. D. Howat, A. A. Hejja

The effect of the reactivity of lime on desulphurization efficiency in the basic oxygen furnace A. A. HEJJA, Dipl. Ing. (Budapest) (Visitor) D. D. HOWAT, B.Sc. (Glas.), Ph. D., F.I.M. (Fellow) P. R. JOCHENS, Pr.Eng., M.Sc. (Eng.) Rand, Ph.D., A.I.M. (Member) The iron charged to the basic oxygen furnace at the steel plant of Highveld Steel and Vanadium Corporation has a relatively high sulphur content. Considerable emphasis is therefore placed on the reactivity of the lime. An investigation of the lime used at the steel plant showed that its reactivity had deteriorated considerably both during transport from the supplier (Northern Lime Company) and during storage and handling at the steel plant. The deterioration on the steel plant is the more severe, and is due to hydration and carbonation. Rapid deterioration is a characteristic of highly reactive lime when exposed to the atmosphere. Plant tests showed that the desulphurization efficiency decreases with a decrease in the reactivity of the lime. The addition of slag rich in manganous oxide to the furnace considerably improved the efficiency of desulphurization that can be achieved with limes of lower reactivity and with lime that has deteriorated. A decrease in particle size of lime of lower reactivity greatly increased the desulphurization efficiency. Less lime of higher reactivity is required for the same degree of desulphurization to be achieved. Lime of higher reactivity gives rise to slags with lower ferrous oxide contents and hence the steel yield is increased.

By R. E. Gürtunca, D. J. Adams

Writen contribution by J.F.Curtls The subject mater of the paper is interesting in that, instead of 'numerical modeling based on elastic theory' being used for the prediction of energy release rate (ERR) in relation to various types of stope support, including backfil, use is made of stresses in the backfil in an atempt to corect the numerical modeling. Authors' reply to J. F. Curtis We thank Mr Curtis for his contribution to our paper. First of al, it should be emphasized that the object of the paper is not to address the validity of ERR as a tool for the assessment of seismic events or rockbursts, but to determine an in situ modulus for the rockmass with the aid of backfil measurements. Writen contribution by T.R. Stacey Although the authors of the above-mentioned paper have presented some good and interesting information, the title of the paper, and the recommendation that such an in situ modulis should be used for calculations of energy release rate (ERR), are viewed with some concern. The reasons for this concern are as follows. Authors' reply to T.R. Stacey Dr Stacey's comments on our paper are appreciated; we should like to address his concerns as follows.

Jan 1, 1991

By Q. P. Campbell

Activated carbons used in the precious metals extraction industry are characterized by large internal surface areas and a great affinity for metal ions. The purpose of this research is to prepare activated carbon from a South African bituminous coal by physical activation that is suitable and cost-effective for use in the extraction of metals. The quality of the coal-based activated carbon may not prove to be as good as activated carbon produced from other traditional sources, but the production costs involved may make South African coal a feasible alternative feedstock. The activated carbons produced were characterized by Brunauer, Emmett, and Teller (BET) surface area, activated carbon pH, and phenol adsorption studies and the results compared to the results from a commercially available activated carbon, Norit RO 0.8 (control sample). Bituminous coals from various sources including Witbank Seam 4 and Free State coal were used in this study. The preparation method chosen was physical activation using superheated steam. The effects of process variables such as activation time (1-3 h) and temperature (600-800°C) were studied in order to optimize those parameters. The activated carbon surface area was characterized by means of nitrogen adsorption isotherms at 77K. BET surface area analysis showed that Witbank Seam 4 coal activated at a temperature of 800°C and activation time of 3 hours resulted in a surface area of 340 m2/g. Quality control of each sample was performed by measuring the pH of a known amount of the prepared activated carbon in distilled water over time. Results showed that the pH of some of the prepared activated carbons reached a value of 11. Phenol adsorption results for the different activated carbons prepared corresponded well to the results obtained for the Norit RO 0.8 activated carbon sample.

Jan 1, 2012

By P. W. J. van Rensburg

COLLOQUIUM AND GENERAL MEETING A General Meeting and Colloquium on comminution was held on March 13th, 1974, at Kelvin House, Johannesburg. Mr P. W. J. van Rensburg (President) was in the chair. The Colloquium was attended by 140 delegates and was opened by the President at 9.15 a.m. MINUTES The minutes of the general meeting held on November 14th, 1973, as published in the December issue of the Journal, were confirmed.

Jan 5, 1974

By D. J. Adams, R. G. Gürtunca

In situ measurements and numerical modeling based on elastic theory showed that backfill stresses are considerably higher than originally thought. This has led to a change in understanding of rockmass behaviour. After describing previous work on the behaviour of the rockmass, this paper discusses possible reasons for the high stresses measured in backfil, and identifies the rockmass mechanisms possibly generating these stresses. It is concluded that the joints and the geological stratigraphy can lead to increased elastic convergence, and that the inelastic behaviour of the rockmass is also partly responsible for the increased closure measured in backfill. The use of an in situ modulus is suggested as an interim solution until a new computer model that allows for joints, different layers, and inelastic closures becomes available.

Jan 1, 1991

By G. M. Wright

We are only as good as we are perceived to be by others and, whilst there is every opportunity to revise and polish our written works, there are no second chances with a spoken presentation. At every level, conferences and seminars have been metaphorical graveyards for many an academic reputation.

Jan 1, 1990

A Colloquium and General Meeting was held jointly with the Mine Ventilation Society of S.A. in Kelvin House, Johannesburg, on 17th November, 1971, the theme being "The Economics of Mine Ventilation". Professor D. Howat (President) was in the chair. The Colloquium was attended by 150 delegates and was opened by the President at 9.00 a.m. MEMBERSHIP The President: "I have much pleasure in announcing that the names of the candidates, having been published in accordance with By-Law 5.2.2, Council has elected them to membership of the Institute in the following Grades: Fellows: Frederich-Wilhelm Volk, Peter Bennet Columbine. Members: Allan Colin Lawrence, Karel Anton van Gessel, Christopher Robert Harrison, Christopher Michael George Wartley, Frank Heinrich Deist, Ralph Morris, Benjamin Johannes Nolte. Associates: Wolf gang Freidrich Gottsman. TRANSFERS From Member to Fellow: Hugh Edward Keith Alien. From Graduate to Member: Errol Vincent Bosman, Christopher Roderick Stewart Needes, Bernard Wessels Holthousen. From Student to Graduate: David Robert Fleming. I welcome the new members to the Institute and congratulate them on their election. CO-OPTION TO COUNCIL The President announced that at the Council meeting held on 5th October, 1971, it was agreed, in terms of Rule 3.9 to co-opt Dr T. B. Beeton to Council. COLLOQUIUM The President welcomed visitors and members. He stressed that the discussion would be informal and that any contributor requiring publication should submit his contribution in writing. He then thanked the authors for providing pre-prints of the papers. After the President had concluded his opening remarks, he asked Professor J. de V. Lambrechts to act as Colloquium Chairman for the day and he, in turn, introduced the three Session Chairmen namely, Dr A. Whillier (Chamber of Mines and President of the Mine Ventilation Society); Mr M. Barcza (Managing Director, Corner House Laboratories); and Mr L. W. P. v.d. Bosch (Chief Consulting Engineer, Union Corporation). The following papers were presented: "Fan efficiency investigation on mines of the Union Corporation, Ltd." by J. A. Drummond. Published in the Journal Feb. 1972. "The design of underground cooling towers" by A. Whilliel'. Published in the Journal, Oct. 1971. "Some aspects of the design of cooling plant installations" by R. Hemp. Published in the Journal, Nov. 1971. "The planning of ventilation and refrigeration requirements in deep mines" by D. F. H. Grave and R. M. Stroh. Published in the Journal, Dec. 1971. "Cooling power of underground environments" by D. Mitchell and A. Whillier. Published in the Journal, Oct. 1971. At the conclusion of the three technical sessions the Symposium Chairman commented as follows, indicating that he would prepare a written summing up at a later stage: "The tone of the colloquium has had a sincerely practical note about it. It would have been a pity if the ventilation experts talked only theory and little practice. This practical theme has, I am sure, made the colloquium interesting to both ventilation men and others whose daily tasks do not touch so closely on this fascinating subject. This practical theme was in evidence through all the papers and contributions. Some of you may have felt that there was not enough emphasis on the word 'economics' as advertised in the broad title of the colloquium. I do not think this was really a valid criticism because as someone said 'it all boils down to Rands in the end!' So whether it was a case of low fan efficiency, poor design of cooling towers, wrong planning or low human efficiency due to high heat stress. . . it all boils down to money saving and therefore economics, whenever improvements are forthcoming. The title of the colloquium was thus not misplaced. The views of senior mining men on the production side are appreciated. Let us say that this exchange of views between ventilation engineers and those who have to take the final decisions and spend the money, should prove to be most rewarding." Professor Lambrechts finally thanked the Session Chairmen and everybody who had helped to make the colloquium a success and the meeting closed at 4.0 p.m. In a subsequent written summing up, the Colloquium Chairman gave the following as his impressions of some of the highlights which emerged from the papers and discussion thereof: (The names indicate the authors only). Drummond: It was hinted that the time had arrived to consider the introduction of a South African fan test code which would be better suited to local conditions than the currently acknowledged B.S.S. code which, however, is seldom enforceable in practice. In this connection also, there was prominent reference to the thermodynamic approach of McPherson. Wide variations in the quality of maintenance of, and repair work on, fans were stressed. It was mooted that ventilation engineers responsible for estimating the basic duty specifications for large fans, frequently played safe by overestimating the pressure required, thus ensuring that there would not be a shortfall in air volume delivered. This usually meant reduced fan efficiency and it was suggested that decision makers seemed to lay more emphasis on volume of air delivered than on real eco-

By L. N. Stewart, H. L. Bovey

Since 1955 extensive pressure-leaching testwork has been conducted by Anglo American Research Laboratories (AARL) in laboratory-scale batch autoclaves. In 1958asmall continuous pilot-plantof45 kgofsolids per hourwas operated by AARL. In 1974, when high uranium prices were anticipated, Anglo American, encouraged by successful commercial- scale autoclave operations as practised by Outokumpu, Sherritt Gordon, and Impala Platinum, decided to install a continuous pilot plant at Western Deep Levels. At that time the proposed pilot plant was considered to be of prototype size. The project was funded by members of the Nuclear Fuels Corporation (Nufcor). Since its commissioning in February 1977, the pilot plant at Western Deep Levels, which can treat between 10 and 20 tons of dry solids per hour, has been used to test ores from four different mines. The paper compares the uranium extractions and pyrite oxidation obtained in laboratory batch autoclaves with those obtained in the continuous pilot plant. In general, differences in uranium extraction are not great and can be explained; the differences in pyrite oxidation are less well understood. The effect on plant design of the evolution of carbon dioxide during leaching is discussed. Evaluation of the equipment and materials of construction would have been almost impossible in a small-scale batch autoclave. It is doubtful whether such results would have generated the necessary confidence to permit decisions to install a commercial-size plant. The development and performance of the multistage pumps, instrumentation, shaft seals, and shaft-seal water treatment are discussed. It is concluded that the operation of a largescale continuous pressure-leaching pilot plant to supplement laboratory batch autoclave tests has been a necessary part of the development of this process.

Jan 1, 1979

By L. S. Belyayeva, A. S. Chumak, N. N. Boyko, A. V. Bondarenko

Analysis of results of many years concerned study of the fire hazard parameters of the material of the mine conveyor belts come in for use at the mines of the Ukraine in 1984-2002 that was carried out in the laboratories of the Scientific-Research Institute of Mine-Rescue Work is adduced in the paper. The basic tendencies on raising the fire safety of the conveyor belts that are retraced in their world production are shown.

Jan 1, 2003

Introduction and Background For many years people were aware of the vast deposits of titaniferous magnetite containing vanadium in the Bushveld Complex. From 1957 onwards some exploitation of this ore was carried out by Minerals Engineering of S.A. (later the Vantra Division of Highveld Steel and Vanadium Corporation Limited), who produced vanadium pentoxide via a roast-leach process. Canadian Institute of Mining and Metallurgy The Finance and Executive Committees of the Canadian Institute of Mining and Metallurgy have agreed that members of SAIMM should be invited to register at all future CIM meetings at the same rate as CIM members.

Jan 1, 1980

By P. Harris, N. Heywood

An existing 1 800 m long pipeline, which carried waste mica slurry from kaolin processing, is to be recommissioned. The mica solids throughput is to be substantially increased from 5.2 t/h up to a maximum of9.53 t/h, but with a typical throughput of around 7.5 t/h. Because of this throughput increase, it was unclear whether the existing 80 mm diameter pipe would be adequate. In addition, the pipe route is to be extended by 250 m to 2 050m, and its elevation at discharge to settling lagoons increased from 66.2 m to 80 m. The pipeline hydraulics of waste mica slurry were investigated for the 80 mm diameter pipe using the Saskatchewan Research Council?s (SRC) Two-Layer Flow Model, for the maximum mica solids throughput of 9.53t/h. The pipe operating velocity was compared with the predicted deposit velocity for several mica concentrations, ranging from 20% to 50% by weight. Estimates were made of the total differential pressure across the proposed2 050 m long pipeline, as well as the power imparted to the slurry by the pump, and the specific energy consumption (SEC). Two pipe diameters were assumed: 80 mm when no mica wall deposit is present, and 70 mm when there is a 5mm mica wall deposit. This parameter has a significant effect on the determination of the appropriate pipe operating conditions. For the pipe operating velocity to remain adequately above the deposit velocity (and therefore for the heterogeneous flow pattern to prevail in either horizontal or inclined pipe), it was concluded that if the newly commissioned pipeline contains no mica wall deposit, the pipe should initially be operated at a mica concentration of between 20% and 25% by weight, probably with a target mica concentration of about 23%. A 23% mica

Jan 1, 2007

By F. M. Russell

Scheduling the extraction and rates of production for an underground mining operation is a common task carried out during the life of a mine, from the initial feasibility study through to the final production phase. The scheduling process can be complex when several requirements have to be satisfied, for example, match mill capacity and maximize net present value while constrained by mining sequence and availability of resources. Many mines have computer programs relevant to their operation but because they are site-specific they need considerable reprogramming to be adapted to other operations. Other methods currently in use also suffer drawbacks: manual spreadsheets are laborious, computerized spreadsheets cannot handle sufficient constraints, and operations research techniques require a complex mathematical model to be set up. The use of network analysis techniques has been proposed previously but the unavailability, until recently, of easily used computer programs has not allowed this approach to be developed. There are now many programs which can be used; however, the particular program which has been adapted to mine scheduling is Metier's 'Artemis-PC' running on IBM-XT or compatible machine. The use of network analysis offers many advantages, including the use of a logical mining sequence; activities can be as detailed as required; related activities can be readily incorporated, and costs can be easily extracted. A heuristic approach is necessary to optimize the schedule, but the ease and speed of program execution enables this to be readily achieved, while leaving the mining engineer in full control. The paper discusses the problems encountered in mine scheduling and current solutions. It then details the use of network analysis techniques and the application of the Artemis-PC program to solve mine scheduling problems.

Jan 1, 1987

By T. N. Huffman

Ancient mining and Zimbabwe T. N. HUFFMAN*. Ph.D. (Illinois) (Visitor) Ancient gold mining and Zimbabwe have been commonly associated for over a hundred years, either in terms of an exotic colony for gold export or as an African state based on the East Coast trade. The stratigraphy and radiocarbon dates from Zimbabwe and the known sequence for the Rhodesian Iron Age demonstrate that Zimbabwe was built after AD. 1000. A review of the evidence for ancient gold mining shows a similar antiquity, and a complementary rise in prosperity in Arab settlements on the East Coast indicates that gold was not extensively mined until the eleventh century. Large quantities of imported articles at Zimbabwe indicate the extent of trading during the fourteenth and fifteenth centuries, and the origins of Zimbabwe probably lay in an overflow of wealth from the gold trade during the twelfth and thirteenth centuries. Zimbabwe was abandoned by the sixteenth century because of environmental factors.

Jan 1, 1974

Minutes of the Annual General Meeting held at the St. Helena Club on Wednesday, 27th July, 1977, at 7.30 p.m. Book review Advances in extractive metallurgy, 1977. Proceedings of the third symposium organised by the Institution of Mining and Metallurgy held from 18-20th April 1977. London, the Institution of Mining and Metallurgy, 1977. 244 pp. £18,50. Coal preparation A meeting of the Organising Committee of the Eighth International Coal Preparation Congress took place in Moscow on 24th and 25th May, 1977.

Jan 1, 1978

By R. M. Lamya

A semi-empirical kinetic model was developed for the atmospheric leaching of a Ni-Cu matte in copper sulphate-sulphuric acid solution. Kinetics of the leaching process was studied as a function of initial copper ion concentration, initial acid concentration, temperature, stirring rate and particle size distribution. The kinetic model was developed on the basis of the leaching mechanism and chemical reactions of the leaching system investigated, and was evaluated by comparing the model predictions to experimental data. The model was found to satisfactorily fit the trends in the leaching of the metals, namely copper, nickel, cobalt and iron.

Jan 1, 2009

By W. F. Nothard, J. R. C. Hill

The Rhodesian approach to the vegetating of slimes dams by J. R. C. HILL, B.Sc.(Agric.) (Visitor) and W. F. NOTHARD (Visitor) To prevent environmental pollution from mine dumps, it is necessary to stabilize them either mechanically or biologically. In the long term biological stabilization is more attractive because of its permanent nature. Initially, the basis of stabilization is in the correct siting and construction of the dump. The main toxic factors influencing plant growth on Rhodesian mine dumps are arsenic, antimony, copper, nickel, a high ratio of magnesium to calcium, excessive soluble salts, high pH, and Iow macronutrient content. Root-growth studies in culture solution and pot experiments are used to supplement information on the suitability of plant material obtained from replicated field trials on mine dumps. In addition to the selection of plants for toxic tolerance, it is advisable to provide multiple-layer protection with trees, shrubs, and grasses. Further, a range of different plant species gives greater biological stability. Protection must be provided for young plants against wind erosion and the abrasive effects of windblown sand. Planted wind breaks are preferred to mechanical forms; windrows of garden refuse make good wind breaks and at the same time introduce organic material to the dump and provide a good environment for seedling establishment. The use of artificial fertilizers and sewage effluent is recommended to hasten the development of a complete and protective plant cover.

Jan 12, 1973

A General Meeting, followed by a Colloquium on 'Pilot plants and problems of scale-up', was held on 22nd March, 1978, in the Main Hall, Kelvin House, Johannesburg. The President, Mr P. A. von Wielligh, opened the meeting at 09h15. He thanked the authors and contributors for their co-operation, and announced the names of the undermentioned candidates, who had been admitted to membership of the Institute:

Jan 1, 1978

A General Meeting and Colloquium on 'Motivation and productivity in the mining industry' was held on May 22nd, 1974, at Kelvin House, Johannesburg. Mr P. W. J. van Rensburg (President) was in the chair. The Colloquium was attended by 170 delegates and was opened by the President at 09h25.

Jan 8, 1974

1. New books Extractionmetallurgy'81. London, Institution of Mining and Metallurgy, 1981. 441 pp. $40. Structures and properties of engineering alloys, by W. F. Smith. London, McGraw-Hill, 1981. 512 pp. R89,65. Rock and mineral analysis, by W. M. Johnson and J. A. Maxwell (editors). 2nd ed. New York, Wiley, 1981. 424 pp. $40. Mining methods and equipment, by Mining Information Services. London, McGraw-Hill, 1981. 218 pp. International directory of acronyms in library, information and computer sciences, by P. M. Vaillancourt. New York, Bowker Publishing Co., 1980.516 pp. 2. New journals Trends in analytical chemistry (TRAC), Amsterdam, Elsevier, 12 issues per year. Subs. for Volume I (16 issues) D.H 95.50. Engineering management international, Amsterdam, Elsevier, 4 issues per year. V.S. $32.50, D.H. 70.00. 3. Mineral policy sector publications Mineral Bulletin MR 188. Vanadium: an imported mineral commodity. $3.60. Mineral Bulletin MR 190. Canadian mines: 1980 perspective. $3.00. Canadian mineral survey 1980, by the staff of Mineral Policy and Energy Sectors. $1.00. 4. NIM reports Report 2090 Observations made during the dig-out of a 48 MV A ferrochromium furnace. Report 2110 The investigation of a fracture on one side of a skip bridle in a mine shaft. Report 2111 Pilot-plant tests for the recovery of chromite and the noble metals from the UG-2 Reef at Maandagshoek. Report 2112 The behaviour of UG-2 chromite concentrates during smeUing. Report 2113 M uUivariable control of a milling circuit at East Driefontein Gold Mine. Report 2115 Estimation of material variation in powdered materials Report 2116 Optimum operation of a direct-reading spectrometer with excitation by a 5 kW inductively coupled plasma torch. Report 2121 Five robust indicators of central value. Report 2124 The direct determination, by differential pulse anodicstripping voUammetry at the thin mercury-film electrode,of cadmium, lead, and copper. Report 2127 The preparation of a reference material of South African zirconium concentrate from Richards Bay. Report 2128 The determination, by differential pulse anodic-stripping voltammetry at the thin mercury-film electrode, of cadmium and thallium in six NIMROC reference materials Report 2130 The organizing of conferences. Research grant The Board of Directors of International Precious Metals Institute in conjunction with Gemini Industries, Inc., a California-based refiner of precious metals, recently announced a Gemini Research Grant of $3000 will be awarded annually to a graduate student who is pursuing studies in metallurgy, chemical processes as it pertains to precious metals, or materials sciences, and who is performing or planning research studies in the precious metals. Accidents and diseases The Third International Colloquium for the Prevention of Occupational Accidents and Diseases in the Iron and Metal Industry is to be held on 15th and 16th June, 1982, in Palma de Mallorca, Spain.

Jan 1, 1981