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By A. W. S. Schumann

G. H. HENDERSON INTRODUCTION It is a pleasure to have read Mr Schuman's wide ranging and highly informative paper and also to congratulate him. Before proceeding to give views on the use and preservation of coal in South Africa, it is perhaps apposite to look at the South African scene on the world canvas. Mr Schuman's figures in his Table I are highly revealing. The Table shows expected consumption, export and import demand in the year 1980 by the continents of the world. The Republic of South Africa is shown as one of only four exporting countries at that date, although in the interim, Australia has become an exporter and will continue to grow as an exporter of coal. Huge fields have been proved in recent years. There is reason to think that for some years, coal and its economical uses have been under-estimated. The importation of oil carries a constant question mark and the exciting possibilities expressed in the uses of Dranium a decade ago for power generation, appear to have met with some setback. Present indications are that breederreactors will be delayed until about 1990. The capital cost of such reactors, too, is enormous. By 1980 it has been estimated that 20 per cent of the energy required by the leading ten nations of the world will come from nuclear power, but 80 per cent would then remain for fossil fuels and hydro generation. COAL DEMAND AND USAGE It is of interest to record that coal production in all the countries of Europe has declined markedly in the last 25 years. This is due to competition from oil, gas and nuclear power and also for sociological reasons; but there are signs that efforts will be made to resuscitate, at least in some measure, the mining of coking coals for which there is a strong and growing demand. Possibly all hard coal now mined in Germany has coking properties and that country is self-sufficient in this commodity. Germany might perhaps consider selling coking coal to her neighbours and importing additional coal for power-raising purposes. It has been frequently stated in American publications that the coal reserves of the D.S.A. are sufficient for 1 000 years. What that means, I do not know, but it is at least an indication that America has huge reserves of coal. Domestic and export demand in the U.S.A. in 1968 exceeded production for the first time. In 1969, the United States' output amounted to some 556 million tons, an increase of less than 2 per cent on the previous year. The output achieved fell short of demand, domestic and export, by more than 7 000 000 tons. This has caused and is continuing to cause anxiety in the U.S.A. In many countries young men for a number of reasons, largely environmental and social, are not coming forward in sufficient numbers for mining requirements and the same pattern has revealed itself in the Republic. This is, indeed, alarming because mining men in large numbers will be required to meet the estimated tonnage requirements set out in the following Table: It is difficult to visualise the replacement of these coal requirements either by oil or by nuclear fuels. The coal must be mined and men are required for the purpose. Unless a greater section of the population is allowed to participate in the more responsible aspects of mining, there is a serious likelihood that demand will not be matched by output. In addition to local demand, a lively export trade is possible. Exports are dependent on the future capacity of the South African Railways and Harbours and on Government policy. An export figure of 10000000 tons per year during the decade can be visualised and this figure would raise total estimated sales production to a figure of over 100 000 000 tons in 1980. At this point, it is necessary to examine the desirability or otherwise of exporting coal. How much coal

Jan 11, 1970

By J. Bakken, M. Th. Jonsson, G. Sævarsdottir

A typical three-phase submerged-arc furnace for production of silicon metal and ferrosilicon has arc currents ~100 kA, phase voltages ~100 V and total furnace power ~10 - 60 MW. The arcs burn in gas filled cavities or "craters", where the main atomic components of the plasma mixture are silicon, oxygen and carbon. Two quite different simulation models for high-current AC arcs have been developed: the simple Channel Arc Model (CAM), and the more sophisticated Magneto-Fluid-Dynamic Model (MFD). These models have been described extensively and results reported at INFACON-8 and INFACON-9, respectively. The coupling between the arcs and the AC power source is described by a complete three-phase Electric Circuit Model. Recent numerical modelling studies of industrial AC arcs show that the boundary conditions at the cathode and anode are critical for the simulation results. A novel Cathode/Anode Sub-Model for high-current AC arcs that treats both cathode and anode indicates a completely different cathode behaviour than previously assumed. A cathode spot which serves a high-current electric arc is shown to be dominated by the energy impact from the arc. This leads to lower cathode fall voltage than obtained from previously developed models. The anode fall voltage is negative, as the main function of the potential barrier is to repel plasma electrons. The cathode spot is diffuse in the sense that the arc in fact contracts away from the cathode. Simulation results are compared to measurements on both industrial furnaces and smaller scale pilot furnaces. An important conclusion, supported by our arc studies, is that the arc length in silicon metal and ferrosilicon furnaces does not exceed 15 cm and the arc may burn anywhere on the electrode, not necessarily beneath the electrode tip.

Jan 1, 2004

By G. M. Dowo

The widespread environmental damage caused by slimes dam construction requires rehabilitation as one of the key management strategies towards land restoration. From the time when Mhangura Copper Mine in Zimbabwe was shut down in 2000 due to viability problems, no follow-up studies were carried out on the slimes dams to assess their development with respect to ecosystem function and longterm recovery. The ecosystem function analysis (EFA) method was thus employed to achieve this end. EFA is a monitoring procedure that establishes how well an ecosystem functions as a biophysical system through the use of rapidly assessed field indicators. The field procedure makes use of simple visual indicators that are related to various soil surface processes. Conventional sampling methods are used to collect the vegetation data. The data was first analysed using landscape function analysis (LFA) software packages and then with various multivariate statistical techniques. In total 27 species were recorded from 14 families; 21 of them occurring in the acacia woodland and only 8 on the slimes dams. Hyparrhenia sp. was the dominant grass on Dam 5 and Imperata cylindrica dominated Dam 6. Acacia saligna was the most abundant tree species on the dams. The tree layer on the slimes dams was not as developed as the grass layer. The rehabilitated slimes dams converged with the natural woodland for the LFA indices of stability, nutrient cycling, and infiltration, which suggested a high level of functionality. The main factors affecting the sustainability of the rehabilitation are postulated to be fire, grazing, and tree harvesting. The study contributed to the importance of, and methods used for, assessing ecosystem function on rehabilitated slimes dams in Zimbabwe, which are often ignored as most efforts focus on the establishment of vegetation on the dams. Keywords ecosystem function analysis, EFA, mine tailings, rehabilitation, monitoring, Mhangura Copper Mine, ecosystem function.

Dec 1, 2013

The Annual General Meeting of the Institute was held in Kelvin House, Johannesburg, on Wednesday, 26th August, 1970, at 4.15 p.m. Mr. J. K. E. Douglas (President) was in the Chair. There were also present sixty-three Fellows, thirty-five Members, one Graduate, eight Associates, five Students and nineteen Visitors, making a total of one hundred and thirty-two. The President declared the meeting open at 4.20 p.m. OBITUARIES The President: 'It is my sad duty to announce the deaths of the following members of the Institute. Dr J. A. Papenfus, Fellow, who joined the Institute in 1942 and passed away on the 28th of May, 1970. Mr D. G. Beadle, Fellow, who joined the Institute in 1946 and passed away on the 17th of June, 1970. Gentlemen, Derek Beadle was very well known in this Institute. His papers on dust will be remembered and, at the time of his untimely death, he was one of our assistant editors. As a mark of respect to the memory of the deceased and in sympathy with the bereaved, I would ask you to rise and observe a few moments' silence.' MINUTES The President: 'May we confirm the minutes of the General Meeting held on 15th April, 1970, as published in the July, 1970, issue of the Journal'. Agreed. WELCOME TO VISITORS The President: 'Ladies and Gentlemen, we are honoured this afternoon by the presence of many distinguished guests and I extend to you all a most cordial welcome. We are happy to have with us Dr A. A. von Maltitz, President of the Chamber of Mines of South Africa, who is also Honorary President of this Institute. We also have one of our Honorary Vice- Presidents, Mr T. L. Gibbs, the Government Mining Engineer; Mr D. E. Hamm, President, Institution of Certificated Mechanical and Electrical Engineers, S.A.; Mr S. C. M. Naude, Director, Witwatersrand Technical College; Mr I. R. G. Stephen, Senior Vice-President, The S.A. Institute of Electrical Engineers; Mr G. M. Tompkins, President, The S.A. Institution of Mechanical Engineers; Professor P. B. Ackermann, President of the Geological Society of S.A.; Mr A. S. Robinson, Vice-President of the S.A. Institute of Civil Engineers; Professor W. Mare, President of the Institute of Land Surveyors of the Transvaal; Mr B. D. Charlton, President of the S.A. Institute of Assayers and Analysts; Mr R. Hemp, The President, The Mine Ventilation Society of S.A.; Mr L. J. Prince, The President, The S.A. Association of Mine Managers; Mr J. Botha, The President, The S.A. Institute of Foundrymen; Mr G. Niterl, The President, The Institute of Welding; Mr M. R. Gericke, President, S.A. Council of Professional Engineers; Mr N. A. Honnet, Chairman, Orange Free State Branch; Mr P. R. C. Cooke, Chairman. The South African Chemical Institute (S. Tvl' Section). Gentlemen, we are very honoured indeed, to have these distinguished gentlemen with us this afternoon, as our honoured guests. We are also pleased to have with us, one of our Honorary Fellows, Mr F. G. Hill, and several Past-Presidents. I also extend a very warm welcome to all our lady guests and to all our other visitors.' MEMBERSHIP The President: 'I have pleasure in announcing that the names of the following candidates, having been published in accordance with By-Law 5.2.2, Council has elected them to membership in the following grades: NEW APPLICATIONS Fellows: Herbert Dalton-Brown, Stephen William Morel. Members: Clive Lester Workman-Davies, Basil James Russell Botha. Students: Timothy Nigel Watson, John William Hairbottle. I wish to welcome the new members to the Institute and to congratulate those members who have been transferred to a higher grade.' ANNUAL REPORTOFTHE COUNCILAND ACCOUNTS FOR THE YEAR ENDED 30th JUNE, 1970 The President: 'I now have pleasure in presenting to you, the Annual Report and Statement of Accounts for the year ended June, 1970. These have been handed to you this afternoon and, as is customary, I propose they be taken as read. Before moving their adoption, however, I would like to refer to some of the salient features, leaving as is usual, the task of dealing with the finances, to our Honorary Treasurer. It is encouraging that membership has continued to grow, and now stands at 1,613, an increase of 61 over last year's total. Your Council, however, is aware that there are still people in our mining and metallurgical industries, who could qualify for membership, but who have not yet joined the Institute. A drive to increase membership was accordingly organised, and members of Council were given the responsibility for campaigning in sections of industry, and for publicising the objectives and advantages of belonging to the Institute. Up to now there has not been much reaction to this campaign, but I hope we will see results in the coming year. At the same time, Council has recognised the need for change in the conduct of the Institute's affairs in order to meet the changing needs of our membership. Our members, both mining and metallurgical, are in the first place, geographically more widely dispersed than they used to be, and secondly, with the growth of the metallurgical industry, their technical interests are now more diversified. The Institute must cope with these changing needs if we are to continue to perform a useful function. The

The Annual General Meeting of the Institute was held in Kelvin House, Johannesburg, on Wednesday, 26th August, 1970, at 4.15 p.m. Mr. J. K. E. Douglas (President) was in the Chair. There were also present sixty-three Fellows, thirty-five Members, one Graduate, eight Associates, five Students and nineteen Visitors, making a total of one hundred and thirty-two. The President declared the meeting open at 4.20 p.m. OBITUARIES The President: 'It is my sad duty to announce the deaths of the following members of the Institute. Dr J. A. Papenfus, Fellow, who joined the Institute in 1942 and passed away on the 28th of May, 1970. Mr D. G. Beadle, Fellow, who joined the Institute in 1946 and passed away on the 17th of June, 1970. Gentlemen, Derek Beadle was very well known in this Institute. His papers on dust will be remembered and, at the time of his untimely death, he was one of our assistant editors. As a mark of respect to the memory of the deceased and in sympathy with the bereaved, I would ask you to rise and observe a few moments' silence.' MINUTES The President: 'May we confirm the minutes of the General Meeting held on 15th April, 1970, as published in the July, 1970, issue of the Journal'. Agreed. WELCOME TO VISITORS The President: 'Ladies and Gentlemen, we are honoured this afternoon by the presence of many distinguished guests and I extend to you all a most cordial welcome. We are happy to have with us Dr A. A. von Maltitz, President of the Chamber of Mines of South Africa, who is also Honorary President of this Institute. We also have one of our Honorary Vice-Presidents, Mr T. L. Gibbs, the Government Mining Engineer; Mr D. E. Hamm, President, Institution of Certificated Mechanical and Electrical Engineers, S.A.; Mr S. C. M. Naude, Director, Witwatersrand Technical College; Mr I. R. G. Stephen, Senior Vice-President, The S.A. Institute of Electrical Engineers; Mr G. M. Tompkins, President, The S.A. Institution of Mechanical Engineers; Professor P. B. Ackermann, President of the Geological Society of S.A.; Mr A. S. Robinson, Vice-President of the S.A. Institute of Civil Engineers; Professor W. Mare, President of the Institute of Land Surveyors of the Transvaal; Mr B. D. Charlton, President of the S.A. Institute of Assayers and Analysts; Mr R. Hemp, The President, The Mine Ventilation Society of S.A.; Mr L. J. Prince, The President, The S.A. Association of Mine Managers; Mr J. Botha, The President, The S.A. Institute of Foundrymen; Mr G. Niterl, The President, The Institute of Welding; Mr M. R. Gericke, President, S.A. Council of Professional Engineers; Mr N. A. Honnet, Chairman, Orange Free State Branch; Mr P. R. C. Cooke, Chairman. The South African Chemical Institute (S. Tvl. Section). Gentlemen, we are very honoured indeed, to have these distinguished gentlemen with us this afternoon, as our honoured guests. We are also pleased to have with us, one of our Honorary Fellows, Mr F. G. Hill, and several Past-Presidents. I also extend a very warm welcome to all our lady guests and to all our other visitors.' MEMBERSHIP The President: 'I have pleasure in announcing that the names of the following candidates, having been published in accordance with By-Law 5.2.2, Council has elected them to membership in the following grades: NEW APPLICATIONS Fellows: Herbert Dalton-Brown, Stephen William Morel. Members: Clive Lester Workman-Davies, Basil James Russell Botha. Students: Timothy Nigel Watson, John William Hair-bottle. I wish to welcome the new members to the Institute and to congratulate those members who have been transferred to a higher grade.' ANNUAL REPORTOFTHE COUNCILAND ACCOUNTS FOR THE YEAR ENDED 30th JUNE, 1970 The President: 'I now have pleasure in presenting to you, the Annual Report and Statement of Accounts for the year ended June, 1970. These have been handed to you this afternoon and, as is customary, I propose they be taken as read. Before moving their adoption, however, I would like to refer to some of the salient features, leaving as is usual, the task of dealing with the finances, to our Honorary Treasurer. It is encouraging that membership has continued to grow, and now stands at 1,613, an increase of 61 over last year's total. Your Council, however, is aware that there are still people in our mining and metallurgical industries, who could qualify for membership, but who have not yet joined the Institute. A drive to increase membership was accordingly organised, and members of Council were given the responsibility for campaigning in sections of industry, and for publicising the objectives and advantages of belonging to the Institute. Up to now there has not been much reaction to this campaign, but I hope we will see results in the coming year. At the same time, Council has recognised the need for change in the conduct of the Institute's affairs in order to meet the changing needs of our membership. Our members, both mining and metallurgical, are in the first place, geographically more widely dispersed than they used to be, and secondly, with the growth of the metallurgical industry, their technical interests are now more diversified. The Institute must cope with these changing needs if we are to continue to perform a useful function. The

By C. J. Pretorius

More than 30 percent of the global demand for zircon (ZrSi04) is supplied by South Africa. A significant amount of the zircon is exported, and beneficiated products are then imported for industrial applications locally. Beneficiating the zircon locally could have a positive impact on the local market, since zircon is only one of many such cases. Ammonium acid fluoride serves as an alternative anhydrous fluorinating agent for zircon in the synthesis of several metal fluoridesl.2. It provides an effective dry fluorinating method and is easier to handle than hydrogen fluoride or fluorine gas. Zircon exposed to extreme plasma temperatures dissociates and becomes more reactive. The reaction of the plasma-dissociated zircon (Zr02?SiO2) with the ammonium acid fluoride (NH4F?XHF, where x= 1 to 5) forms two main intermediate compounds (NH4)3ZrFr(s) and (NH4) 2SiF6(s), the latter decomposing to form volatile products at relatively low temperatures, providing easy separation of the silicon and zirconium compounds. The ammonium zirconate compound decomposes to form zirconium tetrafluoride (ZrF4), which can be further manufactured into zirconium metal, to name but one product. Data on the kinetics of the reaction of ammonium acid fluoride with zircon and plasma-dissociated zircon, combined with the thermo-dynamic parameters of the reaction, is essential for the development of an industrial process for the production of a precursor for the manufacturing of zirconium metal, namely anhydrous ZrF4. Both the reaction kinetics and reaction parameters will be included in this study, as well as some proof that the reaction proceeds to ZrF4 on a small batch scale. If the exact reaction parameters can be pinned down, a wide spectrum of anhydrous metal fluorides can be synthesized through this fluorination route.

Jan 1, 2012

By B. Genc

"The risk of spontaneous combustion is well known in the South African coal mining industry. In the coming years it is very possible that the incidence of spontaneous combustion will increase from current levels, due to factors such as an increased rate of mining, re-working of previously mined seams, more stooping and total extraction for underground mines, and higher stripping ratios for surface mines, leading to more spoils. It is also fairly certain that coal mining will face tougher environmental emissions legislation in the near future. To determine the areas where the risks of spontaneous combustion are high, it is necessary to improve on our current laboratory procedures for testing and evaluating coal samples, combining the results with site and field data, and if necessary revising the laboratory rating system to refine our understanding of South African conditions.Currently, laboratory tests are conducted in order to determine both the Wits-EHAC index and the crossing-point temperature which, when combined, give an indication of the spontaneous combustion propensities of the coal samples. This procedure has enabled the establishment of a database of results to review and evaluate South African coal seams. Using this database, the high-risk areas in terms of spontaneous combustion are identified. Tests have been undertaken for five consecutive years, between 2008 and 2012. In total, 119 coal samples from different coal seams and production coalfields have been analysed and classified through a series of laboratory tests. A comprehensive database of these results is available, and is continually being updated as new test results are added. This database will continue to expand, and to provide the basis for an improved risk evaluation methodology for spontaneous combustion"

Jan 1, 2015

By P. R. Beeley

Metal founding - a modern perspective The recent development of metal founding is reviewed in the context of basic requirements for the successful manufacture of cil;5ti,ngs.Progress has been related to the two interdependent fields of process technology and product characteristics. . After a brief review of the growth of the traditional industry. various features of the modern industry are discussed. Reference IS made to current trends in process technology and to the introduction of new techniques affecting production engineering, product quality. and the general nature of the industry. Metallurgical aspects of metal founding are considered, and modern techniques for the control of casting conditions are examined. These aspects are related to the structure and quality of cast metal and to the development of newer types of cast material and product.

Jan 9, 1976

The Barrick North Mara Mine and the Advanced Systems Group at SGS Minerals collaborated on the implementation of a grinding expert system for the control and optimisation of a single semi autogenous (SAG) mill. Over the last 5 years, grinding expert control has gained wide acceptance by mineral processors. In this paper, two key factors for success are highlighted: the adaptability of the software tools and the interaction with site personnel. Created with SGS?s MET expert console (MEC) toolkit, and running on Gensym?s G2 real time inference software, the North Mara expert logic has been set up to keep a steady and on spec leaching feed slurry while striving to maximize throughput. Leach feed stability was achieved by standardizing operating practices across shifts; a result of successful collaboration with site personnel in developing a consistent control strategy. The strategy maintains the SAG load and power draw in an optimised range by manipulating SAG feed rates and inlet water flow. The project life-cycle was slightly longer than average due to site specific constraints. One of these was the high turnover rate of site?s workforce during the project, coupled with the availability of key staff on site due to the fly in fly out work roster. These constraints called for different, and innovative ways of project commissioning and hand-over. This paper describes details of the control solution, its implementation as well as results and conclusions.

Jan 1, 2009

By A. Hotta

Reduction of CO2 emissions is the key driving force behind the development and implementation of new solutions for energy production. One solution is circulating fluidized bed (CFB) combustion technology combined with a high-efficiency once-through water-steam cycle. Foster Wheeler's CFB technology is today commercially available in capacities up to 800 MWe with ultra-supercritical steam parameters. Simultaneously, the Flexi-Burn® CFB technology is being developed to provide capability of flexible operation in air firing and oxy-combustion for carbon capture. CFB technology can offer an attractive solution for the reduction of CO2 emissions, owing to advantages such as fuel flexibility and low emissions that the air-fired CFB technology offers today. Pilot test facilities provide information about the performance of CFB oxy-combustion technology, and the acquired knowledge is being incorporated in boiler modelling and design tools. One of the European R&D initiatives on carbon capture and storage (CCS) is the Technological Centre for CO2 Capture and Transport, which is supported by the Spanish Government through the Fundación Ciudad de la Energía (CIUDEN). CIUDEN is a research and development institution created by the Spanish administration in 2006 and fully conceived for collaborative research in CO2 capture, transportation, and storage. The Technology Development Centre for CO2 Capture and Transport comprises two technologies on oxy-combustion: pulverized coal (PC) and circulating fluidized bed (CFB). This paper will focus on the design and main characteristics of the 30 megawatt-hour thermal capacity (MWth) oxy-CFB boiler. Foster Wheeler is the technology provider of the Flexi-Burn CFB unit, for which commissioning has been completed in the first quarter of 2011. The CFB unit design allows operation either under conven¬tional combustion with air or under oxy-fuel conditions. The size of this experimental boiler is sufficient to allow the scaling of the results to commercial units. In this way, multiple fuels and operating conditions can be tested economically. The results will validate the design of a future 330 MWe supercritical Oxy-Combustion Power Station (OXY-CFB-300 Compostilla Project) intended to demonstrate the CCS technology at commercial scale. The Compostilla OXY-CFB-300 Project is one of the six CCS demonstration projects funded under the European Energy Programme for Recovery (EEPR) of the EU. The project is based on a future 330 MWe CFB supercritical oxy-combustion plant, with CO2 storage in a deep geological formation. The first phase of the project, granted by the EEPR programme and led by the Spanish utility ENDESA, includes all studies and characterization work needed on CO2 capture, transport, and storage, as well the costs, financing, and regulatory and permitting required, prior to the final investment decision for the construction phase of the plant by the end of 2012.

Jan 1, 2012

By R. Chryst, R. Kus

In the Integrated IT Systems proposed by Przedsie? biorstwo Robót Geologiczno-Wiertniczych—Geological and Drilling Company (PRGW) a network connects a database with all of the departments of a mining division. A key element thereof is the common graphics environment—Micro Station supplied by the firm, Bentley. PRGW’s SoftMine software and GMSI’s CadsMine that are used to design and schedule mining operate in this environment. The digital form of the design project facilitates the verification of information and the integration of technical solutions with SAP R/3 type financial—accounting systems. The system has been successfully implemented in the Brown Coal Mine in Poland.

Jan 1, 2003

By K. Arnold

AngloGold Ashanti has been proactive in the field of energy management for many years. AngloGold Ashanti is a signatory to South Africa?s National Energy Accord of 2005 calling for a15% reduction in energy consumption by 2015 for the mining sector. This target also supported our internal targets that were already set. AngloGold Ashanti?s seven South African mines consume on average 440 MW. Due to the dynamics of gold mines, and the large numbers of relatively small energy efficiency initiatives and awareness campaigns made measurement and verification of energy efficiency very difficult at a macro level since some initiatives could get lost in the fluctuating load profile. This paper will discuss the methodology and process followed to quantify the impacts of the combined energy efficiency initiatives at macro level. It will quantify the energy efficiency impacts in megawatt-hours (MWh), financial, and equivalent carbon emissions (CO2e) reduction with reference to our baseline year, 2004, for the Vaal River and West Wits mine clusters.

Jan 1, 2009

By E. Wolmarans

Dowding, Reynard and Associates Mineral Projects (DRAMP) was approached by the ARM/Lion Ore JV during July 2006 to conduct a feasibility study and control budget estimate for a new greenfield project for their NKOMATI Nickel mine 45 km east of Machadadorp. The scope included the evaluation and review of previous studies as well as a techno-economic trade-off on four possible comminution circuits ranging from conventional crushing and ball milling to fully autogenous milling. The following document encapsulates the thought process, decisions and the references used in selecting the final comminution route for the new 375 ktpm MMZ concentrator. Apart from the pilot test work performed, design simulations from a number of sources, performance results from a recently commissioned 100 ktpm MMZ concentrator, together with an understanding of the geology and mineralogy of the orebody and possible variations in the characteristics of the orebody over the life of mine were assessed. The results from all the above-mentioned work indicated that it would be possible to treat the MMZ ore at the desired throughputs to the desired grind sizes in a fully autogenous grinding (ABC-type) circuit. Autogenous milling is generally considered to be one of the higher risk milling circuits. This is mainly due to the fact that the ore, which is utilized as the grinding media, could be variable in terms of hardness and mineralogy/geology. Nevertheless, it is a very popular route as the cost benefits, more specifically the operating cost, are normally very attractive. This is especially the case when large low grade orebodies are evaluated. In North/South America, autogenous and semi-autogenous grinding circuits have been successfully employed during the past 20 years on large scale low grade operations. Taking all the above factors into account, the DRA/Nkomati project team recommended an autogenous circuit with the option to add steel to both the primary and secondary mills (if required) for the new operation in order to create the opportunity for significant operating cost savings. One has to bear in mind that all the new design simulations and decisions are based on previous work and potential unknown variations within the orebody will never be fully understood until the pit is operational for some time.

Jan 1, 2009

By D. Limpitlaw

Industrial mining in Zambia started in the 1930s when the world class copper deposits near the border with Katanga were developed. The discovery of these deposits began at the turn of the century when the first claims in the Copperbelt were pegged at Chambishi, north of what became the town of Kitwe1. World War I and the difficulties of raising sufficient capital for such large scale undertakings delayed the exploitation of these deposits. Following this hesitant start, a large copper mining complex was built, resulting in the development of five major towns, all highly dependent on the mining and beneficiation of copper and cobalt. Copper became so important to the country that, on independence, the only non-mining town to make it onto a list of the top six was the capital, Lusaka. From commissioning of the mines to the end of the colonial period in 1964, copper production increased to just over 640 000 t annually2 (see Figure 1). After the establishment of the new Zambian state, production continued to increase, supported by a benign legislative environment and strong international copper prices. The government of Kenneth Kaunda was intent on improving the conditions of the rural poor and reducing unemployment in urban areas. To this end, the government embarked on an ambitious project of refocusing Zambia's economy away from the colonial role of commodity supply to one of decentralized mass employment. The Copperbelt industrial complex was key to the success of this approach, and in 1969 the Zambian State acquired a 51 per cent stake in Zambia's two main copper producing companies: Roan Selection Trust and Rhodesian Anglo American Corporation. The former became Roan Consolidated Mines Ltd (RCM) and the latter became Nchanga Consolidated Copper Mines Ltd (NCCM). In the year they were nationalized, the mines produced at least 720 000 t of copper? and employed approximately 48,000 workers (see Figure 2)2-4. The subsequent economic policies of the Zambian Government depended heavily on the state's ability to monopolize the proceeds of copper mining.

Jan 1, 2011

By P. M. Scott

The South African Institute of Mining and Metallurgy held a colloquium on 'The Selection of Equipment for Underground Mining' in Johannesburg on 22nd September, 1982, which, judged by the interest shown, was an unqualified success. Mintek 50 As announced earlier, the Council for Mineral Technology (Mintek) will be celebrating fifty years of growth in 1984 and is organizing an international conference, MINTEK 50, on its areas of special expertise. Drilling Once again the South African Drilling Association will be holding a technical symposium in 1983. ILAFA Congresses The Instituto Latinoamericano del Fierro y el Acero (ILAFA) has scheduled the following congresses for 1983:

Jan 1, 1983

By S. G. Gendler

One of the ways of trauma and occupational diseases level reduction is noted to be the improvement of the labour protection measures planning. As an indicator for prospective trends determination in the labour protection planning improvement sphere economic risk has been proposed to be used. The trauma and occupational diseases analysis based on the correlative and regressive methods has been carried out for the “Vorgashorskaya” mine of Pechora coal basin. Trauma and occupational diseases occurrences frequency and economic losses value have been estimated. Trauma and occupational diseases economic risk distribution analysis has been presented in respect to the different subdivisions and occupational groups of “Vorgashorskaya” mine.

Jan 1, 2003

A well known rock mass classification system has been altered slightly to address the issues found under remnant mining conditions. By detail study of the expected fracture patterns and local geology, the rock mass is classified to indicate the condition of the hanging wall prior to mining. The risk level of each mining step is evaluated by calculating input parameters for computer simulations from the actual rock mass condition. Seismic activity is catered for by the understanding that large event rates and large magnitude events reduce the quality of the local rock mass and that the rock mass stiffness should be adapted accordingly. A case study is presented to test parts of the protocol. Un système connu de classification des masses rocheuses a été légèrement modifié pour faire face aux questions posées par les conditions d’extraction de débris. Une étude détaillée des diagrammes de fragmentation et de la géologie locale permet de classer la masse rocheuse pour indiquer la condition du toit avant l’extraction. Le niveau de risque de chaque étape minière est évalué en calculant les paramètres d’entrée pour simulation par ordinateur à partir de la condition réelle de la masse rocheuse. L’activité sismique est prise en compte avec la réalisation que les taux de larges évènements et les évènements de large magnitude réduisent la qualité de la masse rocheuse locale et que la raideur de la masse rocheuse doit donc être adaptée. Une étude de cas est présentée pour tester des sections du protocole. Ein sehr bekanntes Gesteinsmassenklassifikationssystem wurde abgeändert um die Probleme zu behandeln die unter Restabbaukonditionen angetroffen werden. Durch detaillierstes Studium der der zu erwartenden Bruchmuster und der lokalen geologischen Verhältnisse wird die Gesteinsmasse in Hinblick auf die Konditionen der Flözoberseite klassifiziert. Das Risikoniveau für jeden Abbauschritt wird durch die Eingabeparameter aktuellen Gesteinsmassenkondition für die Computersimulation evaluiert. Für die Seismische Aktivitäten wird Sorge getragen durch das Verständnis, daß große Ereignisraten und Ereignisse hoher Größenklassen die Qualität der lokalen Gesteinsmasse reduzieren und daß die Gesteinsmassensteifheit entsprechend adaptiert werden sollte. Eine Fallstudie um Teile des Protokolls zu testen wird präsentiert.

Jan 1, 2003

By N. Andersen

During the preliminary design phases and feasibility study of a proposed vertical shaft, a vertical diamond drill-hole is normally drilled on the site. This paper outlines how rock mass characteristics, in-situ rock stress, rock strength, hydrological characteristics, and structural parameters can be determined using wireline logging of this borehole. In addition, a rock mass classification scheme is developed, based on published work, and in particular the Q-factor is adapted to assess the stability of raise-bored shafts. The ‘stick plot’ is introduced, which combines all geotechnical parameters applicable to the stability of a vertical shaft into a colourcoded format where cross-correlations can readily be made on a day-today basis during the shaft-sinking process.

Jan 1, 2015

By A. D. Pelton, Y. -B. Kang, S. A. Decterov

Computerized thermodynamic databases for solid and liquid metal, slag and solid oxide phases in the Al2O3-CaO-CoO-CrO-Cr2O3-FeO-Fe2O3-MgO-MnO-NiO-SiO2-S system have been developed by critical evaluation/optimization of all available phase equilibrium and thermodynamic data. The databases contain parameters of models specifically developed for molten slags, liquid steel and solid oxide solutions such as spinels, pyroxenes, olivine, monoxide (wustite, periclase, lime), corundum, etc. By means of the optimization process, model parameters are found which reproduce all thermodynamic and phase equilibrium data within experimental error limits. Furthermore, the models permit extrapolation into regions of temperature and composition where data are not available. The databases are automatically accessed by user-friendly software that calculates complex equilibria involving simultaneously slag, metal, refractories and gases, for systems with many components, over wide ranges of temperature, oxygen potential and pressure. A short review of the available databases is presented. The critical evaluation/optimization procedure is outlined using the Al2O3-CaO-FeO-Fe2O3-SiO2and Al2O3-CaO-MnO-SiO2systemsas examples. Several applications of the databases to deoxidation of iron and to inclusion control in steel are discussed. Keywords: thermodynamics, phase equilibrium, phase diagrams, databases, ferrous metallurgy, steelmaking, inclusion control, slags, oxide systems.

Jan 1, 2004

This paper describes an interactive personal computer program, ENVIRON, which simulates cooling and ventilating systems on gold mines. An example of the practical application of the program is given and proposed future developments are discussed. The program consists of two main modules, HEATFLOW and VENT- FLOW. HEATFLOW calculates the heat loads and the effect of air coolers, while VENTFLOW estimates the air flow distribution. As the calculation of the heat loads requires a knowledge of the air flow and vice versa, the two modules are run iteratively until the solution converges. The program is written in Pascal and runs on any IBM-compatible personal computer.

Jan 1, 1987