Search Documents

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 L. W. Helle

This paper summarizes the investigations carried out into a defect involving the corners of billets rolled from continuously cast blooms, which broke open during the rolling process. As it was believed that the defect must be connected with the formation of subcutaneous blowholes in the bloom, the investigations were directed towards an understanding of the roles of the three gases involved in the process. In an extensive trial programme, samples were taken from the heat at all stages of processing, as well as from all the raw materials and alloys. The main sources of nitrogen were found to be re blows, pick-up from the alloys added to the ladle (especially graphite), and open-stream casting. The major source of hydrogen was moisture in the alloys, especially high-carbon ferromanganese and silicomanganese. Further, it was established that the moisture content of the alloys is closely related to the appearance of the defect in steels with a carbon content of less than 0,20 per cent; 72 per cent of all the defects were present in this type of steel. Most of the remaining defects were found in steels with a carbon content of more than 0,60 per cent, where the nitrogen content was substantially higher than in the lower-carbon steels. It is suggested that the defect arises from the combined effect of oxygen. nitrogen, and hydrogen. Its occurrence in low- and high-carbon steels is triggered by the formation of subcutaneous blowholes when the critical oxygen level for carbon monoxide blowholes is lowered by the presence of excessive amounts of hydrogen and nitrogen respectively.

Jan 1, 1984

By S. M. Spottiswoode

Rock mechanics benefits of stope support in deep-level mining originate principally from the ability of the support to resist relative movements between the hangingwall and the footwall. While the role of stabilizing pillars and backfill on reducing the energy release rate (ERR) at the face is well understood on the basis of elastic behaviour of the rock mass, the effect of support on controlling movement of fractured ground around deep-level stopes has not yet been thoroughly studied. As part of a programme of studying the behaviour of this fractured ground, geophones were placed 10 m from the face on the roof and floor of a longwall stope in which packs were used as supports. It was found that differential movement between the roof and floor generally exceeds average stope movement during a seismic event. Conventional support therefore transmits very little seismic energy; this is expected to remain true until complete convergence occurs. In backfilled stopes, backfill can become at least as stiff as the fractured wall rock. This will have the effect of reducing the length of the hanging- wall beam. Amongst other rock mechanics considerations, a shorter hanging- wall beam should: (i) increase the resonance frequency of the hangingwall and thereby decrease the levels of vibration for seismic events with M > 1,0; (ii) reduce absolute vibration levels by increasing the mass of rock immediately adjacent to the stope which is shaken by seismic waves; and (iii) reduce differential movement between the roof and floor and thereby reduce cyclic strain on the backfill and on gully support.

Jan 1, 1988

By R. J. E. Stewart

Another very successful evening meeting was organized by the Johannesburg Branch of The South African Institute of Mining and Metallurgy on 20th November, 1990, when Mr R.D. MacPherson, General Manager of Richards Bay Minerals, gave a presentation on the Richards Bay operations. The function was held in the Ballroom of the Johannesburg Country Club, and the very high attendance (some 250 people) was indeed a reflection of the high profile of the subject mater. It was also a fitting reward for the efforts of Mr MacPherson and his team, who spent a considerable amount of time and effort traveling the country to present 'the other side of the story'.

Jan 1, 1991

By S. L. Crouch

A. C. Dieringt The procedure described by Professor Crouch for the modelling of mining in faulted ground allows the elastic and inelastic deformation to occur simultaneously, that is, fault slip occurs while an element is being mined. The energy release rates (ERR) shown in Crouch's Fig. 10 are apparently calculated from his equation 9 using the i total deformation Din (see the upper load line of Fig. I) Refractories The institute of 'Gesteinsh iittenkunde' of the technical university at Aachen, the Refractories Research Institute at Bonn, and the Verein Deutscher Eisenshiittenleute (VDEh) at Diisseldorf are to hold the XXII International Refractory Colloquium on 27th and 28th September, 1979, at Aachen.

Jan 1, 1979

By F. W. Petersen

For the past thirteen years, the Universities of Cape Town and Stellenbosch have hosted an annual symposium to discuss topics relevant to mineral processing. Since 1987, this Symposium has been held under the auspices of the Western Cape Branch of the South African Institute of Mining and Metallurgy, and has become one of the main events on the national conference calendar. In 1989 and 1993, the symposia took the shape of international conferences. This year the 13th Annual Mineral Processing Symposium was organized by the two universities, the Cape Technikon, and the local branch of the South African Institute of Mining and Metallurgy, and was held at the Van Riebeeck Hotel in Gordon's Bay.

Jan 1, 1994

By A. B. Stewart, I. J. Barker

Traditionally it has commonly been believed that the only problem with inductive reactance in a submerged-arc furnace is that it leads to difficulties with the electricity supply as a result of the Iow power factor. This paper sets out to show that inductive reactance can also give rise to the following problems in the metallurgical operation of a furnace: (i) dead and live phases (fairly well known in openarc furnaces), (ii) lack of sensitivity to electrode movement, (iii) interactions between electrodes. These problems increase with increasing inductive reactance relative to resistance, and thus they increase with furnace size. Each of these effects is discussed in detail, and suggestions are made for their alleviation.

Jan 1, 1980

By M. G. Atmoret

It seems to me to be particularly appropriate that this topic should be discussed at the first prize-giving function of this kind. As you know, this presentation of awards to young mining engineers and metallurgists is to be an annual event, and never before in the dynamic and rapidly changing climate of the South African metallurgical industry has it been more necessary for young, and perhaps older, practitioners to consider the future of their profession and their role in the industry. I look forward with interest to the time, five to ten years from now, when I shall recall my crystal-gazing of tonight to see how far wrong I have been.

Jan 1, 1977

By R. C. Urquhart, W. P. Channon, D. D. Howat

Discussion: The mode of current transfer between electrode and slag in the submBerged-arc furnace by w. P. CHANNON, R. C. URQUHART, and D. D. HOWAT J. MEINTJES I have read the paper with much interest, and I should like to make a few observations. (I) The experimental work deals with resistance heating by an electrode immersed in a slag... AUTHORS' REPLY We thank Mr Meintjes for his critical analysis and helpful comments arising out of his study of our paper. Possibly we should emphasize at the outset that our experiments all related to the conditions in which the lower portion of the electrode was immersed in molten slag. We believe, however,

Jan 12, 1974

By H. L. Monro

The price received for a commodity decreases as the quantity sold increases. all other factors remaining the same. This has been the position with gold since it was demonetized in August 1971. The result is that the marginal revenue per kilogram of gold decreases steadily with increased production. If operating losses are to be avoided, the marginal cost of production must not exceed the marginal revenue. This requirement, although not seriously violated by most invididual mines, is not met by the industry as a whole, resulting in large losses of income to the State and the shareholders. These losses are increasing, and a way of curbing or reversing this trend is described.

Jan 1, 1984

By F. J. N. Stassen

SYNOPSIS The effect of conditioning energy on the flotation of gold, U308, and pyrite was investigated in the range 0,1 to 100 kWh per tonne of dry ore for various combinations of conditioning time and impeller speed in a cylindrical con¬ditioning tank. It was found that, when the conditioning energy was increased to between 5 and 10 kWh per tonne of dry ore, the total recovery and flotation rate of the valuable minerals (expressed as Klimpel parameters) increas¬ed substantially. The Klimpel parameters are dependent on conditioning energy, but are independent of condition¬ing time or impeller speed (at constant conditioning energy). The Klimpel parameters of the gangue are indepen¬dent of conditioning energy.

Jan 1, 1991

Results are presented on the elution of gold cyanide and base-metal cyanide complexes from strongand weakbase resins. It is shown that thiocyanate anions, zinc cyanide anions, and thiourea in acid solution are effective eluants of strong-base resins, but that it is generally necessary for electrowinning to be incorporated in the elution cycle if fast rates of elution are to be achieved. Weakbase resins are eluted with sodium hydroxide solution, which is shown to be far simpler and far more effective than the elution of strong-base resins. The effects of parameters such as concentration of the eluant, temperature, and electrowinning efficiency on the rate of elution of the resins are examined.

Jan 1, 1984

By J. J. Schoeman

In South Africa and in the rest of the world, the two mica minerals that have the most important commercial value are muscovite and vermiculite. Muscovite has been making a comparatively small but steady contribution to South Africa's mineral exports since about 1960. Vermiculite mining and concentration were started by the late Or Hans Merensky at Phalaborwa during 1946. Vermiculite has enjoyed good overseas sales since then, and during the past four years has become an important earner of foreign currency for South Africa. The various aspects of the micas that could be of general interest are briefly reviewed, such as the history of their exploitation, their mineralogy and chemistry, and their mining, concentration, production, sales, and future

Jan 1, 1989

By C. Holck, J. Yarmuch, J. Read

"Steepening of slopes provides the means to reduce waste extraction and increase ore recovery in open pit mines; however, it may also adversely affect safety by posing a higher risk of slope failure. The implementation of slope monitoring programmes is recommended to manage this risk inherent in steeper slopes. In this paper, the design and evaluation of monitoring campaigns to measure subsurface deformation and groundwater pore pressure in open pit mines is presented. The monitoring programmes were applied to a theoretical case of an open pit mine designed using DeepMine software (BOAMine SpA, 2015). Mine plans were developed based on the initial base case scenario with monitoring programmes considered for four types of monitoring instrumentation: two established technologies, in-place inclinometers (IPIs) and vibrating wire piezometers (VWPs); one emerging technology, the ShapeAccelArray (SAA); and a novel technology under development, the Enhanced Networked Smart Markers (ENSMs). Technical and economic appraisals of the monitoring programmes and sensitivity analysis of the developed mine plans showed that using ENSMs spaced every 4 m had the lowest cost per unit of data gathered. IntroductionSeveral open pit mines have already exceeded their design life and, as they become deeper and reach depths over 1000 m, they face higher rock stress levels and tensile deformations (Stacey and Xianbin, 2004; Stacey et al., 2003). The more complex the conditions in modern open pit mines, the more difficult it is to achieve long-lasting, stable pit slopes and to meet the mine’s economic needs: maximize financial returns, minimize risks to operational safety, achieve optimal ore recovery, and minimize waste extraction (Stacey, 2009). Steepening of slopes provides the means to reduce waste extraction and increase ore recovery (Stacey, 2009; Calderon and Tapia, 2006; Bye and Bell, 2001; Jefferies, Lorig, and Alvarez, 2008); however, it may adversely affect operational safety, as steeper slopes are less stable than shallow slopes (Steffen et al., 2008; Mphathiwa and Cawood, 2014)."

Nov 1, 2018

By Z. Hou

ABSTRACT: Short-term strength, damage and healing boundaries for rock salt are experimentally determined and integrated into the Hou/Lux-MDS damage-healing model. This model can be used to describe the mechanical behaviour of rock salt during a damaging process (under high stress to strength ratios) as well as during a healing process (under very low stress to strength ratios with high confining pressure). The development of the damage and the stress to strength ratio in the excavation damaged zone (EDZ) of a storage cavern under a minimum internal pressure as well as the development of the healing of damage and the stress to strength ratio under a subsequent maximum internal pressure are investigated project-related. The results of the investigation make it possible to shift the permissible minimum pressure boundary down, allowing the optimisation of decisive economic characteristics of storage caverns. RÉSUMÉ: Le comportement court terme, l’endommagement et les conditions de colmatage pour le sel gemme ont été étudiés expérimentalement et intégrés dans le model endommagement-colmatage Hou/Lux-MDS. Ce modèle permet de décrire le comportement mécanique de sel gemme pendant le processus d’endommagement (sous fort rapport contrainte-résistance) et le comportement du processus de colmatage sous très faible rapport contrainte-résistance avec forte pression de confinement. Le développement d’endommagement et le rapport de contrainte-résistance dans une zone d’endommagée (EDZ) d’une cavité de stockage avec un maximum de pression de soutènement ont été étudiés. Les résultats de cette étude permettent de conclure qu’il est possible de baisser la pression de soutènement, et par conséquent d’optimiser les caractéristiques économiques décisives des cavité de stockage. ZUSAMENFASSUNG: Für Steinsalz werden Festigkeits-, Schädigungs- und Verheilungsgrenze experimentell ermittelt und in das Schädigungs-Verheilungs-Modell Hou/Lux-MDS integriert. Damit kann das mechanische Verhalten von Steinsalz sowohl bei einem Schädigungsprozess (mit hohen Ausnutzungsgraden) wie auch bei einem Verheilungsprozess (mit niedrigen Ausnutzungsgraden) beschrieben werden. Projektbezogen werden die Schädigungs- und Ausnutzungsgradentwicklung in der Auflockerungszone einer Speicherkaverne unter einem minimalen Innendruck sowie die Verheilungs- und Ausnutzungsgradentwicklung unter einem anschließenden maximalen Innendruck untersucht. Die Untersuchungsergebnisse erlauben, die zulässige Minimaldruckgrenze nach unten zu verschieben, so dass entscheidende wirtschaftliche Kenngrößen von Speicherkavernen optimiert werden können.

Jan 1, 2003

By R. C. J. Goode

"In my Presidential address last year `The Institute in Retrospect and Prospect', I briefly reviewed the past activities of our Institute, I commented on the dynamic growth of the mineral activity of this country and of the great contribution towards this growth made by members of this Institute. I maintained that there was still further growth to come, pointing out that our future would be very much dependent on the availability and skills of our mining and metallurgical men. This Institute had, therefore, a most important task ahead to ensure that this country would have the necessary skilled engineers to develop our mineral industry so that we would be able to compete successfully in the wide world. In my address I highlighted many of the major achievements of our members and of our Institute. In today's review, I have no wish to repeat myself and I would, therefore, ask members and visitors to regard this review as complementary to my presidential address. I must also refer you to the very full resume of our affairs written for a special brochure in March, 1944, by E. H. Johnson, a founder member, on the occasion of our 50th Anniversary. There is no need to repeat what was given there, rather I will attempt to bring that history up to date. Our Institute was founded under the name of Chemical and Metallurgical Society of South Africa on 24th March, 1894, by a group of chemists and metallurgists The name was changed to Chemical, Metallurgical and Mining Society of South Africa early in 1903, and in July, 1956 became The South African Institute of Mining and Metallurgy. We were not the first technical organisation in South Africa, the S.A. Association of Engineers and Architects having been formed in 1892. In that year also the British Institution of Mining and Metallurgy started in London. A chronological table of some of the more important societies is as follows: British Societies: Society of Apothecaries 1617 Royal Society 1660 Geological Society 1807 Institution of Civil Engineers 1818 Institution of Mechanical Engineers 1847 Institution of Chemistry 1877 Institution of Mining Engineers 1889 Institution of Mining and Metallurgy 1892 Other Societies: Mining Society of Nova Scotia 1887 S.A. Association of Engineers and Architects-later the S.A. Association of Engineers which amalgamated with the Transvaal Institute of Mechanical Engineers 1892 Australasian Institute of Mining and Metallurgy 1893 Geological Society of South Africa 1895 South African Society of Electrical Engineers-disbanded 1904 1897 Mechanical Engineers' Association of the Witwatersrand-later, the

By R. Hummel

In the quest to reduce overall costs and improve operating efficiency, the application of GPS based technology in open pit mining has evolved significantly in recent times. Venetia Mine has been leading the way in the De Beers group in the implementation of these systems and the realization of significant benefits from them. Following on from the successful results and the notable benefits obtained from the Wenco Truck Dispatching system and the Caterpillar CAES system on the loading and dozing equipment, Venetia has implemented the first fully functional and integrated GPS based drill monitoring system in southern Africa to its drilling operations. This paper elaborates on the concept of drill monitoring and how the vision for the application of the system at Venetia has developed and been implemented. The paper further describes the workflow involved, beginning with the initial test work done with SSI Kaltex and the Australian Drill Advisor system through to the final details of the integration of the Aquila system with the CATERPILLAR Computer Aided Earthmoving System (CAES) and the alliance with SandvikRock Tools. Most importantly, the paper details the benefits that are derived from drill monitoring and the use of the information generated by such a system. Venetia has pioneered the move towards smart partnerships and alliances with strategic suppliers within the De Beers group. The area of drilling, as the important start of the entire mining process, has been no exception and the final part of the paper covers how drill monitoring provides vitally important information that enables a supply partnership, to function cost-effectively and profitably for both parties involved. By having the type of accuracy, detail, validity and timeousness in the information being received as a result of the implementation of such a system, better management decisions can betaken, creating a more focused and efficient mining environment. In these times of increasing costs and reduced commodity prices, the mining industry will be required to continue pushing the boundaries on these technology applications in order to remain competitive.

Sep 1, 2001

By P. R. Jochhens

The Past. In the past, large metallurgical companies (for example the mining houses) had the necessary infrastructure both to develop metallurgical flowsheets and to undertake the construction and project management of metallurgical plants. Effectively, the sole contribution by contracting companies was the supply, and possibly the installation, of specific items of equipment. OBITUARY: AUSTIN WHILLIER (1927 - 1981) On Thursday, 13th August, 1981, Dr. Austin Whillier passed away peacefully in Johannesburg after a long illness. This event has been a serious blow indeed, and its effects will be felt, not only by the Chamber of Mines of South Africa and the South African mining industry, but also throughout many scientific and technical spheres both in South Africa and further a field.

Jan 1, 1981

By O. S. Lubbe, G. Annandale, J. W. van Wyk

This paper deals with the development and evolution of room and pillar mining in the South African chromitite and platinum mining industry over the past sixteen years. The paper describes the need for cheaper, more effective and safer mining methods in hard rock mining. It also describes how a mining method traditionally only applied in coal mining in South Africa evolved into a method ideally suited to conditions in chromitite and platinum mines. The paper also touches on joint efforts from mining houses, mine management and equipment manufacturers to design and build mechanized equipment custom designed and unique to South Africa in order to overcome challenges presented by the harsh operating conditions encountered in the mines in the Bushveld Complex.

Sep 1, 2001

By K. C. Sole

The International Solvent Extraction Conference takes place every three years, under the auspices of the international Solvent Extraction Committee. ISEC '96 held in Melbourne, Australia, in March 1996, was attended by delegates from 34 countries. South Africa was well represented, with delegates from Amplats, De Beers, Mintek, Western Platinum Refinery, and independent consultant Phillip Lloyd (who represents South Africa on the International Committee). The theme of this year's conference was 'Value Adding through Solvent Extraction'. Five plenary lectures were presented. Dr E. Blass of Germany gave the opening presentation entitled 'Solvent extraction-a historical review', which traced evidence for the use of solvent extraction (SX) from the time of the ancient Egyptians, through the Middle Ages and Renaissance, to the Industrial Revolution.

Jan 1, 1996