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Scrap printed circuit boards were selectively smelted at 1 200°C to produce a metallic alloy having three phases. These phases were identified as a lead-rich phase, a low tin content alpha bronze phase, and a high tin delta phase. Electrochemical leaching studies on this alloy were done in 1 mol/dm3 sulfuric acid or in 2 mol/dm3 hydrochloric acid (adjusted to an ionic strength of 3 mol/dm3). The lead rich phase was more strongly passivated in sulfate media, and in this medium the high tin content delta bronze was more resistant to corrosion than the lower tin alpha bronze phase. In chloride medium the lead phase and both bronze phases corroded readily, but with current densities about an order of magnitude lower than in sulfate medium (static conditions) for the bronze phases. The high tin delta bronze phase was found to form a passivating layer in sulfate media. A similar layer was not seen in chloride medium. The leaching studies in sulfate medium also showed the existence of an alpha bronze phase of lower tin content in the centres of the alpha phase grains. This phase was quite resistant to leaching in sulfate medium.

Jan 1, 2009

Mining is a business involving extraction of commodities of value to society from non-renewable resources. Consequently there is only one opportunity to extract ore from the ore body in order to unlock the value potential encompassed in the asset. It is therefore imperative that the maximum value is unlocked during the extraction programme, considering the relative wealth generated for shareholders and society, the sustainability of society, the environment and the operation. The bulk of the value that is unlocked is usually embedded in the initial design process. How do you measure sucess The most common measure of success is the return on investment, which is unlocked during the extraction process. This is usually only determined and locked-in during the study process. Another measure of success is the profitability that is achieved on a monthly basis. A further measure would be the enhancement the asset affords to the share price of the operation. Increasing focus on sustainable development requires that the impact on the society and environment received high priority as well. All these measures are largely encompassed in the cash flow and the discounted cash flows. This paper focuses on the dynamics of the cash flow and the most significant elements influencing return in investment. These include the mine design, production volume, sustainability, risk and valuation techniques. When do you add the most value? There are many different phases and definitions noted by different authors to demonstrate and standardise the study process for new projects. This paper is based on a process with 3 major components namely a conceptual study, a prefeasibility study and a feasibility study.

Jan 1, 2007

By S. Shamaila

The design and efficient operation of density-based mineral processing units requires regular densimetric analysis to be carried out on the various associated process streams. The results obtained from such analyses can have wide application, including the generation of washability and partition curves, which are critical for process design, control, and simulation. This paper describes some of the collaborative efforts that Kumba Iron Ore, in partnership with Springer New Technology and Anglo Technical Solutions Research, is pursuing in developing a novel density determination technique exploiting X-ray transmission (XRT) and optical imaging. This technique is being developed with the aim to determine sample density distributions that apply to washability characterisation of ores. This technique is aimed to be an alternative to the traditional sink and float method. For certain applications sink and float has required the use of tetrabromoethane (TBE) solution?a chemical that has been classified as harmful and environmentally unfriendly. This paper therefore presents some achievements in developing this novel technique which seems to be very promising.

Jan 1, 2012

By N. J. Roodt

Mine dumps created in terms of the pre-MPRDA regime (old order mine dumps) are currently not regulated by the MPRDA, and the common law owners of such dumps are free to process them without the need to obtain the relevant rights. The MPRDA Amendment Act purports to change this position. However, the wording of the Amendment Act raises a number of problems which render the post-amendment position at best unclear and at worst absurd and unworkable. The primary concern with the Amendment Act is that, on one interpretation, material placed on the same dump at different times may be treated differently at law. Thus, parts of a dump may be subject to one person?s right while others may be subject to another?s right. Moreover, case law has generally regarded mine dumps as movable property and, by extending the MPRDA to apply to all mine dumps, the Legislature is extending the ambit of the Act to cover movable property, a scenario not contemplated by the wording of the Act (even after its amendment) in relation to applications for rights. The better interpretation of the amendments, which are not yet in force, is that they will not apply retrospectively to old order mine dumps.

Jan 1, 2010

By M. C. J. van der Merwe

"Carboxymethyl cellulose is an organic binder used in the iron ore pelletizing industry. The basic principles of how carboxymethyl cellulose (CMC) solutions behave during the pelletizing process and how these principles affect the drop and compression strengths of the pellets are poorly understood. The aim of the investigation was therefore to gain knowledge on the behaviour of CMC during the pelletizing of haematite concentrate.Haematite pellets with different additions of CMC (0.1–0.4 wt%), were subjected to drop tests, compression tests, and free moisture content analysis. The relationship between the drop strength, compression strength, free moisture content, elapsed time, and CMC concentration was analysed.The drop strength had a strong correlation with the free moisture content of the haematite pellets, with a correlation coefficient of 0.94. The compression strength of the CMC-bonded haematite pellets increased as the free moisture content decreased, reaching a maximum upon depletion of the free moisture content. Haematite pellets with CMC concentrations of 0.1 and 0.2 wt% developed most of their strength within the first day after pelletizing, whereas pellets with concentrations of 0.3 and 0.4 wt% developed most of their strength between one and two days after pelletizing. The time within which CMC-bonded haematite pellets develop most of their strength is therefore dependent on the CMC concentration. IntroductionFines are produced during the beneficiation of iron ore. These fines are separated from the lump ore and can be upgraded to produce a concentrate, which is used as a raw material for the production of pellets. Pellets in turn form a key burden material for direct reduction processes as well as the blast furnace (Zhu et al., 2015).Inorganic binders such as bentonite have been used predominantly in the iron ore pelletizing process to obtain pellets with suitable properties (Eisele and Kawatra, 2003). These binders, however, have the disadvantage of introducing impurities into the pellets. This has resulted in organic binders being pursued as suitable replacements for inorganic binders, of which carboxymethyl cellulose (CMC) shows good potential. Although CMC has been used as an organic binder in iron ore pelletizing, the fundamental principles of how it behaves during pelletizing and how these impact on pellet properties are poorly understood."

Jan 1, 2017

By D. -H. Park, G. -j. Kim, Y. -J. Park, C. -S. Hong, S. -Y. Choo

To evaluate the quantitative tunnel behavior influenced by characteristics of discontinuity, this pa-per executes the parametric study using 2 and 3-dimensional DEM analysis. First of all, this study finds that displacement and the stress of shortcrete are proportioned to frequency of joint and rockbolt axial force is adversely proportioned too. Secondly, it is found that the most sensitive in-put parameter used in Barton-Bandis(BB) model is residual friction angle. Finally, when joint sets are encountered at tunnel excavation face, to identify the most critical joint orientation is very crucial for a stability of tunnel. La thèse a pour but d’étudier les influences sur la stabilité du tunnel, au niveau du réseau de la discontinuité et de la valeur de sa nature aquis par le projet récemment exécuté en vue de mener à l’analyse quantitative de cette stabilité, en appliquant chaque différent paramètre comme la fréquence de diaclase, la constante de résistance des modèles de Barton-Bandis(BB) ainsi que la relation entre le sens d’excavation du tunnel et le réseau de diaclase en 3 dimensions. En fait, cette étude nous a montré que la fréquence de diaclase s’accroît proportionnellement au déplacement et à la contrainte du béton projeté. L’angle de friction résiduel s’est montré le plus sensible à la stabilité du tunnel parmi les modèles de BB. Aussi à travers l’analyse à 3 dimensions, il s’est vérifié que si l’angle de pente du groupe de diaclase est horizontal entre l’axe du tunnel et la direction, il donne une influence importante sur le comportement du tunnel. En particulier, l’influence était la plus importante sur un fond rocheux dont la diaclase horizontale est grande. Um das quantitative Verhalten des Tunnels zu bewerten, eroertert dieses Papier eine parametrische Studie mit Hilfe der DEM Analyse. Auch wird hier eine zweidimensionale Analyse von Ver-bindungen verschiedener Frequenzen in der Gesteinsmasse, eine sensitive Analyse von allen der im Barton-Bandis-Modell (BB) genutzten Parameter und eine Dreidimensional-Analyse mit ver-schiedenen dreidimensionalen geometrischen Veteilungen von Verbindungen ausgefuehrt. Erstens: Die Studie findet heraus, dass Vedraengung und Druck im Shortcrete proportional zur Frequenz von Verbindungen und Axialkraft der Steinbolzen antiproportinal ist. Zweitens: Es wird herausge-funden, dass die am meisten Sensitiven der im BB-Modell angewendeten Eingaben die am Ende uebriggebliebenen Reibungswinkel sind. Und schliesslich wird herausgefunden, dass wenn Ver-bindungsteile an der Tunnelaushoelungsoberflaeche ausgemacht werden, fuer die Tunnelstabiltaet die Identifikation der meist kritischen Verbindungsorientierung sehr bedeutungsvoll.

Jan 1, 2003

By N. C. Steenkamp

Lightning has been observed in dust clouds following open-pit blasting. It is proposed that the occurrence of this phenomenon is related to the physical composition and characterization of the mineral fines that comprise the bulk of the dust cloud. Silicate minerals, which are susceptible to fine fracturing during blasting, generate the initial charge. This is further enhanced by collisions and friction during the turbulent upcast in the post-blast dust cloud. Varying size fractions result in different rates at which these particles drop out of suspension and create a secondary temperature gradient. This results in the creation of two charged zones and increases the potential of developing a discharge in the form of lightning. The ideal prevailing meteorological conditions need to be windless to minimize the effect of particle dissipation and have sufficient moisture toenhance the potential of generating lightning.

Apr 14, 2024

By A. Whillier

Recommendations are given for the design of vertical cooling towers for use underground in mines and a method is given for predicting the entering and leaving water temperatures when a given amount of heat has to be dissipated.

By H. L. Monro

The individual supplies of and demands for gold that make up the total supply/demand structure in any year, together with their individual price elasticities, are used to determine the effect of forward sales on the gold price.

Jan 1, 1992

By A. M. Sage

This paper reviews the metallurgical functions of vanadium in high-strength Iow-alloy steels, and discusses the ways in which vanadium is used in various types of steel supplied as reinforcing bars, plates, sections, and strip. Potential developments to meet new engineering requirements are discussed briefly.

Jan 1, 1984

By B. H. Sandelowsky

Prehistoric metal-working in South West Africa by B. H. SANDELOWSKY*, Ph.D. (Visitor) This paper describes a three-hundred year old metal-working site at Rehoboth, and makes a plea for information on such sites elsewhere in South West Africa so that they can be investigated. The technique of ore smelting that was used at Rehoboth appears to be different from that practised elsewhere by Bantu peoples before the modern era.

Jan 5, 1974

COUNCIL FOR 1987/88 President B.C. Alberts President-elect C.E. Fivaz Vice Presidents Senior Junior Dr O.K.H. Steffen H.G. Mosenthal Immediate Past President Dr H. Wagner Honorary Treasurer Dr H. Wagner

Jan 1, 1988

Council for 1995/96 President D.A. J. Ross-Watt President Elect Dr N.A. Barcza Vice Presidents Senior R.P. Mohring Immediate Past President J.A. Cruise Junior J.R. Dixon Honorary Treasurer J.A. Cruise

Jan 1, 1996

By U. S. Kusel

Extractive metallurgy in Iron Age South Africa U. S. KUSEL, B.A. Hons. (Pta) (Visitor) The finds relating to the metal-working of Iron Age Bantu tribes are reviewed, the following metals or alloys being considered: gold, tin, copper, bronze, brass, and iron. Most is known about copper- and iron-working, but even this is very little, and no one has successfully been able to demonstrate how iron was smelted in the primitive furnaces that have been found.

Jan 1, 1974

By C. M. Sellars, W. E. Stumpf

SYNOPSIS The effects of concurrent recovery, prior creep deformation and concurrent high temperature fatigue on the coarsening of some carbides in steels have been studied. It was found that concurrent recovery enhances the coarsening rate by orders of magnitude and prior creep deformation causes an enhancement of about two times. Finally, concurrent fatigue causes an initial greatly enhanced coarsening rate but after prolonged cycling dissolution of the carbides occurs.

By R. G. Jurd

This paper considers the introduction of large-scale longwall mining into South African coal mining, instead of the conventional mechanized bord-and-plllar mining that is widely practised at present. The two methods are compared, and longwall mining is found to have the advantage in several respects in some seams. The most cogent reasons for the introduction of the longwall method In some seams are associated with safety strata control and increased labour costs.

Jan 1, 1978

By D. D. Marsden

The paper briefly outlines the history of the successful development of vegetating techniques for mine-residue deposits. It seeks to place on record the major roles played by M.J. Mrost, who initiated and systematically developed the concept, and W.H. Cook, who continued the trials and successfully directed a stupendous large-scale project. The vegetating techniques currently practised are outlined, and it is concluded that vegetating is still the only surface-stabilizing technique of any significance that is employed throughout the world.

Jan 1, 1987

By R. J. Mason

Background to the Transvaal Iron Age-new discoveries at Olifantspoort and Broederstroom R. J. MASON*, Ph.D. (Visitor) The work being done on Iron Age sites in the Transvaal is described, with particular reference to the finds at Olifantspoort and Broederstroom. The material so far found provides evidence for the production of iron and copper, the farming of cattle and sheep, and the construction of large villages by people who were probably ancestral to the present Bantu population. The material dates from as early as A.D. 270, but clear indications occur from AD. 460 onwards.

Jan 1, 1974

An investigation into the stability of large open stopes at Premier diamond mine, Culinan, South Africa, is described. The open stopes are located in a weak kimberlite orebody, directly underneath a 75 m-thick sill of gabbro. Two and three-dimensional stress analyses were carried out in a back-analysis of the stresses and failure around the first open stope created under the sill. The results were used in the prediction of the future stability of the planned open stopes, intervening pillars, and sill.

Jan 1, 1987

By N. von Stade, G. du Plessis, W. van Niekerk, H. Bosman

Exploration, and other, boreholes are drilled to obtain information about the geological environment. Knowledge of the exact position (dip and direction) of the holes is important to ensure compatibility between the hole and the geological information. Kumba Resources traditionally used mechanical methods to determine the hole characteristics. These are cumbersome and expensive, and as a consequence a new method, the IVEC (Iscor Video Exploration Camera), was developed which utilizes a charged coupled device (CCD) image sensor focused on a three-dimensional compass. This system is rugged, relatively inexpensive and gives real-time results during borehole logging. Keyword: Borehole inclination, deviation, dip and direction, geophysics, exploration.

Sep 1, 2001