Scielo RSS <![CDATA[Journal of the Southern African Institute of Mining and Metallurgy]]> http://www.scielo.org.za/rss.php?pid=0038-223X20120007&lang=es vol. 112 num. 7 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Breakthrough Technologies</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000700001&lng=es&nrm=iso&tlng=es http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000700002&lng=es&nrm=iso&tlng=es <![CDATA[<b>African-based CSMI introduces short courses for professionals</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000700003&lng=es&nrm=iso&tlng=es <![CDATA[<b>The dual-electrode DC arc furnace-modelling brush arc conditions</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000700004&lng=es&nrm=iso&tlng=es The dual-electrode DC arc furnace, an alternative design using an anode and cathode electrode instead of a hearth anode, was studied at small scale using computational modelling methods. Particular attention was paid to the effect of two key design variables, the arc length and the electrode separation, on the furnace behaviour. It was found that reducing the arc length to brush arc conditions was a valid means of overcoming several of the limitations of the dual-electrode design, namely high voltages and arc deflection. <![CDATA[<b>Comparing two mass size distributions</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000700005&lng=es&nrm=iso&tlng=es We consider in this paper the use of a modified version of Hotelling's statistic in the analysis of particle size distributions. The statistic can be adversely affected by the presence of outliers among the data. We propose a competitor to the statistic that is based on ranks, and hence is less sensitive to outlier effects. The results of a Monte Carlo study suggest that the rank test is highly competitive with the Hotelling test in its ability to detect differences between two mass size distributions. The calculation of the rank statistic is explained in detail and its application is illustrated on two sets of data. <![CDATA[<b>A practical knowledge management framework within the pyrometallurgical industry</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000700006&lng=es&nrm=iso&tlng=es In this article, a case is made for the importance of the transfer and management of tacit knowledge to ensure continued sustainable competitive advantage within the pyrometallurgical industry in South Africa. The state of knowledge management (KM) is assessed through a theoretical and empirical study. The empirical part of the study was conducted by means of a survey questionnaire. An important prerequisite within the research entailed determining the current state of KM within the pyrometallurgical industry, and the findings are presented throughout this article. The research argues for initiatives to address the high turnover of pyrometallurgical knowledge workers. This industry needs to entrench tacit knowledge and therefore address the problems associated with the continuous loss of inherent specialized knowledge. Appropriately, emphasis is placed on identifying initiatives required to embed and retain not only human capital lost through mobility, but rather retaining tacit knowledge through a practical KM framework. <![CDATA[<b>An experimental approach to determine the hole-pressure under expansion load</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000700007&lng=es&nrm=iso&tlng=es Applying non-explosive expansion material (NEEM) is one of the safest methods for rock fracturing, especially in a hard rock quarry. An experimental study was conducted to determine the pressure exerted by NEEM in a hole, which is necessary for analysing rock fracturing, particularly in a numerical modelling. Stress distribution was developed in a thick-wall cylinder in order to measure the tangential strain on the external boundary. In the experiments, nine pipes of different materials and varying diameters were selected and then loaded internally with a general type of NEEM. Through electrical strain gauges, the tangential strains were recorded on the external boundary of the pipes. The results obtained from these tests and existing data from previous researchers were utilized for the statistical analysis. A new experimentally-derived formula is proposed for determining the pressure exerted by NEEM by multiple parameter regression with a high correlation coefficient. The proposed model has a nonlinear form with three independent parameters i.e. the hole diameter, the time, and the modulus of elasticity of the material. <![CDATA[<b>High pressure grinding moving ahead in copper, iron, and gold processing</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000700008&lng=es&nrm=iso&tlng=es 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. <![CDATA[<b>Performance evaluation of a new stochastic network flow approach to optimal open pit mine design-application at a gold mine</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000700009&lng=es&nrm=iso&tlng=es The optimal design of production phases and ultimate pit limit for an open pit mining operation may be generated using conventional or stochastic approaches. Unlike the conventional approach, the stochastic framework accounts for expected variability and uncertainty in metal content by considering a set of equally probable realizations (models) of the orebody. This paper evaluates the performance of a new stochastic network flow approach for the development of optimal phase design and ultimate pit limit using a gold deposit as the case study. The stochastic and conventional frameworks as considered here utilize the maximum flow and Lerchs-Grossman (LG) algorithms, respectively. The LG algorithm is restricted to considering an estimated (average-type) orebody model, while the stochastic maximum flow algorithm is developed to simultaneously use a set of simulated orebody realizations as an input. The case study demonstrates that, when compared to the conventional LG algorithm as used in the industry, the stochastic approach generates a 30 per cent increase in discounted cash flow, a 21 per cent larger ultimate pit limit, and about 7 per cent more metal, while it maintains a consistency in phase size. <![CDATA[<b>Operation of a concentrated mode dual-alkali scrubber plant at the Lonmin smelter</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000700010&lng=es&nrm=iso&tlng=es Lonmin Platinum installed a concentrated mode dual-alkali scrubber at the smelter in Marikana in 2002. The dual-alkali scrubber was the technology of choice at that time as a sulphur fixation plant, due to the perceived benefits of handling both the high SO2 concentrations of converter off-gas and the swings in SO2 concentration that are linked to Peirce-Smith operation. Owing to current and impending legislative requirements for air quality and waste, Lonmin is currently considering additions to the dual-alkali plant, but is also evaluating alternative technologies for sulphur fixation. This paper reviews the decision of Lonmin to install a concentrated mode dual-alkali scrubber and presents plant performance achieved. It also describes the important control variables and sensitivities of the plant, and the final product that is produced by the operation of the plant. The legislative requirement that drives the Lonmin technology evaluation is also discussed <![CDATA[<b>Remote sensing in management of mining land and proximate habitat</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000700011&lng=es&nrm=iso&tlng=es Although remote sensing technology has been available for many years, it has rarely been used for monitoring mining activity. Recent studies indicate that remote sensing is also a valuable tool for managing and planning certain aspects of the mining operation. In this paper, we examine areal expansion of marble quarries and the affected vegetation over a period of 10 years in the Mugla region in Turkey, using geographic information system (GIS) and remote sensing (RS) techniques. Images captured by ASTER Level 3A01 (3D Ortho Data Set), Landsat 5, and Landsat 7 satellites between 2001 and 2009 were used for the analysis. Changes in the natural vegetation as a function of the production level in the marble quarry were calculated using the normalized difference vegetation index. According to the study results, land cover and natural vegetation decreased by less than 3 per cent and 1 per cent respectively between 2001 and 2009, following an upsurge in mining activity in the region <![CDATA[<b>Large-scale design and testing of an improved fine coal dewatering system</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000700012&lng=es&nrm=iso&tlng=es Fine coal (-500 |m) is notoriously difficult to dewater. It is not uncommon for a dewatered product to have a moisture content as high as 30 per cent after vacuum filtration. This poses several handling and financial problems to such an extent that a lot of fine coal is discarded onto slurry waste ponds. A novel way of dewatering fine coal was developed at North-West University. It entails deliberately damaging the filter cake during dewatering to allow for an increased flow of air through the cake at the expense of the applied pressure differential. This method resulted in an average improvement in final cake moisture of between 3 per cent and 5 per cent when executed in the laboratory under controlled conditions. A device was designed that could be fitted onto existing belt filters that would damage the filter cake as it passes by. This device was tested on a vacuum belt filter installation at a coal beneficiation operation in the Waterberg coal field in South Africa. The results showed a 3 per cent reduction in final moisture of the cake, proving the validity of the method at full industrial scale. <![CDATA[<b>The establishment of a Mine Design Laboratory for improved teaching of and learning by Mining Engineering students</b>: <b>A case study</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2012000700013&lng=es&nrm=iso&tlng=es Improving student success rates without compromising the quality of graduates is one of the biggest challenges expanding university programmes are facing in South Africa. By establishing a new Mine Design Laboratory (MDL) for higher learning in Mining Engineering, the School of Mining Engineering at the University of the Witwatersrand (Wits Mining) has achieved one of the important goals in its five-year strategic plan, i.e. to improve throughput in all years of study. Although the establishment of the laboratory has been a costly exercise, results so far have shown an improved success rate in most subjects taught in the facility. This paper outlines the design and equipment of the laboratory, the facilities incorporated, a comparison with the old laboratory, and the performance of students-all of which indicate how important it is to have proper facilities to improve the teaching of, and learning by, large classes. Through this initiative, Wits Mining has taken an important step that will contribute to addressing the skills shortages in the mining industry.