Scielo RSS <![CDATA[Journal of the Southern African Institute of Mining and Metallurgy]]> http://www.scielo.org.za/rss.php?pid=0038-223X20100002&lang=pt vol. 110 num. 2 lang. pt <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Black sands, black swans, and teachers</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2010000200001&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>Mining is the most fundamental engineering discipline and the most rewarding</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2010000200002&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>A heat transfer model for high titania slag blocks</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2010000200003&lng=pt&nrm=iso&tlng=pt Titania slag is used as feedstock in the production of titanium dioxide pigment. It (titania slag) is the product of ilmenite smelting, a process whereby ilmenite is reduced at high temperature utilizing anthracite as a reducing agent. Although various slag tapping configurations are employed throughout the ilmenite smelting industry, the method of tapping the slag from the furnace into bell shaped cast steel pots, was the subject of investigation in this study. The paper describes the formulation of a cooling model used to calculate and subsequently predict the temperature profile of a slag block during its cooling within the various cooling environments of pot cooling, air cooling and water cooling. The model was calibrated against actual internal slag temperature measurements and verified with information obtained from both pilot and industrial scale blocks. The paper concludes with solidification results and their practical implication. <![CDATA[<b>Characteristics, recovery and provenance of rutile from the Namakwa Sands heavy mineral deposit, South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2010000200004&lng=pt&nrm=iso&tlng=pt The Namakwa Sands heavy mineral deposit is located along the West Coast of South Africa and the mine is a world class producer of high quality zircon, ilmenite and rutile concentrates from essentially unconsolidated marine and aeolian sands of Cainozoic age. The objective of this study was to characterize rutile with respect to distribution, grain size, textures, colour and mineral chemistry within the Namakwa Sands orebody with the aim to explain its overall poor recovery. A representative suite of heavy mineral concentrates from various sections of the orebody and stages in the recovery circuit has been investigated microscopically and by means of SEM-EDS and LA-ICP-MS. The rutile grain size distribution displays a wide range and is directly related to its variable chemistry and consequently density. In placer deposits such as Namakwa Sands, mineral sorting is a function of hydraulic equivalence, and high density grains are smaller than the lighter grains when deposited under similar conditions. Grain size is also a function of sediment maturity, and the highly mature red aeolian sand (RAS) component of the deposit has a coarser grain size than the less mature orange feldspathic marine sands (OFS). The above primary characteristics of rutile are responsible for the loss of the coarse-grained fraction during screening and, given the empirically determined relationship that increased substitution elements reduce conductivity, also during electrostatic separation. Provenance studies using geothermometry have shown that the heavy mineral suite has been sourced mainly by the proximal medium-to high-grade Namaqualand Metamorphic Complex. The positive relationship between substitution elements and temperature of formation explains their high concentration in rutile of this deposit. The heterogeneity of rutile, produced by the combination of a high temperature primary source and the typical marine-aeolian placer genesis is deposit specific and unfortunately not conducive to high recovery levels in the current Namakwa Sands beneficiation circuit. <![CDATA[<b>A basic triboelectric series for heavy minerals from inductive electrostatic separation behaviour</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2010000200005&lng=pt&nrm=iso&tlng=pt The separation of certain minerals by electrostatic techniques can be difficult due to their similar electrical conductivity, and any technique to improve this can be useful in certain difficult separation applications. Triboelectric differences between minerals can result in certain minerals acquiring small positive or negative charges prior to inductive electrostatic separation. By changing the polarity of inductive separation, relative changes in mineral recovery can be observed, which may be beneficial. In this brief study a JKTech mineral liberation analyser (MLA) was used to evaluate the effect of polarity change on selected minerals present in the Richards Bay Minerals deposit, and an approximate triboelectric series based on this behaviour is presented. <![CDATA[<b>Variability of pump system performance</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2010000200006&lng=pt&nrm=iso&tlng=pt The separation of certain minerals by electrostatic techniques can be difficult due to their similar electrical conductivity, and any technique to improve this can be useful in certain difficult separation applications. Triboelectric differences between minerals can result in certain minerals acquiring small positive or negative charges prior to inductive electrostatic separation. By changing the polarity of inductive separation, relative changes in mineral recovery can be observed, which may be beneficial. In this brief study a JKTech mineral liberation analyser (MLA) was used to evaluate the effect of polarity change on selected minerals present in the Richards Bay Minerals deposit, and an approximate triboelectric series based on this behaviour is presented. <![CDATA[<b>Understanding heavy mineral separation duties using finite element analysis</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2010000200007&lng=pt&nrm=iso&tlng=pt Heavy mineral deposits are becoming more complex in terms of their compositional variation, particle mineralogy and size distributions, and present challenges for the operation of separation equipment to achieve the required grades and recoveries. Changes in equipment design and concepts potentially provide new opportunities for the beneficiation of heavy mineral sands deposits. The development of a framework for the fundamental understanding of separator performance issues is a first step to develop new machines. This paper will present a first step analysis of electrostatic and magnetic separation machines with their application to real separation scenarios <![CDATA[<b>The effect of cation and organic addition on the settling and compaction behaviour of clay-rich slimes</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2010000200008&lng=pt&nrm=iso&tlng=pt A high volume of slimes which are separated out during the mining of heavy mineral sands has a high environmental impact and results in great capital as well as operational expenses. The presence of clay minerals drastically increases the slimes volume that needs to be catered for due to its low settling capability as well as swelling characteristics. By adding coagulants in the form of cations and organics, one can improve the settling rate of the minerals as well as the degree of solid bed compaction. The addition of flocculant, which is currently used in industry to improve settling rate, is detrimental to solid bed compaction. By combining the cations and flocculant one can dramatically improve the solid bed compaction. This combination is, however, detrimental to the settling rate of kaolinite-rich slimes but improves the settling rate of smectite-rich slimes. Organics can also be used to produce a clear supernatant and improve the settling rate.