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Pretoria, South Africa

Steenkamp J.D.,Mintek | Pistorius P.C.,Carnegie Mellon University | Muller J.,Exxaro Resources
Journal of the Southern African Institute of Mining and Metallurgy | Year: 2016

Excavation of an industrial-scale submerged arc furnace, utilized in the production of silicomanganese, identified two high-wear areas in the refractory lining: the tap-hole, built with cold rammed carbon paste and SiC bricks, and the hearth, built with cold rammed carbon paste. To obtain insight into the potential causes of wear, thermodynamic calculations were conducted on eight sets of data, obtained for seven furnaces on three plants based in South Africa. FACTsage software and associated databases - FACTPS, FToxid, and FSstel - as well as the Mn-Fe-Si-C database of Tang and Olsen (2006), were applied. Theoretical indications are that chemical reaction between carbon refractory and slag, as well as dissolution of carbon and SiC refractory in metal, contributed to tap-hole refractory wear; and dissolution of carbon in metal contributed to hearth refractory wear. © The Southern African Institute of Mining and Metallurgy, 2016. Source


Brink G.,Exxaro Resources | Heymann G.,University of Pretoria
Journal of the South African Institution of Civil Engineering | Year: 2014

The behaviour of collapsible soil is often quantified by conducting a Collapse Potential Test or double oedometer test. However, these tests interpret the soil behaviour in terms of total stress, while it is well known that the behaviour of soil is governed by its effective stress. This article shows the results of a test conducted on undisturbed residual granite to study the collapse of the soil in terms of effective stress. The test was conducted in a modified oedometer which allowed the incremental addition of water to the sample during the test. The matric suction was quantified as a function of the moisture content of the soil during the test. The results indicate that the reduction in effective stress plays an important role during soil collapse. In addition it was found that much of the collapse settlement may be due to creep which occurs after the reduction in effective stress. © 2014, South African Institute of Civil Engineers. All rights reserved. Source


Coetsee T.,Exxaro Resources | Zietsman J.,University of Pretoria | Pistorius C.,Carnegie Mellon University
Transactions of the Institutions of Mining and Metallurgy, Section C: Mineral Processing and Extractive Metallurgy | Year: 2014

Previous work showed that manganese ore reduction rates are strongly influenced by the extent of slag phase formation. In this work, the effect of ore composition on slag formation during manganese oxide reduction was predicted using thermochemical calculations; FactSage 6?4 was used to calculate the equilibrium phase relations in the oxide system MnO-SiO2-CaO-MgO-Al2O3. Practically observed differences in ore composition, even within the same orebody, are predicted to cause significant differences in slag formation during reduction, with large differences in ore reducibility expected. - 2014 Institute of Materials, Minerals and Mining and The AusIMM Published by Maney on behalf of the Institute and The AusIMM. Source


Fowler M.,Exxaro Resources | Morkel J.,University of Pretoria
Journal of the Southern African Institute of Mining and Metallurgy | Year: 2010

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. © The Southern African Institute of Mining and Metallurgy, 2010. Source


Meyer E.J.,Exxaro Resources | Craig I.K.,University of Pretoria
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2011

A partition curve is used in dense medium separation to determine the efficiency of the separation of clean coal from discard. The method used to determine a partition curve in coal beneficiation is float and sink analysis. The float and sink dry masses are determined at each density fraction only after complete separation of the material has taken place. This means that the partition curve is a form of a steady-state model. A dynamic model for a dense medium separation circuit is available from first principles. This paper shows how a steady-state model is derived from the dynamic model to generate a partition curve. This partition curve is compared with plant measurements taken from a plant operation. © 2011 IFAC. Source

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