Browsing by Author "Breed, Ashley Wayne"

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    Beneficiation of fine coal using the air-sparged hydrocyclone
    (1992) Breed, Ashley Wayne; Franzidis, Jean-Paul
    The Air-Sparged Hydrocyclone (ASH) is a high capacity flotation device which is alleged to be more efficient for the flotation of fine particles than conventional flotation equipment. The principal aims of this thesis were to investigate the use of an ASH in the flotation of South African coal ultrafines (-150 micron), and to determine the effect of various design and operating parameters on the performance of the process, in terms of the product yields and grades obtainable. The testwork was carried out on a typical Witbank coal, from the Kleinkopje Colliery, with an ash content of 23.7 %. The coal was characterised by means of size, ash-by-size and float-and-sink analyses. Batch flotation experiments were carried out to provide a benchmark against which the ASH could be compared. Preliminary ASH work was carried out to determine the required collector and frother dosages and the optimal slurry feed rate.
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    Studies on the mechanism and kinetics of bioleaching with special reference to the bioleaching of refractory gold-bearing arsenopyrite
    (2000) Breed, Ashley Wayne; Hansford, Geoffrey Spearing; Harrison, STL
    Bioleaching is now an established technology for the leaching of whole-ore copper heaps and the pre-treatment of refractory arsenical gold ores and concentrates. For the case of refractory arsenical gold concentrates, it offers an economically feasible alternative to pressure oxidation and has environmental advantages over roasting with regard to the quality of the liquid and gaseous effluent (Van Aswegen, 1993). The major disadvantage of bioleaching is the low residence time required to achieve high oxidation levels. Other potential complications include the solubilisation of substances in the mineral, or the use of reagents, that are toxic to the micro-organisms.