Chemical Engineering

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Browsing Chemical Engineering by Author "Bhebhe, Siboniwe"

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    Determining Optimum Wet Milling and Leaching Parameters for Maximum Recovery of Gold
    (Research Publish Journals, 2017-12) Mguni, Nonhlanhla G.; Bhebhe, Siboniwe; Danha, Gwiranai; Tshuma, Joel; Hlabangana, N.
    Abstract: The comminution and leaching unit operations play a vital role in the extraction process of valuable minerals from ores. Historical research efforts have focused more on optimizing these two unit operations individually rather than as an entire integrated process. The approach employed in modern day research is now driven by the process intensification philosophy. Process intensification detects that developing an integrated approach to mineral processing systems and flow sheets leads to improved efficiency of the overall process and can help attain optimum recovery and a reduction in energy and material costs. In this article, we present laboratory scale batch grinding and leaching profiles of a mono-sized gold ore sample (-1700 + 850 μm). The sample was obtained from a run-of-mine (ROM) ore of one the leading gold processing plants in South Africa. Various combinations of grinding media fill level and ball size were investigated, showing that breakage is more pronounced for the larger ball sizes tested. We also found that using a higher media filling (J = 30%) and a larger media size (30 mm) consumed more energy with less gold recovered during a 24 hour leaching period, compared to when a smaller J of 15% and 20 mm media was used. Our results show that efficient application of energy is vital and maximum profit is a complex function of energy usage and particle size. Keywords: gold, Historical research, mineral processing, energy, material costs.
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    Optimisation of the Leaching Parameters of a Gold Ore in Sodium Cyanide Solution
    (2018-03) Hlabangana, N.; Bhebhe, Siboniwe; Mguni, Nonhlanhla G.; Danha, Gwiranai; Tshuma, Joel
    The objective of the work reported in this paper is to propose ways of improving the recovery on a low grade gold ore. To date, no work on optimizing this particular ore has been done in order to improve the recovery. Five size fractions used in the leaching tests reveal that recovery is a function of operational parameters. The optimum values for these parameters that gave a maximum recovery were: particle size (-150 + 75 μm) concentration of the lixiviant (210 ppm), temperature (85oC) and mixing speed (900 rpm). We then applied the shrinking core model and ash layer diffusion is the slowest step. An empirical model was then proposed to predict the leaching behaviour of the gold ore. A value of 12, 9 kJ /mol was obtained for Activation Energy (Ea) which is consistent with some results from leading researchers.