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Browsing Engineering by Author "Danha, Gwiranai"
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- ItemDetermining an optimal interstitial filling condition: An Attainable Region approach(Elsevier, 2018) Hlabangana, N.; Madiba, M.S.; Bhondayi, C.; Mguni, Nonhlanhla G.; Danha, GwiranaiIn this article, we present yet another application of the Attainable Region (AR) method to data from a laboratory scale milling of a low grade gold ore. In this particular case, we investigate how to optimize the amount of material in a desired size class for a scenario where the boundaries of the desired size class of interest are changed. The AR approach has never been applied in such a scenario before. Using a mono sized feed of − 1700 + 850 μm, two desired product size classes of interest (− 850 + 150 μm and − 150 + 75 μm) are selected in order to determine the optimum interstitial filling (U) to be used in the mill. Two different values of U, 1.75 and 1.0 respectively, are obtained as optimal. Our results also show that optimal operating conditions are different for different objective functions. We demonstrate that the AR may be used to specify optimal conditions that may be used for particle size reduction processes. We also illustrate how an AR boundary for optimization purposes can in certain cases be extended using the ‘mixing principle’.
- ItemDetermining 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.
- ItemEffect of ball and feed particle size distribution on the milling efficiency of a ball mill: An attainable region approach(Elsevier, 2018-02-09) Hlabangana, N.; Danha, Gwiranai; Muzenda, EIn this article, alternative forms of optimizing the milling efficiency of a laboratory scale ball mill by varying the grinding media size distribution and the feed material particle size distribution were investigated. Silica ore was used as the test material. The experimental parameters that were kept constant in this investigation was the grinding media filling, powder filling and the mill rotational speed. The data obtained from these batch tests was then analyzed using a model free technique called the Attainable Region method. This analysis technique showed that the required product fineness is a function of grinding media and feed material size distributions. It was also observed from the experimental results that in order to increase the milling efficiency of a ball mill, towards optimum production of material in the desired size class, there is a need to correlate the ball size and the feed size distributions
- ItemOptimisation of the Leaching Parameters of a Gold Ore in Sodium Cyanide Solution(2018-03) Hlabangana, N.; Bhebhe, Siboniwe; Mguni, Nonhlanhla G.; Danha, Gwiranai; Tshuma, JoelThe 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.
- ItemProcessing Of Gold-Bearing Sand,Dumps: A Case Study In Zimbabwe(CISA, 2017-10) Hlabangana, N.; Bhondayi, C.; Mguni, N. G; Hildebrandt, D.; Danha, GwiranaiIn this article, we investigate the possibility of reprocessing gold bearing gold dumps for gold as a sustainable way of reviving the mining sector in Zimbabwe. Heap or vat leaching is a process that has been extensively used for the recovery of valuable metals like copper, gold (Au) and silver. The ore is prepared for vat leaching by either crushing or milling it into fine and deslimed material. It is then placed into a container (vat), which has a partial filter floor. Cyanide solution can then be injected either through the filter section of the floor or added to the top of the ore charge.