Engineering

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Browsing Engineering by Author "Danha, G."

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    An attainable region approach for the recovery of iron and zinc from electric arc furnace dust
    (2019) Siame, M.C.; Kaoma, J.; Hlabangana, N.; Danha, G.
    This study investigated the application of the attainable region optimization technique to establish the optimum hybrid hydrometallurgical and pyro-metallurgical process conditions required to treat the electric arc furnace dust. The analysis of the results obtained showed that a combination of an agitation speed of 800 rpm, sodium hydroxide concentration of 8.0 mol/L and a leaching temperature of 80 °C were the optimum conditions for the hydrometallurgical process, while a roasting temperature of 1200 °C, carbon content of 35.27% and a roasting period of 36 h were the optimum conditions for the pyro-metallurgical process. The iron recovered from the dust was recycled in order to upgrade the iron content of the electric arc furnace charge, thereby reducing both process loses and process wastes.
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    Effect of ball and feed particle size distribution on the milling efficiency of a ball mill: An attainable region approach
    (2018) Hlabangana, N.; Danha, G.; Muzenda, E.
    In 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.
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    Investigating the feasibility of using agricultural waste as an adsorbent of gold ions in small scale gold processing plants.
    (2019) Tapfuma, A.; Chakawa, D.P.; Moyo, L.B.; Hlabangana, N.;; Danha, G.; Muzenda, E.
    The recovery of precious metals like gold is increasing each day due to its high market prices along with diverse applications. Bio-sorption represents a biotechnological innovation as well as a cost effective and excellent tool for recovery of precious metals from aqueous solutions. This study offers an overview of a recent scenario of bio-sorption studies carried out on the use of some promising bio-sorbents which could serve as an economical means for recovering gold for small scale gold processing plants. Results show that activated carbon (control) has the highest adsorption efficiency since it contains more active site on the carbon molecules. The activated maize corn cob had the highest adsorption efficiency (77.09%) compared to all other agricultural adsorbents. Banana peels showed a significant adsorption efficiency of 56.87%.
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    Optimization of pulp production from groundnut shells using chemical pulping at low temperatures
    (2020) Musekiwa, P.; Moyo, L.B.; Mamvura, T.A.; Danha, G.; Simate, G.S.; Hlabangana, N.
    Paper production through chemical pulping has been identified as one of the ideal avenues of exploring the uses of groundnut shells as they are rich in cellulose. Ideally, the cellulose can be used to synthesize fibres that can be converted into useful paper products. In this study, chemical pulping was the chosen process for liberating the fibres as it is effective in dissolving lignin embedded within the cellulose. In addition, the fibres produced have superior physical properties compared to mechanical pulping. It is imperative that optimal conditions are identified for the chemical treatment process, in order to ensure that energy and chemical consumption are minimized. All these measures are aimed at reducing production costs and make chemical pulping economically viable, as compared to the mechanical pulping process which is less costly. Response surface methodology (RSM) was used in this study to evaluate the effect of three independent variables (cooking time, temperature, and sulphidity) on pulp yield and kappa number. These parameters are critical in the chemical pulping process and the optimal conditions obtained were 180 min, 100 C and 23.6 wt.%, respectively. At the optimal conditions, the pulp yield was 64.39wt% with a kappa number of 19.5. The results showed that all parameters investigated, had a statistically significant effect on the production of pulp. The increased cooking time was efficient in ensuring complete impregnation of the groundnut shells with chemicals for pulping and ensuring that the dissolution of lignin is not selective and does not result in dead spots inherently compromising the quality of the pulp. On the other hand, lower temperatures limited the peeling effect due to hydrolysis of carbohydrates which increased pulp yield due to a higher cellulose retention. Consequently, this contributed towards obtaining pulp that is well cooked, has a low bleach consumption and a higher quality.