Browsing by Author "Hlabangana, N."

Now showing 1 - 13 of 13
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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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    Determining an optimal interstitial filling condition: An Attainable Region approach
    (Elsevier, 2018) Hlabangana, N.; Madiba, M.S.; Bhondayi, C.; Mguni, Nonhlanhla G.; Danha, Gwiranai
    In 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’.
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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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    Effect 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, 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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    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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    Effect of media shape on particle breakage in a batch ball mill: Lessons learnt from population balance model and attainable region technique. Procedia Manufacturing, 35.
    (Elsevier, 2019) Khumalo, S.; Hlabangana, N.; Danha, G.; Muzenda, E
    The batch grinding equation and the Attainable region technique tools were used in evaluating data obtained from the breakage of quartz ore in a laboratory batch ball mill. Using the same milling conditions and grinding equipment, test results were evaluated through the breakage distributions of different size fractions. Results prove that mixing different grinding media increases volume of grinding zones and that translates to an improvement in grinding kinetics and amount of required PSD. The tools are valuable and practical ways of evaluating the breakage of materials on the size fractional base and results of which can be used in the mathematical modelling and optimising of ball milling unit operations.
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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.
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    Optimisation of using a blend of plant based natural and synthetic coagulants for water treatment: ( Moringa Oleifera-Cactus Opuntia-Alum Blend)
    (2020) Gandiwa, B.I.; Moyo, L.B.; Ncube, S.; Mamvura, T.A.; Hlabangana, N.
    The research presents a comparative study on the effectiveness of blending plant based natural coagulants (Cactus Opuntia and Moringa Oleifera extracts) and a synthetic coagulant (aluminium sulphate or alum) in treatment of raw water. The low production rates of natural coagulants has derailed their commercialization this has driven the idea of blending synthetic coagulants which is envisaged to be the more appropriate means of application in this study. To measure the effectiveness of the coagulant, the following parameters were measured; turbidity, pH, conductivity and total alkalinity. The simplex lattice experimental design was applied using Minitab Software to obtain the optimal coagulant blend. The models were validated by statistical analysis which showed that the model was sufficient and no further modeling was required. The optimization results showed that a combination of alum, Moringa Oleifera and Cactus Opuntia in proportions of 13%, 42.6% and 44.4%, respectively with a total coagulant dosage of 45mg/L gave the best overall results with the resultant water having a turbidity, pH, conductivity and total alkalinity of 2.7 NTU, 6.99, 308 µS/cm and 137.7mg/L respectively. These physiochemical parameters are within required limits for potable water as per WHO guidelines. From the results, it was concluded that aluminum sulphate (alum) can be successfully blended with natural plantbased coagulants for raw water treatment.
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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.
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    Processing Of Gold-Bearing Sand,Dumps: A Case Study In Zimbabwe
    (CISA, 2017-10) Hlabangana, N.; Bhondayi, C.; Mguni, N. G; Hildebrandt, D.; Danha, Gwiranai
    In 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.
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    The novel use of calcium sulphate dihydrate as a bleaching agent for pre-processing beef tallow in the soap manufacturing process
    (Elsevier, 2019) Chakawa, D.P.; Nkala, M.; Hlabangana, N.; Muzenda, E.
    In this article we investigate the use of CaSO4.2H2O as an effective bleaching agent for pre-processing of beef tallow destined for use in the soap manufacturing process before storage. The use of CaSO4.2H2O in this particular novel application has never been demonstrated before. Five respective 100 g beef tallow samples were bleached by agitation using a speed of 120 rpm for 30 minutes at different CaSO4.2H2O weight fractions. The different weight fractions used were 1, 2, 3, 5 and 10 wt. %. After bleaching at a constant melt temperature of 90°C, the respective slurries were filtered and analyzed for red and yellow colors respectively as well as for % ffa. The results indicated an increase in red color bleachability from 0 to 68.75 wt. % with an increase in wt. % CaSO4.2H2O from 1 to 10wt%. Yellow color bleachability also increased from 23.65 to 93 % with increase in wt. % of CaSO4.2H2O from 1 to 10 wt. %. The results demonstrate that CaSO4.2H2O is an effective beef tallow bleaching agent for adsorbing red color, brown color and yellow chlorophyll type contaminants that are present in beef tallow.
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    The use of calcium sulphate dihydrate (CaSO4. 2H2O) as a bleaching agent for crude soya bean vegetable oil.
    (Elsevier, 2019) Chakawa, D.P.; Nkala, M.; Hlabangana, N.; Muzenda, E.
    The use of calcium sulphate dihydrate (CaSO4.2H2O) as a bleaching agent during the refining of crude soya bean vegetable oil was investigated. Different weight ratios of CaSO4.2H2O bleaching agent relative to crude oil (2, 4, 5, 10, 20 and 30 wt. %) were prepared. One sample of raw crude without any bleaching agent added was isolated as a control. Each of the 7 crude oil samples were preheated at a temperature range of 80ºC - 120ºC.The different weight compositions of CaSO4.2H2O were added and the respective slurries agitated for 30minutes.The agitated slurry was then filtered. The experimental results for red color were recorded and % free fatty acids (ffa) and % bleachability were calculated. The results indicated that there was decrease in red color of crude oil from 14R-4.3R with increase in weight ratio of bleaching agent. There was also an increase in red color bleachability from 24.285 % - 60.714% with increase in weight ratio. % ffa and solid nonfat (SNF) remained constant at 0.56% and nil respectively. The results indicate that calcium sulphate dihydrate (CaSO4.2H2O) is an effective bleaching agent in bleaching of crude soya bean vegetable oil.
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    Use of coal fly ash to manufacture a corrosion resistant brick.
    (Elsevier, 2019) Moyo, V.; Mguni, N.G.; Hlabangana, N.; Danha, G.
    In this article, we investigate the use of an environmental waste (coal fly ash) in the manufacture of an ammonium nitrate corrosion resistant brick. Ammonium nitrate (AN) fertilizer spillages and vapors continuously corrode the civil structures in a fertilizer manufacturing plant situated in Zimbabwe. This situation is a safety hazard to more than a hundred plant personnel and hence a priority area for research. Our experimental results show that addition of sodium silicate improved the performance of the brick. Water absorption of bricks generally decreased with an increase in the amount of sodium silicate added. Our results also show that the compressive strength generally increased with increase in amount of sodium silicate added and that the corrosion resistance increases with the amount of sodium silicate added to the coal ash bricks.