Engineering

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Academic staff development strategies in engineering fields of study: case study of Zimbabwe
(2013-06) Mhlanga, S.; Matope, S.; Mugwagwa, L.; Phuthi, N.; Moyo, V. S.
Higher education is the basic instrument of economic growth and technological advancement in any society. The economic meltdown in Zimbabwe which climaxed 2008 with an inflation level of 231million % exacerbated the brain drain. After the economic meltdown, Zimbabwe is in the process of rebuilding the quality of staff and the staffing levels in its higher education institutions. The challenge has been the decision on the mode of study: whether to go via taught masters or master's by research; where to allow the faculty members to study: in the region, or beyond; on a fulltime or on a part-time basis or on a split-site basis. These challenges have been due to the need to have a quick but quality programme of staff development, while maximising on the resources available for staff development. A survey was undertaken of the engineering related departments in Zimbabwe universities focusing on the existing staffing levels, their qualifications, current numbers undergoing study and their levels. The challenges faced by each institution from the administrative side and from the staff side are summarised. Recommendations on staff development strategies are given in conclusion.
Academic staff development strategies in engineering fields of study: case study of Zimbabwe
(2013-06) Mhlanga, Samson; Matope, Stephen; Mugwagwa, Lameck; Phuthi, Nduduzo; Moyo, Vincent S.
Higher education is the basic instrument of economic growth and technological advancement in any society. The economic meltdown in Zimbabwe which climaxed 2008 with an inflation level of 231million % exacerbated the brain drain. After the economic meltdown, Zimbabwe is in the process of rebuilding the quality of staff and the staffing levels in its higher education institutions. The challenge has been the decision on the mode of study: whether to go via taught masters or masters by research; where to allow the faculty members to study: in the region, or beyond; on a fulltime or on a part-time basis or on a split-site basis. These challenges have been due to the need to have a quick but quality programme of staff development, while maximising on the resources available for staff development. A survey was undertaken of the engineering related departments in Zimbabwe universities focusing on the existing staffing levels, their qualifications, current numbers undergoing study and their levels. The challenges faced by each institution from the administrative side and from the staff side are summarised. Recommendations on staff development strategies are given in conclusion.
Adsorption of Mercury by Pterocarpus Anglolensis: Study on Adsorption Isotherms and Kinetics
(Iranian Institute of Research and Development in Chemical Industries (IRDCI)-ACECR, 2022) Mapombere, Garainesu; Nyoni, Bothwell; Sibali, Linda L.; Chiririwa, Haleden; Seodigeng, Tumisang
The efficiency of Pterocarpus Anglolensis sawdust, an abundantly available waste product of the timber industry, capacity as an adsorbent for mercury was investigated. A series of batch experiments was carried out with experimental conditions of metal concentration, adsorbent concentration, pH, and contact time being changed. The concentration of the metal ion was deduced using spectrophotometric means. The adsorption efficiency was found to be pH-dependent with pH 4 being the optimum. 90 minutes was found to be the equilibrium time with particle size range 90-124 μm being the most efficient. Maximum adsorption of mercury was evaluated at 80.33 %. The experimental data was best modeled by the Freundlich isotherm and Pseudo second-order kinetic models. The calculated adsorption parameters are Kf = 0.0002 L/mg, bF = 3.0 and k2 = 0.00016 g/μg.min.
Air pollution control techniques for the cement manufacturing industry: A case study for Zimbabbwe
(2012) Zimwara, D.; Mugwagwa, L.; Chikowore, T.R.
Technological advancement has resulted in cement making companies being able to produce higher volumes compared to the past. However the higher production levels have also been largely labelled as the leading cause of pollution. The main sources of air pollution in the industry include excavation activities, dumps, tips, conveyer belts, crushing mills and kiln emissions. Harnessing appropriate technology for use in the cement industry could go a long way towards minimising on-site wastes and pollution. This review examines various options in practice for reducing pollution at cement manufacturing companies, which help ensure legislative compliance. By adoption of appropriate technology and computer modelling, industry will not only reduce production waste but also comply with legislation to do with environmental protection. The paper examines certain methods of pollution control used for air and looks at how computer modelling can be adopted for the classification, quantification and control of particulate matter; and how efficient energy use can contribute to better air quality. An analysis of gas stack emissions was done for a cement manufacturing company in Zimbabwe where compliance was investigated. Emissions samples were randomly selected at various points within the company and concentration of various emission constituents were analysed.
An attainable region approach for the recovery of iron and zinc from electric arc furnace dust
(2019) M.C. Siamea, M. C.; Kaomab, J.; Hlabanganac, N; Danhad, 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.
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.
Beverage Effluent Treatment Technology
(2016) Tshuma. J.; Maqhuzu, A.; Bhebhe, S.; Mudon, S.; Kaitano, H.; Mashanga, D.; Mpofu, C.; Tshuma, I.; Mkandla, C.K.
A detailed beverage effluent treatment technology was developed in a period of 4 months, using samples from an operating beverage plant. The total number of samples collected were 1304. The volume of the sample collected hourly was 500ml for 4 hours to give a composite sample. The plant operated continuously for 6 days a week and had two-12 hour shifts a day. The technology consisted of four water treatment methods combined consecutively which were chemical, physical, biological and physical treatment methods. The aim of developing the technology was to reduce the sCOD, TSS and pH parameters to the required environmental specification. The untreated beverage wastewater has high solids content, high organic matter, and low pH which need pretreatment before it is discharged into the municipal sewage treatment works. The developed technology reduced the high solid content, high organic load and adjusted the pH to the required Bulawayo Municipality environmental specifications. The average percentage reduction in sCOD and TSS was 91.1% and 90.6% respectively. The pH was adjusted to 8.05. The obtained results indicated that the developed technology was effective for treating beverage wastewater at ambient temperature to meet the quality of effluent that can be discharged into public water works.
Centralised Incubator Control System
(2016-01-27) Mtunzi, B.; Chamisa, M.; Madumbu, Z.; Gonye, N. R.; Nhenga-Mugarisanwa, F.
This paper presents an infant incubator system that protects and helps incubate a premature infant while in hospital. The device is economical, robust, and uses easily replaceable parts. It consists of a control mechanism that makes use of fans, a humidifier and a home heater rod to provide heat. The temperature and humidity were automatically controlled and maintained by a microcontroller. The incubator had a base designed to automatically weigh and log the infant’s weight. A Visual Studio interface was used to provide incubator chamber data and to evaluate the performance of the design. The system could weigh the weight of the infant as well as control the chamber temperature at 36.5°C and humidity at 40%. The system was able to maintain these conditions within a period of 5 seconds
Cost of Quality as a Driver for Continuous Improvement - Case Study – Company X
(2013) Zimwara, D.; Mugwagwa, L.; Maringa, D.; Mnkandla, A.; Mugwagwa, L.; Ngwarati, T.T.
In the manufacturing, metal casting industry is one of the oldest basic principal and most important industries. The casting process is hindered by the occurrence of various defects. High casting reject levels and customer returns have a considerable adverse effect on productivity, delivery performance, customer satisfaction and employee morale. In addition excessive rejection reduces yield, wastes valuable raw materials and involves management time in problem solving. All foundry processes generate a certain level of rejection that is closely related to the type of casting, the processes used and the equipment available. This paper seeks to establish the extent to which cost of quality can impact on continuous improvement of the products and the relationship with the customers of the organization. To determine the cost of quality (COQ) at casting company X, the researchers used existing company records, publications and historical evidence of the company. The researchers utilized techniques such as, bar charts and tables in presenting and interpreting data. The above techniques have the ability to provide methods for collecting, presenting, and analysis and meaningfully interpret data. The research findings estimated the COQ to be 6.6% of sales revenue.
Design of a Control System for a Vending Machine
(Elsevier, 2020) Murena, E.; Sibanda, V.; Sibanda, S.; Mpofu, K.
Vending machines are available in many public places for vending of items like snacks, beverages, newspapers, tickets and smoking cigarettes Recently developed vending machine requires a control system to offer a variety of products to the general public. In this light, this paper, therefore, is aimed at developing a control system for the developed vending machine by developing various inputs required to make the machine function efficiently. The system controls and monitors the vending machine functions, namely: alarm system, product dispensing, refrigeration and payment system. The microcomputer capitalises on the evolution of high-performance processors and stable operating systems to implement control requirements. The project shall use intelligent vending machine input/output board to link other machine peripherals. The control system shall enable the machine to handle coin, mobile and point of sale terminal payment options. Implementation of the control system enhances flexibility in payment, remote machine monitoring and inventory control, and improved user experience through the integration of digital touch screen user interfaces and high-speed transaction processing
Design of a Dual Operating Mode Sheet Folding Machine.
(2013) Gwangwava, N.; Mugwagwa, L.; Ngoma, S.
A sheet folding machine that can be operated through hydraulics by two hydraulic cylinders or manually (with the cylinders disengaged) was designed. The design need emanated from the strained national electrical grid system that has recently seen industrialists and households in Zimbabwe experiencing major power cuts. The machine enables manufacturers to shedule heavier jobs during periods when power supply is up and lighter jobs during power cut periods hence run their workshops throughout the daily production shifts. The two hydraulic cylinders can be disengaged from the machine’s folding beam so that manual operation can be done through a manual clamping lever system. The folding force at full capacity is 294.6 KN (29.46 Ton), total bending length of 1.8 m and working height of 1 m. The folding force decreases significantly in manual operating mode to 500 N, considering that on average an operate can manually exert that force. A student version of Simulation X 3.5 was used to simulate the hydraulic operation of the machine
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’.
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.
Development and Characterisation of a Nanocomposite Membrane Using Polyethersulphone and Graphene Oxide-Magnetite Nanoparticles for Rejection of Chromium Hexavalent Ions from Tannery Wastewater
(2018) Gadlula, S.; Ndlovu, L.N.; Ncube, L.K.
Polyethersulphone (PES) polymer blended with Graphene Oxide (GO) and magnetite ( nano-composite was synthesized using an immersion precipitation process for the filtration of chromium hexavalent ions from leather processing waste water. PES is a synthetic polymer with good chemical resistance, wide pH range (2-13) as well as good mechanical and thermal properties. However, it is hydrophobic and prone to fouling hence its limitations in aqueous separation processes. In order to improve hydrophilicity, porosity, permeability and strength properties of the polymeric membrane, GO was synthesized from coal via a modified Hummers Method and then blended with anhydrous ferrous chloride to form Graphene oxide/ magnetite () hybrid nano-particles. To assess the performance of the membrane pure water flux, Equilibrium Water Content (EWC) and tensile strength test was measured. Structural analysis involved porosity measurement. The filtration efficiency of the membranes was found by testing the waste water for chromium ion concentration before and after filtration. It was established that both the physical properties and chromium ion rejection improved with increase in polymer concentration and addition of hybrid nano-particles.
Development of a condition based maintenance system for a sugar producing company
(2014-07-14) Chindondondo, B.; Nyanga, L.; Merwe, A. V.; Mupinga, T.; Mhlanga, S.
With globalisation taking centre stage in almost every market; traditionally monopolistic manufacturing companies in Zimbabwe are struggling to compete with international companies whose operations are optimised. This paper focuses on maintenance practises of a Zimbabwean sugar manufacturer with an aim to improve the company’s asset care plans. The company’s current maintenance philosophy and its shortcomings on certain equipment in the plant were identified together with the associated annual maintenance costs. A Pareto analysis on the equipment’s breakdown history was used to determine the conditions that can be monitored using Condition Based Maintenance (CBM); and experiments to establish the feasibility of monitoring these conditions were done. The paper then recommends and proposes a CBM system replete with its three main elements of data acquisition, data processing and maintenance decision making to reduce breakdowns on the subject equipment by at most 76%.
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
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.
Effect of frother and depressant interaction on flotation of Great Dyke PGM ore.
(The Southern African Institute of Mining and Metallurgy., 2018-01) Mberi, T.; Mguni, Liberty.L; Ntuli, Freeman
In the optimization of platinum group metal flotation plants, various parameters are considered in order to achieve the desired recovery and grade of the precious metals. There should be a balance in the operating parameters so as to produce a high-grade valuable mineral concentrate without compromising recovery. This project seeks to investigate the individual and interactive effect of flotation reagents at different dosages, using a full factorial experimental design approach with two factors at six levels. Laboratory tests were conducted to illustrate the effect of frother and depressant on flotation. The results were analysed using SPSS and MiniTab. Based on the F-test at 95% confidence level, the frother had no significant effect on the concentrate grade but had a significant effect on 4E recovery, mass pull, and water recovery. The depressant had a significant effect on concentrate grade, water recovery, and mass pull. The interactive effect of frother and depressant had significant negative effect on all responses except concentrate grade. The optimum levels for recovery and grade were analysed assuming equal importance of grade and recovery as well as double importance for grade.
Extraction of magnesium from chrome slag by sulphiric acid leaching at low temperatures
(Novateur, 2018-11) Dube, Samukeliso; Tshuma, Bret; Jele, Thabisile B; Nkompilo, Sikhulile; Tshuma, Lawrencia; Moyo, Langa B; Hlabangana, Nkosikhona; Nkomo, Fortune; Ncube, Phendukani
In this this article ,a solvent extraction method by using sulphuric acid leaching was developed .The process conditions and parameters of sulphuric acid concentration ,leaching temperature ,leaching time and solid to liquid ratio were studied. These studied conditions and parameters were varied from 0.5M to 5M at 0.5 M interval, 30oC to 60oC at 5oC interval and 30 minutes to 240 minutes at 30 minute interval respectively. The solid to liquid ratios used were 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10.The optimum percentage extraction efficiency of magnesium as found to be 66.87% at optimum operating conditions of 4M sulphuric acid concentration 60oC leaching temperature, 120 minutes leaching time and 1:2 solid to liquid ratio.
A flux-correct Green element model of quasi three-dimensional multiaquifer flow.
(American Geophysical Union, 2000-12) Taigbenu, A.E.; Onyejekwe, Okey O.
Transient flow in multiply layered aquifers, separated by connecting layers of aquitards which provide hydraulic interactions between the aquifers, is solved by the Green element method (GEM) in a manner that reveals one of its strengths of being able to correctly model the leakage flux without resorting to adjusting the grid representing the one-dimensional (l-D) flow in the aquitards, as done in the finite element method (FEM). The hydraulic approach of approximating the flow is adopted so that flow in the aquifer takes place in two dimensions and that in the aquitards takes place in the one-dimensional vertical direction. The 1-D Green element (GE) model earlier developed for transient diffusion and referred to as the transient GE (TGE) formulation [Taigbenu and Onyejekwe, 1999] is used in modeling the flow in the aquitards, while the 2-D GE model developed for linear and nonlinear transient diffusion [Taigbenu and Onyejekwe, 1998] is used for calculating the flows in the confined and unconfined aquifers. Both models are coupled to solve regional flow problems in multiaquifer systems of arbitrary geometry which receive point and distributed recharge of arbitrary strengths. The solution procedure, which is iterative, provides information on the hydraulic heads and fluxes in the aquifers and aquitards at various specified times. Because GEM is founded on the singular integral theory, singularities that arise from water abstractions at wells (point recharge) are naturally captured in the singular Green's function, thereby making it possible to use a more coarse grid for problems in which there exist active wells. Furthermore, the implementation procedure of GEM achieves sparsity of the coefficient matrix so that less amount of computing resources is required for its decomposition. The superiority of the current approach over FEM in predicting the leakage flux through the aquitards and achieving comparable accuracy for well problems with coarser grid is demonstrated

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