Electronic Theses and Dissertations (Masters)

Permanent URI for this collectionhttps://hdl.handle.net/10539/38876

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Subject: search.filters.subject.SDG-9: Industry, innovation and infrastructure

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Now showing 1 - 4 of 4
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    Development and Application of activated carbons from Avocado waste: Resource recovery for sustainable applications
    (University of the Witwatersrand, Johannesburg, 2023) Mohale, Lehlohonolo; Mulopo, Jean
    This research sought to produce activated carbons that could be used for hydrogen storage. The effect of hydrothermal pretreatment of the char, the effect of varying the activation ratio of KOH as the activation agent and the effect of activation temperature in producing these activated carbons were evaluated. Hydrothermal pretreatment of the char enhanced the properties of the resulting activated carbons. The best performing activated carbon was produced from the hydrochar pretreated at 200℃. It was observed that activation improved with increased activation agent concentration and activation temperature, to a point, and the best activated carbon was produced at 1:3 activation ratio and 800℃ activation temperature. This activated carbon had the highest total pore and micropore volumes of 1.45cm3/g and 1.16 cm3/g, respectively. The highest surface area of 2529.8m2/g was obtained, which is relatively higher than previously reported surface areas obtained from activated carbons created from coal or biomass. The porosity and the high surface area show well developed activated carbons that have desirable gas adsorption performance. The activated carbons had oxygen containing functional groups that aid in hydrogen sorption, the highest hydrogen sorption at 77K and 1 bar was 352 cm3/g, which supports the use of the produced activated carbons in the hydrogen economy. These activated carbons enable the circular economy. Well developed micropores were observed in the activated carbons produced through this work and their gravimetric capacity meets the DOE targets for hydrogen storage.
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    Investigating operational parameters that would affect the performance of a laboratory impact crusher
    (University of the Witwatersrand, Johannesburg, 2022) Ndlovu, Mangaliso Nhlakanipho; Bwalya, Mulenga; Chipise, Liberty; Chimwani, Ngonidzashe
    Impact crushers are widely used in the mining and construction industries to crush and size various types of materials. However, their performance can be affected by several operational parameters, including the rotor speed, rotor position, number of rotors and relative direction of rotors. The aim of this study is to investigate the impact of these parameters through a numerical model, Discrete Element Method (DEM). A Laboratory scale impact crusher was simulated using various configurations while also making use of a range of materials with known breakage data to predict expected grinding rates in the crusher. The Discrete Element Method (DEM) algorithm is a computational approach utilized to solve complex problems that involve numerous interacting bodies. In this technique, the dissipative forces (such as normal, tangential or frictional forces) at contact points are simulated using a spring-slider-dashpot model. While the movement of particles is computed using Newton's laws of motion. During simulations, the information about contact events are captured and saved in output files, which can later be used for various purposes. The energy spectra, a record of energy involved in every contact event of one such output that is utilised to predict the breakage of particles of different materials provided their breakage characteristics are known. Using the DEM simulation various equipment configurations of a laboratory impact crusher were conducted. The results showed that the rotor speed, number of rotors, rotor direction and rotor position significantly influenced the number of impacts and energy spectrum produced by the crusher. The crusher operation configuration significantly affected the energy spectra obtained. Additionally, the comparison of the crushing characteristics of the double rotor impact crusher to those of the single rotor impact crusher revealed differences in their performance that can be attributed to their design and operating parameters. - 3 - [OFFICIAL] The findings of this study provide valuable insights into the design and operation of impact crushers, and can be used to improve their efficiency and productivity when processing a variety of materials with different operational parameters.
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    Quantification of benefits of digitalisation of process data of a craft distillery
    (University of the Witwatersrand, Johannesburg, 2024) Kankenga, Daniel Pembe; Higginson, Antony
    Craft breweries and distilleries are frequently not digitalised, making them susceptible to regular production losses. Despite this, benefits of investing in digitalising process are often not easily measurable. The purpose of this research study is to develop a comprehensive framework to quantify the benefits of digitalising process data within the brewing process of a craft distillery. The study was based on historical data from Primal Spirit Distillery, located in Johannesburg, South Africa. The data underwent validation through the application of data visualisation techniques as well as a comprehensive statistical analysis. Mass balance calculations were conducted for the mash tun and fermentation processes, as well as an overall mass balance assessment to compare potential alcohol content with actual alcohol produced. Statistical tools, such as correlation analysis and the student t-test, were used to interpret the data and identify opportunities for digitalisation to enhance productivity. The study concluded with an economic analysis, assessing the financial implications and profitability of digitalising process data in the distillery. The conclusion of the research study highlighted the significant potential for improving productivity in craft distilleries and breweries through the digitalisation of process data. The developed framework proved effective in quantifying these benefits, encompassing steps such as historical data collection, visualisation, mass balance, statistical analysis, intervention planning, and economic feasibility assessment. The analysis revealed considerable sugar loss during mashing, with an average of 16.45%. Fermentation resulted in alcohol levels within the acceptable range in only 53.66% of instances, with an average alcohol deviation of 32.29%. The distillery, on average, operated at 67.71% of its potential alcohol production capacity. Correlation analysis and t-tests identified key variables requiring careful monitoring to reduce deviations and enhance productivity. While there are more economical alternatives, the optimal solution involves the use of affordable storage platform for process data, process control instrumentation devices, such as sensors and flow meters. The economic study indicates that a R 200,000 investment to digitalise the distillery's process data could boost productivity by 30%. The investment would be fully recovered in 4 months, with a 25.43% profit gain within 5 months. However, actual profitability may range between 10 to 20% due to potential unforeseen circumstances during production.
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    Dynamic compartmentalised heat transfer modelling for systems with biological applications
    (University of the Witwatersrand, Johannesburg, 2023) Xu, Lan; Moodley, Prebantha; Hildebrandt, Diane
    Proper thermal management is crucial to controlling the temperature of biological systems within an optimized operating range. A biological system is comprised of a multitude of interacting facets, where a system is often disrupted as a consequence of random events such as the change in ambient temperature. In contrast the design of most human engineered chemical systems or processes may assume steady state operation and as a result is relatively straightforward to design and optimise. Yet, often steady temperature ranges are required in unsteady conditions. This sort of unsteady state system requires consideration of the dynamic changes to the conditions and are often required to be within many applications. A narrow temperature band is essential for controlling the outcomes of how biological systems’ function—thermal denaturation of biological components depend on precise control of the transport of heat. Insulin—a hormone peptide drug—is temperature sensitive and undergoes thermal fibrillation when exposed to temperatures above manufacturers' recommendations. To maintain such medication within specific temperature bands is a challenge in the face of energy intermittency from the energy crisis that South Africa is currently facing. Within this dissertation, a medical device to contain thermosensitive biological compounds is designed and modelled as a system undergoing dynamic thermal conditions. This heat transfer modelling is used as a prototyping process for designing the medical device to protect temperature sensitive medication during power outages. The simulated device, when used correctly, is able to keep medication thermally stable under 8°C during Stage 4 load shedding (7.5 hours of power outages within a 24-hour period).