Faculty of Engineering and the Built Environment (ETDs)
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Item Co-gasification of Coal and Solid Waste to Hydrogen Enriched-Syngas in a Fixed Bed Gasifier(University of the Witwatersrand, Johannesburg, 2020-10) Ozonoh, Maxwell; Daramola, Michael O.; Oboirien, Bilainu O.The economic growth of every nation around the globe is centred on energy. Energy can be harnessed from different sources using different conversion systems, but such systems should be sustainable. Liquid fuels such as petroleum and solid fuels (e.g. coal & biomass) are largely used for energy production. Energy recovery from these fuels is usually carried out using thermal chemical processes such as combustion, pyrolysis, and gasification systems. Out of the three technologies, gasification is considered the most attractive based on its efficiency and other qualities. In the gasification process, syngas is produced. It is necessary to produce syngas of high quality such as hydrogen-enriched syngas. Hydrogen-enriched syngas can be used in fuel cells, gas turbines and engines for electricity production. This type of gas burns with little gaseous emissions to the atmosphere, but its production is dependent on the type of fuel and process conditions, and energy conversion system employed. In South Africa, around 95 % of electric power production comes from coal, and the current reserve is projected to last not more than a century [8]. Secondly, the coal is fast depleting and generates a lot of gaseous emissions (e.g. CO2, NOX & SOX) that pose a huge threat to the environment. The emission of the aforementioned gases is a very serious issue in South Africa. Presently, some Carbon Capture and Storage (CCS) projects are on-going in the country, although the CCS is not the fuse of this study. The gasification of biomass waste and coal could assist in gaseous emission reduction. Similarly, large amounts of agricultural wastes (e.g. sugarcane bagasse, corn cob & pine saw dust) and other solid waste such as tyre are in abundance in SA. It is detailed in chapter 2. Majority of the wastes are disposed indiscriminately, hence resulting in environmental pollution. Importantly, the solitary gasification of biomass is very expensive considering the prices of biomass. Besides that, biomass produces large amount of tar hence, resulting in operational difficulties in the gasifier and end user facilities. In this study, co-gasification of coal and solid wastes is considered as a crucial alternative to addressing the aforementioned problems. Particularly, the feedstocks used for this study were coal, biomass (corn cob (CC), pine sawdust (PSD), sugarcane bagasse (SCB)) and waste tyre (WT) and were pre-treated by drying, milling, sieving, and torrefaction (coal was not torrefied). The fuel samples were blended with coal at different ratios as detailed in the thesis and used for the study. For the torrefaction process, the most viable torrefaction process conditions and feedstock were determined, while the torrefaction process model for the feedstocks were developed, using Response Surface Methodology (RSM) and Artificial Neural Network (ANN), respectively. The Performance efficiency of gasification systems was evaluated using experimental data obtained from a few gasifiers (e.g. entrained, fluidised, and fixed bed) operated at varied experimental conditions using blends of feedstocks (e.g. biomass, coal, waste tyre etc.). A backpropagation Levenberg Marquardt (L-M) and Bayesian Regularisation (BR) algorithms of ANN model with Multiple Input- Multiple Output (MIMO) and Multiple Input-Single Output (MISO) layer networks were considered. The results of the MIMO and MISO layer networks obtained from the L-M algorithm were better than that of BR algorithm which is in affirmation with some of the results found in the literature. For model result improvement, Input Variables Representation Technique-by-Visual Inspection Method (IVRT-VIM) and Output Variables Representation Technique-by-Visual Inspection Method (OVRT-VIM) were developed from the study. Estimation of the gaseous emissions and profits from biomass, tyre, and coal fired co-gasification CHP Plant using Artificial Neural Network (ANN) was carried out for 20-year investment period using South Africa (SA) and Nigeria as cases studies via Artificial Neural Network (ANN). Higher profits were obtained from South African feedstocks than that of Nigerian feedstocks due to cheaper price of SA coal WFO and WOFC, but the gaseous emissions (CO, NOX, & SO2) from the Nigerian fuels were lower than that of SA because of differences in compositions of the fuels. The potentials of biomass torrefaction in terms of profitability in a co-gasification CHP plant for a 20-year-investment period was carried out using blends of Coal + SCB, Coal + CC, and Coal + PSD with coal-to-biomass ratio of 50:50, 71:29, and 80:20, respectively. The two financial cases mentioned earlier were considered. Four investment terms including: (A) 1st–5th, (B) 5th– 10th, (C) 10th– 15th & (D) 15th– 20th and two operational cost models; with feedstock costing (WFC) and without feedstock costing (WOFC) were employed. An estimated profit of between USD5.9 million - USD6.5 million and USD7.8 - USD7.9 million was earned at the end of investment plan using WFC and WOFC, respectively. The Internal Rate of Return (IRR) was 5 ± 1 %/yr. and 7 ± 4 %/yr. based on South African electricity price of 0.14 $/c kWh, respectively. The parametric effect of process variables during torrefaction of coal/biomass/waste tyre blends using ANN and RSM models were studied. The variables considered were Higher Heating Value (HHV), Enhancement Factor (EF), and Sold Yield (SY). The most effective operating process conditions (in terms of blending ratio, temperature and torrefaction time: input variables) is of the order: 50:50 at 300 OC and 45 min > 50:50 at 250 OC and 30 min >50:50 at 200 OC and 45 min. Similarly, the most viable fuel follows the order of Coal + Torrefied PSD > Coal + Torrefied SCB > Coal + Torrefied CC and > Coal + Torrefied WT. Coal + Torrefied PSD has HHV of 28.27 % and an EF of 1.41. This corresponded to around 10 % increase in the HHV of the torrefied fuel when compared to the raw fuel and about 25.23% higher than the EF of Coal + Torrefied WT of 1.03. Based on the result of the EF of Coal +Torrefied waste tyre, upgrading of the fuel quality via torrefaction is not recommended. Furthermore, a comprehensive study on tar treatment techniques was carried out using tars produced from biomass and blends of biomass and coal employing biochar based and Ni-biochar based catalysts. Box Behnken Design of Experiment (DoE) method was used. A full quadratic regression model was used to develop a mathematical model for tar treatment based on the feedstocks studied. The Pine Sawdust-Biochar Catalyst (PSD-BC) and Nickel Pine Sawdust-Biochar Catalyst (Ni-PSD-BC) were the most effective in terms of tar treatment and with an average percentage amount of tar conversion of 89.76 and 96.73%, respectively. Ni-PSD-BC was more efficient for tar cracking than PSD-BC, but PSD-BC (waste base) may be more attractive if sustainability and cost effectiveness of precursors are considered. Co-gasification of coal and pine sawdust (PSD) to hydrogen enriched syngas in a fixed bed gasifier was carried out with catalyst (WCAT) at 900 OC and without catalyst (WOCAT), at 700, 800, and 900 OC, respectively. Coal-to-PSD ratio of 1:1 was used, while Nickel-pine sawdust-biochar (Ni-PSD-BC) and pine sawdust-biochar (PSD-BC) were employed as catalysts. The gases produced at 700, 800 & 900 OC using WOCAT cannot be used in fuel cells and gas turbines due to poor quality, while others produced at 900 OC WCAT, can be used in internal combustion engines and gas turbines, but unfortunately, have lower quality to be employed in fuel cells for electricity production. However, the study provides a method of beneficiation of the high ash content South African coal for energy production. The outcome of this study is also instrumental to energy security, efficiency and sustainability as well as waste management in South Africa, Nigeria and other parts of the globe. An assessment of the economic, energy and environmental viability of a 5 MW co- gasification power plant was carried out, using blends of coal and biomass, and two financial cases were considered namely: with feedstock costing (WFC) and without feedstock costing (WOFC). Feedstock profitability in the plant for energy production was evaluated. Equipment consisting was not considered. The power plant used 20,473,451.41 kg, 20,986,049.96 kg, 18,251,806.49 kg, and 15,276,277.85 kg of Coal + SCB, Coal + CC, Coal + PSD, and Coal + WT to produce the 5 MW and 5.56 MW electric and thermal power, annually. Coal + Torrefied PSD was the most profitable of the fuels studied. The use of Coal-to-PSD ratio of 4:1 for the power generation as against Coal-to-PSD blend ratio of 1:1 resulted to an annual loss of about ZAR6, 461,301.77 ($90,458,224.70) and ZAR123,782.47 ($1,732954.58) WFC and WOFC, respectively.Item Dynamic compartmentalised heat transfer modelling for systems with biological applications(University of the Witwatersrand, Johannesburg, 2023) Xu, Lan; Moodley, Prebantha; Hildebrandt, DianeProper 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).Item The dynamics of place branding in Johannesburg: 1994 - 2019(University of the Witwatersrand, Johannesburg, 2023-11) Mbinza, Zenzile; Sihlongonyane, Mfaniseni FanaThis PhD thesis lays the ground for understanding place branding processes from cities of the Global South. It critically explores place branding as an emerging mechanism for urban governance in Johannesburg. It is critical because place branding and its related processes have increasingly gained momentum in countries, regions and cities jostling for niche status in global economics. This thesis explores the different place brands that Johannesburg coined over time, focussing on the period between 1994 and 2019. It explored the city’s place brands under the five mayors that presided over Johannesburg, beginning with Dan Pretorius (1994 – 1995), Isaac Mogase (1995 – 1999), Amos Masondo (2000 – 2011), Parks Tau (2011 – 2016) and Herman Mashaba (2016 – 2019). The thesis employed a qualitative research methodology and case study design. Primary data Archival research and interviews were the primary data collection strategies. The ensuing discussion of place brands in Johannesburg reveals the dynamics and push factors that have contributed to the development of place brands under the time in question. Politics, economics, and activities related to globalisation emerged as leading drivers for the city of Johannesburg to develop its various place brands. The thesis found that Johannesburg followed a template similar to the cities of the Global North in its application of place branding. However, the thesis also found gaps in the city’s place branding processes. For example, there was limited engagement with the city residents when developing Johannesburg’s place brands. It pointed to a unilateral, top-down application of place branding in the city, which precluded it from using these processes as democracy-building tools. It necessitates the exploration of place branding from the perspective of city governments to begin encompassing issues of inclusivity and public participation. In this light, the thesis calls for a more strategic application of place branding in the Johannesburg.Item Exploring the challenges to drone-aided inspections in construction site management(University of the Witwatersrand, Johannesburg, 2024-09) Khorombi, Shadrack; Terblanche, RolienThe construction industry, marked by its complexity and evolving standards, demands attention and commitment to quality. To guarantee that works are going according to plan, standards and regulations, in terms of quality and compliance, routine inspection strategies are implemented as an intrinsic part of the project management plan. Construction inspections are generally performed as a contractual obligation to enable an independent view of construction works and their progress for key stakeholders and the client. However, traditional inspection techniques are generally laborious and risky. Inspectors are often exposed to exterior elements; unfavourable conditions; intrinsic risks. Despite all of this, inspectors are still unable to obtain in-depth information on some of the surfaces due the inability to access surfaces or structures to optimal proximity. Drone technology has been proposed as an alternative method to traditional inspection for safer and more efficient inspections. This study endeavoured to explore key challenges to the implementation of drone technology for construction inspections. The methodological approach that the researcher adopted to achieve the research aim encompassed a qualitative method with document analysis, case study and interviews selected as data collection strategies. Techniques to gather empirical information required included observations and semi-structured interview questions. To present findings that are valid, reliable and generalisable, NVivo software was used as a data analysis tool where content analysis and thematic analysis were employed as data analysis strategies. The utilisation of qualitative, inductive case studies within an interpretivist paradigm was considered necessary to contextualise and deepen the understanding of the nature and occurrence of the challenges impeding key role players from full adoption of drone technology for construction site inspection processes. Key findings entail the lack of capital and resource allocation, concerns about transparency and contractual accountability, and the need for clear evidence of return on investment. Technical complexity, disruption to site activities, lack of interest from key stakeholders, capacity issues, and connectivity issues were also uncovered as challenges in the adoption of drone-aided inspections. Additionally, the findings encompassed strategies to overcome challenges impeding the optimal use of drones in construction projects. This study evaluates the current state and potential for drone technology adoption within the South African construction industry, highlighting practical challenges encountered during actual deployments. By proposing solutions such as streamlining regulatory processes and enhancing stakeholder collaboration, the research offers valuable pathways to optimise drone technology implementation during construction documentation and management.Item An assessment of the necessity of implementing a blockchain based land registry in South Africa(University of the Witwatersrand, Johannesburg, 2024-08) Jeram, Deelan; Saghatforoush, Ehsan; Azasu, SamuelBackground statement: Several nations have recently implemented blockchain-based land management systems, focusing on land registration, titling, recordation, and information management, to enhance transparency, trust, data security, data quality, and immutability through consensus mechanisms. This technology streamlines access and tracking of land records, reducing fraud, corruption, record manipulation, and property resale while lowering transaction costs. These advantages aim to address issues of inefficient and untrustworthy land records in less developed countries. Problem: South Africa faces challenges, ranking 108 out of 190 in property registration according to the World Bank, with lengthy procedures (7), extended transaction times (23 days), and high costs (8% of property value). In contrast, blockchain-adopting countries like Sweden and Georgia are ranked at 9 and 5, respectively. Despite these inefficiencies blockchain technology has not yet made an inroad into the land registration or transaction process. Aim – The aim of this study is to investigate the potential use of blockchain technology to digitize land registration in South Africa. Methods: This paper investigates a blockchain property registry pilot project in Khayelitsha, South Africa, using Peled's theoretical framework and employs qualitative research methodologies, including case study analysis and expert interviews, supplemented by a systematic literature review. Outcomes: The study reveals significant challenges in South Africa's land registration, including unreliable land records, informal land tenure systems, limited access for marginalized communities, corruption, weak legal frameworks, post-colonial property rights legacy, and inefficient real estate transactions. Despite the promise of blockchain, these issues persist, hindering progress. Eight key factors obstruct blockchain adoption in South Africa's land registry, including legal barriers, organizational resistance, technological hurdles, resource constraints, political and social factors, and trust-related issues. The case study identifies additional obstacles, such as misalignment of interests, lack of formal agreements, data quality issues, and further legal barriers. Nonetheless, the pilot project managed to create a "pseudo title deed" with potential benefits for the city. This study suggests the application of blockchain in state-subsidized housing developments to enhance data security and enable electronic land transactions. It emphasizes the need for a combination of expertise, infrastructure readiness, and procedural changes to facilitate innovation in the public sector. Despite the potential, the study concludes that South Africa's land registry is not yet prepared for widespread blockchain implementation, citing legal, technological, and organizational challenges. Significance: This research is the first to explore the limited adoption of blockchain technology for land registration in South Africa, contributing valuable insights to the field. This paper identifies critical factors for successful blockchain-based property registry implementation, offering insights for legislation, policy development, and land registration system design to address inequalities and improve land tenure in developing countries. It outlines a potential path for South Africa's Deeds Registry to implement blockchain technology in state-subsidized housing developments.Item The Role of Chiefs in Land Management in Peri-Urban Customary Areas Of Blantyre, Malawi: The Case of Mpemba(University of the Witwatersrand, Johannesburg, 2022-04) Magwede, Chimwemwe Edith; Williamson, AmandaPeri-urbanisation is a new form of urbanisation and the peri-urban area is a new kind of multi-functional landscape for urban development. How peri-urban areas are managed matters because they are close to the city and due to high urbanisation rates in most developing countries, these areas will soon be part of the city. If urban peripheries are not well-managed, they will be a challenge for sustainable development. In Malawi, peri-urban areas fall under customary land and chiefs are the custodians of customary land. The study unpacks the role of chiefs in land management, how the National Land Policy and land-related legislation position customary leadership in the governance of land management and how municipal and customary land management systems interact with each other in the peri-urban areas. The study employed a qualitative approach. Semi-structured interviews were conducted and policy and legislation were reviewed. The 2002 National Land Policy of Malawi and land-related legislation were reviewed focusing on the role of chiefs in land management. Although the peri-urban areas fall under the jurisdiction of chiefs, the research reveals that this area is treated as no man's land as there exists an overlap of authorities in the peri-urban areas. The chiefs witness land transactions, advise their people on how to secure their land, and partially guide and manage land, although they are not aware of land regulations and standards. The findings also disclose that there is a lack of coordination within municipal land management systems and between municipal land management systems and customary land management systems. Although the legislation states that chiefs have to be incorporated in land management, these laws have not been fully implemented as there are still in the pilot phase.Item Why do equity oriented, ‘progressive’ planning policies fail to redress the apartheid city? An examination of Planning Instrumentality in South Africa(University of the Witwatersrand, Johannesburg, 2023-09) Klug, Neil; Bénit-Gbaffou, Claire; Todes, AlisonIn the immediate post-apartheid period, the fields of urban planning and housing experienced what some have called a ‘golden era’ during which planning played a significant role in the Reconstruction and Development Programme of the government, through developing new and progressive planning and housing policy instruments. Some of these instruments were designed to expedite the release of serviced land and provide subsidised housing, address the apartheid legacy of spatial segregation and housing backlogs. Despite success in the large number of houses delivered to the poor and increased service delivery to previously disenfranchised communities, by the mid 2000s there was growing criticisms of the state’s failure to redress discriminatory apartheid spatial patterns. South Africa was also experiencing growth in unemployment and inequality between emerging elites on the one hand and the majority of previously disadvantaged in society. This study sought to examine what role planning policy instruments played in failing to address the spatial legacies of apartheid. Acknowledging the wide range of potential variables contributing to this lack of efficacy, the study took an in-depth grounded, research approach. Using three case studies on different planning and housing related policy instruments and suits of instruments, at different phases of the policy cycle framework, it examined whether or not the state had managed to address housing and other inequalities. The first case study involved the examination of the processes and practices in formulating a local eviction policy instrument, the second reflected on housing officials’ engagement with the National Housing Code suit of instruments, and the third examined the practices and processes of implementing the Upgrading of Informal Settlements Programme. The findings of these case studies were that equity oriented, ‘progressive’ planning policies fail to redress the apartheid spatial inequalities because they are either not being selected for use or, where they are being applied, had limited impact because they were being implemented in a watered-down fashion. My thesis shows that there are multiple factors, from broad and complex governance structures to the actions of individual actors, that affect the efficacy of policy instruments.Item Developing of a parametrically resonw1t vibrating screen, modelling, simulation and dynamic testing(University of the Witwatersrand, Johannesburg, 2023-07) Mohanlal, Mishal; Li, KuinianA novel coupled spring pendulum vibrating screen is proposed with the goal of developing efficient screening using parametric resonance. A simple spring pendulum is initially studied to provide the basis of the dissertation. The theoretical model of the proposed vibrating screen is developed using Lagrangian mechanics which includes damping and generalized forces. Two derivations of the vibrating screen are proposed, the first being a 4DOF (degree of freedom) system and the second being a 3DOF system. The 3DOF system is found to present better numerical stability and is thus utilized for the study. It is shown that the 3DOF system is comparable to the simple spring pendulum for the case where initial conditions are applied to similar coordinates. The proposed vibrating screen presents motion which is not indicative of traditional vibrating screens. It is found that a system where attributes are sized for parametric resonance requires far smaller excitation forces to achieve higher accelerations and displacements compared to traditional vibrating screens. The proposed vibrating screen is an unfeasible design due to the large displacements; high foundation loads and limitations on mechanical components. Discrete element method (DEM) simulations of the proposed vibrating screen are performed to study the efficiency with varying inclinations of the mesh deck. The results are compared to a linear motion vibrating screen. The proposed screen requires far less energy compared to traditional vibrating screens and achieves higher efficiencies with larger deck inclinations. The derived differential equations are verified by experimental testing using free vibrations. The numerical simulations and experimental tests present a good correlation. Signal processing is implemented to compare the natural frequencies from the experimental testing and numerical simulations, the results present a good correlation.Item Support Design Approach for Crusher Chambers: A Case Study of Palabora Mining Company(University of the Witwatersrand, Johannesburg, 2023-01) Masole, Nyeleti Venus; Stacey, T.R.This report project aimed to design a support system for crusher chambers at Palabora. The research project focused mainly on the two crusher chambers (12m wide by 25m high and 61m long) planned for the Lift 2 project as part of the ore handling system. The main research questions that the researcher sought to answer were; what are the differences between Lift 1 & Lift 2 in rock mass characterisation, classification and the ground control district?; how suitable is the Lift 1 crusher chamber support system for Lift 2?; what could be support requirements for Lift 2 crusher chambers in terms of empirical, analytical and numerical design methods and what are the recommended support design approaches for Lift 2 crusher chambers? The methodology used to design support for the Lift 2 crusher chambers was based on determining the expected failure mode first and then selecting suitable design methods to cater for the extent of failure. This study combined empirical and analytical methods to determine the failure mode and required support system. The results were then validated using Finite Element Method numerical modelling software called RS2 (Phase 2) from RocScience. Research findings revealed that the ground control district, classification and characterisation of rock masses differ slightly between Lift 1 and Lift 2. Jointing in dolerite dykes (DOL) was slightly dense in Lift 2 compared to Lift 1 and was associated with increased mining depth. Furthermore, the Lift 1 crusher chamber support system was found to be suitable for Lift 2 but must incorporate dynamic support. Unwedge (RocScience) analysis simulated wedge type of failure in the crusher chamber walls. The empirical and analytical design approach proposed cable bolt lengths of between 6m and 9 m and 3-4 m for roof bolts with bolt spacing of 1.4 m and 1.0 m respectively. The simulation results using RS2 confirmed that the cable bolt length and spacing were appropriate. The recommended support system was expected to provide sufficient support to the crusher chamber in terms of controlling rock mass deformation and yielding. The general conclusion was that the design approach selected for crusher chambers must be able to adequately represent rock mass behaviour and the support required to maintain long-term stability.Item Provision of personal protective equipment and sanitary facilities to female construction site workers(University of the Witwatersrand, Johannesburg, 2023-09) Nene, Simphiwe; Ozumba, Obinna; Sunjika, BernadetteThe study was based on an aspect of social justice, namely gender equality in the workplace for the female workers who work on construction sites. The area covered in this study was the health and safety of women in construction in the form of the provision of personal protective equipment (PPE) and sanitary facilities to female workers. This specific focus is largely overlooked. The study explored, female workers’ (end-user) perceptions and experiences on the provisions of sanitary and personal protective equipment through a qualitative approach. The main source of data collection was through semi-structured interviews and further supported with site observations in order to triangulate the interview responses. The results of the study found that the availability of PPE for females in the construction industry has improved as women are provided with female size PPE. However, quality and advanced gender sensitive PPE still needs attention. Sanitary facilities at established sites are generally up to standard. However, female workers still share these facilities with their male counter parts. Sanitary facilities at unestablished sites still need attention.