Master of Science (M.Sc.) Theses and Dissertations

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    Investigation of Corrosion Behaviour of Heat Treated Standard Steels in Nigerian Rich Tar Sand.
    (Department of Materials Engineering, Faculty of Technology, Obafemi Awolowo University., 2023) OGUNDARE, Olurotimi Joseph
    This study determined the corrosion rates of as-received and heat-treated standard duplex stainless (UNS S32205) steel in tar sand processing environment, characterized microstructurally the corrosion coupons, and correlated the corrosion rates of the stainless steel with their respective microstructures. These were with a view to assessing the suitability of heat-treated standard duplex stainless steels as candidate materials for the hot water tar-sands pilot plant. The Nigerian-rich tar sand sourced from Ilubinrin town, near Agbabu in Ondo State was chiselled into bits of 6mm and 25 g of it was processed using 0.5 M sodium hydroxide (NaOH), which acted as the surfactant in the bitumen recovery. The as-received stainless samples were subjected to annealing, normalizing, and quenching (water and oil) heat treatments. A processing temperature of 90oC and processing time of 4 hours was employed. After immersion, the corrosion coupons were cleaned with non-bleaching scurry powder and wiped with acetone to remove grease. The corrosion rates were determined by gravimetric technique and the microstructural analyses of the degraded corrosion coupons were carried out using scanning electron microscope while the correlation of the respective microstructures of the corrosion coupons with their uniform corrosion rates was carried out using localized corrosion rates derived from surface profilometry of the coupons. The study showed that water-quenched samples exhibited improved general corrosion resistance with longer precipitation times, while oil-quenched sample with precipitation time of 2 hours showed the lowest general corrosion rate, followed by water-quenched sample with a precipitation time of 4 hours. Microstructural analysis provided insights into the degree of pitting, with the annealed sample showing the highest and the water-quenched sample with a precipitation time of 4 hours displaying the lowest degree of pitting. These variations were attributed to passivity and an imbalance between ferrite and austenite phases due to secondary precipitates. The correlation between uniform corrosion rates and microstructures revealed that the sample with a precipitation time of 4 hours, followed by water quenching, demonstrated the best corrosion resistance. These differences in localized corrosion rates were attributed to chromium and molybdenum depletion in the grain boundaries. This study concluded that the heat-treated standard stainless steels were suitable for the construction of hot water tar sand pilot plant.
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    Open Access
    Development of an improved tractor-mounted kenaf (Hibiscus Cannabinus) Harvester
    (Department of Agriculture Engineering, Faculty of Technology ,Obafemi Awolowo University, Ile - Ife , Nigeria., 2022) Thomas Adebayo Ayorinde
    The study designed and fabricated an improved tractor-mounted device for kenaf harvesting; it evaluated the performance of the machine developed. It also developed mathematical models for the torque, power and energy for the machine; and validated the models developed. These were with a view to developing a kenaf harvesting technology which will improve kenaf production efficiency. The tractor mounted kenaf harvesting machine has a rotary drive mechanism, which was adopted from a forage harvester. A review of the physical and mechanical properties of kenaf stem was made to ensure the accuracy of the design calculation for shaft, chain drive and gear design. The cutting blades, spur gears, bevel gears was designed and fabricated based on the design calculations. Performance evaluation of the machine was carried out at the kenaf experimental field set up at the Obafemi Awolowo University Teaching and Research Farm. The evaluation of the machine was carried out from 10 to 16 weeks after planting, at 2 weeks interval. The factors considered in the evaluation include; crop maturity, crop varieties and forward speed of the machine. The machine parameters which are constant machine values peculiar to the machine performance evaluation include width of cut, speed of operation, height of cut. The performance indices were theoretical field capacity, field efficiency, effective field capacity and operational loses. The results obtained was analysed using 3-level factorial response surface methodology (RSM) of design expert software. A mathematical model was developed to detemine the cutting behaviour of the machine when modelled as a fixed uniform cantilever. An equation to predict the cutting torque, power and energy requirement of the machine during operation was obtained and validated. The effective field capacity was observed to decrease with increase in plant maturity and increase with increase in forward speed of the machine. The highest effective field capacity recorded was 2.13 ha/day with Ifeken 100 at crop maturity of 10 weeks after planting, and forward speed was 5 km/hr. The field efficiency of the machine was found to decrease with increase in crop maturity, and forward speed of the machine. The highest field efficiency was 97%, with Ifeken 100, crop maturity of 10 weeks after planting, and at forward speed of machine of 2 km/hr. The duration of operation was also observed to increase with increase in maturity, and decreased slightly with increase in forward speed of machine. The highest duration of operation recorded was close to 9 hours, obtained when the crop maturity was 16 weeks after planting, during the harvesting of Ifeken di 400 and forward speed of 2 km/hr. Operatiional losses was observed to be uniform as the crop maturity increased, highest during the harvesting of Ifeken 100 and increased with increasing forward speed of the machine. The least operational losses recorded was 6.9% recorded when the plant maturity was 16 weeks after planting, during the harvest of Cuba 108 and when the forward speed of machine was 2 km/hr. There was good agreement between the predicted and experimental values of the cutting torque, power and energy requirement of the machine. The study concluded that with the current level of performance obtained for the machine in the research, it has the potential for inclusion in kenaf production operation.
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    Open Access
    A comparison of different formulations of offset-free nonlinear model predictive control
    (Department of Chemical Engineering, Obafemi Awolowo University, 2023) AYOADE, Micheal Temitope
    This study developed the simulation model of the different algorithms for offset-free nonlinear model predictive control (NMPC), applied the developed simulation model on selected benchmarked processes and on an experimental process rig. The study then made comparison among the different formulations. These were with a view to comparing the various methods of designing offset-free nonlinear model predictive control.
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    Techno-Economic assessment of off grid Hydrokinetic Power infrastructure for urban residential development initiatives in Calabar, Cross River State
    (Faculty of Technology, Obafemi Awolowo University, 2024) Leonard Unimke UGI
    This study determined the electricity demand for urban residential development initiatives in Calabar, Cross River State, established the technological specifications for hydrokinetic power development for the urban residential development initiatives and assessed the economic viability of the hydrokinetic power infrastructure. These were with a view to promoting the adoption of hydrokinetic power infrastructure needed for the urban residents in Calabar, Cross River State, Nigeria. The study was carried out in three different selected urban residential areas, electricity audits of the selected urban residential development initiatives was carried out to obtain their power loads and total time of use. The data obtained was used to determine the electricity loads and energy demand. The obtained results served as the benchmarks for the design of the hydrokinetic power infrastructure. Data on technological specifications for the development of the hydrokinetic power infrastructure was obtained from journal articles and reports of the Cross River Urban-Rural Authority. The information obtained included the location coordinates, the lengths and widths of the river, and the river flow velocity. The specific location with its coordinates was mapped out using geographical positioning system (GPS). Information on appropriate turbine specifications and allied electrical components such as transformers came from equipment vendors and literature. Technological specifications for an alternate diesel power generation and CO2 emission savings were elicited from the International Energy Agency (IEA). The data obtained was analysed using energy planning and foresight analyses methodology. The economic viability of the hydrokinetic power infrastructure was determined using capital and operations costs, interest rates, and project time duration amongst others. The data obtained was analysed using life cycle and engineering economy analyses. The results showed that 815 housing units in the selected area had 9.2 MW power load demand with projected energy consumption of 51.8 MWh/day. The hydroquest turbine was found to be most suitable for the extraction of hydrokinetic power from the Calabar River. From the design calculations, 128 numbers of the suitable turbine (80kW hydroquest 2.80) were needed to produce the said electricity demand of 9.2 MW. The hydrokinetic requires a total investment cost of forty-one billion, nine hundred and three million four hundred and fifty naira (₦41,903.45 ×106). The investment required an annual operating cost of four billion five hundred and twelve million two hundred thousand (₦4,512.20 ×106). The levelized cost of HKP-based electricity was found to be ₦68.99/kWh at present. Subsequently, the levelized cost of HKP-based electricity for the first year of operation was ₦82.79/kWh. The estimated minimum revenue for the HKP-based electricity project was six billion five hundred and twenty-six million naira only (₦6,526.00×106) leading to investment recovery on the 7th year of 25 years life cycle of the project. The result also indicated that 528 metric tons of CO2 can be saved from the atmosphere over the 25 years life cycle of the project. The study concluded that, the establishment and development of hydrokinetic power plant in Calabar is technologically and economically viable.
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    Development of a microcontroller-based integration of renewable energy sources for implementation of a hybrid power supply system.
    (Department of Electronic and Electrical Enigneering, Faculty of Technology, Obafemi Awolowo University., 2023) SAMSON Joseph Bukola
    This study determined the appropriate size for each of the renewable energy sources (RES) to be integrated, developed a microcontroller-based system capable of coordinating and monitoring the energy output power flow of the sources, and simulated and evaluated the performances of the system. This was done with a view to providing a sustainable solution for electrification of areas not connected to main power grid. The wind speed, solar radiation and load demand data of the study site were obtained from Obafemi Awolowo University, Ile-Ife and then averaged into 1-hour intervals for different geographical seasons. The sequential quadratic programming (SQP) approach was used in the study to determine appropriate and economically viable sizes for the integrated energy systems. The SQP approach was used in the study to find optimal and cost-effective sizes for integrated energy systems that meet the specified requirements. Suitable mathematical models, and size optimization were obtained for the system’s components. Using MATLAB (version 2021a), a microcontroller algorithm for optimal power flow in a hybrid renewable energy source (HRES) was both developed and simulated. For the HRES cost analysis, the overall installation cost and cost per kW of each component were estimated, and three different optimal configurations for the site location were compared for techno-economic analysis. The results show that an off-grid energy system based on RES, with biogas backup, is feasible in the examined location. According to the simulation results, renewable energy (RE) contributes 51.4 % of total load demand in December during the academic period of the weekdays and 96.4 % of total load demand over the weekends of the same period in June. The energy contribution from RES from storage facilities ranged between 20.1 % and 44.0 % of total load demand. Among the three different configurations viz wind/PV/pumped-hydro/battery/biogas, PV/wind/battery, and wind/pumped- hydro/biogas, as examined in this work, wind/PV/pumped-hydro/battery/biogas is discovered to be the most cost-effective configuration with Net Present Cost and Levelised Cost of Energy of $3,085,675 and 0.027 $/kW respectively. The optimal and most cost-effective solution proposed configurations consist of 500 kW of PV system, 400 kW wind turbine. In conclusion, the study showed that implementing an off-grid HRES with sufficient storage, utilizing the pumped-hydro storage system, can provide a sustainable solution for electrification of once not connected to the grid.