International Journal of Engineering Research in Africa Vol. 79

Abstract: This study investigates the effects of nickel nitrate modification on the physicochemical, structural, and thermal characteristics of cashew nutshell (CNS)-derived biochar. Biochar is an emerging eco-friendly material used in adsorption, catalysis, bio-composites, and bioenergy. It can be further functionalized to enhance its properties for specific applications. In this study, biochar was prepared via slow pyrolysis at 500 °C with a heating rate of 5 °C min^-1 under argon flow and a residence time of 1 h. The biochar was then loaded with nickel nitrate (0–15 wt% Ni) via wet impregnation and re-pyrolyzed under the same conditions with a residence time of 2 h. The obtained samples were characterized using X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) surface area and pore size analysis. The catalytic activity of the samples was evaluated for syngas production. XRD identified Ni° and NiO crystalline phases within the biochar matrix. XRF analysis indicated that the synthesized samples contained 0.03–10.69 wt% Ni. These results indicate successful Ni loading. Nickel doping altered the chemical composition of inherent oxides, improved thermal stability through strong metal-support interactions, and increased porosity. Among the samples, the 10 wt% Ni (NiBC-2) showed an optimal balance of pore accessibility, nickel dispersion, metal-support interactions, a stable carbon structure, and catalytic activity. Notably, Ni addition increased the specific surface area from 8.09 m²/g (BC) to 13.12 m²/g (NiBC-3), producing nickel crystallites ranging from 17.13 to 21.47 nm. These findings demonstrate that CNS biochar is a promising support material for catalytic applications.

Abstract: This study investigates the physicomechanical, thermal, and structural behavior of polypropylene random copolymer (PPR) a new material reinforced with bamboo particles (BP) for potential use in PPR pipe formulations. Bamboo particles were incorporated at 2.5, 5, 7.5, and 10 wt.% after thermal drying and alkaline treatment using a 20 wt.% NaOH solution to improve compatibility with the polymer matrix. Mechanical testing, melt flow rate (MFR) and density measurements, differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FTIR), and optical microscopy (OM) were conducted to evaluate the influence of particles addition and treatment. Treated particles significantly improved tensile strength and modulus while also affecting other characteristics, such as increasing viscosity (lower MFR) and decreasing the degree of crystallinity. FTIR and DSC confirmed chemical and thermal modifications following treatment, and OM revealed improved fiber dispersion. Overall, the incorporation of 10 wt.% treated bamboo particles led to a marked improvement in the mechanical performance of PPR, with increases of approximately 56.3% in tensile modulus, 24.3% in tensile strength, and 16.2% in elongation at break compared to virgin PPR, highlighting an effective reinforcement while preserving ductility.

Abstract: The reuse of asphalt mixtures has become an essential practice in the construction sector, offering both ecological and economic benefits. This research evaluates the integration of recycled sand, obtained by milling degraded flexible pavements (FRAP), as a partial or total replacement for natural sand. The process is combined with the use of silica fume (SF) as a cementitious additive. Silica fume was incorporated at rates of 10%, 20%, and 30% as a cement replacement to formulate self-compacting mortars (SCM). A superplasticizer was added to compensate for the high water absorption of FRAP and to maintain a consistent flow spread for all mixtures. The results indicate that the use of SF improves plastic viscosity, yield stress, and mechanical strength, while also reducing capillary absorption. 100% FRAP increased yield stress by 71% and plastic viscosity by 125%; 20–30% SF improved 28 day compressive strength by 17–27%. Furthermore, mathematical relationships were established to correlate the different study parameters, demonstrating acceptable correlation coefficients, where these coefficients are 0.99 and 0.98 for the yield stress and the viscosity, respectively.

Abstract: The application of high-density polyethylene (HDPE) pipes in water and natural gas distribution systems is rapidly increasing. While the mechanical strength of HDPE pipes is well established, welding remains a critical issue affecting structural integrity and performance. This study investigates the repair of defective HDPE pipes and proposes a simple approach for identifying weld zones. Artificial longitudinal notches were introduced into 125 mm diameter HDPE pipes and repaired using friction stir welding. Welding parameters optimized from previous studies were applied, with best results obtained at a tool rotation speed of 1100 rpm and a welding speed of 30 mm/min, producing defect-free welds. Weld zone identification was performed using static projection radiography with images taken parallel and perpendicular to the pipe diameter, enabling clear distinction of three weld zones and the base material. Hardness measurements across the welded cross-section confirmed the radiographic findings. The results provide insight into weld bead microstructure and support future studies on the mechanical characterization of individual weld zones.

Abstract: This paper presents a numerical investigation to evaluate thermal-hydraulic performance of double forward facing step. The combined analysis of double forward-facing step geometries and wavy-wall amplitude, which has never been done previously, is what makes this study groundbreaking. With the help of the double-step construction and the undulating upper wall, this special arrangement seeks to improve the thermal-hydraulic performance.The effect of varying wavy amplitude and the relative double step height was evaluated under different turbulent flow conditions. The turbulent flow and energy was modelled by contiuity full Navier-Stockesand energy equations. The effect of turbulent was modelled by k- Ɛ model. The finite volume method based on a simple algorithm was adoped to the discretise the flow and energy models. ANSYS Fluent was used to obtain the target results. The obtained results show that the increasing the amplitude value and the relative step height has a noticeable effect on intensification of average Nusselt number and overall performance with a moderate increase in friction losses. The findings reported that the steps height ratio (H_r= 2.6) provides the best overall performance for all the tested Reynolds numbers.The maximum performance was 1.63 (163%) at Re=10000 for Am=0.03 m.

Abstract: Crude palm kernel oil (CPKO) is a vital industrial and domestic commodity, yet its high level of impurities limits its direct use without refinement. Degumming is a fundamental step in refining, requiring efficient mixing, heating, and removal of phospholipids. In this study, parametric design principles and computational fluid dynamics (CFD) were applied to optimise the geometry and performance of a degumming reactor. Different height-to-diameter ratios (R_h/d = 1.0, 1.05, 1.10, 1.15, and 1.20) were analysed to determine their effect on fluid dynamics, velocity distribution, and thermal uniformity. CFD simulations were conducted using ANSYS Fluent, supported by heat transfer analysis and descriptive statistics, to identify the most efficient configuration. The findings demonstrate that an Rh/d ratio of 1.05 offers the best hydrodynamic stability and thermal performance, making it suitable for small and medium-scale refinery operations. This integration of CFD and parametric modelling highlights the role of digital engineering in improving food process equipment for resource-constrained industries.

Abstract: In heavy industrial processes, such as the treatment of phosphogypsum (a by-product of fertilizer manufacturing), a colossal amount of heat is generated and, in most cases, simply released into the atmosphere. This is a free and abundant source of energy that we are wasting. This research proposes to transform this low-temperature waste heat into usable electricity using smart technology : the Organic Rankine Cycle (ORC). Think of the ORC as a mini power plant (prototype) specially designed for low temperatures. Instead of using water, it uses a special organic fluid (similar to a refrigerant) that boils very easily, allowing it to capture the energy from the residual heat and convert it into electricity. This approach is not only environmentally friendly and economically viable, but it also makes the entire industrial process much more efficient while reducing thermal pollution released into the environment. To ensure the best performance, the investigation tested four different fluids (R245fa, R1233zd, R1234ze, and R227ea) using advanced Aspen Plus simulations. The most powerful organic fluid is R245fa, which proved to be the best performer, capable of converting 16.9% of waste heat into electricity. This study validates that integrating ORC systems into phosphogypsum processing plants is technically feasible and financially sound. It opens the door to more sustainable industrial practices and better management of our energy resources.

Abstract: The main bearing bush is a critical component in marine low-speed engines, responsible for supporting the crankshaft and ensuring stable operation. Given the prohibitive costs and technical difficulties in conducting full-scale bearing tests for marine engines, this study employed fluid-structure interaction simulation to investigate the load capacity characteristics of the main bearing bush. The effects of eccentricity ratio on oil film pressure, bearing load, attitude angle, cavitation, stress, and deformation were analyzed. Results indicate that the load capacity, maximum oil film pressure, stress, and deformation of the bearing bush increase exponentially with higher eccentricity ratios. The stress in the bearing alloy layer is approximately half of the maximum oil film pressure, reaching critical thresholds when the eccentricity ratio exceeds 0.985 (yield strength) and 0.99 (tensile strength). Crankshaft system analysis under peak combustion pressure (19 MPa) reveals maximum bearing specific pressures of 13.9-15.6 MPa, exceeding the critical bearing specific pressure limit of 10.11 MPa that prevents the plastic deformation of the AlSn40 alloy layer, but remains safely below the 16.21 MPa threshold corresponding to the alloy's ultimate tensile strength. The study provides quantitative design criteria for bearing load management and operational safety margins, contributing to enhanced reliability and performance optimization of marine low-speed engine bearing systems.

Abstract: Screw conveyors are widely used in various industries to move agricultural crops, construction materials, food and pharmaceutical products, metal shavings, etc. According to research, their share in loading and unloading operations in certain industries is up to 40%. Flexible screw conveyors (FSC) are widely used in agricultural production and construction, where there is a significant need to quickly change cargo handling routes and there is often difficult access to loading and unloading areas. During their operation, due to instability of material loading and ingress of foreign objects, overloads often occur, leading to significant deformations and breakdowns of the elements of these mechanisms, especially flexible screw working bodies. Overloads of a technological nature can be prevented by ensuring that the conveyed material fills the inter-twist space of the conveyor screw rationally and by improving the loading mechanisms (hoppers, feeders and nozzles). The occurrence of accidental overloads is difficult to predict and can be prevented by using protective mechanisms. Therefore, to ensure the reliable operation of FSC, it is necessary to use effective safety clutches in the design of their drives. Accordingly, the task of developing new designs of protection mechanisms for FSC, including safety clutches, and, accordingly, the theoretical substantiation of their design is relevant.

Abstract: The tomb of Akhmerutnisut represents an important example of the tombs of high officials, reflecting religious, political, social, architectural and artistic aspects of the Old Kingdom of ancient Egypt. In December 2023, the Mastaba of Akhmerutnisut Documentation Project (MAD-P) started its first season to study, document and evaluate the stability and conservation state of Akhmerutnisut’s tomb. Visual examination revealed that the limestone structure of the tomb has been compromised by multiple deterioration agents, resulting in various forms of damage including weakening, granular disintegration, flaking, scaling, cracking, fracturing, salt crystallization, soiling, loss of material and partial collapse. In the current paper, an analytical study of the limestone structure of Akhmerutnisut’s tomb was carried out to understand the composition and condition of its building materials (limestone and mortar). Effective diagnostic tools were utilized, including polarizing light microscope, X-ray diffractometer, scanning electron microscope and EDX unit. The results of the field observation and analytical work clarified the poor state of preservation of the studied tomb, which requires rapid conservation interventions. Based on the obtained data, a suitable conservation plan was proposed to preserve and reconstruct the studied tomb.