Optimization of processing parameters for physical, mechanical and chemical properties of Khaya senegalensis fuel pellets

Flourishing even in less-than-ideal conditions, the rapid growth of the Khaya senegalensis (khaya) tree requires regular pruning, presenting a challenge in waste management. To address this, the study proposes repurposing the pruning waste to manufacture energy pellets, offering an eco-friendly solution to waste removal. Pellets offer improved energy density, bulk density, moisture content, and homogeneity, thereby reducing storage, handling, and transportation costs. Notably, there is a lack of scientific gap on using Khaya senegalensis wood for fuel pellet production. To produce high-quality solid fuel, it is essential to comprehend the properties of wood fuel. Due to this necessity, the current study examines the effects of pelletization temperature, pressure, particle size, feedstock moisture content and binder percentages on fuel pellet properties, particularly on their physical, mechanical and combustion characteristics. In this study, the methodology involved determining the fuel characteristics of Khaya senegalensis wood biomass, including bulk density and calorific value, followed by the fabrication of fuel pellets from varying feedstock parameters. The effects of these parameters on pellet properties were analyzed through a parametric study, and response surface methodology was employed to optimize the processing conditions for enhanced pellet quality. The study achieves its first objective by comprehensively assessing the fuel characteristics of Khaya senegalensis wood, with bulk density measured at 258 kg/m³, moisture content (26.06 %), ash content (5.38 %), volatile matter (83.07 %), fixed carbon (15.46 %), and calorific values (16.11 MJ/kg). The second objective involves a parametric study, investigating the effects of pelletizing parameters on mechanical strength and combustion characteristics. The study successfully establishes relationships and optimized conditions for various parameters, presenting statistically significant findings in response analysis. The third objective employs response surface methodology to optimize pelletizing variables for ideal mechanical and combustion characteristics, resulting in well-validated models and predicted optimized values. Design Expert 13 revealed that khaya pellets performed optimally with factor settings of pelletization temperature at 110 °C, pressure at 5 tonnes, and a binder percentage of 9 %. The optimized values for various responses include axial compressive strength at 55.66 MPa, diametral compressive strength at 9.604 MPa, moisture content at 6.93 %, volatile matter at 87.83 %, ash content at 6.54 %, fixed carbon at 5.31 %, calorific value at 19.08 MJ/kg, durability at 99.93 %, and unit density at 1309.37 kg/m³. In conclusion, all the objectives have been successfully achieved, and the research provides valuable insights into repurposing khaya wood waste for sustainable energy pellet production. Understanding wood biomass, solid fuel qualities, and pelletization parameters for this crop could streamline the production of premium-quality pellets from khaya wood, addressing global energy demands efficiently.