ABSTRACT
Co-torrefaction has been recognized as an exceptionally adaptable technique, increasingly esteemed for its ability to significantly improve the characteristics of a diverse array of biomass waste materials, thereby facilitating their responsible and sustainable application as solid fuels within various energy systems. The primary objective of this academic investigation is to explore the synergistic integration of sub-bituminous coal (SBC) and empty palm fruit bunch (EFB), which serve as the principal feedstocks in the intricate torrefaction procedure, aimed at enhancing their energy attributes. Through a comprehensive and detailed examination, this research scrupulously evaluated three crucial input parameters that are vital to the torrefaction process: specifically, the proportion of empty palm fruit bunch (EFB), the precise temperature during torrefaction, and the duration of residence time, all directed at ascertaining the optimal conditions that yield the desired outcomes. To attain this objective, the study employed an advanced response surface methodology founded on a Box-Behnken design. This robust statistical framework is utilized to optimize the various process conditions, thereby facilitating the maximization of the higher heating value (HHV) and the energy yield (EY) of the torrefied products produced. Subsequent to this optimization phase, a comprehensive analysis of variance (ANOVA) was performed to elucidate the primary and interactive effects of the aforementioned factors on the chemical and physical transformations occurring throughout the torrefaction process. The findings of this investigation underscore the critical significance of temperature, which emerged as the dominant factor affecting the torrefaction process, while also revealing that minimal interaction effects were observed among the evaluated input parameters. Importantly, it was determined that lower temperature settings proved to be more advantageous and beneficial v to the co-torrefaction process, suggesting potential pathways for further optimization. The optimal conditions identified through this thorough investigation resulted in an impressive heating value of 31.98 MJ/kg and an energy yield of 92.18%, corresponding to a specific ratio of empty palm fruit bunch of 20%, a torrefaction temperature fixed at 200.00°C, and a residence time sustained at 60 minutes. Moreover, it is noteworthy that the experimental outcomes acquired from this investigation closely matched the predicted values generated by the model, thereby affirming both the reliability and precision of the research model employed. These significant findings bear extensive implications, as they provide valuable insights and recommendations pertinent to the thermal pre-treatment processes of blended coal and biomass, aimed at applications involving co-firing or co-gasification in energy production frameworks
