Date of Award
1-27-2026
Thesis Type
PhD
Document Type
Thesis
Divisions
Faculty of Engineering
Department
Department of Chemical Engineering
Institution
Universiti Malaya
Abstract
The transition toward renewable energy is critical for reducing greenhouse gas emissions and mitigating dependence on fossil fuels. Biomass, particularly agricultural residues such as palm kernel shell (PKS), offers significant potential as a sustainable energy source due to its abundance, carbon-neutral characteristics, and favorable lignocellulosic composition. However, the direct utilization of PKS in thermal conversion processes is hindered by high moisture content, poor grindability, and elevated levels of alkali and alkaline earth metals (AAEMs) that promote fouling and slagging, reducing heat transfer efficiency and operational stability. To address these challenges, this study investigated the optimization of continuous torrefaction for PKS, integrating feedstock pre-treatment, reactor hydrodynamic characterization, and advanced statistical optimization. The research was conducted in sequential stages. Initially, a water-washing pre-treatment was applied to reduce water-soluble AAEM concentrations, aiming to minimize the potential for slagging and fouling. Subsequently, cold-test calibration of a Helical Screw Induced Rotation (HSIR) reactor was performed to identify steady-state operating conditions and characterize residence time distribution (RTD) parameters, including mean residence time, variance, and axial dispersion. These hydrodynamic insights formed the basis for precise control in subsequent hot continuous torrefaction trials. Torrefaction experiments were conducted at temperatures ranging from 240 to 320 °C under varying Feed Rate Speeds (FRS) and Helical Screw Rotation Speeds (HSRS), covering low, medium, and severe torrefaction levels. To ensure robust process optimization, the study employed a hybrid Design of Experiments (DOE) strategy: Definitive Screening Design (DSD) to identify significant operational factors, I-Optimal design for accurate RTD modeling, and multi-objective desirability optimization to maximize mass yield (MY), Calorific Value (CV), and energy conversion efficiency (ECE) while minimizing RTD variance and axial dispersion. Washed and unwashed PKS were compared under optimized conditions using thermogravimetric analysis (TGA), contact angle measurements, and grindability tests. Results demonstrated that water washing significantly reduced AAEM content, lowering slagging and fouling risk while improving feedstock stability. Reactor calibration revealed the critical influence of FRS and HSRS on RTD behavior, enabling fine-tuned control of residence time and flow uniformity. Multi-objective optimization identified operational settings that balanced product quality and process efficiency, with washed PKS consistently outperforming unwashed samples in hydrophobicity, grindability, and thermal stability. This study provides a novel integration of feedstock pre-treatment, RTD-driven reactor optimization, and advanced DOE techniques for enhancing continuous torrefaction performance. The findings not only advance the understanding of PKS conversion behavior but also contribute a scalable methodology for industrial biomass upgrading processes.
Additional Information
Thesis (PhD) - Faculty of Engineering, Universiti Malaya, 2026.
Recommended Citation
Javanmard, Arash, "Optimization of continuous torrefaction of palm kernel shell in a helical screw-induced rotation fluidized bed reactor: effects of water washing pretreatment and reactor flow behavior" (2026). Student Works (2020-2029). 1956.
https://knova.um.edu.my/student_works_2020s/1956
Creative Commons License
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