Synergistic effects during the co-pyrolysis of rice straw and pinewood sawdust: investigation of thermal decomposition behavior and reaction kinetics

Abstract This study investigated co-pyrolysis of rice straw (RS) and pinewood sawdust (PD), focusing on physicochemical characterization, thermal decomposition, and reaction kinetics. Thermogravimetric analysis was used to examine the thermal decomposition behavior, while the Friedman and Boswell methods combined with the master plot technique were employed to determine the activation energy (Ea), pre-exponential factor (A), and reaction mechanism. Results indicated that compared to PD, RS had a higher volatile matter (VC) and fixed carbon, and greater higher heating value (HHV). Notably, the VC of the blend was higher than both individual samples. PD exhibited a higher ash content (AC) than RS, and this AC decreased when blended with RS. Furthermore, the blended sample exhibited a higher HHV than the PD sample alone. At 10 °C/min, a significant synergistic effect was observed at 326.21 °C. Ea values for the RS + PD blend calculated by Friedman and Boswell methods were consistently lower than those for the individual RS and PD across most of the conversion (α) range. Negative ΔEa values were observed throughout the α range for all samples, with the deviations becoming more pronounced at higher α values. According to the master plot analysis, the pyrolysis mechanism of the samples was governed primarily by reaction-order and diffusion-based kinetic models.