Combustion behavior of various biomass wastes pellet fuel: Thermogravimetric analysis and ash fusion characteristics

This study compared rapeseed straw (RS), flower waste (FW), and tobacco straw (TS) in terms of fuel properties, combustion behavior, kinetics, and ash fusion characteristics. Proximate and ultimate analyses, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), ash fusion tests, and kinetic modeling were conducted to evaluate their energy utilization potential. FW exhibited the highest carbon content and heating value, indicating superior energy density. SEM observations revealed distinct microstructures that influenced oxygen diffusion and combustion behavior. TGA results showed that all samples underwent three combustion stages: moisture evaporation, volatile matter combustion, and fixed‑carbon combustion. TS demonstrated the highest combustion reactivity and stability, whereas FW achieved more complete burnout with lower residual ash. Ash analyses indicated that RS ash was dominated by high-melting apatite phases, resulting in better thermal stability and lower slagging risk, while FW and TS ashes contained more alkali salts and aluminosilicates, which reduced ash fusion temperatures. Kinetic analysis using the Coats–Redfern method yielded activation energies of 59.80, 73.22, and 58.67 kJ·mol −1 for FW, TS, and RS, respectively. Overall, FW showed high energy potential, TS exhibited strong reactivity with ash risks, and RS demonstrated superior ash stability for combustion applications.