Comparison of Rice Husk and Wheat Straw: From Slow and Fast Pyrolysis to Char Combustion

Thermochemical conversion of world top crops (rice and wheat) has been extensively investigated (TGA, DTF, SEM, XRD, BET, EA), and main insights are discussed in light of materials and process kinetics. Overall, the results show that the rice husk presents lower reactivity than the wheat straw for all thermal processes regardless of the final temperatures (300 °C–1300 °C), residence times (0.6 s–300 min), and atmospheres (100–340 mL·min–1 N2/air). The higher reactivity of wheat straw is attributed not only to higher alkali and ash contents but also to differences in both silica morphology and graphitic structure after pyrolysis. Chars produced from slow pyrolysis present more homogeneous characteristics than those produced from fast pyrolysis. Combustion of the chars from slow pyrolysis (up to 900 °C) show similar kinetic parameters with activation energies, Ea, of 101.8 and 101.0 kJ·mol–1 with pre-exponential factor, A, of 4.3 × 107 and 9.6 × 107 min–1 for rice husk and wheat straw, respectively; while c...