Combustion and Flue Gas Evolution Characteristics of Rice Husk in Various Mixtures and Layers with Al2O3 Particles and Char Prepared with Different Pyrolysis Parameters

Abstract

During pyrolysis and combustion experiments, rice husk and Al₂O₃ were combined in two ways, namely blending (rice husk was blended with Al₂O₃) and covering (rice husk was covered by Al₂O₃) modes, respectively. Rice husk biomass (RHB) char was prepared under different pyrolysis conditions. The resulting combustion characteristics and corresponding gaseous evolution of the biochar were compared. The maximum combustion rate decreased as particles accumulated, causing a shift in the thermo-gravimetric curve to higher temperature ranges. The combustion reaction was hindered in the covering mode. The combustion reactivity of the prepared char decreased as the char preparation time increased. During the char oxidation process, the release amounts of H₂O and CO₂ from char combustion increased first and then decreased, while the release amounts of CO, CH₄, and organic components containing C=O gradually decreased with increasing char preparation time. Char prepared with the covering mode exhibited higher burn-out rates and combustion indices but lower activation energies required for combustion reaction. Additionally, the covering mode delayed the timely release of gases from the biomass heating in air, and the quantity of combustion gas released from the char produced at covering mode was greater than that released from the char produced at blending mode. The results obtained can improve the understanding of stacked biomass particles combustion process.