Characterization of rice husk ash produced using different biomass combustion techniques for energy

Rice husk is the main byproduct of industrial processing of rice, and is a widely used byproduct in Brazil and worldwide as biomass in energy production, reducing environmental impacts associated with improper disposal. The ash generated in rice husk combustion has potential economic applications in a variety of sectors. However, the properties of rice husk ash (RHA) are strongly dependent on the combustion method used. This study investigates the physical, chemical, thermal, mineralogical, and morphological characteristics of three types of RHA, produced according to three distinct methods (grate furnace, fluidized bed, and suspension/entrained combustion). The results confirmed that combustion conditions define the characteristics of each RHA, even though the raw material used was essentially the same. The main differences in the characteristics of the silica obtained were observed in the parameters specific surface area (between 11.35 and 39.27 m2 g−1), SiO2 (between 90.02 and 96.71 wt%), total carbon contents (between 2.18 and 8.63 wt%), and the structure of the silica produced (completely amorphous or partially crystalline). Morphological profiles, oxide chemical composition, and specific weight presented similar results.