Combustion and gasification characteristics of rice husk

Abstract

Rice husk when used in gasifiers and boilers yields carbonaceous residue. Combustion and gasification studies of rice husk were carried out to understand the problem of incomplete carbon conversion. Thermogravimetric experiments were carried out using carbon dioxide, nitrogen, air and steam atmospheres under different temperature conditions. At temperatures greater than 700 °C there was incomplete conversion, while at lower temperatures complete conversion occurs. The combustion and gasification kinetics are also very sensitive to the rate of heating. These observations are explained on the basis that the silica undergoes structural changes in the range 700–900 °C. The findings are also supported by SEM analysis of the ash sample obtained under different reaction conditions and X-ray diffraction patterns of the residues. Appropriate and efficient routes for gasification of rice husk for thermal and mechanical/electrical power are proposed, in addition to recovery of amorphous silica.