Oxidation kinetics of maize stover char at low temperature based on surface area and temperature correction

Abstract

In utilization of biomass, kinetic data for char oxidation based on surface area are essential for prediction of burnout time of biomass, which is an important parameter in reactor design. In this study, experiments with maize stover char were performed in a simultaneous thermal analyzer (STA) to obtain these kinetic data. Mass loss and heat effect at different sample sizes were analyzed. A difference between recorded temperature and real reaction temperature of char oxidation was found to increase with increasing sample size. The shift of the mass loss rate curve resulting from this temperature difference was corrected. The CO/CO2 ratio was calculated to be 0.45 at low temperature (<500 °C) according to heat effect data. Based on corrected mass loss rate data and the CO/CO2 ratio, oxidation kinetic parameters (A = 6655 m s−1, E = 91.5 kJ mol−1) were obtained. Analysis also showed that oxygen transport resistance in a crucible was negligible compared with kinetic resistance at low temperature in STA. The oxidation kinetics based on surface area can be efficiently used to predict burnout time of piled combustion of biomass.