Properties of char particles obtained under O2/N2 and O2/CO2 combustion environments

Pulverized coal combustion in O2/N2 and O2/CO2 environments was investigated with a drop tube furnace. Results present that the reaction rate and burn-out degree of O2/CO2 chars (obtained in O2/CO2 environments) are lower than that of O2/N2 chars (obtained in O2/N2 environments) under the same experimental condition. It indicates that a higher O2 concentration in O2/CO2 environment is needed to achieve the similar combustion characteristic to that in O2/N2 environment. The main differences between O2/N2 and O2/CO2 chars rely on the pore structure determined by N2 adsorption and chemical structure measured by FT-IR. For O2/CO2 char, the surface is thick and the pores are compact which contribute to the fragmentation reduction of particles burning in O2/CO2 environment. The organic functional group elimination rate from the surface of O2/CO2 chars is slower or delayed. The present research results might have important implications for further understanding the intrinsic kinetics of pulverized coal combustion in O2/CO2 environment.