Examination of kinetics of non-catalytic steam gasification of biomass/lignite chars and its relationship with the variation of the pore structure

There have been considerable studies on char gasification under catalysis of inherent or extraneous metallic species, while underlying non-catalytic gasification has not necessarily received attention, despite the importance to clarify the intrinsic kinetics and its correlation with the structural parameters, such as surface area. The present authors investigated the noncatalytic steam gasification of chars from the pyrolysis of seven types of biomass and lignite. The chars, which were nearly free from catalytic metals, showed reactivities similar to one another with the activation energy within a range from 228 to 241 kJ mol^-1. The specific rates of reaction were steady over the entire range of the conversion. In contrast, the specific surface areas of the chars increased with the conversion from around 500 to even beyond 2000 m² g^-1. The results demonstrated that the chars underwent the gasification obeying the first-order kinetics, which was independent of the specific surface area.