Investigation of the intrinsic CO2 gasification kinetics of biomass char at medium to high temperatures

•Aerosol method was developed to study high-temperature gasification kinetics.•The intrinsic CO2 gasification kinetics was established from 800 °C to 1300 °C.•In CO2 gasification, char reactivity order was wood > miscanthus > straw.•Biomass char reactivity shows a positive dependence on the O/C ratio in char.•Char reactivity shows a negative dependence on alkali content in this study.

In total eight char samples from pelletized wood, miscanthus, and straw were prepared under various pyrolysis conditions. The CO2 gasification kinetics for each sample was established in the temperature range from 800 °C to 1300 °C by the combination of thermogravimetric analysis (TGA) and a novel aerosol-based method. The aerosol-based method was used for the high temperature range between 1100 °C and 1300 °C, by gasifying suspended char particles (0.5–10 μm) in an oxidizing carrier gas. A tapered element oscillating microbalance (TEOM) was used to measure the change of mass concentrations of particles in the carrier gas, before and after gasification. The results showed that the aerosol-based method could be used to investigate the intrinsic gasification kinetics of biomass char, at least up to 1300 °C. All char samples showed similar reactivity in the low temperature range. However, above 1000 °C there were significant differences in reactivity, and at 1300 °C the conversion of the wood was in the order of 10 times faster than that of straw. The general char reactivity order in this study was wood > miscanthus > straw.