Particle-scale evaluation of the pyrolysis process of biomass material in a reactive gas-solid spouted reactor

Abstract

Biomass pyrolysis is numerically studied in a spouted bed reactor. Thermophysical processes with complex reactions are considered for gas and solid phases under Eulerian and Lagrangian frameworks. After thorough model validations with experimental measurements, particle-scale evaluation of sand and biomass species combined with the segregation phenomenon is presented. The results show that the axial segregation significantly affects the spatial distribution of particle-scale information in three distinct regions. Particle heat transfer coefficient (HTC) has the largest value in the spout region, and then fountain region. A continuous decrease of particle HTC along the bed height appears. Particles close to the spout-annulus interface have a comparatively smaller temperature. Different distribution patterns of the HTC for sand and biomass can be observed. The increase of pyrolysis temperature raises the biomass temperature and HTC, while the effect of gas velocity is negligible. The dispersion intensity of biomass species is obviously larger than that of sand particles. A smaller sand size results in a smaller temperature, but a larger HTC, and a reduced dispersion coefficient.