Effect of Biomass Particle Size on the Torrefaction Characteristics in a Fixed-Bed Reactor

The aim of this study is to investigate the influence of biomass particle size on the torrefaction characteristics under different torrefaction temperatures and times. Paulownia wood with particle sizes ranging from 12 to 2 produced. However, at higher temperatures, decarbonylation reactions were significantly strengthened with more CO generated. The contents of CO2 and CO could account for more than 98 vol% of the product gas. The influence of particle size on the chemical composition of the solid product was much smaller than that of torrefaction temperature and time, but the energy yield of the solid product decreased with the decrease in particle size. The increase in torrefaction temperature and time could significantly increase the C content in the solid product while reducing its O content. It is recommended to use a relatively higher temperature (e.g., 290 °C) for the torrefaction of large particle biomass, as it could significantly reduce the impact of particle size on the torrefaction process and reduce the torrefaction time.