Biomass flash pyrolysis experiments between 1073 K and 1273 K

Analytical experiments are performed in an entrained flow reactor to better understand the kinetic processes involved in biomass pyrolysis under high temperatures (1073-1273 K) and flash heating condition (>500 K.. s/1). The influence of the particle size (0.4 and 1.1 mm), of the temperature range (1073-1273 K), of the presence of steam in the gas atmosphere (0 or 20 vol %) and of the residence time range (between 0.7 and 3.5 s for gas) on conversion and selectivity is studied. Under these conditions, the particle size is the most crucial parameter that influences decomposition. For 1.1 mm particles, pyrolysis requires more than 0.5 s and heat transfer processes are limiting. For 0.4 mm particles, pyrolysis seems finished after 0.5 s. More than 70 wt % of gas is produced. 40 % of the initial carbon is found in CO; less than 5% is found in CO2. The hydrogen content is equally distributed among H2, H20 and light hydrocarbons (CH4, C2H2, C2H4). Under these conditions, the evolution of the produced gas mixture is not very significant during the first few seconds, even if there seems to be some reactions between H2, the C2 and tars. (Résumé d'auteur