Investigation of biomass slow pyrolysis mechanisms based on the generation trends in pyrolysis products

The development of biomass pyrolysis technology is important for alleviating energy shortages and environmental pollution. To investigate the generation trends in three-phase products, biomass pyrolysis experiments at different temperatures were carried out using a tubular furnace. The results showed that hemicellulose and cellulose structures began to dehydrate and break down and that alkyl-aryl lignin began to decompose between 200 degree celsius and 400 degree celsius. After the temperature reached 400 degrees C, CO functional groups in the biochar began to decline, and a part of the biochar was converted into CO. After the temperature reached 500 degrees C, the biochar gradually formed a complex fused-ring structure. The tar yield increased first and then decreased with increasing pyrolysis temperature, reaching a maximum (32.82%) at 700 degrees C. On the one hand, tar generation occurred due to the biomass pyrolysis reaction, mainly at temperatures below 500 degree celsius. On the other hand, it occurred due to the homogeneous transformation reaction of tar, mainly above 500 degree celsius. The maximum value of the H-2 release curve increased with increasing temperature, and its change was most obvious relative to that of the other gases. The formation of H-2 at higher temperatures was mainly due to dehydrogenation, condensation and polycondensation reactions.