Oxidative fast pyrolysis of biomass in a quartz tube fluidized bed reactor: Effect of oxygen equivalence ratio

Abstract

The effect of oxygen equivalence ratio (ER) on oxidative fast pyrolysis of pine sawdust was investigated in a quartz tube fluidized bed reactor. The results showed that the introduction of oxygen into fluidizing gas would mainly oxidize the biochar, thus provided the largest contribution to heat demand during biomass pyrolysis towards autothermal operation. The increase of ER from 0 to 11.15% decreased the biochar yield from 21.03 to 9.5 wt%. The enthalpy for fast pyrolysis of pine sawdust was about 1084.49 kJ/kg, and a theoretical ER to achieve autothermal pyrolysis was thus calculated as ∼3.92%. The addition of oxygen indeed changed the formation and distribution of bio-oil. With ER of 6.47%, although the bio-oil yield decreased slightly, the light compounds in bio-oil (e.g., linear alcohols/carbonyls/acids, furan compounds and cyclopentanones/cyclohexanones) were largely consumed, while the heavy compounds (e.g., phenols/aromatic hydrocarbons and anhydrosugars) were mostly retained with the formation of anhydrosugars being promoted.