Pyrolytic behavior and kinetic of wood sawdust at isothermal and non-isothermal conditions

Abstract

Pyrolytic behavior and kinetic of wood sawdust were studied at non-isothermal and isothermal conditions. The characteristic temperatures of ∼230 °C, ∼300 °C, ∼345 °C, ∼370 °C corresponded to degradation of pseudo hemicelluloses 1, hemicellulose 2, cellulose, lignin under non-isothermal condition, respectively. The release behaviors of gaseous products were closely related to the characteristic temperatures of weight loss. The tar generation could be characterized by CH3 group that was mainly dominated the by decompositions of hemicelluloses and cellulose. Under isothermal condition, the weight of derived biochar was described by a function of wchar = 775.5–2.9T + 0.0037T2-1.6 × 10−6T3. A novel nth-order discrete distributed activation energy model was developed to study the non-isothermal kinetic. The characteristic weight fractions of woody sawdust pyrolysis were found at conversions of 0.29, 0.30, 0.65, 0.84, 0.88 and 0.95. Parallel reaction model could explain the non-isothermal kinetic well with similar reaction orders to discrete distributed activation energy model. The isothermal kinetic of pyrolysis could be described by three or four components parallel reaction with nth-order Avrami-Erofeev model.