Revisiting the reaction scheme of slow pyrolysis of woody biomass

Existing lumped kinetic models have limited accuracy in predicting the pyrolysis behavior of different materials. There is currently no universally accepted model capable of accurately predicting pyrolysis rates and final product yields for various materials under different experimental conditions. This study aims to address this limitation by assessing the sensitivity of a widely used wood pyrolysis kinetic model across multiple sets of experimental data. The analysis reveals that the existing model falls short in accurately predicting the yields of woody biomass at higher temperatures. To overcome this, two new kinetic models were proposed that incorporate additional reactions not accounted for in conventional models. These additional reactions have impact on the formation of secondary pyrolysis phases. The first proposed model introduces a term for secondary tar formation, which takes into account the production of more stable cracked, dehydrogenated, and deoxygenated tars that typically occur at elevated pyrolysis temperatures, possibly influenced by catalysts. The second proposed model expands on this concept by incorporating terms that represent the formation of secondary gases and chars arising from the primary chars. By including these additional reactions, the model enhances its accuracy and predictive capacity for determining the pyrolytic products of various types of woody biomass.