Kinetic Modeling of Tar and Light Hydrocarbons during the Thermal Conversion of Biomass

A model is presented to predict the tar and light hydrocarbons yields during the thermochemical conversion of woody biomass in the temperature range of 700–1000 °C. It takes into account the tar generation during fuel devolatilization and the thermally induced secondary conversion of the tars and light hydrocarbons, accounting for a limited number of species and reactions representing the main conversion mechanisms at temperatures above 700 °C. The stoichiometry and kinetics of the reactions were comprehensively selected from literature. Comparison with measurements from the literature is presented to discuss the applicability of the model to both pyrolysis reactors and gasifiers. The model quantitatively predicts the yields of benzene, tar class 3 (toluene) and 4 (naphthalene), as well as the main qualitative trends of tar class 2 (phenol) and 5 (pyrene) under pyrolysis conditions for different temperatures and residence times. It exhibits larger deviations under autothermal gasification conditions, where partial combustion of volatiles might influence tar and hydrocarbon reactions, but still gives reasonable qualitative predictions. Comparison with other detailed models from the literature shows that the present work improves the prediction capability of existing models.