Unresolved Issues on the Kinetic Modeling of Pyrolysis of Woody and Nonwoody Biomass Fuels

The main objective of this work is to evaluate a number of unresolved issues on the kinetic modeling of the pyrolysis of woody and nonwoody biomass fuels. More specifically, this work aims to provide a better understanding, of the role of the interactions between the main biomass components-cellulose, hemicellulose, and lignin and the role of the presence of extractives on the pyrolysis of those biomass fuels. To achieve these goals, five biomass samples and the three main biomass components were pyrolyzed under slow pyrolysis conditions, up to 700 degrees C, in order to obtain a comprehensive experimental database for model validation. Subsequently, the experimental weight loss curves, product yields, and gas composition were compared with the predictions obtained with the Bio-PolilMi mechanism. Experimental mixtures were obtained by superimposing the experimental curves from the single component pyrolysis tests while satisfying the composition of the biomass samples. The. Bio-PoliMi mechanism predicted with good accuracy the weight loss curves and the product yields of the:single components. Overall, there was a good agreement between the experimental and the predicted characteristic temperatures of CO2 and CO, but the predictions showed a delay in the release of CH4 and H-2 that led to major discrepancies in the gas composition. In the case of lignin, the triangulation method was found to contribute to the observed disagreement between measurements and predictions of the CO2 yield. When analyzing mixtures resembling real biomass, a good agreement between:the experimental mixtures and predicted product yields was observed when the extractives were not considered for both the woody and nonwoody mixtures. Discrepancies were also observed in the case of the gas species yield, and compensation errors were identified in the case of the CO; When extractives were considered, the Bio-PoliMi mechanism showed a good agreement with the product yields of the real biomass, especially with the total gas yield.. However, large discrepancies were observed for the gas composition, meaning that the model is not capable of predicting the pyrolysis gas heating value.