Modeling biomass devolatilization using the chemical percolation devolatilization model for the main components

Devolatilization plays a significant role in biomass combustion processes, and it depends on the biomass form and composition. In the present work, a general model is developed for the devolatilization of biomass under different conditions, particularly under high heating rate (up to 1000 K/s) and high temperature (up to 1400 K). The model was developed extending the chemical percolation devolatilization model from coal to the three main biomass components, that is, cellulose, hemicellulose, and lignin, on the basis of their specific chemical structure and behavior. The model formulation was kept with the same reaction scheme and multimechanisms. The modifications were performed on the structural parameters and reaction kinetics considering a chain structure for the components. The devolatilization of the whole biomass was modeled as the superposition of the independent kinetics of the major components. The structural and kinetic parameters were fixed for the components, while the only fuel-specific input, the mass fraction of the components, can be calculated with a proposed correlation as a function of the conventional proximate and ultimate analyses. Comparisons to the measurements show that the model has been successfully applied to the devolatilization of various biomass types and can reasonably represent the yields of tar, light gases, and char, when considering side chains from tars as secondary products.