Particle-scale modelling of thermally-thick biomass pyrolysis: detailed kinetics coupled with an anisotropic porous media model with resolved fluid-particle coupling

Journal article, 2026

Pyrolysis of thermally-thick biomass particles is a highly complex process involving fluid-particle coupling, anisotropic intra-particle transfer, and detailed pyrolysis reactions in a porous particle. To enable numerical predictions under widely varying operating conditions, a comprehensive biomass pyrolysis model using detailed kinetics coupled with an anisotropic porous media model with resolved fluid-particle coupling is developed. The results show that the detailed model can provide reasonable predictions of biomass pyrolysis in a wide range of conditions, including temperatures ranging from 550 to 1800 K, particle size ranges from 3 mm to 25 mm, moisture contents up to 66.67% (dry basis), various particle shapes, different wood species, as well as radically different flow conditions (natural convection and forced convection flow modes). Intra-particle heat transfer and fluid-particle coupling exert substantial effects on the pyrolysis process, while the influence of anisotropic properties is relatively mild. Sensitivity analysis identifies wood thermal capacity, emissivity, and thermal conductivity as the most critical parameters; three out of 32 reaction rates have significant effects on the modelling results at low-temperature conditions, while all reaction rates show a weak impact on the modelling results at high-temperature conditions, due to a large internal thermal Damköhler number (Da > 10). These findings provide profound theoretical insights into the pyrolysis mechanisms of thermally thick biomass particles, verifying that the model serves as a powerful tool for predicting the pyrolysis behaviors of thermally thick biomass particles, with direct implications for the design and optimization of biomass pyrolysis reactors.