Effect of Particle Structural Irregularities on Pyrolysis Performance: A 3D Multiphysics Model for Industrial-grade Biomass Feedstocks

Industrial-grade biomass feedstocks, such as chipped and shredded waste wood, consist of thermally thick particles with irregular shapes and rough surfaces. These features may complicate particle-scale thermal modelling and require geometry-resolved descriptions for reliable predictions. A procedural geometry workflow was developed to generate a representative irregular, wood-like 3D strip in MATLAB and quantify its morphology against an equivalent regular block. Both geometries were imported into COMSOL Multiphysics as particle-scale pyrolysis models using the finite element method (FEM) for spatial discretisation. A representative waste wood composition defined the seven pseudo-components. The biomass particle was modelled as a reactive porous medium coupled with transport phenomena and a 32-reaction pyrolysis kinetic scheme. Results show that irregular particles heat faster than regular particles, with core temperatures approximately 250 K higher after 20 s and an average surface heating rate of ~278 K/s within the first 2 s, nearly 2.7 times that of regular particles. Comparable primary pyrolysis product formation is reached approximately 6.5 times earlier in the irregular particle, indicating that idealised geometries may underpredict reaction timing and heating rates. This proof-of-concept screening model isolates the effect of particle morphology on pyrolysis behaviour under comparable conditions.