Particle morphology regulation on tar, char and non-condensable gases distribution in eucalyptus pyrolysis—A Lattice Boltzmann study

Biomass pyrolysis is an effective route to convert low-grade biomass into high-value energy carriers (tar and non-condensable gases), with particle morphology exerting a significant regulatory effect on the thermochemical conversion process. As a typical fast-growing hardwood with high cellulose content (48.6%), favorable lignocellulose composition, and excellent thermal reactivity, eucalyptus serves as an ideal feedstock for pyrolysis investigation. This study adopted the Lattice Boltzmann Method (LBM) coupled with a pyrolysis kinetic model (Three Parallel Reactions Model: three parallel primary + secondary reactions) to systematically investigate the effects of particle morphology on eucalyptus pyrolysis characteristics. Three aspects were explored: pyrolysis of elliptical cross-sectional cylindrical particles with fixed horizontal axis and variable aspect ratios (λ), product yields of particles with identical λ but different sizes, and λ variations under constant cross-sectional area. The results indicate that spherical particles promote char formation, while elliptical particles provide higher tar and gas yields. Particle size was negatively correlated with volatile production. Specifically, as λ increases from 0.250 to 1.000, the tar yield decreases by approximately 3% and the non-condensable gases yield decreases by nearly 1%. Reciprocal λ pairs exhibited thermal response asymmetry, with smaller λ(＜1.000) accelerating pyrolysis. Under constant cross-sectional area, adjusting λ affected tar/non-condensable gases yields and shortened conversion time. This study confirms the crucial role of particle morphology regulation in pyrolysis optimization, providing a theoretical basis for targeted product distribution via synergistic control of λ and particle size.