Two-dimensional PR-DNS of cellulose pyrolysis: Parametric and two-particle interaction studies

Biomass pyrolysis is a key thermochemical pathway for sustainable energy production, converting organic matter into biochar, bio-oil, and pyrolytic gases. Its multiscale and multiphysics nature complicates experiments and motivates high-fidelity numerical modeling. This work extends our particle-resolved Direct Numerical Simulation (PR-DNS) framework by incorporating a semi-detailed cellulose pyrolysis mechanism derived from chemical reaction neural networks (CRNN), enabling fully resolved simulations of coupled flow, heat transfer, mass transfer, and cellulose conversion. The resulting framework, implemented in our in-house code DINO, is employed to investigate early-stage cellulose pyrolysis (up to 10 ms) through systematic parametric and two-particle interaction studies in two dimensions. Elevated fluid temperatures intensify convective heat transfer and promote the formation of lighter products. Increasing inflow velocity enhances convective transport but reduces residence time, resulting in only weak variations in surface-averaged product mass fractions within the investigated range. Two-particle simulations reveal pronounced interaction effects: Side-by-side configurations show nearly symmetric behavior, whereas vertically stacked particles exhibit wake shielding effects in the two-dimensional flow field, reducing heat transfer to the downstream particle and modifying local species distributions. These findings provide mechanistic insight into particle-scale flow–heat–chemistry coupling during cellulose pyrolysis and demonstrate the importance of explicitly resolving interparticle interactions.