A CFD model for the solar pyro-gasification of a wood pellet – Influence of pellet height

SORIA, JOSÉ ; MAZZA, GERMÁN

Ciudad Autónoma de Buenos Aires

Congreso; 11th World Congress of Chemical Engineering; 2023

Asociación Argentina de Ingenieros Químicos (AAIQ)

This work aims to develop and validate a comprehensive ComputationalFluid Dynamics (CFD) model for the solar fast pyro-gasification of a singlepellet that can predict the influence of the pellet height on product yieldsand gas composition. A 2D axis-symmetric unsteady model was developedcomprising a competitive, multi-component kinetic mechanism for primarypyrolysis, homogeneous gas-phase reactions, char gasification and tar thermaldegradation. The kinetic parameters for tar decomposition were obtained fromReactive Molecular Dynamics (RMD) simulations. The simulation results were comparedto experimental data previously published by the authors, at a heating rate of50°C/s, for three final temperatures (800, 1600 and 2000°C) and three pelletheights (5, 10 and 15 mm). The comparison of tar and gas yields showed a goodagreement with the reported data. The CFD results showed that crackingsecondary reactions became more significant as the pellet size increased,yielding more gas due to an increase in the intra-particle gas residence time.Similarly, the pellet size influenced the gas product distribution, improvingthe syngas quality as the pellet size increased. Additionally, CFD results showedthat pyrolysis took place in the thermally thick regime, with a thermal frontthat moved from the pellet irradiated surface to the pellet bottom.