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

JOSÉ M. SORIA; GERMÁN D. MAZZA

Buenos Aires

Congreso; 11th World Congress of Chemical Engineering; 2023

Asociación Argentina de Ingenieros Químicos

This work aims to develop and validate a comprehensive Computational Fluid Dynamics (CFD) model for the solar fast pyro-gasification of a single pellet that can predict the influence of the pellet height on product yields and gas composition. A 2D axis-symmetric unsteady model was developed comprising a competitive, multi-component kinetic mechanism for primary pyrolysis, homogeneous gas-phase reactions, char gasification and tar thermal degradation. The kinetic parameters for tar decomposition were obtained from Reactive Molecular Dynamics (RMD) simulations. The simulation results were compared to experimental data previously published by the authors, at a heating rate of 50°C/s, for three final temperatures (800, 1600 and 2000°C) and three pellet heights (5, 10 and 15 mm). The comparison of tar and gas yields showed a good agreement with the reported data. The CFD results showed that cracking secondary 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, improving the syngas quality as the pellet size increased. Additionally, CFD results showed that pyrolysis took place in the thermally thick regime, with a thermal front that moved from the pellet irradiated surface to the pellet bottom.