Numerical modeling of an auger reactor for biomass pyrolysis using a coupled DEM-CFD model

Biomass pyrolysis is a process of significant importance for the production of bio-gas, bio-oil, and biochar. The operating parameters strongly affect the composition and quality of the resulting products. Numerical models enable the analysis of the influence of operating parameters on the process. This study focuses on the numerical modeling of biomass pyrolysis in an auger reactor. A coupled Discrete Element Method-Computational Fluid Dynamics (DEM-CFD) approach was employed, where the gas phase was simulated using ANSYS Fluent software, and the biomass bed was modeled with ANSYS Rocky. The two models were integrated through two-way coupling method. A devolatilization model based on three kinetic reactions was implemented in the DEM framework, with kinetic parameters determined from Thermogravimetric Analysis (TGA) measurements of biomass samples. The developed model enables the simulation of the temperature field within the bed and the analysis of heat transfer conditions influence to biomass devolatilization. Validation was performed against experimental data obtained in a laboratory-scale pyrolysis setup for different residence times and reactor filling levels. The simulation results showed good agreement with the measurements, while also highlighting the need for further model refinement and development. The proposed method provides a useful tool for reactor design and scale-up, enabling prediction and control of product quality in terms of non-uniformity.