Coupling coarse-grained DEM-CFD and intraparticle model for biomass fast pyrolysis simulation and experiment validation

The understanding of complex fluidization hydrodynamics and chemical reactions in biomass fast pyrolysis fluidized bed reactors is lacking and requires further investigation. It is urgent to develop accurate mathematical models capable of describing the complex multiphase reaction system of biomass pyrolysis. A comprehensive multiscale model based on coarse-grained discrete element method (DEM)-computational fluid dynamics (CFD) was developed in open-source MFiX code. It incorporates detailed biomass pyrolysis kinetics and an intraparticle model. To validate the model, measurements were conducted in a fluidized bed pyrolyzer, including quantifying the segmental pressure drop along the height of the bed and determining the yields and compositions of gas, liquid, and solid products. The particle mixing and segregation, axial distribution and residence time, Lacey index, and pyrolysis products were investigated. The study provides experimental and theoretical foundations for designing multiphase fluidized bed reactors and advancing biomass thermochemical conversion.