Hydrodynamic characteristics of pyrolyzing biomass particles in a multi-chamber fluidized bed

Variation of particle diameter during biomass pyrolysis is an important consideration for hydrodynamic char-acteristic of reactor. A hydrodynamic model considering particle shrinkage for multi-chamber fluidized bed is developed, via computational fluid dynamics coupled with discrete element method (CFD-DEM). By comparison with experimental data measured by PIV, it is found that the model can give a better representation of gas-solid fluidization in multi-chamber fluidized bed. Particle swarm-scale analysis is conducted focusing on the spatial and temporal properties of gas-solid hydrodynamics. Results show that pyrolysis of poplar sawdust with average diameter of 0.75 mm can be achieved in 30 s at 550 degrees C. Drying and dehydration, rapid pyrolysis, slow carbonization take 1.5 s, 17.5 s and 11 s respectively. Drying and dehydration occur mainly in the first chamber, and the third chamber is the main region for slow carbonization. Superficial gas velocity has quite limited effect on semicoke distribution.

Automated summary

A hydrodynamic model considering particle shrinkage for multi-chamber fluidized bed is developed in this study, using computational fluid dynamics coupled with discrete element method. The model is found to provide a better representation of gas-solid fluidization in multi-chamber fluidized bed compared to experimental data. Particle swarm-scale analysis reveals that pyrolysis of poplar sawdust with an average diameter of 0.75 mm can be achieved in 30 s at 550°C. Drying and dehydration, rapid pyrolysis, and slow carbonization take 1.5 s, 17.5 s, and 11 s, respectively, with drying and dehydration occurring mainly in the first chamber and slow carbonization in the third chamber. The superficial gas velocity has limited effect on semicoke distribution.