Numerical investigation of the reactive gas-solid characteristics in biomass fast pyrolysis of conical spouted reactor equipped with draft tube

Biomass fast pyrolysis is a promising technology to produce available char and high-value gas due to its green and sustainable ability. In the current work, the biomass fast pyrolysis in draft tube spouted bed has been numerically investigated via the multiphase particle-in-cell model. In this model, gas turbulence is calculated via large eddy simulation and particles are individually tracked in the Lagrangian manner. This model is successfully validated against experimental data. The particle-scale information of sand and biomass feedstock has been discussed, and the influence of draft tube configuration on the pyrolysis performance has been studied. The results show that the equipment of draft tube prevents gas leakage from spout to annulus, leading to large axial gas flux in the spout. Biomass particles in the spout and freeboard have high temperature and heat-transfer coefficient. Some biomass particles move along the outer wall of draft tube, indicating that the equipment of draft tube can avoid back-mixing by preventing direct contact of particles in the spout and annulus. Increasing the height of draft tube results in larger axial gas flux and higher sand heat-transfer coefficient, while decreases biomass temperature in the spout. The simulation results can offer valuable insights into comprehending intricate reactive gas-solid characteristics and conducting operation and design optimization of spouting apparatus.

Automated summary

The numerical investigation of biomass fast pyrolysis in a draft tube spouted bed using a multiphase particle-in-cell model has been successfully validated. The influence of draft tube configuration on pyrolysis performance is studied, and the results show that the equipment of draft tube can prevent direct contact of particles and improve gas flux and heat transfer coefficient. The simulation results provide valuable insights for understanding gas-solid characteristics and optimizing the design of spouting apparatus.