Numerical study of fluid dynamics and heat transfer property of dual fluidized bed gasifier

Abstract In this work, the Eulerian-Lagrangian multiphase particle-in-cell approach is adopted to track the reactive gas-solid motion in the biomass gasification of dual fluidized bed gasifier. Firstly, the mole fraction of dry gaseous products obtained at the gasifier outlet is evaluated and compared with the experimental measurement to prove the accuracy and adaptability of numerical model. Then, the gasification properties of biomass together with the influence of operating parameters in the full-loop system are studied. The results demonstrate that the gas-solid flow with a large particle Reynolds number and vertical flux is relatively fast in the combustor. The combustible gaseous species generated in the biomass gasification mainly locate in the upper part of bubbling fluidized gasifier. Particle temperature is the largest in the standpipe of the full-loop apparatus. Vigorous heat exchange between gas and solid phase occurs in the combustor. Moreover, the heat transfer coefficient of solid phase in the combustor is apparently higher than that in the gasifier. Increasing the steam/biomass ratio and biomass flow rate enlarges the heat transfer coefficient of particles in the bubbling fluidized gasifier but slightly impacts that in the combustor. The results obtained provide meaningful insights for further study of the complex dual fluidized reactor.