CFD studies on biomass gasification in a pilot-scale dual fluidized-bed system

A comprehensive CFD (Computational Fluid Dynamics) model using the MP-PIC (Multiphase Particle-In-Cell) method was developed to simulate a pilot-scale (6 tons/day, 1 MW th) dual fluidized-bed biomass gasification system. In this model the particulate phase was described with the blended acceleration model. The momentum, mass, and energy transport equations were integrated with the kinetics of heterogeneous biomass and char reactions and homogeneous gas-phase reactions to predict the particle circulation, producer gas composition, and reactor temperature. The simulation results were compared with experimental data from the pilot-scale gasification system to validate the model at different operating conditions. Parametric studies were conducted to investigate the impact of gasifier temperature, steam to biomass ratio (S/B), and air supply to the combustor on the producer gas composition. The studies showed that increasing gasifier temperature and steam to biomass ratio (S/B) promoted syngas (CO + H2) production and increased hydrogen content in producer gas. The effect of air supply was minor, because for the dual fluidized-bed system air was not directly involved in biomass gasification.