CFD investigation of the complex multiphase flow of biomass gasification in industrial-scale dual fluidized bed reactor

Abstract

In this work, the process of biomass steam-gasification via a dual fluidized bed with a thermal input of 8MWth is numerically modeled by applying the multiphase particle-in-cell method. This model is successfully validated with the experimental data. Based on the simulation, the results can be epitomized as: distinct fluidization regimes in gasifier and combustor reactors give rise to different flow pattern and dispersion coefficients of solid phase in both reactors. Large particle heat transfer coefficients mainly appear in the upper regions of both reactors due to violent reactions. In this industrial-scale apparatus, the time-averaged heat transfer coefficient of sand in the combustor is larger than that of gasifier sand for about 40 W/(m2·K). Relationships between key variables such as volume fraction, heat transfer coefficient, slip velocity, Reynolds number and temperature of solid phase are discussed. Particles with small volume fraction tend to possess large heat transfer coefficient and slip velocity. The results explored at the particle-level might be useful in the industrial operating regarding the biomass steam-gasification processes.