Numerical study of the biomass gasification process in an industrial-scale dual fluidized bed gasifier with 8MWth input

Abstract

In the present numerical study, biomass steam gasification in industrial-scale dual fluidized bed gasifier with 8MWth input is numerically simulated via the multiphase particle-in-cell (MP-PIC) method, where the gas turbulence is controlled via large eddy simulation (LES), and the solid phase is tracked under the Lagrangian framework. This model has been well validated with experimental measurement. The gas and solid fluxes, gas distribution, gas and solid thermal properties together with the effect of solid inventory and steam-to-biomass ratio on the system performance are discussed in detail. Results show that the asymmetrical structure of the gasifier leads to a nonuniform distribution of gas phase. Product gases released in the gasifier have similar distributions. The vertical gas flux is much higher than those along radial directions, due to the fluidization characteristics. A decrease of the vertical gas temperature in the combustor and an increase of that in the gasifier are observed due to the improvement of solid circulation rate and heat transfer raised by increasing the solid inventory. Enlarging the solid inventory can increase the particle mean temperature at gasifier outlet while decreases that at gasifier inlet, and decrease the sand temperature and heat transfer coefficient along the combustor height. Moreover, the impact of inventory height and S/B on gas thermal properties in both reactors is discussed.