Coal–biomass mixing characteristics in a bubbling fluidized bed of Geldart A particles

Abstract

In an effort to assess fluidization of coal–biomass mixtures, experiments and numerical simulations were used to better understand the dynamics in terms of mixing and bed characteristics. The computational platform MFiX was employed to simulate the particle–particle interactions of coal–biomass mixtures and compare the predictions with experimental data. The mixtures included sub-bituminous coal and hybrid poplar wood, which both are classified as Geldart A particles. Three mass ratio mixtures of 90:10, 80:20, and 70:30 coal:poplar wood were studied, and pressure drop and bed height for various gas inlet velocities were analyzed and compared to the experiments, which were in good agreement. It was found that the bed with 10% poplar wood showed characteristics consistent with a bed of coal and the bed with only 30% poplar wood was similar to a bed of poplar wood. A quantitative analysis of the mixing index confirmed that as the poplar wood mass ratio increased, the quality of mixing improved, with an average mixing index of 62%. Therefore, reasonable amounts of biomass can be added with coal without adverse effects of segregation or elutriation.