Simulation and Analysis of Coal and Biomass Pellet in Fluidized Bed with Hot Air Injection

In this paper, flow and heat transfer of coal and biomass pellet were studied with discrete element method-computational fluid dynamics (DEM-CFD). Three-dimensional numerical simulation was applied and the modified DEM-CFD coupled with heating transfer model matches heating process well in fluidized bed. Properties of binary particles (coal and biomass pellet) in heating process were revealed by particle temperature, mixing index and heat transfer. Cylindrical biomass pellets exist in broader regions, and the desired fluidization state is obtained. The temperature of biomass pellet is 10-20 K lower than that of coal particles. Moreover, biomass addition can suppress temperature rise and aggravates the temperature contrast between biomass pellet and coal. In addition, cylindrical biomass pellets reduce the mixing index of binary particles. Vertical mixing index and horizontal mixing index decrease from 0.85 to 0.65 and 0.85 to 0.75, respectively. Gas-solid heat transfer and gas velocity in Z direction are obviously influenced by inlet air.