Experimental and numerical study on hydrodynamics analysis of coal and blends with sawdust in a bubbling fluidized bed

A better understanding of hydrodynamics is crucial in designing a fluidized bed boiler (FBB) for gasification and co-combustion of biomass. The current research experiments are conducted in a laboratory-scale circulating fluidized bed (CFB) riser of 100 mm diameter and 3000 mm height, along with a 3D computational analysis. The effect of different bed inventories (1.5 kg coal, 2 kg coal, 2 kg coal + 0.2 kg sawdust, and 2 kg coal + 0.8 kg sawdust), superficial gas velocity (0.5–3U mf ), coal particle size (460 and 550 μm), drag and lift force formulations on fluidized bed height, pressure drop, slip velocity, axial and radial coal, sawdust, and gas volume fraction distribution are depicted in the current research. The mixing behavior of coal and sawdust is analyzed by defining the mixing factor. Four different hydrodynamic stages (static, mixing, transition, and segregation) are observed with an increase in superficial gas velocity. It is observed that an 800 g sawdust blend shows better mixing quality than a 200 g sawdust blend. The fluidized bed height, pressure drop, and near-wall solid volume fraction increase in case of blend inventories compared to solo coal inventories. This study will be helpful in the co-gasification and co-combustion of various biomass with coal.