(624e) Hydrodynamic Behaviors of Sand and Plastic Particles in a Large-Scale Triple Bed Combined Circulating Fluidized Bed

Hydrodynamic behaviors of binary mixture of silica sand and nylonshot (coal char substitute) were investigated in a triple-bed circulating fluidized bed (TBCFB). The TBCFB consisted of a downer (Φ 0.1 m × 6.5 m), a bubbling fluidized bed (0.75 m × 0.27 m × 1.9 m), a riser (Φ 0.1 m × 16.6 m) and a gas-sealing bed (GSB, Φ 0.158 m × 5 m). The experiments were carried out at ambient temperature and atmospheric pressure by using air. The initial fraction of the nylonshot in the solid mixture (X_nylon,i) was 15.4% and 30% on mass and volume bases, respectively, or otherwise, 30.7% and 50%. The maximum obtained solids mass flux (G_s) at X_nylon,i of 15.4 and 30.7wt% were 394 and 349 kg/m² s, respectively, when the gas velocity in the riser (U_gr) was 10 m/s. Apparent solids holdups of silica sand and nylonshot were calculated separately from the static pressure gradient across the riser and the downer. The results showed that it is possible to circulate char in the gasifier, which plays a significant role in decomposition of tar from pyrolysis as the primary step of gasification. A novel developed pressure balance model successfully predicted Gs of the binary mixtures in TBCFB well.