EFFECT OF SECONDARY AIR INJECTION ON AXIAL SOLID HOLDUP DISTRIBUTION IN A CIRCULATING FLUIDIZED-BED

The effects of secondary air ratio (0-50 %), height of injection port (1.5-2.5 m) and injection types (radial and tangential) on the axial s olid holdup distribution have been determined in a circulating fulidiz ed bed (0.1 m I.D. x 5.3 m high). As the secondary air ratio is increa sed, solid holdup increases below the secondary air port, whereas it d ecreases slightly above the secondary air injection port. The dense be d height increases with increasing height of the secondary air injecti on port. Different types of secondary air injection system do not prod uce any significant difference in the overall axial solid holdup distr ibution. However, solid holdup just above the injection port in a tang ential secondary air injection system exhibits somewhat higher values than those of radial secondary air injection system. The effect of sec ondary air injection on the axial solid holdup distribution in a circu lating fluidized bed can be predicted by a modified freeboard-entrainm ent model with decay constants determined from the proposed correlatio n.