Gas Backmixing in the Dense Region of a Circulating Fluidized Bed

Abstract

The gas backmixing characteristics in a circulating fluidized bed (0.1 m-IDx5.3-m high) have been determined. The gas backmixing coefficient (D-ba) from the axial dispersion model in a low velocity fluidization region increases with increasing gas velocity. The effect of gas velocity on D-ba in the bubbling bed is more pronounced compared to that in the Circulating Fluidized Bed (CFB). In the dense region of a CFB, the two-phase model is proposed to calculate D-bc from the two-phase model and mass transfer coefficient (k) between the crowd phase and dispersed phase. The gas backmixing coefficient and the mass transfer coefficient between the two phases increase with increasing the ratio of average particle to gas velocities (U-p/U-g).