The effects of gas velocity, solid circulation rate, the secondary air injection ratio, and secondary injection type on the radial
gas-mixing coefficient Dr. in a circulating fluidized bed CFB. 0.1 m i.d., 5.3 m high. have been determined. It increases with
increasing solid circulating rate and the secondary air ratioSAR., but decreases with increasing gas velocity. Based on the present and
previous studies, Dr increases with increasing column diameter. The effect of secondary air injection type on the radial gas-mixing
coefficient is more pronounced with the tangential than with the radial air injection. The radial gas-mixing coefficient in terms of Peclet
number has been correlated based on the isotropic turbulence theory. q2000 Elsevier Science S.A. All rights reserved.