The influence of particle size and density on the radial gas mixing in thedilute region of the circulating fluidized bed

A cold model of a CFB, having a 0.120m ID, 5.75m high riser, was operated a t a superficial gas velocity of 6m/s and at average solids mass fluxes vary ing in the range between 16 and 55kg/sm(2). A stream of carbon dioxide was injected continuously at a fixed position along the riser axis and used as tracer gas. Three solids, belonging to groups A and B of Geldart's classifi cation, were selected in order to investigate separately, the effect of par ticle size and density on the radial mixing of the gas phase. The intensity of radial gas dispersion reduced when larger or heavier particles were use d. The differences in the values of radial dispersion coefficient and Pecle t number were explained, taking into account the role of the particle size with respect to the scale of gas turbulence.