The effect of molecular diffusion on mixing in fluidized beds

Abstract

Gas mixing in a 6·5 in fluidized bed of sand was studied using frequency response techniques with He and CO 2 tracers. Samples taken in the bed, where the probe saw mainly dense phase gas, had a lower amplitude ratio than samples at the top of the bed where the bubble contribution predominated. The gas interchange coefficients showed a small dependence on the molecular diffusivity at about twice the minimum fluidization velocity but no effect of diffusivity at high velocities.