THE MOVEMENT OF SOLIDS THROUGH FLIGHTED ROTATING DRUMS .2. SOLIDS GASINTERACTION AND MODEL VALIDATION

A residence time model for a rotating drum with lifting flights which includes axial displacement of airborne particles due to the drag of t he gas stream has been developed in Part I of this study (Sherritt et al., 1993). Because the particles fall in curtains, the equations for single particle drag overestimated the effect of the gas stream on the displacement of the falling particles. In this paper, large scale win d tunnel experiments, which involved pouring a curtain of particles in to a gas stream, indicated that the shielding effect of the curtain co uld be represented by a lower-than-average gas velocity within the cur tain. The magnitude of the curtain shielding effect is related to the flight discharge rate, the fall distance and the flight length. Incorp orating the results of the experiments into the residence time model p rovides a significant improvement on the effect of the gas velocity, a nd hence the best model available, especially for industrial-scale equ ipment.