Particle Hold-up and Elutriation Rate in the Freeboard of Fluid Beds.

Based on experimental results from three fluid beds of different cross sections (15 × 15 cm, 8 × 8 cm and 7.1 cm i.d.), the effects of superficial gas velocity, freeboard height, cross sectional area and particle properties on the axial particle hold-up distribution in the freeboard and the elutriation rate from the top of the column were investigated. An entrainment intensity R was proposed for the particles to explain the effect of size distribution and density on the particle hold-up. The particle hold-up was found proportional to R1.87, and increased with increasing freeboard height and cross-sectional area. Empirical equations for both the particle hold-up distribution and for the particle elutriation rate were obtained.