RADIAL VOIDAGE PROFILES IN FAST FLUIDIZED-BEDS OF DIFFERENT DIAMETERS

A previously developed method for calibrating an optical-fibre probe for voidage measurement in gas-solid systems has been improved. This was applied to study the influence of operating conditions, particle properties and bed diameters on radial voidage profiles in circulating fluidized beds operating in the fast regime. The present experimental results showed that the radial voidage profile depends solely on the value of the cross-section-averaged voidage, irrespective of operating conditions, solids properties and bed diameters, and can be correlated by the expression epsilon = epsilon-BAR(0.191 + phi-2.5 + 3-phi-11, where epsilon and epsilon-BAR represent the local and cross-section-averaged voidage respectively, and phi-denotes the dimensionless radial distance from the centre of the bed.