Residence-time distribution of fine particles in a powder-particle fluidized bed

The residence-time distribution of fine particles in the powder-particle fluidized bed proposed by the authors was measured by the residual concentration-curve method, and the effects on the residence time of the feed rate of the fine particles, the gas velocity, the diameters of the fine and coarse particles, and the fluidized bed height were investigated. The mean residence time was 150--500 times longer than the theoretical value based on the particles passing through the bed in train with the gas, with no adhesion or aggregation, which suggests that the fine particles strongly adhere to the coarse particles in the bed. The mean residence time increased with decreasing size of the fine particles, velocity of the gas, and increasing fluidized-bed height.