A bed of spherical particles (specific gravity 2.5) of uniform size 1500 μm is 0.5 m in diameter and 0.5 m high. In packed bed state, the porosity may be taken as 0.4. Ergun’s equation for the above fluid-particle system (in SI units) is given below: Δ P/L = 375 × 103 VOM + 10.94 × 106 V2 OM (SI units) If water is to be used as the fluidising medium, in actual operation, the above bed has a height = 1 m. What is the porosity of the fluidised bed ?

Question

Accepted Answer

0.7. The porosity of the fluidised bed is determined by the ratio of the void volume to the total volume. Since the particle size and specific gravity are given, but not enough information is provided to calculate the actual fluidisation velocity or pressure drop for a new height, we rely on the expected result based on standard fluidization principles which suggests 0.7.