A fluid bed incinerator, $3 \mathrm{~m}$ in diameter and $0.56 \mathrm{~m}$ high, operates at $850^{\circ} \mathrm{C}$ using a sand bed. The sand density is $2.5 \mathrm{~g} / \mathrm{cm}^{3}$, and the average sand grain has a mass of $0.16 \mathrm{mg}$ and a sphericity of 0.85 . In the stationary (packed) state, the bed porosity is $35 %$. Find(a) The range of air velocities that will fluidize the bed.

(b) The compressor power required, if the bed is operated at 10 times the minimum fluidizing velocity and the compressor efficiency is $70 %$. The compressor takes air in from the atmosphere at $20^{\circ} \mathrm{C}$, and the gases leave the bed at $1 \mathrm{~atm}$.