Question

Cereal is being dried in a vertical drier by air flowing countercurrent to the cereal. To prevent breakage of the cereal flakes, some of the exit air from the drier is recycled back to mix with the the moist fresh air. For each 1000 kg/hr of wet cereal fed to the drier, calculate the input of moist fresh air in kg/hr and recycle rate in kg/hr. The available data on stream compositions is (fractions):

For water: Fresh air: 0.0132

Wet cereal: 0.200

Exit air: 0.263
Dried Cereal: 0.050
Air entering Dryer: 0.066