Question

Cereal is being dried in a dryer by air flowing countercurrent to the cereal (sec flowchart below). To minimize breakage of the cereal flakes, a portion of the exit air from the dryer is recycled. The moisture content (mass fraction) of the various streams is as follows: Fresh air = 0.0082, wet cereal = 0.200, dried cereal = 0.050, air entering dryer = 0.042, and exit air = 0.181. Take as a basis 1000 kg/h of wet cereal entering the dryer and assume steady state. What is the flow rate (F in kg/h) of the fresh air, and that of the recycle stream (R in kg/h)? Write enough independent equations (neither more, nor less) that, if solved, they will provide F and R.

Answer 1

Here, By given basis i found how much moisture remove from wet cereal and then by doing mass balance over dryer i found flow rate of air enteting and leaving dryer. Now we know B flow rate so, we are mass balance of moisture and total balance for fresh air(A), Recycle air(R) and air entering dryer, from that i fount flow rate of fresh air and recycle stream.