Question

Find the time taken to dry 50% to 40% of moisture (dry basis) if critical moisture content is 30%. If the weight of the wet solid is 5 kg and the product of area and the constant rate is 0.5 kg/min.

(a) 20 sec

(b) 40 sec

(c) 60 sec

(d) 80 sec

I have been asked this question in exam.

My question is from Time period Calculation in Batch Drying in section Drying of Mass Transfer

Answer 1

Correct option is (c) 60 sec

For explanation I would say: Time for drying = ( wet solid weight * change in moisture )/ Area * constant rate

                                                   = (5 * 0.1/0.5) min = 1 min = 60 sec.