It takes 6 hours to dry a wet solid from 50% moisture content to the critical moisture content of 15%. How much longer it will take to dry the solid to 10% moisture content, under the same drying conditions? (The equilibrium moisture content of the solid is 5%) ?
Correct answer: C. 71 min
- A. 15 min
- B. 51 min
- C. 71 min
- D. 94 min
Explanation
During the falling-rate period, drying time is proportional to (Xc − Xe) ln[(Xc − Xe)/(X − Xe)]. Using Xc = 0.15, Xe = 0.05, and the constant-rate time of 6 hours gives about 1.19 hours, or 71 minutes, to reach X = 0.10.
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