Wet sugar that contains one-fifth water by mass is conveyed through an evaporator in which 85.0% of

Question:

Wet sugar that contains one-fifth water by mass is conveyed through an evaporator in which 85.0% of the entering water is vaporized.

(a) Taking a basis of 100 kg feed, calculate (i) XW, the mass fraction of water in the wet sugar leaving the evaporator, and (ii) the ratio (kg H2O vaporized/kg wet sugar leaving the evaporator).

(b) If 1000 tons/day of wet sugar is fed to the evaporator, how much additional water must be removed from the outlet sugar to dry it completely, and what annual revenue can be expected if dry sugar sells for $0.15/lbm?

(c) The evaporator is built to achieve the production rate of part (b), installed, and started up, and the water content of the partially dried sugar is measured on successive days of operation. The results follow.

In subsequent runs, the evaporator is to be shut down for maintenance if xw falls more than three standard deviations from the mean of this series of runs. Calculate the endpoints of this range.

(d) Considering the results of parts (a) and (c) together, what can you conclude about the recently installed evaporator?