A pharmaceutical product is crystallized and washed with absolute ethanol. A 100 kg batch of product containing 10% ethanol by weight is to be dried to 0.1% ethanol by passing 2 m3/min of nitrogen at 35 oC through the dryer. The dryer is operated at 35 oC and 0.1 MPa. Neither N2 nor the pharmaceutical are soluble in liquid ethanol (in other words, liquid ethanol behaves as if it were a pure component); the vapor pressure of the pharmaceutical is negligible. Estimate the rate (mols/min) that ethanol is removed from the crystals and the residence time of the crystals in the dryer:
a) with no assumptions about vapor-phase ideality
b) assuming that the ethanol component follows Raoult’s Law