A pharmaceutical product is crystallized as well as washed with absolute ethanol. A 100 kg batch of product containing 10% ethanol by weight is to be dehydrated to 0.1% ethanol by weight by passing 0.2 m3/min of 50°C nitrogen through the dryer. Approximate the rate mol/min that ethanol is removed from the crystals, presuming that ethanol exerts the same vapor pressure as if it were pure liquid. Based on this assumption estimate the residence time for the crystals in the dryer. The dryer operates at 0.1 MPa as well as the vapor pressure of the pharmaceutical is negligible.