Example 4 Hot soap is chilled on a roller and scraped continuously from the roller onto a moving conveyor belt which carries the soap into a dryer (see below). The entering soap contains 25% water by weight. It is desired to reduce the water content to 15% by weight and to produce 1200 lb/h of nearly dry soap chips. The entering air contains 0.3 mole % water vapour. The dryer manufacturer suggests that the dryer operates efficiently when the nearly dry air/wet soap flow ratio is 3.0. Calculate the unknown flowrates and compositions. Air is 21% oxygen and 79% nitrogen (mole basis) and has a molecular weight of 29.0 g/mol. moist air hot, nearly dry air Soap Dryer wet soap chips dried soap chips