In the final stage of the manufacturing process for a solid organic product, the product is cleaned with liquid toluene and then dried in a process whose flowchart is shown on the next page¹⁰. The wet product enters the dryer at a rate of 300lb_m/h containing 0.200lb_m toluene/lb_m dry solids. A stream of nitrogen at 200?F, 1.2 atm. and containing a small amount of toluene vapor also enters the dryer. (A higher temperature would cause the product to soften and degrade.) Heat is transferred in the dryer from the gas to the wet solids, causing most of the toluene to evaporate. The final product contains 0.020lb_m toluene/lbm dry solids. Gas leaves the dryer at 150?F and 1.2 atm with a relative saturation of 70% and passes through a water-cooled condenser. Gas and liquid streams leave the condenser in equilibrium at 90?F and 1 atm. The gas is reheated to 200?F and reenters the dryer.

(a) Calculate the compositions (component mole fractions) of the gas streams entering and leaving the dryer, the circulation rate of dry nitrogen (lb_m/h), and the volumetric flow rate of gas entering the dryer (ft³/h).

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Cooling water Product + CyH₂(1) N₂. C₂Hg(v) 150°F, 1.2 atm 70% Relative saturation CONDENSER DRYER Product N₂. CyHg(v) 90°F, 1 atm saturated BLOWER C₂H₂(1) 90°F, 1 atm N₂, C₂Hg(v) 200°F. 1.2 atm +++ Stearn REHEATER Condensate