A wastewater stream at 35,000 kmol/h containing benzene at a mole fraction of 0.001 is to be strippied with air in a column operating at 2 bar and 25°C. The outlet water must contain no more than 0.00004 mole fraction of benzene.

The equilibrium between water and air for benzene at 2 bar and 25°C is y = 150x, where y is the mole fraction of benzene in air and x is the mole fraction of benzene in water. The air used is maintained in a closed loop. Benzene is recovered by condensation from the air stream; therefore, the air entering the stripper contains 0.005 mole fraction of benzene.

1. As part of the design evaluation for this process, it is necessary to determine whether it is feasible to use an existing tray tower for this process. If the tower contains 9 equilibrium stages, and an air rate of 325 kmol/h is the limit set by 80% of flooding, can the tower be used?

2. You observe that there is some flexibility in the operating conditions of the tower in Part (a). Suggest one set of conditions under which the existing tower could be used.