Height of a packed-tower absorber a packed tower of the type described in Example 23.5-2 is to be used for removing 90% of the cyclohexane from a cyclohexane-air mixture by absorption into a non-volatile light oil. The gas stream enters the bottom of the tower at a volumetric rate of 363ft3/min at 30°C and at 1.05atm pressure it contains 1% cyclohexane by volume. The oil enters the top of the tower at a rate of 20 lb-mol/hr, also at 30°C, and it contains 0.3% cyclohexane on a molar basis. The vapor pressure of cyclohexane at 30°C is 121 mm Hg, and solutions of it in the oil may be considered to follow Raoult’s law.

(a) Construct the operating line for the column.

(b) Construct an equilibrium curve for the range of operation encountered here. Assume the operation to be isothermal and isobaric.

(c) Determine the interfacial conditions at each end of the column.

(d) Determine the required tower height using Eq. 23.5-24 if k0xa = 0.32 moles/hr · ft3, k0ya = 14.2 moles/hr · ft3, and the tower cross section S is 2.00 ft2.

(e) Repeat part (d), using Eq. 23.5-25.