Question

256 Chapter 6 Absorption and Stripping of Dilute Mixtures 6.26. Stripping of benzene from wastewater in a packed column. Wastewater at 600 gpm, containing 10 ppm (by weight) of benzene, is to be stripped with air in a packed column operating at 25°C and 2 atm to produce water containing 0.005 ppm of benzene. The packing is 2-inch polypropylene Flexirings. The vapor pressure of benzene at 25 C is 95.2 torr. The solubility of benzene in water at 25° C is 0.180 g 100 g. An expert in VOC stripping with air suggests use of 1,000 scfm of air (60°F, 1 atm), At these conditions, for benzene: kLa 0.067 s-1 and kGa = 0.80 s-1 Determine the: (a) minimum air-stripping rate in scfm. (Is it less than the rate suggested by the expert? If not, use 1.4 times your minimum value); (b) stripping factor based on the air rate suggested by the expert; (c) number of transfer units, NoG (d) overall mass-transfer coefficient, Kga, in units of mol/m3-s-kPa and s and which phase controls mass transfer; and (e) volume of packing in m 3.

Answer 1