In a wetted-wall tower where ammonia, NH3, is stripped from an ammonia-water solution into an air stream, the overall gas coefficient, KL is 3:12 ×10-9 kg mol/m2 s Pa. At a plane in the tower, the bulk concentration of the falling aqueous stream is 4 kg mol/m3 of solution and the partial pressure of ammonia in the rising gas stream is 3:04 × 103Pa. For dilute solutions of ammonia in water the equilibrium partial pressure may be evaluated by Henry's law:
PAi = 1360 Pa / (kg mol/m3) CAi
If the gas phase comprises 75% of the total resistance to mass transfer, calculate
a. the individual gas-film coefficient, kG;
b. the individual liquid-film coefficient, kL;
c. the overall liquid-film coefficient, KL;
d. the interfacial concentrations, pAi and cAi.