Wastewater contaminated with 1,2,2-trichioroethane (C₂H₃C1₃, molecular weight 133.5 g/gmole) will be treated in a counter current packed tower using contaminant-free air as the stripping gas. In the present process, 100 kgmole/h of this liquid feed stream will be treated at 20°C and 1.65 atm total system pressure. For this liquid stream, the inlet concentration of 1,2,2 - trichioroethane is x_A1, = 2.0 x 10^-3, and the desired outlet concentration is x_A1 = 2.0 × 10^-4. In this concentration range, the equilibrium distribution of 1,2,2-trichloroethane vapor in water is described by Henry’s law of the form p_A = H · x^*_A, with H = 41.25 atm at 20°C. The tower is packed with 1.5 inch plastic Pall rings. 

a. From the standpoint of inter phase mass-transfer, what is the minimum molar gas flow rate into the tower? 

b. Now consider the outlet gas flow rate is 12.0 kgmole/h, which is above the minimum gas flow rate needed for mass-transfer. At this flow rate, the composition of the outlet gas is 1.5 mole% 1,2,2-trichloroethane and 98.5 mole% air. What is the smallest possible diameter of the tower, calculated at the superficial gas mass velocity where the tower floods, G_f? Assume the properties of liquid water for the wastewater at 20°C, with liquid density of 1000 kg/m³, and liquid viscosity of 0.0010 kg/m · s.