Acetone, a solvent used for cleaning of silicon wafers, is highly volatile with a vapor pressure of 185 mm Hg at 20°C and 148 mm Hg at 15°C. An air handling system at 20°C captures the acetone vapors from the cleaning equipment, which must then be scrubbed out of the air. In the present process, 224 standard m³/h of an air stream containing 9.0 mole% acetone vapor is sent to a packed-bed adsorption tower. The tower is packed with Awesomepack^TMpacking that has a capacity factor (C_f) of 100. The tower is maintained at 15°C and 1.0 atm total system pressure. The equilibrium distribution data for the air-acetone-water system at 1.0 atm total system pressure and 15°C is given the following table. Pure water enters the top of the tower. It is desired to remove 89.8% of the acetone from the gas feed. It is also desired to have no more than 2.0 mole% of acetone dissolved in the liquid water exiting the tower, to avoid overloading the dissolved organics treatment capacity of wastewater treatment system. Finally, it is desired to have an inlet superficial molar gas velocity (G₁) of 20.0 kgmole/m²· h in the tower, which is far below the gas flooding velocity (G_f) in consistent units. At these flow conditions, the volumetric mass-transfer coefficients are k'_Gα = 20 kgmole/m³h · atm · and k'_Lα =50 h^-1for gas and liquid films around the packing. Although the solvent has some dissolved acetone in it, the liquid properties can be taken as ρ_L= 1000 kg/m³and M_w,L = 18 kg/kgmole, and µ_L= 1.0 cP. 

The molecular weight of acetone is 58 g/gmole. 

a. What is the total molar flow rate of liquid exiting the tower in units of kgmole/h at the conditions of operation? 

b. Plot out the equilibrium line and operating line in mole fraction (y_A vs. x_A) coordinates. What is the minimum possible solvent flow rate into the tower from the standpoint of mass-transfer, in units of kgmole/h? 

c. What is the height of packing required at the desired conditions of operation? 

d. What is the gas flooding velocity of the Awesomepackt^TM packing at the conditions of operation? Another engineer claims that Awesome pack packing is not really that awesome and suggests that 0.5-inch ceramic Intalox saddles might be better from a hydrodynamic point of view. What is the new gas flooding velocity? Is the 0.5-inch ceramic Intalox saddle packing better? 

e. Is it possible that any acetone vapor in the air could condense at the conditions of the tower? Back up this answer with a calculation. 

Equilibrium distribution data for acetone-water at 15°C 

(A = acetone): 

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PA (mm Hg) 17.9 0.0205 43.9 0.0556 61.3 3.15 6.12 11.5 0.0033 0.0064 0.013 0.0942 XA