An engineer at a pulp mill is considering the feasibility of removing chlorine gas (C1₂, solute A) from an air steam using water, which will be reused for a pulp bleaching operation. The process will be carried out in a counter current flow gas absorption tower filled with inert packing, where liquid water containing no dissolved C1₂is pumped into the top of the tower (x_A2, = 0), and air containing 20% by volume C1₂(y_A1= 0.20) at 1.0 atm is fed into the bottom of the tower. Gas€“liquid contact is promoted by the inert packing surface as the gas and liquid flow around the packing. As the gas moves to the top of the tower, the C1₂composition decreases, and as liquid moves down the tower, the dissolved C1₂concentration increases. At the gas and liquid flow rates of operation, the liquid leaving the bottom of the tower has a composition of 0.05 mole% (x_A1= 0.00050), and the gas exiting the top of the tower has been lower to 5% by volume (y_A2, = 0.050). At the flow rates of operation, the gas film mass transfer coefficient based on a mole fraction driving force is 5.0 lbmole/ft²· hr, and the liquid film mass-transfer coefficient based on a mole fraction driving force (k_x) is 20 lbmole/ft²· hr. Equilibrium data for the C1₂-water-air system at 20°C and 1.0 atm are provided in the table below. 

a. Draw a diagram of what the packed tower might look like, labeling liquid flow with L, gas flow with G, and terminal steam mole fraction compositions (x_A1, y_A1) and (x_A2, y_A2,) at the bottom and top of the tower. 

b. Plot out the equilibrium line in mole fraction coordinates. Then plot out the operating points (x_A1, y_A1) and (x_A2, y_A2,) for the bottom and the top of the tower respectively. 

c. Determine the local overall mass-transfer coefficients K_y, at the top and bottom of the tower? Why are the values for K_y different?

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6.58E-03 УА 1.11E-04 XA 1.97E-01 1.32E-02 3.95E-02 6.58E-02 1.32E-01 4.49E-04 1.46E-04 3.07E-04 2.37E-04 5.75E-04