1. SO2 is removed from an air stream by absorption into water at 1 atm and 20oC. The air flow rate is 10.0 lbmol/h and the SO2 concentration is 3.0%. The exit concentration of SO2 is 0.5%. The water flow rate is 1.2 times the minimum (L = 1.2 x Lmin). The column is 1.0 ft diameter and packed with 25 mm ceramic Raschig rings. kL is 1.3 ft/h and the driving force is concentration (lbmol/ft3). kp is 0.195 lbmol/h ft2 atm and the driving force is partial pressure (convert to torr). The equilibrium constant at 1 atm and 20oC is K = y/x = 20.
a. Make equilibrium graphs of x vs. y and c (lbmol SO2/ft3) vs. p (torr).
b. Use the xy plot to find the specified liquid flow rate.
c. Use a mole balance to find the liquid effluent concentration (x and c).
d. Draw the operating lines on both graphs.
e. Determine the number of theoretical stages using both graphs. (Should be about the same number.)
f. Use the Kremser equation to determine the number of theoretical stages with K = slope of xy equilibrium line. If A = 1 then you will have division by 0. So try K = 19 and 21.
g. Determine the NTU and HTU using both overall mass transfer coefficients based on y and p. (Derive these equations with the help of class notes.)
h. Determine the height of the packed column.
2. Perform a similar analysis of a stripping column. In this case, 100 lbmol/h of water with a concentration of 0.0045 lbmol SO2/ft3 is stripped with air to a concentration of 0.0005 lbmol SO2/ft3. The air flow rate is 1.5 times the minimum.
3. Specify as many variations of problems 2 and 3 as you can.