Question

(30 points) A packed tower uses an organic amine to absorb carbon dioxide. The entering gas contains 1.26 mol % CO2 and is to leave with only 0.04 mol % CO2. The amine enters pure, without CO2. If the amine leaving is in equilibrium with the entering gas (which it doesnt), it would contain 0.80 mol % CO2. The gas flow is 2.3 molls, the liquid flow is 4.8 mol/s, the tower's diameter is 40 cm and Kya is 5x10 mol/cm s 1. a. What is the concentration of CO2 in the effluent liquid if the column is operated at minimum liquid flow rate, Lmin? b. Calculate Lmin c. Find the number of transfer unit and height of the column.

Answer 1

M.B. Gs (y_1 - y_2) = Ls_min (x_1 - x_2) 2.27 (0.0127 - 4 times 10^-4) = L_min (0.008 - 0) L_min = 3.46 mol/s Again At = 4.8 mol/s Gs (y_1 - y_2) = Ls (x_1 - x_2) 2.27 (0.0127 - 4 times 10^-4) = 4.8 (x_1 - 0) x_1 = 5.816 times 10^-3 Co_2 in effluent stream = 5.816 times 10^-3/5.816 times 10^-3 + 1 = 5.7823 times 10^-3 NTU = integral^y_1_y_2 dy/y - y^= ln y_2/y_2 = ln 0.0127/0.0004 = 3.45 HTU = Gs/Kya = 2.27 (mol/s)/5 times 10^-5 (mol/an^3 - 5) times pi/4 times infinity (40)^2 cm^2 Height = NTU times HTU = 3.45 times 0.3614 = 1.24 M