ASSIGNMENT ON MASS TRANSFER COEFFICIENT DETERMINATION Problem 1: Wetted Wall Column ■ Air-ammonia mixture containing 4% NH3 by volume is being absorbed counter currently with H2SO4 in a wetted wall column of 20 mm diameter and a length of 1 m. The gas enters the column at a rate of 0.25 kmol/hr. The column has a temperature of 25°C and a pressure of 101.325 kN/m2. 85 % of the of the entering NH3 is absorbed. Estimate kG. Ammonia-air H2SO4 Solution y1 = 0.04 (mole fraction of NH3) 0.04 𝑚𝑜𝑙 𝑁𝐻3 𝑌1 = = 0.04167 1 − 0.04 𝑚𝑜𝑙 𝑎𝑖𝑟 𝑚𝑜𝑙 𝑁𝐻3 𝑌2 = 0.04167 0.15 = 0.00625 𝑚𝑜𝑙 𝑎𝑖𝑟 𝑦2 = Rate of air entering = 0.000625 = 0.00621 1.000625 0.25 𝑘𝑚𝑜𝑙 1 ℎ𝑟 𝑘𝑚𝑜𝑙 × × 1 − 0.04 = 6.667 × 10−5 ℎ𝑟 3600 𝑠 𝑠 Solution 𝑅𝑎𝑡𝑒 𝑜𝑓 𝑁𝐻3 𝑎𝑏𝑠𝑜𝑟𝑏𝑒𝑑, 𝐸 = 6.667 × = 2.36 × 10−6 10−5 𝑘𝑚𝑜𝑙 𝑎𝑖𝑟 𝑠 𝑚𝑜𝑙 𝑁𝐻3 0.04167 − 0.00625 𝑚𝑜𝑙 𝑎𝑖𝑟 𝑘𝑚𝑜𝑙 𝑁𝐻3 𝑠 𝑘𝑁 𝑚2 𝑘𝑁 = 101.325 0.00621 = 0.629 2 𝑚 𝑃𝐴1 = 101.325 0.04 = 4.053 𝑃𝐴2 𝑃𝑙𝑚 = 4.053 − 0.629 𝑘𝑁 = 1.838 2 4.053 𝑚 𝑙𝑛 0.629 Solution 𝐸 𝑘𝐺 = 𝐴 ∙ 𝑃𝑙𝑚 20 𝐴 = 𝜋𝐷𝐿 = 𝜋 𝑚 1000 1m = 0.0628 𝑚2 Substituting, 2.36 × 10−6 𝑘𝑚𝑜𝑙 −5 𝑘𝐺 = = 2.04459 × 10 0.0628 ∙ 1.838 𝑠 ∙ 𝑚2 ∙ 𝑘𝑃 ...
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