Gas absorption is used in the field of purification by allowing the transfer of pollutants from the gas phase to the liquid phase, and it helps in meeting the regulatory requirements for the release of gases into the environment. Assume that you are a newly employed Chemical Engineer and your supervisor wants to test how well you understand mass transfer concepts through the following question that deals with the separation of component A. A gas stream contains 4.0 mol% A, and its content must be reduced to 0.5 mol% in a packed absorption tower that operates at 101.325 kPa and 293 K. The inlet pure solvent B flow is 68.0 kmol/h and the total inlet gas flow is 57.8 kmol/h. The tower diameter is 747 mm. The gas-liquid equilibrium data is listed in Table 1, and the local film mass-transfer coefficients are as follows: ka = 0.0739 kmol/m3.s.mol fraction; ka = 0.169 kmol/m.s.mol fraction. If the system obeys Henry's law and/or using the design methods for dilute gas mixtures, determine the height of the absorption tower in cm.
Table 1. The gas-liquid equilibrium data at 1 atm
Mole fraction of A in liquid
Partial pressure of A in gas (mm Hg)
20C
30C
0.0 0.0208 0.0268 0.0309 0.0405 0.0503 0.0737 0.0960 0.1370
0.0 9.0 15.0 18.2 24.9 31.7 50.0 69.9 114.0
0.0 19.3 24.4 29.6 40.1 51.0 79.7 110 179