A gas stream containing solute A at mole fraction of 0.02 is to be cleaned by absorbing 90% of the solute into a liquid stream in a countercurrent packed bed gas-liquid absorber. The gas enters from the bottom and pure aqueous solvent enters at the top of the packed tower as shown in Figure. The liquid exits the column containing the solute at a mole fraction of 0.008.
The inlet gas flow to the column is 60 kg-mol/hr. It is known that the liquid-side mass transfer coefficient is kx= 5x10-3 kg-mol/m2 s and that the gas-side mass transfer coefficient is ky=1x10-2 kg-mol/m2s. The absorption equilibrium curve, given in Figure.
a) Derive the operating line for this system and determine the liquid molar flow rate.
b) Determine the individual (gas and liquid) transfer unit heights as well as the overall gas transfer unit height, HOG, in terms of av*.
c) Determine the height of the column, z, in terms of aV*.
d) Government regulations limit the size of an absorption tower to be between 5 and 15 meters. Determine which of the three packing materials will meet this regulation.
Packing material aV* (m2/m) Berl saddles 1.25 Rasching rings 5.5 Sultzer Wire mesh 25