Problem detail A gaseous mixture containing CO2 and ethanol, with a molar composition of 92%CO2 and 8% ethanol, is evolved from a fermentation process. The ethanol must be recovered by means of a countercurrent absorption process using water as the solvent. The gas mixture will enter the tower at a rate of 4000m3h1, at 25C and 1.1atm, while the solvent (water) will be supplied at a flowrate of 6500kgh1 and also at 25C. The required recovery of ethanol is 97.0%, while the pressure drop for the gas stream should not exceed 250Pam1 of packed height. Assume negligible CO2 is absorbed into the water and the column is isothermal. 1. Equilibrium You may assume that the system obeys the Henry's law and that the value of the Henry's constant for an ethanol-water system operating at 25C is H=0.272atm. Plot the equilibrium relationship for this separation on an XY plot over a suitable scale. [2 marks] 2. Operating line Derive an equation for the operating line of this separation and plot this on your XY plot. [4 marks] 3. Number of theoretical units Find how many theoretical units N0G are required for this separation and show your method. [4 marks] 4. Column diameter Use the KGa and pressure drop performance curves in the brochure to identify a suitable combination of column diameter and NXR packing size given the pressure drop limitation. The F factor is defined by F=wGG0.5, where wG is the superficial gas velocity and G is the gas density. Justify your choices. [8 marks] 5. Height of a theoretical unit HO Use the Ka curve to calculate a value of HOG for your design. [4 marks] 6. Calculate the packing height Calculate the height of packing required for your design. [2 marks] 7. Comment on your design Comment on your design. For example: Do you think it is optimal? Would you recommend this type of packing? What, if any, other types of packing would you recommend considering? Is the choice of water flow rate suitable? [6 marks]