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A complete gas treatment plant often consists of both an absorber to remove solute from air and a stripper to regenerate solvent. The process as

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A complete gas treatment plant often consists of both an absorber to remove solute from air and a stripper to regenerate solvent. The process as similar to the figure below. In this particular application, we wish to remove obnoxious impurity from the air to be treated. - Absorber operates at 1.5 atm and 24C where obnoxious impurity equilibrium is given as y=0.5x (units are mole fractions). - Stripper operates at 1.0atm and 92C where equilibrium is y=3.0x (units are mole fractions). [hint: You will need to plot two equilibrium curves in excel, one for absorber and one for stripper.] Total feed air flow rate to the absorber is 1400 mol/day, and feed gas is 15.0mol% obnoxious impurity, and the remainder is air. We desire a treated air concentration of 0.5 mol\% obnoxious impurity. Total liquid flow rate into the absorber is 800mol/ day, and the liquid feed is 0.5mol obnoxious impurity. The outlet solvent from the absorber is the feed to the stripper and we assume that it is fed to the stripper at the same outlet flowrate from the absorber. Treated air from the absorber is heated and is used as stripping gas and sending to the stripper at a rate of 724mol/ day. The exit solvent from the stripper has the same obnoxious impurity concentration as the liquid feed to the absorber (0.5mol%). 1) Step-by-step approach we learnt in the class helps here. Working on the absorber part alone first, a. Estimate the number of stages in the absorber using McCabe Thiele Analysis [hint: as this is not a dilute system, use mole ratio]. b. Calculate the solute mole ratio in the outlet solvent stream. c. What are the liquid and the vapor mole ratio for stage 6 ? Convert them to mole fractions. 2) Moving to the stripper analysis now, [hint: you may use some calculated data from absorber], a. Estimate the number of equilibrium stages in the stripper b. Calculate the solute mole ratio in the outlet gas stream from the stripper. 3) If you closely look into the operating pressure and temperature of Absorber and Stripper, you will notice that Absorber operates at relatively higher pressure, but at lower temperature than the Stripper. Discuss why these conditions are favorable in Absorption and Stripping

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