Problem 1 - Calculate the minimum air-to-water ratio for a countercurrent packed tower for 95% removal of chloroform and benzene at 10oC.
1. Determine Henry's Law constants for Chloroform and Benzene.
2. Calculate the minimum air-to-water ratio for removal of chloroform and benzene.
Problem 2 - Determine the cross-sectional area and diameter for a packed-tower design based on the conditions given below. Assume 95% removal.
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Contaminant
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Temp,°C
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Water flow rate, ML/d
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Stripping Factor
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Pressure drop, N/m2*m
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Packing
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A
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chloroform
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20
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13
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3.5
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50
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5.1 cm Intalox saddles
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1. Determine Henry's constant for chloroform.
2. Specify the design parameters for the packing factor, air-to-water ratio, and gas pressure drop.
3. Determine the ratio of air mass loading rate to water mass loading rate (Gm/Lm).
4. Calculate Gm.
5. Calculate Lm.
6. Calculate the cross-sectional area of the packed tower.
7. Determine the diameter of the packed tower.
Problem 3 - Determine the overall liquid-side mass transfer rate constant for the compound and tower design for chloroform at 20oC, with a water flow rate of 13 ML/d, Stripping Factor of 3.5, pressure drop of 50 N/m2·m and 5.1 cm Intalox saddles, using the Onda correlations and a safety factor of 0.75.
Determine the liquid-phase diffusion coefficient using the Hayduk-Laudie correlation (Eq. 4-121) and the gas-phase diffusion coefficient using the Wilke-Lee correlation (Eq. 4-123). The packing material is polyethylene.
1. Calculate the liquid diffusion coefficient for chloroform.
2. Calculate the gas diffusion coefficient for chloroform.
3. Calculate the specific surface area available for mass transfer aw.
4. Calculate the liquid phase mass transfer coefficient, kl for chloroform.
5. Calculate the gas phase mass transfer coefficient, kg for chloroform.
6. Calculate the overall liquid-side mass transfer rate constant, kla for chloroform using Onda corrections.
7. Calculate the actual kla for chloroform.
Problem 4 - Determine the packed-tower height (packing depth) required to remove the compound given in Problem 2 of this homework. Use the tower area determined in Problem 2 and the overall liquid-side mass transfer rate constants determined in Problem 3 in the solution of the problem. The influent and effluent concentrations are given below.
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Cotaminant
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Influent Conc.,μg/L
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Effluent Conc.,μg/L
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A
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chloroform
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100
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5
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1. Calculate the height of a transfer unit, HTU.
2. Calculate the number of transfer units, NTU.
3. Calculate the packed tower height, L.
Problem 5 - Design a packed-tower aeration system to treat 6.48 ML/d of water at 20oC and remove benzene (C0 = 40 μg/L), chloroform (C0 = 60 μg/L), and carbon tetrachloride (C0 = 30 μg/L) to a treatment objective for each concentration that equals 5 μg/L. Select an appropriate stripping factor, gas pressure drop, and factor of safety for the overall mass transfer rate, tower diameter, and tower length. Calculate the effluent liquid concentration of each constituent for the completed design condition.
1. Solve for the value of the x axis on the Eckert curve (Figure 11-10).
2. Determine the gas loading rate, Gm.
3. Determine the water mass loading rate, Lm.
4. Determine the cross-sectional area of the packed tower.
5. Determine the diameter of the packed tower.
6. Determine the liquid diffusion coefficient for all compounds.
7. Determine the gas diffusion coefficient for all compounds.
8. Calculate the specific area available for transfer, aw.
9. Calculate the liquid phase mass transfer coefficients for each compound.
10. Calculate the gas phase mass transfer coefficients for each compound.
11. Calculate the over mass transfer rate constant, kla, using Onda corrections.
12. Calculate the actual kla for each of the compounds.
13. Calculate the packed tower height.