Other Bachelor Degree- MASS TRANSFER OPERATIONS (Karunya University, Coimbatore-2011)
Saturday, 24 August 2013 12:24anudouglas
Karunya University
(Karunya Institute of Technology and Sciences)
(Declared as Deemed to be University under Sec.3 of the UGC Act, 1956)
Supplementary Examination - June 2011
Subject Title: MASS TRANSFER OPERATIONS Time: 3 hours
Subject Code: BT236 Maximum Marks: 100
Answer ALL questions
PART – A (10 x 1 = 10 MARKS)1. According to the penetration theory, what is the relationship between mass transfer coefficient ‘k’ and diffusivity ‘D’.
2. Represent graphically diffusion of gas A through non diffusing gas B.
3. Write Fenske’s equation.
4. Draw the T-x-y diagram for minimum boiling azeotrope.
5. State some common problems of packed columns.
6. What type of tower is suitable for corrosive and foamy liquids?
7. Name any two assumptions made in the Langmuir isotherm.
8. How does the ion exchange differ from adsorption?
9. Define selectivity.
10. What do you mean by heap leaching?
PART – B (5 x 3 = 15 MARKS)
11. Distinguish between the fluxes ‘JA’ and ‘NA’. For a binary mixture in gas, write down the equation relating ‘JA’ and ‘NA’.
12. In a binary distillation column, if the feed contains 40% liquid and the rest as vapor, estimate the slope of the q line.
13. Define HTU and NTU.
14. Differentiate chemical adsorption from physical adsorption.
15. Explain a tie line and a solutropic system.
PART – C (5 x 15 = 75 MARKS)
16. a. Explain briefly the analogies and their usefulness in mass transfer studies. (5)
b. Discuss the following theories of mass transfer
i) Film theory ii) Surface renewal theory (5+5)
(OR)
17. a. Calculate the amount of diffusion of acetic acid (A) in 2 hours across a film on non- diffusing water (B) solution 1mm thick at 17 OC when the concentrations on opposite side of the film are respectively 9 and 3 wt% acetic acid. The diffusivity of acetic acid in solution is 0.95 × 10-9 m2/s.
Data at 17 OC:
Density of 9% solution = 1012 kg/m3
Density of 3% solution = 1003.2 kg/m3
Molecular weight of acetic acid = 60.03
Molecular weight of water = 18.02 (8)
b. Derive an expression for the molar flux under equimolar counter diffusion. (7)
18. a. 100 mole of benzene and toluene containing 50 mole % benzene is subjected to a differential distillation at atmospheric pressure till the composition of the benzene in the residue is 33% by mole. Calculate the total moles of the mixture distilled using an average value of 2.4 for the volatility of benzene relative to toluene (10)
b. Explain about azeotropic distillation. (5)
[P.T.O]
(OR)
19. A mixture of 35 mole % A and 65 mole % B is to be separated in a fractionating column, the concentration of A in the distillate is 93 mole % and 96% of all product A is in the distillate. The feed is half vapor and the reflux ratio is to be 4.0. The relative volatility of A to B is 2.5. Calculate the number of theoretical plates in the column and locate the feed plate.
20. An air-ammonia mixture containing 5% ammonia by volume is absorbed in water in a packed column operated at 20oC and 1 atm pressure so as to recover 98% of ammonia. If their inert gas flow rate in the column is 1200 kg/hrm2
Calculate:
a. The minimum mass velocity of water for this column
b. The number of transfer unit in the column taking the operating liquid rate to be 1.25 times the minimum
c. The height of the packed tower taking the overall transfer coefficient, KGa to be 128.0 kgmoles/hr m3 atm. The relationship for equilibrium in the column is y = 1.154x, where y and x are in mole fraction units. (5+5+5)
(OR)
21. a. Discuss the factors to be considered in the choice of solvent for absorption. (5)
b. A packed tower is designed to recover 98% CO2 from a gas mixture containing 10% CO2 and 90% air using water. A relation, y = 14x can be used for equilibrium conditions where y is kg CO2/kg dry air and x is kg CO2/kg water. The water to gas rate is kept 30% more than the minimum value. Calculate the height of the tower if HTUOG is 1 metre. (10)
22. Explain the following: (3x5)
a. Adsorption isotherms b. Industrial adsorbents c. Ion-Exchange and ion-exchange resins
(OR)
23. A solution of washed raw can sugar is colored by the presence of impurities. It is to be decolorized by treatment with an adsorptive carbon in a contact filtration plant. The data for an equilibrium isotherm is given below. The original solution has a color concentration of 9.6 measured on an arbitrary scale and it is desired to reduce the color to 0.96. Calculate the necessary dosage of fresh carbon per 2000 kg solution.
a. For a single stage process. b. For a three stage counter-current operation (8+7)
| Kg carbon/ kg solution |
0 |
0.001 |
0.004 |
0.008 |
0.02 |
0.04 |
| Equilibrium Color |
9.6 |
8.6 |
6.3 |
4.3 |
1.7 |
0.7 |
24. For extraction of dioxane from water, benzene is used as an extraction solvent. At 298K, the equilibrium distribution of dioxane between water and benzene is as given below:
| Weight % dioxane in water |
5.1 |
18.9 |
25.2 |
| Weight % dioxane in water |
5..2 |
22.5 |
32 |
1000 kg of solution containing 25% dioxane is to be extracted with benzene to remove 95% of the dioxane. The dioxane free benzene is used.
a. Calculate the solvent requirement for single batch operation.
b. If the extraction were done in four-stage crosscurrent unit using 750 kg of pure benzene each time, determine the final raffinate concentration and the percentage removal of dioxane from feed solution.
(OR)
25. a. With a neat sketch, discuss the working principle of Bollman extractor. (7)
b. Explain step by step approach for the estimation of number of ideal stages for multistage crosscurrent leaching operations. (8)
| Earning: ₹ 0.00/- |
