R5312305-mass Transfer Andseperation

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Code No: R5312305

III B.Tech I Semester(R05) Supplementary Examinations, May 2009 MASS TRANSFER AND SEPARATION (Bio-Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. Explain in detail the classification of mass transfer operations based on the separating agent required. [16] 2. (a) What is the defining equation for a mass-transfer coefficient? How does it differ from Fick’s law? (b) Write short notes on analogy between heat and mass transfer.

[8+8]

3. In certain equipment used for the absorption of SO2 from air by water, at one section, the gas and liquid phase concentrations of the solute are 10 mole% and 4 mole% respectively. The solution density is 4592 Kg/m3 . At the given temperature (400 C) and pressure (10 atm), the distribution of the SO2 between air and water can be approximately described as pA = 25 xA , where pA is the partial pressure of SO2 in the gas phase in atm. The individual mass transfer coefficients are kx = 10 kmol / (h) (m2 ) (∆ x) and ky = 8. Calculate the overall coefficient, KG in kmol / (h) (m2 ) (∆ p, mm Hg) and xAi and PAi at the gas-liquid interface. [16] 4. (a) What you understand about minimum liquid amount in absorption. (b) Derive operating line equations for an absorber by performing material balance for one component transfer. [6+10] 5. A ten-plate distillation column with re-boiler and total condenser is available for use. An equimolar liquid mixture of A and B at its boiling point is to be separated to get a distillate containing 90% A (mole%). The relative volatility of mixture is 2.6. Calculate: (a) Minimum reflux ratio (b) The yield of distillate and residue for R = 1.2.

[16]

6. (a) Explain the effect of temperature on ternary equilibria. (b) Derive the equations for continuous counter current extractions operation. [6+10] 7. (a) Discuss the properties of a good adsorbent. (b) Raw sugar solution containing 48%by weight is colored by impurities. The impurities are to be removed by activated carbon in a contact filtration Unit. The equilibrium data are as follows: Kg carbon/Kg of dry Sugar 0 0.005 0.01 0.015 0.02 0.03 % color removed 0 47 70 83 90 95 The original solution has a color concentration of 20% and it has to be reduced to 2%. Calculate the amount of carbon required to treat 500kg of solution in a single stage operation. [16] 8. Describe briefly Micro filtration and ultra filtration and also write their industrial applications. [16] ?????

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Code No: R5312305

III B.Tech I Semester(R05) Supplementary Examinations, May 2009 MASS TRANSFER AND SEPARATION (Bio-Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) A narrow tube is partially filled with a liquid and maintained at constant temperature. A gentle stream of gas is passing across the open end of the tube. As the liquid evaporates the level drops slowly. At a given time t, the level is z from the top. Derive an expression to calculate the value of the diffusivity of the liquid vapor in the gas. (b) Write the Fick’s law of diffusion for ‘Z’ direction. What is the significance of diffusion co-efficient.? [10+6] 2. A pan containing water at 25 0 C is placed in a wind tunnel through which dry air flows at a velocity of 19 Kmph. The pan has a length of x=3 m in the longitudinal direction and contains water at a uniform depth of 10mm. The correlations for the local Sherwood number are: Shx = 0.332 (Rex ) 1/2 (Sc) 1/3 for laminar boundary layer flow, Re< 3 ×105 =0.0292(Rex )0.8 (Sc) for laminar boundary layer flow, Re>= 3 ×105 Calculate the time of evaporation of the water. Given pressure = 1 atm; kinematic viscosity of air = 0.153× 10−4 m2 /s; diffusivity of moisture = 0. 28 × 10−4 m2 /s; vapour pressure of water = 26 mm Hg. [16] 3. (a) Write the basic concept of equilibrium between two phases. (b) Equilibrium relation is y=mx . What is the relation between Kx , ky and Kx . What will happen if the gas phase is controlling? Explain. [8+8] 4. (a) Draw operating line and equilibrium diagram and explain driving force line. (b) Explain the procedure how to calculate minimum liquid flow rate in absorption. (c) Write the equilibrium relation for absorption if Henrys law is applicable

[6+6+4]

5. (a) Explain with figure the effect of different feed conditions in a distillation column. Write about the importance of q-line. Also write short notes on feed tray location. (b) Explain P-x-y diagram.

[12+4]

6. (a) What do you understand by constant underflow conditions in leaching? Draw the corresponding equilibrium diagram and show the tie lines. (b) Write short notes on effect of temperature in leaching operation.

[10+6]

7. (a) Explain briefly how to observe the adsorption from liquid solution. (b) Explain briefly heat of wetting. (c) Write short notes on Freundlich equation.

[6+4+6]

8. (a) Explain the phenomena of gas separations in porous membranes. (b) Compare and explain Ultra filtration and Dialysis. ?????

[8+8]

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Code No: R5312305

III B.Tech I Semester(R05) Supplementary Examinations, May 2009 MASS TRANSFER AND SEPARATION (Bio-Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. Explain in detail the classification of mass transfer operations based on the phases involved.

[16]

2. (a) Explain the Colburn analogy extended to mass transfer. (b) Naphthalene free air passes through a naphthalene tube of 1.8 m long and 2.5 cm I.D at a bulk velocity of 15m/sec at 10 0 C and an average pressure of 1 atm. Assume that the naphthalene surface is at 10 0 C. Naphthalene concentration in the existing gas stream is 5 kg moles/m3 . Naphthalene has a vapor pressure of 0.0209 mmHg at 10 0 C and diffusivity in air of 0.05×10−4 m2 /s. Estimate the gas phase mass transfer coefficient. It is that viscosity of air at 10 o C is 0.0186CP. For this situation the mass transfer correlation is given by Nsh = 2 + 0.552 (NRe )0.53 (NSc )1/3 . [6+10] 3. (a) Jasmone is a high value product used in perfumery and cosmetic industries. A suspension of jasmine flowers in water is contacted with an organic solvent to recover the compound. During extraction, the compound diffuses from the aqueous phase to the dispersed organic phase. The individual mass transfer coefficients are 3.5×10−6 cm/s (organic phase) and 2.7×10−5 cm/s (aqueous phase). The solute is 175 times more soluble in the organic phase (y = 175x; y = mole fraction of the solute in the organic phase). The aqueous solution is dilute and the total molar concentration of the organic phase is 10 kmol/m3 . Calculate the overall mass transfer coefficient Ky. Which phase resistance controls? (b) Explain briefly two film theory with neat sketch. [8+8] 4. (a) Write short notes on ideal and non-ideal solutions. (b) What is absorption factor? How is this related to stripping factor? (c) Discuss what factors should be considered in the selection of a solvent for absorption.

[6+4+6]

5. A saturated liquid feed containing 40 mole % chloroform and 60 mole % benzene is fed to a continuous fractionating column to yield a distillate and residue product with 95 mole % chloroform and 95 moe benzene respectively. The VLE data may be represented by the following relationship. Y = 1.29x + 0.25x2 -0.54x3 x,y-mole fractions of chloroform in the liquid and vapor. Determine (a) The minimum number of plates (b) The number of plates when the reflux ratio is such as to make the operating line slope = 1.18. [16] 6. (a) Write briefly about the preparation of solids prior to leaching. (b) Write short notes on liquid-liquid extraction.

[8+8]

7. (a) Name five of the most important commercial adsorbents? What is the distinguishing feature of the molecular-sieve zeolites? (b) What is the BET equation used for? Does it assume physical or chemical adsorption? Does it assume monomolecular or multimolecular adsorption? (c) What is meant by loading in adsorption? [8+4+4] 8. Write and explain basic equations for different types of flow in gas separations. ?????

[16]

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Code No: R5312305

III B.Tech I Semester(R05) Supplementary Examinations, May 2009 MASS TRANSFER AND SEPARATION (Bio-Technology) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) Explain briefly various pressure driven membrane separation process. (b) Explain briefly separation process where surface phenomena is important with suitable examples.

[10+6]

2. (a) Define Sherwood number and Stanton number. (b) A canvas bag commonly used for storing water in the deserts holds some quantity of water a small quantity of which continually seeps through the canvas pores and diffuses in the ambient air with the effect that evaporation of water cools the bag. The surface temperature of the bag is 291K. Determine the ambient temperature of air on the basis of the following parameters at the temperature. Prandtl number = 0.72 Schmidt number =0.61 Density of air = 1.11532 kg/m3 Specific heat of air = 1.0048 kJ/kg. 0 K Latent heat of vaporization of water = 2456 kJ/kg Partial pressure of water in ambient air = 1066.64 Pa. [6+10] 3. (a) Make a sketch to show typical concentration profiles of the solute during mass transfer across an interface. Qualitatively explain the concentration profiles. (b) Write short notes on equilibrium. [8+8] 4. A solvent is to be recovered from a solvent-air mixture by scrubbing with a water in a packed tower at a pressure of 101.3 kN/m2 and at a temperature of 300K. The solvent vapour enters the tower at a rate of 0.1kg/s and has a concentration of 2% by volume. It is necessary to recover 99.9% of the solvent; for the packing selected the optimum gas and water flow rates are known to be 1.3 and 2.0 kg/m2 s respectively. Calculate the height and diameter of the tower. The data required is as follows: Overall mass transfer coefficient KG a = 0.0389 kg/s m2 (kN/m2 ) Equilibrium diagram Pe = 0.02 x; where Pe equilibrium pressure of the solvent kN/m2 and x the mole fraction of the solvent in water. The molecular weight of the solvent and air are 70 and 29 kg/kmol, respectively. [16] 5. (a) An ethanol-water mixture containing 36% by weight of ethanol is differentially distilled at 1 atm. Pressure and the mixture is reduced to a maximum ethanol concentration of 6 mole % . Determine the quantity and composition of the distillate. Molecular weight of ethanol = 46. The VLE data are: Mole frac.of Ethanol in Liquid(x) 0.18 0.16 0.14 0.12 0.10 0.08 0.06 Mole frac. of Ethanol in Vapour(y) 0.517 0.502 0.485 0.464 0.438 0.405 0.353 (b) Write short notes on applications of distillation.

[12+4]

6. A feed solution containing 4000kg of water and 20kg of acetic acid is to be extracted with benzene solvent to recover 80% acetic acid by weight. The equilibrium data is: S.NO 1 2 3 4 5 6

x1 =gm acetic acid per kg water 0.920 1.140 1.525 2.04 3.29 5.23

Y1 =gm acetic acid per kg benzene 1.020 1.620 2.910 5.35 20.10 36.0

Calculate: (a) The number of cross -current stages required, if 1000 kg of benzene per stage is used and (b) The concentration of acetic acid in the combined extract. 7. (a) Write short notes on applications of fixed bed adsorber. (b) Explain the term breakpoint in adsorption wave curve. (c) What is absorption hysterisis? 8. (a) Write short notes on application of dialysis process for kidney failure cases. (b) What are pressure driven membrane process and explain briefly. ?????

[16]

[5+6+5] [8+8]