mass transfer and separations

MASS TRANSFER AND SEPARATION Question Papers (Regular, November 2007)

Wednesday, October 15, 2008
SET :1
1. (a) For a binary gaseous mixture of A and B show that DAB = DBA
(b) A mixture of He and N2 gas contained in a pipe at 298 K and 1.01325×105 N/m2 total pressure, which is constant through out. At one end of the pipe at point 1 the partial pressure pA1 of He is 0.60795×105 N/m2 and other end 0.2 m, pA2 = 0.202655×105 N/m2. Calculate the flux of He at steady state if DAB of He-N2 mixture is 0.687×10−4 m2/sec. [6+10]

2. (a) Give the physical significances of the dimensionless groups in mass transfer
(b) In order to measure the gas-phase mass transfer coefficient in a stirred cell at a given stirrer speed, absorption of ammonia diluted with dry air in aqueous sulphuric acid is carried out for a given period of time. The gas in the cell is well-stirred and the cross-sectional area is 31.5 cm2. If the volume of acid taken is 100 ml at 1(N) concentration and at the end of 20 minutes the liquid
is found to contain 0.82 g mole ammonia per litre, calculate the gas-phase mass transfer coefficient. [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 (40 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) ( Δ x) and ky = 8. Calculate the overall coefficient, KG in kmol /(h) (m2) ( Δ p, mm Hg) and xAi and PAi at the gas-liquid interface. [16]

4. The equilibrium partial pressures (p. p) of carbon dioxide over solutions of mono
ethanolamine are as follows:
X 0.058 0.06 0 0.062 0.064 0.66 0.068 0.070
Partial pressure 5.6 13 29 56 99 155 232
of CO2 (mmHg)
A plant for manufacturing dry ice will burn coke in air to produce a flue gas which when cooled will contain 20% CO2, and 80% N2. The gas will be blown into a bubble tray scrubber at 1.2 atm and 250C to be scrubbed with mono ethanolamine solution entering at 250C. The scrubbing liquid which is recycled from a stripper will contain 0.058 mol CO2/mole of solution. The gas leaving the scrubber is to contain 2% CO2. Assume isothermal operation. Determine the number of theoretical trays required for an L/G ratio of 1.2 times the minimum. [16]

5. (a) A charge of 100kmol mixture containing 50 mol % n-heptane and 50 mol % n-octane is to be batch distilled at atmospheric pressure to get 75 kmol of the liquid distilled. Compute the composition of the composite distillate and residue.
X 0.5 0.45 0.40 0.35 0.30 0.25 0.20 0.15
Y* 0.6846 0.6384 0.5846 0.5307 0.4692 0.4153 0.3307 0.2615
(b) Derive modified Rayleighs equation. [8+8]
6. (a) What are the different coordinates by which liquid-liquid equilibrium can be represented?
(b) Discuss cross current multistage extraction operation of insoluble liquids? [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. Describe briefly Micro filtration and ultra filtration and also write their industrial applications. [16]


SET :2

1. (a) What are various method available to get the relation between NA& NB?
(b) Water in the bottom of a narrow tube is held at constant temperature of 293 K. The total pressure of air (assumed dry) is 1.01×105 Pa and the temperature is 293K. Water evaporates and diffuses through air in the tube and the diffusion path is 0.152 m long. Calculate the rate of evaporation at steady state in kg mol/s m2.The diffusivity of water at 293 K and 1 atm is 0.25×10−4 m2 /sec. [6+10]

2. Discuss the correlation between Sherwood, Schmidt and Reynolds for flow insides pipes, flow outside tubes parallel to axis, flow normal to cylinders, flow normal to tube bundle and flow past single spheres. [16]
3. (a) The solubility of A in water is 0.5 kmol/m3 at a partial pressure of 60 mm Hg. If the total pressure is 1.2 atm and the Henry’s law is applicable, calculate the Henry’s law constant.
(b) What are parameters which will effect the equilibrium diagram.
(c) What is Marangoni effect? [6+6+4]

4. (a) Differentiate between absorption and adsorption with suitable example.
(b) Explain Vant Hoff law of equilibrium.
(c) When ideal solution will be formed. [6+6+4]

5. 100 Moles of an acetonitrile ? nitromethane is differentially distilled in a batch still at a pressure of 70kpa .The feed contains 74mole % acetonitrile. Distillation is continued till the liquid left behind in the still contains 32 mole % acetonitrile. The vapor-liquid equilibrium for the system at this pressure is correlated as follows:
Y*=1.05x+0.13 for 0.3 < x < 0.52 and
Y*=0.77x+0.28 for 0.52< 0.80
Where x and y* refer to the mole fraction of acetonitrile in the liquid and equilibrium vapor respectively. Find the average composition of the distillate collected and also calculate quantities of distillate and residue product. [16]

6. (a) Define leaching?
(b) What is lixiviation?
(c) What is decoction?
(d) Write short notes on applications of leaching operation. [4+4+4+4]

7. Derive an expression for the estimation of height of fixed bed adsorber for given solute removal. [16]

8. Describe briefly Micro filtration and ultra filtration and also write their industrial applications. [16]


SET :3

1. (a) Explain briefly various methods for the estimation of liquid diffusivity coefficients.
(b) Calculate the rate of diffusion of trichloroacetic acid across non-diffusing methanol
solution of 0.1 cm thick at 20 C, when the concentrations on the opposite sides of the methanol film are 6% and 2% by weight of acid. The densities of 6% and 2% acid solutions are 1.012 gm/cm3 and 1.003 gm/cm3 respectively. The diffusion coefficient at infinite dilution of trichloro acetic acid in methanol is 1.862×10−5 cm2/s. [8+8]

2. (a) Write short note on Convective Mass Transfer Coefficients.
(b) A large volume of pure gas B at 1 atm pressure is flowing over a surface from which pure A is vaporizing. The liquid A completely wets the surface which is a blotting paper. Hence the partial pressure of A at the surface is the vapor pressure of A at 298 K which is 0.2 atm. The ky has been estimated to be 6.78 ×10−15 kgmol/s.m2. mol fraction. Calculate NA, the vaporization rate
and also the value of ky and kG. [6+10]

3. Describe the diffusion between phases and show how the equilibrium distribution curve varies as a function of temperature and pressure taking a system of liquid water and gaseous mixture ammonia and air? [16]

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/m2s respectively. Calculate the height and diameter of the tower. The data required is as follows:
Overall mass transfer coefficient KGa = 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 mixture of acetone and phenol (40 mass % acetone) is flashed consecutively in a cascade consisting two flash drums at 1 atm. The feed enters at a rate of 3000 kg/h and half of it is flashed in the first flash drum. The liquid from the first drum is heated and flashed again in the second drum. What fraction of the feed entering the second drum should be vaporized so that the residue contains not more than 1 mass % acetone? The vapour-liquid equilibrium data of the acetone-phenol system are given below. [16]
X: 0.01 0.04 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 0.96 0.99
Y: 0.67 0.776 0.852 0.91 0.94 0.962 0.98 0.99 0.991 0.994 0.997 0.999 0.9996

6. (a) Why are triangular diagrams useful for liquid-liquid equilibrium calculations with a ternary system? On such a diagram, what are the miscibility boundary, plait point, and tie lines?
(b) Explain briefly solutropic system.
(c) Write the procedure for estimation of number of stages if liquid-liquid extraction is carried out in cross current operation. [6+5+5]

7. (a) What is an adsorption isotherm? How can the heat of adsorption be determined from a series of isotherms?
(b) What is ideal fixed-bed adsorption? What assumptions are necessary for it to apply? What is meant by breakthrough? [8+8]

8. Write the working principle of Ultra filtration. Explain commercial application of ultra filtration. [16]


SET :4

1. Ammonia gas and Nitrogen gas are diffusing in counter currently through diffusion a straight glass tube 0.61 m long with an inside diameter of 24.4 mm at 298 K and 101.32 K Pa. Both ends of the tube are connected to large mixed chambers at 101.32 K Pa. The partial pressure of NH3 in one chamber is constant at 20 K Pa and 6.666 K Pa in the other chamber. The diffusivity at 298K and 101.32 K Pa is 2.30×10−5 m2 /sec.
(a) Calculate the rate of diffusion of NH3 in kg mol/s
(b) Calculate the rate of diffusion diffusion of N2
(c) Calculate the partial pressure at a point 0.305 m in the tube and plot pA, pB and pt verses distance z. [16]

2. (a) Discuss the important and applications of mass transfer analogies.
(b) A plate, 0.5 m square, coated with a layer of benzoic acid, is placed in a stream of water flowing at a velocity of 0.25m/sec at a temperature of 21 C. Calculate the average rate of dissolution of the acid per unit area of the plate and also the mass transfer. The following data are available: solubility of benzoic acid in water at 25 C= 3.01 kg /m3; diffusivity of benzoic acid in water =10 −9 m2 /s and velocity of water at 25 C=8.9×10−4 kg/m.s. [8+8]

3. Describe the diffusion between phases and show how the equilibrium distribution curve varies as a function of temperature and pressure taking a system of liquid water and gaseous mixture ammonia and air? [16]

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/m2s respectively. Calculate the height and diameter of the tower. The data required is as follows:
Overall mass transfer coefficient KGa = 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) 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 feedtray location.
(b) Explain P-x-y diagram. [12+4]

6. Write about the system of three liquids -one pairs partially soluble with the help of an equilibrium diagram and suitable example. Also discuss the effect of temperature on the above system. [16]

7. (a) Draw a graph showing different types of absorption isotherms for vapors and explain.
(b) Explain in detail about single stage adsorption. [8+8]

8. (a) Define flux and separation factor for membranes gas separators and also write the relevant equations.
(b) Explain briefly the effects of process flow patterns on separation and membrane area. [8+8]
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LABELS: MASS TRANSFER AND SEPERATIONS (MTS)
MASS TRANSFER AND SEPARATION Question Papers (Regular, November 2007, RR)
POSTED BY M.S.CHOWDARY AT 12:32 AM
SET :1
1. Develop expressions for the estimation of flux in Gaseous systems for ‘A’ through stagnant ‘B’. [16]

2. (a) Distinguish between Eddy and Molecular Diffusion?
(b) Explain Penetration Theory versus Two Film Theory? [8+8]

3. A solution of CCl4 and CS2 containing 50% wt each is to be continuously fractionated at 1 atm at the rate of 4000 kg/hr. Distillate product is to contain 95% wt CS2 and residue 0.5%. The feed will be 30% mole vapourised before it enters the tower. Total condenser will be used and reflux returned at bubble point. Determine
(a) Product rates.
(b) Theoretical trays for a reflux ratio of twice the minimum. The equilibrium data is as follows. [8+8]
X 0.11 0.26 0.39 0.53 0.66 0.76 0.86
Y 0.27 0.49 0.63 0.75 0.83 0.88 0.93

4. A Blend of 50% Toluene liquid and 50% Benzene liquid volume is being separated by fractionation into an over head product that has 10 mole percent Toluene and a bottom product that has 0.5 mole percent Benzene. The blend is fractionated at the rate of 10000 gal/day. How many gallons of each product is produced, if the reflux ratio is 4. A sample of vapour from one of the trays above the feed tray was taken and found to contain 20% Toluene. What was the composition of the liquid from the tray along the point of which the sample of vapour was taken? [16]

5. Explain the terms constant and variable under flow conditions? [16]

6. Explain the method of leaching vegetable oil seeds for extraction of Oil? [16]

7. Explain multistage counter current adsorption. Give some applications. [10+6]

8. (a) Explain types of flow in gas permeation.
(b) In what way pervaporation is different from other membrane separations, explain. [8+8]


SET :2

1. Obtain an expression for the steady state Equimolal counter diffusion of two gases starting from fundamentals? [16]

2. It is desired to estimate the mass transfer coefficient KG in kg mol/m2s p.a for water vapour in air at 338.6 k and 101.32 Kpa flowing in a large duct past different geometry solids. The velocity of the duct is 3.66 m/s. The water vapour concentration in the air is transferred to the solids. Do this for the following geometries.
(a) A single 25.4 mm - diameter sphere.
(b) A packed bed of 25.4 mm sphere with ε = 0.35 [8+8]

3. A liquid feed consisting of 1200 kg moles of mixture containing 30% Naphthalene and 70% Dipropylene Glycol is differentially distilled at 100 mm Hg pressure and final distillate contains 55% of Naphthalene. The VLE data are
X 8.4 11.6 2.8 50.6 68.7 80.6 88
Y 22.3 41.1 62.9 74.8 80.2 84.4 88
(a) Determine the amount of distillate.
(b) Determine the concentration of Naphthalene in residue and distillate? [8+8]

4. A rectification column is fed 100 kg mol/h of a mixture of 50 mol% Benzene and 50 mol% Toluene at 101.32 Kpa abs pressure. The feed is liquid at the boiling point. The distillate is to contain 90 mol% Benzene and the bottoms 10 mol% Benzene. The reflux ratio is 4.52:1. Calculate the kg mol/h distillate, kg mol/h bottoms and the number of theoretical trays needed using Mc Cabe Thiele Method. [16]

5. (a) What is a plait point?
(b) Draw the flow diagram for continuous counter current multistage extraction operation. [6+10]

6. Seeds containing 20 percent by weight of oil are extracted in a counter current plant and 90 percent of the oil is recovered in a solution containing 50 percent by weight of oil. If the seeds are extracted with fresh solvent and 1 kg of solution is removed in the underflow in association with every 2 kg of insoluble matter, how many ideal stages are required? [16]

7. (a) Explain in detail break through curve and its significance?
(b) Indicate how rate of adsorption in fixed beds is estimated. [8+8]

8. Explain the Ultrafiltration, microfiltration and Reverse Osmosis with examples. [4+4+4+4]


SET :3

1. Obtain an expression for the steady state Equimolal counter diffusion of two gases starting from fundamentals? [16]

2. (a) Distinguish between Eddy and Molecular Diffusion?
(b) Explain Penetration Theory versus Two Film Theory? [8+8]

3. A solution of CCl4 and CS2 containing 50% wt each is to be continuously fractionated at 1 atm at the rate of 4000 kg/hr. Distillate product is to contain 95% wt CS2 and residue 0.5%. The feed will be 30% mole vapourised before it enters the tower. Total condenser will be used and reflux returned at bubble point. Determine
(a) Product rates.
(b) Theoretical trays for a reflux ratio of twice the minimum. The equilibrium data is as follows. [8+8]
X 0.11 0.26 0.39 0.53 0.66 0.76 0.86
Y 0.27 0.49 0.63 0.75 0.83 0.88 0.93

4. A rectification column is fed 100 kg mol/h of a mixture of 50 mol% Benzene and 50 mol% Toluene at 101.32 Kpa abs pressure. The feed is liquid at the boiling point. The distillate is to contain 90 mol% Benzene and the bottoms 10 mol% Benzene. The reflux ratio is 4.52:1. Calculate the kg mol/h distillate, kg mol/h bottoms and the number of theoretical trays needed using Mc Cabe Thiele Method. [16]

5. With the help of neat sketches, explain briefly the various types of commercial extraction equipment. [16]

6. Soyabean flakes containing 22 wt% oil are to be leached in a counter current multistage to contain 0.8 kg oil/ 100 kg inert solid. Using fresh and pure hexane solvent.For every 1000 kg soyabeans, 1000 kg Hexane is used. Experiments give the following retention of solution with the solids in the underflow, where N is kg inertsolid/ kg solution retained and YA is wt. fraction of oil in solution.
N 1.73 1.52 1.43
YA 0 0.20 0.30
Calculate the exit flows and compositions and the number of theoretical stages required? [16]

7. Explain Freundlich equation and its application. Explain fixed bed adsorption? [8+8=16]
8. A liquid containing solute A at a concentration C1 = 3 ×10−2 kg mol/m3 is flowing rapidly by a membrane of thickness L=3.0×10−5 m. The distribution coefficient K′=1.5 and DAB = 7.0×10−11m2/s in the membrane. The solute diffuses through the membrane and its concentration on the other side is C2 = 0.50×10−2kgmol/m3. The mass transfer coefficient KC1 is large and can be considered as infinite and KC2=2.02 ×10−5 kmol/m2s mol fraction. Calculate the flux and the concentrations at the membrane interfaces? [16]


SET :4

1. Obtain an expression for the steady state Equimolal counter diffusion of two gases starting from fundamentals? [16]

2. (a) Distinguish between Eddy and Molecular Diffusion?
(b) Explain Penetration Theory versus Two Film Theory? [8+8]
3. An equimolar mixture of A and B is flash distilled such that 65% of the feed is in product distillate of the total moles fed. Compute the composition of the distillate and residue. Vapour liquid equilibrium data is as follows.
X (mole) % 8 10 20 30 40 50 70 80 95
Y (mole) % 37 42 58 67 73 78 87 96 98
x and y represent the composition of A in liquid and vapour phase respectively.[16]

4. A Methanol - water solution containing 36 mole% Methanol at 26.70C is to be continuously rectified at 1 std atmosphere at a rate of 5000 kg/hr to provide distillate containing 91.5 mole% Methanol and a residue containing 99.5 mole% of water. The feed is introduced at its boiling point. The distillation is totally condensed and the reflux is returned at its bubble point. A reflux ratio of 1.5 times the minimum is used. Determine using enthalpy-concentration diagram.
(a) Quantity of products in kg/hr.
(b) Minimum Reflux ratio.
(c) Number of Ideal Plates.
Mole fraction Enthalpies Saturated liquid KJ/Kmol Saturated Vapour
0 8000 48000
1 7500 39000


Mole% of Methanol in liquid X 4 10 20 30 40 50 60 70 80 90 95
Mole%ofMethanol invapour Y 23 42 58 66 73 78 82 87 91 96 98
[5+5+6]

5. A 25% (weight%) solution of dioxane in water is to be continuously extracted in counter current fashion with Benzene to remove 95% of the dioxane in feed. If the feed rate is 1000 kg/hr estimate the
(a) Minimum solvent required and
(b) Theoretical stages needed if 900 kg/hr of solvent is used
Wt% Dioxane in water 5.1 18.9 25.2
Wt% Dioxane in Benzene 5.2 22.5 32.0[8+8]

6. Seeds containing 20 percent by weight of oil are extracted in a counter current plant and 90 percent of the oil is recovered in a solution containing 50 percent by weight of oil. If the seeds are extracted with fresh solvent and 1 kg of solution is removed in the underflow in association with every 2 kg of insoluble matter, how many ideal stages are required? [16]

7. (a) Explain in detail break through curve and its significance?
(b) Indicate how rate of adsorption in fixed beds is estimated. [8+8]

8. A liquid containing solute A at a concentration C1 = 3 ×10−2 kg mol/m3 is flowing rapidly by a membrane of thickness L=3.0×10−5 m. The distribution coefficient K′=1.5 and DAB = 7.0×10−11m2/s in the membrane. The solute diffuses through the membrane and its concentration on the other side is C2 = 0.50×10−2kgmol/m3. The mass transfer coefficient KC1 is large and can be considered as infinite and KC2=2.02 ×10−5 kmol/m2s mol fraction. Calculate the flux and the concentrations at the membrane interfaces? [16]
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LABELS: MASS TRANSFER AND SEPERATIONS (MTS)
MASS TRANSFER AND SEPARATION Question Papers (Supple, February 2007, RR)
POSTED BY M.S.CHOWDARY AT 12:32 AM
SET :1

1. Obtain an expression for the steady state Equimolal counter diffusion of two gases starting from fundamentals? [16]
2. (a) Distinguish between Eddy and Molecular Diffusion?
(b) Explain Penetration Theory versus Two Film Theory? [8+8]

3. A liquid mixture containing 40 mole% n-Heptane and 60 mole% n-Octane is subjected to differential distillation at atmospheric pressure with 60 mole% of the liquiddistilled. Compute the composition of the composited distillate and the residue.Take relative volatility α =2.16. [16]

4. A rectification column is fed 100 kg mol/h of a mixture of 50 mol% Benzene and 50 mol% Toluene at 101.32 Kpa abs pressure. The feed is liquid at the boiling point. The distillate is to contain 90 mol% Benzene and the bottoms 10 mol% Benzene. The reflux ratio is 4.52:1. Calculate the kg mol/h distillate, kg mol/h bottoms and the number of theoretical trays needed using Mc Cabe Thiele Method. [16]

5. (a) What is a plait point?
(b) Draw the flow diagram for continuous counter current multistage extraction operation. [6+10]

6. Soyabean flakes containing 22 wt% oil are to be leached in a counter current multistage to contain 0.8 kg oil/ 100 kg inert solid. Using fresh and pure hexane solvent. For every 1000 kg soyabeans, 1000 kg Hexane is used. Experiments give the following retention of solution with the solids in the underflow, where N is kg inert solid/ kg solution retained and YA is wt. fraction of oil in solution.
N 1.73 1.52 1.43
YA 0 0.20 0.30
Calculate the exit flows and compositions and the number of theoretical stages required? [16]

7. The equilibrium adsorption of Acetone vapour on an activated carbon at 300C and 1 atm is given by the following data
gm adsorbed / gm carbon 0 0.1 0.2 0.3 0.35 0.38
Partial pressure of Acetone mm Hg 0 2 12 42 92 120
The vapour pressure of Acetone at 350C is 283 mm Hg. A one liter flask contains air and Acetone vapour at 1 atm and 300C with a relative saturation of the vapour of 35%. Two grams of fresh activated carbon is introduced into the flask and the flask is sealed. Calculate the final vapour concentration at 300C and the final pressure. Neglect the adsorption of air. [16]

8. (a) Explain with a sketch the general membrane separation process.
(b) Classify the membrane processes based on the driving force.
(c) Differentiate between Ultrafiltration and Reverse Osmosis. [6+5+5]


SET :2

1. Obtain an expression for the steady state Equimolal counter diffusion of two gases starting from fundamentals? [16]

2. (a) Distinguish between Eddy and Molecular Diffusion?
(b) Explain Penetration Theory versus Two Film Theory? [8+8]

3. An equimolar mixture of A and B is flash distilled such that 65% of the feed is in product distillate of the total moles fed. Compute the composition of the distillate and residue. Vapour liquid equilibrium data is as follows.
X (mole) % 8 10 20 30 40 50 70 80 95
Y (mole) % 37 42 58 67 73 78 87 96 98
x and y represent the composition of A in liquid and vapour phase respectively.[16]

4. A rectification column is fed 100 kg mol/h of a mixture of 50 mol% Benzene and 50 mol% Toluene at 101.32 Kpa abs pressure. The feed is liquid at the boiling point. The distillate is to contain 90 mol% Benzene and the bottoms 10 mol% Benzene. The reflux ratio is 4.52:1. Calculate the kg mol/h distillate, kg mol/h bottoms and the number of theoretical trays needed using Mc Cabe Thiele Method. [16]

5. Nicotine in water containing 1% nicotine is to be extracted with kerosene at 200C water and kerosene are insoluble. Estimate the percentage extraction of Nicotine.
(a) If 100 kg of feed solution is extracted in a single stage with 150 kg of solvent.
(b) If 100 kg of feed solution is extracted in three theoretical stages using 50 kg of fresh solvent in each stage. [8+8]

6. Crushed oil seeds containing 55% oil (by weight) is to be extracted at the rate of 4000 kg/hr using 100 kg/min of n-hexane containing 5% oil (by weight) as the solvent. A counter current two stage extraction system is employed. The oil seeds will retain 1 kg of solution per kg of oil free cake. Estimate the percent recovery of oil obtained under the above conditions? [16]

7. (a) Explain in detail break through curve and its significance?
(b) Indicate how rate of adsorption in fixed beds is estimated. [8+8]

8. A liquid containing solute A at a concentration C1 = 3 ×10−2 kg mol/m3 is flowing rapidly by a membrane of thickness L=3.0×10−5 m. The distribution coefficient K′=1.5 and DAB = 7.0×10−11m2/s in the membrane. The solute diffuses through the membrane and its concentration on the other side is C2 = 0.50×10−2kgmol/m3. The mass transfer coefficient KC1 is large and can be considered as infinite and KC2=2.02 ×10−5 kmol/m2s mol fraction. Calculate the flux and the concentrations at the membrane interfaces? [16]


SET :3

1. Obtain an expression for the steady state Equimolal counter diffusion of two gases starting from fundamentals? [16]

2. Prove (or) show the following relationships starting with the equation.
(a) Convert K′C to KY and KG.
(b) Convert KL to Kx and K′x.
(c) Convert KG to KY and KC. [6+5+5]

3. A liquid feed consisting of 1200 kg moles of mixture containing 30% Naphthalene and 70% Dipropylene Glycol is differentially distilled at 100 mm Hg pressure and final distillate contains 55% of Naphthalene. The VLE data are
X 8.4 11.6 2.8 50.6 68.7 80.6 88
Y 22.3 41.1 62.9 74.8 80.2 84.4 88
(a) Determine the amount of distillate.
(b) Determine the concentration of Naphthalene in residue and distillate? [8+8]

4. A rectification column is fed 100 kg mol/h of a mixture of 50 mol% Benzene and 50 mol% Toluene at 101.32 Kpa abs pressure. The feed is liquid at the boiling point.MThe distillate is to contain 90 mol% Benzene and the bottoms 10 mol% Benzene. The reflux ratio is 4.52:1. Calculate the kg mol/h distillate, kg mol/h bottoms and the number of theoretical trays needed using Mc Cabe Thiele Method. [16]

5. Explain the following co-ordinate systems?
(a) Rectangular co-ordinate system.
(b) Triangular co-ordinate system.
(c) Rectangular co-ordinate system on solvent free basis. [5+5+6]

6. Soyabean flakes containing 22 wt% oil are to be leached in a counter current multi- stage to contain 0.8 kg oil/ 100 kg inert solid. Using fresh and pure hexane solvent. For every 1000 kg soyabeans, 1000 kg Hexane is used. Experiments give the following retention of solution with the solids in the underflow, where N is kg inert solid/ kg solution retained and YA is wt. fraction of oil in solution.
N 1.73 1.52 1.43
YA 0 0.20 0.30
Calculate the exit flows and compositions and the number of theoretical stage required? [16]

7. Discuss about fixed bed adsorption and its application in food industry. [16]

8. (a) Explain types of flow in gas permeation.
(b) In what way pervaporation is different from other membrane separations, explain. [8+8]


SET :4

1. Obtain an expression for the steady state Equimolal counter diffusion of two gases starting from fundamentals? [16]

2. (a) Distinguish between Eddy and Molecular Diffusion?
(b) Explain Penetration Theory versus Two Film Theory? [8+8]

3. A continuous fractionating column has to be designed for separating a liquid mixture of 4050 kg/hr containing equimolar amounts ofMethanol. The feed is vapourised. Calculate
(a) Molar flow rate of overhead and bottom product.
(b) The number of Actual plates assuming tray efficiency of 0.7
(c) Use a reflux ratio of 1.75 times the minimum reflux, locate the feed tray. Equilibrium Data
X 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Y 0.417 0.579 0.669 0.729 0.780 0.825 0.879 0.915 0.959

4. A rectification column is fed 100 kg mol/h of a mixture of 50 mol% Benzene and 50 mol% Toluene at 101.32 Kpa abs pressure. The feed is liquid at the boiling point. The distillate is to contain 90 mol% Benzene and the bottoms 10 mol% Benzene. The reflux ratio is 4.52:1. Calculate the kg mol/h distillate, kg mol/h bottoms and the number of theoretical trays needed using Mc Cabe Thiele Method. [16]

5. With the help of neat sketches, explain briefly the various types of commercial extraction equipment. [16]

6. A counter current multiple contact extraction system is treat 50 tons/hr of wet mass fraction. Water ̃ 0.48, pulp 0.04, and sugar 0.20. The strong solution leaving the system is to contain 0.15 mass fraction of sugar and 97% sugar in the sliced beets is to be removed. Determine the number of cells required assuming equilibrium between the under flow and overflow from each cell, if each ton of pulp retains 3 tons of water. [16]

7. (a) Explain in detail break through curve and its significance?
(b) Indicate how rate of adsorption in fixed beds is estimated. [8+8]

8. Explain:
(a) Effects of pressure ratio and separation factor on recovery.
(b) Effects of process flow patterns on separation and area. [8+8]
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LABELS: MASS TRANSFER AND SEPERATIONS (MTS)
MASS TRANSFER AND SEPERATION Question Papers (Regular, 2006)
POSTED BY M.S.CHOWDARY AT 12:31 AM
SET: 4

1. (a) Write the Ficks law of diffusion for ‘Z’ direction. What is the significance of diffusion coefficient?

(b) Derive the equation for steady state diffusion of gas (A) through the wall of a hollow cylinder?

2. (a) Distinguish between Eddy and Molecular Diffusion?

(b) Explain Penetration Theory versus Two Film Theory?

3. (a) Write and explain Rayleigh’s equation?

(b) A binary mixture containing 15 mole percent n-Butane and 85% n-Pentane is

Subjected to simple Batch distillation at atmospheric pressure. If 80% of the Butane

is removed by distillation process, how much Pentane would be removed? What

would be the composition of the remaining liquid? Average relative velocity = 3.5

4. A saturated liquid feed of 200 mol/h at the boiling point containing 42mol% heptane and 58% ethyl Benzene is to be fractionated at 101.32 kpa abs to give a distillate containing 97mol% heptane and bottom containing 1.1mol% heptane. The reflux ratio used is 2: 5: 1. Calculate the mol/h distillate mol/h bottom bottoms, theoretical number of trays and the feed tray chamber. Equilibrium data are give at 101.32 kpa abs pressure for the mole fraction n-Heptane HX and HY.

5. (a) What is a plait point?

(b) Draw the flow diagram for diagram for continuous counter current multistage extraction operation.

6. Acetaldehyde(5%) is in solution in toulene and is to be extracted with water in a five stage co-current unit. If 25 kg water is used per 100 kg feed, find the amount of acetaldehyde extracted and the final concentration. If Y = KG Acetaldehyde/kg water and X = kg Acetaldehyde/kg toulene then Ye = 2.20x represents the equilibrium relation

7. (a) Explain in detail break through curve and its significance?

(b) indicate how rate of adsorption in fixed beds is estimated.
8. Discuss in brief about principles of ion exchange.
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LABELS: MASS TRANSFER AND SEPERATIONS (MTS)
MASS TRANSFER AND SEPERATION Question Papers (Supple, 2005)
POSTED BY M.S.CHOWDARY AT 12:30 AM
SET: 1

1. Obtain an expression for steady state equimolar counter diffusion of two gases starting from fundamentals?

2. On the basis of Colburn analogy, estimate the value of mass transfer coefficient for the absorption of ammonia by the wet surface of a cylinder placed in a turbulent air stream flowing across the cylinder at 4.6m/sec. heat transfer coefficient as 1.357 × 10-4 KJ.

DATA FOR AIR PRANDTL NUMBER = 0.74

CP = 0.49 × 10-3 KJ/Kg K

DENSITY (ρ) = 0.0012 Kg/m3 and for

Dilute ammonia – air mixture Schmidt number is 0.61

3. A liquid mixture containing 50 mol% n- Heptane and 50 mol% n – octane is subject to a differential distillation at atmospheric pressure untill the residual liquid contains 35 mole % n-heptane. Using the equilibrium data determine the percentage of feed that is left over as residue.

X 0.50 0.46 0.42 0.38 0.34 0.32

Y 0.689 0.648 0.608 0.567 0.523 0.49

Where X = mole fraction of n – heptane in liquid.

Y = mole fraction n – heptane in vapour.

4. A continuous fractionating column operating at atmospheric pressure is to separate a feed mixture containing 30% CS2 & 70% CCL4 into an over head product of 95% CS2 and a bottom product of 95 mole% CCL4 . The feed enters as a liquid at its boiling. Assume an over all efficiency of 70% and a reflux ratio of 3:1. Estimate the number of plates needed. All the compositions are in mole %.

Equilibrium data

X 0.0296 0.0615 0.258 0.39 0.532 0.663 0.758 0.860

Y 0.0823 0.1555 0.494 0.634 0.747 0.830 0.880 0.932

5. With the help of neat sketches, explain briefly the various types of commercial extraction equipment.

6. Give an account of the graphical method of calculation of the number of stages for counter current extraction in a solid-liquid extraction system.

7. Write on:

a) Adsorption wave and break through curve

b) Pressure solving and thermal solving methods. BET isotherm.
Write a brief note on counter current flow model for gas permeation.
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LABELS: MASS TRANSFER AND SEPERATIONS (MTS)
MASS TRANSFER AND SEPERATION Question Papers (Regular, 2004)
POSTED BY M.S.CHOWDARY AT 12:29 AM
SET: 1

1. Obtain an expression for steady state equimolar counter diffusion of two gases starting from fundamentals?

2. Estimate the liquid-film mass transfer coefficient for O2 diffusing from an air bubble rising through water at 20 C. Choose a bubble size of 0.04 m. assume a spherical shape and assume rapid circulation of gas inside the bubble. Neglecting the change of bubble size with distance travelled , calculate the fraction of oxygen absorbed from the air in 1m of travel if the water contains no dissolved oxygen.

3. (a) Write and explain Rayleigh’s equation?

(b) A binary mixture containing 15 mole percent n-Butane and 85% n-Pentane is subjected to simple Batch distillation at atmospheric pressure. If 80% of the Butane is removed by distillation process, how much Pentane would be removed? What would be the composition of the remaining liquid? Average relative velocity = 3.5

4. Discuss the steps involved in the determination of thoeritical number of plates by Panchon Savarit Method? What is reflux? Explain the method for determining minimum Reflux by using the above method?

5. With the help of neat sketches, explain briefly the various types of commercial extraction equipment

6. Give an account of the graphical method of calculation of the number of stages for counter current extraction in a solid-liquid extraction system.

7. Determine graphically the quantity of fresh carbon required per 500kg of solution for a single stage operation to reduce the odour to 10% of its original value. Compare the result with that obtained from Freundilich equation.

8. Discuss in brief about principles of ion exchange?

SET: 2

1. (a) Write the Ficks law of diffusion for ‘Z’ direction. What is the significance of diffusion coefficient?

(b) Derive the equation for steady state diffusion of gas (A) through the wall of a hollow cylinder?

2. Prove (or) show the following relationships with the equation.

a) Convert K’C to KY and KG

b) Convert KL to KX and K’X.

C) Convert KG to KY and KC.

3. Explain the process of differential distillation and Rayleigh’s equation.

4. A mixture of 40 mole% Benzene with Toulene is distilled in a column to give a product of 95 mole% Benzene and a waste of 5 mole% Benzene using a reflux ratio of 4. By using the McCabe and Thieles method determine

a) The number of plates required and the position of the feed if supplied to the column as liquid at the boiling point.

b) Minimum reflux ratio possible.

c) Minimum number of plates.

5. Explain the terms constant and variable under flow conditions?

6. a) Discuss in brief regarding the preparation of solid for leaching? Explain the temperature of leaching?

b) Explain how minimum solvent rate required to be obtained for an extraction operation in a counter current multistage contactor?

7. Write on:

a) Adsorption wave and break through curve

b) Pressure solving and thermal solving methods. BET isotherm.

8. Define the membrane separation processes and classify them and explain in detail?

SET: 3

1. The air pressure in a tyre reduces from 2bars to 1.99 bars in five days. The volume of air in the tube is 0.25 m3, the surface area is 0.5 m2 and wall thickness is 0.01 m. the solubility of air in rubber is 0.07 m3/m3 rubber. Estimate the diffusivity of air in rubber.

2. It is desired to estimate the mass transfer coefficient KG in kg mol/m2 p.a for water vapour in air at 338.6k and 101.32 kpa flowing in a large duct past different geometry solids. The velocity of the duct is 3.66m/s. The water vapour concentration in the air is transferred to the solids. Do this for the following geometries.

a) A single 25.4 mm – diameter sphere.

b) A packed bed of 25.4 mm sphere with є = 0.35

3. Derive an equation to determine the minimum number of plates at total reflux conditions for the distillation of a binary mixture ?

4. A blend of 50% Toulene liquid and 50% benzene liquid volume is being separated by fractionation into an over head product that has 10 mole% Toulene and a bottom product that has 0.5 mole % Benzene. The blend is fractionated at the rate of 10,000 gal/ day. How many gallons of each product is produced, if the reflux ratio is 4. A sample of vapour from one of the trays above the feed trays was taken and found to contain 20% Toulene. What was the composition of the liquid from the tray along the point of which the sample of vapour was taken?

5. Explain how the number of stages can be determined for immiscible solvents in cross current extraction?

6. A counter current multiple contact extraction system is treat 50 tons/hr of wet sliced sugar beets with fresh water as solvent. The beets have the following analysis in mass fraction. Water – 0.48, pulp – 0.04 and sugar - 0.20. The strong solution leaving the system is to contain 0.15 mass fraction of sugar and 97% sugar in sliced beets is to be removed. Determine the number of cells required assuming equilibrium between the under flow and overflow from each cell, if each ton of pulp retains 3 tons of water.

7. Explain the various types of equipments commercially used for adsorption with the help of neat sketches?

8. Explain liquid permeation membrane processes and sketch concentration profiles for membrane processes?

SET: 4

1. A tube of small diameter was filled with acetone to 1.5 m from the top and maintained at a temperature of 20 C in a gentle current of air. After 7 hours the level of liquid dropped to 2.25 m. the barometric pressure was 760mm Hg and the vapour pressure of acetone is 185mm Hg. At 20 C, the density of Acetone is 0.79 kg/m3. Determine the diffusivity of Acetone in air?

2. Ammonia from an air – ammonia stream containing 5% ammonia by volume in absorbed by sulphuric acid in a counter current wetted wall column 15mm is 800 mm long. The inlet gas rate is 0.15 kg moles /hr and exit gas contains 0.5 % ammonia by volume. The average temperature is 20 C and the pressure is normal. The change in acid concentration may be neglected.

a) Calculate the value of absorption coefficient kg

b) If the value of heat transfer coefficient is 50 k cal/ hr m2 C

Estimate KG by equating JD and JH .

Data for air Cpm/K = 0.174, Cp = 0.24 for ammonia- air

SC = 0.61. value of PBM MAY BE TAKEN AS UNITY.

3. During the batch distillation of binary mixture in a packed column, the product had 0.60 mole fraction of the more volatile component when the concentration in the still was 0.40 fraction. If the reflux ratio in the use was 20:1 and vapour composition y is related to liquid composition x by the equation Y = 1.25x (x and y are mole fractions)

Over the range of concentration concerned, find the number of plates?

4. A fractionating column operating at 1atm pressure is supplied at the optimum location with a saturated liquid feed containing 40 mole% ethanol and 60 mole% water. The column produces a saturated liquid overhead product containing 80 mole% ethanol and a saturated liquid bottom product containing 20 mole % ethanol. The reflux ratio is 2. Find:

a) The number of thoeritical stages required to give the separation.

b) The optimum feed plate location assuming 100% plate efficiency.

5. Discuss the factors which must be considered in selecting a solvent for liquid- liquid extraction?

6. Explain the method of leaching vegetable oil seeds for extraction of oil?

7. Explain multistage counter current adsorption. Give some applications.

8. Describe the types of equipment for gas permeation membrane process?