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Previous Year Exam Questions of Advanced Mass Transfer of bput - AMT by Bput Toppers

  • Advanced Mass Transfer - AMT
  • 2018
  • PYQ
  • Biju Patnaik University of Technology BPUT - BPUT
  • Chemical Engineering
  • B.Tech
  • 4 Offline Downloads
  • Uploaded 7 months ago
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Registration No : Total number of pages : 03 B.Tech. PCE4D001 4th Semester Regular / Back Examination 2017-18 ADVANCED MASS TRANSFER BRANCH : CHEM Time : 3 Hours Max Marks : 100 Q.CODE : C1139 Answer Part-A which is compulsory and any four from Part-B. The figures in the right-hand margin indicate marks. Assume suitable notations and any missing data wherever necessary. Answer all parts of a question at a place. Q1. (a) (b) (c) (d) (e) (f) Part – A (Answer all the questions) Answer the following questions : An azeotropic mixture of two liquids has boiling point lower than either of them when it i) Shows no deviation from Raoult’s law ii) Shows positive deviation from Raoult’s law iii) Shows negative deviation from Raoult’s law iv) Is saturated Which of the following is the most important to separate a mixture of two volatile liquids by distillation? i) Solubility ii) Relative volatile iii) Density difference iv) Selectivity At azeotropic composition of a binary mixture the relative volatility is i) 0 ii) 1 iii) < 1 iv) > 1 Which of the following system is an example of maximum boiling azeotrope at 1 atm? i) Ethanol-water ii) Benzene-ethanol iii) Acetone-chloroform iv) Benzene-toluene Flash distillation operation is suitable for separating components which i) Boil at very close temperature ii) Boil at widely different temperature iii) From minimum boiling azeotrope iv) From maximum boiling azeotrope If q is interpreted to be a fraction of the feed that is liquid,then the slope of the feed line in distillation operation is i) -(1-q)/q ii) -q/(1-q) iii) -q iv) -q/(q-1) (2 x 10)

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(g) (h) (i) (j) Q2. (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) Q3. Q4. The absorption factor is defined as i) The ratio of slope of equilibrium curve to that of operating line ii) The product of the slopes of operating line and the equilibrium curve iii) The ratio of slope of the operating line to that of the equilibrium curve iv) All of these The absorption factor can be increased by i) Increasing both gas flow rate and solvent flow rate ii) Decreasing both gas flow rate and solvent flow rate iii) Decreasing gas flow rate and increasing solvent flow rate iv) Increasing gas flow rate and decreasing solvent flow rate Which of the following is more accurate to determine the number of theoretical stages required for the separation of non-ideal binary system by distillation? i) McCabe-Thiele method ii) Ponchon-Savarit method iii) Both McCabe-Thiele and Ponchon-Savarit methods are equally good iv) None of these At maximum reflux ratio the operating cost of distillation column is i) Maximum ii) Optimum iii) Minimum iv) Infinite Answer the following questions : Differentiate between analytical and graphical method in distillation. How the values of q determine the conditions of feed? Which solvent is used for absorption of H2S from natural gas? What should be the properties of good adsorbent? Differentiate between minimum reflux ratio and optimum reflux ratio. For vacuum operation why packed towers are desirable? Why low viscosity of solvent is preferred for gas absorption? How adsorption is applied to gaseous separation? Differentiate between minimum boiling mixture-azeotrope and maximum boiling mixture azeotrope. Define adsorption with suitable examples. Part – B (Answer any four questions) 100 moles of benzene (A) and toluene (B) mixture containing 60 % mole of benzene is subjected to a differential distillation of atmospheric pressure till the composition of benzene in the residue is 35 %. Calculate the total moles of the mixture distilled. Average relative volatility is 2.50. An ammonia air mixture containing 3% ammonia at 25⁰C and 1atm is to be scrubbed with water in a tower packed in 2.54 cm stoneware Raschig rings. The water and gas rate will be 1500 kg/hr.m2 each. Water and gas are fed at the top and bottom respectively. Assume that the tower operates isothermally at 25⁰C. At this temperature the partial pressure of ammonia (pg) over aqueous solution of ammonia are as follows. pg,mm of Hg 12.0 18.2 31.7 50.0 69.5 Conc.C Kg NH3/100 kg water 2.0 3.0 5.0 7.5 10.0 166. 0 20.0 For the above packing KG α=62.39 kg.mol/hr m3 atm.Using the logarithmic mean driving force,estimate the required height for the absorption of 95% of the ammonia in the entering gas. (2 x 10) (15) (15)

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Q5. (a) (b) How to calculate number of equilibrium stages by McCabe-Thiele’s method? A mixture of benzene and toluene containing 40 mole % of benzene is to be separated to give a product of 90 mole% of benzene at top and a bottom product with not more than 10 mole % benzene. Using an average value of 2.4 for the volatility of benzene relative to toluene, calculate the number of theoretical plates required at total reflux. Also calculate the minimum reflux ratio, if the feed is liquid and at its boiling point. (8) (7) Q6. (a) (b) Write different parts of distillation column with diagram. Describe briefly the adsorption equilibria. (7) (8) Q7. (a) 5000 kg/hr of a SO2–air mixture containing 5% by volume is to be scrubbed with 200000 kg/hr of water in a packed tower.The exit concentration of SO2 is reduced to 0.15 %.The tower operates at 1 atmosphere.The equilibrium relationship is given by Y= 30X where, Y= (8) (b) X= If the packed height of the tower is 420 cm, estimate the height of transfer unit (HTU). Briefly explain the adsorption hysteresis. (7) Q8. A fractionating column operating at 1 atm pressure is supplied at optimum location with a saturated liquid field 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 2.0. Find i) Number of theoretical stages required to give the separation ii) The optimum feed plate location assuming 100 % plate efficiency iii) The heat load in reboiler in kcal /kg mole of bottom product iv) The heat load in the condenser in kcal/ kg mole of overhead product. Relative volatility of product is 2.4. (15) Q9. A mixture of 30 mole % A and 70 mole % B is to be separated in a fractionating column. The concentration of A in the distillate is 92 mole% and 95 % of all products A is in the distillate. The feed if half vapour and the reflux ratio is to be 4. The relative volatility of A to B is 2.0. Calculate the number of theoretical plates in the column and locate the feed plate. (15)

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