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Indian Institute of Technology Kharagpur (IIT-K) 2007 B.Tech Chemical Engineering Multiphase aration process - Question Paper

Wednesday, 23 January 2013 11:40Web

Chemical Engineering Department, Indian Institute of Technology Kharagpur

Mid-Autumn Semester Examination for Multiphase Separation Processes (CH34005) Wednesday, 19th September, 2007, 1400-1600 hours (Total Marks = 100) Instructions to examinees:

1.    ALL questions are mandatory.

2.    To-the-point, concise, and brief answers are expected.

3.    Neat and labeled schematic diagrams are ESSENTIAL for ALL answers.

 Q. No. Question Description marks 1. Under what condition are the mass average velocity and molar average velocity of all the components of a mixture are equal? 2 2. Under what conditions does the diffusivity of the component / (Dj,m) in a milticomponent gas mixture remain constant over entire the length of the diffusion path? 2 3. Consider two cases: (i) Diffusion of A through non-diffusing B, and (ii) equimolar counterdiffusion of A and B. The respective fluxes are given by the following equations (in the usual notation): DP p - p (i) N = -AJ AL - R 1 ' (pbl - "J '"("m "J 4 5 D (p - p ) (ii) N = AB V A A1 ' A R 1 L In which of the above two cases is NA larger? Explain logically. 4. Give one example each of: (i) mechanical separation, (ii) diffusional separation. 2 5. Give two salient characteristics each of: (i) purely diffusional mass transfer, (ii) convective mass transfer. 4 6. Derive the basic equation for steady state molecular diffusion through a C . dC constant area in a binarv 2as mixture: n =-im + n j - d . * . - J A ( V A B / AB 6 7. Explain the assumptions involved in the film model derivation of flux. 3 8. D . v Derive the film model equation: N = (<: - ( I. A g \ A, A, Bulk/ 6 9. Write the assumptions involved in the derivation of flux using Higbies penetration theory. 3 <> State the governing equation for the flux using Higbies penetration theory, and explain the three initial + boundary conditions needed for the solution. > 5 11. Qualitatively explain the concept of surface renewal rate in Danckwerts surface renewal theory. 3 12. What is an operating line ? How does it differ from equilibrium line ? 2 For interphase mass transfer, derive the expression:~ = + . K k k 4 13. Qualitatively (in terms of the driving forces) explain the difference between Ky and ky. 2 14. What is an Equilibrium / Ideal / Theoretical stage with respect to interphase mass transfer? 2 15. Explain the term stage efficiency with respect to interphase mass transfer. 3

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 (M6. Explain (physically and mathematically) the term Murphree efficiency with respect to interphase mass transfer. 3 Drine volatility and relative volatility for the case of a 2-component vapour-liquid mixture. Derive the expression for relative volatility fora binary mixture. 4 3 Derive the expression for enthalpy of liquid phase: Hl = Cps Mavecaw (T~Tq) + AH&, using the usual notation. 3 v>' Derive the expression for enthalpy of vapour phase: Hv = y Ma {cpA (T-T0) + >.A} + (l-y)MB {cPB (T-T0) + XB}, using the usual notation. 3 20. Can acetone be removed from its mixture with toluene, Qsing steam distillation ? If YES,'why? If NO, why not ? Physical and mathematical explanation 's expected. 4 Derive the expression for feed line for a distillation column operated at steady state. Explain five different types of feed line for a distillation column operated at steady state. 5 5 .X - [x (l - * ,)] / , K Derive Fenskes equation: n + l = in\ { } /in[a 1, using k (' - d)J/ 1 averdgJ the usual notation. List all the assumptions incurred. 6 23. Qualitatively explain the concept of minimum reflux ratio using: (i) x-y diagram, and (ii) H-x-y diagram. Bring out clearly the relation between H-x-y and x-y diagrams ekemkp, using the usual notation. 4 2 i The oper systems a them as ( stripping, t Y / ( T Y ating line CD and the equilibrium cl re given on the X-Y coordinates in th ) cocurrent absorption, (ii) countercurr (iv) countercurrent stripping. B ( M rve OB for four gas-liquid e following figure. Classify ent absorption, (iii) cocurrent * (b) B / SD Q 4 ) X- ( D NC ___ B A (d) B / \c ( ) X -> o X - i

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