Absorption

  1. What do you understand by 'liquid film controlling' in gas absorption? Suggest methods of increasing the rate of transfer for this condition.
  2. Derive Kremser-Brown-Souders equation for the calculation of number of theoretical stages for absorption in a stagewise contact tower.
  3. Compare the performance of bubble-cap column, sieve-tray column and packed bed column. Discuss in detail the operation of any column.
  4. When are the concepts of HETP and HTU used? What is the difference between the two? Drawing an equilibrium diagram, indicate clearly the two concepts.
  5. Illustrate the significance of operating line and equilibrium line for a steady state counter-current process.
  6. Discuss briefly the 'flooding' and 'loading' conditions in a packed tower stating the factors which influence them.
  7. Discuss briefly the important design and operational aspects of
      1. bubble cap column and
      2. sieve tray tower.

  8. Define absorption factor. Indicate its physical significance and uses in the design of absorbers.
  9. Discuss the use of Murphree efficiency for the design of an absorber.
  10. Discuss briefly how the minimum solvent requirement in counter-current gas absorption may be determined.
  11. What is flooding velocity? What role does it play in the design of absorption column?
  12. Specify the important properties a packing material should possess for being used in a mass transfer equipment. Name a few packing materials.
  13. How do you express the efficiency of an absorption plate and an absorption column. Give an idea of an ideal plate.
  14. Indicate the methods used for the design of absorption towers for absorption with chemical reaction. Explain the type of data needed in the design and how this data is obtained.
  15. Adsorption

  16. Compare the several adsorption isotherm you know of and discuss their importance in adsorption steps in a chemical engineering operation.
  17. Draw the break-through curve for an adiabatic batch adsorption bed. Discuss the main features.
  18. What are the characteristics to be possessed by industrial adsorbents? What are the commonly used adsorbents?
  19. Extraction

  20. Discuss the factors which govern the selection of solvents to be used for liquid-liquid extractions.
  21. Write in short the procedure to determine the number of theoretical stages for counter-current multistage extraction.
  22. Leaching

  23. Discuss briefly the typical equilibrium diagrams in leaching
  24. Explain the graphical method of determining the number of theoretical stages in a multistage counter-current leaching.
  25. Distillation

  26. Explain entrainment, foaming, coning and limiting vapor velocity in distillation.
  27. What is flash vaporization? Obtain relationship for liquid to vapor product ratio in terms of enthalpies of different streams.
  28. Derive Rayleigh's equation for differential distillation.
  29. State with reasons whether the following statements are correct or not, give appropriate equations wherever possible.
      1. Rault's law applies to the solute and Henry's law applies to the solvent.
      2. In a rectification column, the heat requirement in the re-boiler gets fixed if the reflux ratio is fixed.
      3. Murphree plate efficiency can be above 100%.

  30. Why the reflux is used and how does it affect the size of the distillation tower?
  31. Explain, with necessary equations, the utility of Ponchon-Savarit method of determining the number of ideal plates in a fractionating column. How is the McCabe-Thiele method a simplification of this?
  32. Indicate how the use of the enthalpy-composition diagram and McCabe-Thiele diagram could be utilized for the design of distillation columns. Specify the application of each method. Explain by means of both the methods to determine:
      1. minimum reflux
      2. the number of plates at total reflux and the
      3. location of the correct feed plate in the fractionation of liquid mixture in a bubble plate column using open steam.

  33. When is distillation by steam used? Explain with necessary expressions, the effect of using vacuum in steam consumption in such an operation.
  34. Discuss the principles, operation and industrial applications of the following giving examples.
      1. Azeotropic distillation
      2. Extractive distillation
      3. Molecular distillation