April 1999

5HB - Mechanical Operations - April 1999

Part A (20 x 2 = 40 Marks)

1. What is a screen?
2. Give the various methods for finding the size distribution of a mixture of particles
3. Define ‘Volumetric mean diameter’ of a particle
4. Increasing the capacity of screen _________ (decreases/increases) the screen effectiveness
5. What is the main difference between tube mill and ball mill?
6. Define ‘Bonds law’ of crushing
7. Give the critical speed of a ball mill
8. Explain crushing efficiency
9. What are flotation agents?
10. Define ‘Hindered settling’
11. Explain the term ‘classification’
12. Differentiate between a thickener and a clarifier
13. Define filtration
14. What is specific cake resistance?
15. Differentiate between incompressible cake and compressible cake
16. Mention some commonly used filter aids
17. Give the purposes of agitation
18. Define power number
19. Name the agitator which is suitable for mixing low viscosity fluids
20. Write the physical significance of Froude’s number in agitation of fluids

    Part B (5 x 12 = 60 Marks)

21. (a) Define sphericity for spherical and non-spherical particles. Critically analyze the differential and cumulative methods of analysis to determine the average particle size

    Or

    (b) (i) What are the various types of industrial screens and how they are employed?

    (ii) Explain the principle of magnetic separation methods

22. (a) State and derive the expression for the three basic laws of size reduction. What is the size range of feed for their applicability?

    Or

    (b) (i) Draw a neat sketch of a smooth roll crusher and explain its operation

    (ii) Derive an expression between particle size, roll dimensions and angle of nip in smooth roll crusher

23. (a) (i) Explain the term ‘Terminal Settling Velocity’ of a particle

    (ii) Derive the equation for the terminal settling velocity of a particle in Stoke’s law and Newton’s law range

    Or

    (b) With a neat sketch, describe the working of a DORR THICKENER

24. (a) (i) With a neat sketch explain the working of a plate and frame filter press

    (ii) Discuss the basic principles in centrifugal filtration

    Or

    (b) Derive an expression for thickness of cake and volume of filtrate for filtration

    1. At constant rate
    2. At constant pressure filtration
25. (a) Discuss the following:
    1. Approximate dimensions of a turbine impeller and baffles used in a batch reactor based on reactor diameter
    2. Power required for impeller mixers

    Or

    (b) (i) Classify mixers for dry powders and state their specific application

    (ii) What are the preventive measures for reducing swirling in agitated tanks?

    (iii) What are the types of mixtures suitable for pastes and plastic masses? Explain any one of them with a neat sketch.