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  • Question
  • __________ baffles are provided in ball mills.


  • Options
  • A. Horizontal
  • B. No
  • C. Only two
  • D. None of these

  • Correct Answer
  • Horizontal 


  • Mechanical Operations problems


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    • 1. Handling of ashes and similar materials can be done best by a __________ conveyor.

    • Options
    • A. flight
    • B. drag or slat
    • C. belt
    • D. ribbon.
    • Discuss
    • 2. Which of the following must be stored in silos and not in open yard?

    • Options
    • A. Coke breeze
    • B. High V.M. bituminous coal
    • C. Sand
    • D. None of these
    • Discuss
    • 3. The mechanism of size reduction by a hammer mill is by impact and attrition between the

    • Options
    • A. grinding element & the housing.
    • B. feed particles.
    • C. both (a) and (b).
    • D. neither (a) nor (b).
    • Discuss
    • 4. Which of the following is not a wet classifier?

    • Options
    • A. Sharpies supercentrifuge
    • B. Hydrocyclones
    • C. Dorr Oliver rake classifier
    • D. None of these
    • Discuss
    • 5. For raschig rings, the sphericity is

    • Options
    • A. 0.5
    • B. 1
    • C. <1
    • D. 3
    • Discuss
    • 6. In ball mill operation, the feed size (Df in meters) and the ball diameter (Db in metres) are related as ( where, K = grindability constant (varying from 0.9 to 1.4 in increasing order of hard ness))

    • Options
    • A. Db2 = K.Df
    • B. Db = K.Df
    • C. Db3 = K.Df
    • D. Db2 = K.Df2
    • Discuss
    • 7. Grinding characteristic of a material is given by its

    • Options
    • A. HGI
    • B. angle of repose
    • C. shatter index
    • D. abrasion index.
    • Discuss
    • 8. A 30% (by volume) suspension of spherical sand particles in a viscous oil has a hindered settling velocity of 4.44 ?m/s. If the Richardson Zaki hindered settling index is 4.5, then the terminal velocity of a sand grain is

    • Options
    • A. 0.90 ?m/s
    • B. 1 ?m/s
    • C. 22.1 ?m/s
    • D. 0.02 ?m/s
    • Discuss
    • 9. In froth floatation, chemical agent added to cause air adherence is called

    • Options
    • A. collector
    • B. frother
    • C. modifier
    • D. activator
    • Discuss
    • 10. Velocity of a small particle of diameter 'Dp' at a distance 'r' from the rotational axis of a cyclone rotating at an angular speed '?' is given by (the other symbols are as per standard notation)

    • Options
    • A.
    • B.
    • C.
    • D.
    • Discuss


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