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Chemical Engineering :: Mechanical Operations

  1. rpm of a trommel at critical speed is given by (where, D = Diameter of trommel in ft)

  2. A.
    B.
    C.
    D.
    76.75 D

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  3. Optimum ratio of operating speed to critical speed of a trommel is

  4. A.
    0.33-0.45
    B.
    1.33-1.45
    C.
    0.5-2
    D.
    1.5-2.5

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  5. The process opposite to 'dispersion' is termed as the

  6. A.
    flocculation
    B.
    sedimentation
    C.
    filtration
    D.
    none of these.

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  7. The cake resistance increases steadily with the time of filtration in a plate and frame filter employing constant __________ filtration.

  8. A.
    rate
    B.
    pressure
    C.
    both (a) & (b)
    D.
    neither (a) nor (b)

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  9. Grinding efficiency of a ball mill is of the order of __________ percent.

  10. A.
    1-5
    B.
    40-50
    C.
    75-80
    D.
    90-95

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  11. Solid particles of different densities are separated by

  12. A.
    filters
    B.
    thickness
    C.
    cyclones
    D.
    sorting classifier

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  13. During agitation of liquids, power consumption during laminar flow is not proportional to the

  14. A.
    density of the liquid
    B.
    viscosity of the liquid
    C.
    cube of impeller diameters
    D.
    square of rotational speed.

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  15. Trommels are revolving screens which normally operate in the range of __________ rpm.

  16. A.
    1 - 2
    B.
    15 - 20
    C.
    40 - 50
    D.
    60 - 75

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  17. The value of work index does not change materially from one equipment to another. If the value of work index determined for close circuit grinding is Wi, then the same for open circuit grinding will be

  18. A.
    0.5 Wi
    B.
    Wi
    C.
    1.34 Wi
    D.
    3.34 Wi

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  19. Maximum size reduction in a fluid energy mill is achieved by

  20. A.
    compression
    B.
    interparticle attrition
    C.
    cutting
    D.
    impact

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