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Mechanical Operations problems

  • 1. Actual operating speed of a ball mill may vary from 65 to 80% of the critical speed. Which of the following duties would require the ball mill to be operated at maximum percentage of critical speed?

  • Options
  • A. Wet grinding in low viscous suspension.
  • B. Wet grinding in high viscous suspension.
  • C. Dry grinding of large particles (upto 1.25 cms).
  • D. Dry grindng of large particles in un-baffed mills.
    • Discuss
  • 2. Sphericity of raschig ring (whose length and diameter are equal) is

  • Options
  • A. >1
  • B. <1
  • C. 1
  • D. 2
    • Discuss
  • 3. With increase in the pressure drop across the cake, the specific cake resistance for the compressible sludge

  • Options
  • A. increases
  • B. decreases
  • C. remains constant
  • D. increases linearly
    • Discuss
  • 4. Particle size range in which dust catcher (gravity settling chamber) works most effectively and efficiently is __________ microns.

  • Options
  • A. < 5
  • B. 10 to 25
  • C. < 74
  • D. > 1000
    • Discuss
  • 5. The most efficient equipment for the removal of sub-micronic dust particles from blast furnace gas is the

  • Options
  • A. venturi atomiser
  • B. gravity settling chamber
  • C. electro-static precipitator
  • D. cyclone separator
    • Discuss
  • 6. Xanthates are used in the froth floatation process as a/an

  • Options
  • A. conditioner
  • B. frother
  • C. collector
  • D. activator
    • Discuss
  • 7. A filter press is

  • Options
  • A. a batch filter.
  • B. not suitable, if the liquid is the main product.
  • C. having prohibitively high maintenance cost.
  • D. not suitable for wide range of materials under varying operating conditions of cake thickness and pressure.
    • Discuss
  • 8. The capacity of a gyratory crusher is __________ that of a jaw crusher with the same gape, handling the same feed & for the same product size range.

  • Options
  • A. same as
  • B. 2.5 times
  • C. 5 times
  • D. 10 times
    • Discuss
  • 9. Use of grinding aids results in the

  • Options
  • A. enhanced production rate.
  • B. finer products.
  • C. both (a) & (b).
  • D. neither (a) nor (b).
    • Discuss
  • 10. A __________ employs a set of screen across a flow channel for the separation of dirt/rust from a flowing liquid stream.

  • Options
  • A. thickener
  • B. classifier
  • C. strainer
  • D. clarifier
    • Discuss

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