Grinding efficiency of a ball mill is of the order of _______________ percent?

Related Mcqs:

1. For achieving maximum capacity of the ball mill, the ball charge should be equal to about ______________ percent of the ball mill volume?

   A. 10
   B. 25
   C. 50
   D. 75

2. In a ball mill, the volume occupied by the balls (when the mill is stopped) is about _______________ percent of the volume of the mill?

   A. 35
   B. 50
   C. 70
   D. 85

3. A _____________ mill is a revolving mill divided into two or more sections by perforated partitions in which preliminary grinding takes place at one end and the finishing grinding at the discharge end?

   A. Compartment
   B. Tube
   C. Rod
   D. Pebble

4. Critical Speed (Nc) of a ball mill is given by (where R1 and R2 are radii of ball mill and the ball respectively) ?

   A. Nc = (1/4π). √(g/R1 – R2)
   B. Nc = (1/2π). √(g/R1 – R2)
   C. Nc = (1/π). √(g/R1 – R2)
   D. Nc = (1/2π). √(R1 – R2/g)

5. Power required to drive a ball mill with a particular ball load is proportional to (where, D = diameter of ball mill.) ?

   A. D
   B. 1/D
   C. D2.5
   D. 1/D2.5

6. ______________________ balls capable of grinding the feed in a ball mill gives the maximum efficiency ?

   A. Cast iron
   B. Minimum size
   C. Maximum size
   D. Elliptical

7. 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 ?

   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 grinding of large particles in un-baffed mills

8. Wet grinding in a revolving mill ______________ as compared to dry grinding ?

   A. Gives less wear on chamber walls
   B. Requires more energy
   C. Increases capacity
   D. Complicates handling of the product

9. Close circuit grinding by a ball mill with air sweeping employs a _______________________?

   A. Classifier
   B. Cyclone separator between mill & classifier
   C. Both A. & B.
   D. Neither A. nor B.

10. The main differentiation factor between tube mill and ball mill is the ___________________?

    A. Length to diameter ratio
    B. Size of the grinding media
    C. Final product size
    D. Operating speed