The critical speed of a trommel (N) is related to its dia D. as _____________________?

Related Mcqs:

1. Optimum ratio of operating speed to critical speed of a trommel is_____________________?

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

2. 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

3. What is the critical rotation speed in revolutions per second, for a ball mill of 1.2 m diameter charged with 70 mm dia balls ?

   A. 0.5
   B. 1.0
   C. 2.76
   D. 0.66

4. The operating speed of a ball mill should be ______________ the critical speed?

   A. Less than
   B. Much more than
   C. At least equal to
   D. Slightly more than

5. The most suitable equipment for removing the fine dust particle (< 1 micron dia.) from air below its dew point will be a/an______________?

   A. Bag filter
   B. Electrostatic precipitator
   C. Cyclone separator
   D. Wet scrubber

6. Pulverised coal passing through 200 mesh screen has a diameter of 0.074 mm (74 micron). The same passing through 50 mesh screen will have a dia of ____________ mm?

   A. 0.007
   B. 0.30
   C. 50
   D. 0.014

7. Mass flow of granular solid (M) through a circular opening of dia, D follows_____________________?

   A. M ∝ √D
   B. M ∝ D2
   C. M ∝ D3
   D. M ∝ D

8. 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)

9. Critical speed of rotation, N (in rps – rotation per second) of a trammel is equal to (where, g = acceleration due to gravity = 9.81 m/sec2 and, r = radius of trammel, metre.) ?

   A. (1/2π). √(g/r)
   B. (1/π). √(g/r)
   C. ½ √(g/r)
   D. 2π. √(g/r)

10. If dp is the equivalent diameter of a non-spherical particle, Vp its volume and sp its surface area, then its sphericity is φs is defined by________________?

    A. φs = 6 Vp/dpsp
    B. φs = Vp/dpsp
    C. φs = 6 dpSp/Vp
    D. φs = dpSp/Vp