Discussion
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- Question
For efficient grinding, ball mills must be operated
Options- A. at a speed less than the critical speed.
- B. at a speed more than the critical speed.
- C. at a speed equal to the critical speed.
- D. with minimum possible small balls.
- Correct Answer
- at a speed less than the critical speed.
- 1. Filtration capacity of a rotary drum vacuum filter depends upon the
Options- A. cake thickness.
- B. characteristics of the feed slurry.
- C. both (a) & (b).
- D. neither (a) nor (b). Discuss
- 2. Grinding efficiency of a ball mill is of the order of __________ percent.
Options- A. 1-5
- B. 40-50
- C. 75-80
- D. 90-95 Discuss
- 3. For a cyclone of diameter 0.2 m with a tangential velocity of 15 m/s at the wall, the separation factor is
Options- A. 2250
- B. 1125
- C. 460
- D. 230 Discuss
- 4. For a sphere falling in the constant drag co-efficient regime, its terminal velocity depends on its diameter (d) as
Options- A. d
- B. d
- C. d2
- D. 1/d Discuss
- 5. Sphericity of pulverised coal is
Options- A. 1
- B. <1
- C. >1
- D. ? Discuss
- 6. About 2-3 hp, power per gallon of a thin liquid provides vigrous agitation in an agitator. 'Power number' in agitation is given by
Options- A.
- B.
- C.
- D.
Discuss
- 7. 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
Options- A. 0.5 Wi
- B. Wi
- C. 1.34 Wi
- D. 3.34 Wi Discuss
- 8. Dust collection efficiency of electrostatic precipitator can be as high as 99.9%. Maximum temperature and pressure of dust laden gas that can be cleaned in an electrostatic precipitator is respectively.
Options- A. 200°C and 5 atm.
- B. 1000°C and 10 atm.
- C. 500°C and 50 atm.
- D. 1000°C and 500 atm. Discuss
- 9. In screen analysis, the notation +5 mm/-10 mm means particles passing through
Options- A. 10 mm screen and retained on 5 mm screen.
- B. 5 mm screen and retained on 10 mm screen.
- C. both 5 mm and 10 mm screens.
- D. neither 5 mm nor 10 mm screen. Discuss
- 10. For the preliminary breaking of hard rock, we use a
Options- A. gyratory crusher
- B. ball mill
- C. tube mill
- D. squirrel-cage disintegrator Discuss
Mechanical Operations problems
Search Results
Correct Answer: both (a) & (b).
Correct Answer: 1-5
Correct Answer: 230
Correct Answer: d2
Correct Answer: <1
Correct Answer:
Correct Answer: 1.34 Wi
Correct Answer: 1000°C and 10 atm.
Correct Answer: 10 mm screen and retained on 5 mm screen.
Correct Answer: gyratory crusher
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