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- Question
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
- Correct Answer
- 1-5
- 1. 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
- 2. 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
- 3. Sphericity of pulverised coal is
Options- A. 1
- B. <1
- C. >1
- D. ? Discuss
- 4. The important dimensional group involved in the power requirement calculation in mixing operation is the __________ number.
Options- A. Reynold's
- B. Froude
- C. both (a) & (b)
- D. neither (a) nor (b) Discuss
- 5. At low Reynold's number, the power (P) required for agitating a fluid in a stirred tank becomes independent of inertial forces. In this limit, indicate which of the following relations is satisfied:
Po = ?/?N3 D5 : Power number
Re = ? N D2/?: Reynold's number
N is the impeller rotational speed, and D is the impeller diameter.
Options- A. Po ? Re-1.0
- B. Po ? Re0.0
- C. Po ? Re0.5
- D. Po ? Re1.0 Discuss
- 6. 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
- 7. 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. Discuss
- 8. 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
- 9. 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
- 10. 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
Mechanical Operations problems
Search Results
Correct Answer: 230
Correct Answer: d2
Correct Answer: <1
Correct Answer: both (a) & (b)
Correct Answer: Po ? Re0.0
Correct Answer: both (a) & (b).
Correct Answer: at a speed less than the critical speed.
Correct Answer:
Correct Answer: 1.34 Wi
Correct Answer: 1000°C and 10 atm.
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