Chemical Engineering - Mechanical Operations

1. 

With increase in the capacity of screens, the screen effectiveness

A. remains unchanged
B. increases
C. decreases
D. decreases exponentially

Answer: Option C

Explanation:

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2. 

As particle size is reduced

A. screening becomes progressively more difficult.
B. screening becomes progressively easier.
C. capacity and effectiveness of the screen is increased.
D. none of these.

Answer: Option A

Explanation:

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3. 

Rittinger number which designates the new surface prduced per unit of mechanical energy absorbed by the material being crushed, depends on the

A. state or manner of application of the crushing force.
B. ultimate strength of the material.
C. elastic constant of the material.
D. all (a), (b) and (c).

Answer: Option D

Explanation:

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4. 

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.

A. 200°C and 5 atm.
B. 1000°C and 10 atm.
C. 500°C and 50 atm.
D. 1000°C and 500 atm.

Answer: Option B

Explanation:

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5. 

For efficient grinding, ball mills must be operated

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.

Answer: Option A

Explanation:

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