CHEMICAL ENGINEERING ::
MECHANICAL OPERATIONS (SECTION
1-3) QUESTIONS AND VERIFIED
ANSWERS|100% CORRECT|GRADE A+
1. Short distance transportation of grain, gravel, sand, ash, asphalt etc. is done by using a __________
conveyor.
A. flight
B. slat or drag
C. ribbon
D. screw - ANSWER D
2. Equivalent diameter of a particle is the diameter of the sphere having the same
A. ratio of surface to volume as the actual volume.
B. ratio of volume to surface as the particle.
C. volume as the particle.
D. none of these. - ANSWER A
3. 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/dp sp
B. Φs = Vp/dp sp
C. Φs = 6 dp Sp/Vp
D. Φs = dp Sp/Vp - ANSWER A
4. 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 - ANSWER C
5. Pick out the wrong statement.
A. Recycled coarse material to the grinder by a classifier is termed as circulating load.
B. Wear and tear in wet crushing is more than that in dry crushing of materials.
C. Size enlargement (opposite of size reduction) is not a mechanical operation.
D. A 'dust catcher' is simply an enlargement in a pipeline which permits the solids to settle down due to
reduction in velocity of the dust laden gas. - ANSWER C
6. In continuous filtration (at a constant pressure drop), filtrate flow rate varies inversely as the
A. square root of the velocity.
B. square of the viscosity.
C. filtration time only.
D. washing time only. - ANSWER A
7. For sizing of fine materials, the most suitable equipment is a
A. trommel
B. grizzly
C. shaking screen
D. vibrating screen - ANSWER D
8.
Which of the following is not categorised as a "mechanical operation" ?
A. Agitation
B. Filtration
C. Size enlargement
D. Humidification - ANSWER D
9. Which of the following is a pressure filter ?
,A. Leaf filter (Moore filter).
B. Plate and flame filter.
C. Rotary drum filter.
D. Sand filter. - ANSWER B
10. Tabular bowl centrifuges as compared to disk bowl centrifuges
A. operate at higher speed.
B. employ bowl of larger diameter.
C. can not be operated under pressure/vacuum.
D. can't be used for separation of fine suspended solids from a liquid. - ANSWER A
11. Pebble mills are tumbling mills widely used for grinding in the manufacture of paints & pigments and
cosmetic industries, where iron contamination in the product is highly objectionable. Pebbles used in
pebble mill are made of
A. bronze
B. stainless steel
C. flint or porcelain
D. concrete - ANSWER C
12. Filter aids like asbestos, kieselguhr, diatomaceous earth etc. are used to increase the porosity of the
final filter cake & reducing the cake resistance during filtration. Filter aid is
A. added to the feed slurry.
B. precoated on the filter medium prior to filtration.
C. separated from the cake by dissolving solids or by burning it off.
D. all 'a', 'b'&'c'. - ANSWER D
13.
Which of the following relationships between co-efficinet of friction (μ) between rock & roll and a (half
of the angle of nip) of the particle to be crushed is correct ?
A. μ > tan α
, B. μ ≥ tan α
C. μ > tan 2α
D. μ ≤ tan α - ANSWER B
14. Pick out the wrong statement pertaining to the roll crushers.
A. Maximum feed size determines the required roll diameter.
B. For hard material's crushing, the reduction ratio should not exceed 4.
C. Both the rolls run necessarily at the same speed.
D. Reduction ratio and differential roll speed affect production rate & energy consumed per unit of
surface produced. - ANSWER C
15. Which of the following is not an ultrafine grinder (colloid mill)?
A. Micronizers
B. Agitated mills and fluid energy mills
C. Toothed roll crusher
D. Hammer mills with internal classification - ANSWER C
16. Two particles are called to be equal settling, if they are having the same.
A. size.
B. specific gravity.
C. terminal velocities in the same fluid & in the same field of force.
D. none of these. - ANSWER C
17. Which of the following is the most suitable for handling fibrous and dense slurries ?
A. Propeller agitator
B. Cone type agitator
C. Turbine agitator
D. Radial propeller agitator - ANSWER B
MECHANICAL OPERATIONS (SECTION
1-3) QUESTIONS AND VERIFIED
ANSWERS|100% CORRECT|GRADE A+
1. Short distance transportation of grain, gravel, sand, ash, asphalt etc. is done by using a __________
conveyor.
A. flight
B. slat or drag
C. ribbon
D. screw - ANSWER D
2. Equivalent diameter of a particle is the diameter of the sphere having the same
A. ratio of surface to volume as the actual volume.
B. ratio of volume to surface as the particle.
C. volume as the particle.
D. none of these. - ANSWER A
3. 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/dp sp
B. Φs = Vp/dp sp
C. Φs = 6 dp Sp/Vp
D. Φs = dp Sp/Vp - ANSWER A
4. 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 - ANSWER C
5. Pick out the wrong statement.
A. Recycled coarse material to the grinder by a classifier is termed as circulating load.
B. Wear and tear in wet crushing is more than that in dry crushing of materials.
C. Size enlargement (opposite of size reduction) is not a mechanical operation.
D. A 'dust catcher' is simply an enlargement in a pipeline which permits the solids to settle down due to
reduction in velocity of the dust laden gas. - ANSWER C
6. In continuous filtration (at a constant pressure drop), filtrate flow rate varies inversely as the
A. square root of the velocity.
B. square of the viscosity.
C. filtration time only.
D. washing time only. - ANSWER A
7. For sizing of fine materials, the most suitable equipment is a
A. trommel
B. grizzly
C. shaking screen
D. vibrating screen - ANSWER D
8.
Which of the following is not categorised as a "mechanical operation" ?
A. Agitation
B. Filtration
C. Size enlargement
D. Humidification - ANSWER D
9. Which of the following is a pressure filter ?
,A. Leaf filter (Moore filter).
B. Plate and flame filter.
C. Rotary drum filter.
D. Sand filter. - ANSWER B
10. Tabular bowl centrifuges as compared to disk bowl centrifuges
A. operate at higher speed.
B. employ bowl of larger diameter.
C. can not be operated under pressure/vacuum.
D. can't be used for separation of fine suspended solids from a liquid. - ANSWER A
11. Pebble mills are tumbling mills widely used for grinding in the manufacture of paints & pigments and
cosmetic industries, where iron contamination in the product is highly objectionable. Pebbles used in
pebble mill are made of
A. bronze
B. stainless steel
C. flint or porcelain
D. concrete - ANSWER C
12. Filter aids like asbestos, kieselguhr, diatomaceous earth etc. are used to increase the porosity of the
final filter cake & reducing the cake resistance during filtration. Filter aid is
A. added to the feed slurry.
B. precoated on the filter medium prior to filtration.
C. separated from the cake by dissolving solids or by burning it off.
D. all 'a', 'b'&'c'. - ANSWER D
13.
Which of the following relationships between co-efficinet of friction (μ) between rock & roll and a (half
of the angle of nip) of the particle to be crushed is correct ?
A. μ > tan α
, B. μ ≥ tan α
C. μ > tan 2α
D. μ ≤ tan α - ANSWER B
14. Pick out the wrong statement pertaining to the roll crushers.
A. Maximum feed size determines the required roll diameter.
B. For hard material's crushing, the reduction ratio should not exceed 4.
C. Both the rolls run necessarily at the same speed.
D. Reduction ratio and differential roll speed affect production rate & energy consumed per unit of
surface produced. - ANSWER C
15. Which of the following is not an ultrafine grinder (colloid mill)?
A. Micronizers
B. Agitated mills and fluid energy mills
C. Toothed roll crusher
D. Hammer mills with internal classification - ANSWER C
16. Two particles are called to be equal settling, if they are having the same.
A. size.
B. specific gravity.
C. terminal velocities in the same fluid & in the same field of force.
D. none of these. - ANSWER C
17. Which of the following is the most suitable for handling fibrous and dense slurries ?
A. Propeller agitator
B. Cone type agitator
C. Turbine agitator
D. Radial propeller agitator - ANSWER B
