Mechanical Operations Processes in Chemical Test - Set 18 - ObjectiveBooks

Mechanical Operations Processes in Chemical Test - Set 18

Practice Test: Question Set - 18

1. Specific surface area is the surface area of a unit __________ of materials.
    (A) Weight
    (B) Volume
    (C) Either (a) or (b)
    (D) Neither (a) nor (b)

2. The cumulative mass fraction of particles smaller than size dj for a collection of Ni particles of diameter di and mass mi (i = 1, 2, 3, ...... ∞) is given by

3. Ultrafine grinders operate principally by
    (A) Slow compression
    (B) Impact
    (C) Attrition
    (D) Cutting action

4. Separation of a suspension or slurry into a supernatant clear liquid (free from particles) and a thick sludge containing a high concentration of solid is called
    (A) Classification
    (B) Sedimentation
    (C) Clarification
    (D) Decantation

5. Sauter mean diameter is the same as the __________ mean diameter.
    (A) Mass
    (B) Arithmetic
    (C) Volume-surface
    (D) Geometric

6. If a force greater than that of gravity is used to separate solids & fluids of different densities, the process is termed as the
    (A) Sedimentation
    (B) Flocculation
    (C) Dispersion
    (D) Centrifugation

7. Rod mills employed for grinding
    (A) Employ a steel shell having L/D ratio of 1.5 to 3.0
    (B) Is useful for handling sticky materials
    (C) Employ steel rods of 2-12 cms diameter extending over full length of the mill
    (D) All 'a', 'b' & 'c'

8. In ball mill operation, the feed size (Df in meters) and the ball diameter (Db in metres) are related as (where, K = grindability constant (varying from 0.9 to 1.4 in increasing order of hardness))
    (A) Db2 = K.Df
    (B) Db = K.Df
    (C) Db3 = K.Df
    (D) Db2 = K.Df2

9. The ratio of the actual mesh dimension of Taylor series to that of the next smaller screen is
    (A) 2
    (B) √2
    (C) 1.5
    (D) √3

10. Crushing efficiency of a machine ranges between __________ percent.
    (A) 0.1 to 2
    (B) 5 to 10
    (C) 20 to 25
    (D) 50 to 70

11. The energy consumed by a ball mill depends on
    (A) Its speed
    (B) Its ball load
    (C) The density of the material being ground
    (D) All (a), (b) and (c)

12. Pick out the correct statement:
    (A) Removal of iron from ceramic material is necessitated (by magnetic separation method) so as to avoid discolouration of ceramic products
    (B) The operating cost of shaking screen is more than that of a vibrating screen
    (C) Screen capacity does not depend upon the specific gravity of the minerals
    (D) Asphalt is best crushed using toothed roll crusher

13. Size reduction of asbestos and mica is done by
    (A) Hammer mills
    (B) Rod mills
    (C) Gyratory crushers
    (D) Crushing rolls

14. __________ baffles are provided in ball mills.
    (A) Horizontal
    (B) No
    (C) Only two
    (D) None of these

15. In case of a hammer crusher, the final product size depends on the
    (A) Feed rate
    (B) Rotor speed
    (C) Clearance between hammer & grinding plates
    (D) All (a), (b) and (c)

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