Mechanical Operations of Chemical Engineering Questions Answers - Set 08 - ObjectiveBooks

Mechanical Operations of Chemical Engineering Questions Answers - Set 08

Practice Test: Question Set - 08

1. Use of baffles in agitators help in minimizing the __________ tendency.
    (A) Swirling
    (B) Vortexing
    (C) Both (a) & (b)
    (D) Neither (a) nor (b)

2. A fluid energy mill is used for
    (A) Cutting
    (B) Grinding
    (C) Ultra-grinding
    (D) Crushing

3. Actual operating speed of a ball mill may vary from 65 to 80% of the critical speed. Which of the following duties would require the ball mill to be operated at maximum percentage of critical speed?
    (A) Wet grinding in low viscous suspension
    (B) Wet grinding in high viscous suspension
    (C) Dry grinding of large particles (upto 1.25 cms)
    (D) Dry grinding of large particles in un-baffed mills

4. Reciprocating screens are normally inclined at an angle of 5° with the horizontal and employ gyratory motion at feed end & reciprocating motion at the discharge end. They are not suitable for the screening of the
    (A) Light metal powder down upto 4 mesh size
    (B) Dry chemicals
    (C) Heavy tonnages of rocks or gravel
    (D) Powdered food & granular materials

5. A tube mill compared to a ball mill
    (A) Has a higher length/diameter ratio
    (B) Produces a coarser product
    (C) Has a higher diameter/length ratio
    (D) Uses much larger balls

6. Gravity stamp mill is meant for the __________ crushing.
    (A) Primary
    (B) Intermediate
    (C) Fine
    (D) Ultrafine

7. Pick out the correct statement.
    (A) The capacity and the effectiveness of a screen are the same
    (B) The capacity and the effectiveness of screen are opposing factors
    (C) The screening surface of a 'reel' (a revolving screen used in flour mills) is made of silk bolting cloth supported by wire mesh
    (D) Both (b) and (c)

8. For spheres, the surface shape factor is given by (where, A = area, V = volume, and D = diameter)
    (A) π = (A/D2)
    (B) π/6 = (V/D3)
    (C) AD/V
    (D) None of these

9. Grizzlies are used for separating __________ solids.
    (A) Coarse
    (B) Fine
    (C) Any size
    (D) None of these

10. __________ mixer is used for devulcanisation of rubber scrap & making water dispersion & rubber solution.
    (A) Tumbler
    (B) Banbury
    (C) Muller
    (D) Ribbon blender

11. In closed circuit grinding as compared to open circuit grinding, the
    (A) Specific surface of product is more
    (B) Product has lesser size uniformity
    (C) Production rate at a given limiting size is lower
    (D) Operation is economical

12. Which of the following is a fine crusher?
    (A) Blake jaw crusher
    (B) Gyratory crusher
    (C) Toothed roll crusher
    (D) Dodge jaw crusher

13. In bag filters, filter fabrics are never made of
    (A) Metallic wire woven mesh
    (B) Polyester fibres
    (C) Cotton fibres
    (D) Nylon fibres

14. Maximum size reduction in a ball mill is done by the, __________ action.
    (A) Attrition
    (B) Compression
    (C) Impact
    (D) Cutting

15. For crushing of solids, the Rittinger's law states that the work required for crushing is proportional to
    (A) The new surface created
    (B) The size reduction ratio
    (C) The change in volume due to crushing
    (D) None of these

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