Mechanical Operations for Chemical Engineers Book pdf Questions - Set 06 - ObjectiveBooks

Mechanical Operations for Chemical Engineers Book pdf Questions - Set 06

Practice Test: Question Set - 06

1. Gyratory crushers compared to the reciprocating jaw crushers
    (A) Have greater capacity per unit of discharge area
    (B) Crush intermittently
    (C) Are less suitable for coarse materials
    (D) Have less steady power consumption

2. Crushing efficiency is the ratio of the
    (A) Surface energy created by crushing to the energy absorbed by the solid
    (B) Energy absorbed by the solid to that fed to the machine
    (C) Energy fed to the machine to the surface energy created by crushing
    (D) Energy absorbed by the solid to the surface energy created by crushing

3. Pick out the wrong statement.
    (A) More commonly used jaw crusher between Dodge jaw crusher and Blake jaw crusher is the later one
    (B) There are only four methods namely compression, impact, attrition and cutting, which the size reduction equipments employ
    (C) Cutting machines mainly employ 'attrition' for size reduction of solids
    (D) Operating principles of Dodge and Blake jaw crushers are combined in the working of universal jaw crushers

4. Screen capacity is expressed in terms of
    (A) tons/hr
    (B) tons/ft2
    (C) Both (a) & (b)
    (D) tons/hr-ft2

5. Size reduction of ice and gypsum can be accomplished suitably by a __________ crusher.
    (A) Blake jaw
    (B) Toothed roll
    (C) Gyratory
    (D) None of these

6. General mechanism of size reduction in intermediate and fine grinder is by
    (A) Cutting action
    (B) Compression
    (C) Compression and tearing
    (D) Impact and attrition

7. __________ are used for the separation of coarse particles from a slurry of fine particles.
    (A) Thickeners
    (B) Classifiers
    (C) Hydrocyclones
    (D) Decanters

8. In a size reduction crushing operation, feed size is 100 to 300 mm. while the product size is 10 to 50 mm. This is a case of the __________ crushing.
    (A) Primary
    (B) Secondary
    (C) Fine
    (D) Ultrafine

9. Use of grinding aids results in the
    (A) Enhanced production rate
    (B) Finer products
    (C) Both (a) & (b)
    (D) Neither (a) nor (b)

10. Percentage of drum submerged in the slurry in case of rotary drum filter is
    (A) 3
    (B) 30
    (C) 85
    (D) 25

11. In a ball mill, the volume occupied by the balls (when the mill is stopped) is about __________ percent of the volume of the mill.
    (A) 35
    (B) 50
    (C) 70
    (D) 85

12. Where the density difference of the two liquid phase to be separated is very small (as in milk cream separator), the most suitable separator is a
    (A) Disc bowl centrifuge
    (B) Sharpies super-centrifuge
    (C) Batch basket centrifuge
    (D) Sparkler filter

13. Washability curve based on float and sink test enables an assessment to be made of the possibility of cleaning a coal fraction based on the
    (A) Density separation
    (B) Differential wettability
    (C) Size
    (D) Volatile matter content

14. The optimum moisture content in solids to be crushed/ground ranges from __________ percent.
    (A) 3 to 4
    (B) 8 to 10
    (C) 10 to 15
    (D) 15 to 20

15. Critical speed of rotation, N (in rps - rotation per second) of a trammel is equal to (where, g = acceleration due to gravity = 9.81 m/sec2 and, r = radius of trammel, meter.)
    (A) (1/2π). √(g/r)
    (B) (1/π). √(g/r)
    (C) ½ √(g/r)
    (D) 2π. √(g/r)

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