Mechanical Operations for Chemical Engineers ebook MCQ - Set 07 - ObjectiveBooks

Mechanical Operations for Chemical Engineers ebook MCQ - Set 07

Practice Test: Question Set - 07

1. Critical Speed (Nc) of a ball mill is given by (where R1 and R2 are radii of ball mill and the ball respectively).
    (A) Nc = (1/4π). √(g/R1 - R2)
    (B) Nc = (1/2π). √(g/R1 - R2)
    (C) Nc = (1/π). √(g/R1 - R2)
    (D) Nc = (1/2π). √(R1 - R2/g)

2. General crushing equation is given by d(P/m) = -K (dS/D̅nS). Bond's crushing law is obtained by solving this equation for n = __________ and feed of infinite size.
    (A) 1
    (B) 1.5
    (C) 2
    (D) 2.5

3. Ribbon blenders are exclusively meant for
    (A) Blending miscible liquids
    (B) Non-flowing powder and thin pastes
    (C) Bath mixing
    (D) Continuous mixing

4. Removal of activated carbon from glycerine is done by
    (A) Plate and frame filter
    (B) Rotary vacuum filter
    (C) Batch basket centrifuge
    (D) None of these

5. Which of the following size reduction equipments employs mainly attrition for ultrafine grinding?
    (A) Jet mills
    (B) Fluid energy mill
    (C) Micronizer
    (D) All (a), (b) and (c)

6. The most suitable equipment for removing the fine dust particle (< 1 micron dia.) from air below its dew point will be a/an
    (A) Bag filter
    (B) Electrostatic precipitator
    (C) Cyclone separator
    (D) Wet scrubber

7. During agitation of liquids, the
    (A) Froude number is independent for the curves between power number and Reynolds number in baffled system
    (B) Power number becomes independent of impellers Reynolds number at high Reynolds number, but is dependent on the geometry of the impeller
    (C) Froude number is used to account for the effect of surface (e.g., the centre vortex) on the power number
    (D) All (a), (b) and (c)

8. Filtration operation carried out by continuous increase of the inlet pressure of slurry, is called the __________ filtration.
    (A) Constant rate
    (B) Varying pressure
    (C) Varying rate
    (D) Constant pressure

9. Chance process is used for the
    (A) Cleaning of coal
    (B) Concentration of iron ore
    (C) Concentration of pyrites
    (D) Water treatment

10. The important dimensional group involved in the power requirement calculation in mixing operation is the __________ number.
    (A) Reynold's
    (B) Froude
    (C) Both (a) & (b)
    (D) Neither (a) nor (b)

11. The controlling resistance in a rotary drum vacuum filter is the __________ resistance.
    (A) Piping
    (B) Cake
    (C) Filter medium
    (D) None of these

12. Separation of particles of various sizes, shapes and densities by allowing them to settle in a fluid is called
    (A) Classification
    (B) Froth floatation
    (C) Thickening
    (D) Clarification

13. Theoretical capacity of crushing rolls in tons/hr is given by (where, V = peripheral velocity, m/sec. W = width of rolls, m Dr = distance between rolls ρ = density of material to be crushed, kg/m3 here, V =πND where, N = speed of the rolls in rotation per second (rps) D = diameter of rolls, m).
    (A) 3.6 V.W.Dr
    (B) 3.6 V.W. ρ
    (C) 3.6 W.Dr
    (D) 3.6 V.W.Dr

14. Ore concentration by jigging is based on the difference in the __________ of the particles.
    (A) Specific gravities
    (B) Wettability
    (C) Shape
    (D) None of these

15. In a size reduction crushing operation, the feed size is 10 to 50 mm, while the product size is 2 to 10 mm. This is a case of __________ crushing.
    (A) Primary
    (B) Secondary
    (C) Fine
    (D) Ultrafine

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