chemical engineering mechanical operations Mcqs
1. Angle of nip of the crushing rolls does not depend upon the_______________?
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A. Product size

B. Feed size

C. Speed of the rolls

D. Diameter of the rolls

2. Which of the following grinding mills has the horizontally arranged rods as the grinding elements thereby delivering more uniform granular products with minimum fines ?
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A. Pebble mill

B. Rod mill

C. Tube mill

D. Compartment mill

3. Flow of filtrate through the cake in a plate and frame filter press is best described by the ______________ equation?
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A. Fannings

B. Hagen-Poiseuilles

C. Kremser

D. Kozeny-Carman
4. Dust collection efficiency of electrostatic precipitator can be as high as 99.9%. Maximum temperature and pressure of dust laden gas that can be cleaned in an electrostatic precipitator is respectively ?
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A. 500C and 50 atm

B. 1000C and 10 atm

C. 200C and 5 atm

D. 1000C and 500 atm

5. Which of the following mechanical conveyors does not come under the division carriers? ?
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A. Belt conveyor

B. Screw conveyor

C. Bucket elevator

D. Apron conveyor

6. Filtrate flow rate in case of a rotary drum vacuum filter (in which Rm < < Rc) is proportional to ____________ and the cycle time (where, ? = filtrate viscosity Rm = filter medium resistance Rc = cake resistance)?
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A. 1/??

B. 1/?2

C. ??

D. 1/?

7. In a size reduction crushing operation, feed size is 300 to 1500 mm while the product size is 100 to 300 mm. This is a case of the ________________ crushing?
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A. Secondary

B. Primary

C. Fine

D. Ultrafine

8. Which of the following is not used as filter aid ?
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A. Diatomaceous earth

B. Asbestos

C. Rice husk

D. Purified wood cellulose

9. Which of the following agitators having a large blade area, rotating at slow speed is used for mixing high viscosity liquids (> 50000 centipoise) ?
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A. Flat blade turbine

B. Helical screw

C. Curved blade turbine

D. Propeller

10. Particle size range in which dust catcher (gravity settling chamber) works most effectively and efficiently is ______________ microns?
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A. 10 to 25

B. < 74

C. < 5

D. > 1000

11. Separation of materials of the same density based on their sizes by using then-different rates of flow is called__________________?
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A. Sorting

B. Elutriation

C. Flocculation

D. Sizing
12. Sphericity of raschig ring (whose length and diameter are equal) is___________________?
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A. < 1

B. 2

C. 1

D. > 1

13. _______________ centrifuge is the most suitable for separation of non-friable crystals?
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A. Tubular bowl

B. Suspended batch basket

C. Disc-bowl

D. Perforated horizontal basket continuous
14. Energy consumed for crushing one ton of material ranges from ______________ kWh?
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A. 4 to 5

B. 0.01 to 0.1

C. 0.5 to 1.5

D. 2 to 3.5

15. Higher is the mesh number, smaller will be the aperture size of the screen. It means that the aperture size of a 200 mesh screen will be smaller than that of 20 mesh screen. This is valid for__________________?
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A. All A., B. and C.

B. British standard screens

C. German standard screens (DIN 1171) etc

D. American standard screens (ASTM and Tyler standard screens)

16. Which of the following gives the crushing energy required to create new surface ?
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A. Rittingers Law

B. None of these

C. Taggarts rule

D. Ficks law

17. The specific surface of spherical particles is proportional to (where, Dp = diameter of particle)?
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A. 1/D2p

B. 1/Dp

C. D2

D. Dp

18. The most suitable filter for the removal of very small amount of precipitate from very large volumes of water is the _____________ filter?
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A. Plate & frame

B. Vacuum

C. Sand

D. Rotary

19. Height of liquid in agitation tank is normally maintained equal to the tank diameter. However, if the tank is too tall and a large liquid hold up is desired, then two or more impellers mounted on the same shaft may be used. The clearance between the tank bottom and the bottom most impeller should be about (where, D = impeller diameter) ?
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A. 2 D

B. D

C. 0.5 D

D. 1.5 D

20. The porosity of a compressible cake is _____________________?
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A. Minimum at the filter medium

B. Same throughout the thickness of cake

C. Maximum at the filter medium

D. Minimum at the upstream face

21. Wheat is ground into flour in a___________________?
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A. Roller crusher

B. Fluid energy mill

C. Hammer crusher

D. Impact mill

22. ____________ conveyor is the most suitable for long distance transportation of cold, nonabrasive granular/irregular shape/fine materials?
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A. Belt

B. Apron

C. Screw

D. Bucket

23. A propeller agitator_______________?
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A. All A., B. and C.

B. Produces mainly axial flow

C. Runs at very slow speed (2 rpm)

D. Is used for mixing high viscosity pastes

24. Which of the following is used for primary crushing of very hard lumpy materials ?
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A. Gyratory crusher

B. Tube mill

C. Toothed roll crusher

D. Ball mill

25. For efficient grinding, ball mills must be operated__________________?
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A. At a speed equal to the critical speed

B. With minimum possible small balls

C. At a speed less than the critical speed

D. At a speed more than the critical speed

26. Sulphuric acid mist is arrested by using a ____________ scrubber?
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A. Co-current

B. Venturi

C. Packed wet

D. Hollow wet

27. Laminar flow region is said to exist during agitation of a liquid in an agitator, when the value of Reynolds number is________________?
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A. < 10

B. < 100

C. > 10

D. > 100

28. For transporting pasty material, one will use a/an__________________?
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A. Bucket elevator

B. Screw conveyor

C. Apron conveyor

D. Belt conveyor

29. Which of the following is a continuous filter ?
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A. Cartridge filter

B. Shell and leaf filter

C. None of these

D. Plate and frame filter

30. Molten ammonium nitrate is mixed with ground limestone in fertilizer plant in a__________________?
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A. Banbury mixer

B. Mixer-extruder

C. Muller mixer

D. Pug mill
31. The process by which fine solids is removed from liquids is termed as _____________________?
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A. Decantation

B. Sedimentation

C. Classification

D. Flocculation

32. Which of the following size reduction equipments employs mainly attrition for ultrafine grinding ?
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A. All A., B. and C.

B. Jet mills

C. Fluid energy mill

D. Micronizer

33. Which of the following oxides is not present in hematite iron ore ?
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A. Manganese oxide

B. Calcium oxide

C. Cobalt oxide

D. Titanium oxide

34. 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, metre.) ?
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A. (1/?). ?(g/r)

B. ?(g/r)

C. (1/2?). ?(g/r)

D. 2?. ?(g/r)

35. Size reduction of moulding powders, waxes, resins & gums are done in a _______________ mill?
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A. Cage

B. Hammer

C. Both A. & B.

D. Neither A. nor B.

36. During agitation of liquids, the_________________?
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A. Froude number is independent for the curves between power number and Reynolds number in

B. er number

C. is dependent on the geometry of the impeller

D. Froude number is used to account for the effect of surface (e.g., the centre vortex) on the

E. fled system

F. Power number becomes independent of impellers Reynolds number at high Reynolds number,

37. General crushing equation is given by d(P/m) = -K (dD? S/D? n S). Bonds crushing law is obtained by solving this equation for n = _____________ and feed of infinite size?
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A. 2

B. 1.5

C. 2.5

D. 1

38. Which of the following must be stored in silos and not in open yard ?
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A. None of these

B. Sand

C. Coke breeze

D. High V.M. bituminous coal
39. Soft & non-abrasive materials can be made into fines by________________________?
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A. Cutting

B. None of these

C. Attrition

D. Compression

40. Which of the following is the most suitable for cleaning of fine coal dust (<0.5 mm) ?
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A. Trough washer

B. Spiral separator

C. Froth floatation

D. Baum jig washer

41. Filtration capacity of a rotary drum vacuum filter depends upon the_______________?
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A. Cake thickness

B. Characteristics of the feed slurry

C. Both A. & B.

D. Neither A. nor B.

42. In continuous filtration (at a constant pressure drop), filtrate flow rate varies inversely as the__________________?
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A. Washing time only

B. Square of the viscosity

C. Filtration time only

D. Square root of the velocity
43. The power number for a stirred tank becomes constant at high Reynolds number. In this limit, the variation of power input with impeller rotational speed (N) is proportional to___________________?
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A. N2

B. N3

C. N1

D. N

44. Pick out the wrong statement ?
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A. versal jaw crushers

B. Operating principles of Dodge and Blake jaw crushers are combined in the working of

C. Cutting machines mainly employ attrition for size reduction of solids

D. er one

E. uction equipments employ

F. There are only four methods namely compression, impact, attrition and cutting, which the size

45. ______________ mill is not a revolving mill ?
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A. Pebble

B. Tube

C. Compartment

D. Cage
46. Which is the most suitable conveyor for transportation of sticky material ?
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A. Pneumatic conveyor

B. Screw conveyor

C. Apron conveyor

D. Belt conveyor

47. Crushing efficiency is the ratio of the ______________________ ?
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A. Energy absorbed by the solid to the surface energy created by crushing

B. Surface energy created by crushing to the energy absorbed by the solid

C. Energy fed to the machine to the surface energy created by crushing

D. Energy absorbed by the solid to that fed to the machine

48. Fluid energy mill comes in the category of________________?
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A. Cutter

B. Grinder

C. Ultrafine grinder

D. Crusher

49. The most suitable equipment for removing the fine dust particle (< 1 micron dia.) from air below its dew point will be a/an______________?
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A. Cyclone separator

B. Electrostatic precipitator

C. Wet scrubber

D. Bag filter

50. Raw materials are charged in the iron blast furnace using____________________?
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A. Skip hoist

B. Bucket elevator

C. None of these

D. Screw conveyor