chemical engineering mechanical operations Mcqs
51. Sphericity is the ratio of the surface area of a spherical particle having the same volume as the particle to the surface area of the particle. Which of the following has the maximum value of sphericity ?
comments icon0

A. Cube

B. Cylinder (L/D = 1)

C. Sphere

D. Raschig rings

52. Maximum size reduction in a fluid energy mill is achieved by___________________?
comments icon0
A. Interparticle attrition

B. Impact

C. Cutting

D. Compression

53. For raschig rings, the sphericity is_____________________?
comments icon0

A. ?3

B. 0.5

C. < 1

D. 1

54. Trommels are revolving screens which normally operate in the range of _______________ rpm?
comments icon0

A. 1 2

B. 15 20

C. 40 50

D. 60 75

55. For removal of very small amounts of precipitate from large volume of water, the most suitable filter is the ______________ filter?
comments icon0

A. Shell & leaf

B. Rotary vacuum

C. Plate & frame

D. Sand
56. Tube mill compared to ball mill_______________________?
comments icon0

A. Is long in comparison with its diameter

B. Produces finer products

C. All A., B. & C.

D. Uses smaller balls

57. Filter aids like asbestos, kieselguhr, diatomaceous earth etc. are used to increase the porosity of the final filter cake & reducing the cake resistance during filtration. Filter aid is_______________?
comments icon0

A. Added to the feed slurry

B. Pre-coated on the filter medium prior to filtration

C. Separated from the cake by dissolving solids or by burning it off

D. All A, B. & C.
58. Filtration rate through a filter cake is proportional to (where, S = filtering surface R = specific cake resistance ? = viscosity of the filtrate) ?
comments icon0

A. 1/?

B. S

C. All A., B. & C.

D. 1/R

59. To get a fine talc powder from its granules, the equipment used is____________________?
comments icon0

A. Roller crusher

B. Ball mill

C. Gyratory crusher

D. Jaw crusher

60. Kicks law assumes that the energy required for size reduction is proportional to the logarithm of the ratio between the initial and the final diameters. The unit of Kicks constant is_________________?
comments icon0

A. kg/sec

B. kWh/sec. kg

C. kW. sec/kg

D. kWh/kg

61. Which of the following is not categorised as a mechanical operation?
comments icon0

A. Filtration

B. Humidification

C. Agitation

D. Size enlargement

62. Width and speed of a conveyor belt depends upon the ______________ of the material?
comments icon0

A. Lump size

B. Bulk density

C. Both A. & B.

D. Neither A. nor B.

63. In filtration, the use of filter aid helps in__________________?
comments icon0

A. Accelerating the rate of filtration

B. Enhancing the cake porosity in case of a dense impermeable cake

C. Deplugging the filter medium

D. Reducing the filtration pressure

64. The reduction ratio for grinders is defined as (where, Df and Dp are average diameters of feed and product respectively) ?
comments icon0
A. Df/Dp

B. Df Dp

C. Dp/Df

D. None of these

65. Which of the following clay mixing devices is vacuum operated for deairation of clay ?
comments icon0

A. Muller-mixer

B. None of these

C. Pug mill

D. Banbury mixer

66. ____________ mills fall in the category of tumbling mills ?
comments icon0
A. All A., B. & C.

B. Compartment

C. Ball and pebble

D. Rod and tube

67. Toothed roll crushers achieve size reduction by___________________?
comments icon0

A. Tearing (shear) and compression

B. Impact and attrition

C. Both A. & B.

D. Neither A. nor B.

68. For a sphere falling in the constant drag co-efficient regime, its terminal velocity depends on its diameter D. as_________________?
comments icon0

A. 1/d

B. d2

C. d

D. ?d

69. Supporting legs of a plate and frame filter is normally made of________________?
comments icon0
A. Cast iron

B. Stainless steel

C. High speed steel

D. Wooden plank

70. Which of the following is the most suitable filter for separation of abrasive solids suspended in a corrosive liquid ?
comments icon0

A. Plate and frame filter press

B. Vacuum filter

C. Batch basket centrifuge

D. Sand bed filter

71. Power consumption during turbulent flow in agitation tank is proportional to the ______________ of the liquid?
comments icon0
A. Density

B. Viscosity

C. Thermal conductivity

D. Surface tension

72. Critical Speed (Nc) of a ball mill is given by (where R1 and R2 are radii of ball mill and the ball respectively) ?
comments icon0

A. Nc = (1/2?). ?(R1 R2/g)

B. Nc = (1/4?). ?(g/R1 R2)

C. Nc = (1/?). ?(g/R1 R2)

D. Nc = (1/2?). ?(g/R1 R2)
73. Tabling process used for separating two materials of different densities by passing the dilute pulp over a table/deck, which is inclined from the horizontal surface at an angle of about________________?
comments icon0

A. 5 to 10

B. 1 to 2

C. 2 to 5

D. 10 to 15

74. The energy consumed by a ball mill depends on__________________?
comments icon0

A. Its speed

B. Its ball load

C. The density of the material being ground

D. All A., B. and C.
75. General mechanism of size reduction in intermediate and fine grinder is by __________________?
comments icon0

A. Compression

B. Compression and tearing

C. Impact and attrition

D. Cutting action

76. 200 mesh screen means 200 openings per_____________________?
comments icon0

A. cm

B. cm2

C. inch

D. inch2

77. Length/diameter ratio of a ball mill is __________________ ?
comments icon0

A. 1.5

B. 1

C. > 1

D. < 1
78. During the washing of cake_________________?
comments icon0

A. Filter medium resistance increases

B. Cake resistance decreases

C. All the resistances are constant

D. Filter medium resistance decreases

79. Two particles are called to be equal settling, if they are having the same ?
comments icon0
A. Terminal velocities in the same fluid & in the same field of force

B. Specific gravity

C. None of these

D. Size

80. Grinding efficiency of a ball mill is of the order of _______________ percent?
comments icon0

A. 90-95

B. 40-50

C. 75-80

D. 1-5
81. Dispersion of a gas through liquid is done by using a__________________?
comments icon0

A. Kneader

B. None of these

C. Sparger

D. Masticator

82. For coarse reduction of hard solids, use ____________________?
comments icon0

A. Impact

B. Attrition

C. Cutting

D. Compression
83. Screen capacity is expressed in terms of____________________?
comments icon0

A. tons/hr

B. tons/ft2

C. Both A. & B.

D. tons/hr-ft2
84. 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____________________?
comments icon0

A. Differential wettability

B. Density separation

C. Volatile matter content

D. Size

85. Tabular bowl centrifuges as compared to disk bowl centrifuges___________________?
comments icon0

A. Cant be used for separation of fine suspended solids from a liquid

B. Cant be operated under pressure/vacuum

C. Employ bowl of larger diameter

D. Operate at higher speed
86. The capacity of a gyratory crusher is ______________ that of a jaw crusher with the same gape, handling the same feed & for the same product size range.?
comments icon0

A. 5 times

B. Same as

C. 2.5 times

D. 10 times

87. A straight line is obtained on plotting reciprocal of filtration rate vs. the volume of filtrate for _______________ flow of filtrate?
comments icon0

A. Compressible cake and turbulent

B. Incompressible cake and laminar

C. Incompressible cake and turbulent

D. Compressible cakes and laminar

88. Rittingers crushing law states that_____________________?
comments icon0
A. Work required in crushing is proportional to the new surface created

B. face to volume ratio of the product

C. For a given machine and feed, crushing efficiency is dependent on the size of the feed &

D. Work required to form a particle of any size is proportional to the square of the surface to

E. Work required to form a particle of a particular size is proportional to the square root of the

F. duct

89. _______________ mixer is used for devulcanisation of rubber scrap & making water dispersion & rubber solution?
comments icon0

A. Tumbler

B. Banbury

C. Muller

D. Ribbon blender

90. The ratio of the actual mesh dimension of Taylor series to that of the next smaller screen is_______________?
comments icon0

A. 1.5

B. 2

C. ?2

D. ?3

91. Which of the following may prove unsuitable for filtering volatile liquids ?
comments icon0

A. Gravity filter

B. Centrifugal filter

C. Pressure filter

D. Vacuum filter
92. Shell and leaf filter as compared to plate and frame filter _____________________?
comments icon0

A. Entails less labor cost

B. All A., B. & C.

C. Provides more effective washing

D. Facilitates filtration under higher pressure

93. Ultra centrifuges are used for the separation of _____________ solid particles?
comments icon0

A. Fine

B. Colloidal

C. Coarse

D. Dissolved

94. Ribbon blenders are exclusively meant for __________________?
comments icon0

A. Continuous mixing

B. Blending miscible liquids

C. Bath mixing

D. Non-flowing powder and thin pastes
95. The critical speed of a trommel (N) is related to its dia D. as _____________________?
comments icon0

A. N ? ?D

B. N ? 1/D

C. N ? 1/?D

D. N ? D

96. Dry powdery solid materials are transported by a ______________ conveyor?
comments icon0

A. Belt

B. Screw

C. Bucket

D. None of these

97. Percentage of drum submerged in the slurry in case of rotary drum filter is ________________?
comments icon0

A. 25

B. 85

C. 30

D. 3

98. With increase in drum speed, in a rotary drum filter, the filtration rate_______________?
comments icon0

A. Is not affected

B. Increases

C. Decreases

D. Increases linearly

99. Which of the following comes in the category of primary crusher for hard and tough stone ?
comments icon0

A. Cone crusher

B. None of these

C. Jaw crusher

D. Gyratory crusher

100. Which one is a filter aid ?
comments icon0

A. Calcined lime

B. None of these

C. Canvas fabric

D. Diatomaceous earth