Mechanical Operations Flashcards

Concepts and heuristics necessary for unit operations and processes involving solids (or with fluids) requiring mechanical operations.

1
Q

Short distance transportation of grain, gravel, sand, ash, asphalt etc. is done by using a ____ conveyor.

A

screw

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2
Q

Equivalent diameter of a particle is the diameter of the sphere having the same

A

ratio of surface to volume as the actual volume

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3
Q

If dp is the equivalent diameter of a non-spherical particle, Vp its volume and sp its surface area, then its sphericity is Φs is defined by

A

Φs = 6 Vp/dp sp

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4
Q

Power required to drive a ball mill with a particular ball load is proportional to (where, D = diameter of ball mill )

A

D2.5

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5
Q

Pick out the wrong statement.

A

Size enlargement (opposite of size reduction) is not a mechanical operation

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6
Q

In continuous filtration (at a constant pressure drop), filtrate flow rate varies inversely as the

A

square root of the velocity

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7
Q

For sizing of fine materials, the most suitable equipment is a

A

vibrating screen

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8
Q

Which of the following is not categorised as a “mechanical operation” ?

A

Humidification

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9
Q

Which of the following is a pressure filter?

A

Plate and flame filter

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10
Q

Tabular bowl centrifuges as compared to disk bowl centrifuges

A

operate at higher speed

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11
Q

Pebble mills are tumbling mills widely used for grinding in the manufacture of paints & pigments and cosmetic industries, where iron contamination in the product is highly objectionable. Pebbles used in pebble mill are made of

A

flint or porcelain

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12
Q

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

a. added to the feed slurry.
b. precoated on the filter medium prior to filtration.
c. separated from the cake by dissolving solids or by burning it off.

A

all ‘a’, ‘b’&’c’

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13
Q

Which of the following relationships between co-efficinet of friction (μ) between rock & roll and a (half of the angle of nip) of the particle to be crushed is correct?

A

μ ≥ tan α

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14
Q

Pick out the wrong statement pertaining to the roll crushers.

A

Both the rolls run necessarily at the same speed

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15
Q

Which of the following is not an ultrafine grinder (colloid mill)?

A

Toothed roll crusher

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16
Q

Two particles are called to be equal settling, if they are having the same.

A

terminal velocities in the same fluid & in the same field of force

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17
Q

Which of the following is the most suitable for handling fibrous and dense slurries?

A

Cone type agitator

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18
Q

____ centrifuge is normally used in sugar mills.

A

Suspended batch basket

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19
Q

Solid particles separation based on the difference in their flow velocities through fluids is termed as the

A

classification

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20
Q

Diatomaceous earth is a/an

A

filter aid

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21
Q

The distribution given by microscopic analysis of powder is

A

number

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22
Q

Number of particles in a crushed solid sample is given by (where, m = mass of particles in a sample, Vp = volume of one particle, ρ= density of particles)

A

m/ρ . Vp

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23
Q

For a non-spherical particle, the sphericity

A

is defined as the ratio of surface area of a sphere having the same volume as the particle to the actual surface area of the particle

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24
Q

In washing type plate and frame filter press, the ratio of washing rate to the final filtrate rate is

A

1/4

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25
Q

Ball mills and tube mills with flint or porcelain balls are used for size reduction of

A

non-metallic ores

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26
Q

Size reduction of ____ is accomplished in steam heated rollers and roll crushers.

A

hard rubber

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27
Q

The capacity of a belt conveyor depends upon two factors. If one is the cross-section of the load, the other is the ____ of the belt.

A

speed

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28
Q

Which of the following is not a part of the Blake jaw crusher?

A

Hanger

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29
Q

If a force greater than that of gravity is used to separate solids & fluids of different densities, the process is termed as the

A

centrifugation

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30
Q

Filter aid is used to

A

increase the porosity of the cake.

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31
Q

Which of the following mineral dressing operations is termed as ‘comminution’?

a. Panning
b. Spiralling’
c. Tabling

A

None of these

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32
Q

The capacity of a pneumatic conveying system depends upon the

a. bulk density of materials.
b. pressure of the conveying air.
c. diameter of the conveying line.

A

all (a), (b) and (c)

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33
Q

Pick out the wrong statement.

A

The equipment used for the removal of traces of solids from a liquid is called a classifier

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34
Q

Gravity settling process is not involved in the working of a

A

hydrocyclone

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35
Q

Froth floatation is the most suitable for treating

A

sulphide ores

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36
Q

The energy required per unit mass to grind limestone particles of very large size to 100 μm is 12.7 kWh/ton. An estimate (using Bond’s law) of the energy to grind the particles from a very large size to 50 μrn is

A

18 kWh/to

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37
Q

Which of the following is the most suitable for cleaning of fine coal dust (<0.5 mm)?

A

Froth floatation

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38
Q

Pick out the correct statement:

A

The operating cost of shaking screen is more than that of a vibrating screen

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39
Q

Range of compressibility co-efficient of the commercial compressible cake obtained in filtration operation is

A

0.2 to 0.8

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40
Q

Highly viscous liquids & pastes are agitated by

A

multiple blade paddles

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41
Q

The value of ‘angle of nip’ is generally about

A

32°

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42
Q

Size reduction of the ____ can be suitably done by ball mills, crushing rolls and rod mills.

A

metalliferrous ores

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43
Q

Sulphuric acid mist is arrested by using a ____ scrubber.

A

venturi

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44
Q

The main size reduction operation in ultrafine grinders is

A

attrition

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45
Q

In case of a hammer crusher,
a. crushing takes place by impact breaking.
b. maximum acceptable feed size is 30 cms.
c. reduction ratio can be varied by adjusting the distance from cage to hammers.

A

all (a), (b) and (c).

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46
Q

Jigging is a technique by which different particles can be

A

separated by particle size.

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47
Q

Crushing of mineral particles is accomplished in a ‘cage mill’, when one or more alloy steel bars are revolved in opposite directions. It is a type of ____ mill.

A

impact

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48
Q

Balls for ball mills are never made of

A

lead

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49
Q

200 mesh screen means 200 openings per

A

inch

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50
Q

____ is the most commonly used ‘filter aid’.

A

Diatomaceous earth

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51
Q

Energy consumed for crushing one ton of material ranges from ____ kWh.

A

0.5 to 1.5

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52
Q

For transporting pasty material, one will use a/an

A

screw colaveyor

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53
Q

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.

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54
Q

A tube mill compared to a ball mill

A

has a higher length/diameter ratio.

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55
Q

Trommels separate a mixture of particles depending on their

A

size

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56
Q

Basic slag is not ground in

A

jaw crushers

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57
Q

Grindability of a material does not depend upon its

A

size

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58
Q

Shape factor for a cylinder whose length equals its diameter is

A

1.5

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59
Q

In case of a hammer crusher, the

A

rotor shaft carrying hammers can be vertical or horizontal.

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60
Q

Dust laden air can be purified using a

A

cyclone separator

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61
Q

Rittinger’s number designates the new surface created per unit mechanical energy absorbed by the material being crushed. Larger value of Rittinger’s number of a material indicates its

A

easier grindability

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62
Q

Capacity (in tons/hr) of jaw/gyratory crusher is equal to (where, L = length of the receiving opening, cm S = greater width of the discharge opening, cm)

A

0.087 L.S

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63
Q

Vacuum is applied in ____ zone, in case of a general type continuous rotary drum vacuum filter.

a. filtering
b. washing
c. drying

A

all (a), (b) & (c)

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64
Q

General crushing equation is given by https://www.indiabix.com/_files/images/chemical-engineering/mechanical-operations/122-368-1.png . Bond’s crushing law isobtained by solving this equation for n = ____ and feed of infinite size.

A

1.5

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65
Q

Which of the follwoing mechanical conveyors does not come under the division ‘scrapers’ ?

A

Bucket elevators

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66
Q

____ mixer is used for devulcanisation of rubber scrap & making water dispersion & rubber solution.

A

Banbery

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67
Q

Which of the following mechanical conveyors does not come under the division ‘carriers’?

A

Screw conveyor

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68
Q

Screen capacity is not a function of

A

atmospheric humidity

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69
Q

Which of the following is a vacuum filter?

A

Rotary disc filter

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70
Q

Pine oil used in froth floatation technique acts as a/an

A

frother

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71
Q

Length/diameter ratio of a ball mill is

A

< 1

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72
Q

Feed size of ≥ 25 cms can be accepted by

A

jaw crusher

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73
Q

Which is the most suitable conveyor for transportation of sticky material?

A

Screw conveyor

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74
Q

The most suitable equipment for removing the fine dust particle (< 1 micron dia.) from air below its dew point will be a/an

A

electrostatic precipitator

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75
Q

Laminar flow region is said to exist during agitation of a liquid in an agitator, when the value of Reynolds number is

A

<10

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76
Q

Filtration of water in a paper mill is done by a/an ____ filter.

A

open sand

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77
Q

Moore filter is a ____ filter.

A

leaf

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78
Q

Sphericity of a cubical particle, when its equivalent diameter is taken as the height of the cube, is

A

1

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79
Q

Ball mill is used for

A

fine grinding

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80
Q

In case of a ball mill,

A

coarse feed requires a larger ball

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81
Q

Maximum size reduction in a ball mill is done by the, ____ action.

A

impact

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82
Q

Increasing the capacity of a screen ____ the screen effectiveness.

A

decreases.

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83
Q

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

A

N2

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84
Q

Bond crushing law

A

calls for relatively less energy for the smaller product particles, than does the Rittinger law.

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85
Q

Flow of filtrate through the cake in a plate and frame filter press is best described by the ____ equation.

A

Kozney-Karman

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86
Q

The controlling resistance in a rotary drum vacuum filter is the ____ resistance.

A

cake

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87
Q

Which of the following is used for primary crushing of very hard lumpy materials?

A

Gyratory crusher

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88
Q

Coal is finally pulverised to 200 mesh size for burning in boilers by a

A

ball mill

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89
Q

Crushing efficiency is the ratio of the

A

surface energy created by crushing to the energy absorbed by the solid.

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90
Q

The resistance offered by the filter used in a bag filter is proportional to (where, c = dust concentration, and s = particle size )

A

c/s

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91
Q

Cement clinker is reduced to fine size by a

A

tube mill

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92
Q

The crushed material received for separation is called feed or

A

heading

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93
Q

For spheres, volume shape factor is given by

A

π/6(=V/D3)

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94
Q

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

A

Helical screw

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95
Q

____ is defined as the geometric mean of the relative rejections and the relative recoveries of two minerals.

A

Selectivity index

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96
Q

The operating speed of a ball mill should be ____ the critical speed.

A

less than

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97
Q

Use of baffles in agitators help in minimising the ____ tendency.

a. swirling
b. vortexing

A

both (a) & (b)

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98
Q

____ are used for the separation of coarse particles from a slurry of fine particles.

A

Classifiers

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99
Q

Fibrous material is broken by a

A

squirrel-cage disintegrator

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100
Q

____ is the most suitable for compounding rubber and plastic solids.

A

Banbery mixer

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101
Q

Out of the following size reduction equipments, the maximum feed size can be accepted by the

A

jaw crusher

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102
Q

Bucket elevators are not suitable for the vertical lifting of ____ materials.

A

sticky (e.g. clay paste)

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103
Q

The most common filter aid is

A

diatomaceous earth

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104
Q

For removal of very small amounts of precipitate from large volume of water, the most suitable filter is the ____ filter.

A

sand

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105
Q

For separation of sugar solution from settled out mud, we use a ____ filter.

A

centrifugal

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106
Q

The sphericity of a cylinder of 1 mm diameter and length 3 mm is

A

0.9

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107
Q

Pulverised coal passing through 200 mesh screen has a diameter of 0.074 mm (74 micron). The same passing through 50 mesh screen will have a dia of ____ mm.

A

0.3

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108
Q

What is the selectivity index, if the grade of tailings & concentrate is the same?

A

1

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109
Q

The most suitable equipment used to devulcanise rubber scrap and to make water dispersion & rubber solution is a

A

boundary mixer.

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110
Q

Traces of solids are removed from, liquid in a

A

clarifier

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111
Q

_________ balls capable of grinding the feed in a ball mill gives the maximum efficiency.

A

Minimum size

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112
Q

The speed of a rotary drum vacuum filter may be about ____ rpm.

A

1

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113
Q

Colloid mills achieve size reduction mainly by

A

attrition

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114
Q

Mesh indicates the number of holes per

A

linear inch

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115
Q

For achieving maximum capacity of the ball mill, the ball charge should be equal to about ____ percent of the ball mill volume.

A

50

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116
Q

According to Bond crushing law, the work required to form particle of size ‘D’ from very large feed is (where (S/V)p and (S/V)f are surface to volume ratio of the product and feed respectively).

A

sqrt(S/V)p

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117
Q

Which of the following gives the work required for size reduction of coal to -200 mesh in a ball mill most accurately ?

A

Rittinger’s law

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118
Q

Electrical energy consumed by a jaw crusher is not a function of the

A

none of these

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119
Q

Size reduction mechanism used in Jaw crushers is

A

compression

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120
Q

Trommels employ ____ for screening of materials.

A

punched plate

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121
Q

A widely used size reduction equipment for ____ is Bradford breaker.

A

coal

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122
Q

Ultra centrifuges are used for the separation of ____ solid particles.

A

colloidal

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123
Q

Specific surface area is the surface area of a unit ____ of materials.

A

either (a) or (b)

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124
Q

A. ____ mill is a revolving mill divided into two or more sections by perforated partitions in which preliminary grinding takes place at one end and the finishing grinding at the discharge end.

A

compartment

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125
Q

The constants (Kb, Kr and Kk) used in the laws of crushing (i.e., Bond’s law, Rittinger’s law and Kick’s law) depend upon the

a. feed material.
b. type of crushing machine.

A

both (a) & (b).

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126
Q

Size reduction does not occur due to compression in case of

A

rod mills

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127
Q

According to Taggart’s rule for selecting between a gyratory crusher and a jaw crusher; the later should be used, if the hourly tonnage to be crushed divided by the square of the gape expressed in cm is less than

A

0.0184

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128
Q

Which of the following represents the plot of filtrate volume versus time for constant pressure filtration?

A

Parabola

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129
Q

Driving force in case of filtration by a centrifuge is the

A

centrifugal pressure exerted by the liquid.

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130
Q

Rod mills employed for grinding

a. employ a steel shell having L/D ratio of 1.5 to 3.0.
b. is useful for handling sticky materials.
c. employ steel rods of 2-12 cms diameter extending over full length of the mill.

A

all ‘a’, ‘b’ & ‘c’.

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131
Q

Production rate ____ with increased fineness, with a given energy input to the size reduction machine.

A

decreases

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132
Q

Gold ore concentration is mostly done using

A

tabling

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133
Q

Mixing of light fine powder such as insecticides is done by

A

impact wheels

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134
Q

Run of mine (ROM) coal is crushed by a ____ for use in domestic ovens.

A

hammer crusher

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135
Q

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?

A

Sphere

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136
Q

The unit of specific cake resistance is

A

gm/cm2

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137
Q

Size reduction of asbestos and mica is done by

A

hammer mills

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138
Q

A pebble mill
a. is a ball mill.
b. employs flints or ceramic pebbles as the grinding medium
c. is a tube mill lined with ceramic or other non-metallic liner.

A

both (b) and (c).

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139
Q

The study on washability of coal is done by using the ____ technique.

A

heavy media separation

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140
Q

Horsepower required for a roll crusher is directly proportional to its

A

both (a) & (b).

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141
Q

A suspension of glass beads in ethylene glycol has a hindered settling velocity of 1.7 mm/s, while the terminal settling velocity of a single glass bead in ethylene glycol is 17 mm/s. If the Richardson-Zaki hindered settling index is 4.5, the volume fraction of solids in the suspension is

A

0.6

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142
Q

____ conveyor is the most suitable for long distance transportation of cold, non-abrasive granular/irregular shape/fine materials.

A

Belt

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143
Q

The specific cake resistance for compressible sludges is a function of the pressure drop

A

over cake

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144
Q

Moisture can be removed from lubricating oil using

A

tubular centrifuge

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145
Q

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

A

2 to 5

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146
Q

Pick out the wrong statement.

A

Crushing efficiency is the ratio of the energy absorbed by the solid to the surfaces energy created by crushing.

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147
Q

Addition of filter aid to the slurry before filtration is done to …… of the cake.

A

increase the porosity

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148
Q

Which of the following terminology is not used for size reduction of materials to fine sizes or powders?

A

Compression

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149
Q

A tube mill as compared to a ball mill

a. employs smaller balls.
b. gives finer size reduction but consumes more power.
c. has larger length/diameter ratio (>2 as compared to 1 for ball mill).

A

all (a), (b) and (c).

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150
Q

Kick’s 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 Kick’s constant is

A

kW. sec/kg

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151
Q

Which of the following gives the crushing energy required to create new surface?

A

Rittinger’s law

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152
Q

In filtration, the use of ‘filter aid’ helps in

A

deplugging the filter medium.

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153
Q

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 = (1/2π)*sqrt(g/(R1-R2))

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154
Q

Gizzlies are used for separating ____ solids.

A

fine

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155
Q

Which of the following clay mixing devices is vacuum operated for deairation of clay?

A

Pug mil

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156
Q

Pick out the material having minimum Rittinger’s number.

A

Quartz

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157
Q

____ mills are termed as impactors.

A

Hammer

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158
Q

In case of a revolving mill, wet grinding compared to dry grinding

A

none of these.

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159
Q

To get a fine talc powder from its granules, the equipment used is

A

ball mill

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160
Q

For a cyclone of diameter 0.2 m with a tangential velocity of 15 m/s at the wall, the separation factor is

A

230

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161
Q

Width and speed of a conveyor belt depends upon the ____ of the material.

A

both (a) & (b)

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162
Q

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

A

all (a), (b) and (c).

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163
Q

Pick out the wrong statement.

A

Capacity of crusher in choke feeding is increased.

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164
Q

Which of the following size reduction equipments employs mainly attrition for ultrafine grinding?

A

all (a), (b) and (c)

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165
Q

Tank filter (e.g., Nutsch filter) is

A

used for small scale filtration work.

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166
Q

In bag filters, filter fabrics are never made of

A

metallic wire woven mesh

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167
Q

Use of ‘grinding aids’ is done in ____ grinding.

A

dry

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168
Q

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)

A

D

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169
Q

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

A

Vacuum filter

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170
Q

All resistances during washing of cake

A

remain constant

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171
Q

A ____ mixer resembles a ball mill without balls.

A

tumbling

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172
Q

____ conveyor is the most suitable for short distance transportation of non-abrasive loose materials like garbage, grain, food wastes etc.

A

Flight

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173
Q

As the product becomes finer, the energy required for grinding

A

icreases

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174
Q

Gyratory crushers compared to the reciprocating jaw crushers

A

have greater capacity per unit of discharge area.

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175
Q

The important dimensional group involved in the power requirement calculation in mixing operation is the ____ number.

A

both (a) & (b)

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176
Q

At low Reynold’s number, the power (P) required for agitating a fluid in a stirred tank becomes independent of inertial forces. In this limit, indicate which of the following relations is satisfied:
Po = ρ/ρN3 D5 : Power number
Re = ρ N D2/μ: Reynold’s number
N is the impeller rotational speed, and D is the impeller diameter.

A

Po ∝ Re-1.0

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177
Q

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

A

Rod mill

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178
Q

Rittinger’s crushing law states that

A

work required in crushing is proportional to the new surface created.

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179
Q

Mechanical conveyors which push the material along an endless trough or tube are called scrappers. Which of the following conveying equipments comes under the category of ‘scrappers’?

A

Both (b) and (c)

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180
Q

Sphericity of pulverised coal is

A

<1

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181
Q

The reduction ratio for fine grinders is

A

as high as 100

182
Q

Which of the following is the hardest material?

A

Corundum

183
Q

General mechanism of size reduction in intermediate and fine grinder is by

A

impact and attrition.

184
Q

A straight line is obtained on plotting reciprocal of filtration rate vs. the volume of filtrate for ____ flow of filtrate.

A

incompressible cake and laminar

185
Q

The work index in Bond’s law for crushing of solids has the following dimensions

A

kWh/ton

186
Q

Ore concentration by jigging is based on the difference in the ____ of the particles.

A

specific gravities

187
Q

Size measurement of ultrafine particles can be best expressed in terms of

A

surace area per unit mass

188
Q

Reduction ratio of crushers is the

A

ratio of feed opening to discharge opening.

189
Q

Which is a secondary crusher for a hard & tough stone?

A

Cone crusher

190
Q

Which of the following equations is Rittinger’s crushing law ? (where P = power required by the machine, m = feed rate, k = a constant = volume surface mean diameter of feed & product respectively.)

A

P/m = K . (1-Dsb - 1-Dsa)

191
Q

Cyclones are used primarily for separating

A

solids from fluids

192
Q

There is practically no alternative/competitor to ____ in the beneficiation treatment of sulphide ores.

A

froth floatatio

193
Q

Separation of isotopes is generally done using a/an ____ centrifuge.

A

ultra

194
Q

Temperature of the product during ultrafine grinding

A

increases

195
Q

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

heavy tonnages of rocks or gravel.

196
Q

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

50

197
Q

Separation of materials of the same density based on their sizes by using then-different rates of flow is called

A

sizing

198
Q

Molten ammonium nitrate is mixed with ground limestone in fertilizer plant in a

A

pug mill

199
Q

Agglomeration of individual particles into clusters (flocs) is called flocculation. To prevent flocculation, the most commonly used dispersing agents are

A

silicates & phosphates

200
Q

For a sphere falling in the constant drag co-efficient regime, its terminal velocity depends on its diameter (d) as

A

d2

201
Q

With increase in the capacity of screens, the screen effectiveness

A

decreases

202
Q

As particle size is reduced

A

screening becomes progressively more difficult.

203
Q

Rittinger number which designates the new surface prduced per unit of mechanical energy absorbed by the material being crushed, depends on the

A

all (a), (b) and (c).

204
Q

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.

A

1000°C and 10 atm.

205
Q

For efficient grinding, ball mills must be operated

A

at a speed less than the critical speed.

206
Q

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

fine

207
Q

For spheres, the surface shape factor is given by (where, A = area, V = volume, and D = diameter)

A

π(=A/D2)

208
Q

The reduction ratio for grinders is defined as(where, Df and Dp are average diameters of feed and product respectively).

A

Df/Dp

209
Q

Pick out the wrong statement pertaining to the turbine agitator.

A

Pitched blade turbine agitator gives only radial flow with complete absence of the axial flow.

210
Q

A fluid energy mill is used for

A

ultra grinding

211
Q

Which of the following is the softest material ?

A

Talc

212
Q

Dry powdery solid materials are transported by a ____ conveyor.

A

screw

213
Q

Fluid energy mill comes in the category of

A

ultrafine grinder

214
Q

Filtration capacity of a rotary drum vacuum filter depends upon the

A

both (a) & (b).

215
Q

About 2-3 hp, power per gallon of a thin liquid provides vigrous agitation in an agitator. ‘Power number’ in agitation is given by

A

https://www.indiabix.com/_files/images/chemical-engineering/mechanical-operations/118-323-1.png

216
Q

____ conveyors are also called scrapers.

A

both (b) & (c)

217
Q

For laminar flow of filtrate through the cake deposited on septum, which of the following will be valid

A

Kozney-Karman equation

218
Q

Which of the following is a continuous filter?

A

None of these

219
Q

During washing of filter at the end of constant pressure filtration, the rate of washing equals the rate of filtration

A

at the end of filtration.

220
Q

In screen analysis, the notation +5 mm/-10 mm means particles passing through

A

10 mm screen and retained on 5 mm screen.

221
Q

rpm of a trommel at critical speed is given by (where, D = Diameter of trommel in ft)

A

https://www.indiabix.com/_files/images/chemical-engineering/mechanical-operations/123-387-2.png

222
Q

Optimum ratio of operating speed to critical speed of a trommel is

A

0.33-0.45

223
Q

The process opposite to ‘dispersion’ is termed as the

A

flocculation

224
Q

The cake resistance increases steadily with the time of filtration in a plate and frame filter employing constant ____ filtration.

A

both (a) & (b)

225
Q

Grinding efficiency of a ball mill is of the order of ____ percent

A

45296

226
Q

Solid particles of different densities are separated by

A

sorting classifier

227
Q

During agitation of liquids, power consumption during laminar flow is not proportional to the

A

density of the liquid

228
Q

Trommels are revolving screens which normally operate in the range of ____ rpm

A

15 - 20

229
Q

The value of work index does not change materially from one equipment to another. If the value of work index determined for close circuit grinding is Wi, then the same for open circuit grinding will be

A

1.34 Wi

230
Q

Maximum size reduction in a fluid energy mill is achieved by

A

interparticle attritio

231
Q

Filtration rate through a filter cake is proportional to (where, S = filtering surface R= specific cake resistance μ = viscosity of the filtrate)

A

all (a), (b) & (c)

232
Q

A centrifugal filtration unit operating at a rotational speed of w has inner surface of the liquid (density ρL) located at a radial distance R from the axis of rotation. The thickness of the liquid film is δ and no cake is formed. The initial pressure drop during filtration is

A

1-2 w2 . δρL (2R + δ)

233
Q

Which one is a filter aid ?

A

Diatomaceous earth

234
Q

To remove dirt from the flowing fluid, we use a

A

strain

235
Q

Which of the following crushers can be considered as a combination of a jaw crusher and a roller crusher ?

A

Gyratory crusher

236
Q

Separation of solid suspended in liquid into a supernatant clear liquid and a denser slurry employs a process termed as the

A

sedimentation

237
Q

Ultrafine grinders operate principally by

A

attrition

238
Q

Half the angle of nip, (α), for a roll crusher is given by (where, dr, dp and df are diameters of crushing rolls, feed particles and rolls gap respectively).

A

https://www.indiabix.com/_files/images/chemical-engineering/mechanical-operations/105-119-2.png

239
Q

Which of the following comes in the category of primary crusher for hard and tough stone ?

A

Jaw crusher

240
Q

Crushing efficiency of a machine ranges between ____ percent.

A

0.1 to 2

241
Q

Screen capacity is expressed in terms of

A

tons/hr-ft

242
Q

A screen is said to be blinded, when the

A

screen is plugged with solid particles.

243
Q

What is the critical rotation speed in revolutions per second, for a ball mill of 1.2 m diameter charged with 70 mm dia balls

A

0.66

244
Q

Percentage of drum submerged in the slurry in case of rotary drum filter is

A

30

245
Q

Filter medium resistance is that offered by the

A

filter cloth and the embedded particle collectively.

246
Q

In a roll crusher, both the rolls

A

all (a), (b) and (c).

247
Q

Tube mill compared to ball mill

A

all (a), (b) & (c).

248
Q

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. )

A

https://www.indiabix.com/_files/images/chemical-engineering/mechanical-operations/120-344-1.png

249
Q

For the preliminary breaking of hard rock, we use a

A

gyratory crusher

250
Q

Filtration operation carried out by continuous increase of the inlet pressure of slurry, is called the ____ filtration.

A

constant rate

251
Q

Pick out the wrong statement.

A

Cake resistance is independent of the pressure drop.

252
Q

Which of the following oxides is not present in hematite iron ore?

A

Cobalt oxid

253
Q

Ribbon blenders are exclusively meant for

A

non-flowing powder and thin pastes.

254
Q

In closed circuit grinding as compared to open circuit grinding, the

A

operation is economical.

255
Q

Pick out the correct statement

A

A hopper is a small bin with a sloping bottom

256
Q

Gelatinous solid (which plug the septum) can be filtered by a ____ filter.

A

precoat

257
Q

During the washing of cak

A

all the resistances are constant.

258
Q

The opening of a 200 mesh screen (Taylor series) i

A

0.0074 cm

259
Q

A gravity decanter is meant for the separation of two ____ density.

A

immiscible liquids of different

260
Q

The most suitable filter for the removal of very small amount of precipitate from very large volumes of water is the ____ filter.

A

sand

261
Q

Separation of solid particles based on their densities is called

A

sorting

262
Q

Activators are those chemicals which help buoying up one mineral in preference to the other in the froth floatation process. Which of the following is an activator?

A

Copper sulphate

263
Q

____ are mixed using ribbon blenders.

A

Dry powders

264
Q

During agitation of liquids, the

A

all (a), (b) and (c).

265
Q

For crushing of solids, the Rittinger’s law states that the work required for crushing is proportional to

A

the new surface created.

266
Q

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

A

primary

267
Q

As per Taggart’s formula, the capacity (kg/hr) of Jaw & Gyratory crushers (for gapes of 10 to 60 cms) is equal to (where, L = Length of feed opening, cms S = Maximum width of discharge opening, cms )

A

93 LS

268
Q

The process by which fine solids is removed from liquids is termed a

A

sedimentation

269
Q

Which of the following crushing laws is most accurately applicable to the fine grinding of materials ?

A

Rittinger’s law

270
Q

Shell and leaf filter as compared to plate and frame filter

A

all (a), (b) & (c)

271
Q

Metallic wire mesh is used as a filtering medium for the separation of dust from dust laden gas in case of a/an

A

air filter

272
Q

Which of the following is a coarse crusher?

A

Gyratory crusher

273
Q

Sorting classifiers employing differential settling methods for separation of particles make use of the differences in their

A

terminal velocities

274
Q

Separation of particles of various sizes, shapes and densities by allowing them to settle in a fluid is called

A

classification

275
Q

The specific cake resistance for incompressible sludges is (where ΔP = pressure drop over cake)

A

independent of ΔP

276
Q

To produce talcum powder, use

A

ball mill

277
Q

Angle of nip of the crushing rolls does not depend upon the

A

speed of the rolls

278
Q

Paddle agitator

A

is suitable for mixing low viscosity liquids.

279
Q

Pick out the wrong statement.

A

Cutting machines mainly employ ‘attrition’ for size reduction of solids.

280
Q

Gummy & sticky materials like molasses, sugar etc. are best transported/handled by using a ____ conveyor.

A

ribbon

281
Q

Soft & non-abrasive materials can be made into fines by

A

attrition

282
Q

In constant pressure filtration,

A

NAME?

283
Q

The critical speed of a trommel (N) is related to its dia (D) as

A

N ∝ sqrt D

284
Q

Which of the following minerals is not subjected to magnetic separation method?

A

Galena

285
Q

Which of the following is not a revolving/tumbling mill used for size reduction?

A

Cage mil

286
Q

Which of the following achieves the least reduction ratio for a given feed size?

A

Roll crusher

287
Q

A fluid energy mill is used for

A

ultragrinding

288
Q

Filtration should be stopped in a filter press, if the

A

both(b)&(c)

289
Q

For coarse reduction of hard solids, use

A

compression

290
Q

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

secondary

291
Q

Traces of liquid tar fog present in coke oven gas is separated using

A

electrostatic precipitator

292
Q

Close circuit grinding by a ball mill with air sweeping employs a

A

both (a) & (b).

293
Q

Work index is the gross energy (kWh/tonne of feed) necessary to reduce a very large feed to such a size that 80% of product particles will pass through a 0.1 mm screen. The value of work index determined for wet grinding should be multiplied with ____ to get the same for dry grinding.

A

1.34

294
Q

Choke crushing (in case of a Jaw crusher) compared to free crushing

A

consumes more power.

295
Q

The specific surface of sherical particles is proportional to (where, Dp = diameter of particle).

A

1/Dp

296
Q

Wheat is ground into flour in a

A

roller crusher

297
Q

Gravity stamp mill is meant for the ____ crushing.

A

fine

298
Q

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.

299
Q

Toothed roll crushers achieve size reduction by

A

both (a) & (b).

300
Q

Pick out the wrong statement:

A

Reduction ratio in crushing operation is defined as the ratio of minimum feed size to the maximum product size.

301
Q

To get ultrafine particles, the equipment used is a

A

fluid energy mill

302
Q

Vacuum filter is most suitable for the

A

none of these.

303
Q

The porosity of a compressible cake is

A

minimum at the filter medium.

304
Q

Which of the following conveyors cannot be recommended for transportation of abrasive materials ?

A

Flight conveyor

305
Q

Separation of materials into products based on the difference of their sizes is called

A

sizing

306
Q

For classification of potable (drinking) water, we use a ____ filter.

A

gravity sand

307
Q

Hot, lumpy & abrasive materials are best transported by using a/an ____ conveyor.

A

apron

308
Q

Additives used for promoting the floccula-tion of particles is a/an

A

both (a) & (b)

309
Q

In case of grinding in a ball mill

A

all (a), (b) and (c).

310
Q

The capacity of a classifier in ‘tons of solid/hr’ is given by (where, A = cross-sectional area, m2 V = rising velocity of fluid, m/sec.S = percentage of solids in the suspension by volume.ρ = density of solids, kg/m3)

A

3.6 AVS.ρ

311
Q

Kick’s law relates to

A

energy consumption

312
Q

____ mill is normally used for grinding of talc.

A

Ring-roll

313
Q

Colloidal mills are used for ____ grinding.

A

ultrafine

314
Q

Fluid medium used in the classification technique of mineral beneficiation is

A

either (a) or (b)

315
Q

The maximum slope of a belt conveyor can be

A

30°

316
Q

The filter medium resistance is controlled by

A

both pressure drop and flow rate

317
Q

The unit of filter medium resistance is

A

cm-1

318
Q

During size reduction by a jaw crusher, the energy consumed decreases with the

A

increasing size of feed at constant reduction ratio.

319
Q

Which of the following can be most effectively used for clarification of lube oil and printing ink?

A

Sharpies supercentrifuge

320
Q

Ultracentrifuges running at speeds upto 100000 rpm is normally used for the

A

separation of isotopes based on their density or molecular weights difference.

321
Q

Sizing of very fine particles of the order of 5 to 10 microns is done by elutriation, which is a ____ operation.

A

classification

322
Q

In the cyclone separator used for separation of dust from dust laden gas, the gas

A

both (b) and (c).

323
Q

The basic filtration equation is given as where, https://www.indiabix.com/_files/images/chemical-engineering/mechanical-operations/136-487-1.png V is volume of the filtrate ; A is the filtration area, a is specific cake resistance, μ is viscosity of the filtrate, and Cis the concentration of the solids in the feed slurry.
In a 20 minutes constant rate filtration, 5 m3 of filtrate was obtained. If this is followed by a constant pressure filtration, how much more time in minutes, it will take for another 5 m3 of filtrate to be produced ? Neglect filter medium resistance, Rm ; assume incompressible cake.

A

20

324
Q

Size reduction of fibrous materials like wood, asbestos, mica etc. is done by a disintegrator exemplified by the

A

cage mill

325
Q

The material is crushed in a gyratory crusher by the action of

A

compression

326
Q

The equivalent diameter of channel of a constant non-circular cross-section of 3 cm by 6 cm will be ____ cms.

A

2

327
Q

Which of the following may prove unsuitable for filtering volatile liquids ?

A

Vacuum filter

328
Q

____ mean diameter of particles is given by

A

volume

329
Q

Mass flow of granular solid (M) through a circular opening of dia, D follows

A

M ∝ D3

330
Q

Sauter mean diameter is the same as the ____ mean diameter.

A

volume-surface

331
Q

Cake resistance is

A

none of these.

332
Q

In paint industries, blending of light paste is done by using a

A

charge can mixer

333
Q

A sand mixture was screened through a standard 10-mesh screen. The mass fraction of the oversize material in feed, overflow and underflow were found to be 0.38, 0.79 and 0.22 respectively. The screen effectiveness based on the oversize is

A

0.5

334
Q

____ is used for producing a thick suspension from a thin slurry.

A

Pressure filter thickener

335
Q

Wet seiving is employed, when the product contains ____ materials.

A

large quantity of very fine

336
Q

Energy requirement (per unit mass of material crushed/ground) is highest for

A

fluid energy mill

337
Q

The energy consumed by a ball mill depends on

A

all (a), (b) and (c).

338
Q

Energy consumption in a crusher decreases with increase in the

A

all (a), (b) & (c).

339
Q

In a mixer, the quantity, (v. L/D) is termed as ____ number(where, v = longitudinal velocity of material, L = length of the mixer, D = diffusivity in axial mixing).

A

Pclet

340
Q

The term ‘angle of nip’ is concerned with the operation of the ____ crushers.

A

roll

341
Q

Cartridge filters are termed as ‘edge’ filters, because of the fact that the

A

bulk of the solids are removed at the periphery of the disks.

342
Q

Vibrating screens have capacity in the range of ____ tons/ft2 .mm mesh size.

A

0.2 to 0.8

343
Q

Cumulative analysis for determining surface is more precise than differential analysis, because of the

A

assumption that all particles in a single fraction are equal in size, is not needed.

344
Q

To remove very small amount of tiny solid impurities from liquid, we use a

A

coagulant

345
Q

Screw conveyors are

A

suitable for sticky materials.

346
Q

____ mills fall in the category of tumbling mills,

A

all (a), (b) & (c)

347
Q

Capacity of flight conveyor in tons/hr is given by (where, W & D = width and depth of flight respectively in metre V = speed of the conveyor, metre/second ρ = bulk density of material, kg/m3)

A

3.6 W.D.V.ρ

348
Q

Which of the following is not a cutting machine?

A

Tube mills

349
Q

Weber number is significant and is concerned with the

A

dispersion of liquid in liquid.

350
Q

Power consumption during turbulent flow in agitation tank is proportional to the ____ of the liquid.

A

density

351
Q

Screen efficiency is

A

none of these

352
Q

For grinding of cereals, grains, spices, pigments, saw dust, cork etc., the most extensively used size reduction equipment is a

A

Buhrstone mill

353
Q

Handling of ashes and similar materials can be done best by a ____ conveyor.

A

drag or slat

354
Q

Which of the following must be stored in silos and not in open yard ?

A

High V.M. bituminous coal

355
Q

Apron conveyors are used for

A

heavy loads & short runs.

356
Q

Sedimentation on commercial scale occurs in

A

rotary drum filters

357
Q

With increase in drum speed, in a rotary drum filter, the filtration rate

A

increases

358
Q

Arrange the following size reduction equipment in the decreasing order of the average particle size produced by each of them.

A

Jaw crusher, Ball mill, Fluid energy mill

359
Q

200 mesh seive size corresponds to ____ microns.

A

74

360
Q

What is the usual value of angle of nip for crushing of ordinary rock in smooth steel crushing rolls ?

A

32°

361
Q

For a turbine agitated and baffled tank, operating at low Reynold’s number (based on impeller diameter), the power number (Np) varies with NRe as

A

Np ∝ 1/NRe

362
Q

Which of the following is not accomplished by agitation of liquids in agitators?

A

Blending of immiscible liquids.

363
Q

Which of the following parts of a jaw crusher is subjected to maximum wear and tear during its operation ?

A

Jaw plates

364
Q

A 30% (by volume) suspension of spherical sand particles in a viscous oil has a hindered settling velocity of 4.44 μm/s. If the Richardson Zaki hindered settling index is 4.5, then the terminal velocity of a sand grain is

A

1 μm/s

365
Q

The specific surface of spherical particles is given by (where D and ρ are diameter and density of particle).

A

https://www.indiabix.com/_files/images/chemical-engineering/mechanical-operations/106-134-1.png

366
Q

Velocity of a small particle of diameter ‘Dp’ at a distance ‘r’ from the rotational axis of a cyclone rotating at an angular speed ‘ω’ is given by (the other symbols are as per standard notation)

A

https://www.indiabix.com/_files/images/chemical-engineering/mechanical-operations/132-461-4.png

367
Q

In froth floatation, chemical agent added to cause air adherence is called

A

collector

368
Q

The sphericity of a solid particle of cubical shape is

A

(π/6)1/3

369
Q

Vertical transportation of materials can be done by a/an

A

both(b)&(c)

370
Q

In a roll crusher, the specific power consumption and the production rate is affected by the

A

both (a) and (b).

371
Q

A cottrel precipitator makes use of the ____ for dusty air cleaning.

A

corrona discharge

372
Q

Pick out the correct statement.

A

Kick’s crushing law is, P/m = K . ln https://www.indiabix.com/_files/images/chemical-engineering/mechanical-operations/122-367-2.png

373
Q

If radius of a batch basket centrifuge is halved & the r.p.m. is doubled, then the

A

centrifugal force is doubled.

374
Q

The ratio of the area of openings in one screen (Taylor series) to that of the openings in the next smaller screen is

A

none of these

375
Q

Compressibility co-efficient for an absolutely compressible cake is

A

1

376
Q

Mixing of plastic solids is generally facilitated by

A

kneading

377
Q

grinding element & the housing.

A

both (a) and (b).

378
Q

Which of the following is not an industrial screening equipment ?

A

Sharpies centrifuge

379
Q

Which of the following is not a wet classifier ?

A

None of these

380
Q

Helical screw agitator is used for

A

mixing highly viscous pastes.

381
Q

For raschig rings, the sphericity is

A

<1

382
Q

For Indian standard (IS) screens, the mesh number is equal to its aperture size expressed to the nearest deca-micron (0.01 mm). Aperture width of IS screen of mesh number 50 will be approximately ____ microns.

A

500

383
Q

____ mills are termed as disintegrators.

A

Cage

384
Q

Supporting legs of a plate and frame filter is normally made of

A

cast iron

385
Q

The cummulative mass fraction of particles smaller than size dj for a collection of Ni particles of diameter di and mass mi (i = 1, 2, 3, …… ∞) is given by

A

https://www.indiabix.com/_files/images/chemical-engineering/mechanical-operations/136-492-2.png

386
Q

Wet grinding in a revolving mill ____ as compared to dry grinding.

A

increases capacity

387
Q

The grinding in a hammer crusher takes place due to the

A

both (a) & (b)

388
Q

A compressible cake has the

A

maximum porosity at the upstream side.

389
Q

Which of the following is not used as a filter medium in case of corrosive liquids ?

A

Cotton fabric

390
Q

In ball mill operation, the feed size (Df in meters) and the ball diameter (Db in metres) are related as ( where, K = grindability constant (varying from 0.9 to 1.4 in increasing order of hard ness))

A

Db2 = K.Df

391
Q

Pine oil and cresylic acid are used as ____ in the froth floatation process.

A

frother

392
Q

Grinding characteristic of a material is given by its

A

HGI

393
Q

Which of the following is not a non-metalliferous mineral?

A

Cassiterrite

394
Q

Filter medium resistance is important during the ____ of filtration.

A

early stages.

395
Q

Float and sink test determines the possibility of cleaning of coal by a process based on the

A

gravity separation

396
Q

____ baffles are provided in ball mills.

A

Horizontal

397
Q

Mixer used for rubber compounding is

A

banbury internal mixer

398
Q

For spheres, the specific surface shape factor is given by

A

AD/V

399
Q

____ mill is not used for grinding wheat into flour and for milling of cereals & other vegetable products.

A

Pebble

400
Q

In case of a hammer crusher, the final product size depends on the

A

all (a), (b) and (c).

401
Q

Sphericity of raschig ring (whose length and diameter are equal) is

A

1

402
Q

Mixing mechanism employed in a pan mixer is by

A

mulling

403
Q

Chance process is used for the

A

cleaning of coal.

404
Q

Which of the following screens has the maximum capacity ?

A

Vibrating screen

405
Q

Stamp mills are generally used for crushing

A

gold ores

406
Q

In case of a plate and frame filter press, filtrate flow through the cake follows ____ flow.

A

laminar

407
Q

Which of the following is a batch sedimentation equipment ?

A

Filter thickener

408
Q

The most suitable equipment for the transportation of 200 mesh size particles is a

A

pneumatic conveyor

409
Q

Which of the following is not used as filter aid?

A

Rice husk

410
Q

Raw materials are charged in the iron blast furnace using

A

skip hoist

411
Q

Pebble mills are tumbling mills widely used for grinding in the manufacture of paints & pigments and cosmetic industries, where iron contamination in the product is highly objectionable. Pebbles used in pebble mill are made of

A

flint or porcelain

412
Q

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

A

all ‘a’, ‘b’&’c’.

413
Q

Which of the following relationships between co-efficinet of friction (μ) between rock & roll and a (half of the angle of nip) of the particle to be crushed is correct ?

A

μ ≥ tan α

414
Q

Pick out the wrong statement pertaining to the roll crushers.

A

Both the rolls run necessarily at the same speed.

415
Q

Which of the following is not an ultrafine grinder (colloid mill)?

A

Toothed roll crusher

416
Q

Two particles are called to be equal settling, if they are having the same.

A

terminal velocities in the same fluid & in the same field of force.

417
Q

Which of the following is the most suitable for handling fibrous and dense slurries ?

A

Cone type agitator

418
Q

____ centrifuge is normally used in sugar mills.

A

Turbine agitator

419
Q

Solid particles separation based on the difference in their flow velocities through fluids is termed as the

A

classification

420
Q

Diatomaceous earth is a/an

A

filter aid

421
Q

The distribution given by microscopic analysis of powder is

A

number

422
Q

Number of particles in a crushed solid sample is given by (where, m = mass of particles in a sample, Vp = volume of one particle, ρ= density of particles)

A

m/ρ . Vp

423
Q

For a non-spherical particle, the sphericity

A

is defined as the ratio of surface area of a sphere having the same volume as the particle to the actual surface area of the particle.

424
Q

In washing type plate and frame filter press, the ratio of washing rate to the final filtrate rate is

A

45295

425
Q

Ball mills and tube mills with flint or porcelain balls are used for size reduction of

A

non-metallic ores

426
Q

Size reduction of ____ is accomplished in steam heated rollers and roll crushers.

A

hard rubber

427
Q

The capacity of a belt conveyor depends upon two factors. If one is the cross-section of the load, the other is the ____ of the belt.

A

speed

428
Q

Which of the following is not a part of the Blake jaw crusher?

A

Hanger

429
Q

If a force greater than that of gravity is used to separate solids & fluids of different densities, the process is termed as the

A

centrifugation

430
Q

Filter aid is used to

A

increase the porosity of the cake.

431
Q

Which of the following mineral dressing operations is termed as ‘comminution’?

A

None of these

432
Q

The capacity of a pneumatic conveying system depends upon the

A

all (a), (b) and (c).

433
Q

Pick out the wrong statement.

A

The equipment used for the removal of traces of solids from a liquid is called a classifier.

434
Q

Gravity settling process is not involved in the working of a

A

hydrocyclone

435
Q

Froth floatation is the most suitable for treating

A

sulphide ores

436
Q

The energy required per unit mass to grind limestone particles of very large size to 100 μm is 12.7 kWh/ton. An estimate (using Bond’s law) of the energy to grind the particles from a very large size to 50 μrn is

A

18 kWh/ton

437
Q

Which of the following is the most suitable for cleaning of fine coal dust (<0.5 mm) ?

A

Froth floatation

438
Q

Pick out the correct statement:

A

Removal of iron from ceramic material is necessitated (by magnetic separation method) so as to avoid discolouration of ceramic products.

439
Q

Range of compressibility co-efficient of the commercial compressible cake obtained in filtration operation is

A

0.2 to 0.8

440
Q

Highly viscous liquids & pastes are agitated by

A

multiple blade paddles

441
Q

The value of ‘angle of nip’ is generally about

A

32°

442
Q

Size reduction of the ____ can be suitably done by ball mills, crushing rolls and rod mills.

A

metalliferrous ores

443
Q

Sulphuric acid mist is arrested by using a ____ scrubber

A

venturi

444
Q

The main size reduction operation in ultrafine grinders is

A

attrition

445
Q

In case of a hammer crusher,

A

all (a), (b) and (c).

446
Q

Jigging is a technique by which different particles can be

A

separated by particle size.

447
Q

Crushing of mineral particles is accomplished in a ‘cage mill’, when one or more alloy steel bars are revolved in opposite directions. It is a type of ____ mill.

A

impact

448
Q

Balls for ball mills are never made of

A

lead

449
Q

200 mesh screen means 200 openings per

A

inch

450
Q

____ is the most commonly used ‘filter aid’.

A

Diatomaceous earth