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DAY 2 > Mechanical Operation > Flashcards

Mechanical Operation Flashcards

1
Q

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

Cone type agitator

A

Cone type agitator

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2
Q

__________ centrifuge is normally used in sugar mills.

Suspended batch basket

A

Suspended batch basket

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3
Q

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

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

classification

A

classification

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4
Q

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

1/4

A

1/4

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5
Q

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

centrifugation

A

centrifugation

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6
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

18 kWh/ton

A

18 kWh/ton

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7
Q

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

Froth floatation

A

Froth floatation

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8
Q

Highly viscous liquids & pastes are agitated by

multiple blade paddles

A

multiple blade paddles

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9
Q

The value of ‘angle of nip’ is generally about

32°

A

32°

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10
Q

Shape factor for a cylinder whose length equals its diameter is

1.5

A

1.5

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11
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

easier grindability

A

easier grindability

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12
Q

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

Banbery

A

Banbery

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13
Q

Which of the following is a vacuum filter ?

Rotary disc filter

A

Rotary disc filter

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14
Q

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

frother

A

frother

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15
Q

Length/diameter ratio of a ball mill is

< 1

A

< 1

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16
Q

Feed size of ≥ 25 cms can be accepted by

jaw crusher

A

jaw crusher

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17
Q

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

electrostatic precipitator

A

electrostatic precipitator

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18
Q

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

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

Carbon black is pulverised in a

ball mill

A

ball mill

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19
Q

Cement clinker is reduced to fine size by a

tube mill

A

tube mill

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20
Q

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

less than

A

less than

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21
Q

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

Classifiers

A

Classifiers

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22
Q

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

Bucket elevators

A

Bucket elevators

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23
Q

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

Dry powdery solid materials are transported by a __________ conveyor.

Screw conveyor

A

Screw conveyor

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24
Q

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

centrifugal

A

centrifugal

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25
Q

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

0.9

A

0.9

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26
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.

0.30

A

0.30

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27
Q

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

1

A

1

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28
Q

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

boundary mixer.

A

boundary mixer.

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29
Q

Traces of solids are removed from, liquid in a

clarifier

A

clarifier

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30
Q

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

Minimum size

A

Minimum size

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31
Q

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

1

A

1

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32
Q

Colloid mills achieve size reduction mainly by

attrition

A

attrition

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33
Q

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

50

A

50

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34
Q

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

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

Rittinger’s law

A

Rittinger’s law

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35
Q

Size reduction mechanism used in Jaw crushers is

compression

A

compression

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36
Q

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

coal

A

coal

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37
Q

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

colloidal

A

colloidal

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38
Q

Size reduction does not occur due to compression in case of

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

rod mills

A

rod mills

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39
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

0.0184

A

0.0184

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40
Q

Gold ore concentration is mostly done using

For benefication of iron ore, the most commonly used method is

tabling

A

tabling

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41
Q

Mixing of light fine powder such as insecticides is done by

impact wheels

A

impact wheels

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42
Q

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

hammer crusher

A

hammer crusher

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43
Q

Size reduction of asbestos and mica is done by

hammer mills

A

hammer mills

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44
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

0.6

A

0.6

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45
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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46
Q

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

over cake

A

over cake

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47
Q

Moisture can be removed from lubricating oil using

tubular centrifuge

A

tubular centrifuge

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48
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

2 to 5°

A

2 to 5°

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49
Q

Gizzlies are used for separating __________ solids.

fine

A

fine

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50
Q

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

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

Pug mill

A

Pug mill

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51
Q

Pick out the material having minimum Rittinger’s number.

Quartz

A

Quartz

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52
Q

__________ mills are termed as impactors.

Hammer

A

Hammer

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53
Q

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

230

A

230

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53
Q

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

dry

A

dry

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54
Q

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

Vacuum filter

A

Vacuum filter

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55
Q

All resistances during washing of cake

remain constant

A

remain constant

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55
Q

A __________ mixer resembles a ball mill without balls.

tumbling

A

tumbling

56
Q

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

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

A

Flight

56
Q

Gyratory crushers compared to the reciprocating jaw crushers

have greater capacity per unit of discharge area.

A

have greater capacity per unit of discharge area.

57
Q

Sphericity of pulverised coal is

<1

A

<1

57
Q

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

impact and attrition.

A

impact and attrition.

57
Q

Reduction ratio of crushers is the

ratio of feed opening to discharge opening.

A

ratio of feed opening to discharge opening.

57
Q

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

Cone crusher

A

Cone crusher

58
Q

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

froth floatation

A

froth floatation

59
Q

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

ultra

A

ultra

60
Q

Temperature of the product during ultrafine grinding

increases

A

increases

61
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

heavy tonnages of rocks or gravel.

A

heavy tonnages of rocks or gravel.

62
Q

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

sizing

A

sizing

63
Q

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

d^2

A

d^2

64
Q

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

at the end of filtration.

A

at the end of filtration.

65
Q

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

10 mm screen and retained on 5 mm screen.

A

10 mm screen and retained on 5 mm screen.

65
Q

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

0.33-0.45

A

0.33-0.45

66
Q

Grinding efficiency of a ball mill is of the order of __________ percent.

1-5

A

1-5

67
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

1.34 Wi

A

1.34 Wi

68
Q

Maximum size reduction in a fluid energy mill is achieved by

interparticle attrition

A

interparticle attrition

69
Q

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

15 - 20

A

15 - 20

70
Q

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

Jaw crusher

A

Jaw crusher

70
Q

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

For the preliminary breaking of hard rock, we use a

Which of the following is a coarse crusher?

Gyratory crusher

A

Gyratory crusher

70
Q

Ultrafine grinders operate principally by

attrition

A

attrition

71
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 ?

0.66

A

0.66

72
Q

Crushing efficiency of a machine ranges between __________ percent.

0.1 to 2

A

0.1 to 2

73
Q

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

30

A

30

74
Q

Ribbon blenders are exclusively meant for

non-flowing powder and thin pastes.

A

non-flowing powder and thin pastes.

75
Q

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

precoat

A

precoat

76
Q

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

0.0074 cm

A

0.0074 cm

77
Q

Separation of solid particles based on their densities is called

A

sorting

78
Q

__________ are mixed using ribbon blenders.

Dry powders

A

Dry powders

79
Q

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

the new surface created.

A

the new surface created.

80
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.

primary

A

primary

80
Q

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

Separation of a suspension or slurry into a supernatant clear liquid (free from particles) and a thick sludge containing a high concentration of solid is called

sedimentation

A

sedimentation

81
Q

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

Rittinger’s law

A

Rittinger’s law

82
Q

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

ribbon

A

ribbon

82
Q

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

terminal velocities

A

terminal velocities

83
Q

In constant pressure filtration,

rate of filtration decreases with time

A

rate of filtration decreases with time

84
Q

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

N ∝ 1/sqrtD

A

N ∝ 1/sqrtD

85
Q

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

Galena

A

Galena

86
Q

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

__________ mills are termed as disintegrators.

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

__________ mill is not a revolving mill.

Cage mill

A

Cage mill

87
Q

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

Roll crusher

A

Roll crusher

88
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.

secondary

A

secondary

89
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.

1.34

A

1.34

90
Q

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

consumes more power.

A

consumes more power.

91
Q

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

1/Dp

A

1/Dp

91
Q

Gravity stamp mill is meant for the __________ crushing.

fine

A

fine

92
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

density separation.

A

density separation.

92
Q

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

apron

A

apron

93
Q

The maximum slope of a belt conveyor can be

30°

A

30°

93
Q

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

2

A

2

93
Q

The unit of filter medium resistance is

cm-1

A

cm-1

94
Q

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

M ∝ D^3

A

M ∝ D^3

95
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

0.50

A

0.50

96
Q

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

0.2 to 0.8

A

0.2 to 0.8

97
Q

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

coagulant

A

coagulant

98
Q

Weber number is significant and is concerned with the

dispersion of liquid in liquid.

A

dispersion of liquid in liquid.

99
Q

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

Buhrstone mill

A

Buhrstone mill

100
Q

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

drag or slat

A

drag or slat

101
Q

Apron conveyors are used for

heavy loads & short runs.

A

heavy loads & short runs.

102
Q

200 mesh seive size corresponds to __________ microns.

74

A

74

103
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

1 μm/s

A

1 μm/s

104
Q

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

centrifugal force is doubled.

A

centrifugal force is doubled.

105
Q

Compressibility co-efficient for an absolutely compressible cake is

1

A

1

106
Q

Mixing of plastic solids is generally facilitated by

kneading

A

kneading

107
Q
A
108
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))

Db2 = K.Df

A

Db2 = K.Df

109
Q

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

frother

A

frother

110
Q

Grinding characteristic of a material is given by its

HGI

A

HGI

111
Q

Mixing mechanism employed in a pan mixer is by

mulling

A

mulling

112
Q

Which of the following screens has the maximum capacity ?

Vibrating screen

A

Vibrating screen

113
Q

Stamp mills are generally used for crushing

gold ores

A

gold ores

114
Q

Which of the following is a batch sedimentation equipment ?

Filter thickener

A

Filter thickener

115
Q

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

For the transportation of ultrafine particles, the equipment used is a

pneumatic conveyor

A

pneumatic conveyor

116
Q

Particle size range in which dust catcher (gravity settling chamber) works most effectively and efficiently is __________ microns.

< 74

A

< 74

117
Q

__________ centrifuge is the most suitable for separation of non-friable crystals.

Perforated horizontal basket continuous

A

Perforated horizontal basket continuous

118
Q

A propeller agitator

produces mainly axial flow.

A

produces mainly axial flow.

119
Q

Reciprocal of sphericity is termed as the

A

shape factor

120
Q

With increase in the pressure drop across the cake, the specific cake resistance for the compressible sludge

increases

A

increases

121
Q

Size reduction of ice and gypsum can be accomplished suitably by a __________ crusher.

toothed roll

A

toothed roll

122
Q

The ratio of the actual mesh dimension of Taylor series to that of the next smaller screen is

sqrt2

A

sqrt2

123
Q

Which of the following is not used as a surface active agent in a flocculation operation?

Quartz

A

Quartz

124
Q

Which of the following is a fine crusher?

Toothed roll crusher

A

Toothed roll crusher

125
Q

The optimum moisture content in solids to be crushed/ground ranges from __________ percent.

3 to 4

A

3 to 4

126
Q

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.

2.5 times

A

2.5 times

127
Q

Dispersion of a gas through liquid is done by using a

sparger

A

sparger

DAY 2 (8 decks)

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