Mechanical Operations Part 2 Flashcards
1
Q
Which of the following gives the crushing energy required to create new surface?
Taggarts rule
Fick’s law
Rittinger’s law
none of these
A
Rittinger’s law
2
Q
In filtration, the use of ‘filter aid’ helps in
reducing the filtration pressure.
accelerating the rate of filtration.
deplugging the filter medium.
enhancing the cake porosity in case of a dense impermeable cake.
A
deplugging the filter medium.
3
Q
Gizzlies are used for separating __________ solids.
coarse
fine
any size
none of these
A
fine
4
Q
Which of the following clay mixing devices is vacuum operated for deairation of clay?
Banbery mixer
Pug mil
Muller-mixer
None of these
A
Pug mil
5
Q
Pick out the material having minimum Rittinger’s number.
Calcite
Pyrite
Quartz
Galena
A
Quartz
6
Q
__________ mills are termed as impactors.
Hammer
Cage
Rolling-compression
none of these
A
Hammer
7
Q
In case of a revolving mill, wet grinding compared to dry grinding
requires more energy.
has less capacity.
complicates handling & classification of the product
none of these.
A
none of these.
8
Q
To get a fine talc powder from its granules, the equipment used is
roller crusher
ball mill
jaw crusher
gyratory crusher
A
ball mill
9
Q
For a cyclone of diameter 0.2 m with a tangential velocity of 15 m/s at the wall, the separation factor is
2250
1125
460
230
A
230
Separation factor = v^2/ rg
Sf = (15)^2 / (0.2/2)(9.81)
Sf = 230
10
Q
Width and speed of a conveyor belt depends upon the __________ of the material.
lump size
bulk density
both (a) & (b)
neither (a) nor (b)
A
both (a) & (b)
11
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
British standard screens.
German standard screens (DIN 1171) etc.
American standard screens (ASTM and Tyler standard screens).
all (a), (b) and (c).
A
all (a), (b) and (c).
12
Q
Pick out the wrong statement.
Cummulative analysis for determining surface area is preferred over differential analysis, because of the assumption that “all particles in a simple fraction equal in size” is not needed for cummulative anslysis unlike differential anlaysis.
A gate diagram is a plot of cummulative percent by weight undersize vs. the reciprocal of diameter, in which the area beneath the curve represents the surface.
Capacity of crusher in choke feeding is increased.
Rolling of pebbles/balls from top to bottom of the heap in tumbling mills is called ‘cascading and throwing of the balls through the air to the toe of the heap is called ‘cataracting’.
A
Capacity of crusher in choke feeding is increased.
13
Q
Which of the following size reduction equipments employs mainly attrition for ultrafine grinding?
Jet mills
Fluid energy mill
Micronizer
all (a), (b) and (c)
A
all (a), (b) and (c)
14
Q
Tank filter (e.g., Nutsch filter) is
a high pressure filter.
a continuous filter.
used for small scale filtration work.
a leaf filter.
A
used for small scale filtration work.
15
Q
In bag filters, filter fabrics are never made of
metallic wire woven mesh
polyester fibres
cotton fibres
nylon fibres
A
metallic wire woven mesh
16
Q
Use of ‘grinding aids’ is done in __________ grinding.
dry
wet
ultrafine
intermediate
A
dry
17
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)
0.5 D
D
1.5 D
2 D
A
D
18
Q
Which of the following is the most suitable filter for separation of abrasive solids suspended in a corrosive liquid?
Sand bed filter
Plate and frame filter press
Vacuum filter
Batch basket centrifuge.
A
Vacuum filter
19
Q
All resistances during washing of cake
increases
decreases
remain constant
none of these
A
remain constant
20
Q
A __________ mixer resembles a ball mill without balls.
banbery
pug mill
tumbling
pan
A
tumbling
21
Q
__________ conveyor is the most suitable for short distance transportation of non-abrasive loose materials like garbage, grain, food wastes etc.
Flight
Screw
Drag
Belt
A
Flight
22
Q
As the product becomes finer, the energy required for grinding
decreases
icreases
is same as for coarser grinding
is 1.5 times that for coarser grinding
A
icreases
23
Q
Gyratory crushers compared to the reciprocating jaw crushers
have greater capacity per unit of discharge area.
crush intermittantly.
are less suitable for coarse materials
have less steady power consumption.
A
have greater capacity per unit of discharge area.
24
Q
The important dimensional group involved in the power requirement calculation in mixing operation is the __________ number.
Reynold’
Froude
both (a) & (b)
neither (a) nor (b)
A
both (a) & (b)
25
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 = rho/rhoN3 D5 : Power number
Re = rho N D2/u: Reynold's number
N is the impeller rotational speed, and D is the impeller diameter.
Po is proportional to Re-1.0
Po is proportional to Re0.0
Po is proportional to Re0.5
Po is proportional to Re1.0
Po is proportional to Re-1.0
26
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 high pressure filter.
Rod mill
Pebble mill
Tube mill.
Rod mill
27
Rittinger's crushing law states that
work required to form a particle of any size is proportional to the square of the surface to volume ratio of the product.
work required to form a particle of a particular size is proportional to the square root of the surface to volume ratio of the product.
work required in crushing is proportional to the new surface created.
for a given machine and feed, crushing efficiency is dependent on the size of the feed & product.
work required in crushing is proportional to the new surface created.
28
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'?
Bucket conveyor
Flight conveyor
Screw conveyor
Both (b) and (c)
Both (b) and (c)
29
Sphericity of pulverised coal is
1
<1
>1
infinite
<1
30
The reduction ratio for fine grinders is
5~10
10~20
20-40
as high as 100
as high as 100
31
Which of the following is the hardest material?
Calcite
Quartz
Corundum
Gypsum
Corundum
32
General mechanism of size reduction in intermediate and fine grinder is by
cutting action.
compression.
compression and tearing.
impact and attrition.
impact and attrition.
33
A straight line is obtained on plotting reciprocal of filtration rate vs. the volume of filtrate for __________ flow of filtrate.
compressible cakes and laminar
incompressible cake and laminar
compressible cake and turbulent
incompressible cake and turbulent
incompressible cake and laminar
34
The work index in Bond's law for crushing of solids has the following dimensions
no units (dimensionless)
kWh/ton
kW/ton
kWh.m1/2/ton
kWh/ton
35
Ore concentration by jigging is based on the difference in the __________ of the particles.
specific gravities
wettabilit
shape
none of these
specific gravities
36
Size measurement of ultrafine particles can be best expressed in terms of
centimetre
screen size
micron
surace area per unit mass
surace area per unit mass
37
Reduction ratio of crushers is the
ratio of feed opening to discharge opening.
ratio of discharge opening to feed opening.
determining factor for minimum dia of the feed and the product.
none of these.
ratio of feed opening to discharge opening.
38
Which is a secondary crusher for a hard & tough stone?
Jaw crusher
Cone crusher
Impact crusher
Toothed roll crusher
Cone crusher
39
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.)
P/m = K/sqrtDp
P/m = K . ln (Dsa-Dsb)
P/m = K . (1-Dsb - 1-Dsa)
none of these.
P/m = K . (1-Dsb - 1-Dsa)
40
Cyclones are used primarily for separating
solids
solids from fluids
liquids
solids from solids
solids from fluids
41
There is practically no alternative/competitor to __________ in the beneficiation treatment of sulphide ores.
classification
tabling
jigging
froth floatatio
froth floatatio
42
Separation of isotopes is generally done using a/an __________ centrifuge.
ultra
disk-bow
both (a) & (b)
neither (a) nor (b)
ultra
43
Temperature of the product during ultrafine grinding
increases
decreases
remains constant
may increase or decrease ; depends on the material being ground
increases
44
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
light metal powder down upto 4 meshsize.
dry chemicals.
heavy tonnages of rocks or gravel.
owdered food & granular materials.
heavy tonnages of rocks or gravel.
45
In a ball mill, the volume occupied by the balls (when the mill is stopped) is about __________ percent of the volume of the mill.
35
50
70
85
50
46
Separation of materials of the same density based on their sizes by using then-different rates of flow is called
sortin
sizing
flocculation
elutriation
sizing
47
Molten ammonium nitrate is mixed with ground limestone in fertilizer plant in a
pug mill
mixer-extruder
banbury mixer
muller mixer
pug mill
## Footnote
Molten...Limestone...Fertilizer...Pug
48
Agglomeration of individual particles into clusters (flocs) is called flocculation. To prevent flocculation, the most commonly used dispersing agents are
carbonates
sulphates
silicates & phosphates
bi-carbonates
silicates & phosphates
49
For a sphere falling in the constant drag co-efficient regime, its terminal velocity depends on its diameter (d) as
d
srt d
d2
1/d
d2
50
With increase in the capacity of screens, the screen effectiveness
remains unchange
increases
decreases
decreases exponentially
decreases
51
As particle size is reduced
screening becomes progressively more difficult.
screening becomes progressively easier.
capacity and effectiveness of the screen is increased.
none of these.
screening becomes progressively more difficult.
52
Rittinger number which designates the new surface prduced per unit of mechanical energy absorbed by the material being crushed, depends on the
state or manner of application of the crushing force.
ultimate strength of the material.
elastic constant of the material
all (a), (b) and (c).
all (a), (b) and (c).
53
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.
200 C and 5 atm.
1000 C and 10 atm.
500 C and 50 atm.
1000 C and 500 atm.
1000 C and 10 atm.
54
For efficient grinding, ball mills must be operated
at a speed less than the critical speed.
at a speed more than the critical speed.
at a speed equal to the critical speed
with minimum possible small balls
at a speed less than the critical speed.
55
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.
primary
secondary
fine
ultafine
fine
56
For spheres, the surface shape factor is given by (where, A = area, V = volume, and D = diameter)
π(=A/D²)
π/6(=V/D³)
AD/V
None of these.
π(=A/D²)
57
The reduction ratio for grinders is defined as(where, Df and Dp are average diameters of feed and product respectively).
Df/Dp
Dp/D
Df - Dp
none of these
Df/Dp
58
Pick out the wrong statement pertaining to the turbine agitator.
Recommended peripheral speed for the turbine agitator is 200-250 metres/minute.
Pitched blade turbine agitator gives only radial flow with complete absence of the axial flow.
Generally, the diameter of the agitator is kept between l/3rd to l/6th of the tank diameter while the blade length is l/4th of agitator diameter (with central disc, it is l/8th of the agitator diameter).
Turbine agitator should be located at a height not less than one agitator diameter length from the bottom. If the depth of liquid in the tank is more than twice the agitator diameter, two agitators should be used.
Pitched blade turbine agitator gives only radial flow with complete absence of the axial flow.
## Footnote
wrong - turbine agitator - pitched blade
59
A fluid energy mill is used for
cutting
grinding
ultra grinding
crushing
ultra grinding
60
Which of the following is the softest material ?
Talc
Feldspar
Corundum
Calcite
Talc
61
Dry powdery solid materials are transported by a __________ conveyor.
belt
bucket
screw
none of these
screw
62
Fluid energy mill comes in the category of
grinder
grinde
cutter
ultrafine grinder
ultrafine grinder
63
Filtration capacity of a rotary drum vacuum filter depends upon the
cake thickness.
characteristics of the feed slurry.
both (a) & (b).
neither (a) nor (b).
both (a) & (b).
64
__________ conveyors are also called scrapers.
Apron
Screw
Helical flight
both (b) & (c)
both (b) & (c)
65
For laminar flow of filtrate through the cake deposited on septum, which of the following will be valid
Kozney-Karman equation
Leva's equation
Blake-Plummer equatio
none of these
Kozney-Karman equation
66
Which of the following is a continuous filter?
Plate and frame filter
Cartridge filter
Shell and leaf filter
None of these
None of these
67
During washing of filter at the end of constant pressure filtration, the rate of washing equals the rate of filtration
at time zero.
at the end of filtration.
when half the filtrate has been obtained.
at the end of filtration, but decreases with time subsequently.
at the end of filtration.
68
In screen analysis, the notation +5 mm/-10 mm means particles passing through
10 mm screen and retained on 5 mm screen.
5 mm screen and retained on 10 mm screen.
both 5 mm and 10 mm screens.
neither 5 mm nor 10 mm screen.
10 mm screen and retained on 5 mm screen.
69
Optimum ratio of operating speed to critical speed of a trommel is
0.33-0.45
1.33-1.45
0.5-
1.5-2.5
0.33-0.45
## Footnote
Trommels
15 - 20 rpm
0.33 - 0.45 operating/critical speed ratio
70
The process opposite to 'dispersion' is termed as the
flocculation
sedimentation
filtration
none of these
flocculation
71
The cake resistance increases steadily with the time of filtration in a plate and frame filter employing constant __________ filtration.
rate
pressure
both (a) & (b)
neither (a) nor (b)
both (a) & (b)
72
Grinding efficiency of a ball mill is of the order of __________ percent
1-5
40-50
75-80
90-9
1-5
73
Solid particles of different densities are separated by
filters
thickness
cyclones
sorting classifier
sorting classifier
74
During agitation of liquids, power consumption during laminar flow is not proportional to the
density of the liquid
viscosity of the liquid
cube of impeller diameter
square of rotational speed
density of the liquid
75
Trommels are revolving screens which normally operate in the range of __________ rpm
1 - 2
15 - 20
40 - 50
60 - 75
15 - 20
## Footnote
Trommels
15 - 20 rpm
0.33 - 0.45 operating/critical speed ratio
76
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
0.5 Wi
Wi
1.34 Wi
3.34 Wi
1.34 Wi
77
Maximum size reduction in a fluid energy mill is achieved by
compression
interparticle attritio
cutting
impact
interparticle attritio
## Footnote
max size red fluid energy interparticle att.
78
Filtration rate through a filter cake is proportional to (where, S = filtering surface R= specific cake resistance u = viscosity of the filtrate)
S
1/R
1/u
all (a), (b) & (c)
all (a), (b) & (c)
79
A centrifugal filtration unit operating at a rotational speed of w has inner surface of the liquid (density rhoL) located at a radial distance R from the axis of rotation. The thickness of the liquid film is (delta) and no cake is formed. The initial pressure drop during filtration is
1-2 w2 . R2 . (rho)L
1-2 w2 . (delta)2 . (rho)L
1-2 w2 . (delta)(rho)L (2R + (delta))
1-2 w2 . R . (rho)L(R + 2(delta))
1-2 w2 . (delta)(rho)L (2R + (delta))
80
Which one is a filter aid ?
Convas fabric
Diatomaceous earth
Calcined lime
None of these
Diatomaceous earth
81
To remove dirt from the flowing fluid, we use a
coagulant
gravity settler
strain
clarifier
strain
82
Which of the following crushers can be considered as a combination of a jaw crusher and a roller crusher ?
Rod mill
Fluid energy mill
Gyratory crusher
Ball mill
Gyratory crusher
83
Separation of solid suspended in liquid into a supernatant clear liquid and a denser slurry employs a process termed as the
coagulation
flocculation
sedimentation
clarification
sedimentation
84
Ultrafine grinders operate principally by
slow compressio
impac
attrition
cutting action
attrition
85
Which of the following comes in the category of primary crusher for hard and tough stone ?
Jaw crusher
Cone crusher
Gyratory crusher
None of these
Jaw crusher
86
Crushing efficiency of a machine ranges between __________ percent.
0.1 to 2
5 to 1
20 to 25
50 to 70
0.1 to 2
87
Screen capacity is expressed in terms of
tons/hr
tons/ft2
both (a) & (b)
tons/hr-ft
tons/hr-ft
88
A screen is said to be blinded, when the
oversizes are present in undersize fraction.
undersizes are retained in oversize fraction.
screen is plugged with solid particles.
screen capacity is abruptly increased.
screen is plugged with solid particles.
89
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
0.5
1
2.76
0.66
0.66
90
Percentage of drum submerged in the slurry in case of rotary drum filter is
3
30
85
25
30
91
Filter medium resistance is that offered by the
filter cloth.
embedded particles in the septum.
filter cloth and the embedded particle collectively.
none of these.
filter cloth and the embedded particle collectively.
92
In a roll crusher, both the rolls
have the same diameter.
are rotated towards each other.
run either at the same or different speeds.
all (a), (b) and (c).
all (a), (b) and (c).
93
Tube mill compared to ball mill
produces finer products.
is long in comparison with its diameter.
uses smaller balls.
all (a), (b) & (c).
all (a), (b) & (c).
94
For the preliminary breaking of hard rock, we use a
gyratory crusher
ball mill
tube mill
squirrel-cage disintegrator
gyratory crusher
95
Pick out the wrong statement.
For the compressible cake, voidage & the specific resistance of the cake can be assumed to be constant.
Cake resistance is independent of the pressure drop.
Crushing of explosive materials are done by employing drygrinding.
Gyratory crusher is a coarse crusher.
Cake resistance is independent of the pressure drop.
96
Which of the following oxides is not present in hematite iron ore?
Titanium oxide
Calcium oxide
Cobalt oxid
Manganese oxid
Cobalt oxid
97
Ribbon blenders are exclusively meant for
blending miscible liquids.
non-flowing powder and thin pastes.
bath mixing.
continuous mixing.
non-flowing powder and thin pastes.
## Footnote
ribbon powder
98
In closed circuit grinding as compared to open circuit grinding, the
specific surface of product is more.
product has lesser size uniformity.
production rate at a given limiting size is lower.
operation is economical.
operation is economical.
99
Pick out the correct statement
Angle of repose is always greater than the angle of slide.
A hopper is a small bin with a sloping bottom
A silo is a short height vessel of very large diameter used for the storage of high volatile matter coal.
Pine oil is used as a 'modifying agent' (for activating or depressing the adsorption of filming agents) in froth floatation process.
A hopper is a small bin with a sloping bottom
## Footnote
correct Hopper Sloping Bottom
100
Gelatinous solid (which plug the septum) can be filtered by a __________ filter.
sparkler
plate and frame
vacuum leaf
precoat
precoat
101
During the washing of cak
all the resistances are constant.
filter medium resistance increases
filter medium resistance decreases.
cake resistance decreases.
all the resistances are constant.
102
The opening of a 200 mesh screen (Taylor series) i
0.0074 cm
0.0074 m
0.0047 cm
74 mili-microns
0.0074 cm
103
A gravity decanter is meant for the separation of two __________ density.
immiscible liquids of different
miscible liquids of different
immiscible liquids of same
miscible liquids of same
immiscible liquids of different
104
The most suitable filter for the removal of very small amount of precipitate from very large volumes of water is the __________ filter.
vacuum
sand
plate & frame
rotary
sand
105
Separation of solid particles based on their densities is called
sizing
sorting
clarification
dispersion
sorting
106
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?
Cresylic acid
Copper sulphate
Calcium carbonate
Sodium carbonate
Copper sulphate
## Footnote
ACS activator copper sulphate
107
__________ are mixed using ribbon blenders.
Lumpy solids and low viscosity liquids
Dry powders
High viscosity liquid
Thick pastes
Dry powders
## Footnote
dry - ribbon
108
During agitation of liquids, the
Froude number is independent for the curves between power number and Reynolds number in baffled system.
Power number becomes independent of impellers Reynolds number at high Reynolds number, but is dependent on the geometry of the impeller
Froude number is used to account for the effect of surface (e.g., the centre vortex) on the power number.
all (a), (b) and (c).
all (a), (b) and (c).
109
For crushing of solids, the Rittinger's law states that the work required for crushing is proportional to
the new surface created.
the size reduction ratio.
the change in volume due to crushing.
none of these
the new surface created.
110
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
secondary
fine
primary
ultrafine
primary
111
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 )
LS
93 LS
250 LS
√ LS
93 LS
## Footnote
Taggart's - Jaw & Gyratory - 93LS
112
The process by which fine solids is removed from liquids is termed a
decantation
flocculation
sedimentation
classification
sedimentation
113
Which of the following crushing laws is most accurately applicable to the fine grinding of materials ?
Bond's crushing law
Kick's law
Rittinger's law
None of these.
Rittinger's law
114
Shell and leaf filter as compared to plate and frame filter
entails less labor cost
facilitates filtration under higher pressure.
provides more effective washing.
all (a), (b) & (c)
all (a), (b) & (c)
115
Metallic wire mesh is used as a filtering medium for the separation of dust from dust laden gas in case of a/an
air filter
bag filter
venturi scrubber
hydrocyclones
air filter
116
Which of the following is a coarse crusher?
Smooth roll crusher
Toothed roll crusher
Gyratory crusher
Tube mill
Gyratory crusher
117
Sorting classifiers employing differential settling methods for separation of particles make use of the differences in their
particle sizes
densities
terminal velocities
none of these
terminal velocities
118
Separation of particles of various sizes, shapes and densities by allowing them to settle in a fluid is called
classification
froth floatation
thickening
clarification
classification
119
The specific cake resistance for incompressible sludges is (where ΔP = pressure drop over cake)
is proportional to ΔP
is proportional to 1/ΔP
is proportional to ΔP
independent of ΔP
independent of ΔP
120
To produce talcum powder, use
ball mill
hammer mill
jet mill
pin mill
ball mill
## Footnote
talcum ball mill
121
Angle of nip of the crushing rolls does not depend upon the
diameter of the rolls
speed of the rolls
product size
feed size
speed of the rolls
122
Paddle agitator
is suitable for mixing low viscosity liquids.
produces axial flow.
moves at very high speed.
none of these.
is suitable for mixing low viscosity liquids.
123
Pick out the wrong statement.
More commonly used jaw crusher between Dodge jaw crusher and Blake jaw crusher is the later one.
There are only four methods namely compression, impact, attrition and cutting, which the size reduction equipments employ.
Cutting machines mainly employ 'attrition' for size reduction of solids.
Operating principles of Dodge and Blake jaw crushers are combined in the working of universal jaw crushers.
Cutting machines mainly employ 'attrition' for size reduction of solids.
124
Gummy & sticky materials like molasses, sugar etc. are best transported/handled by using a __________ conveyor.
drag
ribbon
screw
slat
ribbon
## Footnote
RGS Ribbon Gummy & Sticky
125
Soft & non-abrasive materials can be made into fines by
attrition
compression
cutting
none of these
attrition
126
In constant pressure filtration,
resistance decreases with time
rate of filtration is constant
rate of filtration increases with time
rate of filtration decreases with time
rate of filtration decreases with time
127
The critical speed of a trommel (N) is related to its dia (D) as
N is proportional to sqrt D
N is proportional to sqrt D
N is proportional to D
N is proportional to 1-D
N is proportional to sqrt D
128
Which of the following minerals is not subjected to magnetic separation method?
Rutile
Galena
Chromite
Siderite
Galena
129
Which of the following is not a revolving/tumbling mill used for size reduction?
Compartment mill
Pebble mill
Cage mil
Rod mill
Cage mil
130
Which of the following achieves the least reduction ratio for a given feed size?
Jaw crusher
Roll crusher
Cone crusher
Gyratory crusher
Roll crusher
131
A fluid energy mill is used for
cutting
grinding
ultragrinding
crushing
ultragrinding
132
Filtration should be stopped in a filter press, if the
cake becomes very dense.
liquor stops flowing out to the discharge.
filtration pressure rises suddenly
both(b)&(c)
both(b)&(c)
133
For coarse reduction of hard solids, use
impact
attrition
compression
cutting
compression
134
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.
primary
secondary
fine
ultrafine
secondary
135
Traces of liquid tar fog present in coke oven gas is separated using
electrostatic precipitator
cyclone separator
strainer
none of these
electrostatic precipitator
## Footnote
traces of liquid tar fog electrostatic
136
Close circuit grinding by a ball mill with air sweeping employs a
classifier.
cyclone separator between mill & classifier
both (a) & (b).
neither (a) nor (b).
both (a) & (b).
137
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
both (a) & (b).
1.34
4.34
1.34
138
Choke crushing (in case of a Jaw crusher) compared to free crushing
results in increased capacity.
consumes less power.
consumes more power.
both (a) and (c).
consumes more power.
139
The specific surface of sherical particles is proportional to (where, Dp = diameter of particle).
D2p
Dp
1/Dp
1/D2p
1/Dp
140
Wheat is ground into flour in a
hammer crusher
roller crusher
impact mill
fluid energy mill
roller crusher
141
Gravity stamp mill is meant for the __________ crushing.
primary
intermediate
fine
ultrafine
fine
## Footnote
Fine Gravity Stamp
142
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.
differential wettability.
size
volatile matter content.
density separation.
143
Toothed roll crushers achieve size reduction by
tearing (shear) and compression.
impact and attrition.
both (a) & (b).
neither (a) nor (b)
both (a) & (b).
144
Pick out the wrong statement:
Magnetic separation method can be employed to treat both dry & wet ores.
Reduction ratio in crushing operation is defined as the ratio of minimum feed size to the maximum product size.
Gyratory crusher is used for coarse crushing
Screens are of stationary, moving and vibratory types
Reduction ratio in crushing operation is defined as the ratio of minimum feed size to the maximum product size.
