Mechanical Operations Flashcards
1
Q
Short distance transportation of grain, gravel, sand, ash, asphalt etc. is done by using a __________ conveyor.
A
screw
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
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
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
5
Q
Pick out the wrong statement.
A
Size enlargement (opposite of size reduction) is not a mechanical operation
6
Q
In continuous filtration (at a constant pressure drop), filtrate flow rate varies inversely as the
A
square root of the velocity
7
Q
For sizing of fine materials, the most suitable equipment is a
A
vibrating screen
8
Q
Which of the following is not categorised as a “mechanical operation” ?
A
Humidification
9
Q
Which of the following is a pressure filter?
A
Plate and flame filter
10
Q
Tabular bowl centrifuges as compared to disk bowl centrifuges
A
operate at higher speed
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
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
all ‘a’, ‘b’&’c’
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
14
Q
Pick out the wrong statement pertaining to the roll crushers.
A
Both the rolls run necessarily at the same speed
15
Q
Which of the following is not an ultrafine grinder (colloid mill)?
A
Toothed roll crusher
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
17
Q
Which of the following is the most suitable for handling fibrous and dense slurries?
A
Cone type agitator
18
Q
__________ centrifuge is normally used in sugar mills.
A
Suspended batch basket
19
Q
Solid particles separation based on the difference in their flow velocities through fluids is termed as the
A
classification
20
Q
Diatomaceous earth is a/an
A
filter aid
21
Q
The distribution given by microscopic analysis of powder is
A
number
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
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
24
Q
In washing type plate and frame filter press, the ratio of washing rate to the final filtrate rate is
A
36895
25
Ball mills and tube mills with flint or porcelain balls are used for size reduction of
non-metallic ores
26
Size reduction of __________ is accomplished in steam heated rollers and roll crushers.
hard rubber
27
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.
speed
28
Which of the following is not a part of the Blake jaw crusher?
Hanger
29
If a force greater than that of gravity is used to separate solids & fluids of different densities, the process is termed as the
centrifugation
30
Filter aid is used to
increase the porosity of the cake.
31
Which of the following mineral dressing operations is termed as 'comminution'?
None of these
32
The capacity of a pneumatic conveying system depends upon the
all (a), (b) and (c)
33
Pick out the wrong statement.
The equipment used for the removal of traces of solids from a liquid is called a classifier
34
Gravity settling process is not involved in the working of a
hydrocyclone
35
Froth floatation is the most suitable for treating
sulphide ores
36
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/to
37
Which of the following is the most suitable for cleaning of fine coal dust (<0.5 mm)?
Froth floatation
38
Pick out the correct statement:
The operating cost of shaking screen is more than that of a vibrating screen
39
Range of compressibility co-efficient of the commercial compressible cake obtained in filtration operation is
0.2 to 0.8
40
Highly viscous liquids & pastes are agitated by
multiple blade paddles
41
The value of 'angle of nip' is generally about
32°
42
Size reduction of the __________ can be suitably done by ball mills, crushing rolls and rod mills.
metalliferrous ores
43
Sulphuric acid mist is arrested by using a __________ scrubber.
venturi
44
The main size reduction operation in ultrafine grinders is
attrition
45
In case of a hammer crusher,
all (a), (b) and (c).
46
Jigging is a technique by which different particles can be
separated by particle size.
47
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.
impact
48
Balls for ball mills are never made of
lead
49
200 mesh screen means 200 openings per
inch
50
__________ is the most commonly used 'filter aid'.
Diatomaceous earth
51
Energy consumed for crushing one ton of material ranges from __________ kWh.
0.5 to 1.5
52
For transporting pasty material, one will use a/an
screw colaveyor
53
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
disc bowl centrifuge.
54
A tube mill compared to a ball mill
has a higher length/diameter ratio.
55
Trommels separate a mixture of particles depending on their
size
56
Basic slag is not ground in
jaw crushers
57
Grindability of a material does not depend upon its
size
58
Shape factor for a cylinder whose length equals its diameter is
1.5
59
In case of a hammer crusher, the
rotor shaft carrying hammers can be vertical or horizontal.
60
Dust laden air can be purified using a
cyclone separator
61
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
62
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)
0.087 L.S
63
Vacuum is applied in __________ zone, in case of a general type continuous rotary drum vacuum filter.
all (a), (b) & (c)
64
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.
1.5
65
Which of the follwoing mechanical conveyors does not come under the division 'scrapers' ?
Bucket elevators
66
__________ mixer is used for devulcanisation of rubber scrap & making water dispersion & rubber solution.
Banbery
67
Which of the following mechanical conveyors does not come under the division 'carriers'?
Screw conveyor
68
Screen capacity is not a function of
atmospheric humidity
69
Which of the following is a vacuum filter?
Rotary disc filter
70
Pine oil used in froth floatation technique acts as a/an
frother
71
Length/diameter ratio of a ball mill is
< 1
72
Feed size of ≥ 25 cms can be accepted by
jaw crusher
73
Which is the most suitable conveyor for transportation of sticky material?
Screw conveyor
74
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
75
Laminar flow region is said to exist during agitation of a liquid in an agitator, when the value of Reynolds number is
<10
76
Filtration of water in a paper mill is done by a/an __________ filter.
open sand
77
Moore filter is a __________ filter.
leaf
78
Sphericity of a cubical particle, when its equivalent diameter is taken as the height of the cube, is
1
79
Ball mill is used for
fine grinding
80
In case of a ball mill,
coarse feed requires a larger ball
81
Maximum size reduction in a ball mill is done by the, __________ action.
impact
82
Increasing the capacity of a screen __________ the screen effectiveness.
decreases.
83
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
N2
84
Bond crushing law
calls for relatively less energy for the smaller product particles, than does the Rittinger law.
85
Flow of filtrate through the cake in a plate and frame filter press is best described by the __________ equation.
Kozney-Karman
86
The controlling resistance in a rotary drum vacuum filter is the __________ resistance.
cake
87
Which of the following is used for primary crushing of very hard lumpy materials?
Gyratory crusher
88
Coal is finally pulverised to 200 mesh size for burning in boilers by a
ball mill
89
Crushing efficiency is the ratio of the
surface energy created by crushing to the energy absorbed by the solid.
90
The resistance offered by the filter used in a bag filter is proportional to (where, c = dust concentration, and s = particle size )
c/s
91
Cement clinker is reduced to fine size by a
tube mill
92
The crushed material received for separation is called feed or
heading
93
For spheres, volume shape factor is given by
π/6(=V/D3)
94
Which of the following agitators having a large blade area, rotating at slow speed is used for mixing high viscosity liquids ( > 50000 centipoise)?
Helical screw
95
__________ is defined as the geometric mean of the relative rejections and the relative recoveries of two minerals.
Selectivity index
96
The operating speed of a ball mill should be __________ the critical speed.
less than
97
Use of baffles in agitators help in minimising the __________ tendency.
both (a) & (b)
98
__________ are used for the separation of coarse particles from a slurry of fine particles.
Classifiers
99
Fibrous material is broken by a
squirrel-cage disintegrator
100
__________ is the most suitable for compounding rubber and plastic solids.
Banbery mixer
101
Out of the following size reduction equipments, the maximum feed size can be accepted by the
jaw crusher
102
Bucket elevators are not suitable for the vertical lifting of __________ materials.
sticky (e.g. clay paste)
103
The most common filter aid is
diatomaceous earth
104
For removal of very small amounts of precipitate from large volume of water, the most suitable filter is the __________ filter.
sand
105
For separation of sugar solution from settled out mud, we use a __________ filter.
centrifugal
106
The sphericity of a cylinder of 1 mm diameter and length 3 mm is
0.9
107
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.
0.3
108
What is the selectivity index, if the grade of tailings & concentrate is the same?
1
109
The most suitable equipment used to devulcanise rubber scrap and to make water dispersion & rubber solution is a
boundary mixer.
110
Traces of solids are removed from, liquid in a
clarifier
111
_________ balls capable of grinding the feed in a ball mill gives the maximum efficiency.
Minimum size
112
The speed of a rotary drum vacuum filter may be about __________ rpm.
1
113
Colloid mills achieve size reduction mainly by
attrition
114
Mesh indicates the number of holes per
linear inch
115
For achieving maximum capacity of the ball mill, the ball charge should be equal to about __________ percent of the ball mill volume.
50
116
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).
sqrt(S/V)p
117
Which of the following gives the work required for size reduction of coal to -200 mesh in a ball mill most accurately ?
Rittinger's law
118
Electrical energy consumed by a jaw crusher is not a function of the
none of these
119
Size reduction mechanism used in Jaw crushers is
compression
120
Trommels employ __________ for screening of materials.
punched plate
121
A widely used size reduction equipment for __________ is Bradford breaker.
coal
122
Ultra centrifuges are used for the separation of __________ solid particles.
colloidal
123
Specific surface area is the surface area of a unit __________ of materials.
either (a) or (b)
124
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.
compartment
125
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
both (a) & (b).
126
Size reduction does not occur due to compression in case of
rod mills
127
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
128
Which of the following represents the plot of filtrate volume versus time for constant pressure filtration?
Parabola
129
Driving force in case of filtration by a centrifuge is the
centrifugal pressure exerted by the liquid.
130
Rod mills employed for grinding
all 'a', 'b' & 'c'.
131
Production rate __________ with increased fineness, with a given energy input to the size reduction machine.
decreases
132
Gold ore concentration is mostly done using
tabling
133
Mixing of light fine powder such as insecticides is done by
impact wheels
134
Run of mine (ROM) coal is crushed by a __________ for use in domestic ovens.
hammer crusher
135
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?
Sphere
136
The unit of specific cake resistance is
gm/cm2
137
Size reduction of asbestos and mica is done by
hammer mills
138
A pebble mill
both (b) and (c).
139
The study on washability of coal is done by using the __________ technique.
heavy media separation
140
Horsepower required for a roll crusher is directly proportional to its
both (a) & (b).
141
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
142
__________ conveyor is the most suitable for long distance transportation of cold, non-abrasive granular/irregular shape/fine materials.
Belt
143
The specific cake resistance for compressible sludges is a function of the pressure drop
over cake
144
Moisture can be removed from lubricating oil using
tubular centrifuge
145
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
146
Pick out the wrong statement.
Crushing efficiency is the ratio of the energy absorbed by the solid to the surfaces energy created by crushing.
147
Addition of filter aid to the slurry before filtration is done to ...... of the cake.
increase the porosity
148
Which of the following terminology is not used for size reduction of materials to fine sizes or powders?
Compression
149
A tube mill as compared to a ball mill
all (a), (b) and (c).
150
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
kW. sec/kg
151
Which of the following gives the crushing energy required to create new surface?
Rittinger's law
152
In filtration, the use of 'filter aid' helps in
deplugging the filter medium.
153
Gizzlies are used for separating __________ solids.
fine
154
Which of the following clay mixing devices is vacuum operated for deairation of clay?
Pug mil
155
Pick out the material having minimum Rittinger's number.
Quartz
156
__________ mills are termed as impactors.
Hammer
157
In case of a revolving mill, wet grinding compared to dry grinding
none of these.
158
To get a fine talc powder from its granules, the equipment used is
ball mill
159
For a cyclone of diameter 0.2 m with a tangential velocity of 15 m/s at the wall, the separation factor is
230
160
Width and speed of a conveyor belt depends upon the __________ of the material.
both (a) & (b)
161
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
all (a), (b) and (c).
162
Pick out the wrong statement.
Capacity of crusher in choke feeding is increased.
163
Which of the following size reduction equipments employs mainly attrition for ultrafine grinding?
all (a), (b) and (c)
164
Tank filter (e.g., Nutsch filter) is
used for small scale filtration work.
165
In bag filters, filter fabrics are never made of
metallic wire woven mesh
166
Use of 'grinding aids' is done in __________ grinding.
dry
167
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)
D
168
Which of the following is the most suitable filter for separation of abrasive solids suspended in a corrosive liquid?
Vacuum filter
169
All resistances during washing of cake
remain constant
170
A __________ mixer resembles a ball mill without balls.
tumbling
171
__________ conveyor is the most suitable for short distance transportation of non-abrasive loose materials like garbage, grain, food wastes etc.
Flight
172
As the product becomes finer, the energy required for grinding
icreases
173
Gyratory crushers compared to the reciprocating jaw crushers
have greater capacity per unit of discharge area.
174
The important dimensional group involved in the power requirement calculation in mixing operation is the __________ number.
both (a) & (b)
175
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.
Po ∝ Re-1.0
176
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 mill
177
Rittinger's crushing law states that
work required in crushing is proportional to the new surface created.
178
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'?
Both (b) and (c)
179
Sphericity of pulverised coal is
<1
180
The reduction ratio for fine grinders is
as high as 100
181
Which of the following is the hardest material?
Corundum
182
General mechanism of size reduction in intermediate and fine grinder is by
impact and attrition.
183
A straight line is obtained on plotting reciprocal of filtration rate vs. the volume of filtrate for __________ flow of filtrate.
incompressible cake and laminar
184
The work index in Bond's law for crushing of solids has the following dimensions
kWh/ton
185
Ore concentration by jigging is based on the difference in the __________ of the particles.
specific gravities
186
Size measurement of ultrafine particles can be best expressed in terms of
surace area per unit mass
187
Reduction ratio of crushers is the
ratio of feed opening to discharge opening.
188
Which is a secondary crusher for a hard & tough stone?
Cone crusher
189
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 . (1-Dsb - 1-Dsa)
190
Cyclones are used primarily for separating
solids from fluids
191
There is practically no alternative/competitor to __________ in the beneficiation treatment of sulphide ores.
froth floatatio
192
Separation of isotopes is generally done using a/an __________ centrifuge.
ultra
193
Temperature of the product during ultrafine grinding
increases
194
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.
195
In a ball mill, the volume occupied by the balls (when the mill is stopped) is about __________ percent of the volume of the mill.
50
196
Separation of materials of the same density based on their sizes by using then-different rates of flow is called
sizing
197
Molten ammonium nitrate is mixed with ground limestone in fertilizer plant in a
pug mill
198
Agglomeration of individual particles into clusters (flocs) is called flocculation. To prevent flocculation, the most commonly used dispersing agents are
silicates & phosphates
199
For a sphere falling in the constant drag co-efficient regime, its terminal velocity depends on its diameter (d) as
d2
200
With increase in the capacity of screens, the screen effectiveness
decreases
201
As particle size is reduced
screening becomes progressively more difficult.
202
Rittinger number which designates the new surface prduced per unit of mechanical energy absorbed by the material being crushed, depends on the
all (a), (b) and (c).
203
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.
1000°C and 10 atm.
204
For efficient grinding, ball mills must be operated
at a speed less than the critical speed.
205
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.
fine
206
For spheres, the surface shape factor is given by (where, A = area, V = volume, and D = diameter)
π(=A/D2)
207
The reduction ratio for grinders is defined as(where, Df and Dp are average diameters of feed and product respectively).
Df/Dp
208
Pick out the wrong statement pertaining to the turbine agitator.
Pitched blade turbine agitator gives only radial flow with complete absence of the axial flow.
209
A fluid energy mill is used for
ultra grinding
210
Which of the following is the softest material ?
Talc
211
Dry powdery solid materials are transported by a __________ conveyor.
screw
212
Fluid energy mill comes in the category of
ultrafine grinder
213
Filtration capacity of a rotary drum vacuum filter depends upon the
both (a) & (b).
214
__________ conveyors are also called scrapers.
both (b) & (c)
215
For laminar flow of filtrate through the cake deposited on septum, which of the following will be valid
Kozney-Karman equation
216
Which of the following is a continuous filter?
None of these
217
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.
218
In screen analysis, the notation +5 mm/-10 mm means particles passing through
10 mm screen and retained on 5 mm screen.
219
Optimum ratio of operating speed to critical speed of a trommel is
0.33-0.45
220
The process opposite to 'dispersion' is termed as the
flocculation
221
The cake resistance increases steadily with the time of filtration in a plate and frame filter employing constant __________ filtration.
both (a) & (b)
222
Grinding efficiency of a ball mill is of the order of __________ percent
36896
223
Solid particles of different densities are separated by
sorting classifier
224
During agitation of liquids, power consumption during laminar flow is not proportional to the
density of the liquid
225
Trommels are revolving screens which normally operate in the range of __________ rpm
15 - 20
226
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
227
Maximum size reduction in a fluid energy mill is achieved by
interparticle attritio
228
Filtration rate through a filter cake is proportional to (where, S = filtering surface R= specific cake resistance μ = viscosity of the filtrate)
all (a), (b) & (c)
229
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
1-2 w2 . δρL (2R + δ)
230
Which one is a filter aid ?
Diatomaceous earth
231
To remove dirt from the flowing fluid, we use a
strain
232
Which of the following crushers can be considered as a combination of a jaw crusher and a roller crusher ?
Gyratory crusher
233
Separation of solid suspended in liquid into a supernatant clear liquid and a denser slurry employs a process termed as the
sedimentation
234
Ultrafine grinders operate principally by
attrition
235
Which of the following comes in the category of primary crusher for hard and tough stone ?
Jaw crusher
236
Crushing efficiency of a machine ranges between __________ percent.
0.1 to 2
237
Screen capacity is expressed in terms of
tons/hr-ft
238
A screen is said to be blinded, when the
screen is plugged with solid particles.
239
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
240
Percentage of drum submerged in the slurry in case of rotary drum filter is
30
241
Filter medium resistance is that offered by the
filter cloth and the embedded particle collectively.
242
In a roll crusher, both the rolls
all (a), (b) and (c).
243
Tube mill compared to ball mill
all (a), (b) & (c).
244
For the preliminary breaking of hard rock, we use a
gyratory crusher
245
Filtration operation carried out by continuous increase of the inlet pressure of slurry, is called the __________ filtration.
constant rate
246
Pick out the wrong statement.
Cake resistance is independent of the pressure drop.
247
Which of the following oxides is not present in hematite iron ore?
Cobalt oxid
248
Ribbon blenders are exclusively meant for
non-flowing powder and thin pastes.
249
In closed circuit grinding as compared to open circuit grinding, the
operation is economical.
250
Pick out the correct statement
A hopper is a small bin with a sloping bottom
251
Gelatinous solid (which plug the septum) can be filtered by a __________ filter.
precoat
252
During the washing of cak
all the resistances are constant.
253
The opening of a 200 mesh screen (Taylor series) i
0.0074 cm
254
A gravity decanter is meant for the separation of two __________ density.
immiscible liquids of different
255
The most suitable filter for the removal of very small amount of precipitate from very large volumes of water is the __________ filter.
sand
256
Separation of solid particles based on their densities is called
sorting
257
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?
Copper sulphate
258
__________ are mixed using ribbon blenders.
Dry powders
259
During agitation of liquids, the
all (a), (b) and (c).
260
For crushing of solids, the Rittinger's law states that the work required for crushing is proportional to
the new surface created.
261
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
262
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 )
93 LS
263
The process by which fine solids is removed from liquids is termed a
sedimentation
264
Which of the following crushing laws is most accurately applicable to the fine grinding of materials ?
Rittinger's law
265
Shell and leaf filter as compared to plate and frame filter
all (a), (b) & (c)
266
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
267
Which of the following is a coarse crusher?
Gyratory crusher
268
Sorting classifiers employing differential settling methods for separation of particles make use of the differences in their
terminal velocities
269
Separation of particles of various sizes, shapes and densities by allowing them to settle in a fluid is called
classification
270
The specific cake resistance for incompressible sludges is (where ΔP = pressure drop over cake)
independent of ΔP
271
To produce talcum powder, use
ball mill
272
Angle of nip of the crushing rolls does not depend upon the
speed of the rolls
273
Paddle agitator
is suitable for mixing low viscosity liquids.
274
Pick out the wrong statement.
Cutting machines mainly employ 'attrition' for size reduction of solids.
275
Gummy & sticky materials like molasses, sugar etc. are best transported/handled by using a __________ conveyor.
ribbon
276
Soft & non-abrasive materials can be made into fines by
attrition
277
In constant pressure filtration,
278
The critical speed of a trommel (N) is related to its dia (D) as
N ∝ sqrt D
279
Which of the following minerals is not subjected to magnetic separation method?
Galena
280
Which of the following is not a revolving/tumbling mill used for size reduction?
Cage mil
281
Which of the following achieves the least reduction ratio for a given feed size?
Roll crusher
282
A fluid energy mill is used for
ultragrinding
283
Filtration should be stopped in a filter press, if the
both(b)&(c)
284
For coarse reduction of hard solids, use
compression
285
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
286
Traces of liquid tar fog present in coke oven gas is separated using
electrostatic precipitator
287
Close circuit grinding by a ball mill with air sweeping employs a
both (a) & (b).
288
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
289
Choke crushing (in case of a Jaw crusher) compared to free crushing
consumes more power.
290
The specific surface of sherical particles is proportional to (where, Dp = diameter of particle).
1/Dp
291
Wheat is ground into flour in a
roller crusher
292
Gravity stamp mill is meant for the __________ crushing.
fine
293
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.
294
Toothed roll crushers achieve size reduction by
both (a) & (b).
295
Pick out the wrong statement:
Reduction ratio in crushing operation is defined as the ratio of minimum feed size to the maximum product size.
296
To get ultrafine particles, the equipment used is a
fluid energy mill
297
Vacuum filter is most suitable for the
none of these.
298
The porosity of a compressible cake is
minimum at the filter medium.
299
Which of the following conveyors cannot be recommended for transportation of abrasive materials ?
Flight conveyor
300
Separation of materials into products based on the difference of their sizes is called
sizing
301
For classification of potable (drinking) water, we use a __________ filter.
gravity sand
302
Hot, lumpy & abrasive materials are best transported by using a/an __________ conveyor.
apron
303
Additives used for promoting the floccula-tion of particles is a/an
both (a) & (b)
304
In case of grinding in a ball mill
all (a), (b) and (c).
305
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)
3.6 AVS.ρ
306
Kick's law relates to
energy consumption
307
__________ mill is normally used for grinding of talc.
Ring-roll
308
Colloidal mills are used for __________ grinding.
ultrafine
309
Fluid medium used in the classification technique of mineral beneficiation is
either (a) or (b)
310
The maximum slope of a belt conveyor can be
30°
311
The filter medium resistance is controlled by
both pressure drop and flow rate
312
The unit of filter medium resistance is
cm-1
313
During size reduction by a jaw crusher, the energy consumed decreases with the
increasing size of feed at constant reduction ratio.
314
Which of the following can be most effectively used for clarification of lube oil and printing ink?
Sharpies supercentrifuge
315
Ultracentrifuges running at speeds upto 100000 rpm is normally used for the
separation of isotopes based on their density or molecular weights difference.
316
Sizing of very fine particles of the order of 5 to 10 microns is done by elutriation, which is a __________ operation.
classification
317
In the cyclone separator used for separation of dust from dust laden gas, the gas
both (b) and (c).
318
Size reduction of fibrous materials like wood, asbestos, mica etc. is done by a disintegrator exemplified by the
cage mill
319
The material is crushed in a gyratory crusher by the action of
compression
320
The equivalent diameter of channel of a constant non-circular cross-section of 3 cm by 6 cm will be __________ cms.
2
321
Which of the following may prove unsuitable for filtering volatile liquids ?
Vacuum filter
322
__________ mean diameter of particles is given by
volume
323
Mass flow of granular solid (M) through a circular opening of dia, D follows
M ∝ D3
324
Sauter mean diameter is the same as the __________ mean diameter.
volume-surface
325
Cake resistance is
none of these.
326
In paint industries, blending of light paste is done by using a
charge can mixer
327
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
0.5
328
__________ is used for producing a thick suspension from a thin slurry.
Pressure filter thickener
329
Wet seiving is employed, when the product contains __________ materials.
large quantity of very fine
330
Energy requirement (per unit mass of material crushed/ground) is highest for
fluid energy mill
331
The energy consumed by a ball mill depends on
all (a), (b) and (c).
332
Energy consumption in a crusher decreases with increase in the
all (a), (b) & (c).
333
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).
Pclet
334
The term 'angle of nip' is concerned with the operation of the __________ crushers.
roll
335
Cartridge filters are termed as 'edge' filters, because of the fact that the
bulk of the solids are removed at the periphery of the disks.
336
Vibrating screens have capacity in the range of __________ tons/ft2 .mm mesh size.
0.2 to 0.8
337
Cumulative analysis for determining surface is more precise than differential analysis, because of the
assumption that all particles in a single fraction are equal in size, is not needed.
338
To remove very small amount of tiny solid impurities from liquid, we use a
coagulant
339
Screw conveyors are
suitable for sticky materials.
340
__________ mills fall in the category of tumbling mills,
all (a), (b) & (c)
341
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)
3.6 W.D.V.ρ
342
Which of the following is not a cutting machine?
Tube mills
343
Weber number is significant and is concerned with the
dispersion of liquid in liquid.
344
Power consumption during turbulent flow in agitation tank is proportional to the __________ of the liquid.
density
345
Screen efficiency is
none of these
346
For grinding of cereals, grains, spices, pigments, saw dust, cork etc., the most extensively used size reduction equipment is a
Buhrstone mill
347
Handling of ashes and similar materials can be done best by a __________ conveyor.
drag or slat
348
Which of the following must be stored in silos and not in open yard ?
High V.M. bituminous coal
349
Apron conveyors are used for
heavy loads & short runs.
350
Sedimentation on commercial scale occurs in
rotary drum filters
351
With increase in drum speed, in a rotary drum filter, the filtration rate
increases
352
Arrange the following size reduction equipment in the decreasing order of the average particle size produced by each of them.
Jaw crusher, Ball mill, Fluid energy mill
353
200 mesh seive size corresponds to __________ microns.
74
354
What is the usual value of angle of nip for crushing of ordinary rock in smooth steel crushing rolls ?
32°
355
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
Np ∝ 1/NRe
356
Which of the following is not accomplished by agitation of liquids in agitators?
Blending of immiscible liquids.
357
Which of the following parts of a jaw crusher is subjected to maximum wear and tear during its operation ?
Jaw plates
358
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
359
In froth floatation, chemical agent added to cause air adherence is called
collector
360
The sphericity of a solid particle of cubical shape is
(π/6)1/3
361
Vertical transportation of materials can be done by a/an
both(b)&(c)
362
In a roll crusher, the specific power consumption and the production rate is affected by the
both (a) and (b).
363
A cottrel precipitator makes use of the __________ for dusty air cleaning.
corrona discharge
364
If radius of a batch basket centrifuge is halved & the r.p.m. is doubled, then the
centrifugal force is doubled.
365
The ratio of the area of openings in one screen (Taylor series) to that of the openings in the next smaller screen is
none of these
366
Compressibility co-efficient for an absolutely compressible cake is
1
367
Mixing of plastic solids is generally facilitated by
kneading
368
grinding element & the housing.
both (a) and (b).
369
Which of the following is not an industrial screening equipment ?
Sharpies centrifuge
370
Which of the following is not a wet classifier ?
None of these
371
Helical screw agitator is used for
mixing highly viscous pastes.
372
For raschig rings, the sphericity is
<1
373
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.
500
374
__________ mills are termed as disintegrators.
Cage
375
Supporting legs of a plate and frame filter is normally made of
cast iron
376
Wet grinding in a revolving mill __________ as compared to dry grinding.
increases capacity
377
The grinding in a hammer crusher takes place due to the
both (a) & (b)
378
A compressible cake has the
maximum porosity at the upstream side.
379
Which of the following is not used as a filter medium in case of corrosive liquids ?
Cotton fabric
380
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
381
Pine oil and cresylic acid are used as __________ in the froth floatation process.
frother
382
Grinding characteristic of a material is given by its
HGI
383
Which of the following is not a non-metalliferous mineral?
Cassiterrite
384
Filter medium resistance is important during the __________ of filtration.
early stages.
385
Float and sink test determines the possibility of cleaning of coal by a process based on the
gravity separation
386
__________ baffles are provided in ball mills.
Horizontal
387
Mixer used for rubber compounding is
banbury internal mixer
388
For spheres, the specific surface shape factor is given by
AD/V
389
__________ mill is not used for grinding wheat into flour and for milling of cereals & other vegetable products.
Pebble
390
In case of a hammer crusher, the final product size depends on the
all (a), (b) and (c).
391
Sphericity of raschig ring (whose length and diameter are equal) is
1
392
Mixing mechanism employed in a pan mixer is by
mulling
393
Chance process is used for the
cleaning of coal.
394
Which of the following screens has the maximum capacity ?
Vibrating screen
395
Stamp mills are generally used for crushing
gold ores
396
In case of a plate and frame filter press, filtrate flow through the cake follows __________ flow.
laminar
397
Which of the following is a batch sedimentation equipment ?
Filter thickener
398
The most suitable equipment for the transportation of 200 mesh size particles is a
pneumatic conveyor
399
Which of the following is not used as filter aid?
Rice husk
400
Raw materials are charged in the iron blast furnace using
skip hoist
401
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
flint or porcelain
402
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
all 'a', 'b'&'c'.
403
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 ?
μ ≥ tan α
404
Pick out the wrong statement pertaining to the roll crushers.
Both the rolls run necessarily at the same speed.
405
Which of the following is not an ultrafine grinder (colloid mill)?
Toothed roll crusher
406
Two particles are called to be equal settling, if they are having the same.
terminal velocities in the same fluid & in the same field of force.
407
Which of the following is the most suitable for handling fibrous and dense slurries ?
Cone type agitator
408
__________ centrifuge is normally used in sugar mills.
Turbine agitator
409
Solid particles separation based on the difference in their flow velocities through fluids is termed as the
classification
410
Diatomaceous earth is a/an
filter aid
411
The distribution given by microscopic analysis of powder is
number
412
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)
m/ρ . Vp
413
For a non-spherical particle, the sphericity
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.
414
In washing type plate and frame filter press, the ratio of washing rate to the final filtrate rate is
36895
415
Ball mills and tube mills with flint or porcelain balls are used for size reduction of
non-metallic ores
416
Size reduction of __________ is accomplished in steam heated rollers and roll crushers.
hard rubber
417
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.
speed
418
Which of the following is not a part of the Blake jaw crusher?
Hanger
419
If a force greater than that of gravity is used to separate solids & fluids of different densities, the process is termed as the
centrifugation
420
Filter aid is used to
increase the porosity of the cake.
421
Which of the following mineral dressing operations is termed as 'comminution'?
None of these
422
The capacity of a pneumatic conveying system depends upon the
all (a), (b) and (c).
423
Pick out the wrong statement.
The equipment used for the removal of traces of solids from a liquid is called a classifier.
424
Gravity settling process is not involved in the working of a
hydrocyclone
425
Froth floatation is the most suitable for treating
sulphide ores
426
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
427
Which of the following is the most suitable for cleaning of fine coal dust (<0.5 mm) ?
Froth floatation
428
Pick out the correct statement:
Removal of iron from ceramic material is necessitated (by magnetic separation method) so as to avoid discolouration of ceramic products.
429
Range of compressibility co-efficient of the commercial compressible cake obtained in filtration operation is
0.2 to 0.8
430
Highly viscous liquids & pastes are agitated by
multiple blade paddles
431
The value of 'angle of nip' is generally about
32°
432
Size reduction of the __________ can be suitably done by ball mills, crushing rolls and rod mills.
metalliferrous ores
433
Sulphuric acid mist is arrested by using a __________ scrubber
venturi
434
The main size reduction operation in ultrafine grinders is
attrition
435
In case of a hammer crusher,
all (a), (b) and (c).
436
Jigging is a technique by which different particles can be
separated by particle size.
437
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.
impact
438
Balls for ball mills are never made of
lead
439
200 mesh screen means 200 openings per
inch
440
__________ is the most commonly used 'filter aid'.
Diatomaceous earth
