me op 2 Flashcards
1
Q
Electrical energy consumed by a jaw crusher is not a function of
the
A. average feed size
B. average product size
C. machine capacity
D. none of these
A
D
2
Q
The most suitable equipment used to devulcanize rubber scrap
and to make water dispersion & rubber solution is a
A. boundary mixer
B. propeller agitator
C. sharpies centrifuge
D. none of these
A
A
3
Q
Size reduction mechanism used in Jaw crushers is
A. attrition
B. compression
C. cutting
D. impact
A
B
4
Q
For removal of very small amounts of precipitate from large
volume of water, the most suitable filter is the ______ filter.
A. plate & frame
B. shell & leaf
C. sand
D. rotary vacuum
A
C
5
Q
Trommels employ _______ for screening of materials.
A. fibrous cloth
B. woven wire screen
C. punched plate
D. none of these
A
C
6
Q
Sphericity is the ratio of the surface area of a spherical particle
having the same volume as the particle as the particle to the
surface area of the particle. Which of the following has the
maximum value of sphericity?
A. Sphere
B. Cube
C. Cylinder (L/D = 1)
D. Raschig rings
A
A
7
Q
Run of mine (ROM) coal is crushed by a __________ for use in domestic ovens.
jaw crusher
hammer crusher
ball mill
tube mill
A
B
8
Q
Ultra centrifuges are used for the separation of ______ solid
particles.
A. coarse
B. fine
C. colloidal
D. dissolved
A
C
9
Q
Specific surface area is the surface area of a unit ________ of
materials.
A. weight
B. volume
C. either a or b
D. neither a or b
A
C
10
Q
A _______ mill is a revolving mill divided into two or more
sections by perforated partitions in which preliminary grinding
takes place at one end and the finishing grinding at the
discharge end.
A. compartment
B. tube
C. rod
D. pebble
A
A
11
Q
The constants (Kb, Kr and Kk) used in the laws of crushing (i.e.,
Bond’s law, Rittinger’s law and Kick’s law) depend upon the
A. feed material
B. type of crushing machine
C. both a & b
D. neither a nor b
A
C
12
Q
Size reduction does not occur due to compression in case of
A. rod mills
B. gyratory crushers
C. jaw crushers
D. smooth roll crushers
A
A
13
Q
According to Taggart’s rule for selecting between a gyratory
crusher and a jaw crusher; the latter should be used, if the hourly
tonnage to be crushed divided by the square of the gape
expressed in cm is less than
A. 0.00184
B. 0.0184
C. 0.184
D. 1.84
A
B
14
Q
Which of the following represents the plot of filtrate volume
versus time for constant pressure filtration?
A. Parabola
B. Straight line
C. Hyperbola
D. Exponential curve
A
A
15
Q
Driving force in case of filtration by a centrifuge is the
A. speed of the centrifuge
B. centrifugal pressure exerted by the liquid
C. narrow diameter of the vessel
D. formation of highly porous cak
A
B
16
Q
Rod mills employed for grinding
A. employ a steel shell having l/d ratio of 1.5 to 3.0
B. is useful for handling sticky materials
C. employ stell rods of 2-12 cm diameter extending over
full length of the mill
D. all
A
D
17
Q
Production rate ______ with increased fineness, with a given
energy input to the size reduction machine.
A. Decreases
B. increases
C. remains unchanged
D. may increase or decrease; depends on the machine
A
A
18
Q
Gold ore concentration is mostly done using
A. jigging
B. tabling
C. froth floatation
D. elutriation
A
B
19
Q
Mixing of light fine powder such as insecticides is done by
A. banbury mixer
B. pug mill
C. impact wheels
D. kneader
A
C
20
Q
Run of mine (ROM) coal is crushed by a ______ for use in
domestic ovens.
A. jaw crusher
B. hammer crusher
C. ball mill
D. tube mill
A
B
21
Q
The unit of specific cake resistance is
A. gm/cm2
B. cm/gm
C. cm/gm2
D. gm/gm
A
A
22
Q
Size reduction of asbestos and mica is done by
A. hammer mills
B. rod mills
C. gyratory crushers
D. crushing rolls
A
A
23
Q
A pebble mill
A. is a ball mill
B. employs flints or ceramic pebbles as the grinding
medium
C. is a tube mill lined with ceramic or other non-metallic
liner
D. both b and c
A
D
24
Q
The study on the washability of coal is done by using the ____
technique.
A. tabling
B. elutriation
C. heavy media separation
D. none of these
A
C
25
Horsepower required for a roll crusher is directly proportional to
its
A. reduction ratio
B. capacity
C. both a & b
D. neither a nor b
C
26
The specific cake resistance for compressible sludges is a
function of the pressure drop
A. over cake
B. over medium
C. overall
D. none of these
A
27
Moisture can be removed from lubricating oil using
A. tubular centrifuge
B. clarifier
C. sparkler filter
D. vacuum leaf filter
A
28
A suspension of glass beads in ethylene glycol has a hindered
settling velocity of 1.7 mm/s, while the terminal settling velocity
of a single glass bead in ethylene glycol is 17 mm/s. if the
Richardson-Zaki hindered settling index is 4.5, the volume
fraction of solids in the suspension is
A. 0.1
B. 0.4
C. 0.6
D. none of these
C
29
________ conveyor is the most suitable for long distance
transportation of cold, non-abrasive granular/irregular
shape/fine materials.
A. Bucket
B. Belt
C. Screw
D. Apron
B
30
Tabling process used for separating two materials of different
densities by passing the dilute pulp over a table/deck, which is
inclined from the horizontal surface at an angle of about
A. 1 to 2°
B. 2 to 5°
C. 5 to 10°
D. 10 to 15°
B
31
Pick out the wrong statement
A. Gape is the greatest distance between the crushing
surfaces or the jaws.
B. The angle of nip (2𝛼) is the angle between roll faces at
the level where they will just take hold of a particle and
draw it in the crushing zone.
C. Crushing efficiency is the ratio of the energy absorbed
by the solid to the surface’s energy created by
crushing.
D. Reduction ratio is the ratio of the maximum size of the
particles in the feed to that in the product.
C
32
Addition of filter aid to the slurry before filtration is done to _____
of the cake
A. increase the porosity
B. increase the compressibility co-efficient
C. decrease the porosity
D. decrease the compressibility co-efficient
A
33
Which of the following terminology is not used for size reduction
of materials of materials to fine sizes or powders?
A. Comminution
B. Dispersion
C. Pulverisation
D. Compression
D
34
A tube mill as compared to a ball mill
A. employs small balls
B. gives finer size reduction but consumes more power
C. has larger length/diameter ratio (>2 as compared to 1
for ball mill)
D. all
D
35
Kick’s law assumes that the energy required for size reduction
is proportional to the logarithm of the ratio between the initial and
the final diameters. The unit of Kick’s constant is
A. kW. sec/kg
B. kWh/kg
C. kWh/sec. kg
D. kg/sec
A
36
______ mills are termed as impactors.
A. Hammer
B. Cage
C. Rolling-compression
D. None of these
A
37
Which of the following gives the crushing energy required to
create new surface?
A. Taggart’s law
B. Fick’s law
C. Rittinger’s law
D. None of these
C
38
In filtration, the use of ‘filter aid’ helps in
A. reducing the filtration pressure.
B. accelerating the rate of filtration.
C. deplugging the filter medium.
D. enhancing the cake porosity in case of a dense
impermeable cake.
C
39
Critical Speed (NC) of a ball is given by (where R1 and R2 are
radii of ball mill and the ball respectively).
A. 𝑁= 1/4N SQRT (G/r1-r2)
B. 𝑁=1/2N SQRT (G/r1-r2)
C. 𝑁= 1/N SQRT (G/r1-r2)
D. 𝑁= 1/2N SQRT (r1-r2G/)
B
40
Grizzlies are used for separating ________ solids.
A. coarse
B. fine
C. any size
D. none of these
B
41
Which of the following clay mixing devices is vacuum operated
for deairation of clay?
A. Banbury mixer
B. Pug mill
C. Muller-mixer
D. None of these
B
42
Pick out the material having minimum Rittinger’s number.
A. Calcite
B. Pyrite
C. Quartz
D. Galena
C
43
In case of a revolving mill, wet grinding compared to dry grinding
A. requires more energy.
B. has less capacity.
C. complicates handling & classification of the product.
D. none of these
D
44
To get a fine talc powder from its granules, the equipment used
is
A. roller crusher
B. ball mill
C. jaw crusher
D. gyratory crusher
B
45
For a cyclone of a diameter 0.2 m with a tangential velocity of 15
m/s at the wall, the separation factor is
A. 2250
B. 1125
C. 460
D. 230
D
46
Width and speed of a conveyor belt depends upon the ______
of the material.
A. lump size
B. bulk density
C. both a & b
D. neither a nor b
C
47
Higher is the mesh number, smallr will be the aperture size of
the screen. It means that the aperture size of a 200 mesh screen
will be smaller than that of 20 mesh screen. This is valid for
A. British standard screens.
B. German standard screens (DIN 1171) etc.
C. American standard screens (ASTM and Tyler standard
screens).
D. All
D
48
Pick out the wrong statement
A. Cumulative 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 cumulative analysis unlike
differential analysis.
B. A gate diagram is a plot of cumulative percent by
weight undersize vs. the reciprocal of diameter, in
which the area beneath the curve represents the
surface.
C. Capacity of crusher in choke feeding is increased.
D. 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 heap is called
‘cataracting’.
C
49
Which of the following size reduction equipment employs mainly
attrition for ultrafine grinding?
A. Jet mills
B. Fluid energy mill
C. Micronizer
D. All
D
50
Tank filter (e.g., Nutsch filter) is
A. a high pressure filter
B. a continuous filter
C. used for small scall filtration work
D. a leaf filter
C
51
In bag filters, filter fabrics are never made of
A. metallic wire woven mesh
B. polyster fibres
C. cotton fibres
D. nylon fibres
A
52
Use of ‘grinding aids’ is done in ______ grinding.
A. dry
B. wet
C. ultrafine
D. intermediate
A
53
Height of liquid in agitation tank is normally maintained equal to
the tank diameter. However, if the tank is too tall and a large
liquid hold up is desired, then two or more impellers mounted on
the same shaft may be used. The clearance between the tank
bottom and the bottom most impeller should be about (where, D
= impeller diameter)
A. 0.5 D
B. D
C. 1.5 D
D. 2 D
B
54
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. Compartment mill
B. Rod mill
C. Pebble mill
D. Tube mill
B
55
Rittinger’s crushing law states that
A. work required to form a particle of any size is
proportional to the square of the surface to volume ratio
of the product.
B. 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.
C. work required in crushing is proportional to the new
surface created.
D. for a given machine and feed, crushing efficiency is
dependent on the size of the feed and product.
C
56
Which of the following is the most suitable filter for separation of
abrasive solids suspended in a corrosive liquid?
A. Sand bed filter
B. Plate and frame filter press
C. Vacuum filter
D. Batch basket centrifuge
C
57
All resistances during washing of cake
A. increases
B. decreases
C. remain constant
D. none of these
C
58
A _____ mixer resembles a ball mill without balls.
A. banbury
B. pug mill
C. tumbling
D. pan
C
59
________ conveyor is the most suitable for short distance
transportation of non-abrasive loose materials like garbage,
grain, food waste, etc.
A. Flight
B. Screw
C. Drag
D. Belt
A
60
As the product becomes finer, the energy required for grinding
A. decreases
B. increases
C. is same as for coarse grinding
D. is 1.5 times that of coarser grinding
B
61
Gyratory crushers compared to the reciprocating jaw crushers
A. have greater capacity per unit of discharge area.
B. crush intermittently.
C. are less suitable for coarse materials.
D. have less steady power consumption.
A
62
The important dimensional group involved in the power
requirement calculation in mixing operation is the ______
number.
A. Reynold’s
B. Froude
C. both a & b
D. neither a nor b
C
63
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:
is the impeller rotational speed, and D is the impeller diameter.
A. 𝑃o∝𝑅𝑒^-1
B. Po ∝ 𝑅𝑒^0
C. 𝑃o∝𝑅𝑒^0.5
D. 𝑃o∝𝑅𝑒^1
B
64
Mechanical conveyors which push the material along an endless
trough or tube are called scrappers. Which of the following
conveying equipment comes under the category of ‘scrappers’?
A. Bucket conveyor
B. Flight conveyor
C. Screw conveyor
D. Both b and c
D
65
Sphericity of pulverised coal is
A. 1
B. <1
C. >1
D. ∞
B
66
The reduction ratio for the finer grinders is
A. 5-10
B. 10-20
C. 20-40
D. as high as 100
D
67
Which of the following is the hardest material?
A. Calcite
B. Quartz
C. Corundum
D. Gypsum
C
68
General mechanism of size reduction in intermediate and fine
grinder is by
A. cutting action
B. compression
C. compression and tearing
D. impact and attrition
D
69
The work index in Bond’s law for crushing of solids has the
following dimensions
A. no units (dimensionless)
B. kWh/ton
C. kW/ton
D. kWh.m1/2/ton
B
70
Ore concentration by jigging is based on the difference in the
______ of the particles.
A. specific gravities
B. wettability
C. shape
D. none of these
A
71
Reduction ratio of crushers is the
A. ratio of feed opening to discharge opening.
B. ratio of discharge opening to feed opening.
C. determining factor for minimum diameter of the feed
and the product.
D. none of these
A
72
Which of the following equations is Rittinger’s crushing law?
(where, P = power required by the machine, m = feed rate, k =
a constant 𝐷 & 𝐷 = volume surface mean diameter of feed &
product respectively).
A. 𝑃/𝑚=𝐾/ 𝐷
B. 𝑃/𝑚=𝐾.ln
C. 𝑃/𝑚=𝐾(1/Dsb-1/Dsa)
D. None of these
C
73
Cyclones are used primarily for separating
A. solids
B. solids from liquids
C. liquids
D. solids from solids
b
74
There is practically no alternative/competitor to ______ in the
beneficiation treatment of sulphide ores.
A. classification
B. tabling
C. jigging
D. froth floatation
D
75
Which is a secondary crusher for a hard & tough stone?
A. Jaw crusher
B. Cone crusher
C. Impact crusher
D. Toothed roll crusher
B
76
Separation of isotopes is generally done using a/an _______
centrifuge.
A. ultra
B. disk-bowl
C. both a & b
D. neither a nor b
A
77
Temperature of the product during ultrafine grinding
A. increases
B. decreases
C. remains constant
D. may increase or decrease; depends on the material
being ground
A
78
Reciprocating screens are normally inclined at an angle of 5°
with the horizontal and employ gyratory motion at feed end &
reciprocating motion at the discharge end. They are not suitable
for the screening of the
A. light metal powder down up to 4 mesh size.
B. dry chemicals.
C. heavy tonnages of rocks or gravel.
D. powdered food & granular materials.
C
79
In a ball mill, the volume occupied by the balls (when the mill is
stopped) is about ________ percent of the volume of the mill.
A. 35
B. 50
C. 70
D. 85
B
80
Size measurement of ultrafine particles can be best expressed in terms of
A. centimetre
B. screen size
C. micron
D. surface area per unit mass
D
81
Separation of materials of the same density based on their sizes
by using then-different rates of flow.
A. Sorting
B. Sizing
C. Flocculation
D. Elutriation
A straight line is obtaine
B
82
A straight line is obtained on plotting reciprocal of filtration rate
vs. the volume of filtrate for ______ flow of filtrate.
A. comprehensible cakes and laminar
B. incompressible cake and laminar
C. compressible cake and turbulent
D. incompressible cake and turbulent
B
83
Molten ammonium nitrate is mixed with ground limestone in
fertilizer plant in a
A. pug mill
B. mixer-extruder
C. banbury mixer
D. muller mixer
A
84
Agglomeration of individual particles into clusters (flocs) is called
flocculation. To prevent this, the most commonly used dispersing
agent are
A. carbonates
B. sulphates
C. silicates & phosphates
D. bi-carbonates
C
85
For a sphere falling in the constant drag co-efficient regime, its
terminal velocity depends on its diameter (d) as
A. d
B. √d
C. d2
D. 1/d
C
86
With increase in the capacity of screens, the screen
effectiveness
A. remains unchanged
B. increases
C. decreases
D. decreases exponentially
C
87
As particle size is reduced
A. screening becomes progressively more difficult.
B. screening becomes progressively easier.
C. capacity and effectiveness of the screen is increased.
D. none of these
A
88
Rittinger number which designates the new surface produced
per unit of mechanical energy absorbed by the material being
crushed, depends on the
A. state or manner of application of the crushing force.
B. ultimate strength of the material.
C. elastic constant of the material.
D. all
D
89
Dust collection efficiency of electrostatic precipitator can be high
as 99.9%. Maximum temperature and pressure of dust laden
gas that can be cleaned in an electrostatic precipitator is
respectively.
A. 200°C and 5 atm.
B. 1000°C and 10 atm.
C. 500°C and 50 atm.
D. 1000°C and 500 atm.
B
90
For efficient grinding, ball mills must be operated
A. at a speed less than the critical speed.
B. at a speed more than the critical speed.
C. at a speed equal to the critical speed.
D. with minimum possible small balls.
A
91
In a size reduction crushing operation, the feed size is 10 to 50
mm, while the product size is 2 to 10 mm. This is a case of
______ crushing.
A. primary
B. secondary
C. fine
D. ultrafine
C
92
For spheres, the surface shape factor is given by (where, A =
area, V = volume, and D = diameter)
A. 𝜋(=𝐴/𝐷^2)
B. 𝜋/6(=𝑉/𝐷^3)
C. 𝐴𝐷/𝑉
D. None of these
A
93
The reduction ratio for grinders os defined as (where, Df and Dp
are average diameters of feed and product respectively).
A. 𝐷f/𝐷p
B. 𝐷p/𝐷f
C. 𝐷f−𝐷p
D. None of these
A
94
______ conveyors are also called scrapers.
A. Apron
B. Screw
C. Helical flight
D. Both b & c
D
95
Pick out the wrong statement pertaining to the turbine agitator.
A. Recommend peripheral speed for the turbine agitator
is 200-250 metres/minute.
B. Pitched blade turbine agitator gives only radial flow with
complete absence of the axial flow.
C. Generally, the diameter of the agitator is kept between
I/3rd to I/6th of the tank diameter while the blade length
is 1/4th of agitator diameter (with central disc, it is 1/8th
of the agitator diameter).
D. 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.
B
96
A fluid energy mill is used for
A. cutting
B. grinding
C. ultra grinding
D. crushing
C
97
Which of the following is the softest material?
A. Talc
B. Feldspar
C. Corundum
D. Calcite
A
98
Dry powdery solid materials are transported by a ____ conveyor.
A. belt
B. bucket
C. screw
D. none of these
C
99
Fluid energy mill comes on the category of
A. grinder
B. crusher
C. cutter
D. ultrafine grinder
D
100
Filtration capacity of a rotary drum vacuum filter depends upon
the
A. cake thickness
B. characteristics of the feed slurry
C. both a & b
D. neither a nor b
C
101
About 2-3 hp, power per gallon of a thin liquid provides vigorous
agitation in an agitator. ‘Power number’ in agitation is given by
A. P gc/n^3 D^2p
B. P gc p /u^2
C. n^3 D^3 p/P gc
D. P gc/n^2 D^2 p
A
102
For laminar flow of filtrate through the cake deposited on
septum, which of the following will be valid?
A. Kozney-Karman equation
B. Leva’s equation
C. Blake-Plummer equation
D. None of these
A
103
Which of the following is a continuous filter?
A. Plate and frame filter
B. Cartridge filter
C. Shell and leaf filter
D. None of these
D
104
During washing of filter at the end of constant pressure filtration,
the rate of washing equals the rate of filtration
A. at time zero.
B. at the end of filtration.
C. when half the filtrate has been obtained.
D. at the end of filtration, but decreases with time
subsequently.
B
105
In screen analysis, the notation +5 mm/-10 mm means particles
passing through
A. 10 mm screen and retained on 5 mm screen.
B. 5 mm screen and retained on 10 mm screen.
C. Both 5 mm and 10 mm screens.
D. Neither 5 mm nor 10 mm screens
A
106
Rpm of a trommel at critical speed is given by (where, D =
Diameter of trommel in ft)
A. 76.65/D
B. 76.65/√D
C. 76.65/D^2
D. 76.65√D
B
107
Optimum ratio of operating speed to critical speed of a trommel
is
A. 0.33-0.45
B. 1.33-1.45
C. 0.5-2
D. 1.5-2.5
A
108
The process opposite to ‘dispersion’ is termed as the
A. flocculation
B. sedimentation
C. filtration
D. none of these
A
109
The cake resistance increases steadily with the time of filtration
in a plate and frame filter employing constant ______ filtration.
A. rate
B. pressure
C. both a & b
D. neither a nor b
C
110
Grinding efficiency of a ball mill is of the order of ______ percent.
A. 1-5
B. 40-50
C. 75-80
D. 90-95
A
111
Solid particles of different densities are separated by
A. filters
B. thickness
C. cyclones
D. sorting classifier
D
112
During agitation of liquids, power consumption during laminar
flow is not proportional to the
A. density of the liquid
B. viscosity of the liquid
C. cube of impeller diameters
D. square of rotational speed
A
113
Half of nip, (𝛼), for a roll crusher is given by (where, dr, dp and
df are diameters of crushing rolls, feed particles and rolls gap
respectively).
A. cos𝑎= (dr+dp)/dr+df
B. cos𝑎= (dr+df)/dr+dp
C. tan𝑎= (dr+dp)/dr+df
D. sin𝑎= (dr+df)/dr+df
B
114
Trommels are revolving screens which normally operate in the
range of _____ rpm.
A. 1 – 2
B. 15 – 20
C. 40 – 50
D. 60 – 75
B
115
The value of work index does not change materially from one
equipment to another. If the value of work index determined for
close circuit is Wi, then the same for open circuit grinding will be
A. 0.5 Wi
B. Wi
C. 1.34 Wi
D. 3.34 Wi
C
