Mechanical Operations Flashcards by Pauline Yarah Morales

Short distance transportation of grain, gravel, sand, ash, asphalt etc. is done by using a __________ conveyor.
a. flight
b. slat or drag
c. ribbon
d. screw

screw

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Equivalent diameter of a particle is the diameter of the sphere having the same
a. ratio of surface to volume as the actual volume.
b. ratio of volume to surface as the particle.
c. volume as the particle.
d. none of these.

ratio of surface to volume as the actual volume.

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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
b. Φs = Vp/dp sp
c. Φs = 6 dp Sp/Vp
d. Φs = dp Sp/Vp

Φs = 6 Vp/dp sp

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Pick out the wrong statement.
a. Recycled coarse material to the grinder by a classifier is termed as circulating load.
b. Wear and tear in wet crushing is more than that in dry crushing of materials.
c. Size enlargement (opposite of size reduction) is not a mechanical operation.
d. A ‘dust catcher’ is simply an enlargement in a pipeline which permits the solids to settle down due to reduction in velocity of the dust laden gas.

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

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In continuous filtration (at a constant pressure drop), filtrate flow rate varies inversely as the
a. square root of the velocity.
b. square of the viscosity.
c. filtration time only.
d. washing time only.

square root of the velocity.

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For sizing of fine materials, the most suitable equipment is a
a. trommel
b. grizzly
c. shaking screen
d. vibrating screen

vibrating screen

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Which of the following is not categorised as a “mechanical operation” ?
a. Agitation
b. Filtration
c. Size enlargement
d. Humidification

Humidification

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Which of the following is a pressure filter ?
a. Leaf filter (Moore filter).
b. Plate and flame filter.
c. Rotary drum filter.
d. Sand filter.

Plate and flame filter.

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Tabular bowl centrifuges as compared to disk bowl centrifuges
a. operate at higher speed.
b. employ bowl of larger diameter.
c. can not be operated under pressure/vacuum.
d. can’t be used for separation of fine suspended solids from a liquid.

operate at higher speed.

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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. bronze
b. stainless steel
c. flint or porcelain
d. concrete

flint or porcelain

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Filter aids like asbestos, kieselguhr, diatomaceous earth etc. are used to increase the porosity of the final filter cake & reducing the cake resistance during filtration. Filter aid is
a. added to the feed slurry.
b. precoated on the filter medium prior to filtration.
c. separated from the cake by dissolving solids or by burning it off.
d. all ‘a’, ‘b’&’c’.

all

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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
b. μ ≥ tan α
c. μ > tan 2α
d. μ ≤ tan α

μ ≥ tan α

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Pick out the wrong statement pertaining to the roll crushers.
a. Maximum feed size determines the required roll diameter.
b. For hard material’s crushing, the reduction ratio should not exceed 4.
c. Both the rolls run necessarily at the same speed.
d. Reduction ratio and differential roll speed affect production rate & energy consumed per unit of surface produced.

Both the rolls run necessarily at the same speed.

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Which of the following is not an ultrafine grinder (colloid mill)?
a. Micronizers
b. Agitated mills and fluid energy mills
c. Toothed roll crusher
d. Hammer mills with internal classification

Toothed roll crusher

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Two particles are called to be equal settling, if they are having the same.
a. size.
b. specific gravity.
c. terminal velocities in the same fluid & in the same field of force.
d. none of these.

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

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Which of the following is the most suitable for handling fibrous and dense slurries ?
a. Propeller agitator
b. Cone type agitator
c. Turbine agitator
d. Radial propeller agitator

Cone type agitator

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__________ centrifuge is normally used in sugar mills.
a. Tubular bowl
b. Disc-bowl
c. Suspended batch basket
d. Perforated horizontal basket continuous

Suspended batch basket

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Solid particles separation based on the difference in their flow velocities through fluids is termed as the
a. clarification
b. classification
c. elutriation
d. sedimentation

classification

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Diatomaceous earth is a/an
a. explosive
b. filter aid
c. filter medium
d. catalyst

filter aid

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The distribution given by microscopic analysis of powder is
a. number
b. length
c. area
d. volume

number

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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
b. m. ρ/Vp
c. m . Vp/ρ
d. Vp/m . ρ

m/ρ . Vp

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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.
b. has the dimension of length.
c. is always less than 1.
d. is the ratio of volume of a sphere having the same surface area as the particle to the actual volume of the particle.

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

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In washing type plate and frame filter press, the ratio of washing rate to the final filtrate rate is
a. 4
b. 1/4
c. 1
d. 1/2

1/4

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Ball mills and tube mills with flint or porcelain balls are used for size reduction of
a. asbestos
b. rubber
c. non-metallic ores
d. limestone

non-metallic ores

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Size reduction of __________ is accomplished in steam heated rollers and roll crushers.
a. resins
b. gums
c. hard rubber
d. waxes

hard rubber

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The capacity of a belt conveyor depends upon two factors. If one is the cross-section of the load, the other is the __________ of the belt.
a. speed
b. thickness
c. length
d. none of these

speed

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Which of the following is not a part of the Blake jaw crusher?
a. Hanger
b. Check plates
c. Toggles
d. Pitman

Hanger

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If a force greater than that of gravity is used to separate solids & fluids of different densities, the process is termed as the
a. sedimentation
b. flocculation
c. dispersion
d. centrifugation

centrifugation

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Filter aid is used to
a. increase the rate of filtration.
b. decrease the pressure drop.
c. increase the porosity of the cake.
d. act as a support base for the septum.

increase the porosity of the cake.

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Which of the following mineral dressing operations is termed as ‘comminution’?
a. Panning
b. Spiralling
c. Tabling
d. None of these

None of these

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The capacity of a pneumatic conveying system depends upon the
a. bulk density of materials.
b. pressure of the conveying air.
c. diameter of the conveying line.
d. all (a), (b) and (c).

all

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Pick out the wrong statement.
a. Close circuit grinding is more economical than open circuit grinding.
b. Cod oil, beef tallow or aluminium stearates are used as grinding aids in cement ‘industries’.
c. The equipment used for the removal of traces of solids from a liquid is called a classifier.
d. Size enlargement is a mechanical operation exemplified by medicinal tablet making.

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

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Gravity settling process is not involved in the working of a
a. hydrocyclone
b. classifier
c. dorr-thickener
d. sedimentation tank

hydrocyclone

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Froth floatation is the most suitable for treating
a. iron ores
b. sulphide ores
c. quartzite
d. none of these

sulphide ores

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Which of the following is the most suitable for cleaning of fine coal dust (<0.5 mm) ?
a. Trough washer
b. Baum jig washer
c. Spiral separator
d. Froth floatation

Froth floatation

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Pick out the correct statement:
a. Removal of iron from ceramic material is necessitated (by magnetic separation method) so as to avoid discolouration of ceramic products.
b. The operating cost of shaking screen is more than that of a vibrating screen.
c. Screen capacity does not depend upon the specific gravity of the minerals.
d. Asphalt is best crushed using toothed roll crusher.

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

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Range of compressibility co-efficient of the commercial compressible cake obtained in
filtration operation is
a. 0.01 to 0.1
b. 0.1 to 0.3
c. 0.2 to 0.8
d. 0.2 to 0.4

0.2 to 0.8

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Highly viscous liquids & pastes are agitated by
a. propellers
b. turbine agitators
c. multiple blade paddles
d. none of these

multiple blade paddles

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The value of ‘angle of nip’ is generally about
a. 16°
b. 32°
c. 52°
d. 64°

32°

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Size reduction of the __________ can be suitably done by ball mills, crushing rolls and rod mills.
a. metalliferrous ores
b. non-metallic ores
c. basic slags
d. asbestos & mica

metalliferrous ores

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Sulphuric acid mist is arrested by using a __________ scrubber.
a. packed wet
b. hollow wet
c. venturi
d. co-current

venturi

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The main size reduction operation in ultrafine grinders is
a. cutting
b. attrition
c. compression
d. impact

attrition

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

all

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Jigging is a technique by which different particles can be
a. separated by particle size.
b. separated by particle density.
c. separated by particle shape.
d. mixed

separated by particle size.

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Crushing of mineral particles is accomplished in a ‘cage mill’, when one or more alloy steel bars are revolved in opposite directions. It is a type of __________ mill.
a. impact
b. roll
c. vibratory
d. none of these

impact

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impact

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Balls for ball mills are never made of
a. forged/cast steel
b. lead
c. cast iron
d. alloy steel

lead

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200 mesh screen means 200 openings per
a. cm^2
b. cm
c. inch
d. inch^2

inch

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Energy consumed for crushing one ton of material ranges from __________ kWh.
a. 0.01 to 0.1
b. 0.5 to 1.5
c. 2 to 3.5
d. 4 to 5.

0.5 to 1.5

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For transporting pasty material, one will use a/an
a. apron conveyor
b. belt conveyor
c. screw colaveyor
d. bucket elevator

screw colaveyor

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Where the density difference of the two liquid phase to be separated is very small (as in milk cream separator), the most suitable separator is a
a. disc bowl centrifuge.
b. sharpies supercentrifuge.
c. batch basket centrifuge.
d. sparkler filter.

disc bowl centrifuge.

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A tube mill compared to a ball mill
a. has a higher length/diameter ratio.
b. produces a coarser product.
c. has a higher diameter/length ratio.
d. uses much larger balls.

has a higher length/diameter ratio.

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Trommels separate a mixture of particles depending on their
a. size
b. density
c. wettability
d. electrical & magnetic properties

size

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Basic slag is not ground in
a. jaw crushers
b. ball mills
c. compartment mills
d. tube mills

jaw crushers

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Grindability of a material does not depend upon its
a. elasticity
b. hardness
c. toughness
d. size

size

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Shape factor for a cylinder whose length equals its diameter is
a. 1.5
b. 0.5
c. 1.0
d. 2.0

1.5

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In case of a hammer crusher, the
a. feed may be highly abrasive (Moh’s scale >5).
b. minimum product size is 3 mm.
c. maximum feed size may be 50 mm.
d. rotor shaft carrying hammers can be vertical or horizontal.

rotor shaft carrying hammers can be vertical or horizontal.

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Dust laden air can be purified using a
a. cyclone separator
b. bag filter
c. gravity settler
d. tubular centrifuge

cyclone separator

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Rittinger’s number designates the new surface created per unit mechanical energy absorbed by the material being crushed. Larger value of Rittinger’s number of a material indicates its
a. easier grindability
b. poor grindability
c. high power consumption in grinding
d. none of these

easier grindability

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Capacity (in tons/hr) of jaw/gyratory crusher is equal to (where, L = length of the receiving opening, cm S = greater width of the discharge opening, cm)
a. 0.01 L.S
b. 0.087 L.S
c. L.S
d. L.S/0.087

0.087 L.S

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Vacuum is applied in __________ zone, in case of a general type continuous rotary drum vacuum filter.
a. filtering
b. washing
c. drying
d. all (a), (b) & (c)

all

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Which of the following mechanical conveyors does not come under the division ‘scrapers’ ?
a. Ribbon conveyor
b. Flight conveyor
c. Bucket elevators
d. Drag conveyor.

Bucket elevators

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________ mixer is used for devulcanisation of rubber scrap & making water dispersion & rubber solution.
a. Tumbler
b. Banbery
c. Muller
d. Rubbon blender

Banbery

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Which of the following mechanical conveyors does not come under the division ‘carriers’ ?
a. Belt conveyor
b. Bucket elevator
c. Screw conveyor
d. Apron conveyor.

Screw conveyor

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Screen capacity is not a function of
a. its openings size.
b. screening mechanism.
c. screening surface.
d. atmospheric humidity.

atmospheric humidity.

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Which of the following is a vacuum filter?
a. Filter press
b. Rotary disc filter
c. Batch basket centrifuge
d. Tank filter (Nutsch filter)

Rotary disc filter

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Pine oil used in froth floatation technique acts as a/an
a. collector
b. modifier
c. frother
d. activator

frother

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Length/diameter ratio of a ball mill is
a. 1.5
b. 1
c. < 1
d. > 1

< 1

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Feed size of ≥ 25 cms can be accepted by
a. ball mill
b. rod mill
c. fluid energy mill
d. jaw crusher

jaw crusher

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Which is the most suitable conveyor for transportation of sticky material ?
a. Apron conveyor
b. Belt conveyor
c. Screw conveyor
d. Pneumatic conveyor

Screw conveyor

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The most suitable equipment for removing the fine dust particle (< 1 micron dia.) from air below its dew point will be a/an
a. bag filter
b. electrostatic precipitator
c. cyclone separator
d. wet scrubber

electrostatic precipitator

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Laminar flow region is said to exist during agitation of a liquid in an agitator, when the
value of Reynolds number is
a. >10
b. <10
c. >100
d. <100

<10

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Filtration of water in a paper mill is done by a/an __________ filter.
a. open sand
b. plate and frame
c. vacuum leaf
d. sparkler

open sand

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Moore filter is a __________ filter.
a. leaf
b. press
c. rotary
d. sand

leaf

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Sphericity of a cubical particle, when its equivalent diameter is taken as the height of the cube, is
a. 0.5
b. 1
c. 2
d. 3

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Ball mill is used for
a. crushing
b. coarse grinding
c. fine grinding
d. attrition

fine grinding

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In case of a ball mill,
a. coarse feed requires a larger ball.
b. fine feed requires a larger ball.
c. operating speed should be more than the critical speed.
d. none of these

coarse feed requires a larger ball.

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Maximum size reduction in a ball mill is done by the, __________ action.
a. attrition
b. compression
c. impact
d. cutting

impact

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increasing the capacity of a screen __________ the screen effectiveness.
a. decreases
b. increases
c. does not effect
d. none of these

decreases

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The power number for a stirred tank becomes constant at high Reynolds number. In this limit, the variation of power input with impeller rotational speed (N) is proportional to
a. N°
b. N1
c. N2
d. N3

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Bond crushing law
a. calls for relatively less energy for the smaller product particles, than does the Rittinger law.
b. is less realistic in estimating the power requirements of commercial crushers.
c. states that the work required to form particle of any size from very large feed is proportional to the square root of the volume to surface ratio of the product.
d. states that the work required for the crushing is proportional to the new surface created.

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

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Flow of filtrate through the cake in a plate and frame filter press is best described by the __________ equation.
a. Kozney-Karman
b. Hagen-Poiseulle’s
c. Fanning’s
d. Kremser

Kozney-Karman

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The controlling resistance in a rotary drum vacuum filter is the __________ resistance.
a. piping
b. cake
c. filter medium
d. none of these

cake

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Which of the following is used for primary crushing of very hard lumpy materials ?
a. Toothed roll crusher
b. Gyratory crusher
c. Ball mill
d. Tube mill

Gyratory crusher

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Coal is finally pulverised to 200 mesh size for burning in boilers by a
a. hammer crusher
b. ball mill
c. roll crusher
d. gyratory crusher

ball mill

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Crushing efficiency is the ratio of the
a. surface energy created by crushing to the energy absorbed by the solid.
b. energy absorbed by the solid to that fed to the machine.
c. energy fed to the machine to the surface energy created by crushing.
d. energy absorbed by the solid to the surface energy created by crushing.

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

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The resistance offered by the filter used in a bag filter is proportional to (where, c = dust
concentration, and s = particle size )
a. c/s
b. s/c
c. s . c
d. 1/s . c

c/s

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Cement clinker is reduced to fine size by a
a. roll crusher
b. ball mill
c. tube mill
d. hammer mill

tube mill

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The crushed material received for separation is called feed or
a. tailing
b. heading
c. concentrate
d. middling

heading

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For spheres, volume shape factor is given by
a. π(=A/D2)
b. 2π(=2A/D2)
c. π/6(=V/D3)
d. AD/V

/6(=V/D3)

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Which of the following agitators having a large blade area, rotating at slow speed is used for mixing high viscosity liquids ( > 50000 centipoise) ?
a. Propeller
b. Helical screw
c. Flat blade turbine
d. Curved blade turbine

Helical screw

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__________ is defined as the geometric mean of the relative rejections and the relative recoveries of two minerals.
a. Separation efficiency
b. Selectivity index
c. Concentration ratio
d. none of these

Selectivity index

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The operating speed of a ball mill should be __________ the critical speed.
a. less than
b. much more than
c. at least equal to
d. slightly more than

less than

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__________ are used for the separation of coarse particles from a slurry of fine particles.
a. Thickeners
b. Classifiers
c. Hydrocyclones
d. Decanters

Classifiers

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Fibrous material is broken by a
a. rollcrusher
b. squirrel-cage disintegrator
c. ball mill
d. tube mill

squirrel-cage disintegrator

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_________ is the most suitable for compounding rubber and plastic solids.
a. Banbery mixer
b. Pan mixer
c. Pug mill
d. Charge can mixer

Banbery mixer

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Out of the following size reduction equipments, the maximum feed size can be accepted by the
a. tube mill
b. ball mill
c. jaw crusher
d. jet pulveriser

jaw crusher

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Bucket elevators are not suitable for the vertical lifting of __________ materials.
a. fine (e.g. - 200 mesh size coal)
b. sticky (e.g. clay paste)
c. small lumpy (e.g. grains and sand)
d. free flowing

sticky (e.g. clay paste)

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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

sand

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For separation of sugar solution from settled out mud, we use a __________ filter.
a. sparkler
b. plate and frame
c. centrifugal
d. rotary drum vaccum

centrifugal

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The sphericity of a cylinder of 1 mm diameter and length 3 mm is
a. 0.9
b. 0.78
c. 0.6
d. 0.5

0.9

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Pulverised coal passing through 200 mesh screen has a diameter of 0.074 mm (74 micron). The same passing through 50 mesh screen will have a dia of __________ mm.
a. 0.007
b. 0.30
c. 50
d. 0.014

0.30

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What is the selectivity index, if the grade of tailings & concentrate is the same?
a. 0
b. ∞
c. 1
d. 0.5

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The most suitable equipment used to devulcanise rubber scrap and to make water dispersion & rubber solution is a
a. boundary mixer.
b. propeller agitator.
c. sharpies centrifuge.
d. none of these.

boundary mixer.

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Traces of solids are removed from, liquid in a
a. classifier
b. clarifier
c. sparkler filter
d. rotary vacuum filte

clarifier

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________ balls capable of grinding the feed in a ball mill gives the maximum efficiency.
a. Cast iron
b. Minimum size
c. Maximum size
d. Elliptical

Minimum size

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________ balls capable of grinding the feed in a ball mill gives the maximum efficiency.
a. Cast iron
b. Minimum size
c. Maximum size
d. Elliptical

Minimum size

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The speed of a rotary drum vacuum filter may be about __________ rpm.
a. 1
b. 50
c. 100
d. 500

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Colloid mills achieve size reduction mainly by
a. impact
b. attrition
c. cutting
d. compression

attrition

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Mesh indicates the number of holes per
a. square inch
b. linear inch
c. square foot
d. linear foot

linear inch

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For achieving maximum capacity of the ball mill, the ball charge should be equal to about __________ percent of the ball mill volume.
a. 10
b. 25
c. 50
d. 75

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For achieving maximum capacity of the ball mill, the ball charge should be equal to about __________ percent of the ball mill volume.
a. 10
b. 25
c. 50
d. 75

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Which of the following gives the work required for size reduction of coal to -200 mesh in a ball mill most accurately?
a. Rittinger’s law
b. Kick’s law
c. Bond’s law
d. none of these

Rittinger’s law

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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

none of these

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Size reduction mechanism used in Jaw crushers is
a. attrition
b. compression
c. cutting
d. impact

compression

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Trommels employ __________ for screening of materials.
a. fibrous cloth
b. woven wire screen
c. punched plate
d. none of these

punched plate

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A widely used size reduction equipment for __________ is Bradford breaker.
a. talc
b. coal
c. iron core
d. wheat

coal

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Ultra centrifuges are used for the separation of __________ solid particles.
a. coarse
b. fine
c. colloidal
d. dissolved

colloidal

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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.

compartment

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Size reduction does not occur due to compression in case of
a. rod mills
b. gyratory crushers
c. jaw crushers
d. smooth roll crushers

rod mills

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According to Taggart’s rule for selecting between a gyratory crusher and a jaw crusher; the later should be used, if the hourly tonnage to be crushed divided by the square of the gape expressed in cm is less than
a. 0.00184
b. 0.0184
c. 0.184
d. 1.84

0.0184

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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

Parabola

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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 cake

centrifugal pressure exerted by the liquid.

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Rod mills employed for grinding
a. employ a steel shell having L/D ratio of 1.5 to 3.0.
b. is useful for handling sticky materials.
c. employ steel rods of 2-12 cms diameter extending over full length of the mill.
d. all ‘a’, ‘b’ & ‘c’.

all

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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

decreases

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Gold ore concentration is mostly done using
a. jigging
b. tabling
c. froth floatation
d. elutriation

tabling

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Mixing of light fine powder such as insecticides is done by
a. banbery mixer
b. pug mill
c. impact wheels
d. kneader

impact wheels

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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

hammer crusher

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Sphericity is the ratio of the surface area of a spherical particle having the same volume as the particle to the surface area of the particle. Which of the following has the maximum value of sphericity ?
a. Sphere
b. Cube
c. Cylinder (L/D = 1)
d. Raschig rings

Sphere

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The unit of specific cake resistance is
a. gm/cm2
b. cm/gm
c. cm/gm2
d. gm/gm

gm/cm2

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Size reduction of asbestos and mica is done by
a. hammer mills
b. rod mills
c. gyratory crushers
d. crushing rolls

hammer mills

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The study on washability of coal is done by using the __________ technique.
a. tabling
b. elutriation
c. heavy media separation
d. none of these

heavy media separation

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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

0.6

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_________ 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

Belt

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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

over cake

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Moisture can be removed from lubricating oil using
a. tubular centrifuge
b. clarifier
c. sparkler filter
d. vacuum leaf filter

tubular centrifuge

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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°

2 to 5°

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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 surfaces 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.

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

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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

increase the porosity

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Which of the following terminology is not used for size reduction of materials to fine sizes or powders?
a. Comminution
b. Dispersion
c. Pulverisation
d. Compression

Compression

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

all

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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.

kW. sec/kg

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Which of the following gives the crushing energy required to create new surface?
a. Taggarts rule
b. Fick’s law
c. Rittinger’s law
d. none of these

Rittinger’s law

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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.

deplugging the filter medium.

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Gizzlies are used for separating __________ solids.
a. coarse
b. fine
c. any size
d. none of these

fine

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Which of the following clay mixing devices is vacuum operated for deairation of clay?
a. Banbery mixer
b. Pug mill
c. Muller-mixer
d. None of these

Pug mill

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Pick out the material having minimum Rittinger’s number.
a. Calcite
b. Pyrite
c. Quartz
d. Galena

Quartz

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_________ mills are termed as impactors.
a. Hammer
b. Cage
c. Rolling-compression
d. none of these

Hammer

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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.

none of these.

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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

ball mill

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For a cyclone of 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

230

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Higher is the mesh number, smaller will be the aperture size of the screen. It means that the aperture size of a 200 mesh screen will be smaller than that of 20 mesh screen. This is valid for
a. British standard screens.
b. German standard screens (DIN 1171) etc.
c. American standard screens (ASTM and Tyler standard screens).
d. all (a), (b) and (c).

all

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Pick out the wrong statement.
a. 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.
b. 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.
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 toe of the heap is called ‘cataracting’.

Capacity of crusher in choke feeding is increased.

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Which of the following size reduction equipments employs mainly attrition for ultra fine grinding?
a. Jet mills
b. Fluid energy mill
c. Micronizer
d. all (a), (b) and (c)

all

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Tank filter (e.g., Nutsch filter) is
a. a high pressure filter.
b. a continuous filter.
c. used for small scale filtration work.
d. a leaf filter.

used for small scale filtration work.

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In bag filters, filter fabrics are never made of
a. metallic wire woven mesh
b. polyester fibres
c. cotton fibres
d. nylon fibres

metallic wire woven mesh

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Use of ‘grinding aids’ is done in __________ grinding.
a. dry
b. wet
c. ultrafine
d. intermediate

dry

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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

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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.

Vacuum filter

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All resistances during washing of cake
a. increases
b. decreases
c. remain constant
d. none of these

remain constant

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A __________ mixer resembles a ball mill without balls.
a. banbery
b. pug mill
c. tumbling
d. pan

tumbling

_________ conveyor is the most suitable for short distance transportation of non-abrasive loose materials like garbage, grain, food wastes etc.
a. Flight
b. Screw
c. Drag
d. Belt

Flight

As the product becomes finer, the energy required for grinding
a. decreases
b. increases
c. is same as for coarser grinding
d. is 1.5 times that for coarser grinding

increases

Gyratory crushers compared to the reciprocating jaw crushers
a. have greater capacity per unit of discharge area.
b. crush intermittantly.
c. are less suitable for coarse materials.
d. have less steady power consumption.

have greater capacity per unit of discharge area.

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.

Rod mill

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 & product.

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

Sphericity of pulverised coal is
a. 1
b. <1
c. >1
d. ∞

The reduction ratio for fine grinders is
a. 5-10
b. 10-20
c. 20-40
d. as high as 100

as high as 100

Which of the following is the hardest material ?
a. Calcite
b. Quartz
c. Corundum
d. Gypsum

Corundum

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.

impact and attrition.

A straight line is obtained on plotting reciprocal of filtration rate vs. the volume of filtrate for __________ flow of filtrate.
a. compressible cakes and laminar
b. incompressible cake and laminar
c. compressible cake and turbulent
d. incompressible cake and turbulent

incompressible cake and laminar

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

kWh/ton

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

specific gravities

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

surface area per unit mass

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 dia of the feed and the product.
d. none of these.

ratio of feed opening to discharge opening.

Which is a secondary crusher for a hard & tough stone ?
a. Jaw crusher
b. Cone crusher
c. Impact crusher
d. Toothed roll crusher

Cone crusher

Cyclones are used primarily for separating
a. solids
b. solids from fluids
c. liquids
d. solids from solids

solids from fluids

There is practically no alternative/competitor to __________ in the beneficiation treatment of sulphide ores.
a. classification
b. tabling
c. jigging
d. froth floatation

froth floatation

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

increases

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.

heavy tonnages of rocks or gravel.

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

Separation of materials of the same density based on their sizes by using then-different rates of flow is called
a. sorting
b. sizing
c. flocculation
d. elutriation

sizing

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

pug mill

Agglomeration of individual particles into clusters (flocs) is called flocculation. To prevent flocculation, the most commonly used dispersing agents are
a. carbonates
b. sulphates
c. silicates & phosphates
d. bi-carbonates

silicates & phosphates

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. D^2
d. 1/d

D^2

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.

screening becomes progressively more difficult.

Rittinger number which designates the new surface prduced 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 (a), (b) and (c).

all

Dust collection efficiency of electrostatic precipitator can be as high as 99.9%. Maximum temperature and pressure of dust laden gas that can be cleaned in an electrostatic
precipitator is respectively.
a. 200°C and 5 atm.
b. 1000°C and 10 atm.
c. 500°C and 50 atm.
d. 1000°C and 500 atm.

1000°C and 10 atm.

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

fine

The reduction ratio for grinders is 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

Df/Dp

Pick out the wrong statement pertaining to the turbine agitator.
a. Recommended 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 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).
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

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

A fluid energy mill is used for
a. cutting
b. grinding
c. ultra grinding
d. crushing

ultra grinding

Which of the following is the softest material ?
a. Talc
b. Feldspar
c. Corundum
d. Calcite

Talc

Dry powdery solid materials are transported by a __________ conveyor.
a. belt
b. bucket
c. screw
d. none of these

screw

Fluid energy mill comes in the category of
a. grinder
b. crusher
c. cutter
d. ultrafine grinder

ultrafine grinder

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

Kozney-Karman equation

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

None of these

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.

at the end of filtration.

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 screen.

10 mm screen and retained on 5 mm screen.

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

0.33-0.45

The process opposite to ‘dispersion’ is termed as the
a. flocculation
b. sedimentation
c. filtration
d. none of these.

flocculation

Grinding efficiency of a ball mill is of the order of __________ percent.
a. 1-5
b. 40-50
c. 75-80
d. 90-95

1-5

Solid particles of different densities are separated by
a. filters
b. thickness
c. cyclones
d. sorting classifier

sorting classifier

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.

density of the liquid

Trommels are revolving screens which normally operate in the range of __________ rpm.
a. 1 - 2
b. 15 - 20
c. 40 - 50
d. 60 - 75

15 - 20

The value of work index does not change materially from one equipment to another. If the value of work index determined for close circuit grinding is Wi, then the same for open circuit grinding will be
a. 0.5 Wi
b. Wi
c. 1.34 Wi
d. 3.34 Wi

1.34 Wi

Maximum size reduction in a fluid energy mill is achieved by
a. compression
b. interparticle attrition
c. cutting
d. impact

interparticle attrition

Filtration rate through a filter cake is proportional to (where, S = filtering surface R= specific cake resistance μ = viscosity of the filtrate)
a. S
b. 1/R
c. 1/μ
d. all (a), (b) & (c)

all

To remove dirt from the flowing fluid, we use a
a. coagulant
b. gravity settler
c. strains
d. clarifier

strains

Which of the following crushers can be considered as a combination of a jaw crusher and a roller crusher?
a. Rod mill
b. Fluid energy mill
c. Gyratory crusher
d. Ball mill

Gyratory crusher

Separation of solid suspended in liquid into a supernatant clear liquid and a denser slurry employs a process termed as the
a. coagulation
b. flocculation
c. sedimentation
d. clarification

sedimentation

Ultrafine grinders operate principally by
a. slow compression
b. impact
c. attrition
d. cutting action

attrition

Which of the following comes in the category of primary crusher for hard and tough stone?
a. Jaw crusher
b. Cone crusher
c. Gyratory crusher
d. None of these

Jaw crusher

Crushing efficiency of a machine ranges between __________ percent.
a. 0.1 to 2
b. 5 to 10
c. 20 to 25
d. 50 to 70

0.1 to 2

A screen is said to be blinded, when the
a. oversizes are present in undersize fraction.
b. undersizes are retained in oversize fraction.
c. screen is plugged with solid particles.
d. screen capacity is abruptly increased.

screen is plugged with solid particles.

What is the critical rotation speed in revolutions per second, for a ball mill of 1.2 m diameter charged with 70 mm dia balls?
a. 0.5
b. 1.0
c. 2.76
d. 0.66

0.66

Percentage of drum submerged in the slurry in case of rotary drum filter is
a. 3
b. 30
c. 85
d. 25

Filter medium resistance is that offered by the
a. filter cloth.
b. embedded particles in the septum.
c. filter cloth and the embedded particle collectively.
d. none of these.

filter cloth and the embedded particle collectively.

In a roll crusher, both the rolls
a. have the same diameter.
b. are rotated towards each other.
c. run either at the same or different speeds.
d. all (a), (b) and (c).

all

Tube mill compared to ball mill
a. produces finer products.
b. is long in comparison with its diameter.
c. uses smaller balls.
d. all (a), (b) & (c).

all

For the preliminary breaking of hard rock, we use a
a. gyratory crusher
b. ball mill
c. tube mill
d. squirrel-cage disintegrator

gyratory crusher

Filtration operation carried out by continuous increase of the inlet pressure of slurry, is called the __________ filtration.
a. constant rate
b. varying pressure
c. varying rate
d. constant pressure

constant rate

Pick out the wrong statement.
a. For the compressible cake, voidage & the specific resistance of the cake can be assumed to be constant.
b. Cake resistance is independent of the pressure drop.
c. Crushing of explosive materials are done by employing drygrinding.
d. Gyratory crusher is a coarse crusher

Cake resistance is independent of the pressure drop.

Which of the following oxides is not present in hematite iron ore?
a. Titanium oxide
b. Calcium oxide
c. Cobalt oxide
d. Manganese oxide

Cobalt oxide

Ribbon blenders are exclusively meant for
a. blending miscible liquids.
b. non-flowing powder and thin pastes.
c. bath mixing.
d. continuous mixing.

non-flowing powder and thin pastes.

In closed circuit grinding as compared to open circuit grinding, the
a. specific surface of product is more.
b. product has lesser size uniformity.
c. production rate at a given limiting size is lower.
d. operation is economical.

operation is economical.

Pick out the correct statement.
a. Angle of repose is always greater than the angle of slide.
b. A hopper is a small bin with a sloping bottom.
c. A silo is a short height vessel of very large diameter used for the storage of high volatile matter coal.
d. 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.

Gelatinous solid (which plug the septum) can be filtered by a __________ filter.
a. sparkler
b. plate and frame
c. vacuum leaf
d. precoat

precoat

During the washing of cake
a. all the resistances are constant.
b. filter medium resistance increases.
c. filter medium resistance decreases.
d. cake resistance decreases.

all the resistances are constant.

The opening of a 200 mesh screen (Taylor series) is
a. 0.0074 cm
b. 0.0074 mm
c. 0.0047 cm
d. 74 mili-microns

0.0074 cm

A gravity decanter is meant for the separation of two __________ density.
a. immiscible liquids of different
b. miscible liquids of different
c. immiscible liquids of same
d. miscible liquids of same

immiscible liquids of different

The most suitable filter for the removal of very small amount of precipitate from very large volumes of water is the __________ filter.
a. vacuum
b. sand
c. plate & frame
d. rotary

sand

Separation of solid particles based on their densities is called
a. sizing
b. sorting
c. clarification
d. dispersion

sorting

Activators are those chemicals which help buoying up one mineral in preference to the other in the froth floatation process. Which of the following is an activator?
a. Cresylic acid
b. Copper sulphate
c. Calcium carbonate
d. Sodium carbonate

Copper sulphate

_________ are mixed using ribbon blenders.
a. Lumpy solids and low viscosity liquids
b. Dry powders
c. High viscosity liquids
d. Thick pastes

Dry powders

During agitation of liquids, the
a. Froude number is independent for the curves between power number and Reynolds number in baffled system.
b. Power number becomes independent of impellers Reynolds number at high
Reynolds number, but is dependent on the geometry of the impeller.
c. Froude number is used to account for the effect of surface (e.g., the centre vortex) on the power number.
d. all (a), (b) and (c).

all

For crushing of solids, the Rittinger’s law states that the work required for crushing is proportional to
a. the new surface created.
b. the size reduction ratio.
c. the change in volume due to crushing.
d. none of these.

the new surface created.

In a size reduction crushing operation, feed size is 300 to 1500 mm while the product size is 100 to 300 mm. This is a case of the __________ crushing.
a. secondary
b. fine
c. primary
d. ultrafine

primary

As per Taggart’s formula, the capacity (kg/hr) of Jaw & Gyratory crushers (for gapes of 10 to 60 cms) is equal to (where, L = Length of feed opening, cms S = Maximum width of discharge opening, cms )
a. LS
b. 93 LS
c. 250 LS
d. LS

93 LS

The process by which fine solids is removed from liquids is termed as
a. decantation
b. flocculation
c. sedimentation
d. classification

sedimentation

Which of the following crushing laws is most accurately applicable to the fine grinding of materials?
a. Bond’s crushing law
b. Kick’s law
c. Rittinger’s law
d. None of these.

Rittinger’s law

Shell and leaf filter as compared to plate and frame filter
a. entails less labor cost.
b. facilitates filtration under higher pressure.
c. provides more effective washing.
d. all (a), (b) & (c)

all

Metallic wire mesh is used as a filtering medium for the separation of dust from dust laden gas in case of a/an
a. air filter
b. bag filter
c. venturi scrubber
d. hydrocyclones

air filter

Metallic wire mesh is used as a filtering medium for the separation of dust from dust laden gas in case of a/an
a. air filter
b. bag filter
c. venturi scrubber
d. hydrocyclones

air filter

Which of the following is a coarse crusher?
a. Smooth roll crusher
b. Toothed roll crusher
c. Gyratory crusher
d. Tube mill

Gyratory crusher

Sorting classifiers employing differential settling methods for separation of particles make use of the differences in their
a. particle sizes
b. densities
c. terminal velocities
d. none of these

terminal velocities

Separation of particles of various sizes, shapes and densities by allowing them to settle in a fluid is called
a. classification
b. froth floatation
c. thickening
d. clarification

classification

The specific cake resistance for incompressible sludges is (where ΔP = pressure drop over cake)
a. ∝ ΔP
b. ∝ 1/ ΔP
c. ∝ ΔP
d. independent of ΔP

independent of ΔP

The specific cake resistance for incompressible sludges is (where ΔP = pressure drop over cake)
a. ∝ ΔP
b. ∝ 1/ ΔP
c. ∝ ΔP
d. independent of ΔP

independent of ΔP

To produce talcum powder, use
a. ball mill
b. hammer mill
c. jet mill
d. pin mill

ball mill

To produce talcum powder, use
a. ball mill
b. hammer mill
c. jet mill
d. pin mill

ball mill

Angle of nip of the crushing rolls does not depend upon the
a. diameter of the rolls
b. speed of the rolls
c. product size
d. feed size

speed of the rolls

Paddle agitator
a. is suitable for mixing low viscosity liquids.
b. produces axial flow.
c. moves at very high speed.
d. none of these.

is suitable for mixing low viscosity liquids.

Paddle agitator
a. is suitable for mixing low viscosity liquids.
b. produces axial flow.
c. moves at very high speed.
d. none of these.

is suitable for mixing low viscosity liquids.

Pick out the wrong statement.
a. More commonly used jaw crusher between Dodge jaw crusher and Blake jaw crusher is the later one.
b. There are only four methods namely compression, impact, attrition and cutting, which the size reduction equipments employ.
c. Cutting machines mainly employ ‘attrition’ for size reduction of solids.
d. 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.

Gummy & sticky materials like molasses, sugar etc. are best transported/handled by using a __________ conveyor.
a. drag
b. ribbon
c. screw
d. slat

ribbon

Soft & non-abrasive materials can be made into fines by
a. attrition
b. compression
c. cutting
d. none of these

attrition

In constant pressure filtration,
a. resistance decreases with time
b. rate of filtration is constant
c. rate of filtration increases with time
d. rate of filtration decreases with time

rate of filtration decreases with time

Which of the following minerals is not subjected to magnetic separation method?
a. Rutile
b. Galena
c. Chromite
d. Siderite

Galena

Which of the following is not a revolving/tumbling mill used for size reduction?
a. Compartment mill
b. Pebble mill
c. Cage mill
d. Rod mill

Cage mill

Which of the following achieves the least reduction ratio for a given feed size?
a. Jaw crusher
b. Roll crusher
c. Cone crusher
d. Gyratory crusher

Roll crusher

For coarse reduction of hard solids, use
a. impact
b. attrition
c. compression
d. cutting

compression

In a size reduction crushing operation, feed size is 100 to 300 mm. while the product size is 10 to 50 mm. This is a case of the __________ crushing.
a. primary
b. secondary
c. fine
d. ultrafine

secondary

Traces of liquid tar fog present in coke oven gas is separated using
a. electrostatic precipitator
b. cyclone separator
c. strainer
d. none of these

electrostatic precipitator

Work index is the gross energy (kWh/tonne of feed) necessary to reduce a very large feed to such a size that 80% of product particles will pass through a 0.1 mm screen. The value of work index determined for wet grinding should be multiplied with __________ to get the same for dry grinding.
a. 1.0
b. 0.5
c. 1.34
d. 4.34

1.34

The specific surface of sherical particles is proportional to (where, Dp = diameter of
particle).
a. D2p
b. Dp
c. 1/Dp
d. 1/D2p

1/Dp

Wheat is ground into flour in a
a. hammer crusher
b. roller crusher
c. impact mill
d. fluid energy mill

roller crusher

Gravity stamp mill is meant for the __________ crushing.
a. primary
b. intermediate
c. fine
d. ultrafine

fine

Washability curve based on float and sink test enables an assessment to be made of the possibility of cleaning a coal fraction based on the
a. density separation.
b. differential wettability.
c. size.
d. volatile matter content.

density separation.

Pick out the wrong statement:
a. Magnetic separation method can be employed to treat both dry & wet ores.
b. Reduction ratio in crushing operation is defined as the ratio of minimum feed size to the maximum product size.
c. Gyratory crusher is used for coarse crushing.
d. 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.

Vacuum filter is most suitable for the
a. removal of fines from liquid.
b. liquids having high vapour pressure.
c. liquids of very high viscosity.
d. none of these.

none of these.

The porosity of a compressible cake is
a. minimum at the filter medium.
b. minimum at the upstream face.
c. maximum at the filter medium.
d. same throughout the thickness of cake.

minimum at the filter medium.

Which of the following conveyors cannot be recommended for transportation of abrasive materials?
a. Belt conveyor
b. Apron conveyor
c. Flight conveyor
d. Chain conveyor

Flight conveyor

For classification of potable (drinking) water, we use a __________ filter.
a. gravity sand
b. plate and frame
c. vacuum leaf
d. rotary vacuum

gravity sand

Hot, lumpy & abrasive materials are best transported by using a/an __________ conveyor.
a. apron
b. belt
c. screw
d. flight

apron

In case of grinding in a ball mill
a. wet grinding achieves a finer product size than dry grinding.
b. its capacity decreases with increasing fineness of the products.
c. grinding cost and power requirement increases with increasing fineness of the products.
d. all (a), (b) and (c).

all

The capacity of a classifier in ‘tons of solid/hr’ is given by (where, A = cross-sectional area, m2 V = rising velocity of fluid, m/sec.S = percentage of solids in the suspension by volume.ρ = density of solids, kg/m3)
a. 3.6 AVS.ρ
b. 3.6 A.V.ρ
c. 3.6 A.S. ρ
d. 3.6 AVS/ρ

3.6 AVS.ρ

Kick’s law relates to
a. energy consumption
b. final particle size
c. feed size
d. none of these

energy consumption

_________ mill is normally used for grinding of talc.
a. Tube
b. Compartment
c. Ring-roll
d. Pebble

Ring-roll

Colloidal mills are used for __________ grinding.
a. coarse
b. intermediate
c. fine
d. ultrafine

ultrafine

The maximum slope of a belt conveyor can be
a. 15°
b. 30°
c. 45°
d. 60°

30°

The filter medium resistance is controlled by
a. pressure drop alone
b. flow rate alone
c. both pressure drop and flow rate
d. cake thickness

both pressure drop and flow rate

The unit of filter medium resistance is
a. cm-1
b. gm/cm-1
c. cm/gm-1
d. gm-1

cm-1

During size reduction by a jaw crusher, the energy consumed decreases with the
a. decreasing size of product at constant size of feed.
b. decreasing machine capacity.
c. increasing size of feed at constant reduction ratio.
d. none of these.

increasing size of feed at constant reduction ratio.

Which of the following can be most effectively used for clarification of lube oil and printing ink?
a. Sparkler filter
b. Precoat filter
c. Disc-bowl centrifuge
d. Sharpies supercentrifuge

Sharpies supercentrifuge

Ultracentrifuges running at speeds upto 100000 rpm is normally used for the
a. separation of isotopes based on their density or molecular weights difference.
b. concentration of rubber latex.
c. separation of cream from milk.
d. dewaxing of lubricating oil.

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

Sizing of very fine particles of the order of 5 to 10 microns is done by elutriation, which is a __________ operation.
a. clarification
b. sedimentation
c. flocculation
d. classification

classification

Size reduction of fibrous materials like wood, asbestos, mica etc. is done by a disintegrator exemplified by the
a. Blake jaw crusher
b. cage mill
c. stamp mill
d. Bradford’s breaker

cage mill

The material is crushed in a gyratory crusher by the action of
a. impact
b. compression
c. attrition
d. cutting

compression

The equivalent diameter of channel of a constant non-circular cross-section of 3 cm by 6 cm will be __________ cms.
a. 20
b. 12
c. 8
d. 2

Which of the following may prove unsuitable for filtering volatile liquids?
a. Pressure filter
b. Gravity filter
c. Centrifugal filter
d. Vacuum filter

Vacuum filter

Mass flow of granular solid (M) through a circular opening of dia, D follows
a. M ∝ D
b. M ∝ D2
c. M ∝ D3
d. M ∝ D

M ∝ D3

Sauter mean diameter is the same as the __________ mean diameter.
a. mass
b. arithmetic
c. volume-surface
d. geometric

volume-surface

Cake resistance is
a. important in the beginning of filtration.
b. decreased with the time of filtration.
c. independent of pressure drop.
d. none of these.

none of these.

In paint industries, blending of light paste is done by using a
a. masticator
b. charge can mixer
c. kneader
d. none of these

charge can mixer

A sand mixture was screened through a standard 10-mesh screen. The mass fraction of the oversize material in feed, overflow and underflow were found to be 0.38, 0.79 and 0.22 respectively. The screen effectiveness based on the oversize is
a. 0.50
b. 0.58
c. 0.68
d. 0.62

0.50

_________ is used for producing a thick suspension from a thin slurry.
a. Cartridge filter
b. Rotary drum vacuum filter
c. Pressure filter thickener
d. Plate and frame filter press

Pressure filter thickener

Wet seiving is employed, when the product contains __________ materials.
a. abrasive
b. large quantity of very fine
c. coarse
d. non-sticky

large quantity of very fine

Energy requirement (per unit mass of material crushed/ground) is highest for
a. jaw crusher
b. rod mill
c. ball mill
d. fluid energy mill

fluid energy mill

The energy consumed by a ball mill depends on
a. its speed.
b. its ball load.
c. the density of the material being ground.
d. all (a), (b) and (c).

all

Energy consumption in a crusher decreases with increase in the
a. size of the product (at constant feed size).
b. capacity of the crushing machine.
c. size of feed (at constant reduction ratio).
d. all (a), (b) & (c).

all

In a mixer, the quantity, (v. L/D) is termed as __________ number(where, v = longitudinal velocity of material, L = length of the mixer, D = diffusivity in axial mixing).
a. Weber
b. Peclet
c. Brinkman
d. Schmidt

Peclet

The term ‘angle of nip’ is concerned with the operation of the __________ crushers.
a. jaw
b. roll
c. gyratory
d. none of these

roll

Cartridge filters are termed as ‘edge’ filters, because of the fact that the
a. disks have very sharp edge.
b. solids are not deposited at the edge of the disk.
c. bulk of the solids are removed at the periphery of the disks.
d. none of these.

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

Vibrating screens have capacity in the range of __________ tons/ft2 .mm mesh size.
a. 0.2 to 0.8
b. 5 to 25
c. 50 to 100
d. 100 to 250

0.2 to 0.8

Cumulative analysis for determining surface is more precise than differential analysis, because of the
a. assumption that all particles in a single fraction are equal in size.
b. fact that screening is more effective.
c. assumption that all particles in a single fraction are equal in size, is not needed.
d. none of these.

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

To remove very small amount of tiny solid impurities from liquid, we use a
a. pressure filter
b. vacuum filter
c. centrifugal filter
d. coagulant

coagulant

To remove very small amount of tiny solid impurities from liquid, we use a
a. pressure filter
b. vacuum filter
c. centrifugal filter
d. coagulant

coagulant

Screw conveyors are
a. run at very high rpm.
b. suitable for sticky materials.
c. suitable for highly abrasive materials.
d. all (a), (b) and (c)

suitable for sticky materials.

__________ mills fall in the category of tumbling mills,
a. Ball and pebble
b. Rod and tube
c. Compartment
d. all (a), (b) & (c)

all

Capacity of flight conveyor in tons/hr is given by (where, W & D = width and depth of flight respectively in metre V = speed of the conveyor, metre/second ρ = bulk density of material, kg/m3)
a. 3.6 W.D.V.ρ
b. 3.6 W.D.V.
c. 3.6 W.V.ρ
d. 3.6 D.V.ρ

3.6 W.D.V.ρ

Which of the following is not a cutting machine?
a. Dicers
b. Knife cutters
c. Slitters
d. Tube mills

Tube mills

Weber number is significant and is concerned with the
a. solid-liquid mixing.
b. liquid-liquid mixing.
c. dispersion of liquid in liquid.
d. suspension of solid in liquid.

dispersion of liquid in liquid.

Power consumption during turbulent flow in agitation tank is proportional to the __________ of the liquid.
a. viscosity
b. thermal conductivity
c. surface tension
d. density

density

Screen efficiency is
a. recovery/rejection
b. recovery
c. rejection
d. none of these

none of these

For grinding of cereals, grains, spices, pigments, saw dust, cork etc., the most extensively used size reduction equipment is a
a. Buhrstone mill
b. ball mill
c. crushing rolls
d. hammer mill

Buhrstone mill

Handling of ashes and similar materials can be done best by a __________ conveyor.
a. flight
b. drag or slat
c. belt
d. ribbon.

drag or slat

Handling of ashes and similar materials can be done best by a __________ conveyor.
a. flight
b. drag or slat
c. belt
d. ribbon.

drag or slat

Which of the following must be stored in silos and not in open yard?
a. Coke breeze
b. High V.M. bituminous coal
c. Sand
d. None of these

High V.M. bituminous coal

Apron conveyors are used for
a. heavy loads & short runs.
b. small loads & long runs.
c. heavy loads & long runs.
d. none of these.

heavy loads & short runs.

Sedimentation on commercial scale occurs in
a. classifiers
b. thickeners
c. rotary drum filters
d. cyclones

rotary drum filters

With increase in drum speed, in a rotary drum filter, the filtration rate
a. increases
b. increases linearly
c. decreases
d. is not affected

increases

Arrange the following size reduction equipment in the decreasing order of the average particle size produced by each of them.
a. Jaw crusher, Ball mill, Fluid energy mill
b. Ball mill, Jaw crusher, Fluid energy mill
c. Fluid energy mill, Jaw crusher, Ball mill
d. Fluid energy mill, Ball mill, Jaw crusher

Jaw crusher, Ball mill, Fluid energy mill

200 mesh seive size corresponds to __________ microns.
a. 24
b. 74
c. 154
d. 200

What is the usual value of angle of nip for crushing of ordinary rock in smooth steel
crushing rolls?
a. 16°
b. 32°
c. 40°
d. 46°

32°

For a turbine agitated and baffled tank, operating at low Reynold’s number (based on impeller diameter), the power number (Np) varies with NRe as
a. Np ∝ NRe
b. Np ∝ NRe
c. Np → constant
d. Np ∝ 1/NRe

Np ∝ 1/NRe

Which of the following is not accomplished by agitation of liquids in agitators?
a. Dispersing gas in liquid.
b. Blending of immiscible liquids.
c. Dispersing immiscible liquid in form of emulsion.
d. Suspending solid particles.

Blending of immiscible liquids.

Which of the following parts of a jaw crusher is subjected to maximum wear and tear
during its operation?
a. Check plates
b. Jaw plates
c. Toggles
d. Crush shaft

Jaw plates

A 30% (by volume) suspension of spherical sand particles in a viscous oil has a
hindered settling velocity of 4.44 μm/s. If the Richardson Zaki hindered settling index is 4.5,
then the terminal velocity of a sand grain is
a. 0.90 μm/s
b. 1 μm/s
c. 22.1 μm/s
d. 0.02 μm/s

1 μm/s

In froth floatation, chemical agent added to cause air adherence is called
a. collector
b. frother
c. modifier
d. activator

collector

The sphericity of a solid particle of cubical shape is
a. π
b. (π/6)1/3
c. (π/6)1/2
d. π/3

(π/6)1/3

A cottrel precipitator makes use of the __________ for dusty air cleaning.
a. electric spark
b. corrona discharge
c. alternating current
d. none of these.

corrona discharge

If radius of a batch basket centrifuge is halved & the r.p.m. is doubled, then the
a. linear speed of the basket is doubled.
b. linear speed of the basket is halved.
c. centrifugal force is doubled.
d. capacity of centrifuge is increased.

centrifugal force is doubled.

The ratio of the area of openings in one screen (Taylor series) to that of the openings in the next smaller screen is
a. 1.5
b. 1
c. 2
d. none of these

none of these

Compressibility co-efficient for an absolutely compressible cake is
a. 0
b. 1
c. 0 to 1
d. ∞

Mixing of plastic solids is generally facilitated by
a. dispersion
b. mastication
c. kneading
d. none of these

kneading

Which of the following is not an industrial screening equipment ?
a. Sharpies centrifuge
b. Vibrating screen
c. Grizzly
d. Trommel

Sharpies centrifuge

Which of the following is not a wet classifier ?
a. Sharpies supercentrifuge
b. Hydrocyclones
c. Dorr Oliver rake classifier
d. None of these

None of these

Helical screw agitator is used for
a. mixing highly viscous pastes.
b. blending immiscible liquids.
c. mixing liquids at very high temperature (> 250 °C).
d. none of these.

mixing highly viscous pastes.

For raschig rings, the sphericity is
a. 0.5
b. 1
c. <1
d. 3

For Indian standard (IS) screens, the mesh number is equal to its aperture size expressed to the nearest deca-micron (0.01 mm). Aperture width of IS screen of mesh number 50 will be approximately __________ microns.
a. 5
b. 50
c. 500
d. 5000

500

_________ mills are termed as disintegrators.
a. Cage
b. Compartment
c. Pebble
d. All tumbling

Cage

Supporting legs of a plate and frame filter is normally made of
a. stainless steel
b. cast iron
c. high speed steel
d. wooden plank

cast iron

Wet grinding in a revolving mill __________ as compared to dry grinding.
a. gives less wear on chamber walls
b. requires more energy
c. increases capacity
d. complicates handling of the product

increases capacity

A compressible cake has the
a. maximum porosity at the upstream side.
b. maximum porosity at the filter medium.
c. same porosity throughout the cake thickness.
d. none of these.

maximum porosity at the upstream side

Which of the following is not used as a filter medium in case of corrosive liquids ?
a. Nylon
b. Glass cloth
c. Metal cloth of monel or stainless steel
d. Cotton fabric

Cotton fabric

In ball mill operation, the feed size (Df in meters) and the ball diameter (Db in metres) are related as ( where, K = grindability constant (varying from 0.9 to 1.4 in increasing order of hard ness))
a. Db2 = K.Df
b. Db = K.Df
c. Db3 = K.Df
d. Db2 = K.Df2

Db2 = K.Df

Grinding characteristic of a material is given by its
a. HGI
b. angle of repose
c. shatter index
d. abrasion index.

HGI

Which of the following is not a non-metalliferous mineral?
a. Calcite
b. Fluorspar
c. Quartz
d. Cassiterrite

Cassiterrite

Filter medium resistance is important during the __________ of filtration.
a. early stages
b. final stages
c. entire process
d. none of these

early stages

Float and sink test determines the possibility of cleaning of coal by a process based on the
a. gravity separation
b. wettability
c. particle shape
d. none of these

gravity separation

Float and sink test determines the possibility of cleaning of coal by a process based on the
a. gravity separation
b. wettability
c. particle shape
d. none of these

gravity separation

________ baffles are provided in ball mills.
a. Horizontal
b. No
c. Only two
d. None of these

Horizontal

Mixer used for rubber compounding is
a. mixer-extruder
b. banbury internal mixer
c. muller mixer
d. pug mill

banbury internal mixer

_________ mill is not used for grinding wheat into flour and for milling of cereals & other vegetable products.
a. Buhrstone
b. Roller
c. Attrition
d. Pebble

Pebble

In case of a hammer crusher, the final product size depends on the
a. feed rate.
b. rotor speed.
c. clearance between hammer & grinding plates.
d. all (a), (b) and (c).

all

Sphericity of raschig ring (whose length and diameter are equal) is
a. >1
b. <1
c. 1
d. 2

Mixing mechanism employed in a pan mixer is by
a. mulling
b. kneading
c. dispersion
d. none of these

mulling

Chance process is used for the
a. cleaning of coal.
b. concentration of iron ore.
c. concentration of pyrites.
d. water treatment

cleaning of coal.

Which of the following screens has the maximum capacity ?
a. Grizzlies
b. Trommels
c. Shaking screen
d. Vibrating screen

Vibrating screen

Stamp mills are generally used for crushing
a. iron ores
b. gold ores
c. talc
d. diamond

gold ores

In case of a plate and frame filter press, filtrate flow through the cake follows __________ flow.
a. plug
b. turbulent
c. laminar
d. none of these

laminar

Which of the following is a batch sedimentation equipment ?
a. Dust catcher
b. Filter thickener
c. Dry cyclone separator
d. Rotary sprayer scrubber.

Filter thickener

The most suitable equipment for the transportation of 200 mesh size particles is a
a. bucket elevator
b. pneumatic conveyor
c. screw conveyor
d. belt conveyor

pneumatic conveyor

Which of the following is not used as filter aid?
a. Asbestos
b. Diatomaceous earth
c. Purified wood cellulose
d. Rice husk

Rice husk

Raw materials are charged in the iron blast furnace using
a. bucket elevator
b. skip hoist
c. screw conveyor
d. none of these

skip hoist

Carbon black is pulverised in a
a. hammer crusher
b. ball mill
c. roll crusher
d. gyratory crusher

ball mill

The most efficient equipment for the removal of sub-micronic dust particles from blast furnace gas is the
a. venturi atomiser
b. gravity settling chamber
c. electro-static precipitator
d. cyclone separator

electro-static precipitator

The filtrate flow rate in constant pressure filtration
a. continuously increases.
b. continuously decreases.
c. remains constant throughout.
d. may increase or decrease ; depends on the pressure.

continuously decreases.

The inlet pressure in a constant rate filtration
a. increases continuously
b. decreases gradually
c. remains constant
d. none of these

increases continuously

Particle size range in which dust catcher (gravity settling chamber) works most effectively and efficiently is __________ microns.
a. < 5
b. 10 to 25
c. < 74
d. 1000

< 74

________ centrifuge is the most suitable for separation of non-friable crystals.
a. Tubular bowl
b. Disc-bowl
c. Perforated horizontal basket continuous
d. Suspended batch basket

Perforated horizontal basket continuous

For benefication of iron ore, the most commonly used method is
a. flocculation.
b. froth floatation.
c. jigging & tabling.
d. none of these.

jigging & tabling.

A propeller agitator
a. produces mainly axial flow.
b. is used for mixing high viscosity pastes.
c. runs at very slow speed (2 rpm).
d. all (a), (b) and (c)

produces mainly axial flow.

In coal washeries, three products namely the valuable product (i.e. clean/washed coal), discarded product (i.e. mineral matter) and an additional concentrated product called __________ is produced.
a. concentrate
b. tailing
c. middling
d. none of these.

middling

Actual operating speed of a ball mill may vary from 65 to 80% of the critical speed. Which of the following duties would require the ball mill to be operated at maximum percentage of critical speed ?
a. Wet grinding in low viscous suspension.
b. Wet grinding in high viscous suspension.
c. Dry grinding of large particles (upto 1.25 cms).
d. Dry grindng of large particles in un-baffed mills.

Dry grindng of large particles in un-baffed mills.

A __________ employs a set of screen across a flow channel for the separation of dirt/rust from a flowing liquid stream.
a. thickener
b. classifier
c. strainer
d. clarifier

strainer

Reciprocal of sphericity is termed as the
a. specific surface ratio
b. shape factor
c. sauter diameter
d. surface area per unit mass

shape factor

With increase in the pressure drop across the cake, the specific cake resistance for the compressible sludge
a. increases
b. decreases
c. remains constant
d. increases linearly

increases

Pick out the wrong statement.
a. Hammer crushers operate by impact action.
b. Standard screens have circular opening.
c. With increase in mesh number of screens, their diameter in microns decreases.
d. 200 mesh screen has 200 openings per linear cm.

200 mesh screen has 200 openings per linear cm.

Size reduction of ice and gypsum can be accomplished suitably by a __________ crusher.
a. Blake jaw
b. toothed roll
c. gyratory
d. none of these.

toothed roll

A filter press is
a. a batch filter.
b. not suitable, if the liquid is the main product.
c. having prohibitively high maintenance cost.
d. not suitable for wide range of

a batch filter.

Xanthates are used in the froth floatation process as a/an
a. conditioner
b. frother
c. collector
d. activator

collector

The ratio of the actual mesh dimension of Taylor series to that of the next smaller
screen is
a. 2
b. sqrt 2
c. 1.5
d. 3

sqrt 2

Limestone is normally crushed in a
a. roll crusher
b. hammer crusher
c. ball mill
d. tube mill

hammer crusher

The main differentiation factor between tube mill and ball mill is the
a. length to diameter ratio.
b. size of the grinding media.
c. final product size.
d. operating speed.

length to diameter ratio.

A belt conveyor used for the transportation of materials can
a. run upto 1 km.
b. travel at a speed upto 300 metres/minute.
c. handle materials upto 5000 tons/hr.
d. all (a), (b) and (c).

all

Which of the following is not used as a surface active agent in a flocculation operation?
a. Sodium silicate
b. Quartz
c. Lime
d. Alumina

Quartz

__________ mill is not a revolving mill.
a. Pebble
b. Compartment
c. Cage
d. Tube

Cage

For the transportation of ultrafine particles, the equipment used is a……..conveyor.
a. belt
b. pneumatic
c. screw
d. none of these

pneumatic

During filtration operation, the filtrate encounters the resistance of the
a. filter medium.
b. cake.
c. channel carrying the slurry to the upstream side of the cake and filtrate away from the filter medium.
d. all (a), (b) and (c)

all

Filtration rate does not depend upon the
a. pressure drop & area of filtering surface.
b. resistance of the cake & the septum.
c. properties of the cake & the filtrate.
d. none of these.

none of these

Filtration rate does not depend upon the
a. pressure drop & area of filtering surface.
b. resistance of the cake & the septum.
c. properties of the cake & the filtrate.
d. none of these.

none of these

Which of the following is a fine crusher?
a. Blake jaw crusher
b. Gyratory crusher
c. Toothed roll crusher
d. Dodge jaw crusher

Toothed roll crusher

_________ is a cohesive solid.
a. Wheat
b. Sand
c. Wet clay
d. none of these

Wet clay

The optimum moisture content in solids to be crushed/ground ranges from __________
percent.
a. 3 to 4
b. 8 to 10
c. 10 to 15
d. 15 to 20

3 to 4

The optimum moisture content in solids to be crushed/ground ranges from __________
percent.
a. 3 to 4
b. 8 to 10
c. 10 to 15
d. 15 to 20

3 to 4

The capacity of a gyratory crusher is __________ that of a jaw crusher with the same
gape, handling the same feed & for the same product size range.
a. same as
b. 2.5 times
c. 5 times
d. 10 times

2.5 times

Dispersion of a gas through liquid is done by using a
a. sparger
b. kneader
c. masticator
d. none of these

sparger

Work index is defined as the
a. gross energy (kWh/ton of feed) needed to reduce very large feed to such a size that 80% of the product passes through a 100 micron screen.
b. energy needed to crush one tonne of feed to 200 microns.
c. energy (kWh/ton of feed) needed to crush small feed to such a size that 80% of the product passes a 200 mesh screen.
d. energy needed to crush one ton of feed to 100 microns.

gross energy (kWh/ton of feed) needed to reduce very large feed to such a size that 80% of the product passes through a 100 micron screen.

Removal of activated carbon from glycerine is done by
a. plate and frame filter
b. rotary vacuum filter
c. batch basket centrifuge
d. none of these

plate and frame filter

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