Section 2 Flashcards by Cathrina Chavez

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.

b. 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

c. 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.

a. 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.

a. 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

a. size

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

a. jaw crushers

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

d. 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

a. 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.

d. 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

a. 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

a. 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

b. 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)

d. all (a), (b) & (c)

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

a. Ribbon conveyor
b. Flight conveyor
c. Bucket elevators
d. Drag conveyor.

c. 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

b. 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.

c. 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.

d. 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)

b. 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

c. frother

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

c. < 1

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

d. jaw crusher

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

c. Screw conveyor

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

b. electrostatic precipitator

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

b. <10

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

a. open sand

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

a. leaf

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

b. 1

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

c. fine grinding

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

a. coarse feed requires a larger ball.

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

c. impact

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

a. decreases.

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. N^1 c. N^2 d. N^3

c. N^2

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

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

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

a. Kozney-Karman

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

b. cake

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

b. Gyratory crusher

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

b. ball mill

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.

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

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

a. c/s

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

c. tube mill

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

b. heading

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

c. π/6(=V/D3)

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

b. Helical screw

________ 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

b. Selectivity index

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

a. less than

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

b. Classifiers

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

b. squirrel-cage disintegrator

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

a. Banbery mixer