Section 3 Flashcards by Cathrina Chavez

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

c. 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

b. sticky (e.g. clay paste)

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The most common filter aid is
a. diatomaceous earth
b. calcium silicate
c. sodium carbonate
d. silica gel

a. diatomaceous earth

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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

c. 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

c. centrifugal

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memorize

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

a. 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

b. 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

c. 1

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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.

a. 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 filter

b. 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

b. 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

a. 1

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

b. attrition

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

b. 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

c. 50

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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

a. 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

d. none of these

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

b. 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

c. punched plate

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

b. coal

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

c. colloidal

A. ________ mill is a revolving mill divided into two or more sections by perforated
partitions in which preliminary grinding takes place at one end and the finishing grinding at
the discharge end.

a. compartment
b. tube
c. rod
d. pebble.

a. compartment

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

a. rod mills

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

b. 0.0184

Which of the following represents the plot of filtrate volume versus time for constant pressure filtration ? a. Parabola b. Straight line c. Hyperbola d. Exponential curve

a. Parabola

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

b. centrifugal pressure exerted by the liquid.

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'.

d. all 'a', 'b' & 'c'.

Production rate ________ with increased fineness, with a given energy input to the size reduction machine. a. decreases b. increases c. remains unchanged d. may increase or decrease; depends on the machine

a. decreases

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

b. tabling

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

c. impact wheels

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

b. hammer crusher

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

a. Sphere

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

a. gm/cm2

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

a. hammer mills

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

c. heavy media separation

# memorize A suspension of glass beads in ethylene glycol has a hindered settling velocity of 1.7 mm/s, while the terminal settling velocity of a single glass bead in ethylene glycol is 17 mm/s. If the Richardson-Zaki hindered settling index is 4.5, the volume fraction of solids in the suspension is a. 0.1 b. 0.4 c. 0.6 d. none of these

c. 0.6

________ conveyor is the most suitable for long distance transportation of cold, non abrasive granular/irregular shape/fine materials. a. Bucket b. Belt c. Screw d. Apron

b. Belt

The specific cake resistance for compressible sludges is a function of the pressure drop a. over cake b. over medium c. overall d. none of these

a. over cake

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

a. tubular centrifuge

Tabling process used for separating two materials of different densities by passing the dilute pulp over a table/deck, which is inclined from the horizontal surface at an angle of about a. 1 to 2° b. 2 to 5° c. 5 to 10° d. 10 to 15°

b. 2 to 5°

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.

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

Addition of filter aid to the slurry before filtration is done to ...... of the cake. a. increase the porosity b. increase the compressibility co-efficient c. decrease the porosity d. decrease the compressibility co-efficient

a. increase the porosity

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

d. Compression

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).

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

Kick's law assumes that the energy required for size reduction is proportional to the logarithm of the ratio between the initial and the final diameters. The unit of Kick's constant is a. kW. sec/kg b. kWh/kg c. kWh/sec. kg d. kg/sec.

a. kW. sec/kg