Section 4

Question 1

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

Answer 1

c. Rittinger’s law

Question 2

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.

Answer 2

c. deplugging the filter medium

Question 3

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

Answer 3

b. fine

Question 4

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

Answer 4

b. Pug mill

Question 5

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

Answer 5

c. Quartz

Question 6

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

Answer 6

a. Hammer

Question 7

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.

Answer 7

d. none of these.

Question 8

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

Answer 8

b. ball mill

Question 9

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

Answer 9

d. 230

Question 10

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).

Answer 10

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

Question 11

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’.

Answer 11

c. Capacity of crusher in choke feeding is increased.

Question 12

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

Answer 12

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

Question 13

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.

Answer 13

c. used for small scale filtration work.

Question 14

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

Answer 14

a. metallic wire woven mesh

pg. 17-49

Question 15

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

Answer 15

a. dry

Question 16

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

Answer 16

b. D

Question 17

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.

Answer 17

c. Vacuum filter

Question 18

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

Answer 18

c. remain constant

Question 19

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

Answer 19

c. tumbling

Question 20

________ 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

Answer 20

a. Flight

Question 21

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

Answer 21

b. increases

Question 22

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.

Answer 22

a. have greater capacity per unit of discharge area.

Question 23

At low Reynold’s number, the power (P) required for agitating a fluid in a stirred tank
becomes independent of inertial forces. In this limit, indicate which of the following relations
is satisfied:
Po = ρ/ρN3 D5 : Power number
Re = ρ N D2/μ: Reynold’s number
N is the impeller rotational speed, and D is the impeller diameter.

a. Po ∝ Re-1.0
b. Po ∝ Re0.0
c. Po ∝ Re0.5
d. Po ∝ Re1.0

Answer 23

a. Po ∝ Re-1.0

pg. 18-6

Question 24

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.

Answer 24

b. Rod mill

Question 25

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.

Answer 25

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

Question 26

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

Answer 26

b. <1

Question 27

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

Answer 27

d. as high as 100 | pg. 21-83 Tumbling Mills

Question 28

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

Answer 28

c. Corundum | aka Sapphire

Question 29

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.

Answer 29

d. impact and attrition.

Question 30

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

Answer 30

b. incompressible cake and laminar

Question 31

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

Answer 31

b. kWh/ton

Question 32

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

Answer 32

a. specific gravities

Question 33

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

Answer 33

d. surface area per unit mass

Question 34

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.

Answer 34

a. ratio of feed opening to discharge opening.

Question 35

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

Answer 35

b. Cone crusher

Question 36

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

Answer 36

b. solids from fluids

Question 37

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

Answer 37

d. froth floatation

Question 38

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

Answer 38

a. increases

Question 39

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.

Answer 39

c. heavy tonnages of rocks or gravel.

Question 40

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

Answer 40

b. 50

Question 41

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

Answer 41

b. sizing

Question 42

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

Answer 42

a. pug mill

Question 43

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

Answer 43

c. silicates & phosphates

Question 44

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

Answer 44

c. D^2