S6

Question 1

Pick out the wrong statement.

Answer 1

Cake resistance is independent of the pressure drop.

Question 2

Which of the following oxides is not present in hematite iron ore?

Answer 2

Cobalt oxide

Question 3

Ribbon blenders are exclusively meant for

Answer 3

non-flowing powder and thin pastes.

Question 4

In closed circuit grinding as compared to open circuit grinding, the

Answer 4

operation is economical.

Question 5

Pick out the correct statement.

Answer 5

A hopper is a small bin with a sloping bottom.

Question 6

Gelatinous solid (which plug the septum) can be filtered by a __________ filter.

Answer 6

precoat

Question 7

During the washing of cake

Answer 7

all the resistances are constant.

Question 8

The opening of a 200 mesh screen (Taylor series) is

Answer 8

0.0074 cm

Question 9

A gravity decanter is meant for the separation of two __________ density.

Answer 9

immiscible liquids of different

Question 10

The most suitable filter for the removal of very small amount of precipitate from very large volumes of water is the __________ filter.

Answer 10

sand

Question 11

Separation of solid particles based on their densities is called

Answer 11

sorting

Question 12

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?

Answer 12

Copper sulphate

Question 13

__________ are mixed using ribbon blenders.

Answer 13

Dry powders

Question 14

During agitation of liquids, the

Answer 14

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

Question 15

For crushing of solids, the Rittinger’s law states that the work required for crushing is proportional to

Answer 15

the new surface created.

Question 16

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.

Answer 16

primary

Question 17

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, cmsS= Maximum width of discharge opening, cms)

Answer 17

93LS

Question 18

The process by which fine solids is removed from liquids is termed as

Answer 18

sedimentation

Question 19

Which of the following crushing laws is most accurately applicable to the fine grinding of materials?

Answer 19

Rittinger’s law

Question 20

Shell and leaf filter as compared to plate and frame filter

Answer 20

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

Question 21

Metallic wire mesh is used as a filtering medium for the separation of dust from dust laden gas in case of a/an

Answer 21

air filter

Question 22

Which of the following is a coarse crusher?

Answer 22

Gyratory crusher

Question 23

Sorting classifiers employing differential settling methods for separation of particles make use of the differences in their

Answer 23

terminal velocities

Question 24

Separation of particles of various sizes, shapes and densities by allowing them to settle in a fluid is called

Answer 24

classification

Question 25

The specific cake resistance for incompressible sludges is (where ΔP = pressure drop over cake)

Answer 25

independent of ΔP

Question 26

To produce talcum powder, use

Answer 26

ball mill

Question 27

Angle of nip of the crushing rolls does not depend upon the

Answer 27

speed of the rolls

Question 28

Paddle agitator

Answer 28

is suitable for mixing low viscosity liquids.

Question 29

Pick out the wrong statement.

Answer 29

Cutting machines mainly employ 'attrition' for size reduction of solids.

Question 30

Cutting machines mainly employ 'attrition' for size reduction of solids.

Answer 30

Ribbon

Question 31

Soft & non-abrasive materials can be made into fines by

Answer 31

attrition

Question 32

In constant pressure filtration,

Answer 32

rate of filtration decreases with time

Question 33

The critical speed of a trommel (N) is related to its dia (D) as

Answer 33

N α 1 / sqrt D

Question 34

Which of the following minerals is not subjected to magnetic separation method?

Answer 34

Galena

Question 34

Which of the following is not a revolving/tumbling mill used for size reduction?

Answer 34

Cage mill

Question 35

Which of the following achieves the least reduction ratio for a given feed size?

Answer 35

Roll crusher

Question 36

A fluid energy mill is used for

Answer 36

ultragrinding

Question 37

For coarse reduction of hard solids, use

Answer 37

compression

Question 37

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.

Answer 37

secondary

Question 38

Traces of liquid tar fog present in coke oven gas is separated using

Answer 38

electrostatic precipitator

Question 39

**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.

Answer 39

**1.34**

Question 40

Choke crushing (in case of a Jaw crusher) compared to free crushing

Answer 40

consumes more power.

Question 41

The specific surface of spherical particles is proportional to (where, Dp = diameter of particle).

Answer 41

1/Dp

Question 42

Wheat is ground into flour in a

Answer 42

roller crusher

Question 43

Gravity stamp mill is meant for the __________ crushing.

Answer 43

fine

Question 44

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

Answer 44

density separation.

Question 45

Pick out the wrong statement:

Answer 45

Reduction ratio in crushing operation is defined as the ratio of minimum feed size to the maximum product size.