S5

Question 1

With increase in the capacity of screens, the screen effectiveness

Answer 1

decreases

Question 2

As particle size is reduced

Answer 2

screening becomes progressively more difficult.

Question 3

Rittinger number which designates the new surface produced per unit of mechanical energy absorbed by the material being crushed, depends on the

Answer 3

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

Question 4

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.

Answer 4

1000°C and 10 atm.

Question 5

For efficient grinding, ball mills must be operated

Answer 5

at a speed less than the critical speed.

Question 6

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.

Answer 6

fine

Question 7

For spheres, the surface shape factor is given by (where,A= area,V= volume, andD= diameter)

Answer 7

π(=A/D^2)

Question 8

The reduction ratio for grinders is defined as(where,Df andDpare average diameters of feed and product respectively).

Answer 8

Df/Dp

Question 9

Pick out the wrong statement pertaining to the turbine agitator.

Answer 9

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

Question 10

A fluid energy mill is used for

Answer 10

ultra grinding

Question 11

Which of the following is the softest material?

Answer 11

Talc

Question 12

Dry powdery solid materials are transported by a __________ conveyor.

Answer 12

screw

Question 13

Fluid energy mill comes in the category of

Answer 13

ultrafine grinder

Question 14

Filtration capacity of a rotary drum vacuum filter depends upon the

Answer 14

both (a) & (b).

Question 15

About 2-3 hp, power per gallon of a thin liquid provides vigrous agitation in an agitator. ‘Power number’ in agitation is given by

Answer 15

P . gc / n^3 . D^2 . ρ

Question 16

For laminar flow of filtrate through the cake deposited on septum, which of the following will be valid?

Answer 16

Kozney-Karman equation

Question 17

Which of the following is a continuous filter?

Answer 17

None of these

Question 18

During washing of filter at the end of constant pressure filtration, the rate of washing equals the rate of filtration

Answer 18

at the end of filtration.

Question 19

In screen analysis, the notation +5 mm/-10 mm means particles passing through

Answer 19

10 mm screen and retained on 5 mm screen.

Question 20

rpm of a trommel at critical speed is given by (where,D= Diameter of trommel in ft)

Answer 20

76.75 / sqrt D

Question 21

Optimum ratio of operating speed to critical speed of a trommel is

Answer 21

0.33-0.45

Question 22

The process opposite to ‘dispersion’ is termed as the

Answer 22

flocculation

Question 23

Grinding efficiency of a ball mill is of the order of __________ percent.

Answer 23

1-5

Question 24

Solid particles of different densities are separated by

Answer 24

sorting classifier

Question 25

During agitation of liquids, power consumption during laminar flow is not proportional to the

Answer 25

density of the liquid

Question 26

Trommels are revolving screens which normally operate in the range of __________ rpm.

Answer 26

15 - 20

Question 27

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

Answer 27

1.34 Wi

Question 28

Maximum size reduction in a fluid energy mill is achieved by

Answer 28

interparticle attrition

Question 29

Filtration rate through a filter cake is proportional to (where,S= filtering surfaceR= specific cake resistance μ = viscosity of the filtrate)

Answer 29

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

Question 30

A centrifugal filtration unit operating at a rotational speed of w has inner surface of the liquid (density ρL) located at a radial distanceRfrom the axis of rotation. The thickness of the liquid film is δ and no cake is formed. The initial pressure drop during filtration is

Answer 30

1/2 w^2 . δρL . (2R + δ)

Question 31

Which one is a filter aid?

Answer 31

Diatomaceous earth

Question 32

To remove dirt from the flowing fluid, we use a

Answer 32

strains

Question 33

Which of the following crushers can be considered as a combination of a jaw crusher and a roller crusher?

Answer 33

Gyratory crusher

Question 34

Separation of solid suspended in liquid into a supernatant clear liquid and a denser slurry employs a process termed as the

Answer 34

sedimentation

Question 35

Ultrafine grinders operate principally by

Answer 35

attrition

Question 36

Half the angle of nip, (α), for a roll crusher is given by (where,dr,dpanddfare diameters of crushing rolls, feed particles and rolls gap respectively).

Answer 36

cosα = dr + df / dr + dp

Question 37

Which of the following comes in the category of primary crusher for hard and tough stone?

Answer 37

Jaw crusher

Question 38

Crushing efficiency of a machine ranges between __________ percent.

Answer 38

0.1 to 2

Question 39

Screen capacity is expressed in terms of

Answer 39

tons/hr-ft^2

Question 40

A screen is said to be blinded, when the

Answer 40

screen is plugged with solid particles.

Question 41

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?

Answer 41

0.66

Question 42

Percentage of drum submerged in the slurry in case of rotary drum filter is

Answer 42

30

Question 43

Filter medium resistance is that offered by the

Answer 43

filter cloth and the embedded particle collectively.

Question 44

In a roll crusher, both the rolls

Answer 44

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

Question 45

Tube mill compared to ball mill

Answer 45

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

Question 46

Critical speed of rotation, N (in rps - rotation per second) of a trammel is equal to (where,g= acceleration due to gravity = 9.81 m/sec2and,r= radius of trammel, metre.)

Answer 46

1/2n . sqrt g/r

Question 47

For the preliminary breaking of hard rock, we use a

Answer 47

gyratory crusher

Question 47

Filtration operation carried out by continuous increase of the inlet pressure of slurry, is called the __________ filtration.

Answer 47

constant rate