S4

Question 1

Which of the following gives the crushing energy required to create new surface?

Answer 1

Rittinger’s law

Question 2

In filtration, the use of ‘filter aid’ helps in

Answer 2

deplugging the filter medium.

Question 3

Critical Speed (Nc) of a ball mill is given by(whereR1and R2 are radii of ball mill and the ball respectively).

Answer 3

Nc = 1/2n . sqrt g / R1 - R2

Question 4

Which of the following clay mixing devices is vacuum operated for deairation of clay?

Answer 4

Pug mill

Question 4

Gizzlies are used for separating __________ solids.

Answer 4

fine

Question 5

Pick out the material having minimum Rittinger’s number.

Answer 5

Quartz

Question 6

__________ mills are termed as impactors.

Answer 6

Hammer

Question 7

In case of a revolving mill, wet grinding compared to dry grinding

Answer 7

none of these.

Question 8

To get a fine talc powder from its granules, the equipment used is

Answer 8

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

Answer 9

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

Answer 10

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

Question 11

Pick out the wrong statement.

Answer 11

Capacity of crusher in choke feeding is increased.

Question 12

Which of the following size reduction equipments employs mainly attrition for ultrafine grinding?

Answer 12

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

Question 13

Tank filter (e.g., Nutsch filter) is

Answer 13

used for small scale filtration work.

Question 14

In bag filters, filter fabrics are never made of

Answer 14

metallic wire woven mesh

Question 15

Use of ‘grinding aids’ is done in __________ grinding.

Answer 15

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)

Answer 16

D

Question 17

Which of the following is the most suitable filter for separation of abrasive solids suspended in a corrosive liquid?

Answer 17

Vacuum filter

Question 18

All resistances during washing of cake

Answer 18

remain constant

Question 19

A __________ mixer resembles a ball mill without balls.

Answer 19

tumbling

Question 20

__________ conveyor is the most suitable for short distance transportation of non-abrasive loose materials like garbage, grain, food wastes etc.

Answer 20

Flight

Question 21

As the product becomes finer, the energy required for grinding

Answer 21

increases

Question 22

Gyratory crushers compared to the reciprocating jaw crushers

Answer 22

have greater capacity per unit of discharge area.

Question 23

The important dimensional group involved in the power requirement calculation in mixing operation is the __________ number.

Answer 23

both (a) & (b)

Question 24

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.

Answer 24

Po ∝ Re0.0

Question 25

Which of the following grinding mills has the horizontally arranged rods as the grinding elements thereby delivering more uniform granular products with minimum fines?

Answer 25

Rod mill

Question 26

Rittinger's crushing law states that

Answer 26

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

Question 27

Sphericity of pulverised coal is

Answer 27

<1

Question 28

The reduction ratio for fine grinders is

Answer 28

as high as 100

Question 29

Which of the following is the hardest material?

Answer 29

Corundum

Question 30

General mechanism of size reduction in intermediate and fine grinder is by

Answer 30

impact and attrition.

Question 31

A straight line is obtained on plotting reciprocal of filtration rate vs. the volume of filtrate for __________ flow of filtrate.

Answer 31

incompressible cake and laminar

Question 32

The work index in Bond's law for crushing of solids has the following dimensions

Answer 32

kWh/ton

Question 33

Ore concentration by jigging is based on the difference in the __________ of the particles.

Answer 33

specific gravities

Question 34

Size measurement of ultrafine particles can be best expressed in terms of

Answer 34

surface area per unit mass

Question 35

Reduction ratio of crushers is the

Answer 35

ratio of feed opening to discharge opening.

Question 36

Which is a secondary crusher for a hard & tough stone?

Answer 36

Cone crusher

Question 37

40.Which of the following equations is Rittinger's crushing law? (where P = power required by the machine, m = feed rate, k = a constant  Dsa & Dsa = volume surface mean diameter of feed & product respectively.)

Answer 37

P/m = K. (1/Dsb - 1/Dsa)

Question 38

Cyclones are used primarily for separating

Answer 38

solids from fluids

Question 39

There is practically no alternative/competitor to __________ in the beneficiation treatment of sulphide ores.

Answer 39

froth floatation

Question 40

Separation of isotopes is generally done using a/an __________ centrifuge.

Answer 40

ultra

Question 41

Temperature of the product during ultrafine grinding

Answer 41

increases

Question 42

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

Answer 42

heavy tonnages of rocks or gravel.

Question 43

In a ball mill, the volume occupied by the balls (when the mill is stopped) is about __________ percent of the volume of the mill.

Answer 43

50

Question 44

Separation of materials of the same density based on their sizes by using then-different rates of flow is called

Answer 44

sizing

Question 45

Molten ammonium nitrate is mixed with ground limestone in fertilizer plant in a

Answer 45

pug mill

Question 46

Agglomeration of individual particles into clusters (flocs) is called flocculation. To prevent flocculation, the most commonly used dispersing agents are

Answer 46

silicates & phosphates

Question 47

For a sphere falling in the constant drag co-efficient regime, its terminal velocity depends on its diameter (d) as

Answer 47

d^2