Particle Technology

Question 1

Which of the following sequence is involved in size reduction mechanism?

a. Chipping and cracks
b. Chipping and flaws
c. Chipping, flaws and cracks
d. Chipping, flaws, cracks and cleavage

Answer 1

d. Chipping, flaws, cracks and cleavage

Question 2

Size reduction is sometimes called as?

a. Comminution
b. Diminution
c. Pulverization
d. All of these

Answer 2

a. Comminution

Question 3

When reduction in particle size, it ___________?

a. Increases surface area
b. Decreases surface area
c. Decreases absorption
d. Decreases in site of action in solvent

Answer 3

a. Increases surface area

Question 4

The ratio of the aperture size of the screen of Taylor series of that of the next bigger screen is?

a. √2
b. 1.5
c. 0.5
d. 1/√2

Answer 4

d. 1/√2

Question 5

What are the factors affecting size reduction?

a. Shape and size
b. Temperature
c. Pressure
d. Viscosity

Answer 5

a. Shape and size

Question 6

What is a hammer mill used for?

a. Crush larger pieces into small pieces
b. Break down of liquefied emulsions
c. To compress the raw materials
d. Break smaller pieces into fine powder

Answer 6

a. Crush larger pieces into small pieces

Question 7

Separation of solid particles based on their densities is called?

a. Sizing
b. Sorting
c. Clarification
d. Dispersion

Answer 7

b. Sorting

Question 8

What are the size reduction laws?

a. Rittinger’s Law
b. Kick’s Law
c. Bond’s Law
d. All of these

Answer 8

d. All of these

Question 9

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

a. the new surface created
b. the change in volume due to crushing
c. the size reduction ratio
d. none of these

Answer 9

a. the new surface created

Question 10

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

a. Bond’s Crushing Law
b. Kick’s Law
c. Rittinger’s Law
d. None of these

Answer 10

c. Rittinger’s Law

Question 11

Which of the following is not a method used for size reduction?

a. cutting
b. burning
c. impact
d. shear

Answer 11

b. burning

Question 12

Which of the following statement is incorrect?

a. Soft and non-abrasive materials can be made into fine by attrition
b. Crushing efficiency is the ration of the surface energy created by crushing to the energy absorbed by the solid
c. Rittinger’s crushing law states that work required to form a particle of any size proportional to the square of the surface to volume ratio of the product
d. Bond crushing law calls for relatively less energy for the smaller product particle than does the Rittingers law

Answer 12

c. Rittinger’s crushing law states that work required to form a particle of any size proportional to the square of the surface to volume ratio of the product

Question 13

Which mill is depending on the principle of combined impact and attrition?

a. ball mill
b. hammer mill
c. roller mill
d. disintegrator mill

Answer 13

a. ball mill

Question 14

Size reduction of material has the disadvantage of?

a. High degradation
b. High dessolution
c. High flow of material
d. High surface area

Answer 14

a. High degradation

Question 15

In ball mill, how much volume should be occupied by material?

a. 10%-30%
b. 5%-20%
c. 50%-70%
d. 30%-50%

Answer 15

c. 50%-70%

Question 16

In ball mill, ball charge should be equal to about 50% of the ball mill volume to achieve?

a. maximum capacity
b. 50% capacity
c. minimum capacity
d. 100% capacity

Answer 16

a. maximum capacity

Question 16

Which of the following statement is incorrect?
a. Ball mill is used for line graining
b. Sphericity of raschig ring (whose length and diameter are equal) is greater than 1
c. The main differentiation factor between tube mill and ball mill is the length to diameter ratio
d. Sphericity of pulverized coal is less than 1

Answer 16

a. Ball mill is used for line graining

Question 17

Materials with an average size of 25 cm can be accepted by?

a. roll mill
b. jaw crusher
c. ball mill
d. fluid energy mill

Answer 17

b. jaw crusher

Question 18

What is the mechanism of nut cracker?

a. impact
b. compression
c. shear
d. tear

Answer 18

b. compression

Question 19

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

a. jaw crusher
b. roll crusher
c. cone crusher
d. gyratory crusher

Answer 19

b. roll crusher

Question 20

As the rate of feed increases, the size reduction?

a. increases
b. decreases
c. remains the same
d. equal

Answer 20

b. decreases

Question 21

Critical speed of the ball mill is the speed at which?

a. balls begin to centrifuge with the mill
b. balls are carried up the sides and fall freely on to material
c. balls cascade over one another
d. balls start tumbling

Answer 21

a. balls begin to centrifuge with the mill

Question 22

If the critical speed of the ball mill is 75 m/s, the operating speed of the balls mill is?

a. 75 m/s
b. 150 m/s
c. 70 m/s
d. 40 m/s

Answer 22

d. 40 m/s (not sure)

Question 23

Which of the following equipment normally used for crushing limestone?

a. tube mill
b. roll crusher
c. ball mill
d. hammer crusher

Answer 23

d. hammer crusher

Question 24

Which of the following have minimum Rittinger's number? a. quartz b. calcite c. galena d. pyrite

Answer 24

a. quartz

Question 25

Medium for the separation of dust from dust laden gas is? a. air filter b. bag filter c. venturi scrubber d. hydrocyclones

Answer 25

b. bag filter

Question 26

A fluid energy mill is used for? a. cutting b. grinding c. ultra-grinding d. crushing

Answer 26

c. ultra-grinding

Question 27

Shell and leaf filter as compared to plate and frame filter ______? a. entails less labor cost b. provides more effective washing c. facilitates filtration under higher pressure d. all of these

Answer 27

d. all of these

Question 27

Which of the following is a size reduction unit operation in liquids? a. milling b. mixing c. grinding d. homogenization

Answer 27

d. homogenization

Question 28

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? a. primary b. secondary c. fine d. ultrafine

Answer 28

b. secondary

Question 29

_____ are mixed using ribbon blenders? a. Lumpy solids and low viscosity liquids b. Dry powders c. High viscosity liquids d. Thick pastes

Answer 29

b. Dry powders

Question 30

Cutter mill is fitted with ______ knives. a. stationary b. rotating c. both a and b d. none of these

Answer 30

c. both a and b

Question 31

Which of the following equipment is normally used for primary crushing of hard and tough stones? a. ice crusher b. jaw crusher c. cone crusher d. gyratory crusher

Answer 31

b. jaw crusher

Question 32

The process of levigation is known as? a. wet crushing b. shearing c. wet grinding d. both a and b

Answer 32

c. wet grinding

Question 33

The process by which fine solids is removed from liquids is termed as? a. decantation b. flocculation c. sedimentation d. classification

Answer 33

c. sedimentation

Question 34

Which of the following is a coarse crusher? a. smooth roll crusher b. toothed roll crusher c. gyratory crusher d. tube mill

Answer 34

c. gyratory crusher

Question 35

From the following which can accept maximum feed size? a. ball mill b. tube mill c. jet pulverizer d. jaw crusher

Answer 35

d. jaw crusher

Question 36

Gold ores are commonly crushed by? a. tube mill b. stamp mill c. gyratory mill d. hammer mill

Answer 36

b. stamp mill

Question 37

Size reduction is always carried out in the colloid mill in the presence of? a. inert solid material b. liquid c. gas d. none of the above

Answer 37

b. liquid

Question 38

What is use of edge runner? a. to crush the pieces b. to compress the pieces c. to tear the pieces d. to shear the pieces

Answer 38

a. to crush the pieces