PARTICLE TECHNOLOGY

Question 1

Filter aid is used
a. to increase the rate of filtration
b. to decrease the pressure drop
c. to increase the porosity of the cake
d. as a support base for the septum

Answer 1

c. to increase the porosity of the cake

Question 2

The porosity of a compressible cake is
a. minimum at the filter medium
b. minimum at the upstream face
c. maximum at the filter medium
d. same throughout the thickness

Answer 2

a. minimum at the filter medium

Question 3

Which of the following may prove unsuitable for filtering volatile liquids?
a. pressure filter c. gravity filter
b. centrifugal filter d. vacuum filter

Answer 3

d. vacuum filter

Question 4

. Increasing the capacity of screen
a. decreases the screen effectiveness
b. does not affect the screen effectiveness
c. increases the screen effectiveness
d. none of these

Answer 4

a. decreases the screen effectiveness

Question 5

Screen efficiency is
a. recovery x rejection c. recovery
b. rejection d. none of these

Answer 5

a. recovery x rejection

Question 6

As particle size is reduced
a. screening becomes progressively more difficult
b. screening becomes progressively easier
c. capacity and effectiveness of the screen is increased
d. none of these

Answer 6

a. screening becomes progressively more difficult

Question 7

A screen is said to be blinded when
a. oversizes are present in undersize fraction
b. undersizes are retained in oversize fraction
c. the screen is plugged with solid particles
d. its capacity is abruptly increased

Answer 7

c. the screen is plugged with solid particles

Question 8

The material passing one screening surface and retained on a subsequent surface is called
a. intermediate material c. plus material
b. minus material d. none of these

Answer 8

a. intermediate material

Question 9

In screen analysis, notation + 5 mm/ -10 mm means passing through
a. 10 mm screen and retained on 5 mm screen
b. 5 mm screen and retained on 10 mm screen
c. both 5 mm and 13 mm screens
d. neither 5 mm nor 10 mm screens

Answer 9

a. 10 mm screen and retained on 5 mm screen

Question 10

Mesh number indicates the number of holes per
a. square inch c. square foot
b. linear inch d. linear foot

Answer 10

b. linear inch

Question 11

The hardness of a mineral is a criterion of its resistance to crushing. Which of the following is an example of a hard material?
a. talc c. sapphire
b. calcite d. feldspar

Answer 11

c. sapphire

Question 12

For the preliminary breaking of hard rock, we use
a. gyratory crusher
b. tube mill
c. ball mill
d. quirrel-cage disintegrator

Answer 12

a. gyratory crusher

Question 13

Size reduction mechanism used in jaw crushers is
a. attribution c. compression
b. cutting d. impact

Answer 13

c. compression

Question 14

To get ultrafine particles, the equipment used is
a. ball mill c. hammer crusher
b. rod mill d. fluid energy mill

Answer 14

d. fluid energy mill

Question 15

The operating speed of a ball mill should be
a. less than the critical speed
b. at least equal to the critical speed
c. much more than the critical speed
d. none of these

Answer 15

a. less than the critical speed

Question 16

As the product becomes finer, the energy required for grinding
a. decreases
b. is same as for coarser grinding
c. increases
d. is 1.5 times than for coarser grinding

Answer 16

c. increases

Question 17

The operation by which solids are separated from liquids due to difference in the respective densities is
a. screening c. sedimentation
b. adsorption d. absorption

Answer 17

c. sedimentation

Question 18

Forces acting on a particle settling in fluid are
a. gravitational and buoyant forces
b. centrifugal and drag forces
c. gravitational or centrifugal, buoyant and drag forces
d. external, drag and viscous forces

Answer 18

c. gravitational or centrifugal, buoyant and drag forces

Question 19

Drag is defined as the force exerted by the
a. fluid on the solid in a direction opposite to flow
b. the fluid on the solid in the direction of flow
c. the solid on the fluid
d. none of these

Answer 19

a. fluid on the solid in a direction opposite to flow

Question 20

The terminal velocity of a small sphere settling in a viscous fluid
varies as the
a. first power of its diameter
b. inverse of the fluid viscosity
c. inverse square of the diameter
d. square of the difference in specific weights of solid and fluid

Answer 20

b. inverse of the fluid viscosity

Question 21

Buoyant force
a. for non-symmetrical bodies is not vertical
b. depends on the depth of the submergence of the floating body
c. depends on the weight of the floating body
d. none of these

Answer 21

c. depends on the weight of the floating body

Question 22

Terminal velocity is
a. constant velocity with no acceleration
b. a fluctuating velocity
c. attained after moving one-half of total distance
d. none of these

Answer 22

a. constant velocity with no acceleration

Question 23

In hindered settling, particles are
a. placed farther from the wall
b. near each other
c. not affected by other particles and the wall
d. none of these

Answer 23

b. near each other