Particle Technology Flashcards
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
A
Screen efficiency is
Recovery x Rejection
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
A
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
C
The material passing one screening surface and retained on a subsequent surface is called
Intermediate Material
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
A
Mesh number indicates the number of holes per
Linear Inch
Size measurement of ultrafine particles can be best expressed in terms o
Surface area per unit mass
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
C
For the preliminary breaking of hard rock, we use
Gyratory crusher
Size reduction mechanism used in jaw crushers is
Compression
To get ultrafine particles, the equipment used is
Fluid energy mill
Maximum size reduction in a ball mill is done by
Impact
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
A
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
C
The operation by which solids are separated from liquids due to difference in the respective densities is
Sedimentation
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
C
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
A
Stoke’s law is valid when the particle Reynolds number is
<1
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
B
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
C
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
A
If the radius of a basket centrifuge is halved and the rpm is doubled, then
a. linear speed of the basket is doubled
b. linear speed of the basket is halved
c. centrifugal force is doubled
d. capacity of centrifuge is increased
C
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
C
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
A
Which of the following may prove unsuitable for filtering volatile liquids?
Vaccum Filter
