Particle Technology Flashcards
Increasing the capacity of the screen
Decreases screen effectiveness
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
the screen is plugged with solid particles
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 a 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 of
Surface area/ 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
b. calcite
c. sapphire
d. feldspar
C.
Another term for sapphire and ruby
Corundum
Units of measurement for coarse particles
cm, in, mm
Unit of measurement for fine particles
mesh
Unit of measurement for very fine particles
microns
Unit of measurement for ultrafine particles
cm^2/g
Minerals belonging to the soft category in Moh’s scale of hardness
1 - Talc
2 - Gypsum
3 - Calcite
Minerals belonging to the intermediate category in Moh’s scale of hardness
4 - Fluorite
5 - Apatite
6 - Feldspar
Minerals belonging to the hard category in Moh’s scale of hardness
7 - Quartz
8 - Topaz
9 - Corundum
10 - Diamond
Stages of size reduction
Coarse (greater than 2.96 in)
intermediate (1-3 in)
fine (less than 0.5/0.25 in)
Equipment used for coarse materials in size reduction
Jaw crusher
Gyratory crusher
Hammer mill
Equipment used for intermediate materials in size reduction
Cone crusher
Crushing Rolls
Equipment used for fine materials in size reduction
Ball mill
Rod mill
For the preliminary breaking of hard rock, we use
a. gyratory crusher
b. tube mill
c. ball mill
d. quirrel-cage disintegrator
A.
Mechanisms of size reduction
Coarse particles - compression
Fine particles - impact
Very fine particles - attrition
Size reduction mechanism used in jaw crushers is
Compression
To get ultrafine particles, the equipment used is
a. ball mill c. hammer crusher
b. rod mill d. fluid energy mill
D.
To get fine talc powder from its granules, the equipment used is
a. roller crusher c. jaw crusher
b. ball mill d. gyratory crusher
B.
Maximum size reduction in a ball mill is done by
a. attrition c. impact
b. compression d. cutting
C.
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
Increases
The operation by which solids are separated from liquids due to difference in the respective densities
Sedimentation
Forces acting on a particle settling in a fluid are
Gravitational or centrifugal, buoyant and drag forces
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.
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
B.
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.
Filtration chapter at Perry’s
Chapter 18
Filter aid is used to
Increase porosity of cake
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?
a. pressure filter
b. centrifugal filter
c. gravity filter
d. vacuum filter
D.
Screen effectiveness, E formula
(check your notes for answer)
The formula for capacity (screening)
P/F=(Xf-Xr)/(Xp-Xr)
The alternate equation for screen effectiveness (E)
XpP/XfF (1-((1-Xp)/(1-Xf))(P/F))
The driving force behind a free-falling body
Gravitational force
Which of the following types of filter are made to operate continuously?
a. rotary drum
c. filter press
b. gravity
d. leaf filter
A.
It is the separation of fluid solid mixture involving the passage of most of the fluid through a porous barrier which retains most of the solid particles contained in the mixture.
Filtration
