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Quiz 5
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Q.1
Cake resistance is
Important in the beginning of filtration
Decreased with the time of filtration
Independent of pressure drop
None of these
Q.2
Wet seiving is employed, when the product contains __________ materials.
Abrasive
Large quantity of very fine
Coarse
Non-sticky
Q.3
The main size reduction operation in ultrafine grinders is
Cutting
Attrition
Compression
Impact
Q.4
Which of the following is not accomplished by agitation of liquids in agitators?
Dispersing gas in liquid
Blending of immiscible liquids
Dispersing immiscible liquid in form of emulsion
Suspending solid particles
Q.5
__________ centrifuge is the most suitable for separation of non-friable crystals.
Tubular bowl
Disc-bowl
Perforated horizontal basket continuous
Suspended batch basket
Q.6
As particle size is reduced
Screening becomes progressively more difficult
Screening becomes progressively easier
Capacity and effectiveness of the screen is increased
None of these
Q.7
In case of grinding in a ball mill
Wet grinding achieves a finer product size than dry grinding
Its capacity decreases with increasing fineness of the products
Grinding cost and power requirement increases with increasing fineness of the products
All of the above
Q.8
Pine oil used in froth floatation technique acts as a/an
Collector
Modifier
Frother
Activator
Q.9
What is the critical rotation speed in revolutions per second, for a ball mill of 1.2 m diameter charged with 70 mm dia balls?
0.5
1.0
2.76
0.66
Q.10
Helical screw agitator is used for
Mixing highly viscous pastes
Blending immiscible liquids
Mixing liquids at very high temperature (> 250 °C)
None of these
Q.11
The resistance offered by the filter used in a bag filter is proportional to (where, c = dust concentration, and s = particle size )
C/s
S/c
S . c
1/s . c
Q.12
The material is crushed in a gyratory crusher by the action of
Impact
Compression
Attrition
Cutting
Q.13
Length/diameter ratio of a ball mill is
1.5
1
< 1
> 1
Q.14
The optimum moisture content in solids to be crushed/ground ranges from __________ percent.
3 to 4
8 to 10
10 to 15
15 to 20
Q.15
A pebble mill
Is a ball mill
Employs flints or ceramic pebbles as the grinding medium
Is a tube mill lined with ceramic or other non-metallic liner
Both B and C
Q.16
A propeller agitator
Produces mainly axial flow
Is used for mixing high viscosity pastes
Runs at very slow speed (2 rpm)
All of the above
Q.17
In case of a hammer crusher, the final product size depends on the
Feed rate
Rotor speed
Clearance between hammer & grinding plates
All of the above
Q.18
Energy consumed for crushing one ton of material ranges from __________ kWh.
0.01 to 0.1
0.5 to 1.5
2 to 3.5
4 to 5
Q.19
A 30% (by volume) suspension of spherical sand particles in a viscous oil has a hindered settling velocity of 4.44 μm/s. If the Richardson Zaki hindered settling index is 4.5, then the terminal velocity of a sand grain is
0.90 μm/s
1 μm/s
22.1 μm/s
0.02 μm/s
Q.20
A cottrel precipitator makes use of the __________ for dusty air cleaning.
Electric spark
Corrona discharge
Alternating current
None of these
Q.21
Filtrate flow rate in case of a rotary drum vacuum filter (in which R
m
< < R
c
) is proportional to __________ and the cycle time (where, μ = filtrate viscosity R
m
= filter medium resistance R
c
= cake resistance ).
√μ
1/√μ
1/μ
1/μ²
Q.22
Ball mill is used for
Crushing
Coarse grinding
Fine grinding
Attrition
Q.23
Apron conveyors are used for
Heavy loads & short runs
Small loads & long runs
Heavy loads & long runs
None of these
Q.24
Carbon black is pulverised in a
Hammer crusher
Ball mill
Roll crusher
Gyratory crusher
Q.25
In a roll crusher, both the rolls
Have the same diameter
Are rotated towards each other
Run either at the same or different speeds
All of the above
Q.26
The energy required per unit mass to grind limestone particles of very large size to 100 μm is 12.7 kWh/ton. An estimate (using Bond's law) of the energy to grind the particles from a very large size to 50 μrn is
6.35 kWh/ton
9.0 kWh/ton
18 kWh/ton
25.4 kWh/ton
Q.27
Screen capacity is expressed in terms of
Tons/hr
Tons/ft²
Both A & B
Tons/hr-ft²
Q.28
Supporting legs of a plate and frame filter is normally made of
Stainless steel
Cast iron
High speed steel
Wooden plank
Q.29
In classification, particles are said to be equal settling, if they have the same terminal velocities in the
Different fluids
Same fluid
Same field of force
Both B and C
Q.30
In a grinding operation, the limiting particle size is the size of the __________ particle in the sample.
Smallest
Largest
Either A or B
Neither A nor B
Q.31
Vibrating screens have capacity in the range of __________ tons/ft² .mm mesh size.
0.2 to 0.8
5 to 25
50 to 100
100 to 250
Q.32
__________ is a cohesive solid.
Wheat
Sand
Wet clay
None of these
Q.33
The operating speed of a ball mill should be __________ the critical speed.
Less than
Much more than
At least equal to
Slightly more than
Q.34
Ultracentrifuges running at speeds upto 100000 rpm is normally used for the
Separation of isotopes based on their density or molecular weights difference
Concentration of rubber latex
Separation of cream from milk
Dewaxing of lubricating oil
Q.35
Basic slag is not ground in
Jaw crushers
Ball mills
Compartment mills
Tube mills
Q.36
Size reduction of moulding powders, waxes, resins & gums are done in a __________ mill.
Cage
Hammer
Both A & B
Neither A nor B
Q.37
The specific surface of sherical particles is proportional to (where, D
p
= diameter of particle).
D²
p
D
p
1/D
p
1/D²
p
Q.38
Wet grinding in a revolving mill __________ as compared to dry grinding.
Gives less wear on chamber walls
Requires more energy
Increases capacity
Complicates handling of the product
Q.39
Trommels employ __________ for screening of materials.
Fibrous cloth
Woven wire screen
Punched plate
None of these
Q.40
A widely used size reduction equipment for __________ is Bradford breaker.
Talc
Coal
Iron core
Wheat
Q.41
In a size reduction crushing operation, the feed size is 10 to 50 mm, while the product size is 2 to 10 mm. This is a case of __________ crushing.
Primary
Secondary
Fine
Ultrafine
Q.42
A compressible cake has the
Maximum porosity at the upstream side
Maximum porosity at the filter medium
Same porosity throughout the cake thickness
None of these
Q.43
A filter press is
A batch filter
Not suitable, if the liquid is the main product
Having prohibitively high maintenance cost
Not suitable for wide range of materials under varying operating conditions of cake thickness and pressure
Q.44
Run of mine (ROM) coal is crushed by a __________ for use in domestic ovens.
Jaw crusher
Hammer crusher
Ball mill
Tube mill
Q.45
increasing the capacity of a screen __________ the screen effectiveness.
Decreases
Increases
Does not effect
None of these
Q.46
To get ultrafine particles, the equipment used is a
Ball mill
Rod mill
Hammer crusher
Fluid energy mill
Q.47
In bag filters, filter fabrics are never made of
Metallic wire woven mesh
Polyester fibres
Cotton fibres
Nylon fibres
Q.48
In bag filters, filter fabrics are never made of
Metallic wire woven mesh
Polyester fibres
Cotton fibres
Nylon fibres
Q.49
General mechanism of size reduction in intermediate and fine grinder is by
Cutting action
Compression
Compression and tearing
Impact and attrition
Q.50
The opening of a 200 mesh screen (Taylor series) is
0.0074 cm
0.0074 mm
0.0047 cm
74 mili-microns
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