S5 Flashcards
With increase in the capacity of screens, the screen effectiveness
decreases
As particle size is reduced
screening becomes progressively more difficult.
Rittinger number which designates the new surface produced per unit of mechanical energy absorbed by the material being crushed, depends on the
all (a), (b) and (c).
Dust collection efficiency of electrostatic precipitator can be as high as 99.9%. Maximum temperature and pressure of dust laden gas that can be cleaned in an electrostatic precipitator is respectively.
1000°C and 10 atm.
For efficient grinding, ball mills must be operated
at a speed less than the critical speed.
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.
fine
For spheres, the surface shape factor is given by (where,A= area,V= volume, andD= diameter)
π(=A/D^2)
The reduction ratio for grinders is defined as(where,Df andDpare average diameters of feed and product respectively).
Df/Dp
Pick out the wrong statement pertaining to the turbine agitator.
Pitched blade turbine agitator gives only radial flow with complete absence of the axial flow.
A fluid energy mill is used for
ultra grinding
Which of the following is the softest material?
Talc
Dry powdery solid materials are transported by a __________ conveyor.
screw
Fluid energy mill comes in the category of
ultrafine grinder
Filtration capacity of a rotary drum vacuum filter depends upon the
both (a) & (b).
About 2-3 hp, power per gallon of a thin liquid provides vigrous agitation in an agitator. ‘Power number’ in agitation is given by
P . gc / n^3 . D^2 . ρ
For laminar flow of filtrate through the cake deposited on septum, which of the following will be valid?
Kozney-Karman equation
Which of the following is a continuous filter?
None of these
During washing of filter at the end of constant pressure filtration, the rate of washing equals the rate of filtration
at the end of filtration.
In screen analysis, the notation +5 mm/-10 mm means particles passing through
10 mm screen and retained on 5 mm screen.
rpm of a trommel at critical speed is given by (where,D= Diameter of trommel in ft)
76.75 / sqrt D
Optimum ratio of operating speed to critical speed of a trommel is
0.33-0.45
The process opposite to ‘dispersion’ is termed as the
flocculation
Grinding efficiency of a ball mill is of the order of __________ percent.
1-5
Solid particles of different densities are separated by
sorting classifier
During agitation of liquids, power consumption during laminar flow is not proportional to the
density of the liquid
Trommels are revolving screens which normally operate in the range of __________ rpm.
15 - 20
The value of work index does not change materially from one equipment to another. If the value of work index determined for close circuit grinding is Wi, then the same for open circuit grinding will be
1.34 Wi
Maximum size reduction in a fluid energy mill is achieved by
interparticle attrition
Filtration rate through a filter cake is proportional to (where,S= filtering surfaceR= specific cake resistance μ = viscosity of the filtrate)
all (a), (b) & (c)
A centrifugal filtration unit operating at a rotational speed of w has inner surface of the liquid (density ρL) located at a radial distanceRfrom the axis of rotation. The thickness of the liquid film is δ and no cake is formed. The initial pressure drop during filtration is
1/2 w^2 . δρL . (2R + δ)
Which one is a filter aid?
Diatomaceous earth
To remove dirt from the flowing fluid, we use a
strains
Which of the following crushers can be considered as a combination of a jaw crusher and a roller crusher?
Gyratory crusher
Separation of solid suspended in liquid into a supernatant clear liquid and a denser slurry employs a process termed as the
sedimentation
Ultrafine grinders operate principally by
attrition
Half the angle of nip, (α), for a roll crusher is given by (where,dr,dpanddfare diameters of crushing rolls, feed particles and rolls gap respectively).
cosα = dr + df / dr + dp
Which of the following comes in the category of primary crusher for hard and tough stone?
Jaw crusher
Crushing efficiency of a machine ranges between __________ percent.
0.1 to 2
Screen capacity is expressed in terms of
tons/hr-ft^2
A screen is said to be blinded, when the
screen is plugged with solid particles.
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?
0.66
Percentage of drum submerged in the slurry in case of rotary drum filter is
30
Filter medium resistance is that offered by the
filter cloth and the embedded particle collectively.
In a roll crusher, both the rolls
all (a), (b) and (c).
Tube mill compared to ball mill
all (a), (b) & (c).
Critical speed of rotation, N (in rps - rotation per second) of a trammel is equal to (where,g= acceleration due to gravity = 9.81 m/sec2and,r= radius of trammel, metre.)
1/2n . sqrt g/r
For the preliminary breaking of hard rock, we use a
gyratory crusher
Filtration operation carried out by continuous increase of the inlet pressure of slurry, is called the __________ filtration.
constant rate
