Section 5 Flashcards
With increase in the capacity of screens, the screen effectiveness
a. remains unchanged
b. increases
c. decreases
d. decreases exponentially
c. decreases
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. screening becomes progressively more difficult.
Rittinger number which designates the new surface prduced per unit of mechanical
energy absorbed by the material being crushed, depends on the
a. state or manner of application of the crushing force.
b. ultimate strength of the material.
c. elastic constant of the material.
d. all (a), (b) and (c).
d. 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.
a. 200°C and 5 atm.
b. 1000°C and 10 atm.
c. 500°C and 50 atm.
d. 1000°C and 500 atm.
b. 1000°C and 10 atm.
For efficient grinding, ball mills must be operated
a. at a speed less than the critical speed.
b. at a speed more than the critical speed.
c. at a speed equal to the critical speed.
d. with minimum possible small balls.
a. 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.
a. primary
b. secondary
c. fine
d. ultrafine
c. fine
The reduction ratio for grinders is defined as (where, Df and Dp are average diameters of
feed and product respectively).
a. Df/Dp
b. Dp/Df
c. Df - Dp
d. none of these
a. Df/Dp
Pick out the wrong statement pertaining to the turbine agitator.
a. Recommended peripheral speed for the turbine agitator is 200-250 metres/minute.
b. Pitched blade turbine agitator gives only radial flow with complete absence of the axial flow.
c. Generally, the diameter of the agitator is kept between l/3rd to l/6th of the tank
diameter while the blade length is l/4th of agitator diameter (with central disc, it is l/8th of the agitator diameter).
d. Turbine agitator should be located at a height not less than one agitator diameter length from the bottom. If the depth of liquid in the tank is more than twice the agitator diameter, two agitators should be used.
b. Pitched blade turbine agitator gives only radial flow with complete absence of the axial flow.
A fluid energy mill is used for
a. cutting
b. grinding
c. ultra grinding
d. crushing
c. ultra grinding
Which of the following is the softest material ?
a. Talc
b. Feldspar
c. Corundum
d. Calcite
a. Talc
Dry powdery solid materials are transported by a ________ conveyor.
a. belt
b. bucket
c. screw
d. none of these
c. screw
Fluid energy mill comes in the category of
a. grinder
b. crusher
c. cutter
d. ultrafine grinder
d. ultrafine grinder
For laminar flow of filtrate through the cake deposited on septum, which of the following
will be valid ?
a. Kozney-Karman equation
b. Leva’s equation
c. Blake-Plummer equation
d. none of these
a. Kozney-Karman equation
Which of the following is a continuous filter?
a. Plate and frame filter
b. Cartridge filter
c. Shell and leaf filter
d. None of these
d. None of these
During washing of filter at the end of constant pressure filtration, the rate of washing equals the rate of filtration
a. at time zero.
b. at the end of filtration.
c. when half the filtrate has been obtained.
d. at the end of filtration, but decreases with time subsequently.
b. at the end of filtration.
In screen analysis, the notation +5 mm/-10 mm means particles 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 10 mm screens.
d. neither 5 mm nor 10 mm screen.
a. 10 mm screen and retained on 5 mm screen.
Optimum ratio of operating speed to critical speed of a trommel is
a. 0.33-0.45
b. 1.33-1.45
c. 0.5-2
d. 1.5-2.5
a. 0.33-0.45
The process opposite to ‘dispersion’ is termed as the
a. flocculation
b. sedimentation
c. filtration
d. none of these.
a. flocculation
Grinding efficiency of a ball mill is of the order of ________ percent.
a. 1-5
b. 40-50
c. 75-80
d. 90-95
a. 1-5
Solid particles of different densities are separated by
a. filters
b. thickness
c. cyclones
d. sorting classifier
d. sorting classifier
During agitation of liquids, power consumption during laminar flow is not proportional to the
a. density of the liquid
b. viscosity of the liquid
c. cube of impeller diameters
d. square of rotational speed.
a. density of the liquid
Trommels are revolving screens which normally operate in the range of ________
rpm.
a. 1 - 2
b. 15 - 20
c. 40 - 50
d. 60 - 75
b. 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
a. 0.5 Wi
b. Wi
c. 1.34 Wi
d. 3.34 Wi
c. 1.34 Wi
Maximum size reduction in a fluid energy mill is achieved by
a. compression
b. interparticle attrition
c. cutting
d. impact
b. interparticle attrition
