S4 Flashcards
Which of the following gives the crushing energy required to create new surface?
Rittinger’s law
In filtration, the use of ‘filter aid’ helps in
deplugging the filter medium.
Critical Speed (Nc) of a ball mill is given by(whereR1and R2 are radii of ball mill and the ball respectively).
Nc = 1/2n . sqrt g / R1 - R2
Which of the following clay mixing devices is vacuum operated for deairation of clay?
Pug mill
Gizzlies are used for separating __________ solids.
fine
Pick out the material having minimum Rittinger’s number.
Quartz
__________ mills are termed as impactors.
Hammer
In case of a revolving mill, wet grinding compared to dry grinding
none of these.
To get a fine talc powder from its granules, the equipment used is
ball mill
For a cyclone of diameter 0.2 m with a tangential velocity of 15 m/s at the wall, the separation factor is
230
Higher is the mesh number, smaller will be the aperture size of the screen. It means that the aperture size of a 200 mesh screen will be smaller than that of 20 mesh screen. This is valid for
all (a), (b) and (c).
Pick out the wrong statement.
Capacity of crusher in choke feeding is increased.
Which of the following size reduction equipments employs mainly attrition for ultrafine grinding?
all (a), (b) and (c)
Tank filter (e.g., Nutsch filter) is
used for small scale filtration work.
In bag filters, filter fabrics are never made of
metallic wire woven mesh
Use of ‘grinding aids’ is done in __________ grinding.
dry
Height of liquid in agitation tank is normally maintained equal to the tank diameter. However, if the tank is too tall and a large liquid hold up is desired, then two or more impellers mounted on the same shaft may be used. The clearance between the tank bottom and the bottom most impeller should be about (where,D= impeller diameter)
D
Which of the following is the most suitable filter for separation of abrasive solids suspended in a corrosive liquid?
Vacuum filter
All resistances during washing of cake
remain constant
A __________ mixer resembles a ball mill without balls.
tumbling
__________ conveyor is the most suitable for short distance transportation of non-abrasive loose materials like garbage, grain, food wastes etc.
Flight
As the product becomes finer, the energy required for grinding
increases
Gyratory crushers compared to the reciprocating jaw crushers
have greater capacity per unit of discharge area.
The important dimensional group involved in the power requirement calculation in mixing operation is the __________ number.
both (a) & (b)
At low Reynold’s number, the power (P) required for agitating a fluid in a stirred tank becomes independent of inertial forces. In this limit, indicate which of the following relations is satisfied:
Po= ρ/ρN3D5: Power number
Re = ρN D2/μ: Reynold’s number
Nis the impeller rotational speed, andDis the impeller diameter.
Po∝ Re0.0
Which of the following grinding mills has the horizontally arranged rods as the grinding elements thereby delivering more uniform granular products with minimum fines?
Rod mill
Rittinger’s crushing law states that
work required in crushing is proportional to the new surface created.
Sphericity of pulverised coal is
<1
The reduction ratio for fine grinders is
as high as 100
Which of the following is the hardest material?
Corundum
General mechanism of size reduction in intermediate and fine grinder is by
impact and attrition.
A straight line is obtained on plotting reciprocal of filtration rate vs. the volume of filtrate for __________ flow of filtrate.
incompressible cake and laminar
The work index in Bond’s law for crushing of solids has the following dimensions
kWh/ton
Ore concentration by jigging is based on the difference in the __________ of the particles.
specific gravities
Size measurement of ultrafine particles can be best expressed in terms of
surface area per unit mass
Reduction ratio of crushers is the
ratio of feed opening to discharge opening.
Which is a secondary crusher for a hard & tough stone?
Cone crusher
40.Which of the following equations is Rittinger’s crushing law? (whereP= power required by the machine,m= feed rate,k= a constant Dsa & Dsa= volume surface mean diameter of feed & product respectively.)
P/m = K. (1/Dsb - 1/Dsa)
Cyclones are used primarily for separating
solids from fluids
There is practically no alternative/competitor to __________ in the beneficiation treatment of sulphide ores.
froth floatation
Separation of isotopes is generally done using a/an __________ centrifuge.
ultra
Temperature of the product during ultrafine grinding
increases
Reciprocating screens are normally inclined at an angle of 5° with the horizontal and employ gyratory motion at feed end & reciprocating motion at the discharge end. They are not suitable for the screening of the
heavy tonnages of rocks or gravel.
In a ball mill, the volume occupied by the balls (when the mill is stopped) is about __________ percent of the volume of the mill.
50
Separation of materials of the same density based on their sizes by using then-different rates of flow is called
sizing
Molten ammonium nitrate is mixed with ground limestone in fertilizer plant in a
pug mill
Agglomeration of individual particles into clusters (flocs) is called flocculation. To prevent flocculation, the most commonly used dispersing agents are
silicates & phosphates
For a sphere falling in the constant drag co-efficient regime, its terminal velocity depends on its diameter (d) as
d^2
