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Parti > S4 > Flashcards

S4 Flashcards

1
Q

Which of the following gives the crushing energy required to create new surface?

A

Rittinger’s law

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2
Q

In filtration, the use of ‘filter aid’ helps in

A

deplugging the filter medium.

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3
Q

Critical Speed (Nc) of a ball mill is given by(whereR1and R2 are radii of ball mill and the ball respectively).

A

Nc = 1/2n . sqrt g / R1 - R2

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4
Q

Which of the following clay mixing devices is vacuum operated for deairation of clay?

A

Pug mill

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4
Q

Gizzlies are used for separating __________ solids.

A

fine

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5
Q

Pick out the material having minimum Rittinger’s number.

A

Quartz

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6
Q

__________ mills are termed as impactors.

A

Hammer

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7
Q

In case of a revolving mill, wet grinding compared to dry grinding

A

none of these.

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8
Q

To get a fine talc powder from its granules, the equipment used is

A

ball mill

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9
Q

For a cyclone of diameter 0.2 m with a tangential velocity of 15 m/s at the wall, the separation factor is

A

230

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10
Q

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

A

all (a), (b) and (c).

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11
Q

Pick out the wrong statement.

A

Capacity of crusher in choke feeding is increased.

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12
Q

Which of the following size reduction equipments employs mainly attrition for ultrafine grinding?

A

all (a), (b) and (c)

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13
Q

Tank filter (e.g., Nutsch filter) is

A

used for small scale filtration work.

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14
Q

In bag filters, filter fabrics are never made of

A

metallic wire woven mesh

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15
Q

Use of ‘grinding aids’ is done in __________ grinding.

A

dry

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16
Q

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)

A

D

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17
Q

Which of the following is the most suitable filter for separation of abrasive solids suspended in a corrosive liquid?

A

Vacuum filter

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18
Q

All resistances during washing of cake

A

remain constant

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19
Q

A __________ mixer resembles a ball mill without balls.

A

tumbling

20
Q

__________ conveyor is the most suitable for short distance transportation of non-abrasive loose materials like garbage, grain, food wastes etc.

A

Flight

21
Q

As the product becomes finer, the energy required for grinding

A

increases

22
Q

Gyratory crushers compared to the reciprocating jaw crushers

A

have greater capacity per unit of discharge area.

23
Q

The important dimensional group involved in the power requirement calculation in mixing operation is the __________ number.

A

both (a) & (b)

24
Q

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.

A

Po∝ Re0.0

25
Q

Which of the following grinding mills has the horizontally arranged rods as the grinding elements thereby delivering more uniform granular products with minimum fines?

A

Rod mill

26
Q

Rittinger’s crushing law states that

A

work required in crushing is proportional to the new surface created.

27
Q

Sphericity of pulverised coal is

A

<1

28
Q

The reduction ratio for fine grinders is

A

as high as 100

29
Q

Which of the following is the hardest material?

A

Corundum

30
Q

General mechanism of size reduction in intermediate and fine grinder is by

A

impact and attrition.

31
Q

A straight line is obtained on plotting reciprocal of filtration rate vs. the volume of filtrate for __________ flow of filtrate.

A

incompressible cake and laminar

32
Q

The work index in Bond’s law for crushing of solids has the following dimensions

A

kWh/ton

33
Q

Ore concentration by jigging is based on the difference in the __________ of the particles.

A

specific gravities

34
Q

Size measurement of ultrafine particles can be best expressed in terms of

A

surface area per unit mass

35
Q

Reduction ratio of crushers is the

A

ratio of feed opening to discharge opening.

36
Q

Which is a secondary crusher for a hard & tough stone?

A

Cone crusher

37
Q

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.)

A

P/m = K. (1/Dsb - 1/Dsa)

38
Q

Cyclones are used primarily for separating

A

solids from fluids

39
Q

There is practically no alternative/competitor to __________ in the beneficiation treatment of sulphide ores.

A

froth floatation

40
Q

Separation of isotopes is generally done using a/an __________ centrifuge.

A

ultra

41
Q

Temperature of the product during ultrafine grinding

A

increases

42
Q

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

A

heavy tonnages of rocks or gravel.

43
Q

In a ball mill, the volume occupied by the balls (when the mill is stopped) is about __________ percent of the volume of the mill.

A

50

44
Q

Separation of materials of the same density based on their sizes by using then-different rates of flow is called

A

sizing

45
Q

Molten ammonium nitrate is mixed with ground limestone in fertilizer plant in a

A

pug mill

46
Q

Agglomeration of individual particles into clusters (flocs) is called flocculation. To prevent flocculation, the most commonly used dispersing agents are

A

silicates & phosphates

47
Q

For a sphere falling in the constant drag co-efficient regime, its terminal velocity depends on its diameter (d) as

A

d^2

Parti (9 decks)

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