Mechanical Operations

341. 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. 0.5 W_i
2. W_i
3. 1.34 W_i
4. 3.34 W_i

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342. The work index in Bond's law for crushing of solids has the following dimensions

1. No units (dimensionless)
2. kWh/ton
3. kW/ton
4. kWh.m₁/2/ton

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343. Theoretical capacity of crushing rolls in tons/hr is given by (where, V = peripheral velocity, m/sec. W = width of rolls, m Dr = distance between rolls ρ = density of material to be crushed, kg/m₃ here, V =πND where, N = speed of the rolls in rotation per second (rps) D = diameter of rolls, m).

1. 3.6 V.W.Dr.ρ
2. 3.6 V.W. ρ
3. 3.6 W.Dr.ρ
4. 3.6 V.W.Dr/ρ

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

1. Classification
2. Tabling
3. Jigging
4. Froth floatation

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

1. Roller crusher
2. Ball mill
3. Jaw crusher
4. Gyratory crusher

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346. To get ultrafine particles, the equipment used is a

1. Ball mill
2. Rod mill
3. Hammer crusher
4. Fluid energy mill

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347. To produce talcum powder, use

1. Ball mill
2. Hammer mill
3. Jet mill
4. Pin mill

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348. To remove dirt from the flowing fluid, we use a

1. Coagulant
2. Gravity settler
3. Strains
4. Clarifier

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349. To remove very small amount of tiny solid impurities from liquid, we use a

1. Pressure filter
2. Vacuum filter
3. Centrifugal filter
4. Coagulant

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350. Toothed roll crushers achieve size reduction by

1. Tearing (shear) and compression
2. Impact and attrition
3. Both (A) & (B)
4. Neither (A) nor (B)

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