Mechanical Operations

71. Cartridge filters are termed as 'edge' filters, because of the fact that the

1. Disks have very sharp edge
2. Solids are not deposited at the edge of the disk
3. Bulk of the solids are removed at the periphery of the disks
4. None of these

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72. Cement clinker is reduced to fine size by a

1. Roll crusher
2. Ball mill
3. Tube mill
4. Hammer mill

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73. Chance process is used for the

1. Cleaning of coal
2. Concentration of iron ore
3. Concentration of pyrites
4. Water treatment

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74. Choke crushing (in case of a Jaw crusher) compared to free crushing

1. Results in increased capacity
2. Consumes less power
3. Consumes more power
4. Both (A) and (C)

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75. Close circuit grinding by a ball mill with air sweeping employs a

1. Classifier
2. Cyclone separator between mill & classifier
3. Both (A) & (B)
4. Neither (A) nor (B)

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76. Coal is finally pulverised to 200 mesh size for burning in boilers by a

1. Hammer crusher
2. Ball mill
3. Roll crusher
4. Gyratory crusher

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77. Colloid mills achieve size reduction mainly by

1. Impact
2. Attrition
3. Cutting
4. Compression

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78. Colloidal mills are used for _________ grinding.

1. Coarse
2. Intermediate
3. Fine
4. Ultrafine

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79. Compressibility co-efficient for an absolutely compressible cake is

1. 0
2. 1
3. 0 to 1
4. ∞

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80. Critical Speed (Nc) of a ball mill is given by (where R1 and R2 are radii of ball mill and the ball respectively).

1. Nc = (1/4π). √(g/R1 - R2)
2. Nc = (1/2π). √(g/R1 - R2)
3. Nc = (1/π). √(g/R1 - R2)
4. Nc = (1/2π). √(R1 - R2/g)

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