Fuels and Combustion

281.Oxygen percentage (by weight) in atmospheric air is

1. 19
2. 21
3. 23
4. 29

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282.Oxygen required for theoretically complete combustion of 1 Nm³ methane is _________ Nm³.

1. 2
2. 4
3. 6
4. 1

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283.Pensky-Marten apparatus is used for those oils, whose flash points are _________ °F.

1. > 120
2. > 120
3. > 90
4. 90-110

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284.Percentage of carbon monoxide in blast furnace gas may be around

1. 8
2. 14
3. 22
4. 52

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285.Percentage of hydrogen in coke oven gas may be around

1. 10
2. 25
3. 45
4. 60

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286.Percentage of methane in coke oven gas may be around

1. 5
2. 15
3. 25
4. 50

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287.Percentage of nitrogen in blast furnace gas may be around

1. 5
2. 25
3. 55
4. 80

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288.Pick out the correct statement.

1. Oxygen content decreases from lignite to bituminous coal as the coalification increases
2. The less the oxygen content, better is the coal, as it reduces the calorific value
3. With increase in oxygen content, moisture holding capacity of coal increases and the caking power decreases
4. All (A), (B) and (C)

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289.Pick out the wrong statement.

1. Angle of repose of coal increases with its increasing size
2. Specific gravity of coal increases with its increasing maturity
3. Refractive index and reflectance of coal increases with the increasing rank of coal
4. Specific heat of coal decreases with increases in the volatile matter and decrease in the C/H ratio of coal

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290.Pick out the wrong statement:

1. Carburetted water gas is also called blue gas
2. Coals are divided in four species according to their carbon content in Seylor's classification
3. Carbonisation time in a by-product coke oven is about 16 hours
4. Gross and net calorific value of a fuel is the same, if it does not contain hydrogen or hydrocarbons

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