Fuels and Combustion

331.Tar yield in the low temperature and high temperature carbonisation of dry coal may be respectively _________ percent.

1. 3 & 10
2. 10 & 3
3. 10 & 20
4. 15 & 8

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332.Temperature of coke oven gas just before entering into saturator (for recovery of NH3) is about _________ °C.

1. 30
2. 65
3. 120
4. 180

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333.Temperature of preheated air used for the transportation of pulverised coal through pipes to the burner of a boiler furnace is restricted to a maximum limit of about 300° C to avoid the

1. Requirement of large volume combustion chamber
2. Risk of explosion
3. Chances of clinker formation
4. Incomplete combustion of coal

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334.The advantage of firing pulverised coal in the furnace lies in the fact, that it

1. Permits the use of high ash content coal
2. Permits the use of low fusion point ash coal
3. Accelerates the burning rate and economises on fuel combustion
4. All (A), (B) and (C)

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335.The average molecular weight of a flue gas having the composition by volume as CO₂ = 25%, O₂ = 25%, N₂ = 50% will be

1. 27.6
2. 23
3. 47.3
4. 42.9

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336.The bright glow of a combustion process is the characteristic of _________ temperature oxidation of coal.

1. Fast & high
2. Slow & low
3. Slow & high
4. Fast & slow

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337.The calorific value is the highest out of the following for

1. Producer gas
2. Water gas
3. Coke oven gas
4. Blast furnace gas

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338.The calorific value of 'LPG' (50% propane + 50% butane) is about _________ kcal/Nm³.

1. 5000
2. 25000
3. 10000
4. 15000

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339.The calorific value of a gas of composition CO₂ = 20%, H₂ = 50%, CH₄ = 30%, is y. If the composition of gas is changed to H₂ = 50%, CH₄ = 30%, CO₂ = 10%, N₂ = 10%, then the calorific value will be

1. y
2. 0.95 y
3. 1.05 y
4. 1.8 y

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340.The calorific value of L.D. converter gas is about _________ Kcal/Nm³.

1. 1800
2. 800
3. 4500
4. 10000

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