Fuels and Combustion

161.Fossil fuels mean

1. Solid fuels
2. Liquid fuels
3. Those fuels which are found in the crust of earth
4. Premature fuels with low calorific value

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162.Froth floatation is used for

1. Washing fine coal dust (< 0.5 mm size)
2. Washing lump coal (> 80 mm size)
3. Removing ash from the coal based on difference in specific gravity of coal and ash
4. All (A), (B) and (C)

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163.Fuel combustion is never cent per cent efficient due to

1. Incomplete combustion
2. Dry gas/stack gas loss
3. Moisture loss
4. All (A), (B) and (C)

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164.Fuel consumption in coke making can be reduced by

1. Preheating, blending and de-ashing the coal
2. Stamped charging of coal
3. Dry quenching of coke
4. All (A), (B) and (C)

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165.Fuel for a fast breeder nuclear reactor is

1. Plutonium
2. Uranium
3. Radium
4. Neptunium

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166.Fuel for a nuclear reactor (thermal) is

1. Uranium
2. Plutonium
3. Radium
4. None of these

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167.Fuel gases containing hydrocarbons (e.g. coke oven gas) are not preheated before burning, mainly because

1. The hydrocarbons crack thereby choking and fouling the heat transfer surface by carbon soot
2. It reduces its calorific value tremendously
3. It reduces its flame temperature tremendously
4. There are chances of explosion during preheating

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168.Function of secondary air in pulverised coal firing is to

1. Transport the coal to the burner
2. Dry the coal
3. Ensure efficient burning of coal around the burner
4. Reduce primary air requirement

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169.Furnace oil consumption in a furnace for a given duty employing preheated combination air (at 300°) may be reduced by about _________ percent as compared to the use of atmospheric combustion air.

1. 5
2. 10
3. 20
4. 35

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170.Fusion point of coal ash generally varies from 1000 to 1700° C. Ash having fusion point less than _________ °C is liable to form clinker.

1. 1100
2. 1250
3. 1350
4. 1400

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