Fuels and Combustion
Explosion limit of blast furnace gas is 37 to 71% gas in gas-air mixture. It means that the blast furnace gas will explode when burnt in a confined space, if its concentration in the gas-air mixture is __________ percent.

< 37%
>71%
None of these
In between 37 & 71%

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Fuels and Combustion
Which of the following would require least amount of secondary air for combustion?

Semi-bituminous coal containing 25% ash and 20% volatile matter
Anthracite containing 10% volatile matter and 8% ash
Coke breeze containing 25% ash and 2% volatile matter
Bituminous coal containing 20% ash and 25% volatile matter

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Fuels and Combustion
Coke oven gas is a better fuel than blast furnace gas, because of its higher

Heat release rate (thus requiring smaller combustion chamber)
All of these
Calorific value, cleanliness and relatively low distribution cost (due to its low specific gravity)
Adiabatic flame temperature

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