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

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

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Fuels and Combustion
A sample of natural gas containing 80% methane (CH₄) and rest nitrogen (N₂) is burnt with 20% excess air. With 80% of the combustibles producing CO₂ and the reminder going to CO, the Orsat analysis in volume percent is

CO₂ : 6.39, CO : 1.60, O₂ : 3.99, H₂O:25.96, N₂:72.06
CO₂ : 6.26, CO : 1.56, O₂ : 3.91, H₂O :15.66, N₂ : 72.60
CO₂ : 7.42, CO : 1.86, O₂ : 4.64, N₂:86.02
CO₂ : 7.60, CO : 1.90, O₂ : 4.75, N₂ : 85.74

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Fuels and Combustion
Prime coking coal is always blended with medium or non- coking coal before ear-bonisation

Because, it alone produces unreactive coke
Neither A nor B
To check against its excessive swelling during heating, which may exert high pressure and damage coke oven walls
Both A & B

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