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

Anthracite containing 10% volatile matter and 8% ash
Semi-bituminous coal containing 25% ash and 20% volatile matter
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
Fixed carbon in coal is defined as

Hundred minus the percentage of volatile matter, ash and moisture
That present in volatile matters
The one which is present in the residue after combustion
The total quantity of carbon present in the coal

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Fuels and Combustion
Rate of low temperature oxidation of coal due to bad storage conditions

Decreases with increase in surface area
Is accelerated by storage in large heaps with small surface to volume ratio
Is more for low volatile coal compared to high volatile coal
Does not vary with increase in surface area

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Fuels and Combustion
Low temperature carbonisation

Is meant for the production of 'metallurgical coke'
Produces higher quantity of gas than high temperature carbonisation
Is mainly for producing the smokeless domestic coke
Produces less quantity of tar than high temperature carbonisation

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