Fuels and Combustion
A carbonaceous fuel (containing no H₂ or hydrocarbons) is burnt and the resulting flue gas contains 21% CO₂. It means that

Complete combustion of fuel has taken place
21% excess oxygen has been used for combustion
21% excess air has been used for combustion
No excess air has been used for combustion

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Fuels and Combustion
With increase in the temperature of carbonisation of coal

Calorific value of the coke oven gas decreases due to cracking of hydrocarbons which is not compensated by increase in CO & H? content
Hydrogen content of coke oven gas increases due to cracking of hydrocarbons
Methane content in the coke oven gas decreases and carbon monoxide content increases
All of these

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Fuels and Combustion
The main drawback of supplying more excess air in the combustion of fuel is the

Excessive power requirement of air blower
High exit flue gas temperature from the furnace
Intermittant and uncontrolled combustion of the fuel
Enhanced sensible heat loss in the flue gas

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