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

Adiabatic flame temperature
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)

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Fuels and Combustion
Ratio of primary air to secondary air increases with increase in the rank of coal, because the

Oxygen content progressively decreases
High rank coals have higher amount of volatile matter
Calorific value of the coal increases
Ratio of fixed carbon to volatile matter increases

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