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

Neither A nor B
Because, it alone produces unreactive coke
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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Fuels and Combustion
Fuel gases containing hydrocarbons (ie.g. coke oven gas) are not preheated before burning, mainly because

There are chances of explosion during preheating
It reduces its calorific value tremendously
It reduces its flame temperature tremendously
The hydrocarbons crack thereby choking and fouling the heat transfer surface by carbon soot

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