Fuels and Combustion
Preheating of combustion air is done to

Complete the combustion of fuel
Reduce its requirement for effecting the complete combustion
Increase the calorific value of the fuel
Increase the adiabatic flame temperature

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Fuels and Combustion
Beehive coke oven

Gives larger yield of coke (around 85%) as compared to by-product ovens
Facilitates by-products recovery
Produces coke with very poor strength
Takes 2-3 days for coking of coal but requires no external fuel for heating

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

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

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Fuels and Combustion
Sometimes water is sprayed during coal charging in the coke oven, which helps in

Controlling the dust nuisance while charging the coal
Reducing the cracking of hydrocarbons in the gas and increasing the percentage of CO & H₂ in the gas (due to the endothermic reaction represented by C + H₂O = CO + H₂)
All of these
Prevention of clinker formation in the oven

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