Fuels and Combustion
During coal carbonisation process, the conversion of semi-coke to coke is accompanied by an increase in the __________ of the mass.

Electrical resistivity
None of these
Porosity
Density

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Fuels and Combustion
A liquid/gaseous fuel containing hydrocarbons and high amount of sulphur is burnt with 40% excess air. The flue gas still contains large amount of carbon monoxide. This may be due to the

Presence of large quantity of hydrogen in the fuel
Lack of thorough mixing of fuel with air
High sulphur content in the fuel
Low calorific value of the fuel

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

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
Controlling the dust nuisance while charging the coal

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