Fuels and Combustion
Compound coke ovens are those which can be heated by

Rich gas (e.g., coke oven gas)
Both steam and electrical power
Lean gas (e.g., B.F. gas)
Both B and C

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Fuels and Combustion
Froth floatation is used for

Washing fine coal dust (< 0.5 mm size)
All of these
Washing lump coal (> 80 mm size)
Removing ash from the coal based on difference in specific gravity of coal and ash

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