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

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

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Fuels and Combustion
Froth floatation is used for

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

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