Steam Boilers, Engines, Nozzles and Turbines
For maximum discharge through a chimney, the condition is that height of hot gas column producing the draught should be

Two times the height of chimney
One-half the height of chimney
Four times the height of chimney
Equal to the height of chimney

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Steam Boilers, Engines, Nozzles and Turbines
Spontaneous combustion is a phenomenon in which

Explosion in furnace
All the fuel burns instantaneously producing high energy release
Fuel burns with less air
Coal bursts into flame without any external ignition source but by itself due to gradual increase in temperature as a result of heat released by combination of oxygen with coal

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