Steam Boilers, Engines, Nozzles and Turbines
Tertiary air is the air used to

Convert CO (formed in lower zone of furnace) into CO₂ at higher zone
Cool the scanners
Provide air around burners for obtaining optimum combustion
Transport and dry the coal

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Steam Boilers, Engines, Nozzles and Turbines
Blow off cock in a boiler is used to

Put off fire in the furnace of the boiler when the level of water in the boiler falls to an unsafe limit
Increase the temperature of saturated steam without raising its pressure
Control the flow of steam from the boiler to the main pipe and to shut off the steam completely when required
Empty the boiler when required and to discharge the mud, scale or sediments which are accumulated at the bottom of the boiler

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