Furnace Technology
Overfire burning in a furnace is a phenomenon characterised by

Supply of excess air
Burning carbon monoxide and other incombustible in upper zone of furnace by supplying more air
Supply of excess fuel
None of these

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Furnace Technology
Recuperator is

Not used for fuel gas preheating
A continuous waste heat recovery equipment
Heavier than regenerator meant for the same duty
An intermittant waste heat recovery equipment

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