22-01-2013, 04:40 PM
Boiler
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ABSTRACT
A component of a steam-generating unit that absorbs heat from the products of combustion after they have passed through the steam-generating and super-heating sections. The name, accepted through common usage, is indicative of savings in the fuel required to generate steam.
An economizer is a forced-flow, once-through, convection heat-transfer device to which feedwater is supplied at a pressure above that in the steam-generating section and at a rate corresponding to the steam output of the unit. The economizer is in effect a feedwater heater, receiving water from the boiler feed pump and delivering it at a higher temperature to the steam generator or boiler. Economizers are used instead of additional steam-generating surface because the feedwater, and consequently the heat-receiving surface, is at a temperature below that corresponding to the saturated steam temperature; thus, the economizer further lowers the flue gas temperature for additional heat recovery. See also Boiler feedwater.
Generally, steel tubes, or steel tubes fitted with externally extended surface, are used for the heat-absorbing section of the economizer; usually, the economizer is coordinated with the steam- generating section and placed within the setting of the unit. See also Air heater; Boiler; Steam-generating unit.