Economizer water recirculation system for boiler exit gas temperature control in supercritical pressure boilers

摘要

#$%^&*AU2016201493B220171116.pdf#####ABSTRACT A method of increasing and controlling the temperature of a flue gas exiting an economizer in a boiler includes receiving at least a flow of fluid from a fluid stream from a furnace to a superheater, combining at least a portion of the received flow of fluid with a feedwater stream, and directing the combined received flow of fluid and feedwater stream to an economizer. A temperature of the combined received flow of fluid and feedwater stream to the economizer is controlled to decrease heat absorption in the economizer, thereby increasing a temperature of the flue gas exiting the economizer and enabling a selective catalytic reactor through which the flue gas is received to remain in service at the minimum allowable design temperature at lower boiler steam flows than would be possible otherwise without an economizer fluid recirculation system.