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

A fluid recirculation system [30] includes an arrangement of a flow control valve [50] located to receive a flow of fluid from an inlet. The system [30] further comprises an economizer inlet mixing device [54] located to receive the flow of hotter fluid from the arrangement of the flow control valve [50] and from a cooler feedwater stream. An economizer inlet mixing device [54] located upstream of an economizer [22] in a supercritical pressure boiler [10] includes a sparger assembly through which a flow of fluid from the waterwall [14] outlet is received, an inlet through which a flow of fluid from a feed stream is received, and a wave breaker assembly [84] through which an outlet stream from the economizer inlet mixing device [54] is directed. A method of increasing and controlling the temperature of a flue gas exiting an economizer [22] in a supercritical pressure boiler [10] includes receiving at least a flow of fluid from a fluid stream [37] from a furnace [12] waterwall [14] outlet, combining at least a portion of the received flow of fluid [37] with a feedwater stream, and directing the combined received flow of fluid and feedwater stream to an economizer [22] inlet to decrease the economizer [22] heat absorption.