A fluid recirculation system includes an arrangement of a flow control valve located to receive a flow of fluid from an inlet. The system further comprises an economizer inlet mixing device located to receive the flow of hotter fluid from the arrangement of the flow control valve and from a cooler feedwater stream. An economizer inlet mixing device located upstream of an economizer in a supercritical pressure boiler includes a sparger assembly through which a flow of fluid from the waterwall outlet is received, an inlet through which a flow of fluid from a feed stream is received, and a wave breaker assembly through which an outlet stream from the economizer inlet mixing device is directed.