| 摘要 |
An improved method and system for flue gas recirculation (FGR) from the ID Fan located downstream of a scrubber (or other Air Quality Control Equipment including cyclones, baghouses, etc., hereafter "AQC equipment") back to the scrubber (or other AQC Equipment) inlet to maintain the minimum required flue gas throughput during low-load conditions, thereby eliminating the need for a separate booster fan. A flue gas recirculation duct is connected from downstream of the ID Fan to the inlet of the scrubber (or other AQC Equipment). A variable flow restrictor is placed in the duct downstream of the ID Fan for controlling pressure of the recirculated flue gas. The flow restrictor is controlled in accordance to a function of boiler load or flue gas flow to produce the required backpressure that enables the flue gas to flow through the recirculation duct back to the inlet of the scrubber (or other AQC Equipment) at low loads. This side stream of treated gas is recirculated from the discharge of the ID Fan to the inlet of the AQC Equipment to maintain the appropriate gas velocity regardless of boiler load conditions. The pressure differential between fan discharge and the AQC Equipment inlet enables recirculation of a sufficient amount of treated flue gas using only a small duct and simple flow control damper, without using a booster fan.
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