The invention provides a feedwater replacement type
economizer system for whole commissioning of a denitration device. The feedwater replacement type
economizer system is characterized in that the feedwater replacement type
economizer system comprises a first bypass, a second bypass and a third bypass, the first bypass and the second bypass are arranged between a downcomer and a feedwater pipeline, the first bypass is provided with a vessel pot, a stop valve, a
circulating pump, a flow control valve, a stop valve and a
check valve in sequence from the downcomer to the feedwater pipeline, the second bypass is provided with a stop valve, a flow control valve and a
check valve in sequence from the feedwater pipeline to the downcomer, one end of the third bypass is in the position between the flow control valve and the stop valve of the first bypass, the other end of the third bypass is connected with the downcomer, the third bypass is provided with a stop valve, and a flow control valve is arranged between the first bypass and the second bypass in the feedwater pipeline. By means of the feedwater replacement type economizer system, economy of a boiler is not sacrificed under
heavy load, the
smoke temperature of an inlet of the denitration device can be increased under
low load, and the feedwater replacement type economizer system is suitable for boilers with the
smoke temperature of the denitration device inlet under
low load reaching 40 DEG C.