Abstract: Aiming at the problem of unusable SCR denitrification system due to the low inlet flue gas temperature during the medium and low load operations of a 300 MW coal-fired boiler, an economizer feedwater bypass technology is applied to raise the SCR inlet flue gas temperature. Based on the bypass tests at typical loadings, the effect of the economizer feedwater bypass on the enhancement of the flue gas temperature is validated and the influence on the boiler operation is studied. Besides, considering the potential risks of the evaporation of the saturated feedwater on boiler safety, a real-time bypass safety flow-rate computing model is established. Therefore, the real-time safety flow-rate is obtained, which can guide the application of the bypass technology. The study results can provide valuable reference for the wide-load denitrification of power plants.

Key words: power plant boiler, economizer feedwater bypass, wide-load denitrification, safety flow-rate, control strategy