The Effects of Flue Gas SO<sub>3</sub> on the Operation of Coal-Fired Units and Countermeasures

There exists a certain amount of SO₃ in flue gas discharged from coal-fired power plants. The implementation and “ultra-low emission” retrofitting of SCR in China greatly increased the concentration of SO₃ in flue gas, which will lead to fouling, erosion and plugging of the SCR reactor and the air preheater downstream. With the lowered dew point of the flue gas, the ammonia sliped from the SCR reactor together with the SO₃ in flue gas will leads to dust accumulation in the Electric Precipitator or in the Bag-house Filter, too. In this study, the main effects and its mechanism of SO₃ on the safety, stability and efficiency of units were analyzed, and measures to control SO₃ were proposed.