Impact of boiler load and limestone addition on SO3 and corrosive cold-end deposits in a coal-fired CFB boiler

Abstract The risk of cold-end corrosion caused by two different phenomena was studied: the well-known sulfuric acid-induced corrosion and corrosion caused by hygroscopic fly ash deposits. Measurements were performed in a full-scale circulating fluidized bed boiler firing bituminous coal with high contents of sulfur and chlorine. The boiler was run both with and without limestone addition to reveal the effects of limestone on corrosion. Furthermore, the impact of boiler load on corrosion and deposit composition was studied. Corrosion probe, SO3, and dew point measurements were performed up- and downstream of the electrostatic precipitator. Ash deposits were collected from the different sides of the corrosion probe and were analyzed. The formation of SO3 was low in all cases (