WATER QUALITY DIAGNOSIS AND CORROSION PROTECTION OF AIR-STEAM HEAT EXCHANGER

The corrosion failure of an air-steam heat exchanger was analyzed by means of SEM,EDS and XRD,water quality analysis,temperature response of pH and conductivity.The inefficient boiler water pretreatment caused presence of plenty of O2 and HCO-3 in the steam/water cycles.When temperature dropped,O2 and CO2 dissolved into the water film on the surface,resulting in acid corrosion and oxygen corrosion.In addition,the stress concentration,which was caused by the elliptic tube,increased the corrosion.Based on the diagnosis results,some corrosion protection measures were proposed.