XINLI BOILER

Biomass boiler, what is decommissioning corrosion

07 Jan, 2022

　　The corrosion damage that occurs during the cold standby, hot standby or overhaul of the biomass boiler is called out-of-service corrosion. The boiler shutdown corrosion is mainly caused by the incomplete drying of the inner surface of the metal and the continuous leakage of oxygen in the atmosphere during the shutdown period. Although the internal and external corrosion of the heating surface of the boiler occurs at the same time during the shutdown, the internal corrosion is more serious than the external corrosion, so the stop corrosion mainly refers to the internal corrosion of the heating surface.

Causes of corrosion of biomass boilers out of service

　　After the boiler is shut down, with the decrease of pressure and temperature, the water vapor in the boiler will condense into water, and a vacuum will appear inside the boiler, and the outside air will leak into the furnace. Oxygen is easily produced on the metal in the presence of moisture and water vapor. corrosion. Due to the structural reasons of the boiler, if certain measures are not adopted, it is inevitable to stop corrosion. For example, using a vertical superheater cannot drain the water in the superheater. When there is water-soluble salt scale inside the heating surface of the metal, it will form a high concentration of salt solution when it absorbs water, which will aggravate the corrosion of the stop and form the corrosion in the ulcer. This situation is often present at the entrance of the superheater. Because the separated saturated steam always contains a small amount of boiler water when it enters the superheater, the saturated steam absorbs heat after entering the superheater, the boiler water evaporates into steam, and the salt in the boiler water is deposited on the inner wall of the superheater inlet pipe.