Most fossil fuels contain constituents (like sulfur, vanadium, sodium) that may cause corrosion on the fire side of boiler components. And in different temperature regimes, different boiler corrosion due to the fossil fuel constituents may occur. Through research we find three temperature regimes where corrosion occurs.
When temperature is less than 300°F. Dew-point corrosion occurs when sulfuric acid condenses. The combustion of most fossil fuels, natural gas being one exception, produces flue gases that contain sulfur dioxide, sulfur trioxide and water vapor. At some temperature, these gases condense to form sulfurous and sulfuric acids. The exact dew-point depends on the concentration of these gaseous species, but it is around 300°F. Thus surfaces cooler than this temperature are likely locations for dew-point corrosion.
When temperature is 500-750°F. Water cooled wall-tube corrosion occurs in coal-fired units by the formation of pyrosulfates of sodium and potassium. In refuse-fired boilers, mixtures of chlorides of zinc, lead, iron and sodium are the likely causes of corrosion. We offer coal, biomass fired chain grate type boiler that use membrane water cooled wall structure, high efficiency, good sealing, less heat losses.
When temperatures is greater than 1000°F. The cause of superheater and reheater ash corrosion depends on the fuel. The corrosive species are different for coal and oil-fired boilers. Mixtures of vanadium pentoxide and sodium oxide or vanadium pentoxide and sodium sulfate are the principal offensive compounds in oil ash. For coal-fired boilers, sodium and potassium iron trisulfates are the liquid species blamed for high-temperature corrosion.
Once boiler corrosion occurs, timely maintenance should be taken, or it might affect boiler service life and work efficiency. We Boiler Manufacturer ZG is specialized in boiler designing, manufacturing, marketing, installation and maintenance, welcome to consult and get boiler price and specifications.